Vibration of circular plate with multiple eccentric circular perforations by the Rayleigh-Ritz method

The free vibration of a circular plate with multiple perforations is analyzed by using the Rayleigh-Ritz method. Admissible functions are assumed to be separable functions of radial and tangential coordinates. Trigonometric functions are assumed in the circumferential direction. The radial shape functions are the boundary characteristic orthogonal polynomials generated following the Gram-Schmidt recurrence scheme. The assumed functions are used to estimate the kinetic and the potential energies of the plate depending on the number and the position of the perforations. The eigenvalues, representing the dimensionless natural frequencies, are compared with the results obtained using Bessel functions, where the exact solution is available. Moreover, the eigenvectors, which are the unknown coefficients of the Rayleigh-Ritz method, are used to present the mode shapes of the plate. To validate the analytical results of the plates with multiple perforations, experimental investigations are also performed. Two unique case studies that are not addressed in the existing literature are considered. The results of the Rayleigh-Ritz method are found to be in good agreement with those from the experiments. Although the method presented can be employed in the vibration analysis of plates with different boundary conditions and shapes of the perforations, circular perforations that are free on the edges are studied in this paper. The results are presented in terms of dimensionless frequencies and mode shapes.     

工程设计的发展趋势和未来

论述了工程设计的发展趋势。介绍了未来社会环境与需求，现代设计概念与方法学和工程设计管理。     

阻尼减振结构参数特性分析及动态优化

对阻尼减振结构参数的关取特性、阻尼材料的温度－振频效应及结构的断面形式对结构损耗因子的影响进行了分析。提出在变温度、振频状态下，实行参数解耦，把阻尼材料参数拟合成多项式方程，进行参数动态优化的方法。最后对推土机行走系的轮式阻尼减振结构进行了实际应用，进行了结构参数优化和试验，结果表明试验数据与理论分析相吻合。     

现代航空发动机健康管理技术与应用

介绍当前航空发动机健康管理系统的发展背景以及现状,讨论航空发动机健康管理系统所采用的几种常用的,如流道分析法,滑油以及碎屑分析法、振动分析等方法,并对每种方法都进行了较为详细的讨论。在流道分析法（GPA）中重点介绍了算法实现以及其优缺点,讨论了其局限性。最后,指出了当前航空发动机健康管理系统所应面对的问题和挑战。     

一种数字频率电压紧急控制装置的设计与实现

介绍了一种频率电压紧急控制装置的设计与实现方法。装置采用32位嵌入式单片机作为核心控制芯片,利用双电压回路进行电压测量,硬件和软件相结合实现频率测量,提高可靠性,确保测量准确。对任一故障的判断和决策都采用多个不同的条件,多重闭锁机制,有效防止误动和拒动;大屏幕液晶实时显示电压、频率等信息。嵌入式双网通信接口,采用国际标准或按用户要求定制通信规约。     

Resonance methods for microwave studies of dielectrics (Review)

The general properties of microwave resonators with dielectric inclusions, which are important in dielectric measurements, are described. The methods for measuring the permittivity and dielectric losses in isotropic and uniaxial dielectrics with the use of cavity, open, and dielectric resonators are considered. Approximations that are often used in the theory and practice of measurements and limit accuracy are analyzed. The formulas used in calculations and results of measurements of the dielectric parameters of various samples, including films, coatings, and substrates, in the range 1.5–75.0 GHz are presented. The possibilities of local measurements and measurements of parameters of media are discussed.     

轮轨关系研究中的力学问题

简单论述世界铁路发展状况和铁路交通运输的优越性。详细论述轮轨关系的研究问题,其研究包含轮轨滚动接触作用和稳定性问题、轮轨粘着和强度、接触表面磨损和滚动接触疲劳破坏、轮轨噪声、轮轨蠕滑率／力理论和轮轨三维弹塑性滚动接触问题。在这些问题研究中,蕴涵十分复杂的力学和强度问题。文中就这方面的研究现状和存在问题以及问题研究的难点进行讨论,并分析今后可能的研究方向。     

Spatially resolved analysis of packaging-induced strains in diode laser bars using the deformation potential effect

Methods of experimental investigations of the stress distributions in semiconductor laser crystals, which are based on the deformation-potential effect, are presented. The results of the development of the system and methods for measuring the spatially resolved emission spectra of laser-diode bars, which are incorporated in radiators produced by the All-Russian Research Institute of Technical Physics, are presented. The values of the packaging-induced stresses in laser-diode bars are quantitatively assessed for several variants of the materials in radiator structures, which differ in their physical and mechanical characteristics.     

