• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.91-93
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• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.

• Journal of the Korean Institute of Gas
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• v.16 no.2
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• pp.18-24
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• 2012

This research seeks to evaluate damage on type II gas cylinder by an acoustic emission test when executing 20000 cycles fatigue test and thereafter burst test. Used gas cylinders in the experimental are three types as follows; one is sound cylinder, others are cylinders which contain longitudinal and transverse artificial defect. The size of artificial defect is a depth of 3 mm, width of 3 mm and length of 50 mm. In the case of the cylinder which artificial defect, unlike the expectation that it will burst in low pressure, the burst pressure of the cylinder did not differ much according to whether or not there were defects. However, when there was longitudinal defect, the location of burst was near the location of defect. This leads to the effect in which the thickness of the composite material becomes thinner according to the length of the longitudinal defect and this is judged to have an effect on the location of initiation and growth of crack in the liner. Also, for the acoustic emission signal, when there is longitudinal defect, the ratio of an event occurring at defect position among overall hits is more than 50 %, and the source location also accords very precisely with defect position.

• Genomics & Informatics
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• v.21 no.3
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• pp.33.1-33.11
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• 2023

Type 2 diabetes mellitus (T2DM) is a multifactorial, polygenic, and metabolically complicated disease. A large number of genes are responsible for the biogenesis of T2DM and calpain10 (CAPN10) is one of them. The association of numerous CAPN10 genetic polymorphisms in the development of T2DM has been widely studied in different populations and noticed inconclusive results. The present study is an attempt to evaluate the plausible association of CAPN10 polymorphism SNP-19 (rs3842570) with T2DM and T2DM-related anthropometric and metabolic traits in the Noakhali region of Bangladesh. This case-control study included 202 T2DM patients and 75 healthy individuals from different places in Noakhali. A significant association (p < 0.05) of SNP-19 with T2DM in co-dominant 2R/3R vs. 3R/3R (odds ratio [OR], 2.7; p=0.0014) and dominant (2R/3R) + (2R/2R) vs. 3R/3R (OR, 2.47; p=0.0011) genetic models was observed. High-risk allele 2R also showed a significant association with T2DM in the allelic model (OR, 1.67; p=0.0109). The genotypic frequency of SNP-19 variants showed consistency with Hardy-Weinberg equilibrium (p > 0.05). Additionally, SNP-19 genetic variants showed potential associations with the anthropometric and metabolic traits of T2DM patients in terms of body mass index, systolic blood pressure, diastolic blood pressure, total cholesterol, and triglycerides. Our approach identifies the 2R/3R genotype of SNP-19 as a significant risk factor for biogenesis of T2DM in the Noakhali population. Furthermore, a large-scale study could be instrumental to correlate this finding in overall Bangladeshi population.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.523-530
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• 1999

Acrylic pressure-sensitive adhesive has been made utilizing organic solvents, but nowadays it is made by solvent-free system due to environmental problems. In this study, emulsion polymerization were carried out at $40^{\circ}C$ with methacrylic acid(MAA), n-butyl acrylate(n-BA) and 2-ethylhexyl acrylate(2-EHA) as monomers in the presence of anionic(sodium dodecyl sulfate, SDS) and nonionic(ethylene oxide types) surfactant mixtures. The overall conversion of the polymerization reaction in a mixed surfactant system was found to be higher than that in a single surfactant system. Emulsion stability in mixed or anionic surfactant systems was found to be over 12 week, which was better than that in nonionic surfactant system. Emulsion particle size decreased as surfactant content increased. The Tg and molecular weight of emulsion polymer were inependent of the type, the amount and the mixing ratio of surfactant. Based on the results of stability and peel strength, the optimum nonionic surfactant ratio in total 4 g of surfactant mixture systems is found to be 40~60% by weight where the nonionic surfactant has 50 ethylene oxide groups and 16~18 carbon atoms in hydrophobic alkyl chain.

