• 한국해양공학회지
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• 제16권5호
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• pp.15-20
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• 2002

In this research, the finite difference lattice Boltzmann method(FDLBM) is used to analyze gravity currents in the lock exchange configuration that occur in many natural and man-made situations. At a lock those are seen when a gate is suddenly opened, and, in the atmosphere, when the thunderstorm outflows make a cold front. At estuaries in the ocean, the phenomenon is found between fresh water from a river and salt water in the sea. Since such interesting phenomena were recognized, pioneers have challenged to make them clear by conducing both experiments and analysis. Most of them were about the currents of liquid or Boussinesq fluids, which are assumed as incompressible. Otherwise, the difference in density of two fluids is small. The finite difference lattice Boltzmann method has been a powerful tool to simulate the flow of compressible fluids. Also, numerical predictions using FDLBM to clarify the gravity currents of compressible fluids exhibit all features, but typically observed in experimental flows near the gravity current head, including the lobe-and-cleft structure at the leading edge.

• 한국환경과학회지
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• 제23권12호
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• pp.1999-2014
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• 2014

A meteo-tsunami occurred along the coastline of South Korea on 31 March 2007, with an estimated maximum amplitude of 240 cm in Yeonggwang (YG). In this study, we investigated the synoptic weather systems around the Yellow sea including the Bohai Bay and Shandong Peninsula using a weather research and forecast model and weather charts of the surface pressure level, upper pressure level and auxiliary analysis. We found that 4-lows passed through the Yellow sea from the Shandung Peninsula to Korea during 5 days. Moreover, the passage of the cold front and the locally heavy rain with a sudden pressure change may make the resonance response in the near-shore and ocean with a regular time-lag. The sea-level pressure disturbance and absolute vorticity in 500 hPa projected over the Yellow sea was propagated with a similar velocity to the coastline of South Korea at the time that meteo-tsunami occurred.

• 한국응용과학기술학회지
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• 제37권5호
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• pp.1402-1408
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• 2020

에너지를 절감하기 위해 고효율 히트펌프를 개발하기 위한 많은 연구가 이루어지고 있으며, 실외기 코일에 발생하는 서리가 발생하는 현상을 줄이거나 없애기 위한 연구도 동시에 이루어지고 있다. 계절에 관계없이 히트펌프의 실외기에 서리가 발생하지 않는 연구를 진행할 수 있도록 자연상태와 동일한 조건에서 실험할 수 있는 항온챔버를 구축하였다. 실험장치의 타당성을 검증하기 위해 실험장치인 항온챔버 내의 실외기 앞 덕트의 직선 길이를 3가지 조건으로 나누어 시뮬레이션 하였다. 그 결과 덕트 관경의 10배 길이만큼 직선 공간을 확보해야 한다는 것을 알게 되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.764-769
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• 2001

Brake-induced vibrations of a vehicle such as brake judder are determined by the excitation of brake torque variations and by their transfer to the driver's contact points via suspension, body and steering system. The formation of brake torque variation is mainly determined by static and dynamic disk thickness variations. The vibration transfer from the excitation by brake torque variation to the perception by the driver depends on the kinematic and dynamic behaviour of the components in the transfer path. Optimization of the judder performance can be achieved either by minimizing the excitation or by reduction of the judder sensitivity of the vehicle. In this paper, the optimization process of a front rotor is suggested to reduce brake judder considering the cooling performance of the rotor, the judder sensitivity of the vehicle and durability of the rotor.

• 한국가정과학회지
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• 제3권2호
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• pp.135-153
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• 2000

Shoes originated from the practical purposes : to protect feet from heat, cold. etc., and developed into various shapes. representing ornamentation and hierarchy. It was revealed that the aesthetic value was differently manifested from the practical one by different natural environments and socio-cultural Phenomena of the times in the East and the West. Comparing shoes in the East with those in the West, this study finds out the origin of shoes in the East and the West, and shapes and characteristics of shoes through the changes of times. Investigating various kinds of shoes in the East and the West, it also finds out the differences in status representations. Shoes are classified into the following styles : in the West. (i) sandal in which the instep was almost exposed, tied with strips and fixed with band, (ii) closed shoes covering the instep, (iii) boots that arose above the ankle: in the East, (i) shoes without shoe neck (리) boots with shoe neck (화) and wooden shoes (극). Status was also represented in shoes. In the West. the status difference was manifested mainly by jewelry or embroidery ornamentation. In particular, it was realized by the way they tied the shoes in Rome and by the length of the pointed front of the shoes in Romanesque and Gothic period. In the East, China, Korea and Japan, on the other hand, the use of shoes was regulated in detail by the official costume system, where material and color played an important role in marking the status.

