实体造型中的几何约束

实体造型是一个基于约束的过程，完成从功能约束到几何约束、再到代数约束的转化而得到实体模型。本文讨论了几何约束的层次性及其表示，并且对几何约束同设计意图的关系进行了研究，提出了基于ＣＳＧ／ＧＣＧ／Ｂ－ｒｅｐ的模型表示。     

实体造型技术在新型高速低阻犁犁体曲面优化设计中的应用

将实体造型技术应用于农业机械CAD中是一次探索性尝试，本文研究分析了实体造型在犁体优化设计中所发挥的重要作用。结合实体造型技术开发的，面向新型高速低阻犁的CAD软件系统，通过几何建模和实体造型处理，能够生成犁体的静、动态真实感图象，并可模拟土壤在犁体曲面上的运动轨迹，使设计人员可直接在屏幕上进行交互式修改，避免实物模型的制作和实际不可能实现的错误设计，缩短了研究、优化与开发过程，提高了设计质量。     

三维几何造型的理论与技术

本文综述了三维几何造型的理论与技术在ＣＡＤ／ＣＡＭ领域中的应用与发展概况；同时介绍了三维几何造型的理论与技术发展的三个里程碑——线框造型、曲面造型和实体造型；并简要论述了用质点系模型和流质系模型解决模糊实体造型的理论与技术问题     

CAD系统中的产品模型定义技术

本文在就实体造型、尺寸公差建模、非簇建模、参数化建模、约束建模和特征建模等技术作简要的评述后，提出了在现有ＣＡＤ系统基础上，实现产品特征建模系统开发的方法。系统利用特征定义将实体模型和特征模型紧密联系起来，特征识别和基于特征设计技术相互配合，使用户可自由地选取实体建模操作或特征建模操作来构造具有完整定义的产品模型。     

以复形为基础的非流形造型与基于物理的造型相结合的物体表示

提出一个新的表示物体的框架。通过非流形造型与基于物理的造型相结合，从拓扑结构和几何信息两个方面扩大了模型的表示范围。以代数拓扑中的复形为基础的非流形造型的作用是生成物体的拓扑框架，既可以表示ＣＡＤ的物体，更适合表示具有复杂拓扑结构的自然物体。基于物理的造型的作用是在拓扑框架上生成最终的几何信息。二者的结合提供了一种新的几何造型手段。     

面向与历史无关造型的三维约束求解方法研究

以基于历史的造型系统中应用较为成熟的两项技术——特征编码和二维约束求解为基础，基于特征进行三维约束建模，从而打破传统的基于历史造型系统中特征之间的单向依赖关系；然后将三维约束关系映射到二维草图进行处理，简化了问题．该方法在InteSolid 2．0上实现．     

基于三维实体造型的舰船立体布置CAD系统

舰船立体布置系统是基于计算机三维实体造型技术的新一代辅助设计系统，为论证设计人员提供了形象、直观的仿真设计环境，大大提高了舰船论证研究与设计的效率和质量。本文主要介绍该系统的三维模型、结构、功能、实现方法和特点。     

一种适用于特征造型的参数化设计方法

本文提出了一种面向特征造型的参数化设计方法，该方法对三维几何约束在初始设计阶段采用高层表示，并基于面向特征造型的高层几何约束模型与约束传播实现尺寸驱动几何，从而能够有效地支持特征设计，初始设计。     

基于面片的钢结构节点的虚拟装配

为解决在传统计算机辅助设计方法下进行钢结构节点的装配设计中缺乏直观性、灵活性的问题,对钢结构节点的虚拟装配进行了研究.以面向对象的参数化的方法,基于面片进行钢结构部件的三维实体造型;基于面片的拾取保证了面片的交互式获取;基于面片之间的几何约束进行几何变换确定了铜结构部件在装配体中的几何位置.通过程序的开发,实现了高精密度的三维实体造型、交互式的三维操作、可视化的三维视图的结合,表明了此虚拟装配解决方案的可行性.     

