带有反馈与起动故障的M/G/1重新访问排队系统的适定性分析

文章研究一个带有贝努利反馈且系统服务台经常遭受启动故障的重新访问排队系统模型,利用线性算子半群理论,通过对描述其系统行为的偏微分方程组的研究,证明了该模型所描述的系统所确定的算子是闭稠定耗散算子,生成C0压缩半群,从而得到系统的适定性.在证明1是算子的预解点时,采用了共轭方法.     

The first,the biggest,and other such considerations

We investigate the relation between the underlying dynamics of randomly evolv ing systems and the extrema statistics for such systems. Independent processes, Fokker-Planck processes and Lévy processes are considered.     

An experimental study of impact-induced failure events in homogeneous layered materials using dynamic photoelasticity and high-speed photography

The generation and the subsequent evolution of dynamic failure events in homogeneous layered materials that occur within microseconds after impact were investigated experimentally. Tested configurations include three-layer and two-layer, bonded Homalite specimens featuring different bonding strengths. High-speed photography and dynamic photoelasticity were utilized to study the nature, sequence and interaction of failure modes. A series of complex failure modes was observed. In most cases, and at the early stages of the impact event, intra-layer failure (or bulk matrix failure) appeared in the form of cracks radiating from the impact point. These cracks were opening-dominated and their speeds were less than the crack branching speed of the Homalite. Subsequent crack branching in several forms was also observed. Mixed-mode inter-layer cracking (or interfacial debonding) was initiated when the intra-layer cracks approached the interface with a large incident angle. The dynamic interaction between inter-layer crack formation and intra-layer crack growth (or the so-called “Cook–Gordon Mechanism”) was visualized for the first time. Interfacial bonding played a significant role in impact damage spreading. Cracks arrested at weak bonds and the stress wave intensity was reduced dramatically by the use of a thin but ductile adhesive layer.     

采动诱发岩体移动破坏过程数值模拟研究

本文基于岩石介质的宏观非线性主要是由非均质性和各向异性造成的, 应用新的数值计算软件RFPA(2D), 对采动引起岩体失稳破坏的全过程进了数值模拟研究。     

平面坡体渐进破坏模型及其应用

平面坡体渐进破坏模型旨在通过在坡体稳定性分析中引进渐进坡坏的概念,来较合理地考虑岩土材料的峰值强度和残余强度在稳定性分析中的不同作用。通过与其它稳定性分析方法进行比较以及实例应用研究,证明该计算模型可用于初步判断坡体稳定状态并估算其破坏变形范围。这一研究也说明了水对边坡破坏的重要作用。     

材料的动态损伤和失效

本文对动载荷下材料内部损伤演化过程的研究进行了较为全面、系统的介绍和总结,并对现有的各种动态损伤模型(包括笔者所提出的模型)进行了必要的比较、讨论和评述。     

参数拟二次规划法及其在复合材料失效过程分析中的应用

本文介绍关于不连续线弹性静力学问题的多变量变分原理与相应的参数拟二次规划算法在复合材料层压板强度分析及纤维增强脆性基体材料单元细观失效过程分析中的应用。     

多模式自适应重要抽样法及其应用

针对多模式的可靠性分析，研究了其失效概率计算的自适应重要抽样法，该方法用模拟退火 算法来自动调整每个失效模式的重要抽样函数，使其逐渐趋近于估计方差最小的重要抽样 函数. 对于多个模式系统失效概率的计算，采用混合加权自适应重要抽样的方法, 反映了每个 失效模式对系统失效概率的贡献；对于系统失效模式所含基本变量不全相同的情况，提出了 扩展自适应重要抽样法, 来统一所有失效模式中的基本变量，从而使得混合自适应 重要抽样, 可以方便地求解变量不全相同时的系统失效概率. 对估计值方差和变异系数的计算公 式进行了推导. 验证算例结果, 充分说明方法的合理性与可行性.     

具有多种失效模式的抗震结构的模糊可靠性分析

由于地震荷载和结构抗力具有明显的模糊性,在文献[1,2]中我们提出了具有单一失效模式的抗震结构的模糊可靠性分析.本文将上述概念和方法推广到具有多种失效模式的抗震结构,为此,又提出了结构的“模糊有效域”和“模糊失效域”的概念。