• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.168-174
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• 2005

In this study, the numerical simulation of drying processes for porous materials is performed by employing the hierarchical multi-scale modeling and the nano-scale material properties obtained from the molecular dynamics simulation. The multi-scale simulation system is set up using pre- and post-processors and the drying process of electric porous ceramic insulator is simulated. The temperature, moisture, residual stress, and displacement distributions are compared with those based on homogenized properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.114-116
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• 2004

적층형 piezoelectric ceramic actuators를 제작하여 신뢰성을 평가하였다. 소자의 신뢰성 측정을 위하여 3kV/mm, 5kV/mm, 7kV/mm의 정류된 교류전압을 인가하였으며, 실험중 온도와 습도를 일정하게 유지하기 위하여 항온항습조안에서 실험을 실시하였다. 각 실험의 경우에 16개의 소자를 동시에 평가하였으며, 평균파괴시간을 Weibull 통계방식을 이용하여 계산하였으며, Arrhenius model, Power law model을 이용하여 사용 조건하에서 예상수명을 예측하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.300-300
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• 2023

기후변화의 영향 중 하나인 무강우일수의 증가는 우리의 삶에 다양한 피해를 야기하고 있다. 영산강·섬진강권역은 2001년 이후 가장 심한 가뭄을 겪고 있으며, 이로 인해 하천의 건천화, 수질악화, 농업피해 등이 발생하고 있다. 무강우일수의 증가로 인한 피해는 농업지역에만 국한되지 않는다. 도시지역에 무강우가 지속될 경우 공기 중의 미세먼지가 효과적으로 제거되지 못하는 문제가 발생한다. 미세먼지로 인한 환경문제는 특정 배출지역에 국한되지 않고 기상조건에 따라 오염물질이 이동할 수 있으므로 타지역 및 타국가와의 갈등을 유발할 수 있다. 따라서, 정확한 분석을통해 원인을 규명하고 해결방안을 강구하는 것은 중요한 일이다. 이를 위해 본 연구에서는 먼저 한국환경공단에서 운영 중인 523개의 도시대기 측정소에서 관측된 PM₁₀ 시단위 자료를 이용하여 미세먼지의 추세를 분석하였다. 다음으로 미세먼지의 이동과 소멸과 연관성이 있을 것으로 판단되는 강우량, 습도, 풍속 등의 기상요소 및 무강우일수와 미세먼지 농도의 관련성을 분석하였다. 무강우일수는 전국에 분포된 103개 지상관측소의 시단위 강우자료를 통해 계산하였으며, 무강우일수와 미세먼지 농도의 관계는 각각의 무강우일수에 대응되는 미세먼지의 농도분포를 통해 년단위 및 월단위로 지역별로 분석하였다.

• Annual Conference of KIPS
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• 2023.11a
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• pp.1012-1013
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• 2023

본 논문의 사회적 취약지구를 위한 전용 화재감지 AI'sTory 플랫폼은 달동네와 판자촌과 같이 소외계층이 집약된 곳이라면 노후된 기기와 전선들이 많을 것이고 그렇다면 전기적 요인으로 인한 화재가 발생할 것이라는 가설에서부터 시작한다. 피해의 최소화를 위해 고안한 사회적 취약지구를 위한 전용 화재감지 AI'sTory 는 스파크를 감지하고, 전선 주위의 발열량을 모니터링하며, 화재를 감지한 즉시 소방서로 연락을 취하는 인공지능 시스템이다. 더 나아가 센서로부터 데이터를 받아 매일 온·습도, 전력 접촉부의 온도, 계절 등 여러 환경을 고려해 화재가 발생할 확률을 계산한다. 또한 화재가 발생하지 않아도 매일 화재 발생 위험률을 제공한다. 이 정보를 제공하기 위해 사회적 취약지구를 위한 전용 화재감지 AI'sTory 는 하드웨어와 소프트웨어, 인공지능으로 구성하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.23-29
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• 2003

