• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.13-15
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• 1998

EM(Electro Magnetic) pump is used for the purpose of transporting liquid sodium coolant with electrical conductivity in the LMR(Liquid Metal Reactor). In the present study. pilot EM pump has been designed by using of equivalent circuit method which is commonly employed to analyze linear induction machines for the test of removal of residual heat. The length and diameter of the pump have fixed values of 840 mm and 101.6 mm each by taking account of geometrical size of circulation loop for the installation of EM pump. Flowrate versus developing pressure is related from Laithwaite's standard design formula and the characteristic analyses of developing force and efficiency are carried out according to change of input frequency. From the characteristic curve, input frequency of 13 Hz is determined as the design frequency. On the other hand, The annular air gap size of 6.05 mm is selected not to bring about too much hydraulic loss. Resultantly design analysis makes pump have the electrical input of 604 VA and the hydrodynamical capacity of 1.3 bars and 40 l/min.

• Ocean and Polar Research
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• 제25권4호
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• pp.503-518
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• 2003

This study examines the relationship among temperature, wind, and sea level pressure to understand recent warming in the vicinity of the Antarctic Peninsula. To do this, the surface air temperature, NCEP/NCAR reanalysis wind data and sea level pressure data for the period of 40 years are analyzed. The 40-year surface air temperature data in the Antarctic Peninsula reveals relatively the larger warming trends for autumn and winter than other seasons. The variability of the surface air temperature in this region is compared with that of the regional atmospheric circulation. The surface air temperature is positively correlated with frequency of northwesterlies and negatively correlated with frequency of southeasterlies. This relation is more evident in the northern tip of the Antarctic Peninsula for autumn and winter. The trend analysis of wind frequency in the study area shows increasing and decreasing trends in the frequency of northwesterlies and southeasterlies, respectively, in the northwestern part of the Weddell Sea for autumn and winter. And also it is found that these winds are closely related with decreasing of sea level pressure in the southeastern region of the Antarctic Peninsula. Furthermore from the seasonal variation of sea level pressure in this area, it may be presumed that decreasing of sea level pressure in the southeastern region of the Antarctic Peninsula is related with warming in the vicinity of the Antarctic Peninsula for autumn and winter. Therefore it can be explained that recent warming in the vicinity of the Antarctic Peninsula is caused by positive feedback mechanism, that is, the process that warming in the vicinity of the Antarctic Peninsula can lead to the decrease of sea level pressure in the southeastern region of the Antarctic Peninsula and these pressure decrease in turn lead to the variation of wind direction in northwestern part of Weddell Sea, again the variation of wind direction enhances the warming in the Antarctic Peninsula.

• 한국환경과학회지
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• 제18권10호
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• pp.1089-1101
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• 2009

In this paper, changes in the intensity (e.g., central pressure and maximum sustained wind speed) of Tropical Cyclone (TC) in summer in the regions located at $30^{\circ}N$ in East Asia from 1988 to 1991 were found. The intensity of TC from 1991 to 2007 was much higher than that of TC from 1965 to 1988. The reason for this was that the frequency of TCs passing China from 1991 to 2007 was much lower than that of TCs from 1965-1988 because a northeasterly wind caused by high-pressure circulation in East Asia got severer along the East Asian coast. Instead, TCs moved from the eastern region of the Tropical West Pacific to Korea and Japan mainly after passing the East China Sea due to the low-pressure circulation strengthened in the subtropical waters of East Asia. In addition, low Vertical Wind Shear (VWS) was created along the mid-latitude regions of East Asia and the main path of TCs from 1991 to 2007. Most of the regions in the Northwestern Pacific showed higher Sea Surface Temperature (SST) from 1991 to 2007, and had a good environment where TCs were able to maintain a higher intensity on the mid-latitude. In particular, a low sensible heat flux occurred due to high snow depth in East Asia in the spring of 1991 to 2007. Accordingly, the lower layer of East Asia showed high-pressure circulation, and the sea surrounding East Asia showed low-pressure circulation. Thus, the typical west-high, east-low pattern of winter atmospheric pressure was shown. The possibility of snowfall in East Asia in spring to be used as a factor for predicting the summer intensity of TC in the mid-latitude regions of East Asia was insinuated. The characteristics of TC in a low-latitude region were the same in Korea. The latest intensity of TCs got higher, and the landing location of TCs gradually changed from the west coast to the south coast.

