• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.969-983
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• 2021

Evapotranspiration, one of the hydrometeorological components, is considered an important variable for water resource planning and management and is primarily used as input data for hydrological models such as water balance models. The FAO56 PM method has been recommended as a standard approach to estimate the reference evapotranspiration with relatively high accuracy. However, the FAO56 PM method is often challenging to apply because it requires considerable hydrometeorological variables. In this perspective, the Hargreaves equation has been widely adopted to estimate the reference evapotranspiration. In this study, a set of parameters of the Hargreaves equation was calibrated with relatively long-term data within a Bayesian framework. Statistical index (CC, RMSE, IoA) is used to validate the model. RMSE for monthly results reduced from 7.94 ~ 24.91 mm/month to 7.94 ~ 24.91 mm/month for the validation period. The results confirmed that the accuracy was significantly improved compared to the existing Hargreaves equation. Further, the evaporative demand drought index (EDDI) based on the evaporative demand (E₀) was proposed. To confirm the effectiveness of the EDDI, this study evaluated the estimated EDDI for the recent drought events from 2014 to 2015 and 2018, along with precipitation and SPI. As a result of the evaluation of the Han-river watershed in 2018, the weekly EDDI increased to more than 2 and it was confirmed that EDDI more effectively detects the onset of drought caused by heatwaves. EDDI can be used as a drought index, particularly for heatwave-driven flash drought monitoring and along with SPI.

• Korean Journal of Remote Sensing
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• v.30 no.4
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• pp.525-536
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• 2014

In this study, a method to assess and monitor hydrological drought using remote sensing was investigated for use in regions with limited observation data, and was applied to the Upper Namhangang basin in South Korea, which was seriously affected by the 2008-2009 drought. Drought information may be obtained more easily from meteorological data based on water balance than hydrological data that are hard to estimate. Air temperature data at 2 m above ground level (AGL) were estimated using remotely sensed data, evapotranspiration was estimated from the air temperature, and the correlations between precipitation minus evapotranspiration (P-PET) and streamflow percentiles were examined. Land Surface Temperature data with $1{\times}1km$ spatial resolution as well as Atmospheric Profile data with $5{\times}5km$ spatial resolution from MODIS sensor on board Aqua satellite were used to estimate monthly maximum and minimum air temperature in South Korea. Evapotranspiration was estimated from the maximum and minimum air temperature using the Hargreaves method and the estimates were compared to existing data of the University of Montana based on Penman-Monteith method showing smaller coefficient of determination values but smaller error values. Precipitation was obtained from TRMM monthly rainfall data, and the correlations of 1-, 3-, 6-, and 12-month P-PET percentiles with streamflow percentiles were analyzed for the Upper Namhan-gang basin in South Korea. The 1-month P-PET percentile during JJA (r = 0.89, tau = 0.71) and SON (r = 0.63, tau = 0.47) in the Upper Namhan-gang basin are highly correlated with the streamflow percentile with 95% confidence level. Since the effect of precipitation in the basin is especially high, the correlation between evapotranspiration percentile and streamflow percentile is positive. These results indicate that remote sensing-based P-PET estimates can be used for the assessment and monitoring of hydrological drought. The high spatial resolution estimates can be used in the decision-making process to minimize the adverse impacts of hydrological drought and to establish differentiated measures coping with drought.

• Solar Energy
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• v.17 no.4
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• pp.23-33
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• 1997

In this paper, performance of various working fluids is evaluated for the closed Ocean Thermal Energy Conversion(OTEC) power plant operating on Rankine cycle. The evaporator and condenser are modeled via UA and LMTD method while turbine and pump are modeled by specifying isentropic efficiencies. R22, Propane, Propylene, R134a, R125, R143a, R32, R410A and Ammonia are used as working fluids. Results show that newly developed fluids such as R410A and R32 that do not cause stratospheric ozone layer depletion perform as well as R22 and ammonia. The superheat at the evaporator exit and subcooling at the condenser exit do not affect the performance of the simple OTEC power cycle. Turbine efficiency and heat exchanger size influence greatly the performance of the Rankine cycle. Finally, it was shown that closed OTEC power plants can practically generate electricity when the difference in warm and cold sea water inlet temperatures is greater than $20^{\circ}C$.

• KOREAN POULTRY JOURNAL
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• v.40 no.11
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• pp.168-170
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• 2008

