A new approach to performance modelling of Client/Server distributed data base architectures

The recent technological advances in the field of computer and communication lead to distributed data base (DDB) architectures based on the Client/Server paradigm. Available DDB performance prediction methodologies are not sufficiently adequate being too expensive both in the model definition and in the model analysis because of the structural complexity and the large system dimension.

This paper concentrates on a new approach to performance modeling of DDB systems called “independent modelling approach”. This approach separates the DDB software model from the DDB machinery model, and models from solution techniques. This way the aspects related to data contention can be analysed as a pure software characteristic and separated from resource contention, considered as a machinery characteristic. Furthermore, it is possible to analytically model some system aspects (e.g., the software only, or part of it, without involving the machinery model), and apply combined analytical/simulation methods for the remaining system aspects. This results in higher flexibility at lower computational cost in the performance analysis of complex DDB architectures.

A case study is developed and experimental results are discussed to show the effectiveness of the approach.     

面向集成的特征基产品建模系统研究

本文归纳总结了面向集成的产品建模CAD系统的当前特征及其发展趋势，指出了其发展的主要研究内容，并由此提出了面向集成的产品建模系统新的体系结构，重点论述了基于约束的特征基产品描述方法。     

Development of a distributed collaborative design framework within peer-to-peer environment

Distributed collaborative design and manufacture enables manufacturing organizations to maintain competitiveness in the fiercely competitive global industry. This requires that the distributed system not only maintains data consistency across globally-distributed locations seamlessly, but also allows team members to access the storage system and computing resources transparently and securely. Current grid applications mainly based on client-server architecture are inflexible and rigid for fast changing collaborations among manufacturers, especially for small and medium enterprises. In this paper, a distributed collaborative design framework is presented with a hybrid of grid and peer-to-peer technology. In order to access computational resources for design, analysis and process simulation, a meta-scheduler is designed and implemented. It helps in resource discovery and optimal utilization of resources. A test bed is established, based on the framework proposed to demonstrate a distributed collaborative design and manufacturing environment.     

A distributed collaborative product design environment based on semantic norm model and role-based access control

With the boom of Internet Technology, it becomes possible to combine designers from different disciplines into one team to support product design globally. In this paper, a distributed collaborative product design environment is presented to support top-down process oriented product design. In conceptual design stage, the artifact is managed by semantic norm model (SNM). In SNM, the designers can define virtual components at early design stage and instantiate those components at later detailed design stage. By role-based access control (RBAC), different roles with corresponding permissions could be assigned to distributed designers, and the designers could concurrently modify different components of the product relevant to his or her roles. Based on the SNM and RBAC system, a distributed collaborative product design environment is developed and the top-down oriented product design process is demonstrated.     

Feature-based design and material blending for free-form heterogeneous object modeling

In this paper, a new feature-based method is proposed to represent and design heterogeneous objects. Material governing features are defined to control material composition inside the objects. Interrelations between the material governing features and material attributes are established in the design process and retained in the object model. Free-form B-spline functions are used to represent complex shapes of geometry and material features. A new material feature blending method is used to determine continuous material variation. To obtain the best material features, an optimization problem is constructed based on the object's functional requirements. Variant models are easily generated by changing the geometric and material features using the constraints between them. Implementation and examples are also presented in this paper.     

A distributed and interactive system to integrated design and simulation for collaborative product development

The goal of applying collaborative product development in industry has raised the need to develop software tools supporting system integration and group collaboration. Current methods and tools mainly focus on the collaborative creation of design components and assemblies. However, few of them support the collaborative work in developing simulation models so that proposed design concepts and solutions can be evaluated by integrating expertise from several disciplines. The purpose of this research is to develop a distributed and interactive system on which designers and experts can work together to create, integrate and run simulations for engineering design. To develop such a system, a number of issues, e.g. effectiveness and efficiency of modeling work, the re-use of models, interaction and cooperation, accuracy of simulation, collaborative operation on models, etc., need to be addressed. This paper describes an open architecture to developing simulations for engineering design in a distributed and collaborative environment, identifies a set of key issues raised in this architecture, and presents the techniques employed in our solution.     

