《led照明毕业论文中英文资料外文翻译文献(DOC 19页)》由会员分享，可在线阅读，更多相关《led照明毕业论文中英文资料外文翻译文献(DOC 19页)（25页珍藏版）》请在金锄头文库上搜索。
1、led照明毕业论文中英文资料外文翻译文献Renewable and Sustainable Energy ReviewsHigh-brightness LEDsEnergy efficient lighting sources and their potential in indoor plant cultivationABSTRACTThe rapid development of optoelectronic technology since mid-1980 has significantly enhanced the brightness and efficiency of light
2、-emitting diodes (LEDs). LEDs have long been proposed as a primary light source for space-based plant research chamber or bioregenerative life support systems. The raising cost of energy also makes the use of LEDs in commercial crop culture imminent. With their energy efficiency, LEDs have opened ne
3、w perspectives for optimizing the energy conversion and the nutrient supply both on and off Earth. The potentials of LED as an effective light source for indoor agriculturalproduction have been explored to a great extent. There are many researches that use LEDs to support plant growth in controlled
4、environments such as plant tissue culture room and growth chamber. This paper provides a brief development history of LEDs and a broad base review on LED applications in indoor plant cultivation since 1990.Contents1. Introduction 2. LED development.3. Color ratios and photosynthesis 4. LEDs and indo
5、or plant cultivation.4.1. Plant tissue culture and growth4.2. Space agriculture84.3. Algaculture4.4. Plant disease reduction5. Intermittent and photoperiod lighting and energy saving6. Conclusion1. IntroductionWith impacts of climate change, issues such as more frequent and serious droughts, floods,
6、 and storms as well as pest and diseases are becoming more serious threats to agriculture. These threats along with shortage of food supply make people turn to indoor and urban farming (such as vertical farming) for help. With proper lighting, indoor agriculture eliminates weather-related crop failu
7、res due to droughts and floods to provide year-round crop production, which assist in supplying food in cities with surging populations and in areas of severe environmental conditions.The use of light-emitting diodes marks great advancements over existing indoor agricultural lighting. LEDs allow the
8、 control of spectral composition and the adjustment of light intensity to simulate the changes of sunlight intensity during the day. They have the ability to produce high light levels with low radiant heat output and maintain useful light output for years. LEDs do not contain electrodes and thus do
9、not burn out like incandescent or fluorescent bulbs that must be periodically replaced. Not to mention that incandescent and fluorescent lamps consume a lot of electrical power while generating heat, which must be dispelled from closed environments such as spaceships and space stations.2. LED develo
10、pmentLED is a unique type of semiconductor diode. It consists of a chip of semiconductor material doped with impurities to create a pn junction. Current flows easily from the p-side (anode), to the n-side (cathode), but not in the reverse direction.Electrons and holes flow into the junction from ele
11、ctrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon. The color (wavelength) of the light emitted depends on the band gap energy of the materials forming the pn junction. The materials used for an LED have a d
12、irect band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.The key structure of an LED consists of the die (or light-emitting semiconductor material), a lead frame where the die is placed, and the encapsulation which protects the die (Fig. 1).Fig.1LED development
13、began with infrared and red devices made with gallium arsenide. Advances in materials science have made possible the production of devices with ever-shorter wavelengths, producing light in a variety of colors. J.Margolin reported that the first known light-emitting solid state diode was made in 1907
14、 by H. J. Round. No practical use of Rounds diode was made for several decades until the invention of the first practical LED by Nick Holonyak, Jr in 1962. His LEDs became commercially available inlate 1960s. These GaAsP LEDs combine three primary elements: gallium, arsenic and phosphorus to provide
15、 a 655nm red light with brightness levels of approximately 110 mcd at 20mA. As the luminous intensity was low, these LEDs were only used in a few applications, primarily as indicators. Following GaAsP, GaP (gallium phosphide) red LEDs were developed. These device sex hibit very high quantum efficien
16、cies at low currents. As LED technology progressed through the 1970s, additional colors and wavelengths became available. The most common materials were GaP green and red, GaAsP orange, and high efficiency red and GaAsP yellow. The trend towards more practical applications (such as in calculators, digital watches, and test equipment) also began to develop. As the LED materials technology became more advanced, the light output was inc
