基于建筑CAD协同设计的权限管理系统

通过对现代集团的企业调研和建筑CAD协同设计系统的特点进行分析,将基于角色的权限管理模式与建筑协同设计相结合,将建筑CAD协同设计中的用户、角色、权限相关联,完成了协同设计系统中权限管理的设计和开发。     

RBAC中关于角色权限继承问题的研究

本文分析了经典的RBAC96模型中角色的继承及私有权限问题。借助面向对象中的访问限定符public、private和protected的概念，将角色的权限划分为：私有权限、保护权限和公有权限。并明确：私有权限不能被任何子角色继承，公有权限能被所有子角色不限制地继承，而保护权限则可以被部分子角色继承。然后，提出了两条角色权限的继承规则。最后给出了一个求角色权限集的算法。在该算法中，通过定义的两条角色权限的继承规则，可以实现子角色对父角色中非私有权限的不同形式的继承。     

有限元领域中多态模型误差分析方法

基于特征造型技术的三维CAD系统目前已广泛应用于产品设计,同时CAE在产品设计与优化中也起到了越来越重要的作用.而有限元是最为广泛使用的CAE方法之一.由CAD系统建立的模型在进行有限元分析之前,通常需要根据分析需要对模型进行简化,如何分析模型简化前后对有限元计算结果的影响程度是CAD模型到CAE模型自动转化的首要步骤.将模型因特征的简化而形成的各种状态的模型称为多态模型.针对确保一定分析精度,节省计算资源的需求,根据有限元误差理论提出了分析不同简化模型对有限元分析结果造成的误差的方法,且通过数据实例得到验证,根据误差分析方法提出模型误差层次的概念,为有限元领域中多态模型的生成提供了新的思路.     

层次结构文档下支持权限管理的实时协同技术研究

针对传统实时协同系统中各站点之间无约束操作的缺点,提出采用权限分工的方式来支持不同团队之间的文档管理。给出了支持权限管理的层次结构文档的形式化定义,描述了用户角色设置过程,定义了权限及权限操作格式,讨论了站点ID的设置及初始化过程,并提出采用改进的地址空间转换算法来保证权限操作在各分布式站点的正确执行。分析了改进算法的效率提升,并通过其在Co-AutoCAD中的应用证实了策略的有效性。     

基于系列化配置原理的产品设计技术研究*

在分析零件事物特性表的基础上,提出了基于系列化配置原理的产品设计技术。分析了使用该技术的产品开发的一般流程。研究了将产品配置和工艺配置在同一配置表中的存储技术;从三维CAD产品模型中进行特征提取的算法;零件工序简图的自动生成技术等关键技术和算法。以发动机气门产品为研究对象,使用UML的包图设计了发动机气门产品设计系统的组件模型,基于该组件模型和SolidWorks 三维CAD平台,使用Visual C++6.0实现了原型系统。     

异构CAD系统协同框架与互操作

协同CAD通过网络支持不同地域的设计人员实时地完成产品设计或决策任务,以提高群体协同工作效率;异构CAD系统协同将分布的不同的CAD系统,如ProE、UG、SolidWork等业界比较成熟且是主流的商业CAD系统,集成在一个框架平台下,从而支持人们更方便地协同工作;文章讨论了异构CAD系统协同的体系结构与共享感知问题,提出了一个支持共享感知的复制式系统结构模型;进一步将现有商业CAD系统引入到该模型中,给出了一个基于构件的协同CAD中间件框架模型,讨论了中间件接口和CAD系统的互操作。     

一种基于RBAC的数据权限模型的设计与实现

分析基于角色的访问控制模型,提出一种基于RBAC模型的数据权限模型,数据权限模型加强了对数据权限的管理,使得数据权限管理具有更好的扩展性和实用性。本文给出了数据权限模型的设计和实现方法,对于具有多层次数据权限管理需求的系统软件权限管理的设计和开发具有参考价值。     

