• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.68-74
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• 2021

Gas diffusion layer (GDL) compression is important parameter of polymer electrolyte membrane fuel cell (PEMFC) performance to have an effect on contact resistance, reactants transfer to electrode, water content in membrane and electrode assembly (MEA). In this study, the effect of GDL compression on fuel cell performance was investigated for commercial products, JNT20-A3. Polarization curve and electrochemical impedance spectroscopy was performed at different relative humidity and compression ratio using electrode area of 25 ㎠ unit cell. The contact resistance was reduced to 8, 30 mΩ·㎠ and membrane hydration was increased as GDL compression increase from 18.6% to 38.1% at relative humidity of 100 and 25%, respectively. It was identified through ohmic resistance change at relative humidity conditions that as GDL compression increased, water back-diffusion from cathode and electrolyte membrane hydration was increased because GDL porosity was decreased.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.131-131
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• 2017

작물의 체온인 엽온은 작물의 증발산량 또는 작물의 스트레스와 관련이 있으며, 일반적으로 일사, 풍속, 습도 등 기상조건과 잎의 크기, 형태 등 생리작용 등에 의해 지배된다. 엽온을 작물의 수분스트레스지수, 증발산량 등을 산정하기 위한 인자로 많이 활용되고 있으며, 최근 ICT 기술의 발달로 인해 열영상 카메라, 적외선 센서 등을 활용해서 실시간 측정을 하고, 정보를 작물 생육환경 제어에 활용하는 연구들이 많이 이루어지고 있다. 본 연구에서는 시설오이를 대상으로 캐노피 온도(Canopy temperature, $T_c$)와 대기온도(Air temperature, $T_a$)간의 상관관계, 또 ($T_c-T_a$)와 포화수증기압차(Vapor pressure deficit, VPD)와의 관계를 분석하였다. 대기온도와 상대습도를 이용하여 산정된 VPD가 엽온에 미치는 영향을 분석한 결과, 엽온 증가에 따라 VPD가 증가하였으며, 캐노피와 대기온도간의 차이 또한 VPD간에 음의 상관관계($R^2=0.82{\sim}0.89$)가 나타났는데, 이는 대기온도에 따른 엽온과 포화수증기압의 상승이 원인인 것으로 나타났다. ($T_c-T_a$)와 VPD값을 이용하면 작물 수분스트레스(Crop Water Stress Index, CWSI)를 산정할 수 있는 데, 결과값을 분석한 결과 $T_c$와 $T_a$의 차가 적은 경우 CWSI값이 증가함을 알 수 있었다. 향후 연구에서는 추가적으로 다양한 재배환경에서의 캐노피 온도, 포화수증기압차, 그리고 CWSI를 산정하여, 적정 생육 환경조성을 위한 지표로 활용할 계획이다.

• Korean Journal of Food Science and Technology
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• v.4 no.4
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• pp.265-270
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• 1972

An attempt was made in this study to investigate the possibility of processing squid along with pork into an intermediate moisture food, as an acceptable new item in Korea. To obtain a palatable and low cost product, portions of mixture consisting of equal amounts of ground squid and pork were cooked in soy sauce for 20 min, soaked in glycerol for 20 min at $80^{\circ}C$, and then air dried for 90 min at $60^{\circ}C$. During storage for 42 days in saturated humidity incubator at $37^{\circ}C$, the total microbial counts of the products packaged in polyethylene (0.05 mm), polypropylene (0.05 mm) and plastic laminated aluminum foil were decreased from 230 per gram to 40, 20 and 10 per gram respectively. In another long range storage test of 6 months, the results paralleled the above trends. Even though the TBA value of the samples increased during the storage, it was not so serious as to damage on the organoleptic quality of this product. The results indicate that stored product was as acceptable as the freshly prepared one.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.3
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• pp.19-31
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• 2007

