High Order IMEX Stochastic Galerkin Schemes for Linear Transport Equation with Random Inputs and Diffusive Scalings

In this paper,we consider the high order method for solving the linear transport equations under diffusive scaling and with random inputs.To tackle the randomness in the problem,the stochastic Galerkin method of the generalized polynomial chaos approach has been employed.Besides,the high order implicit-explicit scheme under the micro-macro decomposition framework and the discontinuous Galerkin method have been employed.We provide several numerical experiments to validate the accuracy and the stochastic asymptotic-preserving property.

Numerical Simulation of Bed Load and Suspended Load Sediment Transport Using Well-Balanced Numerical Schemes

Sediment transport can be modelled using hydrodynamic models based on shallow water equations coupled with the sediment concentration conservation equation and the bed con-servation equation.The complete system of equations is made up of the energy balance law and the Exner equations.The numerical solution for this complete system is done in a seg-regated manner.First,the hyperbolic part of the system of balance laws is solved using a finite volume scheme.Three ways to compute the numerical flux have been considered,the Q-scheme of van Leer,the HLLCS approximate Riemann solver,and the last one takes into account the presence of non-conservative products in the model.The discretisation of the source terms is carried out according to the numerical flux chosen.In the second stage,the bed conservation equation is solved by using the approximation computed for the system of balance laws.The numerical schemes have been validated making comparisons between the obtained numerical results and the experimental data for some physical experiments.The numerical results show a good agreement with the experimental data.

A Genetic Fuzzy Analytical Hierarchy Process Based Projection Pursuit Method for Selecting Schemes of Water Transportation Projects

The optimal selection of schemes of water transportation projects is a process of choosing a relatively optimal scheme from a number of schemes of water transportation programming and management projects, which is of importance in both theory and practice in water resource systems engineering. In order to achieve consistency and eliminate the dimensions of fuzzy qualitative and fuzzy quantitative evaluation indexes, to determine the weights of the indexes objectively, and to increase the differences among the comprehensive evaluation index values of water transportation project schemes, a projection pursuit method, named FPRM-PP for short, was developed in this work for selecting the optimal water transportation project scheme based on the fuzzy preference relation matrix. The research results show that FPRM-PP is intuitive and practical, the correction range of the fuzzy rained is both stable and accurate; preference relation matrix A it produces is relatively small, and the result obtherefore FPRM-PP can be widely used in the optimal selection of different multi-factor decision-making schemes.

Fourth-Order Conservative Transport on Overset Grids Using Multi-Moment Constrained Finite Volume Scheme for Oceanic Modeling

With an increase in model resolution,compact high-order numerical advection scheme can improve its effectiveness and competitiveness in oceanic modeling due to its high accuracy and scalability on massive-processor computers.To provide high-quality numerical ocean simulation on overset grids,we tried a novel formulation of the fourth-order multi-moment constrained finite volume scheme to simulate continuous and discontinuous problems in the Cartesian coordinate.Utilizing some degrees of freedom over each cell and derivatives at the cell center,we obtained a two-dimensional(2D)cubic polynomial from which point values on the extended overlap can achieve fourth-order accuracy.However,this interpolation causes a lack of conservation because the flux between the regions are no longer equal;thus,a flux correction is implemented to ensure conservation.A couple of numerical experiments are presented to evaluate the numerical scheme,which confirms its approximately fourth-order accuracy in conservative transportation on overset grid.The test cases reveal that the scheme is effective to suppress numerical oscillation in discontinuous problems,which may be powerful for salinity advection computing with a sharp gradient.

GENERALIZED UPWIND SCHEME WITH FRACTIONAL STEPS FOR 3-D PROBLEM OF CONVECTION DOMINATING GROUNDWATER TRANSPORT

A generalized upwind scheme with fractional steps for 3-D mathematical models of convection dominating groundwater quality is suggested. The mass transport equation is split into a convection equation and a dispersive equation. The generalized upwind scheme is used to solve the convection equation and the finite element method is used to compute the dispersive equation.These procedures which not only overcome the phenomenon of the negative concentration and numerical dispersion appear frequently with normal FEM or FDM to solve models of convection dominating groundwater transport but also avoid the step for computing each node velocity give a more suitable method to calculate the concentrations of the well points.

Intelligent Transportation System and Night Delivery Schemes for City Logistics

Intelligent Transportation System （ITS） integrates information and communication technologies with location based technologies into roads, vehicles, traffic and transport management systems. Application of ITS can improve situation in major cities where due to the increasing number of residents and level of motorization traffic congestion represents important issue. Another problem arises from this facts and that is that cities have contradictory needs as grooving need for goods within urban areas as well as need for less vehicles in the same area. The urban logistics activities by private companies within urban areas represent an integral part of city logistics that aims to improve the efficiency of urban freight transportation, reduce traffic congestion, mitigate environmental impacts, reduce costs and fuel consumption. This research presents application of ITS technologies and vehicle routing problem for night delivery scheme planning as one of the core techniques for modelling city logistics.

