相位差波前检测方法应用于平移误差检测的实验研究

相位差波前检测方法由于其结构简单,对环境要求低,测量精度较高等优点,被应用于诸多领域.本文针对拼接型天文望远镜中主镜的共相位检测问题,对相位差波前检测方法在拼接主镜各子镜间平移误差测量进行理论分析,并搭建了实验光路.实验结果表明:相位差波前检测方法对拼接镜平移误差的测量精度高于λ/20(λ为波长),满足系统对拼接平移误差的要求.     

Nonlinear flutter analysis of stiffened composite panels in super-sonic flow

The flutter instability of stiffened composite panels subjected to aerodynamic forces in the supersonic flow is investigated. Based on Hamilton's principle,the aeroelastic model of the composite panel is established by using the von Karman large deflection plate theory,piston theory aerodynamics and the quasi-steady thermal stress theory. Then,using the finite element method along with Bogner-Fox-Schmit elements and three-dimensional beam elements,the nonlinear equations of motion are derived. The effect of...     

气液耦合振动对热声发动机性能的影响

进行了气液耦合振动驻波型热声发动机定量模拟.重点比较分析了单纯气体振动系统和引入[EMIM][BF_4]室温离子液体作为液体活塞的气液耦合振动系统的运行参数,并考察了液体活塞的质量对热声发动机谐振频率、压力振幅以及板叠热端温度等的影响.     

On the Second Law of Thermodynamics and the Piston Problem

The piston problem is investigated in the case where the length of the cylinder is infinite (on both sides) and the ratio m/M is a very small parameter, where m is the mass of one particle of the gaz and M is the mass of the piston. Introducing initial conditions such that the stochastic motion of the piston remains in the average at the origin (no drift), it is shown that the time evolution of the fluids, analytically derived from Liouville equation in a previous work, agrees with the Second Law of thermodynamics. We thus have a non equilibrium microscopical model whose evolution can be explicitly shown to obey the two laws of thermodynamics.     

Beam Recombination Characteristics in Array Laser Amplification Using Stimulated Brillouin Scattering Phase Conjugation

Beam recombination characteristics were numerically investigated in array laser amplification using stimulated Brillouin scattering phase conjugation. To clarify the effect of piston errors due to imperfect phase locking, spatial intensity profiles of the beam recombination output were calculated in both the near and the far field on the basis of Rayleigh-Sommerfeld diffraction theory. The analyses indicate that piston errors are seriously detrimental to the quality of a beam recombination output and should be eliminated by a proper phase locking. It is also found that the gap between the beam splitting-combining wedges has a negligible effect.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan.     

无障板圆形活塞换能器的辐射阻抗*

辐射阻抗是换能器的最重要辐射声场特性参数之一,影响着换能器的谐振频率、频带宽度、效率以及辐射声功率等。经典声学理论用一阶贝塞尔函数和斯特鲁夫函数给出了圆形活塞换能器辐射阻抗的数学表达式,但仅适用于无限大障板条件。该文用ANSYS有限元软件计算了无障板圆形活塞换能器的辐射阻抗,给出了数值解结果,通过与无限大障板条件下的理论结果相比较,显示了二者之间的偏离情况,尤其是在低频时差异显著。为了借助MATLAB工具模拟无障板圆形活塞换能器的辐射阻抗,并给出较准确的数学表达,选择了一系列初等函数以及它们的复合函数进行曲线拟合,最终给出了辐射阻和辐射抗关于ka的函数表达式,在ka值从0.08到20范围内与有限元计算结果很好吻合。     

Transient modal radiation of axisymmetric sources: Application to loudspeakers

The present study proposes a transient model of the acoustic radiation of axisymmetric structures. The pressure field is approximated by the Rayleigh integral corresponding to a monopole source distribution over the non-planar vibrating surface. The displacement field is expanded on the linear modes of the structure and a change of variables in the Rayleigh integral is then proposed in the case of a monotonic profile function to compute the Spatial Impulse Response associated to each mode of vibration efficiently. The results are compared to the formulation obtained in the case of planar and spherical sources. The method of calculation is then derived in the case of a typical loudspeaker profile (association of a truncated cone with a spherical cap). Finally, the present approach is used to estimate the nonlinear radiation pattern of a prototype loudspeaker and predictions are compared to measurements in anechoic room.     

依据光谱研究闪电回击通道核心的特征参数

闪电回击通道核心中的大电流及其强电磁辐射是引发多种雷电灾害的主要根源.随着现代科技的飞速发展,闪电防护工作显得越为重要.为了完善闪电防护系统,需要从描述闪电回击通道核心的特征参数入手深入研究闪电通道形成和发展过程的微观物理机制.截至目前,光谱观测是获取闪电通道核心特征参数的最佳手段.2015年夏天在青海高原地区的野外试...     

活塞激光热负荷应力场数值模拟

活塞激光热负荷就是通过光学转光片改变激光在空间的能量分配比例.结合活塞激光热负荷试验工况,建立了活塞激光热负荷应力场模拟数学物理模型,模型中考虑了材料的热物性参数随温度的变化.结果表明:由于活塞顶凹坑位置靠近通油孔,导致其应力波动幅值比激光辐照区域大;活塞凹坑、通油孔和靠近活塞顶面的活塞内腔由于和冷却介质直接接触,是活...     

The optimal path of piston motion for Otto cycle with linear phenomenological heat transfer law

An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and w...