• Korean Journal of Medicinal Crop Science
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• v.17 no.6
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• pp.407-411
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• 2009

Hepatoprotective and antioxidant activities of Acer mono and A. okamotoanum were compared after being extracted by low temperature and high pressure (LTHP) at 20 MPa and $60^{\circ}C$ for 15 minutes. Extraction yield of both A. mono and A. okamotoanum was increased about 40~43% by this extraction process. On scavenging activities, the bark of A. okamotoanum from this extraction process showed the highest activity as about 97%. This value was higher than that from conventional water extraction and A. mono extracts. Both of A. mono and A. okamotoanum showed high ability on nitrite scavenging, but decreasing tendency according to increasing of pH. On SOD-like test, A. okamotoanum had the highest activity as 46.28% at $1.0\;mg/m{\ell}$ concentration. A. okamotoanum extracted by LTHP also showed the highest activity as 197.38% in adding $1.0\;mg/m{\ell}$ concentration. Generally, the extracts from low temperature and high pressure extraction process are higher hepatoprotective and antioxidant activities than that from conventional water extraction. It can conclude that the bark of A. okamotoanum has better biological activities than other parts of A. mono.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.25-34
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• 2008

In this paper, three-dimensional multiblade row unsteady Navier-Stokes simulations at a hot streak temperature ratio of 2.0 have been performed to reveal the effects of rotor tip clearance on the inlet hot streak migration characteristics in low pressure stage of a Vaneless Counter-Rotating Turbine. The hot streak is circular in shape with a diameter equal to 25% of the high pressure turbine stator span. The hot streak center is located at 50% of the span and the leading edge of the high pressure turbine stator. The tip clearance size studied in this paper is 2.0mm(2.59% high pressure turbine rotor height, and 2.09% low pressure turbine rotor height). The numerical results show that the hot streak is not mixed out by the time it reaches the exit of high pressure turbine rotor. The separation of colder and hotter fluid is observed at the inlet of low pressure turbine rotor. Most of hotter fluid migrates towards the rotor pressure surface, and only little hotter fluid migrates to the rotor suction surface when it convects into the low pressure turbine rotor. And the hotter fluid migrated to the tip region of the high pressure turbine rotor impinges on the leading edge of the low pressure turbine rotor after it goes through the high pressure turbine rotor. The migration of the hotter fluid directly results in very high heat load at the leading edge of the low pressure turbine rotor. The migration characteristics of the hot streak in the low pressure turbine rotor are dominated by the combined effects of secondary flow and leakage flow at the tip clearance. The leakage flow trends to drive the hotter fluid towards the blade tip on the pressure surface and to the hub on the suction surface, even partial hotter fluid near the pressure surface is also driven to the rotor suction surface through the tip clearance. Compared with the case without rotor tip clearance, the heat load of the low pressure turbine rotor is intensified due to the effects of the leakage flow. And the numerical results also indicate that the leakage flow effect trends to increase the low pressure turbine rotor outlet temperature at the tip region.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.763-767
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• 2010

High-pressure phase behavior for the binary mixture of 1-propanol with supercritical $CO_2$ has been measured by means of a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The equilibrium loci of the pressure - composition and pressure - temperature were obtained for the binary mixture of 1-propanol + $CO_2$ system at 305.15 K, 313.15 K, 323.15 K and 333.15 K, and from 2 MPa to 11 MPa. The critical temperature of the mixture increased with the temperature. The pressure-composition line for the binary mixture of $CO_2$-1-propanol system showed a typical type-II phase behavior. The experimental P-x envelopes were correlated by using the Peng-Robinson equation of state in a satisfactory manner to obtain the parameters with $k_{ij}=0.116$ and ${\eta}_{ij}=-0.065$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.396-399
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• 2015

We analyzed the correlation between breakdown voltage(BDV) of liquid nitrogen(LN2) and factors. The chosen factors affecting the breakdown are the diameter of electrode, gap length, temperature of LN2, and pressure of LN2. The BDV of LN2 was increased with increasing the diameter, the gap length and the pressure. And The BDV of LN2 was increased with decreasing the temperature. However, correlation coefficient was different from each other depending on the situation. The BDV exhibited a very high correlation coefficient of 0.92227 to dependence on the diameter. And a very high correlation coefficient of 0.94980 to dependence on the pressure under sphere(D 7.5 mm)-plane electrode. When the pressure is applied, sphere-plane electrode is the correlation coefficient was higher than that of the needle-plane electrode. It shows the dependence of a temperature coefficient of -0.758290 ~ -0.39946 under needle-plane electrode.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1276-1281
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• 2004

