Modeling of the Thermophysical Processes in Sintering Glassware

A complex approach to the modeling of the thermophysical processes in glassware obtained by the sintering technique is proposed. A onedimensional model of radiativeconductive heat exchange in a layer of a transparent scattering material formed from glass particles and a model of twodimensional heat conductivity in a multilayer molding rig with an article are considered. The results of mathematical modeling are presented.     

木质托盘铺板的受力分析与设计

针对木质托盘在储存和运输过程中容易出现铺板受损的问题,进行典型工况下托盘的受力分析,建立铺板在几种常见工况下的受力模型并确定了挠度方程.根据托盘的许用刚度要求,提出了铺板在多种载荷条件下的设计方法,为木质托盘的设计和生产应用提供理论依据.     

Modeling of Heat Outflows to a Probe in Thermophysical Testing

The nondestructive method developed by the author with the use of a linear pulsed heat source makes it possible to determine the thermophysical characteristics of solid materials on the basis of the portions of thermograms that correspond to the regularization of the thermal regime in the region of the heater and temperature detectors. Consideration has been given to the influence of the outflows of heat to a probe on the error in determining the thermophysical characteristics of materials in the case where two semiinfinite bodies are in ideal contact. A mathematical expression upon the fulfillment of which one may disregard the heat loss to the material of the probe substrate has been obtained. In the work, consideration has also been given to the problem of heat loss to the probe material in the case where it occurs only in the region of the heater. It has been shown that the temperatures of the first and second bodies in the contact area will become closer with time. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 108–116, July–August, 2005.     

The Sensibility of Thermophysical Property Data for Simulating Casting Processes

The numerical simulation of casting processes is finding a steadily growing acceptance in the foundry industry worldwide. Advanced computer technologies like MAGMASOFT^® have turned out to be powerful tools for continuous process optimization. The availability of accurate thermophysical data for all material groups in the whole casting system is a very important aspect in this context, as the simulation results used to analyze the casting process are very much dependent on the material data applied. Especially with sand mold materials, the definition of thermophysical properties becomes more complicated, as they exhibit a nonreversible behavior during the process due to the thermal decomposition of the binder materials and the evaporation of the water contained in the sand. Hence, the cooling power of the mold will be stronger during the heating cycle at the beginning of the process and weaker at the end when the system is cooling again. For iron castings, showing a solid-state phase transformation after an extended cooling time in the mold, this aspect may become very important. This paper gives an insight into the required accuracy of the thermophysical properties by analytical and numerical methods, using the MAGMASOFT^® simulation code.     

Numerical Modeling of Heat-Exchange Processes in a Gas Curtain

The authors give results of calculating the distribution of the efficiency of a gas curtain and heat transfer behind a row of individual orifices in a solid wall through which a coolant is injected into the main flow. A complete system of Navier–Stokes equations that are Reynolds-averaged and supplemented with a low-Reynolds k– model of turbulence is used.     

Special Features of the Thermophysical Modeling of Instrument Cubicles of Spacecraft

Mathematical models which allow for the main mechanisms of heat transfer in instrument cubicles of modern spacecraft are presented. Results of numerical modeling of thermophysical processes in a typical module of the instrument cubicle of a communications spacecraft are given. On the basis of an analysis of multidimensional temperature fields we have drawn conclusions on the presence of substantial nonuniformity in the distribution of the temperature field in devices of radioelectronic spaceborne equipment.     

基于图元的板式家具产品快速建模

分析了目前家具设计中存在的问题，提出了将常见结构作为基本图元，由图元构建家具产品的建模方法。详细论述了基于图元的产品建模原理、图元的3个层次、图元的面向对象表示。在此基础上，建立了板式家具的特征图元对象、板块图元对象和部件图元对象，实现了板式家具产品的快速建模，有效的保证了家具产品设计的继承和变异性。为缩短产品设计周期、提高产品质量，降低产品成本提供了必要的条件。     

Modeling the Processes Involved in the Leakage of Gas from a Spacecraft Module

Analytical expressions are obtained to describe the change in the pressure and flow of a gas over time through openings of different shapes in the hull of a spacecraft. Results are presented from experimental studies.     

Theoretical Analysis and Procedure for the Calculation of Thermophysical Processes Occurring in a Cryogenic Vessel under Conditions of Nonvented Storage

A theoretical analysis is made of the processes which define the rate of pressure rise in a vessel with cryogenic liquid under conditions of nonvented storage. Different methods of the calculation of pressure are treated. The determining part played by thermal stratification in the liquid phase is demonstrated. A new procedure is suggested for the calculation of pressure and thermal stratification in a liquid.     