Humidity and strain were estimated for understanding the relation between humidity change by self-desiccation and shrinkage in high-performance concrete with low water binder ratio and containing fly ash and blast furnace slag. Internal humidity change and shrinkage strain were about 10%, 10%, 7%, 11%, 11% and $320{\times}10^{-6}$, $270{\times}10^{-6}$, $231{\times}10^{-6}$, $371{\times}10^{-6}$, $350{\times}10^{-6}$ respectively on OPC30, O30F10, O30F20, O30G40, O30G50 and from the results, fly ash made humidity change and strain decrease but slag increase comparing with ordinary portland cement. Considering only relation internal humidity and shrinkage by self-desiccation, humidity change and shrinkage represented the strong linear relation regardless of mineral admixture. For specifying the relation on internal humidity change and autogenous shrinkage strain, shrinkage model was established which is driven by capillary pressure in pore water and surface energy in hydrates on the assumption of a single network and extended meniscus in pore system of concrete. This model and experimental results had a similar tendency so it would be concluded that the internal humidity change by self-desiccation in HPC originated in small pores less than 20nm, therefore controlling plan on autogenous shrinkage might be focused on surface tension of water and degree of saturation in small pore.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.131-138
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• 2008

Humidity and strain were estimated for understanding the relation between humidity change by self-desiccation and shrinkage in high-performance concrete with low water binder ratio. Internal humidity change and shrinkage strain were about 10%, 4% and $320\times10^{-6}$, $120\times10^{-6}$ respectively on concrete with water binder ratio 0.3, 0.4 and from the results, humidity change and shrinkage represented the strong linear relation regardless of mixture. For specifying the relation on internal humidity change and autogenous shrinkage strain, shrinkage model was established which is driven by capillary pressure in pore water and surface energy in hydrates on the assumption of a single network and extended meniscus in pore system of concrete. This model and experimental results had a similar tendency so it would be concluded that the internal humidity change by self-desiccation in HPC originated in small pores less than 20 nm, therefore controlling plan on autogenous shrinkage might be focused on surface tension of water and degree of saturation in small pore.

• Reproductive and Developmental Biology
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• v.28 no.2
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• pp.119-126
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• 2004

The present study was carried out to examine the effect of four different media (NCSU (North Carolina State University)-23, PZM (Porcine Zygotes Medium)-3, PZM-4 and TCM (Tissue Culture Medium)-l99) and two oxygen concentrations (39 , 5% $O_2$, 5% $CO_2$ and 90% $N_2$, 5% $CO_2$ in air) on in vitro production of porcine IVM/IVF embryos. The results were summarized as follows: The rates of GVBD and nuclear maturations were not significantly different (p>0.05) for 44 hours of culture with four media in two oxygen concentrations. The rates of polyspermy, penetrated sperm(s) and male and female prouclei formation were not significantly different (p>0.05). among four media in two oxygen concentrations. The cleavage rates were not significantly different (p>0.05) among four media in two oxygen concentrations. At day 7 under gas atmosphere of 5% $O_2$, 5% $CO_2$ and 90% $N_2$, the blastocyst formation was significantly higher (p<0.05) in PZM-3 (19.9$\pm$2.4) than other media. Also, NCSU-23 medium gave high rate of blastocyst formation at day 7 under gas atmosphere of 5% $CO_2$ in air (p<0.05). Based on the result of differential staining of porcine blastocyst at dat 7, inner cell mass cell and total cell numbers were not significantly different (p>0.05) among four media in two oxygen concentrations. However, the observed total cell number was higher in PZM-3 medium (36.8$\pm$6.5) than other madia. In conclusion, these results suggested that in vitro production of porcine embryos in PZM-3 medium under a gas atmosphere of 5% $O_2$, 5% $CO_2$ and 90% $N_2$ was effective on the blastocyst formation rate and total blastocyst cell number.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.6
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• pp.519-528
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• 1985

