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[ [ "<PERSON>\nAs someone who was disappointed by <PERSON> projects this year, <PERSON> and <PERSON>; 'Dunki' is the best I could have expected from <PERSON> this year. <PERSON> is the biggest reason for me to watch this movie, the legend behind my all time favorite movies, PK and 3 Idiots. His new movie, 'Dunki,' is a very enjoyable film that I found myself appreciating. <PERSON> has done his best, as he always does. You feel the story deeply in your heart with powerful storytelling. Jokes, emotional moments, romance, everything landed perfectly for me. And the beautiful songs make the movie even more wonderful.", "577" ], [ "Tbh I expected more from this movie when I went to the theater. I mean, it's a <PERSON> movie. But I am not sure if it paid off as much as I anticipated. Imo I don't think 'Dunki' is anywhere close to PK and 3 Idiots, and it's not better than Sanju either. It probably falls within the same tier as Sanju. Nevertheless, 'Dunki' is still a damn good movie. I highly recommend everyone to watch it. You'll certainly have a good time.", "577" ], [ "<PERSON>\nThis movie is incredibly unique and original. The story might seem somewhat familiar, but the storytelling, dialogues, score, set design, cinematography, and the overall theme are exceptionally original. The entire main cast, especially <PERSON>, <PERSON>, and <PERSON>, deliver outstanding performances and are perfectly cast. <PERSON> has the potential to become the next big star in Hollywood. I'm glad I went to see this movie without knowing anything about it, just heard good things, and I recommend you do the same.", "529" ], [ "Don't even watch the trailer; dive straight into the movie. That way, you'll definitely enjoy it more. 'Saltburn' is one of the best movies to come out this year. I wouldn't mind watching this again someday. I highly recommend it to everyone. You won't be disappointed", "583" ], [ "Marriage Story\nAfter hearing all the hype for this movie, I went in expecting a masterpiece. Watching Marriage Story, I quickly realized this isn’t the same kind of masterpiece that Parasite is. It’s a masterpiece because the story, acting and cinematography is entirely human and real. The long takes, the superb acting, and the pensive atmosphere creates masterful story telling. I watched this not wanting it to end.\n<PERSON> creates scenes that if it were another movie would seem too long, but here fit perfectly and still keep your attention. <PERSON> & <PERSON> give their best performances ever.", "217" ], [ "This is a new standard of filmmaking. One that is more human, cutting out the fluff of current Hollywood. The score is incredible too. The tone is set the first ten minutes thanks to the beautiful score.\nThe only problem is, I wish this was shown in theaters nationwide. To start and stop this movie, as one does with Netflix, is a disservice to the movie as whole.\nOverall this movie is perfection. 5 stars.", "583" ], [ "Scarface\nHaving just watched Scarface, I now understand why, even after 40 years since its release, this movie still remains a topic of conversation. It's just exceptional. So brutal at times that it almost feels overwhelming. The movie delves deep into the worst of humanity for a relentless three hours.", "387" ], [ "Everyone portrayed is a cold hearted, ruthless individual, yet somehow, it all comes together seamlessly. Despite its intensity, I had a lot of fun watching it. Undoubtedly one of the best gangster movies ever made, and I'm glad I finally decided to give it a go. Probably I'm the only one late to the party, but if anyone out there missed this masterpiece, I strongly urge you to watch it.", "583" ], [ "Lessons in Chemistry\nI’ll admit it, initially this didn’t peaked my interest. The story wasn’t intriguing enough for me to give it a go despite <PERSON> being in it. But because <PERSON> got nominated for it, I decided to give it a chance and boy, it showed me! This satisfying and ENTERTAINING 1950s prestige drama turned out to be so much better than what I anticipated.", "577" ], [ "<PERSON> in unlike any role i’ve seen her play, gives one of the very best performances of her career with an autistic-like energy that she brings to the role. <PERSON>, <PERSON> & <PERSON> put together very strong performances on the supporting side. Yeah, this was awesome!", "883" ], [ "<PERSON> and the Prisoner of Azkaban\nThis was my favorite <PERSON> film when I was younger and I don't think the others will beat it. I love the story. I love how this film is dark and spooky. Werewolves? Sign me up. There are a lot of creepy imagery.", "475" ], [ "<PERSON> does a solid job behind the camera. The cinematography is fantastic. <PERSON> score is phenomenal per usual. I'm a fan of <PERSON> and he's great in this film. <PERSON> is also a standout. I was excited to watch this again after so many years and it holds up beautifully.", "594" ], [ "<PERSON>\nThe best film of the year so far. Such an odd choice by me and many other people to watch this in a double feature with <PERSON>.\nThe acting here is so good…<PERSON>, <PERSON>, <PERSON>, <PERSON>, and <PERSON> are all outstanding and <PERSON> completely destroys THAT scene.\nThis is going to definitely be one to rewatch so I can take in the absolute scope and density of this film. The score was insane and the cinematography through out this film felt unreal.\nIs this one of <PERSON>’s best?", "217" ], [ "The Woman in the Window\nI can't even express how disappointed I'm. I've been trying to read the book. Then I heard <PERSON> is going to adapt this book into a movie. I felt like WOW! As he already made one of my all-time favorite \"Atonement\", I was really excited about it. And I've been waiting for the movie ever since. But sadly this is not what I've expected.\n\"The Woman in the Window\" could've been an outstanding psychological puzzle. Instead, it became a fine example of All-books-shouldn't-be-adapted-into-films. The movie couldn't capitalize on the promising concept of the book and thus totally fell flat. There's no depth in plot, no story build-up, no character arcs.", "952" ], [ "Most of the time, it felt like they were rushing, skipping, and jumping from one scene to another. Also, twist and mystery revelation were so terrible. Out of nowhere plot started to reveal. Tbh, I haven't probably watched any film in a recent year with such bad screenwriting. Plus, it's way too many casts, but no one got enough screen time.\nThere are only two good things in the film. <PERSON> was remarkably good. And cinematography was genuinely amazing and eye-pleasing. Overall, \"The Woman in the Window\" had a real potential to be a subtle psychological mystery thriller. The filmmakers completely blew it off.", "269" ] ]

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[ [ "Although it's hard for me to actually recommend the movie American History X to someone, I do it anyway because I got some lessons out of it and have looked back on that movie many times over the years. It gave me a new understanding of the \"gang\" type mentality and how serious it is and how real it is when you grow up with it.", "426" ], [ "The move stars <PERSON>, who I love! He receives a prison sentence for killing 2 black men and the movie is about how his views change once he's summoned to work with a black man while in prison. The movie follows their friendship, his release from prison and his effort to save his younger brother from going down the same road he is. It's hard to watch but worth your time!", "325" ], [ "My Dinner with <PERSON>\nAs much as I love bottle movies I wasn’t sure how to feel about this at first. Between <PERSON>’s excessive narration and <PERSON>’s never ending stories, I started to feel like this wasn’t gonna be for me. However, as the film went on, I realized how unique this movie really is. It was by far the most I’ve ever actually thought to myself while watching a movie whether it was picturing the things these men spoke of or trying to relate the conversation to my own life or figuring out who I agree with more.", "647" ], [ "Even though this meant that at times my focus would drift away from the actual conversation, it was a really cool experience to sort of reflect on my own life through the movie. It’s crazy how they were able to make this an engaging movie through a fascinating conversation and great performances with a premise that really should not work. So yes, the dialogue can be quite exhausting but it is truly a one of a kind movie. 8.7/10", "596" ], [ "I'm currently loving the Nextflix series Sweet Magnolias. It was recommended to me by all my friends once I finished watching Hummingbird Lane. It's a fun series that follows 3 adult friends with families through their jobs, ups and downs and life discoveries.", "948" ], [ "It's calm and quiet with no violence or anything that's hard to watch at bedtime. I find it a great early morning coffee show as well. It's like getting cozy with a great book! It stars <PERSON>, <PERSON> and <PERSON> as they juggle life, careers, kids and relationships in a small town where everyone knows way too much about everyone. It's a nice quiet easy show to watch that helps me feel relaxed and happy!", "883" ], [ "Interview with the Vampire\nMy movie watching lately has pretty much been the occasional theater appearance and following up with the books I have been reading. I finished Interview With The Vampire last month and now I finally got to a rewatch. I think the film does a good job at capturing the main structure of the novel.", "79" ], [ "It is much breezier and things are changed and left behind but nonetheless, it’s a solid film. The casting was spot on if you ask me. I had a great time rewatching this after not see in for roughly 20 years.", "583" ], [ "<PERSON>\n<PERSON> is a lesson on how the media and government can get things really, really wrong.\nNot gonna lie, it took me a while to get into the movie, and it really starts to get good when <PERSON> character enters the picture. <PERSON>, <PERSON> and <PERSON> give great performances.", "577" ], [ "<PERSON> does a great job in making you feel sympathy for <PERSON>.\nWhere the film goes wrong for me are in its depictions of its villains. For being a true story, <PERSON> and <PERSON>’s characters seemed too much like cartoony villains to me. <PERSON> especially had moments where her character seemed like she was the villain in a Disney fairy tale rather than real life 1996 Atlanta.\nOverall the movie was a pleasant watch, and I definitely left feeling like I learned something new.\n3 stars.", "577" ], [ "I'm watching the series The Waltons right now and I started with the very first episode. It's a wholesome family show from the 1970's and it takes place on the Blue Ridge mountains of Virginia in the 1930's during the depression. I was looking for something calming and quiet as opposed to watching the news before bed. I wanted something that wouldn't wind me up and that would just make me feel happy and calm.", "948" ], [ "I'm on season 5 our of 9 right now and I'm loving it so much. The show centers around the grandparents, their son, his wife and their 7 children. It's a great show and very kid friendly as well. Sort of comparable to Little House on the Prairie.", "948" ], [ "<PERSON>\nThe first half of this is so good. The second half, I think was difficult for the filmmakers to make sense out of (and how can you make sense of senseless tragedy? I’m not sure, but that is why we create art, in the end).\nThe chemistry between the brothers and how they all were suffocating under the pressure from their father was done so well.", "306" ], [ "But when tragedy strikes, it devolves into scene after scene of unfortunate events that feel isolated and without much meaning. <PERSON> character is great, but the other brothers don’t get nearly enough fleshing out to fully appreciate their arcs. That said, I understand it’s a delicate balance because it’s a true story.\nThe tail end brings it home, though.", "352" ], [ "<PERSON>\n<PERSON> was amazing, <PERSON>, you’re awesome and I love you.\nI don’t know how I feel about the film. I mean the acting was great, and the way everything was shot was fabulous. I’m very happy for <PERSON> because it seems like this is a dream project for him, both as director and actor.\nI feel like I just lost interest in some of the dialogue scenes. Some of them happen for like 2+ minutes in a single shot, and I have a TikTok attention span. I sometimes suck to watch movies with.", "217" ], [ "Our generation (me) is chalked.\nEach conductor scene made me happy on the inside. I feel like I have a hidden love for orchestras that I didn’t know existed. I am now going to drive home from the theater while blasting classical music.\nP.S. To the old man sitting next to me in the theater who was laughing and having a good time throughout the film, I really wished I got to talk to you before you walked out. You seem like a nice fella, and I hope you have a good rest of your night.", "583" ] ]

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[ [ "Well, Yoda is (of course) a figment of the imagination. This is the first time he appears in this collection of stories and I believe that this was not some \"act\" on this characters part to dupe or test Luke. This is the way that Yoda was meant to be portrayed and was only later refined into some great leader of the Jedi to fill his role in earlier episodes. It is a major flaw that we Star Wars fans strive to correct by inventing these multiple theories. These theories that we concoct are wonderfully creative and I will gladly read and ponder them but, let us be earnest here. The character of Yoda, if a REAL living being, would be considered to be at best severely bipolar, and most likely he would be psychotic/and or in the grip of a multiple personality disorder. Please be kind to me in your replies. I LOVE SW...even the last 3 films and the cartoon(s). My wife makes fun of me and my buddies when we nerd out on SW. I do truly believe that when created Yoda was to be a much more hermit like individual with NO social graces. I don't think Lucas foresaw him EVER being a leading member of the Jedi High Council or schmoozing with dignitaries as he negotiated policy for millions upon millions of sentient beings. This high council Yoda would NEVER rifle through someones belongings and consume their food/steal trinkets and then have fisticuffs with a droid over it. NOT logical for someone that is SO in tune with the force. So, with that(and many other unlisted points) in mind I stand with my aforementioned premise that it is simply poor character development or character planning. Maybe he should have had Yoda suffer some type of brain damage that was not properly diagnosed or treated.....this I could believe would cause him to act in the manner he does when he meets Luke in the swamp. Damn, that is a pretty good idea! Just thought of that as I typed. Maybe some type of viral infection/mechanical injury that damaged his brain or neural chemistry could be worked into story. Sounds like a great fan fiction short story. If you want to collaborate on said premise with me(or if you just run with it on your own) contact me at <EMAIL_ADDRESS><PERSON> is (of course) a figment of the imagination.", "999" ], [ "This is the first time he appears in this collection of stories and I believe that this was not some \"act\" on this characters part to dupe or test <PERSON>. This is the way that <PERSON> was meant to be portrayed and was only later refined into some great leader of the Jedi to fill his role in earlier episodes. It is a major flaw that we Star Wars fans strive to correct by inventing these multiple theories. These theories that we concoct are wonderfully creative and I will gladly read and ponder them but, let us be earnest here. The character of <PERSON>, if a REAL living being, would be considered to be at best severely bipolar, and most likely he would be psychotic/and or in the grip of a multiple personality disorder. Please be kind to me in your replies. I LOVE SW...even the last 3 films and the cartoon(s). My wife makes fun of me and my buddies when we nerd out on SW. I do truly believe that when created <PERSON> was to be a much more hermit like individual with NO social graces. I don't think <PERSON> foresaw him EVER being a leading member of the Jedi High Council or schmoozing with dignitaries as he negotiated policy for millions upon millions of sentient beings. This high council <PERSON> would NEVER rifle through someones belongings and consume their food/steal trinkets and then have fisticuffs with a droid over it. NOT logical for someone that is SO in tune with the force. So, with that(and many other unlisted points) in mind I stand with my aforementioned premise that it is simply poor character development or character planning. Maybe he should have had <PERSON> suffer some type of brain damage that was not properly diagnosed or treated.....this I could believe would cause him to act in the manner he does when he meets <PERSON> in the swamp. Damn, that is a pretty good idea! Just thought of that as I typed. Maybe some type of viral infection/mechanical injury that damaged his brain or neural chemistry could be worked into story. Sounds like a great fan fiction short story. If you want to collaborate on said premise with me(or if you just run with it on your own) contact me at wrgower2508@gmail.com. This is most likely a ZOMBIE post...I am tired and did not look at the date of the last post to this thread. Thanks for a great question and all the ppl that took time to post on this.", "663" ], [ "****edit *disclaimer****\n****This is a negative review based completely on my own opinions and experiences. Clearly my own opinion isn't the only one. If you would like to read a positive review please go ahead and click on the numerous other ones posited on <PERSON> page. This review was in response to the copious amounts of positive reviews. Based on the positive and negative comments I have received I can easily say that this is quite a polarizing game that I suggest everyone to play a few times before purchasing. This disclaimer does not mean I have changed my opinion, it is simply a response to all harsh critiques I have received. From now on I will think twice before giving my opinions on this site and if I do decide to contribute again I will downplay the pathos of my opinions.\nThanks, <PERSON>****\nI don't even know where to begin.\nI am writing this out of sheer confusion and frustration. I was surfing through the rankings when I hit this one currently ranked somewhere in the upper 300's. I was so shocked and enraged that I checked through the forums just to see that this game has been getting praise by users and critics alike.\nUnbelievable...\nI bought this game on release as soon as it came out because I loved Arkham Horror so much. Boy was I surprised when this game came out to be an unbalanced version of Yahtzee.\nIssue 1: Gameplay\nI consider this the most disastrous issue of the game. There is simply not much to it. You choose a room and roll. THAT'S IT!!! Sure you might have some modifiers here and there but all they do is add a die to your roll. You gain elder signs and whatnot and then you fight the enemy if you didn't manage to seal him off. It all turns out to be an exercise in boredom and frustration as a game that should be a filler turns out to easily take over an hour. Which brings me to my next point.\nIssue 2: Length\nThis game is LONG. Even if you all you want is a Yahtzee variant, do you honestly want a 60+ min Yahtzee variant with very little variety? With any game over 60 min you should expect a meaty experience, not a filler.\nIssue 3: Theme\nI love <PERSON> as I know many others do. While this game is <PERSON> flavored, the theme is empty. The very minimum they could have done is put a little flavor text to make it more interesting. Another place the theme falls flat is the fact that you can enter any room. If you are supposed to believe you are walking through a museum shouldn't there be a room order? Not every room connects to every other one.\nIssue 4: Scalability\nThis game scales horribly. I played this game a few times with different numbers just to see if it gets any better. Let me just tell you it doesn't.", "504" ], [ "More than 3 and the game just drags. Others have nothing to do during your turn. I played an 8 player game as well. THIS WAS THE WORST GAMING EXPERIENCE I HAVE EVER HAD. Everyone was bored waiting for their turns even two turns in. Most of them just left after 30 min.\nIssue 5: Price\nI paid full price $40 for this game. Where did my money go? For a few dice and a little bit of cardboard. Ended up selling it for less than half that. I will never buy another game blindly like that again.\nIssue 6: Balance\nElder Sign is completely broken in it's current form. Since you can enter any room in the museum, the best route is just to enter the easiest rooms and gear up. With 3 players we beat the game entirely too easily. I saw that some people have tried to create variants to balance this game on the forums. I just think that no game I buy should be this broken right out of the gate. Was it even playtested?? I doubt it.\nConclusion:\nNow I really wanted to like this one. I have tried this game with over 20+ different people just to make sure. Every single one was completely bored and called it a long Yahtzee variant. PLEASE PLEASE PLEASE don't buy this game before trying it out. I have no idea how this game shot up so high in the charts. I guess when you put a <PERSON> theme in a game people buy it up. Please help me by reconsidering your ratings on here. We need to lower Elder Sign's ranking. How could this game be better than <PERSON> Discworld or Betrayal at the House on the Hill? This game is broken and everyone knows it. Help me ensure that others don't make the same mistake I have.\nThanks for listening to my disorganized rant and I hope some of you disagree so I don't look so contrary.", "386" ], [ "Take Your Breath Away Mask DIY!!!\nIntroduction: Take Your Breath Away Mask DIY!!!\nWow! What a challenging topics masks are. I am not here to debate the philosophical or health issues so lets just look at the mechanical problem that they are supposed to solve and some of the problems they create.\nEverything I have seen for why masks are recommended is to stop both doplets (Which are the large ones that fall onto surfaces quickly because of their size and weight) and microdroplets (you guessed it the small ones that stay suspended on air currents for a long time) from eventually contacting touchable surfaces or people directly. It is the microdroplets that have so many people concerned. They are light enough be be carried on air currents within a room allowing them to stay aloft and spread for several minutes.\nSharing is not always caring so what can we do to capture these droplets before we take them to the potluck of human experience?\nMasks are designed to keep the water droplets that a person breaths, speaks, or coughs from entering general air circulation where they could come into contact with other people. The way that this has been done historically is to cover our microdroplet ports (nose and mouth) with something to catch the droplets before they escape. This has meant that people cover their nose or mouth with enough fabric that the droplets and microdroplets of water that are projected from a person's nose or mouth are caught in the fabric. This raises all sorts of questions about how effective different fabrics are at stopping these droplets and it has been interesting seeing the different research about which types are effective and very interesting to see that there are even fabrics that are counterproductive in that they make regular droplets into microdroplets increasing the hang time.\nSo that is what masks are supposed to accomplish but they also do so much more. One of their favorite things to do is fog up my glasses so in general it is nice to not wear a mask when I can. This is because I like to see people's faces which is easier if my glasses are not fogged up and also if their face is not also covered by a mask. The idea of having a mask that does not cover a person's face is not new. Looking through instructables I stumbled across some guides for masks that use clear mouth covers that are helpful for the deaf and hard of hearing that rely on lip reading to help understand people.", "225" ], [ "Here is one of the great examples by <PERSON>:\nhttps://www.instructables.com/Face-Mask-Adapted-fo...\nBUT!!! What if there was a way of stopping the droplets and microdroplets without having to wear a piece of material over your face? What if there was a solution that literally took your breath away and pulled the water from the air before it went into general circulation?\nWell that is exactly what the Take Your Breath Away Mask is in this instructable.\nUsing a centrifugal fan to create a zone of negative air pressure (Think like a small vacuum) in front of my nose and mouth I am able to catch and collect the droplets and microdroplets that I breath out or that come out from speaking! Once the centrifugal fan catches these droplets it pushes them through a collection of desiccant beads to absorb the water. I have even found some that change from orange when they are dry to green when they are saturated because everyone knows that green means sick and that is what these beads are supposed to catch. The final result is a dry stream of air ejected downwards away from people rendering it safe.\nHowever this would not be a very good infomercial introduction if I did not say, \"BUT! That is not all... This has a whole host of benefits\n1. You can see the wearer's face!!!\n2. Reusable filter that is not touching your face. Easily rechargeable with heating which kills the virus.\n3. Breathing in is not restricted in anyway which makes it comfortable to use\n4. There is nothing pressing on your face or hanging from your ears to make them sore\n5. It will not muffle your voice!\n6. Your glasses will not fog up!\nThe goal is make this small, effective, and quiet so that a person can still clearly understand me.\nLets take a look at what parts are need to make this happen and then get down to it.\nFTC Disclaimer: I earn a percentage of the sales through the affiliate links provided through Amazon.\nIf you click on the link it helps fund future projects but bear in mind it might not be the best price for this materials.", "440" ], [ "According to all that's been said and done, one must assume (an educated assumption therefore) <PERSON> went with <PERSON> to the West, regardless if to Valinor or one of the off-shore isles. The \"West\" has always been a place of paradise and everlasting, this would include the Islands off the coast of Vailor, otherwise, why even go when you can live in Middle Earth to the same age, AND among friends and family and familiarity? It would not make sense to go to another land and die there at the expected age, without your people in full comfort. Did <PERSON> go because of the beauty of <PERSON>? While he loved her it would seem that would not alone grant him to live in the West. He went because of his bond with <PERSON> and that he was involved in the Fellowship, closely connected to the wishes and wants and needs of <PERSON>, <PERSON>, <PERSON>, all elves or West-sent. It is very clear both <PERSON> and <PERSON> left Middle Earth for the undying lands, on elvish ship, which is stated in the books. They were accepted because they were \"ring bearers\" namely, but also part of the same Fellowship Gimli was. The healing was simply part of the package, or part of life in Valinor or the isles. <PERSON>'s leaving Middle Earth was not an invitation, and here is where it can get grey. The Valar could not change the laws or rules their God had created on the lands, and mortals. Mortals could only live for a while in the West. But what of the isles off the shore of Valinor? What we have are NOTES <PERSON> had, notes that were likely unfinished ideas, theories.", "88" ], [ "It must be said that <PERSON>, <PERSON> and <PERSON>, were INVITED to go and live in the West. In the books, The Silmarillion, The Hobbit, The Lord Of The Rings, we are not told any direction on how to interpret what would become of them had they been invited, accepted as Live-among-us type, which should lead us to believe they were GIVEN a gift, not to go there and die even with an added 50 years, and for what(?), but to live among elves as immortals. We have the books, notes which were likely not finished, and reason to go along with. As it goes in this story, there are always exceptions to rules, or new or different ways of seeing something, as <PERSON> kept writing. I must believe according to all I have read, the three invited guests had to have lived as immortals in the West. As for <PERSON>, he was in deed a ring bearer, but he was mortal and not invited. Or, was he, as ring bearers have the right of passage. Had <PERSON> lived ten or fifteen more years, we may have had more clear answers. <PERSON>, <PERSON> and <PERSON> therefore, for me, lived in the West for ever, while <PERSON> is a question. But why go only to have <PERSON> and others see him die. It doesn't make sense. All who are welcomed in Valinor or the isles therefore should be granted life forever.", "381" ], [ "I want to write a novel or collection of stories that instil happiness in the reader in a way that makes them want to pass on that feeling (think Pay it Forward or 13 Reasons Why)\"\nIt sounds like you want to write a story that is inspirational. Most fiction does inspire in some way. The typical (non-tragic) story goes thus: 1. Main Character wants X 2. Main Character tries to get X, but fails 3. Main Character overcomes personal flaw and gets X\nThat's usually pretty inspiring in its own way. To take it to the next level where I think you want to take it, you'll probably also want to introduce an inspiring idea on top of that story.\nIf you remember nothing else from my answer, please remember this: Never make your story ABOUT your inspiring idea. Instead, make your movie about 1 or more characters overcoming a personal flaw that helps them achieve the thing they want most(even if they don't know they want it at the beginning of the story). That's a really abstract description of what I'm trying to say, so I'll give a couple examples of what to do and not do.\n\"Pay it forward\" is a good example of what you should do. If you study the structure of the movie(I didn't read the book, so I can't comment), it's not REALLY about changing the world by \"paying it forward\". Instead, it is a movie about a broken family and a teacher with a \"haunted\" past. Only when the teacher overcomes his haunted past, and <PERSON> character learns to respect herself, do those characters get what they want: a \"REAL\" family.", "846" ], [ "The whole \"idea\" of the kid trying to change the world by \"Pay it Forward\" is almost incidental to the story.\nIf you want to write a story that inspires people don't make it about that idea alone. That's too in your face. You want it in the background and let it seep in as part of the story. We as people are jaded and are leery of a story that says \"Do this, do this, do this!\". Instead, give us a well-developed character or two that must overcome a personal struggle. The character might also be trying to achieve an external goal - that external goal can be your inspiring \"idea\" as long as it is distinct from the characters internal struggle.\nI'm getting really abstract again, so I'll give a tried & true example. If you want to write an inspiring tale about kids standing up to a bully, don't make it the primary(and definitely not only) conflict. Instead, the story could be about the kid or (kids) learning to love and respect themselves. Then, once they've done that, they can stand up to the bully. Or, maybe the story could be about a bully's friend who has to learn it's okay to stand out from the crowd to do what's right. Once he learns that lesson, then he can tell his friend, publicly, to quit being a bully.\nWhatever you end up writing about, the key to making people want to share it is that you have a character with a deep desire and a person with an equally deep personal flaw(screenwriters sometimes call it an \"emotional wound\") that they must go through a deep personal hell to overcome. If your character does that, and at the end is able to achieve something inspiring(\"Change the world\", \"save the kid\", \"find true love\", etc...), your audience(myself included) is going to want to shout to the world about it.\nHope that helps.\nStandard disclaimer: This is not the ONLY way to inspire someone. This is only a very common way that many storytellers have found successful.", "846" ], [ "A few thoughts up front:\nA perfect sphere is normally thought of as a sphere that is completely seamless across its surface. There are no cracks, indentations, valleys or hills. This would create a world that would exist sort of like this: Sphere made of a single element.\nFollowing this idea... The Earth existing as a perfect sphere would mean some very drastic changes:\nPlate Tectonics\nEarth is not one single element but a diverse collection of many, possibly infinite materials (at least on the more and more micro level) materials. A macro example of this is the Farallon Plate that is now subducted deep into the earth. This process is essential to everything that exists right now and would exist very differently within a world that had to stay a perfect sphere.\n1. Protrusions from the surface...\nWithout some contour, providing friction and anchoring to a surface, all of these items would be in constant motion, sliding around the surface of the planet like a giant ice rink. Different organisms might arise. Beings that existed as a sort of cloud that could envelop the planet rather than be anchored on the planet's surface.\n1. Internally, assume the Earth is still the same.\nInternally it might be, but without some way to move through molten material up through the planet's surface, creating breaks in that surface, how would the process stay the same? Perhaps through a brief quantum fluctuation, where momentarily both the internal surface and the external surface existed and then they switch places?\n1.", "208" ], [ "Assume that said setup is unaffected by natural processes. I'm guessing...\nPlate Tectonics and the very nature of the earth would have to be changed. You could have a planet surface that was made entirely of water and the material beneath would be some sort of hydrophobic material, the water on top forming a membrane all the way around and floating above the actual inner core of the planet.\nThe Planet in Hypothetical\nWhat we have now is a planet with a molten core, churning away. It is made of a hydrophobic substance that is perhaps in a different state of physical matter than we currently are aware of: A kind of supercooled plasma perhaps?\nIt has to move to retain some of the levels of complexity that you want to exist as part of this world, but the motion of the surface of the planet retains an unbroken surface equilibrium. Water makes up the majority of the surface of the planet. Maybe with thin veins of other some other concentrated material structures running at perfect level with the surface of the planet.\nBeings, intelligent and otherwise\nAs life progressed on this planet it gathered first above the surface, living in a contiguous atmospheric cloud above the surface of the planet. From here the concentrations of material gave off a mild magnetic field and the planet's weak blue sun gave some cold light. These organisms progressed through Millions of years.\nThey feed off the brief interplay between the mild magnetic field of the planet and the dim light of the stellar body that sits at the center of the solar system. They have just reached the level where they can communicate to each other, a brilliant yet fading pulse. A single conversation takes them 500 years.", "258" ], [ "Yellowstone!! The very NAME itself conjures up images of Spanish galleons firing grapeshot across the faces of the helpless and praying English sailors, tangled inextricably in their own vessels' rigging.... What? What's that you say? Bison? Elk??? What do you MEAN this game is about getting herds of animals from one spot to another and back again? Food points??? What the HELL are food points?\nThere was a time when I would purchase every single Avalon Hill title that didn't have the word \"Blitz\" anywhere on the box, or a picture of somebody lying bleeding under a flag. Apparently, during a detour to Yellowstone that my wife and I took during our honeymoon trip from L.A. to D.C., I exercised that privilege at a Yellowstone Park gift store. I remember well how it went, that night, safely ensconced in our room at that lodge in Yellowstone, during the summer of 1988, as the park burned on three sides of us.... The smell of burning bison, elk, bighorn sheep, and mule deer could not keep us from either consummating our wedded bliss or playing our newly acquired board game.\nFast forward, fourteen years. We never played it again. I think that speaks VOLUMES for both the game, and our marriage. Not even as a sentimental attempt to rekindle our dwindling passion would I DREAM of trying to foist this game off on my wife, let alone an innocent human being. However, since this is ostensibly a game \"review\" and not a trip down my skewed version of memory lane, here we go:\nThere are a lot of hexes on the gameboard. Animals naturally move through hexes in the wilderness, so it's no stretch to assume they'd do it in this game. Each of the four herds you can control has its winter grazing area represented in the middle of one of the four edges of the board.", "504" ], [ "Did I mention that the board has a lot of hexes? Okay, hexes are good, so this game is probably good, too. The summer grazing areas for the herds are all adjacent to each other in the MIDDLE of the board! Neat. What sets this game apart from all other \"get your animal to his various grazing areas and back\" games is that in this one, you have to cross almost the entire board, regardless of which herd you choose! Talk about balance. Pretty impressive, really. Here's where it gets scary, and perhaps younger children shouldn't read much of this next bit: There are coyotes and bears parked near all the summer grazing areas. Yes, I warned you. It's NOT pretty when you've just watched your mule deers mate and have a baby, and then this little baby gets coyotified.\nThe game distinguishes between \"food points\" and \"animal points\", and thank goodness it does! If not, none of the other rules would make any sense. Unlike lots of the other \"winter-summer-winter\" games you've played, this one is played in turns. Each game of Yellowstone encompasses all four seasons, and even though you might feel like the game really does last a year, I assure you, it does not.\nBottom line on this game, before I wear out my brain trying to remember it any more: The rules ALL make sense in the context of what you are trying to achieve. The different movement allowances for both the herds and the predators make perfect sense, and are implemented well. There IS empathy involved in attempting to adopt a \"hivemind\" outlook (okay, \"herdmind\") as you try to guide your charges to their ranges and back. It's a very decent, enjoyable game for up to four players who are interested in trying a simulation of something that they will never, ever, ever be able to otherwise simulate in their lives.\nAll review ratings are on a scale of 1 to 5, with 5 being \"Head of herd\" and 1 being \"runt of the litter left to be coyotified by its mother\":\nPlayability--3\nReplayability--1\nTeachability--5 (easy to set up, explain, and play)\nEnjoyability--2 (not exactly left to be devoured by coyotes, but damned close)", "579" ], [ "Even though the film itself was nice and had quite of a growth for <PERSON> that one duel and also a scene before are very strange. But lets start with the beginning shall we?\nHe is too old you say The too old I always got the feeling that it was just an excuse so that the one who was declined does not feel that bad about it. In addition to that though the older one is the more bonds one has formed already and Jedi shouldn't have bonds as those can be used to make them fall to the dark side.\nThe 1 scene I mentioned\n! The interrogation scene with <PERSON>. <PERSON> was able to get into her mind until he made an error and said something that made her will go strong. At this time she EASILY overpowered someone who has trained such things FOR YEARS. As we know from the prequels raw force potential says nothing (<PERSON> lost to <PERSON> in Episode 2......easily) without any training. So there are 2 options for this part. Either <PERSON> had a training and forgot about it (during her unknown childhood part before <PERSON>) or she has a WAY HIGHER force potential than <PERSON>. High enough that she is even untrained way more powerful than he is.\nThe duel\n! <PERSON> was on the defensive and he clearly toyed with her....only for one reason (and despite his terrible wounds). He wanted to train her in the dark side and make her fall. He had her at his mercy until she closed her eyes and did what <PERSON> did during the battle of <PERSON>. She calmed her mind and let the force flow instead of blocking it out.", "865" ], [ "Then she beat him fully. Here we can only speculate how she could beat someone who has way more training than her with the force and the lightsaber than her. Possible is as stated above that she has training that she doesn't remember OR that she is WAY more powerful than him (would also explain how the Great leader and <PERSON> could feel her awakening). Additionally pointing into the WAY more powerful direction is the fact that <PERSON> tried at the beginning of THEIR duel to telekinetically call the lightsaber........and it flew but not to him but to <PERSON>.\nA bit here additionally (personal points):\n! In addition though is what I personally find confusing about the duel. The stormtrooper who seemingly is NOT force sensitive easily shot <PERSON> first and then attacked him. Even with his wounds <PERSON> should have easily been able to vanquish him without even getting a scratch. Then <PERSON> beats him easily as soon as she does not act like she wants but lets the force flow. So aside from the two possibilities above there could be another one that <PERSON> is just not as powerful as he wants to be. That is coutnered though by his blaster freezing in the beginning of the film. So he IS powerful. And she has to be stronger as it seems. One thing we know for sure though is that <PERSON> is NOT as powerful as <PERSON> was (yet). As it is still his fear that he never becomes THAT powerful.", "865" ] ]

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[ [ "CNNs: understanding feature visualization Channel Objectives (SOLVED)\nI'm trying to follow a paper on deep NN feature visualization using beautiful examples from the GoogLeNet/Inception CNN. see: https://distill.pub/2017/feature-visualization/\nThe authors use backpropagation to optimize an input image to maximizes the activation of a particular (Inception) neuron/feature, or entire channel.\nFor example, Inception Layer 4a, Unit 11 is feature 12 of 192 from the 1x1 convolution path of Inception Layer 4a before filter concatenation (see: https://distill.pub/2017/feature-visualization/appendix/googlenet/4a.html#4a-11).\nFor Layer 4a 1x1 convolution the shapes are: ```\nLayer 4a\ninput: [14,14,480] output: [14,14,512]\n1x1 convolution\nkernel: [1,1,480] # total 192 kernels output: [14,14,192] # channels [0..192] of Layer4a output Layer4a slice: tf.slice( layer4a_output, (0,0,0), (14,14,192) )\nLayer4a Unit 11\nlayer4a_unit_11 = tf.slice(layer4a_output, (11,0,0), (1,1,1)) # numpy [11,1,1] ```\nIn a related article, the authors state (see: https://distill.pub/2018/building-blocks/) ,\n\"We can think of each layer’s learned representation as a three-dimensional cube. Each cell in the cube is an activation, or the amount a neuron fires. The x- and y-axes correspond to positions in the image, and the z-axis is the channel (or detector) being run.\"\nFurthermore, they offer a diagram which super-imposes the cube of Layer4a over the input image with the (x,y) axis overlaying the image itself.\nI understand that the Neuron Objective is the input image that produces the highest activation for Layer 4a, Unit 11 which can be found at index=[11,0,0] of Layer 4a output=[14,14,512]. In this case, (x,y)=[11,0]. Each [1,1,480] kernel generates a feature map of shape=[14,14,1] with a total of 196 activations.\nkernel => channel or feature map and activation => neuron or feature.\nQuestion\nBut what is the intuitive concept of the (Positive) Channel Objective? In this example, Unit 11 sits in the same channel as 14x14=196 other neurons, but the channel objectives for all these neurons are different.", "740" ], [ "If the optimized image for the Channel Objective maximizes the sum of neuron activations for channel 0, (e.g. slice=[14,14,0] of 192 1x1 convolutions or 512 total layer 4a channels) wouldn't it be the same for all 192 neurons in the same channel? Obviously, by the examples we see this is not true.\nHow does the Channel Objective relate to the Neuron Objective for Unit 11?\nANSWER\nI understand that the Neuron Objective is the input image that produces the highest activation for Layer 4a, Unit 11 which can be found at index=[11,0,0] of Layer 4a output=[14,14,512].\nThis is where my understanding went off the rails. Layer 4a Unit 11 is actually channel/feature 12 of 192 for the 1x1 convolution. It is NOT the 12 of 196 neuron of channel 1. My fault for confusing 192 channels with 196 neurons/channel.\nInstead, as mentioned the in answer, Unit 11 is a single neuron in channel 11, usually located near the center, e.g. Neuron Objective is (x,y,z)=(7,7,11) and Channel Objective is (x,y,z)=(:,:,11)", "740" ], [ "Method 2:\nThis is original batch Normalization as suggested in the paper [<PERSON> & <PERSON>, 2015].\nIt is the most common approach. It is very well explained here [d2l.ai]\nSimilarly, with convolutional layers, we can apply batch normalization after the convolution and before the nonlinear activation function. When the convolution has multiple output channels, we need to carry out batch normalization for each of the outputs of these channels, and each channel has its own scale and shift parameters, both of which are scalars. Assume that our minibatches contain m examples and that for each channel, the output of the convolution has height p and width q . For convolutional layers, we carry out each batch normalization over the m⋅p⋅q elements per output channel simultaneously. Thus, we collect the values over all spatial locations when computing the mean and variance and consequently apply the same mean and variance within a given channel to normalize the value at each spatial location\nI'm not sure what the authors mean by \"per feature map\", does this mean per channel?\nYes, two trainable parameters per Channel/Feature map.\nMethod 3:\nThis was the idea suggested as \"Layer Normalization\". [Paper]\nIt fixed the issue of BN i.e.", "740" ], [ "dependence on a Batch of data and also it worked for sequence data. But the paper didn't claim anything great for CNN.\nWe have also experimented with convolutional neural networks. In our preliminary experiments, we observed that layer normalization offers a speedup over the baseline model without normalization, but batch normalization outperforms the other methods. With fully connected layers, all the hidden units in a layer tend to make similar contributions to the final prediction and re-centering and rescaling the summed inputs to a layer works well. However, the assumption of similar contributions is no longer true for convolutional neural networks. The large number of the hidden units whose receptive fields lie near the boundary of the image are rarely turned on and thus have very different statistics from the rest of the hidden units within the same layer. We think further research is needed to make layer normalization work well in ConvNets\nMethod 1:\nThis is averaging across the Feature Maps on every pixel. I am not sure of its aplication.", "740" ], [ "Your Example\nIn your example we have 3 input and 2 output units. To apply convolutions, think of those units having shape: [1,1,3] and [1,1,2], respectively. In CNN terms, we have 3 input and 2 output feature maps, each having spatial dimensions 1 x 1.\nApplying an n x n convolution to a layer with k feature maps, requires you to have a kernel of shape [n,n,k]. Hence the kernel of you 1x1 convolutions have shape [1, 1, 3]. You need 2 of those kernels (or filters) to produce the 2 output feature maps. Please Note: $1 \\times 1$ convolutions really are $1 \\times 1 \\times \\text{number of channels of the input}$ convolutions.", "740" ], [ "The last one is only rarely mentioned.\nIndeed if you choose as kernels and bias:\n$$ \\begin{align} w_1 &= \\begin{pmatrix} 0 & 1 & 1\\ \\end{pmatrix} \\in \\mathbb{R}^{3}\\ w_2 &= \\begin{pmatrix} 2 & 3 & 5\\ \\end{pmatrix} \\in \\mathbb{R}^{3}\\ b &= \\begin{pmatrix}8\\ 13\\end{pmatrix} \\in \\mathbb{R}^2 \\end{align} $$\nThe conv-layer will then compute $f(x) = ReLU\\left(\\begin{pmatrix}w_1 \\cdot x\\ w_2 \\cdot x\\end{pmatrix} + \\begin{pmatrix}b_1\\ b_2\\end{pmatrix}\\right)$ with $x \\in \\mathbb{R}^3$.\nTransformation in real Code\nFor a real-life example, also have a look at my vgg-fcn implementation. The Code provided in this file takes the VGG weights, but transforms every fully-connected layer into a convolutional layers. The resulting network yields the same output as vgg when applied to input image of shape [244,244,3]. (When applying both networks without padding).\nThe transformed convolutional layers are introduced in the function _fc_layer (line 145). They have kernel size 7x7 for FC6 (which is maximal, as pool5 of VGG outputs a feature map of shape [7,7, 512]. Layer FC7 and FC8 are implemented as 1x1 convolution.\n\"Full Connection Table\"\nI am not 100% sure, but he might refer to a filter/kernel which has the same dimension as the input feature map. In both cases (Code and your Example) the spatial dimensions are maximal in the sense, that the spatial dimension of the filter is the same as the spatial dimension as the input.", "740" ], [ "Fine tuning accuracy lower than Raw Transfer Learning Accuracy\nI've used transfer learning on Inception V3 with ImageNet weights on Keras with Tensorflow backend on python 2.7 to create an image classifier. I first extracted and saved the bottleneck features from Inception and used them to train a fully connected layer. This FC gave me around 86% training accuracy.", "458" ], [ "I then 'fine tuned' the model by sticking the trained FC layers on top of a topless Inception V3 and retrained along with the top two convolutional blocks with SGD, a low learning rate and high momentum. I also used Image Augmentation on the training images, but only during fine tuning stage. Instead of accuracy improving, this model hardly gives me 60% accuracy and performs worse than the bare transfer learning model.\n1.Why is this happening?\nOptional: 2.What can I do to improve my accuracy in 'general' on this model? The images I am trying to classify are from the BreakHis breast tumor database and is quite a difficult classification task. Is Transfer learning even appropriate for this task?\nCode for Transfer learning with bottleneck features:\nimport numpy as np\nfrom keras.preprocessing.image import ImageDataGenerator\nfrom keras.models import Sequential\nfrom keras.layers import Dropout, Dense, GlobalAveragePooling2D\nfrom keras.applications.inception_v3 import InceptionV3,preprocess_input\nfrom keras.utils.np_utils import to_categorical\nfrom keras.callbacks import ModelCheckpoint, EarlyStopping\nimport math\nimg_width, img_height = (299, 299)\nweight_path = 'bottleneck_fc_model.h5'\ntrain_dir = 'Cancer_Data/Train'\nvalidation_dir = 'Cancer_Data/Validate'\nepochs = 150\nbatch_size = 128\ndef train_top_model():\ndatagen_top = ImageDataGenerator(preprocessing_function=preprocess_input)\ngenerator_top = datagen_top.flow_from_directory(\ntrain_dir,\ntarget_size=(img_width, img_height),\nbatch_size=batch_size,\nclass_mode='categorical',\nshuffle=False)\nnb_classes = len(generator_top.class_indices)\nnp.save('class_indices.npy', generator_top.class_indices)\ntrain_data = np.load('bottleneck_feature_train.npy')\ntrain_labels = to_categorical(generator_top.classes, num_classes=nb_classes)\ngenerator_top2 = datagen_top.flow_from_directory(\nvalidation_dir,\ntarget_size=(img_width, img_height),\nbatch_size=batch_size,\nclass_mode='categorical',\nshuffle=False)\nvalidation_data = np.load('bottleneck_feature_validation.npy')\nvalidation_labels = to_categorical(generator_top2.classes, num_classes=nb_classes)\nmodel = Sequential()\nmodel.add(GlobalAveragePooling2D(input_shape=train_data.shape[1:]))\nmodel.add(Dense(1024, activation='relu'))\nmodel.add(Dropout(0.5))\nmodel.add(Dense(nb_classes, activation='softmax'))\nmodel.compile(optimizer='adam', loss='categorical_crossentropy', metrics=['accuracy'])\ncallbacks_list=[ModelCheckpoint(weight_path, monitor='val_acc', verbose=1, save_best_only=True),EarlyStopping(monitor='val_acc',patience=10,verbose=0)]\nmodel.fit(train_data, train_labels, epochs=epochs, batch_size=batch_size,\nvalidation_data=(validation_data, validation_labels), callbacks=callbacks_list)\n(eval_loss, eval_accuracy) = model.evaluate(\nvalidation_data, validation_labels, batch_size=batch_size, verbose=1)\nprint(\"[INFO] accuracy: {:.2f}%\".format(eval_accuracy * 100))\nprint(\"[INFO] Loss: {}\".format(eval_loss))\ntrain_top_model()\nCode for Fine Tuning:\nfrom keras.applications.", "338" ], [ "Bilinear Interpolation\nI am trying to implement bilinear interpolation as described in the paper Spatial Tranformer Networks by <PERSON> et. al (see link to paper). They describe bilinear interpolation in Equation 5 as:\n$$ V_i^c = \\sum_{n}^{H}\\sum_{m}^{W} U_{nm}^c \\max(0,1-|x_i^s - m|)\\cdot\\max(0,1-|y_i^s - n|), $$ where:\n* $V_i^c$ is the resulting pixel value in the new image\n* $H$ and $W$ are the height and width of the original image (or feature map) in pixels\n* $c$ refers to the channel (e.g. RGB)\n* $(x_i^s, y_i^s)$ are the coordinates where the original image is sampled (where the image is normalized such that $-1 \\le x_i^s, y_i^s\\le 1$)\n* $U_{nm}^c$ is defined as the pixel value at location $(n,m)$ in channel $c$.\nI am having trouble interpreting the variables $n$ and $m$. Are these\n* coordinates in the normalized image (i.e. $-1 \\le n, m\\le 1$, where you would sum $n$ from $n=-1$ to $H=1$ in steps of the normalized resolution, e.g. steps of $1/100$ for an image that is 100 px in height)\n* or are these row and column values (e.g.", "1021" ], [ "you sum $n$ from $n=0$ to $n=100$ for an image that is 100px in height)?\nI have tried out both to do downsampling of an image, but don't get consistent results.\nIf someone can help me out interpreting this, I would appreciate it very much.\nBelow I have included what I understand of bilinear interpolation. Maybe that someone can help me out based on this.\nIn the below figure, a single channel feature map (or image) with one channel is displayed that consists of four pixels with values $ U_{nm} $, where $ n $ and $ m $ are the coordinates of the center of the pixels, i.e. $ m,n \\in {-0.5, 0.5} $. If we index $ m $ and $ n $ as $ m_k, n_k $, with $ k \\in [1,4] $, we can also index the pixel values as $ U_{n_km_k} $. The values of all four pixels can be reduced to a single value $ V $ at position $ (x_i^s, y_i^s) $ by applying bilinear interpolation.\nThe procedure can be divided into three linear interpolations. First the value $ U_1' $ at position $ (x_{U_1'}, y_{U_1'}) $ can be computed by interpolating the values $ U_{n_1m_1} $ and $ U_{n_2m_2} $: \\begin{equation} U_1' = \\Delta x_2\\ U_{n_1m_1} + \\Delta x_1\\ U_{n_2m_2}. \\end{equation} As the sum of $ \\Delta x_1 $ and $ \\Delta x_2 $ is equal to one, due to normalization of the axes, the above equation can be rewritten as: \\begin{equation} U_1' = (1-\\Delta x_1) U_{n_1m_1} + (1-\\Delta x_2) U_{n_2m_2}. \\end{equation} The terms $ \\Delta x_1 $ and $ \\Delta x_2 $ can be expressed as: \\begin{align} \\Delta x_1 = |x_i^s - {m_1}|\\ \\Delta x_2 = |x_i^s - {m_2}|, \\end{align} which, substituted into the equation for $U_1'$ yields: \\begin{equation} U_1' = U_{n_1m_1}(1-|x_i^s - {m_1}|) + U_{n_2m_2}(1-|x_i^s - {m_2}|).", "1021" ], [ "but what was being trained when training=True?\nLet's try to understand BatchNormalization(BN) layer first as it has more elements.\nTL;DR -\nγ, β are learned. These are initialized just like normal weights and learned in Backpropagation.\nMay read this crisp and spot-on answer on these parm Stat.SE\nFormally, BN transforms the activations at a given layer x according to the following expression:\nBN(x)= γ⊙(x−μ)/σ + β\ncoordinate-wise scaling coefficients γ and offsets β.\n[Quoted - http://d2l.ai/]\neach BN layer adds four parameters per input: γ, β, μ, and σ (for example, the first BN layer adds 3,136 parameters, which is 4 × 784). The last two parameters, μ and σ, are the moving averages; they are not affected by backpropagation, so Keras calls them “non-trainable”. However, they are estimated during training, based on the training data, so arguably they are trainable. In Keras, “non-trainable” really means “untouched by backpropagation.”\n[Quoted - Hands-on machine learning with scikit-learn keras and tensorflow, <PERSON>\ntraining=True: The layer will normalize its inputs using the mean and variance of the current batch of inputs.\ntraining=False: The layer will normalize its inputs using the mean and variance of its moving statistics, learned during training. [Quoted - Keras doc for BN]\nSo, if you will not set it False it will continue updating μ and σ with every batch of test data example and normalize the output accordingly.", "695" ], [ "We want it to use the values from the Training phase.\nBy default, it is False and fit method set it to True.\nDropout\nDropout is simpler of the two. We need this Flag here so that we can compensate(during testing) the loss to the Output value(on an average basis) due to the switched-off(during Training) Neurons.\nSuppose p = 50%, in which case during testing a neuron would be connected to twice as many input neurons as it would be (on average) during training. To compensate for this fact, we need to multiply each neuron’s input connection weights by 0.5 after training. If we don’t, each neuron will get a total input signal roughly twice as large as what the network was trained on and will be unlikely to perform well. More generally, we need to multiply each input connection weight by the keep probability (1 – p) after training. Alternatively, we can divide each neuron’s output by the keep probability during training (these alternatives are not perfectly equivalent, but they work equally well)\n[Quoted - Hands-on machine learning with scikit-learn keras and tensorflow, <PERSON>\nOn the example of Models difference\nThough, these are subjects to try and check.\nBut I believe generally we start to fine-tune when we believe that the upper layer is smoothened to match with the initial layers, to avoid a large flow in forward and backdrop. So the logic stated to keep it Flase in 2019 example might not hold too strong every time.", "740" ], [ "Why Tensorflow does NOT quit when CUDA_ERROR_OUT_OF_MEMORY\nIt was my understanding that when trying to create a tensorflow session, if the amount of available GPU memory is not enough for what the program asks for, the program should raise an error and exit. But it seems to be not this case, and this behavior is very annoying and hard to detect especially when using Jupyter Notebook.\nCode\nI was trying to run the following program (supposedly debug.py)\nimport tensorflow as tf\na1 = tf.constant([0.0,0.0])\nb1 = tf.constant([2.0,2.0])\nmse1, update1 = tf.metrics.mean_squared_error(a1,b1)\nmse2 = tf.losses.mean_squared_error(a1,b1)\nwith tf.Session() as sess:\nsess.run(tf.local_variables_initializer())\nupdate1.eval()\nprint(mse1.eval())\nprint(mse2.eval())\nThis program simply calculate the mean_squared_error (MSE) between the two vectors a1 and b1, and the correct output (from the two print() lines) should be 4.0 and 4.0. If no other python programs are using my GPU, this is indeed the output.\nUnexpected behavior\nIf another program is using the GPU (say, another jupyter notebook running something with tensorflow without limiting its GPU usage by gpu_options.per_process_gpu_memory_fraction), then the above code would output something different.", "695" ], [ "The first print line (mse1) would output some random number, e.g. \"0.0\" (most common), \"3e-45\", \"nan\", etc, which is obviously wrong. The second print line (mse2) always print the correct answer: 4.0.\nRunning this code by python debug.py SOMETIMES generate an error message\nE tensorflow/stream_executor/cuda/cuda_driver.cc:924] failed to allocate 176.44M (185008128 bytes) from device: CUDA_ERROR_OUT_OF_MEMORY\nBut the program does NOT exit, and still prints the results, although incorrect.\nIn other cases, running this code by python debug.py generate another error message\nE tensorflow/core/common_runtime/direct_session.cc:170] Internal: failed initializing StreamExecutor for CUDA device ordinal 0: Internal: failed call to cuDevicePrimaryCtxRetain: CUDA_ERROR_OUT_OF_MEMORY; total memory reported: <PHONE_NUMBER>\nand the program quits without printing any output.\nThe most annoying thing is, running the same code in Jupyte Notebook ALWAYS generates no error or warning messages, though the output is incorrect. That's why I always thought I misunderstood about how to call tf.metrics.mean_squared_error without realizing there could be a memory error.\nSystem\nI verified the problem with my two computers running Tensorflow 1.3 and 1.4 respectively, both with CUDA 8, Ubuntu 16.04 and Nvidia GPUs (1080 and 770M).\nMy Questions\n(0) Is there anything wrong with my code?\n(1) If you also use Tensorflow with Jupyter Notebook, do you ever get the wrong output (printing anything other than 4.0, 4.0) when running the above code? If so, does Jupyter alerts you about any error?\n(2) What is the nature of this problem of returning the wrong mse1? Is it a GPU memory leak?\n(3) Why could there be such inconsistent behavior when the problem occurs? To be specific, why the debug.py sometimes quits, sometimes not? Why Jupyter Notebook never quits or raises an error?\n(4) Why the mse2 never goes wrong when mse1 goes wrong? My understanding is that tf.metrics.mean_squared_error is a streaming operation and therefore need to store some variable in a different place.", "695" ], [ "CNN for classification giving extreme result probabilities\nI'm having issues with my CNN, using Keras with Theano backend. Basically, I need to classify 340x340 grayscale images into 6 categories. The problem is my CNN gives too \"hard\" probabilities, for instance it will rarely give predictions with some uncertainty, and always tries to push for a 90%+ for one class. The problem is that for my coursework, the penalty used is very harsh for complete miss classification, and uncertainty is much preferred.", "458" ], [ "( so having a prediction like [0.6, 0.3, 0.2, ...] is much better than having [0.9,0.03,0.02,..].\nI'm unsure why this is happening. My dataset consists of 2400 images, which are from different CCTV, and task is about recognising possible objects. Only 800 of the samples are actually from the data, the other 1600 have been generated through data augmentation. Note that it is therefore extremely likely a that some pictures are either identical, or extremely similar (e.g. the same scene, one second later)\nmodel = Sequential()\n#1\n# Few filter to take big stuff out\n# Also, first layer is not conv so that I can reuse that layer separately\nmodel.add(Dropout(0.1, input_shape=(1,340,340)))\nmodel.add(Convolution2D(64, 4, 4, border_mode='same'))\nmodel.add(Activation('relu'))\nmodel.add(MaxPooling2D(pool_size=(2, 2), dim_ordering=\"th\"))\n#2\nmodel.add(Dropout(0.1))\nmodel.add(Convolution2D(128, 4, 4, border_mode='same'))\nmodel.add(Activation('relu'))\nmodel.add(MaxPooling2D(pool_size=(2, 2), dim_ordering=\"th\"))\n#3\nmodel.add(Dropout(0.1))\nmodel.add(Convolution2D(256, 4, 4, border_mode='same'))\nmodel.add(Activation('relu'))\nmodel.add(MaxPooling2D(pool_size=(2, 2), dim_ordering=\"th\"))\n#4\nmodel.add(Flatten())\nmodel.add(Dense(1024))\nmodel.add(Activation('relu'))\n#5\nmodel.add(Dense(512))\nmodel.add(Activation('relu'))\n#6\nmodel.add(Dense(6))\nmodel.add(Activation('softmax'))\nopt = SGD(lr=0.001)\nmodel.compile(loss='categorical_crossentropy', optimizer=opt, metrics=['accuracy'])\nprint \"Training..\"\nfilepath = \"log/weights-improvement-{epoch:02d}---{val_acc:.2f}.hdf5\"\ncheckpoint = ModelCheckpoint(filepath, monitor='val_acc', verbose=1, save_best_only=True, mode='max')\ncallbacks_list = [checkpoint]\nmodel.fit(X_t, y_t, validation_split=0.1, nb_epoch=500, batch_size=32, callbacks=callbacks_list)\nHow do you suggest I fix this? Thank you in advance!", "338" ] ]

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[ [ "<PERSON> model subject to reversing constant strain rate\nI've been reading about viscoelastic models and using Excel to plot some of their characteristics. I'm particularly interested in their response to a constant strain rate which reverses periodically and goes into tension as well as compression.\nI've read a number of texts that discuss the <PERSON> integral and a couple that also include the solution to the integral. Initially, I calculated the integral piece-wise in Excel and integrated it numerically. This seemed to produce a sensible force time history but, of course, is dependent on the time resolution and so looks a bit course at the strain rate turn-around.\nI then used the given solution between two time limits to give me the force time history directly. A simple switching function reverses the strain rate every half a cycle and resets the start of the strain time. The problem I now have is that the function 'starts again' from zero every half cycle; it doesn't 'remember' the force at the end of the previous half.", "474" ], [ "It's as if I am missing a constant of integration. Unfortunately I don't have the mathematical skills to progress any further so I wonder whether someone out there can guide me to an appropriate solution or a text that discusses this specific case?\nThe equation for the integral I first used is:\n$$F(t)=\\int_{-\\infty}^tke^{-k(t-t_0)/\\eta}\\frac{d\\varepsilon(t)}{dt}dt$$\nWhere the derivative is the strain rate (actually the displacement rate in my case), k is the Maxwell model spring rate, $\\eta$ is its damping coefficient, and $t_0$ is the time the strain started, which I set to one quarter of a cycle in the past and which then starts from 0 every half cycle. As I say, numerically integrating this works fine.\nThe solution to the integral that I've obtained from another text is:\n$$F(t)=\\frac{d\\varepsilon(t)}{dt}\\frac{\\eta}{k}G_0\\Bigl(1-e^{-k(t-t_0)/\\eta}\\Bigr)$$\nWhere $G_0$ is also k and so cancels the adjacent denominator k out. It has been tricky dealing with the changes in algebraic definition and double meaning of some letters, such as $\\tau$. However, as I say, the force time histories from the two methods are the same for the first quarter of a cycle, except that the first method starts from F=0 at t=0 and the second method give F=0 at t=-1/4 cycle, but that's fine and expected. The problem arises at the end of the first quarter cycle when the second method gives F=0 at t=1/4 cycle, instead of reducing from the existing force level at t=1/4 cycle, as shown in the following image.\nClearly, I could just fudge it and add the offset, but I'd rather see a proper mathematical treatment of it if possible. I'd be grateful for any clues as to how I can solve the issue.\nMany thanks,\n<PERSON>.", "394" ], [ "This is well-known theory in finite element analysis. There are two different effects that contribute to the effective stiffness of the structure in addition to the elastic stiffness $K_e$ given by Euler-Bernoulli-Timoshenko beam theory, and you need to include both of them to get the right answer.\n(1) Rotating the beam creates axial tension in the beam, which will be zero at the tip and increases to a maximum value at the rotation axis. This tension creates an additional stiffness that opposes lateral bending of the beam, in the same way that the tension in a guitar string affects its vibration frequency and hence the pitch of the note produced. (Of course in a guitar string, $K_e$ is negligible, unlike your beam).", "333" ], [ "This stiffness term was traditionally called the \"geometric stiffness\" (for reasons which aren't worth explaining) but a more logical name is \"stress stiffness\" often denoted by $K_\\sigma$, since it depends only on the internal stresses in the structure and not on the material properties.\nIncidentally, $K_\\sigma$ for a compressive stress is what causes <PERSON> buckling in columns. At the \"critical load\" for buckling, $K_\\sigma$ \"cancels out\" the elastic stiffness and when $K_e + K_\\sigma = 0$, the structure can't resist the applied loads. For tension stresses, $K_\\sigma$ increases the stiffness of the structure.\n(2) If the beam deflects from its original straight configuration, the direction and/or the point of application of the centrifugal loads changes.\nIf the beam rotates about a vertical axis and the beam deflects vertically, the CF load on each particle of the beam is still in a horizontal direction, and therefore the CF loads at the beam tip will create a bending moment that tends to straighten out the beam.\nBut if the beam deflects tangentially (for example while you are ramping up the rotation speed from zero) the direction of the CF load is radially away from the axis, and that generates a bending moment that tends to increase the bending of the beam, not reduce it.\nThe usual name for both these effects is \"follower forces\", because the direction of the applied loads \"follows\" the deflection of the structure. The corresponding stiffness terms are usually called the \"load stiffness\" and denoted by $K_L$.\nThe original equation for statics using only the elastic stiffness, $$K_e u = F$$ becomes $$[K_e + K_\\sigma(\\omega) + K_L(\\omega)]u = F.$$ In principle you could get expressions for $K_\\sigma$ and $K_L$ for a simple situation (e.g. a rectangular straight beam) but in practice it's much easier to use a Finite Element package that includes these effects.", "333" ], [ "Finite strain FEM using an existing code that solves small strain elasticity\nI have an existing FEM code that solves the linear elasticity problem. I would like to use the same code for large strain rates, still using a simple material law (Saint Venant–Kirchhoff model).", "232" ], [ "[The problem I want to solve is a contact problem in which strain is larger than 1 very locally, close to the contact point]\nI believe I have two steps to take: take into account the nonlinear part of strain $\\nabla u \\cdot \\nabla u^T$, and solve the mechanical balance in the deformed configuration.\nCan this be done by successive iterations of the linear elasticity problem, e.g. using iterative mesh deformation and a fixed-point algorithm for the nonlinear strain term? Does this converge? References which would highlight the steps to be taken from small-strain elasticity are welcome.\nEDIT\nI would for instance like to know whether such an algorithm would work (there may be a couple mistakes in the details, for now it's rather the spirit of it I'm enquiring about):\nI want to solve $K u + \\nabla u^T\\cdot \\nabla u= Mf$.\nLet $(f^i)_{i\\leq n}$ be a sequence of functions with $f_n = f$, with each increment small enough.\nLet $i=0$, $U^0=0$, $K^0=K$.\n* Solve linear elasticity problem $K^i \\delta u^i = M f^i$.\n* Construct configuration $\\Omega^{i+1}$, and a change of variable $X^{i+1}$ from $\\Omega^{i}$ to $\\Omega^{i+1}$\n* let $U^{i+1} = U^i \\circ X^{i+1} + \\delta u^i$\n* Calculate $K^{i+1} = K_{\\Omega^{i+1}} + \\nabla {U^{i+1}}^T\\cdot \\nabla$ (there's probably something to do here as we develop $u=U+\\delta u$ in the double product, it doesn't write out nicely in tensor notation but should in the linear problem)\nAgain, the above is not to be taken as something thought over but rather the sort of thing I'd like to find in some report/textbook/publication. But maybe there's a crucial problem I don't see which would be the reason why finite strain codes are not presented as an extension of small strain ones?", "935" ], [ "Help debugging finite element solution in nonlinear elasticity\nI'm writing some code to solve problems in nonlinear elasticity using finite element methods. I have been following <PERSON>'s book but I am having trouble with some nagging details.\nMy question is related to which configuration variables to use for calculating different quantities. I'm working on static problems in the updated Lagrangian formulation, so for each \"time\" $t$ I have a loading coefficient $\\lambda_t$, and a displacement $\\sideset{^t}{}{U}$. In chapter 6, <PERSON> derives a linearization of the principle of virtual work, resulting in the equation (6.103): \\begin{equation} \\left(\\sideset{^t_{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{\\text{NL}}{K}\\right)U=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F \\end{equation} where $\\sideset{^t{t\\,}}{\\text{L}}{K}$ is the \"linear\" part of the incremental stiffness matrix in the configuration with displacement $\\sideset{^t}{}{U}$, $\\sideset{^t{t\\,}}{_\\text{NL}}{K}$ is the \"nonlinear\" part, $U$ is the displacement increment, $\\sideset{^{t+\\Delta t}}{}R$ is the externally applied load at \"time\" $t+\\Delta t$, and $\\sideset{^t_t}{}F$ is the nodal point force resulting from the stress, at \"time\" $t$.\nMy question is about actually implementing this as a system of nonlinear equations to be solved via <PERSON>'s method.", "935" ], [ "As I understand it, the idea is to consider a function $H(\\sideset{^{t}}{}U)=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F$, where $\\sideset{^t_t}{}F$ is a function of $\\sideset{^{t}}{}U$ via the stress.\nWe want to find a displacement $\\sideset{^{t+\\Delta t}}{}U$ s.t. the unbalanced force vector is zero: \\begin{equation} 0=H(\\sideset{^{t+\\Delta t}}{}U)\\approx H(\\sideset{^t}{}U)+\\nabla H(\\sideset{^t}{}U)\\left(\\sideset{^{t+\\Delta t}}{}U-\\sideset{^t}{}U\\right)=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F - \\left(\\sideset{^t_{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{\\text{NL}}{K}\\right)U \\end{equation} so that $\\left(\\sideset{^t{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{_\\text{NL}}{K}\\right)$ is minus the Jacobian of the unbalanced force vector $\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F$. Is this interpretation correct? Is the sum of the incremental stiffness matrices derived by <PERSON> exactly equal to minus the Jacobian of the unbalanced force vector, when all are evaluated in the same configuration? In implementing <PERSON>'s method, an iteration is introduced, so that we can write $U^{(k)}$ for the incremental displacement at the $k$th iteration. How does this affect the terms in the system of equations? At iteration $k$, are the integrals still calculated over the volume $\\sideset{^t}{}V$, or over $\\sideset{^{t+\\Delta t}}{}V^{(k-1)}$? What about the stress, and the stiffness matrices?", "804" ], [ "Why do we use cubic fluid elements when deriving fluid equations?\nRecently I've been delving into fluid dynamics but is frequently troubled by a conceptual issue that I could never get my head around with.\nTo derive fluid equations, we have to separate fluid into smaller elements and analyse the forces and acceleration of each of the small element. While I can understand this, I don't see how the choice of cubic fluid elements fulfills the physical requirements of the fluid.\nFor instance, in the derivation of the Bernoulli's equation, it is quite common to analyse the pressure and acceleration of a cubic region of fluid.\nBy equating the acceleration of the fluid element to the forces acting on both sides of the element, we obtain\n$(\\rho d^3) (u \\frac{\\partial u}{\\partial x}) =-d^2(\\frac{\\partial p}{\\partial x}d)$\nCancelling out $d^3$ from both sides and integrating the resulting equation, we obtain\n$p + \\frac{1}{2}\\rho u^2 = c$\nWhich is the well known <PERSON>'s equation we know and love.\nMy confusion arises from the fact that whenever we consider a case of a constricting cavity, it is clear that the streamlines are not perpendicular to the x-axis. Instead, they look something more like this:\nIn the case of such streamlines, the pressure gradient should not be the sole force acting on the fluid element.", "232" ], [ "It is quite clear that the streamlines collide with the fluid element, transferring some of its horizontal momentum to the fluid element as well. However, <PERSON> equation continues to hold, while its assumptions are violated.\nI thought a better choice of fluid element is probably this trapezium element where the sides are parallel to the streamlines as it would not encounter such issues. However, to my knowledge, there is no analysis that is done with fluid elements of such shapes when deriving <PERSON>'s equations.\nWhy does the cubic fluid element method even work in the first place, if its assumptions may not hold? Also, why is there little analysis done with non cubic shapes of fluid elements?\nThank you!", "346" ], [ "By symmetry you know that the stress at each plane of symmetry must be perpendicular to the plane. Take two planes of symmetry at 30 degrees from each other to section off 1/12th of the hexagon. Now you just have a beam with a constant pressure and two point loads at the corners.\nSince the net force must be zero, the component of the force applied at the hexagon corner that is perpendicular to the beam, must cancel the force of the pressure on that beam.\n$$\\sin(30 deg)\\,F_c=P\\,a$$\nWhere $F_c$ is the magnitude of the force per container length at the corner, $P$ is the pressure, and $a$ is the length of half the side of the hexagon.\nThen the forces parallel to the beam must balance:\n$$F_m=\\cos(30 deg)\\,F_c$$\nNow we have the beam loading, so we can do a beam analysis:\n$$\\text{Shear stress}=P\\,x$$\n$$\\text{Bending Moment}=\\frac12 P\\,x^2+C$$\n$$\\text{Slope}=\\frac1{E\\,I}\\left(\\frac16 P\\,x^3 + C\\,x + D\\right)$$\nNow by symmetry we know the slope must be zero at the ends:\n$$0=\\frac1{E\\,I}\\left(\\frac16 P\\,0^3 + C\\,0 + D\\right)$$ $$0=D$$ $$0=\\frac1{E\\,I}\\left(\\frac16 P\\,a^3 + C\\,a\\right)$$ $$C=-\\frac16 P\\,a^2$$\n$$\\text{Bending Moment}=P\\left(\\frac12 x^2-\\frac16 a^2\\right)$$\nNow that we have the tension $F_m$ and the bending moment we can calculate stress on the inner and outer surface of the skin:\n$$\\sigma=-\\frac{F_m}{t}\\pm \\frac{P}{t^2}\\left(\\frac12 x^2-\\frac16 a^2\\right)$$ $$\\sigma=-\\frac{\\cot(30 deg)P\\,a}{t}\\pm \\frac{P}{t^2}\\left(\\frac12 x^2-\\frac16 a^2\\right)$$\nThis has a maximum of: $$\\sigma=-P\\left(\\frac{\\sqrt{3}\\,a}{t} + \\frac{a^2}{3t^2} \\right)$$\nNow we can compare this to a cylinder as an inscribed circle $a=\\frac1{\\sqrt{3}}r$\n$$\\sigma=-P\\left(\\frac{r}{t} + \\frac{r^2}{9t^2} \\right)$$\nThe first term, which comes from the tension in the beam is the same as the stress for the cylinder.", "333" ], [ "The second term, which comes from the bending stress dose not appear in the case of the cylinder as there is no bending. This bending stress will dominate the expression for thin walled vessels to the point were it is likely they would just deform until they resembled a cylinder.\nAs an added bonus this analysis works for any regular polygon:\n$$\\sigma=-P\\left(\\frac{r}{t} + \\tan(\\alpha)^2\\frac{r^2}{3t^2} \\right)$$\nWhere $\\alpha$ is half of the central angle of the polygon. As the number of sides increases, $\\alpha$ approaches zero as does the bending moment term, converging on the solution for the cylinder.", "333" ], [ "I know this is an old question, but I have just set a similar problem for myself today and found this question after solving it.\nDisclaimer: I was only concerned with the equilibrium shape (the \"catenary\" for discrete case), so if the OP was after the dynamics of such a system, this won't serve as an answer. However, the last comment from the OP indicates the interest in the following method.\nAs <PERSON> said in the comments, to compute the equilibrium shape (the \"catenary\" for discrete case) the most simple way seems to be the method of Lagrange multipliers.\nFor (my own) convenience, the g vector is up instead of down, so the catenary is standing.", "359" ], [ "Also, I'm using Cartesian coordinates.\nThe example of the result is above, with the smooth curve representing a catenary in the usual sense, with the arc length equal to the sum of all \"rod lengths\" between the point masses. I have taken the support points out of consideration and set the supporting rod length to be half of the length between two masses, just for convenience.\nThe arc length is taken as the fixed value $L=3$ with $l=L/6=1/2$; and the distance between support points is $2$.\nSolution for the particular case above, since it's simple enough to infer the general case without additional comments.\nDue to the symmetry, it's enough to consider only the part with $x>0$.\nThe one and only equilibrium condition in this case is the minimum value of the potential energy for the system, and since I have directed the gravitation up, we need to maximize the sum of $y_k$:\n$$\\text{maximize} \\quad f=y_1+y_2+y_3$$\nSubject to constraints:\n$$\\begin{cases} g_1=(y_1-y_2)^2+(l/2-x_2)^2-l^2=0 \\ g_2=(y_2-y_3)^2+(x_2-x_3)^2-l^2=0 \\ g_3=y_3^2+(x_3-1)^2-l^2/4=0 \\end{cases}$$\nLagrangian multiplier method involves introducing additional variables for each constraint, and writing down the Lagrange function:\n$$L=f-\\sum_k \\lambda_k g_k$$\nThen the necessary (but not sufficient) condition for the maximum of $f$ will be:\n$$\\nabla L=0$$\nThen the general method requires building a Hessian matrix with the second derivatives, but there's no need in this case! We know that all $x_k,y_k$ should be real and positive, and as far as I can see, there's always a single solution like that (for any arc length I tried I mean).\nConsidering all the partial derivatives, we recover our original constraint equations, and $5$ additional ones:\n$$\\begin{cases} (y_1-y_2)^2+(l/2-x_2)^2-l^2=0 \\ (y_2-y_3)^2+(x_2-x_3)^2-l^2=0 \\ y_3^2+(x_3-1)^2-l^2/4=0 \\ 1-2 \\lambda_1 (y_1-y_2)=0 \\ 1+2 \\lambda_1 (y_1-y_2)-2 \\lambda_2 (y_2-y_3)=0 \\ 1+2 \\lambda_2 (y_2-y_3)-2 \\lambda_3 y_3=0 \\ \\lambda_1(l/2-x_2)-\\lambda_2(x_2-x_3)=0 \\ \\lambda_2(x_2-x_3)-\\lambda_3(x_3-1)=0 \\end{cases}$$\nThe only solution with real and positive $x_k,y_k$ is:\n$$\\begin{array}( x_2=<PHONE_NUMBER> \\ x_3=0.904152 \\ y_1=<PHONE_NUMBER> \\ y_2=<PHONE_NUMBER> \\ y_3=<PHONE_NUMBER> \\ \\lambda_1 = 1.59714 \\ \\lambda_2 = 2.35603 \\ \\lambda_3 = 6.49642 \\end{array}$$\nNumerical solutions are obtained with Wolfram Mathematica. The resulting diagram (also created with Mathematica) is presented above.", "101" ], [ "The statement of the question, using \"internal/external stresses\" is confusing. I don't understand what \"external stress\" can be here. You can have external forces but not external stresses. From the question elaboration, it appears to ask whether the internal state of stress affects vibration modes, yet the questioner's example of a \"tension line\" cannot change the internal state of static stress without altering the boundary conditions on the beam. Altering the boundary conditions will certainly affect vibration modes. In addition, an \"internal state of stress\" always exists in a material, whether undergoing vibration or not. It seems that the questioner is asking whether the \"static\" state of stress affects the modes, and static stress are internal stresses of motionless material. I suggest the questioner clear up these issues, and I'll give the answer to the simple question which I believe he really wants to ask: \"Does the static internal state of stress affect vibration modes of a beam\"?\nThe answer to that question is No, as long as the elastic limit of stress in the material is not exceeded. A different static state of stress can result in total stresses during vibration that exceed the elastic limit, which may affect the vibration modes.", "1018" ], [ "But the answer to that would be too complicated to discuss here. For purposes here, the simple answer is \"No.\"\nExplanation is that, first of all, vibration of a taught string is a different phenomenon, where the restoring (spring) force is the tension itself. With the beam, called a \"bar\" in vibration science, the restoring force is the elastic force, and even more, it's the change of elastic force, not the total (change + static), caused by the vibration. Static forces don't enter into the equations of motion. If you change the static situation, the dynamic changes of internal stress only occur about a changed mean value, and as long as the response is elastic (obeys <PERSON>'s law), the dynamic solution will not change.\nIn fact, we know very well that the static state of internal stress normally has no effect on vibration modes Most all hardened metals have some nonzero internal static stresses, and we are not concerned with them when we calculate vibration modes in such materials.\nFor instance, with 1095 Swedish spring steel, there can be residual internal stresses in high temperature quenching during the hardening process that are not eliminated by sufficient uniform annealing (tempering), and that doesn't affect the vibration of a cantilever made of such material. Such a device is used as sound source in free reed musical instruments, and makers aren't directly concerned with the internal state of stress in the reeds they make. Now, there are complications when you consider other practical effects, such as metal fatigue and breakage. Fatigue can occur over many cycles when stress levels are even below the elastic limit, a static concept. There is also an \"endurance limit,\" which is below the elastic limit, above which fatigue lifetime is greatly reduced.", "333" ] ]

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[ [ "DIY Wooden Sign W/ Woodburning\nIntroduction: DIY Wooden Sign W/ Woodburning\nWelcome to my Instructable Tutorial!\nI created a Wooden sign and created a special logo on it using wood-burning. I will be showing how to create a sign and the process of wood-burning and shading, Keep in mind that this is more challenging than it seems as a lot of effort has to be put in, in order to create a nice appearance. There is a short video that can be used for visual learning and to see exactly the process of the wooden sign.\nI will provide all the necessary steps and tips required to help you create the same high-quality product to use as a decorative piece or give as a gift!\nSupplies\nThe Materials and Machine work required for this are =\n* Scroll Saw\n* Replacements=\n* Coping Saw\n* Band Saw\n* Jig Saw\n* Saw Knife\n* Sanding Block\n* Sanding Paper\n* P60\n* P150\n* P320\n* Wood-burning/Pyrography Toolset\n* https://www.asigo.eu/en/pyrography-tool-kit.html\n* Wood Varnishing\n* https://www.rustins.ltd/rustins/our-products/indoor/danish-oil\n* Basic Tools =\n* Pencils, To create an outline\n* Eraser, Remove any mistakes\n* Plywood\n* 0.5cm in Width\nStep 1: Outline the Shape of the Sign\nThe first step is to create an outline of the sign shape you want. I would recommend choosing the top of the sign to start with the design. Also to first create the outline barrier of the plywood which allows you to make the lines inside of the barrier keeping it neat and having guiding lines for the next step: The scrolling saw\nFor the wooden sign I decided to make the edges curved and the top curves larger to provide better structure, as the bottom of the sign has a straight and non-bumpy texture which will help it stay up better.\nStep 2: Cut Out the Outline Using the Scroll Saw\nThe Second Step is to start cutting out the outline using the scroll saw. In order to be able to cut the plywood, you have to push the wood into the blade to be able to cut it.", "401" ], [ "Firstly you should cut out the barrier outline, so the big pieces are out of the way and you can cut out the intricate lines easily and quickly. A small tip is to let the scroll saw guide it, and if you make a mistake in a line you can get the blade out of the line by carefully pulling the wood out of the blade.\nPrecautions =\n* Press onto the board, Because when cutting it with the blade the board will start vibrating which can break the board.\n* Do not bring the fingers/ Hand too close to the blade, The blade is quick, sharp, and can lead to an injury. If your hand is coming closer to the blade reposition it somewhere else and maintain the control\n* Wear Safety Goggles to avoid Saw Dust and Splinters getting in your eyes\n* Work in a focused environment, and stay focused on the scroll saw\nStep 3: Sand the Edges\nThe Third Step is to sand the edges, and sanding paper is fine but if you want to be more precise firstly sand the edges using the sanding paper P60, It will leave the edges rough but will sand out any mistakes and create straighter lines, the second sandpaper that should be used is P150 which will begin to smoothen the edges and create a nicer curve on the edges finally the Sanding Paper P320 which will smoothen the edges and make it easier to cut.\nWhen sanding the edges go in a back and forth motion and do it quickly, The edges won't be smooth enough if you sand in a slow-motion and in an irregular motion and the splinters at the edges will become more relevant.\nStep 4: Creating the Pyrography/Wood-burning Design\nThe fourth step is to create the logo, which is up to you. But in order to create a neat and presentable logo, I recommend having Guidelines for the text to keep a common size and a balanced text. Make the outline light so it's easily erasable and won't smudge. Additionally adding slight shading in a few parts of the object can be a guide for wood-burning. This step is up to you.\nI decided to make the text bigger to make it easier to play around with the wood-burning additionally to fill up the sign more and avoid empty spaces.\nStep 5: Woodburning/Pyrography\nThe Fifth Step =\nSetting up =\nEvery kit should have at least wood-burning tips, a pyrography pen, and a Pyrography stand.", "599" ], [ "How to Make a Danish Organic Table\nIntroduction: How to Make a Danish Organic Table\nHi! In this Instructable I will explain in detail how to make this project.\nThe first thing I will say: Do not feel intimidated. This could be a beginner project if you follow the step by step guide + watch the YouTube Video and ONLY if you feel comfortable using a table saw.\nMake sure to subscribe to my YouTube Channel since I will publish furniture making videos and How To's forever\nI focus on Design Icons so here is the link: https://www.youtube.com/feed/my_videos\nConsider becoming a Patron: Become a Patron!\nSupplies\n+ Table saw\n+ Jigsaw\n+ Hand Planer or any sort of planer/ jointer\n+ Router\n+ Sandpaper Grit: 60, 120, 240\n+Lathe or Lathe Jig for the Table saw\n+Drill, bits and 27mm Hole Saw\n+Clamps\n+Square\n+Hammer\n+Screwdriver\n+Wood Glue\n+Wood finish (of your preference) I used Beeswax\nStep 1: Lumber & Table Top\nThe table top was made using 5 boards of 10cms or 3.94\" so that you get a table top of 50 x 81cms or 19.7 x 31.9\". You will need to joint the edges so that when you glue them the table top does not show any gaps and to do so the picture shows my method for jointing with a table saw.", "431" ], [ "Just put the final board over a flat board that you can trust has straight edges, then put the straight edge against the fence and slide, you will need to attach both of them with double sided tape.\nAfter jointing edges plane the lumber and attach the boards using wood glue clamp it with even pressure, 3-4 clamps are good enough.Let it dry for 48h.\nStep 2: Plane & Sand\nNow you have to plane the whole surface, I used a Stanley #4 hand planer, though I would not advice to do so, use a #6 or #7 if you can an electric planer or a Kanna (japanese hand plane) take your time to level and do it properly.\nAfter that just sand the surface starting with 60 grit, move to 120 and finally 240.\nStep 3: Cutting the Kidney Shape\nNow to make the organic shape you can design your own, I suggest to cut it in a 5mm MDF or thicker\nOnce you have it just trace the layout and proceed to cut it with the jigsaw, do not try to make it perfect, actually cut a bit to the outside since later we will trim the excess with the router using a flush trim bit and to do so, just clamp the template over the roughly shaped kidney and slowly route clockwise.\nStep 4: Cleats\nStart by cutting 3 pieces of 5x4x12 cms or 1.57x1.97x4.72\". Then tilt your table saw blade to 8º and using a jig for bevel cuts, clamp it on top of the piece as shown in the picture after that you can trim the excess in the crosscut.\nWhen done, drill 4 holes with a 1/4\" spade bit or with a countersink, these are to screw the bolts to the tabletop, then using a 27mm or 1-1/18\" hole saw, drill the center making sure not to tilt the drill, otherwise you will lose the 8º angle.\nStep 5: Legs\nThe fancy part of the project.\nCheck out this video on how to make the jig:\nWhen done, cut 3 4x4cm or 1.57x1.57\" to 42.5cm or 16.73\" length and screw them to the lathe jig, as indicated in the video you have to trim the corners first to prevent an accident, then attach a drill at the back and make it spin whilst the blade is running. Make sure to adjust the angle first, the inclination is 1º for these and then ready to sand with 60, 120, 240 grit.\nStep 6: Attaching the Legs\nThe last step is to cut a slot exactly the thickness of the blade (whatever you have) in the middle of the thicker side of the leg so that you can introduce a wedge to get a tight fit into the hole of the cleat, to do so first pour lots of glue and hammer the wedge until snug, then trim the excess wedge and attach cleats to the table top using screws, be careful with the length of bolts so that they do not go through the board.\nStep 7: Finish\nFor this project I used a Beeswax mix with turpentine, it is easy to apply by just using a sponge or steel wool, just 2 coats and it gets sealed and slightly glossy, plus, the smell is delightful.", "599" ], [ "My First Ever Router Table!\nIntroduction: My First Ever Router Table!\nThis project has been inspired by Woodsmith Magazine. By far I think, is one of the best designs over the interweb, though I am not going to share exact dimensions, I want you to have a rough idea of what this design features so that you can make your own.\nI have a YouTube video that makes things way clearer and exciting.\nSupplies\n+Lumber (pine)\n+Router\n+Woodglue\n+3/8\" bolts, washers and nuts\n+Knobs\n+Outlet switch\nStep 1: Legs and Stretchers\nTo make the frame start by cutting half laps one on top and one on bottom. Do that by cutting on your table saw and remember that there are four legs and three stretchers, all of them made out of 2x4\"s. After that glue them forming two frames that are solid enough to stand alone, you can plane them if you want everything to sit flush.\nStep 2: Structure Assembly\nOnce you have two frames, make a template to drill the holes so that you can pass the bolt through and join the legs and stretchers, use a ratchet to adjust them and right after that, attach the angle brackets to fasten the table top.\nStep 3: Table Top\nI made the table top out of two tops that were prefab at the homecenter and glue them together to form a reliable top that is dead flat.\nThen I rounded the corners with a template to trace, rough cut with my jigsaw and flush trim with my router.\nStep 4: Insert\nThe insert is the part to attach your router to the main table.", "599" ], [ "I made this one out of acrylic because it is strong and transparent. Simply cut it to final depth and mark the position on the table top with a marking gauge. Drill 1\" holes for your fingers to pass through and holes to pass the screws for the router base.\nStep 5: Table Top Hole\nYou'll need to make a hole to sit the insert and router through. Drill a 1\" hole through the table top and rough cut the shaoe with a jigsaw, then use some straight edges to flush trim everything, including that you'll have to route a recess of the thickness of the insert to sit flush.\nStep 6: Groove and Safety Accesory\nUse your flush trim bit to route a groove so that you can slide jigs and sliders later. A safety accesory will prevent your hand from ever touching the bit, so temporarily clamp a piece of lumber to use it as a fence, and route two slots for height adjustment in a 1/2\" board, once done, use a template to make an acrylic semi-circle and finally screw them together.\nStep 7: Fence and T-Track\nRip cut two pieces to make the fence, using your table saw, cut some sort of mortises to pass the bolts for the sliders through and then attach both pieces.\nOn top of the fence the design features a T-Track that is used to place the hand safety device, feather boards and other type of jigs, to make it cut two identical boards route a 1/2\" groove and then make half a T with the table saw, then glue both of them together, and you have a T-Track, glue and clamp it on top of the fence and trim the excess.\nFinally cut an opening for the bit to pass through using the table saw.\nStep 8: Clamps and Knobs\nI made my own knobs with plywood, but you can purchase them.\nIf you want to DIY them, laser cut the template attached and stick it to the plywood with double-sided tape, then use your router table to free hand the shape using a flush trim bit with a bearing on top.\nMake a clamp of the thickness of the fence and drill a 3/8\" hole to pass a bolt through, the importance of making a kerf in it is to align it with the fence and hold it firmly.\nRepeat this with the knobs for the back as well and clamp everything to the table top.\nYou now have a router table.", "599" ], [ "Designing a Segmented Vessel\nIntroduction: Designing a Segmented Vessel\nIn this article, I will explain how to make a set of plans to create a segmented Vessel.\nI want to thank my good friend and mentor, <PERSON> from Knox City Texas for providing the information and encouragement for this project. Items in quotation marks are taken directly from a paper written by <PERSON>.\nSupplies\nThe only tools you will need are a pencil, an eraser, a ruler and a sheet of paper large enough to create a full scale model of what you want.\nIn addition I like to use a digital caliper.\nStep 1: Basic Information Used in Segmented Turning\nJust a couple basic terms that segmented turners use.\nThe length is how long the back edge of the segment is.\nThe Width is the board width when you start cutting.\nThe thickness is how thick your ring will be.\nI know it is pretty basic, but it is easy to get the thickness and width mixed up.\nStep 2: Getting Started\nThe first thing you need to do is decide what you want to make.\nI suggest you start with something small.\nThe video link is to a YouTube video that I made covering all aspects of how I Design and Build a Segmented Vessel.\nStep 3: The Initial Layout\nBegin by drawing a vertical line in the center of your paper a couple inches longer than the height of your vessel.\nStep 4: Setting Up You Grid\nAfter that, draw horizontal lines to correspond with the thickness and number of layers you have in your vessel.\nStep 5: Initial Sketch\nSketch the outer edge of your vessel. I am usually pretty generous with the thickness of the wall.\nYou can always make an eighth inch wall from a quarter inch wall, It's pretty hard to go the other way.\nStep 6: Finding the Variables to Use in the Formulas\nDraw vertical lines on both sides of the wall.", "110" ], [ "When first starting out, I suggest you add a bit extra.\nStep 7: Finding the Measurements of Each Ring\nYou can use a ruler to measure the width of the segments in that ring. The bottom one can be skipped if you plan on using a solid piece of wood for the bottom of your vessel.\nStep 8: My Way of Measuring\nI prefer using decimals instead of fractions when using formulas.\nTo find the outside radius of your vessel (R_out), measure from the center line to the outer line of the drawing.\nTo find the inside radius, (R_in) measure from the center line to the inner line of the drawing.\nStep 9: The Variables That I Use in the Formulas\n(R_in) = Inside Radius of the ring.\n(R_out) = Outside Radius of the ring.\n(C) = Circumference of the ring.\n(N) = Number of segments in each ring.\n(W) = Width of the segments in that ring.\n(L) = Length of the segments in that ring.\n(A) = Segment angle.\n(CA) = Segment cut angle.\n(BL) = Board length. This is the minimum length of wood needed to cut the segments in that ring.\nStep 10: Finding the Circumference of Our Rings\nC = 2π(R_out)\nRing 1 (R_out) is 4.8 inches. Circumference of ring 1 would be C=2(3.14)(4.8) which equals 30.144\nI will not go through the rest of the calculations at this time.\nStep 11: Finding the Angle of Each Segment\nA = C/N = Segment angles.\nCA = A/2 = Cut angle.\nIn this example our vessel will have nine 3/4 inch layers and will have 24 segments in each layer.\nIf you are using a table saw, you will only need to know the angle of each segment.\nTo find the angle of each segment, divide 360 by 24 = 15 degrees.\nIf you are using a chop saw or band saw you will use the Cut Angle, which is the above angle Divided by two.\nThe cut angle would then be 7.5 degrees.\nStep 12: To Find the Width of Each Segment\nW = (R_out) –( R_in) = Width of each segment.\nTo find the width of each segment, simply subtract (R_in) from (R_out)\nThe inner radius from the outer radius.\nWidth of ring one would be 4.8 - 3.0 or 1.8 Inches.\nYou will need this measurement for each layer.", "76" ], [ "Simple Small Desktop Wooden Stand / Holder for Different Purposes\nIntroduction: Simple Small Desktop Wooden Stand / Holder for Different Purposes\nI made this simple Instructable as a gift for a friend.\nI saw that he asked on a Woodworking's Facebook Group (that by chance I was a member in), if someone can create such horizontal stand for him, with charge of course...\nSo while having a lot of free time during the Coronavirus lockdown, I immediatelly sent him a private message - \"Don't worry, I making the stand for you\" (free of course...)\nHe needed the stand for putting a tool related to smoking (the one you can see at the picture) and gave me the dimensions.\nOf course that you can make this stand for other different purposes, that you want to put on your desk, like a pen, or other decorative items...\nI took some scrap wood / leftovers and started this quick project.\nThe last name of the friend is <PERSON>, so I decided to surprise him and combine his name in the stand. He liked it a lot :)\n------------------\nYou're welcome to visit my YouTube Channel, subscribe, and also watch my additional projects.", "668" ], [ "Don't forget to click the 'bell' button in order to get new videos notification.\nThank you! :)\nSupplies\nGeneral List of tools I'm using - https://www.itzikdiy.com/tools-list?m=1\nTools in this Instructable:\n* Miter saw or other saw\n* Measuring tape.\n* For the rounded cuts I used my dremel with the following tools:\n* Dremel & Line & Circle Cutter (678) Accessory - UK - https://amzn.to/36NxASj - US https://amzn.to/32Z6EOj\n* Dremel 561 Multipurpose Cutting Bit - UK - https://amzn.to/3nC0kEp US - https://amzn.to/3nC0kEp\n* Kreg KHCCC 90° Corner Clamp: UK - https://amzn.to/3lW9jzC US - https://amzn.to/3lW9jzC\n* Drill & Wood drill bits.\nMaterials:\n* Scrap wood\n* Screws.\n* Wood glue.\n* Foto Transfer Potch (Optional)\n* Clear protective topcoat\nStep 1: Cutting a Piece of Wood for the Base\nI started by cutting a 18mm pine board to the required dimensions (~22cm*7cm), using the miter saw.\nStep 2: Preparing the Dremel Circle Cutter\nI prepare my Dremel 4000 & the Line & Circle Cutter Accessory (678), to cut the rounded shapes.\nFinally I found a use for this Dremel accessory :)\nYou can use a Jigsaw as well, but it's less accurate to make the rounded shapes manually...\nThis accessory uses a special cutting bit (Dremel 561 Multipurpose Cutting Bit).\nStep 3: Marking the Half Circle Position on the Base\nI marked the center of the wood from all edges of the rectangle sides.\nThe Dremel circular cutter has a nail which should be placed in the center of the circle, as an axis. The cutting bit turns arround the axis for cutting accurate circles. This accessory is great!\nStep 4: Cutting the Half Circle Shape on the Base\nCutting the circle.\nNote that you put the center axis at the side of the wood that isn't visible later, so you won't see the axis hole :)\nStep 5: Sanding the Base\nI sanded the base using a Sanding paper / Sander.\nStep 6: Marking the Text & Vertical Pices Positions on the Base\nAs I wrote at the intro, I wanted to put a text in the middle, between the vertical pieces of the stand, so I measured and marked the positions.\nThe vertical pieces position is ~12cm from each other.\nStep 7: Marking the Text \"O\" Letter Holes Position on the Base\nThe last name of my friend is <PERSON>.\nSince the name has 2 Symmetrical \"O\" letters, I decided to make it more special, and drill the \"O\" letters.\nSo, I put the printed text to see the position, and marked the \"O\" positions.\nI took a drill bit which matches to the size of the letters in the printed text.\nStep 8: Drilling the \"O\" Letter Holes on the Base\nI drilled the 2 \"O\" letter holes on the base.\nStep 9: Sanding the Holes on the Base\nI sanded the 2 \"O\" letter holes, using a dremel sanding attachment.", "493" ], [ "Skateboard Rack\nIntroduction: Skateboard Rack\nHi, my name is <PERSON> and I am a high school student in Monterrey, Mexico. My brother has a skateboard which he always leaves laying around on the floor. I decided to make this small, sleek skateboard rack that he can hang on a wall to hold his skateboard. This project takes about 4-5 hours to make. It is difficult and you will need help from someone that is comfortable working on the project and using the tools.\nStep 1: Supplies\n1. Hacksaw\n2. Hand Saw\n3. Hammer\n4. Wood Chisel\n5. Tape Measure\n6. Drill\n7. Wood Paste\n8. Wood Paint\n9. String\n10.", "668" ], [ "Sand Paper\n11. Pencil\n12. Wood 27 1/2 inches long, 3 3/4 wide, 1 1/2 inch thick\nStep 2: Sanding the Wood\nSanding the wood is important, it not just cleans the surface but also makes it smoother and easier to work with.\nStep 3: Cover Up Any Wholes\nUse the wood paste to cover up any holes. You can use a card to apply it, but your finger works too.\nStep 4: Outline Your Measurements\nDraw the lines where you will cut the wood, I personally did a diagonal cut that ended at the middle. I used 4 inches of space in between cuts and made the cuts 1 3/4 inches long. So it would be 4 inches, cut 1 3/4 inches, then 4 inches again...\nStep 5: Cutting\nThis part is not just the longest, but the most difficult. Cutting diagonally is harder than expected. Make sure to be very careful, one mistake might ruin the entire project. I recommend using the Chisel, you could use a Drill but I don't recommend it since it's very unpredictable.\nStep 6: Sanding the Cut and Finishing Touches\nAfter cutting the wood, make sure to sand the cut. If any new wholes appear make sure to patch them up.\nStep 7: Make a Hole at the Top (Cut Pointing Down)\nMake a hole with the drill so you can hang it up later. You don't have to hang it, you could work on making legs for it but I think it looks better hung.\nStep 8: Coat Your Wood With Wood Paint\nThe Wood Paint will give the wood a fine look and also make it more durable and resistant. Make sure to coat every inch of the wood don't leave out any hidden spaces. It takes about a day and a half to two days to dry. Be careful with it, it does not come off.\nStep 9: Hanging the Rack\nCongratulations, you made it this far now it's time to hang it. Put a nail on the wall and hang it with a string.", "76" ], [ "Epoxy and Wood Coasters\nIntroduction: Epoxy and Wood Coasters\nI tired many different methods to make epoxy and wood coasters. There was a fairly big learning curve. I feel that these are the best of the coasters I made and I wanted to share the process.\nAllie Nichols- PATHS Woodworking\nSupplies\nTape Measure\nCombination Square\nPencil\nHeat Gun\nTable Saw\nDado Blade\nSafety Glasses\nMeasuring Cups & Mixing Stick\nSandpaper & Sander\nMasking Tape\nTwo Part Epoxy\nEpoxy Dye\nWalnut Oil\nClean up rags\nGloves\nTooth Pick\nStep 1: Choose Your Wood\nChoose your piece of wood for your project, I chose 3⁄4” walnut.\nCut your wood to at least 17” inches long with a width of 4” inches.\nStep 2: Plane Your Wood\nAfter you get your choice of wood run it through a planer and bring it down to a thickness of ½ an inch or thicker or just a little thinner if you want.\nStep 3: Make Your Groves\nTake your wood over to a table saw, lower or raise the blade to a little over half the depth of the board and run it across to get a thickness of groves/dado through your board that you like. This is the area where the epoxy will go.\nYou can choose to make 1 grove or you can make more.\nStep 4: Epoxy and Supplies\nYou will need a two part epoxy, two measuring cups, a mixing cup, and masking tape a stir stick for the next part.\nStep 5: Tape the Edges\nTape off the ends of your wood to make sure no epoxy spills out. Be sure the tape is secure.\nStep 6: Mix Your Epoxy\nAdd equal parts of part A and part B of the epoxy and pour them into your mixing cup. Follow the directions on the epoxy container. (I used about 2oz of each). Add your color of choice and mix till combined evenly.\nStep 7: Pour Your Epoxy\nSlowly pour the epoxy into your groves.", "76" ], [ "Make sure you are on a flat surface and your epoxy is even throughout the board.\nBe as neat as possible.\nStep 8: Wipe It Clean\nMake sure you wipe any epoxy off that is not in the right place so you don't have to sand a lot afterwards.\nStep 9:\nUse a heat gun or a blow dryer to remove as many bubbles as possible. Keep the heat gun back a little bit so none of the epoxy gets blown out.\nStep 10: Add Swirls\nAdd white drops of dye to the wet epoxy, use a toothpick to spread it around to make lines and swirls. Use the white cautiously you can always add more but can not take it away.\nLet dry on a flat surface for at least 24 hrs.\nStep 11: Sand the Coasters\nNext sand just the wood and clean up the edges, try not to touch the epoxy with the sander so it doesn’t get scratched. If the epoxy is sitting higher or lower than the wood you can sand over the epoxy but it scratches it and will be harder to see the swirls.\nYou can put masking tape on top of the epoxy so it does not get sanded. You can also hand sand the coasters.\nStep 12: Set Up the Stop Block\nPut a block of wood 4” inches away from the blade of the table saw clamp it in place , This stop block will make sure all coasters are the same size.\nStep 13: Cut Coasters to Size\nMaking sure your board is sitting flush with the back of the saw and is clamped down if needed. Then cut straight down to make a clean cut.\nStep 14: Clean Up the Edges\nYou can sand down the edges of your coasters to clean them up . You can also sand the back a little to thin the coasters out.\nStep 15: Final Step Oil It\nUse a tack rag to clean off any dust . Apply oil, stain, or finish of your choice to your coasters. I used walnut oil for mine.\nStep 16: Finished Project\nNow you are all done and can keep them or give it to someone as a gift.", "76" ], [ "Pi Pie Stand\nIntroduction: Pi Pie Stand\nTo celebrate Pi Day I decided nothing would be better than making a pun! So, I made a Pi stand. I feel like people who are quirky enough to celebrate their love of pie and Pi would get a kick out of this unique twist on the traditional cake stand, and the added strip of walnut inlay gives this Pi stand enough character to make it stand out beneath the pie its holding.\nSupplies\nMaterials needed:\nFor the Pi piece\n10 inch long x 6 inch wide x 2 inch thick Piece of Maple ( I used maple because it was what I had on had)\nFor the round plates\nTop Plate: 14 Inch long x 10 1/2 wide x 1 inch thick Piece of Maple ( the top and bottom plate will be cut from the same piece of maple)\nBottom Plate: 12 Inch long x 7 inch wide x 1 inch thick Piece of Maple\nWalnut Inlay: 10 inch long x 2 inch wide x 1 inch thick ( you will cut you inlays from this one piece)\nTools Needed:\n* 220 grit sand paper\n* 150 grit sand paper\n* Metal Files\n* Wood glue\n* Nail Gun\n* 1 1/4 Brad Nails\n* Band Saw\n* Jointer\n* Planer\n* Table Saw\n* Disc Sander\n* Circular Saw\n* Clamps\n* Pencil Compass\n* String\n* Tape Measure\n* Pencil\n* Oil/Stain/Paint\nStep 1: Cutting Walnut\nFirst ALWAYS REMEMBER SAFETY FIRST! PLEASE WEAR PROPER EYE AND EAR PROTECTION WHEN WORKING WITH DANGEROUS TOOLS!\nTOOLS NEEDED:\n* Band saw\n* Tap measure\n* pencil\nFor this project I used rough cut wood, this will come up later as it will need to be jointed and planed, but first we need to make our cuts!\nWe will need to cut our walnut for the inlay. The three pieces of inlay will all be cut from the same piece of walnut, I only had a 10 inch piece so that was the max that I could do, but for this project that is perfect.\nCutting Initial Piece\nI used my band saw with the fence as a guide to cut all my pieces to the desired width. Before cutting make sure to mark your wood with all the correct measurements.\nCut a piece of walnut down to a strip to 10 L x 2 W x 1 thick. I drew a diagram of this in the pictures for reference.\nCutting Pi Piece\nNext is cutting the Pi piece.", "415" ], [ "Once again I adjusted the fence on my bandsaw to help me cut a strip off that measured\n10 inch L x 2 inch W x 1/4 inch thick. As stated above, I drew a diagram for reference.\nCutting Plate Pieces\nFinally, time to cut the strips for the top bottom and middle pieces. Take the leftover walnut and use it to cut the final two strips for your two plates.\nFor the bottom plate:\nFirst cut a strip 10 inch L x 1 inch W x 1/4 inch thick\nFor the top plate:\ncut a strip 10in L x 1 W x 1/4 inch thick\nYay! You have now cut your inlays!\nStep 2: Cutting Maple\nTOOLS NEEDED:\n* Table saw\n* Circular saw\n* Tape Measure\n* Pencil\nNow for this step we will be cutting the maple for the top and bottom plate and for the Pi shape. The top and bottom plates are fairly easy and straight forward since the wood is already the desired thickness of 1 inch so they only need to be cut to length x width.\nTop & Bottom Plate\nFor this cut I used a circular saw because my board was pretty long and it was easier to maneuver the circular saw than maneuver the board around. I clamped the board to my work table and made sure that I had my eye and ear protection on and made first my top cut of\n14 in L x 10 1/2 in W x 1 in thick\nAfter this cut, I made my bottom plate cut to\n12 in L x 7 in W x 1 in thick\nYou can use any method you like to cut your wood to your dimensions, such as a compound miter saw, hand saw, or table saw, like I said I just used my circular saw for ease.\nPi Piece\nSometimes things work out well in life and it turns out I already had a piece of maple that was perfectly sized for this project, so I did not need to cut this piece. However, I do know the wood fairies do not visit everyone and bestow perfect pieces of cut wood in their garages so they may need to cut their own.", "76" ] ]

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[ [ "You might find this link useful. In AIT, when you try to \"estimate\" (we are talking about non computable values here, in the general case ) the complexity of a finite string, those constants (related to the programming language) matter. Only in the asymptotic limit the original theory makes sense. The second point is that you are talking about a scientific theory (physics), so the guiding principles ( for example the mathematical framework , Lagrangian, Hamiltonian formalism, min action principle , etc) are part of the \"programming language\", you need more than just the computation of a <PERSON> machine (in the definitions, though Turing machines might be enough to define some principles). That one line of compact mathematical notation representing the standard model is based on such principles, and some of them are metatheoretical. Anyway, if you study <PERSON>' s work in greater depth, you might find some answers.\nA more interesting problem to think about (I think ) is this. Maybe the Lagrangian/Hamiltonian/min action mathematical framework represents just one \"programming language\".", "915" ], [ "Maybe there are others, even more powerful out there. This problem allows a multitude of perspectives, this is just one of them.\nYou can also consider a more simplistic approach, discarding any metatheoretical arguments and complex analogies. <PERSON>'s sixth problem (1900) deals with the axiomatization of physics. Depending on the nature of the axioms, you could have in principle a Turing machine encoding these axioms (if ever found). Then you could define the complexity of the scientific domain under consideration (in this case physics) as the length of a binary string encoding the inner workings of this Turing machine. A similar approach has been considered for mathematics (automatization of the process of mathematical discovery), but <PERSON> incompleteness results showed the serious limitations of this process (well, there's a lot to be said here, and there might be ways to deal with these limitations, but there is no room here for that discussion). A similar phenomenon might appear as related to physics, and there are scientists who consider a full axiomatization of physics impossible.\nAs for the standard model, I would dare to guess that a few million bits of information should be sufficient, as an upper bound. I might be exceeding a true, tighter upper bound by two orders of magnitude.", "484" ], [ "I will try to address why the concepts of NDTM and NP are useful, and possibly what motivated their study.\nNDTM is one of many variants of turing mahcine. For example, the classical (deterministic) Turing machine can be equipped with multiple heads and tapes, randomness or quantum states. It can also be constrained by a limited alphabet, limited tape or pre-determined head-movements (see here).\nA TM is said to decide a language (a set of words using a pre-defined alphabet), if it can halt on any input written on the tape, and accept precisely inputs belonging to the language. A language is called decidable if any TM decides it. Similarly, a function $f$ on natural numbers is said to be computable if there exists a TM which, given an input $n$, halts with $f(n)$ written on the input tape.\nIt turns out that all of the mentioned variations of TMs (including NDTM) are equivalent in the set of functions they can compute (similarly, the languages they can decide). This holds for other, much more different models than TMs, and has led to the <PERSON>-Turing thesis, which informally hypothesizes that any \"reasonable\" model of computation is equivalent to the classical Turing machine. In this aspect, NDTMs are useful as an example of fantastical computational models that are nonetheless as strong as a classical TM, supporting the <PERSON>-Turing thesis.\nAs far as I understand (see here and here for history), <PERSON> himself did not focus on complexity classes, and so the previous reason might have been his sole motivation. However, later on it was discovered that different TM variants are not equivalent in the set of problems (languages and functions) they can solve in a certain amount of computation steps (time), bound on working-tape size (memory) and success probability. With this finer resolution, it turns out that the different models are very different, resulting in a zoo of complexity classes for problems.\nI hope this is helps show why NDTMs (and the NP complexity class) are not a definite model for the problems science could potentially solve efficiently, but just one of many variations of computational models (less realistic than random and quantum machines, for example).", "915" ], [ "There are, however, some reasons for why the specific class of nondeterministic polynomial time ($NP$) is such a popular attraction of the zoo:\n1. It is relatively easy to explain and reason about. While researchers are working on many other open problems in complexity theory, the question of whether $P\\neq NP$ requires only basic knowledge in math to understand, and the concept seems so intuitive that it invites many solution attempts from amateur researchers.\n2. Whether a problem is solvable in polynomial time in a computational model is seen as an approximate measure of practical tractability (this is <PERSON>'s thesis).\n3. Any complexity bound derived by NDTMs can be seen as a bound on verification time by classical TMs (see here for why). Since classical TMs are used as models of practical computation, this has practical implications.\n4. Many real-world important problems just happen to be not just in $NP$, but $NP$-complete. This means that if $NP$ is indeed a different complexity class than $P$, all of these important problems are not solvable in polynomial time with classical TMs.\nNote that the fourth reason is unrelated to how realistic NDTMs are as a computational models (compared to classical TMs or other variants), or to any initial motivation for the invention of the concept. NP-complete problems are just surprisingly common in real life, and the scientific interest in them mirrors that.", "915" ], [ "Most answers so far rest on significant misconceptions about the nature of computation. I'll try to address these from a mathematical / computational perspective, and then we can come back to physics at the end.\nMisconception: computation implies purpose or agency\nSeveral answers include a line like \"things happen because they happen\", which I read as an abbreviation for \"computation implies purpose or agency, which the universe does not have\".\nComputation, as studied by computer scientists and mathematicians, implies nothing of the sort. Computation is simply the processing of information according to determined (but not necessarily deterministic) rules. For example, the cellular automata mentioned in <PERSON> answer are computational processes, which are fully characterized by their mathematical definitions, independently of any electronic or other physical implementation.\nMisconception: computation cannot handle infinite or continuum-sized structures\nPeople who have worked with computer algebra systems may remark that (physical) computers can handle exact symbolic manipulations involving $e$, $\\pi$ etc. But there's a far more literal sense in which computation using real numbers and their relatives is meaningful.\nThink of computation on bit streams: you're provided a stream of bits as input, and asked to produce a stream of bits as output, where each new bit of output is determined by some computation on the input bits that you've received so far. Since at each stage you only need a finite amount of input to produce a finite amount of output, you can do this using \"ordinary\" finite computation. But the result looks like you're computing with an infinite amount of information: for example, you can add, multiply etc. arbitrary real numbers in this manner. This approach is called Type Two Effectivity, and it's been an active area of research for decades now.\nThe same idea applies to all the structures and processes that we care about \"in applications\": differential equations, stochastic processes etc.", "855" ], [ "are all essentially computational in nature, which is what allows us to solve them in the first place. Even apparently discontinuous phenomena such as measures and distributions are more properly defined in terms of continuous maps between \"hyper\"spaces of open, compact, etc. subspaces, and can therefore be handled computationally.\nA common philosophical objection here is that any finite computation can only handle finite approximations to these infinite objects. But I think most people working in this area would respond that if every infinite object we care about can be presented as an endless, converging sequence of finite approximations, and our finite algorithms can transform these into other sequences which converge to the correct output, then whether we're \"actually\" computing with infinite objects becomes a matter of mere semantics. For all practical purposes, we are.\nConclusion\nThe scope of \"computational processes\" is far broader than is often imagined. If a process is well-defined, such that its behaviour could be tested against an appropriate model (even if that model is not known) then it can be interpreted as a computational process. This includes processes with parameters, and even entire families of processes where the parameters take on every possible value in some domain.\nIt does not include so-called \"supertasks\", such as \"toggling a binary switch infinitely many times then checking its state at the end\", precisely because their behaviour is not well-defined. But it does include \"continuum-sized\" processes such as differential equations, as long as their behaviour is not so irregular that it simulates a supertask. In particular, it includes any process that can be modelled and tested / predicted in principle, even if in practice the appropriate model or tests cannot be found or carried out.", "855" ], [ "Symmetry breaking: The current \"paradigm\" that has been proved to be so useful in high-energy physics (i.e. what we may pragmatically call \"fundamental physics\") is that at the small scale some exact symmetry is there, and then (at a large scale) the symmetry may be broken. Effective theories (i.e. theories that are less \"fundamental\") must be formulated to describe physics after a symmetry breaking: this kills the idea of \"reductionism\" since (because of symmetry breaking) theories at different scales have little in common and it's very difficult to derive them from the \"fundamental\" one (i.e., the most symmetric one available on the market at a certain moment).\nThis is well explained in a wonderful paper: I suggest you to read \"More is Different\" by <PERSON>, where there is a beautiful and clear discussion of how emergent physics is related to symmetry breaking.", "675" ], [ "Also, this question is extremely interesting as it remarks that the \"symmetry of objects\" should be distinguished from the \"symmetry of laws\".\nThe opposite of symmetry breaking: What you are asking is the opposite of what <PERSON> describes in his paper (a sort of \"symmetry restoration\", or \"emergent symmetry\"). Apart from the idea of \"emergent symmetry\" (see this and this questions), another possible interpretation of what you are asking for is that of universality class, where emergent phenomena in large systems behave in the same way despite some microscopic details may be different. Note that the idea of universality class is not really that of \"symmetry restoration\", but just something philosophically related in the sense that \"details are not important\". After all, symmetry tells us that a particular operation can be performed without changing some result: the idea of universality class is that you can add some kind of \"irrelevant\" interactions and this does not affect the large-scale behaviour of the system at criticality. In this sense, it may be considered a sort of emergent symmetry: all the systems belonging to the same class are the same.\nAlternatively, there are accidental symmetries, see this or Wiki, but they are more the exception than the rule (they need fine-tuning and are not exact), so I think that this concept does not really fit your question.", "682" ], [ "As encouraged in the comments, I'm giving a more general answer regarding constraint violation or constraint propagation in search in the context of CSP solvers. In a sense, the theory of search in CSP/SAT majorizes other approaches. My answer deals with complete search methods, although hybrids exist (combine local search with inference).\nA constraint satisfaction problem (CSP) as a triple $\\langle X,D,C \\rangle$, where $X$ is a set of variable, $D$ a set of domains (one for each variable), and $C$ is a set of constraints that limit or specify allowable combinations of values. Solving CSP problems is obviously hard (SAT is a special case). Also, the obvious way of solving a problem is search. Search can be replaced or at least combined with a specific kind of inference called constraint propagation. For example, consider modeling a Sudoku puzzle as a CSP. After a variable has been assigned to some value (a number placed into a cell), we an call an algorithm, that propagates the consequences of that variable assignment. If we notice this leads to a non-solution, we undo that variable assignment, and try another one. Many different algorithms for propagation exist, such as Mackworth's AC-3. As is with the type of inference used, the variable and value selection heuristics all play a major role in the efficiency of the solver.\nA key aspect that was noticed early on was that effective heuristics were \"fail-first heuristics\". Whatever we choose (what variable to assign next, what value to assign to it), it should be most likely to fail soon, thereby pruning the search tree.\nA popular heuristic for choosing a variable is the minimum-remaining values (MRV) heuristic: pick the variable with the fewest legal values. This is a \"fail-first heuristic\" that was already proposed in 1965 by <PERSON> and <PERSON>. Much effort has since gone into understanding and enhancing this already powerful heuristic. It was noted that MRV only exploits information about the current state of the problem.", "399" ], [ "The heuristic can be made adaptive by exploiting the information about the previous states as well. The so called dom/wdeg heuristic proposed in 2004 is still widely considered to be the most effective general approach known. The idea is as follows:\n1. Associate each constraint with a weight, initially set to 1\n2. Everytime a constraint is responsible for a dead-end, its weight is incremented\n3. When choosing a variable, first choose the one with fewest legal values\n4. In case there are multiple choices, broke ties by dividing with the weighted degree, which is the sum of weights of the constraints involving the variable in question, and at least one other unassigned variable\nWhat good does this do? Well, the weight on the hard constraints increases as the search progresses. In other words, the search is being guided towards hard parts of the problem. Once again, obviously one is more likely to fail when faced with a hard problem, and here we again see the \"fail-first principle\" in work.\nBy the way, the dom/wdeg heuristic has been observed to have a nice synergy with specific random restart strategies in 2008 by <PERSON> [1]. <PERSON> observed the so-called geometric strategy was the most suited one, making the dom/wdeg even more powerful.\n[1] <PERSON>, <PERSON> (2008). A study of adaptive restarting strategies for solving constraint satisfaction problems. In Proc. 19th Irish Conference on Artificial Intelligence and Cognitive Science-AICS (Vol. 8, pp. 33-42).", "915" ], [ "The categorization in that list is certainly still current.\nPerhaps one new category has emerged, namely, dependently-typed programming languages. These are essentially automated theorem provers where the primary goal is not proving theorems, but programming. Due to the <PERSON>-Howard correspondence, these two concepts are strongly intertwined. The ultimate goal of such programming languages is to write programs that have much stronger guarantees than regular typed programming languages. People also use these for theorem proving. Some new systems falling into this category include Agda and Epigram. One of the key characteristics of such languages is that they put a lot of effort into making it easier for programmers to define inductive families of datatypes.", "904" ], [ "A simple example is a vector, which depends upon natural numbers (defined inductively).\nRegarding which ones are still very active, I think they all are. Coq, Isabelle, Twelf, and PVS are used a lot in the programming languages community. Maude is used extensively in modelling systems. (Personally, I've used Coq and <PERSON>.)\nI'd never heard of a few of them. In the pdf you link to, there are links to the theorem provers. Some links are current, some are broken. <PERSON> now seems to be some sort of bearded wizard.\nThe theorem provers mentioned in “A Review of Theorem Provers” are:\n* ALF: subsumbed by ALFA, Coq, and Agda.\n* ALFA: seems to no longer unsupported.\n* COQ: actively supported.\n* MetaPRL: seems to be no longer supported.\n* NuPRL: actively supported.\n* HOL: actively supported.\n* PVS: actively supported.\n* Isabelle: actively supported.\n* TWELF: actively supported.\n* ACL2: actively supported.\n* INKA: seems to be no longer supported.\n* GANDALF: seems to be no longer supported.\n* TPS: may still be active, but has only a small following.\n* OTTER: may no longer be supported.\n* SETHEO: replaced by E-SETHEO, which seems to no longer be supported.\n* SPASS: seems to be still active.\n* EQP: seems to be no longer supported.\n* MAUDE: very actively supported.\n* OMEGA: seems to be no longer supported.\n* Mizar: actively supported.\nThere are undoubtedly many new automated theorem provers that have not been mentioned in this list.\nFor completeness, as suggested by <PERSON>, there are site archiving proofs made using various tools. For example:\n* The Archive of Formal Proofs for Isabelle\n* Formalized Mathematics for Mizar\n* The Constructive Coq Repository", "904" ], [ "The search for a Unified Field Theory posits that there is one fundamental field. It is expected that all four forces will be unified at the Planck scale, which is many orders of magnitude outside current experimental reach, although gravitational observatories and cosmological models may provide insights.\nThree of the four fundamental forces have been integrated with each other, and mass and special relativity, in quantum field theory (QFTl. That only leaves gravity, which the leading attempts to unify are strinv theory and loop quantum gravity. It should be noted that this will have to involve dealing with the nature and emergence of time, which is not included in QFT.\nThe three linked fundamental forces have been shown to arise from three fundamental symmetries and their associated conservation principles, in time (energy), in space is translation and rotation (momentum), and internal symmetry (particle identity and quantum numbers). These considerations give rise to understanding particle-families as local gauge symmetry symmetry groups, that pair boson and virtual particle exchanges into what we call the fundamental forces or fields. We have the Higgs boson from which mass derives, but no evidence for the graviton expected to mediate it.\nSo, the fundamental forces are revealed as being related to the properties of our universes topological properties.", "800" ], [ "String theory posits a wider domain of possibilities for physical laws. We find that significant properties giving rise to complexity in our universe seem to be a result of fine tuning, and we live in a fine tuned universe which appears to violate assumptions we make about 'naturalness'. It seems inevitable that there is some kind of probability space in which these fundamental constants are different, which is typically called the multiverse, making the fine tuning problem one of locating our own universe within that.\nThe broad responses to these issues are, disputing the fine tuning (in particular as subjective anthropocentrism) , criticism by lack of imagination (our inability to explore 11 dimensional topolgies gives us very little idea of the other options), and the anthropic principle (many variants including the simulation hypothesis.\nI do not claim to be an expert in this, or even very knowledgable. It only seemed to me this ground was not covered in other answers. From which I see, a high degree of scepticism and reluctance about these issues, despite them as I see it being self-evident results and open problems of modern physics. I would love anyone to correct me with references and where possible by disputing statements in my references.", "283" ], [ "Revisiting this due to some related research I am doing, the disagreement between myself and some of the others who answered, can be assimilated into a holistic understanding in which we were all correct. But IMO the adopted computer science terminology “bounded nondeterminism” is an incorrect oxymoron (which was my point before).\nThey key point is to distinguish between bounded and unbounded nondeterminism.[1]\nNondeterministic Turing machines (aka “NTMs”) have bounded nondeterminism in that each state transition has a bounded number of possibilities, i.e. the number of programs (aka “configurations”) is finite. The tape remains unbounded, so the proof of termination remains undecidable. But for any given input that halts, the output is deterministic and bounded in time― i.e. for any input the result is deterministic or doesn’t terminate. Also NTMs execute all possible configurations in parallel, so they execute exponentially faster than emulation of NTMs on deterministic Turing machines (aka “DTMs”).[2]\nThere really isn’t any nondeterministic relationship between inputs and outcomes in NTMs because the outcome is always the same for any input or initial state, which is evident because they they can be emulated by DTMs without any added randomness.[2] Undecidable is not the antithesis of deterministic, because not halting is also a deterministic result. Deterministic machines always have the same outcome for a given input, even when that outcome is to not halt. The localized nondeterminism of NTMs is in each state transition of the executing algorithm.", "915" ], [ "It is undecidable a priori which path of the tree might terminate providing the output state. But undecidability is not nondeterminism. Thus the term “bounded nondeterminism” is intended to describe the localized indeterminacy within the state machine but not the relationship of inputs to results, hence the concept of “bounded”. I still think the term “bounded nondeterminism” is an oxymoron and it could have been more accurately described as a “parallelized state transition” <PERSON> machine.\nWhereas, for any given input or initial state, unbounded nondeterminism (aka “indeterminism”) has an unbounded number of possible states. Unbounded nondeterminism involves not just the number of possible configurations of programs, but some unbounded external state which is not part of the input or initial state, such as unbounded delays. And thus outcomes can vary on repeated executions for the same input or initial condition; thus is not a deterministic relationship between inputs and outcomes.[3]\nRandomized and probabilistic algorithms employ some nondeterminism, i.e. random selection of possible configurations possibly bounded in number of configurations, but they don’t execute all the possible configurations as NTMs do. Thus they are not deterministic unless the randomness is deterministic (e.g. PRNG) and the initial state of the entropy for the randomness is considered to be part of the input.\n[1] https://en.wikipedia.org/w/index.php?title=Unbounded_nondeterminism&oldid=710628370#Nondeterministic_automata\n[2] https://en.wikipedia.org/w/index.php?title=Non-deterministic_Turing_machine&oldid=754212081#Equivalence_with_DTMs\n[3] <PERSON>, <PERSON> and <PERSON>: The Actor Model (everything you wanted to know...). Jump to the 17:44 minute mark.", "915" ] ]

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[ [ "One Day\nBy the time it reached the final episode it became clear to me that this was a tv show (book) which had been written backwards. <PERSON> wanting to explore the relationship between memory and grief primarily, but unfortunately also wanting to use the death as a somewhat hacky twist bait and switch, which feels like manipulation designed to heighten emotion in an unearned way.\nAs a tv show I often found it very frustrating. The characters are not written beyond the confines of the episodes and often the places in which we find them each year seem very contrived. In converting everything to this episodic structure it is a lot easier to see these faults, whereas perhaps on the page or in a film there is more flow between the years, a chapter or a scene does not need to standalone as a piece of art, in the same way an episode of television does.\n<PERSON> is really fantastic throughout the series. From scene to scene she is finding interesting line readings and subtle gestures.", "80" ], [ "Elevating the material. She is always working to find the character despite the writing's occasional jumps leaving gaps in her development.\n<PERSON> has moments of brilliance. The final episode will probably make him a star. I found when he was without his co-star there was a lack of focus to his characterisation. He is a new star for a rogues gallery of sad boy actors, but unfortunately his sad character has fairly boring reasons for being sad for most of the series. It is really lazily written, and unfortunately I always felt like Woodall could not hold the weight of the bad writing in the same way <PERSON> could.", "132" ], [ "Poor Things\nI read the book this month and it instantly became one of my favourites. It is such an amazing and many faceted piece of literature that it is hard not to see this film now as a slight failure. There is a lack of ambition in how <PERSON> drops the setting, the framing structure and some level of mystery. It feels like the <PERSON> of 10 years ago might have tried and failed, but perhaps the sense of <PERSON> now is not to try at all. He instead hones in on specific elements of the novel, playing them to perfection.", "647" ], [ "It'd just hard for me not to spend a little time imagining what could have been.\nWhat’s left is a masterpiece in its own right. As so much is excised to focus on the mental journey of <PERSON>. The cinematography, costumes, score, production design. All emphasising what it is like to see the world through the eyes of a child, to be free of worldly pressure, but in <PERSON>’s unique case not to be treated as a child or to know the feeling of being under authority. Perhaps it would be better for the world if we were all afforded such a luxury.\n<PERSON> is sensational, but as is the full cast. <PERSON> really just cannot miss an opportunity to do a perfect line delivery.", "529" ], [ "The Royal Hotel\nThoroughly enjoyed. <PERSON> has the juice and can direct actors better than almost any of her peers.\nI would describe this as a successful attempt to take a lot of the ideas behind The Assistant and reapply them to a different setting and genre. It’s a film for a big crowd and it works extremely well.\n<PERSON>’s strength is in her character work. She never takes an easy out for the sake of drama, and even the villains of this film are full of contradiction and drawn with a lot of empathy.", "657" ], [ "Surprisingly a significant amount of the conflict exists between the two leads, and their different approaches for dealing with drunken chauvinism. At times this dynamic felt mildly underwritten to me, however I feel like I owe the film another watch while considering this relationship more.\nThe real revelation here compared to The Assistant is how <PERSON> blocks and shoots her scenes. Most of the film is set in a fairly packed bar, with around a half dozen distinct patrons. Fantastic use of the space is made and the camera always feels like it is finding the most interesting spot. <PERSON> knows when not to show certain parts of the bar and a lot of tension is mined from a fear of what might be happening just outside the frame.\nMost importantly performance is king and the actors are never lost in the fray while trying to show off with a set piece.\n<PERSON> is sensational once again.", "217" ], [ "The Glass Menagerie\nIt’s always satisfying to finish off a director’s CV especially one as good as <PERSON>. He’s a great director because he can balance script, style, and performance with a seeming ease. Just look here at the sister being informed of the gentleman caller.", "529" ], [ "The camera is this roving monster with fast edits showcasing the emotional imbalance the moment provides for her smashing into a mid point shot of the characters opposed just as she begins to find the strength and settlement of mind to find her position on the matter.\n<PERSON> really should be spoken of in conjunction with all the greats though here he’s clearly aiming for <PERSON>. <PERSON> is the most blatant example of this seemingly being tasked to do with shadows and grain exactly what he was doing in the ‘70s. This is a kind of gross looking film that hides its playfulness in plain sight.", "132" ], [ "<PERSON>\nThe Mango Tree begins with some allusions to themes that suggest a film concerned with grand narratives and myths of the old world as experienced by Australians in the early decades of the 20th century. In this newly conquered Eden perhaps the mango tree will stand-in for that ancient apple tree? Maybe it does, but this film is solely focused upon actors and moving through the narrative. It feels like much has been shorn from the source material, except there is no source material. <PERSON> is a main character in that we open with him on a train, then fade back to the town from which he is departing. Not that this is especially clear either. There is nothing to suggest this is all a flashback, and it absolutely does not need to be. The Mango Tree is so generic that it almost becomes a joke. But there is a warmth here. It may basically be a fantasised episode of A Country Practice as taking place during The Great War Years, but it has a way of presenting death that is honest and lacking in manipulation. These deaths don't get much meaning as the film leaps from one short vignette on social issues of the time to another.", "295" ], [ "But they happen with a simple suddenness that does reflect life. Plus there's a mad preacher on the loose with a shotgun for a bit, which was an unexpected delight.\nThe Mango Tree is kind of nothing. For the most part it is overly manicured and detached. It doesn't capture a sense of place very well, which is a shame as I was most curious about that. My grandfather and father were both Queenslanders, <PERSON> was fighting somewhere in Europe at this time in history. I would have liked a better sense of physical place. From the stories and experience my Dad told me, however, they certainly captured the pig-headed nastiness of it. It falls to <PERSON> to counter this nastiness with her own dedication to not being a dick. She breathes fire and passion into The Mango Tree, almost single-handed, as <PERSON>. Even <PERSON> is only a brief backup chorus to her resolute humanity. For her alone it is worth watching (and the deranged preacher subplot).", "80" ], [ "<PERSON>\nThe effects sequences that represent the neural link between possessor and possessed are truly inspired. The physicality of the facial effects and the editing techniques suggest a much better film. As a feature length narrative this is dreadful and manages to be a step backward from the promising, if not cliché, Antiviral. It doesn't help that the son sets up a comparison to the father, aping <PERSON> the elder's masterpiece Videodrome (not only in plot but in elements of the design).", "5" ], [ "But apart from a handful of \"interesting ideas\" (critic speak for how do I justify sitting through this) this is among the more inept indie horror films of the past decade. It is entirely reliant on the visual styles of the day, which I must admit, I find to be suggestive of a cohort of filmmakers more interested in packaged effect than in cinematic expression. Like The Devil's Candy, Hereditary, or Beyond the Black Rainbow this is obsessed with an aesthetic of portent, but lacks the cinematic brain to imagine such an aesthetic. I cannot wait for the era of symmetrical compositions, slow zooms, and synth scores to die as brutal a death as we are subjected to witnessing in these woefully generic films.", "645" ], [ "The Hypnosis\nA comedy about anxiety, how it’s both a prison and a necessity. Hilarious first half before the uncomfortable second.", "471" ], [ "The leads make it work but I can’t help but feel it could have been a lot more if the couple felt more fleshed out. As hilarious as it was to watch <PERSON> stare at his girlfriend in horror for much of the film it never felt like there was a real sense of shared history outside of a few key moments.\nLikewise the tech setting feels like distracting window dressing, the film has almost nothing to say about it, and to be fair I don’t think it really needs to necessarilly. However it leans on it a little too heavily for it to be so apathetic about it.\nGreat ending", "325" ], [ "<PERSON>\nAdmittedly, I did not register this as a comedy until 40 minutes in at which point after realizing this everything the film was doing became crystalized and threatened to break the film in two. The mood piece about alienation as an immigrant worker is nearly overtaken by a dead pan humor that is somehow too arch and too subdued, best exemplified by <PERSON> performance that threatens into becoming a caricature every time the film returns to him.", "132" ], [ "Fortunately, the film finds it's footing again at it's closing with <PERSON> mechanic. Very much of a piece with <PERSON>'s Fallen Leaves as a film that perfectly captures the feeling of living in current moment even if it isn't as fully realized as <PERSON>'s film. I imagine this plays better in a theater with an attentive crowd.", "529" ] ]

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[ [ "A rubber ball gets thrown horizontally from $H$ height find the horizontal distance of the ball till it hits the ground\nThere's a rubber ball that has mass $m$, it gets thrown horizontally (from $H>0$ height) with initial velocity of $\\vec V(0) = V_0 \\hat X$ ($\\hat X$ is the axis, meaning horizontal) in addition to the gravity, there's wind resistance given by $\\vec f(\\vec V)=-b \\cdot \\vec V$ 1) find the horizontal and vertical velocity equations 2) find the horizontal distance of the ball till it hits the ground ( first time it hits the ground)\nMy try: for the horizontal axis $(\\hat X)$ according to <PERSON>'s second law of motion $\\sum F_x = m \\cdot a_x$ $\\to$ $-b \\cdot V_x=m \\cdot a_x$ $\\to$ $a_x= \\dot V_x= \\frac{-b \\cdot V_x}{m}$\nAnd for the vertical axis $(\\hat Y)$ $\\sum F_y = m \\cdot a_y$ $\\to$ $-b \\cdot V_y -m \\cdot g =m \\cdot a_y$ $\\to$ $a_y = \\dot V_y= \\frac{-b \\cdot V_y}{m} - g$\nthis is for the first part.\nMy try for the second part:\nSolve the $ODE$ for both horizontal and vertical in order to find the $V_y(t)$ and $V_x(t)$ $$\\dot V_y(t) = \\frac{-b \\cdot V_y}{m} - g $$ $\\to$ $$V_y(t) = A \\cdot e^{\\frac{-b}{m} \\cdot t}-\\frac{m \\cdot g}{b}$$\nthen we substitute $V_y(0)=A \\cdot 1 - \\frac{m \\cdot g} {b} = 0$ $\\to$ $A= \\frac {m\\cdot g} {b}$\nthen we substitute the $A$ we found $$V_y(t) = \\frac {m\\cdot g} {b} \\cdot e^{\\frac{-b}{m} \\cdot t}-\\frac{m \\cdot g}{b}$$\nnow we solve the $ODE$ for the horizontal axis $\\dot V_x= \\frac{-b \\cdot V_x}{m}$ $\\to$ $V_x(t) = A \\cdot e^{\\frac{-b}{m} \\cdot t}$ then we substitute $V_x(0)= V_{0_x}=A$ $\\to$ $V_x(t) = V_{0_x} \\cdot e^{\\frac{-b}{m} \\cdot t}$\nafter we found $V_x(t)$ and $V_y(t)$ what i tried to do is find the $y(t) = 0$ by doing an integral on $V_y(t)=V_y(0) + \\int_0^t V_y(t) dt$ (and the answer is $y(t)=H - \\frac {g \\cdot m} {b} \\cdot (\\frac {m}{b} \\cdot e^{\\frac {-b}{m} \\cdot t } +t)$ in order to find the time it did hit the ground and then use that time in the horizontal distance equation to find that distance when it first hit the ground\nbut I got stuck and I do not know if this way is even correct as I could not continue from here\nSorry if there are some translation mistakes to English hopefully it is still understandable", "512" ], [ "It's not like that as you are thinking It's correct and it will be\n$a = \\frac{20}{3} \\frac{m}{s^2}$ only. Let's find out how.\nFirst I'll go with the second diagram\nFor this system the equation for both the masses will be as:-\nFor the block of mass $m_1$ (which is in this case 4kg)\n$m_1 g-T = m_1 a_1$ $----eq 1$\n{took the positive direction downwards}\nAnd For the block of mass $m_2$ (which is in this case 2kg)\n$T=m_2 a_2$ $-----eq 2$\n{Took the RHS direction positive}\nHence we can say that this is the constraint motion so for this, the total work done by the tension in the system will be zero.\nWorkdone by the tension on 4 Kg block that's $m_1$ will be\n$W_1 = \\vec{T} . \\vec{x_1}$\nSo the displacement and the tension are exactly in the same direction so the angle between the would be 180 degrees\nAnd workdone will come out to be\n$W_1 = T x_1$\nSimilarly for $m_2$ block with mass 2Kg the workdone by the tension will be:-\n$W_1 = \\vec{T} .", "512" ], [ "\\vec{x_2}$\n$W_1 = -T x_2$\nSo by the conclusion that the total workdone by the tension on the whole system will be zero then:-\n$T x_1 - T x_2 = 0$\nCancelling out the tension on both sides we get\n$x_1 = x_2$\nSo on differentiating both sides two times w.r.t time we will get the acceleration.\n$a_1 = a_2$\nSo this means both the blocks accelerate with the same rate.\nSo by putting $a_1 = a_2 = a$\nBy solving all of the equations above we get\n$m_1 g - T=m_1 a$\nAnd for m_2\n$T = m_2 a$\nBut in this case mass of $m_1$ is 4 Kg and the block with mass $m_2$ which is 2 Kg so by substituting the masses and acceleration due to gravity in $eq 1$ and $eq 2$ we get\n$40-2a = 4a$\n$40 = 6a$\n$a=20/3 \\frac{m}{s^2}$\nNow as we know that according to the second law of motion the net force on the object will be equal to it's mass times acceleration. So from this equation the net force on block with mass $m_1$ (in this case it's 4kg) will be $m_1 g-T$. T will be negative just because it's acting in the opposite direction and we have fixed the downward direction as positive and anything which will happen in its opposite direction will be considered as negative.\nAnd on the block with mass $m_2$ (in this case it's 2kg) only one force is acting that's tension so the net force on that block will be only T.\nSo by just substituting we will get the answer.\nAnd man don't go with any shortcut formulae they are just made to make our life a bit easier (and this is one of it) they will not be valid everywhere just go through the with the concepts and pull out as much as you can.\nThis system has only three pulling forces they are the tension on both the blocks and the gravitational force acting on block with mass $m_1$ so according to your formula:-\n$A = \\frac{T-T+40}{6} m/s^2$\n$A = \\frac{20}{3} m/s^2$\nIt again comes out to be true\nThis formula for which you are struggling to find how it comes is like this:-\nWe assume the single block instead of assuming two blocks with the mass equal to the sum of masses of both the blocks and assuming that the system has only one block and calculate the net force on it, the tension here vanishes out because there are no threads connected anywhere because the system has only one block now.\nAnd the formula comes out to be\n$Fnet = ma$\nWhere here $m$ is the mass of that single block which has mass equal to sum of masses participating in the system.\nThat is $m = m_1+m_2+.....", "512" ], [ "The force of gravity will simply move the equilibrium point, being a costant force. So if $l_0$ is the initial lenght of the spring, the applying the orizontal component of the force $Mg\\sin \\theta$, you'll get the new lenght in equilibrium that is (<PERSON>'s Law) $$ \\vec{F} = -k\\vec{(x - x_0)} \\Rightarrow x = F/k + x_0$$ $$x_1 = Mg\\sin \\theta / k + x_0$$ Since gravity is costant over time, any displacement applied to the string will act as if the initial lenght of the string is $x_1$, not $x_0$. So the amplitude of harmonic oscillation won't change, but you must consider the amplitude relative to $x_1$, not $x_0$.", "766" ], [ "You have to put the $0$ in your ruler on $x_1$, rather than $x_0$.\nYou can prove this statement solving the differential equation: $$F = ma = m\\frac{d^2x}{dt^2} = -k(x - x_0) + Mg\\sin \\theta $$ $$ m\\frac{d^2x}{dt^2} +kx = kx_0 + Mg\\sin \\theta $$ there is no $x$ in the $Mg\\sin \\theta$ so you can simply consider $$kx_0 + Mg\\sin \\theta$$ as a costant term $kx_1$ so you'll get $$ \\frac{d^2x}{dt^2} + \\frac{k}{m}x = \\frac{k}{m}x_1 $$ the amplitude is given solving the differential equation http://en.wikipedia.org/wiki/Ordinary_differential_equation it doesn't depend on $x_0$ or $x_1$.\nConsidering the problem using conservation of energy, you'll get: Let's say that $h_0$ is the height relative to $x_0$ so $h = x\\cos \\theta $ energy at $x_0$ will be $$ mgh_0 + \\frac{1}{2}m\\upsilon^2 + \\frac{1}{2}k(x_0 - x_0)^2$$ energy at a displacement $\\Delta x$ from $x_0$ $$mgh_0 + mg\\Delta h + \\frac{1}{2}m\\upsilon^2 + \\frac{1}{2}k(\\Delta x)^2$$ every force is conservative so $$ mgh_0 + \\frac{1}{2}m\\upsilon_0^2 + \\frac{1}{2}k(x_0 - x_0)^2 = mgh_0 + mg\\Delta h + \\frac{1}{2}m\\upsilon_1^2 + \\frac{1}{2}k(\\Delta x)^2$$ if the cart is release with $\\upsilon_1 = 0$ $$ \\frac{1}{2}m\\upsilon_0^2 = mg\\Delta x \\cos \\theta + \\frac{1}{2}k(\\Delta x)^2$$ the speed at $x_0$ depends only from the inital displacement $\\Delta x$ and not from $x_0$ or $x_1$ absolutely.\nTheoretically the amplitude won't change, but since there are other factors as friction, measures aren't perfectly matching to theory. The inclined plane present less friction rather than an horizontal plane due to the vertical component of the weight of the cart. So taking friction into account total energy will decrease while the cart is moving so, it will decrease the amplitude of motion.\nHope this help!", "526" ], [ "Q1 Is $F=\\frac{d(mv)}{dt} just a definition or is there something \"more\" behind the formula for force?\n$\\vec{p} = m\\vec{v}$ is a definition! $\\vec{F} = m\\vec{a}$ is not! Pratically speaking, you can measure both Force (using an elastic material and its deformation) and acceleration (double derivative of space respect to time), <PERSON> discovered they're proportional so, since they're definite indipendently, $\\vec{F} = m\\vec{a}$ is the relation between $\\vec{F}$ and $\\vec{a}$ not the definition of force! You can't measure momentum, so you'll need to define it! The definition is $\\vec{p} = m\\vec{v}$ and the reasons are perfectly explained on <PERSON> books.\n$$\\vec{F} = m\\vec{a} = m\\frac{d\\vec{v}}{dt} = \\frac{d(m\\vec{v})}{dt}$$\nQ2 Is W=∫F⃗ ⋅ds⃗ just a definition or is there something more behind? I mean, can you derive the formula for work not by taking the formula for the kinetic energy as given.\n$$W = \\int \\vec{F} \\cdot d\\vec{s}$$ is the definition of work done by a force $\\vec{F}$ along a path, you do not need kinetic energy to define work. Energy is the possible work doable by a moving body.\nQ3 How to derive the formula for the kinetic energy and work only form the conservation of momentum Σmivi→=const.?\nYou know that $\\vec{F} = \\frac{d(m\\vec{v})}{dt} = \\frac{d\\vec{p}}{dt}$ but since $\\vec{p}$ is costant, is derivative will be zero.", "512" ], [ "In case it is moving with costant speed $\\vec{v_0}$. Now, imagine a costant force applied to the mass, you'll have that $v^2 - v_{0}^2 = 2as$ (from cinematics) $Fs = W = \\Delta E$, $mas = W \\Rightarrow$ $$v^2 - v_0^2 = 2W/m$$ $$W = \\frac{1}{2}mv^2 - \\frac{1}{2}mv_0^2$$ The applied force is going to stop the mass, so the mass reacts with an opposite force, and since energy is the possible work done by the moving mass. Since it is opposed and $v= 0$ we obtain: $$ W = \\frac{1}{2}mv_0^2$$ Energy depends only on the initial velocity because momentum (before the costant force applies) is conservating.", "512" ], [ "A charge q moving in vacuum with a constant velocity v has conserved overall energy because the Electric field density on the direction of v increases while the field density in the other direction decreases.\nFor sake of argument let's consider the following example: particle position is [x, y, z] = [0, 0, 0] at time t1 = 0 v = [vx, vy, vz] = [1, 0, 0] = 1 m/s (moving along x axis)\nElectric field along x-axis at time t1\nat E(-1, 0, 0) = q / (4π ε x2) = q / (4π ε)\nat E( 1, 0, 0) = q / (4π ε x2) = q / (4π ε)\nAt time time t2 = 0.5s the particle position will become [0.5, 0, 0]\nthe electric field alonx x-axis is now\nat E(-1, 0, 0) = q / (4π ε (-1 - 0.5)2) =q / (4πε 2.25)\nat E( 1, 0, 0) = q / (4π ε (1 - 0.5)2) = q / (4πε 0.25)\ndE(-1, 0, 0) = (q / (4πε 2.25) - q / (4π ε) ) is negative while\ndE( 1, 0, 0) = (q / (4πε 0.25) - q / (4π ε) ) is positive\nMoving particle field is conserved. In front of the particle the field increases at every point, while in the back it decreases at every point (with respect to previous position).\nThe potential energy of the field in front of the particle is increasing and vice verse for the back.\nEpot = (1/2) ε * dE2 * dVolume\nIf one will integrate over all volume the potential field energy is constant, but the energy density will increase along the direction of movement while it will decrease in the opposite direction.\nPS: we have a non relativistic velocity v << c, but the change in field will propagate with the speed of light that means that the field density on the direction of the movement in greater than in the back. This is like red/blue shifting. If you are in front of an ray emitting object the light will come blue-ished while if you are in the opposite direction of speed it will come red-ish.\nNote: to make my explanation shorter I've only considered electric field along one axis; but you can deduce by your self what happens in all other directions.", "780" ], [ "Goldstein Classical Mechanics exercise 5.17 (3ed) conceptual\nI am having difficulty understanding a concept in the \"Heavy symmetric top\" type of problems. I will include all of my efforts as to hopefully have someone easily point out what it is that I'm missing. The question reads:\nA uniform right circular cone of height $h$, half-angle $\\alpha$ and density $\\rho$ rolls on it's side without slipping on a uniform horizontal plane in such a manner that it returns to it's original position in a time $\\tau$ . Find expressions for the kinetic energy and the components of the angular momentum of the cone.\nI begin by finding the volume (since I memorize no such things) and decide on the obvious choice of cylindrical coordinates.", "15" ], [ "My mass will then be $$\\rho\\int_0^h \\int_0^{2\\pi} \\int_0^{z \\tan{\\left(\\alpha\\right)}}r \\, \\mathrm{d}r \\, \\mathrm{d}\\theta \\, \\mathrm{d}z = \\frac{\\pi \\rho R^2h}{3} $$ then while I'm at it I likewise find the center of mass (in the $z$) $$\\frac{1}{V}\\int_0^h \\int_0^{2\\pi} \\int_0^{z \\tan{\\left(\\alpha\\right)}}zr \\, \\mathrm{d}r \\, \\mathrm{d}\\theta \\, \\mathrm{d}z = \\frac{3h}{4} $$ moving onto the moments for the inertia tensor, I use$$ I_{ij} = \\int_V\\rho \\left(\\delta_{ij} \\Sigma_k x_k - x_i x_j\\right) \\, \\mathrm{d}V $$ and find that $\\bf{I}$ is already diagonal, I get elements $I_1 = I_2 = \\frac{3M}{20}\\left(R^2+4h^2\\right)$; and $I_3 =\\frac{3M}{20}\\left(2R^2\\right)$ so that the inertia tensor about the apex at the origin of the coordinate system is given by $$ \\bf{I} = \\begin{bmatrix} \\frac{3M}{20}\\left(R^2+4h^2\\right) & 0 & 0 \\ 0 & \\frac{3M}{20}\\left(R^2+4h^2\\right) & 0 \\ 0 & 0 & \\frac{3M}{20}\\left(2R^2\\right)\\end{bmatrix} $$\nnow in the event I should need $\\bf{I}{CM}$ I also get that out of the way and find that using the parallel axis theorem, $ I{1_{CM}} = I_{2_{CM}} = \\frac{3M}{20}(R^2+\\frac{h^2}{4}) = \\frac{3M}{80}\\left(4R^2+h^2\\right)$; and $ I_{3_{CM}} =\\frac{3M}{80}\\left(8R^2\\right)$ so that $$ \\bf{I}_{CM} = \\begin{bmatrix} \\frac{3M}{80}\\left(4R^2+h^2\\right) & 0 & 0 \\ 0 & \\frac{3M}{80}\\left(4R^2+h^2\\right) & 0 \\ 0 & 0 & \\frac{3M}{80}\\left(8R^2\\right)\\end{bmatrix} $$\ngreat. So it seems that I may use either the inertial frame OR the body frame, however this is where I'm getting confused. As I understand it, if I change my coordinates to the center of mass body coordinates, I will not need to consider the translational kinetic energy of the center of mass. But can I even do this here? In any event I find $v_{CM} = \\frac{3h}{4} \\cos(\\alpha)\\dot{\\phi}$ where $\\phi$ is the azimuthal angle about the fixed inertial $z$-axis, and I can find various relations for this based on the no-slipping condition though its not clear which I should want. Now that I have gotten most of the legwork done, I want to write my expression for the kinetic energy.", "402" ], [ "Friction influencing the motion of a mass and non-inertial frame of reference\nSo... recently a Newtonian-mechanics related exercise has raised in me many questions basically ragarding which forces influence a given system and how, I know they might sound bit too \"noobish\" but I just had to get them out of my chest (yes it really gave me something to think about in the last day).\nperhaps you should take a look at the above mentioned exercise to better understand what I am trying to figure out\nSo, I'm trying to figure out how this system works... the exercise says (please forgive me for all the grammatical errors you will eventually find):\nProblem\na cube with a mass $\\ M=50Kg$ is standing on a plain surface and can move on it without friction.", "766" ], [ "On that cube is standing another cube with a mass $\\ m=10Kg$, at a given distance $\\ d=0.5 m$ from the upper-left corner of the cube. Initially, when everything is stationary, a force $\\ F=100N$ is applied to the bigger cube horizontally (I assume that the force $\\ F$ is constant); at the moment $\\ t=2s$ the smaller cube falls. Calculate the friction coefficient between the two cubes.\nVariables used:\n$\\ μ$= friction coefficient\n$\\ g$= gravitational acceleration on earth =$\\ 9.81 m/s^2$\n$\\ a_M$= acceleration of the bigger cube ($\\ M$)\n$\\ a_m$= acceleration of the smaller cube ($\\ m$)\n$\\ F_f$= friction force\nSo, I assume that the bigger cube carries the smaller one which moves with a constant, negative acceleration until it falls (please correct me if I'm wrong), with equation of motion\n$\\ x(t)= x_0 + v_0t + 1/2 at^2$\nso $\\ 0.5m = - 1/2 at^2$ ------> $\\ a= -0.25 m/s^2 $\nnow...\n$\\ F- μ mg = Ma_M$\nin other terms (and again please correct me if I'm wrong): $\\ F$ is partially dissipated by the friction between the cubes, and the bigger cube moves under the influence of a force which equals to the applied force $\\ F$ minus the friction force $\\ F_f= μ mg$\nnow the universe collapses: the solution says:\n$\\ μmg = ma_m$\n$\\ a_r = a_M - a_m = [ μg (m + M) -F] / M$ which leads to $\\ μ=0.15 $\nBut... what leads to those last two equations?", "512" ], [ "This is because of greater shear strain you will experience if you run on the train while its accelerating. But us humans do not deform when subjected to this stress but they fall down.\nThere are two factors involved here\n1. Shear force(assuming uniform acceleration)\nWithout using complicated terms, let's assume that you're a passenger(A) watching another passenger(A) standing inside the train. According to you when the train accelerates at $a m/s^2$., the passenger(A) inside accelerates at $a m/s^2$. Let his mass be $m*kg$. Humans generally run at an angle of $15 \\deg$\nNow person (A) has started to accelerate in the opposite direction at $a_1 m/s^2$ at an angle of $15\\deg$*.Due to <PERSON>'s Third Law the force exerted by the train will oppose passenger A\nForce at your feet(when running) $$ \\sum F_{xz}=ma - \\cos(15 \\deg)ma_1$$ $$ \\sum F_{xz}=ma - 0.96ma_1$$\nIn very few cases this force would be in direction of $\\overrightarrow{ma}$.", "771" ], [ "Believe it or not except high speed bullets, normal trains accelerate very slowly.\nAlso due to Newton's Third Law, the forward acceleration of your head will be equal to the backward acceleration\nShear stress tends to deform originally rectangular objects into parallelograms. The most general definition is that shear acts to change the angles in an object.\n$$\\tau_{xz} = \\frac{F}{A_{xz}}$$\nAnd if you also want to know shear strain $$ \\tan \\gamma_{zx} = \\frac{\\Delta x}{z}$$ $$\\gamma_{zx} = \\tan^{-1} \\Bigr ( \\frac{\\Delta x}{z} \\Bigr)$$\n* z is height of the person\n* $\\Delta x$ = ? $$\\sin(15 \\deg) = \\frac{\\Delta x - s_{net}}{z}$$ $$\\sin(15 \\deg)z = \\Delta x - s_{net}$$ $$0.25z + s_{net} =\\Delta x$$\n* Let $a-0.96a_1$ be $a_{net}$\n$$s_{net} = ut + \\frac{1}{2}a_{net}t^2$$\nSince humans are not rectangular, this is just an approximation, also air resistance and friction do not come in this approximation.\nNow if passenger (A) were just to stand, he would not exert any force on the train, nor would the train exert any force on him due to <PERSON>'s third law. Thus\n$$\\tau_{xz} = \\frac{0}{A_{xz}}$$ $$=0N/m^2$$ Since there is no force there is no displacement and person is perpendicular to the ground while standing,shear strain equals zero too. $$\\sin(90 \\deg) = \\frac{\\Delta x -0}{z}$$ $$\\frac{\\Delta x -0}{z} = 0$$\n$$\\gamma_{xz} = \\arctan (0)=0$$\n1. Friction\nAll of us know that without friction we won't be able to stand. While running friction is lesser as compared to state of rest of an object in contact with the ground. Therefore a moving object will experience less friction, and will be more likely to fall.\nConclusion : You are more likely to fall if you run in the opposite direction of the train's acceleration than standing still on the train", "766" ] ]

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[ [ "Guatemala: A Violin in Silence After Murder of Youth · Global Voices\nThe latest victims to violence in a situation that Amnesty International describes as “Millions of Guatemalans are now living under the threat of violence and poverty,” are a young violinist, <PERSON> and his two companions <PERSON> and <PERSON>. The murders took place in the outskirts of Guatemala City and their bodies were found in an area called La Quebradita of the village of Valle de la Cruz [es].\nPhoto by Midiman and used under a Creative Commons license\nBloggers are mourning the loss of <PERSON>, who was a member of the Symphonic Orchestra Conservatory, had been playing the violin for the 11 of his 18 years. The news hit <PERSON> of Una Hoja de Papel [es] especially close to home because <PERSON> was his sister's best friend as he writes in his post “The Orchestra Mourns a Violin, My Sister Mourns a Friend”:\nLa casa de estudios musicales de <PERSON> se llenó de familiares, conocidos, amigos y compañeros de Orquesta tras el funeral. Interprentando una melancólica pieza, prorrumpieron en llanto aquellos que con un rostro cansado de tan gran sollozo, frotaron sus arcos y soplaron con el alma una hermosa melodía proveniente más que de sus instrumentos, del corazón, dedicada a quien en vida fue un joven ejemplar.\nThe Music School which <PERSON> used to attend was crowded with family members, friends and their orchestra mates following the funeral.", "186" ], [ "They played a melancholic piece, and people started to weep with their faces reflecting their tearful suffering, they placed their fingers on the strings and played a beautiful melody, which did not come from the musical instruments, but from their hearts dedicated to an exemplary young man.\n<PERSON> [es] confesed that it was difficult to write about the topic, but it was also an obligation to say something for the memory of <PERSON> in the post “A Murdered Violin”:\nEscribo éstas lineas, que seguramente no leerán sus familiares, para expresar y lamentar que lo que ha sucedido. ¿qué esperanza podemos tener en un pais en donde se asesina a jovenes artistas? ¿que podemos hacer para consolar a la patria, a nuestra sociedad, a la orquesta del conservatorio? ¿acaso hay algo que podamos decir a su padre el Maestro <PERSON>, a su madre, a sus amigos y familia? Es vergonzoso, un joven que se dedica a tratar de ser diferente -todo artista lo es- ve truncada su vida por un asesino, mientras la mayoria lee la noticia y lamentablemente como es normal y usual, es simplemente una nota roja mas; y no es que la vida del joven <PERSON> sea mas valiosa que la de otro joven, ni mucho menos; pero sin duda su muerte debe ser el ejemplo mas claro de la estupidez humana en éste país en los últimos tiempos. El violín asesinado debe estar interpretando una sonata de dolor y de decepción, esa que todos escuchamos todos los días en este ingrato pais.\nI am writing this lines, which probably none of his family members will ever read, but I want to express and regret the situation. Is there still any hope for a country where young artists are murdered? What can we do to express our condolences to a nation, our society, to our National Orchestra? Is there any possible word to say to his father, to his mother, to friends and family? It is a real shame, a teenager that tries to be special – all artists are special – and their life is shattered by a murder, while the people read the news, and regrettably, it is the normal attitude of people, for them is just another violent piece of news. I am not saying that <PERSON>'s life is more valuable than the life of other young people, but I have no doubt that his murder is the clearest example of human stupidity of our country in our times.", "186" ], [ "Argentina: The Conflict between Teatro Colón and the City of Buenos Aires · Global Voices\nIt's been more than twelve years since the last performance of the famous tenor <PERSON> in Argentina. The concert [es], planed for March 23 in Buenos Aires, was therefore meant to be a special tribute from the Spanish singer to the country where he started in 1972. The first part of the concert was to take place in the Teatro Colón, the prestigious Buenos Aires opera house, and the second one was to take place outdoors with 20,000 people expected to attend. These were great news for opera fans, but things didn't turn out exactly as planned.\nFirst, the outdoor part of the concert was postponed to March 24 because of rain. Then, the concert at Teatro Colón was canceled as the very musicians of the theater refused to play for the event because of their conflict with the city's administration.\nIn an open-letter [es] published on their website, the Teatro Colón's musicians explain their decision:\nLas razones a enumerar son interminables; no olvidemos que la Dirección del Teatro nos está agraviando sistemáticamente, apodándonos terroristas psicológicos, cuasi mafiosos… Este gobierno vino con la decisión de precarizar a todo el personal del Teatro, tercerizanado, disciplinando, entre tantos otros atropellos laborales, incluso avasallando nuestro derecho constitucional.\nThe reasons to name are endless; let's not forget that the Theater's Administration is systematically worsening our situation, by calling us psychotic terrorists, almost mafia… This government came in with the decision to make all the situation of the Theater's staff precarious by outsourcing, disciplining, among so many other labor abuses, even subjugating our constitutional right.\nThe interior of the Teatro Colón, by Flickr user <PERSON> (CC BY 2.0)\nThe conflict started with the reopening of the Teatro Colón in 2010. It has been worsening since then, disturbing the end of last year's season with the cancellation of several performances.", "497" ], [ "As a consequence, the director of the Theater, <PERSON>, declared last week that the sale of opera subscriptions would be adjourned this year.\nIn the article “El público amante de la ópera que esta solo y espera…” (Opera lovers are alone and waiting…), <PERSON> [es] laments last year's perturbation and wishes that the new season starts peacefully:\nEspero que la apertura del Teatro Colón sea definitiva, después de una temporada como la del año pasado, forzosamente más breve y finalmente interrumpida, después de un largo receso. Que los importantes títulos programados para la que se inicia puedan llevarse a cabo.\nI hope that the opening of the Colón Theater will be definitive, after a season like the we had last year, forced to be shorter and in the end interrupted after a large break. May the important shows programmed for the new season be performed.\nThe Teatro Colón employees denounce several issues before the conservative governor of Buenos Aires <PERSON>, who is in charge of the administration of the opera house. A summary of their complaints can be found on Habitúes del Teatro Colón [es]. Among other things, they criticize staff cuts and the physical management of the theater, as well as the sanctions adopted against some of the leaders of the protest.\nThe blog En defensa del Teatro Colón [es] (Defending Teatro Colón) explains why the restoration plan designed by the city's government is damaging the architecture of the theater, inaugurated in 1908.\nHace seis años el Gobierno de la Ciudad de Buenos Aires inició un ambicioso plan de renovación y restauración de este Monumento Histórico Nacional. El denominado “Masterplan” … diseñado y ejecutado por profesionales con escasa experiencia en la materia pone en grave riesgo la integridad y autenticidad de la estructura histórica … y acústica, calificada como la mejor entre todas las salas líricas del mundo.\nSix years ago the Buenos Aires’ government started an ambitious plan of renovation and restoration of that national monument [Teatro Colón]. The so-called “Masterplan”….", "186" ], [ "Rendition of Trinidad & Tobago’s national anthem strikes wrong note with the country’s president · Global Voices\nScreenshot taken from a YouTube video rendition of Trinidad and Tobago's national anthem, uploaded by JR Videos.\nTrinidad and Tobago have just finished hosting the Caribbean Festival of Arts, more popularly referred to as Carifesta, which took place at various locations throughout the twin-island republic from August 16-25, 2019.\nThe event was created in 1972 as part of an effort to bring people of the region together through art and culture, music and literature, film, crafts, dance and heritage exhibitions. The event received a warm public reception, but the biggest point of discussion has been the delivery of Trinidad and Tobago's national anthem during the closing ceremony.\nShortly afterward, the Office of the President issued a media release, which took issue with the rendition. President <PERSON> stated:\nBetween August 16 and 25, 2019, we […] were reminded of the things that bind us and the possibilities that exist, through culture, for harmony among nations. […]\nHowever, a discordant note was struck at the closing ceremony, when an unacceptable rendition of our National Anthem was performed. The National Anthem must be sung in its original music; no introduction or coda can be added or other artistic licence taken in its rendition. The offence is compounded when it occurs at an official function, as was the closing ceremony of CARIFESTA XIV.\nThe president added, “Our National Anthem, like our National Flag and Coat of Arms, identifies us as a nation and must at all times be accorded the utmost respect.” The website of the Office of the President addresses the issue of protocol regarding the national anthem, which was composed by <PERSON> in 1962, the year Trinidad and Tobago achieved its independence from Great Britain:\nThe National Anthem should be accorded the respect due to it when played, and on no occasion should it be treated with scant courtesy.", "1019" ], [ "While it must be played in the original music, the pitch, speed and tone can be changed.\n“Pitch” is defined as a standard measure of highness or lowness, “speed” refers to the pacing of the rendition and “tone” describes the pitch, quality, and strength of a sound.\nThe reaction on social media was split: Some felt that the president was simply fulfilling her role in reiterating the protocol for national emblems; others — among them, musicians — believed that her stance was unprogressive.\nOn Facebook, musician <PERSON> wrote:\nAs a musician and musical curator of a 5,000 member T&T music network myself, I would say that personal aesthetic musical opinions of officials ought not to become the official state legal position based on their rank. I'm defending our musical sistren from charges of disrespecting the anthem…take a look, this may be unusual but it is a very respectful performance…the musical variation preceding and post anthem are not disrespectful either…aesthetically, it is fair to criticize if you don't like the rendition but not to assign disrespect to her intentions […]\nHe continued:\nIf the national anthem is played on [steel] Pan for example, it won't be standard or original either, but it's not inherently disrespectful to vary from the original […] take some time to look at artistic reinterpretations of other countries anthems at sporting events, whether hit or miss. In art, the creative door must be open and not closed…\nIn a telephone interview with Global Voices, music educator <PERSON> noted that every instrument — including the voice — has its own unique tonal quality which is often shaped by performance. She was cautious about the inference that there should be strict adherence to the anthem's original score, since many renditions veer away from it. The line “islands of the blue Caribbean Sea,” <PERSON> explains, should be sung with an even rhythm, but deviation from this is quite common, as is including a fermata at the end, which is not part of the original composition.\n“Music is a living thing,” <PERSON> says. “If <PERSON> had said that the rendition didn't appeal to her stylistically, that would be a different conversation, but I can attest to the fact that quite often when the anthem is played on the steel pan, or played in another genre of music, ‘artistic license’ is taken.”\nHowever, musician and teacher <PERSON>, who also spoke with Global Voices by phone, said that this instance was not a case of melodic paraphrasing and that the way <PERSON> sang the first line (even though she sang it correctly a second time) “misrepresented the anthem”.", "495" ], [ "Guatemala: Esquipulas and Rabinal, Two Symbols of Peace · Global Voices\nPhoto by <PERSON> of Cofradía en Rabinal\nTwo villages in Guatemala celebrate very important festivities in January. These feasts are “Esquipulas” and “Rabinal”. Esquipulas has become a transnational celebration and attracts devoted pilgrims that arrive from other countries in order to venerate an image of a Black <PERSON>. This was also the symbol of the Peace Negotiations througout Central America. The image of <PERSON> in Esquipulas is a special one as Hecho en Guatemala [es] explained on his post Esquipulas, city of faith\nEl referido Cristo, es una imagen de <PERSON>, a la cual, millones de devotos de Centroamérica, le rinden culto desde hace más de 400 años en el templo católico que lleva el nombre de este pintoresco poblado. El adjetivo de “negro”, se debe a que con el paso de los años (según muchos, al humo de las velas), el color de la madera en que fue tallado el cristo, se fue tornando oscura, hasta adquirir el color negro de la actualidad.\nIt is an image of a cruxified <PERSON>, which millions of Central Americans have been devoted to for the last 400 years, and is located in the church with the name of the picturesque town.", "186" ], [ "The adjective “black” is due to color of the wood of the sculpture turned dark (according to many, due to the smoke from the candles), and nowadays it is black.\nEsquipulas is located in the department of Chiquimula, but the faith and devotion for the image crosses borders, according to El nuevo blog de Esquipulas [es]:\nLa devoción por el Señor de Esquipulas ha trascendido fronteras hasta hacer de <PERSON> la ‘Capital Centroamericana de la Fe’ y también ha sido adoptada por católicos latinoamericanos residentes en Estados Unidos. Esta tradicional celebración del ‘Señor de Esquipulas’ se viene llevando a cabo anualmente en los diferentes condados de la ciudad de Nueva York y desde hace tres años se celebra en la Catedral de San Patricio, gracias a las gestiones de la señora <PERSON>, cónsul general de Guatemala en Nueva York y la Hermandad Arquidiocesana del Señor de Esquipulas NY. También se festeja en Nueva Jersey y finalmente la solemne celebración culmina en el condado de Brooklyn.\nDevotion for the Christ of Esquipulas has crossed borders and has made Esquipulas the Central American Capital of Faith, and it has also been an image that has been adopted by Latin American Catholics living in US. The traditional celebration of <PERSON> has taken place every year in the different counties of New York, and it began to be celebrated in St. Patrick's Cathedral three years ago, thanks to the actions of <PERSON>, general consul of Guatemala in New York and the Archdiocese Brotherhood of the Christ of Esquipulas in NY. It is also celebrated in New Jersey and the celebration concludes in Brooklyn.\n<PERSON> [es] tells what an old lady of his town thinks about the festivity:\nNos Cuenta Doña Clemencia de 85 años de edad, junto a su familia, nos dice que ella tiene aproximadamente 20 años de estar viajando a este Municipio de Esquipulas en estas fechas para darle gracias a <PERSON> por permitirle terminar un año mas, y empezar uno nuevo, a la vez deja su ofrenda en Río de los deseos, para pedirle un deseo a <PERSON> y que se lo haga realidad.\nMrs. <PERSON>, who is 85 years old, tells us that she has been visiting <PERSON> with her family for approximately 20 years to thank God for giving her another year of life and for beginning a new one.", "186" ], [ "Lady <PERSON> received <PERSON>'s letter about witches' prophesy and became ambitious, immoral and a tempter. She did say\nUnsex me here\nBut this has nothing to do with her gender, a lot of times it has happened in history that women have played deceitfully, immorally and cruelly for example you can take <PERSON>, wife of <PERSON> and daughter of <PERSON>'s General <PERSON>, was cruel and ambitious too.\nThe only way for Lady <PERSON> to gain power is through <PERSON> using her rhetoric.\nThat was true, she rewired the brain of <PERSON> (which was already fighting with the ambitious Devil) and made him to do what he feared. But not only she used rhetoric but also showed masculinity by taking the blooded daggers from <PERSON> and placing it there. But again this rhetoric persuasion should not be related with gender, as we find in <PERSON>; <PERSON> persuaded <PERSON> with murderous thoughts.\nDo you think that the tragedy of Macbeth is the consequence of <PERSON> is being too sensitive to masculinity? What does Masculinity mean for <PERSON>?\n<PERSON> was not less masculine, in Act 1 Scene 2 he is depicted as:\nfor brave <PERSON> – well he deserves that name\nand he is considered violent too:\nHe unseamed him from the nave to th’chops\nbut it is unjust to think of his pure conscience as a sensitive masculine character, he after murdering the king <PERSON> expresses his inner voice as:\nI am afraid to think what I have done; Look on't again I dare not.\nSo, considering the above saying of <PERSON> and comparing it with \"He unseamed him from the nave to th’chops\" it doesn't seem that <PERSON> was afraid of blood, he was afraid of himself and Higher Self, even at his death his last words were\n.", "247" ], [ ". .my soul is clog’d with blood—\nI cannot rise! I dare not ask for mercy—\nIt is too late, he drags me down; I sink,\nI sink, — my soul is lost forever! — Oh! — Oh!\nHe thinks and worries about his soul, his feeling of guilt was overtaking him. The hallucination of <PERSON> was just another portrayal of how deeply <PERSON> was aware of his murderous sin.\nThere are some of the lines in Macbeth that do demonstrate gender hierarchy, <PERSON> said to Lady <PERSON>\nBring forth men-children only;\nFor thy undaunted mettle should compose nothing but males\nand Witches warned <PERSON>\n<PERSON>! be bloody, bold and resolute;\nlaugh to scorn the power of man;\nfor none of woman born shall harm <PERSON>.\nTo re-quote your question\nWhat does Masculinity mean for <PERSON>?\n<PERSON> was valor, and respected by whole men of <PERSON>. <PERSON> knew what sins always bring to the sinners at last, his extreme feeling of guilt and consequential hallucination was because of the transparency of his heart.", "773" ], [ "It is with great sadness that we inform you of the death of our dear <PERSON>, known for his kindness and generosity, and he died peacefully at his home on <DATE_TIME> after living among us for <DATE_TIME>, which he spent helping people and spreading love and happiness in the souls of everyone.\n<PERSON> worked as a theater actor, won 7 acting rewards, played roles in more than 150 plays, and had a great impact on the souls of his fans and colleagues.\nHe survived by his loving wife <PERSON>, his children <PERSON> and <PERSON> and his granddaughter <PERSON>.\nA memorial service to honor his memory will be held on <DATE_TIME>, at Springfield Community Church, followed by burial in Springfield Cemetery.\nHe will be missed by his family and friends, but his legacy will live on for ever, may his soul rest in peace.", "4" ], [ "Guatemala: June 30th, A Day to Remember · Global Voices\nPhoto taken by <PERSON> and use by permission.\nEvery year on June 30, Guatemalans celebrate a festive day, when the Guatemalan Army goes on a parade in the city's center. This year was exceptional because bloggers were the real reporters of the event, and experienced something unusual that happened.\nWhy is there a celebration on June 30? in Guatemala Blog [ES] you can find the answer:\nEl presidente <PERSON>, en el año de 1965, en conmemoración de <PERSON>, siendo su fundador, establece el 30 de junio como el Día del Ejército.\nIn 1965, President <PERSON> commemorated the achievements of former President <PERSON>, who founded the Guatemalan Army, by establishing June 30 as Day of the Army.\nOpinions are as diverse as bloggers. One day before the parade, blogger <PERSON> [ES] in an extensive critique of the armed forces on his post “En la víspera” delcared:\nYo no me quedare de brazos cruzados ire de parte del pueblo, con el pueblo y por el pueblo por medio de una marcha de protesta que habra ese dia a manifestar mi repudio a dicha institución\nI will not stand with my arms crossed. I will go the protest representing the people, with the people, and for the people to voice my dissent towards such an institution.\nAnd next day, <PERSON>, the Parade and the protest took place organized by H.I.J.O.S, an association of Sons and Daughters for Identity and Justice Against Silence, whose members are relatives of those who suffered the loss of a family member during the armed conflict in Guatemala.", "186" ], [ "But many things happened at the parade and protest. Sometimes a picture says more than hundred words, as journalist and blogger <PERSON> shows on his blog.\nHis photo report´s title is “The March for Remembrance Halts Military Parade” There you can see the events unfolding step-by-step with some accompanying explanations. The picture on this post is part of it, and he kindly provided authorization to use it.\nHowever, in rural Coban, the festivities were quite different as you can see in the pictures by Blog Verapaces [ES].\nCon un tradicional desfile y la participación de bandas colegiales y seguramente algunas actividades especiales, el Ejercito celebró su día en la ciudad de Cobán.\nWith a traditional parade and the participation of school music bands, and some special activities, the Army celebrated the day in the city of Coban.\nGuatemala is a small country with huge contrasts, different views, but short coverage by the press. Things that really matter are now shown by bloggers, in an open way.", "186" ], [ "Guatemala: Town’s oldest school to be demolished…and teachers on strike · Global Voices\nPublic school teachers in Guatemala will protest “again” today, and this time they will ask for “amnesty.” They want the government to eliminate the sanctions imposed on them, because they took illegal actions when they were “on strike”. Such illegal actions took place just before Holy Week break, which was the second time in the year. They were not asking for a better system or nicer schools, but for a raise of 12% in their salaries. This is a contrast with two situations:\n1. In San Pedro La Laguna, a group of teachers are working for free, supporting a little school located in the middle of town, a school that the Mayor of San Pedro wants to demolish.\nThat was denounced [ES] by blogger and journalist <PERSON>:\nEl alcalde de San Pedro La Laguna, <PERSON>, abusando del poder que le otorga la municipalidad, intenta cometer una arbitrariedad al pretender derrumbar la Escuela Oficial Urbana Mixta Humberto Corzo Guzmán, para construir en su lugar un mercado, con lo cual limita la posibilidad de muchos niños y niñas de estudiar, viola además sus derechos humanos y los de toda la población\nThe mayor of San Pedro La Laguna, <PERSON> is abusing his position in the municipality by arbitrarily trying to demolish the Co-ed Urban School Humberto Corzo Guzmán, and trying to build in its place, a market.", "497" ], [ "This will limit the possibility that many children have to study, which violates their human rights and those of the entire village.\nHer opinion is supported by Blogger <PERSON> on “depuis d´Europe [ES]” where he narrates the whole story and contrasts it with the protests of teachers.\nEl país ya tiene suficientes problemas, para venir a acarrear uno mas y este que es tan sin sentido (según mi punto de vista) de querer hacer un mercado en lugar de una escuela…”\nThe country has enough problems already for another one to be solved and this one is senseless (in my opinion) to build a market in place of a school\n2. Even when they are “on strike” the Ministry of Education will give them PC´s for US$100.00 with Windows Software, and a lot of bloggers discussed the topic:\n<PERSON> [ES] said:\nEs falta de visión por parte de las autoridades a cargo del proyecto, que bien pudieron optar por el uso de Software Libre y con el dinero ahorado en Software comprar más equipo. Lo que me da tristeza es que en realidad no exista un grupo de promotores del Software Libre que haya podido hacer esta propuesta al Gobierno\nIt is a lack of vision by the authorities in charge that they did not consider Free Software for the project, because with the savings they would have been able to buy more equipment. But I am sad because here there is no group promoting free software, that could have made a serious proposal to the government\nThis opinion is supported by the post of <PERSON> [ES]:\nPara quienes creen que el tema de software libre y open souce es cuestión de filosofías o de extraños gustos informáticos, me pareció interesente continuar en la linea de presentar números interesantes para los tomadores de decisiones\nFor those who might think that free software and open source is just a philosophy or weird informatic tastes, it is interesting to show interesting statistics for the decision makers”.\nAlso, there´s a debate on whether they deserve or not the benefits of such system. <PERSON> [ES] said that if the government will sponsor those teachers that had been on strike, it would be a waste of money even when costs only US$100.", "186" ] ]

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[ [ "Am I too late to vaccinate the cat?\nI found a kitten in trash dumpster 5 months ago, and I gave him some food and he started to follow me. He was very small and I didn’t want to leave him near that trash dumspter so I took him with me. He was covered with fleas and ticks so for next few days, I cleaned him and bathe him (thanks to youtube on how to bathe cats). But I was in no financial condition to provide him any vaccination. Infact, I have been hiding him from landlord becauce I can’t pay extra rent. I posted a post on facebook groups of my locality hoping someone could adopt him but I had no luck on that.", "176" ], [ "I have been skipping my lunch every other day so I can get cat food and litter sand. He has been strictly indoor for 5 months, with only one instance when he got out for few hours and then came back home.\nNow that I have been learning more about cats, I learned cats can have so many diseases and rabies was fatal. I have been bit by him many times and I dont know if he has rabies or not. Is it too late for him to get vaccination for rabies? And where can i find cheap vaccinations. I have saved $130 but last time I called a clinic, they said it would be $320 after everything. I am confused at this point. I dont want him or me to die of rabies but I also dont know how to get vaccinations.\nThanks for reading so long post.", "176" ], [ "Am I too late to vaccinate my cat?\n6 months ago, I found a kitten near trash dumpster. I gave him some food and he started to follow me back so I took him in. I am not a cat person and I was in no way financially fit to even vaccinate that kitten.", "176" ], [ "I just managed to skip my lunch few times a week to get his cat food and litter. Infact, I hid him from landlord because I couldn’t pay for him. I did post on facebook so someone could adopt him but I haven’t had any", "940" ], [ "Change in behavior\nMale cat who is 8 years old and is neutered.\nI took my cat the the vet 3 weeks ago and ever since he came back home he's been agitated and growling and hissing at not only myself and my mother but also our other cat. He seems angry and doesn't want us to touch him or even pick him up.", "954" ], [ "He is also treating our other cat like he did when we first were introducing them 9 months ago. When she's in his presence he snorts and growls and hisses and if we try to interact with him while she is around his takes his aggressions out on us. He is acting like a new cat is in the house again.\nI did take the other cat to the vet about a month ago 4 times for an emergency so I thought maybe her scent might be off but his aggression only started that I noticed after we took him for his yearly work up.", "954" ], [ "Are cats more affectionate when recovering from something?\nOr maybe its because he is an outdoor cat. Anyway, I've been feeding and gaining the trust of 4 feral cats for over a year, since they were kittens. Prior to this, I had no care experience with cats, as all my pets have been dogs. I was able to gain their trust enough to pet all of them and pick up 3 of them (the other is a VERY flighty and sassy calico, so I rarely try to pick her up).\nThe other day one of them had half of his tail entirely degloved down to the bone. We don't know from what, but luckily the vets said it was a clean wound and not a bunch of torn ligaments.", "961" ], [ "They amputated it and told us to keep him in doors, which we were hesitant about as our home is not cat proof, but decided to keep him in a bathroom as I've seen people on YT do with newly adopted cats.\nHe usually is not that affectionate. Yes, he will let us pet him and likes his neck scratched but he doesn't seek us out that often. But as of now (its only been 2 or 3 days), he is on constant purr mode when I enter the room, pacing back and forth to get me to scratch his butt or neck. He also rolls over on the floor, like his brother (the most affectionate of them) does when telling us \"oh get this spot here\" (he is very spoiled lmao). This morning he climbed into my lap and laid down to go to sleep. When I tried with any of them before to put them in my lap, they'd immediately jump down.\nSo is this normal?", "311" ], [ "Help!\nMy dog just got his leg bone out of the pubic bone after an accident with a much bigger dog that did not have a leash on. We got him to the doctor, now his leg is back on, he needs to have some cage rest for 2 weeks.", "833" ], [ "Now the big question, how can I make him do his needs inside? He is 14 years old and almost never poops or pees inside. He uses his leg a lot when he pees and poops. What should I do? What cand be done for him to get to poop inside on a poopie mat? (They told us at the vet that he should poop any minute but we have yet to see that, it’s been 6 hours)", "833" ], [ "Putting a cat up for adoption\nI have 4 cats, 2 bonded, the others over time. The bonded ones I don’t believe are truly bonded, they don’t seem to care about each other at all.", "176" ], [ "One of them is very shy, terrified of any movement and of the other cats. She only comes out to eat and use the litter box and on occasion she wants to be petted but acts like she is terrified of me and the other cats are all times. Is it wrong for me to want to regime her in hopes that she would do better in a single quiet household? I’ve had her 1.5 years and she is 2.5 years old.", "679" ], [ "Head twitching advice needed\nCame home for lunch and my cat seemed fine. After I finished lunch I noticed my cat was sleeping on the bed and his tongue had been sticking out with drool on the sides of his mouth. Every minute or so he sticks his tongue out and his head twitches. All he ever wants to do is play and eat. Wont play.", "954" ], [ "Won’t eat treats. He is a very affectionate cat and I was petting him and he hissed at me which he’s never done. Cat pretty much only wants to lay on the bed. He is reacting to everything differently. Anyone know what’s going on or what I can possibly do??", "954" ], [ "Kitten won’t stop peeing everywhere\nHello, any help would be greatly appreciated. I got my kitten (10 months old) when he was 2 months old. He used to pee around the house every couple of weeks, now almost every day, 9/10 times when I’m asleep. However, he poops in the litter box.", "311" ], [ "The vet tested his pee and found that he had a bacterial infection. We gave him the medicine, and he should have been responding to it by now, but he hasn’t. The vet recommended a diffuser to calm him down. But it’s a hundred dollars, and I’m not sure if it will work. What should I do?", "833" ] ]

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[ [ "As encouraged in the comments, I'm giving a more general answer regarding constraint violation or constraint propagation in search in the context of CSP solvers. In a sense, the theory of search in CSP/SAT majorizes other approaches. My answer deals with complete search methods, although hybrids exist (combine local search with inference).\nA constraint satisfaction problem (CSP) as a triple $\\langle X,D,C \\rangle$, where $X$ is a set of variable, $D$ a set of domains (one for each variable), and $C$ is a set of constraints that limit or specify allowable combinations of values. Solving CSP problems is obviously hard (SAT is a special case). Also, the obvious way of solving a problem is search. Search can be replaced or at least combined with a specific kind of inference called constraint propagation. For example, consider modeling a Sudoku puzzle as a CSP. After a variable has been assigned to some value (a number placed into a cell), we an call an algorithm, that propagates the consequences of that variable assignment. If we notice this leads to a non-solution, we undo that variable assignment, and try another one. Many different algorithms for propagation exist, such as Mackworth's AC-3. As is with the type of inference used, the variable and value selection heuristics all play a major role in the efficiency of the solver.\nA key aspect that was noticed early on was that effective heuristics were \"fail-first heuristics\". Whatever we choose (what variable to assign next, what value to assign to it), it should be most likely to fail soon, thereby pruning the search tree.\nA popular heuristic for choosing a variable is the minimum-remaining values (MRV) heuristic: pick the variable with the fewest legal values. This is a \"fail-first heuristic\" that was already proposed in 1965 by <PERSON> and <PERSON>. Much effort has since gone into understanding and enhancing this already powerful heuristic. It was noted that MRV only exploits information about the current state of the problem.", "399" ], [ "The heuristic can be made adaptive by exploiting the information about the previous states as well. The so called dom/wdeg heuristic proposed in 2004 is still widely considered to be the most effective general approach known. The idea is as follows:\n1. Associate each constraint with a weight, initially set to 1\n2. Everytime a constraint is responsible for a dead-end, its weight is incremented\n3. When choosing a variable, first choose the one with fewest legal values\n4. In case there are multiple choices, broke ties by dividing with the weighted degree, which is the sum of weights of the constraints involving the variable in question, and at least one other unassigned variable\nWhat good does this do? Well, the weight on the hard constraints increases as the search progresses. In other words, the search is being guided towards hard parts of the problem. Once again, obviously one is more likely to fail when faced with a hard problem, and here we again see the \"fail-first principle\" in work.\nBy the way, the dom/wdeg heuristic has been observed to have a nice synergy with specific random restart strategies in 2008 by <PERSON> [1]. <PERSON> observed the so-called geometric strategy was the most suited one, making the dom/wdeg even more powerful.\n[1] <PERSON>, <PERSON> (2008). A study of adaptive restarting strategies for solving constraint satisfaction problems. In Proc. 19th Irish Conference on Artificial Intelligence and Cognitive Science-AICS (Vol. 8, pp. 33-42).", "915" ], [ "Find dominated or subsumed linear inequalities efficiently\nProblem statement\nGiven a set of $N$ linear inequalities of the form $a_1x_1 + a_2x_2 + ... + a_Mx_M \\geq RHS$, where $a_i$ and $RHS$ are integers. The inequality $A$ dominates or subsumes inequality $B$ if all its coefficients are less or equal and $RHS_A \\geq RHS_B$. Most inequalities are sparse, i.e. most coefficients are zero. Usually, both $N > 1000$ and $M > 1000 $. I'm trying to identify dominating or subsuming inequalities efficiently.\nWhat are quick ways to find a) if an inequality is dominated by any other inequality, and b) which inequalities are dominated by a given inequality?\n(Monte-Carlo algorithms are fine, that only report correct results most of the time)\nProposed solutions in the literature\n<PERSON>, N. and <PERSON>, A., 2005, June. Effective preprocessing in SAT through variable and clause elimination. In International conference on theory and applications of satisfiability testing (pp. 61-75). Springer, Berlin, Heidelberg. (chapter 4.2) discuss a variant of this problem in the context where all coefficients are binary, i.e. $a_i \\in {0, 1}$. They propose occurrence lists, one per variable $x_i$, containing all inequalities with non-zero coefficients $a_i$. Additionally they use a hashing scheme, similar to Bloom filters, to quickly eliminate candidates. I don't see how to translate this to non-binary coefficients.\n<PERSON>, T., <PERSON>, R.E., <PERSON>, Z., <PERSON>, <PERSON> and <PERSON>, D., 2020.", "603" ], [ "Presolve reductions in mixed integer programming. INFORMS Journal on Computing, 32(2), pp.473-506. (chapter 5.2) discuss a variant of the problem, but don't solve it. They first hash inequalities by indices of non-zero coefficients and the coefficient values. Additionally, they limit their search to a small subset of inequalities.\n<PERSON>, S., 2013. Simple and efficient clause subsumption with feature vector indexing. In Automated Reasoning and Mathematics (pp. 45-67). Springer, Berlin, Heidelberg. describes Feature Vectors for clauses and a kd-tree-like data structure to query combinations of feature vectors.\nThings I've tried\n* The trivial solution is to check all pairs of inequalities in $O(n^2)$. Unfortunately, that's too slow for my application where I have millions of inequalities.\n* I tried performing a random projection of the coefficients for every inequality, resulting in a projection $p_j$ for every inequality. An inequality $j$ can only dominate inequality $k$ if $p_j \\leq p_k$. Thus we don't have to check all pairs. I repeat this process 10 times with multiple random projections, and use the random projection where I have to check the fewest pairs. In practice this is not effective, as most coefficients are zero - and it's unlikely that a random projection focusses exactly on the few non-zero elements. It doesn't help nearly enough.\n* Similarly I implemented Feature Vectors, but couldn't replicate the performance reported by <PERSON>.\n* AFAIK, multi-dimensional data structures break down in high-dimensional scenarios (curse of dimensionality). I'm not aware of indexing techniques that work for high-dimensional range queries.\n* I thought about Bloom filters, unsuccessfully.\n* I thought about randomized algorithms, unsuccessfully.\nDo you have any other ideas?", "603" ], [ "I will try to address why the concepts of NDTM and NP are useful, and possibly what motivated their study.\nNDTM is one of many variants of turing mahcine. For example, the classical (deterministic) Turing machine can be equipped with multiple heads and tapes, randomness or quantum states. It can also be constrained by a limited alphabet, limited tape or pre-determined head-movements (see here).\nA TM is said to decide a language (a set of words using a pre-defined alphabet), if it can halt on any input written on the tape, and accept precisely inputs belonging to the language. A language is called decidable if any TM decides it. Similarly, a function $f$ on natural numbers is said to be computable if there exists a TM which, given an input $n$, halts with $f(n)$ written on the input tape.\nIt turns out that all of the mentioned variations of TMs (including NDTM) are equivalent in the set of functions they can compute (similarly, the languages they can decide). This holds for other, much more different models than TMs, and has led to the <PERSON>-Turing thesis, which informally hypothesizes that any \"reasonable\" model of computation is equivalent to the classical Turing machine. In this aspect, NDTMs are useful as an example of fantastical computational models that are nonetheless as strong as a classical TM, supporting the <PERSON>-Turing thesis.\nAs far as I understand (see here and here for history), <PERSON> himself did not focus on complexity classes, and so the previous reason might have been his sole motivation. However, later on it was discovered that different TM variants are not equivalent in the set of problems (languages and functions) they can solve in a certain amount of computation steps (time), bound on working-tape size (memory) and success probability. With this finer resolution, it turns out that the different models are very different, resulting in a zoo of complexity classes for problems.\nI hope this is helps show why NDTMs (and the NP complexity class) are not a definite model for the problems science could potentially solve efficiently, but just one of many variations of computational models (less realistic than random and quantum machines, for example).", "915" ], [ "There are, however, some reasons for why the specific class of nondeterministic polynomial time ($NP$) is such a popular attraction of the zoo:\n1. It is relatively easy to explain and reason about. While researchers are working on many other open problems in complexity theory, the question of whether $P\\neq NP$ requires only basic knowledge in math to understand, and the concept seems so intuitive that it invites many solution attempts from amateur researchers.\n2. Whether a problem is solvable in polynomial time in a computational model is seen as an approximate measure of practical tractability (this is <PERSON>'s thesis).\n3. Any complexity bound derived by NDTMs can be seen as a bound on verification time by classical TMs (see here for why). Since classical TMs are used as models of practical computation, this has practical implications.\n4. Many real-world important problems just happen to be not just in $NP$, but $NP$-complete. This means that if $NP$ is indeed a different complexity class than $P$, all of these important problems are not solvable in polynomial time with classical TMs.\nNote that the fourth reason is unrelated to how realistic NDTMs are as a computational models (compared to classical TMs or other variants), or to any initial motivation for the invention of the concept. NP-complete problems are just surprisingly common in real life, and the scientific interest in them mirrors that.", "915" ], [ "This question is a bit strange. I see it's based on the Wikipedia article, but that article is also a bit strange. I will try to clarify some concepts.\nFirst, we have a language that can be used to make claims whose meaning are formally defined. Such a language may allow us to say, for example, that if $x$ is a Person, then $x$ is a Human, which can be done in first order logic as $\\forall x (\\neg\\mathsf{Person}(x) \\vee\\mathsf{Human}(x))$, in a rule language like Datalog as $\\mathsf{Person}(x) \\rightarrow \\mathsf{Human}(x)$, in description logics as $\\mathsf{Person} \\sqsubseteq \\mathsf{Human}$ and so forth.\nSecond, we have semantics, which formally defines the meaning of claims in the language. One way in which the semantics of a language can be defined is using model theory, which essentially maps terms in the language to sets, elements, and relations between sets; for example, we can map the term $\\mathsf{Person}$ to a (hypothetical) set $P$ and $\\mathsf{Human}$ to a (hypothetical) set $H$, and define the above claims as formally meaning $P \\subseteq H$. This gives rise to the notion of models, where for example, $P := { \\mathrm{Fred}, \\mathrm{Jill} }$ and $H := { \\mathrm{Fred}, \\mathrm{Jill}, \\mathrm{Tom} }$ is a model satisfying a given set of formal claims (since $P \\subseteq H$), while $P := { \\mathrm{Fred}, \\mathrm{Tom} }$ and $H := { \\mathrm{Fred}, \\mathrm{Jill} }$ is not a model (since $P \\not\\subseteq Q$). In turn, models give rise to entailment between sets of formal claims, where for example, given ${ \\mathsf{Person}(\\mathrm{Tom}), \\mathsf{Person} \\sqsubseteq \\mathsf{Human} }$ (in whatever language), we know this entails ${ \\mathsf{Human}(\\mathrm{Tom}) }$ as any model of the former set of claims must be a model of the latter set of claims.\nThird, we have reasoning procedures to decide entailment.", "330" ], [ "One way in which this is done is to use inference rules. For example, we may derive a rule such as $(\\mathsf{C} \\sqsubseteq \\mathsf{D} \\wedge \\mathsf{C}(x)) \\rightarrow \\mathsf{D}(x)$ to support reasoning with respect to the $\\sqsubseteq$ operator in description logics. This rule may be applied for forward-chaining or backward-chaining. But there are many forms of reasoning procedures suitable for different types of languages; for example, for more expressive description logics, (a finite set of Horn) rules is not sufficient to guarantee complete reasoning, and so tableau-based methods are often used. Also one reasoning procedure can be useful for reasoning in different languages, where Datalog, for example, is natively based on rules.\nReturning to the question:\nReasoner is forward chaining inference engine (https://en.wikipedia.org/wiki/Semantic_reasoner) as opposite to Prolog backward chaining SAT solver (for queries).\nA \"reasoner\" can adopt multiple strategies, including, but not limited to, forward-chaining on rules. Engines that apply tableau-based methods, backward chaining, resolution, etc., are also \"reasoners\". (The article you base the question on never claims that reasoners are forward chaining rule engines, but mentions this as one strategy.)\nWhy there is reasoner for description logics and not for other logics?\nThere are reasoners for other logics. For example, Vampire is a reasoner for first-order logic, XSB is a reasoner for Prolog, or just check here for a list of different reasoners for different languages.", "904" ], [ "Revisiting this due to some related research I am doing, the disagreement between myself and some of the others who answered, can be assimilated into a holistic understanding in which we were all correct. But IMO the adopted computer science terminology “bounded nondeterminism” is an incorrect oxymoron (which was my point before).\nThey key point is to distinguish between bounded and unbounded nondeterminism.[1]\nNondeterministic Turing machines (aka “NTMs”) have bounded nondeterminism in that each state transition has a bounded number of possibilities, i.e. the number of programs (aka “configurations”) is finite. The tape remains unbounded, so the proof of termination remains undecidable. But for any given input that halts, the output is deterministic and bounded in time― i.e. for any input the result is deterministic or doesn’t terminate. Also NTMs execute all possible configurations in parallel, so they execute exponentially faster than emulation of NTMs on deterministic Turing machines (aka “DTMs”).[2]\nThere really isn’t any nondeterministic relationship between inputs and outcomes in NTMs because the outcome is always the same for any input or initial state, which is evident because they they can be emulated by DTMs without any added randomness.[2] Undecidable is not the antithesis of deterministic, because not halting is also a deterministic result. Deterministic machines always have the same outcome for a given input, even when that outcome is to not halt. The localized nondeterminism of NTMs is in each state transition of the executing algorithm.", "915" ], [ "It is undecidable a priori which path of the tree might terminate providing the output state. But undecidability is not nondeterminism. Thus the term “bounded nondeterminism” is intended to describe the localized indeterminacy within the state machine but not the relationship of inputs to results, hence the concept of “bounded”. I still think the term “bounded nondeterminism” is an oxymoron and it could have been more accurately described as a “parallelized state transition” <PERSON> machine.\nWhereas, for any given input or initial state, unbounded nondeterminism (aka “indeterminism”) has an unbounded number of possible states. Unbounded nondeterminism involves not just the number of possible configurations of programs, but some unbounded external state which is not part of the input or initial state, such as unbounded delays. And thus outcomes can vary on repeated executions for the same input or initial condition; thus is not a deterministic relationship between inputs and outcomes.[3]\nRandomized and probabilistic algorithms employ some nondeterminism, i.e. random selection of possible configurations possibly bounded in number of configurations, but they don’t execute all the possible configurations as NTMs do. Thus they are not deterministic unless the randomness is deterministic (e.g. PRNG) and the initial state of the entropy for the randomness is considered to be part of the input.\n[1] https://en.wikipedia.org/w/index.php?title=Unbounded_nondeterminism&oldid=710628370#Nondeterministic_automata\n[2] https://en.wikipedia.org/w/index.php?title=Non-deterministic_Turing_machine&oldid=754212081#Equivalence_with_DTMs\n[3] <PERSON>, <PERSON> and <PERSON>: The Actor Model (everything you wanted to know...). Jump to the 17:44 minute mark.", "915" ], [ "In general, this is a very relevant and interesting research question. \"One way is to run existing solvers...\" and what would this even tell us exactly? We could see empirically that an instance seems hard for a specific solver or a specific algorithm/heuristic, but what does it really tell about the hardness of the instance?\nOne way that has been pursued is the identification of various structural properties of instances that lead to efficient algorithms. These properties are indeed prefered to be \"easily\" identifiable. An example is the topology of the underlying constraint graph, measured using various graph width parameters. For example it is known that an instance is solvable in polynomial time if the treewidth of the underlying constraint graph is bounded by a constant.\nAnother approach has focused on the role of hidden structure of instances. One example is the backdoor set, meaning the set of variables such that when they are instantiated, the remaining problem simplifies to a tractable class. For example, <PERSON> et al., 2003 [1] show that even when taking into account the cost of searching for backdoor variables, one can still obtain an overall computational advantage by focusing on a backdoor set, provided the set is sufficiently small. Furthermore, <PERSON> et al., 2007 [2] note that a solver called Satz-Rand is remarkably good at finding small strong backdoors on a range of experimental domains.\nMore recently, <PERSON> et al., 2008 [3] propose the use of the tree-like space complexity as a measure for DPLL-based solvers. They prove that also constant-bounded space implies the existence of a polynomial time decision algorithm with space being the degree of the polynomial (Theorem 6 in the paper).", "915" ], [ "Moreover, they show the space is smaller than the size of cycle-cutsets. In fact, under certain assumptions, the space is also smaller than the size of backdoors.\nThey also formalize what I think you are after, that is:\nFind a measure $\\psi$, and an algorithm that given a formula $\\Gamma$ decides satisfiability in time $O(n^{\\psi ( \\Gamma )})$. The smaller the measure is, the better it characterizes the hardness of a formula.\n[1] <PERSON>, <PERSON>, <PERSON>, and <PERSON>. \"Backdoors to typical case complexity.\" International Joint Conference on Artificial Intelligence. Vol. 18, 2003.\n[2] <PERSON>, <PERSON>, <PERSON>, and <PERSON>. \"Tradeoffs in the Complexity of Backdoor Detection.\" Principles and Practice of Constraint Programming (CP 2007), pp. 256-270, 2007.\n[3] <PERSON>, <PERSON>, <PERSON>, <PERSON>, and <PERSON>. \"Measuring the Hardness of SAT Instances.\" In Proceedings of the 23rd National Conference on Artificial Intelligence (AAAI’08), pp. 222-228, 2008.", "915" ], [ "I think your problem is not the algorithm itself but a few surrounding notions.\n1. A literal is a variable or its negation: $a$ or $\\neg a$ for example.\n2. A clause is a disjunction of literals: $a \\lor b$\n3. A unit clause contains only one literal: $\\neg a$ is an example\n4. The empty clause contains no literals and is written ${}$ or $()$ or $\\Box$. The empty clause is not satisfiable and you can think of it as equivalent to $False$.\n5. A conjunctive normal form (CNF) formula is a conjunction of clauses: $(a \\lor b)\\land(\\neg a)$\n6. The empty formula contains no clauses and is written $\\emptyset$. The empty formula is satisfied by every assignment and you can think of it as $True$.\nPlease notice the difference between an empty clause and an empty formula. These are the basic objects that the algorithms manipulates. Now we come to the operations.\n1. The unit rule says that if we have a unit clause $\\neg a$ and a clause $a \\lor \\theta$, then to satisfy the formula, we must satisfy the clause $\\theta$.", "904" ], [ "This is because to satisfy the unit clause $\\neg a$, the variable $a$ must be set to $False$ meaning, we cannot satisfy $a$, so we must satisfy $\\theta$. Unit propagation repeatedly applies the unit rule.\n2. Observe that in implementing the unit rule as above, we are deleting unsatisfiable literals from a clause and leaving only literals that may help satisfy the clause. If we delete all literals, we have the empty clause, which means that no constraint of that clause is satisfiable, in turn meaning that the entire formula is not satisfiable.\n3. The pure literal rule is based on the observation that if a variable occurs only with one polarity in the entire formula, meaning we either only have $a$ or only have $\\neg a$ in the formula, then there is never going to be a constraint of the form $a \\land (\\neg a \\lor b)$ in the formula. So we can make that literal true. This will satisfy every clause in which that literal occurs, so we can delete those entire clauses.\nThere is a difference between unit propagation and the pure literal rule. Unit propagation deletes literals from inside a clause and brings us closer to discovering if there is an empty clause, in which case the formula is not satisfiable. The pure literal rule deletes entire clauses and brings us closer to the empty formula, in which case the formula is trivially satisfiable.\nIf you consider the two cases above, you see that it does not cover all possible behaviour. Specifically there may not be any unit clauses and there may not be any pure literals. In this case, to make progress, we pick a literal that does not occur in a unit clause and assign it a value. The choose-literal step can be viewed as adding a unit clause to the formula, which has the effect of triggering more unit propagations.", "915" ], [ "Thanks for your answers. As <PERSON> pointed, the second problem: Given a directed graph and three distinct vertices S and T and I, deciding if there exist a simple path from S to T going through I, is indeed NP complete.\nFrom the paper from <PERSON> and <PERSON> and <PERSON>, it is clear that the pattern graph S->I->T is one for which the fixed directed subgraph homeomorphism problem is NP complete since it is a tree of depth 2.\nHere are few definitions from this paper: \"The subgraph homeomorphism problem is to determine: if a pattern graph p is homeomorphic to a subgraph of an input graph G. The homeomorphism maps nodes of P to nodes of G and arcs of P to simple paths in G. The graphs P and G are either both directed or both undirected. The paths in G corresponding to arcs in P must be pairwise node-disjoint. The mapping of nodes in P to nodes in G may be specified or left arbitrary.", "433" ], [ "This problem can be viewed as a generalized path-finding problem. For example, if the pattern graph consists of two disjoint arcs and the node mapping is given, then the problem is equivalent to finding a disjoint pair of paths between specified vertices in the input graph.\"\nBasically, only the pattern graphs that are trees of depth 1 and their reverse graphs (with possibly loops arcs on the root) can be solved in polynomial time.\n\"Let C be the collection of all directed graphs with a distinguished node called the root possessing the property that either the root is the head of every arc or the root is the tail of every arc. Note that the root may be both the head and tail of some arcs and thus loops at the root are allowed. Equivalently, a graph is in C if, when all loops at the root are deleted and multiple arcs between pairs of nodes are merged into single arcs, the resulting graph is a tree of height at most one.\"\n\"Next we show that for each pattern P not in C the fixed subgraph homeomorphism problem with pattern P is NP-complete.\"\nI have not read the proof yet so I'll stop here.\nThere is also a close connection from the problem I have just mentionned and the two disjoint paths problem as pointed out by one of my collegue. The two dijsoint paths problem is:\n\"Given a directed graph and four distinct vertices S1, T1, S2, T2, decide if there exist two paiwise node disjoints simple paths from S1 to T2 and from S2 to T2\".\nThis problem for directed graphs is well known to be NP-complete. However, there is a simple transformation from the two disjoint paths problem to the S->I->T problem. In order to do that we need to add one extra node I and the two extra edges T1->I and I->S2.\nIf there was a polynomial algorithm to solve the S->I->T problem, we could use it to solve the two disjoint paths problem in polynomial time with the simple transformation above and by solving the S1->I->T2 problem.", "433" ] ]

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[ [ "Beau Is Afraid\nLoved the chaos and anxiousness of the first hour. The comedy that came with his living situation, the medication, and figuring out his trip to see his mother had me from the get-go. Moving into the strange suburban setting eventually introducing the forest play and its unique prop-set piece story telling was thrilling.", "700" ], [ "Loved the sense of development and exploration of themes it got into. The absurdity brought plenty of sprinkled mystery like plot points which kept me piecing things together and trying to figure out where <PERSON> was going. The final hour unfortunately had me feeling the runtime and things felt like they went from absurd and in control, to completely go off the rails.", "577" ], [ "The Killer\n75/100\nA “not quite” total return to form for <PERSON> while still giving you that sweet spot you love from his films. Like one of those where I had a giant fucking smile the entire time in the theater, but also scratched my head when we jumped to the 4-5th location thinking, “okay when we gonna have something big pop off, or where we heading with this?” type experience. <PERSON>’s monotone narration is cocky, cool, and obsessive.", "698" ], [ "It immediately sucks you in from the opening in Paris. The hilarious bits that ensue of his fuckups deliver tension, globetrotting adventure, and Chicago (extra points for that)! It does feel to be missing that extra <PERSON> magic to boost this to the top of his filmography, but the theater viewing sounded and looked stunning. Not too shabby!", "698" ], [ "Triangle of Sadness\nSitting on Triangle of Sadness for a couple days now and I’m still not fully sure. It’s obviously a harsh and stressful push on the rich, and their familiar overprivileged, stuck-up fiasco of a life, but it also examines the cruel survival of society and it’s very rich and complex on those matters. Sure there are plenty of topics that this film symbolizes that I didn’t pick up on, and some I might never, but the whole thing is for those who think. You must pay attention and you must be willing to let your interpretation of the events of this film run free, especially the ending.", "541" ], [ "Each performer in this film does their job right, molding on each dramatic commentary of this film so well and they emphasize such intensity when they speak that it just makes it even more interesting. <PERSON>, <PERSON>, <PERSON>, <PERSON>, and an immaculate performance of beauty and pain from the late <PERSON>. While I do feel it was too complicated for me at point where I wasn’t quite sure where to be with the characters or just weirded out, the whole film really is a form of masterclass when it’s all put into perspective. <PERSON> is a great thinker and it’s very clear in this latest film, and is one to definitely stack your opinion on upon rewatches.\n🔙<PERSON>", "529" ], [ "<PERSON>\nThe first half of this is so good. The second half, I think was difficult for the filmmakers to make sense out of (and how can you make sense of senseless tragedy? I’m not sure, but that is why we create art, in the end).\nThe chemistry between the brothers and how they all were suffocating under the pressure from their father was done so well.", "306" ], [ "But when tragedy strikes, it devolves into scene after scene of unfortunate events that feel isolated and without much meaning. <PERSON> character is great, but the other brothers don’t get nearly enough fleshing out to fully appreciate their arcs. That said, I understand it’s a delicate balance because it’s a true story.\nThe tail end brings it home, though.", "352" ], [ "The Hypnosis\nA comedy about anxiety, how it’s both a prison and a necessity. Hilarious first half before the uncomfortable second.", "471" ], [ "The leads make it work but I can’t help but feel it could have been a lot more if the couple felt more fleshed out. As hilarious as it was to watch <PERSON> stare at his girlfriend in horror for much of the film it never felt like there was a real sense of shared history outside of a few key moments.\nLikewise the tech setting feels like distracting window dressing, the film has almost nothing to say about it, and to be fair I don’t think it really needs to necessarilly. However it leans on it a little too heavily for it to be so apathetic about it.\nGreat ending", "325" ], [ "The Funhouse\nStill holds up so well, childhood favorite horror film scared the bejesus outta me growing up watching this on late night cable. The premise is simple yet totally engaging a teenage girl lies to her parents who forbid her from going to a traveling carnival, she goes against her better judgment to fit in with her friends.", "79" ], [ "This doesn’t sit well with her because she doesn’t like lying to her father. The peer pressure of attending the carnival ramps up to the double date to sneak of the funhouse ride and stay the night\nThe atmosphere is eerie and really sets the tone even if the story doesn’t get crazy til the third act. The unmasking of <PERSON> is probably in my top ten most shocking movie moments of my childhood!\n#1 in the books", "465" ], [ "How to Train Your Dragon: The Hidden World\nWicked cool trilogy, can’t believe I put it off for this long. The leaps in improvement with the animation between films was incredible to watch. Then I realized there was a four and five year gap between the sequels. I can’t even comprehend that long of a wait; I was buzzing with excitement to hop right back into the world. But boy, do I wish I was there for the waiting. Mainly because the growth of the lead characters between the films was so well done—so organic, so fulfilling and warm and made sense.", "462" ], [ "They weren’t just the same characters by name in new situations; they were different characters with each movie, only wiser, stronger, more confident. A lot of animated films have their characters learn a lesson but are cut-and-paste caricatures with each follow-up. Neat to see a trilogy geared towards kids take that stuff seriously. I wish we had more, while wishing it ended differently. But I’ll never stop thinking of <PERSON>, <PERSON>, and <PERSON>’ story arcs. That’ll stay with me. You know the lot at Dreamworks Animation is doing something right when you feel like you’ve watched dear friends grow up before your eyes.", "19" ], [ "Talk to Me\nFeels like the good concept-heavy horror films of the 2010s like It Follows but bogged down by the more modern Hereditary / Us family drama that I really don't find much interest in. If this didn't screech to a halt halfway through to focus on a non-interesting mother-daughter plotline then it'd be really really good for me I think.\nI still don't care much for the ooey gooey designs of the spirits, but the vibes are fun until that point and the concept is real neat throughout. Some great haunting moments here and there, but I'm getting very tired of the <PERSON>-bash-his-head-into-school-desk shtick.\nHaving spoken negatively about the main plotline however, I do think a film has never won me over by such a far margin as this one by its ending.", "823" ], [ "Brings it all back in a really rewarding way that condemns the character appropriately. Made me smile all silly like. Sequel already in the works tho 🪨", "583" ] ]

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[ [ "<PERSON>\nMy thoughts primarily align with my original review, so I'll direct you there rather than scrape after a novel rephrasing, as it's one I find worth a smidge've pride. There is, however, one point of mine I wanna relitigate here, the statement running, \"We're off to the races, and won't make contact with more sensible reality for a good hour,\" with regards to <PERSON> devil popping from behind a parish in the second movement.\nWhile it's true the opening chapter's play at pure filmed lecture stylings with the direct source citations and the pointer tapping over medieval woodcarvings remains by the wayside in favor of vignettes depicting all-consuming witch hunts, midnight rides with the horned one, and hysterical outbreaks in secluded convents, I don't think my claim fair in view of the trials and persecutions which span chapters three through five. These are the meat of proof <PERSON> does not shift from academia to spookhouse tactics as simple means of shocking the audience or indulging a belief in witchcraft as undoubtedly real. Anything fantastical presented before the inquisitors is explicitly coerced under torture of physical and psychological natures alike, or else the spiteful curses of a long-wronged woman dragging those who denigrated her with false accusations down to this level.", "417" ], [ "The shots of witches smearing mixtures of piss and mud upon a victim's door, or dancing naked as they smooch Satan's ass in the pale moonlight, they're filmed with as much grungy veracity as their counterparts in chapter two, but the context of edited storytelling matters a great deal, and <PERSON> clearly means these delves into fantastical as tragic moments when the victimized break beneath the lash and rack, giving their tormentors precisely the proof they need to exercise injustices they meant to perpetrate no matter what. A full-throated confession from out the thumbscrews will prove the existence of witchcraft in this body just so well as demanding tears on command and declaring dry eyes a smoking gun, after all.\n'Tis a sobering demonstration of his thesis, that idea of superstition as the readiest expression and excuse for prejudice. Flying so far off the handle in visual depiction of the ghastliest practices, only to cast these shadows as concrete-solid for the power and justification they inspire in the minds of those entrenched and enabled by status to cast their own subtler, crueler spells. We've our feet firmly upon the ground during these wildest of fancies, for one cannot escape the roots nor reasons behind such beliefs in devilry and the inherent purity of the accuser's heart. Those weirdest and wooliest of conjurations exist near-always in service of minds which wish pain and suffering for the most mundane reasons; to fail at recognizing the relation is to fail at steeling ourselves against whatever weaknesses in our own belief systems might make us susceptible to such insidious, prosaic bewitching.", "285" ], [ "The Detective\nA film whose visual storytelling and thematics fall perfectly in-tune with its protagonist. The restrained yet hungry camerawork, the attentive detail in decoration on certain sets, and the highly controlled acting all communicate The Detective as a film working in mores decades strong at time of release, a hard-boiled procedural about crime and death in the big city, where the weary are worn a little thinner every day but ultimately get their man because that's just the way of things. In content and restlessness, though - its heavier than expected emphasis on the systemic pervasiveness of corruption and brutality within the police force, its serious examination of the consequences born from homophobic rage directed outward and inward alike, its brushes with explicit sex and violence - mark a film eager to participate in the rising ways and ideas of New Hollywood. We want so desperately to explore these exciting, murkier corners of the human spirit and societal rot, yet see no reason their illumination shouldn't be done with the same class and level heads so long in vogue. <PERSON> <PERSON> makes an ideal lead within this push-pull approach, a man who regards himself as basically good in contrast to the proud jackboots and career yes-men populating his department, and for this noble-minded separation cannot deny his own failings in love and prejudice and desire for everything they offer you to toe the line. Every time he stares long and hard into the camera or crumples his face in the corner, you feel he knows just where the next generation dictates the wind blows, tries to orient his feet to follow, but can't escape the ingrained magnetism back to status quo no matter how rotten.\nBeing so caught between eras does introduce aspects one might call flaws: extended introspection through flashback can get draggy while you're waiting on the next explosive moment, and some efforts to amplify tension through action scenes in the new way come across hokey (doubtless did back then too).", "217" ], [ "<PERSON>'s personal sacrifices at the finale and the plot work leading into them also edge a bit too close to reassurance one singular hero can put it all right again for my taste, despite dialogue establishing this very likely isn't the case. This is a picture which honestly means its marketing line about exploring the world of police work with a properly mature audience in mind, so even near-indulgences of Leland's future cinematic mutation into <PERSON> leave me uneasy. In view of how hard this hits when it really wants (\"Keeping 'em naked makes 'em easier to handle. I got the idea from a documentary on the Gestapo,\" says the black rookie hungering after a promotion) and how the style choices render it so unlike any predecessors or successors, I can accept these weaknesses as the consequences of dancing so boldly on a knife's edge. World's not remotely a nice place, the best of intentions are but grist for the mill, and prejudices kill best when held by those who can't examine them, or won't because there's something in it for temporary blindness. This mother can still crush if you're open to it.\n(Surprisingly small part for <PERSON>, all things considered.)\nShrink the Watchlist Challenge! Theme 2 - the most recently added (at the time I made this list like three years ago) film!", "698" ], [ "Night of the Living Dead\nIt's funny the film that immediately inaugurated the modern conception of zombies and with it the fantasy of zombie survivalism makes the prospect of surviving against the zombie horde look so unappealing. Like, such is standard for zombie survival movies, you're never under any illusion it's gonna be pretty or easy defending the homestead or bunker or wherever you're holed up, but <PERSON> places a lot of emphasis on the gnawing paranoia. The pacing all round the borders reinforcing and doubly reinforcing potential points of entry, sitting down believing you've done enough and then getting up to go at it again because you can't ever let yourself think it's enough. The struggle to get any two people on the same page about basic strategic angles, much less wrangle an entire house full of people experiencing sickness and breakdowns and threats to their ego into agreeing on anything sensible.", "965" ], [ "The clammy second guessing what keeps you in one place too long and renders slow, thoughtful options inert within minutes. The chance those who do have their feet under them will only regard you as another ghoul to wipe out when their organized patrols sweep through your infested area.\nOn average, your ordinary person will react to distressing new challenges with retreat and paralysis and ploys to defend whatever status they clung to in the beforetimes, even if the beforetimes were a mere two hours ago. There is frighteningly little chance controlled mobilizations and mass media reporting can deal with threats outside their comfort zone, not when early days already finds them massaging prejudices and clawing after reasons why rather than the concrete hows of effective crisis management. One out've context problem, one night dominated by a threat we can't readily address with pre-designated tools, and the terminus of civilization's already on the roll. No amount of prepping and planning will save your skin or your soul while the basic facts of human inadequacy remain in play.\nI mean I'd never accuse those who indulge zombie survival LARPing of having especially strong media literacy skills, but it's still a bit funny THIS movie of all pictures kicked off their favorite \"what if it were legal for me to shoot people indiscriminately\" fantasies.", "999" ], [ "The Toll Gate\nThe \"de facto\" end of the Western journey that began with King of the Bullwhip sees us escape the typical constraints and admitted repetition of Poverty Row and instead farther in time towards Paramount's lot during the silent age, with cinematographer <PERSON> being a tangential link to the mystic, foreboding, and quite eerie snapshots of 1932's Mystery Ranch, a film I may have to hunt down in due time. I'll start with the visuals of the film because these hold some very lovely, yet rugged shots that make even the usual workmanlike angles feel alive, detailed shots of posses hunting for their wanted man illuminated by grave shadows, dramatic tinting that makes nighttime focus of the lone town in the horizon as uninviting and distant befitting of our main character, outlaw <PERSON>, fleeing for uncertain safety, and some really ornate intertitles occupied by objects and faces important for their scenes, a game of craps interrupted with words and a pair of dice, <PERSON>'s thoughts of intense plotting captured by his masked visage, it's got a lot going for it that stuns me, a person who admittedly doesn't venture into the silent era often, and while both shots and intertitles yield more impressive results in other films from the era, seeing these in a genre that, at this point, required the most simplest of results is a breath of fresh air.\nSeparating itself from the typical Western as well (or at least the Westerns that would flood theaters 20 years from now), <PERSON> lands in a much more ambiguous role as our leading man, not quite a white-hat hero yet never truly a black-hat villain to scorn, merely a man who hides any personal connection behind a stoic stone-face, and the film finds his journey towards not only getting revenge on the man who betrayed him, but also find salvation and redemption from the damage he's committed, in a path most unforgiving and most unglamorous.", "217" ], [ "<PERSON> becomes the type of man unwilling to let a member of his gang leave scot-free as the <PERSON> of his inverted disciples, yet also becomes the type of man unable to let an innocent child drown whilst a mortified mother watches, equal parts murderous and sympathetic that results in a tough read on the man and ensuing tension towards how <PERSON>'s story will unfold, and in similar fashion to the Western deconstructions from after the genre's heyday, the film's conclusion finds bittersweetness only natural for such a complicated desperate man like the wanted <PERSON>.\nThe Biblical tones of The Toll Gate are evident right from the title, as <PERSON> cannot shed himself towards a new life without paying the price of his sins from his old life, stopped at the gate and unable to move on until all his loose ends wrap themselves up, regardless of whether <PERSON> can begin a new life to begin with. It's a film that seems genuine, filled with heart and soul towards the many lines seeped in this uncertain conflict between the law and the outlaw that oozes a \"je ne sais quoi\" quickly discarded once we enter the <PERSON> model of Westerns, and co-writer/star <PERSON> recognized the absorbing power that gritty realism in a time as marketably unforgiving as the Western could capture in a viewer, inserting a level of craftmanship that helps it stand out from its peers. For those looking for a very early, sophisticated Western, your wages are worth spending on this one.", "698" ], [ "Law of the Lash\nIt's telling that Law of the Lash's introduction makes special notice that its inclusion as part of a roundhouse of Poverty Row Westerns for Gold Ninja's supplemental marathon has less to do with its individual merits and moreso for completion's sake, as this is <PERSON> first film as a leading man painting the West with the refined, cool personality that would permeate through the rest of his starring days, so in that effect the film does succeed in introducing a new star for the common man to flock to. Otherwise, however, its competence can't outweight just how extremely lightweight it is, boiling down the usual \"gang invades town\" plotline to downright banal degrees (like the villain being identifiable through being....left-handed, yeah really pales compared to masked desperado) and lacks anything to really separate itself from the other films I've covered thus far (such as the subgenre inclusion of familiar melodrama of Between Man or the temporal lateness of The Trigger Trio), making for a film that, true, offers simple thrills like others I've positively reacted to (such as <PERSON>'s later King of the Bullwhip) but coasts exclusively in that regard, unpretentious and garden-variety with even the comedy stylings of <PERSON> barely registering as repetitious groans. I'm being generous with applying a rating here mostly because I have a hunch my tired feelings are moreso out of fatigue from a genre/era combo that, admittedly, offers an approach to filmmaking antithetical to the type of analysis I favor and also because this is film #5 in what amounts to same shit, different day (I'm also a little salty that we don't get nearly as much bullwhip in this one, like c'mon it's on the POSTER but it's only used for like the final piece of action), but given how sloppy the fistfight choreography is and how uninspired the chases/shootouts are filmed as well I think I'm more than accurate in criticizing this as misbegotten aftermath of the assembly-line approach. Mercifully, the last film in this brief PRW voyage offers some variance, but it's safe to say that this one is best for those who are \"hardcore\" for the genre or, perhaps most apt, those who have never seen a Poverty Row Western.", "952" ], [ "<PERSON>\nI don't know if I'd call this mid-60s MGM sex comedy good but there's a sanitized innocence that only the era and studio system could generate that I found quaintly entertaining. There's some kooky stylization and goofy gags that probably have varied mileage.", "170" ], [ "Ultimately safe by comparison and baring nothing more than midriffs, this mainstream title came out the same year independent mavericks were putting out titles like Sin in the City; Another Day, Another Man; Take Me Naked; and Mondo Topless, pushing more in the direction of roughies having already sapped their seedy markets for nudie cutie fare. Would we have gotten a studio picture featuring a fake autobiography inspired by sex pulp novels and sexpot <PERSON> sliding around in paint if they hadn't forged the path prior? Who's to say. Maybe I'm looking for parallels and influence where none actually exist.\nDefinitely not a watch I ever would have actively sought out but it came as a freebie with an order of <PERSON> last films from from dvdrparty.com and it was a nice, lighthearted way to burn 85 minutes on an afternoon off.", "378" ], [ "Desistfilm\nA Pilgrimage, ft. <PERSON> (1/63)\nTo try and categorize <PERSON> requires placing him within the umbrella of labels reserved for those in which categorization otherwise fails, <PERSON> is the outsider artist, the avant-garde maestro, the lyrical poet who often didn't need a story to express insights on the world and instead let his acrylic paints and scratched-on film canisters do the speaking for him, and as such it makes for a great challenge for saps like me to try and talk at length about him but DAMMIT I'm gonna do my hardest to make it through this pilgrimage as a being more experienced with the boundary-breaching world of the avant-garde that <PERSON> has been oft cited as the champion of.", "464" ], [ "The journey begins, however, atypically from the form that <PERSON> would associate himself with, as Desistfilm has elements like actors, post-synch sound, even a plot of sorts simply because <PERSON> looked at other traditional movies as inspiration while trying to find firm footing for his voice, and while not his first film it does represent the first baby steps for the man ready and willing to break and protest narrative and social norms all at once.\nA social gathering is our basis for <PERSON>'s camera, following teenagers and young adults engaging in debaucherous and risky behavior, seeking to desist from the norms and rigid structure of the world outside in an expression of desire, frustration, and a fleeting sense of escape. <PERSON>'s eyes sees teenage rebellion as not a form of freedom for the youth, but rather claustrophobia, as the room these youths trap themselves in merely isolate themselves into their own activities, burning matches, collapsing towers of books, playing the strings of a mandolin, and though <PERSON> has claimed a more neutral conscious awareness of the usual activities partaken by beatniks at the time during the making of the film (with the characters within suggested to be smoking tobacco rather than pot), it's hard not to make connections towards the negative anti-social consequences that subjects like drugs, violence, and sex (or in this case voyeurism) tend to cause and what <PERSON> is showing on-screen, taking account that too much indulgence can lead to frayed senses and frightful behavior, such as the more innocent couple's rightfully shocked expressions in seeing the grotesque display of humanity staring out at them in the form of their close peers.\n<PERSON> is essentially making a horror film about the plights of the youth through Desistfilm, expressing how desisting too much from reality can turn existence into a waking nightmare, and this is embellished through the speakers-blown, alien sounds of a torch song, atonal as it covers up any and all dialogue in favor of letting the unknown and the unrecognizable inform tension, heightening our vision of a world somewhat unclear due to its fragmentations and flusters about in a similar drunk manner, perhaps in order to give us further insight and a greater grip into bringing us into the party, only with just one or two shots in our system to recognize with clarity the terror that teenagers bored with life can cause and why they rightfully scare the shit out of some. An interesting, if unindicative, introduction to a man that will further his glance at subjectivity as his career goes on.", "285" ], [ "The Lost King\n<PERSON> is <PERSON>, responsible for spearheading the effort to locate the remains of one of England's most notorious kings, <PERSON>. But not only to find him, but also rehabilitate his legacy which is coloured in most people's eyes by his portrayal by <PERSON>.", "464" ], [ "This is a fairly straightforward telling of the real-life events by <PERSON>, save the lurking presence of the king himself, played by <PERSON>. <PERSON> is reliably engaging, while <PERSON> gives prickly as only he can, will most of the academics are portrayed as naysayers and latter day converts. Safe but rather unremarkable despite the rather amazing discovery.", "285" ] ]

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[ [ "Energy absorbed by a system in isothermic process in which the phase changes from liquid to gas\nA system contains $x$ mole of material, with surface area $S$ is pressed by a mass $M_1$ (no fraction and no any other outer forces involves). Let $\\Delta H_{l\\rightarrow g}$ be the transition enthalpy from liquid to gas. The system is position in $(T,P_1)$ such that the material phase is liquid for those temperature and pressure values ($T$ and $P_1$). Now instantaneously the mass $M_1$ is decreased to to an unknown value which we denote $M_2$ so the pressure decreases.", "749" ], [ "In case that the temperature stays constant until the inner pressure is equal to the outer pressure $(T,P_2:=\\frac{M_2g}{S})$ system gets to back to equilibrium, and the material phase in $(T,P_2)$ is gas, I wish to calculate how much energy was absorbed by the system till it gets to pressure equilibrium $(T,P_2)$.\nIn the question is says that the volume of the liquid can be neglected when compared to gas' volume. And that the volume of the water is independent of the pressure.\nWhat I did so far:\nThe chemical equilibrium pressure (i.e the pressure in the phase transition point) can be calculated because the exercise gives the triple point $(T_\\triangle , P_\\triangle)$ so using the transition enthalpy constant and the constant $T$ of the process, one can calculate $(P_{l\\rightarrow g eq},T)$ (using Clausius–Clapeyron relation). And by $PV=nRT$ one may calculate $V_{eq} = \\frac{nRT}{P}$ the volume in the chemical equilibrium point. By the unstruction $V_{eq}$ is the total volume of the material (we neglect the liquid volume)\nWe know the starting inner pressure which is $\\frac{M1g}{S} [Pa] $ and by the given instruction the the pressure doesn't change the liquid volume we learn that until the phase transition point, the volume of of the system stays constant $V_{eq}$ which we calculated above.\nWhen the system gets to pressure equilibrium point $(T,P_2=\\frac{M_2g}{S})$ we don't know the volume or $P_2$ because $P_2$ is unknown how every we not that its larger then $V_{eq}$.\nI'm pretty much stuck here, I don't see how to translate this information to evaluate the amount of energy absorbed. It seems to me that maybe one more piece of information is needed, but the exercise doesn't give one.", "749" ], [ "Thermodynamic definition of an adiabatic process\nI am posting about this because it seems to be a big issue and misconception in the thermodynamic literature. My issue is about adiabatic processes. As I see it there are two intrinsically different definitions of adiabatic processes:\n1. Processes for which $\\delta Q_\\mathrm{irr}=Td_iS+Td_eS=0$ ($Td_iS$ is the irreversible heat produced and $Td_eS$ the heat due to heat transfer). This means that in these processes there is no heat generation whatsoever.", "749" ], [ "This also means that any adiabatic process is isentropic. Actually, I think this definition is wrong, because every irreversible process will produce entropy $Td_iS$ which cannot be compensated, because the system is thermally isolated ($Td_eS=0$), so that $\\delta Q_\\mathrm{irr}>0$.\n2. (I think the right definition) Processes for which $\\delta Q_\\mathrm{rev}=Td_eS=0$. This means that no heat transfer is allowed into the system, but still irreversible processes can generate heat.\nThe second one should be in principle correct, as an adiabatic, irreversible expansion of a gas can heat it up due to entropy production. To name an example for definition 2, I could name the expansion of the universe which is adiabatic in the sense of no heat transfer (no environment). Still, the entropy is increasing, since $Td_eS\\neq 0$ (while it is assumed to be 0 in definition 1).\nHowever, large parts of the literature work with the first definition also.\nOne example for the use of the first definition is https://chemistry.stackexchange.com/questions/16260/derivation-of-the-relation-between-temperature-and-pressure-for-an-irreversible or https://chemistry.stackexchange.com/questions/38127/reversible-and-irreversible-adiabatic-expansion Here, the authors claim that they derived the expression for the volume change of an irreversible, adiabatic process and starts with the equation (I have seen exactly the same equation in Lecture notes of my Thermodynamics class and other books):\n$\\mathrm{d}U=-p_\\mathrm{ex}\\mathrm{d}V$\nHowever, according to the first law:\n$\\mathrm{d}U=\\delta Q_\\mathrm{irr}+\\delta W_\\mathrm{irr}=\\delta Q_\\mathrm{irr}-p_\\mathrm{ex}\\mathrm{d}V$\nSo to reproduce the equation above $\\delta Q_\\mathrm{irr}=0$ which means that the use of the above equation assumes definition 1, which makes no sense in my opinion.\nIn my opinion, for any process we should have:\n$\\mathrm{d}U=\\delta Q_\\mathrm{rev}+\\delta W_\\mathrm{rev}=0-pdV=-pdV$\nwhich means that no matter the reversibility, a specific volume change will always induce the same change in the internal energy.\nI would appreciate any opinion on this issue.", "749" ], [ "Derivative of internal energy with respect to pressure at a constant volume\nI need to obtain the derivative of internal energy $U$ w.r.t. pressure $p$ at a constant volume $V$.", "453" ], [ "Solution to <PERSON>'s Law for a volatile binary solution (no pun intended)\n<PERSON>'s Law\nIn a closed container, $$P_A=P_A^\\circ x_A$$ where $P_A$ is the pressure of compound in gaseous phase, and $x_A$ is the mole fraction of the liquid component A in the liquid mixture. If the liquid is alone in the container, $x_A=1$.\nProblem I'm trying to solve\n$A$ moles of compound $A$ and $B$ moles of compound $B$ are stored in container closed with a piston. External pressure on the piston is maintained as $P_e$. Find moles of $A$ and $B$ that will be found in the gaseous phase at equilibrium.", "474" ], [ "($P_A^\\circ$ and $P_B^\\circ$ are known values)\nAttempt at solving\nLet $a$ moles of A and $b$ moles of B exist in gaseous phase. This means $A-a$ and $B-b$ moles of respective compounds are leftover in the liquid phase.\nNow Raoult's Law gives us\n$$a \\frac{RT}V = P_A^\\circ \\left(\\frac{A-a}{A+B-a-b}\\right)$$ $$b \\frac{RT}V = P_B^\\circ \\left(\\frac{B-a}{A+B-a-b}\\right)$$\n(Ideal gas equation used implicitly)\nAlso total pressure of gases inside should equal $P_e$\n$$(a+b) \\frac{RT}V = P_e$$\nThese are not ordinary linear equations, so I'm not totally sure my calculations are correct, but I'm getting the solution as\n$$P_A^\\circ \\left(\\frac Aa -1\\right) = P_B^\\circ \\left(\\frac Bb -1\\right) = \\frac{AP_B^\\circ (P_e-P_A^\\circ)+BP_A^\\circ(P_e-P_B^\\circ)}{(A+B)(P_A^\\circ+P_B^\\circ-P_e)}$$\nSo far so good, but it turns out that on plugging in specific values for $A,B,P_A^\\circ,P_B^\\circ,P_e$, $a$ and $b$ attain negative values.\nMathematically it can be proved that this happens when the rightmost expression is negative. The rightmost expression can be rewritten as\n$$P_e \\left[\\frac {\\frac{\\frac{A}{A+B}}{P_A^\\circ}+\\frac{\\frac{B}{A+B}}{P_B^\\circ}-\\frac{1}{P_e}} {\\frac{1}{P_A^\\circ}+\\frac{1}{P_B^\\circ}-\\frac{1}{P_e}} \\right]$$\nLet $N$ mean numerator and $D$ mean denominator of this expression. We can prove that $N0$ if and only if $N>0$ or $D<0$ holds.\nQuestion 1\nAssuming all the calculations are correct, this seems to be a rather arbitrary mathematical condition. Can someone explain the physical significance of this? Like a more intuitive way to understand why we must check such an arbitrary condition rather than something as simple as $P_e>P_A^\\circ+P_B^\\circ$?\nQuestion 2\nIf $\\frac ND <0$, is the solution always $a=A$, $b=B$ (which means no liquid evaporates)?", "565" ], [ "Is the pressure always the same for each phase of a two-phase system?\nI am currently reading a textbook called Engineering and Chemical Thermodynamics but I am stuck in one part about the State Postulate and the Gibbs Phase Rule. The Gibbs Phase rule says that the number of independent intensive properties that one needs to specify to constrain the properties of a given phase is:\nn = Number of Chemical Species - Number of Phases + 2\nTherefore, if there is a two-phase system with one chemical species, such as boiling water, one needs to specify one property in each phase to constrain all the other properties of that phase. However, the author states that we can take advantage of the fact that \"the properties Temperature and Pressure are equal in both phases, thus, if we know either T or P of the system, we constrain the properties in each of the phases\". This statement confused me a lot because the author didn't mention if this applies only for a saturated system. For me, it is logical that the temperature of both of the phases should be the same even if the system is not saturated, however, I am struggling to understand why the pressure of the system is the same for both phases always? The water could be boiling at 100 ºC, which means that the vapor pressure of the liquid water should be 1 atm, but the system could not be saturated and therefore the pressure of the vapor would not be 1 atm.\nI assume that the author says that this applies even for unsaturated systems because of the following lines:\nTo illustrate this concept, consider a pure system of boiling water where we have both a liquid and a vapor phase. The phase rule tells us that for the liquid phase of water, we need only one property to constrain the state of the phase. If we know the system pressure, P, all the other properties (T, vl , ul...) of the liquid are constrained. The subscript “l” refers to the liquid phase. It is omitted on T since the temperatures of both the liquid and vapor phases are equal. For example, for a pressure of 1 atm, the temperature is 100 °C. We can also determine that the volume of the liquid is 1.04x10-3 m3/kg, the internal energy is 418.94 kJ/kg, and so on.", "749" ], [ "The system pressure of 1 atm also constrains the properties of the vapor phase. The temperature remains the same as for the liquid, 100 °C; however, the values for the volume of the vapor (1.63 m3/kg), the internal energy (2,506.5 kJ/kg), and so on are different from those of the liquid.\nThen he said:\nThe pressure (and temperature) in each phase of a two-phase system is equal; hence, if we know P (or T), we know the values of all the intensive properties in both phases. However, we have not yet constrained the state of the system. To do so, we need to know the proportion of matter in each phase. Thus, a second independent intensive property that is related to the mass fraction in each phase is required. Specifying that a system of boiling water is at 1 atm does not tell us how much liquid and how much vapor are present. We could have all liquid with just one bubble of vapor, all vapor with just one drop of liquid, or anything in between.\nIf my question isn't clear enough: if we have \"all liquid with just one bubble of vapor\", how is it possible that the pressure in each phase is equal?, this is confusing me a lot. The only explanation that I can find is that the vapor pressure of the liquid is the same as the vapor pressure of the vapor, however I don't know if the concept of vapor pressure applies for a vapor.\nI would appreciate if someone can clear my doubts on this question. For more details, the chapter of the textbook is 1.5 of the 2nd edition. If I didn't explain myself enough, please let me know. Thanks in advance.", "749" ], [ "What is the problem of this thermodynamic fallacy?\nConsider the following (alleged) cycle:\n1. Quasi-static adiabatic expansion of a vapor in such a condition that it results in the condensation of part of the mols*;\n2. Out of equilibrium adiabatic compression;\n3. Quasi-static isochoric heating;\nStatements:\n1. The latent heat required to change the state of part of the mols during steps 1 and 2 is due to the work done by the vapor;\n2. Each infinitesimal compression dV during step 2 being done farther away from equilibrium than an infinitesimal expansion of same size done in step 1 at the same volume, grants that if the internal energy in both cases were also the same (ie all other factors being equal), a smaller molar fraction would be recovered to vaporous state than it was lost, so that\n3.", "749" ], [ "(lesser mols - lower energy feedback) with lesser mols recovered at each point of step 2, there is lower energy than in step 1, which implies a lower pressure, which implies a lower infinitesimal work done by each infinitesimal compression, which implies lower gain of latent heat, which yields an even lower recovery of vapor mols;\n4. Steps 1 and 2 being done adiabatically, all the difference of work came from the internal energy of the mols. The initial state of step 1 and final state of step 2 have the same volume and different energies, and thus, step 3 can go from the latter to the former simply by means of a quasi-static heating.\n5. We have, thus, performed a closed loop in the space of thermodynamic states, whose only effect is the total transformation of heat into work, in other words, a heat engine with efficiency 1**.\nThe experiment can be more easily conceived by a piston that connects with a separated chamber that has the exact volume of condensed (or sublimed) mol fraction in the liquid (or solid) state. During step 1, the referred mol fraction 'rains' (or 'snows') into that chamber that is then closed so to completely prevent it to be recovered to the vapor fraction during step 2, regardless even of how near the equilibrium it is done. After step 2, the chamber is reopened, thus allowing those mols to be recovered to the vapor state in step 3.\nThe few experts on thermodynamics whom I have consulted haven't achieved to solve this apparent fallacy, which, I actually came up with before actually having formally studied thermodynamics, in my school days, back in 2008.\nThe change of physical state to one of lower energy due to adiabatic cooling* does happen, for example, in the formation of some types of clouds and in the sublimation of gaseous CO2 into dry ice in fire extinguishers.", "273" ], [ "Unmixing of gases: What is the relevant temperature for my Entropy?\nThis answer to a question about unmixing gases states:\nHowever, let us now assume we have to hand a source of mechanical work, and a large heat reservoir at temperature $T$. I'll assume that we'll use the work (somehow) to unmix the fluids, and that any excess heat that gets generated will be dumped in the heat reservoir.\nIn general the mixed and unmixed states of the fluid system will have different energies. I'll call the difference $\\Delta H$, with positive $\\Delta H$ meaning that the unmixed state has a higher energy than the mixed one. (I'm guessing that for real miscible fluids this is usually a small positive value, but it needn't necessarily be.)\nWe'll assume it takes us an amount $W$ of work to unmix the fluids. $W$ has been lost from the work source, and $\\Delta H$ has been gained from the fluid system, so the first law says that the energy of the heat bath must increase by $W-\\Delta H$.\nWe can now calculate the total change in entropy. The fluids' entropy has decreased by $\\Delta S_\\text{mixing}$, and the heat bath's entropy has increased by $(W - \\Delta H)/T$, so the total is\n$\\Delta S_\\text{total} = \\frac{W - \\Delta H}{T} - \\Delta S_\\text{mixing} \\ge 0,$\nor\n$W \\ge T\\Delta S_\\text{mixing} + \\Delta H.$\nChanging this to an equality gives you the minimum amount of work required to unmix the fluids.", "749" ], [ "But note that the expression involves $T$, which is the temperature of the heat bath that I assumed to exist. Without the heat bath there would be nowhere for the energy from the work source to go once it's used up.\nAlso note that $T$ is not necessarily the temperature of the mixed fluids, which could be different from that of the heat bath. I didn't need to make any assumptions about the fluids' temperature in order to work out the above. In practice you'd usually assume the fluids to be in contact with the heat bath, so that the two temperatures are in fact equal. In this case (and only in this case), the minimum work required is equal to the difference in Helmholtz free energy between the mixed and unmixed states.\nNow what $is$ the temperature of my heat bath? I know that it should be indiepenent of the process used: We are looking at the pure change in entropy of the unmixing, this is path independent. But is it safe to assume it's the temperature of the gas? Before or after unmixing?", "749" ], [ "Use of Helmholtz free energy in problem involving spring-gas subsystem in thermal contact with a reservoir\nI have come across a problem from \"Biological Physics\" by <PERSON> (pg212) which involves finding the equilibrium position of a spring, $x_{eq}$, which is compressing an ideal gas whilst in contact with a heat reservoir of temperature, $T_{res}$. A diagram of the setup is shown below:\nI believe that solving it involves the minimisation of the system's free energy $F$:\n$$F = U - TS $$ $$dF = dU - TdS - SdT $$\nwhich simplifies to\n$$ dF = -SdT -pdV$$\nusing $dU = TdS - pdV$.\nSince the system is at thermal equilibrium with a head bath, $dT = 0$.", "474" ], [ "Also, the pressure and volume can be written in terms of the spring extension and constant: $V = A(L-x_{1})$ and $pA = \\frac{1}{2} kx^{2}$ (when at equilibrium) so that $dV = -Adx_{1}$ and $ dp = \\frac{k}{A}x$.\nHowever, setting the equilibrium condition $dF=0$ leaves me with\n$$ dF (=0) = dW = -pdV = \\frac{1}{2}kx^{3}dx $$\nwhich gives an extension of 0 as a (somewhat unhelpful) result.\nA second attempt involved writing $dW$ as\n$$ dW = fdx_{1} $$ where $f$ is the force on the compression plate so that\n$$ f(x_1) = \\frac{1}{2}x_{1}^{2} - pA $$\nwith the solutions of $f(x_1) = 0$ giving the equilibrium position of the plate assuming the ideal gas law $pV = pA(L-x_{1}) = nRT$. I believe this involves solving\n$$ x_{eq}^{3} - Lx_{eq}^{2} - \\frac{2nRT}{k} = 0 $$\nHowever, this solution appears to avoid all thermodynamic arguments, and just simplify to solving a simple mechanical problem assuming ideal gas behavior, which makes me believe I have make a mistake somewhere along the derivation.\nAny advice with the exercise, and on understanding the application of free energies to thermodynamic problems would be much appreciated.\n---------------------EDIT-----------------------\nI realise that I erred on the penultimate equation ( $f(x_{1}) = kx_{1} - pA$), which then leads to the equation $kx_{eq}(L - x_{eq}) = nRT$. This seems to suggest that the total internal energy of the system can be split into the energy of the spring, and the energy of the gas so that $$dU_{total} = dU_{gas} +dU_{spring} = -pdV + kxdx$$ It appears that my mistake was to treatthe spring as a seperate entity, and forgetting its energy addition to the total internal energy of the system", "37" ] ]

