• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.4
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• pp.1-6
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• 2002

A numerical heat transfer analysis and the structural analysis were performed for the design of sub-scale combustion chamber's coolant passage. The heat flux through the combustion chamber wall was estimated by 2-D heat transfer analysis of compressible hot gas and the result was applied as a thermal boundary condition of 3-D analysis. The heat flux estimated by the present method agreed well with the experimental correlation and proved to be insensitive to cooling condition. So the same thermal boundary condition was applied for various operating conditions. The maximum temperature of combustion chamber wall was predicted by 3-D analysis for single coolant passage and the result will be used for the development of a regeneratively cooled combustion chamber. Also estimated were the stress distribution and structural safety of coolant passage through the static structural analysis.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 1999.07a
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• pp.117-129
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• 1999

Acute effects of locally applied of static magnetic field (SMF) and extremely low frequency electromagnetic field(ELF-EMF) to the cutaneous tissue within a rabbit ear chamber (REC)were evaluated under conscious conditions. Rabbits with the REC were subjected to intravital microscopical investigation by use of microphotoelectric plethysmography(MPPG). There was no dose-response relationship between the extent of vasomotion changes and frequencies(0,20,50, 100Hz)or power levels (1, 5, 10, 25, 50, 100, 200 mT). Under low vascular tone the both fields induce vasodilatation. The effects of SMF (1 mT) on the cutaneous microcirculatory system induced the vasodilatation with enhanced vasomotion under nor-adrenaline-induced high vascular tone as well as the vasoconstriction with reduced vasomotion under acetylcholine-induced low vascular tone. This suggests that the SMF can modulate vascular tone due to the modification of vasomotion biphasically in the cutaneous tissue.

• Journal of Climate Change Research
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• v.9 no.4
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• pp.377-384
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• 2018

The chamber method is widely used for measuring methane emission from paddy rice fields. The closed static chamber has advantages of easy installation and removal in the field and low manufacturing cost. However, the manual chamber method requires a lot of labor and has a limited sampling time and frequency. To overcome the disadvantages of the manual chamber, the auto-chamber system is used for measuring methane emission. We compared the differences in methane flux between the auto-chamber and manual chamber. To investigate methane emissions by the two methods, a chamber was installed for each of the following treatments : control without rice straw (NA), spring plowing after autumn rice straw application (SPRA) and autumn plowing after autumn rice straw application (APRA). The total methane emission was lowest in the control and highest in APRA with both methods. There was no significant difference in total methane emission between the methods, but dynamic fluctuation in methane with temperature change was accurately measured in the auto-chamber. Measuring methane emission with an auto-chamber system is expected to reduce uncertainty and increase accuracy, accompanied by labor reduction.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2642-2647
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• 2007

This study represents numerical study on the thermal and fluid flow characteristics of exhaust gas in a motorcycle muffler. The reference engine was used 124.cc small displacement. Numerical analysis with computational fluid dynamics(CFD) was carried out to investigate the exhaust gas that flow into a motorcycle muffler. The STAR-CD S/W used to three dimensional steady state CFD analysis in a muffler. And than We got the information of static pressure it is used to structural analysis ant the first baffle plate using the commercial CAE code ANSYS workbench. Exhaust gas flow third chamber from frist chamber and running second chamber. A simulation result shows that each chamber of muffler temperature is about 460 K, 445 and 463K and pressure is about 22,000 Pa, 16,000 Pa and 10,000 Pa.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.659-666
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• 2009

This paper proposes a new method for dynamic modeling of electrorheological(ER) damper considering fluid compressibility. After describing configuration and operating principle of the ER damper, a quasi-static modeling of the ER damper is conducted on the basis of Bingham model of ER fluid. Subsequently, the dynamic model for describing the ER damper considering compressibility of ER fluid and gas chamber is obtained using the lumped parameter method. This method includes dynamic motions of annular duct, upper chamber, lower chamber and connecting pipe. The hysteresis behavior of the ER damper is evaluated through computer simulations and compared with experimental results. In addition, the hysteresis behavior due to the compressibility of ER fluid and gas chamber is investigated through computer simulations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.438-443
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• 2009

This paper proposes a new method for dynamic modeling of electrorheological (ER) damper considering fluid compressibility. After describing configuration and operating principle of the ER damper, a quasi-static modeling of the ER damper is conducted on the basis of Bingham model of ER fluid. Subsequently, the dynamic model for describing the ER damper considering compressibility of ER fluid and gas chamber is obtained using the lumped parameter method. This method includes dynamic motions of annular duct, upper chamber, lower chamber and connecting pipe. The hysteresis behavior of the ER damper is evaluated through computer simulations and compared with experimental results. In addition, the hysteresis behavior due to the compressibility of ER fluid and gas chamber is investigated through computer simulations.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.2
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• pp.51-61
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• 2001

A numerical study has been conducted to characterize the transient pressure in a simple water supply pipe system with an air chamber by utilizing a commercial code that employs the method of characteristics. Some results produced for validation in the study agree quite well with the previously reported. Several parameters are than varied. Among them are the valve closure time, the wave speed, the static pressure, the polytropic exponent, the air chamber volume, the diameter and the shape of orifice in the air chamber, etc, while the water temperature and velocity are kept constant at $20^\circ{C}$ and 0.8m/s, respectively. Results reported in this parametric study may be useful to understand the unsteady behavior of the system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.961-967
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• 2009

A 3-dimensional numerical investigation of a WIG effect vehicle with DUP (direct underside pressurization) is performed to predict aerodynamic characteristics and the static height stability. DUP can considerably reduce take-off speed and minimize the hump drag while the vehicle accelerates on the water to take off. The DUP of the model vehicle, Aircat, consists of a propeller in the middle of the fuselage and an air chamber under the fuselage. The air accelerated by the propeller comes into the camber through the channel in the middle of fuselage and augments lift by changing its dynamic pressure to static pressure dramatically. However, the air accelerated by a propeller produces excessive drag and reduces static height stability.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.646-651
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• 2001

The present study is an experimental work of the sonic/supersonic air ejector-diffuser system. The pressure-time dependence in the secondary chamber of this ejector system is measured to investigate the steady operation of the ejector system. Six different primary nozzles of two sonic nozzles, two supersonic nozzles, petal nozzle, and lobed nozzle are employed to drive the ejector system at the conditions of different operating pressure ratios. Static pressures on the ejector-diffuser walls are to analyze the complicated flows occurring inside the system. The volume of the secondary chamber is changed to investigate the effect on the steady operation. the results obtained show that the volume of the secondary chamber does not affect the steady operation of the ejector-diffuser system but the time-dependent pressure in the secondary chamber is a strong function of the volume of the secondary chamber.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.4
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• pp.50-56
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• 2001

The present study is an experimental work of the soni $c^ersonic air ejector-diffuser system. The pressure-time dependence in the secondary chamber of this ejector system is measured to investigate the steady operation of the ejector system. Six different primary nozzles of two sonic nozzles, two supersonic nozzles, petal nozzle, and lobed nozzle are employed to drive the ejector system at the conditions of different operating pressure ratios. Static pressures on the ejector-diffuser walls are to analyze the complicated flows occurring inside the system. The volume of the secondary chamber is changed to investigate the effect on the steady operation. the results obtained show that the volume of the secondary chamber does not affect the steady operation of the ejector-diffuser system but the time-dependent pressure in the secondary chamber is a strong function of the volume of the secondary chamber.er.