Coupled thermal/mechanical analysis for the fracture of functionally graded materials under transient thermal loading

A comprehensive treatment of fracture of functionally graded materials (FGMs) is provided. It is assumed that the material properties depend only on the coordinate perpendicular to the crack surfaces and vary continuously along the crack faces. By using a laminated composite plate model to simulate the material non-homogeneity, an algorithm for solving the system based on Laplace transform and Fourier transform techniques is presented. Unlike earlier studies that considered certain assumed property distributions and a single crack problem, the current investigation studies multiple crack problem in the FGMs with arbitrarily varying material properties. Transient thermal stresses are presented. Project supported by the National Natural Science Foundation of China (Nos 10102004 and 19902003).     

再谈静电能的损失

本文从暂态过程的角度和能流的观点分析和讨论电容器并联过程中能量的损失问题.     

A statistical process control approach to selecting a warm-up period for a discrete-event simulation

The selection of a warm-up period for a discrete-event simulation continues to be problematic. A variety of selection methods have been devised, and are briefly reviewed. It is apparent that no one method can be recommended above any other. A new approach, based upon the principles of statistical process control, is described (SPC method). Because simulation output data are often highly autocorrelated and potentially non-normal, the batch means method is employed in constructing the control chart. The SPC method is tested on seven data sets and encouraging results are obtained concerning its accuracy. The approach is also discussed with respect to its ease of implementation, simplicity, generality of use and requirements for parameter estimation.     

热晕瞬态效应的数值模拟

根据瞬态四维（４Ｄ）热晕程序，研究了激光大气传输中热晕瞬变效应及如何过渡到等压近似下的热晕状态，并与等压近似下４Ｄ热晕程序计算结果作了对比，在大约四倍流体力学时间，瞬态４Ｄ热晕程序计算结果逼近等压近似下的结果；另外，还作了相位补偿计算，对光强每平方厘米几千瓦的情况，在理想的自适应光学系统动力学条件下，瞬变阶段的热畸变能相当有效地实时补偿。     

三维热传导型半导体问题的交替方向有限元方法

1　引　　言三维热传导型半导体器件瞬态问题的数学模型由四个非线性偏微分方程描述[1 ,2 ] ,记 Ω为 Ω=[0 ,1 ] 3的边界 ,三维问题-Δψ =α( p -e+ N( x) ) ,　　 ( x,t)∈Ω× [0 ,T] ,( 1 .1 ) e t= . ( De( x) e-μe( x) e ψ) -R( e,p,T) ,　 ( x,t)∈Ω× ( 0 ,T] ,( 1 .2 ) p t= . ( Dp( x) p +μp( x) p ψ) -R( e,p,T) ,　 ( x,t)∈Ω× ( 0 ,T] ,( 1 .3 )ρ( x) T t-ΔT =[( Dp( x) p +μp( x) p ψ) -( De( x) e-μe( x) e ψ) ] . ψ,　　　　　　 ( x,t)∈Ω× ( 0 ,T] . ( 1 .4 )ψ( x,t) =e( x,t) =p( …     

船舶液压推进的可行性探讨

通过对液压推进系统的能量传递方式，扭矩特性和转速控制的分析，介绍了液压推进的优点，对液压推进的可行性作了初步探讨。     

杜芬方程的1/3纯亚谐解及过渡过程的分形特征研究

通过谐波平衡法和数值积分法研究了杜芬方程的1／3纯亚谐解．提出假设解，找出了亚谐频域，并对参数变化的过渡过程的敏感性和初始值扰动的过渡过程进行了研究．考察了亚谐响应幅值系数对阻尼的敏感性及亚谐振动谐波成分的渐近稳态性．此外，运用广义分形理论对杜芬方程纯亚谐解过渡过程进行了分析．分析表明，广义维数的敏感维数能清楚地描述杜芬方程纯亚谐解过渡过程特征；并对改变初始扰动、阻尼系数、激励幅值情况下，其两个不同频域的杜芬方程纯亚谐解过渡过程的不同分形特性显现出敏感性．     

利用皮秒脉冲激光驱动瞬态X射线激光

报道了利用皮秒激光驱动产生瞬态类镍银X射线激光的实验结果.采用一路脉冲宽度为数百皮秒的激光作为预脉冲，配合另一路皮秒激光作为主脉冲联合驱动平面靶，获得了一定强度的类镍银X射线激光输出，输出能量约为5—10nJ. 关键词： 瞬态X射线激光 长短脉冲联合驱动 皮秒脉冲激光     

An Extremal Problem Arising in the Dynamics of Two-Phase Materials That Directly Reveals Information about the Internal Geometry

In two-phase materials, each phase having a non-local response in time, it has been found that for some driving fields the response somehow untangles at specific times, and allows one to directly infer useful information about the geometry of the material, such as the volume fractions of the phases. Motivated by this, and to obtain an algorithm for designing appropriate driving fields, we find approximate, measure independent, linear relations between the values that Markov functions take at a given set of possibly complex points, not belonging to the interval [-1,1] where the measure is supported. The problem is reduced to simply one of polynomial approximation of a given function on the interval [-1,1] and, to simplify the analysis, Chebyshev approximation is used. This allows one to obtain explicit estimates of the error of the approximation, in terms of the number of points and the minimum distance of the points to the interval [-1,1]. Assuming this minimum distance is bounded below by a number greater than 1/2, the error converges exponentially to zero as the number of points is increased. Approximate linear relations are also obtained that incorporate a set of moments of the measure. In the context of the motivating problem, the analysis also yields bounds on the response at any particular time for any driving field, and allows one to estimate the response at a given frequency using an appropriately designed driving field that effectively is turned on only for a fixed interval of time. The approximation extends directly to Markov-type functions with a positive semidefinite operator valued measure, and this has applications to determining the shape of an inclusion in a body from boundary flux measurements at a specific time, when the time-dependent boundary potentials are suitably tailored. © 2022 Wiley Periodicals, Inc.