Transient Characteristics of Thermal Conduction in Dispersed Composites

The effective thermal conductivity of dispersed composites with a hot-melt-adhesive matrix, measured using the steady-state method, is compared with the apparent thermal conductivity calculated from the average heat capacity and from the thermal diffusivity measured by the laser-flash method. The transient effect has been observed obviously at higher volume percentages for various dispersed particle sizes and ratios of the thermal conductivity values of dispersed and continuous phases. All of the experimental results are compared with those calculated by existing models and by the finite element method (FEM). An attempt has been made to show how the criterion for the homogeneity of dispersed composites under transient conditions is affected by the percentages of dispersed phase, dispersed particle size, and ratio of the thermal conductivity values of dispersed and continuous phases.     

极小极大拟合准则下的线性模型选择方法

本文指出了在极小极大拟合准则下进行线性模型选择的基本途径,设计了具体的选择方 法,并应用这种方法研究了两个实例.应用结果可以说明这种方法的有效性.     

Exploiting temporal coherence in nonlinear plan construction

Correct conventional nonlinear planners operate in accordance with Chapman's modal truth criterion (MTC). The MTC characterizes the conditions under which an assertion will be true at a point in a nonlinear plan. However, the MTC is not all one requires in order to build a realistic planning system: it merely sanctions the use of a number of plan modifications in order to achieve each assertion in a developing plan. The number of modifications that can be made is usually very large. To avoid breadth-first search a planner must have some idea of which plan modification to consider. We describe a domain-independent search heuristic called temporal coherence , which helps guide the search through the space of partial plans defined by the MTC. Temporal coherence works by suggesting certain orderings of goal achievement as more appealing than others, and thus by finding bindings for plan variables consistent with the planner's overall goals. Our experience with a real nonlinear planner has highlighted the need for such a heuristic. In this paper, we give an example planning problem and use it to illustrate how temporal coherence can speed the search for an acceptable plan. We also prove that if a solution exists in the partial plan search space defined by the MTC, then there exists a path to that solution which is sanctioned by temporal coherence.     

Fracture toughness diagrams of a notched body

To describe fracture toughness diagrams of notched bodies, a model of the cohesion zone near the notch root and an averaging criterion of stresses in this zone were employed. The geometric stress concentration factor and biaxiality coefficient affect greatly the shape of fracture toughness diagram. The notch root critical stress intensity factor is a decreasing function of geometric stress concentration factor. __________ Translated from Problemy Prochnosti, No. 5, pp. 142–148, September–October, 2006. Report on International Conference “Dynamics, Strength, and Life of Machines and Structures” (1–4 November 2006, Kiev, Ukraine).     

YBa2Cu3O7?X 500–600 K Isostructural Phase Transition and Its Influence on Critical-Current Value

YBa₂Cu₃O_7–X ceramic samples voltage–current characteristics at 77 K and acoustic emission activity during thermocycling 500–600 K region have been studied. Partial oxygen sorption by these samples through heating has been established by critical-current value and acoustic emission activity at 540–550 K. During thermocycling an acoustic emission maximums have been observed on 3rd and 6th thermocycles, and these maximums correlate with some decrease of the critical-current value. It is shown that observed acoustic emission maximums are because of a phase-work hardening during thermocycling of these samples. A mechanism of this phase-work hardening influencing the critical-current value in YBa₂Cu₃O_7–X ceramic samples is discussed.     

An approximate method of determination of maximum strain hardening levels in metals under nonproportional low-cycle loading

Using the findings of analysis of deformation curves for metallic materials under static and cyclic loading, an approximate method is put forward for the determination of maximum strain hardening levels in the case of non-proportional low-cycle loading with strain monitoring. Based on the correlation between strain hardening data obtained from the static and proportional and nonproportional cyclic deformation curves, an approximate analytical relationship is built up which allows for predicting maximum strain hardening levels under nonproportional low-cycle loading. __________ Translated from Problemy Prochnosti, No. 2, pp. 29–38, March–April, 2006.     

使变量叶片泵径向力为常量的设计准则

用内力分析的方法研究作用在泵轴上的径向力，提出使连续分布的径向力为常量的设计准则，为提高轴承的使用寿命提供了方便的设计手段。     

Energy increment criteria for evaluation of train derailment

The criteria for evaluation of train derailment were studied. The worldwide commonly used evaluation criteria for wheel derailment were summarized and their main problems were pointed out. The mechanism of train derailment was expounded on the basis of system dynamics stability concept. And the energy increment criteria were proposed to evaluate train derailment. By applying the criteria, the calculated results concerning 6 cases of freight train derailment on tangent railway line and 6 cases of freight train derailment on bridge were obtained, which are all in agreement with the practical situation. The safety, comfort and stability results concerning 3 cases of freight train running on bridge were analyzed. In addition, the running speed limits of freight train on the Yanconggou and Donggou bridge in the Beijing-Tonghua railway line of 50 km/h and 60 km/h, respectively, were proposed. And the running speed of freight train on the Nanjing Yangtze River Bridge can reach 70 km/h.     

冻融环境下引气混凝土双轴拉-压强度和破坏准则的试验研究

本文对掺引气剂混凝土进行了不同次数快速冻融试验，用电子显微镜观察了经受不同次数冻融循环后混凝土微观结构的变化，并进行了6种应力比下的双轴拉-压试验，观察了试件破坏形态，测得了混凝土试件的抗拉强度和抗压强度。试验发现，掺引气剂混凝土在双轴拉-压荷载作用下，其抗拉强度和抗压强度均随冻融循环次数的增加而明显降低。在此基础上，分析了双轴拉-压极限强度随冻融循环次数的变化规律，并在主应力空间和八面体应力空间建立了同时考虑冻融循环次数和拉压比的破坏准则。