A hybrid parallel genetic algorithm for yard crane scheduling

This paper aims at postulating a novel strategy in terms of yard crane scheduling. In this study, a dynamic scheduling model using objective programming for yard cranes is initially developed based on rolling-horizon approach. To resolve the NP-complete problem regarding the yard crane scheduling, a hybrid algorithm, which employs heuristic rules and parallel genetic algorithm (PGA), is then employed. Then a simulation model is developed for evaluating this approach. Finally, numerical experiments on a specific container terminal yard are used for system illustration. Computational results suggest that the proposed method is able to solve the problem efficiently.     

A polynomial-time heuristic for the quay crane double-cycling problem with internal-reshuffling operations

One of great challenges in seaport management is how to handle containers under reshuffling, called reshuffles. Repositioning reshuffles in a bay (internal reshuffling) can improve the efficiency of quay cranes and help ports to reduce ship turn-around time. This paper studies the quay crane double-cycling problem with internal-reshuffling operations, and presents a fast solution algorithm. To reduce the number of operations necessary to turn around a bay of a vessel, the problem is first formulated as a new integer program. A polynomial-time heuristic is then developed. The analysis is made on the worst-case error bound of the proposed algorithm. Results are presented for a suite of combinations of problem instances with different bay sizes and workload scenarios. Comparisons are made between our algorithm and the start-of-the-art heuristic. The computational results demonstrate that our model can be solved more efficiently with CPLEX than the model proposed by Meisel and Wichmann (2010), and the proposed algorithm can well solve real-world problem instances within several seconds.     

A robust optimization approach to the integrated berth allocation and quay crane assignment problem

This paper investigates the integrated berth allocation and quay crane assignment problem in container terminals. A deterministic model is formulated by considering the setup time of quay cranes. However, data uncertainties widely exist, and it may cause the deterministic solution to be infeasible. To handle the uncertainties, a robust optimization model is established. Furthermore, to control the level of conservativeness, another robust optimization model with the price constraints is proposed. A genetic algorithm and an insertion heuristic algorithm are suggested to obtain near optimal solutions. Computational experiments indicate that the presented models and algorithms are effective to solve the problems.     

Optimizing the block size in container yards

A block is the basic unit of storage space in container terminals. This study proposes two methods for optimizing the block size, by considering the throughput requirements of yard cranes (YCs) and the block storage requirements. To estimate the YC performance, cycle-time models of various handling operations of YCs are analytically derived. Two types of container yards are examined: those with blocks that are laid out parallel to the quay and those laid out vertical to the quay.     

Heuristics for the integration of crane productivity in the berth allocation problem

In this paper, the combined problem of berth allocation and crane assignment in container terminals is investigated. The proposed problem formulation includes important real world aspects such as the decrease of marginal productivity of quay cranes assigned to a vessel and the increase in handling time if vessels are not berthed at their desired position at the quay. To solve the problem a construction heuristic, local refinement procedures, and two meta-heuristics are presented. These methods perform well on a set of real world like instances. The results emphasize the important role of quay crane productivity in berth planning.     

Effect of block width and storage yard layout on marine container terminal performance

Block widths ranging from two to fifteen rows in a marine container terminal are evaluated by a fully-integrated, discrete event simulation model. Experiments consider dozens of yard configurations and four container terminal settings that are designed to reproduce the microscopic, stochastic, real-time environment at a multiple-berth facility. Results show that the quay crane rate is concave with respect to block width when the yard storage capacity and amount of yard equipment is constant. The optimal block width ranges from 6 to 12 rows depending on the amount of equipment deployed and the size, shape, and throughput of the terminal.     

Prospects for shared electric velomobility: Profiling potential adopters at a multi-campus university

