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931.
932.
空间目标的可见光散射与红外辐射 总被引:22,自引:6,他引:16
利用Lowtran7大气传输模型计算了0.4~0.8μm可见光波段的太阳辐射、大气自身的热辐射以及天地背景辐射。利用粗糙面光散射理论与双向反射分布函数计算了空中目标表面对太阳辐射、云层对阳光反射的散射。并利用传热学和背景辐射理论,根据能量守恒定律建立了空间目标表面温度的热平衡方程。以气球为例,计算了不同表面涂层材料的气球在不同地理位置、不同高度、不同时间、温度及辐射功率的变化。分析了空间目标红外辐射特性的一般规律和特征。 相似文献
933.
报导了ZnSCu水溶液和ZnSCu/PVA复合膜的制备过程,分析了分散剂所起的作用.研究了室温下复合膜的激发光谱和发射光谱,以及室温和液氮温度下的分时光谱.初步探讨了ZnSCu纳米超微粒的发光过程. 相似文献
934.
In this paper simple closed form expressions of surface wave fields for microstrip dipoles on grounded substrates are presented.
The surface power, radiated power and radiation efficiency are calculated. It is shown that the radiation efficiency decreases
with the increase of substrate electrical thickness. Hence new type antennas are needed to radiate millimeter wave because
of the effect of the surface waves in substrate. 相似文献
935.
Qizheng Dou Xiaomin Zhu Karin Peter Dan E. Demco Martin Möller Claudiu Melian 《Journal of Sol-Gel Science and Technology》2008,48(1-2):51-60
Based on a volatile-free silica liquid precursor polymer—hyperbranched polyethoxysiloxane (PEOS), an industrial compatible in situ sol–gel process for the preparation of polymer/silica nanocomposites has been developed. It has been shown that in the presence of a catalyst water vapor induced a fast conversion of liquid PEOS to solid silica in polypropylene (PP) melt in a twin-screw microcompounder. Solid state NMR showed that the in situ conversion of PEOS proceeded to a large extent. With small amounts of PEOS this procedure yielded PP/silica composites with particle size less than 100 nm. The particle size increased with the PEOS amount blended with PP. Nevertheless, the particles were observed to be homogeneously dispersed within the polymer matrix. PP/silica composites prepared by in situ sol–gel technology showed improved thermal properties, but almost not affected mechanical properties in comparison with pure PP. 相似文献
936.
In this communication a note on the coupling efficiency between an antenna and a Gaussian beam is presented. The calculations of the coupling efficiency from both methods, a nomorlized inner product between the antenna radiation pattern and the Gaussian-beam pattern or alternatively, between the electric field at the antenna aperture and a two-dimensional field representation of a Gaussian beam, are compared for different aperture size in wavelength. How a correct solution can be gotten is stated. 相似文献
937.
Several kinds of waveguide components such as curved waveguide bends, arbitrary angle waveguide bends and T-junctions have been analyzed with boundary element method in this paper. A new discretization method for the boundary element method to solve the waveguide discontinuities has been given. The numerical results obtained agree well with the experimental results and numerical results in other literature. Especially, the scattering characteristics of Forded E-, H-plane T-junctions in 3mm band have been analyzed using boundary element method and the calculation results are presented. 相似文献
938.
Effects of N2 and glow discharge on growth behaviours of carbon nanotubes prepared by the hot filament chemical vapour deposition method 下载免费PDF全文
Carbon nanotubes (CNTs) are prepared by the hot filament chemical vapour deposition method using CH4 and H2 as reaction gases, and the growth behaviours are investigated by scanning electron microscopy and transmission electron microscopy. The results indicate that the CNTs prepared in the absence of N2 or glow discharge are bent; however, they are in an aligned state after introducing N2 into the chamber or forming glow discharge under a negative biased voltage. The results also indicate that the CNTs are of a bamboo-like structure when N2 is intruded as a reaction gas and the alignment degree of the CNTs grown under glow discharge is higher than that grown in N2. This illustrates that the nitric environment and glow discharge play important roles in the growth of CNTs. Combining with the theory related to alloy thermodynamics and collisions, we have analysed the growth mechanism of the CNTs in nitric environment and glow discharge. 相似文献
939.
We calculate the first four cumulants of the integrated current of the one-dimensional symmetric simple exclusion process of N sites with open boundary conditions. For large system size N, the generating function of the integrated current depends on the densities ρ a and ρ b of the two reservoirs and on the fugacity z, the parameter conjugated to the integrated current, through a single parameter. Based on our expressions for these first four cumulants, we make a conjecture which leads to a prediction for all the higher cumulants. In the case ρ a =1 and ρ b =0, our conjecture gives the same universal distribution as the one obtained by Lee, Levitov, and Yakovets for one-dimensional quantum conductors in the metallic regime. 相似文献
940.
利用光刻,反应离子刻蚀以及电化学阳极氧化技术在铝基底上构建出了微米纳米相结合的三维金属铝图案。首先在铝片的表面形成一层具有图案的二氧化硅阻碍层,阳极氧化过程中,在二氧化硅阻碍层之下会形成侧向生长的倾斜孔道和残留的金属铝微结构。形成机制可阐述为:由于表面二氧化硅阻碍层的存在造成局域电场方向的偏折,影响到反应过程中离子的输运,从而导致侧向倾斜孔的形成,而在远离阻碍层的区域孔道则会正常垂直表面向下生长。这种垂直与侧向阳极腐蚀的同时进行导致在二氧化硅阻碍层之下形成了金属铝微结构。 相似文献