基于实时CORBA的分布式虚拟环境研究

构建一个规模可扩展、功能可扩充、高效的异构型分布式虚拟环境(Distributed Virtual Environments,简称DVE)系统是一个极具挑战的课题.针对DVE系统的规模扩展性问题,文章提出了融合空间分区、兴趣管理、一致性/并发控制和状态推算(Dead Reckoning)多种技术的一个通用框架,并对这些关键技术进行了研究;针对DVE系统的功能可扩充和异构性问题,文章提出了采用实时CORBA/TAO支持DVE系统实现的方法.上述方法为解决DVE系统的规模扩展性、功能扩充性和异构性提供了一个框架和技术上的完整方案.最后,文章给出了依据该方案开发的一个DVE系统实例.     

可扩展主动兴趣管理技术研究

兴趣管理是提高分布式虚拟环境扩展性的基本方法,然而经过近十年的发展,扩展性问题仍然是困扰分布式虚拟环境乃至兴趣管理方法的首要问题.传统兴趣管理方法可分为直接利用IP组播和采用混合通讯结构两种.IP组播本身面临诸多扩展性问题,而混合结构仍不能解决瓶颈问题和扩展问题.最近提出的主动兴趣过滤方法将主动路由思想引入到兴趣管理方法中,虽使通讯量大为减少,但这种方法没有解决兴趣管理系统本身的扩展问题,为此提出了可扩展的主动兴趣管理方法,该方法是通过结合主动路由技术,基于内容的发布-订购模式和应用层组播技术来构造一个基于内容(兴趣)进行过滤和转发的通讯架构,该技术既提高了分布式虚拟环境的扩展性,又满足了动态快速改变通讯关系的要求,即提高了兴趣管理系统本身的扩展性.     

分布式虚拟环境中的DR算法研究

在分布式虚拟环境(DVE)取得巨大应用发展的同时,解决系统规模的扩展性已成为首要问题。本文从DR算法的模型和原理入手,针对常规DR算法存在的问题,提出了模糊推算定位DR算法和基于知识DR算法。     

一种适合分布式虚拟环境的XML路由技术

在分布式虚拟环境中,XML技术的应用提高系统的实用性和扩展性。本文针对分布式虚拟环境系统中的XMI。路由问题,提出一种新的XML路由技术BPfilter。该技术根据分布式虚拟环境的特点,在Bloom过滤器算法的基础上,引入语法树以处理XPath查询中判定词,实现了对系统中XML数据快速地匹配和路由。实验结果表明,该技术是可行和有效的。     

分布式虚拟环境中兴趣管理技术的分类研究

分布式虚拟环境作为虚拟现实与网络技术的结合有着广泛的应用，但却面临着扩展性的问题。而兴趣管理正是解决这一问题的有效技术之一。本文提出了基于(表示模型、过滤规则、体系结构)三个要素对兴趣管理进行分类的新方法，并据此对以往的分布式虚拟环境系统中采用的兴趣管理技术进行了分析和总结，籍以促进兴趣管理技术的进一步发展，此外简要介绍了南京大学AIMNET中所采用的兴趣管理技术。     

基于网格的分布式虚拟环境仿真海量数据管理

分析了分布式虚拟环境仿真的特点,提出了基于网格的分布式虚拟环境仿真的海量数据管理框架.该框架结构采用分层结构,自底向上依次为网格节点、高性能通信系统、数据存储与处理系统和计算系统.给出了一个基于上述体系结构的原型系统.对该原型系统的仿真结果表明,该海量数据管理体系结构设计符合虚拟环境仿真实时性、稳定性和高可靠性的要求.     

大规模分布式入侵检测系统的研究与探讨

本文首先分析了入侵技术及入侵检测系统的发展趋势,然后给出了一种大规模分布式入侵检测系统的整体模型,并在系统中综合运用了多种入侵检测方法,使整个系统具有良好的规模扩展性和高的入侵检测性能.     

