Datasets:

Hieuman

/

en_HRS_11_22_24

like 0

[ [ "Mrs. <PERSON>\nI know I have been on record in the past saying that TV is “the least important artistic medium,” but then again, give me a show exploring the complexity and hypocrisy of Conservative propagandists to defeat progressive platforms, and of course I’m gonna vibe with it. Half my apartment is filled with books on subject. Throw a dart at any one of my reviews and take a guess how I felt watching this schadenfreude.\nDoes it suffer from the same issues of all television - a hodgepodge of writer’s tones, unbalanced character development, over-balanced character growth, plotting issues, and pacing issues, especially toward the end? Yes to all the above.\nBut do we love to ogle at our enemies? 555-come-on-now - of course we vibe.", "480" ], [ "My Kid Could Paint That\nF for Fake: Redux.\nMy Kid Could Paint That wraps up the always-intriguing mystery of art forgery with the plebian but never-ending debate over the legitimacy of contemporary abstract art. If either of those questions intrigue you, this documentary will work, but I think there are YouTube video essays I’ve seen that are more insightful takes on both questions. I also know that, given the fact that I live with a museum worker, both questions are kind of...played out, at least to my ears. They’re interesting in a way that is very entry-level, but anyone with any previous interest in art, the art market, and art forgery will find <PERSON>’s story to be ironically paint-by-numbers.\nA large portion of the blame for why this feels uninteresting goes to the director, who, in my view, injects so much of himself into the narrative that the bias conquers the film, and validates the leading questions.", "862" ], [ "I think what the film starts out as - a portrait of a protege as a young woman - is much more intriguing. Does it matter if they’re 100% her ideas? To my mind, no, because the point of the film isn’t about the greatness of a protege, but rather the development, and even the greatest of artists are “taught” to a degree. What My Kid Could Paint That is showing is the teaching process, but by conflating “teaching” with “forgery,” I think the documentary tries to appeal to the lowest common denominator while ignoring the nature of artistic development.\nWhat I want is a followup with <PERSON>, who seems to still paint, but largely as a sort of half-hobbyist half-professional, and I think without a true arc post-documentary, what we have is a very biased,very basic portrait of the artist at a young age that insists that there is no artist, which clearly isn’t true, 15 years forward. All views I disagree with, and, like the questions asked, that I find troublingly simplistic.\nDoes that mean this is a bad documentary? Not at all, especially because forgery, to me, is interesting, even if I think it’s a bad reading here. What I think is that My Kid is a very base documentary, and believe that, while it works as a starting point if you’ve never confronted these questions before, I personally think there are more interesting ways to ask these questions, and more interesting answers to be found.", "80" ], [ "The Passion of Joan of Arc\nIn another year, another lifetime, a time when I was more willing to lean into being a pretentious snob with a big brain, I would have rated this exquisitely-framed, emotively-acted, slow-burn, genre-defining arthouse classic a 4.5, discussed its merits as craft, praised its anti-institutional themes against the church as an organization, gender norms, and general conformity, yet in the last 100 words of a 2,000 word essay no one asked for, I would argue that the paper thin plot, with its singular setting and narrow scope, undercuts the gravitas of the “epic” <PERSON> clearly saw in St. Joan of Arc’s biography, and quickly argue the case that silent films work better for me when the plot is simple but clear, as abstraction feels subjectively obtuse without language behind it.\nBut bitch, this ain’t 2019, I’m mentally and physically exhausted, and I’m over trying to intellectualize my taste just because some internet algorithm says I should measure my hobby against some list. Because when you’re bored, you’re bored.\nIf you love this, you’re a smarter person than I am frankly, or at lest have the patience of a saint, so more power to you. But I’m a dumbass with dumbass taste, and at a certain point, you gotta play the cards in your hand, y’know?\nWatched with:\nAnchor\nBrian\n<PERSON>", "480" ], [ "Dog Day Afternoon\nThank God I did not know anything about this movie because the experience I just had was transcendent.\nThe opening was so funny I was asking myself if this had been a comedy all along, until I realized that the absurdism was just a reality of the overall situation. It’s funny, yes, but it’s also tense and thrilling and tragic all over, to the point where I sobbed my eyes out during that one phone call towards the end.\nWhat a heartbreaking little moment that oddly encapsulates the personal cost of queerness, the lengths to which society can push you by means of rejection.", "471" ], [ "When a society doesn’t afford you dignity, you are forced to demand it.\nAlso, the actual bank robber <PERSON> is playing was as hot, if not hotter, than <PERSON> himself. No wonder the tellers were like “whatever you say, handsome”. Like, same.", "86" ], [ "<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 Opposite of Sex\nThe Mutual Cinematic Education of José and Camilo #38 (<PERSON>’s Choice)\nSurprisingly post-modern in its insane mix of 90’s irony poisoning and genuine sincerity. A gay writer/director throwing a lot of preemptive (?) homophobia at the wall in order to expose the real complexities and liberate himself of the audience’s baggage.\nMy boyfriend says that seeing this when he was a teenager made him feel a lot stronger and liberated as a gay teen, especially given the lack of conversations about queerness at the time. It makes it all the more special in hindsight; that we also get to indulge in messy and complex art that’s as messy and complex as our own experience.\nAlso, <PERSON> is a TREASURE.", "378" ], [ "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" ], [ "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" ] ]

[ 6134, 6960, 3127, 9344, 3297, 4114, 562, 9086, 8648, 5897, 5961, 146, 8049, 4057, 2630, 7594, 6374, 3914, 3802, 7247, 7349, 1977, 6200, 727, 1779, 5090, 3604, 11202, 11393, 296, 7106, 885, 11313, 2091, 6400, 8817, 8288, 9867, 2049, 9642, 927, 394, 7503, 8210, 6298, 8175, 10139, 10778, 3851, 6249, 8448, 8330, 8329, 10530, 9906, 716, 8437, 4426, 9107, 11085, 10850, 6915, 5609, 3599, 8828, 8052, 6559, 11292, 1834, 5554 ]

[ [ "Dilemma in race between muon and light\nI have a dilemma concerning my understanding of Special Relativity. Maybe I am understanding or calculating something wrong and would hear so.\nThe problem is based on muons created in the upper atmosphere by cosmic rays. Basically, what happens when we time the difference between such a muon and light created the same place at the same time.\nSince the muon travels at 0.994c, it arrives 301 nanoseconds later than the light. However this is from observation on earth. From the muon's observation, the point of creation and the destination on the earth's surface are moving at 0.994c and the distance is contracted from 15 Km to 1638 m, so the light arrives 33 nanoseconds earlier.\nFurther, from the muon's observation, a clock on earth will experience time dilation and should only record 3.6 nanoseconds of time. So how much time does the earth clock record?\nDetailed Description: In practice, identifying one muon and whether it would not decay in the journey would be problematic. Since we are using observations from the muon, replace it with a spaceship traveling at the (now arbitrary) velocity of 0.994c. If you do not like crashing the spaceship into the surface of the earth, or worry about general theory effects from the earth or sun, move the thought experiment to space, say the midpoint between Sol and Alpha Centauri.\nA point m, is 15.0 Km above a point on the surface of the earth, e. At point me is a space station, Muse.\nA space ship traveling at 298 m/μs constant velocity passes point m and then point e.\nWhen the spaceship passes point m, the Muse Space Station turns on a light. A photographic plate at point e collects light only from the Muse Space Station. This will be our clock, and we will measure how long an exposure to light is indicated by the photographic plate at the time where the space ship reaches point e.", "275" ], [ "(Perhaps when the space ship passes we close a shutter on the plate.)\nThe light takes 50.03461 μs to reach point e. The spaceship takes 50.03461 μs to reach point e, 301 nanoseconds later. So the photographic plate is exposed to light for 301 ns.\nHowever, from the space ship's reference, the space ship is not moving, but points m and e are moving at 298 m/μs constant velocity. When point m reaches the space ship, it turns on a light.\nBecause of length contraction predicted by special relativity, the distance between points m and e is 1637 m. The light from point m takes 5.49540 μs to reach point e. Point e reaches the (\"stationary\") space ship after 5.46254 μs. So the photographic plate is exposed to light for 32.9 ns.\nSo how much has the exposure to light darkened the photographic plate? As much as expected for 301 ns or 33 ns?\nFurther, since from the space ship's observation, the photographic plate at point e is moving at a speed close to c. So it should experience time dilation according to special relativity.\nIf instead of leaving the light on when point m passes the space station, the light at point m was only turned on for 1 nanosecond, the clock timing that nanosecond would be slower observed from the space station, and would be on for 9 ns. Then the 9 ns of light would only expose the plate at e as much as for 1 ns of light, because of the time dilation at point e. So, observed from the space ship for every 9 units of time that the plate at point e is exposed to light, it only reacts as much as for one unit of time. So the 33 ns of light when point e reaches the space ship, the plate should only show 3.6 ns of exposure.\nSince we are comparing times in microseconds, and subtracting to get a time difference in nanoseconds, to get four digit precision in our result, we need to start with and carry seven digit precision in our thought experiment, even when the input was arbitrary.\nEarth Observation:\nDistance of segment em: 15 000.000 000 m\nSpeed of muon space ship: 298.000 000 m/μs\nSpeed of Light: 299.792 458 m/μs\nTime for space ship to reach e 50.335 57 μs\nTime before light reaches e 50.034 61 μs\nTime of exposure of p-plate 301.0 ns\nMuon Space Ship Observation:\nDistance of segment em: <PHONE_NUMBER> m\nRel Speed of e & m to muon space ship:\n298.000 000 m/μs\nSpeed of Light: 299.792 458 m/μs\nTime for space ship to reach e 5.", "562" ], [ "Since you would like to avoid mathematics, you can always break down the process into a series of steps.\n1. Say you apply an upward force to the atom on the right for a very short time, the atom on the right will gain some momentum. Meanwhile the atom on the left is still stationary during this time. It hasn't felt the effects immediately. Information travels at the speed of light.\n2. The right atom will move up. When the right atom moves up, the bond stretches. This causes the atom on the left to experience a component of upward force also a component of force to the right. Essentially, the left atom moves up during this small time at the start. This is expected, you apply a force on an object you at least expect the centre of mass motion to move in the direction of the force, not the opposite.\n3. Since your force is off centre of mass then your combined system will also rotate about the center of mass. As I explained above you will also have other components of force not just up and down.", "343" ], [ "The bond is changing orientation with time. Factoring in that the atoms are moving as well. These forces (including the up and down) will contribute the oscillation of the atoms in a 2D plane. This results in rotation.\nSo after going through this process what we have determined is that centre of mass moves upwards however you will get also get rotation.\nThe 2nd picture you have drawn in the image is actually in the centre of mass frame of reference. (i.e. you are moving with the centre of mass). In the stationary frame both atoms will ultimately move upwards.\nPlease let me know if I have answered your question or if you would like clarification.\nEdit: Additional sketch for clarification. The image shows the state of the system at different times $t_{3}>t_{2}>t_{1}>0$. At each time step I show the force due the bonding and the velocity that resulted from the prior time. Then I show the new velocity vector.For the next time, I displace the atoms in the direction the new velocity vector is pointing. I do this for a couple of times to demonstrate that you will end up getting rotation. Also I assumed I am working in the centre of mass frame when I sketched these diagram.\nAlso for $t_{3}$ I accidentally displaced the atoms in the same time step. The velocity directions are correct however the displacement occurs in the next time step.", "766" ], [ "Energy in orbit of satellites around the earth lost?\nIf the total mechanical energy in a satellite's orbit (assuming circular) is greater when it is closer to the earth, and hence smaller when it is farther from the earth, then we can say that as the moon drifts from the earth, the moon loses energy in translational speed and gravitational potential energy. If only those two are taken into consideration, then there is a net energy loss from the moon.\nI had first thought that the energy a satellite has increases as it goes on a larger orbit, but I ran some numbers and it didn't appear so. If I went wrong somewhere, please someone, correct me. Here are my numbers:\nFor a geostationary satellite (r = 42 164 km, v = 11 068 km/s, m = 1 kg), its total energy is PE + KE. PE = mgh, but g = 0.22416 m/s^2. The result is PE = 9 451.650 kJ, KE = 4 726.582 kJ\nFor a satellite at r = 45 000 km , m = 1kg, then v = sqrt(GM/r) = 2 976.06 km/s.", "1023" ], [ "g at that height is g = 0.19680 The result is PE = 8 856.094 kJ, KE = 4 428.047 kJ\nAt the larger orbit, both PE and KE are lower than if it was at a lower orbit. Is this right?\nNow, the earth slows down its rotation, which allows the moon to go into a larger orbit by conservation of angular momentum. Since the moon goes into a larger orbit, it loses energy. But, since the spin of the earth has slowed down, it also loses energy. Moreover, the moon is still tidally locked with the earth, so its rotational speed isn't increasing.\nAll in all, there seems to be an energy loss that's going on. How is this being compensated? Is it in the translational speed of the moon (so that the moon is actually moving faster than it should be to maintain a stable orbit)? That seems reasonable - there could be an increase in translational and rotational speed to compensate for the energy loss, maintaining the moon to be tidally locked.\nBut that's just me. What really happens? How does the energy transfer occur, and are there mathematical equations describing this exchange?", "1023" ], [ "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" ], [ "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" ], [ "While it is true that, at least over time, Earth will equilibrate so the mountain sinks down, displacing the denser material below, this would also mean that the material just beside the mountain is less dense, and thus there is a similar reduction in g due to this when standing beside it.\nAnd while the increased mass is quite small relative to Earth, you are also a lot closer to it. So you need to consider both factors.\nIf we do a first order approximation for the change in gravity due to the height of the mountain, we get; $$ dg=\\frac{2 G M h}{R^3} $$ where $R$ is the radius of Earth, $M$ is the mass of Earth and $h$ is the height of the mountain.\nIf we treat the mountain as a sphere with a diameter of $h$ and a density of $\\rho$, then the acceleration due to gravity when standing on top of it is: $$ a=\\frac{G \\rho (4/3) \\pi (h/2)^3}{(h/2)^2} =\\frac{2 G \\pi \\rho h}{3} $$\nAnd with that we end up with a ratio of the 2 forces dependent upon the density of the mountain (as both are linearly dependent upon the height) $$ \\frac{a}{dg}=\\frac{\\pi \\rho R^3}{3M} $$ So for a spherical mountain you need a density of roughly 22000 kg/m^3, e.g.", "15" ], [ "a mountain of osmium, to have the gravity due to the mountain increase your weight more than the extra height decreases it.\nHaving mass in addition to that sphere (without taking away from that sphere) would reduce that density requirement. But even if you modelled it as a cylinder where h=d to calculate the mass, and overestimated the force due to gravity by treating it as a sphere/point mass, you end up needing a density of roughly 15000 kg/m^3.\nHowever the effect is much greater than the 0.2% suggested by userLTK. With a specific gravity of 2.7, the effect of the mass of the spherical mountain is 12% that of the effect of the increased distance from Earth.", "921" ], [ "Using relative velocity between two frames and the time elapsed between events in one frame to find the time elapsed/event separation in the other\nQ from text: A second transporternaut is beamed to a much more remote galaxy that is moving away form Earth at .87c. This time, too, she stays in the remote galaxy for one year as measured by clocks moving with the galaxy before returning to Earth by Transporter. How much has the transporternaut aged when she arrives again back at Earth?\nIn this question, of which this above is part e, the transporters send the person as data at light speed form place to place, and disassembly and reassembly time is negligible. From a previous part, I found that she will not age on the trip there or back, as she is travelling at the speed of light, and the interval for her is 0 (her time elapsed as seen form earth is, say, 2E6 ly to get to andromeda, but andromeda is 2E6 ly away, so I = (t^2-d^2)^(0.5) = 0).\nAll her aging, then, is on this galaxy, for one year galaxy time. I want to find out how long that is in Earth time. In the galaxy's frame, the event of her arriving and leaving occur at the same place, and since one year elapsed the interval is 1 ly light travel time.", "272" ], [ "This must be the same as calculated form Earth. I was trying to find the distance, as seen form Earth, that the galaxy moved. This would be the separation between the events of her arrival and departure form the galaxy, as seen form Earth, and with this and the interval I could find the time elapsed between the events as seen form Earth.\nI could use the relative speed between Earth and this galaxy, to find the distance between them. But what frame will I be finding this distance in? Example, If I use the time elapsed as 1 year, I get .87 ly distance, but this is as seen from this new galaxy. From Earth it wasn't a year elapsed, which is the point to begin with. If observers both on earth and on the galaxy see the same relative velocity between them (I assume they do), but they can experience different amounts of time being elapsed from the arrival and departure of the transporternaut, they must find different distances moved by the galaxy in the meantime. So I shouldn't be able to use the relative velocity, which is the same measured in either frame, and the time as measured in the galaxy, which differs from that measured on Earth, to find the distance as seen form Earth, should I? If I can, how comes? What other info do I have that could solve this problem?\nIt seems like I have both the time elapsed and the distance the Earth moved away, as seen form the galaxy, whereas I ahve none of this info for the observer in Earth's frame.\nIf I use the .87 ly as the distance between events, seen on Earth, and the interval as 1 ly, I get 1.3 ly time elapsed, so 1.3 years aging.", "272" ], [ "There is an ambiguity in what is meant by the path of the light.\nIf you mean the path of any particular photon (i.e., the light emitted at a given time), then your picture is right: This path is straight in the elevator frame by the Einstein Equivalence Principle. However, it is horizontal only if it was emitted at the moment the elevator was at rest relative to the laser. Otherwise, it is tilted because the velocity of the photon has a vertical component in the elevator frame.\nIf you mean the instantaneous locus of all photons in flight (i.e., the light existing at a given time in the elevator frame), then this path bends downward in the elevator frame -- opposite to the picture you attribute to your teacher. This may be counterintuitive, but consider the elevator after it has been falling at acceleration $-g$ for a time $T$ since being at rest relative the laser. Assume the vertical velocities involved are small compared to $c$, so the horizontal velocity of light is essentially $c$ (up to higher-order terms).", "562" ], [ "In the elevator frame, the photon at horizontal coordinate $x$ (the laser is at $x = 0$) was emitted at time $\\tau = T - x/c$, when the laser was at vertical position $+g\\tau^2/2$ and had vertical velocity $+g\\tau$. Thus the photon, after traveling in a straight line for time $x/c$, has current vertical position $g\\tau^2/2 + g\\tau(x/c) = g(T^2 - x^2/c^2)/2$. This is a downward-bending parabola. The same effect would be seen in Newtonian physics with, say, a hose emitting water or a machine gun emitting bullets.\nNote that the above \"paths\" are defined in terms of the reference frame of the elevator (notional grid of clocks and rulers), and for the case of light, neither of these paths would be straightforward to observe by what someone naively (optically) sees in the elevator. For example, if there is smoke that scatters the light so it can be seen from elsewhere in the elevator, the instantaneous appearance of the light beam would not correspond to the second interpretation (locus of all photons in flight), because of the differing time for propagation to the observer's eye from different parts of the beam.", "562" ] ]

[ 11315, 632, 9490, 2600, 5630, 6819, 3097, 259, 10904, 9079, 3389, 3497, 4059, 3060, 1924, 1282, 6860, 9917, 11081, 3335, 1063, 3309, 5223, 493, 4047, 9985, 5316, 11090, 8887, 3080, 6365, 9950, 3350, 1502, 8199, 4134, 10838, 8726, 2988, 10115, 10794, 2441, 9421, 10476, 5355, 6787, 2565, 2535, 8217, 1432, 1347, 2632, 6237, 7704, 3977, 706, 4996, 6196, 6870, 4520, 7931, 3995, 8690, 3848, 8194, 1375, 10679, 337, 5140, 1500 ]

[ [ "A Very Good Girl\nfilms that try and claim to be campy fail so much because they don't get the formula just right and in a very good girl, this is the case. it tries to be a lot of things but the film never really found the right balance for all of these genres to work. maybe if the humor was drier... maybe if it fully embraced its darkness...", "269" ], [ "maybe if the script was developed for at least two more years... some of the creative decisions are a bit questionable too (its style sometimes can be off putting that it renders the story too dramatically than it needs). love that <PERSON> is now choosing these projects cause her and <PERSON> is as good as always. i just need them to be in a decent project (together and individually), that'll be enough.", "577" ], [ "Where the Crawdads Sing\nelvis was long, but this felt longer. one of the most boring films i’ve ever watched. It’s so long and nothing happens. great idea, not great execution.", "144" ], [ "they thought this was an art film but it just didn’t go that way. not only was i disappointed, but i ultimately felt confused as to the specific direction this film takes. a poor attempt at writing a functioning narrative, mixed in with a poor attempt at addressing real issues. some laughable cgi and atrocious old person make up. the ending was so poorly written, it made the movie worse.\nstill don’t know what a fucking crawdad is", "596" ], [ "Fallen Leaves\nman this was depressing…but cute. <PERSON> and his characters say little, but the films say a lot.\n\"the falling leaves, drift by the window...\"\nthere’s just a unique and lovely feeling that comes after watching <PERSON>’s work, even if most of his films are somewhat similar to one another. he continues to make his minimalist yet effective drama comedies drenched in equal amounts of melancholy and glee.", "698" ], [ "they always remain effortlessly engaging and satisfying!\nthe humor, pathos and loneliness in fallen leaves was relatable. the deadpan simple scenes with misunderstandings, punctuated by the karaoke scenes worked really well. athough this is contemporary, it feels like it’s from a different era, without tech. that was so so refreshing but also sad what the world has become.\nalso i loved how <PERSON> leaves nice touches for cinephiles — i could see posters for the Sicilian clan, <PERSON>, <PERSON> and his brothers.", "529" ], [ "<PERSON>\n“we still love each other, right?”\nmommy is such an incredibly disturbing film. <PERSON> offers such a complicated examination of a mother-son relationship and what it means to truly love someone unconditionally.\n<PERSON> truly hit the ball out of the park with this film. there is such an intensity that carries through the whole film from start to end without it ever feeling bogged down by sudden climax’s or dilemmas. this is probably my favourite <PERSON> film to date.", "529" ], [ "i think it truly encapsulates all that makes him such a unique and great director. he has such a unique style when it comes to presenting his stories. i know some people find it pretentious, but his use of aspect ratios mainly in this film, but also out of focus scenes, shots that are a little too close, all staples i associate with a dolan film. not to mention the cinematography is always stunning and the score on this film is especially delightful.", "594" ], [ "5 to 7\nmy desire to see <PERSON> do a before sunrise finally outweighed my fear of this movie being as bad as the writer/director's other movie, Destination Wedding, which is one of my least favorite movies of all time. just the worst writing you've ever heard, delivered by beloved actors rendered powerless to overcome it. nails on a chalkboard. terrible flick\nbut anyway.", "144" ], [ "this was not so terrible! pleasant, formulaic, the kind of movie you'd watch on a plane and forget you watched it by the time you hit the baggage claim. the dialogue is mostly bad and there's a bunch of needless plot and it's nakedly wish fulfillment for the wistful-aspiring-writer-who-just-needs-a-break-and-also-a-girl-to-fix-him set but that also means you get to spend a lot of time watching the lead actor act so it's impossible to say if it's good or not. a little maddening to watch <PERSON> cook even in lighter roles like this. he was so good dude", "132" ], [ "Killers of the Flower Moon\n<PERSON> is unreal, i have no idea how she got me to buy into <PERSON>'s relationship with <PERSON>'s dumb as rocks <PERSON> without sacrificing her intellect and identity, and especially with such minimal dialogue and limited screentime. i will say i was expecting to get to spend more time with <PERSON> considering how long this mf is and am sad to not get to see more of her beyond her interior life, either with her family or the other members of the Osage Nation or even just with <PERSON>.", "132" ], [ "i think the movie thrives because it damningly follows <PERSON>'s POV and makes its audience complicit in his actions (and inaction), but within that choice still very much had the space to expand <PERSON> further. speaks to <PERSON>'s absolutely ridiculous performance within those limitations that all i want is to see more of her. let the woman COOK", "132" ], [ "Trolls\nsurprisingly relevant watch before a dry night out, but this is pretty mediocre. visuals are fun and colorful, everything else is lacking. even some of the soundtrack choices (the most important part of the film) are questionable, and i'm usually a defender of jukebox musicals!! if you're going to stick in <PERSON> just because the first line of the hook is 'i ain't happy' and ignore the rest of the lyrics, you might as well just write your own song. waaaay too many like...", "698" ], [ "<PERSON> quirky <PERSON> characters, <PERSON> and <PERSON> are very two-dimensional, <PERSON> & umm... the... the twist villian i can't remember his name (?) had promise but needed more time/development. i had a great time at the club, though!", "577" ], [ "Poor Things\n“i must go punch that baby.”\npoor things is a extremely strange story that leaves you in tears laughing but also shying away at the raw examination of people and feelings. it offers a unique and at times disturbing examination of what it means to be human.", "352" ], [ "it questions are current knowns and the boundaries we put on ourselves as people. it has the usual <PERSON> strangeness, but combine: with a <PERSON>-esque story, it’s absolutely thrilling.\n<PERSON> is absolutely stellar in this, and after watching it i can see the oscar for lead actress being between her or <PERSON>. which is gonna be a very exciting race to watch.\n2023 Ranked\n<PERSON> Ranked", "378" ] ]

[ 1299, 4082, 4330, 7861, 1723, 8118, 10503, 2152, 10957, 8943, 3062, 6888, 3575, 6808, 1596, 5128, 3343, 4696, 8924, 4549, 3233, 10093, 10567, 4640, 984, 8685, 10592, 2268, 473, 2333, 4747, 2693, 10235, 5609, 8266, 10954, 2439, 1643, 8693, 4553, 1955, 3302, 2974, 7430, 9162, 3841, 7040, 8716, 9646, 1898, 11049, 8905, 6901, 5890, 5581, 3538, 8710, 409, 2423, 9558, 6619, 2225, 6960, 5408, 918, 9019, 1958, 2638, 4367, 2324 ]

[ [ "Efimov states in general\nEfimov states are special states of three praticle systems. Their existence is a purely quantum effect, because \"size\" (i.e. cross-section) of these states can be much greater than the range of underlying particle-particle interaction. (1,2)\nFor each system having an <PERSON> state there are in fact infinitely many of such states. Some properties of Efimov states are universal and do not depend on the nature of underlying particle-particle interaction: (1,2)\n1) size of $n$-th <PERSON> state is $s_0 \\approx 22.7$ times the size of $(n-1)$-th state\n2) energy of $n$-th <PERSON> state is $s_0^2$ times the energy of $(n-1)$-th state\n$s_0$ is the solution of the following transcedental equation (3):\n$s_0 \\cosh(\\pi s_0/2) = \\frac{8}{\\sqrt{3}} \\sinh(\\pi s_0/6) $\nThere can be <PERSON> states, so bound three particle states, when there are no bound dimer states. This is often depicted with borromean rings, since if we take one of the praticles away, the resulting two particle state will be unbound.\n<PERSON> states and halo nuclei\nThe original <PERSON> work treated three identical bosons.", "469" ], [ "However, the particles need not be identical, they can have different mases. The <PERSON> theory can also be extended to describe fermions. (2)\nHalo nuclei, that can be viewed as <PERSON> states, are the nuclei with two-neutron halos:\nA two-neutron halo is exhibited by ${}^6He$, ${}^{11}Li$, ${}^{17}B$, ${}^{19}B$ and ${}^{22}C$. Two-neutron halo nuclei break into three fragments, never two, and are called Borromean because of this behavior (referring to a system of three interlocked rings in which breaking any ring frees both of the others). (Atomic nucleus-Wikipedia)\nThe two neutrons in the halo \"do not stick together\", so we indeed have a three-particle system. It is interesting, that\n[lithium-11] has an exceptionally large cross-section of 3.16 fm, comparable to that of ${}^{208}Pb$. (4)\nFor an introduction to halo nuclei and Efimov states see the presentation Halo world: The story according to <PERSON>,<PERSON> and <PERSON> by <PERSON>: http://www.boseinst.ernet.in/capss/talks/2011/IndranilMazumder.ppt\nI also advertise the freely available Physics.APS.org article on <PERSON> states: http://physics.aps.org/articles/v3/9", "1020" ], [ "Could the fractional model of Quarks electric charge turn out to be false?\nThe delta baryons (also called delta resonances) are a family of subatomic hadron particles which have the symbols $\\Delta^{++}$, $\\Delta^{+}$, $\\Delta^{0}$, and $\\Delta^{−}$ and electric charges +2, +1, 0 and −1 elementary charge respectively.\n\"existence of the $\\Delta^{++}$, with its unusual +2 electric charge, was a crucial clue in the development of the quark model.\"\n* , three same quarks $\\Delta^{++}=uuu$, and two electric charge, isn't it impossible?!.\n* Could the fractional model of Quarks electric charge turn out to be false? (leptons don't have fractional electric charge)\nHere are some resources to help you quit smoking:\nQuarks do not exist. Everything is made up of positrons and electrons\nAll real free particles have a charge of -1 , 0, +1 - only quarks have fractional charges which I find unncessary since all particles could be made up of whole charge positrions and electrons. Can anyone cite a particle that could not be made up of positrons/electrons and must be made up of 1/3 charge fraction quarks?\"\nFractional Electric Charges were not proposed by QCD, but by the quark model, which came beforehand.\nQCD offered a number of inconclusive predictions, such as Color Force and Fractional Electric Charges, Wrong. Fractional Electric Charges were not proposed by QCD, but by the quark model, which came beforehand.\nOn the breakdown of Quarks fractional electric charge values.\nthis \"thought\" that Quarks have a fractional electric charge values may not be true!. according to <PERSON> research in the field of QCD (Quantum Chromo Dynamics) three times the elementary charge (depending on flavor) Up, Charm and Top Quarks (called Up-Type Quarks) have electric charge of zero! 0 (Which means Up- Type Quarks are uncharged ), while Down, Strange and Bottom Quarks (called Down- Type Quarks) just Could have a electric charge of plus or minus one! (+1, -1) in <PERSON>'s model down-type Quarks are results of electroweak interaction between charged leptons and anti leptons and Up-type Quarks, and this is the reason that Quarks do not have fractional electric charge values. Which means charge of hadron is not the sum of the charge of its constituent quarks, it is just sum of the charge of Down-Type Quarks...\"\nNuclear Forces – part 2\nIn the early 1960’s when a physicist by the name of <PERSON> put forward the hypothesis for the existence of quarks, he speculated that the charge of an up quark was two thirds of a proton’s, and the down quark was one third of an electron’s charge.", "1020" ], [ "In this way a proton consisting of two ups and one down quark would have a charge of +2/3 +2/3 -1/3 = +1. The benefit of such fractional charges is that a neutron could then be said to consist of two downs and one up quark, giving it a net charge of -1/3 -1/3 +2/3 = 0; i.e. a neutral charge. I would suggest that this neutron model must surely be wrong. We know that a neutron decays into a proton and electron. For this model to be correct, it would require that a down quark transform itself into an up quark – changing both its charge type and strength from -1/3 to +2/3 – and that an electron essentially be produced from nowhere! Perhaps this is possible but a simple ‘neutron = proton + electron’ model seems far more likely....\"\nhere is the solution:\nIf anyone can disprove the existence of three triplets of quarks for $u,u,u \\neq \\Delta^{++}$ or prove that $\\Delta^{++}$ have electric charge of zero then fractional model of Quarks electric charge will breakdown!.", "531" ], [ "Lower limit for atomic number in case of imaginary ion with Z < 1\nIn my programming project I calculate the minimal energy of an atom with 2 electrons in the $L=0, S=0$ state, using a Hylleraas wave function.\nThe values I find for $Z=2$ (He) and $Z=1$ (H$^-$) are in good correspondence with what can be found in literature (Pekeris, 1962):\n* $E_0({\\rm He}) \\approx -2.903~{\\rm a.u.}$\n* $E_0({\\rm H^-}) \\approx -0.528~{\\rm a.u.}$\nHere a.u. are the atomic units in which the energy of the hydrogen atom is $-0.5$. However, the next part of the project is to find a lower limit for $Z$, e.i. imagine a theoretical ion with $0<Z<1$ $(Z\\in \\mathbb{R})$, what is the minimal value for $Z$ in order for the two-electron system to remain bound? This is equivalent with asking: for which value of $Z$ is $E_0=0$?\nI cannot find any references about this theoretical lower limit online, but I don't think my results are correct: the $E(Z)$ relation, also shown in the graphs below, looks like a power law.", "474" ], [ "This means that $E_0\\to0$ for $Z\\to0$, but in this case you just have two electrons and you would expect a very positive energy as the two will strongly repel each other.\nI do not expect you to help me with the programming project, but maybe someone could provide some useful thoughts or a reference about this theoretical lower limit? I keep finding it strange that the results for $Z=1,2$ are correct with errors of only 0.01% and everything seems to go wrong for small $Z$.\nNote: how are these energies exactly calculated? We start with a Hylleraas wavefunction subjected to a coordinate rescaling factor $\\alpha$: $$ \\langle\\vec{r}1\\vec{r}_2|\\Psi\\alpha\\rangle = \\sum_{STU}C_{STU}N_{STU}{\\rm e}^{-\\alpha s/2}(\\alpha s)^S(\\alpha t)^T(\\alpha u)^U $$ with $s = r_1 + r_2, t = r_1-r_2, u=r_{12}=|\\vec{r}1-\\vec{r}_2|$, $S,U\\in\\mathbb{N}$, $T\\in2\\mathbb{N}$ and $\\alpha\\in\\mathbb{R}^+$. Three matrices can be calculated: the overlap matrix $[M]$, the kinetic energy $[T]$ and potential energy $[V].$ They scale like: $$\\langle\\Psi\\alpha|\\Psi_\\alpha\\rangle = \\langle\\Psi|\\Psi\\rangle/\\alpha^6 $$ $$\\langle\\Psi_\\alpha|T|\\Psi_\\alpha\\rangle = \\langle\\Psi|T|\\Psi\\rangle/\\alpha^4 $$ $$\\langle\\Psi_\\alpha|V|\\Psi_\\alpha\\rangle = \\langle\\Psi|V|\\Psi\\rangle/\\alpha^5 $$ Variation to the expansion coefficients in $\\langle\\Psi_\\alpha|(T+V)|\\Psi_\\alpha\\rangle/\\langle\\Psi_\\alpha|\\Psi_\\alpha\\rangle$ leads to a generalized eigenvalue problem: $$ \\left(\\alpha^2[T]+\\alpha[V]\\right) C_\\alpha = E_\\alpha[M]C_\\alpha $$ The lowest energy eigenvalue $E_\\alpha^0$ gives a function of $\\alpha$ of which the minimum needs to be determined. This minimum is the best variational approximation of the ground state energy.\nUPDATE: It is interesting to plot the evolution of the coordinate rescaling factor $\\alpha$ as a function of $Z$. Apparently, there is a discontinuity around $Z\\approx 0.89841$, which is close to the critical value of $Z\\approx 0.91$ found in literature. I would suppose this point has a significant meaning, but I have failed so far to give it a physical interpretation (I hope to find an interpretation which has to do with the ionization of at least 1 electron).", "394" ], [ "Let me give you the crazy idea that the radius of an electron and a proton is fixed but complex, where the real part is the mean and the imaginary part is the standard deviation. Then the classical radius of an electron and a proton determines the mean value, and the root-mean-square value is variable in its meaning. The electron radius is pointwise at high energies, when relativistic corrections are applied, and the scattering cross section is proportional to the square off classical electron radius.\nThe formula for the scattering cross section of a photon by an electron does not need to be regularized and determines the scattering cross section $$Re\\sigma=\\sigma(0)-\\sigma(\\infty)=\\frac{8}{3}\\pi r_e^2;\\sigma(x)=\\sigma(\\frac{\\hbar \\omega}{mc^2})$$ In this case, the radius in complex form is $$R_e=r_e(1\\pm\\sqrt{(Re\\sigma-\\pi r_e^2)/\\pi}i)=r_e(1\\pm 1.29i)$$ its modulus determines the scattering cross section $$|R_e|=r_e|1\\pm1.29i|=1.63r_e=\\sqrt{\\frac{8}{3}}r_e$$ The formulas for the cross section of the scattering of an electron by an electron and the annihilation of an electron and a positron with the formation of two photons require regularization. The regularization parameter must be chosen so that the size of the electron coincides with the size of the electron when a photon is scattered by an electron. It turns out that the three formulas equally determine the size of the electron.\nThere is no unambiguous value for the size of elementary particles. Elementary particles do not have a finite size and it is impossible to determine an unambiguous final size by their charge.", "795" ], [ "For an electron, there are scattering cross-sections of various reactions, and with their help I was able to determine the complex size of an electron. The complex size of an electron is determined up to the imaginary part. For a proton, this cannot be done, since there are no formulas describing the cross-sectional area of ​​reactions. Nuclear forces are not described by the perturbation theory, therefore only measurements are made and there are no theoretical formulas. The classical radius of the electron is greater than the classical radius of the proton. But this does not mean anything, the size of the proton is unknown.", "969" ], [ "The Hamiltonian of an atom commutes with the square of the total angular momentum $\\hat{J} = \\hat{L} + \\hat{S}$ and one component, disregarding very small hyperfine splittings. Knowing the energy $E$, $J$ and $J_z$ amounts to solving the fine structure of the atom. Since $\\hat{J}$ is an angular momentum there are 2J+1 degenerate components in the absence of an external magnetic field. For non heavy atoms the Hamiltonian also approximately commutes with $\\hat{L}^2$, $\\hat{L}_z$, $\\hat{S}^2$ and $\\hat{S}_z$, the orbital and spin angular momenta, so you can have approximately well defined energy and $L$, $M_L$, $S$ and $M_S$ quantum numbers. These states have the right (or approximately right) symmetry, so you want to have your eigenstates with all those labels, say $|E,L,M_L,S,M_S,J,M_J\\rangle$.\nIn typical Quantum calculations, however, you write the n-electron wave function as a <PERSON> determinant of {\\it atomic orbitals}, which have well defined one-electron orbital and spin angular momenta, $l_j$, $m_{l,j}$, $s_j$ and $m_{s,j}$. The number of micro-states that you can find specifying the lower case quantum numbers $l_j$, $m_{l,j}$, etc. (you only need to consider electrons that don't fill a \"shell\") is the same as the number of \"real\" states (or microstates) that you find specifying the upper case quantum numbers $L$, $M_L$, etc. {\\bf but} the wave functions are not the same. However you can transform from one representation to the other by a unitary operator.", "976" ], [ "In the case of two electrons (or holes) in the outer open shell, the coefficients of this transformation are the well known Clebsch-Gordan coefficients.\nIn particular the micro-states specification is related to a single <PERSON> determinant of atomic spin-orbitals, but open shell quantum states with well defined angular momentum typically require a sum of several <PERSON> determinants. There are several simple techniques that show you how to find the right linear combination of <PERSON> determinants. <PERSON> pointed to the most usual one. Since for the highest possible $M_L$ there is only one possible single determinant, you can generate the linear combination for the other $M_L$ states with the same $L$ by using ladder angular momentum operators. The same procedure can be used to generate the different $M_S$ states sharing equal $S$. Somewhat more generally, you can also use projection operators. See for instance <PERSON>, Adv. Phys. 5, 1 (1956).", "469" ], [ "The main reason for the peak in the reactivities is a nuclear resonance effect. To show this, it's worth looking into the rich physics of cross-sections (see <PERSON> & <PERSON>, Nuclear Fusion, 1992). There are three main factors that affect fusion cross-sections (plotted above with data from Bosch & Hale), \\begin{equation} \\sigma = S(E) \\frac{1}{E}\\exp{\\left(-\\frac{B_G}{\\sqrt{E}}\\right)}\\,. \\end{equation}\n1. The factor $\\frac{1}{E}$ derives from the effective size of a particle due to its de Broglie wavelength, \\begin{equation} \\text{effective size} \\sim \\pi \\lambda_{\\mathrm{dB}}^2 = \\pi\\frac{h^2}{p^2} =\\pi \\frac{h^2}{2mE} \\propto \\frac{1}{E}\\,. \\end{equation}\n2. The exponential factor derives from the tunneling probability through the potential barrier created by the Coulomb repulsion between the reactants, \\begin{equation} \\text{tunneling probability} \\propto \\exp{\\left(-\\frac{\\pi \\alpha Z_1 Z_2 \\sqrt{2m_rc^2}}{\\sqrt{E}}\\right)} \\equiv \\exp{\\left(-\\frac{B_G}{\\sqrt{E}}\\right)}\\,, \\end{equation} where $Z_1$ and $Z_2$ are the atomic numbers of the particles, $m_r$ is the reduced mass of the system, $\\alpha={k_e e^2}/{\\hbar c}$ is the fine structure constant, and $B_G$ is known as the Gamow constant (well-explained in this wiki entry).\n3.", "246" ], [ "The factor $S(E)$ is the so-called S-function and was introduced by astrophysicists to capture the remaining, relatively slowly varying nuclear physics contribution to the cross-section. In fact, the S-function varies so slowly that it can be plotted on linear scales (plotted below with data from Bosch & Hale). Hence it is often more useful to compare the S-functions of similar reactions, rather than the cross sections. (For more information about the astrophysical origin of the S-function see this review article by <PERSON> et al., Rev. Mod. Phys., 1957.)\nThe peaks in the S-functions are due to resonances, which arise only at certain energies when the relative phase and amplitude of the internal bound wavefunction and external traveling wavefunction of the quasi-particle match well and facilitate tunneling. This causes the cross sections and reactivities to peak for DT and $\\mathrm{D}\\,^3\\mathrm{He}$, while the DD reaction is far from resonance in the plotted energy range.", "469" ], [ "<PERSON> in his text on field quantisation tries to justify this exact same point in example 10.2:\nIt is very difficult to find an exact description of the bound states of the $e^+e^-$ system since this would amount to solving the relativistic two-body problem...\nAccording to the general principle of Lorentz invariance the state vector of positronium $|Ps\\rangle$ can be classified by the eigenvalues of the operators $P^\\mu$, $\\mathbf J^2$ and $J^z$. In addition we have the operators of space inversion P and charge conjugation C, which commute with the set of kinematic operators. The corresponding eigenvalues are $$P|Ps\\rangle = \\pi_P |Ps\\rangle, C|Ps\\rangle = \\pi_C |Ps\\rangle\\tag{1}$$ where $\\pi_P = ±1$ denotes space parity and $\\pi_C = ±1$ denotes charge parity. Now we make the following ansatz for the state vector of positronium in the center-of-mass system $(P = 0)$: $$|Ps\\rangle=\\int d^3\\vec p\\sum_{s,s'}R(\\vec p,s,s')b^\\dagger_{\\vec p,s}d^\\dagger_{-\\vec p,s'}|0\\rangle\\tag{2}$$ where $R(\\vec p,s,s')$ is the wave function in momentum space.", "66" ], [ "Here $s$ and $s'$ are the projection of the electron and positron spins onto the z axis. The state (2) contains one electron-positron pair with a combined momentum of zero and is an approximation to the true bound state since the particle number in QED is not a conserved quantiy. In general higher multi-pair configurations with total charge zero, such as $b^\\dagger b^\\dagger d^\\dagger d^\\dagger|0\\rangle$ etc., can contribute to the state vector. In positronium, however, such admixtures are very small, owing to the essentially nonrelativistic nature of this system. In any case, for the purpose of classifying the bound states it is sufficient to use the ansatz (2); any complicated higher-order admixtures would have the same symmetry properties.\nFor now, I'll take this as an explanation which invalidates my previous understanding\nthe creation and annihilation operators for these states(positronium atom creation/annihilation operator in this case) are independent of the creation and annihilation operators for the constituent particles.\nSince now the creation operator of positronium atom, for the positron and for the electron don't commute pairwise.\nAny additional remarks/clarification/answers are welcome!", "976" ], [ "No, you cannot say that there is a particular order in which the shells are filled.\nRelation between $\\mathrm{p_x,p_y,p_z}$ with $\\mathbb{m_l}$ values\nThe magentic quantum number ${m_l}$ represents the projection of the angular momentum $\\vec{l}$ of an electron in an orbital, on an axis, usually taken to be the z-axis. The orbitals, and their $\\mathrm{m_l}$ values, come from the solution of the <PERSON>'s equation for a Hydrogen atom.\nNow, the problem is, the solution for the orbitals with ${l=1}$ (i.e. p orbitals) produces one real wavefunction (corresponding to $m_l=0$), and two other complex wavefunctions (corresponding to $m_l=1$ and $m_l=-1$). If the main axis is taken to be z, then the $m_l=0$ orbital has the usual dumb-bell type shape and points in the z-direction, so it is the $\\mathrm{p_z}$ orbital. However, the complex orbitals are conjugates of each other, and if you plot the real part, they both look like donuts. (You can find more on this here and here). So the other two orbitals, let's call them $\\mathrm{p_1}$ and $\\mathrm{p_{-1}}$, do not really correspond to anything we usually see in the chemistry textbooks.\nHowever, wavefunctions themselves don't hold any physical meaning, because we cannot observe them. We can only observe things like electron energy, electron density etc. So, we can take linear combinations of the two complex orbitals to get two new real p orbitals, as long as it conserves the total energy.", "976" ], [ "However, doing this means that the new $\\mathrm{p_x}$ and $\\mathrm{p_y}$ orbitals are no longer eigenfunctions of the $\\hat{L_z}$ operator (i.e. they have no well defined angular momentum along the z-axis, so no well defined $m_l$ value). In most cases angular momentum is not really important, so we can safely use $\\mathrm{p_x}$ and $\\mathrm{p_y}$.\nI suspect that there is a similar case with the d orbitals as well.\nWhich orbital is filled in first?\nInside one shell (e.g. 2p) the electrons are indistinguishable, so it is not possible to say which orbital is occupied by which electron. However, if a shell is not completely filled, i.e. there are unpaired electrons, then there would be an total orbital angular momentum and total spin angular momentum coming from all of those electrons combined. It is possible to identify states which have different angular momenta, as they have different energies. This forms the basis of the coupling schemes (LS coupling or jj coupling). However, you still cannot say exactly which electrons are residing in orbitals with which $m_l$ values, because multiple arrangements (microstates) can contribute to the same energy level (term).", "976" ] ]

[ 7507, 5700, 10278, 10639, 6481, 5777, 3230, 11050, 6178, 5451, 4376, 1006, 2462, 2125, 7533, 1086, 1347, 9487, 2725, 4831, 9330, 1088, 10469, 270, 189, 4722, 1152, 6961, 9504, 3311, 9638, 4996, 6448, 10066, 11099, 4522, 1954, 4875, 1474, 7722, 6957, 2718, 1867, 6306, 8661, 10997, 11355, 3768, 8032, 10838, 5140, 8845, 5643, 9473, 1426, 9926, 9574, 5384, 36, 4457, 3134, 4736, 6860, 3063, 6507, 5947, 10230, 6410, 10869, 4763 ]

[ [ "Micro-Bit Arcade Machine\nIntroduction: Micro-Bit Arcade Machine\nIn this Instructable you will be hooking up a joystick to a Micro-bit and making a machine you find at arcades. Inspiration to make this project came when I decided to figure out how to add parts onto Micro-bits, like joysticks. Once I completed my original goal, I decided to go further and instead of a Micro-bit, Joystick, and a million messy wires in between, I challenged myself to make an Arcade style box to put it in and I hope you will too!\nSupplies\nYou will need:\n* A light cardboard box (see step 1)\n* A hole puncher\n* A Micro-bit with some sort of extension board\n* A battery pack and USB cable\n* 4 Micro-bit buttons\n* 4 connector wires, 1 black, 1 red, and 2 random\n* A computer (pretty sure you have one!)\nStep 1: Measuring the Box\nFirst let's get some cardboard,\nThis arcade machine should be made out of light cardboard, slightly thicker then a cereal box, but not corrugated. The end result should be about the width and length of your micro-bit extension board.\nFor this project I will be using the measurements for this extension board (in the kit). Most extension boards that are smaller then 3.25 inches should work though.\nNow you can use the pictures as a guide to measure your box, clicking them enlarges the pictures.\nStep 2: Cutting and Adding to the Box\nNow that we have box measured, it is time to cut it. Simply cut it out along the edge of the boarder,\nAlso looking at the pictures for text boxes.\nLet us begin to measure holes to put things in.\n1.", "997" ], [ "Starting with the hole for the Micro-Bit, outline the uppermost part of the box upside down with your Micro-Bit, as in the pictures.\n2. Now use a hole puncher to make a hole right were the battery pack is going to go through.\n3. Finally, make a hole on the end of the box just big enough to fit your joystick.\nStep 3: Micro-Bit Side\nFirst let us download the code that we are using for this project.\nUse a USB to plug in your micro-bit into your computer, then download the code to your computer using the download below this step, then download it to your Micro-Bit using its file (found in your computer's files)\nOnce completed, your Micro-Bit should light up \"A\" on its screen.\nOnce you put your Micro-bit into the extension board, you should look for four pins on it, the Ground pin, 3V(volts) pin, pin 1, and pin 2.\nStart putting in your connector wires, connect one end of the black connector to ground, the red connector to 3V, and the two random ones to pins 1 and 2.\nFinally, take the other ends of each and put the black connector to Ground on the joystick, the red to 5V, pin 1 to VRX, and pin 2 to VRY.\nVRX makes an output between 0 and 1023, depending on the x position of the joystick(or horizontal position) VRY outputs the Y position (or vertical position).\nNow we will be putting on the Micro-bit to the arcade box.\nDownload Here\nStep 4: Gluing the Box\nStart by using hot-glue to glue the Micro-bit extension board onto the box, as shown in the picture. then push your joy-stick into the hole you made earlier, then gluing it in place.\nAt this point you should have cut out the box and put on the Micro-bit. You are now ready to glue the box together\nput glue on one of the tabs, like in the picture. Then fold that tab into another side, so that it folds up the box.\nrepeat this until you have all the tabs folded in, making sure that all the electronical parts don't move in the middle of it.\nOnce you have glued the whole box together, the last step is to plug in the battery to the Micro-bit and try it out!", "259" ], [ "Library Book Reminder\nIntroduction: Library Book Reminder\nI was part of a Digital Making and Learning course at my university, and our final project aimed to solve real problems. Now I have pretty terrible object permanence and have a pricey habit of forgetting to turn my library books in on time.\nSo I aimed to solve that problem, by creating a library book reminder board, which I have been lovingly calling my Book Buddy.\nIn this instructable, I will walk you through step-by-step to help you create your very own Book Buddy!\nSupplies\nMaterials\n* A piece of a wooden plank, any size will do, just try to get a piece that is not too thick, since we will be cutting holes into it later.\n* two external buttons (These are the ones I used)\n* one LED light of whatever color you'd like (This is the one I used)\n* Adhesive whiteboard\n* Circuit playground (I used the classic version)\n* Alligator clips (These are the ones I used)\n* An easel (optional)\n* Whiteboard marker\n* A type of strong adhesive (I used J-B Weld)\nTools\n* a drill\n* small square-shaped file (Similar to ones found in these sets)\n* measuring tape\n* a pencil\n* a permanent marke\nStep 1: Step 1: Measuring the Board\nThe first thing you'll need to do is measure and mark the board to map out where the buttons, LED light, and whiteboard sticker are going to sit.\nI left about an inch of space between the edge of the board and the whiteboard and left a space at the top of the board for the light and buttons to sit. Then I put the buttons evenly spaced between the top of the whiteboard and the top of the wooden board, and I evenly spaced them out between the left and right edges of the board to the best of my ability.\nMake sure to mark these lightly with a pencil! Once everything is placed we will erase any marks that are still visible!\nStep 2: Step Two: Placing the Whiteboard\nOnce the plan has been mapped out on the wooden board, measure and cut out a piece of the adhesive whiteboard to match the space you drew on the board. Then simply remove the back layer of the whiteboard and lay the sticker on flat. I used an old hardcover book to flatten the whiteboard out and squeeze out any bubbles.\nStep 3: Step 3: Trace the External Buttons and LED Light\nGo back to the markings that you put on the board for the button and light placements. Take your pencil and lightly trace around the edges of each button and light.\nIt's ok if they aren't perfect! We will adjust these later when we actually cut them out, we just need a base to work from.\nStep 4: Step 4: Cut the Holes\nNow we can start cutting out the holes for our buttons and LED light.\nFor the LED light, just use a drill bit that is roughly the same size as the circle that you drew for the LED light. It's generally safer to err on the small side, as it is easier to make the hole bigger than to make it smaller.\nThe square buttons will take a bit more time.\nFirst, drill a hold in the center of the squares that are drawn on the board. Then take the square-shaped filer and start to shape the holes into squares.", "74" ], [ "I recommend checking the size of the holes frequently by placing the button on these holes to see if it will fit. Keep filing until the buttons can be inserted nicely into the slots.\nStep 5: Step 5: Securing the Buttons and Light\nIt is important that we secure the buttons on the board so they do not pop out the back when pressed.\nYou could add an adhesive around the edge of the button to secure it to the board. I personally used J-B Weld apoxy to secure mine. If you use J-B Weld, be sure to follow the instructions of the product carefully. You can also add glue to the LED light as well if it is not staying in the board.\nStep 6: Step 6: Getting Started on Coding\nNow we will begin coding for our Circuit Playground.\nFollow this link to the makecode website that we will be using.\nClick the \"New Project\" button to get started. You should be greeted with this screen. In the far left corner you will see the circuit playground, and to the right of that is the menu. This menu holds all of the functions that we will be using to code our project.\nStep 7: Step 7: Creating Variables and Assigning Pins\nFirst, we will need to create two separate variables.\nClick the pink Variable tab in the menu, and click \"Make a Variable.", "259" ], [ "Mouse the Self-driving Robot\nIntroduction: Mouse the Self-driving Robot\nMouse is a simple maze solving robot to teach students and young engineers about robotics and the use of a micro-controllers.\nThe robot uses a Micro:bit connected to a Kitronic motor diver board and an ultra-sonic sensor to find information and make a decision as a result.\nThis project is designed with a simple and easy to understand program that allows the robot to drive itself and turn when it detects an object in its path.\nWhile creating this project I designed it so that the idea of the vehicle is easily changeable without having to change the hardware.\nI hope that anyone recreating this project will expand on my program and come up with new functionality. Other features that I tried was add RC features with the addition of a second Micro:bit that is used as the control panel and can send, receive and display data to the robot.\nFind the repository for this project at: https://github.com/juneberries/mouse006\nSupplies\nElectronics:\n* MicroBit V1 or V2\n* Kitronik Motor Driver Board V2\n* 2x Right Angle Geared Motor\n* Ultrasonic Distance Sensor HC-SR04\n* Wires\n* Battery Pack\nOther Supplies:\n* Cardboard Sheets\n* Hot Glue\n* Electrical Tape\n* Double Sided Foam Tape\nTools:\n* Utility Knife\n* Hot Glue Gun\n* Screwdriver\n* Soldering Iron\n* 3D printer (optional)\n* Laser Cutter (optional)\nStep 1: Create a Base\n* I designed a base that would have enough room for all the components and left space to the sides of were the motors would go, this is for the wheels.\n* When designing the base it is important to keep in mind the position of where the wheels will be, in this case I used two wheels so I made sure to keep them in the front of the robot.\n* I measured and drew out the design on a thick piece of cardboard\n* I cut out the shape with a box cutter and cleaned the edges with a pair of scissors.\n* To finish I covered all the sides in black electrical tape to hide any rough edges.\nBelow I left a 3-D model of the base that can also be 3-D printed or laser cut.\nLink for Base\nStep 2: Put in Components\n* I set out the motors and the driver board first, these were some of the biggest and most important parts.\n* I used double sided foam tape to stick down the motor driver board and hot glue for the motors.", "949" ], [ "I find double sided foam tape is perfect for sticking down all types of PCB's as it sticks well, non-permanent and cushions the connections of solder on the underside.\n* Next I used hot glue to glue down the ultrasonic sensor with the pins facing upwards.This allows for easier wiring that can be accessed if needed at a later time.\n* Lastly I added a dot of hot glue to the motor connections for the wheels and put one wheel on both sides.\nStep 3: Wiring!\n* I took a battery snap and screwed each wire to its matching place in the terminal ports on in the power section on the right side of the board.\n* I ran two wires from each motor into the terminals MOTOR1 (m1) and MOTOR2 (m2), m1 being the right side motor and m2 being the left side, it does not matter with side the two wires go as it can be easily changed in the code later on.\n* I added a small dot of solder to all of the connections on the motors to make sure no wires came loose.\n* I soldered a wire to each of the four pins on the ultrasonic sensor. Then I connected these wires to the pins on the back, gnd to GND, vcc to 3V. For the input and outputs I used the front terminals, echo INPUT1, P1 and trig to INPUT2, P2.\nStep 4: Coding the Ultrasonic Sensor\nThe sensor should be wired as shown:\n* VCC 5v\n* GND GND\n* Trig P2\n* Echo P1\n* I initialise the variable were we are going to store the data from the readings of the sensor.\n* I send a signal to the trigger pin telling it to play for 10μs then stop.\n* I finally tell the code to read how long (in μs) P1 is getting a signal, divide my 36 (which I found to give the distance in cm) and write that number to are variable \"dis\".\nStep 5: Coding\nNow we have to code the mirco:bit.", "611" ], [ "How to Make a Garage Door (EASY!!!)\nIntroduction: How to Make a Garage Door (EASY!!!)\nThis is a EASY arduino project that you could create to impress your teacher and friends. This project is an IR sensor-controlled garage door. It uses 2 Servo motor's to move the garage door into an opened and closed orentation. The inferred sensor (IR) is effective and long range with a range of 1-5 meters. This project is great When paired with an arduino car project.\nSupplies\nElectronics:\n* 2 Servo Motor's\n* 1 Infarred Sensor (IR)\n* 1 Infarred Remote (IR) (any tv remote works)\n* 2 Resistors\n* 5-10 LED's (optional)\n* 1 Breadboard\n* 1 Arduino Uno\nAccessories:\n* Frame (wood, 3D printed)\n* Construction Paper (Garage door)\nTools:\n* 1 Wire Cutter\n* 1 Glue Gun\n* 1 Soldering Iron\nPower/Connections:\n* Wires\n* 2 9v Batteries\n* 1 battery cap (buckle connector)\n* 1 battery cap (male DC plug)\nStep 1: Research\nThere was a planning process before I started this project to figure out what to do. I wanted to create something unique that had never been done before, and I couldn't find anything on garage doors. So, right there, I confirmed my project idea. This section contains background information on the most important and intricate components.\nArduino:\n* Arduino is an open-source electronics platform that uses simple hardware and software to make it easy to use. Arduino boards can take inputs - such as light from a sensor, a finger on a button, or a Twitter message - and convert them to outputs - such as turning on an LED, triggering a motor, or publishing anything online. The arduino uses the format code of C++.\nInfarred Receiver (IR):\n* IR(Infrared) Receiver Extender cable, which consists of an IR receiver and a plug connected by a wire, is used to conveniently receive and amplify the infrared remote controller signal. The epoxy package and shell of an infrared receiver can filter out visual interference.\nServo Motor:\n* A servomotor (or servo motor) is a rotary actuator or linear actuator that can control angular or linear position, velocity, and acceleration precisely. It consists of a suitable motor coupled to a position feedback sensor.\nTransistor (NPN):\n* The NPN transistor is designed to pass electrons from the emitter to the collector (so conventional current flows from collector to emitter).", "769" ], [ "The emitter \"emits\" electrons into the base, which controls the number of electrons the emitter emits.\nStep 2: Wiring Part 1\nBefore Starting the wiring let me tell you what each wire color represents:\nBlack = Ground\nRed = Power\nGreen = Arduino Output To BredBoard\nBlue = Arduino Output To Component\nSteps:\n1. Connect power and ground from the arduino to the bredboard\n2. Connect the first servo to pin 11 on the arduino\n3. Connect the second servo to pin 3 on the arduino\nNote : connecting the servos to the arduino will allow it to send code straight to the servo\nStep 3: Wiring Part 2\nIn this wiring step, we will connect the IR receiver. The IR Reciver is the most important component in this project because it connects to a controller, which sends signals to the arduino and then to the servo to tell it to move up and down when pressed.\nSteps:\n1. Connect the IR Reciver to pin 7 on the arduino\n2. connect the IR Reciver to Power and Ground\nNote : For the IR Controller you will program that in the coding section. also make sure that the IR reciver in facing in the downwards direction of the bredboard\nStep 4: Wiring Part 3 (optional)\nThis step is optional; it simply adds a spark to the project by turning on a light when the garage opens and off when the garage closes. Instead of just one led, I soldered eight together to make a chandalier. Looking at the diagram, the inner circle connects to ground, while the outer circle connects to power.\nSteps:\n1. Connect Arduino pin 4 to the transistor's base (make sure the connection is through a 1k OHM resistor)\n2. Connect the LED's negative side to the emitter and positive side to power from the bredboard (make sure poweris connected thorugh a 330 OHM resistor)\n3. Connect the transistor's collector side to ground directly.\nStep 5: Code\nSimply copy and paste the code into the Arduino editor and connect your computer to the Arduino to upload it.", "991" ], [ "How to Make a Basic Ultrasensor Keyboard Prototype With Arduino\nIntroduction: How to Make a Basic Ultrasensor Keyboard Prototype With Arduino\nFor this Instructable, I have made a primitive musical soundboard using an ultra sensor as a keyboard. Here I will show you the basic steps on how to create such a device yourself. Later on, in December, I will demonstrate to you how to make a more complex or soldered version of this soundboard with the Arduino.\nSupplies\nWhat You Need (some examples of the materials are demonstrated above):\n* Wooden board to make the keyboard sturdy, approximately 27cm x 32cm is wide enough.\n* One passive buzzer\n* One ultrasonic (HC-SR04) sensor module\n* 1-2 breadboards\n* Approximately 5-10 woodscrews\n* Approximately 2-3 male-to-male wires\n* 4 female-to-male or Dupont wires\n* One Arduino\n* 6-12 woodscrews\nOther Basic Materials\n* ruler (preferably one that measures in cm or mm)\n* pencil and/or pen\n* tape\n* screwdriver\nBONUS:\n* 1 RGB led\n* 4 more male-to-male wires\n* Possibly 3 220 Ω resistors.\nCode requirements:\n* Arduino Libraries “pitches,” “SR04.h”\n* Buzzer Code\nMOST IMPORTANT REQUIREMENTS:\n* Patience\n* Self-confidence\n* Self-love\n* tenacity\nStep 1: Setting Up the Board\nThe first thing you would want to do is set down your wooden board. Then place your Arduino, Ultrasensor, and breadboard in a way that they are accessible and close to one another, yet spacious enough for the Keyboard. As you can see with my finished prototype, I originally intended to have more components in my project, which is why mine is so spacious, but due to time constraints and issues with the button switches, I had to remove those components. Oh well, it's just a prototype in this stage; less is more, I suppose. Will probably add them later on in December.\nAnyway, I recommend you arrange your board like this, as you can see above in the diagram.\nStep 2: Drawing the Notes\nThe next step of this process would be to measure the sides of your wooden board. The first thing to do is make a mark 6-8 cm away from the ultra sensor. The next thing to do is after you make after your first mark is make an additional 2 cm marks all the way to the end as seen in the diagram above. Say, if you plan to have eleven notes, draw twelve lines.", "769" ], [ "If you plan more, do more, but make sure they're at least 2 cm apart, otherwise you would have to reprogram your prototype later on.\nImportant note:\nIt would also probably help if you mark some distance that is even numbered so it would be easier to program later on.\nStep 3: Securing the Board\nAfter you place your components in a way you prefer, mark over them with a pencil or pen. Then use the woodscrews and screw them into the holes on the side of the Arduino (if you don't get it yet, those little protruding holes on the side of your Arduino are for woodscrews) and the soundboard. Since this is a prototype and it doesn't need to be too fancy, you can use tape, another wooden block, or even glue if you so choose to secure the ultra sensor. For my prototype, I used tape. Just make sure that the ultra sensor has a clear area and is not blocked by the tape, a woodscrew, etc. You can refer to the diagram with the black dots, each black dot signifies a woodscrew, which gives you a general idea of where to place your screws.\nIf you want to, you can even take off the adhesive strip and attach the breadboard to the wood, but I wouldn't recommend that if you plan to use that breadboard again.\nImportant note:\nWhen it comes the wood you have and the material,the minimum number of screws needed to secure your Arduino would be two, the minimum number of woodscrews for the breadboard would be four. You can add more if you wish, but its already secure as is. That is the number I went with for my prototype.\nStep 4: Wiring the Ultrasensor\nNow, this is the fun part. The first thing you want to do is wire your ultra sensor to the Arduino. Now, its time to get your female-to-male wires. With these pins, connect one to The Echo slot so the pin goes into pin 11, and the trigger pin goes into pin 12.", "259" ], [ "Easy Makey Makey & Scratch\nIntroduction: Easy Makey Makey & Scratch\nThis is my first instructable! I am going to explain how to integrate Scratch (programming language) with Makey Makey, I will make a cat Meow and walk in an easy to follow steps.\nThe best practice I use, is to do all the programming in Scratch then change it to Makey Makey. I hope this will help you with your projects.\nSupplies\n* Scratch\n* Makey Makey\nStep 1: Let Us Get Scratch\n* You can work with Scratch online. You don't need to join Scratch and have an account to start creating, just hit \"Start Creating\" and you are ready to start. Make sure to save your project into your computer, otherwise you will loose it.\n* Or you can work offline by downloading Scratch. I prefer the offline version because I don't have reliable Internet connection. Scratch is available for Windows, Mac, ChromeOS and Android.\nStep 2: Setting Up the Stage\nSprite: The default sprite used in Scratch is the lovely cat !\nYou can change this by selecting a new sprite, click the cat face to the right lower corner and choose\n* The library (click Choose a Sprite)\n* Draw your own (click Paint)\n* Upload one from your computer (Upload Sprite).\nI am going to stay with the cat.\nBackground: You can choose different backgrounds from the library, draw your own or upload from your computer.\nI will choose from the library the \"Colourful City\" background.\nStep 3: Let's Make the Cat Say Hello!\nNow, let's make our cat say something. You need to make sure that you are selecting the cat sprite before placing your code.\nDrag a \"When space key pressed\" block from Events, and a \"Say Hello for 2 sec\" block from Looks to your workspace. What this will do is that it will make the cat say hello for 2 seconds.\nNote that you can change the phrase and the time duration as you like.\nStep 4: Give Your Cat a Sound\nDrag a \"Play sound until done\" block from sound and place it before the \"Say hello\" block. You can change the sounds by going to the \"Sounds\" tab, you can even record your sound!\nStep 5: Let's Walk in the City\nIt gets a little bit tricky here. Don't worry !\nLet's get back to math for a second, we have two axis.", "141" ], [ "X axis is the horizontal and Y axis is the vertical. If we go to right from the zero on the X axis, it will increase X (Positive X). If we go to the left of zero, it will decrease X (Negative X). The same will apply to our cat! if we want it to go to the right then we move it by a positive step and if we want it to go to the left, we move it by negative step.\nTo do this:\nDrag two \"When space key pressed\" blocks to your workspace, to change the space to the arrow keys (right and left) press the drop down menu and select accordingly. Attach a \"Move 10 steps\" to the \"When right key pressed\" and \"Move -10 steps\" to the \"When left key pressed\", you can find the move step block in Motion. Now, change the 10 steps to 5, we don't want it to be super fast.\nDoes it look like walking? Apparently not! in order to fix that, you need one more step. Drag \"Next Costume\" block from looks and place it before the move steps block to make your cat looks like walking, try it on!\nStep 6: Finally Makey Makey\nAll what you need now is to connect your Makey Makey. You need to use the space, right arrow and left arrow in your Makey Makey.\nTo Programm it in Scratch, add the Makey Makey extension and you will see new blocks appear. Replace the \"When space key pressed\", \"When right arrow key pressed\" and \"When left arrow key pressed\" with the ones from Makey Makey blocks. Enjoy!", "149" ], [ "How to Design a Button Box Housing With Schematic and PCB\nIntroduction: How to Design a Button Box Housing With Schematic and PCB\nA couple months ago, I started a project on Tinker CAD, this would later become my fully working Button Box that I now regularly use in sim games and even for shortcuts in Fusion360. Up to my Tinker CAD project, I had limited skills in CAD and electrical design. After some time researching, I consider myself abled in both CAD design and electrical design (By no-means am I a professional so please take this advice with a grain of salt and feel free to let me know of any errors or improvements). For this Instructable, I will betrying to teach you the skills to design your own Button Box, as opposed to a set-in-stone final product, so my final product may look a little different than my examples.\nFor this Instructable, I recommend some exposure to Fusion360 or CAD software as I do not go in-depth on the basics of CAD.\nSome skills you can expect to learn in this Instructable are:\n* How to utilize Parameters in Fusion360 to create your Button Box Housing\n* How to create your own schematic for your own button box\n* How to utilize your own schematic to create a schematic in Fusion360\n* Howto create your own electrical library for your schematic in Fusion360\n* How to transform a schematic in Fusion360 to a PCB\n* How to Auto-Route nets for your PCB\nUnfortunately, I will not be teaching you to code your button box, as I do not yet feel comfortable in sharing code that I've designed. I have just started coding and do not want to damage or hurt anyone, but you can refer to the Additional information section at the end of this Instructable for some great coding resources.\nSupplies\nSome Buttons, Switches, and Encoders to think about using for your Button Box:\n* Momentary Push Buttons (12MM) -- Amazon\n* Momentary 2 Position Rocker Switches -- Amazon\n* Rotary Encoders (5 Pin) -- Amazon\nSupplies you should remember:\n* Screws M4x14 -- Amazon (I used metric because metric heat set inserts are most common)\n* USB - USB Micro -- Amazon (For use with Arduino Pro Micro)\n* Brass Heat Set Inserts M4 -- Amazon\nSpecial Notes or Comments:\nI recommend beginners in Arduino/electronics to start with an Arduino Leonardo because it pretty easy to protype designs using a bread board without soldering, but you can use an Arduino Pro Micro if you feel that you are good with soldering.\nIf you are going to use a 3D printer to create you Button Box Housing, I recommend using PETG filament for its strength and ease of printing qualities\nLastly, I used Carbon Fiber Vinyl for my Button Box Lid, but this is purely aesthetic.\nStep 1: Where It Started\nMy project started a couple months ago as a simples design in TinkerCAD, and I was waiting to learn some new skills that I would be able to apply once I started designing in Fusion360. I have to say, now that I have started using Fusion360, it has open many doors to all sorts of cool designs that I was not able to do in TinkerCAD. So, after learning some skills in Fusion360, I decided I would make this project that has been put aside for some time and make it my first purpose made design in Fusion360.", "737" ], [ "So, as I talk about some skills for the duration of this Instructable, keep in mind that I am learning alongside you and that you can also learn some skills from additional resources. You can refer to some great resources for learning CAD and designing your own Button Box on the final \"Step\" of this Instructable.\nStep 2: Creating a Schematic for Your Button Box\nButton Matrix\nIn order to create your button box, you will likely need to create a button matrix. Essentially, the purpose of a button matrix is to save pins on your Arduino so you can have more buttons. If you are wondering how a button matrix works, its similar to how you would find cells in a spreadsheet: you would use the rows and columns to find the cell, for example, cell A4 would be located on row A, column 4. Something to keep in mind if you are using this simple button matrix is that if you want to use multiple buttons at the same time, you will likely encounter random button activation called \"Ghosting\" , this is why I wouldn't recommend latching buttons. If in your case you do not need as many buttons, you could also simply connect your buttons directly to the Arduino. If you want to do some more research on button you can refer to this article.\nRotary Encoders\nAs for your rotary encoders, they must be connected individually to the Arduino, not through the button matrix.", "1014" ], [ "The Super Easy Pico Keyboard\nIntroduction: The Super Easy Pico Keyboard\nThis is the easiest Raspberry Pi Pico to Keyboard tutorial. You can make in easy visualized steps a functioning Macro keyboard, Password keyboard, or anything that you can do with a keyboard.\nI am also the original author and have made this tutorial in Dutch for the Makersbase. I am Tomodesigns and I do cool stuff on my Youtube and also Instagram! I am a dutch student with a passion for making and teaching others.\nThis tutorial is well tested on an audience with a beginner knowledge of soldering and coding. So you can also do this!\nYou can make your button casing with my laser-cut wood file or 3dprint file. You will only have to follow the wood or 3dprint steps depending on your chosen method. If you have a Pico and a button you can also follow this tutorial without building the buttonholder.\nSupplies\nThese are all the parts we need for this Instructables:\n* Button: https://amzn.to/3HKzllj (Diameter of 7mm)\n* Wire (Red and color of your choice):\n* 4mm wood or 3dprint filament\n* Micro USB cable\n* Raspberry Pi Pico: https://amzn.to/3neec9Q\n* Solder tin\nHere are all the tools we're going to need for this Instructables:\n* Soldering Iron https://amzn.to/39NkQk9\n* Lasercutter or 3Dprinter (Or nothing if you don't want to make a case)\n* Cable stripper: https://amzn.to/39KrTdh\nStep 1: Preparation Gluing (Wood)\nBefore we start making the box that contains all your electronics, we first have to collect the right parts. These are:\n* Wood glue\n* Wooden box parts\nThe wooden box parts file is included. You can laser cut this part or go to step 3 for the 3dprinted box if you don't have a laser cutter.\nStep 2: Gluing (wood)\nAs you can see in the video above, you can now glue the box together.\nNB! Do not glue the lid on the box yet.", "996" ], [ "This must still be able to open to put in all the electronics.\nStep 3: Download and Printing Parts (3D Printing)\nDownload these files from this link: https://www.printables.com/model/241877-pico-keyboard\nYou don't have to use any supports for this print and it is around 1,5 hours of printing.\nInfill doesn't matter.\nStep 4: Preparation Soldering\nFor soldering you need a number of things:\n* The Pico\n* A button\n* Two wires (red and color of your choice)\n* solder tin\nAnd we need some tools:\n* Cutting pliers\n* Cable stripper\n* Soldering iron\n* Little helper\nStep 5: Little Helper (Info)\nThis is the Little Helper. This handy tool has a magnifying glass and two little hands.\nWith these hands he can, for example, hold your Raspberry Pi Pico while soldering. So that everything is easily kept in one place. In the other hand, it can even hold the cables that you are going to attach to the Pico.\nHere is a link to buy this handy tool!\nAlways use the Little Helper when you can when soldering!\nStep 6: Cable Stripper\nTo solder cables to your Knop and Pico, you must first remove the casing from the cables. This is called stripping cables.\nWe do this to expose the part of the cable that conducts the current hole. You can recognize these conductive smaller cables by the silver/bronze color. We are going to solder these on the Pico and Button.\nStrip both sides of both your cables.\nStep 7: Pico Soldering\nIn this step, we are going to solder both cables to the Pico.\nWe do this by first putting some solder tin on the pico where we will connect the wires.\nWe are going to do this on pin 3.3V and GP10 (see image)\nStep 8: Button Soldering\nIn this step, we will solder the cables that we soldered to the pico in the previous step to a button. You have 2 pins on the button. Solder one wire per terminal.\nMake sure the ends of the wire do not touch!\nMake sure you soldered everything to the right points!\nStep 9: Attaching Button\nNow we put the knob through the hole in the lid and tighten it with the nut!\nStep 10: Download Ciruitpython\nClick https://downloads.circuitpython.", "819" ] ]

[ 6294, 631, 4718, 8265, 8000, 2894, 4653, 9381, 9953, 2130, 8186, 3296, 3263, 930, 9840, 10099, 10175, 5005, 10377, 5132, 10143, 1784, 6720, 5232, 3574, 837, 11376, 7596, 5454, 2037, 3051, 2543, 6168, 6846, 3101, 6590, 2729, 8074, 9743, 2405, 7855, 8691, 2430, 2515, 9109, 8879, 2385, 9363, 4428, 4265, 5273, 6335, 10886, 515, 4397, 3443, 771, 8670, 10591, 8366, 11320, 9844, 8463, 3777, 1974, 8301, 5075, 6554, 7615, 3418 ]

