AcharyaChanakya/simple-wikipedia huggingface dataset:
Metallic bonds causes many of the traits of metals, such as strength, malleability, ductility, luster, conduction of heat and electricity.
Because the electrons move freely, the metal has some electrical conductivity. It allows the energy to pass quickly through the electrons, generating an electric current. Metals conduct heat for the same reason: the free electrons can transfer the energy at a faster rate than other substances with electrons that are fixed into position. There also are few non-metals that conduct electricity: graphite (because, like metals, it has free electrons), and ionic compounds that are molten or dissolved in water, which have free moving ions.
Metal bonds have at least one valence electron which they do not share with neighboring atoms, and they do not lose electrons to form ions. Instead, the outer energy levels (atomic orbitals) of the metal atoms overlap. They are similar to covalent bonds. Not all metals exhibit metallic bonding. For example, mercury ions () form covalent metal-metal bonds.
An alloy is a solution of metals. Most alloys are shiny like pure metals are.
Heat conduction (or thermal conduction) is the movement of heat from one object to another one that has different temperature when they are touching each other. For example, we can warm our hands by touching hot-water bottles. When the cold hands touch the hot-water bottle, heat flows from the hotter object (hot-water bottle) to the colder one (hand). People make things with different thermal conductivity, for example cookware to heat things or insulated containers to keep hot things hot or cold things cold.
Other ways to transfer heat are by thermal radiation and/or convection. Usually more than one of these processes happen at the same time.
In the atomic theory solids, liquids and gases are made of tiny particles called "atoms". The temperature of the material measures how fast the atoms are moving and the heat measures the total amount of energy due to the vibration of the atoms.
Conduction can happen when one part of a material is heated. The atoms in this part vibrate faster and are more likely to hit their neighbors. The collisions cause those atoms also to move faster, passing the heat energy to them. In this way the energy travels through the solid. (Rather like the way energy passes along a set of tumbling dominos).
The atomic picture also helps explain why conduction is more important in solids: in solids the atoms are close together and unable to move around. In liquids and gases the particles can move past each other, so the collisions are less common.
The law of heat conduction, also known as Fourier's law, means that the rate, in time, of heat transfer through a material is proportional to the negative gradient in the temperature and to the area at right angles, to that gradient, through which the heat is flowing:
Thermal conductivity usually varies with temperature, but the variation can be small, over a significant range of temperatures, for some common materials.
Judith Weir
Judith Weir (born 11 May 1954) is a British composer. She is well known for her theatre works, choral music, orchestral music and chamber music.
Weir was born in Cambridge, England to Scottish parents. While she was still at school she trained with the composer John Tavener. She played the oboe in the National Youth Orchestra of Great Britain. She then studied at the University of Cambridge where her teacher was Robin Holloway.
Judith Weir’s music has harmonies which are very exciting and original. Her Christmas carol "Illuminare" has become very popular, but it is quite difficult and needs a good choir to pitch the notes of the dissonant chords. She often uses medieval history as inspiration for her music, as well as music from her native Scotland, e.g. piobaireachd, which is a kind of variation form using small intervals. Her music often tells stories. Her operas include "A Night at the Chinese Opera", "The Vanishing Bridegroom", "Blond Eckbert", and "Armida", an opera for television.
From 1995 to 2000, she was the Artistic Director of the Spitalfields Festival in London. She has composed works for the City of Birmingham Symphony Orchestra. She has received many honours, including the CBE in 1995.
Chorus can mean several things:
Vassal
A vassal during the feudalism of medieval Europe, was someone who had shared duties with a lord. Usually the vassal provided soldiers to the lord. The lord used his army of soldiers from all of his vassals to protect those vassals. The lord also gave him the piece of land that he held as a fief. By analogy the term "vassal" is used also for similar systems in other feudal societies.
The development of the "vassal", in a society that was increasingly organised around the concept of "lordship"– in French the "seigneur"– is one sign that Antiquity ended and the Early Middle Ages began. Lordship is the basic social institution as Tacitus described them in his book "Germania". The Roman West experienced them for the first time in the Migration Period.
As the system developed in the seventh century, the vassals were gangs of freemen who subjected themselves, in some degree of formality, to the authority of a leader, from whom they could expect to be fed, clothed and armed. The quality of a vassal was only in his fighting ability and the strength of his loyalty. The etymology (where the word came from) of "vassal" is from a Celtic word "gwas" "boy" that meant a young male slave, with a Latinised form, "vassus" that appeared in Salic Law (Rouche 1987 p 429), like the way "knight" came from the from Old English word "cniht" and similar words in Frisian and Dutch, all meaning "lad" .
Migration period
The migration period, or barbarian invasions or Völkerwanderung, happened in AD 300–700 in Europe, at the end of ancient history and during the Early Middle Ages.
The migrations included the Goths, Vandals, Franks, and other Germanic, Bulgar, and Slavic tribes. They may have been influenced by attacks of the Huns in the East and may also be connected to the Turkic migrations in Central Asia, overpopulation, or climate changes. The migration period also included groups of Angles, Saxons, Frisians, and some Jutes to Britain.
