Facility layout problem (FLP) is an optimization problem of placing given facilities in a specific space to minimize overall logistics transportation cost or maximize its efficiency. Unequal area FLP (UA-FLP) means the layout design problem in that each facility has a different area. This study provides the performance of the modified coral reefs optimization on UA-FLP through experiments. Coral reefs optimization (CRO) is relatively new, and few studies have applied this method to layout design. There are two ways of placing facilities. One is flexible bay structure (FBS) and the other is slicing tree structure (STS). STS is known as a more difficult method than FBS. There have been no studies combining coral reefs optimization with slicing tree structure. By applying levy-flight to coral reefs optimization, it can easily escape from the local minima, and by applying an iterated local search method, the solution has been easily strengthened. We experimented with cases taken from previous literature and compared the results with either the optimal or best-known solutions from those studies. As a result, the problems of 7, 8, 9, 12, 20, 30 facilities were effectively addressed, and especially, AB20 and SC30 were found to have a better objective function value than previous studies.

Yard crane (YC) operations are critical to the overall productivity of container terminals, especially as terminals move toward higher levels of automation. This study proposes a score-based dispatching strategy for twin RTGCs operating within a single yard block. The proposed logic evaluates each job using four factors—distance between crane and job, job waiting time, estimated processing time, and an elasticity term inspired by spring mechanics that reflects the tendency of each crane to stay within its preferred working zone. These factors are normalized and combined into a single score, and the corresponding weights are optimized by a genetic algorithm (GA). Jobs with lower scores are given higher priority for assignment. A discrete-event simulation model of a twin RTGC system is developed using AutoMod® to assess the performance of the proposed strategy. The score-based rule is compared with conventional dispatching policies such as First-Come-First-Served (FCFS), Nearest-First-Served (NFS), and their weighted combination under various workload scenarios. Relative to the score-based strategy without elasticity, the inclusion of the elasticity term reduces average and maximum truck turnaround time by 7.51% and 7.79%, respectively; these improvements translate into higher yard throughput and strengthen the advantage over the benchmark dispatching rules. In particular, the elasticity term effectively mitigates crane interference while maintaining a balanced spatial distribution of work between the two cranes. These findings indicate that the proposed dispatching logic provides a practical and implementable control strategy for retrofitting existing RTGC systems and integrating them into terminal operating systems.

The facility layout problem (FLP) has been a prominent subject of research due to its practical significance and computational complexity. In the course of our study, we explored widely used benchmark problems and observed significant discrepancies in the reported outcomes for one particular instance, AB20. A prior study reported exceptionally good results on this problem, prompting further investigation. Our analysis revealed that, unlike other benchmarks, AB20 exhibits considerable variation in results due to inconsistencies in the underlying dataset, despite being referenced by the same name across multiple studies. This lack of standardization undermines the comparability of results and may lead to misleading conclusions. In this work, we systematically review previous studies that employed the AB20 benchmark and evaluate the consistency of the datasets used. Based on our findings, we propose guidelines to promote fair and reproducible benchmarking practices in FLP research. The study highlights the need for greater transparency and standardized datasets to ensure valid comparisons across future work.

Self-driving technology is on the verge of commercialization and is expected to be utilized in delivery services. At the same time, low efficiency and physical limitations of last mile robots (especially for non-standardized cargo, stairs, etc.) are being pointed out. In addition, as leading overseas companies design robots to complete delivery through interaction with the recipient, it may be difficult to implement the robots in delivery environments like South Korea, where most parcels are not delivered face-to-face. Therefore, this study considers a parcel delivery model in which a person, not a robot, is on-board an autonomous truck for door-to-door deliveries. This study takes three expected effects of a self-driving vehicle into consideration: (i) reduced travel time, owing to alleviation of traffic congestion; (ii) reduced service time, owing to relaxed parking restrictions; and (iii) benefits from en route preparation (planning and collecting in advance of arrival) that can be realized when a person is not required in the driver's seat. The findings from a case study conducted in Seoul indicate that advanced self-driving capabilities and en route preparation can potentially lead to a doubling of the delivery capacity at a terminal, along with a reduction of over 40% in operating costs per box. As suggested in this study, the en route preparation activities are verified to bring benefits.

