• 국제학술발표논문집
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• The 4th International Conference on Construction Engineering and Project Management Organized by the University of New South Wales
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• pp.187-194
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• 2011

Optimizing truck dispatching-intervals is imperative in ready mixed concrete (RMC) delivery process. Intervals shorter than optimal may induce queuing of idle trucks at a construction site, resulting in a long delivery cycle time. On the other hand, intervals longer than optimal can trigger work discontinuity due to a lack of available trucks where required. Therefore, the RMC delivery process should be systematically scheduled in order to minimize the occurrence of waiting trucks as well as guarantee work continuity. However, it is challenging to find optimal intervals, particularly in urban areas, due to variations in both traffic conditions and concrete placement rates at the site. Truck dispatching intervals are usually determined based on the concrete plant managers' intuitive judgments, without sufficient and reliable information regarding traffic and site conditions. Accordingly, the RMC delivery process often experiences inefficiency and/or work discontinuity. Automatic data collection (ADC) techniques (e.g., RFID or GPS) can be effective tools to assist plant managers in finding optimal dispatching intervals, thereby enhancing delivery performance. However, quantitative evidence of the extent of performance improvement has rarely been reported to data, and this is a central reason for a general reluctance within the industry to embrace these techniques, despite their potential benefits. To address this issue, this research reports on the development of a discrete event simulation model and its application to a large-scale building project in Abu Dhabi. The simulation results indicate that ADC techniques can reduce the truck idle time at site by 57% and also enhance the pouring continuity in the RMC delivery process.

• 한국시스템다이내믹스연구
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• 제12권1호
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• pp.89-114
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• 2011

With steady increase in the demand for door-to-door delivery services, courier service providers are facing a constant pressure to reduce delivery price in order to secure quantity order and to improve the efficiency and reliability for customer service. The objective of this research is to explain the structure of the door-to-door delivery including door-to-door delivery service demand, sorting capacity in the hub-terminal, and the system performance measures such as service reliability networks using causal loop diagram(CLD). Based on causal relation, this research describes a comprehensive approach to examine how capacity reliability contributes to the renewal of the firm's competences through its reciprocal relationship with travel time reliability and connectivity reliability. Also, this research suggests the policy alternatives to improve effectiveness and efficiency of door-to-door delivery network in response to increase customer satisfaction and profit maximization of the courier service providers: operational, tactical, and strategic levels.

• 산업경영시스템학회지
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• 제41권4호
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• pp.138-145
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• 2018

In the field of optimization, many studies have been performed on various types of Vehicle Routing Problem (VRP) for a long time. A variety of models have been derived to extend the basic VRP model, to consider multiple truck terminal, multiple pickup and delivery, and time windows characteristics. A lot of research has been performed to find better solutions in a reasonable time for these models with heuristic approaches. In this paper, by considering realtime traffic characteristics in Map Navigation environment, we proposed a method to manage realistic optimal path allocation for the logistics trucks and cargoes, which are dispersed, in order to realize the realistic cargo mixing allowance and time constraint enforcement which were required as the most important points for an online logistics brokerage service company. Then we developed a prototype system that can support above functionality together with delivery status monitoring on Map Navigation environment. First, through Map Navigation system, we derived information such as navigation-based travel time required for logistics allocation scheduling based on multiple terminal multiple pickup and delivery models with time constraints. Especially, the travel time can be actually obtained by using the Map Navigation system by reflecting the road situation and traffic. Second, we made a mathematical model for optimal path allocation using the derived information, and solved it using an optimization solver. Third, we constructed the prototype system to provide the proposed method together with realtime logistics monitoring by arranging the allocation results in the Map Navigation environment.

• Architectural research
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• 제8권1호
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• pp.57-68
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• 2006

Global competition and reduced project life cycle ultimately puts greater performance requirements on the capital project delivery systems used to maintain competitiveness. Despite continuing improvements in delivery cycle time, business owners of facilities continue to demand greater improvements in project delivery cycle time. Therefore, it is very important to investigate the various techniques and methods leading to reduction in project cycle time and also identify the applicability of identified techniques and methods. This paper introduces reduction techniques identified through literature review (i.e, Schedule Reduction Techniques (SRTs), Management Techniques (MTs), and Construction Institute Industry (CII) Best Practices (BPs). In order to collect applicability of these techniques under different project phases (Pre-project planning (PPP), Design (D), Material Management (MM), Construction (C), and Start-up (SU)), the Essence Applicability Matrices (EAM) is used.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2012년도 추계학술대회
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• pp.63-64
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• 2012

