• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.138-141
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• 2006

This paper considers a two-machine flow-shop scheduling problem for minimizing mean flow time. Each job has three non-preemptive operations, where the first and third operations must be Processed on the first and second machines, respectively, but the second operation can be processed on either machine. A lower bound based on SPT rule is derived, which is then used to develop a branch-and-bound algorithm. Also, an efficient simple heuristic algorithm is developed to generate a near-optimal schedule. Numerical experiments are performed to evaluate the performances of the proposed branch-and-bound and the heuristic algorithm

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.10a
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• pp.303-306
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• 1996

This paper proposes a heuristic method for job shop scheduling with alternative machines. Our heuristic suggests four machine-selecting rules and two priority dispatching rules for modifying existent ones considering alternative machines, and then it extends existing nondelay/active job shop schedule generation. This heuristic provides good criteria(rules) in the selection of a proper machine among those performing a specific operation and for the dispatch of an operation to a selected machine and thus these rules permit the efficient job shop scheduling with alternative machines. The performances of our four machine-selecting rules in addition to the two priority dispatching rules, applied together with the existing 17 rules, are experimented and evaluated, respectively.

• Journal of Korea Multimedia Society
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• v.23 no.10
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• pp.1270-1285
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• 2020

As a representative concept of the fourth industrial revolution era where everything is digitized, digital twin means analyzing and optimizing a complex system using a simulation model synchronized with the system. In this paper, we propose a digital twin simulation model for the efficient operation of urban railways in Busan. Due to the geopolitical nature of Busan, where there are many mountains and narrow roads, the railways are more useful than other public transportation. However, this inversely results in a high level of congestion, which is an inconvenience to citizens and may be fatal to the spread of the virus, such as COVID19. Considering these characteristics, the proposed model analyzes the congestion level of the railways in Busan. The model is developed based on a mathematical formalism called discrete-event system specification and deduces the congestion level and the average waiting time of passengers depending on the train schedule. In addition, a new schedule to reduce the congestion level is derived through particle swarm optimization, which helps the efficient operation of the railways. Although the model is developed for the railways in Busan, it can also be used for railways in other cities where a high level of congestion is a problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.932-938
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• 2017

This paper presents the structure of an energy management system for distributed energy resources of a grid-connected microgrid. The energy management system of a grid-connected microgrid collects information of the microgrid such as the status of distributed energy resources and the time varying pricing plan through various protocols. The energy management system performs forecasting and optimization based on the collected information. It derives the operation schedule of distributed energy resources to reduce the microgrid electricity bill. In order to achieve optimal operation, the energy management system should include an optimal scheduling algorithm and a protocol that transfers the derived schedule to distributed energy resources. The energy management system operates as a rolling horizon controller in order to reduce the effect of a prediction error. Derived control schedules are transmitted to the distributed energy resources in real time through the international standard communication protocol.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.326-329
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• 2001

The main purpose of HITES(Highly Integrated Total Energy System) is to build and develop an integrated energy system for power system operational planning and analysis which consists of load forecast, economic generation schedule, stability analysis and relational database system. The HITES can be utilized to supply a stable electric power and operate KEPCO's power system facilities economically. This system was put into operation in 1999. This paper describes the present condition for operation of HITES and proposes the plan to improve this system after installation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.127-137
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• 1997

This paper proposes a heuristic method for job shop scheduling with alternative machines. Our heuristic suggests two machine-selecting rules and two priority dispatching rules for modifying existent ones considering alternative machines, and then it extends existing nondelay/active job shop schedule generation. This heuristic provides good criteria(rules) in the selection of a proper machine among those performing a specific operation and for the dispatch of an operation to a selected machine and thus these rules permit the efficient job shop scheduling with alternative machines. The performances of our two machine-selecting rules in addition to the two priority dispatching rules, applied together with the existing 17 rules, are experimented and evaluated, respectively.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.57-64
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• 2011

Recently, all-electrified houses have constructed and some tasks are being carried out to monitor energy consumption patterns. The energy monitoring includes various elements such as temperature, pressure, water flow, $CO_2$, and electricity. In this monitoring, electricity consumption is one of the essential factors because the performance and energy saving levels are described by this physical quantity. This quantity depends on materials, structure, operation of the house, which operation means consumer's life style and usage patterns of home appliances furthermore. Firstly, this paper shows a control simulation method which were developed a few years ago. And some different methods are proposed considering flexible experimental condition.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1839-1850
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• 2009

The Korean railway system is a mass transit system in which a various types of trains such as common trains, high-speed train (KTX), Metropolitan Express Railway (EMU) are operated. It is operated based on a timetable and provides us with safety, regularity, quickness and comfortable service. The objective of this study is to propose a method for estimating line capacity considering high-speeding and diversification of trains. In particular, the focus of this study is on the closing gap between the result of the existing line capacity estimation method and the real-world line capacity of the operating agency of the Korean railway. For this, this study introduces a new railway capacity definition by considering TPS of line alignment according to the operation type, train control and signaling system, etc. The verification of the proposed method using a practical schedule diagram exemplification is discussed as well.

• Corrosion Science and Technology
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• v.3 no.2
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• pp.59-66
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• 2004

In construction of new ships and large steel bridges in Korea, pre-construction primers (PCP), also known as shop primer, are routinely used and retained as an integral part of the protective coating system. Retention of PCP's can significantly reduce building schedule and cost. Retaining PCP through the so-called "sweep blasting" procedure eliminates or minimizes the necessity of a second blast operation, thus shortening overall schedule as well as reducing labor cost and hazardous waste disposal cost. This study evaluates the feasibility of retaining PCP as the part of primer for high performance protective coating systems applied to ships' hull, bottom and ballast tanks. Upon proving that the retention of the PCP is a viable option, the process of coating application can he improved significantly in terms of cost and working schedule of new ships and large steel bridges. Results indicate that use of the PCP via sweeping blasting in conjunction with standard high performance protective coating systems does not degrade the overall performance of the coating systems. At the same time, it is also highly recommended that the secondary surface preparation should consist of grit blasting of weld burnt and other damaged areas to SSPC SP-IO grade (Sa 2.5 Gr.), Near White Blast Cleaning with proper application and attention to detail.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1682-1685
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• 2004

Gas Turbine combustors for power plant can be reduced NOx emissions using lean premixed combustion technology. But the combustors are likely to occur combustion oscillations which damage operation reliability and mechanical life of the gas turbines. In this paper, characterizations of oscillation in a gas turbine combustor for power plant are presented. Combustion dynamics occur $1{\sim}1.5$ psi in amplitude with low frequency less than 140Hz during normal operation. An abnormal high level dynamics, 2.0 psi amplitude occur at 125 Hz frequency. Abnormal combustion oscillation is reduced by modulation of fuel supply valve control schedule.