• Journal of the Korean Wood Science and Technology
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• v.42 no.3
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• pp.339-345
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• 2014

For enhancing productivity of glulam, high frequency (HF) curing technique was researched in this study. Heat energy is generated by electromagnetic energy dissipation when HF wave is applied to a dielectric material. Because both lamina and adhesives have dielectric property, internal heat generation would be occurred when HF wave is applied to glulam. Most room temperature setting adhesives such as phenol-resorcinol-formaldehyde (PRF) resin, which is popularly used for manufacturing glulam, can be cured more quickly as temperature of adhesives increases. In this study, dielectric properties of larch wood and PRF adhesives were experimentally evaluated, and the mechanism of HF heating, which induced the fast curing of glue layer in glulam, was theoretically analyzed. Result of our experiments showed relative loss factor of PRF resin, which leads temperature increase, was higher than that of larch wood. Also, it showed density and specific heat of PRF, which are resistance factors of temperature increase, were higher than those of wood. It was expected that the heat generation in PRF resin by HF heating would occur greater than in larch wood, because the ratio of relative loss factor to density and specific heat of PRF resin was greater than that of larch wood. Through theoretical approach with the experimental results, the relative strengths of ISM band HF electric fields to achieve a target heating rate were estimated.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.73.1-73.1
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• 2010

For the successful cold starting of a fuel cell engine, either internal of external heat supply must be made to overcome the formation of ice from water below the freezing point of water. In the present study, switchable vanadium oxide compounds as variable temperature-electrical resistance materials onto the surface of flat metallic bipolar plates have been prepared by a dip-coating technique via an aqueous sol-gel method. Subsequently, the chemical composition and micro-structure of the polycrystalline solid thin films were analyzed by X-ray diffraction, X-ray fluorescence spectroscopy, and field emission scanning electron microscopy. In addition, it was carefully measured electrical resistance hysteresis loop over a temperature range from $-20^{\circ}C$ to $80^{\circ}C$ using the four-point probe method. The experimental results revealed that the thin films was mainly composed of Karelianite $V_2O_3$ which acts as negative temperature coefficient materials. Also, it was found that thermal dissipation rate of the vanadium oxide thin films partially satisfy about 50% saving of the substantial amount of energy required for ice melting at $-20^{\circ}C$. Moreover, electrical resistances of the vanadium-based materials converge on an extremely small value similar to that of pure flat metallic bipolar plates at higher temperature, i.e. $T{\geq}40^{\circ}C$. As a consequence, experimental studies proved that it is possible to apply the variable temperature-electrical resistance material based on vanadium oxides for the cold starting enhancement of a fuel cell vehicle and minimize parasitic power loss and eliminate any necessity for external equipment for heat supply in freezing conditions.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.2
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• pp.196-203
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• 2017

The renewable energy sources can be thought of one of the major measures to reduce greenhouse gas emissions in the industries. However, the utilization technology for those sources is approaching in the different matters. One of them, thermoelectric generation might be applicable to fishing industry. A various of internal combustion engines are used in a wide range of fisheries. After the ignition process, the heat passed out from the exhaust outlet. Recycling the heat could be not only an energy source but also reduction of green gas emission. Therefore, this study was designed to verify the feasibility of generation from wasted exhaust gas and analyze the performance. The designed experiment devices were connected with a data logger and an electric loader to quantify the currency and voltage. The devices were installed in a coastal fishing vessel for a gillnet fishery. During the whole fishing trips, the amount of generation was measured by engine rpm and the fishing operation procedures including vessel operations. At the maximum 1,500 rpm in the practical range, the generation amount was 113.6 W. The amount difference in relation to connection method was within 5 W: serial connection was 111.4 W and parallel connection was 115.8 W.

• Proceedings of the Safety Management and Science Conference
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• 2012.11a
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• pp.245-252
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• 2012

Internal engine is the main power source of vehicle and is the main source of air pollution. To satisfy this getting rigorous emission regulation, it must be solved simultaneously the dilemma of reducing emission gas and increasing heat efficiency. Diesel engine is preferred compare with gasoline engine in aspect of energy consumption but it must be solved reducing the containing of NOx, CO and HC. In this study 1. Looking for alternative of performance improvement of Exhaust Gas Recirculation(EGR) which is emission gas reduction system, 2. Reducing malfunction of controlling emission gas 3. Made possible precision control.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.694-700
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• 2013