Research Progress and Preliminary Scheme of Space Transportation System for Human Mars Exploration

Human Mars exploration has significant values in terms of exploring extraterrestrial life,interplanetary immigration,promoting science and technology development,and the progress of human society.This paper summarizes the research progress on human Mars exploration and the corresponding proposed space transportation systems in the world,and analyzes the development trends.A preliminary scheme including the human Mars exploration mission architecture and corresponding space transportation system is then proposed,and the related key technologies are identified.The results can be a reference for future further research.

天然气水合物试采多相输送的弯管段防护研究

天然气水合物浆液中混杂的泥砂颗粒在低流速管段容易产生堆积阻塞,在高流速管段经常发生冲蚀磨损,目前国内外针对以液体为连续相流动的气液固多相流冲蚀研究较少。为此,以欧拉(Euler)气泡流模型与离散相模型(DPM)耦合的多相流数学模型为理论基础,对多相流中气液相间分布及管壁冲蚀磨损进行了数值模拟,开展了冲蚀磨损试验并提出耐磨防护方案。研究结果表明:可以从减弱弯管段湍流剪切作用、颗粒对弯管内壁的直接碰撞及减少动能传递进行防护设计;15°楔形垫层对应的最大冲蚀速率减幅74.55%,在1.0~2.2 m/s的流速范围内防护效果更明显;陶瓷涂垫层防护对冲蚀-腐蚀交互作用有明显的抑制效果。研究结论可为管道输送工程防护措施的制定提供技术参考。

菏兰铁路引入兰考南站方案研究

研究目的:设计方案比选是一个多目标、多因素、多层次的系统工程。因引入新增线路,结合预测运量,既有线路的通过能力远期已趋于饱和,需进行各方案的优缺点分析,并合理选择引入方案。本文通过菏兰铁路引入兰考南站方案研究,选择合理的引入方案,确定合理的线路走向,达到降低工程难度和节省投资的目的。研究结论:(1)本文通过对运输组织、技术经济、车站咽喉疏解近期工程、同步实施线下工程、已实施工程等诸多方面的研究,结合河南省最新城际铁路网规划,分析各方案的优缺点,确定出相对优化的推荐方案,即上下行联络线分别在东西咽喉疏解方案;(2)通过运营条件、线路长度、工程投资等诸多方面的分析,结合沿线村镇分布、联络线设置条件等因素,对引入兰考南站线路方案进行了研究,推荐东绕仪封乡以R=3 000 m限速引入兰考南站方案;(3)本文研究可为类似项目的方案比选奠定理论基础,具有一定的参考价值。

大型枢纽车站铁路信号系统增改工程设计与施工

新建广州白云火车站是未来广州市的重要交通枢纽,其规模庞大,情况复杂。该文结合现场施工实际状况,以广州白云火车站改造为例,详细描述白云火车站在新建和改建过程中,信号系统具体设计思路和施工总体技术方案,针对施工可能出现的问题,制定相应措施,确保改造工程顺利进行,为今后轨道交通枢纽信号系统施工积累经验。

横风下基于滚动GAPSO算法的列车速度曲线优化

针对普通环境下高速列车目标速度曲线优化算法不适用于横风环境的问题,提出一种横风环境下基于滚动GAPSO(遗传粒子群)算法的列车速度曲线优化方法。首先,考虑横风风速阻力作用改进列车动力学模型,并建立列车运行多目标优化模型;其次,基于GAPSO算法寻优巡航构建列车在起始阶段的最优目标速度曲线,引入滚动优化框架实时调整目标速度曲线,并在横风限速区按照改进快行策略运行;最后,在列车进站前采用GAPSO算法寻优惰行点生成目标速度曲线。仿真实验结果表明:GAPSO算法较GA算法和PSO算法具有搜索能力强、收敛速度快的优点;滚动GAPSO算法能在不同横风环境下实时生成优化后的目标速度曲线,并与改进快行策略和RH-PSO算法相比,具有较优的节能性和准时性。横风下基于滚动GAPSO算法的列车目标速度曲线优化可为横风环境下列车节能、准时运行提供一种可行的解决方案。

