A mathematical model of symmetry based on mathematical definition

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 clarify: (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.

The Optimal Precursors for ENSO Events Depicted Using the Gradientdefinition-based Method in an Intermediate Coupled Model

The predictability of El Ni-o-Southern Oscillation (ENSO) has been an important area of study for years. Searching for the optimal precursor (OPR) of ENSO occurrence is an effective way to understand its predictability. The CNOP (conditional nonlinear optimal perturbation), one of the most effective ways to depict the predictability of ENSO, is adopted to study the optimal sea surface temperature (SST) precursors (SST-OPRs) of ENSO in the IOCAS ICM (intermediate coupled model developed at the Institute of Oceanology, Chinese Academy of Sciences). To seek the SST-OPRs of ENSO in the ICM, non-ENSO events simulated by the ICM are chosen as the basic state. Then, the gradient-definition-based method (GD method) is employed to solve the CNOP for different initial months of the basic years to obtain the SSTOPRs. The experimental results show that the obtained SST-OPRs present a positive anomaly signal in the western-central equatorial Pacific, and obvious differences exist in the patterns between the different seasonal SST-OPRs along the equatorial western-central Pacific, showing seasonal dependence to some extent. Furthermore, the non-El Ni-o events can eventually evolve into El Ni-o events when the SST-OPRs are superimposed on the corresponding seasons;the peaks of the Ni-o3.4 index occur at the ends of the years, which is consistent with the evolution of the real El Ni-o. These results show that the GD method is an effective way to obtain SST-OPRs for ENSO events in the ICM. Moreover, the OPRs for ENSO depicted using the GD method provide useful information for finding the early signal of ENSO in the ICM.

MODULE DEFINITION MODEL FOR MODULAR DESIGN AND MANUFACTU－RING OF HEAVY DUTY MACHINE TOOLS

The key techniques of modular design of heavy duty NC mathine tools are described. Amodule definition modelfor modular design and manufacturing of heavy duty NC machine tools isbulit and the essential composition of the module definition model (MDM) is discussed in detail. Itis composed of two models: the part definition model (PDM) and the module assembly model(MAM). The PDM and MAM are built and their structures are given. Using object-oriented know-ledge representation and based on these models, an intelligent support system of modular design forheavy duty NC machine tools is developed and implemented This system has been applied to thepractical use of Wuhan Heavy Duty Machine Tool Works

A Feature Definition Hierarchy for Supporting Design Process

The adaptability of features definition to applications is an essential condition for implementing feature based design. This paper makes attempt to present a hierarchical definition structure of features. The proposed scheme divides feature definition into application level, form level and geometric level, and provides links between different levels with feature semantics interpretation and enhanced geometric face adjacent graph. respectively. The results not only enable feature definition to abate from the specific dependence and become more extensive, but also provide a theoretical foundation for establishing the concurrent feature based design process model.

一种基于内容模型图的XML Schema Definition的提取方法

使用XML Schema能够对XML文档进行有效性验证以及对查询、转换等操作进行优化,但是实际应用中大量XML文档缺失关联的Schema。提出了一种根据XML文档自动提取对应的XML Schema Definition(XSD)的方法XSDInfer,先根据合并规则将XML解析过程中分析得到的模式信息记录在内容模型图中,再根据生成规则将其转化为内容模型表达式,进而得到XSD。XSDInfer能够在内存消耗比较少的情况下快速地处理超大规模、深度嵌套的XML文档,同时支持XSD的上下文相关的内容模型,提取出的XSD也具有更好的可读性。实验表明,与同类方法相比,XSDInfer具有更好的可扩展性和表达能力。

Spatial Boundary Definition of Urban-rural Fringe in Beijing City

Through reviewing domestic and overseas literatures about the definition of urban-rural fringe,it can be found that the combination of qualitative and quantitative definition methods has become a dominant one.This paper makes out the principle and basis,uses the data of villages and towns,and establishes an index system from three angles:population,land use and landscape.And then the gravitational model is applied to define the urban-rural fringe with Beijing as an example.

24Model与LCM原因因素定义对比研究

为探究损失致因模型(LCM)原因因素定义与事故致因“2-4”模型(24Model)存在的异同和优缺点,梳理2个模型各层面原因和结果的定义,对比定义内容及其对事故原因分析等安全实务的指导作用,并以一起瓦斯爆炸事故为例加以实证分析,获得二者分析结果之间的差异。研究结果表明:LCM是首个将管理因素纳入事故致因分析的一维事件序列模型,可明确各层面原因因素的定义和因素间的逻辑关系,但部分定义存在交叉重复的问题,并没有揭示安全工作指导思想等深层次事故致因因素;24Model作为系统性事故致因模型,对各类因素的定义均以组织为主体,描述事件、事故、安全的概念内涵,划分个体安全动作、安全能力和组织安全管理体系的类别并给出含义解析,探究组织安全文化层面的问题并以32个元素体现;2个模型的事故原因分析方法均建立在对各层级原因因素定义的基础上,并适用于模型理论体系本身。

