• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.911-917
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• 2016

DC-based power system is paid attention as interests in energy efficiency and power quality are increased. However, standardization and researches for commercializing Low Voltage DC(LVDC) distribution system are still insufficient. Protection system, which is closely related with reliability, power quality, safety, and life expectancy of components in power system, is also included. This paper therefore analyzes fault response characteristics in LVDC distribution system as a preliminary study on protection schemes. A stepwise analysis on fault current from both AC/DC converter and DC/DC converter is performed and related expressions are derived. And then, modeling and simulation with various conditions are conducted by using ElectroMagnetic Transients Program (EMTP) to verify analysis results. Based on research results in the paper, direction for development of protection schemes for LVDC distribution system is suggested.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.838-846
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• 2015

This paper deals with the modified modeling of PV system based on the PSCAD/EMTDC and optimal control method of customer voltages in real distribution system interconnected with the photovoltaic (PV) systems. In order to analyze voltage variation characteristics, the specific modeling of PV system which contains the theory of d-q transformation, current-control algorithm and sinusoidal PWM method is being required. However, the conventional modeling of PV system can only perform the modeling of small-scale active power of less than 60 [kW]. Therefore, this paper presents a modified modeling that can perform the large-scale active power of more than 1 [MW]. And also, this paper proposes the optimal operation method of step voltage regulator (SVR) in order to solve the voltage variation problem when the PV systems are interconnected with the distribution feeders. From the simulation results, it is confirmed that this paper is effective tool for voltage analysis in distribution system with PV systems.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1183-1194
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• 2021

Traditionally, electric power systems have been known as the centralized structures, which is organized into placing customers at the end of the supply chain. However, recent decades have witnessed the emergence of distributed energy resources(:DERs) such as rooftop solar, farming PV system, small wind turbines, battery energy storage systems and smart home appliances. With the emergence of distributed energy resources, the role of distributed system operators(:DSOs) will expand. The increasing penetration of DERs could lead to a less predictable and reverse flow of power in the system, which can affect the traditional planning and operation of distribution and transmission networks. This raises the need for a change in the role of the DSOs that have conventionally planned, maintained and managed networks and supply outages. The objective of this research is to designed the future distribution operation system with multi-DERs and the proposed distribution system model is implemented by hardware-in-the-loop simulation(HILS). The test results show the normal operation domain and reduction of distribution line loss.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.1
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• pp.43-48
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• 2022

Although the distribution system has been structured as complicated as a mesh in the past, the connection points for each line are always kept open, so that it is operated as a radial distribution system (RDS). For RDS, the line utilization rate is determined according to the maximum load on the line, and the utilization rate is usually kept low. In addition, when a fault occurs in the RDS, a power outage of about 3 to 5 minutes occurs until the fault section is separated, and the healthy section is transferred to another line. To improve the disadvantages of the RDS, research on the construction of a networked distribution system (NDS) that linking multiple lines is in progress. Compared to the RDS, the NDS has advantages such as increased facility utilization, load leveling, self-healing, increased capacity connected to distributed generator, and resolution of terminal voltage drop. However, when a fault occurs in the network distribution system, fault current can flow in from all connected lines, and the direction of fault current varies depending on the fault point, so a high-precision fault current direction determination method and high-speed communication are required. Therefore, in this paper, we propose an accurate fault current direction determination method by comparing the peak value polarity of the fault current in the event of a fault, and a communication-based protection coordination method using this method.

• ETRI Journal
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• v.25 no.6
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• pp.423-436
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• 2003

This paper describes our design of a contents distribution framework that supports transparent distribution of digital contents on the Internet as well as copyright protection of participants in the contents distribution value chain. Copyright protection must ensure that participants in the distribution channel get the royalties due to them and that purchasers use the contents according to usage rules. It must also prevent illegal draining of digital contents. To design a contents distribution framework satisfying the above requirements, we first present four digital contents distribution models. On the basis of the suggested distribution models, we designed a contract system for distribution of royalties among participants in the contents distribution channel, a license mechanism for enforcement of contents usage to purchasers, and both a packaging mechanism and a secure client system for prevention of illegal draining of digital contents.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.2
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• pp.146-151
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• 2005

