• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.4
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• pp.423-429
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• 2009

This study was conducted to investigate the effects of pine (Pinus densiflora) needle extracts on hepatic antioxidative system in rats fed high-cholesterol diet. Eight-week old Sprague Dawley rats were divided into four groups; normal diet group (CON), 0.5% cholesterol diet group (0.5% CHOL), 0.5% cholesterol diet and pine needle extracts prepared by using hot water group (HOT water), and 0.5% cholesterol diet and pine needle extracts prepared by using sub-supercritical $CO_2$ group (Sub-supercritical). The serum ALP, AST, and ALT activities were increased by 0.5% cholesterol diet supplementation, but treatment with pine needle extracts showed decrease compared with 0.5% CHOL group. The SOD activity in liver at 0.5% cholesterol diet group was more decreased than control group while Sub-supercritical group had significantly higher SOD activity than 0.5% CHOL group. Moreover, groups with pine needle extracts supplementation had higher level of GPx in liver than 0.5% cholesterol diet group. These results suggest that pine needle extracts increased antioxidative activities.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.348-353
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• 2011

Characteristics of cryogenic single jet flow were investigated. Liquid nitrogen was injected into a high-pressure chamber and formed single jet. Ambient condition around jet was changed from subcritical to superctirical condition of nitrogen. Injector geometries also were changed. A shape of the jet and core diameter were measured by flow visualization technique, and core spreading angle was calculated. Flow instability was found at atmospheric pressure condition. As ambient pressure increased, core spreading angle was increased and maintained after certain pressure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.475-481
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• 2017

In this paper, high speed camera images were used to analyze the supercritical injection behavior of liquid hydrocarbon compounds used as main components of propellant fuel. Decane and Methylcyclohexane (MCH), which have different critical points among kerosene constituents, were selected as experimental fluid and Shadowgraphy technique was used for the analysis. The difference in the temperature variation from the initial injector state of the subcritical condition until the vaporization occurs was represented by the different behaviors of Decane and MCH. However, under the Supercritical conditions, the enthalpy of vaporization near the critical point approaches zero and the phase change to the Supercritical phase occurs instead of vaporization process. In the phase change of the Supercritical system, there was no rapid density change, so the liquid state image was observed in both the Decane and MCH.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.2
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• pp.163-168
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• 2015

In order to perform estimations with high reliability, it is necessary to deal with the tail part of the cumulative distribution function (CDF) in greater detail compared to an overall CDF. The use of a generalized Pareto distribution (GPD) to model the tail part of a CDF is receiving more research attention with the goal of performing estimations with high reliability. Current studies on GPDs focus on ways to determine the appropriate number of sample points and their parameters. However, even if a proper estimation is made, it can be inaccurate as a result of an incorrect threshold value. Therefore, in this paper, a GPD based on the Akaike information criterion (AIC) is proposed to improve the accuracy of the tail model. The proposed method determines an accurate threshold value using the AIC with the overall samples before estimating the GPD over the threshold. To validate the accuracy of the method, its reliability is compared with that obtained using a general GPD model with an empirical CDF.

• Journal of Life Science
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• v.19 no.4
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• pp.508-513
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• 2009

Pine needles have long been used as a traditional health-promoting medicinal food in Korea. To investigate the effects of pine (pinus densiflora) needle extracts on blood flow and serum lipid improvement were assessed in vivo. 8 week-old Sprague Dawley strain rats were divided into four groups of seven rats each; CON, 0.5% CHOL, HOT water and Sub-supercritical group. Serum total cholesterol and triglyceride contents were lower in the CON group than the 0.5% CHOL group. Three weeks of feeding hot water and sub-supercritical extract resulted in a decrease in serum triglyceride and total cholesterol level. The level of HDL-cholesterol in the 0.5% CHOL group was significantly (p<0.05) reduced compared to the CON group, but it had a tendency to increase with pine needle extract supplementation. Blood passage time of the pine needle extracts supplemented group was higher than the 0.5% CHOL group. Microscopic observation showed that whole blood passed smoothly through the micro channels in pine needle extracts supplemented groups. The platelet aggregation ability of the groups treated with pine needle extracts was less than that of the 0.5% CHOL group. All these results suggest that pine needle extracts might improve blood homeostasis mediated via antiplatelet activities.

