某发动机连杆强度计算分析

为分析某增压发动机连杆组受力情况和疲劳强度,依托发动机AVL综合试验台架以及专用分析仪器,以实际测量发动机不同工况下爆发压力变化曲线作为输入,对连杆体进行有限元计算分析。研究结果表明:通过各关键工况以及爆发载荷耦合计算,连杆体和连杆盖应力分布结果与实际吻合;连杆各个危险部位在各工况下均满足运行条件,连杆在运行中连杆盖和连杆体没有发生脱离现象,满足运行工况要求。     

基于ANSYS的矿用车结构有限元分析

针对矿用卡车在ANSYS中首先建立起有限元模型,然后对其工作过程中常遇到的工况进行分析,确定出危险的工况进行结构有限元分析,并得到整个卡车在各工矿下应力值及大应力的危险部位,为矿用卡车的进一步改进提供了强有利的依据。     

轮胎集装箱式龙门起重机结构强度分析

随着计算机技术和数值分析方法的发展有限元方法在机械结构分析中得到广泛应用,取得了令人瞩目的成果,已成为现代机械产品设计的一个重要工具。运用有限元软件Nastran对某公司提供的一轮胎集装葙式龙门起重机的结构进行了强度分析。首先利用Patran建立有限元模型。通过Nastran的后处理得到静栽、跨中纵移、跨中横移、端部纵移、端部横移五种工况下的应力云图和位移分布图,根据最危险工况下应力和位移分布情况,得出该龙门起重机满足结构强度和刚度要求的结论。本论文旨在运用有限元思想对龙门起重机的结构进行强度分析。     

基于ANSYS对低温运输半挂车的内筒支撑管进行应力分析

半挂车在运行过程中,筒体容易上下振动和左右摆动。支撑管是支撑和固定内筒的核心结构。利用ANSYS软件对支撑管建立有限元模型,然后仿真三种典型工况,即半挂车静止、急刹车、急转弯情况下支撑管的受载情况。通过求解,得出支撑管上的等效应力分布状况及危险位置,为工程实践提供指导意义。     

考虑积雪漂移效应的单层柱面网壳结构承载能力研究

雪荷载随机分布对空间结构的稳定性和承载能力影响较大,风致积雪漂移和积雪融冻造成过重大工程事故。为研究雪荷载随机分布对柱面网壳结构承载能力的影响,利用有限元软件ANSYS对某30m跨单层柱面网壳结构进行了数值分析,通过研究雪荷载半跨均布渐增随机分布、满跨不等值均匀随机分布、半跨三角形不等值随机分布和半跨节点雪荷载随机分布及组合等工况,总结了450种雪荷载随机分布工况下结构变形发展规律和最不利雪荷载工况。结果表明,当风致积雪漂移产生的附加雪荷载分布于靠近柱面网壳底部1/4跨区域,或除雪不及时造成单侧屋盖积雪融化或除雪不彻底造成的单侧屋盖无雪,都将使结构变形超过最大设计值,属于更不利的雪荷载布置工况。     

浙江省诸暨市农村山区不稳定斜坡危险性分析

浙江省诸暨市农村山区曾发生大量的地质灾害,同时造成了巨大的经济损失,为了确保农村人口的安全和减少经济损失,通过对全市不稳定斜坡调查和统计,基本查明诸暨市不稳定斜坡的分布与发育特征,进行不稳定斜坡危险程度分析和危险程度评价。建立应急体系,提出防治措施建议,为政府组织开展群测群防、监测预警、避让搬迁、勘查治理和村镇规划,最大限度地避免和减少损失。     

基于ADAMS/CAR的爆胎时整车运动性能的仿真研究

针对汽车行驶过程中时常会发生爆胎这一危险工况,利用ADAMS/CAR软件建立了某轿车的整车动力学近似模型,通过改变爆胎时车轮的位置和行驶速度等条件,进行整车运动性能的仿真试验,仿真结果表明运用此种方法来研究车辆行驶爆胎时的操纵稳定性是确实可行的。     

三维VOF模型在云南某台阶式溢洪道水流特性分析中的应用研究

台阶式消能段可以有效迫使水流发生旋滚,有效消耗水流能量,是水电站溢洪道目前最常用的消能措施之一。为进一步了解台阶布置形式对水流流态分布影响,提高溢洪道消能效率,同时研究实例工程,即云南澜沧江上游某大型水电站溢洪道的最佳台阶布置形态,本文将三维VOF方法引用至水利工程水流形态计算研究中,分析了四种体型工况在设计工况和校核工况下的水流特性。结合整体流态、流速、脉动压力分布和消能效率对比,本文最终推荐体型方案三作为推荐方案。     

凝汽器进出口水室强度分析

本文对凝汽器进出口水室进行实体建模,使用ANSYS有限元软件对水室在设计工况下的应力进行强度计算,通过分析水室在设计工况下的应力分布情况,对凝汽器进出口水室提出改进措施,为水室的优化设计提供参考。     

