Steady-State Frictional Heat Generation on a Periodic Sliding Contact

We investigate the motion of a periodic system of rigid, isolated, parabolic dies along the surface of a half-space. The action of friction forces results in heat generation in the contact region. We assume that the surfaces of the dies are thermally insulated and the half-space is a heat conductor. We reduce the problem under consideration to a set of two integral equations for the contact temperature and pressure. We solve these equations numerically and investigate the influence of thermal deformation on the distributions of temperature and pressure and on the dimensions of the contact region.     

Criticality conditions for some random environment population processes

Some random environment population processes are considered. Using a coupling argument, a criticality condition is obtained. The criticality parameter governs whether the process dies out or fluctuates about a positive finite constant, which is explicitly computed.     

抛物线模拔速度场的曲线积分问题

文章采用ｖｏｎＫａｒｍａｎ基本假设对模面函数为抛物线（又称喇叭模）的拔制问题设定了运动许可速度场，并经曲线积分与变上限积分得到拔制力的上界解析解。     

Thermal models for copper-alloyed dies in pressure die casting

A recent innovation in pressure die casting is the use of copper-alloyed dies suitably protected with a thermally sprayed steel layer. The thermal response of copper-alloyed dies is dictated principally by the deposited layer, the cooling arrangement and the casting geometry. This paper is concerned with the development of efficient numerical models for the prediction of both steady-state and transient thermal behaviour of the new die designs. Die temperatures are cyclic but useful information is obtained from a steady-state model, which provides for time-averaged temperatures and energy fluxes. The modelling strategy presented in the paper involves the indirect determination of transient temperatures. A perturbation approach is adopted, where a model for the difference between transient and steady-state temperature is developed. It is shown that this approach can be utilised to determine transient temperature efficiently once steady-state information is available with the transient perturbation model only involving surfaces where a significant variation in temperature occurs.     

On a principle of predatory exclusion

Suppose two prey species have the same rate of reproduction, and they are subjected to predation. Then the species more susceptible to predation dies out. So that in effect the predator introduces competition between the prey species.     

Approximations for the Long-Term Behavior of an Open-Population Epidemic Model

A simple stochastic epidemic model incorporating births into the susceptible class is considered. An approximation is derived for the mean duration of the epidemic. It is proved that the epidemic ultimately dies out with probability 1. The limiting behavior of the epidemic conditional on non-extinction is studied using approximation methods. Two different diffusion approximations are described and compared.     

CONDITIONED SUPERPROCESSES

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Exceptional planes of percolation

Consider the standard continuous percolation in ℝ⁴, and choose the parameters so that the induced percolation on a fixed two dimensional linear subspace is critical. Although two dimensional critical percolation dies, we show that there are exceptional two dimensional linear subspaces, in which percolation occurs. Received: 1 April 1997 / Revised version: 20 January 1998     

女性吸毒者在HIV/AIDS传播中的作用

利用数学模型,探讨了女性吸毒者在HIV/AIDS传播中的作用.通过理论分析和数值模拟,揭示了女性吸毒者对HIV/AIDS传播和流行的重要作用:当HIV/AIDS在吸毒人群和一般男性人群中流行时,若切断女性吸毒人群和一般男性人群间的传播途径(商业性行为),则疾病不但在一般男性人群中会消亡,在一定的条件下,甚至会在吸毒人群中消亡.     

线材无模拉拔成形力数学模型研究

采用上限法确定了钨合金线材无模拉拔成形速度场及力能参数物理模型.分析了钨合金线材无模拉拔成形的变形模型、速度场以及力能参数的影响因素及影响规律,无模成形力能参数的影响因素主要有冷热源间距、断面减缩率、变形温度、拉伸速度、冷热源移动速度以及材料种类等,为无模拉拔成形工艺工业化应用奠定基础.     

