Poland
Poland the Republic of Poland, is a country located in Central Europe. It is divided into 16 administrative subdivisions, covering an area of 312,696 square kilometres, has a temperate seasonal climate. With a population of 38.5 million people, Poland is the sixth most populous member state of the European Union. Poland's capital and largest metropolis is Warsaw. Other major cities include Kraków, Łódź, Wrocław, Poznań, Gdańsk, Szczecin. Poland is bordered by the Baltic Sea, Russia's Kaliningrad Oblast and Lithuania to the north and Ukraine to the east and Czech Republic, to the south, Germany to the west; the establishment of the Polish state can be traced back to AD 966, when Mieszko I, ruler of the realm coextensive with the territory of present-day Poland, converted to Christianity. The Kingdom of Poland was founded in 1025, in 1569 it cemented its longstanding political association with the Grand Duchy of Lithuania by signing the Union of Lublin; this union formed the Polish–Lithuanian Commonwealth, one of the largest and most populous countries of 16th and 17th century Europe, with a uniquely liberal political system which adopted Europe's first written national constitution, the Constitution of 3 May 1791.
More than a century after the Partitions of Poland at the end of the 18th century, Poland regained its independence in 1918 with the Treaty of Versailles. In September 1939, World War II started with the invasion of Poland by Germany, followed by the Soviet Union invading Poland in accordance with the Molotov–Ribbentrop Pact. More than six million Polish citizens, including 90% of the country's Jews, perished in the war. In 1947, the Polish People's Republic was established as a satellite state under Soviet influence. In the aftermath of the Revolutions of 1989, most notably through the emergence of the Solidarity movement, Poland reestablished itself as a presidential democratic republic. Poland is regional power, it has the fifth largest economy by GDP in the European Union and one of the most dynamic economies in the world achieving a high rank on the Human Development Index. Additionally, the Polish Stock Exchange in Warsaw is the largest and most important in Central Europe. Poland is a developed country, which maintains a high-income economy along with high standards of living, life quality, safety and economic freedom.
Having a developed school educational system, the country provides free university education, state-funded social security, a universal health care system for all citizens. Poland has 15 UNESCO World Heritage Sites. Poland is a member state of the European Union, the Schengen Area, the United Nations, NATO, the OECD, the Three Seas Initiative, the Visegrád Group; the origin of the name "Poland" derives from the West Slavic tribe of Polans that inhabited the Warta river basin of the historic Greater Poland region starting in the 6th century. The origin of the name "Polanie" itself derives from the early Slavic word "pole". In some languages, such as Hungarian, Lithuanian and Turkish, the exonym for Poland is Lechites, which derives from the name of a semi-legendary ruler of Polans, Lech I. Early Bronze Age in Poland begun around 2400 BC, while the Iron Age commenced in 750 BC. During this time, the Lusatian culture, spanning both the Bronze and Iron Ages, became prominent; the most famous archaeological find from the prehistory and protohistory of Poland is the Biskupin fortified settlement, dating from the Lusatian culture of the early Iron Age, around 700 BC.
Throughout the Antiquity period, many distinct ancient ethnic groups populated the regions of what is now Poland in an era that dates from about 400 BC to 500 AD. These groups are identified as Celtic, Slavic and Germanic tribes. Recent archeological findings in the Kujawy region, confirmed the presence of the Roman Legions on the territory of Poland; these were most expeditionary missions sent out to protect the amber trade. The exact time and routes of the original migration and settlement of Slavic peoples lacks written records and can only be defined as fragmented; the Slavic tribes who would form Poland migrated to these areas in the second half of the 5th century AD. Up until the creation of Mieszko's state and his subsequent conversion to Christianity in 966 AD, the main religion of Slavic tribes that inhabited the geographical area of present-day Poland was Slavic paganism. With the Baptism of Poland the Polish rulers accepted Christianity and the religious authority of the Roman Church.