Transonic two-phase flow of Saturated humid air, in which relative humidity is 100%, with various condensation processes around thin airfoils is investigated. The study uses an extended transonic small-disturbance(TSD) model of Rusak and Lee [11, 12] which includes effects of heat addition to the flow due to condensation. Two possible limit types of condensation processes are considered. In the nonequilibrium and homogeneous process, the condensate mass fraction is calculated according to classical nucleation and droplet growth rate models. In the equilibrium process, the condensate mass fraction is calculated by assuming an isentropic process. The flow and condensation equations are solved numerical1y by iterative computations. Results under same upstream conditions describe the flow structure, field of condensate, and pressure distribution on airfoil's surfaces. It is found that flow characteristics, such as position and strength of shock waves and airfoil’s pressure distribution, are different for the two condensation processes. Yet, in each case, heat addition as a result of condensation causes significant changes in flow behavior and affects the aerodynamic performance of airfoils.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.276-282
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• 2017

The aim of this study was to compare and analyze air temperature and humidity distribution and energy consumptions according to using air circulation fans in single-span greenhouses. The greenhouses located in Cheongnam-myeon, Cheongyang-gun, Chungcheongnam-do, Korea. There were cherry tomatoes in the greenhouses and the size of greenhouses was as follows;ridge height : 3.2 m, wide : 6 m, length : 95 m. The heating system was composed of a hot-water boiler and 6 FCUs(Fan Coil Unit)-4 FCUs were on bottom with duct and 2 FCUs were installed at 2.0 m. A total of 18 air circulation fans(impeller's diameter : 230 mm) were bilaterally arranged in 2 rows in the experimental greenhouse. The sensors for measuring air temperature and humidity were located at a quarter and three quarters of a length. The height of sensors were 0.8 m, 1.8 m. To calculate energy consumption in greenhouses, water temperature at inlet and outlet in a water pump, volume of water were measured. Form February 3rd to March 23th, temperature, humidity and energy consumptions were measured during heating time(6pm~7am). In a greenhouse without fans, the average differences of temperature and humidity were $0.75^{\circ}C$, 2.31%, respectively. The operation of fans showed their differences to $0.42^{\circ}C$, 1.8%. The standard deviation of temperature and humidity between measuring points in the greenhouse with fans was lower than the greenhouse without fans. Total energy consumptions in a greenhouse without fans were 4,673 kWh. In the greenhouse with fans, the total energy consumptions were 4,009 kWh. The energy consumptions in a greenhouse with fans 14.2% were less than the greenhouse without fans. Therefore, air circulation makes temperature and humidity uniform and saves energy consumptions for heating.

• Korean Journal of Environmental Agriculture
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• v.23 no.4
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• pp.264-271
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• 2004

A three-dimensional numerical mesoscale model by Pielke's estimation (University of Virginia Mesoscale Model, UVMM) was applied to investigate the effects of land characteristics including land-humidity, land-roughness and land-albedo on some micro-climatic coefficients and the air cooling capacity. The results indicated that land-characteristics exposed a significant effect on air cooling. Air cooling effects between in urban and agricultural areas were compared and the effects were much higher in agricultural area. Air cooling effects of weed species were different and when converted into economic values by diesel oil price the effects were ranged from 411 to 816 Won/plant.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.6
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• pp.504-511
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• 1990

Weather data acquisition and potential evapotranspiration (PET) calculation procedure were investigated to support the agricultural development efforts in the mid-altitude mountainous region of Cheju Island. Automated weather stations (AWS) were installed at two points representing the east and the west of the study area. A personal computer was employed to collect the near-real time weather data from AWS through the public telephone line. Hourly data were available for solar radiation, air and soil temperature, relative humidity, wind speed and direction, and precipitation. Based on the data for the month of June 1989, daily climatic features were comparatively analyzed for the two areas and the Penman equation was used to calculate PET. Air temperature was higher by 1 to 2 degree C in the east due mainly to the higher solar radiation and partly to the Fohn effect caused by the daytime southwesterly blowing over Mt. Halla. Diurnal march of soil temperature lagged by 4 hours behind that of air temperature and the diurnal range for 10cm subsurface soil was 3 degree C. Wind was consistently stronger and a marked sea-land breeze circulation was detected in the west. Calculated PET values were higher in the east by 6% than in the west. Overall values from the east and the west of the mid-altitude mountainous region were higher by 30% than those of the coastal region, which were estimated from the Class A Pan evaporation measured by the Korea Meteorological Service Offices.