• Atmosphere
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• v.28 no.3
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• pp.305-315
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• 2018

This study investigates the characteristic spatial patterns and dynamic processes associated with the summertime extreme temperature events in South Korea during the last 20 years (1995~2014) using Self-Organizing Map (SOM). The classified SOM patterns commonly have high temperature and anticyclonic circulation anomalies over South Korea. The two major teleconnection patterns are identified: one is from the subtropical western North Pacific (WNP) affecting to the north and the other is from the North Atlantic (NA) affecting downstream region. The meridional teleconnection pattern is related to the forcing of positive sea surface temperature (SST) anomaly over the WNP. The northward propagating Rossby wave generates the East Asia-Pacific (EAP) pattern to form an anticyclonic circulation anomaly over South Korea. On the other hand, NA SST anomalies generate an eastward Rossby wave train across the Eurasian continent, leading to the development of an anticyclonic circulation anomaly over South Korea. The EAP pattern occurs more frequently in July and August, whereas the midlatitude teleconnection pattern associated with NA SST anomalies develops more frequently in early summer (June).

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.28-33
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• 2005

A resource recovery technique using sub- and supercritical water hydrolysis was applied to recover amino aicds from waste fish entrails. The effect of reaction parameters such as temperature and time necessary for the control of reaction towards optimum yield of amino acids was investigated using semi-batch and batch reactors. Results showed a maximum yield of total amino acids (137 mg/g-dry entrails) from waste fish entrails at T=$250^{\circ}C$ (P=4 MPa) and reaction time of 60 min in a batch reactor. Under supercritical conditions (e.g., T=$400^{\circ}C$, P=45 MPa), the yield decreased due to rapid decomposition compared to production rate of amino acids. As a result, the low temperature and the short reaction time were needed to produce a maximum yield of amino acids.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.281-286
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• 2009

Bitumen extraction and sulfur removal from Athabasca oil sand were conducted using water in sub- and supercritical condition. Bitumen yield in micro reactor was investigated in the pressure range of 15~30 MPa, the temperature of 360 and $380^{\circ}C$ and water density $0.074{\sim}0.61g/cm^3$ for 0~120 min. Bitumen yield increased with reaction pressure irrespective of temperature and dramatically increased in especially supercritical region due to hydrogen formed from water gas shift reaction. Total amount of gas product decreased with reaction pressure but the portion of sulfur and hydrogen increased a little with increasing pressure to 25 and 30 MPa. It is seen that supercritical condition was favourable to the hydrogen formation and sulfur removal. Bitumen yield and sulfur removal from original oil sand reached a maximum 22% and 40% respectively in supercritical condition(the reaction time of 60 min at $380^{\circ}C$ and 25 or 30 MPa).

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.59-66
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• 2013

Spray characteristics of single round jet with liquid nitrogen and coaxial spray with liquid nitrogen and gaseous argon were observed. Shadowgraph method was used for spray visualization, and density gradient magnitude image was used to analyse the result. In subcritical condition, irregularity of the jet surface was harder in the coaxial spray. In supercritical condition, diffusion of nitrogen injected from shear coaxial injector was faster than single jet. Jet diameter was induced by averaging images, in supercritical condition, difference of diameter of coaxial jet was rapidly decreased than that of single jet.

• Food Engineering Progress
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• v.14 no.2
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• pp.166-172
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• 2010

The extraction of polyphenol and flavonoid from citrus peel was performed by the ethanol, sugar, hot water (80$^{\circ}C$), and subcritical water extraction methods. The maximum yields of total polyphenolic compounds (27.25${\pm}$1.33 mg QE/g DCP, QE and DCP indicate quercetin equivalent and dried citrus peel, respectively) and flavonoids (7.31${\pm}$0.41 mg QE/g DCP) were obtained by subcritical water extraction (SWE) with operating conditions of 190$^{\circ}C$, 1300 psi, and 10 min. The yields by SWE were over 7.2-, and 8.5-fold higher than those of total polyphenols (3.79${\pm}$0.73 mg QE/g DCP) and flavonoids (0.86${\pm}$0.27 mg QE/g DCP) obtained using the ethanol extraction, which showed the highest extraction efficiency among tested conventional methods, respectively. Antioxidant activities of extracts obtained by different methods showed no significant differences. However, the relative antioxidant yield per 1 g dried citrus peel by SWE (190$^{\circ}C$, 10 min) was over 9.5-fold higher than that by the ethanol extraction.