The design of the exhaust manifold for the pulse converters of a 4 strokes high power medium-speed diesel engine is presented in terms of fatigue analysis. The said system undergoes thermal expansion due to high temperature of exhaust gas and is exposed to intrinsic vibration of the internal combustion engine. Moreover, the exhaust pulse generates pressure pulsating along the runner inside manifold. Under such circumstances, the design and construction of exhaust manifold must be carried out in a way to prevent early failure due to fracture. To validate the design concept, a test rig was developed to simulate the combination of thermal and vibrational movements, simultaneously. Experimental results showed that a certain sense of reliability can be achieved by considering a field factor obtained from the results of engine bench tests.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.1-10
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• 1998

A header is the device that makes uniform flow distribution in all branches from header of heat exchangers, pipe burner or chemical equipments. In this study, experimental tests have been performed in order to investigate the flow distribution characteristics in a straight header and tapered header which have 6 and 11 glass pipe branches. The experimental equipment consists of a water circulation system where the fluid velocity in each glass pipe is measured by Ar-ion LDV system. From the experiments and the theoretical equation, it could be recommended that tapered header should be determined so that its internal velocities inside the header become uniform according to taper of the header and number of attached branches for uniform flow distribution in energy systems.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.299-304
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• 1999

Cracking of concrete is one of the main issues of structural design next to ensuring the load-bearing capacity. Thermal cracking is a recurring concern in the production of concrete structures in particular when large, massive structures are considered. Thremal stresses arise from the differential temperature distribution either within s sturcture or between newly cast sectons and adjoining older parts. There are many different methods of reducing thermal stresses. A method often used for reducing temperature within a structure, is to cool the inner core with embedded cooling pipes. In this study, finite element method is employed for thermal analysis of concrete structures. To calculate water temperature variation in pipe, the conservation of thermal energy in internal flow was adopted. The cooling effect of pipe cooling is studied with several factors like convective coefficient, water temperature, concrete heat characteristics

• Journal of computational fluids engineering
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• v.1 no.1
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• pp.123-141
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• 1996

In this paper the upwind flux difference splitting Navier-Stokes method has been applied to study the perfect gas and the equilibrium chemically reacting hypersonic flow over an axisymmetric sphere-cone(5°) geometry. The effective gamma(γ), enthalpy to internal energy ratio was used to couple chemistry with the fluid mechanics for equilibrium chemically reacting air. The test case condition was at altitude(30km) and Mach number(15). The equilibrium shock thickness over the blunt body region was much thinner than that of perfect gas shock. The pressure difference between perfect gas and equilibrium gas was about 3 ∼ 5 percent. The heat transfer coefficient were also calculated. The results were compared with VSL results in order to validate the current numerical analysis. The results from current method were compared well VSL results ; however, not well at near nose. The proper boundary condition and grid system will be studied to improve the solution quality.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.203-212
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• 1995

In this paper the upwind flux difference splitting Navier-Stokes method has been applied to study the perfect gas and the equilibrium chemically reacting hypersonic flow over an axisymmetric sphere-cone($5^{\circ}$) geometry. The effective gamma($\bar{r}$), enthalpy to internal energy ratio was used to couple chemistry with the fluid mechanics for equilibrium chemically reacting air. The test case condition was at altitude(30Km) and Mach number(15). The equilibrium shock thickness over the blunt body region was much thinner than that of perfect gas shock. The pressure difference between perfect gas and equilibrium gas was about $3\sim5$ percent. The skin friction coefficient and heat transfer coefficient were also calculated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.171-177
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• 1984

균일하게 분포된 내부발열을 갖는 유체가 든 경사진(수평에서 45.deg.까지)정사각형 단면의 밀폐 공간 내에서의 2차원 자연대류 유동 및 열전달에 관한 수치적인 연구가 수행되었다. 4개 벽면온 도가 동일한 경계조건에서 내부발열로 인한 자연대류 유동이 Rayleigh수 1.5*$10^{5}$까지는 층 류유동 영역의 가정하에서 수치적으로 수렴되었다. 경사진 밀폐 공간에서의 유동형태 및 온도분 포는 수평인 경우에 비하여 윗쪽 벽면 근처에서 그 상이점이 많이 나타났다. 경사각도가 증가함 에 따라 평균 열전달율이 아랫쪽 벽과 오른쪽 벽에서 증가하였고 왼쪽 벽에서 감소하였으며 윗 쪽 벽에서는 거의 일정하였다.다.