• Journal of the Korea Society for Simulation
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• v.18 no.2
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• pp.19-27
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• 2009

This paper addresses the berth allocation problem in naval ports. Navy vessels need various services such as emergency repair, missile loading, oil supply and many others while commercial vessels only unload and load container at the port. Furthermore, naval vessels have to shift frequently due to a limited capacity of the port. The objective of this paper is to minimize the total number of nesting vessels at the naval port. In other word, the objective is to maximize the total number of naval battleships engaging in the sea. A mixed integer programming(MIP) model is developed and experiments are conducted with ILOG CPLEX 11.0. We compare the computational results of the MIP model to the current scheduling approach by the ROK Navy. The results showed that MIP model performed well by minimizing the number of nesting vessels. and avoiding unnecessary shifts.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.4
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• pp.1624-1647
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• 2020

Vehicular network is one of the most important subjects for researchers in recent years. Anycast routing protocols have many applications in vehicular ad hoc networks. The aim of an anycast protocol is sending packets to at least one of the receivers among candidate receivers. Studies done on anycast protocols over vehicular networks, however, have capability of implementation on some applications; they are partial, and application specific. No need to say that the lack of a comprehensive study, having a strong analytical background, is felt. Mathematical modeling in vehicular networks is difficult because the topology of these networks is dynamic. In this paper, it has been demonstrated that vehicular networks can be modeled based on time-expanded networks. The focus of this article is on geographical anycast. Three different scenarios were proposed including sending geographic anycast packet to exactly-one-destination, to at-least-one-destination, and to K-anycast destination, which can cover important applications of geographical anycast routing protocols. As the proposed model is of MILP type, a decentralized heuristic algorithm was presented. The evaluation process of this study includes the production of numerical results by Branch and Bound algorithm in general algebraic modeling system (GAMS) software and simulation of the proposed protocol in OMNET++ simulator. The comprehension of the result of proposed protocol and model shows that the applicability of this proposed protocol and its reactive conformity with the presented models based on presented metrics.

• Journal of the military operations research society of Korea
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• v.33 no.1
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• pp.105-115
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• 2007

It is essential to give a fatal damage to the enemy force by using prompt and accurate fire in order to overcome the lack of artillery force. During the artillery fire operations, minimizing the firing time will secure the adapt ability in tactical operation. In this paper, we developed a mathematical model to schedule the artillery fire on the multiple targets to decrease total fire operation time. To design a program to describe a real firing situation, we consider many possible circumstances of changes such as commander's intention, firing constraints, target priority, and contingency plan to make a fire plan in an artillery unit. In order to work out the target sequencing problem, MIP is developed and the optimum solution is obtained by using ILOG OPL. If this analytical model is applied to a field artillery unit, it will improve the efficiency of the artillery fire force operations.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.4
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• pp.9-21
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• 2018

In South Korea, Jeju Island has a role as a test bed for electric vehicles (EVs). All conventional cars on the island are supposed to be replaced with EVs by 2030. Accordingly, how to effectively set up EV charging stations (EVCSs) that can charge EVs is an urgent research issue. In this paper, we present a case study on planning the locations of EVCS for Jeju Island, South Korea. The objective is to determine where EVCSs to be installed so as to balance the load of EVCSs while satisfying demands. For a public service with EVCSs by some government or non-profit organization, load balancing between EVCS locations may be one of major measures to evaluate or publicize the associated service network. Nevertheless, this measure has not been receiving much attention in the related literature. Thus, we consider the measure as a constraint and an objective in a mixed integer programming model. The model also considers the maximum allowed distance that drivers would detour to recharge their EV instead of using the shortest path to their destination. To solve the problem effectively, we develop a heuristic algorithm. With the proposed heuristic algorithm, a variety of numerical analysis is conducted to identify effects of the maximum allowed detour distance and the tightness of budget for installing EVCSs. From the analysis, we discuss the effects and draw practical implications.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.4
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• pp.32-42
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• 2021

The printing process can have to print various colors with a limited capacity of printing facility such as ink containers that are needed cleaning to change color. In each container, cleaning time exists to assign corresponding inks, and it is considered as the setup cost required to reduce the increasing productivity. The existing manual method, which is based on the worker's experience or intuition, is difficult to respond to the diversification of color requirements, mathematical modeling and algorithms are suggested for efficient scheduling. In this study, we propose a new type of scheduling problem for the printing process. First, we suggest a mathematical model that optimizes the color assignment and scheduling. Although the suggested model guarantees global optimality, it needs a lot of computational time to solve. Thus, we decompose the original problem into sequencing orders and allocating ink problems. An approximate function is used to compute the job scheduling, and local search heuristic based on 2-opt algorithm is suggested for reducing computational time. In order to verify the effectiveness of our method, we compared the algorithms' performance. The results show that the suggested decomposition structure can find acceptable solutions within a reasonable time. Also, we present schematized results for field application.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.236-242
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• 2022

