关键词： 同步服务器   移动计算环境   主表   复制表   数据库动作   数据上载  

摘要： 该文主要阐述同步服务器的设计与实现,以及在此基础上进行的应用实例开发.第一部分介绍移动数据库的一些数据同步技术和目前市场上的一些具有类似功能的数据库产品.第二部分介绍同步服务器的基本设计思想,基本功能模型.第三部分介绍同步服务器的一些具体实现方法.第四部分结合一个基于OpenBASE Mini的应用实例来描述实际数据库应用程度的开发.

关键词： mobile computing   messaging server   MicMac   network security   agent   LDAP  

摘要： The Personal Mobility Management System (PMMS), an agent-based message-oriented mobile computing application developed at Multimedia and Mobile Agent Research Laboratory, aims to provide personalized services and resources access to its nomadic users within a virtual network across different organizations. This paper analyses and discusses the security weaknesses exposed in the system architecture, then proposes several security frameworks to overcoming these security concerns. The paper tries to address and provide a general architectural solution to ensure secure communications for a typical message-oriented mobile computing system.

关键词： mobile computing   coordinated checkpointing   causal dependency   nonblocking  

摘要： Mobile computing raises many new issues such as lack of stable storage, low bandwidth of wireless channel, high mobility, and limited battery life. These new issues make traditional checkpointing algorithms unsuitable. Coordinated checkpointing is an attractive approach for transparently adding fault tolerance to distributed applications since it avoids domino effects and minimizes the stable storage requirement. However, it suffers from high overhead associated with the checkpointing process in mobile computing systems. Two approaches have been used to reduce the overhead: First is to minimize the number of synchronization messages and the number of checkpoints;the other is to make the checkpointing process nonblocking. These two approaches were orthogonal previously until the Prakash-Singhal algorithm [28] combined them. However, we [8] found that this algorithm may result in an inconsistency in some situations and we proved that there does not exist a nonblocking algorithm which forces only a minimum number of processes to take their checkpoints. In this paper, we introduce the concept of "mutable checkpoint," which is neither a tentative checkpoint nor a permanent checkpoint, to design efficient checkpointing algorithms for mobile computing systems. Mutable checkpoints can be saved anywhere, e.g., the main memory or local disk of MHs. In this way, taking a mutable checkpoint avoids the overhead of transferring large amounts of data to the stable storage at MSSs over the wireless network. We present techniques to minimize the number of mutable checkpoints. Simulation results show that the overhead of taking mutable checkpoints is negligible. Based on mutable checkpoints, our nonblocking algorithm avoids the avalanche effect and forces only a minimum number of processes to take their checkpoints on the stable storage.

关键词： 计算机   计算机技术   移动计算技术   量子计算机   纳米计算机   光子计算机  

摘要： 在刚刚过去的二十世纪里,以计算机和通信为代表的信息技术迅猛发展、广泛普及.1946年第一台电子管计算机ENIAC(电子数字积分计算机)问世,其后,计算机历经晶体管、集成电路、大规模集成电路、超大规模集成电路几个发展阶段.

关键词： COMPUTER systems  

摘要： This paper is designed to relate the rationale used by the Department of Defense, to utilize Telemedicine, to meet increasing global crises, and for the U.S. military to find ways to more effectively manage manpower and time. A mobile Telemedicine package has been developed by the Department of Defense (DOD) to collect and transmit near-real-time, far-forward medical data and to assess how this improved capability enhances medical management of the battlespace. Telemedicine has been successful in resolving uncertain organizational and technological military deficiencies and in improving medical communications and information management. The deployable, mobile Teams are the centerpieces of this Telemedicine package. These teams have the capability of inserting essential networking and communications capabilities into austere theaters and establishing an immediate means for enhancing health protection, collaborative planning, situational awareness, and strategic decision-making.

关键词： Point-of-Care Systems   Computers   Equipment Design   Systems Integration   United States  

摘要： Focuses on several point-of-care workstations (POCW), mobile computers being used in patient care, launched in the United States by medical apparatus manufacturers. Benefits of POCW; Features of the POCW from Ergotron Inc.; Information on the POCW from Tremont; Details of the POCW from Datalux Corporation.

关键词： 病毒防治   恶意程序   天气预报   气象预报   政府上网   特洛伊木马   移动计算  

摘要： 如果说1999年是政府上网年,2000年是企业上网年,那么今年应该是网络安全年。对于病毒,我们该出手时就出手。展望2001年,病毒防治提供商、新闻记者和独立研究机构中已经有不少人已经对预防问题发表了自己的见解。

关键词： 笔记本   始终   键盘   计算能力   笔记本电脑   移动计算  

摘要： 毫无疑问,购买笔记本电脑就是用来随时随地实现移动计算.而且,笔记本电脑在计算能力方面与台式产品的差距越来越小,笔记本产品的需求量已经开始超过台式产品的需求量。比如,1999年美国市场上,笔记本电脑的市场增长率首次超过台式产品,而同一时间,日本市场笔记本电脑产品的增长率也非常接近台式产品。在中国市场也不例外,笔记本电脑的市场增长率始终保持着很高的水平.那么,作为一个消费者,在选择笔记本电脑时,需要怎样衡量笔记本电脑的水准呢?首先,作为移动计算需求而诞生的笔记本电脑来说,首要考虑的是笔记本电脑的体积和重量.俗话说百里无轻物,

关键词： 消费电子市场   企业   企业管理   PDA   自身优势   移动计算   商人   厂商  

摘要： 提供“贴近本地市场的企业和行业应用解决方案”,将是国内PDA厂商发挥自身优势的机会所在

关键词： 中国   计算机网络   学会   学术   会议   国家重点实验室   算机辅助设计   数据库系统   浙江大学   北京   主办单位   移动计算   计算机系   信息学   协同式   图形学   应用   人民   名称   昆明  

摘要： 会议名称及内容　　地点　　时间　　主办单位　　联系人及地址　　第3届国际协同式数据库系统高级应用会议（CODAS 2001）　　北京　　4月23～24日　　数据库专委　　孟小峰，中国人民大学信息学院，100872;E-mail: codas2001@***　　第7届国际计算机辅助设计与图形学会议(CAD/Graphics 2001)　　昆明　　8月20～22日　　中国计算机学会　　胡敏, 浙江大学CAD/CG国家重点实验室,310027; Tel: 0571-7951045; Fax：0571-795 1780;E-mail: CADGraphics@***　　国际计算机网络与移动计算会议（ICCNMC 2001）　　北京　　10月16～19日 　　中国计算机学会、IEEE-CS　　李晓明,北京大学计算机系,100871; E-mail: lxm@***; 杜子德，中国计算机学会，100080，Tel: 010-62527486; Fax: 010-62527485;　　E-mail: zidedu@***