• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1631-1637
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• 2018

Electric utilities has been considered the necessity to introduce asset management of electric power facilities in order to reduce maintenance cost of existing facilities and to maximize profit. This paper aims to provide data that can helpful to make profitable decision in terms of power transformers which have a significant part in the power system. Therefore, this study is modeling input cost for power transformer during its entire life and also the life cycle cost (LCC) technique is applied. In particular, the variation of transformer state related with maintenance and the variation of the EUAC curve based on cost and effect of maintenance is examined. In this study, the trend of the equivalent uniform annual cost (EUAC) according to maintenance cycle and cost of equipment is analyzed. In line with that, sensitivity analysis influenced by the changes of other cost factors was performed.

• 한국농공학회논문집
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• 제54권5호
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• pp.141-153
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• 2012

In this study, we estimated probable precipitation amounts at the target year (2020, 2030, 2040) of 55 weather stations in Korea using the 24 hour annual maximum precipitation data from 1973 through 2009 which should be useful for management of agricultural reservoirs. Not only trend tests but also non-stationary tests were performed and non-stationary frequency analysis were conducted to all of 55 sites. Gumbel distribution was chosen and probability weighted moment method was used to estimate model parameters. The behavior of the mean of extreme precipitation data, scale parameter, and location parameter were analyzed. The probable precipitation amount at the target year was estimated by a non-stationary frequency analysis using the linear regression analysis for the mean of extreme precipitation data, scale parameter, and location parameter. Overall results demonstrated that the probable precipitation amounts using the non-stationary frequency analysis were overestimated. There were large increase of the probable precipitation amounts of middle part of Korea and decrease at several sites in Southern part. The non-stationary frequency analysis using a linear model should be applicable to relatively short projection periods.

• 한국의류학회지
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• 제46권6호
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• pp.1004-1022
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• 2022

This study seeks to investigate K-fashion's external image by examining the trends in global media reporting. It applies Dynamic Topic Modeling (DTM), which captures the evolution of topics in a sequentially organized corpus of documents, and consists of text preprocessing, the determination of the number of topics, and a timeseries analysis of the probability distribution of words within topics. The data set comprised 551 online media articles on 'Korean fashion' or 'K-fashion' published on Google News between 2010 and 2021. The analysis identifies seven topics: 'brand look and style,' 'lifestyle,' 'traditional style,' 'Seoul Fashion Week (SFW) event,' 'model size,' 'K-pop,' and 'fashion market,' as well as annual topic proportion trends. It also explores annual word changes within the topic and indicates increasing and decreasing word patterns. In most topics, the probability distribution of the word 'brand' is confirmed to be on the increase, while 'digital,' 'platform,' and 'virtual' have been newly created in the 'SFW event' topic. Moreover, this study confirms the transition of each K-fashion topic over the past 12 years, along with various factors related to Hallyu content, traditional culture, government support, and digital technology innovation.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.331-337
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• 1998

This study was carried out to derive optimal design floods by Weibull-3 distribution with the annual maximum series at seven watersheds along Man, Nagdong, Geum, Yeongsan and Seomjin river systems. Adequacy for the analysis of flood data used in this study was acknowledged by the tests of Independence, Homogeneity, detection of Outliers. Parameters were estimated by the Methods of Moments and L-Moments. Design floods obtained by Methods of Moments and L-Moments using different methods for plotting positions in Weibull-3 distribution were compared by the rotative mean error and relative absolute error. It has shown that design floods derived by the method of L-moments using Weibull plotting position formula in Weibull-3 distribution are much closer to those of the observed data in comparison with those obtained by method of moments using different formulas for plotting positions in view of relative mean and relative absolute error.

• 현장농수산연구지
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• 제13권1호
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• pp.83-102
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• 2011

The purpose of this study carried out to analyze production status, pricing trend and distribution status of landscape plants, so that it could predict the demand of landscape plants for the balance of supply and demand. The production amount of landscape plants made constantly increased. The annual output of shrubs increased more higher than that of trees. The prices of trees have raised consistently, but shrubs were susceptible to price fluctuations. And there were still many problems in the distribution structure. The landscaping work has focused on the metropolitan area. And large-scale nationwide projects were scheduled for coming years, so the demand of landscape plants was expected to expend. However, the lack of increase in production amounts of landscape plants, it is cause to supply problems. So, demand forecast was necessary to control the production of landscape plants.

• 한국해안·해양공학회논문집
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• 제32권1호
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• pp.26-38
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• 2020

설계파고 추정에 사용한 AM 자료의 IID 가정에 대한 검정을 수행하였다. 검정은 독립 검정, 분포 차이 검정으로 구분하고, 각각의 검정은 태풍, 비태풍 조건에서의 연안 격자, 연안 내부격자 각각 210개, 310개 지점의 AM 자료 세트를 대상으로 수행하였다. 독립 검정 결과, 비태풍, 태풍 자료 세트에 대하여 각각 1.8~5.3%, 1.4~6.0% 범위의 기각 비율을 보여, 대부분의 자료가 독립 검정을 만족하는 것으로 파악되었다. 한편 태풍 자료와 비태풍 자료의 분포 차이 검정은 연안 격자와 연안 내부격자 모두 검정 방법에 따라 47~79% 범위로 동일분포 가설이 기각되는 것으로 파악되었다. 따라서 극치해석에 의한 설계파고 추정에서 두 자료를 구분하여 각각 설계파고를 추정하는 과정이 적절하다.