On the definition of fractional derivatives in rheology

During the last two decades fractional calculus has been increasingly applied to physics, especially to rheology.It is well known that there are obivious differences between Riemann-Liouville (R-L) definition and Caputo definition,which are the two most commonly used definitions of fractional derivatives.The multiple definitions of fractional derivatives have hindered the application of fractional calculus in rheology.In this paper,we clarify that the R-L definition and Caputo definition are both Theologically unreasonable with the help of the mechanical analogues of the fractional element model.We also find that to make them more reasonable Theologically,the lower terminals of both definitions should be put to—∞.We further prove that the R-L definition with lower terminal—∞and the Caputo definition with lower terminal—∞are equivalent in the differentiation of functions that are smooth enough and functions that have finite number of singular points.Thus we can define the fractional derivatives in rheology as the R-L derivatives with lower terminal—∞(or,equivalently,the Caputo derivatives with lower terminal—∞) not only for steady-state processes,but also for transient processes.

Mathematical model of cylindrical form tolerance

Tolerance is essential for integration of CAD and CAM. Unfortunately, the meaning of tolerances in the national standard is expressed in graphical and language forms and is not adaptable for expression, processing and data transferring with computers. How to interpret its semantics is becoming a focus of relevant studies. This work based on the mathematical definition of form tolerance in ANSI Y 14.5.1 M-1994, established the mathematical model of form tolerance for cylindrical feature. First, each tolerance in the national standard was established by vector equation. Then on the foundation of toler-ance's mathematical definition theory, each tolerance zone's mathematical model was established by inequality based on degrees of feature. At last the variance area of each tolerance zone is derived. This model can interpret the semantics of form tolerance exactly and completely.

Rural Tourism Development in China:Principles,Models and the Future

Rural tourism in China,has undergone a rapid development in the last three decades.It is an emerging and effective catalyst that promotes industrial restructuring,agricultural development and the upgrading of rural areas.However,there remains little understanding about the core issues of rural tourism in China:the exact connotation,the principles,the development models and the future directions.This review paper identifies the key issues based on literature analysis,national statistics and press reports to form a general picture of the past,the current and the future prospects of China's rural tourism.The paper firstly addresses the definition,content and principles of rural tourism,and then provides an overview and brief evaluation of the progress and the current development models in China.Finally,based on the analysis of the experiences and problems,the authors sum up with five pathways of the future development of China's rural tourism from the perspective of rural tourism resources,product,market and promotion.

Evaluation Model of System Survivability

This paper puts forward a survivability evaluation model, SQEM （Survivability Quantitative Evaluation Model）, based on lucubrating the main method existed. Then it defines the measurement factors and parses the survivability mathematically, introduces state change probability and the idea of setting the weights of survivability factors dynamically into the evaluating process of SQEM, which improved the accuracy of evaluation. An example is presented to illustrate the way SQEM works, which demonstrated the validity and feasibility of the method.

Stabilization strategy of a car-following model with multiple time delays of the drivers

An extended car-following model with multiple delays is constructed to describe driver's driving behavior.Through stability analysis,the stability condition of this uncontrolled model is given.To dampen the negative impact of the driver's multiple delays(i.e.,stability condition is not satisfied),a novel control strategy is proposed to assist the driver in adjusting vehicle operation.The control strategy consists of two parts:the design of control term as well as the design of the parameters in the term.Bifurcation analysis is performed to illustrate the necessity of the design of parameters in control terms.In the course of the design of parameters in the control term,we improve the definite integral stability method to reduce the iterations by incorporating the characteristics of bifurcation,which can determine the appropriate parameters in the control terms more quickly.Finally,in the case study,we validate the control strategy by utilizing measured data and configuring scenario,which is closer to the actual traffic.The results of validation show that the control strategy can effectively stabilize the unstable traffic flow caused by driver's delays.

Analysis of Quality of Life in Cancer Patients by Structural Equation Model

Many people have been dead of cancer. The life quality of patients with cancer has aroused great concern from the public and specialists. In this paper, an index system of life quality is proposed to evaluate the quality of life, which includes 6 first-level indexes and 34 second-level indexes. Then, a structural equation model (SEM) based on these in-dexes and relationships among them is constructed for the analysis of quality of life in cancer patients. Furthermore, we offer a definite linear algorithm for the calculation of SEM. This method is more objective and scientific compared with traditional methods, such as descriptive analysis, some simple test methods and so on.

