几何知识库的设计与实现

设计通用几何知识库,实现不同动态几何软件的数据重用与共享,为几何软件提供数据支持是目前知识管理工程研究的新方向。通过分析几何软件的数据需求,研究几何知识数据的标准化和结构化问题。为了应对几何知识数据的复杂性,我们采取先封装再组织的策略,提出了将几何知识标准化和结构化的思路和框架,并据此设计实现了一个初级的几何知识库系统。     

非成熟领域软件复用过程模型

将一个软件企业或开发团队实现有组织的软件复用分为4个阶段,针对可复用资源积累阶段的特点,提出了非成熟领域软件复用过程模型,应用系统分析设计与领域分析适当结合,经数次迭代,逐步积累领域知识,使面向提交的应用系统开发平滑过渡到基于复用地开发,使该领域尽快成熟.该过程模型还考虑了应用系统开发时效和软件开发团队运营成本问题,此阶段软件复用不强调领域工程,应用系统开发是面向提交的,但需要使用基于构件的软件开发.     

基于知识图谱的测试用例复用方法

为提高测试用例复用的准确率及软件缺陷的发现率,提出一种基于知识图谱的测试用例复用方法,根据已有的项目测试数据,构建测试用例复用模型。对测试用例领域进行研究,分析测试用例的特征,利用本体设计构建测试用例知识图谱,通过问题模板与知识图谱匹配,改进朴素贝叶斯分类模型,利用多属性、多条件检索相似度最高的测试用例。基于模型匹配精度和知识图谱检索效率对复用方法进行验证,实践对照表明该方法能够提升测试用例复用率以及缺陷发现率。     

基于构件的面向项目评审领域应用框架技术研究

软件复用是在软件开发过程中避免重复劳动的解决方案,但要设计在许多领域都通用的可复用业务组件是很困难的,而面向领域的复用是在一个特定应用领域中实现复用;因此,设计大粒度复用的应用框架对于提高软件的生产率和软件质量具有重要的意义;文中以软件复用为出发点,基于构件化软件的开发思路,对软件的构件技术、领域工程、面向领域的应用框架技术进行了深入的研究,提出了基于需求驱动的面向领域应用框架的开发方法,并详细说明了该方法在项目评审领域的应用.     

面向平面几何的自然语言作图研究

在计算机几何作图软件日趋成熟的情况下,如何让用自然语言描述的几何命题自动生成几何图形一直是几何作图软件研究中的难题。结合已有几何作图软件的需求,通过对几何自然语言的研究,建立了一套有效可行的语言理解模型,设计并开发了由几何自然语言向几何作图命令转换的接口,实现了将自然语言描述的几何命题自动转换为几何作图命令并生成几何图形的功能。测试结果表明,其转换正确率在84.17%以上。     

几何约束求解的去并拟合方法

依据有向图理论提出了去并拟合方法,由此导出了对于几何约束求解问题的去并拟合的并行处理及串行处理策略,进而得到了一套求解几何约束问题的完备算法。通过将该理论引入到参数化CAD的设计中,使得在算法复杂度增加不大的情况下,几何自动作图的范围大大拓宽。还将其应用于智能动态几何软件的设计中,取得了较好的结果。     

笔式服装工艺设计系统的研究与实现

为了满足服装CAD的领域需求,提高服装工艺设计的效率,采用笔式用户界面进行草图勾画与知识编辑,通过对用户设计意图的隐式理解,利用几何约束求解技术,设计并实现了面向非计算机专业用户的基于笔交互的服装工艺设计系统.该系统与传统CAD软件相比改善了人机交互的方式,降低了用户的认知负担,提高了设计效率.     

一种基于对象属性关注度的QoS传输控制方法

针对分布式虚拟环境中几何资源分配不均匀的问题,提出一种基于对象属性关注度的QoS传输控制方法以及模型传输QoS管理模型.该方法扩展了基于几何属性的模型传输控制传统方法,将对象几何属性与非几何属性综合作为传输中Qos控制参数.结合动态QoS控制的思想,针对分布式虚拟环境实时性要求较高的特点,在运行时刻考虑网络带宽对服务质量的影响,进行动态的QoS协商,并给出了一种针对该问题的动态协商算法.实验结果表明该方法能够全面反映用户对虚拟对象的关注程度,并随着网络带宽变化,在保证实时性的前提下更好地进行模型传输.     