However, the transition from paganism was not a smooth and instantaneous process for the rest of the population as evident from the pagan reaction of the 1030s. Poland began to form into a recognizable unitary and territorial entity around the middle of the 10th century under the Piast dynasty. Poland's first documented ruler, Mieszko I, accepted Christianity with the Baptism of Poland in 966, as the new official religion of his subjects; the bulk of the population converted in the course of the next few centuries. In 1000, Boleslaw the Brave, continuing the policy of his father Mieszko, held a Congress of Gniezno and created the metropolis of Gniezno and the dioceses of Kraków, Kołobrzeg, Wrocław. However, the pagan unrest led to the transfer of the capital to Kraków in 1038 by Casimir I the Restorer. In 1109, Prince Bolesław III Wrymouth defeated the King of Germany Henry V at the Battle of Hundsfeld, stopping the Ge
Electromagnetic radiation
In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space, carrying electromagnetic radiant energy. It includes radio waves, infrared, ultraviolet, X-rays, gamma rays. Classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light, which, in a vacuum, is denoted c. In homogeneous, isotropic media, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave; the wavefront of electromagnetic waves emitted from a point source is a sphere. The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves of different frequency are called by different names since they have different sources and effects on matter. In order of increasing frequency and decreasing wavelength these are: radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
Electromagnetic waves are emitted by electrically charged particles undergoing acceleration, these waves can subsequently interact with other charged particles, exerting force on them. EM waves carry energy and angular momentum away from their source particle and can impart those quantities to matter with which they interact. Electromagnetic radiation is associated with those EM waves that are free to propagate themselves without the continuing influence of the moving charges that produced them, because they have achieved sufficient distance from those charges. Thus, EMR is sometimes referred to as the far field. In this language, the near field refers to EM fields near the charges and current that directly produced them electromagnetic induction and electrostatic induction phenomena. In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
Quantum electrodynamics is the theory of. Quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation; the energy of an individual photon is greater for photons of higher frequency. This relationship is given by Planck's equation E = hν, where E is the energy per photon, ν is the frequency of the photon, h is Planck's constant. A single gamma ray photon, for example, might carry ~100,000 times the energy of a single photon of visible light; the effects of EMR upon chemical compounds and biological organisms depend both upon the radiation's power and its frequency. EMR of visible or lower frequencies is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules or break chemical bonds; the effects of these radiations on chemical systems and living tissue are caused by heating effects from the combined energy transfer of many photons. In contrast, high frequency ultraviolet, X-rays and gamma rays are called ionizing radiation, since individual photons of such high frequency have enough energy to ionize molecules or break chemical bonds.
These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating, can be a health hazard. James Clerk Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry; because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave. Maxwell's equations were confirmed by Heinrich Hertz through experiments with radio waves. According to Maxwell's equations, a spatially varying electric field is always associated with a magnetic field that changes over time. A spatially varying magnetic field is associated with specific changes over time in the electric field. In an electromagnetic wave, the changes in the electric field are always accompanied by a wave in the magnetic field in one direction, vice versa; this relationship between the two occurs without either type of field causing the other.
In fact, magnetic fields can be viewed as electric fields in another frame of reference, electric fields can be viewed as magnetic fields in another frame of reference, but they have equal significance as physics is the same in all frames of reference, so the close relationship between space and time changes here is more than an analogy. Together, these fields form a propagating electromagnetic wave, which moves out into space and need never again interact with the source; the distant EM field formed in this way by the acceleration of a charge carries energy with it that "radiates" away through space, hence the term. Maxwell's equations established that some charges and currents produce a local type of electromagnetic field near them that does not have the behaviour of EMR. Currents directly produce a magnetic field, but it is of a magnetic dipole type that dies out with distance from the current. In a similar manner, moving charges pushed apart in a conductor by a changing electrical potential produce an electric dipole type electric
Quantum dot
Quantum dots are tiny semiconductor particles a few nanometres in size, having optical and electronic properties that differ from larger LED particles. They are a central theme in nanotechnology; when the quantum dots are illuminated by UV light, some of the electrons receive enough energy to break free from the atoms. This capability allows them to move around the nanoparticle, creating a conductance band in which electrons are free to move through a material and conduct electricity; when these electrons drop back into the outer orbit around the atom, as illustrated in the following figure, they emit light. The color of that light depends on the energy difference between the conductance band and the valence band. In the language of materials science, nanoscale semiconductor materials confine either electrons or electron holes. Quantum dots are sometimes referred to as artificial atoms, emphasizing their singularity, having bound, discrete electronic states, like occurring atoms or molecules.