Electric velomobility (e-velomobility) encompasses human movement using electric-assisted bicycles (pedelecs, or e-bikes), and the associated practices, systems and technologies. It is emerging as an active mode in developed economies. Electric bicycle sharing (EBS) schemes can attain higher per-vehicle use time and provide more equitable access than personal ownership. University campuses are ideal testing beds for such systems as young and lower-income groups are present there. The goal of this study is to understand the segmentation of the market for a hypothetical electric bicycle sharing scheme located in a multi-campus university. A cross-sectional survey was conducted at a multi-campus university in South East Queensland, Australia. Motives, reasons, and intention of students and staff for potential future use of a potential campus-based EBS scheme were revealed. Three distinctive potential user groups with varied modal, socio-demographic, and psychological characteristics emerged in the clustering analysis, namely: “multimodal enthusiasts” (28%), “car-loving pragmatics” (46%), and “car-loving skeptics” (26%). We identify the key market segments and potential adopters' demographics (residential location, country of origin, income, and academic major). Our results indicate that respondents who are more multimodal, especially those cycling often and with shared mobility experiences, are more positive about using e-bike sharing. Largely mono-modal car users tend to be more negative toward the scheme. International students also tend to be more positive. The individual preferences and attitudes toward campus-based shared e-velomobility, as revealed in this paper, provide important insights for planners, policymakers and sharing operators seeking to launch or improve uptake of such schemes.     

Modeling the mixed storage strategy for quay crane double cycling in container terminals

A mixed storage strategy was proposed to improve the efficiency of yard operations and horizontal transportation to corporate with quay crane double cycling. The effects of the mixed storage strategy on terminal operations, including truck travel distance, yard crane operations and the number of required trucks, were analyzed. An approach based on cycle-time models, the queuing theory was proposed to evaluate the performances from long-term run. Results show using the mixed storage strategy, the truck travel distance can be decreased and the number of required trucks and yard crane’s operation time can be reduced by 16% and 26% respectively.     

Determining fixed crane areas in rail–rail transshipment yards

To enable rapid container transshipment between freight trains in modern rail–rail transshipment yards efficient computerized scheduling procedures are indispensable. This paper proposes a dynamic programming approach, which determines yard areas for gantry cranes, so that the workload is evenly spread among cranes and, thus, train processing is accelerated. In a straightforward simulation of transshipment yard operations, the effect of optimal crane areas vs. equally sized areas is studied, the latter being a common real-world policy. The results indicate a remarkable speed-up of train processing if optimal crane areas are applied.     

Optimization of loading sequence and rehandling strategy for multi-quay crane operations in container terminals

In this paper, we consider the optimization of loading sequence and rehandling strategy in the terminal operation. We present an optimization strategy to minimize the number of rehandles, and establish a mathematical model to integrate the loading sequence and the rehandling strategy under the parallel operation of multi-quay cranes. Furthermore, we give an improved genetic algorithm to solve the model. We show the efficiency of the optimization strategy and algorithm by comparing them with previous strategies and heuristics.     

进路搜索的数据结构与算法及其仿真

对铁路车站计算机联锁中的进路搜索,提出基于站场数据结构的进路自动生成搜索算法。在确定对象节点数据结构的基础上,给出了进路搜索算法的步骤。同时将站场设计功能也包含在程序中,进而可以虚拟出各种不同的站场,根据实验选择不同的进路始点和终点,可达到良好的仿真效果。     

德国柏林中央客运站铁路车场设置及作业方式研究

德国柏林中央客运站集高速铁路、普速铁路、城市快轨和地铁于一体,日接发列车1300多列,是欧洲铁路网中重要的客运枢纽。柏林铁路枢纽的东西线和南北线在该站交汇,东西线方向设有2个独立的铁路车场,南北线方向设有1个共用的铁路车场,3个铁路车场均为贯通式布置。为提高车站接发车能力,该站主要办理通过列车,兼有部分始发终到列车。每个车场设置各有特点,列车作业组织紧凑有序,到发线利用率高。柏林站车场设置及作业方式可以作为大型铁路枢纽车站设计与作业组织的典型案例。     

A model for taxi pooling with stochastic vehicle travel times

Taxi pooling means the sharing of a taxi by more than one passenger with at least a semi-common route. Currently, a trial-and-error process is adopted, taking into account expected travel times, for taxi pooling, a method which is neither effective nor efficient. This is because stochastic disturbances arising from variations in the taxi travel times that occur in actual traveling are neglected. In the worst case scenario, where vehicle travel times fluctuate wildly during operations, the planned schedule can be disturbed enough to lose its optimality. Therefore, in this study, a network flow technique is used to construct a stochastic taxi pooling model incorporating stochastic vehicle travel times. A solution algorithm is also proposed to efficiently solve the problem. The performance of the proposed models and the use of the solution method in practice are evaluated by executing numerical tests using real data with suitable assumptions. The test results show that the stochastic model and the solution method could be useful references for practice.     

