• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.2059-2064
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• 2004

Texture analysis is an important role for automatic visual insfection. This paper presents an application of wavelet extension and Gray level co-occurrence matrix (GLCM) for detection of defect encountered in textured images. Texture characteristic in low quality images is not to easy task to perform caused by noise, low frequency and small dimension. In order to solve this problem, we have developed a procedure called wavelet image extension. Wavelet extension procedure is used to determine the frequency bands carrying the most information about the texture by decomposing images into multiple frequency bands and to form an image approximation with higher resolution. Thus, wavelet extension procedure offers the ability to robust feature extraction in images. Then the features are extracted from the co-occurrence matrices computed from the sub-bands which performed by partitioning the texture image into sub-window. In the detection part, Mahalanobis distance classifier is used to decide whether the test image is defective or non defective.

• 한국지능시스템학회논문지
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• 제23권2호
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• pp.126-132
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• 2013

본 논문은 웹페이지에 포함된 의학용어의 출현 빈도와 웹페이지 간의 하이퍼링크로 이루어진 웹사이트의 구조에 기반하여 인터넷 웹사이트를 분류하는 방법을 제안한다. 제안하는 방법에서는 (1)웹페이지에 포함된 전체 용어에서의 의학용어 출현빈도와 (2)웹페이지에 포함된 중복을 제거한 용어에서의 의학용어 출현 빈도를 인자로 하여 웹페이지의 의학분야 적합도를 측정한다. 그리고 (3)홈페이지로부터 특정 웹페이지에 접근하기 위해 거쳐야 하는 하이퍼링크의 개수를 이용한 전체 웹페이지의 적합도 연산을 통해 웹사이트의 의학분야 적합도를 측정한다. 인터넷 포털 사이트의 디렉토리 검색 서비스에 등록된 80 개의 의학분야 웹사이트와 127 개의 비 의학분야 웹사이트를 대상으로 제안한 방법에 기반하여 웹사이트 분류 실험을 수행하였고, 82.5 %의 분류 정확률을 확인하였다.

• 대한지리학회지
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• 제46권1호
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• pp.36-49
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• 2011

본 연구에서는 오호츠크해고기압이 한반도에 영향을 미치는 날과 강도의 변화를 규명하고자 하였다. 지상 일기도와 기상자료, 재분석자료 등을 분석하여 다음과 같은 결과를 얻었다. 4월의 주변 육지기온이 높은 해일수록 오호츠크해고기압의 첫 출현일이 일러지는 경향이다. 최근 오호츠크해고기압의 출현일수는 감소하였으며, 그 강도는 6월 해수면온도와 주변 육지기온의 차이가 클수록 강해지는 경향이다 4 5월, 6월, 7월의 오호츠크해고기압 출현일수는 주변 육지기온이 상승할수록 증가하며, 해수면온도와 주변 육지 기온의 차이가 커질수록 강도가 강해진다. 오호츠크해고기압의 첫 출현일이 일러짐에 따라 4월과 5월의 오호츠크해고기압 출현일수는 증가하고 강도는 약해질 수 있다. 그러나 6월에는 반대의 경향이 나타날 수 있다.

• 한국항해학회지
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• 제18권3호
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• pp.19-30
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• 1994

