• Journal of Photoscience
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• v.9 no.2
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• pp.252-254
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• 2002

Djungarian hamsters show distinct seasonal rhythms in several physiological parameters. One of them is daily torpor that occurs in winter with decreased body temperature (about 1O-20$^{\circ}$C) during daytime. Daily torpor is induced by short-day photoperiod, food restriction and castration. But the mechanism to induce daily torpor has not been clarified. In the present study, we tried to clarify the process of daily torpor induction in detail. Adult male hamsters were kept in long photoperiod and high temperature (LP-HT) before the experiment and, thereafter, the animals were transferred to short photoperiod and low temperature (SP-LT), and they were kept in this condition for about six months. The daily rhythms of locomotor activity and body temperature were recorded every three-minutes by using the Minimitter telemetry system. Locomotor activity and body temperature showed very closely synchronized rhythms. All animals under LP-HT showed daily rhythms with higher locomotor activity and body temperature in nighttime than in daytime. Under SP-LT, there were two types of animals with and without showing daily torpor. Thus, they have individual differences in the response to SP -LT.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.1002-1009
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• 2004

Direct contact air conditioning systems, in which heat and mass are transferred directly between air and water droplets, have many advantages over conventional indirect contact systems. The purpose of this research is to investigate the cooling and heating performances of direct contact air conditioning system for various inlet parameters such as air velocity, air temperature, water flow rate and water temperature. The experimental apparatus comprises a wind tunnel, water spray system, scrubber, demister, heater, refrigerator, flow and temperature controller, and data acquisition system. The inlet and outlet conditions of air and water are measured when the air contacts directly with water droplets as a counter flow in the spray section of the wind tunnel, and the heat and mass transfer rates between air and water are calculated. The droplet size of the water sprays is also measured using a Malvern Particle Analyzer. In the cooling conditions, the outlet air temperature and humidity ratio decrease as the water flow rate increases and as the water temperature, air velocity and temperature decrease. On the contrary, the outlet air temperature and humidity ratio increase in the heating conditions as the water flow rate and temperature increase and as the air velocity decreases.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.205-214
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• 2021

Currently, the interim storage pools of spent fuels in South Korea are expected to become saturated from 2024. It is required to prepare an operation plan of a domestic dry storage facility during a long-term period, with the researches on safety evaluation methods. This study modified the FRAPCON code to predict the spent fuel integrity evaluation such as the axial cladding temperature, the hoop stress and hydrogen distribution in dry storage. The cladding temperature in dry storage was calculated using the COBRA-SFS code with the burnup information which was calculated using the FRAPCON code. The hoop stress was calculated using the ideal gas equation with spent fuel information such as rod internal pressure. Numerical analysis method was used to calculate the degree of hydrogen diffusion according to the hydrogen concentration and temperature distribution during a dry storage period. Before 50 years of dry storage, the cladding temperature and hoop stress decreased rapidly. However, after 50 years, they decreased gradually and the cladding temperature was below 400 K. The initial temperature distribution and hydrogen concentration showed a parabolic line, but hydrogen was transferred by the hydrogen concentration and temperature gradient over time.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.1
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• pp.72-79
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• 1987

When the wall temperature is very high, a stable vapor film covers the heat transfer surface. The vapor film creates a strong thermal resistance when heat is transferred to the liquid though it. This phenomenon, called "film boiling" is very important in the heat treatment of metals, the design of cryogenic heat exchangers, and the emergency cooling of nuclear reactors. In the practical engineering problems of the transient cooling process of a high temperature wall, the wall temperature history, the variation of the heat transfer coefficients, and the wall superheat at the rewetting points, are the main areas of concern. These three areas are influenced in a complex fashion such factors as the initial wall temperature, the physical properties of both the wall and the coolant, the fluid temperature, and the flow state. Therefore many kinds of specialized experiments are necessary in the creation of precise thermal design. The object of this study is to investigate the heat transfer characteristics in the transient cooling process of a high temperature wall. The slow transient cooling experiment was carried out with a copper block of high thermal capacity. The block was 240 mm high and 79 mm O.D.. The coolant flowed throuogh the center of a 10 mm diameter channel in the copper block. In the copper block, three sheathed thermocouples were placed in a line perpendicular to the flow. These thermocouples were used to take measurements of the temperature histories of the copper block.

• Journal of the Korean Ceramic Society
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• v.49 no.5
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• pp.454-460
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• 2012

The nano-sized zirconia powders were synthesized in an impregnation method using pulp and $ZrOCl_2{\cdot}8H_2O$ as an initial material. The synthesized powders were characterized by XRD and FE-SEM. The particle size of the powder was controlled by preparation conditions, such as drying temperature and time. As a result of the various drying and calcination conditions, 30~50 nm sized homogeneous zirconia particles were obtained at $800^{\circ}C$ for 1 h. Crystallization and the rapid growth of particles were accelerated with increasing calcination temperature and time. Tetragonal phase generated below $800^{\circ}C$ were transferred to monoclinic phase with increasing calcination temperature and time. Moreover, above $800^{\circ}C$, heat treatment time had very large influence on the particle growth, and the change of drying condition also had large influence on the growth of a crystal.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.763-768
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• 2002

This paper presents a mathematical model predicting the temperature distribution in rotating GMA welding. The bead width increases with rotation frequency at the same rotation diameter because the molten droplets are deflected by centrifugal force. The numerical solution is obtained by solving the transient three-dimensional heat conduction equation considering the heat input from the welding arc, cathode heating and molten droplets. Generally in GMA welding the heat input may be assumed as a normally distributed source, but the droplet deflection causes some changes in the heat input distribution. To estimate the heat flux distribution due to the molten droplet, the contact point where the droplet is transferred on the weld pool surface is calculated from the flight trajectory of the droplets under the arc plasma velocity field obtained from the arc plasma analysis. The numerical analysis shows a tendency of broadened bead width and shallow penetration depth with the increase of rotating frequency. The simulation results are in good agreement with those obtained by the experiments under various welding conditions.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.255.2-255.2
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• 2014

Electrode erosion is indispensable for atmospheric plasma systems, as well as for switching devices, due to the high heat flux transferred from arc plasmas to contacts, but experimental and theoretical works have not identified the characteristic phenomena because of the complex physical processes. Our investigation is concerned with argon free-burning arcs with anode erosion at atmospheric pressure by computational fluid dynamics (CFD) analysis. We are also interested in the energy flux and temperature transferring to the anode with a simplified unified model of arcs and their electrodes. In order to determine two thermodynamic quantities such as temperature and pressure and flow characteristics we have modified Navier-Stokes equations to take into account radiation transport, electrical power input and the electromagnetic driving forces with the relevant Maxwell equations. From the simplified self-consistent solution the energy flux to the anode can be derived.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2231-2235
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• 2008

Thermal performance of fusing system in laser printer is determined by FPOT(First print out time) required and toner fusing quality. FPOT is influenced by the thermal resistance of fusing system between heat source and nip region. Also FPOT is depended by the heat source power and toner fusing temperature. The fusing quality of toner is decided by the temperature, pressure and duration time in nip region. In this study, I have performed thermal analysis for the toner fusing system. Computational simulation has been used to understand the effect of heat source power and printing speed etc. on the temperature distribution of the fusing system. Also in order to predict fusing quality, numerical simulation of the process that paper is continuously supplied to the nip regions were performed. In comparison with the experimental results of the fusing quality vs transferred calory to the toner layer, I could evaluate various fusing condition parameters effected on the thermal performance.

• Journal of the Semiconductor & Display Technology
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• v.19 no.2
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• pp.16-21
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• 2020

How accurately reproducible energy is delivered to the wafer in the process of making thin films using PE-CVD (Plasma enhanced chemical vapor deposition) during the semiconductor process. This is the most important technique, and most of the reaction on the wafer surface is made by thermal energy. In this study, we studied the method of monitoring the change of thermal energy transferred to the wafer surface by monitoring the temperature change according to the change of the thin film formed on the showerhead facing the wafer. Through this research, we could confirm the monitoring of wafer thin-film which is changed due to abnormal operation and accumulation of equipment, and we can expect improvement of semiconductor quality and yield through process reproducibility and equipment status by real-time monitoring of problem of deposition process equipment performance.

• Journal of Institute of Convergence Technology
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• v.1 no.1
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• pp.5-8
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• 2011

Thermal analysis of a cooling module using Peltier elements are performed using a commercial software, CFD-ACE+. A standard k-e two-equation turbulent model is applied in order to represent the turbulent shear stress. Computed values are compared with the theoretical values for the validation. The effect of mass flow rates and transferred heat amounts on the temperature distributions inside the cooling system is analyzed. It was found that the increase in the mass flow rates causes the exit temperature rise. The increase in the absorbed heat amount diminished the overall temperature on the fin surfaces. In the present analysis, the material characteristics of the Peltier element itself are not considered. In the future, the effect of the turbulence models and material characteristics will be studied in detail.