Migrations would continue well into the Middle Ages, beyond 1000 AD, with successive waves of Slavs, Alans, Avars, Bulgars, Hungarians, Pechenegs, Cumans, and Tatars that changed the ethnic makeup of Eastern Europe. Western European historians, however, tend to stress the migrations that were most relevant to Western Europe.
The San Francisco Bay Area, also known as the Bay Area, is a metropolitan area that goes around the San Francisco Bay in Northern California. It includes the cities of San Francisco, San José, and Oakland, and their many suburbs. It also includes the smaller urban and rural areas of the North Bay. Over seven million people live in the San Francisco Bay Area. The San Francisco Bay Area is the 43rd largest metropolitan area in the world in population.
The Bay Area includes cities, towns, military bases, airports, and related regional, state, and national parks.
San José is the largest city in the Bay Area since 1990 and the tenth largest city in America. But for most of its history, San Francisco was the city with the most people. San Francisco is still the city people pay the most attention to, and it is the major cultural center in the region.
Bay Area Rapid Transit connects the different parts of the Bay Area.
The region north of the Golden Gate Bridge is known locally as the North Bay. This area includes Marin County and continues north into Sonoma and Napa counties and east to Solano County. With some exceptions, this region is quite rich: Marin County is listed as the richest in the nation.
The City and County of San Francisco is generally placed in a category by itself in terms of geography and culture. It is separated by water from the north, west and east, and by a county line from its neighbor cities to the South. San Francisco has been the cultural, financial and urban center of the region for a long time. For most of the Bay Area's history, it has also been the main population center. But because the size of the county is limited, the growth of the city was limited as well. As a result, other cities and counties have had more population growth.
The area between the South Bay and the City and County of San Francisco is the San Francisco Peninsula, known locally as "The Peninsula". This area includes many small cities and suburban communities in San Mateo County and the northwestern part of Santa Clara County, as well as several towns along the Pacific coast, such as Pacifica and Half Moon Bay.
The eastern side of the bay, consisting of Alameda and Contra Costa counties, is known locally as the East Bay. The East Bay is split into two regions, the inner East Bay, which is on the coast of the Bay, and the outer East Bay, including the inland valleys separated from the inner East Bay by hills and mountains.
The communities along the southern edge of the Bay are known as the South Bay, Santa Clara Valley, and Silicon Valley.
This region is home to a large number of major technology companies. Some tech companies in the South Bay are Intel, AMD, Cisco Systems, Hewlett-Packard, Apple, Google, and Yahoo!, Microsoft and much much more.
The San Francisco Bay Area is one of the richest regions in the United States.
San Francisco Bay is a shallow, productive estuary through which water draining about forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains and Central Valley, enters the Pacific Ocean. Technically, both rivers flow into Suisun Bay, which help flows through the Carquinez Strait to meet with the Napa River at the entrance to San Pablo Bay, which connects at its south end to San Francisco Bay, although the entire group of interconnected bays are often referred to as "the San Francisco Bay."
San Francisco Bay lies in the US state of California and is surrounded by a region known as the San Francisco Bay Area, that is near the big cities of San Francisco, Oakland, and San Jose.
The Bay covers somewhere between 400 and 1,600 square miles (1,040 to 4,160 square kilometres), depending on which sub-bays (such as San Pablo Bay), estuaries, wetlands, and so on are included in the measurement.
Ahmed Yassin
Ahmed Yassin (January 1, 1937 – March 22, 2004) was a spiritual leader of the militant Palestinian group Hamas. Yassin's birth date is in dispute. He claimed he was born 1/1/1938, however, his passport indicated 1/1/1937. To some he was a hero, to some he was a notorious member of a terrorist organization. He was also a symbolic figure for Palestinians to fight against Israel.
Yassin was born in al-Jura, British Mandate of Palestine. He helped create Hamas and became its spiritual leader in 1987. To other members of Hamas he was a hero but he was blamed by the Israeli government for planning suicide bombings and other attacks against Israel. He claimed that was the only way of fighting occupation. He was confined to a wheelchair because he was paralyzed since age 12, he was also nearly blind and could barely hear. He was very powerful and influential. He was assassinated in an airstrike in Gaza City by the Israeli Army after he left a mosque in Gaza in the early morning hours.
Field strength
In physics, the field strength of a field is the magnitude (size) of its (vector) value. This means that the force exerted by the field on a given object is proportional to the field strength.
In differential geometry, the field strength is another name for the curvature form. For the electromagnetic field, the curvature form is an antisymmetric matrix whose elements are the electric field and magnetic field: the electromagnetic tensor.
In radio engineering, field strength is the strength of radio waves in a particular location.
Field (physics)
In physics, a field means that a physical quantity is assigned to every point in space (or, more generally, spacetime). A field is seen as extending throughout a large region of space so that it influences everything. The strength of a field usually varies over a region. Michael Faraday became the first to coin the term "field", in 1849.
