The unsteady flow generated by an oscillating wall with transpiration

In this work, an analytical solution for the fluid behavior over flat plates with impulsive and oscillating motions, starting from rest, and with wall transpiration, is presented. The classical solution of this problem is given by Panton [7] and is found to be an especial case of the solution here presented. The analytical solution is obtained without the use of any special transformations, such as Laplace or Fourier transforms. Instead, an extension of the variable separation technique is used together with similarity arguments. A non-dimensional number—the transpiration rate—is used to take into account the injection or suction of fluid at the wall. This parameter is shown to be of great influence on the proposed velocity solution.     

Wavelet-Galerkin method for solving parabolic equations in finite domains

A novel wavelet-Galerkin method tailored to solve parabolic equations in finite domains is presented. The emphasis of the paper is on the development of the discretization formulations that are specific to finite domain parabolic equations with arbitrary boundary conditions based on weak form functionals. The proposed method also deals with the development of algorithms for computing the associated connection coefficients at arbitrary points. Here the Lagrange multiplier method is used to enforce the essential boundary conditions. The numerical results on a two-dimensional transient heat conducting problem are used to validate the proposed wavelet-Galerkin algorithm as an effective numerical method to solve finite domain parabolic equations.     

脉冲电势调制型电化学气体传感器

根据暂态电化学原理 ,使用微电极并融合计算机控制的快速电势调制技术和数据采集、处理功能 ,提出并建立了一类全新的集信号提取、处理与结果显示等功能于一体的“脉冲电势调制型气体传感器” .在优化传感器性能及其新的功能开发和集成方面取得了重要进展 ,是一类为常规电化学气体传感器无法比拟而有发展前景的暂态电化学多组份气体传感器 .     

高分子熔体和浓溶液流变性能的研究

基于多重缠结网络结构模型和高分子链上缠结点在流动中可进行动态解缠和再缠结的多重蠕动机理,用统计力学和动力学相结合的方法,分别计算出了缠结链组的末端距分布函数;处于缠结状态下高分子链构象统计分布函数;受力下聚合物熔体粘弹性形变自由能和解除外力下高分子挤出体可回复性粘弹性形变自由能,提出了高分子挤出体可回复形变的粘弹性分子理论。推导出的高分子熔体的回忆函数、简单剪切流下的本构方程和物料函数,并采用一种新的方法测定出物料的四种参数： η0、 GN0、 n′和 a。对于高分子挤出体,可回复性粘弹性形变由快速弹性形变和慢速粘弹性形变两者组成,当把两种形变量的复合结构参数－分子链的反式构象分数引入两种形变自由能表达式后,就从理论上得到了可回复形变量同挤出胀大比间的定量表达式,从而建立起一个具有分子链结构参数的新的挤出胀大比方程,可回复形变量同挤出条件（温度、挤出速率和量以及口模长径比不同的挤出机）和树脂结构特征（分子量及分布）的关系式以及在特殊情形下的简化表达式,并用几种高分子熔融体系的挤出胀大比和可回复性形变量的实验数据对理论进行验证,理论方程同实验数据较好的符合。     

三维热传导型半导体问题的特征有限元方法和分析

本文研究三维热传导型半导体瞬态问题的特征有限元方法及其理论分析,其数学模型是一类非线性偏微分方程的初边值问题,对电子位势方程提出Ｇａｌｅｒｋｉｎ逼近;对电子,空穴浓度方程采用特征有限元逼近;对热传导方程采用对时间向后差分的Ｇａｌｅｒｋｉｎ逼近．应用微分方程先验估计理论和技巧得到了最优阶Ｌ＾２误差估计。     

瞬变平面热源法测定常压下四氢呋喃水合物的导热系数

采用瞬变平面热源法,测定了常压、温度233.15～273.15K下四氢呋喃水合物的导热系数,其范围在0.45～0.54W·m-1·K-1之间。实验结果表明,常压下四氢呋喃水合物的导热系数呈现随温度升高而增大的趋势,与玻璃体的变化特性相同。常压下四氢呋喃水合物的导热系数与高压下的数值相比差别很小,但常压下测得的四氢呋喃水合物导热系数的玻璃体变化特性比高压下明显。     

Transient Characteristics of the Yield Surface of Electrorheological Clutch

The characteristic of transient yield surface in electrorheological clutch has been studied. It shows that the characteristics of clutch are dependent on the parameterβ, which is in the yield stress formula of ERF, when extra electric field was applied suddenly. In the case ofβ>2, the yield surface generates from the inner cylinder. In the case ofβ<2, the yield surface generates from the outer cylinder. The direct numerical results deriving from the Crank-Nicoson finite difference method with the regulation parameter model are also presented.     

用传输线和时域有限差分法计算电缆X射线响应

 介绍了时域传输线和时域有限差分两种计算电缆X射线瞬态响应的方法,并利用电缆芯线总电荷以及介质层的电荷分布,结合实验结果,分别给出了时域传输线模型中的电流源和时域有限差分模型中电流密度的计算方法。作为例子,在60 keV单能X射线垂直于电缆轴向辐照的条件下,采用两种方法计算了电缆两端接匹配负载时负载上的电流响应;采用传输线方法计算了不同能量X射线辐照电缆时的芯线负载电流响应。计算结果表明,两种方法计算的电缆X射线瞬态响应是一致的;电缆介质层中存在静电场;X射线能量不同时,电缆芯线负载电流存在最大值。计算中,电缆与X射线的作用采用蒙特卡罗方法计算。     

Equilibrium and sensitivity analysis of a spatio-temporal host-vector epidemic model

Insect-borne diseases are diseases carried by insects affecting humans, animals or plants. They have the potential to generate massive outbreaks such as the Zika epidemic in 2015–2016 mostly distributed in the Americas, the Pacific and Southeast Asia, and the multi-foci outbreak caused by the bacterium Xylella fastidiosa in Europe in the 2010s. In this article, we propose and analyze the behavior of a spatially-explicit compartmental model adapted to pathosystems with fixed hosts and mobile vectors disseminating the disease. The behavior of this model based on a system of partial differential equations is complementarily characterized via a theoretical study of its equilibrium states and a numerical study of its transient phase using global sensitivity analysis. The results are discussed in terms of implications concerning the surveillance and control of the disease over a medium-to-long temporal horizon.