[ [ "Calculating vertex factor for scalar field theory\nI am practising basic QFT and am having some trouble with calculating the vertex factor of an interacting theory involving two real scalar fields, $\\phi_{1}$ and $\\phi_{2}$.\nIf I create a generic Lagrangian with interaction terms:\n$$\\mathcal{H}{\\text{int}}=g\\phi{1}^{2}\\phi_{2} + q\\phi_{1}^{2}\\phi_{2}^{2}$$\nI want to calculate the vertex factors associated with these interactions. So to calculate the $\\phi_{1}^{2}\\phi_{2}$ vertex, I calculate the three-point Green's function:\n$$G^{(3)}(x,y,z)=\\langle\\Omega|T\\phi_{1}(x)\\phi_{1}(y)\\phi_{2}(z)|\\Omega\\rangle = \\frac{\\langle0|T\\phi_{1}(x)\\phi_{1}(y)\\phi_{2}(z)\\exp\\left(-i\\int_{-\\infty}^{\\infty}\\mathcal{H}{\\text{int}}\\:\\mathrm{d}^{4}s\\right)|0\\rangle}{\\langle0|T\\exp\\left(-i\\int{-\\infty}^{\\infty}\\mathcal{H}_{\\text{int}}\\:\\mathrm{d}^{4}s\\right)|0\\rangle}$$\nWe can expand the exponential involving $\\mathcal{H}_{\\text{int}}$ to first order in $g$ and $q$:\n$$\\exp\\left(-i\\int_{-\\infty}^{\\infty}\\mathcal{H}{\\text{int}}\\:\\mathrm{d}^{4}s\\right)=1-ig\\int{-\\infty}^{\\infty}\\phi_{1}^{2}(s)\\phi_{2}(s)\\:\\mathrm{d}^{4}s-iq\\int_{-\\infty}^{\\infty}\\phi_{1}^{2}(s)\\phi^{2}_{2}(s)\\:\\mathrm{d}^{4}s$$\nClearly by <PERSON>'s theorem, any term without an even number of $\\phi_{1}$ or $\\phi_{2}$ terms will disappear, so the denominator will become:\n$$\\langle0|T\\exp\\left(-i\\int_{-\\infty}^{\\infty}\\mathcal{H}{\\text{int}}\\:\\mathrm{d}^{4}s\\right)|0\\rangle = 1-iq\\int{-\\infty}^{\\infty}\\langle0|\\phi_{1}^{2}(s)\\phi_{2}^{2}(s)|0\\rangle\\:\\mathrm{d}^{4}s = 1 - iq\\int_{-\\infty}^{\\infty}\\:\\mathrm{d}^{4}s\\Delta_{F}^{(1)}(0)\\Delta_{F}^{(2)}(0)$$\nWhere $\\Delta_{F}^{(1)}(z)$ is the Feynman propagator for $\\phi_{i}$.\nMy understanding is (from this other question I asked), that terms containing a tadpole diverenge ($\\Delta^{(i)}{F}(0)$) can be set to zero using the requirement that $\\langle \\phi{i}\\rangle = 0$, so the denominator evaluates to $1$.", "281" ], [ "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" ], [ "Getting the wrong sign in optical theorem\nIn Peskin&Schroeder chapter 16.3 we are showing how ghosts ensure unitarity in non-Abelian theories. My problem comes when I try to calculate a specific amplitude.", "843" ], [ "In equation 16.37 we have the term $$ \\frac{1}{2}(i\\mathcal{M}^{\\mu\\nu})g_{\\mu\\rho}g_{\\nu\\sigma}(i\\mathcal{M}'^{\\rho\\sigma}) $$ where the amplitude $i\\mathcal{M}^{\\mu\\nu}$ corresponds to the annihillation of a fermion=anti-fermion pair to a pair of gauge bosons while the amplitude $i\\mathcal{M}'^{\\rho\\sigma}$ corresponds to the creation of a fermion-anti-fermion pair from a gauge boson pair. My problem is in the calculation of the second interation.\nBefore going there let me explain that the above expression is within a phasespace integral and using the completeness relation for the metrics we get $$ i\\mathcal{M}^{\\mu\\nu}\\left(\\epsilon^{-}\\mu\\epsilon^+\\rho+\\epsilon^{+}\\mu\\epsilon^-\\rho-\\sum_{i=1}^2\\epsilon^T_{i\\mu}\\epsilon_{i\\rho}^{T}\\right)\\left(\\epsilon^{-}\\nu\\epsilon\\sigma^{+}+\\epsilon^{+}\\nu\\epsilon\\sigma^{-}-\\sum_{i=1}^2\\epsilon_{i\\nu}^T\\epsilon_{i\\sigma}^{T}\\right)i\\mathcal{M}'^{\\rho\\sigma} $$ where most of the terms are zero and the only contributions we have are $$ i\\mathcal{M}^{\\mu\\nu}\\epsilon^{-}\\mu\\epsilon\\nu^{+}\\epsilon^+\\rho\\epsilon^-\\sigma i\\mathcal{M}'^{\\rho\\sigma}+i\\mathcal{M}^{\\mu\\nu}\\epsilon_\\mu^{+}\\epsilon_\\nu^{-}\\epsilon_\\rho^-\\epsilon_\\sigma^+ i\\mathcal{M}'^{\\rho\\sigma}=\\ \\left(i\\mathcal{M}^{\\mu\\nu}\\epsilon^{-}_\\mu(k_1)\\epsilon^{+}\\nu(k_2)\\right)\\left(i\\mathcal{M}'^{\\rho\\sigma}\\epsilon^+\\rho(k_1)\\epsilon^-\\sigma(k_2)\\right)+\\left(i\\mathcal{M}^{\\mu\\nu}\\epsilon^{+}_\\mu(k_1)\\epsilon^{-}\\nu(k_2)\\right)\\left(i\\mathcal{M}'^{\\rho\\sigma}\\epsilon^-\\rho(k_1)\\epsilon^+\\sigma(k_2)\\right) $$ where we omit contributions of the transverse polarization vectors because they will vanish in our calculation of the Ward Identity.\nNow I haven't found anywhere a clear calculation of the amplitude $i\\mathcal{M}'^{\\rho\\sigma}$ so I tried to go through it on my own. The calculation is identical to $i\\mathcal{M}^{\\mu\\nu}$ but there is an extra negative sign which I don't understand where it comes from.", "818" ], [ "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" ], [ "Calculating a four-point Green function using <PERSON>'s theorem (problem 12.1 in Mandl & Shaw)\nIn problem 12.1 in Quantum Field Theory, Mandl & Shaw the aim is to calculate the four point green function\n$$ G^{\\mu\\nu}(x,y,z,w) = \\frac{\\langle 0 | T\\big(A^{\\mu}A^{\\nu}\\psi(z)\\bar{\\psi}(w)S\\big)| 0 \\rangle}{\\langle 0 | S | 0 \\rangle} $$\nin second order perturbation theory, where the interaction Lagrangian in S is the one for QED, $\\mathcal{L}I = eN\\big(\\bar{\\psi}\\gamma{\\alpha}A^{\\alpha}\\psi \\big)$, N is the normal ordering operator. I have seen similar examples and done this for some simpler numerators, but the number of factors in the time-ordered product causes the number of terms to increase significantly. This makes me question if I am applying <PERSON>'s theorem correctly and if there are any shortcuts I am missing and should be aware of.\nI start by taking $ S = S^{(0)} + S^{(1)} + S^{(2)} $ in second order, which gives the denominator as\n$$ \\langle 0 | S | 0 \\rangle = 1 + \\frac{ie^2}{2} \\int d^4x_1d^4x_2 \\big( \\bar{\\psi}^{\\bullet} \\gamma_{\\alpha}A^{\\bullet \\bullet\\alpha} \\psi^{\\bullet \\bullet \\bullet} \\big){x_1} \\big( \\bar{\\psi}^{\\bullet \\bullet \\bullet} \\gamma{\\beta}A^{\\bullet \\bullet\\beta} \\psi^{\\bullet} \\big)_{x_2}, $$\nwhere the term with $S^{(1)}$ gives no contribution due to it having an odd number of electromagnetic field operators.\nThe numerator is similarly expanded as\n$$ \\langle 0 | T\\big(A^{\\mu}A^{\\nu}\\psi(z)\\bar{\\psi}(w)S\\big)| 0 \\rangle = \\ \\langle 0 | T\\big(A^{\\mu}A^{\\nu}\\psi(z)\\bar{\\psi}(w)S^{(0)}\\big)| 0 \\rangle + \\langle 0 | T\\big(A^{\\mu}A^{\\nu}\\psi(z)\\bar{\\psi}(w)S^{(1)}\\big)| 0 \\rangle + \\langle 0 | T\\big(A^{\\mu}A^{\\nu}\\psi(z)\\bar{\\psi}(w)S^{(2)}\\big)| 0 \\rangle = \\ \\langle 0 |F^{(0)} 0| \\rangle + \\langle 0 |F^{(1)} 0| \\rangle + \\langle 0 |F^{(2)}0| \\rangle.$$\nThen I evaluate the terms in different order of perturbation theory one at a time.\n$$ \\langle 0 |F^{(0)} 0| \\rangle = \\langle 0 | T\\big(A^{\\mu}A^{\\nu}\\psi(z)\\bar{\\psi}(w)\\big)| 0 \\rangle = iD_F^{\\mu\\nu}(x-y)iS_F(z-w),$$\nthese I believe are the only non-vanishing contractions. $D_F$ and $S_F$ are the <PERSON> photon and fermion propagators.", "324" ], [ "Then once again due to $S^{(1)}$ having an odd number of electromagnetic field operators\n$$ \\langle 0 |F^{(1)} 0| \\rangle = 0. $$\nHopefully so far the calculations make sense. It is when evaluating $ \\langle 0 |F^{(2)} 0| \\rangle $ I start encountering problems. Applying <PERSON>'s theorem to this expression seems to generate a very large number of terms and in general I find it difficult to keep track of all the possible contractions in problems like these. Could someone who is more comfortable with this theorem for problems like these list all the contractions or at least tell me how many there are supposed to be? I know some of these will probably be identical under a change of integration variables, which makes evaluating them at the end a lot simpler.", "324" ], [ "Extra term when calculating variation in Lagrangian density under infinitesimal Lorentz transform\nConsider an (active) infinitesimal Lorentz transformation:\n$$ x^\\mu \\rightarrow x^\\mu + {\\omega^\\mu}_\\nu x^\\nu, $$\nso that any scalar field is transformed as\n$$ \\phi(x) \\rightarrow \\phi'(x) = \\phi(x) - {\\omega^\\mu}\\nu x^\\nu \\partial\\mu \\phi(x) + O(\\omega^2). $$\nNow consider a Lagrangian density function $\\mathcal{L(\\phi, \\partial\\phi)}$ (with no explicit spacetime dependence). Every scalar field is associated to a Lagrangian density field $\\mathcal{L}\\phi := \\mathcal{L}(\\phi(x), \\partial\\phi(x))$, which is itself a scalar field. Therefore, it transforms with variation:\n$$ \\delta \\mathcal{L} = -{\\omega^\\mu}\\nu x^\\nu \\partial\\mu \\mathcal{L}[\\phi] = -\\partial_\\mu ({\\omega^\\mu}_\\nu x^\\nu \\mathcal{L}[\\phi]), \\tag{1}$$\nwhere the second equality arises because $\\omega$ is antisymmetric. Since the Lagrangian only varies by a four-divergence, the action is unchanged.", "818" ], [ "This makes perfect sense: all we've done is shift around spacetime by an orthogonal transformation, moving around the $d^4 x\\ \\mathcal{L}$ terms in the action integral, so the total action integrated over the whole of spacetime isn't going to change. So far so good.\nThe problem arises when I try to calculate $\\delta \\mathcal{L}$ a different way. I think we should be able to calculate the variation using:\n\\begin{align} \\delta \\mathcal{L} & = \\mathcal{L}[\\phi'] - \\mathcal{L}[\\phi] \\ & = \\frac{\\partial\\mathcal{L}}{\\partial\\phi}\\delta\\phi + \\frac{\\partial\\mathcal{L}}{\\partial(\\partial_\\mu \\phi)} \\delta(\\partial_\\mu \\phi) \\ & = - \\left [ \\frac{\\partial\\mathcal{L}}{\\partial\\phi} {\\omega^\\alpha}\\beta x^\\beta \\partial\\alpha \\phi + \\frac{\\partial\\mathcal{L}}{\\partial(\\partial_\\mu \\phi)} \\partial_\\mu ({\\omega^\\alpha}\\beta x^\\beta \\partial\\alpha \\phi) \\right ] \\ & = - {\\omega^\\alpha}\\beta x^\\beta \\left[ \\frac{\\partial\\mathcal{L}}{\\partial\\phi}\\partial\\alpha \\phi + \\frac{\\partial\\mathcal{L}}{\\partial(\\partial_\\mu \\phi)} \\partial_\\mu \\partial_\\alpha \\phi \\right] - \\frac{\\partial \\mathcal{L}}{\\partial (\\partial_\\mu \\phi)}{\\omega^\\alpha}\\mu \\partial\\alpha \\phi \\ & = -\\partial_\\alpha({\\omega^\\alpha}\\beta x^\\beta \\mathcal{L}) - \\frac{\\partial \\mathcal{L}}{\\partial (\\partial\\mu \\phi)}{\\omega^\\alpha}\\mu \\partial\\alpha \\phi.\\tag{2} \\end{align}\nAs you can see, there's a second term that's appeared out of nowhere! Where have I gone astray?\nI've tried double-checking that $\\delta (\\partial_\\mu \\phi) = \\partial_\\mu (\\delta \\phi)$ and it seems to work out, so I don't think that's the problem. I found this very old post but I find the argument that\n$$ \\frac{\\partial \\mathcal{L}}{\\partial (\\partial_\\mu \\phi)} \\propto \\partial^\\mu \\phi \\tag{3}$$\nunconvincing. Say, for example, you had a $\\frac{1}{2} \\partial_\\alpha \\partial_\\beta A^{\\alpha\\beta}$ term - that's fine, because differentiating w.r.t. $\\partial_\\mu \\phi$ symmetrises $A$, so it works out that the extra term is zero, but the proportionality doesn't hold.", "818" ], [ "Sign error when deriving Weyl spinor transformation laws (3.37) in <PERSON>\nI am having some trouble deriving the transormation laws for the weyl spinors, equation (3.37) in the <PERSON> book on quantum field theory.\nBeginning with the realtion $\\psi\\to(1-\\frac{i}{2}\\omega_{\\mu\\nu}S^{\\mu\\nu})\\psi$ from (3.30) and the form of the transformation matrices in equations (3.26) and (3.27), I get\n$1-\\frac{i}{2}\\omega_{\\mu\\nu}S^{\\mu\\nu} = 1-\\frac{i}{2}\\omega_{0\\nu}S^{0\\nu} + \\frac{i}{2}\\omega_{i\\nu}S^{i\\nu} = 1 - \\frac{i}{2}\\omega_{00}S^{00} + \\frac{i}{2}\\omega_{0i}S^{0i} + \\frac{i}{2}\\omega_{i0}S^{i0} - \\frac{i}{2}\\omega_{ij}S^{ij}$\n$ = 1 - 0 + i\\omega_{0i}S^{0i} - \\frac{i}{2}\\omega_{ij}S^{ij} = 1+i\\omega_{0i}\\frac{-i}{2}\\begin{pmatrix}\\sigma^i & 0 \\ 0 & -\\sigma^i\\end{pmatrix} - \\frac{i}{2}\\omega_{ij}\\frac{1}{2}\\epsilon^{ijk}\\begin{pmatrix}\\sigma^k & 0 \\ 0 & \\sigma^k\\end{pmatrix} $\nThe discussion at the end of section 3.1, leading to equations (3.20) and (3.21) then suggest the identification $\\omega_{0i} = \\beta_i$ and $\\omega_{ij} = \\epsilon_{ijk}\\theta^k$.", "818" ], [ "<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" ] ]

[ 6148, 2133, 8741, 2105, 1448, 4529, 191, 8190, 10730, 10820, 6444, 1029, 9555, 8956, 6242, 2311, 2578, 9656, 2160, 9058, 439, 3970, 10692, 10811, 8553, 3712, 2561, 10815, 9833, 6531, 10682, 5328, 6763, 3166, 3726, 6658, 11194, 932, 6054, 758, 672, 4080, 9731, 7947, 4271, 483, 1243, 8874, 1709, 10572, 571, 2742, 1159, 1842, 2354, 6046, 6457, 3858, 2419, 7170, 1917, 3775, 7722, 2402, 8027, 1593, 8484, 6824, 7261, 5959 ]

[ [ "A Modern Take on the Phenakistoscope\nIntroduction: A Modern Take on the Phenakistoscope\nThe Phenakistoscope is an early optical illusion device that uses static images to create the illusion of motion through the principle of persistence of vision. It is regarded as one of the first forms of moving media entertainment that paved the way for the motion picture industry.\nWe are not sure how big is the community currently interested in phenakistoscopes, however, from browsing through the internet, there seems to be quite a huge interest in this subject.\nIf you do not know how a phenakistoscope works, you may visit https://youtu.be/r4B3FHHt_k8 to see one in action.\nIt may be amazing to watch the mirror reflected images come to life by peeking through the slits or slots of phenakistoscopes, however, it can be quite tiresome when viewing for an extended period of time.\nIn this instructable, we are going to build a modern phenakistoscope. The phenakistoscope disc shall be mounted on a motor rotating at a speed that works with a strobing LED strip to make the images on the disc magically come to life when viewed with our naked eyes.\nA traditional phenakistoscope is normally used by a person at a time. Our design allows a few people to view the animation at the same time which should be much more fun.\nOur modern phenakistoscope can be controlled to rotate the disc in either clockwise or anti-clockwise direction, change the speed of rotation as well as vary the frequency of the strobe light. We will also be able to adjust the brightness of the strobe light for better viewing.\nTo build this project, basic electronics component soldering skill and some knowledge on using the Arduino are required.\nYou may like to view the following YouTube video to see what we are going to build for this project.\nCAUTION:\nFor a small percentage of people with epilepsy, exposure to flashing lights at certain intensities or to certain visual patterns can trigger seizures.\nThis project requires strobing of the LED strip lights. If you experience discomfort looking at the images on the rotating disc or the light from the LED strip, you should stop looking at them immediately.\nStep 1: Building the Electronic Circuit Board\nFor this project, we need a motor to spin at a consistent speed for the best visual effect.\nWe tested with cheap DC motors but they are not able to spin at a consistent speed over time.", "134" ], [ "Motor speed slowly drifts lower after running the motor for a while and this is quite noticeable for this project as we have to regularly compensate by adjusting the strobe light frequency in order to stabilize the animation. We may be able to mitigate this using PID motor control but this will require motor feedback and more elaborate program codes.\nWe have some faulty CDROM drives lying around and the salvaged CDROM Brushless DC (BLDC) motors from these drives work great for this project. We were able to drive these BLDC motors at a much consistent speed without using any feedback mechanism. The CDROM motor disc holder also allows us to easily mount a CD/DVD disc with a phenakistoscope image pasted onto it.\nWe will not be showing how to salvage the BLDC motors from CD or DVD drives as this information is readily found online such as the following Instructable\nhttps://www.instructables.com/Disassembling-a-CDDVD-reader-and-reusing-its-parts/\nand YouTube videos such as the following which also show where to connect to the 3 phases of the BLDC motor.\nhttps://www.youtube.com/watch?v=GntH4ZcVKPU&t=244s\nThe electronic circuit and program codes to drive the CDROM Brushless motor are adapted from the following two Instructables:\nhttps://www.instructables.com/Run-A-CDROM-Brushles...\nhttps://www.instructables.com/Arduino-CDROM-BLDC-M...\nWe will be using two L293D ICs for driving the CDROM BLDC motor and we will be using a DC to DC Step-down module to supply power to the motor.\nWe will be driving the BLDC motor in open-loop operation mode without the need for rotor position sensors since reliability is not critical here and also to simplify the electronic circuit.\nIn our design, we will need 2 potentiometers. One for strobe light frequency control and another for motor direction change as well as for motor speed change.\nA toggle switch will be used for the brightness control of the strobe light. Light will be brighter with each switch toggle and return to default brightness level after 10 brightness incremental steps.", "16" ], [ "A DIY Flapping-wing Robotic Bat With Arduino, 3D Printed, and Lego-compatible Parts\nIntroduction: A DIY Flapping-wing Robotic Bat With Arduino, 3D Printed, and Lego-compatible Parts\nIntroduction\nBats use their forelimbs as flapping wings. They are the only mammals capable of true flight. Bats have been one of the symbols of Halloween. It is believed that witches worshipped horned figures with wings, possibly bats. Although bats have a creepy reputation, they have been widely used as Halloween decorations. In this tutorial, a flapping-wing robotic bat has been made that can be used as part of a Halloween decoration. The general view of the robotic bat is shown below. The current bat is made of some Lego-compatible parts, an Arduino board, a motor driver, an off-the-shelf DC gear motor, two red LEDs, a PIR motion detector sensor, and 3D printed parts. The red LEDs resemble scary eyes for the bat. Sensitivity to motion is another feature that has been added to the bat. When an object or a person passes nearby, the bat starts flapping its wings.\nStep 1: General View of the Robotic Bat\nIn this tutorial, we will make the body structure and the wing mechanisms of the bat using Lego-compatible parts. However, the wings are designed and 3D printed.", "949" ], [ "Then, a DC gear motor drives the crank mechanism of the bat to flap its wings. Since an Arduino Nano onboard is used, we can attach a diverse set of sensors and modules to the project. This enables us to get the most creative and let our imagination go limitless.\nStep 2: A Crank Mechanism for the Flapping Wings\nAs a creative decoration for the Halloween season, we can make our robotic bat scare people off by flapping its wings whenever a person passes by using a PIR motion detection module. The PIR motion detectors are similar to the ones used in automatic hallway lamps. Thanks to the open-source nature of the Arduino board that allows such developments.\nStep 3: PIR Motion Detector\nFor more sophisticated applications, an Arduino NANO board is added to the bat to significantly increase the expandability and programming elements of the project. As you know, various add-on shields can be added to any Arduino board to expand the project’s capabilities.\nStep 4: The Red LEDs of the Robotic Bat\nFor instance, the Arduino board allows us to add two super flux red LEDs to the bat so that they can be turned on whenever the bat detects any motion nearby. These features enable us to make our projects fun and interactive.\nStep 5: Materials\nList of electronic parts\nA) 1x Arduino Nano\nB) 1x PIR sensor\nC) 1x Mini Switch\nD) Jumper wires\nE) 1x Breadboard, Mini Size\nF) 2x RED LEDs\nG) 1x Power Jack, Barrel Type\nList of Lego Technic components\nA) Frame, 5x7 module\nB) TT Gear Motor\nC) 3D Printed Gear Motor Housing\nD) 3D Printed Lego-Compatible Coupling\nE) Gear, 40-tooth\nF) M3 x 25 Machine Screw\nG) M3 x 10 Machine Screw\nH) Axle, 12-module\nI) Axle, 6-module\nJ) Axle, 3-module\nK) Beam, 3-module\nL) Beam, 5-module\nM) Beam, 7-module\nN) Angular beam, 3x5 module\nO) Beam with crosshole, 2-module\nP) Gear, 24-tooth\nQ) Gear, 8-tooth\nR) Axle connector with axle hole\nS) Connector peg, 2-module\nT) Connector peg with the axle, 2-module\nU) Bushing, module\nV) Axle, 2-module\nW) Connector peg with friction, 2-module\nX) Bushing, 1-module\nStep 6: Assembly of Mechanical Parts\nLet’s start off by assembling the body structure and wing mechanisms of the bat. The body structure holds everything together including the gears, wings, and electronics. Prepare the Lego-compatible pieces according to the part list, and follow the step-by-step video tutorial below.\nStep 7: 3D Printed Parts\nIn order to hold the DC gear motor in place and make a proper connection to the Lego pieces, we have used custom-designed, Lego compatible, 3D printed motor housings, and shaft couplings. The wings are specially designed and 3D printed to give a proper outlook to the bat. Download and print out the motor housings, couplings, wings-1, and wing-2. Then prepare the required Lego-compatible parts from the part list, and follow the step-by-step mechanical assembly tutorial.", "832" ], [ "A DIY Zipline Robot With Arduino, 3D Printed, and Lego-compatible Parts\nIntroduction: A DIY Zipline Robot With Arduino, 3D Printed, and Lego-compatible Parts\nIntroduction\nHave you ever thought of robots that are involved in sports and recreation activities? Robots that could mimic the act of athletes like runners and, gymnasts. Such robots are extremely interesting for robotics enthusiasts, makers, and inventors. One of the sports and recreation activities that attract boys and girls, young and adults are ziplining. Ziplines are designed to transfer cargo or a person from the top to the bottom of the inclined cable. The cargo or the person is propelled by gravity and moves on the cable through a freely rotating pulley. The zipline robot that we are going to make looks like a monkey that moves on a cable by using its two arms. Making such a creature that uses its arms for locomotion on a cable is a challenging task.", "949" ], [ "However, in this tutorial, we are going to make a fun and easy-to-build zipline robot with Lego Technic components, an Arduino board, and some off-the-shelf electromechanical components. The instructions are prepared in a way that you can build them at home.\nStep 1: General View of Biped Robot\nThe zipline robot hangs itself from a cable and uses its two arms for locomotion across the cable. In its simplest setup, the zipline robot is made of Lego Technic components, an off-the-shelf DC gear motor, 3D printed parts, and an ON/OFF toggle switch.\nStep 2: Combination of Body Structure and Gear Motor\nFor more sophisticated applications, an Arduino NANO board is added to the zipline robot to significantly increase the expandability and programming elements of the project. As you know, various adds-on shields can be added to any Arduino board to expand the project’s capabilities.\nStep 3: Electrical Assembly\nFor instance, in the current project, a microphone from Adafruit is added to the zipline robot that enables a user to control the motions of the robot by clapping. This feature adds a lot of interactivity to the zipline robot. For example, you can control the speed of the robot by clapping, so that, the faster you clap, the faster it goes. Very fascinating.\nStep 4: Zipline Robot With Arduino Board and Microphone\nIn this tutorial, we will make the zipline robot’s body structure out of Lego Technic pieces and then drive the arm’s mechanical mechanism using an off-the-shelf DC gear motor that is attached to the body structure through a 3D-printed housing. The gear motor’s torque is transferred through a pair of bevel and worm gears to both arm mechanisms.\nStep 5: Materials\nList of electronic parts\nA) 1x 9v Battery Connector, Male DC Connector\nB) 1x TT Gear Motor\nC) 1x 3D Printed Gear Motor Housing\nD) 1x 3D Printed Lego-Compatible Coupling\nE) 2x Breadboard, Mini Size\nF) 1x Arduino Nano\nG) 1x M3 x 10 Machine Screw\nH) 1x M3 x 30 Machine Screw\nI) 1x L298N Mini Motor Driver\nJ) 1x MAX4466 Microphone Module\nK) 1x Power Jack, Barrel Type\nL) 1x Mini Switch, Toggle Type\nM) Male to Male Jumper Wire\nList of Lego Technic components\nA) Frame, 5x7-module\nB) Beam, 5-module\nC) Beam, 3-module\nD) Double bevel gear, 36-tooth\nE) Gear, 24-tooth\nF) Worm gear\nG) Double cross block, 3-module\nH) Connector peg with friction/axle, 2-module\nI) Connector peg with friction, 3-module\nJ) Bevel gear, 12-tooth\nK) Gear, 8-tooth\nL) Angular block 2, 180\nM) Axle, 2-module\nN) Bushing/axle extender, 2-module\nO) Bushing, 1-module\nP) Angular block, 5(157.", "832" ], [ "LOOPIE - DIY RGB LED Lamp\nIntroduction: LOOPIE - DIY RGB LED Lamp\nMeet Loopie, a minimalistic, enticing RGB LED lamp that can easily fit everywhere in your living space. The unique mystic shape of this lamp will make you lose all sense of time.\nStep 1: Meet Loopie\nStep 2: Why This Design ?\nIn this project, we've chosen a rounded rectangle shape that is not commonly used for LED lamps. But Why?\nLet's learn some psychology.\nThere are many interesting facts to consider when working with different shapes in design. It takes less cognitive brainpower to see rounded rectangles than it does to register sharp-cornered ones. This means it takes the visual senses more time to register the points of a rectangle than with an ellipse of the same shape. It seems that a shape with sharp corners literally interrupts thought by forcing the brain to pause at each point until they complete the circuit.\nThe first and foremost meaning of rounded shape is eternity since they have no beginning or end. The circle has a long association with the sun and Earth as well as other cosmic objects while the ellipse is similar to the whole universe. That’s why round shapes may give the feeling of magic and mystery. In addition, unlike the shapes, rounded shapes don’t have angles so it makes them softer and milder. As a result, by choosing this rounded rectangle shape, Loopie can provide an eternal, magical, and pleasant feel to the viewers.\nStep 3: Materials Needed\nThese are the major electronic components required for this project. Arduino is too big or too much for this project, so here we are going with the Digispark Attiny85, as the MCU.", "51" ], [ "It is similar to the Arduino line mostly in regarding the programming way, it is cheaper, smaller, and quite powerful. It is an MCU based on ATtiny85.\nJust as most Arduino boards come with a USB port for programming and sometimes as a source of power, Digispark comes with an onboard USB connector that can be plugged directly into a computer for programming of the device. The board can be powered via the USB port which will feed 5V to the board or from an external source via its VIN pin that can accept ~7 to 35V which will be regulated down to 5V through an onboard 78M05 voltage regulator.\nNote: If you are using more than 100 Led's, please use any powerful MCU.\nFor lighting up this project, we are using WS2812B 5V Addressable RGB LED Strip is extremely flexible, easy to use and each LED of the strip can be controlled separately by using a microcontroller. Each LED has been equipped with an integrated driver that allows you to control the color and brightness of each LED independently.\nThe LED strip should be powered using a 5V power source, and Digispark will also work in 5V. Our device needs around 22 Led's, so we need at least a 1.5 A current for the power supply. 5V 2A AC to DC adapter will do the job.\nNote:Make sure you select a power source that matches the strip’s needs.\nWe also used some thin silicone wires for making connections.\nFor this project, we are using leftover MDF pieces from the earlier project. The proper diffusion is possible even if there is a considerable distance between the acrylic and the MDF board. That's why we used this wood, with this much thickness.\nMaterials and Parts\n* 1 X Digispark Attiny85\n* 1 X WS2812B 5V Addressable RGB LED Strip\n* 1 x 5V 2A AC to DC adapter\n* 5m 28 AWG Silicone Wires\n* 2 x SS 304 ST2.9 X 13 mm Self Tapping Philips Head Screw\n* Plank of Woods(We used 18mm thickness MDF board)\n* Thin Wood Sheet(We used 4mm MDF board)\n* Wood Primer(Optional)\n* Enamel Paint(Optional)\nTools\n* Jigsaw\n* Wire Cutter\n* Sander\n* Chisel\n* Driller\n* Hot Glue\n* F- Clamp\n* Soldering Iron\n* Ruler\nStep 4: Testing\nFor uploading the code from Arduino IDE to Digispark Attiny85, just follow the instructions here .Then we uploaded our code to the MCU. You can grab the code from here.\nAfter, we connected the components as per the schematics and powered it up. The Led is working flawlessely. The library here used is Adafruit Neopixel. You can read more about here.\nThen we can move onto the wood working.\nStep 5: Edge to Edge Gluing\nSo we can join these two MDF boards to get the required length for the project, by means of the instant glue.", "635" ], [ "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" ], [ "3D Printed Jigsaw Puzzle\nIntroduction: 3D Printed Jigsaw Puzzle\nA jigsaw puzzle is something that everyone has played with once in their lifetime. The best thing I feel about this puzzle is that even though it looks simple but can take quite a while to crack. The complexity of the puzzle keeps on increasing as the number of pieces keeps on increasing even though it is a simple matter of putting the right pieces in the right place. For many kids, this was their first puzzle and they seem to be able to learn to solve it quite themselves. Give them a small puzzle to start with and let them solve. Eventually, they would and when they do, they realize that they can apply the same learned techniques to any kind of image. We started learning problem-solving from the moment we solved our first jigsaw puzzle!\nUsually, we are provided with a reference image that helps us solve the puzzle. For a simple image, sometimes, the reference image is not even required. Removing the reference image as an element just adds more surprise as to what the end product might look like. Imagine embarking on a journey whose end is still unknown but as you go on solving, the picture starts becoming more and more clear! You see - there is a relationship between life and a jigsaw puzzle.\nAt the same time, a jigsaw puzzle provides the possibility of customization and personalization. Imagine gifting a kid a jigsaw puzzle on the birthday. Personalize it by adding a custom message or image and see the face light up when the last piece of the puzzle finally maps into its place. You can gift your loved ones and customize it the way you want. You can even make a puzzle for the upcoming Christmas and New Year and arrange a puzzle-solving activity with your family and loved ones. You can even make one for yourself, vary it with the complexity that you want.", "729" ], [ "Solve it together or solve it with a group of people for a nice time together. Either way - if we happen to saw a jigsaw puzzle then we know we ought to solve it!\nIn this Instructables I will be guiding you to build your own 3D Printed Jigsaw Puzzle from start to the finish. We will be using Tinkercad for the 3D designing and you if you are a beginner then this is a good start to learning some 3D techniques. You will be able to customize the shape and size and learn some neat tips and tricks as you build the puzzle. So what are you waiting for? Lets get started!\nStep 1: Parts, Materials & Tools\nFor the 3D designing, we will be using Tinkercad as it provides a good starting point for beginners and lots of customization options even for the experts. You can access the same by clicking on this link: Tinkercad Dashboard\nIf you have access to a 3D printer then well and good, otherwise based on your country of residence you can find an online service that will help you turn your 3D masterpiece into reality and that will be your exercise.\nYou will be required to print an image which then will be applied on the final printed jigsaw pieces but you may choose to paint over the pieces as well. For this instructable, we will be using the self-adhesive paper which works best in such scenarios.\nAdditionally, for the scope of this instructable, the following materials will be typically used:\n* Pencil and Eraser\n* Ruler (to help with the cutting)\n* X-ACTO Knife (Scissor will do too)\nDepending on the way you want the end product to look like, following are the optional materials that may be required:\n* Glue (to stick the image on top of the puzzle)\n* Sand Paper (to provide finishing and adjustments to the final printed pieces)\n* Brush, Paints, Sketch Pens etc. (if you want to color the pieces yourself)\nCaution: Safety comes first. Handle the knife/scissor with caution. If you are using the X-ACTO knife then do put something beneath and between the table and the paper so as to not ruin the table with the knife marks.\nStep 2: 3D Designing\nA. After you have successfully logged into the Tinkercad dashboard, navigate to the 3D Designs tab and click \"Create new design\" to open up the 3D designing workspace. You will get a page similar to mine as you can see below.\nOn the top-left, you will find the project name which you can rename by clicking on it. You can find the basic shapes and other premade models on the right-hand side. The center of the workspace is where the object will be dragged and customized. On the left of the workplane are some of the ways you can control the angle and perspective.\nB. Follow along with the video below to see how you can create a basic jigsaw shape in Tinkercad.", "110" ], [ "Open Theremin From Scratch: Building a PCB From Open Source Plans\nIntroduction: Open Theremin From Scratch: Building a PCB From Open Source Plans\nThis Instructable shows the steps I took to build my own open source theremin (Open Theremin) when there was none available to buy online. The lovely thing about open source is that the plans are freely available to make and modify.\nA theremin is an electronic musical instrument that you play waving your hands in proximity of its two antennas to modify the sound.\nThe Open Theremin is an Arduino based open sourced hardware implementation of the instrument designed by <PERSON> in Switzerland. The open theremin PCB is a shield installed on top of an Arduino.\nWhat led me to make this was I was looking to get an Open Theremin for my nieces birthday gift but at the time they were all out of stock. Here is a video of the build and short demo of playing it for first time.\nSupplies\n1. Soldering Iron\n2. solder\n3. flux\n4. Tweezers\n5. Stereoscope (optional)\n6. Computer\n7. tooth brush\n8. isopropyl alcohol\n9. Printer\n10. Arduino Uno\n11. USB A to B cable\n12. stereo audio cable\n13. Test lead with banana plug\n14. 1/4\" copper tubing\n15. Banana plugs and jacks\n16. Mini Tripod\n17. Nuts and Bolts\n18. Scrap Metal\nStep 1: Download Open Source Gerber Files and BOM\nFor this open source project, the link to the plans were conveniently posted on the Open Theremin website. The actual files are hosted on github.\nhttps://github.com/GaudiLabs/OpenTheremin_V3_Shield\nThe gerber's are what the board house will need to build the board.\nThe bill of materials (BOM) are what the assembler will need to make a finished board. I chose to assemble the PCB's myself so I simply purchased all the parts to have them shipped to my house.\n1. Download the design files from github\n2. Extract the folder to get the gerber files and bill of materials\nStep 2: Ordering PCB's From JLCPCB\nThe open theremin boards only have 2 layers.", "485" ], [ "I used JLCPCB.com to order them since they have the lowest price. They have a minimum order of 5 PCB's.\nThe gerber's from the file package don't need any modification and can be sent directly to the vendor. You may need to view the gerber's in order to gather overall dimensions and number of layers of the PCB to be entered into the JLCPCB quote.\n1. put the gerber's into a zip file\n2. goto JLCPCB.com and make an account\n3. Start a quote and enter the board dimensions, number of layers, surface finish, etc. (I used lead free HASL)\n4. Upload the zip file with gerber's\n5. Pay\nStep 3: Ordering the Parts Off of the Bill of Materials (BOM)\nThe bill of materials contains a list of all the electronic components that will be installed onto the PCB. For the open theremin project, the bill of materials file is a Libre Office spreadsheet (*.ODS format).\n1. Using Libre Office, I exported this spreadsheet into an Excel .xls format\n2. Login to Mouser.com\n3. Goto BOM tool\n4. Uploaded the .xls spreadsheet to Mouser to create a shopping cart.\n5. Buy multiples of how many PCB's you want to make + 1 or 2 extra of each line item in case of mistakes\nStep 4: Assembly: Soldering Parts to PCB\nThis is the most tedious or fun part depending on if you enjoy soldering or not. With extra payment to the PCB manufacturer, this entire step can be done for you. Since I enjoy soldering, I chose to assemble the PCB myself. Take your time and be careful in this step. It is easy to create solder bridges or miss a terminal. Soldering problems can a primary cause of electronic problems when trying to bring up your boards.\n1. Print out or display the Bill of Materials\n2. Organize all the parts into categories: SMT IC's, passive SMT components (resistors capacitors), thru-hole components.\n3. solder SMT IC chips first\n4. solder SMT passive components\n5. solder thru-hole components last\nStep 5: Clean and Dry PCB's\nWhether using no-clean flux or not during soldering, I always clean the PCB after finishing soldering. This part is particularly important with sensitive electronics. Sometimes problems can arise from not cleaning flux/residue or not properly drying the PCB's.\n1.", "472" ], [ "A DIY Biped Robot With Arduino, 3D Printed, and Lego-compatible Parts\nIntroduction: A DIY Biped Robot With Arduino, 3D Printed, and Lego-compatible Parts\nIntroduction\nMaking Biped robots that can mimic human walking has always been the focus of scientists, makers, and inventors for many years. In fact, biped robots are mobile robots with articulated leg mechanisms that provide locomotion. To compare with wheeled robots, they can go upstairs and pass on obstacles, although, at a slower speed. Building humanoid biped robots have always been difficult due to the high number of joints and maintaining stability during walking. If you have no academic knowledge on forward, inverse kinematics, and control engineering, it is absolutely no problem. In this tutorial, we are going to make a fun and easy-to-build biped robot with Lego components, an Arduino board, and some off-the-shelf electrical components. The instructions are prepared in a way that you can build them at home.\nStep 1: General View of Biped Robot\nIn this project, the biped robot uses an interesting mechanical mechanism that mimics human walking with only one DC gear motor. The result is quite interesting.\nIn this tutorial, we will make the structure of the body and the leg mechanisms of the biped robot using Lego Technic parts. Then, one DC gear motor will drive the leg mechanism through bevel and spur gear trains.\nStep 2: Electrical Assembly\nIn the next step, we will add an Arduino Nano as the brain of the biped. Arduino Nano uses a small-size powerful microprocessor that makes it suitable for low-weight and small-size projects.\nVarious off-the-shelf motors, sensors, and shields can be easily connected to Arduino boards. This feature enables us to do a variety of tasks with the biped.", "949" ], [ "For instance, you can tell the biped to move back and forth and dance by programming the Arduino board.\nStep 3: Materials\nList of electronic parts\nA) 1x TT Gear Motor\nB) 1x 3D Printed Gear Motor Housing\nC) 1x BreadBoard, Mini Size\nD) 1x Arduino Nano\nE) 1x Neo Pixel LED Ring\nF) 1x Power Jack\nG) 1x 3D Printed Lego-Compatible Coupling\nH) 1x L298N Mini Motor Driver\nI) 1x Pushbutton\nJ) 1x M3 x 30 Machine Screw\nK) 2x M3 Machine Screw\nL) Male to Male Jumper Wire\nList of Lego Technic components\nA) Frame, 5x7-module\nB) Double bevel gear, 36-tooth\nC) Bevel gear, 12-tooth\nD) Beam, 9-module\nE) Beam, 5-module\nF) Beam, 3-module\nG) Angular beam, 3x5 module\nH) Bushing, 1-module\nI) Axle, 8-module\nJ) Angular block 2, 180\nK) Double cross block, 3-module\nL) Beam with cross-hole, 2-module\nM) Axle with stop, 4-module\nN) Beam, 3-module\nO) Axle, 2-module\nP) Connector peg with friction/axle, 2-module\nQ) Connector peg with the axle, 2-module\nR) Tube, 2-module\nS) Connector peg with bushing, 3-module\nT) Connector peg with friction, 3-module\nU) Connector peg with friction, 2-module\nV) Axle connector with axle hole\nW) Angular block 1, 0\nStep 4: Assembly of Mechanical Parts\nLet's start assembling the biped's body-structure and leg mechanisms. The leg mechanism consists of a parallelogram mechanism that is driven by a four-bar linkage mechanism. Prepare Lego Technic pieces according to material figure, and follow the step-by-step video tutorial below.\nStep 5: 3D Printed Parts\nLego Technic components only match with LEGO gear motors. In order to transmit power from the shafts of the off-the-shelf gear motors to Lego gears or axles, we need to print a housing for the gear motor as well as a coupling. The housing will serve as an interface or an adaptor between the gear motor and the Lego Technic beams. The coupling connects the gear motor shaft to the Lego Technic axle. These 3D printed parts are called Lego compatible housing and shafts. We have also created front and back body covers for the robot. The back cover look likes the oxygen capsule and protects the electronic part. The front cover acts similarly to armor. Please download the 3D files and print the motor housing, Lego-compatible coupling, and front and back covers with your 3D printer or use the ones in a maker space nearby.", "832" ] ]

[ 573, 8514, 137, 3369, 1805, 7678, 1588, 6793, 4675, 10377, 11138, 1399, 10564, 11320, 4920, 5958, 6745, 3074, 4726, 2245, 4031, 675, 4445, 4463, 5232, 8337, 2130, 5725, 3507, 7843, 5003, 5834, 9070, 5005, 2515, 2621, 423, 5132, 8089, 2292, 5459, 3263, 5441, 3671, 11001, 3443, 3648, 7887, 1461, 7339, 9254, 10324, 4602, 7844, 7797, 1564, 2732, 7702, 1784, 8550, 4451, 9278, 2841, 515, 8265, 10941, 5338, 921, 7536, 10867 ]

[ [ "I can point out a lot of reasons. But most of them are about the main character himself: <PERSON>.\n1. The most obvious reason is \"Humour\". <PERSON> can be a pretty complex character, but one thing that is certain about him is humour, which contributed greatly to his movie becoming a people's fave. He's not only making fictional humour, as in, humour that only applies in the movie. In the movie, he makes fun of even Marvel itself, and other superheroes/movies like Wolverine and Green Lantern. The character <PERSON> (<PERSON>), also played as another superhero in the movie Green Lantern, in which he had a green CGI animated suit. In the Movie <PERSON>, he says ***“don’t make the suit green or animated”***, referring to his superhero suit, and poking fun at the suit he (<PERSON>) wore in the movie Green Lantern. This makes him a different kind of superhero, not like the \"standard\" superheroes that are serious and uninteresting.\n2. The movie's length is just perfect. A lot of superhero movies feel the need to be over two hours long! This movie is just 1 hour 48 minutes. Just enough time to tell a story with some action and comedy without padding it out with pointless scenes\n3. Deadpool contains very little racial, political and social conspiracy theories. Most superhero movies seem to have hidden political translations.", "387" ], [ "An example is the X-Men Franchise. It draws deliberate parallels between the oppression of mutants and that of other marginalized groups, like the blacks and the LGBT community. But Deadpool doesn't contain any such content/tradition.\n4. The movie is balanced. It perfectly balances humour and drama/action, without completely overwhelming the audience with either. The movie gives you enough drama without being totally overwhelming. Most movies tend to bore out the viewers by over-emphasis of an event or plot. For example, <PERSON> suffered very much when he was experimented on. But his suffering is not forever showcased in the movie. every movie with <PERSON> (X-Men Character), who experienced the same suffering from the same types of experiments (from the same organisation too), is constantly darted with flashbacks and references to the times he suffered. In the end, it becomes depressing as the movie comes out to be a suffering story, rather than being an action feature.\nDeadpool went through so much and is no longer mentally well or sane but is ALLOWED to be funny by the movie. If Marvel had gone with the tradition of their other movies, Deadpool would either be a \"scary psychopath/sociopath\" with no feelings. Deadpool is a unique and even uplifting portrayal of someone with mental health problems\nIn conclusion, Deadpool is a likable, fun , compelling and even sympathetic character. And the movie is well crafted, and that's why people love it.", "387" ], [ "NOTE: I WROTE THIS MYSELF (no copy paste)\nThe Matrix is Good. And we’re not just talking about the movie. We are talking about the Matrix, the programmed simulation that almost the entire human race is forced to live inside.\nIn the 1999 movie The Matrix we find out that it is the future and machines have enslaved almost the entire race into living in a simulation of and using them as a power source. Outside the Matrix, there is a group of people called The Resistance, with their life goal being finding “The One” and putting an end to The Matrix.\nThere's a natural, simple thought that The Matrix encourages. This is that there's something bad about being inside the Matrix. We here think that this is what the movie got wrong! And that the Matrix is actually the best thing to ever happen to the human race!\nBut before we explain why, let’s talk about why some people and the movie claim that living inside the Matrix is bad. Everyone living inside the Matrix is being deceived about the real world, and The Resistance say that they need to realise that they are living a lie.\nBut why is the Matrix not good? Actually, people living in the matrix are much better off than people in the real world. In the real world, everyone lives underground and eats mush for every meal of the day. But in the Matrix, everyone lives at the peak of human civilization. It’s a pretty easy choice!!!!!\nSure, the Matrix still has lots of problems. For example there are still hundreds of thousands of people suffering from poverty and hunger. There are still bad people. But not everyone’s life is working a desk job and hacking the pentagon like <PERSON>.\nBut why? Why is the Matrix Not Good? Would people rather live in a polluted dystopian world run by machines where you have to eat mush for breakfast, lunch and dinner. Would people rather live in a world suffering from global warming and terrible diseases? Would people rather live in a world where there isn’t even sunlight? Of course not! The machines are doing a good thing for humans, even though they don’t know it. It is like a prison for humanity, but the only downside is how people feel about it.", "973" ], [ "An argument for why the matrix is bad is that people should know the truth. But in the world in this film, not knowing about the badness of reality is probably for the better (like RAC).\nThe Matrix is good, and here’s how to prove it: What would happen if <PERSON> was victorious? What would happen if the Matrix was destroyed, and all the world’s humans woke into reality? Well, there’s only one city and we’re guessing there’s not a lot of food slop to go round for billions of people. So, most of the people would just die. And that’s not counting the fact that there are huge armies of robots wandering around, ready to pretty much kill everyone (important fact). So, almost all of the Matrix-humans would end up dead pretty quickly.\nWithout the Matrix, life would be alright in the future, but we would also have to adapt to global warming and that sort of stuff. In the Matrix, humans don’t need to worry about the big stuff, so we can be much more productive. And since the Matrix runs on human-power, it’s environmentally friendly! So basically, the Matrix is better than the real world. I think.\nIn the movie The Truman Show, there is a similar occurrence occuring. <PERSON> believes to be living in a normal world until he realises that his life is <PERSON>’s Cave analogy or whatever. He finds out that he is living in a scripted world, this is not good. It's different from The Matrix because the only person being deceived is <PERSON>, the sole victim and his life would be much better outside of his small fake world. For example, there is no Fiji in his Dome, while there is in the real world.\nOn the other hand, there's no Fiji in the real world, but there is in the Matrix.\nIn the book Ready Player 1 there is another similar occurrence occurring. The world is basically destroyed, the majority of the world is suffering from poverty, the world is completely polluted and wrecked and most of humanity spends the majority of their time living inside a simulation called the Matrix whoops I mean the Oasis. The Oasis started as a video game until humans turned into their second life. In the Matrix, most of humanity is “forced” to live inside a simulation, and they don’t even know it exists, while in Ready Player 1 most of humanity sees the Oasis as an escape from their broken world.", "973" ], [ "Need help portraying a character's personality in my First Person POV Narrative\nI'm writing a First-Person POV story that is following the main protagonist. I'm trying to get to the main plot, but I can't do that without making the story enticing enough to make the readers want to keep reading up to that point, obviously. I'm not sure how to, but I want to clearly show my main characters arrogance through his dialogue and actions, but like I said I'm not sure how to. If it helps, here's some info:\nPlot Summary <PERSON>, a 15-year-old male, lived a pretty uneventful life until he got into a heated argument with his close friend, <PERSON>. The argument ends in a falling out, but their falling out doesn't last long as <PERSON> realises they are in danger. <PERSON> is oblivious to the serial killer approaching him, so <PERSON> pushes him out of the way and dies, something he never thought he'd do. When he opened his eyes again he was in a dark void with only him and the beautiful angel, <PERSON>. She tells <PERSON> that a dreadful force of evil has been born on Earth and only he can stop it.", "522" ], [ "<PERSON> is re-born onto Earth (Thus the name of the story, Re-Birth.) with all of the memories of his past life and is tasked with removing this 'evil' from it.\nAbout <PERSON>\n<PERSON> is a tanned male with azure eyes and jet black hair. Ever since his father passed away, he and his mother would sit in the house and barely communicate. He often lets his arrogance get the better of him and, even though he doesn't like to admit it, he is overly caring (Meaning he cares about others, even if he doesn't know them.). After his death, <PERSON> begins to change his ways and also his personality.\nI don't need to worry about his new, changed personality just yet; his arrogant persona is what I need. Like I asked before, I need to know the best ways to show his arrogance through his character. Anyone know how I can do this effectively? I just feel like I won't do it very well. If I need to write some more information then let me know and I will comment to you what you need. Thanks.", "624" ], [ "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" ], [ "<PERSON>\nI want to start with something that isn't directly connected to this movie but there are certain other stories that came to my mind when I thought about it. And those aren't stories this movie took inspiration from. The stories just have a similar feel to them.\nI'm a big fan of the game Shadow of the Colossus. A big silent world which never explains what happened there or how it even functions. Or the Neverending Story is a Story (emphasis on story I'm not directly refering to the movie) which even shares the fact that the Protagonist get's sucked into a fantastical world which exceeds our mind (he even has to learn a lesson before he can leave it).", "952" ], [ "Nothing get's explained we have to figure it all out ourselves. I don't have any problems with that. I don't need details on how this world functions. I can make them explanations up myself if the world gives me enough to work with.\nBut this isn't really what this movie is about. It's about a boy mourning the death of his mom and learning to accept his new mother (which is his aunt). That whole magical world thing is just a vehicle to make him see his mom for one last time and to give us some good old adventure 😎 (this is not a criticism)\nI'm just thankful that I finally got to see <PERSON> work in a cinema and for the first time even in japanese.", "80" ], [ "Heads up, this movie was also released under the Title \"Alien Uprising.\" I live in the States and that's how it is listed in my Netflix.\nThis movie is about a shadow invasion/conquering of earth by Extraterrestrials, where their goal is to minimize collateral damage. I.e. they don't want to destroy the world, only conquer it and rule over us. To this end, they disrupt communication networks to prevent organized resistance. Furthermore, a major threat to causing collateral damage is human panic. No communication prevents wide-spread panic.\nThe story follows 4 friends <PERSON>, <PERSON>, <PERSON>, and <PERSON>'s girl, <PERSON>, as they go clubbing, one picks up a girl, and the next day they wake up to find power, phones, radio, and TV all not working. On the second day, large flying saucers arrive over the cities.\nCarrie (<PERSON>) is the girl <PERSON> (<PERSON>) picks up at the club at the beginning of the movie.\nShe also is an alien/extraterrestrial visitor.\nThe Aliens have been living secretly among us.\nThe soldier (also an alien) guarding the Chemist shop moves to attack and kill the girl who knew he had \"the purple mark,\" presumably to conceal the alien existence.", "829" ], [ "<PERSON> attacks him, which could lead us to believe there are two factions.\nThe friends eventually wind up at <PERSON>'s (<PERSON>'s uncle) place (<PERSON>). <PERSON> is one of those ex-military, knows top secret stuff kind of guys.\nAt the end of the movie, the flying saucers (cylindrical ships) are locked into a space battle with pyramid shaped ships. We also the see soldier who was guarding the Chemist shop back to life. (Or at least a copy of him.)\nSo the way I see it, there are two possible endings here, which are ambiguous.\n(Ending 1) When <PERSON> killed the Soldier in the Chemist shop, she knew she wasn't truly killing him. So when the fighter ships are destroyed, the aliens are destroying ships, but they are not losing any life as they stage this battle for our benefit. The Aliens staged a fake war so that humans could come out of the event feeling like they had won, when in fact, the aliens had quietly assumed power.\n(Ending 2) The aliens are trying to do a shadow take over, but humans have built a massive fleet of space ships, copying technology that has crashed on earth over the years. As the movie concludes, the human space fleet is moving into higher orbit around earth, taking the fight to the enemy.\nI think Ending 1 is much more consistent with the theme of the movie focusing on mankind's capacity for violence, almost as if the movie is passing judgment on mankind and pronouncing him unworthy to continue living.\nI think you could probably come up with some other theories that fit the movie as well. It definitely is not the most clear ending in movie history.", "829" ], [ "Transformers: Dark of the Moon\nMy ultimate Guilty Pleasure to this day. And I want to tell a little story. The first time I saw this movie it was in the starting week on a friday. It was like 7:00 pm and a friend of my class suddenly called me. I picked up the phone and all he asked was: \"Do you want to watch Transformers 3 with me?\" (In German of course)\nMe who already was a big fan of the franchise back than said \"yes\" of course.", "1004" ], [ "So we met up and went to the Cinema.\nWhen we showed our tickets the employee asked us about our age. I was 12 and My friend was 13 at the time. So we were old enough to watch it legally (in germany). But then they told us we weren't allowed to watch it cause to movie would be over at 11:00 pm (or later). So I had to call my mom and let her talk to the cinema employee. So what she then had to do was the following: she had to come to the cinema to watch the movie with us so we had somebody who brought us home when the movie was over xD\nAfter that movie all my mom sad to movie about it: \"Yeah the effects were good.\"\nAnd yeah the effects are still crazy good to this day.", "79" ], [ "The Fast and the Furious: Tokyo Drift\nTokyo Drift was the first Fast & Furious-Movie I've ever seen. And to this day it's the movie of the franchise I've seen the most.\nTokyo Drift was always one of my alltime Guilty Pleasures.", "462" ], [ "I even stood to that when my whole reputation of the franchise was: it's just Point Break with Cars.\nI love japan and nearly everything connected to it.\nBut I have to admit: it was really bold casting the 23-year old <PERSON> as a 17-year old highschooler. As the japanese student I'd buy it. (Japanese school is much longer from what I know)\nBut yeah I still like it :D", "577" ] ]

[ 3787, 6450, 1663, 9061, 4954, 1757, 6962, 8371, 1566, 7584, 6874, 5077, 9200, 8731, 8322, 4426, 8982, 4756, 4053, 2766, 6797, 4863, 6134, 11134, 10778, 7579, 3129, 10562, 6371, 2955, 8942, 3646, 11076, 9841, 9038, 2562, 10314, 1552, 6094, 10404, 4587, 7311, 2901, 4346, 6121, 9377, 1077, 10451, 8258, 2478, 8813, 3489, 4498, 8139, 1722, 8621, 1290, 1379, 5540, 3807, 5000, 769, 6290, 6183, 2676, 59, 5889, 9318, 3801, 2046 ]

[ [ "Why pilgrims from India and Nepal throng to see an orchid that blooms in April · Global Voices\nShrine dedicated to gardener sisters whom <PERSON> used to meet at the Salahesh fulbari in Siraha district of eastern Nepal. Image by <PERSON>.\nAn orchid that blooms around mid-April in a garden of historical and cultural significance in Siraha, eastern Nepal attracts hordes of pilgrims from both India and Nepal every year.\nThe locals in the area of the garden, known as the Salahesh Fulbari, believe that the flower blooms on the very first day of the year, 1st of Baishakh (the first month in the Nepali Calendar). According to legend, the orchid symbolizes the garland offered to the folk hero <PERSON> by his beloved malin (a Maithili word for a female gardener).\nअनौठो फूल !\nपूर्व–पश्चिम राजमार्गअन्तर्गत सिरहाको पडारिया चोकदेखि दक्षिणमा रहेको ऐतिहासिक तथा प्राचीन फूलबारीमा नयाँ वर्ष वैशाख १ गते मात्र फुल्ने फूल । ‘सल्हेस’ फूलबारी ‘हारमको’ रुखमा एकाबिहानै सुनाखरी आकारको फूल फुल्छ र साँझ ओइलाएर जान्छ । तस्वीर: रासस pic.twitter.com/SCRYHquX0I\n— Saral Patrika (@SaralPatrika) April 13, 2018\nStrange flower!\nA flower that blooms only on the New Year 1st of Baishakh at the historical and ancient garden located in the south of Siraha’s Padariya Chowk on the East-West Highway. The orchid blooms on the haram tree in the Salahesh Garden early in the morning and wilts in the evening. Photo: RSS (National News Agency)\nFascinating folklores, cultural demigod\nNot much has been written about <PERSON>, also known as <PERSON> (the king of mountains) and Jayavardhan. However, in the southern plains of eastern Nepal and adjoining states in Bihar of India, there are many folklore stories featuring <PERSON> and his adventures.", "765" ], [ "Different versions of folktales handed down from one generation to the other talk about <PERSON>’s bravery and his love for his malin.\nAccording to one legend, <PERSON> used to visit the Salahesh Fulbari to pick flowers for use in religious rituals after performing his ablutions. He would meet four sisters who were gardeners there, and in due course, he fell in love with one of them. The orchid which blooms in mid-April every year, according to locals, symbolizes that love. Young couples visit the garden on the Nepali New Year’s Day to receive blessings for their love and express hope that their love would last long just like that of <PERSON> and his gardener love.\nAccording to many stories about <PERSON>, he was a Dusadh, a member of the so-called untouchable community. He is also claimed, however, by the Danuwar community. But <PERSON> is worshipped by all, irrespective of caste and ethnicity. With time, he has evolved for several communities from a Dalit hero into a demigod.", "351" ], [ "The Indigenous Tharu People of Nepal Risk Losing Their Once-Mandatory Art of Tattooing · Global Voices\n<PERSON>, 61, remembers her younger days when talking about the tattoos of betel nut palm, peacock and other motifs inspired by nature on her body. Photo: <PERSON>. Used with permission.\nFor centuries, tattooing has been an integral part of life for the indigenous Tharu people living in the southern plains of Nepal. Now, as the Tharu people face modernization, the tattooing practice is losing its importance among younger generations.\nTharu women wear tattoos on their arms, legs, and chests as a beautification practice. The tattoos, called khodaha and godna in the Tharu language, are inspired by nature. The most common tattoo motifs are lines, dots, crosses and other various natural elements.\nThe names of the tattoo patterns echo their natural counterparts: badam butta (groundnut shrub), suruj ke daali (rays of the sun), thakari mutha (a handful of hair combing materials), supari ke gachh (betelnut palm), and majur (peacock) among others.\nView this post on Instagram\nA post shared by <PERSON> (@iamshankarchaudhary)\nView this post on Instagram\nA post shared by <PERSON> (@iamshankarchaudhary)\nTraditionally, young women could decide to wear tattoos as permanent jewelry, whereas all married women must have compulsory tattoos on their legs applied prior to marrying, typically in the month of March during the wedding season (the months of Falgun-Chaitra in the Bikram Sambat calendar). Today, however, neither the married nor the young Tharu girls choose to wear tattoos.\nIn ‘Tatooing Among the Tharus of Dang Deokhuri, Far Western Nepal’ a paper published in 1975, researcher <PERSON> captures the aesthetic essence of tattooing among the Tharu:\nThe main reason for tattooing among these Tharus is aesthetic. According to them, young and unmarried girls do not need and hence do not have to decorate themselves by tattooing because their bright and colourful cholyas (a kind of blouse with its opening in the back) are beautiful and decorative; but a married woman has to get herself tattooed to compensate for the lack of beauty or decoration brought about by donning jhulwa or dainaha jhulwa, a kind of ladies’ shirt with full sleeves, double-breasted and opening in the front.\nThe tattoos on the lower part of the legs generally represent sitha (stick or straw), chulha (stove) and phunna (hanging motifs), whereas tattoos on the middle part represent majur (peacock) and sithas in between and tattoos on the top part of the legs represent a single peacock in the centre and some phunna or other motifs on three sides of it, making a frame for a single peacock at the centre.\nTraditional tattooing practices were painful and gruesome. Tikaniya (tattooers in Tharu) used tattooing needles and natural black ink obtained from the soot of a mustard lamp.", "168" ], [ "The slow process sometimes caused fainting.The artist rubbed the body part to be tattooed with cow dung and later cleaned the area with water. After drying, mustard oil was applied to soften the surface of the skin. The tikaniya then marked the designs and pricked the skin with tattooing needles.\nOne Tharu elder from Chitwan, Nepal recollects:\nIn the old days, when girls of my age were young, a man from India would come and do these tattoos in our bodies. When my friend was being pierced, I could see tears in her eyes because of the pain and I remember being afraid as I was next. That night I couldn't sleep. The next day I asked my mother why I had to get the tattoo. She said, ‘Who will marry a girl without a tattoo? No one will take you unless you have them.’\nView this post on Instagram\nA post shared by Stories of Nepal (@storiesofnepal)\nAside from beautification, another key reason Tharu women tattooed themselves was to avoid the attention of The Royal Nepalese, who hated tattoos associated with tribal and indigenous peoples. Tharu tattoos prevented nobles from abducting and keeping them as sex slaves.\nView this post on Instagram\nA post shared by <PERSON> (@sankuchy)\nDespite a rich tattooing history, Tharu youngsters do not get tattooed. Experienced tikaniyas are no longer found in the villages and younger generations have not yet come forward to steer this age-old tradition.", "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" ], [ "Jordan’s Magic Sorcerers Continue to Be Sought After · Global Voices\nAmman, Jordan. Taken by <PERSON>. Used with permission.\nThe demonological conception of Islam regards the “jinn” (الجن‎‎), anglicized as “genie”, as a servant of Allah, similar to the human. What makes the subject of magic practices and beliefs in Jordan all the more fascinating is the conflicting relationship of simultaneous opposition and tolerance between religion and “the Occult”. Indeed, Islam does not reject the existence of magic; quite the contrary: several Quranic verses refer to magic-doing, if only to condemn the practice.\nWhen asked by Global Voices whether he believed in magic, Amman-based taxi driver <PERSON> said, “Every Muslim should believe in magic because of the story of Prophet <PERSON> in the Quran”. According to the Chapter of al-A‘raf in the Quran, upon arrival in front of the <PERSON>, <PERSON> had a confrontation with the Pharaoh’s sorcerers, who used black magic to turn their rods into snakes. With God’s approval, <PERSON> turned his rod into a serpent, forcing the sorcerers to kneel before him and accept his prophecies, stunned by the miracle observed.\nThis episode illuminates the Quranic distinction between magic and miracle, whereby in the words of <PERSON> , one of the most prominent Muslim historians, “a miracle is a divine power that arouses in the soul [the ability] to exercise influence. The [worker of miracles] is supported in his activity by the spirit of God.", "773" ], [ "The sorcerer, on the other hand, does his work by himself and with the help of his own psychic power, and, under certain conditions, with the support of devils” .\nIn Jordan, the acceptance of the existence of “jinn” and its believed ability to possess people is one of many commonplace magic beliefs, such as the greedy “ evil eye ”, amulets and Al-matuom — the practice of using the deemed “dirty” menstrual blood to ensure someone’s love towards you.\nBut from a religious perspective, magic is frowned upon, to say the least. The Imam of Masjed Al-Edlbe in Na’ur, <PERSON>, summarized religion’s attitude towards magic by explaining that “magic is the deed of the Sheitan (Devil) and teaching, learning, and practicing magic is haram (sin)”.\nHowever, although magic is strictly forbidden, in his concurrent role as the mosque’s sheikh, <PERSON> gets called to dispel magic at least twice a week on average. Because Al-Masjed is perceived as the home of God who has the ultimate power over all creatures, individuals possessed by “jinn” avoid setting foot in the mosque, thus requiring the sheikh to visit their homes.\nThe last case Sheikh <PERSON> recounted for Global Voices involved a 22-year old woman “of exceptional beauty”:\nOver forty men had asked for her hand and yet each engagement had broken off right before becoming official. Desperate, her family invited me to their house to read to her Quranic verses, thought to be the best way to dispel magic. I then began conversing with the ‘jinn’ who possessed the woman and learned that the magical creature had fallen in love with her. Thus, whenever someone came to offer her marriage, the genie would cause her face to temporarily deform. Upon the unpleasant sight of her suddenly ‘monstrous’ face, all candidates would run away with no intention to come back. Yet, once I finished reading the Quran, the jinn left the woman’s body and soon after she got married.\nAlthough religious leaders are unanimous in their view that casting spells on others is an utmost sin, being a sheikh al-sihr (magic sorcerer) is a profitable occupation not without demand. A simple Google search lands pages of results, featuring advertisements of Amman-based sorcerers who profess to “break magic”, “cast magic”, or do both.\nScreenshot sample of a Google search for “Magic sorcerer in Amman, Jordan”.\nGlobal Voices got in touch with someone who offers wizardry and learned that the cost of casting black magic depends on its “kind” and ranges from 200 (US $282) to 100,000 (US $141,014) Jordanian dinars.\nFinancial well-being, marriage and maledictions against others are amongst the biggest motivators for people to seek sorcerers.", "361" ], [ "Lost in Translation in Central Asia: Keep it in the Family · Global Voices\nA Kyrgyz family in the village of Sary-Mogol, Osh province. Photo by Betta27. Image for illustration purposes only. Creative commons.\nThe following post is part of a special Global Voices project, ‘Lost in Translation in Central Asia’, that explores the quirks of the region's languages.\nIn the HBO hit serial The Sopranos, lead character <PERSON> tells his son, <PERSON>: “In the end your friends will always let you down. Family: they're the only ones you can depend on.” This is a sentiment that many Kyrgyz would appreciate.\nThe Kyrgyz word tuuganchylyk consists of two parts. ‘Tuugan’ translates as a relative, or kin, while ‘chylyk’ is a suffix used to express the essence of a certain quality. Hence, tuuganchylyk is a word that signifies the primacy of family and kinship.\nListen to a native Kyrgyz speaker say, “You should adhere to tuuganchylyk because regardless of what situation you are in your kins will always be there for you”:\nhttps://ia801506.us.archive.org/23/items/Voice0021_201707/Voice_002_1_.mp3\nA strength and a weakness\nTuuganchylyk is the core idea behind the familial support networks which have helped Kyrgyzstan wade through more than a quarter of a century of economic struggle following the collapse of the Soviet Union. Yet it is also a debilitating disease that gnaws away at the country's body politic.\nReflective of the centrality of tuuganchylyk to Kyrgyz people is the fact that the Kyrgyz language has specially designated words for each extended family member. For example, the ‘younger sister of your husband’ is a kainsingdi, while the ‘younger sister of your wife’ is a baldyz. In English, both words would be translated simply as ‘sister-in-law’.\nScenes from a Kyrgyz wedding. Photo taken by <PERSON> some time in the 1860s. Creative commons.\nThe boundaries of tuuganchylyk, i.e., the people a Kyrgyz person includes in his or her conception of family, can vary depending on the context.", "811" ], [ "In everyday life, you give first preference to your immediate family members, then to your paternal cousins. After your paternal cousins come the great grandchildren of your paternal great grandfather; your second cousins on your father's side. But tuuganchylyk can be expanded to include more than one tribe or region if the context is important enough.\nEvery traditional Kyrgyz, especially men, should know their forefathers up to at least seven generations. This means that family trees often appear to sprawl towards infinity. One local joke runs that <PERSON> once ordered a Kyrgyz man shot dead without questioning. Had he questioned him, <PERSON> suspected, the Kyrgyz would have shown him proof that they were somehow related.\nKyrgyzstan Facebook user <PERSON> shared a news article on US President <PERSON> appointing his son-in-law <PERSON> as a senior adviser with the ironic caption: “Our person!”\nTuuganchylyk can be a source of either personal pride or shame. When a member of a given tribe has achieved something outstanding, that pride is dispersed across other members of the tribe. If a member of an extended family or tribe has done something shameful, fellow members will work hard to play it down in front of outsiders.\nThis support network is particularly useful for divorced women, who suffer social stigma. Often a tribe will make an effort to include their divorced female kin in important events such as feasts, weddings and funerals, in order to show them their support and to reinforce the centrality of the family.\nSome Kyrgyz tribes struggle under the weight of long-standing stereotypes. For example, a stereotypical sayak tribe member is crafty and mischievous, while a stereotypical solto tribe member should be brave and honourable. According to an oft-quoted saying, “Solto are the sated ones, while sayak are the naughty ones.”\nKyrgyzstan's 2010 revolution left around a hundred protesters dead but succeeded in ejecting the nepotistic <PERSON> family. Photo by <PERSON>. Creative commons.\nVote for your blood, or at least your region\nIn the post-independence period, the word tuuganchylyk has become increasingly synonymous with a powerful culture of political nepotism.", "1010" ], [ "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" ], [ "The hung <PERSON> and the crucified <PERSON>\nThe god who dies but resurrects, is an often-re-appearing legend in many religions. Amongst the deities that die and then come back to life are: Horus, <PERSON>, <PERSON> and <PERSON>. <PERSON> and <PERSON> are also, for sure, crucified. Apart from the sacrificial death itself, there also is a thorough description that <PERSON>, <PERSON> and <PERSON> have been born the 25th of December. All of them also have twelve disciples and they create miracles. On a shrine dedicated to <PERSON> it is written “You have saved us through your shed blood”. This shrine is nowadays situated beneath the Sancta Prisca church in Rome.\nParts of these mythological stories also fit quite well to the Germanic god <PERSON>, or Wotan.\nMidwinter Blót was held to honor <PERSON> around the time of Winter Solstice, which in the old days occurred on December 25th. <PERSON> has twelve lower ranked gods under him, and one of them (<PERSON>) is a traitor. <PERSON> is hung upon the tree of Yggdrasil for three days, according to <PERSON>. After his death, <PERSON> gets more power than before it. In the Christian tradition, <PERSON> has increased his powers after he died and resurrected after three days. Crucifixion, which was a common way to execute slaves, thieves and traitors in the ancient Mediterranean world, has not been practiced in the Germanic territories, and hanging has instead been seen as a dishonoring way to die. Executions with guillotine or sword have been seen as a more honoring way to die rather than hanging, all the way into our modern times. Both <PERSON> and <PERSON> get stabbed with spears during their sacrificial deaths. <PERSON> was hung upon a tree, and <PERSON> was hung upon a cross made out of wood.", "351" ], [ "According to some Christian beliefs, that cross was made out of a tree that <PERSON>, the first man, had planted. <PERSON>, but also several other Egyptian gods, are depicted holding a hieroglyph known as “the Ankh”. That symbol is very similar to the cross that the Christians are using, and both symbols mean life and resurrection.\n<PERSON> was not born of a virgin, since the <PERSON> are mentioning that he had both a father and a mother, <PERSON> and Bestla. It can though be said that <PERSON>, the father of <PERSON> was born when he got licked out of a block of ice by the cow Audhumbla.\nExperts in religion have mentioned that <PERSON> is similar to the god Mithra, the main savior deity of the late ancient world, who also has twelve disciples, all of whom are represented by the twelve signs of the Zodiac. But it looks like the idea of the god that dies and resurrects is around 5000 years old, if you go all the way back to the myth of <PERSON>. <PERSON>’s most ecstatic aspect is pretty similar to the description of the Greek god <PERSON>. Both Mithra and <PERSON> were celebrated at the Spring Equinox, and the Christians celebrate Easter at spring as well.\nIn other words, it is more than likely that the Christians took over an elder myth and blended it into their own belief system. The Jews were strongly influenced by the Egyptians, and monotheism was grounded in Egypt. The first Christians were most likely Jews who were inspired by the pagan world’s ideas about salvation, and thus added those ideas into their own belief system. The pagan teachings about salvation did not claim to be the only way to salvation, and thus accepted other religions. The idea that everyone must think in the same way and fight for the same belief system, did not exist amongst the polytheistic religions.\nBoth <PERSON> and <PERSON> were celebrated with mystery plays, and also in partially secret societies. It is thus believable that the first Christians believed in a mythological savior that was born, lived, created miracles and then got executed, just to resurrect and come back to\nEarth. Later on, when Christianity increased in popularity, some of the Christians started to believe that their savior was a real, physical being, that lived and acted in a recent past. The Christians started to think that the “physical” savior lived and died in the 30-s of our time. Since the Christians converted as many as possible to Christianity, their converts literally believed everything that was taught to them. The monotheistic religions are struggling even nowadays with their so called literalism.\nhttp://ideellkulturkamp.", "72" ], [ "On World Poetry Day, Some Verses Straight From Persia’s Heart · Global Voices\nAzerbaijani folk art based on the <PERSON> and <PERSON> novel by <PERSON>. CC BY 3.0.\nHow might someone in Tajikistan, the only Persian-speaking republic in the former Soviet Union, describe a beautiful and lively night spent in the company of family and friends?\nPerhaps he or she would use the word dilafruz, which literally means ‘firing the heart’.\nIf that person spent the night alone in a depressed state, however, the word chosen might be diltang, which would indicate a ‘narrowing of the heart’.\nIn a country where poetry runs in the blood, falling in love can be described in a dozen different ways. One can be dil bastan (heart-tied), or have a dil gum zadan – a racing heart.\nCorrespondingly, the person that triggers this state might be called a dilrabo (heart stealer), while freezing someone's heart is dil khunuk shudan, a somewhat dramatic take on getting dumped.\nLanguages full of heart – and verse!\nThe Tajik language is closely related to the Indo-Iranian languages spoken in Iran (Farsi) and Afghanistan (Dari).", "148" ], [ "In Farsi, the literary word for heart is closer to del in pronunciation. Dari's dil is like the Tajik.\nWorld map adapted by Mani1 to show areas where Persian is spoken. Creative Commons.\nMoreover, across the Eurasian sub-region indicated above, dil (written “дил” in the Cyrillic alphabet Tajikstan still uses) is the heartbeat of a rich poetic tradition stretching back at least as far as the first milennium AD.\nOne of the most famous proponents of this tradition was <PERSON>, the roaming 13th century wordsmith and philosopher beloved by all Persian-speaking peoples.\nҲар чӣ дар дил дорӣ аз макру румуз,\nПеши мо расвосту пайдо ҳамчу рӯз\nWhatever secret and lies you have in your heart,\nWe see them all like a day with our eyes,\nThe heart has no country…\n<PERSON>'s romanticism is eclipsed however by <PERSON>, a bard writing in the century before him.\n<PERSON> hailed from Ganja (his name literally means <PERSON>) which is part of modern-day Azerbaijan.\nHere are some couplets from his epic Khosrow and Shirin, in which the Sasanian ruler (<PERSON>) engages in a poetry battle with his love rival <PERSON> over the heart of an Armenian princess, <PERSON>.\nБигуфт: Аз дил шудӣ ошиқ бад-ин сон?\nБигуфт: Аз дил ту мегўӣ, ман аз ҷон.\nБигуфто: Ишқи Ширин бар ту чун аст?\nБигуфт: Аз ҷони ширинам фузун аст!..\nБигуфто: Дил зи меҳраш кай кунӣ пок?\nБигуфт: Он гаҳ, ки бошам хуфта дар хок…\nБигуфт: Аз дил ҷудо кун ишқи Ширин.\nБигуфто: Чун зиям бе ҷони ширин?\nAsked: Did you fall in love from the heart?\nAnswered: You talk about the heart, I talk about the soul.", "990" ] ]

[ 2226, 11341, 5365, 10984, 8196, 341, 6553, 2953, 346, 5373, 8222, 10851, 1414, 2298, 11344, 7524, 9156, 3724, 1734, 9193, 9189, 7610, 1916, 9198, 10982, 6296, 1720, 6272, 7376, 1991, 43, 8065, 3028, 6881, 6662, 735, 10459, 1422, 4037, 3898, 4966, 6398, 6421, 5101, 4865, 9658, 5169, 10908, 6780, 10526, 3627, 2388, 3337, 9262, 525, 10450, 1525, 9103, 5443, 4642, 3515, 8959, 7804, 9933, 4341, 9781, 3483, 563, 7892, 9714 ]

[ [ "There is actually a pion exchange between nucleons. This is the basis for the residual strong force.\nWhen a proton and neutron interact, one of the interactions we get is\n$$\\rm proton^+ +neutron \\rightarrow proton^++pion^-+proton^+ \\rightarrow neutron+proton^+$$\nSo the proton becomes a neutron and then the neutron becomes a proton by transferring a negative pion.\nEdits: <PERSON>: That's fair, my answer didn't really answer.\nThe proton and neutron aren't identical particles and so aren't limited by Pauli Exclusion between each other. They can have the same spin state and for some reason having parallel spins gives the combination a lower energy and so more stability.\nWhen I look for why parallel spins have a lower energy, I just see it stated as a fact or in better references, an equation that gives the details of the energy difference is given.\nWhat I haven't seen is a physical explanation for why parallel nuclear spins have lower energy.\nHere's my hunch (which I will try to verify). If it's correct then it's probably out there somewhere already.", "969" ], [ "If it's wrong, it's because I just thought the idea through myself.\nWhen a proton and neutron have all the same quantum numbers (and so their spins are parallel), then when a neutron transfers a negative pion to the proton, the final state is identical to the initial state. This means there are two different paths from the initial state to the final state: doing nothing and passing a negative pion both give you the same final state.\nIn quantum when two different events are possible because they both give the same initial and final state there is an interference term. For instance, in the collision of two identical atoms with identical spins states, colliding and not colliding can give the same final state, and so the two possibilities interfere.\nIn the case of a proton and a neutron with antiparallel spins, transferring a negative pion would give a different final state than the initial state. It could transfer back to then give the same final state, but (roughly speaking) every step a process needs makes the contribution of that process less important.\nIn the case of a diproton or dineutron, the transferring a neutral pion would also give the same final and initial state.\nSo I further suspect (again, all on me if it's wrong) that while the proton-neutron parallel pair has dominant exchanges of both neutral pions negative pions, the diproton and dineutron only has neutral pions giving the proton-neutron pair about twice the binding.\nSo the two key ideas I'll try to track down are: (1) Does a process having identical initial and final state make it more important? (2) Does having twice the number of similar interactions mean that there is about twice the binding energy involved?", "969" ], [ "Uses of the Angular Momentum 4-Tensor\nThe angular momentum 4-tensor has 6 independent components, three angular momentum components and three new guys. Some call these new guys the 'boosts', but since they are the conjugate momentum of the Lorentz Transformation (aka the actual boosts) I think 'boost momentum' is a better name.\nThese quantities are related to energy and momentum by (up to a sign, depending on the text)\n$\\vec K=\\frac{E}{c} \\vec x-ct \\vec p$\nWhile conservation of angular momentum is pretty useful for a lot of problems, conservation of the boost momentum seems to be a loose end.\nIt seems like conservation of the boost momentum only serves to ensure continuity of motion. A particle undergoing a discontinuous jump (hopping from one point to another in an unphysical way) could conserve energy, momentum, and angular momentum, but it wouldn't conserve boost momentum.\nAre there physical problems where conservation of boost momentum could be as useful as conservation of angular momentum?\nEdit: I don't think I unpacked the idea I was thinking about very well.", "617" ], [ "Here's one thing I'm looking at with a lot more detail:\nStarting with\n$\\vec K=\\frac{E}{c} \\vec x-ct \\vec p$\nWe can use\n$\\vec p=\\frac{E}{c^2} \\vec v$\nto get\n$\\vec K=\\frac{E}{c}(\\vec x-\\vec vt)$\nIf our velocity is constant, then we have\n$\\vec x=\\vec x_0+\\vec v t$\nand so\n$\\vec K=\\frac{E}{c} \\vec x_0$\nWhat I'd like to do from here is get a sense about what $x_0$ means. We know it's a relativistic version of the terms we add up when finding the center of mass.\n$\\bar x=\\frac{m_1 x_1+m_2 x_2+...}{m_1+m_2+...}$\nAnd there are a couple of nice problems, like a guy walking on a board with frictionless wheels where the combined center of mass stays the same and so\n$m_1 \\Delta x_1=-m_1 \\Delta x_2$\nWhich tells us that no matter how weird the motion of the guy walking on the board is, the center of mass stays put and the motion of the board is a scaled reflection of the guy's motion.\nSo here's what I'm getting at: What is the relativistic version of this like? What (if any) scenarios do we have where the conservation of boost momentum gives us a simple insight into a physical process? That's what I'm trying to get at.\nThe other item, the continuity of motion, is related to a discussion I saw on a great <PERSON> lecture, Lecture 3 - The Great Conservation Principles where he considers the idea that maybe an object could disappear in one place and appear in another at the same time. <PERSON> then shows how this couldn't work, since that would mean in one frame that object would be missing for a while and in another that object would appear at the new location before it disappeared in the first.\nI haven't figured it out too much, but it seems to me that means there is a nice connection between the conjugate momentum of the Lorentz Transformation and continuity of motion. Also, where conservation of the momentum of a particle doesn't prevent it from disappearing in one place and appearing in another, conservation of boost momentum would, since it would change the $\\vec x_0$ from above and nothing else.", "512" ], [ "Attractive higgs force and inflation\nInflation was the extreme accelerating expansion of the universe, see here: http://en.wikipedia.org/wiki/Inflation_(cosmology) It worked in a similar way to dark energy but was so strong it would easily tear atoms apart (if it wasn't far to hot for atoms to form in the first place).\nThe weird thing about inflation and dark energy is that they are under tension.\n[Optional reading]: Explanation of how pressure works backwards in general relativity\nIn general relativity, pressure itself is attractive. This is not because it takes energy to compress materials, the energy put in to compressing something simply shows up as extra mass. This is an extra effect.\nSuppose you dive deep into a (non-rotating) neutron star (pretend the center is liquid) and measure the central density (as a swimmer would gauge the inertial resistance of water). You then move 1mm away from the core, release a pellet of dark matter (which goes right through everything so it has no buoyancy), and measure the acceleration towards the center (because of the shell theorem and the slow maximum speed of the pellet (~10 m/s), you can assume newtonian gravity in the local vicinity).\nThe measured acceleration will be greater than the calculated acceleration, up to almost twice as much. This is a consequence of light bending twice as much as \"expected\" and can be derived from special relativity using a reference frame with constant acceleration.\nPressure is equivalent to an exchange of fast-moving particles. These \"virtual\" particles \"bend more\" toward a mass and conversely the mass is pulled back more toward it.", "781" ], [ "The inflation field was under enormous tension, which is the exchange of negative mass particles, and it created a repulsion. Another effect is that work must have been done on the inflation energy as space expanded, just as it energy is added to a rubber band when you pull on it. This work showed up as more inflation energy, and meant that it does not dilute when space expands. Eventually, the pressure/density ratio, (equation of state) went above the critical value of -1 and the field began to dissipate. The -1 \"critical value\" also causes that the fluid to be <PERSON> invariant, which means there is no preferred reference frame.\nThe question itself\nThe Higgs particle is a purely attractive force, see here:\nhttp://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-forces-of-nature/the-strength-of-the-known-forces/\nCould the Higgs force create a strong enough tension (perhaps with help from other forces?) to overwhelm the positive pressure effects of quantum degeneracy and heat and leave enough tension to cause inflation? If so you would not need GUT or TOE speculations for the mechanism of inflation. Furthermore, you could quantify it's strength and the nature of it's eventual decay.", "651" ], [ "Let me give you the crazy idea that the radius of an electron and a proton is fixed but complex, where the real part is the mean and the imaginary part is the standard deviation. Then the classical radius of an electron and a proton determines the mean value, and the root-mean-square value is variable in its meaning. The electron radius is pointwise at high energies, when relativistic corrections are applied, and the scattering cross section is proportional to the square off classical electron radius.\nThe formula for the scattering cross section of a photon by an electron does not need to be regularized and determines the scattering cross section $$Re\\sigma=\\sigma(0)-\\sigma(\\infty)=\\frac{8}{3}\\pi r_e^2;\\sigma(x)=\\sigma(\\frac{\\hbar \\omega}{mc^2})$$ In this case, the radius in complex form is $$R_e=r_e(1\\pm\\sqrt{(Re\\sigma-\\pi r_e^2)/\\pi}i)=r_e(1\\pm 1.29i)$$ its modulus determines the scattering cross section $$|R_e|=r_e|1\\pm1.29i|=1.63r_e=\\sqrt{\\frac{8}{3}}r_e$$ The formulas for the cross section of the scattering of an electron by an electron and the annihilation of an electron and a positron with the formation of two photons require regularization. The regularization parameter must be chosen so that the size of the electron coincides with the size of the electron when a photon is scattered by an electron. It turns out that the three formulas equally determine the size of the electron.\nThere is no unambiguous value for the size of elementary particles. Elementary particles do not have a finite size and it is impossible to determine an unambiguous final size by their charge.", "795" ], [ "For an electron, there are scattering cross-sections of various reactions, and with their help I was able to determine the complex size of an electron. The complex size of an electron is determined up to the imaginary part. For a proton, this cannot be done, since there are no formulas describing the cross-sectional area of ​​reactions. Nuclear forces are not described by the perturbation theory, therefore only measurements are made and there are no theoretical formulas. The classical radius of the electron is greater than the classical radius of the proton. But this does not mean anything, the size of the proton is unknown.", "969" ], [ "The two pictures obviously can't refer to the same thing.\nActually, they do.\nYou see, $FE(E,T)$, the Fermi function, is the mean number of fermions in the state of given energy E at temperature T. Hopefuly, it is bounded between 0 and 1 so only zero or one fermion in these quantum states. In this case, $\\mu$ is the limit of energy at wich you have one half of a chance to found a fermion in you gas. Lower energy levels will mostly be filled and higher ones will be empty.\nObviously, in order to generalise the distribution it is common to normalize regarding $k_bT$ i.e $\\beta = \\frac{1}{k_bT}$. $\\mu$ actually depends on your system and mostly on your system's reservoir and so is fixed with regards to N and T (else the distribution isn't valid, meaning you don't have enough particles or the temperature is too high).\nI did a plot of two characterising limit $\\nu$ (sorry for notation change, it's old) relatively different to the temperature of their systems as $\\nu = 10k_bT$ and $\\nu = 50k_bT$.", "28" ], [ "e is in $k_bT$ units.\nAs you can see, as the distribution is exponentially decaying between $\\nu-5k_bT$ and $\\nu+5k_bT$. This gives you the density of distribution of your fermions in the different energy states around.\nIf you keep an eye on a constant $\\mu$ (or $\\nu$ in the case of my plot) you will see the distribution sharpen as you decrease the temperature. This defines the so called \"Fermi sphere\" in the p space containing all the energy levels of your fermions at zero temperature. As such you define it's radius as $p_F$ giving you a total number of quantic states (for electrons): $$\\frac{4}{3}\\pi p_F^3\\frac{V}{h^3}2=N$$ (2 is due to the 1/2 spin of electrons) As such, you can define the Fermi energy as $\\epsilon_F = \\frac{p_F^2}{2m}$ giving you the fermi level at $0\\ K$: $\\mu_F=\\epsilon_F$.\nRemember that $\\mu$ depends on the system bath and that the distribution along the energy states varies with $T$. Hope this helps a bit.", "28" ], [ "At an in-principle level, no, it doesn't change the laws of physics, but it could change how we write the equations we use to describe them.\nThe laws of physics depend on the dimension Time. Any given clock is simply an instrument to measure time. The standard scientific unit, which we measure in, for time is the second.\nThe second is currently defined based on the vibration of certain atoms, but was originally defined as a fraction of an minute which was in turn defined as a fraction of an hour and so on - ultimately the second was originally based on the rotation of the earth. This could be considered one \"clock\" in the way you mean, if i understand you correctly.\nChanging the definition to be based on atomic vibrations allowed a more accurate definition of the size of the unit, but didn't change any fundamental physics, which ultimately relate to the dimension, time. Choosing to define it based on the vibrations of a different atom wouldn't have changed anything except the ease/accuracy/reliability with which we could measure the unit.\nIf you mean choosing a different unit size, other than what we currently know as a second, that would either have resulted in different choices of other unit sizes, or different looking fundamental equations - but they would only have differed by the constants needed to make the units work.\nTake <PERSON>'s Second Law.", "432" ], [ "The fundamental law is that force is equal to the rate of change of momentum. Given constant mass, that results in the familiar $$ F = ma $$ This is given use of kg for mass and meters per second per second for acceleration. However, if we wanted to measure acceleration in miles per hour per hour we could. The equation would then be $$ F = Kma $$ Where K is a constant (approximately 8052.985) to make the units work. The fundamental physics is the same.\nIn this case, we pretty much define the unit of force (Newtons) so that this holds (i.e. so that the constant K = 1 and can be left out altogether)\nIn practice, it would probably have resulted in changes in some other units to make things nicer, rather than just shoving in a bunch of constants.", "131" ], [ "While Sir <PERSON>'s post is a very intriguing answer, but I'm afraid it's wrong. The sun's surface is clearly in motion, but that does not necessarily result in the radiation of audible sound, even if the sun and earth where in a fluid medium (such as a air) that would allow sound transfer.\nTo explain why, we can actually apply the same line of analysis to the earths's ocean. The surface moves a lot, so sound should be radiated. However, we hear nothing unless you are really close by and have breaking waves.\nLet's run the math with rough numbers: The ocean has a surface area of about 510 million square kilometers. $150 \\cdot 10^{12} m^2$. Let's say the average wave height is 1m and the average wave frequency is 0.1 Hz (1 wave every 10 s).", "840" ], [ "If the ocean where a sherical source this would create a sound power of $5 \\cdot 10^{24} W$ and the sound pressure at 1000 km away would be 240 dB SPL. That's obviously not the case, otherwise we'd be all dead.\nSo why not? In order for sound to actually radiate, the surface must move uniformly. For every ocean wave that moves air up there is a wave nearby that moves air down and so the contributions simply cancel. Technically speaking, we need to calculate the power by integrating the normal intensity over the entire surface, the intensity has equal amounts of positive and negative components and the sum over those is zero.\nThat's the same reason why you put a loudspeaker in a box: in open air the air motion from the front of the cone and from the rear of the cone will simply cancel out, so you put it in a box to get rid of the sound from the rear.\nSo I think the real answer here is: you would hear absolutely nothing since the sound contributions from different parts of the sun's surface would cancel each other out. Sound radiation over that distance would only occur if the sun's surface moves uniformly, i.e. the whole sun expands or contracts. That does happen to some degree but only at very, very low frequencies which are inaudible and where sound radiation is a lot less efficient.", "309" ], [ "(3 - hard) Electrons have spin 1/2. This means that their wave function comes back to itself after a rotation by 4π. In the cyclotron motion, what happens to the wave function phase after one full orbit around B in physical space: did the phase rotate by 2π or by 4π, or by another value?\nAttempt of an answer: Along a path in a magnetic field with vector potential $A$, the phase $\\delta$ acquired by the wave function of a charged particle is $(e/\\hbar) \\int A dx$.", "246" ], [ "After one complete orbit, the phase change is therefore given by $\\delta= e \\Phi / h = e B \\pi r^2 / h$, where $r$ is the radius of the orbit and where $h= 2 \\pi \\hbar$. Using the cyclotron radius $r=m v / eB$ we appear to get $$\\delta = \\pi (m v)^2/(e B h)$$\nI hope this is correct! This result of the phase $\\delta$ acquired by an orbiting electron thus depends on its speed and on the magnetic field. In any case, the relation for the orbital phase change is not a simple, fixed multiple of $\\pi$, as we could have wished for.\n(2 - simple) Is it correct to say that in spin up state, therefore the spin points always away from the axis above the rotation plane, and for spin down it always points away below the rotation plane? (Assuming \"above\" is where the magnetic field B points to.)\nThis question should be answered \"yes\" by a graph from hyperphysics:\nIn the spin up state, the spin points always away from the axis and above the rotation plane, and for spin down it always points below the rotation plane and outside.\n(1 - simple) (A) Is it correct to say that the electron(s), when looking in the direction of the field, orbit(s) with/along the clock, due to the negative charge? (B) And that the spin precesses in the same direction/sense?\n(A) This should be answered \"yes\" by this graph from hyperphysics on the cyclotron, which is for positively charged particles though:\nIndeed, the electron(s), when looking in the direction of the field, orbit(s) clockwise.\n(B) The question on precession for negatively charged particles should be answered \"yes\" by this picture from wikipedia, where the large red arrow is the magnetic field:\nThe sense of precession is the same as the sense of rotation.", "649" ] ]