Nowadays CFCs and HCFCs refrigerants are restricted because it cause depletion of ozone layer. Accordingly, this experiment apply the ammonia gas and not CFCs and HCFCs for refrigerant to study the performance characteristic from the superheat control and improve the energy efficiency from the high performance. The condensing pressure of refrigeration system is increased from 15.0bar to 16bar by 0.5bar and superheat temperature is increased from $0^{\circ}C$ to $10^{\circ}C$ by $1^{\circ}C$ at each condensing pressure. As the result of experiment, when the superheat temperature is $0^{\circ}C$ at each condensing pressure, the refrigeration system has the high performance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.259-264
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• 2005

The shrinkage of the product in injection molded part occurs due to the volume change with variation of temperature and pressure and is influenced by the processing conditions of injection molding. Mold designers greatly concerns the shrinkage of parts for a high dimensional accuracy. In this study, bar type HIPS specimen with 15x19 grid on the surface was tested. The amount of shrinkage of flow and transverse directions was examined with respect to the injection molding conditions such as melt temperature, injection speed, holding pressure, mold temperature and cooling time. As the packing pressure increased, the difference of shrinkage of both directions is decreased and the absolute shrinkage value also decreased.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1085-1091
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• 1995

Molybdenum disilicide (MoSi2) was synthesized from Mo, MoO3, Si and Al powders by self-propagating high temperature synthesis (SHS). The effect of processing parameters such as Mo/MoO3 molar ratio, Ar gas pressure in the reactor and pressing pressure of compacts in synthesis of MoSi2 were investigated. h-MoSi2 was transformed into t-MoSi2 with increasing the Mo/MoO3 mole ratio, and only t-MoSi2 phase was identified above 3.5 : 1 (molar ratio). The synthesized phases did not change with the variation of Ar gas pressure and pressing pressure of compacts. It was found that the combustion temperature was above 2,50$0^{\circ}C$. The products were separated into MoSi2 (s) and $\alpha$-Al2O3 by the difference of their specific grativities. Bending strength, hardness and density of sintered specimen exhibited 82 MPa, 5.368 GPa and 5.43 g/㎤, respectively.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.71-78
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• 2005

A high-pressure hose includes rebar layers of the synthetic fiber such as nylon or a steel wire to control internal pressure. The hose assembly is manufactured through the swaging process to clamp the hose into the metal fittings. Usually, the hose behavior is affected by the resultant of the longitudinal and circumferential forces produced by the internal pressure. The rebar layers can appear the most ideal rebar effect when they are arranged to the same direction as the resultant force. The braid angle applied in the rebar layers is an important factor in determining ultimate burst pressure and overall hose life. Failure can occur on the contacted parts of a hose with the metal fittings under severe operating conditions such as high pressure and temperature of the inner fluid. In this paper, the mechanical behavior between the hose and the metal fittings during the swaging process and the stress variation characteristics of a high-pressure hose under a constant applied pressure are analyzed with respect to the braid angle of steel wire using the finite element method.

• Journal of Hydrogen and New Energy
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• v.31 no.5
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• pp.411-418
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• 2020

A reformer is a device for producing hydrogen used in fuel cells. Among them, methanol steam reformer uses methanol as fuel, which is present as a liquid at room temperature. It has the advantage of low operating temperature, high energy density, and high hydrogen production. The purpose of this study is to improve the internal flow of the pressure vessel when a bundle of methanol steam reformer in the pressure vessel goes out to a single outlet. An analysis of equilibrium reaction to methanol steam reforming reaction was conducted using Aspen HYSYS^® (Aspen Technology Inc., Bedford, USA), and based on the results, computational analysis was conducted using ANSYS Fluent^® (ANSYS, Inc., Canonsburg, USA). For comparison of the results, the height of the pressure vessel, outlet diameter, and fillet was set as variables, and the optimum geometry was selected by comparing the effects of gravity and the amount of negative pressure.

• Journal of ILASS-Korea
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• v.29 no.3
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• pp.147-154
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• 2024

This study explores the rate of injection (ROI) and injection quantities of a solenoid-type high-pressure injector under varying conditions by integrating experimental methods with machine learning (ML) techniques. Experimental data for fuel injection were obtained using a Zeuch-based HDA Moehwald injection rate measurement system, which served as the foundation for developing a machine learning model. An artificial neural network (ANN) was employed to predict the ROI, ensuring accurate representation of injection behaviors and patterns. The present study examines the impact of ambient conditions, including chamber temperature, chamber pressure, and injection pressure, on the transient profiles of the ROI, quasi-steady ROI, and injection duration. Results indicate that increasing the injection pressure significantly increases ROI, with chamber pressure affecting its initial rising peak. However, the chamber temperature effect on ROI is minimal. The trained ANN model, incorporating three input conditions, accurately reflected experimental measurements and demonstrated expected trends and patterns. This model facilitates the prediction of various ROI profiles without the need for additional experiments, significantly reducing the cost and time required for developing injection control systems in next-generation aero-engine combustors.