• Journal of Bio-Environment Control
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• v.22 no.2
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• pp.182-187
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• 2013

In closed plant production system like plant factory, changes in environmental factors should be identified for conducting efficient environmental control as well as predicting energy consumption. Since high relative humidity (RH) is essential for crop production in the plant factory, transpiration is closely related with RH and should be quantified. In this study, four varieties of lettuces (Lactuca sativa L.) were grown in a plant factory, and the leaf areas and transpiration rates of the plants according to DAT (day after transplanting) were measured. The coefficients of the simplified Penman-Monteith equation were calibrated in order to calculate the transpiration rate in the plant factory and the total amount of transpiration during cultivation period was predicted by simulation. The following model was used: $E_d=a*(1-e^{-k*LAI})*RAD_{in}+b*LAI*VPD_d$ (at daytime) and $E_n=b*LAI*VPD_n$ (at nighttime) for estimating transpiration of the lettuce in the plant factory. Leaf area and transpiration rate increased with DAT as exponential growth. Proportional relationship was obtained between leaf area and transpiration rate. Total amounts of transpiration of lettuces grown in plant factory could be obtained by the models with high $r^2$ values. The results indicated the simplified Penman-Monteith equation could be used to predict water requirements as well as heating and cooling loads required in plant factory system.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.155-155
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• 2017

최근 애플망고 스마트 농가에 에너지 사용량이 증가됨에 따라 에너지 절감을 위한 대책들과 화석연료를 대체하는 다양한 신재생에너지 도입에 대한 요구들이 늘고있다. 본 연구에서는 애플망고 스마트 농가에 여러 에너지원들을 혼합하여 사용할 수 있도록 실증시험 모델을 구축하고 운영함으로써 그 효용성을 검토하고자 하였다. 우선 애플망고 특성을 고려한 비닐온실의 최대 냉난방부하량과 에너지모델을 분석하여 신재생 에너지원들의 혼합 및 기존 공조설비와의 연계를 계산하였다. 애플망고 시험 농지로는 재배에 적합한 제주도 서귀포를 선정하였으며, 기존의 경유 난방기를 사용하는 비교시험 하우스, 기존의 경유와 태양광, 지하 공기 히트펌프 난방기를 혼합하여 사용하는 실증시험 하우스, 경유와 지하공기 히트펌프 난방기를 사용하는 대조시험 하우스를 10~11월 두 달간 운영하여 그 결과들을 평가하였다. 온실 내외부에 온도, 습도, CO2를 측정할 수 있는 6점의 센서부들을 설치하였고, 적산 전력계와 유량계를 설치하여 데이터를 수집하였으며, 모든 시험 데이터는 모바일 원격으로 제어 및 모니터링이 가능하도록 구성하였다. 시험 결과, 각 하우스들에서 수확한 과실의 수량과 품질은 유사하게 평가되었지만, 실증시험 하우스의 난방비가 비교시험 하우스보다 절감되었다. 하지만 실증시험 하우스의 경우 높은 시설유지비로 인해 이를 고려한 사용료는 비교시험 하우스보다 더 비싸게 평가되었다. 본 연구를 통해 생산된 잉여전력을 매전할 때 이로 인한 이용비는 비교시험 하우스보다 더 경제적임을 확인할 수 있었다. 또한 기존의 경유와 지하공기 히트펌프 난방기를 혼합한 대조시험 하우스의 난방비용이 경제성에서 더 유리함을 알 수 있었다. 따라서 본 연구를 통해 애플망고 스마트 농가에 적합한 에너지-믹스 모델을 구축할 수 있었으며, 다양한 신재생에너지들의 효용성들을 검토할 수 있었다.