• 한국항만경제학회지
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• 제18권1호
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• pp.27-41
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• 2002

This paper deals with the development of a simulation model for the container terminal, which consists of 3 berths, 8 container cranes, and 16 yard blocks with each yard crane and 90 yard trucks in order to evaluate the various operational rules. The proposed operational rules are 3 ship-dispatching rules, 3 berth allocation rules, 2 crane allocation rules, 2 yard allocation rules, and 2 yard truck allocation rules. These rules are simulated using 4 performance measures, such as ship time in the terminal, ship time in the port, the number of ships processed, and the number of containers handled. The simulation result is as follows: 1) there is no difference among 3 ship-dispatching rules, 2) berth allocation rules depend on performance measures, 3) dynamic crane allocation is better than fixed policy, 4) pooling yard allocation is better than short distance yard allocation rules, and 5) fixed yard truck allocation by berth is a little better than pooling policy.

• 한국시뮬레이션학회논문지
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• 제12권2호
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• pp.25-34
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• 2003

Because of explosive growth in demand for web-based multimedia applications, proper proxy caching for large multimedia object (especially video) has become needed. For a video object which is much larger in size and has different access characteristics than the traditional web object such as image and text, caching the whole video file as a single web object is not efficient for the proxy cache. In this paper, we propose a proxy caching strategy with the constant-sized segment for video file and an improved proxy cache replacement policy. Through the event-driven simulation under various conditions, we show that our proposal is more efficient than the variable-sized segment strategy which has been proven to have higher hit ratio than other traditional proxy cache strategies.

• 한국산업융합학회 논문집
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• 제23권6_2호
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• pp.957-969
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• 2020

The primary objective of this study is to develop a determination system for an optimal combination of earthwork equipment that improves the traditional way in convenience, prediction accuracy, and productivity. For this, the following research works are conducted sequentially; 1)literature review, 2)technology development trend analysis, 3)develop a determination system for the optimal combination of earthwork equipment, 4)simulation of a developed system. As a result, core considerations are deducted for the development of a determination system. Furthermore, site simulation is performed using a developed system. Site simulation result, Cluster 1(R1200LC 7㎥, CAT 775G 65ton×2) was selected from 6 clusters because of its production cost (￦491/㎥). It is expected that the application range and impact on the construction industry will be enormous due to the availability of the developed system.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2020년도 추계학술대회
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• pp.151-152
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• 2020

운영 중인 터미널을 대상으로 운영 정책을 변경하기 위한 계획 및 실행 과정에서 현장 적용 결과 실패 가능성이 있어, 시행착오를 줄이기 위해 많은 시간과 노력이 요구된다. 터미널 운영 정책을 변경하기 위한 계획 단계에서 시뮬레이션 기술을 활용하여 의사결정을 지원할 수 있다. 본 연구는 시뮬레이션 기술 중 가상화 터미널 시스템을 활용한 사례를 제시한다.

• 한국디지털정책학회:학술대회논문집
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• 한국디지털정책학회 2006년도 춘계학술대회
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• pp.87-109
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• 2006

The purpose of this paper is to examine the present performance evaluation methods and to make Monte Carlo Simulation Model for the IT-based Government innovation project. It is suggested the proper ways in applying of Monte Carlo Simulation Model by integration of present evaluation methods. It develops the theoretical framework for this paper, examining the existing literature on proposing an approach to the key concepts of the economic impact analysis methods. It examines the actual conditions of performance evaluation focusing on the It-based Government Innovation project. It considers how the simulation model is applied to the performance management in the public innovation project focusing on the framework, process and procedure of performance management.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1997년도 춘계 학술대회 발표집
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• pp.124-127
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• 1997

A key element in the control of Automated Guided Vehicle Systems (AGVS) is dispatching policy. This paper proposes a new dispatching algorithm for an efficient operation of AGVS. Based on an evolutionary operation, it has an adaptive control capability responding to changes of the system environment. The performance of the algorithm is compared with some well-known dispatching rules in terms of the system throughput through simulation. Sensitivity analysis is carried out varying the buffer capacity and the number of AGVS.

• 대한기계학회논문집A
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• 제24권8호
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• pp.2131-2142
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• 2000

As recent production facilities are usually operated with unmanned material-handling system, the development of an efficient schedule with deadlock avoidance becomes a critical problem. Related researches on deadlock avoidance usually focus on real-time control of manufacturing system using deadlock avoidance policy. But little off-line optimization of deadlock-free schedule has been reported. This paper presents an optimization method for deadlock-free scheduling for Job-Shop system with no buffer. The deadlock-free schedule is acquired by the procedure that generates candidate lists of waiting operations, and applies a deadlock avoidance policy. To verify the proposed approach, simulation resultsare presented for minimizing makespan in three problem types. According to the simulation results the effect of each deadlock avoidance policy is dependent on the type of problem. When the proposed LOEM (Last Operation Exclusion Method) is employed, computing time for optimization as well as makespan is reduced.

• 공업화학
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• 제20권1호
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• pp.104-108
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• 2009

본 연구에서는 이산화탄소/수소 혼합기체가 관 모양의 Pd-Ag 막을 통과할 때 관 안에서의 이산화탄소 및 수소의 몰분율, 수소 분압, 그리고, 속도 구배 등을 CFD (Computational Fluid Dynamics) 기법을 사용하여서 다양한 유입 속도에 대해서 모사하였다. 모사 결과에 의하면 유입 속도가 증가할수록 관의 길이 방향을 따라서 이산화탄소의 몰분율이 더디게 증가함을 알 수 있었다. 또한, 혼합 기체의 유입 속도와 관의 길이가 수소 회수율에 미치는 영향에 대해서 살펴보았으며 낮은 유입속도와 긴 관의 경우에 수소 회수율이 큰 것을 알 수 있었다.

• 로봇학회논문지
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• 제16권2호
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• pp.137-146
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• 2021

When controlling manipulator, degree of freedom is lost in singularity so specific joint velocity does not propagate to the end effector. In addition, control problem occurs because jacobian inverse matrix can not be calculated. To avoid singularity, we apply Deep Deterministic Policy Gradient(DDPG), algorithm of reinforcement learning that rewards behavior according to actions then determines high-reward actions in simulation. DDPG uses off-policy that uses 𝝐-greedy policy for selecting action of current time step and greed policy for the next step. In the simulation, learning is given by negative reward when moving near singulairty, and positive reward when moving away from the singularity and moving to target point. The reward equation consists of distance to target point and singularity, manipulability, and arrival flag. Dual arm manipulators hold long rod at the same time and conduct experiments to avoid singularity by simulated path. In the learning process, if object to be avoided is set as a space rather than point, it is expected that avoidance of obstacles will be possible in future research.

• 대한산업공학회지
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• 제43권1호
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• pp.1-11
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• 2017

Stochastic resource-constrained project scheduling problem is an extension of resource-constrained project scheduling problem such that activity duration has stochastic nature. In real situation where activity duration is not known until the activity is finished, open-loop based static policies such as activity-based policy and priority-based policy will not well cope with duration variability. Then, a dynamic policy based on closed-loop decision making will be regarded as an alternative toward achievement of minimal makespan. In this study, a dynamic policy designed to select activities to start at each decision time point is illustrated. The performance of static and dynamic policies based on variable neighborhood search is evaluated under the discrete-event simulation environment. Experiments with J120 sets in PSPLIB and several probability distributions of activity duration show that the dynamic policy is superior to static policies. Even when the variability is high, the dynamic policy provides stable and good solutions.