• 한국해안·해양공학회논문집
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• 제35권6호
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• pp.109-120
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• 2023

광해역의 표층 해수유동을 준 실시간으로 측정하는 장비인 해양 고주파 레이다(High Frequency Radar, HFR)는 특정 전파대역(HF)의 주파수를 해수면으로 발사하고 후방으로 산란된 전파를 분석하여 표층 유속 벡터를 측정한다(Crombie, 1955; Barrick, 1972). 본 연구에서 사용되는 Codar사의 Seasonde HF radar의 경우, 무지향성 안테나에서 송·수신한 전파의 브래그 피크(Bragg peak)의 강도와 다중신호분류(Mutiple Signal Classification, MUSIC) 알고리즘을 통하여 방사형 해류(Radial Vector)의 속도와 위치를 결정하게 된다. 이때 생산된 해류는 관측 전파 수신 환경의 특성이 고려되지 않은 이상적인 전파환경(Ideal Pattern)이 적용된 자료로써 이를 보정하기 위하여 안테나 패턴 측정(Antenna Pattern Measurement, APM)을 시행하여 보정된 방사해류장(Measured Radial Vector)을 계산하게 된다. APM의 관측원리는 안테나로부터 수신되는 각 위치별 신호 강도값을 측정하여 해류의 위치 및 위상 정보를 수정하는 것으로 일반적으로 선박에 안테나를 설치하여 실험을 진행한다. 하지만 선박을 활용할 시, 기상조건과 해양 상황 등 다양한 환경에 의해 최적의 APM 결과를 산출하기까지 많은 제약이 따른다. 따라서 APM 실험에 대하여 해상 상황에 대한 의존도를 낮추고 경제적인 효율성을 높이기 위하여 무인항공기인 드론을 이용한 APM 활용 가능성을 검토하였다. 본 연구에서는 전남 완도군 당사리 당사도등대에 설치된 고주파레이다를 활용하여 선박을 활용한 APM 실험과 드론을 활용한 APM 실험을 진행하였으며 선박과 드론으로 관측된 결과가 적용된 방사형 해류와 계류된 고정부이를 활용하여 그 결과를 비교 분석하였다.

• 전력전자학회논문지
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• 제10권4호
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• pp.356-362
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• 2005

본 논문에서는 외부 이그니터가 없는 간단한 고효율 안정기를 만들기 위해 커플 인덕터와 주파수가변. 동기 정류기를 이용한 하프 브리지 방식의 안정기를 제안한다. 램프 점등시 고압을 발생시키기 위해 벅 컨버터 내부의 LC 공진이 사용되었고, 정상상태의 리플을 줄이기 위해 커플 인덕터가 사용되었다. DC/DC컨버터로는 동기형 벅 컨버터가 사용되었다. 안정기의 효율을 높이기 위해 가변 주파수 방식을 제안하였다. 이 방식은 순환 전류와 정전력 동작 하에서 MOSFET 스위치의 턴 오프 손실을 감소 시켜 고정 주파수 방식에 비해 안정기 효율을 약 4$\%$ 향상 시킨다. 회로 구성은 PFC와 안정기 2단으로 구성된다 결과는 실험을 통하여 검증된다.

• 한국지구과학회지
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• 제32권4호
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• pp.347-359
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• 2011

이 연구는 우리나라 영향 태풍을 먼저 분류하고, 이후 경유하게 될 가능성을 진단하는 지수를 개발하였다. 우리나라 영향 태풍의 접근 진단 지수는 여름철에 북서태평양 고기압의 서쪽 가장자리의 발달강도를 표현하는 지수로서, 우리나라 영향 태풍의 빈도와 남북류 (500-hPa)의 강도사이의 상관관계에서 나타나는 양의 최대 상관지역(우리나라 부근)과 음의 최대 상관지역(일본 남동쪽 해상)간의 남북류의 속도 차이로 계산된다. 우리나라 영향 태풍 진단 지수로 추출된 우리나라 영향 태풍의 저빈도 해에는, 고기압성 순환 아노말리의 중심이 우리나라 북서쪽에 위치하기 때문에 우리나라로부터 중국 동해안과 남중국해까지 북동류의 성분이 강화되고, 태풍은 이에 따라 필리핀 동쪽해상으로부터 중국 동해안 및 중국내륙 쪽으로 서편하는 경향을 보였다. 반면에 고빈도 해에는 고기압성 순환 아노말리의 중심이 일본 동쪽 해상에 위치하기 때문에 동중국해 및 우리나라, 일본에서 유도된 남서풍이 더 많은 태풍을 우리나라 영역으로 접근시켰다. 결과적으로 태풍의 북상 동안 역학모델로부터 실시간으로 예측된 500 hPa 남북류를 이용하여 이 지수를 산출하면 태풍의 우리나라 접근 가능성을 진단할 수 있음을 이 연구는 제안한다.

