大体积承台裂缝控制计算分析与设计措施

针对大体积承台施工的特点,通过对机场2号大桥承台浇筑前裂缝控制计算分析,并采取有效的温度控制措施,达到预期的效果。     

基于断裂理论的大体积混凝土裂缝分析

基于断裂力学理论分析大体积混凝土微裂缝的发展特性,大体积混凝土早期裂缝主要是由温度差引起的,适宜控制温度能有效遏制初期裂缝发展,从而为提高大体积混凝土结构施工期质量并减少结构内部初始微裂纹提供理论基础。研究结果表明施工期减小大体积混凝土内外温差是进一步限制裂纹生成的关键。     

大学英语四六级网考探析

相对传统形式的四、六级考试,网考不但采用了计算机考试,而且考察内容的侧重点也发生了改变,由传统的重读写转变为为重听说。为适应大学英语四六级网考新模式,大学英语教与学也必须做出相应改变。大学英语四六级机考在推行的过程中也应注意多方面的问题,力争让四六级网考在全国早Et推广。     

交通拥挤收费政策的经济影响分析

针对交通拥挤收费政策普遍采用的成本—效益分析(CBA)框架存在的缺陷,首先回顾了拥挤收费的经济学原理。然后从研究方法和研究内容两方面剖析CBA框架存在的问题,指出时间价值计算不严谨及交易成本被忽视等问题将对政策实施效果带来负面影响,并就伦敦和斯德哥尔摩拥挤收费案例社会净收益计算结果的可靠性提出质疑。接着结合各参与方的净收益分析、收费区商业影响及其他产业影响等内容,指出CBA分析框架可扩展的内容。最后提出了改进的经济影响分析框架,为全面评价拥挤收费政策效果提供参考。     

The economic impact of logistics infrastructure: the case of PLAZA – the Zaragoza Logistics Platform

Abstract

The economics literature offers many examples of studies of the economic impact of transportation infrastructure such as highways, ports, and airports; however, little attention has been paid to other types of infrastructure such as logistics platforms. This article is a first assessment of the economic effects of the largest logistics platform in Europe – PLAZA, the Zaragoza Logistics Platform – located in Spain. More precisely, this paper analyzes the economic significance of PLAZA on the economy of the Aragon region where it is located. The methodology is based on the application of input–output analysis to the final demand of logistics platform-based companies in a manner that is similar to well-established studies of the economic impacts of tourism on tourist expenditure. This makes it possible to quantify the various levels of economic effects (direct, indirect, and induced) in terms of jobs, salaries, and wages, turnover, gross operating surplus (GOS), and gross value added (GVA). The conclusions reveal the economic importance PLAZA has for the regional economy of Aragon, representing just over 2% of total GVA and 3% of turnover.     

内流对洪水冲击下管跨临界长度影响研究

为了研究洪水冲击管道时形成的管跨临界长度,分别介绍了洪水作用下管道的动力特性以及内流对管道特性的影响。针对管内流动与管外洪水冲击对于管道的作用,建立了内流、外流共同作用下的管道动力控制方程。结果表明:对于洪水冲击管道的问题,不应仅考虑洪水的作用,也应该考虑内流对于管道的作用;内流流速增大、压强增大、密度减小都将缩短临界长度。考虑内流的管跨临界长度,对设计及现场抢维修都具有借鉴作用。     

An individual information system for visualizing the bus and subway network

The system described in this paper allows the user to visualize the Montreal transportation system. The user is provided with several different maps.

The complete subway network and all regular bus lines have been included. The subway network and the bus lines can be selectively displayed. The most attractive feature of this system is the possibility of obtaining all possible routes between two different places. The input is based on the menu technique.

The system can be easily adapted to other large urban transportation systems.     

车用预热固体继电器的优化设计

给出优化设计后车用预热固体继电器的主要技术指标,详细介绍该类产品的优化设计方法,重点阐述输入电路增加下拉电阻设计、优化放电电路设计、增加延时电路设计和增加短路失效时切断主回路电路设计等优化设计。     

发动机水温传感器响应时间研究

响应时间是温度传感器的重要指标,特别是在温度变化较快的应用环境以及对温度变化敏感的场合显得格外重要。一般标准要求发动机水温传感器的响应时间为30s以内。随着对汽车节能、环保要求的提高,需要更精确地感知和控制发动机冷却液温度,因此,迫切需要大幅缩短传感器的响应时间。通过改变壳体材料、形状尺寸,改善导热介质材料、注入工艺等方法,可以将响应时间缩短至6s以内。     

基于多元线性回归法估算车辆外部环境温度

通过采用多元线性回归的方法,提出一种基于发动机进气温度、发动机冷却液温度、汽车行驶速度、发动机瞬时喷油量来估算汽车外部环境温度的方法,可适用于一些精度要求不高的场合(如精度要求不超过±2.5℃)。