[ 4875, 7138, 2092, 7817, 4456, 1924, 4763, 6010, 7722, 1133, 2125, 3309, 3579, 4281, 10476, 6230, 11036, 8661, 3959, 4457, 9330, 632, 5316, 10521, 11172, 5173, 8611, 8032, 11315, 5947, 3063, 11282, 8887, 5384, 1436, 1323, 4472, 11142, 10085, 6211, 11403, 4174, 1093, 1709, 41, 9727, 8221, 36, 721, 4385, 2218, 1113, 4683, 8345, 2355, 10290, 9167, 9370, 6401, 2743, 3314, 1873, 6306, 75, 4955, 3798, 2925, 6870, 469, 3995 ]

[ [ "Dances with Wolves\nThe majesty of a good epic is unlike anything else that cinema (or any art form, really) can offer, and this movie is a damn good example of that. Flaws aside, of which there are many, witnessing a journey as thoroughly as this and with as skilled a narrative hand as this can be deeply enlightening, here emphasizing just how meaningless almost any conflict is and how much potential the human race really has to love and care for one another. <PERSON> isn't the most captivating screen presence out there, but I'll be damned if the sheer scope doesn't more than account for that.\nGoodfellas is still better", "217" ], [ "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" ], [ "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" ], [ "Killers of the Flower Moon\nFrequently fantastic, bold, sweeping, and bloated. <PERSON> crafts a handsome and classical drama that explores a very real historical atrocity. The choice to focus on the perpetrators of the crimes is an intriguing one that mostly works, specifically in how it shows how one can lie to themselves to justify their horrific actions, and the corrupting power of greed. But it also means we miss out a lot of the point of view of the <PERSON>.", "217" ], [ "I understand that Scorcese may not be the best choice to tell that side, but while watching I felt like we were missing an integral part of the story. There's clearly an effort to be as respectful as possible, though, and I appreciate the conversations this film will spark. It's not just a one-and-done. It's dense as hell, and I'm glad I got to catch this in a cinema.", "596" ], [ "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" ], [ "Phantom Thread\nI didn’t think that this would ever become my current favorite PTA movie, yet here I am. Magnolia and Boogie Nights capture a moment in time that’s hard to beat, but of all his character studies since then, Phantom Thread has emerged as the fine wine candidate. It may not even be in your top 5 PTA for a set of years, with sexier projects of his dropping before and after (Inherent Vice and Licorice Pizza are far more fun, but Phantom quietly sits with you in a way that revisiting it actually becomes a quite comforting sit through). Or I just grew up, and that’s why it resonates deeper now.", "462" ], [ "I was freshman in college at the time of its release, so all that serious adult couple crap flew over my head a bit. <PERSON> simply seemed like a huge asshole tormenting this poor girl. The thing is, I still see it exactly that way, while recognizing just how complicated the relationship is (as well as relationships in general). But without acknowledging that he is an obsessive artist whose craft and talent is top tier, sought after by rich folks, and considered to be the best in his respective profession, yes the guy is probably difficult to have a happy cup of tea with. I’m speaking PTA threepeating with DDL into existence now.", "577" ], [ "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" ], [ "Godzilla: Final Wars\nNearly incomprehensible to me in terms of plot, but an impressively fun experience. I know little to no information about <PERSON> lore, so I adopted the phrase \"don't try to understand it; feel it\" and let the atmosphere of the film soak in, and it was fantastic.\nI don't really usually care about the human characters in these films but here they were oddly entrancing - especially dug how over-the-top the two leads were in terms of their growing rivalry with some of the most hectic yet well stylized action I've seen in a while. I can see myself revisiting this in the future - it's a super enjoyable movie.", "995" ] ]

[ 4123, 4335, 5609, 9397, 7326, 6930, 9867, 727, 562, 8861, 6644, 385, 9313, 8828, 507, 1350, 10530, 7990, 9082, 3233, 2164, 7040, 11024, 2601, 6454, 3949, 69, 5314, 9850, 1312, 3802, 6786, 7341, 7850, 2689, 4931, 4386, 9642, 8648, 5554, 7919, 4584, 4498, 6974, 7899, 3308, 1722, 10055, 885, 9598, 713, 1651, 296, 10376, 3735, 5076, 4524, 8047, 3098, 2468, 3730, 6956, 7759, 10653, 7889, 676, 8329, 2735, 6960, 8330 ]

[ [ "Last Date.\nIntroduction: Last Date.\nMy father once told me <PERSON> song \"Last Date\" was playing at the time he asked my mother to marry him on their \"last date\" and, well, she said yes!\nThis model, \"Last Date\", is in remembrance of their \"last date\" and their forever marriage until their passing. We love and miss you both and wouldn't be here if not for your \"Last Date\"!\nAs usual I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to comment as I do make plenty of mistakes.\nDesigned using Autodesk Fusion 360, sliced using Ultimaker Cura 4.7.0, and 3D printed in PLA on Ultimaker S5s.\nSupplies\n* Soldering iron and solder.\n* Thick cyanoacrylate glue.\n* Sandpaper or emory cloth.\n* Lite machine oil.\n* AWG28 stranded wire.\n* Indelible ink pens (blue, red).\n* Double sided tape.\nStep 1: Parts.\nI acquired the following parts:\n* One N20 100RPM 6VDC gear motor.\n* One 2AAA battery holder with on/off switch.\n* Two AAA batteries.\n* One normally open momentary pushbutton switch (must fit a 13.00mm hole).\n* One micro lever switch (search for \"CYT1073\")\n* Thirty six inches of 1.15mm (3/64\") diameter music wire.\n* Two 3mm (diameter) by 1.5mm (thick) neodymium magnets.\n* Two 6mm (diameter) by 1.5mm (thick) neodymium magnets.\n* Four M2.5 by 16mm cap screws.\n* Four M2.5 nuts.\nThe attached file \"Parts.pdf\" contains the name, quantity, infill, layer height and support of all 3D printed parts I printed for this mechanism. Note parts with a \".3MF\" extension are dual extrusion prints.\nThis mechanism is a high precision print and assembly using at times very small precision 3D printed parts in confined spaces with highly precise alignment. I printed the gears, levers, arms, cams and wheels using the Ultimaker Cura 4.7.0 \"Engineering Profile\" on my Ultimaker S5s, which provides a highly accurate tolerance requiring minimal if any trimming, filing, drilling or sanding.", "654" ], [ "However, prior to assembly, I still test fitted and trimmed, filed, drilled, sanded, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on your slicer, printer, printer settings and the colors you chose, more or less trimming, filing, drilling and/or sanding may be required to successfully recreate this model. I carefully filed all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth using small jewelers files and plenty of patience to perform this step.\nThis mechanism also uses threaded assembly, so I used a tap and die set (6mm by 1, 8mm by 1.25) if required for thread cleaning.\nStep 2: Pushrods.\nTo create His pushrods, I performed the following tasks:\n* Cut a 160mm length of music wire.\n* Created a 90 degree bend, 15mm long, in one end of the cut length of music wire.\n* Placed the 15mm bend into the hole in \"Jig, His, Pushrod.stl\".\n* Created a 90 degree bend in the remaining end of the cut length of music wire.\n* Cut the last 90 degree bend to 5.5mm in length.\n* Removed the wire from the jig.\n* Sanded the cut ends smooth.\nTo create Her pushrod, I performed the following tasks:\n* Cut a 150mm length of music wire.\n* Created a 90 degree bend, 10mm long, in one end of the cut length of music wire.\n* Slid the straight end of this wire into the slot in \"Jig, Hers, Pushrod.stl\", then placed the 10mm bend in the hole in the jig.\n* Bent the straight end up 90 degrees.\n* Cut this bend to 3mm in length.\n* Removed the wire from the jig.\n* Sanded the cut ends smooth.\nStep 3: Base.\nTo assemble the base, I performed the following steps:\n* Attached the two micro lever switches to the base using the 2.5mm bolts and nuts.\n* Placed \"Arm, His, Pushrods.stl\" into the base assembly.", "784" ], [ "Valentine Heart Pinwalker.\nIntroduction: Valentine Heart Pinwalker.\nWith Valentine's Day only a few days away, I decided to create \"Valentine Heart Pinwalker\" for the Valentine in my life. The model walks via a pin style walking mechanism while the eyes scan side to side looking for a Valentine!\nUnfortunately, the file \"Heart.stl\" exceeds the size limitation for this site and the .zip file format is not accepted, so click on this link: \"Heart.stl\"to my YouTube channel where links to the heart can be found in the description.\nAs usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.\nDesigned using Autodesk Fusion 360, sliced using Cura 4.121, and printed in PLA on Ultimaker S5s.\nOne final note, I receive no compensation in any form for the design, parts and/or materials used in this model.\nSupplies\nSoldering Iron and Solder.\nThick cyanoacrylate glue.\nStep 1: Parts.\nI acquired the following parts:\n* One 3.7vdc 100ma Lithium Battery (https://www.adafruit.com/product/1570).\n* One JST PH 2-Pin Cable (https://www.adafruit.com/product/3814).\n* One N20 6VDC 100RPM gear motor.\n* One micro switch (Uxcell a12013100ux0116 High Knob 3P 2 Position 1P2T SPDT Vertical Slide Switch, 0.5 Amp, 50V DC, 50 Piece, 3 mm).\nI 3D printed the following parts at .15mm layer height, 20% infill, and no supports:\n* One \"Axle, Eyes.stl\".\n* Two \"Axle, Leg.stl\".\n* One \"Base.stl\".\n* One \"Cam And Axle.stl\".\n* One \"Cam.stl\".\n* One \"Chassis.stl\".\nEither:\n* One \"Eyes, Black.stl\".\n* One \"Eyes, White.stl.\nOr:\n* One \"Eyes.3mf\".\nThen:\n* One \"Gear, Crown, Axle.stl\".\n* One \"Gear, Crown, Motor.stl\".\n* One \"Heart.stl\".\n* Two \"Leg.stl\".\n* One \"Tie.stl\".\nThis is a precision print and assembly model using at times very small parts and in very tight spaces. Prior to assembly, test fit and trim, file, sand, etc.", "654" ], [ "all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing and/or sanding may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step.\nThe model also uses threaded assembly, so I used a tap and die set (6mm by 1) for thread cleaning.\nStep 2: Chassis Assembly.\nTo assemble the Chassis, I performed the following steps:\n* Soldered the switch and JST connector the the motor so that the motor, when viewed from the axle end, rotated clockwise.\n* Pressed the motor assembly into \"Chassis.stl\".\n* Pressed \"Gear, Crown, Motor.stl\" onto the motor shaft.\n* Positioned \"Gear, Crown, Axle.stl\" into the chassis assembly, over the small chassis side hole.\n* Slid \"Cam And Axle.stl\" into the large chassis side hole, through the axle crown gear, and out the small chassis side hole.\n* Pressed \"Cam.stl\" onto the cam and axle such that it was 180 degrees out of phase with the cam on the cam and axle.\n* Secured one \"Leg.stl\" to the chassis assembly using one \"Axle, Leg.stl\".\n* Repeated the previous step for the remaining leg and leg axle.\nStep 3: Final Assembly.\nFor final assembly, I performed the following steps:\n* If you printed the eye black and white components separately, press the two \"Eyes, Black.stl\" into \"Eyes, White.stl\".\n* Positioned the eye assembly into \"Heart.stl\".\n* Secured the eyes to the chassis assembly using \"Axle, Eyes.", "784" ], [ "A New Marblevator.\nIntroduction: A New Marblevator.\nThis simple Marblevator uses a cam synchronized stair assembly to transport a ball bearing around an oval track.\nAs usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.\nDesigned using Autodesk Fusion 360, sliced using Ultimaker Cura 4.12.1, and 3D printed in PLA on Ultimaker S5s.\nSupplies\n* Thick cyanoacrylate glue.\nStep 1: Parts.\nI acquired the following part:\n* 8mm ball bearing.\nUnless otherwise noted, I 3D printed the following parts at .15mm layer height and 15% infill:\n* One \"Base.stl\".\n* Five \"Cam.stl\".\n* One \"Cover.stl\".\n* One \"Handle, Axle.stl\".\n* One \"Knob, Handle, Axle.stl\".\n* Three \"Track, Center.stl\".\n* Two \"Track, End.stl\", .06mm layer height.\nThis is a fairly high precision print and assembly. Prior to assembly, test fit and trim, file, sand, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces.", "654" ], [ "Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing and/or sanding may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step.\nThe model uses threaded assembly, so I used a M4 by 0.7 tap and die to clean the threads.\nStep 2: Assembly.\nTo assemble the model, I performed the steps as seen in the video and as listed below:\n* Threaded and glued \"Knob, Handle, Axle.stl\" into \"Handle, Axle.stl\".\n* Assembled the cam shaft by inserting each \"Cam.stl\" into \"Base.stl\", then pressing the handle / axle into the cam, noting that each cam is rotated 180° from the previous. When completed, the cam shaft must rotate with ease.\n* Assembled the cover by inserting the two \"Track, End.stl\" and three \"Track, Center.stl\" into \"Cover.stl\", making certain that each track raised and lowered independently with ease.\n* Snapped the base assembly onto the cover assembly.\nAnd that is how I 3D printed and assembled \"A New Marblevator\".\nI hope you enjoyed it!", "784" ], [ "A 3D Printed Animated Angel Christmas Tree Topper.\nIntroduction: A 3D Printed Animated Angel Christmas Tree Topper.\nI designed \"A 3D Printed Animated Angel Christmas Tree Topper.\" for our 2020 Christmas Tree.\nThe model may be assembled without motorization for a static tree topper or centerpiece, and may also be illuminated using an LED from a 3VDC \"flickering tea lamp\".\nAs usual I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to comment as I do make plenty of mistakes.\nDesigned using Autodesk Fusion 360, sliced using Ultimaker Cura 4.7.0, and 3D printed in PLA on Ultimaker S5s.\nSupplies\n* 28AWG Stranded Wire.\n* Soldering iron.\n* Solder.\n* Heat shrink tubing.\n* Thick cyanoacrylate glue.\nStep 1: Parts.\nI acquired the following parts:\n* One N20 6VDC 50RPM gear motor.\n* One 3VDC power supply.\n* One 3VDC flickering tea lamp LED and diffuser.\nI 3D printed the following parts:\n* One \"Arm, Left.stl\", .1mm layer height, 20% infill.\n* One \"Arm, Right.stl\", .1mm layer height, 20% infill.\n* Two \"Axle, Arm.stl\", .15mm layer height, 20% infill.\n* One \"Base.stl\", .15mm layer height, 20% infill.\n* One \"Body.stl\", .15mm layer height, 20% infill.\n* Two \"Bolt, Mount, Motor.stl\", .15mm layer height, 20% infill.\n* One \"Cam.stl\", .1mm layer height, 20% infill.\n* One \"Guide, Yoke.stl\", .15mm layer height, 20% infill.\n* One \"Mount, Tree.stl\", .15mm layer height, 20% infill.\n* One \"Mount, WIng, Left.stl\", .1mm layer height, 20% infill.\n* One \"Mount, WIng, Right.stl\", .1mm layer height, 20% infill.\n* One \"Retainer, Mount, Wing, Left.stl\", .1mm layer height, 20% infill.\n* One \"Retainer, Mount, Wing, Right.stl\", .1mm layer height, 20% infill.\n* One \"Wing, Left.stl\", .15mm layer height, 20% infill.\n* One \"Wing, Right.stl\", .15mm layer height, 20% infill.\n* One \"Yoke.stl\", .1mm layer height, 20% infill.\nThis mechanism is a high precision print and assembly using at times very small precision 3D printed parts in confined spaces with highly precise alignment. I printed parts using the Ultimaker Cura 4.7.0 \"Engineering Profile\" on my Ultimaker S5s, which provides a highly accurate tolerance requiring minimal if any trimming, filing, drilling or sanding. However, prior to assembly, I still test fitted and trimmed, filed, drilled, sanded, etc.", "654" ], [ "all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on your slicer, printer, printer settings and the colors you chose, more or less trimming, filing, drilling and/or sanding may be required to successfully recreate this model. I carefully filed all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth using small jewelers files and plenty of patience to perform this step.\nThis mechanism also uses threaded assembly, so I used a tap and die set (6mm by 1) if required for thread cleaning.\nStep 2: Base Assembly.\nTo assemble the base, I performed the following steps:\n* Soldered 60mm lengths of red and black wire to the motor.\n* Pressed the motor into the motor mount on \"Base.stl\".\n* Pressed \"Cam.stl\" onto the motor shaft.\n* Placed \"Guide, Yoke.stl\" onto the base assembly, then secured in place with two \"Bolt, Mount, Motor.stl\".\n* Positioned \"Yoke.stl\" into the base assembly.\n* Secured \"Arm, Right.stl\" onto the base assembly using one \"Axle, Arm.stl\".\n* Secured \"Arm, Left.stl\" onto the base assembly using the remaining \"Axle, Arm.stl\".", "784" ], [ "Marblevator, Perpetual?\nIntroduction: Marblevator, Perpetual?\nI designed this model to mimic the operation of a few \"perpetual motion\" devices that have been recently appearing in my suggested video feed. \"Marblevator, Perpetual?\" is not only not perpetual, it is also not very quiet. But the kids and grandkids enjoyed it!\nAs usual I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.\nDesigned using Autodesk Fusion 360, sliced using Ultimaker Cura 14.12.1, and 3D printed in PLA on Ultimaker S5s.\nStep 1: Parts.\nI acquired the following parts:\n* One Micro 130 DC Motor.\n* One twin AAA battery holder with wires and switch.\n* Two AAA batteries.\n* Four R08 O-Rings.\n* One 8mm ball bearing.\nI 3D printed the following parts at .15mm layer height with 20% infill:\n* One \"Axle, Wheel, Idler.stl\".\n* Six \"Bolt (8 by 1.25 by 8).stl\".\n* One \"Bowl Bottom.stl\".\n* One \"Bowl Top.stl\".\n* Four \"Column.stl\".\n* One \"Mount, Motor.st\".\n* One \"Track.stl\".\n* One \"Wheel, Idler.stl\".\n* One \"Wheel, Motor.stl\".\nThis is a high precision print and assembly model. Prior to assembly, test fit and trim, file, sand, etc.", "654" ], [ "all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing and/or sanding may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step.\nThe model also uses threaded assembly, so I used a tap and die set (8mm by 1.25) for thread cleaning.\nStep 2: Top Assembly.\nTo assemble the top, I performed the following steps:\n* Placed the batteries in the battery holder then installed the battery holder lid.\n* Soldered the battery holder wires to the motor making certain with power applied the motor shaft rotated clockwise when the motor is viewed from the motor shaft end.\n* Pressed the motor into \"Mount, Motor.stl\".\n* Placed two O-Rings on \"Wheel, Idler.stl\".\n* Placed two O-Riings on \"Wheel, Motor.stl\".\n* Attached the idler wheel to the motor mount using \"Axle, Wheel, Idler.stl\", making certain the idler wheel spun freely.\n* Pressed the motor wheel onto the motor shaft.\n* Carefully aligned the motor position so that the O-Rings on each wheel were aligned.\n* Pressed the battery holder into \"Bowl Top.stl\".\n* Attached the motor mount assembly to the bowl top using two \"Bolt (8 by 1.25 by 8).stl\".\n* Pressed \"Track.stl\" into the motor mount assembly.\nStep 3: Bottom Assembly.\nTo assemble the bottom, I performed the following steps:\n* Secured one \"Column.stl\" to \"Bowl Bottom.stl\" using one bolt.\n* Repeated the previous step for the remaining columns.\nStep 4: Final Assembly.\nFor final assembly, I performed the following steps:\n* Carefully positioned the track into the rectangular hole in the bottom assembly, noting the rectangle is offset to provide clearance for the track insertion pin.\n* Slid the track assembly into the bottom assemble by rotating the top assembly into position.\nTo operate the model, I lift the lid, slide the battery holder switch to the on position, and lower the lid.\nAnd that is how I 3D printed and assembled \"Marblevator, Perpetual?\".\nI hope you enjoyed it!", "784" ], [ "Butterfly Automaton\nIntroduction: Butterfly Automaton\n\"Butterfly Automaton\" is a simple, press together manually operated butterfly automaton. Simply turn the handle and the butterfly's wings come alive.\nAs usual I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to comment as I do make plenty of mistakes.\nDesigned using Autodesk Fusion 360, sliced using Ultimaker Cura 4.12.1, and 3D printed in PLA on Ultimaker S5s and an Ultimaker 3 Extended.\nSupplies\nThick cyanoacrylate glue.\nSmall jewelers files.\nStep 1:\nI 3D printed the following parts at .15mm layer height, 20% infill:\n* One \"Arm, Left.stl\".\n* One \"Arm, Right.stl\".\n* One \"Axle, Cam.stl\".\n* One \"Axle, Handle.stl\".\n* One \"Axle, Wings.stl\".\n* One \"Base.stl\".\n* One \"Cam.stl\".\n* One \"Handle.stl\".\n* One \"Head.stl\".\n* One \"Tail.stl\".\n* One \"Wing, Left.3mf\", dual extrusion.\n* One \"Wing, Right.3mf\", dual extrusion.\n* One \"Yoke.stl\".\nThis model is a fairly high precision print and assembly using at times very small precision 3D printed parts in confined spaces with highly precise alignment. I sliced my parts using Ultimaker Cura 4.12.1 \"Engineering Profile\" which provides a highly accurate tolerance requiring minimal if any trimming, filing, drilling or sanding.", "654" ], [ "However, prior to assembly, I still test fitted and trimmed, filed, drilled, sanded, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on your slicer, printer, printer settings and the colors you chose, more or less trimming, filing, drilling and/or sanding may be required to successfully recreate this model. I carefully filed all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth using small jewelers files and plenty of patience to perform this step.\nStep 2: Butterfly Assembly.\nTo assemble the butterfly, I performed the following steps:\n* Pressed \"Axle, Wings.stl\" into \"Tail.stl\".\n* Slid the axle part way into the rear axle hole in \"Wing, Left.3mf\".\n* Positioned \"Wing, Right.3mf\" between the axle holes in the left wing.\n* Slid the axle all the way forward.\n* Pressed \"Head.stl\" onto the axle.\n* Made certain the wings pivoted freely on the axle.\nStep 3: Base Assembly.\nTo assemble the base, I performed the following steps:\n* Slid \"Axle, Handle.stl\" into \"Handle.stl\".\n* Pressed the handle assembly into \"Axle, Cam.stl\" (a small dot of glue may assist in securing this assembly).\n* Slid \"Yoke.stl\" into the yoke slots in \"Base.stl\".\n* Positioned \"Arm, Right.stl\" over the pin on \"Arm, Left.stl\".\n* Slid the right arm pin into the hole in the yoke assembly.\n* Slid the yoke down to hold the arms in place.\n* Positioned \"Cam.stl\" such that the cam pin was in the yoke slot and the cam hexagonal hole aligned with the cam hole in the base.\n* Slid the cam axle of the handle assembly into the hole in the base.\n* Pressed the cam onto the cam axle (a small dot of glue may assist in securing this assembly).\nStep 4: Final Assembly.\nFor final assembly, I performed the following steps:\n* Aligned the pins on the left and right arms with the pin holes on the left and right wings.\n* Slid the butterfly forward onto the pins.\n* Pressed the butterfly tail pin into the base.\nAnd that is how I 3d printed and assembled \"Butterfly Automaton\".\nI hope you enjoyed it!", "784" ], [ "\"Walk N' Roll!\"\nIntroduction: \"Walk N' Roll!\"\nI've designed, 3D printed and assembled a number of rolling and walking mechanisms, but never a rolling AND walking mechanism, so \"Walk N' Roll!\" is my first attempt at a walking and rolling \"transformer\" mechanism.\nTwo cams control when the mechanism rolls and walks, and the same two cams create the walking motion for the four legs. Each leg contains a \"one way\" wheel that allows each wheel to roll when the leg moves from back to front and lock when the leg moves from front to back. This allows the model to walk forward. By simply reversing the polarity of the battery, the model will roll backwards then walk forwards.\nAs usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.\nDesigned using Autodesk Fusion 360, sliced using Cura 4.12.1, and 3D printed in TPU and PLA on Ultimaker S5s.\nOne final note, I receive no compensation in any form for the design, parts and/or materials used in this model.\nSupplies\n* Soldering iron and solder.\n* Thick cyanoacrylate glue.\n* Double sided tape.\nStep 1: Parts\nI acquired the following parts:\n* One \"uxcell 16mm DC 6V 60RPM Speed Torque Gear Box Electric Motor for Robot\".\n* One 3.7V 1200mAh lithium battery (https://www.adafruit.com/product/258).\n* One JST PH 2-Pin Cable (https://www.adafruit.com/product/3814).\n* Four 9.2mm lengths of 2mm diameter music wire (used as leg wheel axles).\nUnless noted otherwise, I 3D printed the following parts in PLA at .15mm layer height, 20% infill and no supports.\n* One \"Arm, Left.stl\".\n* One \"Arm, Right.stl\".\n* Two \"Axle, Cam.stl\".\n* Four \"Axle, Leg.stl\".\n* One \"<PERSON>, Left.stl\".\n* One \"<PERSON>, Right.stl\".\n* One \"Chassis Base.stl\".\n* One \"Chassis, Left.stl\".\n* One \"Chassis, Right.stl\".\n* One \"Gear and Axle, Wheel (2m 12t).stl\".\n* One \"Gear, Cam (1m 48t).stl\".\n* One \"Gear, Motor (1m 12t, 2m 12t).stl\".\n* Two \"Gear, Wheel (2m 12t).stl\".\n* One \"Leg, Left, Front.stl\".\n* One \"Leg, Left, Rear.stl\".\n* One \"Leg, Right, Front.stl\".\n* One \"Leg, Right, Rear.stl\".\n* Two \"Wheel Well, Left.stl\".\n* Two \"Wheel Well, Right.stl\".\n* Four \"Wheel, Foot.stl\" in TPU on a TPU raft.\n* Four \"Wheel.stl\" in TPU on a TPU raft.\nThis is a high precision print and assembly model using at times very small parts and in very tight spaces.", "654" ], [ "Prior to assembly, test fit and trim, file, sand, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing and/or sanding may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step.\nThe model also uses threaded assembly thus an M8 by 1.125 tap and die will assist with thread cleaning if necessary.\nStep 2: Chassis Base Assembly.\nTo assemble the chassis base, I performed the following steps:\n* Slid the wires from the JST connector through the small tunnel in \"Chassis Base.stl\".\n* Pressed the motor into the base assembly, then soldered the wires to the motor such that the motor runs clockwise when viewed from the motor shaft end of the motor.\n* Pressed \"Gear, Motor (1m 12t, 2m 12t).stl\" onto the motor shaft.\nStep 3: Chassis Left Assembly.\nTo assemble the chassis left side, I performed the following steps:\n* Placed \"Arm, Left.stl\" into \"Chassis, Left.", "784" ], [ "Marblevator, Halloween.\nIntroduction: Marblevator, Halloween.\nA Halloween themed Marblevator, Happy Halloween!\nDesigned using Autodesk Fusion 360, sliced using Ultimaker Cura 4.11.0 Engineering Profile, and 3D printed in PLA on Ultimaker S5s.\nSupplies\n* Red and black 28AWG stranded wire.\n* Soldering Iron.\n* Solder.\n* Thick cyanoacrylate glue.\nStep 1: Parts.\nI acquired the following parts:\n* One N20 6VDC 60RPM gear motor.\n* One 6VDC power supply with a male coaxial connector.\n* One coaxial female connector compatible with the power supply connector that fits in a 9mm hole with a 12mm mm shoulder\n* Seven 8mm ball bearings.\nI 3D printed one each of all parts at .15mm layer height, no supports.\nPrior to assembly, I test fitted and trimmed, filed, drilled, sanded, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces.", "654" ], [ "Depending on your slicer, printer, printer settings and the colors you chose, more or less trimming, filing, drilling and/or sanding may be required to successfully recreate this model. I carefully filed all edges that contacted the build plate to make absolutely certain that all build plate \"ooze\" is removed and that all edges are smooth using small jewelers files and plenty of patience. Using the track and guide, I then manually tested the marble lifting mechanism and carefully filed and sanded the exit and entry track areas as required for smooth entry and exit operation.\nStep 2: Assembly and Operation.\nTo assemble the model, I performed the following steps:\n* Glued \"Stem.stl\" to the top of \"Head.stl\".\n* Glue \"Lifter.stl\" into the lifter slot inside of the head such that the lifter aligned with the top of the slot (the slot end closest to the top of the head).\n* Glued \"Face.stl\" into the head assembly.\n* Slid \"Guide.stl\" into \"Track.stl\" and aligned the guide slot with the exit ramp on the track.\n* Glued \"Cam.stl\" onto the guide such that the highest point on the cam faced opposite of the slot in the guide.\n* Pressed \"Hinge Pin.stl\" partway into the hinge inside the head assembly.\n* Positioned the head assembly around the hinge slot in the track, then fully inserted the hinge pin.\n* Soldered a red wire to the motor \"+\" terminal, and a black wire to the motor \"-\" terminal.\n* Slid the motor into the track assembly.\n* Pressed \"Gear, Motor.stl\" onto the gear motor shaft.\n* Ran the wires down through the wiring holes in the track assembly then out through the bottom.\n* Pressed \"Cover, Motor.stl\" onto the track assembly.\n* Soldered the motor wires to the female coaxial connector then applied power and made sure the motor turned counter clockwise when viewed from the motor gear.\n* Slid the coaxial connector into the hole in \"Base.stl\", then secured in place with the included washer and nut.\n* Carefully positioned the wires away from the gears then pressed the track assembly into the base assembly.\nAs seen in the video, I plugged the 6VDC power supply into the coaxial connector, added seven marbles, and off it went!\nAnd that is how I 3D printed and assembled \"Marblevator, Halloween\".\nI hope you enjoyed it!", "784" ] ]

[ 841, 1665, 3811, 7255, 1434, 5907, 1392, 7153, 5698, 9865, 4194, 423, 5377, 4511, 8009, 2732, 11274, 8031, 7403, 6723, 1206, 552, 9434, 7843, 8686, 2740, 7274, 8463, 10479, 1784, 1493, 6612, 10941, 4576, 10029, 4988, 2003, 4923, 7900, 8252, 9844, 2175, 1844, 7203, 3574, 9573, 11306, 9782, 1341, 6699, 2637, 3623, 3490, 3207, 3614, 1773, 2536, 6732, 3904, 3111, 1328, 5338, 3611, 559, 4602, 11140, 10649, 7791, 6335, 3633 ]

[ [ "If I’m reading your question correctly, the answer really depends on what you choose for the characteristics of your engines and generators; their efficiency, waste products, energy requirements, operating lifetimes, and so on.\nIf your conversion process is fast, clean, efficient, and truly fuel-agnostic, then it doesn’t matter what you use - you won’t need much of it anyway. Depending on the service life of your generators, you might even buy one with a lifetime of fuel already built in. At 100% efficiency, 1kg of mass converts to 9e18 J using the usual formula. That’s more than a 2 gigaton nuclear bomb, which is a problem if you decide to crash at full speed, but that’s another discussion. Thermodynamics will most likely limit how much of that you can use for propulsion, but its still a ridiculous amount. The current annual world energy consumption could be produced by converting just 61kg of mass if you assume perfectly efficiency (1).\nYou mentioned a fueling infrastructure - tankers, stations and fuel deliveries. That implies that while people could use anything and everything as fuel, at least some people don’t. Somebody goes to the trouble and expense of operating a fleet of tankers and filling stations in a world where fuel is free, so we need a reason for that. The tankers also imply that this fuel comes from a limited number of locations and has to be transported rather than being manufactured everywhere it’s used - again, we need a reason.\nConsider a real-world example as a point of reference: A conventional 3000MW fission reactor converts pretty close to 1 kg of mass to energy every year (2). To accomplish this, it consumes 25 tons of enriched uranium fuel and produces 1 kg less than that in waste. That’s only 0.004% efficiency give or take, but it is genuine mass-energy conversion. The energy takes the form of heat, which we use to generate electricity. We could theoretically convert that same mass and generate that same heat using lots of other, cheaper processes, but we use uranium fission because it produces energy at a good rate, is a controllable reaction, it isn’t too short lived, isn’t too rare, and so on.", "435" ], [ "These same considerations could apply to your fuel. What characteristics could make a good fuel worth transporting if you can have other fuel for free?\n1) Performance: some materials could convert more efficiently than others. If it takes several tons of cheap junk to produce the same power as one gram of good stuff, it will be well worth it for anybody who needs better acceleration, longer flight times, or bigger payload capacities. 2) Safety: some materials might be riskier than others - maybe you can control the reaction rate better with some things than others, or maybe using the wrong thing risks damaging your generator or worse. Sure, you can save a few credits by connecting your generator to the san, but they used cheaper fuel rods at Chernobyl too and see where that got them. 3) Convenience: some materials could produce nastier waste products than others, making waste storage, handling and disposal a real show stopper. Perhaps pure rocket fuel converts cleanly and completely, while random junk will convert just fine and get you where you’re going, but it spews out loads of hard radiation in the process and leaves you with a residue of poisonous radioactive acid potion smeared all over the engine room. 4) Legality: Depending on your setting, smart devices and materials could be a consideration. Your generator might refuse to accept any other fuel than the genuine original manufacturer’s special blend. A government could even issue fuel that carried an encrypted signature so that your generator would only burn it while on a registered flight path. That might serve as a solution to the Kzinti Lesson(3) or the aforementioned 2 gigaton bomb problem as well.\nOn the other hand, maybe those tankers and fuel stations don’t really dispense fuel at all, and are called that for historic reasons. If those electric engines you mentioned are regular reaction engines you’ll need to take on reaction mass from time to time. That's what the tankers and stations are all about. For fuel, you just siphon off a few grams of reaction mass to feed your generator since you have tons of it with you anyway.\n(1) https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy.html\n(2) https://www.nuclear-power.com/nuclear-power-plant/nuclear-fuel/fuel-consumption-of-conventional-reactor/\n(3) http://www.projectrho.com/public_html/rocket/spacegunexotic.php#id--Propulsion_Systems", "435" ], [ "Sounds like you're in the market for a brand new torch ship! Step right this way...\nhttp://www.projectrho.com/public_html/rocket/torchships.php\n<PERSON>'s site goes over various definitions for a torch ship, but it boils down to any rocket which has both high thrust and high specific impulse (fuel economy). In general this means getting away from chemical rockets and moving over to rockets which use some kind of nuclear reaction.\nOnes we might be able to build in the near future are mainly based on fission - Orion drives and nuclear salt water rockets. These are every bit the radiological hazard you might expect them to be, so you wouldn't want to operate them in a planet's atmosphere. Not one that you cared about, anyway.\nMore speculative versions are based on fusion. Some of these (deuterium-tritium rockets, for instance) are still pretty dirty. Others (proton-boron and proton-proton) are much cleaner, but you still wouldn't want to be anywhere near the exhaust when the engine was running.\nNaturally, the cleaner reactions are much harder to initiate and sustain than the dirtier, more neutronic ones. Thanks, universe.\nAll of these have the potential to get you to a closer planet like Mars in pretty short order. The exact amount of time will depend on how much delta-V your ship's engine and fuel fraction gives you, but think in terms of days instead of months.\nThis has a lot of advantages.", "199" ], [ "For one thing, shorter trips mean less radiation exposure for passengers and crew. Engines that aren't as mass-limited mean that you can push more cargo and carry more shielding. The spacecraft is reusable, which keeps costs-per-trip down. You can reach the asteroid belt in only a little more time than it would take to reach Mars, so you can potentially extract raw materials from there to maintain your space effort, instead of having to lift them out of a gravity well.\nIt's not all roses though.\nIf you're using an engine with a highly radioactive exhaust, you'll probably only want to use it in space. That means that you'll need a more conventional way to escape Earth's gravity well to get to your interplanetary craft.\nFortunately, that falls into the realm of reusable rockets (now not actually science fiction any more) and spaceplanes. Check out the Wikipedia page for SpaceX for a breakdown of their current and future reusable launch vehicles, or Skylon for an idea of how a spaceplane might operate.\nProject Rho is a veritable gold mine of engine ideas, as well as in-depth discussions on any other facet of spacecraft design you can think of. All of it's are based in real physics, too. Scroll down to the bottom of the page for a full list of subject areas.\nEverything listed represents a significant engineering challenge, but none of it is physically impossible.", "199" ], [ "The technology could go absolutely anywhere. Lists are usually off-topic, so I won't just suggest a list of possible inventions - I'm sure you can imagine them anyway. Instead, let's look at how the world might be a little different, and how that might direct the development of science and technology.\nIf you intend to go with a very large deviation between inertial and gravitational mass then probably your biggest problem would be earthquakes. Lots and lots of earthquakes. The reason for this is that different elements on Earth will attempt to follow different orbits around the Sun. Normally, if you combine your two equations the two $m_{2}$ terms cancel and you get an orbit that doesn't depend on the nature of the satellite. Unfortunately in your case, you have $m_{g2}$ and $m_{i2}$, which do not cancel. At the extreme end, if the largest values of this ratio differ from the smallest by a factor of thousands then the surface of the Earth will be violently ripped off into space. (At the surface of the Earth, the gravitational force due to Earth is about 1600-1700 times the gravitational force due to the Sun.) For values less than this, but still large, the surface of the Earth will only almost be ripped off into space - hence, earthquakes. Gravitational \"stirring\" of the Earth's core and mantle will also be exaggerated by the same ratio, increasing the heating effect due to friction. For a large enough ratio, this frictional heat generation might rival radiogenic heating (which is dominant on Earth), again leading to earthquakes as it the convection of this heat that leads to plate movements.", "921" ], [ "This means that as tempting as it might be to build giant, low-tech skyscrapers out of \"gravitationally light\" materials, it probably isn't all that safe.\nI would also expect a scientific lull leading to a delay in post-Newtonian science and technology, as deriving the equivalent of <PERSON>'s second law might be a lot harder. Attempting to derive the laws of motion by experiment will yield different results for different test materials and it would probably take some time to isolate the factor responsible (probably wasting a LOT of time on shape). We only really understand the concept of inertial mass in reference to this law, so plucking the idea from thin air in a world in which inertial mass cannot be related to any other known property (such as weight in our own) would be a truly insightful leap of genius. In your setting you can solve this issue by just having everything start a little earlier and have historical societies a little more advanced than us up to <PERSON> and then level after.\nFlight will probably be the single most significant technological deviation from our own history - with the right materials even some of <PERSON> designs might have achieved flight. This might have profound consequences for society. The relative ease of travel afforded by flight has been credited with bringing the world together in the second half of the 20th century and for reducing nationalist and xenophobic sentiment. Your world may be a more tolerant place, if not necessarily more peaceful. Contrary to the previous paragraph, this might actually lead to faster advances in scientific development as scientists are more inclined to collaborate across borders.\nFor $m_{g}/m_{i}$ values that don't destroy the earth, spaceflight is probably still off the table until the development of liquid fuel rockets - Napoleonic Wars through American Civil War era solid fuelled rockets are wildly imprecise by the standards needed for spaceflight. It might be possible for a highly reactive, extremely \"gravitationally light\" metal (I'd go for aluminium) to always be found in nature bonded to a \"gravitationally heavy\" element, such that the compound isn't immediately stripped off into space. Such a strongly bonded ore could only be refined by electrolysis making it very rare in your setting, but not unheard of. By the time of your story enough material might have been gathered for the world's first attempt at a steam powered rocket launch - it would make a nice news item even if you didn't want your players going into space.\nThat's probably a long enough post by now. Try to keep the mass ratios within a reasonable limit (10s or at most 100s) and just use your imagination.", "693" ], [ "Many of the issues you described stem from forgetting one key fact: Velocity is not an absolute. It is relative.\nShips flying at 1000 km/s are not inherently immune to projectiles flying 1 km/s if those proectiles are fired by another ship going 1000 km/s in the same direction, because the projectiles' 1 km/s is added to the firing ship's 1000 km/s. If it wasn't, then firing a forward-aimed gun while in motion would be suicide - you'd hit yourself because you're moving faster than the projectile you fired.\nTo put it another way, a bullet fired from an AK-47 has a muzzle velocity of 710 m/s. I am currently moving at a velocity of approximately 30 km/s (relative to the sun), or about 42 times the bullet's speed. Does this make me immune to gunfire? No, because the gun is moving at the same 30 km/s (relative to the sun) as I am, and the 710 m/s of the bullet's muzzle velocity is added to that, not an independent quantity.\nTo have a prolonged engagement (longer than a single salvo as they fly past each other), ships don't need to \"slow down\", they need to match velocities - but the final matched velocity can still be absurdly high (relative to the local star, or planet, or whatever other reference point you might prefer) as long as they are more-or-less at rest relative to each other.\nRegarding evasion, you're right that it's extremely effective against dumb projectiles at long ranges, but this is purely a function of the time it takes for the projectile to reach the target and the rate at which the target can accelerate to evade.", "898" ], [ "The velocity of the target is not a factor, aside from how it affects the projectile's time to target - a very high velocity towards the attacker makes evasion harder, not easier, because it reduces the available time in which to evade the attack.\nAnd that pirate who's running dark? They can still be moving at a very high speed because, in space, you only need to burn engines to change your velocity, not to maintain it. So, if they know that ships tend to pass through an area with a specific velocity (both speed and direction are relevant here!), they can match that vector at a distance beyond sensor range, then coast through the target area with engines off until they notice potential prey nearby and fire up the engines to make minor course corrections and approach.\nIn overall conclusion, though, deep-space combat, as a rule, isn't entirely realistic in the first place, unless the aggressor already knows where exactly their target is going to be, either because the target is following a known trade route or because they have intel on the target's planned movements. Why? Because \"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.\" (<PERSON>)\nThe Earth's oceans are microscopically tiny compared to even the volume of space within the moon's orbit, never mind the solar system as a whole or looking at interstellar space, but, even so, terrestrial naval battles tend to happen near ports or other significant locations, or along major trade routes for things like commerce raiding, not at random locations on the high seas. Similarly, space combats are most likely to happen near planets, Lagrange points, or other significant locations, not because closer ranges and lower relative velocities make targeting easier, but because it's nigh-impossible to even find your target anywhere else.", "947" ], [ "In this answer, I’ll attempt to address two primary concerns impacting the habitability of your moon:\n* atmosphere retention\n* absorption of solar radiation\nYou will undoubtedly have to tweak the parameters of your planet in order to get the desired weather patterns. However, these two factors seem most important with respect to habitability.\nBefore getting into the weeds, here’s a list of definitions for variables I’ll use:\n* $R_m$, the moon’s radius\n* $M_m$, the moon’s mass\n* $L_{s}$, the combined average luminosity of the three-sun system\n* $D$, the distance of the planet-moon system from the three-sun system\n* $G\\approx 6.7\\cdot 10^{-11} \\space\\text{Nm}^2/\\text{kg}^2$, the gravitational constant\n* $k\\approx 1.4\\cdot 10^{-23}\\space \\text{J}/\\text{K}$, the <PERSON> constant\nAlright, let’s go! (Note: I’m bound to have made some computational error somewhere below. Hopefully it doesn’t affect my estimates too much, and they’re still within the right order of magnitude. Bonus points if you find a mistake!)\nAtmosphere retention\nNo matter how massive or cold your planet is, it will always continuously lose some of its atmosphere (as long as this atmosphere is gaseous). This is because not all of the atmospheric gas molecules have the same speed - their speeds are random, following the Maxwell-Boltzmann Distribution. At all times, some of the molecules will be moving fast enough to escape.", "24" ], [ "The question is - how long do you want your atmosphere to last?\nThe escape velocity for your moon is approximately equal to $$v_{\\text{esc}} = \\sqrt{\\frac{2GM_m}{R_m}}$$ and the root-mean-square velocity of gas molecules in a gas of temperature $T$ is equal to $$v_{\\text{rms}} = \\sqrt{\\frac{3kT}{2m}}$$ where $m$ is the mass of the gas molecule in question. You certainly don’t want $v_{\\text{rms}}>v_{\\text{esc}}$, or your whole atmosphere will be gone in an instant. So, at the very least, you need\n$$\\sqrt{\\frac{3kT}{2m}} \\lt \\sqrt{\\frac{2GM_m}{R_m}}$$\nor, for a molecule of diatomic oxygen,\n$$\\frac{M_m}{R_m T} \\approx 2.92\\cdot 10^{12}\\frac{\\text{kg}}{\\text{m}\\cdot\\text{K}}$$\nFor a moon the size of Deimos (which is almost certainly much smaller than yours) and with an average surface temperature equal to Earth’s, the LHS of this inequality is approximately $8.3\\cdot 10^{8}$. That’s well below this rudimentary upper limit - so far, so good.\nLet’s get a little more nitpicky. Remember what I said before about how some of your planet’s atmosphere will always be escaping?\nAssuming the atmosphere’s depth is negligibly small compared to the planet’s radius, we have that the surface area of atmosphere exposed to space is approximately $4\\pi R_m^2$. According to the Maxwell-Boltzmann distribution, if $T$ is the average temperature, then the proportion that have achieved escape velocity at any given time is equal to\n$$\\begin{align}\\alpha_{\\text{esc}} &= 2\\sqrt{2\\pi}\\int_{\\sqrt{GM_m m/kTR_m}}^\\infty v^2 e^{-v^2}dv\\ &= \\frac{2\\xi e^{-\\xi^2}+\\sqrt{\\pi}\\text{erfc}(\\xi)}{4}\\ &\\sim \\frac{\\xi e^{-\\xi^2}}{2} \\end{align}$$ for reasonably small values of $\\xi$, where $$\\xi=\\sqrt{\\frac{GM_m m}{kT}}$$\nAs an estimate, let’s use the Moon’s mass and radius and Earth’s surface temperature (and consider diatomic oxygen molecules). This yields approximate values of $$\\xi\\approx 18.5$$ $$\\alpha\\approx 2.", "24" ], [ "Considering that carbon nanotubes as a \"rope\" fiber would have extremely strong tensile strength but no compressive strength, the question then becomes: How do I use tensile strength to help avoid compression?\nThere are at least three ways to do this, two of which are already common in modern engineering.\n1) Air supported structures - Imagine a giant, vertical dirigible. Now imagine many of these, long and narrow, used as a support structure. A carbon nanotube woven fabric could be made to withstand very high pressures within, creating a very rigid \"beam\" that is, strictly speaking, a balloon. (Side note, balloon animals for giants!)\n2) Pretension - Similar to reinforced concrete, tension added to compression members before loading is already used to minimize flexing, allowing taller construction.\n3) Active support structures - This one is my favorite, and incidentally, while requiring the most advanced technology, is capable of the tallest structures. Similar to the air-supported concept, active structures use a non-solid medium to keep a structure's form. Structural support provides thrust. That thrust is usually static, and it is exactly opposite the downward force of gravity.", "333" ], [ "Now, structural supports are not the only way to provide thrust - otherwise it would be very hard to get rockets off the ground. It's possible to use such an active system to support a building as well, but a rocket would not do, as the reaction mass is continuously lost. Instead, the idea for such a structure (commonly called a space fountain) is to force magnetically charged particulate matter in a stream through an evacuated tube, where they will be deflected back downward at the top through a return tube. That deflection provides the thrust to support the building. So far, this is irrelevant to the use of high tensile strength cables such as the carbon nanotube ropes. However, we would want our fountain tower to be rigid, to avoid our penthouse guests losing their lunch. Hmmmm, rigidity? This calls to mind the second method I described. Tension would allow for excess thrust to hold the tower at precisely the wanted height, and by using sufficiently angled stay lines to compensate for sideways thrust (from wind, earthquakes, etc.), just as on the mast of a ship, the tower would be held vertical.", "513" ], [ "If you're operating near a sun (\"near\" being a relative term, but inside 2 AU is a quick rough estimate), you will probably need to have good heat management to deal with all the energy hitting the ship's skin from the sun. Even if you're far away from the sun, you will still need some heat management to deal with the heat generated by your ship's engines, equipment, and personnel. In either case, you have to deal with moving heat around.\nStirling engines generate power from the movement of heat from one place to another. They do so with higher efficiency and using lower gradients than many traditional engines. You can also put power into a Stirling engine to move heat against a gradient.\nSo, would a Stirling engine interact well with a heat management system? Unlikely but it's plausible.\nIf I wanted a pseudo-realistic version of this, I would go for something like an outer hull layer with many radiative/absorbtive baffles. That lets you pull heat in or radiate it out as efficiently as possible (and it might look cool.", "184" ], [ "Ships could have fur, or moss, or whatever other motif). Inside that, wrap the ship in a layer of Stirling pumps, all in battery. You'll get something like a big Peltier-effect blanket. It would take a little handwaving to say why this is better than just using Peltier elements, but that's just an engineering problem (\"the shared gas pool does better with load-balancing for hot spots; the mechanical system is more resilient to cosmic rays; the medium provides additional shielding; Peltier belts tend to short out in big chunks; etc).\nSo, that gives you an element of your ship which protects from heat, provides warming and cooling, and generates some power (maybe) near anything that pumps heat into your system. If stealth is important to you, this might provide that too (pump all the heat out of the side of the ship facing the sensor). Functionally, you have something that can degrade without breaking, can leak and be fixed with chewing-gum-style patches, makes noises as needed, is very important to the safe operation of the ship, and isn't immediately fatal on failure. Also, it can run on whatever unobtanium you want as its gas medium.", "898" ], [ "Of course you have transparent food\nYour question is “what transparent food can transparent humans consume”. The answer is “whatever food you want”. It’s your world. You decided there would be transparent humans. If you want to decide there is transparent food, I don’t see how that would be a problem to anyone. The hard leap of faith is to believe in a fully transparent body (complete with transparent bones, transparent blood, etc, etc). If you’re comfortable making your reader accept that, there’s really no problem in telling him that some pigs are transparent too.\nIf you feel the need to “justify” the existence of transparent food\nAgain, you don’t need to. You can just say it exists. But if you think it needs to be justified, nothing more straightforward, since you already consider having transparent humans. If we assume your humans have naturally evolved to be transparent, then there is a whole evolutionary branch of mammals that is gradually more and more transparent, all the way up to transparent humans.", "759" ], [ "You have plenty of transparent cattle, because somehow developing a fully transparent body is a huge evolutionary leap that took millions of years. It didn’t suddenly appear; it went along with the other changes that led to the emergence of homo sapiens.\nEven if for some reasons, your transparent people just became transparent at the snap of a finger, scientists will have definitely studied the bio-mechanisms that allow their bodies to be transparent. From there, they have been able to mimic this property and produce transparent GMOs for your people to eat.\nYou don’t need transparent food\nYou could have other mechanisms to avoid showing the content of your guts. For example, if evolution led to animals becoming transparent, it would make sense that they also evolved other traits to help them actually be transparent. As such, those animals have a much faster digestion system; in the wild, they hide to eat and digest everything in about 10 minutes and poop out the rest. Once they are done, they can come out of hiding and comfortably be transparent again. Your humans would just have to eat their tacos in private and wait 10 minutes before they are socially acceptable again.\nClothes?\nHumans have already come up with a strategy to cover parts of their bodies they don't want everybody to see. Clothing. Just don't go to your restaurant naked (transparent is not invisible by the way, so if showing your genitalia is still awkward in your world, you're gonna need pants. And invisible or not, it's kind of awkward to rub your genitalia on the same chair as everyone else, no?)", "335" ] ]

[ 9891, 6906, 3256, 10932, 10823, 9457, 5352, 7103, 4355, 9737, 6517, 3669, 2622, 9032, 3934, 1039, 10072, 9995, 187, 9055, 561, 5023, 8855, 8882, 7609, 7660, 4171, 5311, 4980, 5839, 7562, 3774, 5852, 1753, 10672, 6477, 5165, 4987, 2922, 10819, 2329, 8719, 7819, 4150, 10204, 7426, 7154, 2256, 5854, 36, 3689, 1692, 4276, 7941, 9163, 3856, 9253, 5480, 10046, 1088, 10804, 9600, 6016, 9039, 8604, 8683, 7266, 10542, 3214, 5593 ]

[ [ "Light Bulb Base Repair\nIntroduction: Light Bulb Base Repair\nIntroduction\nHave you had a light bulb base oxidize and stop working? Furthermore, when you remove the bulb, the bulb comes out and the base remains in the socket? The reason for this instructable is to replace the base of an LED or CFL light bulb.\nThe Story:\nOne night the LED flood light stopped working. When I went to replace the bulb, it came out and the base stay behind. What a pain. Of course, it was supposed to be a simple twist out, twist in job. Not a repair to be done at night, so the next day I removed the base from the socket and inserted a new flood light.\nI started to think just because the base separated from the light, could the bulb still work? I attached the bulb to a power cord and Yes, it did work. Wow. Now I started to think could I replace the base? Yes, I think I could… Where do I find a base? It is not an item on Amazon. I removed the base from a burnt out CFL.", "854" ], [ "With a “replacement” base, I can solder it to the baseless LED Flood Light.\nA bulb without a base and means to repair.\nBecame another item trashed in despair.\nNow with solder and glue,\nthis bulb is made anew.\nNext Tools and Supplies\nStep 1: Tools and Supplies\nTools:\nSoldering Iron (More than 35 watts)\nSupplies:\nReplacement Light Bulb Base,\nSolder,\nJB Weld,\n100, 240 and 400 Grit Papers.\nLet’s go replace the Base.\nNext Replacement Base\nStep 2: Replacement Base\nAlign the replacement Base with the bulb wires.\nThe Hot wire to be aligned with the hole. The Ground wire is bent over the edge of the bulb and squeezed between the threads of the replacement Base and the threads of the bulb. See image with description.\nNext Solder\nStep 3: Solder\nBend the “Hot” wire and solder to the replacement Base.\nUse the Solder Iron and Solder to secure the replacement Base and Hot wire.\nThe highest Solder Iron I had, was 35 watts. It can be done, but will be easier with a higher wattage Solder Iron.\nNext Clean Solder\nStep 4: Clean Solder\nHere is where you will clean and smooth the soldered Base.\nI used 100, 240 and 400 Grit Papers.\nNext Secure Base\nStep 5: Secure Base\nHere is where you use the JB Weld to secure the replacement Base to the bulb.\n1) Mix enough JB Weld,\n2) Apply it where the replacement Base and bulb meet,\n3) Let dry,\n4) Insert bulb and test.\nNext Observations and Summary\nStep 6: Observations & Summary\nObservations\nI have found little information regarding how to prevent base oxidation, everyone knows it happens but there is not a consensus or easy solution on how to prevent this issue. This occurs because of heat and moisture.\nMy preventive intervention will be to loosen and tighten the bulb, monthly, at a minimum. In addition, after windy rains; take the bulb out and wipe the base and inside dry. The idea is to keep the bulb base and bulb socket dry, preventing the oxidation from building. Furthermore, removing the bulb should prevent any bonding from occurring. I will be exploring other options to replace my constant interaction.\nThe benefits of this design are:\n1) Removing repairable items from the waste stream,\n2) Reusing items saves money,\n3) Knowledge is a powerful tool.\nSummary\nI am satisfied with the results.", "819" ], [ "Dryer Fix and Re-paint\nIntroduction: Dryer Fix and Re-paint\nI fix things. A lot. But one problem I have with fixing things is that if you do it well no one can tell it was ever broken. It’s kind of a thankless job. “What? That used to be broken? And now it’s not? Oh. OK.”\nSo sometimes when I fix a thing I like to improve it. Or at least make it clear that it’s not just a new one.\nSo when the dryer stopped turning, and I had a few days to wait before a new drive belt would arrive, I thought, “why not have some fun with the colors?” The pieces come apart easily, and I already had the front taken off. So here is how I did it.\nStep 1: Take Out the Lint Screen\nTake out the lint screen, and remove the two screws underneath.\nStep 2: Open the Top\nThe top pops up with a little prying with a screwdriver. Use a bungee or rope to prop it open.\nStep 3: Front Panels\nThe front panel is held on with two screws inside the dryer in the top front corners. Remove those and the front lifts off. The bottom panel just needs a tug on the top to remove.\nStep 4: Remove the Drum\nIt just lifts out. It's a good idea to vacuum out the inside at this stage.\nStep 5: Check the Rollers\nOne of mine would barely turn. This is what caused the old belt to break.\nStep 6: Take Off the Seized Roller.\nThere is a little plastic clip that holds the roller on its shaft. Pry it off with a screwdriver, and the wheel will slide off.\nStep 7: Clean and Grease the Roller and Shaft\nIt took a little scrubbing to get it clean.", "320" ], [ "Then I used lithium grease to lube it.\nStep 8: Put the Roller Back On\nSlide it on. Make sure it turns freely. Then put the plastic clip back on.\nStep 9: Put the Drum Back in and Place the New Belt Around It\nThe belt needs to feed through idler pulley assembly and go around the motor pulley.\nStep 10: Make Your Mark.\nBefore putting it all back together, visualize the improvement you want to make. I checked out my spray paint supply and found some colors that I liked together. Then I tried a few combinations in Sketchbook.\nStep 11: Spray Paint\nSet up some saw horses. Then spray your parts. You obviously have to do this in stages, one color at a time. But spray paint dries pretty quickly. On a breezy day I was able to re-coat or change colors after 20 minutes. I didn't want to take the top off the dryer, so I painted it with a brush and some black enamel.\nStep 12: Reassemble and Done.\nJust reverse your disassembly steps. Done. Smile. Take pictures. Write an instructable. You just saved $400 and didn't have to put a perfectly good dryer in the landfill.", "220" ], [ "Step2 Kid Alert Makeover\nIntroduction: Step2 Kid Alert Makeover\nIntroduction\nOur Step2 Kid Alert Visual Warning Signal (aka Turtle Man or Green Man) has seen a few weathered days. He was faded; the stickers were either gone or pealing. He was in need of a complete makeover and that is what I have chronicled for you.\nRead on to Makeover your Step2 Kid Alert.\nNext Materials\nStep 1: Materials\nMaterials:\n1) Fluorescent Orange paint,\n2) Fluorescent Green paint,\n3) Fluorescent Red paint,\n4) Clear UV protective spray,\n5) Reflectors (these are from a broken Triangle Roadside reflector),\n6) Letters – 2 of each “S”,”L”,”O”,”W” (these Letters are 3 inches high).\nNext Tools\nStep 2: Tools\n1) Glue,\n2) Paint brushes,\n3) Cup,\n4) Putty Knife,\n5) Vice Grip,\n6) Fine Sand Paper 120 – 200 grit (Not Shown).\nSkill Level:\nEasy\nNow that you have your Materials and Tools, let’s Makeover your Step2 Kid Alert.\nNext Removal & Clean\nStep 3: Remove & Clean\nRemove Cap, reflectors, stickers and flag then clean everything with soap and water.\n1) Pry up the push rivet with the putty knife,\n2) Remove push rivet with vice Grip,\n3) Scrap reflectors with the Putty Knife,\n4) Lift off the \"Slow!\" stickers.\nNote: If the glue for the original stickers does not come off with soap and water, use rubbing alcohol.\nNext Flag & Cap\nStep 4: Flag & Cap\n1) Paint the Flag with the Fluorescent Orange paint,\n2) Sand the Cap and wipe off the dust with water,\n3) Paint the Cap with the Fluorescent Red paint,\n4) Apply 2 Coats of Orange and Red paint.\nNext Sand\nStep 5: Sand\nSand the Green Man with the sand paper, this is to remove any blemishes and provide a ruff service for the paint to adhere better. Remember to sand both sides.\nNext Paint Green Man\nStep 6: Paint Green Man\nWipe off the dust from sanding with water. Now Green Man is ready for his 2 coats of Fluorescent Green paint.\nFollow directions of the paint to let dry and lightly sand between coats.", "353" ], [ "Remember to paint both sides.\nNext Restore Green Man\nStep 7: Restore Green Man\nNow the paint is dry.\n1) Glue the reflectors,\n2) Attach the letters and\n3) Pin the cap.\nRemember to attach the reflectors and the word SLOW on both sides.\nThen apply 2 coats of sealer on Green Man and the flag to finish the makeover.\nNext Observations & Summary\nStep 8: Observations & Summary\nObservations\nDoes he look marvelous.....\nGreen Man looks great since the makeover. He makes a bolder statement to go SLOW. With the fluorescent paints he glows more than the original colors. The new reflectors are a better quality. The letters are 3 inches high compared to the original 2 inch high sticker.\nThe benefits of this makeover are:\n1) Inexpensive and easy,\n2) The new colors are bold and make him stand out more.\n3) The letters are BIG and BOLD.\nSummary\nI am satisfied with the results.", "6" ], [ "Needle Probe for Electronic Testing\nIntroduction: Needle Probe for Electronic Testing\nElectronic components have shrunk and very small components are now closely spaced on printed circuit boards (PCBs). The close spacing makes electrical measurements with most probes difficult, with the probe tips being much larger then the pads and PCB traces that are being probed. The probe tips can cause a short circuit on adjacent pins of components or closely spaced traces.\nWhile there are several versions of narrow and pointed pointed probes commercially available, I found them to be to large for many of the small components being used at present.\nWhat is needed is a probe that is narrow, with a sharp tip that will not deform under the pressure of pushing it against solder joints on a PCB. This description reminds me of a sewing needle.\nI created a needle probe, using a sewing needle, that can probe the smallest lead and trace spacing that I have found. A sewing needle has several advantages for use as an electronic probe. They are available in several sizes with very narrow and sharp points. They are hardened steel and will not deform when pressed against the PCB while making measurements.\nSupplies\nParts List:\nPlastic rod about 6 inches long ( I used ABS Plastic with a 5mm, about 0.2 inch, diameter)\nSewing needle about 1.25 inches long\n8 inches of 30 gauge insulated wire\n0.025 inch square pin (removed from a header strip)\nSolder\nHot glue\nRosin flux\nTools:\nNeedle nose pliers\nSoldering iron\nHot glue gun\nStep 1: Inserting the Needle Into the Plastic\nHeat the eye end of the needle with the soldering iron while holding the needle with the needle nose pliers.\nInsert the eye end of the needle into the end of the plastic rod about ¼ to 3/8 inch while holding the soldering iron against the needle just above the surface of the plastic.", "98" ], [ "The needle should be hot enough to melt the plastic, then the plastic will solidify around it to hold it in place.\nStep 2: Inserting the Square Post Into the Plastic\nUsing the same procure as the needle, the square post is heated and inserted, about 1/3 its length, into the opposite end of the rod.\nStep 3: Soldering the Wire to the Needle\nStrip about ¼ inch of insulation off one end of the wire. The bare wire is wrapped around the needle at the end near the rod. Apply a drop of flux on the wire, then solder the wire to the needle. The flux will help the solder wet the steel needle.\nStep 4: Soldering the Wire to the Square Post\nStrip the insulation off the other end of the wire so the insulation does not touch the square post at the other end of the rod. Wrap the wire around the post 2 to 3 turns and cut off the access. Solder the wire to the square post.\nStep 5: Attach the Wire to the Rod\nPlace three to four dots of hot glue on the wire to attach the wire to the rod.\nThe needle probe is finished.\nStep 6: Using the Needle Probes\nTo use the needle probes, I use test leads that have a spring clip that attaches to the square post and a banana plug on the other end to attach to the meter. The needle probes are then used to contact various pins on a PCB with out shorting adjacent pins or traces.", "372" ], [ "Corrugated Metal Backsplash\nIntroduction: Corrugated Metal Backsplash\nThe pictures show what the kitchen looked like before we started and after. You can see we didn't have any backsplash besides the paint except the area behind the stove. In addition, I installed the piece of wood over the sink before I started to connect the cabinets together and give me a place to hang a light fixture in the future. On my honey to-do list is (1) paint the kitchen, (2) make new kitchen cabinet doors and (3) install a new backsplash to name a few. The better half decided on a metal backsplash and I would call the style rustic or country I guess. Anyways, here is what my son and I did to install the Corrugated Metal Backsplash. A video link is at the end of the steps if you are interested.\nSupplies\n* Corrugated Panels (Home Depot or Lowes)\n* Straight Edge (Any hardware store or Harbor Freight)\n* Scratch Awl (Any hardware store or Harbor Freight)\n* Drill (Any hardware store or Harbor Freight)\n* Screwdriver (Any hardware store or Harbor Freight)\n* Measuring Tape (Any hardware store or Harbor Freight)\n* Plastic Wall Anchors w/ Screws (Any hardware store or Harbor Freight)\n* Angle Grinder (Harbor Freight)\n* Tin Snips (Any hardware store or Harbor Freight)\n* Metal File (Any hardware store or Harbor Freight)\n* Receptacle Extension Box (Amazon)\n* Receptacle Screws 1-1/2\" (Amazon)\n* Center Punch (Any hardware store or Harbor Freight)\n* Hammer (Any hardware store or Harbor Freight)\nStep 1: Paint and Electrical Work\nThe first thing I did was paint and add extension boxes on the existing receptacles so the outlets would stick out the wall and be flush with the metal. Those are the blue boxes on the receptacles. You don't need to do this but if you don't you will need to build some kind of frame around the metal where you cut it out so it looks better. I bought those off Amazon and they were 1/2\" deep. If using these, you will also need longer receptacle screws that are about 1-1/2\" long, also from Amazon. Be careful when working with electric.\nStep 2: Measure Twice & Mark Your Cut\nWe got the Corrugated Metal from Home Depot.", "443" ], [ "The sheets were 8' long by 2' wide and cost about $16 per sheet. These could be cut with Tin Snips or an Angle Grinder with cut-off wheel. You may even be able to use a Dremel Tool w/ cut off disk but that may take a while. After measuring twice, we laid out lines using a straight edge and used a Scratch Awl to mark a line in the metal.\nStep 3: Cut the Metal\nHere I am using Tin Snips to cut across the ribs which is not too hard to do, but when cutting the opposite way it is very difficult because you can't move the metal out of the way during the cutting process. An Angle Grinder is much better in those cases.\nStep 4: Cut Out for Electric Box\nHere I am using the Angle Grinder with a Cut-Off Wheel to cut the metal where the receptacle will be. Watch my video to see more angle grinding cuts. There's one of those blue extension boxes on the table.\nStep 5: Set Panel in Place\nNow we set the piece in place to make sure it fits around the outlet and also nicely against the wall. If the wall is not plumb you will need to scribe a line using a compass for a perfect fit.\nStep 6: Measure and Mark Hole Locations\nI wanted this screwed to the wall in case we hang something on it so it wouldn't be flimsy so we measured and marked hole locations to what we thought looked best. I used a Spring Loaded Center Punch to make dimples in the metal so the drill bit wouldn't wonder around.\nStep 7: Drill Holes in Panels\nWe then held the panel in place and drilled 1/4\" holes in the metal and through the wall. The 1/4\" hole matched the Plastic Wall Anchors I had but your size may be different. Don't let the panel move too much so your holes stay lined up. Also be very careful to make sure you don't hit any electric wires that may be in the wall. As you can see, we used a Vacuum to suck up the debris while drilling to make clean up a little easier.\nStep 8: Insert Wall Anchors\nThen we put 1/4\" Plastic Wall Anchors in the holes we just drilled and hammered them all the way in.", "56" ], [ "Hidden Storage Step\nIntroduction: Hidden Storage Step\nIntroduction\nHere is a project a friend asked me to help build. The design was to have a compartment in the stairs with access by lifting the tread, simple enough. After reviewing his idea, I suggested we install it on the bottom step and add a second compartment below the first compartment, surely if they found the first compartment who will look for a second? They would be proud and pat themself on the back after finding the first compartment.\nThis instructable is building a hidden compartment inside of a hidden compartment.\nNext Tools and Supplies\nStep 1: Tools and Supplies\nTools:\nScrewdriver,\nDrill & Bits,\nTape,\nPencil,\nCombination Square,\nSaw and\nHammer.\nSupplies:\n2x6x1’ Pine Board,\n1x8x3’ Pine Board,\nFloating Floorboard (or other thin material),\nCabinet Latch,\nCable Staple,\n2 in Finish Nails,\n4d (Penny) Wood Nails and\n3 Plastic Boxes.\nNext 1st Compartments\nStep 2: 1st Compartment\nHere is where you will add bottoms for your divided hidden compartments. We used the Floating Flooring Board, use or buy a thin board to conserve on space.\n1) Remove Step,\n2) Measure inside bottoms (Left and Right),\n3) Cut inside bottoms (Left and Right) and insert.\nNext 2nd Compartment\nStep 3: 2nd Compartment\nHere is where you will create you hidden compartment accessible through the bottom of the first hidden compartment. We used the Floating Flooring Board, use or buy a thin board to conserve on space.\n1) Measure between Landing Joist and Landing Frame,\n2) Cut 2nd Compartment bottom,\n3) Hammer Cable Staples in the Landing Frame and Landing Joist to support 2nd Compartment bottom,\n4) Insert Box and add False top cover to hide Box.\nNext Back Board\nStep 4: Back Board\nHere is where you will add your back board.", "401" ], [ "The back board is from the 1x8x3’ Pine Board and the triangle fillers are from the 2x6x1' Pine Board.\n1) Measure inside between the outer Stair Stringers (Left and Right) and cut the 1x8x3' Pine Board,\n2) Measure inside between Middle Stair Stringer and outer Stair Stringers for the notch,\n3) Cut a notch in the Back Board at the \"middle\" so the Back Board will be flush with the frame of the landing,\n4) Drill a pilot hole and nail the Back Board to the Middle Stringer,\n5) Cut the triangle filler out of the 2x6x1' Pine Board to cover the gap between the Back Board and the Stringers (Left and Right),\n6) Drill a pilot hole and Nail the triangle filler to the Stringers (Left and Right) and the Back Board.\nNext Lock\nStep 5: Step Lock\nHere is where you will add a lock. We chose a simple Cabinet Latch after deciding against a magnetic or bar locking mechanism.\nAlign and attach the Cabinet Latch to the riser and step.\nNext Observations & Summary\nStep 6: Observations & Summary\nObservations\nThis is a low-cost, no new parts build, everything was resourced from what we had on hand. While this build is a retrofit in a place not frequently visited, most sizes (measurements) are not square, e.g. the \"middle\" riser is not in the middle, there is more space on the right side than the left side. The landing is not square with the stairs or level with the basement floor. There were adjustments made along the way to compensate to make this work.\nYour compartments will vary in size, but persevere.\nSummary\nI am satisfied with the results especially having to make adjustments due to the quality of the original stairs and landing installation.", "56" ], [ "Tube Converter\nIntroduction: Tube Converter\nOne of the biggest challenges to working on vintage electronics is getting the right component, tube, or the right substitute tube. Some tubes like the tubes 6AN8 or 6AN8A are hard to get or don’t have a substitute tube. However you can make a substitution by finding a compatible tube and rewiring the tube socket or using a tube adapter to make a substitute.\nWhen I started this Instructable I was unable to find a tube converter for the 6AN8 tube I wanted to replace. In this Instructable I will be demonstrating how to make the simplest tube adapter.\nSupplies\nSolder\nWire\nTube\nsockets\nSoldering Iron\nMulti Meter\nSpacers\nLarge Shrink Tube\nTube\nSubstitution Guide\nTube Data Book\nStep 1: Tektronix 515A\n1. I got my hands on a Tektronix 515A oscilloscope, that wasn’t working.\n2. From the manual I figured out the 6AN8 tube wasn’t up to snuff.\n3.", "226" ], [ "I opened the case by turning two screws just one turn and removing the side panel.\n4. I removed the tube cover.\n5. Then I removed the 6AN8 tube and tested it.\nThe tube was bad.\nStep 2: A Tube to Convert\nLooking at my supply of tubes I found I didn’t have a replacement tube and checking my Tube Substitution Guide, the only substitution is a 6AN8A tube which is just a more modern 6AN8.\nNext I found the datasheet for the 6AN8 tube. It is a Triode Pentode tube.\nPin 1 triode plate.\nPin 2 triode grid.\nPin 3 triode cathode.\nPins 4 &5 Heater. 6.3 volts, 450 mA\nPin 6 pentode plate.\nPin 7 pentode grid 2.\nPin 8 pentode grid 1.\nPin 9 pentode cathode, grid 3, and shield.\nThe first number in the tube part number usually denotes the heater voltage.\nStep 3: Substitution Guide\nGo back to the Substitution Guide and look up the tube you need to substitute.\nUnder the Basing column there is a number 9DA, the 9 stands for the number of pins.\nGo to the Basing Diagrams in the back of the Substitution Guide and look up 9DA, remember what a Triode Pentode tube looks like.\nThen start at the beginning of the 9 series record all the Triode Pentode tube diagrams.\n9AE, 9DA, 9DC, 9DZ, 9EX, 9FZ, 9HX, 9JE, 9JF, 9JT, 9KZ, 9LC, 9LY, 9LZ, and 9QT.\nStep 4: Finding All the Triode Pentode Tubes\nFinding all the Triode Pentode Tubes in 6 volt heaters is easy.\nGo back to the Substitution Guide 6 series tubes and check under the Basing column for all the tubes with the Basing Diagram codes, 9AE, 9DA, 9DC, 9DZ, 9EX, 9FZ, 9HX, 9JE, 9JF, 9JT, 9KZ, 9LC, 9LY, 9LZ, and 9QT.\nI found 6BM8, (9EX), 6FY8, (9EX), 6GE8, (9LC), and 6GW8, (9LZ), all of which had no substitutes.\nThen I found 6GH8 and 6GH8A, (9AE8A) which had ten substitutes.\nStep 5: Selecting a Tube to Convert\nThe A at the end of the part number is just a newer manufacture.\nSince the 6GH8-A, have about ten tubes you can plug and play substitute I stopped there.\nThe internal plates and grids of 6GH8, are similar in value as 6AN8 just a different pin out.\nThe heaters are the same voltage and current, so it doesn’t matter if all the heaters in the vintage electronics are connected in series or parallel.\nHowever to substitute a 6GH8 tube for a 6AN8 tube you do need a tube converter.\nStep 6: The Tubes\n6AN8 VS 6GH8, remember vacuum tubes are like transistors they only need to be in the ball park.\n6AN8-A\nPin 1 triode plate.\nPin 2 triode grid.\nPin 3 triode cathode.\nPins 4 &5 Heater. 6.3 volts, 450 mA\nPin 6 pentode plate.\nPin 7 pentode grid 2.\nPin 8 pentode grid 1.", "996" ], [ "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" ] ]

[ 5243, 3648, 9391, 8142, 11320, 10591, 1796, 10886, 2198, 3367, 467, 9683, 7981, 11157, 8965, 9284, 3074, 5322, 1987, 865, 10618, 9856, 2292, 1665, 4649, 2337, 10714, 6366, 10377, 10164, 10370, 4881, 9953, 9109, 6294, 6404, 6065, 1075, 8867, 3111, 11067, 8143, 11009, 6025, 10990, 631, 313, 10693, 2894, 6699, 2175, 3805, 8423, 7855, 4091, 361, 8841, 2677, 3574, 1817, 2353, 6013, 2263, 3907, 5290, 6486, 9915, 11286, 8025, 1833 ]

