Static and free vibration analyses of functionally graded porous variable-thickness plates using an edge-based smoothed finite element method

The main purpose of this paper is to present numerical results of static bending and free vibration of functionally graded porous (FGP) variable-thickness plates by using an edge-based smoothed finite element method (ES-FEM) associate with the mixed interpolation of tensorial components technique for the three-node triangular element (MITC3), so-called ES-MITC3. This ES-MITC3 element is performed to eliminate the shear locking problem and to enhance the accuracy of the existing MITC3 element. In the ES-MITC3 element, the stiffness matrices are obtained by using the strain smoothing technique over the smoothing domains formed by two adjacent MITC3 triangular elements sharing an edge. Materials of the plate are FGP with a power-law index (k) and maximum porosity distributions (Ω) in the forms of cosine functions. The influences of some geometric parameters, material properties on static bending, and natural frequency of the FGP variable-thickness plates are examined in detail.     

军用车载电源异常电压监测模块的研制

对由蓄电池供电的某军用特种车辆供电系统的异常电源信号进行监测模块的设计,为系统控制终端进行分析及故障排除提供参考数据。监测模块采用C8051F040单片机为控制核心,通过对"系统DC26V"和"系统DC5V"电源进行监测,记录超出正常范围的异常电压值,并可以通过RS-485通信方式将异常数据上传到控制终端。该模块具有体积小,采集速度快,记录时间标记和运行稳定的特点。通过实际应用证明可以准确地记录各种在运行过程中电源异常的情况。     

作战系统MAS中的作战行动域与实际组元逻辑关系分析

建立作战系统多Agent系统(Multi-Agent System,MAS)组织,必须首先建立由作战系统实际组元到Agent的映射。围绕作战系统MAS的建立,在提出由作战系统实际组元到Agent的映射过程与方法的基础上,提出了作战系统领域概念视图、作战行动域及其各层次概念、实际组元逻辑关系分析的基本方法,为实现基于多Agent的作战系统建模与仿真奠定基础。在基于多Agent的信息化战场多传感器仿真演示系统中,证明了该方法的可行性与有效性。     

Bayesian inference based on partial monitoring of components with applications to preventive system maintenance

Consider a binary, monotone system of n components. The assessment of the parameter vector, θ, of the joint distribution of the lifetimes of the components and hence of the reliability of the system is often difficult due to scarcity of data. It is therefore important to make use of all information in an efficient way. For instance, prior knowledge is often of importance and can indeed conveniently be incorporated by the Bayesian approach. It may also be important to continuously extract information from a system currently in operation. This may be useful both for decisions concerning the system in operation as well as for decisions improving the components or changing the design of similar new systems. As in Meilijson [12], life‐monitoring of some components and conditional life‐monitoring of some others is considered. In addition to data arising from this monitoring scheme, so‐called autopsy data are observed, if not censored. The probabilistic structure underlying this kind of data is described, and basic likelihood formulae are arrived at. A thorough discussion of an important aspect of this probabilistic structure, the inspection strategy, is given. Based on a version of this strategy a procedure for preventive system maintenance is developed and a detailed application to a network system presented. All the way a Bayesian approach to estimation of θ is applied. For the special case where components are conditionally independent given θ with exponentially distributed lifetimes it is shown that the weighted sum of products of generalized gamma distributions, as introduced in Gåsemyr and Natvig [7], is the conjugate prior for θ. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 551–577, 2001.     

GM(1,1)和SVR的雷达电子部件状态趋势预测模型

为提高雷达电子部件状态趋势预测的精度,根据测试数据特点,提出了基于GM(1,1)与支持向量机回归(SVR)的组合预测模型。采用粒子群优化算法分别对GM(1,1)和SVR模型进行了改进,提高了单一模型的预测精度。在此基础上,结合GM(1,1)模型对趋向性数据的预测优势和SVR模型对数据波动的强适应性,达到了取长补短、相得益彰的效果。实验结果表明该组合模型不但具有更高的预测精度,而且对不同预测对象有更强的适应能力。     

动态路由算法研究

北电多业务交换机MSS（Multipleservice Switch）7400在公用网和专用网中应用广泛,其路由部分的特点是基本路由和业务路由分开,在基于OSPF基本路由的基础上,采用动态分组路由DPRS和面向通道路由PORS两种业务路由机制,支持面向连接业务和无连接业务,实现单一网络中综合业务的寻址与转发。     

基于dsPIC30F5015的无刷直流电机控制系统

根据管道探测机器人电机驱动控制要求和当前数字控制技术水平状况,提出了以dsPIC30F5015芯片为核心的无刷直流电机数字信号控制系统,并介绍了该控制器的系统功能、电机控制PWM模块工作原理、传感器译码、外围电路设计以及驱动控制系统的软件开发。实践证明该驱动控制系统安全可靠。     

空间推进系统工作过程的模块化建模

建立空间推进系统仿真模块(包括液体管道模块、三通模块、充填模块、推力室模块等)的数学模型.虽然采用的是集中参数方法,但同时考虑了液体的惯性、粘性和压缩性,所以本文建立的常微分方程组能在一定程度上反映供应系统工作过程的分布特性.     

多芯片焊球阵列封装体受热载荷作用数值模拟

针对典型高密度多芯片BGA(焊球阵列)封装体建立三维有限元分析模型,研究不同尺寸封装体在稳态热载荷作用下的结构变形和应力情况,在此基础上引入包含等效梁和危险焊球真实几何形状和间距等在内的简化模型以进行序列分析,研究各设计参数对力学参量的影响。数值结果反映了封装体应力分布及其变化特点,表明影响封装体变形和应力的主要参数;提出的建模方法简便有效,可以方便地用来分析不同类型的BGA封装,并扩展应用至不同的分析目的,为此种结构的设计和优化提供一定参考。     

射频发射模块非线性效应的消除方法

射频模块存在相位特性的非线性效应,群延迟随频率的变化不再是一个常数,并可能造成输出射频信号的波形失真,而影响精密射频信号源的输出精度。基于递归最小二乘算法的自适应滤波器,提出了消除其非线性效应的新方法。并以GPS模拟源为例,利用其自校模块,采用软件无线电和数字信号处理技术,精确估计出射频模块的模型参数。将基带合成信号通过一个数字逆滤波器,以消除相位的非线性和群延迟随频率的变化。利用自编的仿真程序包,在Matlab中进行了相应的模拟计算。仿真结果表明,该方法可有效地消除相位非线性效应对射频信号的影响,输出信号的波形失真在理论上可控制在0.01%以内。