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CAO Yan-long LIU Yu-sheng MAO Jian YANG Jiang-xim 《浙江大学学报(A卷英文版)》2006,7(11):1810-1818
INTRODUCTION Tolerance is imperative for seamless integration of computer-aided design (CAD) and computer aided manufacturing (CAM) (Bjorke, 1989; Wu and Yang, 1999) and influences greatly the quality, process planning, measurement, cost and assembly of the product. Many researches have been conducted on tolerance (Baer, 1979; Requicha, 1982; 1983; 1992; Clement, 1991). Most of these researches are focused on tolerance analysis and tolerance synthesis. In some commercial CAD/CAM sy… 相似文献
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Tolerance is imperative for seamless integration of CAD/CAM (Computer Aided Disign/Computer Aided Manufacture) which is just
a text attribute and has no semantics in present CAD systems. There are many tolerance types, the relations between which
are very complicated. In addition, the different principles of tolerance make study of tolerance difficult; and there may
be various meanings or interpretation for the same type of tolerance because of the literal definition. In this work, latest
unambiguous mathematical definition was applied to study, explain and clarfy: (1) the formation and representation of tolerance
zone, and (2) the formation and representation of variational elements; after which, the mathematical models of symmetry of
different tolerance principles and different interpretations were derived. An example is given to illustrate the application
of these models in tolerance analysis.
Project supported by the National Natural Science Foundation of China for Innovation Research Groups(No.60021201) and NSFC(Nos.59705022
& 69973045). 相似文献
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朱建平 《华侨大学学报(哲学社会科学版)》2014,(2):56-70
塔斯基关于真的语义学定义和逻辑后承的里程碑式的著作是对现代语义学研究最重要的贡献。塔斯基用满足和归纳的方式给出的真的递归定义,循序渐进的句法定义,语义模型的概念,逻辑真和逻辑后承的概念等一系列理论和方法构成了当代语义学理论的核心部分。诸如模型论语义学、可能世界语义学、戴维森的意义理论、蒙太格的内涵语义学,甚至作为生成语法的分支的逻辑形式(LF)等无一不体现或者渗透着塔斯基原理和思想。 相似文献
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在MasterCAM三维模型生成的工程图中没有提供形位公差代号和表面结构符号的标注方法,工程图图框和标题栏也不符合要求。为了解决这一问题,开发了形位公差图形库、表面结构符号库与标准图框和标题栏,这对于将三维模型快速地生成符合国家标准的工程图样具有重要的意义。 相似文献
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关于德国数学教育标准中的数学能力模型 总被引：4，自引：0，他引：4
徐斌艳 《课程.教材.教法》2007,(9)
为保障各联邦州数学教育质量的均衡发展,2003年底德国首次颁布全联邦性数学教育标准。这是一个较为典型的能力导向的教育标准,它提出学生应该发展的六大数学能力:(1)数学论证;(2)数学地解决问题;(3)数学建模;(4)数学表征的应用;(5)数学符号、公式以及技巧的熟练掌握;(6)数学交流。根据不同的认知要求这六大能力又分别被细化为三个能力水平。这个能力模型强调学生数学能力的可持续发展。 相似文献
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数学公式的计算机表达 总被引：5，自引：0，他引：5
数学公式由于使用特殊符号繁多,排版格式复杂多变,因而在计算机上处理特别困难,这也制约了利用计算机和网络开展数学辅助教学的发展。该文针对这一情况,介绍了如何利用计算机表示数学公式的各种方法:先介绍了常用的图形表示方法和使用字处理软件编写数学公式的方法;然后介绍了目前国际流行的数学排版标准语言Tex及其相关应用软件;最后介绍未来的数学公式表达语言MathML,这是一个基于XML语言的表示数学公式的新标准,虽然现在还处于制定和发展之中,但相信在不久的将来,MathML一定会成为数学公式表达的标准语言。 相似文献
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ERP软件选型是ERP项目管理中的重要内容．本文介绍选型流程及相应的层次分析方法,并基于国家标准质量模型,构建了具有五层结构的ERP软件供应商的选择模型,通过案例,运用AHP方法确定各层元素的权重．实践证明：该解决方案简单易行,可以有效地将定性分析转化为定量分析． 相似文献
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<工程塑料模塑塑料件尺寸公差标准>是国家规范和指导模塑塑料制件设计与生产的基础性文件.由于此标准采用表格形式表达模塑件基本尺寸与其制造公差的关系,因而存在一些局限.通过分析发现该关系在很大范围内可以采用解析式表达.以解析式表达不但可以克服表格式表达的局限,而且在计算机条件下使用起来更加便捷准确. 相似文献
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It is well established that early general language during preschool is critical for children's mathematical abilities. In an attempt to further characterize this association between language and mathematics, an increasing number of studies show that one specific type of language, namely mathematical language or the key linguistic concepts that are required for performing mathematical activities, is even more critical to children's mathematical abilities. The purpose of this systematic review is to summarize the evidence on mathematical language and mathematical abilities. We focus on preschool children as nearly all of the existing work has been done at this age. We first explain how mathematical language has been defined across studies, and report how it has been evaluated in studies in preschool. Next, we present the results of our systematic review. Following the PRISMA guidelines and after a critical appraisal, we ended with a set of 18 papers that were all of sufficient methodological quality. In these studies, mathematical language was defined as terms that are about numbers and operations on numbers (e.g., nine), but also included linguistic