Quantum dots have properties intermediate between bulk semiconductors and discrete atoms or molecules. Their optoelectronic properties change as a function of both shape. Larger QDs of 5–6 nm diameter emit longer wavelengths, with colors such as orange or red. Smaller QDs emit shorter wavelengths, yielding colors like blue and green, although the specific colors and sizes vary depending on the exact composition of the QD; because of their tunable properties, QDs are of wide interest. Potential applications include transistors, solar cells, LEDs, diode lasers and second-harmonic generation, quantum computing, medical imaging, their small size allows for QDs to be suspended in solution, which may lead to use in inkjet printing and spin-coating. They have been used in Langmuir-Blodgett thin-films; these processing techniques result in less expensive and less time-consuming methods of semiconductor fabrication. There are several ways to prepare the principal ones involving colloids. Colloidal semiconductor nanocrystals are synthesized from solutions, much like traditional chemical processes.
The main difference remains dissolved. Heating the solution at high temperature, the precursors decompose forming monomers which nucleate and generate nanocrystals. Temperature is a critical factor in determining optimal conditions for the nanocrystal growth, it must be high enough to allow for rearrangement and annealing of atoms during the synthesis process while being low enough to promote crystal growth. The concentration of monomers is another critical factor that has to be stringently controlled during nanocrystal growth; the growth process of nanocrystals can occur in two different regimes, "focusing" and "defocusing". At high monomer concentrations, the critical size is small, resulting in growth of nearly all particles. In this regime, smaller particles grow faster than large ones resulting in "focusing" of the size distribution to yield nearly monodisperse particles; the size focusing is optimal when the monomer concentration is kept such that the average nanocrystal size present is always larger than the critical size.
Over time, the monomer concentration diminishes, the critical size becomes larger than the average size present, the distribution "defocuses". There are colloidal methods to produce many different semiconductors. Typical dots are made of binary compounds such as lead sulfide, lead selenide, cadmium selenide, cadmium sulfide, cadmium telluride, indium arsenide, indium phosphide. Dots may be made from ternary compounds such as cadmium selenide sulfide; these quantum dots can contain as few as 100 to 100,000 atoms within the quantum dot volume, with a diameter of ≈10 to 50 atoms. This corresponds to about 2 to 10 nanometers, at 10 nm in diameter, nearly 3 million quantum dots could be lined up end to end and fit within the width of a human thumb. Large batches of quantum dots may be synthesized via colloidal synthesis. Due to this scalability and the convenience of benchtop conditions, colloidal synthetic methods are promising for commercial applications, it is acknowledged to be the least toxic of all the different forms of synthesis.
Plasma synthesis has evolved to be one of the most popular gas-phase approaches for the production of quantum dots those with covalent bonds. For example and germanium quantum dots have been synthesized by using nonthermal plasma; the size, shape and composition of quantum dots can all be controlled in nonthermal plasma. Doping that seems quite challenging for quantum dots has been realized in plasma synthesis. Quantum dots synthesized by plasma are in the form of powder, for which surface modification may be carried out; this can lead to excellent dispersion of quantum dots in either organic solvents or water. Self-assembled quantum dots are between 5 and 50 nm in size. Quantum dots defined by lithographically patterned gate electrodes, or by etching on two-dimensional electron gasses in semiconductor heterostructures can have lateral dimensions between 20 and 100 nm; some quantum dots are small regions of one material buried in another with a larger band gap. These can be so-called core–shell structures, e.g. with CdSe in the core and ZnS in the shell, or from special forms of silica called ormosil.
