• 한국산학기술학회논문지
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• 제16권3호
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• pp.1658-1663
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• 2015

실내의 습도제어를 위하여 공조기 내에는 가습소자가 설치된다. 지금까지 대부분의 가습소자는 유리섬유로 만들어진 외제품이 널리 사용되어 왔다. 본 연구에서는 이 외제품을 대체할 셀룰로오스와 PET 복합체로 만들어진 가습소자를 개발하고 유리섬유로 만들어진 Glasdek 소자의 성능과 비교하였다. 시험은 소자를 항온항습실 내에 설치된 흡입식 풍동입구에 설치하고 물질전달량과 압력손실을 측정하였다. 실험결과를 $j_m$과 f인자로 나타내었을 때, 개발품의 $j_m$값이 33%~39%크고, f인자는 개발품이 0%~51% 작게 나타났다. Glasdek에 비하여 개발품의 $j_m$값이 큰 이유는 흡수도가 월등히(50% 가량) 크기 때문이고 f인자가 작은 이유는 소자 표면이 확연히 매끄럽기 때문이다. 한편, 동일 소비동력 대비 물질전달을 나타내는 $j_m/f^{1/3}$ 의 경우, 개발품이 약 36~63% 크게 나타났다.

• Journal of Microbiology and Biotechnology
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• 제30권10호
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• pp.1495-1499
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• 2020

The study of climate and respiratory viral infections using big data may enable the recognition and interpretation of relationships between disease occurrence and climatic variables. In this study, real-time reverse transcription quantitative PCR (qPCR) methods were used to identify Human respiratory coronaviruses (HCoV). infections in patients below 10 years of age with respiratory infections who visited Dankook University Hospital in Cheonan, South Korea, from January 1, 2012, to December 31, 2018. Out of the 9010 patients who underwent respiratory virus real-time reverse transcription qPCR test, 364 tested positive for HCoV infections. Among these 364 patients, 72.8% (n = 265) were below 10 years of age. Data regarding the frequency of infections was used to uncover the seasonal pattern of the two viral strains, which was then compared with local meteorological data for the same time period. HCoV-229E and HCoV-OC43 showed high infection rates in patients below 10 years of age. There was a negative relationship between HCoV-229E and HCoV-OC43 infections with air temperature and wind-chill temperatures. Both HCoV-229E and HCoV-OC43 rates of infection were positively related to atmospheric pressure, while HCoV-229E was also positively associated with particulate matter concentrations. Our results suggest that climatic variables affect the rate in which children below 10 years of age are infected with HCoV. These findings may help to predict when prevention strategies may be most effective.

• 대한기계학회논문집B
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• 제22권4호
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• pp.551-561
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• 1998

This paper was studied to understand the characteristics of heat transfer coefficients and surface temperature distributions around a circular combustion chamber within the heat-intercept duct of kerosene fan heater. The experiment was carried out in the heat-intercept duct of kerosene fan heater attached to the blow-down-type subsonic wind tunnel with a test section of 240 mm * 240 mm * 1200 mm. The purpose of this paper was to obtain the basic data related with normal combustion for new design from conventional kerosene fan heater, and to investigate the effect of surface temperature, local and mean heat transfer coefficients versus flow-rate of convection axial fan according to the variations of heat release conditions from kerosene fan heater during normal combustion. Consequently it was found that (i) the revolution of convection axial fan during combustion had a smaller value than that of non-combustion because of the thermal resistance due to the high temperature in the heat-intercept duct, (ii) the pressure ratio P$_{2}$/P$_{1}$ had a comparatively constant value of 0.844 according to the revolution increase of turbo fan and the heating performance of kerosene fan heater had a range of 1,494 ~ 3,852 kcal/hr, (iii) the local heat transfer coefficient around a circular combustion chamber had a comparatively larger scale in the range of 315 deg. < .theta. < 45 deg. than that in the range of 90 deg. < .theta. < 270 deg. as a result of heat transfer difference between front and back of a circular combustion chamber, and (iv) the mean heat transfer coefficient around a circular combustion chamber increased linearly like a H$_{m}$=95.196Q+104.019 in condition of high heat release according to the increase of flow-rate of axial fan.n.