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[ [ "La Jetée\nFilm is a beautiful coming together of literature, art, theater, and music. And La Jetee is a film that strips itself as a medium down to the bare bones. A series of still images, assisted only by narration and music, clocking in at only 28 minutes long, La Jetee is still somehow more beautiful, heartfelt, and just straight up better at storytelling than 90% of movies coming out today. The images that are locked in place melt away as our imaginations are asked to fill in the gaps.", "583" ], [ "The limitations bestowed on this film forces <PERSON> as a filmmaker to find new clever ways of storytelling, and in the process makes the message and impact astronomically stronger. That's what good filmmaking is.\nIt says that they time travel in this film, but it never ever feels that way. The melancholic music transports and dissolves us back in time into this dreamlike moment, but it never gives up its sense of it being a memory that we can never fully grasp. La Jetee feels like a dream we never want to wake up from, and when we do, we'll go right back to sleep hoping to go right back. If and whenever somebody invents time travel, i bet that they did it not to kill <PERSON>, or to stop the cause of deadly pandemic, but because they yearned for their own distant past memory.", "529" ], [ "The Fall\n\"We're a strange pair, aren't we?\"\nA well-acted and touching film that soars high with its excellent art direction. It's all about the encounter between a movie stuntman who lost his fiancée and attempted suicide with a little girl whose arm was broken after falling from a tree while picking oranges and whose father was murdered. Assigned to the same hospital, <PERSON>, our stuntman, tells a story shaped by what he's feeling throughout, and <PERSON>, our little girl, imagines the story with people and elements surrounding her.", "529" ], [ "The art direction really does a great job at making these scenes look childlike. The exotic settings, bright costumes, and satured photography give life to the images. This is beauty in excelsis.", "79" ], [ "<PERSON>\nAdmittedly, I did not register this as a comedy until 40 minutes in at which point after realizing this everything the film was doing became crystalized and threatened to break the film in two. The mood piece about alienation as an immigrant worker is nearly overtaken by a dead pan humor that is somehow too arch and too subdued, best exemplified by <PERSON> performance that threatens into becoming a caricature every time the film returns to him.", "132" ], [ "Fortunately, the film finds it's footing again at it's closing with <PERSON> mechanic. Very much of a piece with <PERSON>'s Fallen Leaves as a film that perfectly captures the feeling of living in current moment even if it isn't as fully realized as <PERSON>'s film. I imagine this plays better in a theater with an attentive crowd.", "529" ], [ "The Innocents\nShot to perfection in CinemaScope, this dark, claustrophobic thriller is fully detailed in its lighting and evocative atmosphere. <PERSON> plays the lead wonderfully, as much of her screen presence allows for a range of emotions much needed in a mood piece like this. Even the kids do a lot of the heavy lifting, as what’s required from them is a stark contrast to <PERSON>’s anxious persona.", "883" ], [ "It goes to places I’d never expect it to go, concluding in a distorted, twisted ending that leaves you more shocked than relieved. It builds and builds with no release, leaving you wanting more than what you bargained for.\nO Willow Wally will forever be haunting to hear, as its allure pulls you in slowly and creepily- a gothic undertone that permeates throughout the whole film. A tune that is the connective tissue to the symbolism of everything The Innocents represents. It’s eerily beautiful and holds up extremely well.", "583" ], [ "<PERSON>\nWhat a film! Holds up incredibly well for a film almost 100 years old. The Swan lake classical music that places over the titles to the absolutely terrific performance by <PERSON>. Something so unique, and so parodied, that I don't think you could immitate it nowadays for fear of being seen as too hammy or cliched, but <PERSON> does such a unique and creepy take on the character that it's hard to think about <PERSON> without at least having his iconic performance (and appearance) cross your mind.", "217" ], [ "The film takes advantage of an abundance of mood and atmosphere to create an adaptation that feels much more faithful to the novel as opposed to subsequent adaptations, but manages to pace itself tremendously well within a 75 minute runtime. Something that seems unthinkable to consider knowing the length of the novel, but somehow they manage with tremendous efficiency and earnesty. Great film. Fully recommend.", "583" ], [ "Once Upon a Time in the West\nA railroad is such a perfect symbol. Having it as the centerpiece of your film does half your thematic work for you. It’s a paradox of progress and colonial destruction. And as with all engines of progress and colonialism it has its dark personalities outside the official political structures, personified by <PERSON> here.\nThe main strength of Once Upon a Time in the West is not its themes though.", "352" ], [ "It’s the basics of image and sound, culminating in one of the most impactful moments in cinematic storytelling. The “keep your lovin brother happy” scene is practically worth 5 stars on it’s own. An example of cinematic mastery. And it’s no shock that <PERSON>’s score is sheer perfection at this moment and every other one for that matter. But the film as a whole falls about one star short of that moment.\nStill, an all time great Western.", "529" ], [ "House\nThe birth of absurd cinema and it really is that in its finest from. From from very off, the film is entertaining and energetic. It’s funny, touching, creepy and of course completely bananas. Technically speaking this film goes off the charts. It sort of feels like a crazy school project, but at the same time there’s so many different implications and original beauty to it.", "583" ], [ "For the 70s, it’s unbelievably beautiful to look at. One of the most visually striking movies I’ve ever seen. The music is the technical highlight here because it dominates the feels in every scene. The movie feels like one fucked up dream which is not for everyone but I’m here for it. What a ride.", "583" ], [ "Triangle of Sadness\nSitting on Triangle of Sadness for a couple days now and I’m still not fully sure. It’s obviously a harsh and stressful push on the rich, and their familiar overprivileged, stuck-up fiasco of a life, but it also examines the cruel survival of society and it’s very rich and complex on those matters. Sure there are plenty of topics that this film symbolizes that I didn’t pick up on, and some I might never, but the whole thing is for those who think. You must pay attention and you must be willing to let your interpretation of the events of this film run free, especially the ending.", "541" ], [ "Each performer in this film does their job right, molding on each dramatic commentary of this film so well and they emphasize such intensity when they speak that it just makes it even more interesting. <PERSON>, <PERSON>, <PERSON>, <PERSON>, and an immaculate performance of beauty and pain from the late <PERSON>. While I do feel it was too complicated for me at point where I wasn’t quite sure where to be with the characters or just weirded out, the whole film really is a form of masterclass when it’s all put into perspective. <PERSON> is a great thinker and it’s very clear in this latest film, and is one to definitely stack your opinion on upon rewatches.\n🔙<PERSON>", "529" ] ]

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[ [ "The little-known beauty of rice sheaf artistry from India and Nepal · Global Voices\nA ‘jhutti’ made from rice sheaves. Photo by CK <PERSON>. Used with permission.\nRice has been a diet staple in Asian communities for centuries, so it is no surprise that this important food source has been a feature of artwork in the region. While some artists have sketched and painted this grain, other communities have continued the little-known, age-old practice of weaving rice sheaves into beautiful forms to decorate their homes.\nKathirkula\nIn the southern Indian state of Kerala, kathirkula – rice sheaves woven together into a bunch – is hung in houses and temples. It is believed to bring good health, wealth and prosperity to the home.\nView this post on Instagram\nŃĔĹĶÁŤĤĨŔ is the dried rice seed. Kathirkula (Bunch of Paddy) an ethnic image used for prosperity in homes. Kathirkula is a plaited bunch of paddy earheads shaped like a bouquet and is usually hung in the houses of Kerala. #kerala #my #home #traditon #nelkathir #kathirkula #paddy #rice #bunch #hanging #home #decor #gods_own_country #village #nikon #nikond90 #d90 #nikonphotography #insta #just_for_fun\nA post shared by <PERSON> (@jithinjacob2700) on Jul 29, 2016 at 9:01am PDT\nFacebook page, <PERSON> also writes about hanging sheaves of rice in Kerala, India:\n“Nelkathir” is a bunch of artistically plaited bouquet of rice seeds, usually hung in front of the entrances to old ancestral homes (Tharavadu) in Kerala.\nThis symbolizes prosperity in homes. It is linked to a traditional custom called “Illam Nira”-(House filling with Paddy). This ritual heralds the farming and harvesting in Kerala. […] This can also be seen in front of all temples in Kerala as a symbol of opulence.\nDeepthi Menon (RCP)\nA nostalgic symbol of a bygone era #Kathirkula .", "765" ], [ "pic.twitter.com/AMX6Gysqwp\n— <PERSON> (@DhanyaMN) November 14, 2013\nJhoti\nIn the eastern Indian state of Odisha, jhoti or chita – a traditional Odia art made from rice paste – is drawn on walls and floors during festive occasions. During Deepawali, the festival of lights, motifs of paddy stacks or rice sheaves are drawn. The Odia Language and Culture Department states:\nDuring this auspicious occasion, the mud walls and floors are decorated with murals in white rice paste or pithau. They are called jhoti or chita and are drawn not merely with the intention of decorating the house, but to establish a relationship between the mystical and the material, thus being highly symbolical and meaningful. […] For each occasion a specific motif is drawn on the floor or on the wall. For instance, in Lakshmipuja a stack of paddy or rice sheaves is drawn on the walls structured like a pyramid. […]\nJhutti\nWhile jhoti are drawn on walls in India, a jhutti is made of rice sheaves in southern plains of Nepal just like Kerala’s kathirkula, but shaped into more intricate forms. After harvesting rice, select rice sheaves are woven into jhuttis and hung high on the meh (the bamboo pole to which the oxen are tethered while threshing rice). The Tharu people are especially known for preparing jhuttis for each variety of rice they harvest.\nFrom left to right: kakahi – the comb, maur – the groom’s headdress, kauwa tholi – the crow’s beak and Patiya – the mat. Photo by <PERSON>. Used with permission.\nJhuttis are of different shapes and sizes. They are inspired by the nature and the things around like, kauwa tholi – the crow’s beak, patiya – the mat, kakahi – the comb, jhunjhuna – the baby’s toy, bena – the fan, bakhari – the granary, maur – the headdress of a groom, among others.\nThe belief is that, after the rice is harvested, there remains nothing for the birds to peck at.", "765" ], [ "South Asian examples show the centrality of nature in indigenous art · Global Voices\nRice sheaves artistry from southern plains of Nepal. Photo by <PERSON>. Used with permission.\nThis article by <PERSON> was first published on The Record (Nepal) and an edited version is republished on Global Voices as part of a content-sharing agreement.\nIn 2014, I was contacted by a Nepalese scholar who wanted me to take a closer look at a photo of a minutely carved door from the Chitwan district in southwestern Nepal. Although I was able to easily recognize the 30 or so figures on the small door panels—elephants, camels, oxen, cobras, donkeys, cranes, leopards, monkeys, deer, and horses, along with humans—the writing, although legible, didn’t make much sense.\nThis beautiful decorative door dating back to the 19th century was eventually revealed to belong to an indigenous Tharu household of elephant handlers. All the animals, except for the camels and the only bird depicted on the door, were from Chitwan, and the writing was eventually translated by the scholar himself to be the names and professions of the elephant handlers who lived in that home. The unique icons, motifs, colours and style spoke of the people’s local, living reality. More importantly, they depicted an age-old human relationship with nature—the trees, animals and birds—and its conservation. It’s a relationship that still persists, despite modernity’s intrusion into indigenous lives, and one that indigenous artists still attempt to recall through their work.\nEvery element in indigenous art tells a story.", "765" ], [ "“The taproot of indigenous aesthetics,” says Cherokee writer <PERSON>, “is our stories, families, lands, artists, ceremonies, and language.”\nIn the plains of northern India and southern Nepal, women have, for generations, taken time out from their daily chores to paint the walls of their homes with artwork featuring decorative motifs, birds, animals and trees from their surroundings.\nThe Kochila Tharu women, for example, decorate their houses, granaries and verandahs with motifs of recurring geometric and floral patterns, along with birds and animals—peacocks and elephants, in particular. Peacocks feature prominently because they are regarded as symbols of luck.\n“The work is one moment in the continuum of time,” write <PERSON> and <PERSON>, who spent four years exploring Tharu art in nearly 300 villages across Nepal, in an article for Asian Art, an online journal. “The anonymous artist borrows from the elders, makes some changes, is free to improve on it, within the constraints set up by the culture, and this culture belongs to all.”\nImportance of nature\nMany indigenous people in Nepal depict nature in their art. For example, during the Hindu festival Krishnashtami, the Tharus of western Nepal adorn their adobe house walls with Ashtimki paintings. Basing their work on the Tharu folk epic Gurbabak Jalmauti, the artists start drawing from the bottom of the wall and move towards the top in the order, according to Tharu folklore, that the elements and creatures were created by <PERSON>, the creator of Earth: water, fish, crab, tortoise, crocodile, and other water creatures, along with a boat carrying <PERSON>, his disciples, and his books. Tharus believe that during a past apocalypse, <PERSON> (accompanied by his disciples and books) sailed to a sanctuary and created the new world.\nThe centre stage in an <PERSON> painting is occupied by the Kadam tree, with Kanha, or <PERSON>, on top of its canopy, along with the sun, moon, monkeys, and images of <PERSON>, <PERSON>, and the Pandavas from the Hindu epics Ramayana and Mahabharata. In it, the artists include creatures like elephants, horses, camels and peacocks.\nBy adding auspicious figures and observing austere rituals while creating Ashtimki paintings, the artists imbue their work with religious significance. But Ashtimki has also evolved beyond religion to include quotidian details that are part of modern Tharu life. “While much of this art is rooted in devotional activities, today’s artist seldom knows the significance of the designs, but still clings to the graphics of the elders, occasionally introducing contemporary designs such as a bus or aeroplane,” added <PERSON> and <PERSON>.\nMuch of the subcontinent’s indigenous art still draws inspiration from how things were in the past, when man and nature coexisted far more intimately.", "765" ], [ "Retelling indigenous Tamang people’s torment and trauma through sacred seeds, handmade paper and slates · Global Voices\nArtist <PERSON> uses the seeds of the tree of Damocles, considered sacred by many indigenous peoples in Nepal, as his canvas. Photo by <PERSON>. Used with permission.\nTranslucent seeds of the tree of Damocles (Oroxylum indicum), meticulously glued together, form Nepali artist <PERSON>'s canvas. The round seeds, known for their medicinal values, are considered pure and sacred since they are enclosed in sword-shaped pods — far from the touch of bumblebees and other insects. In a nod to the seeds’ potential to grow into trees, <PERSON> tells the stories of discrimination and oppression meted out to indigenous Tamang people by the State — the Rana rulers in particular.\n“Called ko ko mhendo or heart flower in Tamang language, these seeds are ingrained in Tamang culture and rituals,” said <PERSON>, talking to Global Voices. “The Tamangs attach these seeds to invitations sent out on auspicious occasions. They have become symbols of Tamang identity.”\nThat’s why <PERSON> chose the sacred seeds to tell the stories, called Kaiten in the Tamang language. Kaiten is the Tamang oral story of origins of human life, culture and tradition, usually told by an elder storyteller, called <PERSON>. Like shamans using the seeds to heal sick people, <PERSON> uses them as a medium to heal wounds of the past, the wounds of torment and trauma.\nAlso read: Art series sheds light on the marginalization of indigenous Tharus in Nepal\nThe Tamang men were reduced to mere porters, palanquin carriers, hookah and umbrella bearers, and construction labour. The Tamang women, likewise, would work as nursemaids and wet nurses, while also singing, dancing and entertaining the rulers.\nPipa I, artwork by <PERSON>, shows the fate of Tamang people reduced to menial labourers. Photo by <PERSON>. Used with permission.\nThe Tamangs were barred from joining the British Army. The only rank for them in the Nepal Army was that of the pipa, the menial workers at the lowest rungs of the army.", "765" ], [ "They could never rise up the ranks. <PERSON> illustrates this through his artwork Pipa I, showing four men carrying doko, wicker baskets, on their backs.\nHis woodcut print on ko ko mhendo titled Gole Kaila features the protagonist <PERSON> aka <PERSON> who was martyred in 1950 in Biratnagar, a city in eastern Nepal. Though he died fighting against the <PERSON> regime to establish democracy, he was never accorded the status of a martyr.\n<PERSON>, woodcut on ko ko mhendo, portrays the protagonist <PERSON> who was never accorded the status of a martyr despite his sacrifice. Photo by <PERSON>. Used with permission.\nAnother medium <PERSON> chooses for his artworks is lokta, handmade Nepali paper, the same paper that his kinsmen produced from the bark of the Nepali paper plant and carried to palaces in the capital city Kathmandu as corvée (forced unpaid labour in lieu of taxes). The same paper carried orders and laws that would torment them further. But <PERSON> retells the story of his community’s anguish through the same paper. His artworks Kagaji Rakam, <PERSON> and <PERSON> show men in traditional attire but with their heads covered by, respectively, a bouquet of lokta flowers, a sheet of handmade paper and a bunch of mangoes.\nThe artworks Kagaji Rakam, <PERSON> and <PERSON> show how Tamangs were made to work as corvée labour. Photo by <PERSON>. Used with permission.\nExpanding on his work, <PERSON> said:\n“In order to pay taxes, Tamangs had to work for free for the State. The Tamangs from Bumtang of Nuwakot District had to collect lokta barks, process them into paper and carry those papers to the palace. Each household would need to produce 200 sheets of paper. Likewise, Tamangs had to work in fruit orchards and carry the fruit, especially mangoes to the palaces in Kathmandu. They had to leave Kathmandu the same day after dropping the fruit.”\nAlso read: ‘Opposite Dreams: The Politics of Local’: Art raises awareness around social issues in Nepal\n<PERSON> doesn’t stop here.", "765" ], [ "‘Opposite Dreams: The Politics of Local’: Art raises awareness around social issues in Nepal · Global Voices\nOne of the artworks from the exhibition ‘Opposite Dreams: The Politics of Local’. Image by the author. Used with permission.\nArTree Nepal, a group of six Nepali artists, is on a mission to make communities aware of social issues and foster meaningful dialogue through their contemporary art. The group has raised pertinent issues like Dr. <PERSON>’s hunger strike to reform the medical sector, Nepali youth migrating for foreign jobs, discrimination on the basis of caste and ethnicity, and human trafficking among others.\n<PERSON> and <PERSON>'s strong Performance art #Protest to support Dr. <PERSON> with Artree #IamwithDrKC #SaveDrKC pic.twitter.com/r9fvk8c7T9\n— ????? ?????? <PERSON> (@aannda) July 23, 2016\nIn March 2019 and earlier in October-November 2018, they exhibited their work titled ‘Opposite Dreams: The Politics of Local’ showcasing how Nepal’s history has excluded the stories of marginalized, underprivileged, and indigenous peoples.\nThe group wrote on Facebook:\nFor hundreds of years, the mainstream historical narrative of Nepal has excluded the stories and experiences of numerous marginalized, underprivileged and indigenous communities. Although there have been sporadic instances of vocal demands and protests for an equal representation of diverse identities, cultures, languages, and religions, the state has consistently and strategically oppressed them.\nThe exhibition, ‘Opposite Dreams: The Politics of Local’, draws attention to these problematic social hierarchies and invasive international influences. It attempts to highlight the misuse of power and state sponsored violence by focusing on acutely localized situations with an empathetic eye. By using an anthropological perspective and inquiring the socio-physical environments, the exhibition seeks to unfold these deeply entrenched unjust laws.\n‘Opposite dreams’ exhibition- it challenges the ‘mainstream Nepali history’ as we know it, as we were taught, as we've been made to believe. Great to see such critical discourses happening in an accessible manner! Convinced, art can do a better job than words! #ArtreeNepal pic.twitter.com/8AnxuFhMOk\n— <PERSON> (@Sangita_Thebe) November 18, 2018\nHave a look at their artwork:\n‘Mahendra Mala’ by <PERSON>. Image by the author.", "765" ], [ "Used with permission.\nArtist <PERSON>'s installation art ‘Mahendra Mala’ delves into the chapters of the Nepali book of the same name that promoted a single religion, a single language, and a single culture. He has minutely carved the chapters on slates used for roofing in rural areas. The slates can be flipped around and they have chapters from the book on one side while the other sides make up the name of the book.\nThe artist spoke with Global Voices, stating that “One day, a Danphe (Nepal’s national bird Lophophorus) pecked the grains left to dry on the sun by Lamas, the Tamang people.” Explaining one of the stories in the book, he added, “The <PERSON> drove the bird away northwards. In the winter, the Lamas descend to warmer Terai but <PERSON>, afraid of the <PERSON>, never ventured a journey to the Terai, the southern plains. The information given in the book itself is wrong. While <PERSON> is a Himalayan bird living in the Himalayas, the <PERSON> have been presented as cruel in nature.”\n‘Death of Civilization’ by <PERSON>. Image by the author. Used with permission.\nIn ‘Death of Civilization’, <PERSON> has carved the Basantapur Durbar Square on pieces of wood and bulldozed parts of it with huge tire prints.\nIn ‘How I Forgot My Mother Tongue’, <PERSON> showcases a collection of books read by his father. His artwork emphasizes how the curriculum promoted a single language Nepali, thus making others forget their vernaculars.\n‘Masinya’ by <PERSON>. Image by the author. Used with permission.\nThe artwork ‘Masinya’ by <PERSON> delves into the issue of categorization where the Tharu people were grouped as Masinya Matwali (enslavable alcohol drinkers).", "765" ], [ "Lost and found: Repatriation of <PERSON> statue to Kathmandu Valley’s Patan · Global Voices\nPatan Durbar Square, a World Heritage Site in Kathmandu Valley’s Lalitpur District. Photo by <PERSON>. Used with permission.\nNot hundreds but thousands of sculptures and art objects have been stolen from Kathmandu Valley since the 1950s. Removed from sites of worship, they landed up in private collections and art museums. After art historian <PERSON> published the highly acclaimed book Stolen Images of Nepal in 1989, the repatriation of the artefacts began. However, only a fraction of the plundered items has made its way back home.\nThe re-installation of the half male and half female statue of <PERSON> in Patan’s Patko is the latest example of the homecoming of the stolen idols. Taken in 1984, the 12th to 15th century bronze idol was auctioned by Sotheby's in New York in 1989 and loaned to the Dallas Museum of Art.\nWhen artist, researcher and the founder of the Himlayan Art and Cultural Heritage Project, <PERSON> came across a blurry image of <PERSON> in the Dallas Museum while doing a Google search for her project Remembering the Lost Sculptures of Kathmandu, she at once recognized the statue. She painted the stolen images with 23 karat gold and visually repatriated them in their respective sites.\nRead More: American Artist Returns Stolen Sculptures to Nepal With Her Paintbrush\n<PERSON> was delighted to see the same statue being repatriated at its original site, the Narayan Temple, on December 4, 2021.\nThough I painted Lakshmi-Narayan 2013-14 and located it in the @DallasMuseumArt in 2015, today was my first time meeting #LaxmiNarayan in person. Thank you for capturing the moment, @KanakManiDixit ! https://t.co/cI5U7im1Pa\n— <PERSON> (@JoyLynn_Davis) December 4, 2021\nDr. <PERSON>, lecturer in criminology at the University of Glasgow, tweeted:\n🎉 Laxmi-Narayan is home! 🎉 Made possible through the collaboration of so many different parties, today was an incredibly joyous day and so important for Patan, Kathmandu Valley and Nepal #livingheritage #lootedheritage #returnofthegods #intangibleheritage #community pic.twitter.com/Cc1Rf5SoJC\n— <PERSON> (@DrEmilineSmith) December 4, 2021\nPhotographer <PERSON> captured the return and reinstallation of <PERSON> through his lens.\nThe statue of <PERSON> being taken to Patan Museum after it was transferred to Nepali custody. Photo by <PERSON>. Used with permission.\nThe half male and half female statue of <PERSON>.", "765" ], [ "Photo by <PERSON>. Used with permission.\nThe idol of <PERSON> being taken on a palanquin to Narayan Temple, its home, from Patan Museum. Photo by <PERSON>. Used with permission.\nThe pedestal cleared for the reinstallation of Laxmi-Narayan. Photo by <PERSON>. Used with permission.\nThe Narayan Temple, abode of <PERSON>. Photo by <PERSON>. Used with permission.\nThe idol of <PERSON> reinstalled at the Narayan Temple. Photo by <PERSON>. Used with permission.\nThe God has returned to its home and a modern security system has been installed to protect the deity. However, many statues still await their repatriation, and more antiques from Nepal continue to be stolen — such as the recent theft of Bhairav from Kathmandu’s Halchowk.\nIt is very sad to know that Halchowk Bhairab has been stolen from the site yesterday night. :( pic.twitter.com/abONnsxmCy\n— <PERSON> (@r0shanmishra) December 7, 2021", "765" ], [ "18 Stunning Photographs of the Rana Tharus From the Southern Foothills of Nepal · Global Voices\nRana Tharus – The silver white looks strikingly beautiful on the bright dress and black shawls. Image by <PERSON>. Used with permission\nOnce rich landlords, Rana Tharus — the natives of Kailali and Kanchanpur districts in far-western Nepal — have witnessed loot, encroachment and discrimination.\nTheir isolated villages have been regularly looted by dacoits. They were displaced when the Shuklaphanta Wildlife Reserve was being extended, and many lost their ancestral land during a land settlement programme. The Tharus in Chitwan were reduced to occupying only 14 percent of their area after an anti-malaria programme sprayed DDT (Dichloro Diphenyl Trichloroethane) around their homes. Earlier, they occupied almost 90 percent of the area.\nIt is hard to find written documents about the Rana Tharus as they have lived in isolation, writes <PERSON> in his blog:\nIn India Rana Tharus of Khiri, and Nainital are under scheduled tribes. In case of Nepal in terms of habitats Rana Tharus are the native residents of Kailali and Kanchanpur since 16th century and are the first settlers of the two districts later they were joined by Dangauras of Dang and after the eradication of malaria and resettlement plan of Panchayat regime, Khasiyas [tribes] joined.\nHowever, despite of all odds, they have not forgotten their culture and tradition. Their way of life remains distinct and their traditional clothes and ornaments are a delight to every photographer and designer.\n<PERSON>, a German photographer who lives and works in Japan, travelled to the Kanchanpur district of western Nepal to capture the daily lives of the Rana Tharus.", "765" ], [ "Here is what she saw:\nAs the sun peeks from the window of the mud house, an old Rana lady is busy preparing meal. The mighty rays illuminate the surrounding and the dark corner of kitchen turns into a portrait painted in ochre.\nThe morning chores comprise cleaning the premises and taking the cattle out in the open.\nThe morning chores comprise cleaning the premises and taking the cattle out in the open.\nThe young one is a helping hand in looking after the goats and bringing grass for the animals.\nThe lady in her bright blouse sits on a rope cot and makes clay figurines for her grandchildren to play with in the upcoming festival. She draws inspiration from the nature, the tattoos on her arms and the bright colours of her blouse.\nLike <PERSON> Solitary Reaper, the lady reaps the paddy alone. Her bright costume stands out in the sea of yellow.\nWhen her friend joins her, it seems like a competition between the traditional dress she is wearing and the modern dress her mate is adorning. Both the colours burn bright in the yellow field.\nThe coming together of the community for a bountiful catch is a moment to watch.\nThe joy of working together and sharing the catch – there’s plenty to learn from them.\nThe catch is enough for everyone.\nIt's the marriage season and the ladies show off their ornaments.\nMirror! Mirror! Who is the fairest of all?\nTell me if I don't look good.\nAnd they don’t even leave the legs. They are laden with the silver ornaments.\nLike the beautiful patchwork in their dresses, the colours chosen by <PERSON> form a melange of vivid colours inspired by nature.\nThe young ones, careless and carefree, play and roam around the village. Their smiles are precious and innocent.\nWhether the young ones will follow the footsteps of their forefathers and conserve the rich culture – the future will decide.\nAll images used with permission. A version of the story was published in the blog Voice of Tharus.", "765" ], [ "A conversation with <PERSON>, one of the last speakers of a dying Nepali language · Global Voices\n<PERSON>. Image by author.\nFor years, people knew very little about the Kusunda language of western and central Nepal. The 2011 Census conducted by Nepal’s Central Bureau of Statistics puts the population of Kusundas, a forest tribe of western Nepal, at around 273. To learn more about the language and the culture of the Kusunda people, Global Voices spoke with <PERSON> — one of only two fluent speakers of the dying Kusunda language.\n‘The kings of the forest’\nIt was hot and humid, the roads were empty, and not even the battery-powered Tuk-Tuk drivers were willing to offer us a ride. With heavy tripods, cameras and other filming equipment, we headed to <PERSON> house in Kulmor village in Nepal’s Dang district. <PERSON>, in her early 80s, is one of the only two fluent speakers of the dying Kusunda language. The population of Kusundas is believed to be 273; however, field studies by researchers have shown only 150 of them dispersed in the Dang, Rolpa, Pyuthan, Arghakhanchi, and Surkhet districts of Nepal.\nKusundas have settled in villages after their forefathers spent their lives in jungles and caves as nomadic tribesmen. They would visit the villages only to beg alms, and many Kusundas still feel embarrassed to reveal their surname as they are still treated as ‘people from the jungle’. However, nowadays they have taken Thakuri surnames such as <PERSON>, <PERSON>, and <PERSON> — surnames connected with the ruling clan of Nepal. Kusundas claim themselves to be ban rajas, the kings of the forest.\nRead more: Indigenous Nepali Language With Only Two Fluent Speakers Sees Pages of Hope in Newly Launched Dictionary\nKusunda language is an isolated language which means it is not related to any other languages in the world. Unfortunately, it is also defined by a younger generation, that has stopped speaking it — leaving the language to slowly fade out as the older generations pass away. Besides <PERSON>, her sister <PERSON>, in her early 50s, is another fluent speaker of the language from their community.\n<PERSON>, a researcher devoted to reviving the Kusunda language, also speaks Kusunda language. However, <PERSON> fears whether her granddaughter <PERSON> will ever speak her mother tongue and keep the tradition alive. When we met <PERSON>, she was busy peeling green mangoes together with her granddaughter.", "811" ], [ "She was teaching her granddaughter to peel, slice and dry the mangoes for future use but unfortunately, they were talking in Nepali.\n<PERSON> with her granddaughter. Image by author.\nNo hooves, only claws\nAs we started talking to <PERSON> and she started telling us about their culture and tradition, a stray cow entered the barn. She suddenly rose from her seat, climbed down the ‘lisno’ (a wooden log shaped into a ladder), and shooed away the bovine. When she returned back, she talked to us about Kusunda food habits. She said, “Kusundas avoid animals with hooves but love eating ones with claws.” They wouldn’t even touch cattle including goats and pigs. They would neither kill a deer nor eat venison which shows how they co-exist with nature.\nHowever, they love eating birds, a pheasant being their favorite. And the monitor lizard is their preferred hunt. It's so special that it has become a part of the bridal ceremony, as they need to present its egg, meat, clothes and of course some money to the would-be bride's family. If they can’t find a monitor lizard egg, the initial conversation can’t happen between the interested parties. And no monitor lizard meat means ‘no marriage’ at all.\nThe bag and the snare. Image by author.\nStill hunting and gathering\nShe then unpacked a tangled bulk of cords. The mesh of cords was a snare to trap jungle fowls and bag meant to carry the trapped birds. Made from cords extracted from wild creepers, the snare is called ‘aant‘ and the bag is called ‘aamji‘ in Kusunda language. The Kusundas tie the snare between two trees, hide nearby and make sounds like pheasants by putting cycas leaves between their lips. As the birds pass through the trees, they get trapped and then they catch and carry those birds in this bag with perforations.", "811" ], [ "The Spiny Babbler, Nepal’s only endemic bird, fascinates ornithologists and bird lovers alike · Global Voices\nSpiny Babbler, the bird found only in Nepal. Photo by <PERSON>. Used with permission.\nAlthough more than 800 bird species are found in Nepal, the Spiny Babbler (Turdoides nipalensis) is the only bird that is endemic to the country. The greyish-brown bird, called Kaande Bhyakur in Nepali, lives in dense scrub and can be spotted more easily at elevations ranging from 500 meters to 2135 meters. Although the Spiny Babbler has been fascinating ornithologists the world around for years, environmental degradation is threatening this unique, much-loved bird.\nNepal has 876 bird species, with 1 endemic (Spiny Babbler). #AsianBirdFair\n— <PERSON> (@Varanussalvator) November 1, 2015\nThe medium-sized bird is shy in nature and it’s difficult to observe them, except early in the breeding season when males often sing in the open.\nView this post on Instagram\nFinally, a sight of the Spiny Babbler – a bird that occurs only in Nepal! Though they are Babblers, they sing a variety of rather loud & melodic songs from their hideouts amongst thick bushes, which resounds across the hills nearby – waking you up the possibility of seeing them. However, the amount of activity seems quite subdued in Winter. Spring & Summer season is probably the best time to catch a glimpse of this special bird which is recorded only in a few spots in Nepal. Makes one wonder what came to be that these birds have restricted themselves to only this geographical & political region. Thanks to @tharu_hunk & @nikitakhamparia for this. #spinybabbler #endemic #endemicbirds #nepal #chitwan #birdsofnepal #birdsoftheindiansubcontinent #birdsoftheworld #uperdangadi #nepaltourism #nuts_about_birds #birdingenthusiast #natureinfocus #nepalphotography #nepalphotoproject @insta.nepal #nepalnature\nA post shared by <PERSON> (@bombaywhite) on Jan 28, 2018 at 2:22am PST\nSong of a Spiny babbler (Turdoides nipalensis), the only endemic #bird ?of #Nepal known so far.", "447" ], [ "#Spinybabbler #BirdsofNepal #काँडेभ्याकुर pic.twitter.com/CoQtwJvnUp\n— ?<PERSON>? (@SonamTaC) October 30, 2017\nThe book The Status of Nepal’s Birds: The National Red List Series states:\nIt seeks insects almost entirely on the ground among low bushes, appearing only occasionally. Spiny Babbler mounts branches of bushes or small trees to sing, bill pointed upward and tail down. It is a good mimic, with squeaks, chuckles and chirps. It is most easily located by its song and occasionally sings as late as September and October. The species is subject to seasonal altitudinal movements.\nThe Spiny Babbler, found only in Nepal, has fascinated ornithologists and bird lovers from around the world. <PERSON> writes about ornithologist <PERSON>’s account of the bird in his book Search for the Spiny Babbler:\n“It was a species that had defied scientists for years, since 1843 or 1844. At that time <PERSON> Nepali collectors working for him in the unknown vastnesses of Nepal had secured several specimens,” he writes. The Spiny Babbler “had remained a mystery ever since, one of the five species of Indian birds, which, along with the Mountain Quail, had apparently vanished from the face of the earth. But not quite, for if my guess was right, here it was hopping about large as life on the wooded slopes above Rekcha.”\nLikewise, former-American ambassador to Nepal <PERSON> spent years trying to spot and photograph this bird.\nBirder <PERSON> tweeted:\nThe Ornitholidays group made the long drive from Kathmandu to Chitwan yesterday. The highlight was seeing Nepal’s only endemic bird, Spiny Babbler. @55birder pic.twitter.com/i0aBnvCbFE\n— <PERSON> (@DavidWalsh22) March 15, 2018\nThe bird is threatened by the clearance of scrub for agriculture and expansion of urban areas.", "447" ] ]

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[ [ "Easter in Trinidad & Tobago looks (and tastes) like this · Global Voices\nView this post on Instagram\nA post shared by <PERSON> (@barefoot.wanderer868) on Apr 11, 2019 at 4:00am PDT\nThe Easter holidays fall smack dab in the middle of Trinidad and Tobago's dry season — which means that “staycationers” choose a lot of outdoor activities to pass the time. Here's a glimpse at some of them, as well as a few other celebrated traditions that define Easter in the twin-island nation.\nAdmiring the Poui trees\nThis is the time of year that the Tabebuia (or Poui, as it is locally known) goes into full bloom, dotting the hillsides and roadsides with blazing yellow flowers. One strain of Poui produces delicate pink flowers, reminiscent of Japan's cherry blossoms. No matter the colour, the sight of a Poui tree in full bloom is nothing short of breathtaking, and each year, social media users share their snaps on Facebook and Instagram.", "482" ], [ "It just wouldn't feel like Easter without that Poui perfection!\nView this post on Instagram\nA post shared by Trinidad & Tobago (IZATRINI) (@izatrini_com) on Mar 22, 2019 at 7:22am PDT\nView this post on Instagram\nA post shared by <PERSON> (@riaz_mohammed_) on Mar 23, 2019 at 6:21pm PDT\nEnjoying a snow cone\nIt's a delicious treat any time of year, but this brightly coloured combination of crushed ice, syrups of varying flavours and (quite often) condensed milk, seems extra refreshing around Easter time. Vendors frequent popular beaches and the Queen's Park Savannah (the capital's main green space) to attract potential customers.\nView this post on Instagram\nA post shared by InSeason Tours Ltd. (@inseason.tours) on Dec 20, 2018 at 8:51am PST\nView this post on Instagram\nA post shared by Natalake ???? (@iamnatalake) on Feb 15, 2019 at 9:33am PST\nFlying high\nAnother popular Easter tradition is kite-flying, with a contest held each year on Easter Sunday at the Queen's Park Savannah.\nView this post on Instagram\nA post shared by <PERSON> (@petal1hunned) on Feb 4, 2019 at 6:34pm PST\nEaster Sunday kite-flying contestants, Queen's Park Savannah, Trinidad. Photo by <PERSON>, CC BY-NC-SA 2.0.\nPlaying some cricket\nIt's also a common sight at this time of year to see cricket teams decked out in their “whites”, playing friendly matches in community sports grounds (and yes, at the Savannah).\nView this post on Instagram\nA post shared by <PERSON> (@leuenbergerchris) on Feb 14, 2019 at 5:06am PST\nMunching hot cross buns\nEaster wouldn't quite be Easter without the special treat of hot cross buns. As far as religious denominations go, Trinidad and Tobago's population is predominantly Christian, and the buns are traditionally eaten on Good Friday.\nView this post on Instagram\nA post shared by <PERSON> (@pechepatisserie) on Apr 11, 2019 at 8:27am PDT", "482" ], [ "Trinidad & Tobago Carnival 2017 Crowns Its King and Queen · Global Voices\nGloria Dallsingh portrays “Glamour Queen” for the band Kallicharan Carnival. Photo by <PERSON>, used with permission.\nTrinidad and Tobago Carnival prides itself on its traditional masquerade, but Carnival lovers are just as appreciative of the “big” mas — the incredible and often massive costumes that compete for the coveted titles of King and Queen of Carnival. Not only are they works of art; they are also feats of engineering!\nThese individual costumes are usually part of larger Carnival bands, which each have their following and portray different themes from year to year. Widely shared on Facebook, here's a quick look at some of the beauties that photographer <PERSON> captured as they crossed the main stage at the country's Carnival mecca, the Queen's Park Savannah, for Carnival 2017.\nOther countries, different cultures\nCarnival is an escape from the rigors of everyday life. Many Carnival King and <PERSON> contenders transport spectators to other lands (Africa, China, Arabia) and other worlds (enchanted rainforests and underwater kingdoms). Either way, you are immersed.\n“Wings of Africa” portrayed by <PERSON>; photo by <PERSON>, used with permission.\n<PERSON> portrayal of “The Yellow Emperor And The Winged Dragons”, for the band “Chinese Dynasty”. Photo by <PERSON>, used with permission.\nThe beauty of Trinidad and Tobago\nSome costumes this year represented various aspects of life in Trinidad and Tobago. “Down de islands” (DDI), for instance, depicted in the portrayal below, refers to an idyllic cluster of islands off the north west coast of Trinidad that is home to the country's boating industry. It is also a favourite domestic tourism getaway.\n<PERSON> portrays “Down The Islands” for the band Soar! Photo by <PERSON>, used with permission.\nThe 2007 King and <PERSON> contenders also included a nod to the country's national instrument, the steel pan, which was birthed in Trinidad and Tobago and is the only surviving non-electronic instrument to have been invented in the 20th century.\n<PERSON> portrays “Musical Vibrations” in the Fancy Sailor category for the band “Swirls!” Photo by <PERSON>, used with permission.\nThere was also a modern take on the Midnight Robber, one of the most iconic traditional Carnival characters.", "264" ], [ "Reminiscent of a bad-guy cowboy with his wide-brimmed, fringed hat, the robber is very flamboyant, sporting a cape that goes well with his signature “robber talk”, which is rather highbrow and quotes liberally from biblical verses, Shakespearean monologues and other famous literary sources. The character typically uses props (fake pistols, swords and even miniature coffins) to enhance his intimidation quotient.\nMasquerader <PERSON> portraying a costume entitled “Doodad Daddy”. Photo by <PERSON>, used with permission.\nSocial commentary\nOther portrayals depicted topics of interest — social, political and otherwise — with originality and a bit of humour. The Zika threat in the region and the election of U.S. President <PERSON> were just two of the issues covered.\n<PERSON> as “De Injector”; photo by <PERSON>, used with permission.\n<PERSON> “Category 5 – Hurricane Trump” for the band “D’ Element – Earth, Wind and Fire”. Photo by <PERSON>, used with permission.\nFancy Indian mas\nThis is one aspect of traditional Carnival that maintains its allure year in and year out. Featuring colourful and elaborate headdresses adorned with hundreds of feathers, the more modern King and <PERSON> costumes for these bands are expensive to make, due to their sheer size and the materials used. The most popular bands of this genre tend to spring from south Trinidad, with longtime band designer Kallicharan leading the charge.\n“Lady in Blue” is portrayed by <PERSON> for the band “Kallicharan Carnival”. Photo by <PERSON>, used with permission.\n<PERSON> portrays “Monia Haka – Out of the Ashes” for the band “San Fernando Heartbeat”. Photo by <PERSON>, used with permission.\n<PERSON> “Queen Chirapaq – A Tribute to <PERSON>” for the band “Lionel Jagessar and Associates”; it eventually placed third in the Queen's competition.", "264" ], [ "Caribbean cooking in the time of COVID-19 · Global Voices\nChanna (ckickpeas), beans, and “roti” (a Trinidadian hybrid of a soft naan bread). Photo by <PERSON>, used with permission.\nCheck out Global Voices’ special coverage of the global impact of COVID-19.\nEach Caribbean territory has its own individual customs, quirks, and cultural and social traditions. Naturally, this extends to cuisine.\nJamaica, for instance, is known for its ackee and saltfish or jerk-style meats; Barbados, its flying fish and cou-cou; Trinidad and Tobago, its pelau, shark and bake or doubles — but it's likely that Carribeans enjoy all types of food from every region. This is especially true for members of the diaspora, for whom Caribbean cooking brings a sumptuous whiff of home.\nAmid the COVID-19 pandemic, one Trinidadian diaspora blogger decided to use the mandated isolation time to get creative in the kitchen. “Not wanting to go out unnecessarily,” Isle Chile writes, “we are trying to utilize the ingredients we have at home to make our meals.”\nThe result is a batch of easy-to-make, flavourful recipes, often accompanied by amusing anecdotes or Caribbean-centric musings, that may very well make time spent in isolation more pleasant. Here are a few highlights…\nA favourite rice dish\nA version of “pelau”, a beloved rice dish in Trinidad and Tobago. Photo courtesy Isle Chile, used with permission.\nThis one-pot meal, involving browned rice, peas and your choice of meat, is hugely popular. <PERSON> explains:\nI can’t think of a specific time when Trinis eat pelau.", "941" ], [ "It works any time of year, at any festival or celebration […] It can be stored for the week in the fridge and the staler the pelau, the nicer it tastes, in my opinion.\nAs far as the method goes, she says, “pelau is all about cooking down the food together.” She said that a couple of tablespoons of coconut milk to ramp up the flavour, which may contribute to the fact that in her version, the rice is not as brown as in a typical pelau dish. However brown the pelau, however, the secret is to find “that sweet spot in the cooking time where [the] dish is not overly dry and not soggy”.\nReady-to-eat roti\nA wrapped “roti”, a Trinidadian dish in which a soft type of naan bread is filled with an array of curried ingredients. Photo by <PERSON>, used with permission.\nWhile the blogger is comfortable making curry, making the dhalpouri (roti skins made from flour and split peas) in which to wrap them is not her forté. Thankfully, these are often pre-packaged, and she happened to find some in her freezer, so a short while later, there was both chicken and beef roti to be enjoyed. She writes:\nIn Trinidad, my family, like many, would accompany a roti with a red soft drink (pop), sweet drink or as we would call it (cutting off the last letter of the first word) a sofdrink or a sweedrink. Of course, I didn’t have one […] so I got creative and made a cranberry spritzer instead…Look, it red oui [yes], and I was happy to pretend.\nRoti is so beloved in Trinidad and Tobago that there's a saying, “You cannot please everyone. You are not roti.” In this vein, Isle Chile mused, “There is nothing more tasty, more special and no better way to say ‘I love you’, in my opinion than bringing me roti…”\n‘Sunday lunch’\nStewed chicken, pigeon peas and macaroni pie, all typical “Sunday lunch” fare. Photo by Isle Chile, used with permission.\nFor most West Indians, the concept of “Sunday lunch” is a big deal. Not only does it usually come with some measure of pomp and circumstance, bringing out the “good” flatware and cutlery, but it's also an opportunity for families and friends to come together.", "851" ], [ "Who will win Trinidad & Tobago Carnival’s 2019 Road March? · Global Voices\nA carnival masquerader “jumps up” to soca music on stage at the Queen's Park Savannah, on Carnival Tuesday, 2009. Photo by <PERSON>, used with permission.\nWhen revelers take to the streets each year for Trinidad and Tobago Carnival, they do so with a soundtrack. Their playlist is always an energetic mix of that year's hottest soca music hits, but the Road March — the song that is played the most at specified judging points along the parade route — is a title that comes with both a valuable prize package and the prestige of being part of a proud history.\nFor most soca performers, the appeal of winning the Road March is, quite literally, street cred. Claims in the last decade or so of the competition being rigged — ostensibly by a group of powerful radio station owners, DJs and music industry executives known as the “soca mafia” — have not eroded the belief that the Road March represents the voice of the people.\nSoca star <PERSON>, who has won the coveted Road March title a whopping nine times thus far, describes it as “the song that make[s] the people feel the most vibes and come out of [them]selves” — and which artist wouldn't want to lay claim to that?\nBut don't be fooled into thinking that the road to the Road March is solely based on creative merit. A Road March song must have certain key ingredients to even be in the running:\n1. A danceable, yet powerful melody that makes people want to “break away” on stage, with lyrics that capture the feelings of joyful release and abandon that Carnival represents.\n2. A refrain that the audience can echo, in the call and response tradition of the calinda, from which calypso — and its modern-day hybrid, soca — originated.\n3. A well-timed release. If a song peaks too early in the season and doesn't have staying power, competing tunes can usurp its position. Conversely, if a great tune is released too late, masqueraders may not have enough time to get familiar with it during pre-Carnival events.\nSometimes, the Road March contest has a clear favourite that never gets challenged; at others, the competition is so stiff that it's simply too close to call.", "264" ], [ "In no particular order, here are some the songs that we think are the biggest contenders for Trinidad and Tobago Carnival's 2019 Road March …\n1. “Savannah Grass” by <PERSON>\nThe Queen's Park Savannah, an oasis of green space in the middle of Trinidad's capital, is the hub of the country's Carnival celebrations and home to the festival's main stage. This song perfectly captures the significance of the space, and the memories it has helped create for masqueraders through the years.\nThere is a reverence about the tune: as if the Savannah is the sun at the centre of the Carnival universe and everything else just has the privilege of revolving around it. “Savannah Grass” is an invitation to experience this magical world. Oxymoronically, the loose steadiness of the percussion is a nod to both the regimented dedication of Carnival lovers and their easygoing way of enjoying themselves.\nThe tune is both melodious and energetic, with a pace that makes it a good song for “chipping” (the light shuffle step with which masqueraders walk/dance down the road). By its clever incorporation of archival Carnival footage, the official video further elevates the genius of the song by showing how it seamlessly spans generations and builds on the foundation blocks of calypso to produce a fresh soca offering. Even if it does not win Road March (though it has a very good chance!), “Savannah Grass” will go down in the annals of soca music as one of the timeless tunes that stir the emotions of Carnival lovers everywhere.\n2. “Rag Storm” by <PERSON>, featuring 3 Canal\nAn interesting idiosyncrasy of “playing mas'” and dancing to soca music is that somehow, people's hands go up in the air, usually with whatever they are holding at the moment, from drinks to facecloths. Colloquially called “rags”, these come in handy for soaking up the sweat while “jumping up”. The practice was not lost on <PERSON>, who wrote a song called “Get Something and Wave”, that won the 1991 Road March.\nHe echoed the concept a few years later with “Bacchanal Time”, in which he commanded masqueraders to “start to wave” as the brass section played the familiar “F-jam” or “tantana” melody in the background.", "264" ], [ "Trinidad & Tobago’s Carnival lovers will only be getting a ‘taste’ of the festival this year, but do they even want it? · Global Voices\nFrame grab of a Blue Devil, a traditional Trinidad and Tobago Carnival character, from the NGC “This is Home” Carnival series. Image by <PERSON>, used with permission.\nIf these were “normal” times, Trinidad and Tobago's world-famous Carnival season would already be well underway, with fetes and soca concerts drawing large crowds, and the early rounds of steel pan and masquerade competitions in full swing, all leading up to the two-day street parade on the Monday and Tuesday preceding Ash Wednesday, which falls on March 2 this year. But these are times of pandemic and, with the 2021 festival cancelled and creatives feeling the fallout, the government devised a way to make a version of Carnival happen for 2022.\nEnter “A Taste of Carnival” — an attempt to allow every sector of the Carnival landscape to have events at three designated “safe zones”. These three COVID-19 protocol-compliant venues — the Queen's Park Savannah, the traditional mecca of the local festival, and Queen's Hall, both located in the capital, Port of Spain; as well as the Naparima Bowl, a performance art space in south Trinidad — will only be accessible to fully vaccinated patrons and performers.\nUnlike the recently staged Miami Carnival, the approach involves the use of pods, whereby people will be physically distanced from one another within their own social bubbles while patronising any of the carded events. Most notably, the beloved J'ouvert celebrations, which herald the start of the street festival, and the Parade of the Bands will not be on offer, but other events are scheduled to begin on February 4.\nPublic reaction to the news has been mixed.", "1019" ], [ "Not only is Trinidad and Tobago in the throes of community spread of the Omicron variant, with daily new positive cases at around the 600 mark and an estimated 49.5 per cent of the population fully vaccinated, but the thought of the government dedicating what was initially said to be just over TTD 30 million (just under USD 4.5 million) on an untried and scaled down version of the festival seemed like fickle economics to some cultural activists.\nFollowing some criticism, the budget has since been reduced to TTD 20 million (just under USD 3 million), with the lion's share being allocated to three key stakeholders: Pan Trinbago, the Trinbago Unified Calypsonians Organisation (TUCO), and the Trinidad and Tobago Carnival Bands Association.\nIt was a move that did not go down well with facebook user <PERSON>, who said:\n[S]lashing the budget for ‘A Taste of Carnival’ does not make the event better, and worse does not make the public outcry go away. Pods build without confirmation of an expenditure budget. Why <PERSON>, chair of the National Carnival Commission] still have a job? Why NCC still spending government money? Why it so late in execution and marketing? A $15M ‘signal that the entertainment sector is reopening’ is one way of spending the People's money. The sector response is muted as high demand talent has left these shore to explore the markets overseas: foreign exchange, jobs, and audiences. A plan that began too late is now reduced to thing to show that ‘we care.’ Not good enough.\nOn Facebook, <PERSON> noted:\nHow this money is to be allocated should be underpinned by international Best Practice understandings of the role of government money and the role of practitioners.\nSome of the measures he suggested include a merit-driven grant funding evaluated by peer-based assessment, respect for the artistic process, and corporate sector support.\nOn Twitter, photographer <PERSON> shared a statement by the estate of the late Carnival designer <PERSON>:\nThe estate of <PERSON> spoken on @ncc_tt‘s #TasteOfCarnival. pic.twitter.com/bJ0mb3hPls\n— DavidWears🇹🇹 (@DavidWearsPhoto) February 3, 2022\nSocial media users also raised concerns about transparency, the wisdom of prioritising an event of this nature given citizens’ current economic and healthcare needs, and the fact that the majority of the nation's school age children have been out of physical classes since March 2020.\nPhotographer <PERSON> asked:\n33 Million allocated for carnival and some goat pens [referring to the pods] and we cannot use this money to get children back to school! Really?", "892" ], [ "Take a hike! Some of the Caribbean’s most scenic trails in photos · Global Voices\nHikers stopping to look at the view on Jamaica's famous Blue Mountain Trail. Photo by <PERSON>, used with permission.\nThe United States enjoys hiking so much that it dedicated an entire day to it: National Hiking Day, celebrated on November 17. Although the footprint of Caribbean hiking trails may not be able to rival the 60,000 miles the U.S. can boast of, the region has many avid hikers, the views are just as breathtaking, and—in the midst of not only the COVID-19 pandemic but the climate crisis, which poses an existential threat to many island nations—it may be more important than ever to connect with nature.\nIn that spirit, here are a few photos from various Caribbean territories that may just inspire you to dust off your hiking boots and hit the trails!\nBeautiful bamboo\nEntrance to the Bamboo Cathedral in Chaguaramas, Trinidad. Photo by <PERSON>, used with permission.\nLocated in Tucker Valley in Trinidad's Chaguaramas National Park, the Bamboo Cathedral is so named because the tall stalks of the bamboo lining the trail overlap to form basilica-like arches. Several watercolor paintings by Trinidad’s revered 19-century artist, <PERSON>, were inspired by this trail, which has remained more or less the same for over 150 years.\nView of the sea along the road to the Tracking Station at dusk. Photo by <PERSON>, used with permission.\nThe trail, which offers stunning glimpses of Macqueripe Bay and the north coast, ascends to the Tracking Station where a massive satellite dish dating back to the Cold War dominates the landscape. Chaguaramas, on Trinidad's western peninsula, was also used as a United States military base during World War II.\nThe abandoned satellite dish at Tracking Station, Chaguaramas, Trinidad. Photo by <PERSON>, used with permission.\nBrilliant beaches\nA family on a coastal hike from Harbour View in the parish of St. Andrew, to Bob Marley Beach in St. Thomas, Jamaica. Photo by <PERSON>, used with permission.\nPart of the charm of Caribbean hiking is that many trails lead to the beach, like this trail on Jamaica's southern coast that runs from St.", "482" ], [ "Andrew, the parish in which the capital, Kingston, is located, to the neighbouring parish of St. Thomas on the island's south-eastern tip.\nBeach along Trinidad's north-east coast. Photo by <PERSON>, used with permission.\nThere are many hiking trails along Trinidad's north coast, including Rio Seco, which leads to a waterfall, Shark River, which is a pleasant trek along a winding river, and this unnamed trail frequented by locals, which leads to this scenic pebble beach.\nWonderful waterfalls\nBreadnut Valley Estate, Maggotty, St. Elizabeth, Jamaica. Photo by <PERSON>, used with permission.\nJamaica is not called “the land of wood and water” for nothing. The island has some of the most breathtaking locales in the region, including this waterfall, at Jamaica's Breadnut Valley Estate, which is off the beaten track, but well worth the trek.\nEdith Falls, Chaguaramas, on Trinidad's northwestern peninsula, and Avocat Falls, Blanchisseuse, along the island's north coast. Photos by <PERSON>, used with permission.\nThe hike to Trinidad's Edith Falls involves a fairly short and easy walk until you get you the rocky section, located upriver, which involves some climbing. The fall itself is really more like a water wall, as the water flows down various sections of the expansive rock face—especially during the rainy season, when it is more impressive. The hike to Avocat can be approached from opposite directions, one mostly via land and part of the other involving trekking through the Marianne River.\nTrafalgar Falls, Dominica. Photo by <PERSON>, used with permission.\nThe trail to Dominica's impressive Trafalgar Falls is a comfortable 10- to 15-minute walk, but if you need a respite before reaching the waterfall itself, there are warm sulphur pools you can take a dip in en route. Depending on how agile you are, you can climb a bit further and swim in the pools and springs beneath the falls.\nGoing green\nOn the Blue Mountain Trail. Photo by <PERSON>/Jamaica Conservation and Development Trust, used with permission.\nOne of the great joys of hiking in the Caribbean is its viridescence. Although dry seasons in the Caribbean can be harsh, the trails are typically lush and leafy, providing a real escape from the rigours of the world.\nThe Bull Head Mountain trail, Clarendon, Jamaica, and the route to Mount St.", "482" ], [ "COVID-19 causes Trinidad and Tobago to cancel its Carnival for 2021 · Global Voices\n“Carnival Tuesday meggie”: Carnival lover <PERSON> gives a “meggie” – a hand gesture that brings the thumb and four fingers together in a sign of derision, scorn or rejection. Photo by <PERSON>, CC BY-NC-ND 2.0.\nIt may have been anticipated, but now it's official: thanks to the COVID-19 pandemic, Trinidad and Tobago's 2021 Carnival celebrations have been cancelled.\nPrime Minister <PERSON> made the announcement on the afternoon of September 28, calling the national festival “the perfect environment for the spreading of the virus.” Despite the inevitable economic blow the decision will have, he said, he's not prepared to take the risk.\nReaction, predictably, was split. While most people applauded the decision, calling it both “expected” and “solid”, others wondered about the fate of those whose income depends on the national festival. When one Facebook user called the decision “insane”, <PERSON> retorted:\nNO! it's realistic and logical is what it is. Everyone else has already gone ahead and cancelled theirs. I do not possibly see how any “right thinking” citizen of T&T could possibly think to put the country under further threat from Covid-19.\nTrinidad and Tobago Carnival 2020 was already over by the time the country recorded its first case of COVID-19 in March.\nOther countries that host annual Carnivals, including Brazil, have already postponed their 2021 events, but it is only the third time in history that Trinidad and Tobago has put theirs on hold—a history that Trinidadian author <PERSON> chronicled in his book “Parade of the Carnivals of Trinidad, 1839-1989″.\nIn the chapter etitled “Carnival in a World of War,” <PERSON> noted that the festival continued as usual during World War I, which was fought largely in Europe. After the war ended, the 1919 celebrations were known as “Victory Carnival”.", "1019" ], [ "During World War II, the festival did not take place at all between 1942 and 1945, although “spontaneous” celebrations happened on May 8 and 9, 1945 in honour of Victory in Europe (VE) Day, and on Aug 15 and 16, 1945 for Victory over Japan (VJ) Day.\nThe country's street festival was postponed from February 1972 to May 1973 because of the threat of the polio virus, so it is not as if the move to put off next year's Carnival celebrations is unprecedented. In fact, many netizens saw it coming, but hoped that a virtual celebration might take its place.\nIn a Facebook status update on June 24, <PERSON> predicted that “promoters are going to have to Zoom in fete-goers to the music and the vibe from concert halls in ‘foreign’ [abroad]!” Virtual Carnivals are something that costume designers like <PERSON> have already been experimenting with—the band she and her husband created for Notting Hill Carnival 2020 was showcased online.\nTrinidad and Tobago's Carnival stakeholders have also expressed excitement about the opportunity to share their creativity in the virtual realm. Facebook user <PERSON> suggested:\nWe keep forgetting that there are elements of carnival that are outside the realm of the street parade. We should adapt and showcase our calypso, pan, extempo and dimanche gras much like how sporting events are still being carried out.\nBoth calypso music and the steelpan instrument originated in Trinidad and Tobago. Extempo refers to an extemporaneous form of calypso, and Dimanche Gras, literally translated as “Big Sunday,” is a grand show at which coveted titles like the Calypso Monarch are decided.\n<PERSON> of Trini Good Media, which produces the “Talk ‘Bout Us” podcast, crowdsourced opinions on what a virtual Carnival might look like. Most commenters felt that simply delaying the celebrations would be best, with <PERSON> suggesting that it may be an opportune time “to re-focus to community Carnivals and limit the size of large bands.”\n<PERSON> added:\nAside from the issue of a vaccine being made available globally, it’s difficult to envision any Carnival 2021 at all, due to the commercialization of the festival, and the limitations of two major sources of revenue: Government expenditure will be prioritized elsewhere, and corporate entities will slash sponsorship budgets.\nHaving a 2021 Carnival may jeopardize the planning cycle for one in 2022. It will be almost impossible to execute, as Carnival mas [costume] production is essentially a 12 month cycle.", "264" ], [ "World Environment Day should mean more in Trinidad & Tobago this year · Global Voices\nScreenshot of turtle hatchlings at Trinidad's Emperor Valley Zoo, taken from the video shared on Senator <PERSON>'s Facebook page.\nTrinidad and Tobago greeted this year's World Environment Day, celebrated every June 5, with mixed emotions.\nWhile there was heartening news, such as the century-old South American river turtle living at the Emperor Valley Zoo in Port of Spain welcoming 18 new hatchlings, there were also concerns about the continued negative impact that humans have on the environment.\nSenator <PERSON>, the country's minister of agriculture, land and fisheries, shared a video of the turtle hatchlings on his Facebook page, noting that the mother laid the eggs during the peace and quiet of the country's COVID-19 lockdown:\n100 years old, 18 babies! […] It’s a signal made clear by COVID 19. As our planet develops at unprecedented speed, we must care for nature. Just over two months ago the Zoo announced the turtle laid eggs on land within its enclosure instead of the pond it had previously laid. The Zoo felt this was due to the closure of the facility in mid-March and the comfort the turtle may have felt in venturing out the pond and onto the sandy area to deposit the eggs. The hatching today is excellent news and demonstrates the importance on World Environment Day of striking the balance between human activity and care for nature. As UN Secretary General <PERSON> says in his 2020 message, to care for humanity we must care for nature.\nMeanwhile, the Facebook group The Land of the Hummingbird posted stunning photos of various types of hummingbirds, explaining:\nTo celebrate World Environment day, six of our little hummingbird gems.", "1019" ], [ "Trinidad and Tobago are so blessed to have 19 recorded species of hummingbird.\nIn that same vein, Facebook user <PERSON> thought World Environment Day the perfect opportunity to acknowledge the contributions of some of the region's environmentalists, singling out two “top birders in Guyana,” who she says are “so humble and willing to share their knowledge.”\n<PERSON>, a well-respected environmentalist and past president of the world-renowned Asa Wright Nature Centre, was hopeful that the day would be marked meaningfully and shared a few ideas of how that could be done:\nI am […] aware that the current COVID-19 Pandemic will put a ‘damper’ on celebrations. Nevertheless, I am hopeful that our Prime Minister and the Minister of Agriculture will take time off from their busy schedules to each plant a suitable tree of their choice on the perimeter of the Queens Park Savannah or in the Botanical Gardens. It is my wish that the newly appointed Chief Secretary of the Tobago House of Assembly and the Secretary for Agriculture of the THA, will each also plant a Flowering Tree in an appropriate place.\nDespite the state TV station broadcasting a series in the lead-up to World Environment Day which focused on everything from a “little fish from Trinidad which has given scientists a new understanding of evolution and natural selection” to the “delicate balance […] struck between commerce and nature,” other social media users were more pragmatic.\nPhotography studio Rapso Imaging was realistic about the challenges, reposting images of the country's main landfill — shots that won photographer <PERSON>'s first place in the professional category of the European Union's 2019 competition on the environment:\nWe are all connected to our garbage dumps as it is we who generate this waste that in turn severely impacts our environment. Venturing into the middle of stink of it was the only way that he was able to return with an image that tells the story of what we choose to ignore.\nOf course, we could easily share the pretty, the beautiful, and the breathtaking images, while ignoring the fact that we are choking our planet with the pollution we are generating, if we are not careful, humanity will pay the price.\n<PERSON> himself added:\nToday on World Environment Day, I chose not to share a pretty picture, this is our truth, our reality and it is time to stop burying our collective heads in the sands. This is simply [no] other issue that needs to be addressed in our World today, Our very survival depends on it.\n#sharethetruth, #worldenvironmentday\nUndoubtedly, the country and the wider Caribbean region have a lot a stake when it comes to the environment. Small island developing states are at the greatest risk for the devastating effects of climate change, including rising sea levels, coral bleaching, and the impact of tourism developments on coastal areas. Each Atlantic hurricane season, monster storms have been ravaging the region with increasing intensity.", "142" ] ]

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[ [ "It doesn't orbit us - it orbits the Sun, just like we do.\nHowever:\nbizarrely and amazingly, it \"stays with us\" ...\nit keeps position outside us - it takes JWT 365 days to go around, just as it takes us 365 days to go around.\nHow is this achieved?\nWe have an incredibly long piece of string attached to it.\nWe (the Earth) spin around just like on a playground ride. We hold on to the string, and the JWT goes around \"outside\" us, and stays in place.\nNah, no string but bizarrely gravity works exactly, precisely, like a string would - if you are at exactly the right distance.\nVarious interesting spacecraft hang out at this \"L2\" region. I have included an accurate drawing of our astounding GAIA spacecraft in the diagram.\nThe JWT is kind of the \"strongman\" of our space telescopes. The <PERSON> -quarterback type in high school. You know ... tallest, strongest, goes on to marry <PERSON>, etc. GAIA is kind of the \"class smartass and superbrain\" type. (Beyond all belief, GAIA is ...", "419" ], [ "mapping the milky way. No, really.)\nAll of this was invented by the French (this guy called Lagrange - the \"L\" in \"L2\"), so today naturally the French just assume that JWT, etc, are all, basically, French things - after all, they thought of it, someone else just did some welding.\nThe actual \"detailed\" manner in which GAIA for example flies is a Lissajous orbit. (Yup - another French guy!) Coincidentally Lissajous sounds a bit like \"lasso\", and on nice diagrams such as here you can see it looks like a lasso. Giddyup, space telescopes!\nNASA, err, France's blokes who worked this out:\nBonus factoid - you might be wondering why the effort to put it in this particular place. This was explained very nicely by @A.Leistra in a comment.\nHave a careful look at the diagram and put yourself in the place of the yellow JWT... Try it at different points around the diagram.\nNow - from any where on the circle, look towards the Earth and the Sun.\nNotice that ......... they are in the same place from your point of view.\nThe Sun & Earth are total troublemakers to space telescopes. Because they are always in exactly the same direction, the JWT can keep its back to them at all times, always. The JWT has one big shield, which will always shield both the Sun & Earth.\nHow clever are the French?", "758" ], [ "A variant on what has already been proposed here - the danger is again, from space, because astronomy and astrophysics is SO cool.\nBlow the horns, sound the alarms, we are on a collision course... with a BLACK HOLE.\n1. Noone would know about it. Normal, run-of-the-mill, friendly neighbourhood sized black holes (as opposed to wallmart sized monsters at the centers of the galaxies) are super difficult to spot if You are not actively trying to find them because You had clues that they are there in the first place. And it just so happens that this particular black hole is rather small and has been travelling in space without any companionship. No accretion disk, no large body to affect with gravitational field, nothing.\n2. An astronomer spotted it because of luck. He was drunk and was bragging to his non-science buddies 'muh scienz' and typed random coordinates in the sky with his telescope at home and pushed 'track this spot in the sky'. He didn't see much of course at the time, but hangovered in the morning, he spotted something wierd with the image from the telescope, it was tad bit too... empty. Especially after the few hours of data gathering. So he found some free time on some real sized telescope... and wet his pants seeing the gravitational lensing.", "73" ], [ "It's like winning a lottery, spotting a black hole like that. Muh papers! Muh recognition! A few months later and 10 publications in PNAS, someone calculates (for the fun of it) the current velocity and direction of the black hole. Well, bad news, it's going to go straight through the solar system in ...\n3. You can have this disaster happen with any time delay You want. The first effects may be seen in a month, may be seen in 100 years. Calibrate it however You want.\n4. There IS no way to stop it. One does not simply change the trajectory of a black hole.\n5. Put it close enough, and there IS no escape (it wouldn't be detectable without enormous amount of luck) until literally on our doorstep - and then it's too late to start building interstellar colony ships.\n6. The sheer unprobability of this event is interesting. One type of religious people start arguing this is an argument for the existence of god, and that he IS mad. Other type of religious people praying day and night, hoping that it's just a test and in the end the reality devouring monster will be deflected by saviour. UFO theorists shout about Kardashev level LOTS civilisation which decided to eradicate humanity in this, rather baroque, manner. So what is the truth about this? Epic bad luck? Malevolent intelligence with a penchant for overkill of epic proportions? Angry god? Or just god testing the faithfull? Or maybe something more curious...?", "337" ], [ "No need to make it complicated: what about this...\nJust scribble a rectangle on a piece of paper, and say \"there are 100 billion stars in our galaxy\"....\nThen, color off (let's say) 1/3 of the rectangle, and say \"only one third of those are the sort of star that could have life, so that's blah billion\"\nThen, color off (say) 9/10ths of that box, and say \"we believe about 90% of those have planets - so that's blah billion\"\nThen, color off (say) 1/20th of that box, and say \"of those with planets, it seems that about 1 in 20 have Earth-like planets. Now we're down to blah billion...\"\nand so on.\n(Note: the <PERSON> equation has a number of fairly silly terms relating to \"nuclear war!\", which were added as political sops in that era; suggest ignore these unless you want to sound 90 years old!)\nSo just scribble a box or draw a line on a piece of paper ... or maybe use \"a bag of marbles\" as the other answer suggests.\nJust BTW there is in fact an entire documentary (I noticed it on \"Netflix\") called \"The Drake Equation\" which does exactly what you say...\n.. it is not really very good as I remember.", "840" ], [ "I think the guy simply draws a line in the ground, to do the \"fractions\" demo, you know? (ie, they just erase more and more of the line). It doesn't need to be more complicated than that.\nIt's worth noting that the <PERSON> equation simply points out:\n(i) if you multiply those three or four fractions together, you get the number of civilizations in the galaxy. Which is self-evident.\nbut, the whole point is\n(ii) we have utterly no clue - not even vaguely - what most of the fractions are,\nYou could say it's a written formula, which, helps clarify our thinking on, something we are utterly clueless about. So rather than just vaguely saying \"we're utterly clueless,\" we can speak more clearly about the nature of our cluelessness!\nalthough interestingly,\n(iii) very admirably, the issue of \"How many stars have planets?\" ... one could say that issue has been somewhat settled these very years, as we speak - that's great.", "682" ], [ "It's simply because the sun and planets were formed out of a big pile of dust. Originally the dust was spinning. So once the dust became planets, it kept spinning around. That's all there is to it - that's why the solar system is spinning around.\nIt's was once a pile of dust that was spinning a bit; it's still spinning.\nYou then ask,\n\"For example, if you turned off gravity, why would the planets carry on moving?\"\nTHat's just the same as asking \"if I spin something around on a string, and break the string, why does it keep moving?\"\nFor that matter, it's the same as asking \"What is momentum?\" So, if you push something ...... why does it keep moving?\nAt this stage in history, we have utterly no clue, at all, what the heck time, space, matter, and momentum are. \"Why does momentum do what it does?\" is for now just one of those super-deep questions like \"What is time\" or \"So what caused the big bang\" or \"What is gravity\" or \"What's the explanation for this quantum stuff?\" or indeed ... \"What is momentum\"?\nSo, why do the planets keep moving?: answer \"momentum\". If you want to know \"what causes momentum?\", that is one of the basic total mysteries.\nFor now, nobody has a clue.", "135" ], [ "You may as well ask ... what is space, what is time, etc.\nRegarding momentum, you might like to read up about the so-called \"<PERSON>'s conjecture\". The famous <PERSON> was, like you, fascinated by the question \"WTF is momentum anyway?\" One sort of general thinking-point originating with this smart guy called <PERSON> is that momentum could have something to do with \"all the other mass in the universe\". Nobody has a clue about this, and it's just a vague general idea.\n<PERSON> was a pretty smart guy (if a bit whacky), and in the end he found gravity so mysterious, he just put it down to God. He probably found momentum as mysterious, and he was one of the first guys to think about it clearly.\nAn interesting point: actually everything astronomers look at (all galaxies, all structures of galaxies) in fact does not (!) behave the way small things (our solar system, as in your question) behaves in terms of gravity and momentum. This is usually explained by invisible unknown matter (\"dark matter\") or for a few scientists, that gravity works differently than we think presently. So the fact is with issues like gravity/momentum you ask about ... not only do we have no clue \"why momentum works\" but when you look through a telescope, issues like \"orbits\" work totally differently anyway!", "135" ], [ "It couldn't be easier to answer this question.\nIt's utterly commonplace in English that words have different meanings. When you, OP, say \"clouds\" you are almost certainly talking about \"cumulus clouds\" ... cartoon clouds.\nA key thing to know is the clouds you are seeing, the bottoms are typically\nabout one or two kilometers off the ground.\nThe tops are typically\n3 or 4, up to about 10 kilometers off the ground.\nAny number of simple references about cumulous clouds can be googled up to gain these facts.\nYou can read-up online about the visual characteristics of \"cumulous clouds\" so that when you see one you can be more certain it likely conforms to these approximate sizes. Just as you say, you'll now know whether it is merely 100 meters across and close, or conversely 100s of kilometers away.\nAs I say, a good thing to bear in mind is that the bottoms of cumulous are usually 1 to a few km off the ground - that will give you a sense of scale, at least give you an order of magnitude anyway.\nNote that - of course, obviously - there are many types of clouds from small wispy ones to planet-sized clouds.\nRegarding non-cumulous clouds - you know nothing from this post :) Read up on them separately. But it's very likely you meant, and from your description you likely meant, \"cumulous clouds\".\nNote too that you make an excellent point, OP, that it is in fact impossible to judge the size of many clouds you see.", "204" ], [ "You, me, and a scientific measuring team would be equally clueless. (The only way to do so would be to have multiple cameras far apart, and perhaps use fast aircraft.) It is, as you say, quite simply impossible to know how far away a cloud is - unless you use \"standard candle\" techniques such as identifying a cumulous, as mentioned here.\n(Comments that \"clouds can't be measured - because of Fractal!\" are naive. You can't measure ANYTHING - say a coastline length - \"because of Fractcal!\" Of course, when you ask the length of a coastline, there's a reasonable fractal dimension that is meant, in context, and you can give a reasonable answer in context -- as with every issue of language.)\nNote. If you want to know\nThe apparent angular size\nof a cloud (or a UFO, or of anything), that is trivial.\nAlways remember the full moon is about one half degree. It's that simple.", "840" ], [ "You'd explain it the same way you'd explain it to a fifty year old person.\nWhat about this...\n\"As you know, there are different colours ... red, green and so on. The air likes to bounce around these colours. Amazingly enough, the air most likes to bounce around blue. The other colours don't get bounced around as much ... they just go away. So when you look up at the sky, we see all the blue being bounced around. The air is bouncing the blue around!\"\n(Older children may then ask, \"Awesome! But why does the air bounce around blue and not some other colour?\" The best answer then is something like, \"It's because of the different size and speed of the different colours. It turns out that air is best at bouncing around blue. The others just pass through - they go away. Look up at the sky, and you see all the blue bouncing around!\")\nFurther, for three year olds, there's nothing at all wrong with introducing the colours as \"little balls\"1 within this explanation, if desired.\nLooking to the other superb answers, also talk about how big the air is. (It's possible that three year olds know what the \"space station\" or \"satellites\" are these days, with endless Netflix and iPad. Using the techniques in the other answers, you could show how much air there is, \"all the way to the space stations!\" \"where it is black\" because there is \"no air to bounce the colours around\" up there.)\nSecondly from the other answers, you can make the excellent point about sunset.", "781" ], [ "\"When you're looking more at the sun, at sunset, the red balls make it through the air to you - the air bounces away the blue balls.\" (Of course, this is getting less and less precise - let us say more and more 19th century - by and by.)\nSo that's how you explain the sky being blue to anyone, including three year olds. You explain it by explaining how it is. The air bounces blue around. But first!...\nBut first!!!!\nCritically, as a pedagogical matter I would preface the whole explanation like this: this is more important than the actual explanation.\n\"That is a REALLY HARD question. It's important that you know, nobody had a clue about this until very recently. Like, when your grandmother {whatever} was alive. There was this great man called <PERSON> who figured it out* {I'm not totally sure if three year olds know from TV the cliché of \"<PERSON>\" as our great scientist - if so, bingo, that's good enough}. Before that it was really a mystery. It's still a mystery.\"***\nI'm not quite sure of the best way to express it to a three year old, but it is critical to impress on the three year old, in terms they can understand, that\n* humans presently know almost nothing\n* it's only since the Enlightenment - very recently - that we have tried to figure things out. (Give a quick synopsis of the Enlightenment, starting with the renaissance in Italy)\n* don't forget we only had electricity, phones, visited the moon, etc very recently (\"you're grandmother got them\")\n* many many questions you can ask are very very difficult - your Mom doesn't know the answer, even your Aunty who works at the Big School with the 30 km tunnel underground doesn't know the answer\n* when you're a little older, you, too, can start trying to figure out these questions, along with Mr <PERSON>, your Aunty etc\nThis \"little speech\" will dwarf in life significance any explanation of why the sky is blue. (BTW asking \"why the sky is blue\" is astounding for a three year old, I'm sure the kid is almost four!)\nTrials\nUnfortunately I don't have a three year old on hand at the moment - that is awfully young - but testing shows this is perfectly understandable to 7, 8 year olds.\nThe bottom line three year old explanation is: \"air likes to bounce around the different colors. But mostly it likes to bounce around blue. So when you look up at the air, you see all this blue.\"\n(The other colours \"pass through\" or \"go away\" ... \"pass through\" is too complicated a concept for three year olds, so wing it there.)\n1 given that currently, our base understanding of the fundamental nature of energy and matter is: Utterly Nothing Whatsoever: there's nothing wrong at all with talking about \"little balls!\" to a THREE year old!", "781" ], [ "Century\nFirst, you'd have to watch through a night to see if Polaris wobbles - currently, the radius is about 1° I think, but that changes with precession (and nutation, but that's small enough to ignore).\nOnce you know that, you can try to find a point in the sky that stays still all the time (like Polaris nearly does in our time). This is celestial pole, the direction the axis of earth points to.", "188" ], [ "It moves in a circle with ~23° radius ( = obliquity of the ecliptic, currenty ~23,4°). The center of the circle is roughly between Polaris and Vega, that makes it easy.\nThen, you have to see whether Polaris is approaching or departing it on its way on the \"precession circle\".\nIf you can measure the angle $\\alpha$ it has travelled on its way on this circle, you can estimate which century you have been transported to: $year = 2000 + \\alpha \\frac {26000} {360}$\nIf you take exact values and do all the calculations and especially the measurements very very exact, you might get more than just the century.\nIf you really want to prepare, print this and pin it somewhere you will see it every day: https://en.wikipedia.org/wiki/File:Precession_N.gif\nBeware that if you are transported more than 13,000 years back or forth, you will guess wrong.\nIn this case, you'll have to take the proper motion of the stars into account - you'll have to know not only the sky but also the motion of the stars (or at least a few) very very good. Which is the first thing that is really hard to do.\nMaybe you'd have to invent something with sticks for the measurements.\nYear\nI guess you need to know the planets positions (especially Jupiter because it's bright and not to fast) of the time you are transported to to derive the year - but you'd have to be a walking ephemeris for this.\nTime of the year\nThe time of the year is actually much easier than the year - most of the time, you can even feel it.\nIf you still need to calculate it, it is a direct function of the position of the sun in the sky:\nYou need to know the orientation of the ecliptic in the sky and the equinox of our time - in Pisces, you can see it in the image in that Wikipedia link: the intersection of \"0°\" and the ecliptic.\nYou measure the time in hours $h$ that passes from either the spring or the fall equinox (of our time) is at midheaven until the sun is at midheaven (noon).\nThe current date of the year, measured (roughly) from january to december in values from 0 to 1 is: $ y = h/24-0.2+\\frac \\alpha {360}$\nIf you took the fall equinox, you have to add or substract 0.5, whichever fits.\nWithout the $-0.2$, it would be measured from spring equinox (~ march 23rd) to spring equinox.\nGeographical latitude\nThe angle of the celestial pole mentioned above and the ground (as long as it's horizontal) helps you calculate the geographical latitude $ \\phi = 90°-angle$.\nGeographical longitude\nSorry, that's the thing I could not do.", "204" ], [ "Jumping on <PERSON>'s answer, this is physically difficult (but not impossible) and what most suggestions have said so far is somewhat incorrect realistically. This is because of <PERSON>'s Laws (Specifically the Third here)\n1. For every action, there is an equal and opposite re-action\nThis means in our example two things:\n1) When a mass moves linearly, as in \"rocket-firing\" it, it also creates an equal force in the opposite direction. So look at the ground here:\nThat air and fuel is moving with a lot of force! Neglecting the exhaust problem of a steam rocket, a human weight (~62 kilo says google) hammer hitting forwards at fast velocities would hit a human forwards with an imparted force, but the imparted force is equally applied to the wielder backwards, including joints and bones, and in the opposite direction. So hitting forwards with some force would push you backwards with the same force. Breaking concrete? Not useful for a human wielder bluntly, unless you had some sort of intricate counter weight.\n2) When a mass moves from a \"tether\" like a handle, it exerts an opposite rotation force. For example, <PERSON> has some interesting ways of killing megafauna, swinging them by the tail!\nHe's got some strong legs! Suppose my hammer \"jerks\" forward from my arm by rotation. Something has to counter-balance that, and it's not going to be my wrist if the force could break bones.", "621" ], [ "Maybe my muscles, but probably not from an arm all the way down...\nMy conclusion is that a blunt \"warhammer\" would not work for this with a human wielder holding the force. And about that concrete: it's a fun fact that a human femur, the largest bone in the human body, is about as strong as concrete. Not stronger: you won't do it bluntly.\nNeeds to be effective in hurting and killing humans, mega-fauna, and break through concrete and steel.\nThe more gears, the better.\nBut of course, I neglected two thirds of the important laws.\n1. Force is equal to the change in momentum per change in time: Force is equal to mass times acceleration\nAre you familiar with flywheels? You could use a flywheel churned by a steam engine and TONS of gears to do a torque differential - then impart its momentum by having it strike something or \"gear stop\" suddenly. Say the flywheel is ~150-200lbs, the bullet-shaped hammer head is ~30lbs, that's a lot for the rest of the contraption - but it would be more like a siege weapon.\nSomething that would break concrete could be sharp, but not steel. The steel would bend under mass but jackhammers are no good, even if it was ultra-hard like Tungsten. It would need to be blunt because steel doesn't chip away to my knowledge, and steam isn't hot enough to do something heat wise to steel (It's at least 212 F, but steel melts > 1000 F, that steam would cut out of pipes and slice people but even water has a hard time cutting steel under pressure - unless they found and rigged up a water-jet).\nAnother idea is two hammers on a pivot that rev up and hit, maybe on some sort of tank. But that would be a lot bigger, I should think - maybe something you could put on trained mega-fauna or a tank of some sort.\nAnyways, this is my mostly realistic answer. But this isn't the Physics SE.", "621" ] ]

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[ [ "Split Operator 2D-->3D\nI am trying to modify my simulations on population dynamics using the split-operator method from 2D two-level real Hamiltonain $$H_{2D} =T(x,y)\\otimes1_2 +\\begin{pmatrix} -z & y\\ y & z\\ \\end{pmatrix},$$ to a complex 3D two level Hamiltonian $$H_{3D} =T(x,y,z)\\otimes1_2 + \\begin{pmatrix} -z & x+iy\\ x-iy & z\\ \\end{pmatrix}.$$ To simplify things for myself, I've thrown away the potential contributions and I am just focusing on the kinetic terms ensuring that norm/energy conservation is good. Loosely speaking, the split operator method follows as $$e^{-iH\\Delta t} \\approx e^{-iT\\Delta t}e^{-iV\\Delta t} +\\mathcal{O}(\\Delta t)^2$$ and for our case $e^{-iH\\Delta t} \\approx e^{-iT\\Delta t}$, with no error as it can be shown that $\\text{Error } =[T,V] = 0$. In the 2D case: ``` import numpy as np import scipy as sp import matplotlib.pyplot as plt import scipy.special as scl import numpy.matlib as mat import scipy.fftpack as fft from mpl_toolkits.mplot3d import Axes3D from matplotlib import cm from matplotlib.widgets import Slider, Button\nSplit-Operator\nConstants\nω = np.array([1,1]) #Frequency for each coordinate\ngs = np.array([0,0]) #Inital Wavepacket shifts\ng = 0.0825 # g-vector:(g_j-g_i)/2\nh = 0.0430\ns_y = 0# s_y vector (g_jy+g_iy)/2\ns_z = 0.125 # s_y vector (g_jz+g_iz)/2\nLocation of conical intersection: (0,0,0)--> you can translate to coordinates in article if desired\nIf you want to switch what surface WP is propagating on, change here\niS = 0 # Intial starting state\ny0c = gs[1]\nz0c = gs[0]\nintial Momenta\nkIz = 0\nkIy = 0\nSet up a grid #Lets see how this goes\nMy = 128*2\nMz = 128*2\nNumber of states\nN = 1\nNumber of time steps\nTsteps = 600\ndt = 0.005\nGrid Lengths\nLy = 10\nLz = 10\nLyT = Ly*2\nLzT = Lz*2\nGrid of M points\ny0 = np.linspace(-Ly,Ly,My)\nz0 = np.linspace(-Lz,Lz, Mz)\nParameters\nk0[1xM] = Grid of M momenta points from 0->L\nk0y = np.linspace(-Mynp.pi/LyT,Mynp.pi/LyT-2*np.pi/LyT,My)\nk0z = np.linspace(-Mznp.pi/LzT,Mznp.pi/LzT-2*np.pi/LzT,Mz)\nProperties\nPostion and momenta grids\ny0op = (np.tile(y0,(Mz,1))).T\nz0op = np.tile(z0,(My,1))\nk0yop = (np.tile(k0y,(My,1))).T\nk0zop = (np.tile(k0z,(Mz,1)))\nInital wavefunction: 2D gaussian\nψ_0 = np.zeros((N,MyMy),dtype = 'complex') σ_x = np.sqrt(2/ω[0]) σ_y = np.sqrt(2/ω[1]) σ_z = np.sqrt(2/ω[1]) temp = np.tile(np.exp(-((z0-z0c)/(σ_z))2)np.exp(1.jkIzz0),(My,1))\ntemp_y = np.tile(np.", "402" ], [ "Why is the central difference method dispersing my solution?\nI am solving numerically the ODE $\\ddot x(t)=-c\\dot x(t) -\\sin(x(t))+F\\cdot \\cos(\\omega t), \\;\\dot x(0)=x(0)=0$ for $t\\in [0,20\\pi]$ on an $N=2000$ dimensional grid. I am working on Python, and I replaced the time derivatives by the finite difference operators \\begin{align} \\dot x(t)&=\\frac{x(t+dt)-x(t)}{dt}, & \\ddot x(t) &=\\frac{x(t+dt)-2x(t)+x(t-dt)}{dt^2} \\end{align} Thus, the discretized ODE can be solved by the extrapolation scheme $$x(t+dt) =\\frac 1{1+c\\cdot dt}\\Bigr( x(t)\\bigr(2+c\\cdot dt\\bigr) +x(t-dt) + dt^2\\bigr( -\\sin(x(t))+ F\\cdot \\cos(\\omega t)\\bigr) \\Bigr) $$ I performed this scheme and the result was great. To compare, I also reduced the 2nd order ODE to a system of two 1st order ODE's \\begin{align} \\begin{cases} \\dot x=y\\ \\dot y(t) =-cy(t)-\\sin x(t)+Fcos(\\omega t) \\end{cases} \\end{align} with initial values $(x(0),y(0))=(0,0)$.", "935" ], [ "Solving this system with a Forward-Euler scheme, yields the a solution that starts similar to the first scheme, but is not quite the same. Note that using the Forward-Euler scheme is the same as solving for $x(t+dt)$ after replacing the derivatives by the forward difference operator $f'(t)=\\frac1 {dt}(f(t+dt)-f(t)).$ However, if we rather replace the derivatives with the central difference operator $$f(t)=\\frac{f(t+dt)-f(t-dt)}{2\\cdot dt}, $$ we obtain the following extrapolation scheme: \\begin{align} \\begin{cases} x(t+dt) = x(t-dt)+2\\cdot dt \\cdot y(t)\\ y(t+dt) = y(t-dt) + 2\\cdot dt \\bigr( - c y(t) -\\sin x(t)+ F\\cdot \\cos(\\omega t) \\bigr) \\end{cases} \\end{align} Performing this scheme with values $c=0.05, \\; \\omega = 0.7, \\; F = 0.4$ yields a horrible solution. I do not know what is going on, here are the plots for the solutions obtained in each scheme.\nAlso, here is the code I wrote\n```import numpy as np import matplotlib import matplotlib.pyplot as plt\ntmax = 20 * np.pi tmin = 0 n = 1000 dt = (tmax-tmin)/(n-1) t = np.linspace(0,(n+1)dt,n) c = 0.05 w = 0.7 F = 0.4 x = np.zeros(n) y = np.zeros(n) for i in range(1,n-1): \"\"\" First method \"\"\" x[i+1] = (x[i] * (2+ cdt) - x[i-1] + (dt 2) * (-np.sin(x[i]) \\ + F * np.cos(wt[i])) )/(1+cdt) plt.scatter(t,x,s = 0.5) plt.title('Second order ODE scheme') plt.xlabel('t') plt.ylabel('x') plt.show() plt.close()\nfor i in range(1,n-1): \"\"\" Second method \"\"\"\nx[i+1] = x[i] + dt * y[i] y[i+1] = y[i] + dt * ( - c * y[i] - np.sin(x[i])\\ + F * np.cos(w * t[i])) plt.scatter(t,x,s = 0.5) plt.", "509" ], [ "Estimation of number of states to be used to obtain Wigner-Dyson distribution in a chaotic coupled oscilllator\nA coupled harmonic oscillator with quadratic coupling - $$ H = \\frac{1}{2}(p_x^2 + p_y^2) + \\frac{1}{2}(x^2 + y^2) + g x^2y^2, $$ is known to be non-integrable, hence chaotic (for reference look at Quantum-chaos, <PERSON>). That means if I find the neighborhood level spacing ($ e_i - e_{i-1} $) distribution, I should be able to see Wigner-Dyson (WD) distribution.\nTo find the neighborhood level spacing distribution (NLSD), I need to find eigenvalues of the Hamiltonian.", "768" ], [ "As the underlying Hilbert space, in this case, is infinite-dimensional, one usually finds a given number of eigenvalues, and plots the NLSD, in principle as the number of states used to find NLSD is increased, the distribution tends more toward the WD. Is there a way to estimate how many states I need to get a distribution approaching the WD? My naive approach is given below.\nAs I am not sure about how many states to take, I am trying a brute force method with an increasing number of states used in the calculation of how the NLSD approaches WD and how the mean level spacing ratio approaches 0.53.\nI am numerically solving the time-independent <PERSON>'s equation over a box of dimension $20\\times20$,\n$$ -\\nabla^2 \\psi_n(x,y) + \\left( \\frac{1}{2}(x^2 + y^2) + g x^2y^2 \\right)\\psi_n(x,y) = E_n \\psi_n(x,y), $$ subjected to the Dirichlet boundary condition $\\psi_n(x,y)|_{\\text{boundary}} = 0$ and finding a number of lowest (100 in this case) eigen-states in Mathematica$^®$\n{eval, evec} = NDEigensystem[{ -1/2 (D[u[x, y], {x, 2}] + D[u[x, y], {y, 2}]) + 1/2 (x^2 + y^2) u[x, y] + x^2 y^2 u[x, y], DirichletCondition[u[x, y] == 0, True]}, u[x, y], Element[{x, y}, Rectangle[{-20, -20}, {20, 20}]], 100, Method -> {\"PDEDiscretization\" -> {\"FiniteElement\", \"MeshOptions\" -> {\"MaxCellMeasure\" -> 0.05}}}];\nThen the NLSD is obtained by the histogram of eval[[2 ;; -1]] - eval[[1 ;; -2]] Histogram[eval[[2 ;; -1]] - eval[[1 ;; -2]]]\nThis doesn't look like WD at all and has a mean level spacing ration $\\left \\approx 0.87$ which is also not correct. There can be two problems, 1) the number of states that I am using is too low, and 2) probably I should look into a parity sector where all the states are uncorrelated other than looking at the whole Hilbert space wh to get WD.\nIf there is an estimation of how many states to take to get a good approximation of WD, probably some completeness argument, i.e., how many states do you need to get a good approximation of completeness relation that might be helpful here.", "935" ], [ "solve_ivp - Overflow encountered in double_scalars\nI'm modeling an electron that orbits the nucleus. Of course, charged particles radiate away there energy so it'll crash into the nucleus. My approach has been to to evaluate the coulomb force and add the reaction force (given by the <PERSON>-Lorentz formula). The equation of motion would be\n$F = ma = \\frac{1}{r^2} - \\beta\\dot{a}$\nwhere $\\beta = \\frac{2}{3c^3}$ in my units, and m =1. Rearranging this the def eq to solve is\n$F = \\dot{a} = (\\frac{1}{r^2} - a) \\frac{1}{\\beta}$\nand I multiply by $\\frac{x}{r}$ or $\\frac{y}{r}$ to get the x or y directions respectively.", "394" ], [ "The implementation is below\n``` import numpy as np from scipy.integrate import odeint, solve_ivp import matplotlib.pyplot as plt\nc = 137.0 B = ((3.0c*3)/2.0)\ndef func(t, o): # [0x, 1y, 2vx, 3vy, 4ax, 5ay] r = np.hypot(o[0], o1) dodt = [o[2], o[3], o[4], o[5], Bo[0](-(1/r3.0) - o[4]/r), Bo1(-(1/r3.0) - o[5]/r)] return dodt\ninitial = [br, 0.0, 0.0, 1.0, -1.0, 0.0] # [x, y, vx, vy, ax, ay] span = [0.0, 10.0] time = np.linspace(span[0], span1, 10000)\n%% Solve differential equation\nsol = solve_ivp(fun=func, t_span=span, t_eval=time, y0=initial, dense_output=True, max_step=0.05).sol xe, ye, xve, yve, axe, aye = sol(time)\nprint(xe[-1], ye[-1])\n%% Plot states\nplt.plot(xe, ye) plt.plot(xe[-1], ye[-1], 'ro') plt.plot(xe[0], ye[0], 'yo') axx = plt.gca() axx.set_aspect('equal') plt.show() `` I was using odeint before and got the error messageExcess work done on this call` which from this post I know can be solved using a solver that can handle events, however it seems that these events only terminate the solver before it breaks, but I want it to continue as it shouldn't break to begin with if that makes any sense. Using odeint I get the following plot\nAt least it finishes at the origin which it's what it's supposed to do, but it should go around it a few times first. I guess my question is evident, how can I solve the ode without it breaking? Thanks in advanced.\nEdit: I have found the problem (I think). When we get close to the center 1/r^3 becomes too large and breaks everything. However I would like this to go all the way, how do I get around this issue?", "509" ], [ "Jacobian Elements for Coupled Drift-Diffusion System using Vertex-Centered Finite Volume\nI'm trying to solve the fully coupled drift-diffusion system using Newton's Method. Although I eventually plan to potentially use a Jacobian-Free Newton-Krylov approach, this is still something that I want to implement and look into.\nA bit of notation for the equations presented below:\n$d_{ij}$ and $l_{ij}$ are control area/volume constants, not physical entities. The $i$ and $j$ indices are for the central point being considered ($i$), and all neighbouring points that are connected ($j$'s). $A_{\\Omega_i}$ is the control area/volume associated to each vertex/node, and is also constant.\nAll quantities that are explicitly required during calculation are at node points. In the equations $B(\\Delta_{ij}) \\equiv B(\\phi_i - \\phi_j)$, the Bernoulli function, used as a smoothing method for the differences. This difference should technically exist between node points, but that's for another time.\nHere are the equations: $\\phi$ is electrostatic potential, $n$ and $p$ are carrier concentrations.", "232" ], [ "These are the independent variables to solve for. Everything else is either a constant, or a function of one of these variables.\n$$\\sum_{j\\ne i} \\frac{d_{ij}}{l_{ij}}(\\phi_i - \\phi_j) = -\\frac{q}{\\epsilon}(p_i - n_i - N_{D_i}^+ - N_{A_i}^-)A_{\\Omega_i}$$\n$$\\frac{\\partial{n_i}}{\\partial t}A_{\\Omega_i} = D_n \\sum_{j \\ne i} \\left[\\frac{d_{ij}}{l_{ij}} {n_iB(\\Delta_{ij}) - n_j B(-\\Delta_{ij})}\\right] + (G_i - R_i)A_{\\Omega_i}$$\n$$\\frac{\\partial{p_i}}{\\partial t}A_{\\Omega_i} = D_p \\sum_{j \\ne i} \\left[\\frac{d_{ij}}{l_{ij}} {p_iB(-\\Delta_{ij}) - p_j B(\\Delta_{ij})}\\right] + (G_i - R_i)A_{\\Omega_i}$$\nIn residual form, and assuming equilibrium conditions so all time derivatives go to 0, these equations are:\n$$\\Phi = \\sum_{j\\ne i} \\frac{d_{ij}}{l_{ij}}(\\phi_i - \\phi_j) +\\frac{q}{\\epsilon}(p_i - n_i - N_{D_i}^+ - N_{A_i}^-)A_{\\Omega_i} = 0$$\n$$N = D_n \\sum_{j \\ne i} \\left[\\frac{d_{ij}}{l_{ij}} {n_iB(\\Delta_{ij}) - n_j B(-\\Delta_{ij})}\\right] + (G_i - R_i)A_{\\Omega_i} = 0$$\n$$P = D_p \\sum_{j \\ne i} \\left[\\frac{d_{ij}}{l_{ij}} {p_iB(-\\Delta_{ij}) - p_j B(\\Delta_{ij})}\\right] + (G_i - R_i)A_{\\Omega_i} = 0$$\nNow, my question is whether I have these Jacobian elements correct. Here is the Jacobian element formula that I've tried to come up with. Only a few equations have been derived, since the remainining elements are just trivial variations of these 3 formulations. This post is mostly about getting more experienced eyes to look at these equations, and potentially see something that I haven't quite seen yet. Are these formulations for the Jacobian elements correct, or is there something wrong with them that I'm missing?", "65" ], [ "Large-scale rotational invariance in lattice space\nIt is often claimed among physicists that rotational invariance can emerge at large scales in lattice space. Let's focus on quantum mechanics for now. I interpret this claim as follows (I am a philosopher, so I will be relatively wordy and not technically sophisticated but I focus on conceptual clarity):\nClaim. Suppose space is discrete and every point can be represented by members of $\\mathbb{Z}^n$. For any quantum mechanical system $\\alpha$ with initial position $x\\in\\mathbb{Z}^n$, for any $y,z\\in\\mathbb{Z}^n$ that have approximately the same Euclidean distance to $x$, the amplitudes of $\\alpha$ at $y$ and $z$ are approximately the same when the Euclidean distance in question is sufficiently large.\nQuestion: is this claim true? If it is true, what is the proof? If it is false, is there a true claim in its vicinity? I calculate the wavefunction in this lattice space, and cannot infer this claim. In addition, I did some numerical evaluations at Wolframalpha and the result suggests that the Claim is false. Here're my main steps:\n1.", "187" ], [ "Assume that $$ \\frac{\\partial}{\\partial x^i}\\Psi (t,x) =\\Psi(t, x+e_i)-\\Psi(t,x) \\textrm{ or} =\\Psi(t,x)-\\Psi(t, x-e_i)$$\n2. Start from the <PERSON> equation in lattice space. The discrete Hamiltonian is $$\\hat{H}\\Psi(t,x)=-\\frac{1}{2}\\sum_i(\\Psi(t, x+e_i)+\\Psi(t,x-e_i)-2\\Psi(t,x)).$$ Here, $\\Psi$ is the position space wavefunction: $\\mathbb{Z}^n\\to\\mathbb{C}.$\n3. Its fourier series in the momentum space is: $$\\tilde{\\Psi}(t,p)= \\sum_{x\\in\\mathbb{Z}^n} e^{-2\\pi i p x} \\Psi (t,x) $$ with $\\tilde{\\Psi}(t): \\mathbb{R}^n\\to \\mathbb{C}$.\n4. Since $\\tilde{\\Psi}(t)$ is periodical, we can just represent its domain by $B=[-1/2,1/2]\\times [-1/2,1/2]$. The momentum space Hamiltonian is: $$\\tilde{H}\\Psi(t,p)=-\\frac{1}{2}\\sum_i(e^{2\\pi i p_i}+e^{-2\\pi i p_i}-2)\\tilde{\\Psi}(t,p)$$ with $p_i=p\\cdot e_i$.\n5. Solve the <PERSON> equation in the momentum space, we have $$\\tilde{\\Psi} (t,p)=(e^{-i\\tilde{H}t}\\tilde{\\Psi})(p)=e^{-i\\mathbf{Cow}(p)t}\\tilde{\\Psi}(0,p)$$ where $\\mathbf{Cow}(p)=-\\frac{1}{2}\\sum_i(e^{2\\pi i p_i}+e^{-2\\pi i p_i}-2)$. Transform it back to the position space: $$\\Psi (t,x)=\\int_{p\\in B} e^{2\\pi i px}e^{-i\\mathbf{Cow}(p)t}\\tilde{\\Psi}(0,p)dp=\\int_{p\\in B} e^{2\\pi i px}e^{-i\\mathbf{Cow}(p)t}dp$$\n(the above integral seems to be equal to $e^{-nit}\\prod_nI_{x_n}(it)$ where $I$ is modified Bessel function.)\n1.", "526" ], [ "Calculating the species mass consumption from implicit reaction-term in diffusion-reaction equation\nThe 1D diffusion equation with a chemical source term has the following form: $$\\frac{\\partial Y}{\\partial t} = D \\frac{\\partial^2 Y}{\\partial x^2} - k Y,$$ where $Y$ is the molar concentration of the diffusing species (mol/m³), $D$ is the diffusion coefficient (m²/s), and $k$ is the reaction rate coefficient (1/s).\nThe boundary conditions are: $$\\frac{\\partial Y}{\\partial x}|{x=0} = 0, $$ $$-D \\frac{\\partial Y}{\\partial x}|{x=xN} = mtc (Y_c - Y), $$ where $Y_c$ is the species concentration outside the simulation domain (mol/m³), and $mtc$ is the mass transfer coefficient (m/s).\nI can solve this equation numerically stable using an implicit approach: $$Y(t=t_0) = A\\cdot Y(t=t_0+dt),$$ where the matrix $A$ has a term that depends on $k$ in the diagonal only.\nMy Problem is the following: I need to know how much species mass was converted by the chemical reactions at each grid-point, so I can calculate the heat generated/consumed at each grid-point as well as know how much of an additional stationary solid phase was converted in the process. As I solve the equation implicitly I do not know how to split the diffusive contribution and the reactive contribution to the final $Y$ at each grid-point. It is further complicated by mass not being conserved in the system due to the flux at the right BC.\nWithout reactions I can always calculate the difference of $Y$ before and after a time step and I know how much mass was transported in total to or from this grid-point in the given time.", "565" ], [ "If I add the reaction term then this difference is a combination of mass being converted due to the reaction and mass being transported by diffusion.\nI have spent some time researching reaction-diffusion equations and their solutions, however, I have not been able to find any information about how to calculate how much of my species was converted chemically at each grid-point.\nThe only workaround I have found so far was to explicitly calculate a chemical source term using the initial value of $Y(t=t_0)$ at a given time-step and then including it as an explicit source in the above equation. The problem with this approach was that this leads to me having to severely limit the size of the time-step such that only a fraction of the available mass at a grid-point is converted in each time step. However, this leads to unsustainably small time-steps for some examples I encountered.\nI would be grateful for any help regarding this issue. I doubt there is an exact way to split the contributions of diffusion and reaction and am happy for workarounds or approximations of all sort.", "565" ], [ "2D Ising model, understanding autocorrelations, Monte Carlo\nI've been struggling quite a bit with implementing an autocorrelation code into my current project. The autocorrelation as it is now, is increasing exponentially from 1 at the start of my MC run, and hitting 2 halfway through the MC simulation regardless of how many sweeps I do through the lattice.\nThe system\n10x10 square lattice with no external magnetic field and ferromagnetic coupling. The reason for 10x10 is for fast execution of the code in order to build it.\nHere is what I've done so far:\n1. Letting the Metropolis Monte Carlo work until the system is in equilibrium (checking this by running two different initial states with different random seeds).\n2. Then I start sweeping through the lattice, updating the energies and magnetization for each attempt at flipping one spin. When I've done one sweep over the lattice, the last value of the energy and magnetization gets stored. Then it continues to the next sweep and updating the values further. Thus, the energies and magnetization only gets stored once per sweep.\n3.", "373" ], [ "When I've done, say 2000 sweeps, I calculate the autocorrelation for the system according to Newman & Barkema (Eq 3.21 in http://itf.fys.kuleuven.be/~fpspXIII/material/Barkema_FPSPXIII.pdf). The formula reads: $$\\chi(t)=\\frac{1}{t_{max}-t}\\sum_{t'=0}^{t_{max}-t}m(t')m(t'+t)-\\frac{1}{t_{max}-t}\\sum_{t'=0}^{t_{max}-t}m(t')\\times\\frac{1}{t_{max}-t}\\sum_{t'=0}^{t_{max}-t}m(t'+t)$$ where t defines number of sweeps of the lattice, i.e the displacement/lag from some value.\nMy problem From my simulation at $k_{b}T/J$, where $k_{b}$ is set to 1, $J=1$ is the ferromagnetic coupling, and $T=1$ the autocorrelation function grows. I've tried to normalize it by dividing by the first value resulting in a start at 1, but it acts strange as stated. Thus, I started to calculate by hand trying to see if I had coded something wrong. I worked with a system where each spin in the lattice had spin 1 for every $t\\Rightarrow m(t')=m(t'+t)=\\langle m \\rangle=1$. I then cutoff the autocorrelation at $t$=1000 when running 2000 sweeps. The formula then reduces down to $$\\chi(t)=\\frac{1}{2000-t}\\sum_{t'=0}^{2000-t}1-\\frac{1}{2000-t}\\sum_{t'=0}^{2000-t}1\\times\\frac{1}{2000-t}\\sum_{t'=0}^{2000-t}1$$. Then for some values: $$\\chi(0)=\\frac{1}{2000}\\sum_{t'=0}^{2000}1-\\frac{1}{2000}\\sum_{t'=0}^{2000}1\\times\\frac{1}{2000}\\sum_{t'=0}^{2000}1$$ $$=\\frac{2001}{2000}-\\left(\\frac{2001}{2000}\\right)^{2}\\approx-5\\cdot10^{-4}$$ $$\\chi(500)=\\frac{1501}{1500}-\\left(\\frac{1501}{1500}\\right)^{2}\\approx-6.6\\cdot10^{-4}$$ $$\\chi(1000)=\\frac{1001}{1000}-\\left(\\frac{1001}{1000}\\right)^{2}\\approx-1\\cdot10^{-3}$$ As we see, the autocorrelation value has doubled when check for half of the number of sweeps through the lattice.\nQuestions:\n1. I'd expect that the correlation function would behave as an exponentially decaying function like $e^{-t/\\tau}$ where $\\tau$ is the correlation time, but rather, the plots show exponential growth with values as calculated above.\n2.", "394" ] ]

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[ [ "Taiwanese Writer Finds Poetry in Laid-off Workers’ Railway Protest · Global Voices\nLaid-off factory workers facing a lawsuit from the Taiwanese government over “unpaid debt” protested February 5, 2013 [zh] by lying across the tracks at a Taipei train station, bring traffic to a standstill.\nThe group of workers, who lost their jobs 16 years ago when many factories fled Taiwan for China and other countries to cut labor costs, received money at the time from the government body in charge of protecting labour rights meant to help them get back on their feet. But last year, that government body, called the Council of Labour Affairs, decided to sue the victims, demanding that they return the so-called “loan”.\nImage from <PERSON>.\nNot so many people are sympathetic to the plight of these desperate workers. So, inspired by the latest protest, Taiwanese writer-animator ‘BoTh Ali Alone’ [zh] created an illustration to show his support for these victims of de-industrialization.\n<PERSON> illustration is accompanied by a poem titled “Lying on the Railway”, which he wrote to describe a demoralized world in which people view other people's misery without any sympathy:\n《臥軌》\nLying on the Railway\n有一座小島，人從出生就住在電車裡。\n居民的人生目標就是沿著軌道向前衝\n手持車票的居民\n從未見過外面的世界，\n因為車窗上都是螢幕\n播着美麗的風景\nThere is an island, where people live in the train since they were born.\nThe goal of their life is moving ahead along the railway.\nThey have the tickets for the train,\nbut they have never seen the world outside.\nAll the windows are covered by the monitors\nthat show all the beautiful scenery.\n別下車\n下車你就回不去了\n你會發現\n政府不停地建設鐵路\n電車能去任何地方\n卻讓整座島變得沒有任何值得去的地方\n除了一望無際的鐵路之外一片荒蕪\nDo not get off the train.\nIf you get off the train, there is no way to go back.\nYou will find that\nthe government keeps building railways,\nso the train can go everywhere,\nbut there is no place on the island worth going anymore,\nbecause there is nothing other than the railways.\n而買不起車票的人，\n住在鐵軌的夾縫中間求生存。\n被碾過的時候，\n車裡的人還會抱怨路途顛簸。\n— with 需要被支持的人.\nFor those who cannot afford the ticket,\nthey try to survive between the railways.\nWhen they are crushed by the train,\nthose on the train only complain about the jolt.\n–with those who need to be supported.", "368" ], [ "Laid-off Workers Turn from Victims to Debtors in Taiwan · Global Voices\nIn a rather ironic case, Taiwan's Council of Labour Affairs (CLA), a government body in charge of protecting labour rights, wants to sue workers who were laid-off by factory owners sixteen years ago. The council seeks money from the Legislative Yuan to bring legal action against more than 2,000 workers, who they say never returned the ‘loan’ the government offered as compensation for being laid off.\nSince July 2012, members of the Alliance for Workers of Closed Factories (AWCF) and their supporters have been protesting against the CLA‘s [zh] decision. One of the most widely reported action was the occupation of the Taipei Subway station on August 10, 2012.\nVictims turn into debtors\nOn August 10, 2012, workers from AWCF occupied the Taipei Subway Station against the CLA's lawsuit. Photo from coolloud.org. Permission for non-commercial use.\nThe story begins in 1998, when many factories in Taiwan relocated to China and other countries [zh] to cut their labour costs. Some of these factory owners announced bankruptcy and refused to pay their workers salary, retirement and other compensation. Many of the factory owners fled to other countries and reopened their factories, leaving the workers in Taiwan protesting in despair. The CLA was then assigned to negotiate with these labourers and the factory owners.", "310" ], [ "While the factory owners refused to pay the compensation, the CLA decided to settle the conflict by granting “loans” to the workers to release them from financial burden before they found new jobs. The understanding was that the workers would not have to pay-back the so-called “loan” as the workers were also victims.\nBut recently, the CLA broke their promise and asked the Legislation Yuan for NTD20.56 million (approximately USD 709,000) to sue more than 2,000 workers who have not paid back their “loan”. In reaction to the decision, the AWCF protested in front of the Legislation Yuan [zh] on Oct 31. The CLA's action is outrageous, as <PERSON> pointed out [zh] in his blog:\n一個勞工工作了近半輩子結果領了退休金竟然還要做償還，\n如果事件發生在你我身上的話，你不會想上街頭為自己討回公道嗎？\nA worker spent half of his life-time working and finally get his pension. Now he has to pay it back. If such a thing happens to you or me, won't you demonstrate and seek justice?\nTo avoid further conflict, the CLA agreed to suspend the lawsuit, but refused [zh] to revoke the budget for the lawsuit, which means it may pursue the lawsuit later. In fact, according to Taiwan independent media, coolloud.org's report [zh] CLA's representative <PERSON> (李庚霈) insisted that the money distributed to the workers 16 years ago was a “loan”:\n不管過去的政府跟工人們談過什麼，現在也沒有記錄作憑證，目前勞委會只想找到一個雙方都能接受的處理方式。\nNo matter what the government negotiates with these labourers, we do not have any record as evidence. Now CLA only wants to find a solution that both CLA and these labourers can accept.\n<PERSON> and the beanstalk questioned [zh] the function of CLA:\n勞工局不是應該要替勞方權益著想嗎?\n現在竟然為了控告勞工,編列了2千萬預算……\nIsn’t it CLA’s responsibility to take care of labours’ right?\nOn the contrary, CLA is asking a budget of 20 million to sue these labourers…", "720" ], [ "China’s New Premier Promises Cleaner Government in First Press Conference · Global Voices\nCombining pragmatism and modeled political language, <PERSON>, the newly installed Chinese premier, promised a cleaner government and less bureaucracy in his first press conference at Beijing’s Great Hall of the People on March 17, 2013.\nWhen asked about pollution that has grappled much of China recently, he said: “Like everyone of you, I also feel pain in my heart”. Since January we have reported on Beijing's record-breaking air pollution, extreme water pollution, China's cancer villages linked to pollution and 12,000 dead pigs being found in Shanghai River.\nFollowed by the closing of China’s annual parliamentary session that has seen the completion of the once-a-decade leadership makeover, the routine press conference [zh] by the premier, broadcast live on Chinese state TV, was watched by many who hope to get a glimpse into core leadership's policy inclination, which otherwise would been wrapped up in much secrecy given China's opaque politics.\nA netizen from Beijing called “<PERSON>” wrote [zh] on the popular Chinese microblog Weibo:\n李克强总理今举行中外记者会，谈到个人经历。讲述：＂为人要正，办事要工，以民为天。＂更谈到了很多关于中国未来建设的规划。希望在新一届政府的统治下， 城镇化建设能够实现，农民能够过上更好的日子，中国现在存在的许多问题，能够完善的解决，希望在不久的将来我们中国会变的更好。\nIn the press conference by premier <PERSON> attended by journalists from home and abroad, ( <PERSON>) talked about his experience. He said: “ we need integrity, justice and fairness, [we need to] be people-oriented”. He also talked about China's future plans.", "49" ], [ "He hopes the new government can realize the goal of urbanization, and farmers could live a better life, China now has a lot of existing problems, (he hopes) they would be solved (soon), (he hopes) China will be better in the future.\n<PERSON>, also from Beijing, showed [zh] some skepticism:\n听了李总理的答记者问，还是没搞清什么是城镇化。是让农民都进城里来，还是把农村都建成城市的模样？大概估计是大城市都被前任们建完了，他们这一任要去中小城市大建一番。只是不要把PM2.5又带到了农村。\nAfter hearing premier <PERSON>’s answer to the journalist, I still couldn’t figure out what urbanization is. Do we let all farmers in, or build the countryside into city-like places? Perhaps big cities have already been built by the predecessors, the new government will build big time in middle and small cities, I hope they won’t bring PM2.5 into the countryside.\nOf all the 11 questions [zh] raised at the press conference, four came from foreign news outlets, covering issues of China’s alleged cyber attack towards US, plans to streamline the government, China-Russia relations, pollution and food safety. Chinese reporters focused on re-education through the labor system, urbanization, government goals, Hong Kong and government reforms. Questions by reporters were largely prearranged.", "49" ], [ "Taiwanese Wonder If They’re Just a Chip for <PERSON> in Negotiating With China · Global Voices\nImage from the Standnews, non-commercial use.\nUS President-elect <PERSON> tweeted on December 2 that the president of Taiwan, <PERSON>, called him to offer her congratulations for winning the US election — breaking with decades of US protocol. Shortly afterward, he questioned in an interview, “I don't know why we have to be bound by a ‘one China’ policy, unless we make a deal with China having to do with other things, including trade.”\nAs Wikipedia correctly explains, the “one China” policy refers to the idea that there is only one state called “China”, so countries that want diplomatic relations with the People's Republic of China must break official ties with the Republic of China (Taiwan) and vice versa.\nSoon after <PERSON>'s interview aired on Fox News, Formosan Association for Public Affairs, or FAPA, a Washington, D.C.-based nonprofit organization that seeks to build worldwide support for Taiwan's independence, published a statement:\nWe at FAPA are heartened to see President-elect <PERSON> challenge the outdated “One China Policy”. Taiwan has never been a part of the People’s Republic of China.\nHowever, Taiwan’s right to self-determination and democracy should not be a bargaining chip. Using Taiwan in any sort of “deal” with China is against the very ideals on which our nation is founded.\nThis statement reflects that many Taiwanese are unsure if <PERSON> is just using Taiwan as leverage to negotiate with China, or if he really wants to re-evaluate the US-Taiwan relationship.\nFor example, <PERSON>, a policy fellow at the very same Formosan Association for Public Affairs, was annoyed by <PERSON> putting the “one China policy” alongside possible trade dealings.", "871" ], [ "She quoted <PERSON>, then commented:\n“I fully understand the ‘one China policy,’ but I don't know why we have to be bound by a ‘one China policy’ unless we make a deal with China having to do with other things, including trade.”\n假裝很灑脫傲嬌 但交換條件講ㄉ蠻細ㄉ\n「誰管你啊 ～除非你給我A跟B跟C，不然我才不理你ㄋ。」\n如果這句話放在他的twitter大寫的字會是TRADE？？？？\n真的是好煩啊….\n“I fully understand the ‘one China policy,’ but I don't know why we have to be bound by a ‘one China policy’ unless we make a deal with China having to do with other things, including trade.”\n<PERSON> tried to be free and easy, but he is very specific about the exchange deal: ‘Who cares [about the the one China policy]?—Unless you give me A and B and C, or I won't give a damn.’\nIf his words were put on his Twitter account, I guess the capitalized word would be TRADE????\nThis is annoying…\nAs the geopolitics in the South China Sea and East China Sea changes, the US has moved seemingly more and more towards a new paradigm in manifesting its military strength. Under the administration of President <PERSON>, the US government has strengthened strategic ties with Taiwan. The US Congress passed the Taiwan Relations Act and the “Six Assurances” this April, which reaffirms Taiwan's position as an “important partner” to the U.S.\nIn May, when the US House of Representatives passed the military budget for 2017, there was an amendment that directs the US secretary of defense to grant Taiwan military forces observer status in maritime exercises known as the Rim of the Pacific Exercise. In addition, on December 8, the US Senate passed the annual defense policy bill, including a provision recommending that the US conducts yearly high-level military exchanges with Taiwan.\nThough <PERSON>'s Twitter performance has been viewed as a more proactive move to reaffirm the strategic partnership, Taiwanese are still worried that <PERSON> as a businessman is only using Taiwan to negotiate a better trade deal with China.", "871" ], [ "Taiwanese Netizens Aren’t Exactly Thrilled With the Upcoming China-Taiwan Meeting · Global Voices\nImage from Facebook Taiwan Explorer.\nThe buzz online has been non-stop since the announcement of a meeting between President <PERSON> of Taiwan (R.O.C.) and President <PERSON> of the People’s Republic of China (P.R.C.) to take place on Saturday, November 7, in Singapore.\nWhile <PERSON>'s government stressed that the two presidents would address each other with the title “Mr.”, which implies the two are on equal footing in the meeting, reactions online show that netizens aren't buying such political camouflage as the diplomatic and military power imbalance between the two is so obvious.\nIn contrast with the positive reactions from Taiwanese political parties and international media, the majority of Taiwanese views online expressed concerns over the perceived threat that China represents to Taiwan’s much cherished sovereignty and democratic processes. Taiwan has made great effort to better its relations with China for economic benefit over the past decade, but without much payoff, observers argue. China hasn't made any indication that it's willing to recognize Taiwan as sovereign, while Taiwan's gross domestic product (GDP) is forecast to continue contracting and wealth inequality remains a pressing issue.\n‘Ni hao! I'm the president of China!’\nChina claims Taiwan as a rogue territory ever since the Kuomintang (KMT) retreated to the island following defeat at the hands of the communists in the Chinese civil war during the late 1940s, although the mainland has no control over the self-ruling state of Taiwan. Beijing has threatened using force to retake Taiwan if it were to ever make a formal bid for independence.\nThe leaders of the Chinese Communist Party and the KMT haven't met together since 1945. Some reactions to the historic meeting took the form of satirical caricatures, drawing on the public's reactions and predicting the possible scenarios and conditions for the cross-strait summit.", "871" ], [ "On Facebook, TaiwanExplorer made fun of the claim that both presidents are the rightful leaders of China (see image on top).\nAnother caricature making waves is of a panda, representing China's President <PERSON>, riding a wooden toy horse, symbolizing Taiwan’s President <PERSON>.\nMr. <PERSON> (panda) riding on Mr. <PERSON> (horse). Image from Facebook user Taiwanfugue.\nNetizens also shared a video showing President <PERSON> back in 2011 when he made a public promise not to meet with any Chinese officials during his term as president.\nCalls for his impeachment have also circulated, as many accuse <PERSON>, who belongs to the Kuomintang (KMT) party, of trying one last attempt to put himself into the history books without caring for Taiwan’s democratic process. But such views have been repressed by pro-government media. A professor wrote on the opinion page of Taiwanese publication CommonWealth Magazine, which is an advocate of the current government's policy on forging closer economic ties with China, criticizing the meeting and calling for President <PERSON>'s impeachment, but the piece was taken down by the editorial board for being inappropriate.\n‘We want to know what the benefits of cross-strait exchanges are’\n<PERSON>, a former student activist, raised a number of questions on his Facebook page immediately after the news of the meeting was announced:\n我們都知道「馬習會」是馬英九夢寐以求、朝思暮想的重要時刻，但為何卡關了那麼久，如今突然之間成局了？\n想請問，兩岸交流的成果到底是什麼？馬習會要鞏固的是什麼樣的成果？這些馬政府眼裡所謂的兩岸交流成果是台灣人民要的成果嗎？", "871" ], [ "Pandas Steal Spotlight from Taiwan’s Endangered Formosan Bears · Global Voices\nThe exhibition of 1,600 pandas and 200 Formosan black bears. Photo by figarotwo. CC: NC.\nBaby panda <PERSON> has been spotlighted by the Taiwanese media since her birth in July 2013. While many have gone to Taipei Zoo to see the young bear, some have questioned why the panda has received so much media attention compared to Formosan black bears, which were voted the most representative wildlife of Taiwan back in 2001. <PERSON> parents were gifts from mainland China to Taiwan and are considered part of an act of diplomacy.\nSince January this year, in addition to the wide and constant media coverage of the pandas in Taipei Zoo, the Taipei City Government has been hosting an exhibition of 1,600 papier-mâché pandas designed by <PERSON> to promote wildlife preservation. Even though the artist also designed another 200 papier-mâché Formosan black bears and one tree frog for the exhibition, the public attention has been mainly on the pandas.", "495" ], [ "Some have criticized the government's active role in the public promotion of pandas.\nForestry Bureau wildlife conservation section head <PERSON> attempted to clarify the situation by explaining the source of funding [zh] for pandas:\nSatire on the lack of attention given to Formosan black bears: the mother bear paints her baby bear white while saying, ‘It is my fault for letting you grow up here.’ By 布魯斯 (<PERSON>). CC: NC. CC: NC.\n最近很多人質疑：政府只關心大陸來的貓熊，反而對本土的台灣黑熊不聞不問。\n其實農委會（林務局、特生中心）、各國家公園對黑熊的保育工作每年投入的經費也有好幾百萬，倒是沒給貓熊一毛錢。貓熊的經費都是台北市立動物園自己編的，但他們確實很會行銷，廠商業者贊助資源更多。\nRecently many people have been asking this question: why does it seem like our government only cares about the pandas, [which are gifts] from China, and not the Formosan black bears endemic to Taiwan?\nThe Council of Agriculture and Taiwan's national parks currently has a budget of millions for the conservation of Formosan black bears. On the other hand, the government does not fund the conservation of pandas. Taipei Zoo (partially funded by the Taipei City Government) has its own budget for pandas. In addition to that, they have raised a lot of funds for pandas from companies wanting to promote their businesses.\n<PERSON>, the president of the Taiwan Black Bear Conservation Association [zh], wishes more attention were given [zh] to Formosan black bears:\n貓熊是國際上公認的保育代言人。例如，世界自然基金會（WWF）以貓熊為會徽，作為保護所有生物的象徵。因此，對我們而說，貓熊之所以來台灣，不就是來關心牠的熊族至親台灣黑熊嗎？", "368" ], [ "Taiwanese Are Disappointed With the Foreign Media’s Response to <PERSON> Tweet · Global Voices\nU.S. President-elect <PERSON> and Taiwan's president, <PERSON>. Photo credit: Taiwan's Central News Agency.\n<PERSON>, the next president of the United States, surprised Taiwanese on Dec. 2, when he tweeted about a congratulatory phone call he'd received from Taiwan's president, <PERSON>.\nThe President of Taiwan CALLED ME today to wish me congratulations on winning the Presidency. Thank you!\n— <PERSON> (@realDonaldTrump) December 3, 2016\nDue to the “one China” policy in diplomacy, Taiwan has been isolated from the international scene for decades, at least officially. After <PERSON>'s tweet, the number of Google searches for “Taiwan” spiked worldwide, tripling in some places.", "871" ], [ "Furthermore, for many people around the globe, <PERSON>'s decision to refer to <PERSON> as “the President of Taiwan” signals American recognition of Taiwan as an independent democratic country.\nCapturing the mood sarcastically in The Atlantic, <PERSON> wrote, “[T]he island once had a seat on the U.N. Security Council. Now a simple phone call with its leader is international news.”\nIn an interview with Fox News anchor <PERSON>, <PERSON> elaborated his position on China and Taiwan:\nI don't know why we have to be bound by a “one China” policy, unless we make a deal with China having to do with other things, including trade.\nThis, again, surprised Taiwanese. For decades Beijing has used the “one China” policy to break other countries’ official ties to the Taiwanese government while they want to establish diplomatic relations with the People's Republic of China.\nNetizens in Taiwan expressed concerns that President-elect <PERSON> is only using their country as a negotiating chip with China, but some say the next U.S. president's scheme could give Taiwan the opportunity to improve its standing internationally.\nSome Taiwanese netizens complained about being bullied by the international community, following the response of the outgoing <PERSON> administration and the world mass media to the tweet, which warned that Beijing would be enraged, and the possibility of damaging U.S.-China relationship — all before the Chinese government even issued a formal statement on <PERSON>'s comments.\nA sample of the headlines right after <PERSON>'s tweet.\nTaiwanese netizens criticized the international media for being so quick to focus on Beijing's diplomatic line without describing the voices from Taiwan.\n<PERSON>, the co-founder of the “Taiwan March” activist group and one of the student leaders during the 2014 Sunflower Movement, wrote on Facebook after his article was published in The Washington Post:\n我們在行文最後想表達的本意其實很簡單：這通電話的意義是正面的，它提供了重新檢視台美關係的機會。[…]令人遺憾的是，美國大多數一向傾向自由派的主流媒體，包括《紐約時報》、《CNN》，在第一時間，就搶在中國都還沒回應之前，就大幅度警告「此舉將會觸怒中國」。乃至近幾日的報導也環繞著中國學者、民眾的反應，卻少見來台訪問台灣人自己的看法。\nWhat we want to express at the end of this article is very simple: The meaning of this phone call is positive, because it provides a chance to re-evaluate the Taiwan-U.S. relationship.", "871" ], [ "An 8-Year-Old Schoolgirl’s Murder Has Taiwan Debating the Death Penalty · Global Voices\nA sign in Taiwan's airport warns that drug trafficking is punishable by death in Taiwan. Photo by Flickr user <PERSON>. CC BY-NC 2.0\nThe murder of an 8-year-old girl has recently sparked a heated debate about capital punishment in Taiwan.\nThe schoolgirl, called “Little Girl <PERSON>” by local media outlets, was killed by an intruder in her elementary school. The suspected attacker, later identified by Taipei police as 29-year-old <PERSON>, randomly picked her as his victim when she went alone to use the restroom. He told the police that he did it because she seemed to be the easiest target he could tackle and that the voices in his head, which he says have spoken to him for a long period of time, told him to do it.\nThe death penalty was similarly put under the spotlight last year when a 21-year-old thrill seeker killed four innocent people in the city's metro and was sentenced to death for the act of violence.\nThe majority of Taiwanese are in favor of the death penalty and that strongly influences their decision on who they vote for at the polls. According to a recent online poll, 81% of those that voted did not want to abolish capital punishment.", "871" ], [ "Hence, despite having ratified the International Covenant on Civil and Political Rights and the International Covenant on Economic, Social and Cultural Rights, the government continues to allow capital punishment be an option for crimes such as murder, treason and kidnapping (in practice, however, the majority of crimes that receive the death penalty are murders). The state's current execution method is by shooting.\nThis latest murder poses a great challenge to the movement to abolish the death penalty advocated by many local human rights groups. As a result of the renewed public debate, human rights activists have taken to the Internet to remind the public that the death penalty would likely not have prevented another killing like this from happening.\nAs the Taiwan Alliance to End the Death Penalty expressed in a recent press statement:\n「當我們凝視暴力，我們必須停止以施暴者的邏輯來回應暴力。冷靜下來，把多餘的標籤撕下，才能阻止任何人成為不在乎一死而施暴的人。 」…在這樣令人心痛的時候，台灣人民別無選擇，只能一起面對，共同找出度過這些社會危機的方式。\nOnce we are faced with violence, we must cease using violent responses to respond to an aggressor. We need to calmly remove the labels in order to stop individuals from becoming careless about death and violence… In this painful moment, the Taiwanese people have no choice but to come together and face this crisis collectively, finding ways to overcome it.\nOn the other hand, “Object to Abolition of Death Penalty”, a pro-death penalty group on Facebook, called for rallies in front of the country’s legislative body for continuing capital punishment and to urge stricter regulation against offenders. Some believe all those convicted of killing children or committing mass murder should receive death penalty.\nAmid fierce online debate between the pro- and anti-capital punishment clan, many choose to remain neutral on the topic. An online user surnamed <PERSON> commented:\n對廢不廢死這個問題還沒有深思過，但是看了贊成廢死和反對廢死的說法，感覺廢死聯盟的想的比較深，邏輯性比較強；反廢死的想法比較淺，比較情緒性。", "720" ] ]

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[ [ "<PERSON>'s Revenge\nEarlier this afternoon a friend put me onto <PERSON> electronic poem Project for Tachistoscope [Bottomless Pit], which I found remarkably striking, putting esoteric evil geology and natural disaster in conversation with the language of advertising and the optical mechanics of projection (even though it’s a work built in Flash) in pretty intriguing ways that had me thinking about <PERSON>’s deeply menacing masterclass in hostile typography and its relationship to the home office, international terrorism and celluloid film mechanics. Revisited this film to find it even scarier than I remembered! My eyes hurt!", "475" ], [ "Memory of Red\nIt’s really endlessly frustrating to me when a <PERSON> film (impossibly textured, deeply engaged with film form in really exciting and fresh ways) inevitably ends up becoming a <PERSON> film (lines go brrrrrrr), feels like just starting to lose yourself in a <PERSON> when suddenly it’s a <PERSON>. I like both, but the whole point is that one is overpowering in its subtleties and hidden depths and the other is hard-edged, loud and surface level (not in a philosophical sense necessarily but a flatly aesthetic one), and so often they don’t really comment on or constructively add to each other, cuz how or why would they be expected to? The film that followed this one in tonight’s screening, Barva (not on tMDB/LB at the time of this writing), on the other hand, gave me an unexpected amount of meaningful points of conversation between the complexity and nuance of <PERSON> the experimental filmmaker engaged with the process of making art within the world and the whirling abstract beauty ranging from serene to frenetic of <PERSON> the animator, with none of the tacky goofiness of <PERSON> the wannabe psych rock music video director - easily a highlight of the program, really beautiful stuff", "80" ], [ "Drive My Car\nThe first <PERSON> I saw was this year's Wheel of Fortune and Fantasy and it was a revelation. I was so blown away by it that I fear I may have let comparison and expectation rob me of a sober engagement with Drive My Car. This second <PERSON> is clearly the work of an emotionally sophisticated and visionary auteur, but I found it much too neat and a little contrived to fully engage with it. I haven't read any <PERSON>, but this felt constrained by the kind of conventions one finds in literary fiction, the kind that frequently turn me off to such writing. A defense of the work could easily point out that this is kind of the point: the conventions of the theater, <PERSON>'s rhythmic methods, and the parallels of art and real life are clearly animating the work.", "83" ], [ "And it's depiction of grief as a kind of repetitive numbness is really quite brilliant. But it was precisely these connections, along with some its narrative symbolism, that just felt a little too calculated for emotional effect. There were passages of brilliance, of course, and moments were I was quite moved. But this felt constrained and at 3 hours, often quite dull. I will give this another view some time in the future, perhaps after I go back and see his other films.", "831" ], [ "Exotica\nThe tension here in the way this uses the knowingly false constraints of hip post-Twin Peaks 90’s deadpan semi-surrealist arthouse drama (or, in this case, the knowingly false walls of a strip club) as a pressure cooker for authentic undiluted Toronto freak shit makes for one of the most potently fucked vibes I’ve ever seen. I think <PERSON> overplays his hand once or twice to the point that it starts to border on parody (parroty?), but it’s also probably the most a movie has legitimately upset me in years (nearly had me throwing up by the end), which counts for a lot! Gotta be the least erotic thriller of all time - ostensibly a movie about tax fraud!", "306" ], [ "<PERSON>: Part One\nMore of a journalistic recreation of a Wikipedia article than a movie, but it kind of lands due to the magnitude of it all. It has no characters, just historical figures, but it works with the overall approach.", "698" ], [ "It’s meant to make you feel like a witness of history. <PERSON> embodies <PERSON> as much as he obscures him, feeding into the myth.\nHilarious how neither <PERSON> nor <PERSON> could stick with an accent for <PERSON>, but at least <PERSON>’s has been living abroad for a while. What’s <PERSON>’s excuse?", "585" ], [ "Hot Ticket\nthe <PERSON> piece on this is essential writing. very mysterious work, a fascination with ritualistic rhythms of the theatergoing experience, their application to labor and action in the world, a transaction flipped upon its head.", "464" ], [ "rather curiously bills well with the <PERSON>/<PERSON> short I recently watched: in the former a creator and collaborator is engulfed by a beacon of heavenly light as he exits his matinee, while <PERSON> disappears in her black trenchcoat and hat amongst the shadows of the street and the traffic of the sidewalks, becoming one with the world that the screen reflects in distortion and fantasy... can’t wait to revisit this many times (and hopefully find a way to read Ms. <PERSON>’s novels too!) love u <PERSON> <3", "464" ], [ "The Zone of Interest\nSinglehandedly shatters the film industry’s entire history of exploiting the Holocaust for narrative, right down to attacking every minutiae of cinematic language itself. All of this is in service of the most startling horror, all of which goes unseen. Far and away the single most vital and important movie made this decade thus far.", "269" ], [ "The ending of this left me feeling nauseous and at a loss for words. Contains one of the most striking uses of on screen subtitles I’ve ever seen in any film ever made. Would make for a psychosis inducing double bill with Skinamarink.", "958" ], [ "Poor Things\nFor several decades in British literature there has flourished a genre that borrows the settings and narrative conventions of the Victorian novel while modernizing it with all the sex, violence, and other improprieties that were off-limits in the famously prudish Victorian era. The film industry, despite its frequent and tedious revisitations of the original Victorians, has largely ignored this genre.", "269" ], [ "So in a sense Poor Things feels overdue, and its occasional overexcitedness at its own irreverence is excusable on the grounds that it’s more or less the first movie to embrace the horny “what if Jane Eyre fucked” spirit that English novelists have been working with since the ‘80s (if not earlier). Plus, when did <PERSON> take a funny pill? His comic turn as a louche cuck is a pleasant surprise, as is the film’s rather moving story of self-determination. If this has haters, they’re trying too hard.", "585" ] ]

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[ [ "The STRI3 element is a shell element has 3 integration points according to the ABAQUS manual.\nForget 3D coordinates (global X,Y,Z) for the moment. Just think of the shell's local 2D coordinate system in x,y. Take the isoparametric representation of any triangle as having coordinates (0,0), (1,0) and (0,1) as shown below:\nThe integration points in ($\\xi$, $\\eta$) coordinates for this element are: $$A = (\\frac{1}{6}, \\frac{1}{6})$$ $$B = (\\frac{2}{3}, \\frac{1}{6})$$ $$C = (\\frac{1}{6}, \\frac{2}{3})$$\nIn your I-beam example you have provided it is probably fairly simple as they all look like right-triangles and match the same shape as isoparametric representation of the triangle. The integration points are 1/6 or 2/3 along the base/height depending on which integration point you're looking at.", "7" ], [ "So you probably wouldn't need to worry about shape functions.\nIf your triangles were not simple right-triangles and lied anywhere in space then you would need to do the following...\nWe can relate the ($\\xi$, $\\eta$) coordinate system to the ($x$, $y$) coordinate system with these shape functions: $$N_1 = 1 - \\xi -\\eta$$ $$N_2 = \\xi$$ $$N_3 = \\eta$$\nAt integration point A we have $\\xi = 1/6$ and $\\eta = 1/6$. Therefore: $$N_1 = 2/3$$ $$N_2 = 1/6$$ $$N_3 = 1/6$$\nSo if our triangle had ($x$, $y$) vertices of $(0,0)$, $(3,2)$ and $(1,3)$ then the coordinates of A are: $$ x_A = \\sum N_ix_i = N_1x_1 + N_2x_2 + N_3x_3 = \\frac{2}{3}(0) + \\frac{1}{6}(3) + \\frac{1}{6}(1) = \\frac{2}{3}$$ $$ y_A = \\sum N_iy_i = N_1y_1 + N_2y_2 + N_3y_3 = \\frac{2}{3}(0) + \\frac{1}{6}(2) + \\frac{1}{6}(3) = \\frac{5}{6}$$\nI have very cruedly drawn this example above and you can see that the point coordinates $(2/3,5/6)$ match the position for A in the diagram quite well.\nYou can repeat this for B and C. Then you would have the coordinates of A, B and C, which are the integration points in the shell's local coordinate system. Then you would have to use a transformation matrix based on the shell's vertices to convert those local x,y coordinates to the global 3D coordinate system in X,Y,Z.", "490" ], [ "I've taken a look on these equations.\nI know you have a 1D element, but rewriting the equation would eliminate confusion if you want to write elements in 2D and 3D.\nTherefore your stiffness matrix should be\n\\begin{equation} \\mathbf{K}{el} = \\sum{i}^{n_{gauss}} \\mathbf{B}^T \\mathbf{E} \\mathbf{B} w_{\\xi,i} det(J). \\end{equation}\nfor the numerical integration with Gauss. Your stiffness matrix formula used $J$ instead of $det(J)$, which is not wrong. The determinant of the Jacobian is only significant for multidimensional cases.\nThe formula for your Jacobian should be \\begin{equation} J = \\sum_{i}^{n} \\frac{\\partial N_{i}}{\\partial \\xi}x_{i}. \\end{equation}\nThe Jacobian in the one-dimensional case is defined as $J = \\left[ \\frac{\\partial x}{\\partial \\xi} \\right]$ for \\begin{equation} \\begin{bmatrix} \\frac{\\partial N}{\\partial \\xi} \\end{bmatrix} = J \\begin{bmatrix} \\frac{\\partial N}{\\partial x} \\end{bmatrix} \\end{equation}\n\\begin{equation} \\begin{bmatrix} \\frac{\\partial N}{\\partial \\xi} \\end{bmatrix} = \\begin{bmatrix} \\frac{\\partial x}{\\partial \\xi} \\end{bmatrix} \\begin{bmatrix} \\frac{\\partial N}{\\partial x} \\end{bmatrix} \\end{equation}\nThe Jacobian in the isoparametric concept approximates the transformation by the derivatives of the shape function.", "526" ], [ "Here $\\frac{\\partial x}{\\partial \\xi}$ has to be approximated. Like the x-coordinate in the element would be calculated by \\begin{equation} x = \\begin{bmatrix} N_1 & N_2 & N_3 & N_4 \\end{bmatrix} \\begin{bmatrix} \\hat{x}_1 \\ \\hat{x}_2 \\ \\hat{x}_3 \\ \\hat{x}_4 \\ \\end{bmatrix} \\end{equation} $\\frac{\\partial x}{\\partial \\xi}$ is approximated by \\begin{equation} \\frac{\\partial x}{\\partial \\xi} = \\begin{bmatrix} \\frac{\\partial N_1}{\\partial \\xi} & \\frac{\\partial N_2}{\\partial \\xi} & \\frac{\\partial N_3}{\\partial \\xi} & \\frac{\\partial N_4}{\\partial \\xi} \\end{bmatrix} \\begin{bmatrix} \\hat{x}_1 \\ \\hat{x}_2 \\ \\hat{x}_3 \\ \\hat{x}_4 \\ \\end{bmatrix}. \\end{equation}\nImportant: The definition of the Jacobian in many books covering finite elements is not consistent to the mathematical definition. So be careful when you are doing your transformations.\nWhen you are doing the transformation of the derivatives of the shape function, you should have \\begin{equation} \\begin{bmatrix} \\frac{\\partial N_1}{\\partial x_1} & \\frac{\\partial N_2}{\\partial x_2} & \\frac{\\partial N_3}{\\partial x_3} & \\frac{\\partial N_4}{\\partial x_4} \\end{bmatrix} = \\mathbf{J}^{-1} \\begin{bmatrix} \\frac{\\partial N_1}{\\partial \\xi_1} & \\frac{\\partial N_2}{\\partial \\xi_2} & \\frac{\\partial N_3}{\\partial \\xi_3} & \\frac{\\partial N_4}{\\partial \\xi_4} \\end{bmatrix}, \\end{equation}\nso that seems to be ok, except that you have the matrix transposed.\nYour stiffness matrix then is wrong. Note that you have a dyadic product, where in this case you get a $4 \\times 4$ matrix out of $1 \\times 4$ vectors.", "804" ], [ "Order of element vs Degrees of freedom of the element\nI have read that the order of the element is the order of the polynomial used to approximate/represent the field variable in that element. If we consider a one-dimensional, 2 degrees of freedom element (with 2 nodes) the polynomial would be a linear polynomial and if this element happens to have an interior node (so totally 3 nodes, and 3 DOF), then the polynomial would be a quadratic polynomial.\nI have also read that the degree of the polynomial we choose also depends on the degrees of freedom of the element. So, if we consider a 4 DOF element, then the polynomial would be cubic polynomial. But even though we use a cubic polynomial the element is still a linear element.\nHere is my confusion: Would a quadratic polynomial still be able to represent a one dimensional, 3 noded elements (i.e. with 1 interior node) with 2 DOF at each node (so a 6 DOF element)? I am asking this because usually a 1 dimension 3 noded element would be called a quadratic element...but the textbooks always assume a single degree of freedom at each node. Would this element (with 3 nodes) still be called a 'quadratic-element' if the number of degrees of freedom per node is increased to 2?\nThis is what I have been referring to study FEM along with notes from NPTEL:\nThe beam element has 4 DOF, given by transverse displacement and its slope.\nThe displacement field variable is approximated by a cubic polynomial. So is the beam element a cubic element?\nUpdated question:\nAfter studying about Hermite interpolation I know that it not only ensures continuity of the given DOF (let's take x-displacement) but also the continuity of its derivative till a given order of the derivative. So applying this understanding to my question I know come to understand why this is important as the rotation DOF is the derivative of the displacement DOF.\nNow knowing this I would like to refine my previous question with which I think should clear this up for me.\nLet's take 2 cases.", "986" ], [ "Each case comparing a 1D 2-noded element and a 1D 3-noded element (ie with 1 interior node):\nCase 1: Each node has 2 DoF for the 2 elements. Let them be x-displacement and rotation. In this case, I know we use hermite shape function. So the approximation function for x-displacement will be given as\nu(x) = sum(ui * Ni) + sum(u'i * Mi)\nWhere u(x) is the approx function for displacement, ui is the nodal displacement, Ni shape function for nodal displacement, u'i is the derivative of nodal displacement at the node, and Mi shape function for derivative of displacement.\na) What about the value for rotation DOF? Will, there be an approximation function for the rotation DOF as well?\nb) Taking the 2 noded element, I know that this element has a total of 4 DOF. For this will we be using a cubic polynomial? Also, what will the order of the element be? (Is it a cubic element even though it has just 2 nodes?)\nc) Taking the 3 noded element, I know that this element has a total of 6 DOF. For this will we be using a 5th order polynomial? Also, what will the order of the element be? ( Is it a 5th order element or will it be a quadratic element as it has 3 nodes?\nCase 2: Lets again consider that each node has 2 DOF. But this time let the DoF be x-displacement and temperature (or x-displacement and y-displacement).\na) In this case would the approximation function for x-displacement be :\nu(x) = sum(ui * Ni) + sum(Ti * Mi) where Ti is the nodal temperature and Mi is the shape function for temprerature DoF.\nb) What about Temperature? Would there be approximation function for temperature DoF too? (some thing like T(x) = sum(Ti * Si) + sum(ui * Qi) ??\nc) What will the order of the element be for the 2 noded element and the 3 noded element?\nPlease help me out with this. Thank you", "232" ], [ "Typically your sampled fluid velocity data would 'live' on a specific element of the mesh. For example in 3D, the velocity field 'lives' on the faces of your volume mesh. They are scalar values on faces representing the flux of fluid through that face.\nThis is a good explanation of how you calculate differential quantities on the discrete mesh. http://www.geometry.caltech.edu/pubs/ETKSD07.pdf\nThe flux on a mesh is a 2-form and the gradient of that would be a 3-form, meaning it lives on cells of the mesh. In data it would be 3 numbers stored at the cells representing difference in flux in the x direction, y dir, and z dir. The gradient operator on the mesh is literally a difference flux1-flux2. So your numbers at a cell become [flux(x+)-flux(x-), flux(y+)-flux(y-), flux(z+)-flux(z-)]. I assume you're on a regular cube mesh... If not, then everything is a little different... This is an implicit representation of gradient of u.", "432" ], [ "Which is a diagonal matrix in the basis representing the orientation of the cell.\nPresumably your pressure data also lives on cells of the mesh so you can simply multiply by the identity and add them to your grad(u)+grad(u)T. Your result in data would be a 3x3 matrix at each cell of the mesh.\nThis is an implicit representation of your stress tensor. I believe the resulting diagonal matrix will represent stresses in the orientation of the cell. The choice of discretizing velocity as fluxes forces your stress matrix to be diagonal. You can rotate the basis of the stress tensor to something else, if needed, then it won't necessarily be diagonal.\nIf for some reason the data you recorded for velocity doesn't 'live' on faces, that's still ok. You can do an additional step to convert from wherever your data lives to the faces. For example, if you chose to represent velocity data as (x,y,z) vectors at the cells of the mesh, you can integrate the implied velocity field across the faces, resulting in the flux representation of your velocity field. You would need an interpolation scheme to do the integration, like HBR said. But a super simple method could just be to take the difference between the component of your (x,y,z) velocity in the direction of the cell face, with the component of the (x,y,z) velocity on the other side of the cell face. This is clearly not a smooth interpolation though. There's lots of interpolation schemes.", "7" ], [ "Finite strain FEM using an existing code that solves small strain elasticity\nI have an existing FEM code that solves the linear elasticity problem. I would like to use the same code for large strain rates, still using a simple material law (Saint Venant–Kirchhoff model).", "232" ], [ "[The problem I want to solve is a contact problem in which strain is larger than 1 very locally, close to the contact point]\nI believe I have two steps to take: take into account the nonlinear part of strain $\\nabla u \\cdot \\nabla u^T$, and solve the mechanical balance in the deformed configuration.\nCan this be done by successive iterations of the linear elasticity problem, e.g. using iterative mesh deformation and a fixed-point algorithm for the nonlinear strain term? Does this converge? References which would highlight the steps to be taken from small-strain elasticity are welcome.\nEDIT\nI would for instance like to know whether such an algorithm would work (there may be a couple mistakes in the details, for now it's rather the spirit of it I'm enquiring about):\nI want to solve $K u + \\nabla u^T\\cdot \\nabla u= Mf$.\nLet $(f^i)_{i\\leq n}$ be a sequence of functions with $f_n = f$, with each increment small enough.\nLet $i=0$, $U^0=0$, $K^0=K$.\n* Solve linear elasticity problem $K^i \\delta u^i = M f^i$.\n* Construct configuration $\\Omega^{i+1}$, and a change of variable $X^{i+1}$ from $\\Omega^{i}$ to $\\Omega^{i+1}$\n* let $U^{i+1} = U^i \\circ X^{i+1} + \\delta u^i$\n* Calculate $K^{i+1} = K_{\\Omega^{i+1}} + \\nabla {U^{i+1}}^T\\cdot \\nabla$ (there's probably something to do here as we develop $u=U+\\delta u$ in the double product, it doesn't write out nicely in tensor notation but should in the linear problem)\nAgain, the above is not to be taken as something thought over but rather the sort of thing I'd like to find in some report/textbook/publication. But maybe there's a crucial problem I don't see which would be the reason why finite strain codes are not presented as an extension of small strain ones?", "935" ], [ "Help debugging finite element solution in nonlinear elasticity\nI'm writing some code to solve problems in nonlinear elasticity using finite element methods. I have been following <PERSON>'s book but I am having trouble with some nagging details.\nMy question is related to which configuration variables to use for calculating different quantities. I'm working on static problems in the updated Lagrangian formulation, so for each \"time\" $t$ I have a loading coefficient $\\lambda_t$, and a displacement $\\sideset{^t}{}{U}$. In chapter 6, <PERSON> derives a linearization of the principle of virtual work, resulting in the equation (6.103): \\begin{equation} \\left(\\sideset{^t_{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{\\text{NL}}{K}\\right)U=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F \\end{equation} where $\\sideset{^t{t\\,}}{\\text{L}}{K}$ is the \"linear\" part of the incremental stiffness matrix in the configuration with displacement $\\sideset{^t}{}{U}$, $\\sideset{^t{t\\,}}{_\\text{NL}}{K}$ is the \"nonlinear\" part, $U$ is the displacement increment, $\\sideset{^{t+\\Delta t}}{}R$ is the externally applied load at \"time\" $t+\\Delta t$, and $\\sideset{^t_t}{}F$ is the nodal point force resulting from the stress, at \"time\" $t$.\nMy question is about actually implementing this as a system of nonlinear equations to be solved via <PERSON>'s method.", "935" ], [ "As I understand it, the idea is to consider a function $H(\\sideset{^{t}}{}U)=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F$, where $\\sideset{^t_t}{}F$ is a function of $\\sideset{^{t}}{}U$ via the stress.\nWe want to find a displacement $\\sideset{^{t+\\Delta t}}{}U$ s.t. the unbalanced force vector is zero: \\begin{equation} 0=H(\\sideset{^{t+\\Delta t}}{}U)\\approx H(\\sideset{^t}{}U)+\\nabla H(\\sideset{^t}{}U)\\left(\\sideset{^{t+\\Delta t}}{}U-\\sideset{^t}{}U\\right)=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F - \\left(\\sideset{^t_{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{\\text{NL}}{K}\\right)U \\end{equation} so that $\\left(\\sideset{^t{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{_\\text{NL}}{K}\\right)$ is minus the Jacobian of the unbalanced force vector $\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F$. Is this interpretation correct? Is the sum of the incremental stiffness matrices derived by <PERSON> exactly equal to minus the Jacobian of the unbalanced force vector, when all are evaluated in the same configuration? In implementing <PERSON>'s method, an iteration is introduced, so that we can write $U^{(k)}$ for the incremental displacement at the $k$th iteration. How does this affect the terms in the system of equations? At iteration $k$, are the integrals still calculated over the volume $\\sideset{^t}{}V$, or over $\\sideset{^{t+\\Delta t}}{}V^{(k-1)}$? What about the stress, and the stiffness matrices?", "804" ], [ "This is well-known theory in finite element analysis. There are two different effects that contribute to the effective stiffness of the structure in addition to the elastic stiffness $K_e$ given by Euler-Bernoulli-Timoshenko beam theory, and you need to include both of them to get the right answer.\n(1) Rotating the beam creates axial tension in the beam, which will be zero at the tip and increases to a maximum value at the rotation axis. This tension creates an additional stiffness that opposes lateral bending of the beam, in the same way that the tension in a guitar string affects its vibration frequency and hence the pitch of the note produced. (Of course in a guitar string, $K_e$ is negligible, unlike your beam).", "333" ], [ "This stiffness term was traditionally called the \"geometric stiffness\" (for reasons which aren't worth explaining) but a more logical name is \"stress stiffness\" often denoted by $K_\\sigma$, since it depends only on the internal stresses in the structure and not on the material properties.\nIncidentally, $K_\\sigma$ for a compressive stress is what causes <PERSON> buckling in columns. At the \"critical load\" for buckling, $K_\\sigma$ \"cancels out\" the elastic stiffness and when $K_e + K_\\sigma = 0$, the structure can't resist the applied loads. For tension stresses, $K_\\sigma$ increases the stiffness of the structure.\n(2) If the beam deflects from its original straight configuration, the direction and/or the point of application of the centrifugal loads changes.\nIf the beam rotates about a vertical axis and the beam deflects vertically, the CF load on each particle of the beam is still in a horizontal direction, and therefore the CF loads at the beam tip will create a bending moment that tends to straighten out the beam.\nBut if the beam deflects tangentially (for example while you are ramping up the rotation speed from zero) the direction of the CF load is radially away from the axis, and that generates a bending moment that tends to increase the bending of the beam, not reduce it.\nThe usual name for both these effects is \"follower forces\", because the direction of the applied loads \"follows\" the deflection of the structure. The corresponding stiffness terms are usually called the \"load stiffness\" and denoted by $K_L$.\nThe original equation for statics using only the elastic stiffness, $$K_e u = F$$ becomes $$[K_e + K_\\sigma(\\omega) + K_L(\\omega)]u = F.$$ In principle you could get expressions for $K_\\sigma$ and $K_L$ for a simple situation (e.g. a rectangular straight beam) but in practice it's much easier to use a Finite Element package that includes these effects.", "333" ], [ "The biggest problem in answering to this question is that it's not as straightforward as you might think to see the physics in the equations until you see them fully developed, and even then you're doing your best to assign a meaning. As a graduate student in mechanical engineering, this was hard for me because I was used to using my physical intuition to guide me through the math forest.\nFor a FEM problem applied to modal analysis, you basically start with a strong form equation. For example, a free vibration of an elastic rod is given by: $$ \\lambda \\rho u + (Eu,x),_x = 0,\\ x \\in (0, L) $$ Here, $\\rho$ is the density, $E$ is the modulus of elasticity, and $u$ is the displacement. Let's apply a fixed boundary condition ($u(L) = 0$) and a free boundary condition (e.g. $-Eu,_x(0)=0$). You can transform it into the equivalent weak form by using a weighting function $w$: $$ \\int_0^Lw,_xEu,_xdx\\ -\\lambda\\int_0^Lw\\rho u\\, dx = 0 $$ This is where the math ends up losing it's physical interpretation. From here (and skipping a lot of rigor for brevity in this answer), we would basically restrict $w$ in a subset of the <PERSON> space, apply the <PERSON> approximation by discretizing the domain which creates the finite dimensional weighting function $w^h$ and solution $u^h$, make $u^h$ the sum of a <PERSON> function $v^h$ and a given function $g^h$, and then define the functions $w^h$ and $v^h$ as a finite sum of linearly independent basis functions (i.e $v^h = \\sum{A=1}^N c_A N_A$ and $w^h = \\sum_{B=1}^N d_A N_A$). By applying some linear algebra theorems and rearranging a lot, you eventually get the following equation: $$ (K-\\lambda^h_kM)\\psi_k = 0 $$ Here, $\\psi_k$ is the kth eigenvector, which represents the displacement. It's hard to get an appreciation for the math that I've glossed over. The book The Finite Element Method has the full explanation for how this is developed (Chapter 1 goes over the basics of the method, and Section 7.3 develops the frequency analysis portion).\nJust to clarify, we've simply called these matrices K and M, and the form of the equation bears a resemblance to a simple modal analysis for a beam, so we simply assign that as the physical interpretation. Really, the K and M matrices are highly dependent on the mesh and how the elements are connected.", "418" ], [ "These large matrices are constructed from each element in the mesh.\nThe discretization is really important. Physically for this problem, the nodes represent points at which we're calculating the displacement, and the elements connected to that node restrict its movement under an applied force. You can also think of the mesh for this problem as having $n$ number of rods connected to each other. In that way, each rod piece only really affects those it's connected to. Each element is represented by a small matrix. The element matrices are calculated like this: $$ m_{ab}^e = \\int_{\\Omega^e} N_a \\rho N_b\\,d\\Omega \\ k_{ab}^e = \\int_{\\Omega^e} N_{a,x} E N_{b,x}\\,d\\Omega $$ Here, $\\Omega^e$ is the domain of the element itself. When the element matrices get assembled into the global matrix, some elements in the large matrix will have terms added from several smaller matrices. This is a representation of how the topology from the mesh affects the global matrix.\nThe $N_a$ and $N_b$ symbols are the basis functions that span the subset of the Sobolev space we chose. These are very important because different basis functions changes the solution. We can choose to use linear or parabolic functions, or even different types of functions, like Lagrange or even B-spline basis functions.\nAgain, I don't know how much FEM theory the OP has, and it's been really hard to try to sum up how all this works. This may not be sufficient, but hopefully it serves to highlight some of the theory behind the FE method.", "333" ] ]

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[ [ "What will be the consequences of opening secret-research facilities to public (e.g. Area 51)?\nIn this Earth-like world, governments of several countries have decided to allow tourists to visit most of their secret research facilities in a similar way to what happened in Jurassic Park.\nThis time the visitors will not have the chance to be eaten by researched subjects. They will have guided tours through the laboratories (no touch and no interference policy strictly enforced by transparisteel) and they will be able to watch live demonstrations of the technologies being developed.\nA few main reasons for the governments' decision were:\n1. direct funding from tourism;\n2.", "385" ], [ "increase awareness of technological advancements with the ultimate goal of allowing joint researches with public institutes;\n3. increase researchers and possible test subjects recruitment;\n4. allow the general public and military to (re)gain confidence in the governments that manage these research facilities.\nA few options have already been considered for the opening process:\n* send a few familiar/knowledgeable persons first and get their feedback (a.k.a. Jurassic Park style);\n* open them only to graduated scientific researchers;\n* entrance will only be given to those who scored over 70% on a specific psychological test.\nEven with precautions like these, how could the related governments manage most of the direct and indirect consequences of opening these facilities to public?\nTL;DR\nWhat would be the most effective approach of launching these research facilities as tourists attractions and their consequences?\nUpdate (2016-09-09)\nI am revamping the question due to some points that may not have been sufficiently cleared out:\n* I used the sci-fi word transparisteel since I am not familiar of one-sided transparent metals capable of blocking explosions and various kinds of waves and radiation (as a sci-fi space-ship supposedly does).\n* Any visitor would need to sign an agreement which discloses that the tour guide management or the facility itself will not be held liable in case of death or injury inside the facility (if anyone manages to blow up something, it's not the management's fault).\n* Most researchers will not be aware of visitors passing by through the tunnels.\n* The tunnels will only pass through non-critical research operations rooms.\n* The way the research is shown to the visitor does not provide a chance of the research itself to be copied or reverse-engineered or to identify the researchers working on them (e.g. this transparisteel manages to blur out anything that may identify someone, similarly to Google Maps face blur).\n* Visitors will not be able to leave the tour tunnels (there is literally no access to the facility rooms, even to tour guides).\n* Different tours will require different sets of access permissions from the visitor which may depend on, for example, psychological test results, education level or simple monetary contributions (expensive tickets).\n* The rooms will present things that have never been seen before by the public (if you are having a hard time figuring out what is going to be shown, you can think of a live presentation of <PERSON> unknown technology).\n* Some of the rooms may display actors testing and presenting a relatively safe technology (or open rooms outside the facility may be created in order to perform shows where safe, known but rare technology is demonstrated to an audience).", "89" ], [ "Name of a YA sci fi anthology?\nI have been trying to locate an anthology of young-adult sci fi short stories that I read in primary school in the late '90s (I do not know when the book itself was published). I can only remember a few elements:\n1. A story featuring an astronaut working on the Moon, who is caught in a blast and discovers a blinded and disoriented person who is recovering from it. He has a long chat with this person, who (unaware his savior is a human) openly states that he and his fellow aliens are planning an invasion of Earth.\n2. A story involving a spacecraft getting caught in an event horizon. The story ends with people in another ship watching as the first ship undergoes spaghettification.\n3. A story involving a group of commandos (the leader of which is distinct by wearing black, and his 2IC in brown), attacking some large ground craft (with tank-like tread) and eventually taking it over.", "944" ], [ "They then drive it to the enemy base pretending that the enemy side had won the engagement. One thing they did was lay out the bodies of dead commandos (along with fake-dead ones) on the front of the vehicle as they approached the base, to 'show the trophies' of the 'enemies' they'd killed, and once inside they leap up and begin attacking (a sort of Trojan Horse arrangement). The plan sort of works and a fierce fight breaks out; all the team are killed except their deputy leader; each of them (leader and 2IC) have a very powerful bomb (there are only two available), and the lone survivor uses his to detonate the base in a suicide run.\n4. A story of two people who get on a spacecraft or rocket that sends them to a planet filled with nature with no other humanoids. For some reason, water causes their tunics and other clothes to melt away. Their craft cannot be used anymore so they are stranded on this planet. It is then revealed that they are <PERSON> and <PERSON>.\nThe cover art of the one I was reading featured a large greyish land vehicle like the one described in 3. I remember there also being a lot of yellow used on the cover.", "322" ], [ "Four superpowered soldiers as global threat\nI’m writing a story in which the beginning of superheroes arises when four people with vendettas commit extreme acts of violence using elemental abilities against a few countries.\nPowers are as follows: -\n1. <PERSON>: As long he is covered in water either by being physically covered in water or his clothes are wet with water he gains in invulnerability and super-strength along with the ability to cause agitation, fear, paranoia and schizophrenia in anyone in his immediate vicinity lasts for several hours after <PERSON> Initiated the effect. Although if the water dries completely he loses his Super strength and invincibility. So most of his body must be covered in water.\n2. Zero point: <PERSON> of Clea’s. Paradox of motion selective invincibly when she is in motion all things in her immediate vicinity slowing to a halt and can’t reach her.", "322" ], [ "So if the bullet was fired at her it would not hit her it would look like it stopped in front of her. However it is unable to protect against fire And concussive blasts not to mention poison however energy attacks does not work Her entire body does not have to be in full motion for the effect, it can just be body part of her body.\n3. Stormfront: Can create an area of effect about 47.34 mi² in size And produce any natural weather phenomenon at any size or scale from semi-accurate lightning blast to Extreme and sudden heat. But must stay within this radius for the effect to be maintained and is immune to the effects of the weather phenomenon. It can only be used at full affect for upwards of an hour and takes about another hour to recharge.\n4. Exchange: can reverse the entropy of anything she comes into contact However the effect is temporary depending on how large the object is and how orderly it is She could freeze the Atlantic ocean but it only stays frozen for maybe two seconds smaller scale uses of this power more effective\ncould a team with this power set and military training Be seen as a global threat to a world where superpowers have just emerged or an international threat that should been eliminated immediately?", "279" ], [ "Would a time-travelling blockchain destroy a cryptocurrency?\nThe story\nSo <PERSON>, the multi-billionaire, is a wealthy person today but in a not so far away future he will lose quite a chunk of his wealth and become just an ordinary millionaire.\nFuture <PERSON> is no longer building diamond studded swimming pools and he actually had to melt a few of his solid gold Humvees. He is especially upset because he knows that his great loss was due to his long-life investments in international banks' products. His loss is related due to the following sequence of (future) events:\n1. the greatest global economic crisis in history hit the world in 2017;\n2. there was a sequential collapse of several major currencies;\n3. people panicked and started withdrawing most of their money from banks or buying what valuable things they could afford;\n4. most banks in order to cope with the sudden withdrawal, started to restrict withdrawals (some completely refusing) and, with governments agreements, they were taxing heavily any transferences or larger payments;\n5.", "54" ], [ "the value of precious metals and jewels rose up and most wealthy people who could still afford them, invested heavily in purchasing everything that could be found on the market and placing them in banks' vaults (this is when <PERSON> started melting his gold Humvees);\n6. cryptocurrencies saw a steady rise in the beginning of the crisis and since there was no viable way to track most of them and tax payments/transferences, they became a plague for bankers, governments and wealthy people who traded little and kept their precious stuff in vaults (<PERSON> for a very long time refused to buy any crypto-coins);\n7. over the years, precious metals value started declining and governments tried to contain cryptocurrencies by request(forc)ing internet providers to turn off their services in order to block their nodes; once alternative internet providers (altnets) started mushrooming everywhere, large EMPs were being systematically detonated by governments in an attempt to disable general electronic devices;\n8. cheap handheld manual and solar powered EMP-proof devices were being illegally and randomly dumped in the mailboxes and on the doorsteps of middle and lower class citizens in order to allow them to trade without money and keeping alive crypto-markets and non-governmental industries.\nWatching his wealth diminishing everyday and no profitable business to run, <PERSON> focused on one of his old research hobbies based on his favourite time travelling trilogy. With the help of a few kidnapped mad scientists, he managed to produce a piece of hardware that was able to connect to the internet of a previous point in the past. Initially he thought of warning his past self (in our current timeline) to invest and transfer his wealth into cryptocurrencies, but one mad scientist let slip the unthinkable:\n* I wonder what would happen if today's altnets blockchains connected to that past internet and synchronized... That would reveal all the trades that were made up until now to them, wouldn't it?\n<PERSON> thought better, and he started liking this idea much better: not only he would be able to render useless these things that were harming his precious \"real\" wealth, he would be considered a hero amongst governments all over the world and history would be rewritten by himself alone! He would also be finally able to fulfil his dream of replacing the sand of his island with diamonds and rubies.\nThe question\nIf <PERSON> succeeds in synchronizing future blockchains (containing millions of transactions in the future) into our timeline's cryptocurrencies, what does he really accomplish with that?\nWould it really force them to shut down or would it backfire and make them stronger by providing knowledge of the future and opportunities of trade?\nNotes: I previously asked a smaller, summarized but broader question in here that I did not have the time to detail it in a Worldbuilding perspective (it is now closed). In Bitcoin.SE however, I asked about the technical details of this event's possibility and I must say, I am pleased with the detailed answers, and they may help answering this question.", "207" ], [ "Can <PERSON> planet actually exist in our universe?\nThis is a drawing by my daughter which inspired one of the elements in my story/world:\nThe perspective is a little bit mixed here (certainly I don't have a 15 meter-high volcano in this world), but for the sake of this question let's assume that such planet is between 1 and 2 kilometres in diameter or 500-1000 meters in radius. Planets like this are sold by various agencies in the world of my story.\nGiven the fact that the whole story is set in exactly the same universe, as ours (only a little bit into the future), with exactly the same physics and other laws, the question is, if such planet:\n* could exists naturally (what are the limits here) or\n* these companies are selling artificial creations.\nWhat is the smallest possible planet that can exists naturally in our universe? Must I assume that such small planets cannot exist naturally?\nEdit: Here are some answers to the questions given in comments. In short, think about compressing Earth to as smallest size as our current physics allows.\n1. The planet must be habitable, with gravity as close to Earth's one as possible.\n2. Any round rock orbiting the sun or other stellar body does the trick. Meeting IAU's or other definitions is not needed.\n3. Buildings required. Other stuff as well. Full recreation of Earth's look & feel very welcome. This should be private planet as we now understand a private island.\n4. Escape velocity and other physical, chemical or geological parameters as close to the Earth as possible. So, again, a rock in space, not a small gas body.\n5. Again, circling the Sun or other stellar body.", "710" ], [ "No comets lost in space, please. Light and day-night conditions and yearly seasons as close to Earth as possible, please.\n6. No rain, snow or clouds needed, though nice to have. Breathable atmosphere is a must.\n7. This should be a habitable planet, but for a single person or a small group of people. As you can see in the image, we don't need more than 3-5 story buildings. So the fact that breathable atmosphere would be as thick as 500-1000 m above the ground isn't necessary a problem.\n8. Extremely dense core sounds like a good idea, but that might ruin the \"as close to Earth physics as possible\", if I am not mistaken. And it would also most likely fail under \"habitable\", as we would need some underground water sources etc.\n9. A black hole in a center of a planet certainly sounds good as long as above conditions are met.\n10. Asteroid might work as well as long as above conditions are met.\nThe planet must be habitable and easily accessible. So, if by any mean, planet's atmosphere would be filled with some orbiting rocks or other space trash, disallowing any easy navigation and landings, then this is out of question.\nThe company wants to sell a fully-featured product, where you can spend the rest of your life. Not just a rock in space, that you can show off on your pictures, but that you cannot land on and live on.", "591" ], [ "Watermarks visible during DNA fingerprinting?\nLet's say we have a human man that was somewhat genetically modified from the very beginning (conception?) by a team of scientists, and is also a product of careful selective breeding. They did this hoping to produce a specimen that would certain physical characteristics such as superior size and strength, speed, vision, sense of smell, things like that that would result in a \"perfect soldier\" type of man.\nIs it plausible that the team of scientists, like <PERSON> team, could have installed Watermarks in this man's DNA that would show up on a DNA fingerprint? A DNA fingerprint done by the American FBI?\nA user on this forum suggested this possibility in a former thread, so I mean no disrespect to that user by asking this question. I'm just interested in feedback from others. I am writing a novel and this is research for the story. Without getting too deep into specifics, I'm trying to find a way for the authorities to become alerted to the fact that this man is abnormal from other humans.\nAny input greatly appreciated.\nEDIT:\nBasically, I am dipping my toe into the deep end of the pool. I know only the very basics of DNA fingerprinting and Genetic engineering, so technical language is hard for me to follow.", "683" ], [ "I appreciate the answers very much but I'm still a little in the dark. Another user on this forum suggested that possibly \"watermarks\" might show up on the test, which is why I'm attempting to rephrase the question.\nI have written a scene into my novel wherein my main character, a man that has been genetically engineered, unbeknownst to him, gets into a fracas with some bad guys and he wreaks havoc and escapes. The American FBI gets some of his DNA from the scene and works up a DNA Fingerprint on him, purely for the purposes of identification if they catch him. so, yeah, just like on CSI or whatever on TV. When the technicians complete the fingerprint, they recognize that something is different about this person and they contact the lead investigator to let him know. Perhaps they see some evidence of genetic modification or something that raises their eyebrows and they feel it's worth mentioning.\nSo, essentially all I'm asking is if that is at all possible, and what could they conceivably have seen in the fingerprint? If it's completely not plausible then I'll either delete the scene or rewrite it.\nThanks.", "683" ], [ "War in a dystopian setting\nIn a world where there is ever-declining population due to a phenomenon that has no satisfactory explanation, what could cause war or large-scale armed confrontations between countries or sections of the society?\nAssumptions:\n* No births have happened for a while. No new pregnancies are happening.\n* The cause for this population decline is unknown and there is no apparent cure/solution.\n* The decline is unstoppable; humanity will soon be extinct.\nGiven that humans realize they will soon be gone for good, what could create a situation where human lives are intentionally harmed?\nEDIT:\nI noticed that I need to word my question better, so I'll add here what I posted in a comment.\nMost of the answers so far assume the worst of humanity; stuff like \"Might as well do anything I want, since I'll die one day\". The thing is, that is true for all humans even now. Why would the possibility of there being zero humans a few decades from now foment conflict today?\nFor additional clarity, consider the following:\n* The realization that there are more humans dying that those being born sinks in slowly.", "934" ], [ "This isn't a T-virus/asteroid/alien invasion scenario, where humanity is given a few weeks till extinction.\n* For most people, news about economic indicators like labor costs or population decline isn't worth a lot of attention. So it's conceivable they carry on with their lives (for what I assume will be quite a while) until this starts affecting them personally. By then, governments & society are likely to grasp the fact that every human life is \"precious\", much like tigers or pandas today.\nSo, I guess my question is, when governments are actively engaged in (however futile) efforts directed towards conservation of human life, what would cause war or any armed conflict between humans?\nEDIT 2:\nA lot of excellent answers. I'm going to have to pick out elements from each answer and cook up a cascading series of events that form the basis for some bitter resentment between the principal actors and a spark that starts the fire.\nIf only I could accept more than one answer...", "934" ], [ "Put human bodies into suspended animation caskets (SACs)\nThis will be the most sustainable option because you do not need a lot of materials to run actual space. Living spaces must at all times be:\n* sanitized\n* monitored\n* air-conditioned\n* pressurized\n* lighted\n* gravitated\nThese requirements are just for designing a general livable space. Specialized living spaces like bathrooms, bunkbeds, kitchens, living rooms, cockpits, laboratories, viewing windows, etc., require a lot more conditions, meaning a lot more resources.\nBUT if you just put everyone to sleep, then you just need highly sophisticated bunk beds that also function as dining rooms, comfort rooms, and all sorts of utility rooms. Your only problem will then be all about running a place where interaction is necessary and/or encouraged, i.e. cockpits, laboratories, and living rooms.", "548" ], [ "My solution is just to\nPut human minds in full-immersion virtual realities (FIVRs)\nEverything in an FIVR is limited only by what computational power your ship can allot for such simulations. The only thing you need to ensure is the hierarchy of command within the ship, the accuracy of your simulation compared to real-world physics, and the correlation of the simulation with the control processes of the ship.\nBasically, you need to provide an interface for the simulation and the real world such that if the captain in the simulation decides to crank a simulated lever to steer the ship leftward, the ship will steer leftward based on the value of the cranked lever.\nIt would be like controlling the ship itself from within the simulation.\nThis simulation-reality correlation can be extended to all the other functions of the ship like\n* running the simulation\n* regenerating food sources\n* administering intravenous nutrition\n* navigating through space\nSummarizing: The freedom and safety you desire can be efficiently provided by virtual spaces. You can place a sophisticated, self-sustained, single-size bed anywhere on your ship. You only need that bed to be able to read and carry out the thoughts of the person on it. Maybe just add propulsion and the bed itself can become the ship, or link several of these beds together and equip them job-specific extra utility functions.\nTL;DR: By making the ship, the humans, and the interfaces between the two to be as integrated as possible, you do not need to know specifically where inside the ship should you put your humans.", "500" ] ]

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[ [ "I tried to get a estimate for an upper-bound with currently deployed instruments. Assuming that, resolution-wise, the James Webb Space Telescope is the best telescope we have today, I looked into its FAQ at https://jwst.nasa.gov/content/about/faqs/faq.html#sharp to find its angular resolution:\nWhat is Webb's angular resolution, and how will its images compare to Hubble's? Will they be as beautiful?\nWebb's angular resolution, or sharpness of vision, will be the same as Hubble's, but in the near infrared. This means that Webb images will appear just as sharp as Hubble's do.\nWebb will have an angular resolution of somewhat better than 0.1 arc-seconds at a wavelength of 2 micrometers (one degree = 60 arc-minutes = 3600 arc-seconds). Seeing at a resolution of 0.1 arc-second means that Webb could see details the size of a US penny at a distance of about 24 miles (40 km), or a regulation soccer ball at a distance of 340 miles (550 km).\nNow imagine we can distribute stars at will around the celestial sphere.", "758" ], [ "The best distribution I can imagine, to fit the maximum number of stars while still keeping angular resolution, is to put them evenly spaced at the celestial equator, at 0.1 arc-second intervals. And then do the same for every parallel circle above and bellow, separated by 0.1 arc-seconds of celestial \"latitude\" (as the parallel circles shrink by cos(latitude angle), its necessary to adjust the number of stars accordingly). The following Pharo 10 code calculates approximately how many stars we could fit this way:\n| resolution starsAtEquator starsInHemisphere |\nTranscript clear.\nresolution := 0.1. \"Resolution in arc-seconds\"\nstarsAtEquator := 360 * 60 * 60 / resolution.\nstarsInHemisphere := ((0 to: starsAtEquator // 4) collect: [ :each |\n(each * Float pi / (starsAtEquator // 2)) cos\n* starsAtEquator round: 0 ]) sum.\nTranscript\nshow: 'Stars in whole celestial sphere: ';\nshow: 2 * starsInHemisphere\nThe result is about 5.35e13, or about 50 trillion objects individually resolvable, at <PERSON> resolution.\nCorrection: In the first version of this answer, I said that If it took only one second to reposition the telescope to look at a different point, it would take more than one and a half million years to cover the entire sky, assuming it would have to reposition at every point. But as pointed by @planetmaker, the field of view of the James Webb telescope is 3' x 3', so the time to cover the entire sky would be much lower.", "371" ], [ "We can use the same expression that is commonly used to estimate the apparent magnitude of a planet or asteroid in the Solar System*:\n$$\\boxed{m=5 \\log \\frac{1329}{d \\cdot \\sqrt p}+5 \\log (D_s \\cdot D_e)-2.5\\log f(F)}$$\nWhere:\nm is the apparent magnitude\nlog is the decimal logarithm\nd is the diameter in km\np is the albedo\nDs is the distance to the Sun in Astronomical Units (AU)\nDe is the distance to Earth in Astronomical Units (AU)\nf(F) is the phase function\nIf we want to apply this expression to the James Webb Space Telescope, the values to use are as follows.\nAs the surface area of the JWST solar shield is $S=21\\cdot 14=294$ square meters:\n$$d=\\sqrt{\\frac{4\\cdot S}{\\pi}}$$\nEquivalent diameter \"d\"\nd = 0.01935 km\nThe satellite hosting the Webb Telescope will be placed in a halo orbit around Lagrange L2 Sun-Earth, a point located 1.5 million kilometers from the Earth (see drawing). The radius of the halo orbit is 0.8 million km.\n$$D_e=\\sqrt{1.5^2+0.8^2}=1.7$$\nDe = 0.01136 AU\nDs = 1.01004 AU\nAs a phase function we will use the usual one:\n$$f(F)=\\dfrac{1+\\cos F}2$$\nThe phase angle \"F\" is calculated using basic trigonometry from the drawing\nIt is obtained:\nF = 27.8º\nAnd we see that the contribution of the corresponding summand is almost negligible:\n$$-2.5 \\log f(F)=+0.06$$\nThe albedo \"p\" of the heat shield will be high, to reflect the maximum amount of heat possible.", "371" ], [ "But since the albedo of the solar shield is unknown to me, I add the table below showing the estimated apparent magnitude value, for different albedo values.\nThe table tells us that the apparent magnitude of the JWST when it reaches its halo orbit around L2 will be of the order of +15 and therefore this should be visible with some powerful telescopes of amateur astronomers.\n*Reference: Binary asteroid population. 1. Angular momentum content, by <PERSON> and <PERSON>\nBest regards.", "758" ], [ "Interesting question. Assuming the figure of 10 million stars per cubic parsec is correct, there's still one missing piece of information to try getting a estimate: The size of this region with a very high concentration of stars. But at least we know it can't go very far, because at such densities (d), it would take a sphere with radius r = (3 10^11 / 4 * pi * d)^(1/3) ~= 6.2 parsecs to hold about 100 billion stars, on the order of the actual number of stars in the entire galaxy. So I will guess this region of high star density (r) holds only about 1% of that, corresponding to a radius of (3 10^9 / 4 * pi * d)^(1/3) ~= 1.34 parsecs.\nTo get a estimate of the brightness of the sky near the galactic center, I coded a simulation using Pharo 10 (a Smalltalk dialect):\nThis simulation just populates a spherical region of space randomly with points representing stars, assigning each of then a power output following the distribution of known stars near the solar system. Then it sums the luminance component of each star above a plane that passes through the center, and perpendicular to it. This is done 10 times and the average is taken, to average out the effect of a particular run where by chance we get a star very close to the center point, where we assume the planet of the observer is located. This estimate makes some assumptions:\n* Stars near the core are randomly distributed in every direction;\n* Stars don't obstruct each other. Probably mostly true, as the size of the stars is very small, when compared to the distances that separates them;\n* The radiation has a path mostly free of dust, doubtful when talking about the Milkyway core;\n* Luminance (total W/m^2) is a good proxy for what you would actually see with your eyes.", "921" ], [ "Probably not that realistic, as stars different of the sun radiate a lot of the energy outside the visible spectrum, as ultraviolet or infrared;\n* We can take the known stars near the solar system as a representative sample of those near the galactic core. That's doubtful, as there's probably lots of still undiscovered brown and red dwarfs near us, and the near earth sample doesn't contain some kinds of stars that are surely present at the galact center, like red giants, outside the main sequence.\nGiven those disclaimer, here is the code for the simulation, as executed in <PERSON>'s playground:\n| sunPowerOutput au moonAverageDistance moonRadius moonAlbedo sun radii t0 |\nsunPowerOutput := 3.828e26. \"In W/m^2\"\nau := 1.5e11. \"In meters\"\nmoonAverageDistance := 3.844e8. \"In meters\"\nmoonRadius := 1.7374e6. \"In meters\"\nmoonAlbedo := 0.1. \"Dimensionless\"\nradii := #( 0.1675 0.335 0.67 1.34 ). \"In parsecs\"\nsun := CelestialBody\nwithX: 0\nwithY: 0\nwithZ: 0\nwithPower: sunPowerOutput.\nTranscript\nclear;\nshow: 'Solar constant estimate (W/m^2): ';\nshow: (sun fluxDensity: au);\ncr.\nmoon := CelestialBody\nwithX: 0\nwithY: 0\nwithZ: 0\nwithPower:\nmoonAlbedo * (sun fluxDensity: au) * Float pi\n* moonRadius squared.\nTranscript\nshow: 'Lunar constant estimate (W/m^2): ';\nshow: (moon fluxDensity: moonAverageDistance);\ncr.\nTranscript\nshow: 'Stellar constant estimate (W/m^2): ';\nshow:\n(GalaxyCore withRadius: 150 withDensity: 0.14) centerPowerDensity;\ncr.\nTranscript\nshow: 'Radius';\nshow: ';';\nshow: 'W/m^2';\ncr.\nt0 := DateAndTime now.\nradii do: [ :radius |\nTranscript\nshow: radius;\nshow: ';';\nshow: (((1 to: 10) collect: [ :each |\n(GalaxyCore withRadius: radius withDensity: 1e7)\ncenterPowerDensity ]) average round: 4);\ncr ].", "371" ], [ "What is the frequency distribution for luminosity classes in the Milky Way Galaxy?\nI'm working on a game concept that does some mild simulation of realistic stellar classes and luminosities. In particular, I'd like to roughly model the general frequencies of the classes and luminosities of the stars in the Milky Way.\nSeveral sources, including Wikipedia's entry on stellar classifications, show a chart that includes the frequency distribution for spectral classification: the OBAFGKM categorization. So that's fine.\nWhat I'm having trouble finding is any frequency distribution chart similar to that one but for the <PERSON> luminosity categories: Ia+, Ia, Iab, Ib, II, III, IV, V, sub-dwarf and dwarf. I have a copy of the Hipparcos database, which contains a \"Spectral Types\" field, but it's highly incoherent text. Still, I could write some code to parse the values in that field to try to get a rough count of luminosity categories in those roughly 116,000 stars...", "224" ], [ "but I'm a little perplexed that no such chart appears to exist already somewhere in Internetland. (Either that or my search-fu is weaker than usual.)\nIf anyone can point me to a chart of the frequency distribution for the luminosity categories noted above, or suggest a reasonably simple way for me to calculate those values myself, I'd appreciate it.\nEDIT: Out of curiosity, I went ahead and did my own simple parsing of the spectrum fields from the Hipparcos dataset.\nOut of 116472 rows, only 56284 (fewer than half) provided luminosity class data in the Spectrum field. Those 56284 rows broke down this way:\nIa0 16 0.03%\nIa 241 0.43%\nIab 191 0.34%\nIb 694 1.23%\nI 17 0.03%\nII 1627 2.89%\nIII 22026 39.13%\nIV 6418 11.40%\nV 24873 44.19%\nVI 92 0.16%\nVII 89 0.16%\nNote: Around 1000+ rows gave an either/or value for luminosity class (e.g., \"M1Ib/II\"). In these cases, I counted only the first value provided. This probably skewed the results slightly compared to counting both luminosity classes.\nI'm still very curious to know whether anyone else has produced or located a similar table of frequencies for the luminosity classes, if only to see how my very trivial analysis compares.", "224" ], [ "This question has been addressed by a few studies in the past decade. These studies ran climate models for planets with eccentric orbits. I'm aware of three scientific papers on the topic (I'm co-author of one): here, here and here.\nThe simple answer is: what matters first and foremost is the mean flux received by a planet over the course of its orbit. The orbit-averaged flux $F$ scales with the orbital eccentricity $e$ and semimajor axis a as $F\\sim a^{-2} (1-e^2)^{-1/2}$. You need a big eccentricity for it to make a big difference on the climate (e.g., for an eccentricity of 0.5 the increase in orbit-averaged flux is just 15%, easily compensated by increasing the planet's semimajor axis by a smidge):\nFor a planet on an eccentric orbit, there is a short hot summer and a long cold winter. But most of the relevant climatic timescales are much longer than the orbital time so only the orbit-averaged flux matters.", "188" ], [ "This plot shows the orbit-averaged Flux (blue curve), the aphelion to perihlion ratio dmax/dmin (green curve), and the ratio of flux received at peri- vs apo (red curve).\nFYI, I once wrote a blog post on exactly this subject: https://planetplanet.net/2014/10/06/real-life-sci-fi-worlds-1-the-eccentric-earth/ and there are plenty of interesting details. My favorite was that we imagined (and performed climate simulations of) a planet on a very stretched-out orbit that was also tilted on its spin axis. The planet ended up being a global iceball except at the point that received the strongest heat pulse from the Sun -- at the South pole in this case, which thawed for about a month per year. Here is an illustration (white = frozen over, blue = just above freezing).\nFYI there is another interesting situation in which a planet's orbital eccentricity changes in time due to gravitational interactions with other planets in the system. If you're interested see here: https://planetplanet.net/2014/10/08/real-life-sci-fi-worlds-3-the-oscillating-earth/\nOn that note, in a simulation of rocky planet formation I once produced a pair of planets that straddled the habitable zone but that exchanged eccentricity such that they took turns having excursions outside the habitable zone. FYI, in this image time 2 is about 20,000 years after time 1 (details on that simulation here or here).", "188" ], [ "Same area, different shape. pro's & cons\nPure speculation about a future replacement for the JWST that I almost certainly won't live to see.\nThe JWST's mirror (and then some) would fit unfolded and flat into the Starship's 8m diameter payload volume. In the following image that is shown by the 18 grey 1.5m AF hexagons, giving a 7.5mØ and a light gathering area (LGA) of 35m². (A useful 40% increase over the JWST and no moving parts. (So far!))\nNow it is easy to see that adding 6, 3-hexagon wings (ala JWST) to each of the sides, folded back for launch, would increase the mirror to 10.5mØ and double the effective LGA to 70m²; nearly 3 times that of the JWST.\nBut there is a problem, in that without using a second fold per wing, one of the hexagons on each wing would protrude beyond the 8m circle.", "758" ], [ "(Attempting to fold the wings more that 90° causes collisions.)\nSO, why not move that mirror out between the other two on that wings as show by the light green hexagons above. Same LGA, mass etc. and if anything slightly easier mechanically; as it provides space within the 8m diameter in which to put attachment points for the secondary mirror supports.\nNow to my basic question. Optically, are there any insurmountable caveats of using a star shaped mirror?\nCasting around for an answer I read that the increase in diameter (with no increase in LGA) can enhance the spatial resolution of instrument. Hence why radio telescope arrays using interferometry always place a few dishes (sometimes just one) far outside the diameter of the main signal gathering radius:\nAlthough they do not contribute much to the S/N ratio, if individual points from their weak signal are correlated with the same point in the strong signal from the main array, it greatly increases the accuracy of the location of that point.\nWhether the modest increase in here is valuable I do not know?\nTo reiterate my main question: Does a star shaped mirror present problems either optically, or in signal processing over a more nearly circular mirror?\nThanks. <PERSON>", "758" ], [ "How do I calculate the moment of inertia of an idealized Earth's equatorial bulge?\nI am working on calculating an idealized Sun-Earth-Moon three-body system. As part of this I want to calculate Earth's axial precession, which requires knowing the torque that is acting on it. Wikipedia gives this equation for the torque caused by a celestial body's gravity acting on the Earth: $$\\vec{T} = \\frac{3GM}{r^3} (C − A) \\sin(δ) \\cos(δ) \\begin{pmatrix} \\sin(α)\\ −\\cos(α)\\ 0\\ \\end{pmatrix}$$\nWhere\n* $GM$ is the standard gravitational parameter, the product of the gravitational constant $G$ and the mass $M$ of the perturbing body;\n* $r$ is the distance between the center of the Earth and the center of the perturbing body;\n* $C$ is the moment of inertia around Earth's axis of rotation;\n* $A$ is the moment of inertia around any equatorial diameter of Earth;\n* $(C − A)$ is the moment of inertia of Earth's equatorial bulge (C > A);\n* $δ$ is the declination of the perturbing body (positive for north of the equator, negative for south of the equator); and\n* $α$ is the right ascension of the perturbing body (east from vernal equinox)\nI have all the numbers needed except for the moments of inertia around Earth's axis of rotation and around \"any equatorial diameter of Earth\". I don't know how to calculate these, or even what the difference between them is, and Googling hasn't been much help.", "483" ], [ "For the value of $C$ I found one source that says Earth's moment of inertia is $8.04 × 10^{37} \\text{ kg m}^2$; and another that says the moment of inertia of an oblate spheroid around its shorter axis is $\\frac{2}{5} M r^2$, where $r$ is the major radius, which with my numbers gives me $9.699 × 10^{37} \\text{ kg m}^2$. These two numbers are at least the same order of magnitude, which makes me think I'm on the right track, but there's still a large error factor I'd like to eliminate which I'm assuming is related to Earth not being a point mass or of uniform density. That also still leaves me without any idea of what the value of $A$ represents and how it differs from $C$.\nIn my idealized system, the Earth is an oblate spheroid whose shape is given by the equation $(\\frac{x}{6372})^2 + (\\frac{y}{6372})^2 + (\\frac{z}{6349.875})^2 = 1$, making the equator 22.125 km farther from the center of the Earth than the poles. For density I'm using the Preliminary Reference Earth Model (PREM, en.wikipedia.org/wiki/File:RadialDensityPREM.jpg) and assuming both that the mass is evenly distributed and that the distances in the PREM scale evenly with the radius at any given latitude.", "15" ], [ "Horseshoe orbit cycle times\nI asked on Worldbuilding originally, but was directed here instead\nI've been working on a habitable moon system for a story, and I'm now trying to populate the other moons around the parent planet. I'm considering placing one (Moon B) in a co-orbit, horseshoe configuration, with my habitable moon (Moon A).\nWhile I understand the general concept of horseshoe orbits, the actual calculations of the orbital times is beyond my mathematical capabilities.\nI understand that on a horseshoe orbit there is an inside section and outside section where Moon B is catching up to, or falling behind, Moon A, respectively.\nI understand that if the 'inside ring' is nearer the parent body (the 'planet' in the case of co-orbital moons) than the L1 Lagrange point of Moon A, then Moon B will escape the horseshoe orbit and just start orbiting the planet directly. And, similarly, if the 'outside' ring is outside of L2 Lagrange point of Moon A, Moon B will escape and orbit the planet directly. And if either ring is too near the actual orbit of Moon A, it will be a tadpole orbit(never passing the L3 Lagrange point of Moon A before returning to Moon A from the same direction it left it), instead of a full horseshoe.\nWhat I can't figure out (again, math skills limitation) is How long it would take (longest and shortest possible times) for Moon B to make one complete cycle of the horseshoe? And so I can't decide if I should use this type of orbit or not. For example, 3753 Cruithne takes about 770 years to complete it's horseshoe cycle relative to Earth, far too long to be useful for my story. But I don't know how to calculate ho long my co-orbit scenario would take.", "710" ], [ "I'm confident it could be made significantly shorter than 770 years, but exactly how short it would be is still a key factor in the decision.\nI would like to know how often the two bodies would approach each other at the two extremes of possibilities, the longest possible time between complete cycles, and the shortest possible time between cycles.\nFor this question: Planet mass is 477 Earth masses, Moon A's mass is 0.11 Earth masses, Moon B's mass is 0.01 Earth masses. Moon A's semi major axis is 4 million kilometers. (please let me know if any other variables or details are needed)\nTo re-word the original question: By adjusting the semi major axes of the inner and outer rings of Moon B's horseshoe orbit, either closer to or farther from the semi major axis of Moon A, what are the longest cycle time, and shortest cycle time possible for a horseshoe orbit in this system?\nHere is a visual representation of the types of orbit changes I'm referring to. The contour lines inside the highlighted one (nearer L3 L4 and L5) are what I'm referring to when I mentioned adjusting the horseshoe orbit Axes nearer to the semi major axis of Moon A. And the contour lines outside of the highlighted one are what I'm referring to when I mention moving those axes farther from the semi major axis of Moon A. When I refer to a complete 'cycle', I mean the time it takes for Moon B to go from Point A on that image, through Points B, C, D, and E and back to A.", "710" ] ]

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[ [ "How to indicate the topic has been changed without using words?\nI am writing an an article to share knowledge, not novel. Usually, when you change the current topic, at the beginning of the new paragraph you would like to use some transition words such as Addition, Next, etc. However, if you don't want to use those words, you need a stronger indicator to tell the readers that the topic has been changed. I think drop caps are the best for this, but I'm using a platform which only support trivial characters. You can say that I must stick to Notepad. Is there any efficient ways to not using transition words?\nRespond to <PERSON>: Thank you for taking time answering my question. To clarify, I'm not rebelling anything. I acknowledge that those rules will help me structuring the article a lot. I just want to be a little different to give the readers a new taste.\nI'm not prefer the horizontal rule, since it's like splitting my article into sections, which I don't intend it to be.", "213" ], [ "Saying the topic will be changed completely after I start a new paragraph is not exactly right. It's like listing the ideas with bullets, but instead one sentence per bullet, you have one paragraph per bullet. Each paragraph starts with a topic sentence.\nI do aware that I should use white space, I just don't know how to use it properly. When I write a story, I usually use lines with one dot only to sign the readers to take a breath, like this:\n.\nOr this, if I want to give them more room to breath:\n.\n.\n.\nBut I'm not writing a story, I'm writing an academic article.\nRespond to what: thank you for taking time answering me. Of courses the sections are related to each other. Let's take my SOP as an example. The purpose of SOP is to tell the professors that you have quality to their research (it's like the cover letters when you apply to a job). Here are three points I want to convey in my SOP:\n* I believe that I was born for scientific research.\n* I think I have been familiar to the scientific activities.\n* I want to shift the discipline to biology after spending 4 years in physics.\nThen I develop each point to a paragraph. Therefore, my whole SOP has this structure:\nI believe that I was born for scientific research...\nI think I have been familiar to the scientific activities...\nI want to shift the discipline to biology after spending 4 years in physics...\nI don't want to use the structure below, since it will fail to put the topic sentence to the beginning of the SOP, which I intend it to be:\nI believe that I was born for scientific research...\nSecondly, I think I have been familiar to the scientific activities...\nThirdly, I want to shift the discipline to biology after spending 4 years in physics...\nWithout a strong indicator, I think that this structure can confuse the readers a little bit since it change the point so quick. I understand that transition words are very strong, but I would like to find another method.", "487" ], [ "Here is my extensively review of various books I had read. For meta discussion, see I have several book reviews. How should I answer in the book request?.\nBooks being reviewed:\n* <PERSON>, Group theory in physics\n* <PERSON>, Group Theory in a Nutshell for Physicists\n* <PERSON>, Physics from Symmetry\n* <PERSON>, Mathematical Physics A Modem Introduction to Its Foundations\n* <PERSON>, Group Theory: A Physicist's Survey\n* <PERSON>, Group Theory and Physics\n<PERSON>, Group theory in physics\nIts approach isn't go from general to specific, but from intuition to generalization. For example, many books explain isomorphism after homomorphism, because the former is a specific case of the latter. But in this book, the order is reversed, because we can imagine isomorphism better than homomorphism.\nTogether with many connections and discussions between chapters and subsections, it shows that the author has a pedagogical mind. In specific, the book:\n* Boldly uses ' for mappings (see def 2.5 for example). I've never seen this kind of notation before, and at first I think using this will make more confusion. But turns out it's not\n* Important theorems are named, not just numbered\n* Avoids study all groups in detail\n* Has many advanced example without proof, because they are just illustrations, not a topic for you to study\n* Proofs are deferred after discussing significance\nA trivial thing: theorems and definitions have different numbering systems. So when you are told to refer to Def. 1.3, then make sure you are not reading Theorem 1.3.\nI highly recommend this book, even though it's quite old (50 years or so).\n<PERSON>, Group Theory in a Nutshell for Physicists\nThe book is written in xkcd style: funny and lots of footnotes, with quotes and historic stories. However, most footnotes are at the end of the chapter (endnotes), so when an idea is noted, you can't read it immediately but have to turn to the end of the chapter. This is where the frustration starts: most of the notes are funny comments.", "855" ], [ "Having to break the reading flow and spend more effort just to get a tiny detail or a funny comment is not fun at all. But some of the notes are actually serious and you really don't want to miss it, so every time I see a note I have a mixed feeling.\nHere and there there are some insights or unexpected facts (mostly in the introductions and appendices of each chapter), but the rest are verbose and can be reduced, especially when math is involved, so you may want to have good foundation before skipping them. The author explicitly states that he tends to \"favor those are not covered in most standard books, such as the group theory behind the expanding universe\", and his choices reflect his own likes or dislikes. So if you want to have a standard knowledge in standard book, this is not your choice. The contract of the author with Oxford requires the title to have the bit \"in the nutshell\", which I think misleading.\nYet, I think you should take a look at the fruitful bits. They do give you new perspectives and insights.\n<PERSON>, Physics from Symmetry\nIts structure:\n* It starts with special relativity,\n* then the symmetry tools (Lie group and Lagrange formalism),\n* then the basic equations (free and interaction theory),\n* then their specific applications: quantum mechanics, quantum field theory, classical mechanics, electrodynamics and gravity.\nWhile the physical meanings of mathematical objects are emphasized, mathematical meanings of mathematical objects are underconsidered. Trace is only a sidenote thing, not the character of equivalent irreducible representations. <PERSON>'s lemma is mentioned only in one sentence. The whole representation theory is discussed very fleeting (only one subsection in the <PERSON> group theory section), before going straight to important groups: $SU(2)$, <PERSON> group, <PERSON> group.\nOther books\nHere are some books came after I had acquired a good understanding of group theory, so I didn't have much motivation to read them. But I think they are good, and you may want to take a look.\n* <PERSON>, Mathematical Physics A Modem Introduction to Its Foundations\nIt has side column for notes and summaries; convenient for skimming. At some pages, there are many emboldened characters at a place, quite confusing to read. It also discusses about $Endk$, $Lk$.", "800" ], [ "How to combine a visual and textual outline\nI am a Ph.D. student in engineering, so most of my writing fits into a fairly strict idiom: the IMRaD or Introduction, Methodology, Results, and Discussion. In general, I like to use an outline to help structure the paper and each section of the paper. So I will create something like the following list.\n* Introduction\n* blah\n* blah\n* Methodology\n* blah\n* blah ...\nAlthough I do not always label the sections so strictly by the IMRaD format, this works as a good example for my problem.\nTo get the content of the outline for each section if my paper, I usually do what I call a brain dump; i.e. I write every possible topic and content item that I can imagine falling under this section. I then try to reorganize the pieces and make something coherent. In theory, I suppose this process should produce a nice outline.", "373" ], [ "In practice, however, as I start writing from my outline I end up realizing that I forgot to explain some crucial details, and then I need to go back and revise my outline to take these into account. Normally, I would accept this as part of the revision process, but I would like to help work out some more of these kinks by adding a step to my outline process.\nI want to try some sort graphical or visual outline, either in parallel or in series with my textual outline, to help show which ideas or topics need to be explained first. This ordering will help ensure that I am not using a term without defining it. My question is, how can I coordinate the visual outline and the textual outline in a time efficient manner? I can work on a computer or by hand. I don't really have a preference, except that I will always use a computer to generate the bulk of my prose. Most of my final writing will be done using a text editor (such as EMacs) to write my document using LaTeX (a system for typesetting that is particularly math friendly), so systems that are compatible or complementary to these would be ideal, but it is not required. I especially would like to hear people's experience using two outline methods concurrently.", "373" ], [ "The order of words tends to have grammatical restrictions that don't allow for you to change this. Everything else however, especially for a first draft, can/should be changed.\nThe idea behind reading aloud is that by hearings one's words read out loud, one notices what sounds good and what doesn't. For me, it takes a few days before I can see these \"errors\" in my writing, so make sure to give it some time, before returning to writing. Here a few, more or less, objective guidelines:\n* Every consecutive sentence should be of different length. This keeps the writing interesting and engaging, and excites the reader because they won't know what comes next.\n* Replacing simple words with more complex ones is good, but don't overdo it; Often, the simplest words are best. If the complex word does not serve any other purpose than to tick off the requirement, replace it with a simpler one.", "487" ], [ "Else, choose the right complex word (e.g. I ran/walked/stampeded/speeded/wandered/trudged to school). Also make sure that you don't use the same complex verbs twice in a paragraph, unless it makes more sense when it's the same (I used the word \"simple\" multiple times to underline the duality of complex vs simple words)\n* That being said, when you have a sentence starting with a conjunctive, do not allow the next few sentences start with one as well.\n* Unless several paragraphs have passed, do not use the same conjunctives (while, although, yet, and, etc.). I am guilty of this myself, and it's tough to go around this sometimes.\n* Use few adverbs (astonishingly, guiltily, happily), and instead say what a character does/scenery is, that makes it astonishing, or guilty or happy. Again, tough, but in my experience, most of my edits are because of this rule.\n* Another way to improve flow is for every sentence to be followed by a sentence that describes what the reader is interested in next. I know you may want to hear an example for this, so I would, for example, dedicate this sentence to giving you one.\nI haven't read your manuscript, so I cannot give you more feedback. But these guidelines take me very far in improving my writing.", "487" ], [ "Out of the two, I think vocabulary is easier to tackle. I used Vocabulary.com to actively learn new words and their meaning. Although, the site itself is good. I would recommend to either write down the words and their short meaning in a notebook or an excel table. The words you write should either be the words you found useful, or words that you might have heard before, but not used them or didn't know their precise meaning. Now the reason why I recommend Excel table is for it's sorting function. Having an alphabetically sorted list is a much nicer and easier to navigate way than it's alternative, simple notebook. There is also a possibility to search for the keywords, which I found amazing.\nThe other thing you should do is to simply read more. The thing I would recommend is to have an audiobook playing while reading the book. My reasoning behind this is that when I'm faced with a difficult word I might just skim over it.", "873" ], [ "Taking its meaning from the concept of the sentence. However, if I hear the word as well as read it. The word itself sticks in my mind easier. Meaning I might use it more often, therefore extending my vocabulary by it.\nRegarding the style, I think you can only read and write more. I remember reading the first <PERSON> book by <PERSON>. I loved its short sentences shadowed by, what seemed to me as, calculated force. The writing fit the main character who's an ex-military cop, a gentle giant ready to burst in action. In my opinion, the style you use will mimic the authors you read, and that's not the bad thing. I also think it's hard to blunder the style. If your characters are believable and story sound you won't have to worry about your style.\nIn the end, I would recommend a couple of books, which helped me write clearer and be more confident when writing.\n* Stein on Writing by <PERSON>\n* The Elements of Style by <PERSON>\nThe first book focuses on the process of writing, storytelling techniques and writing for yourself as well as the reader.\nThe second book is the collection of rules to follow when styling the text. How to format dialogues, use active voice and basic punctuation.", "873" ], [ "How is light produced?\nTo be clear here, My question arises from studying Electromagnetic induction and polarisation and photoelectric effect. From here I've gained the knowledge that creation of a photon involves:\n* Electromagnetic Induction - The fact that a time varying spatial magnetic field which creates a closed loop electric field [Super Confusing as to why universe does that]\n* Polarisation - In the books, they show that light is oscillating electric field vectors and magnetic field vectors\n* Photoelectric Effect - Creation of light has something to do with an electron returning to a lower energy state, not saying that it's the only way.\nSo how does light get produced? I'm seeking in-depth explanation.\nSome Context\nThe question arose when I was talking to my friend about a hypothesis of mine where I was saying that If I released a photon from , say a torch. I could, under some known error margin, say at what instant the photon was created but according to what I've heard multiple times, time stops at light speed. So, any photon at 'c' would basically never had experienced any time. So, from the perspective of the photon, its birth can't be defined. We seem to reach a paradox here, if I observe a time at which the photon was created but the photon has no notion of time, it has no notion of a beginning or an end.", "187" ], [ "Then, I tried to expand the concept of the hypothesis to say that maybe in a similar sense, the universe doesn't hold a concept of beginning or an end. As we experience it's perspective, we can't determine its birth time using our maths which has been cultivate throughout this universe, and we also know that maths do break down when we try to solve equations for the t=0 time of Big Bang. NOTE: This talk was just to have fun, I just like physics and like to talk about the universe, however, I understand that I might have just annoyed someone by ignoring a dozen of laws and theorems that I'm yet to find out about. APOLOGIZES!\nI'm expecting a somewhat dumbed down explaination, now don't get too carried away by that. I'm a high school student but I do love a bit of technical mumbo jumbo but I'm just asking to keep in mind that I'm in high school. Example:\nSay we have an equation: x3+x2-x+44=0 Instead of saying the degree of equation is 3 maybe say the highest power in the equation is 3.", "764" ], [ "There are many ways to express the same thought - many more than you might realize.\nVocabulary\nThe first thing is the difference between active and passive vocabulary, also known as productive and receptive knowledge. You may recognize a word and its meaning when reading it, but you may not use that word when talking or writing yourself. It's just a word that you have used so few times that it wouldn't cross your mind to use this word.\nTo take an example from a recent discussion here on Writers.SE (How to talk about certain anatomy without sounding vulgar or cowardly?): you may understand the word Gluteus Maximus and what part of the body I am alluding to, but using a medical term in a normal conversation wouldn't cross your mind. Using posterior on the other hand feels more natural, though in general I would probably use butt. Your usage will probably vary. Maybe because you like medical terms, or because you don't like defensive descriptions like posterior.\nTo cite the Wikipedia article I linked before:\nAn average 20-year-old knows 42,000 words coming from 11,100 word families\nNow you have to ask yourself: how many words are there in total?\nAccording to the Oxford dictionary:\nIt's also difficult to decide what counts as 'English'. What about medical and scientific terms? Latin words used in law, French words used in cooking, German words used in academic writing, Japanese words used in martial arts? Do you count Scots dialect? Teenage slang? Abbreviations?\nIt's not that easy to find out how many words there are. And the number changes all the time because people are creating new words and older words are slowly forgotten.\nBut to give at least a rough idea the link also contains the following phrase:\nThe Second Edition of the 20-volume Oxford English Dictionary contains full entries for 171,476 words in current use, and 47,156 obsolete words. To this may be added around 9,500 derivative words included as subentries.\nUsing these very simple statistics we can say that the average 20-year-old knows about a fourth of the currently used words in the Oxford English Dictionary.\nBut you have to adjust this number: the german article about vocabulary mentions that the standard vocabulary contains around 75,000 words - while the total is estimated to be somewhere around 500,000 for everyday conversations. If you are taking into account specialised terminology this number goes up into the millions, with the example of chemistry having probably around 20 million words.\nThe average 20-year-old may have a pretty good grasp of the normal everyday language and know quite a lot of those words and he may understand a good amount of stuff that he wouldn't use himself, but there are so many more words in the world that he never heard about that it's unrealistic to say that he will have the same style of talking and writing as his peers.\nThe bottom line is that you are probably vastly underestimating the amount of words that your native language contains. The active vocabulary of you, your friends and your family may be similar, but if you are asking a different group you may find huge differences, just because there are so many possibilities.", "312" ], [ "The same applies to sentence structure and other parts of writing.\nYou also asked about example - take a look through this answer. I tried to hide a few different ways of speech here.\nDid you catch the difference in referring to other sources? In the third paragraph I linked another question and paraphrased the content. Afterwards I changed to citation from Wikipedia and other sites. It's not unreasonable to see this as one part of my voice. Am I using a lot of paraphrasing or citations? Or a mixture? How much paraphrasing sounds good? There are some grey areas here, allowing for different voices if you just compared this simple attribute throughout the site.\nSentence length\nThe easiest thing to express different voices is through the use of longer or shorter sentences. Look at your own post: I can clearly see that you prefer longer sentences. You used a lot of commas and and's to extend your sentences and except for your last paragraph each paragraph contains exactly one sentence and is at least 1.5 lines long. Your last sentence would only be half a line, which is probably why you didn't bother making it a paragraph of its own.\nI also like long sentences. Most of the time, at least. Sometimes shorter sentences are better. They are easier to understand for the reader.\nBut then again, longer sentences may sound more eloquent, which might be the desired effect when writing. This completely depends on your target audience - are you writing for younger people, who may have problems following long, complicated sentences, or academics who seem to have a knack for this kind of sentence structure?\nPunctuation\nDid you realize how often I use dashes and colons to split a sentence and at the same time continue the thought?", "873" ], [ "Without going back to an outline, you could do the following:\n* Print your draft on paper.\n* Take some fluoresecent colored pens and mark all the words that are specific to your paper. Not words like \"the\" and \"research\", but words like \"unification algorithm\" or \"eukaryotic cell\". Use different colors for different topics in your paper.\n* If you see the same words/colors in many remote places, move those sentences closer together (you're obviously back behind your computer now ;-). Ideally, each section talks about a single topic, so it should have more or less only 1 color. Since your paper was a \"sea of words\" to begin with, you lose nothing by moving things around. Never mind the \"flow\" for now: just the topics.\n* Now that the topics are \"sealed\" into sections, remove all duplicate sentences.", "487" ], [ "Keep only the ones that give new information.\n* Order the sentences so that new terminology/ideas are introduced in a logical order, i.e. new words/concepts are defined before they're used.\n* From each group of sentences, make a temporary title and put it in front of the group. It may not make it as a title into the final paper, but it brings an outline back into the paper for yourself.\n* Now, and only now, start looking at the grammar and the flow. Turn each group of sentences into a few paragraphs right there underneath their temporary title. Make sure that each group expresses exactly the idea in their temporary title.\n* For better \"flow\", start larger sections with a summary of what you explained in the previous section, and then show the connection to the new section. You can quickly see what you explained in the previous section by going over their temporary titles.\n* At the end, take all your temporary titles and turn them into a summary. You can use this as the introduction, the conclusion of the paper, or even both if you rewrite it slightly.\n* Then remove most of the temporary titles, keeping only the \"big\" ones to structure the paper for your readers.\nRegardless of which technique(s) you use from the many excellent answers, let us all know how it worked out for you! Good luck.", "487" ] ]

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[ [ "Sesame-Miso \"Nice Cream\" on Dacquoise\nIntroduction: Sesame-Miso \"Nice Cream\" on Dacquoise\nI don't know how to make ice cream, but I do know how to make \"nice cream\": It's frozen banana blended up. But I wanted something interesting, so I decided to make sesame miso nice cream. To top it off, I decided to put it between two sesame dacquoise cookies, and roll it in sesame seeds. Sesame makes everything good.\nSupplies\nIngredients you will need:\nNice cream\n* 1 banana (overripe)\n* 1 tablespoon tahini\n* 1 tablespoon milk\n* 1/2 teaspoon miso\nDacquoise\n* 1 1/2 tablespoon tahini\n* 1 egg white\n* 1/8 teaspoon cream of tartar\nFinish\n* 5 grams of sesame seeds\nTools you will need:\n* Mixing bowl\n* Hand mixer (or whisk)\n* Freezer container\n* Blender\n* Oven\n* Measuring spoon\n* Cooling rack\n* Baking sheet\n* Parchment paper\n* Spatula\n* Spoon\nStep 1: Nice Cream: Freeze Banana\nPeel an overripe banana and freeze it. Chopping it up before freezing may make the next step easier. I left it overnight in the freezer.\nStep 2: Nice Cream: Blend and Freeze\nBlend your frozen banana with the milk until slightly chunky, scraping down the sides once in a while. Then, add the miso and the tahini and blend until well incorporated and smooth. Then, put it inside a container and put it into the freezer.\nStep 3: Dacquoise: Whip Egg Whites\nIt's time to make the dacquoise.\nFirst, preheat the oven to 350 F. Then, separate the egg yolk from the egg white and put the white in the bowl. You can make something else with the yolk since we are not going to use it in this recipe. Add the cream of tartar and whisk until stiff peaks.", "567" ], [ "You can test if it's stiff by flipping it over your head.\nStep 4: Dacquoise: Fold in Tahini\nNow, normally people would fold in sifted almond flour, but I already had tahini so I decided to use this instead, and it seems to work.\nSo, gently fold in a third of the tahini into a small corner of the egg whites, then fold it with the rest. After that, you can add the rest of the tahini and fold until it is evenly distributed. Don't worry too much about it being deflated, it turned out well for me even if mine deflated.\nStep 5: Dacquoise: Place and Bake\nPut a piece of parchment on your baking sheet and spread the dacquoise mixture into a circle with a spoon. I made three since I wanted to use the third one for something else, but I think making two big ones will fit this size of ice cream sandwich as I had some leftovers.\nAnyways, bake it in the oven (which was preheated to 350 F) for 5-7 minutes or until browned. Once out of the oven, place it on a cooling rack to cool.\nStep 6: Sandwichify\n\"Sandwichify\" is probably not an actual word. But anyway, it is time to assemble our nice cream sandwich.\nPour out the sesame seeds. I used 10g, but I didn't end up using all of it. Take your completely cooled dacquoise and slather some of your (completely frozen) nice cream from the freezer, then roll the ice cream part in the sesame seeds. You might need to sprinkle the sesame seeds. It has to be frozen or else the filling will just melt (which is what happened to me). So, if you want, freeze it and then apply the sesame seeds. If it's not sticking, you can moisten the sides with a bit of water and they should stick better.\nQuickly put it in the freezer for a couple of hours until it is completely frozen again, and enjoy!", "567" ], [ "Matcha and White Chocolate Turtle Bread\nIntroduction: Matcha and White Chocolate Turtle Bread\nIn this instructable I'll show you how to make super cute, Japanese inspired, matcha infused, chocolate filled turtle bread.\nIf you ever had any sort of Asian cake, Japanese especially, you will know what type of bread I'm talking about. Fluffy, soft, almost cloud like dough. Not too sweet, but plenty satisfying. There is a special method widely popular in Asia when it comes to making bread. They use tangzhong, cooked flour and milk/water paste that, once incorporated within the dough, will keep the bread soft, light and moist.\nSupplies\nTangzhong paste:\n* 1.5 tablespoons pastry flour\n* 120ml milk\nSweet bread:\n* 270g strong bread flour\n* 5g yeast (2 teaspoons)\n* 10matcha\n* 100g white sugar\n* 1 teaspoon of salt\n* 30g melted butter\n* 70ml milk\n* 1 large egg\n* green food dye\nDutch crunch paste:\n* 50g rice flour\n* 1 tablespoon sugar\n* 1 teaspoon yeast\n* pinch of salt\n* 1 tablespoon cocoa powder\n* 1 tablespoon sunflower oil\n* 60ml water\n*****When using matcha as both a flavouring and a colourant, use good quality, baking grade matcha. Flavour can be achieved using inferior matcha powder, but the colour will be too pale or even brown. I used a combination of matcha powder and a bit of green dye to give the turtles nice, vibrant colour.", "305" ], [ "If you are not a fan of matcha, you can leave it out and just add more vanilla paste.\nStep 1: Tangzhong\nStart by whisking the cold milk and flour in a saucepan. Once everything is incorporated and there are no lumps, heat it up and cook on medium for 2-3 minutes, until the paste cooks and thickens. You have to stir it continuously and vigorously, so it doesn't burn.\nOnce cooled, transfer it to a bowl and cover it while it cools down.\nStep 2: Sweet Bread Dough\nNormally, when I make yeasty dough I just use a bread maker, but mine recently broke, so I did it all completely by hand.\nI sifted all dry ingredients and dried yeast into a large bowl and mixed it thoroughly.\nIn a separate container I put melted butter, milk, vanilla paste and an egg and mixed it well.\nOnce <PERSON> cooled down, I added it to wet ingredients and stirred well.\nThen, I made a hole in the middle of the dry ingredients, poured wet ingredients into the hole and combined roughly with a knife or fork, much as you would when making pasta from scratch.\nSince I didn't have any machines to aid me with this task, I had to get my hands dirty and knead the dough myself. Tedious task, but if you imagine the lump of dough is your boss' head, it will go much easier.\nIt takes about 10 minutes of continuous kneading to get it to the right consistency. Have some flour nearby if the dough is too sticky and you need to sprinkle some.\nPut the dough ball in a container and cover with a tea towel and let it rise in a warm room for 1.5 hours.\nStep 3: Dutch Crunch Paste\nMix all dry and wet ingredients. Paste has to be spreadable, thick enough to stay on top of the turtles without sliding, but thin enough to be easily maneuvered. If the paste is too thick, add a teaspoon of water and mix again to achieve the desired consistency.\nStep 4: Turtle Body\nAfter the dough have risen, sift some flour on your kitchen table and put the whole dough on top.\nTake a large knife and cut the ball into 8 equal pieces.\nPut two pieces aside, they are used to make heads, tails and limbs.\nTake each of your 6 pieces of dough and flatten it as much as possible, place two squares of chocolate ( or 1 tablespoon of chocolate chips or any other filling) in the middle and seal the filling inside the ball by crimping the edges together.\nForm a small ball and place it on a baking sheet covered by silicon pad or baking paper.\nRepeat that with all 6 pieces.\nStep 5: Heads, Limbs and Tails\nTake the two remaining dough pieces and cut one of them into 6 equal pieces (heads), and the second one into 30 small balls (24 legs and arms and 6 tails).\nTake the head piece and flatten it a little bit on one side, then slide the flattened part under the body of the turtle. Then use the same method to the legs and arms and tails until all turtles are formed.\nStep 6: Eyes\nIf you have black sesame seeds or flaxseed on hand, use them to create eyes.", "195" ], [ "Galaxy Macarons\nIntroduction: Galaxy Macarons\nThis lovely galaxy-themed macarons are a deliciously and stunning cookie you can make to take your friends to a galaxy far far away! They are also gluten free!!\nSupplies\nIngredients\nMacaron Shell:\n* 200g Sifted Almond meal (You will need more as you will sift out lumps)\n* 200g Pure Icing sugar (again may need slightly more) (It is important to use our icing sugar as using icing mixture can change the texture, this step also makes it gluten-free)\n* 80g Old egg whites, room temp (old egg whites refer to separated egg whites that have been cracked 3-5 days beforehand, covered in a cling wrapped container. this gives a better meringue)\n* 70g Fresh egg whites, room temp (cracked at the time)\n* 50ml water\n* 200g caster sugar\n* Edible food colouring (ideally gel or powdered, not liquid)\nFilling:\n* Use any filling that you like, such as a chocolate-based ganache or salted caramel, I have a separate video for the salted caramel but the ingredients are.\n* 250g caster sugar\n* 70ml water\n* 120ml thickened cream\n* 200g butter\n* 1-2 tsp vanilla bean paste\n* 1-2 tsp salt (I recommend trying this and adding more salt than you think, the shells are quite sweet, therefore having a salty filling complements the flavour really well)\nEquipment:\n* Small saucepans\n* candy thermometer\n* standing mixer with the whisk attachment and metal mixing bowl\n* oven\n* spatula/scraper\n* circle macaron print templates (I use one off of google images with XXXcm diameter circles)\n* Baking paper (NOT wax paper)\n* Piping bags 11mm round piping tip\n* toothpicks or skewers\n* Whisk\nStep 1: Make Your Filling\nI typically make the filling for my macarons the night before I make my macarons so that it can chill adequately.\nI have a separate full video for this on my channel but here are the pictures\nFor the salted caramel filling:\nPlace the 250g caster sugar and 70ml water in a small saucepot and put on high heat until it changes colour. For a sweeter caramel let it go yellow, for a slightly bitter caramel let it go darker (I recommend this as the darker more bitter caramel tastes lovey with the sweet macaron shell).\nOnce it changes colour, immediately whisk in the thickened cream (WARNING) This will steam quickly so be careful not to burn yourself. Then whilst mixing, add a candy thermometer and allow it to come to 108 degrees Celcius (226.4F). Immediately place the pot into cold water to stop the caramel from getting hotter.\nOnce cooled for a minute, add the vanilla bean paste, salt and whisk in half of the butter. (do this quickly so that the butter doesn't melt and separate from the caramel). Then add the rest of the butter and whisk. taste it and make sure it is to your liking.", "305" ], [ "I would make it slightly saltier than expected as the shells are quite sweet.\nYou can fill them with any delicious filling and I have some other options on my channel if you want to try different ones.\nSuch as raspberry and white chocolate ganache, vanilla white chocolate ganache etc.\nStep 2: Prepare Dry Ingredients\nIn a large metal, bowl sift/whisk together the almond meal and pure icing sugar.\nStep 3: Make the Meringue\nPrepare a standing mixer with a whisk attachment and metal mixing bowl. Ensure the bowl is properly clean with no water, dust or oils, it needs to be clean for a good meringue.\nIn a small saucepan heat 200g caster sugar and 50ml water to a boil. With a candy thermometer heat it up to 117.5 Degrees Celcius (243F). Once it reaches this temperature immediately plunge the pot into cold water to stop the sugar syrup from heating up further. Once the syrup stops making small bubbles it is ready to add to the egg whites.\nOn a medium-high speed quickly beat the egg whites for 30 seconds. Then slowly drizzle in the hot sugar syrup so that\n1. The egg whites don't cook\n2. the sugar syrup does not clump and cool on the bowl\nThen continue to beat the meringue on a high speed for about 8-10 minutes, or more until it creates stiff peaks and that the bowl is cool to the touch.\nStep 4:\nIn the metal bowl with the dry ingredients add the 70g new egg whites and mix them all together to form a paste. Then slowly fold in half of the meringue into the mixture.", "136" ], [ "Cookie House on a Cup (no Gingerbread!)\nIntroduction: Cookie House on a Cup (no Gingerbread!)\nIf you like the idea of a gingerbread house but you don’t really like the taste of gingerbread, then you’ve come to the right place! Today I'll teach you how to make a chocolate dough and turn it into tiny houses you can place over your hot cups of milk!\nSupplies\nFor the dough:\n* 1 egg\n* 50 gr bitter cocoa\n* 450 gr of white flour (if you don't want to use cocoa, use 500 gr instead)\n* 250 gr of butter\n* a pinch of salt\n* 150 gr of powdered sugar\n* a tablespoon of vanilla essence\nFor the glaze:\n* 250 powdered sugar\n* a few drops of lemon\n* 1 egg white\nFor the decorations (optional but suggested!):\n* M&Ms or smarties\n* sprinkles\n* chocolate chips\nStep 1: Making the Dough\nPour flour, cocoa and powdered sugar in a large bowl, mixing everything together. Then add the salt and mix again. Then, pour the egg and a spoonful of vanilla essence. Cut the butter in thin leaves and add it to the bowl, then start mixing again. You can use a planetary mixer or knead by hand.\nAt the end, you should get something like the last picture. The dough forms very rapidly and has a very nice smell.\nWrap the dough in cellophane and let it rest for one hour and a half in the fridge.\nStep 2: Working the Dough\nTake the dough out of the fridge and lay it between two sheets of greaseproof paper. Press it using a rolling pin until it is of uniform thickness (about 4-5 mm). You will get something that looks like the fourth photo.\nUsing the template shown in the last picture of this step, start cutting the dough (you will need two of each piece to make one cookie house), then lay it onto a pan.\nTurn on the oven on 170°C and place the pan in the fridge until the oven is hot, then bake the cookies for no more than 10 minutes! Be careful not to burn them!\nStep 3: Making the Glaze\nWhip the egg white (not too much) in a large bowl.", "305" ], [ "When it starts to become foamy, add the powdered sugar bit by bit, while continuing to whip. Add a few drops of lemon.\nWhen you achieve a good consistency, the glaze is ready. Put it in a sac à poche (with a small tip) before it hardens!\nStep 4: Decorating the Roofs\nPick the roof pieces and start decorating them in couples. Feel free to improvise and be creative!!!\nYou can use the glaze as a decoration or as a glue for sprinkles or M&Ms, as shown in the pictures.\nStep 5: Decorating Walls\nIt is time to decorate the walls and faces of the tiny houses! Try drawing a few windows like I did, or outline the faces.\nStep 6: Assembling the Houses\nPut quite a bit of glaze on both sides of one face piece. Take a side piece and place it against the face piece. Repeat the same with another face and another side, until you complete the four walls.\nTo add the roof, don't forget to first put some glaze on the top side of the house! You may keep decorating the faces and roof until you're satisfied. For example, you can easily create the effect of snow that is falling from the roof!\nStep 7: Done!\nThe tiny cookie houses are done! Make as many as you want and try to decorate them in different ways. I can assure you it is a lot of fun!!!\nI hope you liked this little project, thank you for you attention :)\nBye!!", "706" ], [ "Easy Salted Caramel & Peanut Butter, Chocolate Dipped Banana Popsicles\nIntroduction: Easy Salted Caramel & Peanut Butter, Chocolate Dipped Banana Popsicles\nI've always liked frozen bananas dipped in chocolate, but I was looking for a way to make them even better.\nFrozen bananas dipped in chocolate taste pretty good. Frozen Bananas filled with salted caramel and peanut butter and dipped in chocolate taste amazing!\nThese popsicles are easy to make and, while there is a bit of cooling and freezing time involved, they come together fairly quickly.\nSupplies\nYou will need:\nBananas\nPopsicle Sticks (2 per banana)\nDark chocolate ( how much you need will depend on the container you use for dipping)\nPeanut butter (about a teaspoon per banana)\nFor the Salted Caramel Sauce:\nThe recipe makes much more than you need for a few bananas but there's no such thing as too much salted caramel sauce! Left over sauce can be stored in a sealed container in the fridge.\n1/2 cup Sugar\n1/4 cup Water\n1/4 cup Cream\n28g Butter (cut into cubes)\n1/4 teaspoon Salt\n1/4 teaspoon vanilla extract\nTools and Utensils:\nFreezer safe container\nMicrowave safe / heat proof bowls\nSmall saucepan\nWhisk\nKnife\nMeasuring spoons\nHeat proof spatula\nContainer for dipping the bananas (I used a small glass)\nPastry brush\nKitchen scale\nStep 1: Making the Salted Caramel Sauce\nPlace the Sugar and water in a small saucepan over medium heat and slowly stir until the sugar is melted. Do not stir the sugar after this.\nIf sugar crystals form on the sides of the saucepan, brush them off with a pastry brush dipped in water. Swirl the pot carefully to mix the sugar if it's not changing colour evenly.\nBring the sugar to a boil and heat until it's a golden brown/amber/caramel colour. A darker colour will result in a more bitter tasting caramel. If you accidentally take it too far, try adding more salt to balance out the bitter taste. I've saved very dark caramel this way.\nRemove the sugar from the heat, add the cubed butter and stir with a whisk to combine.\nAdd the cream, vanilla extract and salt and stir with a whisk.\nTransfer the sauce to a heat proof bowl and leave it to cool to room temperature.\nStep 2: Cut and Scoop the Bananas\nWhen the caramel sauce has cooled to room temperature, cut each banana in half crosswise.\nThen cut each half in half, lengthwise. Make sure you keep the matching quarters together.\nUsing a small spoon ( I used a quarter teaspoon measuring spoon) scoop out about half a teaspoon of the banana, leaving the top and bottom intact.\nStep 3: Assembling the Popsicles\nMelt the peanut butter in a microwave safe bowl 20 to 30 seconds at a time. I had about a tablespoon of peanut butter and it took about a minute to melt.", "604" ], [ "Put the melted peanut butter in a plastic bag or piping bag and cut off a small piece of the tip.\nPipe a line of peanut butter in each banana quarter. Alternatively you could spread the peanut butter in the banana with a knife, but the bananas are quite slippery, so you might not get even peanut butter distribution this way.\nFill each scooped out banana quarter with salted caramel. In my case it took about a 1/2 teaspoon per quarter.\nPlace a popsicle stick on one of the banana quarters and then place the matching quarter on top. My bananas were too short for my popsicle sticks, so I cut about a third off each popsicle stick.\nThe caramel shouldn't ooze out of the sides, but if it does or if you're worried that it will, you can wrap them in tin foil or cling wrap before you freeze them.\nPlace the filled and assembled bananas in a freezer safe container and freeze them until they're solid. I put them in the freezer for about 2 hours.\nStep 4: Prepare the Chocolate for Dipping\nHow much chocolate you need will depend on the container you're using for dipping. I used a small glass that was just big enough to dip and cover half a banana. Preferably the container should be microwave proof, in case you need to reheat the chocolate.\nTo start I filled the glass with chocolate pieces to measure how much I would need. A glass and a half of chocolate pieces melted down to about a glass. I ended up using 180g of chocolate.\nI used 1.", "136" ], [ "Mango Falooda Ice Cream Sundae\nIntroduction: Mango Falooda Ice Cream Sundae\nThe dessert I would like to share came straight out of my imagination. Having drunk falooda (an Indian dessert drink) many times before, I decided that I wanted to shake up this common dessert and make not only a mango version but also a solid version of it. The dish presented here is not only refreshing, but tart, sweet, and delicious. This is a perfect summer treat and I hope you get to try it!\nSupplies\nFor Tukmeria Seeds:\n1 tsp Tukmeria (Sweet Basil) Seeds\n3 tbsp Water\nFor Mango Jelly (Optional):\n1/3 cup Mango Pulp\n2/3 cup Water\n1 tsp Agar Agar Powder\nFor Assembly:\n1-2 cups Vanilla Ice Cream\n3/4 cup Mango Pulp\n3 tbsp Tukmeria Seeds\n1/3 cup Mango Jelly\nFor Topping:\nPinch of Cardamom\n2 tbsp Crushed Pistachios\nStep 1: Hydrate Tukmeria Seeds\nTukmeria, or sweet basil seeds can be found at any Indian store near you. Not only do they add a great texture to the dish, but tukmeria seeds are extremely healthy. Tukmeria seeds are packed with minerals and fiber, and can be compared to chia seeds in terms of nutrition.\nTo use this versatile ingredient, just place one teaspoon of dry seeds into a bowl with 3 tablespoons of water and mix it around a bit. After less than 5 minutes, the seeds should be hydrated and burst in your mouth once you eat them.\nStep 2: Make Mango Jelly\nThis agar agar jelly is incredibly easy to make and yields a very unique-textured jelly that goes well with the sundae. I decided to replace an original ingredient of the falooda, vermicelli, with this jelly because I thought it would give more texture to the sundae and be an original touch to the dish. Nevertheless, this part of the sundae is completely optional and just adds another texture to the bowl.\nTo make this jelly, first place 1 tsp of agar agar, 1/3 cup of mango pulp, and 2/3 cup of water in a bowl and mix well.", "567" ], [ "After mixing, add this emulsion to a pot and heat on medium heat until it boils. This is to activate the agar agar. Immediately after boiling, pour the emulsion into a bowl or mold and place this in the fridge until it hardens and cools. This is normally 20-30 minutes.\nAfter hardening, unmold your agar agar jelly and cut it into small strips. Then, set it aside for assembly. I used about 1/3 of this amount in my one sundae.\nStep 3: Assemble Ice Cream\nBefore assembling the sundae, you must get all of your ingredients together (I learned this the hard way). First, crush two or three cardamom seeds (not pods). Then, crush two to three tablespoons of pistachios to add a crunch to the sundae.\nAfter prepping all of the toppings, scoop the ice cream (one to two cups) into a bowl. Then, add the mango pulp as the main sauce topping. Next, sprinkle the tukmeria seeds, some mango jelly (to your taste), the pistachios, and cardamom on the top.\nI hope you enjoy this modern and refreshing twist on a traditional and beloved dish!", "567" ], [ "Parmesan-Olive Savory Cookie\nIntroduction: Parmesan-Olive Savory Cookie\nSavory cookies are great with beer, replace store-bought snacks and can be customised to suit your allergies and tastes. They are not crackers, more like crispy cookies, but not thin enough to snap (unless you want them to snap, then roll them thinner). Simple to make, even without a food processor.\nSupplies\n90g grated parmesan\n180g all purpose flour\n120g cold, cubed butter\n3TBS herbs (fresh or dry, rosemary works best)\n1tsp sweet or hot paprika\n1TBS sugar\n1/2 tsp salt\n2 garlic cloves, minced\n75g black, pitted olives\negg and a splash of milk for glazing\nfood brush, additional p\nStep 1: Olives\nDrain olives, dry them using kitchen towels and chop them roughly. Once chopped, blot them as much as possible, we don't want any additional liquid in the dough.\nDivide into 60 and 15g. Reserve 15g for decoration.\nStep 2: Mix Dry Ingredients\nCombine flour, cheese, spices, herbs, sugar and salt in a food processor. Pulse until combined.\nAlternatively, you can whisk dry ingredients in a large bowl.\nStep 3: Add Butter\nAdd butter and pulse until mixture resembles crumbs.\nAlternatively, you can rub butter into flour with your fingertips.", "851" ], [ "Do it quickly and work while butter is still cold.\nStep 4: Olives and Garlic\nLastly, add 60g chopped olives and minced garlic. Pulse until combined. Your dough won't be crumbly, parmesan makes it pretty soft, so you won't have to add any liquids. Wrap the dough in a cling film and chill in the fridge for 4 hours.\nStep 5: Rolling the Dough and Baking\nRoll the dough to about 5mm thickness, sprinkle with remaining olives and push them into the dough with a rolling pin. You want the dough to be 3-4mm thick in the end. Cut into shapes, I cut mine with a knife, not a cookie cutter, to save the dough and time. Once cut, brush with an egg wash (whisked egg and a splash of milk), separate the cookies and put in the oven.\nBake at 180°C (350°F) for 12-15 min.\nStep 6: Parmesan Option\nYou can skip topping the dough with olives, and instead sprinkle it with parmesan for another variation of the same dough.\nStep 7: Finished", "195" ], [ "Margherita Pizza-Style Chicken Sandwich\nIntroduction: Margherita Pizza-Style Chicken Sandwich\nStory time! The Margherita pizza was made by <PERSON> a pizza garnished with tomatoes, cheese and basil. To represent the colors of Italy's flag and honor the Queen consort of Italy, <PERSON>.\nThis sandwich is based on this pizza, but we will be adding chicken just to make it more filling.\nYou will need the following:\nLoaf of bread (16 oz) - I'm using Ciabatta bread, as it's crispiness is similar to that of a pizza crust.\nMozzarella cheese (8 oz) - You can also use Goat cheese as a substitute.\nCan of diced tomatoes (14.5 oz)\nGarlic cloves (3 cloves) - 2 will be used for the sauce, 1 for garlic butter\nRoma Tomatoes (2 ea.) - You can use other types, but it's the one typically I've seen in Margherita pizza.\nButtermilk (~8 oz)- This will be used to prep the chicken.\nChicken Breast (2 ea.) - This will be cut horizontally and left in the buttermilk the day beforehand.\nFresh Basil Leaves (~10 ea)\nOlive Oil (3 tbsp)\nSalt\nSupplies\n* Blender\n* Oven / large skillet / large toaster\n* Baking pan (if using oven)\n* Bread Knife\n* Basting brush\n* Skillet (If not using oven/toaster you will need another skillet or just clean it after step 1)\nStep 1: Prep-Work\nChicken:\nSlice the chicken length wise (horizontally).\nPlace in a bowl and cover with buttermilk, for 1 hour. I usually do this the day before, that way they're really tender.\nTomato:\nYou can cut them in slices. I decided to cut them into 1/8\", since it looks nicer in the picture.\nCheese:\nCut the cheese in 1/4\" slices or buy one that is already sliced. (Especially if it's at the same price!)\nGarlic:\nPress (or dice, if no presser) 3 garlic cloves.", "265" ], [ "Leave one diced/pressed clove to the side for the garlic butter.\nGarlic Butter:\nMelt 1/2 tbsp of butter, with 1 pressed garlic and 1/8 tsp of the basil. This will be used in the final step to brush the top of the bread and bottom of the baking pan. This will give some added flavor and crunch to the bread after taken out of the oven.\nHeat:\nPre-heat the oven/toaster press to 350F.\nStep 2: Chicken\nRemove the chicken from the buttermilk and pat dry.\nWe're going very simple with the chicken, just seasoning it with 1/2 tsp of salt and 1/4 tsp of black pepper.\nOnce the skillet is hot, add 1 tbsp of butter and 1 tbsp of oil. Wait for the butter to completely melt before adding the chicken.\nCook the chicken on medium low, once it get's a little color, it's ready.\nStep 3: Sauce\nIn the blender, add the pressed garlic, can of tomato, 1/8 tsp of basil and 1 tbsp of sugar. Blend until smooth.\nTaste the sauce, if it's too acidic, add more sugar until desired taste.\nStep 4: Bread\nCut both ends of the loaf, then slice the loaf like pictured.\nStep 5: Build Your Sandwich\nSpread the sauce on the bottom slice of the loaf.\nStart with placing the chicken, tomato, mozzarella, basil and top slice.\nThe only reason I specify the order here, is to keep the Italian flag order.\nYou can add them any way you wish, I confess.... mine was not the most practical.\nFinish with spreading the garlic butter, with the baster, on the top slice and coating the baking sheet/ toaster / skillet.\nStep 6: Add Some Heat!\nPlace the sandwich in the oven or toaster for 10 mins at 350F, or until the cheese starts to melt.\nIf not using an oven/toaster place the sandwhich on the skillet on medium heat 5 mins on each side, or until the cheese melts.\nRemove from heat, cut in desired sizes, and enjoy!!", "808" ] ]

