• IE interfaces
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• v.21 no.3
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• pp.333-342
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• 2008

Warehouses form an important link in a supply chain network. Among a variety of activities in warehouses, order picking is the process of retrieving a number of items out of storage to meet customer orders. Today, as the transactions through direct sales are wide spread, warehouses often receive a large amount of small orders to be handled within tight time windows, which makes fast and efficient order picking more important than ever. This paper examines a new order picking method where the concept of bucket brigade (BB) is applied. Bucket brigade is a way of dynamically coordinating workers who progressively perform a set of operations along a flow line. In bucket brigades, a worker is not assigned his jobs in a static way. Each worker takes a job from his predecessor when he is free. We identify some considerations when bucket brigades are applied to order picking activities. A new BB picking protocol is presented to improve existing BB picking protocols. Through simulation experiments, the performance of BB order picking is evaluated under various logistics environments.

• Journal of the Korean Statistical Society
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• v.4 no.1
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• pp.79-87
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• 1975

However, the mechanism for producing revised estimate is the principal means of varying the resulting precisions of estimate. Therefore, a scheduling system including physician's revision should be checked by a computer simulation to evaluate possible gains to admissions scheduling accruing from the use of these estimates. The ability to accurately predict bed occupancy has long been an objective of hospital management. If the one were able to anticipate bed accupancy, then the one could more accurately plan for bed needs, schedule personnel, allocate service and supply. We may conclude that even though the Markov chain analysis would not lead to ready-made answers for the scheduling system of elective patients, it can provide the more detailed and systematic knowledgy for the solutions on the weekly base as well as the foundations for long run planning in relative sense.

• Proceedings of the Safety Management and Science Conference
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• 2013.04a
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• pp.173-177
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• 2013

공급사슬관리(Supply Chain Management)의 목적은 공급사슬에서 발생하는 재고 및 운송에 관련한 비용을 최소화하는 것이다. 여기서 발생하는 비용은 여러 변수에 의해 결정되기 때문에 공급망 전체를 하나의 시스템으로 보고 모델링하여 분석할 필요성이 있다. 여러 구성요소들을 시간의 흐름에 따라 변화하는 모습을 분석하기 위해 수학적 접근방법을 사용하는 것 보다 시뮬레이션 방법을 사용해 모델링하는 것이 더 효과적이다. 따라서 본 연구에서는 중국의 H자동차의 조달물류의 문제점을 파악하고 이를 개선하기 위한 방안을 마련하기 위해 시뮬레이션 방법을 활용하여 조달물류의 최적 배송주기를 도출하고, 재고관리의 문제점을 개선 하고자 한다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.742-749
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• 2002

This paper deals with a continuous-review two-echelon inventory model with one-for-one replenishment and Poisson demand where transshipments among retailers are allowed. Two classes of inventory systems are considered by the number of distribution centers(DCs) which provide each retailor with inventory items. 1:N class inventory system and M:N class inventory system respectively. Two-phase model is constructed to find out the optimal inventory positions which minimize supply chain costs. Approximations for customer service levels of the system are evaluated in the first phase, and the optimal inventory positions are found subject to the constraints for service level in the second phase. Simulation tests are performed to assure the effectiveness of the proposed model. The effect of transshipment is evaluated.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.2
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• pp.9-18
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• 2011

Vender prioritization process is one of the most critical tasks of production and logistics management for many companies. Determining the most critical criteria for vender prioritization process is a vital means for a purchasing company to improve its supply chain productivity. This study discuss the use of a Fuzzy analytic network process (Fuzzy ANP) model which is an efficient tool to handle the fuzziness of the data involved in deciding the preferences of different criteria which are not independent. Also, the comparison of classical ANP and Fuzzy ANP is described using simulation with triangular distribution random number generation. It is shown that Fuzzy ANP model possesses some attractive properties and could be used as an alternative to the known vender prioritization methods.