[ [ "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" ], [ "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" ], [ "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" ], [ "Deep Hole in a Small Box, a Different Take on the Infinity Mirror.\nIntroduction: Deep Hole in a Small Box, a Different Take on the Infinity Mirror.\nFirst off I must give credit for the inspiration to these two Reddit posts, this is the first one I saw and this is the one that inspired that first one.\nHaving seen these I knew it was something I wanted to make. I hope this Instructable inspires you to pick up the tools and give it a go.\nI completely messed up my first attempt by trying to use some beach and ash offcuts that I unsuccessfully jointed, this is version 2 and so much better.\nThe final product is impressive, even if I do say so myself.\nSupplies\nMost of the supplies will depend on the size of the box you're planning to make.\nI used some really nice B/BB plywood, this is such a great material and so different from the 'normal' plywood you get from the big box stores. Very few (if any) voids and with the B grade face it's pretty much blemish free. It's a little heavier and quite a bit more expensive, I would say it's worth it for any 'public' facing project.\nThe size of the box I made was determined by the mirror that my wife was throwing out, this was used as the bottom mirror.\nYou'll need enough wood (ply) to make the four side of the box to a height of about 325 mm (13 inches).\nI decided to go for a bulkhead light for the inside of the box as I thought this was in keeping with a mine shaft. You'll also need a length of mains cable.\nThe bottom mirror is a standard mirror but the top is where the 'magic' happens.\nStep 1: The Bottom Mirror\nTo reinforce the bottom mirror I mounted it to a piece of 4 mm plywood using some double-sided carpet tape.\nThis gave a total thickness of 8 mm, you'll need to remember this measurement for later as this is the size of the router bit you'll need for the rabbet.\nStep 2: Make Your Ladder\nI had originally planned to get an old ladder and chop one of the rungs off. After searching Gumtree, Facebook marketplace and local skips I didn't manage to find anything cheap enough (free).\nI wasted so much time looking around, it actually took me less time to make a quick single rung ladder.\nUsing a couple of 70 x 50 mm pine offcuts and an old broom handle I knocked up a little single rung ladder.\nI distressed the pine by knocking it about with a hammer and painted it black to add to the mine shaft authenticity.\nThe height of you ladder will be determined by the space between your two mirrors, you want to make sure the ladder is tight up against the top mirror as any large gap will ruin the illusion.", "787" ], [ "You also want to make sure the rung is in the middle for the same reason.\nStep 3: Making the Box Sides\nAs I do with most projects I drew up the basic plan first. I've attached the Sketchup file of the plywood layout.\nFor added strength I decided to join the sides using super sized finger joints, to do this I made a quick jig, this allowed me to make multiple blade passes on my table saw, these were also at an exact 90º.\nI started by measuring the end of the long sides and dividing it by 5 to get the size of the fingers. These were then marked out on both ends of the two longer sides. Once I had made the cuts to make the fingers I then used the cutouts to mark up the corresponding fingers on the short side pieces.\nUsing the cutouts to mark up the second pieces ensures that the fingers line up.\nI dry fitted the box together to ensure a good fit before the glue up.\nStep 4: Routing the Slot for Top and Bottom Mirrors\nUsing an 8 mm router bit mounted into my router table I routed a slot for the bottom mirror around the bottom of each of the four sides. In the shorter sides this slot was stopped before the edge, so I was not visible from the outside.\nIn one of the short sides I cut a 50 mm hole, this is centred around the bottom mirror slot, it's to allow the mains cable to pass past the mirror, through to the light.\nAgain, another dry fit, this time with the mirror in place.\nI then routed a slot all around the top edge of each side, this slot was 4.5 mm deep as I was planning to use a 4 mm top mirror. The slot was cut to half the width of the sides, this gives the top mirror enough area to rest on.\nAll the top slots were stopped to line up with the corresponding slot on the joined piece.", "599" ], [ "How to Build Benchtop Router Table\nIntroduction: How to Build Benchtop Router Table\nA benchtop router table is a must if you are a DIYer, working on a job site, or off of a truck. I love my full-size router table, but they can get costly. With the benchtop router, you can connect it to the top of the bench or to the side of a worktable. In this post, I’ll show you how easy it is to build one on your own. Keep in mind this is built for a cordless trim router, but it could be used for a 1/4 trim router or even a full-size router. This is a compact router table that is lightweight and stable.\nCheck out the plans here!\nSupplies\n(1/2) Sheet of plywood 3/4in X 48in X 48in\n(10) 1 1/2in wood screw (assembly)\n(4) 1in brackets\n(8) 3/4in wood screws (for the brackets)\n(2) 2in 1/4-20 screw (for router fence)\n(2) 1/4-20 wing nuts\nOptional: 4 (1 1/4in) machines screws for the router base\nWood glue\nFurniture finishing wax\nTools Used\nTable Saw (optional)\nCircular saw\nRouter\nDrill\nSpeed square\nClamps\n3/8’’ <PERSON> Drill bits\n1 -3/4’’ Hole saw\nStep 1: Build the Benchtop Router Table Sides\n* Countersink the holes and install the screws securing the bottom to the sides. Be sure to apply wood glue and use two to three screws in this location. Repeat this step twice.\n* Apply wood glue to the legs and line them up to the back. Then clamp the parts.\nStep 2: Add the Back to the Benchtop Router Table\n* With the back clamped to the legs, mark the location for the screws.\n* Countersink the holes deep enough to plug after the screw has been installed.\nStep 3: Plug the Screw Holes\n* Plug the hole using a dowel rod that’s appropriate to fit the holes drilled.\n* Use a flush-cut saw to cut the dowel off.\nStep 4: Make a Bit Holder for the Benchtop Router Table\nAdding the bit holder is optional, but I felt it’s pretty convenient for your most used router bits.\n* Cut a small piece of wood with a 45-degree miter on both ends.\n* Space the router bits apart to your liking, drilling a hole straight down while holding the bit holder at an angle.\n* Apply wood glue to the top side of the bit holder and the sides.\n* Fit the bit holder within the opening and let the glue dry.\nStep 5: Transfer the Holes From Your Router Plate to the Router Tabletop\n* Remove the base plate from the router, then use it to mark the hole for the tabletop’s router base.\n* You can use a <PERSON> bit or a paddle bit to drill out the center hole.\n* Mark the mounting holes for the router base, then countersink the holes.\n* I did this in two stages. I drew the larger hole first, so the head of the screw sits below the surface of the table. Then I drilled a smaller hole.", "493" ], [ "Chances are your existing screw in your router may be too short to go through the plywood and into the router base. So you will more than likely need to replace these screws.\nStep 6: Route the Slots for the Benchtop Router Table\nThis benchtop router table will have a fence to go along with it. I figured you could go about this one of two ways.\n* Option 1 build a fence and clamp it to the top of the router table.\n* Option 2 route in a slot, use a screwing a nut and keep the table and the fence as a self-contained setup.\n* To do this, you need to route in two places, one on each end towards the back of the router table. To route the slots, it depends on the screw you choose to use. I used a 1/4 -20 (2) inch screw in this case paired with wing nuts. On the first pass, I used a 1/4 router bit of or one that’s the size of the screw. This went all the way through. Then I made a second pass making a larger slot for the head of the screw. Once routing is done, the screw should sit lower than the surface of the plywood. Keep in mind these holes are routed from the bottom of the router tabletop. These screws need to face up.", "599" ], [ "Retro Mason Jar Nightstand Lamp\nIntroduction: Retro Mason Jar Nightstand Lamp\nThis is one beautiful piece that will look great in your home. Moreover, its super easy to build and you can buy almost all the parts at your local thrift shop and home improvement store!\nSupplies\n* Old Lamp\n* Large Wide Mouth Mason Jar With Lid\n* Retro Style Light Bulb\n* (3x) 5\" x 3/4\" Metal Pipe Pre-Threaded\n* (2x) 45 Degree Metal Angle Pieces 3/4\"\n* (1x) 90 Degree Metal Angle Piece 3/4\"\n* Scrap Piece of 2x8 Board around 12\" long\n* Switch\n* Stain\n* Spray Paint\nTools:\n* Scissors\n* Soldering Iron\n* Drill With Bits\n* Handsaw or Tablesaw\n* Chisel\n* Wire Strippers\nStep 1: Take Apart the Lamp\nMAKE SURE YOUR LAMP IS UNPLUGGED.\nAC CURRENT IS VERY VERY DANGEROUS.\nWith the Lamp I used, I cut the wire at both sides of the pre-existing switch since I will be adding my own Switch. Next I unscrewed all the parts holding my lamp together in order to leave just the head (where you screw in the light bulb) and the cable attached to it. It will vary from every lamp stand so make sure to preserve the head of the light as well as the cable coming from it, and you should be good to go.\nStep 2: Assemble the Metal Frame\nGrab the: (3x) 5\" x 3/4\" metal tubes that are pre-threaded and attach them together using the (2x) 45 degree angles and the one 90 degree angle on the end (See picture above).\nStep 3: Build the Bulb Cover\nUsing the lid of the Mason jar, we cut a hole in the middle of it. Make sure it is the same size as the head of the lamp where you put the light bulb in (See picture above). The metal plate on the top of the jar is thin enough to cut with scissors, just make sure that there are some little pre drilled holes that way you have a starting point for when you cut. After cutting out the hole, place the head of the lamp in the hole and either glue it in place or tighten with the nut. Some lamps will have a nut while others won't. If yours doesn't have a nut then glue it into the inside of the lamp, that way the glue will be hidden. Make sure to spray paint it if you would like to before gluing it in. Otherwise good luck getting it out!\nStep 4: Cutting and Forming the Base\nFor the Base of the Lamp, I used a 2x8 Board scrap. You can find these for free in trashes of worksites or other places like that. Take it home and cut it to size. It is easier to do with a table saw but it is possible to be done with a handsaw.", "56" ], [ "I cut mine into a piece that was 12\" x 6.5\" and kept the stock thickness the same. Using my table saw, I also cut bevels into the sides of the base to make it more visually appealing.\nThe Next part of this step involves cutting the hole for the switch, and the hole for the metal frame to fit into.\nFirst I put a 1\" Drill bit on the end of the drill and made a hole at about a 30 degree angle. Doing so would give me the desired look from the lamp stand. Afterwards, drill a 1/4\" hole coming through the back into the bottom of the bigger hole. After this I stated to mark and cut out the hole for the switch. If you take your time, it is possible to do this without drilling a hole through the whole piece. Lastly, drill a hole from both sides that way you can run your cables from the power socket and the bulb into the compartment for the switch (See picture above).\nStep 5: Painting and Staining\nThis step is purely subjective. What that means is that you can paint or stain it however you like. I am going to be both painting the metal and staining the wood. I will also put a finish coat over the wood and show you exactly how I do both methods.\nStaining the wood:\nTo Stain the wood all you have to do is get your desired color and grab an old t-shirt or rag. It is important to make sure the surface has been sanded smooth because splintered or rough wood may rip the rag. After you surface is clear of dust and is smooth, soak the rag in the stain. Slather it all over the wood allowing it to soak in. The longer it soaks, the darker it gets (THIS IS IMPORTANT). Once you get to your desired color, let it dry overnight.", "959" ], [ "How to Make a Wooden Box Joint Box\nIntroduction: How to Make a Wooden Box Joint Box\nwww.howidothingsdiy.com\nIn this video I'm going to show you how to make a wooden box with box joints. However, there is a twist. Most boxes use hinges or a sliding lid, this box opens in a unique way you won't usually see. But you’re going to need to watch the video to see what that is!\nI’ll show you how to cut the frame, cut box joints, use wood glue to glue the frame together, build the top and bottom assembly and finally, apply finish.\nMost of the work was done on my DeWalt table saw with the help of my box joint jig and my cross cut sled. Links below.\nSubscribe for more videos like this!\nTools\nTable saw w/ box joint jig and cross cut sled (videos to build them on my channel)\nDrill and drill bits\nRouter\nOrbital Sander\n<PERSON> nailer\nDado blade set\nSupplies\n1x6 pine board\nWood Glue\nWood filler\n<PERSON> nails\nStep 1: Cut Frame to Size\nDecide how big you want to make your box and cut the1x6 pieces to size.\nStep 2: Cut Box Joints\nInstall your dado set and get out your box joint jig. Now cut all your box joints in all four frame pieces.\nStep 3: Dry Fit Frame\nAssemble the frame with no glue just to make sure all the joints are cut properly.\nStep 4: Make Corner Supports\nNow reinstall your standard table saw blade and cut 4 corner pieces to keep the box square but also to stop the lid mechanism when fully opened and closed.\nStep 5: Assemble Frame\nApply glue to the box joint ends making sure to get glue on all edges of the joints. Now assemble the box together. Make sure everything is fully seated and square. Now clamp in the corner pieces. Use a scrap piece of the lid material to space the supports from the top.", "493" ], [ "The supports should hold the lid flush with the top of the frame.\nStep 6: Build Top/bottom Assembly\nCut top and bottom pieces that fit nicely but but still slide freely. Now cut two pieces for either side of the box that connect the top on bottom. They will need to be narrow enough to fit in between the corner pieces install earlier. Test fit all pieces.\nNow drill a finger hole in the top piece. I used a 1\" forstner bit. Now glue and brad nail the components so when they are assembled, the top/bottom assembly can slide up and down to open the box. The top and bottom should be flush with the frame and the assembly should stop in the opened and closed position on the corner pieces.\nSink all brad nails just below the surface.\nStep 7: Apply Finishing\nFill all small holes with wood filler. Then sand with 80, 120 and 220 grit sand paper until its all perfectly smooth. Finally, wax the entire box and the mechanism with paste wax. Test for smooth operation.\nIf you like this concept but want a different size box, you can scale it up and down.\nEnjoy your cool little box for storing small things.", "56" ], [ "Ultimate Router Station\nIntroduction: Ultimate Router Station\nHey guys! In this Instructable I’ll show you how I added tons of storage space to my router table to create the ultimate router station! I added enough room to store over 100 bits as well as quick access to commonly used tools as well a big storage drawers for router and accessories. Basically everything I own for my routers in one place!\nKeep reading and I’ll show you how I did it!\nIf you like this instructable be sure to check out my most popular instructables below:\n5 Pro Tips for Making Cutting Boards\nHow to Make an End Grain Butcher Block\nHow to Make a Slab Flattening Mill\nThe Ultimate Table Saw Fence\nIf you like this instructional content you can also find me at:\nMy Website (full tutorials, plans, videos): https://mwawoodworks.com\nMy YouTube (all my build videos): https://youtube.com/c/mwawoodworks\nMy Instagram (behind the scenes stuff): https://instagram.com/mwawoodworks\nMy Pinterest (things I find inspirational) : https://pinterest.com/mwawoodworks\nSupplies\nTOOLS AND SUPPLIES IN THIS PROJECT:\n►2-Sided Tape - https://amzn.to/3yha6ly\n►True Position Drawer Hardware Jig - https://amzn.to/3ePbWSJ\n►Mag Switch - https://amzn.to/3ePbWSJ\n►18\" Drawer Slides - https://amzn.to/3ePbWSJ\n►1/4\" router bit for locking rabbet joint - https://amzn.to/3ePbWSJ\n►Black Edge Banding - https://amzn.to/3ePbWSJ\n►Power Switch with Paddle - https://amzn.to/3ePbWSJ\nStep 1: Final Pics and Tour\nI was able to squeeze just about every square inch of storage space I could get out of my Woodpecker router table. I added a HUGE bottom drawer for storing handheld my handheld routers and accessories.\nThere's a 4\" drawer just below the router dust box for my coping sled and larger router bit sets.\nOn the right, I added a small drawer to hold my most used tools (collet wrenches, plate inserts and router lift tool)\nAnd finally I added this awesome slide out bit storage that has room for 100+ router bits in 1/2\" and 1/4\" shank sizes.\nEverything I own related to routers can be stored in this router station! Score +1 for shop organization!\nStep 2: Prepping for the Build (really, Deciding What I Want to Do LOL)\nOne thing I need to do before I get started is measure how much room I have under the dust box. I want to squeeze in a shallow drawer here to really maximize the storage space in this cabinet. I also measure for my side panels and the bottom drawer as well.\nAnd now I can remove the dust box to get it out of the way.\nI also need to drill a few screw holes to help me mount the panels.\nOnce all that is done I can begin cutting my cabinet parts.\nStep 3: Cutting the Side Panels\nSince the top and rails of the router table are black I wanted to find a way to make the whole cabinet black. At first I considered painting plywood because I really didn’t want to use black melamine. I’m really not a fan of particle board, but then I found something I’d never seen before at my local plywood dealer.\nIt’s called shelf liner and its got a melamine like coating on top of a plywood core.", "493" ], [ "This fits exactly with what I was thinking for this project.\nThe first step here is to cut the side panels of the cabinet and doing this at the MFT is pretty simple. I need four panels total.\nThe only other thing I need to do to these is cut notches on two corners and these allow space for the bolts that connect the frame of the router table. To do this I like to set up a mag switch to act as a positive stop. I just set the fence into position and I can knock these cuts out fast and each one is the same. To get the short side of the notch I just reposition the fence and the magnet and keep on cutting.\nStep 4: Installing the Side Panels\nThese fit in really nice with those notches cut out. I cut the back\npanels out of ½” ply. And for the top panel I needed to make an access for the dust collection as well as some air vents for the router.", "599" ] ]

[ 10735, 9959, 10400, 4773, 6755, 1117, 8746, 10348, 4670, 6105, 8135, 1688, 5880, 5095, 775, 2337, 3763, 10636, 10970, 1288, 3740, 10060, 4881, 7538, 9756, 6173, 1076, 9889, 7225, 4599, 1661, 33, 2865, 8363, 1542, 11169, 2605, 7398, 10995, 6188, 981, 6783, 7449, 4465, 5271, 9460, 1658, 10166, 4701, 5207, 4507, 9075, 11039, 8043, 1933, 10340, 1099, 10104, 7854, 8416, 2833, 9284, 11150, 6934, 2162, 4477, 7286, 342, 7338, 3050 ]

[ [ "Crimes and Misdemeanors\nI surely don't have time- to myself, or otherwise- to be sullenly rewatching <PERSON> movies (without even a monetizable work hook!) and yet here I am. I think this'll be the last one, after HUSBANDS AND WIVES last week and <PERSON> about a month ago - a trio that, taken together, but each in different ways, probably constitute the best directing he ever did. (The official over/under on \"Woody Allen: Ranked\" featurettes online when he eventually dies, sooner or later, is 0.5; the odds he'll somehow keep churning out movies post mortem, from a Hell presided over by <PERSON>, are slightly better).\nAnyway: CRIMES is spare and swift in a purposeful way, distinct from the more haphazard \"effortlessness\" of post-2000s, \"late style\" <PERSON>; MATCH POINT, which is basically a remake, isn't remotely as precise or effective despite its Highsmithian airs. The cutting in the sequence leading up to <PERSON> murder is maybe <PERSON> finest hour, a stately fugue of anticipatory dread synced perfectly to <PERSON>. And the image of <PERSON>'s dead, staring eyes -- crept up to by an uncharacteristically low-angled camera, which holds for a small eternity before scuttling away - is genuinely nightmarish, although I suppose it says something that a character given zero dimension beyond her status as an obstreperous plot point has her best onscreen moment as a corpse.\nThis was one of <PERSON> problems with <PERSON>'s \"film of ideas;\" that <PERSON>'s unfortunate <PERSON>, rubbed out by gangsters hired by her married, older lover after she threatens to bust up his marriage, inspires no sympathy - and thus no real sense of tragedy in the aftermath.", "698" ], [ "I think she's right about this, and that <PERSON>'s ominous line, \"I will not be destroyed by that neurotic woman,\" is probably one of the top ten jaw-droppers in <PERSON>'s filmography, category of \"veiled confessional,\" though of course this movie predates his major personal controversies - it'd have to with <PERSON> cast as the idealized object of his own character's affections. In a way, it's that precise *lack* of plausible, red-blooded, mammalian emotion - of feelings any deeper than fight-or-flight, the condition embodied perfectly in <PERSON>'s skilled, gestural acting- that makes CRIMES so bracing to me. <PERSON>'s movies, whether comedy or drama (the two modes juxtaposed so blatantly here in the titles and cross-cutting structure) are almost always chill, functional little edifices that instrumentalize their characters, so making that tendency explicit - in effect doubling and tripling down on it through parallel narratives in which evil prospers and idealism goes (literally) out the window - is a solid artistic choice; I sort of feel like this (and HUSBANDS, and I guess DECONSTRUCTING <PERSON>) feel like the last time this filmmaker was really *making* choices, instead of just flying on autopilot. None of this explains why I spent ninety minutes last night with a movie that I already know is pretty good, and yet isn't exactly likely to reveal new depths or meanings, or even provide much pleasure except as ambient audiovisual background noise (I watched it while revising a book proposal on something totally different). But I've been thinking of <PERSON>'s eyes - and the bride kissing her own blind father gratefully on the cheek - all afternoon, so I guess I don't regret it.", "698" ], [ "Natural Born Killers\n<PERSON> had a lot of chips in 1994 and he cashed them in on a movie that on some level is his crowning achievement, though if like me you think he's often a fundamentally unserious filmmaker - a zeitgeist-surfing, fast-twitch opportunist as opposed to a vanguard artist - that's not a compliment. Points for managing to shove something mostly free-form and story-less into several hundred American cinemas, and for a few effectively quasi-surrealist touches, like the sitcom of the damned starring <PERSON>, which really does make you sit up straight and pay attention; it’s appalling, and inspired as satire. But for the most part, NBK's hyper-formalism, switching formats and framings, shoehorning in Godardian text and turning numerous scenes into rear-projected palimpsests, only exacerbates the material’s essential and irrecuperable paltriness. Having worked very hard with a host of talented people to develop a distinctive cinematic language, <PERSON> uses it to simply say the same thing, over and over again, and not too convincingly. While it might seem like a cop out to ding a movie like this for its gratuitousness, it's more that said gratuitousness - on every front, from acting to editing to gore to needle-drops - is ultimately the wrong kind of alienation effect for this material, which needs, to paraphrase <PERSON> on Peckinpah, to have some sting in its death.", "698" ], [ "<PERSON> gives us Wild Bunch -style scorpions aplenty, but no sting; instead of using cartoon stylization to deepen and contextualize real-life horror (sexual and emotional abuse; the predations of the carceral state) he ends up reducing (and banalizing) his subject and its potentially juicy complexities into a display of lizard-brained showmanship. I thought on this viewing of <PERSON> tough, unyielding Henry: Portrait of a Serial Killer, and how one short, horrifying scene involving a television suggests most of what <PERSON> is preaching about here and more; I thought of the shivery lyricism of Badlands and the blocky naturalism of The Honeymoon Killers and the bravura camerawork of Man Bites Dog and even the po-mo pedantry of Funny Games, which has aged into even more of a critical pinata than NBK (<PERSON> having <PERSON> to go full-scold mode against \"enemy films\" that had their gore and ate it too) and realized I'd rather be watching its precisely-tuned situationist shtick. For a movie that means to castigate the history of representation and the complicity of mass media in a culture of violence, Natural Born Killers lags behind the pace-setters in its own genre and even looks draggy compared to unpretentious inheritors like <PERSON>/Taylor, whose movies are far less pious about revelling in shit in order to say something about our collective pungency. One note about <PERSON> Aussie let TV trash-humper <PERSON>: this could have been a brilliant performance if it had been allowed to stand apart tonally from the rest of the movie, on its own plane of reality, <PERSON>-style. Integrating the character into the second half of the film - and into the prison riot section that finds <PERSON> going for broke and getting there, especially via <PERSON> rape attempt on <PERSON> -is a real mistake, one among many.", "698" ], [ "Maestro\nGenuinely shocked that I pretty much loved this, may write more later\nThe More Later: my major frustration with The Holdovers (a movie I enjoyed) was that for all the internet yelling about its peerless attention to period filmmaking detail, it lacked the electric irresponsibility of the best 70s movies. What you gain in precision and pathos, you lose in \"this could fall apart at any second\" excitement. It's not just The Holdovers - it's a major difficulty for all kinds of period pieces set in the age of Hollywood. If I could watch actual work from the time, why would I watch a self-conscious, sanded-down imitation?\nIn that context, <PERSON>'s glorious untidiness and unchecked ego feel extremely refreshing. The pace is crazy, it covers 40+ years but ignores huge life events (not just artistic achievements, but like, the births of children), the balance between the two lead performances is always uneasy, it's got a genuinely uncomfortable sense of humor that's always jumping out at inopportune moments (the doctor costume... chilling), everybody's murmuring over each other all the time. Yeah, <PERSON> is jacking a lot of style from latter-day PTA (even more than from producers <PERSON> & Steve imo) but he's still got some of coke-era PTA's brashness and his very own willingness to dive headlong into dicey audiovisual metaphors (the West Side Story needle drop, etc). It's all very exciting to me, a person who loves mess. This movie has so many ideas piled on top of each other, and none of them are pre-chewed! There are definitely all kinds of legitimate criticisms you can make, but I think it earns its epigraph, a feat that I absolutely didn't think it would manage when <PERSON>'s words appeared onscreen up top. And I guess you could call it \"Oscar bait\" in the sense that you can tell <PERSON> really wants an Oscar, but good lord, if this looks anything like a limp and condescending Miramax biopic to you, I don't know what to say.\nA statistical addendum, for my fellow dweebs:\nIf you count the shots with \"invisible\" transitions separately (like when <PERSON> & <PERSON> flee lunch to go to their dream ballet, or when the backstage background fades behind <PERSON>), there are 314 shots in Maestro (also not counting the archival over the credits).", "378" ], [ "I'm not attaching any value judgment to that number, but it's significant - it's somewhere around a quarter of what you'd consider \"normal\" for a two-hour Hollywood drama of this scale. From first shot to credits is 118 minutes (followed by very long credits), which makes the average shot length almost 23 seconds. Very long. Having the opportunity to hold things for that long is what creative control looks like. Also interestingly, the movie slows down to about half-tempo when it switches to color - there are 174 shots in the first 46:21 and 140 shots in the remaining 71:37. So averages of about 16 seconds per shot and 31 seconds per shot, respectively. Most of the shots in the black and white section occur in the early phase of Lenny & <PERSON>'s relationship - about 90 in 11 minutes, so that skews things a bit. Median would really be the more robust measurement to use here but it's a bit more work to calculate that. Might make a spreadsheet about it tomorrow. The rhythms of this thing are very musical and it feels rewarding to pull it apart.", "862" ], [ "<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" ], [ "<PERSON>\nThe contrarian impulse to plant a flag for MADAME WEB is strong, but it'll take somebody braver—or more bored or more reckless—than me to give it a real try. There are passages and exchanges here which are, by any objective measure, absolutely terrible: cutting, framing, background, line readings, palpable ADR. These are flaws as opposed to being enjoyably relaxed ad/or off kilter choices smuggled through the studio quality control filter, which is one potential line of defence for anybody feeling protective of what feels like a broken production, and to an extent a parable of protectiveness (<PERSON> is a mama-bird figure) and an allegory of itself (the theme is trying to salvage the future and how hard that it is). Instead of repeating the obvious jokes about individual bits, I'll note something about the movie that I quite enjoyed, and which is neither unintentional nor \"so-bad-it's-good,\" and that's the use of a TERMINATOR-style stalk-and-run plotline that solves one major, recurring problem of superhero movies, which is the basic invicibility of all involved, and keeps the stakes small and urgent. It cannot overstated how ridiculous the movie's villain, <PERSON>, is on a scene to scene, line to line basis—he walks through giant-ceilinged rooms in a suit and shoeless, looking like an evil <PERSON>Inarritu, voicing his every anxious thought and endlessly berating his one loyal employee, who is <PERSON> from GIRLS.", "698" ], [ "But there is something nightmarish about him using a combination of magic powers and circa Bush II surveillance tech to hunt down a group of vulnerable young women whose protector is basically helpless beyond a few flashes of intuition; it says something that I got caught up in the left-to-right-momentum of the story, which is more than I can say ftly, but I felt less drained). As for <PERSON>, she's fine: this is not a case of an expert comedienne making a meal of garbage or a movie star reduced to collateral damage, but another iteration of real, basic charisma that is rooted partially in seeming slightly out of it at all times. In other news: the soundtrack is more period evocative than Saltburn; the product placement is more shameless (and weaponized) than <PERSON>; the winky Marvel shtick is relatively underemphasized. Meanwhile, the climax is seriously goofy (I wonder if <PERSON> likes Raising Cain), while the coda hammers home the abject industrial failure of the whole thing by having our badly damaged yet sanguine heroine imagine future adventures with her intrepid, spider-powered harem— a vision made sadly ironic in the context of her new blindness. Those girl-bossy spin-offs will never be made, at least not in our time-line; more likely, MADAME WEB might end up as a throwaway joke in the next DEADPOOL sequel (maybe they're ADRing it in now), or a decent case study option in undergraduate cult cinema courses- one that doesn't really teach us anything while remaining a learning experience.", "698" ], [ "The Curse\nSometimes you have to go to extreme lengths to make your point! <PERSON>’s screen presence is a bit of a complicating and frustrating factor for me, although all three leads are uniformly excellent - this is really compelling as a super-weird slow-motion <PERSON> moving-parts-in-a-pressure-cooker thriller about white-saviorism, gentrification, New Mexican liberalism, contemporary art and reality TV (the specificity and depth of the venom here, my god!), and the much-discussed WTF ending actually makes about as much sense as anything else would in that context, but in casting himself <PERSON> places this firmly within his artistic project of finding new ways to expose himself as pathetic on television, which has pretty consistently held diminishing returns for me since Finding Frances, when the interiority actually came as a surprise rather than being par for the course. You mean <PERSON> plays a cosmic cuckold with a micropenis? You mean he’s gonna get grilled on camera about his personal failings and the end of his last relationship? Or, tee-hee, is it a show about why and how the constraints of reality TV might make him look like a loser? Haven’t we been through this before? Is there really anything more to be milked out of the <PERSON>-both-<PERSON>-and-<PERSON> stuff? I’m not so sure, especially now that it’s had a perfect formal payoff with “the pottery scene.” Viewed in that light, I’m hoping this is a final kiss-off to that side of his work, but I was saying that that about The Rehearsal too, so I’ll believe it when I see it.\nAnyway, whatever it all amounts to, it’s pretty magnetic television. I don’t think the 10 episode format does it any favors - it’s not that it’s too long, exactly, as much as it feels like a pitch for a limited series of 4 two-hour episodes cut into a full season; those previously-ons are obviously at least somewhat part of the show’s parodying of TV, but the show itself isn’t really doing a ton of that, so...", "282" ], [ "they mostly just end up serving the purpose of reminding the viewer what themes they should have in mind for the next 45 minutes. The amorphousness is by and large perfectly harnessed within the episodes themselves (<PERSON> as director is the biggest revelation here, just unbelievably good stuff), although Episode 8 in particular stuck out as an exception to that, but as a Season Of Television I’m not sure how functional it is. Happy to settle for electrifying, alienating, hysterical and perfectly-performed, tho!", "282" ], [ "Benediction\nAnother in a series of not-so-disguised autobiographies, about on a par with A QUIET PASSION, though maybe not as rigorously focused. Very episodic, with long passages of arch, backbiting dialogue, a lot of which is funny and adds to the sense of a kind of British arts-world historical pageant, with <PERSON> at its center; the tonal shifts are deliberate and ambitious but still jarring, and ditto the integration of ragged archival footage into the gleaming period-piece visual scheme. I’d read about the final scene and it still worked me over pretty good - a great piece of acting wedded to a disarming and mournful stretch of poetry.", "594" ], [ "The Abyss\n“LOVE YOU WIFE”\n<PERSON> 2001: A Sea Odyssey.\nThis is something of a mess; you can tell <PERSON>’s trying to do a Hawksian ensemble thing here, and I appreciate the attempt, but the schlocky 80s action movie characterizations leave the supporting characters feeling closer to a more forgettable version of the Alien crew than, say, the Only Angels Have Wings gang. The central (nakedly autobiographical) divorce melodrama between <PERSON> and <PERSON>, however, really sings, and the staggering level of verisimilitude found in the insanely-staged underwater sequences provides some pretty overwhelming spectacle.\nI found my attention starting to lag at about the 90-minute mark, as <PERSON> fairly rote villain begins to take on a more significant role, and the proceedings started to feel a bit conventional to these eyes. Imagine my surprise when I found my hair blown back by the onslaught of surrealistic imagery and downright emotional terrorism <PERSON> serves up in the final hour — I’ve read some reviews that compare this to Interstellar, and while it does contain a similarly loopy blend of bleeding-heart sentimentality and abstract, wildly ambitious sci-fi, I still found myself thoroughly moved. A truly singular cinematic experience — see the 3-hour director’s cut.", "378" ] ]

[ 8049, 5510, 4169, 1202, 7106, 1373, 657, 5119, 1258, 2434, 5357, 7689, 7221, 3119, 8779, 213, 479, 7349, 296, 8817, 252, 1487, 7594, 1549, 3283, 11202, 9107, 2945, 7558, 6901, 5408, 8978, 5904, 242, 7206, 6738, 4753, 1121, 3334, 3127, 5897, 7326, 6624, 5647, 2750, 5063, 10953, 4468, 3301, 2609, 2811, 9642, 8488, 8112, 10223, 10983, 5042, 10803, 5206, 8703, 3320, 10028, 3878, 2147, 5490, 10623, 9930, 1280, 2454, 8175 ]

[ [ "I seem to recall a ritualistic which <PERSON> was \"reborn\" a spirit without a body is for all intents and purposes dead. Reinhabiting a body... any body after being removed from your original body makes you undead. The use of powerful magics to bind the soul to an object before death seems (even in standard D&D Liches) to be a precursor to the Lichdom. If a wizard can't very well wait until they are already dead to create a Phylactary. We must ask ourselves, would <PERSON> EVER have died? If the answer is no, then he is clearly either divine, demonic, or undead. <PERSON> is how a Lich begins. An unnatural act to avoid death by a powerful Wizard. A d&d wizard who createds a Phylactary by whatever infernal magics puts their soul there. <PERSON> was not the first to do such a thing, he was the first to make multiple Phylacraries in the <PERSON> world. Nothing would stop a D&D Wizard from doing the same, provided he could find a way to divide his soul. Other clues that <PERSON> is undead are that he survives the destruction of his body.", "773" ], [ "A lich, once the body is destroyed, will reform after a time, just as <PERSON> did. Their soul will be protected (or trapped) by their Phylactery and they will experience exactly what <PERSON> describes. No death, especially not in the permanent sense, but also not really alive. <PERSON> is a Lich whose body was destroyed who reformed that Body (as Liches are want to do) and wasn't able to be defeated until his Phylacteries (Horcruxes) were destroyed... honestly it's a basic <PERSON> plot-line in D&D. The only debate here comes from <PERSON> fans who either want to idolize <PERSON>, saying she didn't have any inspiration or want to avoid admitting that <PERSON> is fantasy just like Lord of the Rings... btw, while we're at it, <PERSON> is where the fantasy genesis of the <PERSON> comes from his Phylactary is the One Ring. Remember in The Hobbit, he was merely called \"<PERSON>.\"\nIt all comes from LoTR, the granddaddy of D&D, Wheel of Time, the modern fantasy concept of elves and dwarves, Star Wars, and Harry Potter. Yep potterites, I guarantee you'd love picking up a Polyhedron and building your own Wizard. You'll recognize all the spells that are used in Harry Potter. Although I'd probably recommend more fireballs than disarming telekinesis... but that's up to you. Hey <PERSON> is a great PowerWord Kill, don't you think?", "773" ], [ "I think there is an anime exploring that idea. The Church would wield much more power- and most likely that Church would be Catholic or Orthodox as it already possess sacraments (physical things transmitting spiritual power) which that could fight them. They also both have a fairly centralized organization that is Global. Many Protestant Churches are not like this and may be overshadowed or simply unable to coordinate any meaningful resistance. It will have well trained exorcists already capable of fighting other evils. Sacramentals are the physical elements which are used to dispense the sacraments.", "752" ], [ "You could even combine blessed holy water or the relics of a Saint with Weapons (a Sword, or Gun's bullets..?) Vocations to the Priesthood would increase dramatically and all of a sudden people would give the Church heed on moral stances on sin.\nDeacons, men having some vows but not fully priests, would probably become almost warrior like because they can handle some of the responsibilities of a priest (other than administering sacraments).\nGovernments would probably start trying to meddle in Church affairs again because Bishops are once again influential, powerful leaders. They'll start trying to appoint their favorite candidates for Bishop- this could lead to increased corruption. There would be a struggle for autonomy for the Church. On the plus side for the Church, they can make demands of secular governments and society.\nAreas where the Church is already powerful will be the most protected in the short term and may become bases of operations from which to launch re-conquests of Vampire held areas. (example: Italy may be used to reconquer Northern Europe with Poland's help..)\nSuperstitions and the growing new Paganism may collapse if they can't replicate any of the power that the Church has. It may validate the existence and power of the God of <PERSON>.\nI'd look to how the Church grew in influence at the beginning of the Dark Ages as a model for the transition from now to your setting as one reason it was like that was that Bishops were the only Roman officials who didn't abandon their stations; people rallied around their leadership.", "274" ], [ "The place a Reverend Mother dare not look is the ancient force that \"takes\"\nMasculine and Feminine are broken down into a more fundamental concept, Creation and Destruction. Looking inward to the force opposite your gender will be \"overwhelming.\"\n<PERSON> said, \"There is in each of us an ancient force that takes and an ancient force that gives. A man finds little difficulty facing that place within himself, where the taking force dwells, but it's almost impossible for him to see into the giving force without changing into something other than man. For a woman the situation is reversed.\"... \"These things are so ancient within us that they are ground into each separate cell in our bodies, we are shaped by such force. You can say to yourself, yes I see how such a thing may be, but when you look inward, and confront the raw force of your life unshielded, you see your peril. You see that this could overwhelm you. The greatest peril to the giver is the force that takes. The greatest peril to the taker is the force that gives.", "674" ], [ "It's as easy to be overwhelmed by giving as it is by taking.\nwhat is the force that takes? (relating to physics)\nThe B.G. ability to see into maternal ancestry is a product of awakening to the \"giving\" force. A Reverend Mother can see the succession of bio-reproductive creation which culminated in her birth, giving them an unparalleled understanding of the past. Prescience, a common thread in dune, is the cognition of the future. Quite the opposite of other memory which deals only in the past. In physics, Entropy is the destructive force which moves a system from ordered to disordered. To glimpse the future is to see death and destruction of the present (reason why it's frightening). A few times in Dune, it is said that \"time becomes space.\" Observing possible futures would take an understanding of the possible paths entropy could take on it's journey to the entropic heat death of the universe. To understand the future you must understand destruction. It's a reasonable postulate that the \"force that takes\" is the root of prescience, which <PERSON> (nearly) masters after drinking the water of life.", "283" ], [ "One main inspiration for <PERSON> was the Christian Bible. Valinor is a parallelism relating to the likes of Heaven and the Elves who have a very strong resemblance likened to the chosen ones, etc.... All of the books have the prototypical evil vs good story background as does the Bible (as do many other literary sources). Men are corrupted and easily influenced by power and live in the middle earth. <PERSON> was banished, but he returned as Satan was to according to scripture. <PERSON>, the dark overlord and his minions and mordor are all highly resembling of Hell, Satan and Demons.\nAlthough <PERSON> was a devout Christian... He obviously was trying to create a unique story and had an awesome imagination and I don't believe his intentions were to mask the concepts in the Bible as opposed to creating an awesome and truly unique literary work of science fiction. Some other/additional possible influences with the detailed aspects of the races possibly come from Northern Mythology.\nThe ring exhibits a general object of desire. One that is sought after so much that it ultimately and permanently corrupts a soul who is then tortured and tormented at the loss of a material object.", "72" ], [ "Objects of desire in the recorded history of the world tend to lead to wars, murder, etc... I believe this is his main use of the ring as a illustrative tool. Another corollary comes when <PERSON> states (Around 1:24 in The Fellowship of the Ring): \"There is only one Lord of the Ring, there is only one who can bend it to his will and he does not share power.\" Obviously that's a reference to <PERSON> and is illustrative of the concept of <PERSON> and/or God and how they are not subject to the desires of normal man. And just as <PERSON> carried the burden of man and relieved him of his sin - <PERSON> does the same (at least in concept) for all the races of middle earth. I'm not aware of any prior works that have a similar concept of a single ring aside from what's already been mentioned in the other answers.\nHere is a excerpt from the link below:\nReligious influences\n<PERSON> once described The Lord of the Rings to his friend, the English Jesuit Father <PERSON>, as \"a fundamentally religious and Catholic work, unconsciously so at first, but consciously in the revision.\"1 Many theological themes underlie the narrative, including the battle of good versus evil, the triumph of humility over pride, and the activity of grace, as seen with <PERSON>'s pity toward <PERSON>. In addition the epic includes the themes of death and immortality, mercy and pity, resurrection, salvation, repentance, self-sacrifice, free will, justice, fellowship, authority and healing. <PERSON> mentions the Lord's Prayer, especially the line \"And lead us not into temptation but deliver us from evil\" in connection with <PERSON>'s struggles against the power of the One Ring. <PERSON> has also said “Of course God is in The Lord of the Rings. The period was pre-Christian, but it was a monotheistic world” and when questioned who was the One God of Middle-earth, <PERSON> replied “The one, of course! The book is about the world that God created – the actual world of this planet.”\nCheck this link:\nWikipedia - Tolkien Influences", "72" ], [ "OK, My $0.02:\nFirst: Gunpowder isn't just \"Charcoal, Saltpetre, and Sulphur.\" Yes, those are the ingredients, but the ratios between the ingredients are really critical, and there are some interesting production methods that need to be applied in order to make what we think of as real Gunpowder.\nSecond, gunpowder itself doesn't explode, it just burn quickly without the need for outside air. without seriously restricting the expansion of the produced gasses, no explosive or propulsive effects will be observed. Alchemists might understand the principles and uses of gunpowder, but in all probability in a magic system, the presence of \"Flashing Powder\" would probably be the mark of the charlatan. Think of any suggestion of using it in weapons as akin to approaching a general about the combat application of Silly String(tm) (Not that silly string doesn't have combat uses...) Or basing a weapons system on pyramid power.\nIf we look historically at the period where what we think of as \"guns\" took over from the Bow-type ranged weapons, we find that there was a period where the gun was a curiosity, rather than an accepted weapon. The reason that guns finally took over was not due to technologies or logistics, but user training. If you start with a raw recruit, with no weapons experience, a musketeer can be trained in a couple of months, while a skilled archer needs a couple of years of intensive training. It's a subtle point, but it's what provided the tipping event in our \"guns-vs-bows\" debate.", "523" ], [ "If there were other factors involved, that argument could have easily tipped the other way.\nTaking this, assume that your magic is Uncommon, rather than Rare. A village shaman or even a military-trained Archomancer could easily provide some enchantments to arrows (increased range, target seeking, improved damage, or magical explosive, just to name a few) that could easily make up for a lower level of training in the archers corps, and would provide a significant, and ready made multiplier to the bow side of the question. This makes guns, while the principle would be understood, a distant second choice on the battlefield.\nAs to explosives, I don't think that you can restrict those without seriously restricting any industrial capability, or even magical capability. An explosion is a sudden release of energy. Any energy. You're going to have to assume that any rational magical system would have come up with this, even if only by accident. Once the principle is discovered, there's no putting that genie back into its bottle. Under those assumptions, cannons and artillery are almost a given, they just might not be gunpowder-based.", "523" ], [ "What reason would give the most benefits to a Progenitor race for creating sub-races?\nQuestion has been put On Hold while I develop another question in the Sandbox area of StackExchange. Didn't know about the Sandbox?\nCheck it out: StackExchange Sandbox for Questions\nWhat reason would spark the most benefits a Progenitor race of beings would use genetic engineering to create multiple sub-races on various planets in a galaxy?\nEnvironmental Adaptability is the most obvious answer, so I'm looking for other reasoning.\nExample:\nA race of beings (Progenitors) use their own DNA and mix it with Ape DNA to create humans on planet Earth.\nThey use their DNA and mix it with Cat-like DNA to create \"elves\" on a different planet.\nThey use their DNA and mix it with Armadillo-like DNA to create \"dwarves\" on a different planet ... and so on and so forth to explain the existence of Fantasy Races.\nThe Progenitors are ONLY using DNA from Pre-Historic Earth to mix with ... so environmental adaptability is already accounted for and Alien DNA/Other is avoided in this setting.\nThe Progenitors of most stories are either the first Species to advance technologically (Science Fiction) or the first Species created by the Gods, or the Gods themselves (Fantasy) ... or some combination/alteration of those.", "759" ], [ "Usually the Progenitors have disappeared from a setting due to Enlightenment/Evolution, Catastrophe, War, etc. and only leave behind artifacts or ruins which inform or hint at their previous existence. This link leads to further ideas about Progenitors/Precursors.\nMy worldbuilding is a Science Fantasy setting 300 years in our Earth's Future (but the Progenitors are from our distant past) in a parallel Universe where both Magic and Science work and compliment each other.\nExample: My Progenitors have ascended to a higher level of existence and act as Gods in the parallel universe ... they create the sub-races as a part of ongoing and changing games for gaining/losing points and rank amongst themselves ... so my own answer to this question is basically: For the Progenitors' Amusement.\nBut I put forth this question to hear about Your Progenitors and Your Reasons for inclusion in Your Worldbuilding.\nMy Pinterest Board of Inspiration:\nAkasha Universe", "183" ], [ "It should be noted that The Wheel Of Time having 7 spokes for seven ages (time without end) is an in-universe cosmology. For the 'reality' of what is happening, I only really consume what <PERSON> has said, and the opening narration from each book, which is presented as omniscient. Every other source is presented as fallible or untrustworthy (e.g. The Dark One)\nWhat we 'know':\n* <PERSON> had stated at various times that Wheel Of Time takes place on Earth of the future and of the past. He had never (to my understanding) indicated how far in the future or how far in the past.\n* It is never stated what mechanism can refresh the world between turnings of the wheel, or to what extent it does.\n* It is stated that the One Power is not always known to humanity in all ages or turnings, but the One Power appears to be a prerequisite for opening the Dark One's prison (the Bore) and sealing it.\n* The Ogier are not native to Earth. It is unknown if they always arrive and always leave, or if it was a one-time event\n* We have no idea what the shape or state of the world is before the breaking. Only that the world is 'much changed'. The Two Rivers sits on land that used to be the western coast of some land-mass.", "54" ], [ "Some mountains existed from prior to the Breaking, and others are new (The Mountains of Mist are new, The Mountains of Dhoom are new, and it is implied that so is much of The Spine Of The World). The land around Tar Valon survived roughly intact before and after the breaking.\n* Many of the Seanchan beasts were brought to the prime world via Portal Stone. They are not akin to any earth biology.\n* Tel'Aran'Rhiod exists everywhere and every time. It binds all possible worlds together.\n* The only source who could know the truth in-universe is <PERSON>. If it is to be believed, then this happens over and over again, not exactly, but as variations on a theme. <PERSON> states something similar to this, but he has no way of knowing, and it is implied by The Dark One itself that what <PERSON> thinks he knows is incorrect.\nThe conflict with The Dark One isn't really the doing of The Dark One. People cause it. Is that inevitable as the wheel turns? It's unclear. Are the effects the same every time? Who knows.", "88" ], [ "Book 6, chapter 23: <PERSON> telling <PERSON> \"Yes, <PERSON>, you can love.\" ... \"When given everything that has happened to you, is a great and remarkable thing. You are still too young to understand how unusual you are, <PERSON>.\" ... \"You are protected, in short, by your ability to love! The only protection that can possibly work against power like <PERSON>'s. ... <PERSON>, have you any idea how few wizards could have seen what you saw in that mirror? ...\" While not outright information about obscurials, it does shed some light on <PERSON> that we can use to postulate a few theories perhaps. When you compare what we know of <PERSON>'s life to what little glimpses we got to see of <PERSON> sad and abused life, heard about the eight year old imprisoned girl from Sudan and <PERSON>'s account of his sister <PERSON>'s experience, we can see that a pattern of sorts emerges.", "573" ], [ "The individuals who developed these parasitic forces have been mistreated and abused, whether it was a single traumatic event or prolonged exposure and multiple events. We don't know when <PERSON> actually developed into an obscurus. Was the scene in the movie where we first see <PERSON> his first incident? We're there others? Since <PERSON> and his creatures are blamed or the events and deaths we can only assume that it burst out of <PERSON> at such a level around the time of <PERSON>'s arrival. We know from <PERSON> that her adopted son <PERSON>'s mother was \"a wicked, unnatural woman\". I wonder what <PERSON> did to <PERSON>'s mom that she was able to take <PERSON> away from her and keep him? Is she dead? Murdered in some horrific witch trial by the Second Salamers? Did <PERSON> see or know about it? In addition to the beatings and punishments he suffered at <PERSON> hands, he was also called freak and trash by the Senator, and in general, ignored and likely made fun of by most people.\nAnother aspect I found fascinating was the similarities between how the dementors being the wizarding equivalent of depression are the obscurials the wizarding equivalent of another mental illness or feelings made manifest? Then we also have examples of <PERSON>'s mother, <PERSON>, and <PERSON> and even <PERSON> to a certain extent, losing their powers from unrequited love. So we can see a precedent that your emotional state is relevant to your power and abilities as well as your knowledge and experience. I see these all as related because they are aspects of the human condition and show a variety of different choices and outcomes. So what do you think?", "247" ] ]

[ 6530, 126, 10058, 9365, 7332, 9038, 4828, 5889, 7066, 5541, 9200, 418, 4, 5547, 8993, 1391, 6464, 11185, 5617, 9106, 2396, 9515, 1948, 7757, 8711, 9561, 4995, 6226, 7521, 10463, 9645, 3787, 6290, 9628, 553, 4862, 1351, 3946, 7865, 6958, 3812, 1477, 3682, 7883, 7789, 3093, 7026, 7580, 766, 5115, 1599, 10382, 388, 3888, 10194, 8574, 10158, 7904, 6784, 10413, 10883, 533, 3015, 3966, 1573, 9244, 897, 3483, 10187, 7313 ]

[ [ "Hedges for Toy Farm / Model Farm\nIntroduction: Hedges for Toy Farm / Model Farm\nInexpensive model hedging for toy farm / model farm in 1/32 scale. When playing with a toy farm it is often useful to be able to mark out a field or two with some sort of model hedging. Field edging, hedging, fencing etc tends to be expensive. In the past I had made hedging using stained 1/4 inch plywood, but these proved to be a bit bulky to store and expensive to make. This instructable recycles plastic from plastic milk bottles and so is very low cost.\nI'm sure there are many ways to improve this project and look forward to your suggestions\nSupplies\nEmpty 4 pint plastic milk bottles (two bottles per 15 inch section of finished hedge)\nScissors\nCraft knife and steel ruler\ntwo pieces of scrap timber around 3/4 x 3/4 x 16 inches\nCraft heat gun\n2 small g clamps\nsmall piece of sandpaper\nAwl, embroidery silk and needle to fit\nCheap acrylic art paints in greens / browns and paintbrush to suit.\nSmall piece parcel tape\nStep 1: Design\nDesign stage\nAt 1/32 scale an 8 ft high hedge needs to be 3 inches tall. It also needs to have a base about 1 1/2 inches wide to stand unsupported.\nStep 2: Cut Up Milk Bottles\nRemove the labels from two four-pint plastic milk bottles. With a pair of scissors cut the top and bottom from the two bottles. Cut the remaining middle bands of the bottles vertically. This leaves you with two flat pieces of thin plastic, each approximately 5 inches by 15 inches, Trim these down with a craft knife and metal ruler to two rectangles 3.75 inches x 15 inches, With a pair of scissors cut a wavy edge along one long side of each piece of plastic. These wavy edges will become the top of the finished hedge.\nStep 3: Re-shape the Plastic\nThe plastic used in these milk bottles is HDPE (high density polyethylene) with a number 2 in the recycling triangle. This plastic melts at 125 degrees and with the application of a little heat below that temperature can, to some extent, be reshaped. Read up on this online and satisfy youtrself that this process can be tackled without safety risks. Essentially what we are going to do next is to put a right angled fold along the long edge of each piece of plastic. As a heat source I have used an inexpensive crafting heat gun.\nTo hold each piece of plastic while putting in the folds, clamp the plastic between a couple of pieces of scrap wood around 3/4 inches square and 16 inches long with 3/4 inch strip protruding. It would help to hold the whole arrangement in a vice. Apply a little heat to the protruding strip while pressing it down to make a right angled fold.", "401" ], [ "This needs a little experimentation gradually adding more heat until the fold is right. You are not trying to actually melt the plastic, just to warm it enough to enable it to be re-shaped. Be careful not to burn yourself with the heat gun.\nStep 4: Construction\nOnce you have put the folds in each piece of plastic use a small piece of sandpaper to rough up the surface of the plastic to enable paint to stick to it later. The two pieces of plastic now need sticking together back to back. The two 3/4 inch folds make the base of the model hedge. I thought that a glue gun would be the easiest way of sticking the pieces together. Unfortunately hot glue will not adhere to the plastic. Packaging tape might work but I have no idea how long it would last. Some sort of physical joining would be best. Staples or eyelets will work, but might leave sharp edges, not ideal for little fingers. Sewing works. Here I have used an awl and some embroidery silk. The curved needle was used because it was the only one I had with a large enough eye for the thread. Carefully done this sewing could outline wavy edges of the bushes or trees in the hedge. My sewing is rubbish. The pieces of parcel tape in the illustration temporarily hold the two pieces of plastic together during the sewing.\nStep 5: Painting\nThe final stage is to paint the plastic hedge. Cheap artists acrylic paint works OK and a mottling effect of greens and browns adds some realism.", "959" ], [ "Open Face Bird Feeder\nIntroduction: Open Face Bird Feeder\nI have a number of bird feeders in the tree in our front garden. The trouble is that our local robins never eat from them, they are always on the scraps that fall on the ground.\nDoing a little research I found that robins will feed from tables or open feeders, I wanted something to hang from the tree so decided I would make an open feeder.\nSupplies\nA bandsaw\nA log not too big to go through your bandsaw\nSome wood glue\nA few screws (optional)\nClamps\nSome rope to hang the feeder\n4 x screw in eyes\nA drill with drill bit to make the holes for rope\nStep 1: The Woodwork Step\nThe woodworking steps are very similar to making a bandsaw box.\nEverything in this step was done freehand on the bandsaw (carefully).\nFirst off I wanted to get the two ends flat and parallel to each other. For this I used a 13 mm 6 tpi blade.\nAs this is 'just' a bird feeder I didn't actually measure anything and did it by eye.\nOnce the log was squared off I chopped both ends off at about 15 mm thickness.\nI marked out the section to be removed and because the curves were a little tighter, swapped out the blade for a 6 mm 10 tpi blade.\nThis was the first time I had made a cut of this depth using the band saw, and I was incredibly impressed with how it sliced through 220 mm of green oak.\nThe first curve was a little more open than I had planned, I don't think I was putting enough forward pressure with the turning pressure.", "431" ], [ "However, the cut was perfectly 90º upright through the whole cut.\nI could now reattach the end pieces to close off the box. This was done with some waterproof wood glue and a couple of stainless screws. I left it clamped overnight to make sure the glue set.\nStep 2: Stringing It Up\nThis step was a little tricky as I wanted to make sure that the feeder couldn't tip forward and spill out all the food or tip back and make it so the birds wouldn't be able to perch and feed.\nI decided to go with 4 screw in eyes, this allowed me to tie on 4 suspension lines. These lines were run through holes in a top bar.\nThe conjunction of the 4 lines and top bar made it possible to balance the feeder front to back and left to right.\nI was able to get it perfectly balanced on the single hanging line passed through the top bar.\nStep 3: Feeders First Visitor\nSUCCESS, the feeder had only been up about an hour and I got the first visitor, a very skittish robin came in and fed 4 or 5 times.\nHere's hoping it becomes a regular feeding spot.", "599" ], [ "Wooden Bouquet\nIntroduction: Wooden Bouquet\nIn the previous ible Recycle Flower I made a single large flower out of wooden circles to decorate the shed door.\nIn this next variant I will use very much the same process to make a bouquet of smaller wooden circular flowers.\nThe main difference will be that the flowers will be made of plywood and require far less screws and brackets.\nSupplies\n3.6 mm Plywood\n9 mm Plywood\n30 mm Hole saw\n55 mm Hole saw\nSaw\n6 mm dowels\nPaint - mixture of colours\nExterior Glue\nSanding Paper\n2 x M6 bolts x 60mm minimum length\n2 x M6 nuts\n2 x M6 flat washers\nWood (L) 25cm x (W) 12cm x (H) 2.4cm - Qty 2\nStep 1: Cutting the Flowers\nEach flower is made of 9 mm plywood from which seven 30 mm circular discs are cut.\nClamp the plywood to a sacrificial board on the work surface.\nWith the Hole-saw cut seven discs.\nOnce the discs are cut, sand smooth any rough edges and surfaces.\nThis project consists of 6 flowers therefore 42 discs are required.\nStep 2: Cutting the Backing\nEach flower is held together by a larger disc that sits behind the smaller discs.\nThe support disc is made of 3.6 mm plywood.\nUsing a 55 mm Hole-saw, cut seven discs.\nOnce the discs are cut, sand smooth any rough edges and surfaces.\nThis project consists of 6 flowers therefore 6 discs are required.\nStep 3: Painting\nThe central part of the flower (pistil), consisting of 6 discs will be painted in yellow.\nThe remaining 36 discs (petals), are split in to 6 groups of 6 discs and will be painted using 6 varieties of colours.\nThe colours chosen are Red, Dark Blue, Light Blue, White, Orange & Pink.\nFirst all 42 disc are given a coat of white undercoat and left to dry.\nOnce dry lightly sand flat any rough areas.\nThey are then painted in one of the chosen colours in batches of 6 discs and left to dry.\nApply two coats of your chosen colour.\nStep 4: Flower Assembly\nTake a yellow centre and surround it with 6 discs of the same colour all face down.\nUsing an exterior glue suitable for wood apply this to the support disc, centralise it with the central disc by aligning the drill holes and apply firm downward pressure while it sets.\nPlacing a weight on the flowers while they set removes the requirement to apply manual pressure.\nOnce the glue has set remove the weight and set to one side.\nIn the meantime cut various lengths of 6 mm dowels for stems to suit each flower.\nGlue and/or staple the dowels to the back of the flowers.\nStep 5: Support Assembly\nThe support consists of 2 pieces of wood into which the flowers stems are sandwiched.\nArrange the flowers as into a hand fan shape and staple or glue into what will be their final positions on to one of the supports.\nPlace the next support directly over the lower piece.\nClamp the two support pieces together and drill two 6mm holes into which two 6 mm bolts will be inserted.\nFit a flat washer to the back followed by a nut and tighten.\nStep 6: Display\nDisplay on its own inside or outside or attached to something else.\nIf leaving the flowers outside protect with a clear lacquer/varnish\nJob done.", "401" ], [ "Ramp Walking Elephant\nIntroduction: Ramp Walking Elephant\nI have always been drawn to old fashioned toys, ones that do not need batteries or upgrading and that use clockwork, or as in this case, gravity.\nThere is a timelessness to them - we have a small collection of them and my wife and I often take time to play with them in the kitchen!\nIf you are intending to make this little elephant, please look at step 10 before you start. There is an alternative template with a slightly more 'bulbous' body that may involve less fiddling than the one posted in step 1.\nThis Instructable involves the use of cutting tools.\nPlease make sure that you are properly acquainted with how to use them safely - if in doubt, seek advice and/or guidance, before starting.\nSupplies\n* Pencils, graphite and charcoal.\n* Small Tri-Square.\n* Rule.\n* Glue stick (for paper) - can use watered down white glue.\n* Scissors.\n* White glue.\n* Vernier slide caliper.\n* Bench vise.\n* Small clamps.\n* Tenon saw.\n* Junior hacksaw.\n* Wood chisel - 3/4 inch. (Optional)\n* Files, woodworking – 6 inch -coarse, half round and round.\n* Needle file set.\n* Hand drill with 2 mm drill bit (1/16th inch).\n* Shooting board (described in text).\n* Jack plane.\n* Pliers and metalworking vise (Optional).\n* Soft metal wire, 2 mm thick (1/16th inch) - short length, about 50 mm (2 inches).\n* Centre punch or a nail.\n* Small hammer.\n* Flat washers 2 mm (2), stainless steel preferably.\n* Cocktail sticks.\n* Wood - reasonably hard. Small piece - the elephant is 35 mm high (1 3/8 inch) and 15 mm thick, (just short of 5/8th inch). You will also need wood for the legs (2 X 4 mm wide,3 mm thick and 35 mm long) and front and back foot (50 mm long and 15 mm wide). This foot length allows one to grip it in the vice)\nStep 1:\nI drew out the template (pic 1 above) and cut out the image with scissors. Use charcoal pencil to scribble on the back (pic 2).\nTrace onto the piece of wood selected - pic 3 - result - pic 4.\nMark out the cutting lines - pic 5.\nCut off the excess wood - pic 6.\nMark the pivot hole and the hole for the leg stop with a centre punch and drill a 2 mm (1/16th inch) hole through the points - pic 7-9.\nStep 2:\nA brief digression on the subject of shooting boards.\nNothing at all to do with firearms - a useful tool for 'shooting' the ends of cut pieces of wood. Useful also for planing the edges of small pieces of wood - indeed, I have done all the surfaces in just a few minutes.", "286" ], [ "An advantage is that one can look down at the work and watch the progress.\nA brief Google search tells me that these are not available commercially - construction is very easy. See the photos above.\nIt consists of a flat board, (mine is 12 mm, (1/2 inch) multi-ply), 40 cm (15 3/4 inches) long and 20 cm (7 7/8 inches) wide - pic 1.\nThere is a piece of wood running the length of the shooting board, attached to it with screws. This can be gripped in the vice to secure it while working. If you are building one of these, attach the flat board to the runner first - pic 2. (Mine is 6 cm (2 23/64 in) by 4.5 cm (1 3/4 inches).\nThere is a thin 'mezzanine' of 3 mm ply on top, aligned with one long edge of the multiply, leaving enough space from the opposite edge to the edge of the base to accommodate the side of a jack plane. (Mine is 14.7 cm (approx 6 inches) by 30.5 cm(1 foot approx). The 'mezzanine' is skinned with Formica (or any similar composite), as is the 'runway' for the jack plane. (pic 3 ).\nThe blade of the jack plane does not extend right across the sole - the 'mezzanine' is to lift the working surface to allow all the work to be 'shot' full access to the blade - pic 4. In addition, I use a scrap of wood to further raise the wood to the middle of the blade, when necessary.\nThere is a stop attached at a right angle to the multiply base with screws from underneath.", "668" ], [ "Telescope Setting Circles\nIntroduction: Telescope Setting Circles\nI have been considering the best way to improve my telescope viewing activities and Setting Circles seem to be an improvement I could make to my two Dobsonian Skywatcher telescopes that provide a quick win.\nHere is a view of the Setting Circle on my smaller 130p telescope, there are more images of this and my larger 305p telescope later in this instructable.\nSupplies\n* The Smaller Telescope is a Skywatcher Heritage 130p D130mm F160mm on a Dobsonian Mount\n* The Larger Telescope is a Skywatcher Skyliner 300p Flextube D305mm F1500mm on a Dobsonian Mount\n* The wooden annular rings were sourced from this eBay company who were excellent and helped me work through the design, size, thickness, etc. I highly recommend them\nhttps://www.ebay.co.uk/itm/Circle-MDF-400mm-diamet...\n* I used the following website to prepare and print the scales to go on the annular rings https://www.blocklayer.com/circle-divider.aspx\n* I also looked at a number of other people’s designs on a variety of websites and forums to get ideas\nStep 1: First Thoughts\nIn planning my design I worked with the following ideas and principles:\n* Each setting circle will be placed over the appropriate telescope and placed around the top base disc:\n+ For the smaller telescope the annular ring will rest on the lugs of the lower base disc\n+ For the larger telescope suitable supports will be fitted to the lower base disc, protruding out, that the annular ring will rest upon\n* In use the telescope is aligned North – South (using a compass) and the annular ring rotated until the 0° is under the pointer\n* The pointer will be fixed to the base using a magnet so that it can be removed and replaced easily whilst maintaining pointer alignment - I didn't actually do it like this as I found a simpler solution\n* When the telescope is rotated the annular ring remains in situ hence showing the angle that the telescope is now pointing (Azimuth)\n* The annular ring will have 360 degrees marked on it so that the telescope can be aligned to a single degree accuracy\n* The inside diameter of the annular ring quoted for each telescope is the actual measurement therefore some tolerance is required to allow the telescope turntable to move without catching on the annular ring\n* I’ve allowed 2 mm all round for clearance\n* The actual width of the annular ring is not vital as there is sufficient clearance once the ring is laid over the base\n* I have worked with 30 mm as that will allow sufficient space for the angle graduations to be placed easily – probably using a paper template\n* 25 mm thick MDF for both annular rings is probably best to maintain strength\n* Minimise any permanent changes to the telescopes or their mounts by reusing existing holes, mounts, etc.\nStep 2: 130p Telescope Plans\nThis instructable will show the steps primarily for the smaller 130p telescope, but the larger 305p telescope steps and principles are basically the same.", "737" ], [ "I have attached a pdf at the end of this instructable which have all of the steps and a few more pictures which might help in understanding why I did what I did and what you might want to change/adapt.\nStep 3: Designing the Paper Scales\nThere are a number of scale production websites out there but I found this site gave me a good range of options to parameterise to my needs the scales to go on the annular rings\nhttps://www.blocklayer.com/circle-divider.aspx\nThere are more photos and details on producing the paper scales in the pdf at the end of this Instructable.\nStep 4: Printing the Paper Scales\nIdeally the scales should be printed on a single page but I was limited to an A4 printer. Under normal times I might have considered using a printing service but as it turned out separate arcs printed on A4 then pasted on the annular ring works very well.\nStep 5: Completing the Annular Rings\n* The paper scale was glued onto the wooden annular ring with PVA glue\n* The scale was sealed with Jigsaw Puzzle Conserver as I happened to have some handy. I believe an alternative would be Modge Podge although I’ve never used it myself\n+ Although I am not planning to have the telescopes out in the rain there is a risk of damp when in use\nStep 6: Centralising and Supporting the Setting Circles\nAlthough the Setting Circles sit well on the telescopes, I wanted to ensure that any errors were minimised so the Setting Circles should be centralised around the telescope base and ideally limited in its movement once aligned.", "646" ], [ "Using Tinkercad to Create a Strip Cutting Tool\nIntroduction: Using Tinkercad to Create a Strip Cutting Tool\nEvery table top wargamer needs scenery and half the fun is building it yourself. To make things like this modular wall (from a Black Magic Craft tutorial here), you need to be able to accurately cut strips. Many of us don't have hot wire cutters and even if we do, it's nice to have a quick and easy tool that cuts cleanly with no melting and without casting 'Stinking Cloud' level 2 in our crafting rooms.\nWhen I bought my house, I found a few tools in the corner of an old shed, including a leather cutting tool for making laces. I found the tool perfect for cutting styrofoam strips (see pictures), so useful that I wanted another one for my son to use when we craft together.\nI decided to use Tinkercad to draft up a version without the handle (which I find gets in the way) to 3D print so I could make as many copies as I wanted.\nIf you want to follow the drafting process, it's a great learning experience. If you just need the tool, skip ahead to the printing step, the files are attached there.\nSupplies\nTinkercad (sign up for free at tinkercad.com)\nA 3D printer or an online 3D printing service\nA few bits of hardware. I used two M3x25 screws to hold the blade on and a 10-24 x 1 1/2\" machine screw with a nut for the adjusting thumbscrew knob (or try an M4x35 or M5x35 screw)\nA blade - either a scalpel blade (X-acto blade) or a piece of 9mm break-away blade from small craft knife works well.\nStep 1: Drafting the Fence\nTo draft the fence, I created a 25mm high x 25mm wide x 110mm long box in Tinkercad. Click the ruler button and drag a ruler to the front bottom left corner of the piece. It makes the next steps much easier.\nNow, create a box 'hole' that is 13.5mm high x 27mm wide x 25mm long. Position it by typing in the values (-1, 12.5, 15) as shown in the image.\nGroup the two boxes. Now draft a cylinder 'hole' that is 4mm x 4mm x 20mm high. Position it by typing the values (10.5, 23.5) as shown in the image. This is the hole for the adjustment screw to tighten into. We've made it a bit undersized so that it can be drilled to fit whatever hardware you're using.\nGroup the cylinder with the fence to finish this part.\nStep 2: Drafting the Adjustment Bar\nCreate a box 25x25x110mm to be the adjustment bar. Move the ruler to the bottom left corner of the box.\nWe need a slot cut through the bar to allow adjustment.", "668" ], [ "Create a box 'hole' that is 5mm wide, 27mm high and 85mm long. To tidy the ends up, create two cylinder 'holes' that are 5mm x 5mm x 27 mm high. Drag them onto the ends of the box 'hole'. I needed to type in half millimetre values to get things lined up perfectly. Group the two cylinders with the box hole.\nDrag the hole so that it is centred horizontally on the adjustment bar block, 15mm back from the front edge. Group it with the bar.\nNow, create a cylinder 'hole' for the blade mounting screws, 3mm x 3mm x 20mm long. Rotate it 90 degrees as shown, then position it 11mm up and 4mm from the left edge of the shape. Copy it (ctrl-c) and paste it (ctrl-v), then position the copy 11mm up and 18mm from the left edge of the shape. Group both holes with the adjustment bar, which is now complete.\nStep 3: Drafting the Blade Clamp\nStart with a block that is 25x25x15mm. Move the ruler to the bottom left corner.\nCreate two 4mm cylinder holes for the screws to pass through. They should be positioned 10.5mm high. One should be 3.5mm from the left edge and the other should be 17.5mm from the left edge. Bonus marks if you can figure out how to place the second hole by measuring 3.5mm from the right edge :).\nTo give a more finished look, create counterbore holes for the screw heads. Mine are 6mm in diameter, so they are both 9.5mm high and are 2.5mm and 16.5mm from the left edge.\nStep 4: Printing the Tool\nExport your file as an STL or OBJ and use it to print your file.", "56" ], [ "Wooden Triceratops\nIntroduction: Wooden Triceratops\nI do a little bit of woodworking in my garage and I got asked if I could make a wooden triceratops dinosaur. I googled images of what Triceratops is believed to have looked like and decided to make one from cheap,planed pine timber which is readily available from a timber yard or DIY store. I had already made a slightly different version which is on my Pinterest (<PERSON>) but wanted to try a more ‘3d’ look. I purchased a 6’ length of pine 120mm wide x 18mm deep which I thought was adequate for a decent size body.\nSupplies\nLength of pine timber.\nVice/vise or clamp.\nBandsaw ideally although a fret saw or even a hand saw would suffice but would take a lot longer.\nSander or sandpaper.\nWood glue.\nPyrography wood burner (not absolutely necessary).\nStep 1: Drawing the Body on the Timber.\nFirst I drew a freehand Triceratops outline on cardboard and cut it out to use as a template. For this template it’s important to draw the outline with legs and both downward facing horn and upward pointing horn. Next draw around the template on the timber 3 times, remembering to draw two bodies with legs and downward pointing horn and one body with no legs and upward pointing horn. If you use pencil to draw round the template, the legs and horn can be rubbed out as required on each part so you end up with the correct body outlines.\nStep 2: Cutting Out the Pieces.\nThe completed triceratops will consist of three glued-together pieces to form one body. The three pieces drawn on the timber now need cutting out. I used a bandsaw which is very easy and quick, but a fretsaw would do the job as would a hand saw but will obviously take a lot longer. Remember that the piece with the upward pointing horn has no legs and will be the middle section of the completed dinosaur. The other two pieces should be exactly the same and will form the outside sections.\nStep 3: Sanding\nAt this point, prior to any gluing, sand the body parts to form points on the horns and take the edges off the 4 legs and round them off slightly. I used a belt sander for pointing the horns and a mini detail sander for the legs and other difficult to access areas, although sandpaper will do the same job, but slower.\nStep 4: Gluing the Body Together\nWhen you are happy with the shape of the legs and horns, the body pieces can be glued together.", "401" ], [ "Spread a thin layer of wood glue on both sides of the middle piece (the piece with no legs and upward pointing horn, remember!) and attach the outer pieces. Place the pieces in a clamp or vice, wipe off excess glue and allow the glue to set. I use Evostik wood glue for all my wood projects as I find it fairly quick setting and it forms an extremely strong bond, but any decent wood glue will do. The three pieces will probably require some further sanding to make the joints perfectly flush.\nStep 5: More Sanding!!!\nThe glued up body will now require more sanding. I ‘round’ the body off on the belt sander and sand the tail to a point and also remove a little of the jaw to make it slightly more pointed and not as wide. I use the detail sander to sand the joins flush with each other as the pieces will not be exactly the same shape when cut out.\nStep 6: Cut the Mouth\nTriceratops mouth is more ‘beak’ like, so the last stage prior to adding the collar is to cut the mouth out. I did this on the bandsaw, lying the body flat on the saw bed and making two cuts to remove a section of wood to create an open mouth.\nStep 7: Triceratops “collar”.\nThis is probably the most difficult step….Take a piece of pine timber and measure the thickness of the triceratops body immediately behind the top horns and approx 1” down. Cut out a section of the timber to match these dimensions. Try this to fit over the body and adjust depth/width accordingly. Then draw a semi-circular crest with a number of points around the circumference. Cut out this shape. There’s quite a lot of trial and error in this stage…..Once you have a good fit, glue in place to rest on the start of the top horns.\nStep 8: Eyes and Finishing Touches\nI use the pyrography tool to burn eyes into the design and also a hint of colour where the toes would be, at the point of the horns and the tip of the tail.", "599" ], [ "Tensegrity Shelf\nIntroduction: Tensegrity Shelf\nHaving created a set of tensegrity models, what better way to display them but on a purpose built shelf.\nBut in keeping with the models to be displayed this is to be no ordinary shelf.\nThis is to a be Tensegrity shelf, employing the same methods as applied to the models.\nHowever, were the previous models have been 3D printed this project is to hand made.\nA three tier Tensegrity shelf to be constructed from wood and copper pipes.\nSo lets get down the to process of making this next project.\nSupplies\nPlanks (L) 380mm x (W)120mm x (H) 24mm - Qty 3\n4mm Screw in ring eyelets - Qty 4\n15mm copper earth clips - Qty 8\nCopper elbows (D) 15mm diameter- Qty 8\nCopper Pipe (L) 35mm x (D) 15mm - Qty 8\nCopper Pipe (L) 178mm X (D) 15mm - Qty 8\nCopper End caps (D) 15mm - Qty 8\nChain (L) 90mm - Qty 4. Link diameter to suit earth clip screw diameter.\nCord (L) 70cm x (D) 3.5mm - Qty 4\nCable ties - Qty 4\nSpirit level\nScrew driver, tip type dependant upon earth clip screw head\nCutter to cut chain.\nRuler/Tape measure\nTri square\nPen/Pencil\nDrill bit 4mm\nDrill Bit 3mm\nForstner Drill bit 15mm\nPlumbers Solder\nNon Corrosive Flux\nSaw\nWire Wool\nBlow Torch/Pipe Soldering Iron\nSand Paper\nWood coating - Stain, Paint or Oil as required and as suits ones tastes.\nPPE - Associated with the activity to be undertaken.\nStep 1: Plans\nDimensional details for the pipes and the shelves.\nStep 2: Woodwork\nYou will need three wooden shelves with dimensions of (L) 380mm x (W)120mm x (H) 24mm, I cut these from a longer left over piece of decking I had been using to build a fence.\nEach of these three pieces needs to be drilled to accommodate the copper pipes and the stabilising cords.\nIdentify one shelf that will be the middle tier and with a 15mm Forstner drill bit make two holes 15mm deep, diagonally opposite each other in the corners at the intersection of 35mm on the long edge and 25mm on the short edge. Repeat the process at the other location.\nTurn the shelf over and repeat the process but ensure that there is no hole directly behind the hole to be made.\nThese holes are to accommodate the copper pipes.\nNext from the corner measure 20mm on the long edge and 10mm on the short edge and at the intersection drill a 4mm hole. Repeat this in each corner.\nThese are the pass through holes for the stabilising cords.\nThe two remaining pieces will make up the lower and top tiers but these are only drilled to accept the pipes on one side only.\nWith a 15mm Forstner drill bit make two holes 15mm deep, diagonally opposite each other in the corners at the intersection of 35mm on the long edge and 25mm on the short edge.", "735" ], [ "Repeat the process at the other location.\nDo this in the remaining shelf.\nFinally, from the corner measure 20mm on the long edge and 10mm on the short edge and at the intersection drill a 3 mm hole, which is to accommodate the screw-in eyelets. Repeat this in each corner.\nWith all the drilling complete its time to turn our attention to the copper pipes.\nStep 3: Metalwork\nCut 4 x 15mm copper pipes each 178 mm long.\nThen cut 4 x 15 mm copper pipes each 35 mm long,\nEnsure that the end of the pipe is not rounded but flat as any slack in the mounting hole in the shelf will reduce the supporting depth increasing any lean.\nA pipe cutter is a quick and clean method of cutting but will round the edge of the pipe, this is not an issue for all but the base of the pipe that will plug into the shelf. Either file, grind or use a saw for this part of the operation to prevent this.\nIf the copper tubes are plated with chrome or some other coating you will need to remove~15mm of this from the end as this will prevent the solder melding with the copper. This can be accomplished with a file, sanding paper or a grinder\nIts still recommended to clean and roughen the end in preparation for soldered even if there is no plating to improve adhesion.", "735" ] ]

[ 2223, 10102, 5147, 1472, 2833, 1437, 2138, 6971, 6942, 4878, 5195, 10808, 10771, 8425, 1288, 7636, 8009, 1759, 2175, 6800, 8783, 4044, 1374, 361, 5543, 10060, 5021, 9647, 11422, 10236, 4616, 7538, 8423, 9798, 5991, 7779, 795, 9565, 5440, 7561, 2438, 6566, 6612, 5482, 3050, 1988, 5281, 893, 3481, 7564, 8899, 9008, 7725, 11306, 2635, 2685, 847, 5265, 768, 715, 819, 9538, 6541, 6528, 7581, 10166, 677, 7537, 3633, 1796 ]