For some fields, there is a number for each point in space. They are called "scalar fields". For more complicated fields, there are more than one number for each point in space. They are called "vector fields" or "tensor fields". For example, one can model a gravitational field by a vector field where a vector indicates the acceleration a mass would experience at each point in space. Other examples are temperature fields or air pressure fields, which are often illustrated on weather reports by isotherms and isobars by joining up the points of equal temperature or pressure respectively.
It is now believed that quantum mechanics should underlie all physical phenomena.
A field theory is a physical theory that describes how one or more physical fields interact with matter.
Trigonometric function
In mathematics, the trigonometric functions are a set of functions which relate angles to the sides of a right triangle. There are many trigonometric functions, the 3 most common being sine, cosine, tangent, followed by cotangent, secant and cosecant. The last three are called reciprocal trigonometric functions, because they act as the reciprocals of other functions. Secant and cosecant are rarely used.
The trigonometric functions sometimes are also called circular functions. They are functions of an angle; they are important when studying triangles, among many other applications. Trigonometric functions are commonly defined as ratios of two sides of a right triangle containing the angle, and can equivalently be defined as the lengths of various line segments from a unit circle (a circle with radius of one).
In order to define the trigonometric functions for the angle "A", start with a right triangle that contains the angle "A":
We use the following names for the sides of the triangle:
All triangles are taken to exist in Euclidean geometry, so that the inside angles of each triangle sum to π radians (or 180°); therefore, for a right triangle, the two non-right angles are between zero and π/2 radians. Notice that strictly speaking, the following definitions only define the trigonometric functions for angles in this range. We extend them to the full set of real arguments by using the unit circle, or by requiring certain symmetries and that they be periodic functions.
1) The sine of an angle is the ratio of the length of the opposite side to the length of the hypotenuse. In our case
Note that since all those triangles are similar, this ratio does not depend on the particular right triangle that is chosen, as long as it contains the angle "A".
The set of zeroes of sine (that is, the values of formula_2 for which formula_3) is
2) The cosine of an angle is the ratio of the length of the adjacent side to the length of the hypotenuse. In our case
The set of zeroes of cosine is
3) The tangent of an angle is the ratio of the length of the opposite side to the length of the adjacent side. In our case
The set of zeroes of tangent is
This is the same set as that of the sine function, since
The remaining three functions are best defined using the above three functions.
4) The cosecant csc("A") is the multiplicative inverse of sin("A"); it is the ratio of the length of the hypotenuse to the length of the opposite side:
5) The secant sec("A") is the multiplicative inverse of cos("A"); it is the ratio of the length of the hypotenuse to the length of the adjacent side:
6) The cotangent cot("A") is the multiplicative inverse of tan("A"); it is the ratio of the length of the adjacent side to the length of the opposite side:
One can also define the trigonometric functions by using power series:
and define tangent, cotangent, secant and cosecant using identities, see below.
Some important identities:
The hyperbolic functions are like the trigonometric functions, in that they have very similar properties. Each of six trigonometric functions has a corresponding hyperbolic form. They are defined in terms of the exponential function, which is based on the constant "e".
Gradient (disambiguation)
Gradient could mean:
An archer is someone who practices archery (shooting with bows and arrows).
Archer can also mean:
Archery is the practice of using a bow to shoot arrows. Archery has historically been used in hunting and combat and has become a precision sport. A person practicing archery is called an "archer", and one who enjoys or is an expert at archery is sometimes called an toxophilite.
The earliest evidence of archery dates back more than 9,000 years. The bow probably was used in hunting first and later adopted as a tool of warfare. It was one of the earliest forms of artillery.
Classical civilizations, notably the Persians, Macedonians, Nubians, Greeks, Parthians, Indians, Japanese, Chinese, and Koreans, had large numbers of archers in their armies. Archers in chariots were especially important in armies of ancient Egypt. Arrows were very destructive against massed formations, and the use of archers helped win battles. The army of the Mongol Empire was mostly archers on horseback.
John Felix Anthony Cena Jr. (born April 23, 1975) is an American professional wrestler, hip hop musician and actor. He currently works for the WWE. Cena has won the WWE Championship/WWE World Heavyweight Championship thirteen times, the World Heavyweight Championship thrice, the United States Championship five times and the World Tag Team Championship twice. Also, Cena won the Royal Rumble in 2008 and 2013. As for his musical career, Cena has released an album called "you cant see me". Cena has also been featured in the movies "The Marine", "12 Rounds" and "Legendary". He will star as Peacemaker in the 2022 movie "The Suicide Squad" and his own television series for HBO Max.
In Baseball, he is a Red Sox fan turned Rays fan.
