• Journal of the Korean Electrochemical Society
• /
• v.11 no.4
• /
• pp.273-283
• /
• 2008

GDL(Gas Diffusion Layer) is one of the main components of PEM fuel cell. It transports reactants from the channel to the catalyst and removes reaction products from the catalyst to the channels in the flow filed plate. It is known that higher permeability of GDL can make it possible to enhance the gas transport through GDL, leading to better performance. And MEA's temperature is determined by gas and heat transport. In this paper, three dimensional numerical simulation of PEM fuel cell of parallel channel and serpentine channel by the permeability of GDL is presented to analysis heat and mass transfer characteristics using a FLUENT modified to include the electrochemical behavior. Results show that in the case of parallel channel, performance variation with change of permeability of GDL was not so much. This is thought because mass transfer is carried out by diffusion mechanism in parallel channel. Also, in the case of serpentine channel, higher GDL permeability resulted in better performance of PEM fuel cell because of convection flow though GDL. And mass transfer process is changed from convection to diffusion when the permeability becomes low.

• Journal of the Korean Ceramic Society
• /
• v.25 no.3
• /
• pp.207-216
• /
• 1988

Effect of $SO_3$ on the formation of $C_3S$ and its properties were investigated through studies for diffusion of reacting component, the size variation of $C_3S$ and compositional change of the phases in the clinker. When less than 2.0% of $SO_3$ was added to the clinker composition, the formation of $C_3S$ was enhanced, however, addition of more than 2.0% of $SO_3$ rather restrained the reaction remarkably. The diffusion coefficient of Si into the melt was about $3.6~4.2{\times}10^{-7}Cm^2$/sec and it was slightly decreased with the amount of $SO_3$. The crystal size of $C_3S$ formed in the clinker was grown gradually according to the amount of $SO_3$, when more than 1.0% of $SO_3$ was added. With increasing of $SO_3$ content in the clinker composition of CaO and decreasing of $SiO_2$ were found in the melt of the clinker. Consequently, it is considered that the decreasing of $C_3S$ formation is caused by dissolution and transportation of CaO component into liquid phase is interrupted.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.833-841
• /
• 2013

In the case of composite material, a variety of characteristics were expressed depending on the materials that were composed of. In this study, the materials showing non-linear shear behavior were investigated among FRP composite. Each specimen was designed and analyzed according to ASTM D4255 method: regulations on the 2-rail. The dependent variables included in this experiment were a variety of fiber, fiber volume ratio, fiber array direction, temperature, material homogeneity. For determination of characteristics based on the fiber array, fiber array direction of 0, 30, 45, and 60 degrees were selected for test specimen. Temperature of 25, 40, 60, and $80^{\circ}C$ were considered for investigation of FRP materials'shear behavior based on the external temperature. Nonlinear shear behavior was observed throughout the FRP composite material in this study. Also, using vinyl ester resins, high fiber volume ratio, and fiber array direction of 45 degree appeared to show the most prominent nonlinear shear behavior. As for the findings related to the temperature change, non-linear behavior was decreased as the external temperature increased. For factory manufactured product, non-linear behavior was relatively at parity in comparison to the behavior found in the hand lay-up FRP composite specimen.

• The Journal of Engineering Geology
• /
• v.24 no.4
• /
• pp.631-641
• /
• 2014

Characteristics of water-level changes in the Temporary Gulpocheon Discharge Channel were identified by observing and analyzing changes in the subterranean water level induced by hydrological stresses the underground aquifer. The subterranean water level refers to the level at which the pressure of subterranean water passing through the corresponding position has an equipotential value that is in equilibrium with the atmospheric pressure at that location. This water level is not fixed but changes in response to hydrological stress. It can be identified by repeatedly measuring the distance from the observation point to the surface of the subterranean water. The subterranean water-level change equation and the variance range of the hydrological curve of subterranean water over 24 hours at the Gimpo-Gimpo National Groundwater Monitoring Network (NGMN) were used as assessment factors. The variance characteristics of the subterranean water at the 18 monitoring system locations were classified into three impact, observational wish, and non-impact. The impact type accounted for 50% of the subterranean water of and accurately reflected the water-level changes due to hydrological stress, showing that distance is the major controlling factor. The observational wish type accounted for 27.8% of the subterranean water, and one of the two assessment factors did not meet the assessment factors. The nonimpact type accounted for 22.2% of the subterranean water. This type satisfied the two assessment factors and represents subterranean water-level changes response to precipitation.

