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31.
32.
柳国宪 《长沙航空职业技术学院学报》2011,11(1):41-44,66
针对LED的特点提出开关型恒流驱动电路,通过电流与电压负反馈技术的采用,将LED的输入电流控制在一个稳定的电流数值下,同时使电路防止过电压的能力提高,可靠性大为增强. 相似文献
33.
Fucci RL Gardner J Hanifin JP Jasser S Byrne B Gerner E Rollag M Brainard GC 《Acta Astronautica》2005,56(9-12):1017-1024
Light is being used as a pre-launch countermeasure to circadian and sleep disruption in astronauts. The effect of light on the circadian system is readily monitored by measurement of plasma melatonin. Our group has established an action spectrum for human melatonin regulation and determined the region of 446-477 nm to be the most potent for suppressing plasma melatonin. The aim of this study was to compare the efficacy of 460 and 555 nm for suppressing melatonin using a within-subjects design. Subjects (N=12) were exposed to equal photon densities (7.18 x 10(12) photons/cm2/s) at 460 and 555 nm. Melatonin suppression was significantly stronger at 460 nm (p<0.02). An extension to the action spectrum showed that 420 nm light at 16 and 32 microW/cm2 significantly suppressed melatonin (p<0.04 and p<0.002). These studies will help optimize lighting countermeasures to circadian and sleep disruption during spaceflight. 相似文献
34.
We propose a technique to derive the coronal density irregularity factor
, wheren is the electron density. The absolute photometric comparison between the intensity of UV lines and the white-light K-coronal polarized brightness (pB) provides an unique constraint on the inhomogeneity of the corona. The ratio of the measured H I Lyman (Ly-) line intensity to the resonant-scattering dominated H I Lyman (Ly-) intensity can be used to extract the collisonal component of the Ly-. This component yields an estimate of
. The quantity
is then obtained from white-light K-coronal measurements. The use of lines of the same atomic species minimizes the effects due to outflow velocities (i.e., Doppler dimming), and reduces the errors introduced by the uncertainties in the ionization balance, the atomic parameters, and the solar abundances. The UVCS/SOHO unique capability of performing cotemporal and cospatial measurements of the Ly- and Ly- lines, and ofpB makes this instrument ideal for implementing this technique. 相似文献
35.
航天器星敏感器自主定位方法及精度分析 总被引:13,自引:4,他引:13
用星敏感器和地平仪测量星光与地平之间的“星光抑角”为观测量,利用推广卡尔曼滤波方法实时估计航天器的最佳位置,使航天器在失去地面遥控的情况下,能够自主准确地确定运行轨道。由于航天器自主定位系统在工作期间会受到硬、软件等诸多因素的影响,因而使其定位精度达不到预计要求。在此我们通过大量仿真计算,指出一些对自主定位系统精度影响较大的因素,并对它们进行了比较分析。 相似文献
36.
星载激光遥感技术的发展及应用 总被引:1,自引:0,他引:1
文章简要介绍了星载激光遥感的技术原理与特性,并对几种星载激光雷达在大气探测、星体测绘、冰盖监测及全球高分辨率测绘等领域的应用做了介绍,最后分析了中国发展星载激光遥感现阶段的已有基础及对未来的发展展望。 相似文献
37.
Selection of candidate salad vegetables for controlled ecological life support system 总被引:1,自引:0,他引:1
L. Qin S. GuoW. Ai Y. Tang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(5):768-772
Higher plants, as one of the essential biological components of CELSS, can supply food, oxygen and water for human crews during future long-duration space missions and Lunar/Mars habitats. In order to select suitable leaf vegetable varieties for our CELSS Experimental Facility (CEF), five varieties of lettuce (“Nenlvnaiyou”, “Dasusheng”, “Naichoutai”, “Dongfangkaixuan” and “Siji”), two of spinach (“Daye” and “Quanneng”), one of rape (“Jingyou No. 1”) and one of common sowthistle were grown and compared on the basis of edible biomass, and nutrient content. In addition, two series of experiments were conducted to study single leaf photosynthetic rates and transpiration rates at 30 days after planting, one which used various concentrations of CO2 (500, 1000, 1500 and 2000 μmol mol−1) and another which used various light intensities (100, 300, 500 and 700 μmol m−2 s−1). Results showed that lettuce cvs. “Nenlvnaiyou”, “Siji” and “Dasusheng” produced higher yields of edible biomass; common sowthisle would be a good source of β-carotene for the diet. Based on the collective findings, we selected three varieties of lettuce (“Nenlvnaiyou”, “Dasusheng” and “Siji”) and one of common sowthistle as the candidate crops for further research in our CEF. In addition, elevated CO2 concentration increased the rates of photosynthesis and transpiration, and elevated light intensity increased the rate of photosynthesis for these varieties. These results can be useful for determining optimal conditions for controlling CO2 and water fluxes between the crops and the overall CELSS. 相似文献
38.
在分析光学角反射器速差补偿两种经典方法的基础上,指出在实际工程设计中速差补偿方案的选取不是由某一种方法独立实现的,而是两种方法的综合体现。据此给出了适合工程设计特点的差速补偿方法考虑。 相似文献
39.
通过对玻璃强度理论的综述,分析了舷窗玻璃的强度特性。指出舷窗玻璃强度设计必须以玻璃的断裂机理为依据,而不能仅按传统上的杭张强度或抗折强度等指标作为选材标准。舷窗玻璃的强度受表面微裂纹影响很大,要保证舷窗玻璃强度达到设计和使用要求,必须对玻璃表面的裂纹进行严格的控制和检测。考虑到玻璃的亚临界裂纹生长,舷窗玻璃使用前应避免在大气环境中长时间受力。在舷窗结构设计时还应避免使处于张应力的表面与水分接触。 相似文献
40.
K. Durga Prasad S.V.S. MurtyT. Chandrasekhar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
A novel and versatile wireless light sensing device has been designed and tested for stellar and planetary photometric observations. The device weighing few 10 s of grams finds a number of potential applications in the fields of astronomy and in situ planetary exploration. A Wireless Sensor Network (WSN) using a number of these devices has been deployed to successfully carry out simultaneous photometric observations under different conditions viz. sunlight, twilight, moonlight etc. Observation of a star of known magnitude for flux calibration at low intensity has been carried out by coupling the device to a 1.2 m telescope which demonstrates its sensitivity. A WSN using these devices is further capable of spatio-temporal investigations of sky background intensities. Such a network can also be used to effectively monitor certain astronomical events (lunar eclipse, asteroid occultation etc.) simultaneously from several locations. The capability of the device, level of miniaturization and its versatility makes it a potential tool for many photometric applications. 相似文献