Modeling of Bonding at an Interface Crack

A mechanical and mathematical model is suggested for an interface crack with bonding in its end zones. Normal and shear bond tractions occurring under the action of the external loads are searched for by solving a system of two singular integrodifferential equations. The stress intensity factors at the crack tip are calculated taking the compensating action of the bonds into account. Energetic characteristics of the interface crack (the deformation energy release rate and the rate of the energy absorption by the bonds) are analyzed. A sensitivity analysis is performed of the force and energetic characteristics of the interface crack to the end zone size, bond compliance and limit stretching. This revised version was published online in July 2006 with corrections to the Cover Date.     

Josephson Current Between d-Wave Superconductors Through an Interface with Finite Transmission

We consider an interface with finite transmission between two superconductors. We show that in some cases the general non-linear boundary condition for the quasiclassical Green’s function derived independently by Kieselmann and Zaitsev can be factorized into a linear effective boundary condition. This result is then applied to the josephson current-phase relationships for junctions between two super conductors. In particular we study the phase difference χ_m across a junction where its energy is at a minimum as a function of the temperature and orientations of the superconductors. Experimental implications are discussed.     

Modeling the Ultrasonic Radiation of a Planar Transducer Through a Plane Fluid—Solid Interface

Three types of transducer beam models are developed for obtaining the bulk waves generated by a plane piston transducer radiating through a planar fluid—solid interface. The first type, called the surface integral model, is based on a Rayleigh—Sommerfeld-like integral that requires a two-dimensional surface integral to be evaluated. The second model, called the boundary diffraction wave (BDW) paraxial model, simplifies the two-dimensional integration of the surface integral model to a one-dimensional line integration. The third type of model, called the edge element model, is shown to be a novel way of efficiently evaluating the two-dimensional surface integration of the surface integral model. The limitations of these models for simulating inspections near critical refracted angles and near the interface are discussed. It is shown that the introduction of the paraxial approximation in the BDW model allows that model to be computed with a very large (300—1) speed advantage over the surface integral while retaining the same accuracy in most cases. The edge element model, while having a smaller (5—1) advantage over the direct numerical integration of the surface integral model, retains the accuracy of the surface integral model in cases where the paraxial approximation fails and can be easily generalized to more complex testing situations (focused probes, curved interfaces, etc.).     

近十年面向老年用户的界面可用性研究

目的通过对近10年国内外相关文献进行综合分析,分析面向老年用户的界面可用性研究的现状及发展趋势,为提升面向老年用户的界面设计可用性提供思路和指导,以期通过提高面向老年用户的界面设计水平,激发老年用户积极参与互联网生活,提升老年用户的生活品质。方法利用Citespace软件和CNKI计量可视化分析工具,分析国内外面向老年用户的界面可用性研究的关键文献、热点领域、研究机构及测量方法等问题。结论当前面向老年用户的界面可用性研究主要基于老年人的功能能力,以认知障碍为主要线索进行研究;主要集中在康复医疗、机器人等领域,且致力于提升老年用户在新技术环境下的使用体验;面向老年用户的界面可用性测量方法更加多样化,利用新技术评估界面可用性水平可提高可用性测量的准确性。     

复杂包装耦合界面动态性预测的改进逆子结构理论

以产品、包装、运载体组成的产品运输系统为研究对象,在动态逆子结构理论基础上建立适合这一系统特性的改进理论,研究包装界面动力学特性的反向建模技术并实验验证。结果表明：新方法能有效预测复杂包装耦合界面动力学特性。研究结论为产品运输包装设计提供新的理论基础。     

熔融接枝法提高膨胀型阻燃聚丙烯的相容性和阻燃性能

通过熔融共混工艺,采用熔融接枝和阻燃剂表面处理技术,利用双螺杆挤出机制备出无卤膨胀型阻燃聚丙烯(PP)。研究了聚磷酸胺(APP)、季戊四醇(PER)、三聚氰胺(MEL)作为一种混合体系对PP的阻燃作用,并用对比法分析讨论了三种组分分别在体系中所起的作用。研究了多组分体系下不同单体熔融接枝PP对各组分间的相容性和阻燃性能的影响,结果表明,极性较大单体MAH接枝处理PP,能够有效地提高体系的相容性和阻燃性能。     

Determination of Materials Selection Performance Indices Through the Combination of Numerical Modeling and Optimization Methods

After translation, the first stages traditionally involved in the materials selection are filtration and classification, which require formulation of criteria (constraints or objectives) deduced from information written in the set of material requirements. These criteria, which are representative of the behavior of the material and the studied structure, must be formulated analytically in order to be used during selection stage. However, for complex behavior, analytical processing of models is no longer possible and it can be replaced by a combination of numerical resolution methods and an optimization method which make it possible to obtain approximate formal expressions of the criteria. In this paper, a complete selection method is proposed. The method is applied to the constraints as well as the objectives, in order to carry out the filtration and classification stages at the same time. The study of the thermomechanical behavior of a machine tool frame has been used to demonstrate the validity of the proposed method.     

