• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.96-102
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• 2019

This study investigated the heat dissipation characteristics of a heat-sensitive LED. More than 80% of the power supply is converted into heat energy, which has a fatal impact on the lifetime of the LED. Therefore, the effective heat dissipation characteristics of a heatsink, such as a 30W floodlight, through forced convection were grasped and the heat transfer characteristics were tested. As a result, it was confirmed that the smaller the number of fins, the more the temperature distribution varies according to the wind velocity. In addition, the larger the number of fins, the smaller the temperature difference according to the wind velocity. Therefore, it was found through this experiment that excellent heat dissipation performance was exhibited as the heat dissipation area and wind velocity increased.

• Journal of Powder Materials
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• v.28 no.4
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• pp.301-309
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• 2021

In this study, an AISI 316 L alloy was manufactured using a selective laser melting (SLM) process. The tensile and impact toughness properties of the SLM AISI 316 L alloy were examined. In addition, stress relieving heat treatment (650℃ / 2 h) was performed on the as-built SLM alloy to investigate the effects of heat treatment on the mechanical properties. In the as-built SLM AISI 316 L alloy, cellular dendrite and molten pool structures were observed. Although the molten pool did not disappear following heat treatment, EBSD KAM analytical results confirmed that the fractions of the low- and high-angle boundaries decreased and increased, respectively. As the heat treatment was performed, the yield strength decreased, but the tensile strength and elongation increased only slightly. Impact toughness results revealed that the impact energy increased by 33.5% when heat treatment was applied. The deformation behavior of the SLM AISI 316 L alloy was also examined in relation to the microstructure through analyses of the tensile and impact fracture surfaces.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.8
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• pp.598-604
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• 1999

This paper describes the research to minimize the film stress and maximize the aspect ratio of photoresist structure, especially about SU-8 for electroplating mold. UV LIGA process using SU-8 allows fabricating high aspect ratio polymer structures. However, it is hard to get fine patterns in the high aspect ratio structures because of high internal stress and difficulty of removing SU-8. The purpose of this paper is to setup the process condition for the obtainment of both low film stress and high aspect ratio and to find design rules that make the pattern be less dependent on stress problem. Firstly, the process of heat treatment and exposure of SU-8 are proposed. These two conditions control the amount of cross-linkage in polymer structure, which is the most important parameter of both pattern generation and remaining stress. Heat treatment is dealed with soft bake and post-exposure-bake. Temperature and time duration of each step are varied with heat treatment condition. Some test patterns are fabricated to evaluate the proposed process. Nickel electroplating is performed with the mold fabricated through the proposed process to confirm the SU-8 as a good electroplating mold.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.5
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• pp.288-296
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• 2005

The corrosion behaviors of Zr-based alloys were very sensitive to their microstructures which were determined by manufacturing process. The specimens of Zr-based alloy named as HANA-4 for nuclear fuel cladding were investigated in order to get the optimized manufacturing process such as the intermediate annealing temperature and cold working steps after the ${\beta}$ quenching. From the microstructural analysis, cold worked microstructure of the samples was changed to the recrystallized microstructure by performed process. The corrosion behaviors of HANA-4 alloy were affected by the different manufacturing process. The ${\beta}$-Zr phase was formed in the matrix and the Nb concentration in the ${\beta}$-Zr phase was increased as progressing the manufacturing process. So, it was found that the corrosion rate of HANA-4 alloy was affected by the Nb concentration in the matrix.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.243-250
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• 2003

The present study discuss about numerical methods to analyze design parameters of pyrolysis-melting incineration system. Various numerical methods of different viewpoint are introduced to simulate the performance of the system. Process analysis of the overall system is the beginning procedure of basic design process. Heat and material flow of each element are connected and are influential to each other, hence, an appropriate process modeling should be executed to prevent from unacceptable process design concepts that may results in system failure. Models to simulate performance of each elementary facility generate valuable informations on design and operation parameters, and, derive the basic design concept to be optimized. A pyrolysis model derived from waste bed combustion model is introduced to simulate the mass conversion and heat transfer in the pyrolysis process. CFD(Computational fluid dynamics) is an effective method to optimize the thermal reacting flow in various reactors such as combustor and heat exchanger. Secondary air jets arrangement and the shape of the combustor could be optimized by CFD technology.