建筑施工企业在施工中对关键危险因素的控制措施

施工安全事故是人们所不希望发生的一种事件。但在建筑施工过程中却隐藏着许多可能导致事故发生的危险因素。准确无误地找出导致事故发生的危险因素（导致事故发生的原因）,要先了解与控制可能导致事故发生的危险因素是必要且关键的,对保证建筑工程的施工安全（事故不发生）是极其重要的。进行危险因素预防控制的目的,在于保证避免或减少安全事故,使之与安全计划目标相一致,最终实现建筑工程项目施工的各项预期目标。本文结合茂名华厦投资置业有限公司1#、2#商品房的建设,对关键危险因素的控制措施进行分析。     

根平方平均的最优凸组合不等式

本文得到最大值α和最小值β,使得对所有的a,b>0,a≠b双向不等式αC(a,b)+(1-α)A(a,b)相似文献   

Projects as communicating systems: Creating a culture of innovation and performance

Although often downplayed and instrumental, there is evidence that communication in projects is essential in achieving value creation. Our main interest in this paper is on temporary continuity, a situation where the temporary becomes a permanent condition in social systems. The question that we have address is: What characterizes project communication in a situation with temporary continuity?We argue for the need to transform communication processes into communication capabilities. In a situation with temporary continuity, there is a need to connect to a large number of value-creating processes, and communicating capabilities need to be a part of a communication system, where the aim is to bind together value-creating processes and communication capabilities. We construct a viable system consisting of five sub-systems. To become a viable system, projects in the form of temporary continuity, must handle the potential conflict between a culture of performance and a culture of innovation. This involves developing social mechanisms for coordination and interaction, with a focus on developing communication capabilities, in parallel with focusing on all of the five value-creation processes.     

1961-2013年华北晋冀山地和黄土高原区树木生长季变化趋势

为预测气候变化下的森林植被生长季特征变化,本文基于华北晋冀山地区和黄土高原区两个区域44个气象站1961-2013年日气温数据,分析了华北湿润半湿润地区两个区域树木生长季特征的变化趋势。定义生长季开始时间为当连续5天日平均温度≥5℃,选第5天作为生长季开始时间;生长季结束时间为当秋季连续5天日平均温度<5℃,选第5天作为生长季结束时间。结果表明:①1961-2013年晋冀山地区和黄土高原区以及两个区域整体树木生长季开始时间呈现显著提前趋势,变化速率分别为-1.7d/10a、-2.1d/10a和-1.9d/10a;树木生长季结束时间均呈现显著延后趋势（p<0.05）,变化速率分别为0.9d/10a、1.1d/10a和1.0d/10a;研究区树木生长季长度表现出明显的延长趋势,晋冀山地区和黄土高原区以及两个区域整体的树木生长季长度时间变化速率分别为2.6d/10a、3.2d/10a和2.9d/10a,树木生长季长度分别延长13.3d、16.4d和14.8d;②1961-2013年,海拔对树木生长季指标的影响,除了对晋冀山地区的树木生长季开始影响不大以外,对于两个研究区的其他树木生长季指标均有显著影响;研究区树木生长季指标（生长季开始时间,结束时间和生长季长度）与春季和秋季气温都显著相关;③1961-2013年,树木生长季开始时间变化趋势在整个研究区空间上大部分呈提前趋势,树木生长季结束时间大部分呈延后趋势和树木生长季长度的变化趋势在空间上则大部分呈延长趋势。     

爱就是教育

教师必须加强自身修养,培养师爱的观念,因为爱是一种意识,是一种信任,是一种良心,是一种积累,是一种力量。爱就是一种教育,每一个教师要把对学生的热爱、尊重、理解和期待,融合在整个教学过程中,实现人民教师爱岗敬业、教书育人的价值。     

关于寂寞的自白——《艾格妮丝·格雷》

日记是秘密性最强的一种私人文献,可以毫无顾忌地真诚面对自己的灵魂,真正的日记作者,内心深处都隐藏着一种挥之不去的、强烈的孤寂感。安妮·勃朗特根据日记撰写的《艾格妮丝·格雷》叙述的是一个家庭女教师的故事,实际上是家庭女教师寂寞、孤独的自白,这部自白既是私人的,也是集体的,是19世纪英国社会一个特殊知识阶层痛苦、压抑的精神自白。     

Website usage metrics: A re-assessment of session data

Metrics derived from user visits or sessions provide a means of evaluating Websites and an important insight into online information seeking behaviour, the most important of them being the duration of sessions and the number of pages viewed in a session, a possible busyness indicator. However, the identification of session (termed often ‘sessionization’) is fraught with difficulty in that there is no way of determining from a transactional log file that a user has ended their session. No one logs out. Instead a session delimiter has to be applied and this is typically done on the basis of a standard period of inactivity. To date researchers have discussed the issue of a time out delimiter in terms of a single value and if a page view time exceeds the cut-off value the session is deemed to have ended. This approach assumes that page view time is a single distribution and that the cut-off value is one point on that distribution. The authors however argue that page time distribution is composed of a number of quite separate view time distributions because of the marked differences in view times between pages (abstract, contents page, full text). This implies that a number of timeout delimiters should be applied. Employing data from a study of the OhioLINK digital journal library, the authors demonstrate how the setting of a time out delimiter impacts on the estimate of page view time and the number of estimated session. Furthermore, they also show how a number of timeout delimiters might apply and they argue that this gives a better and more robust estimate of the number of sessions, session time and page view time compared to an application of a single timeout delimiter.     

