非刚性固相表面短程引力场与固－气相间压力

认为固相表面短程引力场对其邻近气相分子有加速作用这个提法不妥，并假定在不发生吸附且忽略分子间作用力的条件下，用统计热力学的结果讨论了非刚性固相表面短程引力场作用下，固－气相界面的气体分布及其施于固相表面之压力。     

Estimation of Basins of Attraction for Uncertain Systems with Affine and Lipschitz Dynamics

This paper is devoted to estimation and numerical approximation of basins of attraction for a class of uncertain systems. We consider systems described by a differential equation depending of a disturbance known by its bounds. By using viability theory tools, we derive basins of attraction lower and upper estimates. We present numerical simulation results of the viability kernel algorithm to basin of attraction approximation problems.     

基于双信息素的MMAS在TSP中的应用

正反馈机制是蚁群算法的一个重要特征,它通过信息素的累积作用对蚂蚁的寻径产生诱导,从而吸引更多的蚂蚁,加快了发现较优解的速度,但是同时也为陷入局部最优埋下了隐患,在此基础上,引入了负反馈机制,通过排斥信息素来实现。实验表明,负反馈机制的应用增强了算法发现最优解的能力,是实际可行的。     

PID Control of Planar Nonlinear Uncertain Systems in the Presence of Actuator Saturation

This paper investigates PID control design for a class of planar nonlinear uncertain systems in the presence of actuator saturation.Based on the bounds on the growth rates of the nonlinear uncertain function in the system model,the system is placed in a linear differential inclusion.Each vertex system of the linear differential inclusion is a linear system subject to actuator saturation.By placing the saturated PID control into a convex hull formed by the PID controller and an auxiliary linear feedback law,we establish conditions under which an ellipsoid is contractively invariant and hence is an estimate of the domain of attraction of the equilibrium point of the closed-loop system.The equilibrium point corresponds to the desired set point for the system output.Thus,the location of the equilibrium point and the size of the domain of attraction determine,respectively,the set point that the output can achieve and the range of initial conditions from which this set point can be reached.Based on these conditions,the feasible set points can be determined and the design of the PID control law that stabilizes the nonlinear uncertain system at a feasible set point with a large domain of attraction can then be formulated and solved as a constrained optimization problem with constraints in the form of linear matrix inequalities(LMIs).Application of the proposed design to a magnetic suspension system illustrates the design process and the performance of the resulting PID control law.     

用胞映射方法讨论一类MKdV方程

利用简单胞映射方法对一类MKdV(Modified Korteweg de Vries)方程未受扰系统，周期激励系统进行了讨论.首先利用行波法将MKdV方程化为常微分方程组并用四阶Runge kutta方法画出其相图，然后用简单胞映射方法得到了MKdV方程的全局吸引域和有限步吸引域.该结果与相应的相图很好的吻合起来.     

Control of aluminum phosphate coating on mullite fibers by surface modification with polyethylenimine

Aluminum phosphate (AlPO₄) is a promising oxidation-resistant and weak interface for ceramic-matrix composites. In this research, AlPO₄ coating was deposited on mullite fibers by an improved liquid-phase method based on electrostatic attraction. A cationic polyelectrolyte, polyethylenimine (PEI), was used for surface modification of mullite fibers. The formation process, phase evolution and microstructure of the coating were studied. The zeta potential of AlPO₄ particles, PEI-adsorbed AlPO₄ particles, and PEI-adsorbed mullite particles was characterized to find the proper pH value for improving electrostatic attraction. The obtained AlPO₄ coating was porous and continuous, whose thickness could be controlled by multiple coating cycles. The relatively low calcination temperature (600 or 1000 °C) was a useful heat treatment method to develop bonding between coating and fiber as well as reduce the fiber strength degradation. The phase transformations of AlPO₄ have little volume change, and cristobalite AlPO₄ is thermal compatible with mullite. Therefore, the coating structure was preserved after calcining at 1200 °C. The technique is also applicable for other fibers contained mullite phase to fabricate high-performance AlPO₄ coated mullite/mullite composites.     

高阶非线性系统状态反馈抗饱和跟踪控制

针对参数未知的高阶非线性系统,提出了一种简单有效的反馈抗饱和控制方法,并进行了状态反馈抗饱和控制吸引域估计.利用反馈控制思想,借助于李亚普诺夫稳定性理论,设计出了相应的状态抗饱和反馈控制器,并借助于Matlab进一步求出了控制器的参数.将所设计的抗饱和控制应用于Duffing混沌系统,仿真结果验证了该控制方法的有效性.     

ASYMPTOTIC INFERENCES FOR AN AR(1) MODEL WITH A CHANGE POINT: STATIONARY AND NEARLY NON‐STATIONARY CASES

This article examines the asymptotic inference for AR(1) models with a possible structural break in the AR parameter β near the unity at an unknown time k₀. Consider the model y_t = β₁y_{t − 1}I{t ≤ k₀} + β₂y_{t − 1}I{t > k₀} + ϵ_t, t = 1,2, … ,T, where I{ ⋅ } denotes the indicator function. We examine two cases: case I | β₁ | < 1,β₂ = β_2T = 1 − c ∕ T; and case II β₁ = β_1T = 1 − c ∕ T, | β₂ | < 1, where c is a fixed constant, and {ϵ_t,t ≥ 1} is a sequence of i.i.d. random variables, which are in the domain of attraction of the normal law with zero means and possibly infinite variances. We derive the limiting distributions of the least squares estimators of β₁ and β₂ and that of the break‐point estimator for shrinking break for the aforementioned cases. Monte Carlo simulations are conducted to demonstrate the finite‐sample properties of the estimators. Our theoretical results are supported by Monte Carlo simulations.     

用胞映射法计算摩擦对齿轮吸引域的影响

针对计及摩擦的单对齿轮传动系统的时变非线性模型,应用胞映射方法对系统进行了吸引域计算,得到了在不同的摩擦系数、时变刚度和激励频率参数下系统的吸引域和全局特性,分析了这些参数变化时系统吸引子吸引域的演变规律.研究表明,系统的竞争吸引子是互相缠绕的,摩擦能改变周期运动吸引子的性态,也能降低混沌时的Lypunov指数,有利于提高系统的全局稳定性.     

Repulsion or attraction?: Group membership and assumed attitude similarity.

Three studies investigated group membership effects on similarity-attraction and dissimilarity-repulsion. Membership in an in-group versus out-group was expected to create initially different levels of assumed attitude similarity. In 3 studies, ratings made after participants learned about the target's attitudes were compared with initial attraction based only on knowing target's group membership. Group membership was based on political affiliation in Study I and on sexual orientation in Study 2. Study 3 crossed political affiliation with target's obnoxiousness. Attitude dissimilarity produced stronger repulsion effects for in-group than for out-group members in all studies. Attitude similarity produced greater increments in attraction for political out-group members but not for targets with a stigmatic sexual orientation or personality characteristic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)