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.     

Anion Substitution in Porous Aromatic Frameworks: Boosting Molecular Permeability and Selectivity for Membrane Acetylene Separation

Precise tailoring of pore chemistry is indispensable for efficient membrane gas separation, particularly for the challenging acetylene system. Here, a strategy called “anion substitution” is reported, to strengthen the interaction between anions and acetylene within the pores, for radically improving gas selectivity and permeability. The anions F⁻ and OH⁻ are infixed in iPAF-1 to replace the original Cl⁻ ion. Their small anionic radii allow retention of the original high porosity of iPAF-1-Cl in iPAF-1-F and iPAF-1-OH. Highly basic F⁻ and OH⁻ confined in the pores attract acidic acetylene strongly and preferentially. Nanoparticles of iPAF-1 are processed to form mixed matrix membranes, represented by iPAF-1-OH/6FDA-ODA. The prepared membranes exhibit remarkable performance in separating acetylene from ethylene and ethane. Transplantation of porous and functional iPAF-1-OH into 6FDA-ODA significantly enhances both acetylene permeability (sevenfold) and permselectivity (fivefold) for acetylene over ethylene and ethane, which is crucial for membrane acetylene gas separation.     

基于场协同理论的冷藏展示柜内流体对流换热分析

目的研究冷藏柜内对流换热机理,增强冷藏柜内流体对流换热效果,提高冷气流冷却效率。方法从冷藏柜出风口角度出发,建立数学模型,通过Ansys流体分析软件对冷藏柜内流场进行模拟仿真,应用场协同理论研究冷藏柜内流体流动及传热机理。结果出风口角度在30°附近时冷藏柜内换热效率较高且温度分布较为均匀,此时商品壁面的存在改变了冷气流流动方向。在壁面增加半圆突起后,气流沿圆弧切线方向流动,改善了速度与温度梯度之间的协同程度,从速度场、温度场及其相互作用的角度增强了冷藏柜内的对流换热效果,整体换热效率提高了38.65%。结论冷藏柜内流体流动及传热强化的根本在于流体的扰动,而出风口角度的改变和壁面凸起的存在加强了商品对流体的扰动,两者共同作用改变了冷藏柜内场的分布,进而提高了冷藏柜整体的冷藏效率,该研究可为冷藏柜的工厂化生产提供参考价值。     

磁流变液摩擦磨损特性研究进展概述

磁流变液作为一种耗能低、出力大、反应快的智能材料,已在诸多工程领域展现出巨大的应用潜力。近年来,磁流变液摩擦磨损特性对材料本身和周边器件的影响受到学术界的广泛关注。本文结合磁流变液摩擦磨损特性的研究现状,对改进磁流变液摩擦性能的处理方法和研究手段进行了概述,并综述了磁流变液壁面滑移的研究进展及其在测试和应用中的影响,着重介绍了目前的研究手段和处理方法的优势与局限及其发展方向。最后,结合磁流变液摩擦磨损特性研究中存在的问题提出了一些观点。     

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。     

Innovation dimensions and firm performance synergy in the emerging market: A perspective from Dynamic Capability Theory & Signaling Theory

ContextIn this rapidly changing business environment, innovation is the key requirement to gain a sustained advantage over competitors. Innovation helps firms grow more quickly than others grow, survive in the harsh & highly competitive business environment, and eventually become a market leader.PurposeIndia is an emerging market, and many companies are entering here and making it highly competitive. The limited study is available to measure the effect of innovation in Indian Business. Thus, the study establishes a relationship between innovation and firm performance in the Indian setting.Design/methodology/approachThis is a perception-based study and used established subjective scales to measure innovation and firm performance. I validated the scale using the measurement model in AMOS. The survey used to collect around 250 cross-sectional data from middle & higher management executives of Indian firms. Structural equation modeling in AMOS was used to test the hypothesis.FindingsThe results showed that product and marketing innovation has a significant and positive impact on the dimensions of firm performance. In contrast, Process innovation showed an indirect effect mediated through marketing innovation. These outcomes will be beneficial for the industries for taking proactive measures.Originality/valueThe examination of mediation relationships between Marketing innovation and Product & Process innovation is limited. Novelty also lies in analyzing the impact of multiple innovation types on multiple dimensions of firm performance in Indian firms to verify dynamic capability and mediating effect of marketing innovation in Indian demography to validate the signaling theory perspective. Rigor in research methods like Scale and sampling method verification test, i.e., CMB. Heteroscedasticity and Endogeneity test for applicability of OLS and verifying exogenous variables.     

Practitioner advice: Approximation of the cumulative density of left-sided truncated normal distribution using logistic function and its implementation in Microsoft Excel

The left-sided truncated normal distribution is especially important in quality engineering where we remove the left side of the distribution, for example, due to estimation of the life of used products. Although the theoretical background of truncated normal distribution is already established, there is very little work on mathematical approximation of the probability density and the cumulative probability density functions. In this article, a high accuracy mathematical approximation of the left-sided truncated normal distribution is proposed. A full analysis of errors and recommendations for implementation using Microsoft Excel are provided at the end of this article.     

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。