Numerical Comparison of WENO Finite Volume and Runge–Kutta Discontinuous Galerkin Methods

High order WENO (weighted essentially non-oscillatory) schemes and discontinuous Galerkin methods are two classes of high order, high resolution methods suitable for convection dominated simulations with possible discontinuous or sharp gradient solutions. In this paper we first review these two classes of methods, pointing out their similarities and differences in algorithm formulation, theoretical properties, implementation issues, applicability, and relative advantages. We then present some quantitative comparisons of the third order finite volume WENO methods and discontinuous Galerkin methods for a series of test problems to assess their relative merits in accuracy and CPU timing.     

一种安全电子招标系统中专家抽取的方法*

介绍了基于PKI架构的公开电子招标系统中专家管理信息系统的专家抽取方法。该方法通过使用加密技术解决专家抽取过程中的安全问题。采用盲签名协议保证抽取信息的机密性、真实性和不可否认性;通过随机算法保证抽取结果的随机化。在基于Web的客户端,监督方在监控抽取过程中对抽取信息未知的情况下签名,确认抽取结果,抽取结果在公布时,获得带有监督方签名的抽取结果。     

Adaptive channel allocation for large-scale streaming content delivery systems

Scheduling algorithms are used in content delivery systems to control the resource allocation rate. They not only improve system efficiency, but also increase user satisfaction. Lower renege rate and less waiting time for users are the main goals for a scheduling algorithm. Among existing algorithms, On-Demand strategy does not perform well, while rate control channel allocation policies performs much better. Pure-Rate-Control (PRC) and Multiple-Service-Class (MSC) belong to the rate control algorithms. MSC performs well, but a drawback is that it uses the Hot Index, which is hard to decide and has significant effects on the performance. In order to solve this problem and to improve the overall system performance, two new algorithms, Modified MSC(MMSC) and Adaptive Algorithm (AA), are proposed in this paper. Both of them solved the problem of MSC very well and improved the overall performance. For example, the renege rate of AA is about 5.4% less than that of MMSC, and about 9.8% less than that of MSC.

用通信中间件实现B2B与ERP的系统集成

ERP系统是B2B系统的基础,企业电子商务常常建立在已有的企业内部网上,为保证电子商务有效工作,二者之间必须实现无缝集成。这就要求企业电子商务网站的数据库服务器与企业内部网的数据库服务器之间进行双向的数据通信,通信中间件产品提供了实现这种数据通讯的有效手段,本文介绍了IBM的通信中间件产品MQSeries,并用实例说明了利用它实现系统集成的方法。     

Mechanical behaviour of cadmium-boron and cadmium-tungsten particulate composites

Mechanical behaviour of particulate composites of cadmium containing 0.6 to 3 m size particles of boron and tungsten (up to 30 vol %) were studied from –196 to 260° C (0.13 to 0.9T _m). The marked strengthening of cadmium by the presence of fine particles is attributed to significant grain size and texture strengthening effects as well as to dispersion hardening effects.     

我国中压动态无功补偿装置的发展及展望

从无功补偿装置应用的必要性出发,介绍了无功补偿装置的原理及组成,分析了常见无功补偿装置的优缺点,论述了国内外无功补偿装置的应用现状。着重介绍了新技术在SVC装置中应用,对比分析了无功补偿装置中的电力电容器、控制方案和投切元件,最后展望了智能型SVC的广泛应用是中压无功补偿装置的发展方向。     

基于非负矩阵分解的鲁棒哈希函数验证性研究

矩阵分解是实现大规模数据处理与分析的一种有效工具。矩阵的非负矩阵分解NMF(Non-Negative Matrix Factorization)变换是一种正交变换,是在矩阵中所有元素均为非负的条件下对其实现的非负分解。鲁棒哈希技术利用密钥提取多媒体内容的某些鲁棒特征,通过进一步压缩产生哈希值,通过比较跟随媒体内容传送来的哈希和接收端产生的哈希,实现对媒体内容的真实性认证。     

WENO Scheme with Subcell Resolution for Computing Nonconservative Euler Equations with Applications to One-Dimensional Compressible Two-Medium Flows

High order path-conservative schemes have been developed for solving nonconservative hyperbolic systems in (Parés, SIAM J.?Numer. Anal. 44:300?C321, 2006; Castro et al., Math. Comput. 75:1103?C1134, 2006; J.?Sci. Comput. 39:67?C114, 2009). Recently, it has been observed in (Abgrall and Karni, J.?Comput. Phys. 229:2759?C2763, 2010) that this approach may have some computational issues and shortcomings. In this paper, a modification to the high order path-conservative scheme in (Castro et al., Math. Comput. 75:1103?C1134, 2006) is proposed to improve its computational performance and to overcome some of the shortcomings. This modification is based on the high order finite volume WENO scheme with subcell resolution and it uses an exact Riemann solver to catch the right paths at the discontinuities. An application to one-dimensional compressible two-medium flows of nonconservative or primitive Euler equations is carried out to show the effectiveness of this new approach.     

Model experiment on anti-deformation performance of a self-supporting transmission tower in a subsidence area

A large number of high-voltage power transmission towers have recently been constructed in mining areas prone to subsidence.In order to ensure the safety of the transmission towers and the safe operati...     

基于富客户端技术的心语墙系统的设计与实现

通过使用微软的富客户端技术Silverlight实现了心语墙系统。用户可以利用系统,在不同的场景下描述心语,比如在广场墙上发布心语,在地图上发布心语。在程序架构上,服务器端使用分层架构思想,客户端使用MVVM模式,从而大大提高了系统的稳定性。