• 대한기계학회논문집A
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• 제36권7호
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• pp.731-738
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• 2012

본 논문은 상용 유한요소코드인 ANSYS Workbench 12.1과 CFX 12.1을 이용하여 NREL Phase VI Rotor에 대한 공력특성을 입구풍속 7m/s 경우에 대해 연구하였다. 공탄성 효과를 고려하기 위해 약결합 양방향 유체구조 연성기법을 사용하여 타워구조를 제외한 로터파트에 대해서 해석이 수행되었다. 블레이드 끝단의 초기 피치각은 $3^{\circ}$로 설정하였고, 구조해석모델은 등가강성기법을 적용하였다. 신뢰성 있는 수렴판정 결과의 확보를 위해 블레이드 루터부의 굽힘모멘트를 실시간으로 모니터링 하였다. 해석의 신뢰성을 검증하기 위하여 해석결과를 NREL/NASA Ames 풍동 실험결과와 비교 분석하였다.

• 대한기계학회논문집B
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• 제26권1호
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• pp.82-93
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• 2002

The effects of the interaction between the flow and temperature field and a boundary layer due to a variety of the height of a vortex generator are experimentally investigated. The test facility consists of a boundary-layer wind tunnel with the vortex generator protruding from the bottom surface. In order to control the strength of the longitudinal vortices, the angle of attack and the spacing distance of the vortex generator are 20 degree and 40 mm, respectively. The height of the vortex generator (H) is 15 mm, 20 mm and 30 mm and the cord length of it is 50 mm. Three-component mean velocity measurements are made using a 5-hole probe system and the surface temperature distribution is measured by the hue capturing method using thermochromatic liquid crystals. By using the method mentioned above, the following conclusions are obtained from the present experiment. The boundary layer is thinned in the downwash region where the strong downflow and the lateral outflow of the boundary layer fluid occur and thickened in the upwash re,3ion where the longitudinal vortex sweeps low momentum fluid away from the bottom surface. In case that the height of the vortex generator increases, the averaged circulation and the maximum vorticity of the vortex pair decrease. The contours of the non-dimensional temperature show the similar trends fur all the cases (H=15 mm, 20 mm and 30 mm). The peak augmentation of the distribution of the local non-dimensional temperature occurs in the downwash region near the point of minimum boundary-layer thickness.

• 한국유체기계학회 논문집
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• 제8권4호
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• pp.27-38
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• 2005

The present study investigated the effect of relative position of the blade on blade surface heat transfer. The experiments were conducted in a low speed wind tunnel with a stationary annular turbine cascade. The test section has a single turbine stage composed of sixteen guide vanes and blades. The chord length of the blade is 150 mm and the mean tip clearance of the blade is $2.5\%$ of the blade chord. The Reynolds number based on blade inlet velocity and chord length is $1.5{\times}105$ and mean turbulence intensity is about $3\%$. To investigate the effect of relative position of blade, the blade at six different positions in a pitch was examined. For the detailed mass transfer measurements, a naphthalene sublimation technique was used. In general, complex heat transfer characteristics are observed on the blade surface due to various flow characteristics, such as a laminar flow separation, relaminarization, flow acceleration, transition to turbulence and tip leakage vortices. The results show that the blade relative position affects those heat transfer characteristics because the distributions of incoming flow velocity and turbulence intensity are changed. Especially, the heat transfer pattern on the near-tip region is significantly affected by the relative position of the blade because the effect of tip leakage vortex is strongly dependent on the blade position. On the pressure side, the effect of blade position is not so significant as on the suction side surface although the position and the size of the separation bubble are changed.

