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21.
A database system of mechanical components based on geometric and topological similarity. Part I: representation 总被引:3,自引:0,他引:3
A database of mechanical components is an important issue for some manufacturing activities such as cost estimation, process planning, and design by case-based reasoning. In this paper, we give the representation scheme of the CAD model in such a database. Components are represented using attributed graphs in which the nodes correspond to the surfaces of the component and the links correspond to the edges of the component. The graph is based on the standard for the exchange of product information (STEP) physical file of the component. STEP file should be unique for a single component regardless of the underlying CAD system. The process of creating the graph of a component constitutes two sub-tasks: (i) importing the CAD model from the CAD system in STEP format and (ii) transforming the STEP data into attributed graph-based representation. The graph and its attributes describe the topology of the component completely together with some geometric data that are not dependent on any coordinate system such as surface type and curve type. These geometric data are helpful in the retrieval and matching processes in the database. 相似文献
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1.引言 1.1 产品信息集成的现状和面临的局限产品信息描述格式的不统一使得传统CIMS之间产品信息不能共享,数据交换产生障碍。STEP标准及其EXPRESS语言统一了产品信息的建模标准和数据结构,使得产品信息由原来的机器不可读(machine-unreadable)变为机器可读(machine-readable),从而在数据格式上解决了产品信息的共享和交换问题。但是,分布、开放、动态的计算环境,使得企业内部及企业 相似文献
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本文分析了数据交换技术的发展,指出STEP技术可以满足集成化系统开发的需要,而面向对象技术则很好地解决了模型间的数据交换,并据此提出了一基于面向对象和STEP的注塑模产品模型,该模型分为总体信息模型、主特征模型、结构信息模型及辅助装置模型,并用EXPRESS-G对其作了进一步阐述。 相似文献
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SDAI是STEP的数据接口规范,它为工程应用与EXPRESS描述的数据模型间定义了一个功能界面。本文讨论了关系数据库上SDAI实现的方法,阐述了STEP模型与关系模型的一种转换机制,开发了关系数据库上数据交换SDAI接口函数库,为STEP的工程应用奠定了基础 相似文献
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STEP标准数据存取接口SDAI在工程应用模型与STEP模型间定义了一个功能界面,使数据应用与数据存储分离成为可能。本文阐述了一种SDAI的建模理论和方法,并实现了材料质量信息的SDAI建模。 相似文献
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企业产品三维模型信息在产品的整个生命周期中占据着重要的地位。该文提出了一个基于Web的产品三维模型信息共享方案:以VRML文件和数据库作为产品三维模型信息的载体,结合XML和ASP技术实现了产品三维模型信息的跨平台共享,为实现网络化产品设计提供了技术基础。 相似文献
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Manolis Patiniotis 《Centaurus; international magazine of the history of science and medicine》2013,55(4):361-384
The aim of this paper is to discuss two historiographical issues pertaining to the history of science in the European periphery. The first issue concerns the wide use of the centre‐periphery dichotomy in historical accounts discussing the diffusion and institutionalization of science across the world. The second issue concerns the use of appropriation (instead of transfer, or adaptation) as a means to overcome the diffusionist model in history of science. Recent work at the intersection of history of science with post‐colonial studies will provide the framework for reassessing these matters. As it will be shown, theoretical discussions about the history of science in post‐colonial context can help historians overcome the centre‐periphery dichotomy and turn European periphery into a privileged standpoint for showing the actual diversity of ‘European science.’ At the same time, the experience of post‐colonial studies can also help sharpen the historiographical tool of appropriation. The assumption that will be made is that by focusing on appropriation rather than on discovery and innovation (the favourite categories of much of mainstream historiography), or on transfer and adaptation (the favourite categories of the diffusionist model), historians of science can not only set aside the artificial distinctions of the diffusionist model, but also bring forward the re‐inventions, the conceptual shifts and the cultural adjustments, which are responsible for the emergence of science as a global phenomenon in the periphery. Especially concerning European periphery, the use of appropriation may bring forward the particular historical circumstances under which certain knowledge patterns gained universal epistemic authority as constitutive elements of an imagined European intellectual identity. 相似文献
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