国家科技奖励综合业务处理平台权限控制实现

应用用户／角色／任务权限／任务/权限的模型，实现了国家科技奖励综合业务处理平台的权限控制系统，阐述了权限控制系统的设计原则和方法。在开发过程中，将任务权限层加入T-RBAC模型，解决了任务细分困难的问题；在用户表中加入了结构信息，隔离了不同结构之间的数据信息；使用了字段子表，在Oracle内实现了字段级数据安全控制；使用权限信息表和数据库用户共同控制权限，对数据做了双层保护。用C#语言开发了C／S模式的权限控制系统图形界面，简化了权限控制，用户使用灵活方便。     

基于微机平台的注塑模型腔CAD/CAM一体化的实现

本文分析了注塑模型腔CAD／CAM实践中具体的曲线曲面造型处理方法，讨论了CAD／CAM实现中的各项关键技术，并成功地在微机系统上实现了注塑模型腔CAD／CAM的一体化。     

基于系列化配置原理的产品设计技术研究

在分析零件事物特性表的基础上,提出了基于系列化配置原理的产品设计技术.分析了使用该技术的产品开发的一般流程.研究了将产品配置和工艺配置在同一配置表中的存储技术;从三维CAD产品模型中进行特征提取的算法;零件工序简图的自动生成技术等关键技术和算法.以发动机气门产品为研究对象,使用UML的包图设计了发动机气门产品设计系统的组件模型,基于该组件模型和SolidWorks 三维CAD平台,使用Visual C 6.0实现了原型系统.     

A quantitative analysis of parametric CAD model complexity and its relationship to perceived modeling complexity

Digital product data quality and reusability has been proven a critical aspect of the Model-Based Enterprise to enable the efficient design and redesign of products. The extent to which a history-based parametric CAD model can be edited or reused depends on the geometric complexity of the part and the procedure employed to build it. As a prerequisite for defining metrics that can quantify the quality of the modeling process, it is necessary to have CAD datasets that are sorted and ranked according to the complexity of the modeling process. In this paper, we examine the concept of perceived CAD modeling complexity, defined as the degree to which a parametric CAD model is perceived as difficult to create, use, and/or modify by expert CAD designers. We present a novel method to integrate pair-wise comparisons of CAD modeling complexity made by experts into a single metric that can be used as ground truth. Next, we discuss a comprehensive study of quantitative metrics which are derived primarily from the geometric characteristics of the models and the graph structure that represents the parent/child relationships between features. Our results show that the perceived CAD modeling complexity metric derived from experts’ assessment correlates particularly strongly with graph-based metrics. The Spearman coefficients for five of these metrics suggest that they can be effectively used to study the parameters that influence the reusability of models and as a basis to implement effective personalized learning strategies in online CAD training scenarios.     

A survey of CAD model simplification techniques for physics-based simulation applications

Automated CAD model simplification plays an important role in effectively utilizing physics-based simulation during the product realization process. Currently a rich body of literature exists that describe many successful techniques for fully-automatic or semi-automatic simplification of CAD models for a wide variety of applications. The purpose of this paper is to compile a list of the techniques that are relevant for physics-based simulations problems and to characterize them based on their attributes. We have classified them into the following four categories: techniques based on surface entity based operators, volume entity based operators, explicit feature based operators, and dimension reduction operators. This paper also presents the necessary background information in the CAD model representation to assist the new readers. We conclude the paper by outlining open research directions in this field.     

SOLIDWORK设计的CAD模型水印嵌入策略

通过对SOLIDWORK软件设计的CAD模型数据特点及软件本身自动成环检测技术,以曲线可以用相交面来替代为例,构造出相交曲面的CAD表示冗余信息,通过修改冗余信息进行水印嵌入;另外还提出可以将水印信息嵌入在CAD模型颜色等属性和CAD模型数据编码冗余信息中,具体嵌入方法可以借鉴已有图像水印方法.     

Design gene based secure mechanism for collaborative product development

In collaborative product development, a CAD model needs to be effectively shared among partners to facilitate co-design. In the meantime, it is essential to preserve the intellectual property information (design knowledge) of the shared CAD. To resolve the above dilemma, this paper presents a novel approach to share CAD models to support collaboration, as well as conserving confidential design knowledge in the models. The motivation of the approach is to develop collaborative mechanisms pertaining to an innovative concept of design genes, which imitate biological genes that are responsible for the heritable characteristics of an organism during evolving. The approach consists of the following steps. Firstly, design genes are defined to represent the design knowledge in CAD models. Secondly, a filter is introduced to retrieve design genes from the CAD model flexibly. An encryption algorithm is then designed to encrypt the design genes, and ensure the geometrical validity of the model to support effective collaboration. Finally, case studies are used to validate the developed approach. The complexity of the case studies can demonstrate that the approach is applicable to real-world application scenarios.     