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[ [ "Leaked Documents Show That Ethiopia’s Ruling Elites Are Hiring Social Media Trolls (And Watching Porn) · Global Voices\nEPRDF rally in Addis Ababa in 2010. Photo by <PERSON>/BBC World Service via Flickr (CC BY-NC 2.0)\nOver the past two months, a series of leaked documents from Ethiopia’s powerful political elites have been circulating online.\nAmong other revelations, the leaks show that the Ethiopian government has been paying online commenters to influence social media conversations in the ruling party's favor. The documents include hundreds of pages of chat logs and email correspondence of Ethiopia’s top government officials, multiple government planning documents and top-secret meeting records.\nThe leaks have come at what may be a turning point in Ethiopia's recent political crisis. Since mid-2015, thousands across Ethiopia rose up, demanding more political freedoms and social equality and a stop to government land grabs in the Oromia region, which represents Ethiopia's largest ethnic group. The government response was brutal: Hundreds have been killed, thousands have been arrested, and critical voices — both on and offline — have been systematically silenced.\nAmong the recent leaks, which began to circulate on Facebook in November 2017, one of the most revealing documents is a list of individuals who appear to have been paid to promote the ruling coalition on social media. The list shows the names of the so-called “social media commentators” along with their job titles and a precise amount of money that they apparently received for their online postings. Most of the people listed are government employees.\nThe list corroborates previous evidence that the Ethiopian government has been hiring online commenters to promote its agenda and harass its opponents.\nOnline communities in Ethiopia have been calling these paid commenters “cocas”, a colloquialism in Amharic (the most widely spoken language in the country) that can be translated as “contemptible cadres.” In Amharic, this term typically refers to people who sell themselves for easy money. But in this case, most of the commenters listed in the leaked directory are already on the government payroll.\nWho is responsible for the leaks?\nThe origin of the leaks has been rumored and contested at several levels. The documents were originally sent to diaspora activists from the at least two Facebook accounts, both of which belong to government employees, in November 2017.\nThe first known leak, of the “coca” list, came from the Facebook account of <PERSON>, an employee of the communications affairs office of the Tigray state.", "960" ], [ "<PERSON> first denied sending the documents, claiming his account was hacked. But he then backtracked on this claim. It is now rumored that he has been dismissed from his job.\nSoon after the initial leak, more documents began arriving in the inboxes of diaspora activists, this time coming from the Facebook account of the Director of the Federal Communications Affairs office, <PERSON>. Shortly thereafter, <PERSON> began to publicly shame those government officials who are implicated in the leaks. On January 18, he denigrated Deputy PM <PERSON> in a public Facebook post.\nIt is unclear whether <PERSON> sent the documents himself have been hacked.\nSocial media ‘cocas’ push pro-government discourse\nThe revelations of political and state officials paying “cocas” to promote the ruling party agenda online correspond with a recent rise in polarization and hate speech on social media, alongside increased online persecution of independent journalists.\nThe leaked “coca” list reveals that at least thirteen commentators were each paid at least USD $300 (a large sum in Ethiopia, where average GDP per capita was USD $660 in 2016) for blog posts or Facebook messages that they wrote at the behest of the ruling coalition.\nList of paid internet commentators. Image widely circulating on Facebook\nAmong individuals named on the list are <PERSON> and <PERSON>, publishers of two Ethiopian internet news site HornAffairs and Awaramba Times respectively. The two journalists have long been accused of cheer-leading a pro-government information campaign especially during a heightened political tension.\nIn recent years, independent Ethiopian journalists reporting on government affairs, corruption and human rights have been arrested or exiled en masse. The resulting gap in news coverage has thus been filled by opposition activists and protesters who often work with diaspora-based media outlets to draw global attention to the brutal military crackdown on protesters that has killed more than 1200 people and has led to several mass arrests since mid-2015.\nOn the heels of the list came a separate leak of what appears to be a proposal to counter opposition groups using social media platforms. The Amharic-language document from the office of Ethiopia’s longtime governing coalition, the Ethiopian People’s Revolutionary Democratic Front’s (EPRDF), enumerates solutions and strategies to curtail the influence of online diaspora-based activists.", "960" ], [ "Months after pledge to open internet, Ethiopia disrupts connectivity amidst communal violence, tension · Global Voices\nEthiopian Prime Minister <PERSON> sits with Minister of Defense <PERSON>, November 24, 2017. Photo by <PERSON> via Wikimedia Commons CC BY 4.0.\nThis story is the second in a two-part series on online disinformation, shutdowns, and rising political and ethnic tensions in Ethiopia. You can read the first part here.\nOn June 18 of last year, in his second parliamentary address, Ethiopia’s reformist Prime Minister <PERSON> announced his government would no longer block online publications. Within a day, his then-chief of staff, <PERSON>, followed up in a tweet acknowledging the unblocking of more than 250 largely diaspora-based, pro-opposition websites and blogs.\nAt that time, the move was celebrated as a major step toward internet freedom in a country where the ruling regime, the Ethiopian People’s Revolutionary Front, (EPRDF) had for years controlled the flow of information.\nAs the political environment relaxed, comedians, journalists, bloggers and opposition activists voiced thoughts and criticisms that had been bottled up for decades. Ethiopia's embrace of civil liberties, however, has deflated as political rifts resurfaced between non-ruling elites of Ethiopia's two main ethnic groups: the Amharas and the Oromos. With ethnic and political tensions between the two groups manifesting online in the form of hate speech and disinformation, the government responded — on a number of occasions — by imposing restrictions on access to networks and social media platforms.\nPrior to the political reforms introduced by PM <PERSON>, disruptions of internet connectivity, cell phone services, or social media occurred for reasons ranging from curbing mass protest demonstrations to preventing cheating during examinations.\nThis time around, although politics is at the center of internet shutdowns, the dynamics are more complicated than they had been prior to the start of the political reforms.\nDeadly communal violence and a shutdown\nView over Churchill Road in Addis Ababa, Ethiopia. Photo by <PERSON> via Wikipedia.\nIn September 2018, just two months after the government's pledge to open up the internet, deadly communal violence erupted in Burayou, a town located in outskirts of Ethiopia’s capital, Addis Ababa, following the homecoming of two exiled political groups in competition with each other: Patriotic Ginbot 7 and Oromo Liberation Front (OLF).", "960" ], [ "In response, the government resorted to large-scale, deliberate disruptions of internet connectivity, cell phone service, and social media.\nAuthorities believe social media — particularly Facebook — played a central role in stoking communal tension, and they are not alone. The fact that communal tension hit a boiling point in Burayou just as social media made inroads in the area drove many to speculate that the violence was stoked by messages shared on social media.\nHowever, a closer look at the violence reveals there are other deep-rooted factors, too.\nIn recent years, communal tensions have been a fact of life in Ethiopia. Among the many ethnic tensions that dominate Ethiopian politics, perhaps none have been as caustic as the issue of Addis Ababa, Ethiopia's capital city, around which conflict and tension have been building for years.\nAddis Ababa, geographically located in Oromia, is predominantly Amharic-speaking and continues to expand into Oromia, Ethiopia’s largest administrative region.\nIn reaction to the persistent expansion of Addis Ababa into Oromia until 2014, a protest movement started in 2015. After years of struggle, these protests slowed down the expansion of the sprawling city.\nBut the protest movement’s initial claim of halting the unrestrained expansion of Addis Ababa at the expense of Oromo farmers eventually evolved into nationalistic claims defined in terms of ethnic ownership of the city.\nIn the days leading up to the communal violence in Burayou, the supporters of the two rival political blocks spread an “us-versus-them” philosophy through various means of communication. They hoisted and waved flags and banners of the competing groups in the streets of Addis Ababa. There were even physical confrontations and a few violent clashes in the capital.\nWhile many factors contributed to the communal violence in Burayou, such as ethnic and linguistic divides and a lack of faith in the government, the internet was singled out to blame as the main reason.\nThis was the second time (as per available information) that internet services were suspended after authorities promised the government would no longer block the internet nor restrict access to specific apps or websites.\nAuthorities also shut down the internet on grounds of security or public order measure when ethnic violence broke out in eastern Ethiopia in August 2018. Authorities only reversed their decision after a short-lived positive turn — following the political reforms that began in April 2018 under <PERSON>.", "960" ], [ "Ethiopian Protester Sentenced to Six Years Behind Bars for Facebook Posts · Global Voices\n<PERSON>. Photo shared on Twitter by <PERSON> @eyasped\nThis week in Ethiopia, two prominent human rights advocates and critics of the ruling government were given long-term prison sentences for “incitement” on Facebook.\nOn May 25, <PERSON> was sentenced to six years and three months in prison for “inciting” antigovernment protests in nine Facebook updates.\nBreaking: #Ethiopia fed court sentenced former oppos'n Blue party PR head <PERSON> six years & 3 months in jail for terrorism pic.twitter.com/LQKqVh1wne\n— Addis Standard (@addisstandard) May 25, 2017\nThe 30-year-old activist has been an outspoken opponent of government’s violent response to the popular protest movement that has challenged Ethiopia’s ruling party and government since 2015. <PERSON> had previously served as a press officer for the leading opposition Blue Party before resigning in 2015.\n<PERSON> was jailed for nine Facebook posts that expressed solidarity with the protesters, called for open dialogue and pleaded for an end to the violence.\nThe day before his sentencing, <PERSON>’s former colleague <PERSON>, was found guilty of inciting violence for a private message he sent to colleagues through his Facebook messenger app. The former editor-in-chief of opposition newspaper Negere Ethiopia, <PERSON> was sentenced to one year and six months in prison:\nBreaking- #Ethiopia court sentenced <PERSON> editor-in-chief of Negere Ethiopia NP, to 1yr & half in jail, time he already served pic.twitter.com/Pzp3dXCK6A\n— Addis Standard (@addisstandard) May 26, 2017\nThe Facebook message that allegedly contained inciting content made reference to a heckling incident targeting late Prime Minister <PERSON> at a 2012 symposium in Washington, D.C. In the message <PERSON> wrote, “since the political space in Ethiopia is closed heckling Ethiopian authorities on public events [sic] should be a standard practice.”\nThese cases are among many others of less well-known citizens who have spoken out against the regime's violent targeting of protesters demanding protections for land rights and other fundamental freedoms. According to Human Rights Watch, at least 800 people have died at the hands of Ethiopian police, and thousands of political opponents have been imprisoned and tortured during the protests.\nFacebook is a key tool for activists — and law enforcement\nFacebook, along with other social media platforms, has had a central role in interactions between authorities and protesters. Ethiopian authorities have blamed social media for waves of protests that began in April 2014 and have continued ever since. In October 2016, Facebook was blocked in Ethiopia as part of the government's state of emergency. But activists — and likely Ethiopian law enforcement — have continued to use the platform via VPN.\nAlthough it is difficult to know the precise number of detainees, dozens of arrests appear to have been triggered by a person posting, liking or sharing a post on Facebook.", "799" ], [ "Others have been arrested for communicating with diaspora-based activists through Facebook messages.\nThese cases have been compounded by an increasingly common practice in which Ethiopian authorities demand that detainees divulge their Facebook logins and passwords. In some cases, people have been arrested before being charged, forced to hand over their Facebook credentials, and then charged based on what authorities find in their accounts.\nPolice will arrest activists, force them to hand over their Facebook credentials, and then charge them based on what they find in their private message logs.\n<PERSON> was charged with “inciting violence” after he was forced to give his username and password of his Facebook page. The private chat texts on his Facebook message were presented as evidence in his charge sheet.\nWhatever the court decides, friends and family members of <PERSON> and <PERSON> wanted the case to end. So, they would learn their fate, to take their fight to the next stage. But their case, like so many others court cases, had been delayed.\nIn Ethiopia, it is not uncommon for court cases involving bloggers journalists and politicians to take longer than other cases. This causes exhaustion for defendants and brings pain to their loved ones.\n<PERSON> and <PERSON> each spent 18 months in jail before they learned their fate. They were brought before the court at least a dozen times. Their private Facebook accounts were laid bare by authorities. Judges failed to appear in court, and police failed to bring defendants to court on their trial days, causing their cases to drag on for 18 months.\nFacebook has been a critical platform for Ethiopian activists and rights advocates working to document and communicate human rights violations.", "409" ], [ "Ethiopia Imposes Nationwide Internet Blackout · Global Voices\nAn October 2016 protest in London by Oromo people over killings and human rights abuses at the hands of the Ethiopia government. Photo by Flickr user <PERSON>. CC BY 2.0\nOn May 30 at 3pm local time, Ethiopians found themselves unable to access the Internet. The blackout appears to be country-wide.\nIt appears that Ethiopian authorities imposed the nationwide Internet blackout in order to prevent “leaking of exam questions on Facebook” ahead of secondary school exams set to be administered over the next two weeks.\n24 hours after the total Internet blackout, Ethiopia still refuses to say why it shut down. Via @AFP pic.twitter.com/ZzJcX6Vqe8\n— <PERSON> (@zelalemkibret) May 31, 2017\nTwenty-four hours after the blackout, Deputy Communication Minister of Ethiopia <PERSON> told AFP that mobile data also had been deactivated.\nFinally, the Ethiopian government announced that the internet blackout will continue until June 8, 2017, reasoned by fear of ‘exam leaking’.\n— <PERSON> (@zelalemkibret) June 1, 2017\nLast year, the government was forced to postpone the national university entrance exam after the initial session was marred by a leak spread on Facebook.", "960" ], [ "Activists in the diaspora leaked questions on Facebook ahead of the exam in early June in 2016 after the government refused to re-schedule the exam for students who missed an entire semester of classes due to protests.\nBut the current blackout is different from previous mobile Internet and social media shutdowns that have been imposed in an effort to prevent exam leaking. This blackout is broader in scope and scale, effectively eliminating Ethiopia from the map of the global Internet.\nThis is especially easy for the Ethiopian government to do, since all Internet and phone service in the country is provided through through a single government-owned Internet service provider, Ethio Telecom. The blackout thus leaves businesses, banks, Internet cafes in Addis Ababa and social media pages of government media cut off from the rest of the world, making it harder for them to do their day-to-day work.\n‘Cos of the blackout: Banks are out of service, Bulk SMS services are not available, GPS services are not accessible …\n— <PERSON> (@zelalemkibret) May 31, 2017\nThe gravity of this move begs the question: Are authorities really just trying to prevent students from cheating on exams, or is there more to it? Indeed, this is just one among various reasons that Ethiopian authorities have used to justify censorship and shutdowns in recent years.\nEthiopia has blocked the Internet on three occasions since huge anti-government protests exploded in November 2015. Mobile and landline phone networks are also crippled in much of the country’s two biggest regions, Oromia and Amhara, where anti-government protesters have become common over the last two years.\nWhen Ethiopian authorities declared a state of emergency in October 2016 they officially blocked access to Facebook, Twitter and popular messaging apps such as Viber and IMO. Since Internet speeds are already incredibly slow, data-heavy video platforms such as YouTube have been rendered inaccessible even though they are not officially blocked.\nJust two weeks ago, activists inside the country reported that they were finally able to access Facebook freely, after many months of using VPNs and other circumvention tools to login to the social network. But with the country now in total blackout, they are now even more isolated from the rest of the world, and even from each other, than before.", "960" ], [ "How Ethiopia’s ruling coalition created a playbook for disinformation · Global Voices\nA young man in Ethiopia works at a desktop computer. Photo taken on November 28, 2011, via UNICEF on Flickr.\nThis story is the first in a two-part series on online disinformation and politics in Ethiopia. You can read the second part here.\nA deep split that exists within Ethiopia's ruling coalition — the Ethiopian People's Revolutionary Democratic Front (the EPRDF) —was made evident over the last few weeks when a Facebook row broke out between two major political party members who disagreed on the historical accounts of Ethiopia as a modern state.\nThe row revealed how party members within the EPRDF use social media — through posts and memes — to manipulate public opinion and spread misinformation and incendiary content.\nThe EPRDF is a coalition of four ethnically-based parties. Members from these four parties: Amhara Democratic Party (ADP), Oromo Democratic Party (ODP), Southern Ethiopian People's Democratic Movement (SEPDM) and Tigrayan People's Liberation Front (TPLF), currently make up Ethiopia’s top leadership.\nUntil 2018, the TPLF was the dominant party in the coalition, holding absolute power for over 25 years. ADP and ODP have joined forces to put an end to the supremacy of TPLF, yet its members continue their rivalry, with infighting that usually goes under the radar.", "960" ], [ "Tensions have risen steadily since April 2018, when <PERSON> of the ODP was sworn in as prime minister.\nOn October 4, ODP-ADP infighting burst out into the open when members and supporters of ADP and ODP started to bicker over a remark made by the vice president of Oromia Regional State, <PERSON>, in Addis Ababa, on the eve of Irreecha (an annual celebration marking the beginning of spring).\nIn his remarks, <PERSON> hailed the Irreecha celebration in Addis Ababa, which he described as the very place where Oromos were defeated and humiliated by the old regime:\nThe Oromo people were defeated right here, our humiliation started right here.\nIn his speech, <PERSON> struck a triumphant tone and marked the day's celebration in Addis as a turning point in the struggle of the Oromo people. He used the Amharic word neftegna (“riflemen” in English) to refer to the ruling class established in the wake of Emperor <PERSON>'s conquest in southern Ethiopia in the late 19th century.\nToday, many ethnic Amahras view Emperor <PERSON> as a symbol of triumph and defiance of European colonialism, while many Oromos consider him the root cause of their social and cultural subjugation.\n<PERSON>’s use of the term neftegna prompted backlash given that it is often used to refer to members of Emperor <PERSON>’s army after TPLF came to power in 1991.\nThe following day, in a Facebook post, <PERSON>, a top ADP member, accused <PERSON> of employing coded language to intimidate the Amhara people and, in turn, drew the ire of <PERSON>, a top ODP member, who saw <PERSON>’s accusation as a denial of the historical social and cultural subjugation the Oromos suffered.\nDueling statements made by <PERSON> and <PERSON> exemplify the differences in interpretations of Ethiopia’s historical events among the country’s elites. While the ADP considers the formation of a modern Ethiopian state as faultless and virtuous, the ODP understands its formation as a process that led to the subjugation and humiliation of Oromos at the hands of Ethiopian emperors.\n<PERSON> and <PERSON> have several things in common: They are young politicians who aspire to long political careers and whose parties, the ADP and ODP, — have banded together to bring down the supremacy of TPLF in April 2018.\nTheir row on Facebook bolstered their popularity and ushered an intense wave of political polarization freighted with misinformation.\nA screenshot of <PERSON>'s post on Facebook. Screenshot taken on October 16.\nTheir spat led to an outpouring of support on their respective Facebook pages, feverishly gathering up reactions, comments, and shares.\nA screenshot of <PERSON>'s Facebook post. Screenshot taken on October 16.\n<PERSON>’s page, with 56,432 followers, racked up about 5,000 shares and generated 3,500 comments, while <PERSON>’s page, with 45,565 followers, mustered about 3,000 shares and 2,500 comments — just within 24 hours of their posts.", "960" ], [ "Ethiopia’s Anti-Graft Campaign is Rife with Ethnic Tensions · Global Voices\nLocals refer to this building on the outskirts of Addis Ababa as “Steal Display.” They allege a mid-level government official openly looted public funds to build it. Photo sourced from <PERSON> blog.\nLast week, the Ethiopian government announced the arrests of ‘top officials’ accused of ‘misdirecting public funds’ to ‘maximize their private interests,’ employing favored euphemisms for corruption. The names of those arrested were held back until later in the week, however, with one writer on Facebook comparing the delay to a suspenseful drama series.\nUltimately, when a state-backed media website revealed the list of ‘top officials’ as 48 junior government bureaucrats, middlemen and investors, the news was less groundbreaking.\nOn Twitter, some complained that the government had overhyped the corruption story with ‘breaking news,’ noting the list of names released did not include a single top official.\nRuling party affiliated FanaBC reported detention of top officials who are suspected of corruption in #Ethiopia. Names aren't mentioned yet.\n— <PERSON> (@befeqe) July 25, 2017\nThe highest official called out so far is the former chief executive officer of Capital Roads Authority (Addis Ababa), a position that is nowhere near as powerful as claimed by government media.\nEthiopian Prime Minister <PERSON> launched a highly publicized campaign targeting government and state-owned company officials suspected of corruption. The campaign has led to the arrest and prosecution of hundreds of officials since January 2017.\nEven though the government regularly publicizes these kinds of corruption cases, it has not convinced Ethiopian citizens of its sincere interest in ‘cleaning house.’ According to Transparency International’s most recent Corruption Perceptions Index, Ethiopia is listed among countries whose public perceive the pervasiveness of rampant corruption in the public sector.\nOnline public cynicism regarding the ongoing anti-corruption campaign shares an overwhelming opinion summarized in <PERSON> blog:\nThere are practically no non-corrupt officials. Those arrested are corrupt, and most of the top officials who are leading the anti-corruption campaigns are also corrupt. There’s no difference between the corrupt and non-corrupt officials.", "960" ], [ "The only difference is that those who were arrested have not secured the loyalty of senior functionaries that can shelter them.\nOne factor fueling public cynicism is that infrastructure projects are often delayed or stagnate while contractors, subcontractors, and government cronies grow wealthier.\nArresting and prosecuting junior officials won’t change anything said <PERSON> in a post on his widely circulated blog.\nAnother writer on Facebook recently pleaded with the Ethiopian government to stop the anti-graft campaign. He sarcastically warned that if authorities do not stop, Ethiopia will soon become a stateless society. In his view, Ethiopian corruption has permeated so many fields that it is a feature of the Ethiopian condition.\nThe pressure to launch an ongoing anti-graft campaign was driven by protests that began in Oromia, Ethiopia’s largest region, over alleged expropriation of farmlands around Addis Ababa. <PERSON> wrote:\n“Who said that the Oromo demands are about arresting a select few corrupt and depraved officials or their (questionable, because nepotistic) connections? The indictment of the # OromoRevolution is directed at the system, not some junior officials, or their wives, whom the system is disposing of as collateral damage in its combat with the Oromos.”\nCorruption and Ethnic Politics Intersect\nSome observers believe Ethiopia’s crackdown on a few mid-level officials is politically motivated. Many have complained about the discriminatory application of Ethiopia’s anti-corruption laws.\nSuch kind of charges have been used to settle within-party division in the past.\n— <PERSON> (@befeqe) July 25, 2017\nEthiopia is a one-party state in which the ruling Ethiopian People's Revolutionary Democratic Front (EPRDF) monopolizes power. The EPRDF, however, is a coalition of four ethnic-based parties. The four parties purport to represent particular ethnic groups, but they share the same ideology, political association, and policy preferences.\nAuthorities from these four parties – Amhara National Democratic Movement (ANDM), Oromo People's Democratic Organization (OPDO), Southern Ethiopian People's Democratic Movement (SEPDM) and Tigrayan People's Liberation Front (TPLF) – are currently Ethiopia’s top leaders. However, the TPLF is the core of the EPRDF, holding absolute power over the last quarter of a century.", "960" ], [ "For Opponents, WHO Director General Nominee <PERSON> Represents Ethiopia’s Repressive Government · Global Voices\nDr. <PERSON>, Minister of Health, Ethiopia, speaking at the London Summit on Family Planning in 2012. Photo by Flickr user UK DFID. CC BY-SA 2.0\nSome Ethiopians are fiercely campaigning against <PERSON>, Ethiopia’s candidate to replace <PERSON> <PERSON>, as director general of World Health Organization, just a few weeks before member states are set to vote on the final three candidates.\n<PERSON>, a former Ethiopian foreign and health minister, along with Pakistan’s <PERSON> and the UK’s <PERSON> are the three director-general nominees who made the cut from a larger pool of candidates in January.\n<PERSON>, who is running a well-funded campaign, is considered as a prime contender in the race. His candidacy was endorsed by the African Union, and just last week he picked up an endorsement of <PERSON>, the UK’s former international development secretary.\nHowever, he is facing unrelenting opposition from his own citizens.\nEthiopians who feel marginalized by their country's government are campaigning hard against him online, arguing he should not be elected because he represents the interests of Ethiopia’s autocratic ruling elites and not the people.\nThe irony is beyond tragic. The person who is responsible for the crimes against humanity in #Ethiopia is running for #WHODG! #NoTedros4WHO\n— <PERSON>@kiruskyy) April 28, 2017\nThey have set up online petition pages against <PERSON> and produced a documentary film detailing what they consider to be his failures and his alleged mismanagement of funds while he was Ethiopia’s health minister.\n<PERSON> presided and participated in the biggest financial corruption scandal of misusing Global fund in Ethiopia. #NoTedros4WHO\n— Amsalu (@AmsaluKassaw) April 28, 2017\nThey have organized Twitter campaigns under a hashtag #NoTedros4WHO to organize conversations surrounding the topic. To make his Ethiopian government profile at the top of the public’s consciousness, his opponents have share detailed research that accuses <PERSON> of inefficiencies, misreporting, and exaggerations of his achievements when he used to serve in Ethiopia.\nOne of the images that have circulated against <PERSON>, showing his face with an X over it next to the two other candidates. Shared by Twitter user <PERSON>, amid fears that the campaign might diminish his chances, government groups are also running a parallel campaign supporting his candidacy. They have downplayed the opposition as unpatriotic, mean-spirited and trivial jealousy.\nSince April 2014, a popular protest movement in Ethiopia has challenged the government, which has responded brutally.", "960" ], [ "According to Human Rights Watch, at least 800 people have died, and thousands of political opponents and hundreds of dissidents have been imprisoned and tortured. Since October 2016, authorities have imposed some of the world’s toughest censorship laws after it declared a state of emergency.\nThe role of ethnic politics\nSome of <PERSON>’ detractors say they oppose his candidacy because of his alleged incompetence. But a big part of what drives the fierce opposition to <PERSON> is the logic of ethnic politics.\n<PERSON> holds a Ph.D. from the University of Nottingham in community health. He studied biology at Asmera University before he completed a master’s degree in immunology of infectious diseases in London.\nWhen people hear his name, as qualified as he may be, his opponents associate him with a repressive Ethiopian government that has killed people, jailed thousands of political opponents, and imprisoned and tortured dissidents.\nHis meteoric rise to power started soon after he finished his Ph.D. in 1999 when he was tasked to lead the Tigray region’s health department. After two short years in Tigray, he was promoted to Ethiopia’s minister for health by the late prime minister <PERSON>, a Tigrayan himself. In 2012 when <PERSON> died, <PERSON> became Ethiopia’s foreign minister.\nTigray is one of the nine regional states that are federated based on ethnolinguistic compositions.\nOver the past 26 years, the Tigrayan elites have taken center stage in Ethiopia’s political affairs, largely due to their control of the military, security and the economy of Ethiopia. Though accounting for only 6% of Ethiopia’s population, all senior positions of country’s military and security and the most meaningful positions in state institutions are packed by Tigrayan elites. This has always been a sore point with the elites of the Oromo and Amhara ethnicities, who together comprise 65% of Ethiopia’s population.", "409" ], [ "Residents of Ethiopia’s Oromia Region Strike to Demand Release of Political Prisoners · Global Voices\nClosed shops and deserted streets in Bale Robe, a town in Eastern Ethiopia. Photo sourced from <PERSON> Facebook page and widely shared on social media.\nThe Oromos, Ethiopia’s single largest ethnic group, collectively rallied against Ethiopia's ruling regime on Wednesday, August 23, this time by staying at home, skipping work and refusing to open their businesses.\nThe towns and cities of Oromia, Ethiopia’s largest administrative region where the Oromo people are concentrated, are normally bustling. But photos shared on Facebook showed shopping centers and open markets were largely quiet on Wednesday and Thursday. Roads were nearly empty, and public transportation services providers such as buses stopped, forcing government workers who had no other way of reaching their post to take part in the protest.\n#Breaking: Harar and its surroundings under strike; no trade and transport activities observed. Some damaged vehicles were also spotted. pic.twitter.com/YmyOSIt2Tk\n— The Reporter (@TheReporterET) August 24, 2017\nThe strike, which is set to last for five days, was called by a mysterious Oromo youth movement calling themselves “Qeerroo,” referring to their youthfulness in the Oromo language.\nThe secretive activist group’s main demand is the release of political prisoners and jailed activists, in particular prominent opposition figures such as <PERSON> and <PERSON> who were arrested over the last two years of protests and charged with crimes such as terrorism and promoting “regime change using illegal forceful means and threats”.\nTwo years ago, thousands across Ethiopia mainly in the Oromia and Amhara regions rose up, demanding more political freedoms and social equality and a stop to government land grabs. In terms of representation, Oromos make up 35 percent of the country’s 100 million people and Amharas account for about 30 percent of the population. The Tigrayans, on the other hand, represent only 6 percent of the population, yet Tigrayan elites are among the most high-ranking military officers who control the nation's security.\nThe government's response to that uprising was brutal; hundreds were killed and thousands arrested.", "960" ], [ "In October 2016, authorities declared a nationwide, nine-month state of emergency that was lifted on August 4, 2017.\nWith this recent strike, the Qeerroo also want an end to what diaspora-based activists say an unjust tax hike. In July 2017, the government introduced a new tax scheme for small business operators across the country that prompted a similar protest both in the Oromia and Amhara regions. That protest in July quelled without any demonstrable political results, but the demand has resurfaced here.\nAlso, in the middle of all of this, the Oromos have a border dispute with the neighboring Ethiopian Somali. In April 2017, during the state of emergency, the Ethiopian government told the two regions to come to an agreement redistricting their boundaries per the outcome of a referendum that was conducted 10 years ago, in which Oromia lost some land. The government recruited “Liyou Police” or special police of the Somali region as an armed force to enforce the outcome.\nThe Oromos saw this as a plot of the Tigryan elite to weaken them, and they accuse Liyou Police of human rights violations. Ending the alleged human rights violations is contained within demands of the ongoing peaceful protest.\n#Ethiopia – call for an end to “Liyu police anarchy” in #Oromia as stay-at-home strike spreads through the region https://t.co/GbY1YcRhz0 pic.twitter.com/BNnsZ0gnQA\n— Addis Standard (@addisstandard) August 24, 2017\n‘It should be waged at a national scale’\nThe <PERSON> reach to their audience entirely through Facebook, a website, and diaspora-based satellite television networks. <PERSON>, executive director of Oromo Media Network, appears to be a major source of information. His Facebook page has more than one million followers, most of them gathered over the last three years.\nThe only apparent major information hub focusing on the current protest is the Facebook page of America based Oromo activist <PERSON>.\n— <PERSON> (@ZekuZelalem) August 23, 2017\nThe ongoing protest underscores the rise of a potentially treacherous challenge to the ruling Ethiopian People's Revolutionary Democratic Front (EPRDF) monopoly of power: widespread public outrage and a growing willingness of the public to participate in a strike when they are called.\nBut there are concerns about the absence of a single compelling protest message, coming even from supporters of the cause.", "960" ] ]

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[ [ "Master Sword Trinket Dish (Polymer Clay)\nIntroduction: Master Sword Trinket Dish (Polymer Clay)\nI've been seeing a lot of polymer clay trinket dishes lately on my Instagram feed and wanted to make my own. I happened to get a Hylian shield ring in a random cheap jewelry grab bag, and it was the main inspiration for this project. I also happened to be consuming a lot of miniature diorama content lately and wanted to make my own twist on it by turning miniatures into functional home-good items (a bit like a closet-cosplay to their hundreds-of-hours-thousands-of-dollars works of art).\nSupplies\nMaterials:\n* Polymer Clay (here I use Super Sculpey and Papas Clay in a blue and purple mix)\n* Bake and Bond (liquid polymer clay adhesive)\n* Acrylic Paint (in black, white, teal, metallic gold and silver, and various shades of gray and green)\n* Matte and Gloss varnishes (I used varathane water-based polyurethane, but you can check out The Blue Bottle Tree's guide for options if that is not accessible)\nOptional (if you want to add flowers)\n* White, Green, Yellow, and Teal Polymer Clay\n* Thin jewelry wire orflorist wire\n* Wire cutters/Pliers\n* Liquid polymer clay\n* Glow powder\n* Aqua/Teal pigment powder, iridescent shimmer pigment powder\n* (the liquid clay, glow powder, and pigment powders can be substituted with acrylic paint, which is probably more accessible)\nTools:\n* Needle Tool\n* Silicone shaping tool\n* Craft Knife\n* Paintbrush\n* Sponge\n* Cardstock and Paper to make templates\n* Oven\n* Electric sanding tool (such as a nail art file)\n* Modeling Clay (Optional.", "95" ], [ "This is used to make a mockup)\nStep 1: Before You Begin\n* Prepare your clay by conditioning it (knead it until it is soft and workable)\n* Create a mock-up to check that the sword is small enough to fit rings over.\nHere I use Sculpture Pro wax-based clay (similar to Monster Clay) for the mock-up because it is malleable yet stays firm and holds its shape so it can be picked up to test adding rings through it. From this, I would know what size to make a paper template for the Master Sword. Mine ended up being 2 cm across at the largest part of the hilt, and a bit over 0.5 cm for the majority of the rest of the sword).\nYou can also make your mock-up from cardstock to test if rings are able to fit past the sword guards.\nStep 2: Create Templates\n* For the trinket dish, cut out an equilateral triangle the size of how large you want the trinket dish to be from cardstock.\n* Create a template for a smaller equilateral triangle as the pedestal to hold the sword.\n* Trace an image of the Master Sword onto paper. I made mine by zooming in on an image of the sword to match the size of my mock-up on a tablet, then used the tablet as a light table to copy it onto paper.\nStep 3: Master Sword: Shaping\n* Roll out a thick sheet of blue-purple clay\n* Use the sword template to cut out the shape of the Master Sword\n* Thin out the edges of the blade by flattening them, trimming the excess clay back to the template's size\n* Round out the sides of the grip\nStep 4: Master Sword: Carving Details\n* Following a reference image, use the needle tool to indent the details of the sword.\n* Use the silicone sculpting tool to shape and deepen the details on the hilt\n* If there isn't enough clay to sculpt in some areas, add and blend small amounts of clay shaped similarly to the detail they are filling in (I did this by adding thin snakes of clay to the top parts of the wings on the guards, the details in the pommel, and the diamond shape on the hilt)\nOnce you are satisfied with this half of the sword, bake the clay following the directions of your clay packaging.", "987" ], [ "<PERSON> (Legend of Zelda Inspired) Earrings\nIntroduction: Silent Princess (Legend of Zelda Inspired) Earrings\nI didn't grow up with video games, so I was surprised by how far down into the Legend of Zelda fandom rabbit hole I had fallen after picking up a copy of Breath of the Wild. These earrings were inspired by the endangered silent princess flowers from that game.\nSupplies\nPolymer Clay, in colors:\n* white\n* green\n* yellow\n* light blue\nYou will also need:\n* blue/teal pigment (I'm using a powdered resin dye)\n* bakeable adhesive for polymer clay (here I use Sculpey Bake and Bond). In this tutorial, I will refer to it as liquid clay, although it is best to not use products labeled as liquid clay as it is too thin and your flowers can move around before you get a chance to cure the clay.\nEarring Findings:\n* Wire Hoops (here I use \"ear wires\" that I got at Michael's craft store)\n* Earring hooks and jump rings (or, if you find similar hoop findings as I use here, you can use stud earrings)\n* Beads (optional)\nTools:\n* Needle Tool\n* Craft Knife\n* Thin paintbrush for the pigment (I prefer to use nail art brushes)\nStep 1: Prepping the Earring Findings\nHere we will make a base to stick the flowers to the earring wire:\n1. Take a small amount of the green clay\n2. Coat one side of your earring hoops with liquid clay\n3. Roll out the green clay and wrap it around the wire, smoothing it out so both ends of the clay taper off to better blend with the wire findings\nStep 2: Flower Petals\n1. Roll out your white clay\n2. Use a craft knife to cut out petal shapes. You will need 5 per flower, but it is better to have extra in case any become mishappened or tear. The extra will also be useful later on.\n3. Add veining texture using a needle tool\n4. Pick up a small amount of blue pigment with your paintbrush, and dust the bottom center of each petal, as pictured\nStep 3: Putting Together the Flowers\n1. Create a base for your flower by taking a small ball of white clay and adding a dab of liquid clay on top\n2. Gently pinch together the bottom of each petal (this is optional, but you will get a slightly different look to your flowers. These photos show both how the flowers will look pinched off and not, so this is up to your own preference)\n3. Use your needle tool to pick up and stick each flower petal in place onto the small ball of white clay\n4.", "95" ], [ "Once all the petals are in place, gently curl back the tips of each petal. It is helpful to do this over your needle tool.\nStep 4: Flower Sepal\nThe sepal is made similarly to the flower petals, but with a few alterations:\n1. Roll out a sheet of green clay\n2. Cut out leaf shapes, making sure they are thinner and longer than the petals you cut previously\n3. Take a small ball of green clay to create a base, and add a small dab of liquid clay\n4. Place each leaf shape onto the base, arranging them into a flower shape [optionally, you can flatten the edges of each leaf before placing them to minimize the harsh cut edge from the craft knife to make the leaves seem more natural]\n5. Gently curl back each leaf, as you did with the flowers\n6. Add liquid clay to the center of the leaves, and place the flower over top. Arrange this so each leaf peaks out from between each petal.\nStep 5: Stamen and Pistil\nTo create the stamens:\n1. Roll out tiny balls of light blue clay (these are around <1 mm in diameter)\nTo create the pistil:\n1. Mix a bit of white and green clay to create a light green\n2. Roll out a thin snake of clay\n3. Cut a stubby log, around the length of two small stamen balls (~1.5-2mm)\nTo make the stigma (the top part of the pistil):\n1. Roll out and gently flatten a ball of yellow clay, and use the needle tool to add texture so it looks like three pill-shaped bits of clay stuck together\n2. ALTERNATIVELY: roll out three tiny pill-shaped balls of yellow clay and gently shape them together [this is easier if your flowers are larger than the ones I make here]\nTo put it together:\n1. Add liquid clay to the center of the flower\n2.", "987" ], [ "Purple Color-Changing Pajama Squid Figurine\nIntroduction: Purple Color-Changing Pajama Squid Figurine\nI've been making these baby squids for years and recently wanted to make them temperature-reactive. When I found out their colors could range to a purple-brown, I just had to use some purple pigment in them! If I were to remake these, I would use a colorless-to-purple pigment instead of purple-to-pink. I made a more fantastical version of them with colorless-to-blue pigment to test how it might look. These work great just as figurines, or can be attached to jewelry findings to make pins or pendants.\nSupplies\nFor this project, you will need:\n* Translucent polymer clay\n* White polymer clay\n* Temperature-reactive pigment. This can be substituted with UV-reactive pigment.\n* Liquid clay or Bake-and-Bond\n* Black micomarbles (these can be found with glitter or nail art supplies)\n* Xacto knife\n* Needle tool\n* Dotting tool\n* Blending tool\nTIP: To keep your white clay looking cleaner from dust and lint, mix equal parts of white and translucent together. I find that the brightest white clay is Premo frost white glitter, which is used here.\nStep 1: Making Color-Changing Clay\nFlatten a disk of translucent clay\nMix a bit of liquid clay and color-changing pigment in the center of the translucent, and fold within the clay\nKeep mixing until the pigment is uniformly distributed\nSet aside a bit of the purple clay for the eyes\nShape the colored clay and white clay into equally-sized rectangles\nStack the two colors\nStep 2: Creating a Stripe Clay 'cane'\nFlatten the clay, keeping it in a rectangle shape\nCut the clay in half, and stack the halves, creating 4 layers\nFlatten and repeat\nStep 3: Creating a Stripe Cane\nKeep cutting and stacking the stripes until you have enough layers. Be cautious of creating too many layers or the colors will blend together and loose the stripe pattern.\nRemember to keep shaping the clay into a rectangular cube to create a cane.\nStep 4: Creating the Body\nSlice your cane into sheets and select the best looking slices.\nReserve a lesser-perfect looking slice for the arms.\nStep 5: Creating the Body\nTake one of the imperfect slices and form it into a dome.", "994" ], [ "This will fill out the body shape\nPlace a stripe sheet over the body, and shape it around the dome. Round out the top corners.\nUse a dotting and blending tool to create small ruffles around the top of the pajama squid.\nStep 6: Adding the Arms\nTake the sheet of clay reserved for the arms and slice it in half.\nSlice this half and split it into 10 parts: 8 arms and 2 tentacles (here I only made eight)\nRoll out these parts to a taper on one end\nStep 7: Shaping the Appendages\nBlend each arm to the body.\nCurl up the ends of each arm.\nIf the there is difficulty sticking the clay together, add a bit of liquid clay to help blend the arms to the body.\nStep 8: Adding Eyes\nUse the dotting tool to create eye sockets.\nFill the sockets with liquid clay.\nTake the bit of purple clay reserved from earlier and roll it into two equal sized balls. Place the balls into the sockets.\nStep 9: Eye Details\nUse a needle tool to create a place for the micromarbles - this helps with keeping it from sliding in the liquid clay.\nCoat the eyes with liquid clay.\nAdd one micromarble to each eye.\nSet your pajama squid aside to bake. I use an index card over a small silicone loaf pan.\nStep 10: Baking and Finishing\nBake according to your clay packaging directions. Typically it tends to be around 275°F or 130°C, but be sure to read the directions on your clay specifically. Sometimes I use a clay that bakes at 120°-130°C, slightly lower than the regular temperature.\nhint: Be careful to bake your clay thoroughly. Under-baking causes crumbly clay! Also watch your oven and beware of burning!\nOnce your piece is completely cured, add a few layers of gloss glaze, and you are done!\n[once it is edited, I will embed a video of the squid changing colors in ice and warm water]", "987" ], [ "Fly-By-Night: Mary & the Witch's Flower Earrings\nIntroduction: Fly-By-Night: Mary & the Witch's Flower Earrings\nAfter watching Mary and the Witch's Flower by Studio Ponoc, I made a pair of Fly-By-Night earrings for a friend as a Christmas gift. I had been planning on making a pair for myself, so that is what today's tutorial is about. These earrings will also have the added cool of glowing in the dark. Plus, even if no one else recognizes these from that movie when I wear them, they still look cute.\nSupplies\n1. Clay in a light bright blue color.\n2. Roller for clay\n3. Clay knife\n4. Clay stylus tool or other pointed tool\n6. Chalk pastels in varying shades of blue (light to dark) and a medium colored purple\n7. Brush to apply pastels\n8. Eye pins\n9. Round nosed pliers (optional; I use them to help me place eye pins)\n10. Wine corks with toothpicks stuck in them (I use these to place the clay on while I color it so I don't mess it up with my hands)\n11. Glow-in-the-Dark paint (I use Deco Art )\n12. Brush for glow-in-the-dark paint\n13. Black Thread\n14. Glue (I use Aleene's Tacky Glue)\n15. Acrylic paint in a blue-purple color (I am using Blueberry Frost by Apple Barrel, NOT the Blue Bonnet color shown here)\n16.", "95" ], [ "Varnish (optional for polymer clay)\n17. Earring hooks\nStep 1: Basic Form\nSimple enough: roll out two balls from the clay in the *same* size.\n*Or as close as you can :)\nSet these aside.\nStep 2: Calyx\nThe leafy piece on the bottom of a flower where the stem is is called the calyx.\nRoll out your clay thinly. Cut out a six point star shape to cover the bottom of the flower. I use the stylus to draw them before I cut them out.\nStep 3: Star Shapes\nWith the rest of the blue clay, roll the clay out thin.\nWith the stylus tool, trace two little star shapes on the clay. These star shapes should have rounded edges instead of traditional pointy edges. They should be small enough to sit on the little balls and look like bloom ends (like a blueberry. These really look like glowing blueberries.)\nCut these stars out carefully with the knife. You will probably have to smooth them out a bit and redefine the shape after you cut them out, but that is fine.\nPlace the star shapes on top of the blooms on the opposite end of the calyx. Press the stylus tool into the center of the star shapes, affixing them to the round clay.\nStep 4: Eye Pins\nPut an eyepin through the bottom of the bloom, through the calyx. I use my pliers to make sure I get the pin where I want it.\nIf you have eye pins you bought from the store, you may have to trim them to the right size. You want the pin to not go any farther than halfway through the flower. Also, remember to bend a zigzag shape into the bottom of the pin. This will prevent the eye pin from falling or being pulled out.\nIf you want to know specifically how I do this, or you want to learn about making your own eye pins, this tutorial will help you:\nJewelry Basics: DIY Eye Pins for Clay Charms\nStep 5: Handy Tools\nNow you have two little fly-by-night blooms.\nGrab the toothpick/cork tools and place the blooms on the toothpicks. Put the toothpick in the hole in the center of the stars. Don't shove them on to the toothpicks, just enough that they will stay put and not fall off while you are coloring them.\nStep 6: Color\nNow it is time to color the flowers.\nSince I know it is hard to see what colors I am putting where in the photos, I have made a chart to try to explain what colors I have and where they go. Of course, how you want to color it is open to interpretation because I am just trying to imitate what was in the movie. If you see it differently, color it differently.\n*Don't color the calyx and rounded star portion. If you get color on them, no harm done, but we are going to be painting them later.\nThe fly-by-nights in the movie seem to glow from inside, but they have deep purple centers. So I am going to start with purple.", "987" ], [ "Resident Evil Life-Sized <PERSON>! Moving Mouth & Poseable Arms\nIntroduction: Resident Evil Life-Sized <PERSON>! Moving Mouth & Poseable Arms\nI had so much fun making <PERSON> for a local cosplayer who wanted to dress as <PERSON> for a convention. I had some requests for instructions, and thought this was the perfect place to put them! I will be updating pictures as I start work on Angie 2.0, but here are the instructions as I made the original.\nLuckily, Angie is made with easy-to-find materials. Your two more 'high-end' components will be the Apoxie Sculpt and Sculpey, both of which are great materials to have on hand for multiple other purposes. Feel free to message with any questions!\nSupplies\n* Insulation foam sheet- bought for $10 at Home Depot. Had to ask for it to be cut in half to fit in my car.\n* Marker/pen\n* Scrap newspaper\n* Elmer's glue for paper mache\n* Apoxie Sculpt & Sculpey- I used Porcelain Doll, but literally any type of Sculpey will do, including scraps of the little colored blocks. This will be painted so color isn't an issue.\n* Aluminum armature wire\n* Craft paint- any brand will do. I used a mix of shades to achieve the bone color.\n* Hot glue/super glue/adhesive of choice\n* String\n* Plumbing pipe, 1/8\" thick\n* Tinfoil & Masking Tape\nStep 1: General Overview\nTemplate:\nI've included a template for the torso and limbs that I used as a starting point, though keep in mind the carving process will produce different results.\n1. To print the template:\n2. Save the <PERSON> jpg. to your computer.\n3. Open Microsoft Excel. Click Insert, Pictures, and after clicking the file, hit LINK TO FILE, not just insert.\n4. Now in Excel, click the image, and under 'Height' in the top right corner, change to 36\", as <PERSON> is three feet tall. Hit print with standard settings, and your print will come out to 12 pages. These pages can then be taped together to form one blueprint.The steps of this project are pretty simple. It requires using foam and paper mache to create a lightweight torso, bones, and shoes. Details around the shoulders, neck, and breasts are added with Apoxie Sculpt, and hands are sculpted separately with Apoxie Sculpt for durability.", "348" ], [ "These are hooked together using wire, while a tube runs up the body to support the head.\nProcess Overview:\nThe head is made by first sculpting a \"face piece\" as well as a separate chin piece, then attaching foam around the back to create a hollow interior. The inner strings are attached, and once put in place, clay is added around the head to create an opening only in the neck. All parts are secured into place, then the entire piece is touched up and painted. All that's left is the dress!\nStep 2: Torso & Bones- Foam Carving\nPieces:\n1. Start by plugging in your hot glue gun. While it heats, draw (or trace) a general torso shape, drawing a little bigger for safety.\n2. Cut out using your x-acto knife. Pick up your torso piece and and use the marker to draw/touch up the shape. This will be covered and does not need to look perfect. Once you're happy with the look, trace and cut out two more torso pieces.\n3. The torso takes three pieces: Two of <PERSON>'s silhouette, and one piece, cut in two, glued in the middle so that the tube can sit in the center of the body. Layer and hot-glue the pieces as shown.\nFoam Carving:\nThe foam will first be 'whittled' away to create a more rounded, human-like shape from our layers. We want to create an undersized, rounded form to add topography with newspaper.\n* The biggest tip I have is to keep turning the body at different angles and reconsider what it looks like from that direction. Keep in mind the chest and ribcage will be flat at this point, and the shoulders will look like broken little nubs. This is all totally fine. It's better to be undersized then over at this point- make sure the waist is a little under template size.\nStep 3: Torso & Bones- Paper Mache & Apoxie\nNewspaper/Masking Tape Covering:\n1. Use pieces of newspaper to smash up and tape across the body.", "987" ], [ "Foam Pin Sword - Alice in Wonderland\nIntroduction: Foam Pin Sword - Alice in Wonderland\nA few months from now, a small group of my friends are going to an Alice in Wonderland mystery/scavenger hunt event.\nOne of the costumes I am making is <PERSON> from the 2010 movie. To start, I am making a scaled up version of her pin sword.\nThe structure of this sword is entirely foam, a mix of EVA and styrofoam was used in making mine.\nCaution: since this sword is entirely foam it is not especially durable, particularly if being used to hit things.\nSupplies\n15mm foam dowel - cut to desired length (I used a precut 2’ dowel)\nFoam ball (I used 2.5” diameter styrofoam)\nAcrylic Paint (I used silver and black)\nHot glue gun\nScissors\nX-acto or other craft knife\nSandpaper\nStep 1: Cut a Hole in the Foam Ball\nPosition the dowel where you want it to sit, and trace around it with a light colour, I used a yellow highlighter. Then, use the knife to make about a 1/4” indent where the shaft of the pin sword will sit. Once the circle is cut I used the tip of the knife to gently push the foam away from the edges. After that because I used a styrofoam ball I was able to pick out the individual cells of foam. Once you have made the hole insert the dowel to make sure it fits. It should be snug but not too tight. Remove the dowel before going to the next step.\nStep 2: Shape the Dowel Into a Point\nMake a mark roughly centre on one end of the dowel, also mark all the way around the dowel how far you want the taper of the point to go, I ended mine about 1 inch in from the tip. I started by using my x-acto knife to cut out the point but it ended up ripping more than cutting the foam, so I switched to using scissors which worked much better, and made it easier to control where I was cutting.", "644" ], [ "Once you have a rough point cut, then use sandpaper, I had 220 grit, and gently sand any rough patches. I recommend moving the sandpaper in strokes towards the point, rather that starting at the point, I found it easier. The purpose of sanding it is more to blend the imperfections rather than to make it completely smooth. Go back and forth between cutting and sanding until you are satisfied with how the point looks.\nStep 3: Paint Everything\nI used silver acrylic paint to paint the dowel, and black acrylic paint for the ball. I painted the dowel with 3 coats, allowing ample drying time between coats, and did 2 coats on the ball. Since I was also holding the ball while painting it, it can be tricky to cover the entire surface in one go, so I did about half the ball at a time, and once that dried I held it on the dried paint to cover the other areas. Repeat as many times as necessary to get the desired effect.\nNote: depending on the paint you use it will help to stiffen the dowel. I found the dowel curved under its own weight when held in the air from the end, the paint helped to lessen the bending, but did not remove it completely.\nStep 4: Glue the Dowel to the Ball\nOnce all the paint is dried cover the flat end of the dowel in a generous amount of hot glue, and firmly press the dowel into the hole in the ball. Wait 10 minutes or so to allow the glue to dry then gently try to pull the ball off the dowel, to ensure they are securely attached.\nStep 5: Done\nThat’s it! Mine ended up at a length of 26.5 inches.", "556" ], [ "Egyptian Tomb Inspired Book Nook\nIntroduction: Egyptian Tomb Inspired Book Nook\nWelcome to my first Instructable! During 2020, I was taken with beautiful images of \"book nook\" dioramas going around the Internet. I don't have any real experience with miniatures but I decided to give it a try anyway as a quarantine craft. This is the result! I certainly made some mistakes along the way, but overall I'm pleased with how it turned out. This may give you some ideas to try designing a diorama of your own.\nI went with an ancient Egyptian theme mostly because it's cool, but also because I thought I could get away with making things out of foam, which sounded the simplest and cheapest to me.\nSupplies\nMaterials I used:\nA hinged cardboard box\nA craft knife\nA small screwdriver (normally used for electronics)\nFoam (several thin sheets of fun foam and one sheet of 6mm thick foam)\nModge Podge glue (lots of it)\nAcrylic paints\nPaint brushes (mostly the cheap kind that could handle working with glue)\nShrink film - the printer friendly kind\nPrinter paper\nPaperclips\nMetal thumb tacks\nCraft sand\nImage editing software (I used Gimp)\nPopsicle sticks\nA hammer\nA nail file\nStep 1: Preparing the Box\nI found a cardboard box with a hinged lid at the craft store: I wanted to use that as the base because it would be easy to open the box up and access the inside. I used a craft knife to cut the front of the box open. Then I used a little electrical tape to smooth out the cut edges. I picked electrical tape because of the color, but if I did this again I might use masking tape: it has a better texture for painting and gluing over.\nStep 2: The Doorway\nI spent some time looking at images of Egyptian tombs online and found some pictures of doorways carved and painted with hieroglyphs that I wanted to imitate.\nI started by cutting a rectangle of my thicker foam sheet, just slightly smaller than the inside of the box, then cut out the opening. I also added a couple of stacked rectangles at the top to give it more dimension.\nAfter a little experimentation on a scrap foam sheet, I used the tip of a small screwdriver to carve the symbols I wanted into the foam. I don't actually read hieroglyphs; I just copied pictures I saw online. It would be rad if I accidentally cursed myself but most likely it's just gibberish.\nThe most important detail I included was a carving of Ma'at, the goddess of balance. I also used a nail file to weather down some of the edges to try to make it look older.\nFinally I coated the entire thing with a layer of modge podge glue.", "644" ], [ "Foam doesn't hold paint well because it's such a porous material, so the glue creates a seal around the foam that paint can hold on to. All of the foam in this project got the same treatment.\nStep 3: Shrink Film Tomb Painting\nMy parents have a painted sheet of papyrus that my mother got on a trip to Egypt as a teenager; I thought it would be neat to recreate that image as a tomb painting. Rather than try to paint it by hand, I loaded a photo of the papyrus onto my computer and then recreated it in an image editor. I then printed my new version onto a sheet of shrink film.\nI made a mistake here: I forgot that the colors in shrink film become much more saturated when the film is shrunk in the oven. The result ended up a lot darker than I wanted. If I did it again, I would use colors much lighter than what I wanted in the full size print.\nOn the plus side, the shrunk down film has a slightly rough texture that works great for fake stone. It also can be painted, which helped with blending the \"painting\" in with the other surfaces later on.\nStep 4: Foam Stone\nTo get a rough stone-like texture, I grabbed a few sheets of foam and a hammer, then took them outside to the sidewalk. I whacked the back of the foam with the hammer so that the front side would pick up texture from the asphalt. I ended up using two different hammers; a regular one and a rubber mallet, which has slightly different results on the texture.\nI cut one sheet into large bricks that I arranged on one side, leaving space for my tomb painting. I deliberately had some space in between the bricks and uneven edges to try to make it look more realistic. I have to admit, this process was so incredibly fussy that I got sick of it. For the other sides I just carved grooves into a full sheet of foam.", "74" ], [ "Indigo Bunting Necklace\nIntroduction: Indigo Bunting Necklace\nSo, for the Rainbow Contest, I decided to go after that strange, illusive color, Indigo. For me, what pops in my head right away, is the cute little Indigo Bunting. I have seen a lot more of them this year than I have before. They tend to just look like bright flashes of color as they dart past, hiding in the weeds.\nInstead of just portraying the well-known, flashy male, I decided to put him together with his female counterpart. I decided that a lovely little nest scene was a good way to show them. It is also a good way to educate people on what the two of them look like; a stark contrast of one another, the male bright indigo and the female in a drab brown of concealment.\nCome along and create this cute necklace!\nSupplies\n1. Clay in brown and indigo (or as close as you can get - we will add some colored pastel and mica powder to help his bright coloring).\n2. Clay tools (roller, knife, and stylus or needle tool)\n3. Work space\n4. Tiny ball tool (also known as mandala tools or nail dotters)\n5. Small soft brush for using with pastels and paint\n6. Pastels in various shades of brown. Also you should add in green, blue and purple, and a grey if you have it (which I don't).\n7. Acrylic paint in black and grey (Grey not pictured)\n8. OPTIONAL: Mica powder in purple and blue. I think this just adds to his shimmery shininess, but you could also just paint him with metallic purple and blue paint.\n9. Necklace chain with wide links\n10. Two large jump rings\n11. Set of round nose pliers\nStep 1: Sculpt the Nest\nWe will begin with the nest.\nRoll out the brown clay. Don't make it too thick or too thin. With the knife tool or the stylus, sketch a bowl shape on the flattened clay. Trim this out with the knife tool. Set this aside.\nCut out two thin strips of clay from the leftovers.", "95" ], [ "These will be the limbs that the nest sits in between.\nWith the stylus tool, scratch lines into the two limbs, making them resemble the bark of a tree. If you have any silicone stencils that are wood-like this would be a cool time to use them. Just make lines until you are satisfied. Vary the lines in thickness, thinness, and length to make them look more natural. I also used the knife to cut the end of one of the branches and make a small broken branch piece sticking out from it.\nStick the ends of the two limbs together so they make a \"v\" shape. Place the bowl in the middle of the \"v\". Make sure it is tightly adhered.\nStep 2: Nest Details\nWith the stylus tool, scratch and swirl the needle around to make a rough, fiber-like appearance. Their nests are made of twigs, but I have yet to come up with an easy technique to make small twigs that I am satisfied with. This is what I do right now, maybe someday I will figure it out.\nAt the ends of the branch limbs, poke holes all the way through the clay. These are for the jump rings. Make them larger than you think they actually need to be.\nNow get out the brown, green, and grey pastels. With the small brush, dust the branch limbs first with various browns. I made mine pretty dark. Then dust the nest with a variety of the brown, green, and grey. You don't want to make it as dark as the limbs because then it won't stand out.\nSet the nest aside.\nStep 3: Female Bunting\nWith the left over brown clay, roll it out. Sketch a bird with a crest on the flattened clay. I advise looking up images of the Indigo Buntings to help you with this. Indigo Buntings are a member of the Cardinal family, but I have noticed in most photos I have looked at the female's crest is much more apparent than that of the male. They have fat beaks like finches (and Cardinals, duh :).\nTrim out the bird. She doesn't have to be a whole bird; only the top half because she will be sitting on the nest. With the stylus tool, sculpt the little details, like the eye, the beak, and various feathers. I just make pokes and scratches to indicate the feathers.\nColor the bird with pastel. This did not turn out like I liked it, so I added some grey paint later on, so you could just skip this and simply paint her if you wanted.", "879" ] ]

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[ [ "How to structure a device driver software?\nI'm asking here for both the scientific, programmatic, and structural format of a device driver. What does that mean? Basically, I'm not asking how to write a driver in general ... I'm asking how to structure one to behave as a software that can act as the \"middleware\" between higher-level code and the hardware itself. I've decided to embark on a journey of low-level computer programming (e.g. systems programming) to develop reusable software that can \"expose\" accessibility of hardware memory access by driver calls.\nI basically run a freelance group of a small programming team/company, and I've decided to take on development across various retro-gaming platforms from the ground up(those of which have decent documentation, or reverse engineering will endue). What I'm asking here is how would one envision the development or structure of a software that can act as a middleground between the applicable software program and the hardware itself; developmentally, structurally, and programmatically.", "373" ], [ "My choice of console was originally the Nintendo 64's GPU (which I have documentation for). The issue isn't with writing the code to access the GPU, it's with developing a reusable driver/graphics engine(I'm new to it).\nI would have asked this at Programmers.SE, but they reject these kind of questions since they're not about specific programming issues, but about careful design methodologies, modularity, and structuring.\nSo I'll ask again with hope to receive a somewhat explanatory answer on this process ... how do I go about the design methodology, structural format, or developmental logic to create a software that can be accessed by other software to enable device access modularly? In other words, how do I structure and design a driver (i.e. what procedure should I take in creating such software)?\nAgain, to clarify, I am not asking how to write a driver, but how to go about structuring the system, methodology, and behavior of a driver. Are there any specific ways of going about this that prove successful (e.g. certain data types to define behavior for accessibility, methods used in accessing parts of a driver independently, etc.)?", "373" ], [ "General question about how CPUs send and receive data/bytes to hardware?\nRealize I didn't mention x86 or any more details to make this non-specific to any platform, but to just get a general idea of how this is done(this is also a long question with a lot of details).\nI know most PC motherboards for desktop (if not all) computers have two sections; north and south bridge, and a chipset connects them together between the CPU's implementation and the buses carrying data around the board.\nThe x86 CPU has a register, I think, called the accumulator, which has eight bit AL, sixteen bit AX, and thirty-two bit EAX. Data for these registers are typically used for arithmetic operations, general purpose machine instruction, etc.\nAlso, supposedly for I/O access, such as with Port I/O. There is Port I/O and MMIO (memory-mapped input/output), which are two methods of accessing data outside the CPU.\nI have inspected memory maps, but I'm still unclear on whether or not it's part of an instruction fetched from memory (i.e., MOV AL, 0FF) or from some other instruction to actually access hardware.\nMy basic question is, what specific instructions are used to write and read data from hardware, from a bare machine perspective; no device drivers, no operating system, and no firmware interrupts. This is the very essence of how system software must be made, and there's little complete coverage on how this works from the CPU's register to the hardware itself.", "798" ], [ "I have seen BIOS interrupts, but that abstracts away details. Also, the developer had no idea what happens beyond INT 13.\nSo, despite my broad question, is there some specific way this is accomplished, either by instruction, correct value set in a register, etc.?\nExample: Say I want to make a few beep noises. The sound hardware is responsible for making any noise at all, so I would, from a bare machine perspective, once again, have to directly access the hardware and its components, circuitry, or otherwise internal hardware registers or such to make noise. Is there a complimentary way of doing this that is specifically outlined or guidelined per-platform, or does it vary based on every specific piece of hardware and CPU?\nIf so, what would help me unravel that mystery to program for it this way? Would the card be, let's say, mapped a special address you write to? Then I would just set a register and the CPU will just send it there with whatever value it contains?\nI am confused, and nothing makes clarity of this, because abstractions exist even at the low-level that create a barrier of the unknown.", "705" ], [ "What roadblocks are there to HSA becoming standard, similar to floating point units becoming standard?\nI remember when my dad explained to me for the first time how a certain model of computer he had came with a \"math coprocessor\" which made certain math operations much faster than if they were done on the main CPU without it. That feels a lot like the situation we are in with GPUs today.\nIf I understand correctly, when Intel introduced the x87 architecture they added instructions to x86 that would shunt the floating point operation to the x87 coprocessor if present, or run some software version of the floating operation if it wasn't. Why isn't GPU compute programming like that? As I understand it, GPU compute is explicit, you have to program for it or for the CPU. You decide as a programmer, it isn't up to the compiler and runtime like Float used to be.\nNow that most consumers processors (Ryzen aside) across the board (including smartphone Arm chips and even consoles) are SoCs that include CPUs and GPUs on the same die with shared main memory, what is holding back the industry from adopting some standard form of addressing the GPU compute units built in to their SoCs, much like floating point operation support is now standard in every modern language/compiler?\nIn short, why can't I write something like the code below and expect a standard compiler to decide if it should compile it linearly for a CPU, with SIMD operations like AVX or NEON, or on the GPU if it is available? (Please forgive the terrible example, I'm no expert on what sort of code would normally go on a GPU matter, hence the question. Feel free to edit the example to be more obvious if you have an idea for better syntax.)\nfor (int i = 0; i < size; i += PLATFORM_WIDTH) { // + and = are aware of PLATFORM_WIDTH and adds operand2 to PLATFORM_WIDTH // number of elements of operand_arr starting at index i. // PLATFORM_WIDTH is a number determined by the compiler or maybe // at runtime after determining where the code will run.", "125" ], [ "result_arr[a] = operand_arr[i] + operand2; }\nI am aware of several ways to program for a GPU, including CUDA and OpenCL, that are aimed at working with dedicated GPUs that use memory separate from the CPU's memory. I'm not talking about that. I can imagine a few challenges with doing what I'm describing there due to the disconnected nature of that sort of GPU that require explicit programming. I'm referring solely to the SoCs with an integrated GPU like I described above.\nI also understand that GPU compute is very different than your standard CPU compute (being massively parallel), but floating point calculations are also very different from integer calculations and they were integrated in to the CPU (and GPU...). It just feels natural for certain operations to be pushed to the GPU where possible, like Floats were pushed to the 'Math coprocessor' of yore.\nSo why hasn't it happened? Lack of standardization? Lack of wide industry interest? Or are SoCs with both CPUs and GPUs still too new and is it just a matter of time? (I am aware of the HSA foundation and their efforts. Are they just too new and haven't caught on yet?)\n(To be fair, even SIMD doesn't seem to have reached the level of standard support in languages that Float has, so maybe a better question may be why SIMD in general hasn't reached that level of support yet, GPUs included.)", "82" ], [ "To an experienced user, GUIs tend to be slower because of indirect (eg visual) feedback you need to also react to before the next step is taken.\nTake a very analog input element - a rotary switch. For somebody operating this switch or a similarly built one all the time, setting it one step or for example 5 steps is an instant, atomic, single-thought operation that also can be expected to unquestionably have the intended effect. An especially big problem rampant in today's GUIs is how an error condition will require further, and different interaction before the intended input is even finished - so operating a GUI very fast relying on interaction elements always being in a predictable state is error prone.\nA GUI tends to need more focus and interaction, in the worst case for 5 cycles in that example - a universal but proportional input method (eg a mouse or trackball) is going to either need sophisticated haptic feedback technology or be very sensitive to overshoot, errors due to environmental vibration...", "242" ], [ "Compare steering wheels, levers ... compare trained users of mechanical cameras, musical instruments or analog-era test equipment...\nAlso, a GUI becomes extremely confusing to operate if the display is rotated from what you are used to - which can easily happen when gravity is negotiable. If you really want to know, pitch your monitor sideways and try to operate your computer..\nAs for command line interfaces, not only is usage far more easily documentable (though not as self documenting!) without room for error (as was mentioned already), you can also more easily automate-as-you go by reusing the commands in programs, and it is far easier to remote control such a system on a high-latency, limited bandwith link - character data is very small, and the need for constant interaction is limited.\nAlso, the materials used for a graphical display might be too hazardous to a given mission in case of damage - CRTs can implode, throw glass shrapnel around, and leave dangerous voltages exposed; big LCDs or similar could be poisonous to crew or corrosive to other materials if whatever leaks stays in the closed-system atmosphere ...", "284" ], [ "Please HELP me understand how the ISA works and how it is implemented with the microarchitecture\nHow is an ISA written? Is it just a bunch of binary combination encoding presets that is stored onto RAM? In other words, is it basically a “dictionary” of binary being defined as an instruction ‘word’ such as add? Once the instruction ‘word’ is recognized, does that mean an action is defined/assigned in that ‘word’? For example, let’s say 101010 is some encoding in x86 that = add, but then add = 111000, which is some electrical signal of add, then 111000 = action, then action = using ALU take register 1 and 2 and adds them? Also, is storing the result part of that action of add or is it it’s own separate thing? My guess is that it’s part of the action of add.\nFrom my understanding and using my analogy of a dictionary , I’ve thought about it in this way. Instead of thinking of it as one complicated dictionary with meanings on meanings on meanings, I’ve split it into two dictionaries: one dictionary for the encoding of your ISA (the opcodes/instruction format) and the other dictionary for what that encoding means, meaning it’s actions. There’s a microcontroller unit with a ROM aspect that is the dictionary for my so called “action”, which are the electrical signals that correlate to decoded instruction. Then there’s your ISA, set of instructions, that’s located on your RAM which is a dictionary for the instructions when the opcode being called. Am I correct? Please tell me I am.", "705" ], [ "Follow up, how is the ISA loaded into RAM to begin with? What tells it to do that? Is it the microcontroller unit? Also, how does an ISA even go about naming and defining certain registers to have a certain roles and functionalities? I’m genuinely confused. Is the ISA like an OS where as soon as the computer boots, the instructions get stored into RAM (if so, how?) and these registers immediately recognize their names and roles? I definitely feel like I have some sort of misconceptions and misunderstandings here.\nThen there's also the instruction cycle which I learned about separately. It's fetch, decode, execute. What is making it do that? How is the cycle being executed? Is that programmed through the ISA? Is it some kind of hardwired thing at the microarchitecture level? If so, please explain.\nLastly, how exactly does the implementation process of the ISA and microarchitecture work? Do you create the ISA first then implement that onto the microarchitecture level? Or is it created by working hand and hand with each other? By that I mean, does Intel have two teams: one dedicated on creating the ISA and one on creating the design of the microarchitecture(hardware)? If the answer is two separate teams, I do not understand how you can go about creating your digital logic(hardware) efficiently without working close together with the ISA team. Even after creating and finishing their product, how do they implement it with one another? Please help me understand the implementation process :(", "705" ], [ "I would argue that the premise of the question makes a wrong assumption:\nThere is an enormous amount of people that use computers set up to perform a single task. Behind the scenes, they're generic systems running a full OS and having all capability, but the machine has been specialized for some tasks.\nFor example:\n* Cashiers use machines which are commonly running Windows.", "81" ], [ "They do not have access to the computer's OS: the machine boots up in the only interface they'll use during the day and they do not need all the complexity.\n* In supermarkets, devices scanning for prices and even electronic scales are sometimes running a full OS, but the user doesn't see it.\n* Your TV set-top box might be running Linux and could be doing a lot of things, but it is abstracted from you and you just see the interface designed for you.\n* In many offices, people have access to a single piece of software, to perform their tasks, and never see the OS.\nIn the professional world, you have a lot of situation where the complexities of the system are hidden from the user because they are locked in a single software (cashiers are the most obvious example).\nWhen the work is less repetitive, people will have access to the computer OS because they will need a variety of software to perform their tasks; in this case, they'll need some basic computer skills.\nFor economical reasons, it's better to get standard PCs with one of the common OS and then specialize as much as you need from there. This is easier to setup, maintain, update, etc than a custom solution that might be locked in by a vendor.\nSome companies, like http://www.citrix.com for example, are providing solution that turns a full flexible PC (read cheap and common computer) into a specialized device that will run specialized apps so that employees have all technical problems abstracted from them.\nAs I was saying at the beginning: I believe the premise of the question is flawed in the sense that there are millions of flexible computers set up to let employees just use the features they need and nothing else. In that context, all complexity is abstracted and usability is directly linked to the designed of the apps they'll be using.\nWhen it comes to personal computing, it's a different story since every user has his/her own use cases.", "81" ], [ "Machine code: How can an OS prevent user-level programs from accessing each other's memory?\nOkay, I’ve done a lot of research on this, but I can’t seem to wrap my head around it. Essentially, the question is as follows: How can an operating system prevent a machine instruction from a user-level program (Firefox, Word, etc.) from accessing memory locations that it isn’t supposed to access?\nHere’s what I think I understand so far: Machine code, as you would for example find it in a .exe file after building your C/C++ program, is a sequence of binary instructions. These instructions can run directly on the CPU (assuming that the program was compiled for that CPU’s instruction set, e.g. x86). So, you don’t technically need an operating system to “run a program” in a broader sense – which isn’t surprising, since an operating system is just a program itself. Also, the CPU doesn’t work in terms of “programs” or “processes”, but in terms of individual instructions.\nNow, if we do have an operating system (e.g.", "10" ], [ "Windows), part of its job is to assign an encapsulated memory segment to each running user-level program (e.g. Firefox, Word, my own C++ program, …), and to make sure that they can’t read/corrupt each other’s memory.\nThis is where things get fuzzy for me. If I were to write my own operating system (or other bare-metal program), I would need to be able to use machine instructions to read/write to and from any existing location in the entire memory, right? So, how does an operating system make sure that no user-level program sends such instructions to the CPU on its own, without “asking the OS for permission” to access a certain memory location?\nI would actually love to learn more on the entire topic of going from high-level code to machine instructions. For instance, I would also like to understand what user-level program threads and OS-level processes look like on bare-metal, etc. So, if anyone could point me to a good resource, that would be highly appreciated. Nonetheless, this isn’t the core of my post, just a side note.", "10" ], [ "For most of these questions, the Runtime Environment as it seems to be described in your book is more easily understood by comparing a low-level language like C, to a VM (Runtime Environment) language like Java.\nHow does compiler execute the code, it is only supposed to generate the intermediate code right?\nYour quote doesn't say the compiler executes the code. It says that it can start up a RTE which takes over. For lower level languages that don't use a VM/RTE, it can signal the OS to begin execution of the program. In either case, this is a hand-off, not the execution itself.\nAnd does it create runtime environment? I mean there's not a virtual machine that the program runs on, it just runs on your computer right? When does it create a runtime environment?\nPractically speaking, the interpretation of these terms is largely dependant on the language in question.\nAll programs run on the OS, which manages access to hardware for running programs.\nIn a low-level language like C, the Runtime Environment as a concept is arguably indistinguishable from the OS itself.", "77" ], [ "Memory alloc/dealloc requests are made directly from the program to the OS.\nIn a high-level language like Java (the most commonly references \"VM\" language), the Runtime Environment as a concept is used loosely to refer to the program that sits between the executing program and the OS. The Java Runtime Environment consists of the Java Virtual Machine (which handles memory management requests to the OS, among other things), some libraries, and utilities.\nIsn't memory managed by the operating system? Why is allocation of storage done by the compiler and at what point? Probably what variables are needed and how much may be known by the compiler but, how does it communicate this information to the OS?\nHardware memory address reservation is managed by the OS.\nSpecifics of the complexity of memory management intervention provided by the RTE is going to be specific to the RTE implementation. Some provide more features than others.\nThe Java Virtual Machine makes the alloc/dealloc requests to the OS on the behalf of the executing programs. It also has a Garbage Collection cycle which looks for and frees memory reservations that are no longer being used by the program, rather than holding them all until execution halts.\nIn C, it is the explicit responsibility of the executing program to make these requests to the OS. Memory requested remains reserved until the program halts, or the memory is explicitly released by the program.", "10" ] ]

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[ [ "How to Make Regina King's Emmys Dress for Under $20\nIntroduction: How to Make Regina King's Emmys Dress for Under $20\nI've been wanting to recreate a red carpet look for a while now, and I had a blast tackling Regina King's gorgeous Emmys dress in this budget-friendly DIY project! Here's how I made Regina King's 2020 Emmys dress for less than $20 (and right in time for Halloween season). This is definitely a costume that will turn heads. Enjoy!\nFull video:\nSupplies\n* Graduation gown ($12.99 at my local Goodwill thrift store)\n* Craft rhinestones (from the 99cents Only Store)\n* Sewing machine\n* Fabric scissors\n* Sewing clips\n* Hot glue gun\n*Miaira is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.\nStep 1: Cut Dress Pieces\nFirst, cut the sleeves and top from the graduation gown to create a strapless dress base. Then cut the bottom of the dress to create a high-low effect.\nNext, cut two long strips about 2 inches wide each from the excess fabric, but be sure to leave the sleeves in tact for the poof later. The strips will be attached to the sides of the dress to create a belt effect that will tie in the back and cinch the waist of the dress.\nStep 2: Assemble & Sew\nOnce your pieces are cut, assemble them into the dress form. I don't have a dress form so I did this while wearing the pieces. Then sew the pieces together.\nStep 3: Create the Poof\nOne of the most notable features of Regina's dress is the large fabric poof that seemingly floats near her shoulder. To create this, I sewed both sleeves together to create a large tube shape, then I stuffed it with plastic bags.", "316" ], [ "After that, I bent a wire hanger into a curved shape and inserted into the sleeves tube to help keep the curved form in place.\nIn hindsight, I probably would have used a piece of cardboard or poster board instead of the wire hanger to keep the poof in shape and upright.\nStep 4: Add Embellishments to Poof\nOnce the poof shape is created, hot glue the 99cents store rhinestones onto the fabric. For variety, I used different shapes to create the look of flowers with some of the jewels.\nStep 5: Attach Poof to Dress\nYou can either sew the poof onto the dress or hot glue it on (I used hot glue). As mentioned, I don't currently have a dress form so this part was easiest to do while wearing the dress to make sure everything was being attached in the right places.\nStep 6: Create Pillow Dress Effect\nTo create the puffy pillow effect of Regina's dress, I glued more plastic bags to the hemline of the dress in the front, tucking the fabric underneath the bags to make sure everything stayed in place.\nStep 7: Embellish the Dress\nLastly, glue the rhinestones onto the dress in a similar pattern as the poof for consistency. The bling really makes a huge difference!\nStep 8: All Done!\nThat's it! For under $20, I now have a beautiful replica of Regina King's stunning red carpet look for a teeny fraction of the cost. Upcycling doesn't get much more fun than this! Thank you so much for checking out this project. :)\nFollow me on Instagram for more DIY and design inspo! https://www.instagram.com/miairajennings/\nYouTube: https://www.youtube.com/miairajenningstv\nWebsite: http://miairajennings.com\nPinterest: https://www.pinterest.com/miairajennings/\nBusiness Inquiries: <EMAIL_ADDRESS><PERSON> Emmys Dress for Under $20\nIntroduction: How to Make <PERSON> Emmys Dress for Under $20\nI've been wanting to recreate a red carpet look for a while now, and I had a blast tackling <PERSON> gorgeous Emmys dress in this budget-friendly DIY project! Here's how I made <PERSON> 2020 Emmys dress for less than $20 (and right in time for Halloween season). This is definitely a costume that will turn heads. Enjoy!\nFull video:\nSupplies\n* Graduation gown ($12.", "748" ], [ "DIY Dress Out of Curtains (Easy Sewing!)\nIntroduction: DIY Dress Out of Curtains (Easy Sewing!)\nIf you know me then you know that curtains are fair game for sewing projects at any given moment. Here's how I transformed a thrift store grad gown and some sheer curtains into a gorgeous goddess dress (two-piece) with easy sewing!\nFull video tutorial: https://youtu.be/QHW1BymhTi8\nSupplies\n* Dress form\n* Sewing machine\n* Fabric scissors\n* Sewing clips or pins\n* Hooks and eyes\n* Needle and thread\n* Sheer window curtain\n* Graduation gown\n*I may receive a commission for purchases made through product affiliate links in this post.\nStep 1: Cut Bands\nFor the skirt waistband and the bottom band for the top, I cut two 4 to 5-inch strips from the graduation gown, folded the edges inward and ironed them down to smooth the fabric out.\nStep 2: Create the Skirt\nI placed the edge of the sheer curtain along the waistband and created small folds every 1 inch, then pinned them in place and sewed along the pleats. Then I sewed the sheer fabric onto the waistband.\nI did not sew the ends of the waistband together so the skirt would have an opening or slit.", "316" ], [ "I originally wanted to leave the front open but later decided to go with a side slit to show one leg.\nI added a hook and eye fastener to each end of the skirt's waistband at the top of the slit to make it easy to put on and take off.\nStep 3: Create the Top\nI cut another piece of the sheer curtain to create a one-shoulder top. I wrapped the fabric around the bust to create the draped, one-shoulder crop top look. Then I added another strip of the graduation gown across the top for more contrast and sewed all pieces into place.\nFor the back, I sewed channels into the edges on both sides of the band and then ran a strip that I cut from the grad gown through the channels for a tie-back look.\nStep 4: Steam\nOnce everything was sewn, I steamed the fabric for a neat and finished look.\nStep 5: All Done!\nI'm so proud of this budget-friendly set that's giving full goddess glam vibes! Thanks for checking out this project and be sure to connect with me on IG for more fashion transformations.\nYouTube: https://www.youtube.com/miairajenningstv\nWebsite: http://miairajennings.com\nTikTok: https://www.tiktok.com/@miairajennings\nPinterest: https://www.pinterest.com/miairajennings/\nBusiness Inquiries: <EMAIL_ADDRESS>\nShop my Amazon store: https://www.amazon.com/shop/miairajenningstv", "748" ], [ "How to Make a DIY Flower Gown Out of Basic Shapewear\nIntroduction: How to Make a DIY Flower Gown Out of Basic Shapewear\nWith springtime quickly approaching (and Valentine's day just around the corner when I made this), I definitely had flowers on the brain. Here's how to transform basic $10 shapewear into a stunning floral gown that would be perfect for a prom, wedding, red carpet, or any other formal event to show off a handmade creation.\nFull video tutorial: https://www.youtube.com/watch?v=jzP1h5oVq4Y\nSupplies\n* Shapewear dress\n* Sewing machine\n* Sewing clips\n* Fabric scissors\n* Faux flowers and vines (I got mine from the 99cents Only Store)\n* Sheer fabric (I used about 2 yards)\n* White tulle\n* Hot glue gun\n* Fasteners (I used velcro dots but recommend something a bit stronger like metal snaps or hooks)\n*Miaira is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.\nStep 1: Create Skirt Attachment\nWrap the folded sheer fabric around your waist, meeting at the front of one hip. Then attach your fastener at that spot to keep the fabric in place.\nCut a layer of tulle and add it on top of the sheer layers for more dimension. You'll add the flowers on top of the sheer and underneath the tulle later on.\nStep 2: Make Straps Off-the-Shoulder\nFold and clip the straps down so they are off-the-shoulder. Then sew along the folds in both the front and the back to keep them in place.\nStep 3: Add Flowers\nLay your dress out in a spacious area and move the top tulle layer out of the way. Place something like a magazine, piece of cardboard or plastic under the sheer fabric to prevent sticking those layers together. Hot glue the flowers and vines onto the sheer fabric wherever you see fit!\nStep 4: All Done!\nPlace the top tulle layer down over the flowers and your dress is complete! This is such a whimsical and classy look that will surely turn heads at any event.", "316" ], [ "Thanks for checking out this tutorial and be sure to follow my Instagram for more inspo!\nInstagram: https://www.instagram.com/miairajennings\nYouTube: https://www.youtube.com/miairajenningstv\nWebsite: http://miairajennings.com\nPinterest: https://www.pinterest.com/miairajennings/\nBusiness Inquiries: <EMAIL_ADDRESS><PERSON> is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.\nStep 1: Create Skirt Attachment\nWrap the folded sheer fabric around your waist, meeting at the front of one hip. Then attach your fastener at that spot to keep the fabric in place.\nCut a layer of tulle and add it on top of the sheer layers for more dimension. You'll add the flowers on top of the sheer and underneath the tulle later on.\nStep 2: Make Straps Off-the-Shoulder\nFold and clip the straps down so they are off-the-shoulder. Then sew along the folds in both the front and the back to keep them in place.\nStep 3: Add Flowers\nLay your dress out in a spacious area and move the top tulle layer out of the way. Place something like a magazine, piece of cardboard or plastic under the sheer fabric to prevent sticking those layers together. Hot glue the flowers and vines onto the sheer fabric wherever you see fit!\nStep 4: All Done!\nPlace the top tulle layer down over the flowers and your dress is complete! This is such a whimsical and classy look that will surely turn heads at any event. Thanks for checking out this tutorial and be sure to follow my Instagram for more inspo!\nInstagram: https://www.instagram.com/miairajennings\nYouTube: https://www.youtube.com/miairajenningstv\nWebsite: http://miairajennings.com\nPinterest: https://www.pinterest.com/miairajennings/\nBusiness Inquiries: MGJmedia@gmail.com\nShop my Amazon store: https://www.amazon.com/shop/miairajenningstv", "748" ], [ "DIY Mini Dress Out of Beach Balls\nIntroduction: DIY Mini Dress Out of Beach Balls\nThis design idea bounced straight from my brain onto my dress form. I love to challenge myself to create fashion out of unconventional items, and this beach ball mini dress is definitely one of my all-time favorite creations. Enjoy!\nFull video: https://www.youtube.com/watch?v=YbrZG62cpuU&t=86s\nSupplies\nBeach balls (I got mine from the 99cents Only Store)\n* 2\" elastic\n* Sewing clips\n* Sewing pins\n* Sewing machine\n* Tissue paper\n* Iron\n* Fabric scissors\nI may receive a commission for purchases made through product affiliate links in this post.\nStep 1: Create Waistband\nWrap the elastic around your waist or the waist of your dress form and keep it in place with sewing pins.\nStep 2: Prep Beach Balls\nTo prevent the balls from deflating later on once sewn onto the waistband, iron about an inch together (opposite the blow hole side).", "316" ], [ "That way the tiny holes from the sewing machine needle would penetrate the pressed portions and the air would remain in the ball.\nIf you have any other ideas that would have been better than ironing/pressing, please share! :)\nStep 3: Create Skirt\nSlightly inflate the beach balls and attach them around the outside of the elastic waistband (blow holes at the bottom) using sewing clips.\nStep 4: Create Top\nCreate a plunging top using two beach balls and keep them in place by tucking the bottoms under the waistband.\nThen create a halter strap by cutting a strip about 2 inches wide from another beach ball and folding the edges in toward the center.\nStep 5: Sew Pieces\nPlace a sheet of tissue paper on top of the beach ball portions you're sewing to prevent the foot from sticking. Use a zigzag stitch to maintain elasticity and leave a few gaps so the waistband can still stretch. Then gently tear the tissue paper away once you've finished sewing the pieces together.\nStep 6: All Done!\nThis custom mini dress is sure to turn more heads at the beach than any bikini would. ;) Thanks for checking this out! Be sure to connect with me on IG for more.\nInstagram: https://www.instagram.com/miairajennings/\nYouTube: https://www.youtube.com/miairajenningstv\nWebsite: http://miairajennings.com\nTikTok: https://www.tiktok.com/@miairajennings\nPinterest: https://www.pinterest.com/miairajennings\nBusiness Inquiries: <EMAIL_ADDRESS>\nShop my Amazon store: https://www.amazon.com/shop/miairajenningstv", "748" ], [ "DIY Sheer Puff Sleeves Sweetheart Top (Easy Sewing!)\nIntroduction: DIY Sheer Puff Sleeves Sweetheart Top (Easy Sewing!)\nThere are so many ways to transform a basic long sleeve shirt, and I've had so much fun discovering new looks. Follow these simple steps to add classy, sheer sleeves to a plain shirt for a major style upgrade.\nFull video tutorial: https://youtu.be/TXhPXC-LtXY\nStep 1: Gather Materials\n* Sewing machine\n* Fabric scissors\n* Black sheer fabric\n* Sewing clips\n* Black elastic\n* Needle and black thread\n*Miaira is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.\nStep 2: Cut Top\nCut a straight horizontal line across the top of the shirt to create a tube top shape as the base.\nStep 3: Cut Sleeves\nFold the sheer fabric over about 10 inches and cut vertically, depending on how wide you want your sleeves to be. The length will also depend on how long your arms are. Always go a bit longer than you think, just in case! Repeat for the second sleeve.\nFold the top edges over about half an inch and clip in place. This is the casing where the shoulder elastic will be inserted later on. Repeat with the bottom edges for the wrist elastic casing, then clip the side edges.\nStep 4: Sew Sleeves\nSew along the clipped edges. Be sure to leave space at the top and bottom for the elastic casing.\nStep 5: Add Elastic\nCut two elastic strips that will comfortably fit around your shoulders. These will be inserted into the top of each sleeve. Then cut two more that will be the wrist bands.\nAdd a safety pin or paperclip to the end of the elastic strips and slip them through the openings. Then tie knots to secure them in place.\nStep 6: Attach Sleeves\nUse a needle and thread to attach the sleeves to the armpit areas of the top. Make sure the sides with the seams are at the bottom.\nStep 7: Ruche for Sweetheart Effect\nRun the needle and thread through about two inches of the center of the top, scrunching the material together in the area as you stitch.", "748" ], [ "This will create that sweetheart top shape!\nStep 8: All Done!\nYou've now turned a plain tee into a trendy piece that will add some spice to any outfit. Thanks so much for checking out this tutorial! Be sure to follow me on Instagram and subscribe to my YouTube channel for more projects.\nInstagram: https://www.instagram.com/miairajennings/\nYouTube: https://www.youtube.com/miairajenningstv\nWebsite: http://miairajennings.com\nPinterest: https://www.pinterest.com/miairajennings/\nBusiness Inquiries: <EMAIL_ADDRESS><PERSON> is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.\nStep 2: Cut Top\nCut a straight horizontal line across the top of the shirt to create a tube top shape as the base.\nStep 3: Cut Sleeves\nFold the sheer fabric over about 10 inches and cut vertically, depending on how wide you want your sleeves to be. The length will also depend on how long your arms are. Always go a bit longer than you think, just in case! Repeat for the second sleeve.\nFold the top edges over about half an inch and clip in place. This is the casing where the shoulder elastic will be inserted later on. Repeat with the bottom edges for the wrist elastic casing, then clip the side edges.\nStep 4: Sew Sleeves\nSew along the clipped edges. Be sure to leave space at the top and bottom for the elastic casing.\nStep 5: Add Elastic\nCut two elastic strips that will comfortably fit around your shoulders. These will be inserted into the top of each sleeve. Then cut two more that will be the wrist bands.\nAdd a safety pin or paperclip to the end of the elastic strips and slip them through the openings. Then tie knots to secure them in place.\nStep 6: Attach Sleeves\nUse a needle and thread to attach the sleeves to the armpit areas of the top. Make sure the sides with the seams are at the bottom.\nStep 7: Ruche for Sweetheart Effect\nRun the needle and thread through about two inches of the center of the top, scrunching the material together in the area as you stitch. This will create that sweetheart top shape!\nStep 8: All Done!", "748" ], [ "Mason Jar Halloween Lantern\nIntroduction: Mason Jar Halloween Lantern\nDo you need a spooky lantern for your Halloween decorations or a costume prop but only have a Mason jar? Well, here's one option for you: a Mason jar lantern. I think in all, it only took me a few bucks to make. I'll be using this particular lantern as part of my Halloween costume (coming soon!) but it would also look nice on a bookshelf along with other spooky decor.\nStep 1: Supplies & Tools\nSupplies:\n* Mason jar\n* Black and gray cording\n* Ring mount for cellphone\n* Battery-operated string/fairy lights with power switch\n* Halloween gauze-cloth\n* Black acrylic paint\n* Mod Podge (not pictured)\nTools:\n* Hot glue gun\n* Hot glue sticks\n* Scissors\n* Paintbrush\n* X-acto knife (not pictured)\nStep 2: Glue the Cording\nTo make it appear more lantern-like, I decided to make four \"beams\" around the Mason jar. To do that, all I did was hot glue eight 7-inch black cords, two coupled at each \"corner\" of the jar. Then I glued a 10-inch string of cord around the mouth of the jar (as you can see in the next step). Optional: carefully slice off excess dried hot glue with an X-acto knife.\nStep 3: Add the Lights\nTousle the lights and the Halloween gauze-cloth together and loosely tuck them into the jar. The gauze-cloth spaces out the lights and gives the lantern a spookier aesthetic.\nHot glue the wire discreetly between two of the \"beam\" cords, all the way to the bottom. Hot glue the power switch to the bottom of the jar as well.", "644" ], [ "I also hot glued some extra cording in a spiral on the bottom to keep the jar level.\nStep 4: Paint the Beams\nI painted a couple of coats of black acrylic paint in between the coupled black cording. After that dried, I covered it in a coat of Mod Podge.\nThen I hot glued more cording around the bottom of the jar.\nStep 5: Make the Top\nThe carrying loop I used for the lid of my Mason jar was actually a phone mount I found at the dollar store for a few dollars. It had a really strong and sticky 3M backing, so it was perfect for this project. I removed the paper backing and pressed it on the lid, holding it for about 20 seconds. Then I painted the lid and the rim black and tied a short gray carrying handle to the loop.\nStep 6: Finished!\nAfter you screw on the lid (which should be easy to do, despite the string light going outside of the jar), switch on the lights on the bottom of the jar and you're all finished. Like I said in the introduction, I'll be using this for my Halloween costume. So if you don't need to carry it around, you obviously don't need a carrying handle. But I do think it adds to the whole lantern look and feel.", "276" ], [ "Fancy Bowtie Pet Bandana\nIntroduction: Fancy Bowtie Pet Bandana\nAs a dog owner, and crazed fashion enthusiast, I love dressing my pup in cute and colorful outfits. I have found that of all the attire options out there, bandanas are the perfect way to add some flair without being bulky or uncomfortable. Today, I want to share how I make light-weight over-the-collar bandanas for every season, event, and holiday. The best part about this method is that it is completely customizable and can be done in under an hour.\nKeep reading for in-depth instructions!\nStep 1: Gather Your Materials\nFor this project you will need:\n* Card stock paper\n* Scissors\n* Ruler\n* Needle and Thread\n* Two types of fabric\n* Iron\n* Sewing Machine\n* Small rubber band\n* Rotary Cutter (optional)\n* Sewing Pins (optional)\nStep 2: Cutting and Preparing the Fabric\nTo create the stencils for this project, you will need to use scissors and a ruler to cut pieces of card stock for the bandana body and the bowtie. The dimensions for the bandana stencil are as follows:\n* Small dogs - 6.5'' X 6.5''\n* Medium Dogs - 8'' X 8''\n* Large Dogs - 12'' X 12''\nFor the bowtie, cut a 9'' X 5'' and a 1\" X 3\" rectangle out of card stock.\nUse these stencils to cut the appropriate pieces of fabric. For my bandana, I decided to use a patterned fabric for the base and a solid color for the bowtie. However, you can choose whatever fabric combination you like.\nStep 3: Ironing the Fabric\nFor the bandana part of the project, place the right-side of the fabric face down and measure 1.5'' corner sections for two opposing corners. Fold these two corners down, as shown in the image above, and iron to help them stay in position. For the larger piece of bowtie fabric, fold hot dog style, then iron. For the smaller piece, fold both sides into the center, then iron.\nStep 4: Sewing the Bandana\nUse a topstitch with a 1/4'' seam allowance to secure the corners you folded down in the previous step. Repeat this process for both corners, making sure to backstitch at the beginning and end of each run to ensure the stitch holds.\nOnce complete, flip the fabric around, with the right-side facing down, and fold it over hamburger style so the two unfolded corners touch.", "316" ], [ "Refer to the second image above for reference. Iron down the fabric once again, before proceeding to the next step.\nStep 5: Sewing the Bandana: Part 2\nOnce the fabric is ironed, topstitch or zigzag stitch around the perimeter with a 1/4'' seam allowance. When doing this, make sure to start and stop and the ends of each of the folded corners - refer to the images above for reference. This will create an opening for a pet collar to pass through.\nOnce you have completed sewing, flip the fabric inside out and iron.\nStep 6: Sewing the Bowtie\nUse a topstitch to sew the open edge of the folded piece of fabric. Once completed, inside out the tube and iron.\nFold the right-side out tube into the center, making sure to allow a little overlap between the pieces. Use a topstitch to sew down the overlap, as shown in the fourth image.\nStep 7: Sewing the Bowtie: Part 2\nFold the bowtie piece accordion style, and secure with the small rubber band - refer to image 1 for guidance. Once complete, take the smaller piece of fabric with the right-side down and fold over where the rubber band is located. Use the sewing machine to sew down this piece of fabric, and cut off excess fabric with scissors. The final product should look similar to image 3.\nAfter this is complete, inside out the smaller piece of fabric, so it forms an even loop. Refer to image 4 for guidance.\nStep 8: Joining the Bowtie to the Bandana\nUse a needle and thread to attach the bowtie to the bandana.\nStep 9: Congratulations! You're Finished\nCongratulations! Your bandana is ready to take the pet fashion industry by storm.\nIf you liked this project, leave me a vote and heart.\nIf you tried this project or have a suggestion, leave me a comment. I would love to hear your thoughts.", "748" ], [ "Upcycled Skirt\nIntroduction: Upcycled Skirt\nA great way to reduce your impact and avoid fast fashion is to modify your unwanted/damaged clothes into something you will actually wear.\nThis is a simple way to turn a dress into a wearable skirt!\nYou will need:\n* Old/unused dress\n* Sewing machine\n* Quick-unpick\n* Elastic\n* Pins\nStep 1: Unpick at the Seam\nUsing a quick unpick, separate the top and bottom of the dress by unpicking the seam (if there isn't a seam you can use fabric scissors to cut it)\nStep 2: Remove Stray Thread\nRemove any leftover thread by pulling it out or cutting it off.\nStep 3: Neaten the Edges\nNeaten the unpicked edge using a zig zag stitch. Try to sew as close to the edge as you can.\nStep 4: Making the Skirt\nTurn the skirt inside out\nStep 5: Measuring the Length of the Fold\nPlace the elastic across the top of the skirt, leaving a 1cm gap above.", "316" ], [ "Mark the bottom of the elastic with a pin.\nFold the top of the skirt over the pin. Pin it in place.\nStep 6: Sewing the Waist Band\nSew along the edge of the fold, around most of the waist band. Make sure to leave a gap at the end.\nStep 7: Inserting the Elastic\nCut the elastic the length of the waist band\nPlace a safety pin on one end of the elastic.\nUse the safety pin to push the elastic through the gap, into the waist band.\nStep 8: Pushing the Elastic Through\nPull the elastic through the waist band by scrunching the fabric along it and then straightening it out\nDo this until it comes out the other side of the gap\nStep 9: Close the Gap\nFold both ends of the elastic into the gap.\nSew underneath the elastic to close the gap.\nRearrange the fabric around the elastic to make sure it fits the way you want.\nSew a line, vertically down the fabric where the two ends overlap, to hold the elastic in place.\nStep 10: Finished Skirt\nYou now have a finished skirt, ready to wear!", "748" ] ]

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[ [ "Please check out my other reviews at:\nhttp://www.boardgamegeek.com/geeklist/145695/item/3052753#it...\nConclusion:\nI am not a huge fan of Star Trek. I've never seen the show and I've only seen the new movies. Yet, the universe is very popular and it seems to be a very good show. I do like games with a known universe/property as it gives an easy reference point. This nails it with the theme. The game has so much theme and it comes shining through.\nThe ships look fantastic and really draw you into the game. It is fun to have all the ships from the shows bouncing around. In this game, it is the Federation, peace keepers, against the Klingons, warmongers. Both sides play differently and if you want to win you have to play to your strengths.\nDespite the cover of the box, this is not a combat heavy game. Instead, this is a game about exploration. The Klingons will want to fight much more than the Federation. Through out the game, you have missions you are trying to accomplish so it is not a last man standing sort of combat game.\nI like how the game plays differently for both sides. I like that it is not just about combat and rolling dice for results. The game has a lot of variety as the board is modular and different every time you set it up. The ships are different each game and there is a lot of different combinations. In addition, there are a ton of cards in the box and only a fraction are used in any single game.\nI can't explain how much I like this game. It doesn't fall into the same traps that a lot of two player games fall into (tug of war, etc). Instead, it provides a unique and fun atmosphere/game where you really feel like you are exploring the Star Trek Universe.\nKeeper.\nComponents:\nThe components are a mixed bag. There has been a lot of discussion about the components, but this is going to be just my opinion.\nI find some of the components to be very, very good. Others are dreadful.\nThe tiles that make up the modular board are paper thin. Possibly, the thinnest I've ever seen.", "304" ], [ "Paper thin. The art work on the tiles, the organization, the font are all great.\nThe cards, and there are a lot, are fine. I like the art work which is stills from the different shows.\nThe ships. The ships are the star of this show. There are so many ships from the shows. You get to mix and match which ones you use and it is so much fun. The \"hero clix\" ships are fantastic and I've had zero issues with them.\nThis is possibly the most polarizing components I've seen in any game. Some are top notch, others are bad for a print and play. I still recommend the game as you can work with what is in the box.\nRule Book:\nThe rule book is good, not great. You need to digest it before you get to the table. I wish the game had a player aid to use when playing and this is a huge miss.\nThe rules are longer than they need to be. This book needed an \"overview\" section of the rules and then a section that goes into more detail. This was missing and it was felt.\nOther than these few complaints, the rules are very good and you can be up and running after a single run through. There are some rules, like cloaking, that need a little more attention.\nFlow of the Game:\nI will not explain the rules of the game, instead I will attempt to explain the flow of the game.\nOn your turn, you will move around the galaxy. Each ship has a movement score. It is one movement point to move to an adjacent tile and all the tiles have a size on them (which represents how many movement points it requires to move through it).\nAdditionally, you can play command cards with can add crew to your ships or \"break the rules\" in general. This is not a new mechanic. If you use a card, you draw a card.\nYou can also take three actions. Actions can include: fighting enemy ships, scan nearby locations (peaking under a tile to see what is there), cloak your ships (two chits enter the board, one is a decoy), repair your ship, influence locations (build colonies, etc), complete missions.\nThese missions are the main way you score VP (10 VP wins the game). Some of these missions are secret and the majority are known by you and your opponent. As you accomplish these missions, you use an action to play the card or do a system check.\nAs a snapshot, you move around the board finding locations while accomplishing missions.", "629" ], [ "Please check out my other reviews at:\nhttp://www.boardgamegeek.com/geeklist/145695/the-purge-revie...\nConclusion:\nMy first few plays I liked the game. I think I now love it. The game continues to get better the quicker it plays. When I play this game, the minutes fly by.\nI played the first video game for about two hours and never played it again. I wouldn't call myself a fan of the video game at all. Yet, I find the board game a ton of fun and very thematic. I really feel like I'm a grunt and trying to survive. Every decision is hard and it does require luck to win.\nThe difficulty of this game is hard. It is a big challenge to win. You need to keep your guys together and also try to run to accomplish the mission. It is so much fun to challenge yourself to fight the bad guys and also run. It is easy to leave a man behind, but then you are not at full speed.\nThe components are fantastic and really shine through. Each mission has three bad guys, which is enough but of course you always want more. I really want a big expansion for this game!\nThere are really hard decision as your cards reflect the things you can do and also your health. So, if you spend a card to shoot, you tire yourself out and bring yourself closer to \"bleeding out\". Whew!\nThe board is modular so it plays different each time, even if you play the same mission (there are a few missions included in the box). I have to admit this game is hard. When you do win, you will celebrate.\nThe game has a ton of action and sit on the edge of your seat adventure. It is hard to get wrapped up in a game, but this game has the minutes melting away. As my men start to bleed out, you hope they can crawl to you quick enough. The game is a constant battle.\nFor a dungeon crawl, this game has it all. It has a fun theme, lots of action, great components, and fun. Yes, it is actually fun to play.\nI highly recommend this game and it is a keeper.\nComponents:\nThe components in the box are the usual Fantasy Flight Games high quality components we are used to. The cards are going to last you for a long time and are easy to shuffle. The tiles and chits are the highest quality of cardboard.", "304" ], [ "The miniatures are fantastic. The player character minis are a tad hard to decipher from one another. My copy is painted, so that makes the job much easier.\nEverything in this box is beautiful. There is very little to complain about. The board is modular and grows as you explore. Based on the components alone, this is a must buy.\nRule Book:\nThe rule book is very good. I had zero problems with it. I have some minor complaints, but I will get to them. The book is comprised of a full color layout and gives many examples. The book provides instructions with pictures for nearly everything you do in the game. The book is organized well, but the large pictures sometimes interrupt the flow of the rules. This is a minor quibble.\nI wish gamers had been supplied with player aides for the game, but honestly despite the size of the rule book the rules are rather simple.\nI hold this rule book in the highest regard. You can read it once or twice and then jump into a game and start playing. An index would help the first few games flow better.\nFlow of the Game:\nI will not explain the rules, instead I hope to explain the flow of the game.\nYou are trying to accomplish a mission. Usually this means running through the map and killing a bad guy. Other times, it might be doubling back and getting to the \"finish line\".\nOn your turn, you draw 1-2 cards and then play a card. Cards allow you to move, attack, draw more cards, etc. The idea is these cards represent your health/stamina. If you run out of cards you then \"bleed out\". If you bleed out, you can no longer play cards nor draw cards until someone comes to your aid (discards a card in your same area).\nEach character has a special power which can be used whenever applicable.\nAfter playing a card, the bad guys then go. There is a deck of cards and you turn over the top card and do what it says.\nThese cards will move the bad guys, spawn new bad guys, and/or attack with the bad guys. You can play cards from your hand to attack them first or add to the number of your defense die (remember playing cards decreases your health/stamina so do so wisely). Everything is a hard choice.\nPlayer turn:\n1. Draw cards\n2. Play cards\n3.", "629" ], [ "Please check out my other reviews at:\nhttp://www.boardgamegeek.com/geeklist/145695/item/2728438#it...\nConclusion:\nAlien Uprising was a game I had never heard of when I bought it and sat down to play it. What intrigued me was the ability to play cooperatively and/or solo. Boy, was I in for a surprise! What I ended up finding was one of my favorite games I've ever played. I've played this game a lot since acquiring it and have loved every minute of it.\nFirst, this game is hard. It is hard to win and complex to understand. At its core, the game is easy (see below under Flow of the Game). It is all the little rules and a not perfect rule book that gets in the way. Honestly, like Arkham Horror, this is a game you can tweak the rules to in order to get the difficulty just right.\nThis game is dripping in theme. You can purchase miniatures and really make this game look great, but honestly the tiles are nearly perfect and work very well. I prefer the tiles at this point.\nThe game can be taught in minutes and you just figure out the smaller rules as the game progresses. While the game is a little complex, it is nothing that can't be taught in one siting. There have been quite a few questions online about the rules, but I found that if I just sat down and used common sense everything made sense.\nThis isn't a \"perfect\" Euro experience. Instead, we get a \"Castle Panic\" sort of game with a lot more rules, nastier alien/dinos, and a fantastic game. The game has interesting mechanics, most of which we have seen before, but puts it all in one very good package that will keep you wanting to play this game.\nI like the action die mechanic (think War of the Ring) and the unique characters who all play differently. Each character feels different and must be played to their strength if you want to beat this game. This might leave a feeling of doing the same thing over and over, but the different action dice will leave you with a lot of planning to do as a group.\nThere is luck in this game as you will roll dice to conquer the aliens and to accomplish things (ex: building shields). Yet, it all seems to balance out.\nI highly recommend this game. The biggest flaw might be the time required to play it. It can be a long game. It reminds me a lot of Arkham Horror, Castle Panic, and a good Ameritrash cooperative game.\nKeeper.\nComponents:\nThe bits are top notch and there are a lot in the box.", "386" ], [ "You get player mats for the characters and each character gets a unique of cards (they are small). All the tokens and chits are made of very thick cardboard. The characters are represented by tiles on the board (minis are included), but I felt the tiles worked great.\nI did have some issues with the board. I wish the green lines were brighter and more noticeable. It was hard to see it until I got used to the board. The board did have a nice theme to it and it looked great otherwise.\nThe aliens were represented by chits which worked as they needed to be two sided. I think a player aid with more information on it would have been helpful (a turn over view, alien powers, etc).\nAny complaints I have are nit picking and the components are really top notch. Great job!\nRule Book:\nThis a fairly complex game. Wait. No, it is not that complex. The game is pretty basic, but it has a few layers on top of it and a lot of moving parts. Think Arkham Horror (although this does not play like Arkham).\nThe rule could be organized better and perhaps be a little clearer. It helped that I had played Castle Panic (and Dead Panic) before so I was able to sort the game out. The book could be better. I also do not think it is as bad as some are making it out to be. I assume if I can figure the game out, it can't be all that bad. With that said, <PERSON> is not going to pull this off the shelf of Wal Mart and sit down and play this game.\nFlow of the Game:\nI am only explaining the flow of the game, not all the rules.\nThe board is made up of 4 sectors (each side of the board) and three levels inside those sectors. So, Sector 1 has A, B, C as does 2,3,4 (sectors). The aliens are trying to move towards the center of the board to get to your ship thus keeping you from leaving (think Castle Panic). You are a team of \"space marines\" trying to either wait for the rescue ship or to fix your ship so you can leave.", "386" ], [ "Please check out my other reviews at:\nhttp://www.boardgamegeek.com/geeklist/145695/item/2791786#it...\nConclusion:\nWhen this game is described to you (or at least to me) it sounds awful. You immediately think of Stratego and sigh. Why did they have to ruin a Lord of the Rings game. This is one of the most beloved books and movies of all time. Why oh why?\nYet, once you start playing the game you noticed that you judged it unfairly. That perhaps you judged the book by the cover and maybe you should not have. Why oh why did you judge this game so unfairly? You are actually having fun playing this. And this is Lord of the Rings: The Confrontation (Deluxe Edition).\nThe game is rather simple. The only complexity comes from learning the individual powers (listed on the cards and they are simple). Strategy comes next. I might get flamed for this, but, like a game of Chess, this game is a thinker.\nI haven't played the other versions, but this game is very nice to look at and I actually like the art work. The art work is unique and not from the movie license. The reason why this game has a following is the mix of easy to play with deep strategy; the game has risk that you can take and the payoff of a reward.\nOne player plays the light side and one the dark side. It is fun to try and get the fellowship into Mount Doom, while <PERSON> and his crew try to reach the Shire. The movement rules are easy to learn and the fighting is fun. The fighting does come down to card play, bidding, and a lot of bluffing. The fighting is not all luck; you have to watch what cards have been played and the better you know your opponent the more likely you are to win.\nEach character has a unique power that makes sense for the character. It is fun to play a game as the light side and the next game as the dark side. This game likely won't be the main event, but it is a game that you can start playing and find a night has \"wasted\" away and you had a ton of fun.\nThis is a keeper. I particularly like the Deluxe Edition as it has a variant and extra characters (not sure if other editions have these options also).", "366" ], [ "While not a favorite game of mine, it is a game that I can back to over and over. It plays two players (only!), but it plays fast. I highly recommend this game.\nComponents:\nThe components in the box are top notch. While this is not your usual tricked out edition, every thing in the box is very nicely down.\nI will start with the board. The board folds out and shows a map that is the setting of the Lord of the Rings. While not exactly accurate to the maps from the book, things are listed well enough for an abstract version of The Lord of the Rings. The colors used are muted to not take away from the action, but the different areas on the board are easy to see.\nThe bidding cards (for fighting) are good quality. They are large and the art work is great. The characters are represented by plastic holders that have the character cards inserted so you can only see it from one side (your opponent cannot see who is who). They are hard plastic and look very nice. The art work of all the characters are nice, but the font might be on the small side (but not hard to read). Everything in the box is good quality and you will be happy. Just don't expect the super primo pimped out edition.\nRule Book:\nThis is a Fantasy Flight Game (FFG) so you get the big oversized rule book. It is full color and full of pictures and examples. The art work on the front (same as on the box) is fantastic.\nI found this rule book to be wonderful and one of the best from FFG. It is simple to learn this game and the rule book is great at teaching it. There are a lot of examples in the book. There is the regular game and a variant that is explained (it uses another set of cards). The rule book explains all the cards and it is very helpful when you have questions.\nThere are also two Player Reference Sheets (one for each player) that describe all the cards and how they work.\nThe problem with the rule book and Player Reference Sheets (PRS) are they are so big. The PRS is way too big for to be useful on a table. Okay, it is very useful, but a smaller one would be useful and wouldn't take up so much valuable table room.\nFlow of the Game:\nEach player chooses a side: light or dark; good or bad.", "336" ], [ "Please check out my other reviews at:\nhttp://www.boardgamegeek.com/geeklist/145695/the-purge-revie...\nConclusion:\nConcordia plays like a throwback to Euro games. Lots of wooden bits, a tad abstract yet with a theme, and plays in about 1.5 hours. The game is meaty without being overwhelming. On any given turn, you have one decision (which card to play), but you have to plan ahead to accomplish your move.\nThere are a few ways to score and while you can do a little of everything, by specializing you can use the modifiers to your advantage. Sometimes this will be a plan coming together, other times you will have to think on your feet.\nThe biggest flaw of the game is the scoring. It is tough to explain to new players and there is a lot of it. Once you master it, it all plays perfectly with the game. I feel you need to commit to the game for a couple of plays. Also, the intermediate scoring rule is a must for the first game (this allows all players to score during the game one additional time early in the game to get the hang of it).\nOverall, I liked the use of a single card per round to keep down time to a minimum. This really kept the game moving. This is a game that could have been bogged down with AP. Instead, the rounds fly by.\nAlso, the decisions you make really feel they impacted the end game scoring. You are trying to out think and maneuver your opponents. You can build houses or expand out, get more people, get more land, get more cards, etc.\nThis game is currently a keeper. After playing it, I was ready for a lighter game as it can be taxing. While not the deepest game on the market, it is a thinker and theme is pasted on.\nComponents:\nThe components are top notch. While the art in the game is limited, the quality of the components is great. The wooden meeples/ships are solid as are the wooden houses. The board is colorful, easy to read, and double sided. The cards feel great in your hands and will last for a long time. The text is big and easy to read. I had zero complaints about the cards or any of the components.\nEverything is made to last and easy to use. This is a good example of a \"classic\" Euro game.\nRule Book:\nThe rule book led me to believe I was missing something, but I was not. The game is that easy to learn.", "336" ], [ "I wish the player aids were better. Instead of a small card with limited text, I wish it included a player aid with more details on final scoring.\nThe explanation of all the cards was fantastic. The rules are pretty easy: play one card and do what it says. Scoring is the beast here and I wish the examples were more plentiful.\nOverall, I'm happy with the rule book. You can literally start playing within minutes and use the \"intermediate scoring\" to quickly get a handle on scoring.\nFlow of the Game:\nThe flow of the game is rather simple, yet your decisions are important.\nAll players start with the exact same cards. The cards allow you to get other cards, build cities, move armies (abstracted; there is no war in this game), sell/buy items at the market.\nOn your turn, you play one card and do what it says (see above). That's it.\nI'll explain a few things that you can do, but this is not a recitation of the rules.\n1. There is a set of cards you can purchase and add to your hand. These cards cost goods. They allow you to do actions (like the cards that start in your hand) and also have multipliers for end of game scoring. These cards will increase your end of game score by a lot. Sometimes your decision is do you buy a card that will help you get \"things\" you need now or that will help end of game scoring. This is something you must balance.\n2. You can move your armies/ships around the board. This will allow you to build houses. By building houses you will score end of game scoring and to obtain goods.\n3. You can buy and sell goods at the market. You have a warehouse that can hold a finite amount of goods. You cannot just ditch goods you don't need/want, so you have to sell them. Money is going to be tight in this game.\n4. You add additional armies/ships to the board. This helps you get around the board to build more houses. Building these houses can increase the amount of goods you can get and scoring at end of game. The number of people you have on the board also scores end of game points.\n5. You can get more goods.", "629" ], [ "Please check out my other reviews at:\nhttp://www.boardgamegeek.com/geeklist/145695/item/2728438#it...\nConclusion:\nIf you have read these reviews before, you know that a good racing game is something I've been searching for. I've been harsh on the genre before and for good reason: most of the games have a lazy design and don't really make you feel like you are racing. Thunder Alley uses the drafting mechanic to near perfection. It brings NASCAR alive. You do not want to be off on your own in this game. You will move your own team and also the cars of other players due to the drafting mechanic. This is fantastic.\nThunder Alley looks great on the table despite all the cardboard. It is a brillant design. There is luck involved in which cards you get, but the game is more about using your cards to the best of your ability. The game removes dice from movement which is an intersting decision. So many racing games rely upon the dice movement. I find that after all this time it is a lazy mechanic to rely upon.\nThunder Alley is at its heart a very simple game. You play cards to move. You have just a few options in front of you with your card play. Yet, I feel like I get better at the game with more plays. The game doesn't take too long but it can be set up for a season or a longer play with more laps.\nThe truth is I just have fun playing this game. I get the feeling of speed. I try to attach to cars that haven't moved yet so I can move more than once. You don't want to get stuck in the back and not be connected and you don't want to be out front by yourself watching people pass you by. You will make alliances and break alliances throughout this game. There is a huge strategy in when to pit. Luck also exist in the random events that occur. This brings a different level to the game, but can be taken out if desired (although I've never done it).\nOverall, this is the best racing game on the market. I've yet to play Formula D(e) so I can't comment on that game yet. I love the drafting mechanic and how others have to pull (push) you along. Fun stuff!\nKeeper.\nComponents:\nThe components are your classic GMT components. You get a lot of little chits.", "885" ], [ "A lot. And some are very small. You can see the pictures here to see what they look like. The cars are double sided to easily see which ones have been moved. The player mats are not thick cardboard, but get the job done. The cards are high quality and I love the graphic design on them. Good job on the cards! This game pops in an interesting way. It isn't full of plastic, but it is easy to use the components and they still pop in a cardboard sort of way.\nThe game comes with 4 different maps which is a huge plus. This gives you different experiences.\nRule Book:\nThe rules are presented in classic GMT fashion. They are printed in \"war game\" fashion with the rules showcased like: 4.3 Losing a Car - see rule 2.54. The rules show a lot of black and white, but does have some pictures which are in full color. The rules are very wordy, but orgainzed well. Some of the rules are a little tricky at times. There is a misprint in regards to drafting, but it can be easily figured out. The rules include a description of every card for clearification. Overall, I'm happy with a rule set like this, but they can be very boring to read. It fees like you are reading instructions to an IKEA bookshelf.\nFlow of the Game:\nThe goal of the game is to get your cars across the finish line. You have a team of cars and you will get X VP based on what place each of your cars come in. Most VP wins the game.\nA turn in the game is represented by everyone moving all of the cars. This is in contrast to a single player round where the player will play a single card and move a single car as the \"first mover\".\nTurn:\n1. Draw Cards - You draw up to the number of cars you have left +1\n2. Perform Actions -\nA. Choose a car that has not yet moved\nB. Play a card and move the car (and perhaps others) per the directions on the card; this may put wear on the car per the usage on the card\n3. End of Turn -\nA. The car in the lead gets a turn leader marker which is worth VP at the end of the game\nB. Draw and perfrom an Event Card - This could be rain, a crash, nothing, some players get wear on their car, etc.", "629" ], [ "Please check out my Geeklist at:\nhttps://boardgamegeek.com/geeklist/145695/purge-reviews-reco...\nMy video reviews can be found here:\nwww.youtube.com/purgereviewsboardgames\nConclusion:\nLong Shot was my favorite horse racing game and one of my go to party games. It accommodates a lot of players and everyone understands the concept of horse racing. It was and is an easy sell so when the Dice Version was released promising to be smaller, quicker, and just as good I have to admit I was intrigued.\nLong Shot the Dice Game improves on the original in almost every way. I will list a few pros and cons to this game:\n1. The game is short. It usually takes about 30 minutes to play the game. It doesn't over stay its welcome and plays in about the perfect amount of time. The original was more like 60-90 minutes so this is an improvement but you will need another game to play on the same night where the original was a game to center the night around.\n2. While I really like the look of the game, the original is larger and fills up a table better. A lot of people are going to like the compact nature of this game, but it is a tad small for 8 people. I may be in the minority, but I would like a Jumbo version of this game. Larger cards, bigger horses, etc.\n3. The game is easy to teach. You roll some dice and everything works off the dice. People understand instantly the roll and move mechanic and betting on the horses. It takes just a couple of minutes to teach the game and most people will be able to play without any questions.\n4. The game is full of luck. That's the game. It is all about profiting off that luck and pressing your luck to generate more and more cash. The horses are going to move on their own, but you can start to add marks to the horse to influence the horses you want to move. I guess that is the best way to comment on it: you are trying to influence the horses and the outcome. Some people are going to like this and others hate it.\nOverall, I have to admit I love this game.", "581" ], [ "I've been playing the solo game over and over trying to beat that <PERSON> character. I've played this with a lot of different player counts and it does a good job of keeping you invested when it isn't your turn. The game mitigates this by letting you take an action on other players turns. That's a great fix.\nI can highly recommend this game for people who want a horse racing game and like to have fun. This is a dice rolling, horse betting, take out your opponents good time and one I'm willing to play anytime.\nKeeper.\nComponents:\nThe components are top notch for a roll and write and a light filler. The horses are silk screened on both sides and fit the smaller board perfectly. The dice are a tad on the cheaper side, but they do get the job done. You get plenty of dry erase markers which are pretty standard for this sort of game. Everything has a great look to it and I like the choice of sillier art work. The package is very, very good for the price point.\nRule Book:\nThe rule book takes about 15 minutes to read. The rules are full of color and has plenty of pictures and examples. This is a very easy to read rule book and everything seems to flow perfectly as you read through the rules. The book is easy to digest and to use as a reference while playing.\nFlow of the Game:\nThis is a horse racing game. The race is over when 3 horses finish the race. Each horses is awarded a place (1st, 2nd, 3rd).\nPlayer Turn:\n1. Roll both dice\n2. One die is the horse to move; the other die is how many spaces to move (1-3 spaces); then move all the horses listed on the card 1 space only\n3. Then, each player takes an action in turn order based on the die identifying the horse:\na. Bet on the horse rolled\nb. There is a chart where if you finish a line you get money, free bets, move the horses, etc\nc. Add a helmet - this allows you to bet after the horse crosses the no more bets line\nd. Add a jersey - this allows you to mark for another horse to move when this horse is activated\ne. Purchase a horse (each horse as a power that is activated when the number is rolled)\nYou score points if a horse you own places, each helmet/jersey combo is worth 5 points, gain money for bets plus any money left over.\nMost points/money is the winner of the game.\nShould I buy this game?", "629" ], [ "I call this a war/strategy game because I feel it is a war game first, strategy game second. This game is designed to start off fighting and not to let up until you lose or win. The strategy plays itself out with careful order placement and combat decisions. To me, the battle is 100% of the fun!\nI want to first say that I really have enjoyed this game and I think after many plays, I can give a pretty good review of the game. I have played 3 two player, 2 three player, 3 four player, and 1 five player game.\nStarCraft The board game is a very dynamic and highly active and interactive game. As many know it is based off of the computer game, and even though it is similar, it is a very different game. SCBG has all the units and technology that you would find in the PC game (except infected marines) and wraps them up nicely into a great packaged game. The game also introduces to me a very good combat system that uses combat cards instead of dice. I was very skeptical at first, but after many games I have begun to think that this is the core to the game and without it, the game would not be as good.\nSCBG also uses a unique order placement that does a good job at simulating real time to match the game play of the PC. You can win or lose over some poor planning.\nCOMPONENTS:\nSCBG is comprised of tons of plastic and cardboard pieces that are high in detail and looks. The planets are of the same quality as the bits in Arkham horror. Very nice and sturdy. Here are a few hints to make your game look even better.\n1. Use a hair dryer to straighten out warped game pieces. I here of the hot/cold water method, and I for one do not like that. I used my wife’s dryer, heated them up and held them in the position that I felt looked good. Blew on them to cool them off and WHAM… they look as good as they did off of the assembly line.\n2. For the planets: we had troubles early on getting the planets connected with all the connectors. You can tell the sides of the planets that go the same; the actual texture is different on both sides. If you have both planets laid out with the same texture and with the same texture as the connectors, they go together like a glove. It takes a second to match it up, but will help preserve the planets longer.\nThe cards are also a big plus. They are perfect in size and have great art work on them. Just as you would expect from a FF game!\nThe rule book again, like many FF games it tough to handle.", "336" ], [ "I know they try to organize it and this time they put in tons of examples and side notes to point out them one sentence rules that people miss. But I think this time there may be too much. A lot of back and fourth from page to page to iron out any rule in question. I feel the game book is complete, however it is scattered.\nThe Races:\nSTBG has three unique races; Zerg, Terran, and the Protos.\nZerg: The zerg is the race that early on is a numbers game. In the PC game you win by the swarm, in the BG you win by the swarm. You have to outnumber your opponent to get kills. Their zergling units are weak in attack and defense, and you need a 2-1 advantage over the basic units of the other races to have a chance to kill them. The good thing is the zerg has the highest unit count to counter this. They have 9 zergling and 6 hyrdalisks. Way more than the other three races basic units. The Zerg also have some pretty unique techs that with some cleaver unit placement and the right cards, can take on some heavy hitters with some lesser units. Later in the games you can gain the ultralisks and the deadly guardians. With these units you can hang into the nastiest of fights. The Zerg is a formidable opponent.\nTerran: The back bone of the Terran army is the very versatile marine. They can attack both ground and air units that can give them the edge in any battle. They also are very flexible. They can hold more combat/tech cards than the other races which give them the edge heading into combat. They also have the ability to move their base to other friendly areas on the same planet. This could be the key to a successful win or loss. The rest of the terran forces are just as strong. Many of their units have splash damage, which means they have the capabilities to kill more units at the end of battle. Fewer units and more kills are very tough to beat. The tech the terran get as well can really boost them in a fight. Their clocking field for the basic air unit is a must.", "237" ] ]

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[ [ "MQTT Swimming Pool Temperature Monitor\nIntroduction: MQTT Swimming Pool Temperature Monitor\nThis project is a companion to my other Home Automation projects Smart Data- Logging Geyser Controller and Multi-purpose-Room-Lighting and Appliance Controller .\nIt is a pool side mounted monitor that measures the pool water temperature, ambient air temperature and barometric pressure. It then displays the pool water temperature on a local LED bargraph and transmits via WiFi/MQTT to a home system - in my case a software upgraded MQTT compatible version of the Lighting Controller. although it is easy to integrate it into any MQTT compatible Home system.\nThis Instructable focusses on the Pool Monitor design and construction, the upgrade of the Controller (new firmware and addition of an OLED display) will be included in the original controller shortly.\nKey features include:\n* The absence of poolside mains electricity determines a 18650 battery power supply with an integrated 1W solar polar panel to maintain the battery charge, battery life is further optimised by the use of the ESP8266 \"Deep Sleep\" mode. In my system, the unit was able to run over our \"active swimming pool season\" (November through to April) without manual intervention of manual top up charge.\n* An optional local built in 8 LED bargraph displaying the pool temperature in 1 degree intervals.\n* MQTT data transmission via local WiFi connection to any compatible host system.\n* All programming is achieved over WiFi using the Monitor as an Access Point and internal Web Server configuration pages with all programmable parameters being stored in internal EEPROM.\n+ Time intervals between wake up and transmissions. 1 to 60 minute intervals.\n+ Configurable MQTT topic/message formats\no Individual message topics (E.g PoolTemp, AirTemp, BaroPress)\no Single compact topic (E.g. Pool Temp + Air Temp + Barometric pressure)\no Compatible with OLED display mounted on Multi-purpose-Room-Lighting and Appliance Controller (see title figure for example)\n* WiFi network SSID and password\n* Access Point SSID and password\n* LED bargraph control\n* Programable minimum temperature range (15 to 25'C)\n* Programmable permanently ON, permanently OFF, Only on during daylight hours\nAlthough I 3D printed my own enclosure / mounting arrangement and used a PCB board from a previous project, you can literally use what suits your personal preferences as nothing is critical or \"cast in stone\". The last section of this Instructable contains Gerber and STL Files for the PCB boards and ABS housing that I designed specifically for this project\nStep 1: Block Diagram and Discussion About the Choice of Components\nThe block diagram above highlights the main hardware modules of the Pool Monitor.\nProcessor\nThe ESP8266 used can be any of the ESP03/07/12 basic modules through to the more perfboard friendly NodeMCU and WEMOS modules.\nI used the ESP-12, If your pool is some distance from your WiFi router you may prefer the ESP-07 with an external antenna.", "382" ], [ "The NodeMCU/Wemos modules are very board friendly but will result in a slight increased power consumption due to their extra onboard voltage regulator and LEDS - this will affect the ability of the solar panel to daily keep the battery in charge and you may require a periodic manual charge using the USB port on the charger module.\nTemperature sensors - Fig. 2\nI have used the easily available and low cost metal tube + cable versions of the DS18B20 temperature sensors that come with around 1 metre of connecting cable as they are already robust and weatherproof. One using the full length of the cable for the pool water measurement and another with a shortened cable for the ambient air temperature.\nAir ambient sensor\nI have selected the excellent BME280 module to measure the ambient air humidity and barometric pressure. You may be wondering why I did not used the air temperature measurement function of this module.\nThe reason is simple - if, as I did in the original prototype use this function, you end up measuring the static air temperature INSIDE the housing which tends to read high due to internal self heating of the enclosure air space by the outside sun (it reads perfectly at night!). It was quickly realised that the air temperature sensor needed to be mounted outside of the enclosure but in the shade away from the direct sun light so I switched to a second DS18B20 and provided a small mounting point underneath the enclosure. The BME280 temp sensor although is still used as a diagnostic measurement for the in-enclosure temperature and can be monitored on the configuration server main page.\nLED bargraph - Fig. 1\nThe eight local high intensity LED outputs are driven by a PCF8574 IO expander chip which in turns drives each LED by a PNP 2N3906 transistor.", "832" ], [ "Piano Metronome\nIntroduction: Piano Metronome\nThis project was conceived of after I examined the types and styles of various off-the-shelf Metronomes. I am currently learning to play the piano and having a Metronome in order to keep time was necessary. I felt sure that I could build one based on a standard Arduino Uno R3 board. The resultant Metronome has a combined light and sound feature which can be customized to reflect the tempo of the beat. While V1 of the project is complete a V2 is being considered based on some new features such as adding a 18650 Battery shield to allow charging of the batteries via a USB charging cable. I added a simple time display feature in this version, however a future version could include the time in providing a fixed number of beats option.\nSupplies\n1. Arduino UNO R3 card and DC Plug, terminal type\n2. DS1302 Real Time Clock plus 2032 button battery\n3. Two pole switch, coloured wires, PCB female plugs, heatshrink, PCB board, 3mm plastic supports\n4. LED plus 330ohm resistor\n5. PAM8403 Digital Amplifer 3W\n6. Digital Rotary Encoder with central push button\n7. 8 Ohm 1W speaker\n8. 20 X 4 line LCD screen using IC2 communications\n9. 50x90x150mm project box\n10. 4 x Neopixel RGB common anode LEDs\n11.", "485" ], [ "2 x Adjustment push on control knobs.\n12. 2 * 18650 batteries and twin battery holder\n13. two pole switch.\n14. a quantity of plastic M3 20mm board supports and 5mm screws\n15. Blank PCB board, 20mm x 50mm approx.\nStep 1: CONSTRUCTION\nI freely accept that getting all of the above components into a 50x90x150mm project box is not easy and a larger project would have made things easier. However as the completed project shows it is possible. While I have not shown it, I recommend constructing the circuit on a suitable breadboard and testing its operation with the downloaded software. Construction starts with four equally spaced 8mm holes drilled into the top of the project box, to allow the four LED lights to be located there. Additionally, two 5mm holes are drilled on the face plate for the rotary encoder and Amp Volume control, a single 5mm hole is drilled in the center of project box’s side to allow access to the speaker, finally a single 12mm hole is drilled on the side of the project box to allow the Off/On circular two-pole switch to be installed.\nUsing a jigsaw and file a 96mm by 40mm square opening is made in the front panel to allow the 4x20 display to be inserted into the opening. It will also be necessary to drill 10 * 3mm holes in the front (4) and back panels (6) of the project box to allow for the M3 screws. The Arduino UNO R3 is wired to its components as laid out in the attached Fritzing circuit diagram.\nThe faceplate logo print, see attached PDF, is printed cut to shape and attached to the front panel of the project box. The IC2 controller is soldered to the 20x4 LCD screen and this screen is then attached to the front panel, after being inserted into the square cutout and fastened using 4 x M3 screws.\nThe two-pole switch is inserted through the 12mm hole on the side of the project box and the 8W speaker is glued to the inside of the project box so that the middle of the speaker is directly opposite the 5mm hole on the project box’s side panel. The rotary encoder and Amp volume control are attached to the inside of the project box’s lid and both of the knob control bars are past through the face plate so that they finish in the correct position in the center of the logo printout. Finally, the two control knobs are pushed onto the control bars.\nWhen soldering the twin 18650 battery holder, ensure that the batteries are in series so that a total voltage of 7.2V is supplied, via the DC plug, to the Arduino. The 4 RGB LED light array is constructed using a blank PCB board, as per the Fritzing diagram. Where possible connections between components should be soldered, however if Dupont wires are used then it is recommended that all are glued in place after being tested.\nStep 2: OPERATION\nThe Volume control increased the sound level if turned to the left, and decreased the sound level if turned to the right. The Menu/Tempo control initially starts in the Tempo option and turning it to the left will Increase the tempo while turning it to the right will reduce the Tempo.", "996" ], [ "Binary DVM\nIntroduction: Binary DVM\nBinary displays are very popular for clocks so it looked like there a gap waiting to be filled in the measurement area with an instrument that displayed its results in a Binary format. As result I decided that a DVM would be a suitable project to be given a Binary makeover.\nThe Microbit has the means via an ADC (Analogue to Digital Converter), to convert analogue inputs into digital values.", "1003" ], [ "These digital values can then be used to create a myriad of applications.\nIn this case I will describing how to make a Battery powered Digital Volt Meter (DVM), but in addition to this I will have the ability to display the voltage in Binary as well as the usual Decimal values.\n** NOTE ** ENSURE THAT ANY VOLTAGE DIRECTLY APPLIED TO THE MICROBIT DOES NOT EXCEED THE SUPPLY RAIL (~3V), AS YOU WILL DAMAGE THE MICROBIT\nIf you were to apply a DC input to the ADC this being limited by the supply would mean that ~3V would be the maximum.\nHowever, there is a way to overcome this limitation with a few additional components to measure voltages greater than the supply without causing damage to the MicroBit.\nIt must be noted that there is a limitation to what this simple DVM will measure and its only intended for low voltage positive DC applications in this case 0 to 20V.\nSupplies\nMicroBit - Qty 1\nBattery Pack - Qty 1\n9k resistor* - Qty 1\n953R resistor* - Qty 1\n200R multi turn potentiometer* - Qty 1\n1K resistor* - Qty 4\n*All resistors 0.1W or greater.\nVeroboard - Qty 1\nVeropins - Qty 3\nBread:bit Edge Connector Breakout Board - Qty 1 or similar to allow the Microbit to be connected to the potential divider.\nLED red low current - Qty 2\n16 pin DIL socket or SIL socket strip - Qty 1\nDMM\nPSU, fixed or variable voltage.\nPP3, 9V non rechargeable battery.\nIn the absence of a PSU a battery as indicated may be substituted.\n4 pin single in line (SIP), pin header - Qty 2\nStep 1: Potential Divider\nIn order to enable a voltage greater than the supply to be applied to the ADC input we will be using a potential divider network.\nThis network will enable the application of a scaled voltage at the ADC input, this scaling will be accomplished using resistors.\nThe basic network is made up of two resistors which divides the applied voltage across each resistor.\nIf we adopt a scaling factor of 1/10th the input, at the ADC then for an applied voltage of 20V; the maximum voltage at the ADC input would be 2V which is well within the capability of the ADC with a safety margin of 1V.\nIf we create a resistor potential divider using 9K & 1K with 20V across the network the voltage across the 1K resistor will be 20 * (1k/10k) = 2V.\nHowever, components have tolerance and even with 1% resistors the voltage could be between 1.96V and 2.04V\nTherefore, in order to compensate for the +/-40 mV variance we can add some variable resistance into the network to adjust for component, voltage & temperature variation.\nUsing a 1% 9k resistor and a 1k trimming resistor best case typical of 10% [0k9 to 1k1], its resistance would be between 0R (0V) and 1k1 max (2.198V [8K91] or 2.159V [9K09]).\nValues significantly less then the value to be compensated for in this case 2V are undesirable.\nTherefore, if the 1k potentiometer is replaced with a 1% 931R (0k922 to 0k94), fixed resistor in series with a 10% 200R (180R to 220R) potentiometer. This gives a compensation range of 1.84V to 2.3V (-160mV to +300mV).\nTherefore, to set an accurate maximum input at the ADC we set the maximum input to be measured and adjust the potentiometer to get an accurate output. Using a DMM in both cases to set the voltages.\nIn the absence of a DMM to measure the input voltage use a 9V primary non-rechargeable battery as the input to the potential divider and adjust the potentiometer for 1/10th the input voltage (900mV), once the assembly is complete.", "134" ], [ "WiFi Oil Tank Monitor\nIntroduction: WiFi Oil Tank Monitor\nThere are several ways to check how much fuel is left in the heating oil tank. The simplest way is to use a dipstick, very accurate but not much fun on a cold winter’s day. Some tanks are fitted with a sight tube, again giving a direct indication of oil level but the tube yellows with age making reading difficult. Worse still, they can be a cause of oil leaks if they are not isolated. Another type of gauge uses a float which drives a dial. Not particularly accurate and the mechanism can seize up over time.\nThose with deep pockets can buy a remote sensor which can be viewed inside the house. A battery driven sensor, usually ultrasonic, transmits the oil depth to a receiver in the house. A stand-alone mains driven receiver may be used to view the oil level or the receiver may be connected to the internet for remote monitoring.\nWhat is needed is a battery driven WiFi connected sensor that can monitor the tank for years at a time and send email reminders when the oil level gets low. Such a device is described in this Instructable. A sensor measures the oil depth by timing how long it takes for light to reflect back from the oil surface. Every few hours an ESP8266 module polls the sensor and transmits the data to the internet. The free ThingSpeak service is used to display the oil level and send a reminder email when the oil level is low.\nSupplies\nThe main components used in this project are listed below. The most expensive item is the depth sensor, a VL53L1X module which can be found online for about $6. Be careful not to select the previous generation VL53L0X, although cheaper, it has inferior performance and requires different software. The other key item is the ESP8266 module.", "459" ], [ "The versions with onboard voltage regulators and USB interface are certainly easier to use but at a premium of higher standby current, not ideal for battery operation. Instead, the basic ESP-07 module is used with the option of an external antenna for extra range.\nThe components used in this project are:\n* AA battery holder\n* VL53L1X ranging module\n* BAT43 Shottky diode\n* 2N2222 transistor or similar\n* 100nF capacitor\n* 2 x 5k resistors\n* 1 x 1k resistor\n* 2 x 470 Ohm resistors\n* FT232RL serial adapter module\n* AA size Lithium Thionyl Chloride Battery\n* ESP-07 microcontroller module\n* Sundries, wire, box etc.\nStep 1: Choice of Sensor.\nUltrasonic sensors are generally used for oil level measurement both commercially and in DIY projects. The readily available ultrasonic HC-SR04 or the newer HS-100 are often used in homemade monitors at a cost of about $1 or so. They worked fine on the bench but gave random readings when pointed down the oil tank vent pipe to locate the oil surface. This was probably due to reflections from the different surfaces in the steel tank, a plastic tank may work better. As an alternative, a VL53L1X Time of Flight optical sensor was tried instead. The readings from the tank were much more stable and so this type of sensor was pursued as the alternative.\nThe data sheet for the VL53L1X gives information about the resolution of this sensor under differing measurement conditions, see the picture. Using a sampling time of 200ms gives a resolution of a few mm. No doubt the data sheet numbers where taken under the best possible laboratory conditions and so the sensor was given a quick test to check the resolution. The sensor was positioned over the oil tank vent pipe and a few thousand readings logged using a timing budget of 200 ms. A distribution plot of the readings in the tank confirms that this sensor can measure the oil level with a resolution of about +/- 2mm.\nOver longer time period, there is a daily trend where the oil level drops by a few mm overnight and recovers during the day. The most likely cause being the oil contracting as it cooled overnight and expanding again in the warmth of daytime. Perhaps the story about buying oil by volume on a cold day is true after all.\nStep 2: Circuit Diagram\nThe circuit diagram shows how the ESP-07 module is connected to the VL53L1X. An FT242 USB adapter is temporarily connected to the ESP-07 for uploading the software and checking the operation. When the ESP-07 is put into deep sleep, the current drops to about 20 uA, a wake up signal resets the device via the diode.\nIt is possible to put the sensor into standby using the XSHUT pin but it proved easier to power the sensor on and off using a transistor. When the ESP-07 wakes up, the sensor is powered up and then switched off once a reading is taken.", "152" ], [ "Daily Running Tracker\nIntroduction: Daily Running Tracker\nHi All,\nIt's been a while since I made an instructable so I'd like to share something fun that I made recently. During lockdown I made my own yearly \"everyday calendar\" inspired by <PERSON> own idea (no instructable but photo attached for those interested). My better half wanted something similar to track her running (but on a 7 day weekly basis rather than a year). It also had to keep track of how many miles she ran not just a single light indicating a task had been done or not. Additionally, I wanted it to sing and dance and do lots of shiny LED business when she exceeded her target. The idea for the daily running tracker was born, so in summary it must:\n* Log miles ran every day of the week\n* Compare 'miles ran' against a set goal for that day\n* Reward the user with a celebratory song and some flashy lights\n* Be small enough to fit on a desk\n* Remember everything when the power was turned off (comit everything to non-volatile memory)\nSupplies\nFor this project I used:\n1. A 3D printer (for the enclosure designed in FreeCAD)\n2. M3 screws, and brass M3 inserts\n3. A soldering iron\n4. Jumper wires or wires of some kind\n5. x9 momentary push buttons\n6. x7 WS2812 addressable LED's\n7. x7 SSD1306 OLED 128x32 pixel Displays\n8. A 4 Ohm speaker\n9. The DY-SV8F playback module\n10. An Arduino Mega\n11. DC barrel input\n12. The TCA9548A multiplexer\n13.", "769" ], [ "13. Arduino Mega prototyping board\nStep 1: Operation\nPush buttons\nThe user does a short push to enter the distance ran (Distance input mode) for the particular button pressed for the day in question (the DAY button), then uses an UP and DOWN button to increment the miles in 0.01 increments. A long push for more than 3 seconds will allow the user to enter the target/goal (target input mode) for that particular day, and UP and DOWN is used again to set the goal in 0.01 mile increments. A short push of the DAY button will confirm the entry of either the goal or target depending on which mode the unit is place in.\nA long press of the push button allows the targets to be reset by clearing the EEPROM memory. When pushed for more than 3 seconds the displays will ask if the user if they are sure and display UP = YES, and DOWN = NO, to confirm their entry. A short press on the UP button will write a bunch of 0's to the EEPROM and the display will show \"ALL MEMORY ERASED\". I think an encoder would of been a nicer idea but I wanted to use up some push buttons I had in stock.\nLED's\nBy default the LED for each day is red until the distance ran for that day exceeds the target set, in which case it turns to green. When the user enters distance input mode the LED turns light blue to indicate the unit is waiting for the user to input the miles, and deep blue when target input mode is selected. For confirmation of a target/distance when the user pushes the DAY button again to exit the input goal/target mode the LED with perform a colour cascade as an acknowledgement it has received the command. Finally when the user reaches the goal it will flash wildy different colours.\nDisplays\nMy original idea was to use the I2C bus to string multiple OLED's together, however I found out that the SSD1306 OLED's are typically hard coded with the same I2C address. That is why I had to use the TCA9548A multiplexer to allow separate addressing of individual displays. This displays a little running man and some chevrons to indicate the user is in distance input mode, and a crosshair with chevrons to indicate target input mode. I used the purple one picture above. I have included a fritzing diagram above which illustrates an example of how to connect 4 of these sorts of OLED's to an Arduino UNO, although it is the same for 7 OLED's and the MEGA.\nSound playback\nI wanted a module which would handle all the play back of music segments. I wanted it to be simple to use/implement and play at decent quality and volume. The DY-SV8F module pictured above seemed an obvious choice. It plays up to 255 MP3 or WAV files, 10 files which are directly triggered by a logic LOW signal at one of it's input pins. A microSD card was loaded with 7 music MP3 files each about 20 seconds long (cut down and faded in/out using Audacity).", "769" ], [ "Publishing Particulate Matter Sensor Data to Adafruit IO With Maker Pi Pico and ESP-01S\nIntroduction: Publishing Particulate Matter Sensor Data to Adafruit IO With Maker Pi Pico and ESP-01S\nThis article shows how to publish data from three low-cost particulate matter sensors to the Adafruit IO IoT service using the Cytron Maker Pi Pico running a CircuitPython program transmitting the sensors' outputs over Wi-Fi with an ESP-01S module running AT firmware.\nThe WHO identifies PM2.5 particulate matter as one of the greatest environmental risks to health with 99% of the world's population living in places where the WHO air quality guidelines levels were not met in 2019. It estimates 4.2 million premature deaths were caused by this in 2016.\nThe three particulate matter sensors shown in this article are:\n* the Plantower PMS5003 using a serial connection;\n* the Sensirion SPS30 using i2c;\n* the Omron B5W LD0101 with pulse outputs.\nThese optical sensors are similar to the ones found in one type of domestic smoke alarm but they differ in their attempt to count particles of different sizes rather than just alarm at a threshold concentration.\nThe red laser-based PMS5003 is a commonly used hobbyist sensor and can be found in the PurpleAir PA-II air quality sensor. The SPS30 is a more recent sensor using the same principle and can be found in the Clarity Node-S air quality sensor. The infrared LED-based B5W LD0101 sensor has a more primitive interface but is useful for its ability to detect particles larger than 2.5 microns - the other two sensors cannot reliably measure these.\nAdafruit IO offers a free tier with a limited number of feeds and dashboards - these are sufficient for this project. The free tier data is retained for 30 days but the data can easily be downloaded.\nThe Maker Pi Pico board in this article is a sample Cytron kindly sent to me to evaluate.", "152" ], [ "The only difference to the production version is the addition of passive components to debounce the three buttons.\nThe ESP-01S module is likely to need an AT firmware upgrade. This is a relatively complex, fiddly process and may be time-consuming. Cytron sell the module with the appropriate AT firmware on it.\nThe Omron B5W LD0101 sensor is unfortunately being discontinued by the manufacturer with last orders in March 2022.\nSupplies\n* Cytron Maker Pi Pico - Digi-key | PiHut\n* ESP-01S - Cytron's board comes with appropriate AT firmware.\n* ESP-01 USB adapter/programmer with reset button - Cytron.\n* Breadboard.\n* Female to male jumper wires, maybe 20cm (8in) minimum length.\n* Plantower PMS5003 with cable and breadboard adapter - Adafruit\n* or Plantower PMS5003 + Pimoroni breadboard adapter - Pimoroni + Pimoroni\n* Sensirion SPS30 - Digi-key\n+ Sparkfun SPS30 JST-ZHR cable to 5 male pins - Digi-key\n+ 2x 2.2k resistors.\n* Omron B5W LD0101 - Mouser\n* Omron cable described as a harness (2JCIE-HARNESS-05) - Mouser\n* 5 pin male header (for adapting cable to breadboard).\n* solder - crocodile (alligator) clips could work as an alternative to soldering.\n* 2x 4.7k resistors.\n* 3x 10k resistors.\n* 0.1uF capacitor.\n* Battery power for Omron B5W LD0101:\n+ 4AA battery holder for rechargeable NiMH batteries (better choice).\n+ or 3AA batter holder for alkaline batteries.\n* A USB power pack may be useful if you want to run outside away from a USB power source.\nStep 1: USB Programmer for Updating Flash on the ESP-01S\nThe ESP-01S module is unlikely to come with appropriate AT firmware on it unless it is from Cytron. The easiest way to update it is to use a Windows desktop or laptop with a USB adapter which write-enables the flash and has a reset button. Unfortunately a very common, no-brand adapter often described as something like an \"ESP-01 Programmer Adapter UART\" does not have buttons or switches to control these. The video above shows how this can be quickly retrofitted with some improvised switches made from two male-to-female jumper wires cut in two and soldered onto the pins on the underside of the programmer board.", "1003" ], [ "LumiClock\nIntroduction: LumiClock\nThis is a clock based project. The title of which embodies the main means of displaying the time.\nThe \"Lumi\", being an abbreviation for Luminous.\nUtilising lumious paper in conjunction with UV LED's to display the time which fades over a period of time between updates.\nFor a bit of added nostalgia, the numbers are in a dot matrix format.\nIn addition to luminous paper and UV LED's the clock uses a Microbit, RTC, Digital Logic, 3D printing and Mechanical parts.\nSupplies\nMicrobit\nCompact All in One Robotics Board\nDS3231 RTC\nResistor 2k2 - Qty 2\nResistor 10k - Qty 2\nResistors 220R - Qty 8\nCapacitor 100nF MLC - Qty 3\n74HC541 Octal Buffer IC\nMicro Metal DC motor\nMotor connector Shim\nUV LED's 5mm - Qty 8\nPinbetween\nHall sensors - Qty 2\nMicro USB breakout\nMomentary contact push button (SPST) - Qty 2\nPush button (on/off) switch\nToggle switch\nTerminal Posts - Qty 9\nJumper Jerky F/F 185mm\nJumper Jerky Junior F/F 100mm\nJumper Jerky Junior M/M 100mm\n3d Printer\nFilament\nLuminous Paper\nClear Laminating Sheet, Clear sticky back plastic or A4 pocket sleeves.\n20pin DIL IC socket\nStripboard\nBall magnets 3mm - Qty 2\nStainless steel tubes 30cm(L) X 6mm(Dia.) - Qty 2\nM4 threaded rod 32cm long - Qty 2\nM4 threaded rod 34cm long\nFlanged Bearings 8mm OD x 4mm ID - Qty 2\nHex standoffs M4 x 5mm - Qty 3\nM4 nuts - Qty 5\nHex standoffs M3 X 5mm - Qty 4\nHex standoffs M3 X 10mm+6mm - Qty 2\nHex standoffs M3 X 10mm\nHex standoffs M3 X 25mm - Qty 6\nBolts M3 x 12mm - Qty 24\nBolts M3 x 10mm - Qty 2\nBolts M3 x 16mm\nM3 nuts - Qty 8\nCountersunk Bolt M3 x 12mm\nScrews M2 x 8mm self tapping - Qty 2\nGrub Screw M4 x 6mm\nPin Header right angle 22 pins\n3 pin terminal block, 2.54mm pitch - Qty 2\nAcrylic Sheet 24cm (W) x 40cm (L) x 5mm (D) - Qty 2\nSpring (Compression) 10mm free length x 5mm dia.x 0.5mm wire\nMay prove more cost effective to buy a range of values rather than individual values unless you already have them available. Some components may also have a MOL greater than the quantity specified in the component list.\nNo affiliation to any of the suppliers used in this project, feel free to use your preferred suppliers and substitute the elements were appropriate to your own preference or subject to supply.\nLinks valid at the time of publication.\n2mm drill bit\n3mm drill bit\n6mm drill bit\n7mm drill bit\nDrill\nSaw\nClamps\nRuler\nCombination Square\nAllen Keys\nPliers\nSoldering Iron\nSolder\nSanding paper\nKnow your tools and follow the recommended operational procedures and be sure to wear the appropriate PPE.\nStep 1: Principle\nThis project makes use of Photo Luminescence using paper layered with Strontium Aluminate which has a green glow although different mixes can result in different colours and persistence.\nOnce charged, light from the paper will continue to be emitted after the charging light has been remove.", "134" ], [ "The charging light in this case comes from UVA LEDs.\nThe light emitted after charging is initially very bright but quickly decays to a lower intensity becoming further deminished over time, this persistance can last for several hours. if the paper is exposed multiple times in relatively quick succession then multiple ghost images will be present. Therefore, to minimise this effect a delay is applied between successive exposures.\nConsequently, this project is best viewed in a low light environment.\nStep 2: Mechanics\nUV LED's are used to illuminate luminous paper but require some means of moving the LED's over the paper to create the numbers.\nThis is achieved by using a single (x axis), leadscrew.\nThe leadscrew is directly driven by a DC motor which can rotate clockwise and anti-clockwise.", "538" ], [ "Tensegrity Planter Light\nIntroduction: Tensegrity Planter Light\nIn a previous Ible I presented the Tensegrity planter.\nThis update uses the same design and make process with some small additions.\nThe additions are in the form of Neopixel LED's fitted into the two arms of the planter sections.\nThese sections are connected continuously by three very thin enamelled copper wires\nA Microbit is used to control the lighting patterns.\nAdditionally, the filament is luminous and glows for a period after the light is removed.\nSupplies\nTensegrity Planter (previous Instructable)\nNeopixel LED's - Qty 21 (6 + 15)\nMicrobit\n34 SWG/31 AWG (0.236mm/0.226mm) Enamelled copper wire (ECW) or nearest equivalent, thinner wire can be used but is more fragile.\nMicrobit Breakout connector\nM3 bolts * 6\nM3 nuts * 2\nPliers\nPin header SIL * 6 pins\nPin to socket leads * 3\nSocket to socket leads * 3\nVeroboard\nCapacitor 1000uF/6V3\nResistor 470 Ohms/1W\n** No affiliation to any of the suppliers linked and listed above ***\nStep 1: Tensioning Support\nIn order to simplify the tensioning process, I created a tensioning support out of LEGO bricks. But this could equally be made from something else subject to what ever materials are available.\nIt makes levelling easier as it frees your hands from having to simultaneously hold the planter whilst trying to keep the tension even and the top level.\nStep 2: Through Holes\nTaking a 2mm drill bit carefully drill a horizontal hole into the 2nd step from the top of the pyramid.\nThe drill end should protrude in to the planter cavity.\nThis hole will be just below the bolt fixing exit hole, this needs to be close to this hole so that the LED wires are unobtrusive and follow the support wire.\nA hole is required on each pyramid.\nDrill the holes carefully so as not to induce too much heat as this can clog the drill bit trapping the bit.\nStep 3: LED's\nTake 3 lengths (18 inches/46cm) of ECW twist the 3 lengths together at one end and feed from the outside into the cavity, use tweezers or pliers and pull half the length through. Untwist the ends and tin with solder.\nSeparate 6 LED's from a strip and solder the 3 lengths of ECW to V+, GND and DI.\nIdentify the correct wires with a DMM and mark accordingly with tape, sleeve or knots in the wire then tin the free ends of the wire and temporarily fit a 3 pin header and test that the LED's function using the Neopixel tester.\nPosition the LED's into the lowest part of the cavity making sure the plant holder sits at its lowest level.\nThread the other end of the 3 wires through the lower pyramid and solder to the end of the strip with the 15 LED's.\nUsing 3, pin to socket leads solder the pins to the end of the strip, the sockets will connect to the decoupling circuit (Resistor, Capacitor), the other end will connect to the Microbit via 3, socket to socket leads.\nAgain test the LED's function.\nStep 4: Supporting Base\nA base was created to house the microcontroller and support the planter complete with Neopixels.\nThis support base was created in BlocksCAD and then 3D printed.\nDrill a small indentation with a 3mm drill bit coincident with the support base holes into the planter base.\nThe base is held in place with 4 * M3 bolts/screws which grip the planter base.\nStep 5: Control\nControl is based on the code used in the Candelabra which allows remote and/or manual control.\nThe Microbit is mounted on the supporting base that sits beneath the planter with M3 bolts.\nThis holds everything in place having sufficient space in the planter cavity and allows the Microbit to protrude from the back to allow access to the control buttons and the USB lead.\nStep 6: Light It Up\nYou've put it all together, now is the time to light it up", "134" ] ]

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[ [ "How to simulate a Discrete Event Simulation model with a real-time server?\nMy Problem is having to work with real-time server in a DES model. I have the following situation:\nI want to build a discrete event simulation model (Using event scheduling world view). However, this model needs to be connected to another real-time program.\nWithin this model, the event routines create next events based on the answer, that the model gets from a 3rd Party software. In better words, the model needs to make a TCP/IP connection to a server at the beginning and generate next events based on the answers which it receives from the other program.\nAs an example: The model executes event A and within its event routine code, there will be a TCP/IP call to a server which asks \"Should I generate the event B or C?\". Assume the answer from the server is B, an event of type B will be generated, and so on. Based on my knowledge, the simulation model has a virtual time, which it shifts to the next event time in the event list, upon executing the current event.\nNow imagine the following scenario:\nEvent A (event time: 11:00:00) & B (event time: 11:00:01) are on the event list. Event A gets to be executed first, virtual simulation time is now 11:00:00.", "478" ], [ "It makes a call to the server to find out which event to generate next. The Server takes 2 seconds to answer.\nHow should the virtual time of model be shifted?\n* If I consider that 2s delay and shift the virtual time to 11:00:02, the event B will be overpassed (See Edit). But the clock will be the same as it would be in a real-world system.\n* If I ignore this 2s response time, the model will shift the clock to 11:00:01 and execute event B, although the time in the real-world scenario is now 11:00:02. This means, the model does not behave similarly to the real-world.\nI was wondering if someone can guide me to the right direction? How should I deal with the real-time scheduling issue of the DES model? I tried searching online and in literature, but I found nothing which seems to be the solution to my problem. I would appreciate it if anyone can tell me where I can find some useful material on this matter.\nRegards\nEdit: By \"overpassed\" I meant the event will be skipped by the simulation model and not get executed because the simulation time will be set to 11:00:02 which is later than 11:00:01 (execution time of event B). In real world, System does event A and sends a request to server at 11:00:01 and while waiting for the server response for event A, goes on and executes event B on the next second. Later when the response for A is there, it will then decide which event to put on event list. Can't figure out how this \"waiting for response from server while executing the next event\" could be modelled.", "478" ], [ "Stack Permutation Algorithm\nI was recently designing a Forth stack machine. I have an atomic instruction which rotates the top N elements.\nFor example if the top of the stack is on the left, then say the N=3 rotate instruction would do the following:\nA B C D -> C A B D\nA few more examples:\nA B C D -> B A C D (N=2)\nA B C D -> D A B C (N=4)\nIn other words the Nth element is removed and put at the top of the stack.\nThe question arises where I need to be able to permute the top N stack elements, but using the minimum number of rotate instructions.\nHow do I find the optimal sequence of rotations to perform for any given permutation?\nA naive algorithm would be the following:\n1. Starting with the largest rotation (N=4 above), keep applying until the required element is in the 4th position.\n2. Reduce the size of the rotation by one and apply 1) again.\nAn example of the naive algorithm would be:\nPermute: A B C D -> D A C B\nIf we list the rotate instructions in order as a list of numbers, would give:\n4 4 3 3\nBut in fact, the optimal rotates would be:\n3 2 4\nEDIT - Further Investigations\nI thought I would initially just try to enumerate all the optimal sequences for a given size of permutation - i.e.", "864" ], [ "brute force it. And then look for patterns.\nHere is the list I generated for size 4. I've renumbered the stack elements starting from zero, as that is actually more natural (since the top stack element is never moved to the top). So a 1 operation would bring the secondmost element to the top etc.:\n- ABCD\n1 BACD\n12 CBAD\n123 DCBA\n13 DBAC\n133 CDBA\n2 CABD\n21 ACBD\n213 DACB\n22 BCAD\n223 DBCA\n23 DCAB\n232 ADCB\n233 BDCA\n3 DABC\n31 ADBC\n312 BADC\n313 CADB\n32 BDAC\n322 ABDC\n323 CBDA\n33 CDAB\n332 ACDB\n333 BCDA\nA few observations are immediately apparent:\n* The maximum number of operations needed is N-1 for a permuation of size N.\n* There are more optimal sequences starting with 3 than with 2, and more with 2 than with 1.\n* There is a regular pattern to the sequences starting in 1 or 3\n* The longer sequences contain the shorter ones to the left hand side. In other words if 322 appears then so will 32 and 3.\n* There is a unique optimal sequence for each permuation\nThe pattern seems to be the following for those starting with 3 for example:\n3(123)(23) - where the brackets indicate a choice\nor for 1\n1(23)3\nBut the pattern is not so obvious for those starting with 2.\nStill, all that doesn't help in finding the actual sequence for a permutation.\nEDIT\nThanks all for your answers, it was fun!\nI've now implemented the algorithm in my Forth compiler.", "242" ], [ "Constrained/Optimal Topological Order to enhance/reduce the performance/memory usage of other algorithms\nI originally posted this question here\nLets assume we have a highly connected directed acyclic graph (DAG, more edges then nodes). Since it is a DAG, we can retrieve a topological order of nodes to traverse the graph with different algorithms. Lets assume we want to traverse it in a dynamic programming approach to retrieve a specific statistic X.\nUsing the topological order, the dynamic approach would consume up to M much memory, which can be traced by a concept of opened nodes thorughout the traversal:\nBy iterating over the top. order, a node is open if it has at least one edge from a node which already was visited by the topological order. It is closed (or not open) if it gets visited.\nPseudo-Code:\nopened_nodes = list(Boolean(False)), #num_of_nodes)\nopened_nodes[top_order[0]] = True // Initial\npos_at_top_order = list(Integer, #num_of_nodes)\nfor each n, n_idx in top_order:\nopened_nodes[n] = False\nfor each edge in out_going_edge(n):\ntrue_list[edge.target = True\npos_at_top_order[n_idx] = sum_of_all_trues(opened_nodes)\nreturn pos_at_top_order\n(here for the topological order, it can be adjusted for the rev. Top. order)\nA goal here would be to reduce the memory usage M of the dynamic programming approach. To achieve this, the top.", "180" ], [ "order can be manipulated and with the Pseudo-Code we could somehow track, whether the top. order is better or worse then another.\nNow to my question: Is there a way to directly retrieve such a top. Order so that M gets minimal, or could this be a NP-hard (or NP-complete) problem? What about some hard limits like: only retrieve the top. orders where the M is smaller/higher then a set amount of memory usage.\nIs there any literature about such a \"optimization\"? Which search terms could be used to search for this e.g. in Scholar?\nI already tried some different generation methods of top. order (in total 9) All of them look similar to the curves in the figure: (here i used igraphs top sorting algorithm and <PERSON> algorithm with some variations. Not shown but i also tried: DFS- and some \"BFS\" approaches. This is a highly connected graph, containing 14207 nodes and 94113 edges.)\nAny input on this is highly appreciated!", "180" ], [ "I have a problem with my representation of roll in Simulink\nI am currently a French engineering student (I apology about my English) and a member of the aerospace club of my engineering school (ESILV) which is called LéoFly. We’re a team of 12 students and are building a Fusex (Experimental Rocket) for the launch campaign of the CNES in partnership with Planète Sciences association. The goal of our experimentation is to counter the “natural” roll of the rocket after the boost-phase. Thus, I am the one who must program the algorithm that counter the roll using a gyroscope and four solenoid valves (2 for the clockwise direction and the 2 others for the counter clockwise direction). I decided to use Simulink to develop the closed loop control using the following image, equations and data.\nThe image is the cross section of the rocket with the four fins. This is an example of a “natural” roll in the counter clockwise direction, so the program gives the order to the two solenoid valves of the clockwise direction to eject gases and cancel the roll of the rocket.\nHere are the equations with which we have started with.\nThe C’s are the torques considered in the experimentation (Thrust torque and Roll torque), J is the inertia, theta is the angle and theta is equals to the derivative of omega in the time domain. After that, Fa is the force of thrust, Fb is the force of roll, R1 and R2 are two different radiuses of the rocket.\nHere are the data, taken from our experimentations and our rocket.\nThen, in Simulink, I’ve crafted the closed loop thanks to the schematic representation, the equations and the data. We don’t want roll, so the input is 0 (in radiant per second) and the output is the roll of the rocket (in radiant per second). This is a closed loop because of the gyroscope, and the dynamic subsystem is composed of the thrust torque and the roll torque which is the disturbance in this problem.\nThêta-lim is the saturation block that represent the max roll that the rocket can have physically.", "394" ], [ "The White-Noise block is here to add randomness in the representation of the roll torque. The roll torque can be clockwise or counter clockwise and is never always at the maximum of him (here the Roll Torque block is equals to approximately 10 N.m so the disturbance which is added to the thrust torque is between 10 N.m and -10 N.m). Thrust Torque is approximately equals to 0.29 N.m and the inverse of Inertia is equals to 90 m².kg-1. The switch subsystem is here just to permit a better implementation in the Arduino to pin the solenoid valves in the program (which will be generated from Simulink). The PID has the next values: P = 114 and I = 28. I didn’t used the auto-tuner because It gives the values for a step of 1 while we don’t want a step of 1 but an input of 0. Thus, here is what the scope gives me.\nIt is what we wanted for our roll control system: counter the “natural roll” and converge to an angular velocity of 0 radiant per second. Of course, It is a student Fusex so we don’t want to have a perfect curve that converge to 0, we don’t have the time and the money to do that!\nBut the problem is at t = 0+: I put in Simulink (in the integrator block) a “natural” roll (angular velocity) of 2 radiant per second. How is it possible to go from 19 rpm to approximately 0 rpm in 0 second? It does not seem to be physically possible, and we don’t know if It is a problem due to Simulink or if It is a problem in our blocks, if our closed-loop is poorly conceived or if the starting equations are not good. One of our professors told us that It can certainly be the problem of Simulink (because of the side effects apparently).\nThus, what are your impressions about this and what do you recommend me to resolve this (these) problem(s)?", "628" ], [ "Strange simulink error. Professor & TA don't know. Any Ideas?\nI am currently working on developing a simulation for a restricted UAV, and I’m having some issues with Simulink while doing this. I have my mathematical equations which have been approved by my professor, but while I’m trying to simulate the system I am running into strange issues. Moreover, neither my professor nor my TA can figure out what is causing this issue, despite multiple private sessions to troubleshoot. If anyone can shed some light on the issue it would be highly appreciated.\nFirstly, the equation I’ve modeled on Simulink is this:\nMy Simulink block diagram is above. Input 1 Is Fb+Ff which, in this scenario = 6.8. Input 2 is theta which = 0.\nI have annotated the values that should be and are at each of the nodes before the summing junction.", "394" ], [ "In this section of the block diagram the theoretical value and the simulation agree.\nThe problem comes in the more complex half of the diagram. The graph I am validating should look like this.\nThere is an initial rise and then oscillations about a non-zero number. Obviously, my graph will be ideal so oscillations will not persist like they do in the graph above. My final graph is this…\nWhere the y-axis is elevation angle in degrees and the x-axis is in seconds. Obviously these two graphs are in no way similar. In an attempt to analyze where I could have made an error in my block diagram, I analyzed the behavior at each node.\nImmediately after the cos block to the lower right I get oscillating behavior\nImmediately after the summing junction and gain (1/0.91) I get:\nThe above bears a resemblance to the graph I’m validating against.\nAfter the first integrator, however, I get this.\nAdding the two graphs together, should I not be getting a graph that rises and then oscillates about a non-zero number?\nHave I made a mistake in my block diagram somewhere?\nThe only value I’m allowed to change is the gain marked De.\nAt this point I am starting to hit a wall and really need some insight on this. Surely this cant be something wrong with the Simulink source code.\nNothing I do gets me anywhere near the validation graph. Can someone please point me in the right direction or let me know if you see any errors?\nAny insight is highly appreciated, thank you for reading.\nShould you want to view the Simulink file for further analysis, it is available for download here: https://ufile.io/08aqv However please note that the attached file is my entire Simulink project. The circuit reference in the question above is contained in the subsystem \"elevation\".", "563" ], [ "The Process of Designing and Ordering a PCB- Signal Generator Using FPGA\nIntroduction: The Process of Designing and Ordering a PCB- Signal Generator Using FPGA\nAs an electrical engineering student, we had a class in the 5th semester that was entirely evaluated on a project done in less than 2.5 months.\nThis project was a Direct Digital Synthesizer (DDS) based on a Field Programmable Gate Array (FPGA).\nAfter brainstorming the idea was to make a device that synthesizes signals (Sinus, Cosine, Triangle, Saw-tooth, Rectangular and Noise). The frequency range should be between 1Hz and 1MHz, and the whole system should be based on FPGA (Read more about it here and why an FPGA is super cool).\nThe FPGA was programmed in VHDL- a hardware description language using Xilinx software. The FPGA should have a block memory or a BRAM that has the values of each signal to be synthesized or what is known as a look up table (LUT). The FPGA clock would trigger the LUT that has 1024 values and on each cycle, the value in the respective address will be read and sent as a hexadecimal number (12bit).\nThe cool thing about FPGA's everything is done parallel inside its core unlike a microcontroller for example that has to wait a full clock cycle to make a change in a General Purpose Input/Output (GPIO) for example. This allowed the12 bits from the LUT to be sent to 12 different GPIO at the same time.\nSince FPGA are only digital interfaces, those 12bits from the different GPIO's were sent to a 12 bit Digital to analog converter (DAC) which spits out an accurate analog converted signal with the correct clock timing as programmed.\nThe last step of this system is a two stage operational amplifier (Op-Amp)which converts the differential signal coming out of the DAC to a steady pos/neg signal in the first amplification stage. The second stage of aplification was added to change the amplitude of the output signal.\nThis Instructables will only cover the Printed Circuit Board(PCB) design and schematics. More to the theory of the whole device and how it works follow in the next Instructables.\nThis is an entry to the PCB Challenge by Instructables.\nStep 1: Understanding the Functionality Helps With the Hardware Design!\nAs most engineers would say, a good design starts on a paper with a pencil!\nIn this case it was a white board and a marker! I wish I was more organized but this is the only photo that I have and lots of sketches on my notebook that are summed up in the next few steps!\nTo start with the design process, I started laying down all the functionality that I needed in my device to understand the different sections there is and what components I'll need and how everything should be working with each other.\nAfter the brainstorming those were the main functions that I needed for my device in terms of hardware:\n1. FPGA connected with headers (So that it can be replaced)\n2. To have two channels at the output (meaning 12 pins on the FPGA x 2 = 24) + extra GPIO for input/output/clock signals\n3.", "552" ], [ "Frequency Range (Output signal) 1Hz-1MHz\n4. 2 channels 12 bit DAC\n5. 2 channels, 2 stage Op-amp. The First stage is differential and the second is to change the amplitude\n6. The signal should be variable between +/- 1v on the output\n7. Power consumption does not exceed 300mA at any time, and no component use more than 5V\n8. Variable frequency using a Linear Potentiometer, also a Linear Potentiometer to change the amplitude\nAfter gathering this information it was time for component hunting!\nStep 2: Component Hunting! FPGA+ DAC\nNow we know what the board should do a week long component hunting/adventure took place!\nGiven that this was a project for the university almost all the components that are used were provided from the university (Except for the PCB itself).\nTwo of the most important components in this device were already in the university, and we used what's available. Those were the FPGA and the DAC. Provided in the university there was a couple of the CMOD S7 from Digilent and\nIt featured:\n* 32 FPGA digital GPIO pins\n* 2 Internal analog input (Analog to digital converters- XADC)\n* An external power input rail\n* 4 LED's, RGB LED, 2 Buttons all on board\n* Small factory size\n* USB-UART built in with a micro USB onboard\n* 12 MHz onboard RC Clock\nPerfect!", "552" ], [ "Scheduling algorithm with defined starting intervals and processing times\nI need to design an algorithm for opening and closing some valves at regular times. The input schedule will look something like this:\n* Every 5 minutes, open each of valves 1, 2, and 3 for 5 seconds\n* Every 8 minutes, open each of valves 4, 5, and 6 for 10 seconds\nThe main constraint on this schedule is that only one valve can be open at a time.\nIf I were given just the first line from above as my schedule, the result would be like:\n* t % 300 = 0: open valve 1\n* t % 300 = 5: close valve 1, open valve 2\n* t % 300 = 10: close valve 2, open valve 3\n* t % 300 = 15: close valve 3\nAdding in the second line raises some more problems, like what is the overall time period (i.e. the divisor in the %)? I believe this should be the least common multiple of all the time periods: 2400 = 300 * 8 = 480 * 5. The schedules then become 8 and 5 copies, respectively, of the base schedules lined up sequentially.\nI would want to determine if it is possible to fulfill the schedule.", "143" ], [ "A simple sanity check is that the sum of all the open times is less than the total amount of time in the LCM, but I do not believe this is sufficient.\nSecond, I need to determine what the actual combined schedule is. I believe this would be a series of starting offsets for each valve's schedule. In the simple case I illustrated above, the offsets for each of valve 1, 2, and 3 are 0, 5, and 10, respectively.\nI have looked into cyclic static scheduling, earliest deadline first algorithms, etc., but have been unable to synthesize this knowledge into the algorithm that I need here. The difficulty I see is that I do not have an ending deadline but a starting deadline: once the first valve opens at t=0, it must also open at t=300, 600, 300*n.\nOther analogies I have considered are:\n* packing byte patterns into a buffer without overwriting non-null values (view each time slice as a byte and the value at the byte is the number of which valve is open)\n* dispatching trains of different speeds at given intervals and avoiding collisions\n* arranging transparent pieces of plastic with some colored areas in a stack (or cylinder since this is repeated) so that a max of one color is present at any given point\nTo recap: I need to determine a schedule meeting the above criteria. If determining the schedule is computationally intensive, it would also be nice to quickly determine if such a schedule is possible as well.\nAm I on the right track here? What should I search for to move forward in this algorithm design? Has this problem been solved already?", "143" ], [ "Finding model for time dependent functions via global model statement and constraints\nI am interested in implementing a model to predict Load to Truck ratio.\nThe goal of the model and the training process is to find the set of functions that define the interaction between locations.\nWe got $N$ locations, and for a specific $t$ we have a certain amount of Loads $L(t)$ and Trucks $T(t)$. The evolution of the loads in this simplistic first stage model assumes that whenever a load disappears is due only to a truck grabbing it. So this implies that\n$$ \\frac{dL_i}{dt} = - \\sum_{j\\ne i}^Nq_{ij}(t) + s_{L_i}(t) $$\nwhere $q_{ij}$ implies a Load to Truck assignment from location $i$ to location $j$, and this can be seen as a measure of density per unit of time of load assignments between locations (self routed locations are not taking into account because they are non existent, i.e. $q_{ii}=0$). On top of that I've added a source, new load density per unit of time, i.e. $s_{L_i}$.\nOn the truck side of things we got\n$$ \\frac{dT_i}{dt} = - \\sum_{j\\ne i}^Nq_{ij}(t) + \\sum_{j\\ne i}^Nq_{ji}(t-\\Delta t_{ij}) $$\nso the first terms states exactly the same in regards to load assignments. Every time one occurs both Loads and Trucks in that location take a hit. The second term of the right hand side of the equation states that trucks for which a Load Assignment was made $\\Delta t_{ij}$ time units ago is arriving at location $i$.\nI've got information to determine - $s_{L_i}$ - $L(t)$ - $T(t)$ - $\\Delta t_{ij}$\nThe goal here is to find meaningful information, after a successful prediction of $T$ and $L$, on $q_{ij}$.", "143" ], [ "This functions represent the location-to-location interaction.\nWhat is the most direct way of finding this interaction, time-dependent function. I have zero experience in time dependent prediction, and or models. So my naive and for sure costly approach would be,\n* define a function space\n* via numerical propagation find the error of the prediction\n* train\nThe resolution of the numerical approach can manage to be on an hourly basis. Even more. Day resolution is the most desirable value. It must be said that I formulated this in a continuous way, regardless of its discrete nature, because humans are animals of habit.\nDue to consistent intra-day market behavior we could state that $q_{ij}(t)$ on a low time resolution basis is periodic (4-7 day window). Also on a coarse time scale it seems to be as well a periodic function (4 - 6 months window). I guess this can be useful if I want to narrow the model space into a product of coarse and fine grained periodic functions, $f_{c}(t)g_{f}(t)$ via Fourier decomposition. But once again, maybe this is commiting to wrong assumptions.\nAny comments or pointing out resources would be much appreciated.", "232" ] ]

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[ [ "<PERSON> and the Prisoner of Azkaban\nThis was my favorite <PERSON> film when I was younger and I don't think the others will beat it. I love the story. I love how this film is dark and spooky. Werewolves? Sign me up. There are a lot of creepy imagery.", "475" ], [ "<PERSON> does a solid job behind the camera. The cinematography is fantastic. <PERSON> score is phenomenal per usual. I'm a fan of <PERSON> and he's great in this film. <PERSON> is also a standout. I was excited to watch this again after so many years and it holds up beautifully.", "594" ], [ "The Holdovers\nI had no interest in seeing this film. I saw the trailer and thought it looked okay. Then I kept seeing all of the praise from mutuals, so I changed my mind. I'm glad I did because this is one of the best films of the year.\nThis feels like a classic Christmas film. It's got a warm and welcoming feeling that made my day so much better. It's very funny and with a lot of heart. This is a film I'll watch every Christmas season from now on.\n<PERSON> delivers my favorite performance of his. I loved his character and felt for him. Same with <PERSON> character.", "217" ], [ "He was great as well. <PERSON> is also a standout. I hope they all receive Oscar nominations for their performances.\nThis is a beautifully shot film. The score and music choices fit like a glove. The film looked and felt like it was made in 1970. The script is really well done and I loved the dialogue. It deserves a nomination for Best Screenplay.\nThis was a pleasant surprise. It's one of the best films of the year. I'd highly recommend it.", "529" ], [ "<PERSON>\nJake and <PERSON> have such amazing brother/sister chemistry, it’s ridiculous. It’s almost like they’re actually siblings in real life…\nI also totally forgot that <PERSON> was basically a glorified extra in this film.\nWhat a legendary film.", "217" ], [ "This movie is so good and works on so many levels. From its great acting, amazing soundtrack/original score, and having one of the greatest endings in film history, Donnie Darko is a one of a kind masterpiece.\nI understood this film so much better this time compared to when I first saw it at 12 years old. It’s all makes sense now.\nGrade: 91%", "583" ], [ "<PERSON>\nThis film starts off strong. I really enjoyed the first 20 minutes. The sets looked awesome and I liked where the story was going. Unfortunately, the rest of the film isn't nearly as good. <PERSON> continues to be a great Dr. <PERSON>. I just wish he was in better films. This film feels like the greatest hits of all the <PERSON> films up to that point. It has moments and scenes that I recognized from other <PERSON> films.", "577" ], [ "It may seem familiar, but I liked it. Is it original? Not at all, but I prefer it to the first two Hammer Frankenstein films. However, this film has the worst looking Monster I've ever seen. The makeup is fucking atrocious. I cannot believe that was approved. It looks like absolute dog shit. It's unbelievably awful. I could go on, but you get the point. Overall, this is another disappointing Hammer Frankenstein horror film. It's my favorite of the first 3, but that's not saying much.", "1004" ], [ "Guardians of the Galaxy Vol. 3\nI was kinder to the Marvel series than they deserved, I hated Wakanda Forever and I skipped Ant-Man and the Wasp: Quantumania. I guess you could say I had Marvel fatigue. Then <PERSON> drops this emotional and dynamic entry into the MCU. I’d be lying if I said I didn’t cry multiple times because I did. The film’s tone is perfect and usually I can’t deal with Marvel humor very well.", "457" ], [ "This may very well be one of the best entries in the entire MCU. My personal favorite is Winter Soldier. This is <PERSON>’s movie and we get some long overdue backstory. But each member gets their time to shine and we see a side of each <PERSON> that we knew was there and wanted to see. <PERSON>, <PERSON>, <PERSON> (good dog!) and literally everyone is great. I was a bit disappointed in The Great Evolutionary. All in all, the rest of the film overshadows that.", "19" ], [ "Alien³\nHooptober 9 Entry 16 - UK\nA much weaker film than the previous two installments. First off, I hate the fates of the characters from Aliens. Like it's hard for me to consider this canon because of it. The prison created an interesting setting and look into future society, but ultimately doesn't add anything to critical to the overarching lore of the series.", "952" ], [ "There was some really good performances in this and I loved any scene involving the Aliens. It wasn't horrible, but also nothing great either. It's a shame because I really enjoy <PERSON> films and I think he could have done better. Also no <PERSON>, so what's the point?", "549" ], [ "In the Summers\nSundance 2024: Film #29\nOne of my favorites of this year’s festival. Probably my second. When I watch movies that are slice of life and not conventionally structured I get absorbed in the film and forget I’m watching a movie. Then the runtime flies by. This is definitely one of those cases. This is a very three-dimensional film. Not just because of the way it’s presented but also because it is such a good script. There’s lots of very subtle blink and you miss it moments that call back to previous scenes and adds to character arcs. All the acting in it is great too.", "462" ], [ "All the child performances, as well as <PERSON> who plays the complex father character. There were only a couple scenes towards the beginning that I felt were a little too overdramatic, but the rest of the film was totally subtle. I like that the father is not so clearly good or bad. It’s complex and it’s realistic. I thought this was pretty great. This is something that I would totally watch again. Especially in a movie theater where I can just sit and forget where I am.\nI’m really surprised at how great this movie was. I was looking forward to it, but I didn’t think it would be this well done. It has no acquisition yet and no future release date but I hope it comes out soon because I’d like to see it again. On to my final film…", "657" ], [ "<PERSON> and <PERSON>\nThis was much better than I was expecting. I think <PERSON> is great and he has some solid support. I was intrigued by the story. We can’t expect a Temple Of Doom (my favorite) or a Raiders Of The Lost Ark in 2023.", "577" ], [ "We know is going to be CGI heavy but that didn’t take away from my enjoyment. The film didn’t seem as long as it is and it a breezy, fun watch. I did find myself grow annoyed with some of the character but they finally redeemed themselves, as I knew they would. Some nice surprises and there are worst ways to kick off a weekend.", "596" ] ]

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[ [ "To answer your question, I think it is important to understand what the foundation of your new world is. What <PERSON> said about rocks is fun and all, but this can only be believable in a world entirely different than our own. As an example, you could change the fundamental laws of the universe (electromagnetism, strong and weak nuclear forces, and gravity). Perhaps that would be too complex, but there needs to be a reasonable way that consumption of rocks could provide an adequate amount of energy, especially considering the fact that rocks don't contain a lot of readily accessible energy for other organic forms of life. Any way of harvesting that energy would likely release too much energy as a result.\nIs it important to you that the dragon eats something small? Is it important to you that you completely remove the normal circle of life that we are accustomed to? Can we not have a larger planet? This would make it easier to stay consistent with the rest of your world because you could take what we already know and just make the potential for everything to grow bigger because there are more resources. That may also necessitate that your characters (if any) would also be bigger, and be in a world with everything relatively bigger but not bigger relative to themselves. That may take away the appeal of larger creatures because their power is no longer relevant in a world of relatively more powerful creatures (everything is relative).", "693" ], [ "Maybe in order to maintain the majesty of large dragons you make it a world that visitors travel to, perhaps on accident. Then you could have this world of large creatures that remains impressive (this is sounding a little like <PERSON>, which may be a good thing?).\nNo matter what you choose, there needs to be consistency. If what the dragons consume is important, maybe build a new world around that. If something else is more important, build your world around that. State the assumptions of your world, and then we can productively and effectively design a solution that works in your world. If there is no consistency, nor struggle in the world or in its design, then it becomes boring. Ultimate power is not exciting (just ask <PERSON>, who seemed to intentionally develop an allergy to a shiny green rock).", "194" ], [ "Reading through the comments I am having a tough time figuring out if this thread is still active, but I do have a few ideas.\nFirstly, you ask what must be changed to follow some form of logic? As noted, magic usually isn't very logically, however I understand what you mean by this and to me it seems like an additional (9th) domain might be useful (since 7 doesn't seem to work as you mentioned in the comments) to ensure some sort of balance. That is, a rock-paper-scissors mechanic. The main reason to use an RPS mechanic is to make sure that no single ability, or any combination thereof, is head-and-shoulders better than the others. If this were the case, there would be no real reason to ever use the other spirits, or for that matter include them in your world, thus my suggestion to add a 9th.\nA functioning rock-paper-scissors mechanic can only work with an odd number of features. The ability to bind multiple spirits complicates the system, but the combinatorics exist to sort the problem out. My initial suggestion to simplify things here would be to only allow 3 spirits at any given time. This works well as a multiple of 9, and still gives an 24-, 12-, 8-hour time span feature as you mentioned.", "805" ], [ "Should you decide to go that route and run into a specific problem developing a balanced scheme, that may make for an excellent follow-up question.\nAs far as which domains must be added to cover the whole spectrum of a human being? my initial thought was to add a creativity/ingenuity type category, but it would be hard to specify what exactly that might do, especially for the malevolent spirit. One idea that does seem to flow would be an Emotion category. The benevolent spirit would add empathy and the ability to relate to people, thus making them more likely to support your cause. The malevolent form would make you cold hearted and distant, which may be useful for making those \"tough\" decisions. Just an idea.\nOne other thing: the malevolent Appearance spirit doesn't seem fitting. Instead what if that spirit made you intimidating to others. People would be scared of you and thus less likely to oppose you, but also less likely to support your efforts.", "140" ], [ "What immediately comes to mind when considering this question is that the the system is symmetrical - that is, it works exactly the same even if someone from planet 1 is transplanted to planet 2. It is not a subjective exclusion from the current planet. The energy of the current planet is objectively unusable. So what would make that happen? The simplest answer, for me, is that something in the transition from planet X to planet Y is necessary for it to become usable.\nTo find what that is, I would look at the physical layout of a solar system. What is between you and another planet that isn't between you and your own planet? This could be some object in its own orbit, or maybe the energy must be drawn through multiple planets to amplify. But my thought is that it must be drawn through the sun.\nWhy? Well, it's big, bright, and your planet's energy can never ever go through it on its way to you. The sun could act as a focus or an activator of another planet's energy, and that energy must be (inadvertently) drawn through the sun to be useful to a magician. Or perhaps the journey of the magical energy through the sun's radiation between planets activates it and it doesn't physically have to go through the sun, but the idea is the same. Something between the planets (the sun or some other arcane object) acts as a catalyst for magical reactions.", "943" ], [ "The energy around planets is the fuel, but it needs a spark somewhere out in space that just isn't available on the planet you stand on.\nThe other simple observation is the sheer distance involved. I liked it <PERSON>'s inverse square law idea, but I like it better the other way. The further the planet is from you, the greater distance the energy has to build momentum. If you draw it from a paltry 4000 miles from the center of your planet (or less if it's from the atmosphere), it is equivalent to a musket-ball rolling out of the barrel. But, drawing from a Pluto analog 5 billion miles away, your magical bolt comes screaming like an abused particle doing loops somewhere in a Swiss lab.\nThink of it as potential energy in a gravitational field - except the gravity is the magician pulling on the magic. The further it has to fall (be pulled), the more time the force acts upon it, applying an acceleration the whole time. Even a small (whatever small is in magical terms) acceleration over 5 billion miles produces an inordinately larger velocity than an acceleration across 4000 miles. And translating \"velocity\" into magical power, that's the ballgame. The furthest source of magical energy on your planet just isn't far enough for any significant, noticeable power to be built up.", "621" ], [ "If you are looking at this from a programming point of view, most of the software would be functions that make it so the golem doesn't get itself killed and can function in society. Go through an average day and think about how much information you process subconsciously. Just sticking to basic axioms and information consider the following:\n* Do not walk into the ditch.\n* Walk on the right side of the road.\n* Stop at red lights.\n* This animal is a pig.\n* The city map is laid out as follows.\n* Do not throw children out of your way while walking.\n* Ring doorbell and wait before entering.\n* The three laws of robotics.\nThe final list would be exhaustive and we still haven't given the golem the ability to do anything useful yet.\nYou could speed up golem creation by having some method to quickly dump the needed base information into the golem, but perhaps there isn't much room (memory or HD space equivalent) left for it to do anything terribly complicated. So tasks have to be simple, which by definition puts golems into the background of the story.\nOr maybe there is plenty of room for additional instructions, but that opens the door to golem sentience which almost always has negative consequences.\nSmaller, man sized golems could be incredibly useful, but still limited enough to keep them in the background. Examples follow:\nFarming with golems may require a lot of oversight. Okay golems, go plow the field.", "209" ], [ "Now pick out any rocks over 3\". Now plant 3 seeds every 12\". Now go back in the shed.\nA golem could serve food at a highly scripted formal dinner, but it would probably be a terrible cook as it couldn't tell the doneness of meat or whether the soup needed more salt. A golem waiter would also be useless at the local Applebee's as everyone wants their food prepared slightly differently and there is no way the golem could keep track of that.\nA golem could deliver a letter to a specific address, but it has no idea whether the person receiving the letter is Count <PERSON>, his butler, his brother, his arch enemy, or mischievous street urchin. Maybe all it can do is put it into a specially marked mail box and ring a bell indicating a letter has arrived.\nGolems in the army may be great at moving supplies, cutting down trees, or building simple structures. But they would be useless in combat as they are incapable of conceiving of any tactics beyond walk straight and punch the guys in the blue uniforms.\nFrom a narrative point of view, think of golems as magical pieces of farm equipment, machine tools, or roombas. I think you could put them everywhere and they'll still just stay in the background of the story.", "164" ], [ "To balance out the long lifespans, you would essentially need your animals to have long hibernation periods. You could build a world where as the animal grows, the need for food decreases or that the need to feed regularly disappears. Now since the environment is already saturated with magic, I expect the animals to absorb some of it. If they absorb enough, the magic can help regenerate dead cells at a much faster rate. If this continues for long enough, perhaps the animal becomes essentially invincible (e.g., the moment a sword piercing this snake is removed, it heals from the wound). For particularly old animals (30,000 years) you could replace their biological need to eat with absorption of magic in the environment.\nAnother thing that you can do is stop the physical growth. In normal world, animals grow up to a certain size till a certain age and stop growing so much once they reach adulthood.", "227" ], [ "It could be the same there. You could remove the reproductive system after a certain age, even replace hearts with pure magical cores.\nThe skill an animal is learning would also probably depend on their upbringing and inherent abilities. For example, a lame lion would learn speed or stealth while a lion who has generally starved throughout childhood would learn to be a better tracker. For smaller animals you could try increasing their size just enough that its natural predators would be afraid of it.\nLastly, you could make the animals less violent than their normal counterparts. They will generally not pick fights with smaller animals if there is no need. I believe an animal smart enough to learn magic will be smart enough to maintain truce with other animals like itself, i.e., with magical abilities because it will simply not take the meaningless risk just for thrill or food, if it doesn't need it. If you do, however want to make your animals violent, I suggest a specific reason. For instance, if animal A defeats animal B in combat and kills it, A will gain the magical abilities originally belonging to B.", "376" ], [ "Welcome to Worldbuilding, <PERSON>! Do not be discouraged when contributors urge you to do your own research. You will find that frank criticism is far more useful than compliments and ego-stroking when you get down to the serious business of building worlds.\nNow to your question. Is it possible? Yes, because you have provided your merfolk with lungs, but it is, in my opinion, cumbersome from an evolutionary standpoint. Why would a creature so well evolved to live underwater as a mer-person use vocalizations evolved for a gas environment in the marine environment?\nIn this case, I would suggest thinking about common evolutionary adaptations that are readily observable in the world and then expand on them in your own world. Think about the vocal sounds that terrestrial mammals make and why, and then think about the many different ways that marine life communicates without the needs to vibrate a set of vocal cords with a moving gas. Certainly, your merfolk could use something like a highly advanced system of sign and body language, and they probably should, but why stop there? Why not give them special adaptations, like skin with chromatophores (like squid and cuttlefish) with which they can communicate voicelessly through pattern and color? What about bioluminescence? Take some time to study how marine mammals (marine creatures with lungs) communicate underwater to get ideas, such as cetaceans.", "350" ], [ "In the process, don't forget mammals that spend a lot of time in the water, too, such as walrus, seals and otters. The natural world will give you ideas, and then you can layer on your choice of magic or specialized evolution to complete your organism.\nAlso, I would spend some time thinking about whether your merfolk started life as terrestrial and moved a marine environment, or vice versa. This will help to guide you in your biological designs. Do your merfolk ever come out of the water and converse with terrestrial creatures? If they do, must they speak in words? I understand that they have lungs and gills, so you have addressed the issue of oxygenating their tissues, but do they actually have vocal cords? If they do, this suggests that they were first a terrestrial people that moved to the marine world. If they lack vocal cords and instead have something like chromatophores in their flesh, then this suggests that they began as a marine people and made adaptations that encouraged symbiosis with terrestrial creatures.\nRemember, <PERSON>, at all times the study of the natural world will help to inform your creature lab. Hope this helps!", "671" ], [ "Just want to add another perspective by using computers and our understanding of space-time as an analogy.\nFirst, let me state that computers do not recognize time by itself. It requires an external clock that is subsequently mapped to human-understandable time (1 time step -> 0.1 ns, for example). But barring that external clock to quantize (discretize) the executions of computers instructions (note that in computers we artificially synchronize executions based on the clock, otherwise, it will \"just happen\"), the amount of \"time\" (from we as external observer that already understand time) required to accomplish tasks (or a sequence of instructions) are not quantifiable.\nSo for the computers without external clock, time would be something inherent to their fabric of existence.\nAnother perspective before getting to the final point is how we understand the concept of fabric of space-time. (image below from the book \"We Have No Idea\")\nWe can't really measure the expansion of our very fabric of space-time directly, since any measure we use would also be expanding, unless we can find something that doesn't expand with the fabric of space-time.\nNow, back to the computer analogy, I guess it won't be able to see the concept of time, unless there are things in the universe that stays constant with respect to time (something that does not \"expand\" with the chaos of time in your universe).\nHowever, we now do learn about the speed of light and the fabric of space-time (but much much later, definitely not the first thing that we would come up with).", "781" ], [ "So I believe there would be some cases that caused your creatures to try to understand the concept of time, with much difficulty, just as now we try to understand the concept of space-time.\nA final remark would be to note that this might have some similarity if we assume speed of light is much lower than the current speed, that we can move very close to the speed of light. That can cause things to happen differently for different people (think about the different frame of reference in our current universe that might cause ordering of events to be different for different observers). So it might be hard for the creatures in your universe to understand that there are absolute ordering (passage of time) of events. So you might want to start from there.", "562" ], [ "Religion is, by it's very nature, transcendent. The world and the concerns thereof are not the concerns of religion. Religion answers the quest for the highest good by pointing beyond the world of our physical experience. Therefore members of a religion may very naturally anticipate the end of this life (or the world) with hope.\nThere are interesting theological questions around how the world itself is viewed, and each religion answers such questions differently. For instance, a gnostic Christian might reject the material world as evil, while an orthodox Christian would uphold the inherent goodness of the world which is passing away.", "752" ], [ "It sounds fun to flesh out such details (don't forget to include internal conflicts within the religion itself).\nObviously contemporary American religious thought won't yield much good source material, because modern American religion is almost always hedonism in disguise; but it would be interesting to look into the Tao Te Ching, some writings of the ancient Christian ascetics, and some literature about Hindu gods of destruction for a wide range of perspectives.\nThe basis of a positive arguments used to attract followers would be that the coming world is better than this one. This is an easy argument to make given that in our world: 1) people tend to think the world is bad and 2) they also always seem convinced that it is getting worse, in spite of many efforts to make it better. It therefore shouldn't be hard to draw the conclusion that the world must be remade. Of course, a nihilistic argument could be made that life itself is bad (see any bad guy in any movie ever).\nA pseudo-Buddhist argument might go something like desire causes us to suffer; the pleasure does not outweigh the evil of the suffering; it seems impossible to not desire while in the body; therefore all desire must be extinguished by the apocalypse after which we will …\nI guess, in general, I think it is harder to argue for the goodness of the world than it's badness. Therefore I don't think it should be hard for you to construct convincing arguments for it's demise, be they hopeful for a better existence or not.", "590" ] ]

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[ [ "Stain Your Wood Purple Using Red Cabbage\nIntroduction: Stain Your Wood Purple Using Red Cabbage\nDIY-ing and crafting is a great hobby and stress reliever for me, but I'm not set on one particular medium and tend to jump from woodworking to 3D printing to sewing an so on... It's all fun until you sit down and calculate how much money you actually spend on supplies that only get used once or twice. I have cans and jars filled with specialised varnishes, paints, waxes that are slowly drying out because I only needed a little bit for my project , but had to buy a quarter gallon. I like to experiment with home made concoctions whenever possible to cut the costs and possibly come up with new uses for certain products.\nMy newest project focused on home made wood stain, specifically purple dye I needed to stain a wooden chest. Before I used cabbage, I tried staining my wood with diluted food dye and acrylic paint, but final effect wasn't too impressive. Food dye was the worst, no matter what brand I used, I ended up with indigo instead of purple. Out of desperation, I decided to use red cabbage which, if you remember from chemistry lessons, has the ability to change colour. That turned out to be an additional bonus, because I was able to play with it and create different colours I might use in the future.\nSupplies\nYou will need:\n* Red cabbage\n* Juicer or food processor with a grating plate\n* Strainer / sieve\n* Cheese cloth\n* Disposable gloves\nCabbage is not a particularly juicy vegetable, but even without a juicer you will be able to squeeze 1/4 cup of raw juice from a small cabbage. 1/4 cup allowed me to cover about 6 sq. ft of wood (only one layer), so if you have a bigger project in mind, you will need a bigger cabbage.\nUse disposable gloves or even rubber kitchen gloves while working with cabbage. It will stain your hands.", "74" ], [ "It's relatively easy to clean the skin with a bit of soap and a brush, but that juice stains cuticles and gets under the nails, and is very difficult to wash off. I tried everything to clean my fingernails and nothing worked, so for two days my fingers looked like I just escaped the morgue.\nStep 1: Extract the Juice\n* Grate the cabbage in a food processor and transfer (few tablespoons at the time!) to a fine sieve.\n* Push the cabbage with the back of your spoon until there is no more juice left to extract and repeat that process with remaining cabbage.\n* You will be left with a foamy liquid and possibly few stray bits of cabbage. Run that liquid through a cheese cloth or a disposable kitchen towel to purify it.\n* Your cabbage juice is now pure and foam-free. Transfer into a jar and keep in the fridge until needed.\n* You can keep it in a fridge for a few days, but after that it will succumb to mould, so finish your project as soon as possible.\nRed cabbage is used to dye fabric and there are a lot of Instructables and YouTube videos that show you how to do it. Most of them recommend chopping the cabbage and boiling it until all colour leaches into the water. I don't recommend this method, unless you want your house to smell for days. Grating the cabbage and extracting raw juice is quicker, relatively smell-free and final product is more concentrated.\nStep 2: Painting\nUse a regular paintbrush to apply the liquid all over unvarnished wood or plywood. Leave it to dry naturally, don't wipe the excess off. It will be wet and nicely saturated at first, but as it dries, the colour will become more subdued. Second layer of juice, once dry, will give the wood more vibrant colour.\nIf you are not sure about the final result, test it on an offcut to determine how many layers will be needed and how saturated the colour will be once dry. Different woods produce different results and need different number of layers.\nYou can apply clear varnish once everything is dry completely (2-4hours).\nStep 3: Wood Filler?\nFor anyone interested in using the juice over wood filler- this is what happens. White filler turned grey and no matter how many layers of juice I painted over it, it wouldn't blend in.\nStep 4: Experimenting With PH and Different Colours\nYou can experiment with your cabbage juice by adding different quantities of acid (lemon juice/vinegar), which turns the cabbage juice pink-ish, or adding alkali (bicarb of soda/soap/bleach) which turns it blue-green.\nStep 5: Wet V Dry - Different Results\nYou can see from the pictures that wet and dry stripes look completely different.", "994" ], [ "Mini Indoor Fire Pit for S'mores\nIntroduction: Mini Indoor Fire Pit for S'mores\nThis project has been on my mind for a while now and what better time to make it than winter months when bonfires and BBQs are out of question.\nS'mores were introduced to my European-self via American movies and I never even thought to make them myself. That is until I met my newest friend, who happens to be a s'more obsessed American. Unfortunately, since he lives in an apartment in London, he's unable to make them himself and he's constantly trying to come up with alternatives. Believe me, there is nothing sadder than watching a grown man trying to heat up marshmallows with a lighter or spreading marshmallow fluff over saltine crackers and topping it with nutella. I finally took it upon myself to make him an indoor fire pit to satisfy his cravings.\nSupplies\n# Cement or concrete mix + optional powdered pigments\n# Mould - silicone mould, 3D printed mould or DIY homemade mould\nIf you don't have a 3D printer, use plastic containers you have laying around the house to create a simple mould.\n# Mould release - oil based\nIf you are using DIY plastic mould or 3D printed one, you can use any oil based lubricant on hand- cooking oil, baby oil, Vaseline etc.", "74" ], [ "For professional silicone moulds you will need special release agents to prevent damage.\n# Sanding paper, at least 120-320 grit\nOptional: Dremel, concrete polishing pads\n# Concrete sealer - optional\nOnly non-solvent sealer! It can be skipped altogether if you absolutely don't want to use it, but it will look better and cement won't be prone to stains or damage.\nSealer can usually only be bought in large quantities, but sometimes you can buy samples (1-2 oz.) on eBay and Amazon.\nhttps://www.amazon.co.uk/s?k=concrete+sealer&crid=...\n# Decorative stones or pebbles\n# Heat-proof metal container for alcohol burning\n# Methanol, ethanol or isopropyl alcohol (rubbing alcohol) - high concentration\nI tested 70% and 99% isopropyl alcohol and both worked, however 99% burned longer and more consistently.\nOR\n# chafing fuel https://www.amazon.co.uk/Olympia-CE241-Chafing-Fue...\nStep 1: Moulds\nYou can buy special silicone moulds or make them yourself using household items like plastic and metal containers, melamine boards or even cardboard.You can also 3D print them.\nI've found an interesting bowl design on Thingiverse, I tweaked it a bit and made it into a mould. When I'm no longer using the fire pit I will be able to fill the bowl with decorative pebbles, candles or use it as a succulent planter.\nStep 2: 3D Printing Moulds Using CURA's 'MOLD' Mode\nCura has this interesting feature that allows you to print any object in a mould (mold) form. I have no idea what the intended purpose of that mode is, but I use it to print moulds and fill them with cement or plaster. Not all objects can be converted and still be usable, some have to be modified, but it works great for simple designs like bowls, vases, planters.\nOnce you made or downloaded a design of a bowl or planter, import it into Cura and find 'mold' feature in settings.\nPrint your mould upside down.\n* 0.2 or 0.3 layer height\n* 0.4 mm wall thickness\n* 0.8 mm bottom and top\n* 2-10% infill (depends on the size of the object)\n* use raft as build plate adhesion (at least 2 layers), it will also act as a connector between the outer mould shell and the inner part\nStep 3: Cement/ Concrete\nUse cement or concrete mix, either one will work. While concrete is stronger than just cement, on a small scale project like this the lack of aggregates won't matter as much.\nIn fact cement works better than concrete, since there are no gravel pieces and the whole mixture fills small cavities perfectly, so the end result is flawless.\nCement doesn't usually stick to PLA too much, so mould release is not strictly necessary, but I like to spray some WD-40 on the insde of the mould just in case.\nMix a batch or cement- white, pale gray or dark gray (whatever is available in your country), add pigments if you want to and pour into the mould.\nBang the whole mould onto the countertop to release any air bubbles and to spread the mixture evenly.", "254" ], [ "Make Cement Terrazzo With Leftover Resin\nIntroduction: Make Cement Terrazzo With Leftover Resin\nTerrazzo objects made with colourful chips are traditionally made using jesmonite, but I'm going to show you how to fake it and use resin instead. It's a fun project for people who work with casting resin a lot and want to utilize ANY leftovers.\nI've been doing a lot of projects involving casting and every time I mix a new batch of resin, I have to mix 5-10% more than needed just to be on a safe side. In the end, I have a small amount left in the cup and absolutely nothing do with it. I started adding pigments to these leftover mixtures, pouring them out onto a flat surface and letting them cure. I've been collecting them for weeks and finally have enough to use in this project.\nSupplies\n* Resin and pigments (polyurethane or epoxy resin)\n* Small sheet of cellophane\n* Disposable cups and stirrers\n* Kitchen scale\n* Cutting pliers, hammer (optional, depends on the thickness of resin)\n* Plastic or sillicone mould\n* Glue gun (optional)\n* Lubricant\n* White or grey cement\n* Cement pigments (optional)\n* Sanding paper (various coarseness)\n* Spray-on gloss varnish\nStep 1: Resin Pour\nMeasure part A and part B in separate containers, add them together and colour the mixture. Pour the resin onto a sheet of cellophane and spread it out to 2-4 mm thickness. Don't pour it onto wrinkled plastic sheet or clingfilm, because the end result won't be smooth (see pic 3, resin poured over clingfilm)\nStep 2: Cured Resin\nOnce resin is cured you can crumble it into smaller pieces. I used a hammer for some of the resin pieces, some of them were too thin for a hammer and I had to use cutting pliers and/or crumble them by hand. I made the pieces on a small side because my tray had a very thin lip and I wanted to make sure they will be able to access all tight spaces.\nStep 3: Mould\nMy moulds were 3d printed and needed some clean up before I could proceed.", "74" ], [ "Pentagon moulds had to be glued to a flat surface with a glue gun since I printed them without a bottom.\nI used WD-40 and a brush to lubricate my moulds.\nStep 4: Cement\nI used water to measure the volume of each mould in order to prepare correct amount of cement and correct amount of resin chips. I used a ratio of 5 parts mixed cement to 1 part resin chips.\nI mixed dry, grey cement with black pigment and added just enough water to create a thick paste. I then added my resin chips, mixed it really well and poured half into the mould. I had to pound and drop the mould onto the countertop a few times to make sure all air bubbles raised to the surface and cement mixture got into all those tight spaces. Added more cement and used a plastic ruler to smooth and level out the surface. I left it to dry for 12 hours before I unmoulded it.\nI did the same with pentagon coasters, except I used white cement.\nStep 5: Unmoulding\nBefore you unmould, use a craft knife and very coarse sanding paper to level the back of the tray. It will be easier to do it at this point because you will have the mould walls to guide you. Gently unmould in case not all parts are dry yet and, if needed, leave it to dry further for a few hours.\nAt this point terrazzo chips won't be visible, your objects will look like they are just solid cement.\nStep 6: Sanding\nUse a combination of different sanding paper grits (40-240) to reveal resin chips. Seal with a spray-on varnish.\nStep 7: Finished", "254" ], [ "Cheat Resin Art With Two-Part Epoxy Glue\nIntroduction: Cheat Resin Art With Two-Part Epoxy Glue\nResin art has been popular for a few years now. Epoxy resin is more accessible, more affordable and there are so many people involved, that any question you might have can be answered within minutes. It's great, but if you really want to commit to that hobby, you will have to do a lot of research and test different brands of resin available in your country.\nI used two different brands in the past and I wasn't happy with them at all. One brand had a distinctive chemical smell that lingered for 2 weeks, another one took nearly a week to dry. It was just for experiments, I gave up after that and haven't touched clear resin since. Small quantities of resin cost an arm and a leg, it makes more sense to buy it in bulk. So, it can be really annoying if you buy large quantity of unsuitable resin and are forced to throw it out.\nI wanted to encase a small picture in clear resin and since I required 35ml to cover the whole thing, it made no sense to buy 250ml for 26$. I began experimenting with cheap two-part epoxy glue and I came up with an idea on how to use it instead of resin to glaze small projects.\nThis project only makes sense if you want to cut costs and your picture isn't bigger that 10x10inches. Anything bigger will require more epoxy and at that point it will make more sense to buy regular resin.\nIn my instructable I'm using two-part epoxy glue syringes (25ml each) used for gluing plastic, wood, metal and ceramics. I got it at a DIY shop for £1.99 per syringe (that's £8 for 100ml epoxy).\nThis method can be used to coat pictures, create coasters, preserve special mementos like your child's first attempt at writing, ultrasound photos or small paintings.\nSupplies\n* board, sheet, plywood or canvas; no bigger than 10x10inches\n* posters, postcards, pictures, print-outs\n* Mod Podge or PVA glue; brushes\n* two-part epoxy glue syringes (clear in colour and NOT quick setting)\n* acetone or gel polish remover\n* scissors, craft knife, disposable gloves, cups, stirring sticks,\nStep 1: Medium Preparation\nSince this is a small project, I used thin MDF and hardboard sheets (some of them from old picture frames), plywood offcuts, plywood crafting boards.", "74" ], [ "Basically anything that can be cut with scissors, craft knives or Dremel without creating much of a fuss.\nFor the doughnut and pepper, I printed those two drawings, cut them out and outlined them on the thin MDF sheets. I drew a 4-6mm boarder around that outline and I cut the shape out using Dremel.\nNext, I applied a layer of Mod Podge to seal the boards and painted them with white acrylic paint.\nStep 2: Painting\nSince I'm not an artist and can't draw (or paint) to save my life, I usually decoupage pictures, posters and printed designs, but I tried my hand at pepper painting this time to see how acrylic paint layers will look like underneath a layer of epoxy. Once it's dry, everything underneath will be a little bit magnified, so every mistake will be visible. However, the good news is that resin will smooth all uneven and thick layers and visible brush strokes.\nStep 3: Decoupage\nWhen it comes to decoupage, using pictures and thick posters is pretty simple. However, using regular printer paper might be a bit problematic, so you should perform tests beforehand. For example- once decoupaged, some pictures lose their vivid colours, in which case you should print the design with more vibrant colours to allow for any loses. Best way to perform those tests is to simply decoupage samples at the back of the boards and adjust accordingly.\nDecoupage is very easy. Cut the print-outs (or pictures/posters, postcards) out, apply a layer of Mod Podge to the board, place the design on top and smooth all bubbles, cover with a layer of Mod Podge and leave to dry.\nStep 4: Paint Boarders\nWhenever possible, I like to paint the boarders black to make the designs pop. Use a marker or black acrylic paint.\nYou can also use markers to add details or colours after Mod Podge has dried. Take a look at the fourth picture. Once decoupage dried I wasn't happy with the colours, it was too washed up, so I used pink and red markers to add some more colour to the hair and lips.", "1013" ], [ "How to Make Detachable (Faux) Leather Collars Using Recycled Notebooks\nIntroduction: How to Make Detachable (Faux) Leather Collars Using Recycled Notebooks\nOld faux leather notebooks are a great source of leather scraps suitable for small projects.\nThere are many different types of leather that can be used in a notebook cover. Soft and pliable leatherette, thick and robust leather, thin and paper-like vinyl. It's easy to work with them and only takes minutes to remove them from the notebook covers. You can use it in small craft projects, jewellery making or create fashion accessories.\nI wanted to make a detachable leather collar to spruce up my boring tops as well as use it to cover any frayed collar edges in my sweaters.\nYou don't need many supplies for this project: old or new notebook, scalpel, ribbon or jewellery findings. You can use rubber glue, spray contact adhesive glue, E6000, PVA glue or superglue for small details.\nBefore you do anything final, use scraps of your chosen leather to conduct some tests. Check which glue will work better and, if you want to draw or paint on the leather, which art supplies to use and how to varnish them.\nOnce I started cutting old notebooks, I couldn't stop. I ended up with more leather than needed, so I made a few additional statement necklaces like the feather, hands and bows, which are also included in this Instructable.\nStep 1: Notebooks\nAs I said before, notebooks can be covered in different types of fake leather and most of them are workable. However, if you encounter one that rips or stretches and refuses to peel away from the cover, leave it be, it won't be usable. My yellow notebook was like that, once I started cutting it and peeling it, it wouldn't budge. Turned out it was a vinyl sticker, not vinyl leather.\nUsing old notebook covers is better than throwing them away, because they don't get recycled. Once you extract your leather, you will see most notebooks have some sort of foam or plastic backing underneath, as well as layers of glue.\nCut the leather close to the edge, if there are stitches you can remove them to cut a bigger leather rectangle.\nGently peel the leather from the cover, and place the whole thing in a large bowl or sink filled with water.\nLeave it to soak for 15-20 min.", "421" ], [ "After soaking paper backing should just slide off the leather. If there is a thin tacky layer of glue covering the back, you can use a nail brush to gently scrub it off.\nPat dry and leave it out to for a few hours to dry fully.\nStep 2: Ironing the Creases\nIf you have any creases, you can use a regular iron to flatten them out. Instead of using an ironing board, use a piece of melamine board or plywood, or something similar to keep the leather flat. Sandwich the leather between kitchen towels to avoid direct heat. Iron on medium heat until all creases are gone. While the leather is still hot from ironing, weigh it down with something flat and heavy to help preserve the shape while it cools.\nTest it on a small patch first, so you don't end up with melted vinyl. I used 9 different notebooks and had no problems with ironing any of them, but you never know, it's better to test beforehand.\nStep 3: Detachable Collars\nInstead of ribbons, you can use jewellery findings or snap fasteners. I used whatever I had on hand, plus ribbons allow me to control the length of the collar better, they work whether I want the collar high and tight on my neck, or low and loose.\nStep 4: Collar Making\nStart by printing a sketch of your chosen collar. I provided sketches which you can be scale down or up, or modify to fit your needs.\nI cut the flap shape out of a piece of rigid paper, and traced two shapes onto the back of the leather sheet. I carefully cut these two flaps with scissors, then I applied a layer of glue onto the remaining leather sheet and pressed my cut flaps onto the glue.\nI covered the leather sheet with cling film (to protect the book from the glue) and then pressed a very heavy book on top to make sure both flaps set properly.\nI used a scalpel (or sharp scissors) to carefully cut each collar piece out of the leather sheet. If you plan on using a ribbon, make sure to apply the glue the way I did (pic 2), so that the last 1/2 inch of the thinner side of the collar is glue-free. That way you can fit a ribbon end between two pieces of leather (pic 4).", "316" ], [ "Make a Mould of Your Thumb With PVA and Cornstarch\nIntroduction: Make a Mould of Your Thumb With PVA and Cornstarch\nI was looking for a way to make a mould of my thumb to create plaster thumbtacks as a fun afternoon projects for kids. I had limited supplies at home and no way to get anything delivered on time, so I used this old recipe for home made air dry clay using only two ingredients - PVA glue and cornstarch.\nSupplies\nPVA glue\ncornstarch\nplaster for casting pva\npaint\nsmall magnets or thumbtacks\nstrong glue\nStep 1: Mix PVA and Cornstarch\nMix one part glue and two parts cornstarch. Have more cornstarch at hand in case you need it later. Mix it in a bowl, then knead it on a flat surface.\nStep 2: Knead It\nYou have to continue kneading and adding more cornflour, even if it feels like it's too dry. It might feel dry, but it won't be ready until it holds its shape instead of spreading. Pinch a portion of the clay with your fingers, if that indent doesn't change- you are good to go. If it spreads out- you need to add more cornflour and knead it more.\nStep 3: Make a Mould\nPlace clay it in separate small, separate containers lined with cling film (for easy removal).", "556" ], [ "Coat your finger with a thin layer of vaseline (or oil) and press your thumb all the way into the clay and gently pull out. Immediately after that, mix a small amount of thin plaster and pour it in. Move it around to distribute it evenly and leave it to set for 1 hour.\nStep 4: Remove Your Thumbs\nAfter one hour, use cling film to pull the whole clay block out of the container and use your fingers to remove thumbs. Gently clean them with your fingers, to uncover the details and leave it aside to dry fully. Plaster will be too wet to sand yet. You can reuse the 'clay' and create more thumbs, it will still be wet enough for 1-2 tries.\nStep 5: Smooth and Make Holes\nAfter all your thumbs are out of the clay and dried completely, use sanding paper to gently remove any imperfections. Use a knife to carve small holes for magnets or thumbtacks. Dust the particles of plaster with a stiff brush.\nStep 6: Paint and Varnish\nUse acrylic paint to colour the thumbs and nails.Seal with a sealer.\nStep 7: Add Magnets/thumbtacks\nUse strong glue to add small magnets or actual thumbtacks.", "320" ], [ "Strawberry Flower Pot Sculpted With Air Dry Clay\nIntroduction: Strawberry Flower Pot Sculpted With Air Dry Clay\nThis fun strawberry flower pot can be used by fruit lovers to display plants, hold pens or brushes. Made with widely available air dry clay, there is no need to use a kiln. It is painted and varnished with regular art supplies and sculpted mainly with hands and homemade tools.\nI made several of these planters over the year. Each time I sculpted it in one sitting, I listened to tips from sculptors and used fillers to reduce the overall weight of the sculpture. However, I always ended up with one major problem - wobbling. The main reason being the structure was too heavy at the top and too light at the bottom. To overcome this I finally started sculpting it \"the wrong way\" by adding fresh clay on top of dried one. In most cases, when working with air dry clay you can't connect wet clay with dry clay because it shrinks as it dries and newly added pieces simply pop off. In this case however, it wasn't a problem because I used clay slip to connect wet and dry pieces and new, wet clay was wrapped around dry clay, so there was no way it could have popped off. I started using this method to pay special attention to the bottom of the planter to make sure it was level. I took additional 3 days to add layer after layer of clay circles to create a tapered bottom and made sure to let it dry upside down. Once I counteracted the heavy weight of the top part with a large amount of clay at the bottom, I removed the wobbling problem completely. I also realise that I could have made the strawberry with less tapered bottom, but I was dead set on making a sculpture as closely resembling a whole strawberry as possible.\nYou will need:\n* 1kg DAS white modelling clay (I used the entire pack)\n* Tools - If you don’t have specialised sculpting tools, don’t fret, you can always improvise. Use bamboo chopsticks, disposable cutlery, popsicle sticks.", "994" ], [ "For a dotting tool you can use a bead and skewer it with a sharpened chopstick. You will also need a rolling pin, but you can use an unopened can, glass bottle or a plastic pipe.\n* Plastic cup, cling film\n* Scalpel, craft knife\n* Old or disposable brush\n* Fine sand paper\n* Red and yellow acrylic, enamel or spray-on paint\n* Gloss varnish\n* Fast acting, two part epoxy syringe (30ml)\n* 3x6 mm rhinestones for seeds\nStep 1: Plastic Cup & Clay Slip\nI made this planter with a specific plant in mind, so I had to make sure it will fit once finished. To create a hole, I used a cup slightly larger and about 2cm taller than the planter and that’s done on purpose, so that the strawberry pot can be left to dry upside down. I marked that 2cm overhang with a sharpie so I wouldn't forget.\nYou don’t want to use a cup that’s too rigid, as you might have problems removing it from the strawberry once the clay sets. My cup was actually too flexible, so I had to temporarily stiffen the walls by filling it with rice all the way to the top and sealing the opening with tape.\nLastly, I covered the cup with cling film to ease the removal later on.\nPrepare a small amount of clay slip. It will be used later on, but it takes time to dissolve. Take a grape-size amount of clay and rip it into small pieces, put in in a small container, add just enough water to cover the clay and put it aside. You might want to cover the container to keep the water from evaporating.\nStep 2: Day 1\nRoll the clay between 0.7 and 1.2cm thick and cut an appropriate shape to cover the walls. Make sure to leave 2cm space at the top. Seal the edges by pinching them and smooth roughly. This layer doesn't have to be pretty, we just want a hard outline of the cup.\nBe extra careful to keep the clay smooth and level and cut out a circle to cover the bottom. Use a smoothing tool to connect the edges to the walls.\nLeave it to dry upside down for 24 hours.\nStep 3: Day 2\nGently pull the cup out. If it’s stuck, remove the rice and try bending it until you can slide it straight out.\nUse a brush to dab a small amount of clay slip onto the seam cracks. Roll a thin roll of clay and push it in to cover the imperfections, scrape it with a tool and brush it with clay slip to keep it smooth. Fill in the wall cracks too.", "994" ], [ "Enlarging an Image Using a Grid\nIntroduction: Enlarging an Image Using a Grid\nAny home brewers out there?\nI am the king on mediocre home brewing and I'm going to show you how I enlarged one of my beer labels using a simple grid method.\nSupplies\nMaterials\n-Print out the image to enlarge\n-Scissors\n-Boxcutter\n-Ruler\n-Pencil\n-Red marker\n-Black marker\n-Paint\n-Paint brushes\n-Top coat\nTools\n-Jigsaw\n-Orbital sander\nMolding\n-Silicone molds\n-Polymer clay\n-Wood glue\nGold leaf\n-Gold leaf\n-Gilding glue\nStep 1: Draw the Grids\nYou totally remember the \"grid method\" from elementary school, but it basically involves drawing a grid over a reference picture, and then drawing a grid of equal or larger ratio on something else. Once the grids are finished, you draw the image on the new canvas focusing only on one square at a time.\nI doubled my image. I drew a 3x3cm grid on the printout of the beer label and made a 6x6cm grid on a piece of plywood.\n*You'll need to draw the exact same number of lines on the canvas as you did on your reference picture, and that in both cases, the lines must be equally spaced apart.\nIt's super easy and the best part is this is a low-tech, kid friendly way to draw any picture you like.\n*To help yourself focus on a square, use a boxcutter to cut out a matching square in a sheet of paper.\nStep 2: Cutting\nI used a jigsaw to cut out the oval and then I sanded it down.\nStep 3: Clay Moldings\nCreating polymer clay molding is easy!\n-Press polymer clay into the molding, filling every nook and cranny and keeping the top as level as possible\n-Paint a layer of PVA glue, epoxy resin, or gorilla glue onto the surface of where the mold is going.\n-Gently pull the clay out of the silicone mold. Don't wait for the clay to dry.\n-Paint the same glue on the back of the clay you just pulled out, and then gently press it onto the surface.\n-Let it dry for 24 hours.\n*You don't need to paint the surface first. I did, because I was trying to figure out my colors.\nStep 4: Drawing, Painting and More Molds\nI drew the image onto the wood going square by square.\nI started with the oval, painted it and continued on with the banner and \"Pilsner\" font. It was a little time consuming and I made a couple adjustments to the \"Pilsner,\" because it was too straight on the printout.\nStep 5: More Font\nI thought I could pressure engrave the font to where it would show up under a coat of paint.", "74" ], [ "NOPE! I wish I used a dremel tool. A few letters showed through, but I needed to draw arches and measure spaces since the grid was painted over. I also wish I didn't use chalk paint! Dang it! I mean, I really like how it looks, but it would probably look nicer without that chalk paint texture.\nStep 6: Gold Leaf\nFor gold leaf.\n-Brush on gilding glue and wait for it to become tacky. About 20 minutes.\n-Apply the gold leaf by placing it over the glue.\n-Remove the unused leaf by smoothing the wrinkles with your finger or a small paint brush.\n*The glue must be tacky or else the gold leaf is tough to apply. It'll slip around and get stuck to your fingers and brush.\n*Gold leaf gets everywhere too! Really....everywhere! It breaks down into little gold specks while you smooth, so keep cleanup supplies nearby and turn off the ceiling fan.\nStep 7: Finished!\nTop coat and hang!\nI'm starting to like the chalk paint texture now too. This was a really fun project and took me back to elementary school.", "959" ] ]

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[ [ "Quick preface here: I love cyberpunk as a genre; furthermore, I love Android (as crazily crowded as it is with mechanics); for those of you familiar with the <PERSON> sketch (the only thing a guy wants more than sex is to be a part of a heist), the objective of the game was awesome; lastly, I think Dominion is a more than an alright game. That said, I was naturally stoked when I saw this pop on the radar. I was so excited, in fact, that I left work a little early, popped over to Compleat Strategist (my \"LGS,\" whatever the lingo is for your local gaming store), barely made it in the door, paid SRP with a smile, and dashed home to read the rules before my ladyfriend came home.\nUpon opening the box, I was more than happy with the slick-as-can-be production value FFG consistently delivers. The components looked fantastic; it was also nice for a change to open an FFG product not overly rife with components. It was easily discernible that this was going to be a quick game, which I was glad to add to my collection. Good short games are in... well, short supply, as far I am concerned. I sat down and read through the rules, no Herculean feat as they are a mere 12 pages (if you count the cover and back flap, which contains more credits than rules). A testimony to the game's negligible learning curve, as well as nicely written rules (in lieu of many a tragedy in this capacity), the accompanying booklet didn't have so much as a glossary--nor does it need one. So, at a glance, my thumbs were shooting straight up, opinion-wise. Then I played the game...\nPlease know that I did manage to get 5 games of Infiltration in this weekend (the most players being 4, to be objective). The first game, I was beyond excited. The rules were very easy to teach, and, the players present all were drumming their fingers on the table, ready for the heist to begin. We clambered through the facility, one of us pressing deep into the facility, ignoring the allure of data ripe for the picking; another player decided to butterfly net the goodies said player was leaving in his wake; I, on the other hand, did a little of both, managing to do some interfacing and tech lock picking.\nWe were lucky in that we rolled very low during the Security step, and, we never triggered a single alarm. I was holding 'Call for Backup,' so my plan was, hang back, and let the fellow who was darting into the guts of the facility get caught. The other player was dropping various obstacles for us.", "304" ], [ "He opted to collect the data on the first floor, as much as he could, and then he just left--which I found quite odd. I pressed a tad deeper, busting up more locks, offing some lab workers, with a decent pull of data; my plan was okay. Then I got wounded, after <PERSON> found not only the <PERSON> file (an alternate way out of the facility) BUT also a way out from the top floor. In the end, we all escaped, but the risky moves of the player who journeyed forth paid off nearly double.\nSo, sure, this sounds like a hoot. It was a first game, we all got a decent pull of items, we managed to try different strategies; on the whole, not a bad experience. No NPCs were or alarms were triggered. We all felt a bit unrequited, unsure if there was more to be offered. We shuffled up and played a second game, this time with a 4th player in the mix.\nThe second game wasn't much different. We triggered an alarm from the onset, but this really didn't change much. This time we all were rushing forward into the fray, some better than others. 2 of us had pretty lackluster cards, while the other 2 were gassed with jump packs, sledgehammers, and ways to chain a couple of cards for better efficiency. The game felt a little lopsided. We hit an NPC, but he didn't do much more than snatch up a leftover data file and haul tail out of the facility.\nThe scoring was much closer this game, but, still, not much excitement here. The variation in items and room effects was not enough to make the game feel different, or, for that matter, \"exciting.\"\nThe next two games were a bit more like the second game, also with 4 players. We managed to screw each other a few times, but, on the whole: shrug. Each and every single player had basically the same the thing to say: I wanna like this, but there's just not much to it.", "528" ], [ "Okay, I played my first (and quite possibly last) game of Ra: The Dice Game earlier today at the WBC. The game was explained by the ever-delightful <PERSON>, who made the transition from Ra to this dice version seamless and simple. Some credit must go to <PERSON> for this as well, I suppose. The reason I may never play it again is simply that I couldn't find a copy to buy at the vendor booths at the WBC--which was a shame because the game supports two players quite nicely and that's the itch that always needs to be scratched at my gaming venue of choice.\nThe mechanics are simple--Yahtzee rolling scheme, dice that show pharaohs, monuments, civ advances, Nile/floods, Ra's suns, and the wild-card Ankhs. There are some niggling details that must be mastered, such as the fact that suns may not be rerolled, and the color of the dice matter periodically (okay, that was sort of an obvious development) but not always. My favorite goal was simply to roll three suns and two ankhs every turn, which, had I been successful, would have ensured instant gratification to the tune of 5 points each turn. That was--due to the vagaries of probability--very unrealistic, sadly.\nMy opponents were a pair of very lovely Scots who'd been transplanted to the Philadelphia area, and I could tell that they were enjoying the dice decision processes a bit more than was I.", "755" ], [ "I honestly much prefer the original Ra to this game, if only because the Pharaoh and Nile tracks cap relatively early, and if you keep rolling Nile and Pharaoh dice faces to the point of total superfluousness, it's most displeasing. This sort of non-probable yet provably-possible outcome is the sort of thing that used to piss me off no end in Yahtzee. All I need to do is roll three more '2's to get the top bonus!!! What do you mean I keep rolling everything but a '2'?? How can this be? Same thing in Ra: The Dice Game. It's insanely easy to see what you should do with any given roll of the five dice, and the only challenge is in rolling what you need when you need it. So, in other words, it's all the luck of the dice.\nWere the decisions more difficult surrounding the dice allocation (Kingsburg pops into mind here, for no great reason--it's not like it's ever that hard to allocate dice in THAT game--it's just totally a no-brainer in this one) I'd have enjoyed this game a lot more. As it stands, it's a reasonable diversion that's not nearly as messy to deal with as actual Ra, but it's also not nearly as satisfying to me. Ra is generally an 8 out of 10 game for me, and this modification pulls it down into the 5-6 range.\nAs a public service, and to spare future visitors the tedium of the pissing match that I will eventually get into with one of this game's playtesters, here is a link to the game's rules, thoughtfully pointed out by the selfsame playtester:\nRules of Ra The Dice Game", "755" ], [ "Playing with 4, a chronicle so far that has spanned 5 games.\nPlaying so far exclusively on TTS; 3 of us purchased kickstarter and are awaiting our copies (North America)\nLearning the game\nNot nearly as bad as you might think if you hang out in these forums. We started with the playthrough, which is really just the first four turns or so, and then continued on into the gameplay. First game will require rules clarifications, googling these forums (what game doesn't, though?). Only in one case did we have one big confusion in the first game. This led to my post https://boardgamegeek.com/thread/2557132/definition-more-it-..., which ended up in the official errata https://docs.google.com/document/d/1p2tHzbTmQhU8tPfZeK5gSJvm...(I feel cool).\nPlaying the game\nThe best thing about this game is the constant shift in victory conditions, which can see huge swings in what you think to be true. For example, in our last game, we were certain the Chancellor would win. He had an impenetrable fortress of secrets, banners, and a relic that required we first remove it before going after any of his other key items. His citizen, who had been loyal all game, asked for reinforcements. Only then did the citizen make a mind blowing back stab play to campaign against his weakened chancellor and steal these treasures. This then made us certain the traitor citizen would win as the game was nearing the final rounds. This opened the door for me to then go in and campaign against the chancellor's remaining banner which provided me the oathkeeper title, and now it seemed certain I would win.", "366" ], [ "In a matter of a few key and highly strategic plays, the ebb and flow of power was palpable. Guess who ended up winning? None of the three of us! The other exile! Who found the one vision he needed for the win, with the vengeance-filled chancellor backing his win.\nWill you like this game?\nDo you like great stories like Game of Thrones? Do you like emergent narrative? Do you like highly strategic card interplay where spotting a combo at just the right time could catapult you from the back of the game to the front? Where the bullseye on someone's back is always changing? Where the rug gets pulled out from under everyone in succession, and everyone gasps? Then you will love it.\nMy one critique, which really isn't a critique, when I think about it\nKingmaking. There is a lot of kingmaking in this game, so be ready for that. Normally, it would feel a bit deflating to be in the lead, only for another player to hand the victory to a third player out of spite. They couldn't win themselves, but you had taken the win from them, so they pass the win to another. This can happen. However, when you step back and look at it from the story, and thematic point of view - it makes perfect sense. Why would the chancellor not want to pull the win away from the citizen who stabbed him in the back? Et tu <PERSON>?\nClosing thoughts for now\nThis game appealed to me early on, I followed the designer diary. It has quickly risen to a top 3 for me after 5 plays. I believe it has so much more to see, as our chronicle continues. Every single game has felt different from the last. If you are looking at the rulebook or reading the forums about the rulebook and thinking, ugh - I don't want to learn this...I would say, get on TTS, get a few friends, and just try it.", "366" ], [ "***A small update to this review (four year old at the time I am now writing) is posted below with a follow up after a few years of Cthulhu Wars on the table.***\nINTRODUCTION\nAfter five years on this Geek this is my first review. It's a long one and any of you can skim or skip with my blessing; heck, take the extra time you'd gain by doing so and read The Shadow Over Innsmouth instead.\nI am writing a review I actually hesitate to write for a couple of reasons. First, I have played the games three times; I would like to have had more plays before putting the review together. Second, I am hesitant to write this review as I am so squarely in what must be the target audience for this game that I may have a challenge for some on this site in having my thoughts on the game being regarded as having a broader relevance. I hope to address this challenge.\nI have been playing The Call of Cthulhu RPG obsessively for over twenty five years now and my deep gratitude to <PERSON> creativity goes back just as long. I don't think it's generally realized how much he has fleshed out the Cthulhu Mythos in how it is presently conceived (He created the Dark Young; how cool is that?). His work on Doom, Quake and Age of Empires II is even less known. When this Boardgamegeek member heard that <PERSON> intended to make his definitive statement on the Mythos in board game form, it became the dream game for me. As my personal excitement grew, though, the sheer scale and cost of the project gave many in the BGG a skeptical approach to the game; some commenters even seemed unfairly dismissive. I actually found myself hoping it was \"just okay\" so I would not feel the pressure of adding my voice to the discussion. I have strived since I joined BGG to have discussions which are sober, constructive and critical so as to maintain meaningful discussions. Despite my love for many games, I never want to be the fanboy, so pathetically distracted by theme and chrome, so easily dismissed.\nBut it was dropped on my porch last month.\nAnd it was good. It was very good.\nDammit.\nTHE APPEAL OF THE GAME\nAs the components and rules of Cthulhu Wars are well presented already on the site, I will keep my rules overview brief and general. The base game offers a medium weight, three to four player experience (two with a less compelling variant, five with an additional expansion faction).", "504" ], [ "Each player controls a faction of dark, cosmic evil competing with other similar factions for the lion's share of the remains of a defeated, dying Earth. Players push and battle each other to control areas, build gates, gain power, achieve personal goals and unlock special abilities in the form of spell books to make their own faction supreme. The player wins who, having acquired all six of their spell books, accumulates the most Doom Points through holding areas with constructed gates on the board and blind drawing Elder Signs. The miniatures are conspicuously monstrous, appealing and evocative but their ostentatious nature runs the risk of obscuring the game that happens to be in this box, too; I'm going to try to talk about that game here.\nIt is the most wildly asymmetric game I've ever played.\nMy favorite games include , and . I really, really like asymmetric games. I love the feel almost of role playing, settling into the character of your faction; the more faithfully you inhabit them, the better the mechanics become tools of your play. I love the clamor of the different factions crossing each other, each playing their own game, each trying to sit atop the others in The Game.\nCthulhu Wars' asymmetry is so daring one would think it would be game breaking -- but so far, at least, it's not; it's sublime. I am chuckling hearing how imbalanced some gamers claim one or another faction is, but to this point I believe I have heard from different posters how unbeatable all of the factions are. <PERSON> is the designer who was responsible for balancing the seventeen different playable sides of Age of Empires II (which included dozens of upgrades and unit types); I think that experience likely served him well in playtesting and refining Cthulhu Wars.\nIn any case, the four base game factions all have different core abilities that give them a significant advantage in the game. In addition, many of their monsters (generally three unique monster types) have or can acquire different powers. In order to win, each faction must satisfy six different goals mostly unique to their faction. Finally, by doing so, each faction unlocks six unique spell books that either give the monsters the powers stated or provide another faction advantage. I have to date played three of the four base game factions. In the words of the designer, <PERSON> bullies; that player becomes a bully in order to win.", "366" ], [ "Keyper got dropped off at my house yesterday, so I promptly started sorting the insane number of pieces and started a game with two of my roommates! Since the hype for this game is still very much alive, I wanted to share a few of my initial impressions. This will be a review more than a rules summary.\nBackground: I missed the kickstarter but was able to get in contact with <PERSON> to order a copy of the character edition. It arrived in perfect condition, and I'm super pleased that I went in for the characters. They add a lot to the game, both in terms of adorableness and play-ability; the icons on the meeple can help differentiate between the sometimes very similar colors, even for a group of players who have no color distinction deficiencies.\nI'll break this \"\"\"review\"\"\" of sorts down into separate sections to talk about the really good and the weaker points of the game.\nHow Does It Compare to Keyflower?\nAh, the question everybody is asking: is this game better than Keyflower? The answer is a resounding, \"it depends\". Keyper is significantly less tactical than Keyflower. There doesn't seem to be as many opportunities to make a game-defining move, and nearly as many \"take that\" opportunities. It's also not very strategic; sure, you can have a long-term plan, such as \"I'm going to specialize in gems and get the bracelet maker\", but a plan is not a strategy.\nSo, if Keyper isn't really testing your tactic or your strategy, then what is it testing? Efficiency. The winner will be the player who has played the most efficient game. How many actions were you able to pull off in each season, and how many actions did you enable others to pull off in each season? The winner will be the player who keeps that ratio as high as possible; taking all the actions, while also not enabling the other players at the table.\nThe result is that Keyper is much more \"friendly\" than Keyflower. There is a very high degree of player interaction, but the players are not necessarily in direct competition for most of the game. In that regard, it has the diplomatic benefits of a multiplayer-soltaire game without the feeling of isolation. If I were going to play a game with some friends on a Friday evening, I would be more inclined to play Keyper. If I were at a convention or tournament and wanted to flex my competitive muscles, I would always pick Keyflower.\nComponents\nHoly hell this game has a lot of components! There are 6 resources, 8 animals, 3 gems, and wheat. There's 36 meeples and a crap ton of tiles, and they are all very high quality.", "366" ], [ "A few of my octagonal prism pieces (\"finished goods\") were miscut. The gems are a nice hard, slightly translucent plastic forming irregular concave polyhedra, but it was sometimes obvious where they were cut off of the plastic. The painted meeples were gorgeous, although a few of them have the facial expression of an existential crisis. Almost all the animeeples except for the goat and deer can be balanced on their noses if you have a steady enough hand.\nThe folding boards are the MacGuffin of the game. Is it a gimmick? Yes. Does it hold up? Hell yes. They feel very sturdy and durable, the folding is natural and easy, and the layout of the actions on the board is nothing short of genius. For example, gems can not be displayed before fall, no matter how hard you try. There is a progression form \"basic\" resources to more complex actions as the seasons progress.\nI would strongly recommend giving new players a good, long look at the boards at the end of their first season to let them wrap their minds around how to fold the boards. The options available are significantly more numerous than I originally imagined, and there is a large element of discovery in looking for the perfect combination of actions. I definitely think the boards add a meaningful decision in between the seasons and applaud <PERSON> for his creativity and ingenuity in designing them.\nI'm a big fan of the \"Meeple Like Us\" accessibility reviews. Unfortunately, I don't see them rating this game highly in the color department. The grey is very light and easy to confuse with white, and the orange and brown are very similar. The colored boarders on the action spaces often times don't stand out strongly enough against the art on the board and cause a lot of \"what specialty is that?\" questions, and more than once we realized we had joined with the wrong color on the wrong space. None of the players at the table had any type of color deficiency, but we still sometimes had to rely on the picture of the tool being held by the meeple -- \"oh this guy has a pickaxe, he's not a wild!\", etc.", "336" ], [ "Artwork by the unparalleled <PERSON> and <PERSON>.\nTidal Blades: Heroes of the Reef is a game I acquired for its visuals and components alone. Shocking, I know; shouldn't you only buy games you INTEND to play? To provide some background on my tastes as a gamer, I am not a frequent backer of games on Kickstarter: only five titles are backed under my name in the past five years. I don't need a game to have stunning visuals to love it; Lancasterand Concordiaare both in my Top 10 games of all time (you can read the full list of my Top 100 Games of 2020 here). That being said, visuals can certainly pull me in to enjoying a game more, from the woodlands of Rootto the bombastic world of Mechs vs. Minions. But as a rule of thumb, I am more of a \"mechanisms first, theme second\" kind of guy.\nSo when it came to making the decision to purchase Tidal Blades: Deluxe Edition, it was an item I knew I wanted to have in my collection. I've played plenty of worker placement games with mechanisms that excite me, like Calimala's fantastic double activation, or the madcap wackiness of Argent: The Consortiumand its multi-talented wizards. Nothing about the worker placement in Tidal Blades excited me from the Kickstarter. I certainly hoped that its mechanisms would reveal itself to me upon play, and that it would be a game that I would grow to love the gameplay of on top of its brilliant world-building and artwork. I feel that many backers and potential buyers may be in the same boat as me, so let me help you navigate the waters of this massive ocean.\nI'm not here to talk about the visuals of Tidal Blades: Heroes of the Reef. It is the nicest box of components I own, and the presentation is even better than that of Mechs vs Minions, Everdell, and Scythe, in my opinion. If you're reading this review, I bet that the world created here drew you in. Again, there's nothing wrong with that, in my book. As board gamers, we're allowed to like nice things!\nSo, let's talk about the mechanisms in Tidal Blades: Heroes of the Reef. I'll start with two positives, and go into a few misgivings I've developed over my few plays.\nThe sense of character progression and growth is tangible and forefront in your journey in Tidal Blades.", "504" ], [ "Through completing quests and fighting monsters, you're going to find yourself jumping up all four of your dials. All of them feel worthwhile and will give you a great sense of variety from game to game. While getting better stunts and bringing more dice to challenges feels accomplishing, I have to highlight my personal favorite traits to upgrade: Resilience and Synergy. The former allows you to engage with the tremendous dice upgrading mechanism (like a tech tree), and its empowering to upgrade so many dice at the end of each day. In another vein, Synergy lets you customize your character, and it's always a joy to draw new attributes and deck out your champion with asymmetrical powers. I think many will end a game of Tidal Blades feeling proud of the character they've built, and will be eager to see how differently it plays out in future plays. The character growth the star of the show, in my opinion.\nAnd while advancing your traits commands center stage, the dice mechanism is the supporting actor holding the performance together. How you roll dice in Tidal Blades is probably the single most important factor in whether or not you will enjoy this game. Tidal Blades only offers twelve actions (fourteen with the Try-Outs variant), so you know the worker placement can't be doing all of the heavy lifting. No, you will probably spend the majority of your time in Tidal Blades either rolling dice, or watching another player roll dice. If this is a problem for you, then you and I both know this game isn't the right fit for you. But, if like me, you tolerate dice rolling (and potentially even enjoy it!), then I think you'll find a lot to love Tidal Blades' take on the format.\nI tend to play my games in gut-reaction mode, meaning I like to keep the action going and the blood pumping. I'm not one to puzzle over every space combat in ; I'm the kind of guy who will quickly assess my odds in and grit my teeth as I pull that final chip from the bag. Going with your gut is what makes the combat in Tidal Blades enjoyable to me. I'll swipe up my dice, roll them without inhibitions, reassess, and roll again. The results you get are often varied enough that you'll get to roll several times, making tight decisions about when to pull out, or when to push for one final go.", "237" ], [ "All right, so let's say you have this spacefaring race. They've been expanding, getting themselves into new environments, and having babies on completely new planets. The only problem is that some of these babies don't develop too well in these new environments; some are stillborn, some deformed, and some are just straight up missing things. One of these things is the Parthen version of a uterus.\nFor the latter deformed babies, the future looks pretty grim; without the possibility of bearing children, they'll look to other ways of attaining lasting happiness and satisfaction. Some may become doctors and biologists, and in their hi-tech world, they may seek answers as to how to solve their infertility.\nFinally, after decades of research, a solution is devised: they can't repair the uterus, and it's too late to clone and insert a new one, but what they can do is hijack the uterus of a surrogate mother, splicing DNA from both parties to create a hybrid baby.", "1008" ], [ "And since the baby is getting genetic material from both mothers, it's got a fifty-fifty chance of having the same deformity, and needing to use the same process to have its own children.\nI think you said somewhere that some of your Parthans already couldn't reproduce on their own; this solution could work for them too.\nWhat I'm imagining is some sort of cyborg-genitals (never thought I'd say that), but given an advanced enough species I guess it's possible that they could just use some other parts of Parthan anatomy to get the job done. Perhaps the baby would get all of the 'father' DNA, instead of a split; that would make more sense to me, but may not work in your story. Also, with more of a biological solution, there could be more drastic physical changes due to hormones, leading to a more 'masculine' appearance (rather than a woman with a baby-making attachment strapped on).\nAfter a while, this solution might not be the best one (that is, the original problem may have been solved in a more satisfactory fashion), but by then there would be enough 'men' around to sustain a viable population. Plus, by then the Parthans might have found more uses for them, such as the ones other answerers have mentioned.\nWhat I'd like to stress with this answer is that it sounds quick and dirty, but that's exactly why it makes sense: people will go to great lengths to ensure the survival of their genes. The solution may not be the best, but given the direness of the problem, some concessions can be made.", "1008" ], [ "I've been lucky to play this 3 times already since I received my copy on Friday. Here are a few thoughts:\nI'll start with my final takeaway. This is a game where the players' capabilities diverge very quickly. By contrast, in Vital's previous games, all the actions are generally the same for everyone for the duration of the game. However, in Lisboa, you immediately receive a \"clergy tile\" which modifies some action or result for you and you alone, and you can then accumulate more such bonuses--many of which are cumulative with each other--very quickly. If you hammer those bonuses, you will crush. If not, you will have slow and linear progression, which will not be enough to win. In this sense, it feels quite different from his previous games, but in a very good way. **You NEED to specialize, and use your specialization as much as possible.** This is a significant difference from the previous games.\nNext, though, is a big similarity to one of his previous games--Gallerist. This one is obvious. You want as many free actions (during other people's turns) as possible. So, take as many \"favor tiles\" as you can, and don't be shy about spending your influence.\nFinally, it is quite a heavy game.", "237" ], [ "But, re the \"complex for the sake of bring complex\" comments, I fully disagree. Once you understand the theme and think about the game mechanics for the actions they represent, they all make sense and are much easier to track. For example, the variable influence cost to visit a noble represents the number of other people you have to elbow your way past when you enter his salon.\nMy first game was 4 new players. I won that game with 108 points; second place was 100. I had no particular strategy, but i did let my starting clergy tile choice guide my actions as much as possible (I took a tile that let me \"follow\" without spending influence, and made sure I had favor tiles for all 3 nobles as often as possible).\nLast night was my third game. It was me and another guy who had played already, and two new players. This time I had a strategy in mind and better understood how the parts all fit together. I won with 124 points; second place had 87. I pursued an aggressive building strategy, thanks to a couple of treasury cards that gave me a discount when building. I eventually got to a point where I only needed a couple more rubble cubes to trigger the end game, and then took a zillion decrees. I was not shy about spending influence to follow noble actions--my influence hovered below 5 the whole game. I even spent 3 wigs to follow at one point. My final score included 36 points from decree cards (!!).", "366" ] ]

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[ [ "....and her mouse never broke again.\nWe had a contract to supply 3 techs plus a supervisor onsite at the HQ of a large international corporation. I was one of the techs. It wasn't a bad gig, except for that one attorney who insisted we fix an HP LaserJet (this was before personal laser printers; pretty sure it was an LJ III) that had been dropped and had a bent everything. I turned him over to the supervisor, and that's pretty much that story, except for the part that no, we didn't fix that printer.\nI should also mention this supervisor was hired for this position, and as part of the deal to hire him he was being given formal CNE training. Ain't gonna lie: This rubbed us three techs, who were doing the training on our own, pretty bad, but he really wasn't a bad guy. It did take us a bit to warm up to him, and the story I'm about to tell helped.\nThis story involves a user who needed a new mouse about every five or six weeks. It would just stop working and of course she had no idea what was happening to it.", "107" ], [ "This was back in the mid-nineties, folks, and mice (mice with a ball and other moving parts and stuff) weren't as cheap as they are now.\nOne day I was helping a user near her, and every so often I'd hear a bang or thud or smash coming from Mouse Lady's desk. This was an open-floor plan department and I saw what was happening: Every so often she'd pick up the mouse and pound it on her pad. The look on my face must have said something because the person I was helping said, \"She does that all day.\"\nI went back to our little corner of HQ and was telling the guys about it, when the supervisor told us to let us know the next time she needs a new mouse--he'll take care of it.\nAnd he did. He took her a new mouse one day and returned with a disassembled mouse, saying something like we shouldn't be hearing from her in awhile. Of course, we asked what he did and he showed us.\nHe pointed at the logic board for the mouse and pointed at some random component, grinning. \"See the value on that impact capacitor?\" he told us. \"You only see something that high on something that had a couple of bricks dropped on it.\"\nI've been dying to try that on someone since, but alas. No one else is in the habit of slamming their mouse on their desk anymore.\n​", "107" ], [ "Sometimes your IT people know what's best for you\nSometime in the last century, I was contracted out to a large non-profit NGO that everyone thinks is a real Gov. Agency. Their IT infrastructure was non-existent.\nIt was a hodge-podge of . . . things, and my company was brought in to give them a real, unified network (Netware. This is how long ago it was.). Honestly, they had no centralized IT and each department had their own way of running their computers. After bringing in a consultant, they hired an IT Director, who contracted with us to jump-start everything.\nAs I said, each department did their own computer thing, wit the result that one department had a pretty good hobbyist who gave them something resembling a pretty good network, while Marketing used (if memory serves) a Wordperfect peer-to-peer thingy, and most of the rest of the NGO used Sneakernet to transfer data.\nAfter we had ported everything and everyone over to Netware, we then went desk-to-desk to install agents that would run a backup of the users computer (Yes, everyone is going to ask why we just didn't install the agents when we built the new machines.", "760" ], [ "I honestly don't remember; I think someone just f'd up.). Most people didn't mind; the install took only a few minutes and the user could get coffee while we were installing it. But one guy did everything he could to keep us from touching his computer--I'll call him DA.\nDA worked in a two-person department that created critical documents. See, this NGO sold reference standards of various chemicals, and each chemical, when sent to a client, absolutely must be accompanied by a Safety Data Sheet (SDS) for that chemical. As I said, this was a two-person department at the time: The manager researched & wrote the SDSs, and DA entered them into a flat-file dBase+ database, that was, of course, kept on his custom-built, non-standard, tower computer. He also had written a lot of DOOM levels that were pretty popular on the baby internet, and he looked down on us mere technicians. (If you can find anything from Dead Cat Productions, those are his levels.).\nYes, he balked at us installing a backup agent on the only computer in the entire company that held these important documents.\nWe in IT had to get HR, Legal, and VP level people involved in order to force this guy to give us access to his machine. We got the agent installed, but not without suffering nasty looks from him for about 6 business days....\n....until the seventh business day, when he came into our little corner of the building, virtual hat in hand, and asked if we might have any backups of all his data handy. Yep--his HDD had smoked (literally) and both he and his boss had the chemists calling for their heads on platters.\nWe gave him our slowest standard machine (explaining it was all we had and we'd go ahead and order him a faster one), had him install dBase+ and we restored his data, and he and his boss limped along for a few days.\nHe still balked at us touching his new machine, though.", "760" ], [ "\"I'm going to lose this contract if you don't let me use a very expensive software product for free on your servers even though I don't work there.\"\nThe subject is basically the TL;DR, but here are the details.\nMany years ago I worked on the consumer helpdesk for a local reseller. We had a lot of local contracts, but also supported regular customers. One day my phone rang: \"Thanks for calling reseller tech support. My name is <PERSON>; how can I help you?\"\nThe caller asked if we had a piece of software: As I recall, it would help port users of CTOS into DOS/Windows 3.1. I also remember the price: $1750. Further, it was intended to be installed in a Netware environment.", "760" ], [ "As you might imagine, this was late in the last century, so the gist of the remaining conversation follows:\n\"Great! That's what I need.\" I asked him for a method of payment. \"I just need you to install it and let me use it.\"\n\"On our servers?\"\n\"Yes.\"\n\"And then we put it back on the shelf? You want us to do that for free?\"\n\"I need to port over the Office of the Commandant of the Coast Guard* to DOS, and if I can't use this software I'm going to lose the contract and be sued.\"\n\"I'm sorry to hear that, sir, but we can't let non-employees on our system, and we sure can't open up a software package for you...\"\n\"You don't understand! I'll be sued for breach of contract if I can't do this! Who do you have to talk to to make this happen?\" I put him on hold and talked to my manager, who looked at me like I had grown a second head before shaking his head.\n\"Sir? My boss says we're not going to do that.\"\nHe couldn't take that for an answer and demanded he speak with someone else. I gave him my VPs name and number, then gave the VP a heads-up call right after hanging up.\nA few days later, that software package was still in our inventory.\n*The Office of the Commandant of the Coast Guard is important in helping me remember this story. A previous employer was a Convergent Technologies (CT) reseller and had sold a lot of CT AWS and NGEN systems to that office. It seems they were moving into the PC world and this guy's small minority-owned business won the contract to port that office into the wonderful world of DOS. I didn't get the name of his business, but I strongly suspect they no longer existed before the year was out.", "760" ], [ "Two spaces where there should be one\nI once worked, under contract, to help a company set up an IT department. Like a lot of other companies that existed before computers did, each department bought its own computers, and some set up LANs, while others set up peer-to-peer stuff, and others used sneakernet. This company brought in consultants to tell them they needed an integrated IT department & network, and the company hired a CIO who was a damn good one except for when he hired his idiot son because his demon seed couldn't hold down a job, not even as a used car salesman. (I met his other sons. Nice guys--they ran a pretty successful plumbing business.)\nThe CIO started building his IT department and when our contract expired, he let everyone from my company go except for me, because (humblebrag) I'm damn good at fixing hardware. I was still under contract through my old company, though. Important to this story: This was back in the DOS & Windows 3.1 / Netware days. Also, even though the CIO's numbskull son could barely breathe and walk at the same time, this dumbass treated me like a second-rate citizen. Honestly, a dirty dinner plate would have done a better job than this jackass.\nThe CIO was the only person with a laptop, and one day he gave it to his meathead son to fix because Windows stopped launching. This ignoramus had no clue what to do, so he gave it to me.\nHardware checked out. SCANDISK didn't show anything alarming. A few other tests told me nothing. I started scrolling through configuration files, just to see if I could get another idea.\nNow, DOS and WIN 3.1 used a lot of configuration files. You might have heard of the DOS config.sys and autoexec.bat files; they set up the computer by loading drivers and any programs that might be needed down the road.", "760" ], [ "After that you launched Windows--either manually by a command-line command or by putting that command in your autoexec.\nWindows also had a bunch of enormous text-based configuration files that loaded stuff for Windows and made it work, and for the life of me I canNOT remember what those files were called, or even their extensions. But I was scrolling through one of them just to buy time while hoping another idea would come up.\nSo I'm scrolling and scrolling, and I'm not sure my eyes were really focused on what was going past them but suddenly . . . whoa. Scroll back, and I put my cursor just . . . there.\nThere, where there were two spaces where there should only be one. I removed one of the spaces, saved the file, and damned if Windows didn't launch and purr like a kitten. It must have shown on my face, because <PERSON> said something to me, no doubt with a sneer. I turned the laptop toward him, with Windows up and running\n\"I'll take it to my dad,\" dipshit told me.\n\"No, you won't,\" I answered and I took it to the CIO. He asked me, first, why I brought it to him, and I told him. He shook his head ruefully, then asked me how I fixed it. I told him that, too.\n\"You're kidding me,\" he replied, reasonably, IMO.\nI just answered, \"Nope,\" and asked if he had anything else before I left.\nI'd love to know how that second space got there.\n​", "406" ], [ "Just had an unexpected call\nMany years ago I was called out to a new customer's house. He'd bought a laptop with Windows Vista pre-installed. This was a Toshiba, and you'd expect - despite all the shortcomings - that Vista would be OK. Tier 1 manufacturer, drivers all tested and up-to-date*.\nNo. Not good enough. Customer had downgraded to XP with a pirated ISO, despite there being no downgrade path at the Toshiba support website. IOW, no XP drivers for this machine, and of course it was vomiting errors and BSODs almost every day. This wasn't during the transitional period, it was well after Vista was introduced.\n\"Fix it\", he said. I told him that I could try, but as there was no official downgrade path, I couldn't guarantee a positive result. He insisted, so off I went looking for drivers at realtek, intel, etc, and tried it with those. It seemed to work, and was stable for a day or so.\nThen I had another call. Angry, this time. It had fucked up again, it was all my fault, and he wouldn't be paying my bill until I fixed it.", "760" ], [ "I told him he could either pay my bill, and I would come and have another look at it, or he could find someone else to deal with it. You can guess the outcome. Not to worry, life goes on.\nToday, years later, he called me acting like we'd never met, and he wants me to come and deal with some new problems. Initially, I agreed and made an appointment - but what I think I'll do is send him a text:\n\"Mr <PERSON>, I thought your name sounded familiar, so I went looking in my records. It seems that our last encounter resulted in a breakdown of professional trust. I don't think it's in my best interests to deal with you again. Best wishes, ol-gormsby\"\nToo harsh? I really don't want to see him again, but it would be unprofessional to just ghost him. I'm not sure how else to say \"no\".\n*I've even got an old Vista Toshiba in storage, traded in by a customer. I fire it up once in a while and it's fine. I'll probably never ever use it again, but it works, and doesn't throw BSODs.\nUPDATE: I sent the text and put my phone in flight mode until CoB. Within 30 seconds of 5pm I had a text reply claiming \"I don't remember. What was it about?\" which I proceeded to ignore. And 20 minutes later a phone call which I also proceeded to ignore. Firing customers is fun!", "760" ], [ "\"Trust but verify.\" \"No u.\"\nBackground: I was vendor support for a service running on one of this company's servers. We had ruled out any issues on our end and pointed at a local network issue, but I was needed for testing at the end so I got to stay as a fly on the wall. This had turned into a big meeting with several network people, sys admins, several managers and upper management, and one lonely local IT guy who was the only set of hands on the affected machine. We had decided to change the IP on the affected machine.\nA local IT guy (IT), a network guy (Net), and network guy's manager (NetMGR) walk into a bar...\nNet: Alright, I'm going to send you the new IP in the meeting chat. You'll need to set it as a static on the server.\nIT: Got it. Entering it now. ... Done.\nNet: I'm still not able to reach it... Can you try rebooting it?\nOne reboot later.\nNet: Still nothing... Can you send me a picture of the info you entered into the static just to double check?\nIT: Sure, trust but verify.", "760" ], [ "I got you. Give me a second.\none blurry phone picture later, since the machine's offline at this point.\nNet: This doesn't make sense... That's exactly what I sent you. Can someone else try to reach it from a different source?\nNetMGR: Net, can YOU send a screenshot of what you entered on our end for that port?\nNet: I guess? I copied it straight out of the entry...\nNet sends a screenshot that has an IP that clearly does NOT match what he sent in chat earlier. I'm talking <IP_ADDRESS> compared to <IP_ADDRESS>. Not even close. It was probably an IP address from a different entry altogether, but I'll never know.\nComplete.\nSilence.\n(For much longer than was comfortable.)\nIT: And... done! Can you reach it now?\nNet: Yes...\nIT: Cool, can we check to see if the service is working with the new IP?\nMe: Uh, yeah. Testing now.\nThe meeting proceeded and it ended up being something else (still a network issue, just something outside my wheelhouse). I'll never forgot you, super chill local IT guy.", "760" ], [ "Not the usual fare for this group?\nBack in the 80s-90s, I was a developer at a company that made Geographic Information System software. This software run on just about every flavour of Unix out there. It consisted of multiple programs that communicated with each other through queues and semaphores. Also, being Unix it was perfectly possible to run multiple copies of the software at the same time. Every now and then the software would crash and you’d have to manually kill all the queues. We had a shell script called “ipcrm” that cleaned up all the resources that belonged to the current user.\nNow the sharp eyed readers here would have noticed that “current user” thing.", "434" ], [ "Obviously if there were two people using the software at the same time, you wouldn’t want them to be using the same userid. Not just for the ipcrm reason, but also because if you didn’t use separate userid for each user, there’d be no way to track who had done what.\nWhen we set up these systems for a client, we’d send out a tech to help set it up. And the techs had a special account set up so they could do some checking of the setup before the clients started using it. The password on this special account was originally just the first three letters of the month backwards, so in March it would be “ram” and in September it would be “pes”. But the techs didn’t like that, and said it was too confusing, so we made it “*”. (Note: computers weren’t connected to the internet, so this wasn’t as scary as it sounds.)\nBut worse than that, the techs told the users about this account, and users being users, they all used it instead of their own accounts. So no auditing, and every time one person’s session died they would run ipcrm and it would kill everybody else’s session as well.", "760" ], [ "Liquid damage\nApprox 12 months ago, a customer calls me:\n\"Hey, that laptop you sold me? The keyboard's not working\"\n\"Sorry to hear that. What exactly is wrong?\"\n\"The bottom row of keys isn't working. Is it still in warranty?\"\n\"Oh, yes, this machine has a three-year warranty. I'll need to do some troubleshooting before I can send it off. Have you power-cycled the laptop?\"\n\"Yes, it still doesn't work.\"\n\"Okay\" proceeds to talk customer through Device Manager, uninstall keyboard device, reboot.\n\"Still not working\"\n\"Yes, it sounds faulty alright.", "107" ], [ "Do you have an external keyboard you can use in the meantime?\"\n\"Sure.\"\n\"Alright, I'll go ahead and schedule the work. The service depot will send you a courier label. Pack it up, or I can do that for you, put the label on and send it off. It'll take about a week. I can lend you a laptop while it's being fixed.\"\n\"Alright.\"\n\"Now, I have to advise you that if they open it up and find liquid damage, it won't be a warranty claim and you'll have to pay them for a new keyboard and labour before they send it back.\"\n\"Oh, um, well, I can't spare it just now. I'll let you know when I have some time.\"\nApparently she's not been able to spare it for over 12 months.", "648" ] ]

