裂纹试件的冲击试验

本文介绍了楔型冲击加载双悬臂梁(D.C.B)试件的动态测试技术。实测了冲击力随时间变化曲线;裂纹尖端及试件中部应变随时间变化曲线,并由测试结果分析计算试件的动态断裂韧K_(1d)性随时间变化曲线。     

复合材料板受低速冲击时能量吸收的实验研究

利用落锤装置，对玻纤／环氧和碳纤／环氧两种复合材料层合板进行了低速低能量的冲击实验研究。利用传感器技术记录了落锤冲击板过程中速度随时间变化曲线，计算了冲击动能和材料损伤时的能量吸收。通过数学处理得到了冲击载荷和冲击点位移随时间变化曲线。还对多次冲击的能量吸收问题进行了实验研究。     

FAE爆炸抛撒后云雾液滴尺寸的测量

利用Dobbins激光散射的方法建立了一套测量FAE爆炸抛撒后远场云雾液滴尺寸的测量系统,研究了FAE爆炸抛撒后液滴Sauter平均直径在不同空间位置随时间的变化过程。得出的散射光强以及Sauter平均直径随时间的变化表明,云雾区的液滴Sauter平均直径在固定点随时间的增加呈减小的趋势,而云雾区的宽度和云雾区液滴的Sauter平均直径则随距爆心距离的增加而增加。     

轴向移动系统的参数振动问题研究进展

对近二十年来轴向移动系统(移动弦，移动梁和移动带等)的参数振动研究进展进行了详细的评述，特别关注了轴向张紧力和移动速度随时间改变时轴向移动系统的参数振动特性和稳定性等问题。文章首先讨论了所研究问题的控制方程。然后详细说明了目前研究中人们较为关注的几个重点问题，如参数激励的形式，求解方法和所研究的问题等。接着在其后的两节中，分别评述了在张紧力和移动速度随时间变化时，轴向移动弦和轴向移动梁的振动问题近年来的研究进展，详细、深入讨论了模型的类型、张紧力和轴向移动速度随时间变化的形式以及在研究中使用的解题方法和系统的振动特性(振动响应、固有频率和动态稳定性)等；最后给出了在此领域今后研究中应关注的问题。     

风沙跃移运动发展过程及静电力影响的数值模拟

建立了描述风沙跃移运动发展过程以及风场一沙粒互馈机制的风沙跃移运动数值模型，模型中考虑了风场一沙粒之间酌耦合作用以及静电力的影响，同时风场是随时间变化的．模拟了风沙跃移运动从起始阶段至风沙流达到自平衡状态的整个发展过程所需的时间，起沙率与单宽输沙率随时间变化曲线，以及达到稳定后的单位面积输沙率沿高度分布以及贴地风速廓线的影响．计算结果表明，当沙粒平均带电量为60μC／kg时，计算所得的单宽输沙率以及输沙率沿高度分布与实验结果吻合得较好．     

非爆炸且不可还原农用硝酸铵热分解反应动力学的研究

利用加速度量热仪分别对普通硝酸铵和非爆炸且不可还原农用硝酸铵的绝热分解过程进行分析,分析结果通过动力学模型编程在微机控制系统上进行数据分析处理,得到了绝热分解温度与压力随时间的变化曲线、自加热速率随温度的变化曲线、准速率常数随温度的变化曲线、最大温升速率所需时间随温度的变化曲线,计算了分解动力学参数表观活化能、指前因子、不可逆温度和自加速分解反应温度。所有实验结果都表明,非爆炸且不可还原农用硝酸铵具有良好的热稳定性、安全性。     

钢丝的微动磨损及其对疲劳断裂行为的影响研究

采用自制的钢丝微动磨损试验机考察了钢丝的微动摩擦磨损性能，随后将经过一定时间微动磨损试验后的钢丝试样在液压伺服疲劳试验机上进行拉一拉疲劳试验，进而探讨了微动摩擦系数和微动磨损深度随微动磨损试验时间和接触载荷的变化关系；并利用扫描电子显微镜分析了试样磨痕和磨屑的表面形貌．结果表明，在较大的微动振幅下，钢丝的微动摩擦系数变化幅度不大，微动磨损深度随微动磨损试验时间和接触载荷的增加而增大；微动磨损试验后钢丝试样的疲劳寿命同磨损深度成反比关系；可以将疲劳断口划分为4个区域，其同钢丝试样的疲劳断裂过程相对应．     

