• 설비공학논문집
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• 제15권5호
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• pp.432-438
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• 2003

This paper describes a modified Roebuck compression device as a potential compression device of a rotating cryogenic refrigeration system in superconducting machine such as generator or motor. The conventional cryogen transfer method from stationary refrigeration system to rotating system can be eliminated by an on-board cryogenic refrigeration system that utilizes well-designed multi-stage modified Roebuck compression device. This paper shows basic thermodynamic analysis of modified Roebuck compression device and its application for compressing neon at 77 K with substantial pressure ratio when the rotor diameter is 0.8 m with rotating speed of 3600 rpm. The device does not require any moving part in rotating frame, but two separate thermal reservoirs to convert thermal energy into mechanical compression work. The high temperature thermal reservoir is atmospheric environment at 300 K and the low temperature thermal reservoir is assumed as a liquid nitrogen bath at 77 K. The concept of the compression device in this paper demonstrates its usefulness of generating high-pressure neon at 77 K for rotating J-T neon refrigeration cycle of superconducting rotor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1426-1428
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• 2000

A new block system - MAS (Moving Autoblock System) whose efficiency is higher than FAS(Fixed Autoblock System) in the loading capacity is required to accomodate the increasing transport volume. That MAS has higher efficiency has already been verified through various studies, especially in a line with different types of travelling trains. The efficiency of MAS for Korean high speed line with two different train model is analyzed by computer simulation. The results show that MAS is more efficient than FAS in the loading capacity.

• 한국환경농학회지
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• 제23권1호
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• pp.41-46
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• 2004

하천 수질관리 대안을 제시하고자 동진강에 영향을 가장 크게 미치는 정읍천을 대상으로 2002년 1월부터 2003년 12월까지 점 및 비점 오염원으로부터 수질오염물질의 부하량, 유출경로 등을 평가하였다. 계절별 수질 변화는 pH범위가 $6.87{\sim}7.53$으로 봄의 pH 범위가 컸으며, EC 농도는 정읍천 중류가 높았으며, 상류유역은 $83{\sim}95\;{\mu}s/cm$ 범위를 나타냈고, 계절별로 가을에 $517\;{\mu}/cm$로 가장 높았다. BOD의 농도는 상류유역에서 $0.61{\sim}1.27\;mg/L$로 I 급수 수질을 나타내었으나, 중류와 하류에서는 III등급 수준이었다. T-N의 농도는 정읍천 중류 유역이 $6.10{\sim}10.84\;mg/L$로 가장 높았고, T-P의 농도는 타 오염물질에 비해 농도의 편차가 컸으며, 특히 중류에서 T-P의 농도가 $0.41{\sim}0.98\;mg/L$로 높았다. BOD의 배출부하량은 J4 유역에서 553 kg/day로 가장 많았고 T-N 발생부하량은 가축, 인구, 토지이용, 산업의 순으로 켰으며, T-N 배출부하량은 인구 및 산업에 의한 것은 J4 유역, 가축과 토지이용에 의한 부하량은 J5, J6유역에서 높았다. T-N의 유달부하량은 하류 유역에서 높았으며, T-P의 유달 부하량은 BOD, T-N에 비하여 유달부하량이 낮았고 유달율은 $6{\sim}38%$ 범위를 나타냈다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.1291-1292
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• 2012

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.86.2-86.2
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• 2005

• 대한기계학회논문집A
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• 제40권6호
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• pp.539-546
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• 2016

본 연구에서는 C(T) 시편 측면 홈의 유무에 따른 J-R 곡선의 변화가 유한요소 손상해석의 모델변수 결정에 미치는 영향을 알아보았다. 손상해석은 수정 응력 파괴변형률 모델을 이용하였다. C(T) 시편은 SA508 Gr. 1a 배관재에서 채취하였고 일부에 측면 홈이 가공되었다. 시험은 상온과 원전 운전 온도인 $316^{\circ}C$에서 각각 수행되었으며, 시험 결과 얻은 J-R 곡선을 모사하여 손상모델 변수를 얻었다. 그 결과, 측면 홈의 유무에 따른 J-R 곡선의 변화는 손상모델 변수 결정에 영향을 주지 않음을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1758-1760
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• 1997

Automatic detection system to detect acoustic emission pulse and fractal dimension were developed, to observe tree deterioration phenomena in LDPE. The purpose of our work are to use acoustic emission system and fractal dimension and to investigate the treeing phenomena in polymeric insulation under applied AC voltage 11[kV] with an artificial needle-shaped void(1.5[mm]) using the above system. We analyzed and phase angle-acoustic emission pulse amplitude-deterioration time ($\Phi$-AEA-t) pattern and phase angle-acoustic emission pulse number-deterioration time($\Phi$-AEN-t) pattern using statistical operators such as skewness, fractal dimension. In this paper show that the correlation of $\Phi$-AEA-t, $\Phi$-AEN-t, fractal dimension using regression analysis by the method of least squares can be used to predict the breakdown just before the breakdown occurs.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.60-67
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• 1998

In this study, the J-Resistance Curve and material tearing modulus of SA508-C3 steel, which is one of the used nuclear pressure vessel steel, are measured ar room temperature, $200^{circ}C$ and $300^{circ}C$ according to load ratio analysis and ASTM E813, ASTM E1152, respectively. It is observed that J-R curve and Tmat value decrease as the temperature level increase. Applicability of $T_j$ proposed by Paris et al as instability parameter for ductile material is investigated. It is concluded that results are the $T_j$ parameter may be used as a crack instability parameter.

• 소성∙가공
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• 제30권4호
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• pp.165-171
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• 2021

This study was conducted on the manufacturing method of high-strength aluminum bolts. We obtained the displacement-load information by tensile test of the Al 6056 raw material and the T6 heat-treated material and calculated the precise flow stress and fracture limit using repetitive finite element analysis for before and after heat treatment. We designed a multi-stage forging process for T6 heat-treated material, and calculated that the accumulated damage value does not exceed fracture limits by finite element method. We produced the prototype forgings without any harmful defects such as cracks and folding occurring. Bolts made of T6 heat treated material show 9.6%higher tensile strength than T6 heat treated material after wire drawing.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1638-1640
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• 2003

In the recent years, UHF PD measuring technique for detecting partial discharges was proved the effective method for Gas Insulated Switchgear (GIS). However, in case of GIS with a metal flange around insulating spacer, UHF PD measurement using typical external UHF PD sensor is difficult. In this paper, a novel hole-type UHF PD sensor based on Archimedean spiral antenna theory has been proposed and realized. All spacers with metal flange have small hole in order to inject epoxy. Using the novel hole-type UHF PD sensor, it makes detection possible to PD signal that are emitted through the epoxy injection hole. Additionally, the measuring characteristic of UHF PD signals from several artificial defects in GIS and the novel ${\Phi}$-f-q pattern analysis technology are discussed.