농촌진흥청 축산과학원(원장 이상진)은 농장에서 계란을 출하할 때 집하장까지 운송에 소요되는 시간과 온도에 따른 품질을 조사한 결과, 운송시간이 짧고, 운송온도가 낮을수록 계란의 신선도가 높은 것으로 나타났다고 밝혔다. 계란은 작은 중량임에도 불구하고 병아리를 탄생시킬 수 있는 완전영양소를 갖고있기 때문에 요즘과 같이 온도가 높아지는 시기에는 달걀 내부의 호흡작용과 수분증발에 의해 계란의 품질이 현저히 나빠질 수 있다. 시험에 의하면 계란은 운송거리가 5km이내일 때에는 상온 운송차량과 $4^{\circ}C$ 냉장차량에서 계란의 신선도(Haugh unit)에는 차이가 없었으나, 운송거리가 100km이상에서는 냉장운송을 하지 않으면 신선도가 4배 이상 현저하게 낮아졌다. 또한, 난각의 총 미생물 수에서도 운송거리가 5km이내에서는 운송차량의 온도에 따른 차이가 없었으나, 100km이상 운송 시에는 냉장을 하지 않은 계란이 냉장계란에 비하여 2배 정도 높아지는 것으로 나타났다. 농촌진흥청 축산과학원 유영모 박사는 "계란이 농장에서 판매장까지 복잡한 경로를거쳐 유통되는 경우가 많은데, 요즘과 같은 고온기에는 계란의 신선도를 유지하는 냉장유통이 필요하며, 특히 여름철 장거리 운송 시에는 냉장차량을 이용하는 것이 계란의 신선도를 유지하는데 중요하다"고 말했다.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.129-129
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• 2000

태양전지는 태양광에너지를 바로 전기에너지로 전환시키는 소자이다. 최근에는 다결정 태양전지의 응용가능성에 대한 연구가 활발히 진행되어 오고 있다. 이 중 CuInSe2는 여러 가지 좋은 물성을 가지고 있어서, 저가의 고효율 태양전지를 위한 광흡수층 재료로 주목받고 있다. 현재까지 다양한 방법이 시도되었지만, 10% 이상의 고효율을 가지는 고품질을 박막을 얻는 방법은 진공증발증착법과 selenization 방법뿐이다. 이 중 진공증발증착법에 의하여 형성된 박막을 이용하여 가장 높은 효율의 태양전지를 얻을 수 있으나, 진공 장비의 대면적화가 힘들기 때문에 대면적 태양전지 제조가 힘들다는 단점이 있다. 따라서 selenization 방법을 이용하여 CuInSe2 박막을 제조하는 것이 가장 유망한 방법이라 할 수 있다. Selenization 방법은 Cu-In 금속층을 제작한 뒤 이를 selenium과 반응을 시키는 방법이다. 따라서 이 방법을 이용하여 박막을 제조할 때는 Cu-In 금속층의 물성 조절이 이후 생성되는 CuInSe2 박막의 물성향상에 필수적이다. 따라서 Cu-In 금속층의 물성에 대해 많은 연구가 이루어지고 있다. 하지만 Cu-In 이 성분계에서 알려진 반가 없다. 저온에서는 반응속도론적으로 매우 느리게 반응이 일어나기 때문에 열역학적으로 안정한 상을 얻기가 힘들기 때문이다. 따라서 본 실험에 앞서 각 제조 조건에 따른 열역학적인 안정상을 계산하였다. 그 결과, 상온에서 Cu의 양이 증가함에 따라, In$\longrightarrow$CuIn2$\longrightarrow$Cu11In9$\longrightarrow$Cu7In3 상으로 변화하였다. 9$0^{\circ}C$이하의 온도에서는 CuIn2 상이 안정하였고, 10$0^{\circ}C$ 이상의 온도에서는 Cu11In9 상 두 가지로 존재하였고, Cu/In 인가전력비를 변화시켰을 때 조성비가 선형적으로 변하였다. 즉, Cu-In 동시스퍼터링법은 원하는 조성을 간편한 방법으로 정확하게 조절할 수 있는 방법이라 할 수 있다. 증착 온도를 변화시켰을 때는 9$0^{\circ}C$ 이하의 낮은 온도에서 존재하던 CuIn2 상이 10$0^{\circ}C$이상의 온도에서는 완전히 사라지고 In과 CuIn2 상이 사라지고 In 상과 Cu11In9 상이 나타났다. 상전이를 위하여 30$0^{\circ}C$의 높은 열처리 온도가 필요한 것은, 밀 저온 안정상이 형성된 뒤 각 원소들의 확산에 의해 상전이가 일어나기 때문에 이를 위한 충분한 열에너지를 가질 수 있는 온도가 필요하기 때문이다. 조성을 일정하게 유지하면서 챔버 압력을 변화시켰을 때는 형성되는 상의 미세구조난 결정성은 일정하였다. 인가전력, 증착온도, 챔버 압력 변화에 따른 상변화는 앞서 계산한 열역학적 결과와 정확히 일치하였다. 이는 동시스퍼터링 방법이 각 입자들을 원소 단위에서 균일하게 혼합할 수 잇는 방법이고, 또 입자들이 높은 에너지를 가지고 있기 때문이다. 즉, 원소 단위에서 균일한 반응을 하고, 가장 안정한 위치로 쉽게 이동할 수 있기 때문에 열역학적으로 안정한 상을 형성할 수 있는 것이다.

