城市轨道交通财务可持续发展探讨

虽然各城市的财政状况及轨道交通企业体制存在一些差异,但由于城市轨道交通本身的特性,大部分项目都面临着资本金不足、还本付息压力巨大、运营收支无法匹配等问题。从目前我国城市轨道交通财务方面的现状入手,分析其中存在的问题,并从投融资、成本控制、政策扶持等方面提出具体实施建议:减轻轨道交通企业债务成本,采取措施降低运营企业的成本负担,给予轨道交通企业必要的税费优惠政策,建立合理的票价调整机制,实现轨道交通企业收入来源多样化,建立政府购买服务的机制。     

Finite element modeling of hydrostatic stress distribution in copper dual-damascene interconnects

Hydrostatic stresses of copper dual-damascene interconnects are calculated by a commercial finite element software in this paper. The analytical work is performed to examine the effects of different low-k (k is permittivity) dielectrics, barrier layer and aspect ratio of via on hydrostatic stress distribution in the copper interconnects. The results of calculation indicate that the hydrostatic stresses are highly non-uniform throughout the copper interconnects and the highest tensile hydrostatic stress exists on the top interface of lower level interconnect near via. Both the high coefficient of thermal expansion and the low elastic modulus of the low-k dielectrics and barrier layer can decrease the highest hydrostatic stress on the top interface, which can improve the reliability of the copper interconnects.     

郑和宝船的长宽尺寸论证 --兼复张箭先生

1999年第1期的<海交史研究>登我的一篇文章〈中国与葡萄牙的航海和造船技术交流〉,张箭先生读后提出不少问题,发表于<海交史研究>2000年第2期,题目为〈关于中世纪中西航海史的若干问题〉.我很不愿意放下手头正在进行的工作来写这篇文章,因为我想做和能做的事情还很多,而时间又比较少.可是不说也不行,尽管有些问题我认为过去几年学术界讨论是已经比较明朗了的问题.     

Safety modeling for two‐way left‐turn lanes and a procedure to identify two‐way left‐turn lane segments with safety concerns

In the past, two‐way left‐turn lane (TWLTL) median treatments have been frequently used in Florida to inexpensively improve traffic and safety performances. In order to identify factors that may have significant impacts on safety operations in TWLTL sections and to identify TWLTL locations that present existing and future safety concerns, a research project was carried out and results are summarized in the paper. In the research, a three‐year crash history database with crashes and section characteristics from a total of 1688 TWLTL sections all over Florida was developed and used. A negative binomial regression model was developed to determine the statistical relationship between the number of crashes per mile per year and several variables such as traffic volume, access density, posted speed, and number of lanes. In regard to the methodology, in order to identify locations with safety concerns, several steps are needed: development of real crash data distribution, determination of statistical distribution models that better represent the actual crash data, determination of percentile values for the average number of crashes, estimation of crash rates for sections with the same characteristics, estimation of critical values for the variables corresponding to the percentile values for average number of crashes, calculation of tables of critical average annual daily traffic values, and generation of a list of TWLTL locations with critical safety concerns. Results presented in the paper have been used in real applications. Copyright © 2012 John Wiley & Sons, Ltd.     

国家标准、行业标准的制定程序

制定标准、行业标准只有严格按照一定程序才能保证标准的质量和有效实施。这一程度依次为计划阶段、准备阶段、起草阶段、审查阶段和报批阶段。     

适应高爆发压力的高性能柴油机气缸盖设计

以某4DC发动机的基本参数为输入条件,对气缸盖进行了概念定义及详细设计,着重介绍了气道、油道、喷油器、配气机构和冷却水套的定义过程以及为保证气缸盖刚度和强度采取的技术措施,提出了气缸盖"W"型水套的概念。对该气缸盖设进行的设计评估结果表明,其使用性能、冷却性能、结构可靠性、铸造性能均满足设计要求,且气缸盖质量仅为30 kg,实现了气缸盖设计轻量化目标。     

浅析《现代外语》中两篇外语教学的实验报告

章通过对《现代外语》中两篇外语教学实验报告的分析，阐述丁在语言实验研究过程中，处理好各种变量的关系、总体样本与抽样之间的关系以及无关变量的控制对实验报告信度有很大的影响。     

基于OpenGL选择机制的模型变换组件的实现

为了便于用鼠标控制模型的平移、缩放和旋转变换,构建了三种模型变换组件,将3D场景中对模型的多种变换命令用几何图元进行可视化表示,并利用OpenGL选择机制,实现了各种模型变换命令的快速鼠标选择与切换,能够使用鼠标灵活地进行多种模型变换.这些组件已经应用到所开发的虚拟环境及仿真软件中,方便了用户操作,精简了用户界面.     

弧焊机器人工作站焊接质量影响因素分析及改进措施

地板纵梁总成是驾驶室的主要承载件,是整车的关键部件之一,其焊接质量关系到整车的安全性、可靠性。本文分析了重卡驾驶室地板左/右纵梁总成弧焊机器人工作站焊接质量影响因素,并提出了行之有效的改进措施。