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Kjetil Fagerholt 《Maritime Policy and Management》2000,27(2):145-153
In many ship scheduling problems, time windows are imposed at the loading and/ or discharging of the cargoes to be lifted. Up until now, all proposed solution methods to ship scheduling problems have treated the time window constraints as hard constraints. By transforming the time window constraints into soft constraints, some of the loading/discharging operations may be performed outside the time windows, penalized by an inconvenience cost for not meeting the time window. The motivation behind introducing soft time windows is that, by allowing controlled time window violations for some customers, it may be possible to obtain better routes and significant reductions in the transportation costs. The purpose of this paper is to evaluate the trade-off between transportation costs and the time window violations. Computational results based on data from a real ship scheduling problem are presented and used as a basis for the evaluation. 相似文献
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《Maritime Policy and Management》2012,39(8):995-1010
ABSTRACTCombining ro-ro shipping and tractor-and-semitrailer swap transport under land-sea combined transportation can reduce operating costs and improve the safety of maritime transport. In addition, selection of the tractor-and-semitrailer swap mode (i.e., the ship-swap mode and port-swap mode) is a critical factor that affects the efficiency and cost of ro-ro ship loading/unloading. Considering inland pickup/delivery and ship loading/unloading, this paper develops a model that determines the mode of tractor-and-semitrailer swap transport with the objective of minimizing the total cost. This study also considers constraints such as empty semitrailer exchange and multiple time windows associated with customer receiving/delivery locations and the ro-ro ship. A hybrid simulated annealing (SA) is applied to solve the problem. By analysing numerical examples, the results show that the port-swap mode is more suitable than the ship-swap mode when the number of tasks is large because the port-swap mode can perform more tasks with fewer tractors than the ship-swap mode and because the port-swap mode can service receiving/delivery locations and finish ship loading/unloading more punctually than the ship-swap mode. Thus, this research provides a useful reference for road transport carriers and port firms to select the mode of tractor-and-semitrailer swap transport for ro-ro shipping. 相似文献
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Tiago A. Santos 《Maritime Policy and Management》2017,44(7):859-881
A novel methodology is developed for determining the characteristics of a cargo roll-on/roll-off (ro-ro) ship and the fleet size required for a given short sea shipping route. The ship and required fleet size to satisfy the transportation demand (for each pair of speed and freight rate) are determined using a database of existing cargo ro-ro ships to obtain the main technical characteristics of the most suitable ship. The time charter, voyage costs and revenue are then calculated considering the technical characteristics of each ship. Fuel costs are corrected for the actual ship speed and loading condition. A number of restrictions in the transportation problem are considered leading to the exclusion of unfeasible solutions. The maximum profit over the period of a year is identified among the feasible pairs of speed and freight rate. This general methodology is applied in a case study that considers the route between Leixões (Portugal) and Rotterdam (Netherlands). The study allows the identification of the most suitable ship and fleet sizes for different market penetration levels and quantifies the impact on shipping company profit of changes in parameters such as fuel costs, time charter costs, emission control area, installed propulsion power and stacking factor. 相似文献
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High load-carrying capacity of ship windows is important for ship safety. This aspect has recently become significant after several incidents with broken windows in superstructures had occurred. In order to get more insight into the failure behavior and into the interaction between glass windows and surrounding wall structure, experiments and numerical investigations of windows subjected to quasi-static as well as impact loads were performed. In this paper quasi-static ultimate load tests with full-scale test models, each containing a clamped or bonded laminated safety glass window, are described. Finite element modeling of the steel structure, laminated glass, and elastomer bonding or gasket is outlined in detail. Material data are based on small-scale tests of steel and glass specimens, and on published data. Afterwards a method to calculate failure probabilities of glass panes under pressure loads is presented. Failure probabilities for the glass panes in the tests are determined and failure mechanisms are clarified. Finally, hints for designing safe windows and for improving window designs are given. 相似文献
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某轮主机进入高负荷运行,达到某一负荷时会突然出现冷却水压力波动。故障现象及原因都比较特殊。通过对这一故障的分析及处理,发现了船舶管理中存在的一些问题。本文对此进行了论述。以利同行借鉴。同时提出了提高船舶管理水平的有益建议。 相似文献
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为了提高船舶中小组立等中间产品建造作业调度能力,提升船舶建造效率,提出面向多约束的船舶组立建造作业调度方法。首先,分析船舶组立建造的工艺流程和作业调度方法,综合考虑机器小组、工艺和交货期等多种约束条件,以建造周期最短为调度目标,建立船舶组立建造作业调度数学模型;其次,综合运用算法分解策略及调度规则,设计改进的最短作业优先调度算法实现模型求解;最后,以某船厂建造车间一定生产周期(17天)的中小组立先行中日程计划为对象,验证该方法的有效性和实用性。研究结果表明,所提出的面向多约束的船舶组立建造作业调度方法相较于当前的调度方法,排产周期压缩22小时,即缩短了原有周期的16.18%,有效提高了生产计划排产和作业调度效率。 相似文献
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船体结构腐蚀模型对检测及维修规划的影响 总被引:1,自引:0,他引:1
提出了基于风险的船体结构腐蚀优化检测及维修的基本理论框架.最优的检测及维修,是在保证结构在设计工作寿命内的可靠指标大于最低可靠指标的基础上,使结构生命周期内总的期望费用最小.建立了检测、维修及失效事件的安全余量方程,推导了失效及维修概率的计算公式.在此基础上,以船体结构两种常用的腐蚀模型Paik模型和Guedes Soares模型为例,分析了两种模型对最优检测及维修策略的影响.其结果表明,腐蚀模型对最优的检测及维修次数和时间有明显的影响,但是对总的期望费用及失效概率影响不大,而且两种腐蚀模型得出的最优失效概率都是10-3. 相似文献
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Kjetil Fagerholt 《Maritime Policy and Management》2004,31(4):259-268
A real liner shipping problem of deciding optimal weekly routes for a given fleet of ships is considered and a solution method for solving the problem is proposed. First, all feasible routes for each ship are generated together with the cost and the duration for each route. The routes are given as input to an integer programming (IP) problem. By solving the IP problem, routes for each ship are selected such that total transportation costs are minimized and the demand at each port is satisfied. The total duration for the routes that are selected for a given ship must not exceed one week.