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[ [ "Understanding how quicksort operates\nI am having a hard time understanding the quick sort partition operation. I understand what partition is supposed to do, I just don't understand how partition does it. Specifically, I don't understand how the two subarrays (q-1, q+1) are constructed. I have looked at various other SE articles, such as:\n* https://cs.stackexchange.com/questions/81045/how-does-hoares-quicksort-work-even-if-the-final-position-of-the-pivot-after-p\n* https://cs.stackexchange.com/questions/1334/randomized-selection\nI understand the notion of:\n1. Select a pivot (typically the last item in the array, at least in simplified methods)\n2.", "318" ], [ "Create one subarray to the left of items smaller than the pivot\n3. Create one subarray to the right of items larger than the pivot\n4. Recursively call partition on each of the subarrays\nHowever, in the following example, is where I get lost\n8 1 9 3 5 7 6\nHere, 6 is my pivot\n7 is larger than 6, so my array now looks like:\n8 1 9 3 5 6 7\nHere is where I get lost. Does the rest of my sequencing look like:\n8 1 3 5 6 9 7\n1 3 5 6 8 9 7\nWhere:\n1 3 5 is my smaller array and\n8 9 7 is my larger array (where each then get partition recursively called?)\nI am most confused by the proper construction of the larger and smaller arrays and in which order to put the numbers in. Any help is appreciated. I am happy to edit my post for clarity if I am unclear.\nEDIT:\nI tried using some base code from this address, and edited it slightly to create more print statements, but still don't understand why it would sort to:\n1 3 5 6 9 7 8 and not 1 3 5 6 8 9 7 initially\nHere is the code:\nclass QuickSort\n{\n/* This function takes last element as pivot,\nplaces the pivot element at its correct\nposition in sorted array, and places all\nsmaller (smaller than pivot) to left of\npivot and all greater elements to right\nof pivot */\nint partition(int arr[], int low, int high)\n{\nint pivot = arr[high];\nint i = (low-1); // index of smaller element\nfor (int j=low; j<high; j++)\n{\n// If current element is smaller than or\n// equal to pivot\nif (arr[j] <= pivot)\n{\ni++;\n// swap arr[i] and arr[j]\nint temp = arr[i];\narr[i] = arr[j];\narr[j] = temp;\n}\n}\n// swap arr[i+1] and arr[high] (or pivot)\nint temp = arr[i+1];\narr[i+1] = arr[high];\narr[high] = temp;\nreturn i+1;\n}\n/* The main function that implements QuickSort()\narr[] --> Array to be sorted,\nlow --> Starting index,\nhigh --> Ending index */\nvoid sort(int arr[], int low, int high)\n{\nprintArray(arr);\nif (low < high)\n{\n/* pi is partitioning index, arr[pi] is\nnow at right place */\nint pi = partition(arr, low, high);\n// Recursively sort elements before\n// partition and after partition\nsort(arr, low, pi-1);\nsort(arr, pi+1, high);\n}\n}\n/* A utility function to print array of size n */\nstatic void printArray(int arr[])\n{\nint n = arr.length;\nfor (int i=0; i<n; ++i)\nSystem.out.print(arr[i]+\" \");\nSystem.out.println();\n}\n// Driver program\npublic static void main(String args[])\n{\nint arr[] = {8, 1, 9, 3, 5, 7, 6};\nint n = arr.length;\nQuickSort ob = new QuickSort();\nob.sort(arr, 0, n-1);\nSystem.out.println(\"sorted array\");\nprintArray(arr);\n}\n}\n/*This code is contributed by <PERSON> */", "318" ], [ "DFS and BFS Time and Space complexities of 'Number of islands' on Leetcode\nHere is the question description. The first 2 suggested solutions involve DFS and BFS. This question refers to the 1st two approaches: DFS and BFS. Apparently, the grid can be viewed as a graph.\nI have included the problem statement here for easier reading.\nGiven a 2d grid map of '1's (land) and '0's (water), count the number of\nislands.", "923" ], [ "An island is surrounded by water and is formed by connecting adjacent\nlands horizontally or vertically. You may assume all four edges of the grid are\nall surrounded by water.\nExample 1:\nInput:\n11110\n11010\n11000\n00000\nOutput: 1\nExample 2:\nInput:\n11000\n11000\n00100\n00011\nOutput: 3\nI am unclear as to why the time complexity for both DFS and BFS is O(rows * columns) for both. I see how this is the case where the grid is just full of 0's - we simply have to check each cell. However, doesn't the DFS approach add more time to the search? Even if we mark the cells we visited by changing them to 0 in the dfs methods, we still would revisit all the cells because of the two outer loops. If dfs could be have time complexity of O(n) in the case of a big grid with large row and column numbers, wouldn't the time complexity be O(rows * columns * max[rows, cols])? Moreover, isn't the same case with the BFS approach where it is O(rows * cols * possibleMaxSizeOfQueue) where possibleMaxSizeOfQueue could again be max[rows, cols]?\nfor (int r = 0; r < nr; ++r) {\nfor (int c = 0; c < nc; ++c) {\nif (grid[r][c] == '1') {\n++num_islands;\ndfs(grid, r, c);\n}\n}\n}\nHow is DFS's space complexity O(rows*cols)? Is it not possible/common to consider the call stack space as freed when a recursion branch returns? How is the space complexity for BFS O(min(rows, cols))? The way I see it, the queue could be full of all elements in the case of a grid with just 1's thereby giving O(rows*cols) for BFS space complexity.\nDFS Solution\nclass Solution {\nvoid dfs(char[][] grid, int r, int c) {\nint nr = grid.length;\nint nc = grid[0].length;\nif (r < 0 || c < 0 || r >= nr || c >= nc || grid[r][c] == '0') {\nreturn;\n}\ngrid[r][c] = '0';\ndfs(grid, r - 1, c);\ndfs(grid, r + 1, c);\ndfs(grid, r, c - 1);\ndfs(grid, r, c + 1);\n}\npublic int numIslands(char[][] grid) {\nif (grid == null || grid.length == 0) {\nreturn 0;\n}\nint nr = grid.length;\nint nc = grid[0].length;\nint num_islands = 0;\nfor (int r = 0; r < nr; ++r) {\nfor (int c = 0; c < nc; ++c) {\nif (grid[r][c] == '1') {\n++num_islands;\ndfs(grid, r, c);\n}\n}\n}\nreturn num_islands;\n}\n}\nTime complexity : O(M×N) where M is the number of rows and N is the number of columns.\nSpace complexity : worst case O(M×N) in case that the grid map is filled with lands where DFS goes by M×N deep.\nBFS Solution\nclass Solution {\npublic int numIslands(char[][] grid) {\nif (grid == null || grid.length == 0) {\nreturn 0;\n}\nint nr = grid.length;\nint nc = grid[0].", "923" ], [ "Struggling to understand the thought process required to come up with some recurrences for Dynamic Programming problems\nI was doing a few dynamic programming problems and I am struggling to understand the thought process required to come up with recurrences.\nThe first problem I solved was longest palindromic substring and I managed to solve it successfully using the following logic: I have a function f(i,j) which returns the longest palindromic substring between characters at positions i,j in the string. I came up with the following recurrence:\nf(i,j) = true // if(s[i] = s[j]) f(i,j) = true // if(i>j) f(i,j) = true // if(s[i] = s[j] and f(i+1, j-1) == true) f(i,j) = false // otherwise\nUsing this recurrence I managed to solve the problem successfully.\nThe second problem I wanted to solve was Longest valid parentheses (which I want to do using DP not stacks). The question is: Given a string containing just the characters '(' and ')', find the length of the longest valid parentheses substring.\nMy initial thought process was that this was similar to the longest palindromic substring problem that I already solved. So I defined f(i,j) as a function that returns longest valid parenthesis between elements i,j.", "603" ], [ "The recurrence I came up with is as follows - here I use -1 to indicate that f(i,j) does not form a valid parenthesis:\nf(i,j) = -1 // if i == j f(i,j) = -1 // if j=i+1 and ! (s[i] = '(' and s[j] = ')') f(i,j) = 2 // if j = i+1 and s[i] = '(' and s[j] = ')' f(i,j) = 2 + f(i+1, j-1) if s[i] = '(' and s[j] = ')' and f(i+1, j-1) > 0; f(i,j) = -1 // otherwise\nMy code (written in java) for the top-down version of the above is (note: dp[][] was initialized to -2 indicating state i,j is not processed yet):\nprivate int topDown(String s, int i, int j, int[][] dp) {\nif(dp[i][j] != -2)\nreturn dp[i][j];\nif(i == j)\ndp[i][j] = -1;\nelse if(j == i+1 && (s.charAt(i) != '(' || s.charAt(j) != ')' ) )\ndp[i][j] = -1;\nelse if(j == i+1 && (s.charAt(i) == '(' && s.charAt(j) == ')' ) )\ndp[i][j] = 2;\nelse if(s.charAt(i) == '(' && s.charAt(j) == ')' && topDown(s, i+1, j-1, dp) > -1)\ndp[i][j] = 2 + topDown(s, i+1, j-1, dp);\nelse\ndp[i][j] = -1;\nreturn dp[i][j];\n}\nThis does not work for inputs like ()() as it will return 2 instead of 4.\nI was unable to come up with a solution of my own so I looked it up online. I found a solution here.\nIn this case the author defines f(i) as the length of the longest longest valid, balanced parentheses substring which begins at index i. He then describes the recurrence as follows:\nf(i) = 2 + f(i+2) // if s[i] = \"(\" and s[i+1] = \")\" f(i) = f(i+1) + f(i + f(i+1) + 2) // s[i]=\"(\" AND s[i+1]=\"(\" AND s[i+f(i+1)+1]=\")\" f(i) = 0 // otherwise\nI have not written/tested the code for the recurrence but I assume it is correct.\nMy questions are as follows:\n1. When I was solving the problem initially I had not thought of writing it as a function of f(i).", "953" ], [ "Finding which strings in a set of strings have a certain prefix - can it be smaller than O(number of strings*length of prefix)\nIf I have a set of words and need to return which of them start with a certain prefix, can that complexity be less than O(n*d), where n is the number of words and d is the prefix. I'm asking because of this video: https://www.youtube.com/watch?v=QGVCnjXmrNg (1:20 starts discussing the solution), where it says it can be lowered through using a trie with all of the words, but I think the creation of the trie would take O(n*t) complexity, where t is the average length of the words. Assume that all words will be at least as long as d (any word which has length smaller than d is disregarded immediately in the solution below, but is still considered during the creation of the trie in the video).\nMy idea for the solution is the simple one: go through each word and check if it starts with the same prefix.", "864" ], [ "If it does, add it to the list of words which start with that prefix, otherwise don't. The reason I think this is the best solution possible in terms of worst-case complexity is as follows: if we skip even one character or one string, we may return the wrong answer. This is the minimum input that is to be considered and in any other case, it is also considered (for example, in the solution that input is considered during the creation of the trie).\nExample javascript code:\nfunction solve(prefix, words) {\n//startsWith has worst-case complexity O(d) where d is the length of the prefix\nfunction startsWith(word, prefix) {\n//this doesn't change worst-case complexity but means that the only disregardable input is disregarded\nif (prefix.length > word.length) return false;\nfor (let i = 0; i < prefix.length; i++) {\nif (prefix[i] !== word[i]) {\nreturn false;\n}\n}\nreturn true;\n}\nconst wordsArray = [];\n//since there are n (n is the length of the words array) and every iteration has worst-case complexity O(d),\n// we have a worst-case complexity of O(n*d)\nfor (let i = 0; i < words.length; i++) {\nif (startsWith(words[i], prefix)) {\nwordsArray.push(words[i]);\n}\n}\nreturn wordsArray;\n}\nconsole.log(solve(\"do\", [\"dog\", \"dark\", \"cat\", \"door\", \"dodge\"]));\nI'm asking that because in the video it was mentioned that it can be faster than O(n*d), but I believe the solution was wrongly analyzed. I, however, am just a hobbyist and feel like it is more likely I'm missing something here.", "864" ], [ "BFS complexity Why is the complexity\nI'm having a hard time understand the reasoning in the solution of 18.7 in Elements of programming interviews (EPI):\nhttps://books.google.com/books?id=eErBDwAAQBAJ&pg=PA307&lpg=PA307&dq=bfs+time+complexity+elements+of+programming+interviews+18.7&source=bl&ots=Fotetv7x03&sig=ACfU3U1xyJkEMT7Y69cREXJvOrz9bRw4pw&hl=en&sa=X&ved=2ahUKEwiu48TS98fpAhWNsp4KHZF2BS4Q6AEwAHoECAoQAQ#v=onepage&q=bfs%20time%20complexity%20elements%20of%20programming%20interviews%2018.7&f=false\nThe number of vertices is d, the number of words in the dictionary. The number of edges is, in the worst-case O(d²). The time complexity is that of BFS, namely O(d+d²) = O(d²). If the string length n is less than d then the maximum number of edges out of a vertex is O(n), implying an O(nd) bound.\nSo I agree with number of vertices being d, and the worst case number of edges is d². We know that the complexity of BFS is O(V+E), hence O(d+d²) = O(d²), though if we used a set to record visited verices (or removed a vertex once we visited it from the graph), that should reduce BFS's complexity to O(d). But then things get funky.", "923" ], [ "If the string length n is less than d the maximum number of edges out of a vertex is O(n). I don't agree with this. Imagine we have 5 words in our dictionary {ab, ac, ad, ae, af}, so d is 5 and n is 2. All these vertices are connected and you can see that each vertex has 4 edges leaving it... which is more than O(n). You can have 26^n possible edges leaving the vertex, but you only have d vertices in the graph, so the number of edges leaving a single vertex should be O(d).\nI ultimately agree that the final complexity of the algorithm is O(nd), but I calculated that simply from we can visit up to d vertices (we use a visited set to prevent cycles) and for each vertex visited one we iterate over the string of length n as we look for differences in the alphabet of lower characters O(26nd) = O(nd).\nInterested to hear what people think, Thanks :)", "180" ], [ "Heapsort for sorted input\nHi I have been reading about heapsort in CLRS and came to a question which is what is the running time of heapsort when the input array is in increasing order; how about decreasing order.\nThe next question asks to prove that worst case of heapsort is O(nlogn). The following starred (hard) question asked to prove that best case running time of heapsort is O(nlogn).\nObviously the later questions render the previous trivial, but I assume that the first 2 can be answered in a more straightforward fashion?\nHere is whaty I have done so far ...\nFor the increasing order (i.e. the order opposite to the output order) I am completely stuck and haven't been able to make any progress because as I see it as soon as we build the max heap the structure completely changes and I cant reason about what the final heap will look like.\nFor the decreasing case I feel like I understand what is going on and will try to describe that below, but its also a long way from a proof. A decreasing array is already a max heap so the array is unchanged by building the max heap. WLOG assume a complete binary tree (else just remove some elements until you get one)\nRemove the first n/4 largest elements.", "864" ], [ "The first element will then be lifted to the top and fall back down a distance of log(n) falling to the left each time (the left element is always the largest).\nBut now the right is larger for each vertex that this last element fell through. So the next vertex will first fall right then fall left the rest of the way. No vertex will fall the same path until this has been rectified. So elements moved to the top of the tree continue to fall the full length of the tree. Rectifying the tree seems like it will take a linear time because it has length logn and it feels like you have to go down a constant fraction of the other routes before it is done. But this is really wordy and sort of garbage.\nI apologise if this could be written better but I tried my best to say what I mean.\nNote I have read the proof for the general best case but I was looking for something more straightforward due to the extra information.\nThanks", "441" ], [ "Thought process to solve tree based Dynamic Programming problems\nI am having a very hard time understanding tree based DP problems. I am fairly comfortable with array based DP problems but I cannot come up with the correct thought process for tree based problems and I was hoping somebody could please explain their thought process.\nI will talk about my thought process behind array based problems and then explain my troubles with tree based DP problems.\nMy thought process for array problems\nThe way I think about DP in array based problems is as follows. Let us consider a problem like Minimum Path Sum. Here the objective is to get from the top left to bottom right positions in a matrix such that we minimize the cost of the path. We can only move left and right.\nThe way I would approach problems like this is as follows:\n* First I would construct a recurrence. In this case the recurrence is as follows\nThe recurrence is:\nf(i, j) = a[i][j] // if i == m and j == n\nf(i, j) = a[i][j] + f(i, j+1) // if i == m\nf(i, j) = a[i][j] + f(i+1, j) // if j == n\nf(i, j) = a[i][j] + Math.min( f(i, j+1), f(i+1, j) ) // Otherwise\n* Next I look at the equations which tells me the problem can be solved using DP as there are overlapping subproblems in f(i+1, j) and f(i, j+1). There is also an optimal substructure.\n* I can also tell the time/space complexity just by looking at the recurrence.\n* Because we must compute all states which is all (i,j) pairs and because time per state is O(1) (adding a[i][j] to result) the time complexity is O(n^2).\n* Looking at the recurrence, i depends only on i+1 and not on i+2, i+3 ... similarly j depends only on j+1 and not on j+2, j+3...", "603" ], [ "so we can get away with using only 1 extra row (either i+1 or j+1) instead of the entire matrix so space complexity is O(n).\nHence I would come up with a n^2 time and n space solution. I can do this without any problems.\nMy thought process for tree problems\nHowever I am having a hard time applying the same thought process to tree based DP problems. As an example let us consider the problem Diameter of Binary Tree where the objective is to find the longest path between any 2 nodes in the tree.\nI can come up with a recurrence for this problem which is as follows:\nf(n) = 0 // if n == null f(n) = max( 1+height(n.left) + height(n.right), // longest path passing through root f(n.left), // longest path in left subtree f(n.right) ) // longest path in right subtree\nBecause f(n.left) for example is computed by doing 1+height(n.left.left) + height(n.left.right) I can tell that DP must be used.\nSo my approach would be to create a cache of size 'n' that stores all the heights of the nodes. So the space complexity would be O(n).\nHowever the optimal solution of this problem has a space complexity of O(1) and I am having a hard time figuring that out just by looking at the recurrence. How does the recurrence tell you that space complexity can be reduced and that O(1) space is enough and O(n) is not needed? How do you know what value(s) to store in this case? In array based problems I can get the answers to both these questions just by looking at the recurrence but for tree based dp it is not so obvious to me.\nMy questions:\n1. What can you tell about this problem just by looking at the recurrence for the tree problem? Putting aside my own thought process, if I gave you this recurrence and nothing else what conclusions would you reach and how would you write the program? I am curious about your thought process.\n2. For array based problems I can tell just by looking at the recurrence both how much space I needed to solve the problem AND what exactly I needed to store (I need to store values of row i+1 in min path sum and nothing else). How can I do the same for the tree problem?\nThanks.", "743" ], [ "Duplicate elements in Queue for BFS Maze Algorithm\nI'm fairly new to studying data structures and algorithms.\nI've implemented a non-recursive BFS on a 2d \"maze array\" which seems to work well. It finds the position of 2 in an array of 1s (walls) and 0s (spaces), marking visited positions with 3.\nHowever, I notice that there are duplicate values in the Queue.", "923" ], [ "I understand that I should avoid visiting already visited positions. However the queue contains only \"prospective\" positions which are yet to be visited. Should I modify the algorithm to not enqueue positions which it already contains? Will the algorithm still work if I do so?\nAs far as I know I have implemented the following algorithm:\nCreate a queue for positions yet to explore, and enqueue the entrance (0,0)\nWhile the list is not empty\ndequeue\nIf it is the goal position,\nexit displaying position and success message\nOtherwise,\nmark the position as visited, and enqueue all valid neighbors (not walls and not visited)\nIf the list is empty and the method has not returned, there is no path\nSome sample output is below:\nEnqueueing (0,0)\nQueue contents: [(0, 0)]\nPress Enter to continue:\nDequeueing\nCurrent position: (0, 0)\nMarking (0, 0)\n[3, 1, 1, 0]\n[0, 0, 0, 1]\n[0, 0, 1, 0]\n[1, 0, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.\nQueue contents: [(0, 1)]\nPress Enter to continue:\nDequeueing\nCurrent position: (0, 1)\nMarking (0, 1)\n[3, 1, 1, 0]\n[3, 0, 0, 1]\n[0, 0, 1, 0]\n[1, 0, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.\nQueue contents: [(1, 1), (0, 2)]\nPress Enter to continue:\nDequeueing\nCurrent position: (1, 1)\nMarking (1, 1)\n[3, 1, 1, 0]\n[3, 3, 0, 1]\n[0, 0, 1, 0]\n[1, 0, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.\nQueue contents: [(0, 2), (2, 1), (1, 2)]\nPress Enter to continue:\nDequeueing\nCurrent position: (0, 2)\nMarking (0, 2)\n[3, 1, 1, 0]\n[3, 3, 0, 1]\n[3, 0, 1, 0]\n[1, 0, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.\nQueue contents: [(2, 1), (1, 2), (1, 2)]\nPress Enter to continue:\nDequeueing\nCurrent position: (2, 1)\nMarking (2, 1)\n[3, 1, 1, 0]\n[3, 3, 3, 1]\n[3, 0, 1, 0]\n[1, 0, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.\nQueue contents: [(1, 2), (1, 2)]\nPress Enter to continue:\nDequeueing\nCurrent position: (1, 2)\nMarking (1, 2)\n[3, 1, 1, 0]\n[3, 3, 3, 1]\n[3, 3, 1, 0]\n[1, 0, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.\nQueue contents: [(1, 2), (1, 3)]\nPress Enter to continue:\nDequeueing\nCurrent position: (1, 2)\n[3, 1, 1, 0]\n[3, 3, 3, 1]\n[3, 3, 1, 0]\n[1, 0, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.\nQueue contents: [(1, 3), (1, 3)]\nPress Enter to continue:\nDequeueing\nCurrent position: (1, 3)\nMarking (1, 3)\n[3, 1, 1, 0]\n[3, 3, 3, 1]\n[3, 3, 1, 0]\n[1, 3, 0, 2]\nEnqueueing coordinates of valid positions in 4 directions.", "180" ] ]

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[ [ "Django Unchained\n<PERSON> really doesn’t miss. Not only is he an exceptional director, but one of the greatest ever writers in cinema too.", "594" ], [ "I also love how he cameos small roles in a few of his films.\nDjango Unchained is a brilliant revenge story and presented to us in such captivating fashion, full of <PERSON> flair and easily up there with his best work. <PERSON> and <PERSON> were superb, but <PERSON> gave us some flawless acting, both this and Inglorious Basterds I’ve absolutely loved him in. The final act for me was just incredible - action packed, outrageous kills and seriously gory which is a given in any <PERSON> flick.", "549" ], [ "Dune: Part Two\nNot only does <PERSON> adapt <PERSON> behemoth sci-fi odyssey to perfection, it also just so happens to be the absolute peak of big budget filmmaking, or maybe just the peak of cinema in general. The hype is real.\nThis proves that audiences want something made with genuine care, where they will notice when a big group of people are passionate enough to bring something like this to life. Every single person involved in this should genuinely be so proud. I never wanted this to end and I wanted to live in this world forever.\nA monumental film in every single way.", "19" ], [ "This is the most pure form of passion displayed on screen I’ve ever seen. You can tell <PERSON> had this in his mind his entire life. He delivered. It’s time for everyone else to step it up, because this is the new gold standard.", "529" ], [ "Lessons in Chemistry\nI’ll admit it, initially this didn’t peaked my interest. The story wasn’t intriguing enough for me to give it a go despite <PERSON> being in it. But because <PERSON> got nominated for it, I decided to give it a chance and boy, it showed me! This satisfying and ENTERTAINING 1950s prestige drama turned out to be so much better than what I anticipated.", "577" ], [ "<PERSON> in unlike any role i’ve seen her play, gives one of the very best performances of her career with an autistic-like energy that she brings to the role. <PERSON>, <PERSON> & <PERSON> put together very strong performances on the supporting side. Yeah, this was awesome!", "883" ], [ "Sweet Smell of Success\n“You're dead, son. Get yourself buried.”\nOne of the greatest screenplays of the Golden Age.", "291" ], [ "Probably has over a dozens of lines that would be the single best quote in any other film, and here they’re just churned out constantly over 90 minutes. But it’s not just the dialogue that sucks me in – it’s how we’re introduced to this world, how we see these characters come in and out of focus and change face depending on who they’re with. Any sense of morality is out of the window right from the beginning, and in its place we get some some good old narcissism.", "796" ], [ "Driveways\nYou’re never gonna find a more simple yet beautiful, lighthearted film ever again watching Driveways. Led by a beautiful score and layers of subtlety from <PERSON>, this film is compassionate and daring. And phenomenal, critical and emotional chemistry between <PERSON> & <PERSON>.", "883" ], [ "Their bond was something so special and so personal, you could sense the love and the warmth <PERSON> feels for Del. I won’t spoil anything, but there’s one scene that involves <PERSON> running through the neighborhood in anger, and he stops in the street and coming around the corner was <PERSON>, and it took my breath away.I Love when these underground films come to view and they pay off. Beautiful!\nNominated for Best Female Lead (<PERSON>)\n&\nBest First Screenplay at Film Independent Spirit Awards\nYou can watch this film for free on YouTube(and please do).\n🔙Tully", "883" ], [ "People Having Fun\nDefinitely <PERSON>’s most ambitious and out-there film. It’s the type of thing that truly makes you wonder where the hell it’s going next, and thankfully not in a way that’s annoying or amateur as each section brings about various vibes and situations both perplexing and strange.\nI haven’t been interested in filmmaking for awhile now, or watching independent films for that matter.", "647" ], [ "But I’m glad I decided to watch this. It’s been quite a long time since I viewed a <PERSON> film, and it was a great to be back in the mind of this wholly unique artist. A DIY king.\nGood job dude.\nYou have until Monday to watch, before it’s taken off YouTube for idk how long!!\nhttps://youtu.be/W1UfBHZhO7k?si=Yphp8reJyS2Yuxvd", "410" ], [ "Game of Thrones: The Last Watch\nAnd now your watch is ended\nLook, I know working on movies is all I ever really talk about, but you gotta understand, it’s undoubtedly the greatest thing there ever was. A truly beautiful delve into, to be fair, a pretty shit season, The Last Watch is amazing. There’s so much love, so much passion, so much camaraderie in this fucking production.", "291" ], [ "I truly love films about filmmaking, and having finally worked on film sets of this scale, having been able to experience what this documentary shows firsthand, it’s a beautiful thing. Being able to recognize everything that’s going on, how it works. The fog of mystery behind filmmaking has lifted and its even more magical than ever. I love Game of Thrones more than maybe any other show, and what an amazing, bittersweet homage to it’s farewell.", "291" ], [ "Scenes from a Marriage\n“Happiness is contentment.”\nI don’t know if a film has ever broke me the way <PERSON> Scenes from a Marriage crushed me. There’s this profound intimacy that almost makes watching the film feel wrong.\nThere has never been an actor like <PERSON>, she is truly such a chameleon. Her raw vigor and emotion truly drained me. There’s this haunting hopelessness; this feeling that a grip is being let loose.", "1009" ], [ "This brutal honestly shines in both performances. As wonderful as <PERSON> is, <PERSON> is just as incredible.\nThere’s this moment in Episode Four that is so charming on the surface but the underlying weight hits like a freight train. This film is so beautifully haunting and depressing, there’s this obvious love that’s under the surface but the weight and pressure is so crushing.\nWould Recommend!\n“You were awfully attractive as a socialist.”\nNote:\nRe-posting this 2019 review unedited because I logged the wrong cut. Didn’t know the TV cut had its own entry!", "1009" ] ]

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[ [ "Ginkgopolis is <PERSON> fifth (I believe) game, following Royal Palace(2008), Carson City(2009), Troyes(2010), and Tournay(2011), along with a smattering of expansions for some of the above. This is the first of <PERSON>’s game I have played, and is currently ranked 325 in BGG (April 8th, 2013). Both Troyes and Carson city rank higher (39th and 167th respectively).\nI admit that I have not played Ginkgopolis exhaustively – as I only have 3 plays under my belt at the time of writing (one each at 5 players, 3 players, and 2 players). Despite this, I found myself enamored with the game, both its flaws and its successes, and spent considerable time thinking about it.\nReactions to Ginkgopolis seem a bit of a mixed bag. The primary criticisms of the game being lack of theme integration with the mechanics and the high level of apparent randomness and uncertainty in the game. I decided to write this review to explore these two criticisms and examine the overall gameplay dynamics at work. I will conclude with my thoughts on how Ginkgopolis “fits” into the overall gaming scene and why I think it will be a compelling but underappreciated game.\nRule Time!\nI am not one for doing exhaustive mechanics/rules overview, but for those not familiar with the game, here are the key bullet points on the rules and gameplay:\n(1) Players are (abstractly) building “up” and building “out” the city of Ginkgopolis to earn VPs (called “Success Points”, but I’ll call them VP’s in this article).\n(2) The gameplay revolves around card drafting (e.g. 7-Wonders style) from a hand of cards; to do one of 3 actions each round: (1) placing tiles to build out (urbanizing), (2) placing tiles to build up (construction) or (3) activating tiles/cards directly (exploiting).", "92" ], [ "The cards you select determines the location or existing tile where your new one will go, in the case of urbanizing or constructing respectively, or determines what existing tile is activated (exploiting).\n(3) “Building up” feeds the tableau building aspect of the game. When you build on a tile, you get to place that tiles card in front of you to derive a game-long benefit or end-game bonus scoring.\n(4) Tile placement and tableau building drives an engine-building system, netting players VP’s, resources, and tiles during the game for performing certain types actions.\n(5) Placing new tiles also drives a shared deck-building mechanic, where new cards are added (and subsequently removed) from the deck of cards as tiles are added to the city (and subsequently built on).\n(6) In addition to endgame bonuses from your tableau, VP’s are also earned based on players’ relative control over the city’s districts (i.e. area control).\n(7) The game ends when a player has placed all their resources or the stack of tiles is exhausted for the second time (the first time it is exhausted, players can turn tiles back into the stack for VP’s).\nClear as mud?\nThe promise...\nI will say this about the game’s mechanics; they are intricate. Yet when you boil it down, Ginkgopolis is not a complex game (there really aren’t many rules) – but the major mechanical elements (drafting, tile placement, deck building) all interconnect in such a way that it can be hard to describe and teach the game in a linear manner. The learning is certainty front loaded, and it often takes a few rounds for new players to get a sense of how all the pieces fit together. Once you “grok” the game, it comes together in a very elegant and fluid way.\nHowever, Ginkgopolis has the paradox of being both elegant and fiddly at the same time. The interaction between the mechanical elements of the game is very tight and is where the originality (and innovation) of the game resides. It IS elegant how you build cards to your tableau, covering the associated building tile, and then add a new card to deck based on the new tile you placed. It’s quite cool to see these different systems so well intertwined.\nYet the actual play experience is considerably more fiddly.", "349" ], [ "Abstract\nCarcassonne: Hunters & Gatherers (\"Hunters\") is a standalone version of the classic tile-laying Carcassonne, (designer <PERSON>), and was released in 2002. I have played over 100 games of Hunters (89 recorded plays), with the vast majority of these plays being 2-player games. Hunters stands out as a game that strikes a paradoxical balance between its outward appearance and accessibility as a light game and its hidden and genuine depth that can sustain many repeat plays. Hunters’ mechanics are straightforward yet flexible enough to foster good tensions and a competitive edge throughout the entire game.\nIntroduction\nThe Backstory\nI was late to the modern boardgame party. Despite having played a variety of games my entire life (both physical and digital) I really didn’t play many modern euro-style games until a few years ago. In one of my first game purchase binges (x-mas 2010 as it was), I looked to grow a modest collection of games and asked for recommendations.\nCarcassonne is always in the top of the list of recommendations as a gateway game because of its potential widespread appeal, easy rule set, and engaging gameplay. In researching the Carcassonne line, I came across Hunters & Gatherers, and after reading reviews and comments, got the impression that Hunters functions as a better standalone game with more depth, and better suitability for 2-players, compared to the original (unexpanded) Carcassonne. Plus I liked the look of the artwork and theme more. Ultimately, I was pushed to buy it upon reading that a couple working abroad in Central America had only taken along Hunters, and they never tired of it for years. Whow! So into the cart it went!\nFast-forward to the present, and I’m happy to say that I have likely played over 100 games of Hunters (89 recorded plays thus far). The majority of these plays have been 2-player games, between me and my wife. Hunters has been a success in bridging our differences in gaming preferences and providing a game experience we enjoy every time we pull it off the shelf.", "504" ], [ "This review reflects primarily my experiences with Carcassonne as a 2-player game.\nGameplay Synopsis\nHunters is a tile-placement game, and sharing a lineage with the original Carcassonne(2000) puts it within the realm of genre defining euro-style games. Unlike Carcassonne’s medieval setting, Hunters uses a pre-historic theme. For the uninitiated, below is a basic overview of the gameplay:\nPlayers take turns drawing a single tile and placing it next to an adjacent tile where the edges match. Tiles contain portions of woodlands, rivers, and hunting grounds in various combinations. After placing a tile, that player has the option to then place one of their 5 meeples onto the tile that was just played in one of the landscape regions, provided no other player already has a meeple in that region.\nOnce placed, meeples remain in place until the region is closed in the case of woodlands and rivers (and players earn points for these closed areas). In the case of hunting ground regions meeples remain in place until the end of the game. Each player also has two huts which may be placed onto any river or lake system that doesn’t already have another player’s hut somewhere in that system. If two regions with different player’ meeples and/or huts on them are connected through subsequent tile plays, both players score points for the region.\n* Comparison with original Carcassonne:\nDiscussion\nThesis\nCarcassonne: Hunters & Gatherers stands out as a game that bridges a lot of gaps. It provides a solid balance between simple rules and relatively deep gameplay. It can satisfy many styles of play and appeal to a wide variety of gamers, from those wanting to play a low-conflict casual game to those looking to squeeze out every opportunity for competition and conflict. It packs a modest level of depth into a game with low overhead and that is easy to learn. Overall, Hunter’s success is attributed to how well it balances these potentially competing interests; luck and skill; ease of learning and depth of play; passivity and aggression; casualness and seriousness.\nDecision Space\nHunters poses two decision points to players on their turn; tile placement and meeple/hut placement.\nDecision #1: Tile Placement\nRegarding the first decision, players only have one tile in their hand and it has to be played. At the broadest level, your choice of tile placement is constrained by the legal moves for placement, meaning that it must be placed in a way that avoids mis-matched edges.", "84" ], [ "CO2has been a rare game for me in that my esteem for the game has risen each time I have played it. This is because the game creates a fascinating system of buttons and levers you can use to bend your opponent to your will. There is almost a psychological beauty to this game, as it becomes important to understand your opponent’s motives behind their play, as well as understanding how you react to their play. Like life, CO2rewards those who are cunning enough to get the largest slice of any given pie.\nBe warned, however, that this type of depth comes at a price: and that price is commitment to the systems. The tactics and strategies for good play are not apparent at first blush. Understanding where the pressure points in the game system are easy. The difficult thing to master is how to use these pressure points effectively when coupled with erratic decision-making by your opponent. Ideally, you should have multiple plays with the same opponents, or there is a high likelihood that the game will fall flat. I have played lots of CO2 as a two player game against a single opponent and have found a fascinating, semi-opaque vehicle for player manipulation. This is not an optimization multi-player solitaire Euro. It is a hot glorious gladiatorial mess, and that is why I love it.\nThe economy of CO2 is a unique cyclical beast which serves to ensure tension in the gaming system even before players start to get in each other’s way. There are three distinct currencies in the game (cash, carbon emission permits (CEPs), and resource cubes). Often, you must spend one to get another which in practice means you will have to decide how best to balance your long-term plans within your short-term currency constraints. The CEPs themselves are also part of a nifty dynamic market which is subject to the whims of the players. Supply and demand sets the market value for CEPs, and like most everything in this system, can be manipulated to bring pressure onto other players or flush you with resources at the right time (and if you are a great player, you can do both simultaneously!).\nThe semi-cooperative nature of the game also helps create a unique two-player experience that is more akin to gaming with a larger group. Some of my favorite games rely on shared incentives and temporary alliances. My problem is that I rarely have the three or more seasoned players that are required for these types of systems to work as intended. CO2 can create comparable dynamics in a 2 player game because of the specter of shared loss.", "237" ], [ "In essence, the game itself acts as a third player that sometimes forces the players to collude against it. Others find this type of game distasteful because it doesn’t foster all-out competition whereas I find that the ticking-time bomb of the pollution track results in some sticky decision making. Who will shoulder the burden to continue the game? What should be my position-proportional payment to continue the game? Additionally, shared losses become shared experiences that form the cornerstone of what I consider quality gaming. They serve as launching points for post-game discussion, and provide the single point of narrative depth in an otherwise abstract experience.\nWhat sets CO2 ahead of other games is the level of interactivity inherent in the system. I have just discussed the brinksmanship of the shared loss mechanic, but that is just the tip of the iceberg. The system exacerbates interaction through a gradual process of development. Completing a single power plant on your own will require no less than three turns. At any point, your opponent may swoop in and assume ownership of the project, but there is a cost for doing so. This sets up a rarity in gaming: take-that type play, when both perpetrator and victim can make strategic gains.\nAdditionally, a constrained board helps to ensure player-to-player interaction after the earliest development phases. The proposal spots provide choke points in the game to extort your opponent into proposing projects elsewhere. Controlling a high cash payout space will help exclude competition from cash-poor players. Sitting on a particular space may be a wise move if you think it will dis-incent other players from developing that continent. Should they pay to move you off the space and give you a short term boost for their long term plans? Controlling certain spaces beings to feel like a game of chicken and can allow players in weaker positions to retain area control. It can also sound their death knell if it ties up limited resources for too long. Finding the right balance is more about accurately reading your opponent than maximizing benefits from zero-sum decisions.\nCO2, despite my praises, is not without its flaws. Although the shared loss can create a narrative element CO2 lacks any real narrative arc. There is also no link between the theme and the mechanics. This creates a level of abstraction that can make the rules a little more difficult to internalize. You would be hard pressed to pronounce a game of CO2 as a thematic experience.", "237" ], [ "I have now played 2 games of Black Angel; I have also played Troyes 4 times, all in the past year. I would like to do a comparison of the two games for those who have perhaps played and enjoyed Troyes and would like a rundown of how the two games differ, as clearly they are siblings.\nTL;DR\nThe game state in Black Angel is easier to read because the game has 3 single-use currencies (ships, resources, debris) and one multi-use currency (robots).\nBlack Angel has a lot more going on in terms of upkeep/fiddliness.\nThe end of game timer is harder to get a read on in Black Angel as the game moves forward in many small irregular steps instead of a few regular steps.\n(b) The current score is much more clear: Black angle has a score track whereas Troyes has private scoring tokens. Black angle has face-up end of game scoring tiles that score linearly, whereas Troyes has hidden scoring that scores non-linearly.\nBlack Angel has a technology tableau which provides a bit of engine building that did not exist in Troyes (outside of banking future actions)\nTroyes' core action selection mechanic is more interesting than Black Angel (choosing up to three dice vs. exactly one).\nIn Black Angel, even though the missions and technology are abstract, the theme feels more integrated into the mechanics.\nEdit: After three plays, I can am beginning to feel that the sum of the differences between Black Angel and Troyes result in a game that feels more wide-open. You often feel like you have a number of good options on your turn; Black Angel feels like exploration, whereas Troyes feels like mitigation.\nActivities vs. Missions\nTroyes: Activities come up randomly, you see only 25% of them each game. Activities may be purchased (with coins) and you get to do the activity the first turn you place a meeple there. They can be selected by all players, but those who come first get victor point bonuses. One you buy-in, you have access to that activity for the remainder of the game, unless you choose to abandon it to reuse that meeple. Some of these are immediate effects, and others give you the potential for stronger actions later in the game. The suits (yellow/white/red) have very different focuses and personalized artwork. Activities each feel very unique.\nBlack Angel: Players draft missions and hold them in their hands. Those missions are either one time or ongoing. They then play them out onto the conveyor-like space board. The ongoing missions all have immediate effects when activated, but must be activated on a separate turn after playing them out. Most are time-limited (will eventually fall off the board).", "349" ], [ "When they fall off the board they may be worth 2 points at the end of the game (if you attach them to the right scoring tile). One-time missions activate when they fall off of the board, but you do not need to invest any more actions into them.\nThe suits (yellow/green/grey) are symmetrical feel kind of \"samey\"; Missions do not even have titles or artwork. Players own missions and gain a benefit from other players using them (for ongoing missions). Missions are limited (only two players can dock ships with them at one time). Missions must be paid for with \"ships\" as well as robots.\nMeeples vs Robots\nTroyes: Meeples are drafted with Influence, a common currency that is also used for dice manipulation. Meeples give you access to dice and to activities. Meeples can abandon their posts at any time to be used in a different capacity.\nBlack Angel: Robots are added through specific actions in the game, choosing to draft more robots via missions or technology activations. Robots are used to gain more dice and to work at missions. Robots in workstations (where they give you more dice) must be moved to the \"breakroom\" before they can be assigned to missions (this doesn't really happen). Robots in ships may be flown between missions to change what actions you have available.\nDice Manipulation\nTroyes: Can flip up to three dice for a high cost, or reroll one at a low cost. Uses a common currency for dice manipulation and drafting new meeples (Influence). Influence can score at the end of the game, but only if the secret scoring card is in play. You can only manipulate your own dice.\nBlack Angel: A separate currency (debris) is used for dice manipulation. The manipulation is always deterministic (one cube flips one die). This changes a 0 to a 2 or a 1 to a 3. Debris can score at the end of the game if you draft the appropriate scoring tile. Generally, you can only manipulate your own dice.", "50" ], [ "“He’s crossed all the oceans all around the world.” <PERSON>, The Sound and the Fury\nArchipelago is an obtuse, conflicted, and wildly engaging Euro game full of chaos and caustic judgment. On the surface it feels like a stream of consciousness design with mechanical quip and obfuscated layers making the journey more difficult than necessary. The truth is, Archipelago is spiritually the board game equivalent of a <PERSON> novel, with its unrelenting prose proving a forest upon your path. Like much of <PERSON>’s work, beyond the outright chaos and seeming hodge-podge is a deep and enrapturing experience that is exceptionally enjoyable and surprisingly focused.\nThis is a Euro game as only <PERSON> could fashion. The philosophy behind the design unsurprisingly mirrors the ideology present in its Ameritrash brother Earth Reborn. Layered mechanics give way to depth and are integrated in a streamlined fashion which beckons you to return again and again. One could posit that <PERSON> is cut from the same cloth as <PERSON>, although the former’s games tend to have a greater degree of coherency and direction that elevate them to a level of grandeur rather than toil in a realm of overwhelming difficulty.\nArchipelago can be dissected into 3 vital organs and spheres of interaction that form the guts of the title. The Action Wheel provides for the turn to turn momentum and pace of player manipulation as each participant places action disks worker placement style. The hex board is built as players branch out and explore, discovering new vistas and resources to exploit. The final and most powerful element is the market system which dictates the vitality and health of the raging economic undercurrent that players interact with on a constant basis. All of these are nuanced and developed, comprising fleshed out interfaces to manipulate and be manipulated by.\nThe box is packed full of cardboard goodness.\nThe Action Wheel is made up of a plethora of spaces for players to utilize. Each player takes a turn placing one of their action disks (workers) and then executing the corresponding action. Actions are tight and you will often want to accomplish much more than you are afforded. Options include harvesting resources, constructing buildings, taxing the locals, birthing or hiring additional workers, and exploring.", "937" ], [ "Most actions are pretty straightforward and indicative of the typical fare. Exploration is the most fascinating and reminiscent of <PERSON>’s search mechanic from the earlier mentioned Earth Reborn. When you explore you may either take the top tile from the stack or the tile beneath it. Tiles are double sided and you are able to attempt to place either side, but you can only see the top-most face which is readily visible. The difficulty arises in that tile placement is restricted based on respecting land features – so a mountain must connect to a mountain, sea to sea, and so on. So, when presented with the desire to explore but the only visible tile face is not currently place-able, do you take that risk and go with the tile below it? If you fail, then your entire action is wasted. This is a chief example of that aforementioned chaotic current interwoven throughout the game that forcefully shoves the design in the opposite direction of its genre associates. The risk/tension is fascinating and in no way feels tacked onto the game or shoddy.\nOne of the most interesting elements of the Action Wheel is the fact that some spaces allow only limited placement while others permit freedom of being able to be repeatedly selected. There is no limit to the number of people that can harvest Exotic Fruit, but if you want to explore you are only able to place your disk on the space marked with your color. Once you have done this, you may explore with a subsequent action by placing your action disk on one of the multi-color spaces, as long as they haven’t already been occupied. This hybrid of limited and free action selection adds to the tightrope struggle of balance embedded in the design’s nature. While this intrinsic elegance is belied by the cluttered and busy graphic design of the Action Wheel, the simplicity and strategic engagement rises to the surface quickly upon engaging.\nThe map is built of these hexes that players explore and place, branching out and taking shape like watching a map being charted by a cartographer in accelerated real-time. The tiles themselves are beautiful and a joy to gaze upon, erecting a flourishing portrait as players place Citizens, Buildings, and Boats on the map, giving life to a newfound culture sprouting from its energetic roots. The map is perhaps the most forgiving element of the design as you can readjust, move, and shift focus all at the cost of an action or two. Placement of your Citizens and the tiles themselves due limit you in scope, but the game offers enough breadth of strategy that you can often make do no matter the draw.\nGorgeous artwork sets the backdrop for the Archipelago.", "349" ], [ "These days, it’s not uncommon to find card games that disguise themselves as something much more. They push the envelope and redefine how complex, strategic, and/or thematic a card game can be. Guillotine is the antithesis to these, a basic card game that makes no pretensions. Two decks of cards, a toy (non-working) head-chopper, and that’s all it needs to be a cut above your average filler.\nComponents: See above. The two decks of cards – the action deck and nobles deck - are colorfully designed (with tongue firmly in cheek) on decent quality stock and nicely coated. (Despite all the execution, there is no ‘die’ to roll). Not much more to say on that!\nTheme/Object of the game – You are one of the executioners during the French Revolution just trying to make a name for yourself by executing the highest ranking nobles (based on point value) in line. Of course, other executioners are also out for the fame and fortune you desire. Your job is simple: behead the first noble in line at the end of your turn. But playing the right action card at the right time can make all the difference in the world. The person with the most points at the end of three days of executions is the winner.\nRules: Dirt Simple. You start out with five action cards in your hand and 12 nobles in line to lose their head during day one of executions. You have the option of playing an action card at the beginning of your turn.", "237" ], [ "If so, you execute (pun intended) the action immediately. Whether you’ve played an action card or not, you then must behead the first noble in line, then take another action card from the deck. When there are no more nobles in line, lay out 12 more for the next day. The game is over after three days of executions. Any exceptions to these rules are printed on the cards themselves.\nGameplay: I’m not just sticking my neck out when I say that this is where the game shines. The action cards in your hand allow you to do a variety of things – rearrange the line (or prevent people from rearranging it), add or subtract nobles to the line, assess penalty points to other players, reverse the order of nobles, etc. While this may not be the most strategically challenging exercise, it is unpredictable and fun. Sure, there’s a hefty amount of luck involved, but having a few decisions on which is the best play at any one time is just enough to give you bragging rights when you win.\nGood Stuff – This is a card game that plays in about 15-20 minutes and is a great filler game. Selling for about $15, it’s also a pretty good deal. You can always play fewer hands (days) than prescribe, or reformat the game to make the game longer (but remember, there are only so many nobles cards). Having no small parts also makes this very portable.\nBad Stuff – The game can wear out its’ welcome if it’s played too much, and the theme might be a turn-off for those who are easily offended.\nFinal Words. Guillotine is a wonderful find – a multi-player filler game with a warped sense of humor and an air of unpredictably. It’s not very deep nor is it grandiose, but is a lot of fun. I can see myself picking up this game and keeping it in the car to play at coffee shops or wherever the opportunity presents itself.", "237" ], [ "A review based on 7 plays (4 losses, 0 successful aborts, and 3 wins), all 2-player.\nMissed opportunities.\nThis is the phrase that comes to mind when I think of Shadowrun: Crossfire. Don’t misunderstand me – I think this is a solid game, one which my partner and I will play again many times. But it could so easily have been something more, a precious game worth dozens upon dozens of plays. Let me explain.\nThe idea of persistence, of game events whose effects last for multiple games, has long been a mainstay of video games and is one of the most exciting recent trends in the world of board games. Players become especially invested in games like Risk: Legacy and Pathfinder because their actions, as well as other events in the game world, have truly long-term consequences. Shadowrun: Crossfire is another entry into this genre, and it also happens to be a deck-builder in the vein of Dominion. Each player will build a persistent character who gains several experience points, called “karma,” for successfully completing missions and gains much less experience for successfully aborting a failed mission. These points may be spent on upgrades which give characters enduring special abilities, such as the ability to start missions with extra cards or health.\nGame overview\nEach player will build a starting character by combining a race (human, troll, orc, elf, or dwarf) and a class (mage, hacker, fighter, or support). The race determines your character’s starting health, money, and cards in hand, while each class has its own starting deck. In the core scenario of the game, “Crossfire,” these characters will face a series of enemies (“obstacles”) in three progressively more challenging stages. To defeat an enemy, you must play cards with symbols matching all types of damage (blue, red, green, black, or colorless, which can be matched by any color) listed on the enemy card. Most importantly, these levels of damage must be done in order, which gives the game a very puzzle-solving feel. Defeating an enemy yields money, which can be used to purchase much more powerful cards which go directly into your hand.", "755" ], [ "You win by defeating all enemies, lose if every runner is at certain levels of low health (“staggered” or “critical”), and successfully abort otherwise. But every round you will draw a dangerous new Crossfire event (though you get a reprieve of 1-2 rounds with fewer than 4 players), many of which become more powerful still if a certain number of Crossfire events have already occurred, so you must try to defeat enemies at a brisk pace.\nFeel of the game\nThis game requires a great deal more focused thought than any other deck-builder I’ve played, including Dominion, Ascension, and Thunderstone. Solving the puzzle of exactly how and to whom to deal damage is challenging and, for me at least, very satisfying. You will frequently have to make tough and meaningful decisions, like whether to buy a decent card now or a terrific card later, or whether to completely kill a weaker enemy or partly damage a stronger enemy.\nThe Crossfire event deck is also a terrific idea, though I am not delighted with the execution. Since these events usually get much more powerful if a certain number of events have already occurred – in other words, if a certain number of turns have passed – the atmosphere becomes progressively more tense.\nMost importantly, it is difficult to overstate the emotional attachment that comes with building a permanent character who grows stronger over the course of many missions. Time spent playing the game yields not only the hope of immediate victory in that mission, but also the promise of a long-term improvement in your character, the hope of nurturing your puny novice into a grizzled and powerful veteran. What a sparkling idea!\nIf only it were better executed.\nCriticisms\nI’ll start with a sin that Shadowrun Crossfire shares with many eurogames: the sin of purely nominal differences. The game includes four different roles, each with a different starting deck. But in practice, all of the starting decks are identical. For example, the fighter’s deck contains 4 cards which deal 1 black damage and 1 card each dealing red, green, and blue damage, while the mage gets 4 cards dealing 1 blue damage and 1 card each dealing red, green, and black damage. The starting cards have no further abilities, so the difference in starting decks is a difference in color only. How dull! The starting deck for each role should have included at least one asymmetric ability.\nTo be sure, the cards available for purchase differ greatly depending on role: the fighter cards deal moderate damage and distract enemies from attacking other players, the mage cards sporadically deal large bursts of damage, etc. That’s wonderful, but it does not excuse the starting symmetry in roles.", "755" ], [ "Playing with 4, a chronicle so far that has spanned 5 games.\nPlaying so far exclusively on TTS; 3 of us purchased kickstarter and are awaiting our copies (North America)\nLearning the game\nNot nearly as bad as you might think if you hang out in these forums. We started with the playthrough, which is really just the first four turns or so, and then continued on into the gameplay. First game will require rules clarifications, googling these forums (what game doesn't, though?). Only in one case did we have one big confusion in the first game. This led to my post https://boardgamegeek.com/thread/2557132/definition-more-it-..., which ended up in the official errata https://docs.google.com/document/d/1p2tHzbTmQhU8tPfZeK5gSJvm...(I feel cool).\nPlaying the game\nThe best thing about this game is the constant shift in victory conditions, which can see huge swings in what you think to be true. For example, in our last game, we were certain the Chancellor would win. He had an impenetrable fortress of secrets, banners, and a relic that required we first remove it before going after any of his other key items. His citizen, who had been loyal all game, asked for reinforcements. Only then did the citizen make a mind blowing back stab play to campaign against his weakened chancellor and steal these treasures. This then made us certain the traitor citizen would win as the game was nearing the final rounds. This opened the door for me to then go in and campaign against the chancellor's remaining banner which provided me the oathkeeper title, and now it seemed certain I would win.", "366" ], [ "In a matter of a few key and highly strategic plays, the ebb and flow of power was palpable. Guess who ended up winning? None of the three of us! The other exile! Who found the one vision he needed for the win, with the vengeance-filled chancellor backing his win.\nWill you like this game?\nDo you like great stories like Game of Thrones? Do you like emergent narrative? Do you like highly strategic card interplay where spotting a combo at just the right time could catapult you from the back of the game to the front? Where the bullseye on someone's back is always changing? Where the rug gets pulled out from under everyone in succession, and everyone gasps? Then you will love it.\nMy one critique, which really isn't a critique, when I think about it\nKingmaking. There is a lot of kingmaking in this game, so be ready for that. Normally, it would feel a bit deflating to be in the lead, only for another player to hand the victory to a third player out of spite. They couldn't win themselves, but you had taken the win from them, so they pass the win to another. This can happen. However, when you step back and look at it from the story, and thematic point of view - it makes perfect sense. Why would the chancellor not want to pull the win away from the citizen who stabbed him in the back? Et tu <PERSON>?\nClosing thoughts for now\nThis game appealed to me early on, I followed the designer diary. It has quickly risen to a top 3 for me after 5 plays. I believe it has so much more to see, as our chronicle continues. Every single game has felt different from the last. If you are looking at the rulebook or reading the forums about the rulebook and thinking, ugh - I don't want to learn this...I would say, get on TTS, get a few friends, and just try it.", "366" ] ]

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[ [ "The Counselor\nNobody ever really talks about <PERSON> acting in this movie, probably because there isn't much to talk about. Where <PERSON>, <PERSON> and <PERSON> are all at minimum vivid–the beneficiaries of very careful styling and costume design—<PERSON> is vague, blurry, and out of focus even within the pitiless digital clarity of <PERSON> cinematography. He's playing a cipher so empty he doesn't even have a first name, much less the kind of inner life that would make his final recognition of his transgressions—and their tragic, lethal consequences—register on an emotional level.", "295" ], [ "But then for this cold stainless-steel bolito of a movie to work, at least in the way its supporters claim, the Counselor's ultimate despondency has to be more bleakly funny than anything else—the cartel-thriller equivalent of \"fuck around and find out.\" Sadly <PERSON>, for all his talents, is not the guy you go to for a precisely managed satirical tone, which is why, for all the compelling, heartfelt claims that this is some kind of stealth comic masterpiece, it's really only fitfully outrageous and entertaining, and otherwise dully beguiled by its own pretentiousness— the antipode of No Country For Old Men, which is so perfectly controlled it skirts (and of course transcends) monotony en route to feeling actually profound. I'm also not sure <PERSON>'s the guy you go to for world-weary cynicism about the inevitability of the profit motive, as he's such an unrepentant mercenary, and he's no better (or more thoughtful) than his spiritual inheritor <PERSON> when it comes to aestheticizing Mexico as a jaundiced abbatoir or lazily implicating the US of A in cycles of suffering. Throw another one on the pile (literally) the movie snickers, effectively emblematizing its own po-faced, disposable sadism.", "698" ], [ "Weird: The <PERSON> Story\nWhat gives this a leg up on Walk Hard is that it's not just roasting the biopic genre, but an actual biography. Yet this is burdensome, in a way: the movie is sort of doomed by the inevitability that the funniest thing about it will simply be the fact that it exists. That this is <PERSON> own version of a <PERSON> biopic is, on its face, very funny.", "952" ], [ "The movie itself is almost an afterthought, more amusing than hilarious, but the amusement value is pretty high—especially if you're a comedy nerd who likes playing spot-the-cameo. The other noteworthy business going on here is <PERSON> incredibly legit evocation of <PERSON>. The movie is all silliness but here's <PERSON> playing it like she's in a straight <PERSON> biopic (yet still sensitive to the film's humorous contours). <PERSON> deserves enormous credit as well for running full-speed at this absurd concept.", "585" ], [ "Nostalgia\nFor all the poetry and transcendence and desperate sincerity there also is something so sour about this movie. I mean there's a lot of bitterness in <PERSON> in general that the One Perfect Shot crowd doesn't talk about so much (thinking of <PERSON>'s first reaction to seeing <PERSON> in Solaris) but in particular the moment when <PERSON>'s tape player craps out before his, uh, big moment in Rome is almost unbearably cruel.", "698" ], [ "But funny, too! Or the long take of <PERSON> drunkenly rambling to a small Italian child... It feels like the scene in Lenny when <PERSON> is bombing, but this time the room is halfway underwater. Knowing the backstory of this project it almost seems like it should be a self-pitying disaster, but it's all just sadistic enough to follow me around all day like a dark cloud.", "549" ], [ "Criminal\n<PERSON> is absolutely correct that The Fugitive would be better if the first half of it were <PERSON>, his wife, and a lady cop all being intensely horny for each other in various permutations.\nAfter that, he reluctantly does remake The Fugitive, but you can kind of tell he doesn't much want to. He underplays all that movie's most iconic scenes--or outright skips them--and gives <PERSON>, in the <PERSON> role, basically nothing. He's much more interested in the tortured yearning between policewoman <PERSON> (a character very much not present in the original) and <PERSON> (in the <PERSON> role).", "698" ], [ "The second half's best scene is the only one that's just the two of them, and it's much more in <PERSON>'s preferred lane.\nIt's such a stark contrast to his approach when remaking It Happened One Night, where he treated nearly every beat with reverence. He's not wrong that It Happened One Night is a better movie, but given that, why remake The Fugitive at all? Especially if you're only going to spend about forty minutes of your 2.5 hour movie doing so?\nOther flaws include some disappointingly limp action beats (including the most perfunctory handling imaginable of the big jump off the dam), weak villains, and a pretty dull villain scheme motivating the action.\nBut this is still pretty good, owing to the strength of that (shockingly horny) first hour, that one <PERSON>/<PERSON> scene in the second (which is really the only scene after the interval that much feels like <PERSON> being <PERSON>), some great music from <PERSON>, and a very strong core three performers in <PERSON>, <PERSON>, and <PERSON>. It doesn't quite live up to the promise it seems to have early on, when you think that lovelorn (and ultimately scorned) <PERSON> is playing the <PERSON> role and adding a whole lot of interesting emotional layers and deeply personal stakes to an already proven dramatic dynamic, but alas that's not where it's going. That version of this movie might have been a classic, this one is just pretty fun.", "698" ], [ "<PERSON>\nSomething I'd been mulling since my first viewing: is <PERSON> actually any good? The person, not the movie. From what we see, she doesn't seem to be a particularly gifted composer, despite her EGOT status. She's regarded as a great conductor, but what does that really mean? When asked to explain why she's more than just a human metronome who's only there to mark time, her answer is basically, \"Well, that IS why I'm there, but it's a very important job.\" As articulate and self-regarding as she is, the best she can offer as a justification for her own existence is a tepid piece of musical trivia: the opening bar of <PERSON>'s Fifth begins on a rest, so someone has to be there to start the clock.\nTellingly, though, she makes that point with such piercing charisma that it's almost convincing. When we see her at work, leading the Berlin Philharmonic through rehearsals, her celebrity status seems fully deserved. The absence of subtitles on her rapid-fire German lets us take her in as pure sensory experience, and she's mesmerizing. This is the medium of her brilliance: performance — not of music, but of herself. You could watch her for hours. It's no surprise she sells tickets.\nA lesser version of this movie would have opened with <PERSON> in coattails, conducting an orchestra for some hushed, well-heeled crowd.", "80" ], [ "Instead, we see her sitting in a chair and talking about herself. This is her truest distillation. <PERSON> on Tár.\nAll of this wraps around, in a beyond-meta way, to <PERSON>'s performance, which is one of the trippiest feats of acting I've ever seen. Watching her makes me think about Eyes Wide Shut, and not just because of our friend <PERSON>. The hyper-deliberate speech in that film, and its weirdly hypnotic effect, has echoes here. <PERSON> as <PERSON> is a performance as \"conscious\" (this is the most appropriate word I can think of) as any ever filmed: a person (<PERSON>) playing a person (<PERSON>) playing a person (<PERSON>) of her own invention (<PERSON>'s, <PERSON>'s, and <PERSON>'s too), each layer perceptible and acutely self-aware. Every little gesture and mannerism seems at once uncalculated and delicately practiced. Every sentence sounds spontaneous and yet somehow recited. There is a perfect and impossible geometry here — some kind of shape we may not have the math for yet — but the effect is a simple crystal thing: against all odds, Tár is real.", "295" ], [ "The Seven Year Itch\nKind of insufferable at the beginning with the Voice of God narration and <PERSON> unconvincingly uttering his every thought aloud for the audience's (supposed) benefit, and only mildly entertaining thereafter, The Seven Year Itch somehow manages to be passable. <PERSON> hated this film and said that it is meaningless if <PERSON> remains chaste (he doesn't in the play), but it's in fact precisely this fact that redeems the film.", "144" ], [ "Not for any moral reason, of course, but because <PERSON>'s <PERSON> is the most uncharismatic and irritating character imaginable and that, along with the presence of <PERSON>, means that we're looking at a male fantasy bordering on the self-aware.\nThis is a film about the typically masculine idea that one's confidence could make up for countless character flaws and allow you to score even someone as beautiful as <PERSON>—that is, if not for the stifling institute of marriage. It's a fantasy from start to finish, one that achieves self-awareness with \"wouldn't you like to know [who's in my kitchen]? Maybe it's <PERSON>!\" There is no reason for <PERSON> to sleep with <PERSON>, because his goal is merely to prove that he could have, to be assured that he would have made 100% of the shots that he didn't take. If <PERSON> had his way, or if the protagonist had a single redeeming feature, it would blunt the only edge the film has.", "698" ], [ "Anatomy of a Fall\nA movie about how deeply unserious and misogynistic the French are.\nIt doesn’t really do much new that other family-centered courtroom dramas haven’t done better save for exposing the many, often tiny biases against women that are engrained in society. The opposite of that same preconception that helps <PERSON>’s case in Kramer vs. Kramer mixed with <PERSON>’s uphill battle in Marriage Story.\nFunny how mockumentary-ish the filmmaking was at points, which was clearly meant to evoke immediacy but instead took me out of it.", "306" ], [ "It works to its favor that it’s helmed by an immaculate leading performance. <PERSON> carefully balances fear and doubt and so much constrained emotion. She probably won this the Palm d’Or all by herself.", "464" ], [ "Poor Things\nFor several decades in British literature there has flourished a genre that borrows the settings and narrative conventions of the Victorian novel while modernizing it with all the sex, violence, and other improprieties that were off-limits in the famously prudish Victorian era. The film industry, despite its frequent and tedious revisitations of the original Victorians, has largely ignored this genre.", "269" ], [ "So in a sense Poor Things feels overdue, and its occasional overexcitedness at its own irreverence is excusable on the grounds that it’s more or less the first movie to embrace the horny “what if Jane Eyre fucked” spirit that English novelists have been working with since the ‘80s (if not earlier). Plus, when did <PERSON> take a funny pill? His comic turn as a louche cuck is a pleasant surprise, as is the film’s rather moving story of self-determination. If this has haters, they’re trying too hard.", "585" ] ]

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[ [ "Spider-Man 2\nYou can't outlive pioneer status\nWhy would <PERSON> be Spider-Man when being Spider-Man is destroying his life.\nHe wouldn't, and never wanted it\nWhy would anyone do anything that only brings them pain\n<PERSON>'s turmoil is so abundant that his dead Uncle's last meaningful words to him aren't enough.\nIt completely ruins him to do the only thing that will bring any form of hapiness into his heartbreakingly depressing and emotionaly complex life.\nHe loses all will\nThe hospital scene is more terrifying the longer I think about it.\nI will always stare in amazement watching <PERSON> give absolutely everything in the confession, and stopping the train.\nI will never not take it personal.\nI can never hold back tears.\nGot to make you mad not to know who you are.\nYour soul disappears.\nMaybe you're not supposed to be <PERSON> climbing those walls. That's why you keep falling.\n<PERSON>, all the times we've talked of honesty, fairness, justice, out of those times I counted on you to have the courage to take those dreams out into the world.\nI can't live your dreams anymore. I want a life of my own.\nIt is a movie so heavy.\nIt is the best Superhero movie.\nIt is so fucking dense.", "387" ], [ "<PERSON>: Mask of the Phantasm\nThe cowl\nThe armor of <PERSON> little by little decends and fades to black, and the walls which <PERSON> has built between himself and his world of turmoil vanish\nWhats left is to find eyes of a demon that isn't defined by violence and crime, but by heartbreak\n\"Really <PERSON> it's almost as if you pick them because you know theres no chance for a serious relationship\"\nWe witness a man who prefers loneliness. A persona who picks souls that are doomed to fail because he knows they can never hurt him\nLetting rooftops of rain express his solace, his longing for someone to see every part of him the sickness the ugliness, and still want to share it with him, and allow him to do the same. <PERSON> in <PERSON>'s mind was that one glance of life beyond a vow that will never bring back what was taken\nPlease. Tell me it's okay\nThe Bat and the Phanstasm.\nTwo who deal with their torment by choosing to be symbols rather than people.", "295" ], [ "All a facade to hold back tears.\nThe purple suit, is the Jester who swathes in a world of broken dreams and false desires, and Evil laughing, pure evil thriving knowing that it stands in the way of true happiness. Real evil laughs joyfully at the realisation that none of it will ever work, be sane. Extinguishing her light to leave <PERSON> in nothing but darkness.\nMaybe after this is settled. Maybe then\nIt's all lost dreams, an idealised future which in every case is difficult to actualise, because fantasies aren't real.\nthat is <PERSON> torment\nThe Gotham Skyline and the rain\n- That is all he has now.\n‏‏‎ ‎‎‏‏‎ ‏‏‎ ‏‏‎ ‎ ‎‏‏‎ ‏‏‎ ‏‏‎ ‎ ‎ ‎ ‎ ‏‏‎ ‎‎‎ ‎‏‏‎ ‎‎‏‏‎ ‎‎‎ ‎ ‏‏‎‎ ‎ ‏‏‎ ‎‎‎ ‎‎‎ ‎ ‏‏‎ ‎ ‏‏‎ ‎‎‎ ‎ ‏‏‎ ‎‎‎ Perhaps it's all he's ever had...", "313" ], [ "The Children\nThe editing bay wins this movie.\nThere are some really cool cuts and shots when \"the children\" start act out.\nI'm a sucker for evil kid movies. I feel kids are evil to begin with, so when they start attacking and killing it just makes sense.", "965" ], [ "Their true nature seems to come to the surface.\nWhen there are more than one, they become more terrifying than a horde of zombies.\nWhat I really liked about this movie is that they have some nasty kid kills. What I mean is that the evil kids actually get put down. Usually filmmakers steer clear of killing kids but <PERSON> just jumps in neck deep.\nI'm not 100% sure I buy into the ending, but I liked everything else so much that I didn't care.", "965" ], [ "Guardians of the Galaxy Vol. 3\nFull disclosure, I'm writing this review after watching this for a second time.\nI love <PERSON> broken space folks. His style of writing imperfect characters is something that I adore, as it injects a much needed element of humanity and pathos into even the most exaggerated creatures and concepts. Because everything is grounded in a sense of compassion, he's able to return to his Troma roots in the best ways. Because of this, Guardians 3 is pretty much my favourite MCU project and a perfect topper to this trilogy.\nEvery character arc comes full circle perfectly in a way that very few other MCU arcs have done (Endgame notwithstanding).", "387" ], [ "I'm so pleased with every concluding moment here. Even <PERSON>, who doesn't really have a character arc to speak of, instead gets to show off the full range of his powers in the best ways.\nCreature effects and eclectic designs are my cinematic catnip, so I was in heaven throughout this. The OrgoCorp sequence, Counter-Earth, and basically everything parallel to the High Evolutionary was filled to the brim with genuins designs and goopy, creepy effects. That's the kind of shit I love in movies, and <PERSON> went all-out for his final Marvel swing.\nThere's so much more I can praise about this, but it can basically all be boiled down to me loving everything about this. The alchemical mix of comedy to drama to sheer spectacle is perfected here, with not a single moment gone to waste in the structure of it all.\nI think this cements the trilogy as the best cape trio of films out there. I'll miss seeing this group in future projects, but with a conclusion this potent I'm happy they've been seen off in the best way possible.", "19" ], [ "The French Dispatch\nEvery film <PERSON> makes feels like a love letter to cinema and this was no exception.\nThe French Dispatch is four stories in a film, which works really well with his style. In everyone of them he gets to explore different sides of the magazine and the city. And introduce a whole other set of quirky characters.", "594" ], [ "It's a smart choice, because nothing outstays it's welcome or drags on for to long.\nThe cast is huge, it feels like everyone is here. You just don't say no when you get asked for an <PERSON> film.\nFor me the last story, with <PERSON>, was the strongest or most fun. It's a crazy journey from a dinner in the police precinct to a chase through the city streets to catch a kidnapper.\nI laughed, I cried and I marveled at every frame <PERSON> created with his team. He used every trick in his playbook and somehow it all came together in this wonderful film.", "529" ], [ "The Little Mermaid\nPretty flippin' cute.\nI am the first one to hate on Disney's lack of creativity and money grab behavior, but this proved itself necessary, as it improves upon on the original tale in ways I believe essential for the kiddos. Happy for them!\nIf they had to do it, at least you can tell that they took the time to formulate a pitch perfect cast.", "252" ], [ "<PERSON> is the obvious stand out, but <PERSON> brings a stellar energy to sidekick <PERSON> that will no doubt be gifted <PERSON> status. Reviewers will criticize <PERSON>'s song, but how can you blame them, the children respond to the work of <PERSON>.\nI found everything on land to be much more compelling than the under water sequences, mostly because of the stunning chemistry between <PERSON> and <PERSON>, but also because their love story feels cared for and made believe-able by the writers, unlike the animated classic.\nI also thought it looked fine despite what thousands of online adults have prematurely complained about. Flaws of course, but I'm not in the mood to bring this movie down anymore than it has been.\nAlternative review: <PERSON> girls are no longer pick-me girls.", "252" ], [ "Spider-Man: Across the Spider-Verse\n\"I just don't wanna go home...what's waiting for me at home is really bad.\"\n\"What's waiting at home?\"\n\"I don't know. When I get home, there's something I'm worried about about my life.\"\n\"What is it?\"\n\"I don't know.\"\n\"Is there really something?\"\n\"I don't know.\"\nI Think You Should Leave\nThis was the most more I've seen in a sequel since the second Pirates and Matrix movies. I liked it.", "995" ], [ "I did want it... I was maybe hoping for something tighter? I could see Sony execs behind every drawn out moment milking the blood out of these artists. And I mean they did get to do a lot of cool art, so I can't be mad at it? But also I guess I'm the only one who found this to be kind of bloated and self indulgent a lot of the time?\nI don't know.", "645" ], [ "<PERSON> in the Multiverse of Madness\nTake note those who made the mishandled X Men Dark Phoenix: This is how you show the struggle when a <PERSON> gets temporarily Baddified by too much power.\nI just love this version of <PERSON>.\nLike all the best wrestling villains, she genuinely believes that she is justified in her actions. There’s logic, albeit damaged and selfish logic, behind her intentions.\nFollowing the traumatic past with her fantasy children and of course blasting a hole in her husband’s head, wouldn’t you crave the opportunity to go somewhere where all that pain can be ignored.\nThe falling sequence where <PERSON> & <PERSON> pass into alternate New York is fantastically trippy - perfect to watch at 4:20 😉\nWonder if the zombie <PERSON> was in the script before <PERSON> got involved…", "282" ] ]

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[ [ "Gauging fixing in the classical $U(1)$ gauge theory\nMy question concerns the gauge fixing in classical v.s. quantum $U(1)$ gauge theory. I will ask about the gauging fixing in quantum $U(1)$ gauge theory in a separated Phys-SE post.\nFor the classical $U(1)$ gauge theory,\nwe have the electric $\\vec E$ and magnetic $\\vec B$ written as the scalar $\\phi $ and vector $\\vec A$ potentials: $$ \\vec E = - \\vec \\nabla \\phi -\\frac{\\partial}{\\partial t} \\vec A. $$ $$ \\vec B = \\vec \\nabla \\times \\vec A. $$\nMy understanding about the gauge fixing for this gauge theory is that we can chose for example, $(\\phi, \\vec A)$ to give a set of $\\vec E$ and $\\vec B$ fields.\n1. But we can also shift to $$(\\phi, \\vec A) \\mapsto (\\phi + C_0, \\vec A + \\vec C)$$ where arbitrary choices of $(C_0, \\vec C)$ still give the same solutions of $\\vec E$ and $\\vec B$. So a certain but arbitrary choice of $(C_0, \\vec C)$ can be regarded as a way of gauge fixing? correct?\n2. Furthermore, we can also shift to $$(\\phi, \\vec A) \\mapsto (\\phi + \\phi_0, \\vec A + \\vec A')$$ such that the followings are satisfied: $$\n3.", "298" ], [ "\\vec \\nabla \\phi_0 -\\frac{\\partial}{\\partial t} \\vec A'=0 $$ $$ \\vec \\nabla \\times \\vec A'=0 $$ Then we have a choice of $(\\phi, \\vec A) \\mapsto (\\phi + \\phi_0, \\vec A + \\vec A')$ such that any choice is a way of gauge fixing? correct?\n4. In a classical differential equation, we have $$\n5. d * F = J $$ $$ dF=0 $$ so $F=dA$ with $ d * dA = J$ is a solution. Say $F=dA'$ with $ d * dA' = J$ is also a solution. And the gauge fixing implies a different solutions of $F=dA$ and $F=dA'$ where $A$ and $A'$ are both valid solutions. What are the differential equation constraints then? Is my understanding complete to include ONLY: $$\n6. d * d (A-A')=0 $$ or do we need more constraints to do gauge fixing?\nAm I correct to say that $A$ and $A'$ are in the same gauge profile thus should be regarded as the same gauge equivalent classes. Choose $A$ or choose $A'$ is simply a choice of gauge fixing?", "418" ], [ "<PERSON>-Higgs Mechnism\nConsider an abelian gauge field coupled with a complex field: $$\\mathcal{L}=-\\frac{1}{4}F_{\\mu\\nu}F^{\\mu\\nu}+(D\\varphi)^\\dagger D\\varphi+\\mu^2 \\varphi^\\dagger\\varphi-\\lambda(\\varphi^\\dagger\\varphi)^2.$$ In polar coordinates $\\varphi=\\rho e^{i\\theta}$, we have $$\\mathcal{L}=-\\frac{1}{4}F_{\\mu\\nu}F^{\\mu\\nu}+\\rho_0^2(\\partial_\\mu\\theta-eA_\\mu)^2+\\cdots$$ where I have ignored the fluctuation of $\\rho$ by setting $\\rho=\\rho_0$.\n(I). The standard way to deal with it is to redefine $$B_\\mu\\equiv A_\\mu-\\frac{1}{e}\\partial_\\mu\\theta$$ thus we have $$\\mathcal{L}=-\\frac{1}{4}F_{\\mu\\nu}F^{\\mu\\nu}+e^2\\rho_0^2 B^2$$ thus the massless gauge field eats a Nambu-Goldstone boson and becomes a massive gauge field which has 3 degrees of freedom.\n(II). Instead of doing that, let us expand $(\\partial_\\mu\\theta-eA_\\mu)^2$ directly and impose Lorentz gauge at the same time $\\partial_\\mu A^\\mu=0$, we have $$\\mathcal{L}=-\\frac{1}{4}F^2+\\rho_0^2e^2 A^2+\\rho_0^2 (\\partial_\\mu \\theta)^2,$$ where the cross term vanishes because of the <PERSON> gauge. And this <PERSON> gauge is satisfied by the equation of motion of the gauge field $A_\\mu$ naturally.", "474" ], [ "It seems we have both massive gauge field and a Goldstone boson.\nMy questions are:\n1. How to reconcile the two approaches above?\n2. If we want to examine the dynamics of the bosons (for example, apply a boson current and see how this current propagates), will this current be a supercurrent in the presence of a dynamic gauge field? This boson current will be a supercurrent(like a current in a superconductor) in the absence of a dynamic gauge field. When we couple this boson system to a dynamic gauge field, the dynamics of phase $\\theta$ of the boson field is hidden somehow in the approach (I) and it is not clear whether this boson current will be a supercurrent or not. But from approach (II), it seems this boson current will still be a supercurrent.", "298" ], [ "Moduli Stabilization in 6D Einstein-Maxwell theory - Fluxes and O3 planes\nI'd like to do the maths for the moduli stabilization of 6D Einstein-Maxwell Gravity $$ S= \\int d^6X \\sqrt{-G_6}(M_6^4R_6[G_6]-M_6^2|F_2|^2), $$\nwhere the 6D metric is specified by $$ ds^2 = g_{\\mu\\nu}(x)dx^{\\mu}dx^{\\nu}+R^2(x)\\hat{g}{mn}(y)dy^mdy^n, $$ and $\\hat{g}{mn}$ is the metric of a compact 2D manifold with unit volume.\nThe setup of this model can be found in Denef, Douglas, Kachru, starting on page 10.\nNow I want to perform the dimensional reduction of the theory and thereby obtain the correct effective potential $V(R) = \\frac{\\chi}{R^4}-\\frac{n^2}{R^6}$.\nI could manage to derive the first part of the potential by rewriting $$ ds^2= R^2(x){\\frac{g_{\\mu\\nu}(x)}{R^2(x)}dx^{\\mu}dx^{\\nu}+\\hat{g}{mn}(y)dy^mdy^n} $$ which allows me to rescale the 6D action by $G{MN}=R^2\\tilde{G}{MN}$. Then we are left with a product space, i.e. we can write $R_6[\\tilde{G}_6]=R_4[\\tilde{g}]+R_2[\\hat{g}]$, where $\\tilde{g}{\\mu\\nu}=\\frac{1}{R^2}g_{\\mu\\nu}$. Further rescaling brings a factor $R^{-4}$ for the term $\\chi$, while a factor $R^2$ has been absorbed in order to write $M_4^2=M_6^4R^2$.\nHowever, I'm not sure how to obtain the term $\\frac{n^2}{R^6}$.", "818" ], [ "I'd appreciate any help.\nMy idea is as follows: $$ \\int d^6X \\sqrt{-G_6}M_6^2 |F_2|^2 = \\int d^6X R^6 \\sqrt{-\\tilde{G}_6}M_6^2 |F_2|^2 = \\ = \\int d^4x \\sqrt{-\\tilde{g}}\\int d^2y\\sqrt{\\hat{g}} R^6M_6^2 |F_2|^2 = \\int d^4x \\sqrt{-g}\\int d^2y\\sqrt{\\hat{g}} R^2M_6^2 |F_2|^2 \\sim \\ \\sim M_6^2 \\int d^4x \\sqrt{-g}R^2 (\\frac{1}{R^2})^2 \\cdot (\\frac{n}{R^2})^2 = M_6^2 \\int d^4x \\sqrt{-g} \\frac{n^2}{R^6} $$\nIn the last line, we obtain a factor $R^{-4}$ because of $\\gamma^{m\\hat{m}}\\gamma^{n\\hat{n}}F_{mn}F_{\\hat{m}\\hat{n}}$ and the second factor comes from $F_2 \\sim \\frac{n}{R^2}$, since $$ \\int_{M_2} F_2 =n. $$\nHowever, I'm puzzled because the factor of $M_6^2$ remains. If I want to rewrite the action s.t. we have a factor $M_4^2$ in front, then the term I obtain reads $\\frac{1}{M_4R} \\frac{n^2}{R^6}$ (reminder: $M_4^2 =M_6^4R^2$).\nSo, where is my mistake?\nFurthermore, it is claimed that O3 planes give rise to an additional term $\\frac{m}{R^4}$ (after <PERSON> rescaling), but I've no idea how it arises. I would start with a CS term $\\int C_4$ for the action...\nIt would be great if anyone could help me with these questions.", "521" ], [ "BRST as gauge symmetry or global symmetry or the generalization (e.g. in Peskin and Schroeder 16.4)\nIn Peskin and Schroeder (PS) Chap 16.4, such as after eq.16.45, in p.518, PS said: \"local gauge transformation parameter $\\alpha$ is proportional to the ghost field and the anti-commuting continuous infinitesimal parameter $\\epsilon$.\"\nSo the gauge parameter $$\\alpha$$ and BRST anti-commuting continuous infinitesimal parameter $$\\epsilon$$ are related by $$ \\alpha^a(x) = g \\epsilon c^a(x) $$ where $a$ is the Lie algebra (in the adjoint) index. In this sense, it looks that the BRST \"symmetry\" contains \"all of the gauge symmetry transformations of the original gauge theory\".\nSo is this correct to say that\nquestion 1. BRST \"symmetry\" contains all gauge symmetries thus BRST \"symmetry\" generalizes the gauge symmetries?\nLater in p.518, PS also claimed: \"BRST transformation (16.45) is a global symmetry of the gauge fixed Lagrangian (16.44), for any values of gauge parameter $\\xi$ for the Lagrangian adding an auxiliary commuting scalar field $B$ as $\\xi B^2$.\" So is this correct to say that\nquestion 2. BRST \"symmetry\" is a global symmetry of the gauge fixed Lagrangian? Whose symmetry generator or the charge is $Q$?\nBy reading PS only in p.518:\nquestion 3. How come the BRST \"symmetry\" contains both the interpretation of global symmetry and gauge symmetry (contains all gauge symmetries of the original gauge theory)?\nIs this simply that BRST \"symmetry\" is a generalization of gauge symmetry, but can contain the global symmetry (if we eliminate the spacetime $x$ dependence say writing $\\alpha^a = g \\epsilon c^a$?\nBy staring at this formula $\\alpha^a(x) = g \\epsilon c^a(x)$ long enough, I would claim that\nBRST global symmetry parameter $\\epsilon$ (which has no spacetime dependent $x$) relates the arbitrary commuting scalar gauge parameter $\\alpha^a(x)$ (with spacetime dependent $x$) to the anti-commuting <PERSON> scalar ghost field $c^a(x)$. - So $\\epsilon$ itself reveals the BRST transformation as a global symmetry (?).", "1020" ], [ "- And the $g\\epsilon c^a(x)=\\alpha^a(x) $ reveals that the BRST transformation can become also a gauge symmetry known from $\\alpha^a(x) $. Do you have comments on this?\np.s. Previous other posts also ask whether BRST symmetry is a gauge symmetry. But here I am very specific about the statements in <PERSON> and <PERSON><PHONE_NUMBER>, in p.518, PS said: \"local gauge transformation parameter $\\alpha$ is proportional to the ghost field and the anti-commuting continuous infinitesimal parameter $\\epsilon$.\"\nSo the gauge parameter $$\\alpha$$ and BRST anti-commuting continuous infinitesimal parameter $$\\epsilon$$ are related by $$ \\alpha^a(x) = g \\epsilon c^a(x) $$ where $a$ is the Lie algebra (in the adjoint) index. In this sense, it looks that the BRST \"symmetry\" contains \"all of the gauge symmetry transformations of the original gauge theory\".\nSo is this correct to say that\nquestion 1. BRST \"symmetry\" contains all gauge symmetries thus BRST \"symmetry\" generalizes the gauge symmetries?\nLater in p.518, PS also claimed: \"BRST transformation <PHONE_NUMBER>) is a global symmetry of the gauge fixed Lagrangian <PHONE_NUMBER>), for any values of gauge parameter $\\xi$ for the Lagrangian adding an auxiliary commuting scalar field $B$ as $\\xi B^2$.\" So is this correct to say that\nquestion 2. BRST \"symmetry\" is a global symmetry of the gauge fixed Lagrangian? Whose symmetry generator or the charge is $Q$?\nBy reading PS only in p.518:\nquestion 3. How come the BRST \"symmetry\" contains both the interpretation of global symmetry and gauge symmetry (contains all gauge symmetries of the original gauge theory)?", "1020" ], [ "Does the commutator between the total derivative term of a symmetry generator and a quantum field always vanish?\nI am trying to understand the following derivation in <PERSON> section 28.2 as to how Noether Charges can be thought of as symmetry generators.\nWe start with the definition of $Q$ (for simplicity let's consider a single scalar field):\n$$ Q=\\int{d^3x}\\frac{\\delta L}{\\delta\\dot{\\phi}}\\frac{\\delta\\phi}{\\delta\\alpha}.\\tag{28.5} $$ Using the fact that $\\frac{\\delta L}{\\delta\\dot{\\phi}}(x)=\\pi(x)$ and $[\\pi(x),\\phi(y)]$=$-i\\delta^{(3)}(\\overrightarrow{x}-\\overrightarrow{y})$ we find $$ [Q,\\phi]=-i\\frac{\\delta\\phi}{\\delta\\alpha} $$ which is the desired result for $Q$ to be a symmetry generator (from my understanding).\nHowever this derivation neglects the possibility of a total derivative term in the current. For full generality we need to modify the charge expression to $$ Q=\\int{d^3x}\\frac{\\delta L}{\\delta\\dot{\\phi}}\\frac{\\delta\\phi}{\\delta\\alpha}+\\Lambda^0.", "818" ], [ "$$\nThus I would expect the relation to be modified to $$ [Q,\\phi]=-i\\frac{\\delta\\phi}{\\delta\\alpha}+\\int{d^3x[\\Lambda^0,\\phi]}. $$\nMy question is: for every example I have seen in QFT so far, $[\\Lambda^0,\\phi]=0$ and so the formula $[Q,\\phi]=-i\\frac{\\delta\\phi}{\\delta\\alpha}$ seems to hold. Is this true in general, and if so, is there a proof of this? Without this missing element I feel that the derivation in <PERSON> is incomplete, as many currents have boundary terms.\nTo give an example, consider the super-current in the free Weiss Zumino Model, which contains the following total derivative term $$ \\Lambda^\\nu=-\\theta\\sigma^\\mu\\bar{\\sigma}^{\\nu}\\psi\\partial_{\\mu}\\bar{\\phi} + \\theta\\psi\\partial^{\\nu}\\bar{\\phi}+\\bar{\\phi}\\bar{\\theta}\\partial^{\\nu}\\phi $$ We see that $$ [\\Lambda^0,\\phi]=[-\\theta\\sigma^\\mu\\bar{\\sigma}^{0}\\psi\\partial_{\\mu}\\bar{\\phi} + \\theta\\psi\\partial^{0}\\bar{\\phi},\\phi]=[-\\theta\\sigma^0\\bar{\\sigma}^{0}\\psi\\partial_{0}\\bar{\\phi} + \\theta\\psi\\partial^{0}\\bar{\\phi},\\phi]=[-\\theta\\psi\\partial_{0}\\bar{\\phi} + \\theta\\psi\\partial_{0}\\bar{\\phi},\\phi]=0 $$ where we used the fact that $\\partial_0\\bar\\phi$ is the conjugate momentum to $\\phi$, and $$ [\\Lambda^0,\\psi]=0 $$ as none of the terms in the current contain the conjugate momentum to $\\psi$ ($\\pi=-i\\sigma^{0}\\bar\\psi$).\nIs there a fundamental reason why this should always be true for any theory and any current?", "818" ], [ "<PERSON> is right. It is very simple to see it: just consider for a moment to add this extra superpotential term $$ \\delta W(\\Phi_i)=\\frac{1}{2}m_{i j}\\Phi_i \\Phi_j $$ where $\\Phi_i$ are chiral superfields. This extra $W$ corresponds to an extra lagrangian term $$ \\delta\\mathcal{L}=-\\frac{1}{2}m_{i j}(\\psi_i\\psi_j+\\text{h.c.})- \\bar{\\phi}iM^2{ij}\\phi_j\\qquad M^2_{ij}=\\bar{m}{ik}m{jk}\\,. $$ Therefore, starting with $W$ and adding a soft mass for the fermions $\\delta\\mathcal{L}{\\mathrm{soft}-\\psi}=-\\frac{1}{2}m{i j}(\\psi_i\\psi_j+\\text{h.c.})$ $$ W(\\Phi)\\rightarrow \\mathcal{L}=\\mathcal{L}{SUSY}+\\delta\\mathcal{L}{\\mathrm{soft}-\\psi} $$ is just the same as doing starting with $W+\\delta W$ (with $\\delta W$ in the first equation above) and add a soft mass terms for the scalars, $\\delta\\mathcal{L}{\\mathrm{soft}-\\phi}=+\\bar{\\phi}_iM^2{ij}\\phi_j$ $$ W(\\Phi)+\\delta W(\\Phi)\\rightarrow \\mathcal{L}=\\mathcal{L}^\\prime_{SUSY}+\\delta\\mathcal{L}{\\mathrm{soft}-\\phi}=\\mathcal{L}{SUSY}+\\delta\\mathcal{L}_{\\mathrm{soft}-\\psi} $$\nIn other words, it is intuitive that only the mass splitting between fermions and boson that matters and should be considered. Adding soft masses that respect susy, that is that do not split fermions and bosons, it is just like adding a mass term to $W$.", "804" ], [ "Therefore, the mass term for the fermion is soft, in the sense that does not give rise to quadratic divergences, since it is equivalent to a new superpotential with soft scalar masses that we know do not generate quadratic divergences. Perhaps, the only possible subtle point left that I see would be about the vacuum stability, since the soft masses for the scalars come flip in sign. But in any case, this is not about their being soft.\nExtra Edit about possible exceptions: prompt by a comment below ,I should point out that this reasoning works only when the trilinear non-holomorphic couplings induced by the mass term, schematically of the form $$ \\delta L_{soft-\\psi} \\propto m^{ij} y{ikl} \\phi^_j \\phi_l \\phi_k+h.c., $$ involves no gauge singlets. I think that <PERSON> and <PERSON> (as well as most of textbooks on susy) assume this is the case , so that such a term is just another soft term which doesn't worsen the UV behavior. When instead gauge singlets are around, such a trilinear may generate quadratic divergences (I think from generating tadpoles).", "298" ], [ "Dilaton is the generic name of the Goldstone Boson (GB) associated with spontaneous breaking of scale invariance. Any model that break scale invariance spontaneously will give rise to a dilaton. N=4 SYM for example has a moduli space and any modulus away form the origin will break conformal invariance, and a massless dilaton would appear. The Radion is just the 5D holographic realization of a 4D CFT that break conformal symmetry spontaneously.\nAs for any GB, the dilaton $\\sigma(x)$ provides a non- linear realization of scale invariance $x\\rightarrow x^\\prime=x/\\lambda$, $$ \\sigma(x)\\rightarrow \\sigma^\\prime(x)= \\sigma(\\lambda x)+\\log\\lambda $$ where the effective lagrangian reads\n$$ L=\\frac{f^2}{2}(\\partial\\chi)^2- k f^4\\chi^4+\\frac{(\\partial\\chi)^4}{\\chi^4}+\\ldots $$ with $f$ is the analog of the pion decay constant and $\\chi$ is just shorthand for $\\chi=e^{\\sigma}$. Since $\\chi$ transforms as a field with dimension $\\Delta=1$, $$ \\chi(x)\\rightarrow \\lambda\\, \\chi(\\lambda x) $$ the action $\\int d^4 x L$ is left invariant under the scale transformation. In practice, any term with dimension 4 in the lagrangian must be written down. The only difference wrt to an ordinary GB is that the symmetry is a spacetime symmetry so that acts also on $x$. Analogous expressions hold for the full conformal group tang simply forbids certain operators that are allowed by scale invariance only. Notice that a pure quartic potential is allowed in principle (although it would require a curved space for consistently be non-vanishing\\ldots)\nLet's move now to the radion that arise in extra dimensional theory. To show that it is just a special realization of a dilaton from extra dimensions, we derive its effective action and matches to the one for the dilaton. Let's take the <PERSON> model that is a slice of 5D AdS space\n$$ ds^2=\\frac{L^2}{z^2}\\left(dx^2_4-dz^2\\right) $$ between an UV brane and an IR brane at $x=z_{UV}$ and $z_{IR}$ respectively.", "364" ], [ "$L$ is the AdS curvature. Of course, one of the isometries of AdS is $$ x\\rightarrow x/\\lambda\\,,\\qquad z\\rightarrow z/\\lambda $$ which is broken softly e.g. by the IR brane that gets moved $z_{IR}\\rightarrow z_{IR}/\\lambda$. There are various ways to get the effective action for the radion. One possibility would be looking at the metric perturbations and disentangle the spin-2 (graviton) from the spin-0 (radion) since both have zero modes. But, actually, a faster and more intuitive way comes from remembering that the radion is supposed to give the size of the extraD. In fact, it is clear that $z^{-1}{IR}$ that breaks the scale isometry has to be identified with the vev of $\\chi$. We can thus integrating out the bulk of the extra dimension but letting the IR brane free to move and bend, so that you end with a 4D effective action for $z{IR}$ $$ L=-\\frac{1}{M_^3}\\int_{z_{IR}}^{z_{UV}} dz \\sqrt{|g|} R+\\mbox{boundary terms} $$ where the boundary terms contain the localized actions on the branes and the <PERSON>-hawking term. The resulting action is exactly the one for a dilaton up to identifying $\\chi\\sim z^{-1}{IR}$. For example, the bulk and the boundary terms give rise to an exact quartic potential (after using the bulk eom's that link the 5D cc $\\Lambda _5$ to the 5D curvature $L$, and the 5D Planck mass $M$) $$ V=k z_{IR}^{-4}\\qquad k\\propto\\Lambda_{5}L-V_{IR} $$ that is indeed the only non trivial potential that a scale invariant theory can admit. If the 4D space is actually flat then it results $k=0$ by consistently tuning the bulk cosmological constant $\\Lambda_5$ and the localized IR potential to be the same.", "649" ], [ "Electroweak interaction: From $W^{1}_{\\mu},W^{2}_{\\mu},W^{3}_{\\mu},B_{\\mu}$ to $W^{\\pm},Z_{\\mu},A_{\\mu}$\nEDIT: Additional question at the end\nI am trying to illuminate how the \"unphysical\" gauge bosons $W^{1}{\\mu},W^{2}{\\mu},W^{3}{\\mu},B{\\mu}$ will be the \"physical\" $W^{\\pm},Z_{\\mu},A_{\\mu}$ when diagonalizing the mass matrix. Notice that it is in Euclidean time, so we do not have to care about the Lorentz indices. Furthermore $\\sigma(x)$ is the Higgs field and $v$ is the vacuum expectation value.\nAfter the symmetry breaking $$ SU(2)_L\\times U(1)_Y \\rightarrow U(1), $$\nand inserting the vacuum expecation value, I got the following Lagrangian (just the dynamical part):\n$$ \\frac{1}{2}D_{\\mu}\\phi^{\\dagger}D_{\\mu}\\phi = \\frac{1}{2}\\partial_{\\mu}\\sigma \\partial_{\\mu} \\sigma + \\frac{(v+\\sigma)^2}{8}(g^2W^{1}{\\mu}W^{1}{\\mu} + g^2W^{2}{\\mu}W^{2}{\\mu} + (gW^{3}{\\mu} - g'B{\\mu})(gW^{3}{\\mu} - g'B{\\mu})) .", "818" ], [ "$$ $W^{\\pm}=W^{1}{\\mu}\\pm W^{2}{\\mu}$ is clear, but retrieving $Z_{\\mu}$ and $A_{\\mu}$ not. I tryied the following, since the last part of the Lagrangian can be written like:\n$$ (W^{3}{\\mu},B{\\mu}) \\begin{pmatrix}g^2 & -gg'\\-gg'& g'^{2} \\end{pmatrix} \\begin{pmatrix}W^{3}{\\mu}\\B{\\mu} \\end{pmatrix} $$ The diagonlized matrix reads $$ M_D=\\begin{pmatrix}0 & 0\\0& g^2 +g'^{2} \\end{pmatrix} $$ and does not give the right linear combinations of $Z_{\\mu}$ and $A_{\\mu}$, which are given in my literature as $$ A_{\\mu} = \\frac{g'W^{3}{\\mu} + g B{\\mu}}{\\sqrt{g^2+g'^2}},\\qquad Z_{\\mu} = \\frac{gW^{3}{\\mu} - g' B{\\mu}}{\\sqrt{g^2+g'^2}} $$ My question is now, how to get these combinations, it looks like I am close, but only close. And the other question where comes the normalization conditions for the field from?\nCheers!\nEDIT:\nI finally found the linear combinations, mass eigenstates, like they are in the literature, by inserting not only the diagonlized mass matrix $M_D$, but by inserting $M = PM_DP^{-1}$ As I was looking at the covariant derivative to find out how the fields couple to the Higgs doublet I was wondering how I could possibly turn the following matrix into mass eigenstates of the gauge fields:\n$$ \\frac{i}{2}\\begin{pmatrix}gW^{3}{\\mu} + g'B{\\mu} & 0\\ 0& g W^{3}{\\mu} + g'B{\\mu}\\end{pmatrix} $$\nagain, cheers!", "818" ] ]

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[ [ "How to Personalize a Utility Knife With Acid Etching\nIntroduction: How to Personalize a Utility Knife With Acid Etching\nI've been wanting to try this for quite awhile. I thought it would be a cool way to personalize a utility knife by etching it with nose cone art from a World War II era P40 airplane.\nSupplies\nUtility Knife\nBelt Sander\nSand Paper Various Grits\nSpray Paint\nFerric Chloride\nWater\nPlastic Container\nStyrofoam\nElectrical tape\nIce Pick or equivalent\nDrill Press or Drill\nCountersink Bit\n3/16\" drill bit\nStep 1:\nI bought a two pack of the classic Stanley 99 utility knife and disassembled one of the knives. One screw and it comes apart.\nStep 2:\nNext I sanded off the Stanley logo because it would have gotten in the way of the etching. I used a belt sander for this be careful don't sand too much because the aluminum is not very thick so you can burn right through it.\nStep 3:\nNext paint both the inside and outside of the shells with black spray paint. Make sure you get good coverage because this will act as the resist to the acid bath so any exposed material will get etched by the acid.\nStep 4:\nNext I used an ice pick to scribe the image on to the front of the two shells. I drew guide lines on to the rest of the piece using a white map pencil because I want to add dots to simulate the rivets on a plan. But in reality I could have waited to draw on the guide lines as I ended up having to redraw them anyways. If you make a mistake with the drawing you can use an acrylic paint pen to touch up any areas. Just go over the area with the pen let the paint dry and correct your mistake.\nStep 5:\nOnce I was happy with the design I used some electrical tape to attach the shells to some Styrofoam make sure to leave the design clear of any tape. The Styrofoam allows you to suspend the piece upside down in the acid bath which results in a better etch. I use Ferric Chloride mixed with water in a 1:1 ratio to make my etching solution.", "74" ], [ "I keep the etching solution stored in a plastic Tupperware tub.\n*The acid will not eat through the plastic or the Styrofoam.\nStep 6:\nI left them in the acid etch for 30 minutes which was probably too long, 15 minutes would have been plenty of time. Later you can see one of the shells where the acid ate right through the aluminum. I think this was also partly due to sanding off too much material. If I do this again I will definitely try to be more careful and leave it in the etch for a shorter time.\nWhen you remove the pieces from the etching solution make sure to rinse them off thoroughly in a bucket of water. I used a 5 gallon bucket of water mixed with baking soda to neutralize the acid. Then I dried off the pieces with paper towels.\nStep 7:\nAs I mentioned earlier I wanted to simulate the look of rivets so I used a countersink bit and my drill press to make a bunch of tiny indentations. I used the guide lines as reference lines for the \"rivets\". Once I was happy with the look I used some Acetone to remove all the spray paint from the outside.\nStep 8:\nAfter removing the paint I cleaned up the finish using some 400 grit sandpaper. I was going for more of a brushed aluminum look. I also spray painted one of the razor blades red just to mimic the look of the red nose cones on P40s. There were a couple of spots near the top where the metal had thinned out so I decided to drill three 3/16\" holes to help hide the damage which I feel added to the finished knife.\nOverall I am really happy with how this turned out. The etch is pretty deep and turned out pretty good despite my poor artistic skills.\nThis was a fun and easy project and I could see how this could be personalized in tons of different ways especially for the artistically inclined.\nThanks for reading and I hope you enjoyed this Instructable.", "626" ], [ "From Firewood to Mallet Using Only Hand Tools\nIntroduction: From Firewood to Mallet Using Only Hand Tools\nI am not a hand tool guy per se but I do like a good challenge. I wanted to see if I could make a plastic mallet using only hand tools.\nSupplies\nLumber\nAxe\n5lb. Hammer\nHammer\nBench Vice\nHand Saw\nTrim Saw\nHand Plane\nRasp\nChisels\nSandpaper\nEpoxy\nCasting Resin\n2-1/2 inch PVC\n3/8 Dowel\n3/8 brass Tube\nLighter\nMarker\nHot Glue\nPacking Tape\nRazor or Utility Knife\n5 Minute Epoxy\nMold Release\nAcetone\nStep 1:\nFirst step is to split the firewood using an axe and 5lb. mini sledge hammer. This is basically like splitting firewood along the grain except you keep splitting the wood until you get a manageable piece you can work with. Its like whittling only less accurate and more crude results.\nStep 2:\nNext I have to trim the wood to length so I chuck the wood in my bench vise. I don't have an exact measurement for any of this, I'm just going by what looks and feels right. After cutting it to length I needed to rip the piece to remove the excess thickness, the blue mark shows approximately where I want to make my cut.\nStep 3:\nNow the piece is a little more manageable and taking shape. I use my chisel to remove some large piece of gnarly wood then I take my rasp and start to sort of give the piece shape. At this point I realize that I will have to follow the grain and contour of the wood in order to be able to use this piece. I have two flat-ish sides and two sides with some pretty wild curves. So I used my hand plane to flatten the two sides that are somewhat flat and then use the rasp and sandpaper to refine the curved sides.\nStep 4:\nAfter working on the handle I felt like the handle was still too thick so I chucked the piece in my bench vise and ripped it again. You can see in the second pic that the handle is about 1 by 1 inch on the top. I reworked the flat sides with the hand plane again and sanded all of the handle up to 220 grit starting with 80 grit.\nStep 5:\nIn order to attach the handle to the hammer head I needed to make a 1/2 inch peg on the top of the handle. I used a 1/2 piece of brass tube to draw a circle on the top of the handle as a reference.", "34" ], [ "Then I used a trim saw and a rasp to shape the peg. The handle is done for the moment so I set it aside to work on the hammer head.\nStep 6:\nI take a piece of 2 inch PVC pipe and measure and cutoff a 3-1/4 inch section. This will be my hammer head mold. Since my cut was not very straight I had to use a file to clean up my cut line.\nStep 7:\nNext I mark the center of the PVC pipe and using a Zippo lighter I heat up a 3/8 inch brass tube and use that to make a hole at my mark. Make sure to wear proper PPE and work in a well ventilated room as PVC fumes are toxic and you don't want to breath them in.\nStep 8:\nIn order to prepare the mold I use packing tape to seal off one end of the PVC pipe. I liberally spray the pipe and the dowel with mold release. Then I used the lighter to heat up a glue stick so that I could seal off the dowel hole. I wanted to make sure that I wouldn't have any leaks.\nStep 9:\nThis is the fun part. I mix equal parts of the casting resin in a container, this stuff has a very short working time under 2 minutes so you have to work fast. Before you start mixing make sure you have everything ready to go for the pour, you don't have time for mistakes. I mix the resin for 30 seconds and then pour slowly straight in to my mold. It hardens in 10-15 minutes, the stuff is amazing it cures really fast and hard.\nStep 10:\nOnce the resin cures its time to demold, be careful because it will be hot. Since I used mold release the dowel and the hammer head blank pop right out with no really issues. I use my razor knife to trim any flashing.\nStep 11:\nThe reason I used a 3/8 inch dowel for the mold was because I planned to use a 1/2 inch tap to thread the hole in the hammer head. Then I use a die to cut some 1/2 threads on the peg of the handle.", "254" ], [ "How to Make a Small Parts Cleaner\nIntroduction: How to Make a Small Parts Cleaner\nI am making a small batch of handscrew clamps (How to Make Handscrew Clamps) and decided to make all the hardware myself out of brass. There are about 40 barrel nuts that I made, they all had either black marker on them or blue marking fluid on them. I used some Acetone in a small metal cup to clean off the marker and marking fluid which worked but the next day the Acetone was completely evaporated. I knew that I needed to have a dedicated container for cleaning up small hardware but didn't have a good way to fish out the small barrel nuts from the bottom of a jar. So I made a small brass basket that can fit inside and be stored inside a glass jar.\nSupplies\nGlass jar\n4x4 inch brass plate\n1/8 inch brass rod\nMarking fluid\nMarking Calipers\nRuler\n1/8 inch drill bit\n3/16 inch drill bit\nPortable band saw table\nBelt Sander\nBlow Torch\nSolder\nSoldering Flux\nBench Vice\nHammer\nStep 1:\nI used some marking fluid to cover the entire brass plate then using my ruler I found the center and used my spring center punch to make a mark. If you don't have a center punch you can use a nail and hammer to make the center mark.\nStep 2:\nNext I measured the mouth of the jar using some calipers and divided that by half, I switched from fractions to millimeters because the math is a lot easier to do. I set my spring divider to the correct distance and marked a circle on the brass plate. This circle represents the opening of the jar minus a millimeter. This allows for the finished basket to have some room on either side of the mouth of the jar.\nStep 3:\nAgain using my ruler I marked out a grid pattern, in this case the grid is 10mm x 10mm it doesn't have to be perfect you just want something that resembles even spacing.\nI also used my drill and a 3/16 inch drill bit to drill the center hole. This hole will be for the handle in a later step.\nStep 4:\nNext I took the brass plate over to the drill press and using a 1/8 inch drill bit drilled all the drain holes.\nStep 5:\nThe basket was going to need walls to hold the small hardware so again using my spring dividers I drew a larger circumference circle on the brass plate.", "582" ], [ "I made the circle as large as I could given the material I was working with.\nI also used my ruler as a straight edge and marked several angled lines coming out from the edge of the smaller circle to the edge of the outside circle. These will be cut lines and will make more sense in a later step.\nStep 6:\nI took my brass plate over to my portable bandsaw table and removed most of the excess. I got as close to the larger diameter circle cut line as I could then I used my belt sander to sand up to the line of the outer circle.\nStep 7:\nThen I went back to the portable bandsaw table and cut each of the angle lines up to the line of the smaller circle. I actually made the cuts just to the inside of the smaller diameter circle. Next I bent up all the segments one by one and used the horn of my vice to curve each segment.\nWhen I finished hammering and shaping the basket was too large and wouldn't fit in to the mouth of the jar so I unfolded all the segments.\nStep 8:\nI took it back to the portable band saw table and removed small pie shaped sections out of all the segments and then folded it back up in to a basket. Again I used my hammer and vice to shape the segmented wall, this time it fit. I also sanded smooth the cut edges on all the segments.\nStep 9:\nI cut a 3-3/4 inch piece a 3/16 inch brass rod to use as the handle. I hammered one end of the brass rod to expand, sort of like a rivet, it so that when it is inserted in to the basket it will not slide out.\nStep 10:\nIn order to solder the handle I added some flux to the brass rod then I placed the basket upside down on my bench vice with the brass rod handle hanging down. I then heated the parts with my torch and when the flux began to bubble I touched the soldering wire to the brass which melted and joined the two pieces.\nI made sure to let it cool before touching it.\nStep 11:\nI have a small collection of decorative brass odds and ends. I wanted to use a piece as the topper for the handle just to make it a little nicer and easier to grab hold of.", "972" ], [ "How to Make a Cheap Spotlight With Telescoping Stand From a Curtain Rod\nIntroduction: How to Make a Cheap Spotlight With Telescoping Stand From a Curtain Rod\nI made this spotlight so that I could make my YouTube videos using a single light source. When I film I like to isolate the subject as much as I can so that the viewer has no choice but to focus on what is in frame. When I first started making YouTube videos I would just film in my garage with the garage lights on which was fine but you could see all the miscellaneous items in the background. I felt this was distracting so I started trying to film with just one light source. This worked okay but there was still a lot of light bleed in the background. The miscellaneous junk in the background could still be seen just in dimmer light. So I came up with this idea to make a spot light that could be moved around that wouldn't take up a large foot print like a tripod. This is a fairly inexpensive build since I used an old curtain rod that I had in my attic and the rest of the materials aren't very expensive.\nSupplies\nRound Curtain Rod\n3 inch screws\nDrill w/drill bits and drivers\n1/4\"-20 Tap and Drill\n1/4\"-20 Screw with Knob\n1/2\" screws\nScrap Wood 12\"x12\"\n5 gallon Bucket\n9 quart Bucket\nGarden Trowel\n1 60lb. Bag Cement\nSpring Clamps\nLevel\nGloves\nClamped Work Light\nVise\nWork Bench\nHammer\nAluminum Flashing\nBlue Tape\nBlack Spray Paint\nYellow Spray Paint\nSharpie Marker\nRuler or Straight Edge\nPliers\nLight Bulb\nPPE\nStep 1:\nFor the stand I used an old curtain rod that I had in my attic that could be expanded in length, one rod fits inside of the other making adjustable by sliding it in and out. I first drilled several pilot holes in the bottom of the largest of the two rods we will call this the \"lower rod\" of the stand. Then I partially screwed in the screws. These are just randomly spaced around the bottom these will help the cement attach securely to the rod. Basically you want to create something for the cement to grab on too. The screw length isn't super important as long as its at least an inch long. Screw type doesn't matter either as you can see in the last pic there are a couple of types of screws that I used for this part.\nStep 2:\nOn the same lower I drilled and tapped a 1/4\"-20 hole. This will be for the adjustment knob. This did eventually fail after a lot of usage.", "582" ], [ "The thin wall of the curtain rod just isn't strong enough to take repeated use. Eventually I ended up welding a small 1/4\"-20 nut over the hole that could take the abuse. If you don't have a welder you can probably get away with using some 2 part Metal Epoxy like JB Weld to secure a nut to the rod. I also bought a better knob as the small one I had originally used was difficult to tighten due to its small size, I couldn't get much leverage resulting in loose rods, this actual knob works much better.\nStep 3:\nIn order for the rod to sit straight up and down I took a piece of 1/4\" scrap plywood and drilled a hole the same diameter as the rod. This scrap piece will help make sure the rod sits vertically while the cement dries this will make more sense in a later step.\nStep 4:\nNext I mixed up some cement in a 5 gallon bucket and filled the 9 quart bucket with the lower rod held in place.\nStep 5:\nNext I slid my scrap piece of plywood over the lower rod and let it sit on the top of the 9 qt. bucket. I checked it for square with my level and used some spring clamps to secure the plywood in place. This took a little bit of adjustment but eventually I was able to get it pretty close to vertical. I let cement cure overnight.\nStep 6:\nOn the smaller rod, the upper rod, I taped off a 3-4 inch section and painted it yellow. This will serve as a height indicator of sorts. When I am raising the upper rod and see the yellow part I will know to stop so that I don't pull the upper rod completely out of the lower rod. Its basically my max height adjustment indicator.\nStep 7:\nThe first pic shows my setup. In the second and third pics you can see the up and down adjustment of the stand. The stand worked great and was easy to adjust. The bucket was not very large so it didn't take up a large footprint and couldn't be kicked over by accident either. Overall I was happy with the stand. The light on the other hand was a whole other story.", "220" ], [ "Wands Made With Epoxy Resin - No Lathe\nIntroduction: Wands Made With Epoxy Resin - No Lathe\nThis project was inspired by <PERSON> who made a hidden forest wand on his YouTube channel. I thought it would be neat to try and make something similar but instead of making the resin clear I wanted to add some color. I was hoping that it would almost look like the wands were glowing with power. I don't know if I achieved that specific effect but I am happy with how they turned out.\nSupplies\n3/4\" x 3/4\" x 14\" wood\nBench\nVise attached to Bench\n3lb. Hammer\n1\" x 30\" belt sander\nParchment Paper\nDuck Tape\nEpoxy Resin\nC clamp or Hand Screw Wood Clamp\nPigment Powder\nDisposable Mixing cup and Stir Stick\nRazor Blade\nSand Paper Various Grits up to 600\nSmall Round File\nClear Acrylic Spray Paint\nStep 1:\nI looked through my scrap pile and found some walnut that was 3/4 x 3/4 inches square. The pieces was about 12 inches long. You don't need a long piece of scrap a short 6 inch piece will work just as well.\nStep 2:\nI was originally going to try and replicate the \"hidden\" forest look. When going for this look you want to break the wood so that it has a lot of interesting edges at the point of fracturing. So I chucked my scrap walnut in my bench vise and gave it a good whack with a 3lb. hammer. This took a couple of good whacks until it snapped. The only real thing to consider here is to make sure you tighten the vice really well and you also make sure that the broken piece is at least 3-4 inches long so make sure to mount it in the vise with enough wood protruding out of the bottom of the vise so you end up with a long enough piece. A longer piece will work as well but I think 3 inches is as small as you want to go.\n*A note about the hidden forest look, I didn't end up going for this look in the end because I realized that if I used clear epoxy I would end up with a lot of bubbles since I didn't have a pressure pot at the time. The cracked wood still works though because it allows for better adhesion to the epoxy resin.\nStep 3:\nWith pieces broken I used my 1x30 belt sander to round over the edges as best I could. To get a decent result I just keep turning the wood as I apply pressure to the sander. Eventually all the edges are smoothed out and the handle starts to take shape.", "981" ], [ "It is far from a perfect cylinder but that doesn't really matter. There is more sanding to come.\nStep 4:\nNext I cut some strips of parchment paper that are wide enough to create a cylinder all the way around the walnut handle. I used clear tape to seal off the edge of the parchment paper. Nothing really sticks to parchment paper so here you are really just creating a seal by wrapping the clear tape around it self several times making sure to overlap. You want to make sure you wrap the tape around multiple times to prevent any leaks. Basically here you are creating the mold for the epoxy. You can make it as long or as short as you like, I think I made mine about 10 inches long so with the wood handle I will end up with a wand that is 12-13 inches long. Remember to leave some room for waste on both the wood side and epoxy side.\nStep 5:\nSo this part is a little tricky but it can be done. I used a piece of 3/4\" electrical conduit that had lying around, you can use a wood dowel or a piece of PVC, as the form for my parchment paper mold. I slip the conduit in to the parchment paper cylinder then I use some duct tape to seal the seam running length wise on the parchment paper. I then turn the piece over and apply another strip of duct tape to the opposite side completely encasing the parchment paper cylinder mold in duct tape. With the conduit still in place reinforcing the shape I make sure to squeeze the duct tape all around to get good adhesion. For extra security you can apply more pieces of duct tape and make sure to extend the tap all the way down to the wood, this will also help prevent leaks. Once I am happy with the duct tape application I remove the electrical conduit.\nStep 6:\nNow its time for epoxy! I use a clamp to hold the wand up vertically. I mix my epoxy per the instructions and I add some blue metallic powdered pigment. I don't know how much to mix so I just guess. This epoxy has a decent working time so if I under estimate I can just quickly mix some more.", "254" ], [ "TARS Robot From Interstellar - Steel Action Figure - No Welding\nIntroduction: TARS Robot From Interstellar - Steel Action Figure - No Welding\nMy favorite character from Interstellar, TARS the surplus military ex-Marine robot. Initially I thought it was the dumbest design for a 'military' robot that I had ever seen on a movie screen. Then the voice actor started to win me over, his sarcastic comic relief was quite charming, it was strange how much humanity he was able to convey. Then they show what the robot is capable of and all of its various configurations which really caught me by surprise, I loved it! After the movie I took a semi deep-dive in to all things TARS, I assumed the majority of it was CGI but learned that there were a ton of practical effects for the movie. Scenes I thought were 100% CGI where in fact a mix of both. My hats off to the amazing prop builders it is a great piece and a wonderful character. Also, huge shout out to <PERSON> who was the puppeteer for TARS; I've always been a big fan of his ever since I first saw him on Sesame Street.\nSupplies\n1/2-inch Square Steel Tube\n3/8-inch Solid Square Steel Bar\n1/8-inch Steel Rod\n1/8\" x 3/8\" x 5/32\" Sealed Z2 Lever Bearings\nHacksaw or Portable Bandsaw\nRuler\nFine Point Sharpie Marker\nGold Paint Marker - Fine Tip\nBlack Spray Paint\n1x30 Belt Sander or Files\n4x36 Belt Sander\nSandpaper 220 grit - 2000 grit\nBlue Dykem\nCenter Punch\nHammer\nCalipers\nDrill Press\nDrill Bits ranging from 1/8 inch to 3/8 inch\nBlue Tape\nExacto Knife\nSuper Glue\nAcetone\nPaper Towels\nStep 1:\nI decided that TARS should be about 4 inches tall, it seemed to look the most proportional considering that I was using 1/2-inch square tube to make the pieces. I used my portable bandsaw table to cut the pieces. You could use a hacksaw and a clamp or bench vice but it will just take longer.\nStep 2:\nAll the cut pieces were not the exact same length so I used my 1x30 belt sander to sand them to the correct length. First, I found the shortest of the pieces and then sanded the rest to match that one. I would just sand a little at a time until I got to the right length.", "215" ], [ "This also cleaned up all the cut edges.\nStep 3:\nNext, I took the pieces over to my 4x36 inch belt sander and sanded all the sides smooth to 120 grit. This step could be done my hand sanding as well.\nStep 4:\nI needed to drill holes for the bearings so I used some layout fluid and marked the centers of all the pieces. I used a center punch and hammer to mark the drilling point on each piece.\nStep 5:\nThe final hole has to be 3/8 inch in diameter in order to fit the bearings. My drill press could probably drill a 3/8 hole through the steel but I decided to start by first drilling a 1/8' hole and then stepping up the drill sizes, drilling slightly larger holes until I got to the 3/8 inch drill bit. I figured this would give me a more accurate and cleaner hole.\nRemember that the two outer pieces of TARS only get one hole in one wall and the two center pieces get drilled all the way through from one side to the other.\nStep 6:\nThe square tubes have a slight lip (its a weld seam I believe) on the inside that will interfere with the next operation of the build so these have to be filed down. You don't have to file down the entire length of the seam, just a few millimeters will be enough. You can use a file or if you have a Dremel that will work too.\nStep 7:\nWith the inside seam filed down you can now insert your 3/8 inch steel bar in to tube. I slid it in as far as it would go, in my case about 1/2 inch. I used a fine tip Sharpie to mark the square bar.\nStep 8:\nI took the square bar over to my portable bandsaw table and cut off the small piece. After it cooled, I checked the fit inside the square tube. It sat just proud of being flush which was perfect because I could use my hammer to hammer it in to place getting a nice and secure friction fit.\nStep 9:\nNext, I took the capped off square tube and sand it flush, this helped clean up the cut marks from the bandsaw. I repeated this process 7 more times for the remaining pieces.", "599" ], [ "Modern Geometric Candle Holders\nIntroduction: Modern Geometric Candle Holders\nWood prices have nearly tripled recently. This makes it the perfect time to hunt and scavenge for free materials. The wood for these candle holders was rescued from a construction site dumpster and turned into these modern geometric candleholders. They are fun to make and very fast and easy to batch out making them a very good product to sell. Back when local craft shows were a thing before the lock down these candle holders were one of my best selling products and would sell out almost immediately.\nThis project truly embodies the spirit of Trash to Treasure as I turned wood headed for a landfill into a product that customers loved and generates profit to fund future projects and tools.\nUsing a few basic tools found in most small garage woodshops, I will show you how to build a few of these Geometric Candle Holders of your very own.\nIf you would like a copy of the template I designed I have a link to it in the video description.\nSupplies\n2 x 3 Dimensional Lumber\nPolycrylic Clear Matte\nTea Light Candles\nHot Glue\nMaking Tape\nSandpaper\n3 inch Nails\nStryofoam Sheet\nColor Spray Paint (optional)\nStep 1: Getting Started\nThe wood for this project came from two, roughly four foot sections of 2x3's I found in a construction site dumpster. I spoke with the construction crew and asked if it would be ok to take a few pieces and they gave me the go ahead. I always ask before I take any material from construction sites just to be sure it's ok.\nI started this project by printing and laminating a copy of the template I made. Laminating the template isn't required, but it does keep the template from ripping and tearing when using it multiple times. I've made hundreds of these candle holders using the same laminated template! With the template laminated I cut it out using a hobby knife.\nStep 2: Cutting the Blanks\nI marked out a line on my miter saw fence 8 inches away from the blade. Using a clamp and a scrap of wood I clamp it to my miter saw fence. This will allow me to butt up my wood to the stop block and make repeated cuts over and over again without having to measure every time.\nI cut both 2x3's into 8 inch long blanks.", "401" ], [ "I was able to get 10 blanks out of both pieces with very little wood left over.\nStep 3: Drilling the Holes\nWith the blanks cut to size I chose which face I wanted for the top. I tried to avoid any knots or major defects. Once I chose my top I lined the template up to the blank and transferred the center mark using a scratch awl. This left me with three impressions I will use at the drill press. I repeated this process until all of the blanks had marks on the tops.\nWith a 1 and 5/8ths inch forstner bit chucked up in my drill press I lined up the center of the bit with the marks I made and drilled three holes into each candle holder blank.\n**Pro Tip**\nSave those wood shavings! You can make so many cool things with them, like the Water Resistant Fire Starters I showed you how to make in a previous Instructable found here\nhttps://www.instructables.com/Cheap-Water-Resistant-Fire-Starters/\nStep 4: Creating the Facets\nI set my miter saw fence to random degrees and cut the ends of the blanks into random angles. I switched the angle every two or so cuts as I wanted a lot of variation between the candle holders. To further randomize the angles I also tilted the blade to random angles. This process leaves the candle holders with really nice randomized facets on the ends.\nStep 5: Cutting Randomized Side Profiles\nUsing the cut off scraps from the miter saw, I attached them to the bottom of the candle holders using masking tape. This will give me a random side profile when I run them through the bandsaw. When cutting the sides on the bandsaw, I kept constant downward pressure on the middle of the piece so that it wouldn't pivot under the pressure from the blade.\nAfter cutting one side I removed the cut offs, mixed them up, reattached them to the candle holders, and cut the other side.\nAlternatively you could tilt the table on your bandsaw, but I like how random the cuts turn out using the cut off method.\nStep 6: Sand the Pieces Smooth\nI use my belt sander to remove all of the band saw marks and sand the pieces smooth. To sand the faceted ends I used the disc sander attached to my belt sander and adjusted the angle to match the angle of the facet.", "599" ], [ "How to Make a Utah Monolith Christmas Ornament\nIntroduction: How to Make a Utah Monolith Christmas Ornament\nIts been a couple of weeks since the discovery of the Utah Monolith and as the weeks go by new structures are being discovered around the world. While I don't have any theories as to what or why they are appearing, I assume its for Arts sake, everywhere I do find it very interesting. So to commemorate the moment I decided to make a Utah Monolith Christmas Ornament.\nStep 1:\nThe Utah Monolith is said to be about 10 feet tall and 23 inches wide. I have not been able to get 100% confirmation as to its actual dimensions so I am going to make my version 10 cm by 20 cm. I am using some 1/8 inch plywood to make the base structure. I first measure 10 cm and make a line on all three pieces of the plywood.\nStep 2:\nI make the cut using my portable bandsaw table (Portable Bandsaw Table).\nStep 3:\nNext I make a mark at 20 cm on all 3 pieces length wise. Then I cut each section using my portable bandsaw.\nStep 4:\nI tried to setup a 60 degree guide on the table of my belt sander but to be honest this didn't really work so great. Lining up the wood to try and sand a 60 degree angled miter was a little difficult. Instead I got to what looked close and then checked the fit with the other pieces until I got close to having an equilateral triangle.\nStep 5:\nI used super glue and blue painters tape along the seams to glue up the triangle.", "599" ], [ "The painters tape acts as a clamp to keep the pieces tight together while the glue dries.\nStep 6:\nAfter the glue dried I used the hard edge of a punch to compress the corners then I further cleaned up the edges by lightly sanding them on the belt sander.\nStep 7:\nI used some aluminum flashing that I would use to wrap the wooden base in. Its pretty thin and can be easily cut with a pair of scissors.\nStep 8:\nNext I folded the aluminum flashing around the wooden base I used a paper napkin to protect the finish on the aluminum. I used my belt sander to remove any excess from the top and bottom of the piece making sure to leave it flush with the wood.\nStep 9:\nAfter sanding it flush I used super glue on all sides of the wooden base to glue it to the aluminum flashing. I made sure to apply pressure across the entire piece to get good contact between the two surfaces. Once the glue dried I used the shaft of my punch to compress the one open seam to try and close it up.\nStep 10:\nFor the top and bottom caps I traced the outline on to a piece of aluminum flashing and used the scissors to cut out the triangular shapes then I used super glue to attach them to the top and bottom. I just applied pressure with my fingers while the glue dried.\nStep 11:\nOnce the glue dried I used my utility knife to cut the excess flashing. You will have to make several passes to cut through the aluminum flashing. Using the utility knife is the best way to get a flush cut. Next I used a 1/16 inch drill bit to make a hole in the top of the Monolith, or Minilith in this case, and then used a traditional hook from an ornament to hang it in the tree. The final piece is pretty light so just fishing the hook through the hole is good enough, the hook is plenty strong to hold the weight of the ornament.\nStep 12:\nAnd finally the hardest part was finding a spot for it on our tree as its pretty full but I managed to find a nice branch to hang it from.\nThis was a quick and fun project that I hope at the very least you all found entertaining and or even amusing.", "599" ] ]

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[ [ "Keras Error: An operation has `None` for gradient\nLets assume, that you want to build a GAN in keras. The generator transforms an image from domain A to domain B. Normally the image B is now passed into a discriminator, to get a feedback for the generator for example like : (yeah your generated image B (lets call it B`) is nearly as good as the real B).\nLets assume that we want to distinguish spartial information because domain A and B are just too different there, and the discriminator can easy find patterns in this spartial domain.", "338" ], [ "So he should just use Histogramm data (HSV, or texture information like LBP) to differ between B and B´.\nThe problem now is, that you have to use custom-keras-layers to transform the B´ images from RGB to HSV, and extract texture like LBP, before passing the images into the discriminator. This custom layer has no weigths obviously because its basicly only counting and reshaping (besides the HSV-transformation).\nBut Keras has its problems with layers without weigths, after using the generator. Somehow the graph cannot be build correctly, and some gradients cant be found. Any ideas why, and how i could fix this error ?\nCustom layer\nfrom keras import backend as K\nfrom keras.layers import Layer\nclass Identity_Loss(Layer):\ndef call(self, x):\nassert isinstance(x, list)\ninput_1,input_2=x\n# Transform BGR to RGB and than to HSV\nchannels = tf.unstack (input_1, axis=-1)\nRGB = tf.stack ([channels[2], channels[1], channels[0]], axis=-1)\nRGB=tf.cast(tf.multiply(tf.truediv(tf.add(RGB,1.0),2.0),255.0),dtype=tf.int32)\nRGB=tf.cast(RGB,dtype=tf.float32)\nHSV=tf.image.rgb_to_hsv(RGB,name=None)\n############################################################\nSV=HSV[:,:,:,1:]\n############################################################\n# make mask binary and multiply with image\ny=tf.math.greater(input_2, 0)\ny=tf.cast(y, tf.float32, name=None)\nHSV_mask = tf.math.multiply(HSV, y)\n######## Count color occurences ###########################\nshape=tf.shape(HSV_mask)\nlength=shape[1]*shape[2]\n# transform\nHue=HSV_mask[:,:,:,:1]\nHue=tf.cast(tf.multiply(Hue,255.0),dtype=tf.int32)\nHue2 = tf.reshape(Hue, [length])\n# prevent that the shape changes\nfiller=tf.range(0,length, 1,dtype=tf.int32)\nfiller = tf.reshape(filler, [length])\nHue3 = tf.stack([Hue2,filler],axis=-1)\nHue3 = tf.reshape(Hue3, [2*length])\n## Count Hue\ny1, idx1, count1 = tf.unique_with_counts(Hue3)\nmaximum=tf.cast(tf.math.reduce_max(count1[1:257]),dtype=tf.int32)\ndiff=tf.reshape(count1[1:257],(16,16))\ndiff=tf.expand_dims(diff, axis=-1)\ndiff=tf.expand_dims(diff, axis=0)\ndiff=tf.truediv(diff,maximum)\ndiff=tf.cast(diff,dtype=tf.", "338" ], [ "Losses of keras CNN model is not decreasing\nI am working on Street view house numbers dataset using CNN in Keras on tensorflow backend. I have queries regarding why loss of network is not decreasing, I have doubt whether I am using correct loss function or not. First I preprocess dataset so my train and test dataset shapes are:\n('Training set and labels', (26721,32,32,1), (26721, 6) )\n('Validation set and labels ', (6680,32,32,1), (6680,6) )\n('Test set and labels', (13068,32,32,1), (13068,6) )\nReason why labels array has 6 columns, because maximum digits in one image is 6.", "338" ], [ "For suppose, if image has 2 digits \"1 and 2\", then labels array is considered as [1,2,10,10,10,10] , where 10 represents no digits.\nNow this is my model definition:\ndef modelCNN(input_shape, num_classes):\nmodel = Sequential()\nmodel.add(Convolution2D(16, 7, 4, border_mode='same',\ninput_shape=input_shape))\nmodel.add(PReLU())\nmodel.add(MaxPooling2D(pool_size=(3, 3), strides=(2, 2), border_mode='same'))\nmodel.add(BatchNormalization())\nmodel.add(Convolution2D(32, 5, 3, border_mode='same'))\nmodel.add(PReLU())\nmodel.add(MaxPooling2D(pool_size=(3, 3), strides=(2, 2), border_mode='same'))\nmodel.add(BatchNormalization())\nmodel.add(Convolution2D(64, 3, 3, border_mode='same'))\nmodel.add(PReLU())\nmodel.add(MaxPooling2D(pool_size=(2, 2), strides=(2, 2), border_mode='same'))\nmodel.add(Flatten())\nmodel.add(Dense(512))\nmodel.add(PReLU())\nmodel.add(Dropout(0.5))\nmodel.add(Dense(num_classes))\nmodel.add(Activation('softmax'))\nreturn model\nI tried with different customs model, but nothing seems working. I do compilation, loss and optimization like this:\nmodel.compile(optimizer='adam', loss='categorical_crossentropy',\nmetrics=['accuracy'])\nprint(model.summary())\ncsv_logger = CSVLogger('training.log')\nearly_stop = EarlyStopping('val_acc', patience=200, verbose=1)\nmodel_checkpoint = ModelCheckpoint(model_save_path,\n'val_acc', verbose=0,\nsave_best_only=True)\nmodel_callbacks = [early_stop, model_checkpoint, csv_logger]\nK.get_session().run(tf.global_variables_initializer())\nmodel.fit_generator(train,\nsamples_per_epoch=np.ceil(len(train_dataset)/batch_size),\nepochs=num_epochs,\nverbose=1,\nvalidation_data=valid,\nvalidation_steps=batch_size,\ncallbacks=model_callbacks)\nNow, What I think that categorical_crossentropy loss needs one hot vector representation, but I am not sure how should i convert my labels array. Because unlike Mnist dataset, I have multiple labels in each image.\nIs there any loss function that I can use? or Any suggestion to make things work?\nNote: I am using CNN just for classification only, not for detection.\nThanks very much in advance", "422" ], [ "CNN for classification giving extreme result probabilities\nI'm having issues with my CNN, using Keras with Theano backend. Basically, I need to classify 340x340 grayscale images into 6 categories. The problem is my CNN gives too \"hard\" probabilities, for instance it will rarely give predictions with some uncertainty, and always tries to push for a 90%+ for one class. The problem is that for my coursework, the penalty used is very harsh for complete miss classification, and uncertainty is much preferred.", "458" ], [ "( so having a prediction like [0.6, 0.3, 0.2, ...] is much better than having [0.9,0.03,0.02,..].\nI'm unsure why this is happening. My dataset consists of 2400 images, which are from different CCTV, and task is about recognising possible objects. Only 800 of the samples are actually from the data, the other 1600 have been generated through data augmentation. Note that it is therefore extremely likely a that some pictures are either identical, or extremely similar (e.g. the same scene, one second later)\nmodel = Sequential()\n#1\n# Few filter to take big stuff out\n# Also, first layer is not conv so that I can reuse that layer separately\nmodel.add(Dropout(0.1, input_shape=(1,340,340)))\nmodel.add(Convolution2D(64, 4, 4, border_mode='same'))\nmodel.add(Activation('relu'))\nmodel.add(MaxPooling2D(pool_size=(2, 2), dim_ordering=\"th\"))\n#2\nmodel.add(Dropout(0.1))\nmodel.add(Convolution2D(128, 4, 4, border_mode='same'))\nmodel.add(Activation('relu'))\nmodel.add(MaxPooling2D(pool_size=(2, 2), dim_ordering=\"th\"))\n#3\nmodel.add(Dropout(0.1))\nmodel.add(Convolution2D(256, 4, 4, border_mode='same'))\nmodel.add(Activation('relu'))\nmodel.add(MaxPooling2D(pool_size=(2, 2), dim_ordering=\"th\"))\n#4\nmodel.add(Flatten())\nmodel.add(Dense(1024))\nmodel.add(Activation('relu'))\n#5\nmodel.add(Dense(512))\nmodel.add(Activation('relu'))\n#6\nmodel.add(Dense(6))\nmodel.add(Activation('softmax'))\nopt = SGD(lr=0.001)\nmodel.compile(loss='categorical_crossentropy', optimizer=opt, metrics=['accuracy'])\nprint \"Training..\"\nfilepath = \"log/weights-improvement-{epoch:02d}---{val_acc:.2f}.hdf5\"\ncheckpoint = ModelCheckpoint(filepath, monitor='val_acc', verbose=1, save_best_only=True, mode='max')\ncallbacks_list = [checkpoint]\nmodel.fit(X_t, y_t, validation_split=0.1, nb_epoch=500, batch_size=32, callbacks=callbacks_list)\nHow do you suggest I fix this? Thank you in advance!", "338" ], [ "Keras - Autoencoder different from Encoder + Decoder\nI build a CNN 1d Autoencoder in Keras, following the advice in this SO question, where Encoder and Decoder are separated. My goal is to re-use the decoder, once the Autoencoder has been trained.", "458" ], [ "The central layer of my Autoencoder is a Dense layer, because I would like to learn it afterwards.\nMy problem is that if I compile and fit the whole Autoencoder, written as Decoder()Encoder()(x) where x is the input, I get a different prediction when I do\nautoencoder.predict(training_set)\nw.r.t. if I first encode the training set in a set of central features, and then let the decoder decode them. These two approaches should give identical answers, once the Autoencoder has been trained.\nfrom tensorflow.keras.layers import Input, Dense, BatchNormalization, Flatten, Lambda, Activation, Conv1D, MaxPooling1D, UpSampling1D, Reshape\nfrom tensorflow.keras.models import Model\nfrom tensorflow.keras import optimizers\nfrom tensorflow.keras.layers import GaussianNoise\nimport keras.backend as K\nfrom tensorflow.keras.layers import Add\nimport tensorflow as tf\nimport scipy.io\nimport sys\nimport matplotlib.pyplot as plt\nimport numpy as np\nimport copy\ntraining = # some training set, 1500 samples of 501 point each\ntesting = # some testing set, 500 samples of 501 point each\n# reshaping for CNN\ntraining = np.reshape(training, [1500, 501, 1])\ntesting = np.reshape(testing, [500, 501, 1])\n# normalize input\nX_mean = training.mean()\noscillations -= X_mean\nX_std = training.std()\ntraining /= X_std\ncopy_of_test = copy.copy(testing)\ntesting -= X_mean\ntesting /= X_std\n### MODEL ###\ndef Encoder():\nencoder_input = Input(batch_shape=(None, 501, 1))\ne1 = Conv1D(256,3, activation='tanh', padding='valid')(encoder_input)\ne2 = MaxPooling1D(2)(e1)\ne3 = Conv1D(32,3, activation='tanh', padding='valid')(e2)\ne4 = MaxPooling1D(2)(e3)\ne5 = Flatten()(e4)\nencoded = Dense(32,activation = 'tanh')(e5)\nreturn Model(encoder_input, encoded)\ndef Decoder():\nencoded_input = Input(shape=(32,))\nencoded_reshaped = Reshape((32,1))(encoded_input)\nd1 = Conv1D(32, 3, activation='tanh', padding='valid', name='decod_conv1d_1')(encoded_reshaped)\nd2 = UpSampling1D(2, name='decod_upsampling1d_1')(d1)\nd3 = Conv1D(256, 3, activation='tanh', padding='valid', name='decod_conv1d_2')(d2)\nd4 = UpSampling1D(2, name='decod_upsampling1d_2')(d3)\nd5 = Flatten(name='decod_flatten')(d4)\nd6 = Dense(501, name='decod_dense1')(d5)\ndecoded = Reshape((501,1), name='decod_reshape')(d6)\nreturn Model(encoded_input, decoded)\n# define input to the model:\nx = Input(batch_shape=(None, 501, 1))\ny = Input(shape=(32,))\n# make the model:\nautoencoder = Model(x, Decoder()(Encoder()(x)))\n# compile the model:\nautoencoder.compile(optimizer='adam', loss='mse')\nfor layer in autoencoder.layers: print(K.int_shape(layer.output))\nepochs = 100\nbatch_size = 100\nvalidation_split = 0.2\n# train the model\nhistory = autoencoder.", "695" ], [ "Handling dimensions for RGB data with Keras CNN\nI'm trying to make work the code from kera's documentation getting started. I'm getting there but there is something I do not understand about handling RGB data. I made one work with MNIST data (which is greyscale), but I can't seem to figure out the CIFAR10.\nHEIGHT = 200\nWIDTH = 200\ndef build_model():\ninputs = keras.Input(shape=(HEIGHT, WIDTH, 3))\n# making things simple, I don't CenterCrop, just set the input to whatever I'm feeding it\n# I do rescale to 0-1 values\nx = Rescaling(scale=1.0 / 255)(inputs)\n# this basically the doc's architecture\nx = layers.Conv2D(filters=32, kernel_size=(3, 3), activation=\"relu\", )(x)\nx = layers.MaxPooling2D(pool_size=(2, 2))(x)\nx = layers.Conv2D(filters=32, kernel_size=(3, 3), activation=\"relu\",)(x)\nx = layers.MaxPooling2D(pool_size=(2, 2))(x)\nx = layers.Conv2D(filters=32, kernel_size=(3, 3), activation=\"relu\",)(x)\nx = layers.GlobalAveragePooling2D()(x)\noutputs = layers.Dense(10, activation=\"softmax\")(x)\nmodel = keras.Model(inputs=inputs, outputs=outputs)\nreturn model\n# fake data, easier to play with shapes than with the actual CIFAR10 data to debug\n# shape is (500, 200, 200, 3), cifar10's is (60000, 32, 32, 3)\ndata = np.random.randint(0, 255, size=(500, HEIGHT, WIDTH, 3)).astype(\"float32\")\n# shape is (500,1) cifar10's is (60000,1). Just 10 categories to match the output layer\nlabels = np.random.randint(0,9, size=(500,1)).astype(\"int8\")\nprint(\"got fake data...", "856" ], [ "\")\nmodel = build_model()\nprint(\"model built... \")\nmodel.summary()\nmodel.compile(optimizer=keras.optimizers.RMSprop(learning_rate=1e-3),\nloss=keras.losses.CategoricalCrossentropy())\nprint(\"model compile...\")\nmodel.fit(data, labels)\nprint(\"done\")\nFor some reason, I get:\nValueError: Shapes (None, 1) and (None, 10) are incompatible\nStrangely, if change the label's fake data to size=(500, 10) then it \"works\". But obviously that makes no sense, since it would mean I have 10 labels for each sample. The MNIST dataset that works which I refer to can also be found in the linked documentation. The architecture of the network is much simpler (only Dense layers linked together).\nWhat am I missing here? Why would it be so different for a colored image than it is for a greyscale?\nEDIT: I also tried the work with the data from train, test = cifar10.load_data(), but it yields the same results.", "392" ], [ "Remedies to CNN-LSTM overfitting on relatively small image dataset\nNotes\nUsing a pretrained model, trying data augmentation (not possible knowing nature of images, lowering number of parameters in the network, all didn't help)\nContext\nI have a sequence of images. Target is a multivariate continuous time series. I am trying LSTM on CNN without using a pretrained model. Training a CNN model didn't got me a satisfying results. A very sure reason is that train is only on one year.", "650" ], [ "While predicting with test images present is on several months.\nAny image augmentation is nearly impossible from nature of images, satellite images on a fixed geo-location, tracking passing clouds.\nAlong with images, I have time features, and trend, seasonality of target which is known for test set, as it can be scientifically calculated (it's about GHI, estimated by the <PERSON> and <PERSON> model).\nProblem\nThe problem is with over-fitting, tracking best model on validation set is done by early stopping.\nValidation set is a small fraction from train, .9 for train, so train set is furthermore made fewer.\nTrain is a set of 8804 images, and target variable. Timed Model layers take series of 31 sequences. For example train takes (255,31) and validation takes (29,31).\nThe model, I came up with is the following:\nlosses_weights=[[1, .4]];\nmain_input__ = Input(shape=(31, 120, 120, 1), name='main_input__')extraction\nx__ = TimeDistributed(\nConv2D(8, kernel_size=(3, 3), strides=(1, 1) , activation='relu')\n)(main_input__)\nx__ = TimeDistributed(MaxPooling2D((2, 2), strides=(2, 2)))(x__)\nx__ = (TimeDistributed(BatchNormalization()))(x__)\nx__ = TimeDistributed(Conv2D(8, (2,2), strides=(1, 1), activation='relu'))(x__)\nx__ = TimeDistributed(MaxPooling2D((2, 2), strides=(2, 2)))(x__)\n# extract features and dropout\nx__ = TimeDistributed(Flatten())(x__)\nx__ = (TimeDistributed(Dense(8, activation='relu')))(x__)\nx__ = Bidirectional(LSTM(lstm, return_sequences=True, dropout=0.3))(x__)\nlstm_out__ = Bidirectional(LSTM(lstm, return_sequences=True, dropout=0.3))(x__)\nauxiliary_output__ = Dense(8, name='aux_output')(lstm_out__)\nauxiliary_input__ = Input(shape=(31, 10), name='aux_input')\nz__ = keras.layers.concatenate([lstm_out__, auxiliary_input__])\n# We stack a deep densely-connected network on top\n# z__ = (LSTM(lstm, return_sequences=True, dropout=0.4))(z__)\nz__ = Bidirectional(LSTM(lstm, return_sequences=True, dropout=0.3))(z__)\nmain_output__ = Dense(8, name='main_output')(z__)\n################################################################################\nloss=[loss_mse_warmup, loss_mse_warmup];\n#;\nmodel__ = Model(inputs=[main_input__, auxiliary_input__], outputs=[main_output__, auxiliary_output__])\nmodel__.compile(loss=loss_mse_warmup, optimizer='adam', loss_weights=loss_weights)\nhistory__ = model__.fit(x=[x_train, aux_train],y=[y_train, y_train], epochs=100, batch_size=2, validation_split=.9, callbacks=callbacks)\nloss_mse_warmup is just a mean_squared_error that ignores 5 first training input signals.\nTries\n1. Several Batch-size lengths: [32, 16, 8, 2].\n2. loss weights ranging in [[1, .4], [1, .3], [1, .2]].\n3. Different variants of number of nodes in CNN: [8,16,32].\n4.", "695" ], [ "but what was being trained when training=True?\nLet's try to understand BatchNormalization(BN) layer first as it has more elements.\nTL;DR -\nγ, β are learned. These are initialized just like normal weights and learned in Backpropagation.\nMay read this crisp and spot-on answer on these parm Stat.SE\nFormally, BN transforms the activations at a given layer x according to the following expression:\nBN(x)= γ⊙(x−μ)/σ + β\ncoordinate-wise scaling coefficients γ and offsets β.\n[Quoted - http://d2l.ai/]\neach BN layer adds four parameters per input: γ, β, μ, and σ (for example, the first BN layer adds 3,136 parameters, which is 4 × 784). The last two parameters, μ and σ, are the moving averages; they are not affected by backpropagation, so Keras calls them “non-trainable”. However, they are estimated during training, based on the training data, so arguably they are trainable. In Keras, “non-trainable” really means “untouched by backpropagation.”\n[Quoted - Hands-on machine learning with scikit-learn keras and tensorflow, <PERSON>\ntraining=True: The layer will normalize its inputs using the mean and variance of the current batch of inputs.\ntraining=False: The layer will normalize its inputs using the mean and variance of its moving statistics, learned during training. [Quoted - Keras doc for BN]\nSo, if you will not set it False it will continue updating μ and σ with every batch of test data example and normalize the output accordingly.", "695" ], [ "We want it to use the values from the Training phase.\nBy default, it is False and fit method set it to True.\nDropout\nDropout is simpler of the two. We need this Flag here so that we can compensate(during testing) the loss to the Output value(on an average basis) due to the switched-off(during Training) Neurons.\nSuppose p = 50%, in which case during testing a neuron would be connected to twice as many input neurons as it would be (on average) during training. To compensate for this fact, we need to multiply each neuron’s input connection weights by 0.5 after training. If we don’t, each neuron will get a total input signal roughly twice as large as what the network was trained on and will be unlikely to perform well. More generally, we need to multiply each input connection weight by the keep probability (1 – p) after training. Alternatively, we can divide each neuron’s output by the keep probability during training (these alternatives are not perfectly equivalent, but they work equally well)\n[Quoted - Hands-on machine learning with scikit-learn keras and tensorflow, <PERSON>\nOn the example of Models difference\nThough, these are subjects to try and check.\nBut I believe generally we start to fine-tune when we believe that the upper layer is smoothened to match with the initial layers, to avoid a large flow in forward and backdrop. So the logic stated to keep it Flase in 2019 example might not hold too strong every time.", "740" ], [ "Prepending Input layer to pre-trained model\nI'm trying to input numpy arrays of shape (1036800,) - originally images of shape (480, 720, 3) - into a pre-trained VGG16 model to predict continuous values.\nI've tried several variations of the code below:\ninput = Input(shape=(1036800,), name='image_input')\ninitial_model = VGG16(weights='imagenet', include_top=False)\nx = Flatten()(initial_model(input).output)\nx = Dense(200, activation='relu')(x)\nx = Dense(1)(x)\nmodel = Model(inputs=input, outputs=x)\nPrevious variations of the above code yielded errors related to the input being the wrong dimensions, input_shape needing to have 3 channels (when using (1036800,) for that parameter in the initialization of VGG16), and the most recent error that results from running the above code is this:\nTraceback (most recent call last):\nFile \"model_alex.py\", line 57, in <module>\nmodel = initialize_model()\nFile \"model_alex.py\", line 20, in initialize_model\nx = Flatten()(initial_model(input).output)\nFile \"/home/aicg2/.local/lib/python2.7/site-packages/keras/engine/topology.py\", line 596, in __call__\noutput = self.call(inputs, **kwargs)\nFile \"/home/aicg2/.local/lib/python2.7/site-packages/keras/engine/topology.py\", line 2061, in call\noutput_tensors, _, _ = self.run_internal_graph(inputs, masks)\nFile \"/home/aicg2/.local/lib/python2.7/site-packages/keras/engine/topology.py\", line 2212, in run_internal_graph\noutput_tensors = _to_list(layer.call(computed_tensor, **kwargs))\nFile \"/home/aicg2/.local/lib/python2.7/site-packages/keras/layers/convolutional.py\", line 164, in call\ndilation_rate=self.dilation_rate)\nFile \"/home/aicg2/.local/lib/python2.7/site-packages/keras/backend/tensorflow_backend.py\", line 3156, in conv2d\ndata_format='NHWC')\nFile \"/usr/local/lib/python2.7/dist-packages/tensorflow/python/ops/nn_ops.py\", line 639, in convolution\ninput_channels_dim = input.get_shape()[num_spatial_dims + 1]\nFile \"/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/tensor_shape.py\", line 500, in __getitem__\nreturn self._dims[key]\nIndexError: list index out of range\nHere is the full code. Here is the sample data file used in the script.\nOne of the possible approach towards fixing this might be to resize the raw image files to 224x224 and turn them into numpy arrays of shape (224, 224, 3) so they can be plugged into the pre-trained model's first layer. However, I don't want to warp the images or waste another night pre-processing data when I should already be training.\nBesides that, I all I can think to do is Google my problem and try to adapt the found solutions or aimlessly tweak various shape related parameters and functions -- neither of which has gotten me very far over the past 4 hours.\nPlease excuse the noob question -- it's my first time using Keras and my first time attempting deep learning -- I'm a little flustered as I'm competing in a competition and the deadline is next week!", "695" ] ]

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[ [ "Gibbs sampling in R\nI have the following model:\n$y_{it}=\\alpha + x'{it}\\beta{i} + \\epsilon_{it}, \\text{ } i=1,2,...,N, \\text{ } t=1,2,...,T$ (1)\n$\\beta_{i}= z'{i}\\gamma+\\eta{i}$ (2)\nwith $\\epsilon_{it} \\sim N(0,\\sigma_{\\epsilon_{i}}^{2})$ and $\\eta_{i} \\sim N(0,\\sigma_{\\eta}^{2})$\nAlso i consider the following prior specifications:\n$p(\\beta,\\gamma) \\propto 1 \\ p(\\sigma_{\\epsilon_{i}}^{2}) \\propto \\sigma_{\\epsilon_{i}}^{-2} \\ p(\\sigma_{eta}^{2}) \\propto \\sigma_{\\eta}^{-2}$\nwhich has the following likelihood function:\n$p(Y|\\theta)=\\prod_{i=1}^{N}\\int_{\\beta_{i}} \\left( \\prod_{t=1}^{T}\\frac{1}{\\sigma_{\\epsilon_{i}}\\sqrt{2\\pi}}exp \\left( -\\frac{1}{2\\sigma_{\\epsilon_{i}}^{2}}(y_{it}-\\alpha-x'{it}\\beta{i})^{2}\\right) \\right) \\times \\frac{1}{\\sigma_{\\eta}\\sqrt{2\\pi}}exp \\left( -\\frac{1}{2{\\sigma_{\\eta}^{2}}}(\\beta_{i}-z'{i}\\gamma)^{2} \\right) d\\beta{i}$\nI would like to estimate the parameters $\\theta=(\\alpha,\\gamma,\\sigma_{\\epsilon_{i}}^{2},\\sigma_{\\eta}^{2})$. So $\\theta$ is the parameter vector. Only $\\beta_{i}$ is random. So I consider $\\beta_{i}$ as the latent variables.\nI would like to estimate these by using the following Gibbs sampling schema:\nsample $\\alpha$ given ${\\beta_{i}}{i=1}^{N},\\gamma,\\sigma{\\epsilon}^{2},\\sigma_{\\eta}^{2},Y$\nsample $\\gamma$ given ${\\beta_{i}}{i=1}^{N},\\alpha,\\sigma{\\epsilon}^{2},\\sigma_{\\eta}^{2},Y$\nsample $\\sigma_{\\epsilon}^{2}$ given ${\\beta_{i}}{i=1}^{N},\\gamma,\\alpha,\\sigma{\\eta}^{2},Y$\nsample $\\sigma_{\\eta}^{2}$ given ${\\beta_{i}}{i=1}^{N},\\gamma,\\alpha,\\sigma{\\epsilon}^{2},Y$\nsample ${\\beta_{i}}{i=1}^{N}$ given $\\gamma,\\alpha,\\sigma{\\epsilon}^{2},\\sigma_{\\eta}^{2},Y$\nI know that:\nTo sample $\\alpha$ I re-write (1) as $y_{it} - x'{it}\\beta{i}=\\alpha + \\epsilon_{it}$, so the full conditional distribution of $\\alpha$ is normal with mean $\\hat{\\alpha}=\\frac{1}{T\\times N} \\sum_{i=1}^{N}\\sum_{t=1}^{T} (y_{it} - x'{it}\\beta{i})$ and variance $\\frac{\\sigma_{\\epsilon}^{2}}{T \\times N}$.\nTo sample $\\sigma_{\\epsilon}^{2}$ I consider the regression model in (1) , hence it can be sampled from an inverted Gamma-2 distribution with parameter $ \\sum_{i=1}^{N}\\sum_{t=1}^{T} (y_{it} - \\alpha - x'{it}\\beta{i})^{2}$ with $N \\times T$ degrees of freedom.", "402" ], [ "How to create a prediction interval with the fact that the residuals follow a specific distribution (in python)\nI am looking at a software development pipeline where I am predicting the lead time of different products flowing through the pipeline.\nAfter applying a boxcox transformation on the lead time (target variable) and creating a XGBoost regressor model I can see that the residuals follow a t-locationScale distribution.\nSo now I looked at this guide which describes a method to create a prediction interval for any regression model assuming that the residuals are normally distributed. https://qucit.com/a-simple-technique-to-estimate-prediction-intervals-for-any-regression-model_en/\nBut I tried to tweak it to my distribution.\nSo a t-locationScale distribution has a $\\sigma$, $\\mu$ and $\\nu$ parameter. The variance is only defined for $\\nu>2$.", "509" ], [ "My specific distribution has $\\nu = 2.56$ and $\\mu = 0.04$, $\\sigma = 0.97$ So I could take the 95% interval of this distribution and say that for any $\\hat{y}$, the prediction interval is the 95% interval of the residual distribution.\nBut I want to take into consideration that the prediction interval should change with different inputs. I created a regressor model, which I trained and then made predictions using the validation set. I then took the square of the error and trained an additional error model on this data. Such that the error model could predict the variance of the residuals distribution.\nxgb = XGBoostRegressor()\nxgb.fit(X_train,y_train)\ny_hat = xgb.predict(X_val)\nval_error = (y_hat-y_val)**2\nxgb_error = XGBoostRegressor()\nxgb_error.fit(X_val, val_error)\nvariance_hat_residuals = xgb_error.predict(X_test)\nThe relationship between variance and $\\sigma$ and $\\nu$ for a t-locationScale distribution is\nvar = $\\sigma^2 *\\frac{\\nu}{\\nu-2}$\nNow here is where I make an assumption which I am not sure makes sense.\nI assume that the degrees of freedom $\\nu$ is the same as for all residuals, $\\nu = 2.56$ and then I solve for $\\sigma$ through the following.\n$\\hat{\\sigma} = \\sqrt{\\frac{\\hat{var}*(\\nu-2)}{\\nu}}$\nAnd estimate the lower and upper quantiles from this distribution.\nresidual_distribution_lower_quantile = scipy.stats.t.ppf(q = 0.025, df = 2.56, scale = sigma)\nresidual_distribution_upper_quantile = scipy.stats.t.ppf(q = 0.0975, df = 2.56, scale = sigma)\nI then predict the lead time $\\hat{y}$ and say that the mean of the distribution is $\\hat{y}$\npred = xgb.prediction(X_test)\nlower_interval = pred + residual_distribution_lower_quantile\nupper_interval = pred + residual_distribution_upper_quantile\nDoes it make sense to make the claim of $\\nu$ is static? My score for the prediction interval is now $81\\%$ since I am clearly simplifying the problem.\nAny suggestions for improving my method?", "509" ], [ "Yes, you are right that the term $\\frac{1}{\\pi_\\theta(a_t|s_t)}$ itself is favoring the less likely actions. But don't forget how $\\nabla \\pi_\\theta(a_t|s_t)$ is calculated, and you will see that $\\nabla \\pi_\\theta(a_t|s_t)$ is over-emphasizing on the first action and $\\frac{1}{\\pi_\\theta(a_t|s_t)}$ is correcting it.\nRecall that the derivative for y =softmax(x) is $\\frac{\\partial y_i}{\\partial x_j} = y_i(\\delta_{ij}-y_i)$.", "915" ], [ "Notice that $y_i$ is multiplied in the front, i.e. over-emphasizing the more likely $y_i$. By multiplying $\\frac{1}{y_i}$ in the front, the over-emphasizing effect is being corrected.\nIn your example, when ${\\pi_\\theta(a_t|s_t)}=[0.5, 0.1, 0.1, 0.1, 0.1, 0.1]$, we can write down that $$\\nabla \\pi_\\theta(a_t|s_t)=\\left(\\begin{array}{cccccc} 0.5\\times0.5 & -0.5\\times0.1 & -0.5\\times0.1 & -0.5\\times0.1 & -0.5\\times0.1 & -0.5\\times0.1\\ -0.5\\times0.1 & 0.1\\times0.9 & -0.1\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 \\ -0.5\\times0.1 & -0.1\\times0.1 & 0.1\\times0.9 & -0.1\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 \\ -0.5\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 & 0.1\\times0.9 &-0.1\\times0.1 & -0.1\\times0.1 \\ -0.5\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 & 0.1\\times0.9 & -0.1\\times0.1 \\ -0.5\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 & -0.1\\times0.1 & 0.1\\times0.9\\ \\end{array}\\right)$$ And by multiplying it with $\\frac{1}{\\pi_\\theta(a_t|s_t)}=[\\frac{1}{0.5},\\frac{1}{0.1},\\frac{1}{0.1},\\frac{1}{0.1},\\frac{1}{0.1},\\frac{1}{0.1}]$, you effectively get $$\\nabla \\log\\pi_\\theta(a_t|s_t)=\\frac{1}{\\pi_\\theta(a_t|s_t)}\\nabla \\pi_\\theta(a_t|s_t)= \\left(\\begin{array}{cccccc} 0.5 & -0.5, &-0.5, &-0.5, &-0.5, &-0.5, \\ -0.1 & 0.9 & -0.1 & -0.1 & -0.1 & -0.1 & \\ -0.1 & -0.1 & 0.9 & -0.1 & -0.1 & -0.1 & \\ -0.1 & -0.1 & -0.1 & 0.9 & -0.1 & -0.1 & \\ -0.1 & -0.1 & -0.1 & -0.1 & 0.9 & -0.1 & \\ -0.1 & -0.1 & -0.1 & -0.1 & -0.1 & 0.", "374" ], [ "How to curve fit an unknown function?\nI have data which can be described by $y=f(x,z)$ where $z$ varies from 170 ~ 154. Now values given by $ks$ are known sample values that equals value given in the table header, $uks$ are unknown samples. $$ \\begin{array} & z & x_{ks_{1}=0} & x_{ks_{2}=50} & x_{ks_{3} = 60} & \\cdots & x_{uks_{1}}& \\cdots & x_{uks_{n}}\\newline 170 & 3.5 & 5 & 6 &\\cdots & 5.3 & \\cdots & 12 \\newline 168 & 3.7 & 5.1 & 6.6 &\\cdots & 5.6 & \\cdots & 13.2 \\newline \\vdots & \\vdots & \\vdots & \\vdots &\\ddots & \\vdots & \\ddots & \\vdots \\newline 154 & 6.8 & 9.52 & 10 &\\cdots & 11.5 & \\cdots & 26.5 \\newline \\end{array} $$\nPlotting values of $y$ vs. $x$ for various $z$, I get this plot:\nand on a semi-log plot:\nNote the values on $y-axis$ are the values given by the subscripts of $x$ in the table headers.\nMy objective is to find the value of $y$ for the corresponding $x_{uks_{1}}, x_{uks_{2}}, \\cdots, x_{uks_{n}}$ for different $z$.There might be alternate methods, such methods are most welcome. And my approach is as follow:\n1. I try to fit a linear function of the form:\n$$y = \\frac{A_{i}}{ln[x]^{3}} + B_{i},\\quad \\text{i for each z}$$\nthis gives me plots as follows:\n1.", "1021" ], [ "Since $A_{i}$ and $B_{i}$ is different for $z$, I can fit a function. Therefore $A_{i} = f(z)$ and $B_{i} = f(z)$. For step 1, I used the following function:\n$$A = a_1 z^3 + a_2 z^2 + a_3 z + a_4$$ $$B = b_1 z^2 + b_2 z + b_3$$\n1. Using the correlation:\n$$y = \\frac{a_1 z^3 + a_2 z^2 + a_3 z + a_4}{ln[x]^{3}} + b_1 z^2 + b_2 z + b_3$$\nAnd substituting different values of $x_{uks}$ I get corresponding $y$, but when I plot them vs. $z$, I get plots of the form:\nNow, my questions are as follows:\n1. How am I getting $y$ to be a linear function of $z$?\n2. Is this approach a valid one?", "1021" ], [ "Chose the right regression analysis\nIn R I have data where head(data) gives\nday promotion profit new_users\n1 105 45662 33\n2 12 40662 13\n3 44 46800 20\n4 203 54102 46\nNow day is simply the day (and is in order). promotion is simply the promotion-value for the day, the profit is the profit that day and new_users is the number of new users that day.\nI want investigate the relationships between promotion to profit and new_users. We see a clear positive correlation between promotion and profit, and there is also a positive correlation between promotion and new_users. In R I simply test correlation\ncor.test(data$promotion, data$profit, method=\"kendall\", alternative=\"greater\" )\ncor.test(data$promotion, data$new_users, method=\"kendall\", alternative=\"greater\")\nwhich both gives a low p-value, ie we have a positive correlation.\nI want to find a point where where the increase of promotion don't increase profit or new_users that must, ie a sweet spot.\nHere is 2 plots and the R code for these\nplot(data$promotion, data$profit, col=\"brown\")\nplot(data$promotion, data$new_users)\nHow should this be done?\nMy thoughts where to make a regression model. For the first one \"promotion vs.", "650" ], [ "new_users\" one could use a poisons model because it's a count-process, so a model like this would be a good chose?\nglm(formula= data$new_users ~ data$promotion, family=\"poisson\", data=data)\nNext what regression model should one chose for the next one. Is it fair to say that this regression model is a good chose ? (I use sqrt command)\nglm(formula=data$profit ~ sqrt(data$promotion) , data=data)\nOr maybe it's not even necessary to use a regression model at all to find a sweet spot?\nThanks.\nI have now looked at 'good' new users. For each day we have a promotion value and we have a count value which is the number of new good users. This plot shows us the number of good new users we get for a promotion for each day. For example for promotion value 90 we have a day where we got 8 new good users and a day where we got 14 new good users.\nWhat would be the right approach to find a sweet spot for the use of promotion ?", "587" ], [ "Solving for $C$ in $Q = YCZ$ using least squares in Matlab\nI am trying to solve for the matrix $C$ in $Q = YCZ$ in matlab. I have preliminary results but they don't seem realistic. Here, $Q$ is $n \\times m-1$, $Y$ is $n \\times p$, $C$ is $p \\times m$ and $Z$ is $m \\times m-1$.\nThe value of $n$ is very large, say $n = 10000$. On the other hand, $m$ and $p$ are of the same order of magnitude. In the case I considered, $m=201, p =175$.\nAmong all matrices above, $Z$ is the only one with a seemingly unique structure. By eliminating the first row of $Z$, it becomes upper triangular and invertible.\nIn matlab, I tried to solve for $C$ using: $C = Y\\backslash (Q/Z)$. However, I ran into the following issues:\n1) The last column of $C$ is all zero which is unrealistic in my problem. It turns out that the last column of $Q/Z$ is also a zero vector which is probably the cause of this. Are there suggestions how to compute $Q/Z$ without having the last column being 0?\n2) If I want to find $C$ such that every row of $C$ has minimum norm, how can I modify my problem in matlab? Based on the motivation below, every row of $C$ corresponds to values of a function on the unit interval. It is highly preferable for these functions to not be highly oscillatory in contrast to what I'm seeing now.\nThanks for any suggestions on how to proceed.\nThe motivation of the problem is as follows: let $Q(x)$ be a stochastic process defined as $Q(x) = \\int_0^x P(s)\\,ds$ where $P(s)$ is another stochastic process.", "490" ], [ "Suppose that $P(s) = q_1(s)Y_1 + \\dots + q_n(s) Y_n$ where $Y_1,\\dots,Y_n$ are random variables and $q_i(s)$ are deterministic functions of $s$. It will be assumed that the domain of $P(s)$ and $Q(x)$ is the interval $[0,1]$. Suppose that I have observations of $Q(x)$ at discrete time points and that this information is stored in $Q$. Each row of this matrix is an observation while every column corresponds to a point in the spatial discretization. In addition, suppose that I have observations of $Y_1,\\dots,Y_n$ stored in a matrix $Y$ where every row is an observation and every column corresponds to $Y_i$. My interest is to estimate the deterministic functions $q_1(s),\\dots,q_n(s)$. To do this, I use a Finite element basis, i.e. example, such that $q_i(s) = \\sum_{k=1}^m c_i^k \\phi_k (s)$ where $\\phi_k$ are the basis functions and $c_i^k$ are the nodal values. The matrix $C$ is then obtained such that $C_{ik} = c_i^k$ using notation above and is the quantity of interest. The definition of $Z$ follows from the relationship $Q(x) = \\int_0^x P(s) \\,ds$.", "490" ], [ "R - Function for 10 fold crossvalidation\nI have written a function for 10 fold crossvalidation that I want to use for different models, e.g PPR, MARS. However, I get an error when running it and I cannot figure out why it does not work? My CV function:\ncv10 <- function(reg.fn, formula, dataset, ...)\n{\nset.seed(201)\n### Number of observations\nnrow <- nrow(dataset)\n### Create a permutation of the observations indices\nInd <- sample.int(nrow,nrow, replace = FALSE)\n### Compute the size of each of the 10 folds\nM <- nrow / 10 # 'fold size'\n### Initialize the score\nscore <- 0\n### The first fold will then contain the observations which correspond to..\n### ..the indices of the first M elements of Ind.\nfor(i in 1:10){\nbeg <- i*M\nend <- (i+1)*M\n### Data to train the model\ndata.train <- dataset[Ind[-beg:-end],]\n### Data to test the model\ndata.fold <- dataset[Ind[beg:end],]\n### Fit the model\nmodel <- reg.fn(formula,data=data.train,...)\npredicted.y <- predict(model,data.fold)\n### Update the CV-score\nscore <- sum((predicted.y - data.fold[,1])^2) / M\n}\nreturn(score/10)\n}\nTesting using ppr:\ncv.scores <- numeric(10)\n### Some code\nfor(i in 1:10){\nscore <- cv10(reg.fn = ppr, formula = y~.,\ndataset = data, nterms=i)\ncv.scores[i] <- scores\n}\ncv.scores\nThe traceback:\nError in matrix(NA, length(keep), object$q, dimnames = list(rn, object$ynames)) : length of 'dimnames' [1] not equal to array extent 4. matrix(NA, length(keep), object$q, dimnames = list(rn, object$ynames)) 3.", "613" ], [ "predict.ppr(model, data.fold) 2. predict(model, data.fold) 1. cv10(reg.fn = ppr, formula = y ~ ., dataset = data, nterms = i)\nThe data I am using:\nstructure(list(y = c(23.<PHONE_NUMBER>, 27.8893494373006, 3.32468370559938,\n-13.5852336127512, -5.14668013186906, -<PHONE_NUMBER>, -14.328750654513,\n-4.26428395686341, -2.75486620989581, 17.3107345018601, 25.6193450849393,\n<PHONE_NUMBER>, -1.30909806542865, 2.<PHONE_NUMBER>, -19.1193524499977,\n-1.46508279385589, 2.65778970954973, 14.8513018374104, -2.87449028138997,\n1.37368992108124, -1.43518738939116, 0.0199676357940499, -1.549025998582,\n-4.<PHONE_NUMBER>, -9.15130335901099, -2.62794216480131, -1.68473200963303,\n3.15144283445608, 7.78027589015824, 9.<PHONE_NUMBER>), x1 = c<PHONE_NUMBER>,\n-<PHONE_NUMBER>, 0.325763726232689, -1.69658096808073, -1.2854825202758,\n-0.<PHONE_NUMBER>, <PHONE_NUMBER>, 0.<PHONE_NUMBER>, -2.30403430891787,\n0.189004139305415, <PHONE_NUMBER>, <PHONE_NUMBER>, <PHONE_NUMBER>,\n1.01347438447768, -<PHONE_NUMBER>, <PHONE_NUMBER>, 0.207342703528518,\n0.", "856" ], [ "Here is the code I wrote to answer my question. It might not be the most efficient one but it works. Sharing is caring :)\nniter<-10000\nN<-nrow(Y)\nT<-10 # I will take into consideration until t=10 to estimate my parametres and then I will forecast the rest values t=11,12,... etc\nresult <- matrix(0,nrow = niter, ncol = 3) #Here I store 3 parameters: alpha, sigma_epsilon, sigma_eta.", "416" ] ]

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[ [ "Leaning and turning are independent in the case of an uncoordinated turn, but this only occurs during transitions in lean angle or perhaps a pothole dodge maneuver (described below). Uncoordinated turns are only temporary, eventually a bike will fall inwards or outwards in an uncoordinated turn.\nThe key point I'm making in my answer is that the linear component of this is the same regardless if the bike is falling or not. Centripetal acceleration is equal to the centripetal force exerted by the pavement on to the contact patches of the tires divided by the mass of bike and rider (force = mass x acceleration, so acceleration = force / mass), regardless if the bike is leaned properly or not (falling inwards or outwards).\nThe purpose of leaning properly is to keep the bike from falling inwards or outwards during a turn.\nIn a coordinated turn, the bike needs to lean inwards enough so that the outwards torque related to inwards centripetal force at the tire contact patches and the outwards reaction force at the center of mass is exactly countered by the inwards torque related to gravity pulling down at the center of mass and the pavement pushing up at the contact patches.\nIn an uncoordinated turn, such as dodging around a pot hole, a bike can be quickly turned to get the tires out from under the bike to go around the pothole, but the bike ends up leaning the \"wrong\" way, and this lean has to be corrected for after passing by the pothole.\nMore common cases of uncoordinated turns occur during transitions in lean angle during corner entry or corner exit.\nIn case the OP is asking how lean angle effects steering inputs, I'm adding this geometrical explanation in this part of my answer.\nIn a steady turn, the path of a bike is a circle, and the radius is from the path of bike to the center of the circle.", "544" ], [ "Ignoring factors such as tire deformation or slippage, the radius is a function of steering angle and lean angle.\nIn the imaginary case where a bike was vertical and not leaned, the center of the circle would be where the imaginary extension of the front and rear axles intercept. In the case where a bike is leaned over, the intercept point is below the pavement, and the center of the circle would be a point on the pavement directly above the intercept point below the pavement, and the circle and radius would be smaller. I'm thinking that the effect of lean angle probably multiplies what would be the \"vertical\" radius by the cosine of the lean angle. So if leaned at 45 degrees, the radius is cos(45) ~= 70.7% of the \"vertical\" lean angle radius.\nNote that this doesn't have anything to do with balancing of the bike, it's just the geometrical combined effect of steer and lean angles.", "544" ], [ "Late answer, but I'm hoping this clarifies what is going on. Whenever the front tire is turned, the bike will turn in that direction. In the case of countersteering, the rider steers in the opposite direction in order to cause the bike to lean, as shown in this image. The description in the image is not quite right, as both front and rear tires will out-track from under the bike, and the parts of the bike above the roll center will in-track.\nIf the bike is initially vertical, then the initial counter-steering input will cause the bike to turn \"outwards\" while it leans inwards.", "544" ], [ "That same outwards force that is causing the tires to track outwards (so that the bike leans inwards) is also causing the bike's center of mass to accelerate outwards. If steering right to lean for a left turn, the bike is initially turning right until the steering is brought back to neutral and then left, and vice versa. Out tracking can be used to quickly dodge potholes, you steer away from the pothole to get the tires to clear the pothole, which also causes the bike to lean, so after clearing the pothole, you have to steer the other way to get the bike back to vertical.\nThe steering geometry for a typical bike locates the contact patch behind where the extended axis of steering would intercept the ground. When leaned over, the ground is pushing up at the contact patch, while gravity related downforce is exerted at axis of the tire, causing the front tire to steer inwards in response to lean angle, causing a bike to return to vertical orientation (absent other inputs).\nIn the original question's video, there's mention of angular momentum or gyroscopic effects on steering, but at all but very slow speeds, the gyroscopic effect at the front tire results in too slow a rate of precision that slows down the self-correcting steering torque related to trail, acting as a damper (opposing self-correction), and at high speeds (100+ mph or 160+ kph), it's enough to virtually eliminate self-correction and a bike at high speed will tend hold a lean angle rather than return to vertical.\nRegardless if a turn is coordinated (steady lean) or not (lean angle changing), there is a <PERSON> third law pair of forces, the pavement exerts a centripetal force onto the tires, coexistent with outwards force exerted by the tires onto the pavement. If the turn is coordinated (steady lean) the outwards force is the same as the centrifugal reaction force related to the centripetal acceleration of bike and rider time the mass of bike and rider.", "544" ], [ "First of all a side note:\nThe angle of the blue lines isn't the same, as the tires have a certain cross section and shape. As soon as the bike is tilted, the point where it touches the ground moves out of the center line, into the tilt direction. In an extreme case, the bike could stay vertically, and only the driver tilts sidewards.\nHowever, I see three reasons, why b) is safer:\nWhile a) feels / is more stable as bike and driver are one unit, it needs more force to erect both into a vertical position. This force is not applied by the driver himself, as he can't erect the bike. Instead, he steers the front wheel deeper into the curve, which causes the whole unit to erect. At that moment, the force onto the ground increases, and the horizontal component may exceed the static friction.\nIn case of b), the bike is in a more vertical position and the driver can erect on his own. This causes less force onto the ground.\nFor almost the same reason, the driver can react faster when he sees that the condition of the street ahead changes, or may be, when the wheels already start to loose friction (which needs high skills).\nAs driver, you may imagine driving a curve very slow, once in the 'normal position', and once 'tilted'.", "544" ], [ "Imagine you manage to stop within 0.5m, because a ball is rolling on the street or similar. It's quite impossible to erect from the 'normal' into the vertical position, while it shouldn't be a problem from the 'tilted' position.\nAnother reason is additional torque on the tires. The surface of the tire which touches the ground has the size of... may be an egg. In a curve, the inner and outer side of this surface have a slightly different speed over ground, while the speed of an upright wheel is the same. This difference has to be compensated by the rubber of the tire, and creates a torque around the vertical axis.\nFor a certain angle of the wheel, this torque can be canceled out, as the inner side of the surface touches a point of the tire, where the wheel radius is lower. However, this usually happens at a fairly small angle, and with increasing angle, torque increases into the opposite direction. And of course, this torque should not exceed the static friction.\nSo, even in this case, b) is safer, as this torque is lower.", "544" ], [ "Power to weight ratio is one factor, but another key factor for 0 to 60 mph of a motorcycle versus a front or rear wheel drive car is the motorcycle's relatively high center of mass means that more weight is transferred to the rear tire, or all of the weight in the case of a wheelie, which in turn allows for more relative friction at the driven wheel, typically resulting in over 1 g of acceleration on higher end motorcycles.\nThe situation may have changed with some all wheel drive hybrid cars like the Tesla Model S P100D, with a launch controlled acceleration of 0 to 60 mph in 2.5 seconds, provided there's enough traction (probably a drag racing track with VHT is needed). The Ferrari LaFerari takes 2.4 seconds and the Porsche 918 Spyder 2.2 seconds. This matches or exceeds the fastest bikes with the best riders hunched down over the tank to reduce the wheelie factor.", "234" ], [ "Some bike testing is done with the front end strapped down and the rear shocks set to max stiffness and height or locked into position.\nIn a street situation, it seems unlikely that even with smooth torque applied by the electric motors to all 4 wheels, there simply won't be enough traction for the cars to achieve sub 3 second 0 to 60 mph times.\nHowever, once past 60 mph, or more like 80 mph, since that's 1st gear on the high end bikes, the bike accelerate harder than almost all cars, due to power to weight ratio.\nAs for the bikes, the high end bikes are around 200 hp now (Ducati V4R is 230 hp with optional exhaust), but due to wheelie factor, 0 to 60 mph times haven't improved much, stuck at around 2.5 to 2.6 seconds. For example the 175 hp first generation Suzuki Hayabusa matches the 0 to 60 mph time of the 200 hp current ZX-14R, which is 40 lbs heavier, and possibly with a center of mass that is further back and/or higher. The ZX-14R is about 0.25 second quicker than the Busa in a 1/4 mile run (9.5 versus 9.75 with a pro rider on a good track).", "234" ], [ "I notice the same thing on my bicycle. As I approach a certain radar sign it says I'm going 10 mph, so I start peddling faster to see how fast I can go, but by then the sign is more off to the side instead of in front of me and the readout on the sign is decreasing!\nThe radar unit is probably measuring how fast I am approaching it, not my speed over the ground. In other words, it is measuring the component of my velocity in the direction of the sign relative to my position. If I was doing 40 mph and the sign was reading 32 mph, the angle between my velocity vector and the position vector from me to the sign would be $\\arccos{(32/40)} \\approx 37^{\\circ}$. If the sign was about 10 feet from my straight-line course, i.e. from the middle of the lane, I would be about $10/\\tan{37^{\\circ}} \\approx 13.3 ft$ from the point in my path that is closest to the sign. That is pretty close, practically passing the sign.\nSo to me it would be reasonable for you to see the sign reading 32 mph when you are about one car length from passing it at 40 mph. I would say the radar sign is functioning as it was intended. On the other hand, if you are still a block away from the sign, and see the sign reading 20% less than your speedometer, well, I could not explain that.\nThe following is a more technical explanation of how the radar sign determines speed. The sign sends out a radio pulse and listens for the pulse to echo off a vehicle. The sign measures the time between sending the pulse and receiving the echo. That time is converted to a distance.", "234" ], [ "Then the process is repeated to get a new distance. The new distance is different because the vehicle has moved (closer). The calculated vehicle speed is determined by the two distances and the time between the measurements. The send-listen-calculate process can be repeated many times per second.\nThe speed calculated by that procedure could be called the velocity of approach, which is not the true velocity of the vehicle. The true velocity consists of how fast the vehicle is approaching and how fast it is veering, or going around the sign. Even though the vehicle is moving in a straight line, the direction of the vehicle from the sign is changing. This change in apparent direction is what I am calling veering, meaning to go clockwise around the compass. As the vehicle gets closer to the sign, the veering effect becomes more significant, which means the calculated speed becomes less accurate.\nFor example, on a north-south street the vehicle may approach the radar sign from the north. As it nears the sign, the vehicle may be off to the northeast and then due east as it passes the sign. However, the sign does not detect the change in direction, only the change in distance. The sign is only sending out a pulse and waiting for an echo without regard to the direction of the echo. A navigation radar would be able to measure the true velocity, but the radar in the sign is not that sophisticated.", "234" ], [ "When walking down an incline there is greater acceleration due to gravity. In order to maintain a walking speed, a braking force is needed to counteract the acceleration, and this braking force is given by the contact force of the initial footfall of each step as it's in front of your center of mass creating a force vector pointing away from your direction of acceleration. When going down a slope it's much more difficult for your initial footfall to be in front of your center of mass due to the limited reach of your legs as well as it being easier for your center of mass to pass in front of your supporting legs creating unbalance and downward acceleration. In addition your legs will more often be behind your center of mass than in front creating additional torque on your body that also has to be countered by your braking force.\nThere are several ways to counter each of these variables that cause you to lose balance. * Taking shorter steps will broaden the range of your braking force vector (relative to your center of mass) and will help prevent overextending your legs to better prevent your center of mass from passing too far in front of your supporting legs.", "174" ], [ "Depending on your speed this may not be viable since shorter steps will require an increased frequency of steps. * Lowering your center of mass will also help as then your legs can reach the ground sooner than from a higher position and thus create a braking force sooner and stronger with a broader range for your braking force vector and increase the distance your center of mass has to travel before being in front of your supporting legs. * Debatable, but walking backwards may help as some may find it easier to lower your body closer to the ground with one leg supporting your center of mass and have one leg extending backwards to provide the braking force than facing forward and having one leg extended forwards. The downside may be that if the torque on your body is great enough to cause you to rotate backwards it may more difficult to catch yourself and recover than if you're rotating forwards. This likely varies per person and the slope/walking situation at hand.", "174" ], [ "Anytime you push off the ground to take a step forward, it's the frictional force on your rear foot that allows you to do so. The contact between your foot and the ground will determine how hard you can push - based on the coefficient of friction and the normal force, there is some upper limit of force which friction can provide. If you try to push off harder, friction can't fully oppose the force of your foot pushing backwards, so your foot will slip.\nWhen you take small steps, you push off lightly, lowering the amount of force exerted through your back foot, as well as the opposing force of friction that pushes back. If you took large steps, your rear foot would exert a large force, and friction might not be able to provide a force that large, which would result in your foot slipping. In this sense, taking small steps decreases the frictional force exerted, keeping it under the limit where slipping would occur.\nI'll also note the difference between static and dynamic friction. When your foot starts to slip, it is governed by dynamic friction rather than static friction, which is always less than static friction.", "544" ], [ "In this senes, taking small steps without slipping can provide more friction than you'd get by slipping while taking large steps.\nOverall, the question seems very poorly worded to me. Taking smaller or larger steps certainly does not affect the normal force. I'd also interpret \"larger friction\" and \"smaller friction\" to refer to the coefficient of friction, which is also unchanged by the step size. If we take it to mean \"larger frictional force\" or \"smaller frictional force\", the question is still unclear. Smaller steps will reduce the amount of force supplied by friction, if both step sizes are non-slipping. But if the large step size does slip, smaller steps can result in a larger frictional force, due to the difference between dynamic and static friction. So, the answer will depend on if the large step slips or not - if it does, the small step may provide a larger frictional force; if it does not, the small step provides a smaller frictional force.", "544" ], [ "As <PERSON> points out, the ratio of torque to tension is lower the lower the lead angle is. Since the important measure of bolt tightness is generally the tension in the bolt, we want to achieve that minimum pretension with the least effort possible. Assuming we have to maintain a certain shear area of the thread (so the the threads are stronger than the bolt when fully engaged) having two starts means we double the lead angle and greatly increase the amount of force required in the wrench to tighten the fastener appropriately. On its own though, this isn't the end of the world in practical applications because a big enough torque arm, (or a shear wrench) makes this just a matter of using a bigger motor.\nThe bigger problem is that we want bolt threads to be self-locking. That is, we wouldn't want the pretension in the bolt to cause it to loosen.", "333" ], [ "Imagine if the bolt had 10 starts, and therefore a very steep helix for the threads - no matter how hard we tighten the bolt, the pretension will immediately loosen the bolt when we let go of the wrench. This is because the lead angle lets so much force transfer into the rotation of the bolt (or nut) that it can overcome the friction between the internal and external threads. This would make the bolt not very effective without an external locking device. By contrast, standard single start fasteners are often pretensioned (or simply made snug tight) and trusted to self-lock based on their shallow lead angle. In situations with high vibration or thermal cycles, additional locking elements may be used, but they aren't normally required if the bolt is properly tightened.\nThis is why single start threads are typically used for fasteners (things that aren't supposed to move) but multiple-start threads aren't uncommon for leadscrews (which are supposed to move freely, or have an external brake.)\nScrews which form their own mating thread in another material are often two-start, as they have an additional resistance to unscrewing from the compression and roughness of the substrate they displaced around the threads. This is the case with some sheet metal screws, and also most wood screws.", "333" ] ]

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[ [ "Make Your Own Square Kumihimo Disk From Foam Packaging\nIntroduction: Make Your Own Square Kumihimo Disk From Foam Packaging\nKumihimo is a Japanese art of braiding. You can buy foam disks round and square and learn to braid using them. Rather than buy a square disk used for flat braids you can easily make one from foam packaging. It may be slightly less sturdy than a bought one but is good enough to learn some basic braids.\nFor this instructable I'm using imperial measurements - inches (\"). Please scale and convert if you want to use metric (cm).\nSupplies\nFoam packaging (at least 6 inches x 6 inches), 1/2 inch thick\nRuler\nScissors\nCraft Knife\nPen\nPermanent marker pen\nStep 1: Cut Out Your Square\nMeasure out a 6 inch square on your foam packaging.\nCut our using a craft knife or scissors.\nStep 2: Mark the Edges\nMeasure in 1/4\" from the side of your square. Now measure in a further 1/2\" and make a mark.", "294" ], [ "Keep making marks every 1/2\"until you have 10 marks.\nRepeat this for all 4 sides of the square.\nStep 3: Lengthen Your Marks\nNow go round your square with a ruler and make each mark 1/2\" long\nStep 4: Cut Along Your Marks\nNow using scissors snip along each mark.\nStep 5: Label Your Square Kumihimo Disk\nNow using a permanent marker pen label your kumihimo square.\n1 to 10 along the top, 11 to 20 along the bottom.\nA to J down the left hand side, a to j down the right hand side.\nStep 6: Measure and Draw in the Centre Slot\nPlace your ruler along across the disk from E to e. Draw a line from 2 1/4\" to 3 3/4\"\nNow place your ruler across the disk from F to f. Draw a line from 2 1/4\" to 3 3/4\"\nPlace your ruler from top to bottom at 4 to 14. Draw a line to form the side of the rectangle.\nPlace your ruler from top to bottom 7 to 17. Draw a line to complete your rectangle.\nStep 7: Cut Out the Centre Slot\nNow using your craft knife, scissors and ruler, cut out the centre slot.\nStep 8: Ready to Use\nNow your square kumihimo disk is ready to use. Try it out with some ratttail satin.", "6" ], [ "Hearts Leather Lace Bracelet Made on the Kumihimo Square Disk\nIntroduction: Hearts Leather Lace Bracelet Made on the Kumihimo Square Disk\nI have recently got hooked on kumihimo - the Japanese art of braiding. Here we try out a flat braid made with round leather lace. The braiding isn't difficult.\nSupplies\nKumihimo square disk - buy one or follow my instructable to make your own.\n3mm leather lace in two colours (I'm using red and black) - 300cm (120 inches) black and 100cm (40 inches) red\nTape\nGlue (E6000 or similar)\nRuler\nNylon Thread\nBlack permanent marker pen\n9 inches 1mm / 18 gauge silver coated copper wire\nWire cutters\nRound nose pliers\nFid\n120cm / 4 feet of faux leather lace - black\nStep 1: Cut Your Leather Lace\nFor this instructable you need 8 lengths of 3mm leather lace each 50cm (20 inches) long.\nCut 2 red and 6 black\nStep 2: Bind Ends of Leather\nGather the ends of your leather lace and either tape or bind with thread. I found that the tape didn't stick very well and I needed some glue to stop the ends coming loose.\nStep 3: Set Up Your Kumihimo Board\nPush the ends through the centre of the kumihimo plate and lay out the laces in the pattern shown.\nRed in slots E and e\nBlack in slots 5,6,15,16,G and g\nStep 4: Weaving 1st Step\nTake the leather lace from 5 and move it to h, then take the leather lace from 6 and move it to H\nBe careful you don't mix up your order or your lower and upper case letters)\nStep 5: Weaving 2nd Step\nNow take the lace from 16 and put it in D. Then take the lace from 15 and put it in d.\nStep 6: Weaving 3rd Step\nNow take lace from E and move it to 15. Then take lace from e and move it to 16.\nStep 7: Weaving 4th Step\nTake the lace from G and move to 5, then take the lace from g and move to 6.\nStep 8: Reposition Cords\nNow reposition your cords.\nD to E\nH to G\nd to e\nh to g\nAnd we're back at the starting position again\nStep 9: Repeat, Repeat, Repeat\nNow it's just a case of repeating the steps.\nHere is a condensed form of moves:\n5 to h then 6 to H\n16 to D then 15 to d\nE to 15 then e to 16\nG to 5 then g to 6\nReposition D to E, H to G, d to e, h to g\nJust keep repeating and you will see your braid forming at the back of the disk.\nStop when you have run out of cord or have the required length for your bracelet.\nStep 10: Remove From Disk and Bind End\nHold tight to your cords when removing from the kumihimo disk and bind the cord ends to stop them coming unravelled. I found nylon thread works well.\nStep 11: Bind Glue and Cut to Size\nMeasure how long you want your bracelet to be.", "421" ], [ "Mine is going to be 7.5 inches (19.5cm) plus the fastenings\nBind your woven cords using nylon thread, just behind where you are going to cut. Also add glue to hold it (E6000 or similar)\nLeave to dry before cutting.\nCut the ends.\nStep 12: Colour the Cut Ends\nColour the cut ends using a permanent marker pen\nStep 13: Make Your Own Toggle Clasp Findings\nI was hoping to just buy some clasps for finishing off this bracelet, but I've struggled to find anything that fits, so not one to accept defeat I've decided to make my own findings.\nI made a toggle clasp.\nFor the loop part you will need 4 inches of 1mm / 18 gauge silver coated copper wire. Start from the middle and form the loop - I'm using the top of a glue bottle to help get it circular. Now made a twist and fold the ends in, so you have the shape in the picture. If the ends are too long snip off the excess.\nFor the bar part you will need 5 inches of wire. Make a bend at 2 inches and fold, then make a bend at 3 inches and fold to make the T bar. Where the wires cross in the centre, fold out at 90 degrees, make a double twist, and then fold the ends in like you did for the loop. You should be able to follow the picture.\nFlatten your findings a little using a hammer and anvil.", "276" ], [ "Orange Suede Statement Necklace\nIntroduction: Orange Suede Statement Necklace\nDo you want to make an impact - then wear a statement necklace. This is an easy to make necklace. I've used orange suede, but use whatever colour you like to go with what you are wearing.\nSupplies\nFor this project you will need:\nPiece of Suede (orange) 2mm thick\nSome beads - I'm using 18 x 6mm wooden beads. If your beads are bigger then you may not need as many.\nScissors\nPencil or tailors chalk\n70cm of 3mm faux leather lace or leather lace for stringing\nFid\nHole punch\nCardboard\nMagnetic clasp (4mm hole)\nSuperglue\nStep 1: Draw and Cut Out Your Pattern\nFor this project I'm using a petal shape in three sizes. Draw your own or download a flower petal shape from the internet.\nI've drawn mine onto a piece of cardboard retrieved from the recycling (old biscuit packet). Use this as a template for transferring to your suede.\nStep 2: Copy Your Pattern Onto the Suede\nNow trace round your pattern onto the back of the suede.", "673" ], [ "I'm using a pencil so it doesn't leave marks. You could also use dressmakers chalk.\nThere are 5 of the large petals, and 2 of each of the smaller sizes.\nStep 3: Cut Out Your Petals\nNow carefully cut out your petal shapes.\nStep 4: Punch Holes Into Your Petals\nNow fold each petal vertically and punch a 3mm twin hole into the top. Do this for all your petals.\nStep 5: Prepare the Lace and Pieces\nScrew the lace onto the fid (cut the end of the lace at an angle and just screw it in until it is tight)\nArrange your petals and beads into threading order.\nYou may notice I only have 3 large petals in this picture - that's because I changed my mind and added 2 extra large petals making 5 large in total.\nStep 6: Thread the Pieces Onto the Lace\nThread all the pieces onto the lace. When you have finished threading adjust the lace so the pieces are in the middle.\nStep 7: Choose Your Necklace Length\nTry the necklace round your neck and decide how long or short you want it to be.\nI've decided that I want each lace to be 16cm from the last bead to the clasp.\nDepending on the kind of clasp you use you may need to allow for any folding at the clasp.\nFOr my magnetic clasp I'll need to fold the end of the lace so I need 2cm extra on each end.\nStep 8: Attach the Clasp\nI'm using a magnetic clasp. The end of the lace needs to be folded in 3 to fit snugly.\nPlace a drop of superglue in the clasp and push in the folded lace. Don't overdo the superglue or you'll glue your fingers like I did :-)\nStep 9: Ready to Make a Statement!\nNow your necklace is ready to wear. Go out and make a statement!", "748" ], [ "\"Hugs and Kisses\" Rattail Satin Elasticated Cat / Kitten Collar\nIntroduction: \"Hugs and Kisses\" Rattail Satin Elasticated Cat / Kitten Collar\nCat collars need to be elasticated so that they can't get trapped by their collar. This is an easy to make collar from elastic and rattail satin with a hugs and kisses (XOXO) motif. Choose your own colours to go with your cat.\nSupplies\nSmall side release buckle\n2 colours of 2mm rattail satin - lengths required depend on the size of your cats neck. Allow 1 foot (30cm) per inch (2.5cm) of the main colour (bronze), and half of that length for the secondary colour (green).\nScissors\nFid\n2mm round elastic - length twice the circumference of your cats neck\nSuperglue\nOptional bracelet jig, pet tag, small split ring\nStep 1: Measure the Cat, Cut and Glue the Elastic\nUsing a piece of string (or the elastic you are going to use - measure round the cats neck. Don't make it tight - allow for getting two fingers underneath the collar.\nCut your elastic to the size your just measured and then glue the ends with a dab of superglue to make a circle.\nStep 2: Attach the Elastic to Both Ends of the Buckle\nMake a loop in the elastic , thread it through one of the buckle ends and flip the loop over the buckle end. Do the same for both ends making sure that the buckle fastens straight and you don't have any twists in your elastic.\nStep 3: Attach Your Main Colour (Bronze)\nNow fold your main colour of rattail satin in half.", "748" ], [ "Take the loop and thread through one end of your buckle and flip the loop over the buckle to attach.\nYou can see in this picture that my elastic join is part way down the main length of elastic.\nStep 4: Attach the Buckles to Your Jig\nAdjust your jig to size and loop the buckles over the ends.\nIf you don't have a jig - use some nails hammered part way into a piece of wood set to the right length.\nStep 5: Tie a Cobra Knot\nUsing your main colour, using the right hand thread form a backwards \"S\" loop to the left hand side (see 1st photo) .\nNow pass the left hand thread through the lower half of the \"S\" behind the elastic and up through the top half of the \"S\" (2nd photo)\nThis is a cobra knot.\nStep 6: Attach Your Second Colour (Green)\nBefore you tighten your cobra knot. Fold your second colour in half and thread through your untightened knot and behind the elastic (see the photo)\nNow you can tighten your knot.\nStep 7: Form a Cross With Your Second Colour (Green)\nNow form a cross with your second colour (green in my case). Take the green threads behind the bronze threads and position out of the way at the top of the jig.\nStep 8: Tie a Second Cobra Knot\nNow tie a second cobra knot (on the opposite side). Use the left hand thread to make your forwards \"S\" this time.\nNow pass the right hand thread through the lower half of the \"S\" behind the elastic and up through the top half of the \"S\".\nPull the knot tight.\nStep 9: Position Green Threads\nTake your green threads and pull them straight down with the bronze threads out to the side (Photo 1)\nNow take the green threads up and over the bronze threads and leave them at the top of the jig out of the way (Photo 2)\nStep 10: Tie Your Next Cobra Knot\nNow use the right hand thread to tie a cobra knot out to the left side. (Same as step 5)\nPull it tight.\nStep 11: Make Your Next Cross With the Green Thread\nAnd now we're back to forming the next cross (as in step 7).\nMake sure you make your crosses all the same way.\nStep 12: Repeat Repeat Repeat\nKeep following the pattern, repeating steps 8, 9 ,10,11\nStep 13: Right to the End\nRepeat the pattern until you run out of room. You may find the last few knots a bit tricky as there isn't a lot of room.\nNow remove your collar from the jig.\nStep 14: Finishing\nTo finish off we need to tuck the ends of the satin in.\nI'm using a fid to thread each of the satin cords along the back of the collar.\nStep 15: Cut the Ends and Seal\nNow cut the satin ends and seal using a lighter.\nStep 16: It's Mine\nNow your cat collar is finished.", "748" ], [ "Easy to Make Dragonfly Pendant\nIntroduction: Easy to Make Dragonfly Pendant\nThis is a dragonfly pendant made from scrap pieces of paracord and a small piece of scrap suede or leather. It's easy and fun to make and looks good too.\nI don't like waste so I save tail ends of paracord and offcuts of leather and suede from other projects. This is a great way to use some of those up.\nStep 1: What You Will Need\nSome scrap ends of paracord - ranging in size from 6cm to about 12cm\n2 small pieces of suede 2cm x 8cm\n15cm piece of bendable wire\n70cm length of rattail satin / suede / cord or whatever you want for going round your neck.\nScissors\nPliers\nSmall hole punch or something that will make a hole through the suede\nSuperglue\nStep 2: Make a Paracord \"bead\"\nTake a length of paracord, cut the ends off and pull the core out of the middle.\nUsing a lighter gently heat the paracord ends and squash flat.\nNow roll up the paracord into a \"snail\" and using superglue stick the end down.\nStep 3: Make More Paracord \"beads\"\nMake more paracord roll-up \"beads\".", "177" ], [ "I've varied the length of the paracord from 6cm for the smallest to 12cm for the largest.\nIt's up to you what colours you use and may depend on what colours you have.\nI've chosen shades of blue and turquoise, but the choice is yours.\nStep 4: Make Dragonfly Wings\nUsing a piece of suede, cut out 2 pieces 2cm wide by 8cm long.\nShape the ends of the wings.\nGlue the wings in the middle with a spot of glue.\nPunch a small hole through the wings so they can be threaded.\nStep 5: Prepare the Wire\nTake a piece of bendable wire about 15cm long.\nUsing pliers make a circular loop at one end.\nStep 6: Thread the \"beads\" and Wings\nDecide on the order of your paracord beads. I've laid it out on my board to decide what looks best.\nAs you will see I have several left over \"beads\" for another time.\nNow thread the beads and wings onto your wire.\nStep 7: Finishing Off the Wire.\nPull the beads tight on the wire then using the pliers form a loop on the top of the top bead.\nThis will stop the beads separating.\nNow form a double loop of wire so the pendant can be hung.\nStep 8: Hang Your Dragonfly Pendant\nCut a length of rattail satin or whatever you are using for your necklace. I've used about 70cm, so it will go over my head. Heat the ends of the satin to stop fraying.\nLoop the satin through the pendant wire and knot the satin ends.\nYour dragonfly pendant is now ready to fly.\nStep 9: Wear Your Creation\nNow your dragonfly pendant is ready - put it on and take it for a fly.", "177" ], [ "Washi Tape Koinobori\nIntroduction: Washi Tape Koinobori\nKoinobori, are Japanese carp shaped streamers that are traditionally flown on Children's Day - May 5th.\nThis version is made out of a empty toilet paper roll, some wide tape and lots of colorful washi tape.\nIt's really easy to make and comes out very pretty and colorful.\nSupplies\nToilet paper roll\nWide tape (5cm) - I used white tape because my toilet paper roll was not white.\ncolorful washi tape\nscissors.\nOptional:\nwooden bbq sticks\nhot glue gun\nStep 1: Heads and Tails\nFlatten and tape closed one end of the toilet roll. Over that add an additional layer of wide tape leaving an edge of tape at the end.\nIf you need to - cover the other end of the toilet roll with white tape (because my roll was not white).\nOn the open, mouth side - cover the edge with colored tape and tuck the overlap into the mouth.\non the closed, tail side - cover with a band of tape all around, then mark out scales and cut them out.\nStep 2: Add the Scales\nFor each row of scales -\n1. Cut a long piece of wide tape and fold over 1cm (fold the entire length).\n2. On the non tacky side you add a long piece of colorful tape. Then cut the scalloped 'scale' shape along the colored tape.\n3. Wrap the wide tape around the roll so that each row of 'scales' partially overlaps. Cut off the excess tape.\n4. Make the next line of scales..\nStep 3: Add Fins\nWhen you have about 60% of the length of the roll covered (from the tail end), its time to add fins.\n1.", "6" ], [ "Make 1 more line of regular scales. Remove about 2cm of those scale on each side.\n2. Cut a length of wide tape (about 6cm). Fold the long end over by 2cm now, leaving 1cm of tacky tape.\n3. For each fin use 2 pieces of 5cm color tape (going in the other direction now). Make sure not to cover the tacky part of the white tape.\n4. I shaped each fin like a large scale with a width of 2cm.\n5. Tape each fin into the gap you left in the last row of scales.\nStep 4: Finish Up\nAdd 1 last row of scales to partially cover the row of the fins.\nDraw some googly eyes.\nIf you want - add a spot of hot glue at the bottom and attach a bbq stick... now it can decorate a plant\nDone!!!", "636" ], [ "Double-sided Earrings\nIntroduction: Double-sided Earrings\nCanvas + Yarn = Double-sided Earnings was the immediate title I could think of :-) These handmade earrings are simple, easy, and very much affordable within a short time span. Come along with me to learn this new double-sided earring. The leaf pattern and the web pattern. These earrings can be flipped and worn either way. The other side could also be colored differently or used as a mix and match option.\nSupplies\n1. Plastic canvas\n2. Yarn (white and yellow)\n3. Scissors\n4. Needle\n5. A pair of earring hooks\n6. A pair of circle rings\n7.", "557" ], [ "Pliers\n8. Transparent glue\nStep 1: Pattern Symbols\nWith 11 Rows and 11 Columns, there are 121 boxes in total\nR = Row\nC = Column\nR1 = Row 1\nC1 = Column 1\nR5C5 = Row 5 and Column 5\nStep 2: Get the Canvas Ready\nIn this step, I cut the canvas with 11 x 11 squares (4 total) as seen in image 2. As you can see in this image the edges are rough. To make it more elegant and neat, I trimmed the edges neatly to make it perfect and smooth. Now, image 3 shows the squares are in perfect shape.\nStep 3: The Leaf Pattern With Yellow Yarn - Step 1\nI started working first on the leaf pattern. This looks impressive.\nPattern is\nStitch 1 (Image 2)\nR11C10 -> R10C10\nStitch 2 (Image 2)\nR10C11 -> R10C10\nStitch 3 (Image 3)\nR11C8 -> R8C8\nStitch 4 (Image 3)\nR8C11 -> R8C8\nStitch 5 (Image 4)\nR11C6 -> R6C6\nStitch 6 (Image 4)\nR6C11 -> R6C6\nStitch 7 (Image 5)\nR11C4 -> R4C4\nStitch 8 (Image 5)\nR4C11 -> R4C4\nStitch 9 (Image 6)\nR11C4 -> R4C4\nStitch 10 (Image 6)\nR4C11 -> R4C4\nI repeated this pattern on the second square as well. This completed 2 squares with the leaf pattern with yellow yarn.\nStep 4: The Leaf Pattern With White Yarn - Step 2\nNow flip the image by 90 degrees and it should look as in image 2. I started working on the leaf pattern with the white yarn. This is the second half of the leaf pattern.\nThe Pattern is\nStitch 1 (Image 2)\nR9C1 -> R9C3\nStitch 2 (Image 2)\nR11C3 -> R9C3\nStitch 3 (Image 3)\nR7C1 -> R7C5\nStitch 4 (Image 3)\nR11C5 -> R7C5\nStitch 5 (Image 4)\nR5C1 -> R5C7\nStitch 6 (Image 4)\nR11C7 -> R5C7\nStitch 7 (Image 4)\nR3C1 -> R3C9\nStitch 8 (Image 4)\nR1C9 -> R3C9\nStitch 9 (Image 5)\nR1C1 -> R1C11\nStitch 10 (Image 5)\nR11C1 -> R11C11\nI repeated this pattern on the second square as well. This completed 2 squares with the leaf pattern with yellow yarn.\nStep 5: The Leaf Pattern With the Middle Running Stitch\nIn this step after completing both the yellow and white yarn as shared in the steps above, I then completed the running stitch as shared in the pattern below\nR11C1 -> R10C2\nR9C3 -> R8C4\nR7C5 -> R6C6\nR5C7 -> R4C8\nR3C9 -> R2C10\nR1C11 -> R2C10\nR3C9 -> R4C8\nR5C7 -> R6C6\nR7C9 -> R8C4\nR9C11-> R10C2\nWith this, the central running stitch in yellow yarn completed the leaf pattern. I then dittoed this on the second square as shown in image 1.\nStep 6: The Web Pattern With White and Yellow Yarn\nThis web pattern is a different one and can be used as the second side. Flip onto the other side.", "294" ], [ "How to Make a Paracord Plant Hanger\nIntroduction: How to Make a Paracord Plant Hanger\nTake some nice bright paracord and make yourself a plant hanger. Paracord is great for indoor or outdoor use and can handle the weight of any plant and pot you care to put in it.\nStep 1: Gather Your Supplies\nSo here is what you'll need for this project:\n1 metal ring 38mm\n2 colours of paracord 6m of each - I'm using yellow and orange\nScissors\nA lighter for sealing the ends of the paracord\nA ruler or tape for measuring with\nA ceramic pot\nSome string or spare paracord for suspending your project while working\nStep 2: Cut Your Paracord\nFrom the orange paracord cut 2 lengths each 2m 50cm long. Seal the ends with a lighter to stop them fraying.\nThen cut 2 lengths each 2m 50cm from the yellow paracord, and seal the ends.\nStep 3: Attach Paracord to Metal Ring\nTake the first piece of orange paracord and find it's midpoint by folding it in half. Take the midpoint loop and put it through the metal ring from the back. Take the two ends of the paracord and pull them through the loop.\nNext take a piece of yellow paracord and do the same>\nRepeat with the 2nd orange cord and the 2nd yellow cord.\nNow all your paracord is attached to the ring and you have 8 dangling ends.\nStep 4: Make a <PERSON> Knot - Example\nThe 8 strand <PERSON> knot is the most complicated part of the project.\nIf you want to watch a video there is a great one from the Paracord Guild here - They start tying the knot at 2:14: I've added photos from an example knot I tied that has 8 different colours.\nThe colour order is turquoise, purple, grey, red, navy, yellow, green, orange.\nI arranged the cords out flat in the colour order above.\nStarting with the turquoise cord make a loop.", "401" ], [ "Pass the turquoise cord around the back of all the other cords and thread it back through it's own loop.\nNext take the purple cord. Pass it through the turquoise loop, then around the back of all the other colours and back through its own loop (ONLY it's own loop)\nNow on to the grey cord. Pass it through both the previous loops (turquoise and purple), round the back of all the colours and through it's own loop.\nI think you'll be getting the idea of this now.\nEach cord you take from the back - pass it through ALL the previous loops, take it round the back of the remaining cords and through just it's own loop.\nBy the time you have done all 8 cords it looks like you are holding a pinwheel.\nNow to start tightening - pull each cord in turn out to the side gently while trying to keep the colours in order.\nOnce you have tightened up a bit, Take the turquoise cord which is at the bottom and move it to the top.\nNext take the purple cord and move it to just below the turquoise. Then the grey to just below the purple and the red just below the grey.\nNow everything is in the right position you can continue to tighten, gently working your way round the cords until you have a nice looking knot\nIt took me a few attempts to get the hang of these knots - so don't despair.\nStep 5: 1st Project <PERSON> Knot\nNow that you have learned to tie a <PERSON> knot, we tie the first one in our project.\nWith the ring at the bottom and the cords facing upwards splay out the cords so you have 2 yellow, 2 orange, 2 yellow, 2 orange.\nMeasure 10cm from the ring and grasp the cords at that point. This is where we want our knot.\nStarting with the left hand yellow cord, make a loop, pass the cord right round the other cords and tuck it into it's own loop.\nProceed with each leftmost cord - remember the cord goes through ALL the preceeding loops, wraps round the other cords and finishes by tucking into its OWN loop.\nTighten gently, then raise the bottom yellow cord to the top, the next yellow one just below that, then the orange to just below the yellow and the next orange just below that.\nTighten properly and you'll have a <PERSON> knot 10cm down from the ring.\nStep 6: Getting Ready for the Pot\nFor this next part I find it easier if I suspend the project by the loop over the pot you are going to use.\nDecide how far down you want the pot to be from the ring.", "694" ] ]

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[ [ "Why closed bottle change its weight when I put effervescence tablet?\nI use several shape, several type of material (glass, metal, plastic), I use two different balances with 0.01g of accuracy. I put oil on gasket, and put upside down (like that I can see if water escape). But always it's the same result, when I put one, two or more effervescence tablets, the weight decrease:\none tablet => -0.03g\ntwo tablets => -0.06g\nthree tablets => -0.09g\nSure the difference is not big. But if I put an object without effervescence tablet, the weight is always the same (move sometimes +0.01 or -0.01g but never more). The time for decreasing is about 2 minutes so it's not enough for change something from temperature I think especially with glass container.\nSo, maybe someone has done this experimentation before and know where is my error ? Or maybe someone can test and try this experimentation ?\n<PERSON>: \"Recall that the air density is about 1.3 grams per cubic centimeters\", you're sure ? it's not 0.0013 ? Yes, I have the same values for glass (2 mm of thickness and one of 3 mm of glass) with a metal cover of 0.8 mm of metal. I done about more than 100 measures.", "1018" ], [ "After 2 minutes, the tablet is full dissolved in water and weight move very few after (-0.01g next 2 minutes) but never more.\nMaybe I found: when bubbles move up in water, they have gas in it (CO2), this gas move up with a speed, so there is a quantity of movement, the weight losses is the sum of mass of bubbles multiply by speed. Like quantity of movement is conserved, the weight don't change.\nIt's possible to use the formula of <PERSON>: force=2mv if top speed is 0.25 m/s the weight losses is 20.3/10000.25/10 = 0.015 g with 0.3 g of CO2, image show speed that I found on Internet. If it's that, the weight must change with a ball full of air (ping-pong ball) in water. But the CO2 in a tablet is very powerfull, 0.3g give 0.187 liter of CO2, even the ball move faster the volume is not great in a bottle. The ball must be down before close the container. And the gas must relax when the ball reached surface.\nIs it possible it is the rotation of Earth that change the pressure in water due to the centripetal forces ? This give -0.03N for each kg of water.\nGood day", "439" ], [ "Density of repulsive particles in a circle\nNB: the external circle (where particle or water is in it) is fixed !\nIt's a 2D theoretical problem (just for understand something in particular). Here, no gravity, no temperature. I put in a disk a lot of repulsive charges from center. Particles have the same charge +1. OK, if I put 40 particles in the same time, all will go at outer circle. But, if I add later 2 another particles why they will go to outer circle? I can repeat this time after time and add a lot of particles that never go to outer circle. So my questions are:\n1) If I'm wrong, can you explain how new 2 particles (for example but it can be one particle) will go to outer circle (it's possible to imagine big circle).\n2) If I'm wrong at (1), and if particles have a radius (not a point particle) it's not possible to put infinite particle at outer circle, so new particles need to take another layer, no?\nSo if I add and add particles (with radius not 0) all the sphere can be fully at 70 % for example. And my last question is:\n3) How is the density? For me, the density (number of particles for one volume) increase with radius but I'm not sure.\nMaybe this problem is already studied and I would appreciate some information about if you have.\nEdit for first reply:\n4/ Thanks for links :) For reply to your first paragraph (I'm not sure to understand): I'm agree that all particles at circumference are free to move but if I add 2 another particles, they repulsive themselves, until when ? each new particle has force from another new particle (in one direction) and force from all others particles (in the contrary direction), for me at a moment these forces are equal (absolute value) and new particle stop to move somewhere from the center to the outer circle. It's evidence if I add a single new particle in the center, why it would move at outer circle, all forces on this new particle want to let it in the center.\n5/ If density change with radius, not linear. Now I add in the big disk an object compose of 2 vacuum disks, please look: . Disks have same radius but are not at the same radius inside big disk. These vacuum disks are fixed together, this object (2 vacuum disks) can turn around the center of big disk.", "439" ], [ "Each vacuum disk take place of particles. This change the force on each disk. One disk has more force from another due to the lack of particles (it's not the same density). So, even this change the global density everywhere (I don't drew all forces), for me this give a torque on the object. Sure, it's not possible but I would like to understand how particles do for have a torque at 0 ? Maybe you have another link for help me ?\n----------------------------------------------------------------\nWith gravity it's easier to study, 2 vacuum object or one only:\nIt's evidence that force for sphere of gas is only radial (<PERSON>) because all is symmetrical. So even the sphere of gas is attached to the sphere of water this don't change the torque. The sphere of water has less force due to the lack of matter of the sphere of gas. The pressure around sphere of water changing due to the lack of matter of the sphere of gas but the density change with the radius and change due to the presence of sphere of gas. The density is not linear and the law of attraction is not linear $k/d^2$ too, how the force of attraction and the force of pressure can be the same ?\nor:\neasier to calculate with:\nthe cosine function is nonlinear and it is use more in the calculation of one force than other, this can't be compensate by law in $k/d^2$. And the asymmetry from the circle ?\nLike this it's easier to understand there is a problem with torque. Density is not the same everywhere, greater with small radius. And the position in the circle of spheres of gas give not the same height of water above them.\nMore easier, with walls like part of circle ! Can't give a big torque at top even there is a difference of pressure. In the contrary, the other give a torque.", "439" ], [ "I found 3 perfect ideas to explain the mass of a shapeshifter:\n<PERSON> - Hemlock Grove\nThis method is better to explain mass loss but can be used in both ways.\nWhen the user decide to transform into a smaller been he left behind his transformation a mass of fresh flesh (remants of their last body) that he can eat later to turn back to his normal body.\nThis video shows the transformation in the serie.\nSteam condensation - Shingeki no kyojin (Attack on Titan) and this\nWell, in the serie isn't explained how transformation happen but fans have made a lot of theories.\nThis method is better to explain mass increase but if you want you can do the opossite effect.\nWhen the user decide to transform it release an energy blast, fans believe that this persons absorbs the molecules of the air to make their bodies.\n* This explain why after the transformation their bodies are so heat, chemical reactions usually produce heat.\n* This transformation doesn't need nutrients to work, only air (maybe earth?) and energy to make \"the transmutation\".\n* Because they would need a lot of food to get the energy they could use solar light. In the serie titans need light to move or regenerate, in dark they \"sleep\".\nVirtual matter and teletransportation - Ajin\nI don't remember if it is also a fan theory or not.\nIn Ajin there are some persons who can't be killed, if you kill them (e.g: split in two) after a few seconds one of the 2 part would regen in almost 10 seconds while the other would desintegrate (teletransportation? maybe...). This doesn't break matter conservation law (but yes momentum law, or I think...), but you want to make matter so this won't work for you.\nWell, <PERSON> (inmortal persons) has more abilities, they are able to summon an IBM (Invisible Black Matter), don't ask about invisible because it isn't important here, also you can change black matter to standard matter in your mind.\nThey can make a creature of virtual matter.", "337" ], [ "Virtual matter isn't like normal matter, is normal matter WITH one exception: virtual matter was made out of nowhere -breaking law of conservation and other laws- so virtual matter need to be desintegrated in really short time to \"don't break these laws\".\nThink that the universe is a human, if you break a law, it punish you (I am not sure but I think a black hole would be spawned of nowhere if you break a physic law).\nHumans are living beens, and like animals can make mistakes, if you make something wrong your boss/teacher/parents would punish you but not instantly, maybe they take a few seconds or minutes to realice of your mistake. The universe is the same but it doesn't need seconds or minutes, it take yoctosecond (10−24s). By some [insert magical or sci-fi reason here] they are able to delay this and they can make virtual matter for some hours (e.g: in Ajin IBM can be used by 5 minutes).\n* You don't need nutrients.\n* You don't need solar light.\n* Maybe you have only this two disadvantages:\n* You can't stay to much time transformed.\n* You need some coldown time.", "337" ], [ "Each gram of water has an specific heat of 4 J/(K.g)*. So heating $\\pu{100 g}$ of water from $\\pu{15 °C}$ to $\\pu{70 °C}$ would take:\nHeat = (70°C - 15°C) * 100g * 4 J/(K.g) = 22,000 joules = 22 kJ\n$\\pu{20 g}$ of ethanol would be:\nEthanol mol = (20g / 46,07 g/mol) = 0.43 mol\nSo this means that:\n0.43 mol = 22 kJ\nmol = 22 / 0.43\nmol = 50677 J = 50.67 kJ\nSo ethanol has 50.67 kJ/mol vs 53.72 kJ/mol said by you. I would say that you have made fine your homework, there is a very little difference (I have used some decimal to calculate, maybe you not. (Below you can find a more accurate answer)).\n* Water specific heat: water changes it's specific heat when it changes it's heat.", "108" ], [ "For example: (Wikipedia)\nWater at 100 °C (steam) 2.080 J/(K.g)\nWater at 25 °C 4.1813 J/(K.g)\nWater at 100 °C 4.1813 J/(K.g)\nWater at −10 °C (ice) 2.05 J/(K.g)\nNormaly it's used: 4.1813 J/(K.g)\nA better table can be found in a french page.\nUsing this table we can do a better aproximation:\nWater heat = (70°C - 15°C) * 100g\nWater heat = (293.03 J - 63.04 J) * 100g\nWater heat = 229.99 J * 100g\nWater heat = 22,999 J = 22.999 kJ ≈ 22.9 kJ\nEthanol mol = (20g / 46.07 g/mol) = 0.43 mol\nExactly: 0,4341219882787063164749294551769 mol\n0.43 mol = 22999 J\nmol = 22999 / 0.43\nmol = 52978.19 J = 52.97819 kJ ≈ 52.97 kJ\nExactly: 52978,196500000000000000000000001 J\nAnswer: Ethanol has 52.97 kJ/mol. A value closer to your own value.\nPD: I am only a normal person who like chemistry, maybe I am wrong. For example in the theory I have no idea what means $Q = c \\cdot m \\cdot \\Delta{}T = \\pu{4.2 \\frac{J}{g \\cdot K}} \\cdot \\pu{100 g} \\cdot \\pu{55 K} = \\pu{23100 J}$ Well, I have some ideas but I haven't learned it in the school.\nEdit:\nI notice that you have your own mol of ethanol (46 g/mol instead of my 46.07 g/mol) and your own specific heat of water (4.2 J/(K.g)). You have to do:\nWater heat = (70°C - 15°C) * 100g * 4.2 J/(K.g)\nWater heat = 55°C * 100g * 4.2 J/(K.g)\nWater heat =\nWater heat = 23100 J = 23.1 kJ\nEthanol mol = (20g / 46 g/mol) = 0.43 mol\nExactly: 0.43478260869565217391304347826087 mol\n0.43 mol = 23100 J\nmol = 23100 / 0.43\nUsing mol decimals (0.43478260869565217391304347826087)\nmol = 53130 k = 53.13 kJ\nUsing only 2 decimals (0.43)\nmol = 53720,93 J ≈ 53.72 kJ\nExactly: 53720,930232558139534883720930233 J\nAnswer: Ethanol has 53.13 kJ/mol (With decimals) or 53.72 kJ (with 2 decimal). So yes! You have done right!", "979" ], [ "How and where does air that is displaced by a constant moving vehicle flow?\nHow does air that is displaced by a constant moving car move?\nWhen a car is driving with constant speed, there is air displaced in front of the car. Let's say the surface of the car view flat from front is 2m² and the vehicle is moving at 40m/s, that is 80m³/s. What I am trying to figure out is approximately where and how fast this air moves around the car.\nNow I have trouble comparing a moving car to a wind tunnel, actually I can't understand why it would behave the same. What is giving me a headache:\nFirst what I currently imagine from pictures or videos of cars in a wind tunnel: Air is blown with constant speed at a car. The area of the airflow is larger than the car. Then the wind lines compress around the roof of the car, meaning the wind has to go faster. Also the lines move up. From wind tunnel videos it can be seen that they compress quite a lot. It looks approximately that if the car height is e.g.", "1018" ], [ "1.5 meters and the air blown has a height of 3 meters than in the end it passes a section with a height of less than 1.5 meters above the car - which would mean more than double of the velocity?\nNow if I imagine car moving at same speed along a road, no wind. Relative to an observer the air some space in front of the car has 0 velocity. Now as the car is moving air in front of it has to be displaced (a lot actually). Now my expectation is that the displaced air is being pushed across the car in backward direction of travel, and again the flow is being compressed due to the cars shape, so relative to an oberserver the displaced air moves in reverse direction of the car approximately with the same speed as in the wind tunnel.\nBut this means, if the car is moving 40m/s from right to left, then the air has to be moving from left to right (with more than 40m/s as the area is also compressed) at least as long as it passes the roof of the car. It can't move forward as it is pushed by the air ahead of the car. Is that correct? This means the relative speed between the air and the car across the roof is more than 80m/s.\nNow I have some trouble thinking about this, as I can read in different publications that air close to vehicles is not moving in opposite direction, actually it is being dragged in the direction of the vehicle but with a low speed. I found articles about this: For trains A review of train aerodynamics Part 1 – Fundamentals https://core.ac.uk/download/pdf/185479708.pdf - speed of air relative to the train is positive in the diagrams\nOr this: Researchgate Drag explained by Newtonian mechanics https://www.researchgate.net/profile/Nicholas-Landell-Mills/publication/337934778_Why_drag_and_KE_are_proportional_to_velocity2/links/6239df1259c2363ae65f3b04/Why-drag-and-KE-are-proportional-to-velocity2.pdf?origin=publication_detail which depicts 2m/s air speed in direction of travel when the car is moving 33m/s.\nAlso I saw exercises with a train driving in a confined space (tunnel) where the pressure in he tunnel should be calculated and found contradicting opinions: Some people saying ideally all the displaced air is flowing in reverse direction in the tunnel, other saying the air is pushed ahead in front of the train.\nBut know that gives me a real headache. If the air is moving in direction of the vehicle (with a low speed, a lot lower than the travel speed) - where does the displaced air then move? Is it just pushed \"away\" far away of the vehicle and not into the airflow lines closes to the vehicle at all? This seems to be indicated by the measurements. But then I do't understand how there would be a lift and higher air speeds across vehicle tops at all. Or is this about different layers that some of the displaced air is being pushed close over the car (how close) and some of the air pushed far away to the sides (how far)? Is compression involved or can I imagine that air is not compressed? I don't want to calculate the exact numbers, but I want to get a basic understand of the movement, speed and volumes involved.\nI also tried to imagine the extremes, a flat surface with maximum drag, and an airfoil with minimum drag, I end up with the same question.\nQuestion summarized: Where and how fast does the displaced air from a constant moving vehicle move?", "483" ], [ "1/ It seems possible to stop evolution !\nThere are lots of examples of earthlings species which evolution has stopped at a certain point, for example this bacteria living in the deep ocean has not changed since 2 billions years.\nAdd crocodiles, trilobites and other species. They found a place in nature that fits them so perfectly they (quite) stopped their evolution.\nYou could imagine a specie that stop evolving while finding the perfect balance, like my very old bacteria.\n2/ Except it is not possible.\nIn fact, some species did evolve from these, but the original specie was not extincted as the new one did not replace them. These species seems freezed in evolution, but if they are so perfect, why don't they rule the world ?\nThey have a very specific place and climate they are adapted to. They don't spread worldwide. If they become too numerous, they die (from hunger and lack of vital resources).\nI'm not sure how a unique plant could evolve and how climate could be the same everywhere, but let's assume that the case, you have the same plant everywhere, and the climate is... perfectly perfect. The plant grows. And grows.", "671" ], [ "It spreads worldwide. Wow.\nIf nothing threatens your plant, then nothing stop it from growing. Your plant become its own ennemy : the nutrient the plant needs to grow will lack. The shadow from the grown-up plants will hide the sun from the youngs. Or, if it's perfectly flat, the place will lack for the youngs and nothing will replace an old dying plant on a ground without the essential nutrients (as the old plant has already deeply used it to grow)\nAs a result, the young plants will die, except the ones with a small mutation allowing them to accept another kind of nutrient, or less sunlight, or growing above the other. A new specie is born. Evolution strikes agains.\nYou could argue that the young plants can live from the dead old plants (That sounds creepy) but on earth, a lot of other species are needed to decompose a plant (worms, bacterias...). If the plant can \"eat\" herself still living or not decomposed, it will have a serious bad time with its \"child\", but that could be the one and only way your unique plant could rule the world, all alone.\nAnd even with that solution, I'm not sure it's not already a new specie, as the first generation eats from the ground and the new generation eats froms the old plants, and might develop another way to absord nutrients.", "731" ], [ "How exactly is kinetic energy transferred between two moving objects when a force is applied?\nI have a question about how kinetic energy is transferred between two objects when a force is applied between them. It sounds simple but when thinking about \"what really happens\" I have some questions. I also checked other entries but couldn't find a detailed explanation.\nI will use a basic example, the elastic collision.\nLet's say I have two objects with the same mass, a spring (considered with no mass) is attached to the first object.\nt=1: Object 1 accelerated from 0m/s to 10m/s. Object 2 is not moving.\nt=2: Object 1 has reached object 2 and the spring between them is compressed. Object 1 and object 2 are now both moving with 5m/s. 1/4 of the initial kinetic energy is stored in each object, 1/2 in the compression of the spring.\nt=3: While the spring expands to its original state, object 1 is decelerated until it reaches 0m/s, object 2 is accelerated until it reaches 10m/s.\nFor the numbers, momentum and energy conservation everything is fine.", "512" ], [ "Momentum and energy has not changed. At t=2 a part of the energy is stored in the compressed spring.\nWhere I have some questions: From t=2, the spring decelerates object 1. The kinetic energy from object 1 is transferred to object 2.\nWhat is the mechanism how the energy \"flows\" through the spring from object 1 to object 2? I have trouble seeing how the object that is pushed back can propagate its energy.\nI can imagine that if I would stop object 2 for a short time, the spring will be compressed further by object 1 (kinetic energy is converted). If I then stop object 1 for a short time the spring will expand and thus accelerate object 2.\nBut as the transition happens continuously, I wonder how this mechanism works in detail. As long as object 1 is faster than object 2 it is clear to me, as object 1 is still compressing the spring. I have trouble to imagine what happens exactly when object 1 is slower than object 2 but it still passes on the momentum and energy.\nIs there any model what happens in detail? Some backgrounds would be highly appreciated. It's one of the questions where I can observe and calculate the behaviour, but would like to have more explanation.", "927" ], [ "What is the age of planet Earth, if we are not looking for the age on sea the level?\nI remember to learn at school that our planet is approximately 4.543 billion years old.\nBut since the time is affected by mass of an object, this number is actually the age on the sea level, where the mass of our planet equals 1g.\nBut what about the center of the planet? In the very center there is no gravity (or better lets say the gravity is equally distributed to all directions) so in fact 0g. I guess there is still some momentum generated by Earth orbiting the Sun...but still - should not it be different than on the surface?\nDoes this mean that the cores of planets has in fact different age than their surface? And if so should we measure the age of cosmological objects by two numbers - by age on the surface and the age on the center of gravity?\nWhile I understand how time dilation works when we travel away from the the surface, or when we are lets say on the surface of Mars...in case of going to center of Earth I actually do not know if the time \"speed up\" or \"slow down\".\nAlso while this idea...if correct...makes sense to me for planet Earth, for stars it seems to be a whole new level. I was trying to calculate the difference between the time on the surface of the Sun and the center of its gravity but to be honest I just have no idea how to begin.", "319" ], [ "To me it seams that if the surface of the Sun is 4,6 billion years old and it has around 274 m*sec^-2 (or around 28g) on its surface and the gravity in the center is closer to 0g than in case of Earth...than the age of the center of gravity of the Sun is in negative numbers...? Is it by any chance possible that the age of the surface of the Sun was calculated like if it had 1g?...probably not... Can anyone help me to understand this and point out the errors in my logic?\nI mean I kind of understand that object such as planet or start do not have two different ages and what is incorrect is the human definition of the force we call \"time\"...So let me little bit change the question - is it possible that during one periodic duration of certain physical process in the center of the planet the same process happens on the surface many more times? It seems even more confusing definition...sorry about that. But I hope you will understand what is the point of my question.\nThank you in advance", "319" ] ]

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[ [ "This makes some sense. It would definitely kill people. However, the hurricane-force winds part is probably not realistic. A meteor impact that melts half the Earth won't just make air get flung into space: the air will become no longer exist as it dissociates into its constituent atoms, which probably means no vacuum. You can't just \"fling\" air. The rain part doesn't make sense to me, as it's likely that the ratio of water/air is the same (remember, the water vapor on the impact side was dissociated into O2 and H2). Additionally, an impact large enough to turn half the planet to lava would almost surely destroy the whole Earth.", "513" ], [ "The meteor would likely have mostly kinetic energy, and for enough kinetic energy to turn into thermal energy to actually melt half the Earth, the meteor would have to disobey the laws of physics (as a meteor with enough KE to do that would just shatter the Earth and fling the pieces a couple billion miles through the galaxy, instantly destroying the whole thing, and in that case likely won't melt half the Earth, since the Earth won't be able to stop it and turn enough of its KE into heat [Kinetic energy - heat occurs when something bumps into something else and slows down/stops via friction of the normal forces; such a massive/fast meteor wouldn't stop]). If half the Earth actually DID turn into lava, and half the atmosphere id disappear, the planet would become uninhabitable as not enough atmosphere and oxygen would remain to support life (the atmosphere shields us from the hazards of space). In addition, the Earth would probably collapse if half of it turned into a liquid (and likely settled into the core), as a hemisphere is not a viable planet shape. Finally, your \"impending doom\" is going to happen another way: even if the meteor wasn't big/fast enough to melt half the Earth, the shockwave from the impact would race around the Earth, killing everyone it hits as dust from the blast is flung into the air, obscuring the sun. This even happens FAAAAR before half the Earth melts from an impact (which would shatter the Earth anyway). I'd say that people would have time to leave Earth before the shockwave flattens them. A meteor that would do this would probably be about small continent size (Europe).\n(also pretty sure Richter 15 means the Earth explodes)\nP.S. if only a little bit of the Earth around the impact melts, lava falling from the sky seems possible and would be cool.", "208" ], [ "Single-use nuke-propelled mass driver spaceship\nSo this is in the context where space battles are fought by ships that are little more than giant railguns (or other electromagnetic mass drivers), and therefore are fought at extreme ranges with very fast projectiles.\nI have this rather fanciful idea of a single-use spaceship that is essentially a giant tube housing a projectile and a nuke, plus some aiming and targeting systems. While the nuke would cause irreparable damage to the rest of the ship, the idea is that there would be enough time for the detonation to accelerate the projectile (or what remained of it) out of the barrel. The back end of the projectile would presumably have to be made from some ablative material.\nIgnoring things like expense, practicality, targeting etc, I would like to know two things:\n1. Is this even a feasible design?\n2.", "898" ], [ "How would one estimate the velocity of such a projectile, given the projectile mass $M_p$, the ship mass $M_s$ and the yield of the nuke used (which let's say for simplicity is of the range of current nuclear weapons, from 10 kt 100 t to 25 Mt)?\nI am aware of Operation Plumbbob, where they detonated a 300 t nuke underground with a steel lid on the shaft weighing 900 kg. The lid was estimated at moving above 66,000 m/s, which is six times earth escape velocity.\nEDIT: comments have pointed out that some sort of transference of thermal energy to gaseous kinetic energy is needed. Below is my revised picture. Where A stands for ablator (not quite the right word I know, but I can't think of the right one off the top of my head), a mass of material that readily converts to a gas with high kinetic energy (I'm thinking of a slug of ice or solid ammonia, due to the hydrogen content) which then pushes on the projectile. I acknowledge that a megaton nuke is likely to disintegrate the entirety of the ship before any meaningful acceleration can be imparted on the projectile, but suspect that smaller ordnance will be better suited for creating appreciable acceleration on the projectile.", "912" ], [ "How large would a chunk of ice have to be to do lasting harm if it were 'thrown' at Earth?\nI'm working on a story involving life on Europa being upturned dramatically by contact from a probe sent from Earth. I know the chances of life, let alone intelligent life, are pretty slim on Europa, but I'm ignoring that for the sake of the story. The driving force of the story is that a probe that's come from Earth crashes/malfunctions after melting through the ice.The probe sinks to the bottom of a trench and sets off some sort of ecological disaster/collapse, that then has cascading effects on the civilizations living there.", "912" ], [ "In retaliation, a fairly advanced society that has adapted to living in the ice (most of society is less advanced and lives on the sea floor), makes plans to retaliate against the Earth by breaking off a chunk of the crust and hurling it at Earth.\nHow big of a piece of ice would be needed to cause considerable damage to Earth? I'm thinking even if it burns up entirely on impact, if it adds enough water to our atmosphere it could really do some damage, but I'm not really sure what sort of size would make sense? I'm thinking it would need to be as little as possible while still big enough to ensure it does real harm to Earth. It would probably not be going very fast since they don't have engines attached or anything like that, and are purely working with controlling water pressure to push it the way they want (my idea is that they are basically creating their own plumes as initial propulsion out of orbit, and then just riding that momentum or possibly sling-shotting around other celestial bodies to compensate). I'm also just going to assume they have the capacity to calculate the trajectory correctly. So they are reasonably sure it will hit Earth.\nI don't know much about physics, so I'm not sure how much Jupiter's gravity would have an impact, or whether they would be able to use that somehow to slingshot it around at their target and maybe increase it's speed that way, or if it would most likely just never be able to break free of Jupiter's orbit at all without a more powerful propulsion.\nThank you for your help!", "912" ], [ "Ok, gotta quote XKCD on this.\nThis is not how space works:\nThis is:\nGravity in low Earth orbit is almost as strong as gravity on the surface. The Space Station hasn't escaped Earth's gravity at all; it's experiencing about 90% the pull that we feel on the surface.\nTo avoid falling back into the atmosphere, you have to go sideways really, really fast.\nThe reason things in space tend to stay in space, or why things \"float\" in the international space station is because they're going so fast gravity doesn't do anything more than keep those objects moving around the planet: the parabolic trajectory that all falling objects have is so wide that it misses the horizon and comes back around again. Aka, orbit. As the space station and all of its contents are moving at the same speed, and are in constant in free fall, things appear to float: there's no object at rest for things to fall towards; everything is falling and everything is falling at the same speed, all the time.\nIf the ISS had an arm long enough1 and someone put something perfectly still in the center of the space at the far end, that object wouldn't stay there. It would be ever so slightly off the orbital path that the station would either catch up to it, or fall away from it. But it would be very, very slow.", "461" ], [ "And it would happen because the ISS as a whole and the \"floating object\" would be in slightly different, intersecting, orbits.\nStill, why does that gravity not influence satellites and other objects there.\nIt does. It just isn't very strong. Gravity falls off at an inverse-square relationship with distance, just like light does. Except that gravity is way way weaker of a force than electromagnetism is (\"no its not, I can feel the Earth right now!\" Yes, and the Earth is a few trillion-trillion times heavier than you are, how about a table? Can you feel the table's gravity?). The gravitational acceleration towards the sun is on the order of about 0.005m/s2 (and that's still 50 million times greater than the gravitational pull from all the spiders everywhere).\n1. Technically this is already true, just that the effect is so subtle I'm not sure you'd see it in timespans less than \"days.\" In either case, my google fu isn't strong enough to find any videos of such an experiment.", "393" ], [ "The first problem with things in space is that everything moves fast - REALLY fast. For example, when you're near a planet, it's not that gravity is just too weak to pull you in - it's that you're going really fast and are counteracting gravity. To put a number to it, the international space station is traveling at 17,000 MPH.\nWith today's bi-propellant technology, if your shield were in the ISS's orbit and 90% of it was fuel and a missile was coming in behind you, the best you could do is go roughly 6,000 MPH in the other direction. However, you wouldn't actually go 6,000 MPH in the other direction: you would instead start falling back to Earth irritatingly quickly.\nChanging orbits with today's technology is very difficult.\nFurthermore, missiles flying in space are limited in what they can do because they have to carry all their fuel with them and accelerate it as well. This is why ballistic missiles are just ballistic: it's hard to affect changes in your trajectory when you would also have to carry fuel... so they just don't carry fuel and fly. We then lob little things at them to get in their way (EKV: Exoatmospheric Kill Vehicle, which is literally a thing that gets in the way of incoming missiles and runs into them - sound familiar?). These are incredibly expensive and rely heavily on the other target being predictable (in this case, ballistic) so they can minimize fuel usage and cost.\nBut you asked about the future...\nWhy did I say everything above? Because, in the future, if you have interplanetary travel, you must have solved the engine inefficiency problem and made it trivial to produce engines that can just do whatever you want.", "199" ], [ "However, your space ships still have structural issues, so they can only maneuver so quickly (unless, I suppose, the entire hull is lined with small engines so it can perfectly distribute forces). Presumably they may have also created some sort of an inertial damper to let them maneuver more quickly.\nSo let's say the enemy missiles and you both have the technology to make everything maneuver exactly how you want: you still lose because you're still playing defense and defense is always reactionary. If you get your shield right in the way of the missile (because your technology lets you do this effectively), then their missile would just change its course (because their technology also lets them do that). So you figure out how their algorithm works and make your shield predict theirs, so they change theirs. (Note: this is exactly how defense works nowadays too).\nRegardless of your level of technology between now and then, you CAN put a shield (whether it be something already in space or something like EKV) between you and them, but you always have a disadvantage that they will have the same maneuverability abilities and they control the game (again, defense is always reactionary). Plus your [big metallic] shield tends to get destroyed when it gets hit. Plus yours has to be a lot more expensive because it has to be more capable than theirs, so they can always exhaust your resources by just firing lots of them at you.\nA shield like that really isn't any more effective than shooting their missile with your missile - except that your missile doesn't have to happen to be in the right spot [as much] as a shield does.\nThis, by the way, is the genesis of energy weapons.\nSome more related examples\nUsing some numbers from wikipedia...\nThe US's \"Minuteman\" ballistic missiles cost $7 Million and [technically] only take a few people to operate them from a single silo.\nThe US's EKV program is hard to estimate the cost of, but [1] says they cost about $90+ Million each. It costs more than 10 times as much to defend against a single ICBM as it does to launch one. But this isn't the whole story, because to be able to hit a flying thing, you first have to detect the flying thing (with radars, which have limited range and precision) and transmit that information (which can be jammed) and launch against it, so you have the cost of all of those pieces too.\nThis cost differential has always been and probably always will be so.\n[1] - http://mostlymissiledefense.com/2012/07/24/ballistic-missile-defense-how-much-does-a-gbi-interceptor-cost-july-24-2012/", "898" ], [ "These are to the best of my knowledge, the physics of super human strength related to punching (if there is such a thing):\nTo start, when a human being punches, he/she generates force by one of the following:\nTorque - generate centripetal force by swinging the weight of the arm\nLeverage - pushing off the ground slightly and/or against one's own weight or speed\nIn order to generate escape velocity, a human being would not be able to use those means because:\nTorque - The person would have to anchor the centripetal force with their body somehow, so unless they have super-human obesity (or density) or super-human physics, they're not really going to be able to aim using torque.\nLeverage - The person's feet and body would sink into the ground like a bullet and their punch would miss (which would be funny)\nSo basically you need to answer this question: Where does the super force come from and when does it work?\nWhere does it come from?\nIf the force comes ex nihilo or in another way that does not obey the laws of physics, then all bets are off, but then you can have someone get punched into the atmosphere (totally worth suspending physics).\nA Dilemma\nLet EV = <PERSON>'s required to generate escape velocity\nYou are stuck in a catch-22 I like to call the super-cancelling dilemma. If a person can punch with super human force, they can also absorb that amount of force (dissipating it \"into the universe\" or whatever) otherwise they have to break the laws of physics. So the puncher generates EV newtons by creating and simultaneously absorbing that force in his/her own body thus reaching the punchee with the force and transferring it. But here's the catch 22...\nIf BOTH brawlers can absorb that amount of energy, they will not be able to force each other at all (EV - EV = 0), and the fight wouldn't appear to be super human unless a regular object or person got in the way in which case it would be obliterated.\nThe one brawler would need superhuman means, so the ball is back in your court since you got them into this predicament to begin with - now you have to get them out.\nThe fight would look normal if they could absorb exactly the same amount as they could dish out, so if one is slightly stronger than the other but multiplied by hundreds of thousands of Newtons, you're talking about guys flying through the atmosphere again, but that means the one person must be roughly twice as strong as a super-human who can generate EV or more force (2EV - EV).", "621" ], [ "If there is some fluctuation (as there is in a real fight), and that fluctuation can be in the thousands of Newtons, now you're talking about a one punch fight. One guy punches punches with EV + 1 Ns and the other guy absorbs Ev - 1 Ns of force. Well, if they are immutable, now you've got that guy flying with ~2000 Ns in whatever direction he was struck.\nFurther considerations\nIf a punch misses, can that puncher \"reabsorb\" the force even though they absorbed it once already to create it, or will that person go flying in the direction of their swing?\nCan the super-human body absorb at the same ratio as a regular human? if so, it will appear like a normal fight. If not, they'll obliterate one another at the first punch with a only a tiny variation relative to the normal godly force.\nIf there is an angle, deflection, speed, or interference at all, you need to recalculate (in other words, you are facing a myriad of variables)\nSo No, that's not possible based only on the parameters you gave. They would need a way to create and absorb the force at the same time.", "621" ], [ "Anything is possible. This post assumes an Earth-like technology with basically just space-enabled technology. So space-missiles, space-ships, space-mines, etc.\nPossible the most effective way to attack an Alcubierre drive ship is to attack it's end point. The Wikipedia article taking about the Alcubierre drive talks about how to travel at very fast speeds using it, you need to begin the process of that travel as many years before as the destination is lightyears away.\n<PERSON> and <PERSON> comment that <PERSON>'s finding \"does not mean that <PERSON> bubbles, if it were possible to create them, could not be used as a means of superluminal travel. It only means that the actions required to change the metric and create the bubble must be taken beforehand by some observer whose forward light cone contains the entire trajectory of the bubble.\" For example, if one wanted to travel to Deneb (2,600 light years away) and arrive less than 2,600 years in the future according to external clocks, it would be required that someone had already begun work on warping the space from Earth to Deneb at least 2,600 years ago, in which case \"A spaceship appropriately located with respect to the bubble trajectory could then choose to enter the bubble, rather like a passenger catching a passing trolley car, and thus make the superluminal journey.\"\nSo if one knew where the ship would end up, one could set-up an attack on the destination.\nOne could also send a projectile into \"the bubble.\" The missile will then either hit the ship during travel or immediately after it arrives.", "947" ], [ "This would not prevent a ship from arriving, necessarily, but it would likely prevent it from doing anything.\nThis rest of this post assumes that the \"bubble\" of space-time created by the Alcubierre-drive does not push all space away from it, so that only the space \"native\" (i.e. in the bubble when it was created) ever actually enters the bubble. If this is the case, sabotage would be required to attack an Alcubierre-drive ship in-flight.\nThe most effective way to attack/defend a moving Alcubierre-drive ship would be a mine that attached to the ship. An Alcubierre-drive still requires the ship to pass over all the space it travels through, it just does so at a very fast rate.\nAnother way is to send a projectile into path of \"the bubble\" (see quote above) that the ship will be traveling through. It would have to travel along the same route of the ship, but in the opposite direction, because estimation of an <PERSON> ship's position would be difficult to impossible.\nWikipedia says that the above to methods could work, because\nA paper by <PERSON> published in 2002 argues that crew members could not control, steer or stop the ship because the ship could not send signals to the front of the bubble.\nSo even if they knew the mine was in their path while in the bubble, they could do nothing to prevent the inevitable explosion. This might result in the sending out of \"dummy ships\" to blow up mines and missiles before the main, expensive ship comes.", "947" ], [ "Though I believe the other answer is right, in that a planet as small as you're suggesting would be unable to keep an atmosphere (and therefore an ocean) due to lack of gravity, there are ways for a smaller planet to maintain a liquid ocean that supports life:\n\"Owing to a greater depth of hydrothermal circulation from thermal cracking in brittle mantle material, small ocean planets in the Solar System may have the capacity to support ecosystems that are stable on geologic timescales, with greater amounts of bioavailable energy than previously suggested. \" http://online.liebertpub.com/doi/pdf/10.1089/ast.2007.0075\nAssuming there is some sort of force keeping the water on the surface (not to mention the atmosphere), you'd be dealing with several things:\n1. Reduced water pressure - If you've got 1/2 moon gravity, that's about 8% earth gravity, so the water pressure would be reduced as the weight of the water would be less. I'd guess that would mean that creatures would either more easily traverse greater depth ranges or be confined to smaller ranges of pressure than earth creatures. Interestingly, this doesn't mean less dense water, as water is essentially incompressible, and the difference in ocean water density has more to do with temperature and salinity than pressure.\n2. Lack of light - There's a possibility of oceans existing underground or beneath ice on smaller planets, so organisms would likely have to exist either without or with very limited exposure to sunlight. In that case, this probably limits the food chain to very small, efficient organisms.", "258" ], [ "Bacteria, etc. See the above-quoted article for more information on the placement of oceans.\n3. Ice - If your ocean is too deep, the high pressure would turn the water to ice. So watch for that.\n4. Ocean coverage - If the ocean covers the entire planet, some of the precursors to earth-like life would be difficult to come by. On earth, phosphorous is washed by rainwater into oceans from rocks on exposed land, and that's a necessary element for the development of plankton and similar life, so depending on your planet, those might not exist.\n\"It turns out that water worlds may be some of the worst places to look for living things. One study presented at the meeting shows how a planet covered in oceans could be starved of phosphorus, a nutrient without which earthly life cannot thrive. Other work concludes that a planet swamped in even deeper water would be geologically dead, lacking any of the planetary processes that nurture life on Earth.\" https://www.nature.com/news/exoplanet-hunters-rethink-search-for-alien-life-1.23023", "279" ] ]

