Dynamic user equilibrium with side constraints for a traffic network: Theoretical development and numerical solution algorithm

This paper investigates a traffic volume control scheme for a dynamic traffic network model which aims to ensure that traffic volumes on specified links do not exceed preferred levels. The problem is formulated as a dynamic user equilibrium problem with side constraints (DUE-SC) in which the side constraints represent the restrictions on the traffic volumes. Travelers choose their departure times and routes to minimize their generalized travel costs, which include early/late arrival penalties. An infinite-dimensional variational inequality (VI) is formulated to model the DUE-SC. Based on this VI formulation, we establish an existence result for the DUE-SC by showing that the VI admits at least one solution. To analyze the necessary condition for the DUE-SC, we restate the VI as an equivalent optimal control problem. The Lagrange multipliers associated with the side constraints as derived from the optimality condition of the DUE-SC provide the traffic volume control scheme. The control scheme can be interpreted as additional travel delays (either tolls or access delays) imposed upon drivers for using the controlled links. This additional delay term derived from the Lagrange multiplier is compared with its counterpart in a static user equilibrium assignment model. If the side constraint is chosen as the storage capacity of a link, the additional delay can be viewed as the effort needed to prevent the link from spillback. Under this circumstance, it is found that the flow is incompressible when the link traffic volume is equal to its storage capacity. An algorithm based on Euler’s discretization scheme and nonlinear programming is proposed to solve the DUE-SC. Numerical examples are presented to illustrate the mechanism of the proposed traffic volume control scheme.     

9000DWT多用途船轮机设计

[9000DWT多用途船是上海船舶研究设计院自主开发设计的一型中小型多用途船,具有轻巧灵便,装载类别范围广等优点,受到多国船东青睐,先后在宜昌、重庆、浙江地区的多家船厂建造。介绍了9000DWT多用途船的主要设备选用概况。结合机舱布置、货舱通风等方面的技术难点,通过分析,有针对性地提出了合理的解决方案。     

沙颍河航道安徽段航道整治工程航道尺度研究

通过对沙颍河航道安徽段航道现状、船型现状的调查研究及运量的预测分析,结合京杭运河标准船型,提出了沙颍河航道安徽段设计船型,据此分析研究沙颍河航道安徽段航道整治工程设计航道尺度,对航道的通过能力进行了分析计算,提出了推荐方案.     

广深港客运专线福田站及相邻区间隧道通风系统研究

广深港客运专线福田站及相邻区间隧道为单洞双线隧道,具有时速高、断面大、阻塞比小、活塞效应弱和散热量大的特点。为保证隧道内人员舒适性要求,必须解决隧道内温度和新风量控制等关键技术问题。从区间和车站活塞风井设置、风井面积及车站排热风量3个方面进行研究,主要结论如下:1)隧道内共需设5处活塞风井,分别为益田路1#风井和2#风井、福田车站两端活塞风井、皇岗公园风井;2)福田车站两端活塞风井面积均为60 m~2,其余3处活塞风井面积均为40 m~2;3)福田车站排热风量为540m~3/s;4)优化后隧道最高温度为39.3℃,人均新风量为76 m~3/h,均满足设计标准要求。     

What determines rail transit passenger volume? Implications for transit oriented development planning

Transit oriented development (TOD) has been an important topic for urban transportation planning research and practice. This paper is aimed at empirically examining the effect of rail transit station-based TOD on daily station passenger volume. Using integrated circuit (IC) card data on metro passenger volumes and cellular signaling data on the spatial distribution of human activities in Shanghai, the research identifies variations in ridership among rail transit stations. Then, regression analysis is performed using passenger volume in each station as the dependent variable. Explanatory variables include station area employment and population, residents’ commuting distances, metro network accessibility, status as interchange station, and coupling with commercial activity centers. The main findings are: (1) Passenger volume is positively associated with employment density and residents’ commuting distance around station; (2) stations with earlier opening dates and serving as transfer nodes tend to have positive association with passenger volumes; (3) metro stations better integrated with nearby commercial development tend to have larger passenger volumes. Several implications are drawn for TOD planning: (1) TOD planning should be integrated with rail transit network planning; (2) location of metro stations should be coupled with commercial development; (3) high employment densities should be especially encouraged as a key TOD feature; and (4) interchange stations should be more strategically positioned in the planning for rail transit network.     