分布式虚拟环境AIMNET的关键技术概述

本文概要介绍南京大学自主研究开发的分布式虚拟环境AI MNET的关键技术。AI MNET借鉴了兴趣管理的思想,提出了双向-共享组播树的通讯结构,从而大大降低了网络通讯量,并保证了AI MNET系统良好的扩展性;AI MNET中静态数据采用分布式存储结构,同时为了实现场景的远程渲染而采用了负载均衡、数据压缩、累进式渲染、航位预测算法以及数据预取等技术。     

分布式虚拟环境综述

在分布式虚拟环境中,位于不同物理位置的多个用户或多个虚拟环境通过网络相互联结,进行信息共享和交互.该文结合作者的研究工作,从分布式虚拟环境的产生、需求和特征、模型和结构以及系统关键技术这几个方面对分布式虚拟环境的研究情况进行综述,讨论了存在的问题和进一步的发展方向.     

分布式虚拟环境的网络通信机制研究与应用

分布式虚拟环境(Distributed Virtual Environments,简称DVEs),其网络通信模块的开发,技术复杂,工作量大.而WTK支持分布式虚拟环境,可实现高效系统开发.介绍了WTK的网络体系结构,重点分析了分布式虚拟环境的网络结构、通信模型,深入研究了状态更新消息传递机制.在此基础上,给出了一个基于WTK实现分布式虚拟环境的设计方案,并介绍了应用程序仿真循环.实验结果表明:基于该设计方案的DVEs应用可较好满足交互的动态性和一致性要求,具有可行性.     

A self-configurable large-scale virtual manufacturing environment for collaborative designers

As manufacturing environments are getting distributed and increasing in size, the related virtual environments are getting larger and more closely networked together. This trend has led to a new paradigm—large-scale virtual manufacturing environment (LSVME). It supports networked and distributed virtual manufacturing to meet manufacturing system requirements. Since it contains a large number of virtual components, an effective data structure and collaborative construction methodology are needed. A metaearth architecture is proposed as the data structure for representing LSVME. This architecture consists of virtual space layer, mapping layer, library layer and ontology layers, which describe interaction among virtual components and has the ability to analyze the characteristics of virtual environment. In addition, it increases reusability of virtual components and supports self-reconfiguration for manufacturing simulation. A heuristic construction method based on graph theory is proposed using this architecture. It prevents redundant design of virtual components and contributes to an effective construction scheduling technique for collaborative designers.     

Virtual distributed environments in a shared infrastructure

We have developed a middleware system that integrates and extends virtual machine and virtual network technologies to support mutually isolated virtual distributed environments in shared infrastructures like the grid and the PlanetLab overlay infrastructure. Integrating virtual network and on-demand virtual machine creation and customization technologies makes virtual distributed environments a reality. The Violin-based middleware system integrates and enhances such technologies to create virtual distributed environments.     

A two-phase approach to interactivity enhancement for large-scale distributed virtual environments

Distributed virtual environments (DVEs) are distributed systems that allow multiple geographically distributed clients (users) to interact simultaneously in a computer-generated, shared virtual world. Applications of DVEs can be seen in many areas nowadays, such as online games, military simulations, collaborative designs, etc. To support large-scale DVEs with real-time interactions among thousands or even more distributed clients, a geographically distributed server architecture (GDSA) is generally needed, and the virtual world can be partitioned into many distinct zones to distribute the load among the servers. Due to the geographic distributions of clients and servers in such architectures, it is essential to efficiently assign the participating clients to servers to enhance users’ experience in interacting within the DVE. This problem is termed the client assignment problem (CAP) in this paper. We propose a two-phase approach, consisting of an initial assignment phase and a refined assignment phase to address the CAP. Both phases are shown to be NP-hard. Several heuristic assignment algorithms are then devised and evaluated via extensive simulations with realistic settings. We find that, even under heterogeneous environments like the Internet where accurate input data for the assignment algorithms are usually impractical to obtain, the proposed algorithms are still beneficial to the performances of DVE.     

An evaluation framework for deploying Web Services in the next generation manufacturing enterprise

In today's competitive manufacturing environment, the ability to effectively and efficiently manage the flow of information is a vital competency. Manufacturing enterprises must be able to integrate their internal business processes horizontally and vertically, and they are increasingly required to support federated business processes with other members of their respective virtual value chains. Web Services, an emerging form of service-oriented architecture for distributed computing, have the potential to serve as a key enabling technology to support these requirements. Leveraging the inherent interoperability of Internet and Worldwide Web technologies, they enable cooperative processing across heterogeneous computing environments. This paper presents a framework for evaluating the viability of Web Services technologies to be incorporated into enterprise information architectures to support the business needs and requirements of next generation manufacturing enterprises. It examines economic, technical, and organizational contexts that will influence the ability of manufacturing-related enterprises to deploy advanced information architectures based on Web Services to support the complex business processes needed to collaborate with suppliers, customers, and other stakeholders in virtual enterprise environments.     

