• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.307-312
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• 2023

In this study, a catalytic oxidation-heat recovery system was designed that can remove unreacted with a concentration of about 1% to 6% in the exhaust gas of hydrogen fuel cells and recover heat to ensure safety in the hydrogen economy. The safety system was devised by filling hydrogen oxidation catalysts at room temperature that can remove unreacted hydrogen without any energy source, and an exhaust-heat recovery device was integrated to efficiently recover the heat released from the oxidation reaction. Through CFD analysis, variations in pressure and fluid within the system were shown depending on the filling conditions of the hydrogen oxidation system. In addition, it was found that waste heat could be recovered by optimizing the temperature of the exhaust gas, flow rate, and pressure conditions within the heat recovery system and securing hot water above 40 ℃ by utilizing the exhaust gas oxidation heat source above 300 ℃. Through this study, it was possible to confirm the potential of utilizing hydrogen processes, which are applied in small to medium-sized systems such as hydrogen fuel cells, as a safety system by evaluating them at a pilot scale. Additionally, it could be a safety guideline for responding to unexpected hydrogen safety accidents through further pilot-scale studies.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.705-720
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• 2023

In South Korea, ongoing incidents related to drinking water quality have eroded consumer trust. Specifically, beyond quality incidents, there have been complaints about taste, odor, and other issues stemming from the presence of chlorine. To address this, water service operators are employing various management strategies from both temporal (scheduling) and spatial (rechlorination) perspectives to ensure uniform and safe distribution of chlorine residuals. In this study, we focus on the optimal monthly management of chlorine residuals, based on water distribution network analysis. Water quality reaction coefficients, including bulk fluid and wall reaction coefficients, were estimated through lab-scale tests and EPANET water quality simulations, respectively, accounting for temperature variations in a large-scale water distribution network. Utilizing these estimated coefficients, we examined the monthly variations in chlorine residual distribution under different chlorine injection conditions. The results indicate that the efficient concentration for chlorine injection, which satisfies the residual chlorine limit range, varies with temperature changes. Consequently, it is imperative to establish a specific and quantitative chlorine injection plan that considers the accurate spatial distribution of monthly chlorine residuals.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.51-60
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• 2024

Hi Air Korea and Hanwha ocean are currently developing an Onboard Carbon dioxide Capture System (OCCS) to absorb CO₂ emitted from ship's engine using a sodium hydroxide(NaOH) solution, and converting the resulting salt into a solid form through a chemical reaction with calcium oxide (CaO). The system process involves the following steps; 1)The reaction of CO₂ gas absorption in water, 2)The reaction between carbonic acid (H₂CO₃) and NaOH solution to produce carbonate or bicarbonate, and 3)The reaction between carbonate or bicarbonate and CaO to form calcium carbonate (CaCO₃). And ultimately, the solid material, CaCO₃, is separated and discharged using a separator. The OCCS has been installed on an ship and the test results have confirmed significant reduction effects of CO₂ in the ship's exhaust gas. A portion of the exhaust gas emitted from the engine was transferred to the OCCS using a blower. The flow rate of the transferred gas ranged from 800 to 1384 m³/hr, and the CO₂ concentration in the exhaust gas was 5.1 vol% for VLSFO, 3.7 vol% for LNG and a 12 wt% NaOH solution was used. The results showed a CO₂ capture efficiency of approximately 42.5 to 64.1 vol% and the CO₂ capture rate approximately 48.4 to 52.2kg/hr. Additionally, to assess the impact of the discharged CaCO₃on the marine ecosystem, we conducted "marine ecotoxicity test" and performed Computational Fluid Dynamics (CFD) analysis to evaluate the dispersion and dilution of the discharged effluent.

• The Journal of Engineering Geology
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• v.34 no.3
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• pp.473-496
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• 2024

This study reviewed image analysis techniques used in non-destructive investigations of solute transport mechanisms in porous media during contaminant transport. Commonly employed image analysis methods include X-ray imaging, light-transmission visualization, and light-reflection visualization using ultraviolet or visible light. These techniques provide precise, high-resolution data on solute concentration distributions, fluid flow dynamics, and multiphase systems. Through continuous monitoring without alteration of the experimental setup, they provide accurate insights into solute transport mechanisms. We outline the principles, applications, advantages, and limitations of each method, and explore their contribution to the understanding and prediction of solute transport. We also examine case studies in which these methods have been effectively applied. This review provides a comprehensive understanding of how image analysis techniques can contribute to addressing environmental issues such as groundwater contamination.