• Journal of Welding and Joining
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• v.35 no.2
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• pp.35-42
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• 2017

The GMA welding process involves large number of interdependent variables which may affect product quality, productivity and cost effectiveness. The relationships between process parameters for a vertical weldment and mechanical properties are complex because a number of process parameters are involved. To make the vertical-position welding, a method that predicts bead geometry and accomplishes the desired mechanical properties of the weldment should be developed. In addition, a reliable welding process and conditions must be implemented to reduce weld structure failure. In this study, the welding process analysis of investigates the interaction between the heat input and welding parameter(Welding current, Arc voltage, Welding speed) for predicting the weldment hardness.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.304-310
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• 2009

Recently, manganese nodule has been focused on alternative resources because of its high grade of noble metallic elements such as Co, Ni, and Cu etc. From the viewpoint of an optimization the operating variables for energy efficiency of smelting reduction process, thermodynamic model for smelting reduction process of Manganese nodule was developed by using energy and material balance concept. This model provided that specific consumption of pure oxygen and coke was strongly depended on post combustion ratio (PCR) and heat transfer efficiency (HTE). The dressing and dehydrating process of low grade manganese can be proposed an essential process to minimize the specific energy consumption with decreasing slag volume. The effect of electricity coal base smelting reduction process was also discussed from the energy optimizing point of view.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.3
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• pp.354-363
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• 1997

The purpose of the present work is to show the best thermal storage material and the sensitivity of the parameters on the thermal performance by experimentally investigating the effects of the parameters on the thermal performance of the spherical capsule system using paraffins superior to the commercial one. The paraffins were n-Tetradecane and the mixture of n-Tetradecane 40% and n-Hexadecane 60%. The experimental parameters were the Reynolds number of 8, 12, and 16 and the inlet temperature of-7, -4, -1, and $2^{\circ}C$. The charging and the discharing time, the dimensionless thermal storage amount, and the averge heat transfer coefficient in the tank were obtained by utilizing the local temperature variation in the tank. The local charging and discharging time in the tank was axially and radially different a lot. The effects of the inlet temperature on the charging and the discharging time were larger during the charging process than during the discharging process, but the effects of the Reynolds number on the charging and the discharging time were in reverse order. The paraffins were better by 11~72% than the water with the inorganic material in the charging time aspect, but no difference in the discharging time aspect. The effects of the Reynolds number on the dimensionless thermal storage amount were smaller than the effects of the inlet temperature during the charging process, but in reverse order during the discharging process within the working range of the experimental parameters. The effects of the inlet temperature and the Reynolds number on the average heat transfer coefficient were larger during the discharging process than during the charging process. The average heat transfer coefficient for the paraffins was larger by 40% maximum than that for the commercial material during the charing and the discharging process.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.3
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• pp.150-155
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• 2010

Generally, plasma nitriding process has composed with a nitriding layer within glow discharge region occurred by energy exchange. The dissociations of nitrogen molecules are very difficult to make neutral atoms or ionic nitrogen species via glow discharge area. However, the captured electrons in which a double-folded screen with same potential cathode can stimulate and come out some single atoms or activated ionic species. It was showed an important thing that is called "hat is a dominant component in this nitriding process?" in plasma nitriding process and it can take an effective species for without compound layer. During a plasma nitriding process, it was able to estimate with analyzing and identification by optical emission spectroscopy (OES) study. And then we can make comparative studies on the nitrogen transfer with plasma nitriding and ATONA process using plasma diagnosis and metallurgical observation. From these observations, we can understand role of active species of nitrogen, like N, $N^+$, ${N_2}^+$, ${N_2}^*$ and $NH_x$-radical, in bulk plasma of each process. And the same time, during DC plasma nitriding and other processes, the species of FeN atom or any ionic nitride species were not detected by OES analyzing.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.56-64
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• 2020

The safety related heat exchangers have been evaluated for their performance during the operation of the nuclear power plant. The evaluation program for the safety related heat exchanger was developed in 2010 and used by KHNP based on EPRI TR-10739 algorithms. The spend fuel pool heat exchanger is one of the safety related heat exchanger in the nuclear power plant and also evaluated for their performance. Recently the performance evaluation for the spend fuel pool heat exchanger was not available because of the decreased heat in the spend fuel pool due to the long term overhaul. This paper analyzes the main cause of evaluation failure in the evaluation process and suggests the criteria for the heat exchanger performance evaluation during the long term overhaul.