• 전기학회논문지
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• 제60권7호
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• pp.1410-1416
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• 2011

A corrosion detecting system for 22.9 kV distribution power line insulation cable, which can travel autonomously along the live line, is proposed. Eddy current test method is employed to detect the corrosion, and the system developed here is capable of detecting internal corrosion of a ACSR-OC. Somewhat details of the electrical and mechanical mechanism of the system and traveling algorithm are introduced. Experimental results applied to the sample cables having artificial corrosion and the operating distribution lines are provided. From the result, we confirmed that the system is useful for detecting internal corrosion of a ACSR, and is expected to be a new non-destructive testing equipment in the area of diagnosis for the distribution power line.

• 전기학회논문지
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• 제61권9호
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• pp.1226-1231
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• 2012

The demand for electrical power has been significantly increased to satisfy the customers. As a result, a power distribution system have been advanced by power system's interconnection, installation of distributed generator(DG) and so on. The improvable power distribution system included the problem of increasable fault current. Superconducting fault current limiter (SFCL) is one of the solutions to limit a fault current. Therefore, to solve the problem of fault current by SFCL, simulation was progressed and the simulation used a PSCAD/EMTDC.

• 조명전기설비학회논문지
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• 제17권3호
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• pp.87-94
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• 2003

배전계통에서의 사고 발생시 정전으로 인한 수용가의 손실을 최소로 하기 위하여 정전구역에 대한 신속한 복구가 이루어져야 한다. 본 논문에서는 배전계통의 정전복구를 위한 전문가 시스템을 제안하였다. 제안된 전문가 시스템은 복구과정에서 전문가의 경험적 규칙을 이용함으로써 복구에 소요되는 스위칭 횟수를 최소화 하도록 하였다. 복구 과정은 일반적인 위상구조 지식 기반의 응용을 통해 전문가 시스템의 상태공간에서 타당한 경로를 찾는 문제로 표현하였다. 또한, 다양한 배전계통 구조를 고려하기 위해 다중 부하절체 기법을 제안하였다.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.1043-1050
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• 2014

Obsolescent control systems for power systems are evolving into intelligent systems and connecting with smart devices to give intelligence to the power systems. As networks of the control system are growing, vulnerability is also increasing. The communication network of distribution areas in the power system connects closely to vulnerable environments. Many cyber-attacks have been founded in the power system, and they could be more critical as the power system becomes more intelligent. From these environment, new communication network architecture and mitigation method against cyber-attacks are needed. Availability and Fault Tree analysis used to show that the proposed system enhances performance of current control systems.

• 동력기계공학회지
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• 제2권1호
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• pp.25-30
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• 1998

In order to investigate the droplet size distribution and Sauter Mean Diameter in a ultra high pressure diesel spray, fuel was injected with ultra high pressure into the environments of high pressure and room temperature by an Electronic Hydraulic Fuel Injection System. Droplet size was measured with the immersion liquid sampling technique. The immersion liquid was used a mixture of water-methycellulose solution and ethanol. The Sauter Mean Diameter decreased with increasing injection pressure, with a decrease environmental pressure (back pressure) and nozzle diameter. Increasing the injection pressure makes the fuel density distribution of the spray more homogeneous. An empirical correlation was developed among injection pressure, air density, nozzle diameter and the Sauter Mean Diameter of spray droplets.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.403-405
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• 2004

A service restoration is one of the most important missions in distribution system operation. This paper proposes a multi-agent system approach to distribution system restoration. Every relay is developed as an agent by adding its own intelligent, self-tuning and communication ability. Relay agent calculates and corrects its restoration index by itself through communication with neighboring agents and its own intelligence. The proposed algorithm is applied to a simple network to show how to calculate restoration index. Keywords Multi-Agent System, Service Restoration, Distribution Networks

• Journal of Communications and Networks
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• 제18권5호
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• pp.688-698
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• 2016