不同风场下TNT炸药爆炸烟云的扩散模型及特性

为获取不同风场下TNT爆炸烟云扩散时空分布规律与高度变化模型，本文理论描述了爆炸烟云扩散过程与机理，开展了不同水平风速下烟云扩散的计算流体力学（computational fluid dynamics, CFD）仿真和外场时空分布实验，建立了不同水平风速下烟云高度随时间变化模型及烟云最终高度计算模型，分析了烟云扩散过程中形态、温度、密度、速度变化规律。研究结果显示:CFD方法仿真烟云分布结果与实验结果基本一致，大气稳定且无风条件下烟云高度随时间呈指数0.5的幂函数关系，最终高度与爆炸当量可拟合为指数0.47的幂函数模型；水平风会加快烟云与空气混合的速度，导致幂函数模型中指数参数随风速变大而呈线性减小规律，风速越大烟云上升速度衰减越快、上升时间越短、最终高度越低。     

油气条件下供油时间对弹流润滑性能的影响分析

采用油气发生器,通过润滑剂厚度测量试验,建立了表面油层随供油时间变化关系.基于点接触乏油润滑模型和滚道表面油膜衰减模型研究了不同速度、载荷和表面粗糙度条件下自由表面油层厚度对润滑性能的影响.结果表明油气润滑条件下建立充分供油条件所需时间基本不随工况条件而变化,存在最佳供油时间和供油间隔.     

Maxwell粘弹性球体的湿应力

谷物烘干时，谷粒内部的热－湿应力太大，可能使谷粒出现裂纹．基于这一实际问题，本文研究了当初始湿度和平衡湿度给定时，Ｍａｘｗｅｌ粘弹性圆球内的湿应力分布，及其随时间的变化情况．     

地下开采过程损伤场演化与地表变形的时变分析

以形状随时间变化的物体——时变体为研究对象，将损伤理论与时变力学结合，引入与时变过程相关的损伤参数，形成损伤时变力学分析方法。针对岩石介质特性给出了弹性损伤时变力学本构方程，并利用虚功原理建立相应数值化方法和分析过程。利用损伤时变力学分析方法对某地下煤层开采过程进行计算机仿真分析，给出形状时变引起的损伤场与地表移动的动态演化过程，并对比了非时变以及施工分析结果。研究表明，损伤时变分析可得到连续变化的位移及损伤演化图，相比非时变的常规分析和施工分析能更好地模拟连续施工，为工程施工分析与预测提供更加科学和有效的手段。为实现开采过程的经济和安全，应该采用损伤时变力学的分析方法。     

Parametric variational solution of linear-quadratic optimal control problems with control inequality constraints

A parametric variational principle and the corresponding numerical algo- rithm are proposed to solve a linear-quadratic （LQ） optimal control problem with control inequality constraints. Based on the parametric variational principle, this control prob- lem is transformed into a set of Hamiltonian canonical equations coupled with the linear complementarity equations, which are solved by a linear complementarity solver in the discrete-time domain. The costate variable information is also evaluated by the proposed method. The parametric variational algorithm proposed in this paper is suitable for both time-invariant and time-varying systems. Two numerical examples are used to test the validity of the proposed method. The proposed algorithm is used to astrodynamics to solve a practical optimal control problem for rendezvousing spacecrafts with a finite low thrust. The numerical simulations show that the parametric variational algorithm is ef- fective for LQ optimal control problems with control inequality constraints.     

New augmented Lyapunov–Krasovskii functional approach to stability analysis of neural networks with time-varying delays

This paper is concerned with the problem of stability analysis for neural networks with time-varying delays. By constructing a newly augmented Lyapunov functional and some novel techniques, delay-dependent criteria to guarantee the asymptotic stability of the concerned networks are derived in terms of linear matrix inequalities (LMIs). The improvement of feasible region of the proposed criteria comparing with the previous works is shown by two numerical examples.     

