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991.
992.
A design method along with its results, for a space optical system with high resolution and wide field of view, is described. Such optical systems can be used in the infrared as well as visible configurations. The proposed design is based on an on-axis Ritchey-Chrétien system with corrected lens element while the primary mirror is a segmented aperture. Here the on-axis concept allows wide-field enabling a variety of observations designed for the multi-object spectrometer instruments, optimized for low scattering and low emission of light. The use of segmented mirrors in the optical system allows adopting any method for its fabrication purposes. Segment results are discussed and the image quality of the design based on these results is evaluated in this paper. 相似文献
993.
Chao Song Jun Xu Quanbiao Wang Guowei Zha Kunji Chen 《Solid State Communications》2011,151(9):697-700
Phosphorus- and boron-doped hydrogenated amorphous silicon thin films were prepared by the plasma-enhanced chemical vapor deposition method. As-deposited samples were thermally annealed at various temperatures to get nanocrystalline Si with sizes around 10 nm. X-ray photoelectron spectroscopy measurements demonstrated the presence of boron and phosphorus in the doped films. It is found that the nanocrystallization occurs at around 600 °C for the B-doped films, while it is around 700-800 °C for the P-doped samples. For the P-doped samples, the dark conductivity decreases at first and then increases with the annealing temperature. While for the B-doped samples, the dark conductivity monotonously increases with increasing annealing temperature. As a result, the carrier transport properties of both P- and B-doped nanocrystalline Si films are dominated by the gradual activation of dopants in the films. The conductivity reaches 22.4 and 193 S cm−1 for P- and B-doped sample after 1000 °C annealing. 相似文献
994.
We propose and demonstrate a novel and simple dual-parameter measurement scheme based on a cascaded optical fiber device of long-period grating (LPG) and photonic crystal fiber (PCF) modal interferometer. The temperature and refractive index (RI) can be measured simultaneously by monitoring the spectral characteristics of the device. The implemented sensor shows distinctive spectral sensitivities of -30.82 nm/RIU (refractive index unit) and 47.4 pm/°C by the LPG, and 171.96 nm/RIU and 10.4 pm/°C by the PCF modal interferometer. The simultaneous measurement of the temperature and external RI is experimentally demonstrated by the sensor. The temperature shift and RI shift calculated by the sensor matrix agree well with the actual temperature and RI change in the experiment. 相似文献
995.
利用蒙特卡罗方法分别研究了3种能量X光机的光子穿透不同厚度铝的硬化情况及3种能量光机作为光源测量面密度的过程,并开展了相关实验研究,根据模拟结果对比分析了不同能量光机X射线硬化对面密度测量灵敏度的影响,结果表明:对同种能量光机的光子而言,随着面密度变大,射线硬化程度越严重,导致测量灵敏度下降;光子能量越低,测量灵敏度随面密度变大下降越快,反之亦然;对于某一范围面密度被测物,调整X光机电压使X光子刚好穿透并形成有效图像,可获得最理想的测量灵敏度。 相似文献
996.
应用有限元方法, 研究金纳米球壳对的几何结构参数及物理参量对其表面等离激元共振的散射及消光光谱的影响, 并根据等离激元杂化理论进行了理论分析. 结果表明, 随着金壳厚度的增加, 金纳米球壳对的散射及消光共振峰先发生蓝移而后红移, 而随着金纳米球壳间隙的减小, 或者随着金纳米球壳的内核尺寸或内核介质折射率的增大, 散射及消光共振峰均发生红移; 随着金壳厚度或内核尺寸减小, 或者随着内核介质折射率增大, 金纳米球壳对的散射与消光共振强度减弱, 而随着金壳间隙的减小, 金纳米球壳对的散射共振强度先增强后减弱, 而消光共振强度逐渐增强, 数值模拟与理论分析一致. 相似文献
997.
998.
Variational principles are constructed using the semi-inverse method for two kinds of extended Korteweg—de Vries (KdV) equations, which can be regarded as simple models of the nonlinear oceanic internal waves and atmospheric long waves, respectively. The obtained variational principles have also been proved to be correct. 相似文献
999.
A single-mode fiber (SMF) acousto-optic tunable filter (AOTF) with a tuning range of more than 300 nm is demonstrated. The SMF used in the experiment has a ring of symmetric holes within the cladding, which causes a larger mode-index difference between the first and the second higher-order antisymmetric modes than those of a conventional SMF. As a result, the difference in beatlengths between the core mode and the higher-order modes is highly increased, which makes it possible for the SMF AOTF to exhibit a single resonance peak in the transmission spectrum over the wavelength range of 1.3-1.6 μm for given acoustic frequencies of 3.1-3.8 MHz. 相似文献
1000.
We present a four-dimensional flash trajectory imaging method to image object trajectories over time in three-dimensional space. In the method, time-delay-modulated range-gated viewing with multiple exposures is presented so that the time evolution of object trajectories free from background interference is directly given without complicated image processing and the motion parameters of objects can be estimated. The method is demonstrated by a ball oscillating as a pendulum. 相似文献