Aggregation Processes Modeling in Physical-Chemical Systems

In article, the methodology of mathematical modeling of periodic reactors with agitating in the conditions of formation and sedimentation of insoluble solid phase in a working zone on the basis of diffusive model is suggested. Also equations for calculation of the general concentration and average order of clusters of insoluble phase in the periodic reactor are offered. The methodology of calculation of processes of insoluble solid phase aggregation in systems with chemical reactions of the first and pseudo-first orders is developed, namely： equation for calculation of evolution of total clusters＇ number and average order of globules in system are developed, by taking into account kinetic constants of chemical reaction and elements of aggregation matrix.     

Numerical Modeling of Casting Processes

Recent progress on work related to numerical modeling of casting processes at the Industrial Materials Institute (IMI) is presented. Depending on the type of casting process involved, two different modeling approaches are used. The first, applied to simulate laminar or turbulent flow in the cavity of thin wall castings, is based on a 2D shell element model. This has the advantage of being computationally efficient from the CPU standpoint while, at the same time, provides a reasonably accurate solution to the problem. In the second approach, a 3D finite element method is used for parts that are thick (such as in low pressure or gravity casting), or where the problem is associated with both the part and mold (such as in heat transfer calculations). Whatever the technique chosen, in performing numerical modeling, the foundry hopes to use the results to optimize die and part design, as well as to reduce manufacturing costs. By being able to predict filing, solidification, stresses and shrinkage, a good idea of product quality and performance can often be obtained at the initial stage of the product development cycle.Examples of simulations conducted using an experimental die, an automotive housing and a wheel in an aluminum alloy are given.     

On Gert Modeling of a Class of Finite Queueing Processes

A set of formulas relating two random variables is developed. With these results, the branch parameters of GERT network models for reliability and queueing problems can be calculated. Two examples illustrating the technique are presented. The basic results can be applied to a variety of queueing problems of the M/G/1 and G/M/1 type.     

Dimensional Analysis as a Tool for Modeling Fracture-Mechanics Processes

We use the universal graph method to propose a new procedure of deducing formulas for the fatigue crack growth rate in isotropic bodies. These formulas were earlier obtained by using the energy approach based on the first law of thermodynamics according to which the rate of variations of energy is determined by changes in the area of the crack under cyclic loading.     

Modeling of the Rheological Behavior of Wood in Compression Processes

A rheological equation of state for wood which allows for the running values of its porosity and humidity is considered.     

Automated System for Calculating Thermophysical Properties of Fluids and Thermal Processes of Cryogenic Plants

An automated system for calculating thermophysical properties of gases and liquids over a wide range of parameters has been developed. On the basis of values of the properties, the processes of isothermal compression, adiabatic throttling, polytropic expansion, heat exchange in two- and multi-stream heat exchangers, separation of vapor-liquid mixtures in the liquid vessel, and rectification in an air separation plant can be analyzed. For a specified structure scheme of a cryogenic plant, optimization of a corresponding thermodynamic cycle can be fulfilled.     

Computer Modeling of the Processes of Elastoplastic Deformation of a WIre in the Course of Winding

An algorithm is proposed for the numerical solution of the problem of elastoplastic torsion of a rod for constant values of a longitudinal force and a torque with regard for the effect of hardening of the material. The dependences of the bending moment, relative elongation, and torsion of the rod on the curvature are obtained. It is shown that the plastic properties of the material of the rod exert significant influence on the numerical results. The three-dimensional diagrams of normal and tangential stresses are presented for different stages of the rod loading.     

小型燃料电池堆动态特性的模拟

概述了燃料电池的工作原理;介绍了利用参数模拟方法建立燃料电池的稳态模型,该模型表明了输出电流、电池温度、氢气压力和氧气压力等参数对燃料电池的输出电压均有影响;通过在燃料电池的稳态模型上增加一个电容,来模拟它的动态电压,进而模拟出小型燃料电池堆的动态特性。     

DVD租赁问题的模型设计及求解

本文讨论了DVD在线租赁的服务供应商可能遇到的问题与其解决方案。模型Ⅱ解决了在已知订单与各种DVD数量的情况下，如何分配DVD使得满意的人数最多，且总的满意度最大。模型Ⅲ解决了在已知订单的情况下，在一定的满意率与总满意度最大的约束下，如何以最小的成本购买各种DVD，并确定分配方案。模型Ⅴ对原问题作了更深入的推广，解决了在DVD数量有限且租赁费用与租赁时间成正比的条件下如何选择性地出租DVD以获得最大收入的问题。本文所讨论的问题均为最优化问题，但是各题的约束条件均不相同，本文对各个问题建立不同的网络模型，经过严密的理论论证，并用统一的费用流算法在微机上实现，充分利用了网络流模型适用面广，结果精确，计算简单的优点，对DVD租赁的现实问题提供了高效的解决方案。