The vehicle routing problem (VRP) attempts to find optimal (minimum length) routes for a set of vehicles visiting a set of locations. Solving a VRP calls for a cost matrix between locations. The size of the matrix grows quadratically with an increasing number of locations, restricting large-sized VRPs from being solved in a reasonable amount of time. The time needed to obtain a cost matrix is expensive when routing engines are used, which solve shortest path problems in the back end. In fact, details on the shortest path are redundant; only distance or time values are necessary for VRPs. In this study, an artificial neural network (ANN) that receives two geo-coordinates as input and provides estimated cost (distance and time) as output is trained. The trained ANN model was able to estimate with a mean absolute percentage error of 7.68%, surpassing the quality of 13.2% with a simple regression model on Euclidean distance. The possibility of using a trained model in VRPs is examined with different implementation scenarios. The experimental results with VRPs confirm that using ANN estimation instead of Euclidean distance produces a better solution, which is verified to be statistically significant. The results also suggest that an ANN can be a better choice than routing engines when the trade-off between response time and solution quality is considered.

In this study, a system constituting an integral part of a continuous sequence of operations or machines in a line is presented as a form of "in-line" system.Due to the sequential nature of the production line, the throughput rate of the line depends on the slowest process.This paper presents one example of an in-line system that is used for pallet re-use by sorting, washing, and drying in a continuous processing line.Basically, a well-structured in-line system provides high throughput because of the non-stop flow of materials in the system.However, there is a hidden loss in the system efficiency.The object of this paper is to evaluate some of the possible alternatives to solve these hidden inefficiency problems and to improve throughputs through simulated models.The three outcomes from this simulation indicate that exchanging the robotic arm with a sorter and adding additional spin-drying machines could reduce overhead costs and the average waiting time for the spin-drying machine and improve the utilization of the resources in the washing process.

Unequal area facility layout problems deal with the placement of departments in a particular area. In these problems, unsettled rectangular-shaped blocks with an aspect ratio limitation are arranged in a given space. This has been widely studied for facility planning design and operating efficiency. Therefore, many metaheuristic approaches have been suggested to determine optimal solutions. In this study, monarch butterfly optimization, a recently developed algorithm, is presented to solve an unequal area facility layout problem. A slicing tree representation is used to form a layout structure as well as greedy acceptance, which accelerates the monarch butterfly optimization’s search performance. A set of well-known instances from existing studies is tested to evaluate the algorithm’s effectiveness. Meaningful results are obtained from various categories. The proposed algorithm generates solutions that match the best results from previous research, and it provides such solutions within a comparable amount of time.

Despite their importance, relatively little attention has been paid to vehicle routing problems with asymmetric costs (ACVRPs), or their benchmark instances. Taking advantage of recent advances in map application programming interfaces (APIs) and shared spatial data, this paper proposes new realistic sets of ACVRP benchmark instances. The spatial data of urban distribution centers, postal hubs, large shopping malls, residential complexes, restaurant businesses and convenience stores are used. To create distance and time matrices, the T map API, one of the most frequently used real time path analysis and distance measurement tools in Korea, is used. This paper also analyzes some important issues prevailing in urban transportation environments. These include the challenges of accounting for the frequency and distance in which air travel differs from reality when measuring closeness, the differences in distance and time for outgoing and return trips, and the rough conversion ratios from air distance to road distance and to road time. This paper contributes to the research community by providing more realistic ACVRP benchmark instances that reflect urban transportation environments. In addition, the cost matrix analyses provide insights into the behaviors of urban road networks.

Path planning for mobile agents is one of the areas that has drawn the attention of researchers’, as evidenced in the large number of papers related to the collision-free path planning (CFPP) algorithm. The purpose of this paper is to review the findings of those CFPP papers and the methodologies used to generate possible solutions for CFPP for mobile agents. This survey shows that the previous CFPP papers can be divided based on four characteristics. The performance of each method primarily used to solve CFPP in previous research is evaluated and compared. Several methods are implemented and tested in same computing environment to compare the performance of generating solution in specified spatial environment with different obstacles or size. The strengths and weakness of each methodology for CFPP are shown through this survey. Ideally, this paper will provide reference for new future research.