Sub-monolayer shells can be effective ways of passivating the quantum dots, such as PbS cores with sub-monolayer CdS shells. Quantum dots sometimes occur spontaneously in quantum well structures due to monolayer fluctuations in the well's thickness. Self-asse
Violet (color)
Violet is the color at the end of the visible spectrum of light between blue and the invisible ultraviolet. Violet color has a dominant wavelength of 380-450 nanometers. Light with a shorter wavelength than violet but longer than X-rays and gamma rays is called ultraviolet. In the color wheel used by painters, it is located between blue and purple. On the screens of computer monitors and television sets, a color which looks similar to violet is made, with the RGB color model, by mixing red and blue light, with the blue twice as bright as the red; this is not true violet, for it does not match the color of a single wavelength shorter than that of blue light. The color's name is derived from the violet flower. Violet and purple look similar, but violet is a spectral color, with its own set of wavelengths on the spectrum of visible light. Purple is a dichromatic color, made by combining red. Amethyst is a notable violet crystal, its colour arising from iron and other trace elements in quartz. In history and purple have long been associated with royalty and majesty.
The emperors of Rome wore purple togas. During the Middle Ages violet was worn by bishops and university professors and was used in art as the color of the robes of the Virgin Mary. In Chinese painting, the color violet represents the harmony of the universe because it is a combination of red and blue. In Hinduism and Buddhism violet is associated with the Crown Chakra. According to surveys in Europe and the United States, violet is the color people most associate with extravagance and individualism, the unconventional, the artificial, ambiguity. From the Middle English and old French violette, from the Latin viola, the names of the violet flower; the first recorded use of violet as a color name in English was in 1370. Violet can refer to the first violas which were painted a similar color. In the traditional color wheel used by painters and purple are both placed between red and blue. Purple occupies between crimson and violet. Violet is closer to blue, less intense and bright than purple. From the point of view of optics, violet is a real color: it occupies its own place at the end of the visible spectrum, was one of the seven spectral colors of the spectrum first described by Isaac Newton in 1672.
In the additive color system, used to create colors on a computer screen or on a color television, violet is simulated by purple, by combining blue light at high intensity with a less intense red light on a black screen. The range of purples is created by combining red light of any intensities. Violet is one of the oldest colors used by man. Traces of dark violet, made by grinding the mineral manganese, mixed with water or animal fat and brushed on the cave wall or applied with the fingers, are found in the prehistoric cave art in Pech Merle, in France, dating back about twenty-five thousand years, it has been found in the cave of Altamira and Lascaux. It was sometimes used as an alternative to black charcoal. Sticks of manganese, used for drawing, have been found at sites occupied by Neanderthal man in France and Israel. From the grinding tools at various sites, it appears it may have been used to color the body and to decorate animal skins. More the earliest dates on cave paintings have been pushed back farther than 35,000 years.
Hand paintings on rock walls in Australia may be older, dating back as far as 50,000 years. Berries of the genus rubus, such as blackberries, were a common source of dyes in antiquity; the ancient Egyptians made a kind of violet dye by combining the juice of the mulberry with crushed green grapes. The Roman historian Pliny the Elder reported that the Gauls used a violet dye made from bilberry to color the clothing of slaves; these dyes made a satisfactory purple, but it faded in sunlight and when washed. Violet and purple retained their status as the color of emperors and princes of the church throughout the long rule of the Byzantine Empire. While violet was worn less by Medieval and Renaissance kings and princes, it was worn by the professors of many of Europe's new universities, their robes were modeled after those of the clergy, they wore square violet caps and violet robes, or black robes with violet trim. Violet played an important part in the religious paintings of the Renaissance. Angels and the Virgin Mary were portrayed wearing violet robes.
The 15th-century Florentine painter Cennino Cennini advised artists: "If you want to make a lovely violet colour, take fine lacca, ultramarine blue..." For fresco painters, he advised a less-expensive version, made of a mixture of blue indigo and red hematite. In the 18th century, violet was a color worn by royalty and the wealthy, by both men and women. Good-quality violet fabric was expensive, beyond the reach of ordinary people. Many painters of the 19th century experimented with the uses of the color violet to capture the subtle effects of light. Eugène Delacroix made use of violet in the sky and shadows of many of his works, such as his painting of a tiger; the first cobalt violet, the intensely red-violet cobalt arsenate, was toxic. Although it persisted in some paint lines into the twentieth-century, it was displaced by less toxic cobalt compounds such as cobalt phosphate. Cobalt violet appeared in the second half of the 19th century. Cobalt violet was used by Paul Signac, Claude Monet, Georges Seurat.
