• 한국세라믹학회지
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• 제34권8호
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• pp.908-913
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• 1997

Multilayer NbCxC1-x/Y2O3/Ti were sputter-coated on the alumina substrate, starting with a 0.7 ㎛ thick NbCxC1-x layer grown on substrate, followed by 0.7 ㎛ thick Y2O3 layer and 1 ㎛ thick Ti layer. To find out the optimum conditions for thickness uniformity and adhesion, sputtering works have been done with the variation of sputtering power and Ar pressure. After vacuum annealing at 950℃ and 1000℃, the thermal stability of the NbCxC1-x/Y2O3/Ti coated alumina substrates has been investigated by peel off test. The coating scheme didn't cause any debonded layer after an annealing at 950℃ for 3hrs. However, it was peeled off after annealing at 1000℃ for 3hr. It was found that the thermal stability of Al2O3/NbCxC1-x/Y2O3/Ti coating scheme changed with the NbCxC1-x composition.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.641-646
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• 1998

In order to enhance the dynamic and interactive simulation capability of a system thermal hydraulic code for nuclear power plant, applicability of flow network models in SINDA/FLUIN $T^{™}$ has been tested by modeling feedwater system and coupling to DSNP which is one of a system thermal hydraulic simulation code for a pressurized heavy water reactor. The feedwater system is selected since it is one of the most important balance of plant systems with a potential to greatly affect the behavior of nuclear steam supply system. The flow network model of this feedwater system consists of condenser, condensate pumps, low and high pressure heaters, deaerator, feedwater pumps, and control valves. This complicated flow network is modeled and coupled to DSNP and it is tested for several normal and abnormal transient conditions such turbine load maneuvering, turbine trip, and loss of class IV power. The results show reasonable behavior of the coupled code and also gives a good dynamic and interactive simulation capabilities for the several mild transient conditions. It has been found that coupling system thermal hydraulic code with a flow network code is a proper way of upgrading simulation capability of DSNP to mature nuclear plant analyzer (NPA).

• 대한전기학회논문지
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• 제41권7호
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• pp.703-711
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• 1992

As the underground area of the metropolitan becomes denser recently, an introduction of forced cooling system is under study to maximize the carrying capacity of existing cables in tunnels. Indirect water cooling system laid within trough will probably be adopted for the next 345KV class underground power cables in this country. The system covers a distance of 1.5-3.0Km for one water cooling interval and one water cooling interval is composed of several sub-sections that have different thermal analysis conditions. Thus the distribution of temperature in each sub-section is described by different conditions in general. In this paper a method that can accurately match the temperature of the coolant in the boundary between sub-sections has been suggested. An algorithm to find the temperature distributions effectively in the thermal system has also been presented. A computer program using this method has been tested in a smaple system and the results have shown the usefulness of this program.

• 한국정밀공학회지
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• 제7권2호
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• pp.74-84
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• 1990

The machine tool structures for ultra-precision machining muxt be manufactured with materials which have high static and dynamic stiffness, high damping, a long term dimensional and thermal stability. This study aims at the development of new composite material Epoxy-Granite which exhibits the satisfactory characteristics as a material of ultra-precision mchine tool bed. The Epoxy-Granite testpieces that use epoxy resins as a binder and granite particles as a aggregate have been manufactured so as to examine the material properties about mechanical, thermal and damping characteristics. Experiments were carried out to obtain the proper manufacturing conditions of Expoxy-Granite specimens by varying the several testing conditions such as types of epoxy resins, particle sizes of granite and mixture ratio of epoxy resin and aggregate. Also, when Epoxy-Granite was compared with cast iron, GRANITAN which was imported from CMS of U.K. and granite materials, it has exhibited the superior or almost the same mechanical and damping properties and thermal conductivity, except for the thermal expansion.