• Journal of Yeungnam Medical Science
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• v.14 no.1
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• pp.168-174
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• 1997

Alphafetoprotein(AFP) is a glycoprotein synthesized by the fetus early in gestation by the yolk sac and later by the gastrointestinal tract and liver. The concentration of AFP is highest in fetal serum and amniotic fluid around 13th week, and 32nd week in maternal serum. Some conditions are associated with abnormal maternal serum AFP concentration. For examples, neural tube defects, omphalocele, renal anomalies are associated with elevated maternal serum AFP and fetal death, chromosomal trisomies are associated with low level of maternal serum AFP. So maternal serum AFP screening plays a significant role in assessing candidates for prenatal diagnosis and prenatal counselling in pregnant women. This study evaluates the normal ranges of AFP using enzyme immunoassay in normal pregnant women. We studied 500 normal pregnant women who visited the Department of Obstetrics & Gynecology, Yeungnam Medical Center, Yeungnam University during the period through January, 1993 to September, 1996. The group of the study were selected randomly at various gestational ages from 8 to 41 weeks. The results were summarized as follows: 1. The lowest level of AFP in our study group was 2.1ng/ml at 8 weeks of gestation. Thereafter serum alpha-fetoprotein concentrations rose rapidly to reach a peak value at 32nd week. 2. The mean levels of AFP in the primipara and multipara were $166.37{\pm}12.06ng/ml$, and $223.78{\pm}14.00ng/ml$, respectively, showing stastiscally significant difference between these two groups(p<0.01). 3. The mean levels of AFP between mothers who delivered male and female babies were $192.96{\pm}13.00ng/ml$, and $194.29{\pm}13.84ng/ml$, respectively, without statistically significant difference(p>0.05). 4. The normal ranges of maternal serum AFP according to each gestational week were evaluated.

• Journal of Animal Science and Technology
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• v.51 no.1
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• pp.45-52
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• 2009

This experiment was conducted to observe the effects of anaerobic cellulolytic bacteria culture (Ruminococcus flavefaciens H-20 and Fibrobactor succinogenes H-23) on in vivo ruminal fermentation characteristics in Hanwoo heifers. Four ruminally cannulated Hanwoo heifers ($221\pm7.5kg$) receiving a basal diet containing 3 kg of mixture hay (tall fescue and ochardgrass) and 2 kg of concentrate per day were in a $4\times4$ Latin square with 21-day periods. Treatments were the basal diet without the culture additive (control), the basal diet plus 50 ml/day of bacteria culture of H-20 and H-23 (1%), 150 ml/day of H-20 and H-23 (3%), and 250 ml/day of H-20 and H-23 (5%). In the whole experimental periods, ruminal pH did not differ between treatments. However, the concentration of ruminal ammonia-N was increased in the 3% treatment relative to control and the 1% treatment at 1 hr post-feeding (p<0.05). Avicelase and CMCase (carboxymethyl cellulase) activities in rumen fluid showed no significant difference among treatments. However, xylanase activity was higher in the 5% (119.49, xylose ${\mu}mol$/ml/min) than the 3% treatment (71.02, xylose ${\mu}mol$/ml/min) at 0 hr post-feeding (p<0.05). Concentrations of ruminal total VFA, acetate, propionate and valerate were unaffected by treatments, while butyrate was higher in the 3% treatment (24.48 mM) than control (15.71 mM) at 1 hr post-feeding (p<0.05). Results indicate that minimum 3% inclusion of cellulolytic bacteria cultures improved ruminal fermentation, especially ammonia-N concentration and butyric acid production.

• Journal of Embryo Transfer
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• v.16 no.3
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• pp.203-211
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• 2001

