高精度高速度曲面建模的3维地表模拟和漫游算法

三维真实感地形场景是生态系统模拟、虚拟地理环境和三维GIS不可或缺的要素,而高精度高速度曲面建模方法可以动态实时构建高精度曲面模型。论文引入高精度高速度曲面建模方法,提出了一种可以动态生成地表模型并实时绘制和漫游三维真实感地表的方法。该方法实时动态建立高精度DEM,结合改进的视点依赖多分辨率绘制方法,随视点改变动态重建并绘制当前DEM。首先建立当前可见场景的DEM,然后通过依赖于视点的简化等处理建立层次细节模型,进行实时场景绘制和漫游,随视点改变,在当前场景基础上动态加点和减点更新DEM及层次细节模型,生成当前可见场景,以次循环。实例测试表明,算法可产生真实感较强的场景,实时漫游效率较高,模拟精确。     

电缆三维模型可视化及数据高效索引研究

针对电缆三维可视化场景的加载速度慢问题, 提出一种用于电缆工程场景下的三维模型外表面提取简化算法与多细节层次R-树索引数据调度组织方法. 首先对占据三维场景中大量内存的电缆井和管沟模型进行LOD层级简化, 实验结果显示数据量大幅度减小; 然后根据多细节层次的R-树索引结构对简化后的数据进行组织调度, 与传统R-树相比, 该方法构建的R-树在节点筛选和节点分裂时构造了更优的树形, 使得在进行数据的索引和调度时, 对电缆工程三维场景加载速度的提高有明显效果, 有效地实现了电缆工程中三维模型的流畅展示.     

基于连续HLOD的大规模场景快速绘制算法

大规模场景的快速绘制是虚拟现实技术重要的研究课题之一.为了加速场景的绘制,一般采用层次细节模型和可见性裁剪方法,但是现有算法在处理大规模场景时存在着局限性.本文提出了一种新的大规模场景快速绘制算法,该算法在场景层次划分的基础上,利用拓扑结构可变的网格简化方法为场景层次计算连续的分层层次细节模型（HLOD）;然后在实时绘制阶段,对场景分层层次细节模型进行视点相关的全局和局部细化,并结合快速有效的视域裁剪,从而大大加速了场景绘制速度.实验结果表明该算法是简单有效的,并且算法还可以进一步扩展到外存方式.     

基于LOD建模的视景仿真生成技术研究

细节层次(LOD)模型是指对同一个场景或场景中的物体,使用具有不同细节的方法得到一组模型以实现三维场景仿真,而视景生成会使仿真过程更直观形象。文中提出一种利用地形、景物数据库数据,采用LOD建模方法实时生成三维视景,实验结果表明该方法具有一定理论和实用价值。     

Web环境下产品虚拟展示系统的场景优化

在Web环境下,由于较慢的网络传输速度和过大的虚拟展示系统场景文件问题,导致展示场景首次加载时间长,场景漫游时出现卡顿和模型闪烁.针对以上情况,提出了双层次细节渐进优化(Gradually Optimize Two Level of Detail)和模型-贴图过渡显示优化方法.GOTLOD技术通过分割场景和异步加载场景文件,使用低精度模型快速搭建展示场景,利用视距远近动态切换不同精度的模型.模型-贴图过渡显示优化技术利用视距改变的差值大小,在模型和贴图间进行多层级切换.实验结果表明,采用GOTLOD和模型-贴图优化技术,场景初次加载时间减少71％,场景漫游时的FPS值提高了3.9倍.该优化技术有效减少了场景加载时间,有效解决了场景高真实度运行时漫游的流畅性问题.     

三维自然景观场景的交互式生成

提出了一个交互式三维自然景观场景的生成方法。该方法通过地形的规则网格表示方法和特定的记录植物分布信息的文件格式实现了三维地形及其分布的交互式编辑,很大程度地缩减了表达景观所需的几何数据量。同时以OpenGL为平台,实现了三维真实感场景的显示与全方位漫游。     

基于多线程并行的大规模场景交互漫游研究

针对大规模三维场景的交互漫游,提出了一种基于多线程并行调度解决方案,并给出了相应的交互漫游算法.该方法使用离散层次细节技术结合视点相关的动态连续层次细节选择和过渡的批LOD技术.在预处理阶段,对大规模场景进行分层分块处理;在实时漫游阶段,采用多线程并行技术:绘制线程利用四又树层次进行可见性剔除和视点相关简化获取当前可绘地形,并将其提交给GPU进行绘制.预取线程通过预测视点的位置,从外存预取相关的几何数据并调入内存.将该方法应用于具体实例,取得了良好效果,证明了该并行方法的有效性.     

一种适合VRML应用的三角网格简化算法

交互虚拟环境中，VRML作为三维场景描述语言得到广泛应用，场景中的物体常常用三角形网格模型来描述，本文提出了一种适合VRML应用的网格简化算法，该算法不仅可以快速减少模型中的画片数目而且能保持模型良好的视觉效果，算法中给出了一种有效的误差控制方法，能在用户指定的误差范围内通过使原始网格中的边折叠达到大量简化的目的，该算法实现简单且速度快，另外能够有效地支持细节层次模型的表示，最后给出实例证明了该算法的有效性。     

基于LOD建模的视景仿真生成技术研究

细节层次（LOD）模型是指对同一个场景或场景中的物体，使用具有不同细节的方法得到一组模型以实现三维场景仿真，而视景生成会使仿真过程更直观形象。文中提出一种利用地形、景物数据库数据，采用LOD建模方法实时生成三昝视景，实验结果表明该方法具有一定理论和实用价值。     

基于Web的三维协同设计模型及其关键技术

为在虚拟环境下进行产品异地实时设计和装配,提出一种基于Web的三维协同设计模型.该模型使用户既可以通过浏览器在客户端的虚拟场景中进行个性化设计,也可以与其他用户进行协同设计.通过详细分析协同设计过程,研究任意形状基本实体的表征、零件扩展属性的描述、基本操作的表示、零件之间装配关系和部件运动仿真属性等的建立.基于ACIS和ECSG的三维造型技术和层次细节模型的生成算法,研发以某产品为对象的原型系统,证实该三维协同设计模型的可行性和先进性.     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate