• 대한산업공학회지
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• 제35권2호
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• pp.150-159
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• 2009

The heterogeneous fleet vehicle routing problem(HVRP) is a variant of the classical vehicle routing problem in which customers are served by a heterogeneous fleet of vehicles with various capacities, fixed costs and variable costs. We propose a new conceptual HVRPCR(HVRP with customer restriction) model including additional customer restrictions in HVRP. In this paper, we develop hybrid particle swarm optimization(HPSO) algorithm with 2-opt and node exchange technique for HVRP. The solution representation is a n-dimensional particle for HVRP with N customers. The decoding method for this representation starts with the transformation of particle into a priority list of customer to enter route and limit of vehicle to serve each customer. The vehicle routes are then constructed based on the customer priority list and limit of vehicle to serve. The proposed algorithm is tested using 8 benchmark problems and it consistently produces high-quality solutions, including new best solutions. The numerical results show that the proposed algorithm is robust and efficient.

• Management Science and Financial Engineering
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• 제22권1호
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• pp.5-12
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• 2016

We consider a time-cost tradeoff problem with multiple milestones under a chain precedence graph. In the problem, some penalty occurs unless a milestone is completed before its appointed date. This can be avoided through compressing the processing time of the jobs with additional costs. We describe the compression cost as the convex or the concave function. The objective is to minimize the sum of the total penalty cost and the total compression cost. It has been known that the problems with the concave and the convex cost functions for the compression are NP-hard and polynomially solvable, respectively. Thus, we consider the special cases such that the cost functions or maximal compression amounts of each job are identical. When the cost functions are convex, we show that the problem with the identical costs functions can be solved in strongly polynomial time. When the cost functions are concave, we show that the problem remains NP-hard even if the cost functions are identical, and develop the strongly polynomial approach for the case with the identical maximal compression amounts.

• 한국항해항만학회지
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• 제38권6호
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• pp.567-575
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• 2014

In recent times, an obvious strategy in liner shipping markets that has come to the fore is slow steaming. Nowadays, most liner shipping companies have decelerated the voyage speed to 15-18 knots on major routes, and some leading liner shipping companies have a plan to reduce it to below 15 knots. Slow steaming is helpful in reducing the operating cost and the amount of greenhouse-gas emissions on a single vessel with lower fuel consumption. However, it also creates various negative effects such as the opportunity cost, additional fixed costs and an in-transit inventory cost on a loop. Hence, the net operating cost on a loop is changing dynamically due to the changes of voyage speed based on various slow steaming effects. The aim of this study is to analyze the slow steaming effects in the liner shipping, and to find the best voyage speed that minimizes the operating cost on a loop. Moreover, this study suggests the recommendable strategy for liner shipping companies. To achieve the aim of this study, a simulation model has been designed using System Dynamics.

• The Journal of Asian Finance, Economics and Business
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• 제5권4호
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• pp.101-105
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• 2018

Price discount is one of the commonly used promotion strategies to increase sales and revenue. If a discount is perceived before the purchase (i.e., pre-purchase discount), consumers are likely to perceive it as a potential gain. If it is noticed after making a regular-priced purchase (i.e., post-purchase discount), consumers may develop negative emotions and attitudes. Based on the rising transparency and omnipresence of price and discount information through web and mobile platforms, we attempt to tackle an understudied topic on the negative effect of post-purchase price discount. Specifically, post-purchase discount information may increase consumers' perception of monetary loss, which may affect consumers' decision to return the product, potentially increasing the operating costs borne by retailers. Based on a close scrutinization of the current market environment and previous academic literature, we suggest a novel conceptual framework to understand consumers' perception, attitude, and behavior (perception of loss, willingness to return) upon perceiving various formats of discount promotion (absolute value vs. percentage discount) posterior to the purchase of a product. We also look at the effect of price level (low-priced vs. high-priced). For marketing practitioners, we intend to suggest optimal promotion formats that can alleviate consumers' negative perceptions and prevent additional operation costs.

• Management Science and Financial Engineering
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• 제19권2호
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• pp.19-29
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• 2013

Refuse collection network design, one of major decision problems in reverse logistics, is the problem of locating collection points and allocating refuses at demand points to the opened collection points. As an extension of the previous models, we consider capacity and maximum allowable distance constraints at each collection point. In particular, the maximum allowable distance constraint is additionally considered to avoid the impractical solutions in which collection points are located too closely. Also, the additional distance constraint represents the physical distance limit between collection and demand points. The objective is to minimize the sum of fixed costs to open collection points and variable costs to transport refuses from demand to collection points. After formulating the problem as an integer programming model, we suggest an optimal branch and bound algorithm that generates all feasible solutions by a simultaneous location and allocation method and curtails the dominated ones using the lower bounds developed using the relaxation technique. Also, due to the limited applications of the optimal algorithm, we suggest two heuristics. To test the performances of the algorithms, computational experiments were done on a number of test instances, and the results are reported.

• 대한안전경영과학회지
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• 제6권3호
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• pp.141-152
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• 2004

Supply chains for agricultural commodities with their various constraints such as production lead time, seasonal production, and methods of storage are limited in the extent to which techniques like Just-in-Time (JIT) inventory management can be applied. It is beyond the ability of producers to control harvest time and many agricultural products are perishable so that they can incur exceptional losses in storage if they are not handled correctly. This is a source of additional costs and inefficiency in supply chain management. The purpose of this study is to reduce or eliminate such sources of loss and inefficiency and to identify success factors for the JIT inventory management system where it can be applied for agricultural products. Where JIT techniques can be applied in supply chain management for agricultural products, costs such as transportation, inventory, and storage losses can be reduced with concurrent increases in efficiency. In the paper, some of the problems associated with applying JIT inventory control methods in supply chain management for agricultural commodities will be reported through a series of case studies.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2004년도 춘계학술대회
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• pp.191-201
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• 2004

Supply chains for agricultural commodities with their various constraints such as production lead time, seasonal production, and methods of storage are limited in the extent to which techniques like Just-in-Time (JIT) inventory management can be applied. It is beyond the ability of producers to control harvest time and many agricultural products are perishable so that they can incur exceptional losses in storage if they are not handled correctly. This is a source of additional costs and inefficiency in supply chain management. The purpose of this study is to reduce or eliminate such sources of loss and inefficiency and to identify success factors for the JIT inventory management system where it can be applied for agricultural products. Where ]IT techniques can be applied in supply chain management for agricultural products, costs such as transportation, inventory, and storage losses can be reduced with concurrent increases in efficiency. In the paper, some of the problems associated with applying ]IT inventory control methods in supply chain management for agricultural commodities will be reported through a series of case studies.

• 한국항해항만학회지
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• 제28권8호
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• pp.709-714
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• 2004

본 연구는 최근 물동량이 빠른 속도로 증가하고 있는 대련항, 천진항, 청도항, 상해항 등을 화물의 목적항으로 설정하고, 선박의 운항패턴 시나리오를 바탕으로 부산항에서 환적하는 경우와 중국항 직기항 등의 총운송비용 차이를 분석하였다. 이를 바탕으로 하여 부산항에서 환적할 때 직기항하는 경우보다 초과 발생하는 비용을 항만 당국이 선사에게 보전해 주는 인센티브 규모로 하고, 이를 충당할 수 있는 전대사용료 산정 방법을 제시하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2014년도 추계학술대회
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• pp.91-93
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• 2014

Philippine fisheries code of 1998 (Republic Act 8550), which is enacted to achieve food security by managing, conserving and protecting fishery resources, obliges local governments to designate no less than 15% of jurisdictional municipal water as fisheries resource protection zone. Accordingly, Marine Protected Areas (MPAs) are the most extensively established as fisheries management and conservation tool and over 1,500 MPAs are reported in the Philippines. But there has been debate on the pros and cons of implementing MPAs because of the positive and negative impacts on local communities and fishermen. A dichotomous-choice contingent-valuation survey was conducted in the two municipalities of Guimaras, Philippines to investigate public opinion in debates over MPAs and to estimate willingness to pay (WTP) for MPAs to protect and conserve marine habitats for fishery resources. For the benefits and costs of MPAs, 43.6% of respondents thought the costs would be larger than the benefit, but 91% respondents voted in favor of increasing MPAs for fisheries resources as a protective measure. Finally, the estimated Turnbull lower-bound mean WTP (36.75ha) was php 493.6(US$ 11.3) per household to establish the additional MPA (36.75ha) in their municipality waters.

• 대한전기학회논문지:전력기술부문A
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• 제51권7호
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• pp.349-361
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• 2002

Occasionally, equipment in a distribution system fails due to damage from weather, vandalism, or other causes. Failures and unexpected events do not always occur as and where expected. Therefore, a good contingency plan, multi-zone or otherwise, provides flexibility by locating switches at various strategic locations so that parts of a feeder can be picked up in the event of line outages at various places. It is possible to create feeder system layout that achieve remarkable contingency support economics, even as their normal peak loading levels approach thermal capacity, by utilizing six, seven, or even nine switchable zones per feeder. But many switchable zones per feeder are of questionable practicality and effectiveness, because of the complexity and time required for the switching operation. In practice, a zonal scheme with between three and four zones will usually provide complete contingency backup for all feeders. Line switches have both capital and maintenance costs, the planning for multi-zonal schemes is considerably more difficult than or loop or single-zone systems, and the required switching operations required during contingencies take more time. But multi-zonal schemes are used because these costs come to far less than the cost of additional capacity required for loop or single-zone. In this paper, we present the optimal number of switchable zones per feeder in Kora distribution system.