基于混合遗传算法的非均匀宽带阻抗变换器设计

当对阻抗变换器总长度有一定限制时,传统的均匀宽带阻抗变换器中的特性阻抗可能超出实际能实现的范围;对于非均匀宽带阻抗变换器,由于取消了对每段传输线长度的限制,设计时有了更大的自由度;为了得到最佳的传输线网络参数,采用了混合遗传算法进行优化设计,引入了动态惩罚函数对适应度函数进行处理;数值仿真表明,用该方法设计的宽带匹配变换器的性能优于现有的其它设计方法。     

The multi-user computer-aided design collaborative learning framework

New developments to computer-aided design (CAD) software transform a once solitary modelling task into a collaborative one. The emerging multi-user CAD (MUCAD) systems allow virtual, real-time collaboration, with the potential to expand the learning outcomes and teaching methods of CAD. This paper proposes a MUCAD collaborative learning framework (MUCAD-CLF) to interpret backend analytic data from commercially available MUCAD software. The framework builds on several existing metrics from the literature and introduces newly developed methods to classify CAD actions collected from users’ analytic data. The framework contains two different classification approaches of user actions, categorizing actions by action type (e.g., creating, revising, viewing) and by design space (e.g., constructive, organizing), for comparative analysis. Next, the analytical framework is applied via a collaborative design challenge, corresponding to over 20,000 actions collected from 31 participants. Illustrative analyses utilizing the MUCAD-CLF are presented to demonstrate the resulting insight. Differences in CAD behaviour, indicating differences in learning, are observed between teams made up entirely of novices, entirely of experienced users, or a mix. In pairs of experts and novices, we see both a perceived high-satisfaction apprenticeship experience for the novices and preliminary evidence of an increase in expert design behaviours for the novices. The proposed framework is critical for MUCAD systems to make the most of the educational possibility of combining technical skill-building with team collaboration. Preliminary evidence collected in a fully-virtual design learning activity, and analyzed using the proposed MUCAD-CLF, shows that novice students gain advanced CAD design knowledge when collaborating with experienced teammates. With the user data captured by modern MUCAD software and the MUCAD-CLF presented herein, instructors and researchers can more efficiently assess and visualize students’ performance over the design learning process.     

Interactive computer-aided formwork design

While disciplines such as structural analysis are reaping the benefits of computer implementation, temporary works design lags well behind. Some of the reasons given by temporary works designers are that their designs are very practical and depend largely on the designer's experience and engineering judgement. By designing a highly interactive user friendly interface, a comprehensive program that runs on IBM compatibles has been developed. The program can be used to design formwork for walls and soffits using traditional timber and/or proprietary formwork components. The program incorporates many features commonly associated with business oriented software interfaces, placing special emphasis on the ease of use and at the same time allowing users to incorporate their own engineering judgement. The user interface features include the use of bar menus, windows and data entry screens. Formwork design may involve the use of material components from different sources, therefore, it is highly data dependent. Consequently, a database management system (DBMS) is used to manage a database of material properties, costs and other attribute data. Formwork members are designed using a rational approach to BS5975: 1982 and the recommendations of the Concrete Society's book Formwork: A Guide to Good Practice. The program produces design details, a schedule of quantities, a cost comparison between purchased and hired proprietary formwork and a cost estimate.     

World survey of computer-aided design

The International Institute for Applied Systems Analysis, iiasa, was established at the end of 1972 as a joint creation of countries from both East and West.iiasa is a nongovernmental, multinational autonomous scientific institution, founded for the purpose of research into problems which are either global (knowing no frontiers) or universal (applying to all nations), and into the application of systems analysis to their solution.iiasa is situated at Schloss Laxenburg, near Vienna, Austria, and scientists from all the member nations work together on various research projects, some of which tackle specific problem areas, and others of which develop methodologies in a general context.Early in 1974, the industrial-systems project identified computer-aided design as a developing technology which would be likely to influenced the development of industry considerably. In collaboration with the computer-systems project, the industrial-systems project commissioned a world-wide survey of cad. The survey covers many countries in both Eastern and Western Europe, and includes the USA and Japan.     

Model-based computer-aided design environment for operational design

To meet the increasing market challenges in chemical industry, it is imperative to improve process design and the supportive computer-aided engineering tools so that they can support lifecycle activities. This research work proposes detailed mechanism of operational design approach on the basis of operational design modeling methodology where lifecycle activities are considered during design stage. Computer-aided design environment called CAPE-CAD is proposed, which supports operational design approach. CAPE-CAD encompasses a friendly user interface to capture and maintain plant topology and to link process behaviors and plant operations with corresponding plant structure units. The proposed design environment can be used during design and operation stages, as well as for operator training. Case study of chemical process is used to explain the proposed solution.     

