Generation of interfacial instabilities in charged electrified viscous liquid films

This study is concerned with the stability of a two-dimensional incompressible conducting liquid film surrounded by a passive conducting medium, when an electric field is applied in a direction parallel to the initially flat bounding fluid interfaces. Currents generate charges at the bounding interfaces which in turn affect the stress balances there. In the absence of an electric field, the viscous liquid film is stable (instability can be induced by the inclusion of van der Waals forces for ultra thin films). A complete model is presented, at arbitrary Reynolds number, which accounts for conductivity and permittivity contrasts between the fluid and surrounding medium, as well as surface tension. The linear stability of the system is considered for arbitrary Reynolds numbers and it is shown that the stable film can become unstable if, (i) σ _R ɛ _p >1, or (ii) σ _R ɛ _p <1 and (σ _R −1)(1−ɛ _p )<0, where σ _R is the ratio of outer to inner conductivity and ε _p is the ratio of inner to outer permittivity. Instability is possible only if the electric field is non-zero and the scalings near bifurcation points that can be used to construct nonlinear theories are calculated. Several asymptotic limits are also considered including zero Reynolds numbers and short or long waves. The instability criteria given above are constructed explicitly in the case of Stokes flow.     

Effects of Spatial Characteristics on Smart Antenna System with Uniform Linear Antenna Array

1IntroductionCurrently,smart antenna technology can greatly en-hance system performance and i mprove the system ca-pacity so that it has been considered as a keytechnologyinthe third generation wireless communicationsystems .The researches on channel model , beamforming algo-rithms and receive algorithms have been widely carriedout and a great many of proposition have beensubmittedtothe 3th Generation Project Partner (3GPP) . Fromthe viewpoint of link-level and system-level research,many asp…     

基于MATLAB在化工优化设计中的应用

结合化工优化计算的实例，着重介绍如何应用MATLAB7．0提供的优化工具箱来对线性规划及非线性规划模型进行求解。     

Dynamic Multicast Session Provisioning in WDM Optical Networks with Sparse Splitting Capability

In this work, we study dynamic provisioning of multicast sessions in a wavelength-routed sparse splitting capable WDM network with an arbitrary mesh topology where the network consists of nodes with full, partial, or no wavelength conversion capabilities and a node can be a tap-and-continue (TaC) node or a splitting and delivery (SaD) node. The objectives are to minimize the network resources in terms of wavelength-links used by each session and to reduce the multicast session blocking probability. The problem is to route the multicast session from each source to the members of every multicast session, and to assign an appropriate wavelength to each link used by the session. We propose an efficient online algorithm for dynamic multicast session provisioning. To evaluate the proposed algorithm, we apply the integer linear programming (ILP) optimization tool on a per multicast session basis to solve off-line the optimal routing and wavelength assignment given a multicast session and the current network topology as well as its residual network resource information. We formulate the per session multicast routing and wavelength assignment problem as an ILP. With this ILP formulation, the multicast session blocking probability or success probability can then be estimated based on solving a series of ILPs off-line. We have evaluated the effectiveness of the proposed online algorithm via simulation in terms of session blocking probability and network resources used by a session. Simulation results indicate that our proposed computationally efficient online algorithm performs well even when a fraction of the nodes are SaD nodes.     

基于DTW算法的语音识别系统实现

动态时间归整(DTW)算法的实现简单有效,在孤立词语音识别系统中得到了广泛的应用.介绍了将DTW算法移植到TMS320VC5402上实现孤立词语音识别的原理、系统硬件组成和软件设计.研究结果表明,系统能满足实时性能要求,识别效果良好.     

基于光敏自组装多层膜的液晶光控取向膜

采用layer-by-layer(LBL)的方法，将基板依次在具有光敏双键的季铵盐水溶液和聚乙烯基苯磺酸钠水溶液中浸泡，石英基板表面形成了自组装多层沉积膜。经线性偏振紫外光辐照后，LBL多层膜表现出明显的紫外吸收各向异性。将两片带有各向异性薄膜的基板做成平行液晶器件。在正交的偏光显微镜下观察，发现取得均一、稳定的取向效果。该种光控取向膜有望用作LCoS微显示的取向层。     

A p‐version,first order shear deformation,finite element for geometrically non‐linear vibration of curved beams

A p‐version, hierarchical finite element for curved, moderately thick, elastic and isotropic beams is introduced. The convergence properties of the element are analysed and some results are compared with results published elsewhere or calculated using a commercial finite element package. It is verified that, with the proposed element, shear locking does not affect the computation of the natural frequencies and that low dimensional, accurate models are obtainable. Geometrically non‐linear vibrations due to finite deformations, which occur for harmonic excitations with frequencies close to the first three natural frequencies of vibration, are investigated using Newmark's method. The influence of the thickness, longitudinal inertia and curvature radius on the dynamic behaviour of curved beams are studied. Copyright © 2004 John Wiley & Sons, Ltd.     

Application of piece‐wise linear weight functions for 2D 8‐node quadrilateral element in contact problems

The present study is a continuation of our previous work with the aim to reduce problems caused by standard higher order elements in contact problems. The difficulties can be attributed to the inherent property of the Galerkin method which gives uneven distributions of nodal forces resulting in oscillating contact pressures. The proposed remedy is use of piece‐wise linear weight functions. The methods to establish stiffness and/or mass matrix for 8‐node quadrilateral element in 2D are presented, i.e. the condensing and direct procedures. The energy and nodal displacement error norms are also checked to establish the convergence ratio. Interpretation of calculated contact pressures is discussed. Two new 2D 8‐node quadrilateral elements, QUAD8C and QUAD8D, are derived and tested in many examples, which show their good performance in contact problems. Copyright © 2004 John Wiley & Sons, Ltd.     

Updated semi‐discretization method for periodic delay‐differential equations with discrete delay

An updated version of the semi‐discretization method is presented for periodic systems with a single discrete time delay. The delayed term is approximated as a weighted sum of two neighbouring discrete delayed state values and the transition matrix over a single period is determined. Stability charts are constructed for the damped and delayed Mathieu equation for different time‐period/time‐delay ratios. The convergence of the method is investigated by examples. Stability charts are constructed for 1 and 2 degree of freedom milling models. The codes of the algorithm are also attached in the appendix. Copyright © 2004 John Wiley & Sons, Ltd.