• Journal of computational fluids engineering
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• v.4 no.3
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• pp.21-27
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• 1999

In this paper, tile characteristics of flow resulting from the configurations of piston head and intake-port of the cylinder in a gasoline-direct-injection engine are investigated numerically. Calculations are carried out from intake process to the end of compression. GTT code which includes the third order upwind Chakravarthy-Osher TVD scheme and κ-ε turbulence model with the law of wall as a boundary condition. As a result, a piston head with a smaller radius of curvature and larger radius gives stronger reverse tumble. It is also shown that as the maximum tumble ratio increases by the configuration of the intake-port the tumble ratio at the end of compression stroke increases. It is concluded that flows at the end of compression stroke can be controlled by the optimum design of intake-port and piston head.

• Journal of computational fluids engineering
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• v.5 no.3
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• pp.1-7
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• 2000

In high-pressure diesel engine, the injected fuel spray impinges on the piston cavity surface due to the short distance between the injection nozzle and the cavity wall. The behavior of the impinging spray has the great influence on the dispersion of fuel, the evaporation, and the mixture formation process. In this study, the numerical simulation using the GTT code was performed to study the gas flows, the spray behaviors, and the fuel vapor distributions in the combustion of a D.I engine for variation of spray angle and swirl ratio.

• Journal of computational fluids engineering
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• v.5 no.1
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• pp.8-13
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• 2000

In this study, the spray models incorporated into the GTT code were tested for sprays injected in quiescent swirling gases and for the sprays impinging on a flat wall, and the validity of the models has been confirmed by comparing the calculated results with the experimental data. Using this code, the gas flow, spray behavior and fuel vapor distributions in the combustion chamber of a D.I engine have been numerically analyzed with respect to the constant injection pressure and the injection pressure varying with injection time.

• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.557-563
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• 2002

In this paper, the characteristics of flow and spray motions affected by from piston head configurations were investigated numerically. Calculations were carried out from intake process to the end of compression. GTT (Generalized Tank and Tube method) code, which includes a third order upwind Chakravarthy-Osher TVD scheme and k-$\varepsilon$ turbulence model with fuel spray analysis was used for the calculations. As a results, piston heads with smaller radii of curvature were found to give stronger reverse tumble than those with larger radii of curvature. Similar results are shown in the convection and diffusion of fuel sprays.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.18-27
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• 2000

The spray models incorporated into the GTT code were tested for free spray, spray in swirling flows and the sprays impinging on a flat wall. And the validity of the models has been confirmed by comparing the calculated results with the experimental data. Using this code, the spray behavior in the diesel combustion chamber have been numerically analyzed for variation of nozzle diameter. Also, the effects of nozzle diameter in diesel combustion was investigated experimentally by measuring the performance in a D.I engine. This study provides the information for the spray characteristics and emissions with variation of nozzle diameter. As a result, it has shown that decreasing nozzle diameter resulted in improving smoke and specific fuel consumption in a middle speed range.

• Korean Journal of Veterinary Service
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• v.33 no.2
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• pp.199-206
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• 2010

To evaluate the hypoglycemic effect of nano powder propolis, streptozotocin (STZ) induced diabetic rats were divided into 2 groups : diabetic control group and nano powder propolis (0.9ml) group. Then the rats were fed with nano-powder-propolis for 4 weeks. After 4 weeks, oral glucose tolerance test (oral GTT) was performed and blood sugar levels after 16 hours fasting, body weights, and blood lipid levels were measured. Finally, pancreas were collected and examined by histopathology and immunohistochemistry. In conclusion, the nano-powder-propolis was effective in the treatment of diabetes due to the reduction of blood sugar level and the regeneration of damaged ${\beta}$-cells observed in streptozotocin-induced diabetic rats.

• Korean Journal of Veterinary Research
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• v.48 no.3
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• pp.327-336
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• 2008

