• Proceedings of the Korea Society for Simulation Conference
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• 1998.10a
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• pp.213-216
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• 1998

수원시에 소재한 T 물류센터는 제품의 종류를 고려하여 랜덤 불출정책에 의해 운영되고 있는 단위적재 형 out-of-aisle in-process 자동창고 형태이다. 랜덤불출의 결과 팔렛에 잔량의 제품이 발생할 수 있으며, 잔량의 제품 팔렛은 저장경로를 통해서 랙으로 재저장이 이루어진다. 현재 T 물류센터에서는 상당한 양의 재저장이 발생되고 있으며, 이로 인하여 저장공간이 비효율적으로 이용되고 있으며, 운송기계(S/R 기계)의 이동시간 및 이동거리의 증가, throughput의 감소, 대기시간의 증가 등이 심각한 문제로 나타나고 있다. 본 연구는 시뮬레이션 기법을 활용하여 이 물류센터에서 사용할 수 있는 4가지 불출정책 대안을 비교·분석하여 최적의 불출정책을 도출하는 것을 목적으로 하고 있다. 시뮬레이션 기법을 통해 결정된 최적의 불출정책을 도입함으로써 T 물류센터에서는 저장공간 이용률의 최소화, 운송기계의 이동시간 및 이동거리 최소화, 재저장 횟수의 최소화를 통해 효율적인 불출작업과 저장공간의 활용도를 증가시키는 효과를 기대할 수 있을 것이다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.57-58
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• 2023

The working time for loading and transporting containers in the container terminal is one of the factors directly related to port productivity, and minimizing working time for these operations can maximize port productivity. Among working time for container operations, the working time of yard tractors(Y/T) responsible for the transportation of containers between berth and yard is a significant portion. However, it is difficult to estimate the working time of yard tractors quantitatively, although it is possible to estimate it based on the practical experience of terminal operators. Recently, a technology based on IoT(Internet of Things), one of the core technologies of the 4th industrial revolution, is being studied to monitoring and tracking logistics resources within the port in real-time and calculate working time, but it is challenging to commercialize this technology at the actual port site. Therefore, this study aims to develop yard tractor working time prediction model to enhance the operational efficiency of the container terminal. To develop the prediction model, we analyze actual port operation data to identify factors that affect the yard tractor's works and predict its working time accordingly.

• The KIPS Transactions:PartA
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• v.9A no.4
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• pp.555-562
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• 2002

The total processing time nay vary according to the order of visit when a mobile agent is sequentially migrated to another node. An effective migration algorithm is one in which the processing time is kept to its minimum from the initial state to the destination state by ordering the process. The total time spend for the process can be minimized by adopting an effective migration algorithm. Existing mobile agents such as Aglets. Voyager, and Odyssey do not guarantee the effectiveness by not taking the status of the network and the node to be moved into upon the migration. This paper proposes AMIS as the method used for the migration of the mobile agent. AMIS minimizes the total migration time of the mobile agent, and provides a firm and safe order for the migration of the mobile agent.

• Korean Journal of Construction Engineering and Management
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• v.1 no.3 s.3
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• pp.75-80
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• 2000

In scheduling multi-unit projects, several alternatives can exist in network construction due to repetitiveness of their activities. Project duration is affected not only by the duration of each activity but also by the arrangement of repeating activities in such projects. This paper provides a network compression method that assigns predecessors to each activity to minimize its float time. Different to the previous efforts that utilized line of balance as the base scheduling-model, this research adopts precedence diagram arranged in two coordinates, the space axis and the resource one. This method seeks the most appropriate predecessors for each activity in each direction of the two coordinates for the purpose of minimizing the idle resource and space. This activity arrangement method was applied to a multi-unit apartment-construction project, to prove its capability of network compression. The result shows that the method successfully sought room for saving construction duration by changing the activity arrangement. The network compression method presented in this research can be utilized in multi-unit construction projects such as apartment complex projects.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.2
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• pp.183-194
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• 2002

The clustering environment with heterogeneous workstations provides the cost effectiveness and usability for executing applications in parallel. Load balancing is considered a necessary feature for a cluster of heterogeneous workstations to minimize the turnaround time. Previously, static load balancing that assigns a predetermined weight for the processing capability of each workstation, or dynamic approaches which execute a benchmark program to get relative processing capability of each workstation were proposed. The execution of the benchmark program, which has nothing to do with the application being executed, consumes the computation time and the overall turnaround time is delayed. In this paper, we present efficient methods for task distribution and task migration, based on the relative load index. We designed and implemented a load balancing system for the clustering environment with heterogeneous workstations. Turnaround times of our methods and the round-robin approach, as well as the load balancing method using a benchmark program, were compared. The experimental results show that our methods outperform all the other methods that we compared.