Some distributions have been used for diagnosing the lead time demand distribution in inventory system. In this paper, we describe the negative binomial distribution as a suitable demand distribution for a specific retail inventory management application. We here assume that customer order sizes are described by the Poisson distribution with the random parameter following a gamma distribution. This implies in turn that the negative binomial distribution is obtained by mixing the mean of the Poisson distribution with a gamma distribution. The purpose of this paper is to give an interpretation of the negative binomial demand process by considering the sources of variability in the unknown Poisson parameter. Such variability comes from the unknown demand rate and the unknown lead time interval.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.4
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• pp.79-84
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• 2005

Some distributions have been used for diagnosing the lead time demand distribution in inventory system. In this paper, we describe the negative binomial distribution as a suitable demand distribution for a specific retail inventory management application. We here assume that customer order sizes are described by the Poisson distribution with the random parameter following a gamma distribution. This implies in turn that the negative binomial distribution is obtained by mixing the mean of the Poisson distribution with a gamma distribution. The purpose of this paper is to give an interpretation of the negative binomial demand process by considering the sources of variability in the unknown Poisson parameter. Such variability comes from the unknown demand rate and the unknown lead time interval.

• Journal of Distribution Science
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• v.11 no.4
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• pp.89-97
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• 2013

Purpose - The purpose of this study is to systematically review the background of the Korean distribution promotion policy and distribution adjustment policies along with related regulations and policies. Research design, data, and methodology - Domestic distribution policy and relevant laws were examined through a review of existing research literature. The results of the development process of the domestic distribution policy, promotion policies, and adjustment policies are summarized below. Results - The results are summarized as follows. First, the purpose of the development of the domestic distribution promotion policy was to strengthen the competitiveness of the small and medium business industry through structural advancement of the small and medium industry. By expanding the managerial base for the small and medium industry, a new balance could be created in the national economy. There was a requirement for an early assistance policy for small and medium businesses as a base of these businesses in the distribution industry developed from their original model of catering to a traditional market of retail shops. Since 1996, there was a need for this early assistance policy due to the expansion and rapid growth of large scale stores causing a change in the consumption pattern for distribution markets and the decline of large enterprises. Second, the government supports small and medium business distribution through distribution promotion policies by supporting an organization promoting small business and supporting innovation in the distribution system. Third, in 1961 a business mediation system was established to protect small and medium industries. The Small and Medium Business Administration advises conglomerates to postpone acquisitions, restrain expansion of the business, or to reduce business scale if small businesses undergo an adverse effect such as decreasing demand because large companies are expanding into their areas. Fourth, the Distribution Adjustment Policy managed large-scale store regulation as follows: ① limitation on construction by urban planning ordinance, ② limitation on location based on traffic impact assessments, ③ regulation based on business guidelines by chiefs of autonomous bodies, ④ regulation on mandatory holidays and limitation of business hours. This large-scale store regulation is a policy introduced by authority to increase competitiveness of small and medium business distribution by the government. Conclusions - As discussed in this study, the distribution promotion policy and distribution adjustment policy are government distribution policies focused on the protection of the small and medium distribution businesses. This study is timely, since it was planned when the strengthening of the revisions of the Distribution Industry Development Act, aimed to protect small and medium retailers and merchants, was under discussion. The significance of this study is that it offers insights for the development of new policies in the future and an opportunity to consider the background of the distribution policy by the government.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.306-309
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• 2008

A system realization for video surveillance with interframe probability distribution analysis is presented in this paper. The system design is based on a high performance DSP processor, video surveillance is implemented by analyzing interframe probability distribution for scanning objects in a restricted area and the video analysis algorithm is decided for forming a different image from the probability distribution of several frames compressed by the standardized JPEG. The algorithm processing time of D1($720{\times}480$) image per frame is 85ms.

• Journal of the military operations research society of Korea
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• v.11 no.1
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• pp.87-110
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• 1985

This paper presents optimum policy of water supply distribution of the Osaka Prefecural Waterworks System located in the midwest of Japanese Islands. Owing to the ever increasing demand for water, the Osaka Prefectural Government endeavors to expand potable and industrial water distribution system to satisfy the growing water demand of the constituents under its jurisdiction. In this regard, the paper discusses a problem of establishing an efficient and effective water distribution system. The criteria to be considered are stability of water level at the reservoirs, stability of flow in the network, and the water treatment and distribution cost. These objective functions may be combined to form a multiple objective optimization problem or may be used independently and formulated into single objective optimization problems.