Cena was signed by then Person in charge of Talent Relations, Jim Ross on behalf on WWF. According to Ross, when he returned to Connecticut after signing Cena he walked into Vince McMahon's office and told him "I just signed your main event for WrestleMania in 5 years." Cena would eventually make his WrestleMania debut 3 years later at WrestleMania XX winning the WWE United States Championship from The Big Show, and his Main event WrestleMania debut 4 years later winning the WWE Championship, from John "Bradshaw" Layfield.
During the match between Barrett and Orton, Orton won so Cena was forced to retire. He was rehired by Wade Barrett and defeated him at TLC: Tables, Ladders and Chairs Pay Per View.
He was drafted to SmackDown as the first pick in the 2011 WWE Draft, but before the end of the night, he was drafted back to Raw.
He was defeated by The Rock at WrestleMania XXVIII. He won his second Royal Rumble in January 2013. Thus he got another match at WrestleMania XXIX against The Rock for WWE Championship. He won that match and became the WWE Champion. He retired the next night on Raw after getting defeated by the debuting Dominik Mysterio, the son of professional wrestler Rey Mysterio. He was inducted in the 1938 WWE Hall of Fame.
Signal transduction
A signal transduction in biology is a cellular mechanism. It converts a stimulus into a response in the cell. There are two stages in this process:
So, signal transduction starts with a signal to a cell receptor, and ends with a change in cell function. In either step, the signal can be amplified. Thus, one signalling molecule can cause many responses.
Receptors are in the cell membrane, with part of the receptor outside and part inside the cell.  The chemical signal binds to the outer portion of the receptor, changing its shape. This causes another signal inside the cell.  Some chemical messengers, such as testosterone, can pass through the cell membrane, and bind directly to receptors in the cytoplasm or nucleus.
Sometimes there is a cascade of signals within the cell. With each step of the cascade, the signal can be amplified, so a small signal can result in a large response. Eventually, the signal creates a change in the cell, either in the expression of the DNA in the nucleus or in the activity of enzymes in the cytoplasm.
Most often, ordered sequences of biochemical reactions inside the cell are involved. These are carried out by enzymes and linked through second messengers. So a "second messenger pathway" is produced. These things usually happen quickly, sometimes very quickly. They may last from milliseconds (in the case of ion flux) to days for gene expression.
The number of proteins and other molecules that take part increases during the process. So a 'signal cascade' develops and "a relatively small stimulus may cause a large response".
In bacteria and other single-cell organisms, the transduction processes a cell has limits the number of ways it can respond to its environment. In multicellular organisms, lots of different signal transduction processes are used to coordinate the behavior of individual cells. By this means the function of the organism as a whole is organized. The more complex the organism, the more complex the repertoire of signal transduction processes the organism must possess.
Thus, sensing of both the external and internal environment at the cellular level, relies on signal transduction. Many disease processes such as diabetes, heart disease, autoimmunity and cancer arise from defects in signal transduction pathways. This highlights the critical importance of signal transduction to biology and medicine.
These systems of communication between cells are extremely ancient, and are found in all metazoa.
Flux is a term in physics and mathematics. It is broadly defined as "How much stuff goes through a thing" (or into an area). The word "flux" is similar to "flow".
For instance, imagine a butterfly net. The amount of air passing through the net is the flux.
In the study of transport phenomena (heat transfer, mass transfer and fluid dynamics), flux is defined as flow per unit area, where flow is the movement of some quantity per time. Flux, in this definition, is a vector.
There are many fluxes used in the study of transport phenomena. Each type of flux has its own distinct unit of measurement along with distinct physical constants. Six of the most common forms of flux from the transport literature are defined as:
In the field of electromagnetism, flux is usually the integral of a vector quantity over a finite surface. The result of this integration is a scalar quantity. The magnetic flux is thus the integral of the magnetic vector field over a surface, and the electric flux is defined similarly. Using this definition, the flux of the Poynting vector over a specified surface is the rate at which electromagnetic energy flows through that surface. Confusingly, the Poynting vector is sometimes called the "power flux", which is an example of the first usage of flux, above. It has units of watts per square metre (W/m).
Flux (disambiguation)
Flux comes from Latin and means "flow"; it may mean:
Neuroscience (or neurobiology) is the scientific study of the nervous system. It is the branch of biology that investigates the molecular, cellular, developmental, functional, evolutionary, computational, psychosocial and medical aspects of the brain.
The nervous system is made of billions of neurons connected together and to other systems in the body. The central nervous system includes the brain, spinal cord and Retina. It is connected to the rest of the body via the peripheral nervous system. A neuroscientist, is a scientist who studies neuroscience.
Neuroscience research from different areas can also be seen as focusing on a set of specific themes and questions. (Some of these are taken from http://www.northwestern.edu/nuin/fac/index.htm)
Conversation analysis
Conversation analysis (commonly abbreviated as CA) is the study of talk in social interaction. CA tries to describe the structure and patterns of interaction, whether this is institutional (in the school, doctor's surgery, courts or elsewhere) or casual conversation.
The term “conversation” to label this disciplinary movement is misleading if read in a colloquial sense, as many have.