• Korean Journal of Community Nutrition
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• v.28 no.1
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• pp.48-60
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• 2023

Objectives: The purpose of this study was to compare the sex-associated differences in the dietary intake of gastric cancer patients in Korea. Methods: Data from the Korea National Health and Nutrition Examination Survey (KNHANES) the 7^th (2016-2018) were analyzed in the present study. The subjects included 122 gastric cancer patients aged over 40 years (75 male, 47 female). General characteristics (age, marital status, household income, education, food security, comorbidities, alcohol drinking, and smoking), anthropometric characteristics (height, weight, body mass index, and blood pressure), blood biochemical characteristics [fasting plasma glucose (FPG), blood urea nitrogen (BUN), creatinine, triglyceride, total cholesterol, and HDL-cholesterol)], and quantity and quality of dietary intake were compared between male and female participants. Results: Males had higher rates of having a spouse, prevalence of hypertension, alcohol drinking, and smoking than females. The proportion of males with a normal range of FPG, BUN, and HDL-cholesterol was lower than that in females. The total cholesterol levels above the normal range were higher in females than in males. We also found that females had a higher percentage of intakes below the estimated energy requirement (EER) and intakes below the estimated average requirement (EAR) for carbohydrates, niacin, phosphorus, and iron than males. The index of nutritional quality (INQ) for phosphorus and folate, nutrient adequacy ratio (NAR) for vitamin C, thiamine, niacin, folate, calcium, and phosphorus, and the mean adequacy ratio (MAR) were lower in females than males. Conclusions: In Korean gastric cancer patients, management of comorbidities such as diabetes and hypertriglyceridemia, lowering FPG, and raising HDL-cholesterol level management is required for males, whereas management of lowering total cholesterol and raising hematocrit is required for females. The quantitative and qualitative nutritional intakes were poor in gastric cancer patients, especially in females, who had a lower nutritional intake than males. We suggest that nutritional interventions are needed to improve the overall nutritional intake in both male and female gastric cancer patients. In particular, we propose that support is urgently needed for females whose nutritional intake is lower than that of males. In addition, family, social, and national support for nutritional management of female gastric cancer patients is highly necessary.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5159-5168
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• 2014

The study examined the relationship among metal health, metabolic syndrome and nutrient acceptance according to gender. Implemented until 2010-2012, the 5th Korean National Health and Nutrition Examination Survey, as an original document, was used for the study. The target was problem drinkers with more than 12 points under AUDIT. Regarding mental health, it was classified into stress, depression and suicidal impulse. Metabolic syndrome was defined when three causes of BMI, waist circumference, FBS, HDL and BP were out of the normal range. The nutrient intake was obtained to confirm the energy intake of nine non-nutrients (Nutrient adequacy ratio: NAR) and the proper intake of the average non-nutrient (Mean adequacy ratio: MAR). These variables were analyzed by frequency, cross analysis and multiple regression analysis through SPSS18.0. In the general features, there was a significant difference according to age, occupation and marital status. In mental health, stress, depression and suicidal impulse were examined. Metabolic syndrome was dependant on FBS, HDL and BP. The nutrient acceptance depended on calcium, vitamin A, thiamine, riboflavin, niacin, vitamin C, and MAR. Logistic regression analysis performed on the variables showed significant differences. Stress, depression, and thoughts of suicide was significantly higher in men aged 19-29 years, and women aged 30-49 years. In the case of the male, those who employed have metabolic syndrome more than those who unemployed. In terms of female, those who were belonged into the middle - low economic level have undergone with metabolic syndrome. In the part of a Mean adequacy ratio(MAR), the male who unmarried, employed, were in the middle low economic levelwere higher. In the case of the female, it was higher for those who were in the middle - low economic level. Overall, an effective way of planning the solution regarding mental health, metabolic syndrome and nutrient intake can be found by considering these features.

• Journal of Chest Surgery
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• v.51 no.2
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• pp.100-108
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• 2018

Background: The question of which type of prosthetic aortic valve leads to the best outcomes in patients in their 60s remains controversial. We examined the hemodynamic and clinical outcomes of aortic valve replacement in sexagenarians according to the type of prosthesis. Methods: We retrospectively reviewed 270 patients in their 60s who underwent first-time aortic valve replacement from 1995 to 2011. Early and late mortality, major adverse valve-related events, anticoagulation-related events, and hemodynamic outcomes were assessed. The mean follow-up duration was $58.7{\pm}44.0$ months. Results: Of the 270 patients, 93 had a mechanical prosthesis (mechanical group), and 177 had a bioprosthesis (tissue group). The tissue group had a higher mean age and prevalence of preoperative stroke than the mechanical group. The groups had no differences in the aortic valve mean pressure gradient (AVMPG) or the left ventricular mass index (LVMI) at 5 years after surgery. In a sub-analysis limited to prostheses in the supra-annular position, the AVMPG was higher in the tissue group, but the LVMI was still not significantly different. There was no early mortality. The 10-year survival rate was 83% in the mechanical group and 90% in the tissue group. The type of aortic prosthesis did not influence overall mortality, cardiac mortality, or major adverse valve-related events. Anticoagulation-related events were more common in the mechanical group than in the tissue group (p=0.034; hazard ratio, 4.100; 95% confidence interval, 1.111-15.132). Conclusion: The type of aortic prosthesis was not associated with hemodynamic or clinical outcomes, except for anticoagulation-related events.