By use of the recent tropical cyclones' data in the Northwest Pacific Ocean, the occurrence frequency and region of typhoon as well as the features of the monthly mean track were analyzed. As the result of this study, (1) mean occurrence frequency of typhoon per year is 27.5, and 68% of total typhoons were formed in July to October and shown the highest frequency in August. (2) The ave-rage duration of typhoons is 8.5 days, and super typhoon which maximum sustained surface wind speeds is more than 130 knots occurs most frequently in October and November. (3) The highest frequency ap-pears around the Caroline, Mariana and Marshall Islands, and in wintertime, typhoon occurs in lower lati-tude comparing with those in summertime. (4) The typhoon track depends upon the distribution of pres-sure system and steering current in neighbouring areas. The mean track of typhoon can be classified into three types such as westward-moving type, northward-moving type and abnormally moving type. The west-ward-moving typhoons make landfall on the southern China by way of the South China Sea in June and July, on mid-part of China in August and September, and on Indo-china Peninsula in October and Novem-ber. The northward-moving typhoons approximately move on north~northwestward track to $20~30^{\circ}N$ from the occurrence region, then recurve to the East Sea through Korean Peninsula and Kyushu Island in June and July, to the Noth Pacific Ocean along the Japanese Islands in August and September and to the North Pacific Ocean through the seas far south off the Japan in October and November.

• 대한토목학회논문집
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• 제26권4B호
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• pp.399-404
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• 2006

권혁민 등(2004)은 우리나라 동해안의 실해역 극치파고 및 조위발생빈도분포를 고려한 기대월파확률 산정기법을 제안했다. 권 등의 연구는 동해안의 묵호와 부산지역을 비교하여 조위발생빈도분포가 기대월파확률에 크게 영향을 준다는 것을 예시했으며 그 분포의 표준편차가 크면 클수록 기대월파확률이 작아짐을 보였다. 본 연구는 권혁민 등이 제안한 기대월파확률 계산방법을 준용하여 우리나라 동 남 서 해역의 기대월파확률 특성에 대하여 현행 설계방법에 의해 결정된 마루높이에 대한 평가를 시도하였다. 본 연구결과, 개략적으로 동 남 서 해역으로 갈수록 기대월파확률이 작아짐을 알 수 있다.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.23-31
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• 2024

Ratcheting is the cyclic buildup of inelastic strain on a structure resulting from a combination of primary and secondary cyclic stress. It can lead to excessive plastic deformation, incremental collapse, or fatigue. Ratcheting has been numerically investigated on a cantilever beam, considering the current study's primary and secondary bending loads. In addition, the effect of input frequency on the onset of ratcheting has been investigated. The non-linear dynamic elastic-plastic approach has been utilized. Analogous to Yamashita's bending-bending ratchet diagram, a non-dimensional ratchet diagram with a frequency effect is proposed. The result presents that the secondary stress values fall sequentially with the increase of primary stress values. Moreover, a displacement amplification factor graph is also established to explain the effect of frequency on ratchet occurrence conditions. In terms of frequency effect, it has been observed that the lower frequency (0.25 times the natural frequency) was more detrimental for ratchet occurrence conditions than the higher frequency (2 times the natural frequency) due to the effect of dynamic displacement. Finally, the effect of material modeling of ratcheting behavior on a beam is shown using different hardening coefficients of kinematic hardening material modeling.

• 한국환경과학회지
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• 제31권4호
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• pp.369-372
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• 2022

This study was conducted to determine the injury type and frequency of bearded dragons during single and group breeding according to stocking density, for 16 weeks. A total of 14 bearded dragons compromising three groups were selected for this study. Six and four bearded dragons bred in a cage of 45 cm × 45 cm × 45 cm were designed as group A and B, respectively. Group C was made of four partitions (20 cm × 20 cm × 20 cm) of equal size in the kennel, and the dragons, four in number, were reared alone. Injury type criteria were given 1 score each in 6 stages. Most of the injury types in group A were primary tail cutting, which was 1 point, depending on the score, except for 4 scores. The injury type of group A varied, that is 1, 2, 3, and 5 scores, and the pattern lasted for 2 to 9 weeks. After 10 weeks, the dragons showed no response to injury type, except 4 scores at 11 weeks and 2 scores at 14 weeks with a frequency of one, respectively. The representative injury types of the group B were primary tail cutting, which was 1 point, and the scores of the injury type from 2 to 11 weeks were the highest; the frequency of occurrence at 1 and 2 scores was 5 times and 3 times, respectively, and the frequency of occurrence at 3 scores was twice. In addition, 5 scores were found to have the lowest frequency of occurrence. Solitary breeding showed no response to the type of injury for 16 weeks. Consequently, single breeding with an appropriate stocking density did not affect stress, and it could be expected a positive aspect for pet welfare.