Today, cobalt ammonium phosphate, cobalt lithium phosp
Homestar Runner
Homestar Runner is a Flash-animated surreal comedy web series created by Mike and Matt Chapman known as The Brothers Chaps. It mixes surreal humor, self-parody, references to 1970s, 1980s, 1990s, early 2000s pop culture, in particular video games, classic television, popular music. While the site centered on the title character, Homestar Runner, the Strong Bad Email cartoon skits became the site's most popular and prominent feature, with Strong Bad becoming a breakout character. Since 2000, the site has grown to encompass a variety of cartoons and web games featuring Homestar, Strong Bad, numerous other characters. At the peak of its popularity, the site was one of the most-visited sites with collections of Flash cartoons on the web, spreading via word of mouth; the site has never featured advertisements. The Brothers Chaps have turned down offers to make a television series. After a four-year hiatus beginning in 2010, Homestar Runner returned with a new Holiday Toon on April 1, 2014, for April Fools' Day.
Afterwards, co-creator Matt Chapman announced plans to give the site semi-regular updates starting in fall 2014, due to the positive reception given to the April Fools' Day cartoon. More cartoons have since been released on the website on an occasional basis to celebrate holidays. Homestar Runner was created in Atlanta in 1996 by University of Georgia student Mike Chapman and friend Craig Zobel, who wrote the original picture book, The Homestar Runner Enters the Strongest Man in the World Contest while working summer jobs surrounding the 1996 Summer Olympics. Matt described the origin of the name "Homestar Runner" as a in-joke between themselves and James Huggins, a childhood friend of the Chapman brothers while growing up in Dunwoody, Georgia, it comes from a friend of ours. There was an old local grocery store commercial, we live in Atlanta, it advertised the Atlanta Braves, it was like, "the Atlanta Braves hit home runs, you can hit a home run with savings here!" And so there was this player named Mark Lemke, they said something like "All star second baseman for the Braves."
And our friend knows nothing about sports, so he would always do his old-timey radio impression of this guy, not knowing any positions in baseball or whatever, he would just be like, "homestar runner for the Braves." And we were just like, "Homestar Runner? That's the best thing we've heard!" The idea to use "Homestar Runner" for a children's book came while Mike and Craig were in a bookstore, commented on how "terrible" the children's books were, prompting the idea to create their own. They spent around two hours designing the look of Homestar Runner, Pom Pom, Strong Bad, the Cheat, completed the book within a day, they only printed about five to ten copies to share with friends, had no intention to publish it. However, they were unaware that their father had sent out the book as a manuscript for submission to about 80 different publishers, but they only got rejection letters back, if anything, they used the Super NES video game Mario Paint to create the first cartoon featuring the characters.
Around 1999, Mike recognized how popular Flash animation was taking off, he and his younger brother Matt Chapman started to learn Flash on their own. Looking for something on which to practice, they found inspiration in the old children's book, their initial cartoons were launched on their dedicated website, homestarrunner.com, by 2000. Mike animated the cartoons, Matt provided the voices of the male characters, Mike's girlfriend Missy Palmer provided the voice of Marzipan, they aimed to create the animations to resemble Dexter's Laboratory and The Powerpuff Girls, started off with shorts that featured competitions between Homestar Runner as a heroic character and Strong Bad as the villain, but these did not capture viewers. Mike and Matt came up with the idea of animating the scenes between competitions. From May 2000 to February 2001, the website and cartoons started out with different art styles. In February 2001, it gained a new look, which has remained consistent to the present with minor changes.
