• Journal of information and communication convergence engineering
• /
• 제21권3호
• /
• pp.233-238
• /
• 2023

This study presents a method for identifying partial discharge defects in an eco-friendly gas insulated system using a backpropagation algorithm. Four partial discharge (PD) electrode systems, namely, a free-moving particle, protrusion on the conductor, protrusion on the enclosure, and voids, were designed to simulate PD defects that can occur during the operation of eco-friendly gas-insulated switchgear. The PD signals were measured using an ultrahigh-frequency sensor as a nonconventional method based on IEC 62478. To identify the types of PD defects, the PD parameters of single PD pulses in the time and frequency domains and the phase-resolved partial discharge patterns were extracted, and a back-propagation algorithm in the artificial neural network was designed using a virtual instrument based on LabVIEW. The backpropagation algorithm proposed in this paper has an accuracy rate of over 90% for identifying the types of PD defects, and the result is expected to be used as a reference database for asset management and maintenance work for eco-friendly gas-insulated power equipment.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1998년도 추계학술발표회요약집
• /
• pp.237-237
• /
• 1998

• 한국산학기술학회논문지
• /
• 제13권2호
• /
• pp.522-528
• /
• 2012

본 논문의 목적은 AZ31 마그네슘합금의 균열성장거동의 경향을 묘사할 수 있는 실험적 피로균열전파모델을 평가하여 적합한 모델을 제시하는 것이다. 3가지 최대하중 조건을 변화시키면서 피로균열전파실험을 수행하여 평가에 필요한 통계적 균열성장 데이터를 획득하였다. 평가에 사용된 실험적 모델은 Paris-Erdogan 모델, Walker 모델, Forman 모델, 수정된 Forman 모델이며, 각 모델의 파라미터를 통계적으로 추정하기 위하여 최우추정법을 사용하였다. 마그네슘합금의 균열성장거동의 경향을 잘 묘사하는 모델은 Paris-Erdogan 모델과 Walker 모델이며, 모델의 파라미터 중 피로균열성장속도지수는 재료상수가 될 수 있음을 밝혀내었다.

• 대한기계학회논문집
• /
• 제19권6호
• /
• pp.1510-1517
• /
• 1995

A theoretical method is described to simulate the propagation of turbulent premixed flames in a closed vessel. The objective is to develop and test an efficient technique to predict the propagation speed of flame as well as the geometric structure of the flame surfaces. Flame is advected by the statistically generated turbulent flow field and propagates as a wave by solving twodimensional Hamilton-Jacobi equation. In the simulation of the unburned gas flow field, following turbulence properties were satisfied: mean velocity field, turbulence intensities, spatial and temporal correlations of velocity fluctuations. It is assumed that these properties are not affected by the expansion of the burned gas region. Predictions were compared with existing experimental data for flames propagating in a closed vessel charged with hydrogen/air mixture with various turbulence intensities and Reynolds numbers. Comparisons were made in flame radius growth rate, rms flame radius fluctuations, and average perimeter and fractal dimensions of the flame boundaries. Two dimensional time dependent simulation resulted in correct trends of the measured flame data. The reasonable behavior and high efficiency proves the usefulness of this method in difficult problems of flame propagation such as in internal combustion engines.

• 천문학회보
• /
• 제38권2호
• /
• pp.96.1-96.1
• /
• 2013

A Forbush decrease(FD) is a depression of cosmic ray intensity observed by ground-based neutron monitors(NMs). The cosmic ray intensity is thought to be modulated by the heliospheric magnetic structures including the interplanetary coronal mass ejection(ICME) surrounding the Earth. The different magnitude of the decreasing in intensity at each NM was explained only by the geomagnetic cutoff rigidity of NM station. However, sometimes NMs of the almost same rigidity in northern and southern hemispheres observe the asymmetric intensity depression magnitudes of FD events. Thus, in this study we intend to see the effects on cosmic ray intensity depression rate of FD event recorded at different NMs due to different ICME propagation direction as an additional parameter in the model explaining the cosmic ray modulation. Fortunately, since 2006 the coronagraphs of twin spacecraft of the STEREO mission allow us to infer the propagation direction of ICME associated with the FD event in 3-dimension with respect to the Earth. We confirm that the asymmetric cosmic ray decreasing modulations of FD events are determined by the propagation directions of the associated ICMEs.