缝合增强复合材料帽型加筋壁板界面拉脱性能

为了防止复合材料帽型加筋壁板结构在服役过程中发生筋条与蒙皮的脱粘失效,引入了缝合技术来提高筋条-蒙皮界面拉脱性能.采用单线弯针缝合设备缝合纤维编织布,通过真空辅助树脂灌注技术(VARl)固化成型,制备缝合帽型加筋壁板试样.通过对试样进行筋条拉脱试验和有限元数值模拟,研究界面的失效机制及缝合参数对帽型加筋壁板界面结合性能的影响规律.结果表明:在拉脱载荷作用下,缝合试样的峰值载荷比未缝合试样明显增大.帽型试样的拉脱承载力随缝合密度的增大先增加后减小,在缝合密度(注:缝合密度表示缝合针距(单位mm)×行距(单位mm),下文同)为5×10时,相比未缝合试样,最高增加了26.7％;帽型接头的拉脱承载力随缝线细度的增加而增加,在缝线细度为1500 D时增加了39.7％.蒙皮/筋条厚度比为2时,结构拉脱承载力增加了27.35％,缝合的增强效果最明显.     

On Stochastic Modeling of Interface Defects in Composite Materials

The article presents mathematical and computational research dealing with the problem of stochastic interface defects occurring in composite materials between their constituents. A mathematical model of the periodic composite with such defects is presented in detail, as well as probabilistic numerical methods enabling computational experiments which are shown in a further part of the text. The fiber-reinforced and laminated composite has been tested in numerical tests as well as the superconducting coil cable-four-component composite to verify how the structural defects considered, according to the model introduced, influence the static behavior of the composites analyzed. All the results obtained and discussed in the article are summarized in concluding remarks which show the directions of further model development, while numerous references enable the reader to study the problem further.     

虚拟环境中的三维用户界面研究

从人机交互的角度,分析了目前传统GUI在虚拟环境中的局限和尴尬,探讨了虚拟环境中的三维用户界面的产生背景、特性以及相关的设计过程和设计原则。     

协同环境中3D替身交互行为动态控制的实现

协同环境中用户之间的协同感知程度和实时交互性直接影响到协同工作的质量。目前,部分CSCW 应用系统通过向虚拟协同环境CVEs 中添加3D 替身来提高用户之间的协同感和交互感。但经研究发现,其场景中所有的替身只是在用户的控制下机械地使用VRML 中提供的行为机制进行运动,替身之间也不存在交互行为,用户交互程度仍然不足。为了进一步解决这个问题,笔者着重研究了CVEs 中3D 替身之间交互行为的实现,通过替身行为机制的建立,利用VRML 和Java 实现了替身之间交互行为的动态控制,从而增强了用户的协同感和交互感,提高了协同工作的效率。     

镀膜组件对螺旋线慢波结构性能的影响

本文利用实验测试和软件仿真的方法,分析研究了镀膜组件的应用对慢波结构的散热性能和高频特性的影响.研究表明:在螺旋线外表面镀膜可以改善慢波结构的散热性能和高频损耗;金属化夹持杆实现焊接装配,可以有效地提高慢波结构的散热性能;在夹持杆的两侧镀膜可以显著地调节慢波结构的高频特性.     