• 대한건축학회논문집:구조계
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• 제33권12호
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• pp.99-106
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• 2017

Recently, the condensation and mold problems of apartment buildings has been growing due to high insulation and high air-tightness performance for energy saving. Most of all, occupants in residential buildings has suffered from property damages due to the condensation and mold of built-in furniture. Condensation at built-in furniture were generally found in winter at the of furniture's back panels, adjacent surfaces of wall, floor and ceiling. The aim of paper is to analyze the characteristics of adjacent area around built-in furniture's condensation problem and the thermal environment around the built-in furniture in winter through the field measurements at apartment buildings. In this research, the thermal conditions and surface temperature around the built-in furniture were measured during winter season. In this research, we analyzed thermal conditions for built-in furniture which were applied and not applied auxiliary heating device. In results, it is important to consider increasing surface temperature for using heater and decreasing absolute humidity due to the occupants' behavior around built-in furniture for preventing condensation.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.93-98
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• 2000

Turbulence on the journal bearing operation is examined. And the thermal variability is studied for isothermal, convective and adiabatic conditions on the walls within some degree of journal misalignment. An efficient algorithm for the solution of the coupled turbulent Reynolds and energy equations is used to examine the effects of the various factors. The calculation data of turbulent analysis are compared with the ones of laminar analysis. Heat convection is found to play but a small role in determining friction and load. The friction distribution patterns through inside a journal bearing now appear different with high values at the front part of the bearing due to the high speed and low temperature, and a sudden decrease past the pressure maximum.

• International Journal of Automotive Technology
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• 제6권6호
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• pp.563-570
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• 2005

A numerical study of high pressure and temperature droplet vaporization and combustion is conducted by formulating one dimensional evaporation model and single-step chemical reaction in the mixture of hydrocarbon fuel and air. The ambient pressure ranged from atmospheric conditions to the supercritical conditions. In order to account for the real gas effect on fluid p-v-T properties in high pressure conditions, the modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties. Some computational results are compared with Sato's experimental data for the validation of calculations in case of vaporization. The comparison between predictions and experiments showed quite a good agreement. Droplet surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• 한국수소및신에너지학회논문집
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• 제26권1호
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• pp.71-78
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• 2015

This study was performed to optimize the integrated thermal-alkali pre-treatment of flotation scum for the enhanced biodegradability. The optimum conditions of the integrated thermal-alkali pre-treatment were obtained using response surface methodology. The disintegration degree of carbohydrate (69.2%) and protein (57.3) were estimated under the optimum conditions. Although the optimum conditions were different, the disintegration degrees were similarly. A fermentative hydrogen batch test was conducted to evaluate the hydrogen production from scum with and/or without. The maximum hydrogen production from scum with pre-treatment was of 0.64 mol H2/mol hexoseadded, which about 1.4 times higher than without pre-treatment.

• Nuclear Engineering and Technology
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• 제29권4호
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• pp.269-279
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• 1997

The errors associated with incorrect sampling and transport of radioactive aerosol from radwaste thermal process off-gas are analyzed and the conditions of representative sampling and correct transport of radioactive aerosol for off-gas system evaluation are discussed. An estimation method of sampling errors for individual radionuclides is proposed and applied to simulated vitrification melter aerosols. Prediction methods for particle deposition in sample transport tube under laminar as well as turbulent flow conditions are also described by example calculations with simulated incinerator off-gas From the results of example calculations and plots, instrumental and operational conditions of radioactive aerosol sampling system with minimized errors and correction methods for nonideal sampling and transport are recommended.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.92-102
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• 2001

The effect of ethanol-blending on the performances of the MPI gasoline engine was examined. The experiments were carried out for the stoichiometric conditions under MBT spark timing over various operating conditions. The blending rate of ethanol were determined as 10 to 30 percent according to the analysis of the properties of blended fuels. The engine with ethanol-blended fuels showed improved performances such as brake torque, brake power, brake thermal efficiency and exhaust emissions compared with those of pure gasoline over most operating conditions. Though the brake specific fuel consumption was increased by ethanol-blending due to their lower heating values, the increasing rates of the brake specific fuel consumption were limited to the half of the blending rates owing to the increase in the thermal efficiency.