顾及高程时计算两点间大地距离的实用方法

对考虑高程影响时大地距离的计算问题进行了研究,构造了一个过地球表面两已知点的新椭球,确定出了新椭球的有关参数,得到了两已知点在新椭球上的坐标,在此基础上给出了计算大地距离的非迭代法和大椭圆法。算例分析表明,当对大地距离的计算精度要求较高时,必须考虑高程的影响,该文方法可以满足高精度大地距离计算的需要。     

动态管理模式下路侧停车泊位占有率预测方法

城市停车已逐步实现信息化和动态化管理，本文对动态管理模式下大范围路侧泊位占有率预测方法进行研究.在收集美国旧金山492万条停车交易数据的基础上，利用可同时提取数据空间关联和时序趋势特征的卷积长短时记忆神经网络(Convolutional LSTM Network，ConvLSTM)，分别构建考虑停车费率和时限动态变化的有政策模型，和没有动态管理信息输入的无政策模型.结果显示，有政策模型的训练效率和预测精度会显著提升.在政策平稳阶段，两种模型均能够有效预测泊位占有率；在政策发生变化时段，无政策模型的预测误差出现激增，但有政策模型的预测误差依然保持平稳，表明本文提出的方法能够很好地应对动态管理模式下停车需求的变化.     

基于LTE(长期演进)技术的地铁乘客信息系统组网方案分析

介绍了郑州地铁1号线基于LTE(长期演进)技术的乘客信息系统组网方案。第三方测试结果表明,该组网方案LTE车地无线通道性能符合标准要求。分析了该组网方案在实际使用和维护过程中出现的一些主要问题,并针对问题提出了相应的改进建议:提高车辆段/停车场库内带宽;LTE系统独立组网;车载交换机采用三层交换机。     

城市轨道交通网络规划的站点布局标准探讨

为了提高轨道交通网络中站点分布规划的合理性，分析巴黎、东京等城市的轨道交通网络层次和站点分布特征，总结不同区域站点分布密度及不同线路站间距指标特性，从区域协调性、交通功能需求等角度，分析轨道交通网络站点合理分布的理论化，确定具体的规划指标和标准。表明轨道交通站点分布应系统考虑区域协调性，通过网络层面的覆盖率指标考量对出行需求的满足，以及轨道交通服务水平。     

由推进器尾流计算确定动力艇合理牵引间距研究

针对动力艇尾流作用于被牵引船只,造成水阻力增加而使牵引效率下降的问题,提出通过数值模拟方法计算动力艇尾流场,进而确定合理的牵引间距的方法.文章应用理想推进器理论,给出了确定推进器尾流出口横截面面积和喷水流速的方法.在此基础上,通过数值模拟计算推进器尾流场的影响,并通过分析估计出给定牵引航速下的合理牵引间距.该方法可以结合动力艇的拖钩拉力与航速曲线,确定组合体可能达到的最大设计航速.     

浅埋大跨超近距多洞室暗挖施工监测分析

大跨车站开挖过程中,受浅埋近距离多洞室等复杂情况的影响,隧道围岩呈现出非线性沉降,因此这种地铁车站开挖必须实施信息化施工。通过地表监测及时掌握围岩力学状态,及时采取对策,实施动态施工,以确保隧道暗挖施工安全。     

考虑界面相对滑移的钢-混凝土组合梁力学性能分析

根据钢和混凝土的应力应变关系,提出该组合梁考虑钢与混凝土界面相对滑移的力学性能分析方法,并由此编制计算分析程序,求解竖向集中荷载作用下组合梁的承载力、荷载-挠度曲线以及钢与混凝土的相对滑移分布,并通过与试验对比,表明按该文分析方法得出的结论与试验吻合较好。     

Optimization of nonlinear control strategy for anti-lock braking system with improvement of vehicle directional stability on split-μ roads

In a hard braking on a split-μ road, the achievement of shorter stopping distance while maintaining the vehicle in the straight line are of great importance. In this paper, to achieve these conflicting aims, an optimal nonlinear algorithm based on the prediction of vehicle responses is presented to distribute the wheel braking forces properly. The base of this algorithm is reducing the maximum achievable braking forces of one side wheels, as low as possible, so that the minimum stabilizing yaw moment is produced. The optimal property of the proposed control method makes it possible to get a trade-off between the shorter stopping distance and the less deviation of the vehicle heading from the straight line. The special case of this algorithm leads to the conventional anti-lock braking system (ABS) which generates the maximum braking forces for all wheels to attain the minimum stopping distance. However, the ABS cannot control the vehicle directional stability directly. The simulation results carried out using a nonlinear 8-DOF vehicle model demonstrate that the designed control system has a suitable performance to attain the desired purposes compared with the convectional ABS.     

A travel time reliability model of urban expressways with varying levels of service

Urban expressways usually experience several levels of service (LOS) because of the stop-and-go traffic flow caused by congestion. Moreover, multiple shock waves generate at different LOS interfaces. The dynamic of shock waves strongly influences the travel time reliability (TTR) of urban expressways. This study proposes a path TTR model that considers the dynamic of shock waves by using probability-based method to characterize the TTR of urban expressways with shock waves. Two model parameters are estimated, namely distribution of travel time (TT) per unit distance and travel distances in different LOS segments. Generalized extreme value distribution and generalized Pareto distribution are derived as distributions of TT per unit distance for six different LOS. Distribution parameters are estimated by using historical floating car data. Travel distances in different LOS segments are calculated based on shock wave theory. The range of TT along the path, which can help drivers arrange their trips, can be obtained from the TTR model. Finally, comparison is made among the proposed TTR model, generalized Pareto contrast model, which does not consider different LOS or existence of shock waves, and normal contrast model, which assumes TT per unit distance as normal distribution without considering shock wave. Results show that the proposed model achieves higher prediction accuracy and reduces the prediction range of TT. The conclusions can be further extended to TT prediction and assessment of measures to improve reliability of TT in a network.     

长引桥码头加压泵设置及管道水击分析

东营某新建油品码头距后方库区约20 km,船泵扬程不足以克服沿程摩阻将物料直接输送至库区.通过分析与计算,提出码头上设置加压泵站的方案,充分利用码头平台空间.在此基础上,对管道进行水击分析,检验瞬时水击压力是否超过管道设计压力,并对超压工况提出调整方案.