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Among the challenges being faced to improve the efficiency of LED-based white light sources is the development of more efficient phosphors. As of 2010, the most efficient yellow phosphor is still the YAG phosphor, with less than 10% Stoke shift loss. Losses attributable to internal optical losses due to re-absorption in the LED chip and in the LED packaging itself account typically for another 10% to 30% of efficiency loss. Currently, in the area of phosphor LED development, much effort is being spent on optimizing these devices to higher light output and higher operation temperatures. For instance, the efficiency can be raised by adapting better package design or by using a more suitable type of phosphor. Conformal coating process is frequently used to address the issue of varying phosphor thickness.
What is one method that can lower the efficiency of phosphor-based LEDs?
A: unanswerable

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According to the Sichuan Department of Commerce, the province's total foreign trade was US$22.04 billion in 2008, with an annual increase of 53.3 percent. Exports were US$13.1 billion, an annual increase of 52.3 percent, while imports were US$8.93 billion, an annual increase of 54.7 percent. These achievements were accomplished because of significant changes in China's foreign trade policy, acceleration of the yuan's appreciation, increase of commercial incentives and increase in production costs. The 18 cities and counties witnessed a steady rate of increase. Chengdu, Suining, Nanchong, Dazhou, Ya'an, Abazhou, and Liangshan all saw an increase of more than 40 percent while Leshan, Neijiang, Luzhou, Meishan, Ziyang, and Yibin saw an increase of more than 20 percent. Foreign trade in Zigong, Panzhihua, Guang'an, Bazhong and Ganzi remained constant.
By how much did foreign trade increase in Sichuan in 2008?
A: 53.3 percent

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Due to its very low elevation, the Marshall Islands are threatened by the potential effects of sea level rise. According to the president of Nauru, the Marshall Islands are the most endangered nation in the world due to flooding from climate change.
What feature makes the Marshalls susceptible to harm due to rising sea levels?
A: its very low elevation

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Many of the instruments used to perform medieval music still exist, but in different forms. Medieval instruments included the wood flute (which in the 21st century is made of metal), the recorder and plucked string instruments like the lute. As well, early versions of the organ, fiddle (or vielle), and trombone (called the sackbut) existed. Medieval instruments in Europe had most commonly been used singly, often self accompanied with a drone note, or occasionally in parts. From at least as early as the 13th century through the 15th century there was a division of instruments into haut (loud, shrill, outdoor instruments) and bas (quieter, more intimate instruments).
Medieval instrument in Europe were commonly used how?
A:
singly