随机利率下的增额寿险

我们考虑即时给付的增额寿险模型,根据保费的实际投资情况以及突发事件对利率的影响,将随机利率采用反射布朗运动(RBM)和Poisson过程联合建模,给出即时给付的增额寿险的给付现值的各阶矩,并在死亡均匀分布的条件下得到矩的简洁表达式．最后用数值例子说明模型与计算方法的正确性与有效性．     

Flow and heat transfer of non-Newtonian fluids in enameling dies

The present work analyses computationally the flow inside wire enameling dies within the framework of the lubrication theory approximation. Non-Newtonian flow behavior and heat transfer are accounted for as well. It is shown that the developed approach most accurately predicts the momentum and heat fluxes along the wire. As such it is proven as a reliable and computationally efficient tool for the design of flow optimized die shapes. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Contact interactions and optimization of locally loaded shell structures

Methods for the solution of different problems of contact interaction of elements of shell structures with one another and dies of different types are generalized. We consider schemes of determination of breaking loads using the limit equilibrium theory and critical loads of local stability for shell systems under the indicated loading. Schemes of optimization of the shape of structural elements under local loads are presented. Results of experimental investigations are presented.     

A problem of rights arbitration from the Talmud

A man dies leaving certain amounts of his estate to each of his sons, but the amounts sum to more than the total available. Various solutions are discussed, some based in the theory of games. The method endorsed here regards the problem as one of rights arbitration in which the division is based on interpreting the applicable rules, rather than on weighing the parties' powers and possible benefits.     

Asymptotic Profile of Species Migrating on a Growing Habitat

This paper deals with a diffusive logistic equation on one dimensional isotropically growing domain. The model equation on growing domains is first presented, and the comparison principle is then proved. The asymptotic behavior of temporal solutions to the reaction-diffusion problem is given by constructing upper and lower solutions. Our result shows that when the domain grows slowly, the species successfully spreads to the whole habitat and stabilizes at a positive steady state, while it dies out in the long run if the domain grows fast. Numerical simulations are also presented to illustrate the analytical result.     

基于模糊相似比较的模具报价方法的研究

为克服模具报价工作对报价人员经验的依赖性,简化报价操作,在分析了报价系统的要求和传统的模具报价进程的基础上,提出了利用模糊数学来提取模具报价领域中专家的经验,模拟专家行为,根据预测技术理论,得出模具价格的模糊相似比较法构想.在此基础上,推导其公式.以冲裁模为研究对象,阐述了工件特征集合构成、模糊相似关系和权值、贴近度计算等关键问题.从理论上为模具报价这一实际问题的解决提供了基本原则和方法.     

The survival analysis for a population in a polluted environment

This paper concentrates on studying the long-term behavior of a single species in a polluted closed environment. We improve the rudimentary population model of Hallam and the classical Gallopin resource–consumer model, assuming that a born organism takes with it a quantity of internal toxicant, and the amount of toxicant stored in each living organism which dies is drifted into the environment. Sufficient criteria for persistence or extinction of the consumer population are obtained. The threshold between persistence and extinction will be established in some cases.     

随机利率下的增额寿险

寿险中的利率随机性问题，是近年来保险精算研完的热点之一，本文以即时给付的毒额寿险为对象，对随机利率采用Gauss过程建模，研究给付现值及其各阶矩，并在死亡均匀分布假设下得到矩的简洁表达式。     

Threshold dynamics for compartmental epidemic models with impulses

The basic reproductive number and its calculation for general impulsive compartmental epidemic models, with pulses on both the infected and the uninfected compartments, are established. Theoretical results show that the basic reproductive number serves as a threshold parameter: the disease dies out if the basic reproductive number is smaller than unity, and breaks out if it is larger than unity. The global dynamics of a viral dynamical model with impulsive immune response is analyzed to study how the vaccination strength and the vaccination interval affect the basic reproductive number and virus progression.     

Objective Functions for the Shape Optimization of Temperature Control Channels in High-Pressure Die Casting

In high-pressure die casting, the quality of the produced cast parts highly depends on the die quality. One die component are temperature control channels. The state-of-the art approach for the temperature control channels are boreholes drilled from the sides into the die that are afterwards formed into a closed flow channel by inserting plugs. Since additive manufacturing methods are available to manufacture the dies, an obvious step is to construct more advanced temperature control channels. The shape of these free-form channels can be obtained by numerical optimization. To find the optimal shape of the channels, appropriate objective functions are required. This contribution is focused on such objective functions. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)