• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.616-618
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• 2000

This paper describes the recent research and technical trend of power cable system. Compact sizing with long length and large capacity is the main trend of the power cable. From the manufacturing process to the monitoring of the underground power line, various new techniques are being developed for reliability and high quality such as in-line monitoring system, triple common extrusion, PD measurement system, new type completion test, etc.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권2호
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• pp.121-130
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• 2009

The power law process model the Rate of occurrence of failures(ROCOF) with monotonic trend during the operating time. However, the power law process is inappropriate when a non-monotonic trend in the failure data is observed. In this paper we deals with the reliability modeling of the failure process of large and complex repairable system whose rate of occurrence of failures shows the non-monotonic trend. We suggest a sectional model and a change-point test based on the Schwarz information criterion(SIC) to describe the non-monotonic trend. Maximum likelihood is also suggested to estimate parameters of sectional model. The suggested methods are applied to field data from an repairable system.

• 대한원격탐사학회지
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• 제33권1호
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• pp.25-35
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• 2017

Spatial downscaling with fine resolution auxiliary variables has been widely applied to predict precipitation at fine resolution from coarse resolution satellite-based precipitation products. The spatial downscaling framework is usually based on the decomposition of precipitation values into trend and residual components. The fine resolution auxiliary variables contribute to the estimation of the trend components. The main focus of this study is on quantitative analysis of impacts of trend component estimates on predictive performance in spatial downscaling. Two regression models were considered to estimate the trend components: multiple linear regression (MLR) and geographically weighted regression (GWR). After estimating the trend components using the two models,residual components were predicted at fine resolution grids using area-to-point kriging. Finally, the sum of the trend and residual components were considered as downscaling results. From the downscaling experiments with time-series Tropical Rainfall Measuring Mission (TRMM) 3B43 precipitation data, MLR-based downscaling showed the similar or even better predictive performance, compared with GWR-based downscaling with very high explanatory power. Despite very high explanatory power of GWR, the relationships quantified from TRMM precipitation data with errors and the auxiliary variables at coarse resolution may exaggerate the errors in the trend components at fine resolution. As a result, the errors attached to the trend estimates greatly affected the predictive performance. These results indicate that any regression model with high explanatory power does not always improve predictive performance due to intrinsic errors of the input coarse resolution data. Thus, it is suggested that the explanatory power of trend estimation models alone cannot be always used for the selection of an optimal model in spatial downscaling with fine resolution auxiliary variables.

• 한국물환경학회지
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• 제26권6호
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• pp.895-902
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• 2010

The effect of seasonality on water quality variation is very significant. Generally, it reduce the power of the trend extraction. A parametric time-series model was used for detecting trends in historic constituent concentration data. The effect of seasonality is able to remove from time series decomposition technique. According to such statistic methode, long-term water quality trend analysis system (NTrend 1.0) was developed by Nakdong River Water Environmental Research Center. The trend analysis of BOD variation was conducted with NTrend 1.0 at Goreong and Moolkum site in Nakdong river to show the effect of water quality management action plan. Power test of trend extraction was tried each case of 'deseasonalized and deannulized' data and 'deseasonalized' data. Analysis period was from 1989 to 2006, and it's period was divided again three times, 1989~1993, 1994~1999 and 2000~2006 according to action plan period. The BOD trend was downward in Goreong site during three times and it's trend slope was very steep, and upward in Moolkum during 1989~1993, but it was turned downward during 1994~1999 and 2000~2006. It was revealed that it's very effective to reduce the concentration of BOD by water quality management action plan in that watershed. The result of power test was shown that it is high for trend extraction power in case of 'deseasonalized' data.

• 한국산학기술학회논문지
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• 제16권11호
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• pp.7957-7963
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• 2015

전동차 보조전원장치는 차량에 취부되는 냉난방장치, 형광등, 제어장치 등에 전원을 공급하는 중요한 장치이다. 산업용과는 달리 전동차용 보조전원장치는 내진동, 내노이즈성이 우수해야 한다. 또한, 유지보수가 편리하고 경량화된 장치이어야 한다. 여기서는 전동차용 보조전원장치의 국내외 기술개발 내용과 관련 특허분석을 살펴보고, 이를 통해 국내 기술개발 방향을 제시하고자 하였다. 이를 위해 2014년 2월까지의 한국, 일본, 유럽 및 미국 출원(등록) 공개된 특허를 대상으로 WIPS DB를 이용하여 공개 및 등록된 특허를 대상으로 분석을 수행하였다. 먼저, 전력변환기와 변압기로 대분류한 후, 전력변환기는 공진형 DC/DC 컨버터, 공진형 Half bridge 인버터로 구분하였다. 변압기는 고주파 변압기, 페라이트 변압기, 매칭 변압기로 다시 중분류를 수행하였다. 새로운 전동차의 보조전원장치 기술을 성공적으로 개발하기 위해서는 기존 보조전원장치에 대해 철저한 분석이 이루어져야 한다. 이를 위해, 특허를 활용하여 전동차용 보조전원장치에 대한 기술 동향을 분석하여 기술 발전이 어떻게 이루어져왔는가를 살펴보았다. 본 연구를 통해, 향후 보조전원장치 기술 발전 추세가 어떤 식으로 전개가 진행될 것인가를 예측하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.501-503
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• 2001

