可结合性

This property of composition is called associativity.

复合的这个性质叫做可结合性。

If we consider the integers with ordinary multiplication we have closure , associativity, and identity element.

如果我们考虑整数集且用通常的乘法，我们有封闭性，可结合性，和一个单位元。

A secure system consists of many sub——systems, even though every one of those sub-systems satisfies a certain security property, the composed system may not be secure, i.e. the composition maybe not satisfy the security property. It does mean that the security property should be composable.

安全系统是由许多子系统组成，每一子系统都必须满足一定的安全性质，但这不能保证由这些子系统组合而成的系统也是安全的，即组合的系统不一定也满足给定的安全性质，所以要求系统的安全性质满足可结合性。

This article use the improved integral inequalities with the deviate variable and some skills of inequalities as well as related knowledge about second-order differential equation,to obtain the following results: the classification of limit point case or limit circle case and boundedness for second order differential or difference equation with deviative variable,discussed the classification for certain n-order differential equations,Criteria for the classification of second order differential equation with deviative variable.

本文利用推广的具有偏差变元的积分不等式，结合不等式的一些技巧以及常微分方程的相关知识对一类二阶具有偏差变元的微分方程及一类二阶差分方程极限圆型的分类问题作了相关的研究工作，并且讨论了一类n阶具有偏差变元的常微分方程解的平方可积性与有界性和一类二阶非线性具有偏差变元的微分方程解的有界性。

In section one, we introduce some background of the topic, in section two we review some basic and recent results about the structure and hierarchies of the computably enumerable degrees which are closely related to our topic- the algebraic structure of the plus cupping Turing degrees, in section three, we outline the basic principles of the priority tree argument, one of the main frameworks and tools of theorem proving in computability theory, and in section four, we prove a new result concerning the algebraic structure of the plus cupping Turing degrees that there exist two computably enumerable degrees a, b such that a, b ? PC, and the join a V b of a and b is high.

度结合为0′。本篇论文分为4个部分：第一部分介绍了这个领域的一些背景知识；第二部分主要回顾了前人在研究可计算枚举度的结构和层谱时所取得的一些基本和最新结果，这些结果与我们的主题—加杯图灵度的代数结构密切相关；在第三部分中，我们概要的描述了优先树方法的基本原理，此方法是可计算性理论中定理证明的一个重要框架和工具；第四部分证明了一个加杯图灵度代数结构的新结果：存在两个可计算枚举度a，b，满足a，b∈PC，而且a和b的并a∨b是一个高度。

The development tendency of mechanical, electrical and hydraulic technology is integrated in this dissertation. To meet the demands of fast speed, reliability and stability, a kind of forging hydraulic press system with either high proportion of performance-price or good reliability and maintainability is developed.

本文从锻造液压机的快速性、平稳性与可靠性要求出发，结合机、电、液技术的最新发展趋势，研制了一种既具有高性能价格比，又具有高可靠性和可维护性的锻造液压机系统，并对其进行了理论与实践研究。

In this paper, by using conditional cnormalityof some special subgroups(such as minimal subgroups, maximal subgroups, Sylowsubgroups, maximal subgroups of Sylow subgroups)of G, we obtain some sufficient or necessaryconditions for a finite group to be solvable, supersolvable, nilpotent. Some previouslyknown results are generalized.

本文结合有限群的某些特殊子群(如，极小子群，极大子群，Sylow子群，Sylow子群的极大子群)的条件c-正规性来研究有限群的可解性，超可解性，幂零性，得到了有限群可解，超可解，幂零的若干充分和充要条件，推广了有限群的一些结果。

It will expose the design problem of maintainability of civil airplane to the early stage of design. This paper discusses the composing of the virtual maintenance environment, builds non-immersion virtual maintenance environment of undercarriage, and establishes a part library management system. The characteristic of maintainability models and maintainability analysis based on virtual technique is researched to give the maintainability frame model of civil airplane virtual maintainability analysis. All levels of maintenance time model and maintenance man-hour model are established. Analog-Huffman code is proposed to optimize space partition method in traditional collision detection arithmetic."Maintenance therblig"is brought into the broken down of maintenance tasks, and the new maintenance tasks broken down method is proposed. The demands of human measure, position, and equipment layout in human engineering are discussed, and the verification methods of human measure, position and equipment layout in virtual maintenance are given. Basic principle and verification procedure of maintainability virtual verification is developed primarily, and the reachablity, the visibility, and posture-comfortability are verified.

本文论述了虚拟维修环境的组成，构建了某型飞机主起落架非沉浸式虚拟维修环境，建立了维修对象的零件库管理系统；研究了基于虚拟技术的维修性模型特点及维修性分析流程，给出了基于虚拟技术的民机维修性分析框架模型，并结合传统维修性模型，建立了各级维修时间模型和维修工时模型；提出类HUFFMAN编码，结合人因工程的要求，优化了传统碰撞检测算法中的空间分割法，使之适用于柔体；在维修性分解中引入"维修动素"，给出了与CATIA、DELMIA等应用软件结合紧密的维修任务分解方法；论述了人因工程中对人体尺寸、姿势、设备布局的要求，给出了虚拟维修中人体尺寸、姿势分析、民机内设备布局的验证方法；初步制订了维修性虚拟验证的基本原则和验证程序，并结合具体实例对可达性、可视性、干涉性以及人体姿态舒适性进行了验证，较清晰、真实地反映了维修人员的维修状态。

S scheme which is a combination of Mambo et al.\'s proxy signature scheme and Zheng\'s signcryption scheme. Our analysis demonstrates that their scheme cannot guarantee strong unforgeability, strong identifiability, non-repudiation, and prevention of misuse.

他们的体制本质上是Mambo等人的代理签名体制和Zheng的签密体制的结合，安全性分析表明他们的体制不能满足强不可伪造性、强可识别性、不可抵赖性，也不能防止滥用。

Based on the selection of similar structure, a method for predicting the rock drillability of wildcat well is proposed.

该方法首先应用已钻相似构造井的地震资料、测井资料以及岩心测试资料，建立岩石可钻性钻前预测遗传神经网络模型，然后将神经网络与遗传算法有机结合起来，以神经网络理论为基础，利用遗传算法优化隐含层神经元个数和网络连接权值，最后利用野猫井的地震资料进行岩石可钻性钻前预测。

Fancy gold-plated dangling earrings with facetted White Opal crystals.

花式镀金悬垂耳环与facetted白欧泊水晶。

This essay chooses the study aim from biology teachers in middle school in Shi Jiazhuang which tells us that most of the middle school biology teachers in Shi Jiazhuang have the"burnout", lower successfulness, individualize.

本文选取石家庄市初中生物教师作为研究对象，运用问卷调查的方法对石家庄市初中生物教师职业倦怠的现状进行调查，调查结果发现，石家庄市初中生物教师这一群体普遍存在职业倦怠，情感枯竭程度偏高，成就感偏低，去个性化程度最为严重。