Transshipment hub port selection for shipping carriers in a dual hub-port system

ABSTRACT

This paper investigates the factors affecting transshipment (T/S) hub port selection by a feeder port and helps shipping carriers make a decision about T/S hub port selection in a dual hub-port system. By employing established evaluation factors, a case study is conducted to weigh the priority of factors and to select an alternative T/S hub port, such as between the Shanghai and Ningbo ports from the Nanjing feeder port in the Yangtze River delta (YRD). A combined multi-criteria decision-making (MCDM) framework utilizing the analytic hierarchy process (AHP) and the consistent fuzzy preference relations (CFPR) method is employed to both reduce the number of pairwise comparisons by AHP and to obtain experts’ knowledge in the decision-making process. The result indicates that the cost, availability of hub port’s space allocation, and the connectivity between feeder port and hub port are crucial factors for T/S hub port selection by shipping carriers. In the case study, Shanghai is selected as the T/S hub port from the Nanjing feeder port. Nevertheless, Ningbo port has the advantage of cost, and if the relationship with feeder port can be improved, Ningbo port would be preferred over Shanghai as a T/S hub port for shipping carriers in a dual hub-port system.     

Monte Carlo Simulation of Electron Swarms Parameters in c-C4F8/CF4 Gas Mixtures

The swarm parametes for c-C4F8/CF4 mixtures, including the density-normalized effective ionization coefficient, drift velocity and mean energy were calculated using Monte-Carlo method with the null collision technique. The overall density-reduced electric field strength could be varied between 150 and 500 Td,while the c-C4F8 content in gas mixtures is varied in the range of 0-100%. The value of the density-normalize deffective ionization coefficient shows a strong dependence on the c-C4F8 content, becoming more electronegative as the content of c-C4F8 is increased. The drift velocity of c-C4F4/CF4 mixtures is more affected by CF4. The calculated limiting field strength for c-C4F8/CF4 mixtures is higher than that of SF6/CF4.     

Formalizing a subset of ERTMS/ETCS specifications for verification purposes

ERTMS is the standard railway control-command and signaling system which aims to ensure railway interoperability throughout Europe while enhancing safety and competitiveness. ERTMS is composed of two main subsystems which include GSM-R, a radio system for enabling communication between the train and the traffic management center and ETCS, an automatic train protection system (ATP) to replace the existing national ATP systems. The ERTMS specifications are defined by means of standard documents which set out the requirements ensuring interoperability. These documents evolve regularly to give rise to successive versions. The ERTMS/ETCS standard defines different levels and operation modes according to various trackside and onboard setups and some operational conditions. Given the complexity and the high criticality of railway operation, verification and validation (V&V) are crucial tasks in railway application development.In this paper, after setting the background and the motivations, a mechanizable formalization of a subset of ERTMS/ETCS specifications relative to ETCS modes and transitions is developed. The present work aims to offer a readily available model for formal V&V. Using formal techniques to check SRS is highly recommended to tackle the complexity of the defined requirements and prevent specification errors. Model-checking technique, which is targeted here, offers exhaustive analysis of the system behavior based on its model and is highly automated, since it is supported by software tools. Based on the last available version of SRS specifications, a progressive process is undertaken to get a formal model which makes explicit the various modes characterized by their respective active functions, as well as the numerous combinations of conditions for switching between modes. The various steps guiding the translation of the SRS literal specifications into a formal model are explained. As will be shown through different examples, the obtained model is a convenient basis to check safety, interoperability and liveness properties.     

可在线涂装的“碳纤维/钢”复合结构汽车B柱分总成的研发

为提高汽车安全性和轻量化水平,开发了一种可在线涂装的“碳纤维/钢”复合结构B柱分总成,该分总成包括钢制B柱加强板和碳纤维增强复合材料(CFRP)B柱中部支撑板,采用结构胶粘接而成。研究了真空袋压与热压罐成型工艺对CFRP层压板涂装前后性能的影响,并对“碳纤维/钢”的粘接强度、B柱分总成的刚度和强度等力学性能进行了研究,结果表明,复合结构B柱分总成在涂装前后的性能均优于传统钢制总成,CFRP中部支撑板减重64.1%。     

共享停车泊位的分配-定价-收益分配机制

为科学管理共享停车资源,构建一种共享停车泊位的分配-定价-收益分配机制。首先,以存在多个地块的区域为对象,根据出行者对不同地块及停车时间模式的选择偏好构建停车许可证的最优分配-定价模型,其中,最优分配模型为组合拍卖竞胜标确定问题(NP困难问题)。其次,利用Benders分解原理、对偶理论及新型升价拍卖代理系统构建调优法对停车许可证进行拍卖。最后,为调动共享泊位提供者的积极性,利用沙普利值法构建基于对社会福利贡献程度的停车收益分配模型。由理论分析及数值试验可知,运用上述机制可精确实现社会福利最优状态,最小竞争均衡价格与公平的收益分配。结果表明:①相较VCG机制与Leonard机制,调优法不仅可精确求解停车许可证的最优分配-定价,而且在算法最坏时间复杂度方面拥有更高效率;②在调优法的每个步骤中,即使停车许可证的分配并非最优,通过机制所实现的收费定价依然具有防止策略性操作的重要性质;③调优法可在较少的步骤之内实现较高的社会福利;④新型升价拍卖代理系统拥有多项式型的最坏时间复杂度;⑤通过最优分配-定价机制可获得每位出行者的选择偏好,进而可计算不同泊位提供者组合条件下的社会福利,实现沙普利值法在现实应用中的可计算性。     

挖掘机动臂结构模态分析

运用Pro/Mechanica软件对挖掘机动臂结构进行模态分析,得到了挖掘机动臂模态的各阶频率与振型及挖掘机动臂的模态频率与挖掘机发动机工作频率之间的关系;通过与针对性试验结果进行比较,验证了Pro/Mechanica结构分析结论的可靠度。     

战术数据链中的波形设计

波形设计是数据链系统设计的关键.深入剖析了国外几型战术数据链的波形设计思路,提出了战术数据链的波形设计原则,针对新型战术数据链的波形设计,给出了相应建议.     

用AT89C2051实现PS／2矩阵键盘的研究

在嵌入式PC应用系统中，作为人机交互设备的键盘往往采用结构简单，按键少的矩阵键盘。标准键盘虽然能直接与嵌入式PC的PS／2接口连接，但是体积大，按键多，不能满足要求。本文提出了一种用AT89C2051单片机实现具有标准PS／2接口的矩阵键盘，并给出了电路原理图和C51源程序。     

时速120 km地铁梯形轨枕轨道现场测试与分析

为详细评价速度120 km/h地铁中梯形轨枕轨道的减振效果,通过对某地铁线路现场测试的方法,在时域和频域内对比分析梯形轨枕轨道较普通长枕整体道床轨道的减振效果。结果表明:梯形轨枕轨道从振动根源处就得到了有效的减振且减振的效果较好。普通长枕整体道床轨道能有效减弱振动加速度从钢轨至道床的传播,但是从道床至隧道振动加速度的衰减效果要弱于梯形轨枕轨道。梯形轨枕轨道减振效果整体好于普通长枕整体道床轨道,且能有效地降低中高频段的噪声。     

客车前后顶三维造型设计及模型模具制作

简述利用UG软件进行客车前后顶的三维造型设计模型制作和模具翻制。