In Southeast Asian cities, it is common for logistic companies to operate a heterogeneous fleet of delivery vehicles with motorcycles being the preferred vehicle to handle the final phase of delivery. In such scenarios, heterogeneous fleet vehicle routing problem (HFVRP) is generally applied to plan an optimal delivery. However, in many downtown cores of large and rapidly developing Southeast Asian cities, HFVRP is neither viable nor reliable because of road usage restrictions. The purpose of this article is to develop and test a different approach that accurately takes these restrictions into account and provides viable and more sustainable results. Restrictions in this paper refer to situations of urban areas in Vietnam where (i) certain vehicle types are prohibited in specified areas or where narrow alleyways limit the utilization of vehicles that exceed the road capacity and (ii) certain roads are exclusive to certain vehicle types. In networks, limited access and exclusive lanes are represented as links, or arcs, exclusive to one or another. Taking these limitations into consideration, we have developed a unique model, which we have termed Vehicle Routing Problem with Exclusive Links (VRP-EL). The model was validated and tested for its performance on scenarios with varying ratios of exclusive links. Scenarios up to 500 customers were tested on a meta-heuristic algorithm, simulated annealing. VRP-EL produces realistic outcomes. Limiting certain links to be selected according to vehicle types increases overall travel distance. However, this increase outweighs the cost of re-planning and rerouting had they not been constrained initially. The reduction in traveling distance leads to fossil fuel reduction for the overall system. The estimation of reduced carbon emissions through applying the proposed model is presented. Considering the severe traffic congestion and carbon emissions caused by motorcycles in Vietnam, the proposed model leads to a sustainable road environment.

This study investigates appropriate attributes— physical environment, outcome, and interactional quality—to measure users' satisfaction that influences airport users' satisfaction level. With these three attributes and users’ perspectives for air travelers and service providers, we generate a conceptual model of airport service quality and satisfaction. The findings indicate that different perceptions exist between airport service providers and air travelers. Air travelers are more concerned with interaction and outcome (convenience) quality attributes, while services providers reflect on interaction and physical environment (servicescape) quality attributes. The airport service quality is found to be significantly related to airport reuse, and destination revisits. An appropriate service-training program is needed to reduce the gap in the level of satisfaction.

The manufacture of semiconductor products requires many dedicated steps, and these steps can be grouped into several major phases. One of the major steps found at the end of the wafer fabrication process is the electrical die sorting (EDS) test operation. This paper focuses on dispatching policies in an EDS test facility to reduce unnecessary work for the system. This allows the semiconductor manufacturing facility to achieve better overall efficiency, thereby contributing to sustainable manufacturing by reducing material movements, the use of testing machines, energy consumption, and so on. In the facility, wafer lots are processed on a series of workstations (cells), and the facility holds identical parallel machines. The wafers are moved by an automatic material handling system from cell to cell as well as within cells. We propose several scheduling policies consisting of intercell and intracell material movements for efficient system operation. For this, four intercell scheduling policies and two intracell scheduling policies are introduced, and the effects of combinations are tested and evaluated through simulation experiments to obtain performance measures such as cycle time and work in process. The most efficient results among the combinations are presented as a proposed scheduling policy for a given EDS test facility.

This paper presents the double row layout problem which determines an arrangement of machines on either side of a central corridor so that the total material moved is minimized when the material handling path is the straight line along the corridor. We propose a mixed integer programming (MIP) model which modifies a recently proposed model in the literature by introducing tighter constraints. For the performance comparison, models in the literature and the new model that we propose are tested to solve 26 well known instances and two additional instances introduced in this paper. Computational results show that the new model performs remarkably well compared with the models in the literature. Specifically, the new model solves larger problems, and the shortest processing time is obtained by the new model for all instances.

Facility layout problems (FLPs) are concerned with the non-overlapping arrangement of facilities. The objective of many FLP-based studies is to minimize the total material handling cost between facilities, which are considered as rectangular blocks of given space. However, it is important to integrate a layout design associated with continual material flow when the system uses circulating material handling equipment. The present study proposes approaches to solve the layout design and shortest single loop material handling path. Monarch butterfly optimization (MBO), a recently-announced meta-heuristic algorithm, is applied to determine the layout configuration. A loop construction method is proposed to construct a single loop material handling path for the given layout in every MBO iteration. A slicing tree structure (STS) is used to represent the layout configuration in solution form. A total of 11 instances are tested to evaluate the algorithm's performance. The proposed approach generates solutions as intended within a reasonable amount of time.