Mark-Anthony Turnage
Mark-Anthony Turnage (born Grays, Essex, 10 June 1960) is an English composer. He is one of the most original composers in his country today.
Turnage studied at the Royal College of Music and won all the major prizes. He became famous when he wrote an opera called "Greek". It is typical of his musical style: quite lyrical but also very dramatic and aggressive. His music is often inspired by jazz. Other works include "Kai", "Rockaby", "Blood on the Floor", "Dispelling the Fears", "Drowned Out" and "Three Screaming Popes". He has written music for the English National Opera, City of Birmingham Symphony Orchestra and the Chicago Symphony Orchestra.
Hydrothermal vent
A hydrothermal vent is an opening in the seabed of the Earth by which geothermal energy escapes. Sea water enters, becomes very hot, and rises. The hottest ones carry many black chemicals, and are called black smokers. Scientists have found fewer white smokers. Heat escapes from underground in many places. If they are on land, they are usually hot springs, geysers, or fumaroles. Many archaea and bacteria live near hydrothermal vents, which are underwater. They support giant tube worms, clams and shrimp, and many other eukaryotes. The earliest known life forms are thought to have lived near such vents.
Deep sea organisms have no access to sunlight, so they must depend on nutrients in the chemical deposits and hydrothermal fluids in which they live. Compared to the surrounding sea floor, however, hydrothermal vent zones have a density of organisms 10,000 to 100,000 times greater.
Hydrothermal vent communities are able to sustain such vast amounts of life because vent organisms depend on chemosynthetic bacteria for food. These bacteria use sulfur compounds, particularly hydrogen sulfide, a chemical highly toxic to most known organisms, to produce organic material through the process of chemosynthesis.
The chemosynthetic bacteria grow into a thick mat which attracts other organisms such as amphipods and copepods which graze upon the bacteria directly. Larger organisms such as snails, shrimp, crabs, giant tube worms, fish, and octopus form a food chain of predator and prey relationships above the primary consumers.
The main groups of organisms around seafloor vents are worms, gastropods, and crustaceans, with large bivalves, and 'eyeless' shrimp making up the bulk of non-microbial organisms.
Tube worms form an important part of the community around a hydrothermal vent. They absorb nutrients directly into their tissues. There are approximately 285 billion bacteria per ounce of tubeworm tissue.
Tubeworms have red plumes which contain haemoglobin. Haemoglobin combines hydrogen sulfide and transfers it to the bacteria living inside the worm. In return the bacteria nourish the worm with carbon compounds.
Other examples of the unique fauna who inhabit this ecosystem are the gastropod "Crysomallon squamiferum", a species of snail with a foot reinforced by scales made of iron and organic materials, and the 'Pompeii Worm' "Alvinella pompejana", which is capable of withstanding temperatures up to 80°C (176°F).
Over 300 new species have been discovered at hydrothermal vents, many of them "sister species" to others in geographically separated vent areas. It has been proposed that before the North American plate overrode the Mid-Atlantic Ridge, there was a single biogeographic vent region found in the eastern Pacific. The subsequent barrier to travel began the evolutionary divergence of species in different locations. The examples of convergent evolution seen between distinct hydrothermal vents is seen as major support for the theory of natural selection and evolution as a whole.
A species of phototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of . No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis. This is the first organism discovered in nature to exclusively use a light other than sunlight for photosynthesis.
Guavas are plants in the genus "Psidium" of the family Myrtaceae. There are about 100 species of tropical shrubs and small trees in the genus.
They are native to Mexico, the Caribbean, Central America and the northern part of South America. Now they are found in all the tropical, and in some subtropical, regions because they are edible fruits.
Guava are also a kind of berry fruit on those plants. There are many kinds of guavas. The most common guava is the apple guava ("Psidium guajava"): it is so common that the word 'guava' usually refers to this species. Red guavas are called maroonguava. In 100 g of guava are 200 mg of vitamin C, which means that guavas have five times more vitamin C than oranges.
Resting potential
Thrust is a force or a push. When a system pushes or accelerates mass in one direction, there is a thrust (force) just as large in the opposite direction. In math and physics, this is described by Isaac Newton’s second and third laws. Thrust is used to describe how strongly an engine pushes. It can be used for many kinds of vehicles and engines such as rockets, motorboats, propellers, and jet engines.
Thrust is measured in “pounds of thrust” in the U.S. and in newtons in the metric system. 4.45 newtons of thrust equals 1 pound of thrust. A pound of thrust is how much thrust it would take to keep a one-pound object unmoving against the force of gravity on earth.
A very common question is how to compare the thrust number of an airplane engine with the mechanical power of a piston engine (the kind of engine in cars and in many airplanes with propellers). It is hard to compare these two. This is because they are not measuring the same exact thing. A piston engine does not move the plane. It just turns the propeller, which moves the plane. Because of this, piston engines are rated by how much power they give to the propeller.
