• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.410-417
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• 2009

The objective of this paper is to study the discharge phenomenon for a point-plane air interval using an original fuzzy logic system. Firstly, a physical model based on streamer theory with consideration of the space charge fields due to electrons and positive ions is proposed. To test this model we have calculated the breakdown threshold voltage for a point-plane air interval. The same model is used to determine the discharge steps for different configurations as an inference data base. Secondly, using results obtained by the numerical simulation of the previous model, we have introduced the fuzzy logic technique to predict the breakdown threshold voltage of the same configurations used in the numerical model and make estimation on the insulating state of the air interval. From the comparison of obtained results, we can conclude that they are in accordance with the experimental ones obtained for breakdown discharges in different point-plane air gaps collected from the literature. The proposed study using fuzzy logic technique shows a good performance in the analysis of different discharge steps of the air interval.

• 대한토목학회논문집
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• 제12권1호
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• pp.115-122
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• 1992

실시간 유출예측에서 주로 쓰이는 추계학적 강우-유출 과정모형은 모형구조가 간단하고 상태 공간 모형으로 수식화하기에 용이한 TF모형이다. 이 모형을 이용하여 실시간 유출예측을 효율적으로 수행하기 위해서는 정확한 모형구조의 결정이 선행되어야 하며, 특히 예측초기의 오차를 줄일 수 있는 방법이 요구된다. 본 연구에서는 이를 위하여 유역의 초기습윤상태를 나타낼 수 있는 5일 선행강우지수를 threshold개념으로 도입하고, 각각의 TF모형을 Box-Jenkins 방법으로 등정하여 비교 검토하여 보았다.

• 대한조선학회논문집
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• 제43권4호
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• pp.494-503
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• 2006

Inherent damage zone model is presented to explain the fatigue properties near the fatigue limit and the crack growth threshold consistently Inherent damage zone model assumes that the stress at a point which is located at a small distance, $r_0$, an inherent length of the material that represents the size of effective damage zone, from the crack initiation position governs the fatigue characteristics regardless of the geometric configuration of the specimen; smooth specimen, notched specimen or cracked specimens with short and long crack length. A special feature of the paper is using the exact stress distributions of notched and cracked specimens at the strength evaluations. Analytical elastic solutions by Neuber and Westergaard are employed for this purpose Relationship between fatigue limit of smooth specimen and threshold stress of cracked specimen, occurrence condition of non-propagating crack at the root of elliptic notch and circular hole and relationship between stress concentration factor and fatigue notch factor are discussed quantitatively based on the proposed model.

• 한국컴퓨터정보학회논문지
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• 제4권4호
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• pp.101-112
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• 1999

NPEG은 ISO 산하의 표준화 위원회에서 동영상 압축 기술의 필요에 의해 표준화된 동영상 압축 기술로 통신상에서 더 높은 비트율의 고화질 동화상 실현의 요구에 의해 1995년에 MPEG 2가 개발되었다. 본 논문에서는 VBR MPEG의 코드화된 완전한 동화상 통신을 위해 비선형 시계열 방식으로 효율적이고도 정확한 TAR모델 설계 알고리즘을 제안하며 실질적인 동영상 비디오 추적에 대한 통계적 특성을 보여주는 시뮬레이션 결과를 제시하고자 한다.

• Nuclear Engineering and Technology
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• 제39권4호
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• pp.313-326
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• 2007

In this paper, an algorithm to reconstruct two orthogonal images into a three-dimensional image is developed in order to measure the bubble size and volume in a two-phase boiling flow. The central-active contour model originally proposed by P. $Szczypi\'{n}ski$ and P. Strumillo is modified to reduce the dependence on the initial reference point and to increase the contour stability. The modified model is then applied to the algorithm to extract the object boundary. This improved central contour model could be applied to obscure objects using a variable threshold value. The extracted boundaries from each image are merged into a three-dimensional image through the developed algorithm. It is shown that the object reconstructed using the developed algorithm is very similar or identical to the real object. Various values such as volume and surface area are calculated for the reconstructed images and the developed algorithm is qualitatively verified using real images from rubber clay experiments and quantitatively verified by simulation using imaginary images. Finally, the developed algorithm is applied to measure the size and volume of vapor bubbles condensing in a subcooled boiling flow.