基于C/S的计算在颗粒运动仿真中的应用研究

该文介绍了一个基于服务器和客户机分布式计算的颗粒运动仿真系统。在仿真实验中，单机系统无法满足仿真的各项指标要求，特别是用户交互的响应速度。针对各个仿真模块的特点，按功能特性将其分布到客户机和服务器上。基于空间数据分割和对相邻区粒子的预测，大大地减少了任务重新分配时客户机和服务器之间的通信。在局域网上，实现了客户机和服务器的互联和管理。实验表明。仿真实验的计算效率等得到了提高，提高了系统的人机交互响应速度。     

VSculpt : a distributed virtual sculpting environment for collaborative design

A collaborative virtual sculpting system supports a team of geographically separated designers/engineers connected by networks to participate in designing three-dimensional (3D) virtual engineering tools or sculptures. It encourages international collaboration at a minimal cost. However, in order for the system to be useful, two factors need to be addressed: intuitiveness and real-time interaction. Although a lot of effort has been put into developing virtual sculpting environments, only limited work addresses collaborative virtual sculpting. This is because in order to support real-time collaborative virtual sculpting, many challenging issues need to be addressed. We propose a collaborative virtual sculpting framework, called VSculpt. Through adapting some techniques we developed earlier and integrating them with some techniques developed here, the proposed framework provides a real-time intuitive environment for collaborative design. In particular, it addresses issues on efficient rendering and transmission of deformable objects, intuitive object deformation using the CyberGlove and concurrent object deformation by multiple clients. We demonstrate and evaluate the performance of the proposed framework through a number of experiments.     

分布式通用消息的设计与实现

文中介绍在Ｕｎｉｘ进程间通信与网络通信的基础上，实现适合分布式应用程序环境的分布式通用消息，它为分布式处理提供了一个应用程序的方法。     

基于三层结构的分布式商品身份数码识别系统

文章对传统的两层客户／服务器体系结构和三层客户／服务器体系结构进行了比较,介绍了三层客户／服务器体系结构的基本组成,最后阐述了基于三层结构的分布式数据处理技术在商品身份数码识别系统中的应用。     

BIM extension for the sustainability appraisal of conceptual steel design

Contemporary advancements in Information Technology and the efforts from various research initiatives in the AEC industry are showing evidence of progress with the emergence of building information modelling (BIM). BIM presents the opportunity of electronically modelling and managing the vast amount of information embedded in a building project, from its conception to end-of-life. Researchers have been looking at extensions to expand its scope. Sustainability is one such modelling extension that is in need of development. This is becoming pertinent for the structural engineer as recent design criteria have put great emphasis on the sustainability credentials in addition to the traditional criteria of structural integrity, constructability and cost. With the complexity of designs, there are now needs to provide decision support tools to aid in the assessment of the sustainability credentials of design solutions. Such tools would be most beneficial at the conceptual design stage so that sustainability is built into the design solution starting from its inception. The sustainability of buildings is related to life cycle and is measured using indicator-terms such as life cycle costing, ecological footprint and carbon footprint. This paper proposes a modelling framework combining these three indicators in providing sustainability assessments of alternative design solutions based on the economic and environmental sustainability pillars. It employs the principles of feature-based modelling to extract construction-specific information from product models for the purposes of sustainability analysis. A prototype system is implemented using .NET and linked to the BIM enabled software, Revit Structures™. The system appraises alternative design solutions using multi-criteria performance analysis. This work demonstrates that current process and data modelling techniques can be employed to model sustainability related information to inform decisions right from the early stages of structural design. It concludes that the utilized information modelling representations – in the form of a process model, implementation algorithms and object-based instantiations – can capture sustainability related information to inform decisions at the early stages of the structural design process.     