实体法铣削仿真效率改善及应用算法

轴向切削深度和径向切削宽度是铣削仿真模型求解的几何边界条件,也称为啮合几何参数。根据对啮合参数提取的三类途径的比较,针对直接布尔操作途径仿真效率低的问题,运用集合论描述了实体法铣削仿真中模拟材料去除的布尔运算过程,从时间复杂性角度分析影响实体法铣削仿真效率的因素,提出改善仿真运行效率的4种途径;在此基础上,从几何造型和切削过程两方面给出在仿真计算位置处布尔运算次数由4次减少为1次的可行性分析,提出在简化布尔运算次数情况下的切削几何边界条件的识别和判断算法,对判断算法的有效性和减少布尔运算的时间复杂性进行分析、给出在铣削力仿真中的应用示例,并说明应用范围,从而在保证切削几何边界条件准确提取的同时提高仿真效率,为铣削力等仿真模型的求解奠定基础,推动相关物理仿真研究成果在工程实际中得到切实应用。     

汽车传动系相关NVH问题的动力学研究论述

总结汽车传动系相关NVH问题的难点,典型振动、噪声现象的特征及产生机理和国内外研究进展,介绍传动系噪声、振动与声振粗糙度(Noise, vibration and harshness, NVH)动力学问题的主要研究内容及路线。从仿真和试验的角度展开论述：在仿真研究中,详细分析系统动力学、多体动力学、结构动力学模型及系统、结构动力学混合模型的四种传动系力学模型及其各自的特点,总结建模所使用的坐标与坐标系,并针对传动系NVH问题的动力学研究,从定量与定性两个方面总结主要的仿真研究方法;在试验研究中,介绍试验研究的主要内容、数据处理的方法及试验的主、客观评价方法。     

用量纲方法分析旋流场中的应力

在全面阐述旋流场应力的基础上,运用量纲分析比较的思想对旋流场中的应力作了分析比较。由分析可知在粘性应力中,切向和径向剪切应力占主导地位;而在湍流条件下,雷诺应力是粘性应力的若干倍数,此倍数在量级上即为雷诺数。由于各应力值的不同,故各应力在旋流场中的作用也各不相同。     

The stereology of projected images

A generalized, geometrical approach is adopted in reviewing the basic relationships of projected structures. Projections of features from a plane to a projection line, and from a three-dimensional foil to a projection plane are considered briefly. The relationships that apply to apparent and total projections are next assembled for lines, surfaces and bounded regions. The properties of convex bodies, the geometrical attributes, and the related projected quantities are enumerated. The inter-relationships of important microstructural parameters are expressed for convex bodies in space, in sections, and in the projection plane. Based on the important concept of total projection, expressions are obtained that correct for truncation and overlap of particles in foils. Approximations to the total projection are developed for lines obscured by surfaces, and for points hidden by surfaces in space. Finally methods for determining size distributions of particles in thin foils are reviewed and recent modifications to the original procedures are discussed.     

应用于油气钻采的磨料水射流喷嘴优化设计与试验研究

为了优化总长度和出口直径被限制的喷嘴的内部结构,进行喷嘴内外流场数值模拟、喷嘴流量系数测试以及喷嘴对砂岩冲蚀深度的试验。对试验结果进行分析表明,各喷嘴射流轴心线上的速度在喷嘴的内部达到最大后开始减小;数值模拟结果和流量系数测试结果相吻合,即喷嘴外部射流速度最大的喷嘴流量系数也最大,该喷嘴的工作性能最好;在设计试验的喷嘴范围内,进口收缩角为30°,出口圆柱段长度为11mm的喷嘴性能最好,其对砂岩的冲蚀深度高出其他喷嘴的200mm~300mm。     

A mixed integer programming formulation for scheduling of virtual manufacturing cells (VMCs)

We present a multi-objective mixed integer programming formulation for job scheduling in virtual manufacturing cells (VMCs). In a VMC, machines are dedicated to a part family as in a regular cell, but machines are not physically relocated in a contiguous area. Cell configurations are therefore temporary, and assignments are made to optimize the scheduling objective under changing demand conditions. We consider the case where there are multiple jobs with different processing routes. There are multiple machine types with several identical machines in each type and are located in different locations in the shop floor. The two scheduling objectives are makespan minimization and minimizing total traveling distance. Since batch splitting is permitted in the system, scheduling decisions must tell us the (a) assignment of jobs to the machines, (b) the job starting time at each machine, and (c) the part quantity processed on different machines due to batch splitting. Under these decision variables, the objective function is to minimize the sum of the makespan and total traveling distance/cost. Illustrative examples are given to demonstrate the implementation of the model.     