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[ [ "Holy Spider\nLike other taut psychological thrillers about serial killers, HOLY SPIDER (<PERSON>, 2022) delivers a gut-wrenching twist – that works NOT on plot level, not for what the killer did, but what he incited on people. Too bad it indulges too long on the killer's mind.", "269" ], [ "The problem with films that depict serial killers (especially inspired by true events) is that the story tends to humanize them, finding (or sometimes providing) motivation. HOLY SPIDER does exactly this; there's where it suddenly falls into an exploitative & misogynistic shaft.\nThe fact that it also follows a feminist protagonist gives a hint on what the film tries to actually do; but, in the end, her existence feels like a mere resonance of how the titular killer bizarrely polarized public opinions. (2/4)", "387" ], [ "<PERSON>\nThere's a wonderful visual gag early on that I thought was there just to skewer the vapid world of social media influencers, but in context with the rest of the film it also serves as a reminder to the viewer to keep on your toes.\nI tuned in hoping for another HOST or an UNFRIENDED-like experience, but this only dabbles with that sort of thing and is equally SCREAM and going on from there.\nAnd it's odd that this is yet another horror film I've seen in the very recent past that is playing with the \"killing dogs in genre films\" taboo. Seems to be a recent wave of that and I am glad to see it.", "645" ], [ "Those <PERSON>\nSimplified black and white morality makes for do-gooder main characters that are dull and unsympathetic in their quest to build a sanctuary for migrating geese at any cost (they literally lose their house over it, a decision the <PERSON> matriarch is not involved in). Once again, Disney's attitude to animal rights is ambivalent - or, less generously, hypocritical - and more a mask for the deeper fault line between old fashioned, small town rural life (which is exalted) and city people (who evilly encroach on the former): <PERSON> and his father kill animals to sell their fur which is good, while out of town businessmen hunting geese for sport is wrong...", "295" ], [ "Dog Tags\n\"IF <PERSON> AND HIS ZOMBIES WANNA RIDE OUT, THEY GOTTA MAKE IT TO CHECKPOINT 2!\"\nAwwwwwwww, if only there WERE zombies! Only 20 minutes in and I was looking at my watch. The problem with DOG TAGS is that is suffers from PLATOON-itis. Released a year after (that terrible movie) PLATOON, DOG TAGS takes itself way too seriously. A group of POW's (this is during the Vietnam War) held in tiger cages are rescued by an Army Captain who takes them on a secret mission.\nSoon the men find a cache of gold bars and that ole devil greed takes over. So yes, this is basically TREASURE OF THE SIERRA MADRE in the jungle. But there the similarity with that superb movie ends. Going in, the synopsis led me to believe this would be kinda a KELLY’S HEROES type of movie but it’s not fun at all. The mention of a “cache of gold” brings to mind more of a fun caper movie in the jungle (which this is not). Seriously in need of the editor’s scissors. Also most of the ‘emotional beats’ in the film are not earned so we get the clichéd Vietnam soldier mental breakdowns etc. without any emotional lead-up to them hence they seem even more clichéd and we couldn’t care less.", "645" ], [ "These characters/actors constantly emote different emotional states but they have not been established by the script or the performances so they are basically faceless nonentities whom we also couldn’t care less about.\nThe one ‘<PERSON> in <PERSON>’ character with the monstrously oversized eyeglasses was the only one I hooked onto and . . . well . . . let’s just say don’t get too attached to him. The thing is beautifully shot and the new Vinegar Syndrome print is flawless! The script is way too heavy-handed and melodramatic so I can’t really slam the actors for not being able to do anything with it. If the direction for the film wasn’t going to be ‘fun’ then it’s perfectly acceptable for it to be a serious action flick but there’s precious little action in it and, when there is action, it’s oddly anti-climactic and uninvolving. Director <PERSON> also directed the video nasty NIGHTMARE IN A DAMAGED BRAIN which I own but haven't watched yet. I certainly hope <PERSON> brings more life to that one. Kinda really disappointed with this.", "698" ], [ "Die Hard 2\nFirst rewatch in 15-20 years and I'm surprised by how much I dig this. <PERSON> reputation precedes him and casts a pall over the film, but honestly this is a pretty solid, often great, action film. It goes without saying that it lacks the magic that <PERSON> brought to the first and third installments. But DIE HARD 2 is maybe the greatest example of a sequel cash-in that merely restages everything about the first. Coming off of my first rewatch of HOME ALONE 2 in nearly 30 years, I was shocked by how lifeless and lazy it retraces the formula of the first, much like THE HANGOVER PART II. But DIE HARD 2 really makes the most of copy-pasting it's predecessor into a new, more sprawling locale. It also helps that this one minimizes the returning supporting cast and features a killer new line-up of characters (<PERSON>! <PERSON>! <PERSON>! <PERSON>!).", "995" ], [ "And while the villain of the Colonel is nowhere near as dynamic as either <PERSON>, <PERSON> breathes life into such an underwritten role.\nIt's politics are more fascinating than the film itself and stands as a crucial example of how most films have incoherent ideologies. By the measure of today's woke liberal cultural analysis, this technically qualifies as copaganda, and like most every action film it's values are right-wing conservative. But DIE HARD 2 constantly oscillates between a pro and anti stance on everything it depicts. <PERSON> is an individualist supercop, while the other officers are bureaucratic buffoons. The military is both the villain and savior (only later revealed to be a ruse). But it's pro-authoritarian individualism is also steeped in an anti anti-communism, with it's entire plot revolving around the murderous insanity of American military cold war beliefs (the plot is literally a US army officer murdering countless civilians to protect a CIA-backed right wing fascist who killed communists). But that's not to say that this is pro-communism. Even it's depiction of the media is confusing and mercurial: journalism creates panic, gets in the way of authority, but also can be a force for good? If anything, this might be the perfect text on the confusion and contradictions of American individualism, one that worships systems of authority while conveniently making them the enemy when they challenge the supercop individual.", "952" ], [ "The Banshees of Inisherin\n<PERSON> returns to his roots for an In Bruges reunion with this theatric tragicomedy, THE BANSHEES OF INISHERIN (2022), a folkloric take on male friendship & solitude blunted with human’s vengeful nature — that’s reflective of its Irish Civil War setting.\n<PERSON> Irish Isle setting gives the profound depth his story aims for as <PERSON> & <PERSON> gets into a showdown that doesn’t seem plausible in a glance, but feels real under the skin. That’s what makes it ironically poetic & hilarious at the same time.\nLike some of his best works, THE BANSHEES OF INISHERIN feels like an ever-escalating build-up whose punchline is done after the end-credit rolls. Another masterclass (even though at some points of the story, this reminds me of <PERSON> work instead).", "905" ], [ "Burn After Reading\nOne of the most relentlessly evil comedies I can think of. Honest though. Brutally honest.\nI made too much hash out of delineating the Brothers in my DRIVE AWAY DOLLS blurb, but there there really is something breathless about the PERFECT editing and Cinematography calibration of these comedies.\nThe right lenses give the right weight, the right edits play the right moments.", "862" ], [ "An almost obsessive interest in character behavior punctuated and reveals.\nI have some understanding that DRIVE AWAY DOLLS is attempting to embrace a visual language that is separate from that formal control...I just prefer the violent effectiveness of the formal control. That's just me though. I wish it was present in that movie.", "645" ], [ "The Zone of Interest\nWatching this film was annoying, but part of the discourse surrounding it is even more hollow. There's no such thing as an \"unethical\" way to portray a tragedy, unless a filmmaker CLEARLY misrepresents factual events to deny the harm that was done to the victims, or in order to attack them in any way, shape or form. Cinema is a lie that tells the truth. Whether you see a particular film as \"entertainment\", it is still part of the postmodern desert we inhabit as viewers where we consume ourselves in media through which our history, desires, identity, thoughts are replicated and sold to us as products. These filmmakers want your money and adulation just like anyone else selling you a commodity. So to scoff at Schindler's List in your praise for this film is silly.", "133" ], [ "This movie's supposed metatextuality doesn't make it any less exploitative. If one were to make the argument that this is yet another film in the profitable, Oscar-reaping enterprise that Hollywood has manufactured through its commodification of the Holocaust, it'd be valid.\nNow onto the movie...\nMy gripe with this film is that it doesn't justify its runtime. Once you realize that there's no real plot, the juxtaposition of quotidian nazi life at the forefront and the steady thrum of the Auschwitz massacre in the background gets old pretty quickly. Lots of people have described this movie as a chilling, frightening watch but, I mainly felt boredom, especially past the halfway mark.\nThere's no shortage of great films depicting the banality of evil. The difference is that they do it through much more engaging narratives. One of my all-time favorite films is <PERSON>'s The Conformist. Just like The Zone of Interest, it's a movie showing the banality in which a bureaucrat/duty-bound soldier engages in fascist ideologies but it's more subtle and less monotone in its approach.", "269" ] ]

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[ [ "Customers can’t find open register with the light on\nI’m helping my manager do things around the store, mainly packaways on register 2. I turn on the light for register 1 and leave our bell out. Then I put the “register closed” sign up on register 2 and start scanning the items.\nI suddenly hear a thunk. I look up to find a woman unloading her cart at register 2. I tell her, “Ma’am this register is closed.” And gesture to the closed sign. She asked, “Well which one is open then?” I pointed to register 1 and tell her I can check her out over there.\nI finish some of the packaways and decide while waiting on my manager to bring more I will do some go-backs. I come back up to the front to grab another basket of go-backs to see a man standing at register 3. He says he’s ready to check out.", "866" ], [ "I tell him that register is closed. Again, he asks which one does he need to go to. I tell him register 1. Before I go over there, I double checked that both registers 2 and 3 have their respective “register closed” sign. They do.\nYet again I step away from the registers and come back to find two women at register 3. I have to repeat myself and tell them register 3 is closed. They both start looking around like lost children and ask, “Well, then which one do we go to? Which one is open?” I tell them I can check them both out on register 1. Ya know, the one with the light on.\nWhat was it with these customers? Had they never been in a store with lights above the register? Can they not read a very clear sign that says “register closed”? Don’t they know the light being on means the register is open and if it’s off the register is closed?\nIt’s not that hard to look up!!", "866" ], [ "She already yelled at me\nTwo stories in one day! This one just happened so I’m still pretty annoyed about it. standard mobile disclaimer\nIf you didn’t see my last post, I work at blue Swedish furniture. Most of the items you pick up yourself in our warehouse, but some things live behind our safety gates so we can run forklifts during the day. We only give out locations to customers if they can get the item on their own. Otherwise, the tag will direct them to see a coworker.\nSo a woman comes up to me to get something from behind the gates.\nCustomer: I need something from bin 58 but there’s a gate blocking it off.\nMe: Can I ask how you have that location?\nC: Uhhhhhh because the lady told me that’s where it is. pulls up a picture of our scanners with the info\nMe: Oh. She shouldn’t have done that because you can’t go back there.", "931" ], [ "What’s the article number?\nWoman reads me the number so I can put in the order for her while her husband walks up. I couldn’t hear his question but she tells him that I yelled at her. I ignore that comment in the interest of not getting into an argument. I printed off the order form and explain, as pleasantly as I can, how to pay for their item and pick it up.\nC: starting to walk away Okay. Sorry YOUR coworker did something wrong, NOT me.\nMe: Well, yeah. That’s why I asked. So I would know who to talk to.\nI’m not sure if she was just having a bad day or if she’s always that unpleasant, but I bet she and her husband get into a lot of fights.", "536" ], [ "Customers cannot understand a subtotal so I had to break it down to them like they were 5 year olds.\nCustomer buys about 10 things. 3 of the items were 6.99–2 with tax and 1 without tax. 6.99 x 2 = 13.98\nCustomer’s daughter comes back in to tell me that I overcharged them. So I asked to see the receipt knowing I did not. I asked her where was the mistake and she said that I charged her 13.98 and they got nothing for that price.\nMe: You got 2 things for 6.99 so that’s the subtotal of the 2 items.\nDaughter: Yeah but then you charged us 6.99 again. We only got 2 things you’re saying.\nMe: Yes you did, you got that other thing and that has not tax.", "468" ], [ "That’s why it’s separate.\n<PERSON>: Could you do the sale again? It’s not right.\nSo I do it again, as I’m able to void out sales, and it came out correctly. She begins to shake her head and her mother comes in and pulls out the calculator on her phone and they start going at it again.\nMother and daughter: YOU SEE?!?! You over charged us. We got nothing for 13.98!!!!!!\nI began to explain it and point at their things and show them which ones were 6.99 and they still could not understand that 6.99 twice equals 13.98… So then the daughter gets loud and says, “Well you don’t have to give us an attitude!”\nAnd I said, “Well, I shouldn’t have to explain things with apples and bananas so that you could figure out that 6.99 x 2 equals 13.98. 1 banana plus 1 banana equals 2 bananas.”\nIn disgust, they look at me and tell me that it was wrong. The amount they got on their calculator was not equalling the amount on the receipt because they forgot about taxes. I just don’t know how these morons get through life.", "468" ], [ "Customers act suspicious and get mad\nThe store I work at closes at 8:00, and two men came in around the time of 7:45 to 7:50.\nThe assistant manager and I were both up at the register when they came in and we assumed that they were just normal customers which they did turn out to be.\nWhen most people come in they can tell the difference between where the display or the store ends and where the warehouse starts at and these two guys marched right back to the warehouse. They did not look around or anything. They literally marched back to the warehouse like they were on a mission.\nNow the guy who currently works in the warehouse has had some issues with drugs in the past and I admit I was worried that these two guys were going back there to have a confrontation with him.\nThe assistant manager even admitted that he felt the same way.\nWe both thought that the best case scenario was they were just late night truck drivers dropping something off, but the assistant manager did admit that even he thought they were going to confront <PERSON> about something because of how they just power walked to the back.\nCustomers are not supposed to be walking into the back. They can be back there if someone who works in the store leads them back there and knows about it, but they cannot just walk into the back.\n<PERSON> and I went to the back to check out what was going on and for some reason even though we both went to the back to see what these two guys wanted they only expressed a problem with me.\nOne of the guys literally started freaking out and saying that I was tweaking and he starts saying stuff to me like how I don't have to worry because he's not there to steal anything.\nI'm just standing there like dude I didn't even say anything about you stealing.", "156" ], [ "It's my job to come back here and see why you just came into the back of our store.\nWhen I ask what you're doing it's not an accusation. It's genuinely a question. I'm asking what are you doing?\nHe just keeps it up though. He just starts this whole tirade about how he doesn't want to be around me because I'm tweaking.\nI just it honestly really ticked me off.", "750" ], [ "Customer Always Right - NOT!!!\n“The customer is always right” is a nice sentiment, but there is nothing right about people who steal from us, lie to us, or abuse us!!!!!\nI had a real PSYCHO a few days ago! Our store is very busy; often I’m not able to get off the register for long periods. This woman came up, had a bunch of stuff in her cart, and I proceeded to scan her order, being polite and pleasant to her all along. I was nearly finished when she asked if we kept baby formula behind the counter. I told her no and which aisle is was on. I looked down to finish bagging the last of her items, and when I looked up again, she was nowhere to be found. Bear in mind we had people waiting in line behind her. This entitled <PERSON> believed that everybody waiting behind her should have to wait for her to go get her baby formula! I called out, “Ma’am, we have people waiting behind you.” She eventually came back with a container of baby formula, which I proceeded to scan and bag.", "931" ], [ "As I did so, she started telling me that I needed to work on my customer service. I kept on trying to be nice to her, in spite of the fact that she was obviously unhappy that I had reminded her that people were waiting in line behind her. Things just escalated from there, and she turned downright abusive! She called me a few unprintable names, including a c_nt, and then began THROWING the bags of things at me!!!! I mean, this grown woman was having a tantrum just like a toddler!!!!\nWe still aren’t sure we won’t get some repercussions from corporate about this - IF she actually had the nerve to contact them after the way she behaved! She should be embarrassed at her own behavior, but chances are, she’s not. (Also, she could have asked about the baby formula much sooner and would have had plenty of time to go get it while I kept scanning her order, but no, she waited till I had almost finished!)\nYou know, I really feel sorry for her. If she thinks it’s okay to act like that out in public and have a two-year-old tantrum, something is seriously wrong with her!!!!\nNeedless to say, I won’t bother pointing out the fact that there are people waiting ever again! If they aren’t considerate enough to care about those in line behind them, nothing anybody says or does will make them care. By the way, MOST people, if they’ve realized at the last minute that they need something else and there are people waiting behind them, will go ahead and pay for what they already have, put it in the car, and then come back in for whatever they need. They do NOT think they deserve to make others wait for them to finish shopping!", "931" ], [ "I love dealing with rude customers\nKinda not being sarcastic. I use my best customer service skills. I'm so slow and patient with them. I make sure I'm doing everything perfectly.\nHad a lady today being rude and she was almost on top of the 1st register behind another customer. I get called for backup and I take her all the way back to register 7.", "931" ], [ "So she had to walk back. Then she had a return that was left at the first register. No problem, let me just walk back and grab it ofc taking my time.\nOh this return is past the time limit? We need to put it on a gift card even though you're buying other stuff and I could do it all at once but I'll do it in 2 different transactions. Oh wait this register doesn't have the cards so I'll have to go to another register and grab some.\nThe whole time this lady was complaining, \"Oh you're just wasting a gift card since in going to use it right away\", \"why cant you give me the number to look up this transaction up in my email\"(mind you, she didnt ask about it, just starting swinging). I just said \"Okay\" or didn't answer.\nShe waa rude to me on the sales floor when we didnt have a lot of a certain product in stock and she accused another person who was coming for backup of shopping when she was checking which register we were assigned to.\nSome people just want to be miserable.", "931" ], [ "All of this happened today.\n40 min into my shift a customer wanted to argue with me about our return policy. It's store credit for anything that was alive that is now passed away (its a pet store - fish). Not a cash refund.\nI explain this and I'm met with\n'No, I want a cash refund' -We don't do cash refunds. Store credit only.\n'they gave me cash the last time' -No they didn't. Not for a kosher return. Stop lying to me to get your way.\n'Call a manager' -Okay, but he's going to tell me to repeat myself to you.\n'When did that policy change?' -Lady, It's never changed. In fact, it's literally plastered on the wall behind me in a faded sign from 1980.\n'Well that's not your policy...' -Ma'am, Yes it is, and any employee who handed you cash in the past for a return wasn't doing their job appropriately.\n'Yes, they were doing their job because they gave me my money back' - If breaking store policy is doing a good job than we'd all be in trouble.", "245" ], [ "The lack of logic.\nThen I have another one. She has a bunny and wants to talk to me, the cashier, about bunny health. Leaning on the register, asking all the questions in the world. The line behind her starts to get longer and she's oblivious.\nI see one customer slap down some plants, get out of line and walk towards the door. I see another group of customers behind her do the same. The customer who was holding them all up starts to cause a scene about the other people causing a scene.\nThe couple who walked out yells back inside the store to the oblivious one 'You know they have employees in the back who you're supposed to get help from! You're not supposed to walk up here to ask all your questions!' and she was fucking 100% on the spot correct.\n'Oh wow, I didn't realize some people are so rude'.\nSeriously lady...YOU'RE the idiot here. I'm not a quizlet or a vet - I'm supposed to be ringing those people out.\nI'm really interested in medical coding. Bought some textbooks I'm going to study...Can't wait to walk out of this store and never come back.", "931" ], [ "Customer started crying in the dressing room and wouldn’t leave the store…\nThis is my first week working retail as I’m normally a teaching assistant but needed extra income for the summer.\nIt was Saturday and so we were pretty busy. A woman came in with 5 or 6 dresses to try on that, in all honesty, I could tell were not going to fit. After about 15 minutes I went back to check on her because a line had formed for the 4 dressing rooms we had and she wasn’t out yet. I asked her if everything was alright, she kind of shakily said yes, so I went away.\nAnother 10 minutes, I check again.\n“Still doing okay?” A bit more firm now, she responds. “Yes, I’m fine!”.\nI stood nearby to keep an eye on things and kept hearing sniffles. Another 5 minutes went by, I knocked on the door this time.\n“Ma’am, are you almost done? There are other customers waiting for the dressing rooms.”\nShe stuck her head out the door and I could see then for sure she had been crying. She handed me all the dresses.\n“Put these back.” And then she closed the door.\nI kinda stood there confused for a minute and responded through the door again.\n“Are you alright?”\n“…”\n“I’ll put these back and give you a minute, but I’m sorry, we really do need the dressing room.”\nAnother 15 minutes went by.", "931" ], [ "By now she’s been in there a total of 45 minutes crying. The manager wasnt there that day and all my coworkers were less than helpful, so this was all on me and I had no idea what to do. I knocked on the door one more time, a bit forcefully.\n“Ma’am. You’ve been in there for a very long time and while I can see you’re having a bad day, we can’t let you just stay in there. You don’t have any clothes in there even. I can give you another 5 minutes but if you won’t leave by then I need to call security.”\nThe door FLEW OPEN and this woman, red faced and teary eyed scream-whispered at me about how if the store wasn’t going to carry any “normal” sizes then the least they could do was give her space when it made her feel bad! She went on a mini rant about unfair sizing and catering to normal sized people and the beauty industry.\nI do sympathize, and honestly our sizes do run a bit small, but they still fit the normal “straight size” range of 0-14. I felt bad because I know how frustrating that can be, but also I didn’t need that anger directed at me.\nI just looked at her and told her again “You need to leave now.” Thankfully she did, but she flipped me off at the door.\nWeird situation that has really put me off for the rest of the week. I’m sure it’s pretty tame compared to a lot of the stuff in here, but this is in fact my first rodeo and I did not enjoy it.\n——\nETA: This is a repost since my last one was removed! Fixed the problem.", "430" ] ]

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[ [ "This will become a little off-topic, but the topic itself is, too.\nThe camera's focal length is 24mm, which I understand to be relatively similar to the human eye\nFocal length is only one of two parameters determining the field of view. In fact, for an object at given distance, it determines the size of its projection on a screen. For a simple, thin lens, sizes and distances (from the lens axis / lens) are given by\n$$\\frac{\\text{object size}}{\\text{object distance}}=\\tan\\alpha=\\frac{\\text{projection size}}{\\text{projection distance}}$$\nFor objects far, far away, one can approximate $\\text{projection distance}\\approx\\text{focal length}$.\nSo, the projection of the moon by a 24mm lens is just 0.22mm in diameter!\nThe second important parameter is the size of the image generating area. An expensive DSLR camera has an image sensor of 36x24mm, the cheaper ones (APS-C size sensor) 22x15mm, a mobile phone may be 5x4mm or smaller. Only on the phone sensor, the moon starts to become more than a small dot compared to the entire image, and due to all that megapixels, the image also has some details when zooming in.\nAlso the human eye has a high resolution, so you can see the details, but the brain also plays some tricks to let the moon appear larger than it is.\nOne can assume that the virtual image sensor of a 3D software also is in the order of 36mm, see next paragraph.", "586" ], [ "But the moon is not only tiny on the image, since a FullHD image has just 2 megapixels, there aren't even any details visible when zooming in.\nA 24mm lens on a 36x22mm sensor gives a horizontal field of view of 73°, which is about the value of the human eye, as stated in the comments. But this value does not only determine the field of view, it also determines how \"3D\" the image is. A photo taken from larger distance with high focal length appears flat compared to low distance and low focal length. And images taken at very low focal distance feel like taken by a mouse. Now, those guys using 55\" TVs as monitor on their desk would like to reduce the focal distance, because, well, they are like mice in front of that screen. So, this is the reason why many games allow to adjust this parameter.", "896" ], [ "That photograph is a composite of two images taken with different exposure times.\nTo be correct we'd have to say that the exposure of the two photographs is different, i.e. the outer photo was created by absorbing more light. In this case we can assume that the focal ratio (derived from Hubble's lens aperture) and the luminance of the scene (how much light is travelling in the lens' direction) are identical for both photographs, which leaves only the exposure time as a free variable when it comes to determining exposure.\nThis is necessary because we're photographing objects with very different brightness. For Pluto to show up a relatively short exposure time is required, but its moons reflect much less light and would need a longer exposure time to visible. As long as the sensor is exposed, Pluto would continue to increase in brightness to the point that it becomes washed out. Objects that are significantly brighter become over-exposed resulting in a loss of detail and fidelity, known as blown-out highlights in photography. In our case Pluto would turn into a solid white dot compared to the more detailed picture that is now possible.", "758" ], [ "You can draw a parallel with false color images rendered from infrared: this composite is not what the human eye would see if it was capable of picking up this level of light and detail.\nIn another Hubble image, NASA explained the reason why composite imaging is used:\nThis is a composite image because a single exposure of the stellar background, comet Siding Spring, and Mars would be problematic. Mars actually is 10,000 times brighter than the comet, so it could not be properly exposed to show detail in the Red Planet. The comet and Mars also were moving with respect to each other and could not be imaged simultaneously in one exposure without one of the objects being motion blurred. Hubble had to be programmed to track on the comet and Mars separately in two different observations.\nSource: Hubble Sees Comet Next to Mars\nVery long exposure times are often necessary since relatively little light is coming our way from distant planets and stars. As the Hubble website explains for its Deep Fields images:\nHubble has made a series of very deep observations taken in very dark parts of the sky. Like using a long exposure on a digital camera, these long exposure shots (up to several weeks) reveal very faint details that are not normally visible in shorter exposures.\nSource: \"What are the Hubble Deep Fields?\", Spacetelescope.org FAQ.\nWikipedia summarises a paper by <PERSON> and the HDF team, \"The Hubble Deep Field: Observations, Data Reduction, and Galaxy Photometry\" as follows:\nBetween December 18 and December 28, 1995—during which time Hubble orbited the Earth about 150 times—342 images of the target area in the chosen filters were taken. The total exposure times at each wavelength were 42.7 hours (300 nm), 33.5 hours (450 nm), 30.3 hours (606 nm) and 34.3 hours (814 nm), divided into 342 individual exposures to prevent significant damage to individual images by cosmic rays, which cause bright streaks to appear when they strike CCD detectors. A further 10 Hubble orbits were used to make short exposures of flanking fields to aid follow-up observations by other instruments.\nSource: Hubble Deep Field, Wikipedia, retrieved 2014-12-09", "758" ], [ "How to photograph Saturn\nI have been given an old telescope (Newtonian, 910mm) and I got a mount for my DSLR and I'm trying to take some pictures of various objects. In particular, I'm trying to photograph Saturn, but I'm having some difficulty getting a decent image. This is about the best I could get:\nThis was taken with a 2x Barlow T-mounted to my DSLR via an extender, basically a metal tube about 2.5 inches long (without both of these my focuser doesn't have enough range unless I drop an eyepiece into the extender, then the Barlow isn't needed). I shot on a one second delay to allow any vibration from the shutter opening to subside. Focus was manual via the telescope itself, and was at the sharpest spot I could find. I had been outside for some time and temperature difference between the air and the scope were minimal.\nI'm wondering if there are any pointers or maybe an idea of what I might be doing wrong.", "758" ], [ "This above exposure was 1/10s, ISO 5000. I thought maybe the ISO setting was too high, but the image below was at 1/15s, ISO 2000 and doesn't look any better:\nThere seems to be some chromatic effect, in the first image the upper-left side has a blue tint which works its way across the spectrum to red in the lower-left.\nThe scope was collimated using the star method as I don't have a tool, so it may not be perfect but it's pretty good.\nThe thing that I am really puzzled about is that through the lens the image did not look like either of these pictures. Although a bit small, I could make out the variations in color and some of the texture of the planet and its rings. The image was sharp and there were no chromatic aberations. Aside from having the rough shape of Saturn, the pictures have almost no resemblance to what I saw right before I took the pictures. (This is looking directly through the lens of the camera through the optical viewfinder, live preview also looks ok, but the screen resolution isn't as great.)", "758" ], [ "The lenses which make up the scope will always reflect some light (~0.5%).\nAll optical materials will reflect some amount of light. This is due to the fact that light travels slower inside of the medium than it does in the surrounding air. The slowing down of a wave always results in some reflection; in optics it is governed by the Fresnel equations, but there are analogous reflections in electronic circuits and waves traveling along a string.\nThere are techniques which use destructive interference between multiple reflections at successive boundaries to give optical devices very, very low reflectivities at a specific wavelength. However, for a rifle scope it is important that the reflectivity be low for the entire visible range. Browsing the coatings offered by Edmunds shows that a good coating can reduce the reflectivity down to about 0.5% across the entire visible range.\nThe lens tube cannot simply be extended without degrading the image quality.\nThere is a lot of information on hoods on photography.SE (here and here for instance), but I'll briefly summarize. The length of the hood is limited by the field of view. Essentially, light from every point in the scene needs to be able to reach every part of the front lens.", "538" ], [ "I.E. it is not enough for the light to reach only the center portion of the lens.\nFor this reason, simply extending the tube beyond the front of the objective lens is not an option because light from the edge of the scene would not reach the edge of the lens. The hood must have a radius which is larger than the objective lens itself before it can be extended; otherwise you are throwing away light from part of the scene. Pay attention next time you see a professional photographer (or enthused amateur) with a lens hood and you will immediately notice this. The most effective hood is actually a cone with an angle set by the field of view which will start to make the scope very large and bulky.\nThe reflection is less noticeable than you might imagine.\nSince the objective lens of the scope is a focusing lens, the outer surface is curved like a diverging mirror. This means that the light redirected toward the enemy sniper is significantly less intense than it would be for a flat mirror. For a flat mirror the entire surface of the mirror redirects light from the sun to the enemy's eye, while a curved mirror has a much smaller area which gives the correct angle between the enemy's eye and the sun.", "538" ], [ "Precise meaning of collimation/alignment of a binocular\nMy question is about what exactly is meant by a binocular being collimated/aligned. I'm familiar with optics in general, but not with the nitty gritty of binocular design.\nThere are various resources online (here is one example) that describe different methods to align binoculars (sometimes also called collimation but I will avoid this term here to prevent confusion), usually without explaining in detail what alignment means. One might think (perhaps naively) that alignment means making it so that the optical axes of the left and right \"telescopes\" extending beyond the objectives are parallel, i.e. both \"telescopes\" are pointing in the same direction. But I'm not sure if this is the case for reasons I'm about to describe.\nI currently have two binoculars, one is a Celestron 8x56 and the other is a new Oberwerk LW 12x60. With both binoculars, the fields of view (FoV) I get through the left and right \"telescopes\" of the binocular are considerably different: namely there is a horizontal shift. This is not due to parallax because even when an object at infinity (e.g. a star) is at the center of the left eye FoV, it is to the left of the center of the right eye FoV.", "758" ], [ "This tells me that the optical axes of the left and right \"telescopes\" extending beyond the objectives are not exactly parallel, i.e. they are pointing in slightly different directions. Am I right? If so, why aren't the optical axes parallel?\nVarious resources on aligning binoculars say such a shift is \"normal\", but without explaining exactly how much shift is \"normal\" and why (I understand the brain is capable of merging the two images even in the presence of an undesirable shift). But why should there be such a shift at all in a perfectly aligned binocular? Is this always an unintentional consequence of the left and right components becoming misaligned over time, or is the non-zero angle between the optical axes a design parameter? The former would mean both of my binoculars (including the new Oberwerk) are significantly misaligned, while the latter possibility I also find unlikely because when looking at an object at infinity without a binocular, the \"optical axes\" of the eyes (each intersecting the retina at the fovea) should be parallel.\nAny insights are appreciated.\nEdit: Regarding how much of a \"shift\" I'm talking about: I have not tried to quantify it yet. I will try to estimate the shift when I have time later. But it is small enough not to cause \"double vision\" when looking at a star, and large enough that it is very easily seen by closing one eye and then the other when looking at a star. I thought this horizontal divergence of the optical axes might be intentional since I see it with both of my binoculars (with no appreciable vertical divergence), and at least one manufacturer (Oberwerk) makes a big deal of how well they collimate their binoculars. But I'm not sure.", "758" ], [ "The totality of light that fills space, even in a geometrical optics approximation, is a complicated light field that is difficult to visualize in full. Each point in space generally receives rays of various colors and from various directions simultaneously. We do not perceive or measure the light field unless something is placed in it to absorb or scatter the light -- ultimately our retinas.\nMany surfaces that interact with light are not strongly sensitive to the direction from which it comes. These include matte (diffuse) screens, photographic film/CCDs, and our retinas (but not mirrors). At each point, the response effectively integrates rays over all incoming directions.\nAt a random point in space, this is likely to work out to a general ambient illumination that does not select for where the light originally came from -- i.e., does not form an image. Forming an image requires a specially manipulated light field (often, as in the eye, using a lens) that counteracts the tendency of bundles of rays to diverge and mix.\nNow, we can clarify the pinhole situation (diagram inspired by seeking to clarify and correct pwf's answer). A pinhole is designed to form an image on a surface (screen or film) without the need for a lens.", "530" ], [ "This is accomplished by restricting the light field without bending any rays. The image is, of course, inverted (relative to the actual objects).\nWhen your eye is looking directly through the pinhole, an image will form on the retina. The lens of the eye has makes relatively little difference in this case, assuming your focus is relaxed enough to look \"through\" the hole rather than \"at\" the hole. The image on the retina is inverted (relative to the actual objects) just as if you were looking at the same scene without any barrier. Therefore, your perceived view of the objects is non-inverted.\nIf you place a screen (not shown in diagram) facing the pinhole, it will show the inverted image. However, this is visually observed via diffusely reflected/transmitted light from the screen that forms its own light field. This light field is inverted relative to the original light field because its source (the pattern on the screen) is inverted relative to the original objects.\nYou perceive what is on the screen when your eye forms an image from this new light field. Therefore, the image of the screen that is formed on your retina is non-inverted (relative to the actual objects), and perceived as inverted.", "530" ], [ "Cheap and accurate angle measurement for PID feedback control\nI'm working on a PID-controlled barn door tracker mount for astrophotography in an isosceles configuration:\nFor those not familiar, the purpose of the barn door tracker is to compensate for the rotation of the earth during astrophotography. The axis of rotation of the tracker is aligned with Polaris, and the upper arm of the tracker rotates about that axis once in a sidereal day (approximately once per 24 hours). So the movement is very slow, but not unnoticeable.\nA lot of people use a curved bolt configuration to make it so you can simply set the motor at a constant rate of rotation and get a constant angular rate, but I don't like the inability to address sources of error with that configuration. Instead, I would like to use PID control.\nMy motivation is both for a fun project, but also to create something that is more accurate than a curved-bolt configuration and cheaper than entry-level equatorial mounts. Ignoring the cost of microcontrollers, I'm aiming to have the entire setup cost less than $120. If I can't make it for that cheap, then I might as well get a professionally-made mount.\nI've been looking at different methods of getting angular feedback, and I'm most interested in two: encoder and accelerometer. An encoder would be fairly easy to implement in code and resolution could be influenced by hardware.", "229" ], [ "However, a quadrature encoder would use up almost half of my budget, and I'm skeptical of using just an incremental encoder, in case my PID tuning is off. Not to mention I would have to implement an additional way to home the tracker.\nAfter playing around with an app that lets me see the sensor outputs on my smartphone, I wondered whether an accelerometer might be a cheap alternative. There are plenty of sensors that are USB or Arduino-compatible out of the box. My biggest concern, however, is that of accuracy. The angular change is only about half a degree per minute, but in the isosceles configuration, the rate of the motor must change accurately to maintain a constant angular speed. I need something that will be able to capture that slow of a change accurately.\nI'm not a controls or robotics guy, so for all I know I'm completely missing some other component that might fit the bill. Any thoughts on the advantages or disadvantages of the sensors I've mentioned? Or places I might look for more affordable types of sensors?", "288" ], [ "What can you tell from a picture of some stars?\nAt the very least, you need a recognisable asterism\nIf the exposure is too low or the light pollution too high to identify unambiguously an asterism of three or more stars, you're simply not going to be able to tell much from the photo.\nAn asterism on its own can only tell you where the picture wasn't shot.\nIf a star in a picture has a declination of $60^o$, you can rule out all shooting locations south of $-30^o$ latitude. A star like Polaris can only really be seen in the northern hemisphere, while Sirius can be seen everywhere south of Svalbard.\nAn asterism plus the horizon is sufficient for determining latitude\nIf the edge of land in the picture is sufficiently close to being the actual horizon (and not a range of mountains) and it is present alongside a recognisable asterism in the photo, you can calculate the latitude. This is true for any magnification, as you can use the angular distance between stars (a known quantity) to measure the angle to the horizon. I can't think of any special locations where you wouldn't be able to determine the latitude from the stars + horizon.\nI haven't really done the math for how accurately one would be able to determine the latitude, but here are some considerations: There are two sources of error, the position of the stars and the position of the horizon. The star image may spread out over several pixels, and if the picture was shot through a standard camera and not a telescope, there would be an error, at a wild guess, of around ten arcminutes.", "758" ], [ "The horizon can appear lower than $0^o$ depending on your distance above ground, but the effect is small. Looking out from Mt Everest, the horizon will appear a twentieth of a degree lower down than it ought to. I believe the horizon's exact position can also be obscured through atmospheric refraction.\nAll in all, the error in the angle between an identified star and the horizon equals the error in latitude of your identified position. For a 10 arcminute error, that corresponds to ten arcminutes of latitude, which is about 18 kilometres.\nFor longitude, you need global, not local time\nIf you only have local time, the photo could have been taken anywhere along that latitude. If you have some form of global time (UTC, GMT, whatever, it doesn't matter which as long as you know what it is) you can figure out longitude from there.", "204" ] ]

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[ [ "<PERSON>, the creator of Batman, found inspiration in several sources, and it seems that he did not specifically set out to create a human, crime-fighting analogue to <PERSON>. However, one of his influences was <PERSON>.\n<PERSON>’s initial idea was a superhero with bird wings. From Batman: The Complete History by <PERSON>, page 18:\nWhen <PERSON> sat down at his drawing board in the Bronx, he immediately sketched in a figure similar to <PERSON>’s... Then he ... began experimenting with variations in the costume. He tried a pair of bird wings, perhaps inspired by an alien race in one of his favorite strips, <PERSON> <PERSON>.\nHawkmen from <PERSON>\n<PERSON>\nFrom Batman: The Complete History, page 144 (emphasis mine):\nThere has always been a subliminal association between vampires and <PERSON>; this was a hero who was designed to frighten his foes, and <PERSON> admitted that one of his inspirations was <PERSON> performance in the 1931 movie Dracula.\nThe Bat\nAlso, as <PERSON> points out in his answer, another inspiration for <PERSON> was the 1930 film The Bat Whispers.", "167" ], [ "That film is about a criminal called The Bat, who turns out to be an ordinary man, but the other characters in the story suspect at times that the <PERSON> is supernatural.\nI wasn’t able to find a copy of The Bat Whispers online, but it was based on a 1920 play, The Bat, which was novelized in 1926. The novelization makes no mention of vampires or <PERSON>, but the characters do suggest that the <PERSON> is supernatural. A batlike, supernatural enemy lurking in the dark is reminiscent of vampires in much the same way that <PERSON> is, but this isn’t a direct reference to vampires. It does fit in nicely with <PERSON>’s stated desire to terrify superstitious criminals, however.\n<PERSON> ornithopter\nAs mentioned in <PERSON> answer, another of <PERSON>’s inspirations was an ornithopter designed by <PERSON>. Someone flying this machine would be a sort of mechanical bat-man, with no particular association with vampires.\nFrom Batman: The Complete History, pages 18 and 20:\nFrom his boyhood reading, he [<PERSON>] recalled the ornithopter, a flying machine designed by <PERSON>. This device was essentially a glider, with wings built like those of a bat.\nPicture from Wikipedia\nOther influences\n<PERSON> answer and Batman: The Complete History mention other inspirations including Zorro, but the influences above were the closest batlike or vampiric influences I could find for Batman.", "167" ], [ "In the original books, no, a sister is never mentioned. However, in a very roundabout way, the seeds of her origin are contained within the books.\nThe only sibling mentioned in <PERSON>'s books is <PERSON>'s brother <PERSON>, who appears in \"The Adventure of the Greek Interpreter\", \"The Final Problem\", and \"The Adventure of the Bruce-Partington Plans\" and is mentioned in \"The Adventure of the Empty House\". In the books he appears as much the same character depicted in the TV series - a high up government official who is involved in many aspects of government policy.\nThe closest mention to '<PERSON>' (the sister's name in the TV show) comes in the story \"His Last Bow\", published in 1917 (set in 1914). The story ends with <PERSON>' addressing his assistant Doctor <PERSON> on the eve of the First World War:\n\"There's an east wind coming, <PERSON>.\"\n\"I think not, <PERSON>. It is very warm.\"\n\"Good old <PERSON>! You are the one fixed point in a changing age. There's an east wind coming all the same, such a wind as never blew on England yet. It will be cold and bitter, <PERSON>, and a good many of us may wither before its blast.", "247" ], [ "But it's God's own wind none the less, and a cleaner, better, stronger land will lie in the sunshine when the storm has cleared.\"\nIn Greek mythology, <PERSON> was the god of the east wind, one of the four directional Anemoi, or Wind-Gods. In the books, the 'east wind' was used as a metaphor for the destruction that WWI would bring. It seems that in the TV show, it was personified as '<PERSON>', another east wind bringing destruction of a similar nature.\nThe connection is also alluded to in the closing scenes of 'The Lying Detective' (4x02), where <PERSON> begins to realise that his therapist is not who she seems:\nJ: Who are you?\nE: Isn't it obvious? Haven't you guessed? I'm <PERSON>.\nJ: <PERSON>?\nE: Silly name, isn't it? Greek. Means \"the east wind\". My parents loved silly names, like <PERSON>... or <PERSON>... or <PERSON>.\nE: Oh, look at him. Didn't it ever occur to you, not even once, that <PERSON>'s secret brother might just be <PERSON>'s secret sister?", "660" ], [ "Edited to add in the correct info about the first minority super hero.\nIn DC Comics All-Star Western #117 published in February 1961 the first Native American superhero appeared with the horrible name of Super-Chief.\nA summary of his origin can be found here The Crowning of Super-Chief. Super-Chief appeared in the next two issues and then the series was cancelled.\nMarvel introduced the Black Panther in Fantastic Four #52 in July of 1966.\nHowever, it may not be accurate to say that the character is a minority. <PERSON> is in reality <PERSON>, King of the fictional African country of Wakanda. Although he would be seen as a minority in the United States due to being African he is not part of teh African-American minority in the US.\nDC introduced its first minority superhero the Black Racer in June 1971 in New Gods #3.\nThe Black Racer may not really qualify as a superhero though. The character is part of <PERSON> Fourth World series. The corporeal form of the Black Racer is an African-American Vietnam veteran named <PERSON>.", "167" ], [ "When <PERSON> brought the war of the New Gods of New Genesis and Apokolips to Earth the Source, a sort of God like universal shared consciousness, contacted <PERSON> and turned him into the deity known as the Black Racer. The Black Racer's job is to collect the souls of the New Gods when they die and deliver them to Hadis the Fourth World version of Hades.\nSo where does that leave us if we ignore these two entries. Marvel's next African-American hero was the <PERSON> introduced in Captain america #117 in September 1969.\nThe <PERSON> is the alter ego of <PERSON>. He was trained by <PERSON> after he fought beside him against a group of former Nazis working with the Red Skull. The Falcon did have one definite first in that the word 'Black\" wasn't part of his superhero name.\nDC's next black superhero appeared in Green Lantern #87 published in December 1971.\nThis is the previously noted <PERSON>. Artist <PERSON> resisted the powers that be who wanted to name the character <PERSON>.\nHowever, all that being said these were not the first non-stereotyped or non-racist African-American characters in comics. These were just the first superheroes.", "167" ], [ "The question required that we reference instances of time travel that are not simply \"a misperception of the amount of time that passed\". One could argue that King <PERSON>'s story in the Mahabharata was such a misperception. Others might argue differently, but here's an alternative answer for the first group:\nAlthough not 2000 years old, there are examples from before The Time Machine (1895) that involve actually jumping from one time to another.\nA Connecticut Yankee in King Arthur's Court (1889) by <PERSON>\nThis is the first one I thought of. Partial summary from Wikipedia:\nIn the book, a Yankee engineer from Connecticut is accidentally transported back in time to the court of <PERSON>, where he fools the inhabitants of that time into thinking he is a magician—and soon uses his knowledge of modern technology to become a \"magician\" in earnest, stunning the English of the Early Middle Ages with such feats as demolitions, fireworks and the shoring up of a holy well.\nThis is very clearly time travel. The Yankee was in modern times, then he was in the past.\nThe Chronic Argonauts (1888) by <PERSON>\nThis is a short story precursor to the Time Machine. Partial summary from Wikipedia:\nA third-person narrator describes the arrival of a mysterious inventor to the peaceful Welsh town of Llyddwdd. Dr. <PERSON> takes up residence in a house neglected after the deaths of its former inhabitants. The simple rural folk become apprehensive about <PERSON>'s activities in the house and suspect him of witchcraft. ...", "54" ], [ "reveals that <PERSON> is an \"Anachronic Man\" whose genius drives him to seek out a time more suited to his abilities.\nI haven't read the story myself, but according to @Hypnosifl, the story describes the travel as \"Locomotion along lines of duration\". This might be some kind of continuous movement, but considering how it's going backwards it would be hard to characterize it as a misperception of the passage of time.\nThe Clock that Went Backward (1881) by <PERSON>\nThis is a short story that Wikipedia claims is \"the first instance of using a time machine for time travel, and the first instance of a temporal paradox in fiction\". The citation for this claim links to a book by <PERSON> called Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction which contains a review of time travel in fiction. It describes the time travel device like so:\nThe mechanism of <PERSON>'s time machine, an eight-foot-high, sixteenth-century Dutch clock, is quite simplistic, even bordering on fantasy. It is simply stated that if the clock runs backward, then it travels backward in time - a rather disappointing explanation.\nLike the Chronic Argonauts, this appears to be a continuous motion backwards through time. According to @Hypnosifl, the story states that\nThe hands were whirling around the dial from right to left with inconceivable rapidity. In this whirl we ourselves seemed to be borne along. Eternities seemed to contract into minutes while lifetimes were thrown off at every tick.\nAgain, though, this is movement backwards. As this is movement through time in a different direction, rather than simply at a different speed, it seems to be a clear example of time travel.\nThat may be the earliest use of a device to travel in time, but in a Wikipedia article called Time Travel, there is a section on the history of the time travel concept, in which there are multiple possible examples earlier than 1881. The earliest of those examples which looks to me to be clearly not a dream or vision, and not someone simply sleeping into a later time <PERSON> style, is from 1836.\nIn The Forebears of Kalimeros: Alexander, son of Philip of Macedon (1836), by <PERSON>\nthe narrator rides to ancient Greece on a hippogriff, meets <PERSON>, and goes on a voyage with <PERSON> before returning to the 19th century (Wikipedia)\nIn my research, I ran across numerous blogs referring to this as the first Russian science fiction novel, and as the first novel using time travel. These aren't exactly authoritative sources, though.", "54" ], [ "Might be Spy Hard (1996).\nSecret agent WD-40 <PERSON> (<PERSON>) has his work cut out for him. Along with the mysterious and lovely <PERSON>, Agent 3.14, he must rescue the kidnapped <PERSON> and stop the evil genius, a General named <PERSON> (<PERSON>), from seizing control of the entire world.\n<PERSON> was wounded in an earlier encounter and no longer has arms. However, he can \"arm\" himself by attaching robotic limbs with various weapons attached. <PERSON> is talked out of retirement by an old friend, agent <PERSON> (<PERSON>), and given his new assignment by The Director (<PERSON>), who also is testing out a variety of elaborate disguises. At headquarters, <PERSON> encounters an old agency nemesis, <PERSON> (<PERSON>), and flirts with the Director's adoring secretary, referred to as Miss <PERSON> (<PERSON>).\nOn the job, <PERSON> is assisted by an agent named <PERSON> (<PERSON>), who gives him rides in a never-ending variety of specially designed cars.", "285" ], [ "They seek help from <PERSON> (<PERSON>), a blond child, home alone, who is very good at fending off intruders. <PERSON> resists the temptations of a dangerous woman (<PERSON>) he finds waiting for him in bed. But he does work very closely with Agent 3.14 (<PERSON>), whose father, Professor <PERSON> (<PERSON>), is also being held captive by <PERSON>.\nEverything comes to an explosive conclusion at the General's remote fortress, where <PERSON> rescues both <PERSON> (<PERSON>) and Miss <PERSON> and launches a literally disarmed <PERSON> into outer space, saving mankind.\nClip of the chair scene: https://www.youtube.com/watch?v=xqJ3lx43lMg\nFrom CrankyCritic.com:\nIn some ways Spy Hard is a twisted inside out and played on its side version of <PERSON> and <PERSON> Get Smart television series. This time though, Agents 86 and 99 are nowhere to be seen. <PERSON> is now the Director (played by <PERSON>) and he has moved up in the world, impersonating furniture, rugs, Venetian blinds and other large household items. Borrow the undersexed secretary and secret weapons designer from the <PERSON> movies, stir it all up and see how many jokes about flatulence you can come up with.", "295" ], [ "Adding some detail to the accepted answer by <PERSON>.\nTL;DR version:\nSimilarities between <PERSON> and <PERSON>:\n* <PERSON> was explicitly intended to replace <PERSON> in <PERSON> rogue's gallery.\n* <PERSON>'s costume and weapons are based on those of the Green Goblin.\n* The versions with super-powers have generally had the same powers (enhanced strength, speed, agility).\n* Both have <PERSON> as their primary opponent.\n* Both have had a number of people take on the name, though the first to use each name is the one most strongly associated with it.\nDifferences: The most notable difference may be that most versions of the <PERSON> have been sane, while most versions of the Green Goblin have been insane.\nTo provide a bit more detail on the characters from the comics:\nThe Green Goblin first appeared in AMAZING SPIDER-MAN #13 (July 1964). His origin and identity weren't revealed for a couple of years (issue #39-40).\nThe original Green Goblin was <PERSON>. His mind was affected following a chemical accident at his company, basically causing him to have a split personality: <PERSON>, the father who may have been a bit too occupied with his business, and the <PERSON>, the evil criminal mastermind. Before the revelation of his dual identity, <PERSON> and <PERSON>'s son <PERSON> met at college, and eventually became best friends.\nOver the next few years, <PERSON> was mostly the busy businessman and father, with occasional returns to being the <PERSON>. In (what was at the time) his next-to-last appearance, seeing <PERSON> in danger following a drug overdose shocked him from the <PERSON> back to <PERSON> (issue #98, July 1971).\nAbout 2 years later, <PERSON> again became the Green Goblin (issues 121-122, June and July 1973). This was the story where he killed <PERSON> then-girlfriend, <PERSON> (in 121), then inadvertently killed himself (he tried to attack <PERSON> by using his remote to steer his Goblin Glider, which was damaged and had a sharp piece of metal sticking out; <PERSON>'s spider-sense warned him something was up, and he dodged - which left <PERSON> right in the path of the glider, which hit and killed him (or so we believed at the time)).\nFollowing his father's death, <PERSON> had a breakdown. His grief over his father, combined with his inadvertent discovery that <PERSON> was <PERSON> (and, probably, <PERSON>'s incipient relationship with <PERSON>'s ex-girlfriend, <PERSON>), combined to drive <PERSON> crazy. He located a cache of his father's <PERSON> equipment, and attacked <PERSON> as a new Green Goblin (issues #136-137, September and October of 1974). <PERSON> was locked away for a short while, received therapy, and returned with no memory of <PERSON>'s identity.\nUnfortunately, his therapist, <PERSON>, upon learning about all that happened with <PERSON>, took advantage. He got <PERSON> to reveal the location of one of his father's stashes of equipment, and became the third Green Goblin (issues 176-180, January-May of 1978). Under the circumstances, it's assumed that this is <PERSON> until the end of the story.", "167" ], [ "To the best of my knowledge, <PERSON> has not been seen again (and certainly has not taken over the Green Goblin role again). <PERSON> resumed his identity as the second <PERSON> long enough to stop <PERSON>, then forgot about it again. (Note: this was when he fell in love with <PERSON>, his wife until his apparent death years later).\nA quick sidebar: when <PERSON> related the Goblin's origin, he notes that he was trying out a formula he'd taken from a former business partner, which exploded. He was apparently hospitalized for weeks, undergoing multiple surgeries to save his life. According to the surgeons, the explosion caused brain damage that was too deep for an operation to reach. <PERSON> claimed he wasn't brain damaged: \"... the accident made me more brilliant than I had ever been!\" He also claimed that he was \"... stronger ... smarter ... tougher than anyone else!\"\nIn context, this is almost certainly his insanity talking. In his encounters with <PERSON>, he generally doesn't seem to be a physical equal to <PERSON> - he relies on weaponry to even the odds against <PERSON>'s powers.", "86" ], [ "Could this be <PERSON>?\nMost well known as a book series, <PERSON> is a tween boy with an encyclopedic knowledge of minutiae who uses them to solve various crimes or mysteries.\nThe book series spawned a TV series of the same name in 1989, aired on HBO. The Wikipedia link above lists the episodes, and I have quoted them here:\nThe series began with an hour-long special, \"The Case of the Missing Time Capsule\", and subsequent six episodes were 30 minutes long.\n1. \"The Case of the Missing Time Capsule\" (hour long special first aired on March 2, 1989, to kick off series and aired over 200 times on HBO) \"Idaville is celebrating its 100th birthday by opening a time capsule left by the town founder. But before anyone can discover what riches it contains, the capsule is stolen! When <PERSON> and his friend <PERSON> investigate, they find no shortage of suspects.\n2. \"The Case of the Missing U.F.O.\" (Case #529) aired first on 3/9/90 . Something eerie is going on in Idaville when a flying saucer and flashing lights appear in the night sky. <PERSON> and his side-kick <PERSON> interrupt their relaxing camping getaway to brave the unknown and uncover the mystery of the U.F.O.\n3. \"The Case of the Amazing Race Car\" (case #524) first aired 3/16/1990 <PERSON> looks like a sure winner in a funny car derby, that is, until someone steals his car. Encyclopedia Brown steps in to solve the mystery.\n4. \"The Case of the Ghostly Rider\" (case #525) aired 3/23/1990 The ghost of the WildCat Kid has returned to haunt Old Glennville, can <PERSON> and <PERSON> with a little help from <PERSON> save the day?\n5.", "167" ], [ "\"The Case of the Flaming Beauty Queen\" (case #932) first aired 6/5/1990. Encyclopedia Brown investigates who set the fires in the library and whether the case of the hidden money is a scam or not.\n6. \"The Case of the Incredible Culpepper\" first aired 7/10/1990. This episode does not seem to have been released to VHS. The big <PERSON> magic show is spoiled when a mountain lion belonging to The Incredible Culpepper is stolen. <PERSON> and <PERSON> are immediately on the case and identify several suspects. With their typical detective skills they soon solve the crime and return the lion to <PERSON>. The magic show finally entertains all the good folks of the town- Thanks to Encyclopedia Brown.)\n7. \"The Case of the Burglared Baseball Cards\" (case #523) first aired 9/1/1990 Encyclopedia looks into the late night theft of a priceless collection of baseball cards.\n8. \"Encyclopedia Brown, The Boy Detective in One Minute Mysteries\" released straight to video (This includes 5 of the <PERSON> stories from the books, \"The Case of the Scattered Cards\", \"The Case of the Foot Warmer\", \"The Case of the Bitter Drink\", “The Case of the Civil War Sword\", and \"The Case of the Great Merko\". This was also released to VHS.)", "167" ], [ "Statement from the writer\nA fan theory1 claims that the amniomorphic spell creates pots, based on the alternate etymology below. Since Starswirl has a beard, he is “hairy,” and since he invented a spell for making pots, he is a potter: a hairy potter. This would make the spell a <PERSON> joke.\nFrom this interview2 with <PERSON>, the writer of that episode, he denies that the name of the spell was intended to be a <PERSON> joke, although he likes the idea.", "817" ], [ "He didn’t state any source for the origin of the word.\nIf we accept his joking agreement as a retcon, then the amniomorphic spell creates pots.\nStraightforward etymology\nWithout a definitive statement from the author, we can look at the etymology of amniomorphic.\nAll English words that start with amnio- relate to the amnion, a membrane surrounding an embryo.\nDefinition of -morphic from the Oxford English Dictionary:\n-morphic: Forming adjectives with the sense ‘having a form or character denoted or described by the first element of the compound’.\nA straightforward reading of the word would be, “having the form or character of an amnion.”\nAlternate etymology\nSomeone named <PERSON> decided to dig deeper into the prefix amnio-, trying to find other possible meanings.\nEtymology of amnion from the Oxford English Dictionary:\namnion: Greek ἀμνίον the caul, diminutive of ἀμνός lamb.\nEtymology from the Online Etymology Dictionary4:\namnion: Modern Latin, from Greek amnion “membrane around a fetus,” said to be originally “bowl in which the blood of victims was caught” [<PERSON> & <PERSON>], which is variously said to be of unknown origin, from ame “bucket,” or a diminutive of amnos “lamb.”\nConclusion\nFrom the etymology, the word presumably means something like, “related to the form or character of an amnion, a lamb, or some type of bowl or bucket.” An anmiomorphic spell could do anything from turning something into a bucket to making someone sheepish (the character of a lamb). In any case, it wasn’t an intentional reference to <PERSON>. It’s entirely possible that the writer just made the word up, without considering its etymology or deciding what the spell was meant to do.\n1 Claim about being a <PERSON> joke is here. Link provided by <PERSON>\n2 Link provided by <PERSON>\n3 Link provided by <PERSON>\n4 Link provided by <PERSON>", "817" ] ]

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[ [ "In general, time could be multidimensional. The reason we work with time being a positive real number (1D) is that we can easily observe (measure) changes of the \"magnitude of time\" (elapsed time). However, there are a many nuances to be considered:\n1. By itself in isolation, time is just a characteristic of events, e.g., order of occurrence, duration, etc. The concept of \"time\" can certainly be defined, tracked and interpreted in many different (mathematical, philosophical) ways. For instance, \"time\" can be mathematically defined in multiple dimensions, formulated as spanning the smallest complete field containing the real line where all polynomial equations of order \"n\" have precisely \"n\" solutions, i.e., the complex plane (complex time is referred to as \"kime\"). This is all mathematically well-posed, however, it may draw some criticism from experimental physics, as physical “reality” demands concrete “observable” evidence in support of the (higher dimensional time) math model.\n2. The utility, value, and universal relevance of time come from its tight integration with the spatial dimensions into \"<PERSON> spacetime\", a continuous universal model coupling 3D space and 1D time dimensions. The longitudinal order of events in the flat (Euclidean) 4D <PERSON> spacetime universe is represented by a continuous positive real number, we refer to as \"time\".\n3. One can of course, entangle the first two scenarios and consider the universe as a higher-dimensional (5D+) space with multi-dimensional time. The easiest approach for that is to introduce complex time (kime) that effectively and completely unifies the spatial and temporal dimensions, i.e., traversal, measurements, trajectory paths, etc. in space are naturally extended in their space-kime counterparts. Below are 3 examples that illustrate specific higher dimensional universal models that agree with the 4D <PERSON> spacetime observable universe. There are interesting ramifications of such dimensionality lifts of the classical 4D spacetime to higher-dimensional manifolds using multi-dimensional time.\n4. Spacekime theory proposed by University of Michigan researchers defined Spacekime as a 5D universe with 3 spatial and 2 complex-time (kime) dimensions. In this framework, longitudinal measurements (e.g., time-series) are represented as kime-surfaces where time is encoded as the magnitude of the radial displacement, and the second degree of freedom, kime-phase, represents the orientation of the event (cf.", "298" ], [ "mathematical parameterization of the complex time plane via polar coordinates).\n5. <PERSON> at the University of Southern California proposed a 2T theory, which utilizes an additional time dimension.\n6. Another Multi-institutional consortium proposed the 5D space-time-matter (5DSTM) theory to model the universe.\nLifting the dimensions of time results in some profound and about the universe and our interpretation of reality, truth, observations, space travel, and event causality. For instance:\n1. Ordered events like classical time-series curves morph into complex kimeseries surfaces where order is relative to parametric descriptions of simple paths/curves, see this animation. There are interesting applications of this generalization to scientific inference or process prediction, and longitudinal data analytics.\n2. Increasing the dimensional of time resolves many of the problems of time, like the “arrows of time paradoxes”. Time is actually not just uniformly and automatically marching forward. Our human frame of reference is inertially moving through the 5D+ universe. Time passage is observed as an incremental (time-dimensional) change in this motion. Time traversal is identical to spatial traversal from one location to another (on specific curves/paths). While it's practically impossible, having infinite energy and infinite information allows the theoretical reversal of this spacetime motion (e.g., travel exactly back in time) by applying the inertial motion/transformation in reverse.\n3. In higher time-dimensions, and under certain conditions, <PERSON> uncertainty principle does not apply. In other words, in 5D spacekime, one may observe simultaneously and with perfect accuracy both the position and momentum of a particle. The manifestation of the uncertainty principle in 4D spacetime is just due to the presence of a 1 degree of freedom when we project 5D spacekime down to the 4D <PERSON> spacetime. In other words, the observer reflection of uncertainty arises by the natural projection of 5D onto the 4D spacetime and is due to the unobserved complex-time (kime) phase direction.\n4. Theoretically, complex-time (kime) permits the existence of simple closed 2D kime curves (CKC).", "562" ], [ "The concept of \"evolution relative to the <PERSON> equation\" is an insightful means of considering your questions via a holistic interpretation of the reality to which most of modern physics seems to point. One should recognize that interacting with a measurement device is another aspect of interacting with \"the world\". This concept of the photon as a wave \"interacting with the world\" over \"many paths\" simultaneously is a much more significant element of determining the final outcome of all the interactions in which what we are taught to think of as a photon is involved than a semi-classical interpretation of the photon as a particle some of the time and a wave some of the time might suggest. (What we call a photon is, fundamentally, no more than our perception of the localization of a collection of properties associated with specific, quantum fields via a mode of \"bundling\" that interact in a pre-defined manner with particles with specific properties.)\n\"The world\" exists in a multi-dimensional framework that includes time. \"The world\" evolves in time, as must all experiments performed in \"the world\" that we detect as beings made of matter. The perception of a wave function as being uniquely linked to one photon that is somehow in one position in some temporal interval associated with measurement in a detector may be one cause of the questions that have been posed. Stop thinking of photons as highly localized in space and time in the same manner that one might think of a little ball as being highly localized in space and time when what is called a photon is, in fact, better conceived as a disperse, wave-like field that interacts with localized objects called atoms that we have learned to use to make what we call \"particle detectors\" (using a concept based on classical thinking).\nThe stuff that we use to interact with the photon in a detector is in a complex form that we call \"an atom\".", "800" ], [ "Because it is in this complex, atomic system, it is bound by rules that are defined by quantum physics relative to energy states and other particle properties. The photon in free space (in the classic, quantum description of what physics calls a \"photon\") is a free agent until it \"gets mixed up\" with the particle \"crowd\" that comprises the atom. The atom has a great deal of mass relative to the \"photon\", and it has a great deal of power to produce what we perceive as localized phenomenon in time and space, because the atom is, due to its mass (and, formally, momentum), a relatively localized phenomenon.\nRe-think the photon crudely as electro-magnetic energy in the environment (manifested in quantum fields) that is bundled by an atom due to the atom's relatively high momentum, which forces its probability wave to be relatively localized. Think of the electro-magnetic energy of what we call a \"photon\" as being highly interactive with \"the world\" until it has sufficiently interacted with the particle detector's energy \"bundling\" atoms to produce a result. At that point, we get some output data from the machine.\nBecause of the highly interactive nature of the photon with the world around it given its \"many paths\" aspect, we may find the results a bit surprising if we are too used to digging a rut in the same logical path by forming what one author described as \"cog-webs\" that define the photon as a particle some of the time. If we think of detection of a photon by a measurement device as a means of localizing (\"bundling\") electro-magnetic energy that is disperse in the environment (that follows \"many paths\" that overlap with other photons' \"many paths\"), and think of the speed of light as the rate at which electro-magnetic energy can be localized by atoms (with mass) to produce quantized changes in energy in things called atoms that we can use to detect the electro-magnetic energy in the environment, then it might come as no surprise that we begin to gather data about the environment that exceeds our expectations in some three-dimensional, directional sense in a given, laboratory experiment.\nIf we use an electro-magnetic energy source in a particular position sending energy in a more or less directional manner to provide most of that electro-magnetic energy being put into a given environment in which an experiment is occurring, it should come as no surprise that we detect information that is biased relative to a specific directional thumb-print in space and time, because most of the energy we gather carries a certain amount of information due to its point of origin, and objects in the related path. Because we are gathering electro-magnetic energy from the environment, should we expect all of the information reflected in what we call \"a signal\" to originate from one direction?", "800" ], [ "Is vortex physics key to understand the universe simulation hypothesis?\n<PERSON>, US computer scientist and Professor of Mechanical Engineering and Physics at the renowned Massachusetts Institute of Technology (MIT) says that the universe itself is a giant quantum computer, calculating itself and its own evolution.\nThe following short interview (2 min 14 sec) was recorded back in November 2010 at the Institute for Quantum Computing, University of Waterloo.\n<PERSON> on the Universe as a Quantum Computer\nhttps://www.youtube.com/watch?v=Qh8QfKVcvFA\n“In fact, when we are building Quantum computers, it is not like we are starting from scratch and saying, “Oh we have these dumb Qubits and they are not computing, they can’t do anything, let us make them compute”…ähm…that is not the way it works, it is more that the universe itself is already processing information at this microscopic level all the time and when we build a quantum computer we are just coming in and highjacking the ongoing computation to make it compute something that we would like it to compute rather than what it would normally be computing. So yes, I mean if you would like to think of yourself when you are building a quantum computer is simply participating in a larger computation in a productive way, I think that is a nicer way to think than to saying \"We are going to force the universe to compute at the microscopic level.\" So, we are participating in the universal computation rather than forcing the universe to compute.\"\nAn argument for this hypothesis could be the superfluid time crystal structure (hexagonal <PERSON> vortex lattice) shown below, which could serve as the underlying naturally generated quantum mechanical transition matrix (hardware).\nAbrikosov Vortex Lattice [Entangled, Holographic, Naturally Occurring] Source: https://jila.colorado.edu/bec/CornellGroup/gallery/images/vortexnuc_color.jpg\nIt is important to note that the quantum mechanical nature of a BEC-superfluid can lead to very unusual phenomena.", "855" ], [ "A particularly striking consequence is that a BEC-superfluid cannot rotate like a classical liquid. Instead, when a BEC-superfluid is set into rapid rotation, vortices enter the condensate and arrange themselves into a regular lattice (Abrikosov vortex lattice).\nQuestion: Is the universe a quantum computer and the hexagonal Abrikosov vortex lattice the underlying naturally generated quantum mechanical transition matrix?\n*Note: This question is not a duplicate to the pure philosophical or the mathematical model based universe simulation hypothesis as it adds a novel aspect with the recently discovered superfluid hexagonal Abrikosov vortex lattice for which convincing experimental evidence can be found on the US National Science Foundation Website. https://www.nsf.gov/news/mmg/mmg_disp.jsp?med_id=59577&from=", "298" ], [ "Investigating Non-Linear Resonance in Chua's Circuit\nIntroduction: Investigating Non-Linear Resonance in Chua's Circuit\nWhat is non-linear resonance?\nResonance is defined as a physical phenomenon where the response of a dynamical system reaches a maximum amplitude as a result of an applied periodic force. Nevertheless, what are dynamical systems and periodic forces? Brief explanations will be provided in the following lines to lay out a conceptual intuition before diving into the experiments.\n**** Note that readers with a background in physics or mathematics can skip the first part of the introduction and dive right into the project objectives and experiments.\n1.Dynamical system\nNouns are used to represent everyday objects. For example, if one observes an assembled piece of metal supported by four wheels travelling on the highway, the word car comes to mind. Qualitative description allows us to communicate and describe everyday objects without having to spend too much brainpower. Although being extremely useful, qualitative representation does not take into consideration the full complexity of our surroundings. Quantification becomes necessary when specific details are required. A set of physical values such as dimension, temperature, mass are assigned to bring further clarification. For the most part, the quantified values assign to an object remain constant over time. However, special kinds of objects require a different form of quantification to represent their full complexity. Specifically, the quantified values used as descriptions do not remain constant over time. For instance, the precise dimension of a flower can not take a specific value since it is slowly evolving at any moment in time. It requires a function to describe how the dimension evolves. Namely, the flower is what we referred to as a dynamical system. Many other examples exist in nature, giving rise to fascinating behaviour.\nEveryday examples of dynamical systems:\n- Swinging Pendulum (Constant periodic change between potential and kinetic energy)\n- Population Growth (Constant periodic increase and decrease of the population as a result of predator/prey interactions and reproduction)\n- The Human Brain (A constant periodic change of chemical signalling concentration across neuronal cells)\n2.", "855" ], [ "Periodic Force\nForces induce change. It is often referred to as a transfer of energy upon which a given object changes its natural state. For example, a cup of tea sitting at a precise position on a table will change if a small force is applied toward a given direction. A force becomes periodic when the applied stimulus is not constant over time. For example, pushing a child sitting on a swinging pendulum every time a maximum height is reached is considered periodic since the external action only occurs at specific moments in time. It is such periodic external actions that induce a change on a system or object that is referred to as periodic forces.\nEveryday examples of periodic forces or stimuli:\n- Human senses - Light waves interacting with photoreceptors of the eyes and allowing vision. Sound waves stimulating the eardrums and making music enjoyable.\n- Seasons - Periodic alteration of environmental conditions such as temperature that affect biological ecosystems.\n- Alternating Current - Periodic input signal altering the internal dynamics of an electronic circuit.\nHaving now gained a brief intuition about the principle of dynamical systems and periodic perturbations, we are forced to wonder about the possible responses a dynamical system can exhibit due to a periodic stimulus. For example, what would happen to the child sitting on a swinging pendulum if the amplitude of the external push keeps increasing to infinity while the applied frequency matches perfectly with the natural swinging frequency of the pendulum? Doubtlessly, nature is capable of shocking responses!\n3. Resonance\nResonance occurs when the amplitude of a dynamical system is driven to a maximum value due to an applied periodic force. For example, the amplitude of a swinging pendulum increases dramatically even when a minimal force is applied at the right moment in time. For instance, finding ourselves sitting on a swinging pendulum with a child applying a minimal push would nevertheless increase the swinging amplitude to a maximum if, and only if the child applies the external push periodically when the potential energy of the pendulum is at a maximum. Under such circumstances, the external actions of the child are referred to as inducing resonance on the swinging pendulum.\nAfter all, why should we care about resonance phenomena?\nSurprisingly, our life depends on resonance in many aspects:\n* Telecommunication - Radio communication occurs by a resonant action of an electromagnetic signal acting on electronic circuits.\n* Nuclear Magnetic Resonance - The resonant action of an electromagnetic field on the atomic nucleus allows to gain physical information about various chemicals and biological materials.\n* Tacoma Narrow Bridge disaster - Ignoring the power of resonance can lead to unexpected failures. For example, a small wind perturbation led to the collapse of the Tacoma Narrow Bridge. Note that it is still debated whether resonance served as the underlying cause of the disaster. Regardless, the Tacoma Bridge disaster demonstrates the often surprising response nature can exhibit due to small periodic perturbations.", "855" ], [ "Unintended implications of using a celestial object as a \"weight\" for a digital currency?\nI have a sci-fi universe that's meant to be astronomically accurate, scaled around cataloged stars and known open clusters/nebulae like the Orion Complex or the Hyades. Space faring civilizations rely on luminous stars for FTL as the more luminous stars generate a special particle* any interstellar civilization needs. Aliens are more alien, but not xenocentric (though they're not relevant here).\nIn the year 2421 Humans are partially unified (but historically was completely unified) under FAHI-The Federal Association of Human Interests. A notable tenet FAHI has is that the organization claims sovereignty on part of every human being and in theory acts on the part of human interests. In practice FAHI ended up acting on terran interests instead due to poor representation for people living in the colonies. A side effect of FAHI making mass colonization of space one of its main tenets.\nIn order to make a universal currency for humanity that wouldn't to subject to financial fluctuations, the ministry of finance decides on using the mass of a nearby celestial object to give a set weight to the digitized \"universal\" human currency. There is a set limit of credit that exists in circulation in order to avoid inflation, of which is set at 100 trillion credits.", "302" ], [ "The currency's value is centered around said celestial object. I am a bit back and forth on what celestial object, but for now assume one of the following possibilities:\n* Sagittarius-A* super massive black hole\n* The Milky Way Galaxy as a whole\n* The Sun\n* A Nearby neutron star (Like Calvera)\n* Earth\nNot sure which one would be the most logical or thematic, but the general idea should be the same. A currency that has its weight not in gold, but in a celestial object of arbitrarily defined importance. The issue is I have no clue if using a cosmic object as a currency weight would actually work in practice given the expansionist nature of my human civilization.\nSince I am not really good at economics, can anyone who knows their economics tell me what unintended implications of this idea may entail given the scenario and/or celestial object used? I'm not completely sure where to look.\n*Detail: The \"special particle\" in question is called the \"Lux Particle\". It exists only in the corona of stars and must exist in plasma. Lux Particles allow ships to not only have FTL, but also fast-as-light travel and teleportation for spaceships. Brighter stars have more lux. I might have intentionally devised lux as a way to screw red dwarves over.", "302" ], [ "Are there any natural forms of communication as robust as speech/vocalization?\nVocalization has a number of features that make it a very robust natural form of communication:\n* Variable volume from whisper to shout, roughly scaling from direct to omnidirectional;\n* Equally effective in daylight and total darkness, doesn't require visual contact;\n* Precision of hundreds of distinct phonemic combinations;\n* Works over significant distance, even through/around some barriers.\nConsidering the possibilities of alien physiology and environments, is this as good as it gets or are there other methods as (or more) robust?\nExpanded\nThe bounty expires tonight so I'm going to go through some of the suggested answers below to illustrate how they fall short of vocal communication, in the hopes it will inspire more answers.\nRemember: I'm not saying it's impossible for these forms to evolve, I'm saying they are fundamentally more restrictive than vocalization.\nSmell\n* Prevailing wind conditions limits the direction of communication. \"Speaking\" to someone upwind of you could be impossible, even over a short distance in a light breeze.\nTouch/tactile\n* Speaking to someone out of arm's length would be impossible, and the ability to speak to multiple people is limited to the number of appendages you have.\nBioluminescence/infrared/skin pattern\n* Requires visual contact by the recipient and a narrower range of ambient lighting conditions, and may be impossible during the brightest part of the day or at night/in darkness.\nWriting\n* This also requires visual contact, but even more restrictive is the necessity of writing media and tools. It's also arguable that any form of natural communication can develop written/recorded forms, so a writing-only language would be inferior to all others.\nPotential\nThere are a few references to electromagnetic communication (such as, but not just, radio) I think are begging to be explored more.", "350" ], [ "Such a mode of communication could penetrate barriers and distances that stop vocalization and conceivably allow greater directionality (e.g. the ability to \"whisper\" to someone in another room, to speak to someone at the bottom of a pool, etc). But can a case be made for it evolving in nature?", "350" ], [ "Classification system amd measure of progress for science and technology branches and other areas of life\nI'm working on modeling how a civilization can progress from some known state making conscious choices about the fields in which to apply its resources. Is there some good / theoretically sound / well-known nomenclature for various branches of science & technology as well as other areas of life to somehow classify all possible choices?\nWe know how in many computer games you can decide to \"research pottery\" after which you gain a pre-defined list of improvements and access to further (also known in advance) techs in the research tree. Not so IRL where you don't know what you'd get eventually (and even less so, what you'd get first) if you start spending 80% of your GDP on agricultural research centers. And it may even occur that while you are spending enormous researchers on agriculture a break-through comes in some other field, like nuclear physics. Simply because some genius was enthusiastic enough about that field to work their despite the lack of support. And I'm not even starting on commercialization and inter-relationships between government vs private funded research.\nStill, it should be possible for a civilization or some group within to decide \"Let's focus our efforts on XXX\", and spend it's resources on that in various forms (grants, time, social pressure, access to rare capabilities/equipment/research, competitions, etc) to increase the probabilities of the progress in the chosen area.\nIdeally, I'm looking for a universal classification system that includes not only the things, which are traditionally included in science & tech (physics, chemistry, biology, health sciences, ... ; transportation, energy, ...), but also other aspects of life.", "693" ], [ "They may decide \"Let's focus on improving education methods\", \"reducing crime\", \"optimizing our financial system\", \"improving ethics/morale\", \"working on nurturing stoutness and courage in each individual\".\nBut I realize that such universal system is unlikely to exist. So, I'd appreciate pointers to the systems that cover some large facets of our life.\nA separate question is how to measure rough order of the magnitude for the progress in a given area. For natural sciences and technologies one good approach is thinking in the terms of various measurement units. Did they reach the stage when they understand the processes and can operate at nano/pico/femto (or otherwise, at light-years or galaxy-size scale) in various disciplines. Or, the same thing for energy units - the famous Kardashev scale. But what about other areas, like social sciences and aspects of life. To some extent linear/energy scale approach is applicable there (ability to operate at nano-level may affect our educational process or crime prevention). But I feel like I measure everything through \"physics\", missing out on other important factors.", "693" ], [ "Note: Was going to comment on <PERSON> answer, but Without the 50 reputation yet, I'd like to build off their example of living organisms being a local system with a decrease in entropy, and how this is balanced out.\nAs <PERSON> pointed out about living organisms:\nBut although they can reduce entropy locally, they must increase the entropy of their surroundings by at least as much in the process.\nThis is the crux of your answer. Although a local reduction of entropy does not increase the entropy of it's surroundings, but rather the constant reduction of entropy in the surroundings enable these local low entropy states to exist in order to approach equilibrium. It is crucial distinction to make, between a region of lower relative energy vs. a region who's entropy is constantly being reduced.\nThe solar system is a great example for visualization purposes, although it is itself a subsystem of a larger system, ad infinitum.\nIn order for any life on Earth to exist in a manner that reduces entropy; so much so that 7+ billion humans can exist, build cities that remain rigid, and coexist with trillions of other organisms, somewhere outside of the system there must be a region of spacetime with a very high entropy interacting with this system.", "943" ], [ "The sun, a region of very high energy, directly interacts with the Earth. There are no true closed systems.\nAside\nI am currently working on a personal theory (inspired by the work of <PERSON> and <PERSON>) that the second law of thermodynamics is the most fundamentally important reason that life exists; that the formation of amino acids, and complex life is a necessary byproduct in every solar system (with the proper precursors) in order to approach equilibrium.\nAny solar system as an isolated system (each star is so far apart from the next, it's isolated enough) and entropy cannot decrease over time, even as the entropy of the star is reducing through nuclear fusion. As energy from the star is added to say, the ocean of a planet, the entropy increases locally before being dissipated through the medium. Along the way, areas of uneven energy cause molecules and atoms to organize themselves in a manner which is conducive to (a) the medium of energy, and (b) the manner in which entropy equilibrium is reached (the environment). These reorganized molecules would themselves be local areas of low entropy, further altering the manner in which entropy/energy is dissipated through the system.", "943" ] ]

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[ [ "I think the difference between the representation of the spin operator in the <PERSON> vs. the <PERSON> models is due to the fact that in the <PERSON> model, one tries to describe the situation of spin-1/2 fermions sitting in a lattice, whereas, in the <PERSON> model, the spins are distinguishable and hence have neither fermionic nor bosonic symmetry.", "469" ], [ "In general, the second-quantized representation of one-body operators follows the same structure for either fermions or bosons, e.g.,\n$O_1 = \\sum_{pq} \\langle p | o_1 | q \\rangle a_p^+ a_q,$\nwhere $|p\\rangle$ and $|q\\rangle$ represent the single-particle states with which we are describing the problem and $a_p^+ (a_p)$ is the creation (annihilation) operator that obeys either the fermionic or bosonic (anti)commutation relations.\nFor both the <PERSON> and <PERSON> models, the single-particle states are the spin-1/2 states, $|\\alpha\\rangle \\equiv |1/2,1/2\\rangle$ and $|\\beta\\rangle \\equiv |1/2,-1/2\\rangle$. If we follow the above recipe for calculating a one-body operator, we can evaluate the form of each component of $\\vec{S}$ using the usual raising and lowering operators $S_+$ and $S_-$.\n$S_{x} = \\langle \\alpha | s_x |\\alpha\\rangle a_\\alpha^+ a_\\alpha + \\langle \\alpha | s_x |\\beta\\rangle a_\\alpha^+ a_\\beta + \\langle \\beta | s_x |\\alpha\\rangle a_\\beta^+ a_\\alpha + \\langle \\beta | s_x |\\beta\\rangle a_\\beta^+ a_\\beta = \\frac{\\hbar}{2} a_\\alpha^+ a_\\beta + \\frac{\\hbar}{2} a_\\beta^+ a_\\alpha$\n$S_{y} = \\langle \\alpha | s_y |\\alpha\\rangle a_\\alpha^+ a_\\alpha + \\langle \\alpha | s_y |\\beta\\rangle a_\\alpha^+ a_\\beta + \\langle \\beta | s_y |\\alpha\\rangle a_\\beta^+ a_\\alpha + \\langle \\beta | s_y |\\beta\\rangle a_\\beta^+ a_\\beta = -i\\frac{\\hbar}{2} a_\\alpha^+ a_\\beta + i\\frac{\\hbar}{2} a_\\beta^+ a_\\alpha$\n$S_{z} = \\langle \\alpha | s_z |\\alpha\\rangle a_\\alpha^+ a_\\alpha + \\langle \\alpha | s_z |\\beta\\rangle a_\\alpha^+ a_\\beta + \\langle \\beta | s_z |\\alpha\\rangle a_\\beta^+ a_\\alpha + \\langle \\beta | s_z |\\beta\\rangle a_\\beta^+ a_\\beta = \\frac{\\hbar}{2} a_\\alpha^+ a_\\alpha - \\frac{\\hbar}{2} a_\\beta^+ a_\\beta$\nThe above expressions coincide with how it is usually written in terms of the Pauli spin matrices, namely, $\\vec{S} = \\frac{\\hbar}{2} a^+ \\vec{\\sigma} a$. In fact, in the <PERSON> model (and other fermionic/bosonic models), we likely would have other quantum numbers related to the particle's spatial wave function (such as momentum $\\vec{k}$ of a plane wave or an orbital label $p$), thus the more complete form of the spin operator for these situations would be $\\vec{S} = \\sum_{pq} \\delta_{pq} \\frac{\\hbar}{2} a_p^+ \\vec{\\sigma} a_q$, where the $\\delta_{pq}$ is explicitly included to show that the spin is diagonal in the spatial degrees of freedom.", "66" ], [ "The relationship between exchange symmetry and parity is something that has also greatly confused me. Definitions:\n* Parity refers to whether a quantum state picks up a minus sign when all the spatial coordinates are inverted, rather like an even or odd function.\n* Exchange symmetry refers to whether the combined state for a system of two particles picks up a minus sign when the particle labels are exchanged.\nAt first, there seems to be no obvious link between these two symmetries.\nLet's begin with parity. In spherical polar coordinates, a parity transformation is equivalent to $\\theta \\rightarrow \\pi-\\theta$, $\\phi \\rightarrow \\pi+\\phi$ with $r$ remaining the same. In any system with spherical symmetry, the part of the spatial wavefunction which depends on $\\theta$ and $\\phi$ is given by the spherical harmonics $Y^M_L(\\theta, \\phi)$. It can be shown that the spherical harmonics have parity\n$$Y^M_L(-{\\bf r})=(-1)^LY^M_L({\\bf r})$$\n(see https://en.wikipedia.org/wiki/Spherical_harmonics#Symmetry_properties). Thus, the spatial wavefunction will have parity $(-1)^L$.\nExchange symmetry is more complicated. Since you are interested in the exchange symmetry of the spatial wavefunction, we can ignore spin and only think about orbital angular momentum.", "976" ], [ "Let the two individual particles have orbital angular momentum eigenstates $\\vert j_1 m_1 \\rangle$ and $\\vert j_2 m_2\\rangle$. The eigenstates of the combined system of two particles are then\n$$\\vert LM\\rangle = \\sum_{m_1}\\sum_{m_2}C^{LM}_{j_1m_1;j_2m_2} \\vert j_1 m_1 \\rangle \\vert j_2 m_2 \\rangle \\tag{1}$$\nwhere $C^{LM}_{j_1 m_1;j_2 m_2}$ are the Clebsch-Gordan coefficients. The Clebsch-Gordan coefficients have well-defined exchange symmetry given by\n$$C^{LM}{j_2 m_2; j_1 m_1}=(-1)^{j_1+j_2-L}C^{LM}{j_1 m_1;j_2 m_2}$$\n(see https://en.wikipedia.org/wiki/Clebsch%E2%80%93Gordan_coefficients#Symmetry_properties). Let's assume that the two particles have the same $j_1 = j_2 = j$. The exchange symmetry factor then becomes\n$$(-1)^{2j-L}.$$\nThis factor can be taken outside the sum in equation (1), so also gives the exchange symmetry of $\\vert LM\\rangle$. Since $2j$ is even, the exchange symmetry of the spatial wavefunction is\n$$(-1)^L$$\nAHA! We have found that both the parity and exchange symmetry of the spatial wavefunction are given by $(-1)^L$. However, this has arisen from the assumption that $j_1=j_2$, so there doesn't seem to be a deep connection between these two symmetries.", "956" ], [ "The realness of the interorbital coupling $t$ can indeed tell us something about the symmetries of the system. Here, it entails at least one symmetry: spinless time-reversal symmetry.\nConsider the Hamiltonian of non-interacting spinless particles that live on a periodic chain with two orbitals in each unit cell as in OP's example. In this case, the Hamiltonian can be block-diagonalized by using the periodicity of our system: \\begin{equation} H = \\sum_k \\begin{pmatrix} c^\\dagger_{k1} & c^\\dagger_{k2} \\end{pmatrix} H(k) \\begin{pmatrix} c_{k1} \\ c_{k2} \\end{pmatrix} \\end{equation} where $H(k)$ is a $2\\times 2$ block, labelled by the momentum $k$, called the Bloch Hamiltonian. Now assume that the system has time-reversal symmetry. This means that $[H,T]=0$ with $T$ the time-reversal operator. For spinless particles it is given by $T=K$ with $K$ complex conjugation with respect to the position representation (see e.g. <PERSON>). Since $T c_{k,i} = c_{-k,i}$, we find \\begin{equation} H = THT^{-1} \\Rightarrow H(-k) = TH(k)T^{-1} = H(k)^.", "526" ], [ "\\end{equation} In OP's example, a periodic chain of cells with no tunnelling between them is considered. Essentially an infinite amount of isolated atoms. The Bloch Hamiltonian is \\begin{equation} H(k) = \\begin{pmatrix} \\epsilon_1 & t \\ t^ & \\epsilon_2 \\end{pmatrix} \\end{equation} so that the total Hamiltonian $H$ is not time-reversal symmetric if $t$ is not real.\nAnother example which illustrates the effect of spinless time-reversal symmetry in a periodic system is given by graphene. Here, spinless $T$ and inversion protect the nodes in the band spectrum (Dirac points) locally since combined they forbid any $\\sigma_z$ term which would open the energy gap. The two Dirac points can only be destroyed if they merge in a time-reversal-invariant point of the Brillouin zone.\nGenerally, if time-reversal symmetry is present, the energy spectrum plotted as a function of $k$ (the so-called energy bands) is symmetric with respect to $k$: $E_i(-k) = E_j(k)$. However, the converse is not true since spatial symmetries such as inversion can also enforce a symmetric spectrum.\nSpinful time reversal\nIn the case of a half-integer spin system, it can be shown that the time-reversed state $T\\left| \\psi \\right>$ is orthogonal to $\\left| \\psi \\right>$ as a result of $T^2 = -1$ (<PERSON>' theorem). This means that the energy bands have to become degenerate in time-reversal-invariant points $k = -k + G$ where $G$ is a reciprocal lattice vector. A system with two bands is therefore always a metal. The simplest model for an insulator requires four bands.", "526" ], [ "Undefined amplitudes in the Coordinate Bethe Ansatz for the XXX model?\nRather specific question for someone familiar with the Coordinate Bethe Ansatz... I am considering the Heisenberg XXX-model, consisting of a one-dimensional chain of L sites with a spin-1/2 particle at each site and periodic boundary conditions, i.e. $S_{n+L}=S_n$. The Hamiltonian is given by\n$H=-\\frac{J}{2} \\sum_{n=1}^L S_n^+S_{n+1}^-+S_n^-S_{n+1}^+ +S_n^zS_{n+1}^z$ with $J$ a coupling constant.\nChoosing the $z$-axis as a quantization axis, we can write $S^z = \\frac{L}{2} - M $, where $M$ is the number spins down.", "656" ], [ "Due to conservation of $S^z$ we can find the eigenvectors of the Hamiltonian by looking at each value for $M$ separately.\nFor $M=2$, write a state as $|\\psi> =\\sum_{1\\leq n_1< n_2\\leq L}^L f(n_1,n_2) |n_1,n_2>$, where $|n_1,n_2>$ denotes the basis state where the spins at site $n_1$ and $n_2$ are down. The Coordinate Bethe Ansatz for the eigenvectors is\n$f(n_1,n_2)=Ae^{i(k_1n_1+k_2n_2)}+Be^{i(k_2n_1+k_1n_2)}$ with A and B constants.\nApplying the Hamiltonian to $|\\psi>$, without using the Coordinate Bethe Ansatz, then yields an equation for the eigenvalue, as well as the following condition:\n$2f(n_1,n_1+1) = f(n_1,n_1) + f(n_1+1,n_1+1)$.\nNow the question: the condition above was derived without use of the Bethe Ansatz (see for example these notes, pages 62-63). It contains amplitudes $f(n_1,n_1)$, which are however not defined by the general expansion $|\\psi>$ since there we have that $n_2>n_1$! Only by inserting the Bethe Ansatz afterwards, we yield the desired equations to solve for the spectrum of $H$. Can we make sense of this condition without using the Bethe Ansatz, i.e. why should it be well defined? Also, why does the Bethe Ansatz also have to hold for $n_2=n_1$ here? I could imagine just defining $f(n_1,n_1) = 0$ since the amplitude $f(n_1,n_1)$ doesn't appear in the expansion $|\\psi>$ anyways.\nI hope this is clear...", "66" ], [ "Lagrange multipliers in quantum systems are usually (always?) implemented on the level of expectation values - often specifically ground state expectation values. That's also the case for these two papers. So, given an extended Hamiltonian $$ H'= H_\\mathrm{MF}+H_\\mathrm{constraints}$$ where $H_\\mathrm{constraints}$ contains the Lagrange-multiplier-enforced constraints, we want to find a ground state of $|\\psi\\rangle$ of $H'$ that satisfies the constraints. For reasonable constraints this will be possible by finding appropriate values for the Lagrange multipliers. Note that $|\\psi\\rangle=|\\psi_0\\rangle+|\\delta\\psi\\rangle$, where $|\\psi_0\\rangle$ would be the ground state of $H_\\mathrm{MF}$. That is, ground state expectation values $\\langle\\psi|\\hat{O}|\\psi\\rangle$ of some operator $\\hat{O}$ will depend on the Lagrange multipliers $a_i$, and we can tune the $a_i$ until we find expectation values compatible with the desired constraints.\nOf course, we could use the same approach for excited states, but then we i) would expect different values for the Lagrange multipliers, and ii) might require additional constraints to make sure the state is orthogonal to lower-energy states. In other words, <PERSON>'s Lagrange multiplier terms are enough to enforce the constraints on the ground state, but you shouldn't expect them to be enough to enforce the constraint on the full Hilbert space. Compare the situation with the most familiar example of a Lagrange multiplier in stat. mech. or condensed matter systems - the chemical potential $$\\mu \\left( \\int |\\Psi \\left(\\mathbf{r}\\right)|^2 d\\mathbf{r} - N \\right). $$ It can be used to enforce a fixed particle number $N=<\\hat{N}>$ in a thermal state, but excited states are allowed to have other occupations.\nAdditional comments:\nAs you note, <PERSON>'s constraints are site-dependent. This is often rather inconvenient, particularly in numerical calculations.", "976" ], [ "Hence, often when searching for a translationally invariant mean field solution, the site-dependent local constraints can be relaxed to global ones, i.e. you might go from $\\sum_i \\lambda_i \\left( f_{i\\sigma}^\\dagger f_{i\\sigma} - 1\\right)$ to $\\lambda \\left(\\sum_i f_{i\\sigma}^\\dagger f_{i\\sigma} - N\\right)$, which now enforces half-filling on average. This is commonly done in the $t-J$ model theory for high-$T_c$ superconductivity, for example, see e.g. this review. Ideally, using the relaxed constraint can allow an easier path to a solution that satisfies the local constraints.\nIt might also be instructive to look at how one might solve such a constrained mean-field problem numerically and self-consistently. One algorithm would be\n1. Start by making initial guesses for the values of the mean field parameters (e.g. $\\chi$)\n2. Find values for the Lagrange multipliers such that the constraint is satisfied\n3. Calculate new expectation values ($\\chi_{current}$)\n4. Update guesses for the mean field parameters (e.g. by conservative mixing $\\chi_{new}=(1-x)\\chi_{old} + x\\chi_{current}$ where $x$ is small)\n5. Return to step 2, and repeat until the parameters converge.", "915" ], [ "The first thing that comes to mind is the fact that energy eigenstates have a periodic phase factor, $e^{iEt/\\hbar}$. In general we usually say that states are defined up to a phase factor, so for a single particle in an energy eigenstate we can ignore it, but this phase factor can manifest physically when you have a state which is a superposition of energy eigenstates, each with its own oscillating phase. A simple example of this which actually results in periodic behavior would be a spin-$1/2$ particle in a magnetic field. Such a system will have a Hamiltonian proportional to the Pauli spin matrix $\\sigma_z$.", "789" ], [ "So our time-evolution operator is $U(t) = e^{i\\omega \\sigma_z t}$. Recall that the Pauli matrices are idempotent, so when we Taylor expand this we can group our terms together and we will find\n\\begin{equation} U(t) = \\cos\\left(\\omega t\\right)+ i\\sigma_z \\sin\\left(\\omega t\\right) \\end{equation}\nFor eigenstates of $\\sigma_z$ this isn't particularly interesting. The $\\sigma_z$ will give us just a + for $\\vert \\uparrow \\rangle$ or a - for $\\vert \\downarrow \\rangle$ and of course the modulus of the state won't change but it will have a time-oscillating phase factor. Instead let's think about a superposition of such eigenstates, like $\\vert \\psi \\rangle \\equiv\\frac{1}{2}\\left(\\vert \\uparrow \\rangle + \\vert \\downarrow \\rangle\\right)$.\n\\begin{equation} \\begin{split} U(t) \\vert \\psi \\rangle = \\frac{1}{2}\\cos\\left(\\omega t\\right)\\vert \\left(\\vert \\uparrow \\rangle + \\vert \\downarrow \\rangle\\right) + \\frac{i}{2} \\sin\\left(\\omega t\\right) \\left(\\vert \\uparrow \\rangle - \\vert \\downarrow \\rangle\\right) \\ = \\frac{1}{2} e^{i\\omega t} \\vert \\uparrow \\rangle + \\frac{1}{2} e^{-i \\omega t} \\vert \\downarrow \\rangle \\end{split} \\end{equation}\nNot incidentally, this state was chosen to have a spin of $+\\hbar/2$ along the $x$ direction, but we can see in the above equation that when we evolve it in time we reach a point where it will have spin $-\\hbar/2$ along the $x$ direction, when $\\cos(\\omega t) = 0$ and $\\sin(\\omega t) = 1$, so the expectation value of the $x$ spin of this particle is periodic.\nBecause the Hamiltonian operator is Hermitian by assumption, it can be diagonalized and the operator exponential can be rewritten as a manageable <PERSON> series, but this nice periodic form only works because the square of our Hamiltonian is proportional to the identity matrix, so we could group terms in the <PERSON> expansion to give us a cosine multiplied by the identity and a sine multiplied by the $\\sigma_z$ operator. In general this procedure does not work out quite as nicely, but you can always think about the interference of the phase factors I mentioned in the first paragraph.", "66" ], [ "This is a good question that I have also had, so I'm answering this even though it is two years old! It looks like your definitions are all fine, but I would use\n\\begin{equation} \\hat{\\mathcal{P}}\\hat{\\psi}^{}{A}\\hat{\\mathcal{P}}^{-1} = \\sum{B} \\hat{\\psi}{B}^{\\dagger}(U{P})_{B, A} \\end{equation}\nas it simplifies notation. I'll also refer to the particle-hole operator as $\\hat{\\mathcal{P}}$ to keep my notation clear, but that's just a personal preference.\nUsing the above definition we implement the transformation of $\\hat{\\mathcal{P}}$ on $\\hat{H}$ as\n\\begin{equation} \\begin{split} \\hat{\\mathcal{P}}\\hat{H}\\hat{\\mathcal{P}}^{-1} &= \\sum_{A, B} \\hat{\\mathcal{P}} \\hat{\\psi}{A}^{\\dagger} \\hat{\\mathcal{P}}^{-1} \\hat{\\mathcal{P}} H^{}{A, B} \\hat{\\mathcal{P}}^{-1} \\hat{\\mathcal{P}} \\hat{\\psi}^{}{B} \\hat{\\mathcal{P}}^{-1}\\ & =\\sum{A, B} \\sum_{C, D} (U_{P}^{})^{\\dagger}{A, C} \\hat{\\psi}{C} H_{A, B} \\hat{\\psi}{D}^{\\dagger} (U{P}^{})^{}{D, B} \\ &= \\sum{A, B}\\sum_{C, D} \\delta^{}{C, D}(U{P})^{\\dagger}{A, C}H^{}{A, B}(U_{P})^{}{D, B} - \\hat{\\psi}^{\\dagger}{D}(U_{P})^{}{D, B}H^{}{A, B}(U_{P})^{\\dagger}{A, C}\\hat{\\psi}^{}{C} \\ & = \\sum_{A, B}\\sum_{C, D} (U_{P})^{\\dagger}{A, C}H^{}{A, B}(U_{P})^{}{C, B} - \\hat{\\psi}^{\\dagger}{D}(U_{P})^{}{D, B}H^{T}{B, A}(U_{P})^{\\dagger}{A, C}\\hat{\\psi}^{}{C} \\ & = \\sum_{A, B}\\left( \\delta^{}{A, B}H{A, B} - \\sum_{C, D}\\hat{\\psi}^{\\dagger}{D}(U{P})^{}{D, B}H^{T}{B, A}(U_{P})^{\\dagger}{A, C}\\hat{\\psi}^{}{C} \\right) \\ & = \\text{Tr}(H) - \\sum_{C, D} \\hat{\\psi}^{\\dagger}{D}H^{}{D, C}\\hat{\\psi}^{}_{C}, \\end{split} \\end{equation}\nwhere we have used the anticommutation relation ${\\hat{\\psi}^{}{A}, \\hat{\\psi}^{\\dagger}{B}} = \\delta^{}{A, B}$ between the second and third lines and the unitarity of $U{P}$ between the fourth and fifth lines. We require $\\hat{\\mathcal{P}}\\hat{H}\\hat{\\mathcal{P}}^{-1} = \\hat{H}$ if our Hamiltonian respects PHS, demanding the conditions that\n\\begin{equation} \\begin{split} \\text{Tr}(H) &= 0 \\ H = -U_{P}&H^{*}U_{P}^{\\dagger} \\end{split} \\end{equation}\ni.e.", "526" ], [ "the Hamiltonian is traceless. We have also used the Hermicity of the Hamiltonian in the second equality. Thankfully, these two conditions are complementary, since $H = -U_{P}H^{*}U_{P}^{\\dagger}$ implies that our Hamiltonian has a symmetric spectrum.", "526" ], [ "Thanks for your hints so far. The question was to some extend already discussed here: (https://physics.stackexchange.com/questions/109343/eigenstate-of-field-operator-in-qft). <PERSON>, I give a more verbose and down-to-earth answer to my question. There is also a remark why I was confused first...\nEigenstates of the annihilation field as classical states\nWe assume a real valued scalar quantum field $A(x)$ of the form (neglecting normalization)\n\\begin{equation} \\hat A(x) = \\int \\hat a^{*}(k)e^{ikx} \\, d^{3} k + \\int \\hat a(k)e^{-ikx} \\, d^{3} k = \\hat A_c(x) + \\hat A_a(x) \\end{equation}\nwhich is split in a creation and annihilation part.", "669" ], [ "We are looking for a eigenstate $| \\psi \\rangle$ of the annihilation operator $\\hat A_a(x)$. Such a state is the tensor product of single mode coherent states: $| \\psi \\rangle = \\otimes_k |\\alpha(k) \\rangle_k$, since every single mode state in the tensor product is an eigenstate of the corresponding annihilation operator $a(k)$ with eigenvalue $\\alpha(k)$. Hence $\\hat A_a(x) | \\psi \\rangle = \\int d^{3} k' e^{-ik'x} \\hat a(k')\\otimes_k |\\alpha(k) \\rangle_k =\\int d^{3} k' e^{-ik'x} \\alpha(k') \\otimes_k|\\alpha(k) \\rangle_k = \\psi(x) | \\psi \\rangle$\nwith the eigenvalue $\\psi(x) = \\int d^{3} k e^{-ikx} \\alpha(k)$. The eigenstate $| \\psi \\rangle$ is also called coherent and can be written as \\begin{equation} | \\psi \\rangle = \\otimes_k e^{\\alpha(k) \\hat a^{}(k)} |0 \\rangle = e^{\\int d^{3}k \\alpha(k) \\hat a^{}(k) } |0 \\rangle = e^{\\int d^{3}x \\hat A_c(x) \\psi(x)} |0 \\rangle = e^{\\int d^{3}x \\hat A(x) \\psi(x)} |0 \\rangle \\end{equation} The first part of the above equation is more or less by definition true (refer to single mode coherent states) the second part is valid since all $\\hat a^{*}(k)$ commute, the third part is valid since (Fourier expansion of field and eigenvalue)\n\\begin{equation} \\int d^{3}x \\hat A_c(x) \\psi(x) = \\int \\int d^{3} k d^{3} q \\, \\int e^{i(k - q)x} d^{3}x \\, \\alpha(q) \\hat a^{} (k) = \\int d^{3} k \\alpha(k) \\hat a^{}(k) \\end{equation}\n(The space integral results in a delta function $\\delta(k-q)$). The last part of the defining equation above is true since $\\hat A_a |0 \\rangle = 0$ and hence $e^{\\int d^{3}x \\hat A_a(x) \\psi(x)} |0 \\rangle = 0$.\nCorollary: $\\langle \\psi |\\hat A_a(x) |\\psi \\rangle = \\langle \\psi |\\psi(x)|\\psi \\rangle = \\psi(x) \\langle \\psi |\\psi \\rangle = \\psi(x)$.", "66" ] ]

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[ [ "Can black holes with the same mass evaporate with different speeds?\nI am curious about the following observations:\n(1) For a normal Schwarzschild black hole, it evaporates according to $dm/dt=-1/m^2$;\n(2) We have eternal black holes which do not evaporate (though only a thought extreme case);\n(3) Their difference is the microscopic state of the black hole(an eternal black hole is maximally entangled with another black hole in the sense that the density matrix of the black hole is I with a dimension of $2^{m^2}$).\nSo we have two extreme cases, either 'definitely evaporate following the fixed $m^3$ rule' or 'never evaporate' following '0 speed rule'.\nThen due to continuity, the real world should allow the intermediate case, that is, black holes that evaporates with a speed between $m^3$ rule and 0 speed, depending on how a black hole is entangled with another black hole. For example, may it be possible to add some mass to eternal black holes to trigger it's evaporation?\nIt seems that this goes to the ER=EPR idea.", "187" ], [ "According to <PERSON>, a single black hole has a 'bridge to nowhere' and it evaporates; for eternal black holes the double sided ER bridge between the maximally entangled black hole pairs has a maximal radius and they do not evaporate. Then how about the case where there is only a narrow ER bridge between two partially entangled black holes? Will they have different evaporation speeds depending on the ER bridge sizes?\nNote: A simple idea on why normal black hole evaporates is that, if the evolution of the black hole is unitary, then the entanglement between subparts of a black hole will increase with time till saturate, so the 'bridge to nowhere' attached to a normal black hole is not dense enough at the beginning period of the black hole formation procedure, like a leaky basket, this allows the possibility of black hole evaporation. But for the eternal black holes, the entanglement always saturates, so the bridge is always dense and the spacetime basket holds water, then the eternal black holes can not evaporate.\nBut if the black hole pairs are not initiated from 'maximally entangled' states but from a 'partially entangled' state, then the 'basket bottom' will be denser than normal black hole but sparser than the eternal black hole case, then will it evaporate with a different speed?", "43" ], [ "A question about relations between twistor, entanglement and light ray\nIn his book 'The road to reality', <PERSON> wrote:\nIt is possible to regard twistor theory as a continuation of the spin network programme to obtain a relativistic scheme, in which idealized light rays (or their generalizations, with spin) appear to be, in a sense, the carriers of quanglement. Ordinary spacetime notions are not initially among the ingredients of twistor theory but are to be constructed from them. This has a good deal in common with the underlying philosophy behind my original spin networks, where spatial notions are to be constructed from the spin networks, rather than the spin networks being thought of as inhabiting a previously assigned spatial geometry.\nMy understanding of his words is that:\nIf a twistor is a light ray, and a light ray is a way to carry quantum entanglement, then a twistor is closely related with quantum entanglement.", "682" ], [ "Of course we can easily associate a twistor $z=[z_0,z_1,z_2,z_3]$ (4 complex numbers) with a 2 qubit state $|\\psi>=z_0|00>+z_1|01>+z_2|10>+z_3|11>$ by just normalizing $z$.\nYes, the above mapping between a twistor and a 2 qubit state does show something interesting, since it can be easily verified that a separable pure state can not correspond to a null twistor and only entangled states (with respect to a local unitary transformation) might correspond to null twistors.\nBut the problem is that, the above picture seems to say: any entangled 2 qubit state corresponds to a light ray, no matter how strong the entanglement is. For me this is not satisfactory since states with different entanglements should not all corresponds to light rays since all light rays are equivalent but states with different entanglements are not.\nFrom another point of view, light rays are supposed to separate causal/noncausal events in spacetime. If the slogan 'entanglement is the glue of spacetime' is true, then it's natural to regard light rays as the boundary between entangled and non-entangled states since this means that 'beyond the light ray, spacetime/causality is broken'. For me, causality seems to stand for 'events strongly connected by spacetime glue/entanglement'.\nAnother fact is that the (1/2,1/2) spinor representation of Lorentz group and the formation of entanglement of 2 qubit states also show some signs of relating separable states with light rays.\nSo I have two different conclusions: twistor connects light rays with both strong and weak entanglement, quantum information theory connects light rays with the boundary between entangled/separable states.\nMy question is:\nIs a light ray something to carry entanglement as <PERSON> said, or it's something to separate entangled/nonentangled states? Or if light rays stand for 'strong/sticky glue/entanglement carrier', then what stands for the 'very weak glue carrier'? Or light rays can be both strong and weak glue?\nOr I am confused by the question: Is a light ray something to deliver the strongest correlation/causality/entanglement or to deliver the weakest correlation/causality/entanglement?", "298" ], [ "Diameter of the space of unitary operation manifold for quantum computation?\nI am considering the unitary operation manifold for quantum computation. In order to examine the computational complexity of an algorithm using n qubits, we need to define the complexity of a certain unitary operation $U\\in SU(2^n)$, where $U$ carries the initial state to the final state of the computation. Usually this is done by define it as the minimal number of simple gates (working on less than 2 qubits) to approximate $U$. <PERSON> shows a Riemannian geometrical description of it where a certain Riemannian metric is defined on $U\\in SU(2^n)$ to only count the 'number' of simple gates but put a high penalty on complex gates. Then the complexity problem is understood as finding the shortest geodesic connecting $I$ and $U$ with the given Riemannian metric on $SU(2^n)$. He also indicated that the curvature of this manifold is almost negative everywhere.\nMy question is: How can I judge the diameter of this manifold? I know usually there are upper bound of the diameter for a manifold with a positive lower curvature bound.", "364" ], [ "But I can not find results on negative curvature manifold. Can I assume that this manifold does not have a finite diameter?\nThis is very important to understand the complexity of quantum computation and also the complexity of quantum states. We know that every unitary operation $U$ can be APPROXIMATED with an arbitrary accuracy with $e^{n}$ simple gates. For a quantum state, we can also define the complexity of the state as the minimal number of simple operations to achieve it from a simple initial state, for example a product state 000...0000. So this complexity should not be 'approximated' as in quantum computation since the word 'approximation' itself involves the definition of distance. My idea is that if the diameter of the above mentioned manifold is not finite, then we have states with an infinite complexity. If this is the case, and if also this is true for typical states of the state space, then this will change our understanding of quantum system since currently we think the maximal state complexity is $e^n$.", "298" ], [ "<PERSON> and the crank's proposals have problems with them.\nTake <PERSON>'s proposal first. Let's say there is an external system which is initially fully entangled with some infalling information. Then, the black hole fully evaporates, and assuming purity, this external system is now fully entangled with the outgoing Hawking radiation. <PERSON>'s assertion is that during intermediate periods before the black hole has fully evaporated, there is some tripartite entanglement between the external system, the Hawking radiation which has already been emitted, and the metric outside which determines the mass, location and velocity of the black hole. This tripartite entanglement means neglecting the external metric, there is no entanglement between the external system and the outgoing Hawking radiation. Well, just after the information has passed through the horizon, there could be a random snap decision by the external system whether to jump into the hole and catch up with the infalling information and check if they are still maximally entangled, or remain outside and collect all the remaining Hawking radiation. It takes a time period of about the Schwarzschild radius before it's no longer possible to catch up with the infalling information, which leaves that as a critical window of time. If he decides to jump in and compare notes, he will find maximal entanglement with the infalling information inside. This would seem to suggest even if he chooses to remain outside, he is still maximally entangled with the information inside. By the monogamy of entanglement, he can't also be correlated at all with anything outside the black hole, and this includes the metric outside. Of course, this is a counterfactual conclusion, and maybe such counterfactual reasoning is inadmissible. But if it fails, it can only be because there is no tensor product structure for the Hilbert space for internal and external black hole states.\nThe crank's proposal has the following difficulty; suppose there is no black hole initially. A control qubit is set up in the superposition $\\frac{1}{\\sqrt 2}[|0\\rangle +|1\\rangle ]$. If its value is zero, don't create a black hole.", "43" ], [ "If it's one, create a black hole. The initial state is $|\\psi_i\\rangle\\otimes \\frac{1}{\\sqrt 2}[|0\\rangle +|1\\rangle]$. If there's no black hole, presumably, $\\rho_f=1$. If there's a black hole, presumably $\\rho_f=\\rho_s$ is some positive operator less than the identity operator. So, $\\rho_f = |0\\rangle\\langle 0|+\\rho_s\\otimes|1\\rangle\\langle 1|$. So, $\\langle \\psi_f | = \\frac{1}{\\sqrt 2} \\left[ \\langle\\psi_i|\\otimes\\langle 0| + \\langle \\psi_i|\\rho_s \\otimes\\langle 1|\\right]$. Now, measure the relative probabilities for the value of the control qubit. It no longer interacts with the system after determining whether or not to create a black hole. True, we normalize $|\\psi_i\\rangle\\langle \\psi_f|$, but that doesn't alter the relative probabilities for getting 1 as opposed to 0. The ratio is given by $\\langle \\psi_i|\\rho_s|\\psi_i\\rangle/\\langle\\psi_i|\\psi_i\\rangle$. In general, this ratio will be less than one. This violates unitarity. One way out is to assume $\\rho_s$ actually has some eigenvalues greater than 1. Another way out is to assume time evolution is nonunitary inside the black hole.", "66" ], [ "How can be sub-poissonian and super poissonian statistics distinguished from bunching and antibunching?\nThis is my first post here, so I apologize if there's something wrong.\nI am studying quantum optics and I found myself in trouble with the difference between bunching/antibunching and super poissonian/sub-poissonian light.\nAccording to <PERSON>, Quantum theory of light, pag. 248 bunching and anti bunching depends on the fact that $g^{(2)}(\\tau)$ (the degree of second order coherence) is less or greater than $g^{(2)}(0)$:\n* bunching $g^{(2)}(\\tau)$ < $g^{(2)}(0)$\n* random $g^{(2)}(\\tau)$ = $g^{(2)}(0)$\n* anti-bunching $g^{(2)}(\\tau)$ > $g^{(2)}(0)$\nAnd <PERSON> and <PERSON>, Photon anti-bunching and sub-Poissonian photon statistics, 1989 stated that the joint probability for detecting one photon at time t and another at time $t + \\tau$ is proportional to $g^{(2)}$, hence $p_2(t, t + \\tau)$ decreasing or increasing when $\\tau$ increases according to bunching and anti-bunching, while the value of $g^{(2)}(0)$ dictate sub or super poissonian statistics. I think this is the correct definition and it's coherent with the treatment of <PERSON>, while other textbooks and papers seem to make confusion on the two different aspects.\nFor example this answer doesn't seem correct: https://physics.stackexchange.com/q/139833/\nA threefold classification of light according to the second-order correlation function can be made as following: - bunched light: $g^{(2)}(0) > 1$, - coherent light: $g^{(2)}(0)= 1$, - antibunched light: $g^{(2)}(0) < 1$.\nThis implies sub or super poissonian not bunched or anti bunched.\nSo, I have three related questions:\n1. Why there is this confusion and what is the correct answer? I almost sure that <PERSON>, <PERSON> and <PERSON> are right.\n2. I understand the math but I don't see completly the physical meaning and how to distinguish the different effects experimentally.", "346" ], [ "I understand that bunching means that photons tend to come in bunches on the detector, but super poissonian seems similar because you have $\\Delta n^{2} = + ^{2}$. It seems to imply an excess of number of photons.\n3. The Hanbury Brown and Twiss interferometer measure the correlation of intensity of electric field. This tell us automatically if the source is bunched or anti bunched and super or sub poissonian at the same time? (I guess yes because if we have knowledge of $g^{(2)}(\\tau)$, we can know it's value at zero and if it increases or decreases with $\\tau$. This is valid only if the definition of Loudon is correct).", "795" ], [ "The physical picture of uncle Hamiltonian?\nUncle Hamiltonian was built to show the complex relationship between MPS (Matrix Product State) states and Hamiltonians, which claims that for a block injective MPS state, we can build a local frustration free uncle Hamiltonian with a continuous spectrum and the MPS state is a ground state of it.\nI am a little confused about the physical picture of it. The procedure of building the uncle Hamiltonian is:\n(1) For a MPS state with parameter $A$, the original parent Hamiltonian $H(A)$ has degenerated ground states but the Hamiltonian is gapped.\n(2) A perturbation on the MPS $A\\rightarrow A+\\sigma P$ leads to a correspondent perturbed parent Hamiltonian $H(A+\\sigma P)$. If the limit $lim_{\\sigma \\rightarrow 0}H(A+\\sigma P)$ exists, we get a so-called uncle Hamiltonian.\nQuestions:\n(1)No matter with or without the perturbation, $H(A)$ and $H(A+\\sigma P)$ are both parent Hamiltonians of MPS states so that they are both gapped.", "656" ], [ "Then how can the uncle Hamiltonian, as a limit $lim_{\\sigma \\rightarrow 0}H(A+\\sigma P)$, be gapless? How and when is the gap closed here? Is there an intuitive picture of the mechanism (the change of the spectrum)?\n(2) What's the meaning of introducing the uncle Hamiltonian? Is it just a descriptive artifact so that there is no real physical effect? Does this mean the uncle Hamiltonian is only a temporary phenomenon and therefore we do not need to worry about it? What can we learn from the construction of the uncle Hamiltonian?\n(3) If it's really an artifact or a very fine-tuned situation, can we resolve it for example by adding noise to the Hamiltonian? Is it possible that a minor random perturbation on the uncle Hamiltonian will open the gap again?\n(4) For a given MPS state, the Hamiltonians(gapped and gapless) that taking it as its ground state can be regarded as a manifold. What's the structure of this manifold? Or we can construct a fibre bundle taking the Hamiltonians as the fibre and the MPS states as the base space. Then what's the structure of the fibre bundle?", "298" ], [ "How a quantum system (eg. particle physics QFT) governed by <PERSON> equation can break the $T$ symmetry (or $CP$ symmetry) microscopically at all?\nWhy and how a quantum system (like our quantum vacuum of our universe) governed by <PERSON> equation can break the time-reversal $T$ symmetry (or $CP$ symmetry) microscopically at all?\np.s. the $T$ symmetry (or $CP$ symmetry) breaking is known and verified in neutral kaons. See also the Wikipedia texts on $CP$ violation and strong $CP$ problems.\nThe <PERSON> equation governs the quantum system (regardless relativistic or not) looks: $$ i \\frac{\\partial}{\\partial t} |\\Psi{}(t) \\rangle = H(t) |\\Psi{}(t) \\rangle. $$ It is easy to check the <PERSON> equation is time-reversal $T$ invariant if\n1.", "346" ], [ "$H(t)$ has no explicit time dependent, or time-reversal symmetric, then $ H(-t)=H(t)=H$. 2. Since we do not want to make $t=0$ becomes a special fixed point, we also require the time translational symmetry $H(t)=H(t+\\Delta)$ for some arbitrary time interval $\\Delta$.\nWe can do a time reversal transformation on the whole equation, $$ T i T^{-1} T\\frac{\\partial}{\\partial t} |\\Psi{}(t) \\rangle = T H(t) T^{-1} T|\\Psi{}(t) \\rangle $$ $$ =T i T^{-1} T\\lim_{\\Delta \\to 0}\\frac{ |\\Psi{}(t+\\Delta) \\rangle- |\\Psi{}(t) \\rangle}{\\Delta} = H(-t) |\\Psi{}(-t) \\rangle $$ $$=Ti T^{-1} \\lim_{\\Delta \\to 0}\\frac{ |\\Psi{}(-t-\\Delta) \\rangle- |\\Psi{}(-t) \\rangle}{\\Delta} = H(-t) |\\Psi{}(-t) \\rangle $$ $$ =T i T^{-1} (-)\\frac{\\partial}{\\partial \\tilde t} |\\Psi{}(\\tilde t) \\rangle \\Big \\vert_{\\tilde t = -t} = H(-t) |\\Psi{}(-t) \\rangle. $$\nAs we already knew, the <PERSON> equation is time-reversal $T$ invariant requiring that $$T i T^{-1} =-i$$\nMy question is that there seems to have no room to ask any quantum system governed by <PERSON> equation to break the $T$ symmetry (or $CP$ symmetry) microscopically, if we already demand a microscopically time-reversal symmetric Hamiltonian $ H(-t)=H(t)=H$.\nNow my puzzle is, - our quantum universe does break $T$ symmetry (or $CP$ symmetry) microscopically. - our quantum universe is governed by <PERSON> equation (regardless relativistic or not). How can such a microscopically time-reversal symmetric Hamiltonian $ H(-t)=H(t)=H$ break the $T$ symmetry?", "955" ], [ "As a start to an answer, the formula for the temperature of the interior of a black hole is known. In particular:\nFor small black holes, we study their black body radiation and see so little emission that the temperature is about 1/10,000,000 of a degree above absolute zero. Larger black holes would be even colder because they let less radiation escape. That means black holes are colder than space itself (about 2.7 degrees above absolute zero).\nBut, the harder question is whether a black hole would transform the ordinary matter, dark matter (if such thing exists), and photons that fall into it into gravitons.\nThe average density of a black hole, measured as mass divided by volume within the event horizon, is never more than slightly more dense (a few percent or so) than a neutron star which keeps the lion's share of its mass in the form of ordinary matter (i.e. neutrons)1, rather than transforming any substantial share of its mass into gravitons. And, in the absence of better and experimentally validated models of the structure of the interior of a black hole (which may be not just practically, but theoretically impossible), there is no way to test the composition of the interior of a black hole and no really compelling reason for it not to be made of really cold ordinary matter.\nOne can imagine a black hole composed of a Bose-Einstein condensate, as the two articles cited in the comments to the question do. <PERSON> (2012) argues that a work around to the entropy problem that I identify below can make this possible:\nWe reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The <PERSON> modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography.", "688" ], [ "They also open an intriguing possibility of simulating black hole information processing in table-top labs.\nBut, as far as I know, this article's hypothesis about entropy is not widely accepted. The cited follow up article to <PERSON> (2012), which is <PERSON> (2016), seems to be a bit more carefully reasoned. <PERSON>'s abstract states:\nWe analyze in detail a previous proposal by <PERSON> and <PERSON> that black holes could be treated as consisting of a Bose-Einstein condensate of gravitons. In order to do so we extend the <PERSON>-Hilbert action with a chemical potential-like term, thus placing ourselves in a grand-canonical ensemble. The form and characteristics of this chemical potential-like piece are discussed in some detail. After this, we proceed to expand the ensuing equations of motion up to second order around the classical Schwarzschild metric so that some non-linear terms in the metric fluctuation are kept. We argue that the resulting equations could be interpreted as the Gross-Pitaevskii equation describing a graviton Bose-Einstein condensate trapped by the black hole gravitational field. Next we search for solutions and, modulo some very plausible assumptions, we find out that the condensate vanishes outside the horizon but is non-zero in its interior. Based on hints from a numerical integration of the equations we formulate an ansatz and eventually find an exact non-trivial solution for a mean-field wave-function describing the graviton Bose-Einstein condensate in the black hole interior. Based on this we can rederive some of the relations involving the number of gravitons N and the black hole characteristics, summarized in its Schwarzschild radius, along the lines suggested by <PERSON> and <PERSON>. These relations are parametrized by a single parameter —a dimensionless chemical potential.\nIt is less clear in the follow up article that the graviton BEC must be the sole content of the black hole and neither paper addresses any process by which ordinary matter sucked into a black hole is transformed into part of a graviton BEC.\nI am not aware of any known process that would convert ordinary matter to gravitons in an ordinary black hole and I am not aware of research that really singles out this possibility. Indeed, a conversion of ordinary matter absorbed by the black hole into gravitons would violate baryon number and lepton number conservation and so this interaction is forbidden in the Standard Model and any reasonably plausible quantum gravity theory that preserves B and L conservation.", "688" ] ]

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[ [ "So how much has the exposure to light darkened the photographic plate? As much as expected for 301 ns or 33 ns ?\nFor 33 ns. That is the time that the clock inside the ship-muon indicates. We measure 301 ns of exposure, but a much shorter time was experienced by the moving photographic plate. This question is tricky also because the light will be red-shifted by <PERSON> effect, but lets forget about this detail.\nThese questions about \"what the other observer would observe that I observe\" are complicated. I suggest to follow the approach of the invariants: there are quantities that, measured by any observer, give the same result. One of them is the proper-distance between events. An event is any time and position (in this example, height) coordinate. There are only two important events in this problem: the muon enters the atmosphere at 15 km above the ground (lets called it $E_1$), and the muon reaching the ground ($E_2$). The specific coordinates given to the events depend on the observer. For example, for the muon, assuming that it sets its clock to zero when it enters the atmosphere:\n$E_1: (t,z)_M=(0 s,z_0)$\nIs $z_0=0$ for the muon? well, it could be $z_0=15$ km, or $z_0=100$ km, it really does not matter. What it matters is that for the event 2, for the muon:\n$E_2: (t,z)_M=(t_M,z_0)$,\nthat is, both events, for the muon, happen at its same spatial position. What about us from the ground? well, lets assume we set our clock to zero when the muon reach the top of the atmosphere (but it does not matter really):\n$E_1: (\\tau,\\zeta){\\rm Earth}=(0,15~{\\rm km}),\\quad E_2: (\\tau,\\zeta){\\rm Earth}=(\\tau_M,0~{\\rm km})$.\nI am using Greek letters for my coordinates.", "272" ], [ "Now, special relativity tells us that the proper distance between these events is the same as measured by any observer. The proper distance is the squared difference of the time (times $c^2$) minus the spatial distance squared. That is: $$c^2(t_M-0)^2-(z_0-z_0)^2=c^2(0-\\tau_M)^2-(15~{\\rm km}-0)^2\\tag{1}$$ And that's it. Forget about that one will be contracted measured by the other, and one time is dilated, etc...Lets divide Eq. (1) by $c^2\\tau_M^2$: $$ \\left(\\frac{t_M}{\\tau_M}\\right)^2=1-\\left(\\frac{15~{\\rm km}}{c\\tau_M}\\right)^2$$ but we know that $(15~{\\rm km}/\\tau_M)=0.994 c$, and therefore you have it, the time dilation. Since $\\tau'_M=301~{\\rm ns}$, therefore $t'_M=301~{\\rm ns}\\,\\sqrt{1-0.994^2}=33~{\\rm ns}$. I use a $'$ to denote the fact that we are not talking of the first event at 15 km from the ground, but from a much closer distance. The time dilation factor is the same.\nOk, lets solve the original problem that has three events:\n1. Muon enters the atmosphere at 15 km of height.\n2. The ray of light that the muon emitted toward the ground reaches the ground.\n3. The muon reaches the ground.\nAgain, latin letters for the muon coordinates and greek for the ground observer. For the first event: \\begin{align} E_1: &(0,0) \\quad\\text{ for the muon.}\\ &(0,15~{\\rm km}) \\quad\\text{ for the ground observer.} \\end{align}\nFor the second event: \\begin{align} E_1: &(t_2,z_2) \\quad\\text{ for the muon.}\\ &(15{\\rm km}/c,0) \\quad\\text{ for the ground observer.", "272" ], [ "Model: Let's simplify the model of a current in a wire, so we can be definite about what we are talking about. Take a wire (in the wire's frame) to have fixed positive charge density $\\rho_{+}$ and assume the electrons at rest w.r.t the wire, with electron density $\\rho_{-}$.\nIntroducing a current sets these electrons moving at some speed $v_{drift}$ w.r.t wire, but leaves the positive charge fixed. We ask the following question:\nWhat is the relationship between $\\rho_{-}$ (the electron charge density at rest), and the electron density with current?\nAnswer: The density measured by the observer stationary w.r.t a current carrying wire is not the same as if the charges were stationary. They are related by a Lorentz transformation.", "780" ], [ "Let's write the 4-current of the electrons when at rest, and when moving (with $c=1$): $$J^\\mu_{rest} = (\\rho_{-},\\vec{0})^\\mu,~~~~~~~~~~~~~J^\\mu_{moving} = (\\tilde{\\rho},\\vec{j})^\\mu = {\\Lambda(v)^\\mu}\\nu J^\\nu{rest}$$ where $\\Lambda(v)$ is the Lorentz Boost between these two frames. Note in particular that $\\boxed{\\rho_{-} \\neq \\tilde{\\rho}{-}}$ because $$J^2{rest} = J^2_{moving}~~\\implies ~~ \\rho_{-}^2 = \\tilde{\\rho}^2_{-}-\\vec{j}.\\vec{j},$$ and $~\\vec{j}\\neq \\vec{0}$.\nThis means that when you set up your problem, we have two possible scenarios:\n$(i)$ $\\rho_{-}+\\rho_{+} = 0$, that is we ask that the electron density in the electrons rest frame has the same magnitude as the positive charge density in the stationary wire.\n$(ii)$ $\\tilde{\\rho_{-}}+\\rho_{+} = 0$, that is we ask that the electron density in the wire's rest frame has the same magnitude as the positive charge density in the stationary wire. This is the situation of zero force on a stationary external charge you talked about in your edit.\nSo the question you have to ask yourself, is what situation do you want to deal with? It seems that for the \"explanation of magnetic force as a consequence of special relativity\" you are interested in, one should consider case $(ii)$ as this allows you to see how a test charge, moving parallel to the wire with velocity $v$, experiencing a force due to a pure magnetic force in one frame (wire rest frame) $F = q v\\times B$, is the same force experienced by the charge in its rest frame, effected only by the electric force, $F = q E$, in that frame (as in this frame it isn't moving).\nI hope this helps. If you need further explanation, don't hesitate to ask.", "780" ], [ "Part of the argument can be reasoned without using any \"heavy handed\" general-relativity, but it is a long road.\nPart 1: Relativistic objects are \"pulled toward\" gravitational sources more than predicted by newtonian mechanics. Light is pulled twice as much. This needs general relativity, see here.\nPart 2 Pressure results from exchange of moving particles. In an ideal gas, the moving particles cause pressure. In a solid of liquid, it's more complex. There is degeneracy pressure and attractive forces that allow object to exist in tension. This is due the the exchange of negative energy virtual photons.\nA system under pressure (such as a hot gas) contains moving particles that have \"extra\" gravitational attraction to our test mass. Conversely, our test mass feels an extra attraction to these particles. Although the kinetic energy of the particles contributes to the total mass and thus the gravity, the pressure creates extra gravity beyond that of the mass and kinetic energy alone.\nAn example: Consider a thin hollow spherical mirror filled with photons (again, we are working with a weak gravity source).", "343" ], [ "We place a test mass (that does not interact with light) just inside the mirror. Due to the shell theorem we need only consider the tiny amount of mass/energy that closer to the center of the sphere than our test mass. The Newtonian calculation would be G(our_mass)(energy_of_photons)/r^2, but the actual force is twice that due to the pressure. If we are outside the mirror the newtonian formula again applies. Although there is pressure inside, there is tension in the walls of the mirror, in effect it is a a balloon inflated with photons! The pressure and tension terms cancel themselves out. When you are outside of a spherically-symmetric object, only total mass matters and the internal pressures will always cancel.\nWhen pressure is due to gravitational compaction you can't escape hard-core relativity if you want to account for it: On earth, the pressure contribution to gravity in the core is only 1e-9 of the density (mass) contribution. This \"tiny\" amount of pressure isn't canceled out by tension as in the case of our mirror balloon. However, to understand why it gets canceled out we would need to invoke full-beast-mode-general-relativity because relativistic effects are also 1e-9 as strong as Newtonian gravity for Earth (no it's not a coincidence that both are 1e-9). Pressure is only important, in comparison to density, when P ~ (density)c^2, and that c^2 makes even core-of-Earth pressures look small.", "343" ], [ "As the orbit speeds are far below $c$, relativity doesn't matter. The fact that it is a black hole doesn't matter either-it could be a star of the same mass. The gravitational field of a spherical object is the same as a mass point at the center as long as you are outside the object. It takes a lot to change the momentum of the earth that much. The only thing I can think of to eject earth from orbit is to have another massive body come flying through to slingshot the earth away from the black hole. Does that work for you?\nAdded: Here is how I would think about it. You need an orbit simulator to get it really right. I believe there is a free version of Satellite Tool Kit and there must be others on the web. For simplicity, let everything happen in a plane. You need a big body, call it A, to transfer this much momentum to the earth. I would guess 30-100 earth masses, but you might wind up with more. Figure out what velocity change you want the earth to have.", "921" ], [ "I am hoping we can think about the two events separately and let the simulator patch them together. The first is A falling in from infinity on a parabolic trajectory. When it passes earth's orbit, it will be travelling $\\sqrt 2$ times faster than earth. We get to pick the direction, which will be set by the angular momentum of the system. The second is the scattering of A and earth, which we analyze in their CM frame, ignoring the black hole. I think it will be so fast that will be OK. Decide what velocity change (as a vector) you want the earth to feel. Find a set of parameters (incoming velocity and miss distance) in the A-earth frame that results in that velocity change for earth. Now find an angle for A to cross earth's orbit that results in the proper relative velocity of A and earth in their CM and direct A to cross earth's orbit at the correct distance from earth. Try it and see if it works. You only have three parameters-the mass of A, the angular momentum of A around the black hole, and how far ahead of earth A will cross the orbit before you allow for the A-earth interaction.\nLet me know how it works. No guarantees.", "675" ], [ "Your first method is the correct one, as long as the starting time is measured from the simultaneous moment at $t=0$ in the Earth's frame. As you probably know, it's not very natural to talk about simultaneous moments for spatially separated events, and this is where part of the subtlety in this question lies.\nBy the way, your first method can be found more simply by just dividing the Earth frame time $6000s$ by the time dilation factor gamma. $$\\frac{3}{5}6000s=3600s\\qquad \\frac{4}{5}6000s=4800s$$\nNow let's go to one of the ships' frames, say the one moving at .8c. The time $t'=0$ is when that ship starts its 90 minute timer, but the other ship started its timer at some earlier $t'$!\nThe event at which the other ship starts its clock is at $$t'=\\gamma(t-vx)=\\frac{5}{3}(0-.8\\times 8400 s)=-11200 s$$ $$x'=\\frac{5}{3}(8400s-.8\\times 0)=14000s$$ So at $t'=0$ the other ship is at $14000s-.946\\times11200s\\approx3405s$, which does not agree with your Lorentz contracted value.", "562" ], [ "Continuing on from this distance, you will find it is $3600s$ until collision again, as in your first method.\nWhy length contraction failed\nIn order to use the length contraction idea, you need to be transforming a 'proper length.' What that means is that the endpoints of the length are both at rest in the original frame. In your case the endpoints of the distance were the two ships, which were not only not at rest, they were at different velocities.\nBut just to show where length contraction would come in, let's consider the proper length with endpoints given by the worldlines $x=0, \\,x=8400s$. We found the transformed coordinates of the point $x=8400s$ at $t=0$ above. Now in the transformed frame the $x=0$ worldline is moving with velocity $-.8c$, so at $t'=-11200s$ it is at $x'=8960s$, and $14000s-8960s=5040s$ which was the contracted length you found in the second method. You can see it has nothing to do with the distance between the two ships.", "586" ], [ "The fact that $xdist = a/2$ is a condition not an assumption. That must be the case for some angle of the diffraction, and when that is the case you can 'pair' up a portion of the beam with another portion of the beam and you will get complete diffraction. When $xdist$ does not equal $a/2$, then you cannot do this 'pairing up' and some portion of the beam will not destructively interfere. This how is the variation in intensity is explained.\nEDIT:\nThink about it this way: The a/2 condition essentially says that if you were to divide the beam up into two halves with an equally arbitrary resolution of beams in each half, then the first beam of the top half (at 0 measuring from the top of the slit) would destructively interfere with the first beam of the second half (at a/2 measuring from the top of the slit). Every beam in the top half would find a beam corresponding in the bottom half that would lead to destructively interference.\nFor a/4 we have the same case: We can split the beam up into 4 quadrants each containing an arbitrary number of beams. Beam 1 from quadrant 1 would destructively interfere with beam 1 from quadrant 3, etc.", "441" ], [ "quadrant 1 and 3 destructively interfere. Same thing with quadrant 2 and 4, hence we also have a minimum here.\nFor a/5 it does not work: We split the beam up into 5 sections, with 4 of them we can make the same argumentation as before. That leaves us with 1 entire section that does not destructively interfere, no minimum.\nWhat is the difference between a/2 and a/4: Think about it geometrically first. If we use the diagram from the video you posted, the a/4 condition would mean that we have the distance of $xdist=\\lambda/2$ higher up and therefore the angle of the resulting beam would be angled higher. Turns out this is the condition for the second minimum. In fact, you will notice that this works with all multiples of 2, so let's make the algebraic:\n$xdist=\\frac{a}{2m}sin(\\theta)=\\lambda/2$\n$xdist=\\frac{a}{m}*sin(\\theta)=\\lambda$\n$xdist=asin(\\theta)=m\\lambda$ (where m is a non-zero positive integer)\nThis is the condition for all minima in the intensity pattern, i.e. places with complete destructive interference.\nSince you now understand the geometrical shift of the minimum along with a, you can make sense of this condition optically: If a phase shift of $\\lambda/2$ results in a destructive interference, then shifting that phase by a whole $\\lambda$ should again result in a destructive interference.", "441" ], [ "Motion of an electron near a proton\nStatement of the problem:\nConsider an electron and a proton that are initially at rest separated $a$ meters. Do not take into account the movement of the proton, because its mass is much greater than the electron's.\n1. What is the minimum kinetic energy at which the electron must be \"launched\" so that the electron gets to be $b$ meters away from the proton?\n2. What is the corresponding minimum speed for that situation?\n3. What distance away from the proton will the electron reach when it has double the initial kinetic energy?\n(The original problem says 2.00 nm instead of $a$ meters, and 12.0 nm instead of $b$ meters)\nMy attempt:\nQuestion 1 and 2\nWe say $q$ represents the elementary charge, i.e. the charge of the proton (positive) and of the electron (negative). Then I can assume that when the electron is $b$ meters away, the KE is zero.", "483" ], [ "Then the difference in potential energy would be the same as the lost KE. $$\\Delta U=\\frac{1}{4\\pi \\varepsilon_o} \\left ( \\frac{q^2}{a} - \\frac{q^2}{b} \\right ) =K= mc^2 \\left ( \\frac{1}{\\sqrt{1-\\frac{v^2}{c^2}}}-1 \\right ) \\approx \\frac{1}{2}m v^2$$ Doing some algebra we can get $v$, which is what they are asking for.\nMy questions:\n4. Is it possible to have an electron and a proton at rest?\nI imagine we would need another force that is \"pulling\" the electron away from the proton, and that that force cancels out with the electrostatic force from the proton. But, what would be a realistic example of a source of that force? And, how would that source alter the entire system?\n5. How can we launch an electron that is near a proton?\nQuestion 3 suggests that the speed of the electron suddenly goes from zero to some positive value. But, doesn't that (\"launching the electron\") imply infinite acceleration? If that is indeed possible, how can we realistically do it?\nEDIT: The original problem was written in a confusing way. Thanks to the help of @user7777777 I was able to interpret it the right way and fix the wording.", "793" ], [ "From this and your previous question, I suspect your confusion stems from the interpretation of $L$ in the length contraction formula. In fact this is something that confused me a lot when I was starting out.\nConsider two observers attached to frames $S$ and $S^\\prime$, with $S^\\prime$ moving at speed $v$ relative to $S$ in the $x$-direction. Let their coordinates coincide at the origin. When we derive the formula for time dilation, we consider a change in time of $\\Delta t=t_2-t_1$ in the $S$ frame. Performing a <PERSON> transformation then gives a that same change in time in the $S^\\prime$ frame as $\\Delta t^\\prime=t_2^\\prime-t_1^\\prime=\\gamma(t_2-t_1)=\\gamma\\Delta t$ since $x=0$ for the observer in $S$. So we arrive at the familiar $$\\Delta t^\\prime=\\gamma\\Delta t,\\tag*{(1)}$$ which tells us that the time for the observer in $S$ to reach $t_2$ is seen to be dilated to the observer in $S^\\prime$.\nNaively, we might try next to do the same thing for the spatial coordinate(s). Say we consider a length $\\Delta x=x_2-x_1$ at $t_1=t_2=0$. Going through the same motions, we find that $$\\Delta x^\\prime=\\gamma\\Delta x.\\tag*{(2)}$$ But wait.", "562" ], [ "This isn't the correct form of the length contraction formula. It should really be $\\Delta x^\\prime=\\Delta x/\\gamma$. What gives?\nThe way to understand this is to realize that $L$ is supposed to be a length. Equation 2 is the $x^\\prime$ distance between two points (the ends of the rod, say) at different times. This is obviously no good. While for the derivation of the time dilation formula it was okay to compare the intial and final times despite the fact that each observer had changed spatial position from the perspective of the other, the same is not okay for measuring the length of a rod. You need to measure the spatial positions of either end at the same $t^\\prime$ coordinate.\nThis is something that can be made much clearer by a spacetime diagram:\n(<PERSON>, 2008)\nConsidering the diagram on the right, the $x^\\prime$ distance between the pair of diagonal dashed lines is the $\\Delta x^\\prime$ in eq. 2. The contracted length however is the $\\Delta x^\\prime$ shown in the diagram, which is a distance between points at simultaneous $t^\\prime$.", "586" ] ]

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[ [ "That's a tricky one. <PERSON> was fanatical when it came to his hatred of dark wizards, but he does also strike me as someone who would try to make his students aware of the stakes, and make sure that they were prepared.\nI don't know about using the curses on students, but I could see him showing them the curses. That seems completely feasible. You have to remember, <PERSON> was supposed to be as convincing as possible, so it seems likely that even if the real <PERSON> wouldn't do that, his reputation and/or his personality made people who knew him believe he was capable of it. In fact, if <PERSON> had thought it would arouse suspicion by using the curses, he would never have used them.\nI could also see him comforting <PERSON>, and probably being even more of a mentor to him than the fake was. As an auror and a member of the Order of the Phoenix, <PERSON> would have felt a sense of camaraderie with the <PERSON> family (he even talks about them when showing <PERSON> the picture of the original Order). He might have even felt he owed them to teach <PERSON> to defend himself and that <PERSON> had a right to be able to take revenge. With his background, <PERSON> might have been one of the only people <PERSON> felt he could trust.\nHe might even have seen <PERSON> as someone who would hate dark wizards as much as <PERSON> himself, if not more, and could want to train him to be a sort of successor.\nTo be entirely fair, we like to make antagonists completely evil.", "773" ], [ "<PERSON> might have had a little good left in him when he took <PERSON> under his wing. <PERSON> hated death eaters who were never punished, and his father for not protecting him, but he had no real problem with <PERSON>. He might even have felt a little guilty about what he did to the <PERSON>, even if giving <PERSON> that book was intended to give <PERSON> a clue.\nHis devotion to <PERSON> may have been because of his long imprisonment in Azkaban, then at his father's hands. <PERSON> freed him from prison, but when he was sent to trial, he didn't show any of his later fanatic devotion, even denying that he had anything to do with the Death Eaters. It may simply have been loyalty. As for the <PERSON>, I always got the impression that it was a random senseless act of violence brought on by poor decisions by <PERSON> than a planned move directed by <PERSON>.\n<PERSON> praises <PERSON> several times, and he might actually have liked him as a person, as he never personally seemed to hold a grudge. He only wanted to kill <PERSON> out of his devotion to <PERSON>. It might be possible he genuinely enjoyed teaching and actually cared a little for his students, so long as they were not obstacles to his master.", "86" ], [ "In-universe, maybe <PERSON> made up a name for him without realizing its normal use.\nCalling Lord <PERSON> <PERSON> is the Death Eaters' term of respect for him. It's not something said by people who oppose him. However, <PERSON> would most likely not know that. She is young, and would not know much about him or the Death Eaters.\nIn her love poem, she is saying a lot of things that she likely made up herself. She's comparing <PERSON>'s eyes to toads and his hair to a blackboard, and I doubt that even in the wizarding world, those are common idioms or that she's heard anyone else using those analogies.\nSo it's possible she made up her own way of referring to Lord <PERSON>, and it's just a coincidence that it happened to be the name that the Death Eaters call him by. She wouldn't have thought twice about using the term she made up, because she wouldn't realize its usual significance.\n(Although he wasn't lovestruck and writing a poem at the time, this may be the case for why <PERSON> called Lord <PERSON> the Dark Lord as well.)\nOut-of-universe, it could be a continuity error.\nWhen commenting on the question, <PERSON> pointed out something interesting.", "247" ], [ "Also in Harry Potter and the Chamber of Secrets, <PERSON> called Lord <PERSON> the Dark Lord as well.\n(<PERSON> calling him <PERSON> makes sense. Up until <PERSON> freed him, he was the house elf to the <PERSON>. <PERSON> was a Death Eater, so he would call Lord <PERSON> the Dark Lord, and so would all the other people frequently around him. <PERSON> would have learned the term from them, and called Lord <PERSON> the only name he knew for him, despite his opinions on the Dark Lord being different from the <PERSON>'.)\nMy theory is that when this book was written, <PERSON> hadn't yet decided that she wanted the Death Eaters to call him <PERSON>, and was just using it as a general term. Later, when both Lord <PERSON> and the Death Eaters were a bigger part of the story, she decided to make \"<PERSON>\" be the term of respect that the Death Eaters used for their master.\nI'm fairly sure that after the Death Eaters become a large part of the story, they and the people around them or controlled by them are the only ones to call him <PERSON>. <PERSON> doesn't count, because he was pretending to be one, so would have to use the same name they would.", "247" ], [ "Why didn't <PERSON> ask the house elves to search for the Chamber of Secrets?\n<PERSON>, presumably knowing that house elves have powers that wizards do not, (such as being able to apparate within Hogwarts), could have asked them to help search for the chamber of secrets, since he knew it existed and <PERSON> had opened it, though he could not find it. He also knew that <PERSON> died when it was opened, so I expect that he asked her about it. If she told him the same that she told <PERSON> (that she was in the bathroom, heard a boy's voice and died instantly after seeing a pair of great big yellow eyes), he would definitely have guessed that the bathroom had a lot to do with the chamber. The tap for the sink in front of her toilet had a copper snake engraved, and she said that the tap never worked.", "773" ], [ "This is more than enough for <PERSON> to surely want to investigate the tap, so even if he could not sense the concealed entrance (though he certainly could by the time he entered the locket cave), he would know where to start searching. So why did he not get all the help he could? He was certainly not ignorant of the house elves and could understand them quite well (witness how he knew <PERSON>'s involvement in <PERSON>'s case).\n<PERSON>'s razor tells me that it was a plot hole. But is there a good possible explanation consistent with the rest of the story? If he never asked <PERSON>, why not? If he asked, why did he not find the tap and then the entrance? If he found the entrance but could not open it, why did he not ask the house elves to help? (And their apparation abilities would be useful here.) <PERSON>'s phoenix Fawkes was also able to apparate into the chamber of secrets when <PERSON> mentioned <PERSON> to <PERSON> (he appeared atop a pillar). There were just too many ways <PERSON> could have gotten into the chamber once he found the entrance, so is there evidence for why the house elves could not have helped him find it?", "573" ], [ "Because the case of creatures was safest in the care of <PERSON>, a trained magizoologist.\nIn figuring out why <PERSON> made the decision he did, there are a few things that are very important to remember.\n* There was no one more capable than <PERSON> at handling magical creatures, and caring for the creatures in the case.\n<PERSON>'s case contains several magical creatures, many of which are dangerous to the average wizard. From what we know of the wizarding world's attitudes toward magical creatures at the time, if <PERSON>'s statement is similar to what an average wizard thinks, they would mostly consider these creatures things to be killed or avoided, not cared for. Even if other wizards are tolerant of magical creatures, <PERSON> is likely the only wizard at the time who is actually capable of caring for this variety of creatures. There was likely no one who would be capable of taking care of the case while <PERSON> went to take <PERSON> home. So, he took the case along with him so he could continue to take care of the creatures himself.\nIt's perfectly logical to think the best way of handling a case of magical creatures is for it to stay with the magizoologist who's trained and capable of caring for them, and despite the problems it caused, this was still probably the best solution. Remember, the case of creatures would have needed to be taken care of for as long as it took for <PERSON> to take a steamboat to New York, return <PERSON> to the desert in Arizona, and travel back. In that time, the creatures within would likely need some kind of basic care unless the case was enchanted to feed them using magical methods. However, we see <PERSON> feeding some of his creatures, and one of Gamp's Laws states food cannot be conjured from nothing. Therefore, while this is not definitive proof because <PERSON> could possibly just like feeding his creatures even if the case could do it automatically, the case may not have any way of feeding them itself. Anyway if <PERSON> knew he wasn't intending to let the case out of his care, he'd only need such a function if he was somehow made incapable of caring for his creatures by sickness or injury.\n<PERSON> also has a special skill with his creatures.", "194" ], [ "They seemed to mostly have some kind of affection or at least tolerance for him, getting them to cooperate with him and be more compliant. For example, <PERSON> the Bowtruckle is highly unlikely to willingly accept being out of <PERSON>'s care. They likely would be even more difficult to manage for another wizard of equal skill with creatures simply because they are used to <PERSON> as their caretaker. In addition, being a skilled wizard in general doesn't mean someone can manage the creatures. Skill with handling magical creatures is different than skill at spellcasting and. A wizard who's gifted in Transfiguration might be terrible at brewing potions, so it's similarly wrong to presume that a good enough wizard can take care of the creatures.\n* The only creature who escaped while the case was actually with <PERSON> was the <PERSON>.\nMost of the creatures escaped when <PERSON> no longer had the suitcase, and it was instead in the possession of <PERSON>, a Muggle who had no idea of the contents. When <PERSON> had the suitcase he was able to watch it better, and only the mischievous <PERSON> kept escaping. <PERSON> also misplaced the <PERSON> egg, which was possibly in his pocket, but the hatched <PERSON> didn't escape while the case was with <PERSON>. If the case was with someone who wasn't as experienced as <PERSON> was in handling magical creatures (whether it was in New York or left with someone somewhere else) it's possible more creatures would have escaped.\n* <PERSON>'s reason for going to New York was to return a magical creature home.\nHe needed a way to transport <PERSON> from wherever he left from to New York, and keeping him in the case with the other creatures was a good way to safely transport him. It kept the other creatures within <PERSON>'s supervision, and also was a successful method of hiding a Thunderbird to get it past Muggle customs until <PERSON> could return him to his native home.\n* <PERSON> couldn't be expected to plan for the majority of the events that took place.\nThe only thing <PERSON> could have possibly been reasonably expected to have a plan for is the latch breaking on his suitcase, and maybe a way to secure the <PERSON> egg better.", "194" ], [ "In addition to Adamant's Answer. There is a section in Short Stories from Hogwarts of Power, Politics and Pesky Poltergeists which details why <PERSON> had suspicions about what Lord <PERSON> had achieved during the first wizarding war.\n<PERSON> already had suspicions as there was a rumour he had made himself invincible. Then after the defeat of Lord <PERSON>, his suspicions were raised even move given Professor <PERSON> guilt over what he has discussed with <PERSON> at school about Horcruxes. When <PERSON> tries to question him over this <PERSON> retired from the school.\nWhen the wizarding world fell into war, and rumours swirled that <PERSON> had, somehow, made himself immortal, <PERSON> was sure that it was he who had made <PERSON> invincible, by teaching him about Horcruxes (this guilt was misplaced, as <PERSON> already knew how to make a Horcrux, and had feigned innocence in order to find out what might happen if a wizard made more than one). <PERSON> became ill with guilt and fright. <PERSON>, now Headmaster, treated his colleague with particular kindness at this time, which had the paradoxical effect of increasing <PERSON>’s guilt, reinforcing his determination never to tell a living soul what a dreadful mistake he had made.\nLord <PERSON> made no attempt to seize Hogwarts on his first ascent to power.", "773" ], [ "<PERSON> believed, correctly, that he was safest remaining in his post rather than risking the outside world while <PERSON> was at large. When <PERSON> met his match upon attacking the infant <PERSON>, <PERSON> was even more jubilant than most of the wizarding population. If <PERSON> had been killed, <PERSON> reasoned, then he could not have made a Horcrux, which meant that he, <PERSON>, was innocent after all. It was <PERSON>’s extremity of relief, and the disjointed phrases he let fall in the first rush of emotion after hearing of <PERSON>’s defeat, that first alerted <PERSON> to the possibility that <PERSON> had shared Dark secrets with <PERSON>. <PERSON>’s gentle attempts to question <PERSON>, however, caused him to clam up. A few days later, <PERSON> (who had now completed a half century of service to the school) tendered his resignation.", "417" ], [ "Sometimes it was out of his control, in other times it was depending on circumstance.\nFor example, in book 1, <PERSON> was the teacher. He was a teacher in the past but because <PERSON> (who cursed the DADA post so no one would last more than 3 terms) was possessing <PERSON>, he was able to stay longer than others.\nIn book 2, <PERSON> is the teacher. This is because no one else wants the post, not because <PERSON> wanted him in particular. We also learn that the job is essentially cursed.\n\"He was the on' man for the job,\" said <PERSON>, offering them a Y plate of treacle fudge, while <PERSON> coughed squelchily into his basin. \"An' I mean the on' one. Gettin' very difficult ter find anyone fer Y the Dark Arts job. People aren't too keen ter take it on, see.", "417" ], [ "They're startin' ter think it's jinxed. No one's lasted long fer a while now. -Chamber of Secrets\nIn book 3, chances are looking slim for a teacher, but <PERSON> (a werewolf who people are reluctant to employ) gets a chance by <PERSON> to teach. He was by peer judgement a very good teacher (approved by Madam <PERSON>, students, and teachers).\nIn book 4, the Triwizard Tournament takes place, and as <PERSON> points out that <PERSON> is reading the signs, gets Mad eye <PERSON> to take the post, just for 1 year (pointed out to be an teacher experienced in his field even though he turned out to be <PERSON> and placed illegal curses on his students)\nIf it hurts again, go straight to <PERSON> ­ they're saying he's got Mad­Eye out of retirement, which means he's reading the signs, even if no one else is. Goblet of Fire\nIn book 5, it is in the same position as Book 2. No one wants the job, with the public considering it cursed, however, this time the ministry intervene and force <PERSON> to employ a ministry witch (<PERSON>) in essence to spy and cause trouble at Hogwarts.\nIn book 6, <PERSON> needed <PERSON> in order to obtain a memory, and as <PERSON> taught potions, <PERSON> had to move to the vacant role he so longed for (DADA). <PERSON> also knew he was going to die, so gave <PERSON> his wish at teaching DADA knowing that he would play a larger role when <PERSON> goes in the school anyway (technically <PERSON> didn't last longer than 3 months either, he left before the end of the last term, and came back as a headteacher).\nIn book 7, <PERSON> was inactive due to being in the afterlife. Not his fault!", "194" ], [ "In my mind, this question is easily answered. <PERSON> is clearly the better wizard, and here is why.\n<PERSON> is obviously a humble man, mostly due to mistakes made in his youth. On many occasions he says that people calling him \"the most powerful wizard ever\" are flattering him. But you'll notice that he does well to never tell untruths, he just bats around it. For example, in <PERSON> answer, the conversation with <PERSON>, \"He had powers I will never have\". This is true because <PERSON> had Horcruxes and the use of Inferi, but <PERSON> doesn't say, \"<PERSON> would have beaten my pants off in a duel!\" Because he knows he is more powerful than <PERSON>.\nNext, let's look at some quasi-quantitative data. Duels! Let's look at the fights we see <PERSON> win. He defeats <PERSON> at the height of his power against the power of the Elder wand. This takes some doing, but we don't know that <PERSON> couldn't have achieved the same feat. We see <PERSON> defeat four ministry of magic officials in one 10 second duel, 3 if you don't count <PERSON>. And, possibly most importantly, he finishes the duel at the Ministry between the death-eaters and the order. All of the death eaters, who are claimed in the book to be almost as bad as <PERSON> himself, flee before him, and he rounds them up with very little effort. <PERSON> meanwhile, confronts, at most, two at a time. <PERSON>'s unarmed parents, Madam <PERSON>, <PERSON>. Basically, <PERSON> just kills one on one, and normally against the unarmed, although, it is possible he has killed a ton at once, but even this takes little skill. The Avada Kedavra is only one spell. The only time we see him have a real challenge is during the battle of Hogwarts where he duels three at once, <PERSON>, <PERSON>, and <PERSON>(?).", "773" ], [ "He fails to kill any of these three, although he is not overcome by them. Of course this is hard to put definitively, but I would tend to give <PERSON> the edge here.\nSpeaking of the Duel at the Ministry, let's look at the duel between <PERSON> and <PERSON>, their only face-to-face battle, as far as the books tell us. <PERSON> is doing his best to defeat <PERSON>, while <PERSON> knows killing <PERSON> is useless. He seemingly has <PERSON> defeated after encasing him in water, before <PERSON> possesses <PERSON>, then runs away. All the while <PERSON> is charming the statues of the Fountain of Magical brethren to keep them protecting <PERSON>. Now, it isn't clear exactly who is actually superior. <PERSON> is not truly trying to kill <PERSON>, as he knows it's useless, so he may be trying to capture him alive, or gain information about the suspected horcruxes, which would imply that he is not giving it his all, however, he also possesses the Elder wand during this fight, and <PERSON> takes a curse which seems to be lethal, so <PERSON> is not fighting on pure skill. It seems as thought <PERSON> had the upper hand to me, however.\nHonestly, I think the most damning evidence is schoolwork. Yes, it may seem underwhelming, but think about the description of the two wizards at school. We have <PERSON>, the quiet but talented boy who charmed all his teachers. He received top marks in every subject and the award for special services to the school. You know who else scored top marks in every subject? <PERSON>, the constantly confunded Auror, who is one of the ministry officials <PERSON> owns. And that award for special services? He arrested the wrong person, who put up no known struggle, for a crime he committed. What a talented young lad. <PERSON>? According to <PERSON>, he won EVERY prize of note at the school, was published in many research journals including 'Challenges in Charming' and 'Transfiguration Today', aced all his NEWTs, and was soon in correspondence with the most noted magical researchers of the day including <PERSON>, a man who was already hundreds of years old at the time, yet needed the help of a 17 year-old-boy. YEAH, he was talented as no one else ever was. You can try to excuse this by the old, \"yeah, but <PERSON> didn't try at school\", except that he did.", "773" ], [ "<PERSON> panicked and couldn't think of a better lie.\nSaying that she went looking for the troll probably wasn't the best thing she could have said. It worked well enough, since she was able to get both <PERSON> and <PERSON> out of trouble and come out of it with five extra House points. If she was thinking more clearly, she might have been able to say something that would keep all three of them out of trouble, and not get any House points deducted.\nRemember, though, she probably wasn't able to think particularly clearly. She was having a very stressful day. She was crying in a bathroom all day because <PERSON> insulted her, then she was cornered by a troll. She narrowly escaped being either hurt or killed and ended up getting saved by the same student who was the reason why she was there in the first place and his best friend. At this point, she wouldn't have been thinking as logically as she normally does, because she was probably in somewhat of a state of shock.\nBut after <PERSON> and <PERSON> saved her, she didn't want to immediately get the two of them in trouble, so she said the first thing she could think of to make sure <PERSON> wouldn't punish them.", "86" ], [ "What she said was effective in doing that, and she didn't get in that much trouble for saying she went looking for the troll.\nAs for whether the lie she told was the best way to handle the situation, probably not.\nThere's no reason why an excuse involving her just being in the bathroom at the wrong time wouldn't have worked. Keep in mind, we don't know where all the bathrooms are in Hogwarts. They probably aren't very close together, since <PERSON> mentioned really needing one when he found a room of chamber pots (actually the Room of Requirement). Hogwarts is a big place, so sometimes it would take a while to get where you're going. The students were all supposed to be in their common rooms, but if it would have been a while before she got there, this definitely could happen. It would have probably been better for her to say she really needed to go, so she ran off to the nearest bathroom.\nPresumably, there would be available bathrooms somewhere near where they would be keeping the students (though it's never said, I'd expect each House common room would have one), since they might have been there for a long time, but depending on how far away the end point was, someone easily might not be able to make it all the way if they had to go before the evacuation. This is a plausible situation that <PERSON> could believe, since sometimes you just can't wait to get to a bathroom.\nShe also could have said she was in the bathroom during the student evacuation, in this case also blaming some kind of illness like stomach flu/diarrhea/anything else that would make someone spend a lot of time in the bathroom, and didn't realize that there was a troll in Hogwarts and that students were supposed to be in their common room. This is fairly close to the truth, avoids mentioning her crying or <PERSON> insulting her, and keeps all three of them out of trouble.", "821" ] ]

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[ [ "Do some physicists believe that the universe is a three-dimensional space wrapped on a four-dimension doughnut?\nThe astrophysicists believe if this is true, the universe would be finite. The entire cosmos may be only three or four times larger than the limits of the observable universe, which is about 45 billion light-years away. If true, a doughnut-shaped universe also has the possibility of allowing a spaceship that goes in one direction to eventually return to where it started without turning around.\nThe shape of the universe is something that astronomers have been debating for decades. Some believe the universe is flat where parallel lines stay parallel forever. Others believe the universe is closed, being the parallel lines eventually intersect. Astronomers say the geometry of the universe dictates its fate.\nWhile open universes continue to expand forever, a closed universe eventually collapses in on itself. Observations focusing on cosmic microwave background, which is the flash of light released when the universe is only 380,000 years old, have established that our universe is flat and parallel lines will stay parallel forever with an ever-evolving universe.", "764" ], [ "However, there’s more to shape than geometry, and topology has to be considered. Topology allows shapes to change while maintaining the same geometric rules.\nAn example is a sheet of flat paper that has parallel lines that stay parallel. If you roll the paper into a cylinder, the parallel lines are still parallel. If you take that sheet of paper and connect the opposite ends while it’s rolled like a cylinder, you get the shape of a doughnut, which is still geometrically flat. The team believes the warping occurs beyond observational limits and will be very difficult to detect. The team was looking at perturbations, which describe bumps and wiggles in the cosmic microwave background radiation temperature. They believe there could be a maximum size to the perturbations that could reveal the universe’s topology. <PERSON> and his team emphasize their results are preliminary and note that instrument effects could explain some of their results.\nhttps://www.slashgear.com/astrophysicists-believe-the-universe-may-be-shaped-like-a-giant-3d-doughnut-20683133/\nDo some physicists believe that the universe is a three-dimensional space wrapped on a four-dimension doughnut? I was reading this article and was confused about the geometry being discussed, they say the universe is flat, not in the sense that it's two-dimensional, but in the sense that parallel lines remain parallel indefinitely, then they mention that it's wrapped on a doughnut, which is impossible unless they mean a four-dimensional doughnut which would allow parallel lines to join, is this what is being said here? A topological three-dimensional plane wrapped on a fourth-dimensional doughnut would retain its geometrical feature like a two-dimensional plane wrapped on a three-dimensional doughnut would.", "484" ], [ "Researchers have been scratching their heads over this one for years. A lot of people have different opinions on the Big Bang theory, which attempts to explain how our universe came to be. There are those in the scientific community who maintain that the cosmos has always been, while others who believe it emerged from a singularity, a point of infinite density and temperature.\nSome fundamental events discovered through observation of the universe lend credence to the Big Bang idea. One such relic of the Great Bang is the cosmic microwave background radiation. <PERSON> and <PERSON>, who were given the Nobel Prize in Physics for discovering this radiation in the 1960s, were the first people to make this observation. The faint radio wave glow known as the cosmic microwave background radiation is assumed to be left over from when the cosmos was only a few hundred thousand years old. The Big Bang theory is supported by the observation that this radiation comes from a time when the cosmos was extremely dense and hot.\nThe preponderance of light elements in the universe is further corroboration of the Big Bang idea. According to this idea, hydrogen and helium should make up around 75% of the cosmos, with the remaining space filled by trace amounts of other elements. The abundance of these elements is consistent with the Big Bang theory, as indicated by astronomical measurements, which support this prediction.\nEvidence for the Big Bang theory is strengthened by the observed expansion of the cosmos. The expansion of the cosmos was first suspected in the early 20th century when astronomers noticed that faraway galaxies were receding from us.", "764" ], [ "Because of this, the Big Bang theory was developed to account for the expansion of the universe after the original explosion. Many separate measurements, such as those of the cosmic microwave background radiation and the large-scale distribution of galaxies, have all pointed to the same conclusion: the universe is expanding.\nTo me, the observable uniformity of the universe on enormous sizes is one of the most exciting pieces of evidence for the Big Bang idea. According to the hypothesis, everything in the cosmos should look the same in every direction. Observations of the cosmic microwave background radiation have proven this prediction correct by demonstrating the radiation's great uniformity in all directions. This uniformity is hard to reconcile with a pre-Big Bang universe, as it implies that the cosmos was extremely homogeneous and isotropic right from the start.\nThis entire body of data points to the Big Bang as the origin of the cosmos. Nonetheless, there are competing scientific ideas that imply the cosmos existed before the Big Bang. The cyclic model, for example, proposes that the universe expands and contracts in cycles, with each cycle starting with a Big Bang and ending in a Great Crunch. Yet, the homogeneity of the cosmic microwave background radiation is not explained by this scenario, even though it hints to the possibility of a pre-Big Bang cosmos.\nThe hypothesis of a multiverse is yet another alternative; it holds that there are numerous universes, each with its own Big Bang. The concept of inflation, which proposes a short period of exponential expansion right after the Big Bang, is the basis of this theory. During this time of inflation, several universes may have been created, each with its own Big Bang, according to this theory.", "764" ], [ "The answer to this question lies in cosmology.\nIt's because of relativity in positions. Every galaxy appears to be moving away from us and the universe we see is only the observable universe. Further points are more in the distant past, when you observe the deep field you observe the past. This may seem irrelevant to your question, but the idea of a \"center\" to a universe where any position in the universe, be it from our galaxy or from a galaxy in the Sloan Great Wall is the true center is not consistent with observation. That's because galaxies/clusters of galaxies are moving away from each other, relative to each other.\nEvery galaxy is slowly being pulled apart from other galaxies, save for those in gravitationally bounded clusters. (The whole architecture of the universe, with massive voids of absolute nothing and bunched up clusters of galaxies reflects this quite a bit) If the universe had a central point, this would be easily observed because there would be variation in the color shift of galaxies that could be analyzed to deduce a central point where the galaxies are moving away from.\nThat is not what is observed. Instead, pretty much most galaxies (save for exceptions like Andromeda or the Triangulum, who prove the rule since those galaxies are gravitationally connected to our galaxy via the local group) are moving away from us. The Great attractor being not a path to the center of the universe, but the center of the recently discovered Laniakea super cluster. So if there's attraction between galaxies, it's because of gravitational interactions.", "562" ], [ "The universe is also without any real edge unless you count the edge of the observable universe. The observable universe being more a historical record than what the contemporary universe around us looks like and is a byproduct of light speed being so limited. The speed of light in a vacuum is also the speed of information. The whole universe is far more massive by comparison.\nSo to speak about a center of the universe would require the following:\n1. A region of space that galaxy is moving away from or towards. (Which does not exist, instead relative trajectories and gravitational clustering is all regional at most.)\n2. Edges that are defined enough to pinpoint a center (If such edges exist, they are impossible to observe due to the limited speed information travels in the universe)\n3. Absolute positioning to pinpoint where this center would be. (All positions are relative, the galaxy, the sun and our planet all are moving at extremely fast velocities we don't notice thanks to relativity.)", "781" ], [ "We need to think about just where the time dilation effect occurs. By then thinking about the observations from each point of view, that is the free falling object and the external observer, we can come to terms with just what is happening as opposed to what appears to be happening.\nThe experience of time\nWe must remember that an object moving at a certain speed will travel through time (or the 4th dimension) at a slower rate. This does not mean that it moves slower, otherwise it would obviously not be travelling \"at a certain speed\".\nWhere time slows is in the ticking of the physical processes of the object itself.", "562" ], [ "In other words, my clock would tick twice as slow according to you as I flew past you at 87% the speed of light. I would be waving my arms normally, but according to you, I would appear to be waving my arms twice as slow and would also appear to be squeezed in size (not really relevant to this).\nThe falling object's point of view\nIf you were the object falling into the black hole, you would accelerate as you approached the event horizon, but you would take longer and longer to react to the approach, to the point where you would fall into the black hole in no time at all. From your perspective, your approach to the event horizon would become exponentially faster.\nIn other words, you would fall incredibly fast into the black hole, but you would have barely registered it in your mind because there just wasn't enough time for you due to relativity.\nThe stationary observer's point of view\nNow, the stationary observer outside the black hole's influence would observe something very different. The light (or rather, information) about your descent would become more and more redshifted, but also take longer and longer to actually reach their eyes.\nThis means that according to the observer, the falling object would slow down to a halt at the event horizon and have disappeared.\nSo what really \"happened\"?\n* The falling object fell in very quickly, but hardly realised it happening\n* The stationary observer would think that the object disappeared and never reached the event horizon.\n* <PERSON> taps on some gravity books and saves the human race.", "334" ], [ "All the planets in our solar system rotate on their own axis, therefore having a North Pole and a South Pole, the points where the axis meets the planet's surface. Some planets, such as Mercury, Venus and Jupiter, have an almost perpendicular axis, with the consequence of not having any seasons.\nEarth’s tilt at the present time is 23.5 degrees. This causes the sun to shine on different latitudes at different angles throughout the year, causing the seasons. When the North Pole tilts towards the sun, it’s summer in the Northern Hemisphere and vice-versa.\nThe axis of Uranus has the greatest tilt of all the planets in our solar system, near 98 degrees, so its North Pole is almost at its equator. This causes the most extreme seasons of all the planets, lasting 21 years, as for nearly a quarter of the Uranus year ( 84 earth years), the sun shines directly over one pole, leaving half the planet plunged into a long dark winter. Overall, it’s always cold.\nIf Earth were tilted like Uranus, spring and fall would receive relatively normal light, but in the summer in the Southern Hemisphere, the sun would never set, while the Northern Hemisphere would be plunged into darkness and cold.", "188" ], [ "The South Pole would melt completely, while the North Pole would freeze over, and the opposite 6 months later. These extremes at both ends of the planet would cause tremendously fierce and constant windstorms in the twilight zones. Oceans repeatedly freezing and thawing would greatly affect the planet, probably cooling it due to the greater albedo effect of ice.\nThank goodness Earth’s tilt is nowhere near that of Uranus! But why are the planets tilted differently and could this happen to Earth?\nScientists believe that Earth was struck by a large Mars-sized planet some 4.5 billion years ago, knocking off a big chunk which became the moon. The extreme tilt of Uranus was also caused by a great collision, but Earth’s moon saved it from being tilted as badly. The attraction of the Moon on the Earth keeps its axial precession, that is the variation of the angle of the axial tilt, between 22.1 and 24.5 degrees over a period of 41,000 years. This variation of the tilt has dramatic effects on Earth’s climate, but nowhere near what would happen if it were tilted like Uranus!", "188" ], [ "One of the main theoretical frameworks in physics is string theory, which aims to bring together the laws that govern particle behavior in the quantum realm and those that govern the conduct of large objects in the cosmos, like planets and galaxies. Although scientists continue to research and debate the topic actively, there needs to be definitive empirical evidence to either support or disprove the predictions of string theory.\nTo prove the String Theory wrong, an experiment that contradicts one of its basic predictions should be conducted. The problem is that these predictions relate to the behavior of particles at the minutest level and the highest of energies, making it difficult to test them experimentally.\nOne possible way to discredit String Theory is by attaining evidence that the behavior of particles at high energies does not match the predictions made by the theory. For instance, if the Large Hadron Collider (LHC) were to reveal that the behavior of particles does not match the predictions of String Theory, it would imply that the theory is either incomplete or incorrect.\nAn alternative method would be to search for occurrences that contradict the predictions of string theory. This could include detecting additional dimensions exceeding the four predicted by discovering particles that do not conform to the theory's framework as potential disproofs of its validity. However, it is essential to note that confirming or denouncing string theory would mandate evidence from experiments at energy levels far above what is currently feasible with our technology.\nThat said, experimental outcomes that challenge the theory's predictions would provide valuable knowledge about the universe's nature and could develop new theoretical frameworks that more aptly depict the behavior of particles and the universe in its entirety.\nScientists have long been fascinated by the string theory. While some experts fully support it, others still need to be convinced about its ramifications.", "481" ], [ "If supersymmetry were to be detected, it could disprove string theory.\nThe theory of strings predicts the existence of supersymmetric particles, and their discovery would serve as persuasive evidence for the idea. Additionally, the observation of extra dimensions could also debunk string theory. According to the principles of string theory, these different dimensions are present, and finding them would confirm the theory's validity.\nViolations of <PERSON> symmetry could also play a vital role in disproving it. Lorentz's invariance is a core principle of physics, and any breach of it may cause significant difficulties for string theory. If string theory were ultimately dispelled, it would profoundly impact the scientific community and could inspire the emergence of innovative ideas and approaches.\nIn conclusion, I will finalize by saying that. to prove string theory wrong; one must carry out an investigation that opposes any of its core predictions. Though it is arduous to examine such forecasts, evidence derived from high-energy particle colliders or other phenomena that are inconsistent with the theory's predictions could call into question its legitimacy.", "469" ], [ "Your question basically has two parts.\nHow would something fall up?\nThere are some theories that particles could exist which are affected inversely by gravity, such that rather than being pulled toward the source of gravity, they are repelled by it. We would not normally be able to find such particles, since 1- they would never be near any normal matter, and 2- the particles could never form a large object together on their own through gravity.\nHow would a disease cause this?\nSince you have specified a disease, I assume that you intend for microbes or parasites to be the cause of the effect. So how about this: a microbe that, when it consumes matter, converts it into this type of theoretical anti-gravity matter. The matter would remain inside the human body, despite being pulled in the opposite direction by gravity.", "279" ], [ "And if the chemical properties of the matter were unchanged by the anti-gravity conversion process, then the body's biological processes would treat it like any other matter. The matter would be combined in with normal matter in your blood and cells, where gravity's effect is overcome by strong atomic forces.\nGiven that the human body is already under normal gravitic pull and does not fall apart or suffer some sort of circulatory failure, it is fair to assume that having some of the matter in your body pulled in the opposite direction with identical force would not cause your body to fall apart or die immediately.\nThe greatest danger would be a \"head rush\" - humans who hang upside down for too long can have blood accumulate in their heads, causing loss of consciousness. But in our case, we only need 50.01% of the body's matter to be converted to anti-gravity matter in order for the person to experience weightlessness similar to zero-G that begins to cause them to rise into the air.\nThe biggest obstacle here is: how would microbes do this? Changing the physical properties of matter is no small feat, one would expect a facility like the LHC to be required to carry out this process. But much of Science Fiction is playing with \"what if the rules were a little different?\" scenarios, so if we assume that a microbe can do this, then it could produce the effect you're interested in.", "279" ], [ "Does time stop inside a black hole? How about at it's singularity?\nI'm a layperson who just read Big Answers to Big Question and in the book, <PERSON> proposes that:\nA typical black hole is a star so massive that it has collapsed in on itself. It’s so massive that not even light can escape its gravity, which is why it’s almost perfectly black. It’s gravitational pull is so powerful, it warps and distorts not only light but also time. To see how, imagine a clock is being sucked into it. As the clock gets closer and closer to the black hole, it begins to get slower and slower. Time itself begins to slow down. Now imagine the clock as it enters the black hole—well, assuming of course that it could withstand the extreme gravitational forces—it would actually stop. It stops not because it is broken, but because inside the black hole time itself doesn’t exist.", "334" ], [ "And that’s exactly what happened at the start of the universe.\nI think I understand the notion of time dilation as the clock approaches the black hole but I'm having trouble wrapping my head around the idea that time literally stops inside the black hole. <PERSON> then uses this idea to propose that there was no time before the Big Bang:\nAs we travel back in time towards the moment of the Big Bang, the universe gets smaller and smaller and smaller, until it finally comes to a point where the whole universe is a space so small that it is in effect a single infinitesimally small, infinitesimally dense black hole. And just as with modern-day black holes, floating around in space, the laws of nature dictate something quite extraordinary. They tell us that here too time itself must come to a stop. You can’t get to a time before the Big Bang because there was no time before the Big Bang. We have finally found something that doesn’t have a cause, because there was no time for a cause to exist in. For me this means that there is no possibility of a creator, because there is no time for a creator to have existed in.\nI've done a little bit of googling on the topic and it seems that time doesn't stop in a black hole. Nothing in high school physics or introductory physics in college prepared me for this idea.\nDoes time stop at the center of a black hole? If not, why does Hawking present this idea? How else might can we describe the idea of \"there was no time before the Big Bang\"?", "43" ] ]

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[ [ "Estrous Cycle\nIn the animal kingdom we have the \"estrous cycle\" (when females can get pregnant) and the \"rutting period\" (male mating season). So here's my thinking:\nElves are almost like 4 separate species, represented by 4 different estrous cycles. The \"species\" is revealed by the hair color. This fertility trait is a very dominant trait carried from the mother and coupled tightly with hair color. So blond elven women are only fertile during a time of the year that means they will always bear their children in summer, and their children will be blond and (if female) have the same estrous cycle as the mother.\nI kinda like this idea because I could see it developing as a form of population control. Elves are long lived, so birthing rates are a big deal and overpopulation could be a serious problem so nature's solution (perhaps aided by the elves themselves via some careful breeding over thousands of years) resulted in this pattern where only one-quarter of the female population is ever fertile all at once, and even then only during limited parts of the year. (e.g., assuming an earth-like cycle, summer babies are born in July, with a 9 month gestation period, meaning the blond women are only fertile in November.", "429" ], [ "That's it. Just November.)\nBeing fertile year round lead to overpopulation. Being fertile only part of the year makes things too brittle -- \"oh population is good now, no need for mating season this year. ... Oh no a disaster happened, we need to re-engage population growth but we have to wait a full year now\". Having 4 mating seasons with 25% of the women being fertile per season let the elves have good population control but also better flexibility than once a year.\nOr if you want it based off the men then do the same thing but, er, \"rutting period\", with the dominant gene coming from the men. But I think it makes way more sense to do an \"estrous cycle\" because while one man can make many females pregnant, this estrous cycles is a hard limit on population growth rates, so you have something that is (I think) genetically feasible and also has a bit of world building sense.", "429" ], [ "The undead body is preserved by magic.\nAnd that's the key. Treat magic as an almost-infinite resource easy to obtain but hard to replenish. Is a common setup in magic universes that \"magic\" is a consequence of the existence of living beigns. In other words, just imagine that \"mana\" is available in the whole world, but is more common or concentrated around places where life is more common as well, forests, big cities, etc...\nOn the other hand, living corpses uses magic for living; it could be a delicate ballance between living beigns spreading magic as they live and undead beighs consuming magic as long as they're living.", "227" ], [ "Create too many undead bodies and they wil deplete the magic of the zone quickly, and after that they will die (again) like my cell phone when it run out of battery. Or create just the right amount of undead bodies and they will consume the ambient magic at the same pace as it is replenished.\nIf the ratio of magic creation vs magic consumption is 1:1 (one living being spreads enough magic to sustain one unliving being) you tie the amount of undead bodies to the amount of living bodies so, if in some point of time the undead outnumber the living ones, they wouldn't last for long.\nLife and death are tightly related. It's obvious that one cannot exist without the other.\nNature don't like undeads, but tolerate them.\nIt is not natural for a dead being to be alive, every cell in the body of the undead is craving for resting forever. Well, you can cheat nature using magic but, the longer you cheat mother nature, the more it costs.\nIf the magic cost per day follows the graphic below:\nFor each day of existence (x axis), the magic cost increases (y axis), so after 100 days of unliving, dayly cost is almost twice as the first day and 200 days after the cost is multiplied by 8.\nNo matter how powerful the Necromancer would be, there would be a moment where the magic costs exceeds Necromancers power and this body cannot be kept living anymore.\nMaybe you can use both ideas at the same time! :)", "227" ], [ "Resistance / immunity\nThis explanation has a number of interesting and negative side-effects that may not suit your world.\nEvery planet has a magical field. Life on any given planet has evolved to develop immunity to their own planet's field. It turns out that cellular growth while within a magical field results in too many mutations. Basically, magic acts something like radiation. In order for life to develop, therefore, evolution takes it down a path of very high resistance to the magical field of the planet that life is developing on. However, an evolutionary resistance to the native magic field also means you're not very good at using it.\nSo, an earth wizard using earth magic can exist, but very weakly. He is so immune to his own world's magic field that he can barely interact with it at all.", "227" ], [ "He can do simple cantrips but that's about it. However, this weak interaction was enough to allow wizards to stumble upon the ability to open rifts to other realms, and what a mother lode of easily manipulated magic they found there!\nHowever, this explanation implies some potentially interesting side effects:\n* Visiting another world is a hostile environment that will hurt you. Could be anything from \"instant death by radiation exposure\" to \"you have a somewhat increased chance of developing cancer\". Don't send your kids or pregnant wife to other realms. (The people may not understand exactly what's happening -- cellular damage -- but they recognize that going to another realm is \"toxic\" somehow.)\n* Perhaps this can be mitigated by bringing your native magic field with you. Just as you open a rift to another realm to use their magic, you could travel foreign realms safely if you maintained a rift to your own world, surrounding yourself with your native field for safety. Maybe this is done by maintaining a spell or by carrying, say, a native lump of iron around with you.\n* There's a potential \"kryptonite\" scenario here where assaulting a foreign wizard with his own planet's magic field hugely weakens him.\nHave to think more about the implications but I like the idea that magic is a natural force, slightly different for each planet, which natives are necessarily, biologically immune to.", "227" ], [ "The rules keep changing.\nImagine if, in our universe, the laws of physics kept changing. E=mc^2? Oh well today it's E=mc^3. Every physics formula is subject to change without warning. Basically everything might be fine tomorrow or maybe the universe will explode.\nTurns out, magic is like that. It's energy drawn from a neighboring universe but the \"neighboring universe\" can shift from one to another at any time without warning and the new one may have completely different rules. The original magitek society was built during a time of unusual stability -- the rules for magic may well have been unchanged for thousands or millions of years and they didn't even know it could change. Until it did. When the shift occurred, the magitek devices drawing power (and, perhaps, a relative handful of sorcerers who were actively using magic when the shift occurred) experienced major malfunctions.\nMagic may be in a state of constant flux at the moment. The rules could change daily. Sorcerers can still access the energy, probe it, and use it, perhaps not unlike tapping into a totally unknown power wire where you're not sure what the volts or amps are or if it's AC vs DC. First you find out, then you buffer some energy, then you use it. That's sorcerers. They have not figured out how to make Magitek items that robust. They need a steady, known supply.", "227" ], [ "If magic settles down again, Magitek could take off again. And nothing stops you from making a device today, based on today's rules, but you don't know if it will work for an hour, a week or a month, and if it fails, you don't know how spectacular that failure will be (maybe you can invent a \"magic circuit breaker\" to avoid catastrophe but the constant shifting of rules still means your device stops working and has to be redesigned to fit the new rules, which, again, keep shifting).\n(To expand the electricity analogy, imagine trying to make a hair dryer that can work off of literally any power source. You can plug it into a USB port. Or a 120V US wall socket. Or a 240V wall socket. Or a wall socket in Japan. Or Germany. Or directly to the raw output of a nuclear power plant. It's probably possible but represents a big challenge and ultimately makes your hair dryer impractical -- you're spending more on the converters and buffers than on the device. This is what the people of this world face with magic. They can make the devices but since the properties of the power source keeps changing, the devices become something between impractical and dangerous. The sorcerers themselves might occasionally tap into the magic network and go \"Woo! Wow. Okay. Not using magic today I guess. Check back later.\")", "284" ], [ "How can my dragons use their tongues to control their fire breathing?\nSome background you may or may not skip\nI was daydreaming the other day about how tamed dragons whose magic was somehow harnessed as an energy source by humans could be used as a metaphor for nuclear power in modern societies. While considering this, I surprised myself thinking \"of course they would need to cut the tongue out of tamed dragons so that dragons can't orient their fire anymore\". Don't ask me where I got the notion that dragons need their tongue for that. Still, this got me wondering about what conditions were needed for this thought to be true.\nBackground you should not skip\nIn my world, dragons ...\n* ... fit the stereotypes defined in this somewhat related question\n* ... breathe fire in the way described there except they use magic to conjure the initial flame, inside their mouth.", "160" ], [ "The rest is similar: the liquid fuel is \"sprayed\" from a reservoir towards the flame, ignites and finally breathing is used to expel the burning fuel. It so happens that this is more efficient than using pure magic to conjure a full stream of fire.(1)\n* ... use their tongue to control the direction of the fire they breathe. This constitutes a competitive advantage over their ancestors who had to rotate their heads to do so: (1) the breathing direction can be adjusted to a moving target more rapidly(2) and unpredictably, (2) the head can remain parallel to flight direction for better aerodynamics.\nQuestion\nIf this is possible, what sort of motion / positioning of their tongue could my dragons use to control the direction of their breathing so that the flame is directed? This might be used in combination with other actions that control breathing, much like whistling. All I need is that the tongue be important enough that if the tongue is cut, dragons loose this ability and fall back on the original approach of turning their heads all the way.\nAn ideal positive answer would\n* explain the mechanism,\n* if possible back up its claim with examples in real-world fauna achieving similar purposes,\n* not make use of any more magic.\nAn ideal negative answer would either demonstrate that this is not possible or that a significantly simpler mechanism allows dragons to orient their fire and would lead to the same competitive advantages.\n(1): magic consumes mana, which is hard to store and fluctuating. Fuel is a more secure way of storing energy for dragons.\n(2): please consider that tongue motion of reptiles is faster that that of humans, and snakes can flick their tongue back and forth at around 15 Hz", "160" ], [ "Technically, it's possible, but they're pretty far from humans.\nYou can achieve this via a rather convoluted genetic mechanism. However, the resulting species is majorly different from humans in terms of reproductive mechanism. Your question kind of requires this.\nThe following conditions would create the effect you want:\n* The information related to subspecies is stored on the X chromosome\n* Female (2 X chromosomes) embryos are not viable and die in the womb without exception. This is because vital information is stored on the Y chromosome.\n* Both races are hermaphroditic, but the hairy race develops either one set of genitals or the other randomly in the womb, like a birthmark. This information is stored on the X chromosome.\n* Both races produce egg cells with both X and Y chromosomes, but the X chromosome is necessary for egg development, so the ones with Y chromosomes die immediately.\n* Sperm cells, however, can survive without an X chromosome.\n* The X chromosome is really heavy, due to all of the extra information stored on it. This means that sperm cells containing an X chromosome are too heavy to swim as fast as the Y chromosome sperm.", "1008" ], [ "This ensures that virtually all babies are born XY.\nThe effects of this are:\n* Every child gets the XY genotype, making them all genetically male\n* Hairy fetuses develop either testes or ovaries (maybe these organs are in the same place, so only one can form?), which produces either female or male hormones, depending (the alien equivalent of estrogen and testosterone). This means that they appear and act either male or female, despite being genetically male\n* Tentacle fetuses develop both sets of sex organs\n* When members of different species mate, the mother is the one that provides the egg cell. This cell contains the subspecies-determining X chromosome, so the mother's race is taken on by the child.\n* The other chromosomes determine the other aspects of the body appearance, so both parents give DNA.\nPossible issues with this:\n* Fertility is a little lower than in humans, because embryos with XX die in the womb.\n* Birth defects in the hairy species are common, where both sets of genitals manifest on top of each other. This probably leads to the fetus dying, but that's up to you, the author.\nI can't see this happening by natural evolution: there are too many difficulties on the way there. More likely, they were created by genetic engineering. Maybe a species found a better way to adapt to their environment, say learning to space travel, by messing with there genes, and they created this?", "1008" ], [ "Scientific site\nDespite its lack of natural resource, the island itself is (surprisingly) located miraculously well. It has lots of potential for scientific research. I was thinking astronomy (predictable weather, unobstructed view down to zero-degree elevation) but it could be something else more creative.\nIt can also be used for testing purposes in advanced applied sciences (weaponry, steam engines * wink * who knows). Being in the middle of almost nowhere, you can test stuff there relatively safe away from prying eyes, both your civilians and your rivals' spies alike.\nAuxiliary station, including for emergencies\nOn the plus side, the island can be supplied with various tools, including repair bases, basic infirmary, and other emergency-related stuffs, just in case your ship needs it and can't afford to wait several weeks of trip to your continental landmass. You will also feel a little bit safer from pirates targeting your merchants because you have this station. If the other superpowers want their ships able to use this auxiliary station, they must be nice to you.\nHaving such station in the middle of the ocean can have immense usefulness that perhaps can't directly be measured in $$$ for the short term. The usefulness will manifest in other forms, and potentially in the future.\nExtending your territorial waters\nYou can exclusively claim that the seas around the barren island is yours and yours only.", "537" ], [ "If the second superpower want to use the waters: for fishing or other natural resources, voyage path, emergency reasons, whatever, -- now, or in the future, mind you -- they have to ask for permission or setup a treaty or the likes. You've also got yourself an area denial tool or some sort.\nEven if your world have no global or multilateral treaties regarding what constitutes a territorial sea at the moment, having the island will benefit you quite a lot in the future when such treaties come into effect.\nJustification for exercising power/violence\nIf this island can be rightfully claimed -- not only by vague constitution wording or claims on paper, but also by actual people living there or at least non-trivially using and maintaining the island -- then after some tens of years it can be used (abused?) as a tool to bully the second superpower. If the second superpower dares to trespass the territorial boundaries or stops there without proper permission, you can claim that the second superpower is violating your territorial integrity and you can justify attacking or interning the trespassing ship with higher confidence. You get to claim to be a defender in front of the international community, not an aggressor, if the situation goes sour.\nForward operating base\nIn the event that a war actually ensues, having a forward operating base closer to your enemy's home gives you an advantage. When on the offensive, you can resupply your attacks quickly and reliably. When blockading the enemy coasts, you can resupply the blockade safely and easily. When operating a defensive maneuver, you have at least two defense lines: one near that island, and one near your own continental coasts.\nIt's far better, compared to having no forward operating base at all. What's even worse is having their forward operating base closer to your home.", "207" ], [ "If you are content with 10k or so survivors, never!\nProcedure is as follows:\nday 1: Space station is declared quarantine. All frozen embryos are declared quarantine, along with pre-existing frozen eggs and sperm.\nyear 1: Space station is being resupplied by sterilized food packages. Development in automation commences.\nyear 2: controlled breeding program established in space station (we are at serious risk of inbreeding now but it won't matter too much). The population growth has to be carefully controlled here, as a large population would be fatal to further plans.\nyear 3: sterilized nursery delivered to space station\nyear 10: beginning to divert resources from education to production\nyear 15: large hab modules delivered to space station\nyear 20: all further development proceeds on automation and AI platform\nyear 25: college & electronic library delivered to space station\nyear 30: mass rollout of solar technology\nyear 40: collection of internet library; space station supplies should be extended to +50 years by this point, space station boosted to +50 year orbit. Elderly care starts consuming economy\nyear 50: delivery of 100 long-lasting re-entry capsules to space station. Space station supplied to +70 years, including 3d printers and raw materials. Further resupplies about to cease.\nyear 51: collection of knowledge in libraries and long-lasting electronics should be completed.", "335" ], [ "Elderly care overruns economy.\nyear 52: Space station is on its own.\nyear 60: Mass die-offs begin due to inadequate medical care\nyear 70: Embryo storage power supply is converted to RTGs.\nyear 80: Runaway mass die-offs has reduce quality of life to terrible levels.\nyear 120: Humans extinct on earth by this point. (Yes we have a few 120+ alive now, but without support they won't be). The disease is extinct with them.\nyear 121: The sixth generation returns from the space station. They can tap the remains of the automated systems to begin farming. Female population: 100\nyear 122: Crack open the first of the frozen embryos.\nyear 142: At maximum rate, female population: 500 (200 adults). This assumes that automation development worked and we can sustain this population boom. Once reaching this stage though, it's no longer a problem.\nyear 162: Runaway population boom subsides due to running out of frozen embryos. This brave new world has very few human-specific pathogens.", "998" ] ]

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[ [ "Sculpting a Tree Stump\nIntroduction: Sculpting a Tree Stump\nHey guys!\nIn this instructable, I will show you how to sculpt a tree stump with white cement.\nNOTE:- I have explained my Instructables with step by step images. if you are not understand my writing.\nI have also uploaded video of every steps.\nIf you liked this videos, please Like, Share, & Subscribe!\nSupplies\nStep 1: Items Need\nFor this project you will need:\n1. Cake base or circular wooden disk\n2. Thermocol Disposable Glass\n3. Large and Small Scissors\n4. Fevi Quick / Glue Gun\n5. Packing Box Piece\n6. Marker\n7. White Cement\nhttps://www.amazon.com/12-lbs-White-Portland-Cement/dp/B06X6DY3K7/ref=sr_1_3?keywords=white+cement&qid=1561487865&s=gateway&sr=8-3\n8. Plastic Vessel\n9. Craft Knife\nhttps://www.amazon.com/X-ACTO-2-Knife-Safety-Cap/dp/B000V1QV7O/ref=sr_1_6?keywords=craft+knife&qid=1554542049&s=gateway&sr=8-6\n10. Bradawl\nhttps://www.amazon.com/Square-Birdcage-Woodworking-Scratch-874710/dp/B00IXVQMPU/ref=sr_1_3?crid=1ZVQ1GVZFGX4G&keywords=bradawl&qid=1561487615&s=gateway&sprefix=bradwal%2Caps%2C407&sr=8-3\n11. Hand drill machine\nhttps://www.amazon.com/SPTA-AC110-230V-Electric-Engraving-Polishing/dp/B074SH6CQD/ref=sr_1_1_sspa?crid=R83PWRVROCLE&keywords=hand+drill+machine&qid=1561486751&s=gateway&sprefix=hand+drill+machine%2Caps%2C404&sr=8-1-spons&psc=1\n12. File\nhttps://www.amazon.com/Nicholson-06706N-Axe-File-8-Inch/dp/B006DWT7HG/ref=sr_1_3?keywords=file&qid=1561487499&s=gateway&sr=8-3\n13. Oil Color\n14. Paint Brush\n15.", "401" ], [ "Transparent Resin\nhttps://www.amazon.com/Epoxy-Resin-32-Tabletops-Coating/dp/B00U5BPTPU/ref=sr_1_50?crid=23Y6Z3QSNJB6Q&keywords=resin+kit&qid=1561488216&s=gateway&sprefix=resin+%2Caps%2C543&sr=8-50\nStep 1: Planning, Sketching and Drawing :-\n1.1. Open Google Image :- I have search images of tree stump from google image.\n1.2. Searching Tree Stump :-\n1.3. Open Image on Tabs :-\n1.4. Open New Folder :-\n1.5. Downloading Images :-\n1.6. Checking Images :-\n1.7. Sketching and Drawing (Image 01) :- I have sketching and drawing tree stump on paper.\n1.8. Sketching and Drawing (Image 02) :-\n1.9. Drawing completed :-\nStep 2: Starting the Project :-\n**First take cake base or circular wooden disk. Take two thermocol\nglasses. One glass is cut into center using small scissors and fit in another glass. Using fevi quick fixed it.\n** Take a piece of packing box, cut packing box piece into 12 cm X 6 cm. Remove upper layer of packing box piece and we get line pattern on cupboard piece (packing box). Join two side of cupboard piece[Note line pattern side of cupboard piece remain inside] and steler the joint.Now we get cylinder and fixed it into cake base using fevi Quick and Glue Gun.\n**Take joint glass piece and make cave shape hole using marker. Cave shape hole also holed by using nail or scissor to remove easily.\n2.1.", "981" ], [ "DIY Wooden Flowers Planter Box With Glass Jar | Hydroponics Vase Holder\nIntroduction: DIY Wooden Flowers Planter Box With Glass Jar | Hydroponics Vase Holder\nFrom time to time between my big woodworking projects, I like to make something simple and new for home decoration.\nI had some small jars and I decided to make something using them - Wooden Planter Box / Frame. Why make one? I made 3 in different colors and put in them different flowers and plants.\nYou're welcome to visit my YouTube Channel, subscribe, and also watch my additional projects (Like this Console table on the picture). Don't forget to click the 'bell' button in order to get new videos notification.\nThank you!\nSupplies\nGeneral List of tools I'm using - https://www.itzikdiy.com/tools-list?m=1\nTools in this Instructable:\n* Miter Saw\n* Measuring tape\n* Drill driver with cone drill bit\n* Sanding paper / Sander\n* Paint brush / Roller / Wipe\n* Electric nail gun\nMaterials:\n* Glass Jar (8.5cm H * 5.5cm Diameter)\n* 10mm * 95mm wood profile (pine)\n* Wood glue\n* Wood filler\n* Strong glue (for metal + wood)\n* Very small screws (< 10mm)\n* Chalked paint or another\n* Clear protective topcoat (Varathane Satin Water-Based Interior Polyurethane)\nStep 1: Preparing the Miter Saw for Bevel Cut\nI started by setting the sliding miter saw to bevel cut of 45 degrees.\nIn my saw, there is a handle on the back which should be unlock, and locked again after setting the required vertical angle.\nStep 2: Cutting the Wood Pieces\nI prepared 3 boxes / frames, so I cut 12 pieces of 14cm from the wood profile.\nIn my case, I used 10mm * 95mm pine wood profile.\nStep 3: Pieces Are Ready\nStep 4: Preparing the Top Piece - Hole in the Wood\nBefore connecting the 4 parts of each box, I prepared the top piece which hold the jar, otherwise it will be harder to make it later.\nI drilled a 2cm hole using a cone drill bit.\nStep 5: The Jar\nI used glass Jars with height of 8.5cm and diameter of 5.5cm.\nStep 6: Preparing the Top Piece - Hole in the Jar Cover\nI removed the covers from all jars, and drilled a 2cm hole in each cover, using a cone drill bit.\nStep 7: Gluing the Cover to the Wood\nI connected the jar covers with the holes, to the top box woodedn part with the hole, using a strong glue which is good for many materials (Metal and wood as well).\nStep 8: Connecting the Cover to the Wood\nFor a final secured connection, I connected some very small screws from the cover to the wood.\nStep 9: Checking the Jars Connection\nI checked that each jar can be connected and removed from the cover and the covers are well connected.\nThe jars should be easily removed and connected later, everytime it's required to fill / replace water in the jars.\nStep 10: Gluing the Box\nI connected the 45 degrees box parts using wood glue.\nStep 11: Checking 90 Degrees Angle\nStep 12: Nailing the Box Frame\nAfter the wood glue was drying for few minutes, I nailed one nail in each pair of wood pieces, using an electric nail gun.\nStep 13: Filling Holes\nI filled all the holes in the wooden box, using a wood filler, including the holes made by the nail gun and other holes.\nStep 14: Sanding the Box\nI sanded the wooden box for removing all wood filler leftovers.\nStep 15: Painting the Box - 3 Different Colors\nI decided to have 3 different colors for the boxes, so I painted one in light blue (Chalked paint \"soothing blue\"), one in white and the third was left without paint - natural.\nI didn't make opaque painting, but semi transparent. I also sanded it later on the corners, for a 'vingage' look.\nStep 16: Painting the Box With Clear Protective Top Coat\nFinally, I painted each box with a clear protective top coat.\nStep 17: Boxes Are Ready\nStep 18: Connecting the Jars and Putting Flowers & Plants\nI filled water in each jar, and then connected them to the wooden boxes.\nFinally, I put some flowers and plants in each box.\nStep 19: The Result\nThats it.\nIt's easy to remove the jars and fill or replace the water from time to time.\nWhat do you thing about the result?", "401" ], [ "Simple Small Desktop Wooden Stand / Holder for Different Purposes\nIntroduction: Simple Small Desktop Wooden Stand / Holder for Different Purposes\nI made this simple Instructable as a gift for a friend.\nI saw that he asked on a Woodworking's Facebook Group (that by chance I was a member in), if someone can create such horizontal stand for him, with charge of course...\nSo while having a lot of free time during the Coronavirus lockdown, I immediatelly sent him a private message - \"Don't worry, I making the stand for you\" (free of course...)\nHe needed the stand for putting a tool related to smoking (the one you can see at the picture) and gave me the dimensions.\nOf course that you can make this stand for other different purposes, that you want to put on your desk, like a pen, or other decorative items...\nI took some scrap wood / leftovers and started this quick project.\nThe last name of the friend is <PERSON>, so I decided to surprise him and combine his name in the stand. He liked it a lot :)\n------------------\nYou're welcome to visit my YouTube Channel, subscribe, and also watch my additional projects.", "668" ], [ "Don't forget to click the 'bell' button in order to get new videos notification.\nThank you! :)\nSupplies\nGeneral List of tools I'm using - https://www.itzikdiy.com/tools-list?m=1\nTools in this Instructable:\n* Miter saw or other saw\n* Measuring tape.\n* For the rounded cuts I used my dremel with the following tools:\n* Dremel & Line & Circle Cutter (678) Accessory - UK - https://amzn.to/36NxASj - US https://amzn.to/32Z6EOj\n* Dremel 561 Multipurpose Cutting Bit - UK - https://amzn.to/3nC0kEp US - https://amzn.to/3nC0kEp\n* Kreg KHCCC 90° Corner Clamp: UK - https://amzn.to/3lW9jzC US - https://amzn.to/3lW9jzC\n* Drill & Wood drill bits.\nMaterials:\n* Scrap wood\n* Screws.\n* Wood glue.\n* Foto Transfer Potch (Optional)\n* Clear protective topcoat\nStep 1: Cutting a Piece of Wood for the Base\nI started by cutting a 18mm pine board to the required dimensions (~22cm*7cm), using the miter saw.\nStep 2: Preparing the Dremel Circle Cutter\nI prepare my Dremel 4000 & the Line & Circle Cutter Accessory (678), to cut the rounded shapes.\nFinally I found a use for this Dremel accessory :)\nYou can use a Jigsaw as well, but it's less accurate to make the rounded shapes manually...\nThis accessory uses a special cutting bit (Dremel 561 Multipurpose Cutting Bit).\nStep 3: Marking the Half Circle Position on the Base\nI marked the center of the wood from all edges of the rectangle sides.\nThe Dremel circular cutter has a nail which should be placed in the center of the circle, as an axis. The cutting bit turns arround the axis for cutting accurate circles. This accessory is great!\nStep 4: Cutting the Half Circle Shape on the Base\nCutting the circle.\nNote that you put the center axis at the side of the wood that isn't visible later, so you won't see the axis hole :)\nStep 5: Sanding the Base\nI sanded the base using a Sanding paper / Sander.\nStep 6: Marking the Text & Vertical Pices Positions on the Base\nAs I wrote at the intro, I wanted to put a text in the middle, between the vertical pieces of the stand, so I measured and marked the positions.\nThe vertical pieces position is ~12cm from each other.\nStep 7: Marking the Text \"O\" Letter Holes Position on the Base\nThe last name of my friend is <PERSON>.\nSince the name has 2 Symmetrical \"O\" letters, I decided to make it more special, and drill the \"O\" letters.\nSo, I put the printed text to see the position, and marked the \"O\" positions.\nI took a drill bit which matches to the size of the letters in the printed text.\nStep 8: Drilling the \"O\" Letter Holes on the Base\nI drilled the 2 \"O\" letter holes on the base.\nStep 9: Sanding the Holes on the Base\nI sanded the 2 \"O\" letter holes, using a dremel sanding attachment.", "493" ], [ "Custom Handmade Wood Sign\nIntroduction: Custom Handmade Wood Sign\nwww.howidothingsdiy.com\nIn this video I’ll be showing you how to make a 3D sign for my shop. This is handmade as I do not have a CNC. To make this sign, I printed a stencil on paper using MS paint and then cut it out. I then used spray adhesive to glue it to the board. Then I cut it out using a jigsaw and carved out the lettering using a Dremel with engraving bits. Finally, I painted it and hung it in my workshop.\nPleas SUBSCRIBE to my YouTube channel for more great how-to videos!\nSupplies\nWood\nPaint of your Choice\nMakita Circular Saw\nJigsaw\nDremel Carving Bits\nGeneral Spray Adhesive\nSander\nStep 1: Make Stencil\nTo make the stencil, I used Microsoft paint to resize the logo and printed them on 4 sheets of paper.", "401" ], [ "Then I cut them out with scissors and a razor blade.\nStep 2: Attach Stencil to Wood\nUse general purpose adhesive or tack glue to attach the stencils to the wood.\nStep 3: Cut Outside Shape\nUsing a jig saw and a fine tooth blade, cut out the outside perimeter. This sign has two saw blades slightly offset, so I repeated this step.\nStep 4: Use Dremel to Engrave Inner Details\nUsing a Dremel with a carving bit, carefully engrave the profile of the center details.\nStep 5: Remove Stencil\nTry to pull the stencil off. If it does not come off easily or cleanly, sand the remaining stencil off with a sander.\nStep 6: Use Dremel to Fill in Detail\nOnce the stencil is removed, fill in the details. My logo letters have a hand sketched font, so this process was perfect to replicate it.\nStep 7: Final Sand\nSand the sign with 220 grit sanding paper. Be sure to get all the small detailed areas as well.\nStep 8: Paint\nPaint the sign to your liking with the colors you chose.\nStep 9: Final Assembly\nFinally, assemble your sign. In this case, I just used wood glue and clamped the assembly together and let it dry over night.\nHang your sign and enjoy the life it brings to your space!", "76" ], [ "Wine Bottle Safe\nIntroduction: Wine Bottle Safe\nIn this Instructable, I demonstrate a way to make a hiding place inside of a wine bottle.\nThe finished product will look like unopened wine bottle.\nSupplies\nWhat you'll need:\nAn empty Wine Bottle\n3D Printed Cap/Lid - Downlaod STL attached\nAffiliate links:\n40mm Diamond Hole Saw\nDiamond Cutting wheel for sanding\nDiamond File\nPVC Heat shrink sleeve\nStep 1: Get a Bottle With a \"egg Cup Shaped\" Bottom\nSome wine bottles have a flat-ish bottom - don't use those.\nYou want a bottle with curved IN bottom or egg cup shaped.\nEgg cup shaped - because it could hold and egg, like an egg cup.\nStep 2: Cover the Labels or Remove\nIf you want to keep the labels, make sure to cover them, so they don't get wet.\nI like to use cling-film (plastic wrap) and electrical tape.\nStep 3: ​Drill a 40mm Hole\nPour some water into the \"bottom cup\" and slowly drill a hole.\nStep 4: Sanding the Inner Bottom\nI used a diamond disk to sand the inner bottom.\nApart from making it smooth, we're also doing it so the 3D printed cup would lock properly.\nDon't go crazy with sanding until you try the 3D printed cap.\nHere I am showing another bottle that's not covered with plastic, so it's easier to see.\nStep 5: Sandind Slots for the Cap\nWe need to sand 2 parallel slots for the 3D printed cap.\nYou can flip the cap around to mark the sanding points or do it by eye.\nOn most of bottles you can see the line from the mould. It can be used as a guide.", "74" ], [ "Unfortunately it's not always visible, especially when the bottle is dirty from sanding.\nStep 6: Wash the Bottle and Clean With Alcohol\nWash the bottle and clean it with alcohol to remove all the grease\nStep 7: Spray Painting With Matte Black Paint\nThere are many ways you can paint the bottle.\nI personally prefer to spray paint. I find it easier to use a nozzle from a compressed air can. It does not \"mist\" the paint as good as original nozzle, but I can access hard to reach spots.\nI finished painting with the original nozzle.\nGo slow and paint in steps.\nI usually paint the bottle in 3 - 4 steps letting letting the paint \"look\" dry before painting again.\nStep 8: PVC Heat Shrink Sleeve\nIf you want, you can use the bottle as a \"vase safe\" or alternatively, put on a heat shrink sleeve and use a hair dryer to shrink it.\nIf you want you can put in a cork before heat-shrinking the neck.\nStep 9: Hide Stuff Inside of a Wine Bottle\nIf you need to hide sweets from your partner (not because you're greedy, because you care about his/hers health).........and it happens that they don't drink wine, this is a perfect hiding spot.", "1013" ], [ "Mini Hydroelectric Concrete Dam\nIntroduction: Mini Hydroelectric Concrete Dam\nHi Friends.\nAfter Long time I make a mini concrete dam using cement, sand , water and steel bars.\nFor making this mini hydroelectric dam model you need following Items.\n1. Cement, Sand, Steel, Water.\n2. Gum and Foam Sheet\n3. 3d Printer and PLA Filament of different color\n4.", "120" ], [ "Dc motor, Stepper motor, Bulb and wire\n5. Basic Stationary Material\nSo let's start making.\nStep 1: Watch Full Video on Youtube\nPlease Watch Our Full Dam Construction Video On YouTube by Search our channel in YouTube.\nSearch Creative Construction Channel in YouTube.\nEnjoy Full Video and like, Subscribe and comment your review.\nStep 2: Excavation and Foundation\nMake excavation like pic 1. in your ground.\nThen cut steel bars and bending stirrup like pic 3.\nwe make 14 stirrup and 12 strait bars.\nStep 3: Foundation Reinforcement\nThen we settled all bars and stirrups.\nSpace between two stirrups 4 cm and bars was 2 cm.\nStep 4: Shuttering of Foundation\nWe use 3d Printer for making plastic stepper motor stand.\nWe need two stepper motor stands for upward movement of door.so we placed both side.\nI attached 3d .stl file for making stepper motor stand.\nThen we cut two shuttering for concreting and stick with heels.\nStep 5: Concrete Filling\nAfter some time we pour well mixed concrete and vibrate for no bubble gap of concrete.\nwe need about 1.5 feet3 of concrete for this pouring.\nAfter this pour wait for 24 hours.\nStep 6: Dissemble Shuttering\nAfter 24 hour complete dissemble shuttering and remove tap above stepper motor stand.\nStep 7: Reinforcement of Side Wall\nFor making side wall place steel bars and joint all cross point.\nStep 8: Stepper Motor for Upward Movement of Door\nAfter this place two stepper motor in place of stand.\nStep 9: Slider of Dam Door\nMake slider wall in 3d printer and place both side of stepper motor.\nThen cut shuttering for both side wall and stick with gum.\n.stl file for slider wall is attached in this step.\nStep 10: Concreting of Side Wall\nThen pour concrete and vibrate this. After 24 hours you can dissemble scaffolding.\nStep 11: Slider Parts Installation\nThen again 3d print slider door and place this using 6mm steel bars for sliding smoothly.\nStep 12: Dam Door RCC\nAfter this place steel bars between slider for making door.\nStick two column stirrups for road and place shuttering for dam door.\nStep 13: Concreting of Dam Door\nThen pour concrete inside dam door and wait for 24 hours.\nAfter this time dissemble shuttering and check the slide up and down.\nStep 14: Install Belt for Movement\nThen Install belt for moving mechanically between stepper motor and slide door.\nwiring the stepper motor and check movement.\nStep 15: Dam Road\nAfter check place shuttering for road above dam for moving vehicles.\nStep 16: Reinforcement of Road\nPlace steel bars on road for RCC.\nStep 17: Concreting of Road\nThen pour concrete last time in this road and wait for 24 hours again.\nStep 18: Remove Shuttering\nRemove all shuttering carefully and check movement of door upward and down.\nStep 19: Hydroelectric Dam Installation\nThen make plastic stand for dc motor and turbine using 3d printer.\nPlace dc motor on stand and stick with it, then wiring two dc bulb as per picture.\nStep 20: Practical Working of Dam.\nPlease watch above full video making mini dam con", "438" ], [ "Beach in a Bottle\nIntroduction: Beach in a Bottle\nHi All,\nIn this instructable, I will share how to make a simple beach in a bottle using recycled items.\nPlease share your comments and suggestions\nStep 1: What Do We Need?\n* An old chutney glass jar, with a wider mouth\n* Cardboard for delivery boxes\n* Popsicle sticks from an ice cream stick\n* Green Crape paper\n* Epoxy Resin\n* Dried Blue Poster color\n* PVA glue / fevicol\n* Sand\n* Air Dry Clay\n* Shells\nStep 2: Planning\n* Before we start, we need to visualize/plan\n* We need to decide how we want the beach to look like\n* How steep the beach shore will be\n* Where we want to place the house, size of the house\n* Size and number of trees\nStep 3: Beach\n* We need 4 oval-shaped cardboard\n* These are stuck together to make a beach slope\n* Using PVA glues, stick fine sand, as shown\n* Let it dry for 2 hours\n* Now inspect for holes and stick more sand\n* Let is dry for a day\nStep 4: House and Shells\n* The small shells were part of the sand, I just had to filter them out\n* I choose smaller shells to be used\n* Made a small house using popsicle sticks\n* Stick the shells using glue on the beach\n* House will be stuck later\nStep 5: Trees\n* I used airdry clay to make the tree trunks and paint them brown\n* Leaves are made using crepe paper and stuck together using PVA glue\n* We need 2 trees\nStep 6: Assembly\n* Glue the beach in the bottle\n* And fill any gaps with a paste of glue and sand as shown\n* Let this dry for few days\n* Stick the shells, trees, and the house\n* Let it dry\nStep 7: Epoxy\n* For simulating the sea, we will use Epoxy/resin\n* Caution: Use proper safety while using epoxy/resin\n* I mixed about 16 gms of epoxy ( 12 gms of epoxy + 4 gms of hardner)\n* Added pigment from dried poster color (blue)\n* Pour it in the bottle and leave it for 24 hrs\nStep 8: Finishing Touches\n* After 24 hrs the resin should be completely solid\n* I added a boat that I made from air-dry clay\n* And some waves using white acrylic colors\nWe are done and our new recycled Beach in a bottle is ready", "74" ], [ "Skateboard Rack\nIntroduction: Skateboard Rack\nHi, my name is <PERSON> and I am a high school student in Monterrey, Mexico. My brother has a skateboard which he always leaves laying around on the floor. I decided to make this small, sleek skateboard rack that he can hang on a wall to hold his skateboard. This project takes about 4-5 hours to make. It is difficult and you will need help from someone that is comfortable working on the project and using the tools.\nStep 1: Supplies\n1. Hacksaw\n2. Hand Saw\n3. Hammer\n4. Wood Chisel\n5. Tape Measure\n6. Drill\n7. Wood Paste\n8. Wood Paint\n9. String\n10.", "668" ], [ "Sand Paper\n11. Pencil\n12. Wood 27 1/2 inches long, 3 3/4 wide, 1 1/2 inch thick\nStep 2: Sanding the Wood\nSanding the wood is important, it not just cleans the surface but also makes it smoother and easier to work with.\nStep 3: Cover Up Any Wholes\nUse the wood paste to cover up any holes. You can use a card to apply it, but your finger works too.\nStep 4: Outline Your Measurements\nDraw the lines where you will cut the wood, I personally did a diagonal cut that ended at the middle. I used 4 inches of space in between cuts and made the cuts 1 3/4 inches long. So it would be 4 inches, cut 1 3/4 inches, then 4 inches again...\nStep 5: Cutting\nThis part is not just the longest, but the most difficult. Cutting diagonally is harder than expected. Make sure to be very careful, one mistake might ruin the entire project. I recommend using the Chisel, you could use a Drill but I don't recommend it since it's very unpredictable.\nStep 6: Sanding the Cut and Finishing Touches\nAfter cutting the wood, make sure to sand the cut. If any new wholes appear make sure to patch them up.\nStep 7: Make a Hole at the Top (Cut Pointing Down)\nMake a hole with the drill so you can hang it up later. You don't have to hang it, you could work on making legs for it but I think it looks better hung.\nStep 8: Coat Your Wood With Wood Paint\nThe Wood Paint will give the wood a fine look and also make it more durable and resistant. Make sure to coat every inch of the wood don't leave out any hidden spaces. It takes about a day and a half to two days to dry. Be careful with it, it does not come off.\nStep 9: Hanging the Rack\nCongratulations, you made it this far now it's time to hang it. Put a nail on the wall and hang it with a string.", "76" ] ]

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[ [ "Here is a way to measure it using the person's moment of inertia. Also, compared to many of the other answers to this question, this method is not only feasible, but actually reasonably safe for the subject.\n1. Measure the mass $m$ of the person; the length $l_b$ and average cross-sectional width (from the front) $w_b$ of the person's body (excluding the head); and the length $l_h$ and average cross-sectional width $w_h$ of the head of the person whose head we wish to know the mass of.\n2. Obtain a rigid stretcher that includes restraint straps, like this one:\n3.", "675" ], [ "Securely mount the person whose head is to be measured onto the stretcher, using the included restraint straps, so that the 'front' of the person is facing upward.\n4. Measure the moment of inertia $I_{gross}$ of the person in the stretcher about an axis extending upward through their neckn.\n5. Measure the moment of inertia $I_{tare}$ of the stretcher (without the person in it) about the same axis.\nNow compute the net moment of inertia: $$I = I_{net} = I_{gross} - I_{tare}$$\nFor simplicity, I will model the head and body of the subject as if they were thin rectangular plates rotated about the axis at one end.\nLet $m_h$ be the mass of the head of the person, and $m_b$ be the mass of their body. We know, then that $m_h + m_b = m$, or in other words, that the masses of their head and body together add up to the mass of the entire person.\n$$I = \\frac{m_bh_b^2}{3} + \\frac{m_bw_b^2}{12} + \\frac{m_hl_h^2}{3} + \\frac{m_hw_h^2}{12}$$\nSolving this equation yields:\n$$m_h = \\frac{4 l_h^2 m+w_h^2 m+12 I}{4 h_b^2+w_b^2+4 l_h^2+w_h^2}$$\nGoing further:\nIf you wished, you could use a more accurate model of the person, resulting in a more complicated equation for their moment of inertia. Also, if one wished to obtain a more accurate measure, one could measure the person's moment of inertia about several different axes, in order to compensate for nonuniformities in the density of the body as a whole, rather than just differences in the density of the head and the rest of the body.", "15" ], [ "How long for a mass to slide down a spring-loaded trap door?\nThis is a problem I first proposed to a friend of mine in college. He claimed to be able to solve it by setting up a differential equation, but I've never been able to crack it.\nImagine a spring-loaded trap door, mouse-trap style, one for which $\\tau = k\\theta$: when the door is open, the restorative torque (trying to close the door) exerted by the hinge is proportional to the angle at which it's opened. We'll say the angle can't exceed $\\pi$ so that the door can't open past the floor on which it's installed.\nThe trap door, which is rectangular and physically uniform, has length $\\ell$ and mass $M$. It is opened \"all the way\" and held there, so that $\\theta_i = \\pi$. A small mass $m$ is placed at the end of the trap door.\nWith the mass placed at the end of the door, the system is then released so that the trap door starts to close and the mass starts to slide down the increasingly tilted door.", "512" ], [ "(The reason the mass $m$ is \"small\" is so that it won't hold the door open when it's released.) The coefficient of friction of the mass on the door is given by $\\mu$. For simplicity's sake, assume that only kinetic friction acts the whole time, so there is no \"lurch\" when the object starts moving, and there is no need to distinguish between $\\mu_k$ and $\\mu_s$.\nThe question is this. How do we derive a function $L(t)$ which gives the length along the door which the mass has traveled after a given amount of time? I'd like to use this function to derive an expression for how long it takes the object to slide down the incline and be \"dumped\" into the opening beneath the trap door.\nWork thus far:\n* I've gone down the obvious roads of setting up the static situations. However, I can only come up with equations that involve $L(t)$ related to $\\theta(t)$ in complicated equations, and turning it into a differential equation doesn't make it better; the fact that torque is involved just makes the whole thing blow up because of the product rule.\n* I tried solving the simpler situations of a mass sliding down an incline that tilts at a constant rate, and that's achievable. The fact that $\\theta(t)$ is so difficult to nail down in this case is the villain.\nThe real nut of this problem is that there is nothing constant to tie myself to. Even the moment of inertia of the mass rotating about the hinge changes, since its distance from the hinge changes with time.", "766" ], [ "If you wanted to get an estimate of how fast you'd need to be moving in order to lift yourself with air deflection from running, you need to establish a couple of important parameters:\n1. Body weight $p$\n2. Torso angle $\\theta$ (defined such that $0^\\circ$ would be running upright)\n3. Speed $s$\n4. Torso length $\\ell$\n5.", "229" ], [ "Torso width $w$\n6. Air density $\\rho$\nAfterwards, all you need to do is a little bit of fluid mechanical force balancing. You can estimate that your torso deflects all of the incoming air you come into contact with straight downwards, which is only a decent approximation if your torso angle is high, in which case the lift force you would feel is simply the change in vertical momentum of the air coming at you in your frame of reference:\n$$ \\begin{align} L &= v_{\\text{down}} \\dot{m}{\\text{down}} \\[5px] &= v{\\text{down}} \\dot{m}{\\text{front}} \\[5px] &= v{\\text{down}} \\left(s w \\ell \\cos{\\left(\\theta\\right)} \\, \\rho \\right) \\[5px] &= \\left(s\\frac{\\cos{\\theta}}{\\sin{\\theta}}\\right) \\left(s w \\ell \\cos{\\theta} \\right) \\[5px] &= s^2 \\cot{\\theta} \\, \\cos{\\theta} \\, w \\ell \\rho \\end{align} $$\nYou can see that the approximation is bad for small torso angles since it predicts that you'd shoot off into space if you ran normally $\\left(\\theta = 0^\\circ \\right) ;$ that's because air would most certainly not deflect downwards if you ran this way.\nTo get liftoff, you want this lift to be equal to your body weight:\n$$L = pg$$\nLet's plug in some numbers. If you weigh $p = 175$ pounds, are running with a torso angle of $\\theta = 45^\\circ$, have a torso length and width of $\\ell = 0.5$ meters and $w = 0.4$ meters respectively, you can plug this in along with an air density of $\\rho = 1.225$ kilograms per meter cubed and $g = 9.81$ meters per second squared to find what minimum speed you need to run at:\n$$s^2 \\, \\cot{\\theta} \\, \\cos{\\theta} \\, w\\ell\\rho = pg$$\n$$s^2 \\times \\frac{\\left(0.2 \\times 1.225\\right)}{\\sqrt{2}} \\frac{\\mathrm{kg}}{\\mathrm{m}} = 778.45\\ \\mathrm{N}$$\n$$s = 67.0332 \\frac{\\mathrm{m}}{\\mathrm{s}} \\approx 150\\ \\text{mph}$$\nThere are a great deal of things I haven't considered here, like the amount of body weight your feet are holding up by virtue of running, pressure changes along the vicinity of your body, etcetera. But you can always just slap on some safety factors and run three or four times as fast, since your speed would reduce back to the liftoff value (if not less) if your feet were lifted off the ground.", "707" ], [ "No, there is no reason why the stored energy should be the same in both cases. The only requirement is that the total force supplied by each system of springs is the same, because the two systems are supporting the same load, and each is in equilibrium.\nThe difference in stored energy does not 'go' anywhere because these are two separate cases. You are not converting one case into the other.\nIf you did start with the load supported by the springs in series and converted this to the load supported by the springs in parallel, the difference in elastic energy would not in fact equal the difference in gravitational PE of the load!\nThe tension in each spring would have to be reduced from $W$ to $\\frac12 W$ where $W$ is the weight of the load, and the extension of each reduced from $x$ to $\\frac12 x$. The elastic energy stored in a spring with tension $W$ and extension $x$ is $\\frac12 W x$. The total elastic energy stored in the two springs is initially (ie in series) $2\\times \\frac12 Wx=Wx$ and finally (ie in parallel) $2\\times \\frac12 (\\frac12 W)(\\frac12 x)=\\frac14 Wx$.", "499" ], [ "The decrease in elastic PE is $\\frac34 Wx$.\nAfter the change from series to parallel, the springs initially supply a total upward force of $2W$ while the weight supplies a downward force of $W$. An additional downward external force is required, starting at $W$ and decreasing to $0$, to prevent the system from gaining kinetic energy as the tension is reduced. The work done against this external force equals the KE which the load would have acquired when it reached the equilibrium position had it been released. In that case it would have overshot the equilibrium position and oscillated indefinitely.\nThe work done on the load (average force x distance) by the two springs is $W\\times (\\frac12 x)=\\frac12 Wx$, which is the increase in its gravitational PE. The work done against the external force is $(\\frac12 W)(\\frac12 x)=\\frac14 Wx$. The total work done by the two springs is $\\frac34 Wx$.\nTo summarise : the two springs lost total elastic energy $\\frac34 Wx$ of which $\\frac12 Wx$ increased the gravitational PE of the load while $\\frac14 Wx$ was done against an external force.\nSee Mass dropped on a spring.", "333" ], [ "When an object bounces off of something, the bounce is not instantaneous, and in fact goes through a sequence of changes.\nFirst, the object slows down to a stop, and both the object and the surface are deformed. If they are both hard, then the deformation will be very small, but it will still exist.\nSecond, both the object and the surface reverse their deformations, speeding the object back up in the reverse direction.\nThe difference that makes a softer surface produce lower bounces is that soft surfaces stop that second stage early, leaving the surface still partially deformed. This reduces the time of contact, and thus the impulse of the bounce. The energy lost to this is converted primarily to heat.\nMore spring-like surfaces also do it more gradually, leaving some of the un-deformation still in progress when the object loses contact with the surface. This reduces the force during the time of contact, and thus the impulse of the bounce. The energy lost to this is converted to more macro-scale vibration, which may even be readily visible.\nIllustrating with an example:\nA ball has 1000 kg * m/s momentum when it first touches a soft surface. The ball and surface each exert 100 N force on each other as long as they are in contact.\nThe first stage, the \"impact\", lasts 10 seconds. During the impact, the ball slows to a stop and deforms slightly, and the surface deforms a lot. Both the ball and surface cause an impulse of 1000 N * s on each other, during this stage by itself.\nThe second stage, the \"rebound\", lasts only 5 seconds. During the rebound, the ball accelerates away and un-deforms, and the surface un-deforms only partially.", "621" ], [ "Both the ball and surface cause an impulse of 500 N * s on each other, during this stage by itself.\nThe end result is that the ball bounces off with only half the speed it started with. For a hard surface in the same scenario, the rebound would instead last almost as long as the impact, about 10 seconds, the surface would un-deform all the way, and the ball would bounce with almost as much speed as it started with.\nP.S. Notes on concepts and units:\nMomentum: The product of mass and velocity. It has unit kilograms * meters / second, or kg * m/s. This unit is equivalent to N * s.\nForce: How hard you're pushing on something. Its unit is Newtons, or N.\nImpulse: The product of force and time, and also the change in momentum. It has unit Newtons * seconds, or N * s. This unit is equivalent to kg * m/s.\n<PERSON>'s third law applies to force, and indirectly to impulse. It does not apply to momentum.\nIn typical everyday collisions, gravity applied over some previous time span may be the source of some of the momentum involved, but is inconsequential for the collision itself because it is utterly dwarfed by the forces exerted by the objects on each other. The collision between a ball and a hard floor takes something like a millisecond to finish, but produces an impulse large enough to reverse - not just stop - momentum that took around 500 milliseconds for gravity to build up.", "621" ], [ "Suppose your table or ship is supported by forces $\\vec F_i$ applied at $N$ fixed points. In general, there are two vector equations you need to solve. In order for the ship to remain suspended, the net force on it must be zero:\n$$\\sum_i \\vec F_i=-\\vec G$$ where $\\vec G$ is the weight. In addition, the net torque must be zero so that the table/ship does not rotate: $$\\sum_i \\vec r_i \\times \\vec F_i = 0.$$ where $\\vec r_i$ are the positions at which the forces are applied, relative to the center of mass (which I'm assuming is the same as the center of gravity, i.e. the gravitational field is uniform). $\\times$ here denotes cross product.\nIf all forces are in the same (vertical) direction, the equations you need to solve can be simplified somewhat. Namely, if $\\vec F_i = F_i \\hat z$ and $\\vec G = -G\\hat z$, $$\\sum_i F_i=G$$ $$\\sum_i x_iF_i=0 $$ $$\\sum_i y_iF_i=0 $$\nNote that this is a linear system of three equations.\n1. For $N = 1$, there is an \"unstable\" solution if and only if $\\vec r_1=0$, i.e. the force is applied at the center of mass.", "766" ], [ "The solution is unstable in the same sense as a one-legged table.\n2. For $N=2$, there is an \"unstable\" solution if and only if the center of mass lies on the line connecting $\\vec r_1$ and $\\vec r_2$ (i.e. $\\vec r_1$ and $\\vec r_2$ are colinear with the center of mass). The solution is unstable in the same sense as a two-legged table.\n3. For $N=3$, there is a unique, stable solution as long as no two of the points $\\vec r_1$, $\\vec r_2$ and $\\vec r_3$ are colinear with the center of mass. If you further require that all forces $F_i$ be non-negative, the center of mass must lie in the interior of a triangle defined by $\\vec r_1$, $\\vec r_2$ and $\\vec r_3$ as its vertices.\n4. For $N\\ge4$, except possibly in degenerate cases (where some pairs of \"vertices\" are colinear with the center of mass), there are infinitely many solutions (i.e. no unique solutions).\nA four-legged table with each leg in contact with the ground doesn't actually need to be supported by equal forces applied at each leg. All that is required (besides the condition that the sum of the forces equal the weight) is that the forces on opposite legs be equal. So there are an infinite number of force distributions that will support the table.", "151" ], [ "Cube bouncing off a wall\nAn elastic cube sliding without friction along a horizontal floor hits a vertical wall with one of its faces parallel to the wall. The coefficient of friction between the wall and the cube is $\\mu$. The angle between the direction of the velocity $v$ of the cube and the wall is $\\alpha$. What will this angle be after the collision (see Figure P.1.3 for a bird's-eye view of the collision)?\nThis is Problem 1.3 in A Guide to Physics Problems, Part 1: Mechanics, Relativity, and Electrodynamics. There are things I don't understand in the solution provided in the book.\nThere are two forces acting on the cube. One is the normal reaction $N(t)$, perpendicular to the wall, and the other is the force of friction $F_{fr}(t)$ parallel to the wall\nWe expect that, as a result of the collision, the cube’s velocity $\\textbf v$ will change to $\\textbf v'$. In the direction perpendicular to the wall, the collision is elastic, i.e., the velocity in the $\\textbf{x}$ direction merely changes sign: $v'_x=-v_x=-v\\sin(\\alpha)$.", "512" ], [ "Therefore, the momentum changes by $-2mv\\sin(\\alpha)$ in the $x$ direction. This change is due to the normal reaction $N(t)$\nSo, according to <PERSON>’s second law: $$\\Delta p_x = -\\int_0^\\tau N(t) dt = -2mv\\sin(\\alpha)$$\nwhere $\\tau$ is the collision time. If there were no friction, the parallel velocity component would not change and the angle would remain the same. However, in the actual case, the $y$ component changes and $$\\Delta p_y = -\\int_0^{\\min(\\tau',\\tau)}F_{fr}(t)=-\\int_0^{\\min(\\tau',\\tau)}\\mu N(t) dt$$\nHere $\\tau'$ is the time at which the velocity $v_y$ goes to $0$. So $$mv_y'=mv_y -\\int_0^{\\min(\\tau',\\tau)}\\mu N(t) dt$$\nThe first thing I can't grasp is why the collision is elastic in the $x$ direction. Admitting this, I'm ok with the equation $\\displaystyle \\Delta p_x = -\\int_0^\\tau N(t) dt = -2mv\\sin(\\alpha)$.\nBesides, I don't get why $\\displaystyle \\Delta p_y = -\\int_0^{\\min(\\tau',\\tau)}F_{fr}(t)$. It looks a lot like the previous equation the author got on the $x$-axis, but I don't understand why he considers $\\tau'$ as the time at which the velocity $v_y$ goes to $0$, and why the upper bound of the integral has to be $\\min(\\tau',\\tau)$.", "512" ], [ "Spring whose spring constant is a piecewise function of displacement—is this possible?\nA bungee cord is essentially a very long rubber band that can stretch up to four times its unstretched length. However, its spring constant varies over its stretch [see <PERSON>, P.G. “The Physics of Bungee Jumping.” The Physics Teacher (November 1993) 31: 483-487]. Take the length of the cord to be along the $x$-direction and define the stretch $x$ as the length of the cord $l$ minus its unstretched length $l_0$; that is, $x=l−l_0$. Suppose a particular bungee cord has a spring constant, for $0≤x≤4.88 $ m, of $k_1=204$ N/m and for $4.88 \\mathrm{m}≤x $, of $k_2=111$N/m. (Recall that the spring constant is the slope of the force $F(x)$ versus its stretch $x$.) (a) What is the tension in the cord when the stretch is $16.7$ m (the maximum desired for a given jump)? (b) How much work must be done against the elastic force of the bungee cord to stretch it $16.7$ m?\nThe given answer is (a) 2.32 kN, (b) 22.0 kJ.\nI'm struggling to wrap my head around the idea of a bungee cord with these properties. Suppose I attach a weight to the cord having mass slightly less than $204 \\cdot 4.88 /g = 101.5 $ kg.", "1002" ], [ "Then the cord will hang in equilibrium at just above $x=4.88$ m below the unstretched length.\nThen, suppose I attach a feather to the weight. Now it will sag past $4.88$ m, and the spring constant instantly changes (!) to $111$ N/m, putting the new equilibrium at $101.5 g/111 = 8.97$ m. Am I correct in understanding that the weight would suddenly fall $4$ m? And if I then removed the feather, would the equilibrium point remain at about $8.97$ m, even though its weight has been restored to what it was before (when the equilibrium was at $4.88$ m)? This seems very counterintuitive to me.\nIgnoring my intuition, I proceeded under the assumption that $x=16.7$ (as given in the question) is in the $k=111$ domain. Then the magnitude of the tension is $kx = 1854$ N, which doesn't match the answer given for (a).\nIn (b), I noticed that the spring force $kx$ is a piecewise function of $x$, and integrated like so:\n$$\\int_0^{4.88} 204 x\\, dx + \\int_{4.88}^{16.70} 111x\\,dx = 16586 ~\\mathrm{J}$$\nSwing and a miss.\nIn both cases, I have the correct order of magnitude, so my best guess is that I'm forgetting to account for gravity somehow. But we aren't given the mass of the the bungee jumper, so I don't see how I would incorporate an $mg$ term in here.\nEdit: I think I have a partial guess for what's going on in (a). If we redefine the tension force as\n$$F_s (x) = \\int_0^x k(x')\\, dx'$$\nThen\n$$F_s (16.7) = \\int_0^{4.88} 204 \\, dx + \\int_{4.88}^{16.70} 111\\,dx = 2308 ~\\mathrm{N} \\approx 2.32~\\mathrm{kN}$$\nTo me, this looks like the sum of the tension in two different springs, each having two different spring constants and stretch values. Is this correct?", "766" ] ]

