大气边界层风速竖向相干函数实验研究

采用尖劈、格栅和粗糙元组合的被动湍流发生装置在TJ-2风洞中模拟了大气边界层流场,测量了模拟流场的平均风速剖面,湍流度剖面,湍流积分尺度和脉动风速功率谱等风场特性参数,重点分析了风速的竖向空间相干曲线。针对风速竖向空间相干曲线存在低频“掉头”的现象,给出了修正的指数衰减函数来进行拟合,完善了用传统的简化指数衰减函数来进行拟合时在低频处的不足,结果表明：笔者给出的风速竖向空间相干函数拟合效果更好。     

大气腐蚀电化学测定研究

介绍了自行研制的环境试验中大气腐蚀电化学测定装置,包括Kelvin 大气腐蚀测定仪的工作原理,功能用途,软硬件结构及初步测试结果.自行研制的Kelvin大气腐蚀测定仪采用振动电容法技术,不需与被测量试样及电解液相接触,用Kelvin探针作参比电极,即可测得液膜下金属电极电位及极化曲线,为研究大气环境下的材料腐蚀行为提供了先进的技术和方法.     

用射线法研究复杂目标的电磁散射特征

应用计算机图形学中的曲面造型方法给出目标精确的数学外形,将之离散为三角面元,并采用拓扑结构来描述几何元素之间的关系;利用射线追踪法模拟射线束的多次反射,同时求出扩散因子、磁场方向和相位差;在最终反射点处采用物理光学积分求远场散射,叠加每一射线束的贡献,进而得出耦合雷达散射截面值.为减小射线追踪过程中的计算量,采用了加速算法.给出了作为特例的翼身组合体的计算结果.     

大气等离子加工系统设计及实验验证

建立了面向复杂光学表面的大气等离子抛光系统,并用该系统进行硅片表面加工的实验研究.研究了CF_4、SF_6两种气体的放电特性以及加工效果,得到了加工速率与功率,流量间的关系,并通过原子力显微镜观察了加工后的表面质量.     

Disturbance observer-based robust guidance for Mars atmospheric entry with input saturation

With low-lifting capability taken into account,a robust guidance law for Mars entry vehicles with low lift-to-drag ratios,such as Mars Science Laboratory(MSL),is presented.Consider the nonlinear term in the drag dynamic equation and bounded disturbances as a lumped disturbance,and design a linear disturbance observer(DOB)to estimate it.With the consideration of the control input saturation,an innovative sliding surface and a virtual system are introduced to design the guidance law.Analyses of disturbance observer performance and Lyapunov-based transient performance are also presented.It is shown that the drag tracking error can be adjustable by explicit choices of design parameters.Simulation results confirm the effectiveness of the proposed guidance law.     

水汽对折光修正精度的影响分析

针对当前部分折光修正的工程应用常常忽略水汽影响的现状,选取了国内4个不同地域的气象站点,基于1995年的数百组历史气象探空数据,利用射线描迹法分别仿真计算包含水汽和忽略水汽2种情况下由于大气折射引起的测距误差和测角误差,并对这4个站点不同仰角和不同时间的测距偏差和测角偏差进行统计分析,结果表明：水汽是构成测量残差的一个重要误差源,对于精度要求较高的折光修正系统,水汽的影响不能忽略.该分析结果可为其他需要考虑大气折射效应影响的高精度光学测量工程领域提供参考.     

圆顶相控阵的初步设计

文章介络了圆顶阵的概念、实现宽角扫描的原理;利用几何光学法分析了圆弧阵的口径场幅度、固定移相器的相移;同时,给出了圆顶单元的几种设计方法。最后,对文中推导出的重要公式进行了验证,并从中找到适合工程实现的设计参数：结果表明,几何光学法是分析圆顶相控阵极其有效的方法,圆波导是圆顶单元比较好的选择,圆顶相控阵在实现宽角扫描方面具有成熟的理论依据。     

Large light X-ray optics: basic ideas and concepts

One of the main guidelines for future X-ray astronomy projects like, e.g., XEUS (ESA) and Generation-X (NASA) is to utilize grazing-incidence focusing optics with extremely large telescopes (several tens of m² at 1 keV), with a dramatic increase in collecting area of about two order of magnitude compared to the current X-ray telescopes. In order to avoid the problem of the source's confusion limit at low fluxes, the angular resolution required for these optics should be superb (a few arcsec at most). The enormous mirror dimensions together with the high imaging performances give rise to a number of manufacturing problems. It is basically impossible to realize so large mirrors from closed Wolter I shells which benefit from high mechanical stiffness. Instead the mirrors need to be formed as rectangular segments and a series of them will be assembled in a petal. Taking into account the realistic load capabilities of space launchers, to be able to put in orbit so large mirror modules the mass/geometric-area ratio of the optics should be very small. Finally, with a so large optics mass it would be very difficult to provide the electric power for an optics thermal active control, able to maintain the mirrors at the usual temperature of 20 °C. Therefore, very likely, the optics will instead operate in extreme thermal conditions, with the mirror temperature oscillating between −30 and −40 °C, that tends to exclude the epoxy replication approach (the mismatch between the CTE of the substrate and that of the resin would cause prohibitively large deformations of the mirror surface profiles). From these considerations light weight materials with high thermal–mechanical properties such as glass or ceramics become attractive to realize the mirrors of future Xray telescopes. In this paper, we will discuss a segments manufacturing method based on Borofloat^TM glass. A series of finite element analysis concerning different aspects of the production, testing and integration of the optics are also presented as well.     

激光武器发射转塔尺寸对飞机作战效能的影响

机载激光武器可以主动防御来袭导弹,大幅提升作战飞机的生存能力。为了具备更远的打击距离,激 光武器需要尽可能大的发射镜直径,但几何尺寸较大的发射转塔会对飞机的气动和隐身性能产生不利影响,降低飞机的战场生存能力。利用计算流体力学和物理光学法,分析发射转塔直径对飞机的气动性能和隐身性能 的影响,并采用基于agent的作战仿真方法研究发射转塔直径对飞机在突防作战中作战效能的影响。结果表 明:飞行速度随着发射转塔直径的增大有小幅度降低,降低幅度在2%以内;30、50和70cm 的发射转塔直径分别导致飞机的头向 RCS64%、173%和282%的增加;对于作战效能而言,激光武器发射转塔的尺寸并非越大越 好,相对于无防御措施的无人机执行突防任务,50cm的发射转塔直径可以提高77.2%的任务成功率,是三种 方案中最高的。     

基于Hartmann技术的微小自适应光学系统的研究

采用微小型自适应光学系统提高系统的分辨率具有非常广泛的应用前景。建立了基于Hartmann技术的波前处理机系统,利用MEMS微变形镜进行波前校正并对结果进行了分析,验证了利用微小自适应光学系统校正畸变波前的科学性,给出了建立实用高分辨率传输型微小自适应光学系统的可行性建议。