terms that do not directly refer to numbers, yet are important to understand mathematical concepts (i.e., quantitative and spatial terms such as fewest and middle, respectively). Some of these studies evaluated children's performance on mathematical language tasks, while others evaluated the mathematical language input provided to the child by their (educational) environment (teachers/parents/interventionists). Mathematical language correlated positively with children's mathematical abilities, concurrently and longitudinally. It also directly affected children's mathematical abilities, as was shown by intervention studies. We discuss potential directions for future research and highlight implications for education, arguing for more support for teachers and parents to improve the use of mathematical language in the classroom and in home settings. 相似文献
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浅谈数学创造性思维能力的培养 总被引：1，自引：0，他引：1
杨路娜 《辽宁科技学院学报》2004,6(2):40-41
本文阐述了创造性思维的概念,揭示了数学创造性思维的基本特征,从开发学生智力、引导学生探索和实践环境等方面,提出了培养学生创造性思维能力的途径和方法. 相似文献
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Neurons with complex-valued weights have stronger capability because of their multi-valued threshold logic. Neurons with such features may be suitable for solution of different kinds of problems including associative memory, image recognition and digital logical mapping. In this paper, robustness or tolerance is introduced and newly defined for this kind of neuron according to both their mathematical model and the perceptron neuron＇s definition of robustness. Also, the most robust design for basic digital logics of multiple variables is proposed based on these robust neurons. Our proof procedure shows that, in robust design each weight only takes the value of i or -i, while the value of threshold is with respect to the number of variables. The results demonstrate the validity and simplicity of using robust neurons for realizing arbitrary digital logical functions. 相似文献
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特征技术在设计和制造中的成功应用取决于其形式化理论的建立．本文从形式化定义和可制造性分析两个方面研究了面向制造设计中制造特征的形式化描述方法，提出了基于设计几何材料去除操作选择和规划的相关制造特征定义，给出了相应的可制造性分析算法框架．所提出的方法为基于特征的ＣＡＤ／ＣＡＭ集成，尤其是为设计自动化的实现提供了一种新的思路． 相似文献
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圆度误差数学模型的建立与仿真分析 总被引：4，自引：0，他引：4
齐秀彪 《辽宁科技学院学报》2001,3(2):26-28
按照形状与位置公差国家标准中圆度误差的规定，采用最小二乘圆法建立了圆度误差的数学模型，并对其进行了仿真分析。文中的数学模型和仿真研究研制圆度测量仪和在线测量系统提供了理论依据。 相似文献
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刘璟忠 《湖南科技学院学报》2005,26(11):13-16
学术职业的国际比较研究是美国卡内基教学促进委员会于一九九0年确立的大型课题,其研究成果在一九九六年已出版.本文利用模糊综合评价方法,根据其调查数据,对国际学术职业概况建立了数学模型,并进行了比较研究 相似文献
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The intemational standard ISO 10303.called STEP.has been used to deal with problems in the ex change of product models and the associated data between difierent computer-aided systems.A platform based on STEP for managing product information is presented.This platform includes three components:a product geometry information model,a product feature model and a product visualization model.An information extracting pattern,in which information is extracted from low level elements to high level ones,is adopted in establishing the product geometry information model.Relative elements lists are created based on the extracted product information.With the traversing of these lists,feature extraction methods are proposed,which take advantage of boundary information in product model and avoid the determination of concavity and convexity of curves.Information correlating to features iS stored in a structure named as feature block and the product visualization model iS founded from it.The feature block is used in the platform for information communication and synchronous update among the three components. 相似文献
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以PISA2018中国四省市样本数据为例,应用结构方程方法,研究信息定位、文本理解、评价与反思三个PISA2018阅读素养子能力对数学与科学表现的影响。结果表明,阅读素养的子能力之间高度相关,对科学表现和数学表现有较大的影响;信息定位对文本理解具有决定性的影响,文本理解在阅读对数学与科学的影响中起承上启下的关键作用,评价与反思对数学、科学的影响中很大一部分是通过文本理解间接影响的,阅读三个子能力对科学的影响中,很大一部分可以通过数学路径来解释。 相似文献
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Chris Hurst 《Educational research; a review for teachers and all concerned with progress in education》2017,59(1):107-123
