一种非接触光外差轮廓仪

介绍了一种纳米级非接触超高精度光外差轮廓仪。该量仪是基于普通光路的外差干涉仪,两束具有微小频差的激光束照射到制件表面:其中一束光被会聚后作为测量光针扫瞄制件表面;另一束光则被用作参考光束。这两束光经反射后形成干涉,所得信号的光程差与制件表面高度变化成正比。量仪的横向分辩力小于2μm,垂直分辩力小于1nm。制件不需要进行大的调整。制件表面同时亦被作为测量参考面。经光电转换后,信号由微机处理,从而快速完成测量、计算、显示与打印各种参数与图形。     

EXPERIMENT RESEARCH ON DYNAMIC LOAD IDENTIFICATION TECHNOLOGY BASED ON GENERALIZED ORTHOGONAL POLYNOMIAL THEORY (GOPT)

Dynamicloadisoneoftheimportantoriginalparametersinstructuraldynamicanalysis.Ithasobviousinfluencestodynamicsdesign,vibrationcontrols,activecontroltechnologyandsoon.Sincel97O,manyresearchitemsinthisfieldhavebeenaccomplishedintheworld-Sometheoriesandexperimentalmethodsofdynamicloadidentificationhadbeencreatedinfrequencydomain[l'2J-Howeverftherearesomedisadvantagesthattheycouldbeadaptedonlytoidenti-fythesteady-stateloadandnottoidentifythetransientload,suchasshockloadwithshortsampling.Forvarious…     

当代创新的五个社会特征

本文以当代世界科技创新活动为背景，分析了当代创新的社会性、效用性、时效性、持续性和系统性。     

Simulation analysis for effects of bone loss on acceleration tolerance of human lumbar vertebra

The purpose of the present study was to analyze and predict the changes in acceleration tolerance of human vertebra as a result of bone loss caused by long-term space flight. A human L3–L4 vertebra FEM model was constructed, in which the cancellous bone was separated, and surrounding ligaments were also taken into account. The simulation results demonstrated that bone loss has more of an effect on the acceleration tolerance in x-direction. The results serve to aid in the creation of new acceleration tolerance standards, ensuring astronauts return home safely after long-term space flight. This study shows that more attention should be focused on the bone degradation of crew members and to create new protective designs for space capsules in the future.     

Stability of relative equilibria of the full spacecraft dynamics around an asteroid with orbit–attitude coupling

The full dynamics of spacecraft around an asteroid, in which the spacecraft is considered as a rigid body and the gravitational orbit–attitude coupling is taken into account, is of great value and interest in the precise theories of the motion. The spectral stability of the classical relative equilibria of the full spacecraft dynamics around an asteroid is studied with the method of geometric mechanics. The stability conditions are given explicitly based on the characteristic equation of the linear system matrix. It is found that the linearized system decouples into two entirely independent subsystems, which correspond to the motions within and outside the equatorial plane of the asteroid respectively. The system parameters are divided into three groups that describe the traditional stationary orbit stability, the significance of the orbit–attitude coupling and the mass distribution of the spacecraft respectively. The spectral stability of the relative equilibria is investigated numerically with respect to the three groups of system parameters. The relations between the full spacecraft dynamics and the traditional spacecraft dynamics, as well as the effect of the orbit–attitude coupling, are assessed. We find that when the orbit–attitude coupling is strong, the mass distribution of the spacecraft dominates the stability of the relative equilibria; whereas when the orbit–attitude coupling is weak, both the mass distribution and the traditional stationary orbit stability have significant effects on the stability. We also give a criterion to determine whether the orbit–attitude coupling needs to be considered.     

基于子阵级非周期的有限扫描阵列研究

对基于子阵级非周期的有限扫描阵列进行研究,采用数值仿真和遗传算法对基于不同子阵规模的非周期阵列进行优化设计,分析4?4和2?2两种子阵规模对接收多波束应用中伴随波束方向图的影响,研究表明子阵规模过大会引起伴随波束方向图的旁瓣抬升,通过减小子阵规模可以避免该问题,论证了设计的基于2?2子阵的非周期八角阵可应用于有限视场扫描相控阵中。     

Analytical Calculation Model for Mach Wave Parameters

When a wave shaper is embedded in a liner,Mach wave will emerge above the liner,which affects the head shape of an explosively formed projectile.Mach wave parameters,including radius and pressure need to be determined to effectively match Mach wave with the liner,so that a good head shape can be obtained.An analytical calculation model for Mach wave parameter is presented based on three-shock theory,and the theoretical values agree well with the experimental ones.The analysis shows that when the radius of the wave shaper is constant,the radius of the Mach wave increases,whereas the pressure decreases while increasing the distance between the liner and the wave shaper.When the distance between the liner and the wave shaper is constant,the radius of the Mach wave increases,whereas the pressure decreases when decreasing the radius of the wave shaper.     

过滤式阴极电弧沉积类金刚石薄膜的特性分析

利用自行研制的过滤式阴极电弧沉积装置,在硅片和高速钢基体材料上获得了类金刚石薄膜,分别采用扫描电镜、原子力显微镜、喇曼光谱以及磨损实验等手段对薄膜进行了分析研究。结果表明,所获得的类金刚石薄膜为非晶态,sp3含量最高达70%;基体材料对成膜质量影响较大,在硅片上薄膜的摩擦系数可达0.08;同时偏压的变化会引起喇曼谱线中D峰和G峰位置向低频移动,半高宽σG增大、σD减小。     

低空风切变危险尺度研究

飞机在低空风切变中飞行的危险性评估尺度是机载低空风切变探测、告警、回避系统设计中的关键之一。本文从飞行动力学的基本方程组出发,根据能量高度的概念,从理论上导出了低空风切变对飞行安全的危险尺度,经研究,风切变的危险主要表现在水平风的加速度U_wg和垂直风速度W_wg上。文中研究了U_wg和w_wg对危险尺度的定性、定量关系,提出了用水平风加速度这个目前机载设备能探测的参数来评估风切变的危险程度,为前视式机载低空风变探测传感器的设计提供了基础。     

阻尼振动系统复特征解的摄动分析

当振动系统的质量矩阵和刚度矩阵作小修改时,不重复求解大型广义特征问题,在初始的模态坐标变换基础上,用矩阵摄动法给出修改系统的振动频率和振型;然后利用修改系统的振动频率与比例阻尼参数求出修改系统的阻尼比。工程算例表明,这种方法计算简单,具有较高的精度。