The site grew at first, through word-of-mouth. They were able to sell a "few dozen" T-shirts by 2001. Mike moved back to New York in mid-2001 and he and Matt started crafting the first Strong Bad Email some kinda robot, intending this to be a weekly feature; the Strong Bad Email series proved popular, generating significant interest in the site. Their father suggested Matt quit his full-time job to devote time to creating more Homestar Runner shorts. With the number of visitors to the site growing, by January 2003 the site had outgrown its original web host, Yahoo!. Merchandise sales paid for all of the costs of running the website as well as living costs of the creators, whose retired parents managed many of the business aspects; the brothers considered the period between 2002–2005 to be their most creative and successful, exploring various different media for the shorts, having a large quantity of merchandise. Matt considered a day in February 2004 to be the highlight of the series, having received a demo tape from They Might Be Giants for a song to use in a Strong Bad Email short, a life-size replica of Tom Servo from Mys
Gallium nitride
Gallium nitride is a binary III/V direct bandgap semiconductor used in light-emitting diodes since the 1990s. The compound is a hard material that has a Wurtzite crystal structure, its wide band gap of 3.4 eV affords it special properties for applications in optoelectronic, high-power and high-frequency devices. For example, GaN is the substrate which makes violet laser diodes possible, without use of nonlinear optical frequency-doubling, its sensitivity to ionizing radiation is low, making it a suitable material for solar cell arrays for satellites. Military and space applications could benefit as devices have shown stability in radiation environments; because GaN transistors can operate at much higher temperatures and work at much higher voltages than gallium arsenide transistors, they make ideal power amplifiers at microwave frequencies. In addition, GaN offers promising characteristics for THz devices. GaN is a hard, mechanically stable wide bandgap semiconductor material with high heat capacity and thermal conductivity.
In its pure form it resists cracking and can be deposited in thin film on sapphire or silicon carbide, despite the mismatch in their lattice constants. GaN can be doped with oxygen to n-type and with magnesium to p-type. However, the Si and Mg atoms change the way the GaN crystals grow, introducing tensile stresses and making them brittle. Gallium nitride compounds tend to have a high dislocation density, on the order of 108 to 1010 defects per square centimeter; the wide band-gap behavior of GaN is connected to specific changes in the electronic band structure, charge occupation and chemical bond regions. GaN with a high crystalline quality can be obtained by depositing a buffer layer at low temperatures; such high-quality GaN led to the discovery of p-type GaN, p-n junction blue/UV-LEDs and room-temperature stimulated emission. This has led to the commercialization of high-performance blue LEDs and long-lifetime violet-laser diodes, to the development of nitride-based devices such as UV detectors and high-speed field-effect transistors.
High-brightness GaN light-emitting diodes completed the range of primary colors, made applications such as daylight visible full-color LED displays, white LEDs and blue laser devices possible. The first GaN-based high-brightness LEDs used a thin film of GaN deposited via Metal-Organic Vapour Phase Epitaxy on sapphire. Other substrates used are zinc oxide, with lattice constant mismatch of silicon carbide. Group III nitride semiconductors are, in general, recognized as one of the most promising semiconductor families for fabricating optical devices in the visible short-wavelength and UV region; the high breakdown voltages, high electron mobility and saturation velocity of GaN has made it an ideal candidate for high-power and high-temperature microwave applications, as evidenced by its high Johnson's figure of merit. Potential markets for high-power/high-frequency devices based on GaN include microwave radio-frequency power amplifiers and high-voltage switching devices for power grids. A potential mass-market application for GaN-based RF transistors is as the microwave source for microwave ovens, replacing the magnetrons used.
The large band gap means that the performance of GaN transistors is maintained up to higher temperatures than silicon transistors because it lessens the effects of thermal generation of charge carriers that are inherent to any semiconductor. The first gallium nitride metal semiconductor field-effect transistors were experimentally demonstrated in 1993 and they are being developed. In 2010 the first enhancement-mode GaN transistors became available. Only n-channel transistors were available; these devices were designed to replace power MOSFETs in applications where switching speed or power conversion efficiency is critical. These transistors called eGaN FETs, are built by growing a thin layer of GaN on top of a standard silicon wafer; this allows the eGaN FETs to maintain costs similar to silicon power MOSFETs but with the superior electrical performance of GaN. GaN-based violet laser diodes are used to read Blu-ray Discs; the mixture of GaN with In or Al with a band gap dependent on ratio of In or Al to GaN allows the manufacture of light-emitting diodes with colors that can go from red to ultra-violet.
