空气罐控制输液管道水击研究

采用特征线法对瞬时关闭管道终端阀门 ,在安装和不安装空气罐两种状况时 ,管道压力的变化情况进行了数值模拟 ,并分析了空气罐初始容积、空气罐安装位置等参数对管道瞬态水击压力变化的影响 ,结果表明 :在输液管道的适当位置安装容积一定的空气罐能较好地控制水击的产生     

An Exploration of the Relationship between Timing and Duration of Maintenance Activities

The timing and duration of an activity episode are two important temporal aspects of activity-travel behavior. Understanding the causal relationship between these two variables would be useful in the development of activity-based travel demand modeling systems. This paper investigates the relationship between these two variables by considering two different causal structures – one structure in which time-of-day choice is determined first and influences duration and a second structure in which activity duration is determined first and affects time-of-day choice. These two structures are estimated within a discrete-continuous simultaneous equations framework employing a full-information maximum likelihood methodology that allows error covariance. The estimation is performed separately for commuter and non-commuter samples drawn from a 1996 household travel survey data set from the Tampa Bay area in Florida. The results of the model estimation effort show that the causal structure in which activity duration precedes or affects activity timing (time of day choice) performs better for the non-commuter sample. For the commuter sample, the findings were less conclusive with both causal structures offering equally good statistical measures of fit. In addition, for the commuter sample, all error correlations were found to be zero. These two findings suggest that time of day choice and activity episode duration are only loosely related for the commuter sample, possibly due to the relatively non-discretionary and inflexible work activity and travel.     

成都市城区水域开发工程设计概况

今文介绍了成都市府南河上蓄水、泄洪为一体的水工设施——充水式橡胶坝枢纽工程，并确定了坝址、坝高及坝前所形成的有效水面面积，还讨论了实现城区西侧勾通府南河的设想。     

Hub location with flow economies of scale

A characteristic feature of hub and spoke networks is the bundling of flows on the interhub links. This agglomeration of flows leads to reduced travel costs across the interhub links. Current models of hub location do not adequately model the scale economies of flow that accrue due to the agglomeration of flows. This paper shows that current hub location models, by assuming flow-independent costs, not only miscalculate total network cost, but may also erroneously select optimal hub locations and allocations. The model presented in this paper more explicitly models the scale economies that are generated on the interhub links and in doing so provides a more reliable model representation of the reality of hub and spoke networks.     

汽车操纵动力学十八自由度模型仿真研究

本文介绍了根据多刚体动力学中的凯恩方法建立的一般两轴汽车的十八自由度数学模型。     

汽车轮胎结构非线性有限元分析

本文综述了轮胎力学的发展历史与现状，阐明了轮胎结构分析的几各主要方法、研究内容及其优缺点，并重点介绍了在子午三维非线性有限元结构分析方面的工作，包括轮胎的充气，竖直加载、稳态滚动、滚动阻力及温度场分析，给出了相应的算例。由于采用一些新的方法和技术，考虑了更真实的轮胎材料模型，结构和载荷，使得分析更为有效、精确，分析结果可作为轮胎的设计，试验与改进的依据。     

胶焊,点焊和胶接接头应力分布的比较分析

采用三维弹塑性有限元数值分析方法，比较了分析了胶焊，点焊和胶接接头的应力分布情况，结果表明，胶焊接头与胶接接头的应力分布特征值基本相同，仅在焊点区内略有区别，胶焊接头中的胶粘剂有效地降低了点焊接头中焊点的应力，消除了其焊点过级处的应力集中，所得应力分布可合理解释已有强度试验结果。     

高压喷射注浆技术在基坑管涌处理中的运用

高压喷射注浆法是在注浆法的基础上，应用高压喷射技术而发展起来的一项新的地基加固方法。本文针对武汉市泰合广场基坑在开挖过程中形成管涌或流上而致使附近建筑物遭受严重破坏的问题，采用高压喷射注浆法施工工艺方法，杜绝了基坑壁管涌或流立现象，使基坑开挖和基础施工得以安全进行。     

深圳市“5.24”暴雨洪水灾后的反思

1998年5月24日，深圳市暴雨成灾，经济损失很大。本文总结和分析了暴雨洪水的特性及其成灾的原因，提出防洪减灾的措施和建议。     

谈柴油机废气涡轮增压器的正确使用及故障分析

简要介绍了柴油机废气涡轮增压器的基本工作原理。阐述了对柴油机增压器的正确使用、维护以及常见故障分析。