Comparison of the Non-Interaction and Differential Schemes in predicting the Effective Elastic Properties of Fractured Media

The non-interaction approximation (NIA) formulated in compliances and the differential effective media (DEM) schemes are believed to be the most accurate theories for predicting the effective elasticity of fractured solids. While their predictions are always plausible, the DEM yields consistently softer effective properties than does the NIA. Here I compare these two theories with the finite element (FE) modeling for arrays of randomly located, parallel, penny-shaped cracks. I perform FE simulations by applying the homogeneous strain and homogeneous stress boundary conditions that establish the upper and lower bounds for the effective stiffness tensor. These numerically derived bounds demonstrate that the NIA is more accurate than the DEM.     

A Modified Born Approximation for Scattering in Isotropic and Anisotropic Elastic Solids

A new modified Born approximation (MBA) is presented that significantly extends the range of validity of the Born approximation to include the pulse-echo responses of strongly scattering inclusions in an elastic solid. The MBA also improves on the doubly distorted Born approximation (DDBA), a similar modification of the Born approximation that has been recently developed. These improvements are demonstrated by comparing the MBA, the Born approximation and the DDBA with the exact separation of variables solution for spherical inclusions in isotropic media. Furthermore, it is shown that the form of the MBA remains valid even for the pulse-echo scattering of an anisotropic inclusion in a general anisotropic elastic medium so that it is potentially applicable to a wide class of flaws and materials.     

变速磁流变半主动悬架车辆与随机路面系统的模糊振动控制

建立半主动悬架车辆和随机路面系统模型,在采用磁流变减振器的基础上,应用模糊逻辑控制理论,进行车辆半主动悬架模糊控制器的设计,获得在模糊控制理论下可调阻尼力随时间变化的关系,应用simulink编制车路模型的仿真程序,研究在模糊控制算法下的匀变速行驶车辆路面系统平顺性问题。计算结果表明,与被动悬架的车辆相比,模糊控制的磁流变半主动悬架车辆可以改善行驶平顺性,同时还可减少车对路面的作用力,这对于车路系统是有利的,对于深入分析路面结构动力响应也具有重要的参考价值。     

双中心矩阵反问题及其在电网络理论中的应用

本文研究双中心矩阵反问题。建立了双中心矩阵反问题的最小二乘解,得到了解的具体表达式。讨论了用双中心矩阵反问题的解构造给定矩阵的最佳逼近问题,给出该问题有解的充分必要条件和解的表达式。设计了相应的算法并给出了其在电网络理论中的应用。     

基函数网络逼近:进展与展望

从神经网络,统计估计、逼近论、调和分析等角度研究了多变量目标函数的逼近问题,评述了这些工具的逼近效率和能力,同时研究和评述了脊波（Ridgelet)的发展现状及应用前景,并指这一领域研究的有关问题以及在信号和图像处理中的应用。     

Theory construction in design research: criteria: approaches, and methods

Design involves solving problems, creating something new, or transforming less desirable situations to preferred situations. To do this, designers must know how things work and why. Understanding how things work and why requires us to analyze and explain. This is the purpose of theory. The article outlines a framework for theory construction in design. This framework will clarify the meaning of theory and theorizing. It will explain the nature and uses of theory as a general concept. It will propose necessary and sufficient conditions for theory construction in design. Finally, it will outline potential areas for future inquiry in design theory.     

基于前景理论的项目管理计划行为分析

由于现代项目日益复杂和项目所处环境的日益多变,项目所面临的不确定性和风险都在增加。其中,由于行为不确定性所导致的风险日益引起人们的关注。文章以“前景理论”为依托,对项目决策者在一个单活动项目中的计划行为进行了分析,并建立了决策前景值模型。通过确定项目计划者的主观感知费用函数,定义了决策过程中的参照点,并给出了前景值的计算方法;通过模拟不同的决策环境和决策方案,配合数据仿真,对“期望效用理论”和“前景理论”的决策行为进行了讨论。结果表明,“前景理论”在描述计划行为时能够在一定程度上克服“期望效用理论”的不足,可以较准确地刻画决策者在不确定性条件下的计划行为,为后期进一步深入分析奠定了理论基础。     

Fluid mixtures in narrow cylindrical pores: Computer simulation and theory

We discuss the simulation results of phase separation of a binary Lennard-Jones mixture in a cylindrical pore induced by a temperature quench. The liquid-vapor phase separation proceeds in two stages involving different time scales. First, following the growth of density fluctuations, mechanical equilibrium is rapidly established when the system splits into a dense and a dilute phase. Material equilibrium, however, is reached via the mutual diffusion of the two components and this proceeds on an appreciably longer time scale. We briefly address the rounding of a first-order phase transition in a cylinder. In particular, we explore the possibility of multiple domains of gas and liquid when the aspect ratio is very large. Finally, we introduce an extension of Tarazona's nonlocal density function to binary mixtures of arbitrary size. The new theory is successfully tested against simulations of an additive hard-sphere mixture against a hard wall.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

国外油气井用液体钝感电雷管及其结构

介绍了国外油气井用液体钝感电雷管及其结构特征，同时列出了其中部分电雷管的电性能参数。     

战略集团演变及其与绩效关系的博弈分析

从企业行为和产业环境的角度,在分析战略集团演变的基础上,运用博弈论的方法探讨了战略集团与绩效的关系,为理解两者间的关系提供了一个独特的视角。     

Server-Proxy-Users系统收入分配的对策论模型及解的存在性

用对策论研究了Server-Proxies-Users系统中Server、Proxies和Users之间的收入分配问题，建立了收入分配的对策论模型，得到了三层规划模型。根据三层规划模型的特殊性，把它分解成两个双层规划模型，同时证明了模型的解的存在性。     