Electric power consumption is highly increasing as the social trend requiring comfortable life, the population in a big city and the industrial development. Therefore it has become to be very important to supply the stable high-quality power. As these trend, the underground power transmission facility is highly increasing in the center of a city. As the proportion to increase facility in tunnel, the fire prevention measures of the underground transmission line become very important.

• 한국수자원학회논문집
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• 제46권3호
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• pp.219-227
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• 2013

수문시계열 자료에 변동성, 도약성, 경향성, 주기성 등이 있으면 이러한 자료는 일반적으로 비정상성을 가지며, 특히 경향성 판단을 통한 다양한 방법들이 제시되어 왔다. 그러나 다양한 방법 간의 검정능력에 대한 평가는 많이 이루어지지 않았으며, 그로인해 동일 자료에 대한 다른 방법의 적용으로 반대의 결과가 나오는 경우도 발생하게 된다. 따라서 본 연구에서는 통계적 특성에 따른 경향성 분석의 변화를 파악하고, 경향성 분석방법 간의 검정능력을 파악해 보았다. 이를 위해 경향성 분석기법인 Mann-Kendall 검정, Hotelling-Pabst 검정, t 검정, Sen 검정을 적용하였으며 기울기, 표본크기, 표준편차에 따라 다양한 모의실험을 수행하였다. 그 결과 t 검정이 다른 검정에 비해 상대적으로 높은 검정력을 보였고, Mann-Kendall 검정, Hotelling-Pabst 검정, Sen 검정은 비슷한 결과를 보였다.

• 설비공학논문집
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• 제24권3호
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• pp.212-217
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• 2012

The cooling of data centers has emerged as a significant challenge as the density of IT equipment increased. With the rapid increasing of heat load and cooling system, predictions for electronics power trends have been closely watched. A data center power density projection is needed so that IT organizations can develop data centers with adequate cooling for reasonable lifetimes. This paper will discuss the need for something more than processor and equipment power trend projections which have overestimated the required infrastructure for customers. This projection will use data from a survey of actual enterprise data centers and the ASHRAE projections to formulate a data center server heat load trend projection.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.330-332
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• 2004

Reliance on electric power has increased together with customer's demand for delightful and convenient linging. Recently, as appeared in the rapid growth of the technology of power electronics, the installation and apparatus using semiconductor applicotion is widly supplied and used from a household goods to industrial goods. However, these machine generate harmonics current and voltage for electric power system. The harmonics current is increased voltage distortion and generate a lot of interference in the electric power system. In this paper, the trend of the trend of suppression technology of harmonics outflow and the fundamental theory about the suppression of harmonics current in the distribution system are investigated and evaluated Therefore we look forward to supply electric power of good quality to satisfy the harmonics current guide line which is applied to household goods in the world.

• 대한전기학회논문지
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• 제34권10호
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• pp.389-398
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• 1985

Recently maximum power demand of our country has become to be under the great in fluence of electric cooling and air conditioning demand which are sensitive to weather conditions. This paper presents the technique and algorithm to forecast the long-term maximum power demand considering the characteristics of electric power and weather variable. By introducing a weather load model for forecasting long-term maximum power demand with the recent statistic data of power demand, annual maximum power demand is separated into two parts such as the base load component, affected little by weather, and the weather sensitive load component by means of multi-regression analysis method. And we derive the growth trend regression equations of above two components and their individual coefficients, the maximum power demand of each forecasting year can be forecasted with the sum of above two components. In this case we use the coincident dry bulb temperature as the weather variable at the occurence of one-day maximum power demand. As the growth trend regression equation we choose an exponential trend curve for the base load component, and real quadratic curve for the weather sensitive load component. The validity of the forecasting technique and algorithm proposed in this paper is proved by the case study for the present Korean power system.