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[ [ "Need to finance a vet bill?\nHi everyone! I just wanted to pass this along. If you need to finance a vet procedure, please check out Scratchpay. I had to use this to finance a an emergency with one of my doggos.", "589" ], [ "The service directly pays your vet, and you make payments. It's very easy to apply and you get an answer quickly. I was very, very happy with the kind customer service, even though things went south for my pooch. :( I'll admit it was difficult to make the payments after his passing, but I was glad they were there.\n​", "961" ], [ "Social Distancing Vet Appointments\nFirst of all, I love my vet. We've never had any issues with her diagnoses or advice, and we've been taking our cat to her for 8 years now.\nHowever, one thing has me wondering if this is typical protocol. Since spring 2020, we haven't been able to be in the exam room with our cat.", "961" ], [ "We drop him off, the vet and techs check him out, then bring him outside to our car and let us know how it went. This was of course best practice pre-vax, but at this point I'd really like to be in the room with <PERSON>. He gets a little nervous, and I trust the staff, but mostly I just want <PERSON> to feel safe with us there. Anyone else experiencing this? I feel nervous asking if I can be in there, because I don't know if any of the staff is immunocompromised and I don't want to be insensitive.", "210" ], [ "Please assist me in improving pet health care for all our furry friends\nHey everyone!\nFirst of all, thank you SO MUCH to those who helped me get this project going - your initial input has been invaluable! Based on this, I have a fast, very cute, 12-question survey for owners. Your anonymous, no pressure input (only answer what you feel like!) will hopefully help me make pet care better for all of us.\nBackground:\nI’m working on a special product design project that I could use some help from both pet owners. It is very close to my heart as I just lost my boy to Hemangiosarcoma, and, while our vets were top-notch, I felt I could have benefitted from an additional digital support tool.\nIf you feel motivated to offer feedback out of the goodness of your heart, I would love to hear from anyone about what problems you have with keeping track of your pet's health.", "961" ], [ "Anything that comes to mind - there are no wrong opinions! You can comment any thoughts below, and if you would be willing to, pretty please answer this short, adorable typeform questionnaire!\nI’d love to hear from you, about both negative and positive aspects of your pet's health journey. Please reply to this message or message me directly if you’re open to discussing your experiences. This will help design something that could one day help solve the issues we all face. Thank you!\n​\nhttps://i.redd.it/6sz7b3zgpalb1.gif", "618" ], [ "Looking for pet insurance\nHi, I don’t post often so sorry for the formatting if it’s off! I’m looking for advice, suggestions, tips or anything around finding pet insurance that can cover major surgeries. My dog (8 years old, mutt with some lab in him, 50lbs, male) has a mass in his groin area, we took him to the vet and the test said it’s fat but monitor if it grows or shrinks. Unfortunately it’s grown noticeably in the last 2 weeks and we’re considering surgery to remove it and get a full biopsy, meaning specialists and money we don’t necessarily have. Please let me know, any and all help is greatly appreciated!", "589" ], [ "Pet Insurance\nI have a neutered poodle/pom mix male dog who is 10 years old. We have never had any serious issues with his health. But lately his front paw has gone stiff twice in less than a month. The first time it happened we thought that maybe he hurt it from jumping. He tends to run around and constantly jumps from the tall bed whenever he gets too excited. After massaging it he seemed fine.", "589" ], [ "The second time happened about 30 minutes ago. He was on his dog bed and walked towards us in the living room and we noticed his stiff front paw. We are taking him to the vet tomorrow. I have been researching pet insurance but it’s so confusing. I am hoping someone can offer any type of advice. I know that putting this off for so long is very irresponsible and I am regretting it. Any advice and suggestions are appreciated.", "589" ], [ "Leaving small dogs in our house for 2 weeks while on vacation\nHey all, My mom decided that it’s too expensive to board our dogs in a doggie daycare, and that my dogs will be more comfortable being in our house. She hired our cleaning lady to pet sit our dogs.", "881" ], [ "She committed to coming in our house once every morning and night to walk and feed them. I am still feeling anxious and I am nervous about our cleaning lady fulfilling her commitments as she lives half an hour from our house.\nHas anyone else done something like this before? I know boarding them is ideal, but our older dog literally got traumatized from being boarded as the day care had him Play (small 9 pound yorkipoo) with big dogs who ended up hurting him. So we dont want to risk something like that again with him and our younger dog.", "63" ], [ "Questions regarding Pet Insurance\nHey everyone, I have some questions regarding pet insurance and how it works. I'm a total newbie when it comes to this kind of stuff. Here's my situation:\nI have a 5 year old cat that I have had since he was 6 weeks. I got health insurance right when I adopted him from 24petwatch to cover up to $3k with a $250 deductible and 20% copay.", "589" ], [ "My monthly is $31 right now, it used to be like $22 when I first started. His current plan coverage is May 2023 to May 2024.\nMy cat had surgery 2 weeks ago after swallowing a ribbon and getting clogged with furballs. The first vet (vet 1) I brought him to for the emergency visit charged me $2500 over 2 nights and recommended that I transfer him to another bigger animal hospital for an ultrasound as they couldn't pinpoint the blockage. So I went to this other hospital (vet 2) and paid $7k for the ultrasound + surgery + 3 night hospitalization.\nRegarding my claims, should I submit all the bills from vet 1 and 2 and then keep his current plan? I'm wondering if I should submit just the claims from vet 1 to not have my premiums skyrocket next year (I'm assuming they would skyrocket) if I were to claim a $7k surgery and only get $3k of it covered?\nAfter filing the claims and maxing out the coverage for this current plan, is there an option to cancel and start a new plan? I'm not sure how all this works and if I can even do that.\n​\nThank you!", "589" ], [ "Collars on your pet. Come on folks. Do it right.\nThis is triggering me after about the 100th post on Facebook in the last week where people are posting on community pages their poor sweet dog, and sometimes cats, ran off and are missing. Or someone will find a stray pup or cat and want to get it out there to help find the owner. This is not rocket science folks. Buy a damn collar for your animal that has at least a cell number on it. I had one with my dogs name and my cell on it at one time.", "114" ], [ "Amazon sells many choices and I am sure you can find them local to you. The one my Shadow has on now is maybe 5 years old and is still going strong. Something like $17.00. If you have a dog or cat and you cannot guarantee they will never run off, then you can disregard this. But we know this is not the case in the real world. Any and all pets can run off in the right circumstances. I just get so frustrated when I see these posted and I even get a little angry when I see the follow up that the dog/cat has been claimed. Why? Because they should have been claimed hours ago vs many having to go to the shelter with Animal Control.", "589" ] ]

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[ [ "Turn Old Pocket TV Into Inspection Camera\nIntroduction: Turn Old Pocket TV Into Inspection Camera\nThis is an old pocket tv from the '90s. It's basically useless in its current state since it functions off analog signals that no longer exist. You can pick these up at yard sales or on eBay for almost nothing these days.\nSure you can buy an inspection camera, or you can build your own one of a kind version with a retro vibe.\nStep 1: Choose Your Tv\nHit up yard sales, eBay, or marketplace and pick up whatever suits your fancy. You will find they are plentiful and cheap on eBay.\nStep 2: Pick Up a Tiny Pinhole Camera\nYou will need a camera, a very tiny camera, I chose this pinhole camera because just like this tv, it is analog and can be had for just a few bucks.\nhttps://amzn.to/3kGW2e4\nHowever, this camera with IR built in is probably a better option.\nhttps://amzn.to/3kEK5G4\nStep 3: Make Your Cable\nThe problem we are going to face is this old Casio pocket tv used a proprietary plug for video input, you may be able to purchase a video plug like this somewhere, but in this tutorial we are going to make our own. We can accomplish this by using an old RCA video cable, and the jack off a pair of cheap earbuds.\nCut off the connector on one end of your RCA cable, and cut off the jack from the earbuds (leave an inch or two to work with). Inside the RCA cable you will find two wires, one yellow wire and one bare copper wire. Inside the earbud cable, you will find 3 wires, red, white, and a bare copper wire.", "30" ], [ "Solder your connections as seen above.\nStep 4: Power Your Camera\nOnce you’ve made your connections, use heat shrink or electrical tape to cover each connection and ensure there is no contact between them. These tiny cameras operate at 12v and they almost never come with the power supply. I used this universal power supply for this project.\nhttps://amzn.to/2DRLMPn\nI plan to use this inspection camera for engines, so it is important for this to be mobile. If I want to take this out into the middle of a field I need to be able to do that. So, I will get my power from this portable power bank, it has a standard 115v house plug and it’s capable of jump-starting a dead battery.\nhttps://amzn.to/2XUNvdW\nAlternatively, you could cut off the power connector to the camera and wire it to a small 12v battery like this.\nhttps://amzn.to/3kE3K8Z\nStep 5: Mount Your Camera\nThe final step to making this a cool retro style inspection camera is attaching the camera to the antenna. These pocket tv antennas are perfect for this project since the antenna extends roughly 2 feet. It also has a full range of motion so it allows for perfect 90-degree operation. You can attach the camera various ways to suit your particular needs, just make sure you put a layer of electrical tape on the end so no metal is contacting the PCB board of the tiny camera.\nNow throw it in your toolbox or bag, or keep it handy in your workshop! I hope you enjoyed this project as much as I did.\nVideo Tutorial:\nBlog write-up:\nhttps://technichenews.com/2020/08/12/make-an-inspe...", "713" ], [ "Volume Knob for 2020 Pioneer DMH NEX Car Radios (and Others Too)\nIntroduction: Volume Knob for 2020 Pioneer DMH NEX Car Radios (and Others Too)\nIf you have any radio in the Pioneer DMH NEX series that came out in 2020 (DMH-WT8600NEX DMH-WT7600NEX DMH-WC6600NEX DMH-W4660NEX and DMH-W4600NEX) you probably noticed they don't come with a volume knob. This is annoying because if you don't have steering wheel volume controls, you have to take your eyes off the road to find the area on the screen to touch to adjust the volume.\nBut never fear, there is an answer. You can make a volume knob without knowing much about electronics by using cheap generic parts from ebay and amazon. This knob uses a chip on a small circuit board called an \"arduino\", a longtime favorite for hobbyists and beginners as well as experts.\nI had no experience with electronics before this project. The most I had done is install the radio, which I was forced to do myself because the pandemic had shut down the installation services in my area. But this project was a great (and satisfying!) introduction to the hobby.\nWe aren't modifying the radio, just plugging a cable into the W/R port. It doesn't involve risk of electric shock because these are low voltage components powered by USB. The knob is powered through a USB port somewhere in your car. You can power, though not charge, multiple devices like dash cams with a single USB port using a USB splitter or hub. And if you installed your radio, you know that car panels can be pried off and on and wiring can be safely hidden behind them.\nThis works on this series of Pioneer radios and could work on other brands that have an unused “W/R” port in the back, as long as you can figure out by trial and error or through the internet what the correct resistance levels are that are interpreted by that brand of radio as volume commands. You can use this same code and change the resistance levels in the section of code identified in step 3.\nI’d like to thank the redditor <PERSON> for creating this project first and for helping me do everything you see here. He wrote the arduino code and to him is owed all the credit for coming up with this.\nSupplies\nWhat you'll need is:\n1. A soldering iron and solder (I recommend rosin core solder). If you've never soldered before, watch a youtube video on how to strip and solder wires, and solder pins on electronics components. Here's what I watched: https://www.youtube.com/watch?v=oqV2xU1fee8\n2. A multimeter.\n3. A breadboard. This is a rectangular piece of plastic with a bunch of holes you can stick wires into. It has metal rails inside that make connections between wires you stick into it.", "485" ], [ "It will allow you to test out all the electric connections and make sure your knob works before soldering it all together. This is what they call \"prototyping.\"\n4. Search breadboard wires on amazon. Get a set of male to male, female to male, and female to female wires. You can use these for prototyping and if you don't want buy additional 22 gauge solid wires for the final product, you could also just use these in the final version of the knob you make. Just make sure to actually solder them because if you just connect them they might come disconnected from wear and tear.\n5. A rotary encoder. This is the stem for the knob that senses when you’ve turned it or pressed it. Pressing it will send a track forward command, which I like to use to skip through podcast ads, as it goes ahead 15 seconds in CarPlay. I used the most common cheap version which can be found by searching \"rotary encoder for arduino.\" You can get a nice brass or aluminum knob for it on ebay with the standard 5mm diameter fit if you don't like the plastic one the encoders come with. I recommend \"knurled\" guitar knobs for that nice finger feel.\n6. A 3.5mm male stereo cable. Make sure it has 2 black rings, not one ring which would be mono. You can salvage one from an old set of headphones. This will be the connection to your stereo. It plugs into the \"W/R\" port, which is how steering wheel controls used to connect to radios in the old days. Not sure why they still have that port on a 2020 radio, but this is lucky for us.\n7. An Arduino Nano microcontroller. There are many generic clones of these little things that should cost no more than $3-5 a pop.", "98" ], [ "Joule Thief Torch With Casing\nIntroduction: Joule Thief Torch With Casing\nIn this project you will learn about how to build a Joule Thief circuit and the appropriate casing for the circuit. This is a relatively easy circuit for beginners and intermediates.\nA Joule thief follows a very simple concept, which is also similar to its name. It extracts or \"steals\" joules (energy) out of low-voltage systems. E.g. Most non-functional batteries actually have about 20%-30% of juice still in them. However their voltage is too low, and it is not able to power anything. The Joule thief circuit can actually harvest this low-voltage energy from batteries (or any source) and power a standard 5mm LED light quite brightly. The output is not limited to a LED.\nThis is a very easy, practical, and useful circuit to have in your house. If you can't find a working battery that you need urgently, or you want to make complete use of the batteries you buy, this would be perfect for you.\nFinally, this Instructables will also showcase a 3D printed casing for the Joule thief. However, if you do not have a 3D printer then you can check out my Laser cut acrylic box or design a casing yourself. Even just a plastic box would be satisfactory. I would not recommend leaving the circuit without a casing.\nStep 1: Supplies and Tools\nSupplies:\n1. Perf board\n2. AA battery holder (can be for 2 batteries or 1)\n3. Ferrite toroid (with two coils over it)\n4. Tactile latch switch\n5. 5mm LED (any colour)\n6. 5mm LED bezel + nut\n7. NPN transistor (I used C1815)\n8. 3mm Nuts x4\n9. 3mm Bolts x2\n10. Wires\nTools:\n1. Soldering wire and iron\n2. Wire-cutter pliers\n3. Multimeter (if you don't have one you can make one DIY. Check out my Arduino powered multimeter)\n4. Desoldering pump (optional)\n5.", "98" ], [ "Needle-nose pliers\n6. Pencil/pen/marker\n7. Superglue\nStep 2: Circuit Schematic and How It Works\nHere is a very that very nicely explains how a joule thief works:\nCREDIT TO ELECTRONICGURU FOR IMAGES\nStep 3: Securing Battery Holder to Board\n1. Using a black marker, I marked where the holes in the battery holder were on the PCB.\n2. I used the wire cutter pliers to make the holes in the perf board. Soon enough it was big enough for the 3mm bolt. If you have a handheld or electric drill this process is a lot easier. It is important to test if the holes are big enough for your bolt.\n3. I added an extra set of nuts between the perf board and battery holder to stop the bolt from protruding out of the other end so much.\n4. The two remaining screws were used to secure battery holder onto the perf board.\nStep 4: Understanding C1815 Transistor\nSome transistors have different schematics and pinouts. Therefore, just as clarification, I wanted to state which pins of the transistor are base/collector/emitter\nMoving from left to right with the flat side facing you, the pins are base, collector, and emitter in that order. This is exactly as what is shown in the diagram.\nStep 5: Preparing Ferrite Toroid\nI got the ferrite toroid from a broken RC car circuit\n1. Taking thin enamelled copper wire I wound the coil around the ring-shaped ferritetoroid 7 times. See picture\n2. The wire was cut after 7 coils with length to spare for soldering and connections. The second coil started in the same place where the first coil was started. Following the shape of the first coil, the second coil also was pulled out after 7 winds and cut with excess.\n3. To differentiate between the coils coil 1 had much longer legs than coil 2.\n4. Since my ferrite toroid was very small, I used a very thin copper coil wire. Most likely 26 SWG. If your toroid is bigger then you can use bigger and even normal wires\n5. After this, you would have 4 different wire ends. 2 for coil 1 and 2 for coil 2. These 4 can also be written as 2 for the starting side and 2 for the end side.\n6. To simplify remembering the coils, I gave the following names to the coil ends. S1, S2, E1, E2. The S and E stand for start side and end side. 1 and 2 stand for the coil number.\n7.", "611" ], [ "Borderlands Raspberry Pi\nIntroduction: Borderlands Raspberry Pi\nSo I was in a game store one day and saw this Borderlands prop in the clearance section for $20 and couldn’t resist buying it. After about a week I thought to myself “I could totally gut it and cram a pi inside”. That’s when my adventure began to make a real life Borderlands Echo Device.\nI went out and got an Adafruit display and started prototyping. I ended up getting the 3.2” display so it was easier to see and use with a stylus/finger. The 2.8” display just looked to small compared to the 3.2” when I was in the store. So this is technically a 1:1 scale prop with the exception that the screen is slightly larger.\nI slowly prototyped when I had the time. At one point I was trying to keep the original lights and sounds but that wasn’t happening so I ripped them all out. Then I was thinking about having a speaker for the Pi. I probably could have made space for it but it probably would have drained the battery. Also I really didn’t need it to make sounds or anything although it is possible. Plus there’s also Bluetooth.\nAlthough it’s kinda hard to gauge with the prototyping this should take about an hour to complete maybe two.\nSupplies\nBorderlands 3 Echo Device\nfrom Chronicle Collectibles\nRaspberry Pi\nMicro SD card loaded with a Pi image\nAdafruit PiTFT 320x240 3.2” display\nWireless USB keyboard with trackpad\n(not necessary)\nCell phone power bank\n2 short micro USB cords\nNeedle nose pliers (or Dremel)\nPainters tape (not necessary)\nElectrical tape\nHot glue gun and glue sticks\nCrazy glue\nSmall container\nPhillips head screwdriver\n5/64th allen key\nVise (not necessary)\nStep 1: Gather Up All Your Parts\nI’m using a Raspberry Pi Model A+ for it’s square shape to give me a little more space to work with. It’s running the latest Pi OS along with the installer script for Adafruits Pi hat. All the info you need for the display is here but it really breaks it down at page 12.\nWhile it’s not totally necessary since it’s a touch screen I’m using an Inland mini keyboard with trackpad for typing. You can find an OS that’s made just for touchscreens if you want.\nIt’s all powered by a cell phone power bank. I had a bunch laying around so I just picked one that fit nicely. You can use any kind that you can cram in there. The bigger the battery the less space you have to work with but it will stay powered longer.\nStep 2: Disassemble\nFirst things first. Make sure you have a small container for all the screws.", "769" ], [ "It can turn into a real mess real quick. Keep them altogether. It doesn’t matter what it is. I’m using an Easter egg because that was the first thing I saw laying around when I was ready to start.\nThere are a total of 6 allen screws. The 3 on the front and 2 on the back of the rubber piece need to be taken out with a 5/64th allen key. Then there’s one allen screw in the middle of the door for the batteries. It’s a dummy screw that doesn’t need to come out. It’s just there for aesthetics.\nThere’s one phillips head screw to open the door for the batteries. Then there’s 2 more phillips head screws holding the 2 halves of the body together.\nThe black rubber pieces on the top and bottom are glued in place. Gently pull them off. I’m not to concerned about glueing them back because the allen screws will hold everything in place. Also I want to be able to take it apart easily if I want to work on it in the future. Lift the top rubber piece up gently. It’s glued in but snaps right back into place. Now lastly pry apart the two halves of the body from the right side. Congratulations you made it inside!\nStep 3: Gut and Glue\nOnce your inside there are 2 small circuit boards with wiring that need to be torn out. Then there’s a rectangular piece of white plastic where the display goes. Tear that out.\nNow some of that plastic inside needs to be taken away to make space for all the electronics. You can use a Dremel to remove the plastic inside if you want.", "320" ], [ "Wearable Arc Reactor\nIntroduction: Wearable Arc Reactor\nThis Arc Reactor is a fully customizable under-the-shirt prop. It looks authentic, it is cheap to make, and it makes a great last-minute costume. As an added bonus the Trinket Pro can be programmed to make the Arc Reactor light up in different colors and patterns.\nSupplies\n- 6 LEDs from a programmable light strip (Neopixels etc.)\n- Standard Wire\n- Old USB Cable (Ideally long enough to reach from your chest to your pocket)\n- Small Powerbank\n-Trinket Pro 5v\n- Foam Board or Cardboard\n- Diffuser (Tissue Paper, Clear PLA, Sanded Plexiglass)\n- PLA or PETG Ideally in gray\n- Elastic Band for the Harness\nFor tools, you will need the following:\n- Soldering Iron\n- Hot Glue Gun\n- Wire Strippers\n- Exacto Knife\n- 3D printer\n- Sewing Machine\n- Ideally, some Helping Hands to help you solder\nStep 1: 3D Print Your Piece(s)\nThis is by far the most time-consuming part of the entire project so you will want to get this going while you work on some of the other parts of the Reactor. I used a file by Thingiverse user <PERSON>. I printed only the top part and skipped the back, if you have clear PLA you should also print a Light screen. I would recommend printing the Reactor out of gray or silver PLA.\nhttps://www.thingiverse.com/thing:3579932/files\nStep 2: Create Your Harness\nThis will be what keeps your reactor from falling off and causing panic as the shards of metal in your heart begin to circulate. First off you need to measure your chest, once you have that dimension you should cut a piece of elastic band to that length and sew it into a circle. Once you have stitched the bottom part of your harness, slide it over your head and situate it on your chest. Once you have done that, measure the elastic band length to go over your shoulder and attach it to the front and back of the chest piece. Repeat for the other shoulder and you should have a harness to hold up your reactor.\nOne note: When stitching your elastic you should always stitch a rectangle with an X through it (As shown above) for maximum strength.\nStep 3: Prepare Your Reactor for Electronics\nOnce your reactor is done printing you will need to add in a diffuser to make the LEDs less conspicuous. I used 3 layers of tissue paper. After, you need to cut an insert out of cardboard or foam board to house your electronics. Once you have made the insert, poke a hole in the upper left-hand corner.", "997" ], [ "I recommend adding material along the edges to keep the circuits off your chest. When you have completed this step you will be ready to create your circuit.\nStep 4: Making Your LED Triangle\nWhile this circuit is easy to make it can be tedious to do some of the more precise soldering. if you struggle with soldering I recommend that you watch a video on becoming more precise. With that out of the way the first thing that you will want to do is turn your light strip into a triangular shape. For this, you will want to cut 3 sets of 2 LED sections and arrange them on your insert to get a feel for how long your wires will need to be. Next, you will need to solder wire lengths that match the angle of the strips, this can be very difficult so take your time and work carefully. With your triangle closed on 2 of its corners, you will want to solder 1 1/2 inch wires to one side of your triangle and run them up through the hole you made earlier.\nStep 5: Wiring to Your Trinket and USB\nWith your triangular LED strip completed, you will need to make yourself a power cord, to do this take your old USB cable and cut off the non-USB end. Once you have cut this you will need to strip back the outer casing of your wire and reveal the black and red wires inside, you will need to strip those wires as well. At this point, if this cord does not reach from your chest to your pocket, add wire so that it does reach. With that completed, you will want to twist the black wire of the USB cable to the ground wire from your LEDs. You will need to twist the red wire to the 5v wire from your LEDs. Once both of these connections are made you will need to solder another 1-inch length of wire onto each of these connections. Once these 3-way connections are done you will be ready to solder all of your wires to your trinket. First, solder your ground wire to the G pin, then solder your 5v wire to, you guessed it the 5v pin.", "635" ], [ "Cooler Delivery\nIntroduction: Cooler Delivery\nHey you, yes you. Are you tired of not knowing when your groceries are delivered? Let’s say you don’t want to go to two stores. So, you order online to get it delivered and go out to Target and come back to find all of your groceries are on your door. All of the ice cream is all over the steps and the meat is spoiled and warm. Wow! What a mess but, my friend this is where we come in. The thing you’re about to know how to build will solve all of your problems, in a cheap, easy way. Using a standard cooler, you can keep your delivery cool, alert your phone anywhere, AND provide a mechanism that allows for a no contact situation. Ready? Let’s get started.\n( idea produced and published with my dad's permission by <PERSON>, Age 10 )\nSupplies\n* Any standard cooler\n* String/rope (about 16-18 inches)\n* Duct tape\n* Double sided tape\n* Frozen cooler packs (or ice)\n* Portable USB power stick\n* Raspberry Pi (a 3 is used in this, but it will probably work on any version aside from 1 due to the pinout being different)\n* Door Sensor Contact\n* Optional - computer case front panel wires to splice to the door sensors and the headers on the Pi\n* Optional - electrical tape if you use the computer case front panel wires\nStep 1: Cooler Handle\nSo, the first thing gets about 12-16 inches of rope and open the cooler.\nLook on the other side of the top underneath the lid. This is where you will be looking at for this step. Grab three pieces of duct tape and make sure to lay them of top of your rope in a pattern like in the picture to make it strong.\nAfter you’re done with that make sure you can lift with that rope outside and be able to open and close the cooler freely. If you have a squeaking noise on your cooler that use a spray called WD40. This will make that sound go away like magic.", "98" ], [ "Cool thing is you can use this for your doors too!\nThis mechanism allows the delivery person to just pull the string to open the lid, but when you need to open the cooler, you can use the handle like normal! This is great to not spread COVID!!!\nWhen you're done you’re ready to move on!\nStep 2: Additional Protections (Optional)\nIf you feel like there still might be too much contact, then you can do this option!\nThe next step is to get a box of disposable gloves, you can lay these on a table or on the cooler and tell people to use these when opening and pulling the string on the cooler. Make sure to get a wastepaper basket out there too! The other thing you can do is make a washable cloth covering.\nTo do this you need some cloth and some rubber bands. Cut the cloth so it is as thin as the rope, then use two rubber bands to secure the top and bottom of the cloth to your rope. So, one more time wrap the cloth around the rope and make sure it is tight, the use two rubber bands to secure it at the top and bottom. How this works is they use the rope to open and close the cooler, and put your groceries in. After they are done, they dispose of their gloves in the wastepaper basket. Congratulations! Whatever way you did this is fine, and your done with this part of your cooler project. Give you self a pat on the back. Nice job! Keep up the good work!\nStep 3: Set Up the Pi\nYou made it this far, that's AWESOME!\nHere's the technology part - you'll need to first wire up your Raspberry Pi. Go ahead and load a default Pi image, but make sure you have Python 3. There are a number of guides to this, and we can't show them all here.\nNext, you will need to connect the door sensors to pins 18 and 20 to your Raspberry Pi. You can do this either directly or if you have some old cables from a computer case (the front panel), you can splice the cables to this so you have a nice connector to the pins on the Pi. The sides don't matter (ground/gpio aka 20/18), so just make sure you have solid connections.\nNext either print out a Raspberry Pi case, or use one that you can 3D print - this is what my dad did (\nhttps://www.thingiverse.com/thing:1572173)\nIn the end, it should look like the picture above.\nNext on to programming the Pi.", "259" ], [ "Replace Micro-USB Port With Only a Soldering Iron\nIntroduction: Replace Micro-USB Port With Only a Soldering Iron\nThis instructable documents a useful hack to desolder and replace failing Micro-USB (or USB-C, mini, etc!) ports without use of hot air, solder wick or solder suckers. - Just a soldering iron and some wire!\n(I tweeted about this a week ago, people seemed to find it useful so here it is as an instructable!)\nThe method is definitely a hack, and not best practice at all, if you have access to more advanced tools you can absolutely do this a better way.\nSupplies\nMandatory:\n* Soldering iron - Almost any will work, in this case I use a Pinecil running at 30W.\n* Something to clean your iron tip - I use brass wool.\n* Solder - The lower the melting temp the better.\n* Something to hold your pcb still - I use a vise, but even blu-tac on a desk should work fine.\n* Replacement port - This can be salvaged from another device using the desoldering method detailed below.\n* A short piece of solid core wire - Copper is preferable, but I use a snipped lead from a diode.\nOptional Extras:\n* Solvent to clean flux - Optional but strongly recommended if you have it.\n* Solder wick / Braid - Optional but may be useful when putting a new port on.\n* Multimeter - Optional but recomended.\n* An old usb cable to cut up for checking continuity - Optional but recomended.\nStep 1: Making a Plan\nWe need to identify the joints that need heating to remove the port, and plan the wire route that will channel heat and melt them all at once:\n1. Most SMD USB ports will have 2-4 mechanical joints either side of their main body (and in this case a joint underneath), as well as several data pins.\n2. Try to work out a path to join all these spots that need heat with a small piece of wire, in this case by bending a C shape.\nnote: Pads underneath the main body of the connector will melt if spots nearby are heated, but may make the process take longer.\nStep 2: Forming the Wire\n1. Cut a length of your wire roughly to length.\n2. Bend it to match the shape you planned in step 1.\nStep 3: Tinning Joints and Attaching the Wire\n1. Add a liberal amount of solder to all the joints.\n2. Slide the wire into place.\n3. Join the wire to each blob of solder.\nnote: Don't worry about making neat joints or bridging pins! this will all be gone soon.\nStep 4: Removing the Port\nApply gentle pressure to the connector, pushing towards the edge of the board until the connector slides off.\nIf your connector has through hole mechanical pins, or plastic locator pins that extend all the way through the pcb, tweezers may be needed to pull upwards instead of pushing with the iron.\nnote: This took about 7 seconds for me, with my iron running on a 30W USB-C PD power-bank, which is not optimal, it should be much faster using a higher wattage iron, or higher wattage settings if supported.\nStep 5: Cleaning Up\nTo attach a new port we'll need to first clean the excess solder off the pads:\n1.", "98" ], [ "With a clean iron, drag the tip across the mechanical connection pads, taking solder with it.\n2. Clean the solder off the tip using your brass wire or sponge.\n3. Repeat this until the pads are clean.\n4. Use solvent to clean up any flux left behind. - Optional but recommended (I didn't have any to hand).\nMake sure to leave a little solder on the data pin pads!\nIf you have solder wick / braid to hand this will make this much faster and clean.\nnote: If you are desoldering a port to be re-used, make sure to clean the solder off the bottom of the body too.\nStep 6: Attaching the New Port\nNow we'll put the new port in place and solder it in:\n1. Place the connector on the board - Connectors will often have locator pins, so make sure they are in their holes.\n2. Secure the connector in place temporarily - Optional, I did this without but it can help. (this could be with blu-tac, tape or pressing with tweezers).\n3. Gently connect the mechanical joints using a little solder.", "320" ], [ "TiLite ZR Footplate Light - Harmanie Light\nIntroduction: TiLite ZR Footplate Light - Harmanie Light\nIntroducing the Harmanie light! This project was inspired by my best friend <PERSON>, thus the name. We were walking down a sidewalk in Vancouver at night and I saw that in the spaces between street lights the sidewalk was occasionally very dark and made it hard for us to see obstacles. It occurred to me that she could really benefit from a flashlight that would always be with her chair. <PERSON> is a disabled dance artist who dances in her chair so the light needed to be sleek and nearly hidden so she wouldn't have to remove it for performances. She also had an open footplate design so I decided I could hide a battery between the tubes, put led's along the bottom, and also give her a solid surface for her feet. And <PERSON> loves gold.\nFiles can be downloaded on Thingiverse:\nhttps://www.thingiverse.com/thing:5162785\nStep 1:\nStart printing, or order the completed prints from a reputable online service, or get a friend to print them.\nStep 2:\nInstall the led's, switch, resistors, and solder them up. Sorry, but this is going to be a bit vague. I don't have step by step detailed photos as I was not intending to release this as an instructable. Essentially, you will place all 10 LED's into the footplate with the same orientation to the leads. I put all the + or long leads at the top and all the ground leads at the bottom and glued them in place with a dab of hot glue. Then I bent the ground leads over one on top of each other to form a continuous wire and soldered them all together to give 1 ground connection. On the top I soldered resistors to each led cutting the leads short so they could be fit in a small space. Then I used the lead of each resistor I had left long to also create another wire running off to the left. We will connect power and ground to these leds which are now wired in parallel with a series resistor on each led. The resistor value is not too critical. Looks like I used 200 ohm on these if im reading the bands right.", "492" ], [ "Anywhere from 150 ohm to 215 should be good.\nThe switch is salvaged from a very common dollar store aluminum led flashlight. The type with a click button on the removable end cap where you install the batteries. The switch has a rubber pad which allows for a very sleek look to the bottom of the plate and made it easy for <PERSON>, who is left handed to reach down below and switch it on or off.\nYour power connections are going to be run in series from the power bank, through the switch, through the led's, and back into the power bank. In order to have the battery replaceable I chopped off a USB power cable and connected to the red and black wires. Red is positive, black is ground.\nYou need to permanently install the USB charging cable as well at this time or else you will need to disassemble the footplate to charge it which is hardly convenient.\nVERY IMPORTANT!!! Almost all USB power banks have a built in low current shut off. This means if your led's don't draw enough current the power bank will shut off power after 30 seconds or so and you will have to switch it off and then back on again to bring back the light. I had to add 2 more LED's to this circuit to draw enough current to keep the circuit active. They ended up being hidden inside, also in parallel with the other led's. Test your circuit before you apply hot glue in case you need to make revisions.\nLast step, apply hot glue! We are using this to seal the circuit and help protect the electronics. Also helps to prevent accidental shorts on the led's\nStep 3:\nTest it out!\nAgain, most important, if it turns on successfully, make sure it doesnt turn off after 30 to 60 seconds due to insufficient current draw. If it goes past 1 minute running you're golden!\nStep 4:\nInstall it on the chair.\nStep 5:\nFinal Test!\nTry everything out. Including charging and deploying and stowing the charging cable. It was made to always have a cable on hand, and <PERSON> has not had any problem with the cable falling out and dragging behind her. We also thought we might have to worry about moisture and dirt in the plug, but it seems to attract very little of it so it hasnt been a problem. You could put tape over the hole if youre really concerned.\nvisible in these pics is the switch on the top right, this is the textured rubber circle. The other button can be pressed to tell you how much battery is remaining, and if its charging, but of course not when in the chair.", "713" ] ]

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[ [ "Bulgaria: CME Buys Bulgaria’s Most Watched TV Channel · Global Voices\nOn Feb. 18, 2010, bTV, one of the most popular TV channels in Bulgaria, got a new owner – Central European Media Enterprises. bTV is the first private national TV station in Bulgaria. bTV’s program was broadcast for the first time on June 1, 2000, thus breaking the monopoly of the public national TV station and changing entirely the media environment in Bulgaria.\nFor eight years, bTV firmly established itself as the most watched TV channel in Bulgaria, with nearly 37% share of all viewers and with leading positions on the advertising market. bTV has a 24-hour programming. It targets the family audience, offering a quality selection of movies, reality formats, talk shows and comedy programs.", "363" ], [ "The news and feature programs of bTV established themselves as the information leader with the highest rating of viewers’ trust.\nCentral European Media Enterprises, which has acquired bTV, is the leading television broadcaster in Central and Eastern Europe. The company was founded by <PERSON> in 1994 and together with its local partners it operates TV Nova, Nova Sport, Nova Cinema and MTV in the Czech Republic, PRO TV, PRO TV International, ACASA, PRO CINEMA, Sport.ro and MTV Romania in Romania, TV Markíza, Nova Sport, Television Doma and MTV in Slovakia, POP TV, Kanal A and TV Pika in Slovenia, and Studio 1+1, 1+1 International and Kino in Ukraine.\nOn my blog [BUL], I publish information about this deal:\n[…] Under the terms of the deal, CME will acquire 100% of bTV […]. CME will pay $400 million for 100% of bTV and parts of bTV Comedy and bTV Cinema and 74% of the radio stations N-Joy, Z-Rock, Melody, Jazz FM, Classic FM. […]\n<PERSON> wrote this on his blog Journalist BG:\nThere is nothing new that the deal is being prepared since the middle of last year. […] My sources from Pro.bg informed me that the conclusion of an agreement is only a matter of time, so much for that. Today (January 27th) Reuters said that CME is in the final stage of negotiations for the buying of bTV from <PERSON> News Corporation for $500 million. […]\nAnother blog, BGtelevizor, wrote [BUL]:\n[…] <PERSON>, President and CEO of CME, said the purchase of bTV is the next step in the repositioning of CME after the sale of their business in Ukraine […]", "260" ], [ "Bulgaria: President’s Gift to Pope Provokes Questions · Global Voices\nOn May 24, the Day of Bulgarian Education and Culture, and Slavonic Literature Day, the Bulgarian President <PERSON> visited the Vatican. At a meeting with Pope <PERSON>, President <PERSON> presented a huge Easter egg to him, the work of the Bulgarian sculptor <PERSON>.\nThe egg is made of inox steel and is gold-plated, studded with crystal stones (2,000 ruby-red crystals) in the colors of the rainbow, and consists of 11 sections in the form of diamonds, in the middle of which there is an inscribed cross. The egg is 2.3 meters high and weighs 200 kg – and is also engraved with the letters of the Bulgarian alphabet.\nNo one in the Bulgarian media wrote about the price of this precious gift. Bulgarian netizens, however, responded to the news with many questions.\nOn his blog, Bulgarian journalist <PERSON> posted a picture of the Pope and the Bulgarian President standing next to the egg, and commented [bg]:\n[…] At first glance, the thing is bigger than the President and the Pope combined. A golden cone? No, a Christmas tree? There was an egg, right? A huge “Fabergé” on the gear of an office chair, with an antenna stuck on top of it. But what is inside, will anyone reveal? […]\nIn the social media, the gift has become an object of jokes and humor. Here's a small selection:\n#Terribly tasteless…\n#What does Bulgaria have in common with an egg or Fabergé? What's the message? Maybe that we roost with hens?\n#Huge kitsch. Literally.\n#Such grandiosity… Looks like the Pope was frightened by the size of the egg.\n[…]\n#Seriously! Who made it? How much does it cost? Who paid the bill?\n[…]\nThe good news is that the great gift is not paid for with the public funds. The question is what it symbolizes and what exactly Bulgaria is saying to the world with this gift. Because there's no doubt the photo has made an impression around the world.", "739" ], [ "My first association was with Bulgarian weddings where there it is always more impressive to give a huge washing machine as a gift rather than a small picture. In English, this is called “excessive” […]. Such a gift would be a perfect fit for a visit of <PERSON> [<PERSON> predecessor at the President's post] to [<PERSON>]'s successor […].\nFreelance journalist <PERSON> wrote this on his blog [bg]:\n[…] In the past, the Vatican had tacitly refused to accept an ambassador sent by the [Bulgarian] President. If <PERSON> has decided to do diplomacy through such Kindersurprises, we can only speculate about what he would give to, say, [the German President <PERSON>], to [the U.S. President <PERSON>], or to the French President <PERSON>. […]\nJournalist <PERSON> commented in his column [bg] in Pogled.info that the “Vatican ‘Fabergé’ amidst the [strongest earthquake] in our country is a sign that the president has completely lost.”\nOn Facebook, people are discussing another photo of the Bulgarian President, the Pope and the Egg:\n<PERSON>: I really do not understand why there is a giant fake Fabergé with letters?\n<PERSON> I wonder where they got the money from to buy this “ovule”? From the Bulgarian people, no money for children and pensions – but we have money for such things. I can't stand these politicians……………\nOn the Facebook page “Kvartala.bg,” there was this criticism [bg] of the President's gift:\nNone of our business…. but <PERSON> gave the Pope a 200 kg egg, on the eve of May 24. The giant gift has been handcrafted for two years by 15 artists. Eheeee, that means that <PERSON> had planned and prepared his gifts before he became President, for the time when he would became President. How prescient, how profound.\nIn the comment section of the Dnes.bg's article [bg] about the President's gift, one reader commented:\nHopefully, there will remain some living space for the people in the Vatican after the installation of the egg…\nOn Twitter, there were reactions, too.", "260" ], [ "Political and social crises to blame for the ‘COVID-19 disaster’ in Bulgaria · Global Voices\nSecurity staff checks COVID-19 passes of visitors to the Mall of Sofia, November 6, 2021. Photo by <PERSON>, used with permission.\nOne would think that the political crisis, lack of a government, and the holding of the third consecutive parliamentary elections in a year are hard enough situations for Bulgaria, but on November 1, the country with a population of nearly 7 million, hit a tragic new COVID-19 record—over 6,000 new cases and over 300 deaths. Honestly, I, and I'm pretty sure others in the country, don't even know how to describe the failure, tragedy, and stubbornness that led us here.\nBulgaria has the EU’s lowest vaccination rate, while widespread vaccine hesitancy fueled by misinformation and a lackluster awareness campaign comes amid political turmoil. As the COVID crisis unfolds and affects more and more sectors of the economy and society, the Bulgarian state is making a transition from more than a decade of rule by Prime Minister <PERSON> and his Citizens for European Development of Bulgaria (Gerb) party. <PERSON> stepped back after nearly a year of anti-corruption protests, marked by police violence and wiretapping of political opponents, and even protesters.\nThis toxic situation was preceded by impunity scandals linked to the Prosecutor General, <PERSON>, for refusing to investigate a number of Bulgarian politicians and businessmen who were sanctioned by the U.S. government in June under the Magnitsky Act for links to corruption and human rights abuses. The scandal has become one of the main topics dividing the political elite, and while the caretaker government published a list of 33 companies and 21 individuals connected to blacklisted moguls, the judiciary has not yet taken action against them. Incidentally, Bulgaria is the only European Union member state whose citizens are included in this list.\nFast testing of COVID-19 offered to visitors of Mall of Sofia, Nov 6, 2021. Photo by <PERSON>, used with permission.\nWhile Bulgaria initially reacted quickly by taking strong measures against COVID-19 in March 2020, <PERSON>'s subsequent handling of the pandemic has drawn sharp criticism because the country was severely affected during the autumn months after a loosening of restrictions over the summer. The interim ministers appointed by President <PERSON>, with whom <PERSON> has had a long feud, fared no better—the statistics are grim: 3,117 people in Bulgaria who had tested positive for COVID-19 died in October 2021; 100,330 is the number of new cases for one month, the Sofia Globe reported.", "739" ], [ "November can be even harder with all the anti-measures protests going on.\nAt the time of writing, the whole territory of Bulgaria is already in so-called “dark red zones,” as the cases of COVID-19 infections have passed over 800 per 100,000. A partial lockdown is expected if the number of new cases increases to 1,000/100,000 level, which is already a reality in some of the provinces in the western part of the country, including the capital.\nDaily new confirmed COVID-19 deaths per million people, seven-day rolling average for Bulgaria, European Union and Europe. Graph by Our World in Data, CC BY 4.0.\nIn the background of increasing disinformation and spreading of fake news, as of the beginning of November, there are over 7,000 people hospitalised. In most municipalities, there are no intensive care unit (ICU) beds available. A doctor who works in one of the busiest COVID-19 wards in Sofia told me on October 28:\n“Ruslan, I don't know when I will return home – probably not this week.”\nWhile restaurant owners protest against COVID-19 certificates, in Bulgaria's countryside the situation is grim, and there are no available beds in many hospitals.\nIn the northwestern part of the country, in the provinces of Vidin, Montana, Vratsa, and Lom, there is a lack of hospital staff. Ambulances rushing to regional hospitals can often be seen on the roads. The situation is similar in other parts of Bulgaria. However, the majority of the people are still resisting vaccinations.\nMy cousin is a doctor near Tarnovo, she's already in her 70's and still working. Yes, Bulgaria needs to get more people vaccinated, the doctors are suffering.\n— <PERSON> (@nsc_nana) October 29, 2021\nAs I mentioned before, the political situation is contributing to the crisis, as the country has been continuously in-between elections for over a year. There is an intensification of fake news and disinformation, including dozens of sham sites and social media accounts using the stolen personal information of medics. Several investigations are underway, with no clear results so far.", "739" ], [ "‘Justice for All’ Initiative Seeks Judicial Reforms and an End to High-Level Corruption in Bulgaria · Global Voices\nProtesters in Sofia, Bulgaria carrying the ‘Justice for All Initiative’ banner and photo of assassinated Italian anti-mafia prosecutor <PERSON> on May 23, 2017. Photo by <PERSON>, used with permission.\nSeveral protests were held across Bulgaria on May 23 and May 30 to push for reforms in the judiciary. Led by the ‘Justice for All Initiative’, the protests were part of a broader citizen movement calling for the implementation of the democratic standards set by the European Union (EU).\nIn Central and Eastern Europe, the term “European” does not only refer to geographical position, but it also signifies strong political connotations related to achieving the level of democratic and economic development of the original EU members. Formerly Communist Bulgaria had made great strides in this direction and became an EU member in 2007, although many believe it still needs to implement more political reforms.\nOn May 23, almost 2,000 people gathered in the center of Sofia, the capital of Bulgaria, demanding judicial reforms. They marched united by the slogans ‘March for European justice’ and ‘Protest to release the country from the Mafia’. The protest was supported by several civil society organizations, as well as prominent public intellectuals, lawyers and even some judges.\nProtests were also held in the cities of Plovdiv and Varna.\nThe day of the demonstration was not chosen by accident. On that day, in 1992, the Italian prosecutor <PERSON>, who dared to attack the Sicilian mafia was killed in a car bomb explosion.\nPoster for the May 23 demonstration organized by civil society.", "739" ], [ "The slogans are shown at the top part of the poster: “We will not be silent!” and “March for European Justice”. Photo by Justice for All Initiative.\nThe latest European Commission (EC) progress report on Bulgaria's cooperation and verification mechanism considers the government's anti-corruption strategy as unsuccessful:\nThe development by the government of an updated national strategy for the fight against corruption was an important step, but the challenge remains to ensure its implementation, to adopt the necessary legal framework and to set up the envisaged institutions.\nThe report also mentioned issues of corruption and lack of trust in the judicial system which hinder investments. The EC recommends the enactment of a new anti-corruption law and the creation of an anti-corruption body to deal with high-level corruption and conflict of interest.\nThe appointment of Chairperson of the National Assembly <PERSON> as Minister of Justice disappointed many people who believe she is incapable of implementing reforms because of her extreme loyalty to the ruling party.\nDuring the 2016 presidential election campaign, Prime Minister <PERSON> promised to resign if his party's candidate, <PERSON>, lost the election. On 6 November 2016 <PERSON> finished second in the first round to Bulgarian Socialist Party-backed Major General <PERSON>, receiving only 22 percent of the popular vote compared to <PERSON>'s 25.4 percent. <PERSON> subsequently resigned his position.\nLast March 2017, parliamentary elections were held in Bulgaria amid a political crisis which resulted in a coalition between <PERSON>'s center-right party, Citizens for European Development of Bulgaria or GERB, and the nationalist bloc, the Patriotic Front. <PERSON> became the prime minister again because of the coalition. But this provoked a scandal as photos of some members of the Patriotic Front doing Nazi salutes had been widely circulated in the past.\nOn May 30, the ‘Justice for All Initiative’ returned to the streets by organizing a ‘drinking coffee’ protest in front of the president's office while leaders of political parties and top state officials were entering the building for the meeting of the Consultative Council on National Security. They urged President <PERSON>, who is regarded by many as the symbol of unity in the country, to support their demands for judicial reforms.\n\"Правосъдие за всеки\" иска президентът да поеме инициатива за съдебната реформа https://t.co/iuIGWboH9C\n— Реформи.орг (@ReformiOrg) May 30, 2017\nTweet: “Justice for All” Demands that the president take initiative for judicial reform.\nPhoto: Prime Minister <PERSON> waving to citizens while entering the president's office.\nThe protests were ignored by various mainstream media outlets.", "384" ], [ "Macedonia: Use of New Media in Election Campaign · Global Voices\nAuthors of the Macedonian media blog Komunikacii.net, analyzed (MKD) the “unprecedented” use of the internet and the new media by the leading political parties in the campaign for the early parliamentary elections, scheduled for June 1, 2008.\nMedia experts <PERSON> and <PERSON> provided joint analysis of the web presence of both the incumbent party, VMRO-DPMNE, and the main opposition party, SDSM:\nGood: use of blogs, YouTube channels, Myspace, Facebook, Hi5 etc.\n[…]\nGood also: use of video, audio, posting documents, comments, etc.\nMost of—it seems all—the campaign materials are available online, too. The websites receive regular updates… and heavily use free online services, apparently to cut costs, which seems like a smart move.\nBad: the “social” portion is absent in their use of social media. The blog posts are mainly transcripts of their rally speeches, and the content is basically recycled from their TV commercials and other uses such as to be fed to traditional media, analysts, journalists and similar actors, but not blogs per se. The posts are long, different audiences are targeted in each post, and personal experiences or input from the politicians is lacking. Even the impressions on their events are lacking, depriving their blogs of the essential individual, personal perspective.", "363" ], [ "The video clips are made for TV and not for vlogs, print campaigns which do not fit viral media, photos as décor and not as source of (inside) information. […]\nProbably these are the reasons why these blogs do not receive many visits, there are but a few comments, and are simply left out of the general political discussion (for the time being).\nIn conclusion […], it's great that political parties adopted many new services and channels for electoral propaganda, but the effects will probably be quite small, because the websites are used as web repositories or warehouses for loads of materials tirelessly produced for the electoral campaigns in Macedonia.\nIn a comment to the same post, prominent local blogger <PERSON>, wrote (MKD):\nThe most interesting thing about the bunch of blogs created by political parties for this election is that they have some incompetent idiot appointed as administrator responding to user comments. For instance a response to some relevant question by such person was: “And who's asking?” Bottom! As long as they belittle the power of the blog and the blogosphere, their blogs will receive minuscule visitor flow and only by their praising party members. The situation was the same with the elections in 2006. They advanced in quantity, but not an inch in quality.", "363" ], [ "Bulgaria’s parliament and an educational institute named top privacy violators in ‘Big Brother Awards’ · Global Voices\n<PERSON>, Head of the Legal Team of NGO Access to Information Programme speaking at Bulgarian Big Brother Award in Sofia, 3 Feb 2019. Photo: <PERSON> / Internet Society – Bulgaria, CC-BY.\nAfter a six-year hiatus, leading Bulgarian digital rights organizations have revived their country's version of the Big Brother Awards, an “anti-awards” ceremony designed to shame those who violate people's rights to privacy and data protection.\nOriginated by the international human rights organization Privacy International in 1998, the Big Brother Awards have been adopted by multiple civic society organizations in Europe and beyond. The event is intended to increase awareness about serious issues related to misuse of personal data and the harms that this can bring to individuals and society at large.\nAt a February 3, 2019 ceremony in Sofia, the 2018 awardees were announced: Bulgaria's parliament and Center for Education and Qualification of Pedagogical Specialists Ltd., a well-known educational institute, were the big winners.\nInternet Society-Bulgaria (ISOC-Bulgaria) and Access to Information Program in Bulgaria issued a call for nominations of either governmental bodies, companies or individuals that have violated citizens’ privacy and abused personal data. Members of the public were able to submit suggestions up until the January 24 deadline.\n“Our goal is to show the public the problems, and raise awareness about them”, said a representative of Internet Society of Bulgaria.\nWith companies and private institutions collecting, storing and processing enormous amounts of personal data (often illegally) in the pursuit of more efficient marketing and greater social control, the event committee received many nominations. ISOC-Bulgaria solicited suggestions from the public, inviting anyone to submit nominations via blog comments (which could be posted anonymously) or Facebook.", "363" ], [ "These were evaluated by a jury of unpaid well-known public figures, including lawyers, academics, consultants, journalists, and civil right activists.\nThe jury subsequently presented two awards: one to the state institution and the other to the private organization that had excelled at violating citizens’ privacy.\nThe National Assembly (parliament) building of Bulgaria. Public Domain photo via Wikipedia.\nCompetition was stiff, with government institutions like the National Security Agency, the State Prosecutors Office, and the Anti-Corruption Commission being nominated, but eventually, the 2018 Big Brother Award for a state organization went to the National Assembly of Bulgaria, for its adoption of a personal data law.\nIn addition to setting new standards intended to protect citizens’ data against misuse by companies and institutions, the law sets specific rules for journalists and their reporting, when it touches upon the lives and activities of individuals. The law sets limitations around the impact that disclosing data will have on the personal life of the subject, the circumstances in which personal data becomes known to a journalist, and the importance of the personal data or its public disclosure to the public interest.\nAll of these stipulations, when subject to interpretation by media outlets and courts alike, could result in a threat to media freedom, especially when it comes to reporting on the activities of public officials.\nJury member and media expert <PERSON> explained further:\nСамите критерии са добри. Те наистина помагат на защитата и са по посока на тази чувствителност, която нараства. Въпросът е, че те могат да имат страничен ефект, да нарушат едно друго право – правото на свободно изразяване и на свобода на словото.", "463" ], [ "Macedonia: TEDxSkopje Attracts Attention Online · Global Voices\nParticipants who spoke after it, consider the first TEDx event in Macedonia a great success. The one-day conference organized independently under license from American nonprofit TED (Technology, Entertainment, Design) enabled widening the range of publicly discussed topics and inspiring at least one hundred participants to work on positive change.\nAs IT.com.mk reported [MKD]:\nThe first “idea sharing” is over. You could follow the TEDxSkopje conference via live video stream, or read about it on Facebook or Twitter. In case you missed them, the videos will be published on the TEDxSkopje website.\nThe conference was quite successful. The realization was excellent, minus small technical glitches which were quickly solved. The selection of the speakers was interesting, with various topics composed into two segments. The first part focused more on technology, while the second part focused on education, motivation and inspiration for creation.\nThe live video stream had almost a thousand viewers from all over the world, mostly from Macedonia, curiously followed by France and the U.S.A.\nThe rules of the event prohibited photographing and recording, except by designated official photographers. One of them, <PERSON>, posted a short video about the event.\nAs previously reported by GVO, a controversy arose online after some of the would-be participants did not receive confirmations of their applications. Much of the tension was defused thanks to the willingness of the volunteers who served on the organization committee to openly discuss the issues with the public through a group interview [MKD] conducted via the aggregator Ping.mk.\nAfter the event, the online discussions did not die, with praises from the participants broadcast via Twitter and on the Facebook profile, and some ‘ok, we got it, get off your high horse’ comments by others [MKD]. In a funny twist, one of the most persistent interlocutors during the preparation phase, <PERSON>, even ‘received’ a photo comics [MKD] in which <PERSON> and <PERSON> ask each other whether they attended the event, and conclude that at least they've heard he, <PERSON>, did.\nOn a more serious note, <PERSON>, one of the volunteer organizers, wrote [MKD] on his blog about the discrepancy between the online interest for TEDxSkopje and another project he takes part in – creation of the National Free/Libre and Open Source Software Policy [MKD] through inclusive, citizen-centric process:\nTEDxSkopje and the National FLOSS Policy can't be more different.\nThe first is a private initiative, mainly supported by private entities (except the Youth Cultural Center).", "363" ], [ "It is not exclusive, there can be others like it. It is not very relevant in the wider context of Macedonian society – besides the idea that TED-style presentations can raise the level of public debate, there's not much to it. Still TEDxSkopje has been almost entirely and constantly under the watchful eye of the (Internet) public […]…\nThe second is a public initiative, includes the Ministry of Information Society, Metamorphosis Foundation and Free Software Macedonia as implementers, as well as all stakeholders from universities and the business sector. Making such text is one-off thing. There will be no second version next year. If adopted, it will be a very important contribution to building the information society, especially regarding the transparency of ICT policies of state bodies, and their communication with all of us. The Policy can help shaping the future ICT development in this country and, if successful, it would be a great topic for some future TEDx talk. However, it remains below the radar of the online public (even though they were invited to join a number of times).\nTo this, add the fact that the people determined to post about all TEDxSkopje missteps are educated enough to contribute to the National FLOSS Policy, and you'll realize why I write this.\nBut, since I am an economist, I will remind you that people are selfish. “One's own benefit above all” – and it seems that many people think TEDxSkopje has something to do with their own benefit.\nFinally, as a TEDxSkopje organizer, I can say that in spite of all that traversed, I feel flattered. But as someone who will need to submit an annual balance-sheet to the Central Register, I feel obligated to remind you that the chance to push standards and openness in e-whatever with the state is still open to all of you.", "363" ], [ "UNESCO World Heritage Site at Risk: Bulgarian Government Allows Construction in Pirin, Citizens Protest · Global Voices\nGrazing chamois in Pirin National Park: a rare and distant view, as these high-mountain animals fear nearby human activity. Photo by <PERSON> (2017), used with permission.\nProtesters took to the streets in 29 international cities, accusing the Bulgarian government of corruption and violation of domestic and EU environmental law after it decided to allow further construction in Pirin National Park, a World Natural Heritage site.\nIn December 2017, the Cabinet passed a plan to allow construction activities in 48% of the park — a move that goes against legislation and is seen as a violation of its status as a protected space. After what many felt was the government's failed response to address the public outcry, environmentalists initiated an international outreach campaign in an effort to pressure authorities to uphold the law protecting the natural heritage site.\nPirin National Park was established to protect biodiversity in Bulgaria’s second highest mountain, an area considered to be one of the most well-preserved natural habitats in Europe. The park spans over 403 square kilometers (around 156 square miles) and contains breathtaking landscapes that range from rocky barren peaks to lush forests and glacier lakes to virgin rivers. It is home to numerous threatened flora and fauna species such as the golden eagle, brown bear and chamois. Locals tell stories that the Balkan lynx (an animal long thought to be extinct in the country) is still roaming in the park's territory.\nA tourist track within Pirin National Park. Old-growth forests in this pristine view are no longer protected from ski resort expansion. Photo by <PERSON> (2017), used with permission.\nDue to its precious natural wonders, Pirin was declared a World Heritage Site by UNESCO in 1983. This status added to its world fame as a tourist destination, a trait valuable to many small and medium-sized businesses in the surrounding area.", "739" ], [ "However, as the adjacent town of Bansko‘s ski resort began hosting winter sports competitions and attracting numerous foreign tourists with its low prices, the sporting complex started to rapidly expand in an unsustainable way.\nSince 2001, the Bansko resort has expanded way over its allowed territory, funneling droves of tourists to the small town. Hotels, ski tracks and their supporting facilities have already encroached into the nearby national park by over 160 hectares, causing soil erosion, biodiversity loss and pollution to sources of drinking water. In 2010, UNESCO excluded the tourist area, spanning 0.6% of the park, from the World Heritage Site to become its buffer zone and continues to express concerns over the ski resort's expansion.\nDue to the popularity of the area, Bansko ski resort has a huge accommodation base for a relatively small number of ski tracks and only a single gondola lift line, resulting in traffic jams and long queues of tourists waiting for their lift ticket. The unsustainable development of the ski resort has lead to a rapid increase and then drop in real estate prices. This financial bubble is growing as prospects of even more expansion become reality. In an effort to keep their prices up and sell more properties around Bansko, Ulen (the company that owns ski infrastructure) has spent years lobbying the Bulgarian government to expand concession areas in the national park and to lift restrictions on construction activities in the protected territory by amending its Management Plan (the ten-year framework of what is allowed within the park).\nBulgarian mainstream media, mostly owned by powerful oligarchs, downplayed the opposition from environmental NGOs by obscuring the issues of greatest concern by publishing stories which focus on issues that favor the resort such as the overloaded gondola lift line. Government officials backed this version by claiming the plan is being amended only to allow a second gondola line, although this is not actually mentioned in the actual legislation. The environmental minister unwittingly called the government's argument into question when he refused a change to the language which would specify that only one lift is allowed to be built, an amendment proposed by renowned altitude climber <PERSON>.\nMainstream media also focused on the economic benefits of development and income for the locals. Residents who members work in the concerned companies and their families expressed public support for the resort expansion, regardless of long-term effects on the environment.\nDespite advice from environmental experts who warned against the development of a large ski area due to climate change and the predicted shortened winter season, the decision makers pressed on. Every year, the ski facility increasingly relies on snow cannons using local water supplies rather than on actual snowfall.\nDespite the fact that new construction would downgrade the park's natural defenses against climate change, on its last session of 2017, the Bulgarian government expanded the territories open to construction from 0.6% to 48% of the park — including the zones set aside for the protection of forest ecosystems.", "112" ] ]

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[ [ "Malawi: Moving on Despite the Politics of Section 65 · Global Voices\nThe phenomenal story of 19 year-old Malawian blogger <PERSON> continues to attract attention from around the globe. <PERSON> began making headlines after his appearance at the TEDGlobal 2007 conference in Tanzania, in June, where he talked about how he built a windmill using locally available resources in a remote part of Malawi where the easiest means of energy is fuel, wood, kerosene and candlelight.\nEarlier he had dropped out of school after his parents were unable to afford his tuition fees. After achieving fame through the efforts of Malawian bloggers who first wrote about the story following a news item in a Malawian newspaper, and after hitting BoingBoing.net, Digg, Reddit, and Metafilter, <PERSON> has now been featured on My Hero.\nAs videos from the TEDGlobal 2007 conference become available online, <PERSON>’s speech at the conference can now be accessed through the conference’s website, on Youtube, on his blog, and also as a download. <PERSON> has also been writing about how he is making use of the money people have been donating through his blog, using some of it for home supplies, as well as preparing to go back to school:\nWhen planting season comes, I will use some of the funds to buy seed, fertilizer and urea for my family's crops of maize, ground nuts and beans.\nI have also opened a bank account and put funds in so that my family is now prepared for medical, food or other needs and/or emergencies. I have started saving for the rest of private secondary school, boarding and university, too.\nStill in the tech realm, <PERSON> has had plenty of tech news to report about on his blog. <PERSON> announces a campaign by bloggers around the world to unite against all forms of abuse, by blogging against this vice on September 27, 2007. <PERSON> announces that the campaign is being driven by Blogcatalog. <PERSON> also informs his readers that his blog is now viewable in ten major languages, by use of a free widget, from Google Translator Widget Blog.", "830" ], [ "This makes <PERSON>’s blog now readable in Arabic, German, Portuguese, Chinese, Italian, Russian, Japanese, Spanish, French and Korean. The other piece of news <PERSON> has for his readers is the forthcoming launch, on August 29, 2007 of MyLiveSearch, which <PERSON> says technology enthusiasts have been waiting with bated breath for.\nFor <PERSON>’s African readers and others interested in Africa’s technological solutions, the most exciting news is perhaps what <PERSON> announces as the invention of a new, low cost computer that runs on solar energy.\n<PERSON> points out that over 2 billion people in the developing world live in rural and remote communities that lack basic access to information and communication technologies–telephony, computing, Internet access. In response to this need, Inveneo, a non-profit social enterprise, creates and sells highly affordable and sustainable ICTs that are specifically designed for organizations–governments,NGOs,private enterprises–that serve rural communities with vital services that include education, health care,economic development,relief and telecentres. This is great stuff! You can visit their site and make a paypal donation. Theirs is indeed a great cause.\n<PERSON> reports that the computer is already available in Uganda, for US$941, which the government there says is tax-free. <PERSON> expresses excitement about this innovation, while also observing that the cost is too high for ordinary people in rural areas, the main target of the gadget. <PERSON> ends his post by inviting the company, UK-based Inveneo Inc, to Malawi where he says it will be most welcome.\nMoving on from the world of technology, the political atmosphere in Malawi has been hyper-charged for the past two months. No two terms have so dominated Malawian discourse in the last decade as have “Section 65” and “Budget.” Section 65 refers to the section in the Constitution of Malawi which forbids members of parliament from moving away from the party that sponsored them into parliament to another party also represented in parliament without a by-election.\nPresident <PERSON>, who himself left the party that sponsored him to win the presidency and started his own party, asked the courts to clarify the section, in the hope that the courts would rule in his favor as well as that of more than 60 members of parliament who also left their own parties to join the president in his new party.\nThe courts ruled on June 15 that Section 65 was indeed valid, and tension has been the order of the day in Malawi since then.", "830" ], [ "Malawians on the world stage: academic honors, music, science and technology · Global Voices\nThere is one discernible theme running through the Malawian blogosphere in the month of May. This round-up focuses mostly on what these bloggers have written in this month, now approaching its end. One Malawian has received international honors for his contributions to world scholarship, while two female Malawian musicians have launched their latest music albums outside Malawi. One Malawian scientist calls for the Malawi government to put in place mechanisms to prepare for the looming disaster that might possibly be triggered by global warming, and two Malawians have made their mark in the world of technology. It has been a month of Malawians showcasing their mettle on the world stage, and here with it all.\nHonoring a world class scholar\nBlogger <PERSON>, a Malawian journalist currently a Niemann Fellow at Harvard University, celebrates the news that a Malawian scholar has recently been honored by Rhodes University of South Africa, and that a former Malawi Broadcasting Corporation (MBC) journalist will be teaching at Rhodes University. The two Malawians being celebrated are <PERSON> and <PERSON>. <PERSON> was recently awarded a Senior Doctorate by Rhodes University for his world class scholarship in development studies and political economy. <PERSON> has been the Director of the United Nations Research Institute for Social Development (UNRISD) since 1998. The other Malawian is <PERSON>, who recently announced on his blog that he had resigned from MBC. <PERSON>, himself a journalist with the MBC, writes:\nI wish to congratulate Prof. <PERSON> and <PERSON> for the Rhodes Honours.", "830" ], [ "This comes to mind how quickly our great poets and academics such as <PERSON> and <PERSON> whom I have heard from so many people here at Harvard and beyond asking. <PERSON> and others have become symbols of their nations and ambassadors promoting good. Apart from the two, people like <PERSON> made an impact at the IMF, early May 2007 when I visited the institution I heard fascinating stories on how he used to move from office to office meeting his juniors and seniors alike to hear them. I was proud to be a Malawian when a room full of World Bank and IMF officials, one screamed, “Malawi is unique, it has its best leadership in the Presidency and Minister of Finance.” I hope the this Leadership given at the global institutions will extend into recognition of our achievers and use them as ambassadors to promote Malawi's values.\nMusic for the world\nTwo Malawian female musicians this month launched their latest albums, one in Nairobi, Kenya, and the other in Stockholm, Sweden. In Kenya it was gospel artist <PERSON>, while in Sweden it was musician <PERSON>. <PERSON>, Global Voices author, witnessed the Stockholm affair, and wrote on his blog:\nShe says she decided to launch here [Sweden] because she did not have adequate time to do so in Malawi as she was supposed to leave for studies in Sweden. <PERSON>'s album which has ten tracks (most in Chichewa and others in English) can be bought on Radio Yako (www.radioyako.com).\nIn another posting, <PERSON> writes about the Global Day of Prayer, Sunday May 27, arguing that the day is unlikely to make the headlines because of its religious nature. He reflects on this important day, posting pictures of a celebration of this day last year at Silver Stadium in Lilongwe, Malawi:\nPROBABLY the world's largest unity is to be reflected this Sunday on the Global Day of Prayer when people from over 190 nations will join together and pray for the world.\nBut to put this event in the headlines is direct rebuke to most of our global and national issues so editors prefer to keep it away. After all these are “religious things” and covering it would be ‘like promoting their faith’ they argue.\nMalawi and a warmer globe\n<PERSON>, a scientist with the Malawi National Aquaculture Centre, warns that global warming is real, and that Malawi is part of the areas in Africa that are at greater risk. He calls on government to take measures to address the problem:\nMy questin has been and is always “What is our role as Malawians ?” Do the parliamentarians take this issue with a priority? The image clearly shows that Malawi is in the band of “Areas at most risk”. Let us act now by putting in place necessary policy issues like-irrigation for all crop fields by the year 2030 or 2040, thats 10 yeras before the real thing is on our neck.", "830" ], [ "Malawi: Female Candidates and the Politics of Regionalism · Global Voices\nWith two months to go before Malawians vote in presidential and parliamentary elections on May 19th, 2009, the soup du jour has evolved around two developments, the recent arrest and release on bail, on embezzlement charges, of former president Dr. <PERSON>, and the visits of an African Union delegation of two former African presidents. These developments have overshadowed a major breakthrough that has changed the political landscape for women candidates in Malawi politics.\nIn the first development, Dr. <PERSON> already served two terms from 1994 to 2004, but he claims the constitution allows him to run again, a claim that has received mixed reactions in the country. In the second, former presidents of Ghana and Mozambique, <PERSON> and <PERSON>, are attempting, unjustifiably, according to the blog Chingweshole, to prevent what they fear might be a potential violent conflict in the run up to the elections and possibly in the aftermath.\nHowever, eclipsed behind all this drama are two breakthroughs that in early February everyone was talking about as two Malawian firsts: a woman running mate on a major presidential ticket, and another woman as a presidential candidate in her own right. The two women are Hon. <PERSON>, currently serving as Malawi's Minister of Foreign Affairs, and Hon. <PERSON>, a member of parliament and president of the newly formed, break-away New Rainbow Coalition Party.\nWhile Hon. <PERSON>'s candidacy had been speculated about and expected, it was the choice of Hon. <PERSON> that shook the country when the incumbent president Dr <PERSON> presented his nomination papers to the Malawi Electoral Commission on February 6th, and it became known that the Hon. <PERSON> would be Dr. <PERSON>'s running mate. This was after names of running mates for the main contenders had become a much-discussed guessing game in which it appeared each of the candidates was unsure who to choose, waiting to see who the other would pick first. It was a “stage-managed” and “secretive” process, according to blogger <PERSON>.\nMuch of the speculation on who was going to be Dr. <PERSON>'s running mate centered around Malawi's Minister of Finance, Hon. <PERSON>, a highly respected economist and former International Monetary Fund (IMF) official widely regarded as the brains behind Malawi's economic and agricultural turn-around since 2004, alongside Dr.", "830" ], [ "<PERSON> himself. Hon. <PERSON> was recently awarded a prize as the best performing finance minister in Africa in 2008. Adding to the anticipation was the fact that Hon. <PERSON> comes from the northern region of Malawi, seen as historically marginalized given its relatively smaller population compared to Malawi's two other regions, the center and the south.\nMalawi's first president, Dr. <PERSON>, came from the central region, where political power was concentrated throughout his 30 year rule. From 1994 to 2004 the center for power shifted to the southern region, where erstwhile president Dr. <PERSON>, hails from. Current president <PERSON>, who comes from the southern region, is seen as having given the northern region a much-denied political boost, with <PERSON> finance portfolio being seen as one such example. It was therefore a point of much debated anticipation as to whether <PERSON> was going to select a northerner as his running mate.\nHon. Joyce Banda–Hunger Project Photo\nReactions to the news created a heated debate especially on Internet forums, where it was quickly observed that Dr. <PERSON>'s choice of Hon. <PERSON> was a departure from the norm in which the vice president since 2004 has always been from a region other than the president's. Some also saw it as a betrayal of the northern region, a loyal constituency. Blogger-Journalist <PERSON> observed:\nIts no longer a secret. The Livingstonia Synod of the CCAP has finally come out in the open expressing disappointment over President <PERSON>’s choice of <PERSON> as his running mate instead of Finance Minister <PERSON>, whose name was at the centre of debate as the likely person to pair up with the DPP leader.\nSome claimed the president had played a “regionalistic” card”, while others suggested that the president was being pragmatic as well as promoting gender equality, noting that in fact Hon. <PERSON>'s husband, former Chief Justice <PERSON>, is himself a northerner.\nOther reactions focused on her achievements and rise to influence, observing that she was the 1997 recipient, together with then Mozambican president <PERSON>, of the Africa Leadership Prize, awarded by the New York-based Hunger Project.", "830" ], [ "Zambia: We need Enlightenment to end this instanity · Global Voices\nZambian blogosphere continues to grow and bring diverse voices and opinions online. <PERSON> writes about education in Zambia in his post, “Educated but poor”:\nA majority of youth in Africa today have completed more years of schooling than their parents did but have limited opportunities in employment and remain poor, according to the The World Youth Report 2007 .\nHe also writes about the Open Thread – NCC Allowances :\nSome interesting comments / reports on the National Constitution Conference (NCC) allowances in the media this week. The Post on saturday reported the extent of the proposed allowances: The NCC delegates are entitled to a sitting allowance of K500,000 persitting and subsistence allowance of K650,000 per day. They are also entitled to transport allowance of K100,000 per day and transport refund of K300,000 for those who reside outside Lusaka.\nThe National Constitutional Conference (NCC) was held to prepare for a new Zambian constitution.\nIssues Over Matters discusses the state of Zambian economy and politics:\nWhatever happened to that age-old gem of wisdom that we always spat out when we realised someone was about to take advantage of us as youngsters in playgrounds in Kitwe: takuli kuliilana amasuku pamutwe guys in Bemba.\nIn the Zambian society today, <PERSON> unfortunately has become part of the national culture, and if anybody at any level for that matter, manages to eat fruit from someone else’s head, he assumes heroic status and the victim is deemed ukupwalala or sleepy.\nA good example is the way former President <PERSON> who is appearing in court for various offences allegedly committed while in office, is today seen as a victim rather than what he should be treated, as in The people Vs Chiluba.\nPoliticians in government, politicians outside government, senior civil servants, junior civil servants, private and parastatal company chief executives, junior employees, NGO leaders and just about everybody, including tuntemba owners, are fleecing and want to fleece everyone else.In short, crime in general and corruption in particular, is endemic in the nation. The dominant criminal element in society has impoverished everyone else to a point where being “clean” is considered abnormal.\nWhen I was a student just over two decades ago, we used to band about statistics in Kalingalinga and M’tendere taverns that 95 percent of the nation’s wealth was in the hands of five percent of the population which was then associated with UNIP.\nTwo decades later and 17 years of the MMD in power, I am sure the statistics have shifted: 99 percent of the wealth is in the hands of only one percent of the population.\nThe recent contest for the ANC presidency between the South African president <PERSON> and <PERSON> drew a global attention. Zambian blogger, <PERSON>, writes about the contest in a post titled THABO BRUISING A LESSON FOR AFRICA.", "424" ], [ "He writes:\nThe election of <PERSON> as ANC leader is a good sign for Africa, that democracy can prevail even in ruling parties across the continent used to leaders who grow roots in the seats of power. Not that <PERSON> is the best man for the eventual job of South African president, but <PERSON> is to blame.\nICT Journalist looks at the state of ICT infrastructure and policies in Africa in the context of the Africa Telecommunications Day:\nThe lack of main energy supply in many rural and remote areas is a major obstacle to deploying telecommunication infrastructure.\nWhen we look at the theme for the Africa Telecommunications Day whose theme this year is “Applying emerging technologies to empower rural communities towards attainment of Millennium Development Goals (MDGs),” we see the digital divide between rural and urban area.\nTo bridge the rural digital divide there is need to strengthen human and institutional capacities to harness information and knowledge more effectively. Africa needs to address the following key issues to reduce the digital divide that exists.\nWhen we look at content package on the Internet, it is all in Africa’s foreign languages which are either in English, French, Portuguese, Spanish or Japanese to name but a few. There is need for African communities to locally adapt content and contextualise it. Also there is need for the communities to share content that will build on exiting systems to address diversity.\nRural dwellers however will also need capacity building on the importance of ICTs and how they can benefit from them. It is also important for the rural communities to partner and participate in the World Summit on information Society (WSIS) process.\nIt is also time for the rural communities to have a realistic approach to technologies and work on the high cost and financial sustainability.", "409" ], [ "Malawi: Actor’s Arrest Reminiscent of Past Dictatorship’s Censorship Laws · Global Voices\nMalawi police on Sunday afternoon December 18, 2011, stormed a stage on which a play was being performed, and led the play's main actor away into a waiting police van.\nAccording to posts on Facebook, where the news first broke and reactions came in fast and furious, the play is titled “Semo” produced by Lions Theatre. The lead actor in the play is <PERSON>, son of Malawi's best known playwright and actor, the late <PERSON> The play was being performed at Nanzikambe Amphitheatre in the commercial capital, Blantyre.\nFirst to break the news was <PERSON>, Malawi's leading radio host who works at Capital FM Radio. He was in the audience when the arrest happened and he posted pictures on his Facebook page. <PERSON>'s status update, a little after 3.05 pm Malawi time, read [the content is currently only available to friends]:\nActor <PERSON> being led away for questioning. Photo courtesy of <PERSON>.\nPolice have just stopped a play ‘Semo’ by Lions Theatre at Nanzikambe Amp Theatre.\nReactions flowed in immediately with people wanting to know the police's motive. <PERSON> responded:\nThe play is reported to be too critical of <PERSON> regime.\nHe later added:\nWe are all here. Nobody is moving.\nFor most people commenting on Facebook the scene was reminiscent of the one-party dictatorship when “president for life” Dr. <PERSON> ruled Malawi for 30 years, from 1964 to 1994. The one-party era was characterized by heavy-handed censorship through a government agency known as the Censorship Board.\nThe end of one-party rule in 1994 brought democratic changes, and the Censorship Board no longer played its public censorship role.", "830" ], [ "However despite Malawian activists questioning the presence of the board in post-1994 Malawi, censorship laws have remained, and the board continued existing, albeit in a low profile. It was renamed the Malawi Classification Board, but <PERSON>'s arrest and charging shows the law governing the board remains stuck in pre-1994 Malawi.\nCommenting on <PERSON> update, <PERSON> wrote:\nFast descending into a police state. <PERSON>. [Should we go back to being afraid to even mention somebody's name?] Wasn't 30years enough for this?\nAnother comment, on a separate thread, also alluded to the dictatorship era [the content is currently only available to friends]:\nI heard of more or less similar stories from my late father, but i never thought I could live in similar times. Was his vote in 1993 and 1994 a waste? I am hurting bro.\nSome went even further and alluded to the colonial era when Malawi was under British rule:\n<PERSON> wobwera [At least <PERSON> was a foreigner]\nThat reference was to <PERSON>, the last colonial Prime Minister for the Federation of Rhodesia and Nyasaland. The federation was fiercely hated and opposed by Africans, who fought it and won independence as modern day countries of Malawi, Zambia and Zimbabwe.\nAnother netizen wondered why arrest an actor when a play is authored by a playwright, but online newspaper Nyasatimes reported that <PERSON> co-authored the play together with <PERSON>, a University of Malawi Polytechnic student activist who was found murdered on campus on the morning of September 24, 2011.\nBlogger <PERSON> commented, also on facebook [the content is currently only available to friends], about the paranoia that seemed to be gripping the Malawi government:\nBy now, we all know what an insecure and pessimistic regime is like: it has to arrest anyone who rebukes it\nMore reaction appeared on a Facebook group known as Malawi at 50: Towards a New Crop of Malawian Leaders [Malawi at 50 is a closed group]. On Malawi at 50 the first update on the arrest appeared at 7.40pm Malawi time, from <PERSON>. She wrote:\nPlaywright and actor <PERSON> being led away by Malawi Police for questioning on the “subversive” substance of the creative material in his new play. I'd call it a great opening run;-) Free publicity provided by Malawi Police.\nLater <PERSON> alluded to her fears about what happened to a young Malawian political activist when the police questioned him, a reference to University of Malawi Polytechnic student <PERSON> who was murdered after getting involved with police intelligence gathering. <PERSON> wrote:\nI understand he was frogmarched off stage by police 11 minutes into the performance.", "830" ], [ "Twits and wits: Malawian bloggers on new technologies, nature, myths, Zimbabwe, and a hard work ethic · Global Voices\nSince the last Malawi roundup, the Malawian blogosphere has continued to be abuzz with posts announcing new technologies, news on Internet-based radios, existing radio stations going online, stories about farming initiatives, as well as reflections on nature and Malawian places of mythical, if not mysterious, interest. There have also been entries on the situation in Zimbabwe, politics in Malawi, and the hard work ethic that Malawians espouse when outside the country, among numerous other topics. Here with it all:\nTwitter and new technologies\nMalawian blogger, <PERSON>, writes about Twitter, a cutting edge technological innovation that enables users to update others on what they are doing at a particular moment. According to Soyapi, because of its adaptability between SMS function in cell phones, IM messaging, and webpages, twitter has a much greater potential in Africa, where there are much more cell phone users than Internet users:\nSo the launching of Twitter provides a good alternative considering that the use of mobile phones is much higher than that of computers. In Malawi for example, there are about 50,000 Internet users against about 700,000 mobile phone users out of a population of about 12 million. Twitter allows users to post a small update via SMS, instant messaging client and the web. Anyone who chooses to follow you will get that update on the Twitter home page, or their mobile phone of they choose to. Unlike most mobile phone web services, you can update via SMS from anywhere in the world and from virtually any handset.\nAnd still on technology matters, <PERSON> has issued a call for suggestions providing a name for what he terms an all Malawian Christian Music Internet Radio Station:\nThis is to solicit a name for an all Malawian music Internet Christian radio station. A motto will be a fantastic bonus. I will really appreciate an explanation for the choice of your name. There is no criteria for the name. Sorry that at this point there will be no rewards.\nJatropha, nature and mythical mysteries\nClement Nyirenda asks if there has been any progress in Malawi in the farming of Jatropha, a plant he says is an excellent substitute for tobacco due to its oil content, 50 year life-span, and fertilizer content, among many other unique attributes:\nNowadays, I get very excited when I hear news about the global anti-tobacco policies, although the masses in Malawi and other developing countries are not happy. In my case, I see this as an opportunity for Malawi to look into other useful crops to replace the destructive tobacco. Jatropha is said to be one of those dream crops. Jatropha is a perenial shrub suited to tropical climates with 50 years life span.", "830" ], [ "It starts bearing seeds after two years of planting. Seeds with shell have an oil content of 32%-35%. This oil can be used for the production of biodiesel, soap, mosquito repellent, organic fertiliser etc.\nAnd still on nature, blogger <PERSON> writes on his blog Where Flames Burn the Brightest about myths that surround two natural sites in Malawi, Malawi’s highest mountain, Mulanje, and Mwala wa Nthunzi, a rock said to spew out steam. <PERSON> talks about spirits that are said to haunt the highest peak of the mountain, Sapitwa, which translates into English as “Unsurmountable” or “Unreachable,” or “No go”. In 2003, a 29 year-old Dutch woman, <PERSON>, left fellow climbers behind, somewhere up the mountain, and proceeded to the dreaded Sapitwa Peak, alone. Rescue teams from Malawi and from the Netherlands spent several weeks searching for her, but she was never found. On Mwala wa Nthunzi, <PERSON> writes:\nMwala wa Nthuzi is one rock that has continued to puzzle me. Apparently the rock cant be removed from its original spot. When M1 [the main thoroughfare that runs the length of Malawi from south to north—Editor’s note] was being constructed, contractors would have the rock removed only to find it in its exact spot the following day. They tried removing it on multiple attempts but in spite of all their efforts the rock still returned to its spot. Today the rock is still there and the M1 just by its side.\nIn his other post, <PERSON> writes about the English Football League and comments on the new coach for the Malawi national football (soccer) team:\nFAM officially unveiled <PERSON> as Malawi national team coach. Good luck to the guy. Malawian fans can be really tough. They want results now. It is easy to understand.", "830" ], [ "Tunisia: Remembering Tunisia’s First Internet Prisoner · Global Voices\nTunisian <PERSON> will always be remembered among Tunisian activists as someone who had sacrificed his life for the struggle for freedom of speech.\n<PERSON>, who had adopted the pen name <PERSON> or The Tunisian and was a graduate in economic sciences and Internet journalist, had invited readers of his satirical website TUNeZINE to vote on whether Tunisia was a “republic, a kingdom, a zoo or a prison” on June 2, 2000. Soon after wards, he was picked up from an internet cafe by plainclothes police officers, without an arrest warrant.\nIn November 2003, <PERSON> was released from prison after spending 18 months and on March 13, 2005, he died of a heart attack at the age of 36. During his time in prison, <PERSON> went on hunger strike several times in protest against his imprisonment conditions and supporters claim he was also subjected to torture.\nTo mark his forth death anniversary, The Network of Tunisian Bloggers for Free Blogging reminds us about Tunisia's first Internet prisoner:\nتمرّ اليوم 4سنوات على رحيل زهير اليحياوي مؤسس موقع “تونزين”، وقد توفي الفقيد على إثر نوبة قلبية وهو لا يزال في ريعان شبابه.\nدخل السجن في ربيع 2002 ودفع غاليا ثمن تشبثه بالدفاع عن الحرية مستعملا في ذلك التقنيات الحديثة التي وفرتها شبكة “الأنترنيت”، وهو ما جعله يصبح رمزا للنضال على الشبكة.\nكان ولا يزال يمثل نموذجا للمناضل والمدافع الصلب عن قضايا الديمقراطية ـ و قد دخل عدة مرات في اضراب عن الطعام للمطالبة بتحسين وضعه داخل السجن دون أن تستجيب الادارة العامة للسجون لمطالبه وقد أثرت ظروف اعتقاله على صحته التي تدهورت\nFour years ago <PERSON>, the creator of the web site Tunezine left us following a heart attack, while he still young.\nHe had been thrown in jail in the spring of 2002 and paid heavily for his commitment to defend freedom, using the modern techniques provided by the “Internet”, which made him become a symbol of the struggle on the web.\nHe has been and continues to be a model for activists and defenders of democracy.", "244" ], [ "He had gone on hunger strikes several times to demand better conditions in prison but the Public Administration for Prisons did not respond to his requests. The conditions of his detention had affected his health, which deteriorated.\nAnd the situation seems to have deteriorated even further in Tunisia since <PERSON>'s death. Fellow Tunisian blogger and Global Voices Advocacy editor <PERSON> updates us on the repression of the Internet in his country in this post.", "409" ], [ "Nominations Open for ‘Best of the Blogs’ Award · Global Voices\nBlogging has become a major motivator of social and political change in many parts of the world, as well as a source of information. Here on Global Voices, we curate and publicize some of these blogger voices and translate them into many different languages. A central goal of the community is to promote a cornucopia of perspectives and aspirations. For this reason, we support initiatives such as the Best of the Blogs awards.\nOn December 7, Deutsche Welle in Germany kicked-off the sixth annual international Best of the Blogs awards: the BOBs. The nominated blogs will be sorted in eleven different language categories. Global Voices Online is an official partner alongside Reporters Without Borders, re:publica 2010 [de], TV5 [fr], Al Arabiya [ar], and many others.\nAny person interested in nominating a blog, must first search for it in the BOBs blogopedia and submit the blog of their choice in the competition database if it is not already listed. The jury will select the finalists.", "696" ], [ "Winners will be selected from this group of finalists between March 15 and April 14 through a combination of online voting and a jury selection.\nOn April 15, the winning blogs and podcasts will be announced at the Re:Publica Internet conference in Berlin [de]. The awards ceremony will take place at the Deutsche Welle Global Media Forum in June 2010 in Bonn.\nFor bloggers, the BOBs is opportunity to conquer a broader audience and to be named one of the best bloggers on the Web. So far, there are 15,558 registered blogs in the blogopedia:\nThe Blogopedia is our international online catalogue of Weblogs, podcast and videoblogs. Each blog is entered into the database according to a variety of criteria from topic to country of origin to language. Looking for music podcasts in Brazil or food blogs in China? No problem! Just type your keywords into the search feature or browse through the categories and Tagcloud. Then join the thousands of other Bloggers who have submitted their blogs, podcast and videoblogs into the Blogopedia.\nIn this year's competition, climate change is under the spotlight, with a special prize category for blogs and podcasts discussing the topic. Additionally, the BOBs have also added Bengali (Bangla) to the line up of languages.\nWe're looking forward to seeing the big winners of the BOBs awards 2010. Go nominate your favorites!", "696" ] ]

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[ [ "First time bunny owner\nHi all, me and my boyfriend are about to adopt a bunny from someone who is selling him because they can’t care for him anymore. We plan to allow him to be a free roam bunny as he is litter box trained.", "661" ], [ "They are also providing us with all the main essentials like a hutch, gate, litter box, bedding and food, ect. Is there any do’s and dont’s suggested? Or Guide me to your favorite products. I’ve done some research but I’d appreciate hearing from someone experienced! Thanks so much.", "502" ], [ "Leaving small dogs in our house for 2 weeks while on vacation\nHey all, My mom decided that it’s too expensive to board our dogs in a doggie daycare, and that my dogs will be more comfortable being in our house. She hired our cleaning lady to pet sit our dogs.", "881" ], [ "She committed to coming in our house once every morning and night to walk and feed them. I am still feeling anxious and I am nervous about our cleaning lady fulfilling her commitments as she lives half an hour from our house.\nHas anyone else done something like this before? I know boarding them is ideal, but our older dog literally got traumatized from being boarded as the day care had him Play (small 9 pound yorkipoo) with big dogs who ended up hurting him. So we dont want to risk something like that again with him and our younger dog.", "63" ], [ "Crate Training\nAdvice on crate training a puppy. We have a 12 week old golden doodle who is home with one of us pretty much every single day all day. The golden in him has obviously made him very loyal and attached to us so this has made crate training unbelievably difficult. We put him in the periodically throughout the day and at night and it’s not getting better.", "833" ], [ "We cover the crate so it’s dark he has a snuggle puppy and cozy bed. He gets hot so we leave a tan on for him. But he will howl for an hour before ever calming down. He bites the crate and paws at it and at this point I’m worried he’s going to get hurt. We’re going on week 4 of this and I’m ready to give up.", "210" ], [ "Any advice on dog wards?\nI have a 10 year old poddle mix and I noticed that he has a couple of wards on his back. During his annual physical a couple of months ago the vet told me that wards are normal for older dogs and that I shouldn’t worry.", "63" ], [ "However lately they seem to be growing and I am not sure what it means. His vet won’t have any available appointments until the end of August and I am not sure if I should wait until then or take him somewhere else. I would really appreciate any advice from other dog owners who have experience with this.", "961" ], [ "Spending christmas at my sister’s this year, and…\nMy dog, a two year old female tibetan spaniel, is not allowed to come. The reason for this she says is «allergies».", "888" ], [ "She has three kids, one of them is allergic in the spring, so grass, pollen etc, and one of them is a year and 3/4 months old. She is afraid for the little one because apparently when exposed to animals at a certain age you can develop an allergy to that animal. Is this true? I’m kinda sad about it because I want my dog to be a part of the family, but she is never allowed to visit at my sister’s, which is usually where family gatherings happen.", "888" ], [ "My dog’s having a hard time meeting new kittens\nThe dog is around 13 years old, poodle terrier bigger than a cat. We tried (4 adults) introducing them (after a week behind a door) one adult per kitten and two with dog. He went for invasive sniffing, he barked in a kitten face. He couldn’t calm down.", "1011" ], [ "So we called it a day. A few days later I tried securing the basement, putting dog in his big carrier, and opening door for kittens to approach. He won’t stop anxiously barking, so they stay back. I really need advice! Will time help..??", "954" ], [ "First Time Dog Owner TIPS!\nSpecifically my partner and I are looking to adopt a pug soon. We currently live in a decent sized home with garden space and parks nearby.", "770" ], [ "I work a 9-5, Mon-Fri sort of job while my partner mainly works remotely. We are both quite introverted so prefer to be home most of the time other than the occasional holiday and date nights.\nI really want to be a good mum and make sure I’m giving the pup their best possible life. I know we’re bound to make some errors along the way but would love to know some tips and tricks for first time pup parents!", "502" ], [ "Need advice for going on holiday with 2 6 month old kittens\nHi. As title says, I have 2 outdoor kittens. Brother and sister.", "176" ], [ "We will be going on holiday for 7 days. We were going to get a cat sitter. Would 30mins every morning be enough? This would keep them in the house for the 7 days.\nOr would we have to double up the cost and get 1 hour where they can be let out for 45mins every morning.\nI can't imagine a cattery being a good option.", "176" ] ]

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[ [ "This is an extremely good question despite its seemingly simple nature. It connects everything from <PERSON> to string theory to debunking moon landing conspiracies. I'm surprised that the question has '-1' points at the moment (before I upvoted it to make it $0$!).\nThe concepts surrounding it have a long history involving people from <PERSON> to <PERSON>, <PERSON>, <PERSON>, <PERSON> and even string theorists like <PERSON>. The ideas have been discussed in the context of <PERSON>'s gravity, <PERSON>'s formulation of general relativity, modifications to general relativity and string theory. They have also undergone various, far-reaching, high-precision experimental tests.\n<PERSON>'s second law says that a force ($F$) exerted on an object causes it to accelerate ($a$) with the resistance offered to this acceleration being decided by what is called inertial mass ($m_i$):\n$$F = m_i a$$\nNewtonian gravity says that the gravitational force ($F_g$) experienced by an object depends on the gravitational potential ($\\phi$) and its gravitational mass ($m_g$):\n$$F_g = -m_g \\nabla \\phi$$\nThat $m_i = m_g$, is an empirical fact and/or motivated by deep physical principles. $m_g$ is a measure of how a body reacts to an external gravitational field and is of a different nature than $m_i$. It might very well be the case that $m_i \\neq m_g$.\n<PERSON>'s empirical observation that pendulums of equal length but different masses have the same time period lead to the idea that all objects are affected by gravity identically. <PERSON> was also instrumental in similar experimental observations, concluding that different bodies undergo free fall identically. These developments lead to the idea that $m_i = m_g$, such that all bodies have the same acceleration under free fall. This idea was that of a universal nature of gravity: that every object (irrespective of its composition/mass) falls at the same acceleration rate in a gravitational field. If $m_i \\neq m_g$ then different bodies fall at different rates.\nThe idea of equating inertial mass with gravitational mass was taken many steps further by <PERSON> with the advent of the Equivalence principle.", "766" ], [ "There are various versions of the equivalence principle, most commonly known ones being the Weak, <PERSON> and Strong equivalence principles: WEP, EEP and SEP, respectively.\n1) WEP states that $m_i = m_g$ and therefore, all bodies undergo free fall at the same rate. From the equations of motion, we see that we have a preferred frame, i.e., the free fall frame, where there are no external forces acting on the body. So, locally, being accelerated and being under a gravitational influence have the same physical consequences.\n2) EEP states that, in a gravitational field, locally, all non-gravitational laws of physics reduce to that of special relativity.\n3) SEP supersedes EEP by including gravitational physics laws in addition to non-gravitational ones.\nThe <PERSON> experiment is a classical test of the WEP: it checks the equivalence between $m_i$ and $m_g$. The fractional difference in accelerations of different bodies has been measured up to $2 \\times 10^{-13}$ according to Ref 1 (page 8).\nThere is a way to test WEP indirectly through SEP: <PERSON> effect. See also <PERSON>'s original papers: Refs 2 and 3. If SEP is true, then gravitational self energy should contribute equally to inertial mass $m_i$ and gravitational mass $m_g$. If not, then the difference in $m_i$ and $m_g$ causes different objects to accelerate at different rates, violating WEP. Gravitational self energy is negligible for objects used in laboratory experiments (negligible in the sense that such levels of precision are out of the reach of current experimental limits).\nBut celestial objects have much larger gravitational self-energies. <PERSON> proposed an experiment (see Ref 4) to see if $m_i \\neq m_g$, using laser ranging to measure the distance between earth and the moon. This experiment is called the Lunar Laser Ranging experiment. When Apollo 11 astronauts landed on the moon, they placed a retroreflector there to reflect lasers from earth to moon and back to earth for high-precision distance measurements. (Other missions also planted such retroreflectors.) For more information about this experiment, see Refs 5, 6, 7, 8 and 9.", "766" ], [ "<PERSON> is equating the different length scales associated.\nIn quantum mechanics, the characteristic length scale is decided by the mass of the particle. It is known as Compton wavelength ($\\lambda_c$), and roughly speaking, it sets the length scale where relativistic quantum field theory becomes important for the description of physics; because if you try to localize a particle such that the uncertainty in position is smaller than $\\lambda_c$, the the uncertainty in momentum becomes high enough to (from $E^2 = m^2 c^4 + p^2 c^2$) induce uncertainty in energy of the order of the mass of the particle. This means that at such small length scales, and equivalently, high energy/momentum scales, we must take special relativity and particle production/annihilation into account.", "976" ], [ "The Compton wavelength is given by:\n$$\\lambda_c = \\frac{\\hbar}{mc}$$\nIn general relativity, the characteristic length scale is also decided by mass, but is directly proportional to it. It is known as Schwarzschild radius $r_S$. The event horizon of a static and spherically symmetric object lies at $r=r_s$ and is given by:\n$$r_s = \\frac{2 G m}{c^2}$$\nSubstituting $r_s$ for $\\lambda_c$ and barring a factor of $\\sqrt{2}$, we can write the characteristic mass scale for such a situation in terms of the three fundamental constants of the three fundamental theories: $c$ of special relativity, $G$ of general relativity and $\\hbar$ of quantum mechanics, and it is known as Planck mass:\n$$m_p = \\sqrt{\\frac{\\hbar c}{G}}$$\nSo the Schwarzschild radius of a black hole of mass equal to the Planck mass is its Compton wavelength.\nThe number of microscopic states of a black hole with given macroscopic characteristics (like charge, mass and angular momentum) can be written in terms of the area $A$ of the event horizon. This is known as black hole entropy and is given by:\n$$S = \\frac{kAc^3}{4G\\hbar}$$\nwhere $k$ is the <PERSON>'s constant.\nThe issue that black holes are not entirely 'black' and end up radiating because of particle production when quantum mechanics is involved has led to many debates and open questions that fall under the umbrella term of black hole information paradox.", "688" ], [ "The wikipedia article has some great info. on the historical progression of this question.\nUsing <PERSON>'s equations, one recovers the wave equation for electric and magnetic fields. From these equations, <PERSON> postulated that light can be thought of as an electromagnetic wave since the electric and magnetic fields solve the wave equation with a phase velocity of $c$. This theoretical value of the phase velocity of light waves is exactly $299,792,458 \\frac{m}{s}$.\nI mean is it 100 percent accurate?\nNothing is ever 100% accurate - that's an idealization of the human mind since there is always systematic errors in the measurement process (even if perfect humans are conducting the experiments).", "840" ], [ "So, no, it is not 100% accurate. It's worth noting that there's a difference between accuracy and precision.\nAs the wiki article shows, the precision and the accuracy of the measurements of the speed of light have improved greatly with time: as better measurement techniques are used, the measurements agree with each other better and better, and any one of the measurements agree with the theoretical value of $c$ better and better.\nSo, although we cannot have 100% accuracy in principle, we can have such small uncertainties in the measurement that we might as well consider the value to be 100% accurate. From the wiki article,\nAfter centuries of increasingly precise measurements, in 1975 the speed of light was known to be $299792458 m/s$ with a measurement uncertainty of 4 parts per billion.\nA measurement uncertainty of 4 parts per billion is very small, i.e. 0.0000001% of uncertainty: it's like saying for every million years you live you only fudge 30 seconds of it.\nLastly, in 1983, the meter was redefined in the International System of Units (SI) as the distance traveled by light in vacuum in 1/299792458 of a second. This is justified because, as I said above, the precision of measurements of $c$ are so precise that we might as well just define $c$ to be exactly the value that they all (within certainty) agree upon - this value as it turns out is also what <PERSON>'s equations predict.\nThus, yes the value of $c$ is defined to be exactly that given by <PERSON>'s equations, but importantly this is justified because the measurements are very very very precise.", "840" ], [ "Because motion is generally regarded as relative. In other words, you cannot tell whether sth. is moving or not without a reference object. However, since in the bucket experiment the dynamical effect of rotation and no rotation is distinct without any reference object, he introduces absolute space so motion is no longer relative, but absolute.\nAlso i read that in modern physics (<PERSON>) the accelerated motion of the water in the bucket is explained by the action of gravitational field.\nThis is wrong. Despite the name \"relativity\", <PERSON>'s theory is about the absoluteness of spacetime. Rotation is still absolute; something either rotates or not, without reference.\nOther sources say that the accelerated motion remains a dilemma even for modern physics.\nI don't know any dilemma in this.\nResponse to <PERSON> answer :\n<PERSON>'s principle and general relativity\nIt is true that <PERSON>'s principle inspired <PERSON> to discover his famous general relativity, but <PERSON>'s principle is in fact incompatible with general relativity. <PERSON> himself rejects general relativity for it admits absolute spacetime.\nThe corollary of <PERSON>'s principle about the bucket experiment is that the centrifugal force water experiences results from the dragging of distant star swirling around.", "562" ], [ "This poses a serious question: how does the motion of stars light-years away affects the water instantly?\nIn addition, the well-known result of <PERSON> has shown that while rotating shells (as a model of distant stars or a big and massive enough bucket that drags the water with gravitation itself) do have effects the same as centrifugal forces and Coriolis forces, they also exert axial forces with the same order of magnitude, without a fictitious force counterpart.\nFictitious forces and gravitational field\nThe famous equivalence principle states that fictitious forces and gravitation are indistinguishable locally. This gives people false impression that fictitious forces are actually a product of gravitation. But no, while \"true\" gravitational field is manifestation of spacetime curvature, fictitious forces are a result of non-zero spatial curvature depending on how you slice spacetime into spatial and temporal part. No matter how you rotate the bucket and choose the coordinate system, a flat spacetime is a flat spacetime, and no gravitation is present.\nHolographic principle\nHolographic principle is more of a conjecture than an established theory. It is \"a property of quantum gravity and string theories\" as said by Wikipedia. And it is well-known that none of quantum gravity and string theories have ever been experimentally verified and they are constantly evolving, unlike general relativity. So while it is certainly an interesting way to think about bucket experiment, the holographic perspective is by no means the accepted \"modern view\".", "651" ], [ "As a start to an answer, the formula for the temperature of the interior of a black hole is known. In particular:\nFor small black holes, we study their black body radiation and see so little emission that the temperature is about 1/10,000,000 of a degree above absolute zero. Larger black holes would be even colder because they let less radiation escape. That means black holes are colder than space itself (about 2.7 degrees above absolute zero).\nBut, the harder question is whether a black hole would transform the ordinary matter, dark matter (if such thing exists), and photons that fall into it into gravitons.\nThe average density of a black hole, measured as mass divided by volume within the event horizon, is never more than slightly more dense (a few percent or so) than a neutron star which keeps the lion's share of its mass in the form of ordinary matter (i.e. neutrons)1, rather than transforming any substantial share of its mass into gravitons. And, in the absence of better and experimentally validated models of the structure of the interior of a black hole (which may be not just practically, but theoretically impossible), there is no way to test the composition of the interior of a black hole and no really compelling reason for it not to be made of really cold ordinary matter.\nOne can imagine a black hole composed of a Bose-Einstein condensate, as the two articles cited in the comments to the question do. <PERSON> (2012) argues that a work around to the entropy problem that I identify below can make this possible:\nWe reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The <PERSON> modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography.", "688" ], [ "They also open an intriguing possibility of simulating black hole information processing in table-top labs.\nBut, as far as I know, this article's hypothesis about entropy is not widely accepted. The cited follow up article to <PERSON> (2012), which is <PERSON> (2016), seems to be a bit more carefully reasoned. <PERSON>'s abstract states:\nWe analyze in detail a previous proposal by <PERSON> and <PERSON> that black holes could be treated as consisting of a Bose-Einstein condensate of gravitons. In order to do so we extend the <PERSON>-Hilbert action with a chemical potential-like term, thus placing ourselves in a grand-canonical ensemble. The form and characteristics of this chemical potential-like piece are discussed in some detail. After this, we proceed to expand the ensuing equations of motion up to second order around the classical Schwarzschild metric so that some non-linear terms in the metric fluctuation are kept. We argue that the resulting equations could be interpreted as the Gross-Pitaevskii equation describing a graviton Bose-Einstein condensate trapped by the black hole gravitational field. Next we search for solutions and, modulo some very plausible assumptions, we find out that the condensate vanishes outside the horizon but is non-zero in its interior. Based on hints from a numerical integration of the equations we formulate an ansatz and eventually find an exact non-trivial solution for a mean-field wave-function describing the graviton Bose-Einstein condensate in the black hole interior. Based on this we can rederive some of the relations involving the number of gravitons N and the black hole characteristics, summarized in its Schwarzschild radius, along the lines suggested by <PERSON> and <PERSON>. These relations are parametrized by a single parameter —a dimensionless chemical potential.\nIt is less clear in the follow up article that the graviton BEC must be the sole content of the black hole and neither paper addresses any process by which ordinary matter sucked into a black hole is transformed into part of a graviton BEC.\nI am not aware of any known process that would convert ordinary matter to gravitons in an ordinary black hole and I am not aware of research that really singles out this possibility. Indeed, a conversion of ordinary matter absorbed by the black hole into gravitons would violate baryon number and lepton number conservation and so this interaction is forbidden in the Standard Model and any reasonably plausible quantum gravity theory that preserves B and L conservation.", "688" ], [ "At a basic level, current models of physics describe a force as the exchange of (virtual) bosons. This is just a model, but here's the general gist at what's a very basic level:\nThere are different types of fundamental forces: Strong, electroweak (electromagnetic + weak) and gravitational. On top of this, there is the Higgs Boson.\n* The strong force is mediated by gluons\n* The electromagnetic force is mediated by photons\n* The weak force is mediated by the $W^+$, $W^-$ and $Z^0$ bosons\n* gravitational force is mediated by the gravition, which has not actually been discovered, but is believed to exist\nThe Higgs, in this case, gives mass to the weak bosons by the process known as symmetry breaking.\n'The standard model' in quantum field theory (QFT) describes how these (with the exception of the graviton) interact with each other and the other fundamental particles (fermions). Describing an 'object' as some sort of entangled wavefunction of the smaller objects in a larger Hilbert space:\nTo simplify the explanation, assume that there are only two objects in the universe which (to 'explain' the electromagnetic interaction) both have a net charge, with a negligible mass and are far enough apart that the other interactions have a negligible chance of occurring relative to having an electromagnetic interaction. Let's also assume that they are somehow observed at regular intervals (so that these objects actually have a defined position, albeit with some uncertainty) and that at some time, $t_0$, they are stationary.\nWhat then happens is that these objects 'exchange a virtual photon' (or have some other valid QED interaction), which really means that the maths given by QED give the right solutions to the probabilities, strengths etc. of interactions (really, this is boiling down into physics is just a model - see the answer given by anna v...). What seems to be described by this maths is that one of the objects emits a photon with some momentum and so, by the 'law' of conservation of energy-momentum, experiences a change in momentum. This photon interacts with (gets absorbed by) the other object, which therefore also experiences a change in momentum.", "800" ], [ "In other words: the objects are now moving relative to each other! Having said all this, I need to stress: 'Exchanging virtual bosons' is really physics shorthand for 'the result you are looking for is given by performing the relevant mathematical perturbative expansion in QFT'. As this is difficult for everyday objects (read: practically impossible), we just use classical physics instead. Which, for everyday objects, is good enough.\nThe other interactions work by the same principle, but there are differences (strength of interaction, distance over which the interaction will realistically occur etc.) and relaxing any of the above assumptions means that other interactions also need to be included...\nHowever, we have yet to include gravity. Suffice to say that the path (and hence, 'movement') of a particle is described by a world line, which, in the absence of other forces, is a geodesic\nI've written all of the above as this is hopefully what you're looking for and so, will satisfy your curiosity, but what's important is:\n1. The law of conservation of energy-momentum means that when two or more objects interact (so that they are not in equilibrium with each other), they experience a change in momentum, which is observed as either movement, change in mass, or some mixture of the two. Once an object has started moving relative to another object and it's no longer interacting with anything and its mass/energy is not changing, it stays at that velocity\n2. All of the above is a model that fits an observation. Again, see the answer given by <PERSON>\n3. Whether or not it's due to collapse of the wavefunction, decoherence or a number of other possibilities, is down to whichever interpretation of quantum mechanics you're using, which all give the same experimental results (at least, the valid ones do anyway)", "343" ], [ "Is a vacuum-energy smaller than zero forbidden? Why?\n<PERSON>'s Field Equations allow for the derivation of Newton's law and this, together with the velocity profile of the stars within the galaxies and the galaxies within the galaxy clusters, leads to the introduction of unknown dark matter. We haven't found this dark matter yet, so insisting on questioning whether this introduction is valid and unavoidable is reasonable.\nThere is MOND (modified <PERSON> dynamics), which works quite well for galaxies (not well for galaxy clusters), but seems not to be a real alternative as it does not deal with curved space-time which is an everyday experience for people working on GPS.\nThere are some modifications of the Einstein Field Equations which introduce new fields instead of unknown dark matter—but there is an \"equivalence between dark matter particles gravitationally coupled to the Standard Model fields and modified gravity theories designed to account for the dark matter phenomenon\", which was impressively shown in the paper of <PERSON> and <PERSON> in 2017 in Physics & Astronomy (arXiv: 1702.03832 [gr-qc]).\nThere is essentially more space near the mass than further away (the prefactor $A$ of the space-part in the metric $$\\mathrm{d}s^2 = - B \\mathrm{d}t^2 + A \\mathrm{d}r^2 + r^2 (\\mathrm{d}\\theta^2 + \\sin^2{\\theta}\\mathrm{d}\\phi^2)$$ is bigger than 1). $A$ is approaching 1 in the infinity, leading to Newton's law.\n1. There is curved space-time and the field equations are valid in the solar system.\n2. Dark matter theories and modifications of Einstein's Field Equations introducing new fields are impossible to distinguish experimentally - and neither of them has been found yet.\n3.", "651" ], [ "There is more space near the center of gravity than further away.\n4. The concept of \"space-time is approaching 'flat space-time' in infinity\" works well for the solar system.\nRethinking these points leads to the question of whether it could be possible to simply assume other boundary conditions (4.) for galaxies using the <PERSON> field equations than used for the solar system to explain the dark matter effect.\nUsing not flat space-time, but \"vanishing space-time\" (A approaching 0 instead of 1) as the boundary condition for galaxies leads to the introduction of a vacuum-energy which has to be smaller than 0. The space itself would have to be regarded as a field with negative energy. Regarding space-time of galaxies as a potential well. Obviously, this thinking seems to be very far-fetched as it isn't discussed anywhere in the community. Please, help me to understand why.\nIs that (vacuum energy < 0) known to be forbidden per se? Is it obviously impossible? Why?", "651" ], [ "In my opinion, the most fundamental law of Newtonian physics is the classical limit of the most fundamental law of quantum physics, namely the <PERSON> sum-over-all-histories principle (also known as the <PERSON> path integral).\n<PERSON> discovered that the probability amplitude for a quantum system to evolve from state A to state B is proportional to $$\\sum_{A \\rightarrow B}e^{iS(A\\rightarrow B)/\\hbar}$$ where the \"action\" $S(A\\rightarrow B)$ is a number that depends on how the system evolves between A and B and $\\hbar$ is <PERSON>'s constant divided by $2\\pi$. (The actual probability is proportional to the square of the magnitude of this sum, and the proportionality constant is determined by making the probabilities sum to 1.) With the proper choice of how to compute $S$, this explains quantum systems from the hydrogen atom to the Standard Model of particle physics.\nIn the limit $\\hbar\\rightarrow 0$, the sum-over-all-histories principle becomes the classical Principle of Stationary Action, $\\delta S = 0$, which says that the classical path from A to B is the one from which deviations cause no first-order variation in the action. When the action is written as a time-integral of a Lagrangian, this principle is equivalent to the Euler-Lagrange equations.\nSo a single unifying principle lies behind quantum mechanics, quantum field theory (including the Standard Model), Newtonian mechanics, relativistic classical mechanics, electromagnetism, and General Relativity! I consider it the deepest of all known laws of physics.\nThis leaves the non-trivial question of how to compute $S$. We already know what $S$ is for Newtonian mechanics, for relativistic classical mechanics, for non-relativistic quantum mechanics, for electromagnetism, for General Relativity, and for the Standard Model.\nThe most important thing that stands out about the various expressions for $S$ that we've found is that they are invariant under various symmetries. The symmetries of $S$ are what give rise to the conservation laws.", "976" ], [ "So we know how to invent new possible actions that might be the right one for, say, quantum gravity. The search for the \"ultimate\" action that describes a Theory of Everything is underway, under the assumption that it will be even more symmetric than the actions we already know about.\nIn short: The concept of \"action\" is what unifies physics. The search for the right action to unify all phenomena is what physics is about.\nAs a specific example, to learn about Newtonian gravity in this way, start with the action $$S=\\int_{t_1}^{t_2}(K-U)dt=\\int_{t_1}^{t_2}\\left[\\frac{1}{2}m\\left(\\frac{d\\vec{r}(t)}{dt}\\right)^2+\\frac{GMm}{|\\vec{r}(t)|}\\right]dt$$ for a small test mass $m$ moving under gravitational field of a much larger mass $M$ (assumed to be stationary at the origin). It happens to be the time integral of the kinetic energy of the system minus its potential energy. Show that $\\delta S=0$ leads to elliptical orbits, and that energy and angular momentum are conserved.", "499" ] ]

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[ [ "From the said conversation in Episode 4 and what we know of Episodes 1-3 we know that <PERSON> and <PERSON> know that <PERSON> is a Jedi. Or more was. What is more is that the Jedi were officially discredited and executed in Episode 3.\nWhen <PERSON> met <PERSON> that one went off to find his mother (who was <PERSON> step mother) and rescue her alone from a place where not even a full group of armed men managed to get her from and succeeded easily, bringing her back dead though.\nWhat they know of the Jedi is most likely whatever the Seante put out there in addition from what they saw from <PERSON>. They know that the Jedi are fugitives and if <PERSON> comes even remotely after his father he will be a fugitive and more so he will move out of their lives forever. As both <PERSON> and <PERSON> are very fond of <PERSON> and don't want him out of their lives they have a dislike for that especially <PERSON> who probably didn't even forgive <PERSON> father for leaving the boy alone.\nIf <PERSON> knows that <PERSON> is <PERSON> the chances are.....low very low. First off when <PERSON> brought the baby he thought <PERSON> was dead.", "503" ], [ "Probably later on he learned the truth though BUT admitting it or not he is VERY ashamed of what happeend to his former pupil at that time. One can see it quite clearly in episode 3 that he is hurt and ashamed at the same time. About what happened to his pupil and of his failure to teach him correctly, so that this all could have been avoided. With that in mind it is very unlikely that months or years after he came to <PERSON> and said \"Oh and the gruelsome executor the Emperor has.....is <PERSON> father\". Even taken from the non emotional Jedi perspective it wouldn't have made much sense as in the worst case it would have made <PERSON> unsure if it was wise/save to still keep the baby with them or not. And wouldn't have served any further purpose there aside from that. So very unlikely.", "865" ], [ "Even though the film itself was nice and had quite of a growth for <PERSON> that one duel and also a scene before are very strange. But lets start with the beginning shall we?\nHe is too old you say The too old I always got the feeling that it was just an excuse so that the one who was declined does not feel that bad about it. In addition to that though the older one is the more bonds one has formed already and Jedi shouldn't have bonds as those can be used to make them fall to the dark side.\nThe 1 scene I mentioned\n! The interrogation scene with <PERSON>. <PERSON> was able to get into her mind until he made an error and said something that made her will go strong. At this time she EASILY overpowered someone who has trained such things FOR YEARS. As we know from the prequels raw force potential says nothing (<PERSON> lost to <PERSON> in Episode 2......easily) without any training. So there are 2 options for this part. Either <PERSON> had a training and forgot about it (during her unknown childhood part before <PERSON>) or she has a WAY HIGHER force potential than <PERSON>. High enough that she is even untrained way more powerful than he is.\nThe duel\n! <PERSON> was on the defensive and he clearly toyed with her....only for one reason (and despite his terrible wounds). He wanted to train her in the dark side and make her fall. He had her at his mercy until she closed her eyes and did what <PERSON> did during the battle of <PERSON>. She calmed her mind and let the force flow instead of blocking it out.", "865" ], [ "Then she beat him fully. Here we can only speculate how she could beat someone who has way more training than her with the force and the lightsaber than her. Possible is as stated above that she has training that she doesn't remember OR that she is WAY more powerful than him (would also explain how the Great leader and <PERSON> could feel her awakening). Additionally pointing into the WAY more powerful direction is the fact that <PERSON> tried at the beginning of THEIR duel to telekinetically call the lightsaber........and it flew but not to him but to <PERSON>.\nA bit here additionally (personal points):\n! In addition though is what I personally find confusing about the duel. The stormtrooper who seemingly is NOT force sensitive easily shot <PERSON> first and then attacked him. Even with his wounds <PERSON> should have easily been able to vanquish him without even getting a scratch. Then <PERSON> beats him easily as soon as she does not act like she wants but lets the force flow. So aside from the two possibilities above there could be another one that <PERSON> is just not as powerful as he wants to be. That is coutnered though by his blaster freezing in the beginning of the film. So he IS powerful. And she has to be stronger as it seems. One thing we know for sure though is that <PERSON> is NOT as powerful as <PERSON> was (yet). As it is still his fear that he never becomes THAT powerful.", "865" ], [ "One thing to keep in mind is also the personality of <PERSON>. He is still like <PERSON>. Thus he does not lead from the safe back but instead from the front. And his fall to the dark side also brought out more brutal tendencies than anything else...thus he is even more prone to lead from the front.\nIn rogue one the ship is boarded after getting disabled. <PERSON> naturally was among his men there and boaded the ship. Rushing towards the data as fast as possible when he found out where it was. Then it escaped.\nAs he had to reach the rebel flagship with his troops it can be assumed that they used shuttles to do so.", "865" ], [ "Thus he had enough time to land/board at the same time as his troops.\nThe next time the Tantive IV was seen was over Tatooine. Here though it was different from before. We see the corvette get disabled and docked within mere minutes. During the fight we CAN assume that <PERSON> was on the bridge and when the corvette docked he was on his way to the docking ramp (probalby first waiting to make sure not another surprise happens). As no time was to be wasted though the stormtroopers boarded the corvette as fast as possible.\nSo in essence.....the difference is a matter of time. In rogue one there was more time between disabling and boarding the ship so <PERSON> successfully made his way towards the enemy ship at the same time as his troops. In a new hope there was not enough time for him to get from the bridge onto the enemy ship before his troops already boarded it (and they had to board it immediately.....letting an enemy ship sit within ones hangar even disabled could get the said enemies to get wrong ideas like overloading their reactor to take the star destroyer out with them, ...).\nAt least that is the impression I got from watching both films (never read the novels, so not 100% if the \"time difference\" also comes up in them or not).", "865" ], [ "My answer is more from a personal understanding of <PERSON> than actual canon or facts. But I believe that it was more from a lack of will to live that he became less \"smart\" as the question is asking. <PERSON> had convince <PERSON> that he had indeed killed <PERSON> in an act of aggression. After his mother's death and the betrayals of the council (In his perspective a betrayal) all he had left was padme', and even before that she was his first and top priority, she was what meant most to him in life. Losing that, what point was there to go on?\nHowever, as I have read in the book Star Wars III: Revenge of the Sith, it describes how <PERSON> lungs breathed on their own because of the technology that was permanently attached to him. Therefor he could not stop living even if he wanted to. (I'm not stating that he was or wasn't suicidal.) I know when I thought that I had lost my wife, even standing up felt like I had a giant weight pressed down on me, preventing me from continuing life. He had lost his reason for living, so why try as hard as he did.", "865" ], [ "What was the point?\nHis children were also thought, to him, to have died with <PERSON>'. So <PERSON>'s death, mixed with the fact that he thought he killed her, not to mention his own child (as he didn't know that they were twins until facing <PERSON> at the end of Star Wars VI: Return of the Jedi) and then put on top that his mother was dead, his best friend was evil and manipulated him (In the same book it stated that he realized that he had been deceived by <PERSON> and he tried to kill him with the force, but couldn't.) as well as his father figure, <PERSON>, betrayed him (Again, from his perspective) and the jedi (his last family after the death of his mother) had betrayed him... I'm surprised that his lightsaber didn't end up in his gut....\n(Edited) I also, recently had a conversation with my wife about this. She said that he also grew up. <PERSON> was, for lack of better term, a young buck and was more rash and impulsive than he was as <PERSON>. As we grow up we think about what we do before we do it more and more. Maturity, more or less. If you even read/watch/play, <PERSON>'s decisions weren't always the right one, indicating that he was making a decision more quickly. <PERSON> was in all technicality the more mature and adult <PERSON>.\nI understand that this is a completely different type of answer than you might have been looking for, and of course we cannot ignore the physical agony that he was in constantly, but hopefully it at least helps you.", "865" ], [ "<PERSON> was not cursed to begin with but once he persuaded <PERSON> to ally himself and not kill <PERSON>, he picked up 4 coins and threw back 3 to dramatically say \"every\" (throws down coin) \"last\" (throws down coin) \"One\" (throws down coin). This was a trick to make It seem like he replaced all coin directly back to the chest without really taking any BUT he had a fourth coin and the camera shows him slyly palming It and extending his fingers to indicate an empty hand, classic gamblers trick. He then stepped away from the chest which In turn would curse him. Another factor to this plan working Is that the rest of the pirates loathe the curse having been under It for so long, It probably didn't occur to them that someone would deliberately allow themselves to be cursed just to be temporarily unkillable.\nThe main reason <PERSON> did this Isn't necessarily that he was worried he'd die In general but he knew he'd have to fight <PERSON> who has been suggested to be even better than him at swordplay.\nTo answer some above suggestions that <PERSON> was Immortal since before then, no he wasn't.\nOne of the crew saying \"you're supposed to be dead\" was In reference to him being left on an Island to die but only <PERSON> knew It was a regularly stocked point for merchants.", "516" ], [ "No doubt knowledge from his days working for the East India Trading company and <PERSON> Is known to keep his cards close to his chest.\nThe apple he ate wasn't finished, <PERSON> took It before he had <PERSON> locked up. <PERSON> Inspected the apple and angrily threw It away. This, coupled with the fact <PERSON> rummaged through the apples on the table suggests that <PERSON> Isn't In the habit of poisoning all of the apples, only the top ones and <PERSON> knows his methods having been crew mates and friends.\nAdditional note: <PERSON> and <PERSON> are solid friends but It Is likely the curse made <PERSON> unusually ruthless to get what he wanted. He said he felt nothing, what would this say of his conscience? There probably wouldn't be one, hence why when he was alive again he was far more amicable with <PERSON>, had his honour and \"sense of fair play\".", "417" ], [ "First of all at the beginning of the movie the 'engineer' is wearing a robe rather than the suit as seen in all other engineers. This may lead to the rise that there are 2 beliefs of these engineers. Much like there are multiple religions here on earth. These 2 beliefs (based on the actions of the engineers) are that\n1. The Human-loving engineers believe that human are made for a purpose and a reason which is what the team is hoping to find out. This would explain why the beginning engineer was clearly sacrificing himself using the \"black liquid\" to make human DNA. This would also explain the change in clothing. (robes rather than equipment looking suits).", "900" ], [ "The ship in the background also is different to the on seen in the movie. Possibly a personal carrier used only for transport and as seen in the behind the scenes picture of the elder engineers it is possible that the younger healthier engineers are sacrificed.\n2. On the other side the Human-hating engineers believe that the humans are a failed science experiment and should be destroyed for further experimentation. The change in clothes from robes (usually associated with the church) to the military looking equipment It gives rise to the idea that the engineers on the C-Shaped ship are military personal seeking out the UFO shaped ship to destroy the human life they are creating. It is also most likely the \"black liquid\" seen on this ship is a variation of the one seen at the beginning of the movie. It appears to be a bio-weapon to alter the DNA to create a super-being strengthening the host DNA. The dead (possibly soldier) engineers on this ship were most likely contaminated with the bio-weapon liquid and were self eliminated. However there is a possibility that these suits are merely space suits but is unlikely due to the fact that at the beginning and end that an engineer goes outside without wearing a mask seen by all other suits.\nConcluding i believe because of what i saw represented in the movie that there is a war going on between the engineers. Which isn't hard to believe considering all the war and violence on earth however this seems to be a more technologically advanced war being fought on different planets such as LV-223 (Prometheus) and possibly LV-426 (alien).", "900" ], [ "Regardless of which continuity I have seen so far (aligned and also a few of its predecessors), <PERSON> joined the Decepticons while betraying his old allies.\n<PERSON> himself is not dumb though. He knows 2 things. First that <PERSON> will always stay loyal even if he is not promoted. Second that <PERSON> is power hungry and traitorous AND useful (to some extent). So what position is best than 2nd in command for him?\nIn this position <PERSON> can watch him, while <PERSON> feels important. Additionally <PERSON> can watch <PERSON> without the later trying to assassinate him to obtain the 2nd in command position (which <PERSON> would else do sooner rather than later......he even tried time and again to assassinate <PERSON> himself to gain even more power).", "865" ], [ "And <PERSON> thus is in a position where he can warn <PERSON> or sabotage <PERSON> attempts to undermine/do away with <PERSON>.\nAlso for <PERSON> the feeling important thing is quite important. He has such a strong ego that he needs that, in order to do his duty and ONLY betray his allies when pushed (else he would do so on a whim of a hurt ego even as seen a few times in different continuum episodes).\nSo all in all the 2nd in command is the best solution <PERSON> can come up with. As it brings him a capable warrior, someone he can punch and who comes back to still serve him while minimizing the risk of <PERSON> plans to gain command of the Decepticons. And as soon as <PERSON> is no longer more of an asset than a liability.....he will go the way of all things that displease <PERSON>.\nWhat really is a wonder though is that <PERSON> thinks that Starscreams abilities/plus points outweigh his incompetence/failures. And thus that <PERSON> still lives (despite him always loosing). With Megatrons tendency to even kill loyal failures.....that is something of a mystery there though (and as far as I know not explained in any way in any continuum).\nAdditionally in many of the continuums <PERSON> somehow seems to be amused by <PERSON> AND his attempts to ursurp his position (although this is only an observation and interpretation, thus not part of the answertext above).\nEdit: I found something as to why <PERSON> is not killed by <PERSON> and also what adds to his usefulness (and thus in the end why he ends up in the 2nd in command position). As stated in another question from here: http://scifi.stackexchange.com/questions/49134/why-didnt-megatron-kill-starscream-in-g1?rq=1 According to an answer there by Wikis <PERSON> is not as much a failure as I myself always perceived, but instead very good at his job.", "865" ], [ "No there were 12 like the Enterprise (Constitution class) at the time of the episode \"Tommorrow is Yesterday\" when <PERSON> utters the line: \"There are only twelve like it in the fleet.\"\nThe Star Trek Writer's guide established there were fourteen Constitution Class starships: Constitution, Constellation, Enterprise, Yorktown, Lexington, Farragut, Republic, Intrepid, Exeter, Hood, Excalibur, Valiant, Kongo, Potemkin. The original AMT model decal sheet validates these names.\nThe Constitution Class had been around for at least 13 years and probably longer (The Menagerie) and <PERSON> had served aboard at least two of them before assuming command of the Enterprise. The USS Republic (Court Martial) and the USS Farragut (Obsession.)\nIt is almost certain the Farragut was lost or destroyed when it encountered the Cloud Creature, and that would make <PERSON>'s statement in Tomorrow is Yesterday true when he said it. There were only twelve like it (that were left) in the fleet.\nThe Star Trek Reference manual lists four as destroyed. We saw at least two of them destroyed, Intrepid in Immunity Syndrome and Constellation in Doomsday Machine. These episodes occurred after Tomorrow Is Yesterday. We heard of the destruction of Farragut in Obsession.", "126" ], [ "We also probably saw the destruction of the Excalibur in Ultimate Computer but it was never established that it was destroyed beyond salvage.\nThis leaves the Valiant. This is problematic. It may be bad writing. Other than the ship named 'Valiant' that disappeared two hundred years before the episode 'Where No Man Has Gone Before' we saw no Constitution class USS Valiant. We did however see a USS Defiant (Tholian Web) that wasn't on the writer's guide list. Like the other ship names used from history there was an actual British battleship named Valiant. There was never an actual ship named 'Defiant.' There was a fictional HMS Defiant in the film 'Damn The Defiant' I think somebody messed up, meant to type Valiant but chose to type Defiant instead and it became hard to explain canon.\nEither way there were fourteen original Constitution Class and thirteen left when <PERSON> made his statement in Tomorrow Is Yesterday.\nAnd they were all Constitution class. The model gave you a Constitution class starship and 14 names to choose from.", "126" ] ]

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[ [ "Another Young Environmentalist Is Murdered in Guatemala · Global Voices\nGuatemala's future seems to receive a blow with the death of <PERSON>, a young member of the Center for Social, Legal and Environmental Action (In Spanish, CALAS) Foto taken from Pixabay. From the Public Domain.\nThe murder of 22-year-old <PERSON>, a young environmentalist in Guatemala, has increased concerns over the threats that environmentalist defenders endure and the failure of the state to provide protection to organisations under threat.\n<PERSON> was shot and killed in Guatemala city on November 12. His murder is in many ways a dark symbol for Guatemala, a country in the top ten most vulnerable countries to climate change, where the average age of the population is, precisely, 22 and where at least ten environmental activists – most of them indigenous – were murdered in 2015.\n<PERSON> worked for CALAS, an organization for legal, environmental and social action. He was committed to social justice from a young age. He was the spokesperson of a public high school, where he constantly advocated for better public education.\nThis is not the first time that CALAS has been target of threats. In fact, one of <PERSON>’ seniors and a member of the center, <PERSON>, has been target of numerous death threats through the years, and was once shot in an attempt to silence him. <PERSON> is known inside and outside Guatemala as a human rights and indigenous rights defender. CALAS’ director, <PERSON> has also been also target of death threats through social media.", "202" ], [ "As Front Line Defenders Case Study explained at the time of the threats:\nThe human rights defender was in the offices of CALAS on 29 July 2015 when an unknown gunman riding a motorcycle fired a number of shots outside. He also received a previous death threat in May 2015 when an unknown woman approached him at a bank and said “Soon you are going to pay for the work you are doing. You will see what will happen as a result of the work you are doing against the mining company, you are causing a lot of damage and so they will kill you”…\nIn a recent report, Amnesty International Americas Director <PERSON>, explained how hard is the struggle for the environment in the Central American region:\nDefending human rights is one of the most dangerous professions in Latin America but daring to protect vital natural resources takes these risky jobs to a whole new, potentially lethal level.\nA threat to the youth\nDiverse environmental justice organisations have pointed their fingers at shared partnerships between wealthy countries like Canada, their multinationals, and the silent complicity of governments that host mining operations and fail to protect those who fight for their territories.\nEnvironmental campaigners and advocates are under constant threat all over the continent. Intimidations, violations to the right to protest have become a trend from Canada to the Patagonia. Justice is rarely achieved, and it produces a chilling effect that often leads to further killings. In cases like that of <PERSON> organisation, COPINH, in Honduras, they have managed to kill all the leaders.\nGuatemala is one of the countries championing action against climate change. Guatemala is actively encouraging Canada, and its Prime Minister, to react to the widespread violence against human rights defenders opposing environmental damage by Canadian companies, as explained by the Network of Solidarity with the people in Guatemala (NISGUA):\nThe Justice and Corporate Accountability Project’s report, The ‘Canada Brand’: Violence and Canadian Mining Companies in Latin America, was released on October 24, 2016 and looked at incidents of violence and criminalization in connection with twenty-eight Canadian companies in thirteen countries in Latin America from 2000 to 2015. It found that at least 44 people have been killed during this time, 30 of which were targeted killings, while more than 400 people were injured, not including work-related injuries. They also found that over 700 people were legally persecuted during this period, including arrests and detentions, for their work in defense of their territories, livelihoods, health and environment.\nAs the country struggles for accountability on the crimes of the past and engages in processes against impunity, it is expected that, with the support of the International Community, that Guatemala can also safeguard the leaders and human rights defenders for the sake of its own future.", "202" ], [ "Guatemala: Access to Archives Sheds Light on Case of Forced Disappearance · Global Voices\nBy <PERSON> – Antiguadailyphoto.com under a Creative Commons License BY-NC-SA version 3.0 unported\nAccess to information plays an important role in societies in transition and in the aftermath of a war. In fact, records and official archives are becoming tools to fight impunity, providing the evidence to prosecute perpetrators. Access to archives and databases helped shed light on a landmark case of forced disappearance in Guatemala.\n<PERSON> was 26 years old, an engineering student, labor activist and member of the clandestine Guatemalan Workers’ Party (PGT) when he was seized by police agents off a street in Guatemala City and taken away forever. His disappearance left his young wife, <PERSON>, and an 18-month-old daughter behind. It was February 18, 1984\nThat is how the narrative of the National Security Archive starts when describing the experience by expert <PERSON> on a trial to prosecute those responsible for <PERSON>'s disappearance.\nShe delivered a testimony before Guatemalan Criminal Courts based on U.S. declassified records produced at the time of <PERSON>’s disappearance by the State Department and the U.S. embassy in Guatemala. They describe a planned campaign on the part of the Guatemalan government to kidnap and kill trade union activists and student leaders linked to the opposition.\nThis discovery was possible because of the Freedom of Information Act that permitted the release of classified notes by the government, but it also required extensive work by document analysts connecting the puzzle pieces to reconstruct all the government's strategy. Certainly, as the title of a post on the The Witness Blog about the case indicates, “Archivist can be at the heart of accountability and justice.” Police archives actually led to the arrest of the perpetrators, who were found guilty and sentenced to 40 years in prison.\nThe Witness Blog highlights the increasing use of archival records as criminal human rights evidence; there is a dawning realization of the absolute obligation of state governments to be open and transparent:\n<PERSON>’s work with the <PERSON> case clearly illustrates her point that archivists can play an active role in creating change. Not only was a serious human rights violation committed when policemen forcibly abducted <PERSON>, but there was the grave violation to his wife’s right to information. For years, she begged for information, going to the morgues, the cemeteries, the head of state.", "600" ], [ "<PERSON> stated, “that silence of the state is one of the great crimes.”\nDatabases played an important role too, thanks to the support from Benetech, as they describe in their blog:\nThe Benetech Human Rights Program uses cutting edge computing methods and statistical analysis to provide objective evidence of human rights violations. The scientifically defensible data in our findings serve as a powerful tool to combat impunity and hold perpetrators accountable for their crimes. <PERSON> presented expert legal testimony. <PERSON>’s expert testimony helped the judges in the case remove doubt about the authenticity and reliability of the documents. He showed that the records are consistent in structure and overall content with many other documents in the archive and were not chosen deliberately or selectively. He described the patterns of data found in the documents and the probability that police officials knew about the 667 documents related to <PERSON>. <PERSON>’s statistical estimates about which police units had access to which documents showed evidence of communications between the army and police.\nRelatives of <PERSON>, who have been fighting got justice for 26 years, opened http://casofernandogarcia.org/ to share with the world, in English and Spanish, all the developments of the trial. There you can read the Statement from <PERSON> at the close of her father's trial. This is an abstract:\nI do not seek revenge, neither would my dad have, but I do seek the truth, I want to know where he was taken, I want to know why he wasn’t formally charged, I want to know who gave the order, I want to know where he was taken and who he was handed over to, I want to know what happened to him. My heart cannot rest and be at peace without the truth, as harsh as it may be, the truth always heals the soul.\nUnder international humanitarian law, families have the right to be informed on the fate of missing relatives, and parties in a conflict have a responsibility to search for the missing and facilitate inquiries made by families of the missing. Now new technologies and new tools, such as access to information laws, can help fulfill these obligations and help families remind other generations about the lessons learned from a violent past, by keeping the story alive and open to anyone.", "600" ], [ "Guatemala: Costa Rican <PERSON> to Direct CICIG · Global Voices\n<PERSON>, Attorney General of Costa Rica, has been appointed to direct the International Commission against Impunity in Guatemala (CICIG) and the United Nations is still waiting for his official response. The commission was “established as an independent investigative body by a treaty-level agreement between the United Nations and Guatemala […] with the objective of assisting the Guatemalan State in investigating and dismantling violent criminal organizations believed to be responsible for widespread crime and the paralysis in the country's justice system,” as its website explains. To understand the impact if this new appointment for Guatemala and for future efforts against impunity around the world, Guatemala Solidarity Network explains the importance and the relevance of the CICIG-:\nCICIG is unique in the sense that it is not entirely an international effort, nor is it wholly domestic, it has a bit of both but ultimately has to fit into the Guatemalan judicial system. It is also unique in being able to suggest reform, and includes training local personnel, all taken together ought to create a lasting legacy. In contrast to many other UN tribunals, such as those in the former Yugoslavia or Rwanda, CICIG is not trying to deal with the aftermath of mass human rights abuse. The Historical Clarification Commission tried to get to the truth, and as we know there are some cases proceeding to try to find justice in those cases which the Peace Accords did not make non-prosecutable. In contrast, CICIG is trying to deal with a different legacy of the civil war: the infiltration of the organs of the state by parallel powers, which subvert them to their own ends. It also uses the domestic law and courts of Guatemala rather than international law, which has several benefits: it shows that the legal system can indeed be made to work, it can prosecute powerful individuals, and by working from the inside it can see the weaknesses of that domestic law and suggest improvements.\nDuring a visit to Guatemala a few months ago, <PERSON>: “Although corruption exists, grand corruption comes from people with real political power that influence institutions in order to steal or divert money for their own benefit or that of third parties, and that additionally are untouchable. There is a fear to confront these people who wield enormous power in our society and those fears have to be put to rest. If we do not stop this, the country is seized.” <PERSON>, from the blog Central American Politics, shares his views:\nThe people I have spoken with this week have praised CICIG's work and admitted while imperfect, Guatemala would have been much worse without it.", "271" ], [ "We also weren't convinced that CICIG had successfully dismantled any of the organized crime rings in the country. Individual successes have occurred, really important ones like the arrest of <PERSON> and <PERSON>, his security chief who was taken into custody today, but I don't know how far CICIG's work has dismantled the hidden powers.\nThe blog International Law Girls provides the context for this new appointment, which will replace <PERSON> from Spain:\nLess than 2% of the cases ever make it to trial. It got so bad that after much pressure from civil society, a U.N-sponsored initiative called the Commission Against Impunity in Guatemala (known by its Spanish initials as CICIG) was created in 2008 to help the national prosecutors’ office improve its ability to investigate and try cases. CICIG’s mandate is to investigate the existence of illicit security forces and clandestine security organizations that commit crimes, and to identify their illegal group structures (including links between State officials and organized crime), activities, modes of operation, and sources of financing. CICIG is to support the national Prosecutors’ office, act as a third-party prosecutor, and recommend policies to the government to strengthen the justice system. It does not, however, have the power to initiate its own prosecutions, a power the courts have held is exclusive to the Prosecutors’ Office. Thus, if the prosecutor is corrupt or ineffective, CICIG’s only recourse is through public pressure. Nonetheless, the mechanism constitutes an interesting and innovative half-way house between technical assistance and a full-fledged hybrid tribunal.\n<PERSON>, UK Ambassador in Guatemala, wrote on her blog:\nFor now, CICIG remains an important tool for Guatemala, helping to develop transparent, effective security and justice sectors, which in turn will help to promote economic growth and international investment. Passing into law the various legal reforms that CICIG has suggested will be an important next step. But of course, CICIG is only a temporary body – an opportunity of which we all need to make the most.\nPeace and justice in Guatemala is a neverending process, which will need complete support from citizens.", "271" ], [ "Amid setbacks by the <PERSON> administration, thousands of indigenous peoples march into Brazil’s capital · Global Voices\nFrom April 23 to 27, more than three thousand indigenous leaders from all regions of Brazil gathered in the country's capital. Photo: 350.org, CC BY-NC-SA 2.0\nThis story was reported by <PERSON> of 350.org, an organization building a global grassroot climate movement, and it is published here as part of a partnership with Global Voices. 350.org participated in the National Indigenous Mobilization in Brazil as a supporter.\nThe camp smelled like smoke and urucum, a plant used for body painting. A defiant energy pulsed through the crowd. We could hear chants, ritual mantras, and ceremonial crying.\nThe place resounded with the voices of the more than 3,000 indigenous people from more than 100 different groups from all over Brazil, who gathered for the five-day 2018 National Indigenous Mobilization, held from April 23 to 27 in Brasilia, the Brazilian capital city.\nAlso known as the ‘Free Land Camp’ (‘Acampamento Terra Livre’, in Portuguese), the sit-in is a yearly event organized by the Articulation of the Indigenous Peoples of Brazil (APIB, in the Portuguese acronym). This year's was its 15th edition.\nAccording to the last Brazilian demographic census, there are 305 indigenous populations in Brazil, speaking 274 different languages.", "202" ], [ "Together, they number almost 897,000 — approximately 0.47% of the country's 200-million-strong population.\nMost of them are scattered over thousands of villages, from north to south of the national territory, located in the 715 Indigenous Lands already regularized and formally recognized by the federal government. There are more than 800 cases of indigenous lands awaiting regularization.\nThe ‘Genocide Opinion’ and other blows\nThe movement has been facing a series of political setbacks, which gave renewed thrust to this year's mobilization.\nThe Brazilian National Congress, whose majority is currently dominated by supporters of the agribusiness sector, are trying to approve a bill package that would undermine the rights of indigenous peoples guaranteed by Brazil's 1988 Constitution and other international laws, such as Convention 169 of the International Labor Organization.\nIn the current complex political situation in Brazil, under the controversial administration of president <PERSON>, representatives of the agribusiness sector have gained even greater foothold and managed to also occupy other levels of government.\nOnly days before the Free Land Camp took place, President <PERSON> yielded to pressure from a ruralist caucus and fired the president of the National Indigenous Foundation (FUNAI), replacing him with someone more agro-friendly.\nThe government’s reluctance to grant formal recognition of indigenous lands’ boundaries and the criminalization of the movement’s leaders were major points of concern and grievance for those who gathered in Brasilia.\n<PERSON>, an indigenous leader from the state of Paraná and coordinator of the indigenous program of 350.org in Brazil, recalled the kind of threats he has faced. “I was imprisoned for a time, accused of crimes that were not proven and I have been prevented by a judge from approaching the land where I was born. For four years I couldn’t step on the place where my umbilical cord is buried,” he said.\nIn September 2017, Brazil's attorney general issued a legal opinion asserting that only indigenous peoples who were occupying their territory on the day the 1988 Constitution was promulgated should benefit from the recognition of their right to land.\nKnown as the “time limit” thesis, and sometimes called the “genocide opinion“, it has been endorsed by President <PERSON>. Should it ever become law, it would severely cripple the recognition of new indigenous lands.\n‘We have only one objective here: to resume the process of demarcation of our lands’\nThe night fell as the indigenous leaders stood in vigil in front of the federal government building. At one point, the crowd raised candles and stopped their activities to listen to a lament sung by one of the indigenous women. It was a mourning ceremony.\nOn the following day, the Esplanade of Ministries, the main route where all federal government buildings are located, was occupied again by protesters, who marched towards the seat of the National Congress.", "779" ], [ "Meet the People Blocking a New Gas Mega-pipeline in Southern Italy · Global Voices\nA screenshot of a video of protest against the Trans Adriatic Pipeline. Photo: <PERSON> 350.org, used with permission.\nThis article is based on content originally published on 350.org part of a partnership with Global Voices.\nIn southern Italy, local mothers, teachers, health workers, grandparents and olive farmers are leading a peaceful resistance to protect their land and their community from a planned gas mega-pipeline.\nSince 13 November, hundreds of police imposed a ‘red zone’ around the Trans Adriatic Pipeline (TAP) construction site, prohibiting journalists, citizens and local government officials from accessing the area.\nNevertheless and despite facing a violent response by the police and individual fines of up to €10,000 the local communities of Melendugno are determined to continue their resistance to stop the construction of the TAP.\nThese are some of the people blocking the project:\n<PERSON> is a local artisan who is no longer willing to stand aside as public money is spent for the private gain of multinational companies. She criticises the corruption and criminal interests surrounding the projects.\n<PERSON> calls herself a NoTAP grandma, fighting for the good of the land. She is motivated to protect the environment since her nephew suffers from health problems that have been caused by environmental issues.\n<PERSON> is the vice mayor of Melendugno. He sees TAP as an unnecessary project that destroys the climate and the local economy, which is based on tourism and agriculture.\n<PERSON> opposes TAP because he wants the land protected.", "91" ], [ "The pipeline and gas receiving terminal is due to be built through a protected area with ancient olive groves, aquifers, pristine forest and a stunning coastline.\n<PERSON> is a young woman who takes action to resist an imposed and unwanted project that the state helps a multinational consortium to build without letting the people have their say and despite local opposition for the past six years, straight from the start of the project.\n<PERSON> resists TAP, which she sees as a useless and dangerous project that threatens her livelihood in tourism in San Foca. She stresses that TAP is not just a local but a European problem that should not go ahead in Salento or anywhere else.\nThe locals receive increasing support as banks come under international pressure to reject the loans on which the project relies to go ahead. For example, more and more people are calling on the European Investment Bank to pledge against financing TAP to the tune of €1.5 billion.\nTAP is part of the European Commission’s energy flagship project Southern Gas Corridor. The EU pushes to massively develop new gas infrastructure even though existing infrastructure is already operating below capacity and despite the fact that an expansion of the gas market is incompatible with the Paris Climate Agreement .\nFilms by <PERSON> and <PERSON> for 350.org. Music: Am-Trans by <PERSON> (Attribution-NonCommercial 3.0 International License – www.soundofpicture.com)", "91" ], [ "A Win for Citizen Activism After UNESCO Asks Macedonia to Stop All Construction Projects on Lake Ohrid · Global Voices\nOhrid Lake swans. Photo by <PERSON>, CC-BY.\nThe latest UNESCO mission to the Ohrid region in Macedonia discovered a Natural and Cultural Heritage site threatened by increased traffic and tourism pressure, inappropriate infrastructure projects and uncoordinated urban developments. It immediately released a report requesting the Macedonian government to halt construction projects in the area.\nExisting for over 3 million years, Lake Ohrid in Macedonia is the oldest lake in the European continent holding valuable information on evolution aside from being the home of unique and rare species. In 2016, this lake was put in danger when the Macedonian government started plans to urbanize the lake shore and Galichica mountain and turn both biodiversity hotspots into mega resorts.\nCitizen activists, civil society organizations, and scientists warned about the possible catastrophic impact of these projects on Lake Ohrid and demanded a moratorium on all construction activities in the Ohrid region.\nIn March this year, the UNESCO mission to the Ohrid region validated the concerns of citizens and experts about the projects around the lake. It asked the government to halt the projects to protect Lake Ohrid and instead develop alternative ecotourism programs in the area:\nThe mission strongly recommended to completely abandon the Galičica ski centre project, keep the internal national park zoning as is, and consider developing ecotourism options that would not negatively impact the property. Therefore, it is recommended that the Committee request the State Party to halt the construction projects of the Galičica ski resort, as well as the sub-sections (a) and (e) of the A3 road. – says latest decision by UNESCO World Heritage Committee\nThe Ohrid SOS group has been on the frontlines fighting to save Lake Ohrid from the very beginning. It published the UNESCO decision urging the Macedonian government and European Bank for Reconstruction and Development (EBRD) to stop the further destruction of Lake Ohrid.\n.@UNESCO #recommends “to completely abandon the #Galičica ski centre project, keep the internal national park zoning as it is”. #UNESCOSays pic.twitter.com/YmrehT5SQJ\n— OhridSOS (@OhridSOS) June 9, 2017\nMeanwhile, the Center for Environmental Research and Information Eko-svest from Skopje worked on alternatives to the planned infrastructure project that will not destroy precious nature.", "739" ], [ "A feasibility study for a sustainable transport solution is scheduled to be presented in the Ohrid municipality this year.\nНие сакаме да го одбележиме #ДенотНаЕзерото со нашата визија за велосипедска патека која ќе кружи околу Охридското Езеро. Преубаво! pic.twitter.com/0eY7hvkCKO\n— Eko-svest (@Eko_svest) June 21, 2017\nWe want to mark #TheDayOfTheLake by sharing our vision for a bike trail that would encircle the Ohrid Lake. Beautiful!\nInstead of a new highway that would cut through the national park forests and block access to the water, the group is proposing a combination of transport alternatives that would not interfere with the ecosystem.\nPhoto shows Smart Ohrid transport solution with routes for cycling, solar boats and solar buses arround the lake. Photo by <PERSON>, used with permission.\nTo commemorate 21 June, Lake Ohrid day, the newly elected Macedonian government opened its doors to civil society and held an event in parliament where the president of the Assembly addressed the guests.\nI am especially glad that today in the Assembly of the Republic of Macedonia there is an event related to the initiative of the civil sector for the protection of the Ohrid region as the only region in the Republic of Macedonia protected by UNESCO. – said The President of the Assembly, Mr. <PERSON>\nThe parliament speaker stressed the readiness of the government to discuss and support citizen initiatives for the protection of the environment. An informal group of Members of Parliament from different parties was also formed named “Friends of UNESCO.”\n#Macedonia CSOs present parliament speaker, minister with citizen request to preserve #Ohrid lake and region. Parliament opens to citizens. pic.twitter.", "363" ], [ "Cuba: The State of Human Rights · Global Voices\nThe recent request for information by the United Nations‘ Committee Against Torture with regard to alleged human rights abuses in Cuba has got bloggers talking.\nDiaspora blogger <PERSON> said that despite the fact that “the United Nations has far from a pristine history when it comes to holding the <PERSON> dictatorship accountable for its 50-plus years of repression…the UN's Committee Against Torture deserves applause…” Why, exactly? For causing the Cuban government to deny that anyone “has been persecuted or sanctioned for exercising their rights, including those of free expression and association” – to which the blogger responded:\nNo one, except the thousands of political prisoners, past and present, who have languished in the <PERSON> gulag because they exercised the rights given to them by God.\nNo one, except the activists who every day risk what little liberty they enjoy to ensure that one day they and their successors enjoy those rights freely.\nNo one, except those Cubans, like <PERSON> and <PERSON>, who were permanently silenced, who were murdered by the <PERSON> regime because of the threat that they, and their commitment to those rights, posed to the dictatorship's survival.\nThat one of the dictatorship's flunkies would stand before the world and deny the undeniable, is evidence enough that whatever action the UN takes against Cuba as result of the latest inquiry, the <PERSON> live in fear that their time is up.\nThe Cuban government's position is at loggerheads with two different reports, one by the U.S. State Department and the other by Amnesty International, about the human rights situation on the island. Havana Times blogged about Amnesty's findings, reporting that:\nAccording to Amnesty, the Cuban government continued its ‘repression’ on freedom of expression, association and assembly with hundreds of arrests and brief detentions, although it freed the last 11 prisoners of conscience who had been held since 2003, as well as another 62 ‘political prisoners,’ some of whom had been in jail since the 1990s.\nThe NGO human rights defender, which hasn’t been allowed to enter the country since 1990, also expressed its opposition to the US embargo and highlighted the negative impact the measure has on the health of the Cuban population, especially marginalized groups.\nNotes from the Cuban Exile Quarter, meanwhile, addressed “two (of the many) misstatements by the <PERSON> regime at the Committee Against Torture”:\nFirst false statement, the claim that “the persons mentioned in these questions and the rest of the list of questions are supposed ‘human rights defenders’, do not qualify as established in the The Declaration on Human Rights Defenders adopted by the General Assembly of the United Nations” on December 9, 1998 citing article 3.\nThe Cuban Black Spring of 2003 in which the majority of the organizers of the Varela Project, an initiative that sought to reform the current Cuban constitution to bring it into line with international human rights obligations, were imprisoned and sentenced in summary trials to up to 28 years in prison for engaging in a legal right recognized by the Constitution. The claims made by <PERSON> are demonstrated as patently false by the above mentioned crackdown and the numerous cases of dissidents being imprisoned with the sole purpose of the dictatorship enforcing political conformity.\nSecond false statement, the regime's representative claims that the facts have been misrepresented in order to serve a shadowy conspiracy.", "289" ], [ "At the same time the United Nations Special Rapporteur on Torture was formally invited by the regime on January 28, 2009 and to the present day the dictatorship has not agreed on a date for the visit. International human rights organizations have requested permission to visit the island and be able to study the situation on the ground to be able to arrive at their own conclusions on the human rights situation, but the Cuban regime has denied them all permission to visit the island. Human rights organizations are relying on reports from human rights groups operating inside and outside of Cuba that are slandered and libeled by the dictatorship.\nThe United Nations and human rights watchdog organisations may be waiting for answers, but diaspora bloggers continue to highlight instances of persecution and repression.\nThe thumbnail image used in this post, “United Nations”, is by <PERSON>, used under an Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) Creative Commons license. Visit <PERSON> flickr photostream.", "271" ], [ "RightsCon: Future of Digital Rights in Latin America and Beyond · Global Voices\nActivists, business representatives, thinkers and policy makers are meeting in Rio de Janeiro, Brazil for the Human Rights and Technology Conference, hosted by Access in partnership with the Center for Technology and Society from Getulio Vargas Foundation in Brazil.\nSpeakers and participants discussed everything from social movements and digital natives, to Net Neutrality and the digital divide.\n<PERSON> from Tumblr described the most relevant threats to a free Internet:\nHere are the key battles: Censorship and political control, which is the erection of a technical architecture of control that can be used for ill. Surveillance and piracy is battleground number two, where we see within the rule of law, outside the rule of law, and by companies themselves. And finally, the structure of the internet is under attack, the battles around network neutrality, wireless network neutrality, competition or the lack thereof, and the legislation that would control it, like SOPA/PIPA, ACTA and CISPA.\n<PERSON> from Access at Rightscon Picture by <PERSON> under a Creative Commons License\n<PERSON>, director of Access, highlighted the importance of Latin America in shaping the future:\nWe acknowledge the leadership in Latin America on the many things that are taking place. The marco civil in Brazil, the Costa Rican recognition of access to the internet as a fundamental human right.\nVia video conference, <PERSON>, MEP for the Netherlands, told attendees we are entering a new era of diplomacy:\nA new era of global Internet politics kicked off with the introduction of the idea of the ITU managing the Internet. I don’t believe that a UN body could regulate this effectively, and I don’t believe that government alone, without a multi-stakeholder approach, could govern the Internet. And we must be careful that emerging economies don’t push human rights off the agenda, when economic growth is on the table.", "803" ], [ "Western companies must stop providing technology for censorship and surveillance. IT is a fundamental misunderstanding of the rule of law.\nA roundtable also discussed how digital natives are changing the World, using the #yosoy132 movement in Mexico as an example.\nWhile discussing privacy and security, computer expert and activist <PERSON> advocated for strong protection of privacy and cautious use of social networks. He said:\nFacebook in some ways is Stasibook–you report on your friends all the time.\nHe later explained the importance of security technologies being available for all, even for the “bad guys”:\nAs a planet, I think we need to make a decision to all be secure, even some bad guys, rather than to all be insecure, and policed by governments which are not good at self-regulating, and are not transparent or accountable about what they do with this information.\nA small delegation of Global Voices authors is attending the conference, including <PERSON> and <PERSON> from the U.S.A., <PERSON> from Chile, <PERSON> from Brazil, and <PERSON> from Cuba.\nDuring the conference The Guardian Project, an initiative which aims to create technologies and hardware to protect communications and personal data from intrusion and monitoring, organized the Free Bird Event, a one-day workshop that aims to empower mobile technology users with greater knowledge about security and privacy.\nAt the conference, the Access Innovation Prize was announced, which will distribute USD100,000.00 around the World. The deadline to apply for the prize is August 15, 2012 and anyone in the World can apply for any of its five categories. The award's website explains:\nThe Access Innovation Prize is designed to discover and reward ideas that demonstrate unique promise, opportunity and possibility. You can submit a near to complete project, improve an existing tool or create something totally new.\nThe conference ends today, June 1, with a discussion on the future of digital rights in Latin America and beyond, but the conversation around theses issues is just starting.\nLiveblogging has been facilitated by @krmaher; Live-streaming has also also available, and the Twitter account @rightscon –tweeting in three different languages– is more active than ever. Anyone around the World can send a question to specific panels, so start the conversation and share your comments on how businesses can improve and side with citizens while defending digital freedom.", "696" ] ]

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[ [ "Horseshoe orbit cycle times\nI asked on Worldbuilding originally, but was directed here instead\nI've been working on a habitable moon system for a story, and I'm now trying to populate the other moons around the parent planet. I'm considering placing one (Moon B) in a co-orbit, horseshoe configuration, with my habitable moon (Moon A).\nWhile I understand the general concept of horseshoe orbits, the actual calculations of the orbital times is beyond my mathematical capabilities.\nI understand that on a horseshoe orbit there is an inside section and outside section where Moon B is catching up to, or falling behind, Moon A, respectively.\nI understand that if the 'inside ring' is nearer the parent body (the 'planet' in the case of co-orbital moons) than the L1 Lagrange point of Moon A, then Moon B will escape the horseshoe orbit and just start orbiting the planet directly. And, similarly, if the 'outside' ring is outside of L2 Lagrange point of Moon A, Moon B will escape and orbit the planet directly. And if either ring is too near the actual orbit of Moon A, it will be a tadpole orbit(never passing the L3 Lagrange point of Moon A before returning to Moon A from the same direction it left it), instead of a full horseshoe.\nWhat I can't figure out (again, math skills limitation) is How long it would take (longest and shortest possible times) for Moon B to make one complete cycle of the horseshoe? And so I can't decide if I should use this type of orbit or not. For example, 3753 Cruithne takes about 770 years to complete it's horseshoe cycle relative to Earth, far too long to be useful for my story. But I don't know how to calculate ho long my co-orbit scenario would take.", "710" ], [ "I'm confident it could be made significantly shorter than 770 years, but exactly how short it would be is still a key factor in the decision.\nI would like to know how often the two bodies would approach each other at the two extremes of possibilities, the longest possible time between complete cycles, and the shortest possible time between cycles.\nFor this question: Planet mass is 477 Earth masses, Moon A's mass is 0.11 Earth masses, Moon B's mass is 0.01 Earth masses. Moon A's semi major axis is 4 million kilometers. (please let me know if any other variables or details are needed)\nTo re-word the original question: By adjusting the semi major axes of the inner and outer rings of Moon B's horseshoe orbit, either closer to or farther from the semi major axis of Moon A, what are the longest cycle time, and shortest cycle time possible for a horseshoe orbit in this system?\nHere is a visual representation of the types of orbit changes I'm referring to. The contour lines inside the highlighted one (nearer L3 L4 and L5) are what I'm referring to when I mentioned adjusting the horseshoe orbit Axes nearer to the semi major axis of Moon A. And the contour lines outside of the highlighted one are what I'm referring to when I mention moving those axes farther from the semi major axis of Moon A. When I refer to a complete 'cycle', I mean the time it takes for Moon B to go from Point A on that image, through Points B, C, D, and E and back to A.", "710" ], [ "Please help me calculate acceptable planet sizes & eclipse shadows cast by my binary planet system\nI've been reading here for a little while, but this is my first question. I am trying to come up with either a concrete set of numbers for a single answer for a binary planet system, or a simple formula that allows me to play within a range of acceptable numbers that answer my question. Math and I don't really get along anymore, so the less complex your solution, the better. Even a solution via simple 3D modeling / illustration on spheres or geometric drawings is welcome if it also provides numbers that fulfill the solution.\nALSO I'd like to keep this within the realm of plausibility, so sources for creating my system are listed after the question. I don't mind if the science pushes the boundaries of what we know. Unusual, rare, unlikely, and unique solutions are welcome; impossible ones are not.\nHere are the shadows I'm trying to achieve:\nFigure 1: The two possible shadows cast by each planet when all three bodies are in alignment\nI'm going to leave my inaccurate drawings above for now because they better illustrate the landmasses and ocean areas on both planets. I'll replace them when I'm able. More accurate yet simpler sketches below along with (hopefully) improved wording.\nRequirements:\n1. Binary planets (tidally locked to each other) orbit an M0 parent star at the outermost edge of its habitable zone. (See note1) Neither planet, nor the binary system as a whole, supports a moon.\n2. Both of these planets must be theoretically capable (liquid surface water / atmosphere / pressure / mass / density-wise) of supporting a range of humanoid and other life forms (akin to <PERSON>'s world, minus mankind as an example), and share biomes.\nThey must not be closer to each other than 3 times the radius of Planet B. (See note2)\n1. Planet B must be larger than Planet C and not be wider than 12000 km in diameter (slightly smaller than Earth size); however, I strongly prefer Planet B to be as small as possible within the given constraints.\n2.", "710" ], [ "Planet C must not be smaller than 6000 km in diameter. (See note3)\n3. During A-B-C alignment (Fig 1)\n- A being floating in the center of the night side (it's in the middle of the ocean) of Planet B (point b) will see only a circle of darkness blocking the stars (behind Planet C) when looking toward Planet C. (Fig 1a) Planet C should fall well within the umbra cast by Planet B.\n- A being standing at point c will see a total eclipse of Star A by Planet B when looking starward. Only the corona should be visible (Fig 1b)\n1. During A-C-B alignment, (Fig2)\n- A being standing in the center of the night side of Planet C (point c) will see Planet B as a thin blue ring – with an apparent width not wider than 1/6 the radius of Planet B – with northern polar ice visible. More temperate landmass may be visible closer to the northern side of the equator.(Fig 2a)\n- A being standing at point b will see an annular eclipse of Star A by Planet C because Planet C is not large enough to eclipse it totally (Fig 2b)\n2. Rotation period for the two planet system should not be less than 16 hours nor more than 64.\nIs this plausibly realistic?\nI simultaneously hope this question is not too long and that I've provided enough info. If not, please me know what I can to do improve.\n(note1) ~0.5 solar masses. See Habitable Planets for Man by <PERSON> (second edition) American Elsevier Pub. Co. - 1970 pg. 81. “For a special rare class of planets with extremely large or close satellites, there is an extension of the lower permissible primary mass [of the parent star] down to 0.35 solar masses.” My star falls well with this range, and the binary planet system fulfills the large/close satellite requirement.\n(note2) Can binary terrestrial planets exist? at Phys.org\n(note3) Jim2B’s wonderfully detailed answer to Worldbuilding question Smallest possible habitable planet? (also taking density into account)", "371" ], [ "Questions about the potential characteristics of a hypothetical Planet 9\nSo, I'm writing a story. Most of the main story is set near Planet 9, which has finally been found somewhere far out in the outer solar system.\nSo first, I’ve been working on determining the probable characteristics of Planet 9.\nIn line with predictions, it’s an ice giant (a gas-rich sub-Neptune composed of an icy-rocky core with a H-He rich envelope) which is approx 7 earth masses.\nThe most recent article I can find on the topic from <PERSON> and <PERSON> seems to predict that Planet 9’s perihelion is likely 340(+80/−70) AU, that its aphelion is likely 560(+260/-140) AU, and that the semi-major axis is 460(+160/-100) AU. Unless I am sorely misunderstanding this paper (and I could be), the numbers provided seem to be a range of numbers which they think Planet 9 could fall into.\nhttps://iopscience.iop.org/article/10.3847/1538-3881/ac32dd/pdf\nI’ll assume that the perihelion is 340 AU and that the aphelion is a bit further out - 750 AU.\nThe semi-major axis is half of the major axis, which is the sum of the perihelion and aphelion.\nSo semi-major axis = (perihelion+aphelion)/2.\nThe orbital eccentricity is the ratio between the difference and the sum of the perihelion and the aphelion.\nSo eccentricity = (aphelion - perihelion)/(aphelion + perihelion).\nSo, after crunching the numbers based on these initial assumptions: Its perihelion is 340 AU, its aphelion is 750 AU, its semi-major axis is 545 AU, and its orbital eccentricity is 0.38.\nNow, in order to estimate the orbital period, I’ve applied <PERSON>’s third law of planetary motion for a quick back-of-the-box calculation. If we measure the period (T) in years and the semi-major axis (a) in AU we can use a^3 = T^2.\n545 cubed is 161,878,625.", "710" ], [ "The square root of that gives us an orbital period of approximately 12,723 years.\nI have a few concerns. I'd like to know if my numbers are solid here, and if they are consistent with Planet 9's hypothesised characteristics given what we know.\nFurthermore, I'm planning for it to have two main moons. One is approximately the size and mass of Ganymede, with similar gravity, whereas the other is the size and mass of Charon.\nI have no clue if I can give it moons that large and still have it remain consistent with their models for Planet 9, but I’m unfortunately not well-versed enough in this to tell. If someone could help with this, that would be fantastic.\nFinally, I have a question regarding how to calculate its diameter. I'm not yet sure how I would yet go about doing that.", "710" ], [ "How close would Earth and Mars have to be at conjunction to significantly affect each other's orbits?\nI have returned to this forum from Astronomy with this question because it immediately got down-voted. Maybe these hypothetical questions are more appropriate here? I am happy to take advice from Worldbuilding forum veterans.\nI am in the process of building a hypothetical solar system very similar to ours with only a few changes. I would like to test the viability of my modifications mathematically. Procedural answers are most welcome.", "710" ], [ "As I have been advised in the comments by <PERSON> and <PERSON>, I am adding additional information for clarity below:\nMy objective for moving planets is two-fold: (1) that I can create calendars and astrology specific to my \"Earth,\" and (2) that Venus and Mars will orbit on the furthest edges of the habitable zone and therefore be able to have liquid water in some quantity somewhere on their surfaces.\nMy concern is that by moving my hypothetical Venus, Earth, and Mars so close together they will affect each other so significantly during conjunctions that my solar system build is no longer viable, i.e., the hypothetical planetary orbits will not be stable over billions of years as ours have been.\nAs advised by <PERSON>, I have edited the title question to specify the hypothetical semi-major axes.\nAs advised by planetmaker from Astronomy, I am adding this additional information: planetmaker asked \"How big a disturbance (in planetary orbit) is too big?\" and \"What time scales are we talking about?\" An orbital disturbance is too big if the hypothetical Venus, Earth, and Mars cannot plausibly have retained their proposed semi-major axes long enough for habitable worlds to evolve. \"Habitable\" should be taken to mean a world with a liquid water ocean, temperate climate, and breathable air in at least some regions, which indicates the evolution of complex, oxygen-producing lifeforms. (I am aware that Mars' size is considered responsible in part for the loss of its oceans. I may increase the size of my Martian planet if necessary, but right now it is not relevant.) This leads me to suggest that a timescale of 4.5 billion years should be considered as baseline.\nThank you for your help!", "710" ], [ "A pair of similar celestial bodies coming near each other\nIn my conworld I have two moons (they could be planets if desired as long as they can stay 'close' to a larger nearby body) of habitable size. I want to reality-check and provide an explanation for why they would have certain properties.\nFor my purposes I would like these two bodies to have a couple interesting properties:\n1. Large Equatorial Ridge or Oblong shape.\nWhile I want the body to be large enough to be habitable, I would like it to have, in essence, two sides - like a coin.\nObviously a coin-shaped planetary body would be far too extreme, but something like Iapetus with a moderately more pronounced equatorial ridge would effectively divide the body into two regions.\nBonus if there is some reason why it is extremely difficult for an intelligent to cross to the other side, even with approximately contemporary technology or if there is some reason why they would not do so.\n2. Rare 'approach event' making inter-body transit significantly cheaper\nThe way I picture this, at some point the bodies get much closer to each other than usual. This should be visible to the naked eye and a major event, but should be somewhat uncommon (period of at least a 'year').", "302" ], [ "During this event travel between the two bodies should be much easier than outside of the event (e.g. no need to maintain orbital velocity, just get close enough for the other body's gravity to capture you).\nI want to know how long this 'approach event' could last, and what the distance and relative speed could be. Obviously if they get too close then their gravities will rip them apart and they will cease to be habitable. Obviously if their relative speed is too slow then they will get too close and either collide or have gravity rip them apart - again ruining habitability.\nJust how close, how slow, and for how long can such an approach be made. How cheap can inter-body travel be during this period? Could there be time and proximity enough for a space-elevator-like situation?\nI'd like to know how such a celestial configuration could be possible and what unforseen consequences it could have.", "302" ], [ "No More Looking from the Same Side of a Mostly Liquid Surface Terrestrial-based Moon\nSection 1: Non-Duplicate Proofs.\nSection 2: Background, THE QUESTION, and Useful Info.\nSection 3: Other cited ways of preventing.\nSection 4: Sources and Additional Resources.\nSection 5: TL;DR\nNon-Duplicate Proofs This is not a duplicate of https://worldbuilding.stackexchange.com/questions/27751/tidal-lock-on-a-water-moon. The answer provided there does not answer this question (or that one fully either). I am providing these specific proofs because of the last comment made by <PERSON> another post of mine (https://worldbuilding.stackexchange.com/questions/95094/can-you-have-an-eccentric-horseshoe-orbit-for-long?noredirect=1#comment282046_95094) insisting that the resources in an answer to a question determines its duplication, and not the question itself. If these are not satisfactory, I am also providing question based proofs of non-duplication.\nAnswer based proofs\nThe answer provided by <PERSON> makes many generalizations, which don't always stand true.\n1. <PERSON> insists that those worlds that are close enough to the sun to have liquid water would constantly be losing it, which in and of itself may be true, but given a high enough escape velocity as well as a thick enough atmosphere and magnetosphere, the loss would prove negligible on time scales of millions to billions of years, not to mention possible reintroduction of water from other sources. He does not mention escape velocity, and also provides an answer based on little to no atmosphere as well as magnetosphere, both of which my moon has.\n2. The claim that most moons aren't going to have major amounts of liquid surface also falls flat in that I've seen numerous sources saying that if a moon of a gas giant were to migrate inward, it would be a so called water world (sources at the very end, and I'll provide more if needed).\n3.", "710" ], [ "The fact that <PERSON> cites Titan as having ice under its surface, yet neglecting to mention the fact that much of this ice would melt and populate the surface of Titan with much more water were it to heat up is also a point of contention.\n4. The answer provided by bowlturner does not provide enough qualifiers under the \"hard-science\" tag, and therefore does not answer my question.\nIn summary, not only is the answer given not definitive for my question, much of what is said is actually not true for all or most cases.\nQuestion Based Proofs\n1. My question pertains to any liquid, and not necessarily just water. This allows for different densities, freezing and boiling points, heat absorption and dispersion rate, and many other factors as long as they would be liquid on the surface.\n2. <PERSON> asked a question wondering whether a watery world could and would be tidal locked, whereas my question asks specifically how to prevent tidal locking with any liquid in high quantities under specified parameters for a terrestrial based moon.\nBackground:\nI've been researching tidal locking like no other, and I've seen ways of getting around it, and pretty much all of them have been well explained, except for one.\nI've seen very very vague comments alluding to keeping a world from tidal locking if it's covered in liquid water (or I'm assuming any liquid). After the first one, I thought it was just a fluke or something, and then I saw one or two more, and now I'm very intrigued as to whether this could be a viable natural way of stopping tidal locking (as long as the liquid stays).\nNow it may be specifically because of an atmosphere that this would occur, but I really don't know. I know that in the case of an atmosphere, it has something to do with angular momentum and heat lagging behind the time of when it heats the ground vs the atmosphere or something along those lines, and I'm curious if this could be a similar case that is multiplied more for a mostly liquid surface.\nTHE QUESTION:\nCould you stop or reverse tidal locking on the surface (or mantle) of a terrestrial based moon (see info about pertaining system) by having a mostly liquid (only one main piece of land mostly used as a way to test the tidal lock) covered world? If yes, how much liquid would be needed, and would said liquid need to be of a specific density or viscosity to even be possible? And I would appreciate a \"why\" in any given answers (preferably with linked articles or other proofs).", "710" ], [ "How to make a moondial?\nA question came up on Outdoors StackExchange, How to tell time at night. I wrote an answer to that question, and in my answer I said that a standard sundial wouldn't work without some fiddling, but that an astronomer would know what fiddling was required. (I invite/encourage any qualified astronomers to go there and answer the question, BTW.)\nSo I did some searching around, and some thinking about it. Here's the question. Suppose we have an ordinary horizontal sundial, at a fixed latitude (in the Northern hemisphere), which has been calibrated to correctly show solar time at that latitude. The sundial works.\nNow, suppose there's a Full moon. What adjustments would be necessary, what additional information is needed, what would it take to transform/convert the ordinary sundial into a moondial? The definition of \"success\" would be that we could look at the shadow and get the \"correct\" time, where correct might mean up to the precision of an ordinary sundial which might neglect the Equation of Time (is a different equation needed?).", "710" ], [ "One website I read said that no adjustment was necessary, but I'm not sure I agree.\nIf that's not too bad, how would the answer change if we were some days off of a full moon? (Obviously, if we are sufficiently far off then there will not be enough light to make a discernible shadow.)\nEDIT: I've been thinking about it a lot, and thinking about the E.o.T.. The EoT has two (dominant) parts: the <PERSON> eccentricity part, and the oblique axis part. At first I thought the <PERSON> part wouldn't matter, but then I learned that the Moon/Earth eccentricity (0.055) is even bigger than the Earth/Sun eccentricity (0.017). So it would seem any reliable moondial would need to be corrected for this problem.\nI'm still wrapping my head around the obliqueness part. I understand that the style of the gnomon must be angled from the horizontal (equal to the latitude), but that's to make sure the style points toward true north. In fact, even if a horizontal sundial is used at an incorrect latitude, we can fix it by angling the whole sundial so the style points north. Clearly the Moon is in another orbital plane (apparently by about 5 degrees, I'm guessing that's an average), but if we change the angle of the style to compensate for the Moon then it wouldn't be pointing north anymore. So, at the moment, I'm thinking to leave the sundial as-is and then figure (somehow) the sine-wave that describes the Moon's obliqueness.\nThe further this goes the more it looks like I'm talking about figuring an Equation of Moon Time or similar.", "710" ], [ "Creating a stable, liveable ringworld orbiting a binary black hole/stellar pair\nI'm creating a setting for a sci-fi RPG. I would like to check whether the concept is physically possible. The main action happens on a giant ringworld which centrifugally orbits a paired black hole and star. Here is a diagram of what I mean:\nI am hoping that this setup would provide a day-night cycle. When the star is visible from a point on the ringworld, it is \"day\". When the star goes \"behind\" the black hole, it becomes \"night\".\nConstraints:\n1. The ringworld orbit should be stable.\n2. The star orbit around the black hole should be stable - ie the star is not feeding the black hole (due to radiation issues) and therefore there is no accretion disk.\n3. The radius of the ringworld should be reasonable - between 0.1 - 2 AU.\n4.", "24" ], [ "The mass of the star should be reasonable, erring on the smaller side\n5. The mass of the black hole should be reasonable, erring on the smaller side\n6. The irradiance (watts of radiation per square meter) on the ringworld should be comparable to that of Earth.\n7. The wavelength profile of the irradiance on the ringworld should either: be comparable to that of Earth (preferable) or if the black hole generates insanely dangerous gamma rays (reduced due to no accretion disk?), it should be at least plausible that the ringworld has some sort of magnetic field generation technology powerful enough to deflect them.\n8. The orbital period of the star around the back hole should be comparable to that of a day. Anywhere between 12-48 hours would work though.\n9. Something also to consider: the day/night cycle will break down if the black hole Schwartzchild radius is smaller than the radius of the star. So the radius of the black hole has to be greater than the radius of the star. I imagine this will require a black hole of considerable mass. This can be scifi'd away with \"inertial dampeners\" in the ring or something if required.\nIs such an orbital setup mathematically possible without leading to an absurdly large ring?\nThanks!", "24" ] ]

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[ [ "To extend <PERSON>'s answer... a few things off the top of my head in no particular order. Most of these apply to lower technology human societies where modern technology hasn't compensated for biological differences.\nHumans lack fur because we hunt by running. Humans can out run any animal on earth.\nIt's people without horses catch horses. They jog after horses, never catching them but never letting them rest either. After about 20-25 miles at most, the horse can't run any further, the human walks up and puts a rope arounds it's neck.\nWith flint, wood and bone weapons, hunters wound prey and then run it into the ground.\nIt's hard to cool by sweat with fur. If you ever seen a horse, \"lather up\" you've seen the basic problem. Horses have very thin, fine, close knapped fur yet still it interferes significantly with evaporation.\nSo, first off, humans with fur would have evolved to hunt differently. Likely, we would hunt with traps or with in larger groups like wolves. In either case our entire physiology might shift. We'd be adapted to sprint horses or wolves, to catch game quickly.\nOne affect might be a decrease in sexual dimorphism (overt differences in body shape by sex.) Part of the difference between men and women can be attributed to men being more adapted to protracted exercise. Distribution in muscles, muscle recover time, more sweat glands etc all point to optimization of men for running. If such optimization were not needed, then men and women might be more similar in physiology just like wolves and other canines and just like wolves, there would be less specialize of labor and less specialization in behaviors.\nMost sexually monomorphic species are matriarchal, with the entire group supporting the reproduction of the matriarch, at least in hard times. Human society might be radically different historically although we might start out with something like we have now after technology has leveled the playing field between men and women.\nWe likely would have had trouble with prolonged relative work like most pre-industrial agricultural work. Humans have to be careful not to kill horses and oxen by forcing the animals to work as long as humans do. We would adapt society to allow working in sprint shifts, with two or more individuals tag teaming a single job to keep the work going. If men and women where physiologically similar, they could swap off child care and work for everything except nursing.\nIndividuals might commonly pair up with siblings, other relations or friends for life, both specializing in the same job and together forming a complete work team.", "802" ], [ "So, if someone was a blacksmith, their partner would be as well. People didn't have time to waste so individuals would have some secondary task to occupy them at a lower level of effort while they rested from the main task. Human social structure would be based on this partnership. It would affect everything from military units to marriage.\nHumans would be less mobile in general, at least preindustrial. Unable to walk, march or run as far, they would have to adapt activities to being closer to home. Any systems based on walking, like cities, would be more compact.\nArmies would march and move slower but move faster in battle itself owing to likely greater sprinting speed. Battles would have to be decided faster before exhaustion set in. Battles would be very intense but short. This would favor more organized forms of shock warfare, like Greek Hoplites. The idea would be to hit the enemy hard and fast and do maximum damage in the shortest amount of time. Alternatively, there would be more pressure to develop a rotational system like the Romans used to grind away at an enemy while preventing exhaustion of individuals.\nIf the pair system did evolve, that would be part of the military as well and if men and women were more physiologically similar, then women would participate in combat more. If women could fight, that would increase per capita fighters in the population. Combined with intense shock warfare, battles could be more devastating with more adults overall in a population likely to be killed.\nSlavery might be more difficult both in terms of the danger of going to war to capture slaves, the added difficulty in controlling women and the inability to substitute humans for animals and machines in many circumstance e.g. treadmills. Managing slave work would be more difficult if slaves had to constantly swap out task.\nHaving fewer slaves would likely reduce the profitability of war (slavery being a huge driver of warfare in classical times.) It would also foster technological development because it would be difficult to solve a complex problem just by throwing more slave at it e.g. threshing grain or grinding flour.\nThere would be greater pressure to domesticate animals for transportation and labor and greater pressure to develop vehicles and machines. Riding animals and carts would be more common of basic necessity which would make it harder to restrict horses to military caste aristocrats.", "238" ], [ "You would need:\nEnergy: Nuclear power, fission or fusion. Nuclear waste recycled or glassified and buried.\nElectrical Food Chain:\nPhotosynthesis is just a way to knock electrons off atoms. In principle, it can be done with electricity alone. There's active research on this. Probably soon we'll have microbes that can produce sugar, fats etc from a current.\nMore simply synthesize high energy compounds and let microbes eat them.\nLastly, convert electricity to light, put plants under lights, stack as high as needed.\nRegardless of method, food is produced in highly compact areas in quantity year round.\nCarbon cycle remains closed.\nRaw Materials No real changes, everything recycled simply because there is no place to put waste. Mines and the like are just in the basement.\nHeat\nThe real problem with a planetary city is heat. Urban areas are already heat islands, always hotter than the surrounding natural terrain. Cover the entire planet and you'd heat the entire planet. Might actually cover the entire top in reflectors because really you don't need solar energy (solar panels are thousands of times less dense than nuclear power and they'd generate more waste heat per kilowatt.)\nPresumably the planet starts as a terrestrial planet and has seas. Seas are the major heat conveyers on earth. They are powered by solar evaporation which changes density causes changes in density of seawater at top causing it to fall. If you build over the ocean you will stop the heat conveyers and the poles and the equator will have radically different temperatures which will produce storms.", "208" ], [ "Likely, they will dump some waste heat back into the ocean to mimic solar effects and keep the conveyer going.\nThe real problem will be radiate enough heat into space. There is a phenomena called \"heat pollution\" that will occur when just the heat dumped into the atmosphere by technology starts to alter climate and drive storms.\nMost likely a civilization advanced enough to build a planet city could figure out alternative radiators for the planet e.g. radiating lasers, magnetic radiators or just a bunch space elevator like structures that were just radiators carried huge amounts of heat from the ground to space.\nEconomics: To my mind, the major technical road block to a planetary city would be one of what pragmatic or economic forces would drive that many people to pay the enormous price of cramming that many people together?\nPopulation will not grow as populations urbanize because children cost a great deal in urban areas and unlike under farming, produce no income until well into adulthood. Long before a planet gets paved over, population growth will be flat or even declining.\nDense urban cores, especially ones with skyscrapers, were justified by the need to cram lots of people close together so they could communicate with analog technology. Such dense cores are already technologically and economically obsolete, though not with out their lifestyle appeal for many.\nWe've long passed the stage where people had to be in New York to hit the big time. Major corporations are spread all over the world in urban areas big and small. It's as easy to send email around the world as in the same building.\nI think the most likely scenario might be a completely non-economic reason to cram hundreds of billions of people on a single planet.\n* A prison for a very large galactic civilization, perhaps locking up entire societies for some reason.\n* A refuge of some kind, everyone is there because it's the only place to survive. It could be a hiding place or a fortress. If the latter they would be like people fleeing the barbarians to hide in the castle.\n* Planet city, but mostly empty. For whatever reason, a lot more city got built than needed. Runaway autonomous construction robots is a scenario I've seen once or twice. In that scenario, the city becomes the geography with 99% of it empty but maintained the robots. Spooky.", "99" ], [ "First, let's do greed. Greed is an appetite uncontrolled. Consider, for example, a dog. If he sees food he simply moves directly towards the food and tries to eat it without any other concern or hesitation. He does not consider his co-dogs in the pack. Or his offspring. Nor even whether he is in fact hungry. He just tries to eat the food. This is greed.\nGreed may be a survival trait in some circumstances. For example, in the wild in situations where food is scarce, uneaten food is wasted food.\nGreed is usually counter productive for intelligent species, since it is deeply sub-optimal when you have the ability to produce enough of what you need. If you simply eat everything in your fridge you won't be healthy.", "376" ], [ "So greed might be a problem for intelligent critters that had it as a survival trait in the past, and now have to deal with things like diets. We resemble that. They might take steps to suppress it, remove it, overcome it, etc.\nSelfishness means doing what is good for \"self.\" However, in evolutionary terms, the thing that evolves is the gene. If an action tends to help spread one's genes around, but is bad for the individual, it may still get fixed in through evolution. A mother cat fighting to protect her kittens may get mauled by a dog but leave an extra batch of kittens. Her personal selfishness, running from the dog, and her gene's selfishness may conflict.\nSomewhere though, the gene's selfishness must have at least a modicum of success, or the creature cannot procreate long enough to evolve.\nFor example, an intelligent creature that was evolved from a social insect might be ideally communal, except possibly for the \"royal\" breeder class. The workers and drones might be prepared to nearly-mindlessly sacrifice themselves for the good of the colony.\nAt some point in there, there has to be something that produces conditions that tend to advance its own interest. This is \"selfish gene\" theory, along the lines of the book The Selfish Gene by <PERSON>. This is a metaphor indicating the genes act as though they were selfish. Because if they don't they get out competed by genes that do.\nSo individuals may have their selfishness suppressed. But some part of the creature must act selfishly in some sense for the species to continue to exist.", "376" ], [ "Technology is highly dependent on the supply chain. A technology that can use local materials can be transplanted to a new area and be kept. For example, pottery spreads quickly because it uses local clays. Cell phones are highly dependent on the current supply chain and would not be usable on another world without importing huge amounts of supplies. Imports will be hugely expensive and prohibitive for nearly anyone. A museum might have a cell phone to show people what is done elsewhere.\nVictorian Britain had a lot of technology: steam engines, steel working, automated looms for weaving, coal mining, ship building, brick making, construction, beer brewing, Scotch distilling, barrel making, to name a few. Most of these were built upon centuries of saved up knowledge kept by specialized people.", "658" ], [ "Not every village had knowledge of how to do more than a few of these. The empire traded around the world so that a village didn't need to know how to make most stuff. They traded for the stuff they didn't know how to make.\nSo, if you were thinking of people taking technology and moving to another planet, the technology they can use would have to be stuff that can use whatever materials are locally available. Think of stone tools, pottery, and any plant materials that might be there. If you took only a village, you are taking at random a very select bit of technology knowledge.\nThe process of moving a group of people to a new location is by nature, a bottleneck on the transmission of knowledge. A lot of knowledge will be lost when the first generation of people die as most of what they know will not fit the new location and it will not be passed on to the next generation.\nAttempts to preserve the old ways will doom the village to a death as most of the old ways will not work well or will be extremely expensive.\nThe best you can hope for is to catch a rare general purpose genius who knows how to teach learning skills to the next generation. Instead of keeping the old technology, through trial and error, they will learn and develop the technology that works best in the new environment.", "998" ], [ "I would say, likely never, barring outside influence. Even when you look at Europe, it was a near run thing, more a matter of luck at times than anything, and Europe had lots of advantages.\nIn Guns, Germs and Steel, <PERSON> argue that the Americas would always be slow to develop but the primary orientation of the continents were North-South instead East-West as in Eurasian (Africa has the same problem.)\nThis causes trouble because biomes are largely defined by latitude, which defines their temperature. Closer to the equator, hotter, closer to polls colder. That means that as you move East-West, the temperatures stay more constant than they do moving North-South.\nPlants and animals can migrate or be traded East-West but far less easily North-South. Traveling East-West, you just need one suit of clothes. Traveling North-South you need several, one for each clime you will cross.\nIn civilization and technology building, the key factors are population size and trade. Populations tend to stick to biomes and grow East-West so if you have a primary North-South geography, you see a lot of smaller chopped up cultures and civilizations that are relatively isolated.\nPopulation is necessary just for the surplus material a large number of people can produce and just for all the brain power it provides. Large population can also more easily back up information and survive cataclysms.\nTrade is necessary to increasing technology because no place on earth has enough resources in a radius of 100-200 miles to support a Renaissance technology level. Also, trade is necessary to prevent civilization from collapsing from famines.\nIf your primary travel corridors run North-South, population gets chopped up into small cells, the spread of useful plants and animals is very slow and general travel and commerce, much more difficult.\nThe other problem with Americas is that they do not have native animals that can be domesticated, especially beast of burden. <PERSON> spent a lot of time pointing out that of the millions of mammal species only about a dozen have been domesticated. Domestication requires certain behavioral traits that not all animals possess. Attempts to domesticate Zebras for example, have been attempted by Islamic and then later Europeans (Zebras are immunes to the tsetse that wipes out horses in Africa) but the animals are just to belligerent and easily startled.\nIn the Americas, the only animal that could even be considered for a beast of burden would be the buffalo, and even after a couple of centuries of people trying to raise them, they are still not domesticated just in terms of keeping them for meat and skins. Trying to yoke one is out of the question.\nI think that culture in the Americas would cause a serious block.", "121" ], [ "I would argue that the means of organization are a type of technology themselves, one that allowed them to accomplish more than any other cultures ever did with the same available resources. But they also created a serious early adopter trap that would have prevented further development.\nThe conditions that lead to the flourishing of technology, art and science are not natural and not stable. The progress of humanity is a story of this or that small polity suddenly and usually by chance, being forced to adopt a more egalitarian and merit driven society. Then they have a run of 200 years or so, and then fall back into a static, hierarchal, parton-client system where birth and political connections mean far more than merit and class mobility freezes. Then the locus of advancement jumps somewhere else. Human progress is more about following a golden thread from small pocket to small pocket all over the world for centuries.\nKey to such development is escaping centralized authority and control with a subsequent increase in individual freedom and merit reward. Empires strangle off development fantastically. You can see this in the fall of the Islamic world after the Ottoman Empire absorbed most of it. A dynamic civilization slid into stagnation because Empires seek stability more than anything else and progress does not bring stability.\nBut the cultures of the Americas could not easily dispense with centralized authority. With only stone and wood tools to work with the high civilizations of the First Americas-peoples relied on an incredible level of social and task organization ito marshal vast amounts of skilled human labor to overcome their lack of metal tools and draft animals. They shaped stone by pounding it, not chiseling. They moved stone by huge teams of men, not by yoking oxen and so one.\nWhile powerful, reliance on organization made the societies fragile. In Meso-America, almost any kind of social disruption caused city states to collapse economically and for their people to abandon the city, sometimes for decades or centuries.\nThe kind of wrenching social change in Europe that drove the the Renaissance would have simply destroyed the civilizations of Americans.\nSo, I think the answer would be \"never\" but if they did, it would take thousands of years.", "1006" ], [ "The undead body is preserved by magic.\nAnd that's the key. Treat magic as an almost-infinite resource easy to obtain but hard to replenish. Is a common setup in magic universes that \"magic\" is a consequence of the existence of living beigns. In other words, just imagine that \"mana\" is available in the whole world, but is more common or concentrated around places where life is more common as well, forests, big cities, etc...\nOn the other hand, living corpses uses magic for living; it could be a delicate ballance between living beigns spreading magic as they live and undead beighs consuming magic as long as they're living.", "227" ], [ "Create too many undead bodies and they wil deplete the magic of the zone quickly, and after that they will die (again) like my cell phone when it run out of battery. Or create just the right amount of undead bodies and they will consume the ambient magic at the same pace as it is replenished.\nIf the ratio of magic creation vs magic consumption is 1:1 (one living being spreads enough magic to sustain one unliving being) you tie the amount of undead bodies to the amount of living bodies so, if in some point of time the undead outnumber the living ones, they wouldn't last for long.\nLife and death are tightly related. It's obvious that one cannot exist without the other.\nNature don't like undeads, but tolerate them.\nIt is not natural for a dead being to be alive, every cell in the body of the undead is craving for resting forever. Well, you can cheat nature using magic but, the longer you cheat mother nature, the more it costs.\nIf the magic cost per day follows the graphic below:\nFor each day of existence (x axis), the magic cost increases (y axis), so after 100 days of unliving, dayly cost is almost twice as the first day and 200 days after the cost is multiplied by 8.\nNo matter how powerful the Necromancer would be, there would be a moment where the magic costs exceeds Necromancers power and this body cannot be kept living anymore.\nMaybe you can use both ideas at the same time! :)", "227" ], [ "Very tribalistic\nWhile there may be some genetic mixing, your clone has to be pretty much the same dimensions as you. I'd imagine most phenotypes would be shared between the two. More importantly, if memories are carried over it stands to reason that dogma is transferred over from birth. Wrongdoing from generations ago could carry over as what feels like first-hand memories, but with much more time to diverge from the truth. While in the real world children are taught who the enemy is in this world everyone knows from birth. At the same time, everyone from the other tribe also carries memories of traumatic events (albeit likely very different from yours). While most people consider it wrong to harm children for the wrongdoing of their families no one in this world is ignorant of history and everyone in a lineage may be considered responsible.\nFewer, but more intense taboos\nWe're all adults here everyone is mature enough to curse and talk about reproduction. That said if something is taboo everyone already knows from birth taboos never need to be explained or discussed unless of course, you aren't part of our lineage. A very big difference from humans is that people could potentially remember their birth perhaps the moment of splitting. This could be a more celebrated moment like human birth or something done behind closed doors like sexual reproduction. Either way, there would likely be all kinds of ritual and taboo surrounding it.\nHighly optimised, but less revolutionary\nIt's diffuicult to say how the tasks of a person are delegated to the two new people however it's very likely that they would pick right where they left off. Perhaps the siblings will work together or perhaps they will take on different interests (finally get to start that rock band!). Because memories are kept, there is no training needed for a newborn to get to work which will allow larger projects to be completed faster and with more consistent vision. If the siblings work together they would likely have great synergy starting off with the same amount experience (built over generations) and an intimate understanding of each other.This combination of expertise and solid teamwork would lead to highly optimised products and more success in feilds like math where problems can take generations to solve and many years to even understand.", "335" ], [ "That said with such levels of experience, it would be hard to break into a field or industry which can cuase stagnation. Siblings could prevent this by tag teaming. One works and the other goes on a sabbatical then when the working sibling burns out they switch places to bring a new perspective while minimising the amount of time need to learn the ropes. This can be extended to the whole family tree with a variety of degrees of involvment that regularly changes in accordance to experience, and fresh perspectives (which are somewhat opposed and both inherited) like a royal bloodline however it would be built on experience and knowledge retained making it more utilitarian than human bloodlines. This provides plenty of opportunities for factions and rivalries forming feeding right back to tribalism.\nNot into cuteness or dating\nChildhood and parenthood are incredibly important to forming familiar bonds. Without childhood, relationships in this world would probably built on generations of interaction more along the lines of a fellow countryman. There would be no maternal instinct and no sense of cuteness so say goodbye to Hello Kitty. Without sexual reproduction, there would be no biological drive for romantic relationships. That's not to say there would be no romantic relationships just that they wouldn't be common and may even be frowned upon. Romantic relationships are unlikely to be codifed with concepts like staying faithful or being committed so each relationship would be unique in it's expectations rather than falling into defined categories like dating, boy/girlfriend, and married. It's also important to remember that eventually your significant other will split in half if they don't die first so dating is either short lived or very open. I'd like to mention that people would probably have a weak sense of individuality since they carry the memories of past lives and know that their body and mind will be split and morphed. A sense of self is very important to forming personal relationships so they wouldn't be very common. Overall, the lineage comes first.\nHope this helps best of luck!", "1008" ], [ "How to significantly slow/stop computer development from advancing past the early 1990s?\nI have a world where both computers and biological technology have matured to serve the needs of my people. Both have numerous people researching and making use of their equipment. For example, biological computers can implement things like logic gates, parallel processing, store massive amounts of data, simulate things like neural nets on a truly massive scale while at the same time simulating things like games, movies or dreams etc. On a more machine-like scale, a biological exoskeleton of sorts exist that people can step into and use. Humans in this world discovered and used biological computers well before the first mechanical computer was even developed. Such biological technology is usually something a human interfaces with and operates with their mind.\nComputers in my world also exist but they obviously came later. The major advantage they have over existing bio computers and technology is that they are persistent. A mechanical or digital computer doesn't have to be regrown, they can operate without human input, they can survive certain austere environments better and don't consume resources outside of electricity once built. The major downside is getting the metals and resources for computers requires expeditionary operations to other floating islands that they coast by. However, my floating islanders have been able to construct computers that resemble that of the mid to early 1990s. Especially for military applications.\nHow can I stop or significantly slow computer development from advancing past the early to mid 1990s?\nYear range is 1990-1995 Notes:\n1. The primary users of computers are the military, they have the most incentive to push boundaries on computer development. If anyone is to be impacted the most, it is them.\n2.", "934" ], [ "All floating islands are moving, though they take time. Smaller islands fall to the surface of the planet eventually. Through a process new islands are essentially lifted back into the sky.\n3. There exists two tiers of islands with multiple layers of clouds. Past the first few cloud layers is the first floating island. Radio and wireless communications don't work in this area. Only wired communications work. Past the cloud layer above it, there exists another island. These islands are a bit barren but all forms of radio and wireless communications work, this is also where most combat takes place. Clouds can \"poison\" both living organisms and non-refined metals when a newly formed island lifts up. The peoples' island in both tiers have been tethered to each other and travel in the same direction.\n4. Silicon is the primary semiconductor used and harvested for computers.\n5. Setting takes place on planet that is not Earth. Different materials, metals, weather, and particles exist.", "1006" ] ]

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[ [ "To Resign or Not: Two Attorneys Make Their Case on the ‘No Confidence’ Vote Against Trinidad & Tobago’s Chief Justice · Global Voices\nThe Hall of Justice in Port of Spain, Trinidad. Photo by <PERSON>, CC BY-ND 2.0.\nOnline discussion about the Law Association of Trinidad and Tobago's (LATT) vote of no confidence against Chief Justice <PERSON> continues. Is calling for <PERSON>'s resignation justified or overhyped? Would his exit be a help or a hindrance to accountability? Depends on who you ask.\nSenior Counsel <PERSON> has been one of the most outspoken voices on the controversy underpinning the vote — the bungling of the appointment of <PERSON> to the High Court. <PERSON>, who was previously chief magistrate, had left behind a significant unfinished case load, which has compromised the ability of scores of prisoners to get justice in a timely manner.\nIn a weekend post on the candid Wired868 news site, <PERSON> put forward his rationale for why both <PERSON> and members of the Judicial and Legal Service Commission (JLSC) — which advises the president on the appointment of judges — should resign over the matter. <PERSON> has repeatedly called the no confidence vote “a key moment in the pursuit of accountability by public officials”. He explained:\nThere are two critical components in the exercise of power. One is the lawful authority to exercise the power. The other is the moral authority that underlies the exercise of that power and which rests on the trust and confidence of the citizens. […]\nWhen its acts and omissions were first subjected to legitimate inquiries, the JLSC was utterly dismissive. […] More offensively the JLSC never once acknowledged that it had even a share of responsibility for the now notorious debacle of 53 part heard cases having to be started over.", "957" ], [ "[…]\nThat wrong and strong attitude has destroyed the public trust and confidence in the JLSC and has resulted in the overwhelming passage of the resolutions of no confidence and call to resign. The Chief Justice and the other members of the JLSC as a result, have lost their moral authority to a degree that they have lost their legitimacy to exercise the constitutional authority entrusted to them.\nAttorney <PERSON> — who boycotted the no confidence vote on the grounds that, the chief justice not even being a member of the law association, it was not legitimate LATT business — called <PERSON>'s post “the best of the arguments FOR the resignation of the CJ [chief justice] that you will find amongst the flood of such calls.” However, he still believed “the factual basis for this call for a resignation is slim – despite its hype level”:\nWhat does it allege against him and is it right in its conclusions? The allegation I find in here is failure to do adequate background checks on <PERSON> and a lack of humility in responding to calls for answers. The first was corrected by the JLSC by revoking the appointment, and issuing a statement explaining why. There was also a statement from Ayers-Caesar which accepted responsibility and which she has never publicly disavowed. The second assertion about the lack of humility in replying is not a reason for removing a CJ, or an argument that he lacks transparency or accountability. It might be a reason not to like him- but that's irrelevant.\nWhat is missing from the discussion is what cannot be disputed: there are ancient and very good reasons for securing the office of the CJ from intimidation and politicization. His tenure has to be protected so that he can maintain the body which acts as a final check on the exercise of executive power. No one is mentioning that and that is unfortunate- because it would help the public measure the extent of the alleged transgressions of the CJ. Instead key-words like accountability and transparency are being used to justify the ruin of the arm of government that ensures that the executive is transparent and accountable.\nOn the question of legitimacy, <PERSON> countered:\nIt's incorrect to suggest that the CJ (JLSC)'s ‘legitimacy’ has been lost. The CJ has not lost the ‘moral authority’ to perform its functions because of the vote any more than a government loses the moral authority or legitimacy to tax because a portion of the country sign a petition of no confidence in the government. If our institutions are that fickle we would not be able to maintain law and order.", "600" ], [ "Don’t Politicise the Judiciary, Warn Trinidad & Tobago Jurists · Global Voices\nThe Hall of Justice in Port of Spain, Trinidad. Photo by <PERSON>, CC BY-ND 2.0.\nThe narrative surrounding the chief justice controversy in Trinidad and Tobago is shifting, moving from heated debate about accountability to concerns about the politicisation of the judiciary.\nThe Law Association of Trinidad and Tobago (LATT) passed a no confidence vote against Chief Justice <PERSON> after the Judicial and Legal Service Commission (JLSC) — which he chairs — mismanaged the appointment of <PERSON> to the High Court. <PERSON> had left behind a heavy unfinished case load, which has compromised the ability of scores of prisoners to get justice within a reasonable period of time. She thereafter resigned.\nAs far as the JLSC seems to be concerned, it has dealt with the matter, and planned to return to business as usual with the appointment of two new judges this week — but this was blocked by the granting of an interim injunction on the night of June 5, 2017. The injunction was brought by former attorney general <PERSON> on behalf of former agriculture minister <PERSON>, who are both members of the United National Congress (UNC), a political party which sits in opposition in parliament. It requested that no judicial appointments take place until after the hearing of a case which argues that no more than one retired judge can sit on the JLSC. The body currently comprises two former judges.\nPolitical commentator <PERSON>, whose determination to get answers from the President <PERSON> about his receipt of a controversial housing allowance has resulted in a police investigation, noted:\nWhen <PERSON> exercised a power he didn't have, and helped himself to housing allowance he wasn't entitled to <PERSON>, <PERSON> and <PERSON> were silent.\nNow that <PERSON> exercised a power he does have – to appoint the JLSC and judges – they challenge it in court.\n<PERSON> and <PERSON>\n#DeViceCyahDone\n#StrenkAndPowers\n#CJCovfefe\nThe ruling which was made on the injunction was subsequently overturned by the Court of Appeal.\nMaking the point that Trinidad and Tobago has a history of “a stable and independent judiciary”, attorney <PERSON> — a member of the governing People's National Movement party and one of the voices (among them a former chief justice) calling for <PERSON> to stay in place — noted in an interview that “it is unhelpful to allude that [certain lawyers] are advancing a political agenda”.\nSaying that the lawyers who brought the injunction may be coming from the position “that there needs to be a lot more discourse between the bench, the judiciary and the legal profession”, he did concede that the case is interesting, because it sought to block two new judges with “formidable experience” from taking up their judicial functions — a move he called “counterintuitive to anybody who has an interest in the administration of justice”. The two new judges were sworn in on June 7.\n<PERSON> likened the whole affair to democracy under attack — and he wasn't the only one. Barrister Dr. <PERSON> agreed that judicial independence was under siege, quite ironically “by the very bar that prides itself on independence and self-governance”.", "957" ], [ "Quite bluntly, he explained:\nJudicial independence essentially means that judges and other judicial officers are free to exercise the functions of their office without fear of reprisal, retribution or termination. The elements of such independence are security of tenure, financial security and administrative independence. Each of these elements is essential to ensure that democracy itself functions without undue influence from the State, unsuccessful litigants and third parties—like a select group of lawyers. […]\nAs members of the legal profession, you cannot tout the importance of an independent judiciary while at the same time passing motions for the removal of judges. It is an affront to the very principles that a self-regulated bar—in a democracy no less—is supposed to stand for.\n<PERSON>, one social media user who has been paying attention, summed it up this way:\nThe current situation appears to becoming increasingly politicized. After all the yammering of lawyers, I'd like to see evidence of concrete policy changes and processes. It's an opportunity to do things better and plug gaps. Admittedly the crisis snowballed and was improperly handled at the start but, from where I sit, it now appears to be about settling vendettas and scoring points. We should be getting consensus on how to treat with those persons (including victims) who've been waiting years for justice. Esoteric arguments are important to agree on the philosophy and the way forward, but we also have real issues to sort out.", "339" ], [ "More Twists and Turns in Trinidad & Tobago’s Chief Justice Fiasco · Global Voices\nChief Justice <PERSON> speaks to the first group of graduates of the OAS-supported pilot drug treatment court in 2014. Photo by OEA – OAS, CC BY-NC-ND 2.0.\nThe imbroglio between the Law Association of Trinidad and Tobago (LATT), Chief Justice <PERSON> and the Judicial and Legal Service Commission (JLSC) continues to be fluid and fast-changing.\n<PERSON> speaks out\nIn one of the controversy's latest twists, <PERSON>, the magistrate turned judicial appointee whose untended case load prompted a no-confidence vote aimed at the chief justice, has revealed that she “was put under pressure to resign”.\nHer position was outlined in a letter to President <PERSON>, dated May 19, 2017, in which she asked him to acknowledge that her resignation letter is “of no legal effect” and her removal as a High Court judge “unlawful and unconstitutional”. Copies of the letter were sent to the chief justice and the JLSC.\nAccording to <PERSON> timeline, on April 10, 2017 — two days before her High Court appointment — <PERSON> asked whether she had any part-heard matters. On April 11, she learned that there were 28 outstanding matters at the Port of Spain Magistrates’ Court; she sent the list to <PERSON>. Her appointment as a judge took place as planned on April 12.\nThen, on April 25, she had a meeting with <PERSON> and the acting chief magistrate, who advised her that she actually had 52 outstanding matters. In a meeting with the chief justice the very next day, <PERSON> said that the question of the part-heard matters didn't come up — but the chief justice maintains that <PERSON>-Caesar told him in a telephone conversation that “she had no other outstanding matters”.\nOn April 27, they met again and <PERSON> informed her that the JLSC, at an emergency meeting, decided that the best thing for her to do would be to tender her resignation or have her appointment revoked.\n<PERSON>-Caesar signed the resignation letter, saying she was “unable” to get legal advice before doing so. She also claimed that she was never afforded an opportunity to respond to the JLSC's allegations, and took issue with the chief justice referring to her dismissal of 16 cases on March 22 “unusual”.\nAlthough Section 137 of the country's Constitution says that a judge can only be removed from office for an inability to perform duties or for misbehaviour, Ayers-Caesar does not consider that her actions fall under either of these categories.", "957" ], [ "Further, she has taken the position of her legal counsel, attorney <PERSON>, that her High Court jurisdiction would allow her to hear her outstanding cases in the Magistrates’ Court, saying, “I would expect that within the next few days, if the Judicial and Legal Services Commission agrees with this position, that I will be informed in writing of that agreement.”\nAyers-Caesar's promotion from the Magistracy to the High Court has left scores of prisoners in desperate positions, since their cases will now be further delayed.\nAs soon as the story broke in one of the daily newspapers, political commentator <PERSON> was all over it on Twitter. She did not buy <PERSON> excuses about omitting information pertaining to her case load, nor that someone with enough legal experience to be appointed a High Court judge was coerced into signing a resignation letter:\n<PERSON> say her workload and short notice is why she couldnt remember her full caseload, oui. #MarciaCovfefe\n— <PERSON> (@rhodabharath) June 11, 2017\n<PERSON> say they show her the resignation letter, ask her if it ok and she said, “Whatever”. #MarciaCovfefe\n— <PERSON> (@rhodabharath) June 11, 2017\n<PERSON> say nobody give her permission to get legal advice. Give her permission inno? In 2017? #PermissionPlease #MarciaCovfefe\n— <PERSON> (@rhodabharath) June 11, 2017\nFacebook user <PERSON> also shared his observations:\nI get 2 points from <PERSON> letter.\n1. The Honorable Chief Justice exercised diligence in enquiring into whether the Chief Magistrate had part heard matters and;\n2. It will be difficult for Her Worship to prove that her resignation was not reasonably voluntary.\n‘Specific political interests'?\nMeanwhile, more voices are joining the chorus for the chief justice not to resign over the matter.", "600" ], [ "Cry of ‘Free the [bleeping] weed!’ leads to arrest of Trinidadian cannabis advocate · Global Voices\nActivist <PERSON> is led away by police officers in front of Trinidad and Tobago's parliament on October 18, 2019. Photo courtesy of <PERSON>.\nOn October 18, 2019, activist <PERSON> stood on the pavement outside Trinidad and Tobago's parliament to continue to press the government to enact existing medical marijuana legislation.\nIn a Facebook post that morning, she announced that she would be “outside Parliament from noon to 3 pm reminding the prime minister of his promise to decriminalise cannabis and make it available for personal and medical use by June 30 of this year.”\n<PERSON> has vowed to “be there every Friday until he keeps his promise” — but on this particular Friday, the police arrested her under Section 49 of the country's Summary Offences Act, which deals with “violent language and breach of the peace” — a law which some view as counterintuitive to the freedom of expression that is enshrined in the Constitution.\nJurist and lecturer <PERSON>, for instance, believes the law to be “very oppressive” and thinks “the only limit on obscene language should be when it incites or has the potential to incite violence.”\nAnyone arrested under this law faces a fine of $200 Trinidad and Tobago dollars (approximately $30 United States dollars) or 30 days’ imprisonment.\nImages posted on <PERSON>'s Facebook page show her being led away by a police officer, who also took away her sign reading, “Honk your horn for the herb.”\nSupporters soon began sharing the images, with photographer <PERSON> commenting:\nDr. <PERSON> has been detained while protesting to “Free de Ganja”. Officers advised she will we taken to CPS to be charged and processed. Please share so people can see the real threats to our democracy.\n#FreeTheWeed #LegalizeIt #DemocracyWhere\nIn the thread that followed, <PERSON> said that when the police officers approached, “they said we were ‘inciting others to disrupt parliament’.” While some commenters felt the police were simply doing their job, <PERSON> asked:\nI thought parliament was inside of a building, was she trying to breach the building? Was she found with an IED [improvised explosive device] on her person? Was she in any way harming anyone or influencing harming to anyone in parliament? If all these answers are a no then she is being abused by the police. […] Free the lady let her do her civil duty.\n<PERSON> was released from police custody at around 7:30 that evening.", "957" ], [ "At her October 21 hearing, she pleaded “not guilty” to the charge and the matter was adjourned to November 13, 2019.\nSpeaking with Global Voices by phone, <PERSON> said that she had retained Dr. <PERSON>, <PERSON> and <PERSON> from New City Chambers as her attorneys and was not at liberty to discuss the details of the case. She did confirm, though, that the charge against her was “the use of obscene language to the annoyance of people in the street”. However, photos of the area outside parliament on the day in question do not capture any bystanders.\nVia WhatsApp, Dr. <PERSON> told Global Voices that “there are serious constitutional implications in this matter”:\nHere we have someone exercising her constitutional right to expression and her constitutional right to protest and both of those rights have seemingly been infringed by the state and […] it does appear to be a trend of silencing dissent, silencing unpopular speech in Trinidad and Tobago — so we are very concerned about two constitutional grounds that are triggered here — the freedom of thought and expression and the freedom of association and assembly.\nDescribing the process of arrest and detainment as “traumatic”, <PERSON> said she is nevertheless emboldened to continue her fight for justice. Although the draft cannabis legislation is reportedly ready and simply needs to be laid in parliament, she says neither she nor any of the other stakeholders she has spoken to have been invited to offer feedback to help ensure its smooth passage.\nThe country's president has also turned down <PERSON>'s request to intervene in the medical marijuana issue.\nThe day after her hearing, <PERSON> found herself at the prison located in the capital, Port of Spain — not as an inmate, but as an advocate.", "957" ], [ "Unexplained Wealth Bill in Trinidad & Tobago ruffles some feathers · Global Voices\nScreenshot of Trinidad and Tobago's Attorney General <PERSON> taken from a YouTube video entitled “FACTS: Unexplained Wealth Legislation.”\nOn April 5, 2019, Trinidad and Tobago's attorney general, <PERSON>, finished up the parliamentary debate over the Civil Asset Recovery and Management and Unexplained Wealth Bill, 2019. The legislation targets corruption as part of a larger aim to establish an agency responsible for recovering criminal property and restricting ill-gotten assets.\nBut the bill has come under fire by the country's opposition, as well as some social media users. <PERSON> has firmly defended the bill, however, saying that “innocent people” with nothing to hide should not be concerned.\nThis is not the first time that such legislation has been proposed. Prior to elections in 2015, when the current opposition party was in government, the then-na­tion­al se­cu­ri­ty min­is­ter, <PERSON> (now the country's commissioner of police), brought a civ­il as­set for­fei­ture document to the cab­i­net. Because the legislation was not passed back then, <PERSON> said he was not surprised by the opposition's reaction to the current bill, which they called “draconian” and “unconstitutional.”\nMeanwhile, CoP <PERSON> maintained that passing the bill would help police tackle white-collar crime, which is rampant in Trinidad and Tobago. He added that it would help to block “gang leaders and criminal elements” from getting state contracts, a fairly common occurrence.\nBecause the bill is intended to combat crime, it only needed a simple majority to pass, which some on social media, including Facebook user <PERSON>, took issue with, saying:\nThe Opposition represents approximately 350,000 voters in this country who now will have no voice in the passing of this bill at parliamentary level.\nNetizens are also concerned about the grounds for conviction that the bill lays out. Facebook user <PERSON> acknowledged that it was a “very good law to combat criminal activities, money laundering, corruption and terrorist financing,” but was under the impression that the standard of proof for conviction was no longer based on “reasonable doubt,” but “reasonable suspicion.”\nAttorney <PERSON>, however, posted this public Facebook status update:\nThere is A LOT of misinformation being spread about the Unexplained Wealth legislation. It does NOT allow the government to seize and take your property [merely] on the basis of suspicion.", "957" ], [ "To the contrary, seizure is dependent upon the court concluding that the property is criminal property, and was not acquired by its owner for value and without notice of the criminality.\nOther concerns include the fact that the law will be retroactive, and there seems to be little confidence in how the state agency will carry out its remit. There have been several online discussions about the potential for abuse of power and some local business chambers have spoken out against the bill, saying that in its current form, it could adversely affect citizens and needed further clarification.\nBut in a video widely shared on social media, the attorney general explained:\nThere is no government involved in this. There is no police involved in this. This is the director of public prosecutions telling a handpicked by the president and by the Judicial Legal Services Commission agency — who are insulated away from politicians — that they, the agency, must approach the court and the court must decide […]\nThere can be no forfeiture unless a court says so. […] That means the high court has to say yes. The court of appeal has to say yes. The privy council has to say yes on the recommendation of the director of public prosecutions acting through independent agents […] Only after all of that can your asset be forfeited.\nThat hasn't stopped the circulation, via unsolicited emails, of a petition against the bill.\nInterestingly, much of the official discourse around the bill has focused on targeting the “gold-chain-wearing men that don’t have a job, all day long driving Mercedes Benz and BMWs,” but attorney <PERSON> made the point that “Unexplained Wealth legislation passed by parliamentarians in Trinidad and Tobago is like Satan outlawing the Devil”:\nBecause of a docile population, a fraudulent civil society willing to be bought and a plethora of ‘activists’ who are really applying for a wuk [work], being a parliamentarian IS the most profitable game in town. It’s where you go to get rich. Now they want to know how people got rich.\nPerhaps there also needs to be stronger legislation preventing the acquisition of such ill-gotten gains in the first place.", "957" ], [ "Are Trinidad & Tobago Police Actively Investigating the President’s Housing Allowance Like They Said They Would? · Global Voices\nScreenshot of a section of the letter sent to <PERSON> attorney with regard to a request for information from the Office of the President.\n<PERSON>, the university lecturer in Trinidad and Tobago who, back in September 2016, brought the issue of a controversial presidential housing allowance to national attention, has posted a new Facebook Live video to update netizens on the latest developments — or lack thereof.\nSocial media users in the country have been routinely tuning in to <PERSON>'s updates, and the online conversation has helped to keep the issue of alleged misconduct in public office on the front burner, even when mainstream media and civil society groups appear to not be pushing the matter.\nThe Trinidad and Tobago Police Service (TTPS) announced on January 15, 2017, that its anti-corruption unit would launch an investigation into President <PERSON>'s receipt of a monthly housing allowance of TT$28,000 (US$4,182). The president received this money while living in state housing, which is not allowed. Since then, the public has not been advised as to the status of the investigation or any of its findings.\nChief of Police (CoP) <PERSON> stated in January that at the time the investigation was not a criminal one. In her newest Facebook Live, <PERSON> quipped that as far as she is aware, “the only thing […] that police investigate in Trinidad and Tobago is crime”. She also reminded social media users that she sought expert and independent legal advice based on the evidence she gathered, noting that the police investigation began “after a Queen's Counsel (QC) insisted that the president needed to be investigated”.\nThe apparent lack of progress with the investigation has renewed some netizens’ lack of confidence in the police service.\nPresident <PERSON> has publicly insisted that the Salaries Review Commission (SRC) authorised his receipt of the housing allowance based on a commissioned report. The SRC, however, has since said it gave no such permission.\nIn her latest Facebook Live video, <PERSON> honed in on several new areas of concern. On January 11, 2017, there was a Joint Select Committee (JSC) hearing at which members of the Office of the President — including Accounting Officer <PERSON> — were present.", "957" ], [ "<PERSON>, who tuned in to the broadcast hearing, noted that it revealed “a lot of craziness going on with respect to expenditure and hiring […] up to December 2016, two members of the president's household were on the payroll at the Office of the President”. As a result, she is asking President <PERSON> to clarify whether he has used taxpayers’ dollars to hire family members and even pay for their travel expenses.\n<PERSON> also wants <PERSON> called to account, alleging that he himself has had at least one family member working at the Office of the President:\nWe in Trinidad and Tobago like to pretend that nepotism is not a big deal […] in fact, it is against the law. The Integrity in Public Life Act specifically says that you're not meant to use your position in public office to benefit friends and family members.\nThere's something else on <PERSON>'s radar when it comes to the police investigation — “some sort of link” between the president and Chief of Police <PERSON> — which to her suggests a possible conflict of interest. In 2009, <PERSON>’ wife, Magistrate <PERSON>, faced misconduct charges. The matter was investigated by a one-man tribunal comprising “none other than then Justice <PERSON>”. <PERSON> was subsequently vindicated.\nIn light of that, <PERSON> said she has “serious questions about whether the investigation will take place in an open, transparent and honest fashion”.\nFacebook user <PERSON> commented:\nInteresting observation concerning the CoP's wife, I think there are good grounds for the Integrity Commission to get involved but do not hold you breath on that ever happening.\nThe country's Integrity Commission, for its part, has been besieged by a startling lack of integrity.\nOn the heels of official correspondence that <PERSON>'s attorney received, which “respectfully refused” to disclose information that <PERSON> requested based on the fact that section 5. (1) (a) of the country's Freedom of Information Act (FOIA) excludes the president, <PERSON> made a clear distinction between the president himself and his office:\nThe Office of the President is run by members of the civil service; they are audited by the auditor general and can be called before parliament to answer questions, which essentially means that they can be asked questions by us.", "957" ], [ "Trinidad & Tobago: Down the Rabbit Hole? · Global Voices\nFurther to the outrage expressed by political bloggers in Trinidad and Tobago earlier this week, the country's Parliament convened to debate the controversial Section 34, which resulted in it being repealed – but citizens, both on and offline, seem to be taking limited comfort in the law's recall.\nThe blogger behind The Eternal Pantomime practically live blogged the Parliamentary proceedings on Facebook, then summarized her impressions in a post called “34Gate”:\nIn the aftermath of the Barnum and Bailey Circus Show that passed for a debate…the crucial questions still remain unanswered.\nNo member of the Cabinet has yet satisfied the public’s concern about why they decided to pluck Section 34, along with 4 other minor clauses, out of the Indictable Offences Act and proclaim it on the evening of August 30th while most of the nation was busy with Independence celebrations…and there was I simply thinking is because <PERSON> love to fete! Nope, all the fetes were weapons of mass distraction.\nThe Opposition asked the same questions in each of its presentations: Why were the provisions agreed to by Senator <PERSON> ignored, and parts of the Bill proclaimed; and why was that particular clause pulled out for proclamation when it was proclaimed in the manner it was proclaimed. However they did all manage to agree on repealing the Law retroactively.", "957" ], [ "the Bill now moves on to the Upper House.\nIn a section of the post sub-titled “How It went Down”, the blogger continued:\nWhat we also learned is that our silkened luminaries, after hustling to proclaim Section 34 on August 30th, realised that the Bill was flawed and hustled just as quickly to repeal it, all on their own….no public pressure from the Opposition and the US…they did this for us, the nation, because they always listening to us. Doh mind <PERSON> could never answer any of our questions directly.\nShe also detailed how Section 34 had “a different wording before it was passed in the Lower House and went to the Senate” and how, “when the Bill got to the Senate, under Justice <PERSON>’s stewardship the wording changed”:\nThe Opposition asked why was there a change in the wording of the Bill between both Houses…this question was never answered.\nAt no point in time in the course of the debate did any member of the Cabinet read or quote from the Hansard…which has on record <PERSON> agreeing to undertaking certain provisions before proclaiming the Bill. It was only the Opposition quoting from the Hansard.\n<PERSON> concluded:\nThe biggest blow to the government’s case though is DPP <PERSON>’s claim that he was not consulted on the Bill, and further, after giving the time line of the Bill’s passage and proclamation, arriving at the conclusion that it appears to be a conspiracy.\nThe Opposition has now laid a careful case for why they cannot trust the Government and why the public cannot trust them either.\nPlain Talk, meanwhile, thought that the Section 34 “fiasco” had “the potential for damaging the sanctity of some of this country's highest Offices and bringing into question the credibility of their holders”:\nIf one were to put God out of one's thoughts for a minute and ponder the implications of the issue based solely on the evidence already in the public domain it could appear as if there was a massive conspiracy to utilize the Parliament to create an escape for (at least) two party financiers of the government and if that is what occurred in reality then surely we need to stop the conversation right here and begin whatever passes for impeachment proceedings in this country.\nThe blogger then posed a few critical questions “to see just how deep the rabbit hole goes” and concluded:\nSurely everyone concerned on all sides of the political and national divide must be aware that we have crossed the Rubicon here, that we cannot simply pick up our marbles and move on.\nThis matter has to be taken to a conclusion that restores public confidence in the institutions of governance and ought not to be considered resolved until all those who were involved in any way are, at the very least, removed from public office and investigated for any wrongdoing or misbehavior.\nAgainst this backdrop, diaspora blogger <PERSON> noted that a “certain minister” had “been seen in Tobago sipping champagne with the owner of a resort where his ministry held a retreat” and commented:\nSaid resort is owned by one of the two men currently taken advantage of the proclaimed section 34 of Administration of Justice (Indictable Proceedings) Act.", "289" ], [ "Trinidad & Tobago: Where’s the Integrity? · Global Voices\nTransparency and good governance have been popular topics in the Caribbean blogosphere of late, thanks to stories on financial impropriety, concerns over massive spending of taxpayers’ dollars and anxiety over freedom of the press.\nThe latest debacle over integrity (or lack thereof?) comes from Trinidad and Tobago, where, in the last few weeks, a second attempt to establish an Integrity Commission has come to a crashing halt amidst revelations that the Chair of the Commission, a Catholic priest, had committed acts of plagiarism in his weekly column for a local newspaper. To add insult to injury, Fr. <PERSON> claims that he drew this act to the attention of President <PERSON>, whose job it is to appoint members of the Commission, and was told it was “okay” – this decision allegedly from a man who spent years at the helm of the University of the West Indies. Father <PERSON> has since resigned from his post, citing Canon Law as the primary reason for his withdrawal.\nTo add even more fuel to the fire, the journalist who drew attention to the plagiarism in the first place, has been fired from his post at Newsday, supposedly in retaliation for his actions – and even though the Media Association of Trinidad and Tobago appears to have remained silent on the issue, bloggers certainly have not, even posting their views on Twitter.\n<PERSON>, a Trinidadian journalist-turned bogger who now resides in Barbados, has been following developments from the outset.", "957" ], [ "As early as May 7, he published a letter he wrote to local media houses:\nMy colleague <PERSON> quite responsibly brought to national attention the use by putative Integrity Commission Chair, <PERSON>, of arguments and language copied from (1) an op-ed piece in the New York Times of 9 December; and (2) a column by <PERSON> published in the National Catholic Weekly on 30 March.\nI invite citizens to locate on the Net and compare a column written by <PERSON> in the New York Times on 7 May, 2006, called, “Marshmallows and Public Policy” with one titled, “The Marshmallow Test” published a week later in the Guardian under the byline of the good <PERSON>.\nIf once is mistake and twice, habit, would three times be standard operational procedure? What does this reveal about the integrity of Mr <PERSON>? As with governments, do countries get Integrity Commissions they deserve?\nFellow blogger <PERSON> backs up B.C.'s position in a post from the same date:\nSomehow I don’t feel a self-confessed, under-pressure, serial plagiarist should be allowed to even come within 1000-feet of a member of the Integrity Commission much less chair it.\nIf <PERSON> didn’t point out the plagiarism to The Father would he have confessed? That is the big question but the answer seems horribly obvious. And as <PERSON> said ‘I found the apology unconvincing and I would have let the matter rest there, except I am now wondering what will happen when, as chairman of The Integrity Commission, Mr. <PERSON>, finds himself under pressures rather more intense that writing a weekly newspaper column.’ Please note the inverted commas and thus no plagiarism.\n<PERSON>, himself no stranger to being fired from mainstream media gigs, continued to keep a close eye on the situation, eventually posting this blog entry once he noticed that “Newsday has not run my erstwhile newspaper and still Humanist Association colleague <PERSON>’s column for the last two Fridays. I suspect there is a connection to <PERSON> having done Trinidad & Tobago and the world a favour by uncovering the hypocrisy of our own plagiarizing priest/wannabe Integrity Commission Chair, the good <PERSON> ‘Hey, I Completely Forgot About Copying That David Brooks Column’ <PERSON>.” He then goes on to publish the third column of <PERSON>'s that had failed to appear in print.\nOther bloggers soon rallied to <PERSON>'s cause once it was confirmed that the journalist had indeed been fired. <PERSON> writes:\nAnd so after two weeks of suspense – literally, too, just leaving him dangling, not using columns he dutifully supplied, without the common decency of an explanation – the Trinidadian newspaper, Newsday, has sacked <PERSON>, easily its best writer and the only semi-public figure to have displayed any integrity in the whole Integrity Commission bullshit affair; and you have to take your hat off to Trinidad; nowhere else would have the gumption to publicly punish someone for doing the right thing.", "892" ] ]

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[ [ "Ditch Everest. Switch to Chimborazo in Ecuador. Two reasons: 1) Because it is closer to the equator, it's peak is actually farther from the center of the Earth. 2) Because it is closer to the equator, you get more of a boost from rotation of the Earth. Everest at 29.59 degrees North loses almost 14% of the rotational velocity.\nSo launching from Chimborazo gets you additional altitude, and about 223 km/hr extra launch velocity.\nThe structure you have envisioned is massively beyond our current tech. At both ends.\nDigging a slanted tunnel roughly 100 km long is getting to silly proportions. The deepest mine right now is 4 km deep. This is getting pretty close to the limits of our tech right now.\nThe truss you envision holding the launch tube is grotesquely beyond what we can build now.\nThe launch energy needs to be supplied. You need electromagnets up the length of the tube. The energy they need to supply, assuming a constant acceleration, increases as the speed increases. So you need to run gargantuan power cables up the structure as well.\nYou might get someplace by forgetting the extension above and below the mountain.", "234" ], [ "You could have some sort of electromagnetic launcher that pushed a sled that carried your orbiter. Assuming a 50 km track and only 1g, you get 1 km/s in 100 seconds, pretty close to Mach 1, up the mountain. This is fast enough that the sled could detach and the orbiter take over its own burn. The first 25 km or so of the track would be level then curve up the mountain.\nThere are lots of variations on this. For example, the sled could also be a rocket motor that acted as a first stage. Or you could amp up the acceleration up the hill. At 4 g you get pretty close to Mach 2, in 25 seconds.\nYou can get an idea of what you are gaining from launching from the mountain. At 4g you are basically getting the first 25 seconds of rocket power from your launch sled. Suppose you were able to build the truss and extend the ramp another 50 km. This gives you only about another 10 seconds. The part on the mountain might be worth it. Building this currently-impossible truss seems to be a diminishing return.", "234" ], [ "Must admit I've been toying with a similar idea, except at interplanetary scale.\nThe huge advantage is that you are free of rocket equation constraints. As all the energy is delivered externally, you don't have to hand wave about Bussard Ramjets and the like. The presence of a catcher is also required, unless you are going to try and carry all the fuel for the slowdown phase, which pretty much defeats the point. If you are doing that then you might as well have a detachable 'acceleration phase' stage.\nSo what are the problems:\n1) As mentioned above, massive sustained acceleration, unless you have an amazingly long rail gun assembly. In a zero-g environment, a structure that is 100s of km long is not impossible. I would presume that in a zero-g vacuum environment a barrel would not be required, if your magnets can keep the projectile going straight. Indeed, at the speeds involved a physical barrel would just be a hazard.\nFor the payload, you'd have to go beyond acceleration couches. Think full immersion in a fluid (no air gaps, even in the lungs or ears); possibly freezing solid. You want to avoid any density contrasts within the ship in the acceleration/deceleration phases, to allow for the 100+g loads.", "898" ], [ "Once in cruise phase, you could come out of vitrification.\n2) Safety - Well.. you've accelerated a ship weighing hundreds of tonnes or more to, perhaps, 1000km/s. Going by the kinetic energy formula, e = 0.5mv^2, that would be ~10^17 J According to the Wiki, that's about a Tsar Bomba). So if anything goes wrong and you hit a planet (never mind a KBO) you will leave a noticeable dent. Even under good conditions, your catcher has to dissipate that amount of energy in a very short time. You'll need some very, very big capacitors.\n3) Practicality - As long as the system is reliable and the energy requirements are solved, then it avoids sending huge fuel tanks out on long, tedious orbits. So in many ways better than chemical rockets or solar sails. It also requires some form of hibernation/sleep tech, as above.\n4) Orbital Paths - You would probably need some form of adjustment onboard, but the calculations would be pretty trivial. You'd also want adjustment thrusters in case space junk was detected en-route, as collisions at cruising speed would be very very dangerous.", "947" ], [ "Sounds like a system of space planes that operate in the style of the railway system in the early 20th century. Since you said you already had space elevators in place, then you would need a series of space stations that act as rail stations near the elevators. The plane would dock at the station, which gives you quick turnaround time since they never enter an atmosphere. Since everything is in space the space station could be multilevel allowing several planes to dock at once.\nAs far as propulsion, I don't have an exact method, yet, but I know how to meet the \"2 days to Mars at closest approach\" requirement. An engine that is capable of sustaining 1g (Earth normal gravity) of constant acceleration will get a plane from Earth to Mars, assumed 65 million km separation, in 1d 21h 13m 1s. I would love to take credit for figuring that out, but alas, I can't. Check out How fast will 1g get you there? for a really great set of charts, graphs, and travel times. Somebody figured out all the travels times from Earth to each major body in the solar system.", "947" ], [ "That time is for constant acceleration for half the trip, then the ship flips a 180 and does a constant burn for deceleration.\nAnother benefit of constant acceleration is that it provides Earth normal gravity to the passengers and cargo. For more about this see Space Travel Using Constant Acceleration.\nAs I mentioned in the beginning, I would model the entire system around the railway of the early 20th century. Through a series of transfers, a person could travel across the US with little fuss.\nConstant acceleration even works for interstellar travel as well. It would take 1 year + the number of light years to reach any given star. So Alpha Centauri would take 5.2 years since it's 4.2 light years away.\nWhile I'm writing this I thought of a possible propulsion system, an EM Drive or an RF resonant cavity thruster. I know next to nothing about the science of the drive, but my understanding is that it's a \"fuel-less\" drive system. An engine produces an EM field, which it needs to run the lights and whatnot anyway, it diverts a portion of the EM to the propulsion system and it produces thrust. Anyway, it's a thought.", "947" ], [ "Hitching a lift on a comet is an interesting idea. It gives you a lot of fuel. However there are some pretty big downsides.\nFirst Delta-V: Getting to a comet is hard, but doable, Rosetta proves we can do it. Getting out of the solar system is harder but also do-able see the Voyager probes, the trick here will be finding a comet with an orbit that's easy to modify to take you where you want to go. You need to find a reasonably eccentric comet with the argument of periapsis pointing at the star you want to head towards. You can then use the comet as fuel to make a big burn when near periapsis to push the apoapsis out until you break orbit around the sun and \"whizz\" off to your destination.\nSecond fuel: While you will have a reasonably large amount of it the rocket equation is a problem. Because you have so much fuel you need a lot of it to move it.", "234" ], [ "The other problem is the fuel you have is going to be very low quality. It will be all mixed up, hydrocarbons, water, carbon dioxide, hydrogen, and dust. It will need processing very carefully before feeding into your engines. You will probably have more than one engine, each designed to burn/expel a different type of fuel. Making the big burn at periapsis is useful here because you can make use of solar energy as you make this burn.\nA better option may be to link up with a comet in your generation ship process the comet into fuel. Then when you reach the right point of the orbit detach and make the burn. This way you are only trying to accelerate the mass of the ship not the ship and a dirty great comet.\nLinking up to another comet when you arrive would done as a \"if there happens to be a comet heading in the right direction\" but should not be required as it would be impossible to know if such a comet existed in the target system with out already being there, getting the two orbits to sync up correctly would be extremely unlikely.", "199" ], [ "We can do some simple math here to see what our constraints really look like.\nLet's assume the meteor is mostly made of iron, because I heard that's a common composition in a museum somewhere. Assuming spherical shape, it would be around 3.3 * 10^16 kg. The kinetic energy of the meteor would therefore be 5.3 * 10^24 Joules. We'll assume this is the Kinetic energy at contact with zero gravitational potential energy left. Out of curiosity though, since the escape velocity of Earth is 11.2 km/s, 11.2^2 = 125 and 18^2 = 324, and so gravitational potential energy accounts for at maximum 38% of the total meteor energy.\nNow the one fundamental thing you have to keep in mind here is this: If you really really really want to stop the meteor instead of deflect it, then that is the raw amount of energy you have to deal with. You can dissipate it, you can reflect it, you can eat it (destruction), but no matter what, that is your the raw quantity of your challenge. This is a lot of energy. It is equivalent to 25 million Tsar Bombas. How do you absorb the energy of 25 million Tsar Bombas with a net? <PERSON> even describes this amount of energy as 11 times the estimated energy of the Chicxulub meteor impact that destroyed the dinosaurs (granted, our calculations are very rudimentary, e.g. sphere of iron). How do we stop 11 Chicxulub asteroids with a net? This is the question you may as well be asking.\nThankfully though, you have a very accommodating budget. So let's think of a solution!\nAgain, to emphasize, we have to dissipate energy. When you catch a baseball in a glove, or hit a tennis ball with a racket, the energy is dissipated through sound waves, stress, strain, and friction heat of the catching device. In more extreme catching scenarios, the catching device is specifically designed to break in intentional ways, in order to dissipate large amounts of energy (like table saws with flesh sensors or crumple zones in vehicles).", "921" ], [ "Probably our best approach for a net is to make it out of something really strong, but not so we can hold the meteor in the sky, rather so the meteor has to spend a ton of energy when it breaks the net.\nHere is how I envision it\nYou make a net out of tons of carbon nanotubes. You dissipate the energy by planning on the carbon nanotubes breaking. I'm no mechanical engineer, but I'll see what I can do with rough calculating. Apparently researchers have developed high-strength carbon nanotube films with up to 9.6 GPa of tensile strength before breaking. Say in the next 50 years we get that to 10 GPa (being conservative). It looks like carbon nanotubes usually survive about 15% to 20% stretching before they break. So if we have a net that is carbon nanotubes in one single direction, in a 10km by 10km square, then if force is applied down on the net evenly (such that tension is the main force at play, and we ignore shear forces), we can find out how much energy it costs to break the net at any given net thickness.\n* Pressure when net breaks = 10 GigaNewtons / meter ^ 2\n* Force when net breaks = net thickness * net width * pressure when net breaks\n* Energy when net breaks = force when net breaks * distance over which the force is applied\nSo\n* Energy when net breaks = (15% * 10km) * (10 km) * thickness * (10 GigaNewtons / meter^2), or in other words...\n* Energy when net breaks / thickness = 1.5 * 10 ^ 17 Newtons\nAnd so if we want to stop a 5.3*10^24 Joule projectile, we need a carbon nanotube net 10 Km long, 10 Km wide, and........\n36.... MILLION meters thick!\nSee here\nI'm actually impressed!! My first edit of this answer was so incredibly hilariously wrong! at 18 m/s we need 3.8 meters thick nanotube...... but at 18 km/s we need a 36 million meter thick net! Again, at 10 km wide and 10 km long.... 36 million meters is 5.6 times the radius of the Earth.\nYou can also fine tune it, if you look at the formulas. If you increase the stretch distance, you don't need as thick a material. But it will simply never compensate for that raw amount of energy. This meteor catching exercise is basically futile. but fun in any case!\nThe way the terms work out, you can squint your eyes and make a different net depending on how you interpret it.", "921" ], [ "<PERSON> gave some good information in his answer. Not only some numbers but how to get the numbers. I would like to add to it.\nThe approach I use is different from <PERSON>'s. I try to explain it here. To get acceleration at elevator foot the model subtracts $\\omega^2r$ from $GM_{planet}/r^2$ to get net acceleration. If a moon is the tether anchor, $GM_{moon}/r_{moon}^2$ is also included, whether this acceleration is added or subtracted depends if the tether is above or below the moon.\nThis net acceleration times kilograms gives the newtons payload exerts. This sets the thickness of the first length of zylon. The next length of tether is thicker as it supports the first length as well as payload. The model chops the tether into a 1000 lengths.\nHere is a screen capture from my look at a Mars elevator:\nIt is reassuring to me that my numbers aren't much different from Rominger's. For a safety factor of one, Rominger gives a Zylon taper ratio of 12.449 (vs 13 for my model). For a safety factor of three he gives a Zylon taper ratio of 1929.560 (vs 2016 for my model).\nMy model based on <PERSON>'s spreadsheet also gives ratio of Zylon tether to payload mass. For a safety factor of 1, you'd need 154 times the mass in Zylon as the payload being lifted. By \"payload\" I mean the elevator car and contents. The elevator car would need its own power source and engines.", "234" ], [ "So the actual cargo would be even less.\nWith a safety factor of 1, the slightest nick or scrape will cause a break. Given the large length of this elevator, I'd expect breaks to be frequent. I would not risk valuable cargo on such an elevator, much less human lives.\nGiven a sensible safety factor of three, tether to payload ratio would be 51,824.\nAnd this wouldn't be the entire elevator. There must be tether and a counterweight above Mars synchronous orbit to balance the downward newtons exerted by the lower elevator.\nA Zylon Clarke tower for Mars is implausible.\nHowever I don't write off the notion of Mars elevators. Mars equator isn't the only place to anchor an elevator. There are a number of scenarios I look at:\nLower Phobos Elevator\nUpper Phobos Elevator\nDeimos Elevator\nI am excited about elevators allowing a Zero Relative Velocity Transfer Orbit (ZRVTO) between Phobos and Deimos:\nTaper ratios and tether to payload ratios for these two elevators are quite modest:\nExtend the upper Phobos elevator and you can fling payloads to the Main Asteroid Belt as well as towards earth. And without prohibitive tether to payload mass ratios.\nExtend the lower Phobos elevator 1400 kilometers and you can drop payloads into orbits where periapsis passes through Mars' upper atmosphere. A few periapsis drag passes can circularize at low Mars orbit with a velocity of about 3.4 km/s. EDL would be easier than the 5.5 km/s atmospheric entry a payload incoming from an earth to Mars Hohmann would experience. Especially if the descent vehicle had some propellent and reaction mass from Phobos. Mars EDL could be considerably easier. Given a safety factor of three, tether to payload mass ratio would be .33.\nCan a Zylon Phobos elevator descend all the way to Mars upper atmosphere? If so, tether foot velocity with regard to Mars would only be .6 km/s. That's only about mach 2, the Concorde did that. But alas, given a safety factor of three, tether to payload mass ratio would be 638. I don't think a lower Phobos Zylon elevator 5,800 km long is practical.", "234" ], [ "Make the axial tilt of the planet be parallel to its orbital plane\nUranus does this already with an axial tilt of about 97 degrees off orbital plane though this isn't a great example because Uranus is just cold all the time. All it's a gas giant while the OP is implying a rocky planet.\nTorque required to keep the hot pole pointing towards the star\nThe trade-off to this approach is that without a source of torque to keep the hot pole pointing towards the star, the poles will alternate between extreme heat and extreme cold as the planet orbits the star. While this sounds a bit counter-intuitive, try it with a gyroscope. Pick an object to represent the sun. Spin up the gyroscope then suspend it from string. Walk all the way around the \"sun\". You'll notice that the gyroscope continues to point in the same direction, not towards the sun.", "188" ], [ "To get it to always point towards the sun, you'll need to move it by hand.\nTemperature Profiles\nThis is going to be a very interesting planet to build an ecosystem on. The sun will always move from North to South.\nThe North and South hemispheres will always alternate between extreme hot and extreme cold. Just like on earth, the equator will always receive sunlight though being on the border between the two temperature extremes will make for very interesting living. How fast the planet rotates along its axis will have a huge influence on the ambient temperature. Too slow and everything freezes in the winter. Too fast causes other problems.\nThere is no comparable climate zone on earth to what this planet will experience. In some respects it is close to the Arctic climate zone in that there are wild temperature swings between summer and winter but different in that summer at the poles will get the equivalent of equatorial solar radiation for the entire day.\nThe sun is always up until it dips below the horizon, thus bringing on winter. Astronomers on this planet will notice the gentle spiral of the sun as the year goes by.", "188" ], [ "It is possible.\nFirst, you did the math correctly, a center-to-center distance of 45500 km would result in geosynchronous orbit assume mass = 1 earth.This is well beyond the Roche Limit, so you bodies are stable.\nWhether this could happen is entirely dependent upon how fast the rotations were at the initial conditions. For our Earth and moon, the initial conditions result in a mutual tidal lock in about another 50 billion years -- though the expected red-giant phase of the sun may make this a moot point.\nCertainly Venus is spinning much slower than Earth even though the planets are very similar in other ways. So there is clearly great variety in initial conditions and/and events history to get us to this point in time. Your system is certainly within the realm of the possible.\nSince your planet is mutually locked with your moon, there is actually less tidal stress since the moon is always in the same place in the sky. Your planet would be stretched a little more in the moon direction because the planet would time to fully adjust -- bust this does not mean more strain. Earth bulge due to rotation is many times as large as tidal bulge, but the important factor is not how much out-of-spherical it is, it is how how strain in induced because of regular orbital cycle.\nYour planet tidal strain would be only that of the sun, which presumably would be similar to Earth. On Earth, solar tidal force is about 46% of the lunar tidal force. So, still some tidal strain, but only about one-third as much as on Earth (tidal forces are additive).\nThe difference in Planetary shape due to tidal locking is negligible on Earth (only about 1 meter in the deep ocean).However, since tidal force in your case is based on a moon 0.71 times the moons mass, but 8.4 times closer you should expect a permanent tidal bulge of about 428 meters in deep ocean.", "921" ], [ "Less over land (rock is heavier than water). May sound like a lot, but you would never notice it without good instrumentation.\nIf you want tidal strain, it is easily accomplished. Just make the moon's orbit eccentric. Because your moon is so close, the tidal effects are magnified considerably. Our moon varies from 363,104 to 405,696 km., a bit over 10% variation. Because tides are proportional to distance cubed, a 10% variation results in a 33.1% variation in tidal force. This would result in very significant tidal stress, large ocean tides, etc. The local residents would definitely notice these tides and would be able to correlate them to apparent changes in the moon diameter.", "188" ] ]

