Generalized Hopf Bifurcation for Planar Filippov Systems Continuous at the Origin

In this paper, we study the existence of periodic orbits bifurcating from stationary solutions of a planar dynamical system of Filippov type. This phenomenon is interpreted as a generalized Hopf bifurcation. In the case of smoothness, Hopf bifurcation is characterized by a pair of complex conjugate eigenvalues crossing through the imaginary axis. This method does not carry over to nonsmooth systems, due to the lack of linearization at the origin which is located on the line of discontinuity. In fact, generalized Hopf bifurcation is determined by interactions between the discontinuity of the system and the eigen-structures of all subsystems. With the help of geometrical observations for a corresponding piecewise linear system, we derive an analytical method to investigate the existence of periodic orbits that are obtained by searching for the fixed points of return maps.     

超大规模集成电路波导光互连技术的现状与前景

介绍超大规模集成电路(VLSI)波导(?)互连技术的最新进展,并预测其发展方向,以及如阿解决存在的实际问题。     

氮化硼固相转变的船形模型

 船形转变模型是有rBN结构向wBN结构的固相转变模型。在静高压下，相比于以椅形方式，rBN更容易以船形方式转变。     

求解准确的表面张力—重力波方程的新方法

本文提供一个求解重力和表面张力同时作用的周期前进二维非线性波的新方法.自由表面在计算域转入单位圆后用有限项Fourier级数表示.动力学边界条件用的是完整的非线性形式.Fourier级数的系数用Newton-Raphson方法迭代求解.这是一个精巧的方法.所用计算工作量小而结果精度高.     

Mechanical endurance of polymer electrolyte membrane and PEM fuel cell durability

The life of proton exchange membrane fuel cells (PEMFC) is currently limited by the mechanical endurance of polymer electrolyte membranes and membrane electrode assemblies (MEAs). In this paper, the authors report recent experimental and modeling work toward understanding the mechanisms of delayed mechanical failures of polymer electrolyte membranes and MEAs under relevant PEMFC operating conditions. Mechanical breach of membranes/MEAs in the form of pinholes and tears has been frequently observed after long‐term or accelerated testing of PEMFC cells/stacks. Catastrophic failure of cell/stack due to rapid gas crossover shortly follows the mechanical breach. Ex situ mechanical characterizations were performed on MEAs after being subjected to the accelerated chemical aging and relative humidity (RH) cycling tests. The results showed significant reduction of MEA ductility manifested as drastically reduced strain‐to‐failure of the chemically aged and RH‐cycled MEAs. Postmortem analysis revealed the formation and growth of mechanical defects such as cracks and crazing in the membranes and MEAs. A finite element model was used to estimate stress/strain states of an edge‐constrained MEA under rapid RH variations. Damage metrics for accelerated testing and life prediction of PEMFCs are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2346–2357, 2006     

电荷量子比特与量子化光场之间的纠缠

研究了初态为混合态的电荷量子比特与量子化光场之间的纠缠.通过求解系统的concurrence下限, 研究初态的混合度λ和失谐量Δ对系统纠缠随时间演化的影响. 在弱场中, 电荷量子比特初始是激发态的系统, 其纠缠度远远大于电荷量子比特初始是基态的系统, 并且Δ对系统的纠缠有明显的抑制作用. 在强场中, 电荷量子比特初始分别为激发态和基态时系统的纠缠演化接近一致, 初态混合度最高时系统的纠缠度最小, 并且Δ对系统纠缠的影响变弱. 关键词： 约瑟夫森结 纠缠 混合态 concurrence下限     

A new simple and rapid electrochemical method for the determination of hydroxyl radical generated by Fenton reaction and its application

A simple and rapid electrochemical method to detect the hydroxyl radical is described. This method employed the reaction between.OH and dimethyl sulfoxide (DMSO) to generate quantitatively formaldehyde, which then reacted with hydrazine hydrochloride at pH 6.2. The product showed a second-order derivative cathodic wave with the peak potential of -1.08 V( vsSCE) by single sweep oscillopolarography. The electrochemical behavior of the product was investigated by single sweep oscillopolarography and cyclic voltammetry. The experimental conditions for the measurement were optimized and the scavenging activity of some flavonoids on hydroxyl radicals was studied.     

芦荟大黄素的电化学研究

用单扫示波极谱法研究了芦荟大黄素的电化学行为。在５％Ｎａ２ＣＯ３＋５％ＮａＯＨ（９＋１）底液中，芦荟大黄素于－０．８４Ｖ（Ｐ１）和－０．９７Ｖ（Ｐ２）处产生两个示波极谱峰，利用Ｐ１可测定芦荟大黄素，线性范围为 ０．１１－２４ｍｇ／Ｌ和３．０－２８．６ｍｇ／Ｌ，检测限为０．０６ｍｇ／Ｌ。将该法应用于中药大黄中的芦荟大黄素的测定，结果满意。另外，讨论了芦荟大黄素清除由邻苯三酚自氧化产生的超氧自由基（Ｏ２）的作用。     

白酒中C_9－C_（18）脂肪酸的气相色谱分析

白酒中Ｃ＿９－Ｃ＿（１８）脂肪酸的气相色谱分析周在德，曾永昌（四川大学化学系成都６１００６４）关键词气相色谱法，白酒，Ｃ＿９－Ｃ＿（１８）脂肪酸。白酒中脂肪酸的含量及相互比例关系，极大地影响着白酒的色，香，味，风格￣（［１］［２］）。一般采用的化学分...