人工智能在计算机辅助工艺设计中的应用

随着计算机软硬件技术的不断成熟,计算机辅助工艺设计的理论与方法已发生了质的飞跃。将人工智能理论应用于计算机辅助工艺设计是新近发展起来的研究热点之一,也是工业设计现代化发展趋势。它不仅可以把人工智能领域中的研究成果移植到计算机辅助工艺设计中,而且也扩大了人工智能的应用领域,使两者得到完美结合,促进共同发展。本文简要地叙述了计算机辅助工艺设计和人工智能的基本概念,探讨了人工智能在计算机辅助工艺设计中的应用。     

Anatomical modeling with computer-aided design

Many industrial computer aided design (CAD) programs contain highly developed facilities that can be used to create and analyze three dimensional models of biological structures. In this paper we describe the use of one such program package for modeling the rat brain and a component thereof. Special features of the models of interest to morphologists are illustrated.     

Ergonomic studies in computer-aided design

Abstract

This paper describes the results of an ergonomic survey on interactive graphics workstations for computer-aided design (CAD). A work-sampling study was carried out to characterize the use of keyboard, digitizer tablet and video display. Subjective impressions of CAD software, CAD hardware and health aspects were collected by means of a questionnaire. Working methods and working postures were recorded on videotape. The two most important differences in comparison with other office terminals are: (i) dynamic working methods result in an absence of constrained postures in CAD operators and allow full-body exercise; (ii) CAD operators spend more time (46–68 per cent of working hours) viewing the video display than the average office terminal operator. Some ergonomic recommendations have been deduced for the construction of CAD terminals, as well as for the ergonomic improvement of existing workstations.     

Ten challenges in computer-aided design

This short paper presents 10 challenging research areas in the general field of computer-aided design. The research problems come from the author's personal experience, and as such are highly subjective. All findings and opinions are those of the author and do not represent any of the institutions the author is affiliated with.     

Tolerances in computer-aided geometric design

In the design of discrete part shapes, the specification of tolerance constraints can have major consequences for product quality and cost. Traditional methods for tolerance analysis and synthesis are timeconsuming, and have limited applicability. This paper presents the results of research into the use of solid modeling technology for the automated solution of tolerancing problems. A linear programming method is presented for the solution of tolerance analysis problems on a worst-case basis. A Monte Carlo method is presented for both worst-case and statistical tolerance analysis. Both methods automatically derive all necessary geometric relationships from a solid model of the assembly. Example problems are solved using the experimental GEOTOL geometric design system.     

Ergonomic studies in computer-aided design

This paper describes the results of an ergonomic survey on interactive graphics workstations for computer-aided design (CAD). A work-sampling study was carried out to characterize the use of keyboard, digitizer tablet and video display. Subjective impressions of CAD software, CAD hardware and health aspects were collected by means of a questionnaire. Working methods and working postures were recorded on videotape. The two most important differences in comparison with other office terminals are: (i) dynamic working methods result in an absence of constrained postures in CAD operators and allow full-body exercise; (ii) CAD operators spend more time (46-68 per cent of working hours) viewing the video display than the average office terminal operator. Some ergonomic recommendations have been deduced for the construction of CAD terminals, as well as for the ergonomic improvement of existing workstations.     

CAGD—computer-aided gravestone design

Although the title may seem facetious, the design of objects other than mechanical objects illustrates the same principles that drove the early shape modelling developments. The so-called ‘local operations’ were originally developed to provide specific local changes to models. These were quicker and less expensive than performing the operations using Boolean operations which performed global checks. Later, the notion of locality disappeared as specialised operations were developed for operations such as reflection (symmetry) and, still later, shelling. Although performing global changes, these operations were implemented as sequences of localised changes. The common factor between the original local operations and the later specialised operations was, and is, that they perform conceptually specific changes. The justification for developing these modelling tools is that they allow the user to perform shaping operations in a more natural manner avoiding the necessity of reformulating the intended change in terms of general tools, such as the Boolean operations. The problem is for the software developers that the number of such local or specific operations is unlimited; it is not possible to create a complete set. The type and functionality of these operations depends on the application, hence they need to be developed separately for different application areas, which in turn implies that the development costs have to be shared between a subgroup of the CAD clients, which means that they may be too expensive to justify in commercial terms. This paper describes some of these special operations that may be useful for designers of stone products, for gravestones or for kitchens, for example.