Many herbal extracts have been reported to have a preventive or therapeutic effect of on diabetes mellitus. Momordica Charantia commonly known as bitter melon or karela has been reported to be a medicinal plant for treating various diseases including cancers and diabetes. The objectives of this study were to investigate anti-diabetic effects of bitter melon (BM) as determined by blood glucose levels, glucose tolerance test (GTT), insulin tolerance test (ITT), insulin and HbA1C activities in serum, serum biochemical and lipid levels, histopathology, immunohistochemistry and AMPK-${\alpha}2$ expression of skeletal muscle in male C57BL/6J db/db mice. There were four experimental groups including vehicle control, BM 10 mg/kg, BM 50 mg/kg, and BM 250 mg/kg. BM at doses of 10, 50, and 250 mg/kg was orally administered to the diabetic mice everyday for 8 weeks. The treatments of BM 10, 50, and 250 mg/kg significantly decreased the blood glucose level in the diabetic mice compared with vehicle control (p < 0.05). The treatments of BM 10 and 50 mg/kg significantly decreased the GTT, ITT and HbA1c levels in the diabetic mice compared with vehicle control (p < 0.05). All BM groups significantly decreased GOT, GPT, BUN, LDL and glucose levels in the diabetic mice compared with the vehicle control mice (p < 0.05). The livers of mice treated with the BM 10, 50, and 250 mg/kg showed a remarkable decrease in the number of lipid droplets compared with the vehicle control. The pancreas of mice treated with the BM 10, 50, and 250 mg/kg showed a remarkable increase in insulin concentration of ${\beta}$-cells compared with the vehicle control. In addition, the treatments of BM 10, 50, and 250 mg/kg actually increased the expression of AMPK-${\alpha}2$ compared with vehicle control. These results suggest that BM has a respectable anti-diabetic effect resulting from inhibition of blood glucose level and lipid level in serum and that consumption of BM may give a benefit for controlling diabetes mellitus in humans.

• Korean Journal of Veterinary Research
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• v.50 no.2
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• pp.105-111
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• 2010

Carnosine is a dipeptide $(\beta-alanyl-L-histidine)$ found in mammalian brain, eye, olfactory bulb and skeletal muscle at high concentrations. Its biological functions include antioxidant and anti-glycation activities. The objectives of this study were to investigate anti-diabetic effects of carnosine as determined by blood glucose levels, glucose tolerance test (GTT), glycosylated hemoglobin, and serum biochemical and lipid levels in streptozotocin-induced diabetic mice. There were five experimental groups including normal (ICR mice), control (saline), and three groups of carnosine at doses of 6, 30, and 150 mg/kg b.w.. Carnosine was orally administered to the diabetic mice everyday for 12 weeks. There was no significant difference in body weight changes in carnosine-treated groups compared to the control. The treatments of carnosine at the dose of 6 mg/kg significantly decreased the blood glucose level compared with the control at 2 and 4 weeks. The treatments of carnosine at the doses of 6 and 30 mg/kg significantly decreased the blood glucose levels in GTT and glycosylated hemoglobin compared with the control. Carnosine significantly increased total proteins compared with the control. Carnosine at the dose of 6 mg/kg significantly decreased total cholesterol and triglyceride in the serum compared to the control. These results suggest that carnosine at a low level has a hypoglycermic effect resulting from reduction of blood glucose and that a carnosine-containing diet or drug may give a benefit for controlling diabetes mellitus in humans.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1295-1303
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• 1997

This study determined the effects of addtition of chicory extract on the rate of starch hydrolysis in vitro and blood glucose response in healthy subjects. The rate of corn starch hydrolysis in the presence or absence of chicory extract was determined in an in vitro enzyme/dialysis system for 2hr. Additions of dried or roasted chicory extract (5%, w/w) to corn starch solution reduced the starch hydrolysis and significantly (p<0.05) decreased the area under hydrolysis curve by 16% and 18%, respectively. Groups of five to nine volunteers underwent 60 g glucose tolerance tests (GTT) with 2.5, 5, 10, 20% (w/w) dried or roasted chicory extracts. The addition of chicory extracts significantly (p<0.05) reduced blood glucose concentration during the GTT and reduced the mean peak rise and area under blood glucose curve. The glycemic indices of all dried chicory extract, $5{\sim}20%$ roasted chicory extract groups were significantly decreased compared with glucose control. Chicory extract is therefore likely to be useful in modifying postprandial hyperglycemia.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.125-134
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• 2003

The present paper is concerned to the thermal analysis during the cool-down period of 138,000 m$^3$class GTT MARK-III membrane type LNG carrier servicing with LNG from the Middle East to Korea. It is the cool-down period that cools the insulation wall and the gas in LNG tank to avoid the thermal shock as the start of loading of -162$^{\circ}C$ LNG. For six hours of the standard cool-down period, the temperature of NG falls down from -4$0^{\circ}C$ to -13$0^{\circ}C$ and especially the mean temperature of the 1st barrier in the top side insulation wall falls down from -38.38$^{\circ}C$ to -122.42$^{\circ}C$ in case of IMO design condition. By the 3-D numerical calculation about the cargo tank and the cofferdam, the temperature variation in hulls and insulations is precisely predicted in this paper. And the mean temperature variation of gas is calculated as the function of the spraying rate by the heat balance model during the cool-down period.