现代予力砼结构设计方法的变革

阐述了现代予力砼概念的演变过程并与传统预应力砼概念及设计方法进行分析比较，同时介绍了两种传力体系一予力结构主动传力体系和普筋结构被动承力系统。将予力结构离散为两个结构以建立各自分析计算模型，提出索梁分载法，并列出了设计计算过程和方法。最后提出用配套测力传感器采进行预应力施工验算和控制。     

浅谈钢筋混凝土结构裂缝成因及防治

钢筋砼结构上产生的裂缝,常见于非预应力受弯、受拉等构件中,以及预应力构件的某些部位。对于各类裂缝,必须先查明其性质和产生的原因,进而确定具体的维修方法。钢筋砼结构裂缝根据其产生的原因不同可分为荷载裂缝、温度裂缝、腐蚀裂缝、沉降裂缝等。一、各种裂缝产生原因1)荷载裂缝:结构在荷载作用下变形过大而产生的裂缝。一般多出现在构件的受拉区域、受剪区域或振动严重等部位。产生的主因是结构设计、施工错误、承载能力不足、地基不均匀沉降。钢筋砼结构是由砼和钢筋共同承担极限状态的承载力,需根据地基情况,静、动荷载,环境因素、结…     

混凝土结构裂纹成因分析

从荷载引起的裂缝、砼收缩引起的裂缝、温度变化引起的裂缝、基础不均匀沉降引起的裂缝、砼中钢筋锈蚀引起的裂缝、寒冷地区由冻胀引起的裂缝、砼原材料质量引起的裂缝、施工工艺引起的裂缝等八个方面重点讨论混凝土结构裂纹产生的原因并提出相应地解决措施。     

大体积砼的施工技术与管理

大体积砼结构的截面尺寸较大,由外荷载引起裂缝的可能性很小,但水泥在水化反应中释放的水化热所产生的温度变化和砼收缩的共同作用,会产生较大的温度应力和收缩应力,将成为大体积砼结构出现裂缝的主要因素。为此,现结合实际工作经验,对防治建筑大体积砼裂缝的施工问题进行探讨,并分析了裂缝的成因,最后提出了一些主要管理措施。     

浅谈大体积砼温度裂缝控制措施

在现代工业与民用建筑中，超长、超厚的大体积砼基础已屡见不鲜，但其裂缝的产生时有发生。如何控制大体积砼裂缝的产生，是一项国际性的技术问题。根据现有的理论和实践经验，在实际工程中，也可以控制和减少大体积砼裂缝的发生。     

大体积砼的裂缝控制

钢筋砼是建筑中广泛应用的主要材料,特别是随着国民经济的发展,高层建筑大体积砼基础的应用日益广泛,大体积砼的裂缝控制问题成为当前的一个重要课题。钢筋砼结构的裂缝是不可避免的,但其有害程度却是可以控制的。大体积砼因比表面积较小,水化热散发困难,导致内外温差大,易引起砼出现裂缝,文章主要讨论大体积砼裂缝产生的原因,以及通过设计、施工、材料等方面综合技术措施将裂缝控制在无害范围内。     

大体积砼裂缝成因与防治的探讨

大体积砼裂缝后会加速砼碳化和钢筋锈蚀,并产生恶性循环,严重破坏砼结构的安全性,所以裂缝控制更为重要。     

小议大体积砼的施工技术与管理措施

大体积砼结构的截面尺寸较大，由外荷栽引起裂缝的可能性很小，但水泥在水化反应中释放的水化热所产生的温度变化和砼收缩的共同作用，会产生较大的温度应力和收缩应力，将成为大体积砼结构出现裂缝的主要因素。为此，结合实际工作经验，对防治建筑大体积砼裂缝的施工问题进行探讨，并分析了裂缝的成因，最后提出了一些主要管理措施。     

对建筑工程大体积混凝土施工技术的探讨

随着建筑施工技术飞速发展,砼大体积施工得到了广泛应用,大体积砼施工过程控制不好,结构就有可能产生裂缝,直接威胁到建筑结构的安全性、耐久性。因此,必须采取有效的大体积砼裂缝控制措施,防止结构出现裂缝。     

混凝土桥梁裂缝成因综述

一、荷载引起的裂缝混凝土桥梁在常规静、动荷载及次应力下产生的裂缝称荷载裂缝，归纳起来主要有直接应力裂缝、次应力裂缝两种。直接应力裂缝是指外荷载引起的直接应力产生的裂缝。次应力裂缝是指由外荷载引起的次生应力产生裂缝。实际工程中，次应力裂缝是产生荷载裂缝的最常见原因。次应力裂缝多属张拉、劈裂、剪切性质。次应力裂缝也是由荷载引起，仅是按常规一般不计算，但随着现代计算手段的不断完善，次应力裂缝也是可以做到合理验算的。     

旧水泥混凝土路面沥青加铺层疲劳断裂分析

在道路的使用过程中,沥青加铺层一直经历着交通荷载及温度变化的循环作用,沥青加铺层结构中的裂缝扩展呈现为疲劳断裂特征。沥青加铺层的使用寿命(从开始承载直至破坏所经历的车辆荷载及温度循环次数或作用时间)可分为疲劳裂缝形成寿命和疲劳裂缝扩展寿命两部分。疲劳裂缝形成寿命为由微观缺陷发展到宏观可检裂缝所对应的寿命,目前仍由传统疲劳理论的方法确定;而疲劳裂缝扩展寿命则为由宏观可检裂缝扩展到临界裂缝而发生破坏这段区间的寿命,用疲劳断裂力学方法确定。本文着重对沥青混合料与沥青路面的疲劳断裂进行分析。     

Modeling Item Nonresponse in Questionnaires

The statistical analysis of empirical questionnaire data can be hampered by the fact that not all questions are answered by all individuals. In this paper we propose a simple practical method to deal with such item nonresponse in case of ordinal questionnaire data, where we assume that item nonresponse is caused by an incomplete set of answers between which the individuals are supposed to choose. Our statistical method is based on extending the ordinal regression model with an additional category for nonresponse, and on investigating whether this extended model describes and forecasts the data well. We illustrate our approach for two questions from a questionnaire held amongst a sample of clients of a financial investment company.     