[ [ "Easy & Delicious Indian Flatbread (Paratha)\nIntroduction: Easy & Delicious Indian Flatbread (Paratha)\nMost flat breads from India are unleavened and made primarily from milled flour, usually Atta or Maida, and water. Some flatbreads, especially paratha, may be stuffed with vegetables and layered with either ghee or butter.\nToday, I will be sharing a family recipe for paratha as an entry in the Bread Speed Challenge.\nThis recipe is easy for beginners to make, with minimal ingredients and prep time.\nSupplies\nThe supplies are easy to find:\nIngredients:\n4 cups of wheat flour\n1.5 cups of water\n1 tsp of both salt and sugar\n0.5 cups of ghee or melted butter.\nUtensils:\nA large Bowl (to mix)\nA griddle\nA thin spatula for flipping (I will be using a steel one)\nA surface to roll out the dough\nA pastry brush\nAnd a rolling pin (Or a large dowel, about 1 inch in diameter)\nServing - Serves 2 people if served plain, 4 if served with accompaniments like yoghurt or a savory stew.\nStep 1: Get All Your Supplies Together.\nIt is always useful to assemble everything we need before starting.\nStep 2: Dough\nAdd the 4 cups of flour into our large bowl, along with 2 tbsp of ghee or butter and 1 tsp each of sugar and salt.\nStart mixing with your hands, adding small amounts of water till it starts coming together. Add more water and knead until it has a smooth texture. (Knead about 5 minutes).\nSet aside for 10 minutes to allow the dough to breathe and soften.\nStep 3: Roll Out the Dough\nAfter resting, roll into a large noodle, about 2 inches thick. Cut sections along the noodle, at intervals of 2 inches.\nCoat your hands with the ghee or melted butter and then roll the sections into small round balls.\nRoll the balls in the dry flour\nWith a rolling pin dusted in flour, roll out each ball into a 2 mm thick disk.\nBrush ghee or melted butter on the top of the disk and sprinkle some flour on it.\nStep 4: Fold Into a Paratha\nFirst place the griddle on low heat so it heats up while we fold our paratha.\nCoat your fingers with ghee or melted butter, so the dough will not stick to them. Then follow the following steps carefully\n1.", "863" ], [ "Fold each disc as shown in the above pictures, and brush with ghee or melted butter and sprinkle with flour.\nYou will now have a square piece of dough. dust with flour and roll out, keeping it in a squarish shape.\nStep 5: Cook the Paratha\nPlace the paratha on the griddle (that we already heated up in Step 4) to cook for about 2 minutes for each side. It should have golden brown (NOT black) spots. Brush ghee or melted butter on both sides. Take paratha off the heat and and put it to the side as you cook the others.\nStep 6: Serve\nServe your paratha plain, with stews, with yoghurt, or use it to wrap minced meat and vegetables. The possibilities are endless; it is up to you how you share it with others!", "702" ], [ "Mumbai Grilled Vegetarian Cheese Sandwich Made With Fresh Baked Bread\nIntroduction: Mumbai Grilled Vegetarian Cheese Sandwich Made With Fresh Baked Bread\nThis is a very popular sandwich made by street vendors in India. You can find many recipes of these online. This recipe is unique because, unlike other recipes, this includes the recipe to bake the specific type of bread used by street vendors across India. I have included some photos of my previous experience eating in Mumbai.\nYou may ask what is Mumbai grilled vegetarian sandwich and how is it different than any other sandwich?.. Glad you asked.\nThis sandwich is unique due to (4) distinct reasons:\n1. Bigger Bread (20% bigger). Minimum of 5\" x 5\".\n2. Tons of Veggies\n3. Balance of spice(s)\n4. Very filling (1 sandwich can be 2 servings)\nSupplies\nDIY (Restaurant Style) Sandwich Bread (5\" x 5\")\n* 820 grams of AP flour\n* 12 grams for salt\n* 5 grams of dough enhancer\n* 15 grams of yeast\n* 60 grams of neutral tasting oil\n* 60 grams of white sugar\n* 450 mL of luke warm water (110 F)\nGreen Sauce (Chutney) - Grind everything together in a food blender\n* Fresh Cilantro Leaves\n* Spinach (a few to enhance green color, optional)\n* Green Chilis (optional, preference on spice)\n* 3 large cloves of garlic\nSandwich Masala\n* 2 tbsp of Chaat Masala\n* 2 tbsp of salt\n* 2 tsp of cumin powder\n* 1 tsp of pepper\nSandwich Ingredients\n* 1 medium onion, diced\n* 1 green pepper, diced\n* 1 tomato, thinly sliced\n* 1/2 cucumber, thinly sliced\n* (2) medium potatoes, boiled, and peeled\n* Mozzarella or Light cheddar cheese, grated, thinly sliced\n* 1/2 stick of butter melted\nStep 1: DIY Restaurant Style Bread Loaf\nI strongly recommend baking this bread. It really makes a difference in the overall texture and taste of the sandwich. Alternatively, you buy store bought bread but try to get bread that is baked fresh and can absorb a lot of moisture. This is same type of bread you will often find when ordering this sandwich at a restaurant or street vendor in India.\nUse a stand mixer and mix all of these ingredients first.\n1. 450 mL of luke warm water with (15) grams of yeast\n2. 60 grams of neutral tasting oil\n3. 60 grams of white sugar\n4. 12 grams for salt\nOnce mixed, slowly start mixing about 100 - 200 grams of flour.", "0" ], [ "Do not mix all of the flour at once, allow the mixer to do it's job in slow speed. From time to time, stop the mixer, and use a long spatula to mix the dough by hand. You want to make sure all of the dry and wet ingredients are mixing together.\nOnce properly mixed, gradually increase the speed, and allow the dough to form it's own shape. Do not over mix. Sprinkle some oil on top (to prevent drying), cover with a towel, and allow the dough to rest for about 30 minutes. You want good gluten to form. By using luke warm water the dough will rise a little bit faster.\nStep 2: Prepare and Bake the Dough\nAfter 30 minutes, properly butter the loaf pan. I'm using a loaf pan with a lid. You can use the pan of your choice but for best results, a use the tallest loaf pan you have available. Here is a good one to use available from Amazon (link here).\nButter the loaf pan very well. You want to make ensure no spot is dry. Next, roll the dough properly to roughly the same length as the pan, it should be in a cylindrical shape. Place the dough inside the pan and press on the dough such that the dough spreads evenly, cover with a lid, and towel. Let the dough rise to the top.\nBake the dough in an oven at 400 F for 35 to 50 minutes (depending on your oven).\nStep 3: Prepare Sandwich Ingredients\nThe sandwich masala is the only flavor inside this sandwich. It is important to ensure this flavor is created well otherwise the sandiwch's flavor will be bland.\nThis spice has a mix of savory, sweetness, sourness. Chaat masala is a very common and popular spice added to many Indian snack foods. This flavor is enjoyed by many, the only difference with the sandwich bread masala is that we are adding a lot more salt (since none of the other veggies have salt), cumin powder (slight nutty flavor), and freshly cracked pepper (bitter / spice).\nNext create the green chutney as described above.", "702" ], [ "Fluffy Omelet\nIntroduction: Fluffy Omelet\nGood afternoon, dear viewers and readers! In today's instruction, I will show you an unusual way to make a fluffy egg omelette. This omelette is so easy and quick to prepare and looks very impressive.\nSupplies\nTo prepare an omelette, we need the following ingredients:\n* Eggs 5 pcs.\n* Butter or sunflower oil.\n* Salt & pepper.\n* Cherry tomatoes.\n* Parsley.\n* Cucumber.\n* Dill.\nEssential Equipment:\n* Sharp Knife.\n* Frying Pan.\n* Dish.\n* Deep bottomed bowl.\n* Fork\nStep 1: Separate the Proteins From the Yolks.\nFirst, take the eggs and break the shell and separate the yolk from the protein. Put the yolk and protein in each separate bowl with a deep bottom. This process is repeated for each egg used.\nStep 2: Yolk Preparation\nNext, you need to whipping the yolk until smooth and add salt or pepper to taste. The yolk can be beaten with a fork or whisk.\nStep 3: Protein Preparation\nNext, take a bowl of prepared proteins, salt and pepper to taste. With a fork or a whisk, we begin to whipping the protein to the consistency of a stable foam. If you want to speed up the process of whipping the protein, use a mixer.\nReadiness can be checked by touching the surface lightly with a finger.", "863" ], [ "The protein should be elastic and not stick to the fingers.\nStep 4: Frying in a Pan\nHeat a frying pan with butter or vegetable oil over medium heat. Pour the yolks into the pan and evenly distribute them over the entire surface of the bottom.\nNext, you need to wait 20 - 30 seconds for the yolks to grab a little, then add whipped whites on top of the yolks. Carefully spread the proteins and align them with a spatula or spoon. Cover with a lid and leave at a power slightly below average for 8-10 minutes.\nStep 5: The Fluffy Omelet Is Ready\nCarefully place the finished omelet on a large plate. Cut the omelette into two large pieces and fold in half.\nStep 6: Cooking Result\nThe fluffy omelet is ready! Cut with a knife into three or four parts and serve. For a beautiful presentation of an omelette, you can decorate it with toast and vegetables. Such a lush, tender and unusual omelette invariably causes delight!\nEnjoy your meal and thank you all for watching and reading the article. Don’t forget to like it and subscribe!", "851" ], [ "The King's Thali\nIntroduction: The King's Thali\nNamaste People!\nI have grown up eating vegetables and fruits more than any meat in my entire life. So much so that I love vegetarian dishes more than non-veg. So for this challenge, I would like to incorporate everything I love about Indian cuisine under one heading by making the colorful and nutritious ‘King's Thali’. As the name suggests Thali was a platter served to Indian Kings in the ancient and medieval times. And still it's a prominent thing in Indian households. A Thali is a complete meal served on a single plate, from starters to desert. It's the product of several age-old aspects related to the Indian Culture. For example, the concept of balanced nutritious meals, an interest in the varieties of flavors, and the need for portion control to avoid overeating.\nA traditional Indian Thali consists of 5-30 or more dishes. It is served in small bowls and small quantities in metal cutleries. It mainly comprises of a variety of starter traditional snacks, flatbread/rice, vegetables, lentils, chutney, and dessert, followed by a refreshing drink. It is often served to guests and is a must at Indian weddings.\nBut, I decided to keep my Thali minimalistic yet royal. All the dishes that I'll make will contain some fruits or vegetables.\nHere is the list of dishes I’ll be making:\n* Vegetable Diwani Kadhai (Main Course): Dish made of Mixed Vegetables\n* Pink Beetroot Puri (Deep-fried dough made of beetroots and wheat): Flatbread\n* Mint Coriander Chutney : Dip/ Chutney\n* Carrot Halwa (Dessert made of Carrots and Milk): Dessert\n* Mango Lassi (Mango and Yoghurt drink): Drink\nHope your taste buds get excited enough to savor the flavors and the wholesomeness :)\nSupplies\nUTENSILS REQUIRED FOR THALI PREP\nYou can match the numbers of the given list with their respective images attached in the picture above for your reference.\n1. Wok or Deep Frying Pan or Kadhai\n2. Vessel to boil water\n3. Ladle or Spatula to stir and mix\n4. Slotted Spatula or Slotted Ladle for frying\n5.", "863" ], [ "Flat Spatula to mix and stir\n6. Grinder/Food Processor/Mixer\n7. Grater\n8. Knife to cut vegetables and fruits\n9. Peeler to peel vegetables and fruits\n10. Rolling Board & Pin to roll the dough\n11. Spoon\n12. Bowl - medium size\n13. Bowl - Small Size\n14. Plate - Medium Size\n15. Plate - Large Size for final plating\n16. Glass - to serve the mango lassi\n17. A small cylindrical mold or container to shape the carrot halwa while serving.\n18. A drinking straw\n1. INGREDIENTS FOR VEGETABLE DIWANI KADHAI\nFor base gravy\nIngredients:\n• Oil - 5-6 tbsp\n• Onions - 2-3 medium size (sliced)\n• Cashew nuts - 7-8 nos.\n• Almonds - 7-8 nos.\n• Tomatoes - 2-3 medium size (quarters)\n• Ginger - 1 inch\n• Garlic - 4-5 cloves\n• Dry red chillies - 1-3 nos.\n• Salt to taste\n• Green chillies - 2 nos.\n• Water - 250 ml\nFor half cooked veggies\nIngredients:\n• Cauliflower - 1 cup (florets)\n• Turmeric - ¼ tsp\n• Salt a pinch\n• Carrots - ¼ cup\n• Green peas - 1 cup\n• French beans - ¼ cup\n• 2 cups of water\nFor making the main dish\nIngredients:\n• Vegetable/refined Oil - 2 tbsps\n• Garlic - 3 tbsp (chopped)\n• Green chillies - 2-3 nos. (chopped)\nWhole spices:\n• Cinnamon Stick -1 inch\n• Bay leaves - 2 nos.\n• Green Cardamom - 2 nos.\n• Cloves - 2-3 nos.\n• Black peppercorns - 7-8 nos.\nPowdered spices:\n• Red chilly powder - 2 tbsp\n• Coriander powder - 1 tbsp\n• Cumin powder -1 tsp\n• Blended base gravy\n• Hot water as required\n• Half cooked veggies\n• Fresh cream - ⅓ cup\n• Garam masala powder - 1 tsp\n• Dry fenugreek leaves - 1 tsp\n• Fresh coriander leaves (chopped)\n• Peas - 1 cup\n2.", "0" ], [ "Homemade Falafel in Fresh Pita Bread\nIntroduction: Homemade Falafel in Fresh Pita Bread\nFalafel in Pita is a staple of Israeli cuisine. You can find a falafel stand almost on every other street corner. When you buy it, you get a pita absolutely overflowing with salads, falafel and flavor! (at which point you start eating, trying to keep it off all your clothes).\nSince there are no falafel stands anywhere close to where I currently live, I put together all the parts for making a great Falafel in Pita at home - It really isn't that difficult.\nIt starts from a Pita bread recipe baked in the oven (which even bakes with a pocket) and with a trick to keep it nice and soft. The falafel balls are flavored with garlic, and lots of herbs and spices. And I added what for me are the most necessary salads - red cabbage mayonnaise, the most simple vegetable salad, good hummus and spicy zhug.\nSupplies\nPita Bread:\n1kg all purpose flour\n4 tbsp. sugar\n2 tsp. salt\n500 ml water (warm water in winter)\n10 gr dry yeast (20gr in winter)\na small amount of oil - to keep the dough from sticking\nFalafel balls:\n2 cups dry chickpeas\n1 slice of bread\n5 garlic cloves\n1 tsp. Cumin powder\n1 tsp. Paprika powder\n1 tsp. pepper\n1/2 tsp. salt\n1 small onion\n1/3 cup fresh parsley\n1/2 cup fresh coriander\n1 tbsp. sesame seeds\n1 tsp. coriander seeds\n2 tsp. baking soda\nRed cabbage mayonnaise salad:\n1/2 large red cabbage\n3/4 tsp.", "863" ], [ "salt\n2 tbsp. mayonnaise\n3 tbsp. lemon juice\n1 tsp real maple syrup\nSimplest Vegetable salad- 1 tomato, 1 cucumber, salt, pepper and lemon juice to taste.\nFries - 1 large potato\nHummus - This is the recipe I use.\nZhug (a very spicy pepper paste)- there is a recipe, but you can also substitute it with fresh or pickled sliced chilli peppers.\nStep 1: Pita Bread- 1. Making the Dough\nMix the flour, sugar and salt in a large bowl. Add the yeast and make sure it get evenly distributed.\nSlowly add the water, while kneading the dough.\nKneed the dough for 10 minutes, until is uniform and soft.\nPlace the ball of dough in an oiled bowl. Cover with cling-wrap and a damp towel. Place somewhere warm to rise for about 30-60 minutes.\nStep 2: Pita Bread- 2. Baking (and Special Tricks)\nPreheat oven to 250C.\nRemove the dough from the bowl and pull into a long sausage. Cut into 8-10 equal pieces.\nRoll each into a ball, cover again and let rest for 10 minutes.\nOn a baking sheet place the balls and flatten them to about 1/2 cm.\nBake till they are golden brown 3-6 minutes - don't let them out of your sight, this is really fast!\nA special trick to keep them soft (that I discovered online):\nPrepare a clean cloth kitchen towel and a plastic bag.\nRemove the pita breads from the oven immediately onto the towel and fold them inside for 1 minute - then place them in the plastic bag and close it completely... It works!\nStep 3: Falafel- 1. Chickpea Preparation\nPlace the chickpeas in a large bowl, and cover with water. Leave to soak overnight, or at least 12 hours.\nSoaking overnight will double the size of the chickpeas, so make sure the bowl is big enough and has enough water.\nStep 4: Falafel- 2. Making the Mixture\nSoak a slice of bread in water. Meanwhile, wash and drain the soaked chickpeas.\nChop the onion and the fresh parsley and coriander into very small pieces.\nSqueeze the water out of the bread and crumble it over the chickpeas. Add the cumin, paprika powder, salt, pepper and garlic.\nGrind them together into a uniform grainy paste.\nAdd the flour, chopped onion and herbs.\nLightly blend together.\nMix in the sesame seeds and coriander seeds.\nCover and leave to rest in the fridge for 30-60min.\nNote:\nAt this point you can put the mix in a sealed container and freeze it for later.\nStep 5: Falafel- 3.", "702" ], [ "Mini Semolina Chocolate Cake Pops\nIntroduction: Mini Semolina Chocolate Cake Pops\nI tried these mini semolina chocolate cake pops and were delicious. You can try making these mini pops for kids and they really enjoy them.\nHere Iam using Appam moulds for making these cake pops. Appams are traditional south Indian delicacy that comes in sweet and savory version prepared in Appam moulds. I tried cake pops in these moulds.", "834" ], [ "You can make kids decorate these pops with sprinkles,melted chocolate. (You can buy these Appam moulds online or in market and are easily available)\nSupplies\nHalf cup yoghurt\n1/4 cup cooking oil\nOne cup fine semolina( sooji or rava)\nHalf cup of sugar\nHalf TSP Baking powder\n1/4 TSP Baking soda\n2 tbsp cocoa powder\n1/4 cup All purpose flour\nMelted chocolate\nHalf cup of Milk\nStep 1: Add Oil to Yoghurt and Mix\nFirst step is to take about Half cup of yoghurt in a bowl.\nAdd 1/4 cup Cooking oil to the yoghurt and mix continuosly .\nStep 2: Add Sugar\nAdd half cup of sugar and give a mix\nStep 3: Add Semolina\nAdd One cup of semolina (sooji or rava) and give a mix .\nAfter adding semolina cover it and rest it for 20 minutes.\nStep 4: Sieve Ingredients\nAdd 1/4 cup All purpose flour(maida),1/2 TSP Baking powder, 1/4 TSP Baking soda, 2 tbsp cocoa powder and sieve them.\nStep 5: Add Sieved Ingredients\nAfter 20 minutes rest time add all the sieved ingredients and give a mix .\nStep 6: Add Milk\nAdd about half a cup of milk and give a mix.\nStep 7: Grease the Mould With Oil\nGrease all the holes of the Appam mould with oil.\n(Appam mould is also called as paniyaram pan or ponganalu pan)\nStep 8: Add Tablespoon Prepared Batter to All Holes\nAdd One tablespoon prepared batter to all the holes of the mould\nStep 9: Cover and Cook\nCover it and cook for 3 to 4 minutes on low flame. After 3 minutes remove the lid and cook for one more minute.\nStep 10: Flip and Cook\nFlip and cook for 2 more minutes .\nRepeat the same procedure with remaining batter and make all mini cakes .\nStep 11: Attach Skewer Sticks and Make Pops\nAttach skewer sticks to these mini cakes to form pops .\nStep 12: Dip in Melted Chocolate\nNow dip mini chocolate cake pops in melted chocolate.\nLet them dry for some time.\nStep 13: Enjoy\nEnjoy semolina mini cake chocolate pops. Kids will love them.", "834" ], [ "Vegetable Cheese Wraps\nIntroduction: Vegetable Cheese Wraps\nAre you bored of eating normal sandwiches? Then these vegetable wraps and are perfect for a ready to go meal. These wraps makes wholesome meal and are very nutritious and healthy.\nWe can add any vegetables of your choice and desired fillings. We can prepare these before hand for small parties and get togethers or for a picnic.\nSupplies\nIngredients required for preparing wraps:\n* One cup of All purpose flour( Maida)\n* Half teaspoon sugar\n* 4 tablespoon curd or yoghurt\n* One cup Milk\n* One teaspoon Salt\nIngredients for curry:\n* One finely chopped Carrot\n* One chopped capsicum\n* Few chopped beans\n* Few chopped cauliflower\n* Four Boiled potatoes\n* One finely chopped onion\n* Two chopped green chillies\n* Few chopped garlic\n* Teaspoon grated ginger\nSpices:\n* Teaspoon Coriander powder\n* Half teaspoon Red chilli powder\n* Teaspoon Garam masala powder\n* Teaspoon Chat masala powder\n* Salt as per taste\n* Pinch of turmeric powder\n* One tablespoon tomato sauce\n* Half teaspoon lime juice\n* We also need Grated cheese and cooking oil.\nStep 1: Making Batter for Wraps\nTake a bowl and add One cup of All purpose flour. Using All purpose flour makes the wrap soft.\nAdd half teaspoon sugar and two tablespoon oil.\nStep 2: Add Curd\nNext add 4 tablespoon curd.\nAdd milk little by little and whisk. (Milk used should be in room temperature and not hot)\nStep 3: Add Milk\nAdd milk little by little and whisk. (Milk used should be in room temperature and not hot)\nAdd teaspoon salt. Batter should be thin and flowing consistency.\nStep 4: Preparing Wraps\nBrush the pan with oil. We need very little oil.\nNow take one and half laddle full of batter and pour in the middle of the pan.\nRotate in circular motion using laddle.\nStep 5: Flip and Cook\nWhen upper portion of wrap is dry brush some oil on it and flip.\nStep 6: Wrap Is Ready\nWhen we again flip the wrap we can see brown spots.", "0" ], [ "We need to put the stuffing on this side.\nRepeat the same procedure with entire batter and make all the wraps.\nStep 7: Preparing Stuffing\nTake a pan and add little oil. When oil is heated add one finely chopped onion and 2 sliced green chillies.\nSaute for few minutes.\nNext add chopped garlic and grated ginger.\nStep 8: Add Veggies\nKeep all the chopped vegetables ready. Add one finely chopped carrot and few chopped beans\nStep 9: Add Remaining Vegetables\nAdd finely chopped cauliflower and chopped capsicum.\nSaute all the vegetables for some time.\nStep 10: Add Spices\nAdd teaspoon coriander powder and half teaspoon Red chilli powder.\nStep 11: Add Remaining Spices\nAdd one teaspoon chat masala powder and one teaspoon garam masala powder.\nAdding all spices gives nice flavour to the curry.\nStep 12: Add Salt and Turmeric Powder\nAdd salt as per your taste and pinch of turmeric powder.\nAfter adding all spices mix everything and cook for some time.\nStep 13: Add Tomato Sauce and Give a Mix\nAdd tablespoon tomato sauce and give a mix.\nStep 14: Add Boiled Smashed Potato and Lime Juice\nBoil 4 potatoes and keep ready. Add the smashes potatoes and mix.\nFinally add teaspoon lime juice.\nStuffing is ready.\nStep 15: Make All Purpose Flour Paste\nTake little All purpose flour in a bowl. Add little water and make a paste.\nStep 16: Filling the Wrap\nNow take the prepared wrap. Place little stuffing in the center of the wrap.\nAdd grated cheese on top of the stuffing.\nStep 17: Folding the Wrap\nAfter placing the stuffing fold the top and bottom portion of the wrap towards center.\nBrush little All purpose flour paste and stick the foldings.\nStep 18: Fold Lateral Sides\nBrush little All purpose flour paste and fold both lateral sides towards center as shown in images.\nStep 19: Stuffed Wraps Are Ready\nPrepare all the stuffed wraps and keep ready.\nYou can store these wraps in refrigerator in air tight container. When needed they can be shallow fried.\nStep 20: Shallow Fry\nLast step is to shallow fry these stuffed wraps.\nBrush little oil on a pan. Place the prepared wraps on it and shallow fry until they turn little brown color by flipping on both the sides.\nStep 21: Vegetable Wraps Are Ready\nOur vegetable wraps are ready. Enjoy :-)", "0" ], [ "A Yam-y Dessert (Elephant Yam Kheer)\nIntroduction: A Yam-y Dessert (Elephant Yam Kheer)\nToday I'm going to show you how to make a simple & tasty recipe (Kheer Dessert) from a not so appetizing looking ingredient (Elephant Foot Yam).\nI was familiar with only savoury dishes made from elephant yam, like chips, salads & appetizers, so wanted to try something different & sweet instead; it turned out great and I've been making it since years now.\nSupplies\nThis kheer dessert doesn't need many special ingredients (except the vegetable itself).\n- ½ kg elephant Foot yam\n- 200 g sugar\n- 300 ml full fat milk\n- ½ teaspoon cardamom powder\n- ¼ teaspoon nutmeg powder\n- 1 spoonful ghee (optional)\n- roasted almonds (optional)\nPrep time (boiling & blending): 15-20 minutes\nCooking time : 10 - 12 minutes\nStep 1: Prepare the Puree\nTo puree the yam, first peel off the outer layer using a sharp knife. Discard the peels.\nRoughly dice the yam into pieces and rinse them thoroughly.\nBoil the diced yam in a pot of water till well-cooked. Discard the water and place the cooked pieces in a blender or food processor to make a smooth puree.\nNote: It is better to boil and not steam this vegetable...being an underground tuber, yams sometimes contain mineral allergens. Boiling dissolves & rids the veggie of these particles.", "94" ], [ "Most people are not sensitive to them but I like to take the precaution anyway.\nStep 2: Let's Make the Dessert\n(Note: the video is soundless so don't go on battering the volume button XD. Instead I've added captions in 5 languages including English & Spanish..)\nTake a heavy bottomed pot and mix together yam puree, sugar & milk.\nPut the pot over a low flame, stir continuously and let it simmer for 10 minutes.\nAdd in the ghee and season with cardamom & nutmeg.\nMix well & turn off the heat. Top with roasted almonds.\nStep 3: Serve It Up\nI like it both warm & chilled, depending on the weather. You can go ahead and garnish with your favourite nuts or a dollop of fresh cream or both!\nHope you enjoyed this instructable and let me know if you try the recipe. Feedback & suggestions are more than welcome :)\nHave a delicious day!", "94" ] ]

[ 9463, 3845, 11360, 11182, 9767, 2437, 988, 3874, 1107, 2856, 6862, 8967, 9941, 850, 9914, 6239, 8865, 8107, 1003, 9006, 6715, 4893, 1901, 8357, 5444, 1597, 11037, 1911, 9596, 1949, 10372, 7888, 3707, 520, 6042, 10512, 10967, 9823, 11108, 10171, 11219, 1354, 3709, 9077, 3043, 330, 3032, 11005, 8165, 8195, 5172, 1652, 4663, 4436, 11318, 2289, 1479, 8410, 1439, 7193, 673, 6434, 1197, 7665, 5996, 10428, 589, 881, 10806, 9770 ]

[ [ "Image Courtesy of itiswonThis review continues my series of detailed reviews that attempt to be part review, part resource for anyone not totally familiar with the game. For this reason I expect readers to skip to the sections that are of most interest.\nSummary\nGame Type - Board Game (Tile)\nPlay Time: 80-90 minutes\nNumber of Players: 2-6\nMechanics – Set Collection, Tile Laying, Resource Management\nDifficulty – Moderate (Can be learnt in under 30 minutes)\nComponents - Excellent\nRelease - 2008\nDesigner <PERSON> -(All things Alhambra, Colonia, Eketorp, Granada, High Tide, Immortals, Metro, Neptun, The Rose King, Shogun, Show Manager,Speculation, Timbuktu, Wallenstein)\n+\n<PERSON> -(All 6 Alhambra Expansions, Flandern 1302, All things Fresco, Indus, LancasterExpansions, Lucky Loop, Maharani)\nThis is the fifth in a series of reviews that will analyse each of the 5 Alhambra expansions. I will outline each expansion on its own merits and then comment on how well it interacts with other expansions in the Alhambra Family.\nAs each Boxed Expansion for Alhambra includes 4 Mini-Expansions, I will refer to a box as an Expansion Set and each of the 4 additions within each box as Mini-Expansions. This will hopefully avoid confusion as I discuss each in turn.\nAt the end of this review is a series of links to help find my other Alhambra Reviews.\nNB - Since the time of writing this review initially, a 6th expansion (The Falconers) in this format has been released. I will look to get to this expansion in the near future.\n#17 – The New Score Cards\nComponents - This Mini-Expansion consists of two component types. First there is the Scoring Round Template, which essentially outlines the points available for each round (as per the original Reserve Tile Player Boards).\nImage Courtesy of Uncle G\nThis is essential now though due to the 2nd set of components, which are the alternate Scoring Tokens. There are 18 in all and they effectively randomize the relative values of each building type for each Scoring Round. These are of a size that allows them to sit snuggly into the brackets of the Scoring Round Template.\nImage Courtesy of Uncle G\nImpact – The New Score Cards have major implications for how a game of Alhambra will play out.", "581" ], [ "Randomising the scoring of each building type means that the building type that is king one moment, may be all but worthless in the next. What results is some careful analysis at the start of the game to calculate the relative value of each building type over the course of all 3 scoring rounds. This will appeal to some and not to others.\nThe other implication is the availability of each building type. The base game was deliberately designed to have fewer of the lower scoring buildings and more of the higher scoring ones. This meant that there was more competition to gain a majority for the high scoring Towers and Gardens and with a greater number on offer, there was less chance to miss out on them if you were in ‘the wrong place at the wrong time’ which Alhambra can suffer from.\nNow of course this is not the case and those 7 Pavillions and Seraglios (blue and red buildings) may now be worth major points. Heaven help the players that are just unlucky to see them come out and get purchased before they have a chance.\nStrategy – I’ll state it again, but it is imperative to know the relative values of each building type at the start of the game as this will help you to calculate which buildings are worth overbidding for and which ones are not.\nIt can also be quite important to gain ‘The Power of the Sultan’ (see Mini-Expansion summary below)!\nInteraction with other Expansion Sets – The Power of the Sultan is another Mini-Expansion in this Expansion Box that allows players to nab buildings of a given colour when they are added to the Market. Having one of more <PERSON> cards at your disposal can be crucial in gaining buildings that are in limited supply or are worth big points at scoring.\nNaturally the Vizier’s Favour is another very handy power to use at the right time.\nFeelings – Personally I am a little conflicted about the value of this expansion. Does it throw up an interesting set of considerations, which adds to the analysis and decision making required to play the game, or is it simply another level of randomness that could possibly throw the final result into total chaos and allow for score blowouts?", "755" ], [ "Image Courtesy of myadestesThis review continues my series of detailed reviews that attempt to be part review, part resource for anyone not totally familiar with the game. For this reason I expect readers to skip to the sections that are of most interest.\nSummary\nGame Type - Tile Laying Game\nPlay Time: 80-90 minutes\nNumber of Players: 2-6\nMechanics – Set Collection, Tile Laying, Resource Management\nDifficulty – Pick-up & Play (Can be learnt in under 15 minutes)\nComponents - Excellent\nRelease - 2006\nDesigner - <PERSON> -(All things Alhambra, Colonia, Eketorp, Granada, High Tide, Immortals, Metro, Neptun, New York, The Rose King, Shogun, Show Manager, Speculation, Wallenstein)\nThis is the fourth in a series of reviews that will analyse each of the 5 Alhambra expansions. I will outline each expansion on its own merits and then comment on how well it interacts with other expansions in the Alhambra Family.\nAs each Boxed Expansion for Alhambra includes 4 mini-expansions, I will refer to a box as an Expansion Set and each of the 4 additions within each box as Mini-Expansions. This will hopefully avoid confusion as I discuss each in turn.\nAt the end of this review is a series of links to help find my other Alhambra Reviews.\n#13 – The Treasure Chamber\nComponents - As the namesake of this Expansion Set, The Treasure Chamber offers 3 separate high quality components. First is the Treasure Chamber mini-board. It is slightly shorter and narrower than the Reserve Boards from the base game, and the artwork depicts a set of stairs that lead to 3 separate Treasure Chambers. Each Chamber contains the number 8 and in the bottom left hand corner is a small score chart. I will explain the score chart and 8 values later.\nNext are the treasure chests. There are 42 chests in all (7 of each colour used in Alhambra) and these are made from wood and are a good size.\nFinally this expansion provides a cloth bag in which treasure chests can be drawn from.\nAll 42 Treasure Chests are placed in the tile bag at the start of play and 4 Chests are drawn at random and placed in each of the 3 Treasure Chambers.\nImpact –\nImage Courtesy of <PERSON> Treasure Chamber offers the players a new option each turn – the acquisition of Treasure Chests. To purchase Chests, at least 8 money must be paid, hence the 8 value in each Chamber on the board.", "581" ], [ "This cost can be paid with any combination of money cards and more than 8 can be paid too, however no change is given. Master Builders from Mini-Expansion #2 in this Set can also be used to pay.\nThe goal in acquiring Treasure Chests is to have more than anyone else in order to score points during scoring rounds. The scoring track outlines points for all 3 rounds and like the scoring for buildings, only the player with the most Chests will score points in Round 1, whereas the top 3 Chest owners will score points in Round 3. Round 1 offers 7 points to the leader, whilst the same lofty position will earn 22 points in Round 3. That’s some decent scoring eh?\nThe colour of the Treasure Chests has no bearing on scoring, instead they influence selection and placement. Once a player pays the required amount, they can take any 4 Treasure Chests from a single Chamber. However each Chest must be placed on a tile of a matching colour within a player’s Alhambra. If a player cannot place one or more of the Chests in their Alhambra, they are passed to the next player and added to tiles in their Alhambra if they are able. The Chests pass to all players in this fashion and if no player can find a place for a Chest, it is returned to the cloth bag.\nOnce the placement of Treasure Chests is complete, 4 new Chests must be drawn at random to refill the empty Chamber.\nIf there are not enough Chests in the cloth bag to refill a Chamber to 4, the Chamber remains empty and no Chests are drawn.\nPaying exactly 8 to acquire a set of Chests does not earn a player an extra action.\nIf a tile containing a Chest is removed (redesigned) the Chest is returned to the cloth bag.\nChests cannot be placed on Worker’s Huts from Expansion Set #1.\nChests cannot be placed on tiles on a player’s Reserve Board. They can be added to newly placed tile into a player’s Alhambra on the current turn.\nAllocating points in the case of a tie is the same for Treasure Chests as it is for scoring building tiles.", "84" ], [ "This review continues my series of detailed reviews that attempt to be part review, part resource for anyone not totally familiar with the game. For this reason I expect readers to skip to the sections that are of most interest.\nImage Courtesy of <PERSON>\nSummary\nGame Type - Card Game (Expansion)\nPlay Time: 25-45 minutes\nNumber of Players: 2 – 8 (Best 3+)\nMechanics - Card Drafting, Set Collection, Variable Player Powers, Simultaneous Action Selection\nDifficulty - Pick-up & Play (Can be learned in 10 minutes and only takes 2-3 plays to get a handle on the thinking required)\nComponents - Very Good\nRelease - 2012\nDesigner - <PERSON>( Ghost Stories, Hanabi, Mystery Express, Takenoko)\nWhat’s the New Take with ‘Cities’?\nThematically, 'Cities' introduces those less tangible, less visible elements of a city from antiquity. They might be less savory on the surface but they are no less important to the workings of any city. Slave Markets, Gambling Dens, Black Markets and Hideouts are all to be found in 'Cities'.\nBut then there are those other elements too, those necessities that have a more subtle influence over how the cogs of power turn. These include organisations like Secret Societies and Spy Rings, whilst bureaucracy is represented with Embassies and Consulates.\n‘Cities’ also offers up 2 new City States in the form of Byzantium and Petra, both of which have new Wonders to construct.\nOf course to ensure that this new expansion fits the needs and basic play of the base game and the 'Leaders' expansion, it also provides a selection of new Guild Cards and Leaders, which make use of new abilities offered up by Cities.\nI will not be covering the basic play of 7 Wonders in this review. If you would like to know more about the base game I suggest that you check out my review here –\n7 Wonders - A Detailed Review\nA link to the first expansion can be found at the end of this review.\nThe Components\n'Cities' comes in the same style of box used for the 'Leaders' expansion. Being a cad game, the extra additions are largely cards but there are a few more new bits here than in the last expansion.\nCity Cards – In all there are 27 new 'Cities' cards that are distinctive due to their black background colour. The 27 cards are nicely divided into 9 new cards for each of the 3 Ages, and in terms of design, art quality and design features, everything is up to past standards so the cards fit seamlessly into what has come before. I have seen some complaints that the backs of these cards differ slightly from past 7 Wonders products but that is not the case with my copy.\nOf course new icons are present to help implement the new mechanics introduced with the expansion, but I'll cover those in a moment.\nImage Courtesy of a_traveler\nNew Guild Cards – In all 3 new Guild Cards are provided.", "299" ], [ "I will discuss each of these in turn later in the review.\nImage Courtesy of a_traveler\nNew Leader Cards –6 new Leaders are offered up by 'Cities'. Some feature new icons from this expansion, others tie in with powers first seen in 'Leaders' and then there is a scoring based Leader that completes the set of VP scoring cards seen before now.\nImage Courtesy of a_traveler\nByzantium and Petra City States – 'Cities' offers up not one but two new City States in the forms of Byzantium and Petra. Both are interesting inclusions with one offering big VPs and the other incorporating the new Diplomacy mechanic.\nWhat remains the same is the lovely artwork that depicts the scene in both City States.\nByzantium is the stand out as it features a gorgeous dusk skyline and the splendour of domed buildings. The city curves its way around the harbour and a real sense of scope is created. It's really a lovely vista.\nImages Courtesy of a_traveler\nDiplomacy Tokens – 3 Diplomacy Tokens are included, which are represented by large stand up tokens featuring a dove in flight. They need minimal construction - the insertion of 2 stands in the base. Think of the Stone Age 'go first' token and you pretty much have it.\nImage Courtesy of a_traveler\nDebt Tokens – A new form of token is also introduced in 'Cities' called the Debt Token. These come in -1 and -5 increments and they are square and rectangular in shape. They represent the potential for a City State to be bankrupted and those minus scores are obviously a hit to your end of game VPs. Nasty!", "872" ], [ "Image Courtesy of <PERSON>\nThis review continues my series of detailed reviews that attempt to be part review, part resource for anyone not totally familiar with the game. For this reason I expect readers to skip to the sections that are of most interest.\nSummary\nGame Type - Board Game\nPlay Time: 30-60 minutes\nNumber of Players: 2-8 (Most commonly 2 players)\nMechanics - Card Driven, Scenario Based, Dice Rolling Combat\nDifficulty - Moderate (Takes 5-6 plays to become totally familiar)\nComponents - Excellent\nThis review follows on from my review of the base game in the Memoir System. As such I will endeavour to analyse this expansion on its merits and then comment on what it adds to the Memoir ’44 system. I have owned this expansion for well over 12 months now so I have been patient in learning the game before getting this review to you (20 plays in all at this point). I hope it reflects my understanding of the 'Pacific Theater' and is of use to readers.\nI’ll also highlight the fact that this review will not go into the basic game play of Memoir ’44. I have covered this in detail in the following review and I suggest you read that first if you are unfamiliar with the system - Memoir '44\nOverview\nThe Pacific Theater is the second real expansion of note for Memoir '44 (I discount the Terrain Pack as a solid expansion at this point but will revisit it after the Air Pack is in my hands).\nAs the name suggests the Pacific Theater focuses on the battles that took place in the Pacific and in particular it highlights the key battles fought between the Imperial Japanese Army and the US Marine Corps. The scenarios cover the time period of ’41-’45 and follows the lead taken by the Eastern Front in departing from the time frame of the base game (I recognize that this also occurred in the Terrain Pack).\nAs one would expect the game offers a range of new figures, tiles and terrain, tokens and scenarios. But most importantly it offers new rules that alter the play.\nThe Components\nPart of what makes Memoir stand out as a game, and Days of Wonder as a Company, are the great looking components that help one’s imagination run wild with possibilities.\nFigures\nIn all the Pacific Theater comes with 66 new figures to allow the Japanese to enter the fray. All units follow the standard rules of their unit type unless the Scenario Briefing states otherwise.\nJapanese Infantry (48) – The Japanese Infantry come in a tan or fawn colour (as do all the Japanese units). The poses for the Japanese are unique to all other previously seen infantry used in the game.", "299" ], [ "The Japanese soldier holds his gun in two hands and has a staggered pose, suggesting that he is on the march. A small backpack completes the miniature and together it suggests a highly mobile unit. Although simple, I really like the sculpts for the Memoir expansions.\nThe harder plastic used in the Eastern Front is also evident here and works well.\nImage Courtesy of <PERSON> (Type 95 Ha-Go light tanks) (12) – These units are also unique in design. I don’t have the historical knowledge to know if the sculpt is an accurate representation of the Ha-Go but I am guessing they were made to scale as they are easily half the size of the armour units used by the Germans, Americans and Russians.\n[center]\nImage Courtesy of ColtsFan76\nArtillery (Type 98 75mm) (6) – These are a little more fragile looking than the Russian Artillery and again this is probably due to the Japanese design. You can tell from the appearance that these were designed to be unfolded and set-up quickly (correct me if I'm wrong), helping the Japanese to stay highly mobile. These units are actually referred to as Anti-Aircraft Guns and this highlights the concerns the Japanese had with the Americans in this theater.\nImage Courtesy of <PERSON>\nThe Pacific Theater offers 13 new terrain tiles to freshen up the gaming experience and offer realistic situations found in the Pacific Theater.\nImage Courtesy of ColtsFan76\nBeaches – These tiles now allow a scenario to have scattered beach placed on the all grass side of the board, or placed on the 'beach-head' side to extend a beach as required. The effects for these tiles are the same as regular beach outlined in the base game (link to review can be found at the bottom of this page).\nMountain Caves & Hill Caves – - The artwork here is functional. Mountains are depicted with a white star based center (presumably to represent snow) and holes to represent the dug-out caves. The Hill Caves are similar featuring cave holes with a hill based border. These tiles are double sided, with the reverse side featuring the underlying terrain with no caves (see battle below).", "92" ], [ "Image Courtesy of <PERSON>\nThis review continues my series of detailed reviews that attempt to be part review, part resource for anyone not totally familiar with the game. For this reason I expect readers to skip to the sections that are of most interest.\nSummary\nGame Type - Board Game\nPlay Time: 30-60 minutes\nNumber of Players: 2-8 (Most commonly 2 players)\nMechanics - Card Driven, Scenario Based, Dice Rolling Combat\nDifficulty - Moderate (Takes 5-6 plays to become totally familiar)\nComponents - Excellent\nRelease - 2005\nDesigner <PERSON> -( <PERSON>, Battle Cry, BattleLore, Commands & Colours: Ancients, Commands & Colours: Napoleonics, Heavo Ho!, Hera and Zeus, Liar's Dice, Samurai Battles, <PERSON>, Yahtzee Free for All)\nThis review follows on from my review of the base game in the Memoir System. As such I will endeavour to analyse this expansion on its merits and then comment on what it adds to the Memoir ’44 system. I have owned this expansion for well over 12 months now so I have been patient in learning the game before getting this review to you (22 plays in all at this point). I hope it reflects my understanding of 'Eastern Front' and is of use to readers.\nI’ll also highlight the fact that this review will not go into the basic game play of Memoir ’44. I have covered this in detail in the following review and I suggest you read that first if you are unfamiliar with the system - Memoir '44 - A Detailed Review\nOverview\nThe Eastern Front is the first real expansion of note for Memoir '44 (I discount the Terrain Pack as a solid expansion at this point but will revisit it after the Air Pack is in my hands).\nAs the name suggests the Eastern Front focuses on the field battles that took place in that theatre and in particular it allows for the introduction of the Russians and the Finns in several expansions. The expansions cover the time period of ’39-’44 and this is the first real departure from Memoir ’44, the time frame for conflicts has been expanded beyond the D-Day landings of the original game (I recognize that this also occurred in the Terrain Pack).\nThis was probably a necessity for the Memoir System to move forward and I don’t feel it detracts in any way.", "299" ], [ "As one would expect the game offers a range of new figures, tiles and terrain, tokens and scenarios. But most importantly it offers new rules that alter the play.\nThe Components\nPart of what makes Memoir stand out as a game, and Days of Wonder as a Company, are the great looking components that helps one’s imagination run wild with possibilities.\nFigures\nIn all the Eastern Front comes with 70 new figures to allow the Russians to enter the fray. All units follow the standard rules of their unit type unless the Scenario Briefing states otherwise.\nRussian Infantry (70) – The Russian Infantry come in brown (as do all the Russian units), which is somewhat apt given <PERSON>’s view of the masses – bleh. The poses for the Russians are unique to the infantry poses of the German and American Infantry of the base game and the use of a harder plastic is evident.\nImage Courtesy of Merg\nArmour (T-34s) (20) – These units are also unique in design. I don’t have the historical knowledge to know if the sculpt is an accurate representation of the T-34 but I would hazard to guess that they got it pretty close within the limitations of the model size.\nImage Courtesy of <PERSON>\nArtillery (ZIS-2 Gun) (6) – These are perhaps the coolest looking of the new figures, if for no other reason than they are so superior in quality compared to the artillery offered in the base game. The harder plastic ensures that the barrel is not as flimsy as a Russian Soldier’s eyelash (one of my few component complaints with Memoir ’44) and the design ensures that the artillery point at the enemy in a threatening manner.\nImage Courtesy of <PERSON>\nTerrain\nThe Eastern Front offers 10 new terrain tiles to freshen up the gaming experience and offer realistic situations found on the Eastern Front.\nImage Courtesy of matthew.marquand\nTrenches – The artwork on these tiles is functional at best and at worst, a little confusing as to what it is meant to be. Either way though trenches are a welcome addition.\nMovement – Infantry and Armour must stop when entering a trench and Artillery cannot enter trenches at all.\nLine of Sight – No effect\nBattle – Infantry and Armour that attack a unit in a trench suffer a -1 dice penalty. Armour may not battle when in a trench.", "581" ], [ "Image Courtesy of ny2007\nThis review continues my series of detailed reviews that attempt to be part review, part resource for anyone not totally familiar with the game. For this reason I expect readers to skip to the sections that are of most interest.\nIf you liked the review please thumb the top of the article so others have a better chance of seeing it and I know you stopped by. Thanks for reading.\nSummary\nGame Type – Euro Game\nPlay Time: 40–60 minutes\nNumber of Players: 2–4\nMechanics v Action Points, Area Control/Influence, Pick-up & Deliver, Point to point movement, Set Collection\nDifficulty – Pick-up & Play (Can be learned in 20 minutes)\nComponents – Good\nRelease – 2004\nDesigner – <PERSON> – (Africana, Architekton, Aquaretto, Boss Kito, California, Call to Glory, China, Coloretto, Coney Island, Don, Draco & Co., Dschunke, Felinia, Fist of Dragonstones, Gold!, The Golden City, Han, Industria, Industry, London Markets, Magna Grecia, Mogul, Mondo, Paris Paris, Rat Hot, Sushi Express, Valdora, Web of Power, All things Zooloretto)\nOverview and Theme\nWelcome to Europe in the 14th century and more accurately the Hanseatic city-states that occupy the coastline of the Baltic Sea! It is a time of naval trade, a time when fortunes can be made by the savvy merchant and navigator. All you need is the wind at your back and an eye for the goods that are in demand. Set up your trade networks to take advantage of the supply and demands of the day and the world's power and prestige can be yours!\nHansa is one of those 'under the radar' games by <PERSON> many a new gamer to find the hobby would be quite unaware of. This was released back in the day when Uberplaywould release quite reasonably priced games and months later they would be bargain bin'd on Tanga (which was all the rage back then).\nGrab those trade papers there and help me get these goods on board...we are setting sail for a city a yonder!\nThe Components\nThe components to Hansa are fairly indicative of Euros in that 2004 time period. That is not to say that they are bad in any way, but by today's standards I could only call them functional.\nBoard – The board is a something of a mixture of minimalist meets downright ugly. The map itself is dominated by 9 key cities, the Baltic Sea and arrows that represent trade winds or movement patterns of the trading vessels.", "470" ], [ "The land is largely marked with trees to represent the forests of the age and smaller circles adorn the board to allow for the placement of Goods Tokens.\nThen there is the colour palette. Really this is something bordering on hideous. It's a mouldy green/yellow colour and it really does look like someone has gorged themselves on cheese whiz or something similar, chased that down with a slab of beer and then visited the little boy’s room to relieve themselves of the contents of their stomach.\nI'm not sure if this was meant to simulate an old map of the region or not, but the end result is anything but appealing.\nImage Courtesy of EndersGame\nMarket Booth Tokens – These are represented by the classic wooden discs that were so common in games from 1995 through to about 2007 ( from 2000 springs to mind pretty quickly). These tokens are used to represent the Market Booths that the players have established in the cities of the region.\nImage Courtesy of EndersGame\nMoney Tokens (Talers) – The money tokens or Talers are gold in colour and feature traders in a boat and some sort of commerce based motive in the background. They also have some form of Latin or Celtish-styled writing around the outer edge. This could all be based on some form of coin used in that period or be total creation, I am not sure.\nThese tokens are slightly smaller in diameter than the tokens used for the goods.\nImage Courtesy of EndersGame\nGoods Tokens – These are perhaps the most important component to the playing of the game itself. These tokens display both the type of good on offer (denoted by a coloured background of which there are 6 types) and the quantity - one to three barrels.\nThese are cardboard tokens and the thickness is pretty good. The rear side features the same image used on the board for the Warehouses and this allows these tokens to be placed face-down on the supply circles so the players do not know what is coming next.\nThey do the job well.\nImage Courtesy of <PERSON>\nMoneybag Tiles – This component is a large round cardboard token that represents the Talers that a player has in their possession.", "84" ], [ "This review continues my series of detailed reviews that attempt to be part review, part resource for anyone not totally familiar with the game. For this reason I expect readers to skip to the sections that are of most interest.\nImage Courtesy of ArtEmiSa64\nSummary\nGame Type – Dice Euro Game\nPlay Time: 30-60 Minutes\nNumber of Players: 2-4\nMechanics – Dice Rolling, Area Control/Influence\nDifficulty – Moderate (Can be learned in about 30 minutes)\nComponents – Excellent\nRelease - 2006\nDesigner – <PERSON> - (Jaipur, Jamaica, Metropolys)\nOverview\nYspahan was one of the first Dice Euros to hit the market way back in 2006 and comes to us from a designer that has had more success in recent years with games such as Jaipur, Jamaica and Metropolys.\nYspahan takes us back to the year 1598 when Yspahan becomes the center of the Persian Empire. As merchants the players are hoping to make great riches in this boon time by getting their wares into the many shops of the Souk District, supplying the great Camel Caravans that venture out into the desert and by building new structures as a sign of their new found wealth.\nI should have given this game more love with a detailed review long before now being a fan of dice based Euros.\nThe question is, 'How does Yspahan stack up against the competition now?' given that the genre has exploded in recent years.\nThe Components\nYspahan is a Euro done pretty right in relation to components.\nMain Board – The main board of Yspahan depicts the city which consists of many shops. The city is further divided into four neighbourhoods, which are separated by a road upon which the Supervisor will travel during the game. Each neighbourhood features shops of various colours and a set of like coloured shops is referred to as a Souk. Each set of coloured Souks in a district is worth a certain amount of points and each neighbourhood is given a symbol to help identify it (sack, barrel, vase and chest).\nThe top left hand corner features a day and week track to help mark the passage of time as the game unfolds and a scoretrack surrounds the city.\nThe board is certainly colourful...some may even think it garish but it is functional and pleasant enough to look at.\nImage Courtesy of theo home\nTower Board – The second most important component is the Tower Board. This is placed alongside the main board and is used to allocate the dice that are rolled for each day of play.\nThe board consists of 6 rows, with the four neighbourhoods sitting in the middle, a coin row at the top and a camel row at the bottom. On the right hand side of each row are 3 symbols, which remind players of what they can do with the dice found there.\nImage Courtesy of toulouse\nCamel Caravan – Now we have the Camel Caravan Board which features a series of camels in three rows.", "581" ], [ "This board is used to allow players to send goods to the Camel Caravan in order to score points. The first camel in each row is fainter in shade to reflect that it is not used if only 3 people are playing.\nImage Courtesy of <PERSON>\nPlayer Boards – Each player must take a Player Board which shows a total of 6 buildings, their benefit at the top, their cost at the bottom and a VP tracker on the right hand side. These are a nice bit of design and the boards are suitably thick to stand up to many, many plays.\nImage Courtesy of <PERSON>\nCamels - Games are always more cool when they have Camel Meeple and <PERSON> delivers with some cool stylised wooden camels that make for some great images, which I've used throughout this review.\nOh yeah what was my girlfriend's comment upon her first play this week, \"Yay Camels...they're so cute!\"\nImage Courtesy of Legomancer\nSpecial Cards - Yspahan comes with a total of 18 Special Cards of which there are 9 types in all and 2 of each. These offer up many a special power to help out the players. The cards are of the small format featured in many games and suit their use here (not needing to be held in hand).\nImage Courtesy of dougadamsau\nBits and Pieces - The game then offers up a bunch of odds and sods. Each player takes a set of coloured cubes and these are used to represent their goods. Yellow discs are used to represent gold and a bunch of dice are provided that come in white and three in yellow. A black pawn is used to mark the start player and a white pawn acts as the Supervisor. Two white cubes are used to track the current day and week.\nThere is nothing magical here but it is all does the job.", "872" ], [ "Image Courtesy of VerkistoThis review continues my series of detailed reviews. I have tried to cover every aspect of the game and as such you may prefer to skip to the sections of most interest.\nSummary\nGame Type – Euro Game\nPlay Time: 30-50 min\nNumber of Players: 2-5(6)\nMechanics – Tile Placement, Area Control & Influence\nDifficulty – Pick-up & Play (Can be learned in under 20 minutes and takes only 1-2 plays to fully grasp)\nComponents – Excellent\nRelease - 2003\nDesigner - <PERSON> - (Bali, All things Carcassonne, The Downfall of Pompeii, Mesopotamia)\nOverview\nThis review continues my detailed analysis of the Carcassonne series of titles and is the second of the expansions that I have looked at.\nI have no plans to cover the basic play and strategy of the base game here. If you would like to know more about Carcassonne, I suggest a quick read of this review –\nCarcassonne - A Detailed Review\nTraders Builders was released 3 years after the original game and a year after the highly successful Inns Cathedrals. It comes in a nice smaller box format and it is regarded as one of the ‘better’ expansions for the franchise.\nThis expansion review will outline what new elements and strategy are generated when using Traders Builders and how that changes the feel of the play. It will also look at any interesting interplay that may arise if used in conjunction with Inns Cathedrals.\nComponents\nTiles – Traders Builders offers up an additional 24 tiles to add to the Carcassonne mix and many of these tiles feature icons that represent Trade Goods (more on those later). Tile distribution images like the one below are really handy if you mix a series of expansions together and want to separate them out again.\nImage Courtesy of <PERSON>\nTrade Goods - A series of tokens are provided that feature the icons of the Trade Goods located on many of the new tiles. The number of Goods is not exactly the same for each type.\nImage Courtesy of <PERSON>\nMeeple – In this expansion we also get some specialised Meeple in the form of the Builder and the Pig. All colours are represented including the grey 6th player that was made possible by Inns Cathedrals.\nImage Courtesy of mpot\nCloth Bag – By now the designer and publisher probably realised that fans of the series would likely play with the base game and both the small box expansions, which meant a lot of tiles to mix and stack in piles.", "581" ], [ "So they included a really nice cloth bag, which allows all the tiles to be thrown in there and mixed up in a matter of seconds. It comes in Royal Blue (which matches the colour of the Carcassonne box, although some images on the Geek suggest other colours have been used) and it also features a nice Carcassonne transfer.\nIt is little touches like this that game fans appreciate. It also meant that each expansion to date had included a component that didn't affect the game play but did make the playing experience easier to manage.\nImage Courtesy of <PERSON>\nRules – Like Inns Cathedrals, the rules are printed on a small double-sided sheet, which means you will be able to absorb the new additions and get into playing within 15-20 minutes.\nAll in all the components are up to the usual high standard of any Carcassonne title.\nImage Courtesy of <PERSON>\nNew Elements\nTraders Builders offers 3 new additions to change the play of the basic game. It also offered a couple of little extras.\nNew Tiles – Traders Builders adds 24 new tiles to the Carcassonne mix to make for a total of 96 tiles (using base game) or 114 tiles in play (if also using Inns Cathedrals) per game.\nThe Trade Goods – Justifying the ‘Traders’ part of the title, 20 of the new tiles feature a particular goods symbol. The goods include Wine (9), Grain (6) and Cloth (5). These goods are always located within a piece of City.\nWhen a player places a tile that completes a City, they are allowed to take 1 matching Goods Token for each icon located in the City. This collection is done regardless of who owns the Meeple in the City and they are awarded even if the City contained no Meeple.\nAt the end of the game, 10 points are awarded to any player holding a majority of tokens in any one Trade Good. Thus a total of 30 points can be earned in this way at games end. In the event of a tie all players are entitled to the 10 points.", "84" ] ]

[ 3235, 3075, 5006, 2131, 9901, 2366, 848, 2569, 8952, 6815, 6611, 2930, 8016, 3209, 57, 8145, 7422, 8755, 2457, 4013, 7987, 7453, 7714, 9369, 5285, 7133, 8080, 3424, 9703, 6582, 6254, 10918, 10113, 11161, 8586, 11222, 3674, 2320, 5582, 1105, 1212, 458, 10980, 6678, 10154, 6284, 3936, 3622, 8197, 8226, 1215, 2714, 6548, 6585, 7543, 10946, 8354, 10402, 1173, 2104, 10747, 3133, 5826, 3708, 4494, 1639, 8390, 778, 1832, 9545 ]

[ [ "Easy DIY Pet Bandana\nIntroduction: Easy DIY Pet Bandana\nHi Y'all! Today I will be showing you how to sew a super easy dog bandana! I love making these because they take almost no time at all, and are effortless to make new ones for all the different holidays!\nSupplies\n1. 1/4 Yard of Cotton Fabric\n2. Iron\n3. Ironing Board/ Safe Place to Iron\n4. Scissors/ Rotary Cutter\n5. Cutting Mat/ Safe Place to Cut\n6. Sewing Machine\n7. Thread\n8. Dog/ Cat/ Pet\n9. OPTIONAL: Snap Buttons\nStep 1: Pick Your Fabric\nThis is the best part of the whole tutorial, in my opinion, because you get to go to a fabric/craft store and look around! I chose a simple <PERSON> fabric, in a standard quilting cotton weave. I would recommend using cotton, because for the purposes we will be using it, it better holds a crease and is much easier to sew with than knits or other thinner/ stretchy materials.\nStep 2: Iron Your Fabric\nThe next step is to iron your fabric completely flat. Make sure you are doing this on an iron safe surface. Also, be sure to turn your iron to a steam setting, as dry heat does not work well with cotton. Once you have ironed it flat, it is time to fold it in half. You can measure the circumference of your dogs neck and fold it accordingly- Say, if your dog's neck was 24\", you would fold it in half so that the top fabric equals 12\", or half of your dog's neck size- Or, you can eyeball the length based on what your dog looks like. Here, I just eyeballed it because I've made these a million times.", "316" ], [ "One tip is to make the length about 1/2\"-1\" longer to account for sewing. You can always wrap the fabric around your pet's neck, and add an inch to get an easy measurement too.\nStep 3: Cut Your Fabric\nNow it is time to cut your fabric!! Make sure you have the correct length/size because once you cut the fabric you can't go back!! If you are worried you might mess up, a good rule of thumb is to always cut bigger than you need- You can always cut fabric away, but you can't bring it back!!! I laid my fabric on a cutting board, and used a ruler and a rotary blade to cut a straight line from corner to corner, making sure that the folded end was on the side and the long edge was at the top. When you unfold your fabric you should have a big triangle.\nStep 4: Prep Your Fabric to Sew!\nAfter you have completed steps 1 through 3, it is time to return to your ironing board. Begin by ironing your piece flat once again, then iron down the longest part of your triangle about 1/4\". It doesn't have to be perfect! Start at one end, and slowly make your way across, folding down the edge evenly. Quick Tip!!!: Make sure that you have the right side of the fabric down, and that you are folding the right side back onto the wrong side. To ensure we make an even bandana, we will only be sewing one edge at a time.\nStep 5: Begin Sewing!\nYAY!! It is time to sew! Bring your bandana to your sewing machine and prepare the thread based on your specific machine. I chose to do a wide zig-zag stitch, but you can do whatever stitch you want! Turn your fabric right side up, and begin stitching down the very edge of the fabric. Although you can't see the backside where your fold is, since you are stitching directly on the edge you will still catch the fold and adhere it together. Sew directly down the edge in a straight line, and when you get to the end, feel free to backstitch. Once you remove it from your machine it should look something like this. Trim off the excess fabrics and head back to your ironing board!\nStep 6: Back to the Basics\nTime to repeat the step you just did. Chose one of the other two sides of the triangular bandana, and iron the edges down from the right side down to the wrong side about 1/4\" wide. Once you have your side ironed down, head back to your sewing machine and sew along the edge you just ironed, following the same ideas from the previous step.\nStep 7: Final Sew!\nNow that 2/3 side of your bandana have been sewn, it is time to finish sewing that final edge. Bring your bandana back to your ironing board and iron down the final side. This side is very important though, because it will be the finishing edge of the bandana.", "748" ], [ "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" ], [ "Basic Faux Leather Arm Bracer\nIntroduction: Basic Faux Leather Arm Bracer\nI have had this faux leather material leftover from an old Astrid costume I made several years ago. Over the years of seeing it sitting on my shelf I have attempted multiple projects in hopes of using it, but none ever saw a finished product. So finally I made something simple that I knew I would be able to finish. In this instructable I used supplies that I already had available, so some alternatives may be better, however I still really like the final results! Making these simple bracers are easy and quick to make and are perfect for any fantasy costume or aesthetic touch.\nSupplies\nMaterials\n* Faux Leather\n* Waxed twine or leather craft lace\n* 0.6 cm jump rings\n* embroidery floss\nTools\n* Sewing machine\n* scissors\n* needle and thread\n* Washable marker\nStep 1: Measurements\nUsing a tape measure, measure and record the length around your wrist, the adequate length of your forearm, and the length around your arm where the bracer will end.\nStep 2: Make a Pattern\nThe picture above shows how to make the pattern and where to use each measurement, but below is my confusing attempt of explaining how to make the pattern:\nFirst you make a line that is the length of your forearm measurement. Then there are two lines on either side of that first line. On one side make a line that is the length of your wrist measurement, making sure the first line is perpendicular and connects in the middle of this second line. Next make a line on the other side of the first line that is the length of your arm measurement, making sure that the first line is also perpendicular and connecting in the middle of this third line. Lasly use a ruler to connect the left edge of the second line to the left edge of the third line, and connect the right edge of the second line to the right edge of the third line.\nStep 3: Trace and Cut\nTrace the pattern onto the right side of your faux leather using a washable marker. Then cut out the piece leaving an excess of about an inch.\nStep 4: Prep Your Sewing Machine\nDepending on the type of faux leather you have, you may notice that your faux leather sticks onto your sewing machine which prevents the material from gliding through the machine. An easy way to fix this is to apply a few pieces of matte scotch tape. First remove the sewing footer and place a layer of tape on it and use a craft knife to cut away the excess tape.", "316" ], [ "Then place a couple strips of tape below and around the footer, but make sure not to tape over any part that moves. If needed, use a craft knife to cut the tape for easy access to the bobin.\nStep 5: Cut Corners\nCut part of the material off at the corners.\nStep 6: Begin Sewing\nTo minimize the amount of holes we put into the material, we are going to avoid using sewing pins. This is why we left an extra inch for seam allowance, to allow us to fold the material easily without having to pin it. To begin sewing, fold one side of the material on the line and top stitch over the piece, sewing about half a centimeter away from the edge.\nStep 7: Continue Sewing\nStop sewing about half an inch from the edge and knot the thread. Then pull the piece away from the machine and fold the next side. Repeat steps 6 and 7 until you are finished.\nStep 8: Cut Excess\nOnce done sewing, turn over and cut the excess material close to the stitches. Since this is faux leather it'll be fine leaving the edges raw.\nStep 9: Hand Sew\nMake a mark about every inch with a washable marker. Then take embroidery floss and sew in the closed jump rings, this is the longest step of the project. I added a little bit of glue to the closure of the jump ring for extra safety. If you have grommets available those will probably be a better option, however this is what I had available.\nStep 10: Lace\nLastly, I took three strands of waxed craft lace and braided them to create the lace. Then all you need to do is lace your bracer onto your arm and you are finished!\nStep 11: Finish\nAs of now this is my final result of my bracer, however in the future I might add more details such as paint or embroidery. But nonetheless I am very happy with the results and these bracers fulfill my fantasy dreams of wanting to feel like a brave warrior.", "748" ], [ "<PERSON>!\nIntroduction: Jigsaw Simplicity Kitty!\nAs more generations come and go, sewing has become a lost art. Schools have had to stop teaching it nationally because of educational cuts and the adults who can teach the art do not usually have the time between balancing work and life. Teens may not have access to learn the art of sewing through guardians or teachers, but most have access to the internet. Making sewing tutorials on creating fun things like dresses, backpacks, and stuffed animals is how we can preserve one of the oldest arts to date. In this easy tutorial, you will learn how to efficiently sew a cat plushie.\nThe materials you will need for this project are as follows:\nA sewing machine\nFabric scissors\nFabric chalk (normal chalk will stain your fabric)\n¾ of a yard of fabric (for the main body) ⅜ of a yard of fabric (for the cats designs)\n⅜ of a yard of fusible web\nA 30oz bag of fiberfill\nAn iron and ironing board\nMeasuring tape\nThread\nPins and a pin cushion\nOptional! 34.5cm of twill tape\nOptional! Buttons for the eyes and nose and if you want whiskers get yarn. (The pattern will teach you how to sew eye and nose appliques but I want to do my own, I will also not be adding whiskers to my kitty.)\nSimplicity pattern 8403\nWhen looking at your pattern, you will notice that there are a few cat plushies you can choose from; A, B, C, and D. This tutorial is going to be covering how to sew plushie A.\nStep 1: Iron Your Clean Fabric\nFirst, you’re going to grab your clean washed fabric and lay it nicely on your ironing board. It is ok if some hangs off, you will just need to carefully pull more on to the ironing board as you go. Then, grab your iron and start smoothing out all the wrinkles in your fabric (I did not have an ironing board in this step so I staged the photo! Please do not iron without one). It may be helpful to have a spray bottle on hand for tough wrinkles (most irons have them built in).\nStep 2: Folding Rule\nNext, we are going to take our now smooth fabric and you’re going to fold the fabric in half making sure the salvages are end to end, right sides together; you are working on the wrong side (the side without the pattern). As you pay attention to this, make sure the fabric is on grain (length and width of fabric are matching on both sides of the fabric).\nStep 3: Cut Paper Pattern Pieces\nAfterwards, you are going to open your pattern and find the pattern pieces you need to use to cut out your fabric.", "673" ], [ "You will see that each pattern piece is labeled according to the cat you chose to do. For cat A, we will need pattern pieces 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. After you find the correct pattern pieces, you are going to carefully cut them out.\nStep 4: Body Fabric!\nThen, place pattern pieces, 1, 4, 5, 6, 7, and 8 on the body fabric (the main fabric you want your cat to be). Do not start pinning yet; you need to make sure that all of your pieces fit on the fabric like a puzzle.Your pattern pieces have words on them! These are very important! They tell you how many of that singular piece you will have to cut out. So if the pattern piece says CUT 3 OF FABRIC, you’re going to repin and cut this piece three times so that you have three of it; take into account how much more fabric you will need for the duplicates as you are placing your pieces.\nStep 5: Symbols!\nAs you are placing, pay attention to the symbols on your pattern pieces. Pieces with arrows that are sideways need to be placed sideways on the fabric, pieces with arrows that point upwards need to go upwards and the last arrow will be connected pointing down. This means that piece needs to be pinned on the fold. The reason for this is that most fabrics can stretch one way while they can't be stretched another way. Pattern pieces with triangles on the outline are called notches. You need to cut outward and back in when you get to these. They help you line up the fabric that goes together. Now pin!\nStep 6: Cut the Pieces Out!\nOnce pinned, you are going to very carefully cut your pieces out.\nStep 7: Contrary/Secondary Fabric Pieces!", "879" ], [ "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" ], [ "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" ], [ "Zippable Pouffe and Cover\nIntroduction: Zippable Pouffe and Cover\nWhat is a pouffe?\nThe short answer is comfortable. The longer answer is a cushioned footstool with no back.\nYou may be wondering why a zippable pouffe?\nI have noticed a couple of things with pouffes, firstly that they are super comfortable to sit on or to put your feet on. Secondly, that they can get dirty far too easily and are not always easy to clean. My solution is to make an pouffe with a easy clean fabric, and then make a cover for that pouffe!\nBut then why zippers on both of them?\nI have also found that over the years stuffing can get pretty deflated, so I want the ability to put more stuffing in, or even take some stuffing out, depending on the desired level of floofiness. A zipper on the inner piece allows for that kind of modification, and a zipper on the cover allows for easy removal and cleaning.\nHere are a couple terms to know before we jump in.\nTerms:\nRight side of the fabric: The decorative or patterned side of the fabric that you want to be seen on the completed piece. When the fabric looks the same on both sides this term does not matter as much.\nWrong side of the fabric: The non decorative or patterned side\nSupplies\n- fabric for the inner pouffe (I chose a water resistant one)\n- fabric for the pouffe cover (I chose a decorative fabric with a white liner)\n- Zippers\n-14\" zipper in matching color to inner pouffe fabric\n-16\" +* zipper in matching color or pouffe cover fabric\n*Your zipper on the cover can be longer.", "51" ], [ "If this is something you would like you can check out how to make this happen in the Notes section at the end of this instructable\n- Newsprint to create your stencils\n- Colored pencils to mark fabric\n- Compass or protractor (optional- I found a compass very useful when creating my stencils)\n- Sewing supplies:\n- Fabric scissors\n- Pins\n- Needles\n- Thread (to match your fabric selections)\n- Sewing machine (highly recommended but technically not necessary)\nStep 1: Gather Your Supplies!\nHave some fun picking out what fabric you want to use!\nStep 2: Find Measurements and Create Your Stencils\nThis is where I am going to show you the math of my design.\nYou can either follow my pattern and measurements exactly or follow my process and create a smaller or larger pouffe depending on your preference. I made my stencils out of newsprint but you can use anything similar that’ll do the job.\nFirst decide how big you want your pouffe. I wanted a cylinder shape 14\" tall with top and bottom circle pieces with a 14\" diameter.\nThis gives us:\nHeight (h) = 14\"\nDiameter (d) = 14\"\nRadius (r) = 7\"\nNow we are going to need this formula for circumference: C= 2πr\nWhen we input our values we get:\nC = 2π(7)\nC = 44 (rounded)\nThe 44 inches of the circumference is how long our middle piece will be, with the 14\" of height. When we add the 1/2\" seam allowance the total measurements to 45\" x 15\"\nI just drew these measurements onto the fabric since it is a simple rectangular shape.\nNow we will use the circumference to figure out the size of the triangle pieces. We have 8 triangle pieces to we will divide the circumference by the number of triangles making the circle.\nC = 44\"\n44 / 8 = 5.5\nSo, the 5.5 will be the width of the triangle and the 7\" of the radius will be the height of the triangle pieces.\nTo get the curvature of the triangle stencil measure from the top point of the triangle and dot out a few points so that each point is 7 inches from the tip of the triangle.\nNow that you have the stencil measurements you can add 1/2\" seam allowance to the outside.\nDraw out the triangle measurements on the newsprint making sure to mark the 1/2\" seam allowance. This will be our stencil that we can use to cut out the 16 triangle pieces (8 pieces for the top and 8 pieces for the bottom).\nStep 3: Cut Your Fabric\nMeasure twice and cut once! I used a white colored pencil to mark on my fabric. You could also use chalk here.\nI am choosing to use a water resistant fabric with a clear plastic backing.", "316" ], [ "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" ] ]

[ 10665, 11041, 6617, 10036, 7597, 2877, 2969, 5371, 3386, 4283, 5927, 10300, 11259, 4648, 9543, 11115, 384, 4240, 8832, 4604, 10657, 7279, 2075, 3557, 10308, 8754, 7277, 1476, 9521, 1388, 311, 3653, 8558, 6162, 9272, 7462, 1100, 3381, 5421, 84, 9986, 11136, 7629, 2708, 1595, 5812, 1358, 3651, 11300, 6039, 3800, 10301, 1851, 3649, 8180, 2358, 9852, 9141, 7651, 2407, 8229, 1892, 10388, 1764, 4837, 8092, 9912, 3242, 2086, 5560 ]

[ [ "How to find the trajectory of stationary action of a photon\nI am trying to work through a \"check your understanding\" question on p.393 of the textbook From Photon to Neuron by <PERSON>. The action functional S of a photon's trajectory is proposed to be\n$S [\\underline X^\\mu(\\xi),e(\\xi)] =\\frac{\\hbar}{2} \\int d\\xi (e^{-1}||\\dot {\\underline X}||^{2} )$\nwhere $\\mu$ = 0,1,2, or 3. $\\underline X^\\mu$ are spacetime coordinates; $\\underline X^0$ is $ct$. The parameter $\\xi$ is some index along the trajectory. The variable $e$ is described as a metric necessary so that different parameterizations of the same path give the same action.", "394" ], [ "The dot denotes differentiation with respect to $\\xi$ and $||\\dot {\\underline X}||^{2} $ is the Lorentz invariant interval $ -(c \\dot t)^2 + (\\dot r)^2 $.\nThe reader is asked to show that the equation above is stationary under any trajectory that satisfies\n$0 = e^{-2} ||\\dot {\\underline X}||^{2}$ and\n$e^{-1} \\dot {\\underline X} =$ constant.\nIt's not clear to me if the second equation is implying an <PERSON> summation.\nHere is what I have tried: I introduced a small variation in both the spacetime coordinates and metric along a path and examined the action of this new worldline:\n$S [\\underline X^\\mu+ \\Delta \\underline X^\\mu,e + \\Delta e] =\\frac{\\hbar}{2} \\int d\\xi \\bigl[(e +\\Delta e )^{-1}||\\dot {\\underline X}+\\Delta\\dot {\\underline X} ||^{2} \\bigr]$\n$\\approx \\frac{\\hbar}{2} \\int d\\xi (1 -\\frac{\\Delta e}{e} )\\bigl( ||\\dot {\\underline X}||^2+2 \\dot {\\underline X}\\Delta\\dot {\\underline X}^{2} + ||\\Delta\\dot {\\underline X}^{2}||\\bigr) $\nI then subtracted the action of the original worldline to get\n$ \\Delta S \\approx \\frac{\\hbar}{2} \\int d\\xi \\bigl(\\frac {2\\dot {\\underline X}\\Delta \\dot X}{e}\n+\\frac {{\\Delta \\dot X}^2}{e}\n$ $ +\\frac {2 \\dot X \\Delta \\dot X \\Delta e}{e^2} $ $ +\\frac {\\Delta \\dot X^2 \\Delta e}{e^2} $ $ + \\frac {|| \\dot X||^2 \\Delta e}{e^2} \\bigr) $\nI figured I could neglect terms that were second order in $\\Delta$. That leaves the first and last term in the equation above. The last term must equal zero; this satifies one of the two conditions I set out to show. But shouldn't the first also have to equal zero, not a constant?\nI am hoping someone can help me track down my error(s), explain if one must vary $e$ in addition to $X$, and clarify if the second condition stated above is an <PERSON> summation, i.e. if $ \\dot {\\underline X} = c \\dot t - \\dot r$. Thanks!", "955" ], [ "Trajectories in AdS\nOn page 2 of this paper (http://arxiv.org/pdf/1106.6073v2.pdf), <PERSON> explains (and has a very nice picture) showing the trajectories that a timelike and null particle would take in AdS space.\nOf course, what this diagram really shows is the conformal compactification of AdS - hence the cylinder. To see this, I can consider the metric of, say, $AdS_3$: $ds^2=L^2(-\\cosh^2{\\mu} dt^2 + d \\mu^2 + \\sinh^2{\\mu} d \\theta^2)$ where $\\mu \\in [0, \\infty)$ is the radial variable of $AdS_3$.\nTo conformally compactify, we substitute $\\sinh{\\mu}=\\tan{\\rho}$ and find $ds^2=L^2(-\\sec^2{\\rho} dt^2 + \\sec^2{\\rho}d \\rho^2 + \\tan^2{\\rho} d \\theta^2) = \\frac{1}{\\cos^2{\\rho}} ( - dt^2 + d \\rho^2 + \\sin^2{\\rho} d \\theta^2)$ where $\\rho \\in [0, \\frac{\\pi}{2}]$ is the new angular variable\nWe can then consider the compactified metric $\\hat{ds}^2 = \\cos^2{\\rho} ds^2 = ( - dt^2 + d \\rho^2 + \\sin^2{\\rho} d \\theta^2)$ which is exactly the cylinder metric with radial boundary at $\\rho=\\frac{\\pi}{2}$ representing $\\mu=\\infty$ of the original $AdS_3$.\nNow my concern is that conformal compactification preserves angles (whether curves are spacelike, timelike etc) but it doesn't preserve distances and so we need to be careful whether we are plotting geodesics of $AdS_3$ or of its compactification.\nI agree with <PERSON> as to how the null geodesic looks.", "474" ], [ "Indeed, if I set $ds^2=0$, and supress the motion in the angular direction with $d \\theta=0$ then I can rearrange the compactified metric to find (I denote affine parameter with $\\lambda$):\n$0=L^2(-(\\frac{dt}{d \\lambda})^2+(\\frac{d \\rho}{d \\lambda})^2) \\Rightarrow \\frac{d \\rho}{dt}=\\pm 1 \\Rightarrow \\rho = \\pm (t+t_0)$. In other words, a future directed null ray would travel on a straight line of gradient 1 as shown in <PERSON>'s picture.\nHowever, I disagree with his trajectory for the timelike particle. Here, I have $ds^2=-1$ and so, again supressing the motion in the angular direction with $d \\theta=0$, I can rearrange the compactified metric to find (now denoting proper time by $\\tau$):\n$-1=L^2(-(\\frac{dt}{d \\tau})^2+(\\frac{d \\rho}{d \\tau})^2) \\Rightarrow \\frac{d \\rho}{d \\tau}= \\sqrt{-\\frac{1}{L^2}+\\frac{E^2}{L^4}}$ where I have used that the timelike Killing vector $\\partial_t$ generates a conserved energy $E=-g_{tt} \\frac{\\partial t}{\\partial \\tau} \\Rightarrow \\frac{\\partial t}{\\partial \\tau} = \\frac{E}{L^2}$.\nTo plot this curve on the $(\\rho,t)$ <PERSON> diagram, I use that $\\frac{d \\rho}{dt} = \\frac{d \\rho}{d \\tau} \\frac{d \\tau}{dt} = \\sqrt{-\\frac{1}{L^2}+\\frac{E^2}{L^4}} \\frac{L^2}{E}= \\sqrt{1-\\frac{L^2}{E^2}} \\Rightarrow \\rho(t) = \\sqrt{1-\\frac{L^2}{E^2}} t$ which is again a linear trajectory as opposed to the oscillatory one that he draws!", "394" ], [ "I tis very important to notice that you can do this at a given point, but not at any given curve. In fact, it is true that for geodesics you can define a locally flat coordinate system such that the <PERSON> symbols vanish along the curve. This is compatible with the idea of the equivalence principle for $inertial$ observers.\nHowever, for more general trajectories, it is not possible to define a such a coordinate system: the <PERSON> symbols get corrections due to the acceleration of the trajectory, and these are compatible with the notion of fictious forces that are seen due to non-inertiality.\nThe way to analyze the problem above is by means of the Fermi normal coordinates (FNC).", "578" ], [ "These are a coordinate system that is associated with a timelike trajectory and describes \"what an observer undergoing this trajectory sees\". In case you want learn more about this, I recommend https://arxiv.org/abs/1102.0529. In any case, it is possible to show that the metric in FNC can be written locally around the curve (up to first order in acceleration and curvature) as\n$$\\begin{aligned} &g_{\\tau \\tau}=-\\left(1+2 a_{\\mathrm{i}}(\\tau) x^{i}+R_{0 \\mathrm{i} 0 \\mathrm{j}}(\\tau) x^{i} x^{j}\\right), \\ &g_{\\tau i}=-\\frac{2}{3} R_{0 \\mathrm{jik}}(\\tau) x^{j} x^{k} \\ &g_{i j}=\\delta_{\\mathrm{ij}}-\\frac{1}{3} R_{\\mathrm{ikjl}}(\\tau) x^{k} x^{l} \\end{aligned},$$ where $\\tau$ is the proper time of the trajectory (and the timelike coordinate of the FNC) and $x^i$ denote the proper distance from the trajectory, which are the spacelike trajectories of the FNC. $a(\\tau)$ is the trajectories proper acceleration and $R(\\tau)$ is the curvature tensor along its motion.\nThe <PERSON> symbols to first order in acceleration and curvature then read\n$$\\begin{aligned} \\Gamma_{i j}^{\\tau} &=\\frac{1}{3}\\left(R_{0 \\mathrm{ijm}}+R_{0 \\mathrm{jim}}\\right) x^{m} \\ \\Gamma_{\\tau i}^{\\tau} &=a_{\\mathrm{i}}+R_{0 \\mathrm{i} 0 \\mathrm{~m}} x^{m} \\ \\Gamma_{\\tau \\tau}^{\\tau} &=0 \\ \\Gamma_{j k}^{i} &=\\frac{1}{3}\\left(R_{\\mathrm{j} \\mathrm{km}}^{\\mathrm{i}}+R_{\\mathrm{k} \\mathrm{jm}}^{\\mathrm{i}}\\right) x^{m} \\ \\Gamma_{\\tau j}^{i} &=R_{0 \\mathrm{mj}}{\\mathrm{j}} x^{m} \\ \\Gamma_{\\tau \\tau}^{i} &=a^{\\mathrm{i}}+R_{0}^{\\mathrm{i}}{ }_{0 \\mathrm{~m}} x^{m} \\end{aligned},$$ which can be seen to vanish if $a^i = 0$ (inertial motion) and $x^i = 0$ (on top of the curve).", "804" ], [ "Integrating the geodesic equation to obtain Newtonian energy of test particle\nI am studying General Relativity, and have come across a question that I am finding rather intractable:\nIn Newtonian Theory, the energy equation for a test particle in orbit around a point mass is: $$\\frac{v^{2}}{2} + \\frac{\\ell^{2}}{2r^{2}} - \\frac{GM}{r} = \\mathcal{E}$$ Where $r$ is the radius, $v$ is the radial velocity, $\\ell$ is the angular momentum per unit mass, $\\mathcal{E}$ is the constant energy per unit mass and $-GM/r$ is the gravitational potential. For the <PERSON> solution show that the integrated geodesic equation may also be written in the form: $$\\frac{v_{s}^{2}}{2} + \\frac{\\ell_{s}^{2}}{2r^{2}} + \\Phi_{s}(r) = \\mathcal{E}{s}$$ Where $v{s} = \\mathrm{d}r/\\mathrm{d}\\tau$, and $\\ell_{s}$ and $\\mathcal{E}_{s}$ are constants.\nI am not really sure what it means by integrating the geodesic equation. My understading is that the geodesic equation is given by:\n$$\\frac{\\mathrm{d}^{2} x^{\\lambda}}{\\mathrm{d} \\tau^{2}} + \\Gamma^{\\lambda}_{\\mu\\nu}\\frac{\\mathrm{d} x^{\\mu}}{\\mathrm{d} \\tau}\\frac{\\mathrm{d} x^{\\nu}}{\\mathrm{d} \\tau} = 0$$\nWhere $\\Gamma^{\\lambda}_{\\mu\\nu}$ is the affine connection. However, this leads to a system of equations, none of which, when integrated, yield the form given in the question.\nI'm sure that I am missing something fundamental and simple, but I just cannot find it in any of the references or materials that I have been given.\nI thought that perhaps integrating the geodesic equation directly would be the way to go, but I do not end up with the correct solution:\n$$\\int\\left(\\frac{\\mathrm{d}^{2} x^{\\lambda}}{\\mathrm{d} \\tau^{2}} + \\Gamma^{\\lambda}{\\mu\\nu}\\frac{\\mathrm{d} x^{\\mu}}{\\mathrm{d} \\tau}\\frac{\\mathrm{d} x^{\\nu}}{\\mathrm{d} \\tau}\\right)\\:\\mathrm{d}\\tau = \\mathcal{E}{s}$$\nWe note that as integration is distributive over addition, we find:\n$$\\frac{\\mathrm{d}x^{\\lambda}}{\\mathrm{d}\\tau} + \\int\\left(\\Gamma^{\\lambda}{\\mu\\nu}\\frac{\\mathrm{d} x^{\\mu}}{\\mathrm{d} \\tau}\\frac{\\mathrm{d} x^{\\nu}}{\\mathrm{d} \\tau}\\right)\\:\\mathrm{d}\\tau = \\mathcal{E}{s}$$\nWe note that if we let $\\lambda = r$, then this becomes proportional to $v_{s}$ and thus I am missing a factor of $v_{s}$.\nEdit 2: After the very helpful comments below, I went back and did the question again, this time getting stuck at a different point.\nSo we find that in the $\\lambda = t$ case, the only <PERSON> symbols $\\Gamma_{\\mu\\nu}^{t}$ that are non-zero are when $\\mu = t$, $\\nu = r$ or vice versa.", "394" ], [ "The difference lies in spatial infinity: AdS like spacetimes have timelike infinity while Schwarzschild spacetime has a lightlike infinity.\nIn general the prescription to build <PERSON> diagrams of spherically symmetric spacetimes goes as:\n1) Define the tortoise coordinate except for the constant;\n2) Define null coordinates in the 'usual way';\n3) Define new null coordinates in order to avoid the coordinate singularity in the event horizon;\n4) Reparametrize the null coordinate in order to put it in a finite diagram.\nIn the case of AdS-Schwarzschild spacetime it is a little bit of hard work:\n1) We have a metric of type $g_{\\mu \\nu }= (-f, f^{-1},r^2,r^2\\sin^2 \\theta )$ and $ f = 1- \\frac{2m}{r} + c^2r^2$, $c$ meaning the inverse of the AdS curvature radio. Now, as long as $f$ has always a real positive and two imaginary roots, we have \\begin{eqnarray} r_* = \\int \\frac{1}{f}dr = \\frac{(2r_+^2 + 4p)\\arctan \\left(\\frac{r_++2r}{\\sqrt{4p-r_+^2}}\\right) + r_+ \\sqrt{4p-r_+^2} \\ln \\left( \\frac{(r-r_+)^2}{r^2+r_+r+p} \\right)}{2c^2(2r_+^2+p)\\sqrt{4p-r_+^2}} + constant \\end{eqnarray} in which $r_+$ is the event horizon ($f(r_+)=0$) and $p=r_+^2+\\frac{1}{c^2}= \\frac{2m}{c^2r_+}$. (Assume: $constant \\equiv C$).\n2) The usual null-coordinates, $u$ and $v$ written as \\begin{eqnarray} du=dt-dr_ \\ dv=dt+dr_ \\end{eqnarray} lead the metric to \\begin{eqnarray} ds^2 = -f du dv + r^2 d \\Omega^2 \\end{eqnarray} which is still singular in $r=r_+$ as long as $f=0$ there.\n3) Defining now \\begin{eqnarray} \\tilde{U}=-e^{-\\eta u}\\ \\tilde{V}=e^{\\eta v}, \\end{eqnarray} we have \\begin{eqnarray} ds^2 = \\frac{-f}{\\eta^2}e^{-2\\eta r_*}d \\tilde{U} d\\tilde{V} +r^2 d\\Omega^2 \\end{eqnarray} (being $\\tilde{U}$ and $\\tilde{V}$, also null).", "578" ], [ "If $\\eta = \\frac{c^2(2r_+^2+p)}{2r_+}$, the coordinate singularity is avoided.\nWith these new coordinates, and the proper choice of $C$ (in blocks) we have, \\begin{eqnarray} \\lim_{r\\rightarrow \\infty} \\tilde{U} \\tilde{V} = -1 \\ \\lim_{r\\rightarrow r_+} \\tilde{U} \\tilde{V} = 0 \\ \\lim_{r\\rightarrow 0} \\tilde{U} \\tilde{V} = 1. \\end{eqnarray}\n4) Finally, define \\begin{eqnarray} U = \\arctan \\tilde{U}\\ V = \\arctan \\tilde{V} \\end{eqnarray}\nin which case, the maximal spacetime is placed in a square of size $\\pi / \\sqrt{2}$. To see this, we have to take the 3 limits above, considering the coordinates $U$ and $V$ as in the file bellow.", "804" ], [ "Extra term when calculating variation in Lagrangian density under infinitesimal Lorentz transform\nConsider an (active) infinitesimal Lorentz transformation:\n$$ x^\\mu \\rightarrow x^\\mu + {\\omega^\\mu}_\\nu x^\\nu, $$\nso that any scalar field is transformed as\n$$ \\phi(x) \\rightarrow \\phi'(x) = \\phi(x) - {\\omega^\\mu}\\nu x^\\nu \\partial\\mu \\phi(x) + O(\\omega^2). $$\nNow consider a Lagrangian density function $\\mathcal{L(\\phi, \\partial\\phi)}$ (with no explicit spacetime dependence). Every scalar field is associated to a Lagrangian density field $\\mathcal{L}\\phi := \\mathcal{L}(\\phi(x), \\partial\\phi(x))$, which is itself a scalar field. Therefore, it transforms with variation:\n$$ \\delta \\mathcal{L} = -{\\omega^\\mu}\\nu x^\\nu \\partial\\mu \\mathcal{L}[\\phi] = -\\partial_\\mu ({\\omega^\\mu}_\\nu x^\\nu \\mathcal{L}[\\phi]), \\tag{1}$$\nwhere the second equality arises because $\\omega$ is antisymmetric. Since the Lagrangian only varies by a four-divergence, the action is unchanged.", "818" ], [ "This makes perfect sense: all we've done is shift around spacetime by an orthogonal transformation, moving around the $d^4 x\\ \\mathcal{L}$ terms in the action integral, so the total action integrated over the whole of spacetime isn't going to change. So far so good.\nThe problem arises when I try to calculate $\\delta \\mathcal{L}$ a different way. I think we should be able to calculate the variation using:\n\\begin{align} \\delta \\mathcal{L} & = \\mathcal{L}[\\phi'] - \\mathcal{L}[\\phi] \\ & = \\frac{\\partial\\mathcal{L}}{\\partial\\phi}\\delta\\phi + \\frac{\\partial\\mathcal{L}}{\\partial(\\partial_\\mu \\phi)} \\delta(\\partial_\\mu \\phi) \\ & = - \\left [ \\frac{\\partial\\mathcal{L}}{\\partial\\phi} {\\omega^\\alpha}\\beta x^\\beta \\partial\\alpha \\phi + \\frac{\\partial\\mathcal{L}}{\\partial(\\partial_\\mu \\phi)} \\partial_\\mu ({\\omega^\\alpha}\\beta x^\\beta \\partial\\alpha \\phi) \\right ] \\ & = - {\\omega^\\alpha}\\beta x^\\beta \\left[ \\frac{\\partial\\mathcal{L}}{\\partial\\phi}\\partial\\alpha \\phi + \\frac{\\partial\\mathcal{L}}{\\partial(\\partial_\\mu \\phi)} \\partial_\\mu \\partial_\\alpha \\phi \\right] - \\frac{\\partial \\mathcal{L}}{\\partial (\\partial_\\mu \\phi)}{\\omega^\\alpha}\\mu \\partial\\alpha \\phi \\ & = -\\partial_\\alpha({\\omega^\\alpha}\\beta x^\\beta \\mathcal{L}) - \\frac{\\partial \\mathcal{L}}{\\partial (\\partial\\mu \\phi)}{\\omega^\\alpha}\\mu \\partial\\alpha \\phi.\\tag{2} \\end{align}\nAs you can see, there's a second term that's appeared out of nowhere! Where have I gone astray?\nI've tried double-checking that $\\delta (\\partial_\\mu \\phi) = \\partial_\\mu (\\delta \\phi)$ and it seems to work out, so I don't think that's the problem. I found this very old post but I find the argument that\n$$ \\frac{\\partial \\mathcal{L}}{\\partial (\\partial_\\mu \\phi)} \\propto \\partial^\\mu \\phi \\tag{3}$$\nunconvincing. Say, for example, you had a $\\frac{1}{2} \\partial_\\alpha \\partial_\\beta A^{\\alpha\\beta}$ term - that's fine, because differentiating w.r.t. $\\partial_\\mu \\phi$ symmetrises $A$, so it works out that the extra term is zero, but the proportionality doesn't hold.", "818" ], [ "A problem in deriving the Hamilton Jacobi equation from a variational principle\nas I've already said, I have a problem in understanding a reasoning from which we derive the Hamilton Jacobi equation from a variational principle. Let's take the <PERSON> functional:\n$$ S = \\int_{t_0}^{t_1} [ p_{\\alpha}\\dot{q}^{\\alpha} - H(q^{\\alpha},p_{\\alpha},t) ] dt $$\nThe first variation on the phase space of this functional is, in the most general form:\n$$ (\\delta S){\\bar{\\gamma}} = [p\\alpha \\delta q^{\\alpha} - H \\delta t]{t_0}^{t_1} + \\int{t_0}^{t_1} \\left{ \\left[ \\dot{q}^{\\alpha} - \\frac{\\partial H}{\\partial p_\\alpha} \\right]{\\bar{\\gamma}}\\pi\\alpha - \\left[ \\dot{p}{\\alpha} + \\frac{\\partial H}{\\partial q^\\alpha} \\right]{\\bar{\\gamma}}\\eta_\\alpha \\right} dt $$\nWhere the variation of the functional S is evaluated on the deformation of the curve ${\\bar{\\gamma}} \\to \\gamma$ in the phase space:\n$$ \\bar{\\gamma} : \\begin{cases} q^{\\alpha} = \\overline{q}^{\\alpha}(t) \\ p_{\\alpha} = \\overline{p}{\\alpha}(t) \\ A = { \\overline{q}^{\\alpha}(t_0);\\overline{p}{\\alpha}(t_0) } \\ B = { \\overline{q}^{\\alpha}(t_1);\\overline{p}{\\alpha}(t_1) } \\ \\end{cases} \\qquad t \\in [t_0,t_1] $$ $$ \\gamma : \\begin{cases} q^{\\alpha} = \\overline{q}^{\\alpha}(t) + \\lambda\\eta{\\alpha}(t) \\ p_{\\alpha} = \\overline{p}{\\alpha}(t) + \\lambda\\pi{\\alpha}(t)\\ A' = { \\overline{q}^{\\alpha}(t_0 + \\lambda \\delta t_0) + \\lambda \\eta_{\\alpha}(t_0 + \\lambda \\delta t_0) ; \\overline{p}{\\alpha}(t_0 + \\lambda \\delta t_0) + \\lambda \\pi{\\alpha}(t_0 + \\lambda \\delta t_0) } \\ B' = { \\overline{q}^{\\alpha}(t_1 + \\lambda \\delta t_1)+\\lambda \\eta_{\\alpha}(t_1 + \\lambda \\delta t_1); \\overline{p}{\\alpha}(t_1 + \\lambda \\delta t_1) + \\lambda \\pi{\\alpha}(t_1 + \\lambda \\delta t_1) } \\ \\end{cases} \\qquad t \\in [t_0 +\\lambda \\delta t_0,t_1 +\\lambda \\delta t_1] $$\nWhere $\\eta_{\\alpha}$ and $\\pi_{\\alpha}$ are regular function. Now, in my notes we choose $\\bar{\\gamma}$ e we let $A=A'$, so that we have an initial fixed point.", "955" ], [ "Then we say that on the curve chosen, are satisfied the <PERSON> equation, so that the variation of S becomes only:\n$$ (\\delta S){\\bar{\\gamma}} = [p\\alpha \\delta q^{\\alpha} - H \\delta t]_{t_0}^{t_1} $$\n[First question Is this legit ? If the <PERSON> equation are derived from the same variational principle, can we say ''a priori'' that them are valid on a particular path on the phase space ? ]\nThen we consider the point B movable, so that it depends from time. In this way, S isn't a functional anymore, but instead is a function of time. So the variation can be interpreted as a differential:\n$$ dS= p_\\alpha d q^{\\alpha} - H d t $$\n[Second question I wish to have a mathematical proof for that, because for me isn't trivial as it sounds.", "346" ], [ "<PERSON>'s law for the <PERSON> solution\nI'm puzzled with the following question: find an analog of the <PERSON>'s law for the <PERSON> solution.\n<PERSON> metric is a solution to the vacuum <PERSON> equations $$ds^2=dt^2-\\sum_{i=1}^3a^2_i(t)(dx^i)^2$$ with coefficients $a_i(t)=t^{p_i}$, where $p_i$ are constant parameters satisfying $\\sum_ip_i=1$ and $\\sum_i (p_i)^2=1$. This solution describes anisotropic space.\nIt is known that in the <PERSON>-Walker metric, when coefficients along all axes are the same $a_i=a$ wavelengths of a photon at times $t$ and $t_0$ are related by the scale parameter $a(t)$ as $$\\frac{\\lambda(t)}{\\lambda(t_0)}=\\frac{a(t)}{a(t_0)}$$\nthis is true if the rate if the space expanding $\\dot{a}/a$ is significantly smaller then the frequency of the photon.\nThe question is how to generalize this statement in the case of the <PERSON> metric. A natural idea is to suppose that the statement is generalized directly to the propagation along \"main\" axes $$\\frac{\\lambda_i(t)}{\\lambda_i(t_0)}=\\frac{a_i(t)}{a_i(t_0)}$$ and \"linearly\" for a generic direction, i.e.", "346" ], [ "for $\\vec{\\lambda}=\\lambda_i \\vec{e_i}$ $$\\frac{|\\vec{\\lambda}(t)|}{|\\vec{\\lambda}(t_0)|}=\\frac{\\dot{a}_i(t)\\lambda_i}{a_i(t)\\lambda_i}$$\nHowever, I'm not able to confirm this conjecture by any quantitative argument. I've tried to show that the EOM in a curved space-time $\\nabla^\\mu F_{\\mu\\nu}=0$ admit a solution of a kind $A_\\mu(x)\\sim e_{\\mu}\\exp{\\left(i g_{\\mu\\nu}q^\\mu x^\\nu\\right)}$ with $q^\\mu$ being a rescaled \"minkowskian\" momentum $q^i(t)=\\frac{k_i}{a_i(t)}, \\eta^{\\mu\\nu}k_\\mu k_\\nu=0$ but failed to succeed.\nAfter some time I've realized that one should probably look not for an exact solution of this type (even in the <PERSON>-Walker case the relation $\\lambda(t)\\sim a(t)$ is approximate) but for a \"high-frequency\" approximate solution. But still I'm not currently able to find it.\nSo my questions are:\n1) Is the suggested generalization of the Hubble's law correct?\n2) If so, how to provide quantitative evidence for it? I would be satisfied even with calculations for a massless scalar field if they are simpler to perform in order to achieve the goal.", "346" ] ]