• Journal of the Korean Electrochemical Society
• /
• v.8 no.1
• /
• pp.32-36
• /
• 2005

[ $WO_3$ ] and $NiO-WO_3$ thin films were deposited on a Si (100) substrate by using high vacuum thermal evaporation. The effects of various film thicknesses on the surface morphology $WO_3$ and $NiO-WO_3$ thin films were investigated. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the deposited films. The results suggest that as $WO_3$ thin films became thick, their grain grew up to a $0.6{\mu}m$. On the other hand, NiO-doping to $WO_3$ thin films inhibited the grain growth five times less than undoped $WO_3$ thin films. This results show that NiO doping inhibited the grain growing of $WO_3$ thin films. Also, the variation of NOx sensitivity $(R_{NOx}/R_{air})$ to the thickness of $WO_3$ and $NiO-WO_3$ thin films were measured according to the thickness change of thin films and the working temperature of sensor in 5ppm NOx gas. As a result, $NiO-WO_3$ thin films showed more excellent properties than $WO_3$ thin films for NOx sensitivity.

• Archives of Pharmacal Research
• /
• v.26 no.2
• /
• pp.168-172
• /
• 2003

Radiation synovectomy is one of the most useful methods for treating patients with refractory synovitis because of its convenience, long-term effects, repeatability and the avoidance of surgery. In this study, we investigated the toxicity, stability and biodistribution of a rhenium-188 ($^{188}$Re)-tin colloid to evaluate its suitability as a synovectomy agent. Twenty four hours after injecting the $^{188}$Re-tin colloids (74 KBq/0.1 mL) into the tail vein of ICR mice, most of the $^{188}$Retin colloidal particles was found in the lungs. In addition, there were no particle size changes at either room temperature or at $37^{\circ}C$ after injecting the $^{188}$Re-tin colloids in human plasma and synovial fluid. In vitro stability tests showed that the $^{188}$Re-tin colloid remained in a colloidal form without a critical size variation over a 2-day period. We investigated the leakage of $^{188}$Retin colloids from the intraarticular injection site with gamma counting in New Zealand white rabbits. The $^{188}$Re-tin colloids (55.5 MBq/0.15 mL) were injected at the cavum articular and the mean retention percentage of the $^{188}$Re-tin colloid was 98.7% for 1 day at the injection site, which suggests that there was neither change in the particle size nor leakage at the injection sites. In the biodistribution study with the SD rats, the liver showed the highest radioactivity (0.0427% ID/organ) except for the injected knees (99.49%). In the SD rats, mild toxicities including the skin or a synovium inflammation were observed as a result of a radioactivity of 15 mCi/kg at the intraarticular injection site. However, there was no systemic toxicity. In the Ovalbumin (OVA)-induced arthritic rabbits, the $^{188}$Re-tin colloid improved the macroscopic, the histological score and reduced the knee joint diameter when compared to the arthritic control. In conclusion, a $^{188}$Re-tin-colloid is considered as a strong candidate for radiation synovectomy with a superior efficacy and safety.