黄河现行流路与启用刁口流路不同情景下调水调沙期间入海水沙扩散特征与影响因素

《黄河流域综合规划(2012—2030年)》中指出,规划期内仍主要利用清水沟流路行河,保持流路相对稳定,清水沟流路使用结束后,优先启用刁口备用流路。为探究黄河启用刁口流路后入海水沙扩散特征及其与现行流路的差异,本研究选取黄河水沙入海的主要时期——调水调沙期,通过FVCOM三维数值模式,模拟研究了黄河调水调沙期间经两条流路入海情况下的盐度、悬沙浓度及河口动力特征,对比发现(1)两条流路沿岸流系总体变化趋势一致,入海径流受地转偏向力影响整体向东偏转,局部流场存在差异,刁口流路入海时无明显环流;(2)两种流路下羽流和悬沙的扩散特征对调水调沙不同阶段的水沙变化存在一致性的响应;然而,受河口地形和岸线的影响,刁口流路情景下羽流和悬沙的扩散范围显著大于现行流路;(3)伴随着流路变化,三角洲不同区域的演化特征将产生快速响应:刁口流路启用后,现行河口三角洲将进入蚀退期,刁口三角洲叶瓣进入快速造陆期。此外,模型结果显示,由于刁口外较浅的水深和平缓的地貌特征,相同条件下刁口流路情景下三角洲的造陆速率在短期内可能高于现行流路。

基于天窗基本单元的编组站天窗方案优化研究

编组站接发列车方向多、数量大,机车换挂和调车作业频繁,直接影响施工维修作业。既有固定天窗时长的天窗方案,难以兼顾维修施工作业和运输工作连续性需求,导致天窗兑现率低,增加安全隐患,研究提出基于天窗基本单元的编组站天窗方案优化方法。根据各维修养护工种作业特性、编组站工作人员数量及效率等因素,划分天窗基本单元;考虑编组站维修养护与运输组织需求,以效用、作业完成率和天窗阈值利用率最优为目标,以时序关系为约束,建立基于阈值的天窗方案多目标优化模型,并利用数学软件进行求解;以成都北编组站为例,验证模型的有效性,结果表明,通过合理优化天窗方案,天窗兑现率达100%,有助于缓解编组站维修与运输之间的冲突。

城市轨道交通延伸线路列车编组方案研究--以青岛地铁6号线二期为例

列车编组作为城市轨道交通技术标准之一,对线路建设及后期运营至关重要,在各地线网不断向城市边缘延伸,客流出现中心城区客流大,边缘地区客流小,或初、近期客流小,远期客流大等时空不均衡特征的背景下,对既有延伸线的编组研究刻不容缓。首先,对国内外城市轨道交通编组的使用情况进行总结,说明混跑编组、灵活编组的应用趋势;之后,以青岛轨道交通6号线二期工程为例,根据客流确定固定6编组、4辆、6辆混跑编组的开行方案,基于运营角度选取全日、高峰满载率、全日牵引能耗、车辆购置费等评价指标,对6号线采用两方案进行系统比选;并分析混跑编组方案对站台门系统、通信系统、信号系统、场段规模的改造成本。研究结果表明:6号线采用4辆、6辆混跑后,运营方面初、近、远期客流服务水平均可提高3对/h,同时全日及高峰满载率有所提高,经济性方面车辆购置费可节约1.1亿元,电耗节约6.2亿元,工程、系统改造成本为1.4亿元,综合来看,运营期按25年综合成本可节约5.9亿元。综合运营、经济两方面6号线二期推荐4辆、6辆混跑编组方案。

信控交叉口公交专用车道动态共享实时控制方法

针对目前交叉口拥堵、公交专用车道利用率低的问题,提出一种信控交叉口公交专用车道动态共享实时控制方法。利用GPS定位实时获取交叉口处公交车的位置,并通过交通检测设备获取专用道内小汽车车辆数,结合主信号显示情况综合计算当前时刻公交专用道共享前后交叉口车辆总延误。将延误大小判断结果反馈给车道信号,车道信号显示红灯或绿灯以提醒司机是否能够进入公交专用道。引入受影响车辆概念,建立以减少交叉口车辆总延误为目标的公交专用车道共享控制模型。通过对当前时刻主信号显示红灯和显示绿灯两种情况分析,提出一种综合考虑车辆司乘系数、受影响车辆的交叉口延误计算方法,得到共享公交专用车道前后交叉口车辆总延误差值的表达式。利用示例数值模拟在多种不同场景下车道信号的显示情况,分析了专用道内已有车辆、公交车位置以及主信号显示情况对车道共享的影响。结果表明:该控制方法较符合实际情况,并能有效提高公交专用车道利用率,能够充分利用交叉口绿灯时间,为解决公交专用车道的动态共享、缓解道路拥堵提供了一种新的思路。

