闸墙长廊道输水系统侧支孔均匀布置的水力特性

闸墙长廊道输水系统侧支孔出流不均匀是造成闸室水体流动和闸室水面波浪运动的主要原因。为研究侧支孔均匀布置的水力特性分布规律,通过CFD数值模拟方法分析输水方式、水头差和阀门开启时间对侧支孔出流的影响。结果表明,闸室输水过程中,各支孔流量先增大后减小、支孔流量分配的相对差异也先扩大后减小;闸室灌水时,各支孔流量分配呈由上游至下游逐渐增大然后再稍有减小的趋势,支孔最大流量大致分布在侧支孔出水段的后1/3区域;闸室泄水时,各支孔流量分配从上游至下游逐渐增大;闸室输水时间与水头差和阀门开启时间成正比,闸室灌水比泄水的输水时间稍短。     

长江干线重点支流河口航标配布方案

长江干线重点支流河口航标配布缺乏统一配布原则和方法。采用分类研究的方法,根据河口地形及干线航道布置特点,将河口分为沿岸航道(或偏靠河口侧的河心航道)类、干线航道与支流河口间有一定距离类,确定不同类别河口航标配布所使用的航标种类,并分别根据标示支流河口位置、标示干支航道交汇点、标示干线航道与支流航道连接段航道界限与碍航物、提示支流河口信息的总体原则对不同类别的支流河口提出相应的航标配布方案,为类似工程提供参考。     

“中华之星”号高速列车司机室过渡曲面局部空气压力分布研究

“中华之星”号列车端部流线型长度达到5.5m,且采用双拱外形。司机室向车体顶部过渡曲面曲率较大,容易产生流动分离现象,为检验端部流线型外形设计的合理性,采用数值模拟计算和实车试验相结合的方法对其局部表面空气压力分布进行研究。研究结果表明:动力车司机室向车体顶部过渡曲面局部表面未发生流动分离。     

Impact of telecommuting on spatial and temporal patterns of household travel

A spatial and temporal analysis of travel diary data collected during the State of California Telecommuting Pilot Project is performed to determine the impacts of telecommuting on household travel behavior. The analysis is based on geocoded trip data where missing trips and trip attributes have been augmented to the extent possible. The results confirm the earlier finding that the Pilot Project telecommuters substantially reduced travel; on telecommuting days, the telecommuters made virtually no commute trips, reduced peak-period trips by 60%, total distance traveled by 75%, and freeway miles by 90%. The spatial analysis of the trip records has shown that the telecommuters chose non-work destinations that are closer to home; they exhibited contracted action spaces after the introduction of telecommuting. Importantly, this contraction took place on both telecommuting days and commuting days. The telecommuters distributed their trips, over the day and avoided peak-period travel on telecommuting days. Non-work trips, however, show similar patterns of temporal distribution on telecommuting days and commuting days. Non-work trips continued to be made during the lunch period and late afternoon and evening hours.     

GIS-aided prediction for sea-ice distribution

A method of applying the geographic information system (GIS) to predict sea-ice distribution is proposed. The prediction computations are performed using the distributed mass/discrete floe (DMDF) model. The GIS is used to prepare the initial data for the DMDF model, and to display the simulation results together with a digital map and observational data for evaluation and further use. Two areas in the Arctic Ocean were selected to test the computations in this study. The results of the case studies show that this method can help with (1) free-area and free-scale prediction fitting for various purposes, (2) a high-resolution output to provide more detailed data, and (3) a reasonable combination of different data sets to make the best use of the information obtained. The results also suggest that the DMDF model is a good simulation of the ice motion not only for large-scale but also for local-scale predictions. Received: March 19, 2002 / Accepted: June 20, 2002 Acknowledgments. This study was financially supported by the Japan Science and Technology Corporation. The SSM/I sea-ice data were obtained from the EOSDIS NSIDC Distributed Active Archive Center (NSIDC DAAC), University of Colorado at Boulder. The authors thank the persons concerned. Address correspondence to: H. Yamaguchi (yama@fluidlab.naoe.t.u-tokyo.ac.jp)     

水泥砼疲劳试验数据中含非破坏数据的处理方法

水泥砼疲劳试验数据中常含有非破坏数据 ,人们在处理数据时常将其剔除 ,笔者认为这是不合理的 .据此 ,笔者应用数据统计方法 ,假定数据服从正态 (或对数正态 )分布 ,从理论上推导出了处理这类问题的计算方法 ,并给出了具体算例 .分析发现 ,应用该方法处理疲劳试验数据中含非破坏数据是可行的     

船舶机舱集中监测系统新方法的研究

提出一种基于计算机模式识别技术的船舶机舱集中监测系统新方法，并对其实现方式作了初步探索。这种新方法直接采集机旁一次仪表的图像信息，经分析处理后得到对应数值，从而省却现行结构中的传感器、变送器和屏蔽线缆等，使系统结构大大简化。     

使用F8型空气制动机的快运货车制动系统仿真分析

基于F8型空气制动机的原理和空气流动理论，建立了使用F8型空气制动机的列车制动系统模型，开发出计算机仿真程序。通过比较仿真与试验结果的缸、管压力与制动距离，证明程序的正确性。并使用仿真程序对使用F8型空气制动机的快运货物列车进行制动性能分析计算，计算结果显示快运货物列车各种制动性能正常，紧急制动距离符合《中华人民共和国铁路主要技术政策》中的有关规定，能够在规定距离内安全停车。F8型空气制动机可以作为快运货物列车的制动控制系统。     

一种6～8 GHz超宽带天线的设计分析

设计印刷在有限大聚四氟乙烯板上的叶状偶极天线,设计的工作频带是6-8 GHz。应用结合完全匹配层（PML）技术的时域有限差分（FDTD）方法,对天线的阻抗特性和远区辐射场的分布进行了研究。结果表明：在没有任何加载的情况下,与50Ω馈线相连时,在设计的主频带内,其电压驻波比小于1.6,在几个不同频率点的辐射场方向图表现出良好的稳定性。该天线的特性能够满足超宽带的要求,可用于无载波超宽带无线数据通信系统。     

桁架式天线结构动态性能的有限元分析

以有限元理论为基础,运用有限元分析软件对车载桁架式天线系统进行结构动态分析及稳定性分析。模态分析的结果表明天线系统的低阶固有频率较低,不当的使用会导致结构的共振。稳定性分析表明天线结构的失稳属于局部屈曲行为,进一步的非线性屈曲分析表明,屈曲的临界载荷在正常工作载荷外,不影响系统工作。