保持外观的CAD模型轻量化技术

随着CAD/CAM技术的发展,整个产品的设计、虚拟制造和数字化样机都可在计算机中完成,使得包含大量数据的复杂装配体(即大装配体)的设计成为产品设计过程中的必需元素。由于大装配体模型数据量庞大,在普通PC机中处理极为不便,为了提高处理速度,需要对大装配体模型进行简化。在不改变装配模型格式和整体外观的前提下,提出了两种装配体模型的轻量化方案：1)从装配体中删除隐藏的零部件;2)从装配体中删除隐藏的特征。零件和特征的可见性是通过从多个视点预渲染装配模型,然后读取渲染缓冲区的结果并进行分析而得到。实验结果证实该算法能在不改变CAD模型格式和外观的前提下准确地删除装配体中的隐藏零件和特征。     

网络安全评估方法的研究与实践

网络安全评估技术和方法的研究对网络安全防护体系的建设具有重要意义。该文结合实际工作经验和研究成果,在分析安全评估技术发展现状的基础上,提出了一种定性分析与定量计算相结合的风险评估模型,给出了具体算法及基于该算法的风险评估流程,并加以实际应用。实践结果证明,应用该算法和模型实施的风险评估对被评估单位的网络安全防护和管理工作起到了良好的指导作用。     

基于B-Rep的三维CAD模型盲水印算法

随着信息时代的到来,数字水印不仅在版权保护、来源认证、私有探测领域受到了前所未有的重视,而且在信息安全领域也引起了广泛的关注.提出了一种基于B-rep的CAD模型盲水印算法,该算法主要针对NURBS曲线或曲面来嵌入水印,能精确地保持模型的形状.首先遍历模型找到所有的NURBS曲线,并将其依据曲线的长度进行排序,然后利用...     

Fast global and partial reflective symmetry analyses using boundary surfaces of mechanical components

Axisymmetry and planar reflective symmetry properties of mechanical components can be used throughout a product development process to restructure the modeling process of a component, simplify the computation of tool path trajectories, assembly trajectories, etc. To this end, the restructured geometric model of such components must be at least as accurate as the manufacturing processes used to produce them, likewise their symmetry properties must be extracted with the same level of accuracy to preserve the accuracy of their geometric model. The proposed symmetry analysis is performed on a B-Rep CAD model through a divide-and-conquer approach over the boundary of a component with faces as atomic entities. As a result, it is possible to identify rapidly all global symmetry planes and axisymmetry as well as local symmetries. Also, the corresponding algorithm is fast enough to be inserted in CAD/CAM operators as part of interactive modeling processes, it performs at the same level of tolerance than geometric modelers and it is independent of the face and edge parameterizations.     

Approach for developing coordinated rubrics to convey quality criteria in MCAD training

This paper describes an approach to convey quality-oriented strategies to CAD trainees by embedding quality criteria into rubrics so as to force CAD trainees to understand them early in their instruction. To this end, the paper analyzes how CAD quality criteria can be organized around quality dimensions and embedded into rubrics in order to enforce quality modeling during the CAD training of novice product designers. Hence, the ambit of this study is training with history-based parametric feature-based MCAD systems, although the general conclusions are believed to be adaptable to other CAD training scenarios. Furthermore, it introduces an approach based on progressive refinement, which results in an assertions map that indicates quality dimensions vs. sequence of tasks for CAD models. The map illustrates how the expand–contract strategy adapts the rubrics to CAD trainee progress and assists them in comprehending the different dimensions of the rubrics. The paper also highlights lessons learned on the suitability of using separate rubrics for different tasks, the need of accurately timing the expand–contract process, and on the convenience of supporting rubrics with suitable teaching, which must convey good practices and evaluation tools through rubrics. The experiments describe the different lessons learned and illustrate the suggested process for replicating our approach for further developing rubrics adapted to other scenarios.