回转椭球体可压缩流动数值计算

基于细长体理论和逐次近似计算方法,对水下运动的回转椭球体可压缩流动进行了数值模拟.通过迭代计算得到流动压缩因子,用于确定可压缩流动流场.分析了相同的回转椭球体在不同介质中的临界马赫数以及相同来流马赫数下不同介质中压缩性影响程度.计算结果与相关资料数据进行比较,具有较好的一致性.     

浅谈综合优化技术在公路路线方案比选中的应用

路线方案的比选是公路建设项目前期的一项重要工作,直接影响着项目建设能否达到预期的目标以及项目投入运营中的使用效果。进行路线方案比选时,要考虑路线的线形合理性、对周边地区环境影响、项目经济效益、施工难易等多种因素的影响。通过对公路主要技术指标的综合优化,以获得技术标准的最优组合。     

多跨连续梁桥纵桥向动力特性研究及其地震反应谱简化分析

根据多跨连续梁桥的主要结构特点,采用简化的模型来模拟纵桥向的地震动力反应.通过求解简化模型的动力方程,分析了质量比对连续梁桥纵桥向的动力特性的影响,并用能量法推导了低阶振型地震反应的近似公式.通过与有限元方法的比较,验证了采用几个低阶振型组合计算的反应谱方法的可行性.     

自动变速器换挡机构的建模和结构参数优化

针对某车型平台在更换变速器过程中的换挡机构参数设计问题,利用ADAMS/View建立了自动变速器换挡操纵机构平面运动学模型,并将变速器换挡臂长度和初始位置以及变速器端换挡推拉索的球铰点坐标等关键结构变量参数化,取换挡操纵机构设计更改时换挡手柄行程变动最小作为目标进行优化.与原平台设计相比,优化后的方案仅改变N、D两个换挡手柄挡位就能满足与新变速器换挡的匹配要求,并在实际车辆上得到成功应用.     

动力总成异常振动的研究

针对某SUV车动力总成产生的异常振动,运用自主开发的模态分析系统,通过动力总成单独的模态试验及整车的道路试验和转鼓试验,连续测量换挡杆的振动信号并进行分析处理。结果表明,换挡杆异常振动的根本原因是飞轮壳和离合器壳刚度相对较低,以致动力总成固有频率偏低,落在发动机工作转速对应的2阶激振频率区间而引起共振。通过对飞轮壳的结构进行改进,消除了换挡杆的异常振动。     

大跨径水泥混凝土桥梁沥青铺装层结构组合研究

以五河口大桥桥面铺装层受力薄弱处沥青混合料为研究对象,选取5种结构类型组合,通过复合板双层车辙试验和复合梁疲劳试验,更精确地模拟实际受力状况,并进行了劈裂试验、冻融劈裂试验以及低温小梁等常规路用性能试验,为铺装层结构选择提供依据。研究结果表明:在结构组合设计中,重点考虑铺装上层的抗车辙性能,对于铺装下层混合料设计则更多的关注其他的路用性能;综合考虑组合结构的抗疲劳性能、抗拉性能、抗水损害性能和低温抗裂性能,桥面铺装下层宜选用粒径较小的级配,添加纤维效果尤佳。综合比较路用性能指标,考虑桥面实际施工状况和经济性,铺装上层采用玄武岩SMA-13沥青混合料,推荐SMA-10沥青混合料作为桥面沥青铺装下层。     

施工方案评价中的多目标模糊决策技术

选择合理的施工方案是单位工程施工组织设计的核心。以模糊数学为基础,采用定性和定量相结合的方法建立了多目标决策模型,以全面客观的进行施工方案的综合评价。     

The stabilization control of underactuated surface vessels

The problem of stabilization control of underactuated surface vessels with two independent control inputs is in vestigated inthis paper. Through transformation, a cascade property of the system is revealed. And the original nonlinear system could be divided into two subsystems: a linear subsystem and a nonlinear subsystem. The stabilization laws are derived for the two subsystems separately. A smooth time - varying feedback stabilization law with exponentially convergence rate is obtained. The proposed stabilization law guarantees all the system states converge to the equilibrium exponentially. The aim of stabilization control of underactuated surface vessels is achieved. At last, the effectiveness of the proposed algorithm is illustrated by simulation tests.     

Mass transit systems of Beijing: governance evolution and analysis

Developing a more efficient mass transit system, in highly populated cities, improves the mobility, decreases the dependency of private cars, alleviates traffic congestion, and provides a more environmentally friendly means of travel. Recently, the city of Beijing decided to have a target of becoming as a ‘public-transport city’ with a fascinating mass transit system within a larger plan, of building humanistic, scientific and technological, and green public-transport systems. This work discusses the governance evolution of the mass transit system of Beijing between 1949–2008, comprised of two groups of transit systems, the road surface public-transport system (bus, tram, trolley, etc.), and the subway public-transport system. In addition, a time-series analysis is introduced in an attempt to examine the effect of governance evolution on the two transit systems, and of the impacts of the governance structural changes on the mass transit system. The time-series model is introduced using the annual statistics data of the period 1949–2008. The outcome of the analysis is viewed with precaution because of the incompleteness of the many endogenous and exogenous factors to affect the public-transport demand. Generally speaking it is concluded that the governance evolution provides beneficial effect of the Beijing mass transit activity; however, for satisfying the significant increase of the Beijing city’s travel demand and maintaining sustainable development, the governance-involvement pattern needs to be reformed.     

反坡排水在地下水丰富的下坡隧道中的应用

文章结合侧岭隧道工程实例,分析了地下水对下坡隧道施工的影响,强调排水在隧道施工中的必要性,提出了反坡排水施工组织方案及管理办法。