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[ [ "USB Desk Lamp - Dimmable - 3D Printed\nIntroduction: USB Desk Lamp - Dimmable - 3D Printed\nLamps for buy there are like sand by the sea. But a DIY lamp, with individual coloring, is always something special. I will not hide it, building this 3D printed lamp requires a bit of craftsmanship, especially soldering. You should also be able to handle a fretsaw (or electrical jigsaw), not to saw wood but sheet metal and polycarbonate \"glass\" ... I did both with a fretsaw.\nIn my opinion, the biggest difficulty in this project is definitely the soldering of the cut LED strips.\nThis lamp is very variable in its appearance due to the articulated design of the stand. In addition, light can also be adjusted individually. On the back is in addition to an On/Off switch a dimmer. With the 62 5V USB LEDs - I can say that the dimming works quite good. In order to generate sufficient brightness, a relatively large number of LEDs had to be accommodated, resulting in a rather large head (Ø 140mm).\nDimensions of the lamp: approx. H44 x L15 x W15cm\nFor this project you will need:\n* 1x … Ø 135mm white polycarbonate glass, 3mm thick, 70% translucency (I chose this \"glass\" so that the light area is uniform and you can not see the LEDs.", "492" ], [ "Who does not attach importance to it can instead take 100% translucent material, which of course also increases the light output).\n* 1x … 180 x 120 x 0,5mm tinplate\n* 1 x 2 Position Mini Toggle Switch\n* 1 x LED lighting strip (2m)\n* 1x … Ø M4 x 45mm from a threaded rod\n* 1x … Ø M4 x 65mm from a threaded rod\n* 1x … Ø M4 x 80mm from a threaded rod\n* 2x … Ø M3 x 16mm + 2 matching nuts (to connect head, neck and light panel)\n* 6x … wing nuts Ø 4mm18x\n* 14 ... washers Ø 15 x Ø 4,5mm\n* 6x … self-tapping screws Ø 2,2 x 9,5mm\n* 4x … self-adhesive rubber pads Ø 8x1,6mm\n* ... thin copper wire (for soldering)\n* ... thin 2-wire cable (for the USB power connector)\n* ... USB Type A plug with cable\n* ... soldering iron\n* ... solder\n* … fret saw (jigsaw)\n* ... textile tape\n* ... glue\n* ... screwdriver\nHere you can get some of the necessary parts:\n* LED strip: LED Beleuchtungsstreifen, USB TV Hintergrundbeleuchtung 6.56Ft/2m LED Band, Nicht wasserdicht SMD 3528 5V warmweiß https://www.amazon.de/dp/B07VWRJVCV/ref=cm\\_sw\\_e....\n* IMPORTANT!: I do not advise the installation of another or higher wattage light source, because of too much heat development!\n* Dimmer: ANGEEK PWM Motor Drehzahlsteller Modul Niederspannung DC 1,8V - 12V 2A https://www.amazon.de/dp/B07RM6LYC3/ref=cm\\_sw\\_e...\n* USB charging adapter: AmazonBasics - USB-Ladeadapter mit 1 Anschluss (2,4 Ampere) - <PERSON>; 2 Stück von Amazon.de https://www.amazon.de/dp/B0773BH9MB/ref=cm\\_sw\\_em...\nThe files must be printed in the following number of copies:\n* 1x USB_Lamp_body.stl\n* 1x USB_Lamp_front.stl\n* 1x USB_Lamp_neck.stl\n* 1x USB_Lamp_dimmerknob.stl\n* 1x USB_Lamp_back.stl\n* 2x USB_Lamp_foot.stl\n* 4x USB_Lamp_leg.stl\n* 4x USB_Lamp_spacerwasher.stl\n3D Printing Print Settings:\n* Printer Brand: Prusa\n* Printer: I3 MK3S\n* Supports: No\n* Resolution: 0.2\n* Infill: 20\n* Filament: PLA, Prusa Galaxy Black, ICE Romantic Red\nAfter you have printed all parts start with ….", "858" ], [ "Bedside Lamp (Box) - LED 12V 2.5W - 3D Printed\nIntroduction: Bedside Lamp (Box) - LED 12V 2.5W - 3D Printed\nI have already published a bedside lamp here: https://www.instructables.com/Bedside-Lamp-LED-12V-25W-3D-Printed/ ... lamp head in tube form.\nBut for those who like it more square, this one now has a box shape and was originally the first bedside lamp I have designed and printed. The design is based on \"PLAzzy Dog Lamp - LED 12V 2.5W - 3D Printed\" ...", "858" ], [ "that cannot be denied!\nThe assembly is in many parts identical with \"Bedside Lamp (Tube)\".\nThe files must be printed in the following number of copies:\n* 1x BSL_LED Lamp_head.stl\n* 1x BSL_LED Lamp_back.stl\n* 1x BSL_LED Lamp_neck.stl\n* 2x BSL_LED Lamp_leg.stl\n* 2x BSL_LED Lamp_foot.stl\n* 1x BSL_LED Lamp_spacerwasher.stl\n* 1x BSL_LED Lamp_lightsocket.stl\nPrint settings:\n* Printer brand: Prusa Printer: I3 MK3S\n* Supports: No\n* Resolution: 0,18\n* Infill: 20%\n* Filament brand: Prusa; ICE Filament color: Galaxy Black, Silky Silver; Romantic Red\n* Filament material: PLA\nAfter you have printed your parts ...\nRemark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.\nSupplies\nFor this project you will need:\n* 1x … 64x64x3mm white polycarbonate glass, 70% translucency (or transparent polycarbonate glass or twin wall-sheet). I used polycarbonate glas - because of the more pleasant light.\n* 1x … Ø 4x55mm from a threaded rod (or screw Ø m4 x 60 and saw of the screw head)\n* 1x … Ø 4x45mm from a threaded rod (or screw Ø m4 x 50 and saw of the screw head)\n* 2x … Ø M3x20mm + plus 2 matching washers (to connect head, neck and light base)\n* 4x … wing nuts Ø 4mm\n* 10x … washers Ø 15x4,5mm\n* 5x … self-tapping screws Ø 2,2x 9,5mm\n* 4x … self-adhesive rubber pads Ø 8x1,6mm\n* Switch wire, 10cm\n* Drill, Ø 2mm\n* Fretsaw\n* Soldering Iron\n* Solder\n* Glue\n* Sandpaper\n* Phillips screwdriver\nEspecially for the light installation you need:\n* AC/DC Socket 5,5/2,1 mm\n* 4G bulb socket\n* 2 Position Mini Toggle Switch\n* 4G LED bulb 2,5W/250Lm\n* AC/DC power adapter\nIMPORTANT!: I do not advise the installation of a higher wattage bulb, because of too much heat development!\nSome of these parts you can find here:\n*\n* Light: Trango 5er Pack G4 LED Leuchtmittel TGG415-2.5W - 12V AC/DC - 2.5 Watt 250 Lumen mit 3000K Power SMDs warmweiß https://www.amazon.de/dp/B00LEFGDOM/ref=cm_sw_em_...\n* Power adapter: LEICKE Netzteil 12V 2A | 12V 2000mA | Ladegerät 24W für LCD, LED-Streife https://www.amazon.de/dp/B00LEFGDOM/ref=cm_sw_em_...\n* Bulb socket https://www.amazon.de/dp/B00NP08M4S/ref=cm_sw_em_r...\n* AC/DC Socket https://www.amazon.de/dp/B00EQ1UWX4/ref=cm_sw_em_r...\nStep 1: Preparations - Overview\nBefore you start ... here an overview:\n* All print parts.\n* Different \"glass\" options.\n* All possible parts you need for assembly.\n* All parts you need for the electric.", "858" ], [ "Lamp \"Sunset\" - LED 12V - 3D Printed\nIntroduction: Lamp \"Sunset\" - LED 12V - 3D Printed\nI came up with the idea for this lamp when, just for fun, I held a light source behind the Fruit Basket \"Cradle\", which I published here some time ago (https://www.instructables.com/Fruit-Basket-Cradle-3D-Printed/).\nIf someone had told me a few years ago that I would ever print a lampshade, I probably would have thought he was crazy. Now it has happened!\nA lamp with half sunset colors, with a plain monochrome lampshade or with a classic black and white striped pattern, a lamp whose lampshade and all other parts give free play to the color design! A self-printed lamp, with individual coloring, is always something special!\nA lamp made entirely of printable parts, without any support, easy to assemble and that creates an ambient light!\nAs with some of my other projects you need a little bit of craftsmanship here too, a.o.", "492" ], [ "soldering.\nWith 3000K the light is considered warm white. The power consumption is 2.5 watts.\nDimensions:\n* H over all 29.5 cm\n* H lampshade 25 cm\n* Ø foot 15 cm\n* Ø lampshade bottom 12.5 cm\n* Ø lampshade top 10 cm\nFiles to print:\n* Lamp_Base.stl\n* Lamp_FootDown.stl\n* Lamp_FootTop.stl\n* Lamp_GlassRingBottom.stl\n* Lamp_LampshadeBase.stl\n* Lamp_LampshadeGuide.stl\n* Lamp_LampshadeStrut.stl (20x)\n* Lamp_LampshadeTopGrid.stl (Lamp_LampshadeTopClear.stl/Lamp_LampshadeTopClosed.stl)\n* Lamp_LEDSocket.stl\n* (Lamp_LampshadeLockingRing.stl)\nPrint Settings\n* Printer brand: Prusa\n* Printer: MK3S / Mini\n* Supports: No\n* Resolution: 0,20\n* Infill: 5%\n* Filament brand: Prusa; ICE\n* Filament color: Galaxy Black; Wintershine White, Romantic Red, Young Yellow\n* Filament material: PLA\nRemark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.\nSupplies\nFor this project you will need:\n* 1x … Ø 99 mm polycarbonate twin-wall sheet, thickness 4mm or 6mm (or transparent polycarbonate glass)\n* (1x … Ø 86 mm polycarbonate twin-wall sheet, thickness 4mm or 6mm (or transparent polycarbonate glass))\n* 8x … self-tapping screws Ø 2,2 or 2,9 x 9,5mm\n* threaded screw Ø 4x20mm and matching nut\n* switch wire, ca. 10cm\n* Drill, Ø 2mm\n* Fretsaw\n* Soldering Iron\n* Solder\n* (Super)glue\n* Sandpaper\n* Phillips screwdriver\n* piercer\nFor the light installation you need:\n* AC/DC Socket 5,5/2,1mm\n* 4G bulb socket\n* 2 Position Mini Toggle Switch\n* 4G LED bulb 2,5W/250Lm IMPORTANT!: I do not advise the installation of a higher wattage bulb, because of too much heat development!\n* 12 V AC/DC power adapter\nAll these parts you can find here:\n* Light: Trango 3er Pack LED Leuchtmittel mit G4 Fassung zum Austausch vom G4, MR16, GU5.3 Halogen Leuchtmittel TGG415-2.5W - 12V AC/DC - 2.5 Watt 250 Lumen mit 3000K\nhttps://www.amazon.de/dp/B00LC0DSEC/ref=cm_sw_em_r...\n* Bulb socket: 10 Stück MR16 GU5.3 MR11 GU4 Fassung 12V mit Kabel\nhttps://www.amazon.de/dp/B00279SBDA/ref=cm_sw_em_r...", "858" ], [ "Lamp \"DuoLux\" - LED 12V - 3D Printed\nIntroduction: Lamp \"DuoLux\" - LED 12V - 3D Printed\nI already have some lamps printed and in use here at my place. Inspired by the contest on the subject of lamps, I have now designed this lamp.\nAs with some of my other projects you need a little bit of craftsmanship here too, a.o. soldering..\nAs the name \"Duolux\" suggests, this project involves two light sources.", "492" ], [ "A further development of my project Bedside Lamp \"Tube\" (https://www.instructables.com/Bedside-Lamp-LED-12V-25W-3D-Printed/) , but because of the two light sources with of course a double light output (with 2x 250 lumens). With 3000K the light is considered warm white. The power consumption is 2.5 watts for each LED unit.\nIn colorful version, it can also serve well as a children's room lamp.\nA self-printed lamp, with individual coloring, is always something special!\nDimensions:\n* H 245 mm\n* W (socket) 160 mm\n* W (both tubes) 195 mm\n* L (tubes) 102 mm\nFiles to print:\n* Lamp DuoLux_tuberight.stl\n* Lamp DuoLux_tubeleft.stl\n* Lamp DuoLux_basering.stl\n* Lamp DuoLux_back.stl (2x)\n* Lamp DuoLux_centralmount.stl\n* Lamp DuoLux_centralmounttop.stl\n* Lamp DuoLux_knob.stl (4x)\n* Lamp DuoLux_ledsocket.stl\n* Lamp DuoLux_leg.stl (2x)\n* Lamp DuoLux_sliderail.stl\n* Lamp DuoLux_glassfixingring.stl (2x)\nPrint Settings\n* Printer brand: Prusa\n* Printer: MK3S / Mini\n* Supports: No\n* Resolution: 0,18\n* Infill: 5% except: centralmount, centralmounttop 30% and knobs 50%\n* Filament brand: Prusa; ICE\n* Filament color: Galaxy Black; Romantic Red, Wintershine White\n* Filament material: PLA\nRemark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.\nSupplies\nFor this project you will need:\n* 2x … Ø 65 mm polycarbonate twin-wall sheet, thickness 6mm or 4mm (or white polycarbonate glass 3mm thick, 70% translucency or transparent polycarbonate glass)\n* 2x … Ø 4x45mm from a threaded rod (or screw Ø m4 x 50 and saw of the screw head)\n* 10x … Ø M3x15mm + plus matching nuts (to connect tubes with central mount and LED base to tube)\n* 4x …nuts Ø 4mm (for the knobs)\n* 8x … washers Ø 15x4,5mm\n* 11x … self-tapping screws Ø 2,2x 9,5mm\n* switch wire, ca. 10cm (5cm black, 5cm blue, for a better recognition when wiring)\n* (4x … self-adhesive rubber pads Ø 8x1mm)\n* 2x small luster clumps\n* Drill, Ø 2mm\n* Fretsaw\n* Soldering Iron\n* Solder\n* (Super)glue\n* Sandpaper\n* Phillips screwdriver\n* piercer\nFor the light installation you need:\n* AC/DC Socket 5,5/2,1mm\n* 4G bulb socket (2x)\n* 2 Position Mini Toggle Switch\n* 4G LED bulb 2,5W/250Lm (2x) IMPORTANT!: I do not advise the installation of a higher wattage bulb, because of too much heat development!\n* 12 V AC/DC power adapter\nSome of these parts you can find here:\nLight: Trango 3er Pack LED Leuchtmittel mit G4 Fassung zum Austausch vom G4, MR16, GU5.3 Halogen Leuchtmittel TGG415-2.5W - 12V AC/DC - 2.5 Watt 250 Lumen mit 3000K\nhttps://www.amazon.", "858" ], [ "Presentation Stand - 3D Printed\nIntroduction: Presentation Stand - 3D Printed\nIf you are looking for a presentation stand for a special object ... this one might be it!. The different 3D models shown in the video or in the pictures give you an impression how it could look like. Of course the possibilities of 3D printing are not as manifold as shown in the video.\nThe transparent nylon thread makes it look like the plate is floating between the open arcs.\nDimensions: L200 x H158 x W160mm. Base Ø 80mm, plate Ø 105mm.\nThere are 4 files to print for this object:\n* Arc_big.stl\n* Arc_small.stl\n* Base.stl\n* Plate.stl\nAfter you have printed these parts ...\nRemark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.\nSupplies\nThe plate is held in position by 4 nylon threads. For the assembling you need:\n* Nylon thread Ø 0,35mm\n* Superglue\n* Some patience ;-) … when positioning the plate\nStep 1: Inserting the Big Arc\nStart by gluing the big arc into the base. I used superglue. A small bulge in the middle of the arc will help you with the alignment.\nPress the arc firmly into the recess. Hold it for a moment!\nBefore you continue, wait a little while for the glue to set.\nStep 2: Inserting the Small Arc\nThen you can insert the small arc.", "646" ], [ "I used a screwdriver to press it into place.\nTo ensure a good fit, the fitting accuracy is very tight. It may be necessary to correct the fit with a cutter knife or sandpaper.\nStep 3: Attaching Nylon Threads to the Plate\nNow prepare 4 nylon threads with approx. 20-25cm length. Insert them from the bottom of the plate. A multiple knot is enough to fix the thread to the plate.\nStep 4: Place and Align the Plate\nStart by hanging the plate into the big arc. The thread length between the tip of the arc and the plate should be about 6cm.\nThere is a small slit (W 0,3mm) at the end of the arc - apart from the hole - to trap the thread initially for temporary fixation.\nThen take the threads for the small arc and proceed in the same way.\nWhen the plate is aligned horizontally - at a height of about 10cm from the bottom - you can pull the thread through the hole 1-2 more times and clamp it. This should be enough for a permanent fixation. Now you can cut of the thread ends.\nDue to the material (PLA) the load is limited ... about 150 gr.\nStep 5: Color and Material Suggestions\nSome more color and material combinations in 3D model.", "56" ], [ "Bedside Lamp (Tube) - LED 12V 2.5W - 3D Printed\nIntroduction: Bedside Lamp (Tube) - LED 12V 2.5W - 3D Printed\nLamps for buy there are like sand by the sea. But a DIY lamp, with individual coloring, is always something special. I will not hide it, building this 3D printed lamp requires a bit of craftsmanship, a.o. soldering.\nThis lamp can be printed as switch or dimmer version.\nIf you like the lamp head a bit more square, then you can find another model here: https://www.instructables.com/Bedside-Lamp-Box-LED-12V-25W-3D-Printed/\nSo you have to decide first, what kind of version you want.", "492" ], [ "Whereby I have to say that my dimmable version does not dim smoothly. But at least two brightness levels are available. If you don't like it, you can always change to the switch version later!\nPhotos or a video are giving you suggestions for colours of your lamp.\nAfter you have printed your parts ...\nRemark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.\nSupplies\nFor this project you will need:\n* 1x … Ø 65 mm white polycarbonate glass 3mm thick, 70% translucency\n* 1x … Ø 4x55mm from a threaded rod (or screw Ø m4 x 60 and saw of the screw head)\n* 1x … Ø 4x45mm from a threaded rod (or screw Ø m4 x 50 and saw of the screw head)\n* 2x … Ø M3x20mm + plus 2 matching washers (to connect head, neck and light base)\n* 4x … wing nuts Ø 4mm\n* 10x … washers Ø 15x4,5mm\n* 5x … self-tapping screws Ø 2,2x 9,5mm\n* 4x … self-adhesive rubber pads Ø 8x1,6mm\n* Switch wire, 20cm\n* Drill, Ø 2mm\n* Fretsaw\n* Soldering Iron\n* Solder\n* (Super)glue\n* Sandpaper\n* Phillips screwdriver\nEspecially for the light installation you need:\n* AC/DC Socket 5,5/2,1 mm\n* 4G bulb socket\n* 2 Position Mini Toggle Switch (if you do not want the dimming function)\n* 4G bulb 2,5W/250Lm (IMPORTANT!: I do not advise the installation of a higher wattage bulb, because of too much heat development!)\n* Dimmer DC 1,8V - 12V 2A\n* 12 V AC/DC power adapter\nSome of these parts you can find here:\nLight: Trango 5er Pack G4 LED Leuchtmittel TGG415-2.5W - 12V AC/DC - 2.5 Watt 250 Lumen mit 3000K Power SMDs warmweiß\nhttps://www.amazon.de/dp/B00LEFGDOM/ref=cm_sw_em_...\nDimmer:ANGEEK PWM Motor Drehzahlsteller Modul Niederspannung DC 1,8V - 12V 2A https://www.amazon.de/dp/B07RM6LYC3/ref=cm_sw_em_... (if you do not want the switching function)\nPower adapter: LEICKE Netzteil 12V 2A | 12V 2000mA | Ladegerät 24W für LCD, LED-Streifen\nhttps://www.amazon.de/dp/B01I4YDJZG/ref=cm_sw_em_r...\nThe files must be printed in the following number of copies:\n* 1x BSL_Tube_head.stl\n* 1x BSL_Tube_light_socket.stl\n* 1x BSL_Tube_neck.stl\n* 1x BSL_Tube_back_switch.stl or 1x BSL_Tube_back_dimm.stl\n* 1x BSL_Tube_dimmswitch.stl (this part you only need for the dimmable version)\n* 2x BSL_Tube_foot.stl\n* 2x BSL_Tube_leg.stl\n* 1x BSL_Tube_spacerwasher.", "858" ], [ "„Black Widow“ Mobile - 3D Printed\nIntroduction: „Black Widow“ Mobile - 3D Printed\nA \"Black Widow\" in her web ... waiting for prey! ... a light breeze or a gentle blow will get the spider moving!\nIf you put the \"Black Widow\" installation between a light source and a wall, you can achieve very nice creepy effects. The right thing for Halloween! (see video). However, the light source must consist of only 1 light point. A light source consisting of several LEDs, does not work properly.\nDimensions:\n* H 190 mm\n* W base 110 mm\n* W net 183 mm\nFiles to print:\n* base.stl\n* spider.stl\n* web.stl\nPrint Settings:\n* Printer brands: Prusa, Flashforge\n* Printer: MK3S / Mini / Finder\n* Supports: No\n* Resolution: 0,2\n* Infill: 15%\n* Filament brand: Prusa; ICE\n* Filament color: Galaxy Black, Galaxy Silver; Romantic Red\n* Filament material: PLA\nRemark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.\nAttachments\nSupplies\nTo connect the 3 printed parts you need:\n* 30 cm nylon thread Ø 0.25 mm (or less Ø)\n* super glue\nThe spider web is printed very filigree (this is intended) and must therefore be very carefully released from the printing plate.\nStep 1: Attaching Spider Web Ring to Base\nThe insertion of the spider web ring must be tried before gluing.", "646" ], [ "It is very tightly dimensioned, which is intended. The width of the recess in the base is definitely 0.15 mm wider than the width of the spider web ring.\nSee also „Remark“ in the introduction!\nIn my case, it fits so well that gluing is not necessary at the moment!\nStep 2: Prepare Hanging of the Spider\nTo hang the spider in the spider web ring, there is a hole in the spider that goes vertically through the body.\nTake a nylon thread Ø 0,25 or less, about 30cm long and make a multiple knot at one end. Then pass the thread from through the back of the spider to the front.\nStep 3: Hanging the Spider\nTake the spider with the thread inserted and pass the thread through the hole in the web ring from below.\nNow you have to try to find the position of the spider in the center of the net. This is a bit fiddly and requires - as in my case - several attempts.\nWhen the spider is hanging in the right position, you should try to find the resting position - parallel in the net. You can achieve this by lifting the thread. By turning the knot you can find the right position with a little patience.\nI hope you had no problems with printing and assembling the mobile!\n... and now have fun with the \"BLACK WIDOW\" mobile! Maybe you can also create some spooky effects - like in my video!", "879" ], [ "Plastic Pipe Lamp - LED 12V 4W - (\"Drainpipe Lamp\")\nIntroduction: Plastic Pipe Lamp - LED 12V 4W - (\"Drainpipe Lamp\")\nAfter a renovation in the bathroom were some pipe elements left. These had been lying in the basement for a few years now, waiting to be either disposed of or put to good use.\nWhen I heard about the contest \"Plastic Challenge\" here, I had the idea to make a lamp out of it. Here now comes the result!\nDimensions:\n* Height: 23.5 cm\n* Length: 13 cm\n* Width: 20 cm\nThe pipes are made of polypropylene (PP). Polypropylene is a thermoplastic material.\nSupplies\nThese were the parts that were messing around in my basement. I was able to use two parts of them for this project.\nTo build this lamp you need:\n* PP pipe repair joint with rubber sealing ring 130 x Ø 128mm (lamp \"head\")\n* Drain pipe 800 x Ø 40 x 1.8mm (\"legs\" and \"feet\")\n* Ø 110 mm polycarbonate twin-wall sheet, thickness 4mm or 6mm (or transparent polycarbonate glass)\n* a piece of tin plate 120 x 25 mm\n* 8x self-tapping screws Ø 4 x 20 mm\n* 2x self-tapping screws Ø 2,2 x 9,5 mm\n* 2x threaded screws Ø 2,5 x 10mm with matching nuts\n* 2x screws 30 x Ø 6mm\n* switch wire, ca. 15cm\n* Drills, Ø 2mm, Ø 7 mm, Ø 8 mm\n* 4 wingscrews Ø 6mm\n* 2 nuts Ø 6mm\n* 6 washers Ø 18 x Ø 6,5\n* 150 mm x Ø 6 mm from a threaded rod\n* Miter saw\n* Fretsaw\n* Metal saw\n* Soldering Iron\n* Solder\n* Sandpaper\n* Phillips screwdriver\n* piercer\n...", "582" ], [ "and for the electrics:\n* AC/DC Socket 5,5/2,1mm\n* 4G bulb socket\n* 2 Position Mini Toggle Switch\n* bulb, socket MR16/GU5.3, 12V 4W - IMPORTANT!: I do not advise the installation of a higher wattage bulb, because of too much heat development!\n* 12 V AC/DC power adapter\nAll these parts you can find here:\n* Bulb socket: 10 Stück MR16 GU5.3 MR11 GU4 Fassung 12V mit Kabel\nhttps://www.amazon.de/dp/B00279SBDA/ref=cm_sw_em_r...\n* Power adapter: LEICKE Netzteil 12V 2A | 12V 2000mA | Ladegerät 24W für LCD, LED-Streifen\nhttps://www.amazon.de/dp/B00LEFGDOM/ref=cm_sw_em_...\n* Power jack: HSeaMall 5,5 x 2,1 MM DC Power Jack Buchse 3 Terminals Buchse Panel Mount Stromstecker Adapter mit Staubdicht Kappe 10 STÜCKEvon HiBuyEU\nhttps://www.amazon.de/dp/B07D4DLJ69/ref=cm_sw_em_r_mt_dp_M8NHG5TCTHWVKH32BX59?_encoding=UTF8&psc=1\n* Switch: ELEAR™ 10 X EIN/Aus Mini Miniatur Kippschalter Instrumententafel Wippschalter 2 Polig von Etocars\nhttps://www.amazon.de/dp/B01MXLZ7R1/ref=cm_sw_em_r_mt_dp_K3WEQ7HS7ED846P3X2MY?_encoding=UTF8&psc=1\nStep 1: Cut \"Legs\" and \"Feet\"\nNow you need a miter saw. Take a drain pipe 800 x Ø 40 x 1.8mm.\nSaw off 2 pieces of a length of 20 cm. One side at an angle of 60° and 4 pieces of a length 40 mm. One side also at an angle of 60°. Clean the edges with sandpaper.\nStep 2: Mounting \"Legs\"\nNow that all the parts are cut, you can start assembling. First you need to drill a few holes. The precise drilling of the holes on curves is not so easy, because the holes must be placed exactly at the highest point of the rounding.", "858" ] ]

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[ [ "Help debugging finite element solution in nonlinear elasticity\nI'm writing some code to solve problems in nonlinear elasticity using finite element methods. I have been following <PERSON>'s book but I am having trouble with some nagging details.\nMy question is related to which configuration variables to use for calculating different quantities. I'm working on static problems in the updated Lagrangian formulation, so for each \"time\" $t$ I have a loading coefficient $\\lambda_t$, and a displacement $\\sideset{^t}{}{U}$. In chapter 6, <PERSON> derives a linearization of the principle of virtual work, resulting in the equation (6.103): \\begin{equation} \\left(\\sideset{^t_{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{\\text{NL}}{K}\\right)U=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F \\end{equation} where $\\sideset{^t{t\\,}}{\\text{L}}{K}$ is the \"linear\" part of the incremental stiffness matrix in the configuration with displacement $\\sideset{^t}{}{U}$, $\\sideset{^t{t\\,}}{_\\text{NL}}{K}$ is the \"nonlinear\" part, $U$ is the displacement increment, $\\sideset{^{t+\\Delta t}}{}R$ is the externally applied load at \"time\" $t+\\Delta t$, and $\\sideset{^t_t}{}F$ is the nodal point force resulting from the stress, at \"time\" $t$.\nMy question is about actually implementing this as a system of nonlinear equations to be solved via <PERSON>'s method.", "935" ], [ "As I understand it, the idea is to consider a function $H(\\sideset{^{t}}{}U)=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F$, where $\\sideset{^t_t}{}F$ is a function of $\\sideset{^{t}}{}U$ via the stress.\nWe want to find a displacement $\\sideset{^{t+\\Delta t}}{}U$ s.t. the unbalanced force vector is zero: \\begin{equation} 0=H(\\sideset{^{t+\\Delta t}}{}U)\\approx H(\\sideset{^t}{}U)+\\nabla H(\\sideset{^t}{}U)\\left(\\sideset{^{t+\\Delta t}}{}U-\\sideset{^t}{}U\\right)=\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F - \\left(\\sideset{^t_{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{\\text{NL}}{K}\\right)U \\end{equation} so that $\\left(\\sideset{^t{t\\,}}{\\text{L}}{K}+\\sideset{^t{t\\,}}{_\\text{NL}}{K}\\right)$ is minus the Jacobian of the unbalanced force vector $\\sideset{^{t+\\Delta t}}{}R-\\sideset{^t_t}{}F$. Is this interpretation correct? Is the sum of the incremental stiffness matrices derived by <PERSON> exactly equal to minus the Jacobian of the unbalanced force vector, when all are evaluated in the same configuration? In implementing <PERSON>'s method, an iteration is introduced, so that we can write $U^{(k)}$ for the incremental displacement at the $k$th iteration. How does this affect the terms in the system of equations? At iteration $k$, are the integrals still calculated over the volume $\\sideset{^t}{}V$, or over $\\sideset{^{t+\\Delta t}}{}V^{(k-1)}$? What about the stress, and the stiffness matrices?", "804" ], [ "Finite strain FEM using an existing code that solves small strain elasticity\nI have an existing FEM code that solves the linear elasticity problem. I would like to use the same code for large strain rates, still using a simple material law (Saint Venant–Kirchhoff model).", "232" ], [ "[The problem I want to solve is a contact problem in which strain is larger than 1 very locally, close to the contact point]\nI believe I have two steps to take: take into account the nonlinear part of strain $\\nabla u \\cdot \\nabla u^T$, and solve the mechanical balance in the deformed configuration.\nCan this be done by successive iterations of the linear elasticity problem, e.g. using iterative mesh deformation and a fixed-point algorithm for the nonlinear strain term? Does this converge? References which would highlight the steps to be taken from small-strain elasticity are welcome.\nEDIT\nI would for instance like to know whether such an algorithm would work (there may be a couple mistakes in the details, for now it's rather the spirit of it I'm enquiring about):\nI want to solve $K u + \\nabla u^T\\cdot \\nabla u= Mf$.\nLet $(f^i)_{i\\leq n}$ be a sequence of functions with $f_n = f$, with each increment small enough.\nLet $i=0$, $U^0=0$, $K^0=K$.\n* Solve linear elasticity problem $K^i \\delta u^i = M f^i$.\n* Construct configuration $\\Omega^{i+1}$, and a change of variable $X^{i+1}$ from $\\Omega^{i}$ to $\\Omega^{i+1}$\n* let $U^{i+1} = U^i \\circ X^{i+1} + \\delta u^i$\n* Calculate $K^{i+1} = K_{\\Omega^{i+1}} + \\nabla {U^{i+1}}^T\\cdot \\nabla$ (there's probably something to do here as we develop $u=U+\\delta u$ in the double product, it doesn't write out nicely in tensor notation but should in the linear problem)\nAgain, the above is not to be taken as something thought over but rather the sort of thing I'd like to find in some report/textbook/publication. But maybe there's a crucial problem I don't see which would be the reason why finite strain codes are not presented as an extension of small strain ones?", "935" ], [ "Getting started with FEM: Ill-conditioned matrix when evaluating flux terms in conservation law?\nI have a system of conservation laws of the form\n$$ \\frac{\\partial \\mathbf{q}}{\\partial t} + \\nabla \\cdot \\mathbf{F}!\\left(\\mathbf{q}\\right) = 0 $$\nI want to use finite elements to solve this system. As an initial choice, I am using Legendre polynomials $\\phi$ for my function basis. Let $j$ be a polynomial index. If I substitute the decomposition of my unknown function $\\mathbf{q}$ and the flux function $\\mathbf{F}$,\n$$ \\mathbf{q}!\\left(t, x\\right) = \\sum\\limits_j \\hat{\\mathbf{q}}_j!\\left(t\\right) \\phi_j!\\left(x\\right) $$\n$$ \\mathbf{F}!\\left(\\mathbf{q}\\right) = \\sum\\limits_j \\hat{\\mathbf{F}}!\\left(t\\right) \\phi_j!\\left(x\\right) $$\nand finally write out the weak form (given some test volume $\\Omega$ with boundary $\\partial \\Omega$)\n$$ \\sum\\limits_j \\left(\\frac{\\partial \\hat{\\mathbf{q}}j}{\\partial t} \\int\\limits\\Omega \\phi_i \\phi_j + \\hat{\\mathbf{h}}j \\oint\\limits{\\partial \\Omega} \\phi_i \\phi_j - \\hat{\\mathbf{F}}j \\cdot \\int\\limits\\Omega \\phi_j \\nabla \\phi_i\\right) = 0 $$\nHere, I replaced $\\mathbf{F} \\cdot \\hat{\\mathbf{n}} = \\mathbf{h}$.\nMy problem occurs when I actually try to evaluate the surface second and third terms inside the parentheses. Because my problem is 1-dimensional, the second term amounts to just evaluating $\\phi_i \\phi_j$ at 1 and -1 and taking the difference ($\\hat{\\mathbf{n}} = \\pm \\hat{\\mathbf{x}}$ is the outward-facing normal).", "281" ], [ "In analogy with the stiffness matrix, we could write this as a matrix $\\mathbb{B} = {b_{ij}}$. Any given element $b_{ij}$ will be either 0 or 2 because the Legendre polynomials take the value of 1 or -1 at the edges of the domain. This matrix is sparse but singular. The third term exhibits a similar problem if we try to write it as a matrix $\\mathbb{C} = {c_{ij}}$.\nThe only way I know to solve for the $\\hat{\\mathbf{F}}_j$ and $\\hat{\\mathbf{h}}_j$ coefficients is by solving a matrix equation, but all my attempts to solve them (using PETSc) converge slowly and may not even be correct. I would like to use a preconditioner, but I get errors any time I try (PCSETUP_FAILED due to SUBPC_ERROR), even though I have specified the null spaces of these matrices.\nHave I approached this problem incorrectly altogether? Or is there a common way of overcoming this challenge, in PETSc or otherwise?", "935" ], [ "The biggest problem in answering to this question is that it's not as straightforward as you might think to see the physics in the equations until you see them fully developed, and even then you're doing your best to assign a meaning. As a graduate student in mechanical engineering, this was hard for me because I was used to using my physical intuition to guide me through the math forest.\nFor a FEM problem applied to modal analysis, you basically start with a strong form equation. For example, a free vibration of an elastic rod is given by: $$ \\lambda \\rho u + (Eu,x),_x = 0,\\ x \\in (0, L) $$ Here, $\\rho$ is the density, $E$ is the modulus of elasticity, and $u$ is the displacement. Let's apply a fixed boundary condition ($u(L) = 0$) and a free boundary condition (e.g. $-Eu,_x(0)=0$). You can transform it into the equivalent weak form by using a weighting function $w$: $$ \\int_0^Lw,_xEu,_xdx\\ -\\lambda\\int_0^Lw\\rho u\\, dx = 0 $$ This is where the math ends up losing it's physical interpretation. From here (and skipping a lot of rigor for brevity in this answer), we would basically restrict $w$ in a subset of the <PERSON> space, apply the <PERSON> approximation by discretizing the domain which creates the finite dimensional weighting function $w^h$ and solution $u^h$, make $u^h$ the sum of a <PERSON> function $v^h$ and a given function $g^h$, and then define the functions $w^h$ and $v^h$ as a finite sum of linearly independent basis functions (i.e $v^h = \\sum{A=1}^N c_A N_A$ and $w^h = \\sum_{B=1}^N d_A N_A$). By applying some linear algebra theorems and rearranging a lot, you eventually get the following equation: $$ (K-\\lambda^h_kM)\\psi_k = 0 $$ Here, $\\psi_k$ is the kth eigenvector, which represents the displacement. It's hard to get an appreciation for the math that I've glossed over. The book The Finite Element Method has the full explanation for how this is developed (Chapter 1 goes over the basics of the method, and Section 7.3 develops the frequency analysis portion).\nJust to clarify, we've simply called these matrices K and M, and the form of the equation bears a resemblance to a simple modal analysis for a beam, so we simply assign that as the physical interpretation. Really, the K and M matrices are highly dependent on the mesh and how the elements are connected.", "418" ], [ "These large matrices are constructed from each element in the mesh.\nThe discretization is really important. Physically for this problem, the nodes represent points at which we're calculating the displacement, and the elements connected to that node restrict its movement under an applied force. You can also think of the mesh for this problem as having $n$ number of rods connected to each other. In that way, each rod piece only really affects those it's connected to. Each element is represented by a small matrix. The element matrices are calculated like this: $$ m_{ab}^e = \\int_{\\Omega^e} N_a \\rho N_b\\,d\\Omega \\ k_{ab}^e = \\int_{\\Omega^e} N_{a,x} E N_{b,x}\\,d\\Omega $$ Here, $\\Omega^e$ is the domain of the element itself. When the element matrices get assembled into the global matrix, some elements in the large matrix will have terms added from several smaller matrices. This is a representation of how the topology from the mesh affects the global matrix.\nThe $N_a$ and $N_b$ symbols are the basis functions that span the subset of the Sobolev space we chose. These are very important because different basis functions changes the solution. We can choose to use linear or parabolic functions, or even different types of functions, like Lagrange or even B-spline basis functions.\nAgain, I don't know how much FEM theory the OP has, and it's been really hard to try to sum up how all this works. This may not be sufficient, but hopefully it serves to highlight some of the theory behind the FE method.", "333" ], [ "I've taken a look on these equations.\nI know you have a 1D element, but rewriting the equation would eliminate confusion if you want to write elements in 2D and 3D.\nTherefore your stiffness matrix should be\n\\begin{equation} \\mathbf{K}{el} = \\sum{i}^{n_{gauss}} \\mathbf{B}^T \\mathbf{E} \\mathbf{B} w_{\\xi,i} det(J). \\end{equation}\nfor the numerical integration with Gauss. Your stiffness matrix formula used $J$ instead of $det(J)$, which is not wrong. The determinant of the Jacobian is only significant for multidimensional cases.\nThe formula for your Jacobian should be \\begin{equation} J = \\sum_{i}^{n} \\frac{\\partial N_{i}}{\\partial \\xi}x_{i}. \\end{equation}\nThe Jacobian in the one-dimensional case is defined as $J = \\left[ \\frac{\\partial x}{\\partial \\xi} \\right]$ for \\begin{equation} \\begin{bmatrix} \\frac{\\partial N}{\\partial \\xi} \\end{bmatrix} = J \\begin{bmatrix} \\frac{\\partial N}{\\partial x} \\end{bmatrix} \\end{equation}\n\\begin{equation} \\begin{bmatrix} \\frac{\\partial N}{\\partial \\xi} \\end{bmatrix} = \\begin{bmatrix} \\frac{\\partial x}{\\partial \\xi} \\end{bmatrix} \\begin{bmatrix} \\frac{\\partial N}{\\partial x} \\end{bmatrix} \\end{equation}\nThe Jacobian in the isoparametric concept approximates the transformation by the derivatives of the shape function.", "526" ], [ "Here $\\frac{\\partial x}{\\partial \\xi}$ has to be approximated. Like the x-coordinate in the element would be calculated by \\begin{equation} x = \\begin{bmatrix} N_1 & N_2 & N_3 & N_4 \\end{bmatrix} \\begin{bmatrix} \\hat{x}_1 \\ \\hat{x}_2 \\ \\hat{x}_3 \\ \\hat{x}_4 \\ \\end{bmatrix} \\end{equation} $\\frac{\\partial x}{\\partial \\xi}$ is approximated by \\begin{equation} \\frac{\\partial x}{\\partial \\xi} = \\begin{bmatrix} \\frac{\\partial N_1}{\\partial \\xi} & \\frac{\\partial N_2}{\\partial \\xi} & \\frac{\\partial N_3}{\\partial \\xi} & \\frac{\\partial N_4}{\\partial \\xi} \\end{bmatrix} \\begin{bmatrix} \\hat{x}_1 \\ \\hat{x}_2 \\ \\hat{x}_3 \\ \\hat{x}_4 \\ \\end{bmatrix}. \\end{equation}\nImportant: The definition of the Jacobian in many books covering finite elements is not consistent to the mathematical definition. So be careful when you are doing your transformations.\nWhen you are doing the transformation of the derivatives of the shape function, you should have \\begin{equation} \\begin{bmatrix} \\frac{\\partial N_1}{\\partial x_1} & \\frac{\\partial N_2}{\\partial x_2} & \\frac{\\partial N_3}{\\partial x_3} & \\frac{\\partial N_4}{\\partial x_4} \\end{bmatrix} = \\mathbf{J}^{-1} \\begin{bmatrix} \\frac{\\partial N_1}{\\partial \\xi_1} & \\frac{\\partial N_2}{\\partial \\xi_2} & \\frac{\\partial N_3}{\\partial \\xi_3} & \\frac{\\partial N_4}{\\partial \\xi_4} \\end{bmatrix}, \\end{equation}\nso that seems to be ok, except that you have the matrix transposed.\nYour stiffness matrix then is wrong. Note that you have a dyadic product, where in this case you get a $4 \\times 4$ matrix out of $1 \\times 4$ vectors.", "804" ], [ "This is well-known theory in finite element analysis. There are two different effects that contribute to the effective stiffness of the structure in addition to the elastic stiffness $K_e$ given by Euler-Bernoulli-Timoshenko beam theory, and you need to include both of them to get the right answer.\n(1) Rotating the beam creates axial tension in the beam, which will be zero at the tip and increases to a maximum value at the rotation axis. This tension creates an additional stiffness that opposes lateral bending of the beam, in the same way that the tension in a guitar string affects its vibration frequency and hence the pitch of the note produced. (Of course in a guitar string, $K_e$ is negligible, unlike your beam).", "333" ], [ "This stiffness term was traditionally called the \"geometric stiffness\" (for reasons which aren't worth explaining) but a more logical name is \"stress stiffness\" often denoted by $K_\\sigma$, since it depends only on the internal stresses in the structure and not on the material properties.\nIncidentally, $K_\\sigma$ for a compressive stress is what causes <PERSON> buckling in columns. At the \"critical load\" for buckling, $K_\\sigma$ \"cancels out\" the elastic stiffness and when $K_e + K_\\sigma = 0$, the structure can't resist the applied loads. For tension stresses, $K_\\sigma$ increases the stiffness of the structure.\n(2) If the beam deflects from its original straight configuration, the direction and/or the point of application of the centrifugal loads changes.\nIf the beam rotates about a vertical axis and the beam deflects vertically, the CF load on each particle of the beam is still in a horizontal direction, and therefore the CF loads at the beam tip will create a bending moment that tends to straighten out the beam.\nBut if the beam deflects tangentially (for example while you are ramping up the rotation speed from zero) the direction of the CF load is radially away from the axis, and that generates a bending moment that tends to increase the bending of the beam, not reduce it.\nThe usual name for both these effects is \"follower forces\", because the direction of the applied loads \"follows\" the deflection of the structure. The corresponding stiffness terms are usually called the \"load stiffness\" and denoted by $K_L$.\nThe original equation for statics using only the elastic stiffness, $$K_e u = F$$ becomes $$[K_e + K_\\sigma(\\omega) + K_L(\\omega)]u = F.$$ In principle you could get expressions for $K_\\sigma$ and $K_L$ for a simple situation (e.g. a rectangular straight beam) but in practice it's much easier to use a Finite Element package that includes these effects.", "333" ], [ "Space-time <PERSON> of <PERSON> changes the convection speed\ntldr: Can space-time <PERSON> schemes applied to convection-diffusion problems lead to effects on the convection velocity?\nFor time $t\\in (0,1)$ and the spatial variable $\\xi \\in (0,1)$, I am considering the viscous <PERSON>'s equation\n$$\\dot z + \\frac 12\\partial_\\xi (z^2) - \\nu \\partial_{\\xi\\xi}z = 0 \\tag{*} $$\nwith a viscosity parameter $\\nu$. I have zero Dirichlet conditions in space and as the initial condition $z(0)$, I use a step function, which is one on one half of the domain and zero on the other half.\nWith finite elements in space and Runge-Kutta in time, I get to the expected numerical results.\nNow, if I discretize the equation with a space-time <PERSON> scheme, I get a picture, where, apart from artefacts due to low-dimensional bases, the convection speed is obviously too fast. (The front reaches the border too early)\nIn fact, if I replace the factor $\\frac 12$ by the factor $0.375$ in the equation $(*)$, then the convection looks right.\nSince this factor $0.375$ works for all kind of experiments, namely for various viscosity parameters $\\nu$ and sizes of the space-time bases, I am almost sure that this is not a bug in my code.", "346" ], [ "Thus, my question is: Is there a known issue concerning space-time discretizations of transient convection-diffusion problems that cause this corrections in the convection speed?\nNote that I use continuous Galerkin in time as well, so that there is no interpretation of the time-space scheme, as a space discretization plus time stepping.\nEdit (of the first edit): Here is the result of the space-time <PERSON> simulation for a finer resolution, a smooth initial condition that is consistent with the Dirichlet conditions, and a shorter time frame to avoid the \"clash\" of the wave with the zero Dirichlet conditions:\nAs before, in the low-order space-time <PERSON> approach (right) the wave speed is too high if compared to the FEM/Runge-Kutta solution (left).\nEDIT (and confession) I must admit that it was an error in the implementation. After <PERSON>'s answer and after that <PERSON> from nutils provided me a benchmark simulation of the same problem with high-fidelity space-time finite elements I was convinced to revise my code bottom-up. Anyways, this is how it could look like with a low-dimensional (12, 12) degrees of freedom in (space, time) space time <PERSON> scheme.", "346" ], [ "Navier-Stokes Energy Equation\nI've been assigned (for homework in a mathematical modelling course) the task of deriving the Navier-Stokes energy equation in one space dimension:\nConsider a fluid flowing through a cylindrical pipe (from left to right; also assume the pipe to be horizontal) with constant cross section $A$, velocity $v(x,t)$, density $\\rho(x,t)$, specific internal energy $e(x,t)$, temperature $T(x,t)$, under pressure $p(x,t)$, and subject to viscous stress. (By specific internal energy, we mean internal energy per unit mass. Internal energy arises from intermolecular collisions in the fluid, and should be distinguished from the kinetic energy associated with the macroscopic fluid motion(i.e., $\\tfrac{1}{2}mv^2$). By conserving energy, show that \\begin{equation} \\left[\\rho\\left(\\frac{v^2}{2}+e\\right)\\right]_{t}+\\left[\\rho ve+\\frac{1}{2}\\rho v^3-\\kappa(x)T_x+pv-\\mu vv_x\\right]_x=0, \\end{equation} where $\\kappa$ is thermal diffusivity and $\\mu$ is the viscosity coefficient.\nAttached with the problem is this \"hint\":\nNote.", "453" ], [ "The energy density should be easy to identify. For the flux, consider each of the following, which correspond respectively with terms in the equation above: internal energy, kinetic energy, energy lost to heat, energy lost to work against pressure, energy lost to work against viscous stress.\nI suppose it is intended for us to use the conservation equation $u_t+f_x=0$ (where $u(x,t)$ is some conserved quantity and $f$ is the flux), but I'm having a lot of trouble interpreting the physical phenomena as equations (I'm a mathematics graduate student who knows embarrassingly little physics).\nLooking at the equation above I assume that the energy density at a point is simply the internal energy plus kinetic energy, or $mv^2/2+me$, (since specific internal energy is internal energy is internal energy per unit mass), and then somehow we should be able to argue that $m=\\rho A$, and eventually the $A$ will be divided out. The trouble I have with this however is that I believe the equation is mass $=$ volume $\\times$ density--not area--and I'm having a little trouble conceptually allowing myself the state $m=A\\rho$ with confidence (since any object without three spatial dimensions should have zero volume right?).\nFor the flux, I'm having real trouble interpreting what the \"energy flux\" would be, even with his hint.\nAny help would be greatly appreciated. Hopefully this question hasn't been asked already (I did a good bit of searching) and that it's been tagged correctly. Thanks in advance.\nAlso, any recommendations for a physics book geared towards people with a math background would be greatly appreciated as well.\nPlease let me know if anything is unclear in the statement of the question and I will try my best to clear things up.", "453" ] ]

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[ [ "4-wire Kelvin Precision Resistor Box\nIntroduction: 4-wire Kelvin Precision Resistor Box\nA little side project that can be finished in less than 10 minutes, but still applies as a useful tool for an electronics lab. As I was working on the development of a bigger project, I realised I would need some sort of calibration tool.\nSo, there you have it, a 4-wire Kelvin measurement Resistor box. It is intended to allocate any 2512 footprint resistor and 4 banana plugs.\nThe original idea was to use it with 2412 Vishay Precision resistors, which offer 0.01% precision and 2 PPM temperature coefficient, as a cheap way of calibrating an instrument. But this thing also turn out to be useful as a means of testing shunts and check their actual value with a multimeter.\nStep 1: Features\nThe design is anything but complex:\n- 2512 SMD footprint\n- 4-wire Kelvin connection\n- 4 mm holes for banana jacks\n- 3.2 mm holes for mounting it inside a little case.\nStep 2: Theory of Operation\nA 4-wire Kelvin measurement setup, is a way of measure the value of a resistor subject, neglecting the wires parasitics involved in the process.\nAs shown the picture, the method consists in circulating a known current through the resistor under test via two terminals (or two \"wires\") and then measure the voltage drop across it.\nThis way, we could know the value of very low resistance shunts with very precise results, which is not achievable for the regular multimeter. For this task, we require a good multimeter in the milivolt range and a reliable source of current.\nIf you want to know more about this topic, click on the link bellow:\nhttps://www.allaboutcircuits.com/textbook/direct-c...\nStep 3: Materials\nThe parts list is pretty short as well:\n- PCB Board. You could order it from your favorite supplier.\n- A 2512 resistor.\n- A set of 4, 4 mm banana jacks.\n- A set of 4, 3x10 mm self-tapping screws.\n- 3D printed case.\nStep 4: Experimental Results\nAs you can see, the operation is pretty simple. In the photos, I'm performing some tests to a 0.02 ohm resistor, circulating 2 and 4 amps through it.", "98" ], [ "I have two wires carrying current connected to a pair of red and black terminals, and measuring the voltage drop in the other pair.\nThis way, I could check for the real value of the resistor. In this case:\n- 39.82 mV / 2 A = 0.01991 ohms. 0.5% of variation from 0.02 ohms\n- 81.68 mV / 4 A = 0.02042 ohms. 2.1% of variation from 0.02 ohms\nThis seemed like a really bad temperature coefficient for this resistor.\nStep 5: Documentation\nThe archive below contains all the information to replicate this project.\nCAD files (Fusion 360 and EAGLE 9.X):\n- F360 assembly project (Assembly.f3z)\n- F360 electronics project (F360_Resistor_Box.f3z)\n- F360 Schematic (F360_Resistor_Box_sch.fsch)\n- F360 PCB layout (F360_Resistor_Box_PCB.fbrd)\n- EAGLE Schematic (EAGLE_Resistor_Box_sch.sch)\n- EAGLE PCB layout (EAGLE_Resistor_Box_PCB.brd)\n- STL models of the featured box (Box.stl)\nPrintable files:\n- Schematic (Resistor_Box_Schematic.pdf)\nProduction files:\n- Gerber files (Resistor_Box_Gerber.zip)\nThis project was made entirely with Fusion 360. Electrical files of the project have been exported as Fusion 360 and EAGLE 9.X compatible files. Google Drive link to access the project files:\nhttps://drive.google.com/file/d/1V4Ewm8NjrSIrAq6tA...\nI hope you liked this project! I encourage you to comment and share this article, so I could write better ones in the future. I would be glad to answer all of your questions.\nEnjoy!\nYou can also follow me on Instagram!", "134" ], [ "Programmable Arduino Remote Control (PCB)\nIntroduction: Programmable Arduino Remote Control (PCB)\nWith this small, palm-sized device, it is possible to remote control your PC or your Smartphone. Or to control your PC and your Smartphone at the same time.\nAnd it is freely programmable. You can write programs like: Login to your PC, open and login to instructables.com, play/pause a movie or adjust the volume on your Smartphone.\nHow is that possible? The used micro controller board has a chip that can act as a so called HID device, which stands for Human Interaction Device and simply means keyboard or mouse. And it has another chip, a Bluetooth chip which can act as a Bluetooth keyboard.\nThe programming is intuitive and there are more examples in the User Manual in the Wiki [1]. The syntax is described in the Programming Guide [1]. The video demonstrates a wireless login to a Windows PC with one click and a login to instructables.com with another click.\nWhat makes this remote control unique is that everything is stored in the volatile memory of the micro controller. It is safe to write programs which contain passwords.\nAnd it is unique as Bluetooth remote control which you can program from a long list of possible commands. For more details see also the User Manual [1].\nThis is a improved version of the Programmable Arduino Remote Control. It uses a printed circuit board (PCB) which you have to have manufactured. This costs a little extra. In return, the shape is more that of a remote control and it requires less soldering.\nIn this project, my goal was to make a device that looks more like a remote control. Further, and because I use it every day, I wanted something more robust than its predecessor.\nThe direct material costs are approximately USD 78.\n[1] Parc Wiki on github\nSupplies\n1 Adafruit Feather 32u4 Ble (adafruit.com)\n1 MicroUSB cable\n1 Custom PCB (see step Printed Circuit Board)\n1 IC MCP23008 (adafruit.com)\n1 LiPo 350 mAh (adafruit.com)\n5 Button switch, 6mm (adafruit.com)\n2 Slide switch (adafruit.com)\n1 Stack female headers (adafruit.com)\n1 DIP switch 4 positions (mouser)\n4 Screw M2 x l10\n1 Windows PC\n1 Arduino IDE (https://www.arduino.cc/en/software). Optional: PuTTY (https://www.putty.org)\n1 3D Printer\n1 Soldering iron and soldering wire\n21g PLA filament\nI added links to the Adafruit and the Mouser web shops, but you also get the parts elsewhere.", "379" ], [ "For example for the LiPo battery, search for \"PKCELL LP552035\".\nStep 1: 3D Printed Parts\nPLA and the standard settings (20% infill) can be used. Support structures have to be enabled.\nStep 2: Printed Circuit Board\nI had mine produced by Aisler (https://aisler.net/). At Aisler, it is possible to produce the PCB directly from the attached Fritzing project file.\nIf the manufacturer of your choice does not support Fritzing as import format, then try the Gerber files. \"All\" manufacturer support Gerbers.\nStep 3: Soldering Keypad\nSolder the five push buttons and the two slide switches to the front side of the PCB. Turn the PCB and add the MCP23008. Make sure the direction of the IC is correct.\nAdd the DIP switch.\nFrom a female header stack, break out a piece of three pin sockets. Solder this piece to the back side of the PCB.\nStep 4: Soldering Micro Controller\nSolder the header pins to the back side of the keypad. You can also solder the pins first to the micro controller board and as the second solder it to the keypad.\nSolder the pins flush to the keypad. The plastic distance holder that holds the pins as an array is by default set that the pins look out 1 mm. So you have to push the pins 1 mm down first.\nAfter the pins are soldered to the keypad, remove the black distance holder band. The battery will required all the space in between the two components.\nLastly, add the micro controller board. The battery shall be free movable between the two components.\nStep 5: Assemble\nConnect the battery to the micro controller board. Now you can put whole assembly into the case and use it.\nThat was it basically. Next you will learn how to install the software and program the remote control.\nStep 6: Arduino IDE, Libraries and Boards\nFor the following steps, the Arduino IDE is required.", "379" ], [ "How to Build a Portable Bluetooth Tube Amplifier\nIntroduction: How to Build a Portable Bluetooth Tube Amplifier\nAfter seeing several builds of bluetooth speaker boxes I wanted to try one myself, but with a twist. It has to use vacuum tubes, but small, not a converted tube radio, a scratch build. And it has to use batteries, otherwise, where is the fun?\nBefore we start, be aware that we will use Li-Ion batteries, which if not handled correctly can catch fire and explode.", "58" ], [ "We will also work with high voltages, which can be dangerous. To make things safe, we are going to use an existing and safe charging module, which disconnects the load while the battery is being charged. The high voltage will be supplied at small currents, through a small switched-mode-power-supply (SMPS).\nIn the next steps we will go trough most of the designing and building process. If want to skip the designing part, where we draw and simulate the circuit go you can jump to step 5, where we start with the wooden box.\nFor this build you will need the following tools:\n* handsaw\n* hacksaw\n* hand drill and set of drill bits, including some drills of larger diameters, or something to punch 22 mm holes\n* rotary tool\n* screw drivers\n* metal files\n* sandpaper (180, 400, 600, 1200)\n* dust mask and googles\n* pencil\n* ruler\n* compass\n* box cutter\n* scissor\n* pliers\n* Soldering Iron\n* Multimeter\nSupplies\nThe parts needed for this build listed for each different section:\nWooden box:\n* 1000x100x5 mm wooden board\n* 200x100x1.5 mm brass sheet\n* 1000x5x5 mm wooden stick\n* Wood glue\nTube amplifier:\n* 2x9 pin tube sockets with set of screws\n* 7-way tag strip\n* 1x 10 W 100 v line transformer (or any push-pull transformer with a 10k or 20k primary, for example the Hammond 125A)\n* Resistors:\n+ 1x 1k ohm 1 W\n+ 2x 1.5k ohms 1/4 W\n+ 2x 3k ohms 1/4 W\n+ 2x 68k ohms 1/4 W\n+ 3x 100k ohms 1/4 W\n+ 2x 150k ohms 1/4 W\n+ 2x 220k ohms 1/4 W\n+ 2x 1M ohm 1/4 W\n* Capacitors:\n* 2x 100 nF 50 v\n* 3x 100 nF 400 v\n* 1x 10u F 16 v\n* 1x 10u F 350 v\n* 1x 22u F 350 v\n* 2x 100u F 50 v\nBluetooth module:\n* MH-M18 module\n* B0505S 1W isolated DC/DC converter\n* 2x 10u F 16 v capacitors\n* 1x 100n F 16 v ceramic capacitor\n555 SMPS:\n* 1x 555 IC\n* 1x IRF644Pb mosfet or any other for 250 v or more and Rds_on less than 0.2 ohms.\n* 1x BC547 transistor\n* 1x 47u H 3A inductor low ESR\n* 1x ES2G diode or any other ultra fast diode (UF4004)\n* 1x 1k ohm trimmer\n* Resistors:\n+ 1x 470 ohms 1/4 W\n+ 1x 1k ohm 1/4 W\n+ 1x 10k ohm 1/4 W\n+ 1x 2.2k ohms 1/4 W\n+ 1x 56k ohms 1/4 W\n+ 1x 240k ohms 1/4 W\n* Capacitors:\n* 1x 100p F 50 v\n* 1x 2.2n F 50 v\n* 1x 4.7u F 350 v low ESR\n* 1x 330u F 25 v low ESR\nOther parts:\n* 1x TP4056 charger with separate pads for the load\n* 2x 2.5\" (65 mm) 88 dB speakers\n* 2x oval (70x40 mm) passive bass radiator\n* 1x circular (50 mm) passive bass radiator\n* 4x 18650 batteries\n* 4x DPDT 6 mm push buttons (of good quality)\n* 3 mm LEDs: 1x red, 1x blue, 1x white (or desired colour)\n* 1x 3 mm LED socket\n* 1x 3.", "98" ], [ "4 to 20 MA Industrial Process Calibrator DIY | Electronics Instrumentation\nIntroduction: 4 to 20 MA Industrial Process Calibrator DIY | Electronics Instrumentation\nIndustrial and electronics instrumentation is a very expensive field and it's not easy to learn about it if we are just self-educated or a hobbyist. Because of that my Electronics instrumentation class and I designed this low budget 4 to 20 mA process calibrator that is perfect to test our processes controllers responses to an step or ramp input.\nHere I show you step by step how to make yours.\nIf you are a visual learner I know that a video worth more than 1000 words, so here is a 2 parts Tutorial video. (I am a Spanish speaker, so please consider turning on English subtitles):\nStep 1: Skills Needed\nAs you can noticed, nothing looks very difficult on this project, but you will need some basics knowings about:\n-Welding.\n-Wiring.\n-Industrial Electronics.\nStep 2: Components and Parts List\nPCB I really recommend to use JLCPCB SMT Services to order yours.\nSPDT Switches.\nBanana Jacks\nWiring cables\n10 Turns 100kohm potentiometer\nEnclosure\nStep 3: Circuit Diagram\nHere is the Circuit diagram, it has all the internal conections of the circuit that will allow us to create the PCB design later.\nI also attached the PDF of the Schematics so you can see it better.\nDOWNLOAD Schematics\nStep 4: PCB Design and Ordering\nFor the implementation of a good project we need a reliable assembly for the circuit that makes it up, and there is no better way to do it than with a good PCB.\nHere you can download the Gerber, BOM and Pick & Place Files for free, the ones you need to order your PCB on your PCB manufacturing company.\nI suggest JLCPCB:\n📦$2 for Five - 4 Layers PCBs & cheap SMT (2 Coupons)\nDOWNLOAD ALREADY DESIGNED BOARD, Gerber + Pick & Place + BOM\nStep 5: Enclosure and Housing\nHere you can buy the enclosure and see it dimensions to build or 3D print yours\nStep 6: Project Assembly\nYou can place all the switches and outputs where you prefer, in my case I made some holes with a drill and placed the switches and the potentiometer with it nuts.\nIn the side, I made some holes for the banana jacks for the Loop input and for the current test probe.\nStep 7: Connecting the Loop\n1. From your 24 volts power supply (+ positive) connect to the (+) input of the Loop of the calibrator.\n2.", "472" ], [ "Continue from the (-) to the positive of the grapher.\n3. Close the loop connecting the negative of the power supply with the negative of the grapher.\n4. Connect you ampmeter in the banana jacks in current mode.\nStep 8: Final Test\nTurn on the power supply, and look at the current showed by your ampmeter.\nTest the different steps, and verify they produce the right current. If not, set the trimpots in the circuit until you get the right value.\nFinally, you can see the pictures of the system through the grapher and the lectures in real time. As you can noticed, the steps are succesfully produced, and we also can vary the current with the potentiometer.", "476" ], [ "Automatic Tip Cleaner - ArduCleaner\nIntroduction: Automatic Tip Cleaner - ArduCleaner\nYou can find a soldering iron on the desk of every DIY enthusiast. It's hard to name the number of situations in which it can be useful. I personally use it in all my projects. However, in order to enjoy high-quality soldering for a long time, it is necessary to properly care for the tip. For this purpose, I created the arduCleaner - an automatic tip cleaner, which is designed to smooth the soldering process by keeping the tip clean.\nStep 1: Projecting\nIn the beginning, I started designing the board in Eagle. This device should work in such a way that, after detecting a soldering iron in the device, it will turn on the motor that will drive the brush cleaning the tip. Infrared diodes, LED, LM358, a few resistors, and that's it. Now you need to swap the schematic to pcb project, pcb project to pcb, and pcb to soldered pcb.", "472" ], [ "I ordered the pcb on a great occasion from NEXTPCB, which is one of the most experienced PCB manufacturers in China, has specialized in the PCB and assembly industry for over 15 years.\nStep 2: 3D\n3D design - the most time-consuming part of this project. The first time I dealt with gears. I have also designed rods on which I will put a metal sponge responsible for cleaning the tip, but I will not print it but will create it from an old nail. I cleaned it, marked the cuts and cut it. Then I moved on to 3D printing. After several unsuccessful attempts, the final version was finally made. It took about 24 hours to print the whole thing and the effect is not satisfactory as the parts were detached from the stage.\nStep 3: That Is All!\nI put the electronics board in the designated place for it, soldered the charging socket and infrared diodes. This is what the arduCleaner looks like after the housing is put on. Now you can put a dirty soldering tip in it for a second to continue enjoying high-quality soldering.\nMy Youtube: YouTube\nMy Facebook: Facebook\nMy Instagram: Instagram\nOrder your own PCB: NEXTPCB", "472" ], [ "LED Juggling Knives\nIntroduction: LED Juggling Knives\nThis project was inspired by one of my friends, who is an avid juggler. He was looking for glow in the dark juggling balls and I wanted to try my hand in building it. As I worked through the design I realised that it would be much easier to build knives instead of juggling balls and I moved forward with that. With my knowledge of the 4017 IC, I decided to add a bit of flourish to the lights, which are now in the form of LEDs, and that is how I ultimately ended up with this project.\nA set of juggling knives that can be also used in the dark for better visuals.\nThe LEDs are lit in a sequence, just like a led chaser. This is done by a 555 timer circuit in Astable mode combined with a 4017IC. The housing is relatively simple, and it was 3D printed.\nThis is a relatively challenging project to build with a lot of components required.\nSupplies\nNote: The following supply list covers the making of 3 juggling knives, as all juggling knives usually come in sets of three. If you want to build only 1, you can divide the quantity by 3.\nCircuitry BOM:\n1) 3 x NE555 IC + 8 pin IC holder (link)\n2) 6 x IN4007 Diodes (link)\n3) 3 x 4.7k Ohm resistor (link)\n4) 3 x 3.3k Ohm resistor (link)\n5) 3 x 4.7uF 10V electrolytic capacitor (link)\n6) 3 x 40mm by 50mm Perf Board. (Any size bigger than this is fine. You can trim it down later) (link)\n7) 2 x Male to Male Jumper Cable 40pcs. (link)\n8) 3 x 4017 IC + 16 pin IC holder (link)\n9) 3 x 10k Ohm resistor (link)\n10) 25 x 5mm LEDs in Red colour (5 are extra just in case) (link)\n11) 25 x 5mm LEDs in Blue colour (5 are extra just in case) (link)\n12) 25 x 5mm LEDs in Yellow colour (5 are extra just in case) (link)\n13) 3 x 9V Battery + connecting clips (link)\n14) 12 x 3mm Dia 20mm long bolts (link)\n15) 3 x 3mm Dia 6mm long bolts (link)\n16) 3 x Tactile latch switch (link)\nTools and Equipment:\n1) Soldering Iron + Soldering wire\n2) Desoldering pump\n3) Pliers\n4) Wire cutters + Wire Strippers\n5) 3D printer or access to a 3D printing service provider\nStep 1: Understanding the Circuit (555 Timer)\nThere are two parts of this circuit. 555 timer and 4017 IC. I will be exploring the former in this step. You can ignore this step if you are familiar with the 555 astable circuit.\n555 timer circuit\nThis circuit is a very common favourite of all electronics geeks. The schematic for the circuit can be seen in the first image.", "982" ], [ "Here is a link to the website where I got the circuit image from https://www.electronics-tutorials.ws/waveforms/555...\nFor this project, the circuit is wired up in an astable configuration. This means that the voltage output of the chip alternates between high and low at a constant frequency. The voltage output vs time graph of this circuit can be also seen in the image.\nIt is a square wave. Essentially the circuit produces pulses at a constant rate. This can be used to make an LED blink. The frequency of the pulse can be controlled used the values of the two resistors and the capacitor. These are respectively R1, R2, and C1 in the image. The equation used to calculate the frequency from these values has been given in the equation.\nThe final term is the duty cycle. It is the percentage of time for which the output is high. This can be also calculated with the equation in the image. Unfortunately, if the duty cycle is too high it leads to bouncing (link) or the connecting circuit can't even detect the pulse/low period.\nTo rectify this issue, this circuit has an additional 2 diodes compared to the conventional circuit. This is to make the duty cycle more even 50%-50% between on and off. (link)\nStep 2: Understanding the Circuit (4017 IC)\nThe 4017 IC works with the 555 timers.\nThe 4017 IC has multiple output pins: pins 1-7, 9, 10, and 11. Each of these output pins is set in a sequence as shown in the image.", "552" ], [ "GRBL Based Coil Winder From Water Pipe\nIntroduction: GRBL Based Coil Winder From Water Pipe\nWhen I was working on the Toy Magnetic Levitation project with a solenoid coil, I thought to myself, why didn't I make a coil winder. So I took my times to build a simple coil winder based on GRBL firmware and it was made from PVC pipes. I'm willing to share how I made it, please check out video below and let's get started.\nStep 1: Supplies\nMain components:\n* 1pcs x Arduino Uno R3: Amazon - Banggood.\n* 1pcs x Arduino CNC Shield V3 GRBL: Amazon - Banggood.\n* 2pcs x Stepper Motor Driver A4988: Amazon - Banggood.\n* 2pcs x Stepper motor NEMA 17: Amazon - Banggood.\n* 2pcs x GT2 6mm Closed Timing Belt 200mm: Amazon - Banggood.\n* 2pcs x GT2 Timing Pulley 60 Teeth, Hole diameter 8mm: Amazon- Banggood.\n* 1pcs x Round Bar Shaft Rod Diameter 8mm, Length 400mm: Amazon - Banggood.\n* 3pcs x Round Bar Shaft Rod Diameter 8mm, Length 200mm: Amazon - Banggood.\n* 1pcs x T8 Lead Screw 2mm Pitch, 8mm Lead , Length 400mm with Copper Nut: Amazon - Banggood.\n* 16pcs x F608ZZ Ball Flanged Shielded Bearings 8 x 22 x 7mm: Amazon - Banggood.\n* 2pcs x XH2.54mm – 4P Wire Cable Double Connector: Amazon - Banggood.\n* 1pcs x 5mm DC Female Power Plug: Amazon - Banggood.\n* 1pcs x Power Supply 12VDC: Amazon - Banggood.\n* 1pcs x Clear/White Acrylic, size A3, thickness 5~10mm: Amazon - Banggood.\n* 1pcs x Empty plastic spool. I reused empty plastic spool that is used to coil the soldering tin wires.\n* 2pcs x Small Rubber Guide Roller V type.\n* 6pcs x Elbow PVC Pipe Ø42mm.\n* pcs x Straight connector PVC Pipe Ø42mm.\n* 2 meter x PVC Pipe Ø42mm.\n* 12pcs x Tee PVC Pipe Ø42mm.\n* 12pcs x End Cap PVC Pipe Ø42mm.\nThe pipe and its fittings are shown below:\nTools:\n* Drilling machine with drill bit hole 22mm.\n* Hand saw.\n* Soldering machine.\n* Big scissor.\nStep 2: Schematic\nThe connection diagram is very simple. I just plugged the CNC shield onto the Arduino Uno R3 and connected the cables to 2 stepper motors. Two stepper motor drivers A4988 were also plugged on the CNC shield at X and Y position.\nThere are 2 axes for a coil winder which are called:\n* Feeder axis: connecting to X axis marked on CNC shield.\n* Spindle axis: connecting to Y axis marked on CNC shield.\nThe NEXTPCB support me for this project.", "1000" ], [ "If you have a PCB project, please visit the NEXTPCB website to get exciting discounts and coupons.\n* Only $0 for 1-4 layer PCB Prototype: https://www.nextpcb.com/pcb-quote?act=2&code=tune...\n* New customer get $100 coupons, register at: https://www.nextpcb.com/register?code=tunendd\nHere are mid-summer sales at NextPCB:\n* Up to 30% off for the PCB orders.\n* Up to 20% off for the PCBA orders.\nStep 3: Assembly Work\nFirstly, I’ve tried to figure out how to build the coil winding machine. And it seems easy with PVC pipes. What we need is patience and carefulness.\n1. Building a coil winder frame:\nI assembled a square frame, dimension about 480 x 480mm. It was made of 7pcs x tees, 4pcs x elbows and connecting pipes.\nConnecting pipes should be cut in suitable length so that when we connect elbow to tee or tee to tee, there is no gap between them. With this connecting way, we don't need to do any measurements or alignments later because they are the same size and completely symmetrical each other. As the picture above, we have 3 pairs of pipe that are completely symmetrical each other.\n2.", "819" ], [ "Toy Levitation From Solenoid Coil\nIntroduction: Toy Levitation From Solenoid Coil\nMagnetic levitation has always been in my intention. Summer is here, I am ready to build a toy for my daughter. It's a toy levitation that can make small toys float in the air. My daughter is very naughty and hyperactive so she needs to be trained on concentration with this toy.\nPlease check my testing below before getting started.\nStep 1: Things We Need\nThe main materials are used in this project:\n* 1pcs x Magnetic coil: Amazon - Banggood.\n* 1pcs x Arduino Nano: Amazon - Banggood.\n* 1pcs x KY-024 Linear Magnetic Hall Sensor: Amazon - Banggood.\n* 1pcs x NPN Transistor: TIP122 Amazon , Or TIP120 Banggood.\n* 1pcs x R10K: Amazon - Banggood.\n* 1pcs x N4007: Amazon - Banggood.\n* 1pcs x DIY Double side prototype PCB board 5 x7 cm: Amazon - Banggood.\n* 2pcs x Terminal screw type – 2 pin: Amazon - Banggood.\n* 2pcs x DC Power Male & Female Plug: Amazon - Banggood.\n* 1pcs x Power Supply 5VDC & 12VDC: Amazon - Banggood.\n* 1 meter x 8P/16P Rainbow Ribbon Cable: Amazon - Banggood.\n* 1 meter x 2 Core Power Cable: Amazon - Banggood.\n* Some Neodymium Magnets.\n* 2pcs x Elbow PVC Pipe Ø42mm.\n* 1 meter x PVC Pipe Ø42mm.\n* 1pcs x Tee PVC Pipe Ø42mm.\n* 2pcs x End Cap PVC Pipe Ø42mm.\n* 2pcs x Reducing Tee Ø60mm to Ø42mm.\n* 4pcs x End Cap PVC Pipe Ø60mm.\nTools:\n* Drilling machine.\n* Hand saw.\n* Soldering machine.\nStep 2: Schematic\nThe project schematic is in picture above.\nStep 3: Hall Module Selection\nThere are many magnetic sensor modules sold in the market and according to description they can output both digital and analog signals but that is not true. I bought a few modules but it really has only digital signal and in the end I chose the module called “KY-024 linear magnetic Hall module”.\nThe KY-024 linear magnetic Hall sensor reacts in the presence of a magnetic field. It has a potentiometer to adjust the sensitivity of the sensor and it provides both analog and digital outputs. This module consists of a 49E linear Hall-effect sensor, a LM393 dual differential comparator, a potentiomenter, leds and resistors.\nThe 49E is a linear hall-effect sensor.", "1000" ], [ "It can measure both north and south polarity of a magnetic field and the relative strength of the field. It works as follow:\n* If NO magnetic field is present the 49E will output a voltage around half of the source voltage, around 2.5V.\n* If the SOUTH pole of a magnet is placed near the labeled side of the 49E, then the output voltage will linearly ramp up towards the source voltage (go up to around 4.2V).\n* If the NORTH pole of a magnet is placed near the labeled side of the 49E then the output voltage will linearly drop down toward the ground voltage relative to the strength of the magnetic field (drop to around 0.86V).\nStep 4: Magnetic Coil\nMy magnetic coil is taken from a magnetic lock. I removed the metal housing and core, just keeping the coil. Its operating voltage is 24VDC.\nI used a multimeter to measure coil resistance value, it is about 15.0 ohm. In this project, I use 12VDC to power this coil.\nStep 5: Soldering Work\n1. KY-024 Hall module modification.\n* Cutting 3 pins of Hall sensor 49E on the module.\n* Soldering a 3-core wires connecting the sensor and module.\n2. Main control board\nFollowing the schematic on STEP 2, I soldered all the connections and components on a PCB prototype board size 50x 70mm.\nThe component arrangement is described as follow.\n* Top view\n* Bottom view\nIf you have a PCB project, please visit the NEXTPCB website to get exciting discounts and coupons.\n* Only $0 for 1-4 layer PCB Prototype: https://www.nextpcb.com/pcb-quote?act=2&code=tune...\n* New customer get $100 coupons, register at: https://www.nextpcb.com/register?", "611" ] ]

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[ [ "Manual Camera Settings Explained\nIntroduction: Manual Camera Settings Explained\nHello, I’m <PERSON>. I bring joy to my friends whenever they want a great picture taken. I’m going to show you how to experience the joys of photography. I’m going to show you 8 easy steps to creating a professional looking picture. You will be taking pictures like a pro after reading this. Did you know there are 34,301 professional photographers in the U.S.? So, let’s get started on how to take your own professional pictures.­­\nSupplies\nCamera (I am using a Canon), subject to take a picture of\nStep 1: Set Camera to Manual\nTo take an image that looks professional, first you must set your camera settings to match the light in the room/atmosphere. Turn your dial to set your camera to manual, you should never have the camera set to auto. The auto setting does not always give you the best exposure possible.\nStep 2: Set the Shutter Speed\nThe first setting to adjust is shutter speed. Shutter speed is the length of time your shutter stays open when you take a picture. Use faster shutter speed to freeze motion (if you are taking a picture of something moving or action). Sport photographers use a shutter speed like 1/1000 of a second. Use a slower shutter speed if you are taking a picture of a still object. When taking a picture of a still object a shutter speed of 1/100 of a second would be appropriate\nStep 3: Set the Aperture\nThe next setting to adjust is aperture. Aperture is the size of the opening of the lens.", "843" ], [ "The smaller the number, the larger the opening. If you are taking an image and want a smaller depth where the subject appears sharp while the foreground and the background appear blurry, then you should use very wide apertures like f/1.8 or f/2.8. Using an aperture like f/32, squeezes the light that passes through your lens. It ends up interfering with itself, growing blurrier, and resulting in photos that are noticeably less sharp.\nStep 4: Set the ISO\nThe next setting is ISO. ISO stands for International Organization for Standardization which is an organization that sets international standards for all different kinds of measurements. ISO is simply a camera setting that will brighten or darken a photo or the sensitivity of the sensor. The larger the number the more sensitive that sensor is (that little piece of electronic equipment in your camera to the light coming in). At ISO 200 it is twice as sensitive as it is at 100. As you increase your ISO number, your photos will grow progressively brighter.\nStep 5: Check the Live View\nAfter setting these three things, check your live view. After checking the live view, adjust your settings to make your image the best you possibly can.\nTo get an image that is not shaky you want to use a tripod or both hands to keep the camera stable. Anything you can set your camera on works to, just make sure it is sturdy.\nStep 6: Rule of Thirds\nAnother tip to use is putting your subject on a third. The rule of thirds is a composition guideline that places your subject on the left or right third of an image, leaving the other two thirds more open.\nStep 7: Shot Type\nUse different shot types to help with the psychology of the image. Shot types might include wide shot, medium shot, extreme close up, dutch tilt, etc.\nA wide shot is a shot that shows the subject within their surrounding environment. A wide shot tells the audience who is in the image and where the image is set.\nA medium shot is a shot approximately from the waist up. A medium shot is used to emphasize both the subject and their surroundings by giving them an equal presence in the shot.\nAn extreme close up is shot frames a subject very closely, often so much so that the outer portions of the subject are cut off by the edges of the frame.\nA dutch tilt is an angled camera shot where the horizon line isn't parallel with the bottom of the frame, and vertical lines are at an angle to the side of the frame.\nLastly, snap your picture!", "538" ], [ "Special Bokeh Filters: Give Your Photo's a Creative Twist!\nIntroduction: Special Bokeh Filters: Give Your Photo's a Creative Twist!\nThese filters are a great way to make your give photography a little creative and personal touch, and they cost next to nothing. The filters work best with fast primes, like a nifty fifty, but you could also try it on a point and shoot camera, if you make the cutout small enough. If you have some vintage glass laying around, these should work on there too and give a really cool look!\nSupplies\n1. Black paper\n2. White pencil\n3. box cutter\n4. lens (preferably with a fast aperture)\n5. some small templates of the wanted shape (optional, these are only used to draw your shape.)\n6. rubber bands, or a filter holder if you have one\n7. triangle or ruler\nStep 1: Determine Filter Size, and Draw It on the Paper\n* If you have a filter holder like me, just draw a rectangle with the size of your filters using your pencil.", "294" ], [ "Then, draw the two diagonals to determine the middle of the rectangle.\n* If you don't have a filter holder, no problem! You can also do it without. Measure your filter size, and draw a circle with the same diameter. I just turned my lens upside down, and drawed around it using my pencil. depending on the lens you want to use, you may want to think about how you want to attach the filter (rubber bands, tape, ... )\nStep 2: Draw the Shape You Want.\nI drew a spiral and a star, but you can draw any shape you want here. Some inspiration: a smiley, Christmas tree, heart, fireworks, ... Just any symbol you want, really, as long as it hasn't too much details because these may not show that well on your photo's. Just make sure that you don't make the cutout too big for your lens, look in the table above to determine what the maximum size is.(Click on it to see it fully) If you are using the round design, without filter holder, als add some little flaps to put under the rubber bands.\nStep 3: Cutting\nCut your shapes and filters out. If you are using the round design, also fold the flaps to a right angle. Your filters are ready to go!\nStep 4: Camera Settings\nTo use the filters, put your camera in Aperture priority and use manual focus, and any light points in the background will turn into your chosen shape. I used a lego set and some Christmas lights, which made for a great combo.", "294" ], [ "Make a Document Camera Out of an Old Box and a Mirror.\nIntroduction: Make a Document Camera Out of an Old Box and a Mirror.\nThis project recycles an old box to make a document camera. Distance learning is not great, but this document camera can help a teacher see what a student is writing on. This document camera can also be used by a teacher as a document camera too. This project makes an excellent document camera. I have a link to free app that removes the keystone effect pasted at the end of this instructable. Recycle any mirror for the mirror, but you can also order a $4 mirror here: https://www.tapplastics.com/product/plastics/cut_to_size_plastic/acrylic_sheets_mirror_clear/521\nPlease click the heart button below so I can win this contest!!!!!!!!!!!!!!!\nSupplies\nMaterials:\nAn old box Glue An exacto knife A whiteboard A cutting board A marker A mirror (This can be bought from tapplastic.com for around $4 depending on the size you order. I used a 60mmx70mmx3mm acrylic mirror.). If you buy 20 then the individual price goes down to $2.\nStep 1: Cut Box Into Two 3 Inch Squares\nCut the squares out of the old box. Use the cutting board.\nStep 2:\nMeasure the thickness of you laptop's lid. Transfer this thickness to the cardboard squares.", "175" ], [ "Cut out the width of your laptop lid.\nStep 3: Find the Perfect Angle for Your Mirror.\nSlip the cardboard squares onto the lid of your laptop. Put the mirror over the laptop camera. Angle the mirror so the laptop camera is redirected to your laptop's keyboard. While holding the mirror at the correct angle, use the marker to draw a line along the back of the mirror on the cardboards pieces.\nStep 4: Cut a Groove Into the Cardboard\nCut a groove part of the way through the cardboard along the mirror angle line. Do not cut all the way through the cardboard. Push the mirror down along the groove you cut. Check to see if the mirror fits snuggly. If it doesn't you can start again or fiddle with the cut a second time.\nStep 5: Glue the Mirror in Place\nSmear glue in the mirror groove on both squares.\nStep 6: Glue Mirror in Place\nPut the mirror in the grove of one of the squares. Put the other square on the mirror. Wiggle the mirror into the groove of the second mirror.\nStep 7: Adjust Zoom and Adjusting Keystone Effect\nI made an instructable on how to adjust your Zoom settings here:\nhttps://www.instructables.com/id/3-Clip-on-Documen...\nRemove the keystone effect with the app found here:https://www.ipevo.com/software/visualizer#download", "175" ], [ "How to Make a Paper Kite\nIntroduction: Paper Kite\nAre you thinking of a little birthday surprise for your little one that is obsessed with flying objects? Why not make a kite for them at home and with some love? Also, you can make the process fun by engaging them. This is a fantastic opportunity for them to learn.\nFrom paper and rocket kites to butterfly kites, you can make different kites at home. In this brief, I discuss how to make a simple paper kite at home.\nMaterials\n* Newspaper sheet\n* Two round wooden sticks (20 and 24 inches in length)\n* Scissors\n* Pencil\n* String\n* Masking tape\n* Small handsaw\n* Ribbons\n* Ruler\nStep 1: Cut!\nStart by cutting the wooden sticks to attain 20 and 24-inch lengths. Next, use a handsaw to cut notches at the ends of the sticks.\nStep 2: Position the Dowels\nVertically place the 24-inch dowel and make a mark six inches from the top. Then, create a \"t\" shape by placing the smaller dowel over the marked spot. The next step is wrapping a string around the intersection of the dowels to secure them.", "286" ], [ "You can also conceal the string with tape to secure them further.\nStep 3: Bring in the String\nWrap a string around the kite, making sure it passes through all the notches. This is the step that completes the kite’s frame.\nStep 4: Add the Newspaper\nWith the frame done, bringing in the newspaper is next. Spread it on the floor and carefully place the frame on top of it. After that, measure a one-inch overlap and cut the remainder of the newspaper out of the frame.\nStep 5: Fasten the Newspaper Edges\nIn this step, you’ll be required to fold the edges of the newspaper over the string before fastening them using tape. The string should be about 24 inches long.\nStep 6: Create the Brindle\nCreate holes in the kite’s tips (both top and bottom) and pass the string through them. This form’s your kite’s brindle. If you want to fly your kite, you’ll need to tie the flying string to the brindle string.\nStep 7: Do Not Forget the Tail\nUse a ribbon of a color of your choice to create your kite's tail.\nStep 8: Voila!\nYour kite is now ready to fly, and your little one will love it.", "636" ], [ "How to Draw Stylized Faces\nIntroduction: How to Draw Stylized Faces\nIf you have ever wanted to learn how to draw a face but you didn’t know where to start, then these instructions will hopefully lead you in the right direction. As a beginning artist, despite wanting to draw faces, you may have trouble knowing where certain features should go and why they belong there. In these instructions, I will give you the basics of drawing faces, both stylized and realistic (depending on what you prefer), as well as a few tips and tricks that helped me when I was a beginner as well. Along the way, I will be showing you examples of different features. Feel free to use the examples I have included as a reference for your own drawings. Let’s begin!\nSupplies\nA sheet of paper. Any kind of paper is suitable, but a blank, white sheet is preferable for beginners.\nA pencil. The kind of pencil is a matter of personal preference. You may use art pencils, such as these, but I simply like to use a mechanical pencil!\nAn eraser. Again, you may use an eraser like this one, but I use the eraser on my mechanical pencil.\nA reference image. I will talk more about these below, but here is my Pinterest board of reference images I have compiled.\nStep 1: Find a Reference\nIf you find drawing a face to be intimidating, a good idea is to find a reference image. A reference image is a picture that you, as an artist, can closely analyze and try to imitate on the page. This step is especially helpful for people who are just starting out, and who have trouble knowing where features should go and what each shape should look like. As a beginner, you should try to find a picture of a person who is facing the camera, preferably with little or no facial expression. When you begin to progress, then you can move on to more advanced expressions and angles.\nI like to keep a board on Pinterest filled with images of interesting faces. This may be useful for you as well! Whenever you would like to practice your drawing skills, you can go into this board and pick out a different face. Each time you draw a unique feature, you add to your knowledge. If you would like to use my board of faces, I have linked it above under Supplies & Resources.", "608" ], [ "For this tutorial, I will be using the above image. If you are following along, you may use the same image or pick a different one that you like better.\nStep 2: Sketch Out the Face Shape\nSo, where exactly should an artist begin when drawing the face? The answer is that there isn’t one solid answer. Different artists start drawing the face in different places. However, I find it easiest for beginners to start by making a quick, light sketch of the face shape. Faces come in a bunch of unique shapes and sizes. These shapes include oval, heart, square, round, diamond, and oblong.\nTypically, you can tell by the shape of the jaw, chin, and forehead, and their sizes in relation to one another. For example, <PERSON> has an oval-shaped face because her cheekbones are wider than the widths of her forehead and jaw, creating an oval shape. <PERSON> has a square-shaped face because her jaw is strong and sharp, and it is the same width as her cheekbones and forehead, creating a square shape. And the reference image I have chosen for these instructions has a heart-shaped face, as her forehead is wider than her jaw, and her chin comes to a point, creating a heart shape.\nYour light sketch of the face shape does not have to be perfect. We will be fixing it up later. For now, we just need a general shape where we can put in her facial features. Remember to closely look at your reference image. What shape is her chin? Is it rounded? Pointed? Is there a cleft? How does the chin connect to the jawline? How far up from this jawline are her cheekbones? These are questions to take into consideration during your sketch. Worry less about perfection and more about how your lines interact with each other.\nStep 3: Eyes\nAfter you’ve quickly drawn the general shape of the face, we can now move on to the features. I like to start with the eyes! Eyes, just like faces, come in different shapes. The most common shapes are almond, hooded, downturned, upturned, and monolidded. I've included some examples.\nAlmond eyes look like almonds, hence the name. The inner corner of the eye is in line with the outer corner. Hooded eyes look a bit like almond eyes, but the skin above their eyes and beneath their eyebrows cover portions of the eyelids.", "608" ], [ "How to Make an Angel Halo!\nIntroduction: How to Make an Angel Halo!\nMy name is <PERSON> and I am an intern for UsedEverywhere.com! Since our mascot is the angel (note the halo on the top of the “U” on UsedEverywhere.com) I was given the task of making 50 halos to give out at a golf tournament that we are sponsoring!\nThe amount of stuff you need will obviously vary, as I doubt many of you need to make 50 halos unless you and your friends are going as an army of angels for Halloween…\nSo here we go, these are the necessary items you will need to be successful in your halo-making quest!\n- Thin White Boa\n- Thin Wire (any colour! 20 gauge thickness)\n- Thick Wire (any colour! 12 gauge thickness)\n- Glue Gun (don’t forget the glue sticks!\n- Headbands\n- Scissors\nStep 1: Step 1: Let's Start the Fun\nStep 1:\nTake one piece of the pre-measured thin wire and bend it into a circle. Fasten the two ends together by bending each into a loop and connecting the loops. Make sure you twist the ends like a twist tie to make sure that the ends don’t come apart.\nStep 2: Step 2: Plug in the Glue\nStep 2:\nWrap 14 inches of the thicker wire around the middle of the headband 2-3 times. So it looks like there are antennae sticking out from the headband. If you find it difficult to make it stay use a glob of hot glue to secure it, otherwise just bend it as tightly as possible.", "372" ], [ "Then bend the ends of the “antennae” down to create little hooks.\nStep 3: Step 3: Go Crazy..just Kidding You're Almost There!\nStep 3:\nHook the thick wires around the thin wire circle (creating the base for your halo). Tightly wrap the thick wire hooks around your thin wire circle, try to make it so the wire circle can’t slide around. Doing that is practically impossible so plug in that glue gun and stick another glob wherever you think is necessary!\nStep 4: Step Four: Halos Galore!\nStep 4:\nTake 24 inches (amount will depend on how fluffy your boa is) of your thin fluffy boa of choice and glue the end of it to the tight spiral of thick wire on your halo. Then wrap the boa around the thin wire circle, making sure that you are using it liberally enough to not let any wire show. This amount will vary depending on how many feather have fallen off the boa. Make sure the hot glue is dry and then stick that sucker on your head and prance around like the angel you are!", "372" ], [ "DIY Food Photography Backgrounds\nIntroduction: DIY Food Photography Backgrounds\nThe background surface that you use for food photography can elevate your image to a new level. It should have enough character to draw the viewer's eye into the scene and help tell your story, yet not be distracting and take away from the delicious food you are photographing. I like using marble, vinyl and even colored paper, but was looking for some new options. There are some beautiful backgrounds available for purchase, but they can be very expensive. I will show you how to make your own with just a few inexpensive supplies, and best of all, it's EASY and FUN!\nSupplies\n* 2' x 4' piece of 1/2\" thick laminated plywood\n* joint compound\n* oil based spray paint (I used Rustoleum Robins Egg in matte finish)\n* chalky finish acrylic paint (I used Deco Art Everlasting)\n* acrylic paint (I used Deco Art Turquoise Blue and Titanium White)\n* matte finish spray paint\n* putty knife\n* paint brush and/or sponge\nStep 1: Create Texture on the Plywood\nApply a thin layer of joint compound to the plywood with a putty knife. Use the putty knife or a sponge to move it around to get the texture you like. For the blue board, I spread it with the knife in different directions and then lightly dragged the knife across the surface to get an uneven texture. For the pink board, I used a sponge to stipple the surface. You want the board to end up fairly flat so that the things you place on it to photograph (plates, glasses, food, etc.) will sit evenly, but still have enough texture to add visual interest to your images. Allow to dry for at least 24 hours.\nStep 2: Paint the Board\nPaint the entire board with the colors and techniques that you want. Here is where you can get creative and have fun. Don't worry, if you don't like the way it looks, you can just paint over it.", "644" ], [ "It's best to use a matte finish paint so that you don't get unwanted reflections or glare in your photographs.\nFor the blue board, I sprayed the entire surface with the Robins Egg paint. After that dried, I applied the chalky finish acrylic paint lightly over the top with a brush. I wanted a brighter blue color, so I stippled in some Turquoise Blue and Titanium White irregularly over the top.\nFor the pink board, I painted the entire board with Baby Pink acrylic paint. Then I mixed a lighter shade of Baby Pink and stippled it and some Titanium White over the top. Finally, I used a damp paintbrush to blend the colors a bit.\nStep 3: Protect the Surface With Matte Finish Spray Paint\nWhen the surface is completely dry, apply 2 - 3 coats of matte finish spray paint to protect it. If you like, you can paint the other side of the board in a different color/texture and you have 2-for-1. Here are some tips that I learned along the way. For the pink board, I used colors in the same general family, just different tones. I started with the dark color, then added the lighter colors. I photographed the board along the way, to see how it would look in images. You can blend colors with a damp paintbrush or sponge, or add patches of color to create more dimension. Keep working on it until you have something you love.\nI hope you enjoyed this project and are inspired to create some beautiful surfaces and take your photography to the next level.", "744" ], [ "My Digital Print Making Workflow for Kids 12+\nIntroduction: My Digital Print Making Workflow for Kids 12+\nSince we were in permanent lockdown or only had\nhalf of the class any other week we (teachers) didn’t see our pupils that often. That’s is somewhat of a sad situation for arts teachers. Since I love printing, woodblock, linocut, intaglio (etching and engraving) and often do different projects involving printing techniques, I came up with an easy and free workflow for preparing linocuts or woodprints at home with the extra task to use a CAM program and prepare an NC file for CNC cutting the print.\nIn the process there is a lot to learn including digital graphics design, general understanding of print making and some interesting technical challenges.\nI also accidentally found some interesting new possibilities machining Linoleum that I have never before seen anywhere else.\nSome inspiration comes from artists <PERSON> (massive, photorealistic, monochrome woodblock portrait prints) and <PERSON> which uses CNC maschines formulticolor wood prints and automated drawing/plotting.\nSupplies\nFor the first stages you only need a PC and free (online) software and tools.\nFrom there on you will have to use a CNC router and different print making supplies.\nStep 1: ​The Motive and the Manual Way\nA classic topic for linocuts is portrait. We normally use portrait photos which we just alter the contrast a little and print in A4 or A5, whatever size the Linoprint should turn out. Then we draw on the Photos with a very soft graphite pencil (3B-12B).\nThe paper is then turned and laid on the Linoleum. We use the handle of the cutting tool to press the Graphite on the Linoleum and then retrace the motive.\nIf Text is involved the children can now see that the Text is mirrored on the printing plate.\nStep 2: ​The Digital Workflow\nFor photo editing we use Photopea.com which is a down to perfect online Photoshop clone.\nFor homeschooling I upload a step-by-step tutorial with detailed explanations of the tools (how to set a cropping ratio etc.) I will just assume you are capable of basic image editing here…(or able to google relevant video tutorials if you get stuck).\n1. Open your Image so that it fills out your frame or choose an interesting crop.\n2. Create a new Adjustment Layer using “Curves”.\n3. Create an Adjustment Layer using “Threshold”.\n4. Now you can play with the settings to find a good contrast.\n5. If you happen to have a bad picture with too little contrast or other issues you can try compositing different settings with layer masks.\n6.", "74" ], [ "When you are satisfied with the result you have to flip your image horizontally (or just know you will get the mirror image when printing).\n7. Reduce your layers (you can keep all layer when you first make copies of them) to the backfround.\n8. At this point you might have too many details. A good way to get rid of too much detail is a filter.\nTry the “watercolor” filter from the filter gallery.\n9. You can also reduce the resolution and resize it again or hand edit our unwanted details.\n10.Save your work in PSD format and save a copy in GIF format.\nStep 3: Converting Into Vector Graphics\nHere is another teaching moment. We discuss the difference between pixel/raster and vector graphics and when to use one or the other.\nI use convertio.co or freeconvert.com/gif-to-svg/ to convert the GIF into SVG.\nI have tried many online converters and those two are the best. If you want to have a whole class convert their images in one network at school, convertio will display a limit and stop converting files after the first 20 or so images.\nNow the children can see the difference between the GIF and SVG when they open both in a browser window side by side and zoom in.\nYou also can use InkScape to trace pixel images into vector graphics. Using a converter is just the easy way. There are also converters that will output perfectly useable DXF files.\nStep 4: CAM Software\nI use EstlCam for the process. It can do carves and is free to use indefinitely. There is only a waiting period, which is getting longer and longer with time, when saving or opening different files.\nIt also only takes 2 minutes to install and is so easy to learn.", "110" ] ]

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[ [ "The IVP should be sufficient to find the solution at any time. But with operator or matrix equations it does get confusing. A good approach is to solve the equation(s) first for regular functions and plug them in, seeing if they work for operators as well.\nin this derivation: [solution1], the author assumes that $[S_i,S_j]=i \\hbar \\epsilon_{ijk}S_k$ doesn’t only hold for $t=0$, but for all times, why would that be?\nI will show you here: We know that $U(t)U^\\dagger (t) = U^\\dagger(t) U(t) = 1$. And it is the case that we can write $S_i(t) = U^\\dagger(t) S_i(0) U(t)$ - you can see this directly when trying to go from the schrödinger to the <PERSON> picture, and also I will justify it in my answer to your second question below. So, assuming that at t=0 the commutation holds, we multiply by a bunch of $U^\\dagger$ from the left, by $U$ from the right, and insert the identity in the middle in order to get the time evolved version of all three matrices:\n$$S_i S_j - S_j S_i = i \\hbar \\epsilon_{ijk} S_k$$ $$\\implies U^\\dagger (t) S_i U(t)\\,\\, U^\\dagger(t) S_j U(t) - U^\\dagger (t) S_j U(t)\\,\\, U^\\dagger(t) S_i U(t) = i \\hbar \\epsilon_{ijk} U^\\dagger(t)S_k U(t)$$ $$\\implies S_i(t) S_j(t) - S_j(t) S_i(t) = i \\hbar \\epsilon_{ijk} S_k(t)$$\nIn this solution, discussed on this site: [solution2][2], the OP assumes that $S_j(t)$ is of the form $\\exp(-iHt/\\hbar)S_j(0) \\exp(iHt/\\hbar)$ (and therefore actually already postulates the answer), why can we assume that?\nThis is always true of any operator satisfying the heisenberg equation of motion, as long as it doesn't explicitly depend on $t$:\n$$\\frac{d}{dt}A(t)=\\frac{i}{\\hbar}[H,A(t)]$$\n$$\\implies A(t) = e^{i t H/\\hbar}A(0)e^{-i t H/\\hbar}$$\nYou can check this by plugging it in.", "526" ], [ "And this also means that $A(t)=U^\\dagger (t)A(0)U(t)$, which is just the form of the equation above. It works with any observable operator, and any Hamiltonian. Pretty amazing that you can just write out the solution like that. But the caveat is that this only goes so far... there are much more useful ways to write the solution, as you saw in your post where we can write it explicitly in terms of pauli matrices for example. So some might not consider it actually \"solved\" if it is just written in this form.\nSimilarly, the solution in the <PERSON> picture for any wavefunction can be written\n$$|\\psi (t) \\rangle = e^{-itH/\\hbar}|\\psi(0) \\rangle$$", "526" ], [ "Thanks for your hints so far. The question was to some extend already discussed here: (https://physics.stackexchange.com/questions/109343/eigenstate-of-field-operator-in-qft). <PERSON>, I give a more verbose and down-to-earth answer to my question. There is also a remark why I was confused first...\nEigenstates of the annihilation field as classical states\nWe assume a real valued scalar quantum field $A(x)$ of the form (neglecting normalization)\n\\begin{equation} \\hat A(x) = \\int \\hat a^{*}(k)e^{ikx} \\, d^{3} k + \\int \\hat a(k)e^{-ikx} \\, d^{3} k = \\hat A_c(x) + \\hat A_a(x) \\end{equation}\nwhich is split in a creation and annihilation part.", "669" ], [ "We are looking for a eigenstate $| \\psi \\rangle$ of the annihilation operator $\\hat A_a(x)$. Such a state is the tensor product of single mode coherent states: $| \\psi \\rangle = \\otimes_k |\\alpha(k) \\rangle_k$, since every single mode state in the tensor product is an eigenstate of the corresponding annihilation operator $a(k)$ with eigenvalue $\\alpha(k)$. Hence $\\hat A_a(x) | \\psi \\rangle = \\int d^{3} k' e^{-ik'x} \\hat a(k')\\otimes_k |\\alpha(k) \\rangle_k =\\int d^{3} k' e^{-ik'x} \\alpha(k') \\otimes_k|\\alpha(k) \\rangle_k = \\psi(x) | \\psi \\rangle$\nwith the eigenvalue $\\psi(x) = \\int d^{3} k e^{-ikx} \\alpha(k)$. The eigenstate $| \\psi \\rangle$ is also called coherent and can be written as \\begin{equation} | \\psi \\rangle = \\otimes_k e^{\\alpha(k) \\hat a^{}(k)} |0 \\rangle = e^{\\int d^{3}k \\alpha(k) \\hat a^{}(k) } |0 \\rangle = e^{\\int d^{3}x \\hat A_c(x) \\psi(x)} |0 \\rangle = e^{\\int d^{3}x \\hat A(x) \\psi(x)} |0 \\rangle \\end{equation} The first part of the above equation is more or less by definition true (refer to single mode coherent states) the second part is valid since all $\\hat a^{*}(k)$ commute, the third part is valid since (Fourier expansion of field and eigenvalue)\n\\begin{equation} \\int d^{3}x \\hat A_c(x) \\psi(x) = \\int \\int d^{3} k d^{3} q \\, \\int e^{i(k - q)x} d^{3}x \\, \\alpha(q) \\hat a^{} (k) = \\int d^{3} k \\alpha(k) \\hat a^{}(k) \\end{equation}\n(The space integral results in a delta function $\\delta(k-q)$). The last part of the defining equation above is true since $\\hat A_a |0 \\rangle = 0$ and hence $e^{\\int d^{3}x \\hat A_a(x) \\psi(x)} |0 \\rangle = 0$.\nCorollary: $\\langle \\psi |\\hat A_a(x) |\\psi \\rangle = \\langle \\psi |\\psi(x)|\\psi \\rangle = \\psi(x) \\langle \\psi |\\psi \\rangle = \\psi(x)$.", "66" ], [ "The first thing that comes to mind is the fact that energy eigenstates have a periodic phase factor, $e^{iEt/\\hbar}$. In general we usually say that states are defined up to a phase factor, so for a single particle in an energy eigenstate we can ignore it, but this phase factor can manifest physically when you have a state which is a superposition of energy eigenstates, each with its own oscillating phase. A simple example of this which actually results in periodic behavior would be a spin-$1/2$ particle in a magnetic field. Such a system will have a Hamiltonian proportional to the Pauli spin matrix $\\sigma_z$.", "789" ], [ "So our time-evolution operator is $U(t) = e^{i\\omega \\sigma_z t}$. Recall that the Pauli matrices are idempotent, so when we Taylor expand this we can group our terms together and we will find\n\\begin{equation} U(t) = \\cos\\left(\\omega t\\right)+ i\\sigma_z \\sin\\left(\\omega t\\right) \\end{equation}\nFor eigenstates of $\\sigma_z$ this isn't particularly interesting. The $\\sigma_z$ will give us just a + for $\\vert \\uparrow \\rangle$ or a - for $\\vert \\downarrow \\rangle$ and of course the modulus of the state won't change but it will have a time-oscillating phase factor. Instead let's think about a superposition of such eigenstates, like $\\vert \\psi \\rangle \\equiv\\frac{1}{2}\\left(\\vert \\uparrow \\rangle + \\vert \\downarrow \\rangle\\right)$.\n\\begin{equation} \\begin{split} U(t) \\vert \\psi \\rangle = \\frac{1}{2}\\cos\\left(\\omega t\\right)\\vert \\left(\\vert \\uparrow \\rangle + \\vert \\downarrow \\rangle\\right) + \\frac{i}{2} \\sin\\left(\\omega t\\right) \\left(\\vert \\uparrow \\rangle - \\vert \\downarrow \\rangle\\right) \\ = \\frac{1}{2} e^{i\\omega t} \\vert \\uparrow \\rangle + \\frac{1}{2} e^{-i \\omega t} \\vert \\downarrow \\rangle \\end{split} \\end{equation}\nNot incidentally, this state was chosen to have a spin of $+\\hbar/2$ along the $x$ direction, but we can see in the above equation that when we evolve it in time we reach a point where it will have spin $-\\hbar/2$ along the $x$ direction, when $\\cos(\\omega t) = 0$ and $\\sin(\\omega t) = 1$, so the expectation value of the $x$ spin of this particle is periodic.\nBecause the Hamiltonian operator is Hermitian by assumption, it can be diagonalized and the operator exponential can be rewritten as a manageable <PERSON> series, but this nice periodic form only works because the square of our Hamiltonian is proportional to the identity matrix, so we could group terms in the <PERSON> expansion to give us a cosine multiplied by the identity and a sine multiplied by the $\\sigma_z$ operator. In general this procedure does not work out quite as nicely, but you can always think about the interference of the phase factors I mentioned in the first paragraph.", "66" ], [ "Second Quantization in Matlab\nThis question may be more suited for physics.stackexchange, but I saw this post was recommended for StackOverflow or Computational Science, so I'm asking my question here.\nI am trying to write a program in Matlab to evaluate an expression with fermionic annihilation and creation operators. Define $${f, g } \\equiv fg + gf$$ then the fermionic second quantization operators satisfy $${a_i,a_j } = { a_i^\\dagger, a_j^\\dagger} = 0 \\qquad {a_i^\\dagger, a_j} = \\delta_{ij}$$ $\\forall i, j \\in {1, 2, ..., N }$ for some given $N$.\n$W(t)$ is a $2N \\times 2N$ matrix that I know that gives me the time evolution of the operators in the <PERSON> picture; \\begin{align} a_i(t) &= \\sum_{j=1}^N \\left(W_{2i-1,2j-1}(t)a_j + W_{2i-1,2j}(t)a_j^\\dagger\\right)\\ a_i^\\dagger(t) &= \\sum_{j=1}^N \\left(W_{2i,2j-1}(t)a_j + W_{2i,2j}(t)a_j^\\dagger\\right) \\end{align} i.e. $$\\left(\\begin{matrix}a_1(t)\\a_1^\\dagger(t)\\\\vdots\\a_N(t)\\a_N^\\dagger(t) \\end{matrix}\\right) = W(t)\\left(\\begin{matrix}a_1\\a_1^\\dagger\\\\vdots\\a_N\\a_N^\\dagger \\end{matrix}\\right)$$\nI want to write a function that takes in $W(t)$ (evaluated at a given $t$) and $j$ and returns $$\\langle \\psi | \\left(\\prod_{i=1}^{j-1}\\left(1-2a_i^\\dagger(t)a_i(t) \\right) \\right)\\left(a_j(t)^\\dagger + a_j(t) \\right) | \\psi \\rangle$$ where $$| \\psi \\rangle = \\left(\\prod_{i=1}^N\\frac{1+a_i^\\dagger}{\\sqrt{2}} \\right)|0\\rangle = 2^{-N/2}\\left(|0...0\\rangle + |0...1 \\rangle + |0...1 \\ 0 \\rangle + |0 ...1 \\ 1 \\rangle + ... + |1...1 \\rangle \\right)$$ $|\\psi\\rangle$ is just a normalized, equally weighted linear combination of all states.", "281" ], [ "Note that it does not change with time. The time evolution is encoded in the operators.\nMy thought was to use Matlab's symbolic algebra, and try and code for what each operator does to a state. But the symbolic algebra does not always preserve order, which is crucial because the operators don't always commute. Also, trying to just naively go through is so computationally expensive and grows exponentially with $N$.\nAny ideas?", "82" ], [ "It is posslible to do this proof in a direct way using a slightly different and in my opinion a lot more sensible approach to the creation/annihilation operators. I will write it up here for the benefit of any interested.\nThe inner product of $N$ particle states can be written as: $$ \\langle\\chi_1,...,\\chi_N|\\Psi_1,...,\\Psi_N\\rangle= \\det {\\begin{pmatrix}\\langle\\chi_1|\\Psi_1\\rangle &...& \\langle\\chi_1|\\Psi_N\\rangle \\.\\.\\\\langle\\chi_N|\\Psi_1\\rangle& ...& \\langle\\chi_N|\\Psi_N\\rangle\\end{pmatrix}}$$ Using th Slater determinant for fermion- and the permanent for Boson-states.\nWith this we get a new representation of the annihilation operator $C_a$.", "66" ], [ "We are now looking at $N-1$ particle states:\n$$ \\langle\\chi_1,...,\\chi_{N-1}|C_a |\\Psi_1,...,\\Psi_N\\rangle = \\langle\\Psi_1,...,\\Psi_N|C_a^\\dagger |\\chi_1,...,\\chi_{N-1}\\rangle^ \\ \\langle\\Psi_1,...,\\Psi_N| a,\\chi_1,...,\\chi_{N-1}\\rangle^=\\det {\\begin{pmatrix}\\langle \\Psi_1 |a \\rangle &\\langle\\Psi_1|\\chi_1\\rangle &...& \\langle\\Psi_1|\\chi_{N-1}\\rangle \\.\\.\\ \\langle \\Psi_1|a \\rangle & \\langle\\Psi_N|\\chi_1\\rangle& ...& \\langle\\ \\Psi_N|\\chi_{N-1}\\rangle\\end{pmatrix}}^*$$ from the definition of the determinant we know we can write this equally as: $$=\\sum \\limits_{k=1}^N \\xi^{k-1}\\langle a|\\Psi_k \\rangle \\langle\\chi_1,...,\\chi_{N-1}|\\Psi_1,...,\\sim\\Psi_k,...,\\Psi_N\\rangle$$ whre $\\xi=-1$ for fermions and $+1$ for bosons and $\\sim\\Psi_k$ means $\\Psi_k$ is not part of that state. This gives a new representation of the annihilatinon operator $$C_a|\\Psi_1,...,\\Psi_N\\rangle=\\sum \\limits_{k=1}^N \\xi^{k-1}\\langle a|\\Psi_k \\rangle |\\Psi_1,...,\\sim\\Psi_k,...,\\Psi_N\\rangle$$\nWe now need to look at a one particle Operator $R_{ab}=|a\\rangle \\langle b|$ definied as in the question above: $$R_{ab}|\\Psi_1,...,\\Psi_N\\rangle=\\sum \\limits_i^N |\\Psi_1\\rangle\\otimes..\\otimes \\underbrace{| a \\rangle}{\\text{i-th ket}} \\otimes...\\otimes|\\Psi_N\\rangle \\langle b | \\Psi_i\\rangle $$ with this and the newfound representation of the operators we see that the operator $R{ab}$ can be writtten as $R_{ab}=C_a^\\dagger C_b$. How can we see this?\nFirst $$C_a^\\dagger C_b |\\Psi_1,...,\\Psi_N\\rangle= \\sum \\limits_{k=1}^N \\xi^{k-1}\\langle b|\\Psi_k \\rangle |a,\\Psi_1,...,\\sim\\Psi_k,...,\\Psi_N\\rangle$$ second using the symmetry of the states we get: $$|a,\\Psi_1,...,\\Psi_{k-1},\\Psi_{k+1},...,\\Psi_N\\rangle=\\xi^{k-1}|\\Psi_1,...", "66" ], [ "The answer to this is a bit nuanced so I have now edited the answer to make it as clear as possible.\nThe big picture is: Yes, it is possible to measure a wave function, if it is possible to find or produce particles with that wave function so that repeated measurements can be made (not on the same particle each time, but on a different particle which is known to have the same wave function). This can be done in practice. For example, this experiment effectively measures the magnitude of the wave function in momentum space for an electron in a hydrogen atom: source.\nIf you write $$\\psi(\\vec{r})=A(\\vec{r})e^{i\\alpha(\\vec{r})}$$ For $A,\\alpha$ real, then $A$ can be determined by measurements of position, and I believe it is possible to find $\\alpha$ only from momentum measurements up to a constant offset $\\alpha(x) \\to \\alpha(x) + c$. Because of this constant offset which is not measurable, $\\psi(\\vec{r})$ is not measurable at a point, but $|\\psi(\\vec{r})|^2 $ is, $A(\\vec{r})$ is, and $\\alpha(\\vec{r})$ is up to that \"offset\", which is called a global phase.\nOf course, any finite number of measurements will only give information on a finite number of points of $\\psi(\\vec{r})$, each with uncertainty as well, especially because many measurements are necessary to measure a probability. These measurements must be done by repeatedly preparing a particle in that wave function and then measuring at a chosen later time. The experimentalist does not need to know what the wave function is beforehand, she/he must only know that the wave function is the same for each particle. Then, she can interpolate in between the measured points to come to a good guess for $\\psi$ at all points. In practice, any experimental outcome which is predicted by $\\psi(\\vec{r})$ can also be used to constrain it.\nThere is a practice of measuring states called Quantum Tomography. It has its own wikipedia.", "795" ], [ "It is usually used for finite-dimensional systems. But in reality every system is infinite dimensional, one only treats them as finite-dimensional. One could treat the position space wave function in the same way.\nThat being said, though it can be done in principle, I'm not aware of a full tomography which has been done in practice. If one really doesn't exist, this is a severe experimental weakness of testing the theory in my view. If anyone has a source to one, I'd be interested. I know of many momentum experiments where the fourier transform of the wave function was in fact checked, but not the entire thing.\nI will point out again for clarity, because it seems that others are of the opinion that I have not emphasized this enough, that if you do not have the ability to find or produce many particles in the unknown state $\\psi$ then it is not possible to measure in practice. It seems to me, though, that a clever setup could be used to measure almost any wave function in principle. Whether technology has reached that point is another question. But I will do due dilligence and flag that last statement as opinion, because I cannot provide references or proofs that it must be so.", "795" ], [ "I’m assuming that by cross-terms you mean off diagonal terms.\nFirst, when talking about off-diagonal terms we clearly mean in a fixed basis. For example, in an eigenbasis of $\\rho$ your state has no off-diagonal elements whatsoever.\nSecond, what you say about measuring clearly holds when performing measurements in that basis ($|0\\rangle, |1\\rangle$ in your basis). Or more precisely when we measure an observable that has the same eigenbasis.\nComing to the physical meaning of these off-diagonal terms, they are also called ‘coherences’. They are responsible for the interference effects of a quantum particle. In particular those effects that make them sometime look like waves. The prototypical experiment that reveal quantum coherence is the double slit experiment.\nThe following thought experiment has been put forward by <PERSON> et al. (see [1]) to describe the essence of the quantum coherence and the double slit experiment.\nImagine to prepare the following state\n$$ |\\Psi\\rangle = ( |\\phi\\rangle_L + e^{i \\theta} |\\phi\\rangle_R)/\\sqrt{2} $$\nWhere $|\\phi\\rangle_{L,R}$ are Gaussian wavepackets centered around $L, R$ (left, right) with spread much smaller than their separation. This requirement assures that the two states are essentially orthogonal.", "976" ], [ "The left (right) wave packet is prepared with momentum $p$ ($-p$) such that it travels to the right (left). If you measure the position at $t=0$, you will find two Gaussian blobs around $L$ and $R$ and the phase $\\theta$ is not observable. From this experiment alone the state cannot be distinguished from a classical state.\nNow let evolve the state until the time where the wavepackets collide. At this point it turns out that if you measure position the phase $\\theta$ becomes observable! It’s as if the particle interfered with itself, pretty much like a wave.\nIf you repeat the experiment many times with different phases $\\theta$, and every time you measure the position of the particle (for example, the particle hits a screen), you will indeed see a figure of interference forming on the screen.\nAdded 19/9/22\nMathematical Details\nWe work in a setting where there is a free particle (not subject to any potential) moving on the real line. Hence the Hamiltonian is $H=a p^2$ ($a=1/(2m)$). If you want to be pedantic the Hilbert space is $\\mathcal{H} = L^2(\\mathbb{R})$.\nFirst consider as initial state a Gaussian wavepacket centered around $x_0$ moving with momentum $p_0$:\n$$ \\psi(x)=\\frac{e^{-\\frac{(x-x_{0})^{2}}{4\\sigma^{2}}}}{(2\\pi\\sigma^{2})^{1/4}}e^{ip_{0}x}. $$\nCorrectly $|\\psi(x)|^2$ is a Gaussian centered around $x_0$ with standard deviation $\\sigma$.\nThe probability distribution of position at time $t$ is\n\\begin{align} \\left|\\psi(x,t)\\right|^{2} &=\\frac{e^{-\\frac{(x-x_{t})^{2}}{2\\sigma_{t}^{2}}}}{\\sqrt{2\\pi\\sigma_{t}^{2}}} \\ x_{t} &=x_{0}+2p_{0} a t \\ \\sigma_{t} &=\\sqrt{\\sigma^{2}+\\frac{a^{2}t^{2}}{\\sigma^{2}}}. \\end{align}\nThis means that if $p_{0}>0$ ($p_{0}<0$) the wavepacket travels to the right (left). Moreover the wavepacket spread a bit in time according to $\\sigma_t$.\nNow initialize the system in the following superposition.", "795" ], [ "This is a good question that I have also had, so I'm answering this even though it is two years old! It looks like your definitions are all fine, but I would use\n\\begin{equation} \\hat{\\mathcal{P}}\\hat{\\psi}^{}{A}\\hat{\\mathcal{P}}^{-1} = \\sum{B} \\hat{\\psi}{B}^{\\dagger}(U{P})_{B, A} \\end{equation}\nas it simplifies notation. I'll also refer to the particle-hole operator as $\\hat{\\mathcal{P}}$ to keep my notation clear, but that's just a personal preference.\nUsing the above definition we implement the transformation of $\\hat{\\mathcal{P}}$ on $\\hat{H}$ as\n\\begin{equation} \\begin{split} \\hat{\\mathcal{P}}\\hat{H}\\hat{\\mathcal{P}}^{-1} &= \\sum_{A, B} \\hat{\\mathcal{P}} \\hat{\\psi}{A}^{\\dagger} \\hat{\\mathcal{P}}^{-1} \\hat{\\mathcal{P}} H^{}{A, B} \\hat{\\mathcal{P}}^{-1} \\hat{\\mathcal{P}} \\hat{\\psi}^{}{B} \\hat{\\mathcal{P}}^{-1}\\ & =\\sum{A, B} \\sum_{C, D} (U_{P}^{})^{\\dagger}{A, C} \\hat{\\psi}{C} H_{A, B} \\hat{\\psi}{D}^{\\dagger} (U{P}^{})^{}{D, B} \\ &= \\sum{A, B}\\sum_{C, D} \\delta^{}{C, D}(U{P})^{\\dagger}{A, C}H^{}{A, B}(U_{P})^{}{D, B} - \\hat{\\psi}^{\\dagger}{D}(U_{P})^{}{D, B}H^{}{A, B}(U_{P})^{\\dagger}{A, C}\\hat{\\psi}^{}{C} \\ & = \\sum_{A, B}\\sum_{C, D} (U_{P})^{\\dagger}{A, C}H^{}{A, B}(U_{P})^{}{C, B} - \\hat{\\psi}^{\\dagger}{D}(U_{P})^{}{D, B}H^{T}{B, A}(U_{P})^{\\dagger}{A, C}\\hat{\\psi}^{}{C} \\ & = \\sum_{A, B}\\left( \\delta^{}{A, B}H{A, B} - \\sum_{C, D}\\hat{\\psi}^{\\dagger}{D}(U{P})^{}{D, B}H^{T}{B, A}(U_{P})^{\\dagger}{A, C}\\hat{\\psi}^{}{C} \\right) \\ & = \\text{Tr}(H) - \\sum_{C, D} \\hat{\\psi}^{\\dagger}{D}H^{}{D, C}\\hat{\\psi}^{}_{C}, \\end{split} \\end{equation}\nwhere we have used the anticommutation relation ${\\hat{\\psi}^{}{A}, \\hat{\\psi}^{\\dagger}{B}} = \\delta^{}{A, B}$ between the second and third lines and the unitarity of $U{P}$ between the fourth and fifth lines. We require $\\hat{\\mathcal{P}}\\hat{H}\\hat{\\mathcal{P}}^{-1} = \\hat{H}$ if our Hamiltonian respects PHS, demanding the conditions that\n\\begin{equation} \\begin{split} \\text{Tr}(H) &= 0 \\ H = -U_{P}&H^{*}U_{P}^{\\dagger} \\end{split} \\end{equation}\ni.e.", "526" ], [ "the Hamiltonian is traceless. We have also used the Hermicity of the Hamiltonian in the second equality. Thankfully, these two conditions are complementary, since $H = -U_{P}H^{*}U_{P}^{\\dagger}$ implies that our Hamiltonian has a symmetric spectrum.", "526" ] ]

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[ [ "Actually, you have asked three different questions: 1) [Does algorithm always have a return value?[sic]\"\nThe algorithm by default is not a function/method (or to say program), but it could be. Sticking to the stringent definition of the algorithm. An algorithm is a set of instruction for accomplishing a task. Every piece of code could be called an algorithm e.g. 1) defining a variable or 2) writing a logic for a loop is also an algorithm. So, addressing to your original question \"Does algorithm always have a return value?\" answer is 'NO'. In similar situations like 1), and 2) an algorithm does not return a value.\n2) \"I learned that the algorithm written in programming langauge always have a return value, not necessarily an input value.[sic]\"\nIf you wish to convert/write your pseudo code to a specific program in some programming language e.g. C/C++. Then every program should consist of at least one function. Programming languages like C/C++/JAVA/C# etc., provides default function call Main() in which you can call user defined function(s) (or main itself).\nSo, reaching the end of a function other than main is equivalent to return;.", "242" ], [ "reaching the end of the main function is equivalent to return 0;. reaching the end of any other value-returning function is undefined behavior, but only if the result of the function is used in an expression.\nIn certain languages like C/C++ there are features which allows function to defined as 'no-return' function.\n#include <stdlib.h>\n#include <stdio.h>\n#include <stdnoreturn.h>\nnoreturn void stop_now(int i)\n{\nif (i > 0) exit(i);\n}\nint main(void)\n{\nputs(\"Preparing to stop...\");\nstop_now(2);\nputs(\"This code is never executed.\");\n}\nThe 'noreturn' keyword appears in a function declaration and specifies that the function does not return by executing the return statement or by reaching the end of the function body. This type of adventure could be costly and can cause undefined behaviour to your C/C++ program.\nP.S. When function/method have return type as 'void' they do not return any value, or anything. Control simply returns. It is also important to learn that void doesn't mean nothing. void is a type to represent nothing. That is a subtle difference : the representation is still required, even though it represents nothing.\n3) \"But it we use the main function with void return value, does that algorithm have a return value?[sic]\"\nP.S. If you define return type of main function as 'void' then it does not have any return value. You can actually omite 'return' keyword or simply type 'return' with no expression (or even 0).", "904" ], [ "For most of these questions, the Runtime Environment as it seems to be described in your book is more easily understood by comparing a low-level language like C, to a VM (Runtime Environment) language like Java.\nHow does compiler execute the code, it is only supposed to generate the intermediate code right?\nYour quote doesn't say the compiler executes the code. It says that it can start up a RTE which takes over. For lower level languages that don't use a VM/RTE, it can signal the OS to begin execution of the program. In either case, this is a hand-off, not the execution itself.\nAnd does it create runtime environment? I mean there's not a virtual machine that the program runs on, it just runs on your computer right? When does it create a runtime environment?\nPractically speaking, the interpretation of these terms is largely dependant on the language in question.\nAll programs run on the OS, which manages access to hardware for running programs.\nIn a low-level language like C, the Runtime Environment as a concept is arguably indistinguishable from the OS itself.", "77" ], [ "Memory alloc/dealloc requests are made directly from the program to the OS.\nIn a high-level language like Java (the most commonly references \"VM\" language), the Runtime Environment as a concept is used loosely to refer to the program that sits between the executing program and the OS. The Java Runtime Environment consists of the Java Virtual Machine (which handles memory management requests to the OS, among other things), some libraries, and utilities.\nIsn't memory managed by the operating system? Why is allocation of storage done by the compiler and at what point? Probably what variables are needed and how much may be known by the compiler but, how does it communicate this information to the OS?\nHardware memory address reservation is managed by the OS.\nSpecifics of the complexity of memory management intervention provided by the RTE is going to be specific to the RTE implementation. Some provide more features than others.\nThe Java Virtual Machine makes the alloc/dealloc requests to the OS on the behalf of the executing programs. It also has a Garbage Collection cycle which looks for and frees memory reservations that are no longer being used by the program, rather than holding them all until execution halts.\nIn C, it is the explicit responsibility of the executing program to make these requests to the OS. Memory requested remains reserved until the program halts, or the memory is explicitly released by the program.", "10" ], [ "Instructing operating system - Knowing it's functionalities\nTL;DR: I would like to know how a programming language, the OS and drivers work together to perform a task.\nI (and we all) have used various softwares/modules/packages on the top of our OS which provides us with a very simple API/GUI/CLI to perform tasks. But one question which keeps me disturbing is:\nHow does that software/module/package actually perform any specified action? I mean, it actually should be instructing OS to do that. So, OS should be providing procedure calls. But many functionalities aren't provided by the OS itself but the device driver provides it. So, how does the OS know what functions are supported by this particular device? And how can we instruct a particular device to perform a particular task?\nLike suppose we are planning to change the IP address of a computer, we can do it through the OS's GUI or CLI. IP address is a logical thing and doesn't belong to a specific device (hardware), so we don't need any device driver for that. Keeping this simple, how can I write a module in python (without using already available API functionality) to change the IP address of a computer? Suppose the language itself i.e. python or a module/package written in python provides this functionality that calling a function such as change_ip() does the task. But how does it actually work in background? I know the background job is different for different OSes but I don't know how that module/package/language interacts with the OS. Or is it doesn't actually interact with the OS and performs the operations itself? (Maybe its possible in some cases)\nNow, some other example.", "705" ], [ "Suppose I would like to change the MAC address of the machine. Now, this operation is device dependent (the Network Card). Also, few NICs doesn't support this MAC changing functionality. This is actually dependent on the device driver and not the driver itself. So how can the OS know if the function is supported or not? Also, if the module/package/language is directly performing tasks without the help of OS, how can it know if the functionality is supported?\nA very few might understand this question.. I don't know how to ask.. I am pursuing BE in Computer Engineering and I know several concepts and theories. But our education system makes us learn the things separately and not understand them in a combined manner. Like what would be the benefit if I know Operating System and Python but I don't know how they interact with each other and work in a combined manner. So, this is the base of my query.\nI looked for an answer on Google but never found one.. Thank you..", "705" ], [ "You have to first understand what is the problem here. A problem is usually a relation between inputs and outputs. The complexity is a measure of difficultly for algorithms to obtain input from the output. A single instance of a problem like the one you have are trivial, since there exists an algorithm that would output the answer (whether it is provable, refutable, or neither). However from the practical point of view this is not of much use.\nAsking for $\\mathsf{NP}$-hardness of an instances is a confusion that is not uncommon among non-experts in theoretical computer science. The reason for this confusion is that in algorithms/complexity courses, many students mistakenly view $\\mathsf{NP}$-hardness as \"not solvable in practice\" or \"no algorithm\". $\\mathsf{NP}$-hardness does NOT mean that the instances of the problem cannot be solved in practice (take for example SAT), it neither means that there are no algorithms, and it doesn't even mean that there is no efficient/polynomial time algorithm for the problem ($\\mathsf{P}$ vs. $\\mathsf{NP}$ is still an open problem in theoretical computer science and it doesn't seem that we are close to answer it).\nI am guessing that what you really want to ask is if it is possible to use computer to find the answer to $\\mathsf{P}$ vs. $\\mathsf{NP}$.", "915" ], [ "But this is not a very precise question: what do we mean by using computers to solve an instance of a problem?\nLet me try to clarify this: assume that I know the answer to the question, and I write a one line program that always outputs the same correct answer (e.g. the answer to the question is YES and my program is cout<<\"YES\";). Do we consider this as using computers to find the answer to the question? I would assume no.\nAnother situation to understand the issues: assume that I have a brute-force algorithm and it finds the answer after say 1 billion years. It is an answer after a finite time, so it is a constant time algorithm However it is not really useful for us, since presumably we want to know the answer in a reasonable amount of time (say before we die). What is a reasonable amount of time? It is not a precise concept.\nIn summery,\n* a problem instance cannot be $\\mathsf{NP}$-hard, an problem instance is trivial from complexity perspective (there exists an algorithm that outputs the correct answer in constant time, we know it is one of the 3 programs (always output \"YES\", always output \"NO\", always output \"UNDECIDABLE\") but we don't know which of these 3 programs correctly solves the problem.\n* $\\mathsf{NP}$-hardness is a theoretical concept for a general instance of problems, it doesn't imply that we cannot solved a problem on instances we care about in practice (SAT is $\\mathsf{NP}$-hard but in practice SAT-solvers work amazingly well on instances that some industries case about and understanding why this is the case is an on-going research topic).\n* in practice often we don't care about general inputs, we care about a specific subclass of inputs, and on those inputs we might be able to solve the problem. However we should understand that our algorithm will not work on general examples. Any algorithm that works well on some subsets of inputs needs to exploit some properties of those inputs. If we don't have any idea about the particular properties of our instance then we are in a situation similar to the general case inputs.\n* when we don't know any particular property of an instance of a problem we think of it at that time as being hard as general case.\nOne final point: even if $\\mathsf{P}=\\mathsf{NP}$ and we can solve SAT and proof search for proofs of a given length efficiently (given $\\varphi$ and $n$, is there a proof of length $n$ for $\\varphi$ in theory $T$, think of $T$ as ZFC for simplicity), it is possible that it won't help much with finding a proof of that fact for various reasons, e.g.:\n* although the statement is true, there is no proof of it, so current axioms of mathematics are incapable of settling the question positively or negatively,\n* we have an efficient algorithm for searching for proofs of given length, however the constants in the running time of the algorithm are huge, so even though the algorithm is polynomial time, it is not a practical algorithm (e.g. running time is $10^{1000}n^{500}$).\nAnd similarly if $\\mathsf{P}\\neq\\mathsf{NP}$, it doesn't mean that there isn't a short proof of this particular statement in $T$.", "603" ], [ "What is the logical reasoning behind <PERSON>'s Theorem proof of unique solution?\nGeeksforgeeks contains a proof of <PERSON>'s theorem, asserting that $R=QP^$ is the unique* solution to $R=Q+RP$. The proof is reproduces below.\nMy question is:\nWhat is the logical reasoning to prove that any equation is the unique (only solution)? Particularly in this case, how can the procedure below logically lead to the proof that R=QP must be the unique (only solution)*?\nHere is my understanding of the proof:\n1. Recursively substitute $R$ in $R=Q+RP$ with $Q+RP$\n2. Establish the recursive definition of $R$\n3. Generalize the definition to $R=QP^*$\nDisclaimer: The proof below is second part of a 2-parts proof from the original Geeksforgeeks's proof of <PERSON>’s Theorem. Originally, the proof starts out to prove $R=QP^$ is a solution to $R=Q+RP$. I omitted this part here because I want to focus on the second part of the proof, which is to prove uniqueness. However, to clear any confusions, please allow the proof below to be based on the assumption that $R=QP^$ is a solution to $R=Q+RP$ has been correctly proven prior and that $R=QP^$ can be used as a corollary for proof below, which try to prove $R=QP^$ is the unique solution to $R=Q+RP$, given P does not contain $\\epsilon$**\nGiven that $P$ and $Q$ are two regular expressions over $\\Sigma$, and $P$ does not contain $\\epsilon$.", "330" ], [ "Start with: $$R = Q + RP$$\nNow, replace $R$ by $R = Q + RP$: $$ \\begin{align} R &= Q + (Q + RP)P \\ &=Q + QP + RP^2 \\end{align} $$\nAgain, replace $R$ by $R = Q + RP$: $$ \\begin{align} R &= Q + QP + (Q+RP)P^2 \\ &= Q + QP + QP^2 + RP^3 \\ &= \\cdots \\ &= Q + QP + QP^2 + \\cdots + QP^n + RP^{n+1} \\end{align} $$\nNow, replace $R$ by $R = QP^$ to get $$ R = Q + QP + QP^2 + \\cdots + QP^n + QP^P^{n+1} $$\nTaking $Q$ as a common factor, $$ \\begin{align} R &= Q(\\epsilon + P + P^2 + \\cdots + P^n + P^P^{n+1}) \\ &= QP^, \\end{align} $$ as $\\epsilon + P + P^2 + \\cdots + P^n + P^* P^{n+1}$ represents the closure of $P$.\nThus, $R = QP^*$ is the unique solution to $R = Q + RP$.\nClarifications:\nI asked this question with the assumption that this is a valid proof $R=QP^$ is the unique* solution to $R=Q+RP$ (a). There are two basis for my assumption:\n(1) This is the most popular proof found on the Web, I have included multiple sources as samples below. Across different authors, the proof takes exactly the same form as the procedure demonstrated above. Therefore, through inductive reasoning, I believe that this proof and its similar forms is a valid proof of (a). Otherwise, all those authors somehow collectively give a false proof.\n(2) The procedure is logically and mathematically valid at each and every step, including the generalization of P* given that P does not contain $\\epsilon$ as demonstrated above. Therefore, through deductive reasoning and (1), I believe that this proof and its similar forms is a valid proof of (a) until otherwise disproved through valid and sound counterargument.\nOf course, what missing here is the intuitive reasoning from which one can derive that this proof indeed validly proves (a) to be true. Moreover, I am very curious and interested in the general intuitive and logical reasoning to prove anything as a unique solution.\nI am not asking for a new proof. If for logical and/or mathematical reason, you can prove that this proof is invalid and MUST be discarded. Please present your evidence/counterargument in your answer.", "945" ], [ "For every imperative function, is there a functional counterpart with identical performance or even instructions?\nCurrently, I haven't learned about a functional language that can achieve the same performance as C/C++. And I have learned that some languages that favor functional programming to imperative programming, such as Scala and Rust, use imperative ways to implement their library functions for better efficiency.\nSo here comes my question, on today's comptuters that execute imperative instructions, is this a limitation of the compiler or functional programming itself? For every imperative function with no side effects, either in a language without GC such as C/C++/Rust/assembly or one with GC such as Java, is there a pure functional counterpart in Haskell, Scala, etc. that can be compiled to run with identical performance in time and space (not just asymptotic but exactly the same) or even to the same instructions, with an optimal functional compiler that utilizes all modern and even undiscovered optimization techniques such as tail recursion, laziness, static analysis, formal verification, and so on which I don't know about?\nI am aware of the equivalence between λ-computable and Turing computable, but but I couldn't find an answer to this question online. If there is, please share a compiler example or a proof. If not, please explain why and show a counter-example.", "82" ], [ "Or is this a non-trivial open question?\nSupplementary edits as suggested by <PERSON>:\nTo be more specific, here are 2 examples that led into thinking about this question.\nFor example, tail recursion and accumulators can improve the performance of some recursive functions to be identical to an imperative implementation using for. In some cases they might even have the same instructions.\nAnother example is about laziness in Haskell. Laziness can help avoid unnecessary copying of data structures and make performance better. However, laziness leaves wrappings, closures, etc. in the runtime and still can't make the program as fast as an imperative implementation where there are no such things. So I am wondering whether such things can be statically removed before runtime during compilation.\nSupplementary edits as suggested by <PERSON>:\nThe question can also be stated in this way: is there a language that supports both pure functional programming and imperative programming, paired with an optimized compiler, in which every function with no side effects implemented imperatively can be replaced with one implemented purely functionally, at no cost of performance or even compiled to the same instructions?", "82" ], [ "Naming linear data or non-linear data is a bit misleading and wrong I would say. Instead, there is linear relation and non-linear relation between variables would be better and correct naming. It can easily be explained by example from real life.\n* Non-linear relation: Any kind of relationship that is not linear can be put forward as an example (e.g. quadratic relation: y = intercept + x^2, square root relation: y = intercept + 6 * sqrt(x) etc.) Let's imagine a world where we are not aware of the free fall equation and we use ML to learn and predict it :). In that case (specific and simplified case), the algorithm would need to learn an equation in the following structures = v₀t + (1/2)gt², where t is our independent variable, s is our target or dependent variable and v₀, g would be our coefficients to be learned. In other words, you would want to predict free fall (distance or height) using time. In that fictional world, <PERSON>’s Law of Universal Gravitation (F = G * (M1 * M2) / r^2), Area of a circle (A = π * r^2) would also be a quadratic problem for ML. Linear functions do not meet the requirements of such cases unless you use some kind of transformation, let's say take the square root of r^2 from <PERSON>'s law or the square root of t^2 from free fall then use them in a linear function.", "964" ], [ "The most known example of non-linear real-life relation is a prediction of height using age. Height changes continuously, however, in different rates: until 13 gradually increases, between 13-18 significantly increases, between 18-25 slightly changes, and after 25 it does not change. Thus, it is impossible to fit it into a linear equation, because it is not dependent on a single coefficient or i.o.w. it does not fit into the formula height = intercept + b * age because coefficient (b) is not constant over time (age). Moreover, Graph, Tree, and other similar structures are also fitted into a non-linear relationship. In cases where the result is highly dependent on ifs, linear algorithms are useless because you cannot fit the relationship into y = a + b * x. Let's say, you want to predict who will win a chess game basing on the moves they make, you would use a tree-like (e.g.: alpha-beta pruning) algorithm to predict it.\n* Linear relation: It is simply the relations where those relations can be explained by the y = a + b * x formula or even y = a + b1* x1 + b2*x2 + .... The simplest example is predicting the cost that is spent in the bar (or any kind of entertainment venue). cost = intercept (let's imagine you pay money for entering to the bar) + (the price of a drink) * (the number of drinks bought) + (the price of appetizer) * (the number of appetizers bought) would be our formula.", "716" ], [ "The issue is mostly a historic artifact, not an impossibility of implementation.\nThe way most C compiler build code is so that the compiler only sees each source file at a time, it never sees the whole program at once. When one source file calls a function from another source file or a library, all the compiler sees is the header file with the return type of the function, not the actual code of the function. This means when there is a function that returns a pointer, the compiler has no way to tell if the memory that pointer is pointing to needs to be freed or not. The information to decide that is not shown to the compiler at that point in time, a human programmer on the other side is free to look up the source code of the function or the documentation to find out what needs to be done with the pointer.\nIf you look into more modern low-level languages like C++11 or Rust you'll find that they mostly solved the issue by making memory ownership explicit in the type of the pointer. In C++ you would use a unique_ptr<T> instead of a plain T* to hold memory and the unique_ptr<T> makes sure that the memory gets freed when the object reaches the end of the scope, unlike the plain T*.", "10" ], [ "The programmer can hand the memory from one unique_ptr<T> to another, but there can only ever be one unique_ptr<T> pointing at the memory. So it is always clear who owns the memory and when it needs to be freed.\nC++, for backward compatibility reasons, still allows old style manual memory management and thus the creation of bugs or ways to circumvent the protection of a unique_ptr<T>. Rust is even more strict in that it enforces memory ownership rules via compiler errors.\nAs for undecidability, the halting problem and the like, yes, if you stick to C semantics it is not possible to decide for all programs when the memory should be freed. However for most actual programs, not academic exercises or buggy software, it absolutely would be possible to decide when to free and when not to. That's after all the only reason why human can figure out when to free or not in the first place.", "10" ] ]

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[ [ "If realism is important in your novel, you should bear in mind that all the areas of the brain, although consisting of numerous ‘functions’ (for instance, the Area of Broca and Wernicke’s Area are implicated in the provision of speech, the hippocampus forms part of the emotional memory formation substrate, etc), by and large follow the same processing paradigm – receive inputs; do stuff; push outputs.\nThe elements of this paradigm also follow a predictable physiology – that is, the actual type of neurotransmitter may vary (dopamine, serotonin, GABA, etc), but the operation is the same: neurotransmitters (regardless of type) collect in vesicles and move towards the neural terminal in these vesicles, which merges with the terminal wall, thus causing the neurotransmitter content to be dumped into the synaptic gap. After an interval, a ‘pump’ sucks up the remaining transmitters (called re-uptake); the other transmitters of this collection bind with specific receptor channels on the dendrites of the recipient neuron. As an important note: this does not change for the different areas of the brain.\nAll controlled substances either act as agonists (accelerating this flow), or antagonists (interrupting the flow). Accordingly, your drug will not be able to isolate areas of function, (e.g. decision-making and memory formation), since neurotransmitters are widely shared by the neural functions. The closest we’d get is something similar to cocaine – which antagonises the re-uptake of dopamine, causing heightened states of alertness due to a dopaminergic hyper-flow in the synaptic gap.\nAs a further consideration: in order for the effect of your drug to exist, a substantial portion of the brain will need to be ‘knocked out’. The brain was not designed in a single architectural sitting. It is the product of 3.5 billion years of small, incremental changes. Consequently, there are ancient parts of the brain (including the misnomer ‘Lizard Brain’) and these are typically found at the core of the brain and close to the stem.", "978" ], [ "The anatomically modern neural areas are usually located closer to the surface of the brain and on the extremities (for instance the inferior frontal gyrus, located at the tip off the pre-frontal cortex is implicated in the go\\no-go phase of our decision-making process). For your drug to work, certain modern neural areas such as the primary visual cortex will have to remain operational (or the user will experience vivid visual effects of all sorts, resulting in not being a very capable ‘animal’).\nThe alternative to this knock-out, is to provide the ancient neural areas an unfair advantage (the 'how' remains elusive) – these areas are less complex than their modern equivalents and are therefore (as a rule of the thumb) capable of completing their less complex tasks in less time. That is why it is possible to ‘jump scare’ a human with something as preposterous as a ‘gorilla in the house’ type prank. The modern parts of the brain can compute that gorillas do not belong in your house and that it is a prank when one jumps out at you. However, the ancient pathways do not make such contextual calculations, and respond to ‘big, furry, moving very fast towards me’. The ancient parts of the brain are therefore able to complete their function (triggering the fight/flight reflex) earlier than the modern pathways, and… you utter a species-specific vocal alarm (aka a girly scream), hands fly up in defence, face contort in anticipation, upper body recoils from the threat – a classic early flight response.\nWhy would someone find this effect enjoyable? Some transmitters are associated with the ‘reward system’ (e.g. serotonin – implicated in enjoyable activities, such as food, sex, etc), others with heightened sense of awareness (in itself pleasurable). There are additional effects, such as endorphin (the brain’s own morphine) releases following certain stresses (causing inter alia the knees to go weak, and analgesia), and these too are quite pleasurable.\nAs the answer to your question is: construct a (realistic) reward to a chemical which causes medium term physical alterations to one type of ionic channel – that’ll cause the substance to be super addictive, requiring a substantial rehabilitation to kick (read up on the medium to long term effects of heroin).\nFor something this specialist, you will need further reading if you are to have any hope of staying between the lines. I suggest any of the works of <PERSON>, <PERSON>, <PERSON>, <PERSON> (his work titled The Synapse), <PERSON>, etc.", "762" ], [ "Anatomical considerations\nIf you’re looking at quite deep integration (fused circulation/nervous system) then you are constrained by the fact that the brain issuing motor orders must be somewhat proportionate to the body executing them. Assuming you don’t just want a big female head on a male body, you have a couple of ideas you could consider:\n* Not all animals use an explicit spatial map-like representation for their motor control (a somatotopic map); the octopus delegates this fine topography to large neural bundles in each arm, while the central brain only issues high-order commands. This means that the brain can remain relatively small (only 1/3 of an octopus’ neurons are in the central “brain”) and somewhat detached from the practicalities of how movement is mechanically achieved. Your female may have a similar role, with the bulk of pattern-to-muscle details entrusted to the male, so that her brain would not need to scale with the male’s body size\n* You may not need or want directly fused nervous systems anyway. The way in which the female directs the male could be by compulsion, guidance or persuasion. Imagine that the pair bonding process releases powerful hormones that make the male deeply invested in keeping the female happy, or satisfying her wishes. This relationship might be closer to the commitment of social insects to the hive: a forager bee isn’t following commands from the queen, she just really really wants to collect pollen to take home.\nBut why does the male not just think for himself? One option is that stupidity is used by this species as a sexually selected trait.", "335" ], [ "Putting yourself (and your genes) at unnecessary risk is pretty much the point of the male sex: if you can survive despite being this dumb, you must be really strong, fast, resilient etc. As long as the hobble trait (stupidity) does not manifest in females, it’s a perfect tool of hyperselection. So imagine a teenage phase in which unpaired males just out-idiot each other by swallowing Tide pods and taking selfies next to predators and what have you, which for some reason the ladies find irresistible. After a boy finds a girl, she keeps him straight with good advice and potentially a bit of octopodean mind control.\nReproduction\nI can only respect an answer that brings up hypodermic traumatic insemination, but I really don’t think it makes any sense in this scenario. This is a last-resort solution in some promiscuous species with high male-male competition and very adversarial sexual selection practices, and is detrimental to females (as you might imagine), which fits poorly with a symbiotic relationship with stable pairs. The most obvious solution seems to me just boring old external fertilisation, where females release eggs after pair bonding and males inseminate them on their own time after collecting them. Seahorses had been brought up and are probably the best example.\nIf creating eggs makes the female really particularly vulnerable, this may explain why they developed a relationship so dependent on the male, and why they would evolve a mechanism to select a male who commits physically to protecting them through the next “pre-pregnancy”; the male, in turn, by bonding to the female, ensures that the egg she finally produces is available to be inseminated by him and not a random other male she fancies.", "1008" ], [ "Does acceleration of time explain gravity (rather than the other way round)?\nI have a question about interpreting (explaining, even) the general theory of relativity.\nA common interpretation of GR, as I understand it, is to imagine two-dimensional space represented by flatlanders (ants) living on the surface of a trampoline (or stretched elastic sheet). The third ‘hyper-dimension’ from the point of view of the ants is time.\nIf a heavy object is placed in the middle of the trampoline, it distorts the surface in space-time, so that ‘straight lines’ of motion become geodesics, which are actually curved. A marble rolled across the trampoline curves around the object, because it’s following the shortest path in space-time. So far so good.\nA reader here a while back (http://physics.stackexchange.com/questions/102910/why-would-spacetime-curvature-cause-gravity) posted the question: so why do two stationery objects move towards each other, and the answer was that in space-time, they are not stationery - they are moving through time. And it’s their space-time lines which still try to take the shortest/straightest route, as illustrated very nicely in a YouTube video linked in one of the answers.\nNow I’m interested in getting back to a more intuitive understanding of why an attractive force seems to be exerted on the second object by the first, without getting tied up in the rather complex tensor representations of geodesics etc. At the same time, I want to know WHY a massive object distorts space-time.\nMost texts take the curvature of space-time as an axiom (postulate), without pretending to offer any explanation. Note that (as I understand it) the heavy object on the trampoline is only intended to represent or visualise the curvature - there is no suggestion that it’s a simple matter of heavy objects ‘weighing down’ space time.\nBut I’m thinking, why not take the analogy literally, and follow through on this idea of weighing down?\nIn the analogy, it seems obvious that a heavy object distorts the surface downwards - it’s a result of the external, real gravity in the analogy (acting in a hyper dimension from the ants’ perspective).", "483" ], [ "And the marble, of course, is simply rolling downhill.\nNow as we know from <PERSON>’s principle of equivalence, gravity equals acceleration. The third dimension in ant-world is time - so, what if we suppose that time is accelerating and hence generating that hyperdimensional force?\nFor me, the surface of the trampoline is not simply a snapshot, or slice, of space-time, but far more significant - it is the present universe. (As an aside, because of its distortion, the relative ‘hight’ of points in space time (above ground level) varies. Furthermore different observers (ants on the trampoline) project different tangential planes from their standpoints. Do these two effects explain all the results of special relativity?)\nNow assume that time moves inexorably forwards, and the surface of the trampoline is moving upwards, indeed accelerating. As we know, acceleration and force are the same thing: so the surface of the trampoline is pushing up against all objects in the universe.\nSuppose also that all massive objects have a type of inertia which resists time - then the trampoline surface is retarded, or flexed backwards! That is what causes the distortion.\nNow looking at a stationery marble sitting off to the side of the heavy object in the middle, it too is being pushed forwards (upwards) by time (the surface of the trampoline). Only the surface is now inclined - so there is a sideways component of the force, which pushes the marble towards the heavy object.\nSimple, obvious, and indeed an inevitable consequence of the assumptions that a) time is accelerating forwards, and b) heavy objects have an inertia which resists the passage of time.\nIs this idea complete nonsense, or is it a valid way of interpreting how space-time is bent (and how that generates the appearance of gravity)?\nIs this how some physicists already interpret general relativity - am I wrong to suppose that the analogy is not usually intended to provide a reason for the curvature?\nIt’s really a question for someone very familiar with the mathematical underpinnings of GR - can the curvature of space-time be successfully modelled by an accelerating timeframe and massive objects having an inertia which resists it?", "562" ], [ "The short answer is that the type of campaign you are hoping to represent, was simply not an option for the period described. Most campaigns lasted for three to four months – between the planting- and the harvesting periods. Soldiers were not ‘professional’ as we know today, but in smaller, distributed communities served multiple roles – e.g. also had to help out with the farming activities.\nWhen the army did campaign, their provisions had to be drawn from the surpluses of the farming yield. However, most farming occurred within a framework of feudalism and was subsistent. Surpluses were rare, and had to be supplemented by trade. Therefore, armies on campaigns often suffered hunger (until as late as the Napoleonic era), and this, (along with the related diseases) was the main cause of casualties.\nWhen on campaign, any army of this period would have three sources for provision: what they could take with them, (see previous point), what they could forage, pillage or barter for, and what they could capture from the enemy. The problem is one of planning – it is generally a good idea to know what you are in for, and not plan on capturing enemy stores, so these were mostly a welcome addition to the current. Logistics for water almost exclusively consisted of taking from the rivers and other sources – especially in Europe, with its abundant sources. Fodder for the animals could be supplemented by grazing – not as effective a food source for the beasts, and it required more time for the animals to feed (and large meadows), but it was possible.", "121" ], [ "Soldiers were often paid a stipend to pay for food, and quartering, and when that was not forthcoming, would simply take what they needed. As such, some parts of Europe which suffered the Thirty-Years War still bear the scars (as do those areas of Italy which witnessed <PERSON>’s invasion – or so I’m told).\nThat brings us to the primary source – such provisions that the army could take with them. As other responders have accounted, the army needed a baggage train of waggons – these often exceeded the number of the army itself. However, the baggage train was seldom intended to support the army for the duration of the campaign – these merely served as a first echelon. Many of the campaigns for the period followed the flow of rivers, (or hugged the coast), since boats and barges are more effective at the transportation of large volumes than convoys of waggons (and less susceptible to enemy disruption). These typically served as a second echelon from which the first echelon could draw down on. The third echelon potentially offers you the opportunity to make your story realistic – this consisted of a chain of forts, which were also used as depots. The Romans, for instance, would campaign every year for a few months, every time consolidating their gains by building forts at the logical extremes of the campaign’s progress. Any long range venture can therefore be visualised by the string of mutually supporting forts, each containing its own garrison, and of course, stored provisions. For the next year, the Romans were not required to start the campaign from scratch, (or carry everything with them), but they could pick up where they had left off on the previous campaigning season, thereby push in deeper again into enemy territory for the time available. This, along with their engineering efforts at building roads and bridges, ensured better logistics all along the campaign route, except at the ‘tip of the spear’.\nHow to make this work for your story? You will need a solution to produce a farming surplus, have a professional army (one not involved in the day-to-day survival of the society), have a ‘river-faring’ tradition, perhaps allow some foraging, perhaps even a set of allies on which you can rely, and finally: a multi-year wars, constantly pushing in deeper, and then consolidating gains with engineering works before the onset of winter.", "342" ], [ "Your quote is a piece of text written by someone with very detailed and in-depth knowledge of a small area of human endeavour. Additionally it is laced with jargon and phraseology designed to feel inclusive and stimulating to 'those in the know', but will exclude and baffle people who do not have the same depth of knowledge.\nThis is not a new thing.\nThroughout recorded history, humans have invented cliques and ways of reinforcing a smug feeling of superiority at being a member of one. Medieval aristocrats created a whole bunch of jargon around hunting. English has far too many words for animal dung (scat, spraints, fewmets, etc) because if every game animal has a different word for its poo, then the in-crowd can smirk at the ignoramuses who call things by the wrong word. Elsewhere there is Australian Aboriginal rock art which has different meanings to the male and female members of the community, because there is secret men's knowledge and secret women's knowledge.\nA strong sense of belonging to a group is good for your mental health.", "376" ], [ "If the group help each other out in a practical way (do the baby sitting, loan you a spear, share food in hard times), then belonging to a group boosts your chance of survival. That's natural selection in action, right there.\nSo who were your 'art critics' in the Stone Age?\n* The hunters who had obsessively studied the behaviour of one species of animal. Perhaps these were the men and women who had that lightbulb moment and domesticated the dog or the cow or the horse?\n* The gatherer who obsessively studies the habits and locations of particular plants. Perhaps these were the men and women who had that lightbulb moment and invented agriculture.\n* The shamans who know all the rituals and spells for every ceremonial occasion, and interpret signs and portents.\n* The elders who initiate young men and women into secret societies, warrior brotherhoods and the like.\n* The 'wise woman' or 'memory man' who can recall all the details of which village owes what favours to which other village, back for the last seven generations. They might be the ones who invented accountancy or writing.\n* The storyteller who knows 15 different versions of each of the tribe's myths and legends, and can pick the right one for any particular audience.\n* The trader who has learned 8 different languages and the customs of 8 different tribes, and travels between groups to barter his or her goods.", "164" ], [ "It is easy to imagine the presence of some sort of <PERSON> gene that results in relatively slow variation of an individual's genetic code in some of their cells - You could add a second <PERSON> process that copies 'good' mutations across to other cells, or alternately allow the body to become chimeric, with improved kidney genes only found in the kidneys and good muscle genes found only in some or all muscles.\nBut the problem is in determining what factors provide the 'feedback' signal to determine if a gene is beneficial or detrimental.\nIn a population and in normal evolutionary development, the feedback is purely and simply based on success at passing genes on to the next generations - more or less by definition a 'better-adapted' individual is one who has more reproductive success. In addition it needs a large number of 'trials' via numerous individual's success/failure to filter out the random noise that more significantly effects the reproductive success of individual animals.\nIn your scenario you have to choose some other mechanism to determine adaptive success, and there lies the problem. Your genetic mechanism could make tiny random changes in genetic code and 'watch' for feedback in terms of physical health, or stress levels, or (at a stretch) happiness - but there is an awful lot of noise in the signal - are you (un)healthier because of the change in some gene related to digestion or because you ate lots of vegetables or got food poisoning? As a result of the very low signal to noise ratio there would probably be more random genetic drift than ther would be beneficial changes in any single individual - even over thousands of years.\nIn addition, unless the feedback system is very 'clever' then, even if it does succeed you may not get what you want. Even 'natural' survival-of-the-fittest evolution shouldn't be considered as a path to higher quality. Lets say the <PERSON> relies entirely on bodily health - you may end up evolving you brain function so you are adapted to be ultra-paranoid about any external dangers.", "1008" ], [ "You live like <PERSON> in insane isolation but keep safe from germs. Or say you use happyness as your trigger - you may 'evolve' over time to be happy but really stupid.\nAbout the only way I can see this working would be if the genetic changes were consciously chosen. So either the individual can look through a catalogue (maybe from GenesRUs Inc. or iGenes Ltd.) and 'purchase' improvements in heart function or memory retention - if that is what they want. Or there is some sort of embedded AI process that does the same thing for you.", "335" ], [ "Radial fauna is most commonly found in sea life. I encourage you to check out the gorgeous Kunstformen der Natur for gloriously etched examples. Many of these are microscopic in scale (i.e. radiolarians, diatoms) but larger radially symmetrical organisms or multi-organism structures exist, like jellyfish and corals.\nhttps://upload.wikimedia.org/wikipedia/commons/b/bf/Haeckel_Diatomea_4.jpg\nThe smaller the structures, the closer they tend to resemble geometric shapes exactly, so you may want to think about scaling from a three-way perspective of size, precision and total numbers (e.g. a sea surface of millions of microscopic but geometrically perfect plankton may generate a sort of fuzzy, undirected but perhaps powerful magic field).\nTo get powerful, directed and purposeful geometric magic you want radial symmetry, pattern-generating abilities and intelligent will, which brings us to…\nMagic-wielding octopodes\nThe octopus body plan is already eight-fold symmetric.", "3" ], [ "Many octopuses (or your favourite plural) have the ability to change the pattern of their skin with exceptional control and precision, which they use for feats of camouflage that, as far as I’m concerned, already count as magic. They are also very, very clever. By shaping linear designs onto their arms, they would learn to generate magic patterns for hunting, protection etc. (Or potentially just to amuse themselves! Why not?) This doesn’t need anything evolutionarily beyond what they already have, and their learning abilities are already perfect to get them to experiment by trial and error (I seem to understand that your magic system is weaker for incomplete or imperfect forms, which would be great for experimenting as you could gradually sharpen your design and stop if you feel you’re catching fire or something)\nBonus: magic toadstools\nAnother group of radially symmetrical organisms, land-based this time, are the fruiting bodies of fungi. I’m not an expert in the least but I think, generally, extant mushrooms would be somewhat too simple for your requirements (mostly they have a pattern of straight radial gills underneath, and/or hexagonal textures on top like the bridal veil stinkhorn) but with a bit of selective pressure they may easily develop patterns for thaumaluminescence or spore-ejecting magic.", "671" ], [ "What exactly do you mean by intelligence? Is reasoning and problem solving enough or are we looking for avians that will eventually develop space flight or derive the Standard Model? A number of experiments on ravens show them to be quite capable of the former, whilst the latter will almost certainly never happen without the ability to manipulate sophisticated tools (imagine building a particle accelerator with nothing more than beak!).\nHowever, I would argue that it's an exacting critic indeed who wouldn't recognise reading, 'riting and 'rithmetic as signs of intelligence. I see no obvious barrier to raven's developing beak-graffiti to accompany their spoken (tweeted?) language. This is something that could easily occur spontaneously without much (or even any) physical evolution. As far as we can tell human writing only began around 10-30,000 years ago, whilst we have been largely physiologically unchanged since the rise of Anatomically Modern Human about 200,000 years ago. That is to say, we didn't just develop writing when we became smart enough to understand it - it seems to have arisen spontaneously, seemed useful, and stuck around. Human writing began with simple counting systems, and it is easy to conceive the utility of such a system even to ravens. A savvy raven could mark days to decouple themselves from the environmental cues of changing season and get the jump of the competition when migrating.*\nAn animal with a spoken/squawked language and in the habit of making marks will eventually come to use them for more than numerals. High points might be marked with a \"tag\" to warn off rivals, strings of landmarks might be marked as sign-posts home, allowing the raven to venture further to find food or mate. Reminders can be left of caches of hidden food.", "634" ], [ "None of this writing needs to be any more complex than their already demonstrated prruk-prruked language skills in order to be useful. Eventually the landscape will be dotted with raven writings, and certain pieces of information will pass from one generation to the next - summer last this many days here, this woodland is good for mice, etc.\nIf another species got this far, I wouldn't hesitate to consider them intelligent. There doesn't seem to be any reason at all why a raven couldn't do any of this without any further evolution, and we should not be discouraged by the fact that they haven't done so already - modern humans lazed about for 170,000 years without doing it. But what is exciting is what comes next - what might be possible with a little more evolution.\nSign-posts to hidden food might be read by other ravens, encouraging the use of misleading marks and an encryption/decryption arms- (wings-?) race. A migrating bird might add another 30 day-marks to his calendar before leaving, so that next years rivals postpone their own migration. When a technology proves useful then in time it typically becomes essential - if farming can support a larger population, then in time there will be a population that can only be supported by farming, etc. In this way literacy will eventually become an essential skill among ravens, as the underfed, exhausted illiterates are passed over by potential mates attracted to the new breed of well-fed, glossy-feathered renaissance ravens. And one day, they will be calculating their latitude and performing spherical trigonometry to plan their migrations...\n(* yes, I know most ravens don't migrate, but some do, and this is world-building so I can have ravens migrate if I want. Ravens are the birds most commonly associated with intelligence, and migration seems a behaviour in which intelligence might be advantageous.)", "802" ] ]

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[ [ "This code underwent some revision due to some coding errors! See edit log for more information.\nJBH has a very nice answer, and I have to admit, I mainly wrote this answer because it seemed like a nice programming puzzle.\nMy method: I modeled the likelihood of a woman getting pregnant after a chart I found online here. I did my best to then translate those numbers into a function of months of age since 18 years old. I ended up subtracting the $age_{in\\ months}/8100$ from a starting chance of $20\\%$ each month. That got me close enough to be happy. I then created a system where each person is put into a group, one of free_men, free_women or free_children.", "838" ], [ "If there were enough people available, I create pods out of the free men and women groups, with priority going to the youngest people available. Each month, the women in a pod have a chance of becoming pregnant determined by their age, beginning 20 months after their last conception.\nIf a women dies, she is removed from the pod, if a man dies, the pod is dissolved and the women revert to the old_women group. When a child is born, they are added to the free_children group. Children born have a $51\\%$ chance of being male and $49\\%$ chance of being female.\nThe time is ticked each month and statistics about the group are displayed.\nThese are the statistics for the years you request:\nYear 49\nFree Men: 603\nFree Women: 2\nFree Children: 3529\nOld Women: 75\nPods: 295\nNumber of conceptions this period: 373\nPregnancy rate: 0.33459875566803754\nNumber of births this period: 325\nNumber of deaths this period: 0\nAverage number of children per man: 0\nAverage number of children per woman: 0\nYear 99\nFree Men: 12617\nFree Women: 1\nFree Children: 73572\nOld Women: 2475\nPods: 5871\nNumber of conceptions this period: 6801\nPregnancy rate: 0.3289336345010024\nNumber of births this period: 6412\nNumber of deaths this period: 14\nAverage number of children per man: 37.96969696969697\nAverage number of children per woman: 12.756410256410257\nThis makes some pretty huge assumptions, the biggest of which is that having a child has no impact on your fertility. That's clearly false. Altering the pregnancy_fertility_drop variable from 0 to 1.5 gives us these numbers:\nYear 49\nFree Men: 408\nFree Women: 1\nFree Children: 1766\nOld Women: 272\nPods: 224\nNumber of conceptions this period: 165\nPregnancy rate: 0.312874251497006\nNumber of births this period: 150\nNumber of deaths this period: 0\nAverage number of children per man: 0\nAverage number of children per woman: 6.785714285714286\nYear 99\nFree Men: 5007\nFree Women: 2\nFree Children: 20736\nOld Women: 3041\nPods: 2417\nNumber of conceptions this period: 1859\nPregnancy rate: 0.30061614757485816\nNumber of births this period: 1703\nNumber of deaths this period: 4\nAverage number of children per man: 20.451327433628318\nAverage number of children per woman: 6.909722222222222\nWhich is obviously a stunning drop (especially in the generation that is still under 18).\nHere are some charts that show some statistics :)\nThese aren't as interesting as the ones with the fertility drop, here they are:\nI find the Rates graph interesting, as you can see a significant fluctuation in fertility in 18 year increments, giving some significant generational effects!\nI have the code here on Try it online!", "838" ], [ "In light of the answers from other people, I'd like to offer some basic math for how likely this is to occur.\nThe scenario I'm considering is as follows: You, an ordinary human, have two children. Those children have a child together (yes, I know incest is bad - this is purely hypothetical).\nYou, as an ordinary human, possess 46 chromosomes in 23 pairs. When you have a child, they receive one of each of these pairs from you (assuming nothing strange1 happens). As a side note, barring any medical breakthroughs that I'm not aware of, you would have to be genetically male (XY) so that your two offspring would be able to have children with each other.\nFor simplicity, I'll call the set of chromosomes that your first child got from you 'set A' and those that your second child got from you 'set B'.", "882" ], [ "In order for your grandchild to be an exact genetic duplicate of you, set B must contain all the chromosomes not found in set A, and then both children must pass on those specific chromosomes to their child. (This assumes that you do not have any chromosome pairs where both chromosomes are identical, which you probably don't unless you're the result of inbreeding).\nNow that we have established the scenario, let's talk about the probabilities:\nLet's assume the chance of someone's child receiving one specific chromosome from a pair is 1/2, as there are two possible outcomes.\nWith 23 pairs, the likelihood of passing on any one combination is 1/(2^23) (roughly one in 8 million). In our scenario, we see this happening 3 times: you passed on set B to your second child, your first child passed on set A to your grandchild, and your second child passed on set B to your grandchild. 2\nSo, the likelihood that your grandchild would be a genetic duplicate of you is 1/(2^69), or roughly one in 590 quintillion.\n1 By \"nothing strange\", I mean there are no errors in the replication of the chromosomes, and nothing along the lines of having 3 chromosomes of the same type, such as the case of Triple X syndrome, or anything else I haven't thought to list here.\n2 If you're wondering why I don't count when you passed set A on to your first child, it's because there are actually 2^23 different set A's that are possible, so the math cancels out. This is based off the assumption that there is already some set A you passed on to your first child.", "882" ], [ "Subtracting shared DNA with half-sibling\nI want to note that I am not a biologist. I've been on a nearly 20-year search for the identity of the parents of my 4th great grandfather (not an easy task.)\nI'm using ancestry.com DNA, GEDmatch, and family trees of my matches in hopes of using DNA triangulation to find my ancestors. In addition, I have a half-sibling who also had his DNA tested which allows me to find common ancestors on this side of the family.\nI read the article \"Relatedness\" on the topic of inherited parental dna with two half-siblings and I'm not sure I understand what the writer means when she says:\nIn other words, you and your half-brother should be able to figure out what part of your DNA came from your mom. And if you subtract out that shared DNA, what is left must have come from your dad!\nMy first thought was that a person and their half-sibling wouldn't inherit exactly the same DNA from their mother, could they? For example, the mother has two different alleles for some trait. Her son could get a copy of one and the daughter could get a copy of the other.", "882" ], [ "Therefore, in the author's example, how could subtracting out the shared DNA with the brother give the girl the ability to identify exactly which DNA must have come from her dad?\nI read on and the author addresses this by saying:\nOne brother inherited the green version of the mother’s chromosome 2, while the other brother inherited the blue version. This means that none of the chromosomes match! So testing wouldn’t tell the brothers which version of chromosome 2 came from which parent.\nIt turns out, though, that it’s really unlikely that siblings would have two totally different versions of a chromosome. This is because of something called recombination.\nShe's talking on entire chromosomes here which is different, but it doesn't seem to address fully why the girl should be able to 100% identify what DNA came from her dad by subtracting the shared DNA with her brother. I read that half-siblings share 25% of the DNA, but the mother here surely contributed more than 25% to each of her children.\nIn practice, my half-sibling shows a genetic relationship to people on our shared parent's side that I do not (and likewise, I have genetic relationships to people on our shared parent's side that he does not.) Therefore, I'm positing that my brother and I each inherited some different DNA from our shared parent.\nI would take the writer's word for it, but I'm confused. Where am I going wrong? (Sorry about the bad biology background.)", "882" ], [ "Units of parameters in epidemiological model\nThe simplest malaria model is given by $$\\frac{dI}{dt} = \\frac{\\alpha \\beta I}{\\alpha I + r} (1-I) - \\mu I$$ where $\\mu$ is the death rate of humans, $\\alpha$ is the transmission rate from humans to mosquitoes, $\\beta$ is the transmission rate from infected mosquitoes to susceptible humans, and $r$ is the natural death rate of mosquitoes.\nAssuming the units are given in $d^{-1}$, or per day, we can assume $r$ to be rather large, given that it isn't part of a larger product (and thus isn't a proportion). We can thus assume $r$ to be anywhere from a few dozen to a few hundred, depending on the size of the population. Recall that this is the amount of mosquitoes killed per day.\n$\\alpha$ is the transmission rate from humans to mosquitoes, and does appear to be a proportion, so $0 < \\alpha < 1$. Thus, $\\alpha$ is the probability a mosquito not carrying malaria bites a human $\\textit{with}$ malaria.", "964" ], [ "Assuming nothing more than 15% of a population of humans has malaria, and that 95% of a mosquito population do not carry malaria, this is $0.15*0.95 = \\alpha = 0.143,$ or a 14% probability.\n$\\beta$ is also a proportion, and is the transmission rate from infected mosquitoes to susceptible humans. Rather, $\\beta$ is the probability an infected mosquito will bite a human. Assuming a generous mosquito population (a few thousand at the least), we assume that about 5% carry malaria and (based on our previous assumptions) they have a 85% chance of biting a susceptible human (given that 15% are already infected). So $\\beta = 0.05*0.85 = 0.0425$.\n$\\mu$ is given as the death rate of humans. Neglecting deaths by reasons other than malaria itself, we assume this value to be about $0.3\\%$, given 627,000 deaths in 2012 out out of an estimated 207 million cases that year.\nIs this analysis correct? If not, where can I find values for the above parameters? Are there any case studies where I can calculate the above values?\nThank you in advance.", "655" ], [ "Using a Binomial distribution with number 7.5 billion and probability 0.50, the chances of Earth's death count from a universal unbiased killing resulting outside of 49.99%-50.01% of the total population is 1.7*10^-132, which is less likely than flipping 438 heads in a row with a fair coin.\nUpdated: I was first using a Poisson distribution which is a limiting case of a Binomial distribution (old claim: The chance of >50.01% (or <49.99%) of Earth's population being killed universally randomly is 3*10^-32! This is less likely than flipping 100 heads in a row with a fair coin). I found this site now which can handle the very small numbers involved in the use of the error function.\nSo, it doesn't really matter which interpretation is the true case: Planets with realistic populations and even very accurate census won't notice the difference.\nFull disclosure: I haven't seen the movie, nor have I ever read a comic book or know who any of these characters are. But I'm familiar with statistics and probabilities and have a habit of browsing the network Hot Questions, so...\nExplanation: The Binomial distribution is useful to see the results here. It gives the probability of observing integer random outcomes (like number of people killed) from any expected average (like half of a population). My use depends on the following assumptions.\n* The gauntlet will kill exactly half of the universe's (sentient?) lives (rounded if total is odd).\n* The gauntlet will take absolutely nothing into account -- the chosen to die are chosen randomly to meet this quota. This means the gantlet does not travel planet-to-planet, or choose those to die one at a time, or kill the oldest, the smallest, the smelliest, etc.\n* The population of any planet is a small fraction of the universe's population. If Earth comprised all of the universe, obviously exactly half of us would die.", "921" ], [ "But if 10 googolplex exist, and thus 5 googolplex must die, each of our deaths makes a negligible impact on the quota and our chances of living are unchanged -- 50%.\n* The Marvel universe has no more than a trillion trillion trillion times as many galaxies as our own universe, and each of its stars has no more than a trillion populated planets each. These very large (and very small) numbers can be hard to wrap your head around, but no scientific estimate of the number of galaxies/stars/planets in this universe comes close to legitimizing the chances of the asymmetric planet-wise killings proposed in the comments/answers.\nThe Math: From the binomial wiki page linked, the standard deviation is $\\sqrt{np(1-p)}$, with p=0.50. For the Earth (n=7.5 billion), this is 43,301 people. In terms of sigma, 0.01% of our population (7.5 billion) is 17.32 sigma. As a rule of thumb for statisticians, there is a 99.7% chance of drawing a number from within three sigma from the mean. Likewise, there is a 99.999999...% chance of drawing from within 17.32 sigma from the mean. Put another way, with the error function tool linked above, the chance of drawing outside of 17.32 sigma from the mean is less than 1 in 10^100!\nThe range of likely death counts from this event is much smaller than Earth's census would even notice. Moreover, as others have explained, the \"kill randomly universally\" method also avoids the complication of identifying to which planet (or ship, or rock, or floating naked in space...) each person belongs.", "921" ], [ "If you are content with 10k or so survivors, never!\nProcedure is as follows:\nday 1: Space station is declared quarantine. All frozen embryos are declared quarantine, along with pre-existing frozen eggs and sperm.\nyear 1: Space station is being resupplied by sterilized food packages. Development in automation commences.\nyear 2: controlled breeding program established in space station (we are at serious risk of inbreeding now but it won't matter too much). The population growth has to be carefully controlled here, as a large population would be fatal to further plans.\nyear 3: sterilized nursery delivered to space station\nyear 10: beginning to divert resources from education to production\nyear 15: large hab modules delivered to space station\nyear 20: all further development proceeds on automation and AI platform\nyear 25: college & electronic library delivered to space station\nyear 30: mass rollout of solar technology\nyear 40: collection of internet library; space station supplies should be extended to +50 years by this point, space station boosted to +50 year orbit. Elderly care starts consuming economy\nyear 50: delivery of 100 long-lasting re-entry capsules to space station. Space station supplied to +70 years, including 3d printers and raw materials. Further resupplies about to cease.\nyear 51: collection of knowledge in libraries and long-lasting electronics should be completed.", "335" ], [ "Elderly care overruns economy.\nyear 52: Space station is on its own.\nyear 60: Mass die-offs begin due to inadequate medical care\nyear 70: Embryo storage power supply is converted to RTGs.\nyear 80: Runaway mass die-offs has reduce quality of life to terrible levels.\nyear 120: Humans extinct on earth by this point. (Yes we have a few 120+ alive now, but without support they won't be). The disease is extinct with them.\nyear 121: The sixth generation returns from the space station. They can tap the remains of the automated systems to begin farming. Female population: 100\nyear 122: Crack open the first of the frozen embryos.\nyear 142: At maximum rate, female population: 500 (200 adults). This assumes that automation development worked and we can sustain this population boom. Once reaching this stage though, it's no longer a problem.\nyear 162: Runaway population boom subsides due to running out of frozen embryos. This brave new world has very few human-specific pathogens.", "998" ], [ "Algorithm for choosing unique options with least overall cost\nProblem And Question\nI am looking for pointers for an efficient algorithm for the following problem.\nIt is hard to explain without some data so first I will provide some example data:\nDestination 1:\nSource 1: Cost 26\nSource 2: Cost 32\nSource 3: Cost 98\nCreate New Source: Cost 100\nDestination 2:\nSource 1: Cost 12\nSource 2: Cost 99\nSource 3: Cost 51\nCreate New Source: Cost 88\nDestination 3:\nSource 1: Cost 55\nSource 2: Cost 31\nSource 3: Cost 76\nCreate New Source: Cost 99\nI need to choose one of the sources for each destination, so that each source (excluding 'create new source', which can be used as many times as required) is used zero or one times, and the overall cost is low.\nI do not need (although it would be nice) an algorithm that produces the absolute lowest cost, because I imagine this would require brute forcing. Instead, I just need an algorithm that is rather more efficient than blindly using source $n$ for destination $n$.\nExample Output And Constraints\nThe above data was actually chosen completely at random, but the following general rules apply to the data:\n* It will be very likely that, excluding the 'Create new source' option, the amount of sources will be equal to the amount of destinations.\n* It will be very likely that the cheapest option for destination $n$ will be to use source $n$.\n* It will be very likely that the cost of creating a new source will be one of highest costing options.\n* The example data above uses 3 sources, therefore there are $(3+1)^{3}=64$ total options, and as such, the solution is brute-forcible. At the time of writing, I am actually currently working with 33 sources and counting, there the brute forcing the $(33+1)^{33}=3.45...", "835" ], [ "× 10^{50}$ options is not feasible.\nFor the above data, the following costs are generated:\n/---------------+---------------+---------------+------------+--------\\\n| Destination 1 | Destination 2 | Destination 3 | Total Cost | Valid? |\n+---------------+---------------+---------------+------------+--------+\n| Source 1 (26) | Source 1 (12) | Source 2 (31) | 69 | FALSE |\n| Source 2 (32) | Source 1 (12) | Source 2 (31) | 75 | FALSE |\n| Source 1 (26) | Source 1 (12) | Source 1 (51) | 93 | FALSE |\n| Source 2 (32) | Source 1 (12) | Source 1 (55) | 99 | FALSE |\n| Source 1 (26) | Source 3 (51) | Source 2 (31) | 108 | TRUE |\n\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/‾\\/\nTherefore\n* Destination 1 should use Source 1.\n* Destination 2 should use Source 3.\n* Destination 3 should use Source 2.\n* In actual fact, blindly using source $n$ for destination $n$ with this data actually has a cost of 201, almost double the best choice, and is ranked 15th of the 24 valid solutions.\nBackground To The Problem\nI am working with a series of playlists, which when combined form one master playlist. Each playlist consists of a title in the format of (Master Playlist - Part $n$) and a list of items. These playlists are stored on a server.\nThe program I have written locally calculates the new state the master playlist needs to be in, splits it up with rules that are beyond the context of this question, and then starts making API calls to update the state of the playlists on the server accordingly.\nThe operations that can be done are\n* Create a new empty playlist, giving it a name in the process.\n* Delete an unwanted playlist, and any items inside.\n* Add an item to an existing playlist.\n* Remove an item from an existing playlist.\n* Re-order an item to a new position in the playlist it is already in.\n* Rename a playlist.\nIn the programs current form, for each local playlist part $n$, it will fetch the server state of playlist part $n$, work out whether it is cheaper to delete+recreate or add+remove, and then proceed accordingly.", "835" ], [ "I don't think you need to worry too much about them finding each other because most of your survivors will die, and I think there is almost no chance that the number of survivors will assure the survival of humanity, even if they miraculously find each other. You need a much higher survival rate, which will affect communications and subsequent ability to find each other.\nApproaching this only from a medical perspective, given your scenario (1 in 100K survive without restriction by genetics, age, location, etc. and loss of electricity/technology), about 12,500 will be aged 9 and under. Those under 5 will die in days from lack of water; those from 5 to 9 might live longer, but will likely die of disease, dehydration, exposure, malnutrition, etc. unless found by adults, so let's be generous and say 200 live and can someday integrate.\n6,000 will be elderly (between 65-99) and will be well more than half women. While they will be helpful repositories of knowledge and can do light work, they cannot do too much, and their life expectancy will be dramatically reduced.\n12,000 will be 10-19 years old. Most of those will have little skills or resources to stay alive (they will not know how to forage, let alone farm.) They, too, will be subject to disease and dehydration from unsanitary water and conditions (there are an awful lot of decomposing bodies around), and later by exposure. Being generous, let's say about one third will live more than 9 months. that's 4000, with about 2000 females. About 800 will be of reproductive age.\nThe golden number here is 28,000. That's the number of people alive between the ages of 19 and 45 (not inclusive).", "998" ], [ "Half will be women of childbearing age. With the 10-19 year old surviving females, (14,000 plus 800) that leaves 14,800 women to repopulate the earth under adverse conditions. Of these, 2% will never conceive (296) and 10.5% will be unable to conceive after having one child (1,554) Of those who do conceive the first time (14,504), one in 100 will die from each pregnancy (the rate in underdeveloped countries) from postpartum hemorrhage, eclampsia, obstructed labor, and sepsis, (145 women) with the rate being 1 in 16 chance of dying from childbirth in her lifetime.\nIf all the females of childbearing age find males to reproduce with, after the first year of mating (not taking into account a spontaneous abortion rate of 20% before the 14th week), ~14000 babies will be born (half girls), 10% of the women will become infertile, and women will continue to die in childbirth: ~12930 women will be left for a second round. Miscarriages will increase due to decreased nutrition. Women will not have a baby per year in even the best of circumstances; the highest average number of babies per female in developing nations in the 1980s was 8.3. In the worst of circumstances, it will be much less.\nIn other disasters where a population was forced to become agrarian without technology (e.g. the Cambodia under the Khmer Rouge, after the initial killing of ~3% of the population, close to 25% of the population died in only 4 years (disease, starvation, overwork), and that was in a temperate climate. Your people have to travel to better climates by foot or animal. Think Oregon Trail. Mortality is very significant. A best guess scenario might mean the loss of about 3500 women in maybe 5 years, leaving ~9400 women capable of conceiving.\nSo, under ideal circumstances of every female mating every year, with the infertility, maternal death (and not even taking into account infant mortality, (which, as in developing nations will be significant), and an overall death rate of 20% in the first 5 years only, you'll be left with too few women and children to come close to repopulation.\nIf they are spread across the globe and must travel to find each other, the numbers shrink to a small fraction of the best case scenario.", "838" ] ]

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[ [ "Anti-Aviation Protests in France and the UK Mark a New Wave of Climate Disobedience · Global Voices\nThe ‘Heathrow13′ were on trial for occupying Heathrow's northern runway last July. Photo: <PERSON>\nThis article is based on a piece written by <PERSON> for 350.org, an organisation building a global climate movement, and is republished on Global Voices as part of a content-sharing agreement.\nOn 24 February, 13 individuals who blockaded a runway to protest against expanding Heathrow Airport in London were expected to be sent to prison, but ended up receiving six-week suspended sentences instead. They had packed suitcases and set up their ‘out of office’ email messages anticipating to become the first climate activists in the UK to receive a prison sentence.\nIn the case of the so-called Heathrow 13, this is what happened: In July last year, a commission tasked by the UK government recommended expanding Heathrow. Two weeks later, 13 people from the direct action network Plane Stupid peacefully blockaded a runway at Heathrow in protest of the expanding aviation industry due to its contributions to air pollution and climate change. Their occupation lasted six hours and delayed or cancelled dozens of flights.\nThe group included a 68-year-old atmospheric physicist and 350.org UK Divestment campaigner <PERSON>. In court they argued that they feel a moral responsibility to take action as ordinary citizens where democratic, legislative and political processes fail to address the threat the aviation industry poses to the climate and people’s health.\nThirty-two-year-old Heathrow 13 member <PERSON>, who works for a health charity in London said:\nWhen the political system is so fundamentally flawed that it is unresponsive to an issue of colossal international importance, such as climate change, then every citizen has a responsibility to act. There is a basic human, moral and social duty to take action to prevent this disaster and to wake people up.\nAviation currently accounts for about 2-5% of global emissions, but the industry’s rapid expansion could see that number jump to 22% by 2050, according to a recent study by the European Parliament. It is one of the fastest growing sources of emissions, yet aviation remains largely exempt from emission reduction requirements and enjoys tax breaks that keep air travel costs artificially low.\nA paragraph on emissions from aviation and shipping in a draft version of the agreement reached at the UN climate summit in Paris in December 2015 was taken out of the final text, and new rules by the UN’s International Civil Aviation Organization are much too weak to have a meaningful impact. Besides fueling climate change, the emissions from a third runway at Heathrow could cause 150 premature deaths a year by 2030, according to an MIT estimate.\nEven though the judge recognised that the Heathrow 13 were “principled and passionate people” and that Heathrow is in breach of European Union emission regulations, she found them guilty of “aggravated trespass” and warned them to expect immediate jail sentences when they return to court.\nAggravated trespass is a criminal offence that was introduced under the <PERSON> government (1979-1990) with the aim of curbing protests.", "182" ], [ "In 2013, a UN independent expert recommended that the UK review its public order legislation, in particular with “great concern about the use of aggravated trespass against people staging legitimate protests”. A criminal law specialist described the possibility of a custodial sentence as “extremely surprising”. Ten of the Heathrow 13 had no prior convictions.\nThe ‘Heathrow 13′ outside Willesden Magistrates Court. Photo: <PERSON>\nMeanwhile in France…\nThere is another anti-aviation fight in Europe that is gaining steam. In France, a 40-year battle against plans for Europe’s biggest airport in Notre-Dame-des-Landes (NDDL), about 25 kilometers from Nantes, is heating up in the aftermath of the Paris agreement. A petition arguing that the airport is not compatible with the Paris climate agreement and urging the French government to intervene gathered over 11,000 signatures in just 24 hours.\nThe battle against the airport at Notre-Dame-des-Landes has grown into arguably the most iconic fight of the French climate and social justice movement. Many see the airport project as representing a system of unnecessary expansion that serves the economic interests of a minority at the expense of local communities, farmers’ livelihoods, the environment and the climate.\nHundreds of people have occupied the site for years. Recently, 11 farmer families announced that they will resist an eviction order and are prepared to risk imprisonment. Twenty-thousand people blockaded the ring road around Nantes in January in a protest against the project. Another mass mobilisation is scheduled for 27 February.", "271" ], [ "Protests in Italy Save Hundreds of Ancient Trees on the Chopping Block for Gas Pipeline Construction · Global Voices\nCentury-old olive groves. Photo: <PERSON>\nThis article is based on a piece written by <PERSON> for 350.org, an organisation building a global climate movement, and is republished here as part of a partnership with Global Voices.\nCommunities in Salento, in the southern ‘heel’ of Italy, recently won a small, but important victory in their campaign against the Trans Adriatic Pipeline (TAP), which would carry gas from Azerbaijan to Italy.\nPlanned construction would have seen the removal of ancient olive trees to make way for the pipeline, but following fierce protests, the work was suspended in early April.\nTAP and the Southern Gas Corridor are the largest fossil fuel projects that the European Union is pursuing. They are meant to bring billions of cubic metres of gas to Europe — making them incompatible with Europe’s climate commitments. According to a report by Oil Change International, e xisting fossil fuel operations already hold more carbon than can be released to keep global temperature rise to the limits that Europe and governments around the world agreed to under the Paris Climate Accord. That means that there is no space for any new fossil fuel projects, and certainly not for infrastructure of this scale, which aims to massively expand the gas market in Europe.\nThe pipeline would come onshore in the beautiful seaside town of San Foca. Some fear the construction of the pipeline and a gas-receiving terminal would cause significant damage to the local landscape and coastline.\nDespite the predicted climate impacts of the project and the objections of the local people and local politicians, the Italian government wants to push it through.\nPublic meeting next to the construction site in San Foca. Photo: <PERSON>\nOn 20 March, the stakes were raised when the pipeline company – without having permits for the work, as local mayors and the president of the Apulia region criticised – moved in to remove hundreds of ancient olive trees near the rural town of Melendugno. These trees are essential to many people's livelihoods. Not only that, but they are beloved by the local people and are centuries (some apparently more than a millennium) old.\nLocal organising stepped up a gear and each day since then, hundreds of people have gathered at the site to peacefully resist the construction. The local mayor managed to get the region's prefect to ask the company to stop the works for three days, whilst the permits were investigated.\nPeople in Melendugno protecting olive trees from the Trans Adriatic Pipeline. Photo: <PERSON>\nAfter the three-day break, the question of permits remained unresolved, and works continued.", "91" ], [ "The national government sent in police to defend the interests of the pipeline company, pushing the crowds back with shields and batons to allow the company to continue to explant trees. A number of injuries to local people were reported.\nOver the course of these few days, many trees were uprooted and removed from the area, a heartbreaking sight for many locals.\nThe trees in this picture have in the meantime all been removed. Photo: <PERSON>\nBut they didn’t give in. Public meetings were held regularly, drawing crowds of 500-1,000 people. The campaign has made the headlines in the Italian press, and solidarity actions and messages have been sent by groups in Milan, Bologna and Rome.\nThe protests started to hit national and international news, daily gatherings at the site got bigger and bigger, and one night, people built stone barricades to stop vehicles from accessing the site.\nLocal residents built barricades to block the pipeline works. Photo: <PERSON>\nIn early April, the removal of the trees was suspended because of the barricades and sheer size of the protests. There is just a small window now for the remaining trees to be removed. In a few weeks the growing season starts and the trees must remain for the summer.\nDaily gatherings and public meetings continue. No one knows what will happen next, but the local No TAP Committee is determined to stop the pipeline altogether. They maintain it is an unnecessary project, especially since demand for gas is dropping in Europe, and that it is undemocratic and being imposed by the government against the will of local people. They also argue that it will cause vast economic and irreparable environmental damage to the area.\nTheir message is “né qui né altrove” – “No TAP, not here or anywhere”.\nYou can follow their campaign on Twitter under the hashtag #NoTAP. The local organising committee is on Twitter @no_tap and on Facebook @MovimentoNoTAP.", "91" ], [ "What the Paris Climate Change Agreement Does and Doesn’t Do · Global Voices\nAs world leaders in Paris were finalizing the text of the deal, thousands defied the ban on public protests implemented in France under the State of Emergency and gathered by the Arc de Triomphe on a climate demonstration. Photo: © <PERSON>\nThis article is based on a piece written by <PERSON> for 350.org, an organisation building a global climate movement, and is republished on Global Voices as part of a content-sharing agreement.\nThe representatives of 195 countries agreed to a much-lauded deal to combat climate change on December 12, 2015 while gathered in Paris. Some people are still trying to figure out what this climate agreement will really get us. Here’s a rough (unofficial) overview of some different parts of the agreement.\nTemperature goal\nOne of the biggest battles at COP21 has been the goal of how much we let our planet heat up. Vulnerable countries fought hard for the goal of 1.5°C over pre-industrial levels, after which scientists fear the consequences of climate change could become catastrophic. This wasn’t even on the table to begin with, but it’s now in the agreement (well sort of), and even a recognition of it is great. Much is owed to island nations and climate justice groups\nHere’s what the text does say:\nHolding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change.\n2°C will be the binding part though, so getting countries to really aim for 1.5°C will require a lot of pressure in the years to come. Aiming for 1.5°C could mean a world of difference to countries and communities vulnerable to rising sea levels and extreme weather. Read more about 1.5°C and what that means here.\nWhether it’s 2 or 1.5°C – what’s clear is we have to move to get off of fossil fuels fast.\nDemonstrators drew red lines along Avenue de la Grande Armée to honor the victims of climate disasters and express their fight for climate justice.", "155" ], [ "Photo: © <PERSON>\nIndigenous rights, human rights, women’s rights\nThese have been moved to sections of the text where they aren’t legally protected or operationalized. Read a joint response from indigenous groups about the talks.\nPledges to cut emissions\nThis is stuff we already knew coming into the talks. Countries submitted beforehand their plans to curb or cut emissions, and it will only limit temperature increase by (around) 2.7 – 3.7°C. That’s down from the 5°C or so represented from business as usual. Progress, but more can be done.\nSetting the long term goal to get off fossil fuels\nWhile environmental advocacy groups, among others, pushed hard to make 2050 the goal for when the world would be 100% off of fossil fuels, the final text reads:\nParties aim to reach global peaking of greenhouse gas emissions as soon as possible, recognizing that peaking will take longer for developing country Parties, and to undertake rapid reductions thereafter in accordance with best available science, so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century.\nPeople are still figuring out what “a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases” actually means. Experts are saying it means getting to “net zero emissions” between 2050 and 2100, which could open the door to risky geo-engineering schemes.\nHowever, full decarbonization by 2050 would give us a good chance of keeping global warming below 2°C (staying below 1.5°C or getting back there quickly would require bolder action). That means breaking the power that the fossil fuel industry holds on our political and energy systems.\nFive-year review mechanism\nWe won’t always have Paris. One of the good things about this agreement is the five-year review mechanism. Right now, the contributions from each country will not usher in a safe world, but this agreement would “force countries to come back to the table every five years to review their emissions reduction targets and make new, more ambitious cuts.”\nOften called the “ratchet mechanism,” it could push countries to keep stepping up and help bridge the gap between policy and science. Countries have been asked to start reviewing their pledges in 2018 so that new commitments could be ready to go by 2020.\nSupporting the most vulnerable\nIndigenous representatives from around the world took part in the December 12 ‘Red Lines’ demonstration.", "876" ], [ "The Marshall Island’s Momentum-Changing Proposal for Shipping Carbon Emissions · Global Voices\nA large cargo ship full of shipping containers sailing into port. Photo: stockarch.com. CC BY 3.0\nThis article is based on a piece written by <PERSON> for 350.org, an organisation building a global climate movement, and is republished on Global Voices as part of a content-sharing agreement.\nUPDATE: The International Maritime Organisation shelved the Marshall Islands’ proposal on May 13 after it failed to win much support among member states.\nThis week as the International Maritime Organisation (IMO) meets in London, they’ll be considering a proposal from the Republic of the Marshall Islands calling for a binding global reduction target on shipping carbon emissions. After years of slow movement on reducing shipping emissions, the proposal brings new momentum at a critical time.\nThe Marshall Islands is in a curious position of on the one hand being the holder of the world’s third largest shipping registry, and on the other hand being at very real risk from the unchecked emissions of shipping.", "495" ], [ "Foreign Minister <PERSON> highlighted this in a statement:\nWe are an island nation and shipping is one of our lifelines. At the same time, carbon emissions, including those from shipping, pose an existential threat to our people and our country.\nSince 1990, shipping emissions have increased by approximately 70%, and in 2012, represented 2.7% of global CO2 emissions. If these emissions were reported as a country, maritime transport would rank between Japan and Germany on a table of CO2 emitters. Yet these emissions are not held accountable through the United Nations Framework Convention on Climate Change, and predictions are that emissions will grow even more rapidly in coming decades if left unchecked. It has been left up to the IMO to make progress, which has been slow – as the infographic below from Transport & Environment, an umbrella group representing European environmental and sustainability organizations, highlights.\nIf the Marshall Islands proposal is adopted by the IMO this week, it would bring a crucial breakthrough for reducing shipping emissions, and beyond that, an important momentum builder as the world builds to the UN climate talks in Paris later this year.", "495" ], [ "Meet the People Blocking a New Gas Mega-pipeline in Southern Italy · Global Voices\nA screenshot of a video of protest against the Trans Adriatic Pipeline. Photo: <PERSON> 350.org, used with permission.\nThis article is based on content originally published on 350.org part of a partnership with Global Voices.\nIn southern Italy, local mothers, teachers, health workers, grandparents and olive farmers are leading a peaceful resistance to protect their land and their community from a planned gas mega-pipeline.\nSince 13 November, hundreds of police imposed a ‘red zone’ around the Trans Adriatic Pipeline (TAP) construction site, prohibiting journalists, citizens and local government officials from accessing the area.\nNevertheless and despite facing a violent response by the police and individual fines of up to €10,000 the local communities of Melendugno are determined to continue their resistance to stop the construction of the TAP.\nThese are some of the people blocking the project:\n<PERSON> is a local artisan who is no longer willing to stand aside as public money is spent for the private gain of multinational companies. She criticises the corruption and criminal interests surrounding the projects.\n<PERSON> calls herself a NoTAP grandma, fighting for the good of the land. She is motivated to protect the environment since her nephew suffers from health problems that have been caused by environmental issues.\n<PERSON> is the vice mayor of Melendugno. He sees TAP as an unnecessary project that destroys the climate and the local economy, which is based on tourism and agriculture.\n<PERSON> opposes TAP because he wants the land protected.", "91" ], [ "The pipeline and gas receiving terminal is due to be built through a protected area with ancient olive groves, aquifers, pristine forest and a stunning coastline.\n<PERSON> is a young woman who takes action to resist an imposed and unwanted project that the state helps a multinational consortium to build without letting the people have their say and despite local opposition for the past six years, straight from the start of the project.\n<PERSON> resists TAP, which she sees as a useless and dangerous project that threatens her livelihood in tourism in San Foca. She stresses that TAP is not just a local but a European problem that should not go ahead in Salento or anywhere else.\nThe locals receive increasing support as banks come under international pressure to reject the loans on which the project relies to go ahead. For example, more and more people are calling on the European Investment Bank to pledge against financing TAP to the tune of €1.5 billion.\nTAP is part of the European Commission’s energy flagship project Southern Gas Corridor. The EU pushes to massively develop new gas infrastructure even though existing infrastructure is already operating below capacity and despite the fact that an expansion of the gas market is incompatible with the Paris Climate Agreement .\nFilms by <PERSON> and <PERSON> for 350.org. Music: Am-Trans by <PERSON> (Attribution-NonCommercial 3.0 International License – www.soundofpicture.com)", "91" ], [ "‘Stop Destroying Our Communities For Coal We Cannot Use’ · Global Voices\nThe Rhineland coalfields are Europe's biggest source of CO2. Photo credit: <PERSON>\nThis article is based on a piece written by <PERSON> for 350.org, an organisation building a global climate movement, and is republished on Global Voices as part of a content-sharing agreement.\nIn April, I joined over 6,000 people to create a human chain at the Garzweiler coal mine in western Germany’s Rhineland. We were united in our message to end coal reliance and accelerate the transition to renewable energy that should have begun yesterday.\nThe long-standing villages of Borschemich and Immerath, where the human chain went through, have gradually become ghost villages. Residents have been bought out and communities broken down by the German electric utility company RWE.\nRWE is expanding the ninth largest coal mine in the world, despite debts, despite the destruction of homes and farmland, despite high levels of local pollution and radioactivity, and of course despite the fact we know this is coal we simply cannot keep burning if we want to limit catastrophic climate change.\n<PERSON>, farmer from the village of Holzweiler, Germany. Photo credit: <PERSON>\nI’m not even sure how we began talking. I think I asked him if the tractor over there was his. It was. It was pulling a trailer decorated with banners showing the boundary where people are calling for the mine to end.\nWe met amidst 5,998 or so other people trailing yellow ribbons standing amongst fields of crops that in two to three years time, as it stands, will no longer exist. His village – the village of Holzweiler – was a backdrop to the solemn scene. He did not know yet whether his land too would be pulled up to dig the coal from beneath it.\nHerr <PERSON>, the farmer I met that day, told me the worst thing was not knowing. How do you plan or deal with a situation if you don’t know if in a few years time you and your family will be relocated? Moreover, how does that actually practically happen? How can you replace someone’s field and crops? How can you replace someone’s home, history, and livelihood? He said, for him maybe it wasn’t so bad, but what about his son? What was he going to do?\nIf we close the mines, hundreds of jobs will be lost we are told. But here I hear stories of not just jobs being lost but also communities. And it’s done with dirty tactics. <PERSON> told me RWE comes into communities years in advance of the demolition taking place.", "202" ], [ "When villagers were offered compensation for relocation, their initial reaction was resistance, as you can imagine. “But time softens them,” said Mr <PERSON>. RWE begins to cut things down in the surrounding area, already destroying what they can access, making it feel like the work is already underway. Then some people take the offer. A few people begin to leave and local businesses begin to lose their customers. How can the baker stay open as the village slowly dissipates? Once the first few go, it has a domino effect.\nHe points to a building and tells me it used to be a hospital. Now it’s empty and boarded up. In this village a few residents remain in resistance, but there are no shops left, no church, or other local services. He tells me another four villages, hundreds of years old, are due to be demolished over the next 15 years. He takes me to the other side of his tractor to a banner which names those villages and those – like his – that are under question.\nOn 25th April, more than 6,000 people created a human chain against coal at the open-pit lignite mine Garzweiler in the Rhineland, Germany. Photo credit: <PERSON>\nMr <PERSON> took part in his first human chain here almost exactly 30 years ago. He’s still resisting. It filled me with sadness talking to him, but maybe the seasons are changing and we are on the winning side.\nRWE is in €31 billion of debt; the cost of coal is becoming increasingly expensive, not to mention when you add the external costs; limitations are being made on coal emissions and we’re realising to exactly what extent we can’t burn the black stuff (90% of coal reserves in Europe need to stay in the ground if we want to stay below 2 degrees warming). And well, there’s an ever growing movement ready to resist. This 14-16 August we will be climbing into a 400 metre-deep coal mine to stop the largest diggers on earth.", "202" ], [ "Another Young Environmentalist Is Murdered in Guatemala · Global Voices\nGuatemala's future seems to receive a blow with the death of <PERSON>, a young member of the Center for Social, Legal and Environmental Action (In Spanish, CALAS) Foto taken from Pixabay. From the Public Domain.\nThe murder of 22-year-old <PERSON>, a young environmentalist in Guatemala, has increased concerns over the threats that environmentalist defenders endure and the failure of the state to provide protection to organisations under threat.\n<PERSON> was shot and killed in Guatemala city on November 12. His murder is in many ways a dark symbol for Guatemala, a country in the top ten most vulnerable countries to climate change, where the average age of the population is, precisely, 22 and where at least ten environmental activists – most of them indigenous – were murdered in 2015.\n<PERSON> worked for CALAS, an organization for legal, environmental and social action. He was committed to social justice from a young age. He was the spokesperson of a public high school, where he constantly advocated for better public education.\nThis is not the first time that CALAS has been target of threats. In fact, one of <PERSON>’ seniors and a member of the center, <PERSON>, has been target of numerous death threats through the years, and was once shot in an attempt to silence him. <PERSON> is known inside and outside Guatemala as a human rights and indigenous rights defender. CALAS’ director, <PERSON> has also been also target of death threats through social media.", "202" ], [ "As Front Line Defenders Case Study explained at the time of the threats:\nThe human rights defender was in the offices of CALAS on 29 July 2015 when an unknown gunman riding a motorcycle fired a number of shots outside. He also received a previous death threat in May 2015 when an unknown woman approached him at a bank and said “Soon you are going to pay for the work you are doing. You will see what will happen as a result of the work you are doing against the mining company, you are causing a lot of damage and so they will kill you”…\nIn a recent report, Amnesty International Americas Director <PERSON>, explained how hard is the struggle for the environment in the Central American region:\nDefending human rights is one of the most dangerous professions in Latin America but daring to protect vital natural resources takes these risky jobs to a whole new, potentially lethal level.\nA threat to the youth\nDiverse environmental justice organisations have pointed their fingers at shared partnerships between wealthy countries like Canada, their multinationals, and the silent complicity of governments that host mining operations and fail to protect those who fight for their territories.\nEnvironmental campaigners and advocates are under constant threat all over the continent. Intimidations, violations to the right to protest have become a trend from Canada to the Patagonia. Justice is rarely achieved, and it produces a chilling effect that often leads to further killings. In cases like that of <PERSON> organisation, COPINH, in Honduras, they have managed to kill all the leaders.\nGuatemala is one of the countries championing action against climate change. Guatemala is actively encouraging Canada, and its Prime Minister, to react to the widespread violence against human rights defenders opposing environmental damage by Canadian companies, as explained by the Network of Solidarity with the people in Guatemala (NISGUA):\nThe Justice and Corporate Accountability Project’s report, The ‘Canada Brand’: Violence and Canadian Mining Companies in Latin America, was released on October 24, 2016 and looked at incidents of violence and criminalization in connection with twenty-eight Canadian companies in thirteen countries in Latin America from 2000 to 2015. It found that at least 44 people have been killed during this time, 30 of which were targeted killings, while more than 400 people were injured, not including work-related injuries. They also found that over 700 people were legally persecuted during this period, including arrests and detentions, for their work in defense of their territories, livelihoods, health and environment.\nAs the country struggles for accountability on the crimes of the past and engages in processes against impunity, it is expected that, with the support of the International Community, that Guatemala can also safeguard the leaders and human rights defenders for the sake of its own future.", "202" ], [ "Syria’s dire economy and years of fighting send young ‘mercenaries’ to fight in Ukraine · Global Voices\nRussian soldiers salute President <PERSON> at Hmeimim Air Base, during a 2017 visit. Russia's airbase in Syria serves as the launchpad from which volunteers are flown from Syria to Ukraine to fight alongside the Russian army. The image is used under a Creative Commons Attribution 4.0 International license.\nThis article was first published by Raseef22 on 19 March 2022. An edited version is published as part of a republishing agreement with Global Voices.\nFollowing years of a devastating war that continues to fragment the country, Syria is now exporting professional mercenaries to other hotspots of conflict, including Libya and the Nagorno-Karabakh region, and they are soon expected to arrive in Ukraine. They packed their fighting experience and headed to foreign arenas, some to fight in Russia’s wars and others fighting Turkey’s foreign wars.\nIts like a Syrian once said: “Blackwater Latakia and Aleppo… Welcome to New Syria”.\nWhen it comes to the recruitment of pro-regime fighters, the name of the Russian private military company Wagner Group stands out. The paramilitary organization has a special contract with the Syrian Defense Ministry to fight inside Syria.\nThe company coordinates with the authorities of the Hmeimim Air Base, Russia’s base of operations in Syria, to recruit Syrians for the purpose of sending them abroad. Wagner’s contractors are not openly present on the scene, but rather operate through a front consisting of Syrians to attract those who are willing.\nSince the start of the Russian war on Ukraine in the last week of February 2022, many people, parties, movements, and institutions came out to say: “We are with you, Russia.” These all collectively came as an echo of the official Syrian position which firmly and resolutely stands with Russia — a position that is understandable in the general political context, as no one expects the Syrian regime to stand against its international ally.\nBut sending “mercenaries” to fight in Ukraine's streets is another matter entirely.", "534" ], [ "It seems that the fighters affiliated with the Syrian regime and the forces that support it have once again set their sights on the dollars that working as “mercenaries” (dubbed “volunteers”) would provide, just like when thousands went to provide support for Russia to face the Turks in Libya. How wouldn’t they, when the USD 700 dollars they were getting paid in Libya per month have gone up to a monthly USD 1000?\nOn March 11, 2022, Ukrainian President <PERSON> said that Moscow was deploying Syrian mercenaries in his country. Russia has not officially confirmed this, but its Defense Minister <PERSON> reported that 16,000 “volunteers” from the Middle East are ready to fight alongside Russia’s allies in the Donbas region in eastern Ukraine.\nThe Middle East here refers to Syria — the only place where Russians have allies ready to embark on a mercenary adventure for political conditions and economic hardships the Syrian war created for its people. Also, Syria is the only place that fighters, logistically, can be transferred from to Russia, through the Hmeimim Air Base.\nRussian President <PERSON> added:\nIf you see that there are these people who want of their own accord, not for money, to come to help the people living in Donbas, then we need to give them what they want and help them get to the conflict zone\nPacking their bags\n<PERSON> is a 28-year-old Syrian man residing in Homs. He packed his belongings in preparation for travel and the subsequent fighting in the Donbas region.\nHe told <PERSON> he is a former fighter from a combat group within the backup forces in the Qalamoun region that was dissolved in 2017, referring to the Qalamoun Shield Forces, an auxiliary military group that isn’t affiliated with the government army but fights alongside it, just like the National Defense Forces, the al-Bustan Association, the Qalamoun Shield Forces, and the Tiger ‘Nimr’ Forces (named after the nickname of Brigadier General <PERSON>).\n<PERSON> recounts how he went to Libya in late 2020 and fought there over two periods. Each period of time consisted of five months, and between the two periods, he went back to Syria for three months.\nHe added:\nNow I’ve been contracted with the Hmeimim Air Base to fight in Ukraine alongside our Russian brothers as a fighter with a salary of 1,000 dollars a month. I do not get the salary while I am on the job, but with my leave to return after seven months, I will receive the full amount for all the months as well as an additional month’s salary.", "328" ] ]

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[ [ "As <PERSON> points out, the textbook reason for differential solute and water movement in different parts of the LoH is osmolarity, which is nicely explained in this wikipedia article.\nComing to an interesting point, about the movement of water across cell membranes through aquaporins, this is helpful:{1}\nThe discovery of aquaporin membrane water channels by <PERSON> and co-workers (6, 7, 191, 192) answered a long-standing biophysical question of how water crosses biological membranes specifically, and provided insight, at the molecular level, into the fundamental physiology of water balance and the pathophysiology of water balance disorders. Out of at least 10 aquaporin isoforms, at least 7 are known to be present in the kidney at distinct sites along the nephron and collecting duct.\nAquaporin-1 (AQP1) is extremely abundant in the proximal tubule and descending thin limb where it appears to be the main site for proximal nephron water reabsorption. It is also present in the descending vasa recta. AQP2 is abundant in the collecting duct principal cells and is the chief target for the regulation of collecting duct water reabsorption by vasopressin.\nThe journal further elaborates on these APQ's and their function in detail, do read it if you are interested, but the following diagram sums it up pretty well, so I am just going to expand on this:\nA: schematic representation of the structural organization of aquaporin-1 (AQP1) monomers in the membrane (top and bottom).\n1. Aquaporins have six membrane-spanning regions, both intracellular NH2 and COOH termini, and internal tandem repeats that, presumably, are due to an ancient gene duplication (top).", "171" ], [ "The topology is consistent with an obverse symmetry for the two similar NH2- and COOH-terminal halves (bottom).\n2. The tandem repeat structure with two asparagine-proline-alanine (NPA) sequences has been proposed to form tight turn structures that interact in the membrane to form the pathway for translocation of water across the plasma membrane.\n3. Of the five loops in AQP1, the B and E loops dip into the lipid bilayer, and it has been proposed that they form “hemichannels” that connect between the leaflets to form a single aqueous pathway within a symmetric structure that resembles an “hourglass.”\nB: AQP1 is a multisubunit oligomer that is organized as a tetrameric assembly of four identical polypeptide subunits with a large glycan attached to only one.\nThe direcrion of flow of water, again, depends on osmolarity.\n...Only inward water flow (swelling) was examined, but it was predicted that the direction of water flow through AQP1 is determined by the orientation of the osmotic gradient. Consistent with this, it was later demonstrated that AQP1-expressing oocytes swell in hyposmolar buffers but shrink in hyperosmolar buffers.\nPlease note that the linked journal is brilliantly detailed, so there are several points that I have skimmed over. I recommend reading it if you have time.\n{1}-https://journals.physiology.org/doi/full/10.1152/physrev.00024.2001#:~:text=Aquaporin%2D1%20(AQP1)%20is,for%20proximal%20nephron%20water%20reabsorption.&text=AQP2%20is%20abundant%20in%20the,duct%20water%20reabsorption%20by%20vasopressin.", "171" ], [ "Relaxation of vertebrate skeletal muscle is thought to occur in the absence of ${Ca}^{2+}$ as a result of tropomyosin physically blocking the binding of myosin to actin. This steric blocking model of muscle relaxation predicts that myosin subfragment 1 (S-1) will not bind to actin under conditions where the acto-S-1 ATPase rate is inhibited.[1]\nHowever, in a paper that questions this model, it is concluded that in the absence of ${Ca}^{2+}$, troponin-tropomyosin inhibits the ATPase activity by inhibiting a kinetic step in the cycle of ATP hydrolysis, perhaps $P_i$ release.[2]\nThat is the simple answer, but I think a little elaboration on the above paragraphs might help add some substance:[2]\n* Vertebrate skeletal muscle contraction is the result of a cyclic interaction of thick myosin filaments with the thin filaments, composed primarily of actin, troponin, and tropomyosin, causing these two sets of filaments to slide past each other. This cycling is driven by the hydrolysis of ATP by myosin in a reaction which is activated by actin.\n* When the sarcoplasmic reticulum lowers the free ${Ca}^{2+}$ concentration from $10^{-5}$ to $<10^{−7} m$, muscle contraction ceases and the associated actin-activated myosin ATPase activity is inhibited. The proteins troponin and tropomyosin are responsible for this effect of ${Ca}^{2+}$ on the interaction between myosin and actin.\n* At levels of ${Ca}^{2+}$ low enough to cause relaxation, tropomyosin is positioned away from the central groove of the F-actin filament where it appears that it might interfere with the binding of the myosin cross-bridge.", "171" ], [ "This structural work formed the basis of the steric blocking hypothesis which suggests that relaxation occurs when tropomyosin, in the “relaxed” position, physically blocks the binding of the myosin cross-bridge to actin.\n* Three-dimensional reconstructions from electron micro-graphs have suggested that the myosin cross-bridge and the tropomyosin molecule may be in close contact with each other on the actin filament, a requirement for a steric blocking type model.\n* The steric blocking model predicts that in the absence of ${Ca}^{2+}$ the degree of association of S-11 should be much weaker with regulated actin than with unregulated actin. In fact, in the absence of ${Ca}^{2+}$, the binding of S-1·ADP to regulated actin is strongly inhibited in a cooperative manner.\n* At low levels of saturation of the actin filament with S-1·ADP, the binding of S-1·ADP to the regulated actin filament is about $10^3$ times weaker than at high levels of saturation.\n* However, the fact that S-1·ADP binds weakly to regulated actin does not prove the steric blocking model since, in relaxed muscle, the cross-bridges normally exist with bound ATP (or ADP · Pi) and not bound ADP. Therefore, the steric blocking model predicts that troponin-tropomyosin should inhibit the binding of S-1·ADP·Pi as well as S-1·ADP to regulated actin in the absence of ${Ca}^{2+}$.\nUsing stopped flow turbidity measurements, we have previously measured the effect of ${Ca}^{2+}$ on the association of S-1 · ATP and S-1 · ADP · Pi with regulated actin. Surprisingly, in the absence of ${Ca}^{2+}$, the binding constant of S-1 · ATP or S-1 · ADP · Pi to regulated actin was only decreased to 56% of the value in the presence of ${Ca}^{2+}$ although the rate of ATP hydolysis under the same conditions was decreased to 6% of the rate with ${Ca}^{2+}$ present. These data suggest, in disagreement with the steric blocking model, that inhibition of the rate of ATP hydrolysis, in the absence of ${Ca}^{2+}$, is not the result of inhibition of the binding of S-1 to regulated actin.\n1- https://pubmed.ncbi.nlm.nih.gov/27065174/\n2- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1266292/#FN2", "171" ], [ "* I think you already know the sign convention in calculating the water potential: the addition of solutes lowers the potential (negative vector), while an increase in pressure increases the potential (positive vector).(Another way of saying the same would be more solute = more negative.) {1} This is the same everywhere.\n* Pressure potential: The pressure potential in a plant cell is usually positive. In plasmolysed cells, pressure potential is almost zero. Negative pressure potentials occur when water is pulled through an open system such as a plant xylem vessel.{1} This means that it is negative during a \"suction\" action, otherwise, it is positive.\n* Osmotic potential (solute potential): The relationship of solute concentration (in molarity) to solute potential is given by the Van't Hoff equation:\nΨπ=−MiRTΨπ=−MiRT\n(The formula, note, has a -ve sign.)\nFor example, when a solute is dissolved in water, water molecules are less likely to diffuse away via osmosis than when there is no solute. A solution will have a lower and hence more negative water potential than that of pure water.", "171" ], [ "Furthermore, the more solute molecules present, the more negative the solute potential is.\n* *Turgor pressure* and wall pressure: I recommend reading this for a clearer understanding.\n...This actual pressure which develops within such a cell is called turgor pressure. This term can be applied with equal appropriateness to the actual pressures developing in purely physical osmotic systems such, for example, as a sucrose solution enclosed within a collodion or cellophane membrane and immersed in water. As will become clear in the following discussion, TPs in osmotic systems can sometimes be negative in value.\nWhen the TP is negative, that is, when the cell sap is under tension (see later), the WP is likewise negative, the wall being subjected to a centripetal pull because of its adhesion to the protoplasmic layer and cell sap mass within the cell.\nOn the basis of fundamental physical principles it is generally considered that the WP and TP of a cell are equal in magnitude and oppositely directed. This situation is not difficult to visualize for a cell in an equilibrium condition. For dynamic states in which water is being gained or lost by a cell, however, the validity of this assumption has been questioned.\n{1}-https://en.wikipedia.org/wiki/Water_potential", "171" ], [ "First, an important fact about non ionic detergents- {1}They have a hydrophilic head group that is uncharged and are preferred for their ability to break lipid-lipid and lipid-protein interactions. They have limited ability to break protein-protein interactions and are often referred to as non-denaturing detergents and are used to isolate biologically active membrane proteins.\nGenerally, moderate concentrations of mild (i.e., nonionic) detergents compromise the integrity of cell membranes, thereby facilitating lysis of cells and extraction of soluble protein, often in native form.\nAn example would be Triton X-100. {2} Non-denaturing detergents such as Triton X-100 have rigid and bulky nonpolar heads that do not penetrate into water-soluble proteins; consequently, they generally do not disrupt native interactions and structures of water-soluble proteins and do not have cooperative binding properties. The main effect of non-denaturing detergents is to associate with hydrophobic parts of membrane proteins, thereby conferring miscibility to them.\nThe following article is about the same protein insolubility that I have written above, but in the nuclear membrane of chicken RBC’s. {3}\nProtein has been selectively extracted from isolated chicken erythrocyte nuclear envelope by (1) dilute MgCl2/Triton X-100 followed by (2) concentrated MgCl2/Triton X-100 solutions. Certain proteins appear to be selectively dissolved in the first solvent and may occur in the nuclear envelope primarily as lipoproteins.", "171" ], [ "Among the proteins insoluble in the low MgCl2/Triton X-100 wash, as well as in 500 mM MgCl2 without Triton previously used in the preparation of the envelope fraction, the quantitatively major polypeptides dissolve in a combination of high MgCl2 and Triton X-100. Further, much of this dissolved protein precipitates when the MgCl2 concentration is lowered by dialysis. The insolubility of these proteins appears to result from a combination of ionic and hydrophobic interactions and may explain the resistance of nuclei to various manipulative procedures including nonionic detergent washes.\nThe conclusion is that the protein insolubility of these detergents is what makes the nucleus resistant. You know that the phospholipid bi-layer is common for both- the cell membrane and the nuclear membrane. But underlying the inner nuclear membrane is the nuclear lamina, a fibrous meshwork that provides structural support to the nucleus. The nuclear lamina is composed of one or more related proteins called lamins.\nComing to your last question, using the example of Triton X-100 and leukocyte cells, a paper says: {4}\nLeukocyte membranes except the nuclear envelope were solubilized in a buffer that contained 1% Triton X-100.\nWhich means that all membranes- including mitochondrial, dissolve in the detergent because they do not have an additional protein layer in them, like the nucleus does.\n1-http://www.genotech.com/protein-research/detergent-accessories.html\n2-https://www.thermofisher.com/in/en/home/life-science/protein-biology/protein-biology-learning-center/protein-biology-resource-library/pierce-protein-methods/detergents-cell-lysis-protein-extraction.html\n3-https://pubmed.ncbi.nlm.nih.gov/999948/\n4-https://link.springer.com/article/10.1007/BF00554425", "171" ], [ "The question as it is posed is nonsensical. In chemistry, an element is a pure substance consisting only of atoms which all have the same number of protons in their nuclei; it cannot be further broken down into simpler substances by a chemical reaction.\nTaste is a completely biological concept, an interaction between our taste bud receptors and a combination of many elements making up the substance we are tasting. Pure elements don’t exist in nature to be tasted, so our taste receptors aren’t made to react to them. In fact, most elements would be poisonous, as well as not taste anything.\nThe human tongue contains between 2,000 and 10,000 taste buds, each of which are made up of 50 to 150 taste receptor cells. These cells contain receptors, microvilli called taste hairs, which extend upward inside the taste pore. The microvilli come into contact with tastants, or taste stimulating compounds, dissolved in oral saliva after intake/mastication, which enter the taste pore. They interact at the microscopic level through protein receptors or ion channels. Then the chemical stimuli are transduced through the sensory cell and the electric impulse is conducted to the brainstem by the afferent gustatory nerve fibers.\nThere are five basic tastes: sweet, salty, sour, bitter and umami.", "762" ], [ "A high concentration of Na+/sodium ions in the saliva causes the gustatory epithelial cells to depolarize and release neurotransmitters, interpreted by the brain as a salty taste. Sour tastes occur in a similar process, by direct diffusion of ions, but in response to high H+/Hydrogen ion concentrations, that is, acids. Sour-detecting gustatory cells will depolarise as the concentrations increase. Sweet taste involves the detection of sugars, such as glucose and monosaccharides, by special G-protein coupled receptors rather than direct diffusion of ions. Likewise, bitter taste is the detection of long-chain organic compounds known as alkaloids which contain basic nitrogen ions. Umami taste is a detection of certain amino acids such as glutamine and may be loosely considered as the “taste of proteins”. Hot and spicy flavors are actually pain/temperature sensations caused by the substance called “capsaicin” in food, binding to thermoreceptors whose function is to prevent burning of the mouth and tongue.\nChemical properties do define/direct taste, though not of elements, but of substances, a combination of elements. I would add that any food contains a great number of flavor components , chocolate alone contains over 800. No food is only sweet or only sour, etc… This is what makes tasting so interesting!", "762" ], [ "If you are only given glycogen and ATP as choices, then glycogen is the correct answer. The reason for this is, that muscle cells need ATP also for other very important processes (such as keeping the membrane potential stable and preventing cramps). Thus, while ATP is the actual fuel that powers myosin to create the muscle force, the cell needs to keep the ATP concentration constant in order to avoid negative impacts on other metabolic processes. Therefore glycogen is the actual energy storage.\nHowever glycogen is not the only energy storage used in muscles. The muscle actually uses a quite clever energy management system:\nDuring the first 2-7 seconds it uses phosphocreatine (or creatine phosphate) to quickly replace used ATP (as mentioned in the answer by <PERSON>).", "171" ], [ "This means a 100m Sprint can be almost completely performed using this energy storage system.\nFor the next ~30 min (but can be up to several hours for well trained endurance athletes), the muscle relies mainly on energy stored as glycogen. The glycogen is broken down into glucose and the glucose is then converted into glucose-6-phosphate and then ATP during glycolysis. Glycolysis creates ATP much faster than oxygen respiration. However, a side-effect of this is that glycolysis generates lactic acid which is further broken down by oxygen respiration, and in the liver. Overtraining can cause lactic acid accumulation whcih can acidify the muscle and cause lactic acidose There is much more energy stored in glycogen than in phosphocreatine which also makes this the more likely answer to your question.\nFinally, after glycogen stores are depleted, the muscle needs to reduce its energy output and rely on external energy provided by the liver and by fat reserves of the body. This is the reason why some trainers claim that you need to exercise for more than 30 min to start burning fat and thus to reduce weight but this is wrong because the glycogen stores in the muscles are also restored using energy from body fat (which means that the best and only way to loose weight is to burn more energy than you consume either by increasing exercise or reducing food intake or both).", "860" ], [ "are there other classes of compounds responsible for the red and yellow colors found in flowers?\nInterest in colors, specifically dyes, was a real motivator for serious chemical work. Some of the early efforts were aiming to mimic Tyrian purple, also known as Royal Purple, because in antiquity it was worth its weight in gold.\nTwo classes of molecules come to mind other than anthocyanins in phytochemistry, such as the closely related flavones (its root means yellow) and the distinct carotenes (its root means carrot, but also responsible for flamingo color).\nCan the red colors that give a \"normal\" anthocyanin pH response arise from pigments held in an acidic environment in the plant?\nA real sharp organic chemist by the name of <PERSON> proposed this in the early 1900s. He was working on determining the structure of the pigment responsible for the blue color in cornflower. He extracted the same substance coming from a rose and proposed that all flower colors were due to a different pH in the sap. As your experiment clearly points out, however, alkaline conditions are typically required for the blue anion.", "979" ], [ "A Japanese group argued that alkaline conditions in the sap were unlikely and that instead these different colors can be explained by the formation of metal-organic complexes.\nIt wasn't until 2005 that a definitive crystal structure was determined from the cornflower pigment called protocyanin. It turns out that the blue color comes from a supermolecule containing one Fe$^{3+}$, one Mg$^{2+}$, two Ca$^{2+}$, six anthocyanin and six flavone molecules packaged together in a complex structure. This color, as I vaguely recall, remains blue from pH 7 until pH 1! This agreed with some earlier evidence which suggested a complex species by the temperature dependence of the pigment.\nThese are not easy studies to conduct and I'm not familiar with how in-depth red colors have been studied, but it is certainly possible a complex species is actually how the red pigments form in vivo. Keeping in mind that plant vacuoles have a pH on the order of 5, we'll generally notice a loss in red above pH 3 in solution for a pure anthrocyanin in solution as hydration of the cation occurs. Stability of the color, and thus cation, obviously must be obtained either via copigmentation or with metals in a plant.", "979" ], [ "Relationship between mN and mg in vessel contraction studies?\nWhat is the relationship between mN and mg as the units involved to measure the changes in contraction? A tool most widely used is an instrument called myograph. In these exoeriments, either units of mg or mN is used without any mention of why. Note that the first two examples use an experimental tool called a myograph - used to measure the force produced by a muscle (in this case muscular blood vessels) when under contraction. Both examples mention tension. Wether these myograph experiments are completely different i'm unsure.\n1. This example shows force as 'mN' from this paper Fig 1A a. Those who are interested the caption is as follows \"Effects of Li+-PSS and NMDG-PSS in PGF2α-preconstricted pulmonary arteries. Intrapulmonary arteries (IPA) were first exposed to 80 mM K+, and endothelial function was assessed by relaxation of PGF2α contractions (10 μM) to acetylcholine (10 μM). Following a period of recovery, IPA were preconstricted to 10–15% 80K using PGF2α, and then physiological saline solution (PSS) was replaced by Li+-PSS in the continuing presence of the same concentration of PGF2α in endothelium-intact IPA\"\n2.", "171" ], [ "This example shows units as 'g'. note that some examples from other papers also use units of mg essentiall x1000 similar to other unit conversions from this paper Fig 1a. The caption is pretty much the same as 1. Particularly thromboxane A2 (TXA2) is a pharmacological agent affecting a set of ion channels: \"Requirement of thromboxane A2 (TXA2) for hypoxic pulmonary vasoconstriction (HPV) in rat pulmonary arteries (PAs). A: hypoxia alone (3% PO2) did not induce contraction of PA (left). In the presence of 10 nM U46619, hypoxia induced a strong contraction equivalent with the response to high K+ (80K, right)\"\n3. For a third example click here. It does interestingly state \"The PA rings were stretched to a predetermined optimal passive tension of 750 mg\". As such mg (or g) is an alternative representation of a unit of force as presumed. Figure 1 in this link again demonstrates mg as an y-axis unit of measurement under myograph experiment", "171" ] ]

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[ [ "(Anti)Heroes are romantic by nature. They perform heroically, passionately, in order to attain an ideal. I think the issue you might be facing here is not one of writing, per se, but of psychology.\nYou're probably judging your character. You presume that because he uses 'harsh' methods, that must be his sole definition. He can't like cake and pie? Coffee and tea? Because you use the term anti-hero, we can further presume that maybe you're only offering clarification for sake of brevity in your question, or it could also point to an underlying belief system you hold, that killing people for any reason is bad. Therefore, MC is an anti-hero.\nIf that's the case, I think the first thing you need to do is not worry about your subplot, but learn to love your MC. You have to forgive him as an author, and at least in the abstract, embrace his ideals. You aren't going to be able to convince the reader of his conviction and his passion if you're constantly apologizing for him.\nHe does what he does, because it is the right thing to do. (In his mind.) He is a murderer of murderers, sine qua non, and it is a role he is willing to accept in order to make the world a better place... for those he loves.\nThe opposite of love is not hate, it is apathy Do pardon my <PERSON>, but this is true. If you love something, if it matters to you, and it turns into something you find distasteful, that it is the inception of hate, but its core is still love. If something doesn't matter to you, you don't give a shit either way. Shoelaces for example. I doubt you have a heated, passionate feeling towards shoelaces either way.", "510" ], [ "But the naturalistic right to life, on the other hand, likely sparks you strongly, and you have very specific ideas about how that should be addressed.\nThe point here is that your MC might be angry, spiteful, vindictive, hateful, that does not mean he is evil. While you and I may disagree with his motives, he would argue them to his death, and would have very specific ideas about why what he is doing is right. In his mind, even if he recognizes his actions as questionable, he still finds them justifiable, and therefore good.\nSo if he's hateful, that's because he loves that which he hates. Hm?\nOnce you have come to terms with the MC's psychology/philosophy, likely you will see that there is not only a lack of contradiction in a love story mixed into your primary arc, it actually ADDS to the primary arc. Your reader needs to be able to relate to your MC in order to be invested in him. If he's just a single-minded assassin lacking in humanity, you're going to have difficulty pulling that off.\nBy making him more complex, by adding the fuel of a romance, you have a million opportunities to draw contrasts and metaphors between his actions and his values.\nHow do you handle seemingly contradictory subplots? The same as any other subplot. You lace it into the story. You use it to teach the reader about the world and its characters. Your use it to build empathy for your characters; to draw the reader into your story through the common ground of morality and sexuality, and then leverage it to whatever aims you desire. To humanize the MC. To deliver him. To destroy him.\nI think your subplot, as it is, could be even more powerful than your primary arc. (Perhaps not more important, or maybe that too.) I think maybe you're judging your character, and your subplot. Maybe it's not a subplot at all, but the foundation. You just need to tweak your perspective, and you may realize that it's not the plots that are contradictory...", "425" ], [ "I agree with <PERSON>, but beyond just passive voice (rampant in amateur writers) I see an issue of style. Some sentences read smoother than others, this is absolutely true. So if your question is merely about style, you just have to read a million books and reread your own book a million times until your words flow like syrup on a stripper's thigh.\nIf your question is really about show vs. tell, the only trade-offs there always has 'tell' on the losing end. If you want to maintain pacing, then pace it appropriately. Pacing and showing are mutually exclusive.\nIf you don't want to divulge certain information, don't. Information and showing are also mutually exclusive.\nIf it's awkward, rewrite it. If it's too wordy, use less words. All of the issues of show vs tell are writer issues, style issues, but none mitigate the value of the show.\nThe only time you should tell your reader anything is when there is no emotion or plot involved. When what you're saying is objective and a vehicle to move the story along.\n\"They walked across the tarmac.\"\nNo problem. You can tell that, especially if the plane or the characters or whatever else is what's important.\nBut not if the tarmac is made of meat.", "873" ], [ "That requires a show, not a tell, because a meat tarmac is out of the ordinary and should generate a reaction from the reader. You want your readers to feel the discomfort of their feet squishing on meat, rather than the familiarity and assurety of rough concrete. If you merely tell them it's uncomfortable, it has no impact.\nBooks do not merely tell a story. They evoke them, in ways that not even movies can attain. Movies can impact you through visuals and sounds. You can see a character react and know what they're feeling. You can hear the low, stomach-churning pitch of <PERSON>'s spell razing the amassed soldiers. The music swells, the skies darken, and the wave of magic crashes into the front lines, countless bodies like blackened matchsticks, violently tossed asunder or carried along in its horrific wake.\nA book is internal. You can know the minds of the characters far more than you can with any other medium, and you would be remiss to lose that opportunity to invoke the readers' emotions to your aims. The best books, like the best movies, will make you cry, rage, yearn, laugh, worry, whatever.\nBut you can't tell your reader to cry. You gotta weave magic for that.", "999" ], [ "In short:\nTell the truth.\nWhat do I mean by that? Here's some writing advice from one of my favorite British authors:\nEven in literature and art, no man who bothers about originality will ever be original: whereas if you simply try to tell the truth (without caring twopence how often it has been told before) you will, nine times out of ten, become original without ever having noticed it.\n<PERSON>\nTruth, in this context, is what is true to your characters.\nTry to focus less on making the speech sound \"actually good\", and more on how the speech is going to make the receiving character feel. How are you going to achieve the main character feeling like they suck? If you're going for a serious (not comic) dramatic effect, your ammunition should draw heavily on the flaws of the \"you suck speech\" recipient.\nTake your <PERSON> quote, for example. The reason this quote is a joy to read is because 1) it's true to the characters (<PERSON>'s existence / the testing facility is built on making up facts to influence the test subjects) and 2) it contains a stab of truth: the test subject is, in all likelihood, a clone who doesn't even have a mother.*\nThe quote is untrue (which is why it's funny) and true (which is why it's sad).", "873" ], [ "<PERSON> constructed the \"you suck speech\" with the aim of discouraging the test subject, and the writers constructed the speech to be comical.\nEDIT: I'll echo <PERSON>'s answer, that the ranter, to be true to their character, could rant about what bothers them most about the other character. I'd also add that while the ranter may be annoyed and want to vent, their motives could lie elsewhere. Going back to your example, <PERSON> is probably annoyed that the test subject is misbehaving, but she's making up the \"horrible\" test results in order to influence the test subject.\nThis just makes the point that there can be many different kinds of \"you suck\" speeches and they'll have varying degrees of venting, discouraging, distraction, etc.\n*Please forgive my limited knowledge of the Portal universe--if the test subject has parents, correct me.", "494" ], [ "There are two issues being raised:\n1. How to plan character growth?\nThere is nothing to plan. Growth happens under any circumstances (except perhaps coma, hibernation and the likes)! Your MC is above all a human being. She has the capacity to understand, analyze, think and plan. She can choose her most reasonable reaction to every environmental cue, be it to temporarily adapt to a demeaning situation, or to fight, full on, from the very first moment. She will grow from experience, and she will choose the path that is most suitable in her understanding of the situation.\nFrom your description of the character, an introvert may first adapt and study the situation.", "38" ], [ "She may identify breakpoints in those that wish to abuse her, and she may build trust with others around her who are being abused. She may slowly build the path to weaken the foundations of her cage, put her jailers in agony, and break free. How she does this, that is your plot, and for you to design. I sometimes work these situations backward: for instance, I plan that she will be free after she get her husband's mother to an asylum, which happens after she inherits her husbands fortune, which happens after her son dies, which happens after the husbands' creditor challenges him for a duel, which happens as soon as they hear that the husband ran away with the money, which happens after the husband receives a letter that the MC has forged telling him that he is going to be bankrupt, which is sealed with the stamp, stolen from the lawyer by that maid, with whom the MC has been very kind in times of distress, etc...\n1. the MC itself\nSorry for saying this, but the MC has the colors of <PERSON> in disguise. Being at the same time introvert, non-conformist, and righteous, and being a free spirit one day, and a caged prisoner the next, would be a truckload of flags if I were to review this writeup. I'd suggest to flesh out this character a bit better, make it more human, add a third-dimension to an otherwise flat collection of stereotypes.", "425" ], [ "tl;dr on all the answers here, but I'm actually facing the exact same quandary in my own novel. In addition, the secret the MC is keeping (his career) would come up conversationally between himself and the rest of the characters, so it's a constant struggle.\nI am employing a number of different tactics.\n1. Making the secret a known-unknown to the reader In other words, the reader knows there is a secret, because of the MC's (and exposition's) lack of specificity. By being glaringly obvious that I'm not going to come out and tell them what the MC does, the reader knows that there is a secret to find out, and I can lay breadcrumbs to keep them turning the pages. When I was first concepting the story, this was a sticking point. When I decided, oh wait, this could fun, it became a commodity. It adds a mystique to the MC, and gives the reader something else to look forward to in the book. Plus, it's not a sudden, unprojected surprise.\n2. Misdirection I tweaked my concept once I decided to embrace point 1, adding a couple supporting characters, and voila, I have red herrings everywhere. I am intentionally using specific language and situations to suggest to the reader that the MC does X for a living, and I will often write as though X were indeed true. It helps me to embrace the lie, as the MC does (Method Writing? wink) and further obfuscate the truth. When situations arise in which the MC has to actively cover, I don't hide that from the reader, just the characters.\nWith that in mind, I decided on third-person limited multi-perspective.", "846" ], [ "It allows me to give clues from the MCs POV, and when I'm writing from other characters' POV, I try to fill in the blanks of what the reader might be asking of themselves (wait, if he does X, why would he say that?) and also further misdirection with their own theories of what he does.\n1. I sweat a lot Which is to say that this is really fn hard to write. I'm constantly checking my language and phrasing and keeping notes (Scrivener footnotes and thumbtacks are really helpful for this) on what I say and how I say it. Obviously I don't want it to read clunky, and I don't want to disenfranchise my reader, I want to use that mystery as a subplot to draw them into main plotline. So I read and re-read what I write, and I have a brilliant, sexy, red-headed editor to bounce drafts off of.\nI might recommend finding a writing circle (Write On, Critique Circle, et al), and doing control experiments. Keep one group in the dark, let the other in on the secret, and then ask each to give you their feedback on how it's progressing. Does this make sense? What do you think the secret might be? How did you come to that conclusion? Is it frustrating or fun? Etc. A potential benefit to this technique is that readers can often come up with wonderful theories that you can employ in the book!\n1. Backspace You can use Shft+Left/Right/Up/Down arrow keys to select larger selections of text for deletion. How do I know this little shortcut? I'm using the same tactic! ;)\nDid I mention that this is really hard? Don't expect to get it right the first time. But if you can pull it off, it can only add to the story. Cheers.", "487" ], [ "TL;DR You need to have a well-developed Character with a well-known set of Skills, who adheres to a certain Moral above all else. The reader must share the same Moral, or they will have no recourse to relate. The Moral must be put to the Ultimate Test, wherein the Character's Skill is shown to be at its Strongest, and Moral is at its Loudest.\nSeems to me like all these examples are just a jarring use of slapping you in the face with the 'moral of the story' which has been worked up to all along.\n<PERSON> fought so that his people could have Freedom. Screaming Freedom! at the precipice of ultimate change emotionally reinforces all that we have been working towards. It inspires everyone, giving the notion that 'This is it, this is what we have all been waiting for'\nWhen <PERSON> has been so chivalrous and loving this whole time, and now he finally, willingly, pays the ultimate price for the love of his life, it speaks to the reader. It reinforces all the things we have previously known about <PERSON>, and washes everyone with remorse for <PERSON>'s beautiful, frozen soul.\nWhen good-old <PERSON> inspires poor burdned <PERSON>, even at the Fringes of Middle Earth and on the literal edge of Doom, when all hope seems lost, (I'm getting chills just writing this) he is showing the audience his true colors, which they already knew about him. He is reinforcing our ideas about him, in the best way, by doing what he does best, in the clutch.\n\"Doing what they do best, when it counts\" speaks for all of these scenarios, and many climactic moments, in general.", "999" ], [ "Whether its a wacky group of like-minded people, coming together to take down a larger-than-life opponent using their individual skills (Oceans 11), or a hyperintelligent detective consistently solving the crime (<PERSON>), we get a rush when people use their well-known skills to solve unorthodox or seemingly impossible problems.\nIt becomes a punch in the gut if misfortune befalls the actor, but they still solve the problem they set out to solve (<PERSON>). If they don't even solve the problem, that's pretty tragic, and if the character is crafted to be well-liked, the effect is more jarring than heart breaking. cough cough song of ice and fire\nI'd say LoTR and Braveheart aren't so much gut-punching as heart-wrenching, but they all serve to draw a supreme level of empathy towards the actor. Because they all did what they do best, and their morals shone, to the extreme and in some cases to the end.\nEDIT: I'd like to extend a nuance of this recipe, and in doing so give a shoutout to <PERSON> The Dark Tower Series.\n! <PERSON> is known to love his surrogate son, <PERSON>. <PERSON> is also known to be responsible for <PERSON>'s deaths (multiple), in pursuit of his Ultimate Goal. The Betrayal seed as been set... And then <PERSON> dies for the final time.\nadditional spoilers in link\nhttp://darktower.wikia.com/wiki/Jake's_Eulogy\nIt's utterly gut-punching, heart-wrenching, mind-quailing (to steal another <PERSON> phrase) all in one.\n!I knew I shouldn't have expected anything else, but when it happened, and <PERSON> let his guard down ever so briefly to give us a glimpse into his terrible inner turmoil, and saw <PERSON> off with such love, remorse, loyalty, and compassion, it really tore me up.\nIt reinforced multiple things, <PERSON>'s drive towards the Ultimate Goal above all else, and the very tragic effect this had on his life. The juxtaposition of the two Morals existing at once, (pursuit and love, respectively), and the former consuming the latter, causing terrible grief.\nI would wager that the more \"layers\" of a character you can make as raw as possible in the right moment, the more emotionally impacting the scene will be.", "190" ], [ "So you've got a few adjectives for the character, to start off with. Some people are a fan of the figure-your-character-out-as-you-write approach, and some prefer outlining the character first. Since this is an assignment, and you don't want the character who spontaneously appeared as you wrote to differ from the one described in the assignment, I'd have to recommend the latter approach.\nWhat makes a \"good\" or \"lively\" character:\n* Details! What are his quirks? Does he wrinkle his nose when something disgusts him, or wipe his right hand on his pants?\n* What does the world look from his point of view? What's his job? Does he like it? Any best friends? How'd he grow up? Since he's smart, insightful, and thoughtful, how did this shape his philosophy? You need to know to write him well, and we as readers find difficulty relating to him unless we can get inside his head a little. This will also be crucial for your self-description.\n* Give him flaws. Up until now he seems a little <PERSON>-ish. He's smart, thoughtful, insightful, clever--he's most likely gone far in whatever he's done. Reserved and mysterious? Even better, the girls are swarming and we're all jealous of him and wondering what he's up to.", "425" ], [ "Now balance that out. Is he arrogant because of this? Or is he eager to make people like him and bends over backwards for them? Or does he not have this success at all and is angry at the world for not giving him what he thinks he ought to get? This and the point above will most likely determine how he reacts to others.\n* Last but not least: We don't see his biography, we see him in action. Specific to your situation it seems like you're forced to give a little biography, but my general advice would be not to make it too long, and intersperse the rest of your biography in with the action, if you need to add it at all.\nYou've got a character, you know how he thinks, now it's time to throw him in a situation. Roll dice if you have to: 1 for getting mugged, 2 for being fired, 3 for meeting with an ex, so forth and so on. And build the situation such so that you can show most of his character traits in the situation. Think about what he might do to show the qualities you want to highlight.\nFor instance getting mugged: Your main character stops/talks down the attacker, maybe makes some comment about the mugger's motivation that obviously hits the nail on the head (because he's smart and insightful) , and lets him get away with a \"dummy wallet\" with only a few dollars (clever, well-prepared) and continues on his way. This scene is observed by an acquaintance who is following the main character and wondering what he's doing in that part of town at night, without having told anyone (mysterious and reserved) .", "425" ], [ "Generators, I've found, tend to produce bland characters. There are few, if any, substitutes for spending time with your characters. Obviously you can't meet your characters in-person. What you can do is use writing prompts to put characters in everyday situations and see how they handle themselves.\nA useful tool is stereotyping your character. Think about all your favorite characters, or the characters you want to imitate. Now draw up a character diamond of this stereotype.\nA character diamond is a collection of four traits that best describe a character. Usually one of the traits is negative, called The Flaw, and the other is positive, called The Highlight. People change in bad or stressful situations, and their true nature, which is normally hidden, tends to come out.", "38" ], [ "The trait that emerges during a conflict is called The Shadow. How a character acts in everyday life is called The Facade\nThe Facade is the top of the diamond, The Flaw is on the left, The Highlight is on the right, and the Shadow is on the bottom.\nTo be clear, a character diamond only lists the most dominant of traits, and is just a tool getting a better grasp on who your character really is.\nNow, think, how is my character different? How can I distinguish them from the stereotype? Often, being unique is not a requirement to hold readers attention; an interesting character can be made by a couple degrees of difference. Change either a character's Flaw or Highlight, and either The Shadow or The Facade to some other trait to create an interesting new persona.\nTo help you along, you should take a look at TV Tropes which, despite the name, has many articles, and discussions on characters from novels, as well as stereotypes, and gives more specific examples than I could possibly ever list. Also Google \"character diamonds\" for articles that go into greater depth. Getting a list of character traits is also useful for gaining some ideas.\nBlindly asking questions without knowing who, even in the simplest sense, your character is on the personality level, is a recipe for boring. Answering some basic questions about the character is good, so long as you ask the right questions.\nToo many forms provide a laundry list of physical questions, hair, eyes, height, build, clothing, gender, age, occupation, etc. The problem with this is beginning writers assume that these questions are important; are these questions important, really? The answer to that is only if the answers help tie the character to the narrative, or inspire further development.\nIt is the difference between <PERSON>, thinning hair, who works as a chemistry teacher in some boring this is my life sort of story, and <PERSON>, worried about his thinning hair and thinning health, dying of cancer, and using his occupational knowledge in chemistry to cook meth so his family won't suffer financially when he is gone.\nSpend some time with your characters, their (supposed) to be people too! You want your readers to perceive them as real, right? After all, characters are how your readers connect to the narrative. When a character feels like a person, it engages the reader's suspension of disbelief, so to me characters are the most important part of writing. Don't do your characters, the people of your mind, injustice by asking the wrong questions, and writing them into a narrative before really knowing who they are.", "846" ] ]