• 대한원격탐사학회지
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• 제36권1호
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• pp.41-53
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• 2020

The production of near- and off-shore fisheries in South Korea is decreasing due to rapid changes in the fishing environment, particularly including higher sea temperature in recent years. To improve the competitiveness of the fisheries, it is necessary to provide fish catch information that changes spatiotemporally according to the sea state. In this study, artificial intelligence models that predict the CPUE (catch per unit effort) of mackerel, anchovies, and squid (Todarodes pacificus), which are three major fish species in the near- and off-shore areas of South Korea, on a 15-km grid and daily basis were developed. The models were trained and validated using the sea surface temperature, rainfall, relative humidity, pressure,sea surface wind velocity, significant wave height, and salinity as input data, and the fish catch statistics of Suhyup (National Federation of Fisheries Cooperatives) as observed data. The 10-fold blind test results showed that the developed artificial intelligence models exhibited accuracy with a corresponding correlation coefficient of 0.86. It is expected that the fish catch models can be actually operated with high accuracy under various sea conditions if high-quality large-volume data are available.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.103-111
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• 2006

The spray behavior of direct-injection spark-ignition(DISI) engines is crucial for obtaining the required mixture distribution for optimal engine combustion. The spray characteristics of DISI engines are affected by many factors such as piston bowl shape, air flow, ambient temperature, injection pressure and fuel temperature. In this study, the effect of fuel temperature on the spray and combustion characteristics was partially investigated for the wall-guided system. The effect of fuel temperature on the fan spray characteristics was investigated in a steady flow rig embodied in a wind tunnel. The shadowgraphy and direct imaging methods were employed to visualize the spray development at different fuel temperatures. The microscopic characteristics of spray were investigated by the particle size measurements using a phase Doppler anemometry(PDA). The effect of injector temperature on the engine combustion characteristics during cold start and warming-up operating conditions was also investigated. Optical single cylinder DISI engine was used for the test, and the successive flame images captured by high speed camera, engine-out emissions and performance data have been analyzed. This could give the way of forming the stable mixture near the spark plug to achieve the stable combustion of DISI engine.

• 한국지반환경공학회 논문집
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• 제15권6호
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• pp.75-83
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• 2014

석션버켓기초는 펌프로 버켓 내부의 물을 외부로 배출할 때 발생한 압력차로 지반에 설치되는 기초이다. 버켓기초는 외해의 플랫폼이나 석유 가스 시추시설을 계류시키기 위한 앵커로 주로 사용되었으나, 최근 유럽을 중심으로 해상풍력발전의 기초로 적용되기 시작하면서 국내에서도 큰 관심을 받고 있다. 석션버켓기초의 관입저항력 산정은 석션버켓기초를 성공적으로 시공하기위해 고려해야 할 주요 사항 중의 하나이다. 본 연구는 석션버켓기초를 관입시킬 때 필요한 관입력을 평가하기 위해 실내모형실험을 수행하였다. 실내모형실험은 압입설치 및 석션설치에서 측정한 관입저항력을 관입성능평가에서 많이 사용되는 기존의 이론식과 비교하여 강도감소계수의 적절한 범위를 검토하였다.

• 한국항공우주학회지
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• 제47권4호
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• pp.245-255
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• 2019

본 논문에서는 유도무기의 선두부 형상 절단 비율에 따라서 달라지는 공력특성에 대해 전산유체역학을 이용하여 분석하였다. 해석을 수행하는 형상은 유도무기 동체만 있으며 직경대 길이비는 10.7이다. 선두부 형상은 세 가지를 선택했으며 구형, 25% 절단, 50% 절단형을 비교하였다. 유도무기 동체의 정확한 해석을 위해서 NASA의 풍동시험 데이터를 이용하여 격자 구성법과 해석 기법을 선택하고 검증하였다. 선두부 세 가지 형상에 대해서 비행마하수에 대해 항력을 분석한 결과 절단과 구형이 6~20% 정도 차이 났으며, 동체의 선두부와 기저부의 압력분포를 통해 특성을 분석하였다.