[ 5828, 2578, 10042, 9196, 8948, 2718, 7751, 3199, 1363, 8909, 11211, 1592, 4152, 7229, 788, 7738, 956, 3858, 4740, 5355, 8847, 9794, 5819, 3352, 1282, 7964, 3726, 4008, 11356, 10148, 877, 2821, 8546, 6030, 4913, 5384, 6008, 1538, 9453, 5178, 6759, 8386, 770, 10821, 10483, 7179, 9569, 3612, 9943, 7733, 3166, 9464, 6574, 460, 5731, 6304, 4539, 4484, 4108, 8897, 571, 2645, 1501, 3970, 2115, 8870, 3959, 8687, 4818, 2133 ]

[ [ "CONVERT OLD TOOTHBRUSHES INTO MINIATURE ELECTRIC SANDERS\nIntroduction: CONVERT OLD TOOTHBRUSHES INTO MINIATURE ELECTRIC SANDERS\nThis is a very simple Instructable on how to turn old or new electric toothbrushes and/or facial massages into small electric sanders.\nI make a lot of clay and plaster sculptures and sometimes they are so small or so detailed that using sanding paper is impossible. Dremel is usually great for small details, but it can be too powerful for fragile items. Converting an electric toothbrush into a sander can help with sanding or polishing small and difficult to access places.\nI used a regular electric, rotary toothbrush as well as \"disposable\" vibrating toothbrush. They provide a completely different set of motions. I also used an old electric facial massager/brush to create a sander with a bigger head.\nAll those devices are either powered by batteries or have the ability to be re-charged.", "98" ], [ "They are not very powerful compared to regular electric sanders or dremmel-like tools, but they can be a great help when you require light sanding on small or fragile items.\nStep 1: Supplies\n* electric toothbrushes and/or facial massager https://www.amazon.co.uk/Oral-B-Pro-Expert-Toothb...\n* Velcro (scratchy side) https://www.amazon.co.uk/Soneer-Adhesive-Sticky-R...\n* Gorilla glue epoxy https://www.amazon.co.uk/Gorilla-Glue-25ml-Epoxy/...\n* scalpel or very sharp knife\n* sanding pads for electric sanders(not sanding paper) https://www.amazon.co.uk/YoiYee-Detail-Sander-Sand...\nStep 2: Remove Bristles\nUse a very sharp scalpel to remove the bristles. Use your thumb to press the bristles down and slice them away bit by bit. Make sure they are cut as close to the surface as possible.\nStep 3: Attach Velcro\nUse scissors to cut velcro to fit each toothbrush head.\nMix small amount of Gorilla glue and use it to attach velcro pieces to the heads.\nStep 4: Prepare Sanding Pads\nAs mentioned before, use sanding pads with soft velcro backing. Cut them to fit the heads of the toothbrushes.\nStep 5: Attach Sanding Pads\nOnce the glue is dry, attach the sanding pads to the heads. If you want to replace used pads, simply peel them off and attach new pads.", "320" ], [ "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" ], [ "Shark Scale Inspired Portable Miniature Checkers\nIntroduction: Shark Scale Inspired Portable Miniature Checkers\nThis project might be more acurately named - Magnetic Macro Shark Denticle Miniature Checkers.\nThe pawns were inspired by Scanning Electron Microscope (SEM) images of Shortfin Mako shark scales.\nWith a 8x8cm magnetic checkerboard + drawer for storing the playing pieces, the entire game fits in a 8.6x8.6cm box- perfect travel size.\nThe idea began years ago with a charity art show raising money for shark conservation. In a discussion about the fluid dynamics around a swimming shark, I came across the images of what shark skin looks like under a microscope. Things just spiraled from there.\nAlthough I don't yet have a 3d printer, I have been (slowly) working on my Tinkercad skills to make a design that can be printed, rather than modeled, carved, molded and poured repeatedly...\nSupplies\nPawns:\npolymer clay\nliquid mold making rubber\nVariety of containers for making molds (anything from bottle caps to plastic cups)\nEpoxy resin\nblack epoxy tint\nThick tipped syringe\nmetal wire\nmagnets - mine came from a 1euro store set\nsharp blade\nfine grain wet sand paper\ngel super glue\nBoard:\nblack metal sheet - I got mine from dismantling a 1euro store dry erase board\n1cm washi tape - but any type will do\ngloss finish sealer\nsharp blade\nscissors (that can cut through a thin metal sheet)\nBoard base and drawer:\nThin cardboard 3mm\nThick cardboard 17.5mm - I got mine from IKEA packaging\ntape\nribbon\nPVA glue\nwhite paper\ngold paint\npaint brush\nscissors\nBox:\nI bought a jewelry gift box with lid at the 1euro store.\nThe internal dimensions of the box bottom into which the board will fit are 8.5x8.5 cm with 3.5cm height.\nSimilar sized boxes can be found here.\nStep 1: Pawn Design\nThis is really where the whole project began, from scanning electron microscope images of shark scales. For this project I chose the denticles (scales) of the shortfin mako shark.\nStart by making a polymer clay model of the denticle. This is a very loose shape because the clay is such a soft material, it's hard to get sharp edges (especially because I used Fimo soft brand).\nAfter burning the shape use a sharp blade to trim down the size, carve the shape and get sharper points.\nFinally, sand down the piece with 1500 grain wet sand paper.\n*These final 'carving' are probably much easier if you have a dremel. I don't have one so I used what I have and I'm pretty happy with the results.\nStep 2: Making Rubber Molds\nStand the model upright in a small container, it has to be deeper than the height of the model.\nMix and pour the mold making rubber over it. When it is cured the model can just be pulled out.\n(out of habit I usually also trim the rubber from the sides to make it smaller)\nIf the process worked well your model piece should pull out whole and can be used again to make another mold.\nTip: Choose a mold making fluid that is very flexible and that does not require cutting to remove the piece. Making and working with a 2 piece mold can be tricky.\nStep 3: Pouring Acrylic Pawns\nThis is the repetitive part, since you need 12 clear pawns and 12 black tinted pawns.", "622" ], [ "The only challenge here is, because of the details in the shape, to minimize air bubbles. This is the method I used that usually gave me good results.\nCreate a short blunt piece of metal wire which is flexible. I made mine by twisting a folded thin metal wire. Having a blunt end is important because you don't want to poke holes in the rubber of the mold.\nLoad the prepared acrylic resin into a wide tipped syringe. The material in viscous so it usually would not flow through a thin one.\nInsert the wire into the mold into the tip of the scale. Use the syringe to drip the resin onto the wire close the mold opening. Repeat this with all 3 points of the scale. This way the resin should flow down the wire all the way into the tips of the piece.\nOnce the mold is full squeeze it around a bit to move any trapped air bubbles.\nFor black pieces - mix a tint into the resin.\n*I added an image of my most common pouring pitfalls - air bubbles and pouring clear pieces after having used the mold for black pieces.\n----------------------------------------------------\nI did not add a link to the acrylic resin I used because I was unhappy with it.", "74" ], [ "Spider Pumpkins - Arachnophobia Jack O' Lanterns\nIntroduction: Spider Pumpkins - Arachnophobia Jack O' Lanterns\nIn this instructable I make giant Halloween spiders-pumpkins from scrap rebar. These Arachnophobia inducing Jack O' Lanterns are modeled after the anatomy of Black Widow spiders.\nMATERIALS\n* METAL\n+ 3/4\" round stock\n+ 3/8” rebar\n+ 1/2” rebar\n+ 5/8” rebar\n+ steel ball bearings\nTOOLS\n* FILING, SANDING & GRINDING:\n+ 10\" Disc Sander\n+ Milwaukee Cordless 18v Grinder\n+ DIABLO Round Corner flap disc\n+ DIABLO 41/2 in. Metal Cutoff disc\n* HAMMERS AND POUNDING:\n* 4 Pound Mini Sledge\n* DRILLS, BITS and DRIVERS:\n* Drill Press\n* PENS/PENCILS AND MARKING:\n* Sharpie Marker\n* Silver Streak Metal Marking Pencil\n* RULERS AND SQUARES:\n* Stainless steel Ruler\n* Tape measure\n* Swanson Speed Square\n* SHEARS, SCISSORS & CUTTERS:\n* Rebar cutter and bender\n* WELDING, BRAZING & SOLDERING:\n* ESAB Migmaster Pro\n* Bernzomatic Trigger Start Torch\n* Tillman Welders Gloves\nStep 1: Drawing, Measuring, and Cutting the Parts\nI referenced several images and pulled measurements to get the most life-like leg and leg segment to body (cephalothorax) and abdomen ratios. I then drew a rough sketch of the shape and layout of the Spiders.\nI then cut and bent all of the rebar spider parts. I have a spreadsheet calculator that helps with the rough ratios so the body parts will have the correct proportions. I'll try to make the spreadsheet available for anyone that wants to make a spider pumpkin.\nStep 2: Making the Fangs\nI used a piece of 1/4\" steel dowel to make the fangs. I chucked it into my drill press and carefully ground it to a point. I then heated the points an bent them on my anvil.", "286" ], [ "After they cooled I cut them to the correct size.\nStep 3: Assembling and Welding the Spider's Legs\nI started assembling the body of the spider and added the largest diameter round stock. I then went on to welding the legs. This process is more art than design. You have to play with the angles of the leg sections to make it look the way you like. As I welded each leg I laid it on the sketch to keep track of the location.\nStep 4: Welding the Fangs and Final Assembly\nI then tacked the two ball bearing together and added the 1/4\" bent fangs. After that I could move on to final assembly. I found it useful to have a chuck of steel to prop up the spider parts during welding. I added two spikes to the rear of the spider body to impale and hold the larger pumpkin that will eventually be the abdomen.\nStep 5: Adding the Pumpkins to Make the Illusion Complete\nThis is the fun part! Picking the pumpkins and displaying the spiders!", "276" ], [ "BANANA CANDLES MADE WITH PLASTER AND 3D PRINTING\nIntroduction: BANANA CANDLES MADE WITH PLASTER AND 3D PRINTING\nI saw this weird banana candleholder somewhere on the internet and I failed to save it, so I was forced to make my own version.\nThis candle/candle holder consists of two parts- top part is candle and bottom part is plaster. If you plan on actually lighting the candle, you can save the 3D printed mould and make more candles in the future.\nI'm also showing an example on how to use MOLD setting in CURA and how to cast plaster in 3D printed moulds.\nSupplies\n* 3D PRINTER\n* PLASTER OF PARIS/GYPSUM/CEMENT (OPTIONAL)\n* CANDLE WAX, WICKS\n* SANDING PAPER, SCALPEL, FILLER/PUTTY, DISPOSABLE GLOVES\n* BRUSHES, ACRYLIC PAINTS, TOUGH EXTERIOR VARNISH\nStep 1: BANANA CANDLE MODEL\nI used https://www.thingiverse.com/thing:3664845 as a base for my banana, tweaked it roughly to thicken the peeled sides and added an exposed banana part. Both pieces are overlocking, candle part will fit seamlessly within the plaster part.\nStep 2: LOWER BANANA MODEL\nStep 3: LOWER BANANA PART - PLA COVERED IN PLASTER\nThis part can be printed as you'd normally do and then processed. So, sanding, filler, paint, varnish, as usual.\nI was dead set on using plaster to try and recreate some rough plaster texture and I decided to experiment with covering PLA print with a layer of plaster.\nOnce I printed it in PLA (not a good quality print, 0.3mm layer height, 15% infill, 3 walls...mainly to save time, I had other projects waiting to be printed), I covered it in a thin layer of plaster. I wasn't too optimistic, plaster usually doesn't stick to plastic, but somehow it turned out alright.\nFirst, I used a sanding paper (40 grit) to rough the print up. Then, I mixed a small amount of plaster of Paris (reinforced plaster) to the consistency of heavy cream and used a disposable brush to apply it all over the print. I let it dry, sanded it and added second layer before sanding again.\nStep 4: LOWER BANANA PART- PLASTER CAST Part1\nThere is a magical feature in CURA, that allows you to make moulds (or molds). I have no idea what the intended purpose of this setting is, but I've been using it to print moulds of busts and statues, flower pots and really, anything that could be cast in plaster.\nAll you have to do is go to settings in cura and type MOLD to see your options.", "74" ], [ "Click all available options and you are ready to experiment with moulds.\nHere are some tips:\n-It takes about 2x longer to print a part in mold setting than in normal setting.\n-Print with thin walls- 1-2 walls, but preferably just a single wall\n- You have to print with an infill, depending on the size and shape of your part, you will have to use between 5 and 15%. You can't print without it, it will be too flimsy and plaster will cause the plastic mould to bulge.\n-Pay attention to retraction settings, you don't to end up with stringy parts, especially on the inside, where plaster will go.\n-Certain shapes will require supports. This again will have to be closely monitored. Wrong settings like wrong overhang angle or support placement can mess your print. Basically, you don't want supports being printed inside the mould in places where you won't be able to remove them.\nStep 5: LOWER BANANA PART- PLASTER CAST Part2\nOnce it's printed, take a look inside and make sure there are no holes stringy bits. If necessary, clean it as much as possible, remove supports and if you have any holes, cover them with filler or putty. There shouldn't be any holes if the print is good quality and your printer is well calibrated.\n-Mix plaster (or cement) with water and pour it into the mould.\n-This part had some small, tight places, so I poured plaster into a piping bag, taped a short length of plastic straw to the tip and used this contraption to pour plaster into all those tiny holes.\n-Leave it to set. I can't stress it enough- leave it for days.", "254" ], [ "Handmade Walnut and Steel Ring\nIntroduction: Handmade Walnut and Steel Ring\nI decided to make this ring when I found some old hardwood scraps in a corner that I may or may not have liberated from the woodshop at my high school. I've tried my hand at creating rings of various sorts, but this has been my favorite because of its elegance and simplicity, as well as its far greater durability than purely wooden rings.\nSupplies\nBare minimum:\nAny Type of Hardwood\nCoarse, Round File\nSheet Metal (18-20 will do)\nSheet Metal Snips\nSaw (coping is best, but any will do in a pinch)\nVise/Clamp\nSolder/Heat (torch, soldering iron, etc.)\nSandpaper of Increasing Grit (I used 150 to 1500)\nDrill\nBits\nOptional:\nLacquer/Superglue/Oil (Finish)\nCost: Totally Free!\nIf your'e like me and hoard small scraps for some unknown future project, you're set for this! If not, you can go to Home Depot and snag a couple of hardwood floor samples, which are a great source of free hardwood and also happen to be a very good thickness for this project. There is no need to buy additional tools for this, since you can make do with practically anything you have.\nStep 1: Supplies\nBare minimum:\nAny Type of Hardwood\nCoarse, Round File\nSheet Metal (18-20 gauge will do)\nSheet Metal Snips\nSaw (coping is best, but any will do in a pinch)\nVise/Clamp\nSolder/Heat (torch, soldering iron, etc.)\nSandpaper of Increasing Grit (I used 150 to 1500)\nDrill\nBits\nOptional:\nLacquer/Superglue/Oil (Finish)\nRing Sizers\nRing Sizing Mandrel\nFlux (Very helpful)\nJewelry Mallet\nStep 2: Rough Cut and Shape Wood\nBegin by cutting a circle from your wood of choice (I used walnut). Make this significantly wider than the final ring, since you will lose material as you refine.\nNext, widen the hole in the middle to the point that you can get the file in. Begin filing until the hole is wide enough for the finger you will put the ring on, then stop.\nThe piece of wood I used was far thicker than I wanted the final product to be, so I cut it down to slightly wider than the final width of the ring.\nPro Tip: Wrap a piece of coarse sandpaper around a drill bit. Tape the inside edge lightly to the bit itself, so the paper doesn't slip. You can use this assembly to widen the inside of the ring faster and more accurately than with a file. Of course, if you have the correct size drillbit, this isn't necessary.\nStep 3: Cut and Shape Metal Lining\nCut a strip of your sheet metal a little wider than your ring and just long enough to perfectly fit your finger when bent into a perfect cylinder.", "582" ], [ "If you know your ring size, then you can use the attached chart to find the approximate length of your metal strip.\nForm the strip into a perfectly circular shape the exact size you want the final lining to be, but DO NOT SOLDER yet. bend the edges of the strip in so that the metal forms a D shape, so that the raw edges are aligned on the same plane. Apply flux and solder edges.\nIf you have a ring sizing mandrel, put the soldered loop on and hammer to a circular shape. I did not use a ring sizer for this project, instead I clamped a small piece of round stock that fit just inside the ring and hammered the loop round. Ideally you should use a small rubber mallet for this step, so you don't put dents in the finished shape.If you don't have anything like this, then you can place several layers of tape over the head of a claw hammer or a ball-peen hammer, which will achieve essentially the same effect. Your solder may split during this step, if it does, bend the ring back into the D shape and resolder. The purpose of this it to join the two ends snugly to each other, which makes a stronger solder join. Basically, the ends should meet each other like this || and not like this \\ /. The first is stronger because the solder joins the ends, but in the second you are relying on solder to fill the gap between the ends, and solder is much weaker than the steel itself.\nStep 4: Fit Metal Lining to Wood\nTake your nicely rounded metal strip, and begin VERY CAREFULLY sanding the inside of the wooden section to fit snugly around the metal ring.", "981" ], [ "Artist Stool Made From Reclaimed Materials.\nIntroduction: Artist Stool Made From Reclaimed Materials.\nI made this stool from reclaimed materials as part of an Industrial Design Project at the University of Johannesburg. The importance of the stool as a piece of furniture in the studio or workshop needs to be a form that inspires or stimulates creativity and design. The objects around us while we create have an impact on the work we produce.\nWARNING\nThis project uses dangerous tools and materials, only do what you are comfortable with and under correct supervision. Woodwork and metalwork are dangerous, wear a thick leather apron, Gloves ( When suitable), Hearing protection, a face shield AND eye protection. The aluminium casting releases many toxic fumes and may often spray molten aluminium unpredictably as the gas escapes from the mould. Make sure to wear full PPE and only 100% cotton clothing and thick closed boots.\nThis project used a wide variety of materials and tools to create. There are many alternatives available this is just what I had access to and am comfortable using.\nMaterials:\n1. Seat and legs\n2. Oregon Pine floorboards (Old pallets could also work well)\n3. Old woollen jersey for cushion Variety of foams (yoga mats, electronic packaging and upholstery foam all work well)\n4. Second-hand cork samples for padded feet\nJoint\n1. Used Aluminium Cans and broken Window frames\n2. Rebar or other metal rods\n3. 3D printing filament\n4. Lots and lots of small nuts and bolts\n5. A small Tub of vaseline\n6. Beeswax ( Can be remelted and reused afterwards)\n7. Plaster of Paris, <PERSON> and water for the lost wax mould\nOther materials\n1. 500ml cold glue\n2. 2 part epoxy ( Longer cure time means a stronger joint)\n3. Very long wood dowels and shorter ribbed dowels for joining the strips of wood together\n4. Sandpaper ( 110, 220, 400 and 600 grit )\nTools and equipment\nSeat and legs\n1. Table saw\n2. Band saw\n3. Oscillating drum sander\n4. Jig Saw\n5. Palm Sander\n6. Belt sander\n7. As many clamps as you can buy, and then some\n8. Craft knife\n9.", "787" ], [ "Ruler\n10. Measuring tape\n11. Superglue\n12. Masking tape\n13. Vernier\n14. Drill press\n15. Long 8mm drill bits\n16. Hammer\n17. Nails\nCushion\n1. Seam ripper\n2. Crochet hook\n3. Scissors\n4. Patience\n5. Time\n6. More patience\nJoint moulding\n1. 3D printer ( Local Makerspace)\n2. Stove\n3. Pot of boiling water\n4. Small oven to melt out beeswax ( Apparently you can use a regular cooking oven but I wouldn't risk it )\n5. Sand\n6. Buckets\nJoint Casting\n1. Homemade foundry ( I will eventually make another instructable)\n2. Crucible\n3. Homemade casting tools ( Long spoons, tongs etc)\nStep 1: Photos of the Stool\nStep 2: Detail Photos\nStep 3: Technical Drawings\nHere are a series of technical drawings I created from 3D models that I made in Solidworks.\nStep 4: Sourcing Materials\nStep1: Sourcing materials\nThis project was made from reclaimed materials and as such they must be found. Building sites are fantastic sources for old wood and Aluminium. Window frames are regularly thrown away when damaged and are easy to find, bring a magnet (Al is non-magnetic) to make sure you are not picking up another material. Reclaimed wood often has nails or staples in it so be very careful when cutting and working with it. Second-hand stores often sell cheap or free jerseys with holes in them which are perfect for the cushion, alternatively check in your closet and you might be in luck.\nStep 5: Aluminium Joint 3D Mould\nThe joint was first modelled in SolidWorks (3D modelling software) and using various features ( Shell, extrude and mould) I created a three-part mould. I made it so that each part is identical so it is much easier to 3D print. Using a 3D printer at my university I was able to print the parts in three different colours of PLA.\nSpray a clear coat on each mould part and add a THICK layer of Vaseline to all of the parts.\nAttach the mould together using nuts and bolts and then melt beeswax in a pot of boiling water and pour into the mould when liquid.", "220" ] ]

[ 8063, 5688, 7398, 5543, 2361, 9145, 5926, 9376, 3365, 10102, 4470, 2223, 4011, 8867, 10057, 4052, 10808, 6567, 8089, 4936, 1983, 637, 592, 10833, 1756, 2677, 2933, 1759, 4616, 11175, 8164, 2885, 4760, 8745, 6449, 5265, 5127, 8009, 2603, 4622, 982, 4194, 6712, 6612, 5907, 9447, 8230, 9647, 4881, 1493, 5667, 9284, 6566, 6528, 6935, 2175, 9434, 8578, 6863, 10060, 1844, 2627, 7585, 3207, 7113, 4792, 7923, 4814, 1437, 2163 ]

[ [ "How to add more theta parameters into my logistic regression?\nI am a complete beginner in machine learning and coding in python. I have been tasked with coding logistic regression from scratch in comparison with using sklearn. My question is, with my code below I believe I have set the number of thetas I want with:\n\"X = data[['texture_mean','perimeter_mean','smoothness_mean','compactness_mean','symmetry_mean', 'diagnosis']]\"\nbut I am unsure how to prove this is true with my code below and its definition of theta, if I added more parameters (e.g. all 31 variables of this dataset [https://www.kaggle.com/uciml/breast-cancer-wisconsin-data] which is for classifying tumours) would I just need to add them into this list above? Any help pointing me towards the right direction just to understand this better would be appreciated.\nX_train,X_test,Y_train,Y_test = train_test_split(X,Y,test_size=0.3)\nX = data[\"diagnosis\"].map(lambda x: float(x))\nX = data[['texture_mean','perimeter_mean','smoothness_mean','compactness_mean','symmetry_mean', 'diagnosis']]\nX = np.array(X)\nX = min_max_scaler.fit_transform(X)\nY = data[\"diagnosis\"].map(lambda x: float(x))\nY = np.array(Y)\ndef Sigmoid(z):\nif z < 0:\nreturn 1 - 1/(1 + math.exp(z))\nelse:\nreturn 1/(1 + math.exp(-z))\ndef Hypothesis(theta, x):\nz = 0\nfor i in range(len(theta)):\nz += x[i]*theta[i]\nreturn Sigmoid(z)enter preformatted text here\ndef Cost_Function(X,Y,theta,m):\nsumOfErrors = 0\nfor i in range(m):\nxi = X[i]\nhi = Hypothesis(theta,xi)\nerror = Y[i] * math.log(hi if hi >0 else 1)\nif Y[i] == 1:\nerror = Y[i] * math.log(hi if hi >0 else 1)\nelif Y[i] == 0:\nerror = (1-Y[i]) * math.log(1-hi if 1-hi >0 else 1)\nsumOfErrors += error\nconst = -1/m\nJ = const * sumOfErrors\nprint ('cost is: ', J )\nreturn J\ndef Cost_Function_Derivative(X,Y,theta,j,m,alpha):\nsumErrors = 0\nfor i in range(m):\nxi = X[i]\nxij = xi[j]\nhi = Hypothesis(theta,X[i])\nerror = (hi - Y[i])*xij\nsumErrors += error\nm = len(Y)\nconstant = float(alpha)/float(m)\nJ = constant * sumErrors\nreturn J\ndef Gradient_Descent(X,Y,theta,m,alpha):\nnew_theta = []\nconstant = alpha/m\nfor j in range(len(theta)):\nCFDerivative = Cost_Function_Derivative(X,Y,theta,j,m,alpha)\nnew_theta_value = theta[j] - CFDerivative\nnew_theta.append(new_theta_value)\nreturn new_theta\ndef Logistic_Regression(X,Y,alpha,theta,num_iters):\nm = len(Y)\nfor x in range(num_iters):\nnew_theta = Gradient_Descent(X,Y,theta,m,alpha)\ntheta = new_theta\nif x % 100 == 0:\nCost_Function(X,Y,theta,m)\nprint ('theta: ', theta)\nprint ('cost is: ', Cost_Function(X,Y,theta,m))\ninitial_theta = [0,1]\nalpha = 0.01\niterations = 1000\nLogistic_Regression(X,Y,alpha,initial_theta,iterations)", "422" ], [ "How to add bias consideration into logistic regression code?\nI am a complete beginner in coding and machine learning, and I've been tasked with learning what's under the hood of logistic regression (so I have pieced together the python code below) but I've been asked to figure out how to add bias into this code. I'm completely stuck on at what point it would need to be added into, I think at the point I am defining the hypothesis function - but if anyone would be able to point me in the right direction to figure this out I would really appreciate it.\nIf it helps, this logistic regression is being used to classify if a tumour is benign of malignant with the wisconsin breast cancer dataset (https://www.kaggle.com/uciml/breast-cancer-wisconsin-data)\nX_train,X_test,Y_train,Y_test = train_test_split(X,Y,test_size=0.3)\nX = data[\"diagnosis\"].map(lambda x: float(x))\nX = data[['texture_mean','perimeter_mean','smoothness_mean','compactness_mean','symmetry_mean', 'diagnosis']]\nX = np.array(X)\nX = min_max_scaler.fit_transform(X)\nY = data[\"diagnosis\"].map(lambda x: float(x))\nY = np.array(Y)\ndef Sigmoid(z):\nif z < 0:\nreturn 1 - 1/(1 + math.exp(z))\nelse:\nreturn 1/(1 + math.exp(-z))\ndef Hypothesis(theta, x):\nz = 0\nfor i in range(len(theta)):\nz += x[i]*theta[i]\nreturn Sigmoid(z)enter preformatted text here\ndef Cost_Function(X,Y,theta,m):\nsumOfErrors = 0\nfor i in range(m):\nxi = X[i]\nhi = Hypothesis(theta,xi)\nerror = Y[i] * math.log(hi if hi >0 else 1)\nif Y[i] == 1:\nerror = Y[i] * math.log(hi if hi >0 else 1)\nelif Y[i] == 0:\nerror = (1-Y[i]) * math.log(1-hi if 1-hi >0 else 1)\nsumOfErrors += error\nconst = -1/m\nJ = const * sumOfErrors\nprint ('cost is: ', J )\nreturn J\ndef Cost_Function_Derivative(X,Y,theta,j,m,alpha):\nsumErrors = 0\nfor i in range(m):\nxi = X[i]\nxij = xi[j]\nhi = Hypothesis(theta,X[i])\nerror = (hi - Y[i])*xij\nsumErrors += error\nm = len(Y)\nconstant = float(alpha)/float(m)\nJ = constant * sumErrors\nreturn J\ndef Gradient_Descent(X,Y,theta,m,alpha):\nnew_theta = []\nconstant = alpha/m\nfor j in range(len(theta)):\nCFDerivative = Cost_Function_Derivative(X,Y,theta,j,m,alpha)\nnew_theta_value = theta[j] - CFDerivative\nnew_theta.append(new_theta_value)\nreturn new_theta\ninitial_theta = [0,1]\nalpha = 0.01\niterations = 1000\nLogistic_Regression(X,Y,alpha,initial_theta,iterations)", "422" ], [ "How to interpret a specific feature importance?\nApologies for a very case specific question. I have a dataset of genes, with which I am using machine learning to predict if a gene causes a disease. One of the features I have is a beta value (which is the effect size of the gene's impact on the disease), and I'm not sure how best to interpret and use this feature.\nI condense the beta values from the variant level to the gene level, so a gene is left with multiple beta values like this:\nGene Beta ACE -0.7, 0.1 ,0.6 NOS 0.2, 0.4, 0.5 BRCA -0.1 ,0.1, 0.2\nCurrently I am trying 2 options of selecting a single beta value per gene, one where I select the absolute value per gene (and ignore whether it was a previous negative value) and another where I select the absolute value and return the previous negative numbers back to being negative.", "655" ], [ "I am trying this as for beta values a postive or negative direction indicates the size of the effect a gene has on the disease, so I would think it's important to retain the negative information (as I understand it).\nHowever, I've been advised to use just the absolute values with not retaining negative status, and I'm not sure if there's a way for me to know if one option is better than the other from the machine learning perspective. I am also having a problem in either case where my model values this feature as much more important than any other feature in my dataset. For example gradient boosting gives this an importance of 0.01, the next most important feature is at 0.001.\nSo my question is, how best can I interpret a highly important feature like this? If it is much more important is it actually a bias and is it likely due to my own handling/preprocessing of the feature or is it acceptable that is it just very important? Would it be possible for me to set my model to re-weight the importance of this particular feature? I have a biology background so not sure what is the normal or least biased approach.", "655" ], [ "Encog neural network multiple outputs\nI am a little confused with using encog to create a neural network.\nI am trying text classification with a basic feed forward network. For the input data I have 200 unique words (features/inputs) to input into the network and 100 different pieces of text. so I have a matrix of 100x230, essentially 100 different training items each with the frequency of 230 words. I then have an output which classifies the data as A, B, C, D or E, so one column and 5 different outputs, therefore this is an ordinal column and is part of the CSV data set I read in thus I actually have a matrix of 100X231 where the 231 column is the output I desire to classify.\nI can train and run this neural network no problem but I am confused about the number of output neurons to have.", "458" ], [ "I would have thought there are 5 different classifications therefore I should have 5 different neurons, however I can't setup the code like that, as it complains:\nIMLDataSet trainingSet = new BasicMLDataSet(input, ideal);\nMy input variable is a double[100][230] and the ideal is just the column of expected classifications so double[100][1]. Because I only have one column and the data is normalised those A,B,C... values are turned into numbers between -1 and 1 and therefore when I run the neural net with 5 output neruons it complains that it should be only 1.\nWhen I run the neural net with one neuron output it gives me what looks like correct and accurate answers but the value it gives is between -1 and 1. I am assuming the activation level is being matched to the output?\nMy question therefore is either how to denormalise this output to get back to my actual letter classification or how to use 5 neurons on the output so the network chooses the appropriate classification.\nMy neural network is as follows:\nBasicNetwork network = new BasicNetwork();\nnetwork.AddLayer(new BasicLayer(null, true, 230));\nnetwork.AddLayer(new BasicLayer(new ActivationTANH(), true, 16));\nnetwork.AddLayer(new BasicLayer(new ActivationTANH(), false, 1));\nnetwork.Structure.FinalizeStructure();\nnetwork.Reset();", "458" ], [ "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" ], [ "Creating a complex featureset for regression modeling\nI am currently working a on project that requires me to convert all of the categorical variable to continuous (or binary) variables to build a regression model. The problem is that I am more than 100 categorical values and all of them have different measures. For example, let's say that users who have different types of cars and all of those car models have associated continuous variables such as the price of the cars, size of gas tank, avg price of the gas to fill the gas tank and etc. Here is the example of this dataset below:\n| user | car_make| car_model| price| gas_tank| full_gas_tank_price| | -------- | -------------- |----|--|--| --| | 123_a | Honda | civic| 17000| 12| 19| | 345_b | Lexus | RX| 45000| 16| 35|\nOne way to rebuild this featureset to only contain continuous variables is have the car_make and car_models as columns that each could contain the price, gas_tank and full_gas_tank_price values. For example:\n| user | Honda_price| honda_gas_tank| honda_full_gas_tank_oprice| Lexus_price| Lexus_gas_tank| Lexus_full_gas_tank_price| | -------- | -------------- |----|--|--| --|--| | 123_a | 17000 | 12| 19| 0| 0|0| | 345_b | 0 | 0| 35| 45000| 16|35|\n(I have not included the columns for civic model and RX model because the table is going to be wide). So, if I create the table like above, the table is going to include too many columns.", "856" ], [ "Becuse for each car_make and also car_model, there are 3 different features. So, I decided to create my featureset in a way that all of the car_make and car_models are binary variables and then have other continuous features as they are. Here is the example of the table:\n| user | Honda| Lexus| civic| RX| price| gas_tank| full_gas_tank_price| | -------- | -------------- |----|--|--| --| --|--| | 123_a | 1 | 0| 1| 0| 17000| 12|19| | 345_b | 0 | 1| 0| 1| 45000| 16|35|\nThis sounded reasonable to me because I would have less features, hence, better performance. However, I was a bit worried that it would affect the model's accuracy because this table does not specifically show the price of honda. Is just shows that the user has honda and then the price is on another column. What do you think?\n(I understand that I can potentially remove features that don't correlated with the output, but let's assume that all of the existing features correlate with the output but there are just too many of them)", "946" ], [ "Regression with Neural Networks in Tensorflow problem\nI have recently started learning Neural networks and Python. I am trying out linear regression for a dataset with 14 features and 1 outcome. I have divided the data into training and test data.", "458" ], [ "I have experimented with many parameters (learning rate, nodes per layer, number of layers, number of steps and optimization algorithm) but my test errors are as high as 150%.\nI have posted my code below along with the cost curve (cost vs epochs). It'll be of great help to me if some of you could go through the short code and let me know where I am committing a mistake and what to change. Or if you could please suggest some other important checks. I have added relevant comments as well.\nThank you!\nimport numpy as np\nimport matplotlib.pyplot as plt\nimport tensorflow as tf\n# importing features and observations data for training and validation\ntraining_filename_X = \"training_set_X.csv\"\ntraining_filename_Y = \"training_set_Y.csv\"\ntest_filename_X = \"test_set_X.csv\"\ntest_filename_Y = \"test_set_Y.csv\"\ntraining_features = np.loadtxt(training_filename_X, delimiter=',')\ntraining_observations = np.loadtxt(training_filename_Y, delimiter=',')\ntest_features = np.loadtxt(test_filename_X, delimiter=',')\ntest_observations = np.loadtxt(test_filename_Y, delimiter=',')\n# normalizing training data\ntraining_features_stddev_arr = np.std(training_features, axis=0)\ntraining_features_mean_arr = np.mean(training_features, axis=0)\nnormalized_training_features = (training_features-training_features_mean_arr)/training_features_stddev_arr\n# normalizing validation data with training set mean and standard deviation\nnormalized_validation_features = (validation_features-training_features_mean_arr)/training_features_stddev_arr\n# normalizing test data with training set mean and standard deviation\nnormalized_test_features = (test_features-training_features_mean_arr)/training_features_stddev_arr\n# layer parameters\nn_nodes_hl1 = 20\nn_nodes_hl2 = 20\nn_nodes_hl3 = 20\nno_features = 14\nlearning_rate = 0.01\nepochs = 200\ncost_history = np.empty(shape=[1], dtype=float)\nX = tf.placeholder(tf.float32)\nY = tf.placeholder(tf.float32)\n# defining weights for each layer taken from a normal distribution with variance 2/n\nhl1_weight = tf.Variable(tf.random_normal([no_features, n_nodes_hl1], stddev=np.sqrt(2/no_features)))\nhl2_weight = tf.Variable(tf.random_normal([n_nodes_hl1, n_nodes_hl2], stddev=np.sqrt(2/n_nodes_hl1)))\nhl3_weight = tf.Variable(tf.random_normal([n_nodes_hl2, n_nodes_hl3], stddev=np.sqrt(2/n_nodes_hl2)))\noutput_weight = tf.Variable(tf.random_normal([n_nodes_hl3, 1], stddev=np.sqrt(2/n_nodes_hl3)))\n# defining biases for each layer\nhl1_bias = tf.Variable(tf.random_uniform([n_nodes_hl1], -1.0, 1.0))\nhl2_bias = tf.Variable(tf.random_uniform([n_nodes_hl2], -1.0, 1.0))\nhl3_bias = tf.Variable(tf.random_uniform([n_nodes_hl3], -1.0, 1.0))\noutput_bias = tf.Variable(tf.random_uniform([1], -1.0, 1.0))\n# defining activation functions for each layer\nhl1 = tf.sigmoid(tf.matmul(X, hl1_weight) + hl1_bias)\nhl2 = tf.sigmoid(tf.", "422" ], [ "Why are the regions/decision boundaries overlapping with multi-class classification using SVM in sci-kit?\nI am using the SVM in scikit-learn library for doing multiclass classification. I am wondering why these regions (decision boundaries) are overlapping (as seen in the picture below)?\nCould someone please explain the difference between whether I do one-vs-one or one-vs-all in terms of the regions overlapping? I assumed one-vs-one would have clearly delineated regions with no overlap since it's maximizing the margin against each other class and that one-vs-all could have regions overlapping, but perhaps this is inaccurate because 3 of the 4 models I am training are one-vs-one, and they show overlapping regions.\nI've considered maybe it's a plotting issue as well, but could not determine any issues.", "392" ], [ "If the alpha is 1, then the regions no longer overlap, but I assume this is expected since it's just covering up the other regions it overlays (which is to be expected and doesn't solve the problem).\nHere is the function which creates, trains, and plots 4 different SVM models #(3 different kernels using SVC and 1 with LinearSVC).\ndef createSVMandPlot(X,y,x_name,y_name):\nh = .02 # step size in the mesh\n# we create an instance of SVM and fit out data. We do not scale our\n# data since we want to plot the support vectors\nC = 1.0 # SVM regularization parameter\nsvc = svm.SVC(kernel='linear', C=C).fit(X, y) #1 vs 1\nrbf_svc = svm.SVC(kernel='rbf', gamma='scale', C=C).fit(X, y) #1v1\npoly_svc = svm.SVC(kernel='poly', degree=3, gamma='scale',C=C).fit(X, y) #1v1\nlin_svc = svm.LinearSVC(C=C).fit(X, y) #1 vs rest\nprint(str(x_name)+' vs. '+str(y_name))\nfor i, clf in enumerate((svc, lin_svc, rbf_svc, poly_svc)):\nX_pred=clf.predict(X)\nX_pred1=np.asarray(X_pred).reshape(len(X_pred),1)\nA=confusion_matrix(X_pred1, y)\nprint(A)\nc=0\nfor r in range(len(X_pred)):\nif X_pred[r]==y[r]:\nc+=1\nprint(str(c)+' out of 34 predicted correctly (true positives)')\n=============================================================================\nwith warnings.catch_warnings():\nwarnings.filterwarnings(\"ignore\")\n=============================================================================\nx_min, x_max = X[:, 0].min() - 1, X[:, 0].max() + 1\ny_min, y_max = X[:, 1].min() - 1, X[:, 1].max() + 1\nxx, yy = np.meshgrid(np.arange(x_min, x_max, h),\nnp.arange(y_min, y_max, h))\n# title for the plots\ntitles = ['SVC w/ linear kernel',\n'LinearSVC (w/ linear kernel)',\n'SVM w/ RBF kernel',\n'SVM w/ poly(degree 3) kernel']\nplt.pause(7)\nfor i, clf in enumerate((svc, lin_svc, rbf_svc, poly_svc)):\n# point in the mesh [x_min, x_max]x[y_min, y_max].\nplt.subplot(2, 2, i + 1)\nplt.subplots_adjust(wspace=0.4, hspace=0.4)\nZ = clf.predict(np.c_[xx.ravel(), yy.ravel()])\n# Put the result into a color plot\nZ = Z.reshape(xx.shape)\nplt.contourf(xx, yy, Z, alpha=.5)\n# Plot also the training points\nplt.scatter(X[:, 0], X[:, 1], s=13,c=y)\nplt.xlabel(x_name)\nplt.ylabel(y_name)\nplt.", "392" ] ]

[ 10157, 6172, 1558, 6768, 6482, 3765, 11314, 1669, 6164, 9773, 6348, 4703, 697, 1345, 5096, 1220, 10974, 3892, 1831, 2928, 4890, 585, 7709, 5190, 1122, 3446, 6081, 1223, 3246, 7056, 5306, 4192, 3928, 9324, 7148, 4514, 74, 9234, 10110, 8537, 7245, 2410, 10549, 4633, 10905, 4620, 3717, 7754, 10174, 5194, 8302, 6146, 6663, 6488, 6668, 111, 6814, 5050, 9562, 8370, 9894, 10251, 4659, 7041, 5138, 3428, 7268, 5268, 10965, 4847 ]

[ [ "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" ], [ "Diffusion across an interface and conservation of mass.\nI am reading a physiology book chapter (Mathematical Physiology, by Keener --Respiration chapter) about the gas exchange between capillaries and alveoli. It seems that this gas exchange can be modeled after some simple physical relationships. Since I am not usually studying physics, I do not fully understand some concepts that the author uses to derive a conservation law and I would appreciate any help.\nI do admit, however, that this question may be off-topic since it could be a mathematical lapsus rather than a physics question.\nPreliminaries\nFirst, the author indicates that if a gas with partial pressure $P_g$ is in contact with a liquid, the steady-state concentration $U$ of gas is given by: $$ U = \\sigma P_s $$\nwhere $\\sigma$ is the solubility of the gas in the liquid. I assume that this is a particular version of Henry's Law.\nThen, it explains if there is a difference between the partial pressure of the gas ($P_g$) and the partial pressure on the fluid ($\\frac{U}{\\sigma}$), then there should be some flux between the gas and the fluid and the simplest model would be to assume that this flux is linearly proportional to the pressure difference: $$ q = D_s \\left(P_g - \\frac{U}{\\sigma}\\right) $$\nProblem\nThe author then considers a segment of a capillary (a cylindrical tube) of length $L$, constant cross-sectional area $A$ and perimeter $p$, that is in contact with a gas with partial pressure $P_g$.", "453" ], [ "The fluid moves through the tube with a velocity $v(x)$. Finally, they say that since mass is conserved: $$ \\frac{d}{dt} \\left( A \\int_{0}^{L} U(x,t) dt \\right) = v(0)AU(0,t) - v(L)AU(L,t) + p \\int_{0}^{L} q(x,t) dx $$\nQuestion\nHow is the relationship below derived?\nI understand that $A \\int_{0}^{L} U(x,t) dt$ is in fact the total amount of the dissolved gas in the tube at a given time. I also understand how $\\int_{0}^{L} q(x,t) dx$ represents the total flux of gas across the whole capillary wall. However, I fail to see what the two first elements of the right-hand represent and why is the left-side derived with respect to $t$.", "453" ], [ "How does $dS \\ge 0$ imply a system cannot receive more energy than work supplied?\nI am reading a book that asserts the following:\n\"The second law arises from an equation of the form (Eqn 1)\n$$dS = \\mu\\,dE + \\mu\\,dW $$\nwhere $dS$ is the change in entropy, $dE$ the change in system energy, and $-dW$ is the work done externally on the system. Thus the second law expressed as $dS \\ge 0$ simply asserts that the system cannot receive more in energy than the amount of external work supplied.\"\nI am confused by this. I know we normally have something like (Eqn 2)\n$$dU=T\\,dS-dW$$\nwhere $U$ is internal energy, $dW$ is work done by the system, $T$ is temperature. This makes sense to me.", "749" ], [ "The gain of internal energy is equal to energy flowing in as heat ($T\\,dS$ is positive if heat is flowing in) less the energy flowing out as work ($dW$ is positive if the system is doing work).\nWe can get Eqn 1 from Eqn 2, if we write $U \\to E$, $\\frac{1}{T} \\to \\mu$ and take the $dW$ to the other side. Furthermore, $dW$ in Eqn 2 is the work done by the system, so it is correct to say, with respect to Eqn 1, that $-dW$ is the work done on the system.\nSo Eqn 1 looks fine. The use of $dS \\ge 0$ as a statement of the second law of thermodynamics also looks fine.\nIf we then call the work done on the system $dW'$ so that $dW=-dW'$, we can write Eqn 1 as (Eqn 3)\n$$dS=\\mu\\,dE-\\mu\\,dW'$$\nIf we then assert that $dS \\ge 0$, this implies that\n$$\\mu\\,dE-\\mu\\,dW'\\ge0$$\nwhich implies that $dE \\ge dW'$, i.e. the system must receive more energy than the external work supplied. Not only is this contrary to the statement of the book, but it does not make sense.\nSo how do starting points that make sense lead to something that does not make sense?\nI believe it is something to do with the fact that the $dS$ in Eqn 1 refers to the entropy of the system, while the $dS$ in $dS \\ge 0$ refers to total entropy of system plus surroundings.\nAm I correct that the book is confusing these and leaving out some steps in the argument, so that, as written, it doesn't make sense? Or is the book perfectly correct, and it is me that is missing something?", "749" ], [ "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" ], [ "Impulse and momentum on a system of three particles (equilateral triangle)\nI found this exercise on a textbook which provided solely the description of what is happening and the answers with little explanation. The solution being provided, I am mostly interested in understanding what is happening. Consider the following system composed of three particles, each of mass $m$, connected by rigid massless rods in the form of an equilateral triangle. The system is initially at rest (particle $A$ is above particle $B$ in the initial state). An impulse $\\hat{F}$ is applied to $A$, causing the particle $B$ to slide without friction on a supporting base.\nThe idea is to solve for the values of $\\dot x$ and $\\dot \\theta$ velocities immediately after the impulse; and evaluate the constraint impulse $\\hat{N}$.\nMy initial idea was to use the linear impulse, focusing in the $x$ direction first.", "512" ], [ "Since particle B will be sliding, the linear acceleration of the system would be $3m\\ddot x$. By taking particle B as the reference point, and since the system center of mass would be engaged in an arc motion, its acceleration $x$ component (tangential) directly after the impulse would be $ml\\sqrt{3}\\ddot\\theta$ (the radius would be $l/\\sqrt{3}$).\nSo the impulse would be $\\hat{F}=3m\\dot x+ml\\sqrt{3}\\dot \\theta$.\nBut the textbook solution indicates that $\\hat{F}=3m\\dot x+\\frac{3}{2}ml\\dot \\theta$.\nSo my first problem is: where does the $\\frac{3}{2}$ comes from? Or am I working this completely wrong?\nUpon seeing this solution I wondered if perhaps this $\\frac{3}{2}ml\\ddot \\theta$ tangential component of angular acceleration would be the result of the addition of an $l/2$ radius (along the vertical axis) which would be the vertical distance towards particle C from B; plus the $l$ radius which would be the vertical distance towards particle $A$; multiplied by $\\ddot \\theta$. Which would result in a \"tangential\" component along the $x$ axis of $\\frac{3}{2}ml\\ddot \\theta$. Would this be an acceptable proposition?\nMy idea was then to state the angular impulse as the variation of the angular momentum, resulting in the multiplication of $\\hat{F}$ by the distance between particle $B$ and the center of mass: $l/\\sqrt{3}$. This way I would end up with a system of two equations and two variables and solve for $\\dot x$ and $\\dot \\theta$.\nOnly, again the solution provided is rather far from my idea because it states that $\\hat{F}l = \\frac{3}{2}ml\\dot x + 2ml^2\\dot \\theta$. And I see little relationship with the linear impulse equation.", "101" ], [ "Cooling of a surface due to fluid passing over it\nI am working on a project that requires me to measure the cooling effect of a liquid flowing through a surface. In order for me to effectively calculate the cooling effect, the solution of the below problem will be very helpful to me.\nThe surface that is being cooled by a liquid is rectangular in shape, with a length $a$ and a breadth $b$. It is being cooled by a continuously flowing mass of liquid with a height $l$ flowing across the surface with a constant velocity $v$. A lot of heat is being generated below the surface, so the surface can be assumed to be at a constant temperature $T_h$ all along the rectangle. The liquid that is being pumped in to cool the surface is initially at a temperature $T_0$, and as it picks up heat from the surface, its temperature slowly increases as it flows out.", "707" ], [ "The thermal conductivity of the liquid is $\\kappa$ and has a heat capacity per unit mass of $C$ and density of $\\rho$.\nI have tried solving the problem as follows:\nSince the problem involves the flowing of the liquid at different time instants, I would like to instead simplify the calculations involved by considering a stationary pool of liquid with a height $l$ on the surface with temperature $T_h$ and area $A$. The liquid has a temperature of $T_0$ at $t=0$ and if I am able to solve for $T(x,t)$, where $x$ is the vertical height above the surface and $t$ is the time. I am using this as a simplification of the original problem, where the time $t$ corresponds to the position of the liquid as it flows along the rectangle. Thus, $t=\\frac{a}{v}$ corresponds to the liquid that is flowing out at the end of the surface. I know that this is an approximation (as this calculation will neglect the heat conduction through the liquid, along the length of the rectangle), but since the liquid in my case moves with a good speed $v$, and has a small thickness $l$, so I feel that I am justified in making the approximation.\nNow, for my solution:\n(Note: I am taking $x$ to be the distance along the vertical, ie., along the height of the liquid layer, $t$ to denote the time since the initial condition, and Q(x,t) to be the rate of flow of heat through a cross section of the liquid)\nThe conduction equation: \\begin{equation} \\kappa A \\frac{\\partial T}{\\partial x}= Q(x,t) \\end{equation}\nNow, for accounting for the absorption of heat by the differential layers of the liquid: \\begin{equation} dQ=-\\rho AC\\frac{\\partial T}{\\partial t}dx \\end{equation}\nSince all the heat current passing through a given cross section is used up in heating the layers above it, \\begin{equation} \\int_{x}^{l}\\rho A C \\frac{\\partial T}{\\partial t}= \\kappa A \\frac{\\partial T}{\\partial x} \\end{equation}\nTaking the partial derivative of the above equation wrt $x$, \\begin{equation} -\\rho C \\frac{\\partial T}{\\partial t} = \\kappa \\frac{\\partial ^2 T}{\\partial x^2} \\end{equation}\nAfter this, I assume that the temperature is of the form $T_1 (x)T_2(t)$ (Is this assumption wrong? If so, can someone please help me solve the differential equation?)\nUsing the above, I get: \\begin{equation} -\\rho C \\frac{1}{T_2 (t)} \\frac{\\partial T_2 (t)}{\\partial t} = \\kappa \\frac{1}{T_1 (x)} \\frac{\\partial^2 T_1 (x)}{\\partial x^2} \\end{equation}\nSince they are functions of independent variables being equal to each other, they both must be a constant ($=\\lambda$).\nSolving the above, I get: \\begin{equation} T(x,t)=Ae^{\\sqrt{\\frac{\\lambda}{\\kappa}} x - \\frac{\\lambda t}{\\rho c}} \\end{equation} ($A$ is just a constant)\nand the boundary condition is that $T(x,0)=T_0$ for all $x$. However, from the form of the solution I have obtained, clearly such a boundary condition is not possible.", "707" ], [ "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" ], [ "Can you prove the interesting relation in equilibrium thermodynamics?\nProblem and background\nI noted the following interesting relation in a paper discussing the liquid-vapor phase change, in which it was given directly without any derivation and reference:\n$$d\\ln p^\\text{eq}_\\text{v}=\\frac{1}{ \\rho R T}dp+ \\frac{H}{RT^2}dT, \\quad (1)$$\nwhere $p^\\text{eq}_\\text{v}$ is the equilibrium vapor pressure of a liquid, $\\rho$ is the density of the liquid, $R$ is the gas constant, $T$ is the temperature, $H$ is the molar enthalpy. However, I really want to understand how the differential relation has been obtained.\nI have some basic knowledge of equilibrium thermodynamics and thought that Eq.(1) has a close relationship with the Gibbs-Duhem relation\n$$d \\mu=-sdT +\\nu dp, \\quad (2)$$ in which $\\mu$ is the chemical potential, $s$ and $\\nu$ are the molar entropy and volume, respectively.\nI also noted that Eq.(1) include the Clausius-Clapeyron (C-C) equation in this form:\n$$\\frac{d \\ln p^\\text{eq}_\\text{v}}{dT}=\\frac{H}{RT^2}. \\quad (3)$$ That is, the 2nd term on the right hand side (RHS) of Eq.(1) appears to be from the C-C equation.\nWhat I have tried\nI have tried to derive Eq.(1) along the following two directions.\n1. From Eq.(2), the chemical potential of vapor at equilibrium can be written as\n$$\\mu^\\text{eq}\\text{v}=\\mu^0\\text{v}+RT \\ln p^\\text{eq}_\\text{v}, \\quad (4)$$\nbecause $dT=0$ at equilibrium.", "749" ], [ "Here $\\mu^0_\\text{v}$ is a function of $T$ arising from integration. Plug Eq.(4) in (2)\n$$d \\mu^\\text{eq}\\text{v}=\\frac{d \\mu^0\\text{v}}{dT}dT+R(Td \\ln p^\\text{eq}\\text{v}+\\ln p^\\text{eq}\\text{v} d T)=-sdT +\\nu dp.$$\nSolving for $d \\ln p^\\text{eq}_\\text{v}$ yields\n$$d \\ln p^\\text{eq}\\text{v}=\\frac{1}{\\rho R T}dp+(-\\frac{s}{RT}-\\frac{1}{RT}\\frac{d \\mu^0\\text{v}}{dT}-\\frac{\\ln p^\\text{eq}_\\text{v}}{T})dT, $$ where $p=\\rho RT$ has been used. As you can see, I don't know how to reduce the terms in the parentheses to $\\frac{H}{RT^2}$.\n2. On the other hand, I tried to integrate Eq.(2) for vapor phase from a reference value to equilibrium value,\n$$\\int_{\\mu^\\star} ^ {\\mu_\\text{v} ^\\text{eq}} d \\mu=-\\int_{T^\\star}^{T_\\text{v}^\\text{eq}}s_\\text{v}dT +\\int_{p^\\star}^{p_\\text{v}^\\text{eq}}\\nu dp. \\quad (5)$$\nRecalling that $\\nu=\\frac{RT}{p}$ for vapor.", "374" ] ]

[ 6323, 1086, 9862, 9771, 204, 5349, 7815, 6334, 7189, 5828, 3346, 8358, 10452, 9765, 4722, 7546, 7719, 3581, 4831, 6157, 10133, 10828, 10490, 1375, 9786, 6907, 5117, 4174, 3082, 10647, 6961, 7460, 719, 5150, 8641, 1543, 2285, 4390, 2753, 132, 6686, 8386, 6300, 3292, 3160, 4389, 7593, 6029, 6492, 11322, 2785, 1774, 9662, 5192, 5355, 6995, 4952, 1347, 3938, 460, 8623, 11069, 7635, 10074, 7652, 9943, 5640, 1474, 1323, 9577 ]

[ [ "When using <PERSON> solvers to solve $\\mathbf A \\mathbf x = \\mathbf b$ systems, singularity in $\\mathbf A$ can be pretty benign as long as $\\mathbf b$ is consistent. Consider applying the conjugate gradient (CG) algorithm to a symmetric positive semidefinite $\\mathbf A$ (singular, but all non-zero eigenvalues still positive). Further assume $\\mathbf b$ is in the range of $\\mathbf A$, and we pick the initial guess to be $\\mathbf x = \\mathbf 0$. Then, the search vector/residual $\\mathbf r = \\mathbf b - \\mathbf A \\mathbf x$ will always be orthogonal to the nullspace of $\\mathbf A$ (because in CG, search vectors/residuals are always drawn by applying $\\mathbf A$ to previous residuals, and this multiplication by $\\mathbf A$ can't generate any component in the nullspace).", "768" ], [ "The algorithm can never \"sense\" the singularity of $\\mathbf A$, and will converge to the (unique!) $\\mathbf x$ such that $\\mathbf A \\mathbf x = \\mathbf b$ and $\\mathbf x \\perp \\mathrm {null}(\\mathbf A)$\nA short demo in matlab:\nclear all\nclose all\n% Form positive semidefinite A.\nN = 10;\n[Q,~] = qr(rand(N));\nD1 = linspace(1,N/2,N/2);\nD2 = zeros(1,N/2);\nD = diag([D1 D2]);\nA = Q*D*Q';\nkappa = cond(A) % infinite/singular\n% Form random b in range(A).\nb = A * rand(N,1);\n% Solve A*x=b using CG.\nx = pcg(A,b);\n% Check properties.\nresidual = norm(A*x-b)\nnullity = norm(x'*null(A))\nSimilar arguments can be made for other <PERSON> solvers, but I can't really speak to \"classical\" iterative solvers (Gauss-Seidel etc) .. I doubt they are as well-behaved.\nThere are preconditioning strategies (deflation) based entirely on this idea: find a basis for the eigenvectors of $\\mathbf A$ that are somehow problematic to the solver, then \"deflate\"/project them out (change the operator such that the corresponding eigenvalues are mapped to zero), then apply the same projection to $\\mathbf b$, and iterate away. For more information about deflation preconditioning (which involves convergence analysis for singular systems), I recommend:\n<PERSON>, <PERSON>, et al. \"A comparison of two-level preconditioners based on multigrid and deflation.\"\n<PERSON>, <PERSON>, and <PERSON>. \"Deflation and balancing preconditioners for <PERSON> subspace methods applied to nonsymmetric matrices.\"", "768" ], [ "The derivation of the BFGS is more intuitive when one considers (strictly) convex cost functionals:\nHowever, some background information is necessary: Assume, one wants to minimize a convex functional $$ f(x) \\to \\min_{x\\in \\mathbb R^n}. $$ Say there is an approximate solution $x_k$. Then, one approximates the minimum of $f$ by the minimum of the truncated <PERSON> expansion $$ f(x_k+p) \\approx f(x_k) +\\nabla f(x_k)^Tp + \\frac{1}{2}p^T H(x_k)p. \\quad() $$ That is, one looks for $p$ such that $()$ is minimal and sets $x_{k+1} := x_k + p$. Computing the gradient of $(*)$ -- \"with respect to $p$\" -- and setting it to zero gives the relation $$ H(x_k)[x_{k+1} - x_k] = \\nabla f(x_{k+1}) - \\nabla f(x_k), $$ where $H$ is the 'Jacobian of the gradient' or the Hessian matrix.\nSince the computation and inversion of the Hessian is expensive...\n...a short answer\n(cf.", "768" ], [ "<PERSON>'s update) might be that the BFGS update $H_{k+1}^{-1}$ minimizes $$ \\|H_k^{-1} - H^{-1}\\|_W $$ in a smartly chosen weighted Frobenius norm, subject to\n1. $H[x_{k+1} - x_k] = \\nabla f(x_{k+1}) - \\nabla f(x_k)$ -- this is what one is out for -- and\n2. $H^T = H$, because the Hessian is symmetric.\nThen the choice of the weight $W$ in $\\|H\\|_W := \\|W^{1/2}HW^{1/2}\\|_F$ as the inverse of the averaged Hessian $G:=\\int_0^1 H(x_k + \\tau p) d\\tau$, cf. here for the statement but without proof, gives the BFGS update formula (with $\\alpha_k = 1$).\nThe major points are:\n* One tries to approximate the solution for the actual costs by the solution for a quadratic approximation\n* Computation of the Hessian, and its inverse, is expensive. One prefers simple updates.\n* The update is chosen optimal for the inverse rather than the actual Hessian.\n* That it is a rank-2 update is a consequence of the particular choice of the weights in the <PERSON> norm.\nA longer answer, should include how to choose the weights, how to make this work for nonconvex problems (where a curvature condition appears that requires a scaling of the search direction $p$), and how to derive actual the formula for the update. A reference is here (in German).", "768" ], [ "Assuming $B$ is not angle-dependent, you know the coefficients of each $f_i$ a priori, and $\\mathbf{f}$ can only be evaluated by summing up the spherical harmonics expansion, simplify your problem by making use of the orthogonality of spherical harmonics instead of numerically integrating.\nLet $f_i(\\theta,\\phi)=\\sum_{lm}f_{i,lm}Y_l^m(\\theta,\\phi)$. Then your cost function becomes, using the summation convention: $$ \\begin{align} g &= \\int d\\Omega f_{i,lm}^Y_l^{m}(\\theta,\\phi) (B_{ji}^ + B_{ij})f_{j,l'm'}Y_{l'}^{m'}(\\theta,\\phi)\\ &= f_{i,lm}^f_{j,l'm'}(B_{ji}^ + B_{ij}) \\int d\\Omega Y_l^{m}(\\theta,\\phi) Y_{l'}^{m'}(\\theta,\\phi)\\ &= f_{i,lm}^f_{j,l'm'}(B_{ji}^ + B_{ij}) \\delta_{ll',mm'}\\ &= f_{i,lm}^f_{j,lm}(B_{ji}^ + B_{ij}) \\end{align} $$ Assuming $F_{lm}=(f_{1,lm},\\ldots,f_{n,lm})$, this can be written as $$ g=\\sum_{lm} F_{lm}^\\dagger (B^\\dagger+B) F_{lm}. $$ We see that for each scalar element of the sum $F_{lm}^\\dagger B^\\dagger F_{lm}=(F_{lm}^\\dagger B F_{lm})^\\dagger$, so we can simplify further to $$ g=2\\mathfrak{R}\\sum_{lm} F_{lm}^\\dagger Q L^{-1} F_{lm}. $$ Since you only have control over the elements of $Q$, you can precompute and store as a vector $x_{lm}=L^{-1}F_{lm}$s.", "804" ], [ "Now, you know the $F_{lm}$ and $x_{lm}$ coefficients, and $Q$ is by definition orthogonal. One way to make the sum large is to make $Q$ span the space of the \"largest\" $F_{lm},x_{lm}$. You could take the $k \\leq n$ largest-norm $F_{lm}$ and $x_{lm}$ vectors, put them in a matrix (horzcat in Matlab), take the SVD, and use its column space matrix as your $Q$.\nA similar approach can be easily derived in the case that $\\mathbf{f}$ is cheap to evaluate (i.e., with fewer than $\\mathcal{O}(L^2)$ operations per quadrature point, where $L$ is the maximal degree of spherical harmonics used), with samples of $\\Omega$ taking the place of the $l,m$ indices. I realize that taking the real part in the above expression may change your approach slightly; have not yet thought that through completely.", "976" ], [ "Active Elements in Projected Newton's Method?\nTo those who are familiar with the projected <PERSON>'s method or projected gradient method...\nWe consider a constrained optimization problem with simple bounds. Particularly, minimize f(x) subject to L <= x <= U, where f maps R^n to R. x, L, and U are vectors in R^n. In the projected <PERSON>'s method that is used to solve this problem, the search direction is obtained by solving the linear system (reduced Hessian)*(search direction) = - gradient. Based on this, the active elements of an iterate are moved in the direction of the negative gradients at those elements. By definition of active sets, the gradients at the active elements have to be negative (for upper bound) and positive (for lower bound).", "768" ], [ "Hence, after projection, the active elements are moved back to the boundary.\nMy first question is if x_i is an active element in iteration 1, will it be an active element until convergence? In other words, does the active set only get bigger, not smaller, and members of the active set are only added, not removed?\nMy second question is what if we use epsilon active set instead of just active set? Will it change anything?\nIf you need the definition of active set or any other clarification/background, please feel free to let me know. Thank you so much for your ideas and discussions. This is very important to me.\n%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\nEDIT: We consider the problem: \\begin{equation} \\min f(x) \\quad \\text{subject to} \\quad a \\leq x \\leq b \\end{equation} where $f: \\mathbb{R}^n \\rightarrow \\mathbb{R}$ is continuously differentiable.\nAn active set is defined as \\begin{equation} \\mathcal{A}:= { i | (x_i = a_i \\quad \\text{and} \\quad (\\nabla f(x))_i > 0) \\quad \\text{or} \\quad (x_i = b_i \\quad \\text{and} \\quad (\\nabla f(x))_i < 0) } \\end{equation}\nSuppose our initial iterate $x_0$ is on the boundary, e.g. $x_0 = a$, then it is possible to have some inactive elements where $(\\nabla f(x))_i < 0$, right?\nIn the projected <PERSON>'s method, first with step length $\\alpha = 1$, the active elements move in the directions of the negative gradients, which will point outside of the feasible region. Then, those elements are projected back to the boundaries. The inactive elements move in the <PERSON> directions. Then we test for sufficient decrease...but even when we decrease $\\alpha$, the active elements still move back to the boundaries and those elements still meet the \"active\" criteria in the next <PERSON> iteration?\nI know the active set can shrink...there must be something wrong in my thoughts...", "474" ], [ "As a preamble, I would not expect that splitting $E$ into real/imaginary parts is very profitable. Normally, block 2x2 systems are motivated because one block of unknowns is \"easier\" to solve than the other in some sense (better conditioned? smaller in cardinality? etc). This is not the case for time-harmonic <PERSON>, I think you'd be better off remaining in the complex field. If you can't do that (maybe these frameworks don't support complex variables?), the next best thing would be to probably \"interleave\" the real and imaginary parts and use point-like preconditioners with two degrees of freedom (1 real, 1 imag) per point. I'd expect this to have the same effect as working in the complex field to begin with.\nAll that said, a lot of classical preconditioners that you might try at this point (smoothing, incomplete factorizations, multigrid) are not very effective on time-harmonic Maxwell, because it has basically the same spectral properties as the (bad) <PERSON> equation: unbounded spectrum, indefinite, oscillatory in nature. An excellent survey of these troubles can be found here, you can basically apply the same arguments to time-harmonic <PERSON>.\nIn fact, <PERSON> is even a little more difficult in two ways. The minor way is because it's vector-valued and thus has more unknowns than a <PERSON> problem of equal size and wavenumber. The major way is that <PERSON>'s $\\nabla \\times \\nabla \\times$ operator is more complicated than <PERSON>'s $\\nabla \\bullet \\nabla $ operator, because of the presence of an infinite dimensional nullspace.", "976" ], [ "<PERSON>'s gradient operator has a one dimensional nullspace (spanned by the constant function $1$), but <PERSON>'s curl operator has an infinite dimensional nullspace (spanned by the gradients of scalar functions $\\nabla f$). Many preconditioning schemes rely upon \"coarsening\" the problem down (in a multigrid sense), and the <PERSON> equation enjoys that its nullspace (the constant function) can be approximated with no error on any grid that is arbitrarily coarse. In contrast, when you discretize the <PERSON> equation on a fine grid, the nullspace of the discrete operator will not be exactly representable on a coarser grid, and thus your exchange operations (restriction/prolongation) must be more carefully constructed (otherwise you are likely to take exactly-zero eigencomponents on one grid and map them to close-but-not-quite-zero eigencomponents on another, which wrecks convergence .. see here for some discussion).\nOn a less pessimistic note, a reliable FE solver for low/medium-wavenumber time-harmonic <PERSON> is an excellent tool to have in your pocket, because it can be readily hybridized with high-wavenumber methods (modal expansions, integral equations, asymptotics, etc) but complements their deficiencies (unlike FE, these methods typically only work for homogeneous media). Along those lines, the two approaches I've used most successfully for solving <PERSON>'s equations iteratively are (i) p-multiplicative-schwarz (pMUS) and (ii) domain decomposition (DDM).\nThe former (pMUS) is basically multigrid, but applied in polynomial order (p) instead of mesh size (h). The basic idea is to use a low order p=0 solution to precondition a high order p=(0+1+...) solution. It's easy to implement, but requires some formulation-level effort to tabulate your (Nedelec) basis functions in such a way that they separate the nullspace/range of the curl operator as described earlier (see this paper for a good representative in this class of methods).\nThe latter (DDM) is basically a deflation-like scheme, wherein you partition space into non-overlapping domains, eliminate/substructure away the interior unknowns, then solve the resulting interface-only problem to re-establish the correct field continuity / global solution. Much thought has been put into the right kinds of \"transmission conditions\" that should be used to terminate the subdomains and match them back together, much of the work on <PERSON> has been adapted from similar work on the Helmholtz equation. See here for pioneering work on Helmholtz, and here for its evolution into <PERSON>.", "768" ], [ "Disclaimer: I think I've just figured this out a couple of minutes ago, so some details may be fuzzy.\nThe formal theory is in Computational Geometry: Algorithms and Applications (2008 <PERSON> et al.), in the Linear Programming chapter.\nJust as in 2D linear programming where we know the optimal incremental solution must lie somewhere on the newly-added line segment, in 3D linear programming, we know the optimal incremental solution must lie on the newly-added plane.\nRVO2 defines the constraint plane of a given ORCA line to extend into the Z-axis with a slight tilt, and the infeasible problem we're looking at is just at some slice on an XY-plane.\nNow, consider the intersection of two ORCA planes, slightly tilted on the Z-axis -- their intersection is a slightly skewed line, which can be projected onto the XY-plane. This is the bisecting line that RVO2 defines.(1)\nRemember that the lines of intersection are parametric; geometrically, we can view these t-parameters as the Z-axis component, i.e. where we should decide to take a new \"slice\" of the original system of constraints.\nWhen we solve for LP1 in LP3, we are finding the [tl, tr] interval of these bisecting lines -- that is, we are finding the \"bounding planes\" in the Z-axis between which the optimal solution should be found.\nNote that RVO2.LP3 calls LP2 with an optimal velocity pointing into the feasible region of the iterative constraint -- we know the current system is infeasible, so we want to move as directly as possible into a feasible state.\nAlso note that in LP1, we drop the calculation to find a point closest to the (bisecting) constraint when dirOpt = True -- this is because the linear problem has changed when we project the 3D problem into 2D space.", "586" ], [ "We are no longer looking for minimal perturbation in 2D space, but looking for a shared feasible point among all projected constraints. We have left the minimal perturbation requirement to LP3.\nI'm attempting to re-implement ORCA at the moment, at https://github.com/downflux/go-orca. Hopefully I will have more comments to the effect of this post soon.\n1. N.B.: The XY-slice that LP3 feeds into LP2 is not technically aligned with the constraint plane itself, but is a 2D planar projection into 2D ambient space -- this nicely avoids attempting to deal with 3D lines and makes reasoning a bit easier.", "433" ], [ "We construct an operator based on the assumption that the system is a linear space invariant system. The blurred image is denoted $b$ and the input is denoted $x$.\nSince the convolution is commutative, we can write\n$ \\begin{align} b &= hx\\ &=xh \\end{align} $\nSo we can have two equal representations using the matrices $H$ and $X$ corresponding to the integral operations involving $x$ and $h$, i.e.\n$ \\begin{align} b &= Hx\\ &=Xh \\end{align} $\nSince we know about $b$ and $x$ exactly, we would like to know about $h$. Our task is thus to construct the operator $X$ based on our knowledge on $x$ and the properties of the imaging system.\nHere, I take old code I have lying around to construct the matrix. Forgive me if I forgot some details, but the details for the handling of convolution matrices that have certain structures is nicely explained in the book:\nDeblurring Images: Matrices, Spectra, and Filtering\nAuthors: <PERSON>, <PERSON>, and <PERSON>\nEither way, we construct the matrix $X$ based on the following code. I think this corresponds to periodic boundary conditions, but take it with a grain of salt.\nX = toeplitz(x,circshift(flipud(x),1));\nWe then solve for the optimal $h$ by e.g.", "768" ], [ "gradient descent for the objective function:\n$ \\begin{align} \\vert\\vert Xh-b\\vert\\vert^2_2 \\end{align} $\nWe thus know about the filter coefficients in this case. Conversely, based on the computed coefficients $h$ we can construct the matrix $H$ via the same formula as in the above code. Then, given $b$ and the operator $H$, we would like to compute the optimal $x_{est}$ via solving the objective function:\n$ \\begin{align} \\vert\\vert Hx_{est}-b\\vert\\vert^2_2 \\end{align} $\nSince the original $x$ has sharp edges, using normal gradient descent to solve for the optimal $x_{est}$ would be rather smooth. Since we know that most parts of the image is zero, we choose an additional projection step onto the scaled standard simplex for each iteration (i.e. nonnegative iterative soft-thresholding). The results are shown below.\nNote: To plot the filter coefficients $h$ as a PSF, we need to shift them a little bit via (s being the size of the images):\nhs = reshape(circshift(h(:),(numel(h)+s(1))/2),s)\nFurthermore, I only took a certain color type of your images and subtracted the background such that the background was set to zero.", "768" ], [ "Open Source Quadratic Programming with Piecewise Linear Objective\nI am looking for an open source solver to solve the a quadratic programming problem with an additional piecewise linear objective, as show below. The problem is fairly small ($\\mathbf{x}$ is a vector of dimension 120).\n\\begin{equation} \\max_{x}: \\mathbf{x}^{T} \\mathbf{q_0} - \\mathbf{x^{T}} P_0 \\mathbf{x} - f(\\mathbf{x}) \\end{equation}\nNote that above $P_0$ is positive semidefinite and $f$ is piecewise linear for each variable in $\\mathbf{x}$ but not convex.", "935" ], [ "For each $x_i$, $i \\in \\left{1, ..., 120\\right}$, $f(x)$ would be a vector of coordinate points, e.g.\n[(x_0, y_0), (x_1, y_1), ..., (x_N, y_N)]\nFor any given $x_i$, $f(x_i)$ looks something like the following.\nSince $f$ does not depend on any cross terms in $\\mathbf{x}$, the above optimization could also be written as\n\\begin{equation} \\max_{x}: \\mathbf{x}^{T} \\mathbf{q_0} - \\mathbf{x^{T}} P_0 \\mathbf{x} - (f(x_1) + ... + f(x_{120})) \\end{equation}\nThe are also linear constraints of the form $A\\mathbf{x} < \\mathbf{b}$ are added.\nI have formulated the problem in Gurobi which is fairly straightforward but was hoping to compare this to an open source solver. Looking around it seems like GLPK would work for this, but I have no experience using this library so was hoping for a bit of info related to this or alternative solutions.\nA sample problem for gurobi using the matlab API is shown below.\nN = 2;\nq_0 = [-3.31e3, -5.07e3];\nP_0 = [-0.90e-04 -0.63e-04;\n-0.63e-04 -0.90e-04];\nx = [-2.0000e9, -1.0000e9, -0.8000e9, -0.6000e9, -0.4000e9, -0.2500e9,...\n-0.1000e9, -0.0500e9, -0.0250e9, -0.0100e9, -0.0010e9, 0, 0.0010e9,...\n0.0100e9, 0.0250e9, 0.0500e9, 0.1000e9, 0.2500e9, 0.4000e9,...\n0.6000e9, 0.8000e9, 1.0000e9, 2.0000e9];\ny = [2.938964e6, 0.753364e6, 0.488104e6, 0.280144e6, 0.129472e6,...\n0.053766e6, 0.011007e6, 0.003751e6, 0.001435e6, 0.000465e6,...\n0.000037e6, 0, 0.000037e6, 0.000465e6, 0.001435e6, 0.003751e6,...\n0.011007e6, 0.053766e6, 0.129472e6, 0.280144e6, 0.488104e6,...\n0.753364e6, 2.938964e6];\nparams.outputflag = 0;\n%formulate model\nmodel.obj = zeros(N, 1);\nmodel.Q = sparse(P_0);\nmodel.A = sparse(zeros(1, N));\nmodel.sense = '=';\nmodel.rhs = 0;\nmodel.ub = repmat(1e9, N, 1);\nmodel.lb = repmat(-1e9, N, 1);\nmodel.modelsense = 'max';\n% piecewise tcosts\nfor i = 1:2\nmodel.pwlobj(i).var = i;\nmodel.pwlobj(i).x = x;\nmodel.pwlobj(i).", "935" ] ]