虚拟家居系统的局部调整式墙体建模算法

阐述了虚拟家居漫游系统的功能体系结构，分析了虚拟家居漫游系统中墙体建模的特殊性，建立了墙体的5层信息模型，构造了墙体生成前用户交互语义的确定算法、局部调整式墙体生成算法和相应的后处理算法，该算法既满足了三维环境中交互编辑结果的连续性保存，又使得算法简明易用。最后提供了一个实例，表明基于该算法的漫游系统已经在实际应用中取得了满意的效果。     

A Study of the Potential of Improving Performance of AS20 Diamond Powders Through Altering Their Dimensional and Physico-Chemical Characteristics

We have studied performance of AS20 diamond powders to be used in grinding wheels and have found the ways to improve it through changing the dimensional and physico-chemical characteristics of the powders. It is demonstrated that the wheel wear is influenced by separating the narrowest range of grain sizes 100/90 and providing a uniform powder with a certain grain shape factor; it is preferable to use diamond grains with higher values of the shape factor. It is shown that after diamond powders are separated into magnetic and non-magnetic fractions there is a difference between the fractions in the physico-chemical state of the grain surfaces, and it is preferable to use non-magnetic fractions in resin-bonded wheels in order to improve the wheel wear resistance.     

Improving Problem Solving Performance by Inducing Talk about Salient Problem Features

Background Across many domains, research has shown that students often fail to select and apply appropriate conceptual knowledge when solving problems. Programs designed to support monitoring skills have been successful in several domains. Purpose (Hypothesis ) Critical conceptual knowledge in statics appears to be cued by paying attention to the bodies that are present in a problem, as well as to which ones are interacting and how. The research question addresses whether students can be induced to think about the bodies present, and whether focusing on bodies improves problem solving performance. Design /Method Using a pre‐post test design, written and verbal protocols were obtained for students solving problems before and after instruction. During instruction all students saw the same set of examples and corrected answers, but only the experimental group was asked questions designed to promote body centered talk. Solutions and protocols were coded and analyzed for frequency of body centered talk and solution quality. Results The experimental group showed statistically significant increases in relevant body centered talk after instruction. Both groups improved their ability to represent unknown forces in free body diagrams after instruction, with the experimental group showing a greater, but not statistically significant, improvement. However, for both groups, the error rate in representing unknown forces at an interaction was significantly lower when a student referred to the bodies in the particular interaction. Conclusions Problem solving in conceptually rich domains can improve if, in addition to acquiring conceptual knowledge, students develop strategies for recognizing when and how to apply it.     

交换式以太网NC建模与实时性能分析

交换式以太网的实时性能分析是工业以太网研究领域的一个热点课题，目前还没有一个有效的数学模型来对其进行描述。通过对典型交换机结构的分析，应用网络微积分理论建立了交换机的服务曲线模型，该模型将交换机中的数据流分为实时数据和非实时数据，并得到了最大延迟值和最大缓存需求值等，最大延迟为交换机的实时应用提供了理论边界值，最大缓存需求值为在实时工业环境中的交换机构建提供了理论参考     

供应链管理环境下的单周期库存控制建模及优化

传统的库存控制理论已经不能够适应供应链管理的要求。在建立了供应链库存成本的组成模型的基础上对供应链管理中的单周期库存控制过程进行了深入的分析，建立了相应的数学模型，求出了最优解。     

T-Stress of an Interface Macrocrack Induced by Near Tip Subinterface Microcracks

Determination of the T-stress of an interface macrocrack induced by near tip subinterface microcracks is performed. Based on the general solution of the macro-microcrack interaction, the induced T-stress can be evaluated by using the principle of superposition. Numerical examples of an interface macrocrack interacting with a single near tip subinterface microcrack are considered and the results are shown graphically. The induced T-stress is shown to be significantly dependent on the location and orientation of the near tip microcrack. The induced T-stresses of the upper crack face (Δ T+) and the lower crack face (Δ T-) are different. The difference disappears only when the microcrack is located and oriented definitely, for which both Δ T+ and Δ T- become zero. Δ T+ and Δ T- have the same sign, i.e., simultaneously positive or negative. The positive or negative value is dependent on the location and orientation of the microcrack. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interface separation for an elastic layer loaded by a rigid stamp

The frictionless contact problem for an infinite elastic layer lying on a horizontal rigid plane is considered. The external load is applied to the layer through a rigid stamp. It is assumed that the layer is subjected to uniform vertical body forces due to the effect of gravity. For values of the resultant compressive force P acting on the stamp vertically which are less than a critical value P_cr the continuous contact along the layer-substrate interface is maintained. However, if tensile tractions are not allowed on the interface, for P >P_cr the layer separates from the interface along a certain finite region. The problem is formulated and solved for both cases and numerical results for P_cr, separation initiation distance, contact stresses, distances determining the separation area, and the vertical displacement in the separation zone are given.