客流OD导向下地铁快车停站方案优化

为精细化确定轨道交通市郊线路快车停站方案,提出一套以市郊线路客流OD为核心导向的快车停站优化方案。首先,构建轨道交通区间选择费用函数,根据路径选择费用分配OD客流;其次,在客流分配的基础上,以乘客出行时间最短与企业运营成本最低为目标函数,以断面满载率、车站客流需求、优化时段发车次数约束等多重客观因素为模型约束,建立快车停站方案优化模型;最后,以S市地铁市郊线路16号线基础数据为实例验证,运用带精英策略的非支配排序的遗传算法和GA混合(GA-NSGA-Ⅱ)对停站方案优化模型求解。优化结果表明,在高峰时段乘客人均出行时间节省1.074 min,每个运营日车底运用数减少6列。

基于日照时数分析的地下交通枢纽顶部开口研究

发展地下交通系统成为解决城市化进程中交通拥挤、土地紧张等问题的重要应对措施。地下交通枢纽空间的顶部开口可以缓解地下空间的采光与通风需求,但因此会使地下空间接受较多的太阳辐射量,导致夏季热不适。分析不同顶部开口设计对地下空间的热环境状况影响可以辅助设计人员优化方案,减少建筑能耗。本研究提出一种基于日照时数的热环境评价方法。该方法借助日照模拟分析软件定性与定量分析研究空间的太阳照射时数分布情况,同时基于权重分析法考虑了不同时刻太阳辐射强度变化的影响。在此基础上采取控制变量法讨论开口率、开口数量、开口深度和日照时数之间的关系,确定使地下空间热环境良好的开口设计形态。此外,选取广州市某综合交通枢纽设计项目作为案例研究,详细展示了如何利用所提出的方法评价分析不同顶部开口设计方案的太阳照射时数分布情况。将所总结的方法应用于设计实践中,使其在方案设计阶段确定有利于地下空间热环境效应的开口设计,为后续阶段的热环境优化奠定良好的基础。

沿江货运铁路通道布局及实施方案研究

完善沿江货运铁路通道布局对于充分发挥铁路绿色低碳优势、缓解长江三峡“肠梗阻”问题、加快构建综合立体交通走廊、支撑长江经济带经济发展等具有重要意义。研究首先分析沿江货运铁路通道现状及存在问题;其次,从综合交通的角度出发,统筹考虑铁路趋势运量、“水转铁”运量、“公转铁”运量进行近期(2030年)、远期(2035年)、远景(2050年)需求预测;最后,提出铁路通道布局和分期实施方案,即规划沿江货运铁路通道由北辅助通道、中通道(轻快通路、普货通路、专线通路)、南辅助通道组成。按照“两步走”进行实施,一是对长荆铁路、鸦宜铁路进行扩能改造,二是规划建设常岳九铁路等构建沿江货运专线通路。

盖挖与明挖组合建造地下交通枢纽方案研究

为满足北京城市副中心地下交通枢纽区域内的城市道路先行投入运营的需求,提出采用盖挖法与明挖法组合方法进行地下枢纽基坑开挖与支护的方案,主要特点如下:(1)将地下交通枢纽基坑分割为“盖挖基坑、明挖基坑和多级放坡基坑”等3个并列布置基坑;(2)盖挖区基坑与明挖基坑共用围护结构;(3)先完成盖挖区顶板结构施工,恢复城市道路运营,然后采用逆作法完成盖挖区负一层施工,随后同步开挖支护盖挖区两侧的明挖基坑和放坡区基坑;(4)盖挖区负二层和负三层采用顺作法施工。论文详细阐述了盖挖与明挖组合工法的施工工序,分析了组合工法的优势。鉴于盖挖区钢管柱始终处于基坑开挖扰动中,为此采用数值模拟方法并结合现场监测结果,分析了基坑开挖期间的钢管柱变形规律。结果表明,钢管柱水平变形和隆起变形指标均满足控制要求。本文提出的盖挖与明挖组合建造方案不但能确保地下交通枢纽区域内的城市道路尽快投入运营,而且并列基坑群中的3个基坑开挖支护及结构浇筑基本上相互独立,有效降低了盖挖区和明挖区基坑施工的相互影响,提高了施工效率。

交互式BIM述标在水运工程投标中的应用

针对水运工程投标过程中的BIM述标问题,进行述标需求分析、工具比选和方案可视化流程的研究。结合国内某水运项目投标过程中的BIM述标,采用国产某述标平台全面整合述标内容并发布离线述标文件的方法,解决述标过程中的多类型模型集成、多源数据资源整合、述标内容和方案整合、方案可视化和交互式汇报等问题,最终实现了结合BIM模型完成全部的述标工作。结论是国产化述标平台在水运工程BIM述标及交互式汇报中优势明显,可以满足当前阶段BIM述标的要求,该研究将为水运工程类似投标中的BIM述标提供借鉴和参考。