[ 1244, 7373, 8843, 2429, 811, 10920, 11362, 8518, 4253, 3523, 1557, 1480, 7351, 3559, 9192, 9467, 509, 5818, 3890, 7050, 7958, 1930, 7755, 3238, 5056, 7617, 3271, 10892, 3860, 9532, 2866, 10135, 8592, 8721, 2845, 2189, 1446, 1223, 9616, 5512, 5084, 9902, 4557, 5631, 7233, 4620, 2006, 1090, 8361, 9784, 5479, 10829, 149, 1563, 3492, 4890, 6684, 11018, 8402, 2007, 4514, 7473, 10965, 9031, 3955, 570, 3446, 4192, 1237, 4070 ]

[ [ "The <PERSON>-Sham approach to density functional theory is based on a self-consistency scheme to obtain the ground-state electron density of the investigated material. As a starting point the scheme uses an input density that is some approximation to the ground-state density. It uses the density to determine the effective potential $V_\\text{eff}(\\mathbf{r})$ consisting of the Hartree potential, the exchange-correlation potential, and the external potential due to the atomic nuclei.\nWhen you have this the next step is the solving of the <PERSON>-Sham equations (here in Hartree atomic units) $$\\left. -\\frac{1}{2}\\nabla^2+V_\\text{eff}(\\mathbf{r}) \\middle| \\psi_i \\right\\rangle = \\left. \\epsilon_i \\middle| \\psi_i \\right\\rangle,$$ where the $\\psi_i(\\mathbf{r})$ are the Kohn Sham orbitals. The Kohn-Sham equations are eigenvalue equations that are typically approached by introducing some kind of basis functions $\\phi_i(\\mathbf{r})$ to get a formulation of the problem that can be solved with the tools of linear algebra. With the basis functions we obtain a Hamiltonian matrix $$H_{ij} = \\left\\langle \\phi_i \\middle| -\\frac{1}{2}\\nabla^2+V_\\text{eff}(\\mathbf{r}) \\middle| \\phi_j \\right\\rangle$$ and an overlap matrix $$S_{ij} = \\left\\langle \\phi_i \\middle| \\phi_j \\right\\rangle.$$ The Kohn-Sham equations thus become a generalized eigenvalue matrix problem. It can be solved by turning it into a standard eigenvalue problem and then diagonalizing the matrix for this problem with standard linear algebra methods.", "768" ], [ "In the end you obtain the orbital energies along with the eigenstates of the problem in terms of linear combinations of the basis functions.\nNext would be the determination of an output density with these eigenstates by occupying them with electrons. Then you have to guess an improved input density based on the last input densities and the output density. The loop is iterated again and again until the density is self-consistent, i.e., input and output densities are (nearly) the identical.\nYou mentioned in your question that you already have the electron density, but this is probably only an approximation to the self-consistent density that you obtain from the Kohn-Sham scheme. Otherwise you should have constructed the Kohn-Sham orbitals in the determination of your density.\nNote that the choice of the basis set $\\left\\lbrace\\phi_i\\right\\rbrace$ is critical to obtain reasonable results. If you want to include all electrons in your calculations the orbitals feature strong oscillatory behaviour near the atomic nuclei because of the singularity of the external potential at these points. You need a lot of intuition to design a basis that is capable to represent such orbitals. An example for a basis that is capable to do this is the linearized-augmented plane-wave (LAPW) basis.\nAnother approach would be the introduction of the pseudopotential approximation that cuts away the core electrons and replaces the real external potential by a pseudopotential that yields smooth valence electron eigenstates featuring (for a prototype system) the same energy eigenvalues as an all-electron calculation. These can be represented by a simple plane-wave basis but the transferability of the pseudopotential to materials deviating from the prototype system is not necessarily given.", "976" ], [ "If you want to describe inversion symmetric systems the Hamiltonian matrix is a symmetric matrix and otherwise it is a Hermitian matrix. This is an important property to obtain real-valued energy eigenvalues.\nDepending on the approach to density functional theory this property of the Hamiltonian matrix is not mathematically guaranteed in the first place but has to be ensured by postprocessing measures like the one you describe in the question.\nLet us assume that you are using a (linearized) augmented-plane-wave basis set as it is used in software packages like Wien2k, Fleur, Elk, Exciting and others. With such a representation the unit cell is separated into non-overlapping but nearly touching so-called muffin-tin (MT) spheres around each atom $\\alpha$ and an interstitial region (IR) in between. In the IR such a basis function is a plane wave with wave vector $\\mathbf{k} + \\mathbf{G}$, where $\\mathbf{k}$ is a <PERSON> vector and $\\mathbf{G}$ a reciprocal lattice vector. In the MT spheres each basis function consists of radial functions times spherical harmonics up to a certain angular momentum cutoff parameter $l_\\text{max}$.", "976" ], [ "The radial functions are scaled to ensure continuity in value (and slope) at the MT spheres boundaries. But this matching of course only happens for $l \\le l_\\text{max}$. For higher $l$ the basis functions feature discontinuities at the MT sphere boundaries.\nLet us test whether we obtain a Hermitian matrix with such a basis. Hermiticity means\n\\begin{equation} H_{\\mathbf{G}\\mathbf{G}'}^{\\mathbf{k}} - \\left(H_{\\mathbf{G}'\\mathbf{G}}^{\\mathbf{k}}\\right)^\\ast = 0. \\end{equation}\nWith the sketched basis consisting of IR representations $\\phi_{\\mathbf{k}\\mathbf{G}}^\\text{IR}$ and MT representations $\\phi_{\\mathbf{k}\\mathbf{G}}^\\alpha$ this expression becomes \\begin{align} H_{\\mathbf{G}\\mathbf{G}'}^{\\mathbf{k}} - \\left(H_{\\mathbf{G}'\\mathbf{G}}^{\\mathbf{k}}\\right)^\\ast & = \\left\\langle \\phi_{\\mathbf{k}\\mathbf{G}}^\\text{IR} \\middle\\vert \\hat{H} \\middle\\vert \\phi_{\\mathbf{k}\\mathbf{G}'}^\\text{IR} \\right\\rangle_\\text{IR} - \\left(\\left\\langle \\phi_{\\mathbf{k}\\mathbf{G}'}^\\text{IR} \\middle\\vert \\hat{H} \\middle\\vert \\phi_{\\mathbf{k}\\mathbf{G}}^\\text{IR} \\right\\rangle_\\text{IR} \\right)^\\ast \\nonumber \\ & \\phantom{=} + \\sum\\limits_\\alpha \\left\\langle \\phi_{\\mathbf{k}\\mathbf{G}}^\\alpha \\middle\\vert \\hat{H} \\middle\\vert \\phi_{\\mathbf{k}\\mathbf{G}'}^\\alpha \\right\\rangle_{\\text{MT}^\\alpha} - \\left(\\left\\langle \\phi_{\\mathbf{k}\\mathbf{G}'}^\\alpha \\middle\\vert \\hat{H} \\middle\\vert \\phi_{\\mathbf{k}\\mathbf{G}}^\\alpha \\right\\rangle_{\\text{MT}^\\alpha} \\right)^\\ast \\nonumber \\ & = -\\frac{1}{2} \\left\\lbrace\\int\\limits_\\text{IR} \\left(\\phi_{\\mathbf{k}\\mathbf{G}}^\\text{IR}(\\mathbf{r})\\right)^\\ast \\nabla^2 \\phi_{\\mathbf{k}\\mathbf{G}'}^\\text{IR}(\\mathbf{r}) - \\phi_{\\mathbf{k}\\mathbf{G}'}^\\text{IR}(\\mathbf{r}) \\nabla^2 \\left(\\phi_{\\mathbf{k}\\mathbf{G}}^\\text{IR}(\\mathbf{r})\\right)^\\ast d^3r \\right.", "677" ], [ "This is an important question that is asked by many people entering the field of density functional theory. I think that it should be answered with a high degree of detail and thus I would like to add a few aspects to the answer of supermarche.\n1. As mentioned the <PERSON>-Kohn theorem states that (up to a constant energy shift) the external potential of the Born-Oppenheimer approximation to the many-body Hamiltonian is a unique functional of the ground-state charge density. This implies that this Hamiltionian itself is a functional of the ground-state density and therefore in theory not only ground-state properties of the investigated system are encoded in the ground-state density but also excited-state properties. I mention that this is in theory the case as for practical investigations only for very few properties functionals are known that extract the respective quantities from the density.\n2. It is well known (see, e.g., <PERSON>, <PERSON>: Density-Functional Theory of the Energy Gap, Phys. Rev. <PERSON>. 51, 1888 (1983)) that the fundamental band gap for a system with $N$ electrons is given by the differences of ground-state total energies of systems with deviating numbers of electrons as $$E_g = (E_{N+1} - E_N) - (E_N - E_{N-1})$$ Thus being able to calculate the ground-state total energy for these different systems should be enough to calculate the band gap.", "976" ], [ "Leaving aside the issue of the approximation to the exchange-correlation (xc) functional the ground-state total energy is accessible by density functional theory but this does not imply that the band gap of the Kohn-Sham system is the fundamental gap of the interacting-electron system.\n3. Let us assume fractional particle numbers and take a closer look at the energy and its dependence on the number of electrons. It is known that this dependence qualitatively behaves as sketched in the following figure: The exact xc functional connects the total energies for integer particle numbers by straight lines and features derivative discontinuities $\\Delta^{xc}$ at integer particle numbers. The local density approximation (LDA) on the other hand shows a smooth behavior.\nBased on the equation for the fundamental band gap given above we can derive another expression for the exact xc functional: $$E_g = \\lim_{\\eta \\rightarrow 0^+} \\left\\lbrace \\left.\\frac{\\delta E[n]}{\\delta n(\\boldsymbol{r})}\\right|{N+\\eta} - \\left.\\frac{\\delta E[n]}{\\delta n(\\boldsymbol{r})}\\right|{N-\\eta} \\right\\rbrace$$ where $n(\\boldsymbol{r})$ is the density.\nBy plugging in <PERSON>'s theorem $\\partial E / \\partial n_i = \\epsilon_i$ and the derivative discontinuity one ends up with $$E_g = \\epsilon_{N+1} - \\epsilon_{N} + \\Delta_N^{xc}$$ where $\\epsilon_i$ denotes the energy of i-th electron state in the Kohn-Sham system.\nDetailed derivations of this result are provided in, e.g., <PERSON>, M. Levy: Physical Content of the Exact Kohn-Sham Orbital Energies: Band Gaps and Derivative Discontinuities, Phys. Rev. Lett. 51, 1884 (1983) or <PERSON>, <PERSON>: Density Functional Theory - An Advanced Course, Springer (2011).\nThe essence of this result is that even with the exact xc functional the Kohn-Sham band structure does not provide the fundamental band gap of the real interacting-electron system as it does not include the finite and positive derivative discontinuity.\n1. Local and semilocal approximations to the xc functional like LDA or GGAs do not feature the discussed derivative discontinuities. But one can provide a simple hand-waving reason why the band structure underestimates the gap in this case.\nOne contribution to the energy of the Kohn-Sham system is the Hartree energy $$E_H[n] = \\frac{1}{2} \\int \\frac{n(\\boldsymbol{r}) n(\\boldsymbol{r}')}{|\\boldsymbol{r} - \\boldsymbol{r}'|} d^3 r d^3 r'.$$ By considering a simple single-electron system like the hydrogen atom it is obvious that this energy contribution implies an unphysical self-interaction of the electron with itself.", "649" ], [ "I am not so certain about the terminology because I do not use electronic structure software, but since nobody has answered so far, I will try to see if my answer clarifies something.\nIn a closed-shell configuration you know that a single <PERSON> determinant built from atomic orbitals (or for that matter, any function with angular dependence in terms of spherical harmonics) will be an eigenstate of $\\hat{L}^2$ and $\\hat{S}^2$ with quantum numbers L = S = 0. Additionally in this case there is no spin-orbit coupling, so that J = 0 as well. Therefore the angular momentum properties of this wave function will be well defined.\nIn the simplest ab initio molecular orbital calculation you obtain your atomic orbitals solving the restricted Hartree-Fock equations (RHF). Why restricted? Because if you have n electrons and the dimension of your basis (whatever STO, GTO or more advance basis, assuming you expand your atomic orbitals in a basis) is L > n/2, you populate the first n/2 orbitals and assume each orbital is doubly occupied by two electrons with spins $\\uparrow$ and $\\downarrow$. You could use the unrestricted Hartree-Fock (UHF) method, populating the lowest n spin-orbitals, but then the density of electrons with spin $\\uparrow$ will be in general different than the density of electrons with spin $\\downarrow$. Thus, although the energy of your system will be lower (some restrictions in the variational procedure are lifted) $S$ will not be well defined.\nIn general, for an open shell configuration the angular momentum will not be well defined by a single Slater determinant wave function. How do you create the proper wave function? You can use several strategies.\nThe more general strategy is to use a Multi-Configurational Self Consistent Field (MCSCF) approach, in which you generate several Slater determinants with the L orbitals, in which both the orbitals and the coefficients multiplying the Slater determinants are variational parameters that you have to determine consistently within the MCSCF approach.\nA simpler method including correlation (among the many that exists) is the Configurational Interaction (CI) in which you optimize only once the orbitals and then generate the <PERSON> determinants and then at the end of the day obtain the coefficients of these <PERSON> determinants by diagonalizing the Hamiltonian.\nThe previous methods are called method with dynamic correlation or beyond the HF approach. More simply, you can use the RHF scheme and after obtaining your n/2 populated orbitals force the symmetry by suitable projector operators that generate the other <PERSON> determinants needed so that your overall wave function is an eigenstate of $\\hat{L}^2$ and $\\hat{S}^2$ (and $\\hat{L}_z$ and $\\hat{S}_z$). This is good only in the so-called L-S coupling scheme when spin-orbit coupling is assumed small (small relativistic corrections).", "976" ], [ "But of course you can later diagonalize the Hamiltonian with the spin-orbit coupling terms to resolve the fine-structure of the atom. I believe this is what GAMESS calls the ROHF method but I am not sure. To be sure you have to look at the manual.\nMore commonly, you can use the UHF method and after obtaining you n populated spin-orbitals you force the right symmetry by applying projector operators to filter the \"wrong\" components that give an incorrect spin symmetry. This method is often called the PHF or Projected Hartree-Fock. Finally, you can also use the RHF equations but start from a number of Slater determinants with the coefficients fixed by the projector operator (that is, they are no longer variational parameters) and then variationally optimize the orbitals for this set of determinants. The equations become more difficult and I believe this method, called EHF or Extended Hartree-Fock is not often applied. If you want to work with several <PERSON> determinants you typically use CI or MCSCF.\nNow going back to your examples.\nIn Lithium you have two microstates for the ground state that you can write assigning the 4 quantum numbers $n_j$, $l_j$, $m_j$ and $m_{s,j}$ for each electron $j$, assuming the usual <PERSON> principle. However these two states are degenerate. Therefore you can write two <PERSON> determinants which will give you the same ground state energy. In the absence of an external magnetic field, any of these <PERSON> determinants (or whatever linear combination of the two) is a good description of your ground state.", "976" ], [ "When thinking about the ground state of a material you can consider many different degrees of freedom. Of course, the positions of the atomic nuclei belong to these parameters when you are talking about the ground-state crystal structure. But for density functional theory the positions of the nuclei actually are an external parameter. They are treated separately from the electrons and are considered to be fixed: Before deriving density functional theory you perform the Born-Oppenheimer approximation to separate the motion of the nuclei from your considerations. The Hohenberg-Kohn theorem then states that the external potential (which contains the positions of the nuclei) is a functional of the ground-state charge density of the electrons.\nThis implies that for every possible configuration of atom positions density functional theory has predictive power. For example, this allows you to calculate total energies and forces on the atoms to actually determine the ground-state crystal structure.", "28" ], [ "One can also use experimentally determined crystal structures to calculate with DFT quantities that are not accessible by experiments.\nOf course, quantities that show a strong dependence on the temperature of the electronic system can be a problem: On the one hand it is possible to predict the magnetic structure for a given atom configuration, on the other hand the implied temperature of the electronic system for that atom configuration may already lead to a nonmagnetic state because it is higher than the <PERSON> temperature or <PERSON> temperature. For such a situation one can use the results from the DFT calculations as an input to Monte-Carlo simulations to determine the critical temperature based on model assumptions.\nSo in the end one should always be skeptical about the results of simulations or other calculations. Every calculation implies certain model assumptions and limitations. One should be aware of these. The success of density functional theory is because experience shows that one can obtain good predictions from it for a wide range of materials and many quantities. But that does not mean that it can predict every quantity of every material. And often DFT calculations are only the first step in a calculation because the results have to be refined.", "28" ], [ "I am not so sure whether I understand the question correctly but I will say a few words about the kinetic energy in this context.\nDensity functional theory codes that use a plane-wave basis set rely on the pseudopotential approximation or use the projector-augmented-wave (PAW) approach which is in practice also used as a pseudopotential method because the computational demands required to go beyond the frozen-core approximation are rather large (but it is in principle possible).\nIn the pseudopotential approximation you perform for each chemical element a prototype calculation that includes all electrons. But you are mainly interested in the valence electrons as the chemical bonding of the atoms to other atoms is strongly dominated by these electrons and not by the core electrons or the higher-lying unoccupied states. Therefore you decide that in more demanding calculations beyond your prototype system you only want to consider the valence electrons. This is done by defining a sphere around the atom in which the valence wave functions are replaced by smooth pseudo wave functions that do not feature any nodes. With these pseudo wave functions you then go in the opposite direction and construct a potential for which these wave functions solve the respective <PERSON> equation and the resulting energy eigenvalues agree with those of the all-electron system.\nIn such a representation there are no core electrons any more.", "795" ], [ "The pseudo valence wave functions are the energetically lowest lying energy eigenstates. They feature a rather low kinetic energy and thus can be represented by the plane waves below the kinetic energy cutoff parameter. The real valence and core electron wave functions feature a kinetic energy that can be larger by several orders of magnitude. This is the reason why you rely on the pseudopotential approximation if you use a plane-wave basis: To represent the real all-electron wave functions you would need a gigantic kinetic energy cutoff parameter resulting in a basis set size that makes real computations infeasible.\nPlease note that the pseudopotential approximation is a very successful approach in density functional theory. But, of course, the question whether a pseudopotential is reasonably transferable to a certain chemical environment deviating from the prototype system is not always easy to answer.", "976" ], [ "The Hamiltonian of an atom commutes with the square of the total angular momentum $\\hat{J} = \\hat{L} + \\hat{S}$ and one component, disregarding very small hyperfine splittings. Knowing the energy $E$, $J$ and $J_z$ amounts to solving the fine structure of the atom. Since $\\hat{J}$ is an angular momentum there are 2J+1 degenerate components in the absence of an external magnetic field. For non heavy atoms the Hamiltonian also approximately commutes with $\\hat{L}^2$, $\\hat{L}_z$, $\\hat{S}^2$ and $\\hat{S}_z$, the orbital and spin angular momenta, so you can have approximately well defined energy and $L$, $M_L$, $S$ and $M_S$ quantum numbers. These states have the right (or approximately right) symmetry, so you want to have your eigenstates with all those labels, say $|E,L,M_L,S,M_S,J,M_J\\rangle$.\nIn typical Quantum calculations, however, you write the n-electron wave function as a <PERSON> determinant of {\\it atomic orbitals}, which have well defined one-electron orbital and spin angular momenta, $l_j$, $m_{l,j}$, $s_j$ and $m_{s,j}$. The number of micro-states that you can find specifying the lower case quantum numbers $l_j$, $m_{l,j}$, etc. (you only need to consider electrons that don't fill a \"shell\") is the same as the number of \"real\" states (or microstates) that you find specifying the upper case quantum numbers $L$, $M_L$, etc. {\\bf but} the wave functions are not the same. However you can transform from one representation to the other by a unitary operator.", "976" ], [ "In the case of two electrons (or holes) in the outer open shell, the coefficients of this transformation are the well known Clebsch-Gordan coefficients.\nIn particular the micro-states specification is related to a single <PERSON> determinant of atomic spin-orbitals, but open shell quantum states with well defined angular momentum typically require a sum of several <PERSON> determinants. There are several simple techniques that show you how to find the right linear combination of <PERSON> determinants. <PERSON> pointed to the most usual one. Since for the highest possible $M_L$ there is only one possible single determinant, you can generate the linear combination for the other $M_L$ states with the same $L$ by using ladder angular momentum operators. The same procedure can be used to generate the different $M_S$ states sharing equal $S$. Somewhat more generally, you can also use projection operators. See for instance <PERSON>, Adv. Phys. 5, 1 (1956).", "469" ], [ "Definition of linear response kernel in terms of wavefunctions (<PERSON>/<PERSON>)\nI'm trying to understand the derivation of the linear response kernel in Parr/Yang's \"Density-functional theory of atoms and molecules\". First some background information: We look at a system of $N$ electrons which are described by the Hamiltonian\n\\begin{equation} H_\\text{el}= -\\frac{1}{2}\\sum_i \\nabla_i^2 + \\sum_{i<j} \\frac{1}{|\\boldsymbol r_i - \\boldsymbol r_j|} + \\sum_i v(\\boldsymbol r_i). \\end{equation}\nImagine the potential $v$ to be the Coulomb potential due to the nuclei in a molecule.", "346" ], [ "We call the $k$-th eigenstate to this Hamiltonian $\\Psi_k^{(0)} = \\Psi_k^{(0)}(\\boldsymbol x_1 \\dots \\boldsymbol x_N)$ (the (0) indicating that these are the \"unperturbed\" states, since we will introduce a perturbation soon). The $\\boldsymbol x_i := (\\boldsymbol r_i, m_{s, i})$ are collective spatial and spin degrees of freedom.\nThe electron density associated with the wavefunction $\\Psi_k^{(0)}$ is defined as\n\\begin{equation} \\rho_k(\\boldsymbol r_1) = N \\int \\Psi_k^{(0)*}\\Psi_k^{(0)} dm_{s, 1} d\\boldsymbol x_2 \\dots d\\boldsymbol x_N. \\end{equation}\nNow we introduce a perturbation $\\Delta V = \\sum_i \\Delta v(\\boldsymbol r_i)$ to the Hamiltonian, which we assume to be small such that we can express our perturbed wavefunction by usual first-order time-independent perturbation theory: $\\Psi_k = \\Psi_k^{(0)}+\\Psi_k^{(1)}$ (the first order correction being calculated via the well-known formula).\nParr/<PERSON> then come (on page 15) to the following expression for the change of the electron density due to the perturbation:\n\\begin{align} \\Delta \\rho_k(\\boldsymbol r_1) &:= N \\int \\left(\\Psi_k^\\Psi_k - \\Psi_k^{(0)} \\Psi_k^{(0)} \\right) dm_{s, 1} d\\boldsymbol x_2 \\dots d\\boldsymbol x_N \\ &= 2N \\Re\\left[ \\sum_{j\\neq k} \\frac{\\langle \\Psi_j^{(0)}| \\Delta V | \\Psi_k^{(0)}\\rangle}{E_k^{(0)} - E_j^{(0)}} \\int \\Psi_k^{(0)*}\\Psi_j^{(0)} dm_{s, 1} d\\boldsymbol x_2 \\dots d\\boldsymbol x_N \\right]. \\end{align}\nUp to here it is quite easy (simply ignore terms quadratic in the first-order correction).", "526" ] ]

[ 7693, 9785, 257, 10996, 9487, 3435, 9220, 5478, 5700, 4054, 5333, 303, 9839, 6813, 10163, 1873, 10173, 3068, 10469, 9469, 3579, 10724, 10273, 6642, 3311, 10901, 5786, 3333, 8611, 7353, 11311, 721, 1584, 6055, 8758, 748, 10679, 10639, 10107, 8572, 9330, 6414, 8949, 6202, 3275, 9858, 11050, 8478, 10278, 4046, 11030, 7259, 4472, 10230, 11363, 5261, 5183, 9007, 8893, 7824, 6182, 7014, 5943, 8349, 2891, 1323, 437, 3230, 5633, 8032 ]

[ [ "The problem lies on the notation. The state $|\\psi\\rangle$ is not exactly equal to the eigenfunction $\\psi(x)$.\nThe eigenfunction $\\psi(x)$ is formally defined to be the projection of the state to the position basis $|x\\rangle$ i.e. $$ \\psi(x)=\\langle x|\\psi\\rangle $$\nTherefore the eigenstates $|\\psi\\rangle$ are not \"functions\" of position. Similarly, the operators can be represented as differential operators, but a more correct way of doing so is as follows. For this example I am using the momentum operator in the position representation:\nLet $|x\\rangle$ and $|y\\rangle$ be two orthonormal states in the position basis.", "66" ], [ "We note that $[X,P]=i\\hbar$, therefore $$ i\\hbar\\langle x|y\\rangle = \\langle x|[X,P]|y\\rangle=\\langle x|XP|y\\rangle-\\langle x|PX|y\\rangle=(x-y)\\langle x|P|y\\rangle $$ Since $\\langle x|y\\rangle=\\delta(x-y)$, then $$ \\langle x|P|y\\rangle=i\\hbar\\frac{\\delta(x-y)}{x-y}\\equiv i\\hbar\\frac{\\partial}{\\partial y}\\delta(x-y) $$ Which is a property of the Dirac delta i.e. $\\frac{\\partial}{\\partial y}\\delta(x-y) = \\frac{\\delta(x-y)}{x-y}$. Therefore we see that\n$$ \\langle x|P|\\psi\\rangle=\\int dy \\langle x|P|y\\rangle\\langle y|\\psi\\rangle=\\int dy \\bigg(i\\hbar\\frac{\\partial}{\\partial y}\\delta(x-y)\\bigg)\\langle y|\\psi\\rangle $$ $$ =\\int dy i\\hbar\\frac{\\partial}{\\partial y}\\delta(x-y)\\psi(y)=-i\\hbar\\frac{\\partial}{\\partial x} \\psi(x) $$ From this it is suitable to use the representation \\begin{equation} P\\longrightarrow -i\\hbar\\frac{\\partial}{\\partial x} \\end{equation} As you can see, the operator $P$ in a more general sense is not equal to $-i\\hbar\\frac{\\partial}{\\partial x}$, thus the arrow instead of an equality. It is mere a representation.\nNow that we have this information at hand, in truth when some books or lectures say $$ \\frac{d}{dx}|\\psi(x)\\rangle\\langle u(x)| $$ what they actually mean is $$ \\bigg(\\frac{d}{dx} \\psi(x)\\bigg)u(x) $$ Additional notes:\nWe can see the relationship of the momentum and the position bases states as $$ p\\langle x|p\\rangle=\\langle x|P|p\\rangle=-i\\hbar\\frac{\\partial}{\\partial x} \\langle x|p\\rangle $$ which is a first order partial differential equation, solving this gives $$ \\langle x|p\\rangle=\\frac{1}{\\sqrt{2\\pi\\hbar}}e^{\\frac{ipx}{\\hbar}} $$ i.e. the bases are Fourier transforms of each other $$ |p\\rangle=\\frac{1}{\\sqrt{2\\pi\\hbar}}\\int dx e^{\\frac{ipx}{\\hbar}}|x\\rangle $$ $$ |x\\rangle=\\frac{1}{\\sqrt{2\\pi\\hbar}}\\int dx e^{-\\frac{ipx}{\\hbar}}|p\\rangle $$", "955" ], [ "What is the next step in solving the time derivative of expectation value of the momentum of a particle\nSo this question is a direct follow on from my last question\nI am trying to get an expression for $\\frac{d\\left\n}{dt}$.\nI have my working out below, which was thanks to the Anonymous Physicist's help, (not to mention all the patient people in the mathematics chatroom) I have got to this expression: $$ i\\hbar \\left( \\int\\limits_{-\\infty}^{+\\infty}{ \\frac{-i\\hbar}{2m} \\dfrac{\\partial^2 \\Psi^}{\\partial x^2} \\frac{\\partial \\Psi}{\\partial x} + \\frac{i}{\\hbar}V \\Psi^ \\frac{\\partial \\Psi}{\\partial x} }dx + \\int\\limits_{-\\infty}^{+\\infty}{ \\Psi^* \\frac{\\partial}{\\partial t} \\frac{\\partial \\Psi}{\\partial x} }dx \\right). $$\nAnd now I'm stuck. What can I do about $$ \\int\\limits_{-\\infty}^{+\\infty}{ \\Psi^* \\frac{\\partial}{\\partial t} \\frac{\\partial \\Psi}{\\partial x} }dx $$\nIn particular how to deal with $$ \\frac{\\partial}{\\partial t} \\frac{\\partial \\Psi}{\\partial x}? $$ With the $\\partial t$ in play I don't know how solve the integral...\nAs before, I really would appreciate hints to get me moving in the right direction more than an outright solution.\nMy working so far\nWe are given $\\left\n$ in the text, which is determined by computing $\\frac{d\\left}{dt}$ and multiplying by $m$.\nLets just start with what we know: $$ \\left\n= \\int{\\Psi^*\\left[-i\\hbar \\frac{\\partial}{\\partial x}\\right]\\Psi}dx. $$\nSo taking the time derivative, $$ \\frac{d\\left\n}{dt} = \\frac{d}{dt}\\int{\\Psi^*\\left[-i\\hbar \\frac{\\partial}{\\partial x}\\right]\\Psi}dx. $$\nWe probably should at this point pause, and listen to <PERSON>, (and <PERSON>). So take out the constants before going any further.", "955" ], [ "We get, $$ -i\\hbar \\frac{d}{dt}\\int\\limits_{-\\infty}^{+\\infty}{ \\left( \\Psi^* \\left[ \\frac{\\partial}{\\partial x} \\right] \\Psi \\right) }dx. $$\n(1) Since the variables t and x are independent, you can bring the time derivative into the integral. You can also use the derivative product rule to get two terms in the integral.\nBringing the time derivative into the integral, gives us $$ -i\\hbar \\int\\limits_{-\\infty}^{+\\infty}{\\frac{\\partial}{\\partial t}\\Psi^*\\left[\\frac{\\partial}{\\partial x}\\right]\\Psi}dx. $$\nThen differentiating with the product rule yields, $$ -i\\hbar \\int\\limits_{-\\infty}^{+\\infty}{ \\frac{\\partial \\Psi^}{\\partial t} \\frac{\\partial \\Psi}{\\partial x}+ \\Psi^ \\frac{\\partial}{\\partial t} \\frac{\\partial \\Psi}{\\partial x} }dx. $$\nNow we have two terms in our integral, let's split em up. Let's consider the left handside first, we have $$ \\int\\limits_{-\\infty}^{+\\infty}{ \\frac{\\partial \\Psi^*}{\\partial t} \\frac{\\partial \\Psi}{\\partial x} }dx. $$\nBy <PERSON> this can become, $$ \\int\\limits_{-\\infty}^{+\\infty}{ \\left(\\frac{-i\\hbar}{2m} \\dfrac{\\partial^2 \\Psi^}{\\partial x^2} + \\frac{i}{\\hbar}V \\Psi^ \\right) \\frac{\\partial \\Psi}{\\partial x} }dx.", "955" ], [ "Relation between Clebsch-Gordan Coefficients and Wigner $D$-Matrix\nIt is known that Clebsch-Gordan coefficients are those of a linear transformation from the product basis ${|j_1,j_2;m_1,m_2\\rangle}{m_1\\in {-j_1,...,j_1},m_2\\in {-j_2,...,j_2}}$ to the coupled basis ${|j_1,j_2;J,M\\rangle\\rangle}{J\\in {|j_1-j_2|,...,j_1+j_2},M\\in {-J,...,J}}$ (the double ket to distinguish between the two basis). These two basis are orthonormal basis in the space $\\mathscr{E}(j_1)\\otimes\\mathscr{E}(j_2)$ and that means that there is a unitatry operator $\\hat U$ that transforms one basis to the other. The matrix elements of this operator are by construction the CG-Coefficients.\nOn the other hand a physical rotation $R$ is implemented on a ket in $\\mathscr{E}(j_1)\\otimes\\mathscr{E}(j_2)$ by a unitary operator $\\mathscr D (R)$.\nQuestion:\nIs there a physical rotation $R$ such that $\\mathscr D (R) = \\hat U$, where $\\hat U$ is the change-of-basis operator $\\hat U: {|j_1,j_2;m_1,m_2\\rangle} \\mapsto {|j_1,j_2;J,M\\rangle\\rangle}$ ?\nMy answer is no and here are my two arguments\n1.", "956" ], [ "Diagonalisation of observables (namely $\\mathbf J^2$ & $J_z$) is not possible by physical rotations\n2. The map $\\mathscr D :SO(3) \\to SU((2j_1+1)(2j_2+1))$ may not be surjective, i.e. there are unitary operators $\\hat{ \\mathcal O} \\in SU((2j_1+1)(2j_2+1))$ which do not correspond to physical rotations $R \\in SO(3)$\nThese two arguments do not exclude each other but I hope that someone can make this mathematically more precise, I hope this question makes sense.\nAdded:\nin other words are there e.g. Euler angles $\\alpha, \\beta,\\gamma$ such that matrix elements are something like this $$ \\mathscr D^{(J)}_{M',M}(\\alpha, \\beta,\\gamma) = \\langle j_1,j_2;m_1,m_2|j_1,j_2;J,M\\rangle $$ I know the indices are not consistent, they do not make sense! but this may not be a reason to beleive that there is no $R(\\alpha, \\beta,\\gamma)$ whose representation $\\mathscr D(R)$ does as\n$$\\hat U: {|j_1,j_2;m_1,m_2\\rangle} \\mapsto {|j_1,j_2;J,M\\rangle\\rangle}$$", "956" ], [ "My approach would be: first determine the time evolution of $\\hat{x}(t)$ and $\\hat{p}(t)$. For $\\hat{x}$ you have $$ \\frac{d}{dt}\\hat{x}_H(t) = i[H_H,\\hat{x}_H(t)] = \\frac{i}{2m} [\\hat{p}_H(t)^2,\\hat{x}_H(t)] = \\frac{\\hat{p_H(t)}}{m} $$ and for $p$ you have (assuming $0\\leq t \\leq T$) $$ \\frac{d}{dt}\\hat{p}_H(t) = i[H_H(t),\\hat{p}_H(t)] = -m\\omega_0^2 \\hat{x}_H(t) + F_0\\sin(\\Omega t) $$ These are coupled differential equations, which you can decouple by differentiating them once more with respect to time and performing a substitution. For instance,\n$$ \\frac{d^2}{dt^2} \\hat{x}_H(t) = \\frac{1}{m} \\frac{d}{dt} \\hat{p}_H = -\\omega_0^2 \\hat{x}_H(t)+\\frac{F_0}{m}\\sin(\\Omega t) $$ where I substituted $\\frac{d}{dt} \\hat{p}_H(t)$ by its equation of motion found earlier. You can also get an equation like this for $\\hat{p}_H(t)(t)$, which I leave for you..\nNow, these equations can be solved using your favorite method, provided you give them suitable boundary conditions.", "526" ], [ "Note that you only need one boundary condition for $x$ and $p$ (which is $x_H(0)=\\hat{x}_S$ and $p_H(0)=\\hat{p}_S$ It will give you some expression for $\\hat{x}_H(t)$ and $\\hat{p}_H(t)$ in terms of $\\hat{x}_S$ and $\\hat{p}_S$. The Heisenberg Hamiltonian is then easily determined by substituting $\\hat{x}_H(t)$ and $\\hat{p}_H(t)$.\nWith that expression in hand you should be able to find $\\langle H(t)\\rangle$ (note that you should consider the cases where $t<0$ and $t>T$ separately).\nEDIT: The proof regarding my statement below: In the <PERSON> picture the Hamiltonian is\n$$\\hat H_S=\\frac{\\hat{p}_S^2}{2m}+\\frac{1}{2}m\\omega_0^2\\hat{x}_S^2-\\hat{x}_SF_0\\sin(\\Omega t)$$\nand the <PERSON> picture is given by $H_H = U^\\dagger(t) H_S U(t)$. So if you take for instance the first term you get:\n$$U^\\dagger(t) \\frac{\\hat{p}_S^2}{2m}U(t) =\\frac{1}{2m} (U^\\dagger(t) \\hat{p}_S U^\\dagger(t))(U(t)\\hat{p}_SU(t)) =\\frac{1}{2m} \\hat{p}_H(t)^2 $$\nYou can do the same for the other terms. In the end you just effectively replace $p_S\\rightarrow p_H(t)$ and the same for $x$.", "526" ], [ "What is $\\langle H \\rangle$ in the infinite square well in the state $|\\psi \\rangle = | x_0 \\rangle$, where $0 \\le x_0 \\le L$?\nIn the 1-dimensional infinite square well (with width $L$) the eigenvalues and the corresponding eigenfunctions are $$ E_n = \\frac{\\hbar^2 \\pi^2 n^2}{2L^2 m},\\qquad \\psi_n (x) = \\sqrt{\\frac{2}{L}}\\sin\\left( \\frac{n\\pi}{L}x\\right), \\qquad x \\in [0,L] $$ The general solution of the time-independent <PERSON> equation in the basis of the Hamitonian is $$ \\psi (x) = \\sum_{n=1}^\\infty c_n\\,\\sqrt{\\frac{2}{L}}\\sin\\left( \\frac{n\\pi}{L}x\\right) $$\nQuestion:\nIf the particle is in the state $\\psi_(x) = \\delta(x-x_0)$, where $0 \\le x_0 \\le L$, i.e. the particle is at the position $x =x_0$ at $t = 0$ with certainity, then what is the expectation value of the energy $\\langle H \\rangle$ in this state ? or even what is the probability of getting each of the eigenvalues $E_n$ upon measurement ?\nI don't know if this is the right way but my attempt is as follows:\nI.", "669" ], [ "The coefficients $c_n$ of the expansion using Fourier trick are $$ c_n = \\int_0^L \\sqrt{\\frac{2}{L}}\\sin\\left( \\frac{n\\pi}{L}x\\right)\\delta(x-x_0)\\,dx = \\sqrt{\\frac{2}{L}}\\sin\\left( \\frac{n\\pi}{L}x_0\\right) $$ II. It folows that (I'm not sure if this makes sense) $$ \\langle x_0|x_0\\rangle = \\sum_{n=1}^\\infty |c_n|^2 = \\delta(x_0 - x_0) = \\infty $$ III. The expectation value of the energy is $$ \\langle H \\rangle = \\sum_{n=1}^\\infty E_n\\,|c_n|^2 = \\frac{2}{L}\\sum_{n=1}^\\infty E_n\\,\\sin^2\\left( \\frac{n\\pi}{L}x_0\\right) $$ or differently $$ \\langle H \\rangle = \\int_{-\\infty}^\\infty \\delta(x-x_0)(-\\frac{\\hbar^2}{2m}\\frac{d^2}{dx^2})\\delta(x-x_0)\\, dx = \\cdots $$\nI don't know how to check whether these two expressions of $\\langle H \\rangle$ are equivalent, how does the first converge and how to compute the second ?\nADDED:\nThe first expression should be more completely written as $$ \\langle H \\rangle = \\frac{\\langle \\psi|H|\\psi\\rangle}{\\langle\\psi|\\psi\\rangle} = \\frac{\\sum_{n=1}^\\infty E_n\\,|c_n|^2}{\\sum_{n=1}^\\infty |c_n|^2} = \\frac{\\infty}{\\infty} = \\ ? $$ and I would suggest to get the limit as the limit of the sequence $$ \\langle H \\rangle_m = \\left( \\frac{\\sum_{n=1}^m E_n\\,|c_n|^2}{\\sum_{n=1}^m |c_n|^2}\\right)_{m\\in\\mathbb N} $$ Result: it will not converge", "955" ], [ "While I realise your question is in the second quantized picture and this may not be the answer you're looking for, I just wanted to offer a simple argument in the first quantized picture that would demonstrate the symmetry of PHS Hamiltonians about $E = 0$ (half filling).\nDefine $\\hat{\\mathcal{P}}$ as the particle-hole operator in the second quantized picture. The action of $\\hat{\\mathcal{P}}$ is defined as\n\\begin{equation} \\hat{\\mathcal{P}}\\hat{c}^{}{A}\\hat{\\mathcal{P}}^{-1} = \\sum{B} \\hat{c}{B}^{\\dagger}(U{P})_{B, A} \\end{equation}\nfor some unitary matrix $U_{P}$ (i.e. we turn an electron into a hole and vice-versa).", "526" ], [ "$\\mathcal{P}$ is also linear in the sense $\\mathcal{P}i\\mathcal{P}^{-1} = i$ The action of $\\mathcal{P}$ on the Hamiltonian, $H$, is therefore\n\\begin{equation} \\begin{split} \\hat{\\mathcal{P}}\\hat{H}\\hat{\\mathcal{P}}^{-1} &= \\sum_{A, B} \\hat{\\mathcal{P}} \\hat{c}{A}^{\\dagger} \\hat{\\mathcal{P}}^{-1} \\hat{\\mathcal{P}} H^{}{A, B} \\hat{\\mathcal{P}}^{-1} \\hat{\\mathcal{P}} \\hat{c}^{}{B} \\hat{\\mathcal{P}}^{-1}\\ & =\\sum{A, B} \\sum_{C, D} (U_{P}^{})^{\\dagger}{A, C} \\hat{c}{C} H_{A, B} \\hat{c}{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{c}^{\\dagger}{D}(U_{P})^{}{D, B}H^{}{A, B}(U_{P})^{\\dagger}{A, C}\\hat{c}^{}{C} \\ & = \\sum_{A, B}\\sum_{C, D} (U_{P})^{\\dagger}{A, C}H^{}{A, B}(U_{P})^{}{C, B} - \\hat{c}^{\\dagger}{D}(U_{P})^{}{D, B}H^{T}{B, A}(U_{P})^{\\dagger}{A, C}\\hat{c}^{}{C} \\ & = \\sum_{A, B}\\left( \\delta^{}{A, B}H{A, B} - \\sum_{C, D}\\hat{c}^{\\dagger}{D}(U{P})^{}{D, B}H^{T}{B, A}(U_{P})^{\\dagger}{A, C}\\hat{c}^{}{C} \\right) \\ & = \\text{Tr}(H) - \\sum_{C, D} \\hat{c}^{\\dagger}{D}H^{}{D, C}\\hat{c}^{}_{C}, \\end{split} \\end{equation}\nwhere $H$ is the first quantized Hamiltonian. For the Hamiltonian to respect PHS we require $\\hat{\\mathcal{P}}\\hat{H}\\hat{\\mathcal{P}}^{-1} = \\hat{H}$ and therefore\n\\begin{equation} \\begin{split} &\\text{Tr}(H) = 0 \\ U_{P}H^{*}&U_{P}^{\\dagger} = -H. \\end{split} \\end{equation}\nThese conditions are complementary in the sense that the second condition implies the spectrum is symmetric about $E=0$ (try it!) which implies the first.", "616" ], [ "It is the second, $\\psi(x) = \\langle x|\\psi\\rangle$ which is correct. The first, if $x$ is the position operator, is just the position operator acting on the state $|\\psi\\rangle$. The abstract state $|\\psi\\rangle$ can be expanded in any basis, using a completion relation: $$|\\psi\\rangle = \\underbrace{\\sum_i |i\\rangle \\langle i|}_{1~=~identity}\\psi\\rangle$$ (where the sum can mean sum or integral, depending on this situation) using some complete basis ${|i\\rangle}$. An example of this is the position basis, ${|x\\rangle}$, from which we have $$|\\psi\\rangle = \\int dx~ |x\\rangle \\langle x|\\psi\\rangle$$ This shows us that the wavefunction $\\psi(x) = \\langle x|\\psi\\rangle$, is the coefficient from the expansion of the state $|\\psi\\rangle$ in the position basis $|x\\rangle$, at position $x$.\nEdit to respond to a question asked by <PERSON> in response to <PERSON>'s answer: \"But doesn't an operator acting on the state project the state onto the eigenstates of the operator and is that the same as representing the state in a new basis?\"\nAs I have shown above, the \"projection\" you are talking about is given by applying the identity in terms of the position basis $\\mathbf{1=\\int dx~|x\\rangle\\langle x|}$.\nLet's see what happens when we apply $\\hat{x}$ instead: Just like state vectors can be expanded in a complete basis, so too can operators.", "66" ], [ "In general, if we take our complete basis ${|i\\rangle}$ we can write the operator $\\hat{A}$ in terms of matrix elements $$\\hat{A} = \\sum_{i,j} |i\\rangle\\langle i |\\hat{A}|j\\rangle\\langle j |$$ where the matrix elements are $A_{ij} = \\langle i |\\hat{A}|j\\rangle$. For the case of the position operator $\\hat{x}$ and using the position basis ${|x\\rangle}$ $$\\hat{x} = \\int dx~dy~ |x\\rangle\\langle x |\\hat{x}|y\\rangle\\langle y |\\ = \\int dx~ x~|x\\rangle\\langle x |$$ that is, it is diagonal in the position basis (obviously). Using this we see $$\\hat{x}|\\psi\\rangle = \\int dx~ x~|x\\rangle\\langle x |\\psi\\rangle$$ So we see that application of $\\hat{x}$ can be thought of as a kind of projection, weighted by $x$. So we see that it is not the same as representing the state in the $x$ basis, which is actually $$|\\psi\\rangle = \\int dx~ |x\\rangle \\langle x|\\psi\\rangle$$ as above.", "66" ], [ "Exact eigenfunctions of two interacting identical particles\nWhile I was reading about quantum states of $N$ interacting identical particles, I realized that I don't understand some fundamental things. So In order to clear my confusion, I decided to consider a toy model and work everything out for it: ground state wave-function, energy and first excited state wave-function and energy.\nConsider two interacting identical particles (let's say bosons with spin $0$ or fermions with spin $\\frac{1}{2}$) with Hamiltonian: $$ H=\\frac{p_1^2+p_2^2}{2m}+\\frac{m\\omega^2}{2}(x_1^2+x_2^2)+\\frac{m\\Omega^2}{2}(x_1-x_2)^2. $$ This Hamiltonian can be easily diagonalized using the coordinates $\\xi=\\frac{x_1+x_2}{\\sqrt{2}}$, $\\eta=\\frac{x_1-x_2}{\\sqrt{2}}$:\neigenfunctions $$ \\psi_{n_1,n_2}(x_1,x_2)=A\\exp\\left{-\\frac{m\\omega}{2}\\xi^2-\\frac{m\\sqrt{\\omega^2+2\\Omega^2}}{2}\\eta^2\\right}H_{n_1}\\left(\\sqrt{m\\omega}\\xi\\right)H_{n_2}\\left(\\sqrt{m(\\omega^2+2\\Omega^2)}\\eta\\right), $$ and spectrum $$ E_{n_1,n_2}=\\omega\\left(n_1+\\frac{1}{2}\\right)+\\sqrt{\\omega^2+2\\Omega^2}\\left(n_2+\\frac{1}{2}\\right),\\quad n_1,n_2=0,1,2... . $$ [here $H_n$ - are Hermite polynomials.]\n1) two identical bosons with spin $0$.\nTo get the ground state wave function, which is symmetric in $x_1, x_2$, we take the eigenfunction with $n_1=n_2=0$ $$ \\psi_0(x_1,x_2)=\\psi_{0,0}(x_1,x_2)=A\\exp\\left{-\\frac{m\\omega}{2}\\xi^2-\\frac{m\\sqrt{\\omega^2+2\\Omega^2}}{2}\\eta^2\\right} $$ since it is automatically symmetric in $x_1$ and $x_2$.", "281" ], [ "Ground state energy is $E_{0,0}$. First exited state energy will be $E_{1,0}$ with eigenfunction $$ \\frac{1}{\\sqrt{2}}\\left(\\psi_{1,0}(x_1,x_2)+\\psi_{1,0}(x_2,x_1)\\right). $$ We also get that this system can not have energy $E_{0,1}$ because in that case $$ \\psi_{0,1}(x_1,x_2)+\\psi_{0,1}(x_2,x_1)\\equiv 0 $$ since $H_1(x)$ is an odd function.\n2) fermions with spin $\\frac{1}{2}$.\nGround state is given by $\\psi_0(x_1,x_2)=\\psi_{0,0}(x_1,x_2)$ and corresponds to the singlet state (total spin $S=0$) of the system of two spin $\\frac{1}{2}$ fermions. Since the singlet state spin wave-function is antisymmetric, this means spatial wave-function is symmetric. First exited state energy will be $E_{1,0}$ with symmetric spatial eigenfunction $$ \\frac{1}{\\sqrt{2}}\\left(\\psi_{1,0}(x_1,x_2)+\\psi_{1,0}(x_2,x_1)\\right). $$\nHowever, unlike the boson case above, the energy $E_{0,1}$ is attainable for fermions of spin $\\frac{1}{2}$ in the triplet state (with total spin $S=1$).", "66" ] ]

[ 9209, 281, 7625, 9330, 2354, 8572, 5700, 8497, 3771, 2474, 2092, 10544, 5237, 5359, 3275, 6393, 1647, 8611, 2852, 1318, 2238, 2259, 5589, 2768, 932, 11074, 10078, 2115, 9839, 3073, 6129, 2304, 3204, 3579, 6257, 9068, 4560, 7824, 6088, 6306, 2043, 2040, 10261, 9172, 8345, 4818, 1436, 2097, 6749, 748, 1113, 3435, 9473, 10682, 6763, 4201, 11036, 1133, 5137, 132, 8873, 9504, 3542, 9125, 7031, 2973, 8005, 3556, 1448, 6451 ]

[ [ "Belarus Catches Up to Russia With Its Own Pro-government ‘Troll Factory’ · Global Voices\nBelarusians are noticing suspiciously similar comments under news articles—are government trolls to blame? Images mixed by <PERSON>.\nAs the relations between Russia and the West soured over the ongoing crisis in Ukraine, Kremlin officials have been intensifying their information manipulation efforts. This summer for the first time the world found out about Russian troll factories—the secretive agencies that hire people to write and spread pro-Kremlin propaganda on the Internet.\nIt turns out, there is a online troll factory in Belarus as well. Several months ago local media detected accounts posting similar positive comments about the Belarusian ruble to US dollar exchange rate. The dollar exchange rate has soared almost six-fold during the last five years, with the Belarusian ruble heavily dependent on the state of neighboring Russia's economy, which is currently in deep trouble. At the end of August, 2015, the US dollar surpassed 17,000 Belarusian rubles—a record high. For reference, at the beginning of 2011 one US dollar cost 3,000 Belarusian rubles.\nIt was in August of this year that journalists of the opposition newspaper Nasha Niva (Our field) first noticed that some users were praising the ruble, at the time when it was so unstable. The suspected trolls would write that they “believed in ruble” and that Belarusians would overcome all temporary difficulties: “Don’t panic! Everything's gonna be alright!” Journalists dutifully copied all the “suspicious” comments and published a collection of them on their website (many original comments have since been deleted after the “unmasking.”)\nIn general, the Belarusian trolls are seen using three main tactics.", "564" ], [ "First, one should say that everything is alright and that any concerns about the issue are simply a sign of panic.\nРешили посеять панику? Зря. Валюты в обменниках хватает. Покупайте! И вообще-то, в стране все под контролем)))\nSo you decided to spread panic? It's no use. There is enough currency in exchange offices. Buy it! And, by the way, everything in the country is under control.\nSecond, one should mention that Belarusians don't need dollars, because they spend their money in Belarus, not in the US.\nНавошта мне гэтая амерыканская валюта!? Я усе свае дабро берагу у беларуских рублях. Я жыву у Беларуси, а не у Амерыцы\nWhat do I need this American currency for? I keep all my savings in Belarusian rubles. I live in Belarus, not in America.\nAnd thirdly, always blame the West.\nВсе мы понимаем, почему происходит падения рубля: сейчас это явно спровоцировано из вне. И если бы власть сегодня «показушно» сдерживала курс, то неизвестно к чему бы это привело к концу года.", "564" ], [ "The Dress Rehearsal for the Belarusian Crackdown · Global Voices\nTotal media control, or the unexpected virtue of being <PERSON>. Images edited by <PERSON>.\nThe state of free speech in Belarus enjoys remarkable stability: in 2015, Belarus placed 157th out of 180 countries on Reporters Without Borders’ Press Freedom Index for the third consecutive year. Attacks on the independent media have been commonplace since the 1990s. Restrictive laws, raids on newspapers, politicized criminal prosecutions, travel bans against outspoken reporters, and failing to investigate the murder of several journalists—Minsk has used every possible tool in its arsenal against the free press.\nThe Belarusian president, <PERSON>, who's sometimes called “Europe's last dictator,” once said journalists “hold a weapon of a most destructive power.” That's the reason, he says, the state must exercise such control over the media.\nToday, Minsk controls the media almost entirely. There are a few rare exceptions online, like the opposition news outlets Charter 97, Naviny.by, Belaruspartisan.org, the newspaper Narodnaya Volya, and a few others. <PERSON> would probably be happy to shut down these publications, too, but they provide a semblance of pluralist democracy that's useful when responding to criticisms at home and especially abroad.\n<PERSON> headed a collective farm before the Soviet Union collapsed. Today, he treats the Internet with a mix of awe and caution, regarding it as one of mankind's greatest creations, albeit a potentially dangerous, inherently American weapon.\n<PERSON> and his youngest son <PERSON> during harvesting on the territory of the presidential residence. Image: Press-service of the president of the Republic of Belarus.\nBelarus’ suppression of the media becomes especially violent during election season. During the last election, in December 2010, several opposition websites and some entire social networks went down, targeted by blocking and hacking efforts. Police raided the offices of Belsat TV and European Radio‘s local station, detaining several journalists.", "704" ], [ "<PERSON> declared victory in the election, but an international monitoring group from the Organization for Security and Cooperation in Europe said the election was neither free nor fair. Between 10,000 and 60,000 people gathered in downtown Minsk to protest the voting results, but police special forces dispersed the crowd by force and arrested as many as 700 protesters, as well as seven of the nine presidential candidates.\nThe next election will take place later this year, in November 2015, and the country's political situation promises to be even more volatile. Five years ago, most Belarusians lived in relative comfort, enjoying rising wages and retirement benefits. In 2011, however, the country's currency reserves ran out, and the dollar exchange rate nearly tripled from 3,100 Belarusian rubles in March 2011 to 8,700 by October. (Today, it takes almost 15,000 Belarusian rubles to buy a single US dollar.) The value of oil worldwide, too, has plummeted. <PERSON> has managed to contain the economic crisis thanks mainly to generous loans from Moscow.\nIn 2015, the Belarusian government owes its creditors roughly $4 billion, which is about two-thirds of its entire foreign reserves. The Belarusian economy, dominated by large, inefficient state-owned companies, is little reformed from its Soviet predecessor. The longer the country's financial woes continue, the less likely it is that Russian aid can rescue <PERSON> from a reckoning with voters. Also, Russia's own imploding economy, not to mention <PERSON>'s refusal to endorse the annexation of Crimea, jeopardizes this one remaining lifeline.\nOfficials in Minsk seem to realize that a cataclysm might be ahead, and there are signs that Minsk is moving to address the situation, ahead of presidential elections. Last December, the parliament adopted amendments to regulations on the media, equating the online media with the traditional mainstream media. The reforms also grant the Ministry of Communications and Informatization the power to shut down online resources extrajudicially.\n<PERSON>, founder of the independent website By24.", "704" ], [ "In the heat of political crisis, Belarus launches first nuclear power plant · Global Voices\nAstravets nuclear power plant, Belarus, 2020. Photo (c): <PERSON>, used with permission.\nSince August, Belarus has been rocked by mass protests and strikes. The authorities try not to pay attention, for they are preoccupied with a no less historic development — the construction of a new nuclear power plant. That is controversial in a country which suffered greatly from the 1986 Chernobyl catastrophe in neighbouring Ukraine. Concern at the state of democracy dominates Belarusian public life, but alongside it another urgent conversation continues — about the country’s past experience with nuclear power, and whether it needs a post-nuclear future.\nAll eyes are on Astravets, a small town located near the Belarusian border with Lithuania. In recent years the town’s population has grown significantly: workers are badly needed, and new multi-storey apartments have shot up to house them.\nThe reason for these rapid changes is that Belarus’ first nuclear power plant is located outside the town. Its construction is now coming to an end and it is nearly ready to be started up. As engineers often explain, it takes more than pressing one button to launch a nuclear reactor.\nThat start-up will take place in several phases. The fuel has already been loaded; the plant is expected to generate its first electricity on November 7. This is a national holiday in Belarus, as it is the anniversary of the October Revolution — the revolution from which the Soviet Union was born.\n“I invite everybody. I think that on November 7, a significant day for us, we will be able to visit and say that we have received the first electricity from our own nuclear power plant”, exclaimed Belarus’ longtime ruler <PERSON> at a meeting with officials on September 16. The first of the two reactors is expected to operate at full capacity by the first quarter of 2021. The second reactor will be launched in 2022.\nHaunting memories\nBut not all Belarusians are so jubilant.", "739" ], [ "They remember the explosion in 1986, which released large amounts of radiation into the atmosphere. Belarus suffered more than anywhere else in the Soviet Union; a third of all the radioactive caesium-137 ended up in Belarusian territory. The authorities in Minsk have tried to assuage fears of a second Chernobyl, declaring that the likelihood of accidents is minimal, and that the Astravets nuclear power plant is a safe and profitable project.\n“We are the Chernobyl republic, we have experienced a lot and we know the consequences ourselves. Some US$19 billion has been spent on rehabilitating contaminated areas alone. Therefore, safety measures during the construction of the [Astravets] power station were like something out of wartime”, said <PERSON> in August, just before the presidential elections.\nIn the public discussion about nuclear energy, comparisons between Chernobyl and Astravets are not so uncommon. These parallels are drawn by everybody, including journalists, politicians, ordinary citizens, and surviving liquidators from the Chernobyl catastrophe. They all deeply regret what occurred in 1986, but their opinions on 2020 strongly differ. Some strongly support the new nuclear power plant and hope for an increased standard of living, while others fear another accident.\nBelarusian state media and officials do not shirk from mentioning Chernobyl, either.\n“The memory of the events at Chernobyl is now being instrumentalised and used to legitimise the new nuclear power plant. On the 30th anniversary of the accident, a documentary film was broadcast which began with footage of the 1986 accident and ended with a hint that this time, everything would be alright,” writes <PERSON>, head of public history projects at the European College of Liberal Arts in the Belarusian capital of Minsk.\nOnce the nuclear power plant is fully operational, explained the authorities in the early stages of construction, electricity prices will fall. In 2014, the Ministry of Energy promised that electricity “will become cheaper for the consumer” by 20-30 percent.\nBut some Belarusians seem to be sceptical about promises of cheap energy. They also doubt that the power plant will open at all, given that its launch has already been postponed at least four times. All these views can be seen in local community groups on social media:\n“I work on the construction site of the nuclear power plant, and [acquaintances] sometimes ask me when it will be launched. I think [the plant’s management] don’t even know themselves, they say within two to three years at a minimum”, says <PERSON>, who was born and grew up in Astravets, in a Telegram chat with GlobalVoices.\nDoes <PERSON> expect a drop in electricity prices?", "704" ], [ "Building an Internet Fast Lane in Russia Could Be a Great Way to Stifle Independent Media · Global Voices\nThe net neutrality paradise of information equality may be coming to an end in Russia. Images mixed by <PERSON>.\nThe Federal Anti-Monopoly Service (FAS) may soon allow Internet Service Providers to collect fees from websites willing to pay a premium for prioritized content delivery.\nThe popularity of websites and services content requiring high bandwidth, like YouTube and Skype, has led to a dramatic increase in the amount of data traveling through the Internet, FAS says. The increased load on Russia's telecommunication network necessitates new investment in the national infrastructure, but ISPs complain that they're short on funds.\nAs is the case around the world, Russian Internet service providers are vocal opponents of net neutrality, which exists in Russia largely de facto, without being legally enshrined. Rostelecom, a leading local telcom that is majority-owned by the Russian government, has blamed Skype for gobbling up too much of its bandwidth and in turn allowing users to make calls for “free,” rather than using Rostelecom's telephone services. According to the company, customers’ use of Skype cost it 6.7 billion rubles ($166 million USD) in 2009 alone.\nAlthough network neutrality is not explicitly protected under Russian law, Russian ISPs effectively treat all Internet traffic equally when it comes to its “size” or the amount of bandwidth it requires for transport.", "534" ], [ "It should be noted that Russian ISPs do block some traffic on political grounds—a practice that goes against the principle of net neutrality, which is to treat all traffic equally, without exception.\nDetails about the plan to end Russian net neutrality are still few and far between. So far, FAS has merely submitted its proposal to the government, which will deliberate for nobody knows how long. In fact, FAS’ announcement itself was quite unexpected. Just a few months ago, agency head <PERSON> expressed his support for the principles of net neutrality, saying that ISPs should treat all content equally.\nИ мы можем ещё раз подчеркнуть, что ликвидация мобильного рабства, технологическая нейтральность, сетевая нейтральность, конкуренция между стационарной электросвязью, развитие её с мобильной и так далее являются фундаментальными вопросами, о которых мы мечтали 10 лет.\nWe can stress once again that the end of “mobile slavery” [the introduction of portability for mobile telephone numbers] and the arrival of technological neutrality, Net neutrality, competition between landlines and mobile networks, and so on, all represent fundamental things we dreamed about for the last decade.\nNow, however, FAS officials are citing the Federal Communications Commission in the United States for arguments against net neutrality. FAS’ new proposal would require ISPs to maintain a service “baseline,” but companies would be allowed to charge more money to deliver faster speeds for premium content.\nNet neutrality remains an unresolved issue in the US, as well, where the FCC's position seems irresolute, despite President <PERSON>'s statement on October 9 that he opposes “creating two or three or four tiers of Internet.” When it comes to Internet regulations, Russian officials often model policy on approaches tried in the United States. By “copycatting” the US, Moscow is able to defend itself as “behaving like the Western democracies.”\nDepending on what the FCC does with net neutrality, Russia's FAS might need to reexamine its justifications for policy reform.\nIn Russia, where the online space for independent media is fast shrinking, the prospect of filtering Internet content poses additional dangers.", "704" ], [ "As Russian court announces Telegram ban, users stand defiant, amused… and worried · Global Voices\nRussia bans Telegram; collage by <PERSON>\nAs a Moscow court ordered the ban of messenger app Telegram on April 13, 2018, Deputy Communications Minister <PERSON> assured the public that those who want to keep using it “will look for ways to bypass the blocking.” In a rare moment of consensus with the Russian authorities, many Telegram users agreed.\nThough conceived as a messenger app similar to WhatsApp, Telegram earned its popularity in Russia thanks to its “channels,” a blogging platform somewhere between Twitter and Facebook which quickly attracted political commentators, journalists and officials. Telegram channels are a booming business, too: they are widely used in political and corporate wars. Last year Vedomosti, a Russian business newspaper, claimed that political ads (or damaging leaks) on Telegram's most popular channels could cost as much as 450,000 rubles ($7,500.)\nBut Telegram's CEO <PERSON> has repeatedly and vocally refused to comply with the demand of Russian security services to give up the messenger's encryption keys.\nAnd as the year-long battle between Telegram and the Russian authorities came to a head with the decision to block the app, reactions to the announcement have been passionate.\n“Russia has finally become the world's second largest economy after China! At least in the field of permanently blocking Telegram,” wrote <PERSON>, formerly a press officer for a <PERSON> youth movement.\nOther channels took a defiant stance, encouraging their followers to find ways around the blocking.\n“They are blocking us, and we get stronger!” wrote the author of the Deer of Nizhny Novgorod, a channel focused on politics in the Nizhny Novgorod region.\nLike several other channels, the Deer of Nizhny Novgorod provided links to tutorials on how to circumvent the blocking of Telegram using a VPN or Virtual Private Network. “If you’re not a grandmother, you’ll be able to do it very easily and quickly,” he added.\nBut not all agree that cheating your way out of a government ban is a walk in the park:\nкогда ты гуманитарий и пытаешься понять, как настроить прокси в телеграме pic.twitter.com/M32Ut9EoOI\n— Никотинка с Бровями (@Yoghikitt) 13 апреля 2018 г.\nWhen you majored in liberal arts and are now trying to figure out how Telegram proxies work\nChannels dedicated to Russian politics and the inner workings of the Kremlin – among the most popular on the platform – also largely claimed they were not worried by the ban.\n“About 85% of our users have installed one [a VPN] in the last 24 hours.", "880" ], [ "If you haven’t, here are the instructions,” channel Karaulny (The Sentinel) told its 66,000+ followers.\nThe owner of Nezygar (“Not <PERSON>”, a play on the name of <PERSON>, a Russian political journalist and author of the best-selling book All the Kremlin's Men), one of the most influential political channels with 133,000 followers, told Russian outlet RBC the ban “confirmed Telegram’s status as an independent platform.”\n“Nezygar will stay on the platform and won’t move to another,” he added.\nOthers took a different road. <PERSON>, the deputy of the ruling party United Russia, published on Twitter a video showing himself dramatically deleting Telegram from his smartphone:\nВыполняю решение суда. Соблюдаю законы РФ. pic.twitter.com/BKp0qW7045\n— Сергей Боярский (@sergeyboyarskiy) 13 апреля 2018 г.\nI am following the court decision. I abide by the laws of the Russian Federation.\nChechnya's strongman leader <PERSON>, who was banned from Instagram in December 2017, also said he would not try to make any attempts to bypass the blocking.", "880" ], [ "On Telegram, Russian Politics and Memes Translate Into Big Bucks · Global Voices\nThe most popular Telegram “channels” have many thousands of subscribers. Screencapped by <PERSON>\nWith more than 90,000 subscribers, the Telegram channel “MDK” is not just one of the most popular one-stop shops for Russian-language memes on the messenger app. It’s also a profitable business.\nMDK’s administrator told RuNet Echo he charges 25,000 rubles ($420) for a single ad on his channel, a blogging platform somewhere between a Facebook and Twitter account. He would not comment on how much money the channel was making overall, but sources in Russian media have claimed popular Telegram channels such as MDK can bring in up to 1 million rubles ($17,000) a month. Even that, however, can look like chump change when compared to other, more political, channels.\nThe emergence of Telegram channels is one of the consequences of the growing popularity of the messenger app created by <PERSON>, the tech entrepreneur behind Vkontakte, a Facebook clone that still dominates the Russian social media landscape.\nMost popular chat apps in Russia, graph by @thebell_io pic.twitter.com/X2uHDQfj1o\n— <PERSON> (@fabrice_deprez) 27 de septiembre de 2017\nTelegram channels are a distinct feature allowing the messenger app to also be used as a blogging platform: anyone can subscribe to a channel, but only the creator can post on it. Channels have quickly grown in size and numbers in the last two years, and in some cases have become sizable business operations. One of the most popular Telegram channels made the headlines in the Russian press in September 2017 when it was sold for 5.5 million rubles (US$95,000) just two weeks after its creator had first sold it for 1.2 million rubles (US$20,000).\nThe business side of channels can get murky, however.", "880" ], [ "That is because they have proved attractive not only to news websites and meme aggregators, but also to a whole new brand of anonymous political bloggers who specialize in revealing what they claim to be “insider information” about Kremlin politics.\nOn September 27, Russian business daily Vedomosti reported that Telegram channels had turned into a new market for “political ads,” claiming that business and political actors were ready to pay up to 450,000 rubles (US$7,500) to get information published on these channels. An administrator from the “Karaulny” political channel, which has 26,000 subscribers, told RuNet Echo that offers for publishing information on their channel ranged from 50,000 to 150,000 rubles and were essentially about “corporate conflicts,” but they would not comment on whether or not they accepted the proposals.\nVedomosti's piece does not say what kind of information is being published for this kind of money, though it quotes a source claiming the publication of “negative information” (otherwise known as black PR) can cost two to three times as much as more positive ads.\nThese prices might stem from the growing belief that these channels have gained a loyal readership in the higher ranks of the Russian state apparatus. In January 2017, local outlet Ura.ru claimed Telegram channels were routinely read during morning briefings and meetings of Duma deputies and in various ministries’ cabinets. In September, Vedomosti also revealed the channels were being monitored by Russia's Federal Security Service as well as the defense and interior ministries.\nThanks to a flurry of information and a few scoops, anonymous political channels have become over the previous year a major – albeit controversial – source of insights into Russian politics. “Nezygar,” the most popular of these channels, increased from 16,000 subscribers at the beginning of the year to more than 72,000 in September.\nThis growing popularity has also attracted criticism over the lack of transparency these anonymous channels thrive in. <PERSON>, a Russian journalist and himself an avid Telegram user, told the Rain TV channel in January that “If Russia had good political scientists, active political journalism and strong, independent media, the ‘Nezygar’ phenomenon would not exist.”\nGiven that not only the channels but also the high-ranking officials allegedly reading them are, in most cases, anonymous, doubts remain about their actual influence, while theories abound about their provenance. But whether they are, according to a source quoted by Vedomosti, a “plaything” of the Kremlin’s internal politics department or a new media for political experts, one thing seems clear: it’s a promising business.", "384" ], [ "President <PERSON>’s Controversial Pardon Has Not Put Poles in a Forgiving Mood · Global Voices\nPolish lawyer and politician <PERSON> assumed the office of President in August 2015. Photo by <PERSON>, September 12, 2013. CC 2.0.\nEarlier this month, just a day after the new Polish government was sworn in, President <PERSON> made the controversial decision to pardon <PERSON>, a member of <PERSON>'s former party, Law and Justice.\n<PERSON> was convicted of abusing his powers as head of Poland's Central Anticorruption Bureau, where he served until 2009, during which time the Law and Justice party controlled the Polish government. Before his pardon, <PERSON>'s sentence had not yet entered force, as he was awaiting an appeal trial.\nAlthough the conviction itself was seen as controversial and some considered it a political move made by the previous government (controlled by rivals in Civic Platform), many say <PERSON>'s decision to pardon <PERSON> is surprising and possibly inappropriate. Had <PERSON> lost his appeal, he would have been barred from holding public office ever again, and he may have been sent to prison for many years. <PERSON> currently serves as the head of special services in Poland's new government.\nPolish social media users soon voiced their opinions on Twitter. <PERSON> wrote:\nPrzypominam, że ułaskawienie potwierdza wyrok.", "1017" ], [ "Od dziś o zainteresowanym można pisać per “przestępca”\n— <PERSON> (@konradniklewicz) November 17, 2015\nI want to remind you all that the pardon confirms the ruling. From now on we can call the person in question “guilty”\n<PERSON> also commented on Twitter:\nPAD to chyba zrobił Kamińskiemu krzywdę, bo ułaskawienie nie jest uniewinnieniem. Nie wiąże się z zatarciem. Nie znam się ale to głupie\n— <PERSON> (@FilipLachert) November 17, 2015\nI think that PAD [President <PERSON>] did a disservice to <PERSON>, because the amnesty doesn't mean “not guilty.” It doesn't equal an erasure of conviction. I'm not an expert but I think it was stupid.\nAnother Twitter user, <PERSON>, compared pardons issued by Poland's current and past presidents. As depicted in the picture attached to the tweet, <PERSON>'s pardon was suspiciously just a single sentence long.\nTak na obrazkach wygląda ułaskawienie normalne i ułaskawienie nienormalne: pic.twitter.com/EGi7CXfGBF\n— <PERSON> (@aronsem) November 20, 2015\nOn the attached pictures it can be seen how a normal act of pardon looks like, and how a not normal one looks\n<PERSON> also wrote about the pardon:\nPo to głosowałam na PiS i prezydenta <PERSON> by w moim imieniu ZAWŁASZCZYLI wreszcie państwo , wyrywając je z rąk złodziei i zdrajców\n— <PERSON> (@ISzafranska) November 19, 2015\nThis is why I voted for PiS [Law and Justice] and the Presient <PERSON>, so that they could reclaim the nation and pull it out of the hands of thieves and traitors\nSeveral members of the public complained that <PERSON> has compromised the presidency's impartiality and duty to represent the interests of the nation by indulging in partisan politics. While it's not illegal for the president to pardon a former colleague, <PERSON>'s decision has invited criticisms that he's violated the spirit of his obligations as Poland's leader.\nAlready divided after the elections, Polish citizens continued to be disagree about <PERSON>'s actions.\nPopular blogger and Twitter user <PERSON> posted:\nCoś czuję, że jak będzie za duży jazgot wokół tego ułaskawienia to wkrótce wypłynie jakieś nieznane do tej pory ułaskawienie poprzednika.", "1017" ], [ "Security concerns and legal ambiguities threaten the future of Ukraine’s ‘State in a Smartphone’ · Global Voices\nThe “state in a smartphone” project is one of the most ambitious developments of the current Ukrainian government. Photo by JESHOOTS-com on Pixabay.\nOne year ago, the Ukrainian government released the revolutionary mobile application Diia (Ukrainian for “action”), a cornerstone of President <PERSON>’s campaign promise of making public services convenient and easily accessible via the internet.\nThe Diia mobile app — and its accompanying online e-services portal — allows citizens to digitize their national ID and biometric passport, personal tax number, student ID, and more, and the digital documents wield the same legal power as the original paper ones. Within a year, Ukraine became the fourth European country to have a digital driver’s license and the first country in the world to have a digital passport.\nHowever, a massive data leak last year has raised concerns about the level of protection around users’ personal information. In May 2020, activists discovered about 900 GB of citizens’ personal data being traded by an anonymous chatbot on the popular messaging platform Telegram. The dataset included passport numbers, personal tax numbers, residence information, driver’s licenses, social media passwords, and even bank details of millions of Ukrainians.\nSome public officials accused Diia of leaking data from government registries, while security experts recalled that the Ministry of Digital Transformation had yet to release any security documentation for the app. While journalists and researchers were able to confirm that part of the datasets had come from Ukrainian government registries, no evidence implicating Diia directly has been found.\nOn the anniversary of its launch, Diia app boasts over 6 million users.", "534" ], [ "At the same time, IT specialists and digital rights defenders continue to call on the government to consider all of the risks that e-government and digital identification technology carry, as these may potentially undermine the public's trust.\nDigitizing the nation\nWhile the idea of digitizing public services is not new to Ukraine, Zelensky's is the first administration that has made e-governance a top priority or established a separate ministry entirely dedicated to it — the Ministry of Digital Transformation, headed by <PERSON>.\nOriginally presented in the spring of 2019, the ambitious “State in a Smartphone” program envisioned moving all public services online and providing the majority of the citizens with a means of digital identification. It was later expanded to include goals such as increasing people's digital literacy, expanding internet infrastructure, and creating favorable conditions for the development of the information technology (IT) industry.\nIf implemented successfully, the program could help combat corruption by minimizing the interference and arbitrary decisions of public officials, while significantly reducing state bureaucracy.\nIn addition, Minister <PERSON> has proudly noted that not a single hryvnya from the state budget had been spent on the development of the Diia app — its development team comprised 35 volunteers from the well-known software engineering company EPAM Systems. They later transferred the completed product and relevant technical know-how to the state.\nHow secure are citizens’ data in Ukraine?\nInitially, the ministry announced that Diia used BankID technology from several leading Ukrainian banks for user authorization, and that it utilized a secure cloud server for the transfer of encrypted data.\nStill, few disclosures were made about the security of citizens’ personal data on the app, and security specialists cautiously noted that not enough was known about Diia's security testing.\nNo independent security audit seemed to have been performed, for example — hardly acceptable for technology to which millions of citizens would be entrusting their personal information. In fact, the app's first public bug bounty program was not launched until December 2020.\nThe leaks have made clear that the standard of data security at the state level in Ukraine remains inadequate — including a weak legal data protection regime, poor enforcement, and the lack of appropriate protection measures within state institutions themselves. Synchronization of data from various government registries into one portal or app is therefore likely to result in additional vulnerabilities to external attacks.\nMoreover, in December 2019, the government granted the Ministry of Internal Affairs the power to verify and aggregate citizens’ data from multiple state registries, providing the law enforcement body with access to data from at least five government registries, including those that handle civil, tax, social security, healthcare and voter information. Alarmingly, the data sharing was to be carried out as a part of an “experimental” process that lacked comprehensive legal safeguards ensuring citizens’ right to privacy.\nAccording to an analysis by digital rights advocates from Digital Security Lab, as of August 2020, the interior ministry had not yet developed a methodology for such verification, but this has not prevented it from gaining access to the vast trove of citizens’ personal data.", "609" ] ]

[ 11051, 1683, 10596, 8733, 6571, 746, 9405, 9170, 11344, 6364, 5678, 6090, 402, 110, 6851, 8534, 4128, 4106, 4777, 2791, 5427, 8262, 3114, 414, 9359, 4834, 7650, 5946, 2835, 5936, 5238, 4247, 9151, 10663, 11025, 11373, 10810, 5468, 2208, 11255, 8154, 2472, 9880, 7778, 5873, 2738, 3126, 549, 7275, 8148, 9630, 3981, 97, 5634, 3067, 1125, 5197, 612, 6623, 3506, 5789, 2343, 6299, 5627, 9991, 7474, 2935, 3932, 9524, 5161 ]

