• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.1
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• pp.6-11
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• 2009

This paper presents a new dynamically adaptable polling scheme for efficient support of real-time traffic over an IEEE 802.11 wireless LAN network. The poll scheduling plays an important role in IEEE 802.11 PCF. However, the current version of the polling list management scheme proposed in the IEEE 802.11 standard is inefficient when a variable number of mobile stations have variable packets to transmit. If Point Coordinator has an exact information on the station status, it is possible to efficiently perform polling. In this paper, we suggest an adaptable polling scheme to meet requirements of the stations. In our scheme, each station transmits packets including a piggyback information to inform that it wants to receive a poll in the next polling duration. Simulation results indicate that our scheme may reduces the packet discard ratio and real-time packet transfer delay.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.33-34
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• 2012

As the distributed power system with PV and ESS is highlighted to be one of the most prominent structure to replace the traditional electric power system, power flow scheduling is expected to bring better system efficiency. Optimal energy management system (EMS) where the power from PV and the grid is managed in time-domain using ESS needs an optimization process. In this paper, main optimization method is implemented using dynamic programming (DP). To overcome the drawback of DP in which ideal future information is required, prediction stage precedes every EMS execution. A simple auto-regressive moving-average (ARMA) forecasting followed by a PI-controller updates the prediction data. Assessment of the on-line optimal EMS scheme has been evaluated on several cases.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.365-370
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• 2001

The genetic algorithm that simulates the virus evolutionary theory has been developed applying to combinatorial optimization problems. The algorithm in this study uses only one individual and a population of viruses. The individual is attacked, inflected and improved by the viruses. The viruses are composed of flour genes (a pair of top gene and a pair of tail gene). If the individual is improved by the attacking, the inflection occurs. After the infection, the tail genes are mutated. If the same virus attacks several times and fails to inflect, the top genes of the virus are mutated. By this mutation, the individual can be improved effectively. In addition, the influence of the immunologic mechanism on evolution is simulated.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.98-100
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• 2005

This paper, proposes concept of personal robot middleware core also called streaming layer. Based on openness and portability, the streaming layer is proposed in order to meet requirements of different kinds of applications. The streaming layer architecture provides effective management of data flows and allows integration of different systems with ease regardless software of hardware platform. With extensibility support additional features can be build in without affect to performance. Therefore, heterogeneous network support, real-time communications, embedded boards support can be easily achieved. In order to achieve high performance together with portability into different platforms, the most functions has to be implemented in C language, while critical parts, such as scheduling, priority assignment has to be made using native functions of tested platforms.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.51-60
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• 2002

Currently, many companies are trying to be more competitive by implementing the most appropriate software package called ERP (Enterprise Resource Planning). ERP can support the company's business process. A manufacturing execution system (MES) is an industrial software system, as well as a manufacturing management function in make-to-order and make-to-stock manufacturing environments. This paper presents an architecture of MES. This study develops MES to identify the functional requirements of loading & scheduling in the automobile industry. This study shows the effectiveness of the proposed MES, how to develop MES and interface with ERP package.

• Journal of the Korean Institute of Navigation
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• v.25 no.4
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• pp.323-333
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• 2001

This paper presents a decision making model for the cruise ship management. A network based optimization model has been developed for a single cruise ship operation. It gives optimal itinerary patterns over the planning period for the cruise ship managers wanting to maximize profit from the cruise ship operation. A network solution method to find the optimal solution is also developed. This network model can be equivalently transformed into a linear programming model, which makes the implementation of the model quite practical however complicated the given set of possible itineraries may be. The ship scheduling network developed in this study can also be used as a general framework to describe all possible cruise ship itineraries the cruise ship manager can figure out.

• Journal of Information Technology Applications and Management
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• v.17 no.4
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• pp.127-156
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• 2010

Most companies in the IT service industry have suffered from low profitability although this industry is highly value added, which may result in losing the competitiveness of the industry. The purpose of this study is to identify the influencing factors on the profit improvement rate of IT service projects and suggest how to improve the profit improvement rate, thus recovering the competitiveness of the IT service industry. The 273 IT service projects conducted by an IT service company in Korea during the past three years were analyzed and the project managers who performed these projects responded to the questionnaire developed in this study. The result from the analysis of data collected shows that the influencing factors on the profit improvement rate of IT service projects include scheduling, experience in similar projects, the leadership of project leaders, the level of team skills, relationship with clients, and clients support.

• Journal of applied mathematics & informatics
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• v.26 no.5_6
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• pp.1021-1035
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• 2008

In this paper, we analyze an N-design call center with skill-based routing, in which one pool of agents handles two types of calls and another pool of agents handles only one type of calls. The approximate analysis is motivated by a computational complexity that has been observed in the direct stochastic approach and numerical method for finding performance measures. The workforce staffing policy is very important to the successful management of call centers. So the allocation scheduling of the agents can be considered as the optimization problem of the corresponding queueing system to the call center. We use a decomposition algorithm which divides the state space of the queueing system into the subspaces for the approximate analysis of the N-design call center with two different types of agents. We also represent some numerical examples and show the impact of the system parameters on the performance measures.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1481-1498
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• 2007

As railroad industry face the new Renaissance era, effective and efficient maintenance methods for rolling stock operation are required with advanced railroad technology. All kinds of railroad systems such as high speed long distance train, metropolitan mass transit and light rail require systematic maintenance technology in order to maintain the safe railroad operation. Simulation models for detailed operations of the sample maintenance center are developed. In this study, standard maintenance procedures, layout, equipments and number of workers of Siheung Metropolitan Railroad Maintenance Rolling Stock Depot are considered. The proposed simulation models are developed using simulation package ARENA. Three simulation analysis using the developed simulation model are done. First, the bottleneck operation is identified. Second, the relationship between maintenance center size, number of workers and cycle time is analyzed. Lastly, the scheduling performances between PERT/CPM and Critical Chain Project Management(CCPM) are compared.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.4
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• pp.382-389
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• 2011

Salesperson Monitoring System (SMS) is geographic based information system that supports business auditing, sales area coordinating and customer management for each salesperson. Conventional SMSs focus mainly on the monitoring or logging functions, i.e., a salesperson locating or moving trail tracking. However, the schedules have been planned by human planner, and they have rarely been managed with a software system like SMS. In this paper, a mixed integer programming model for a salesperson routing schedule is provided. Then, 2-phase Genetic Algorithm (GA) is proposed to make salesperson routing schedule. Experimental results show a validity of the proposed method.