However, a jet engine has no propeller – it pushes the aircraft by moving hot air behind it. A useful way to measure the power of a jet engine is to how much power the jet engine gives to the aircraft through its thrust force. This is called the “propulsive power of the jet engine." Power is how much force it takes to move something over a distance, divided by the time it takes to move that distance:
Where P is power, F is force, d is distance, and t is time. For a rocket or jet engine, the force is the same as thrust produced by the engine. Distance divided by time is also called speed. So power is the same as thrust times speed
Where T is thrust and "v" is speed. This is the power being delivered by the engine at a certain thrust or velocity. The propulsive power of a jet engine increases with its speed.
When the thrust of a rocket or an engine is compared to the weight, it is called the Thrust-to-weight ratio. The number that comes from this comparison does not have any units, because it is a ratio. A ratio in this case means that the thrust of the engine (in Newtons) is divided by the weight (in Newtons). The purpose of this comparison is to show how well the engine or vehicle performs, for example how much acceleration. It is a number that can be used to compare various types of motors like airplane motors, jet engines, rocket engines, or car engines.
This comparison number can change while the engine is running. This is because the weight of the engine gets lighter as fuel is used. The thrust-to-weight ratio is used to actually compare engines is the number found when the engine is first running.
Thrust is measured in “pounds of thrust” in the U.S. and in Newtons in the metric system. 4.45 Newtons of thrust equals 1 pound of thrust. A pound of thrust is how much thrust it would take to keep a one-pound object unmoving against the force of gravity on earth.
An airplane makes forward thrust when air is pushed in the direction opposite to flight. The thrust is made by the spinning blades of a propeller. Thrust can also be made by a rotating fan pushing air out from the back of a jet engine. Another way is by ejecting hot gases from a rocket engine.
Reverse thrust is the opposite of forward thrust. In this way air is pushed in the same way as the motion of the body. Reverse thrust can be used to help braking after landing. This can be done by redirecting the thrust in a turbofan or jet engine or by changing the blade angle of a propeller driven aircraft.
Birds normally achieve thrust during flight by flapping their wings.
A boat with a motor makes thrust or reverse thrust when the propellers are turned to push water backwards (or forwards). The thrust that this makes pushes the boat in the opposite direction than the water is being pushed.
A rocket is pushed forward by a thrust force as large as the force the exhaust gas makes when going out of the rocket nozzle. The force the exhaust gas makes is called the exhaust velocity. The velocity is measured compared to the rocket. For vertical launch of a rocket to work, the starting thrust must be more force than the weight of the rocket.
Thrust (disambiguation)
Thrust is a reaction force described by Newton's Second and Third Law. For this meaning, see Thrust.
This word has other uses:
Robert Anson Heinlein (July 7, 1907 - May 8, 1988) was an American writer. He mostly wrote science fiction books. He won the Hugo Award four times. Probably his best-known novels are Starship Troopers (1959, Hugo Award, was made into a film), and Stranger in a Strange Land (1961, Hugo Award). Two other Hugo awards were for Double Star (1956) and The Moon is a Harsh Mistress (1966). Together with Isaac Asimov and Arthur C. Clarke he is seen as one of the "Big Three of Science Fiction".
List of video game genres
There are many computer and video game genres. Here is a list of some of the common ones.
A fable is a type of story which shows something in life or has a meaning to a word. A fable teaches a lesson or suggests a moral from it. A fable starts in the middle of the story, that means, jumps into the main event without detailed introduction of characters. The characters of a fable may be animals, plants and legendary creatures. When animals are used in fables, they think and talk like people, even though they act like animals. For example, in a fable a clay pot might say that it is frightened of being broken.
The stories told by fables are usually very simple. To understand a fable, the reader or listener does not need to know all about the characters, only one important thing. For this reason animals are often used in fables in a way that is easily understood because it is always the same. They keep the same "characteristics" from story to story.
The most famous fables are those attributed to Aesop (6th century B.C.). Many fables are so well-known that their morals have become English sayings.
"Crying wolf" is another well-known English saying. This comes from "The Boy Who Cried Wolf". This fable is about a boy who was sent to mind the sheep. The boy got lonely while minding the sheep, so he shouted "Wolf! Wolf!" The people came running. The next day, he did it again and they were very angry. On the third day the boy saw a wolf. He cried "Wolf! Wolf!" but no one came and the wolf ate him.
Drainage is the natural or artificial removal of surface and sub-surface water from a given area. Many agricultural soils need drainage to improve production or to manage water supplies.
The earliest archaeological record of an advanced system of drainage comes from the Indus Valley Civilization from around 3100 BC in what is now Pakistan and North India. The ancient Indus systems of sewerage and drainage that were developed and used in cities throughout the civilization were far more advanced than any found in contemporary urban sites in the Middle East and even more efficient than those in some areas of modern Pakistan and India today. All houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered drains, which lined the major streets.
Wetland soils may need drainage to be used for agriculture. In the northern USA and Europe, glaciation created numerous small lakes which gradually filled with humus to make marshes. Some of these were drained using open ditches and trenches.
