Global asymptotic stability of positive equilibrium in a 3-species cooperating model with time delay

The asymptotic behavior of the time-dependent solution for a 3-species cooperating model was investigated with the effects of both diffusion and time delay taken into consideration. We proved the global asymptotic stability of a positive steady-state solution to the model problem by using coupled upper and lower solutions for a more general reaction-diffusion system that gives a common framework for 3-species cooperating model problems. The result of global asymptotic stability implies that the model system coexistence is permanent. Some global asymptotic stability results for 2-species cooperating reaction-diffusion systems are included in the discussion, and some known results are extended.     

DC steady-states analysis of lossy uniform transmission lines

1 Introduction In the past 20 years with the rapid development of VLSI (very large scale integration) circuits and continual spread of electric power system scale, theories on transmission lines have become an important research field where finding the analytic solutions to lossy transmission line equations remains a tough nut. Since the mathematical tool cannot provide effective help, there is no universal method to solve transmission line equations [1]. A number of researchers have obtaine…     

BIFURCATION ANALYSIS OF THESTEADY-STATE MODEL FOR A MULTIJUNCTION DEVICE

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Bifurcation and Stability of Nontrivial Solution to Kuramoto-Sivashinsky Equation

1introductionTheKuramoto-Sivashinsky(K-S)equationinonespacedimensionwithperiodicboundaryconditionandofwhere11o(x)isl-periodicandofzeromean.TheK-Sequationmodelspatternt'Ormationindifferentphysicalcontexts[]'3'5]andhasbeenstudiedextensivelyinrecentyears,bot…     

Kuramoto-Sivashinsky 方程中定常解分歧到旋转波解的一个注记

In this paper, we consider the detection and calculation of bifurcation from nontrivial steady-state solutions to ro~ wave solutions of the Kttramoto-Sivashinsky（K-S） equation by using the nonlinear Galerkin method. Numerical results show the efficiency and advantages of the nonlinear Galerkin method over the conventional Galerkin method in this application.     

Mathematical models of steady-state temperature fields produced by multi-piped freezing

The multi-piped freezing method is usually applied in artificial ground freezing (AGF) projects to fulfill special construction requirements, such as two-, three-, or four-piped freezing. Based on potential superposition theory, this paper gives analytical solutions to steady-state frozen temperature for two, three, and four freezing pipes with different temperatures and arranged at random. Specific solutions are derived for some particular arrangements, such as three freezing pipes in a linear arrangement with equal or unequal spacing, right and isosceles triangle arrangements, four freezing pipes in a linear arrangement with equal spacing, and rhombus and rectangle arrangements. A comparison between the analytical solutions and numerical thermal analysis shows that the analytical solutions are sufficiently precise. As a part of the theory of AGF, the analytical solutions of temperature fields for multi-piped freezing with arbitrary layouts and different temperatures of freezing pipes are approached for the first time.     

Analytical Models for Minority Representation in Academic Departments

We present mathematical models for the evolution over time of the proportion of minorities in an academic department or similarly selected group of constant size. Using the models, we analyze both the steady-state and time-dependent behavior of the proportion of minorities, and also obtain a means of evaluating the effectiveness of a department's hiring history. We derive a number of surprising results with importance to institutional hiring policy and affirmative action; and we also present methods, suggested by the model and its behavior, to improve departmental hiring practices.     

In-plane creep buckling of concrete-filled steel tubular arches

The creep-induced deformation of the arch rib of concrete-filled steel tubular （CFST） arches under a sustained load can increase the bending moment, which may lead to earlier stability failure called creep buckling. To investigate the influences of concrete creep on the buckling strength of arches, a theoretical analysis for the creep buckling of CFST circular arches under distributed radial load is performed. The simplified Arutyunyan-Maslov （AM） creep law is used to model the creep behavior of concrete core, and the creep integral operator is introduced. The analytical solutions of the time-dependent buckling strength under the sustained load are achieved and compared with the existing formula based on the age-adjusted effective modulus method （AEMM）. Then the solutions are used to determine the influences of the steel ratio and the first loading age on the creep buckling of CFST arches. The results show that the analytical solutions are of good accuracy and applicability. For CFST arches, the steel ratio and the first loading age have significant influences on creep buckling. An approximate log-linear relationship between the decreased degrees of the creep buckling strength and the first loading age is found. For the commonly used parameters, the maximum loss of the buckling strength induced bv concrete creen is close to 40%     

一种求解与时间有关的二维薛定谔方程的数值算法

在有限差分和径向基函数的基础上,利用无网格法中的特解方法来给出与时间有关的二维薛定谔方程的一种数值算法,同时给出了两个例子来说明这种方法良好的准确性,并取得了比较好的数值结果.     