GaN transistors are suitable for high frequency, high voltage, high temperature and high efficiency applications. GaN HEMTs have been offered commercially since 2006, have found immediate use in various wireless infrastructure applications due to their high efficiency and high voltage operation. A second generation of devices with shorter gate lengths will address higher frequency telecom and aerospace applications. GaN based MOSFET and MESFET transistors offer advantages including lower loss in high power electronics in automotive and electric car applications. Since 2008 these can be formed on a silicon substrate. High-voltage Schottky barrier diodes have been made, they are utilized in military electronics such as active electronically scanned array radars. GaN-based electronics has the potential to drastically cut energy consumption, not only in consumer applications but for power transmission utilities. Unlike silicon transistors which switch off due to power surges, GaN transistors are depletion mode devices.
Several methods have been proposed to reach normally-off operation, necessary for use in power elect
Blue
Blue is one of the three primary colours of pigments in painting and traditional colour theory, as well as in the RGB colour model. It lies between green on the spectrum of visible light; the eye perceives blue when observing light with a dominant wavelength between 450 and 495 nanometres. Most blues contain a slight mixture of other colours; the clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called. Distant objects appear. Blue has been an important colour in decoration since ancient times; the semi-precious stone lapis lazuli was used in ancient Egypt for jewellery and ornament and in the Renaissance, to make the pigment ultramarine, the most expensive of all pigments. In the eighth century Chinese artists used cobalt blue to white porcelain. In the Middle Ages, European artists used it in the windows of Cathedrals. Europeans wore clothing coloured with the vegetable dye woad until it was replaced by the finer indigo from America.
In the 19th century, synthetic blue dyes and pigments replaced mineral pigments and synthetic dyes. Dark blue became a common colour for military uniforms and in the late 20th century, for business suits; because blue has been associated with harmony, it was chosen as the colour of the flags of the United Nations and the European Union. Surveys in the US and Europe show that blue is the colour most associated with harmony, confidence, infinity, the imagination and sometimes with sadness. In US and European public opinion polls it is the most popular colour, chosen by half of both men and women as their favourite colour; the same surveys showed that blue was the colour most associated with the masculine, just ahead of black, was the colour most associated with intelligence, knowledge and concentration. Blue is the colour of light between green on the visible spectrum. Hues of blue include ultramarine, closer to violet. Blue varies in shade or tint. Darker shades of blue include ultramarine, cobalt blue, navy blue, Prussian blue.
Blue pigments were made from minerals such as lapis lazuli and azurite, blue dyes were made from plants. Today most blue dyes are made by a chemical process; the modern English word blue comes from Middle English bleu or blewe, from the Old French bleu, a word of Germanic origin, related to the Old High German word blao. In heraldry, the word azure is used for blue. In Russian and some other languages, there is no single word for blue, but rather different words for light blue and dark blue. See Colour term. Several languages, including Japanese, Thai and Lakota Sioux, use the same word to describe blue and green. For example, in Vietnamese the colour of both tree leaves and the sky is xanh. In Japanese, the word for blue is used for colours that English speakers would refer to as green, such as the colour of a traffic signal meaning "go". Linguistic research indicates. Colour names developed individually in natural languages beginning with black and white, adding red, only much – as the last main category of colour accepted in a language – adding the colour blue when blue pigments could be manufactured reliably in the culture using that language.
Human eyes perceive blue when observing light which has a dominant wavelength of 450–495 nanometres. Blues with a higher frequency and thus a shorter wavelength look more violet, while those with a lower frequency and a longer wavelength appear more green. Pure blue, in the middle, has a wavelength of 470 nanometres. Isaac Newton included blue as one of the seven colours in his first description the visible spectrum, He chose seven colours because, the number of notes in the musical scale, which he believed was related to the optical spectrum, he included indigo, the hue between blue and violet, as one of the separate colours, though today it is considered a hue of blue. In painting and traditional colour theory, blue is one of the three primary colours of pigments, which can be mixed to form a wide gamut of colours. Red and blue mixed together form violet and yellow together form green. Mixing all three primary colours together produces a dark grey. From the Renaissance onwards, painters used this system to create their colours.
The RYB model was used for colour printing by Jacob Christoph Le Blon as early as 1725. Printers discovered that more accurate colours could be created by using combinations of magenta, cyan and black ink, put onto separate inked plates and overlaid one at a time onto paper; this method could produce all the colours in the spectrum with reasonable accuracy. In the 19th century the Scottish physicist James Clerk Maxwell found a new way of explaining colours, by the wa