• The Transactions of the Korea Information Processing Society
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• v.6 no.12
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• pp.3652-3661
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• 1999

To support multimedia applications such as a multimedia communication systems and multimedia broadcasting, an operating system need to predict their timing-constraints. So, In this real-time systems, we must solve the priority inversion problem that may make the behavior of unpredictable systems and need a real-time server model that provides a better preemptability and minimizes a system overhead. In current real-time systems, the single thread server model, the worker model and the dynamic server model are being used for synchronization but they cannot propose an effective structure for managing shared resources. In this paper, the priority inheritance protocol is used to solve the priority inversion problem and the hybrid prioritized worker model is proposed, which can provide a more effective structure and a faster response time minimizing a system overhead. The hybrid prioritized worker model is to combine the static and the dynamic prioritized worker model, and have a better performance than other models in response time which is an important factor in a real-time system.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.194-196
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• 2012

본 논문은 비행체를 위한 실시간 운영체제의 태스크 스케줄링 기법을 제안한다. 기존의 기법은 다음 수행할 태스크를 선택하는 작업을 수행할 때 메모리 오버헤드 또는 일정한 시간 오버헤드가 발생하게 되며 일반적으로 이 둘은 트레이드 오프 관계로 고려된다. 제안하는 태스크 스케줄링 기법은 메모리 오버헤드를 최소화하면서도 우선 순위가 제일 높은 태스크를 찾는 작업을 별다른 연산 없이 수행함으로써 자주 발생하는 작업의 시간을 줄여 스케줄러 시간 오버헤드의 절약을 도모한다. 또한 이 방식은 태스크의 수가 많지 않으며 일정한 파티션된 OS를 주로 사용하는 비행체에 특히 적합하다.

• Proceedings of the Safety Management and Science Conference
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• 2003.11a
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• pp.199-202
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• 2003

반도체 제조 시스템에 대한 다양한 상황과 관련한 연구는 많지 않다 게다가, 모든 상황에 항상 적합한 생산시스템 전략은 없다. 반도체 제조공정 시스템에 대한 스케줄은 생산공정의 재진입, 공정의 높은 불확실성, 급속하게 변하는 제품과 기술과 같은 특성 때문에 반도체 제조공정시스템에 대한 스케줄은 복잡하고 어려운 작업이며, 사이클타임의 절감 및 단위시간당 생산량의 증대와 같은 시스템 목적을 달성하기 위하여, 반도체 제조 시스템에 대한 좋은 방법을 발견하기 위한 많은 연구가 있었다. 반도체 산업의 생산 흐름은 가장 독특한 특징을 가지고 있으며 생산계획과 반도체 제조의 스케줄링과 계획을 어렵게 하고 있다. 각각 다른 단계에 있는 자재는 같은 장비의 사용을 위해 경쟁을 하는데, 이로 인하여 작업시간 보다 단지 기다리는 시간에 상당한 시간을 할애하고 있다. 따라서 본 연구에서는 선행 연구를 바탕으로 반도체 공정에 모듈 생산방식을 접목시켜 공정의 사이클 타임을 줄이고, WIP를 최소화하여, 생산량을 최대화는 방안을 제시하고 공정 모듈 시스템 (Process Modular System)을 구축하고자 한다.

• Journal of Korea Society of Industrial Information Systems
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• v.4 no.2
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• pp.81-87
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• 1999

This paper discusses a bicriterion approach to sequencing with time/cost trade-offs. The first problem is to minimize the total flow time and the maximum tardiness. And second is to the maximum tardiness and resource allocation costs. This approach, which produces an efficient flintier of possible schedules, has the advantage that it does not require the sequencing criteria to be measurable in the same units as the m allocation cost. The basic single machine model is used to treat a class of problems in which the sequencing objective is to minimize the maximum completion penalty. It is further assumed that resource allocation costs can be represented by linear time/cost function.

• Journal of Korea Port Economic Association
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• v.39 no.1
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• pp.47-63
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• 2023

In smart ports and port automation, the number of vertically deployed container terminals is growing. The purpose of this study is to analyze the productivity of horizontally arranged and vertically arranged container terminals by comparing the main ship operation time, and to recommend future strategies for increasing the operational efficiency of vertically configured container terminals. To achieve our goal, we chose two terminals representating each type, and collected berth allocation status data from 2018 to 2022. Then we analyzed the data using the Accelerated Failure Time (AFT) model, a parametric survival analysis technique. Under the assumption that the working circumstances of the C/C (Container Crane) are the same, we find that the productivity of on-board work of the vertically placed container terminal is higher than that of the horizontally placed container terminal. Our result also shows that the productivity is reduced during the COVID-19 period and the European ships show lower onboard work time. On the basis of these findings, we propose strategies to improve the productivity of vertical container terminals.