• 한국콘텐츠학회논문지
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• 제6권4호
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• pp.11-18
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• 2006

본 논문에서는 두 가지 새로운 임펄스 잡음 검출기를 설계하고 총변량(total variation) 최적화를 통하여 영상에 존재하는 임펄스 잡음을 제거하는 방법을 제안한다. 설계된 임펄스 잡음 검출기는 적응 미디언 필터(AMF:Adaptive Median Filter)를 기반으로 하고 있으며 기존의 검출기에 비해 잡음검출의 정확도가 높고 영상의 디테일 정보를 잡음으로 오인하는 확률을 줄였다. 또한 제안하는 검출기는 잡음발생 확률에 무관하게 우수한 성능을 유지한다. 영상에서의 잡음제거는 제안된 검출기에 의해 얻어진 잡음후보 화소에 대해서만 총변량 최적화를 적용하므로 불필요한 계산을 줄이고 영상의 경계선을 잘 보존하면서 잡음을 제거할 수 있다. 실험결과 제안하는 2단 구조의 잡음제거 알고리즘은 다양한 형태의 잡음 밀도에 대해서 기존의 알고리즘에 비해 약 2dB 정도의 화질개선 효과를 얻었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.645-648
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• 1992

In a capacitor-discharge impulse magnetizer, one of the magnetic application system, a magnet is magnetized by the discharging current of capacitors. The conventional design of the magnetizer has been based on many year's experience. The behaviour of flux in the magnetizer should be calculated in order to produce the desired magnets. The analysis of the flux distribution is quite difficult. This is because both the magnetizing current and the applied voltage to the magnetizer are unknown. This paper describes the development of computer model for a capacitor-discharge impulse magnetizer using SPICE. Also, the detailed distribution of the flux density in a magnet magnetized by the impulse magnetizer be analyed.

• 치과방사선
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• 제20권1호
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• pp.113-124
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• 1990

For the study of the influence of kilovoltage and exposure time on radiographic density and contrast, we measured radiographic density of aluminum step wedge which composed of contiguous 8 steps wedges of 2-16㎜ thickness with densitometer. Aluminum step wedge was radiographed on Kodak ultraspeed DF-58 and Ektaspeed EP-21 film with range of 60-90 kVp and 5-60 impulse and subject contrast of aluminum step wedge with constant radiographic density and image contrast percentage without radiographic density was evaluated. Then we evaluated the film quality of teeth and their surrounding structure according to the change of kVp and exposure time by score rating method. The obtained results were as follows: 1. Radiographic density was related to the change of kilovoltage, especially in increased exposure time. 2. With constant radiographic density, subject contrast of thin aluminum step wedges was greater in low kilovolt age than high kilovoltage, but kilovolt age had not great influence on subject contrast of thick aluminum step wedge. On the other hand, radiographic density difference between 2mm and 16mm aluminum step wedge was decreased according to in- creasing kilovoltage. 3. Without constant radiographic density, image contrast percentage was decreased with increasing kilovoltage, but was not related with the change of exposure time. 4. Radiographic contrast of teeth and their surrounding structure which was taken with the range of 60-90 kVp and 6-30 impulse had not great influence on film quality.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.398-403
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• 2006

This paper describes the evaluation of the long duration current impulse withstand characteristics of ZnO blocks for high voltage surge arresters. Four ZnO varistors were manufactured with the general ceramic production method and the long duration current impulse withstand test, electrical uniformity evaluation test and microstructure observation were performed. All varistors exhibited high density, which was in the range of $5.42{\sim}5.46g/cm^3$. In the electrical properties, the reference voltage of samples was in the range of $5.11{\sim}5.25\;kV$ and the residual voltage was in the range of $8.314{\sim}8.523\;kV$. In the long duration current impulse withstand test, sample No.2 and No.3 failed at the 2nd and 4th shot of series impulse currents, respectively, but the rest survived 18 shots during the test. Before and after this test, the variation ratio of the residual voltage of samples survived was below 0.5 %, which was in the acceptance range of 5 %. According to the results of the test, it is thought that if the soldering method is improved, ZnO varistors would be possible to apply to the high voltage arresters like the station class and transmission line arresters in the near future.