Fillets of mackerel (Scomber japonicus) and flounder (Xystrias grigorjewi) which, are representatives in red fleshed fish and white fleshed fish, respectively, were freeze-dried and stored in tightly sealed containers which were controlled to different relative humidity at $25^{\circ}C$. The changes of lipids were examined periodically by measuring the peroxide value (POV), the thiobarbituric acid (TBA) and the acid value (AV). And the fatty acid composition of lipids was investigated by gas-liquid chromatography (GLC). The results obtained are summarized as foollows: From the changes of POV and TBA value during storage, the oxidation of lipids was distinct at the lower relative humidities, $0\%\;and\;23\%$, while inhibited at the higher relative humidities, $52\%\;and\;81\%$. The changes in acid value during storage were more prominent at the hifger relative himidites than at the lower relative humidities. The content of $C_{16:0},\;C_{18:0}\;and\;C_{22:6}$ acids in the fatty acid composition of total lipids was abundant in both fleshed fishes. The content of $C_{18:1}$ acid in the nonpolar lipid and that of $C_{16:0}$ acid in the polar lipid were higher than other fatty acids. In the fatty acid composition of total lipids during storage, polyenoic acids decreased with storage period at $0\%\;and\;23\%$ relative humidities, while the fatty acid composition didn't show a great change at $52\%\;and\;81\%$ relative humidities. In the non-polar lipid, polyenoic acids coherently decreased under all the conditions of relative humidities but the saturated acids and the monoenoic acids increased. In the polar lipid, polyenoic acids decreased at $0\%\;and\;23\%$ relative humidities, while the saturated acids and monoenoic acids decreased at $52\%\;and\;81\%$ relative humidities. On the other hand, the oxidation of lipids was more significant in mackerel than in the flounder, and the changes of fatty acid composition were shown a similar pattern.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.9
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• pp.779-785
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• 2003

The present work proposed a newly developed fluidized bed-type psychrometer that could be applicable to the high temperature and contaminant gases. The psychrometer is a device that test gas passes through the water in a glass bottle as a bubbly flow to obtain the adiabatic saturation temperature. A fluidized bed-type psychrometer was made and its characteristics were compared with the Assmann Psychrometer. The characteristic time was in the order of a hundred seconds, and decreased for the decrease of the mass of water and the increase of the air flow rate. The air flow rate and the insulation of the glass bottle were definitely important in the accurate measurement of the wet bulb temperature. The error in wet bulb temperature became less than 5 percent of the difference of dry and wet bulb temperatures if the air velocity in the glass bottle was greater than 1.5m/s.

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.4
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• pp.299-311
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• 2020

This paper analyzes the distribution of water vapor pressure and relative humidity in complex terrains by collecting weather observation data at 6 locations in the valley in Jungdae-ri, Ganjeon-myeon, Gurye-gun, Jeolla South Province and 14 locations in Akyang-myeon, Hadong-gun, Gyeongsang South Province, which form a single drainage basin in rural and mountainous regions. Previously estimated water vapor pressure used in the early warning system for agrometeorological hazard and actual water vapor pressure arrived at using the temperature and humidity that were measured at the highest density (1.5 m above ground) at every hour in the valley of Jungdae-ri between 19 December 2014 and 23 November 2015 and in the valley of Akyang between 15 August 2012 and 18 August 2013 were compared. The altitude-specific gradient of the observed water vapor pressure varied with different hours of the day and the difference in water vapor pressure between high and low altitudes increased in the night. The hourly variations in the water vapor pressure in the weather stations of the valley of Akyang with various topographic and ground conditions were caused by factors other than altitude. From the observed data of the study area, a coefficient that adj usts the variation in the water vapor pressure according to the specific difference in altitude and estimates it closer to the actual measured level was derived. Relative humidity was simulated as water vapor pressure estimated against the saturated water vapor pressure, thus, confirming that errors were further reduced using the derived coefficient than with the previous method that was used in the early warning system.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.1
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• pp.69-77
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• 2014

Unsaturated hydraulic conductivity of the bentonite-buffer was evaluated using the relative humidity data. The method for calculating unsaturated hydraulic conductivity was deduced from the general analytical equation representing the movement of water in unsaturated media, which was applied to the experimental results of water infiltration tests for identifying the behavior of unsaturated hydraulic conductivity according to the water saturation. Unlike the saturated condition, the hydraulic gradient and water flux were irregularly changed, and the unsaturated hydraulic conductivity was increased with increasing the experimental time. Swelling of bentonite grains due to the water absorption increased the volume and size of pore within bentonite, resulting in the increase of water velocity and unsaturated hydraulic conductivity. This result suggested the necessity of further investigation on the correlation between the swelling degree of bentonite-buffer and unsaturated hydraulic conductivity. The method used in this study can be useful technique for evaluating long-term hydraulic performance of bentonite-buffer in the radioactive waste disposal system.