基于随机最优潮流的电压崩溃临界点算法

文章在最优潮流的基础上,融入基于负荷预测的负荷正态分布及负荷静态电压特性,以系统能够承受的最大负荷为目标函数,对由负荷的不确定性导致的变量随机性建立起相应的机会约束规划,采用非线性规划方法对目标函数进行优化,直接求得满足某一概率约束下的系统最大负荷.以 IEEE3机9节点系统为例进行仿真,验证所提算法的有效性,并讨论负荷分布和静态电压特性对电力系统电压崩溃点的影响     

谈混凝土的施工温度与裂缝

在建筑工程施工中,混凝土裂缝普遍存在,而裂缝的解决也是一个较为棘手的问题.混凝土裂缝产生的原因是多方面的,有变形引起的:如收缩、膨胀、沉降等原因引起的裂缝;有外部荷载引起的:混凝土养护不当;还有外添加剂问题等引起的裂缝.文章就混凝土温度裂缝产生的原因,对现场混凝土温度的控制和预防裂缝的措施等方面进行了总结,以为混凝土在建筑工程建设中的应用提供参考.     

主动齿轮裂纹性质及原因分析

本文对实际生产中主动齿轮裂纹进行了宏观、微观的观察,化学分析及金相组织检查,确定了裂纹的性质及形成原因并分析了裂纹对齿轮工作过程的影响,结果表明此裂纹是由于磨削工艺及组织不良引起的磨削裂纹,并对齿轮的使用产生严重影响,一般情况报废使用。     

民用建筑混凝土结构裂缝原因及控制

裂缝是混凝土结构的一种常见病,文章从荷载应力、变形应力和施工三方面分析了混凝土结构裂缝的起因,并有针对性地提出了裂缝预防措施,之后探讨了裂缝的治理措施。     

Price discovery in stock index: an ARDL-ECM approach in Taiwan case

In this study, we examine the lead-lag effect between stock index futures and its spot markets in Taiwan by employing a newly developed econometrics method, ARDL-ECM approach. The advantage of applying such technique is to avoid earlier ambiguous causality testing procedure, and it can provide more clearly representation of a stable unidirectional price discovery process. By verifying intraday data, we find that the futures prices lead spot markets for about 30 min during the year 2004. Moreover, during the presidential election period which caused political turbulent in Taiwan, the function of future market supposed as the dominated role of price discovery becomes futility. Such findings are consistent with the ‘surprising election outcomes’ phenomenon.     

Production scheduling with capacity-constrained transportation activities

This article presents a model for scheduling activities that are required to manufacture a product batch in a multistage process. The activities include setups, operations, and load movements between operations. In this model, setups may or may not require a unit from the preceding operation; each operation must be performed continuously on the batch once it has started, and capacity constraints apply to transportation activities. Within this context, two productivity-related objectives are sought. The primary objective is to minimize the total production time for the batch; the secondary is to minimize the number of load movements.Considering the capacity constraints, a maximum number of units per load is specified for each “vehicle” and one vehicle is dedicated to each transportation activity. The simplicity of the vehicle restriction facilitates the examination of scheduling interactions among activities, and the results of the research into this model may serve as a foundation for treating more general representations of capacity constraints.The model is used to investigate the scheduling implications of capacity-constrained load movements. It brings into focus interactions between these movements and the other activities in the process. After each operation, units must be grouped and moved in the fewest loads that permit the succeeding operation to begin as soon as possible, while observing setup and continuity requirements for this operation. Further, the departure times of loads depend on the availability of units and the vehicle. The formation of loads that must conform with the vehicle's capacity limit affects the times at which the loads are ready for movement, while the scheduling of previous movements from the operation affects the times at which the vehicle is available.A procedure is developed for scheduling activities that have this complex set of interactions. Computational requirements on test problems indicate that practical-sized applications can be handled with this procedure. These applications would be designed to assist in making production planning decisions by experimenting with factors such as vehicle capacity limits and sequencing of operations to determine their effect on production time requirements and numbers of load movements.The article develops a branch-and-bound routine to solve subproblems of scheduling transportation activities. The efficiency of this routine that results from exploiting the specific structure of the subproblems is critical for the success of the overall procedure. While the subproblems can be solved as zero-one mixed-integer programs, this approach is too computationally burdensome for all but the smallest of problems.     

高层住宅楼地下室墙板裂缝原因分析及处理技术

本文结合工程实例,从检测裂缝的特点,外荷载、不均匀沉降、温度变化、混凝土膨胀和收缩等因素,叙述了高层住宅楼地下室墙板裂缝产生的原因,并针对墙板裂缝产生的原因采取了环氧类浆液进行压力注浆处理技术。     

改进的动态反馈负载均衡算法

本文提出了一种改进的动态反馈负载均衡算法,在负载均衡过程中既考虑后台服务器的当前负载,又考虑后台服务器的处理能力,根据每台服务器当前负载比例值的大小合理分配用户请求,进而调整服务器间处理请求的比例,避免服务器超载时依然收到大量的请求,使平均应答时延和吞吐量等获得较好的性能,集群的整体性能得到提高。