• 한국정보통신학회논문지
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• 제17권4호
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• pp.989-995
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• 2013

영상전송 등의 과정에서 임펄스 잡음에 의한 영상의 열화가 발생하며, 이러한 잡음을 제거하기 위해 활발한 연구가 진행되고 있다. 현재 대표적인 임펄스 잡음제거 방법에는 SM 필터(Standard Median Filter)가 있지만, SM 필터는 임펄스 잡음 밀도가 커짐에 따라 에지 영역에 오류를 나타낸다. 따라서 본 논문에서는 영상의 에지를 보존하기 위해 또한 영상의 왜곡을 줄이기 위해 변형된 적응 메디안 필터 알고리즘을 제안하였으며, 시뮬레이션 결과 제안한 알고리즘은 여러 영역에서 모두 우수한 결과를 나타내었고, 평가기준으로 PSNR을 사용하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.3873-3887
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• 2018

In this paper, we propose a novel method to recover images corrupted by impulse noise. The proposed method uses two stages: noise detection and filtering. In the first stage, we use pixel values, rank-ordered logarithmic difference values, and median values to train a neural-network-based impulse noise detector. After training, we apply the network to detect noisy pixels in images. In the next stage, we use group-based weighted couple sparse representation to filter the noisy pixels. During this second stage, conventional methods generally use only clean pixels to recover corrupted pixels, which can yield unsuccessful dictionary learning if the noise density is high and the number of useful clean pixels is inadequate. Therefore, we use reconstructed pixels to balance the deficiency. Experimental results show that the proposed noise detector has better performance than the conventional noise detectors. Also, with the information of noisy pixel location, the proposed impulse-noise removal method performs better than the conventional methods, through the recovered images resulting in better quality.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.486-487
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• 2007

This paper describes the evaluation of long duration current impulse withstand characteristics of ZnO blocks for high voltage surge arresters. Four ZnO varistors were manufactured with the general ceramic production method and three abroad varistors were also prepared to be compared. All varistors exhibited high density, which was in the range of $5.42{\sim}5.49g/cm^3$. In the electrical properties, the reference voltage of all samples was in the range of 5.11~5.72kV and the residual voltage was in the range of 8.314~9.305kV. In the long duration current impulse withstand test, sample 2 and 3 failed at the 2nd and 4th shot of series impulse currents, respectively, but the rest survived 18 shots during the test. Before and after this test, the variation ratio of the residual voltage of samples survived were below 1.7%, which were in the acceptance range of 5%.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.477-481
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• 2009

본 논문에서는 영상신호의 전송과정에서 임펄스 잡음에 의해 훼손된 영상의 복원을 위해 스위칭 평균 필터를 제안 하였다. 이 필터는 크기가 다른 두 가지 크기의 잡음 검출 마스크를 이용하여 잡음요소와 비 잡음요소로 구분하고 영상내의 검출된 임펄스 잡음밀도에 따라 스위칭 평균 필터를 통해 임펄스 잡음을 제거한다. 대체된 화소는 다음 화소의 처리과정에서 이웃화소로 사용되어지는 재귀형태와 비재귀형태 갖도록 하였다. 그리고 시뮬레이션을 통해 기존의 방법들과 그 성능을 비교하였다.

• Water Engineering Research
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• 제2권4호
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• pp.261-268
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• 2001

This study presents the estimation of the entrainment velocity of sediment particles from the scour hole. Sediment particles are entrained from the scour hole downstream of hydraulic structures by the turbulent vortices. Mathematical form of the entrainment velocity of sediment particles from the scour hole was obtained using the impulse-momentum equation with given value of the vertical component of turbulent velocity of the line vortex. Also, its probability density distribution was obtained with the results that the probability density distribution of the vertical turbulent velocity followed the normal distribution. Experimental results of the entrainment velocity of sediment particles showed relatively good agreements with theoretical ones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1481-1483
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• 1998

we have investigated the effect of aromatic compounds and tree inception and growth in low density polyethylene, for AC voltage and Impulse voltage. 2kinds of aromatic compounds are selected. Each additive (m-cresol, aniline) was mixed in low density polyethylene. For AC voltage, 10wt% $\sim$ 15wt% m-cresol can be shown to be the effective inhibitor to tree initiation. But, For Impulse voltage, 10wt% $\sim$ 15wt% aniline is effective inhibitor to tree initiation.