• 물과 미래
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• 제18권4호
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• pp.335-345
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• 1985

추계학적 이론을 근거로 하는 하천유량의 모의발생 모형에는 여러 가지가 있으며 이는 한정된 짧은 기간동안의 유량 실측치의 통계학적 특성을 재현시키는 일련의 장기적 유량자료를 인위적으로 발생시켜 수자원 시스템의 거동예측이나 조작기준을 보다 완벽하게 설정하기 위한 풍부한 인력 자료를 제공하자는 데 목적이 있다. 본 연구에서는 연유량의 모의발생에 주로 사용되는 Monte Carlo 모형을 연유량 자료를 구성하는 월별 하천유량의 발생에 적용 가능한가를 연구 검토하였다. 비교검토의 목적으로 실측된 월별 유량의 적정분포형을 설정한 후 Monte Carlo 방법에 의해 발생된 월별량과Autoregressive 모형중의 하나인 Thomas-Fiering의 다계절 모형에 의해 발생된 월류량의 통계학적 특성치의 실측치의 특성치와 비교하였다. 한편, 월유량 발생자료의 합성에 의한 연류량 자료의 특성치가 실측 월류량의 합성에 의한 월류량 특성치를 얼마나 잘 재현시키는가를 검사하기 위해 Monte Carlo 및 Thomas-Fiering 모형에 의해 발생시킨 연류량의 통계학적 특성치를 실측류량의 통계특성치와 비교평가하였다.

• 농촌계획
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• 제26권3호
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• pp.91-102
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• 2020

The purpose of study was analyze the pumping characteristics, Irrigation Efficiency(IE), and irrigation pattern by period of rice growing stage with based on the performance of design irrigation water requirement and operational Galshin Pumping(GP) station in GP irrigation district constructed under rural water development project master plan. GP station was located in Yedang reservoir, Yesan-gun, Chungcheongnam-do and has been supplying irrigation water since 2006. The research data are the Irrigation Water Requirement(IWR) and the Pumping Water Amount(PWA) from 2006 to 2015 at the GP station, which is the supplied amount. The IWR were calculated using the Blaney-Criddle formula of the HOMWRS program, Hydrological Operation Model for Water Resource System, developed by Korea Rural Community Corporation. The Blaney-Criddle formula was used to calculate design irrigation water requirement of Galshin rural water development project master plan. During 2006-2015, the study period, the annual average IWR is 763.2(±149.1)mm, the annual PWA of the GP station is 397.4mm to 1,056.9mm, and those average annual PWA is 643.4(±208.4)mm. The annual IE of GP station 96.5% to 169.0%, and the average annual IE is 124.3%, which is higher than the research results conducted in other pumping stations. Analyzing the irrigation patterns of the GP irrigation district, the IWR Ratio per 10days(IWRR) and the PWA Ratio per 10days(PWAR) of the G P station were obtained. The IWRR is the percentage of IWR for each 10 days of a month to total IWR per year, and the PWAR is the percentage of PWA for each 10 days of a month to total PWA per year. The Kolmogorov- Smirnov(K-S) test results of IWRR and PWAR showed the characteristics classification by rice growing stage and stable normal distribution characteristics. Average IWRR(AIWRR) and Average PWAR(APWAR) are presented as irrigation patterns. Irrigation pattern analysis will be able to standardize comparison, analysis and probability calculation of the pumping station characteristics of different pumping stations and apply to objective evaluation of the pumping station district.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2042-2048
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• 2014

In medium voltage electrical distribution networks, reforming the loss reduction is important, and in line with this, the issue of system engineering and use of proper equipment Expansion of distribution systems results in higher system losses and poor voltage regulation. Therefore, an efficient and effective distribution system has become more important. So, proper selection of conductors in the distribution system is crucial as it determines the current density and the resistance of the line. Evaluation of aging conductors for losses and costs imposed in addition to the careful planning of technical and economic networks can be identified in the network design. In this paper the use of imperialist competitive algorithm; genetic algorithm; is proposed to optimal branch conductor selection and reconstruction in radial distribution systems planning. The objective is to minimize the overall cost of annual energy losses and depreciation on the cost of conductors to improve productivity given the maximum current carrying capacity and acceptable voltage levels. Simulations are carried out on 69-bus radial distribution network using genetic algorithm approaches to show the accuracy as well as the efficiency of the proposed solution technique.

• 한국농공학회지
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• 제40권2호
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• pp.59-68
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• 1998

This study was conducted to derive optimal design floods by generalized gamma distribution model of the annual maximum series at eight watersheds along Geum, Yeongsan and Seomjin river systems. Design floods obtained by different methods for evaluation of parameters and for plotting positions in the generalized gamma distribution model were compared by the relative mean errors and graphical fit along with 95% confidence limits plotted on gamma probability paper. The results were analyzed and summarized as follows. 1. Basic statistics and parameters were calculated by the generalized gamma distribution model using different methods for parameters. 2. Design floods according to the return periods were obtained by different methods for evaluation of parameters and for plotting positions in the generalized gamma distribution model. 3. It was found that design floods derived by sundry averages method for parameters and Cunnane method for plotting position in the generalized gamma distribution are much closer to those of the observed data in comparison with those obtained by the other methods for parameters and for plotting positions from the viewpoint of relative mean errors. 4. Reliability of design floods derived by sundry averages method in the generalized gamma distribution was acknowledged within 95% confidence interval.