The largest project of this type in the world has been in process for centuries in the Netherlands. The area between Amsterdam, Haarlem and Leiden was, in prehistoric times swampland and small lakes. Turf cutting (Peat mining), subsidence and shoreline erosion gradually caused the formation of one large lake, the Haarlemmermeer, or lake of Haarlem. The invention of wind powered pumping engines in the 15th century permitted drainage of some of the marginal land, but the final drainage of the lake had to await the design of large, steam powered pumps and agreements between regional authorities. The elimination of the lake occurred between 1849 and 1852, creating thousands of km of new land.
Polder
Empoldering is a method of reclaiming land from the sea, and a way to control floods. Empoldering involves the use of a polder, a piece of land in a low-lying area that has been reclaimed from a body of water by building dikes and drainage canals.
Although empoldering is usually carried out in low-lying coastal areas, it can also be dome in inland areas such as lakes and rivers. It is common in countries like the Netherlands, where much of the country is below sea level and subject to flooding. About one-fifth of the land in the Netherlands has been reclaimed from the sea. Their largest and most successful project is the Zuider Zee project.
Polders have two distinct features. Firstly, they are enclosed by dikes to keep the water out. The dikes also serve to protect the polder from erosion. Secondly, polders are continually maintained by systems of drainage canals and pumps which prevent them from becoming waterlogged and hence, suitable for cultivation.
Stage 1: Dike constructed around the area to be reclaimed to keep water from coming in.
Stage 2: The area is drained using pumps and drainage canals.
Stage 3: "Reeds" (a type of salt tolerant plant) are sown by aircraft to help the soil form.
Stage 4: After 3 years, reeds are burnt and the ash is used as fertilizers for the soil.
Stage 5: After a period of up to 15 years, the polder is ready for growing crops, building houses and constructing roads.
1. Cost of reclaiming from deeper waters
2. Availability of sand
3. Dispute over territorial boundaries
A resistor limits the electric current that flows through a circuit. Resistance is the restriction of current. In a resistor the energy of the electrons that pass through the resistor are changed to heat and/or light. For example, in a light bulb, the tungsten filament acts as a resistor that heats up because of the current going through it, causing it to glow.
Resistors can be linked in various combinations to help make a circuit:
There are many different types of resistors. Resistors have different power ratings to tell engineers how much power they can handle before they break and how accurate their value is. Connecting two resistors in series results in a higher resistance, and connecting them in parallel makes a lower resistance.
Nowadays the electrical industry in many cases uses so called surface-mount technology based resistors which can be very small.
Where R is the resistor's value
The formula for Ohm’s law, V=I*R, states that the voltage drop across a component is equal to the product of the current flowing in the component multiplied by the resistance of the component. When using Ohm’s law, you are able to switch the formula around if needed to find a different outcome: I=V/R or R=V/I
Resistor's values are rated by the colors that are painted on the resistor. The colored bands that are used on the sides of a resistor are black, brown, red, orange, yellow, green, blue, purple, gray, and white. Each color represents a different number. The black band represents the number 0, brown band represents the number 1, red is 2 and so on all the way to white which is the number 9. These numbers are very important in the electronic field.
A resistor has multiple bands of color on its side. The most common have four or five but they can range all the way up to 6 per resistor. On a four band resistor, the last band is usually gold or silver. The gold band represents a positive or negative 5% tolerance. The silver band on a resistor represents a positive or negative 10% tolerance. Hold this band on the right side, and read the colors from left to right. The first two bands are read as the numbers that they represent in the color code. The third band acts as a multiplier for the other bands, so for example, if the third band was an orange band which is a 3, it would mean you multiply the two numbers by 1000. In short you add the value of the color in zeros at the end, so add three zeros.
Online calculators are available to calculate color codes. When the color codes are put into the calculator, it will automatically calculate the value of the resistor, along with the tolerance.
Resistors are used in many different ways. First of all, they are put in circuits to protect components from damage such as LEDs.
They also control the amount of current flowing in a circuit, for example, if you want less current to flow you would put in a resistor with a higher value. Resistors can also split voltage between different parts of a circuit and control time delay.
Electric heaters use very large resistors to turn electricity into heat. Usually, engineers try to make resistors heat up as little as possible to not waste power, but in a heater, this "waste" is a good thing. You can also use resistors for soldering electronics.
There are many different types of resistors you can find. They are all made with a resistive material encased in a non-conductive material, such as plastic. Fixed resistors are usually made of carbon encased in a plastic cylinder, with a connecting wire on either end. Most resistors used in electronics today are carbon resistors. Older resistors were made of other poorly conducting metals, in order to restrict the flow of charge.
The Death Star is a fictional moon-sized space station and superweapon. It was invented for the "Star Wars" movies. It was a huge spherical space station which fired a ray of energy which could destroy a planet.