• Membrane Journal
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• v.26 no.3
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• pp.197-204
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• 2016

The objective of this work was to investigate the performance of pervaporation process for recovery of ester compounds from model aqueous solutions and how the fluxes of esters and water were affected by changes in feed concentration and temperature. The flux of ethyl acetate (EA), propyl acetate (PA), ethyl propionate (EP), butyl acetate (BA), and ethyl butyrate (EB) increased with an increase in feed concentration from 0.15 wt% to 0.60 wt%, and increased with temperature change from $30^{\circ}C$ to $50^{\circ}C$. The flux of esters (EA, PA, EP, BA, and EB) was in order of (EA) < (PA, EP) < (BA, EB). This result meant that the flux strongly depended on affinity between esters and membrane surface; EA is the least hydrophobic because it has one hydrophobic function group ($-CH_2-$), (PA, EP) have two ($-CH_2-$), and (BA, EB) are the most hydrophobic because these have three ($-CH_2-$). As well as such an influence of hydrophobicity of ester molecules on ester flux, the influence of hydrophobicity of membrane surface on ester flux needs further investigation. With increase in temperature, water flux of aqueous EA, PA, EP, BA, and EB solution increased. However, water flux of aqueous ester solutions did not change appreciably with increase in concentration. This experimental results may be used as fundamental data for pervaporation (PV) to improve the aroma recovery process as an alternative to thermal evaporation and distillation processes.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.18-24
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• 2005

Wet compression means the injection of water droplets into the compressor of gas turbines. This method decreases the compression work and increases the turbine output by decreasing the compressor exit temperature through the evaporation of water droplets inside the compressor. This paper provides thermodynamic and aerodynamic analysis on wet compression in a centrifugal compressor for a microturbine. The meanline performance analysis of centrifugal compressor is coupled with the thermodynamic equation of wet compression to get the meanline performance of wet compression. The most influencing parameter in the analysis is the evaporative rate of water droplets. It is found that the impeller exit flow temperature and compression work decreases as the evaporative rate increases. And the exit flow angle decreases as the evaporative rate increases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.34-38
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• 1999

$PbTiO_3$(PT)thin films were prepared by simultaneous of $TiO_2$ and PbO on Si(100) substrate using metaloganic chemical vapor deposition (MOCVD). Titanium tetra-isopropoxide (TTIP) and $Pb(TMHD)_2$were used as source materials. As evaporation temperature and flow rate of TTIP were examined the crystal structure of PT thin films using XRD with setting deposition temperature, flow rate of Pb, and total flow rate of $520^{\circ}C$, 30 sccm, and 750 sccm, respectively. PT thin films could be deposited under 48~$50^{\circ}C$ and 18~22sccm of evaporation temperature and flow rate of TTIP, respectively. It was found that lead, oxygen, and silicon diffused at the iaterface between the film and the substrate.

• Membrane Journal
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• v.26 no.1
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• pp.70-75
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• 2016

The reuse of wastewater is being diffused to manage and develop the water resources. Generally, the treated wastewater is discharged to the river after being treated to meet the effluent quality standard or reused for diverse uses through the reprocessing. And recently, as the reuse of the treated wastewater is activated, the technologies to utilize for the high quality water resources such as industrial water by reusing the wastewater with Membrane Distillation (MD) are under development. In this study, the direct contact membrane distillation (DCMD) process has been applied to treat sewage discharge water for water reuse. The laboratory scale experiment was performed by using a hydrophobic PVDF membrane with the pore size of $0.22{\mu}m$. The influence of operating parameters, such as feed temperature, feed flow rate, feed concentration, on the permeate flux and rejection has been investigated. All filtration tests were conducted till the feed volume reached a concentration factor of 3.0. Thus, the operating period ranged between 19 hr and 49 hr depending on filtration performance. The results showed that above 92% of TN, TP, COD and TOC in the feed could be rejected regardless of an operating condition. The water flux was ranged from 13.8 to 20.3 LMH. The lowest flux was obtained at the operating condition with the feed temperature of $50^{\circ}C$ and feed flow velocity of 500 mL/min while the highest one was measured with $60^{\circ}C$ and 900 mL/min. When the concentration factor reached 3.0, water flux declined by approximately ranged from 14.5% to 33.3%. But the fouling in MD is almost fully reversible, with more than 90% recovery of permeate water flux following a DI water rinse without the addition of chemical cleaning reagents.

• KOREAN POULTRY JOURNAL
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• v.33 no.6 s.380
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• pp.120-125
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• 2001

육용종계는 체내에서 화학적인 반작용에 의해 일정한 열을 생성한다. 이 열이 체온을 상승시켜 폐사하는 것을 방지하기 위해서 열을 발산해야 한다. 계사온도가 상승하면 열 발산이 어려워져서 닭들은 헐떡거림으로 기낭과 폐로부터 수분을 증발하게 된다. 습도가 높을 경우 헐떡거림으로 열을 발산하는 능력을 제한하게 된다. 계사 내의 온도가 $27^{\circ}C$가 넘어가면 고온스트레스와 산란을 감소시킬 수 있으며 $32^{\circ}C$가 넘어가면 스트레스 증상은 뚜렷해진다. $38^{\circ}C$이상이 되면 폐사가 증가하게 되며 특히 과비된 개체가 더 빨리 더 많이 영향을 받는다. 고온스트레스를 줄이기 위해서는 좋은 관리가 매우 중요하며 더위가 오기 전에 미리 준비하는 것이 필수이다.