Performance analysis of distributed information retrieval architectures using an improved network simulation model

The increasing number of documents that have to be indexed in different environments, particularly on the Web, and the lack of scalability of a single centralised index lead to the use of distributed information retrieval systems to effectively search for and locate the required information. In this study, we present several improvements over the two main bottlenecks in a distributed information retrieval system (the network and the brokers). We extend a simulation network model in order to represent a switched network. The new simulation model is validated by comparing the estimated response times with those obtained using a real system. We show that the use of a switched network reduces the saturation of the interconnection network, especially in a replicated system, and some improvements may be achieved using multicast messages and faster connections with the brokers. We also demonstrate that reducing the partial results sets will improve the response time of a distributed system by 53%, with a negligible probability of changing the system’s precision and recall values. Finally, we present a simple hierarchical distributed broker model that will reduce the response times for a distributed system by 55%.     

Location extraction from tweets

Five hundred million tweets are posted daily, making Twitter a major social media platform from which topical information on events can be extracted. These events are represented by three main dimensions: time, location and entity-related information. The focus of this paper is location, which is an essential dimension for geo-spatial applications, either when helping rescue operations during a disaster or when used for contextual recommendations. While the first type of application needs high recall, the second is more precision-oriented. This paper studies the recall/precision trade-off, combining different methods to extract locations. In the context of short posts, applying tools that have been developed for natural language is not sufficient given the nature of tweets which are generally too short to be linguistically correct. Also bearing in mind the high number of posts that need to be handled, we hypothesize that predicting whether a post contains a location or not could make the location extractors more focused and thus more effective. We introduce a model to predict whether a tweet contains a location or not and show that location prediction is a useful pre-processing step for location extraction. We define a number of new tweet features and we conduct an intensive evaluation. Our findings are that (1) combining existing location extraction tools is effective for precision-oriented or recall-oriented results, (2) enriching tweet representation is effective for predicting whether a tweet contains a location or not, (3) words appearing in a geography gazetteer and the occurrence of a preposition just before a proper noun are the two most important features for predicting the occurrence of a location in tweets, and (4) the accuracy of location extraction improves when it is possible to predict that there is a location in a tweet.     

Enhancing children’s activity in browsing/reading together by the installation of the BrowsReader in the children’s room of a library

Reading together draws much attention as a societal concern for children not only to yield emotional reaction but also to gradually advance intellectual thinking. We here aim to build a new environment, in which children’s browsing and reading of picture books together with families and/or friends is steadily enhanced, by installing the BrowsReader in the children’s room of a public library or a kindergarten. The original BrowsReader was a system to assist children in finding and reading picture books. The children, by gathering around the BrowsReader, can browse picture books and then choose and read a book by flipping pages on it. After reproducing each printed, digitized or web picture book as a surrogate picture book consisting of the front-cover image followed by the page images, we first introduce two basic notions: (i) an abstracted bookshelf, which presents the front-cover images of the surrogate picture books in the form where all are linearly arranged, with some of the images bundled in places, and (ii) a unified view, which presents each page of any surrogate picture book in a form that seems like a printed picture book’s page. We then specify, based on these notions, the improved version of the BrowsReader which can be installed in each children’s room so that children together with families and/or friends can easily browse a large number of surrogate picture books as if they are browsing in the physical bookshelves of the children’s room, and can read a wide variety of surrogate picture books as if they are reading ordinary printed picture books on a table. The improvement was carried out in a step by step process based on feedback and results from case studies, and its effects were clarified by seeing whether, in a new environment, the children’s activity in browsing/reading together were steadily enhanced when using the BrowsReader.     

新时期粮食安全观与粮食供给侧改革

粮食安全是事关国家发展与稳定、独立与自主的全局性重大战略问题。我国的粮食安全理念和体系脱胎于计划经济时期,在当前的国内外形势中面临一定挑战。面对新的发展阶段,迫切需要对传统的粮食安全观进行改革,树立新时期粮食安全观,用于指导和助推粮食供给侧改革。文章尝试汇总当前阶段我国粮食供给侧和需求侧的主要形势和面临的问题,阐明当前供给侧改革是树立新时期粮食安全观的重要机遇,应该从理顺政府和市场关系、树立全球视野和双底线思维以及倡导健康与绿色生活方式等方面着眼,为我国粮食安全问题的出路提供科学合理的视角和解决方案。