Scientists at Rensselaer Polytechnic Institute have found a way to grow aluminum nitride crystals large enough to slice into semiconductor substrates. The crystals can be used to make blue and ultraviolet lasers and light-emitting diodes (LEDs). "Semiconductor light sources have always been very attractive because of their ruggedness and economy," says Leo Schowalter, professor of physics at Rensselaer. "But the color of LEDs has been pretty much limited to red. Green and blue LEDs are also needed if we are to create traffic signals, automobile lighting, flat-screen TV sets, and other applications where long life and high efficiency are important." A Rensselaer researcher, Glen Slack, has demonstrated that you can grow aluminum nitride crystals in a tungsten crucible at 2,300C. However, at that temperature, the aluminum attacks the grain boundaries in the tungsten, and the crucible doesn't survive very long. Schowalter and Slack have now solved the problem and formed a company to make the aluminum nitride crystals. E-mail firstname.lastname@example.org.
Major global metropolitan areas are implementing a vast number of technology, energy, transportation, and Internet projects to make the metropolis a friendlier, greener, safer, and more sustainable place to be.
Here’s a look at robots depicted in movies and on TV during the 1950s and 1960s. We tried to collect the classics here, omitting the scores of forgettable B movies such as Santa Claus Conquers the Martians and Dr. Goldfoot and the Bikini Machine. Stay tuned for slideshows of robot stars from later decades.
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