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2015001    美国空军关注天空垃圾\\ DOI: 10.1126/science.347.6218.115

An estimated 500,000 pieces of space junk—old satellites, rocket parts, debris from collisions—swarm in orbit around Earth. Much of it is potentially deadly: NASA officials say anything larger than 1 centimeter in diameter poses a threat to the International Space Station. But current tracking systems can generally only watch objects 10 cm or larger, and the U.S. government currently follows less than 5% of space hazards—just 23,000 objects. That should change with the addition of a powerful new Air Force radar system, scheduled to break ground this month on Kwajalein Atoll in the Marshall Islands. When it comes online in 2019, the flood of information passed along to nonmilitary spacecraft operators will bring reassurance—but also some wrenching choices about which hazards to ignore.

( 摘自Air Force turns a keen eye on space junk, www.sciencemag.org, 2015-1-26)

2015002    装置合力助推太阳能发展\\ DOI: 10.1126/science.347.6219.225

The most efficient photovoltaics are devices called tandems that consist of stacks of solar cells, each tailored to absorb a different slice of the solar spectrum. This complexity makes them expensive and thus better suited for use in space where the extra power they produce is worth the added cost. But now, solar cell researchers are looking to create low-cost, high-efficiency tandems using perovskites, the hottest and cheapest new solar cell material out there. It's still early days, and progress on perovskite tandems remains modest. But researchers say the path to highly efficient perovskite tandems is clear and is expected to occur within the next year or two.

( 摘自Devices team up to boost solar power, www.sciencemag.org,
2015-1-26)