薄板成形计算机仿真中摩擦模型的研究进展

概括和总结了薄板冲压成形计算机仿真中摩擦模型的研究现状，指出了建立实际的摩擦模型应注意的一些问题，讨论了该领域有待解决的问题，指出了进一步的研究发展方向。     

卷到卷制造中基板横向振动研究进展

运动基板的横向振动问题已经成为严重限制卷到卷制造效率和质量的关键。详细介绍了卷到卷制造中运动基板横向振动问题的研究概况。讨论了运动基板横向振动的建模方法,以Hamilton原则为例,推导了基板横向振动的控制方程,结合解析求解和数值求解方法,计算横向振动的频率和模态。分析了基板张力、速度、材料特性、中间支撑和外界环境等因素对基板自由振动特性及动态稳定性的影响。研究了基板参数振动特性,考虑基板张力和速度两个主要参数的波动,阐述了基板横向振动被动控制和主动控制方法。联合基板纵向张力控制和侧向纠偏控制,讨论了横向振动控制在卷到卷制造中的工程应用。最后,展望卷到卷制造工程应用中基板横向振动研究的关键问题。     

无蜗壳风机研发中的几个问题

在无蜗壳风机研发中发现三个问题:市场上有两类不同的无蜗壳风机,但命名混淆;按进气试验法得到的出口总压和效率偏大;采用旋转无叶扩压器能提高性能,但缺乏定量数据说明.本文通过调研和数值模拟对这些问题提出看法.     

磨削加工过程建模的研究进展

综述了磨削加工过程的几何建模过程中砂轮几何模型的建立方法、磨粒去除工件材料机制的研究进展,指出了其中存在的一些问题;阐述了磨削加工过程的物理建模过程中磨削力机理解析建模、经验公式建模的研究动态,分析了这些建模方法的局限性,简要介绍了磨削温度场建模中能量分配和热源形状的研究进展;讨论了对磨削加工过程进行数值模拟所存在的一些难点。     

Gaseous microemboli: sources, causes, and clinical considerations

Patients undergoing open-heart surgery are exposed to gaseous microemboli (GME) from several sources, including bubble oxygenators, which are used in a majority of cases for cardiopulmonary bypass. If present in large quantities, GME can reduce blood flow and delivery of oxygen to tissues and may be responsible, in part, for some of the complications that commonly follow cardiopulmonary bypass. Gaseous microemboli are defined, and the causes of this phenomenon are examined. The literature from the last 30 years on this topic is also reviewed, and measures for reducing GME during cardiopulmonary bypass are recommended. Current considerations for users of cardiopulmonary bypass systems are discussed, and five unanswered questions are raised in the conclusion.     

Arthropod sensilla: morphology and phylogenetic considerations

The structures of different types of arthropod sensilla are compared and theories regarding the evolution of these sensory organs are presented. Arthropod sensilla are built according to a common plan, and are probably homologous to scolopidia. Certain similarities in the structure of sensilla in different arthropod groups can be the result of adaptations to specific environments. The structure of sensilla in insect groups, which are regarded to be ancestral, do not appear to be less sophisticated than in groups considered to be more advanced. The different types of pore systems, as well as the structural differentiations of insect olfactory sensillar types remain unexplained. Olfactory sensilla display a large degree of similarity among terrestrial arthropods, whereas crustacean sensilla diverge in structure. In holometabolous insects larval sensilla appear to be structurally quite advanced, and more complex than in the adult. During the ontogeny of both sensilla and scolopidia, these are differentiated in an epithelial layer, resulting in the formation of both sensory and enveloping cells. The developmental patterns of sensilla in the studied insect groups are similar. During the development of sensilla apoptotic process are usually active.