• 한국환경과학회지
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• 제23권10호
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• pp.1673-1691
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• 2014

Although most natural disaster related studies conducted in Korea recently have been related to typhoons or severe rainstorms, the occurrence frequency of disasters due to windstorms or rainstorms is also high. To reduce the strong wind damage caused by strong windstorms due to climate change, basic studies of strong winds are necessary. Therefore, in this study, the types and representative cases of windstorms that were observed to have been higher than 14 m/s, which is the criterion for strong-wind warnings from the Korea Meteorological Administration, were selected from among those windstorm cases that occurred on the Korean Peninsula for 10 years to conduct a statistical analysis of them and determine their synoptic meteorological characteristics. The cases of windstorms occurring on the Korean Peninsula were divided into six weather patterns according to the locations of the anticyclones/cyclones. Among these types, the SH type, which occurs when Siberian Highs expand into the Korean Peninsula, showed the highest occurrence frequency, accounting for at least the majority of the entire occurrence frequency of windstorms together with that of the EC type, which occurs when cyclones develop on the East Sea, and there was no clear yearly trend of the occurrence frequencies of windstorms. The monthly occurrence frequencies of windstorms were formed mainly by typhoons in the summer and the Siberian Highs in the winter, and the months with the highest windstorm occurrence frequencies were December and January, in which mainly the SH and EC type windstorms occurred. March showed the next highest occurrence frequency with10 times, and SH windstorms occurred the most frequently in March, followed by the CC, SC, and EC types of windstorms, in order of precedence. Therefore, attention to these types of windstorms is required. Countermeasures against storm and flood damage in Korea targeting the summer should be re-reviewed together with pre-disaster prevention plans, because cases of storm and flood damage due to windstorms occur more frequently than those due to typhoons, and they occur throughout the year.

• 한국생산제조학회지
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• 제22권4호
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• pp.723-729
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• 2013

The contraction and expansion noise of a refrigerator are investigated, and some effective methods are proposed to reduce the level and occurrence frequency of noise. First, the noise of a refrigerator is measured to estimate the frequency spectrum and occurrence frequency of noise. Second, a sound visualization was conducted using an acoustic camera to determine the location of the noise source. From the results, it was observed that the internal part mainly producing noise was the third shelf in the freezer room. A method to estimate the acceleration on the location of the noise source is introduced to analyze the contraction and expansion noise precisely and accommodate experimental convenience. Noise reduction methods such as the replacement of the existing shelf with glass shelves, adoption of rail slides, and increase of roughness on the contact surface of the shelf are proposed and tested.

• 한국환경과학회지
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• 제32권12호
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• pp.883-898
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• 2023

To investigate the occurrence characteristics and types of fog on the Korean Peninsula over the past three years (2020 to 2022), data from 96 synoptic meteorological observatories and 21 ocean buoys were collected and analyzed. We included precipitation fog, which occurs after precipitation events, and cloud-base lowering fog, which is caused by the development of lower-level clouds, with a total six subtypes of fog. In the case of cloud-base lowering fog, the occurrence frequency at 2.6% was not high at 2.6%, but the duration of low visibility below 200 m was very long at 6.9 hours. The seasonal frequency of fog is low in spring and winter, high in summer over islands and coastal areas, and high in autumn over inland areas. The frequency of inland fog, which is characterized by high radiation fog and dense fog, requires attention in terms of transportation safety, with an occurrence time of 0500 LST to 1000 LST. Therefore, systematic analysis of precipitation fog and cloud-base lowering, as well as radiation and advection fog, is required in the analysis of recognizing fog as a disaster and causing transportation disorders.