• Journal of Sensor Science and Technology
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• v.28 no.1
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• pp.17-22
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• 2019

As CMOS technology scales down, reliability is becoming an important concern for VLSI designers. This paper analyzes gate-oxide breakdowns (i.e., the time-dependent dielectric-breakdown (TDDB) aging effect) as a reliability issue for combinational circuits with 45-nm technology. This paper shows simulation results for the noise margin, delay, and power using a single inverter-chain circuit, as well as the International Symposium on Circuits and Systems (ISCAS)'85 benchmark circuits. The delay and power variations in the presence of TDDB are also discussed in the paper. Finally, we propose a novel method to compensate for the logic failure due to dielectric breakdowns: We used a higher supply voltage and a negative ground voltage for the circuit. The proposed method was verified using the ISCAS'85 benchmark circuits.

• Korean Management Science Review
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• v.28 no.3
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• pp.1-13
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• 2011

Hub-and-spoke transportation network is a powerful and useful network structure that takes full advantage of economies of scale on routes between hubs. In recent studies, the network structure is extended to hybrid hub-andspoke that allows direct transportation between spokes. In this study, we considered more extended network structure which is called hybrid multiple hub-and-spoke that has multiple hubs and allows direct transportation between spokes. We developed a mathematical optimization model for automotive service parts transportation planning under hybrid multiple hub-and-spoke network structure. The model suggests a long-term transportation route planning and a short-term vehicle assignment planning. The model is verified by simulation and validated in real world application to Hyundai Mobis automotive service parts transportation planning. From the simulation result, the model reduced the transportation cost about 24.7%, the total distance about 6.8% and the CO2 emissions about 8.8%. In real world application for 6 months from July to December 2010, the model reduced the transportation cost about 9.1% by changing the long-term transportation route without daily vehicle assignment planning.

• Journal of Korea Port Economic Association
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• v.18 no.1
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• pp.43-60
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• 2002

Apart from the DEA method, the traditional measuring systems of container terminal productivities generally bring to light the partial productive efficiencies, because they evaluate only the productivity of each individual facility. However, these methods do not play roles of the reasonable productivity measures to compare and evaluate the efficiencies of terminals to meet the requirement of terminal customers like as shipping lines, shippers, etc. with the cutthroat competition in container handling market. As the suppliers of service, the terminals struggle to cope with the needs of buyers' markets due to the lack of suitable criteria to measure the efficiencies. Therefore, this paper uses the simulation approach to reveal which strategies enhance the productivities through the container terminal analysis. An additional intent of this paper is to build the active strategies to present what the experimental indexes like as norm-time exactness ratio, norm-time excess ratio, etc. compare between terminals to measure the total productivities for the age of global supply chain management. However, the experimental productivity indexes presented in this paper require a validation of the exact usefulness, by consideration from all angles in the future, and a development to more reasonable measuring method/indexes for the container terminal productivities.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.4
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• pp.152-161
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• 2011

The operation of vending machine system presents a decision-making problem which consists of determining the product allocation to vending-machine storage compartments, replenishment intervals of vending machines, and vehicle routes, all of which have critical effects on system profit. Especially, it becomes more difficult to determine the operation variables optimally when demand for a product that is out-of-stock spills over to another product or is lost. In this paper, we propose a heuristic for solving the operation problem of the vending machine system and evaluate it by comparing with Yang's algorithm on various test problems with respect to system profit via a computer simulation. The results of computational experiments show a substantial profit increase of the proposed heuristic over Yang's algorithm. Sensitivity analysis indicates that some input variables impact the profit increase significantly.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.814-823
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• 2012

Electric power transmission utilities make an effort to maximize profit by reducing their electricity supply and operation costs while maintaining their reliability. The development of maintenance strategies for aged components is one of the more effective ways to achieve this goal. The reliability centered approach is a key method in providing optimal maintenance strategies. It considers the tradeoffs between the upfront maintenance costs and the potential costs incurred by reliability losses. This paper discusses the application of the Particle Swarm Optimization (PSO) technique used to find the optimal maintenance strategy for a transmission component in order to achieve the minimum total expected cost composed of Generation Cost (GC), Maintenance Cost (MC), Repair Cost (RC) and Outage Cost (OC). Three components of a transmission system are considered: overhead lines, underground cables and insulators are considered. In regards to aged and aging component, a component state model that uses a modified Markov chain is proposed. A simulation has been performed on an IEEE 9-bus system. The results from this simulation are quite encouraging, and then the proposed approach will be useful in practical maintenance scheduling.