Background: Teacher knowledge continues to be a topic of debate in Australasia and in other parts of the world. There have been many attempts by mathematics educators and researchers to define the knowledge needed by teachers to teach mathematics effectively. A plethora of terms, such as mathematical content knowledge, pedagogical content knowledge, horizon content knowledge and specialised content knowledge, have been used to describe aspects of such knowledge.Purpose: This paper proposes a model for teacher knowledge in mathematics that embraces and develops aspects of earlier models. It focuses on the notions of contingent knowledge and the connectedness of ‘big ideas’ of mathematics to enact what is described as ‘powerful teaching’. It involves the teacher’s ability to set up and provoke contingent moments to extend children’s mathematical horizons. The model proposed here considers the various cognitive and affective components and domains that teachers may require to enact ‘powerful teaching’. The intention is to validate the proposed model empirically during a future stage of research.Sources of evidence: Contingency is described in Rowland’s Knowledge Quartet as the ability to respond to children’s questions, misconceptions and actions and to be able to deviate from a teaching plan as needed. The notion of ‘horizon content knowledge’ (Ball et al.) is a key aspect of the proposed model and has provoked a discussion in this article about students’ mathematical horizons and what these might comprise. Together with a deep mathematical content knowledge and a sensibility for students and their mathematical horizons, these ideas form the foundations of the proposed model.Main argument: It follows that a deeper level of knowledge might enable a teacher to respond better and to plan and anticipate contingent moments. By taking this further and considering teacher knowledge as ‘dynamic’, this paper suggests that instead of responding to contingent events, ‘powerful teaching’ is about provoking contingent events. This necessarily requires a broad, connected content knowledge based on ‘big mathematical ideas’, a sound knowledge of pedagogies and an understanding of common misconceptions in order to be able to engineer contingent moments.Conclusions: In order to place genuine problem-solving at the heart of learning, this paper argues for the idea of planning for contingent events, provoking them and ‘setting them up’. The proposed model attempts to represent that process. It is anticipated that the new model will become the framework for an empirical research project, as it undergoes a validation process involving a sample of primary teachers. 相似文献
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Property path is the latest navigational extension of the standard query language SPARQL 1.1 for the Semantic Web.However,in the existing SPARQL query systems which support property path,the query efficiency is very low and does not support reasoning.This paper proposes a new existential semantics which has polynomial-time evaluation complexity and an equivalent relationship with the current semantics,and transforms the property path expressions to the extended nested regular expressions based on the existential semantics and proves the semantic equivalence after the transformation considering the RDFS semantics.The property path query engine is achieved by implementing the nested regular expressions algorithm and the transformation rules from the property path expressions to the nested regular expressions,which maintains the syntax simplicity of property path and the goal-oriented polynomial-time reasoning to avoid computing the RDF graph closure.The experiment results not only show the characteristics of query engine based on the existential semantics in efficiency and reasoning,but also further validate the equivalence between the results based on current semantics and those based on the existential semantics for property path after the removal of duplicate values. 相似文献
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This paper presents a practical three-dimensional mathematical model of circulation and heat transfer in generator of glass
melting furnaces. The model was based on the heat transfer between the smoke flow and the lattice units, and between the air
flow and the lattice units. This model not only bypassed the difficulty of complicated computation of the heat transfer process
in the regenerator of glass furnaces, but also avoided the irrationality of fixing the temperature distribution on the surfaces.
Use of the model yielded very important data and also the method for the design of the regenerator of glass furnaces in practical
production. 相似文献