面向与历史无关造型的三维约束模型构建方法

由于与历史无关的造型系统中约束模型多处于欠约束状态,使求解结果往往不能很好地符合设计意图,为此提出一种基于虚几何元素的约束模型构建方法.该方法根据输入约束的方向特性创建虚几何元素,并将这些约束转换为实体几何元素、虚几何元素间的结构约束和尺寸约束,从而构建基本约束模型;在此基础上,通过几何元素的剩余自由度分析增补相应的几何约束,使约束模型更完备,求解结果更合理.文中方法已在原型系统InteModel中实现,并通过实例验证了其正确性和有效性.     

A study on product modelling for integration of CAD/CAM

Modelling capability for products to be designed and manufactured plays an important role in order to effectively construct and utilize CAD/CAM systems. Product models should represent all the information about products, which is utilized in manufacturing processes. Therefore it is required that they describe functional structures of machine products, and include not only geometric information but also various non-geometric data, such as physical, technological and management data. Presently there do not seem to exist definite methods or theories for constructing product models. In this paper, we first investigate the whole manufacturing process, and propose a system structure for integration of CAD/CAM, in which product modelling plays a fundamental role. Then requirements for product modelling are studied thoroughly, and a new representation framework for product models is proposed. It consists of an object concept called frame, relations among frames and attributes, and it can incorporate the existing various modelling capabilities, such as solid modelling. We use this representation framework in combination with our solid modelling package GEOMAP-III, and show the effectiveness of this approach by performing illustrative design experiments.     

Modelling and solving English Peg Solitaire

Peg Solitaire is a well known puzzle, which can prove difficult despite its simple rules. Pegs are arranged on a board such that at least one ‘hole’ remains. By making draughts/checkers-like moves, pegs are gradually removed until no further moves are possible or some goal configuration is achieved. This paper considers the English variant, consisting of a board in a cross shape with 33 holes. Modelling Peg Solitaire via constraint or integer programming techniques presents a considerable challenge and is examined in detail. The merits of the resulting models are discussed and they are compared empirically. The sequential nature of the puzzle naturally conforms to a planning problem, hence we also present an experimental comparison with several leading AI planning systems. Other variants of the puzzle, such as ‘Fool's Solitaire’ and ‘Long-hop’ Solitaire are also considered.     

专用集成电路静态时序分析

随着制程进入深亚微米时代,芯片设计和片上系统(SoC)设计越来越复杂,此一趋势使得如何确保IC质量成为目前所有设计从业人员不得不面临的重大课题。简单介绍了静态时序分析的基础概念及其在IC设计流程中的应用。     

Modelling and experimental validation of thin-film effects in thermopile-based microscale calorimeters

Calorimeters can be miniaturized to the point where they can be integrated into platforms such as micro-total analysis systems (μTAS) or lab-on-chip. Models of microscale calorimeters currently fail to account for variations of material properties known to be present in thin films. This study attempts to address this deficiency. Resistivity and absolute Seebeck coefficient of gold and nickel thin films were found to vary linearly with the inverse of film thickness in the submicron range. Thin-film thermopiles composed of gold and nickel were fabricated and their resistance and sensitivity were measured. Our results show that thin-film effects can introduce a 15% decrease in sensitivity (temperature-to-voltage conversion ratio) and a 30% decrease in resolution (smallest resolvable temperature difference). Introducing material properties variation with film thickness into models of thermopile performance resulted in improved estimates. Modelling results suggest that grain boundary scattering is a strong contributor to the observed film-thickness-related change of resistivity and Seebeck coefficient. These observations have implications for improving the design and fabrication of thermopile-based, and other microfabricated, microscale calorimeters.     