用稳态近似法推导反应速度方程时应注意的一个问题

用稳态近似法推导反应的速度方程时,最后所导出的速度方程有时会出现由不不同数值而组成的系数。针对这个问题,本文指出了两种避免出现该问题的方法。     

中低温传导型孔隙介质地热田回灌试验研究

以天津武清地热田为例 ,对传导型孔隙介质地热田回灌技术进行研究 .武清地热田主要开采层为第三系馆陶组砂岩 ,热储层温度 76～ 86℃ .根据水动力模型的预测 ,热储水位降深将在近期趋于稳定 .在无回灌条件下 ,如以最大开采量持续开采 ,5年内水位将下降到 10 5 m.回灌可提高孔隙 /裂隙热储中热量的开采 ,减缓水位下降幅度 .此外 ,还计算了回灌过程中不同情况下冷锋面的运移速度 .为查明开采井和回灌井之间的水力联系 ,探讨了示踪剂试验的可行性     

正弦激励下的RL电路的暂态过程

对正弦激励下的RL一阶电路的暂态过程进行了讨论 ,分析了电路在接通正弦交流电源时 ,直接进入稳态响应的条件以及产生过电流现象的原因     

A NOTE ON THE UNIQUENESSTHEOREM FOR STEADY-STATESEMICONDUCTOR EQUATIONS

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ON THE CONVERGENCE OF GUMMELMAPPING FOR STEADY-STATESEMICONDUCTOR EQUATIONS

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Steady-state response of a saturated half-space with an overlying dry layer subjected to a moving load

In this paper, the steady-state response of a saturated half-space with an overlying dry layer subjected to a moving rectangular load is investigated. The governing partial differential equations are solved using the Fourier transform. The solutions in time-space domain are expressed in terms of infinite Fourier type integrals, which can be evaluated only by numerical quadrature. Numerical results show that the influence of a drained or undrained interface on the response is related to the permeability of the underlying saturated soil. Moreover, the effect due to the upper dry layer is associated with the thickness of the layer.     

THE CHANGING FACE OF THE UNIVERSITY AND THE INTERNATIONALIZATION OF TEACHING AND RESEARCH

As everyone knows, the aims and the goals of university life are quite frequently contradictory. This characteristic is no less true of the internationalization of higher education by means of various forms of international co‐operation: faculty and student exchanges and the like. Often the universities of given nations will engage in such ventures so that they and their backers, specific national enterprises, can gain a competitive edge, one over the other, in areas that produce short‐term wealth for specific interests rather than long‐term solutions to such vital world problems as the destruction of the ozone layer, air and water pollution, and the depletion of vital natural resources. Academics who are true internationalists will see to it that solutions for these and for other “real” problems of mankind are given first priority.     

均匀光栅中的双模耦合

本文考虑在两模间发生耦合时,均匀光纤光栅的光特性对反射和透射两种情况均得到简单从无论对线形还是非线形的情况,本文所介绍的模耦合理论,对理解有关原理和设计光栅,都是重要的工具。     

小功率高频数字控制DC/DC 变换器设计

This paper models a low-power high-frequency digitally controlled synchronous rectifier （SR） OUCK converter. The converter is a hybrid system with three operation modes. Digital PID controler is used. Key problems such as quantization resolution of digital pulse-width modulation （DPWM） and steady-state limit cycles of digital control switching model power supply （SMPS） are discussed, with corresponding solutions presented. Simulation of a digital control synchronous buck is performed with a fixed-point algorithm. The results show that the described approach enables high-speed dynamic performance.     

THE RELIGIOUS ZIONIST: TOWARD THE NEW ERA

This essay presents the problems inherent in religious Zionist education on the eve of a new era, and proposes avenues toward solutions. That the Torah is permanent and the world is relative and changing leads to many incongruities within and among components of religious Zionist identity. The cyber‐era will expose the religious Zionist to a great deal of information, some of which maybe harmful and confusing—especially to adolescents—because of the weakness of present religious Zionist educational doctrines. Therefore, religious Zionist identity is in danger of “overload,” due to incongruities among and within systems. This overload may cause some people to abandon religion and others to turn to ultraorthodoxy, impoverishing the religious Zionist community in two ways, and reducing its ability to serve as a bridge between national factions.     

关于定常与时变系统稳定性的注记

给出了线性定常系统存在加权和的Liapunov函数的条件和零解稳定性的一些新的实用判别法,将有关结果推广到线性时变系统;讨论了非线性系统的相应线性化问题．