基于本体的领域分析

软件复用被认为是改善软件质量和提高软件生产力最有希望的技术。为了支持复用,软件开发过程必须考虑两个方面的问题:为复用开发和用复用开发。本体逐渐成为构建信息系统、提供知识共享和复用的重要机制。领域分析是软件复用工程中最重要的工作。本课题利用本体的概念,讨论了领域分析技术中的领域本体的概念、领域本体的形式化描述,本体模型的UML表达,并给出基于本体的领域分析过程,以期对软件复用工程的领域分析过程有所改进。     

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。     

SEMANTIC CONSTRAINT MODELER FOR 2D AND 3D GEOMETRY

Design changes for 2D & 3D geometry are the most important features in the process ofproduct design.Constraint modeling for variationl geometry based on geometric reasoning is one ofthe best approaches for this goal.However,it is difficult for the proposed systems to maintain orhandle the consistency and completeness of the constraint model of the design objects.To changethis situation,a semantic model and its control approach are presented,aiming at the integrationof the data,knowledge and method related to design objects.Aconstraint definition system for in-teractively defining the semantic model and a prototype modeler based on the semantic model arealso implemented to examine the idea which is extended to 3D geometric design too.     

面向领域的快速特征造型的设计与实现

提出了面向领域的快速几何特征造型新方法。受软件工程理论中的“域工程”思想启发,该方法针对特定领域的几何特征造型设计,研究如何将领域知识加以抽象自动化,改良几何造型系统的软件架构设计,优化造型系统的算法设计,从而最终提高特征造型系统的整体效率。基于这一思想方法,讨论并分析了计算机辅助建筑设计中造型的需求,提出了系统实现框架,给出了相应的算法实例。应用实例证明了方法的可用性。     

Computational procedure for optimum shape design based on chained Bezier surfaces parameterization

Optimum design introduces strong emphasis on compact geometry parameterization in order to reduce the dimensionality of the search space and consequently optimization run-time. This paper develops a decision support system for optimum shape which integrates geometric knowledge acquisition using 3D scanning and evolutionary shape re-engineering by applying genetic-algorithm based optimum search within a distributed computing workflow.A shape knowledge representation and compaction method is developed by creating 2D and 3D parameterizations based on adaptive chaining of piecewise Bezier curves and surfaces. Low-degree patches are used with adaptive subdivision of the target domain, thereby preserving locality. C¹ inter-segment continuity is accomplished by generating additional control points without increasing the number of design variables. The control points positions are redistributed and compressed towards the sharp edges contained in the data-set for better representation of areas with sharp change in slopes and curvatures. The optimal decomposition of the points cloud or target surface into patches is based on the requested modeling accuracy, which works as lossy geometric data-set compression. The proposed method has advantages in non-recursive evaluation, possibility of chaining patches of different degrees, options of prescribing fixed values at selected intermediate points while maintaining C¹ continuity, and uncoupled processing of individual patches.The developed procedure executes external application nodes using mutual communication via native data files and data mining. This adaptive interdisciplinary workflow integrates different algorithms and programs (3D shape acquisition, representation of geometry with data-set compaction using parametric surfaces, geometric modeling, distributed evolutionary optimization) such that optimized shape solutions are synthesized. 2D and 3D test cases encompassing holes and sharp edges are provided to prove the capacity and respective performance of the developed parameterizations, and the resulting optimized shapes for different load cases demonstrate the functionality of the overall distributed workflow.     

Development of a semantic product modeling system for initial hull structure in shipbuilding

In the initial stage of ship design, designers represent geometry, arrangement, and dimension of hull structures, which correspond to product model information, with 2D geometric primitives such as points, lines, arcs, and drawing symbols on 2D drawings. However, designers must translate the product model information defined on the 2D drawings more intelligently in the following design stages. Thus, design semantics could be lost and design processes that follow could be delayed because of errors by mistranslating the information. Here, design semantics mean design intents of the designer, that is, functions and structures which the product must have.In this study, a semantic product model data structure of an initial ship hull structure was proposed, and a semantic product modeling system was developed based on the proposed data structure. The proposed data structure can store semantic product model information such as product design results with the use of 2D wire frame geometrical data, part attributes, and design knowledge. Hence, this information can be used to generate a 3D solid model and production material information for CAPP as needed.The applicability of the proposed data structure and the developed system was verified by applying them to the deadweight 300,000 ton of Very Large Crude oil Carrier’s product modeling procedure. The application results showed that the proposed data structure and the developed system can be efficiently used for overall initial ship design environment.     

