• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.3
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• pp.542-559
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• 2011

Most game-theoretic works of Aloha have emphasized investigating Nash equilibria according to the system state represented by the number of network users and their decisions. In contrast, we focus on the possible change of nodes' utility state represented by delay constraint and decreasing utility over time. These foregone changes of nodes' state are more likely to instigate selfish behaviors in networking environments. For such environment, in this paper, we propose a repeated Bayesian slotted Aloha game model to analyze the selfish behavior of impatient users. We prove the existence of Nash equilibrium mathematically and empirically. The proposed model enables any type of transmission probability sequence to achieve Nash equilibrium without degrading its optimal throughput. Those Nash equilibria can be used as a solution concept to thwart the selfish behaviors of nodes and ensure the system stability.

• Journal of Family Resource Management and Policy Review
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• v.2 no.1
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• pp.133-149
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• 1998

The purpose of this study was to analyze the expenditure state of midlife households for elderly life stage and to find out the variables that have influence upon these expenditure. The findings are follows: 1) The expenditure state was influenced by various as like wife’s age, couple’s education, number of children, husband’s retiring allowance, monthly savings, whole assets of households, level of dependence upon own children, etc. 2) The demand for economic preparation, program about elderly life, information and welfare system was related to the practical expenditure state absolutely and relatevely. The result showed that the husbands’retiring allowance was the most effective variable to the expenditure state for the elderly life. In conclusion the rational distribution of economics resources according to the family life stage is very important for the economic welfare of households.

• Journal of the Korea Society of Computer and Information
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• v.22 no.6
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• pp.87-93
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• 2017

In this paper, we design a small low power single channel ECG(Electrocardiogram) system of Chest Belt type with fiber-type electrodes to measure emotional state change of game addict. HRV(Heart Rate Variability) is analyzed through heart rate signal measurement and the psychological stress state is judged by using it. And it verifies its effectiveness through prototype. First, we design HR measurement module through low power MCU(Micro Controller Unit) and implement prototype level measurement system. The results showed that the difference between the addiction group and the general group was confirmed and that the system was effective. The result of this study can be used for health management such as reduction of stress of the user through music and breathing that lowers the stress by detecting the stress state of the general person or the chronic ill person.

• Smart Structures and Systems
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• v.15 no.3
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• pp.609-625
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• 2015

Management of infrastructure stock is essential in sustainability of society, and its analysis and optimization are studied in the light of control system modeling in this paper. At the first part of the paper, cost of stock management is analyzed based on macroscopic statistics on infrastructure stock and economical growth. Stock management burden relative to economy is observed to become larger at low economic growth periods in developed economies. Then, control system modeling of stock management is introduced and by augmenting maintenance actions as control input, dynamic behavior of stock is simulated and compared with existing time history statistics. Assuming steady state conditions, applicability of the model to cross sectional data is also demonstrated. The proposed model is enhanced so that both preventive and corrective maintenance can be included as system inputs, i.e., feedforward and feedback control inputs. Optimal management strategy to achieve specified deteriorated stock level with minimal cost, expressed in terms of preventive and corrective maintenance actions, is derived based on estimated parameter values for corrosion of steel bridges. Relative cost effectiveness of preventive maintenance is shown when target deteriorated stock level is lower.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.232-241
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• 2010

This paper describes the development of robust contingency analysis program for Korean Energy Management System. The important function of contingency analysis is to determine the bus/branch model for contingency, and to calculate the state of the power network based on the network model and topology output. In the proposed method, the bus/branch models for contingencies are determined exactly using a fast linked-list method based on the application common model database. To calculate the state of the power system included contingency, the full-decoupled powerflow approach, the partial powerflow method for contingencies and the proposed contingency screening algorithm are also used to contingency analysis. To verify the performance of the developed processor, we performed a file-based test using several structured input data and online test using the database which resides on memory. The results of these comprehensive tests showed that the developed processors can accurately calculate the power system contingency state from online data and can be applied to Korea Power Exchange system.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.213-219
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• 2022