Synchronous learning best practices: An action research study

Low cost and significant advances in technology now allow instructors to create their own virtual learning environments. Creating social interactions within a virtual space that emulates the physical classroom remains challenging. While students are familiar with virtual worlds and video meetings, they are inexperienced as virtual learners. Over a nine year period we applied iterative cycles of action research through numerous large classes to systematically uncover attributes of success when executing synchronous learning in distributed environments. Findings show technology is not the source of problems; rather, difficulties emerge from human behaviors and their interactions with system features. We conclude with practical takeaway guidelines for video conferencing and immersive virtual environments and a model of nexus of control that elaborates software and classroom management attributes that can lead to successful execution.     

Video game experience predicts virtual, but not real navigation performance

In recent years, studies have shown that video game experience is related to improvements across a variety of cognitive and visuospatial tasks. This study investigated the relationship between prior video game experience and spatial performance in virtual and real environments. Across two experiments, gaming experience was related to performance in desktop virtual environments; those with more video game experience were more accurate in pointing to nonvisible targets. In contrast, gaming experience was unrelated to three different real environment tasks, suggesting that video games may primarily influence perceptual and cognitive abilities in the visual domain over abilities that also involve kinesthetic or vestibular input. Contrary to expectations, gaming experience was also related to performance in immersive virtual environments, which may be related to the use of a joystick interface during immersive travel. Video game experience was also positively related to performance in a dynamic spatial task and to verbal SAT and math SAT scores. Sex differences in desktop virtual navigation and dynamic spatial ability were eliminated when game experience was included as a covariate.     

分布式虚拟环境平台(NPSNET-V)的研究

NPSNET-V由美国海军研究生院开发,其目标是逐步发展形成一个支持互联网上分布式虚拟环境的框架。目前,NPSNET-V是一个支持网络虚拟环境应用的、基于组件的、动态可扩展平台。本文论述了它的基本构思、组件框架、实体模型、典型架构、应用结构、设计启示等。     

Integration of manufacturing services into virtual environments over the internet

Virtual reality (VR) is a rapidly developing technology that has a wide spectrum of industrial and commercial applications. Networked (distributed or shared) virtual environments (VE) are of growing interest to modern manufacturing industry; a dominating use of networked virtual manufacturing environments (VMEs) is on-line visualisation and collaborative control of 3D information. This has to be supported by real-time data transfer. To meet a broad range of common requirements for Internet-based VE communications, particularly for virtual manufacturing and collaborative design and control, this paper presents a networked virtual environment system that is designed to support networked virtual design and manufacturing. The system is implemented with manufacturing message specification (MMS) standards so as to integrate a range of manufacturing services into networked VEs over the Internet.     

e-CAPP: A distributed collaborative system for internet-based process planning

Advances in distributed technologies have enabled engineers to communicate more effectively, collaborate, obtain, and exchange a wide range of design resources during product development. Shared internet-based virtual environments allow experts in remote locations to analyze a virtual prototype, together and simultaneously in centers in which the product is being developed.This paper presents a system for distributed and collaborative environment which could assist manufacturing enterprises and experts in discussing, suggesting, evaluating and selecting best process plans for family of manufacturing parts. The represented e-CAPP system enables the implementation of expert knowledge in an appropriate knowledge repository. The knowledge from this repository is integrated into intra-company CAPP systems and used while generating process plans for new products. The proposed internet-based collaborative environment, dedicated to distributed process planning, is yet another step in the direction advancing of distributed manufacturing.     

分布式虚拟环境软件开发平台YHVRP

通过研究当前的典型分布式虚拟环境软件结构的不足,将复杂行为计算引入虚拟环境。设计并实现了一个软件开发平台ＹＨＶＲＰ以支持复杂行为的分布式模拟环境的开发。