The importance of global logistics is increasing due to the increase of trade among countries and the investment of multinational corporations. In addition to the intermodal transportation system that links the port, airport, and inland logistics bases with the increase in cargoes through e-commerce, trends such as increasing trade in fresh food and increasing importance of reverse logistics are undergoing changes. Environmental issues such as fine dust, ballast water and fuel consumption, and the development and operation of sustainable infrastructure are emerging as issues among countries. In this regard, a special issue is planned to cover “sustainability and global logistics”. There are different problems in different countries and regions and different solutions, but they also face the same problems or issues that need to be addressed jointly. There are technological and industrial changes such as the 4th Industrial Revolution and AI, IoT, autonomous driving, and shared economy, the traditional social values such as urban problems, birth and employment problems, welfare and quality of life. In addition, how to maintain it becomes an important issue. In this special issue, we tried to provide an opportunity to expand the general approaches to other regions and societies through researches on national and regional logistics. The first paper, “Analyzing the costs and benefits of installing unmanned parcel lockers: Focusing on residential complexes in Korea,” written by Hoang Thai Pham and Hyangsook Lee, deals with the increase of courier goods due to a boom of e-commerce in Korea, increasing of the small quantity of multiple items delivered in urban area where the high population density brings about the problems such as traffic congestion, accessibility and pollution. It deals with a final shipping method of the cargo which is the core of last mile delivery in multi-family houses and apartments. A new alternative for home delivery service, parcel locker, were proposed and analyzed its impact in terms of costs and benefit when it comes to the residential area. Although this paper deals with the case of Korea, we may expand to similar problems in other countries and regions where laws and systems are different. The second paper, “A case study on logistics services preferences for supply chain entities in Shandong province, China,” written by Woosuk Seo and Seung Bum Ahn, is on a case in Shandong province of China. Assessment of logistics services in a particular country or region is very important when it comes to improving logistics services in public and private matters and has a guideline on what parts should be raised first and to what extent. In this respect, this study suggests directions in terms of sustainable improvement in international trade and investment including domestic matters. It finds the logistics service factors in supply chain entity in Shandong Province in China and it could be extended to evaluate logistics service attributes which influence overall logistics system. It has been found that four supply chain entities, third party logistics, customs, market, and manufacturers in the region have different service preferences and this would be good reference to the region in similar environment. In this special issue, two papers are covered with the theme of "sustainability and global logistics". However, there are many current and emerging issues in logistics and supply chain management (SCM). Technological changes, the increasingly interdependence of the cold chain and e-commerce in the global market, and the regulation and co-ordination of fine dust, air pollution and various environmental aspects have also not been addressed in this special issue. The research on logistics and SCM is not a matter that can be solved only in some fields such as technology and optimization or private enterprise when it is treated as a complicated problem through increasing linkage and relationship rather than specificity of a specific region. The international aspect of cooperation across countries is becoming more important. More researches will be needed to find ways to improve, sustain, prepare for, and plan strategies and actions in the short term and midand long-term perspectives as well as the global society, the private sector and the public.

Various factors must be considered when running a courier service in an urban area, because the infrastructure of a city differs from those in suburban or countryside areas. Of note, population density is higher, and vehicles encounter greater restrictions. Moreover, air pollution from fossil fuel combustion is more severe. As tailpipe emissions are becoming costly to both corporations and the environment, researchers are increasingly exploring more appealing transportation options. Electric bicycles have become an important mode of transportation in some countries in the past decade. Electric bicycles and automobiles have their respective merits and demerits when used to provide courier services. E-bikes in particular can ply their trade in densely packed areas that are off-limits to cars and trucks. This paper focuses on (1) developing a truck–bike mixture model to reduce operating costs for an existing truck-only service by replacing some of the trucks with bicycles, and (2) exploring the resulting effects in terms of reducing overall carbon emissions. Data from one of the major courier companies in South Korea were utilized. The problem was tackled as a heterogeneous fleet vehicle routing problem using simulated annealing because the actual size of the problem cannot be solved directly with a mathematical approach. The most effective fleet mix was found for the company’s case. Effects on operating costs and reduced emissions were analyzed for 15 different scenarios with varying demands and off-limits areas. Computational results revealed that the new model is viable from economic and sustainability standpoints. They indicated that costs decrease to varying degrees in all scenarios, and that carbon emissions also decrease by around 10% regardless of the selected scenario.

Shuttle-based storage and retrieval systems (SBS/RSs), which are designed to increase throughput capacity and flexibility, are a type of automated storage and retrieval system used for lightweight loads. SBS/RSs can increase throughput capacity by using multiple shuttles and elevators as storage and retrieval machines (SRMs). They can also facilitate improvements in flexibility since they are able to adjust the number of SRMs according to transaction demands. Thus, determining the number of shuttles is an important issue in tier-to-tier SBS/RSs. In this paper, a decision model to determine the number of shuttles is proposed. The model is based on the travel time model, and it considers parameters such as the physical configuration, velocity profile and the probability that the shuttle operates a dual command. Finally, the throughput capacity from the travel time model is compared with that from a simulation-based approach in order to verify the effects of the model. In addition, a critical discussion regarding the characteristics of the tier-to-tier system is provided.