C／S分布环境下核心软构件的设计与集成

1 引言随着计算机硬件技术的高速发展,操作系统功能的加强,网络技术的完善,开放式网络环境下的客户机服务器体系结构已成为分布式处理系统的主流,其体系结构如图1所示。     

Design and implementation of an agent-based collaborative product design system

The evolution of computer science and technology has brought new opportunities for multidisciplinary designers and engineers to collaborate with each other in a concurrent and coordinated manner. The development of computational agents with unified data structures and software protocols contributes to the establishment of a new way of working in collaborative design, which is increasingly becoming an international practice. In this paper, based on the analysis of the dynamic nature of collaborative design process, a new framework for collaborative design is described. This framework adopts an agent-based approach and relocates designers, managers, systems, and the supporting agents in a unified knowledge representation scheme for product design. In order to model the constantly evolving design process and the rationales resulted from design collaboration, a Collaborative Product Data Model (CPDM) and a constraint-based Collaborative Design Process Model (CDPM) are proposed to facilitate the management and coordination of the collaborative design process as well as design knowledge management. A prototype system of the proposed framework is implemented and its feasibility is evaluated using a real design scenario whose objective is designing a set of dining table and chairs.     

Agent co-ordination aided distributed computational engineering design

Co-ordination is a key research area in engineering design and distributed artificial intelligence, as well as a number of other disciplines. This paper highlights the need for co-ordination within distributed computational design environments. The key characteristics of co-ordination identified are coherence, communication, task management, resource management, schedule management, and real-time support. These key characteristics are integrated within a methodology, which is realised in a multi-agent system aimed at co-ordinating distributed computational design. Co-ordination in real-time is responsive and adaptive to changes in the distributed environment, such that the computational design analysis can be performed in an efficient manner. The agent-based co-ordination system has been applied to two case studies. Firstly, to a theoretical research-based case study related to an aspect of structural analysis involved in conceptual aircraft wing design. Secondly, the system is applied to a practical industrial-based case study involving turbine blade design. In both case studies the multi-agent system enables the respective computational design analysis to be conducted in a coherent and organised fashion making more efficient use of time and resources.     

Towards a generic distributed and collaborative digital manufacturing

A framework for distributed manufacturing is proposed to facilitate collaborative product development and production among geographically distributed functional agents using digitalized information. Considering the complexity of products created in a distributed manufacturing scenario, it often requires close collaborations among a number of facilities. In this research work, various functional agents, such as the manufacturability evaluation agent (MEA), manufacturing resource agent (MRA), process-planning agent (PPA), manufacturing scheduling agent (MSA), shop floor agent (SFA), fault diagnosis agent (FDA), etc., can interact coherently for distributed manufacturing. With specific agents having unique functionalities, a manufacturing managing agent (MMA) acts as the centre of this distributed manufacturing system. The MMA agent assists the specific agents’ to work seamlessly and also to collaborate closely with the participating agents. In this way, the production cycle of a part can be optimized from product design to final manufacturing since all the production procedures are considered logically and every procedure is correlated. The agent language based on the knowledge query manipulation language (KQML) includes many pre-defined performatives that ease the participating agents to carry out their tasks intelligently by interpreting commands from one another. Additionally, to ensure the adaptiveness and upgradeability of the system, the internal structure of each functional agent that is based on JATLite is modularized into several components, including a communication interface, central work engine, knowledge base pool, and input/output modifier for possible future methodology enhancements.     

Web-based distributed system and database modeling for concurrent design

This research introduces a new approach for Web-based collaborative concurrent design. In this approach, systems, product libraries, and product databases for modeling different product development life-cycle aspects are distributed at different locations that are linked through the Web. Product modeling libraries are described as class features. A class feature at a remote location can be used for defining a new class feature at the local site. Product modeling systems distributed at different locations are used for creating product databases that are described by instance features. A system at one location can be implemented using the functions provided at other locations as the components. Different life-cycle databases at different locations are associated by their relations. The optimal design considering relevant life-cycle aspects is identified using the distributed product life-cycle modeling systems and databases.     

基于网络的协同CAD特征建模技术研究

探讨了协同工作模式和建模的需求，论述了一种结合C／S和B／S结构优势的三维CAD协同建模系统的结构和实现，通过对三维以数化特征技术，网络通信技术和特征编码技术等关键技术的研究，初步实现了局域网环境下零件级产品协同参数化造型设计和Internet上的模型信息发布。     

基于网络环境下的协作学习教学设计研究

本文采用现代教学设计理念,对网络环境下协作学习的教学设计各环节进行了分析,然后利用行动研究方法对高师院校"计算机文化基础"课进行了教学实践,以期能为协作学习的实践应用提供具体的方法指导。