The real liner shipping problem is solved together with four randomly generated test problems. The computational results show that proposed solution method is suitable for designing optimal routes in several liner shipping problems. 相似文献
The real liner shipping problem is solved together with four randomly generated test problems. The computational results show that proposed solution method is suitable for designing optimal routes in several liner shipping problems. 相似文献
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Tianhang Gao 《Maritime Policy and Management》2013,40(6):669-686
ABSTRACTStraits and canals have always served as key nodes in shipping networks. The blockage of a strait or canal will lead to ship deviations and increased transportation costs. To measure this impact on the Chinese fleet, our study develops a mathematical model that is based on a programming formulation. Each strait or canal is assumed to be blocked in turn, and the increased transportation costs for the Chinese fleet in different scenarios are calculated and compared using the proposed programming formulation in order to measure the impact of the blocked strait or canal on the Chinese fleet. Larger increases in transportation costs have greater impacts on the fleet. The results show that a blockage of the Strait of Hormuz would have the greatest impact of all straits and canals; it would cause the Chinese fleet to lose a portion of its import and export market, and such a blockage cannot be addressed through ship deviations. Based upon increased transportation costs, the four straits or canals that would have the greatest impact if blocked are the Mandeb Strait, the Suez Canal, the Sunda Strait and the English Channel. 相似文献
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The planning, design and development of a container terminal with optimum size and capacity and with a minimum capital cost
is fundamentally dependent upon the loading and discharging operations at the quayside. The quayside function of container
terminals is dependent basically on the number of berths available to service the incoming container ships. The objective
of the container terminals dealing and admitting the ongoing ship calls is to provide immediate berth and loading and discharging
services to the container ships with a minimum costly waiting time and a maximum efficiency. Previously terminal planners
used to build extra berths to provide service. During the last two decades the terminal operators have adopted automation
technologies in loading and discharging operation of the container ships as an alternative to designing extra berths. Ship
owners naturally expect least waiting times for their container ships. On the other hand, it is also natural for port operators
in a container terminal with costly facilities to see a high berth occupancy and productivity at the quayside. This study
uses queuing theory to find a break-even point as a way of evaluating the cost of container ship waiting times and the cost
of berth unproductive service times for container terminals aiming to automate their quayside operation. The analysis illustrates
that automation devices installed on conventional Quayside Cranes (QSCs) significantly reduce the turnaround time of the container
ships calling at the ports. It argues, however, that there should be a balance between the cost of berth unproductive service
times and the cost of vessel waiting times. The study introduces a break-even point to be considered as a benchmark for calculating
such a balance. The analysis in this study can be used as a decision tool for the operators of container terminals in the
medium to small ports to appraise the feasibility of an investment in automation or expansion of the quayside facilities. 相似文献
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使用抓斗负荷16 t以下门机用于港口镍矿卸船作业的属具和工艺研究较为深入,使用30 t和40 t门机进行卸船时若属具仍旧采用铁矿抓斗,斗容小影响每钩镍矿抓取量并且镍矿严重粘斗,降低了船舶接卸效率,结合公司属具保有情况和镍矿作业适宜斗容,提出了抓斗兼容使用设计思路,在现有属具基础上进行结构改进,使镍矿在斗内淤积现象得到消除,改进后船舶综合作业效率由1 200 t/h左右提高到1 400 t/h以上,最高达到1 583t,使卸载5万t镍矿船舶时间控制在40 h内,提高了在港船舶的周转频率,同时,该改进设计可用于含水量高容易粘斗的铁矿作业中,具有良好的推广应用价值。 相似文献
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资源受限的造船生产计划编制专家系统 总被引:7,自引:0,他引:7
采用RCPSP模型和方法研究资源受限的工程计划方法在造船生产计划制定中的应用.利用专家系统开发工具,根据造船生产流程和生产资源约束条件,可实现船体结构生产装配计划制定的自动化.开发了一个原型系统,可以给出合理的满足造船厂生产场地面积、起重能力、人力及生产设备等生产资源限制的造船生产计划.还可以提供造船生产效率、生产资源利用率等生产管理信息.为实现造船生产流程和生产计划编制集成化、自动化提供了一个可行方法,有助于进一步实现从设计到制造的信息集成. 相似文献