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[ [ "Yes, the landscape is scattered with nuclear debris.\nMost nuclear power plant designs will fail spectacularly with long lasting effect on the surrounding area.\nThe notion that nuclear reactors can run for extended periods of time without human intervention is simply not founded in reality.\nKeeping a nuclear reaction from becoming critical is a feat within itself. It's balancing act of maintaining a state that is less than critical.\nIt will fail within a few months to a few years working under the assumption that it is not getting it's cooling water replenished which is entirely plausible.\nMost nuclear power plants in the United States require are light water reactors or pressurized water reactors and require the circulation of water in order to stay within a 'steady state' of operational limits. The two failure scenarios that come into play under an unattended state both involve overheating and a change of state to critical. Other incidents occur on the timeline to critical such as hydrogen explosions but these events are essentially ancillary and aren't central to root cause.\nBackground\nThere are two types of nuclear reactors that can suffer from water related failure.\n* BWR - Boiling Water Reactor\n* PWR - Pressurized Water Reactor\nFailure Scenario - Lack of Water\nBoth water cooled reactor types suffer cataclysmic failure due to a lack of water. Some reactors can be more robust than others depending on the design. Many reactors derive their cooling water directly from their environment using ocean, lake or river water. These reactors are prone to having their water intake ducts clogged with debris thereby restricting the flow of cooling water to their segregated cooling systems. A lack of human intervention in these reactor types can lead to failure.\nCooling towers are used with reactors that are not in close proximity to ocean, river and lake water. Palo Verde Nuclear Power Plant in Arizona is one such example as was Three Mile Island.\nIn the event of an overheating reactor in the United States the Federal Government only requires a 30 day supply of cooling water. This cooling water, called a UHS (Ultimate Heat Sink) is a finite source and dissipates over time due to a number of reasons including evaporation, steam release and lack of re-circulation of primary cooling circuits due to radiation (the water for cooling is used one time only, in some cases, due to the amount of radiation contamination of the water)\nAs the water supply for cooling dwindles and water pressure decreases enough for flow rates to diminish beyond preset thresholds, the reactor undergoes an automatic shutdown called a SCRAM.", "435" ], [ "A SCRAM event does not require electricity. Neutron absorbing control rods are held in place by electromagnets above the fissile pile and upon loss of electricity the electromagnets lose their magnetism and the rods are dropped into place bringing fission to a near halt in the core. These systems are automated and do not require human intervention, however, the continued decay heat of the fissile material continues to create issues with cooling and with a finite water supply, eventually, the reaction pile becomes exposed to air which cannot cool the fissile rods due to simple lack of density.\nAt this point water changes it's state to a gas and becomes steam. The heat increases further and more steam and pressure buildup in the chamber. Water becomes superheated and takes on properties and attributes more akin to an organic solvent. The pressure is so high within the chamber that it eventually prevents the water from boiling. This superheated water's hydrogen bonds are eventually broken and the chamber becomes filled with superheated highly pressurized hydrogen which eventually explodes due to combustion or the failure of the reactor pressure vessel to contain the extremely high pressures. This failure has been made famous by the hydrogen explosion at the Fukushima Daiichi reactor containment vessels in Japan due to the tsunami which did not damage the reactors, it damaged generators that prevented the circulation of water for the cooling systems.\nThe loss of integrity to the reaction chamber is the penultimate step to the catastrophe, all systems are essentially destroyed and now the fissile material can become molten and eventually melt through any concrete casements that require cooling features in order to prevent the molten nuclear pile from actually melting through it. Once this molten pile of nuclear material hit's moisture an explosion can occur sending nuclear debris into the atmosphere and contaminating the surround landscape with fallout. Mind you, this isn't a nuclear explosion it's just an explosion....but you see what the problem is here, it's called a meltdown.\nConclusion\nWater inlets that use water from the environment (rivers, lakes, oceans) for secondary cooling systems require regular maintenance to prevent debris from clogging their inlets.\nUS located closed loop cooling reactors require only 30 days of backup cooling water.\nManual events such as steam or pressure release to prevent containment vessel explosions won't be occurring. There are disaster prevention events that require human intervention.", "435" ], [ "Decompressing airlocks by opening of the outer doors is undesirable as you will lose some of your precious oxygen to the vast emptiness of space. Besides, pressure equalization by opening the hatches may be explosive in nature, as the rate at which the pressure equalizes is uncontrollable. Explosive decompression might cause damage to equipment as well as severe injury or even death.\nThe airlocks hatches shall therefore either open inward (similar to what you'll see on submarines or decompression chambers) or have a pure mechanical interlock which prevents opening the hatches unless the airlock pressure has already been equalized.\nDuring normal operation, the airlocks will be equalized by using an equalization compressor which will evacuate the air from the airlock and store it on a tank. The equalization compressor shall be equipped with emergency push buttons both on the inside and the outside of the airlock, which will stop the compressor and open a valve to bleed the air back into the airlock from the air tank.\nThere will be mechanical valves for emergency equalization of pressure between space and inside the airlock, as well as from within the airlock and to the interior of the spacecraft. The mechanical valves will require specialized tools for operation.", "35" ], [ "The valves for equalizing between space and within the airlock can only be operated from the outside or from within the airlock. Similarly, the valves for equalizing between the airlock and the spacecraft interior may only be operated from within the airlock or the spacecraft itself.\nObviously someone from the outside will have the theoretical possibility of bleeding out the airlock against the will of the crew of the space craft, but this is mostly a hypothetical situation which does not warrant any particular countermeasures unless it first proves to become a issue.\nThe requirements for safe design and operation of airlocks will be a part of the SOLIS-code (Safety Of Life In Space) sanctioned by the International Space Organization (similar to International Maritime Organization) which is an organization consisting of the different governmental space agencies of nations with vested interest in space operations. The codes will require periodic inspection of the safety functions of the space craft. The national space agencies will have the authority to inspect and to place any space craft that does not meet the SOLIS-codes under arrest until the spacecraft is up to standard. The governmental agencies can also blacklist space crafts and impose sanctions on the space craft owners in case they attempt to bypass the inspections by never docking in a regulated space port.", "35" ], [ "How feasible would it be to build and field a tv/radio guided drone against aerial targets without modern technology?\nI have a constantly moving floating island that is looking to augment its air force against numerous threats in the sky. Having long run out of resources that don't grow out of crystals or biomaterial on the island, the majority of its resources come from attacking and excavating other islands. Islands which may have native hostile life or intelligent life.\nAt times multiple islands may be fighting each other or over the same piece of unclaimed land, so control over the skies around the island is critical. The air force operates a range of aircraft. One of which acts like a fleet defense aircraft. Only it defends the island, hurling long range missiles in beyond visual range combat. It combines a powerful radar, high fuel load, and decent computerized technology (pre 2000s military tech). However, due to limited resources and scales of industry they are unable to field many of these platforms. Furthermore, it takes a lot longer to re arm and refuel (does not use normal jet fuel). The large distances involved compound the situation.\nIn offensive actions it acts as a long-range missile platform, however once it expends its ammunition it cannot contribute any offensive action short of EW. To offset this lack of combat capability, drones carrying a load of missiles have been developed. Essentially missile trucks. Once a fighter expends its ammunition, they circle a drone carrier, link with a drone and fly off with one. Essentially a soft reload of sorts.\nWhile their exists automation on the island, there is no artificial learning, machine learning or deep learning. They are unable to make transistors at such a small level with the necessary computer science to enable truly autonomous aircraft control that is combat rated. As such the drone is only capable of basic auto pilot and preprogrammed holding patterns. Some even use electromechanical computers.", "46" ], [ "More advanced maneuvers require the use of a human operator who is in a parent fighter aircraft who establishes a link to the drone.\nThe human operator is essentially a back seater/weapons system officer (WSO) w/ a slightly extended suite. Using a combination of TV and radio guidance, the WSO flies the drone manually from their aircraft. The fighter's onboard radar handles targeting information for the drone. Once a target is locked on, the WSO executes a fire command, from which the drone will fire a missile. The missiles that can be fired include both active and semi active missiles. During such operations, the fighter won't be pulling any aggressive maneuvers except for defensive actions. It'll stay at distance firing away with missiles, aiding older generation fighters. After firing its magazine, the WSO will fly the drone back to an airship and land it while the fighter circles in a holding pattern.\nHow feasible would it be to build and field such a drone that utilizes TV and radio command guidance against air targets without access to modern technology\nAssume technology (military and industrial) is capped to pre 2000s, there is no contemporary AI control or advanced flight mapping technologies that you'd expect to see on either Loyal Wingman or FCAS' drones. All flight maneuvers short of a pre-planned takeoff or basic holding pattern will be done by a human operator over wireless.\nNotes:\n1. Total fuel load of parent fighter aircraft is of no concern\n2. The drone mounts a forward-facing camera and a few sensors across the aircraft. The WSO gets a HUD and relevant data superimposed onto the view they receive from the drone. Their station is equipped to handle these drones.\n3. WSO/back seater is pilot trained and qualified to fly these drones\n4. The targets these drones will be firing at will range from anything involving primitive aircraft to 5th gen aircraft platforms. While the island in question may not be able to build high transistor density chips, that doesn't mean other islands cannot. There are enough flying based organisms that pose a threat to warrant this aircraft to be sortied against them as well.\n5. Size can vary between something as small as a jet powered drone or as big as an F16.", "160" ], [ "Accidental early detonation\nAs stated in other answers stopping the arms race from a technological point of view is hard to impossible. Making scientist and/or the general public unwilling to fund/participate in the development is probably easier. For nuclear power this has precedent in the Chernobyl accident which has had a severe impact on all research into nuclear power that still persist today.\nThe accidental early detonation of the (would be) first atomic bomb while still at the production facility would cause a major set back in the research since it both destroys evidence of what has gone wrong and kills a lot of the scientist and engineers necessary to build the bomb in the first place. Since it will be hard to find out what has gone wrong it will be hard for the scientist to say if it was a minor problem or a major design flaw. The effect will be that anybody will be very hesitant to continue with the project or try to start a new project.\nFor the disclaimers:\n* An accidental atomic explosion can be caused by a simple very small effect such as a faulty wire presumably.", "435" ], [ "Although I am not sure what fail safe mechanisms they had in place during production of the atomic bomb.\n* This scheme would set back the USA but not necessarily the USSR although scientist there might become quite nervous about development. On the other hand if the USA didn't develop the atomic bomb the USSR might be less inclined since there would be no mutually assured destruction arms race.\n* Delaying it to 2010 might not be possible with a single explosion but should come from later treaties. The UN banning the development of nuclear weapons due to the risky nature of it linked to the explosion seems feasible.\n* You could argue that an atomic explosion is in fact an atomic bomb, but I would say that for it to be a \"bomb\" it should be stable and controllable which was not the case in this scenario, thus it should not qualify as an atomic bomb.\n* As a minor side note, but that would completely depend on the story. With no atomic weapons race between the USA and the USSR they have ample opportunities to get into conflict anywhere else, be it normal war, space or anything else. The space race could for instance give such a drain on both of their resources that they wouldn't have enough resources left for the development of an atomic bomb making the year 2010 more viable.", "477" ], [ "Lets start by making this a fission based dragon vs a fusion based dragon so the dragon will have a use for eating all that radioactive material.\nSince the dragon will not be able to use uranium ore directly there will need to be a few steps in its digestion process. The first step will be to grind up the ore by chewing and dissolve the uranium ore \"yellowcake\" in nitric acid in the dragon's stomach to form uranyl nitrate. Then the uranyl nitrate will be passed to the dragon's second stomach where it will be combined with ammonia to create ammonium diuranate. The dragons third stomach will reduce the ammonium diuranate with hydrogen to get uranium dioxide while its 4th stomach will convert that with hydrofluoric acid to uranium tetrafluoride before its 5th stomach oxidizes the results to get uranium hexafluoride \"hex\".\nOnce the food is digested it will have to be enriched and molded into a useable form. The hex will be passed via a special organ in the dragon's body consisting of a huge chain of diffusion chambers used to separate the uranium-238 from the uranium-235. The Uranium hexafluoride gas will be cascaded through the diffusion chambers before being passed to the dragon's 6th stomach that chemically removes the fluoride from the hex and transforms it into Uranium dioxide.", "435" ], [ "The Uranium dioxide is then melted and compressed into pellets that are stored in the dragon's reaction chamber.\nThe dragon's reaction chamber holds the enriched Uranium dioxide pellets close enough to achieve criticality when moderated by the high-pressure water running through it. The high-pressure water is used as both a moderator to keep the reaction critical and as the coolant used to move the energy in the form of heat throughout the dragon's body to its cooling organ, its skin.\nEach scale on the dragon has a copper inner side and a steel outer side. The temperature differential between the outside atmosphere and the high temperature, high-pressure coolant water works as a thermocouple to simultaneously cool down the dragon and generate electricity. This electricity is what is used to power the exotic dragon musculature that allows these majestic creatures to hold their immense two-kilometer bodies aloft without being crushed under their own weight.\nThe dragons breath weapon is powered by pellets generated in its reaction chamber and moved up the dragons esophagus to its breath chamber. When it wants to rain down death on its foes the dragon moves the pellets in its breath chamber together at the same time it opens its mouth and feeds chunks of waste u-238 into its breath chamber. The extreme heat from the breath chamber reaction turns the uranium into a stream of high velocity extremely radioactive uranium plasma.", "671" ], [ "Effects of shielding on length of modern warfare\nIn my setting there are particle shields that can be extended from a central source given enough power and particles to fuel the shield. This is a world where armor has outpaced weapons (nuclear weapons are a non factor). In essence unlike our world, getting the first shot off is not a guaranteed kill, especially for armored conflicts. Machines of war in general are durable because of shielding in this setting. Meaning that units can retreat and fall back faster compared to how we operate today. It would also mean that the actual physical armor isn't completely destroyed compared to a mission/full kill of today.\nHow much of an effect would this have on the durations of war (5,10,15,20 etc years),given that to knock out an enemy would require punching through the shield before the enemy retreats. This is also assuming that factions have built their doctrine on ensuring that their casualties are kept to a minimum and are swapping shielded and unshielded units back from the frontline as much as they can.", "347" ], [ "For the sake of argument assume that the time it takes to recharge a shield from absolute zero can range from a couple of days, to weeks. The shielding system can be mounted on structures and much larger machines etc, an adequate amount of particles just have to be fed to it and sustain coverage over such a large area.\nThis is a world with ETC (electro chemical) guns, railguns, hypersonic weapons etc, basically a little more than near future. A whole slew of other defensive counter measures exist in place as well for the survival onion. The shielding is the last resort. Active defense systems, stealth, advanced camouflage, adversarial camo/camera input, better smokes etc. All designed to make it hard to get close to hitting in the first place.\nTLDR: Would particle shielding increase the duration of near future modern war between peer factions on full war footing/economy, if so by how much.\nEdit: There is an upper limit on how many particles one can charge at once. There's some heavy sunk cost fallacy past a certain point, for example you can't reliably shield a Nimitz Class carrier completely and expect to shrug off a barrage of anti-ship missiles. The generators themselves are heavy and is a design consideration when building things like tanks or shoving generators in buildings or shielding a PART of a ship.", "898" ], [ "How to retrieve cultural artifacts from a world under siege?\nWe do not have a real identity as a 'species' per say- our kind is simply referred to as the \"Collectors\". For our organization's purpose is to preserve the works of art from across the galaxy in an archive spanning millions of artifacts from thousands of civilizations. We specifically are a newly made branch of collectors on our first task- to retrieve artifacts from a civilization before it is wiped from existence.\nThe civilization in question is one that is burned down to its last world, its home world. They had reached out to us earlier to preserve their cultural treasures, but only now have we mobilized the retrieval force.\nWe may have technological advantages in speed and maneuverability, but in raw warfare there is very little we can do to influence the unfortunate outcome of the Siege. Our vessels do not come unarmed, it is simply because the invaders have a whole fleet while we only have a ten ship brigade. Said outcome being the inevitable destruction of this world and its millennia of history. Calling for outside support is not our jurisdiction and it is not why we are here. This world made too many enemies and there is simply no galaxy wide organization dedicated to diplomatic affairs in the current epoch.\nHowever it may just be possible to get artifacts- and ideally living members of the species off world fast enough that we do not get intercepted by the <PERSON>.\nThere is a several obstacles that make this hard.\nThe first obstacle is that there is no stealth in space.\nThe second obstacle is that there is no \"warp drive\" in our universe. Instead our universe has a network of jump points situated near stars that link to other stars.\nThe third obstacle is the formidable invading fleet that despite having little if any means of reinforcement, have managed to secure much of the star system.\nThe architecture of the star system is as follows.\nEach feature/world is labeled in order of distance from the parent star.\nStar Count: One. G4.3-class\nThere is a vulcanite asteroid belt near the Roche-limit. Various patrols are located here. There is six jump points, most of which are well guarded. But only one jump point has the bulk of the invading force pouring in.\n0.12 Au; Barren world with low eccentricity orbit. It is a hot planet with little atmosphere. This world is 3000Km in diameter. Tidally locked.", "46" ], [ "There is not much activity here.\n0.30 Au; Barren world that is 4300 KM in diameter with slow rotation akin to Mercury. It is on this world that the <PERSON> have based themselves on after destroying the native mining facilities.\n0.6 Au; A large world around 13000 Km in size with a thick atmosphere. This world is not in a completely stable orbit. It's a hot world with volcanic activity and a small belt of asteroids that make a tenuous ring. Strip mining of this world has left many deep quarries all over the place. This world has few inhabitants and is not being prioritized by the invaders despite having some patrols in orbit. The invaders are focused on destroying the city world first.\n0.9 Au; At 0.9 Au out is the world that is under siege. It is a city world about 7800 Km in diameter with very developed defense systems, but these defense systems are taking a toll from repeated attempts by the invaders to irradiate entire continents in hit and run attacks. They have space elevators concentrated near the point of their world where tidal locking is most intense. The invaders intently keep watch on this area, but the high amounts of traffic around the world have made it hard for the invading force to know where exactly the defenders are building up which has allowed the defenders to set up more defenses with what time they have. The world is densely urbanized and they are aware of our mission. Communicating is not that difficult despite the blockades, but physical exchange is what our purpose is.\n3 Au; a Jovian world 37000 Km in diameter with two barren moons and a somewhat eccentric orbit. The distance of the world has not prevented it from being targeted by invading forces that bombed apart the infrastructure on the moons.\n6 Au; A large icy world about 6000 Km in diameter that is another hold out due to distance and a underground colony that is laden in defense systems. The invaders, like with the other hold out have put little effort into destroying this place yet.\n12 Au; A dim small ice world further out around 5000 Km in diameter. There's just robots here.\nWith this information, how can artifacts be retrieved from this world in a timely matter while minimizing the destruction of assets?\nWe have a around ten space craft entering from a jump point separate from the main jump point. The leading ship is a cruiser, the other nine are smaller more specialized ships used for rapid retrieval equipped with surface-orbit shuttles.", "99" ], [ "I think electricity will be a problem, and it will be the major one.\nElectricty:\nA synchronized power grid requires a certain balance between supply and demand. It is unclear what the demand in the affected area would be, but I doubt, that the supply could keep up.\nFirst, there is the hydroelectric power plants. The sources that feed their reservoirs would need to be teleported, too, otherwise the plants would become useless as soon as their reservoirs are depleted.\nSecond, wind energy is not reliable enough to serve as the sole producer to supply the base demand of the grid.\nBoth types of power stations cannot be used to satisfy peak demand, unless some of the hydroelectric plants are pumped storage plants, which in turn would make them unusable to cover base demand.\nNuclear power plants, if there are any, might work for quite some time. However, they rely on the availability of an external power feed in order to be operated safely, e.g. for emergency measures. Plus, with an unreliably peaking demand due to an unstable power grid and a lack of means to moderate these peaks, you're probably better off keeping nuclear reactors off the grid.\nThen there is the issue with distribution. I assume that most, if not all, of the significant power stations of the area feed their output into a high-voltage transmission grid. According to this map, there seem to be some major nodes of the western transmission grid located in the area of northern Oregon. Still, it is quite likely that this grid will be disrupted and inoperational. Even if the teleported area still has enough power stations to meet the demand, their output will have no means of reaching the consumers.\nThere might still be areas with decentralized, small power grids, but their power stations would probably rely on rather unpredictable renewables, like wind and solar power or on fossil fuels, that might not be available indefinitely in the new environment.\nBiomass plants could be a long term solution, but they require some sort of functioning agriculture/forestry and they are not feasible for large demands, e.g.", "435" ], [ "the city of Portland.\nWater/Sewers:\nWithout power, these services won't work either. Water pumps, sewer pumps, water treatment facilities; all will shut down in wide areas eventually, even if they can be kept running for a limited amount of time using generators.\nThey could be hooked up to wind/solar power plants, if regionally available, but these are not suitable to run core infrastructure reliably, so there will likely be disruptions in service. That bears the potential of a sanitary crisis, especially in bigger cities.\nCommunications:\nRadio communications, in the form of radio transceivers like walkie talkies, would probably suffer the least, as long as the devices still can be powered. There's not much physical infrastructure needed. A few aerials at most.\nInternet and mobile phone services will most certainly be unavailable or nigh unusable. They might technically be brought back online, albeit in a very reduced state, i.e. with an \"internet\" providing next to none of the well known services and a mobile network not capable of routing calls to any number outside the teleportation zone and with most of the apps and mobile services being broken, because they'd try to communicate with service endpoints and resources that are no longer reachable.\nBringing those minimal forms of modern communication online would require resources and electrical power. Both of which will be in high demand to keep running what is left of the critical infrastructure. With supply lines for spare parts and raw materials severed, not to mention a potential lack of suitable production facilities in the teleported area, I highly doubt that internet and mobile phone services will be publicly available even in the long term. In my opinion, Instagram and Twitter will be the least of a concern in such a scenario.\nOther things:\nGiven the large scale power outage I expect to take place in such a scenario, there's also impact on food supply, medical services and law and order to be expected.\nI think a decentralized society like ours would rather quickly deteriorate under such circumstances, and make room for small, centralized and self-sustained communities.", "87" ] ]

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[ [ "Among Us Inspired Automata\nIntroduction: Among Us Inspired Automata\nThis project is a STEM-based activity for high school or college students with prior knowledge of how simple machines function independently. It is also helpful if the student has knowledge of how to use lab equipment found in an engineering design class such as a table saw, laser cutter and drill press. By constructing an automata, students will be able to learn how cams, levers, linkages and the mechanics of movement function together. The completion of this mechanical sculpture will also show how simple machines can come together to create non-motorized movement.\nSTEL. In order to implement this tutorial in a classroom setting, we will be using Standards for Technological and Engineering Literacy to gauge what students should know and be able to do in order to achieve a high level of technological and engineering literacy.\nThe basic structure we will use to measure this is by first establishing the core disciplinary standards which represent all broad areas of technological activity in our world. Then we will show the practices that can not only be applied to the core disciplinary standards and contexts, but these can be applied to many real world situations as well. Finally, we establish contexts that tie back into the core disciplinary standards by representing 8 specific technology content areas.\nCore Disciplinary Standard.", "226" ], [ "The core disciplinary standard that aligns with this activity is Standard 2: Core concepts of Technology and Engineering. We see this standard reflected in the activity as we create a system by using multiple simple machines together to make non motorized movement. This activity is also a process where we use different resources and sequence of steps to produce our final product.\nAs the teacher/professor it is important to use STEL-2H where you identify all of the resources needed to create this automata, including materials, tools, machines, time and knowledge.\nPractices that are used in this activity include systems thinking; as we will be making separate simple machines function together to provide an output of up and down movement.\nMaking and doing; as we will be modeling, building and using scientific principles to create a physical, non motorized product.\nCritical thinking; as students will use their logic, reasoning and prior knowledge of simple machines to generate movement with only the materials provided.\nContext. The context that aligns with this activity is TEC-6: The Built Environment. We see this context reflected in this activity as students will design a wooden structure with components inside of it that also has to maintain its structure as it is interacted with. This is similar to real world structures such as building structures and students will understand that all structures have subsystems that have specific purposes. This activity also helps with spatial relationships, as students have to make sure things are scaled appropriately. Despite primarily being made of wood, students will notice that a different material would function a lot differently.\nSupplies\nFor this activity each student will need\nBass wood sheets\n* Longest sides- 18cm x 10cm (x2) -- 1/8th inch drilled holes 5cm from the bottom\n* Base- 9.9cm x 9.8cm\n* Inner squares- 9.9cm x 9.2cm (x2) -- 0.9cm x 1.2cm cut in the center\n* Front cover- 7cm x 10cm\n* Back cover- 10cm x 10 cm\nBalsa wood\n* Large wheels 4cm in diameter (x2) -- 1/8th inch drilled holes, 1 hole in center, other hole near edge\n* Large wheel 4cm in diameter -- 0.9cm x 1.2cm rectangle in center\n* Small wheel 2.5cm in diameter -- 1/8th inch drilled in center\nAdditional materials + tools\n* Dowel rod- 15cm, 1/8th inch diameter (x2)\n* Flat rod- 12.5cm x 1cm\n* Foam sheet\n* Among us inspired character- 5.7cm x 4.3cm (provided)\n* Wood glue\n* Ruler\n* Drill press or hand drill\n* Table saw\n* Laser cutter\nBased on the materials purchased, three students could do this project for about $30, with majority cost being in buying the wood\nAll dimensions and drawn parts for the automata can be accessed through this google drive link numbered in parts1-11:\nhttps://drive.google.com/drive/folders/1gc9_obpzO7PdRYqbSs5ck8peBmUeyC6T?usp=sharing\nStep 1: Longest Sides\nUsing a drill press or a hand drill, drill the 18cm x 10cm pieces of bass wood with a 1/8th inch drill bit 5cm from the bottom.\nStep1 needed parts and dimensions for automata can be accessed through this google drive link:\nhttps://drive.google.", "668" ], [ "Trebuchet With Paint Sticks\nIntroduction: Trebuchet With Paint Sticks\nProject Intro\nIn this instructable, I will be going over how to make a trebuchet mainly out of paint sticks. This project is aimed towards high school students but high school teachers can also use this instructable to plan a lesson\nLearning objectives\nStudents will be able to comprehend and create a working trebuchet after going through this instructable.\nStudents will be able to apply their knowledge of making a trebuchet to modify and change the original design.\nSTELs:\nStandards\n* Design in Technology & Engineering Education:\nMaking a trebuchet is an iterative process. You can follow my steps to get to the same conclusion as me, but you can also take it a step farther and modify different parts to see how it changes how the projectile is thrown. You could use a different object for the projectile, change the weight of the counterweight, change the pouch/carrier for the projectile, or even change the lever or frame sizes.\n* History of Technology\nTrebuchets help define history and can be used to teach students about the history trebuchets were involved in and deepen their understanding of the past. Students could learn what technologies influenced and where influenced by the trebuchet. They can also review the positive and negative impacts that trebuchets created.\nPractices\n* Creativity\nStudents can use different materials to make the trebuchet. They can modify and improve the original design to see if they can make the projectile go higher, farther, etc.", "74" ], [ "By doing this, students will fail at times but they will be able to learn from the failure and use it to succeed.\n* Making and Doing\nStudents will follow the guide to make the trebuchet and then they will physically make it. If students choose to modify the design after completing it, they can plan out what they will do first and then act out their plan.\nContexts\n* Built Environment:\nStructures are used by humans in everyday life and serve different purposes. Depending on the structure, different systems can be utilized to support it. For the trebuchet, the base provides stability for the structure when sending the projectile. The lever and axel allow movement in such a way that will launch the projectile.\n* Material Conversion and Processing\nThis context involves the physical creation of things. In this instructable, you will use paint sticks, wood, glue, rope, and more to create a trebuchet. Students could use this project to learn about how the materials used were made, like wood, glue, and rope.\nStep 1: Materials and Supplies\nYou will need the following supplies\n* 11 Paint sticks (1 foot long) ($2.00) https://www.homedepot.com/p/1-Gal-Paint-Mixing-Cra...\n* 3/8'' Wooden dowel rod (about $1.00)\n* Rope (1/8'' braided nylon rope) ($6.59) https://www.acehardware.com/departments/hardware/...\n* Wood glue ($3.97)\n* Scissors ($1.88)\n* Clamps (small ones can be bought for $1.00)\n* Duct tape ($4.98)\n* Ruler/measuring tape ($4.00)\n* Breeching snap (2-1/2 inches) ($1.59) https://www.acehardware.com/departments/hardware/...\n* Eyebolt with nut (3/16x2'') ($1.59) https://www.acehardware.com/departments/hardware/...\n* Coins (87 pennies, 23 nickels, 38 dimes, 74 quarters, total cost is $24.32)\n* Hole punch($3.11)\n* Sharpie/marker (can be bought for $8.54 as a 12 pack)\n* Lighter ($1.99)\n* Paper towels ($5.99)\n* Work gloves ($2.99)\n* Safety glasses ($1.79)\n* Luggage scale ($3.25)\n* Pencil/Pen\n* Table saw (or a saw) ($159.99)\n* Drill press (or a drill) ($74.99)\n* Counterweight container (Pillsbury storage container, holds 16.8 fluid ounces) ($1.00)\n* Miscellaneous heavy items (textbooks, unopened queso, duct tape) -> for applying pressure\nWashers ( I found these at my house so I had to measure them out myself )\n* 1 washer- (outer diameter is 1 inch, inner diameter is 7/16 inches) ($0.", "401" ], [ "Plastic Bottle Water Filter\nIntroduction: Plastic Bottle Water Filter\nThis project was created to give students a look into how a water filter works, and why it is important for clean water to be available for everyone. This project is intended to be used in a middle school classroom and can be done by students in grades 6-8. It is recommended to be used by older students as younger students may have issues using cutting tools independently. If you feel that your students may not be ready to use cutting tools like a box cutter or X-acto knife, scissors can be used instead.\nThis project can be done individually or by students in groups of 2 or 3. Students are recommended to hypothesize how the water will be filtered before conducting the experiment and to discuss amongst themselves why water filtration is important after completing the assignment. This project can be done in conjunction with a presentation on the water cycle or on how clean water isn't available in all areas.\nThis project was created in alignment with the 2020 Standards for Technological Literacy, and the corresponding standards, practices, and contexts are listed below.\nLearning Objective:\nStudents will use plastic water bottles and filtration materials to create a rudimentary water filter; students will gain insight into how water is filtered and will ask questions about why access to clean, potable water is important. The end product is a rudimentary water filter that will clean water using 3 different filtration mediums.\nStandard:\nImpacts of Technology- Lack of access to clean water has negatively impacted developed and developing countries. The introduction of new water filtration technology has made water more accessible and safer to use. Students will learn how to create a rudimentary water filter that will clean water without the use of chemicals or heat. Students will learn the importance of having clean accessible water.\nPractice:\nAttention to Ethics- Students will learn how denying humans access to clean and drinkable water is an ethical issue.", "440" ], [ "By creating a rudimentary water filtration system, students will learn that there are easy solutions to safely filter water. Students should research clean water initiatives and should research how outreach groups are bringing filtration to needy communities.\nContext:\nMedical and Health-Related Technologies- By putting together a rudimentary water filtration system, students will see impurities removed from the water. This will demonstrate visually what unclean water looks like, and how health issues can stem from not having potable water.\nSupplies\nFor this project the students will need:\n* 3 disposable water bottles (preferably sturdy plastic)\n* A box cutter or X-acto knife\n* Aquarium gravel\n* Aquarium sand\n* Cotton Balls\n* Coffee filters\n* Water\nStep 1: Prepping Your Bottles\nAfter gathering supplies, students should use their cutting tools to remove the outer wrapper from the bottle.\nBe sure to not puncture the bottle during this step.\nStep 2: Cutting Your Bottles\nPlease make sure that your students are briefed on sharp object safety before they attempt this step. Be prepared to offer assistance with cutting if needed.\nStudents should use their cutting tools to cut their bottles in half. Some bottles may have a depression at the halfway point that will make cutting easier. If your bottles do not have a depression, don't worry about being exact. Guesstimating the halfway point of the bottle is completely fine.\nYou should have 3 bottle tops and 3 bottoms by the end of this step\nStep 3: Filling Your Bottles\nTake your 3 bottle tops and place a coffee filter in each.\nThen, fill each filter with gravel, sand, and cotton balls respectively. You will want to leave enough room to be able to stack your bottle tops one on top of the other.\nBe sure to check that you have left enough space as you pour the filtration medium in, as it is difficult to put back in the bag after it has been poured.\nStep 4: Prep Your Water\nUsing one of the bottle bottoms, mix sand and water together to create contaminated water.\nThere are no specific measurements for this part, but it is recommended to use lots of water and less sand than you think you'll need.\nBe sure to agitate the mixture by swirling the container or mixing with a finger to make sure the sand and water are fully incorporated.\nStep 5: Construct Your Filter\nStack your bottle tops one on top of the other and place them on top of one of the bottle bottoms. The order should be:\n* Bottom: empty bottle bottom\n* 1st layer: cotton balls\n* 2nd layer: sand\n* Top layer: gravel\nKeep in mind that after construction your filter will be top-heavy. It is recommended that your students keep one hand on the filter at all times after this step.\nStep 6: Use Your Filter\nStudents should once again stir/swirl their contaminated water to loosen up any sediment that has settled.", "440" ], [ "Simple Laser Cut Puzzle in 45 Minutes\nIntroduction: Simple Laser Cut Puzzle in 45 Minutes\nThis is a project to help students in TDE 110, an introductory college class for Technology Engineering and Design Education, learn to use the laser cutter, as well as learning how to transfer images onto wood. It is not meant to take a long time, but instead to give a general overview of these processes\nStudents will be able to:\n* Transfer a picture onto a piece of wood using acetone\n* Edit SVG files in Adobe Illustrator for laser cutting\n* Comfortably set up materials settings and other print settings for Universal Laser Systems.\nSTELs:\nStandards for Technological and Engineering Literacy or STELs are a way of categorizing and describing the instruction of STEM subjects. You will learn more about them in later classes if you choose to continue in TDE. For now though, it is enough to know that they exist and have three levels, Core Disciplinary Standards, Practices, and Contexts.\nCore Disciplinary Standards are exactly what they sound like, the core ideas and standards for understanding STEM education. This project relates to the 'Core Concepts of Technology and Engineering' Standard because you will be learning to use several important tools and processes, as well as having to make decisions regarding which materials to use and how to treat your product based on the time you have available (more on that in Step 6).\nPractices are important knowledge, skills, and thought processes that students in STEM need to master in order to be successful. This project relates to the 'Making and Doing' Practice because you will be, well, making and doing. This is a hands on project and that is a core part of Technology and Engineering Education, as well as this class.\nContexts are how the Standards and Practices relate to the general world, as well as how STEM classes in general relate to the world.", "215" ], [ "This project relates to the 'Computation, Automation, Artificial Intelligence and Robotics' Context. Learning to use a Laser Cutter will give you context of how things can be automated, something that is often used in the real world by major production companies.\nSupplies\nRequired Items\nAcetone\n* Acetone nail polish remover is a perfectly acceptable to purchase this.\nBasswood sheet 20cm x 30cm x 3mm\n* this is a standard size you can find online, other sizes will work, you will just have to adjust the size of your picture file and puzzle file\nPicture slightly larger than your intended puzzle printed with a laser printer\n* If you use an inkjet printer this project will not work. Check your printer, most residential printers are not laser.\nSVG puzzle file\n* I have supplied a file for a 7x10 inch 117 piece puzzle, if you need a file for a different puzzle size you can find one online.\n600+ grit sandpaper\ncotton ball or paper towel\nOptional Items\nroll of blue masking tape\nClear nail polish\n* Another finishing product can be used, using them may take longer than 45 minutes\nCost:\nAcetone costs roughly $5 for 9oz if you buy it as nail polish remover, or approximately $9 for 32oz from a hardware store.\nBasswood sheets vary in cost, but you can find packs of 5 online for $8.\nPrinting a picture costs between 10 and 30 cents, depending on where you go for the service.\n600 grit sandpaper can be purchased in a 10 pack for $7 at a hardware store, and one sheet will last you much longer than you think.\nClear nail polish costs between $2.50 and $10 depending on brand and store, while other clear finishing products start at around $5.\nThis project can cost around $25, which is a little costly, however, with the exception of the printed pictures, all of these items are essentially bought in bulk, and you can get 5 puzzles out of that $25. Additionally, a custom wooden puzzle of the same size can cost upwards of $60. Plus you get a fun learning experience!\nStep 1: Prepare Supplies\nPrepare your wood.\n* If it's not the correct size for your puzzle then you will want to cut it to size, leaving approximately an 8th of an inch margin all the way around to allow for mistakes.\n* Sand with the 600 grit sandpaper it to a soft finish. This will help with making the picture adhere.\n* Make sure you blow off the dust!\nGather your other supplies\nIf you choose to cut your picture out of the larger sheet of paper leave at least a half inch margin around the picture for taping it later\nStep 2: Picking a Picture\nAny picture will do, but in the process of trying this out I've found that dark colors work best. Colors like yellow will not transfer well to the wood as they are nearly the same color as the wood.", "110" ], [ "Cardboard and Marbles\nIntroduction: Cardboard and Marbles\nIn the Cardboard and Marbles workshop, participants use readily available household materials to design, build and play games. The workshop encourages creativity, engagement, and collaboration. Each session is designed around an activity or challenge as well as time for participants to work on individual or small group projects. Over the course of the workshop, participants are introduced to some basic cardboard engineering ideas, simple machines, and the design/engineering process.\nActivities are designed to be supported by an educator, and can work in-person or remotely, in out-of-school-time or more traditional settings. Most materials are readily available or can be supplied to participants through a teaching kit.\nSupplies\n* Recycled corrugated cardboard, and assorted other recycled materials as available\n* Cardboard saw/cutter (alternatively, many pumpkin carving knives work well)\n* Tape\n* Sharp, pointed scissors\n* A sheet of printer paper\n* Marbles, ping pong balls, and/or other small balls (the choice will depend on the projects and what is available.) If you are putting together a kit or maker space, consider including: two sizes of marbles, and ping-pong balls.\n* Other household materials as available. If you are putting together a kit or maker space, consider including: colorful paper, tape, paper fasteners, rubber bands, construction paper, large paper clips, glue stick, hot glue, electric cardboard cutter, paper punch.\nBe Safe: You will need to judge the safety of different tools and materials for your group’s age and abilities. The activities assume that participants will be able to safely cut corrugated cardboard. If this poses an issue for your group, you could substitute thin cardboard (like cereal boxes) that can be cut with scissors, or you can help cut the cardboard.\nStep 1: Introducing the Cardboard and Marbles Workshop\nStart by introducing the group goal for the Cardboard and Marbles Workshop: Building a set of playable games out of cardboard and marbles -- a mini-arcade.", "294" ], [ "You can look forward to playing the finished games together, showing them to others at an open house, or -- if you are working remotely -- sharing them virtually at the end of the workshop.\nSome educators have used the “Caine's Arcade” video (see Resources) as a way of introducing the idea of a cardboard arcade. Group goals and structured challenges along the way provide support for participants with a wide range of experience. In engineering, limits or parameters can result in more creative problem solving and can challenge students to pursue unfamiliar directions. The ideal balance of structure will vary for different participants and groups.\nStep 2: Brainstorm & Initial Plans\nBrainstorm: Start by asking participants to describe any experiences they have had playing arcade games or other games with moving parts. Has anyone been to an arcade or game room? After this initial 1-3 minute invitation, transition to brainstorming a list of games that could be built out of cardboard and marbles, or cardboard and ping-pong balls.\nWhile you do not want to lead a structured lecture about specific designs, it may help to have a few images ready to show if the brainstorm needs encouragement. Also, familiarize yourself in advance with the range of possibilities so that you can suggest possible directions to open up the conversation (the intent is certainly not to have everyone build copies of these ideas, the list is just to suggest possibilities). Here are some possible directions for games:\n* Marble runs, for example: https://www.instructables.com/easy-to-make-cardbo...\n* Skee-Ball type games, for example: https://www.instructables.com/easy-to-make-cardbo...\n* Tilt-a-maze type games, for example: https://www.instructables.com/easy-to-make-cardbo...\n* Pinball games, for example: https://www.instructables.com/easy-to-make-cardbo...\n* Foosball type games, for example: https://www.instructables.com/Cardboard-Foosball-...\n* Table hockey type games, for example: https://www.instructables.com/easy-to-make-cardbo...\nAnd together you can invent more!\nPlan: Have participants think about an idea they would like to build and draw an initial sketch. You can use the project sheet (see downloadable: Our Design Process PDF), or just keep the sketches and add them to the Our Design Process sheet later. The sheet is designed so participants can document their evolving ideas, and to provide an entry point for discussing the design process (see Resources).", "593" ], [ "Barometric Mason Jar\nIntroduction: Barometric Mason Jar\nWeather an everyday preoccupation over which we have no control but affects our daily lives in so many ways.\nHow do we know what the weather will be like from day to day, check the weather bulletins, look out of the window or monitor it yourself.\nUsing a STEAM approach you can create basic tools to aid in weather forecasting.\nScience - Any system of knowledge that is concerned with the physical world and its phenomena and that entails unbiased observations and systematic experimentation.\nTechnology - Methods, systems, and devices which are the result of scientific knowledge being used for practical purposes.\nEngineering - Scientific principles to design and build machines, structures, and other items.\nArts - The expression or application of human creative skill and imagination,\nMathematics - The abstract science of number, quantity, and space,\nWe will be observing the effects of the weather by using a device that responds to atmospheric pressure and by gathering and analysing the data gain an insight into the relationship between the two.\nOne simple method to monitoring atmospheric pressure is a Barometer were we can get an indication of the likely weather conditions.\nBarometer, a device for measuring atmospheric pressure and predicts changes in the weather.\nAtmospheric pressure equates to 1.03 kilogram force per square centimetre, though in reality its affected by weather conditions, altitude and temperature.\nThere are may types of Barometers but the simplest and earliest forms are water based.\nThis Instructable will focus on a water based Barometer, although the aneroid variant could also be made.\nOur simple water based Barometer is not an absolute indicator of weather being a gauge but can complement other data such as wind direction and temperature to provide a more informed assessment.\nSupplies\nMason Jar\nClear or translucent plastic tube or Straw\nWater\nFood Colouring or Dye (Optional)\nGrommet and/or Silicone sealer.\nDrill bit (slightly larger then the straw to enable the grommet to be fitted and create a snug fit when the straw is inserted.).\nShort ruler.\nPTFE tape\nStep 1: Methodology\nHow does the Barometer work.\nIt works on the principle of pressure differential.\nThe difference between the air pressure in the upper part of the jar compared to the atmospheric pressure pushing down on the exposed end of the straw. Hence the reason for leaving the end of the straw open.\nAs the atmospheric pressure increases a force is exerted on the end of the straw which pushes the water this then applies pressure inside the jar trying to compress the air in the upper part of the jar.\nAs the atmospheric pressure decreases the force exerted on the end of the straw reduces, the opposing force from inside the upper part of the jar pushes against the water and the level rises.\nThese changes in atmospheric pressure coincide with the weather conditions, higher pressure for more favourable weather and lower pressure for more inclement weather.\nTherefore by monitoring the level of the water in the straw we can get a determination of the atmospheric pressure and from this the weather.\nStep 2: Preparation\nTake the Mason Jar and remove the lid, setting the jar aside for the time being.\nSome Mason jars come pre prepared with hole in the centre of the lid and a straw and this will make the preparation a little easier.\nIf this is not the case then a hole will have to be drilled in the centre of the lid.\nThe hole in the lid should be slightly larger than the straw to accommodate a grommet and once the straw is fitted in the grommet it should form a air tight seal when the lid is screwed onto the jar.\nThe straw should be a tight fit and not too easy to slide into the grommet, if it slides in too easily air will escape and the Barometer will not work.\nIf the straw is too loose in the grommet get a smaller bore grommet, or a wider straw.\nAdditionally, silicone seal can be applied around the grommet and straw to seal any gaps but only after the height of the straw has been adjusted so that its bottom is one 1/4 of the height of the jar from the bottom.\nA thin line of Silicone seal may also be required around the rim of the jar to aid sealing or PTFE tape can be wrapped around the the rim too.\nIf using Silicone seal ensure it is fully cured before further assembly.\nStep 3: Testing\nOnce the assembly is complete the jar should be tested to ensure there are no leaks around the seals for either water or air.\nSimple tests.\n1:Dry test.\nWith the lid and straw assembly firmly in place, suck on the straw after some initial removal of air there should be resistance to any further air removal unless there are any gaps.\nAny gaps should be sealed with further PTFE tape, silicone sealer or a gasket.", "33" ], [ "Coding the Heritage: Rose Window of Valvisciolo Abbey\nIntroduction: Coding the Heritage: Rose Window of Valvisciolo Abbey\nHave you ever stood in a vast cathedral or church, and looked up at a large circular stained glass window dominating one of the walls? Did you know it was called a rose window?\nRose window is often used as a generic term applied to a circular window but is especially used for those found in Gothic cathedrals and churches. This type of window is called a rose window or a wheel window to refer to the fact that it's made of a series of smaller windows radiating out from the center like wheel spokes or flower petals. The rose window is one of the most representative elements of Gothic art and architecture. Their symbolism lies in geometry and the sense that many parts make a whole. When we study them, we begin to realize that these windows are made of geometric shapes. Whatever the style of window, all of the elements come together in a single cohesive design, the real and symbolic whole\nIn this project, we will use Codeblocks and develop algorithms for the typical geometries of architecture and make a rose window, a characteristic element of medieval architecture. (.STL file attached)\nRecommended grades: 6-8\nEstimated time: 60 minutes\nSkills explored: Identifying the basic solids that make up the object and creating a computer program using variables for control points and count-controlled loops.\nSupplies\n* Computer\n* Internet\n* 3D software (Tinkercad)\n* Computer mice, 3D printer, and filaments for printing(optional)\nStep 1: Know Your Tool: Tinkercad Codeblocks\nTinkercad is a free, kid-friendly online computer-aided design (CAD) program where users can design, modify, and print 3D objects. Tinkercad offers“Codeblocks”: a section of the site dedicated to the production of complex solids through programming with code blocks.\nUsing Codesblocks users can create a sequence of instructions that will lead to the creation of output. The instructions are contained in colored blocks that can be dragged onto the main screen and inserted in a logical order just as if they were bricks.", "974" ], [ "It is characterized by a limited number of solids (primitives) that can be used to compose a more complex object. Codeblocks combine coding with 3D modeling and are great to educate kids in computational thinking and introduce the concept of algorithms.\nCodeblocks expands the functionality of Tinkercad by introducing procedural modeling. Procedural modeling is a type of 3D drawing that automatically or semi-automatically generates a geometry, based on a program script (in this case blocks of code) defined by the user.\nThe Codeblocks Interface:\n* Sign in to your\"Tinkercad\"account.\n* Click on the“Codeblocks” item in the left menu of the Dashboard.\n* Click on the \"Create New Codeblock\" button to access the Codeblocks Workspace.\nThe main sections of the workspace are as follows:\n1. Name of the project: In the upper left part of your screen you can see a random software-generated name. To change the name of the project, simply click with the left mouse button on the temporary name, type in the new desired name, and press the Enter key on the keyboard.\n2. Menu bar: this horizontal menu at the top contains buttons we need to run our code.\n3. Block categories: located on the left, this vertical column is divided into categories to facilitate searches of the blocks.\n4. Block library: is located in the left column and contains all the instruction blocks that can be inserted into the working area.\n5. Working area: It is the space where the user will create the instructions that will make up the solids by “pulling” or “dragging” blocks from the block library\n6. 3D preview: enable the user to see the preview of the solid constructed through the instructions you entered.\nStep 2: Identification and Measurement\nIdentifying the Geometric Elements:\nWe will start with a simplified version of a rose window and try to identify the basic solids that make up the rose window on the facade of Valvisciolo Abbey.\nWe can easily identify seven solids :\n* Central core: the central core is made up of 4 cylinders, with the base pointing towards you.\n* Column: are made up of 12 cylinders all of which are arranged longitudinally.\n* Arch: 12 arches connect the capitals of the columns remain.\n* The Inner core, Outer core, Inner shell, and Outer shell can also be traced back to a cylinder, with the base pointing towards you.\nWe also notice that The arches and columns are arranged according to radial symmetry.", "974" ], [ "Learning the Four Classical Elements: the Constructivism Way\nIntroduction: Learning the Four Classical Elements: the Constructivism Way\nConstructivism is the theory that supports learners constructing knowledge rather than just passively accepting information. This Instructable sets up a learning situation where students create their own meaning of the classical elements using Lego parts.\nEach student (or group of four)is given four 16x16 plates (blue, white, dark tan, and dark bluish gray). Students are asked to create an example of fire, air, water, and earth on each the 16x16 plates. A variety of plates, bricks (regular and modified with studs on sides), tiles, slopes, mountains, fire, technic bricks, and leaves are provided.\nSupplies\nFour 16x16 plates in white, blue, dark blushing gray, and dark tan for each student or group of students.\nVariety of plates, bricks (regular and modified with studs on sides), tiles, slopes, mountains, fire, technic bricks, and leaves.\nStep 1: Earth\nThe photo shows my interpretation of earth. I have included trees, plants, and flowers on the green plate. The dark tan and tan borders on two sides are 2x16 plates which connect the 16x16 plates together.\nStep 2: Air\nThe first photo shows my interpretation of air. The second photo shows the cloud base from above with patches of blue shining through.", "389" ], [ "The 2x16 plates along two sides will be used to use the 16x16 plates. The remaining photos show the creation of an air balloon which floats above the clouds in the \"air\".\nStep 3: Water\nThe first photo shows my interpretation of water. It contains an ocean (made of tiles) with a dolphin and a wave crashing into the beach. Photos two through five show the construction of the wave and the location on the 16x16 where the wave attaches (plates).\nStep 4: Fire\nThe first photo shows my interpretation of fire. The image shows a volcano erupting with lava pouring down the mountain. Cooled black lava is disbursed around the area. The second photo shows the four 16x16 plates connected displacing the four classical elements.\nAllow the students to create their interpretations. Then, have the students share their projects with one another.", "636" ] ]

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[ [ "You have it right, the $V$ function gives you the value of a state, and $Q$ gives you the value of an action in a state (following a given policy $\\pi$). I found the clearest explanation of Q-learning and how it works in <PERSON> book \"Machine Learning\" (1997), ch. 13, which is downloadable. $V$ is defined as the sum of an infinite series but its not important here. What matters is the $Q$ function is defined as\n$$ Q(s,a ) = r(s,a ) + \\gamma V^{}(\\delta(s,a)) $$ where V is the best value of a state if you could follow an optimum policy which you don't know. However it has a nice characterization in terms of $Q$ $$ V^{}(s)= \\max_{a'} Q(s,a') $$ Computing $Q$ is done by replacing the $V^$ in the first equation to give $$ Q(s, a) = r(s, a) + \\gamma \\max_{a'} Q(\\delta(s, a), a') $$\nThis may seem an odd recursion at first because its expressing the Q value of an action in the current state in terms of the best Q value of a successor state, but it makes sense when you look at how the backup process uses it: The exploration process stops when it reaches a goal state and collects the reward, which becomes that final transition's Q value. Now in a subsequent training episode, when the exploration process reaches that predecessor state, the backup process uses the above equality to update the current Q value of the predecessor state.", "915" ], [ "Next time its predecessor is visited that state's Q value gets updated, and so on back down the line (<PERSON>'s book describes a more efficient way of doing this by storing all the computations and replaying them later). Provided every state is visited infinitely often this process eventually computes the optimal Q\nSometimes you will see a learning rate $\\alpha$ applied to control how much Q actually gets updated: $$ Q(s, a) = (1-\\alpha)Q(s, a) + \\alpha(r(s, a) + \\gamma \\max_{a'} Q(s',a')) $$ $$ = Q(s, a) + \\alpha(r(s, a) + \\gamma \\max_{a'} Q(s',a') - Q(s,a)) $$ Notice now that the update to the Q value does depend on the current Q value. <PERSON>'s book also explains why that is and why you need $\\alpha$: its for stochastic MDPs. Without $\\alpha$, every time a state,action pair was attempted there would be a different reward so the Q^ function would bounce all over the place and not converge. $\\alpha$ is there so that as the new knowledge is only accepted in part. Initially $\\alpha$ is set high so that the current (mostly random values) of Q are less influential. $\\alpha$ is decreased as training progresses, so that new updates have less and less influence, and now Q learning converges", "915" ], [ "Structured policies in dynamic programming: solving a toy example\nI am trying to solve a dynamic programming toy example. Here is the prompt: imagine you arrive in a new city for $N$ days and every night need to pick a restaurant to get dinner at. The qualities of the restaurants are iid according to distribution $F$ (assume [0,1]). The goal is to maximize the sum of the qualities of the restaurants that you get dinner at over the $N$ days.", "835" ], [ "Every day you need to choose whether you go to a new restaurant and obtain a utility drawn at random from distribution $F$, or you go to the best restaurant you have attended so far, and obtain a known utility.\nHere is my formulation: - Let $m_t$, the state at time $t$, denote the quality of the best restaurant visited so far. - Let $a_t \\in {Q, E}$ be the action at time $t$; $E$ for EXPLORE, $Q$ for quit. - Given the action set, the rewards are ($W_t$ denotes the random variable of the quality of the restaurant drawn at random at time $t$): $$r_t(m_t | E) = W_t \\sim F $$ $$r_t(m_t | Q) = m_t $$ - The transition probabilities at time $t$ are: $$ p_t\\big ( m_t | m_t, Q \\big ) =1 $$ $$ p_t\\big ( m_t | m_t, E \\big ) =F(m_t), \\text{ with } W_{t} \\in [0, m_t]$$ $$ p_t\\big ( W_t | m_t, E \\big ) =1-F(m_t), \\text{ with } W_{t} \\in ( m_t, 1] $$\nFirst I write down the <PERSON> optimality equations: For $t=N$, I get: $$ u^N (m_N) = \\max{a_t \\in {Q, E}} \\big{ m_N, \\ \\ E(W_N) \\big} $$ For $t<N$, I get: $$ u^t (m_t) = \\max{a_t \\in {Q, E}} \\bigg{ m_t+ u^_{t+1} (m_t) , \\ \\ \\ E(W_t)+ u^{t+1} (m_t) F(m_t) + \\int{m_t}^1 u^*_{t+1} (x) dF(x) \\bigg}\n$$\nWhat I am trying to show is that, if it is optimal to quit exploration in period $\\tau$, then it is optimal to not explore in every period $t=\\tau+1, ..., N$. In agreement with the equations above, I assume: $$m_\\tau- E(W_\\tau) \\geq \\int_{m_\\tau}^1 (u^_{\\tau+1} (x)-u^{\\tau+1} (m\\tau)) dF(x) $$ and I want to show: $$m_\\tau - E(W_{\\tau+1}) = m_\\tau - E(W_{\\tau})\\geq \\int_{m_\\tau}^1 (u^_{\\tau+2} (x)-u^_{\\tau+2} (m_t)) dF(x) $$\nI have been reading the structured policies chapters on <PERSON> and <PERSON> (Vol II) and did not find anything that could get me rolling. Any help or pointer to literature is more than welcome!\nAfter I show this I can argue that there will exist a sequence of thresholds $c_t$ so that is is optimum to stop exploration at time $t$ it $m_t \\geq c_t$.\nEDIT: Distribution $F$ is know to the tourist.", "490" ], [ "experience replay memory: saving the next state required when state does not depend on action?\nso, I am using an agent with a state-action-policy and I am trying to understand the concept of experience replay memory (ERM). As far as I learned until now, the ERM is basically a buffer that stores sets experiences:\ne_t = {s_t, a_t, r_t+1, s_t+1}\nWhere s is the state, a the action and r the reward, as usual. Basically, in order to use a network that learns to predict the correct action from such experiences, the network's input should be exactly of the form of the experiences, i.e.", "458" ], [ "state of current and next step, as well as predicted action and received reward. The network thus has four inputs.\nFirst question, is it correct that the next state s_t+1 is fed into the network as input? Or is it a label?\nSecond question, how is this initialized? The network needs to be trained on experiences, right away, so I assume, the first time we generate action predictions for various state examples, given the initial parameters of our model, until the ERM is completely filled for the first time, and then start optimizing this with SGD (or similar).\nThird question, what if the action that we take just influences the reward we get, but does not have any actual influence on the next state? For instance, think of an agent that decides whether to buy/sell/idle (actions) a stock based on its past price (state), receiving a reward that depends on the taken action as well as the evolution of the price in the next timestep. If we assume that our action does not have any significant influence on where the stock price will go, the next state (price at next step) is independent of our action, yet, we receive a reward that is dependent on our action as well as the next price. How would an experience replay look in that case? In that case, would we also need to save the next state? Or rather just\ne_t = {s_t,a_t,r_t+1}\nbecause firstly s_t+1 is already \"encoded\" in the reward r_t+1 and secondly our action does not change s_t+1?\nThanks! Best, <PERSON>", "458" ], [ "Training value neural network AlphaGo style\nI have been trying to replicate the results obtained by AlphaGo following their supervise learning protocol. The papers specify that they use a network that has two heads: a value head that predicts the winner of the game and a policy head that predicts the next move based on the current state of the board.\nFor the policy head, no problem, the CNN learns to predict the next move.", "458" ], [ "However, the value head does not learn anything and always falls back to always predicting 0 instead of -1/1 for white/black victory. It feels like the model is not complex enough to understand how to predict the outcome of the game so it learns to predict 0 instead to minimize the loss.\nThings that I tried and didn't work:\n* Divide the network into two: one value net and one policy net. But even in this case the value net does not learn.\n* Label the winners as 0/1 instead of -1/1 and therefore use a sigmoid instead of a tanh activation function, but that didn't work either.\n* Different number of residual units (3/5/7/11).\n* Only using 2 channels as input, one for black stones and one for white stones.\n* Copy the weights of the first layer of the policy net and freeze them to force the value net to use the already learned features.\nHere is the model:\ndef residual_block(s):\nshortcut = s\ns = Conv2D(256, (3, 3), strides=(1, 1), padding='same', kernel_regularizer=l2(0.0001))(s)\ns = BatchNormalization()(s)\ns = ReLU()(s)\ns = Conv2D(256, (3, 3), strides=(1, 1), padding='same', kernel_regularizer=l2(0.0001))(s)\ns = BatchNormalization()(s)\ns = add([shortcut, s])\ns = ReLU()(s)\nreturn s\ndef model():\ninputs = Input(shape=(2, 19, 19, ))\n# Convolutional block\nx = Conv2D(256, (3, 3), strides=(1, 1), padding='same')(inputs)\nx = BatchNormalization()(x)\nx = ReLU()(x)\n# Residual block\nfor i in range(11):\nx = residual_block(x)\n# Value head\nx = Conv2D(1, (1, 1), strides=(1, 1), padding='same', kernel_regularizer=l2(0.0001))(x)\nx = BatchNormalization()(x)\nx = ReLU()(x)\nx = Flatten()(x)\nx = Dense(256, kernel_regularizer=l2(0.0001))(x)\nx = ReLU()(x)\nx = Dense(1, activation = 'tanh')(x)\nreturn Model(inputs=inputs, outputs=x)\nAnd here is the training :\nbatch_size = 32\ngen_train = generator(batch_size, sgf_paths)\ngen_test = generator(batch_size, sgf_paths)\noptimizer = SGD(lr=0.01, momentum=0.9, decay=0., nesterov=True, clipnorm=1.)\ncheckp = ModelCheckpoint(filepath=\"weights_ValueNet.h5\", verbose=1, save_best_only=True)\nmodel = model()\nmodel.compile(loss=\"mean_squared_error\", optimizer=optimizer)\nhist = model.fit_generator(\ngen_train,\nsteps_per_epoch = 2048,\nepochs = 100,\nshuffle = True,\nverbose = 1,\nvalidation_data = gen_test,\nvalidation_steps = 300,\ncallbacks = [checkp])", "695" ], [ "The first thing to do is to treat the bias ($\\rho$) as a weight on an extra input whose activity is always 1 so that you won't need a separate learning rule for the bias and then the decision for your binary threshold outputs a 1 iff $\\sum\\limits_{i=1}^{3} w_i x_i \\geq 0$\nTo learn the weights of perceptrons, you are right to start with random weights. The remainder of the procedure is to do the following: if for an input your weights correctly classify an output, you leave the weights alone. If, however, you incorrectly output a zero, add the input vector to the weight vector. And on the other hand, if you incorrectly output a 1, subtract the input vector from the weight vector. I would be able to show you an example run with your inputs and random weights above but you're missing the outputs which map to the inputs in order to correct the weights.\nAlso, note that the above procedure gives you a correct set of weights iff one exists.", "964" ], [ "Otherwise, the learning procedure will fail and you will eventually find it impossible to classify one of the inputs.\nEDIT: Here's another example to try and explain things. Let's use initial weights where $w = (w_1, w_2, w_3) = (1, 0, -2)$, letting $\\rho = 0$, with:\nTarget: $t_1 = 1$, $t_2 = 1$, $t_3 = 0$, $t_4 = 1$, $t_5 = 0$\nInput: $x_1 = (1,0,1)$, $x_2 = (0,1,1)$, $x_3 = (1, 0, 0)$, $x_4 = (1,0,1)$, $x_5 = (1, 0, 0)$\n$y_1 = wx_1 = 1\\times 1 + 0\\times 0 + -2\\times1 =-1 \\leq \\rho$ --> outputs a 0, which does not equal $t_1$. In this case, we add the input to the weight vector so $w\\prime = w + x_1 = (1+1,0+0,-2+1) = (2,0,-1)$, $w = w\\prime$\n$y_2 = wx_2 = 0\\times 2 + 1 \\times 0 + 1\\times -1 = -1 \\leq \\rho $ --> outputs a 0, which does not equal $t_2$. In this case, we add the input to the weight vector so $w\\prime = w + x_2 = (2,1,0)$, $w = w\\prime$\n$y_3 = wx_3 = 1\\times 2 + 0\\times 1 + 0\\times 0 = 2 > \\rho$ --> outputs a 1, which does not equal $t_3$. In this case, we subtract the input from the weight vector so $w\\prime = w - x_3 = (2-1,1-0,0-0) = (1,1,0)$, $w = w\\prime$\n$y_4 = wx_4 = 1\\times 1 + 0\\times 1 + 1\\times 0 = 1 > \\rho$ --> outputs a 1, which equals $t_4$ so the weight vector remains unchanged.\n$y_5 = wx_5 = 1\\times 1 + 0\\times 1 + 0\\times 0 = 1 > \\rho$ --> outputs a 1, which does not equal $t_5$. In this case, we subtract the input from the weight vector so $w\\prime = w - x_5 = (1-1,1-0,0-0) = (0,1,0)$, $w = w\\prime$\nFinal weight vector $w= (0,1,0)$", "945" ], [ "A safer method is to use the integer part of the fraction (after truncating) $n_c \\approx n^{3 \\over 4}$ examples for training, and $n_v \\equiv n - n_c$ for validation (a.k.a. testing). If you are doing cross-validation, you could perform that whole train-test split at least $n$ times (preferably $2n$ if you can afford it), recording average validation loss at the end of each cross-validation \"fold\" (replicate), which is what tensorflow records anyway; see this answer for how to capture it).", "964" ], [ "When using Monte Carlo cross-validation (MCCV) then for each of the $n$ (or $2n$ if resource constraints permit) replicates, one could randomly select (without replacement to make things simpler) $n_c$ examples to use for training and use the remaining $n_v$ examples for validation, without even stratifying the subsets (based on class, for example, if you are doing classification).\nThis is based on a 1993 paper (look at my answer here for more information) by <PERSON> in which he proves that $n_c \\approx n^{3 \\over 4}$ is optimal for linear model selection. At that time, non-linear models such as machine learning (see this answer for yet another discussion on that) were not as popular, but as far as I know (would love to be proven wrong) nobody has taken the time to prove anything similar for what is in popular use today, so this is the best answer I can give you right now.\nUPDATE: Knowing that GPUs work most efficiently when they are fed a batch sized to be a power of two, I have calculated different ways to split data up into training and validation which would follow <PERSON> strategy of making the training set size $n_c \\approx n^{\\frac{3}{4}}$ and where both $n_c$ and $n_v \\equiv n - n_c$ are close to powers of two. An interesting note is that for $n = 640$, $n_c \\approx 127$ and therefore $n_v \\approx 513$; because $127 \\approx 2^7$ and $513 \\approx 2^9$ I plan to go ahead and use those as my training and validation test sizes whenever I am generating simulated data.", "964" ], [ "Stopping condition for goal-directed bidirectional search for shortest path\nSo I have a graph and need to find shortest path between two points in it. I need1 to do it it using bidirectional search. The bidirectional search should be goal-directed, i.e. A*.\nSo let $l(u,v)$ be length of the (oriented) edge $u,v$, $\\pi_f(v)$ the potential of vertex $v$ in forward search and $\\pi_r(v)$ potential of vertex $v$ in reverse search and $d(u,v)$ length of the shortest path from $u$ to $v$. Let $s$ be start vertex, $t$ goal vertex. The algorithm selects vertices by $d(s,v)+\\pi_f(v)$ forward and $d(v,t)+\\pi_r(v)$ reverse.\nLet's call $\\mu$ the length of the shortest path found so far, $n_f$ the vertex on top of forward queue and $n_r$ the vertex on top of reverse queue. I found two ways\n1. The obvious option is to stop forward when $d(s,n_f)+\\pi_f(n_f)\\geq\\mu$ and reverse when $d(n_r,t)+\\pi_r(n_r)\\geq\\mu$.", "835" ], [ "It is also not needed to process edges that were already processed in the other direction. Here the $\\pi_f$ and $\\pi_r$ are independent can be very specific, but the algorithm may need to continue quite long after the shortest path was actually found if the potential function is significantly underestimating.\n2. Create a pair of consistent potential functions as defined in this lecture. The requirements are given as $$\\pi_f(u) + \\pi_r(u) == \\pi_f(v) + \\pi_r(v)$$ for each edge $u,w$ (which really means the sum has to be constant over the whole graph). Without loss of generality we can make $\\pi_r(v) = -\\pi_f(v)$ and use the normal stopping condition from non-goal-directed search expressed as $$d(s,m_f)+\\pi_f(m_f) + d(m_r,t)+\\pi_r(m_r) \\geq \\mu+\\pi_r(t)$$ (assuming we shift $\\pi$ so that $\\pi_f(s) = 0$).\nThis allows easier stop, but the potential function has to only indicate whether $v$ is closer to start or goal and for vertex (equally) far from both will be the same as for vertex in the middle of the shortest path. Therefore it will be less specific.\nNow what I am looking for is:\n1. anything that would give me idea which would be more efficient (without having to implement both and test them) and\n2. whether the second can even be used if the heuristics is not monotonous, i.e. when $d(u,v) - \\pi_f(u) + \\pi_f(v) \\ge 0$ does not hold (the linked lecture assumes that, but not doing so could save me a lot of data and I/O is a bottleneck, so I would prefer not to even though it means occasionally having to reprocess vertex).\n1Some important optimization techniques can only be applied to bidirectional search.", "433" ], [ "That would be the case if the steps taken by gradient descent are \"infinitesimal\" in the mathematical sense. But in fact, it takes steps with some finite length defined by the learning rate. But the problem is, the gradient is calculated at each point, and does not really calculate how the slope changes at some finite length later. If you choose a large learning rate, you may \"offshoot\" from the optimal direction as shown in the figure. If you choose a small enough learning rate those oscillations will be minimal and you may move \"almost\" perpendicular to the contour lines and look like what you describe in the question, but it will take a very long time to complete training.\nThe second part of the question refers to the section titled \"Conjugate Gradients\" and it refers to a specific optimization method. The reason for the perpendicular lines in the second part is because of the vanishing gradient at the turning points. Quoting the text:\nThe method of steepest descent involves jumping to the point of lowest cost along the line defined by the gradient at the initial point on each step\nSuch a point is where the \"directional derivative\" with respect to theta, theta being the parameter in a given direction vanishes.", "810" ], [ "When the derivative vanishes with respect to the parameter of the direction, The only possible way to go will be in a perpendicular direction. That is why they are called \"conjugate\" to each other, hence the name of the optimization method. This is detailed in the text above the figure.\nTo summarize the situation for that figure; An initial direction is chosen at the starting point by calculating the gradient there, and you keep moving in that direction until the gradient vanishes. That point is the minimum in that direction, so if you go any further on that straight line, the cost function will increase. The only direction you can go in which the cost function does not increase can be perpendicular to the initial direction.\nTo visualize this, look at image 4.5 in your first upload - page 88. Starting from that top of the saddle and following the gradient, you go down to the middle of the saddle. At that point going any further in the same direction will only take you up, while you want to go down. The only way to achieve this is to take a 90 degree turn at the middle of the saddle.", "234" ] ]

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[ [ "While I do not see any issues with paradoxes with this \"type\" of time-travelling, there are some odd things that I'd question.\nFirst of all, your example of losing your wallet. While it's great to \"re-live\" your past and remembering that you put it in your couch, how would going back help if you were not conscious that you lost your wallet, by dropping it for example? Your original body would not realize that you dropped it, so even if you go back a second time, you'd still not find it.\nThat goes the same for a pickpocketer. How would you know if someone is doing that to you when you go back? Does your consciousness have an out-of-the-body experience and see what you couldn't see before? Probably not, based on your explanation of doing all the actions and experiencing everything all over again. So, if you get pickpocketed without realizing it, you wouldn't find out even if you go back.\nThen, there's things like sleep.", "283" ], [ "Will your consciousness perceive your original body sleeping? Or will it fall asleep the same as you did before? Would you remember or experience past dreams? Would you still retain information about dreams when you wake up? Will your consciousness stay \"awake\" during sleep instead? If I relive the moment my house got robbed while I was asleep, would I be able to hear the robbers even though I was asleep before? There are a lot of questions to be answered here..\nIf your consciousness relives everything, does that include things that do affect consciousness like drinking alcohol? What if you relive the moment wherein you were drunk? Will the consciousness that went back in the past also become drunk? Wouldn't that mean that you won't be able to retain information during this state because the consciousness that went back is also drunk?\nAnd finally, I'd worry about mental health. What if someone relives a very emotional moment in their life? The feeling of success, joy of being accepted by your partner, winning, pleasure, getting \"high\", etc. What if someone keeps reliving those moments everyday? If you go back to the present, you'd lose those feelings, and might want to do that all over again. That could stagnate someone or even depress them, as they try to compare their past from the present.\nWhile these questions do not refer to having a paradox, it's curious how would this system work for an everyday person.", "620" ], [ "Just want to add another perspective by using computers and our understanding of space-time as an analogy.\nFirst, let me state that computers do not recognize time by itself. It requires an external clock that is subsequently mapped to human-understandable time (1 time step -> 0.1 ns, for example). But barring that external clock to quantize (discretize) the executions of computers instructions (note that in computers we artificially synchronize executions based on the clock, otherwise, it will \"just happen\"), the amount of \"time\" (from we as external observer that already understand time) required to accomplish tasks (or a sequence of instructions) are not quantifiable.\nSo for the computers without external clock, time would be something inherent to their fabric of existence.\nAnother perspective before getting to the final point is how we understand the concept of fabric of space-time. (image below from the book \"We Have No Idea\")\nWe can't really measure the expansion of our very fabric of space-time directly, since any measure we use would also be expanding, unless we can find something that doesn't expand with the fabric of space-time.\nNow, back to the computer analogy, I guess it won't be able to see the concept of time, unless there are things in the universe that stays constant with respect to time (something that does not \"expand\" with the chaos of time in your universe).\nHowever, we now do learn about the speed of light and the fabric of space-time (but much much later, definitely not the first thing that we would come up with).", "781" ], [ "So I believe there would be some cases that caused your creatures to try to understand the concept of time, with much difficulty, just as now we try to understand the concept of space-time.\nA final remark would be to note that this might have some similarity if we assume speed of light is much lower than the current speed, that we can move very close to the speed of light. That can cause things to happen differently for different people (think about the different frame of reference in our current universe that might cause ordering of events to be different for different observers). So it might be hard for the creatures in your universe to understand that there are absolute ordering (passage of time) of events. So you might want to start from there.", "562" ], [ "Your question basically has two parts.\nHow would something fall up?\nThere are some theories that particles could exist which are affected inversely by gravity, such that rather than being pulled toward the source of gravity, they are repelled by it. We would not normally be able to find such particles, since 1- they would never be near any normal matter, and 2- the particles could never form a large object together on their own through gravity.\nHow would a disease cause this?\nSince you have specified a disease, I assume that you intend for microbes or parasites to be the cause of the effect. So how about this: a microbe that, when it consumes matter, converts it into this type of theoretical anti-gravity matter. The matter would remain inside the human body, despite being pulled in the opposite direction by gravity.", "279" ], [ "And if the chemical properties of the matter were unchanged by the anti-gravity conversion process, then the body's biological processes would treat it like any other matter. The matter would be combined in with normal matter in your blood and cells, where gravity's effect is overcome by strong atomic forces.\nGiven that the human body is already under normal gravitic pull and does not fall apart or suffer some sort of circulatory failure, it is fair to assume that having some of the matter in your body pulled in the opposite direction with identical force would not cause your body to fall apart or die immediately.\nThe greatest danger would be a \"head rush\" - humans who hang upside down for too long can have blood accumulate in their heads, causing loss of consciousness. But in our case, we only need 50.01% of the body's matter to be converted to anti-gravity matter in order for the person to experience weightlessness similar to zero-G that begins to cause them to rise into the air.\nThe biggest obstacle here is: how would microbes do this? Changing the physical properties of matter is no small feat, one would expect a facility like the LHC to be required to carry out this process. But much of Science Fiction is playing with \"what if the rules were a little different?\" scenarios, so if we assume that a microbe can do this, then it could produce the effect you're interested in.", "279" ], [ "Can eternal inflation and gravity explain dark energy?\nFirst of all, I have absolutely no background in astronomy and physics. I just watch a lot of \"i-hope-scientific\" youtube channels talking about physics and astrophysics and I can kind of follow the maths and concepts.\nSo, I was thinking, with absolutely no physics to support this:\nREAL QUESTION STARTS HERE:\nSay, the big bang happened everywhere, followed by inflation that never stopped. This is wat eternal inflation described (if i am correct)\nThen, as eternal inflation goes on and more and more universe outside of the observable universe is created. Then there would be an unlimited amount of mass outside our observable universe.\nCan this mass create an gravitational effect on the galaxies in our universe?\nWe are at the center of our observable universe, so the gravitational effect of all the mass outside our observable universe would never affects us. But from the perspective of another galaxy, it would be affected by a bit of universe that is outside our observable universe.\nThen you might explain the effect that galaxies that are farther away from us move faster away from us. And that galaxies closer to use move slower away.", "150" ], [ "Then you can explain this by saying that the galaxies farther away are closer to the \"unlimited\" mass outside our observable universe. And thus are more affected by this. And that galaxies close by are less affected.\nThe theory with dark energy claims that dark energy causes an outward push from the inside of our universe. Wouldn't this be indistinguishable from a gravitational pull from the outside?\nAlso, could this explain the red-shift we see in light from the far end of the observable universe? If I remember correct, gravity can red-shift light if the light moves away from the source of the gravitational pull (as seen near black holes). Light form the far end of the universe has moved trough the gravitational pull away from the \"infinite mass\" of the outside universe.\nThis was my idea, and I would like to see where I am thinking wrong.\nOne thing where I obviously might be thinking wrong is that this effect would be homogeneous throughout the universe and it should cancel out. But is this also true when you throw some relativity into the mix?", "150" ], [ "We need to think about just where the time dilation effect occurs. By then thinking about the observations from each point of view, that is the free falling object and the external observer, we can come to terms with just what is happening as opposed to what appears to be happening.\nThe experience of time\nWe must remember that an object moving at a certain speed will travel through time (or the 4th dimension) at a slower rate. This does not mean that it moves slower, otherwise it would obviously not be travelling \"at a certain speed\".\nWhere time slows is in the ticking of the physical processes of the object itself.", "562" ], [ "In other words, my clock would tick twice as slow according to you as I flew past you at 87% the speed of light. I would be waving my arms normally, but according to you, I would appear to be waving my arms twice as slow and would also appear to be squeezed in size (not really relevant to this).\nThe falling object's point of view\nIf you were the object falling into the black hole, you would accelerate as you approached the event horizon, but you would take longer and longer to react to the approach, to the point where you would fall into the black hole in no time at all. From your perspective, your approach to the event horizon would become exponentially faster.\nIn other words, you would fall incredibly fast into the black hole, but you would have barely registered it in your mind because there just wasn't enough time for you due to relativity.\nThe stationary observer's point of view\nNow, the stationary observer outside the black hole's influence would observe something very different. The light (or rather, information) about your descent would become more and more redshifted, but also take longer and longer to actually reach their eyes.\nThis means that according to the observer, the falling object would slow down to a halt at the event horizon and have disappeared.\nSo what really \"happened\"?\n* The falling object fell in very quickly, but hardly realised it happening\n* The stationary observer would think that the object disappeared and never reached the event horizon.\n* <PERSON> taps on some gravity books and saves the human race.", "334" ], [ "You mean every human was just born this way? Every person just has this field capable of withstanding 20 full force hits from a two-handed long sword?\nThe simple answer is that a lot of medieval weaponry wouldn't have been invented, and what weaponry was created would mostly be for the purpose of hunting animals not humans.\nHumans would most likely have learned to use their energy shields against each other in fights rather than build weapons for that purpose, given that the field as described would have been the hardest, and most durable, thing known to humans at that time.\nFor example: you state that the \"the armor could only become weaker than another point by a user deliberately shifting energy around themselves\", which means that other areas would presumably be made stronger by doing this. The obvious question is: to what extent? Could I condense all of the power of my energy field down to a cylinder 1cm or so in diameter that projected 30-40cm out from my right hand? If so then I could presumably punch that through someone else's energy shield and their body.\nCome to think of it, you describe this as a field, which means that it is not constrained by 3 dimensional physics. I could therefore theoretically project the field outward as a 2 dimensional plane that had width and length, but no thickness.", "477" ], [ "That plane would be able to penetrate other fields because it would have no actual surface area on the leading edge. It also means that it would pass through the person inside the field without damaging them - again 2 dimensions, so no penetration. So what would be the use of this? Well the field wouldn't harm the person as it passed through them, but it would create a barrier that would not allow things like oxygen or blood to pass through it.\nBeyond that most of the weaponry created would probably be designed for distance attacks using projectiles with a high mass since the field allows inertia to be transferred to the user.\nI also expect there would have been a lot more use of fire as a weapon since the field as you describe it seems to resist penetration but otherwise still allow energy to pass through it.", "477" ], [ "Is this time travel scheme internally consistent?\nI know there are similar questions, but not similar enough, and in fact, I don't remember seeing this kind of time travel in fiction.\nBefore I start, it doesn't matter how the time machine works in this world (could even be many different types), and time travel is allowed to violate matter/energy conservation laws (i.e. time traveler or time machine appears out of thin air).\nNow the rules are as follows:\n* Only time travel to the past is allowed.\n* The timeline always changes due to the arrival of the time traveler.\n* There's only one real timeline. The \"old\" timelines are destroyed forever.\n* There's a first ever time traveler by the time of arrival.\nThat last part is important. Clearly, time travel events are countable. So if you go back in the real timeline, you eventually find the earliest arrival. It doesn't really matter when this time traveler departed in their original, destroyed timeline.\nI believe this system is internally logically consistent and doesn't allow for any paradoxes. If you travel back and kill your grandfather, you will just have to live your life knowing your double will never be born.\nHere's an illustration of multiple time travelers (or time travel events) in this scheme:\nAs you can see, time travelers are ordered by their arrival time and nothing else.", "302" ], [ "They can bring records, devices and anything else from their own timeline and all of that will exist, even though the timeline itself is lost.\nThe first ever time traveler doesn't have to be the \"original\" one either. For example, it could have happened like this:\nSomebody invented the time machine, tested it out, which created a new timeline, then somebody else got a hold of the same technology and traveled back far enough to become the first arrival.\nSo what I'm asking is this: * is this system internally consistent?\nEdited due to comments\n* how to explain why somebody later who finds out the arrival time of the 1st (2nd, 3rd) time traveler can't travel father back?\nI mean, that would make everything inconsistent again. Maybe they can and will simply become the first time traveler themselves? But where does it end? Now I'm confused again. Logically it has to end somewhere so we get a final timeline with a set and ordered list of time travelers up to some point.\nMaybe Primer idea is not that bad (for those who haven't seen the movie SPOILERS ahead): we can only travel back to the point when the time machine was first turned on. But I don't like this restriction very much.\nSome extra stuff that's not very important:\nPeople often complain that maleable timeline stories don't have high enough stakes because the character can always go back and change something else, or if multiple realities coexist, then nothing even matters. But here's only one eventual reality and nobody will ever be able to recreate their original timeline, especially due to multiple time travel arrivals after their own.\nI think there's a good narrative potential here. For example, there could be a whole society (or two competing ones) made of time travelers who are all by definition come from different timelines, quite possibly very very different. With different societies, technologies etc.", "159" ], [ "If an immortal, fabricated particle could travel FTL, would it exist in all times, or only the past relative to its present?\nThis seemed too scifi or hypothetical for physics, so here goes.\nSuppose a manipulated quark with 0 mass could travel faster than the speed of light. It's known that the faster you go, the slower time goes for you relative to an outside observer. At 1c, time essentially \"stops\" and everything outside that the particle sees seems to be standing still in time, while it continues to travel according to its own normal internal time. At 2c, outer time can't really get any slower than 0, so my reasoning is that it must start going backwards.\nI am not asserting that my particle can accelerate from 1c to 2c, but rather trying to rationalize what will at > 1c in the first place, which this particle constantly travels at. In that case, wouldn't its vector through spacetime be negative, meaning it is bound to travel ever-backwards in time? Due to the expansion of the universe over time, would the universe would be shrinking for the particle, and all scattered masses of the universe actively unraveling and falling towards a single point in 4 dimensional space? As space compresses, its relative velocity would become slower and slower, until it arrives at the CMB, or if we add its negative time into the equation, the actual beginning of the universe, where negative time starts slowing back towards absolute 0?\nIf we observed this quark for a planck instant in our world, would we know without a doubt this quark has come from the future, and could we use this knowledge to acquire information from the quark, much like in the movie Interstellar, except these quarks come explicitly from the future rather than morse code from a timeless existence? Or would we not be able to detect its existence at all as it passes through our spacetime?\nEDIT: reading the answers and comments so far, I'd like to point out that all or most of you seem to know a lot more about this than I do. To the point that now I am second guessing the validity of my question.", "275" ], [ "In terms of what I deem to be a \"good answer,\" everyone seems to be doing a great job just by providing their thoughts on the matter, even if in some cases your answers are in conflict with one another. I said quark just to give it some validity, as quark is a generic term for subatomic particles, which are the only things I can reasonably imagine to travel FTL in the first place. Tachyons and antiparticles seem to describe this proposed \"quark\" in more cohesive terms. I'm not up on my spin and colour game so I can't speak for that sort of technical jargon, but it makes sense that they would be inverse if they were travelling backwards in time. I said the particle has 0 mass, because I thought it was a necessary prerequisite for FTL in the first place. It's not important that the particle has 0 mass, it actually helps if it could have mass, because then there is logical recourse for the particle to begin to make observations of its surroundings.\nIn the spirit of clarifying concrete questions, are tachyons/antiparticles proposed to travel only backwards in time, by some informed schools of thought? Also, how might we go about identifying them and possibly extracting info from them? If you answered these already, of course disregard. Bonus question, do you feel that my interpretation is accurate, where the particle eventually arrives at the beginning of the universe, where its relative velocity, and the progression of time itself approaches absolute 0? If so, then I'm imagining the beginning of the universe, where there is rapid outward expansion of spacetime, energy, and particles, while at the same time, negative spacetime, negative energy, and antiparticles are all rushing towards point 0 to be consumed by a state of timelessness and non-existence.", "562" ] ]

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[ [ "There are lots of possible options. This is not an exhaustive list, but it covers some of the main options:\nSolid State Thermoelectric generators\nFor lower temperatures (i.e. below the melting point of solid materials), a Thermoelectric generator is your friend. The <PERSON> effect is when a voltage generates over a length of material that has a temperature gradient (i.e. heat flux) across it. Currently, this has some use in small, low power devices (tens to low Kw). With future handwaved technology, it may be possible to create exotic materials with a much stronger <PERSON> coefficient, hence enabling more efficient power conversion.\nBrayton Cycle\nThis is used extensively today, but it fits the bill of not requiring boiling water. Some sort of gas is heated, expands, drives a turbine, cools, and is run through a compressor. This thermodynamic cycle is essentially a closed cycle jet engine. This is used for modern gas turbine power stations (in conjunction with a more conventional steam based cycle), but it is an efficient use of high temperature sources that work at many hundreds of degrees.\nMHD Generator\nIf your thermal source is hot enough to (at least partially) ionise a gas into plasma, then you can use a MHD generator.", "778" ], [ "The hot plasma is ducted down a pipe with a transverse magnetic field. This separates the positive ions and electrons, into two streams, extracting work from the gas/plasma and slowing it down. The separate streams can be passed over high temperature electrodes, which form the terminals of a circuit, creating a voltage difference.\nDirect conversion\nIf your thermal source is extremely high temperature, and directly produces a stream of charged particles (perhaps some exotic fusion reaction) you may be able to directly convert your exhaust. There are a lot of different ways this can be engineered from schemes that look similar to a MHD generator, all the way up to devices that look like a particle accelerator that operates in reverse.\nExotic Photovoltaics\nIf the high temperature source is extraordinarily hot, it may radiate a significant quantity of blackbody radiation. Enclosing it in some sort of exotic photovoltaics could generate electricity. The \"exotic\" part comes in because current photovoltaics are only really suitable to harvest sunlight. You may need some exotic (i.e. handwaved) semiconductors to make them work at higher frequencies (perhaps even x-rays or gamma rays), and with efficiencies that make it worthwhile for your alternate heat source.\nAll of the above\nYou may notice that there is a bit of a hierarchy to the above systems. As temperature increases, the most efficient engineering solution changes. For even more efficiency, you can chain them together! The most efficient system may be one where, for example, the exhaust of a futuristic aneutronic fusion reactor feeds into a direct conversion generator, which exhausts a lower temperature plasma into a MHD generator, which is cooled by a molten salt loop/heat exchanger into a Brayton cycle gas turbine, which is finally topped off with a \"low\" temperature coolant loop through a bank of thermoelectric generators. All of this would face numerous engineering constraints such as the cost/reliability/weight/volume limits of the system.", "284" ], [ "As other answers have said, given enough resources (Methane), your proposed heat engine could work, however I wonder if there could be a more elegant design - especially considering that humans have mastered travel through the solar system.\nSince, in your world, humans are now expanding to other planets and moons I think it likely that through the development process engineers would be working on ways to either encapsulate energy for when it is scarce or ways to transmit energy long distances. Since humans are traveling around the solar system in months and spread throughout it there would likely be some sort of infrastructure in place for cargo transport, etc.\nIf there is no reason that the colony has to be 100% self-sufficient (the energy has to come from Titan), you could take advantage of these cargo routes to transport either fuel or large batteries to colonies with scarce energy along with regular resupply missions. This could be one solution, but the next one I like better:\nWireless Solar Energy Transmission So, you're on Titan. It's cold, dark, full of methane, and you need energy... bad. Luckily the engineers have been working on solutions to maintain a flow of energy to all the colonies.\nIn a close orbit to the sun, you have an array of large solar collection devices.", "199" ], [ "The concentrated energy is used to generate a laser of a specific wavelength that transmits energy to satellite devices spaced along routes through the solar system. Mirrors/Optic systems could create a constantly unobstructed pathway to all of the satellites as they move through their orbit (or in stationary orbit around another planet). After passing through a relay of these satellite devices, the laser ends its journey at a receiver on the destination planet/moon.\nDisadvantages of a laser system such as energy loss through atmosphere wouldn't be an issue transmitting to Titan, but you would certainly not get all of the energy back. This would require a receiver on Titan many hundreds of meters across, and a substantial battery to store the energy as it comes in. Ideally, an unmanned mission would prepare the required infrastructure so that the colonists arrive with several months worth of energy already having been transmitted and stored in the battery.\nSimilar energy transfer can be done with Microwaves, and to my knowledge the energy conservation is much more effective with Microwaves since you aren't losing so much energy to visible light. Current systems can achieve up to 85% efficiency. Microwave however runs the risk of RF interference (which could be a problem unless the system is positioned away from communication channels) and the receiver would have to be larger than that of a laser.\nHere are some stats on current wireless space-solar power systems for reference:", "801" ], [ "The reactor itself, is doable...\nThe amount of highly enriched uranium required to sustain criticality is not massive. Although it can be done with a few dozen kilograms (less if you use plutonium), you would never actually be able to build a reactor this small for practical reasons:\n* More fuel is needed to extend the life of the core.\n* Reactivity decreases as the hot fuel expands, so you need more fuel to compensate. Maybe even neutron reflectors too.\n* If you want to start and stop the reactor, control rods are needed too.\n* Coolant channels make the core larger to cool the core and extract useful heat,\n* Optional instrumentation channels to measure neutron flux (can be done external to core).\n* Optional neutron source to make start-up go quicker and easier.\nStill, even with these limitations, a reactor weighing less than half a tonne is possible. The Russians built reactors weighing less than 300Kg, with thermal outputs in the tens of Kw, so it's certainly possible. If you need to scale up power output, you would need to design the fuel geometry to have a high surface area, probably go for some cermet fuel, use a high thermal capacity coolant (probably molten metal or salt), and you would really need to pump a lot of coolant through it. All of this pushes you in the direction of using a fast reactor reactor than a thermal reactor, and the molten metal/salt can be used at low pressures which means you don't need massive thick pipes, keeping size and weight down. Of course the problem arises in that to run the core at at least 1.5Mw (probably closer to 5Mw when accounting for thermal inefficiencies), you are going to need to extract a lot of heat from that core, hence the real problem.\n...but the power conversion isn't...\nThe reactor is only one part of the system. You also need to take the heat produced by the core, and produce useful electricity and shaft power to drive your tank. Step one of that is a main coolant pump, which for the kinds of flow you are talking about, is already going to be at least the size of a washing machine. Then you need to take that hot flowing molten metal/salt coolant, and do one of two things:\nIf you use a high temperature Brayton cycle, then you will use a heat exchanger to heat some gas, run it through a turbine, then allow it to expand, and run it through a compressor before repeating the cycle. unfortunately, most gasses do not have a high thermal capacity, so your heat exchanger is going to be massive. No way it could be fit within 2 cubic meters.\nIf you use a lower temperature Rankine cycle, then you will use a heat exchanger to boil water then drive a steam turbine. Water has a high heat capacity, so the heat exchanger will be smaller. However in my experience, heat exchangers for a nuclear plant still tend to be at least twice as large as the reactor itself.", "435" ], [ "Furthermore, steam turbines are not small. It's difficult to find weight specs, but this source gives a craneage weight for an 1.5Mw turbine as 3.4 tonnes. You may be able to shave a bit off that with fancy materials and clever engineering, but I doubt you could get it down low enough for the system to weigh less than 2 tonnes.\nBoth of these would then need to reject the waste heat from the system. This would require forced air convective coolers on your tank. Calculating the size of these is non trivial, so I'm not going to comment on how big they would need to be.\n...and safety is impossible.\nWe often make fun of safety for ruining our fun, but there is no point building a tank if the crew is dead 10 minutes after they roll out of the garage. Shielding this reactor in such a confined area is going to be impossible, and a 5Mw reactor would produce a non-negligible amount of radiation. The shield itself would probably need to be at least half a meter thick (probably larger), and may require it's own active cooling. I just don't think it's doable.\nConclusion\nIf you are desperate to have a nuclear powered tank, I would suggest the following options: - The tank is an ultra-heavy monster tank. At 100s or 1000s of tonnes of tank, I would suggest that scaling laws make nuclear power more viable. Of course, this raises other problems. - The tank is a smaller, unmanned drone tank designed for long term deployment. Smaller 300Kg systems are viable, so you might be able to make a smaller unshielded drone. It's still not going to have a fantastic power to weight ratio, so the only advantage to going nuclear is if you want something that can operate without re-fuelling for long periods. - Artistic licence.", "435" ], [ "Must admit I've been toying with a similar idea, except at interplanetary scale.\nThe huge advantage is that you are free of rocket equation constraints. As all the energy is delivered externally, you don't have to hand wave about Bussard Ramjets and the like. The presence of a catcher is also required, unless you are going to try and carry all the fuel for the slowdown phase, which pretty much defeats the point. If you are doing that then you might as well have a detachable 'acceleration phase' stage.\nSo what are the problems:\n1) As mentioned above, massive sustained acceleration, unless you have an amazingly long rail gun assembly. In a zero-g environment, a structure that is 100s of km long is not impossible. I would presume that in a zero-g vacuum environment a barrel would not be required, if your magnets can keep the projectile going straight. Indeed, at the speeds involved a physical barrel would just be a hazard.\nFor the payload, you'd have to go beyond acceleration couches. Think full immersion in a fluid (no air gaps, even in the lungs or ears); possibly freezing solid. You want to avoid any density contrasts within the ship in the acceleration/deceleration phases, to allow for the 100+g loads.", "898" ], [ "Once in cruise phase, you could come out of vitrification.\n2) Safety - Well.. you've accelerated a ship weighing hundreds of tonnes or more to, perhaps, 1000km/s. Going by the kinetic energy formula, e = 0.5mv^2, that would be ~10^17 J According to the Wiki, that's about a Tsar Bomba). So if anything goes wrong and you hit a planet (never mind a KBO) you will leave a noticeable dent. Even under good conditions, your catcher has to dissipate that amount of energy in a very short time. You'll need some very, very big capacitors.\n3) Practicality - As long as the system is reliable and the energy requirements are solved, then it avoids sending huge fuel tanks out on long, tedious orbits. So in many ways better than chemical rockets or solar sails. It also requires some form of hibernation/sleep tech, as above.\n4) Orbital Paths - You would probably need some form of adjustment onboard, but the calculations would be pretty trivial. You'd also want adjustment thrusters in case space junk was detected en-route, as collisions at cruising speed would be very very dangerous.", "947" ], [ "The scenario you have proposed has more problems than just the L3 point's instability. You also have issues with mass, interaction with other planet's gravity, and the shape of Earth's orbit.\nStarting with the mass problem: In order for a Counter-earth to exist, it must have precisely the same mass as Earth does. This is because orbital equations mandate that orbital velocity is a factor of mass and distance from the gravitational body. Assuming a circular orbit to simplify things...\n$$ v = \\sqrt{\\frac{GM}{r}} $$\nIf you wish to maintain velocity with a smaller mass, you must move it closer to the body it is orbiting. The L3 point has forces that try to hold you at a similar orbital velocity, but they wouldn't be strong enough to hold an entire planet there. If your planet had a lower mass, and thus higher velocity than Earth, then it is going to have a wildly elliptical orbit with a different orbital period (meaning we'd have probably crashed into each other by now if we are in the same plane)\nOrbital shape is also an issue. Since Earth sits in an elliptical orbit, in order to sit constantly in Earth's L3, Counter-Earth would need a matching elliptical orbit that is precisely the opposite of Earth's. Your energy needs for station keeping would vary depending on the time of year.\nFor a lower mass planet, with Earth's same orbital velocity, your challenge would be keeping the planet from sliding further out on Earth's orbital path because of its lower mass.\nNow, on to the Lagrange Point issue. The L3 point is the spot at which Earth and the Sun's gravitational pulls line up, so there is no angular force tugging you off-station. Beyond that, it is your centrifugal force from orbital velocity that holds you on-station with respect to distance from the sun.", "801" ], [ "With a mass smaller than the Earth, you would tend to drift further from the sun, so station keeping would mandate that you exert an force propelling you inward towards the sun. Further complications will be introduced by the orbits of other planets, particularly Venus, which will tug inwards.\nNow...on to the math. Ignoring Venus for a moment, lets calculate the gravitational force generated by the Earth/Sun system that you are in the L3 point of. Note that I am also ignoring the in/out drift of Earth and Counter-Earth for this in the name of simplicity and am using the Average distance. If you want to calculate minimum and maximum energy requirements, swap out the distances for the Earth's aphelion distance and perihelion distance. (Remember to double the distance for the gravitational pull between Earth and Counter-Earth)\nForce of Gravity can be calculated like so...\n$$ Fg = \\frac{Gm1m2}{r^2} $$\nSo, to get total Force of Gravity for the system...\n$$ F = \\frac{Gm1.989e^{30}}{149,597,870,700^2} + \\frac{Gm5.972e^{24}}{299,195,741,400^2} $$\nWhere m is the mass of your planet and G is the Gravitational Constant $6.6726e^{-11}$\nPlugging in the '85% Earth Mass' value that you gave, we get a Force of Gravity equal to $3.0119e^{22}N$. In order for our planet to neither fly away, nor fall into the sun, we need for its Centrifugal force (+ generated force) to be equal to the force of Gravity.\nSo, calculating the natural Centrifugal force of our planet, moving at Earth's orbital velocity renders this equation:\n$$ F = \\frac{mv^2}{r} $$\nFor the sake of simplicity, we are going to ignore the fact that the orbital center is not the center of the sun...it's a little bit off, but not by much. So, plugging in values gives us this finalized equation...\n$$ F = \\frac{m*30,000^2}{149597870700} $$\nAgain plugging in our 85% mass, we get a Centrifugal force of: $3.0539e^{22}N$\nThis leaves us having to make up for $4.2015e^{20}N$ of Force on a constant basis. These forces give the planet an outward acceleration of $.0000828m/s^2$ (using $a=\\frac{F}{m}$). Calculating for displacement using...\n$$ x = vt+.5at^2 $$\nShows that our planet will attempt to slip off station by $.0000414m$ every second. This is a quite small number, but we have to keep it perfectly balanced.", "24" ], [ "Neutron stars are not very well understood, unfortunately. The matter on the surface is theoretically different from the matter in the core, due to the increased pressures at depth, but we can examine each layer in detail.\nAtmosphere\nThere is actually an atmosphere around a neutron star, or there could be at least. It would be veeery thin, perhaps only a few micrometers, and likely composed of hydrogen and helium. If returned to \"normal space\" these gasses would likely exist as normal.\nCrust\nBeneath the atmosphere will be solid matter (or possibly liquid if the temperature exceeds about 10^6 Kelvin). The matter will still be mostly charged atomic nuclei crushed into a dense lattice swarming with electrons. This structure would behave metallically, and is thus theorized to be made perhaps of Iron, due to Iron's high binding energy. Iron could be too dense, though, which means the crust could be metallic Hydrogen and Helium. If we lifted this material off the surface, it might expand back into a more recognizable form, either solid Iron or gaseous Hydrogen/Helium. Due to the possible temperatures this material might become plasma.\nInner Crust\nProceeding inward we'd encounter more and more pressure, and so nuclei would be composed of more and more neutrons due to the process of Electron Capture. This process turns a Proton + Electron into a Neutron, at the expense of an escaped Electron-Neutrino. Once these neutrons are formed, they are permanent, and will not turn back into a charged duo.", "473" ], [ "The nuclei at this depth become increasingly unstable, since the Strong Force cannot cope with the number of neutrons. The only thing keeping them in place is the immense gravitational pressures. If we scooped out some of this gunk and set it free most of the nuclei would decay rapidly, releasing radiation and turning into more stable heavy elements. This could potentially become an interesting source of exotic elements if you wanted to risk the process of mining in such conditions.\nOuter Core\nAt this depth the Neutrons are becoming ubiquitous, and electrons and charged nuclei become smaller and more rare. The gravitational pressures involved completely overwhelm the Strong Force binding the nuclei together. Any remaining nuclei would probably still be stable if we removed them, since they have become so small, but there could be some very radioactive isotopes in there somewhere. Mostly all you'd pull out of this goo would be pure neutrons, which are not terribly exciting.\nInner Core\nAt this point there are ONLY Neutrons present. The Electron-Capture process has eliminated all charged particles, and no nuclei exist. If you could somehow get to this depth to remove this material, it would expand as the pressure was released, and the Pure Neutrons would decay rather rapidly into more stable nuclei.\nThere is a possibility that the core is composed of some sort of quark/gluon plasma. The neutrons are basically dissolved when subjected to the conditions in the core, but such a material is exotic and not well understood. I would probably want to stay away from it in case it expanded violently upon release.", "969" ], [ "You’ve done some great research and have outlined an effective theoretical approach to putting people on ice. However, ultimately the success of a cryonic procedure comes down to how good we are at repairing tissue. To thaw out a colonist and have more than meat, you need some sort of nanobot or other cellular repair technology that you can use on your patients as they thaw out. Here are the main examples of damage you would need to treat.\nCold Damage\nWhen you freeze your patient, the most obvious (and acute) source of damage to the body is the formation of ice crystals. Large-scale tissue structures are mulched, cell membranes are blown apart, and even delicate internal structures and proteins are disrupted. As anyone who has thawed and cooked a frozen onion or hamburger can attest, the act of freezing and then thawing results in a noticeable change in texture and flavour (and a significant loss of fluids as everything drains out of the now perforated internal structures).\nI'm listing this one for completeness' sake, but you have a solid theoretical way of avoiding this issue. So with direct mechanical trauma solved, what else is there?\nChemical Activity\nThere are a great many molecular structures in a given cell that are delicate and energetically intensive to maintain. While reducing temperature reduces chemical activity, there is some debate as to how cold you need to get before the more short-lived molecular structures in the body begin to degrade. When your cells are warm enough to engage in homeostasis, this short lifespan is an asset. If it is cold enough to stop biological activity and inhibit chemical activity however, it becomes a liability. These chemical springs will certainly uncoil less quickly, but they will still uncoil.", "815" ], [ "ATP will dephosphorylate, RNA will slowly fall apart, etc.\nTheoretically, you could get around this by freezing people down close to absolute zero, but that’s a challenge even on Earth where heat is a lot easier to get rid of than it is in space. I would imagine a compromise is made here, finding a minimum feasible temperature that balances reduced the decay damage (and repair/thaw time) with the machinery needed to keep everyone frozen.\nRadioactive Decay\nWe contain quantities of radioisotopes of carbon, phosphorus, and other elements. These are constantly decaying, and your body is continually repairing this damage. However, if you are on ice, radioactive decay will continue (it doesn’t particularly care about temperature) but the repair systems are now on hold. Damage from radioisotopes such as C-14 and P-40 undergoing their usual decay will accrue throughout the body, both in the form of the beta particles released and in the form of a generally rather important phosphorus suddenly being calcium and carbon being nitrogen, with knock-on effects for the molecule or protein it is a part of.\nIt’s worth noting that these are both quite stable radioisotopes with long half-lives (10^3 years for C-14, 10^9 for P-40), but we contain a lot of both, and both are incredibly important wherever they are. Carbon is the backbone of essentially every organic molecule, and the change in electronics and available covalent bonds from C to N presents pressing structural issues. And with phosphorus, it's almost worse: each nucleotide in your DNA has two of these, one joining it to each of the nucleotides on either side. Neither are great atoms to suddenly not have, and then there's that beta particle I mentioned - it's also highly likely to find a new friend in the area.\nConclusion\nSo, damage will accrue beyond the initial freezing. Ultimately, what your society will need to make this viable is a solid foundation of cellular repair technology, in whatever form that takes. Nanomachines are generally the most popular take here, and if you are spending three days to freeze someone, spending another three to infuse them with repair bots as they thaw out seems pretty reasonable. This does mean your setting has access to healing nanobots, which will have knock-on effects on human lifespan, disease, and what exactly constitutes ‘serious injury’ and ‘long-term treatment’ if most injuries are curable by a day or so on the slab while the nanites work.\nAdditional Information\nI’ve done a surface level discussion of these topics, but if you want more depth I would recommend a couple YouTube videos by <PERSON>, a physicist and futurist, that discuss this topic. One is more general information on Cryonics (he focuses on the societal aspects of the technology and its uses but also gives more details on limitations), while the other is more focused on sleeper ships like your use case.\nCryonics: Frozen Civilizations\nSleeper Ships", "279" ], [ "According to <PERSON>, CEO of Graphenea:\nGraphene is, basically, a single atomic layer of graphite; an abundant mineral which is an allotrope of carbon that is made up of very tightly bonded carbon atoms organised into a hexagonal lattice.\nHe also states that there are three commonly-known naturally occuring allotropes of carbon - Diamond, Graphite, and amorphous carbon. Graphene's structure is similar to that of Graphite, but Graphene itself is much different because it has a $sp^2$ hybridization, compared to $sp^3$ hybridization of carbon in the form of Diamond, and Graphene has a thickness of just 0.345Nm (nanometers). This means that it does not form tetrahedrals like common carbon atoms, making Graphene similar but special compared to other forms of carbon.\nAlso stating <PERSON> in Graphite-Graphene Comparison:\nGraphene is fundamentally one single layer of graphite; a layer of $sp^2$ bonded carbon atoms arranged in a honeycomb (hexagonal) lattice. However, graphene offers some impressive properties that exceed those of graphite as it is isolated from its ‘mother material’.\nTo elaborate, Graphene has special properties that set it apart. There are similarities: stacking layers of Graphene may be similar to creating Graphite; creating a rope of Graphene may be similar to creating Crabon Nano-tubes; both have $sp^2$ hybridizations.", "724" ], [ "However, Graphene has special properties that make it stronger when stacked because of how it is extracted and isolated.\nAs for the conductivity, <PERSON> states that it's electronic properties is what sets it apart (See Graphite-Graphene Comparison). Fundamentally, Graphene is a zero-overlap semi-metal, with both holes and electrons as charge carriers, that has very high electrical conductivity by itself. Graphite carbon allotropes have 4 electrons in it's valence shell available for bonding, however, Graphene has 3 electrons that are bonded with other Graphene atoms in the 2D Plane (a.k.a. other Graphene atoms next to it on the same one-atom thick sheet). This makes a single sheet very conductive, because the remaining electron that isn't bonded with other Graphenes in the same sheet are in the 3D Plane (above and below the sheet), causing what is called, pi electrons. However, when Graphene sheets are stacked together, their pi electrons bond with each other, thus reducing the electric conductivity of the Graphene.", "724" ] ]

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[ [ "Hand-Sewn Stuffed Cat Plushie MODERATE SKILL LEVEL\nIntroduction: Hand-Sewn Stuffed Cat Plushie MODERATE SKILL LEVEL\nI used this website for the pattern:\nhttps://dollmaker.nunodoll.com/cat/ragdoll.html\nDISCLAIMER: The printed pattern is from a website not owned by me. I did not create this pattern nor the directions on the website myself. All rights are reserved to the original maker of the pattern.\nThere is a small tutorial on the website for the construction, but it was not thorough enough and took a lot of trial and error for me to get right.\nI made this cat for my aunt, in likeness of her late cat <PERSON>. I have made three cat plushies with this pattern total. For the pictures with a blue background, I was at school using one of my teacher's fancy cameras. For the pictures with a brown background, I was at home using my phone. It took me a few days to complete sewing this cat, because I sew by hand.\nSupplies\nHere is a list of the materials I used, but you can change the fabric depending on what you have:\nThings I bought/printed:\n* 1 yard Black and 1 yard White Anti-pill Fleece (from Joann Fabrics) $6.00 a yard - one yard of fabric can make up to 3 cat plushies -\n* Black embroidery floss (from Michael's) $0.62 for individuals\n* Plastic cat eyes (from Joann) $2.50\n* Thin, translucent wire (from Joann) $4.50\n* Polyester Fiber-fill (from Joann) $17.00\n* Printed pattern on paper from Nunodoll.com:\n+ BODY- https://dollmaker.nunodoll.com/cat/ragdoll1.gif\n+ HEAD, BELLY, and TAIL- https://dollmaker.nunodoll.com/cat/ragdoll2.gif\nTotal Cost of Items: $36.62 roughly\nOther supplies I had on hand:\n* Needle and thread, black and white\n* Fabric scissors (I used my Calculus teacher's fancy scissors)\n* Chalk and Washable marker, for tracing the pattern\n* Seam ripper, for mistakes and putting in the eyes\n* Measuring tape, for seams\nYou will also need to know the following hand stitches:\n* \"Back\" stitch - the usual stitch\n* \"Running\" stitch - for closing the head and tail\n* \"Lock\" stitch - for starting and ending each stitch\n* \"Ladder\" stitch - for closing ears and attaching the head & tail to body\n* \"Embroidery\" stitch - for optional details\nStep 1: Print Out the Two Patterns Onto Computer Paper\nPrint the pattern out onto computer paper and cut it out.\n(Optional step) Since paper is so flimsy, I glued the pieces to cardboard, from cereal boxes, with a 1/4 inch border around all the edges, except for the underbelly's slit in the middle and the hind foot's slice.", "673" ], [ "It is hard to explain in words, so I hope the pictures can help explain this better.\nThere is one other piece I made from the fleece that didn't have a pattern, so make sure you have enough material for it (it'll show up later).\nStep 2: Cut Out Pieces for the Head\nWhen cutting pieces out of any material, it is very important to know which side is the good side and which side is the wrong side. The good side is the side that will show up on the outside of the final product. The wrong side is the side that you sew on and will end up on the inside of the final product. With fleece, it is hard to tell which side is which because they are both the same color. However, I found that the good side of fleece is fluffier than the wrong side.\nTrace your patterns on the WRONG side with chalk. I added a 1/2 inch border around the pieces to make them a bit bigger. I do this with every piece, even the ones with the body, but you do not have to do this.\nYou should have these pieces cut out: 10 in total\n* 4 ears/ 2 black and 2 white\n* 1 head, black\n* 1 nose, white\n* 1 cheek, white\n* 1 chin (here I have it black but I ended up changing it to white later)\n* 2 head sides, black\nIn the picture above, I laid out all the pieces with their wrong sides up. Later I will show you what the wrong and good sides look like.", "316" ], [ "Simple No-Sew Jewelry Bags\nIntroduction: Simple No-Sew Jewelry Bags\nThese simple bags make a great way to store your jewelry, give your handmade jewelry as gifts, or sell your handmade jewelry. Making them isn't hard and doesn't take a lot of time, so it saves you more time to make more jewelry!\nSupplies\n1. Hot glue gun\n2. Material in your choice of colors/patterns (I recommend using cottons and no heavy materials like denim)\n3. Yarn or Embroidery thread to match the materials\n4. Ruler\n5. Scissors\n6. Pattern pieces (included in this Instructable)\nStep 1: Measure Material\nLay the material out on a flat surface to measure out the bag size.\nI have included some patterns for sizes that I think are pretty standard jewelry bag sizes. The smaller pattern is for smaller items, the larger pattern is for larger items. If you just want the dimensions to measure for yourself, the smaller pattern is 5 inches X 5 1/4 inches, and the larger pattern is 5 1/2 inches X 6 1/2 inches.\nTrim out the material as neatly as possible, but don't fret over it.\nPlug in your hot glue gun at any time.\nStep 2: Measure String\nThis will be the pull string of the bag. On the patterns I have measurements that are what I used for my string.\nFor the large bag, I cut about 12 inches of string. For the small bag I cut about 10 inches of string.\nCut the string according to the measurements or according to what you think will be best. Remember, it should be a bit longer than the edge of the material so that it can be tightened and loosened to close and open the bag.\nStep 3: Glue the Casing\nLay the material out flat. The reverse side should be facing up!\nLay your string along the top half of the material so that there is material on both sides. You want to have about half an inch above the string so you have enough room to fold it over and make the casing.\nStarting at the end, put a small dot of hot glue beneath the string. Don't get close to the string; you will accidentally hot glue it and it won't work as a pull string.", "316" ], [ "Fold over the fabric from above the string to meet the fabric below the string, enclosing the string in a tube of fabric. Stick the fabric to the glue dot.\nMake another dot of glue next to where the material is now folded down. Fold down the top material to meet it.\nProceed this way until you reach the end. Once the hot glue is dry, pull on the string carefully to see if it slides. It should. If you got a little bit of hot glue on it and it is kinda stuck, you can pull on it a bit and it should let go.\n*The casing is the folded over material that makes a tube in the fabric where string or elastic goes. It allows the string/elastic to move freely. Waists are often made this way.\nStep 4: Glue the Middle Seam\nLay the material so the glued casing is face down.\n*TIP: Place thin cardboard or paper in the middle of the material. This will prevent you from accidentally gluing the front and back sides together.\nFold one of the sides to the middle. Pick the prettiest one because it will show on the outside.\nFold the other side to the middle as well, but overlap the first side.\nUsing the same method as before, hot glue the top piece to the bottom (the first side) by placing dots of glue in between the overlapping pieces.\nStep 5: Glue the Bottom Seam\nNow all that is left to glue is the bottom seam.\nWith the middle seam facing up to you (it should be like this unless you picked it up after the last step), place dots of hot glue all along the bottom of the fabric. Don't place it right on the edge, you need a little space so you can fold the material over.\nFold the bottom up onto the hot glue. Wait for it to dry, then place glue dots in the little open sleeve. This was the other side of the bag. Press that down and wait for it to dry.\nStep 6: Flip Inside Out\nNow all the bag has been glued.\nFlip the bag inside out by sticking your thumbs in the opening of the bag to hold it open. Using you other fingers, push the bottom of the bag up through the opening. Use your fingers to continue to push the fabric until it has all been flipped.\n*TIP: you can use a pencil or pen to push in the corners to make sure they get flipped all the way.\nStep 7: Almost Finished...", "455" ], [ "DIY Chapstick Holder From Quilting Scraps\nIntroduction: DIY Chapstick Holder From Quilting Scraps\nMy grandfather pieces quilts to keep himself busy. He makes log cabin and split rail layouts, then he sends them to someone else who quilts them. They are then sold to family and friends. In the above photos is a photo of one of his quilting squares.\nWith the tons of quilts that he makes, it results in lots of little scrap pieces. These pieces are very small and most of them are long and thin, making it a little tough to figure out what to do with them. He recently gifted us a bag of scraps, hoping we could use them.\nIn the bag were some beautiful material pieces. I especially loved a few pieces I found with a batik-type fabric (I wonder who got that quilt because I never saw it!). I was puzzling over what do with with the quilt pieces when I spotted a chapstick holder hanging on someone's purse. Bingo! The thin pieces were the perfect shape!\nObviously, you can make these out of whatever scraps you have on hand, but my scrap piece measured 2 3/4 inches wide and it was perfect for a regular sized chapstick tube. Your fabric will need to be about 10 inches long to complete the project.\nSupplies\n1. Chapstick\n2. Fabric. Your measurements should be around 2 3/4 inches wide and around 10 inches long\n3. A clip with a ring on the end of it (lobster clasp, dog chain, whatever, it doesn't matter what style of clip)\n4. A sewing machine\n5.", "787" ], [ "Sewing pins\n6. Sewing scissors or just regular scissors\nStep 1: Prep Work\nOne one end of the fabric, fold the cut edge over itself by about a 1/4 of an inch. (fold over the short end, not the long side). You can tack this down with pins if you want to, then sew it down.\nPlace the chapstick down on the material. Fold up the end you sewed so that it makes a pocket over the chapstick. This is just to give an idea of what size your fabric needs to be. Bring the opposite end over the chapstick so you know where you want to cut the fabric. It should meet the pocket end and cover the chapstick completely.\nNow, all along the long sides, fold the fabric over by about 1/8 inch and tack it down with pins. Make sure to fold the fabric so that both the seam lips are on the inside along with the lip of the last seam (see photos).\nSew that down.\nNow you have a long piece of fabric that has been cleaned up a bit. No fuzzies.\nStep 2: Making the Pocket\nOnce again, place the chapstick tube down on the fabric and fold over the \"pocket\". Make it as tall as you want it, then line up the sides seams and put a pin in them at the top.\nTake the chapstick out of the \"pocket\" and pin both sides of the pocket down, lining up the top edges of the fabric with the bottom edges.\nSew the pocket closed by lining up the sewing needle with the side seam you made in step 1 and sewing down the pocket, sealing the two layers of fabric together.\nTrim all the thread fuzzies and you should have a pocket!\nStep 3: Attaching the Clip\nTo add the key chain, scrunch up the fabric end that is opposite the pocket end and put it in the keychain ring, going under, in, and over the ring. The edge of the fabric fold should end up on the front side.\nUsing pins if you want, sew the edge of the fabric down right under the top edge of the pocket (peel back the pocket fabric so you don't catch it and accidentally sew the pocket shut). Once the fabric is let go back to its natural position, it should look like the above photos.\nNow we need to complete the chapstick holder by firmly sewing down the edges of the pocket to the edges of the keyring fold. Simply sew along your former sewing lines and go over both the corner edges of the pocket and onto the edges of the keyring fold, tacking them both down (you don't need to sew all the way up to the key ring, just enough to make it look nice and keep the ring from sliding everywhere).\nStep 4: Finished\nCongratulations! You have made something out of your quilting scraps that you will actually use!\nThat is a lot of my problem with little scraps. I could make something from them, but will I actually use it? This chapstick holder from quilt scraps is both cute and functional and you have to give it more than a glance to realize that someone made it at home and didn't purchase it.", "455" ], [ "Beginner Jewelry: Wooden Photo Earrings\nIntroduction: Beginner Jewelry: Wooden Photo Earrings\nThese are actually some of the first pieces I ever made when I started getting interested in making jewelry. I wanted some fan girl jewelry and couldn't afford to just go buy something, so I needed to make it myself. At the time I was in luck because I had a wooden necklace that had broken and was irreparable, but I had kept the wood pieces, and these became my base.\nSince I was able to do it as a beginner, I think that these wooden photo earrings are definitely a project that the jewelry artist who is just starting out will benefit from. Even those of us who have been making jewelry for a while could get some joy out of earrings with photos of our choice on them.\nI am using my own photos for this Instructable. You can use whatever you like, just please keep in mind that if you sell earrings like this your photos will need to be your own.\nSupplies\n1. Wood pieces: you can use scrap pieces you have or buy some premade. I'll talk more about this is the second step.\n2. Electric drill\n3. Small drill bit: mine is a #55 with a 118 degree point\n4. Sandpaper, fine grit (you may decide you don't need this)\n5. Photos or drawings (not pictured)\n6. A computer or laptop with a word document program (not pictured)\n7. A printer with colored ink (if your photo is colored). Mine is an inkjet. (not pictured)\n8. Regular white copy paper\n9. Scissors\n10. Pen or pencil\n11. Mod Podge or Polyurethane Varnish or some other sealer\n12. Brush\n13.", "95" ], [ "A pin (you don't have to have it)\n14. Round-nose pliers\n15. Jump Rings\n16. Earring Hooks\nStep 1: Wooden Pieces\nThe wooden pieces should have a flat or pretty much flat side to them. They can be whatever size you want, but you want them to be a size that you can wear comfortably.\nAs I said earlier, you can use scrap pieces of wood if you have any. You will probably have more work because you will need to sand your scrap pieces to make them smooth and to shape them.\nIf you don't have scrap pieces, or you don't want to mess with that, you can buy premade little wood circles, squares, and other shapes at craft stores. I bought mine at our local chain craft store. You can even find them at Walmart. You just want pieces that are pretty thin and the diameter you want.\nSince I bought a variety pack, I have a couple sizes to pick from. I am going to use the largest circle size I have (you can see in the photo how big it is), but size is up to you.\nStep 2: How to Remove and Add a Drill Bit\nI put my #55 micro drill bit into the drill.\nOn my drill you hold the chuck (the piece were you put the drill bit) while you run the drill in reverse. This causes the end to open up so you can remove the drill bit that is in the drill.\n(The reverse/forward button is a little push in button that you should find somewhere above the speed trigger. You push on it one way and the drill runs in reverse. Push it in the other way and the drill will run forwards.)\nThen I place my #55 drill bit in the end and hold onto it with a few of my fingers so I can make sure it is straight. I turn the drill to run forwards. Slowly I run the drill until the end closes around the drill bit.\nNow we are ready!\nStep 3: Drill\nPlace your wood piece on a surface that you can safely drill on (not the kitchen table). Remember that your drill bit will be going all the way through the wood.\nYou may want to mark with a pen or pencil where you want the hole. You can carefully hold onto the wood piece with one hand while running the drill with the other. Just make sure your fingers are no where near the drill bit.\nHolding the drill straight up from the wood piece, place the bit where you want the hole. Slowly run the drill forwards until it goes all the way through the wood.\n*Alternatively, hold the piece in your fingers while you drill, but this is more dangerous! Be careful!\nTurn the drill to reverse, and run the drill as you bring the drill bit out of the hole. This helps make the hole smooth.\nMake sure to do this slowly because if you go too fast you may cause your piece to move or you might crack the wood.\nStep 4: Sand (optional)\nThe hole might have little rough edges, so we will sandpaper that.", "56" ], [ "Scrap Glass Pieces Into a Jewelry Set\nIntroduction: Scrap Glass Pieces Into a Jewelry Set\nI will admit that I love little pieces of colored glass. I will pick up pieces if I see them at the river bed, on the sidewalk, or wherever they happen to be. I especially love green and blue pieces, or pieces that are unusual in some way.\nUnfortunately, I just start to amass pieces of scrap glass that I don't know what to do with. I had been toying with the idea of trying to turn some of them into jewelry for a long time, so when the Glass Challenge came up I decided that now was the time. I went for something unique and different, and I used clay to cover the sharp edges, making me able to use the pieces without having to sand/alter them in any way.\nSupplies\n1. Glass Pieces That You Have Collected. These don't have to be random pieces, you could also use the little glass rounds that people use for fish tanks and flower vases.\n2. Clay. I am using black.\n3. Tools for Smoothing Clay. Anything that will smooth fingerprints and join lines from the clay will do.\n4. Tools to Poke Holes. Once again, anything that will poke a hole (pens, sewing pins, etc.).\n5. Pliers (I prefer round nosed)\n6. Jewelry Findings.\nThis depends on what type of jewelry you are making. For this tutorial, I am showing how to make an earring set, a necklace, and a ring, so I am using earring hooks, jump rings, a lobster clasp, and a ring blank.\nIf you are making a ring, you will need a strong glue, such as a type of super glue. Make sure it says it is suitable for gluing glass and metal.\nStep 1: Cleaning the Glass and Picking the Pieces\nFirst off, I had to clean my glass pieces.", "95" ], [ "I used baking soda and an old tooth brush, and I scrubbed the pieces clean.\n*Be careful while doing this. Depending on how the glass broke, it may be very sharp or possibly tiny loose shards will come off while you are scrubbing. Safety first!\nThen I went through the glass pile and picked out what pieces I wanted. I chose them not only by size but by interest as well. I liked the pieces I picked for earrings because they were from the lip of a bottle, so on the backside they had ribbing that made them shine differently in the light. The piece for the ring was chosen because it was small and very uniform. I picked out a pendant for the necklace first, then I chose pieces that were similar so that it was kind of a mirror on each side of the necklace.\nIt is kinda important to try to design necklace pieces before you put them together. You don't have to, but it helps you get an idea of how big they will be, if the pieces look good together, how much chain you need (if using chain or thread), etc. I normally just lay out the pieces I have and then rearrange them to suit my liking.\nStep 2: Basic Frame With Clay & Making a Ring Focus\nTaking the clay, roll it out into a smooth snake. Test if it is thin enough by placing it close to the edge of your chosen piece of glass. Once it as thin as you like it (or as thin as it can be and still cover the edges of the glass), press the clay around the edges of the glass piece. Use your fingers to push the clay up and over the edges to make sure any possibly sharp pieces are covered.\nOnce the clay is wrapped all the way around, pinch off any excess. Using your fingers and your smoothing tool, smooth out the bit where the clay joins, then smooth any fingerprints and bumps in the clay. You can use a pointy object to clean up the edges on the inside and make them uniform (or decently uniform!).\nThis first piece will be the stone for the ring, so it is finished.\nStep 3: Earrings\nBegin the earring pieces the same way that the ring piece was made. Wrap clay around the glass, but then add extra clay to whatever you decide needs to be the top (where the earring hook will be). Smooth the join and then poke a hole in the top.\nStep 4: Necklace Pieces\nFor necklace pieces, do the same steps from the beginning, and then add extra clay to both ends. Smooth the clay, then poke holes in both ends. We will put jump rings in both of the ends so they will be links in the necklace.\nFor a hanging pendant, make it the same way you did the earring pieces.\nStep 5: Finishing Up\nFor polymer clay:\nBake you pieces according to your clay's instructions.", "972" ], [ "Glass Wind Chime - No Drilling\nIntroduction: Glass Wind Chime - No Drilling\nAfter finding them on the internet, I had been wanting to make a glass wind chime but was hesitant because I don't know how to drill glass, nor do I have the resources that are needed. After some consideration of the problem, I decided that I could make a glass wind chime and wouldn't have to drill my pieces. Some simple supplies and gumption was all I needed to get it done!\nFor all these people who can't or are scared to drill glass, this is for you :)\nAnd if you enjoy this tutorial, give it a vote in the Glass Challenge!\nSupplies\n1. Glass cabochons, fish bowl glass, or glass for flower vases (you could also use bits of broken glass if you wanted, just watch your fingers)\n2. Fishing Line (mine is 6 pounds, which means it should stand up to 6 pounds of weight, so it will work)\n3. Steel wire or some other type of wire (I am using 26 gauge steel)\n4. Pliers for shaping the wire (I use round nose pliers)\n5. Wire Cutters for cutting the wire\n6. Aluminum/floral wire for the frame (I am using gold 16 gauge aluminum wire. You want this wire to be a heavier duty wire, somewhere around 18 to 16 gauge so it will hold up to being the frame)\n7. A strong glue (I am using Gorilla Glue)\nStep 1: Wrapping the Glass\nWith the 26 gauge steel wire, hold the wire with the pliers and wrap it around one of the tips of the pliers, rotating the pliers as you go. This will give you a small round circle. I wrapped it two or three times to make sure it was strong enough to not come undone.\nNow we will wrap the wire.", "972" ], [ "You know those really quick stars made up of lines that you can draw without lifting your pencil? That is what this wire wrapping makes me think of.\nLay the stone on top of the wire with the circle at the top. Bend the wire up so that it wraps around the front of the stone and is back up at the top.\nPull the wire over the stone so that it is now on the back of the stone alongside the first bit of wire.\nCross the wire to the front of the stone, pulling it at a diagonal angle.\nBring the wire to the back at an angle.\nPull the wire across the front of the stone in a straight line. See the star?\nWrap the wire once again across the back of the stone. Cut off the wire with your wire cutters, leaving a small amount of extra wire.\nBend the extra wire under one of the other wires in the wrap, then make a loop on the end of it the same way you made the first loop. Finished!\nFor the jelly bean glass, I put the glass on top of the wire like I did for the round pieces. I bent the wire sideways and wrapped it tightly around the piece multiple times until it wouldn't fall out. I snipped the wire off, leaving a bit of extra that I wrapped around the original loop.\nStep 2: Tying the Glass Together\nOnce all your glass cabochons are wrapped, lay them out in the order that you want them. Take your fishing line and hold it out against the line of beads (or whatever you want to call them). Make sure you cut more line than you think you need because you will be amazed when you find out that what you cut wasn't enough line (like I did, ha ha).\n* I know that the fishing line is hard to see in the photos, but that is the idea! I want an \"invisible\" line so that the glass pieces are what really catches your eye with no distractions.\nTake the string and thread it through the top loop of the first piece in your line of beads. Tie it to the loop with a simple knot, making sure to leave an excess of string above the loop. The extra string is for attaching the beads to the frame later, so make sure it is a good amount! Tie a second knot for security reasons ;), and add a dab of glue to the knots to make them hold (fishing wire is so bad about coming out of knots when you want it to stay and staying in knots when you don't want it to).\nTake the line and thread it through a piece of the bottom wrapping on the bead to attach it to the second stone. This is so much simpler than cutting it off and tying an extra knot to attach a second glass cabochon. Attach the second stone by tying it on the string wherever you want, then pull the thread through the bottom wrapping and repeat until you have all the beads you want tied on that line.", "972" ], [ "Mini Needle Felted Dog\nIntroduction: Mini Needle Felted Dog\nThis instructable will teach you how to make a fuzzy mini felted dog :)\nSupplies\n❀ Felting Needle\n❀ Felting Mat\n❀ Needlefelt wool (For mine, I used yellow for the fur, white for the chest, black for the eyes/nose and pink for the scarf)\nStep 1: Make the Basic Shape of the Head\nTake a tuft of needlefelt in the primary colour of your felted dog. Poke the needlefelt on the mat with the needle while rotating it regularly until it becomes a stiff ball.\nStep 2: Make the Body\nRepeat what you did in Step 1 (felting a ball) with two slightly smaller pieces of wool. Then felt the two balls together by poking through both of them until they become shaped like the dog's body.\nStep 3: Finish the Head\nNeedle felt a small ball, about half of the size of the first ball. Felt it onto the ball from the first step (the head). This will be the snout. Then felt two very small triangles (they don't have to be very pointy though). Poke the triangles onto the two sides of the top of the head.", "879" ], [ "(look at the pictures as a reference)\nStep 4: Attach the Head and Body Together\nFelt the head into the body by aligning the head and the body in the position you want, and then felting through both of them so that they stick together.\nStep 5: Add Legs\nFelt four small felted ovoid shapes as the legs on the bottom of the body. You can make them as long/short as you want, it doesn't matter.\nStep 6: Add a Tail\nFelt a loosely felted ovoid as the tail on the end of the body. You can make this as long/short as you want.\nStep 7: Add the Eyes and Nose\nAdd the eyes and the nose. Felt three very small balls of black needlefelt (the nose is bigger than the eye) and attach them as the eyes/nose. Alternatively, you can poke holes and use plastic eye attachments if you have those.\nStep 8: Add Fur Markings and Accessories (Optional)\nIf you want, you can add fur patterns with different colours of needlefelt. For example, I used a little bit of white wool to make the chest and belly white.\nYou can also make accessories. I used a long piece of pink wool to make a scarf for mine.\nStep 9: Now You're Done!\nAdmire your new felted dog! ૮-ᴥ-აฅ", "879" ], [ "Cross-Stitch Minecraft Earrings (Double Sided) (WITH PATTERN)\nIntroduction: Cross-Stitch Minecraft Earrings (Double Sided) (WITH PATTERN)\nThis guide will show you how to make any small cross stitch design you want into a double-sided earring! As an example, this guide uses a lava bucket from Minecraft, but any small (~18x18 or less) design should work. The pattern for these earrings are included, but the possibilities are endless!\nStep 1: Gather Supplies\nYou will need:\n* Clear Plastic Canvas, 14-Count\n+ This count is difficult to find in stores, so you will probably need to look online for some. It comes in white as well, so feel free to go with whatever colors you think work best!\n* DMC 6-Strand Embroidery Floss (For this design: 414, 445, 452, 648, 720, 742, 762, 3024, 3799, 3858, and White)\n+ These are the colors that the pattern uses, but feel free to substitute with whatever colors you have on hand.\n* Scissors\n* Needles and Any Other Cross-Stitching Essentials\n* Heavy-Duty Thread (not pictured)\n+ I use heavy-duty to be safe, and I use black because it's universal, but make the most of what you have. Regular sewing thread would also work, but embroidery thread should be avoided if possible, since it is designed for form over function.\n* 2 Fish Hook Earring Backs\n* 4 Jump Rings\n* Two Pliers\n* Cutting Mat & X-Acto Knife (Optional)\n+ You can get away with just using scissors, but if you have these they can definitely speed up the process.\nStep 2: Cross Stitch Your Design\nThis is the step where you cross-stitch your design on to your plastic canvas. Since this guide is specifically about the process of transforming designs into wearable earrings, this step will largely be glossed over, since there are already many fantastic tutorials on the internet to teach you how to cross-stitch, such as this one.\nThe pattern for the design I made is included in picture form above if you are interested in following along with the same design. It is included in both color and black and white, so you may use whichever form you prefer.\nSince these earrings are designed to be double-sided, the pattern provides the original design, and then the mirrored design as well. Since the outline of the lava bucket is symmetrical it doesn't matter that much in this case, but with other designs, it is important to cross stitch two original designs and two mirrored ones, in order to make sure that they will fit on top of each other.\nOne important thing to note when cross stitching is to leave at least one empty row of holes between each design, so the pieces can be easily separated later. For reference, you can see in the picture included above that there is an empty row of holes between all designs. If you forget to do this, you will run into trouble later, so remember to leave ample room between your designs!\nStep 3: Cut Out Designs\nAfter all of your designs have been stitched, you can start cutting them out! To start, roughly cut them out.", "981" ], [ "In this part of the process, the goal is to separate them from each other, you can focus on making them look nice in the next part. Scissors are the ideal tool, and you want to try to cut down the center of the holes. See the first photo above for reference of what you should have after this step!\nAfter your designs have been cut apart from each other, it is time to make them neater. Use either scissors or an X-acto knife to trim the shapes down so there is one square of plastic canvas on all sides beyond the design. Make sure to never cut into the cross-stitch. If you cut into it accidentally, it will free one of your stitches on one side, and while that piece is potentially still usable, it might not be up to your personal standards, and you may need to restitch one of the shapes. In my experience, you need more caution on this step if you're using scissors instead of an X-acto knife, but you must be careful either way.\nAnother thing you can try to do is to reduce the \"plastic-canvas\" look by shaving away the bumpy bits on the sides that you get when cutting something out of plastic canvas. You can see the results of me doing this in the second photo. While this technique does improve the appearance, it must be done with caution so the design is not destroyed.", "276" ] ]

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[ [ "Maximizing pruned branches in an alpha-beta tree\nPreliminary\nAfter doing some searches of similar questions posted here and elsewhere, i feel like this is the right place to inquire about, now let's get through some boring main notations...\n* A MiniMax tree is an arborescence structure generated by an AI role-playing game to simulate the opponent turns giving notes/scores to each of, and so each turn taken by the player itself, in order that a maximal value is chosen as the actual perfect step against the minimum value which represents the best step taken by the opponent.\nin the image above A is the player, B is the opponent, C4 is the best tack chosen using MiniMax.\n* First thing which would cross your mind, when chosing B1=3, B2=5, is it necessay to visit all child-nodes of B3?, of course the computer wouldnt act stupid if you code it to not be stupid, then it will stop at C8 then breaks the process, why? well that is called Alpha-Beta pruning, it cuts the C9 subtree and all its successors within the subtree B3 because it wont searcg any lower value than 2 when it does consider the maximum for A which must be forcibly bigger than 5. The all process is illustrated below for wiki-joint model.\nAfter thinking a while, I have deduced the presence of a system of mathematical inequalities that allows finding a structure of positive number labeled tree-leafs forming a tree that generates a maximal number of branch-pruning.\nLook here in this example in french, let us assign this data-configuration to terminal leafs ${6,7,1000,4,2000,3000}$ , 4 nodes (3 leafs in two subtrees) of this tree arent visited because:\n$\\begin{eqnarray} \\left{ \\begin{aligned} 7\\;>\\;6\\ \\ (1\\ branch\\ =\\ 1\\ leaf)\\ 4\\;<\\;6\\ (1\\ node\\ =\\ 2\\ leafs)\\ \\end{aligned} \\right. \\end{eqnarray}$\nSo as remarked that the inequality changes direction as long as we mount to higher levels of the tree.\nfrom that base, maximizing branch pruning can be achieved by assigning alternatively bigger than smaller values for specific ranges of leafs, regarding a symbolic binary tree as follow :\n|\n----------------------\n-------------- ---------------\n---------- ---------- ---------- ------------\n| | | | | | | |\nx0 x1 x2 x3 x4 x5 x7 x8\nAs a beginning rule, opting for the maximum from the tree summit underlies the nature of values selected from the base, which is the maximum in this case, this gives a system of inequalities helping us to exclude maximum number of leafs from being visited.\n$\\begin{eqnarray} \\left{ \\begin{aligned} x_2\\;>\\;max(x_0,x_1)\\ \\ (1\\ branch\\ =\\ 1\\ leaf)\\ max(x_4,x_5)\\;<\\;max(x_0,x_1)\\ (1\\ node\\ =\\ 2\\ leafs)\\ ...\\end{aligned} \\right. \\end{eqnarray}$\nNumber of leafs we excluded is $1+2$ , generalized to $(1+2^1)+(1+2^2)+....$ for binary trees defined in an infinite range of positive integers ]0,$\\infty$[ (with duplication).\nThe Question\nConsider that tree is also parsed counter-clockwise, and we want to maximize the unvisited leafs when we parse a n-ary tree both directions as an intersection of two unvisited sets , is there a way to figure out a general system of inequalities for that ? a closed form for the maximum in terms of $n$ the level of this tree ? a O(N) algorithm working along this ground to output a data-set of corresponding leafs?", "835" ], [ "Numerical Boardgame -- Help with with a pruning method (alpha-beta : minimax)\nI'm developing a simple AI to play a boardgame which consists of N x N squares, each with a predefined value.\n44 33 75 12 99 23\n53 89 14 01 32 98\n34 98 67 45 02 38\n89 87 54 21 34 87\n65 84 99 72 95 17\nEach player can either (a) instant claim an unclaimed cell anywhere on the board, or (b) rush an unclaimed cell from a cell already owned. In the case of (b), any enemy cells that are touching the newly claimed cell are converted to your side.\nExample:\n* Player 1: (1,1) -- {89}\n* Player 2: (3,1) -- {87}\n* Player 1: rush->(2,1) -- {98}\nIn the scenario above, after the rush move, Player 1 now owns all three cells (since (3,1) was an adjacent cell to (2,1)).\nI have the MiniMax algorithm working great for this. It's actually quite fun to watch the AI compete against each other. My problem is determining an effective way to prune moves from the tree.", "835" ], [ "I attempted a trivial pruning method of:\n- - If the cell we're claiming is empty\n- - - If the neighbors of the cell we're claiming is empty\n- - - - If the neighbor's-neighbor is an enemy-owned cell\n- - - - - Prune this move\nThe idea above being, we don't want to claim a cell that could immediately result in the opponent rushing towards us, claiming for themselves the cell we just claimed.\nThis didn't go well.\nI'm a bit at a loss for a decent heuristic for pruning moves at this point. Move ordering is a bit difficult because I can't just choose the highest remaining cell (can I?), since there are plenty of opportunities for the opponent to right-out rush that cell as soon as it's claimed. That is to say, if our opponent owns cell (4,4), it wouldn't be ideal for us to choose (4,2) since it could wind up being immediately rushed. But maybe it wouldn't hurt to start at the largest values and just test them out? I don't know.\nAny help here is greatly appreciated.", "835" ], [ "Constrained/Optimal Topological Order to enhance/reduce the performance/memory usage of other algorithms\nI originally posted this question here\nLets assume we have a highly connected directed acyclic graph (DAG, more edges then nodes). Since it is a DAG, we can retrieve a topological order of nodes to traverse the graph with different algorithms. Lets assume we want to traverse it in a dynamic programming approach to retrieve a specific statistic X.\nUsing the topological order, the dynamic approach would consume up to M much memory, which can be traced by a concept of opened nodes thorughout the traversal:\nBy iterating over the top. order, a node is open if it has at least one edge from a node which already was visited by the topological order. It is closed (or not open) if it gets visited.\nPseudo-Code:\nopened_nodes = list(Boolean(False)), #num_of_nodes)\nopened_nodes[top_order[0]] = True // Initial\npos_at_top_order = list(Integer, #num_of_nodes)\nfor each n, n_idx in top_order:\nopened_nodes[n] = False\nfor each edge in out_going_edge(n):\ntrue_list[edge.target = True\npos_at_top_order[n_idx] = sum_of_all_trues(opened_nodes)\nreturn pos_at_top_order\n(here for the topological order, it can be adjusted for the rev. Top. order)\nA goal here would be to reduce the memory usage M of the dynamic programming approach. To achieve this, the top.", "180" ], [ "order can be manipulated and with the Pseudo-Code we could somehow track, whether the top. order is better or worse then another.\nNow to my question: Is there a way to directly retrieve such a top. Order so that M gets minimal, or could this be a NP-hard (or NP-complete) problem? What about some hard limits like: only retrieve the top. orders where the M is smaller/higher then a set amount of memory usage.\nIs there any literature about such a \"optimization\"? Which search terms could be used to search for this e.g. in Scholar?\nI already tried some different generation methods of top. order (in total 9) All of them look similar to the curves in the figure: (here i used igraphs top sorting algorithm and <PERSON> algorithm with some variations. Not shown but i also tried: DFS- and some \"BFS\" approaches. This is a highly connected graph, containing 14207 nodes and 94113 edges.)\nAny input on this is highly appreciated!", "180" ], [ "Terminology:\n* polytope: the object we're talking about, it has dimension N.\n* face: a polytope of dimension N-1.\n* intersection (point): a polytope of dimension N-2\n* edge: a polytope of dimension N-3 Edge\n* volume: quantity in units^N representing encompassed space\nIn principle it's the same deal in any dimension.\n1) find intersecting faces and replace them with segmented versions\n2) procedurally delete all faces and points that are not part of the union (start with faces that are connected to faces whose inside face is facing an outside face)\n3) calculate volume with the irregular volume algorithm (subtract dimension-facing from non-dimension facing)\nIn detail:\n1) Intersectiong faces.\nA polytope of dimension N will have faces of dimension N-1 and intersection points of dimension N-2.\nIf ABC ZYX are two 2-polytopes AB and ZY intersect\nwe find the intersection I by equating the line through AB to the line through BC two times 0=ax+by+c\nThe new segments would be AI, BI, ZI, and YI.\nIf ABCD and ZYXW are two 3-polytopes ABC and ZYX intersect\nwe find the intersection IJ by equating the plane through ABC to the plane through ZYX two times 0=ax+by+cz+d\nand delimiting it by its intersection with the segments AB, BC, AC, ZY, ZX, ZX, and choosing the two inside points of the four valid points (1-2-3-4, 2 and 3 are inside points, 1 and 4 are outside points)\nthe contour line of all line segments can then be used to cut up the faces by various means, such as grabbing the intersegment corners and drawing segments to the surface corners (without segment (e2) overlap)\nIf ABCDE and ZYXWV are two 4-polytopes ABCD and ZYXW intersect\nwe find the intersection IJK by equating the space through ABCD to the space through ZYXW two times 0=ax+by+cz+dw+e\nand delimiting it by its intersection with the planes ABC, ACD, BCD, ABD, ZYX, ZXY, ZYW, ZXY, YXW, and choosing the three inside segments of the six valid segments (draw up possible polytopes and check whether all points not in the polytope are contained, these other points are your intersection segments)\nthe contour plane of all plane segments can then be used to cut up the bodies by various means, such as grabbing the intertriangle corners and drawing segments to the body corners (without triangle e3 overlap)\nIf ABCDEF and ZYXWVU are two 5-polytopes ....\nIf A and B are two N-polytopes and some $X=\\subset A$ intersects with some $Y=\\subset B$ we find the intersection I by equating $\\Sigma_{i=0}^{N} dim_i quant_i$ of X and of Y, and delimit it by the innermost intersection with the valid permutations of X and Y (which should be half of all intersections).\nAs you can see it's recursive.\n2) deciding which faces are extraneous\nAssign an extra quantity to each face maybe to decide whether it's facing in the direction of its normal or not. If the segmented neighbors' normals cross (or reach a minimum (they should cross)) behind the direction of the normals, then one of the two needs to go.", "7" ], [ "use a hidden variable process (such as systems of equations) to figure out which after you've crosschecked the entire neighborhood. then you can either keep all faces attached to \"essential faces\" or delete the disjoined ones.\n3) irregular volume algorithm\nyou should know this: take a face and its projection on one axis, and calculate its volume. add or subtract it from the total volume depending on whether the normal (modified by its modifier) points to or away from the axis.", "964" ], [ "Construction of fair teams\nlet's say we have a set of players that we want to match into teams of aproximatly same strength, so that no team is much stronger than another team.\nEach team consists of two players. One player is taking a defense position, another player is taking an offense position. The teams can decide for themself which of the players if playing at what position. We can assume that the teams try to win and will take the best possible combination of defense/offense player.\nEach player has an offense rating (e.g. discrete number between 0 and 10) and a defense rating (same scale) that describes how strong the player is in the offense or defense position.\nThe strength of a team is determined by the defense strength of the player in the defense position and the offense strength of the player in the offense position.", "12" ], [ "So we can assume:\nTeamStrength = max(PlayerADefense + PlayerBOffense, PlayerAOffense + PlayerBDefense)\nThe question is, what is a good algorithm to find teams of similar strength using above metric.\nMy thinking is that I can easily evaluate a single result by calculating an average team strength and build the sum of difference (square).\nBased on this it is obvious that I can just create random matches and then choose a \"good\" solution. However I'm curious if there is a way to find an optimal solution without brute forcing of all variants.\nAny ideas?\nEdit: There seems to be some confusion about the metric of optimal strength / average strength.\nThe goal is to have teams of similar strength, nothing more nothing less. Specifically I don't care if there are other combinations where the total strength of all teams is higher.\nI can imagine various metrics to achieve this goal. One idea I presented was to use the following metric:\nFor each team t calculate its strength by calculating:\nstrength_t = max(PlayerADefense_t + PlayerBOffense_t, PlayerAOffense_t + PlayerBDefense_t)\nCalculate the average team strength: avgStrength = sum(strength_t) / teamCount\nFor each team t calculate its deviation from the average squared and sum it:\nm = m + (avgStrength - strength_t) ^ 2\nm should be minimal\nI want to minimize the value $m$. I want to emphazize that I'm open to other metrics if they provide comparable results.", "12" ], [ "Miller Shuffle Algorithm\nIntroduction: Miller Shuffle Algorithm\nA new Shuffle algorithm that does not require a persistent data structure resource or give out premature repeats.\nShuffle algorithms are used for MP3 players, and games which deal out from a deck of cards, or some other set of one of a kind items like Boggle or Wordle does. Also by things like software that dole out practice exercise or test material to a student.\nWith the case of an MP3 player, or any play-list shuffle, one might and apparently some do (even on big name electronics and streaming services), simply use an operation like songIndex=random(NumOfSongs). This use of a PRNG will give you a good mathematical randomness to what is played. But you will get many premature repetitions of song selection. With a population of 1000 to choose from you will get ~37% repeats out of 1000 plays. From the start of a listening session on average a song will repeat within ~26 songs. The % of repeats is the same regardless of the selection population size.\nThe accepted goal of a “Shuffle” algorithm is herein defined as providing means to reorder a range of items in a random like manner, where each item is referenced once, and only once, when going through the range (# of items). So for 1-52 (think card deck) you get 52 #s in a pseudo random order, or similarly for a song list of 1000s. Re-shuffling gives a very different mix.\nThe Fisher-Yates (aka <PERSON>) algorithm has been a solution that fixes this unwanted repetition.", "242" ], [ "The 1000 songs play in a 'random' order without repeating. The issue this algorithm does come with is the added burden of an array in RAM memory of 2 times the maximum number of songs (for up to 65,000 songs 128KB of RAM is needed) being dedicated to shuffled indexes for the duration that access to additional items from the shuffle are desired (so as to not give repeats).\nBTW, working RAM is the most scarce and coveted memory resource (over that of non-volatile memory type storage). This is especially true when using a micro-controller like an Arduino. And as for a streaming service, it might have 100 million users each expecting to, on any day, resume playing from their shuffled list where they can step back & forth through the selections. So those shuffled lists must all be maintained. Further there may be a mix of 100 thousand users at a time actively playing. The service would have to pull into RAM & replace as needed the shuffle lists over & over on the fly.\nThe algorithm I present here (I refer to as the Miller Shuffle algorithm) provides basically the same beneficial functionality, as the FY algorithm, with a comparable level of randomness, but without the need of any array or upfront processing.\nBesides the presentation of the Miller Shuffle algorithm source code itself, the remainder of this Instructable will be dedicated to characterizing this new shuffle algorithm as well as comparing and contrasting it with other algorithms used to preform shuffle functions.\nSupplies\nFirst and foremost the crux of this Instructable is the software implementing the \"Miller Shuffle algorithm\". The software is provided here so you can then utilize it in your own personal project.\nAnd here it is:\n// --------------------------------------------------------\n// the Miller Shuffle Algorithm (aka: MillerShuffleAlgo_a )\n// produces a shuffled Index given a base Index, a shuffle ID \"seed\" and the length of the list being\n// indexed. For each inx: 0 to listSize-1, unique indexes are returned in a pseudo \"random\" order.\n// Utilizes minimum resources. As such there is no better choice for a playlist shuffle.\nunsigned int MillerShuffleAlgo_a(unsigned int inx, unsigned int shuffleID, unsigned int listSize) {\nunsigned int si, r1,r2; // randomizing factors, in combination provide ~million different shuffles\nunsigned int p=16183; // arbitrary prime #s must be > listSize\nunsigned int p2=6197; // p~=2.618p2 (not critical)\nunsigned int maxBin, halfBin, xorFlip, topEven;\n// compute reference values for later\nmaxBin=1;\nwhile ((2*maxBin+1) \"<\" listSize) maxBin=2*maxBin+1; // !!!", "242" ], [ "Stopping condition for goal-directed bidirectional search for shortest path\nSo I have a graph and need to find shortest path between two points in it. I need1 to do it it using bidirectional search. The bidirectional search should be goal-directed, i.e. A*.\nSo let $l(u,v)$ be length of the (oriented) edge $u,v$, $\\pi_f(v)$ the potential of vertex $v$ in forward search and $\\pi_r(v)$ potential of vertex $v$ in reverse search and $d(u,v)$ length of the shortest path from $u$ to $v$. Let $s$ be start vertex, $t$ goal vertex. The algorithm selects vertices by $d(s,v)+\\pi_f(v)$ forward and $d(v,t)+\\pi_r(v)$ reverse.\nLet's call $\\mu$ the length of the shortest path found so far, $n_f$ the vertex on top of forward queue and $n_r$ the vertex on top of reverse queue. I found two ways\n1. The obvious option is to stop forward when $d(s,n_f)+\\pi_f(n_f)\\geq\\mu$ and reverse when $d(n_r,t)+\\pi_r(n_r)\\geq\\mu$.", "835" ], [ "It is also not needed to process edges that were already processed in the other direction. Here the $\\pi_f$ and $\\pi_r$ are independent can be very specific, but the algorithm may need to continue quite long after the shortest path was actually found if the potential function is significantly underestimating.\n2. Create a pair of consistent potential functions as defined in this lecture. The requirements are given as $$\\pi_f(u) + \\pi_r(u) == \\pi_f(v) + \\pi_r(v)$$ for each edge $u,w$ (which really means the sum has to be constant over the whole graph). Without loss of generality we can make $\\pi_r(v) = -\\pi_f(v)$ and use the normal stopping condition from non-goal-directed search expressed as $$d(s,m_f)+\\pi_f(m_f) + d(m_r,t)+\\pi_r(m_r) \\geq \\mu+\\pi_r(t)$$ (assuming we shift $\\pi$ so that $\\pi_f(s) = 0$).\nThis allows easier stop, but the potential function has to only indicate whether $v$ is closer to start or goal and for vertex (equally) far from both will be the same as for vertex in the middle of the shortest path. Therefore it will be less specific.\nNow what I am looking for is:\n1. anything that would give me idea which would be more efficient (without having to implement both and test them) and\n2. whether the second can even be used if the heuristics is not monotonous, i.e. when $d(u,v) - \\pi_f(u) + \\pi_f(v) \\ge 0$ does not hold (the linked lecture assumes that, but not doing so could save me a lot of data and I/O is a bottleneck, so I would prefer not to even though it means occasionally having to reprocess vertex).\n1Some important optimization techniques can only be applied to bidirectional search.", "433" ], [ "Dynamic path planning and waypoint sorting\nGood evening everyone,\nI have a question that I am having a bit of trouble formulating properly and thus it is making it complicated to look up literature on the subject. What I am looking for is a name for a more general problem of the same nature, and I think it will have something to do with the title of this question, dynamic path planning and sorting.\nBefore getting into the details, I'll try to summarize the question as best as I possibly can:\nAttempted Summary\nIn a complete and weighted graph, which algorithm(s) should be used to continuously obtain a path which maximizes the reward obtained from visiting vertices if the rewards are dynamic and thus constantly changing?\nAnd now, a bit more context.\nProblem Statement\nSuppose we have a robot:\n* The robot is capable of autonomous movement\n* It is fitted with several sensors\n* The robot must patrol a set of locations L and gather data using its sensors at all of the li ∈ L\n* Some locations are more interesting than others, and may be worth visiting more frequently. What makes these locations \"more interesting\" is that data taken from these locations have a higher variance than the data taken from other locations. Also, it is important to take into account the time since the location was last visited. The longer it has been, the more desirable it will become to visit.\nThe goal is to properly schedule the order in which the different locations should be visited so that we can both maximize the information gain and minimize the energy expended by the robot, e.g: the distance traveled. We can assume the robot can move freely from any point and to any location, not just from location to location.", "103" ], [ "Also, the robot must gather data continuously for a period of time T, so the scheduling has to be done more than once.\nMy view\nTo me, it looks like this problem can be modeled as a graph. The vertices represent each of the locations that the robot must visit, and the edges have a cost associated to them which represent the distance that must be traveled. I believe the robot itself can also be modeled as a vertex in this graph, which has edges connecting it to every single other location. We can assume all locations are also fully connected between each other, since the robot can go from li to lj such that ∀ i, j ∈ L, however some of these pairs will not be desirable given the distance.\nSo we are trying to minimize energy expenditure while maximizing information gain. This part sounds like an optimization problem. If I can model the information gain or \"reward\" obtained from visiting each vertex, taking into account factors such as arbitrary importance of the vertex and variance, it might make sense to use a classical pathfinding algorithm, however I am not too sure how these algorithms behave when used against vertices whose rewards change over time (the overall reward of a vertex will be affected by the amount of time that has passed since it was last visited).\nI have also thought about modeling this as a linear programming problem, however I am not quite sure how to obtain a sorted set using this approach (of course I can get the best and worst locations to visit, but what about the order of the rest?)\nThank you for your suggestions.", "835" ] ]

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[ [ "Easy Home Compost Bin\nIntroduction: Easy Home Compost Bin\nBeing an avid gardener, I have always wanted to have a composting system for my home. Using leftover materials I had from previous projects and experiments I decided to make a compost bin and try it out to turn kitchen and garden waste into food for my plants.\nI hope you enjoy this Instructable and feel free to leave your comments and feedback in the comment section below.\nSupplies\nFor this project I used a piece of PVC pipe from my PVC Ram Pump and an old trash can that I used as an experiment for growing potatoes (It was not a successful experiment btw).\nThe pipe is 3\" in diameter and had the perfect height to fit inside the trash can with the lid on top of it.\nApart from the trash can and the pipe I used a drill and two drill bits: A step drill bit to drill the holes in the trash can and a 3/8\" drill bit for the holes on the pipe.\nStep 1: Bin Preparation\nFor the preparation of the compost bin what you will need to do is drill holes in the bottom of the bin for worms and beneficial fungi to enter and help in the composting process.\nAdditionally, you will need to drill holes in the sides of the bin and throughout the pipe for airflow, as you do not want the system to be anaerobic (without the presence of oxygen) as it will start to ferment and smell, and nobody likes smelly compost.\nMake sure to clean the holes properly as you do not want plastic shavings in your composting process.\nStep 2: How to Use It\nTo assemble and use your new compost bin what you need to do is position your pipe in the middle of the trash can and start filling the donut shape around the pipe with garden soil. The better the garden soil the less time it will take your bin to start working because your garden soil is where the worms and beneficial microorganisms come from.\nAfter putting the initial layer of soil, you can start filling your bin with green materials such as garden and kitchen scraps and then filling with newspaper or leaves or other type of brown material. By adding these layers in your compost you will generate a balanced ecosystem and avoid any anaerobic fermentation or smells.\nMake sure not to fill the inside of the tube as this will be crucial in maintaining airflow throughout your bin!\nStep 3: Finished Compost Bin\nOnce finished you can put your compost bin on top of your garden so that it fills up with worms and other beneficial microorganisms, in my garden when it rains worms tend to crawl up to the surface (to avoid drowning I suppose), so by putting the compost bin on top of the garden as a dryer place for them to live an eat I guess will be a great situation.\nWhen your compost starts to break down you can add more greens and browns and any compost tea can directly fertilize the spot in your garden where the compost bin is located, so no need to put anything to collect it as it goes directly into the soil.\nI hope you enjoyed my easy home compost bin build and make one for your home so you can be greener and make proper use of your compostable scraps.", "727" ], [ "Recycled Tennis Racket Fishing Net\nIntroduction: Recycled Tennis Racket Fishing Net\nI have been searching for a way to catch my fish and successfully land them without having the hook fall out of its mouth while bringing onto land. I have had ideas of making a net myself for many years but never came around to do it, until today!\nThe net should:\n* Be strong enough to hold a fish not exceeding 8 pounds,\n* Light enough to be carried around to locations,\n* Small enough to be incorporated with your tackle\nAfter a couple of hours of brainstorming and prototyping, I have found an effective way to make a fishing net that would actually work.\nIn this instructable, I will show how to make a fishing net as well as some tips while making it to improve the quality of the net.\nStep 1: Materials + Tools\nTools:\n* Drill (optional)\n* Drill bits (optional)\n* Scissors\nMaterials\n* Tennis racket (preferably and old one)\n* Yarn (40ft)\n* Fishing line (8-25 pound monofilament line) (5 yards)\nAll of these materials and tools can be commonly found around your house, or easily bought from the dollar store at a low price. If you are worrying about the drill and drill bits, don't, it is only necessary if you choose thick yarn that can't easily pass through the holes of the racket. I have found that thicker yarn and heavier line helps with structural integrity and is easier to land heavier fish but it makes the holes in between each line wider and more susceptible to smaller fish escaping. The yarn that I am using is quite old and is shedding a lot but should still make a great net.\nStep 2: Starting Your Project\nHave all the materials neatly organize to minimize mess. Start off by placing the racket in your designated workspace. Once again, I highly suggest using a tennis racket that is no longer of use and not cared about. Once you have you tennis racket, you have two options, either cutting the strings or taking off the strings without cutting them. If you choose to cut the strings, then be prepared for a little bit of a mess since there will be small chunks of line. This method is also easier then unravelling and it is the method I used. Use the scissors in this method to cut the lines. If you want to unravel the strings, just untie the knot that keeps them from falling back through the holes and start pulling the strings out one line at a time. This process may take some time but have patience. Whether you choose one method or not, it will not affect the outcome in any way.\nStep 3: Pulling the Yarn\nOnce the old tennis racket lines are out of the way, you can start passing the yarn through the holes. If your yarn doesn't fit, it might be because there are plastic covering the accompanied the holes the original lines went through.", "972" ], [ "If that is the case, then just simply rip them off. The ones on my tennis racket fell off already so I could skip this step. If you do that and the yarn still can't pass through because you choose thick yarn, then this is where you use the drill and the drill bits to widen the holes. Simply choose the right size drill bit, go with one that is just a little bit bigger than the yarn, and start drilling until you go completely through. Be careful since there may be some angled holes that might be difficult to get through. Once you start pulling the yarn through, make sure to leave some extra line through from the beginning. You should make the yarn line bow about 6 inches or more form the bottom of the rim. Make sure to not let the line tighten. This will leave us with an indentation so that the fish doesn't easily escape. Do this process until you are done with the vertical lines and holes.\nStep 4: Weaving the Yarn\nOnce you are done with vertically placing the yarn lines, we can start with the horizontal yarn lines. This is where most of your time will be taken up since there are more holes on this side. Repeat the same process that you did with the vertical yarn line, passing it through the holes. However, when you cross the vertical line, go over and under creating a weaving pattern through the vertical lines. This will help with the strength of the yarn. Remember to leave about 6 inches or however much you left of excess yarn line to create a pocket that the fish can sit in once you net it. I have found that the weaving pattern helps place the fish better and carry more weight that just laying yarn on top or below without weaving it in previous prototypes.\nStep 5: Knotting the Yarn and Tying the Fishing Line\nOnce you have weaved all of the yarn and it is in place, create buds or knots at the ends and beginnings of each strand of yarn to help it not fall back through.", "879" ], [ "Tabletop Sand Grill\nIntroduction: Tabletop Sand Grill\nHaving a small open tabletop grill can be a great centerpiece for any outdoor setting. When looking at the sand it almost takes you back to camping on the beach with a small campfire. I think guests are even more surprised to see it work. I was inspired to make this after visiting a Korean BBQ chain for the first time. It's really cool how you and your friends can all grill on a small tabletop grill rather than having to use a full sized one that only one person gets to operate. I infused this idea of Korean BBQ and a Edo Style Hibachi grill to create a extremely stylish and easy to make tabletop grill that is guaranteed to wow your guests when they come over.\nSupplies\nHere is what you will need to create a successful Tabletop Sand Grill\n* All-purpose Sand\n* A terracotta pot or terracotta saucer\n* Charcoal (preferably Lump charcoal)\n* 4 Terracotta Pot Feet (Will need more to lift your grill off the table if it is shallow like mine)\nOptional Items\n* Extra Terracotta Pot Feet to lift your Grill off of the table (I used custom made concrete feet)\n* A grill grate\nStep 1: Pour Sand Into Your Desired Container and Smooth It Out\nOnce you have your desired Terracotta Pot, (I used a 16 inch Clay Saucer, and a 6 inch Standard Clay Pot), pour your sand in pot. Make sure that the sand is at least a half an inch from the top of your container. This is to prevent potentially hot sand from spilling over the pot.\nOnce you have poured your sand in your desired pot, its time to smooth it out and make any design in the sand that you want. I used my fingertips to create wavy divots in the sand. This is just purely for aesthetic.\nDo this for all of the containers that you will be using. If your pot have a draining hole in the bottom of it make sure that you plug it up somehow. For my 6 inch Standard Clay pot I just used a piece of aluminum foil to cover up the draining hole.\nOnce you have all of your pots filled place them in their respective spots.", "34" ], [ "For example I placed my 6 inch pot towards the edge of 16 inch clay saucer.\n**Note: If you are using Pot Feet to elevate your grill off of the table make sure that you put them on before placing the sand in your pot.**\nStep 2: Place Your Grilling Supports\nAt this point you can use some of those Terracotta Pot feet to use as grilling supports. I placed two of them besides each other so that I could have more grilling space. I used four in total. When placing the terracotta Pot Feet in the sand make sure that they are deep enough in the sand that they don't fall over at the slightest touch.\nFor this part you don't have to use Pot Feet you could shape a piece of metal if you have the tools to do so. Just make sure that the metal will be food grade safe. There are also lots of other options that you could explore too, get creative!\nStep 3: Light and Place Your Charcoal\nLike any other grill you need some type of heat source. Light your charcoals like you would any other grill. I would suggest not using lighter fluid though and instead opt to use a charcoal chimney with some crumpled up newspaper or wax Firestarter.\nI used Pok Pok Thaan Thai Style Charcoal Logs which burn for a long time.\nStep 4: Start Grilling\nThe final step is to find something to throw on the grill. I used some thin cut Sirloin pieces that were marinated in teriyaki sauce.\nRemember that it doesn't just have to be a grill. Charcoal is just like any other heat source and can heat up other things too. For example I placed my teapot on the upper portion of the grill. After a while I even added a grill grate so that I could put one of my mini cast iron pans on there.\nGet Creative!", "34" ], [ "Easy Sawbuck Using 1 Tool and 2 Materials\nIntroduction: Easy Sawbuck Using 1 Tool and 2 Materials\nHere is a different way to make a sawbuck\n(a device for cutting firewood faster and easier).\nI like to build things that are very strong yet quick and easy. It will only take an hour or so to build.\nThis sawbuck is very stable and practicly impossible to tip over, it is also fairly easy to dismantle and to transport for setting up somewhere else. It will not take up much space when stored and all materials are reusable for other purposes.\nSupplies\nMaterials\n5 pieces of rebar\n10 inner parts of jack posts (shoring columns or see step 10 for info)\nTools\n1 auger with hollow handle for bending rebar\nStep 1: Pick a Spot\nSelect a suitable spot with good soil free from obstacles such as stones, pipes or roots. I selected a place in the garden where i have plenty of room to work, not too far from the house to drystack the firewood.\nStep 2: Drill Your 1st Hole and Measure\nDrill a deep enough hole, put the metal jack pole in the hole and measure the distance for the next hole. This is the distance of the length you want your firewood to be. In my instance i used the auger tool handle as a measure but you can use anything you like such as a logg or a foot or whatever.\nStep 3: Repeat Step 2 and Start a New Row\nContinue to drill holes at the same distance (firewood length) and insert the jack poles until you did half of your amount of poles. Then take a piece of rebar and use it to measure where the next row will be drilled. The rebar has to stick out from both sides enough so we can bend it (step5). Make sure to work in a straight and square pattern as much as possible.\nStep 4: Finnish Putting the Poles and Already Usable\nNow you have 2 rows of 5 poles in the ground and if you are in a hurry you can already cut firewood as is, but you would be working on the ground. This has many disadvantages such as dulling the chainsaw when touching the ground, bending your back too much and the sawn wood sitting in the same place as the unsawn wood.", "34" ], [ "So we will add rebar to enable us to work at chosen height.\nStep 5: Bending the Rebar\nInsert a piece of rebar into the holes of one of the jack poles (a corner pole works easiest). Now use the hollow handle of the auger tool to bend the rebar at one end in a 45 degree angle. Insert the rebar again with the longest side pointing up along side of the pole and use the auger handle to bend the short end sticking out into a U-shape.\nStep 6: Select Height and Push In\nSelect a height you feel comfortable with to perform your firewood cutting and push the rebar through the jack pole holes. Start with the straight end and see that the U-shape ends up in the next holes below the chosen height. This may require some wiggle and jiggle or some brutal force by hitting it with a piece of wood or so.\nStep 7: Bend the Rebar to Close at Other End\nTake the auger tool and use the handle to bend the rebar sticking out at the other end of the pole across and bend it down as much as you can so that it sits as close to the pole as possible.\nStep 8: Repeat and Finnish\nDo the same thing for the following poles and try to maintain the same height and lenght. The poles will tend to move a bit in the ground and the rebar will not be the same tightness everywhere but this is normal. When using it a lot it will settle into a solid configuration. Also the rebar wil bend a bit in the middle but this is normal.\nStep 9: Adjust and Ready to Load\nNow that all the poles and rebar are set you can still adjust here and there by knocking some poles deeper into the ground or by pushing them sideways. After doing this make sure none of the rebar sticks out in the gaps between the poles where you will be sawing. Now you are ready to load it up with wood and start cutting.\nStep 10: Extra Tips and Info\nBest is to wait for a couple of rainy days to drill the holes because the auger works easier in moist soil.\nYou can expand this with more poles or make it smaller with less poles, i just used 10 beause that is the material i had.\nI intentionally did not put any specific measures in the description since every country has its own standards for materials.\nWhen sourcing your materials you are not obliged to use jack poles and rebar if you find something that does the same or feels more usefull to you just go with that.", "21" ], [ "How to Turn Any Drone Into a Delivery Drone📦\nIntroduction: How to Turn Any Drone Into a Delivery Drone📦\nHello Everyone!!!\nIn this Instructable I am going to show you how I converted my (Commercial) RC drone into a drone capable of delivering parcels that uses a pulley mechanism that is controlled by the transmitter. I was very excited to publish this Instructable because it was a chance to push my limits and venture into a project that I had only dreamt of doing. I hope you find this as exciting as I do!\nWhy would I want to build a delivery drone from an Arduino?\nThere has been a lot of hype around the development and usage of delivery drones but where are they? Delivery drones have been the talk of the future because of how efficient and convenient they are. Drones are able to deliver products quickly to virtually any location, they offer a safer delivery system and they offer a higher level of efficiency. At a time like now drones have even become an important tool in fighting the COVID-19 pandemic by helping create more resilient supply chains and serving as the perfect device to deliver items from the recommended six feet away.\nThere is obviously a lot of work needed to develop an efficient and safe network for a drone delivery system. There are also a lot of disadvantages that come with using drones as a delivery system. Some of these disadvantages are that drones are still relatively expensive and they require a lot of technical familiarity. These disadvantages might be important to consider if we want to build a massive army of delivery drones but for hobbyists like you and I, we just want to have one of our own delivery drones. That's what I'll be teaching you to build today, a delivery drone capable of picking up and dropping off packages while still in the air! Let's dive into the project.\nSupplies\nThis is a list of all the main supplies needed for this project:\n* Arduino Nano\n* A Drone - I built my own FPV drone. Make sure the Flight Controller supports the PPM protocol and it supports Betaflight.\n* Radio Transmitter and Receiver\n* A Drone Battery\n* DC Motor\n* L293d Motor Driver\n* PCB Board\n* Arduino Uno IDE\n* Betaflight Configurator\n* An Old Shoelace\n* 2 x 4 Lego Brick\n* Lego Technic Axle Connector\n* Lego Technic Axle (size 4)\nThis is a list of all of the tools needed for the project:\n* Soldering Iron\n* Soldering Wire\n* Wire Strippers\n* Electrical Wires (Male - Male and Female - Male)\n* Multimeter (One that has a continuity tester on it)\n* Precision Screwdriver Set\n* Electrical Tape\n* Double Sided Tape\nStep 1: The Theory and the Idea\nThe Theory\nThis project uses a theory from a previous project I build where I controlled the drone solely from an Arduino Uno without the use of a conventional transmitter or receiver.", "120" ], [ "In place of the transmitter I controlled the drone from my phone using Bluetooth. This is the link to the project.\nThe theory behind the method in which the Arduino board sends signals to the drone is the same in this project and the current project you are reading, so read \"Step 1: The Theory and the Idea\" of this project before continuing with the rest of this Instructable. I consider the Bluetooth drone project the predecessor of this project because in the first project we were only sending PPM signals from the Arduino Uno to the drone without interpreting them, now we will interpret the PPM Signals and then send it to the drone.\nThe Idea\nGreat! Now that you understand the basics of PPM signals the rest should be quite easy to understand. The idea behind the project is to create a delivery drone that has a pully mechanism that can drop off and pick up packages while the drone is still in the air. The pulley system will be controlled by the same transmitter that is used to fly the drone using different switches and auxiliary channels. So how will we accomplish this?\nAs we saw in this project we used an Arduino Uno to replace the commercial receiver of the drone and send commands directly from the Arduino Uno. These commands directly translated to the ones my phone sent to the Arduino Uno via Bluetooth.\nWe now know that it's possible to send commands from the Arduino board to the drone but for this project we need to use both a transmitter and a receiver. It might be easier to refer to the diagram attached to understand the order in which the signal will be sent to the drone, but here is an explanation to help aid in understanding the order:\n1. The transmitter will send the input from the pilot to the receiver.\n2. The receiver will then convert the input from the transmitter into a PPM signal which it will send to the Arduino board.\n3.", "120" ], [ "Flowerpot Kamado BBQ\nIntroduction: Flowerpot Kamado BBQ\nIn this Instructable I show you how I made a Kamado style BBQ out of flowerpots.\nFor this project I used:\n* 1 top flower pot to function as a lid\n* 1 bottom flower pot as a base\n* 1 inner flower pot to put the charcoal.\n* a thermometer\n* a gasket\n* a hinge\n* scrap metal for vents\n* scrap metal for metal rings\n* heat proof paint\nSome basic tools, like power drill.\nI weld the metal rings but you can also screw them together.\nStep 1: Check Out My Video!\nI hope this video will help you create a flowerpot BBQ, or at least give you some inspiration for your own project. Along with the video I show you in the steps below how I dit it :-)\nVideo Link\nStep 2: Make Some Pits\nI start to make some pits in the pot to make it look more like a bbq instead of a flowerpot ;-)\nStep 3: Venting Holes\nThen I create the venting holes.", "34" ], [ "So later on it's easy to control the charcoal.\nI make 2 circles out of scrap metal and place them over each other.\nThis way we can open or close the vent.\nThen 1 drill holes in the flowerpot itself and install the metal vent.\nStep 4: Bottom Vent\nFor the bottom I make a sliding plate to function as a vent control.\nStep 5: Frame\nNow it's time to make the frame, so we can connect the top and bottom pot together with the hinge.\nI bend the metal strips around the pots and weld them together.\nAlso I make a wooden handle for the top lid, so it's easy to open it later on while hot.\nIn this step you can also just screw the circles together. If you don't have a welder.\nStep 6: Paint\nWith some heat proof paint, I paint the parts. Now it really starts to look like a Kamado.\nStep 7: Assemble\nNow the only thing left is to assemble the BBQ\nCareful to not tighten the bolds too much, otherwise the pot will crack\n(I had a small crack, it was easy to fix with some paint and dust from the terracotta drilling mixed together)\nAlso I attach the heat proof gasket, the thermometer and I put the inner pot with the mesh inside the pot.\nStep 8: Time to BBQ\nAfter the hard work now it's time to enjoy.\nThank you for checking out my Instructable :-)\nPlease also check out my youtube channel", "34" ], [ "From Bean Bag Toss to Captain America Shield Toss Game\nIntroduction: From Bean Bag Toss to Captain America Shield Toss Game\nThe whole point of this Instructable isn't to take a Captain America Shield and make it in to a bean bag tossing game. Its to hopefully inspire you to take something that you already have and make it your unique or add your own twist to it. We have made several versions of this same game using the original pieces but just changed a few things here and there and we can make it in to something different.\nGrowing up neither my wife nor I had a lot of birthday parties so now we like to go all out when it comes to our kids. Whenever we have birthday party for our kids we make it a themed party. We let our kids decide the theme and then we decorate accordingly to match the theme. The whole family gets involved because we like to try and make a lot of the decorations too or as many as we can. One of things we have come to be known for is out party games. My wife loves to have the kids play different party games for prizes. They play everything from sack races, to hula hoop contest, to limbo contest, these games are always a big hit with little and big kids alike. Since the party is themed we like to try and make the games themed as well. Sometimes its just a name change or we change one of the accessories of the game. For this build I decided to turn our bean bag tossing game in to a Captain America Shield tossing game.\nYou might be thinking I don't need to know how to reinvent a game for a birthday party but in this Instructable I will cover how to make a mold of a plastic toy then duplicate it. This could come in handy for replacing broken toy pieces or missing pieces.\nSupplies\nToy Shield\nDremel\nScarp wood or similar\nHot Glue Gun\nWooden Dowel\nCasting Silicone\nPressure Pot\nRazor Knife\n<PERSON>\nEpoxy\nEpoxy Dye\nStir Sticks\nSand Paper\nPolishing Compound\nStep 1:\nThis toy Captain America shield is from one of my son's action figures. He doesn't play with it anymore so he let me use it for this project. It has a small peg that I cut off using a Dremel with a cut off disc.", "726" ], [ "I could have left this on but it would have made the mold more complex than it needs to be.\nStep 2:\nI took some scrap pieces of a white board, it can be any scrap pieces or even corrugated poster board will work for this part, and made a open faced box. I used hot glue to make sure I sealed up all the edges to prevent any leaks. The box has to be big enough for the shield actually it has to be bigger than shield you want to leave about a 1/4 inch of space all around the edge of the shield as well as the depth of the shield.\nStep 3:\nSince this is the model that I will use to make a mold of I needed to make a pour spout so I took a 3/8 inch dowel and cut it to fit the edge of the shield then I used a hot glue gun to attach it to the shield.\nStep 4:\nThe shield needs to be suspended in the center of the box to make this work I drilled a 3/8 inch hole in the side of the box that would allow me to insert the 3/8 inch dowel. I secured it in place using hot glue.\nStep 5:\nNext I mixed up some two part silicone per the instructions and poured it in to the mold. You want to try and pour in the silicone from a corner and let it fill the all the voids slowly. Once the mold was full I put the entire box in my pressure pot. I pressured it up to 50 psi. and let it cure. This specific silicone cures in 30 minutes but I let it set for a few hours just to make sure it was set.\nStep 6:\nOnce is was fully cured I released the pressure in the pot and then removed my mold from the box and used my razor knife to cut open part of the mold. This is were I realized I probably should have made a two part mold instead. When I cut out the shield my razor went in too deep and created an imperfection in the mold you can see this in the last picture. If I would have made a two part mold this would not have happened. As they say live and learn.\nStep 7:\nI needed to support the mold vertically so I used some scrap plywood and made a mold holder. This is nothing fancy just something that will hold the mold vertically.\nStep 8:\nIt was time for my first attempt at making a duplicate shield. I used some Total Boat Epoxy that I had and mixed it per the instructions.", "254" ], [ "Cloning Carnivorous Sundew (Drosera Capensis)\nIntroduction: Cloning Carnivorous Sundew (Drosera Capensis)\nSundews are amazing, they just are, they break away from the standard image of plants most of us have. They capture and break down prey for food which is an alien idea for most plants. They help show the rich diversity of plant live we share our planet with. And they are just fun to watch, you could look on YouTube right now and find many satisfying time lapses of Sundew eating.\nThis instructable was made out of my love of Sundews and to show how anyone can easily clone new Sundews at home with minimal supplies.\nBut before we begin I want to preface this with saying that I am cloning or propagating a Cape Sundew (Drosera capensis). The processes I use in this instructable should work for most Sundews but some types can't be cloned through these methods or need small changes to these methods. So, there is a lot of room for experimenting with cloning these plants try lots of different ways and have fun with it!\nWith that out of the way lets dive into this instructable.\nSupplies\nScissors (or something like scissors)\nDistilled water\nSundew Plant\nPlant pot\nLighter\nSmall clear container\nCarnivorous plant soil (You won't need much)\nStep 1: Collecting Leaf Cuttings\nThe first step of course is getting leaf cuttings from your Sundew.\nTo begin flame sterilize scissors or other cutting tool with the lighter. Run the flame up and down the blades until it's at a good heat. There isn't any magic temperature or anything like that just heat the blades for a little, sterilizing the blades isn't a big step and in most cases won't hurt your cuttings if done wrong. Let your tool cool before moving on.\nNext we want to select a few leaves, I usually pick older leaves. You can tell which leaves are older by how much dew they have (older leaves have less) and if the tip is turning brown.", "389" ], [ "Take your scissors cut the leaves off, I usually try to get as close to the body of the plant as I can as I don't want to leave to much stem.\nAnd now we should have some leaf cuttings that we can take into the next step.\nStep 2: Preparing Leaf Cuttings\nNow we are going to clean up the leaf cuttings we just got.\nFirst I'm going to cut down the stem a bit more, as I find the stems don't propagate as fast. I will usually throwaway the stems but you can try to experiment with cloning from the stems.\nNext step we are going to remove the brown part at the tip of the leaf, I find that if you leave that part on it will sometimes spread to the whole leaf cutting.\nFinal step is to cut the leaves into small pieces, most of the time I'll just cut them in half but you can cut them in any way. You could cut them into fourths or any number of different ways, and from my experiments the number of cuts you make is the number of plants you will get. So, if you cut it into fourths you could get four plants.\nAlright now that we have our cuttings ready we can move to the next step.\nStep 3: Adding Cuttings to Water\nNow we are going to move the cuttings into a clear container. This container can be anything with my first propagation I just used a soda bottle. I've upgraded now and am using this nice little container I got from a hobby shop.\nNow fill your container with enough distilled water so that it will cover the cuttings. For my container I fill it half way just to be safe.\nOnce you've added water to your container you can now put the cuttings in. After I put the cuttings in I'll put the lid on the container and give it a couple shakes, this is just to make sure the cuttings stay hydrated.\nYour cuttings are now in a state where they can start to grow, YAY! Put the container in a warm spot that gets a good few hours of light a day or under a grow light.\nAfter that we can move on to the longest step.\nStep 4: Waiting\nNow we must wait, there isn't any set time that your cuttings will start to grow. They can start growing from two weeks to two months or even longer. The key here is to have patience, don't throw out the cuttings thinking they have gone bad as long as the cuttings keep a nice green color and don't go black or brown they are still alive.\nThe first sign of growth will be very small bright green tendrils coming out of the cuts on your leaves.", "408" ] ]

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[ [ "Nostalgia\nFor all the poetry and transcendence and desperate sincerity there also is something so sour about this movie. I mean there's a lot of bitterness in <PERSON> in general that the One Perfect Shot crowd doesn't talk about so much (thinking of <PERSON>'s first reaction to seeing <PERSON> in Solaris) but in particular the moment when <PERSON>'s tape player craps out before his, uh, big moment in Rome is almost unbearably cruel.", "698" ], [ "But funny, too! Or the long take of <PERSON> drunkenly rambling to a small Italian child... It feels like the scene in Lenny when <PERSON> is bombing, but this time the room is halfway underwater. Knowing the backstory of this project it almost seems like it should be a self-pitying disaster, but it's all just sadistic enough to follow me around all day like a dark cloud.", "549" ], [ "The Last Man on Earth\nCrazy about the first 20 minutes of <PERSON> just going about a \"normal\" post-apocalyptic day. Also really love the way this mushes together zombie and vampire iconography - not something I've seen before.", "475" ], [ "The rest of the movie is good but it has a certain level of self-seriousness that I just don't think I'm in the mood for. Was probably ruined by seeing and really enjoying The Omega Man first, in which <PERSON> makes <PERSON> look like a paragon of restraint and subtlety. Hard to go back to the comparatively respectable version once you've gotten attached to that.", "698" ], [ "Weird: The <PERSON> Story\nWhat gives this a leg up on Walk Hard is that it's not just roasting the biopic genre, but an actual biography. Yet this is burdensome, in a way: the movie is sort of doomed by the inevitability that the funniest thing about it will simply be the fact that it exists. That this is <PERSON> own version of a <PERSON> biopic is, on its face, very funny.", "952" ], [ "The movie itself is almost an afterthought, more amusing than hilarious, but the amusement value is pretty high—especially if you're a comedy nerd who likes playing spot-the-cameo. The other noteworthy business going on here is <PERSON> incredibly legit evocation of <PERSON>. The movie is all silliness but here's <PERSON> playing it like she's in a straight <PERSON> biopic (yet still sensitive to the film's humorous contours). <PERSON> deserves enormous credit as well for running full-speed at this absurd concept.", "585" ], [ "Fear and Loathing in Las Vegas\nFor as bombastic as this movie is, to me, it is the cowardly younger brother of Apocalypse Now. You know, the one that makes you stand behind him at the computer and watch youtube poop memes.\nEveryone clearly Showed Up to work for this film…production design is fantastic (as expected), <PERSON> is doing some great proto-Rango work…and <PERSON> is responsible for the singular emotionally effective scene in whole thing (at the diner).\nEverything else is flashy immaturity.", "475" ], [ "A <PERSON> aside that goes on for too long. A guy whispering nonesense in your ear while he is chewing something wet. <PERSON> is obsessed with spectacle and iconography and nothing much else underneath, which is maybe fitting for a movie stumbling around Vegas I guess whatevwerrrrreeeeeeee\nanyways time to watch legally blonde 2", "698" ], [ "Signs\nMy most notable Letterboxd review is a pan of Close Encounters. <PERSON>, who loves <PERSON> as we all do, wanted this to be his version of it. I think this one is way better.\nA broken man in an impossible situation relearns how to love and protect his family. <PERSON> crushed it with two great kid actors. Compared to a movie like Independence Day, this is basically a home invasion film.", "369" ], [ "It didn't have to be aliens, it could have been anything (except for the thematic reasons). <PERSON> is a tortured man just barely holding it together, which in retrospect turned out to not be a stretch for him. <PERSON> really didn't need to cast himself as the manslaughtering neighbor. Weirdly for a movie about an atheist preacher mourning his dead wife, this is kind of his funniest movie. It's really pretty cheesy but it works for me unlike Close Encounters.\nAlso, the shared memory people my age have of that footage of the birthday party being one of the most terrifying things in cinema is some sort of fever dream we all had. It's a tense moment but stop citing it as one of the scariest movie moments of all time.", "698" ], [ "Anatomy of a Fall\nI get why this is a Palme d'Or and why fans are falling over themselves lavishing praise on the movie. I do get it. It's great. The script is exceptional, the world (which was a mystery to me - The French courtroom I mean) is engaging and the performances wonderful.\nAnd I give it 4/5.\nIt just never hit me in the chest as hard as it seem to have for everyone else.", "462" ], [ "It never twisted up my mind or enraptured me with it's storytelling. It's an extremely well crafted movie and I'm having just as much fun with the after-discussions and \"theories\" on the plot as I did watching the film. I just never got that \"wow\" factor. Wish I had.", "596" ], [ "<PERSON>: Part One\nMore of a journalistic recreation of a Wikipedia article than a movie, but it kind of lands due to the magnitude of it all. It has no characters, just historical figures, but it works with the overall approach.", "698" ], [ "It’s meant to make you feel like a witness of history. <PERSON> embodies <PERSON> as much as he obscures him, feeding into the myth.\nHilarious how neither <PERSON> nor <PERSON> could stick with an accent for <PERSON>, but at least <PERSON>’s has been living abroad for a while. What’s <PERSON>’s excuse?", "585" ], [ "The Seven Year Itch\nKind of insufferable at the beginning with the Voice of God narration and <PERSON> unconvincingly uttering his every thought aloud for the audience's (supposed) benefit, and only mildly entertaining thereafter, The Seven Year Itch somehow manages to be passable. <PERSON> hated this film and said that it is meaningless if <PERSON> remains chaste (he doesn't in the play), but it's in fact precisely this fact that redeems the film.", "144" ], [ "Not for any moral reason, of course, but because <PERSON>'s <PERSON> is the most uncharismatic and irritating character imaginable and that, along with the presence of <PERSON>, means that we're looking at a male fantasy bordering on the self-aware.\nThis is a film about the typically masculine idea that one's confidence could make up for countless character flaws and allow you to score even someone as beautiful as <PERSON>—that is, if not for the stifling institute of marriage. It's a fantasy from start to finish, one that achieves self-awareness with \"wouldn't you like to know [who's in my kitchen]? Maybe it's <PERSON>!\" There is no reason for <PERSON> to sleep with <PERSON>, because his goal is merely to prove that he could have, to be assured that he would have made 100% of the shots that he didn't take. If <PERSON> had his way, or if the protagonist had a single redeeming feature, it would blunt the only edge the film has.", "698" ] ]

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[ [ "What's the meaning of the performance of I Will Survive at the end of Man On The Moon?\nMan On The Moon is the story of the career of <PERSON>.\nOne of the personas that <PERSON> sometimes adopted was <PERSON>, an obnoxious and terrible lounge singer. <PERSON> is an alter-ego for <PERSON>. In early scenes, when <PERSON> is not famous, audiences believe that <PERSON> is what he appears to be; but later, when <PERSON> is a celebrity, audiences understand that <PERSON> is a character played by <PERSON>.\nIn one scene, <PERSON> is on stage before an audience, and audience are enjoying the performance as a satire of some sort, thinking that the \"<PERSON>\" that they are seeing is really <PERSON> in disguise. But then <PERSON> joins <PERSON> on stage. The audience IN the film, as well as the actual audience OF the film, are confused how this could occur. A few moments later the film discloses that when both <PERSON> and <PERSON> are on stage together, <PERSON> is played by <PERSON>, a friend of <PERSON>'s.\nAs you might expect, <PERSON>'s funeral occurs fairly late in his career.", "295" ], [ "We see the funeral in the film, and in the next scene we see crowds standing outside a theater, and the message \"One Year Later\" is superimposed. The crowds cheer as someone arrives in a limo and emerges, clad in tux and with a bag over his head, and enters the theater. Then we see (obviously) this same person perform the song \"I Will Survive\" on stage -- and it's <PERSON>. Again the audience in the film is reacting happily as <PERSON> does his performance. Since we just watched <PERSON>'s funeral we suppose that <PERSON> is again being portrayed by <PERSON>. But then the camera moves around the room and we see <PERSON> in the audience.\nWhat is this scene about? Are we supposed to understand that after all this is the real <PERSON>, not played by <PERSON> or <PERSON> or anyone else? Did this event occur? Were this scene in the film, and the event it depicts, both supposed to feed rumors that <PERSON> was still alive, as the choice of the song \"I Will Survive\" obviously suggests?\nMy hunch is that this scene does not correspond to any real event but was intended as the sort of scene that <PERSON> would have wanted in the film, another attempt to bewilder the audience and destroy any understanding what is real and what is imaginary.", "918" ], [ "In the film Tootsie, what good does it do <PERSON> to disclose on-the-air that he is a man?\nIn the 1982 film Tootsie, the actor <PERSON> portrayed a character who is also an actor, <PERSON>. <PERSON> pretends to be a woman (\"<PERSON>\") in order to land the role of a female character in a soap opera. The trick works, and the character becomes an accepted part of the soap opera.\nBut eventually <PERSON> wants to tell everyone the truth and quit the soap opera. Various reasons are given for him to maintain the charade. His manager suggests that the disclosure would create problems for them in terms of business or in terms of legal liability.", "378" ], [ "And <PERSON> worries that his friend who auditioned for the same soap opera role unsuccessfully (despite being an actual woman) will be crushed to learn that he got the role, and a man who has proposed marriage to \"<PERSON>\" will be humiliated.\nOne day the cast of the soap opera are informed that part of the recording of the next episode has been damaged, and they will have to play a scene on live television. During this live performance, <PERSON>'s female character on the soap opera goes off script and delivers a long, strange story about her past, which somehow comes to <PERSON>'s removing his wig and female makeup, revealing during a live television broadcast that he is a man.\nIt seems like the film thinks that something is clever about this choice, but I cannot figure out what it is. It seems to be no better for the soap opera, which might have wanted to hide the facts about <PERSON> (and which is now by the way apparently forced to follow that live portion with the tape in which his character is still a woman). All of the problems identified earlier in the film -- bad business, legal liability and hurt feelings -- all seem as bad as ever.\nI feel like it's acceptable within the film to see it as an unreasonable choice by <PERSON>, who is under enormous pressure and just cannot maintain the lies any longer. But is there really no logical reason at all why he shouldn't have just stopped showing up at work, or told everyone the truth while off-camera?", "295" ], [ "What's with the \"one-sided\" dialogue scenes in Midnight in Paris?\nI re-watched <PERSON> Midnight in Paris last night. I noticed that during a lot of dialogue scenes with only two or three people, there will often only be one of the characters in the shot. It gave me the impression that those characters' lines were shot separately and then edited back into the scene, but I'm not sure that that's actually the reason why they are shot this way.\nAn example off the top of my head is the scene in <PERSON> salon when we first meet <PERSON>, the <PERSON> character. She is standing in the doorway of the salon while everyone critiques <PERSON>'s portrait of her. During her lines, she is the only person in the frame, and if I recall correctly she doesn't have any off camera lines, either.\nYou can almost see it in this video but it stops too soon.", "306" ], [ "(I will keep looking for a more demonstrative clip.) The rest of <PERSON>'s shots in that scene are framed exactly like that first shot of her, close in on her, with no other people in the shot and no movement from the camera. It gives me the impression that she isn't really a part of the rest of the scene, like we're cutting to somewhere else when we're looking at her.\nIs this a choice, or were there simply scenes that had to be re-shot later and so they ended up a little funky? I'm not a big <PERSON> buff - is this something that he does frequently? If so, what is the purpose of shooting specific bits of dialogue like this?\nUpdate:\nI found another clip that sort of demonstrates this. It's when <PERSON> first meets <PERSON> in the restaurant. I'm not sure this is the same cut that's in the film - I don't remember that long of a shot on <PERSON> when we first meet him and sit down at the table. But regardless of that issue, once we get into the scene, <PERSON>'s two lines (\"Rhinoceros?\" and \"complex situation\") are shot in the same isolated way as <PERSON>'s first scene.", "663" ], [ "Was the <PERSON>/<PERSON> transformation part of <PERSON>'s hallucination?\nI guess there isn't going to be a 100% proven answer, so I'm more interested in what possibility is most likely. In the answer on <PERSON> IMDB page to the question of whom <PERSON> slept with, the most likely possibility is suggested to be that he slept with <PERSON>, and the brief appearance of <PERSON> in <PERSON>'s place was just a hallucination.\nWhat troubles me about this explanation is that <PERSON> sees the same <PERSON>/Donna transformation when he is playing back the surveillance tapes in the police station. He plays and rewinds a hologram of the surveillance several times and still notices the same effect.\nHis hallucinations generally seemed to be random and brief, so I find it unlikely that he could have had the exact same hallucination both while: (a) lying in bed with <PERSON>/Donna, and (b) reviewing the surveillance tapes. Adding to (b), he didn't just see the transformation once while reviewing the surveillance tapes - the transformation coordinated precisely with his playing and rewinding of them.", "624" ], [ "It's not impossible for a hallucination to be that sophisticated, but it seems unlikely to me.\nOf course, if the <PERSON>/<PERSON> transformation wasn't a hallucination, this begs the question of what actually was going on. All I can think of would be that:\n! <PERSON> (who goes by the name of \"<PERSON>\" while in the scramble suit and who poses as <PERSON>) was wearing some high-tech <PERSON> disguise that briefly glitched while she was lying in bed with <PERSON> (who goes by the name of \"<PERSON>\" while in the scramble suit and who poses as <PERSON>). The glitch was responsible for the transformation, and this would explain why <PERSON> saw the transformation both while lying in bed with <PERSON>/<PERSON> and while reviewing the surveillance tapes. But then... why would <PERSON> sleep with <PERSON>? She seems very concerned about <PERSON>'s well-being when she drops him off at New-Path and later talks with <PERSON> about him (<PERSON> is another undercover agent who poses as a New-Path employee), but why sleep with him? Did she feel so bad for him that she would sleep with him? Or, was she in love with him?", "624" ], [ "Who is <PERSON> talking to in the limo? (s01e07)\nIn the early episodes, the show creators were very careful about putting Mr <PERSON> into scenes, but not having anyone other than <PERSON> interacting with him.\nIn later episodes, they break this pattern. In s01e06, v1ew-s0urce, <PERSON> and <PERSON> have a conversation in a bar about the Dark Army and <PERSON>. Later in that episode, Mr <PERSON> visits <PERSON> at his grow lab, and threatens him to get him to return to F Society.\nIn these scenes, are we meant to believe that it's actually <PERSON>, and not <PERSON>? If so, then it follows that in s01e07, wh1ter0se, it's actually <PERSON> in the limo with <PERSON> having this (paraphrased) conversation:\n<PERSON>: We’re meant to be allies.\nMr <PERSON>: I don't think there’s anything we can possibly agree on.\n<PERSON>: I know your dirty little secret.\nWhat is this secret? Is it about the F Society plan? Seemingly not (unless he's bluffing), because in the last episode (of season 1) he goes to <PERSON>'s apartment begging to know what's going on.", "663" ], [ "Additionally, there's nothing in the earlier episodes between <PERSON> and <PERSON> to suggest they're allied in some kind of plan. Again, in the last episode, <PERSON> tells <PERSON>, \"I told you we were meant to work together.\" I read that as counter to the idea they had previously agreed to be allies. And this banter is unlike any conversation <PERSON> and <PERSON> had before.\nAt this point in the season, it's not been revealed that Mr <PERSON> isn't real, so the show creators want us to believe there's some secret additional plot between Mr <PERSON> and <PERSON>. But it seems to me that this never pans out in any real way.\nSo we're left with:\n* This is <PERSON> and <PERSON> having a conversation, and it makes no sense with the rest of the plot.\n* This is <PERSON> having a conversation with someone else, who for some reason is also <PERSON>.\n* The conversation never actually occurred, and the show creators are just messing with us.\n* <PERSON> is also hallucinating Mr <PERSON>.\n* Since only <PERSON> can see <PERSON>, <PERSON> and <PERSON> are the same person (which makes even less sense than this scene).\n* The whole conversation is actually in <PERSON>'s head, and we see it because <PERSON> talks to us.\nPerhaps there are other possibilities I've not considered.\nWhat was the purpose of this scene, and to whom is <PERSON> actually speaking?", "663" ], [ "I think there are some hints in this interview with <PERSON>: http://www.avclub.com/article/milos-forman-13764\nFirst, I found this amusing:\nO: What about Hair? Did something particular draw you to the play?\nMF: Songs. I saw the very first public preview on Broadway of Hair, when I was here in 1967 for some sort of festival or something. I just loved every song. It's one of the three musicals in history in which every song is a gem.\nBut here he's talking about another film he directed, Taking Off. Notice what he says about hippies in their environment:\nI considered a portrait of these young kids, called hippies in those times. But what I discovered... I spent a lot of time in the Lower East Side, seeing these crash pads, and I found them very, very boring. On the other hand, when I talked to the parents of runaway kids, I found them much more interesting, because they were in panic.", "899" ], [ "They were doing things, they were trying to find their children, they were trying to understand their children. The children just spent their time lying in the crash pad, smoking pot and looking at the ceiling. It was very boring. That's why I turned the focus of Taking Off on the parents.\nSo now it's time to direct <PERSON>; is it likely he's going to retell the story he saw on stage, when he thinks (overall) their lifestyle is boring?\nI think instead he looked for ways to introduce conflict, and that started (with a classic Man vs Man) with <PERSON> meeting <PERSON>. And it's a good setup: a naive, fish out of water, law-abiding, soon to be soldier meets a gregarious, law-breaking, anti-war rebel. <PERSON> <PERSON>, our protagonist, thought he knew is being challenged.\nI agree with what you said about <PERSON>'s infatuation with <PERSON>, but some love interest was necessary in order to provide a reason for the trip to <PERSON>'s base. And also to provide the means to get <PERSON> shipped off to war. After all, it was <PERSON> being just a bit too clever and he lost this one.\nThe really big theme, for me, are the changes designed for the three main characters:\n* <PERSON> goes from naive to getting having his eyes opened\n* <PERSON> leaves the authoritarian high society and is free\n* <PERSON> for the first time in his life has to follow rules\nDespite <PERSON> saying, above, \"I just liked the music!\", I think he made the changes he felt he needed to make to keep the story interesting.", "627" ], [ "Ah, but the prologue doesn't spoil the ending of Romeo and Juliet! Take a look at those lines again:\nFrom forth the fatal loins of these two foes\nA pair of star-cross’d lovers take their life;\nWhose misadventur’d piteous overthrows\nDoth with their death bury their parents’ strife.\nSo these \"star-cross'd\" lovers will die to bury their parents' strife. Many of <PERSON>'s tragedies end with the main characters dying, so it's likely that the audience already knew that the main characters would likely die, and the prologue might be slyly hinting that they will \"take their [own] life\" (although that line clearly means \"take their lives [from forth the fatal loins ...]\", thanks @DLosc!), but doesn't tell you anything about why this death comes about. The audience knows something sad is coming, but they don't know what it will be yet.\nIn my opinion, this prologue sets you up to think that the suicide will be engineered by the lovers, perhaps of the \"if we can't be together, life isn't worth it\" variety. As you watch the play, however, things seems to get better and better for <PERSON> and <PERSON> while things get worse and worse for the <PERSON> and the <PERSON>: they meet! They fall in love! They get married! A cunning plan is hatched so that <PERSON> can run away from her family and be reunited with her husband! All this time, the audience is thinking, \"Wait a minute, this is a tragedy? And the prologue told me that they're going to kill themselves? How will we get there from here?\"\nAnd then, boom, a letter goes awry, <PERSON> decides to kill himself and, just like that, the audience knows where this is going.", "674" ], [ "Without the prologue, they would spend Act 5 wondering if <PERSON>'s plan can be stopped; with it, they are certain that his plan will succeed. This lends additional tragedy to the scenes of <PERSON> planning his death and Friar <PERSON> learning that <PERSON> doesn't know about the scheme, since the audience already knows that these schemes will fail, that <PERSON> will die, and that this will almost certainly lead to <PERSON>'s own death. I'd argue that, without the prologue, Act 5 could have been longer, with more potential interruptions to <PERSON>'s plan -- and further increasing the audience's hopefulness -- before a surprising finish. But <PERSON> opted to let the audience get ahead of the story, giving them a longer period of time to feel sad for the characters before their actions destroy their own lives.\nThis makes this more like the end of <PERSON> (where <PERSON>'s ghost tells the non-history-buffs <PERSON>' final fate, who then has time to reconcile himself to it), rather than the end of Othello (where <PERSON>'s plan succeeds right to the end, when it is unexpectedly revealed and some small sense of justice is restored). It's also a bit like an episode of TV where the teaser shows you, say, a street covered with the debris from an explosion, and the audience then spends the rest of the show trying to work out how that happened.", "190" ], [ "In the Yesterday Movie, what explains the changes to history other than the oblivion of the <PERSON>?\nIn the Yesterday Movie, a miracle somehow consigns the Beatles to oblivion. But it also produces several other changes that are mentioned in the movie without much explanation. Cigarette smoking seems to have been forgotten, and Coca Cola, and here and there a few other things.", "471" ], [ "Several musical groups that existed in fact are noted in the movie for their non-existence.\n* My take on all of this was that other changes resulted from the disappearance of the <PERSON>.\n* But my son, who saw the movie with me, thought that at least some of these changes were independent and not results of the <PERSON>' disappearance.\nNeither alternative seems perfectly sensible to me.\nWhy did they made those changes in the story?\nPOST-SCRIPT\nI just re-read this post (with comments and answers) long after the original post, and I'm struck with a perverse urge to clarify.\nIt seems to me that the Beatles' disappearance was a miracle to benefit <PERSON>, a struggling musician who is thinking of quitting music. This theory is what makes the movie emotionally satisfying: he needed a miracle, and he got one, \"and in the end\" he showed that the Beatles influenced him not just win wealth and fame (to his advantage) but also to tell the truth (at least seemingly to his disadvantage). And of course it also suggests something about the merit of the Beatles' songs that is very gratifying to their fans today.\nSo while the film-makers may have said that they're not interested in the mechanics of how an event could un-happen, I'm still interested in how these other changes make sense within the fantastic theory. It can't be that the film-makers intended to pose only the question of whether the Beatles' music would be popular under the circumstances of the film (introduced at a late date, performed thus, etc); if that were the only interest, there would be no relevance to the long introduction about <PERSON>'s struggles to make it as a musician and about how much it would mean to him.", "952" ] ]

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[ [ "In an ideal truss, this is actually true. As all members in an ideal truss are pin-connected (meaning the nodes cannot support any moments) the members themselves can only be loaded in compression or tension, not shear. Thus, they do not experience any moment either. There are 4 assumptions made for ideal trusses:\n1. joints are friction-less\n2. members are assumed to be weightless\n3. nodes are only at the ends of members\n4. all loads attack at nodes\nThese are some severe simplifications, but this can be accounted for by other means. The main reason why idealised trusses are/were used is because they facilitate calculations a lot.\nIf you have done some calculations on beams, you may know how complex things can get, as soon as you get into statically indeterminate structures.\nBefore computer allowed to solve complex statical problems with methods like FEM, simplified systems like trusses were of great help.\nIt must be noted that e.g. the nodes of truss bridges are not really constructed with pin supports, as this is not really practical for larger structures. Often the members are actually welded or bolted together in a way that doesn't allow rotations like an ideal truss would.", "333" ], [ "But with large enough safety factors, as well as a stiff enough design (steel comes in quite handy with an elasticity of $200$ $GPa$) the necessary rotation in the truss nodes is minimal.\nConcerning points 2 and 4 of the \"ideal truss rules\", this seems to be counterintuitive at first. But firstly, the normal forces modern I-beams for example can take is a multiple of its own weight. Furthermore, methods have been in use to approximate the weight distribution, such as the following: (This is just an example)\nHere, the mass of the entire truss $m$ is approximated by a uniformly distributed load $$q=\\frac{m\\cdot g}{L}$$, which is then replaced by point loads $Q$ at the nodes. $$Q=q\\frac{L}{5}$$\naddendum:\nFixing both supports of the truss creates the same problem as with a regular beam: It becomes statically indeterminate$^{[i]}$. Consider a beam, fixed at both ends. When this beam experiences a change in temperature it would want to contract or expand, however the two fixed supports prevent that from happening. Thus, resulting in tensile or compressive stresses.\nThis is the same for trusses. Note how the truss basically consists of triangles. Imagine one of the members experiencing an increase in temperature, therefore expanding. To allow this, the other two members of said triangles just rotate to allow for that expansion. Consequently no thermal stresses occur.\nIn statically indeterminate trusses this is however prevented by the fixed supports, or by the shape of the truss itself (see footnote $^{[i]}$).\n$^{[i]}$ Note that trusses can be statically indeterminate even when there are not two fixed supports. Basically any truss where you could remove $n$ members without the system collapsing is $n$-fold statically indeterminate.", "333" ], [ "In answer to the question Is the \"SWL\" for different profiles calculatable by a specific formula? - Yes, although it’s not one formula, there are lots of different things to consider, all with sets of formulae depending on the exact situation. Calculating Safe Working Loads (SWL) (or, indeed, starting from a desired working load and calculating the required structural member) is a large part of what structural engineers do.\nA beam can “fail” in many different ways. Most likely for your given case would be exceeding the plastic capacity of the beam in bending, such that a hinge forms in the middle of the beam, causing significant deformation which then pulls the beam off one of its supports. The plastic capacity of a metal beam is relatively easy to calculate, you can use the formula\ns = M/Z\nwhere s is the yield stress of the material, M is the applied bending moment, and Z is the plastic section modulus of your chosen profile.\ns is material dependant, so changing the material will change this. You can get various grades of steel, with yields from 230 to 260 MPa. Aluminium can be supplied with yields from 15 to 20 MPa.\nM depends on the applied loading.", "296" ], [ "In your case it is due to a force F applied in the middle of a 3.0m span, which gives a maximum moment of 0.75F. (Calculating bending moments is a whole separate topic).\nZ depends on your profile. Wikipedia gives some formulae for some basic sections. (Calculating section modulae is a big topic too).\nThis formula will give your theoretical maximum load, and not your SWL. The SWL also takes into account factors of safety, which are used to ensure that the applied load doesn't exceed the capacity. There are design standards which specify these factors (which standards apply depend on the situation).\nTo answer your headline question “How much strength does adding a T piece add?” - it all depends on the dimensions of the T piece. And, as alluded to by <PERSON>, as increase the depth of the T you run the risk of the failure method changing to lateral torsional buckling.", "296" ], [ "This is well-known theory in finite element analysis. There are two different effects that contribute to the effective stiffness of the structure in addition to the elastic stiffness $K_e$ given by Euler-Bernoulli-Timoshenko beam theory, and you need to include both of them to get the right answer.\n(1) Rotating the beam creates axial tension in the beam, which will be zero at the tip and increases to a maximum value at the rotation axis. This tension creates an additional stiffness that opposes lateral bending of the beam, in the same way that the tension in a guitar string affects its vibration frequency and hence the pitch of the note produced. (Of course in a guitar string, $K_e$ is negligible, unlike your beam).", "333" ], [ "This stiffness term was traditionally called the \"geometric stiffness\" (for reasons which aren't worth explaining) but a more logical name is \"stress stiffness\" often denoted by $K_\\sigma$, since it depends only on the internal stresses in the structure and not on the material properties.\nIncidentally, $K_\\sigma$ for a compressive stress is what causes <PERSON> buckling in columns. At the \"critical load\" for buckling, $K_\\sigma$ \"cancels out\" the elastic stiffness and when $K_e + K_\\sigma = 0$, the structure can't resist the applied loads. For tension stresses, $K_\\sigma$ increases the stiffness of the structure.\n(2) If the beam deflects from its original straight configuration, the direction and/or the point of application of the centrifugal loads changes.\nIf the beam rotates about a vertical axis and the beam deflects vertically, the CF load on each particle of the beam is still in a horizontal direction, and therefore the CF loads at the beam tip will create a bending moment that tends to straighten out the beam.\nBut if the beam deflects tangentially (for example while you are ramping up the rotation speed from zero) the direction of the CF load is radially away from the axis, and that generates a bending moment that tends to increase the bending of the beam, not reduce it.\nThe usual name for both these effects is \"follower forces\", because the direction of the applied loads \"follows\" the deflection of the structure. The corresponding stiffness terms are usually called the \"load stiffness\" and denoted by $K_L$.\nThe original equation for statics using only the elastic stiffness, $$K_e u = F$$ becomes $$[K_e + K_\\sigma(\\omega) + K_L(\\omega)]u = F.$$ In principle you could get expressions for $K_\\sigma$ and $K_L$ for a simple situation (e.g. a rectangular straight beam) but in practice it's much easier to use a Finite Element package that includes these effects.", "333" ], [ "Your procedure is correct, but you have made a mistake with the sign convention. Apparently you are using the same convention as I do, where a vertical load/force is negative, and an upward force is positive.\nConsequently, as you've written correctly $$ w(x)=\\frac{w_0}{L}x-w_0 $$\nYour mistake happens as you formulate the force equilibrium equation. With this definition of $w(x)$ you already comply to the sign convention. If you now formulate the shear force equation and write $$ V_1=15-\\int w(x)dx $$ you basically reverse the sign convention again. To formulate the force equilibrium equation you have to sum all forces, not subtract them, thus $$ V_1=15+\\int w(x)dx $$ which leads to $$ V_1=15+\\frac{5}{3}x^2-10x $$ which is the correct result.\nSign convention [edited]\nTake a look at your $w(x)$. It's a force pointing downwards, so it should be negative. You have written it as $$ w(x)=\\frac{w_0}{L}x-w_0 \\qquad \\mbox{for}\\qquad x={0...3}$$ Thus $w(0)=-w_0$, which means your load $w(x)$ is already defined in the coordinate system you specified.", "7" ], [ "If you now sum or integrate and add a minus sign in front of $w(x)$ you basically turn the downward load into an upwards facing load.\nConsider, e.g. $w(x)=const.=-w_0$, i.e. an evenly distributed downwards load, thus a negative value. It's easy to figure out, that the reaction at the bearing is $A_y=\\frac{1}{2} w_0L $. Now to find the shear force distribution, if we use your method, we'd write: $$ V_1=A_y-\\int_0^L (-w_0)dx=\\frac{1}{2} w_0L - (-w_0)L=\\frac{3}{2}w_0L $$ This is the wrong result, because for the shear force distribution calculation we suddenly switch sign convention (subtracting during integration instead of adding).\nIn the first part you said $w(x)$ was $w(x)=-w_0+\\frac{x}{L}w_0$, which goes linearly from $-w_0$ to $0$, which in your example would be $w(x)=\\frac{10}{3}(x-3)$. During your second calculation you managed to get the right result because you changed the sign convention of your $w(x)$, as you inserted $w(x)=\\frac{10}{3}(3-x)$ (which is an upwards load), but then you turned it downwards again by adding a negative sign in front of the whole term.\nI really recommend sticking to one sign convention. Either you say you sum all forces, and defined downward loads as negative, or you subtract downward loads from upward reactions.", "7" ], [ "By symmetry you know that the stress at each plane of symmetry must be perpendicular to the plane. Take two planes of symmetry at 30 degrees from each other to section off 1/12th of the hexagon. Now you just have a beam with a constant pressure and two point loads at the corners.\nSince the net force must be zero, the component of the force applied at the hexagon corner that is perpendicular to the beam, must cancel the force of the pressure on that beam.\n$$\\sin(30 deg)\\,F_c=P\\,a$$\nWhere $F_c$ is the magnitude of the force per container length at the corner, $P$ is the pressure, and $a$ is the length of half the side of the hexagon.\nThen the forces parallel to the beam must balance:\n$$F_m=\\cos(30 deg)\\,F_c$$\nNow we have the beam loading, so we can do a beam analysis:\n$$\\text{Shear stress}=P\\,x$$\n$$\\text{Bending Moment}=\\frac12 P\\,x^2+C$$\n$$\\text{Slope}=\\frac1{E\\,I}\\left(\\frac16 P\\,x^3 + C\\,x + D\\right)$$\nNow by symmetry we know the slope must be zero at the ends:\n$$0=\\frac1{E\\,I}\\left(\\frac16 P\\,0^3 + C\\,0 + D\\right)$$ $$0=D$$ $$0=\\frac1{E\\,I}\\left(\\frac16 P\\,a^3 + C\\,a\\right)$$ $$C=-\\frac16 P\\,a^2$$\n$$\\text{Bending Moment}=P\\left(\\frac12 x^2-\\frac16 a^2\\right)$$\nNow that we have the tension $F_m$ and the bending moment we can calculate stress on the inner and outer surface of the skin:\n$$\\sigma=-\\frac{F_m}{t}\\pm \\frac{P}{t^2}\\left(\\frac12 x^2-\\frac16 a^2\\right)$$ $$\\sigma=-\\frac{\\cot(30 deg)P\\,a}{t}\\pm \\frac{P}{t^2}\\left(\\frac12 x^2-\\frac16 a^2\\right)$$\nThis has a maximum of: $$\\sigma=-P\\left(\\frac{\\sqrt{3}\\,a}{t} + \\frac{a^2}{3t^2} \\right)$$\nNow we can compare this to a cylinder as an inscribed circle $a=\\frac1{\\sqrt{3}}r$\n$$\\sigma=-P\\left(\\frac{r}{t} + \\frac{r^2}{9t^2} \\right)$$\nThe first term, which comes from the tension in the beam is the same as the stress for the cylinder.", "333" ], [ "The second term, which comes from the bending stress dose not appear in the case of the cylinder as there is no bending. This bending stress will dominate the expression for thin walled vessels to the point were it is likely they would just deform until they resembled a cylinder.\nAs an added bonus this analysis works for any regular polygon:\n$$\\sigma=-P\\left(\\frac{r}{t} + \\tan(\\alpha)^2\\frac{r^2}{3t^2} \\right)$$\nWhere $\\alpha$ is half of the central angle of the polygon. As the number of sides increases, $\\alpha$ approaches zero as does the bending moment term, converging on the solution for the cylinder.", "333" ], [ "When the torque is applied the shaft twists. The twist gives rise to a reaction torque that opposes the applied torque. This is analogous to a spring stretching when a force is applied.\nWhen we integrate the differential equation along a uniform circular shaft of length $L$ we find that $T=-\\frac{JG}{L}\\theta$, which is analogous to $F=-kx$. The minus sign indicates T is the restoring torque by the shaft, which is opposite to the applied torque. The torsional stiffness of the shaft is $JG/L$.\nWe can treat each section of the shaft as a separate spring. The twist $\\theta_1$ in the spring on the left will give rise to a restoring torque $T_1$ and similarly for the shaft on the right. For static equilibrium, $T+T_1+T_2=0$. For physical continuity of the shaft, $\\theta=\\theta_1=\\theta_2$.\nA few things to be careful about when dealing with torsional shafts: First, sometimes the shaft is not uniform. It may have a sudden change in diameter or it may be tapered. Second, the shafts are coupled through gears, which complicates the analysis.", "333" ], [ "Third, when possible consider JG to be a single quantity. The calculation will often be simpler and easier to check when the J and G are always together. In other words, calculate the value a JG as a single value on the side and plug it into your formula in the end, if the shaft arrangement allows.\nFourth, here is a tip for how to remember the correct formula for the polar moment of inertia. What I remember is there are two similar formulas. One formula is for $I$, the moment of inertia used for circular beams in bending. The other is the polar moment of inertial, used for circular shafts in torsion. One formula is $\\pi r^4/2$ and the other is $\\pi r^4/4$. The formula for the polar moment of inertia is like $A(x^2+y^2)$ and is twice as much as the other one which is just $Ax^2$ or $Ay^2$. So, the polar moment must be the formula with the 2 in the denominator, because 1/4+1/4=1/2. Or, if one uses diameters, one can remember the denominators are 32 and 64 and then it its easy to know which is used in bending and which in torsion.", "333" ], [ "The statement of the question, using \"internal/external stresses\" is confusing. I don't understand what \"external stress\" can be here. You can have external forces but not external stresses. From the question elaboration, it appears to ask whether the internal state of stress affects vibration modes, yet the questioner's example of a \"tension line\" cannot change the internal state of static stress without altering the boundary conditions on the beam. Altering the boundary conditions will certainly affect vibration modes. In addition, an \"internal state of stress\" always exists in a material, whether undergoing vibration or not. It seems that the questioner is asking whether the \"static\" state of stress affects the modes, and static stress are internal stresses of motionless material. I suggest the questioner clear up these issues, and I'll give the answer to the simple question which I believe he really wants to ask: \"Does the static internal state of stress affect vibration modes of a beam\"?\nThe answer to that question is No, as long as the elastic limit of stress in the material is not exceeded. A different static state of stress can result in total stresses during vibration that exceed the elastic limit, which may affect the vibration modes.", "1018" ], [ "But the answer to that would be too complicated to discuss here. For purposes here, the simple answer is \"No.\"\nExplanation is that, first of all, vibration of a taught string is a different phenomenon, where the restoring (spring) force is the tension itself. With the beam, called a \"bar\" in vibration science, the restoring force is the elastic force, and even more, it's the change of elastic force, not the total (change + static), caused by the vibration. Static forces don't enter into the equations of motion. If you change the static situation, the dynamic changes of internal stress only occur about a changed mean value, and as long as the response is elastic (obeys <PERSON>'s law), the dynamic solution will not change.\nIn fact, we know very well that the static state of internal stress normally has no effect on vibration modes Most all hardened metals have some nonzero internal static stresses, and we are not concerned with them when we calculate vibration modes in such materials.\nFor instance, with 1095 Swedish spring steel, there can be residual internal stresses in high temperature quenching during the hardening process that are not eliminated by sufficient uniform annealing (tempering), and that doesn't affect the vibration of a cantilever made of such material. Such a device is used as sound source in free reed musical instruments, and makers aren't directly concerned with the internal state of stress in the reeds they make. Now, there are complications when you consider other practical effects, such as metal fatigue and breakage. Fatigue can occur over many cycles when stress levels are even below the elastic limit, a static concept. There is also an \"endurance limit,\" which is below the elastic limit, above which fatigue lifetime is greatly reduced.", "333" ], [ "Estimate the reaction force on each leg of a 4-legged table\nAssume you have a table with four legs with a weight placed somewhere inside the boundary created by the legs. The task is to determine the reaction force at each leg. Here are the problem constraints...\n1. The sum of the four reaction forces must equal the total weight set on the table.\n2. The table has no weight of its own.\n3. You cannot directly solve for the reaction of each leg using sum of forces and sum of moments because the structure is statically indeterminate.\n4. We are not allowed to introduce deflection in order to develop a 4th independent relationship between the four reactions\nThere are methods to estimate the reaction force on each leg.", "151" ], [ "One such method uses ratios to determine the four leg reactions.\n\\begin{eqnarray} P_1 & = & \\left(\\frac{y_w-y_b}{y_f-y_b}\\right)\\left(\\frac{x_w-x_l}{x_r-x_l}\\right) \\ P_2 & = & \\left(\\frac{y_w-y_b}{y_f-y_b}\\right)\\left(\\frac{x_w-x_r}{x_l-x_r}\\right) \\ P_3 & = & \\left(\\frac{y_w-y_f}{y_b-y_f}\\right)\\left(\\frac{x_w-x_r}{x_l-x_r}\\right) \\ P_4 & = & \\left(\\frac{y_w-y_f}{y_b-y_f}\\right)\\left(\\frac{x_w-x_l}{x_r-x_l}\\right) \\end{eqnarray} Here is my question. The above solution is only good for a square leg configuration.\nCan this method be modified to work for a trapezoidal leg configuration, like this? Better yet, can this method be modified to work for any leg configuration?\nEdit 1\n<PERSON>, This is in response to your answer. Please forgive me. It's been 15 years since I've worked with summations and linear algebra. I'm having trouble solving the two torque equations for $\\psi$ and $\\varphi$. Please look at what I have below and let me know if I'm on the right track. First I found $F_i$ using your second equation.\n\\begin{equation} F_i=-\\frac{W+k(\\psi(x_i-x_w)+\\varphi(y_i-y_w)}{3k} \\end{equation} Now I substitute this into your two torque equations and attempt to solve.", "151" ] ]

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[ [ "Pi Pie Necklace Charm\nIntroduction: Pi Pie Necklace Charm\nLike with every project, the first step is to gather the materials. For this charm, I used oven-bake polymer clay. Make sure that the clay you use is able to be baked in the oven (sculpting clay will simply melt).\nTechnically, you don't have to use the liquid clay, gloss, or chalk. It really just depends on the detail you want to include in your charm. You can also use toothpicks in place of a needle point tool.\nSupplies\n* tan, red, light purple, and black polymer clay\n* sculpey liquid clay\n* sculpting tools (needle point, ball point, and flat edge tips)\n* wire for charm loop\n* pliers for cutting/shaping the wire\n* necklace chain/ribbon\n* gloss coating (sculpey brand or clear nail polish)\n* small tipped paint brushes\n* brown chalk\n* Oven or Craft Oven\n* Super glue\nStep 1: Shaping the Base of the Charm\nFirst, with the tan clay, roll the clay into a cylinder shape. Then, roll the cylinder at an angle to make a more trapezoidal cylinder. This will create the back angle that will better resemble an actual pie shape.\nOnce the shape is to your liking, take the side of the needle tool and create indented lines across the outer edge of the clay. Do this around the whole edge. Once your done, go back over each ident and continue the indent over the top of the pie. You don't have to go far, just far enough to show the divisions in the crust.\nFinally, with one of the ball point tools, I created indents in the center of each section on the top of the pie to add in some more detail.\nOnce you've completed that, lightly smooth out the indentations with your fingers to soften the look.\nStep 2: Adding the Pie Filling\nNow that we have the pie base, we have to add in the filling. I mixed together red clay with a bit of purple and black in order to create a more realistic berry color.", "95" ], [ "Then, in order to make the filling more malleable, I mixed in some liquid clay until I was happy with the texture. The liquid clay will soften the clay and make it easier to manipulate, but be careful not to add in too much, otherwise it will become sticky.\nAfter getting the right consistency, I placed the filling in the center of the crust base, then spread it out and roughed it up with the flat edge tool to give it texture. Finally, I went back over with a ball point tool to soften some of the rough edges.\nStep 3: Adding Pi\nNow to officially make this a pi pie, we have to add pi! I rolled out a bit more of the tan clay to a width I was happy with, then cut three small pieces off, shaping them slightly into the shape of each section of pi before placing them in the center of my charm. The clay pie filling should help keep the pieces in place due to the liquid clay mixed in, as it sort of acts as a bonding agent.\nOnce I was happy with their placements, I took the large ball point tool and flattened the top, using a needle tool to better shape it into a more accurate symbol.\nStep 4: Adding Digits\nAfter finishing pi, I wanted to add the digits as well, to make the charm a bit more fun. I rolled out the tan clay to an even smaller width, then cut pieces and placed them around the edge of the pie filling. I used a smaller ball point and the needle point tools to shape the numbers.\nStep 5: Adding the Charm and Detail\nTo officially make this a necklace charm, we need some way to attach it to a necklace. I used the pliers to cut off the loop of a piece of jewelry wire, but if you don't have one of those, you can also shape a loop on any piece of wire using the pliers. Just make sure to leave some wire to fit into the charm!\nI inserted the wire into the top of the charm, lining it up so it is above the 3 so when worn, pi and it's digits will be positioned correctly. Finally, I took one of the small paint brushes and dragged it lightly across the brown chalk. Using this brush, I dusted the edge of the pie crust to add a bit of browning to the edges to make it look baked, as well as a bit on pi and the digits to give it a similar look.\nStep 6: Baking and Finalizing\nOnce the shading is completed using the chalk, the charm needs to be baked so it keeps its shape. Heat up an oven to 275 degrees Fahrenheit, and when to temperature, place the charm on a tray to bake.", "69" ], [ "<PERSON> (Legend of Zelda Inspired) Earrings\nIntroduction: Silent Princess (Legend of Zelda Inspired) Earrings\nI didn't grow up with video games, so I was surprised by how far down into the Legend of Zelda fandom rabbit hole I had fallen after picking up a copy of Breath of the Wild. These earrings were inspired by the endangered silent princess flowers from that game.\nSupplies\nPolymer Clay, in colors:\n* white\n* green\n* yellow\n* light blue\nYou will also need:\n* blue/teal pigment (I'm using a powdered resin dye)\n* bakeable adhesive for polymer clay (here I use Sculpey Bake and Bond). In this tutorial, I will refer to it as liquid clay, although it is best to not use products labeled as liquid clay as it is too thin and your flowers can move around before you get a chance to cure the clay.\nEarring Findings:\n* Wire Hoops (here I use \"ear wires\" that I got at Michael's craft store)\n* Earring hooks and jump rings (or, if you find similar hoop findings as I use here, you can use stud earrings)\n* Beads (optional)\nTools:\n* Needle Tool\n* Craft Knife\n* Thin paintbrush for the pigment (I prefer to use nail art brushes)\nStep 1: Prepping the Earring Findings\nHere we will make a base to stick the flowers to the earring wire:\n1. Take a small amount of the green clay\n2. Coat one side of your earring hoops with liquid clay\n3. Roll out the green clay and wrap it around the wire, smoothing it out so both ends of the clay taper off to better blend with the wire findings\nStep 2: Flower Petals\n1. Roll out your white clay\n2. Use a craft knife to cut out petal shapes. You will need 5 per flower, but it is better to have extra in case any become mishappened or tear. The extra will also be useful later on.\n3. Add veining texture using a needle tool\n4. Pick up a small amount of blue pigment with your paintbrush, and dust the bottom center of each petal, as pictured\nStep 3: Putting Together the Flowers\n1. Create a base for your flower by taking a small ball of white clay and adding a dab of liquid clay on top\n2. Gently pinch together the bottom of each petal (this is optional, but you will get a slightly different look to your flowers. These photos show both how the flowers will look pinched off and not, so this is up to your own preference)\n3. Use your needle tool to pick up and stick each flower petal in place onto the small ball of white clay\n4.", "95" ], [ "Once all the petals are in place, gently curl back the tips of each petal. It is helpful to do this over your needle tool.\nStep 4: Flower Sepal\nThe sepal is made similarly to the flower petals, but with a few alterations:\n1. Roll out a sheet of green clay\n2. Cut out leaf shapes, making sure they are thinner and longer than the petals you cut previously\n3. Take a small ball of green clay to create a base, and add a small dab of liquid clay\n4. Place each leaf shape onto the base, arranging them into a flower shape [optionally, you can flatten the edges of each leaf before placing them to minimize the harsh cut edge from the craft knife to make the leaves seem more natural]\n5. Gently curl back each leaf, as you did with the flowers\n6. Add liquid clay to the center of the leaves, and place the flower over top. Arrange this so each leaf peaks out from between each petal.\nStep 5: Stamen and Pistil\nTo create the stamens:\n1. Roll out tiny balls of light blue clay (these are around <1 mm in diameter)\nTo create the pistil:\n1. Mix a bit of white and green clay to create a light green\n2. Roll out a thin snake of clay\n3. Cut a stubby log, around the length of two small stamen balls (~1.5-2mm)\nTo make the stigma (the top part of the pistil):\n1. Roll out and gently flatten a ball of yellow clay, and use the needle tool to add texture so it looks like three pill-shaped bits of clay stuck together\n2. ALTERNATIVELY: roll out three tiny pill-shaped balls of yellow clay and gently shape them together [this is easier if your flowers are larger than the ones I make here]\nTo put it together:\n1. Add liquid clay to the center of the flower\n2.", "987" ], [ "Purple Color-Changing Pajama Squid Figurine\nIntroduction: Purple Color-Changing Pajama Squid Figurine\nI've been making these baby squids for years and recently wanted to make them temperature-reactive. When I found out their colors could range to a purple-brown, I just had to use some purple pigment in them! If I were to remake these, I would use a colorless-to-purple pigment instead of purple-to-pink. I made a more fantastical version of them with colorless-to-blue pigment to test how it might look. These work great just as figurines, or can be attached to jewelry findings to make pins or pendants.\nSupplies\nFor this project, you will need:\n* Translucent polymer clay\n* White polymer clay\n* Temperature-reactive pigment. This can be substituted with UV-reactive pigment.\n* Liquid clay or Bake-and-Bond\n* Black micomarbles (these can be found with glitter or nail art supplies)\n* Xacto knife\n* Needle tool\n* Dotting tool\n* Blending tool\nTIP: To keep your white clay looking cleaner from dust and lint, mix equal parts of white and translucent together. I find that the brightest white clay is Premo frost white glitter, which is used here.\nStep 1: Making Color-Changing Clay\nFlatten a disk of translucent clay\nMix a bit of liquid clay and color-changing pigment in the center of the translucent, and fold within the clay\nKeep mixing until the pigment is uniformly distributed\nSet aside a bit of the purple clay for the eyes\nShape the colored clay and white clay into equally-sized rectangles\nStack the two colors\nStep 2: Creating a Stripe Clay 'cane'\nFlatten the clay, keeping it in a rectangle shape\nCut the clay in half, and stack the halves, creating 4 layers\nFlatten and repeat\nStep 3: Creating a Stripe Cane\nKeep cutting and stacking the stripes until you have enough layers. Be cautious of creating too many layers or the colors will blend together and loose the stripe pattern.\nRemember to keep shaping the clay into a rectangular cube to create a cane.\nStep 4: Creating the Body\nSlice your cane into sheets and select the best looking slices.\nReserve a lesser-perfect looking slice for the arms.\nStep 5: Creating the Body\nTake one of the imperfect slices and form it into a dome.", "994" ], [ "This will fill out the body shape\nPlace a stripe sheet over the body, and shape it around the dome. Round out the top corners.\nUse a dotting and blending tool to create small ruffles around the top of the pajama squid.\nStep 6: Adding the Arms\nTake the sheet of clay reserved for the arms and slice it in half.\nSlice this half and split it into 10 parts: 8 arms and 2 tentacles (here I only made eight)\nRoll out these parts to a taper on one end\nStep 7: Shaping the Appendages\nBlend each arm to the body.\nCurl up the ends of each arm.\nIf the there is difficulty sticking the clay together, add a bit of liquid clay to help blend the arms to the body.\nStep 8: Adding Eyes\nUse the dotting tool to create eye sockets.\nFill the sockets with liquid clay.\nTake the bit of purple clay reserved from earlier and roll it into two equal sized balls. Place the balls into the sockets.\nStep 9: Eye Details\nUse a needle tool to create a place for the micromarbles - this helps with keeping it from sliding in the liquid clay.\nCoat the eyes with liquid clay.\nAdd one micromarble to each eye.\nSet your pajama squid aside to bake. I use an index card over a small silicone loaf pan.\nStep 10: Baking and Finishing\nBake according to your clay packaging directions. Typically it tends to be around 275°F or 130°C, but be sure to read the directions on your clay specifically. Sometimes I use a clay that bakes at 120°-130°C, slightly lower than the regular temperature.\nhint: Be careful to bake your clay thoroughly. Under-baking causes crumbly clay! Also watch your oven and beware of burning!\nOnce your piece is completely cured, add a few layers of gloss glaze, and you are done!\n[once it is edited, I will embed a video of the squid changing colors in ice and warm water]", "987" ], [ "Tiny Fairy Garden Gnome\nIntroduction: Tiny Fairy Garden Gnome\nRecently I have been fascinated with making miniature dioramas. One of my favorite decorations to use are garden gnomes. Today I will be showing you how you can sculpt your own gnomes out of clay.\nSupplies\nMultiple colors of polymer clay\nCutting blade/tool\nCorn Starch\nNeedle tool\nSculpting tools\nOven\nAluminum Foil\nAluminum pan\nOptional:\nPolyester Stuffing\nStep 1: Selecting Clay Colors\nFor this gnome I selected 4 different colors of clay. I sliced off each color and conditioned them by rolling it between the palms of my hands. If you have any clay that is tough or crumbly, you can use a little bit of clay softener to help.\nStep 2: Sculpting Hat and Shirt\nThe gnome's outfit will be brown, roll the clay into an oval shape. You can use corn starch when sculpting clay to help reduce finger prints and to keep the clay for being too sticky.\nCut a third of the oval off to create the hat. Pinch the top of the circle to create a triangular shape. Pinch the rim of the hat to create wrinkles and bends.\nStep 3: Add the Sleeves\nTo add sleeves to the shirt use a blade out a space for them. I used the turquoise color to add a little pop into the outfit. Make sure to blend these pieces together using the stylus tools or even your fingers.\nStep 4: Beard and Facial Features\nTo create the beard I used white clay.", "994" ], [ "Cut a jelly bean shape and small cylinder. Place the jelly bean piece on top of the shirt and then place the small cylinder in the center above it. These will be used to create the beard and mustache.\nFor the nose sculpt a tear drop shaped cylinder and two small balls for the cheeks. I used a light peach color and blended the nose and cheeks.\nStep 5: Put on the Hat\nTo attach the gnome's hat I scraped the two connecting surfaces, to create a better surface adhesion. After blending the hat to the head, you can add detail to the beard. Using a thin tool, I created hairlines into the beard and added texture.\nStep 6: Adding Extra Texture\nAfter revising the hat and reviewing the beard, I added texture to the hat to create a look of fabric. I used the texture of one of my tools as a roller and placed it randomly throughout.\nStep 7: Bake It\nTo baked your gnome you will need to follow the instructions on the clay package. I used SCULPEY III\nBake at 275 °F (130 °C) for 15 minutes per 1/4 in (6 mm) thickness.\nTo keep the clay from burning I add polyester filling to my aluminum tray, this allows the clay to bake while still being supported. Use aluminum foil to cover the tray so the heat remains even throughout.\nStep 8: Enjoy Your New Gnome!\nWait for the gnomes to cool and then you are ready to go! Create different variations and variety's of these little guys and you can have a whole army of mini gnomes. They make for great decorations for miniature indoor gardens or just decoration by themselves.", "987" ], [ "Modeling Chocolate Unicorn Cake Topper\nIntroduction: Modeling Chocolate Unicorn Cake Topper\nModeling chocolate is a great medium for sculpting adorable figures to decorate cakes! Modeling chocolate is made from melted chocolate and corn syrup, mixed together for a moldable, edible clay that can be colored and shaped. It hardens when it sets, so the figures are perfect for cakes or cupcakes. I will show you how to make the modeling chocolate using white candy melts and corn syrup, but you can also buy it ready made if you prefer. Then I will show you, step by step, how to make this sweet unicorn.\nSupplies\nModeling Chocolate:\n* 12 ounces bright white candy melts\n* 3 ounces corn syrup\nUnicorn:\n* modeling chocolate\n* edible gel food colors (pink, yellow, green, blue & violet)\n* edible gold luster dust\n* edible pink luster dust\n* edible black marker\n* small paintbrush\n* modeling tools (small knife and ball tool)\n* toothpicks\nStep 1: Make Modeling Chocolate\nMelt the candy melts in a glass bowl in the microwave. Be careful not to overheat. Microwave in 30 second increments, stirring in between. As chocolate begins to melt, reduce to 10 second increments.\nNext, warm the corn syrup in the microwave to lukewarm (about the same temperature as the melted chocolate. Fold the corn syrup into the melted chocolate and stir until combined. Stop when the mixture starts to seize up. It will take about a minute. Be careful not to overmix.\nWrap in plastic wrap and let set at least 2 hours at room temperature. When ready to use, unwrap and knead until smooth. It can be tinted with gel food colors and molded, rolled and shaped. Wrap in plastic and store in an airtight container when not it use. Note: it will harden with time, so knead to soften before using.\nStep 2: Mold Unicorn Head, Body and Legs\nThis unicorn is about 4 inches tall. I will provide approximate dimensions and weights of the clay used for each component for guidance. Of course you can make in any size and can tweak the shapes however you like.\n1. With a 19 gram piece of clay, form a pear shape for the body. It should be about 28 mm long x 25 mm wide.\n2. Form the head as pictured with a 24 g piece of clay. It will be about 33 mm long and 30 mm wide.", "515" ], [ "Make two small round depressions for nostrils with a toothpick or small modeling tool.\n3. Make 4 tapered cylinders for legs. They are about 25 mm long and 10 mm wide.\n4. To make the horn, roll a snake shape, tapered on both ends, with about 1 gram of clay. Cut in half and twist the two halves together to form the horn shape. Insert a small toothpick.\n5. For ears, form a diamond shape and cut in half. Each ear should be about 10 mm tall and 10 mm wide.\n6. Assemble the ears and horn to the head. Insert a toothpick in the head for attachment to body.\n7. Next roll and flatten 4 small balls, about 1 gram each, to make hooves and attach to the legs.\n8. Assemble legs to the body and then put head on by inserting toothpick into body.\nStep 3: Make Unicorn Mane, Tail, and Flowers\nIt's time to color the clay. Knead a small amount of food coloring into balls of modeling chocolate. You only need a small amount of each color, about 5 gram balls. Pinch of small amounts of each color and roll into snakes, tapered on the end.\nFor the tail, twist together one strand of each color. Attach tail and wrap around body as shown in pictures. Do the same for a mane, using shorter stands, and attach to back of head. Then attach a few strands to front of head as shown.\nMake tiny roses by rolling and flattening snakes of desired colors. Then curl into a rose shape (see pictures) and attach.\nStep 4: Paint Face, Horn and Hooves\nWith a small paintbrush, paint horn and hooves with edible gold luster dust. I used a dry brush, but you can mix the luster dust with a tiny amount of vodka if you prefer. Next draw eyes with edible black marker. Finally, dust cheeks with pink luster dust.\nI hope this inspires you to make a sweet chocolate topper for your next cake!!", "987" ], [ "Skillet of Bacon 'n' Eggs Earrings\nIntroduction: Skillet of Bacon 'n' Eggs Earrings\nWake up in the morning and put on a pair of skillet eggs 'n' bacon earrings to greet the day! Novelty earrings are the rage, and these will definitely catch people's attention. You can make them yourself and then people will notice them even more because of how radiant you will be while you wear them.\n*In this Instructable I have tried to include polymer clay instructions and air dry clay instructions. I will have polymer clay steps marked with an asterisk and in bold.\nSupplies\n1. Clay (air dry or polymer clay) in black or grey, white, yellow, and translucent\n2. Clay tools (roller, stylus, knife, workspace)\n3. Small round cutter (optional)\n4. Nail polish bottle with a smooth top\n5. Eye pin\n6. Acrylic paint in sequin black or iron black (if you are making a cast iron skillet, OPTIONAL)\n7. Small brush\n8. Soft pastels in rust red, brown, orange (or you can use diluted acrylic paint in the same colors)\n9. Gloss Varnish (I use Duraclear Polyurethane ) *OR Liquid Clay\n10. A toothpick or pin\n11. Earring hooks\n12. Round-nosed pliers\nStep 1: Skillet Base\nThe first step is the skillet.\nCondition the clay by kneading it in your hands and rolling it out several times with the clay roller. Once the clay is pliable, roll out the clay thinly, but not so thin that it wants to tear. This will be the frying surface of the skillet.\nWith the round cutters or with your knife, cut out a circle that is bigger in diameter than the top of the nail polish bottle.", "95" ], [ "(I placed my nail polish bottle upside down on the clay so that I could make a pretty even circle by tracing around it with the knife.)\nCenter the circle over the top of the nail polish bottle and press it down around the top. Leaving a bit for the skillet's rim, trim around the top of the nail polish bottle so that you have a little flat bowl shape with nice smooth edges.\n*POLYMER CLAY: You can preassemble the entire skillet and breakfast platter BEFORE baking, or you can bake as you go. I have marked steps where I think baking would be advisable if that is how you choose to do it. If not, just go through all the instructions until you are finished with the project, then bake it.\nStep 2: Skillet Handle\nTake a bit of your black/gray clay and make it flat. Place the eyepin on top of the flate shape and meld the clay over the eyepin. The eye pin inside helps to strengthen the handle of the skillet.\nI roll the clay over the pin to make it cover it. I cut off any excess from the end (because there will be some).\nOnce you have smoothed the clay until there are no visible seams, cut the clay snake just a tiny bit beyond the end of the pin that is inside the clay. Now you have the handle. With a pin, or the stylus, or a toothpick, poke a hole in the handle right where the eye of the pin is. Make it go all the way through so that you can hang the earrings.\nTo attach the handle, place it against the skillet bowl that is on the nail polish bottle and using the stylus or another tool, smooth the two together to form one piece. If you can, make the pin going into the bowl part of the skillet because that will reinforce that join. If you can't, don't worry about it.\nNow the skillet is pretty much finished. Take it off of the nail polish bottle carefully. You will have to kinda press it back into a circle shape after removing it because that will make it slightly warped. Using a tool (your choice), smooth the edges of the skillet bowl so that they are not rough from where you cut the clay.\n*POLYMER CLAY: Pre-bake the skillet for sure if you are planning on painting it. If you want information on how to bake polymer clay, please see <PERSON> over at the Blue Bottle Tree\nOr set aside to dry, depending on your clay type.\nStep 3: Paint the Skillet\nThis step might not be necessary depending on your original clay color or how happy you are with the original color.\nAfter the skillet has dried or been baked, paint it with the acrylic paint. I wanted to paint mine because I have this color called \"Sequin Black\" or something like that, and it reminds me of the way cast iron kinda glistens.\nStep 4: Egg Base\nOn to the egg (p.s: I hate eggs).", "95" ], [ "Sunshine Rainbow Arch Clay Earrings\nIntroduction: Sunshine Rainbow Arch Clay Earrings\nThe arch polymer clay earrings are really trendy, and this design stands out more than your average polymer clay earring. A cute sunshine smiles above a bright rainbow arch to remind you that happy days are just around the corner. I will show you how to make these without using cutters, so don't feel intimidated or pass it by if you don't have any polymer clay cutters!\nSupplies\n1. Clay (polymer or air dry, your choice) in Red, Orange, Yellow, Green, Blue, and Violet.\n2. Clay in Black\n3. A work surface (I am using an acrylic board)\n4. Round Nose Pliers\n5. Two Jump Rings\n6. Two Flatback Stud/Post Earrings\n7. Two flat surfaces (I am using both my workspace acrylic board and a second identical board. You can use your work surface for one flat surface and whatever else for your other flat surface. Just make sure it isn't something that will stick to your clay and can be easily held in your hand. The next step will explain this better so you can know what you need).\n8. Clay Roller tool\n9. Clay Knife tool\n10. Ball tool\n11. Clay Stylus tool (or a tooth pick)\n12. Varnish (optional; I am using Duraclear Polyurethane Varnish in Gloss).\n13.", "95" ], [ "Brush to apply varnish\nStep 1: Rolling Out Clay the Easy Way\nThis is a really easy way to roll out logs of clay. You need two flat surfaces (I am using two small acrylic boards) and your clay.\nPut the piece of clay on your flat surface (first board) and then lay the top board on top of the clay, pressing slightly while moving the top board back and forth. The clay will become a smooth log! How even it is depends on how good you are at pressing evenly on the top board, but it is easy to apply more pressure to one side and even out a lopsided log. I first saw this done by Kaylana Design Tutorials and have since seen other polymer clay artists do this. It really makes rolling logs so easy!\nI included a gif that hopefully works, but if not I included photos as well.\nStep 2: Make the Arch\nStarting with the violet clay, I roll out a thin log of clay in the way I showed in the first step. If you don't want to do that, obviously you can just roll out the logs with your fingers.\nMy clay log is about the thickness of a standard round toothpick.\nWith the violet clay, I bend it into an arch or upside down \"u\" shape with my fingers. This is the start of the arch, so don't make it huge. Mine is a skinny arch.\nSet that aside and move on to the blue clay. Roll it out into a toothpick sized snake, then take your violet arch and carefully wrap the blue log around the violet arch. Make sure the two colors are touching so they bond to each other. Don't worry about loose ends right now; we'll deal with that later. You should now have an arch with a violet middle and blue outside.\nProceed to do the rest of the colors the same way in this order: green, yellow, orange, and lastly red. I didn't include photos of me rolling all the separate colors out because that would get exceedingly boring.\nOnce the red as been wrapped on top of the orange arch, you should have a rainbow arch! Now with the knife tool we will trim the ends even with one another. My arch measures about an inch and an eighth (1 1/8th inches) from the trimmed bottom to the tip of the arch, but you can make it as short or tall as you like. The ruler will come in handy for making sure your second arch is the height of your first arch, or you can just lay the first arch on top of the second one and then trim it evenly.\nWith the stylus tool or toothpick, poke a hole in the top of the arch in between the red and orange layers. This is the jump ring hole.\nMake the second arch in the same way you made the first.\nStep 3: Make the Sunshine\nWith the yellow clay, roll out the clay into a flat sheet. Don't make it too thin. With your stylus tool or your knife tool, draw a small circle on the yellow clay and then cut it out with the knife tool.\n*If you are worried about not being able to make a good circle, lightly press the top of a nail polish bottle onto the clay so it makes a circle you can trace around.\nSet the yellow circle aside.\nRoll out the yellow clay again. This time place the little circle on the rolled out clay.", "994" ], [ "Indigo Bunting Necklace\nIntroduction: Indigo Bunting Necklace\nSo, for the Rainbow Contest, I decided to go after that strange, illusive color, Indigo. For me, what pops in my head right away, is the cute little Indigo Bunting. I have seen a lot more of them this year than I have before. They tend to just look like bright flashes of color as they dart past, hiding in the weeds.\nInstead of just portraying the well-known, flashy male, I decided to put him together with his female counterpart. I decided that a lovely little nest scene was a good way to show them. It is also a good way to educate people on what the two of them look like; a stark contrast of one another, the male bright indigo and the female in a drab brown of concealment.\nCome along and create this cute necklace!\nSupplies\n1. Clay in brown and indigo (or as close as you can get - we will add some colored pastel and mica powder to help his bright coloring).\n2. Clay tools (roller, knife, and stylus or needle tool)\n3. Work space\n4. Tiny ball tool (also known as mandala tools or nail dotters)\n5. Small soft brush for using with pastels and paint\n6. Pastels in various shades of brown. Also you should add in green, blue and purple, and a grey if you have it (which I don't).\n7. Acrylic paint in black and grey (Grey not pictured)\n8. OPTIONAL: Mica powder in purple and blue. I think this just adds to his shimmery shininess, but you could also just paint him with metallic purple and blue paint.\n9. Necklace chain with wide links\n10. Two large jump rings\n11. Set of round nose pliers\nStep 1: Sculpt the Nest\nWe will begin with the nest.\nRoll out the brown clay. Don't make it too thick or too thin. With the knife tool or the stylus, sketch a bowl shape on the flattened clay. Trim this out with the knife tool. Set this aside.\nCut out two thin strips of clay from the leftovers.", "95" ], [ "These will be the limbs that the nest sits in between.\nWith the stylus tool, scratch lines into the two limbs, making them resemble the bark of a tree. If you have any silicone stencils that are wood-like this would be a cool time to use them. Just make lines until you are satisfied. Vary the lines in thickness, thinness, and length to make them look more natural. I also used the knife to cut the end of one of the branches and make a small broken branch piece sticking out from it.\nStick the ends of the two limbs together so they make a \"v\" shape. Place the bowl in the middle of the \"v\". Make sure it is tightly adhered.\nStep 2: Nest Details\nWith the stylus tool, scratch and swirl the needle around to make a rough, fiber-like appearance. Their nests are made of twigs, but I have yet to come up with an easy technique to make small twigs that I am satisfied with. This is what I do right now, maybe someday I will figure it out.\nAt the ends of the branch limbs, poke holes all the way through the clay. These are for the jump rings. Make them larger than you think they actually need to be.\nNow get out the brown, green, and grey pastels. With the small brush, dust the branch limbs first with various browns. I made mine pretty dark. Then dust the nest with a variety of the brown, green, and grey. You don't want to make it as dark as the limbs because then it won't stand out.\nSet the nest aside.\nStep 3: Female Bunting\nWith the left over brown clay, roll it out. Sketch a bird with a crest on the flattened clay. I advise looking up images of the Indigo Buntings to help you with this. Indigo Buntings are a member of the Cardinal family, but I have noticed in most photos I have looked at the female's crest is much more apparent than that of the male. They have fat beaks like finches (and Cardinals, duh :).\nTrim out the bird. She doesn't have to be a whole bird; only the top half because she will be sitting on the nest. With the stylus tool, sculpt the little details, like the eye, the beak, and various feathers. I just make pokes and scratches to indicate the feathers.\nColor the bird with pastel. This did not turn out like I liked it, so I added some grey paint later on, so you could just skip this and simply paint her if you wanted.", "879" ] ]

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