• 한국수산과학회지
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• 제16권2호
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• pp.51-58
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• 1983

한국 남서해 연안에서 여름에 발달했던 성층이 겨울철에 접어들면서 파괴되어 수직적으로 균일한 수온분포를 갖게 되는데 이러한 변화가 11월에 가장 활발하게 일어나는 것으로 나타났다. 이 변절기에 차고 염분이 낮은 연안 수괴가 대마난류와 접한 경계에 전선이 거의 수직으로 발달하며, 대마난류의 세력이 약한 제주해협의 중앙부를 제외하고는 수심 $70{\sim}90m$의 해역에서 수온전선과 염분전선의 위치는 일치하였다. 1980년 11월에 남해연안 중앙부에서 투하한 해류병이 주로 완도 근해에서 회수된 결과는 전선의 연안쪽에 있는 수괴가 서쪽으로 이동하는 남해연안반류의 존재를 뒷받침 해 주었다.

• Wind and Structures
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• 제24권6호
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• pp.565-578
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• 2017

The meteorological model WRF is used to investigate the wind circulation in Valle Camonica, Italy, an alpine valley that includes a large subalpine lake. The aim was to obtain the information necessary to evaluate the wind potential of this area and, from a methodological point of view, to suggest how numerical modeling can be used to locate the most interesting spots for wind exploitation. Two simulations are carried out in order to analyze typical scenarios occurring in the valley. In the first one, the diurnal cycle of thermally-induced winds generated by the heating-cooling of the mountain range encircling the valley is analyzed. The results show that the mountain slopes strongly affect the low-level winds during both daytime and nighttime, and that the correct setting of the lake temperature improves the quality of the meteorological fields provided by WRF significantly. The second simulation deals with an event of strong downslope winds caused by the passage of a cold front. Comparisons between simulated and measured wind speed, direction and air temperature are also shown.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제42권
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• pp.12.1-12.9
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• 2020

Coronavirus is an enveloped virus with positive-sense single-stranded RNA. Coronavirus infection in humans mainly affects the upper respiratory tract and to a lesser extent the gastrointestinal tract. Clinical symptoms of coronavirus infections can range from relatively mild (similar to the common cold) to severe (bronchitis, pneumonia, and renal involvement). The disease caused by the 2019 novel coronavirus (2019-nCoV) was called Covid-19 by the World Health Organization in February 2020. Face-to-face communication and consistent exposure to body fluids such as blood and saliva predispose dental care workers at serious risk for 2019-nCoV infection. As demonstrated by the recent coronavirus outbreak, information is not enough. During dental practice, blood and saliva can be scattered. Accordingly, dental practice can be a potential risk for dental staff, and there is a high risk of cross-infection. This article addresses all information collected to date on the virus, in accordance with the guidelines of international health care institutions, and provides a comprehensive protocol for managing possible exposure to patients or those suspected of having coronavirus.

• Design & Manufacturing
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• 제12권3호
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• pp.60-65
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• 2018

The production of the automotive parts with the ultra high strength steel usually involves large amount of springback as well as fracture during the cold stamping process. Variable blank holding force(VBHF) can be used as one of the effective process parameters to reduce the springback amount with achieving better condition of formability. In this paper, VBHF with respect to the punch stroke is applied to the stamping process of the front side rear lower member for reducing the springback amount. From the analyses with constant blank holding force(CBHF), 24 kinds of VBHF conditions are utilized to investigate the springback tendency. It is noted that springback can be effectively reduced when BHF is increased near the bottom dead center because VBHF provides the tensile force to the blank with an adequate level of deformation without fracture.

• 한국산학기술학회논문지
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• 제19권7호
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• pp.42-49
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• 2018

철강산업에서, 냉연강판제조는 국가의 산업 경쟁력과 높은 부가가치를 창조하기 위한 전 후방 산업의 핵심 중의 하나이다. 특히 중소기업에서, 주요 문제 중의 하나는 소둔공정에서 일어나는 냉연강판의 탄화 현상이다. 이러한 냉간압연 강판 코일의 표면에서 발생하는 탄화는 생산을 감소시키는데 영향을 미친다. 냉간압연 강판 코일 표면의 탄화 현상의 원인을 규명하기 위해 여러 가지 실험을 실시한 결과, 다음과 같은 결과가 얻어졌다. (1) 현장에서 사용되는 압연유의 분석으로부터, 약 40 ppm 정도의 탄화 물질이 포함되어 있음을 발견하였다. (2) FT-IR 분석에 의한 신 압연유와 사용 압연유의 열 변성 특성 비교에서, 2900 및 $1750cm^{-1}$ 피크의 상대 높이 강도가 현저히 감소한 것으로부터 열 변성이 일어났음을 나타내었다. (3) 압연유의 열분해는 $220^{\circ}C$ 부근에서 일어나는 것으로 나타났다. 또한, $200^{\circ}C$에서의 소둔 실험은 시료의 탄화 현상이 실질적으로 관찰되지 않음을 보여 주었다. 그러나 $240^{\circ}C$ 이상의 온도에서는 탄화가 관찰되었다.