• 한국전자파학회논문지
• /
• 제19권6호
• /
• pp.698-705
• /
• 2008

전자파가 대기를 통과할 때 대기를 형성하고 있는 다양한 요인들에 의해 그 특성이 변동하게 된다. 전파 특성에 영향을 미치는 대기의 주요 요인으로는 수증기, 안개, 산소와 같은 대기 입자, 강우, 강설 및 그 외 여러 종류의 에어로졸을 들 수 있으며, 이러한 것들은 지형 및 지역적 특성에 따라 다르게 분포한다. 따라서 대기 환경에서의 전파 특성을 예측하기 위해서는 주어진 환경에 대한 기온, 습도, 기압, 풍속, 에어로졸 및 강우율 등의 통계적 분석이 중요하다. 본 논문에서는 국내 대기 환경에 대한 통계적 분석을 수행하였으며, 이를 바탕으로 국내 대기 환경에서의 전파 특성을 분석하였다.

• 한국생산제조학회지
• /
• 제6권2호
• /
• pp.58-66
• /
• 1997

Ti alloys, with the advantageous tensile strength/density ratio and the chemical stability, have been used widely in the aerospace and chemical engineering industries and their usages are still expanding in various industrial areas. In the automotive industry, because of their superior merits of weight reduction and fuel saving, Ti alloys are expected to be used as various part materials including connecting rods, engine valves, springs and retainers, which are all subjected to the fatigue loads. In this study, using Ti-3A1-2.5V, the effects of temperature and microstructure change on fatigue crack propagation has been investigated. Five different microstructures were tested at the temperatures of room temperature, 20$0^{\circ}C$, 30$0^{\circ}C$ and 40$0^{\circ}C$ under the same frequency 20Hz. Some of the conclusions obtained are as follows: (1)Microstructurally, the morphology of less $\alpha$-phase and finer lamellar structure of $\alpha$ and $\beta$-Ti showed better registance to the fatigue crack propagation. (2)Fatigue crack growth rate increased with test temperature.

• 한국전자통신학회논문지
• /
• 제15권3호
• /
• pp.521-526
• /
• 2020

본 논문은 홍채영상의 이동불변의 특징값 을추출에 탁월한 고차 국소 자동 상관함수를 적용하여 25개의 특징 값을 입력 값으로 적용한 일반적인 HOLP 신경망에 특징 값 25개의 평균값을 추가한 개선된 HOLP 신경망을 구현하여 인식률을 확인하여 보았다. 종류가 상이한 딥러닝 구조들과 비교하였을 때 음성과 영상분야에서 탁월한 성능을 보이는 Back-Propagation 신경망과 특징 추출기와 분류기를 통합한 합성 곱 신경망을 활용하여 홍채인식의 인식률을 비교하여 보았다.

• 동력기계공학회지
• /
• 제15권6호
• /
• pp.73-80
• /
• 2011

The experimental investigation focuses on an influence of artificial aging time in longitudinal butt welded Al 6013-T4 aluminum alloy on the fatigue crack growth resistance. The preferred welding processes for this alloy are frequently tungsten inert gas welding (TIG) process due to its comparatively easier applicability and better weldability than other gas metal arc welding. Fatigue crack growth tests were carried out on compact tension specimens (CT) in longitudinal butt TIG welded after T82 heat treatment was varied in three artificial aging times of 6 hours, 18 hours and 24 hours. Of the three artificial aging times, 24 hours of artificial aging time are offering better resistance against the growing fatigue cracks. The superior fatigue crack growth resistance preferred spatial variation of materials within each specimen in the Paris equation based on reliability theory and fatigue crack growth rate by crack length are found to be the reasons for superior fatigue resistance of 24 hours of artificial aging time was compared to other joints. The highest of crack propagation resistance occurs in artificial aging times of 24 hours due to the increase in grain size (fine grained microstructures).

• 원예과학기술지
• /
• 제32권6호
• /
• pp.788-793
• /
• 2014

Vegetative propagation of walnut is difficult compared with that of other fruit and nut species. The present study assessed three methods of grafting (patch, shield, and chip) at various periods of walnut growth and with different timings of grafting in walnut. Early May was the best time for grafting, at which time the highest success rate was obtained by the patch method (96%), followed by chip-budding (75%), while shield-grafting showed the lowest efficiency (10%). Patch-grafting was also successful (75-80%) in early August and moderately successful in mid-June (51-55%), while the shield and chip methods had no success during these two times (0.00%). Patch-grafting was more efficient and also induced better callus formation and scion growth than the other two methods. The genotypes used did not affect grafting efficiency. The best results were obtained by patch-budding in both tested genotypes. The present findings show the potential value of patch-grafting in early May as a propagation method for walnut for establishment of guidelines for propagation.