kHz激光器在武汉卫星观测站的测距实验

高重复频率激光器是kHz卫星激光测距系统的重要组成部分,提高激光发射频率可以有效地获得更多的观测数据,这是当今卫星激光测距领域的发展方向.针对武汉卫星观测站进行的kHz激光测距实验,介绍了kHz激光器的工作过程和原理,分析了影响高重复频率回波探测的因素.实验结果表明:对实验过程中所观测到的中低轨卫星,观测数据量提高了1...     

热丝化学气相沉积技术低温制备多晶硅薄膜的结构与光电特性

以金属W和Ta为热丝，采用热丝化学气相沉积 ，在250℃玻璃衬底上沉积多晶硅薄膜.研究了热丝温度、沉积气压、热丝与衬底间距等沉积参数对硅薄膜结构和光电特性的影响，在优化条件下获得晶态比X_c＞90%，暗电导率σ_d=10^-7—10-6Ω ^-1cm^-1，激活能E_a=0.5eV，光能隙E_opt≤1.3 eV的多晶硅薄膜. 关键词： 多晶硅薄膜 热丝化学气相沉积 光电特性     

损伤材料裂纹尖端附近的应力场

本文导出了损伤材料的全量理论,导出了全量公式中H的渐近表达式;最后得到损伤材料平面应变条件下的裂纹尖端的应力应变场。     

振荡燃烧的动态测试及信息处理

作者用随机信息处理方法研究了某型火箭发动机的燃烧状况,不仅发现该型发动机存在有振荡燃烧,而且获得了振荡燃烧信息的功率谱及功率谱阵。针对振荡燃烧信息在时间域和频率域上的随机性特点,作者精心地设计了测试系统,并对系统的性能参数进行了全面标定。经多次实测证明该系统工作可靠,信噪比较高。测试与分析结果表明:该型发动机振荡燃烧的主振测率为800Hz,最大振幅为43dB;并存在有1600Hz和2500Hz两个次级振荡频率;而且该发动机的振荡燃烧是以纵向振荡为主。为研究该型火箭发动机振荡燃烧的产生原因和消除方法提供了科学依据。     

Instability of hagen-poiseuille flow for axisymmetric mode

An investigation is described for instability problem of flow through a.pipe of circular cross section. As a disturbance motion, we consider an axisymmetric nonlinear mode. An associated amplitude or modulation equation has been derived for this perturbation. This equation belongs to the diffusion type. The coefficient of it can be negative with Reynolds number increasing, because of the complex interaction between molecular diffusion and convection. The negative diffusion, when it occurs, cause a concentration and focusing of energy within the decaying slug, acting as a role of reversing natural decays.     

An approximate solution considering flow inertia between spherical surfaces

In this paper, the analytical expressions of the pressure distribution, velocity distribution and discharge of the flow between spherical surfaces are found by using the method of iterative approximate solution when the inertia terms of Navier-Stokes equations in spherical coordinates are taken into consideration. Furthermore, using these expressions, we can directly obtain the corresponding analytical expressions of the laminar radial flow between parallel disks, which are fully identical with corresponding results presented by refs. [3,4].     

脊加载曲折波导行波管注波互作用的线性理论研究

提出了一类新型毫米波大功率微波器件——脊加载曲折波导行波管,推导出了引入电子注后的"热"色散方程.通过数值求解此方程,研究了加脊尺寸和电子注参数对小信号增益影响.计算结果表明:通过适当的尺寸设计和工作参数的选择,此结构在Kα波段具有18.51%的3 dB增益带宽和1.15 dB/周期的增益;相比于常规曲折波导结构,脊加载结构在保证一定带宽的情况下,具有更高的增益和电子效率;为了进一步提高增益,可以适当增加脊宽度和高度,也可在一定范围内增加电子注电流. 关键词： 毫米波 曲折波导 脊加载 小信号增益     

Effect of microstructure on thermoelectric properties of CSD-grown Bi2Sr2Co2Oy thin films

Three Bi₂Sr₂Co₂O_y thin films with different microstructures have been prepared by chemical solution deposition on LaAlO₃(001) through varying the annealing temperature. With the decrease in the annealing temperature, both the size and c-axis alignment degree of grains in the film decrease as well, leading to an increase in the film resistivity. In addition, the decrease in the annealing temperature also results in a slight increase in the seebeck coefficient due to the enhanced energy filtering effect of small-grain film. The nanostructured Bi₂Sr₂Co₂O_y film with the average grain size of about 100 nm shows a power factor comparable to that of the films with larger grains. Since the thermal conductivity of the nanostrcutured films can be depressed due to the enhanced phonon scattering by grain boundary, a higher figure of merit is expected in Bi₂Sr₂Co₂O_y thin film with grains in nanometer size.     

Analysis of penetration of axisymmetric projectiles into semi-infinite targets

The process of penetration of a projectile into a semi-infinitetarget is studied in this paper. Using certain assumptions, the propagation of plastic wave in the target is analyzed and the pressure on the surface of penetrator is given. The results calculated from the formulas of this paper agree well with experimental data and numerical results.     

The method of matrices conjoint multiplication for the problem of circular arc corrugated diaphragm

The circular are corrugated diaphragins are taken in this paper and structures of several sections of the ring shells and a central cireular plale I matrices and link matrices are derived by using Prof. Chuen Hei-zang’s general the ring shell[1] and perturbation theory of the circular thin plates. Throngh the meined of matrices conjoint multiplication, the linear exact solution and nonlinear soluaen are obtained. The resutts agree with that of the experiments presented by W. A. Wildhack..