Saturday, January 22, 2011
Graphene
Electronics researchers love graphene. A two-dimensional sheet of carbon one atom thick, graphene is like a superhighway for electrons, which rocket through the material with 100 times the mobility they have in silicon. But creating graphene-based devices will be challenging, say researchers at the National Institute of Standards and Technology, because new measurements show that layering graphene on a substrate transforms its bustling speedway into steep hills and valleys that make it harder for electrons to get around.
Monday, January 17, 2011
Eddy current
Eddy currents (also called Foucault currents) are currents induced in conductors, opposing the change in flux that generated them. It is caused when a conductor is exposed to a changing magnetic field due to relative motion of the field source and conductor; or due to variations of the field with time. This can cause a circulating flow of electrons, or a current, within the body of the conductor. These circulating eddies of current create induced magnetic fields that oppose the change of the original magnetic field due to Lenz's law, causing repulsive or drag forces between the conductor and the magnet. The stronger the applied magnetic field, or the greater the electrical conductivity of the conductor, or the faster the field that the conductor is exposed to changes, then the greater the currents that are developed and the greater the opposing field.
The term eddy current comes from analogous currents seen in water when dragging an oar breadthwise: localised areas of turbulence known as eddies give rise to persistent vortices.
Eddy currents, like all electric currents, generate heat as well as electromagnetic forces. The heat can be harnessed for induction heating. The electromagnetic forces can be used for levitation, creating movement, or to give a strong braking effect. Eddy currents can also have undesirable effects, for instance power loss in transformers. In this application, they are minimised with thin plates, by lamination of conductors or other details of conductor shape.
The term eddy current comes from analogous currents seen in water when dragging an oar breadthwise: localised areas of turbulence known as eddies give rise to persistent vortices.
Eddy currents, like all electric currents, generate heat as well as electromagnetic forces. The heat can be harnessed for induction heating. The electromagnetic forces can be used for levitation, creating movement, or to give a strong braking effect. Eddy currents can also have undesirable effects, for instance power loss in transformers. In this application, they are minimised with thin plates, by lamination of conductors or other details of conductor shape.
Thunderstorms Proven To Create Antimatter
Scientists using NASA's Fermi Gamma-ray Space Telescope have detected beams of antimatter from thunderstorms in the form of positrons hurled into space. Scientists think the antimatter particles were formed in a terrestrial gamma-ray flash, a brief burst produced inside thunderstorms and shown to be associated with lightning. 'These signals are the first direct evidence that thunderstorms make antimatter particle beams,' said Michael Briggs, a member of Fermi's Gamma-ray Burst Monitor team. He presented the findings at a news briefing at the American Astronomical Society meeting in Seattle.
Thermo mirror
As good looking as we are -- and you know we are -- we sometimes get tired of staring into the mirror. Honestly, aside from reminding us of our resemblance to a young Sean Connery, the standard mirror really doesn't do much, but the Thermo Mirror is another story. The device, designed by Japanese electronics firm NEC/Avio, uses an infrared sensor to measure an onlooker's temperature from up to 30 centimeters (about 1 foot) away, without physical contact. The subject's temperature appears on the mirror's surface, and, if they have a fever, an alarm sounds. Thermo Mirror is available in two versions and costs between 98,000 and 120,000 yen (or $1,180 and $1,440). When not in use, its face displays date, time, humidity, and temperature. Now if it could just make us a martini -- shaken, not stirred, of course.
Carcassonne
Carcassonne is a tile-based German-style board game for two to five players, designed by Klaus-Jürgen Wrede and published in 2000 by Hans im Glück in German and Rio Grande Games in English. It received the Spiel des Jahres and the Deutscher Spiele Preis awards in 2001. It is named after the medieval fortified town of Carcassonne in southern France, famed for its city walls. The game has spawned many expansions and spin-offs, and several PC and console versions. The game's wooden follower pieces, colloquially called "meeples," have become a symbol of European board gaming.
Smith chart
The Smith chart, invented by Phillip H. Smith (1905-1987), is a graphical aid or nomogram designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assist in solving problems with transmission lines and matching circuits.Use of the Smith chart utility has grown steadily over the years and it is still widely used today, not only as a problem solving aid, but as a graphical demonstrator of how many RF parameters behave at one or more frequencies, an alternative to using tabular information. The Smith chart can be used to represent many parameters including impedances, admittances, reflection coefficients,, scattering parameters, noise figure circles, constant gain contours and regions for unconditional stability. The Smith chart is most frequently used at or within the unity radius region. However, the remainder is still mathematically relevant, being used, for example, in oscillator design and stability analysis.
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