北京道路交通拥堵原因及对策分析

分析了当前引发北京市区交通拥堵的主要原因,并提出了相应对策,即应从提高全市整体路网循环通行能力入手,克服阻碍交通正常运行的不利因素,促进交通良性循环,使现有路网应有功能充分发挥,以缓解交通拥堵。     

砂卵石地层泥水盾构施工技术难点及控制措施分析——以兰州地铁穿黄隧道工程为例

为解决泥水盾构在砂卵石地层掘进过程中所面临的刀盘结构磨损严重、刀盘开口率调节不便、刀具磨损严重、泥水环流系统堵塞以及泥浆管路磨损严重等工程技术难题,针对兰州地铁穿黄隧道工程富水砂卵石地层条件,提出刀盘结构适应性改进措施、刀具磨损控制措施、环流系统改进措施以及泥浆管路磨损控制措施。研究表明： 1）对刀盘结构进行适应性改进,可有效解决砂卵石地层刀盘结构磨损严重和刀盘开口率调节等问题; 2）将边缘单刃滚刀改为双刃滚刀,导流刀改为撕裂刀,可有效增强盾构刀具的耐磨性能,提高盾构的掘进效率; 3）从碎石系统改进和大漂石、卵石处理2个方面对盾构环流系统进行改进,可有效解决盾构环流系统堵塞的问题; 4）将整体泥浆管路分为3段,相邻管路之间用法兰盘连接,可有效解决泥浆管路局部磨损严重的难题。     

蓝牙车载自动接听系统软件结构分析及应用

本文主要分析了蓝牙车载自动接听系统的软件结构,从系统的通话流程引出蓝牙免提协议栈的结构和原理,对蓝牙子系统中处理器上运行的软件结构进行分析,进而对蓝牙车载自动接听系统的应用进行了介绍。     

高校图书馆流通书库系统出现差错的原因及改进对策

针对图书馆流通书库管理中存在的问题,分析了导致各种差错出现的影响因素,从加强业务工作管理、提高人员素质、加强读者教育和宣传车库方面提出了完善图书馆流通系统管理应采取的措施。     

Numerical investigation of turbulence near a sheared air–water interface. Part 2: Interaction of turbulent shear flow with surface waves

Large-eddy simulations (LES) of the interactions between turbulent shear flow and surface waves are presented. The formation mechanism of Langmuir circulation and its contribution to the vertical momentum transport are investigated in detail. The effect of surface waves is modeled in two ways in the LES runs. One model includes only the phase-averaged effect of the waves as an added source term in the momentum equation, and the other model includes the full effect of the waves by use of the fully nonlinear conditions of the air-water interface. Langmuir circulations are clearly indicated in both cases, indicating that the phase-averaged effect is essential for the formation of this circulation. It is shown that the formation of Langmuir circulations enhances the vertical transport of momentum. As a result, the mean velocity gradient and the streamwise component of the turbulence intensity are decreased, while the spanwise and interface normal components are increased. Examination of the turbulence energy budget equations shows that production is due to the interaction between the vorticity and the Lagrangian drift as the phase-averaged effect of the wave becomes the dominant source of turbulence. Received: August 17, 2000 / Accepted: December 22, 2000     

北京地铁四号线隧道辐射井降水施工实践

在交通复杂、人口密集的城市中心区修建地下隧道,如何降低地下水,是影响施工的关键问题。文中以北京地铁四号线黄庄—中关村区间隧道施工降水为例,从辐射井降水原理着手,介绍了一套占地面积小、降水控制范围大、疏干效果好的施工降水方法。实践证明:竖井采用沉井工艺,水平井采用水力双壁钻杆反循环工艺,可达到快速高效降水的目的,且造价较井点降水节约30%。     

番茄在冷板冷藏车运输过程中的温度分布

冷板冷藏车在运输过程中,车内货物温度场是影响其运输质量的关键因素之一。本文运用多孔介质理论建立番茄在冷板冷藏车内及货物的数学模型,模拟2种不同堆码方式的动态温度场,并对其变化及分布的特点进行分析讨论,指出堆码方式对货物温度场有一定影响,为有较规则几何形状的果蔬货物的冷藏运输提供了理论依据。     

超大型集装箱船甲板最大堆重研究

德国劳氏船级社规范(GL-2013)对集装箱船尤其是超大型集装箱船的横向加速度系数计算进行了调整,大幅度提高了甲板上集装箱堆重。文章根据绑扎计算结果,将规范变化前后的横向加速度系数和最大堆重进行对比,以及对2层箱高绑扎桥和3层箱高绑扎桥的最大堆重进行对比。结果显示,随着规范的更新及绑扎点高度提高,集装箱甲板最大堆重显著增加,堆重分布更加优化合理,为今后超大型集装箱船甲板面堆重设计参数的合理选取提供了一定的参考。     

不同集装箱码头装卸系统下最优堆垛高度分析方法

介绍了一种简单的方法,用来估计在不同技术系统,不同土地面积以及经营成本下的集装箱码头作业效率。论述了此种理论以后,并通过实例的计算分析加以验证。     

Using the SKAGEX dataset for evaluation of ocean model skills

Numerical ocean models are now being applied in numerous oceanographic studies. However, the qualities of the model results are often uncertain and there is a great need for standards and procedures for evaluation of the skills of numerical general circulation models. In this paper measurements from repeated hydrographical sections across Skagerrak taken in 1990, the SKAGEX dataset, are used to evaluate the skills of two σ-coordinate ocean models and to study the sensitivity of these models to model parameters. A methodology for quantification of model skills based on observations from repeated hydrographical sections in general is suggested. Area averages of absolute differences are for Skagerrak completely dominated by the discrepancies in the upper few meters of the ocean and may not be used to assess models' abilities to reproduce the fields in the larger and deeper part of the ocean. Therefore, discrepancies between average values in time from the observed fields and time averaged values from model outputs are related to the natural variability of the fields. The numbers produced with the suggested measure are relative numbers that will be specific for each section and for each series of observation. Ideally we would therefore like to see the measures computed for a number of sections for various models and choices of model parameters in order to assess model skills. The value of the SKAGEX dataset as a tool for model improvements is demonstrated. Evidence to support the importance of applying non-oscillatory, gradient preserving advection schemes in areas with sharp density fronts is given. The method is used to identify that the forcing/initial values/boundary values for the temperature field are inferior to the corresponding values for the salinity field. With the present coarse resolution, 11 layers in the vertical, it is shown that it is far from obvious that the quality of the model results improve when replacing simple Richardson number formulations for vertical mixing processes with higher order turbulence closure in the Skagerrak area.