• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.367-370
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• 2001

본 논문에서는 누설전류 파고분석을 이용한 전력선비의 새로운 열화 진단법을 제안하였다. 현재까지 여러가지 열화 진단법이 제안되었으며, 평가요소로 누설전류의 크기만을 이용하는 것이 일반적이었다. 본 연구에서는 피뢰기, 케이블 등의 전력설비들이 열화가 진전됨에 따라 누설전류의 파고분포도 크게 달라짐을 알 수 있었다. 따라서 전력설비의 열화진단에 누설전류의 파고분포를 이용하면 기존의 누설전류의 크기만을 이용하는 방법보다 더 정확한 평가가 가능하다. 피뢰기, 케이블을 이용한 여러 가지 적용실험으로부터 제안한 열화 진단법은 충분한 성능이 있음을 확인하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권4호
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• pp.152-157
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• 2002

This paper describes an effect of a single- and a quadruple-lightning impulse currents on electrical characteristics of ZnO blocks, and an expert system to diagnose arrestor deterioration. To deduce the parameters needed for diagnosing arrester deterioration, an accelerate deterioration teat is carried out. In the experiment, leakage current components are measured. Also, wave height distribution of the leakage current according to the progress of arrester deterioration is analyzed. From the experimental results, the wave height distribution of the leakage current showed conspicuous difference even in an immaterial leakage current increase. Therefore, the use of wave height distribution of the leakage current in deterioration diagnostic technique makes more accurate diagnosis than the conventional method by using only a leakage currant value. Finally, the expert system based on the experimental results is developed and the system can diagnose arrestor deterioration by measuring the leakage current and its wade height distribution.

• Journal of Ecology and Environment
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• 제35권4호
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• pp.331-341
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• 2012

Using data sets for Japan as a whole, as arranged with approximately $10{\times}10$ km squares (a secondary grid), we investigated the relationship between population density and the habitats of threatened vascular plants listed in the Japanese Red Data Book; depopulated areas in the present and future, areas where under-use may be serious, and those with a predominance of elderly people; and the present state of the habitats in terms of a characteristic land use pattern. Regarding the habitats of threatened vascular plants, the progress of deterioration [$(N_{CR}+N_{EN})/(N_{CR}+N_{EN}+N_{VU})$] in depopulated areas has been confirmed, where $N_{CR}$, $N_{EN}$, and $N_{VU}$ are the numbers of species classified as critically endangered, endangered, and vulnerable, respectively. Moreover, in grid squares used by a human such as farmland, the progress of the deterioration simply increases when population density becomes low. However, for many vascular plants, they are particularly endangered in populous areas. Local populations will decrease throughout Japan with the rate of depopulation in and around large cities being relatively slow. We also propose some issues that need further study. The deterioration by human activity may be reduced. On the other hand, some vascular plants may be adversely influenced by depopulation. Additionally, we should keep a close watch on grasslands and water areas in large cities to preserve vascular plants.

• 한국철도학회논문집
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• 제19권4호
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• pp.547-554
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• 2016

본 연구는 궤도 틀림을 관리하기 위한 궤도 품질 지수(TQI)의 진전율 추정에 관한 것이다. 이와 관련한 기존 연구 대부분은 시간에 따른 TQI 값의 선형 회귀분석을 통해 구해진 기울기를 기준으로 상수 진전율을 제시하는 데 그치고 있다. 본 연구는 과거 데이터 혹은 전문가의 식견으로부터 도출되는 파라미터의 사전 분포를 효과적으로 반영할 수 있으며, 파라미터값의 확률 분포를 유도해 낼 수 있는 베이지안 방법론에 기초한 진전율 추정 모델을 제안하고, 기존의 전통적인 회귀분석 모형과의 비교 연구를 통해, 베이지안 방법론의 활용 가능성을 검토해 보았다.

• Industrial Engineering and Management Systems
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• 제4권2호
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• pp.192-197
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• 2005

Among many amplitude parameters, Kurtosis (4-th normalized moment of probability density function) is recognized to be the sensitive good parameter for machine diagnosis. Kurtosis has a value of 3.0 under normal condition and the value generally goes up as the deterioration proceeds. In this paper, simplified calculation method of kurtosis is introduced for the analysis of impact vibration with one sided affiliated impact vibration which occurs towards the progress of time. That phenomenon is often watched in the failure of such as bearings’ outer race. One sided affiliated impact vibration is approximated by one sided triangle towards the progress of time and simplified calculation method is introduced. Varying the shape of one sided triangle, various models are examined and it is proved that new index is a sensitive good index for machine failure diagnosis. Utilizing this method, the behavior of kurtosis is forecasted and analyzed while watching machine condition and correct diagnosis is executed.

• 한국철도학회논문집
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• 제7권4호
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• pp.307-311
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• 2004

Arresters are the best protective device on electrical power systems against transient overvoltages generated by lightning and/or switching operation. Nonetheless, arresters are deteriorated by absorption of moisture in the environments of its use, repetition in the protective operation to overvoltages, and some defects at manufacturing. It is therefore important to estimate the electrical characteristic changes of ZnO blocks. In this paper, an accelerated ageing test by a standard lightning impulse current was carried out to extract parameters needed for arrester diagnosis, and leakage current components were measured. Total energy applied to the ZnO blocks at each time is about 1,050[J] in 8/20[${\mu}\textrm{s}$] impulse current. From the experimental results, we proposed electrical parameters and leakage current level to diagnose arrester soundness.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.232-235
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• 2000

Design and experiments of a nondestructive system to inspect deterioration of ACSR-OC (ACSR Outdoor Cross-linked Polyethylene Insulated Wire usually used in HV overhead distribution lines presented in this paper. ACSR-OC conductor built to pollutants air for a long period would be easily progress to corrode so that it may lead to the reduction of the effective cross section area of conductors. A fault diagnosis system consisting of a solenoid sensor, a constant current source with RF frequency signal processing unit and a motor driver/controller designed and implemented. This instrument can dot the sensor output variation due to deterioration corrosion, continuously. As a result, it was shown such corrosion detector can readily be utilized estimating the diameter change due to deterioration overhead distribution lines and in giving an warning or inform before severe aged conductor lead to fail.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.142-145
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• 2002

This paper describes an influence of system voltage harmonics on arrester deterioration diagnostic techniques based on leakage current measurement because the resistive current is composed of two components caused by nonlinear characteristics of arrester and by system voltage harmonics. Resistive leakage currents of arresters, which can be evaluated by the third harmonic component of total leakage currents, increase with its deterioration progress. In this paper, we developed a PSpice model for ZnO arrester to simulate the harmonics' effect described above. In simulation, pure sinusoidal voltage and the $3^{rd}$ harmonic voltage are applied to the model, and the leakage current changes are compared. The simulation results showed that the magnitudes of resistive leakage current depend not only on the phase of system voltage harmonics but also on the magnitude of it.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.583-588
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• 2000

While a great progress has been achieved in predicting the ultimate shear strength in the RC members, it is a fact that a method in order to estimate the ductility of RC members still has to be looked for. This study theoretically predict the ductility of RC beams which fail in shear after flexural yielding by considering the deterioration of concrete strength in plastic hinge region.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.311-315
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• 1996

This Paper is to discribe the ac treeing deterioration in Polyethylenetherphthalate (PET) at various temperature. The AC tree was investigated at 77K using L$N_2$. The experimental results show that V-t characteristics was an inverse proportion to temperature. The progress of tree initiation and growth were also to temperature.