Busan Port is operated separately by a number of terminal operators, resulting in a large number of ITT (Inter-Terminal Transportation) volumes. The occurrence of ITT volume causes various problems such as additional transportation cost, empty truck trips, truck delays and terminal congestion, weakening Busan Port's competitiveness. Among them, the empty truck trip problem is a representative factor, that exacerbates the cost problem of the ITT operation at Busan Port. But the ITT backhaul rate at Busan Port remains low. To strengthen the transhipment competitiveness of Busan Port, it is necessary to increase the ITT backhaul rate. In this paper, to improve ITT backhaul rate, we present a mathematical model for maximizing backhaul transport using buffer space. And we analyzed the improving effects of backhaul transport using buffer space through experiments based on actual operating data.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.3
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• pp.233-242
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• 2015

This paper analyzes a multi-product inbound lot-sizing and outbound dispatching problem with multi-vehicle types in a third-party logistics distribution center. The product must be delivered to the customers within the delivery time window and backlogging is not allowed. Replenishing orders are shipped by several types of vehicles with two types of the freight costs, i.e., uniform and decreasing, are considered. The objective of this study is to determine the lot-size and dispatching schedules to minimize the total cost with the sum of inbound and outbound transportation and inventory costs over the entire time horizon. In this study, we mathematically derive a mixed-integer programming model and propose a genetic algorithm (GA1) based on a local search heuristic algorithm to solve large-scale problems. In addition, we suggest a new genetic algorithm (GA2) with an adjusting algorithm to improve the performance of GA1. The basic mechanism of the GA2 is to provide an unidirectional partial move of products to available containers in the previous period. Finally, we analyze the results of GA1 and GA2 by evaluate the relative performance using the gap between the objective values of CPLEX and the each algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.51-58
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• 2010

Wireless Mesh Network has drawn much attention due to wide area service coverage with low system cost. However, there is a bottleneck problem in wireless mesh network since the traffic is aggregated into a gateway. Placement of multi-radio can easy the bottleneck problem, but without careful design it results in unnecessary system cost increasement. In this paper, we propose a system cost minimization through differential antenna placement where optimum antenna placement is determined by the required wireless link capacity. With CPLEX program, optimum number of antennae is determined as a function of local user traffic and gateway capacity. From numerical analysis, it is confirmed that our proposed model can solve bottleneck problem, and at the same time save the system cost.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.2
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• pp.28-36
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• 2016

Recently, owing to the development of ICT industry and wide spread of smart phone, the number of people who use car sharing service are increased rapidly. Currently two-way car sharing system with same rental and return locations are mainly operated since this system can be easily implemented and maintained. Currently the demand of one-way car sharing service has increase explosively. But this system have several obstacle in operation, especially, vehicle stock imbalance issues which invoke vehicle relocation. Hence in this study, we present an optimization approach to depot location and relocation policy in one-way car sharing systems. At first, we modelled as mixed-integer programming models whose objective is to maximize the profits of a car sharing organization considering all the revenues and costs involved and several constraints of relocation policy. And to solve this problem efficiently, we proposed a new method based on particle swarm optimization, which is one of powerful meta-heuristic method. The practical usefulness of the approach is illustrated with a case study involving satellite cities in Seoul Metrolitan Area including several candidate area where this kind systems have not been installed yet and already operating area. Our proposed approach produced plausible solutions with rapid computational time and a little deviation from optimal solution obtained by CPLEX Optimizer. Also we can find that particle swarm optimization method can be used as efficient method with various constraints. Hence based on this results, we can grasp a clear insight into the impact of depot location and relocation policy schemes on the profitability of such systems.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.119-126
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• 2009

A district energy system plays very important role to fulfill energy demand in regional areas. This paper diagnoses the necessity of the development of an economical operation system for the efficient operation of district energy plants located in Seoul. The effect anticipated from the use of the optimal operation system is also analyzed. Production and consumption of energy are estimated for the district energy plants at Suseo, Bundang, Ilwon and Jungang located near in Seoul, Korea. The problem is formulated as a mixed integer linear programming(MILP) problem where the objective is to minimize the overall cost of the district energy system. From the results of numerical simulations we can see that the energy efficiency is improved due to the application of the optimal operation conditions provided by the proposed model.