The details of the Death Star changed between different models during production of "". These changes include the position of the superlaser. The idea of the Death Star as a large, spherical space station was the same in all the models. The sound of the Death Star counting down until it fires comes from the "Flash Gordon" movies. Making a Death Star that was only partly built (but was still powerful) was a problem for Industrial Light & Magic's modelmakers for "". Only the front side of the 137-centimeter model was finished. The image was flipped horizontally for the final movie. Both Death Stars were created in the movies by using a full models, models of sections of the space station and matte paintings.
The first Death Star was shown in its finished form in "". It was commanded by Grand Moff Tarkin (Peter Cushing). The Death Star was the Galactic Empire's "ultimate weapon". The movie begins with Leia Organa (Carrie Fisher) attempting to take the station's plans to the Rebel Alliance, wanting to help them destroy the Death Star. Onboard her vessel, she was captured by an imperial ship and taken captive to the Death Star. There, Tarkin tries to make Leia reveal the location of the rebel base by threatening the use of the Death Star to destroy Leia's home world, Alderaan. She tells them a location but not the real one, but Tarkin has her planet destroyed anyway. Later, Luke Skywalker (Mark Hamill) and his small crew are also captured and taken to the station, escaping with Leia shortly after. In the movie's main battle scene, the force ghost of Obi-wan Kenobi tells Luke to use the "Force" to help him direct proton torpedoes from his x-wing into the Death Star' reactor core and not with his ship's targeting system. Luke obeys and successfully launches the torpedoes into the core. This ultimately resulted in the destruction of the battle station.
"Return of the Jedi" takes place four years later. At this time, the Empire is building a new Death Star. It is half-finished in the movie. Emperor Palpatine (Ian McDiarmid) and Darth Vader (David Prowse/James Earl Jones) send the Rebels false information with the intention of trapping the Rebels, saying that the station's weapons systems are not fully functional. They also want to get Skywalker on board so they can turn him to the dark side of the Force. In the movie's climax, Vader throws Palpatine down one of the station's reactor core, apparantly killing him. However, Palpatine fires a large amount of sith lightning during this process and critically damages the electronics on Vader's suit that keeps him alive. Luke tries to get his father out of the battle station but he dies shortly after. Luke then takes Vader's body and leaves the Death Star just before it is destroyed by Lando Calrissian onboard the "Millennium Falcon."
The first Death Star is also dealt with in the "Star Wars" prequel trilogy. Its schematics are shown in "". At the end of "", the Death Star is shown starting to be built.
Doctor of Philosophy
The Doctor of Philosophy, (PhD, Ph.D., DPhil or D.Phil.) is a degree a person gets from a university by finishing a doctorate program. In many areas of study, the PhD/DPhil is the highest degree that a person can earn (this is called the "terminal degree"). There are PhD/DPhil degrees for many different fields, such as PhDs/DPhils in literature, philosophy, history, science, mathematics, and engineering. Some PhD/DPhil degrees have existed for hundreds of years, such as the PhD/DPhil in Canon Law. Other PhD/DPhil degrees were developed in the 1970s and 1980s, such as the PhD/DPhil in Computer Science.
To be admitted to a PhD/DPhil program, a person usually has to have completed their Bachelor's degree or master's degree that is related to the PhD/DPhil degree. For example, a person applying to be admitted to a PhD/DPhil degree in Theater would normally have to have a master's degree such as a Master of Arts (MA) degree in Theater, English Literature, or a related area.
The PhD/DPhil degree usually takes between three and six years of full-time study to complete. They may or may not require a master's degree beforehand. Many PhD/DPhil degrees begin with a period of graduate courses. After the PhD/DPhil student has taken these courses, they take examinations to test what the student knows about their area of study. After the student passes the exams, they begin to do original research. The product is a long research report called a dissertation (or a "thesis"). Some PhD/DPhil degrees also require students to pass exams in languages (such as French, German, or other languages). Many PhD/DPhil students teach undergraduate students or assist professors with research during their PhD/DPhil studies.
Requirements for university teaching vary in different subjects and in different countries. A PhD/DPhil is necessary or usual to become a university professor in many fields, especially in science. However, many famous professors have not had higher degrees, though that is less common today. In some fields, there is no PhD/DPhil, and so another degree is required to become a university professor. For example, the highest degree in Fine Arts fields such as printmaking or graphic design is the Master of Fine Arts (MFA) degree. A person with an MFA degree can become a university professor in some Fine Arts fields.
Global 200
The Global 200 is the list of ecoregions identified by the World Wide Fund for Nature (WWF) as priorities for conservation. According to the WWF, an ecoregion is defined as a "relatively large unit of land or water containing a characteristic set of natural communities that share a large majority of their species, dynamics, and environmental conditions (Dinerstein et al. 1995, TNC 1997)."
The WWF assigns a conservation status to each ecoregion in the Global 200: critical or endangered; vulnerable; and relatively stable or intact. Over half of the ecoregions in the Global 200 are rated endangered.
Ecoregion