Equilibrium on line method (ELM) for imposition of Neumann boundary conditions in the finite point method (FPM)

Equilibrium on line method (ELM) for imposition of Neumann boundary conditions in the finite point method (FPM) is presented. In contrary to weak‐form‐based methods, strong‐form‐based methods such as the FPM are often unstable and less accurate, especially for problems governed by partial differential equations with Neumann (derivative) boundary conditions. In this paper, a truly meshless approach for imposition of Neumann boundary conditions in the FPM is proposed and adopted for 2D elasticity analyses. In the proposed method, equilibrium on lines on the Neumann boundary conditions is satisfied as Neumann boundary condition equations. Numerical studies show that this method for imposition of Neumann boundary is simple to implement and computationally efficient and also leads to more stable and accurate results. Copyright © 2006 John Wiley & Sons, Ltd.     

基于有限质点法的结构屈曲行为分析

有限质点法是一种新颖的结构分析方法,它以向量力学和数值计算为基础,将结构离散为质点群,采用牛顿第二定律描述这些质点的运动。该方法中引入移动基础架构求解结构单元内力。采用显示时间积分求解运动方程,避免了迭代求解非线性方程组。该文采用有限质点法分析结构的屈曲行为。以空间杆单元为例推导了有限质点法计算公式。利用自编程序,对空间杆系结构的屈曲行为进行了模拟。在不经过任何特殊处理的情况下,该方法不仅可以越过屈曲极值点,而且能够跟踪结构屈曲后的行为。此外,该方法无需分级加载即可模拟结构的屈曲行为,结构荷载可以在计算分析的初始步全部加在结构上,更符合实际情况。通过算例验证表明有限质点法在结构屈曲行为模拟中的适用性和真实性。     

Coupled finite particle method with a modified particle shifting technology

The conventional SPH method has been frustrated with the low accuracy originated from the particle inconsistency. The finite particle method (FPM) is an improved SPH method with a higher‐order accuracy. However, the numerical accuracy and stability of FPM depend on the uniformity of particles. Facing the disorder particles, the conventional FPM may suffer from an ill‐conditioned corrective matrix and is difficult to conduct longtime simulations. A popular and robust particle regularization scheme is the so‐called particle shifting technology (PST), which can effectively enhance the accuracy and stability of particle methods. In the context of FPM, PST is analyzed and discussed, and a modified PST (MPST) is proposed. Modified PST saves great amount of computational cost with respect to the conventional PST and acquires better features of accuracy and stability. Finally, the coupled FPM method by combining MPST and δ‐SPH is developed to simulate a series of viscous flows. The numerical results indicate that MPST is effective in improving accuracy, stability, and efficiency of PST, and the coupled FPM is shown to be robust for simulating viscous flows and has a higher accuracy and stability.     

Finite Pointset Method for biharmonic equations

Finite pointset method is one of the grid free methods that is used to solve differential equations arising from physical problems. It is a local iterative procedure based on weighted least square approximation technique. In this paper, biharmonic equation with simply supported, clamped and Cahn–Hilliard type boundary conditions, is solved using the finite pointset method. Numerical examples illustrate the efficiency of the method.     

一种时间序列频繁模式挖掘算法及其在WSAN行为预测中的应用

该文提出FPM(Frequent Pattern Mining)算法充分考虑频繁模式在时间序列中出现次数和分布。基于这些不同分布的频繁模式扩展MAMC(Mixed memory Aggregation Markov Chain)模型提出FMAMC(Frequent pattern based Mixed memory Aggregation Markov Chain)模型。将FPM和FMAMC应用到实际的智能楼宇项目中,证明和现有算法相比FPM算法具有较好的时间性能,FMAMC模型能够比MAMC模型更准确的预测WSAN节点行为。     

纳米金刚石对橡胶力学性能的影响

纳米金刚石晶粒细小，小表面积大，可以添加在橡胶中来提高它的力学性能。本文对纳米金刚石添加在天然橡胶、氯橡胶后对其力学性能的影响进行了实验研究，对橡胶老化前后进行了力学性能测试。结果表明，纳米金刚石对天然橡胶的性能基本无影响，对氟橡胶老化前起有利作用，对老化后的氟橡胶基本无影响。     

空气和液压油环境中几种耐油橡胶材料γ辐射效应研究

通过提高辐射剂量率,缩短辐射时间,研究了空气和液压油环境中的丁腈橡胶(NBR)、氯丁橡胶(CR)、氟橡胶(FPM)和聚氨酯橡胶(PU),4种耐油橡胶材料在不同吸收剂量和不同剂量率下硬度与质量的变化。结果表明,在0~200kGy范围内,PU的γ辐射效应受所处介质与吸收剂量的影响;剂量率对处于相同介质中的NBR、CR、FPM、PU的辐射效应影响不大;NBR与液压油的物质交换最为明显。     

面向分布式应用管理的混合故障诊断模型

由于分布式应用的动态性、复杂性,传统的人工管理已经不能做到很好的故障管理,应用自主计算的思想实现管理成为一种解决问题的方法.研究基于故障诊断技术实现系统自感知.首先,根据对分布式应用故障管理的分析,提出一种混合故障诊断模型,将故障诊断的过程分为应用服务故障诊断和网络服务故障诊断2个阶段;其次,由于对网络故障症状的观察存在不确定和不准确的特点,将故障诊断模型映射到贝叶斯网络上进行不确定性推理;最后,重点研究了在多层FPM模型中进行推理的算法,给出一种基于变量消元算法的改进算法,实验证明改进算法可加速推理过程.     

氟橡胶与丁腈橡胶并用的研究

将氟橡胶与丁腈橡胶进行共混 ,采用过氧化二异丙苯 /三烯丙基异氰脲酸酯作为共硫化体系 ,测试了不同并用比硫化胶的常规性能及耐化学介质性。结果表明 ,并用胶所采用的共硫化体系是成功的 ,并用胶性能优良。三烯丙基异氰脲酸酯可显著提高氟橡胶与丁腈橡胶的硫化度。     

Gordon板块元算法稳定性研究及其在电磁散射中的应用

本文在分析平面板元上Ｇｏｒｄｏｎ算法与傅里叶变换算法数值稳定性的基础上指出：板块元边缘的任意分割会导致ＦＴ－ＰＰＭ的坏条件计算问题；而板块元边缘的任意分割对于Ｇ－ＰＰＭ而言都是好条件计算问题。