基于灰色理论的电站机组状态监测与故障诊断方法

本文主要研究了灰色理论在大型旋转机械的状态监测与故障诊断中的方法与应用问题。鉴于一般关联度分析方法在故障诊断应用中没有考虑到特征参数对诊断结果的不同影响,本文提出了加权关联度这一新概念,并给出了加权关联度用于旋转机械诊断中的方法与步骤。这种诊断方法能根据诊断结果采用自学习修正方法来修正关联度参数,提高诊断的准确度,并有很好的前景。     

Porous soft magnetic material: The maghemite microsphere with hierarchical nanoarchitecture and its application in water purification

Porous soft magnetic material is a member of soft magnetic material family having large surface area. This kind of material has vast potential in the surface-related applications. In this paper, a kind of maghemite (γ-Fe₂O₃) with large surface area, 82.7 m²/g, specifically, was obtained by the solvothermal method and subsequent calcining process. As shown in the test results, the maghemite microsphere has no magnetic memory in the magnetic field since the residual magnetization is 0.7 emu/g. In the waste water treatment process, Rhodamine B, a model organic pollutant in the water, was removed through the adsorption and desorption cycles by the maghemite microspheres. The maghemite microspheres in the water can be recycled easily by a magnetic separation procedure and regenerated in ethanol at room temperature.     

The Pole Term in Linear Response Theory: An Example From the Transverse Response of the Electron Gas

In linear response theory, the dielectric response at zero frequency sometimes appears to violate the f-sum rule, which has apparent implications for causality. Here, we study the origin of this apparent discrepancy, focusing on Lindhard’s formula for the transverse response of the electron gas. At non-zero frequency, first-order poles contribute to the imaginary part of the dielectric function in the usual way. At zero frequency, second-order poles contribute in a way which forces a careful consideration of the notation of summation and integration to avoid an error. A compact formula for the contribution of the second-order poles is presented. The sense in which the f-sum rule is satisfied is discussed.     

Substitution of Cu by Fe in the superconducting ceramic oxide EuBa2Cu3Oy: Structure, electrical conductivity, and microwave response

A series of EuBa₂(Cu_1–x Fe _x )₃O_y (0.0x0.15) ceramics were prepared and examined by thermogravimetric analysis, X-ray powder diffraction, electrical resistance measurements, and a magnetically modulated microwave absorption technique. The oxygen content (y=6.98±0.03), determined by thermogravimetric analysis in a reducing atmosphere, was independent of the iron concentration forx0.12. The introduction of iron into the EuBa₂Cu₃O _y lattice, via substitution into copper sites, effects a progressive decrease in the superconducting transition temperature with increasing iron concentration. Normal-state conductivity similarly progresses from a low resistivity and negative temperature coefficient behavior, to a semiconducting-like response at the high iron concentrations. X-ray powder diffraction measurements indicate that material containing 6% iron and above is tetragonal, yet it remains superconducting with up to at least 12% iron.     

The comparison of multi-objective particle swarm optimization and NSGA II algorithm: applications in centrifugal pumps

In the present study, multi-objective optimization of centrifugal pumps is performed in three steps. In the first step, efficiency (η) and the required net positive suction head (NPSHr) in a set of centrifugal pumps are numerically investigated using commercial software. Two meta-models based on the evolved group method of data handling (GMDH) type neural networks are obtained in the second step for modeling of η and NPSHr with respect to geometrical design variables. Finally, using the obtained polynomial neural networks, a multi-objective particle swarm optimization method (MOPSO) is used for Pareto-based optimization of centrifugal pumps considering two conflicting objectives, η and NPSHr. The Pareto results of the MOPSO method are also compared with those of a multi-objective genetic algorithm (NSGA II). It is shown that some interesting and important relationships as useful optimal design principles involved in the performance of centrifugal pumps can be discovered by Pareto-based multi-objective optimization of the obtained polynomial metamodels representing η and NPSHr characteristics.     

The Theory of Critical Distances to estimate the static strength of notched samples of Al6082 loaded in combined tension and torsion. Part I: Material cracking behaviour

The present paper is the first of a two-part series reporting an experimental and theoretical study of the fracture of circumferentially notched samples of a commercial aluminium alloy, i.e. Al6082, subjected to tension, torsion and mixed tension/torsion loading. The overall aim of the work was to investigate the use of a particular method of failure prediction, known as the Theory of Critical Distances. This first part reports the experimental data - load-deflection curves and observed material failure modes - and discusses the consequences of these findings for the development of the theory, which is covered in the second part. It was observed that relatively blunt notches loaded in tension failed by a conventional ductile fracture mode similar to plain (unnotched) specimens. However, in tensile specimens containing sharp notches, failure occurred via the initiation, stable propagation and, finally, unstable propagation, of circumferential ring cracks. Under torsional loading, and independent of the notch root radius, static failures of the tested samples always occurred by the formation and stable propagation of ring cracks. Under mixed-mode loading there was a gradual transition between the ductile and brittle modes and between stable and unstable cracking. For all types of loading, it was observed that crack initiation always coincided with peak loading conditions, and that cracks invariably grew on the plane perpendicular to the specimen’s longitudinal axis.