• Korean journal of applied entomology
• /
• v.54 no.4
• /
• pp.359-367
• /
• 2015

Physiological plasticity of insects can be closely related with their epigenetic change. This hypothesis was tested using a polyphagous lepidopteran insect, Spodoptera exigua, by assessing the effects of different diets on development and DNA methylation. Three different diets (Welsh onion (WO), Chinese cabbage (CC), artificial diet (AD)) were assessed by feeding a cohort of larvae from neonate to last instar. There were significant differences in larval developmental rate, pupal weight and adult emergence according to diet treatments. AD-fed larvae exhibited the fastest developmental rate along with the highest pupal weight and adult emergence. Among natural hosts, WO was more favorable for development of S. exigua than CC. Total hemolymph proteins and sugars in the last instar larvae were varied among different diets. Gene expression of an insulin-like peptide (SeILP1) presumably associated with development was also varied among diets. Cytosine methylation of genomic DNA was assessed using a monoclonal antibody. Genomic DNA of S. exigua larvae was methylated. DNA methylation was apparently varied among different diet-fed larvae. The facts that a cohort of S. exigua was differentiated in developmental rate and cytosine methylation by different diets suggest that epigenetic factor(s) may play a crucial role in the physiological plasticity.

• Journal of Sericultural and Entomological Science
• /
• v.46 no.1
• /
• pp.1-5
• /
• 2004

Rutin has many beneficial effects on human health. It was established that rutin antagonizes the increase of capillary fragility associated with hemorrhagic disease, reduces high blood pressure, decreases the permeability of the vessels, and has an antiedema effect, reduces the risk of arteriosclerosis, and shows antioxidant activity. Rutin analysis with mulberry fruits was carried out by high-performance liquid chromatography (HPLC) to reveal the possibility of source of functional food. As a result, mean content of fifty accessions was 0.14±0.050% DW. Among the tested fifty accessions, 'Sabangso' was showed the highest rutin in 0.29%DW, whereas 'Simseol' was the lowest content in 0.05% DW. Also, we researched the change of rutin content according to harvested date. The rutin contents of earlier harvested groups were higher than later harvested groups. Simultaneously, fruity characteristics as well as rutin content were researched and analyzed to select the functional mulberry varieties for the production of fruit. From the six accessions which were contained high rutin content, we selected three suitable varieties such as 'Ficus', 'Kangsun', and 'Palcheongsipyung'.

• Korean Journal of Food Science and Technology
• /
• v.10 no.3
• /
• pp.331-336
• /
• 1978

In an attempt to study the possibility of substituting sweet potato for cereals as raw materials for Kochujang, three kinds of Kochujang were made from barley, sweet potato or 50% barley and 50% sweet potato, The results of component variation during the ripening and the effect of temperature on the aging in the harvesting season of sweet potato were as follows: 1) Kochujang is, usually, manufactured in May, but no difference was observed in aging condition when it was manufactured in September, the season of sweet potato harvest, since the inner temperature of the product was around $20^{\circ}C$. 2) The total reducing sugar content and maturity reached maximum after $40{\sim}50\;days$ of fermentation in the three treatments and crude fat content tended to be slightly decreased during fermentation. 3) Lightness in color of the three kinds of Kochujang decreased by exposure to sunlight. Sweetpotato Kochujang showed a stronger tendency to increase the redness as compared with the rest. 4) Sensory evaluation showed that sweet potato Kochujang was less acceptable than barley Kochujang due to disagreeable flavor of sweet potato but mixed Kochujang showed little difference, as compared with barley Kochujang.

• Journal of the Korean Magnetics Society
• /
• v.24 no.1
• /
• pp.1-10
• /
• 2014

$Co_2Z$-type barium ferrites ($Ba_3Co_2Fe_{24}O_{41}$) were synthesized using variation method. First, M-type, $Co_2Y$-type and $Co_2Z$-type synthesized by hydrothermal method. Second, M- and Y-type precursors for synthesis of $Co_2Z$ hexaferrite by hydrothermal and ball milling method. the morphology, structure and magnetic properties of the barium ferrite particles were characterized using XRD, FESEM, VSM, impedance. As a result, Single phase of M-type and $Co_2Y$-type were obtained. Manufactured powders of M+Y ball milling, M+Y hydrothermal were similar to single phase of $Co_2Z$-type hexaferrite, all powders were obtained theoretical magnetization (50 emu/g). The largest initial permeability were obtained $Co_2Z$ hexaferrite synthesized by reagent precusor, With increasing calcination temperature was lowered the initial permeability. In another synthesis didn't almost that little change could be found.