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71.
文中在分析航行数据记录仪主要组成及功能的基础上,以IMO海上安全委员会通过的航行数据记录仪的相关决议为检查依据,结合港口国监督检查实践经验总结出航行数据记录仪检查要点及方法,结合检查实例进行阐述,以期能给同行提供一些有益的参考。 相似文献
72.
Dynamic traffic routing refers to the process of (re)directing vehicles at junctions in a traffic network according to the evolving traffic conditions. The traffic management center can determine desired routes for drivers in order to optimize the performance of the traffic network by dynamic traffic routing. However, a traffic network may have thousands of links and nodes, resulting in a large-scale and computationally complex non-linear, non-convex optimization problem. To solve this problem, Ant Colony Optimization (ACO) is chosen as the optimization method in this paper because of its powerful optimization heuristic for combinatorial optimization problems. ACO is implemented online to determine the control signal – i.e., the splitting rates at each node. However, using standard ACO for traffic routing is characterized by four main disadvantages: 1. traffic flows for different origins and destinations cannot be distinguished; 2. all ants may converge to one route, causing congestion; 3. constraints cannot be taken into account; and 4. neither can dynamic link costs. These problems are addressed by adopting a novel ACO algorithm with stench pheromone and with colored ants, called Ant Colony Routing (ACR). Using the stench pheromone, the ACR algorithm can distribute the vehicles over the traffic network with less or no traffic congestion, as well as reduce the number of vehicles near some sensitive zones, such as hospitals and schools. With colored ants, the traffic flows for multiple origins and destinations can be represented. The proposed approach is also implemented in a simulation-based case study in the Walcheren area, the Netherlands, illustrating the effectiveness of the approach. 相似文献
73.
Transportation system capacity and performance, urban form and socio-demographics define the influences and constraints conditioning the preferences of urban residents for different transport modes. Changes in characteristics of urban areas are likely to lead to changes in preferences for alternative modes of transport over time; as a consequence, statistical models to forecast mode choice need to be sensitive to both purposeful changes to urban systems as well as exogenous shocks. We make use of the 1996, 2001 and 2006 household surveys conducted in the Greater Toronto and Hamilton Area to study mode preference evolution and model forecasting performance. These repeated cross-sectional household surveys provide an opportunity to investigate aggregate structural changes in commuting mode preferences over time, in a manner sensitive to changes in the urban area. We focus on commuting mode choices because these trips are prime determinants of peak period congestion and peak spreading. We then address how to combine the three cross-sections econometrically in a robust way that allows for use of a single mode choice model across the entire period. Using independent data from 2012, we are able to compare the individual year and combined models in terms of forecasting performance to demonstrate the combined model’s more robust forecasting performance into the future. 相似文献
74.
潘忠岐 《上海交通大学学报(哲学社会科学版)》2000,8(3):45-53
在人类进入21世纪之后,世界需要建立什么样的新秩序才能更好地服务于人类社会?这个问题激发了政治家和思想家们的极大兴趣,他们提出了各种各样的“理论”和“模式”。其中,较具代表性的有:“地球村”模式,世界政府模式,“和平区”与“动乱区”模式,“三大经济区”模式,“明冲突”模式,“单极霸权”或“单极主导下的多极合作”模式,两极或多极均势模式,等等。这些模式各以其独特的视角,试图勾勒出后冷战时代世界新秩序的“地图”。 相似文献
75.
顾建光 《上海交通大学学报(哲学社会科学版)》2000,8(3):97-100
在我国当前的经济建设中,城市面临着模式转型的过程,同时也面对着不断产生的一系列新矛盾和新要求。文章着重对此加以探讨,并就我国新时期城市功能的新定位提出了建设性意见。 相似文献
76.
Jungyong Wang Ayhan Akinturk Neil Bose Stephen J. Jones Yun Young Song Ho Hwan Chun Moon Chan Kim 《Journal of Marine Science and Technology》2008,13(3):244-255
The objective of this study was to investigate the performance of a model azimuthing podded propulsor in ice-covered water.
Model tests were carried out with two different depths of cut into the ice (15 and 35 mm), two different ice conditions (presawn
and pack ice conditions), and four different azimuthing angles. The depth of cut is the maximum penetration depth of the propeller
blade into the ice block. The 0.3-m-diameter model propeller was operated in a continuous ice milling condition. Ice loads
were measured by several sensors which were installed in various positions on the model. Six one-axis pancake-style load cells
on the top of the model measured the global loads and two six-component dynamometers were installed on the shaft to measure
the shaft loads. One six-component dynamometer was attached to the one of the propeller blades inside the hub to measure the
blade loads. The pod unit and propeller performance in ice are presented. Ice-related loads, which were obtained when the
blade was inside the ice block, are introduced and discussed. During the propeller–ice interaction, a blade can experience
the path generated by the previous blade, which is called the shadowing effect. The effects of shadowing, depth of cut, azimuthing
angle, and advance coefficient on propulsor performance are presented and discussed. 相似文献
77.
78.
《铁道标准设计通讯》2017,(12):10-13
轨道质量指数TQI为左高低、右高低、左轨向、右轨向、轨距、水平、三角坑各单项标准差的和。各单项项目的标准差直接体现了此项几何不平顺的输入能量,表现为此项几何不平顺的离散程度,当它的值越大时,表明轨道状态较差,对车辆的激励能量大。针对目前分段标准差计算方式不能完全反映轨道质量状态最差的区段、评判结果存在离散性等缺点,提出利用滑动标准差计算方式对轨道区段状态进行评价的方法。通过研究确定合适的计算长度200 m和移动步长20 m,并利用京沪线9~10月份检测数据进行试用,结果表明:滑动标准差不仅能够找到轨道质量状态最差的区段,还能找出更多超出管理值标准的区段,且在识别不良区段的起止位置(长度)和评判结果一致性方面,也明显好于目前的分段标准差计算方式。 相似文献
79.
80.
Empirical approaches to combining revealed and stated preference data: Some recent developments with reference to urban mode choice 总被引:1,自引:0,他引:1
David A. Hensher 《Research in Transportation Economics》2008,23(1):23-29
This paper replaces the nested logit ‘trick’ used in estimation of a modal choice model, when stated preference (SP) and revealed preference (RP) data are pooled, with an error component mixed logit model that can (i) relax the IID condition attached to subsets of alternatives in nested logit models, (ii) accommodate correlated observations, and (iii) reveal the relevant scale parameter for subsets of alternatives. Such a model can also incorporate state dependence between data types and preference heterogeneity on observed attributes. An example of choice among bus, train and car modes illustrates the difference in empirical evidence, especially elasticity outputs. 相似文献