Free-form geometric modeling by integrating parametric and implicit PDEs

Parametric PDE techniques, which use partial differential equations (PDEs) defined over a 2D or 3D parametric domain to model graphical objects and processes, can unify geometric attributes and functional constraints of the models. PDEs can also model implicit shapes defined by level sets of scalar intensity fields. In this paper, we present an approach that integrates parametric and implicit trivariate PDEs to define geometric solid models containing both geometric information and intensity distribution subject to flexible boundary conditions. The integrated formulation of second-order or fourth-order elliptic PDEs permits designers to manipulate PDE objects of complex geometry and/or arbitrary topology through direct sculpting and free-form modeling. We developed a PDE-based geometric modeling system for shape design and manipulation of PDE objects. The integration of implicit PDEs with parametric geometry offers more general and arbitrary shape blending and free-form modeling for objects with intensity attributes than pure geometric models     

环境动态模拟中的建模技术

环境的动态模拟涉及到的技术问题很多。该文结合奥运规划宣传片的制作,介绍了环境模拟中涉及到的建模技术。在环境模拟的建模中,涉及到房屋等规则几何体和植物等不规则几何体。规则几何体模型的建立可以直接使用三维设计软件提供的建摸工具．但是需要注意精简模型。植物等不规则模型的建立需要撮据植物生成的方法和三维设计软件的特点。结合具体应用的需要开发相应的制作工具.     

基于单幅图像的真实感人体动画合成

由于单幅图像缺失三维信息以及完整的纹理信息,基于单幅图像的真实感三维人体动画合成极具挑战性。针对单幅图像三维信息缺失问题,提出了一种基于SMPL参数模型的三维人体几何重建方法。该方法以单幅图像为输入,先根据输入图像人体轮廓信息变形标准的SMPL参数模型分别生成与目标轮廓一致的正反面的三维几何模型,然后利用基于B样条插值的网格拼接融合算法拼接正反面三维几何,最后为了恢复正确的手部几何,利用基于B样条插值的网格拼接融合算法,将重建后的模型上错误的手部几何用标准SMPL参数模型上正确的手部几何替换。同时,针对单幅图像中纹理缺失的问题,提出了一个称为FBN（front to back network）的对抗生成网络,用于恢复被遮挡的人体背面纹理。实验结果表明,该方法生成的具有完整纹理的人体几何能够由3D运动数据驱动运动,生成具有高度真实感的三维人体动画。     

基于本体的军事装备知识建模及分析

针对本体建模过程中不同受众具有不同应用需求的问题,结合本体建模七步法和软件开发螺旋模型提出基于需求的螺旋反馈法。首先,明确领域知识范畴和用户需求,进行本体总体设计;其次,领域专家依据本体构建原则评估知识体系;再次,组装知识体系模型,定义本体属性,创建实例,完成本体详细设计;最后,用户评估反馈,进行新一轮的增量迭代,直至形成正确可用的知识体系。与七步法相比,所提方法强调本体测试和用户需求,以小的分段来构建领域知识模型。此外,运用该方法实现的军事装备知识体系面向作战需求,为军事作战提供强有力的理论支撑。     

基于Bayes-MeTiS网格划分的3D几何重构

为提升 3D模型几何重构过程的压缩效率,提出一种基于MeTiS网格划分的贝叶斯3D模型几何重构算法。首先,在编码端 采用MeTiS方法 对原始3D网格进行子网划分,采用随机线性矩阵对子网几何形状进行编码,并对边界节点的邻居节点使用伪随机数生成器进行数据序列构建;然后,利用贝叶斯算法进行几何模型重构算法的设计,在理论上给出了均值、方差矩阵以及模型参数学习规则,实现了3D模型的几何重构;最后,将其与图傅里叶光谱压缩(GFT)、最小二乘压缩(LMS)和基于压缩感知的图傅里叶光谱压缩(CSGFT)等算法进行仿真对比。结果表明,所提方法具有较高的比特率压缩指标以及较低的重构误差,计算效率明显提高。