基于虚拟现实技术的流域仿真系统实现

讨论了基于MultiGen_CreatorPro和Vega的流域仿真系统的实现方法。通过采用密云官厅水库上游地区DEM数据及15m分辨率ETM＋遥感数字影像数据进行三维地形建模，开发了一个基于MFC的密云官厅水库上游流域仿真系统，实现了流域仿真系统的基本功能，并探索了多级LOD、多线程调度及虚拟纹理等相关技术。该文通过建立流域三维实时、交互的地形仿真环境，提出了基于虚拟现实技术的一种建设流域仿真系统的解决方案。     

Interactive virtual try-on clothing design systems

Clothing computer design systems include three integrated parts: garment pattern design in 2D/3D, virtual try-on and realistic clothing simulation. Some important results have been obtained in pattern design and clothing simulation since the 1980s. However, in the area of virtual try-on, only limited methods have been proposed which are applicable to some defined garment styles or under restrictive sewing assumptions. This paper presents a series of new techniques from virtually sewing up complex garment patterns on human models to visualizing design effects through physical-based real-time simulation. We first employ an hierarchy of ellipsoids to approximate human models in which the bounding ellipsoids are optimized recursively. We also present a new scheme for including contact friction and resolving collisions. Four types of user interactive operation are introduced to manipulate cloth patterns for pre-positioning, virtual sewing and later obtaining cloth simulation. In the cloth simulation, we propose a simplified cloth dynamic model and an integration scheme to realize a high quality real-time cloth simulation. We demonstrate the robustness of our proposed systems by complex garment style virtual try-on and cloth simulation.     

基于自组织结构的智能车辆系统的可视化仿真系统

介绍了一个智能车辆的可视化仿真系统。智能车辆系统是一个集环境感知、规划决策、自动驾驶等多种功能于一体的综合系统。为方便对系统进行调试和分析,设计和开发了该系统的可视化仿真系统,分别以实时在线和离线重放两种方式来观察和分析系统的运行。实验结果表明了该系统的有效性。     

Approximation methods for networks of queues with priorities

Queuing network models are commonly used to analyze the performance of computer system. Unfortunately, the class of queuing network models which can be exactly analyzed excludes CPU priority scheduling disciplines, conspicuously present in most computer systems.A popular approximation technique which we denote the reduced occupancy approximation, is often used to analyze such priority service disciplines because of its simplicity and intuitive appeal. However, despite its widespread use, questions about its accuracy and applicability have received very little attention. Further compounding this situation, is the existence of proprietary software packages which purport to analyze such priority disciplines, but which in fact exhibit behavior remarkably similar to the roa.In this paper we show where, and more importantly why, the roa fails. This understanding leads to a significantly improved approximation technique which sacrifices neither simplicity nor applicability. Although our primary focus is on a two class preemptive priority closed network structure, the basic idea is quite general and extensions to multiclass and nonpreemptive priority structures are indicated.     

基于VRML的实时离散事件仿真器设计

针对以往仿真控制中存在的场景抖动，易产生仿真逻辑错误的问题，提出了使用VRMLScript构建实时离散事件仿真器的思想，讨论了实时仿真器的仿真策略，时钟推进机制，仿真模型以及实时仿真中所需的仿真器暂停和重新运行处理，给出了仿真器的实现方法。     

虚拟手术训练系统的血流模拟

虚拟手术训练系统的血流模拟是系统中模型模拟的重要部分。实时准确的血流流动效果,可以明显地增强虚拟手术训练系统的真实感。首先基于流体力学的Navier-Stokes方程的数值化解法,模拟血流流动的效果;然后在VTK框架中进行渲染,将血流模块集成到一个已有的、初步成熟的系统中;最后通过实验,表明血流模块的加入使系统的真实感得到较好的展现。     

A virtual plant modeller (VPMOD) for batch-chemical processes

This paper presents a virtual plant modeller (VPMOD), which formally characterizes and integrates chemical product designs, batch-chemical equipment (plants), the real-time scheduling of chemical batches, and the control of chemical transport through the plant. These models provide a framework for agile batch-chemical manufacturing that has the ability to reroute and control chemical product flow automatically in a flexible plant subject to unexpected events, such as changes in demand patterns and equipment failure. A formal logic model is generated to control the actual system events, which are non-deterministic. A simulation environment in VPMOD is used to validate schedules and control logic based on plant models supplied by industry. The formal models have been implemented in an object-oriented language.     

Constrained interactivity for relating multiple representations in science: When virtual is better than real

Virtual models are increasingly used in science education, especially in spatially demanding domains. However, few studies have directly compared the effectiveness of virtual and concrete models, or systematically characterized differences between them. Here, we compared students' accuracy and efficiency using virtual and concrete models to align and produce different representations in the domain of organic chemistry. Naïve undergraduate students learned the conventions of different molecular representations (diagrams and models) and then performed tasks that involved matching models to diagrams and using models to complete diagrams. The results indicated similar levels of accuracy for virtual and concrete models and greater efficiency for virtual models. Students preferred virtual models, but rated the usability of the two model types about equally. The efficiency benefit associated with using virtual models can be explained by their constrained interactivity, which prevented students from making task-irrelevant manipulations and increased the salience of the task-relevant information in the models.     

Action-Level Real-Time Network-on-Chip Modeling

To simulate time-constrained operations and scheduling for Network-on-Chip (NoC) systems, we introduce a new set of component specifications at flit level grounded in Action-Level Real-Time DEVS formalism. These models capture the dynamics of NoC systems through action-based behavior under strict execution time intervals. These DEVS-based models are well-suited for development and simulation of asynchronous NoC architectures. This is achieved by extending the DEVS-Suite simulator to support real-time executions of ALRT-DEVS models. Representative simulation models capturing structure and behavior of prototypical Mesh NoC systems are developed. A set of experiments are designed, implemented, executed, and analyzed to show the kind of real-time simulation capabilities that can be achieved for Network-on-Chip systems.