• Ocean and Polar Research
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• 제43권1호
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• pp.1-14
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• 2021

In this study, extreme wind speeds in the Western North Pacific (WNP) were estimated using reanalysis wind fields synthesized with an empirical typhoon vortex model. Reanalysis wind data used is the Fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) data, which was deemed to be the most suitable for extreme value analysis in this study. The empirical typhoon vortex model used has the advantage of being able to realistically reproduce the asymmetric winds of a typhoon by using the gale/storm-forced wind radii information in the 4 quadrants of a typhoon. Using a total of 39 years of the synthesized reanalysis wind fields in the WNP, extreme value analysis is applied to the General Pareto Distribution (GPD) model based on the Peak-Over-Threshold (POT) method, which can be used effectively in case of insufficient data. The results showed that the extreme analysis using the synthesized wind data significantly improved the tendency to underestimate the extreme wind speeds compared to using only reanalysis wind data. Considering the difficulty of obtaining long-term observational wind data at sea, the result of the synthesized wind field and extreme value analysis developed in this study can be used as basic data for the design of offshore structures.

• Animal Bioscience
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• 제36권8호
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• pp.1151-1155
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• 2023

Objective: This study analyzes interactions of body condition score (BCS) with other factors and the effect of BCS on estimates of genetic paremeters of conception rate (CR) in Japanese Black cows. Methods: Factors affecting CR were analyzed through the linear mixed model, and genetic parameters of CR were estimated through the threshold animal model. Results: The interactions between BCS and each season and the number of artificial inseminations (AI) was significant (p<0.05), but that between BCS and parity showed no significance for CR. High CR was observed with BCS 3 in autumn (0.56±0.01) and BCS 4 in summer (0.56±0.02). The highest CR with BCS 3 (0.56±0.02) and BCS 4 (0.55±0.01) was observed at first AI. With BCS 5, however, the highest CR (0.55±0.08) was observed at second AI. Conclusion: The model with BCS was notably conducive to the estimation of genetic parameters because of a low deviance information criterion of heritability that, nevertheless, was slightly lower than the model without BCS.

• 한국위성정보통신학회논문지
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• 제12권3호
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• pp.35-40
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• 2017

위성의 상태를 파악하기 위해 기존에는 OOL(Out-Of-Limit) 방식을 많이 사용하여 왔다. OOL은 특정 텔레메트리의 상위, 하위 문턱 값을 지정하여 해당 값을 벗어날 경우 문제가 발생한 것으로 인식 하는 방식이다. 이 방법은 파라미터의 특성을 파악하여 각각의 문턱 값을 정확히 설정해야 하는 전문 지식과 노력이 필요하고 텔레메트리 값이 문턱값 내에서 비정상적으로 변할 경우는 검출할 수 없다는 문제점이 있다. 이러한 문제를 극복하기 위해 본 논문에서는 위성이 정상 상태일 때 텔레메트리의 통계적 특징 중 러프집합을 이용하여 중요한 것을 선택, 적용하여 퍼지 모델을 구축하고 이상 상태를 구분하는 시스템을 제안한다. 정상 상태의 데이터만 이용하여 모델을 구축하기 때문에 출력값을 비교 하여 사전에 정의되지 않은 비정상 상태의 구분이 가능 하며 다양한 통계 값을 이용하기 때문에 전문 지식 필요 없이 문턱값 내에서 비정상적으로 변하는 텔레메트리를 검출할 수 있다. 제안한 시스템의 동작 확인을 위해 실제 저궤도 관측위성의 배터리 온도 텔레메트리를 적용하여 시험을 수행 하였고 비정규적 운영 상태에 대한 검출이 성공적으로 이루어 졌다.

• 대한산업공학회지
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• 제23권4호
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• pp.755-767
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• 1997

Analyzing autocorrelated data set is still an open problem. Developing on easy and efficient method for severe positive correlated data set, which is common in simulation output, is vital for the simulation society. Bootstrap is on easy and powerful tool for constructing non-parametric inferential procedures in modern statistical data analysis. Conventional bootstrap algorithm requires iid assumption in the original data set. Proper choice of resampling units for generating replicates has much to do with the structure of the original data set, iid data or autocorrelated. In this paper, a new bootstrap resampling scheme is proposed to analyze the autocorrelated data set : the Threshold Bootstrap. A thorough literature search of bootstrap method focusing on the case of autocorrelated data set is also provided. Theoretical foundations of Threshold Bootstrap is studied and compared with other leading bootstrap sampling techniques for autocorrelated data sets. The performance of TB is reported using M/M/1 queueing model, else the comparison of other resampling techniques of ARMA data set is also reported.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.794-796
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• 2006

This study investigated the Brightness Temperature Difference threshold as criterion between aerosols and clouds in conjunction with radiative transfer model. Surface temperature is caused by a significant error over 50% in the BTD threshold. In addition, The BTD threshold contains the uncertainties about 20% due to the surface emissivity and 8% due to the satellite zenith angle. Therefore, we have composed the Look-up table for BTD between 11㎛and 12㎛ according to satellite zenith angle, surface temperature, and surface emissivity. The modified BTD show the enhanced signal, especially over bright surface such as desert in China. However, a weak aerosol signal over Ocean remains in the modified BTD.