• 한국정밀공학회지
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• 제31권11호
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• pp.1051-1058
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• 2014

In this study, we investigated the improvement effect of obesity by treatment with a developed low frequency electrical stimulation system. Thirty female in their 20's as an experiment subjects divided 3 groups(control, commercialized device, developed device) were treated with electrical stimulation on abdomen for 4 weeks. The body weight, body mass index(BMI), waist-hip ratio(WHR), muscle strength, muscle(transverse abdominis(TrA), internal obliquus abdominis(IO), external obliquus abdominis(EO)), fat thickness and abdominal surface temperature were measured by electromyogram(EMG), ultrasound and digital infrared thermal image(DITI). In the result, the body weight and BMI were decreased. Subcutaneous abdominal fat were significantly reduced after 4 weeks. The muscle strength and TrA muscle thickness was increased 13.2%(p<0.05), and 35.5%, respectively. The fat thickness showed decrease in abdomen (p<0.05). Infrared measurement on abdominal surface temperature as a parameter of improvement in blood circulation was significantly increased(p<0.05). Therefore, the low frequency stimulation showed positive effects on parameters of the obesity improvement.

• 대한의용생체공학회:의공학회지
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• 제27권2호
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• pp.47-52
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• 2006

The purpose of this study was to predict successful defibrillation in ventricular fibrillation using parameters extracted by wave analysis method and neuro-fuzzy. Total 15 dogs were tested for predicting successful defibrillation. Feature parameters were extracted for return of spontaneous circulation (ROSC) and non-ROSC by wave analysis method, and these parameters are an irregularity factor, spectral moments, mean power of level-crossing spectrum, and mean of alpha-significant value. Additionally, two parameters by analyzing method of frequency were extracted into a mean of power spectrum and a mean frequency. Then extracted parameters were analyzed in which parameters result to have high performance of discriminating ROSC and non-ROSC by a statistical method of t-test. The average of sensitivity and specificity were 62.5% and 75.0%, respectively. The average of positive predictive factor and negative predictive factor were 61.2% and 75.8%, respectively.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2003년도 추계학술발표회
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• pp.167-174
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• 2003

Oceanic conditions of the Tsushirm Wann Current (1WC) region in the southern area if the East Sea (the Japan Sea) are examined using data obtained from a CREAMS (Circulation Research if the East Asian Marginal Seas) cruise in June 1996. In 1990s, a lower temperature appears in $19\%$ and in this period, two branch of the TWC exist and the first branch of the TWC flows inshore if the Japanese coastal region compared to tfr1t in the other years, especially in the sfr1llower water layer at less th:1n about 2mm. The TWC cored with the higher salinity (>34.6 psu) is clearly observed over the continental shelf zone in the Japanese coastal region and offshore and identified by geostrophic calculation Intrusion if the TWC into the East Sea through the Korea Strait (the Tsushima Strait) makes the density structure in the water column change and the water mass in the TWC region is unstable based on Brunt- Vaisala frequency.

• 한국군사과학기술학회지
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• 제12권4호
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• pp.415-423
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• 2009

To investigate low frequency acoustic transmissions in the Sub-Polar Front(SPF) of the East Sea, numerical experiments are conducted with Range dependent Acoustic Model(RAM) using Circulation Research of the East Asian Marginal Seas(CREAMS) data and Autonomous Profiling Explorer(APEX)) data. Significant seasonal variations of sea water properties are existed across the Sub-Polar Front(SPF) region from the north and the south. The model results show that Transmission Loss(TL) decrease(about 20dB) with ideal front in the warm region whereas TL increase(about 25dB) with ideal front in the cold region. Regardless of season(both in summer and winter), when the sound source is located in the cold region of the SPF, the model results show weak TL, compared to the case of the source in the warm region(Maximum difference of TL reaches 28dB). This difference between the cases when the source is located in the cold region and the warm region, is accounted for from the different vertical profiles of sound speed in both regions.