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1.
本文在基于约束的参数驱动法的基础上,对图形设计中经常遇到的循环约束现象提出了平面刚体的概念,并对颊刚体的成因、条件作了详细的分析,给出平面刚体的数据结构,并将其思想具体应用于CAD系统的开发中。 相似文献
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A bottom-up method for creating a hierarchy of entity-relationship diagrams (HERD) from a given, flat ER diagram (ERD) is proposed. The hierarchy consists of simple and interrelated diagrams—ER structures—with external relationships to other structures. The HERD-tree diagram, which provides the most general view of the conceptual schema, is located at the top of the hierarchy. The method is based on packaging operations, which group entities and relationships according to certain criteria. These operations are applied in several steps on a given (presumably large-scale) ERD. We describe the new constructs, which are added to the ER model to enable the creation of HERD, and a bottom-up method for creating HERD. We also evaluate HERD from the point of view of user comprehension and preference, based on an experimental comparison to flat ERDs.
相似文献
Peretz ShovalEmail: |
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Peter Barr 《History of Photography》2013,37(1):43-59
This study focuses on the photographs that first brought Berenice Abbott critical acclaim: her Paris portraits from the late 1920s. As a body of work, these images – along with what Abbott had to say about them and the critical attention they generated at the time – provide a rich resource for the study of three interconnected topics: the avant-garde critical climate of Europe in the late 1920s, the American expatriate experience in Paris during this same time and Abbott's nascent photographic values and aesthetic, which helped to inform not only her portraits but also her later, better-known photographs of New York City. The paper first defines the divergent critical responses to Abbott's portrait work in the late 1920s – focusing especially on the published criticism by Florent Fels and Pierre Mac Orlan that helped to secure Abbott's international reputation as a leading modern photographer. It then turns to Abbott's expatriate experience in order to examine the ideas and individuals that she identified as most important to her photographic practice. Specifically the paper explains Abbott's desire to create an alternative approach to photography from the one used by Man Ray, her awareness of the classical style associated with Pablo Picasso and her admiration for the aesthetic theories of Leo Stein. 相似文献
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完整性约束是数据模型的重要组成部分,在应用系统开发中数据库完整性的设计十分重要。本文从实体完整性、参照完整性和用户自定义完整性三方面探讨了数据库完整性理论,并通过实例介绍了在VFP6.0中数据库完整性的设计。 相似文献
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Mircea Fotino 《Journal of microscopy》1983,129(2):171-178
A simple procedure is described for the reproducible and convenient assembly of stereo micrographs, particularly as transparencies, with the help of an apparatus developed for this purpose. Technical features and applications are discussed. 相似文献
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王馥 《常州信息职业技术学院学报》2011,10(4):37-39
在学生了解人像数码摄影概念后,通过任务驱动教学法为学生构建一个真实的人像摄影环境,让学生带着任务学习拍摄人像,在熟练掌握技能的同时,更要注重引导学生去探索发现自己周围的具体形象,练就一双善于发现事物特殊之处的慧眼,不断提高快速抓拍的能力。 相似文献