• The Korean Journal of Nuclear Medicine
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• v.26 no.1
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• pp.72-81
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• 1992

Pharmacologic coronary vasodilation in conjunction with myocardial scintigraphy has become an accepted alternative to dynamic exercise testing for the diagnosis of coronary artery disease. Although dipyridamole has traditionally been used for this purpose, it causes frequent side effect, which at times can be life-threatening. Moreover, dipyridamole dose not elicit maximal coronary vasodilation in a substantial number of patients receiving the usual i.v. dose. Adenosine is an endogenously produced compound that has significant effects as a coronary vasodilator and rapid onset action and extremely short half-life (< 10 seconds). The diagnostic accuracy and safety profile of adenosine $^{99m}Tc-MIBI$ myocardial scintigraphy were evaluated and comparison with exercise $^{99m}Tc-MIBI$ was performed. Twenty-eight subjects underwent $^{99m}Tc-MIBI$ imaging after adenosine infusion and exercise $^{99m}Tc-MIBI$ imaging. Adenosine was infused intravenously at a dose of 0.14mg/kg/body weight per minute for 6 min and MIBI was injected at 3 minute. Adenosine caused an incerease in heart rate ($64{\pm}12$ at baseline versus $74{\pm}16$ beats/min at peak effect, p<0.001), a mild decrease in systolic and diastolic blood pressure and a slightly increase in PR interval(p; NS). Side effects were reported in 92% of patients and were mostly mild in nature and promptly resolved within 1 or 2 minutes of termination of adenosine infusion. Facial flushing (53%), chest pain (36%), mild dyspnea (39%), headache (21%), throat discomfort (21%) were frequent symptoms. ST segment depression (> 1 mm) and second degree AV block in electrocardiography occured in 11% of the patients, respectively. The overall sensitivity and specificity for individual coronary stenoses in 16 patients underwent coronary angiography were 88% and 95%, respectively. The agreement ratio of segmental perfusion between adenosine and exercise images was 92% (Kappa index=0.82). In conclusion, $^{99m}Tc-MIBI$ myocardial perfusion scintigraphy with intravenous adenosine is a feasible, safe and highly accurate noninvasive technique for the detection of coronary artery disease and results are at least comparable with those of exercise $^{99m}Tc-MIBI$ scintigraphy.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.780-787
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• 2019

As a carbon-free, green growth alternative, internal and external interest in hydrogen energy and technology is growing. Hydrogen was added to co-axial methane, methane-propane, and methane-propane-ethane diffusion flames, which are the main ingredients of LNG, to evaluate its effect on flame formation and combustion products. The variation in combustion products produced by adding hydrogen gradually to diffusion pyrolysis at room temperature and normal pressure conditions was observed experimentally by using a gas analyzer, and the shape of diffusion pyrolysis was observed step by step using a digital camera. The experimental results showed that the production volume of nitrogen oxides tended to increase and became close to linear as hydrogen was added to the diffusion pyrotechnic. This is because the relatively high temperature of heat insulation and fast combustion speed of hydrogen facilitated the production of thermal NOx. On the other hand, CO2 production tended to decrease as hydrogen was added to reduce the overall carbon ratio contained in the mixed diffusion flame of methane, methane-propane, and methane-ethane-propane. This means that the mixed fuel use of LNG-hydrogen in ships may potentially reduce emissions of CO2, a greenhouse gas.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.3
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• pp.207-214
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• 2012

This study was conducted to optimize the processing conditions, including the ingredient ratio and extraction time, for a water-soluble fraction of Alaska pollock head and non-forming sea tangle by response surface methodology. Our results indicated that the optimal independent variables for obtaining extracts with a high yield and desirable sensory characteristics were 1.32 for $X_1$ (extraction time), 1.36 for $X_2$ (sea tangle concentration) and 0.93 for $X_3$ (water volume) in coded values, and 5.48 h for $X_1$, 18.18% for $X_2$ and 6.86 times for $X_3$ in uncoded values. The predicted values of $Y_1$ (yield), $Y_2$ (TCA soluble-N) and $Y_3$ (overall acceptance) for extracts produced under these optimized conditions were 22.10%, 1.83 g/100 mL and 5.9, respectively, their experimental values were 21.4%, 1.7 g/100 mL and 5.7, respectively. No significant differences between the actual and predicted values were found.