Direct 3D Manipulation Techniques for Interactive Constraint-based Solid Modelling

This paper presents a novel constraint-based 3D manipulation approach to interactive constraint-based solid modelling. This approach employs a constraint recognition process to automatically recognise assembly relationships and geometric constraints between entities from 3D manipulation. A technique referred to as allowable motion is used to achieve accurate 3D positioning of a solid model by automatically constraining its 3D manipulation without menu interaction. A set of virtual design tools, which can be used to construct constraint-based solid models within a virtual environment, are also supported. These tools have been implemented as functional 3D objects associated with several pre-defined modelling functions to simulate physical tools such as a drilling tool and T-square. They can be directly manipulated by the user, and precisely positioned relative to other solid models through the constraint-based 3D manipulation approach. Their modelling functions can be automatically triggered, depending upon their associated constraints and the user's manipulation manner. A prototype system has been implemented to demonstrate the feasibility of these techniques for model construction and assembly operations.     

Bridging the gap between business models and system models

This paper discusses links that may be made between process models and Unified Modelling Language (UML) software specification techniques, working from an argument that the whole complexity of organisational activity cannot be captured by UML alone. The approach taken is to develop a set of use cases, which would be capable of providing information support to a pre-defined organisational process. The nature of the thinking, which is necessary to derive the use cases, is outlined using the pre-defined process as a case study. The grouping of transactions and state changes into Use Cases is shown to require design choices, which may vary between particular organisational contexts. Conclusions are drawn about the direction of further investigation of links between process modelling and UML.     

Prediction under uncertainty as a boundary problem: A general formulation using Iterative Closed Question Modelling

Making predictions about environmental systems is a challenge due to the high level of uncertainty involved. In this paper we give a general formulation of prediction under uncertainty as a boundary problem. This leads to development of a methodology for making predictions under uncertainty, named Iterative Closed Question Modelling (ICQM). ICQM involves iteratively devising questions and testing the certainty of their answers by creating complete model scenarios (complete taken to include structure, parameters and inputs for each scenario instance). The model scenarios are categorised in terms of which answer they support, and whether they are plausible or not. Using a simple two-parameter flow duration curve model, the paper demonstrates the application of ICQM using eight alternative uncertainty analysis techniques. ICQM provides a useful and generic approach to making predictions under uncertainty, helps to understand how existing techniques address the boundary problem differently and promotes the development of new techniques.     

The Design of the Zinc Modelling Language

Zinc is a new modelling language developed as part of the G12 project. It has four important characteristics. First, Zinc allows specification of models using a natural mathematical-like notation. To do so it supports overloaded functions and predicates and automatic coercion and provides arithmetic, finite domain and set constraints. Second, while Zinc is a relatively simple and small language, it can be readily extended to different application areas by means of powerful language constructs such as user-defined predicates and functions and constrained types. Third, Zinc provides sophisticated type and instantiation checking which allows early detection of errors in models. Finally, perhaps the main novelty in Zinc is that it is designed to support a modelling methodology in which the same conceptual model can be automatically mapped into different design models, thus allowing modellers to easily “plug and play” with different solving techniques and so choose the most appropriate for that problem. We describe in detail the various language features of Zinc and the many trade-offs we faced in its design.     

支持Top-Down整体色彩设计的模型研究

为了在CAD平台上实现TopDown整体色彩设计,在分析色彩设计领域知识的基础上,结合产品色彩方案库,通过色彩设计树建立了产品几何数据与色彩数据之间的映射,构造了支持TopDown整体色彩设计的模型。同时初步完成了原型系统开发,并与CAXA实体设计2005集成,在机床产品的设计中进行了应用。     

PLM paradigm: How to lead BPR within the Product Development field

The design and implementation of a PLM solution in a cross-company environment is a complex and labour intensive operation, which is often coupled with a Business Process Re-engineering (BPR) project to better deploy technologies as well as methodologies and to target the system implementation on the real company needs. Enterprise Modelling (EM) languages are typically used to collect and share process knowledge among the BPR participants. Plenty of techniques are actually available at this scope and it is not always easy to understand how to select and use them in the different steps of re-engineering. The main purpose of this paper is to perform a qualitative analysis of three well known EM languages (IDEF, UML and ARIS) and to propose a new methodology, based on their integrated use, supporting BPR efforts in the Product Development domain.