This study was carried out to determine sex of porcine embryos produced by in vitro fertilization. Porcine oocyte-cumulus complexes were cultured in BSA-free North Carolina State University (NCSU) 23 medium containing porcine follicular fluid (10%), cystein (0.1 mg/ml) and hormonal supplement (10 IU eCG and 10 IU hCG per ml) for 20~22 hrs. They were then cultured in the same medium but without hormonal supplement for additional 20~22 hrs. After culture, cumulus cells were removed and oocytes were co-incubated for 6 hrs with four different concentrations (5$\times$10$^4$, 2.5$\times$ 10$^{5}$ , 5.0$\times$10$^{5}$ and l0$\times$10$^{5}$ ) of porcine sperm. After fertilization, oocytes were transferred into NCSU 23 with 0.4% BSA medium. The cleavage and blastocyst formation rates were evaluated at 48 and 144 hrs, respectively. In this study, the polymerase chain reaction (PCR) was used to determine the sex of porcine embryos in the stage of blastocyst. The PCR was performed using a set of oligonucleotide primers (5‘-TCATGGACCAGGTAGGGAAT-3', 5’-GAAAGACACGTCCTTGGA GA-3') for 491 bp fragment of porcine male-specific DNA sequence. In the flour different sperm concentration (5$\times$10$^4$, 2.5$\times$10$^{5}$ , 5.0$\times$10$^{5}$ and l0$\times$10$^{5}$ ) for fertilization condition, the cleavage rate was 55.95, 67.88, 60.18 and 47.60%, respectivety, and the development rate of blastocysts was 16.03, 20.40, 21.41 and 12.37%, respectively. At 5.0$\times$10$^4$and 2.5$\times$10$^{5}$ of sperm concentrations per ml cleavage rate and development rate of blastocyst were higher than those of 5.0$\times$10$^4$and l0$\times$10$^{5}$ of sperm concentration (P<0.01). The male of porcine embryos was detected at 491 bp by PCR, and 18 of the 31 porcine blastocysts were the male (58.1%) and the rest 13 were the female(41.9%).

• The Korean Journal of Physiology
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• v.9 no.1
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• pp.13-22
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• 1975

From the study of movements of $Ca^{++}$ in frog cardiac muscle, Niedergerke (1963) postulated that $Ca^{++}$ necessary for the cardiac contraction is stored in a specific pool. Langer et al (1967) and DeCaro (1967) also found a close relationship between the change of $Ca^{++}$ flux kinetics and the change of contractile force. According to the studies of several investigators, Ca II (Bailey and Dressel 1968) or phase I and II (Langer 1965, Langer et al 1967, 1971) in the $Ca^{++}$ washout curve was associated with cardiac contractility. This investigation was aimed to elucidate the anatomical region of the contractile active $Ca^{++}$ pool. At the same time, it was assumed in this study that $Ca^{++}$ in the sarcoplasmic reticulumn represents one of the major intracellular $Ca^{++}$ pool and cardiac contractility was also dependent on the intracellular $Ca^{++}$ concentration. Consequently, this experiment was performed at different temperatures to activate to activate inhibit the deactivating process of activated $Ca^{++}$ in the intracellular space to see if changes in the contractility decay curve existed at different temperatures. The isolated hearts of rabbits and turtles (Amyda maackii) were attached to the perfusion apparatus according to the method employed by Bailey and Dressel (1968). The isolated hearts were initally perfused with a full Ringer solution containing 2 mg/ml of inulin for 1 hr, and then $Ca^{++}$ and inulin-free Ringer solution was perfused while the isometric tension was recorded and a serial sample of perfusion fluid dripping from the cardiac apex was collected for 10 sec throughout experimental period. The above procedure was performed at $23^{\circ}C$, $30^{\circ}C$ and $38^{\circ}C$ on the rabbit heart and $10{\sim}13^{\circ}C$, $10^{\circ}C$, $25^{\circ}C$, $30^{\circ}C$ and $35^{\circ}C$ on the turtle heart. After determination of $Ca^{++}$ and inulin concentration of the samples, the $Ca^{++}$, inulin washout curve and the contractile tensin decay curve were analysed according to the method of Riggs (1963). The results were summarized as follows; 1. In the rabbit heart, there are 2 inulin compartments, 3 $Ca^{++}$ compartments and sing1e exponential decay of contractile tension. In the turtle heart, there are $1{\sim}2$ inulin compartments, $1{\sim}2$ $Ca^{++}$ compartments and $1{\sim}2$ phases of contractile tension decay. The fact that the inulin space was divided into 3 compartments in the washout curve in these hearts indicates the presence of heterogeneity in cardiac perfusion, i.e., overfused and underperfused area. 2. Ca I a9d Ca II in these hearts were found to have $Ca^{++}$ in the ECF compartments because their half times in the washout curves were far smaller than those of the inulin washout curves in the rabbit heart and similar to those of the inulin washout curves in the turtle heart. Ca III in the rabbit heart may have originated from the intracellular $Ca^{++}$ store. But no Ca III in the turtle heart was found. This may be due to the fact that the iutracellular $Ca^{++}$ pool in the turtle heart was too small to detect using this experimental procedure since sarcoplasmic reticulumn in the turtle heart is poorly developed. 3. In the rabbit heart, there were no chages in the half time of Ca I, Ca II, inulin I and inulin II at different temperatures, but the half time of Ca III was significantly prolonged at lower temperatures, and the half time of the contractile tension decay tended to be prolonged at lower temperatures but this was not significant. In the turtle heart, there were no changes in the half time of Ca I, Ca II, inulin 1, inulin II and phase I of the contractile tension decay at different temperatures, but the half time of phase II of the contractile tension decay was significantly prolonged at lower temperatures. This finding indicates that intracellu!ar $Ca^{++}$ in these hearts was also responsible particulary for maintaining the cardiac contractility at the lower temperatures. 4. The half times of contractile tension decay were shorter than those of Ca II in the $Ca^{++}$ washout curves in both animal hearts. According to the above results it was shown that $Ca^{++}$ in ECF is primarily and $Ca^{++}$ in the intracellular space is partially associated with the cardic contractility.