中国情报与情报学:概念模型和学科演进

[目的/意义]从历史发展的角度,对于中国情报与情报学概念进行深入剖析,以此为据去认识中国的情报和情报学的过去,思考中国情报学的未来,不仅有助于从历史上认识学科的内容和价值,更是推动学科创新和持续发展的重要基础。[方法/过程]通过文献调研与网络调查广泛收集了在中国文献中记载的155条情报定义和99条情报学定义,进而建立定义分析模型,采用内容分析和时序分析等方法研究了情报和情报学定义的基本形式、内容特征,以及情报与情报学的概念模型,最后依据中国情报与情报学概念的演变分析,探讨和分析中国情报学的学科演变特征。[结果/结论]基于定义分析,清晰揭示了情报是什么以及其性质、作用对象、处理工作和涉及领域,情报学是什么以及其研究对象、研究内容、学科属性和研究目标;结合实践层面的情报活动与情报工作,从信息环境、情报服务对象、情报服务方式和情报认知4个层面,系统地探讨和展现中国情报学的发展演进脉络。

宇航元器件需求工程化研究

面向宇航任务的元器件需求规划,为系统解决宇航元器件需求表达不完整、表征不准确的问题,文章提出了宇航元器件需求工程的概念并阐述了其内涵和范围,建立了宇航元器件需求工程的整体技术体系,研究了需求解析、需求建模、产品定义和需求验证等关键技术,阐述了4个关键技术在载人空间站工程中应用直流-直流(DC-DC)电源产品的典型案例。研究形成的技术体系和方法可以为宇航领域元器件需求规划、研制攻关提供参考。

建筑行业三维标注(MBD)技术研究和应用展望

随着建筑业数字化、工业化的大力发展,业内对三维标注技术(MBD)的需求日益提升。然而在目前的工作流程中,设计、模拟以及生产的数据一体化框架仍不完善,难以满足实际建筑工程的需要。现阶段BIM技术缺乏关于MBD技术的方法与标准,导致即便设计流程采用全三维设计方式,但最终仍需转换为二维图纸交付生产,其与传统设计流程在本质上并未产生明显区别。本文主要围绕建筑行业MBD技术进行研究与应用展望,包括MBD技术发展历程、相关标注标准的体系构建以及应用的潜在方向,旨在为建筑产品全生命周期管理(PLM)提供基础理论技术支持,也为建筑行业发展提供新的发展思路。

基于R-L分数阶定义的CCM Flyback变换器建模与分析

针对电容电感都为分数阶这一事实,利用分数阶微积分R-L定义和状态空间平均法,对工作在电感电流连续模式(CCM)下的分数阶Flyback变换器进行建模与分析。推导CCM分数阶Flyback变换器的静态工作点和小信号传递函数以及变换器工作在CCM模式下的条件。其次,讨论Caputo模型与R-L导数模型的区别,得出在R-L分数阶定义下直流静态工作点不仅与占空比相关,而且还与电感和电容的阶数以及负载有关。最后,在PSIM中搭建R-L分数阶CCM Flyback变换器电路模型,得到不同分数阶电感电容阶数下分数阶Flyback变换器输出电压和电感电流的仿真波形,通过仿真结果与理论计算结果对比,验证所建模型的正确性,得出分数阶电感电容的阶数会影响闭环控制器的设计和分数阶模型能更加精确地描述Flyback变换器的工作特性。

基于MBD的电子装备研发数字化集成协同环境构建

电子装备的研发是一项复杂且系统化的工程,而现有研发模式下存在多专业协同不足、产品研发周期长、技术状态变更频繁、研发成本高等问题,已无法满足市场需求。针对上述问题,以产品研发流程再造和优化为基础,开展数字化集成协同研发环境构建,系统性探索产品多专业协同、多领域共享的研发管控模式。通过基于模型定义(Model-based Definition,MBD)技术,规范了装备研制过程,实现了电子装备基于xBOM的数字化定义和数字量的传递,以及设计工艺一体化数据管理,从而提高了研发效率,缩短产品研制周期10%以上,设计重用率超过30%,降低了研发成本,提高了装备的性能和可靠性。

对化学教学中“模型认知”的认识与思考

模型认知是高中化学课程标准的核心素养之一。当前在中学化学学科领域内,关于模型及建模的研究主要集中在模型认知视角下的教学研究、建模教学在中学化学中的应用、中学化学复习课中模型的建构与应用研究等三个方面。模型的定义和化学模型的分类能帮助教师和学生更好地认识模型。模型定义的核心表达是为了某种特定的目的,利用简化、抽象、类比等方法,对事物的本质进行表征,将抽象思维外显化。化学认知模型和化学认识模型共同指导化学学科知识的学习,基于模型的教学策略是落实模型认知素养的重要途径之一。

学前儿童动商测评模型构建研究

学前儿童动商测评模型构建研究目前处于初级阶段,还存在很多空白,该研究对丰富我国动商理论成果、拓展学前教育研究领域、推动我国教育测评研究发展都具有重要的理论价值和实践意义。借鉴已有系列基础教育测评模型的研究范式,以适应性行为理论为依据,基于学前儿童动商操作性定义,通过定性与定量分析相结合的方式,确定3~4岁学前儿童动商测评指标体系。通过层次分析法、熵值法、最小二乘法获得指标权重,构建学前儿童动商测评模型。最后,从专家认同和实践应用两个层面验证该模型的有效性、可靠性和可操作性。