锥度化方形截面高层建筑的气动力特性

用高频测力天平技术,对不同锥度比的方形截面高层建筑进行了风洞试验,分析了锥度比、湍流度和风向角对方形截面高层建筑基底弯（扭）矩系数、基底弯（扭）矩谱密度与基底弯（扭）矩间相关性的影响.试验结果表明:锥度化措施能减小方形截面高层建筑基底弯（扭）矩系数幅值25%以上,但不能改变基底气动力随风向角的变化规律;锥度化措施能减小所有折减频率范围内顺风向与扭转向基底弯矩谱,但只能减小低频区域横风向基底弯矩谱和谱峰高度,却增大旋涡脱落频率和高频区横风向基底弯矩谱;随来流湍流度增大,锥度化措施对风荷载的抑制效果减弱;折减频率在0.10到0.15时,锥度化措施能增大横风向基底弯矩与基底扭矩间的相关性.      

基于一种新型磁致负刚度结构的低频隔振系统分析与设计

为提高隔振系统对低频微振动的隔离能力,研究了一种新型三磁体负刚度结构,分析了该结构产生负刚度的原理。将三磁体负刚度结构与隔振系统并联使用,在不影响原隔振系统载荷性能的情况下可降低系统的固有频率。分析了隔振器刚度及磁体间初始间隙对并联系统刚度特性的影响,提出从稳定性和隔振性能两方面来进行低频隔振系统设计。     

轨道车辆直流牵引电机噪声的分析与研究

本文在城市轨道车辆牵引电机噪声测试的基础上,分析了牵引电机噪声的产生机理和频率分布以及对室内外环境的影响和传播途径。最后提出了牵引电机的降噪措施。     

Truss Spar平台总体结构强度分析

在南海百年一遇海况条件下,综合考虑风、浪、流载荷的联合作用,在频域范围内计算平台的纵摇和横摇极值响应以及锚缆的张力。根据不同浪向下的结构应力谱分析确定的设计波参数,基于三维势流理论和Morison公式计算一阶波浪力,采用规范推荐的公式计算风、流载荷。在准静力条件下,根据ABS规范推荐的强度准则,针对精细化的混合有限元结构模型进行总体强度分析。     

快速公交（BRT）智能系统规划与设计研究

快速公交系统作为一种新型的客运模式,以其工程投资少、建设周期短、环境污染小、运输效率高等优点而被认为是解决城市交通拥堵问题的有效方式之一,成为世界范围内城市交通领域研究的热点。以大连市快速公交示范线工程建设为背景,对快速公交系统的规划和设计进行了探讨和应用。     

变阻抗桩纵向振动的半解析解

考虑桩周土体的三维波动效应,分析成层黏性材料阻尼土中桩顶受任意轴向激振力作用时变阻抗桩的纵向振动特性,求得桩顶频域响应解析解、复刚度和速度导纳,分析了底部土层模量变化和桩身阻抗变化对桩纵向振动特性的影响。     

应用于舰载天线电磁兼容性分析的改进多层快速多极子算法

  目的  针对舰载无线通信设备布局拥挤、干扰严重以及迫切需要天线功能重构的现状,提出一种跨波段频率可重构的微带准八木天线。  方法  首先,在准八木天线上加载PIN二极管,通过控制二极管的通断,实现多波段的多模式切换;然后,通过附着雪花式开口谐振环（SRR）,以保证天线具有2个稳定的频率谐振点,以及稳定的辐射方位角。  结果  仿真和实测结果表明：该天线实现了C波段（5.77~7.10 GHz,7.40~7.56 GHz）和X波段（8.33~8.64 GHz,8.76~9.27 GHz）内的频率可重构;天线辐射方向图可以稳定地指向容性加载导通的方向;所有模式下的增益水平均大于5.7 dBi,且3 dB波束宽度的平均值约为102°。  结论  该微带准八木天线实现了天线的跨波段频率可重构和低误差波束偏转,有利于提高舰船系统频谱的利用率并避免多天线之间的耦合干扰。     

Estimation of driving style in naturalistic highway traffic using maneuver transition probabilities

Accurately estimating driving styles is crucial to designing useful driver assistance systems and vehicle control systems for autonomous driving that match how people drive. This paper presents a novel way to identify driving style not in terms of the durations or frequencies of individual maneuver states, but rather the transition patterns between them to see how they are interrelated. Driving behavior in highway traffic was categorized into 12 maneuver states, based on which 144 (12 × 12) maneuver transition probabilities were obtained. A conditional likelihood maximization method was employed to extract typical maneuver transition patterns that could represent driving style strategies, from the 144 probabilities. Random forest algorithm was adopted to classify driving styles using the selected features. Results showed that transitions concerning five maneuver states – free driving, approaching, near following, constrained left and right lane changes – could be used to classify driving style reliably. Comparisons with traditional methods were presented and discussed in detail to show that transition probabilities between maneuvers were better at predicting driving style than traditional maneuver frequencies in behavioral analysis.     

Assessment of the effects of highway geometric design features on the frequency of truck involved crashes using bivariate regression

Given the enormous losses to society resulting from large truck involved crashes, a comprehensive understanding of the effects of highway geometric design features on the frequency of truck involved crashes is needed. To better predict the occurrence probabilities of large truck involved crashes and gain direction for policies and countermeasures aimed at reducing the crash frequencies, it is essential to examine truck involved crashes categorized by collision vehicle types, since passenger cars and large trucks differ in dimensions, size, weight, and operating characteristics. A data set that includes a total of 1310 highway segments with 1787 truck involved crashes for a 4-year period, from 2004 to 2007 in Tennessee is employed to examine the effects that geometric design features and other relevant attributes have on the crash frequency. Since truck involved crash counts have many zeros (often 60–90% of all values) with small sample means and two established categories, car-truck and truck-only crashes, are not independent in nature, the zero-inflated negative binomial (ZINB) models are developed under the bivariate regression framework to simultaneously address the above mentioned issues. In addition, the bivariate negative binomial (BNB) and two individual univariate ZINB models are estimated for model validation. Goodness of fit of the investigated models is evaluated using AIC, SBC statistics, the number of identified significant variables, and graphs of observed versus expected crash frequencies. The bivariate ZINB (BZINB) models have been found to have desirable distributional property to describe the relationship between the large truck involved crashes and geometric design features in terms of better goodness of fit, more precise parameter estimates, more identified significant factors, and improved predictive accuracy. The results of BZINB models indicate that the following factors are significantly related to the likelihood of truck involved crash occurrences: large truck annual average daily traffic (AADT), segment length, degree of horizontal curvature, terrain type, land use, median type, lane width, right side shoulder width, lighting condition, rutting depth (RD), and posted speed limits. Apart from that, passenger car AADT, lane number, and indicator for different speed limits are found to have statistical significant effects on the occurrences of car-truck crashes and international roughness index (IRI) is significant for the predictions of truck-only crashes.     

斜拉桥索力测量的可靠度研究

从概率分析的角度探讨频率法测量索力的精度.综合运用响应面-蒙特卡罗法,以及索力-频率对应关系的有限元及样条拟合方法,形成一种计算量少、计算精度高的频率法测量索力可靠度分析方法.该法可以考虑索结构参数和索实测频率变异性对频率法测量精度的影响.采用该法对广州珠江黄埔大桥北汊斜拉桥各施工阶段的索力测量进行可靠度分析,获得理想的结果,检验了方法的正确性与实用性,同时也为该桥索力测量提供概率意义下的精度信息.