新型各向异性核工业石墨断裂力学行为的实验研究和数值分析

本文分别采用激光和白光DSCM(数字散斑相关测量)方法对一种新型各向异性核工业石墨的裂纹尖端位移、应变场进行了实验研究，两种方法都取得了较好的结果。考虑核工业石墨制备过程形成的各向异性特点，本文构建了三维各向异性有限元模型，采用奇异单元，计算模拟石墨裂纹尖端的变形和应力场，通过对实验结果和有限元计算结果的比较可以发现两者具有相近的趋势。     

运动控制的数字随动系统

介绍了采用数字随动系统解决模拟伺服回路的设计技术，即选用智能化运动控制处理器用于无刷或有刷直流电动机控制。这种技术具有实时采集，操作简单，可靠性高，精度高等优点，在导航系统、雷达系统、火炮系统、汽车等领域具有广阔的发展前景。     

白光数字散斑图像频域自动识别技术——用于逐点分析的数字相移法

提出了一种应用于白光数字散斑图像频域位移测量技术的数字相移方法,利用计算机本身的能力,无需增加任何设备,通过计算机生成的四幅图像进行相移计算,得到逐点分析的条纹的未去包裹图像,从该图像确定位移的方向和大小,实现了白光数字散斑图像的全自动化处理。白光数字散斑方法设备简单,对环境的要求低,无需防振和相干光源,引入本文提出的数字相移技术,由于充分利用了计算机数字图像处理的功能,在未增加任何设备的情况下实现了全自动位移测量,是一种适合工业现场测量的有发展前途的位移测试的技术。     

Particle behavior in homogeneous isotropic turbulence

Direct numerical simulations were conducted to investigate the behavior of heavy particles in homogeneous isotropic turbulence. The present study focused on the effect of particle inertia and drift on the autocorrelations of the particle velocity and the fluid seen by particles and the dispersion characteristics of particles. The Lagrangian integral time scale of particles monotonically increased as the magnitude of the particle response time increased, while that of the fluid seen by particles remained relatively constant; it reached a maximum when the particle response time was close to the Kolmolgorov time scale of the flow. Particle dispersion increased as the particle inertia increased for small particles, while for larger particles, it decreased as particle inertia increased; particle eddy diffusion coefficient was maximal, and greater than that of the fluid by about 30%, at the preferential concentration. The concentration field of the particles with τp/τk≈1.0 showed that particles tend to collect in regions of low vorticity (high strain) due to preferential concentration. As the drift velocity of a particle is increased it crosses the paths of fluid elements more rapidly and will tend to lose correlation with its previous velocity faster than a fluid element will. And the correlation of particle velocities along the drift direction is more persistent than that perpendicular to the direction of drift. Simulations also showed that the continuity effect and the crossing-trajectory effect are weakened for particles with infinite inertia.     

随机桁架结构的非平稳随机动力响应分析

本文研究了随机桁架结构在非平稳随机激励下的动力响应问题。在利用随机因子法分析随机结构动力特性的基础上，给出了一种分析随机结构非平稳随机响应的新方法。从结构非平稳随机响应的表达式出发，同时考虑桁架结构的物理参数、几何尺寸的随机性，利用求解随机变量函数矩的方法和求解随机变量数字特征的代数综合法，导出了随机桁架结构在非平稳随机激励下位移响应均方值和应力响应均方值的均值、方差和变异系数的计算表达式。通过算例，分析了结构物理参数和几何尺寸的随机性对结构位移响应均方值和应力响应均方值随机变量随机性的影响。本文方法具有对随机结构进行一次动力分析便可求得动力响应的数字特征，且可以考察结构任一参数的随机性对结构非平稳随机响应分析结果的影响之优点。     

相移数字云纹测量系统

介绍了一种相位移数字云纹变形测量系统．测试系统采用ＣＣＤ摄像系统记录光栅图像，控制采样的空间频率大约为光栅线密度的整数倍，对试件栅进行采样后用数字信号处理的方法，实现空间相位移及进行实时数字云纹条纹显示，并对相移误差及光栅信号的高阶谐波的影响进行了校正     

NUMERICAL STUDY OF PARTICLE DISTRIBUTION IN WAKE OF LIQUID-PARTICLE FLOWS PAST A CIRCULAR CYLINDER USING DISCRETE VORTEX METHOD

Particle-laden water flows past a circular cylinder were numerically investigated. The discrete vortex method (DVM) was employed to evaluate the unsteady water flow fields and a Lagrangian approach was applied for tracking individual solid particles. A dispersion function was defined to represent the dispersion scale of the particle. The wake vortex patterns, the distributions and the time series of dispersion functions of particles with different Stokes numbers were obtained. Numerical results show that the particle distribution in the wake of the circular cylinder is closely related to the particle's Stokes number and the structure of wake vortices: (1) the intermediate sized particles with Stokes numbers, St, of 0.25, 1.0 and 4.0 can not enter the vortex cores and concentrate near the peripheries of the vortex structures, (2) in the circular cylinder wake, the dispersion intensity of particles decreases as St is increased from 0.25 to 4.0.     

数字闭环光纤陀螺复位电压控制技术研究

在数字闭环光纤陀螺(FOG)中，2π复位电压的准确度直接影响到陀螺的标度因数精度，对提高陀螺性能起着重要的作用。中对2π复位电压对标度因数的影响进行了理论分析，并在此基础上提出了建立第二反馈回路以稳定2π复位电压的控制方法。     

STRUCTURAL DAMAGE MODEL OF UNSATURATED EXPANSIVE SOIL AND ITS APPLICATION IN MULTI-FIELD COUPLE ANALYSIS ON EXPANSIVE SOIL SLOPE

Focused on the sensitivity to climate change and the special mechanical characteristics of undisturbed expansive soil, an elastc-plastic damage constitutive model was proposed based on the mechanics of unsaturated soil and the mechanics of damage. Undisturbed expansive soil was considered as a compound of non-damaged part and damaged part. The behavior of the non-damaged part was described using non-linear constitutive model of unsaturated soil. The property of the damaged part was described using a damage evolution equation and two yield surfaces, i.e., loading yield (LY) and shear yield (SY). Furthermore, a consolidation model for unsaturated undisturbed expansive soil was established and a FEM program named UESEPDC was designed. Numerical analysis on solid-liquid-gas tri-phases and multi-field couple problem was conducted for four stages and fields of stress, displacement, pore water pressure, pore air pressure, water content, suction, and the damage region as well as plastic region in an expansive soil slope were obtained.     

圆合成孔径声呐多点定位运动补偿

圆合成孔径声呐(CSAS)的成像性能受平台运动误差影响而下降,利用单侧回波可估计CSAS基阵的斜距误差,但单侧回波在小测绘带时无法估计升沉误差,针对此问题,提出了一种利用单侧回波信号的声呐平台三维运动估计和补偿方法。首先,对CSAS在不同观测角度的目标回波取极大值获得目标回波的到达时间;其次,基于多个点目标的到达时间建立CSAS三维定位模型;然后利用列文伯格-马夸尔特方法对声呐三维坐标进行估计;最后将位置估计结果与时域反投影成像方法结合实现对目标的成像.仿真结果表明:该方法能精确估计声呐平台运动误差,其空间坐标的估计误差小于仿真信号波长的1/8,从而精确补偿了CSAS在不同空间采样点上的阵元回波时间差,显著提高了目标成像质量。湖上试验结果表明,该算法能够实现对CSAS的运动误差补偿。仿真和试验结果均验证了方法的可行性和有效性。