[ [ "Differential Thermal Analysis Using Arduino and PhyPhox\nIntroduction: Differential Thermal Analysis Using Arduino and PhyPhox\nWhen a solid substance is heated the increase in energy manifests itself in the form of an increase in temperature.\nIf the heating rate is constant the temperature increase is also constant as long as there is no change in the structure of the substance.\nAt the time when some kind of transition is initiated in the substance, for example fusion, change of crystal structure or other, the temperature will not increase at the same rate because part of the heating energy will be used in that change of state.\nIf we compare the temperature of the substance that is experiencing the change of state (Sample) with that experienced by another substance that remains stable (Reference) during heating under identical conditions and subtract a temperature value from another (Sample - Reference) we will be performing what is known as Differential Thermal Analysis (DTA).\nThe objective of this Instructable is to show the basics of the DTA using Arduino microprocessor, a home heater and a free access program (PhyPhox) that will allow us to obtain on our cell phones curves of Sample Temperature vs Difference (Sample Temperature - Reference temperature) known as thermograms.\nSupplies\n* Cell Phone (Android or iOS).\n* PhyPhox app (Google Play or AppStore).\n* 1 Plastic container with multiple compartments.\n* 2 Waterproof DS18B20 temperature sensor.\n* 2 Breadbord mini modular.\n* 1 Arduino Nano V3.0 CH340 with mini usb cable.\n* 1 Bluetooth Low Energy BLE CC2541 Bluetooth 4.0 UART.\n* 1 1k ohm resistance.\n* 1 2k ohm resistance.\n* 1 4,7k ohm resistance.\n* Male/Male jumpers wire.\n* Male/Female jumpers wire.\n* 1 Portable battery charger (6000 mAh 3.7V, Out 5V, Output Max. 2.4A).\n* 4 Glass test tubes (approximately 1 cm in diameter and 7.5 cm long)\n* Wooden base (circular or square of approximately 20 cm in diameter or side).\n* 1 Ceiling lampholder (E27).\n* 1 Incandescent light bulb of 25 Watts (E27).\n* 1 Rotary dimmer switch.\n* Approximately 1 m of electrical cable (two cores 0.4 mm thick).\n* 1 Two pin electric socket.\n* 1 Clothes dryer aluminum duct reducer (10.16 cm to 7.62 cm).\n* 2 Disposable circular aluminum plates of approximately 20 cm in diameter.\n* 2 Wire insulate screw cap.\n* Electrical tape.\n* Silicone or Epoxi glue.\n* Plastic fasteners.\nStep 1: Heating Device\nA DTA equipment basically consists of a furnace containing two containers, one for the Sample and one for the Reference and two sensors that measure the temperature of Sample and Reference simultaneously.\nThe temperature inside the furnace and its heating or cooling rate must be very well regulated so the construction of the furnace in professional equipment is an important factor in the design of a DTA apparatus, however for the illustrative purposes of this Instructable it was chosen to make a rather modest design using homemade materials (see supplies list) as indicated below :\n* Fix on a wooden base a ceiling lampholder (E27) provided with two core electrical cable with two pin electric socket.\n* Section one of the cores of the electrical cable and connect a rotatory dimmer switch, using wire insulate screw cap or electrical tape to reestablish the cable connection.\n* Screw an incandescent light bulb (25 Watts, E27) into the ceiling lampholder.\n* With the help of glue, fix on the surface of the ceiling lampholder a clothes dryer aluminum duct reducer (10.16 cm to 7.62 cm) so that the end of smaller diameter is like a chimney around the incandescent light bulb (Caution: Once the bulb is turned on this surface will be hot so there will be a danger of burn).\n* Fold the surface of a disposable circular aluminum plates in such a way as to form a concavity that fits on the chimney formed by the clothes dryer aluminum duct reducer (see video in Step 3).\n* Using another plate repeat the previous operation forming a concavity that fits on the first and in which two holes near the top of the concavity but separated from each other will be drilled, with a diameter that allows to receive the test tubes (approximately 1 cm in diameter and 7.5 cm long) of Sample and Reference.\n* Insert the Sample and Reference test tubes into the drilled holes by pushing until only about 1 cm is left outside. Deform the surface of the aluminum sheet in such a way that they fit on the surface of the test tubes and fix them.", "152" ], [ "Measuring the Boiling Point of Liquefied Gases Using Arduino and PhyPhox\nIntroduction: Measuring the Boiling Point of Liquefied Gases Using Arduino and PhyPhox\nA substance that is in a liquid state is constantly evaporating or passing into the gaseous state (depending on the intermolecular forces and temperature). The pressure exerted by the gaseous molecules produced in this process is known as vapor pressure.\nThe vapor pressure depends on the temperature in such a way that at higher temperature higher vapor pressure. The temperature at which the vapour pressure equals atmospheric pressure is known as the boiling point.\nIn the case of liquefied gases contained in pressure vessels, such as gases used to clean dust, liquefied petroleum gas (LPG) or refrigerant gases, the pressure at which they are kept in the vessel allows a fraction of the gas to be in a liquid state.\nIf this liquid is removed from the vessel and subjected to atmospheric pressure it will begin to evaporate so it will take energy from the surrounding environment lowering the temperature around it. Under these conditions the vapour pressure of the liquid equals the atmospheric pressure and the liquid therefore reaches its boiling point.\nThe aim of this Instructable is to measure that boiling point, which as these are liquefied gases will normally be below 0°C, using an Arduino microprocessor and a waterproof DS18B20 temperature sensor capable of measuring temperatures up to -55°C.\nThe data will be transmitted via Bluetooth to a cell phone provided with the PhyPhox app that will not only allow us to graph and analyze the data but also have access to the sensors of the cell phone, in this case the barometric pressure meter, which will allow us to program the app to correct the boiling point value measured to its standard value referring to atmospheric pressure at sea level or 1 atmosphere.\nThe measured boiling point, in conjunction with other physical tests, e.g.", "152" ], [ "sound speed, can be used for preliminary identification of gaseous substances.\nSupplies\n* Cell Phone (Android or iOS) with barometric pressure sensor (see examples in PhyPhox Sensor DataBase).\n* PhyPhox app (Google Play or AppStore).\n* 1 40 ml Plastic dropper pump (Good Cook brand).\n* 1 Plastic container.\n* 1 Waterproof DS18B20 temperature sensor.\n* 2 Breadbord mini modular.\n* 1 Arduino Nano V3.0 CH340 with mini usb cable.\n* 1 Bluetooth Low Energy BLE CC2541 Bluetooth 4.0 UART.\n* 1 1k ohm resistance.\n* 1 2k ohm resistance.\n* 1 4,7k ohm resistance.\n* Male/Male jumpers wire.\n* Male/Female jumpers wire.\n* 1 Portable battery charger (6000 mAh 3.7V, Out 5V, Output Max. 2.4A).\n* Cutter knife.\n* Silicone glue.\n* Plastic fasteners.\nStep 1: Measuring Probe\nThe measuring probe is basically a conical vessel that is inserted at its narrow end by the DS18B20 temperature sensor leaving enough volume of the cone to completely cover the sensor approximately 5 cm above the end of this one.\nAs a conical container, a plastic dropper pump (40 ml) was used that was cut into two parts, being the narrowest conical end to which the temperature sensor were adjusted and the wider conical end, next to the pump, used as a base.\nThe assembly fits a plastic container that serves as a support and box to hold the Arduino circuit.\nThe following is the procedure for constructing the measuring probe (see images):\nNote: Before mounting the DS18B20 temperature sensor perform the calibration indicated in Step 2.\n* Cut the plastic dropper pump to the height of the 15 ml mark (Caution: cutting hazard).\n* Insert the DS18B20 temperature sensor into the narrowest conical end so that the entire metal body is inside the cone. If necessary increase the diameter of the dropper tip to adjust the sensor.\n* Fix the sensor using silicone rubber or some other low temperature resistant glue. Let dry.\n* Drill a hole in the wider conical base with a diameter that allows the DS18B20 temperature sensor cable to be inserted.\n* Insert into the wide conical base invertedly the conical piece with the sensor inserted passing the cable through the hole previously drilled.\n* Drill a hole in the lid of the plastic container that will serve as a container of the Arduino circuit of such a diameter as to allow the dropper to be inserted by its wider base.\n* Attach the rubber pump to the base of the dropper, under the lid of the plastic container, so that it is fixed to it.", "152" ], [ "Measuring Refrigerant Gases Sound Speed Using Arduino and App Inventor 2\nIntroduction: Measuring Refrigerant Gases Sound Speed Using Arduino and App Inventor 2\nThe purpose of this Instructable is to build a portable device that can measure the speed of sound in refrigerant gases and use this data to identify them.\nThe speed of sound in an ideal gas is related to two characteristics of the gaseous substance, its molecular mass (kg/mol) and its adiabatic constant (heat capacity ratio), or its average values in case of being a mixture of gases.\nIt is for this reason that the measurement of the speed of sound can be used as a preliminary way to identify a pure gas or mixture of gaseous substances.\nThe measurement can be performed using an ultrasonic proximity sensor, to measure the round trip time ( t/2 ) of a sonic pulse in a plastic tube of known length ( x ) (echo method), filled with the gas under study ( v = 2x/t ).\nSince the speed of sound is also absolute temperature dependent, it must be measured using a digital temperature sensor.\nThe values measured by the sensors are captured and processed by an Arduino microcontroller that transmits them via bluetooth to a mobile application, designed with App Inventor 2, which will allow to calibrate the length of the plastic tube using a reference gas whose sound speed is known.\nThe application will use this information to calculate the sound speed of an unknown sample of a refrigerant gas and perform preliminary identification (see disclaimer **).\nSupplies\n* PVC pipe piece approximately 14 cm long and 4.8 cm in external diameter (1-1/2'').\n* 2 PVC pipe caps approximately 4.8 cm in internal diameter (1-1/2'').\n* 2 Toothpaste tube shoulder pressure caps.\n* 1 Piece of leak repair tape about 15 cm x 25 cm.\n* Epoxy glue.\n* 1 Plastic container.\n* 1 Breadbord.\n* 1 Arduino Nano V3.0 CH340 with mini usb cable.\n* 1 HC-SR04 ultrasonic sensor.\n* 1 TMP36 digital temperature sensor.\n* 1 Bluetooth HC-06.\n* 1 1k ohm resistance.\n* 1 2k ohm resistance,\n* Male/male jumpers cable.\n* Male/Female jumpers cable.\n* 1 Male/female usb cable.\n* 1 Portable battery charger (6000 mAh 3.7V, Out 5V, Output Max. 2.4A)\n* Electric tape.\n* Velcro tape.\nStep 1: Measuring Probe\nThe measuring probe is basically a piece of PVC pipe approximately 14 cm long by 4.8 cm external diameter (1-1/2'') to which three holes are drilled, two for gas inlet and outlet (provided with pressure caps of the type used in toothpaste tubes) and another for inserting a digital thermometer.\nThis pipe will be closed at its ends by two PVC pipe caps approximately 4.8 cm internal diameter (1-1/2''). One of the caps will have two perforations to accommodate the emitter and detector of the ultrasonic sensor. This part of the device is going to be the point of emission and detection of ultrasonic pulses, while the flat face of the other cap, opposite the emission point will be the rebound point (echo) of the pulses.\nThe following is the procedure for constructing the measuring probe:\n* From a 1-1/2'' PVC pipe cut a piece about 14 cm long.\n* About 4 cm from each end of the tube piece make two perforations, in opposite directions, approximately 5 mm in diameter.\n* On the perforations made paste with epoxy resin the two pressure caps of toothpaste tubes.\n* Halfway through the tube and perpendicular to the plane formed by the two holes described above open a hole about 1 cm in diameter.\n* Through the above hole insert the temperature sensor TMP36, attached to its connecting cables and with the help of electrical tape stick to the upper inner wall of the PVC tube leaving exposed the sensor head.", "152" ], [ "Fix externally with epoxy glue.\n* Make two perforations approximately 1.5 cm in diameter separated by 2.5 cm to one of the PVC pipe caps so that they adjust the emitter and receiver of the ultrasonic sensor HC-SR04 and that are centered on the face of the cap. Fix the HC-SR04 sensor with expoxi glue making sure to seal all slots. Let the glue dry.\n* Place the cap with the ultrasonic sensor and the cap that will function as a rebound surface, at the ends of the tube (measurement probe). Coat the rest of the exposed externas surface of the tube with leak repair tape so that it is thermally insulated.", "320" ], [ "Simple Arduino Pot Plant Soil Moisture Sensor\nIntroduction: Simple Arduino Pot Plant Soil Moisture Sensor\nArduino Pot Plant Soil Moisture Sensor\nI have been struggling with over watering of my indoor pot plants, especially succulents. To this end I decided to make a simple Soil Moisture sensor that can tell me when the moisture level of my pot is too high (over watered), too low or just right!\nSupplies\n* Capacitive Soil Moisture Sensor V1.2\n* WS2182b mini\n* 3D Printing Filament\n* Arduino\nStep 1: Step 1: Gather Your Components\nI have used an Arduino Leonardo (this is what I had on hand and this project would work with any type of Arduino).\nI soldered wires directly to the Arduino headers. Using the Schematic attached.\nThe Moisture Sensor will work correctly on any Analogue in pin and the WS2812B mini should work on many digital pins however in my case I used D2.\nStep 2: Step 2: Calibrate Sensor\nThe Principle behind the sensor used is that as the moisture content increases so too does the capacitance in the sensors circuit placed in the soil. To use the Capacitive Soil Moisture Sensor V1.2 we supply either a 5V or 3.3V power source (ideally a stable voltage source) we can then read an analogue voltage from the sensor that corresponds to the capacitance of the sensor and therefor the moisture level of our soil.\nGiven there can be variances between manufactures and even parts it is sensible to calibrate the sensor so it works for the specific sensor we have. This may not be 100% necessary however can improve the performance of your sensor.\nCalibrating the Sensor:\n1. Connect Sensor to computer running Arduino Script\n2. Open Serial Monitor (Arduino will output raw values from the ADC on the Arduino. Value between 0 and 1023)\n3. Note the value seen when the sensor is in the air\n4.", "152" ], [ "Submerge the sensor into water up to the point you would in your pot. Note the value seen while in the water.\nNow that you have noted the \"dry\" and \"wet\" value it is time to update the Arduino script with this information.\nGo to Moisture Sensor Setup in Line 19 and update AirValue and Water Value with those you have recorded.\n//Moisture Sensor Setup\nconst int AirValue = 900;\nconst int WaterValue = 680;\nStep 3: Step 3: Select Limits\nEvery plant is different! Some plants like a dry soil and prefer to be watered once and then left for a while. Others need moist soil almost contently and will need watered regularly. At this point we need to decide what we want to consider as over watered and under watered! This differs plant to plant.\nNote: The Arduino Script has some small logic to convert the reading into a percentage where 0% Moisture would be the value you recorded in Air and 100% Moisture being the value you recorded when submerged in water.\nGiven we are now working with percentages we need to pick a percentage Moisture we want to be alerted at when we need to water and one to know when the plant is over watered. Anything in between and the plant will be happy!\nThe table bellow shows the values I have found good for different plants. Comment what values have worked for your plants!!\nPlant Over Watered Percentage Under Watered Percentage Strawberry 90% 35% Butterfly Palm 85% 30% Aloe 70% 15%\nStep 4: Step 4: Print the Case and Assemble\nI 3D printed the case for the sensor to hold it in a small and simple box. I wanted something slim so decided to only use the moisture sensor however with some further work and the inclusion of a simple Light Dependent Resistor this design could be extended to make sure your plants are getting the correct amount of light.\nThe 3D files for the case can be downloaded from Github.\nOnce printed it is time to assemble! You should have the Arduino, sensor and LED soldered together. Now place the LED into the recess hole and the moisture sensor in its location. Place the cover on top and glue in place (I used Blu-Tack).\nStep 5: Step 5: Be the Perfect Plant Parent\nThe LED have three colours to show you the Moisture in your pot!\nSee the table bellow to know what the sensor is saying.\nBlue Over Watered Green Happy Plant Red Needs Water", "33" ], [ "Water Rocket - Electronic Systems Design\nIntroduction: Water Rocket - Electronic Systems Design\nIn this instructable, we are gonna build a Water Rocket with an automatic parachute ejection mechanism, and a data transmission system so we can monitor the rocket's orientation (estimated from accelerometer and gyroscope data) while it's on the air.\nA water rocket is a model rocket that uses water and compressed air inside a pressure chamber (usually a PET bottle) as a thrust motor. The operation of the rocket can be explained by <PERSON>'s third law, where the water in the compression chamber is thrown out by the compressed air as it tries to release its pressure releasing the accumulated potential energy, causing a force to be generated in the opposite direction that propels the rocket.\nSupplies\nRocket airframe\n* 3x PET Bottles 3L size (*It’s important that at least one of the bottles was used to store soda because it has to be able to withstand high pressures)\n* 4x Balsa wooden boards 200*25mm\n* 8x Screw\n* 1x Spray paint\n* 1x Rubber band\n* 1x Parachute (We used an old umbrella, attaching rope to each tip of the cloth)\n* 1x Corrugated plastic board 250*250mm (Also known as Correx or Corriflute)\nElectronics\n* 4x Zip Ties\n* Cardboard\n* 1x Perfboard (Also known as solder-able breadboard)\n* 1x Accelerometer (We used an MPU6050, it has an accelerometer and gyroscope)\n* 2x Arduino board (We used an Arduino nano and an Arduino mega)\n* 1x 3.3 V Voltage regulator (We used the LM317 adjustable voltage regulator)\n+ For the Voltage regulator circuit using an LM317\no 1x Resistor (390 Ohm)\no 1x Resistor (240 Ohm)\n* 1x Servomotor (We used a generic SG90)\n* 2x NRF24L01+ module\n* 1x Battery to supply power to the electronics board (We used a Power Bank)\n* To connect the Power Bank to the electronics board.\n+ 1x USB male type A connector\n* Female & Male headers\n* Tape\n* Double-sided tape\n* Cables & Wires\n* Hot glue\nTools\n* Hot glue gun\n* Cutter\n* Scissors\n* Marker\n* Soldering iron\n* Tweezers\n* Measuring tape\n* Stapler\n* Water Rocket Launcher (We don't explain in this instructable how to make the rocket launcher, but you can check out this amazing article by air command water rockets to build one yourself)\nStep 1: Parachute\nMeasure the radius of the bottle\nFor this measure the circumference as seen in (1), then apply the equation r = c / (2*pi) (where c is the circumference) to find the radius, in our case the radius was 60 mm\nWith this information mark 2 circles with the radius of the bottle minus 1 mm (in or case that was 59 mm) on a cardboard and cut them, as shown in (2) and (3).\nFor each circle, make the lines as shown in (4)\nFor this, we first make a line that goes through the center of the circle, this line will be called line 1\nMeasure 40 mm on one end of line 1 and draw a perpendicular line that touches the borders of the circle, this line will be called line 2\nMeasure 20 mm on the other end of line 1 and draw a point\nNow draw a line between the point and each end of line 2\nMeasure one of the recently drawn lines, this value will be called L\nStep 2:\nTaking the above measurement (L), draw on the cardboard a rectangle 110 mm high, and (L) x 4 mm wide, mark a vertical line every (L) mm (5)\nCut the large rectangle and cut the line at the middle resulting in 2 rectangles of equal size as shown in (6)\nFor each of the rectangles, cut the top layer of the cardboard through the marked line so we can fold them\nPut hot glue on the lines marked on one of the circles and glue one of the folded rectangles, then glue the other rectangle behind the previous one to reinforce it.\nWe need holes for the zip tipes, so mark a line approximately 15 mm from each end of the rectangle, and draw 4 rectangles attached to that line approximately 3 mm high by 5 mm wide that are approximately equal distances apart as shown in (9)\nGlue the other circle on top\nCut the small rectangles and verify that the zip ties fit through the recently made holes.", "120" ], [ "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" ], [ "Model Rocket Motor Dynamometer (Arduino Uno)\nIntroduction: Model Rocket Motor Dynamometer (Arduino Uno)\nHi. My normal YouTube \"job\" has been chasing and shutting down scammers. I've taken a break from that and have recently been playing around with model rockets, drones and airplanes.\nMaking model rocket motors is fun but when it gets serious it becomes necessary to measure the motor's performance so that the effect of fine adjustments can be visualised.\nThis project uses parts available from Amazon (and many other retailers) and there's nothing complicated apart from the code, which of course is downloadable from this instructable later.\nThere are several modules in the project:\n1.Strain Gauge Load Cell\n2.Motor Mounting Platform\n3.Audio and Visual Warnings\n4.Motor Ignition Relay\n5.Control System\n6.Data Retrieval and Storage\nThe whole system is designed to be stand-alone - requiring no PCs/Laptops to acquire the motor data. Once stored on SD card, the data can be safely removed from the system and read by a PC etc to generate graphs / charts.\nSupplies\nSupplies\nNote: All the items listed below are from Amazon. The number in parentheses (Amazon B081JNXBSZ) for example, is Amazon's universal item number for that part. There are many other places to buy the components, mostly competitively priced. This list is what I used to make the project myself.\n1 x Load Cell With Amplifier - DollaTek 10kg Small Scale Load Cell Weighing Pressure Sensor With A/D HX711AD Adapter (Amazon B081JNXBSZ)\n1 x Arduino LCD Shield - KEYESTUDIO LCD Shield Module Display 16x2 Display Module Blue Keypad Shield for Arduino R3 Mega2560 (Amazon B07H3Q3X6C)\n1 x Arduino Relay Module - ICQUANZX 5PCS KY-019 5V One Channel Relay Module Board Shield For PIC AVR DSP ARM for arduino Relay (Amazon B07BVXT1ZK)\n1 x Arduino Uno (compatible) - ELEGOO UNO R3 Board ATmega328P ATMEGA16U2 with USB Cable Compatible with Arduino IDE Projects RoHS Compliant (Amazon B01EWOE0UU)\n1 x SD Card Module - Pxyelec 1pcs Micro SD Card Micro SDHC Mini TF Card Adapter Reader Module For Arduino (Amazon B07F9LT72N)\n1 x PP3 Battery Clip - 5Pack 9V Battery Snap Connector 9 Volt Battery Clips Connector Buckle Plastic Housing, T-type (Amazon B07HD3PBDT)\n1 x Pushbutton - SPST Red Momentary Push Button Switch 1 Circuit 1A 250V off-on (Amazon B082VFKJMF)\nVarious Connection Wires, Heat Shrink, Solder etc.\nCase of some sort\nStep 1: Strain Gauge\nThe strain gauge recommended consists of a bar with some holes drilled in its side. On top and below the holes are some components glued on with epoxy. These components are strain gauge elements. When the bar is pressed at one end, the metal above the hole is stretched. The metal below the hole is squeezed. The elements measure this minute movement by means of a flexible, resistive PCB. As the PCB is stretched the resistance increases.", "769" ], [ "Squeezing the PCB reduces the resistance. Between the Strain Gauge and the Arduino is a processing amplifier which takes the minute resistance changes and converts them into meaningful, readable values.\nThe Strain Gauge amplifier has 6 connections at one end and only 4 at the other. We are going to use the 4 pin connector - Gnd, Vcc, Data and Clock to join the amplifier to the Arduino. The connection of these pins is shown in the overall wiring diagram. There are 4 wires coming from the Strain Gauge itself, Red, Black, White and Green. They are connected as follows : Red to E+, Black to E-, White to A- and Green to A+\nThere is a small modification to do to the strain gauge amplifier board. Originally the sampling rate is 8 per second, which is not good enough for our purposes. If you look at the picture of the board you will see a large component calle U7. At the top right of U7 is a power supply pin (pin 16). The pin below it is the sample rate pin (pin 15). What is needed is to carefully apply heat from a soldering iron to pin 15 and lift it up from the PCB a tiny amount. The carefully bend the pin towards pin 16 so they overlap a little. The just quickly solder pin 15 to the top of pin 16.\nDon't worry, this sounds much harder than it is.", "611" ], [ "Cardboard Racer\nIntroduction: Cardboard Racer\nThis project will describe the process of making a functional cardboard racing car that is powered by an elastic band and with it how STEM (STEAM), [not forgetting the Arts]; can be applied.\nScience will explore Newtons 3 laws of motions.\nTechnology - Practical application of the Science using the car to perform experiments.\nEngineering - Design and building the car.\nArts - Creative expression to customise and individualise the car by modifying it visually whilst maintaining functionality.\nMaths - Calculation used to generate numerical data for analysis.\nSupplies\nCorrugated Card Board (370 x 230 x 4 mm) * 3\nScissors\nCutting Blade\nClear Adhesive Tape\nGlue\nRuler\nPencil or Pen\nElastic Bands * 5\nCloths Pegs as required.\nBamboo Skewers * 2 (160 mm min)\nM4/10mm screw * 2\nM4/20mm threaded standoff\nM4/20mm screw\nM4 washers * 6\n4 mm drill bit\nBradawl\nStep 1: Newtons 3 Laws of Motion\nWhat are Newtons 3 law of Motion.\n1: An object at rest or in motion will continue to do so unless acted upon by an external force.\nThe car continues in motion once the initial force is applied but will eventually come to a stop as a result of frictional forces. Frictional forces can be significantly reduced by the use of bearings and rolling on a hard surface.\n2: When a force acts on an object, it will cause the object to accelerate. The larger the mass of the object, the greater the force needed to cause it to accelerate.", "668" ], [ "Therefore, force = mass x acceleration.\nThe mass is constant but we can change the force to cause greater acceleration.\n3: For every action, there is an equal and opposite reaction.\nThe more you pull the elastic the more force it generates. The applied force is stored as potential energy and is released as kinetic energy with an equal and opposing force.\nStep 2: Experimentation\nNewtons 2nd law states that Force = mass x acceleration\nThe mass of the car of 0.115kg\nIf it accelerates at 1m/s then the force required is 0.115 * 1 = 0.115 N (assuming no losses in the system)\nm/s * 2.237 = mph.\nGreatest acceleration will occur upon release and thereafter reduce due to external forces.\nIf you time the car over a fixed distance you will get an estimation of speed.\nFor acceleration (1m/s), mass (0.115kg), and the measured displacement of the elastic (18cm).\nElastic Potential Energy (Joules) = 1/2 * Force (N/m) * Elastic displacement^2 (m)\nThe Force is the spring constant = F/dX = 0.639N/0.18 = 3.55N/m\nEPE (Joules) = 1/2 * (3.55N/m * (0.18m^2)) = 0.0575J\nVelocity = sqrt((2*EPE)/kg) =sqrt((2*0.0575)/0.115) = 1 m/s\nMore force is required to overcome frictional losses & elastic efficiency in the system 0.639N versus 0.115N.\nFurther experiments looking at the effects on distance and speed can be conducted.\n1: With stronger and weaker elastics. (greater or weaker force).\n2: For variation in mass..\n3: On hard floors (wood/cushion floor) compared to carpet.\n4: The ratio of elastic stretch.\nReview the data using Excel with charts to visualise the results pictorially and numerically.\nStep 3: Main Body - Part 1\nThis is the body and chassis of the car all in one..\nIts designed for rigidity in the 3d form with minimal pieces.\nOrientate the piece of card (370 x 230 mm), with the long edge horizontally.\nWith the pencil and ruler, proceed to mark the card as per the diagram.\nOnce the card has been marked, proceed to cut the card with a sharp blade using the ruler as a guide\nFolds are marked with dotted lines\nHoles are marked with a cross.\nStep 4: Main Body - Part 2\nOnce the pattern for the car has been cut out folds are required to give it shape and strength.\nAlign the centre line on the card with the edge of a table or box and carefully apply pressure close to the line on the card overhanging the edge of the table/box, pushing the card down to form an angle of ~60 degrees.\nProceed to bend the two short tabs inwards to an angle of ~90 degrees.", "343" ] ]

[ 11330, 232, 11138, 3458, 10327, 10436, 2292, 10964, 2716, 6065, 3990, 3369, 5814, 10775, 10164, 4675, 4923, 4377, 5757, 8618, 7615, 7797, 10711, 3907, 1626, 8029, 3835, 3547, 101, 5005, 10618, 5110, 4848, 6089, 6609, 4816, 5389, 2263, 8768, 8653, 2405, 10714, 8767, 2624, 950, 7687, 3671, 631, 9448, 4495, 1884, 5929, 8238, 6745, 2048, 9886, 6988, 5132, 9849, 2675, 3980, 8841, 865, 1677, 8571, 9428, 3777, 6109, 8380, 1461 ]

[ [ "A first problem is that there is in GR no such thing as \"an observers frame\", except in sloppy speech. There are various systems of coordinates. Two systems of coordinates may agree for an observer as much as one likes but differ elsewhere. And all the systems of coordinates are on equal foot, none is preferred.\nWhat could replace the \"observer's frame\"? The most plausible candidate seems to be the use of harmonic coordinates - they really essentially simplify the <PERSON> equations, are used in the Newtonian limit and in the PPN formalism (see here) or in <PERSON> local existence and uniqueness proof, roughly the only reasonable candidate for preferred coordinates. To define harmonic coordinates, one need some initial values, because the harmonic condition is only an evolution equation $\\square X^\\mu = 0$ for them, but this is given by the <PERSON> coordinates before the collapse.", "578" ], [ "This gives, roughly, the Schwarzschild time coordinate, thus, it would be such a system of coordinates where the material of the collapsing star never reaches the horizon.\nFrom point of view of classical GR, the only objection is that these coordinates would not cover the complete solution.\nIf one includes Hawking radiation into the consideration, one should care about the trans-Planckian problem (to derive that Hawking radiation lasts more than a second after the collapse, one has to presuppose that semiclassical theory remains valid for distances of $10^{-1000}$ of Planck length or so). The mainstream way to solve this problem is to rely on some results of <PERSON> and others that some Hawking radiation remains if one considers various regularizations. The problem is that these regularizations break covariance, thus, require preferred coordinates, and they obtain <PERSON> radiation only if the preferred coordinates are those related with the infalling observers. If they are stationary, there will be no <PERSON> radiation. And if one wants to rely on modifications of GR with preferred coordinates, see above for candidates.\nIf one ignores this and assumes Hawking radiation, then one can publish the idea that the BH evaporates before being formed even in Phys.Rev., as done by <PERSON>, PRD 14, 1479 (1976), and get citations by standard textbooks like <PERSON>, <PERSON>, quantum fields in curved spacetime, so it is close enough to being tenable.", "469" ], [ "Would <PERSON>'s law in the solar system be independent from a presumed different fundamental gravitational law?\nA thought experiment:\nLet's assume the gravitational field of a black hole without any neighbors would be stronger than the Schwarzschild metric in the Newtonian limit.\nNow, we let a solar system (sun and planets, much smaller mass than the black hole) orbit around this black hole at $r>> R_s$, so that the tidal forces are nearly zero.\nMy question is, although the fundamental gravity law is \"set\" to be stronger, would the planets around the sun experience <PERSON>'s law?\nThe metric in the solar system can be calculated with the static, sperically symmetric solution of the field equations, namely $ds^2=-Bdt^2+Adr^2+\\text{angular terms}$ using the Newtonian limit (asymptotically flat spacetime), lim A(r) = 1, because due to the free fall (orbit) around the black hole, there are no forces, no curvature experienced by the solar system as it is moving along the curvature in free fall. That would presumably lead to the derivation of the Schwarzschild metric.\nThe question therefore is, whether this solar system does experience an asymptotically flat space because of the free fall around the BH and is this asymptotically flatness of space independent from the underlying gravity law of the black hole?\nRemark: Tidal forces are theoretically possible inside this solar system, because for example a planet experiences another force of gravity if it is behind the sun (in greater distance) in relation to the central black hole, than if it is in front of the sun (in nearer distance) in relation to the black hole.", "397" ], [ "However, these tidal forces are very small at galactic distances (see for example https://physics.stackexchange.com/questions/702248/are-there-tidal-forces-between-the-solar-system-and-the-galactic-centre), even if the gravitational field produced by the black hole were stronger. The difference measured within the solar system between \"black hole gravity is stronger than Newtonian\" and \"black hole gravity is Newtonian\" is even much smaller.\nThis is just a thought experiment. It comes from the idea whether it is possible to create an alternative model of gravity by abandoning the weak field assumption.", "43" ], [ "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" ], [ "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" ], [ "At first glance this seems like a reasonable question, but on closer inspection it turns out to be asking about a non-issue. Furthermore, the answers given so far are incorrect resolutions to this non-issue.\nThe <PERSON> diagram for an astrophysical spinning black hole (as opposed to the <PERSON> spacetime) is not obvious. It may actually look about the same as the <PERSON> diagram for a non-spinning black hole that forms by gravitational collapse. For the sake of simplifying the discussion, let's assume that.\nNow consider an observer at a point P in the exterior region of the spacetime. The second <PERSON> diagram shows three surfaces of simultaneity for this observer.\nAccording to the red notion of \"now,\" this observer wonders where the angular momentum is, and imagines that it must be contained by the singularity. But the same observer could equally well choose the green surface of simultaneity, in which case the mystery is solved, and the angular momentum is in the infalling matter, which is inside the horizon but has not yet reached the singularity. Finally, the same observer can choose the blue surface, in which the black hole hasn't formed yet, and none of the infalling matter has even reached the horizon yet.\nThis shows that the original question is a question about a non-issue. For any Cauchy surface that the observer picks (such as green and blue), there is a perfectly clear explanation of where the angular momentum is. The red surface is not a Cauchy surface, which is defined as a surface such that every inextensible non-spacelike curve intersects the surface exactly once. But if the observer really wants to insist on the red surface, then she can say that the black hole's energy, momentum, and angular momentum are contained in the gravitational fields of the black hole. Gravitational energy is not counted in the stress-energy tensor, and is therefore not localizable, but a distant observer in an asymptotically flat spacetime can say that it exists.\nA bunch of answers here have proposed to resolve the paradox by saying that it's resolved because the singularity is a ring.", "43" ], [ "This is nonsense for one reason and also doubtful for another reason.\nReason #1 is that GR does not define angular momentum in terms of taking a cross product of a radius vector with a momentum vector. This definition can't even get started, because there is no such thing as a displacement vector in a curved spacetime. In asymptotically flat spacetimes, there are ways of defining the total angular momentum, but the way you do it is not as straightforward as just writing down L=rxp from freshman mechanics.\nReason #2 is that a singularity does not have a well-defined shape or geometry. In general we cannot even define its dimensionality or topological properties. If you look at a careful treatment such as Hawking and <PERSON> (p. 276) or <PERSON> ( https://arxiv.org/abs/0706.0622 , p. 28), they will clearly explain that these notions are not really well defined. A singularity is by definition not a point-set and not a point-set where the metric is defined, so we lack the measurement apparatus to talk about its shape or geometry. Statements that a <PERSON><PHONE_NUMBER> , p. 28), they will clearly explain that these notions are not really well defined. A singularity is by definition not a point-set and not a point-set where the metric is defined, so we lack the measurement apparatus to talk about its shape or geometry. Statements that a Kerr black hole has a ring singularity are shorthand for statements that in a certain coordinate chart, if you throw away the physical metric and instead impute a Euclidean metric to the coordinates (as if they were ordinary spherical coordinates), then the coordinates at which the singularity occurs look like a ring.", "43" ], [ "General relativity is a local theory. It only defines motion directly with respect to local reference matter.\nIt is known that prior to developing general relativity, <PERSON> thought very deeply about what he termed <PERSON>’s principle, but controversy has surrounded the question as to whether general relativity actually incorporates the principle, perhaps largely because it was never given clear expression. If the principle merely means that we can only talk of acceleration relative to other matter, then that is clearly the case in general relativity. However, the referenced matter is always local to the matter under consideration and, generally, discussion of <PERSON>’s principle seems to invoke a suggestion that rotation only makes sense in the context of the distribution of matter in the universe as a whole.\nThe origins of the discussion lie in <PERSON>’s rotating bucket argument. <PERSON> had observed experimentally that a concave meniscus forms in a spinning bucket hung from a rope, as the water starts to rotate with the bucket. He argued that in the absence of absolute space it would not make sense to say that the water in the bucket is rotating, and therefore that no concave meniscus would form in its surface.\n<PERSON> appears to suggest that the answer lies in the motion of the water relative to distant stars.", "469" ], [ "This idea is certainly not directly expressed in the assumptions of general relativity, which is essentially a local theory. According to the restatement, N1*, of <PERSON>’s first law as a local law, we need consider only the motion of the particles of water relative to each other:\n* N1*: An inertial body will locally remain at rest or in uniform motion with respect to other local inertial matter.\nThe local structure of spacetime is determined from the interactions of particles locally. An inertial frame is one in which inertial particles can maintain a state of rest with respect to each other while transmitting no net force — in effect this is the situation when there is no meniscus signifying rotation of the water.\nOn the other hand a converse argument can be presented. If spacetime is divided into local, and overlapping, regions, each described in inertial coordinates, then no rotation is possible in the global structure resulting by conjoining the regions. Thus we cannot say that the frame of the non-rotating bucket is determined from the “frame of the fixed stars”, but rather must say that the “frame of the fixed stars” is determined from local structures. In other words, <PERSON>’s principle is a consequence, not an underlying assumption in general relativity.", "562" ], [ "Euclidean derivation of the black hole temperature; conical singularities\nI am studying the derivation of the black hole temperature by means of the Euclidean approach, i.e. by <PERSON> rotating, compactifying the Euclidean time and identifying the period with the inverse temperature.\nConsider the Schwarzschild case as an example. The Euclidean Schwarzschild metric is of course\n$ds^2=\\left(1-\\frac{2M}{r}\\right)d\\tau^2+\\left(1-\\frac{2M}{r}\\right)^{-1}dr^2$\nwhere $\\tau=it$ the Euclidean time. Here $\\tau\\in[0,\\beta]$ with $\\beta=T^{-1}$ the inverse temperature, where the points $\\tau=0$ and $\\tau=\\beta$ are equivalent.", "394" ], [ "(I ignore the 2-sphere part of the metric.)\nOutside but close to the event horizon $r=2M$, we can (after simple some steps) write this as $ds^2=\\frac{\\sigma^2}{16M^2}d\\tau^2+d\\sigma^2$.\nHere $\\sigma^2 \\equiv 8M(r-2M) $, though this is not really relevant for my question.\nNow the next step in all the literature is to require that $\\tau/4M$ is periodic with period $2\\pi$ to prevent conical singularities. I have trouble understanding this.\n* A conical singularity basically means that the point at $\\sigma=0$ looks like the tip of a cone, right? So we have a singularity at $\\sigma=0$. But don't we still have a singularity there for polar coordinates $(r,\\theta)$, since the coordinate chart $\\theta$ is not continuous there?\n* If so, removing the point $\\sigma=0$ would erase the conical singularity, right? Then why do we want to get rid of the conical singularity, why is it any worse than the polar coordinate singularity? Of course polar coordinates just describe flat space without the origin, is this not the case for the conical coordinates?\nClearly I have not understood the concept of a conical singularity...\nLast question: suppose I did understand it, and continued the derivation to get the temperature $T=1/8\\pi M$. Apparently this is the temperature as measured by an observer at infinity, how can I see this? I know the temperature gets redshifted, like frequency, but I don't see where the derivation identifies $T$ with the one measured at infinity.", "272" ], [ "Gravitational redshift of temperature and electrostatic potential\nConsider a charged black hole in four-dimensional <PERSON> spacetime, with charge $Q$, mass $M>Q$:\n$ds^2=-f(r)dt^2+\\frac{1}{f(r)}dr^2+r^2d\\Omega_2^2$, with\n$f(r)=1-\\frac{2M}{r}+\\frac{Q^2}{r^2}$.\nWhen an observer at radial coordinate $r_1$ emits a photon, an observer at radial coordinate $r_2>r_1$ will perceive the photon with a redshifted wavelength. This is easy to interpret.\nA similar thing happens for the temperature. If $\\kappa$ is the surface gravity of the black hole, then the Hawking temperature is $T_H=\\frac{\\kappa}{2\\pi}$. Due to gravitational redshift, the temperature measured by an observer at radial coordinate $r$ is\n$T_{loc}(r)=\\frac{1}{\\sqrt{f(r)}}T_H$.\nThe redshift factor is the same as for a redshifted frequency, which I can understand by associating temperature with the inverse imaginary time period.\nI interpret this redshift as a consequence of the particles which constitute Hawking radiation experiencing gravitational redshift.", "187" ], [ "Is this correct?\nApparently, something similar also happens for the electrostatic potential. The electrostatic potential difference between the outer event horizon $r_+$ and infinity is given by $\\Phi=\\frac{Q}{r_+}$. However, the electrostatic potential between $r_+$ and some coordinate $r>r_+$, \"blueshifted\" from infinity to $r$, is given by\n$\\phi(r)=\\left(\\frac{Q}{r_+}-\\frac{Q}{r}\\right)\\frac{1}{\\sqrt{f(r)}}$.\n(Source: <PERSON>, <PERSON>, Whiting and <PERSON>, Charged black hole in a grand canonical ensemble, PRL Vol. 42 No. 10, 1990, equation 4.15.)\nThis expression seems to tell me that $\\frac{Q}{r_+}-\\frac{Q}{r}$ is the electrostatic potential difference between $r$ and $r_+$ as measured by someone at infinity, and the above expression is this same potential difference as measured by someone at $r$.\nIs there a simple interpretation why the measured electrostatic potential should experience gravitational redshift as well, with the same redshift factor as a frequency? What is the wavelength that is being redshifted in this case, is it the one from the photons mediating the electromagnetic force? (These photons are virtual though, so can they actually be redshifted?)", "187" ] ]

[ 1390, 565, 6231, 2386, 6658, 9588, 1006, 3712, 10020, 10424, 2874, 7738, 2357, 3497, 3401, 270, 10042, 10639, 8546, 10660, 1787, 8085, 10049, 2506, 4152, 6819, 6306, 7947, 6672, 10838, 10066, 6444, 1528, 6392, 2180, 6213, 2519, 5684, 788, 1203, 10190, 9704, 11295, 614, 3029, 11162, 6936, 5830, 11315, 6830, 2299, 3389, 4955, 7301, 584, 566, 11151, 857, 6211, 10517, 7916, 6481, 632, 9112, 2510, 4316, 4964, 8913, 1864, 2135 ]

[ [ "It’s Emancipation Day in Trinidad & Tobago — but is the country free? · Global Voices\nRedemption Song Statue, Emancipation Park, Jamaica. Photo by <PERSON>, used with permission.\nAugust 1 is celebrated in many Caribbean territories as Emancipation Day, marking the freedom of enslaved Africans who were victims of the transatlantic slave trade.\nTrinidad and Tobago was the first country in the world to declare a national holiday to mark the abolition of slavery, but 34 years after that first public holiday was instituted and 185 years after the Slavery Abolition Act first came into effect, great discussion continues over whether or not the twin-island republic is emancipated.\nSpeaking about the issue on July 27, 2019, Prime Minister Dr. <PERSON> observed that among Trinidad and Tobago's diverse population, people of African descent “are not doing as well as we expected”. <PERSON> said that rising levels of violence which are part of the black, urban youth experience, should be inspiring citizens to “focus, reflect and have serious conversations about where we are as a nation”.\nChairman of the country's Emancipation Support Committee, <PERSON>, agreed.\nSome letters to the editor gave examples of modern slavery to make the point that true emancipation still seems a long way off, while others tried to make the occasion a political one, by criticising certain social services and a culture of “handouts.”\nThe Trinidad Express chose to feature an opinion on Emancipation Day which suggested that <PERSON>, <PERSON>, and activist <PERSON> were wrong about why some Afro-Trinbagonians may be underperforming:\nIt is easy for a dominant group to create a system that discriminates and subjugates. Those who do not measure up to that system are categorised as under-performers and relegated to second class or worse. […]\nSo many of our systems, education the leader, put people unfairly in a caste and they are not given a second chance. Every system has a rating and the further away it is from the top, the lower the ranking. Those who find themselves on the bottom rung have great difficulty coping with the elevated systems.", "678" ], [ "Self-esteem is low and in their perceived helplessness may even drive them to employ violence to counter-punch suppression.\nCommentator <PERSON> lauded the country's “commendable history of maturity” when it comes to discussing race-related issues, but he also suggested the problem lay deeper, within the system itself, and suggested the prime minister's message should motivate citizens to examine how institutional racism continues to be a restrictive force.\nSocial media users shared their musings as well. In a public post, Facebook user <PERSON> said:\nOn this day we remember and commemorate the freedom of our ancestors from the physical bondage of slavery.\nToday, many generations later, we the decendants [sic] of slaves struggle with the legacies left by colonialism.\nLegacies which thrive and are perpetuated by stereotypes: We are not savage, we are not violent, we are not predators, we are not just thugs and gangsters. We are leaders, revolutionary thinkers, visionaries, philosophers. We are <PERSON>, <PERSON>, <PERSON>, <PERSON>, <PERSON>. […]\nLet us recognize that colourism is an inherited tool used to divide us […]\nLet us call out respectability politics: a culture of dilution; stop playing down blackness to make it palatable to the masses […] Let us celebrate the rediscovery of our faith and belief systems. They took away the religion of our ancestors, they took away a belief system and sense of values. In today's world of information access you owe it to yourself to explore the belief systems of our ancestors, the reverence and honouring of the elders, the owning of one's actions […] an emphasis on choice and consequence, there is belief in the family, the extended family, the village, the community.\nThis emancipation embrace the fullness and richness of who you are, where you came from, the blood and history that's in your veins. Own with pride who you are, your culture, your identity.", "127" ], [ "More Than a Half Century Later, How Should Jamaica View Its Independence Day? · Global Voices\nJamaican Independence Day celebrations. Photo taken from the WAVE: Galleries, Museums, Archives of Wolverhampton Flickr page. CC BY-NC-SA 2.0\nJamaica achieved its independence from British rule 52 years ago. Like the citizens of most Caribbean states, Jamaicans today wrangle with the ripple effects of the region's history, including social and economic challenges.\nLike many other regional territories, Jamaica was “discovered” by <PERSON> for the Spanish crown in the 1490s; its indigenous population was effectively annihilated, either intentionally or as a result of diseases that the Spanish brought with them. Midway through the 1600s, the island was seized by the British and remained under colonial rule for the next two hundred years as a pawn in the heinous transatlantic slave trade, during which African slaves were brought to the island, primarily to work the sugar estates.\nEmancipation in 1834 brought an economic, social and mental shift to Jamaica and the region as a whole, and signaled the beginning of the separation process from their collective — and forcibly adopted — mother country. These Caribbean territories began to make their intentions known as early as 1958, when they joined together to form the West Indies Federation, which was to function as a single-state political entity that would operate free from British rule. The arrangement failed — partly due to Jamaica's dissatisfaction with how slowly the process of gaining independence was going — and the federation was soon dissolved, allowing each member nation to forge ahead with breaking the chains of colonial rule on its own. Jamaica and Trinidad and Tobago were the first to succeed, becoming independent states on Aug.", "708" ], [ "6, 1962 and Aug. 30, 1962, respectively. Other islands would follow suit well into the early 1980s.\nBut the road to self-governance has not always been smooth. The Westminster parliamentary system, which is strongly based on public opposition, didn't necessarily translate well to the psyche of a region that endured hundreds of years of human rights abuses and is still suffering its effects. The learning curve for a people who historically never had a say, continues to be a steep one, especially in a climate where corruption was already entrenched.\nOn the 52nd anniversary of their country's independence from British rule, a pair of Jamaican bloggers have reflected on the meaning of the occasion.\n<PERSON>, whose post listed many of the island's achievements and compared its gains with what she deemed other less fortunate countries, cited a strong democracy, freedom of the press and citizens’ resourcefulness in the face of economic hardship as noteworthy things to celebrate:\nI will listen to no ‘grinches’ today, those cynics trying to steal my joy in Emancipation and Independence. We keep talking ourselves into this ditch of despair, instead of raising our voices in thanks for our many blessings. If you think we are badly off, please check the international newscasts, where countries are at war and an airplane of ordinary passengers with everyday plans is shot out of the sky.\nHer compatriot <PERSON> wrote about the country's progress and wondered whether “the child” that Jamaica was in 1962 would be proud of “the adult” it has become. She agreed with <PERSON> that some of the island's greatest resources lie in its people, but suggested that Jamaicans are still held back from reaching their full potential, thanks to “psychological slavery”, adding that she saw “a dire need for an evolution of the collective mentality.”", "271" ], [ "Trinidad & Tobago NGO identifies treatment of women as key issue in upcoming elections · Global Voices\n“The finger that voted”; photo by <PERSON> on Flickr, CC BY-NC-ND 2.0.\nTrinidad and Tobago's general elections will take place on August 10, and as much as electioneering in the time of COVID-19 has had some voters calling for campaign ingenuity, the substance of the messages has, for the most part, been more of the same.\nThe nonprofit Womantra, which educates and advocates for policy reform around the issues of women's rights and gender justice, has put out a statement about patriarchy — yet another source of dissatisfaction in the elections:\nAll candidates seeking public office should be meticulously screened, not only for portfolio and party compatibility but also for biases that impact their ability to serve the national community. Sexism is among these biases and one of the most dangerous. […] the words and actions of our politicians have been well documented by local media, the legacy of which informs what is deemed acceptable behaviour for those in authority and continues to haunt us today.", "127" ], [ "In the midst of the 2020 general election campaign, it is clear that this problem persists.\nThe statement identified certain issues the group saw as problematic, including the nomination of a candidate currently facing sexual assault charges; another who has had “online allegations involving sexual offences” being levelled against him; and a third who has had an interim protection order taken out against him by a former partner.\nNo judgement has yet been handed down on the rape charge, no formal charges have been made against the candidate accused of sexual offences, and the protection order against the third candidate expired on July 23, upon which he was due to appear in court regarding the matter.\n<PERSON> described these as “instances of grossly misogynist narratives:”\nWe note that these problems are wide reaching and that aspiring Members of Parliament from at least 3 political parties have come under scrutiny, underscoring the need for urgent and collective attention to end violence against women in politics.\nTheir position was echoed by <PERSON>, a lecturer at the Institute for Gender and Development Studies at The University of the West Indies (UWI), who noted that struggles over democracy are “always interwoven” with those of gender and sexuality, and condemned such “continued tolerance for gender-based and sexual violence, which are not yet considered so abhorrent that they deny men political legitimacy”:\nIf nothing else, understand young women’s fear that these could be the men who hold power over them and to whom they must pay respect, like those abusive uncles who somehow retain their place and authority in the family.\nAs such, <PERSON> has called for amendments to Trinidad and Tobago's constitution so that “persons who are convicted of any offence involving sexual harassment or assault be disqualified from being elected or appointed as a member of the Senate and/or the House of Representatives.”\nLanguage emerged as another key issue, with a request that the booklet on parliamentary language is updated “to admonish the use of sexist statements, comments or words:”\nBorrowing from the 2020 Council of Europe (COE) report, we echo the call for our Parliamentarians to take a strong stand against sexist attacks targeting women and to introduce or revise codes of conduct explicitly prohibiting sexist behaviour and speech in their assemblies. The COE Report also recommends that States be vigilant during election periods with regard to sexist attacks against women and to monitor candidate nomination procedures for inequalities.\n<PERSON> also saw the Trinidad and Tobago Police Service (TTPS) playing a critical role by taking “all allegations made against political officials or aspiring representatives seriously and commence investigations promptly, particularly given the impending election of August 10.”\nSpecial mention was made of revenge porn, the investigation of which falls under the TPPS’ Cybercrime Unit:\nWe stand in solidarity with women candidates who have been the victims of such attacks and firmly denounce the claims that victims of revenge porn should be barred from public office. Such a position is difficult to reconcile with the recent amendments to the Domestic Violence Act, which expand the definition of emotional or psychological abuse to include unwelcome or intimidatory contact through electronic means.\nCiting the case of young political candidate <PERSON>, who allegedly appeared in a video in which a faceless man showered her with money, <PERSON> observed that “gender and sexuality often become weaponised in electoral campaigns.” Although a 29-year-old man has since been charged with harassment and attempted extortion of <PERSON>, <PERSON> maintained that “it’s actually irrelevant what women […] do in private, legal and consensual entanglements”:\nUndermining women’s aspirations for political leadership, through breaking their trust and violating their privacy, is a deliberate containment of their democratic participation. And, it works.", "127" ], [ "Exposing Discrimination or Unfair Trial by Social Media? The Case of a Workplace Hairdo in Trinidad & Tobago · Global Voices\nBlack Power fist; image by <PERSON>, used under a CC BY 2.0 license.\nThe COLFIRE controversy continues to heat up in Trinidad and Tobago. In correspondence dated August 11, 2016, the insurance company's human resources manager signed a letter asking employee <PERSON>, who is black, to adopt a more professional hairstyle. <PERSON> posted a photo of the letter — and his ‘do — to Facebook. Although he thereafter deleted the post, it had already gone viral, sending the local blogosphere into a tizzy over the perceived discrimination against natural hair.\nFour days later, it was revealed that COLFIRE's management had sent <PERSON> on paid leave, pending an internal investigation on the matter. In a statement over the weekend, the company said that it couldn’t publicly discuss the case of an employee and that it “denies the damning allegations that have resulted from the publication of an internal document”. In an update on the matter posted by Facebook user <PERSON> (who supports <PERSON>), he states:\nThe company thought that it was necessary to enforce ‘administrative leave’, because he caused the company great ‘public embarrassment’.\nStaff have been told to use their social media accounts to boost the company's image online and any employee found to be bad talking the company on social media or entertaining such talk will face disciplinary action.\nOn the same Facebook thread, commenter <PERSON> suggested:\nHe [<PERSON>] is wrong to light up his employer so on a public forum … It would have been smarter to comply and then complain.\n<PERSON> replied:\nSometimes we have to shatter the status-quo to make fundamental changes. its how things have happened for centuries.", "957" ], [ "There is always a spark that ignites the change.\nQuizzes, combs and <PERSON>\nChange is what netizens are agitating for. Many interpret the company's conservatism as racial discrimination and believe that this has been the status quo for far too long. University lecturer <PERSON> quoted an excerpt from the 1971 report of the Commission of Enquiry into Racial and Colour Discrimination in the Private Sector:\nWe are impressed generally in the case of the banks that a state of racial and colour imbalance exists because of the inheritance of institutionalized forms of discrimination which have not been completely changed…some banks have been more radical and progressive than others, but in general the older the bank, the more conservative its policy appeared…Even though active discrimination in new appointments may have ceased, the social effects of past discrimination still remain highly visible…this requires in the interest of social justice and public confidence that deliberate institutional measures be taken…to see that this situation brought to an end.\nNearly 50 years later, the country appears to be fighting the same battle, albeit virtually this time. Netizens began to hit back, some in very creative ways. Artist <PERSON> posted two new anti-COLFIRE images on Facebook, which were being widely shared — the first portraying a silhouette of an employee shackled to his desk and the other comparing the insurance firm's stance to United States Republican presidential candidate <PERSON>'s controversial election campaign:\nImage by <PERSON>, used with permission.\nImage by <PERSON>, used with permission.\nThere was even a quiz — the link to which social media users were liberally posting — to determine who had what to took to be a COLFIRE hire.\nA screenshot of the “FIRED” result of the COLFIRE quiz that is being widely shared on social media.\nOn Twitter, Livewired Group commented:\nThat #Colfire quiz. No chill 😂😂 Brands need to remember that consumers are better at content creation than some marketers.\n— Livewired Group (@LivewiredGroup) August 16, 2016\nEven Trinidadian calypsonian <PERSON> put in his two cents’ worth, posting a photo of the Jamaican athlete who won gold in the Men's 110m hurdles in Rio and commenting on his Facebook page:\nA Jamaican, <PERSON>, sporting a ‘Colfire’ wins the 110 m hurdles gold in Rio.\nAnd in case yuh don't know what a Colfire is, it's a now controversial Trinidadian hairstyle.\n‘The internet has created a new class of publishers’\nHumour aside, there is the serious question of possible legal consequences. Some lawyers are telling the media that the employee “doesn't have a legal leg to stand on” if he were to bring a discrimination suit against the company or the company were to take him to court.", "142" ], [ "Amid Black Lives Matter protests, fresh calls to remove statuary that hijacks the Caribbean’s historical narrative · Global Voices\nThe statue of Vice-Admiral <PERSON>, which stands near the entrance to Bridgetown, the Barbadian capital. Photo by <PERSON> on Flickr, CC BY-NC 2.0.\nBlack Lives Matter (BLM) protests have seen a global resurgence following the killing of <PERSON>, an African American, by a white police officer in Minneapolis, Minnesota in the United States.\nOne ripple effect of the protests has been the denigration and defacement of symbols of black oppression. The Caribbean, with its long history of occupation, has its own symbols of oppression to reconsider.\nIn Richmond, Virginia, on June 2, hundreds of protestors assembled in front of the statue of General <PERSON>, a American Civil War Confederate general, shouting, “Tear it down!” The state's governor, <PERSON>, announced that the statue of <PERSON> would be removed; the process has since been blocked by a court order.\nOn June 7, United Kingdom protestors tore down a statue of Bristol slave trader <PERSON> and stomped on it before throwing it into the harbour. A statue of slave trader <PERSON> was also retired in front of the West India Docks in London.\nSome have supported the symbolic act of reclaiming dignity and exposing long-celebrated racists, while others have condemned this method of protest.\nIn the Caribbean, calls to rename certain places have surged. King George V Park in Port of Spain, Trinidad, for instance, is also called Nelson Mandela Park. However, statuary has largely remained.\nMost regional territories have robust examples of public art that honour the slave struggle, including <PERSON>, who led the largest slave rebellion in the history of Barbados; <PERSON>, the leader of a 2,500-strong slave revolt in Guyana; and the “Redemption Song” statue at Jamaica's Emancipation Park, but there are also myriad examples of statues that reinforce the tainted narrative of discovery and ownership.\nSeveral Caribbean nations are challenging the wisdom of having such statuary on public display. Feminist and university lecturer <PERSON> observed on Facebook:\nI don’t think there has been a global uprising of this geographical scope and diversity since the 1970s.", "678" ], [ "[…] Sparked by the BLM movement in the US and now expanded into decolonial struggle and dismantling racism more broadly, it does seem like — for almost the first time in 50 years — we are listening to another world breathing.\nIn Martinique, where a statue of French abolitionist <PERSON> was toppled, two of the young women involved explained their decision in a YouTube video:\nWe, the young people of Martinique, are sick and tired of being surrounded by symbols that insult us. We were not the first to attack these symbols. Many before us have tried in vain to get rid of them […]\nWhat is a statue? It is stating this is someone we admire for the impact he or she has had in the course of our history. […] <PERSON> was in favour of the compensation of the plantation owners; there are many transcripts proving that claim. If he had not, maybe it would have been different.\nAs the pair pointed out, the discussion is not new.\nBarbadians, for instance, have been agitating for the removal of a statue of <PERSON> for decades. In 2017, Sir <PERSON>, vice-chancellor of The University of the West Indies and chairman of the Caribbean Community's (CARICOM) Reparations Committee, referred to <PERSON> as “a vile, racist, white supremacist [who] disposed of black people, and dedicated his political and military life to the cause of protecting Britain’s criminal possession of the 800,000 enslaved Africans held during his lifetime.”\nIn the wake of <PERSON>'s horrific murder, the discussion around such monuments has grown more urgent.\nThere are currently several online petitions circulating in the region, including the Barbadian thrust to do away with <PERSON>'s presence in the nation's capital.\nArtist <PERSON>, who shared the petition, noted:\n[…] while I don't think to destroy the statue of <PERSON> is useful, I do think that relocating it to the museum or somewhere outside of National Heroes Square is viable and worth a national discussion. It is no longer called Trafalgar Square and he is not a hero. Wherever his statue is relocated to, it should include complete signage to clearly demonstrate who he was, what he did and his role in the colonial machinery that oppressed people.\nIn response to a commenter who challenged the idea of taking down the statuary with a “Where will it end?", "678" ], [ "Calls to legislate ‘private hire’ vehicles and stop victim-blaming as another woman is murdered in Trinidad & Tobago · Global Voices\nStop Violence Against Women. Image by <PERSON> on Flickr, CC BY-NC 2.0.\nViolence against women is once again the issue of the day in Trinidad and Tobago after 18-year-old <PERSON> went missing on November 29. The teen, who was last seen getting into what is known as a Private Hire (PH) car, called her boyfriend to alert him that she was on her way, but she never arrived at her destination. Her body was found on December 4.\nTwo men, including the driver of the car, have been detained in connection with her murder and police are searching for a third suspect.\nThe outrage on social media was instant, and the manner in which she was preyed upon hit far too close to home for many, including the mother of <PERSON>, a young bank teller who was found dead on December 8, 2016.\nSocial media users erupted after <PERSON>'s murder as well, saying, “Enough is enough!” but four years later, despite petitions and protests, gender-based violence and femicide remain a real threat.\n<PERSON>'s death comes in the midst of UN Women's 16 Days of Activism against Gender-Based Violence, which aims to draw worldwide attention to what it calls “the already existing pandemic of violence against women.”\nFacebook user <PERSON> recounted her own experience at the age of 18:\nOne morning I took a taxi […] and the taxi driver passed my stop and apologized said, “It’s ok I’ll turn around and drop you.” He then proceeded to a back street and said he’s just making the rounds and started taking the windows up. Immediately I started shouting and asking what he was doing. He started caressing my leg and saying, “It’s ok I’m just putting on the AC.” I started opening the lock and tried opening the door and fumbled with it while trying to fight him off and had to throw myself out of the moving car.\nI keep asking myself had I not done that what would have happened! I can imagine the fear she felt because I was so panicked that it took me quite sometime before I could even breathe.\nIt’s so depressing that as women a routine trip to work or visiting a relative can result in sexual assault whether verbally or physically or in many instances death.", "957" ], [ "I pray for her mother…now being a mother myself it’s heart wrenching and I do pray that we stop telling women to be vigilant but instead ensure that men do better.\nIn a statement about the recent murder, the country's prime minister, Dr. <PERSON>, noted that there was a discrepancy between requirements for registered taxi drivers (who need a certificate of good character to operate) and the “PH” system, which he said contributes to the “danger of every <PERSON>, <PERSON> and <PERSON> being allowed to manage a vehicle and then you end up with this as an outcome.”\nHe admitted that the question now is, “What do we do about it?” The existing Motor Vehicles and Road Traffic Act stipulates that “no person shall use a motor vehicle for a purpose other than that for which it is registered.” There is currently no allotted designation for PH vehicles, but the practice is very common and not policed.\nThe PH arrangement is an informal one whereby a private car is used for hire, often by multiple riders at the same time. It differs from ride share apps like Uber, in that the car is neither summoned by nor tracked through technology. There is also no way of knowing whether or not the driver is plying a legitimate trade, making it a risky choice.\nWhen asked what options women have when traveling at times or to places in which only PH drivers operate, <PERSON> responded, “Given the practicalities of the situation, we have to be always cognisant of our personal safety […] Just be careful.”\nIn 2017, after <PERSON> was murdered by someone she knew in the car park of a popular multiplex, Prime Minister <PERSON> controversially advised women to choose their partners wisely. The statement was widely interpreted as victim-blaming, a stance that netizens have continuously called out in the wake of femicide, even as they attempt to refocus the blame where it belongs.\nOn Facebook, <PERSON> posted:\nMen whom I admire and respect have told me that this wanton violence against women won’t stop until men talk seriously to other men about their behaviour. So please, men, talk to each other – NOW.", "892" ], [ "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" ], [ "Another horrific murder/suicide in Trinidad & Tobago revives discussion about domestic violence · Global Voices\nImage of woman attempting to shield herself from domestic abuse; free use via Canva.\nOn April 1, <PERSON>, a primary school teacher in south Trinidad, acted on the threats he had been issuing against his wife <PERSON>, murdering her at their home in front of the younger of their two children, then taking his own life. The couple was on the verge of divorce after <PERSON> fathered a child outside of the marriage.\nTrinidad and Tobago Guardian -\nSunday 3rd April 2022\nRead today's big stories from a trusted news source…\nTHE TRINIDAD AND TOBAGO GUARDIAN! pic.twitter.com/6SswozYKje\n— T&T Guardian (@GuardianTT) April 3, 2022\nThe murder/suicide has once again drawn attention to the plague of domestic violence in the country. In May 2021, a similar incident took place when 47-year-old <PERSON> was beaten to death by her common-law husband who later killed himself. Even more recently, this past February, 30-year-old <PERSON> was attacked by her husband, who thereafter took his own life. <PERSON> was seriously injured, but survived.\nInstances of domestic abuse have been on the rise since the start of the COVID-19 pandemic, especially earlier on, when there were stricter lockdowns. However, in the wake of a double suicide on March 19, one local psychiatrist, Dr. <PERSON>, predicted an increase in suicides and depression as part of the fallout from the pandemic.\nSocial media users were vocal about the issue. On some comment threads, people expressed concern about the trauma of the children who witness such acts of violence, while others pleaded with women in domestic abuse situations to seek help.\nIt was a sentiment echoed by police commissioner <PERSON>, even as he revealed that “domestic violence and these family situations have been occurring over and over.” <PERSON> said due to the rise in domestic violence cases, the Special Victims Unit of the Trinidad and Tobago Police Service (TTPS) has hired civilian staff to assist:\nWe have a problem and we need to deal with it. […] We have something inherently wrong in society […] serious challenges in communities and within families.\n<PERSON>, “speaking from personal experience,” countered:\n[T]he authorities like to make statements after the fact but you all only talk no action.\nThere needs to be a change in attitudes and behaviour of those in authority and the process. […]\nWhen you seek out help from the Police they make inappropriate remarks and silly responses […] and when your abuser [has] friends in the police station worse yet.", "1019" ], [ "[…]\nAnd people who like to comment and say leave…Leave and go where??? […]\nThere is no help from authorities. […]\nThe law / system seems to favour criminals and abusers.\nFacebook user <PERSON> added:\n[Domestic violence] is a complex issue and women who are victims, need individual support and access to support services to meet their needs. Services that are available 24-hour, seven-days-a-week, services that provide information, support and access to safe accommodation for someone who wants to leave a violent partner or family situation.\nCounselling and other forms of support are available for victims of domestic abuse via the National Family Services Division and other related agencies, such as the Coalition Against Domestic Violence. There are also various shelters throughout the country. However, Facebook user <PERSON> suggested that sometimes, timely access to such services can be mired in bureaucracy.\nOther netizens, meanwhile, surmised that the scourge of domestic violence was rooted in “a misogynist machismo culture which has been inculcated into many men even enabled by their own mothers”:\nThey see a woman as a possession and piece of property not as an individual and someone else's daughter, sister or loved one. They seek control and dominance and their egos are easily bruised.\nOn the heels of this latest femicide, non-governmental organisations like the International Women's Resource Network (IWRN), are pressuring the government to work with the country's civil society in order to improve the support processes for domestic violence, and newspaper editorials have been calling for better state support and accountability.\nThere is no doubt that the issue is a multi-layered and complex one, but for <PERSON>, one particular aspect of the public discourse is “deeply disturbing”:\nIn many posts, it is being suggested that the victim in some way, is at least in part responsible for her own brutal murder. She talked back. She was quarrelsome. She liked bacchanal. She did not help out financially. She did not leave the home after filing for divorce.", "600" ] ]

[ 9080, 2473, 6372, 7420, 8249, 8100, 8986, 9497, 7492, 85, 4868, 6260, 10061, 8885, 6246, 6524, 5249, 2919, 10991, 8541, 6261, 3291, 568, 2113, 5883, 4590, 7354, 7766, 6719, 9379, 10585, 6564, 3918, 8166, 2807, 10634, 6877, 10520, 9294, 3054, 3037, 6370, 11164, 9658, 6356, 4012, 3398, 5590, 1863, 7505, 7603, 8113, 8607, 4990, 5513, 1628, 356, 6069, 1617, 6155, 9287, 2080, 6555, 3518, 10037, 707, 4474, 8442, 5283, 8196 ]

[ [ "I've been also looking for the answer of this question, and I give my different view of Gumbel softmax just because I think this is a good question.\nFrom a general point of view: We use softmax normally because we need a so-called score, or a distribution $\\pi_1 .. \\pi_n$ for representing n probabilities of categorical variable with size n; We use Gumbel-softmax to sample an one hot sample [0..1..0] from this distribution.\nIn more concrete examples: Normally in networks for NLP(which categorize outputs into different word tokens), softmax is used to calculate the distribution of different, say, 5000 word choices at current text position. the cross entropy loss, gives a measure about the difference between the softmax predicted distribution and the real word distribution; For Gumbel-softmax, it is normally used to generate a sample one-hot vector for the constructing the following network, like in some VAE-based models. That's why the temperature factor $\\tau$ is a must for Gumbel-softmax, and in most cases not needed in softmax.\nAt this point, we know the difference of their uses cases, now comes the confusing part: the two formulas are so similar, why they are doing the different things?\nThe first key factor: What makes the difference is the $g_i$ term in the Gumbel-softmax formula. It represents a point sampled from the distribution $Gumbel(0, 1)$. the adding term $log(\\pi_i)$ and the scaling term $\\tau$ is just used to reparameterize it to $Gumbel(log(\\pi_i), \\tau)$ (reparameterization trick is for making it differentiable). This Gumbel distribution is the key distribution for sampling a categorical variable in Gumbel-max method(hard and not differentiable since there is a argmax), and this is also where the name Gumbel comes from in Gumbel-softmax. Every time we use Gumbel-softmax, we need to randomly sample from $Gumbel(0,1)$ and do the reparameterization trick, this is the most different part from softmax.\nI would rather name it soft-Gumbel-max, to indicate it is motivated to make a soft version of Gumbel-max, instead of just intending to add a Gumbel term to softmax.\nThe second most significant difference: is the use of $\\tau$. In most neural networks, softmax is not coupled with this term. Since we normally need a distribution, not a nearly one-hot vector. What's more, in some cases, like beam search, we need to get the second or third most probable choices to explore global optimal searches.", "915" ], [ "In softmax, $\\tau$ is normally added with some domain-specific knowledges to make the distribution steeper. Smaller $\\tau$ not always means better, we need to tune it to best fit the model. For Gumbel-softmax however, in the later stage of the model training, we need the Gumbel-softmax as close to one-hot vector as possible. That's why we need to anneal it smaller and smaller during training.(the $\\tau$ is not too small at the beginning of training for this makes the training more stable). In some implementation like torch.nn.functional.gumbel_softmax, it uses the straight through trick hard - (detached soft) + soft to maintain the output value a one-hot vector as in hard Gumbel-max but with well-defined gradients as in soft differentiable Gumbel-softmax.\nThe most part I disagree with the previous answer is that, Gumbel-softmax will not give you the exact one-hot vector. It is still an estimation of one-hot vector. Even for straight-through, the forward pass is Gumbel-max and only the backward pass is Gumbel-softmax.\nThat's almost all how I understand Gumbel-softmax, Gumbel-max and softmax. Please comment if there is anything unclear or incorrect.\nMORE If you still confuse\nAfter writing this answer, I found that, although the use cases of softmax and Gumbel-softmax are different, but we can still force to apply softmax in the place where Gumbel-softmax is applied without getting any arithmetic problem, and vice versa. Because both of them are soft and not exact, and both of them are differentiable. To make clearer why this is a problem. let's make two very gross examples of misuse.\nSuppose there is a network needing a sample but not a distribution of a categorical variable, e.g.", "915" ], [ "In a variational antoencoder (VAE), the output of the encoder, $\\mu$ and $\\sigma$, is a deterministic function of input data $x$ (you put $x$ into your encoder neural network, and it generates $\\mu$ and $\\sigma$, there is nothing random here).\nThen the hidden representaition $z$ (posterior) is sampled from the Guassian distribution parameterized by $\\mu$ and $\\sigma$. So notice that we don't talk about what 's the distribution of $\\mu$ and $\\sigma$ (since they are deterministic based on $x$, not random variables), but we do talk about the distribution of $z$.\n\"why do we want to feed forward latent matrix with Gaussian distribution?\"\nTo be specific, we feed a Gaussian distributed variable $z$ into the decoder network. This is the basic model assumption of VAE regarding how samples are generated. Notice that one of the main difference between VAE and standard autoencoder is that VAE is a generative model, in the sence that you can randomly generate samples, instead of using a input $x$ to reconstruct something similar to $x$.\nIf we imagine a VAE trained on the MNIST hand written digits dataset, we want to randomly sample $z$~$p(z)=\\mathcal{N}(0,1)$, and feed this $z$ into the decoder network which give us the output distribution (which is again a Gaussian), and sampling from that output distribution results in an image of a digit.\n\"Why compare a distribution of Mu and Sigma matrices? \"\nWe do not compare the distribution of $\\mu$ and $\\sigma$. As explained above, we are talking about the Gaussian distributed hidden variable $z$ (posterior $q_{\\theta}(z|x)$) parameterized by $\\theta=(\\mu,\\sigma)$.", "915" ], [ "We compare the posterior distribution of $z$ with its prior ($p(z)=\\mathcal{N}(0,1)$) and the difference (measured by their KL-divergence) is used as a regularization term in the loss function.\nThe reason for that is we want the latent representation $z$ to be close to its prior (standard Gaussian). This is relevant to how we generate samples from the VAE (we first sample from the standard Gaussian prior). If we encode a $x$ to somewhere very far from this prior, it will be unlikely that we can generate such samples.\nFor example, a well trained posterior (first two dimensions) for MNIST looks like this (photo from here)\nNotice that the posterior for each digit (e.g. dark blue for digit \"0\") is distributed like a Gaussian and not far from $\\mathcal{N}(0,1)$, but difference digits do occupy different area.\nMany online tutorials (e.g. here or here) have more detailed explanation about the concepts in VAE. I would suggest to read them.", "915" ], [ "Here are the answers:\n1. In sequence modeling, we expect a sentence to be ordered sequence, thus we cannot take random words (unlike bag of words, where we are just bothered about the words and not really the order). For example: In bag of words: \"I ate ice-cream\" and \"ice-cream ate I\" are same, while this is not true for the models that treat entire sentence as ordered sequence. Thus, you cannot pick N random words in a random order.\n2. Choosing tokens is model dependent. You can always preprocess to remove stop words and other contents such as symbols, numbers, etc if it acts as noise than the information.\n3. I would like to clarify that lemmatizing and word-piece tokenization is not the same. For example, in lemmatization \"playing\" and \"played\" are lemmatized to \"play\". But in case of word-piece tokenization it's likely split into \"play\"+\"##ing\" or \"play\"+\"ed\", depending on the vocabulary. Thus, there is more information preserved.\n4. max_length should be optimally chosen such that most of you sentences are fully considered. (i.e, most of the sentences should be shorter than max_length after tokenization). There are some models which considers complete sequence length.", "242" ], [ "Example: Universal Sentence Encoder(USE), Transformer-XL, etc. However, note that you can also use higher batch size with smaller max_length, which makes the training/fine-tuning faster and sometime produces better results.\n5. The pretrained model is trained with MAX_LEN of 512. It's a model's limitation.\n6. In specific to BERT,as claimed by the paper, for classification embeddings of [CLS] token is sufficient. Since, its attention based model, the [CLS] token would capture the composition of the entire sentence, thus sufficient. However, you can also average the embeddings of all the tokens. I have tried both, in most of my works, the of average of all word-piece tokens has yielded higher performance. Also, some work's even suggests you to take average of embeddings from the last 4 layers. It is merely a design choice.\n7. Using sentence embeddings are generally okay. But, you need to verify with the literature. There can always be a better technique. Also, there are models specific to sentence embeddings (USE is one such model), you can check them out.", "716" ], [ "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" ], [ "Finding an optimal learning rate is an important step in optimizing a neural network. As discussed at length here it is not a trivial question, but there are some ways to get a good starting value. Main idea here is to plot loss vs learning rate for different values and choose the learning rate where the slope is the highest:\nThis image is from the link above. This figure tells me that anything from a little right of 10-5 to around 10-3 can be a good learning rate. One can also set a relatively high learning rate, and reduce it when the loss function reaches a plateau, so in the above example, you would be better off by starting with the highest end; and lower the rate later as needed. This can be achieved by a learning rate scheduler (such as the one in Keras callbacks). This way, you won't spend a lot of time at the initial epochs where there is a lot to learn and the loss drops quickly.", "964" ], [ "Three key parameters of a scheduler are \"factor\",\"patience\" and \"min delta\" . If the loss function does not change by \"min delta\" in \"patience\" number of epochs, the learning rate is reduced by the ratio defined in \"factor\".\nYou also mention decay in your post, which can be considered as the default learning rate for some optimizers. And if I remember correctly, it actually associates a different learning rates for each parameter, and reduces them at a different rate. You can find a more detailed comparison here. But the main reason to use a LR scheduler even when a decay is present is to have more control on the learning process. When the training reaches a plateau, you might have to wait for a long time before the default decay in <PERSON> (for example) gets to a low enough value to get over that region and start learning again. But with a scheduler, you can define when to lower the learning rate by a significant amount (compared to default decay), so that further learning is possible. Keep in mind that there is not much to learn in the later epochs compared to the ones in the beginning.", "964" ], [ "From a practical and theoretical perspective, when is it beneficial to incorporate Gumbel noise into a neural network, as opposed to just using Softmax with temperature?\nYou don't necessarily need Gumbel-Softmax to obtain \"one-hot like\" vectors, or the ability to differentiate through an indexing mechanism.\nThe LSTM architecture and derived variants are examples of this. They model \"forget/input\" gates using sigmoid outputs, which are deterministic. A \"true\" gating mechanism would be either 0 or 1, but to make things differentiable, LSTMs relax that constraint to sigmoided outputs. You'll notice that there is no \"random\" inputs here, and you can still apply the straight-through trick here to make the gates truly discrete (while backpropagating a biased gradient).\nGumbel-Softmax can be used wherever you would consider using a non-stochastic indexing mechanism (it is a more general formulation). But it's especially useful when you want to backpropagate through random samples of discrete variables.\n* VAE with a Gumbel-Softmax or Categorical posterior (encoder) distribution. Notably, you cannot simply use a deterministic softmax here because it would turn your VAE into a standard autoencoder.", "915" ], [ "Autoencoders lack a way to generate new samples from the prior.\n* Actor-Critic architecture with a Gumbel-softmax or Categorical actor (most policy gradient implementations assume you can re-parameterize the gradients from the critic through the actor without using a score function estimator to estimate the black-box gradient). You cannot simply substitute the deterministic softmax here, because there is a type mismatch: the critic takes as input a action $a \\in A$, while the softmax represents the conditional policy distribution $\\pi(a|s)$\n* The \"probabilistic\" interpretation of a non-random quantization such as an LSTM would essentially be mode-seeking behavior in fitting a density. You have loss function that takes in categorical decisions $c$, so the expected loss $\\mathbb{E}_c[f(c)]$ is minimized by learning some distribution $p(c)$. Quantizing a softmax without sampling the Gumbel noise (e.g. just using a sigmoid or softmax) is akin to choosing the same $c$ every time. For some $f$ this is okay, and for other $f$ this is highly suboptimal (consider the categorical KL divergence as a loss).\nMy best guess is that the introduction of the Gumbel noise enforces stronger exploration before convergence, but I can't recall reading any papers that use this as a motivation to bring in the extra randomness.\nThis is an interesting idea, but there are many ways to inject \"exploration\" noise into the set of parameters you use in a function approximator.", "915" ], [ "How do you measure the degree of influence of pre-training on a fine-tuning task?\nContext\nI have a randomly initialized (deep learning) model A, and a pre-trained model Ap. The two are trained (or fine-tuned, more specifically for Ap) on the same target task* and I call them A' and Ap', respectively.\np(.) is the performance of a model on the target task. Let's admit that, in general, p(Ap') > p(A').\n*Assuming that either with everything identical (seeds, etc), or that I have enough seeds so I can rely on the average behavior.\nWhat I am looking for\nA measure/metric of the robustness/dependency of my method with respect to the pre-training; i.e.", "458" ], [ "something that tells me the degree of dependency of my method on the pre-training process.\nIn the end I want to repeat this process over many fine-tunning methods and compare them.\nEdit 1\nI would like have some conclusion that looks like: \"the fine-tunning method X is more robust to pre-training than fine-tunning method Y based on the fact that even with a worse* pre-training it retains more performance.\nA bit more formally : * say that the training (or, again, fine-tuning) methods X and Y are being compared; * their respective performances after they are applied to the (raw, pre-trained) models are (p(Ax), p(Apx)) and (p(Ay), p(Apy));\nI'd like to make conclusions, based on comparisons between (p(Ax), p(Apx)) and (p(Ay), p(Apy)), that X is more/less robust to the pre-training than Y.\nIdeally... given a method X, I'd like to generate a sequence (p(Ax), p(Ap1x), ..., p(ApNx)) such that the pre-trained models Ap1, ..., ApN are increasingly better in their original (surrogate) task -- and A (without pre-training) is a reference. Then the sequence of performance on the target task (p(Ax), p(Ap1x), ..., p(ApNx)) allows one to take conclusions about X [compared to another fine-tuning mehtod Y].\nA practical (optional) constraint: for the sake of reproducibility, I'd like to use publicly availabe pre-trained models so in a perfect scenario all the model Ap1, ..., ApN should be available or \"easily\" reproducible (i.e. can be programatically generated).", "458" ], [ "Why transform embedding dimension in sin-cos positional encoding?\nPositional encoding using sine-cosine functions is often used in transformer models.\nAssume that $X \\in R^{l\\times d}$ is the embedding of an example, where $l$ is the sequence length and $d$ is the embedding size. This positional encoding layer encodes $X$’s position $P \\in R^{l\\times d}$ and outputs $P + X$\nThe position $P$ is a 2-D matrix, where $i$ refers to the order in the sentence, and $j$ refers to the position along the embedding vector dimension. In this way, each value in the origin sequence is then maintained using the equations below:\n$${P_{i, 2j} = \\sin \\bigg( \\frac{i}{10000^{2j/d}}} \\bigg) $$\n$${P_{i, 2j+1} = \\cos \\bigg( \\frac{i}{10000^{2j/d}}} \\bigg)$$\nfor $i = 0,..., l-1$ and $j=0,...[(d-1)/2]$\nI understand the transormation across the time dimension $i$ but why do we need the transformation across the embedding size dimension $j$? Since we are adding the position, wouldn't sin-cos just on time dimension be sufficient to encode the position?\nEDIT\nAnswer 1 - Making the embedding vector independent from the \"embedding size dimension\" would lead to having the same value in all positions, and this would reduce the effective embedding dimensionality to 1.\nI still don't understand how the embedding dimensionality will be reduced to 1 if the same positional vector is added.", "101" ], [ "Say we have an input $X$ of zeros with 4 dimensions - $d_0, d_1, d_2, d_3$ and 3 time steps - $t_0, t_1, t_2$\n$$ \\begin{matrix} & d_0 & d_1 & d_2 & d_3\\ t_0 & 0 & 0 & 0 & 0\\ t_1 & 0 & 0 & 0 & 0\\ t_2 & 0 & 0 & 0 & 0\\ \\end{matrix} $$\nIf $d_0$ and $d_2$ are the same vectors $[0, 0, 0]$, and the meaning of position i.e time step is the same, why do they need to have different positional vectors? Why can't $d_0$ and $d_2$ be the same after positional encoding if the input $d_0$ and $d_2$ are the same?\nAs for the embedding dimensionality reducing to 1, I don't see why that would happen. Isn't the embedding dimensionality dependent on the input matrix $X$. If I add constants to it, the dimensionality will not change, no?\nI may be missing something more fundamental here and would like to know where am I going wrong.", "563" ] ]

[ 9591, 8122, 1090, 3368, 8592, 8863, 8307, 3559, 8158, 4514, 7617, 3248, 5902, 172, 10251, 10457, 7845, 2540, 4710, 2866, 7627, 3892, 2417, 4419, 4041, 2698, 6240, 1994, 11018, 4890, 2518, 10041, 4567, 290, 1337, 7059, 5502, 3147, 4192, 5498, 1486, 5112, 10174, 8302, 1831, 4301, 10142, 5988, 1220, 6482, 4633, 818, 7041, 10110, 9718, 9091, 7445, 3560, 4280, 6663, 7248, 4042, 9616, 3246, 1053, 10482, 7327, 9806, 4019, 9587 ]