基于模拟器试验超大型集装箱船弯曲航宽研究

运用船舶操纵模拟器模拟试验的方法,通过分析风、流压差角等参数对超大型集装箱船航迹带宽度的影响,提出了超大型集装箱船通过弯曲航道时所需航道宽度的计算方法.     

基于排队延误模型的干线协调控制配时方法

利用有限元排队模型分析信号控制交叉口排队队长与交叉口通行能力、排队延误间的相互关系,在此基础上建立交通高峰期干线协调控制的混合线性规划模型,对干线协调控制的配时参数与相位时序进行优化设计,采用实例验证,该方法能够使干线道路的通过能力和平均延误得到良好改善。     

慢即是快——紧凑道路设计思路

按照联邦州际高速公路系统设定的标准修建、扩容快速路耗资巨大,且对环境产生不利影响.然而由于交通拥堵,仅有少数出行者才能体验到快速驾驶的优势.探讨了道路设计的另一种思路——设计更紧凑的道路,或者说车道数更多但车道宽度更窄的道路.对比常规设计和紧凑设计两种思路下快速路车速、通行能力、行程时间指标,结果显示在高峰时段车辆排队严重时,紧凑设计具有较明显的优势.由于紧凑设计对道路安全性的影响尚未定论,建议设置更低的限速并采取措施禁止超速行为.最后指出,紧凑设计可增加道路通行能力以缓解交通拥堵,因此其适用范围得到扩展.     

Towards improved port capacity investment decisions under uncertainty: a real options approach

ABSTRACT

Port activity plays an important role in facilitating international trade. Sufficient capacity is indispensable for a port to attract flows to a region and retain them. The capacity decision is the result of a trade-off between investment and waiting costs. Traditional methods to value expansion projects do not deal adequately with managerial flexibility in the face of uncertainty from different sources in the complex port environment. In this paper, real options (RO) models are identified as an alternative method to making project valuations and investment decisions, as they attribute the correct value to managerial flexibility under uncertainty. In order to be able to build and use such RO models for port capacity investment decisions, the sources and implications of uncertainty in the port and the different RO model specifications need to be understood. To this end, both the literature about uncertainty in the port context and the literature about real options models are reviewed in order to provide researchers who want to build their own decision-making models, with the necessary knowledge of both fields. The review makes clear that the complex interactions in and competition between the logistics chains and their actors coming together in ports have significant impacts on port capacity. Uncertainty is also caused by uncertain international trade flows and changes in legislation following new technologies and environmental impacts. An analysis of the components of some general RO models shows how the options of flexible output, investment size and timing are valued by RO models in a setting with demand uncertainty. Moreover, the review presents researchers with insights in how to deal with cooperative and competitive interactions in the chain, time to build, cyclical markets and legislation changes. It also shows how to value the expansion and the phased investment options. The new insights resulting from this review are subsequently combined in a framework that serves as a guideline to build RO models for port capacity investments. Finally, an exemplifying application of the framework is used to build an actual port capacity investment decision model.     

Synchronized Production and Transportation Planning Using Subcontracted Vehicles in a Production-Distribution Network

Abstract

Effective management of interfaces between procurement, supply, production and distribution for higher efficiency in the supply chain is an important issue in global manufacturing, where the synchronization of production and transportation planning represents important savings in operational costs. This paper focuses on the synchronization of production planning and transportation planning in a production distribution network, where transportation is subcontracted to a professional transportation enterprise (PTE) for vehicle-hiring. Dynamic and flexible numbers of vehicles are used to cater for fast changing market demands. Thus, the number of vehicles to be hired is viewed from the planning point of view as an operational decision considered simultaneously with production and transportation planning. A mathematical model – SPTP/MTDS – for synchronized production and transportation planning under multiple times and direct shipping strategy (MTDS) is discussed, and a Lagrange relaxation decomposition-based two layer decision procedure (LRD-TLDP) is developed. By introducing artificial decision variables and Lagrange multipliers, SPTP/MTDS is decomposed into a production decision sub-problem (SPTP-PD), and a distribution decision sub-problem (SPTP-DD). A priority-based assignment heuristic and a partial chain-based genetic algorithm are developed to solve SPTP-PD and SPTP-DD, respectively. An illustration of the application of the model in an electronic appliance manufacturing enterprise in China is presented.     

Reduced dwell times resulting from train–platform improvements: the costs and benefits of improving passenger accessibility to metro trains

Abstract

This paper examines whether a dwell time reduction on a high-intensity metro service, as a result of a series of accessibility enhancements, can contribute to an increased level of service and accessible public transport for passengers together with a reduction in costs for the operator. Actual train operation data were collected by on-site observations and from London Underground Ltd. A simple simulation is built to represent the effect on the overall cycle times of trains if certain parameters (e.g. dwell time) are changed. Four models are developed, concerning: (1) step height between train and platform, (2) an assumption of passenger service time to be no longer than 20 s, (3) door width and (4) the combination of step height and door width. From the application of the models it appears that the fourth model provides the highest reduction in dwell time and diminishes the overall cycle times of trains. However, it is the most expensive to implement as it requires work to raise platforms and the purchase of new rolling stock.     

A railway capacity determination model and rail access charging methodologies

This article discusses approaches to the determination of railway capacity and the significance of the following factors on capacity: mix of trains, length and weight of trains, direction of train travel, acceleration and deceleration, stopping protocols of trains, location and length of crossing loops, location of signals, length of sections, dwell times and sectional running times. A more accurate method to calculate railway capacity is developed using previously unaddressed aspects for capacity determination. Capacity and pricing are two key issues for organizations involved with open track access regimes. A train access charging methodology is therefore developed and incorporated into a railway capacity determination model.     

降凝剂在低输量管线中的应用

低输量输油管道运行风险大,且无法通过调整输送工艺从根本上降低运行风险.降凝剂被认为是解决该问题的有效手段之一.文中阐述了降凝剂对原油的作用机理和其在输油管道上的实际应用效果,分析了在任丘-北京输油管线开展的降凝剂应用试验,通过对比试验结果,可以得出：降凝剂改善了油品凝点、黏度等物理性质,降低了低输量管线的运行风险,提高了管线运营的经济效益.     

冻结法开挖水下隧道横通道初探

文章基于冻结法的基本理论,以某水下盾构隧道横通道工程为例,采用大型有限元软件,分析比较了直墙式和曲墙式冻结帷幕的力学性能,设计、验证了能形成曲墙式冻结帷幕的冻结管布置方式。     

近距离低净空下地下连续墙成槽技术研究和探讨

以深圳地铁9号线人民南站地下连续墙成槽技术为例,探讨在近距离及低净空作业条件下采用低净空成槽及吊装设备结合钢筋笼分段下放连接的方法,辅以槽段稳定及临近建(构)筑物的保护措施来实施地下连续墙的相关手段,解决在受限空间内实施深基坑作业的技术问题。相关分析及实施结果表明,施工方案是切实可行及安全可靠的。