Linear feedback controller design method for time-delay chaotic systems

Based on the stability theory of time-delay systems, this paper discusses chaos control and synchronization problem of time-delay chaotic systems. Through the combining of a new theorem and the characters of the chaotic system, we have designed a linear controller to realize chaos control and synchronization for Lorenz system with time-varying lags. Finally, numerical simulations are provided to verify the effectiveness and feasibility of the developed method.     

Pinning control of spatially and temporally complex dynamical networks with time-varying delays

In the present paper, two types of complex delayed dynamical networks with spatially and temporally varying state variables are proposed. The first is that all nodes in the network have the same time-varying delay. The second is that different nodes have different time-varying delays. We respectively investigate the stabilization problem of these two types of complex network models by pinning a small fraction of nodes with negative feedback controllers. With the help of Lyapunov functionals and some inequality techniques, several asymptotic stability and exponential stability conditions are established. Finally, numerical simulations are presented to illustrate the effectiveness of the results obtained here.     

On improved passivity criteria of uncertain neural networks with time-varying delays

In this paper, the problem of passivity analysis for uncertain neural networks with time-varying delays is considered. By constructing an augmented Lyapunov–Krasovskii’s functional and some novel analysis techniques, improved delay-dependent criteria for checking the passivity of the neural networks are established. The proposed criteria are represented in terms of LMIs (linear matrix inequalities) which can be easily solved by various convex optimization algorithms. Two numerical examples are included to show the superiority of our results.     

Passivity analysis of uncertain neural networks with mixed time-varying delays

This paper addresses the passivity problem for uncertain neural networks with both discrete and distributed time-varying delays. It is assumed that the parameter uncertainties are norm-bounded. By construction of an augmented Lyapunov–Krasovskii functional and utilization of zero equalities, improved passivity criteria for the networks are derived in terms of linear matrix inequalities (LMIs) via new approaches. Through three numerical examples, the effectiveness to enhance the feasible region of the proposed criteria is demonstrated.     

Groundwater Fluctuations in Sloping Aquifers Induced by Time-Varying Replenishment and Seepage from a Uniformly Rising Stream

This paper analyses the classical problem of transient surface?Cgroundwater interaction in a stream?Caquifer system under rather realistic conditions. The downward sloping unconfined aquifer is in contact with a constant water level at one end, and a fully penetrating stream at the other end whose water level is rising at a uniform speed. Furthermore, the aquifer is replenished by a vertical time-varying recharge. Closed form analytical expressions for hydraulic head and flow rate in the aquifer are obtained by solving the linearized Boussinesq equation using Laplace transform method. Effects of aquifer parameters on transient water table and flow rate are illustrated with a numerical example. To assess the efficiency of the linearization method, analytical solutions are compared with numerical solutions of the corresponding non-linear equation.     

Exponential synchronization of stochastic delayed discrete-time complex networks

This paper is concerned with the problem of synchronization for stochastic discrete-time drive-response networks with time-varying delay. By employing the Lyapunov functional method combined with the stochastic analysis as well as the feedback control technique, several sufficient conditions are established that guarantee the exponentially mean-square synchronization of two identical delayed networks with stochastic disturbances. These sufficient conditions, which are expressed in terms of linear matrix inequalities (LMIs), can be solved efficiently by the LMI toolbox in Matlab. A particular feature of the LMI-based synchronization criteria is that they are dependent not only on the connection matrices in the drive networks and the feedback gains in the response networks, but also on the lower and upper bounds of the time-varying delay, and are therefore less conservative than the delay-independent ones. Two numerical examples are exploited to demonstrate the feasibility and applicability of the proposed synchronization approaches.     

Robust dissipativity analysis of neural networks with time-varying delay and randomly occurring uncertainties

This paper investigates the problem of robust dissipativity analysis for uncertain neural networks with time-varying delay. The norm-bounded uncertainties enter into the neural networks in randomly ways, and such randomly occurring uncertainties (ROUs) obey certain mutually uncorrelated Bernoulli distributed white noise sequences. By employing the linear matrix inequality (LMI) approach, a sufficient condition is established to ensure the robust stochastic stability and dissipativity of the considered neural networks. Some special cases are also considered. Two numerical examples are given to demonstrate the validness and the less conservatism of the obtained results.