• Journal of Oral Medicine and Pain
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• v.32 no.4
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• pp.365-373
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• 2007

Destruction of oral soft and hard tissues and resulting problems seriously affect the life quality of xerostomic patients. Although artificial saliva is the only regimen for xerostomic patients with totally abolished salivary glands, currently available artificial salivas give restricted satisfaction to patients. The purpose of this study was to contribute to the development of ideal artificial saliva through comparing viscosity and wettability between CMC solutions and human saliva. Commercially-available CMC is dissolved in simulated salivary buffer (SSB) and distilled deionized water (DDW). Various properties of human whole saliva, human glandular saliva, and a CMC-based saliva substitutes known as Salivart and Moi-Stir were compared with those of CMC solutions. Viscosity was measured with a cone-and-plate digital viscometer at six different shear rates, while wettability on acrylic resin and Co-Cr alloy was determined by the contact angle. The obtained results were as follows: 1. The viscosity of CMC solutions was proportional to CMC concentration, with 0.5% CMC solution displaying similar viscosity to stimulated whole saliva. Where as a decrease in contact angle was found with increasing CMC concentration. 2. The viscosity of human saliva was found to be inversely proportional to shear rate, a non-Newtonian (pseudoplastic) trait of biological fluids. The mean viscosity values at various shear rates increased as follows: stimulated parotid saliva, stimulated whole saliva, unstimulated whole saliva, stimulated submandibular-sublingual saliva. 3. Contact angles of human saliva on the tested solid phases were inversely correlated with viscosity, namely decreasing in the order stimulated parotid saliva, stimulated whole saliva, unstimulated whole saliva, stimulated submandibular-sublingual saliva. 4. Boiled CMC dissolved in SSB (CMC-SSB) had a lower viscosity than CMC-SSB (P < 0.01 at shear rate of $90s^{-1}$). 5. For human saliva, contact angles on acrylic resin were significantly lower than those on Co-Cr alloy (P < 0.01). 6. Comparing CMC solutions with human saliva, the contact angles between acrylic resin and human saliva solutions were significantly lower than those between acrylic resin and CMC solutions, including Salivart and Moi-Stir (P <0.01). The effectiveness of CMC solutions in terms of their rheological properties was objectively confirmed, indicating a vital role for CMC in the development of effective salivary substitutes.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.165-174
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• 2010

The numerical modeling of a coal gasification reaction occurring in an entrained flow coal gasifier is presented in this study. The purposes of this study are to develop a reliable evaluation method of coal gasifier not only for the basic design but also further system operation optimization using a CFD(Computational Fluid Dynamics) method. The coal gasification reaction consists of a series of reaction processes such as water evaporation, coal devolatilization, heterogeneous char reactions, and coal-off gaseous reaction in two-phase, turbulent and radiation participating media. Both numerical and experimental studies are made for the 1.0 ton/day entrained flow coal gasifier installed in the Korea Institute of Energy Research (KIER). The comprehensive computer program in this study is made basically using commercial CFD program by implementing several subroutines necessary for gasification process, which include Eddy-Breakup model together with the harmonic mean approach for turbulent reaction. Further Lagrangian approach in particle trajectory is adopted with the consideration of turbulent effect caused by the non-linearity of drag force, etc. The program developed is successfully evaluated against experimental data such as profiles of temperature and gaseous species concentration together with the cold gas efficiency. Further intensive investigation has been made in terms of the size distribution of pulverized coal particle, the slurry concentration, and the design parameters of gasifier. These parameters considered in this study are compared and evaluated each other through the calculated syngas production rate and cold gas efficiency, appearing to directly affect gasification performance. Considering the complexity of entrained coal gasification, even if the results of this study looks physically reasonable and consistent in parametric study, more efforts of elaborating modeling together with the systematic evaluation against experimental data are necessary for the development of an reliable design tool using CFD method.