The main purpose of the study is to determine the main aspects of the introduction of modern management technologies into the security system in the context of socio-economic development and digitalization of the economy. Socio-economic development and a high level of security include growth in income, labor productivity, production volumes, increased competitiveness, changes in the institutional environment, consciousness, activity, social security, the quality of the education system, healthcare, etc. Despite the root cause of economic development, it is not an end in itself, but a tool for ensuring social development. Gaining access for citizens to education, health care, observance of the principles of equality and justice, ensuring protection are directly dependent on the level of economic well-being, the level of economic potential of the country or regions. The research methodology involved the use of both theoretical and practical methods. As a result of the study, the key elements of the introduction of modern management technologies into the security system in the context of socio-economic development and digitalization of the economy were identified.

• Journal of Korean Society for Quality Management
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• v.49 no.3
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• pp.327-340
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• 2021

Purpose: The purpose of this study is to propose a system predicting whether an electricity distribution system is abnormal by analyzing the temperature of the deteriorated system. Traditional electricity distribution system abnormality diagnosis was mainly limited to post-inspection. This research presents a remote monitoring system for detecting thermal images of the deteriorated electricity distribution system efficiently hereby providing safe and efficient abnormal diagnosis to electricians. Methods: In this study, an object detection algorithm (YOLOv5) is performed using 16,866 thermal images of electricity distribution systems provided by KEPCO(Korea Electric Power Corporation). Abnormality/Normality of the extracted system images from the algorithm are classified via the limit temperature. Each classification model, Random Forest, Support Vector Machine, XGBOOST is performed to explore 463,053 temperature datasets. The process capability index is employed to indicate the quality of the electricity distribution system. Results: This research performs case study with transformers representing the electricity distribution systems. The case study shows the following states: accuracy 100%, precision 100%, recall 100%, F1-score 100%. Also the case study shows the process capability index of the transformers with the following states: steady state 99.47%, caution state 0.16%, and risk state 0.37%. Conclusion: The sum of caution and risk state is 0.53%, which is higher than the actual failure rate. Also most transformer abnormalities can be detected through this monitoring system.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.111-118
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• 1998

This paper describes the development of the database system for tunnel management of Korea National Railways. In order to make the system both target independent and accessible by KNR network or modem, authors developed the system as a web-based application using java language and IBM DB2 database. The system includes the searching, reporting, graphical representation and statistical functions for tunnel data, maintenance records and checking records. Later, the system will be extended to include the process for tunnel state rating and maintenace prioritiy decision-making.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2329-2335
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• 2011

The Wireless low floor tram uses the energy more effectively than other systems with onboard battery system. But for this the SOC(state of charge) management of the battery system is required. This paper is focused on the SOC management strategy of battery system for propulsion in wireless low floor tram. For minimizing consumption energy, the SOC management strategy that maximizes the regeneration energy is studied. The SOC operating region is divided to overcome the limited life cycle pointed out as a disadvantage of battery system. And the effective energy management strategy of tram is suggested through the charge/discharge of the battery system according to tram status in catenary/catenary-free section.

• Journal of IKEEE
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• v.22 no.3
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• pp.754-758
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• 2018

Analysis methods in the power system are static analysis, dynamic analysis and online analysis, offline analysis. The static analysis is used for the existing power system analysis method and the static analysis is mainly used for PSS / E. However, in the real system where the value changes in real time which we are using, dynamic analysis is required which can be analyzed in real time for accurate analysis. Therefore, attention is focused on EMS (Energy Management System) and importance is increasing. Among the various EMS systems, we will cover state estimation, which is a static on-line analysis that can receive and interpret data from the acquisition point in real time. DC systems are spreading in various fields such as DC load, DC distribution, renewable energy. As such, much attention and attention are focused on the DC system. In this paper, we have studied the feasibility through the case study and the interpretation of the state estimation that can be applied to the DC system.