Terminal and yard allocation problem for a container transshipment hub with multiple terminals

This paper presents an integer programming model for the terminal and yard allocation problem in a large container transshipment hub with multiple terminals. The model integrates two decisions: terminal allocation for vessels and yard allocation for transshipment container movements within a terminal as well as between terminals. The objective function aims to minimize the total inter-terminal and intra-terminal handling costs generated by transshipment flows. To solve the problem, we develop a 2-level heuristic algorithm to obtain high quality solutions in an efficient way. Computational experiments show the effectiveness of the proposed approach.     

Port multi-service congestion

Port multi-service congestion occurs when port users of two or more different services (i.e., multi-services) provided at the same port node or over the same port link interfere with one another to the extent that they experience service congestion at the shared node or over the shared link. Container port nodes shared in the provision of port multi-services include, for example, the berth and yard. Container port links shared in the provision of port multi-services include, for example, the yard-to-departure-gate link, entrance-gate-to-yard link, berth-to-yard link and yard-to-berth link. If port multi-service congestion exists at a port node (or over a port link), then port multi-service congestion can be propagated to other port nodes and links in the port as long as there is a connecting path.     

Contribution to the study of PPP arrangements in airport development,management and operation

Following the liberalization wave in the airline sector, airports have been gradually taken out of the public sphere and open to the private initiative. This phenomenon is generally referred to as privatization, but not all the cases consist of, in fact, a full divestiture of assets. Although infrastructure management is undertaken by the private sector during a pre-defined period, usually 30 years or more, the property remains public or is transferred to the public domain after that period. This is a form of Public–Private Partnership (PPP) where two different models can be found: institutionalized PPP or a typical contractual regime, such as the concession arrangements. PPP options have been a “hot” topic over the last decade, but few studies can be found in the literature on the PPP projects development in airport systems, for example, as far as risk sharing is concerned. This paper looks at recent developments in airport “privatization”, distinguishing privatizations from PPP arrangements, through a case study approach, and establishing a comparative analysis of different PPP models used for airport management. Some comments are made about the Portuguese model and the announcement of future privatization.     

Integrating berth allocation and quay crane assignments

In this study, a dynamic allocation model using objective programming for berth allocation and quay crane assignments was preliminarily developed based on rolling-horizon approach. Afterwards, a hybrid parallel genetic algorithm (HPGA), which combined parallel genetic algorithm (PGA) and heuristic algorithm, was employed to resolve the proposed model. Furthermore, a simulation was conducted to evaluate the HPGA and to execute relevant gene repair techniques. Eventually, the numerical experiments on a specific container terminal were applied to illustrate the proposed models and algorithms. In so doing, the effectiveness of the proposed approach was verified.     

Variable neighborhood search heuristic for storage location assignment and storage/retrieval scheduling under shared storage in multi-shuttle automated storage/retrieval systems

This paper examines the joint optimization of storage location assignment and storage/retrieval scheduling in multi-shuttle automated storage/retrieval systems (AS/RSs) under shared storage, in which the reuse of empty location yielded by retrieval operation is allowed. From the view of analytical model, the advantage of operational mode under shared storage is verified. A variable neighborhood search (VNS) algorithm is developed to solve the large-sized problems. Various numerical experiments are conducted to evaluate the performance of the proposed algorithm and investigate the impact of different parameters on computational efficiency.     

A heuristic algorithm for yard truck scheduling and storage allocation problems

The yard truck scheduling and the storage allocation are two important decision problems affecting the efficiency of container terminal operations. This paper proposes a novel approach that integrates these two problems into a whole. The objective is to minimize the weighted sum of total delay of requests and the total travel time of yard trucks. Due to the intractability of the proposed problem, a hybrid insertion algorithm is designed for effective problem solutions. Computational experiments are conducted to examine the key factors of the problem and the performance of the proposed heuristic algorithm.     

An operations research model for the evaluation of an airport terminal: SLAM (simple landside aggregate model)

The Simple Landside Aggregate Model (SLAM) is a model for estimating capacity and delays in airport passenger terminals. SLAM is designed to answer “what if” questions about alternative configurations of the various processing and holding facilities in a terminal. It consists of a network of modules, one for each facility of the terminal. These modules are based on a set of quite simple mathematical formulas to be used for the estimation of the capacity of each facility (in terms of passengers per hour) and the level of service (LOS) associated with it. LOS is quantified both in terms of “space available per facility occupant” and waiting time for being processed.