Reducing numerical dissipation in smoke simulation

Numerical dissipation acts as artificial viscosity to make smoke viscous. Reducing numerical dissipation is able to recover visual details smeared out by the numerical dissipation. Great efforts have been devoted to suppress the numerical dissipation in smoke simulation in the past few years. In this paper we investigate methods of combating the numerical dissipation. We describe visual consequences of the numerical dissipation and explore sources that introduce the numerical dissipation into course of smoke simulation. Methods are investigated from various aspects including grid variation, high-order advection, sub-grid compensation, invariant conservation, and particle-based improvement, followed by discussion and comparison in terms of visual quality, computational overhead, ease of implementation, adaptivity, and scalability, which leads to their different applicability to various application scenarios.     

Efficient Low Dissipative High Order Schemes for Multiscale MHD Flows, II: Minimization of ∇·B Numerical Error

An adaptive numerical dissipation control in a class of high order filter methods for compressible MHD equations is systematically discussed. The filter schemes consist of a divergence-free preserving high order spatial base scheme with a filter approach which can be divergence-free preserving depending on the type of filter operator being used, the method of applying the filter step, and the type of flow problem to be considered. Some of these filter variants provide a natural and efficient way for the minimization of the divergence of the magnetic field (∇·B) numerical error in the sense that commonly used divergence cleaning is not required. Numerical experiments presented emphasize the performance of the ∇·B numerical error. Many levels of grid refinement and detailed comparison of the filter methods with several commonly used compressible MHD shock-capturing schemes will be illustratedA condensed version appears in the Proceedings of the International Conference on High Performance Scientific Computing, March 10-14, 2003, Hanoi, Vietnam. This is a revised version of a longer internal report, Feb. 19, 2004. The longer internal report was published as a RIACS Technical Report TR03.10, July 2003, NASA Ames Research Center     

HFC电缆分配系统的建设与思考

结合沧州市网络的实际情况，主要分析HFC电缆分配系统双向传输改造的建设标准和实施方案。     

基于ASP.NET技术的新闻发布系统的设计与实现

完整描述了一种在部队师旅级单位通用的新闻发布系统。首先根据用户的特点,对系统进行了需求分析与功能模块划分,然后在此基础上从系统架构、系统流程和数据库设计等3个方面阐述了系统设计中的关键点,并以设计用户登录界面为例写出了部分功能的实现程序,最后对其在中小型企业建站中的应用进行了展望。     

从数据库到数据仓库——广电未来的制胜武器

在目前数据爆炸、信息匮乏的情况下，需要利用数据仓库系统集成1个或多个独立传统数据库数据，通过分析海量数据发现市场潜在规律，获取商业信息以支持商业决策，这将是广电未来的制胜武器。     

石化企业实时数据管理引擎设计与实现

实时数据管理系统是流程企业控制信息网络与管理信息网络平滑集成的基础，为两者的数据通讯提供桥梁。介绍了笔者在炼油化工C企业IMS建设中的实时数据管理引擎设计与开发，具有其先进性与实用性。     

基于SpatialWare的地理数据访问安全性研究

地理信息系统的应用越来越广泛,特别是基于网络的GIS的发展使地理空间信息通过网络被多用户所共享,因此必须考虑地理数据访问的安全性。文章以MapInfoSpatailWare空间数据引擎为研究对象,给出了基于此模式的数据访问安全性解决方案。     

没有SDC的(t，n)门限秘密共享方案

利用椭圆曲线离散问题对数问题的难解性,给出了基于椭圆曲线密码体制的(t,n)门限秘密共享方案。基于门限秘密共享方案一般分为需要SDC和不需要SDC两类,在分布式环境下,一个被所有成员信任的SDC并不存在,不需要SDC的门限秘密共享方案的安全性得到很大的提高,该方案中由组成员共同生成群公钥和私有密钥。并给出了当新成员加入时,无SDC下的周期密钥分片的更新方案。还给出了一个本方案数据实例,最后对本方案的安全性进行了分析。     

异构数据集成方法研究与实现

为解决异构数据集成的复杂性问题，文章提出了一种异构数据同步的新方法——半集成式中间件法。该方法成功地应用在重庆市社会保障综合信息系统中，具有易于实现、可扩展性、跨平台性和效率高等特点。     

数据库新技术浅析

介绍了数据库技术的发展及现状，数据库技术与多学科技术的有机结合，根据数据库技术的延伸与发展，论述了数据库建设中应注意的几个问题。