In this paper, we investigate the achievable sum rate and energy efficiency of downlink massive multiple-input multiple-output antenna systems with zero-forcing precoding, by taking into account the randomness of user locations. Specifically, we propose two types of non-uniform user distributions, namely, center-intensive user distribution and edge-intensive user distribution. Based on these user distributions, we derive novel tight lower and upper bounds on the average sum rate. In addition, the impact of user distributions on the optimal number of users maximizing the sum rate is characterized. Moreover, by adopting a realistic power consumption model which accounts for the transmit power, circuit power and signal processing power, the energy efficiency of the system is studied. In particular, closed-form solutions for the key system parameters, such as the number of antennas and the optimal transmit signal-to-noise ratio maximizing the energy efficiency, are obtained. The findings of the paper suggest that user distribution has a significant impact on the system performance: for instance, the highest average sum rate is achieved with the center-intensive user distribution, while the lowest average sum rate is obtained with the edge-intensive user distribution. Also, more users can be served with the center-intensive user distribution.

• Journal of Forest and Environmental Science
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• 제36권1호
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• pp.7-16
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• 2020

Tree size distribution modelling is an integral part of forest management. Most distribution yield systems rely on some flexible probability models. In this study, a simple finite mixture of two components two-parameter Weibull distribution was compared with complex four-parameter distributions in terms of their fitness to predict tree size distribution of teak (Tectona grandis Linn f) plantations. Also, a system of equation was developed using Seemingly Unrelated Regression wherein the size distributions of the stand were predicted. Generalized beta, Johnson's SB, Logit-Logistic and generalized Weibull distributions were the four-parameter distributions considered. The Kolmogorov-Smirnov test and negative log-likelihood value were used to assess the distributions. The results show that the simple finite mixture outperformed the four-parameter distributions especially in stands that are bimodal and heavily skewed. Twelve models were developed in the system of equation-one for predicting mean diameter, seven for predicting percentiles and four for predicting the parameters of the finite mixture distribution. Predictions from the system of equation are reasonable and compare well with observed distributions of the stand. This simplified mixture would allow for wider application in distribution modelling and can also be integrated as component model in stand density management diagram.

• 한국유기농업학회지
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• 제15권2호
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• pp.151-169
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• 2007

By the environment-friendly(hereafter EF) agricultural policy and toward the safety food of consumers, there is much glowing supply and demand fur EF agricultural products, in Korea. But, in general, EF agricultural products are blown as unique, unreasonable and high price system. This study aims to make clare the main bodies and competition structure in EF agricultural products and the different from the agricultural products. The mail results of this study are summarized as follows. Firstly, farmers and consumers directly participate in the distribution, and the major distributors participate in the market of EF agricultural products after the certification system is got ready. Because EF agricultural products is not dealt and the price system is not built up in agricultural wholesale market. Secondly, the distribution route of EF agricultural products is organized the unified organization by the main bodies such as farmers, consumers co-op, and special distributors. In any step of distribution, the main body of distribution surely deals with the contracted farmers, consumers co-op, and special distributors. Accordingly, it is said that EF agricultural products has the competition structure between the distribution route organized the unified organization rather than between main bodies in the each steps of distribution.

• 한국물환경학회지
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• 제33권3호
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• pp.359-369
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• 2017

Water distribution systems supply drinking water to consumers' taps. Internal corrosion of metallic pipe used in drinking water distribution systems has reduced water quality and led to increased levels of toxic heavy metals such as lead, copper and nickel. These problems have been experienced to varying degrees by water utilities in many countries. North America has successfully managed and controlled pipe corrosion and corrosive water in water distribution system based on various policies, regulations and rules. Practical and engineering guidelines for evaluation of pipe corrosion and determination of treatment options are also provided to assist drinking water supplies. In addition, the corrosion mechanism in water distribution systems, such as the complex effects of physical and chemical parameters on the corrosion pipes has been improved to accurately predict corrosion rates of metallic pipes in actual water distribution systems. This paper reviews various regulations, policy statement, and treatment produces on controlling corrosion in drinking water distribution systems in US and Canada and then offers suggestion for management of corrosive water and pipe corrosion in drinking water distribution system in Korea.