螺旋箍筋约束高强混凝土柱轴心受压性能试验研究

为探究螺旋箍筋约束高强混凝土柱的轴心受压性能,开展了42根螺旋箍筋约束高强混凝土圆柱的轴压试验,研究了混凝土标准立方体抗压强度(58.0~90.6 MPa)、箍筋屈服强度(480~1 219 MPa)、体积配箍率(1.00%~1.60%)与箍筋间距(45~80 mm)对螺旋箍筋约束混凝土柱受压承载力和变形能力的影响。试验结果表明:箍筋约束混凝土在达到峰值压应力时,约束箍筋可能达不到屈服;约束箍筋的强度和体积配箍率相同时,随着高强混凝土强度的增高,约束混凝土达到峰值压应力时箍筋的拉应变减小;混凝土轴心抗压强度、箍筋屈服强度相同时,随着体积配箍率的提高,约束混凝土峰值压应变增大,相应的横向应变也随之增大,箍筋拉应变也增大。基于试验结果,考察了峰值压应力下箍筋拉应变与体积配箍率、混凝土强度、箍筋屈服强度和箍筋间距之间的关系,建立了峰值压应力下约束箍筋拉应变计算公式。拟合得到了约束混凝土峰值压应力f_cc、峰值压应变ε_cc、下降段曲线的特征参数(峰值压应力后85%峰值应力下的轴向压应变ε_c85、50%峰值压应力的轴向压应变ε_c50)的计算公式。给出了考虑体积配箍率、混凝土轴心抗压强度、箍筋间距和箍筋屈服强度影响的箍筋约束高强混凝土的轴心受压应力-应变关系模型。     

垂直淹没射流对黏性底床冲刷挖掘体积的试验研究

射流冲刷作为一种高效挖掘手段被广泛应用于深海工程领域。针对黏性底床条件下垂直淹没射流冲刷挖掘体积进行研究,利用注浆成型法制备冲刷坑的胚体并利用3 d扫描技术获取冲刷挖掘体积。通过开展室内试验探索了射流流速、射流靶距、冲刷时间以及泥样含水率与冲刷挖掘体积的关系:1)冲击射流挖掘体积随着射流靶距的增加而减小;2)冲击射流挖掘体积随着射流流速的增加而增加;3)冲击射流挖掘体积随着冲刷时间的增加而增加,但逐渐趋于平衡;4)随着泥样含水率的增加,冲击射流挖掘体积也显著增加。最后,利用54组试验数据和无量纲分析得到了冲击射流挖掘体积的经验公式,可为射流挖沟以及射流沉桩等海洋工程实践提供参考。     

电喷摩托车是否选用怠速控制阀的研究

摩托车电喷系统采用的怠速控制阀,在摩托车起动性能、暖机性能、怠速性能和起步性能等方面发辉的作用十分明显,特别是对寒冷地方的用户,有无怠速控制阀或将成为购车的一个主要考虑要素。摩托车企业应根据摩托车的排量和售价,综合考虑是否采用怠速控制阀,对于排量较大、定位较高、销售目标区域在寒冷地区或出口的摩托车,应慎重考虑是否取消怠速控制阀,并需要做大量的试验来验证取消后对整车性能是否有影响及影响的大小,不能一并取之而后快。     

Numerical modeling of exhaust smoke dispersion for a generic frigate and comparisons with experiments

The exhaust smoke dispersion for a generic frigate is investigated numerically through the numerical solution of the governing fluid flow, energy, species and turbulence equations. The main objective of this work is to obtain the effects of the yaw angle velocity ratio and buoyancy on the dispersion of the exhaust smoke The numerical method is based on the fully conserved control-volume representation of the fully elliptic Navier-Stokes equations. Turbulence is modeled using a two-equation （k-ε） model The flow visualization tests using a 1/100 scale model of the frigate in the wind tunnel were also carried out to determine the exhaust plume path and to validatc the computational results. The results show that down wash phenomena occurs for the yaw angles between ψ=10° and 20°. The results with different exhaust gas temperatures show that the buoyancy effect increases with the increasing of the exhaust gas temperature. However, its effect on the plume rise is less significant in comparison with its momentum. A good agreement between the predictions and experiment results is obtained.     

双燃料主机及其系统应用

以大连中远船务28 000 m3绿色LNG运输船作为背景,结合《散装运输液化气体船舶构造与设备规范》、《天然气燃料动力船规范》等相关规范的要求,探讨LNG动力船舶的设计要点.