2008년부터 시작된 세계경제 위축은 전 세계 해상물동량 감소로 이어져 컨테이너선업계의 불황이 더욱 심화되고 있다. 선사들은 불황을 극복하기 위하여 여러 가지 전략들을 구사하고 있다. 대부분의 선사들은 잉여 선박의 추가투입으로 감속운항을 통해 선박 운영비용을 절감하고 있는데, 이와 같은 시도는 선사입장에서는 비용절감이 되지만 감속운항이 화물의 정시성을 저해하는 요소로 작용하고 있기 때문에 화주입장에서는 불만요인이 될 수 있다. 이러한 상황에서 'M'선사는 "On Time Delivery"를 보증하기 위해서 아시아-유럽항로에서 새로운 서비스인 Daily Maersk Service를 2011년 10월부터 적용하고 있다. 본 서비스는 아시아발 북유럽행 특정 기간 포트구간 수송에서 100% "On Time Delivery"를 보증하고, 또한 매일 화물수탁을 가능하게 한 신서비스이다. 본 연구에서는 업계 1위를 달리고 있는 'M'선사가 감속운항을 하면서도 화물의 정시성을 높이기 위해 실시하고 있는 Daily Maersk Service를 통하여 가격 경쟁과 더불어 서비스 경쟁에서도 우위를 확보하려는 전략이 효과를 나타내고 있는 지에 대하여 사례연구를 통하여 확인하였다.

• 대한안전경영과학회지
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• 제25권2호
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• pp.91-97
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• 2023

Ensuring the safe arrival of delivery cargo at its intended destination is of utmost importance. Truck drivers play a crucial role in guaranteeing the secure delivery of cargo without any mishaps. However, there are various factors that may lead to delayed arrival of trucks at their destination, such as late departures or prolonged loading operations. The timely departure of cargo transportation is contingent upon several variables, including the driver's experience, cargo volume, and loading time. If the transportation commencement is delayed, it may increase the risk of accidents due to an elevated operating speed. Consequently, we conducted a study to investigate the correlation between cargo loading time, cargo volume, driving experience, and the likelihood of accidents. Our findings indicate that both cargo volume and driver experience can impact the likelihood of vehicle accidents. Furthermore, all factors can have an interactive effect on the occurrence of accidents. However, extending the loading time may mitigate the impact on the likelihood of accidents.

• 대한산업공학회지
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• 제40권4호
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• pp.435-441
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• 2014

This paper considers a single-product problem for inbound lot-sizing and outbound dispatching at a third-party warehouse, where the demand is dynamic over the discrete time horizon. Each demand must be delivered into the corresponding delivery time window which is the time interval characterized by the earliest and latest delivery dates of the demand. Ordered products are shipped by heterogeneous container types. Each container type has type-dependent carrying capacity and the unit freight cost depends on each container type. Total freight cost is proportional to the number of each container type used. Also it is assumed that related cost functions are concave and backlogging is not allowed. The objective of the paper is to simultaneously determine the optimal inbound lot-sizing and outbound dispatching plans that minimize total costs which include ordering, shipping, and inventory holding costs. The optimal solution properties are characterized for the problem and then a dynamic programming algorithm is presented to find the optimal solution.

• 산업경영시스템학회지
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• 제45권3호
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• pp.40-48
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• 2022

An automated material handling system (AMHS) has been emerging as an important factor in the semiconductor wafer manufacturing industry. In general, an automated guided vehicle (AGV) in the Fab's AMHS travels hundreds of miles on guided paths to transport a lot through hundreds of operations. The AMHS aims to transfer wafers while ensuring a short delivery time and high operational reliability. Many linear and analytic approaches have evaluated and improved the performance of the AMHS under a deterministic environment. However, the analytic approaches cannot consider a non-linear, non-convex, and black-box performance measurement of the AMHS owing to the AMHS's complexity and uncertainty. Unexpected vehicle congestion increases the delivery time and deteriorates the Fab's production efficiency. In this study, we propose a Q-Learning based dynamic routing algorithm considering vehicle congestion to reduce the delivery time. The proposed algorithm captures time-variant vehicle traffic and decreases vehicle congestion. Through simulation experiments, we confirm that the proposed algorithm finds an efficient path for the vehicles compared to benchmark algorithms with a reduced mean and decreased standard deviation of the delivery time in the Fab's AMHS.

• 산업공학
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• 제13권3호
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• pp.455-461
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• 2000

Logistics systems can be evaluated by how productively distribution center operates, how promptly transportation vehicle dispatches, how efficiently facility layout is, and so on. In this paper, a practical vehicle routing scheme with fixed delivery time and fixed vehicle routes is introduced. The method helps the distribution center reduce logistics cost with respect to dispatching vehicles, and satisfy the customer with pre-determined delivery time window constraints. A case study has shown that the proposed scheme not only generates a feasible schedule with time windows, but also balances material flow in warehouse.

• 산업경영시스템학회지
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• 제36권3호
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• pp.71-78
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• 2013

An efficient vehicle routing heuristic for different vehicle moving times for forward and backward between two points is studied in this research. Symmetric distance or moving times are assumed to move back and forth between two points in general, but it is not true in reality. Also, various moving speeds along time zones are considered such as the moving time differences between rush hours or not busy daytimes. To solve this type of extremely complicated combinatorial optimization problems, delivery zones are specified and delivery orders are determined for promising results on the first stage. Then delivery orders in each zone are determined to be connected with other zones for a tentative complete delivery route. Improvement steps are followed to get an effective delivery route for unsymmetric-time-varing vehicle moving speed problems. Performance evaluations are done to show the effectiveness of the suggested heuristic using computer programs specially designed and developed using C++.