• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2080-2093
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• 2008

Disk brake system take charge of maximum braking energy among the mechanical brake systems for high speed train. For this reason, Metallic friction materials and heat resistant steel disk is adopted at disk brake system for high speed train. It was investigated tribological characteristics(friction coefficient, friction stability, wear rate and braking temperature) between some kinds of metallic friction materials and heat resistant steel disk. Cu-based friction material for high speed train have suitable tribological characteristics.

• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.304-309
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• 2008

Magnesium alloys containing $Mg_2Si$ particles, as a promising cheap heat-resistant magnesium alloy for automobile power train parts applications, are attracting more attention of both material scientists and design engineers. Modification of the Chinese script shape $Mg_2Si$ particle is a key for using this alloy in sand or permanent mould casting. In the present work, the modification effect of Sr and Sb on the corrosion properties of the Mg-5Al-2Si alloy was investigated. Sr or Sb addition promoted the formation of fine polygonal shape $Mg_2Si$ particles by providing the nucleation sites. Sr was more effective element than Sb for shape modification of Chinese script shape $Mg_2Si$. Such improved microstructure of the modified alloy resulted in large improvement in corrosion resistance as compared to unmodified Mg-5Al-2Si alloy.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.8
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• pp.681-685
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• 2015

Hastelloy C-276 composed of Cr, Mo, and Ni is a versatile, corrosion-resistant alloy with numerous industrial applications including its use in nuclear reactors, general chemical plants, and as a superconducting base material. Of especial significance, it can be used as a thin-sheet type whereby lap-joint welding is occasionally necessary. The main welding problems for thin-sheet metals are deformation and burn-through from an excessive heat input. Laser welding can minimize these problems because it has a high energy density and low heat effect on the base material. In this study, the laser-welding characteristics of lap-joint Hastelloy C-276 sheet metal were determined. The criteria of the laser-welding variables were chosen using a heat-conduction analysis, and the optimal welding parameters were selected by experimenting with an Nd:YAG laser.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.228-228
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• 2017

Rice production and quality could be changed by temperature condition. Extremely high temperature event have been occurred more frequently for global warming. To increase rice quality against to global warming, breeding of heat tolerance rice cultivar is needed. Ilmi which is the one of Korean leading rice cultivar shows heat stress resistant character during ripening stage. Yield and quality (brown and milled rice) of Ilmi did not show significant different under high temperature condition compared to control condition. However, the main physiological characters for heat resistance of Ilmi have been not investigated yet. Therefore we try to investigate the heat tolerance characters of Ilmi. Two rice cultivars, Ilmi and Ilpum-which is heat susceptible rice cultivar, were cultivated under natural condition in wagnor pot until heading was appeared. After checking heading date, each material was cultivated under different temperature condition, heat($32/22^{\circ}C$) and control($26/16^{\circ}C$) condition. Anti-oxidant enzyme activity was checked during ripening stage in each material. Catalase and ascorbic peroxidase activity of leaf under heat stress condition were higher in Ilmi than Ilpum especially early ripening stage. Analyzing of stress resistance using $H_2O_2$, the flag leaf of Ilmi showed more green color than Ilpum with higher chlorophyll content than those of Ilpum. We also checked the amount of $H_2O_2$ content in young leaf of each material by treating high temperature. $H_2O_2$ content in each material was increased according to treatment time. However $H_2O_2$ content of young leaf in Ilmi was less than those in Ilpum. Also catalase and ascorbic peroxidase activity in leaf increased much faster in Ilmi than Ilpum. With those data, we confirmed that heat stress resistance of Ilmi is due to the higher anti-oxidant activity against to stress condition. We will investigate the heat tolerance characters of Ilmi more in further study to enhance the breeding effect of heat stress tolerance rice.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.125-132
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• 1998

In this study the fire, due to overturning of oil tanker on the bridge induced heat transfer analysis and thermal stress analysis are carried out. The results of analysis for fire history of 1 hour present very large thermal gradient near the surface. However, the temperature increase of tendon & rebar that is the main resistant member of bridge is not sufficient to change material properties. The Von-Mises yield criteria is used to calculate the depth of delamination, The depth of delamination is about 4cm at center of fire and this value is close to measured value.

• Journal of Korea Foundry Society
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• v.13 no.6
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• pp.563-573
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• 1993

The wear resistance of Hyper-eutectic Al-Si alloy, have recently been noticed as a new automobile material, was investigated. For the purpose of developing wear resistant Al-Si alloy, some factors which attribute to wear resistance are examined as follows; refinement of primary Si particle during solidification, and effect of refinement on wear resistance and other mechanical properties. The most effective refinement was accomplished by adding both NaF and S, and this improve wear-resistance in abrasive wear type. The wear losses of specimens cast in metal mold were ruduced to 80% of those in sand mold. T6 heat treatment increases hardness, which resulted in reduction of wear loss about $3{\sim}18%$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.446-452
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• 2016

Recently, heat resistant super alloys (which are wear-resistant, corrosion-resistant, and heat-resistant), have been used as the basic structural material in offshore and petrochemical plants. On the other hand, making valves from very expensive, high heat-resistant alloys increases the production cost and decreases its market competitiveness. To solve these problems, the technique of overlaying only those that flow on the fluid has been used as an effective method. Nevertheless, because the former technique of overlaying the ball is performed manually, it takes too much time and perfect welding is difficult to perform. To solve this problem, this study developed a robot automation system that can make uniformly overlay welding of the ball for ball-valves. The system consists of a 6-axis welding robot with a welding torch and additional 2 axes for the rotation of positioner, the controller, and a robot path OLP (Off-Line Programming). The CAD drawing data was entered in the Off-line program to obtain the robot teaching point and drive source. Overlay welding paths were implemented using Matlab. Through an automated overlaying system that implemented the OLP, the productivity rose 2.58 times, as the amount of time required for work decreased from 88 hours to 41 hours.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.16-22
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• 1998

This paper addresses a method which can be used for analyzing thermal stresses of a functionally graded material(FGM) using semi-analytical approach. FGM is a nonhomogeneous material whose composition is changed continuously from a metal surface to a ceramic surface. An infinite one dimensional FGM plate is considered. The temperature distribution in the FGM is obtained by approximate Green's function solution. To expedite the convergence of the solutions, alternative Green's function solution is derived and shows good agreement with results from finite difference method. Thermal stresses are calculated using temperature distribution of the plate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2134-2140
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• 1996

This study was carried out to anlayze the heat-resistant characteristics of functionally gradient material(FGM) composed with ceramic and metal. The thermal fracture behavior of plasma-sprayed FGM and conventional coating material(NFGM) was exaimined by acoustic emession technique under heating and cooling. Furnace cooling and rapid cooling tests were used to examine the effect of temperature change under various conditions, respectively. At the high temperature above $800^{\circ}C$, it was shown that FGM gives higher thermal resistance compared to NFGM by AE signal and fracture surface analysis.

• Fashion & Textile Research Journal
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• v.4 no.6
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• pp.564-566
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• 2002

Protective clothing for firefighters typically consists of a flame resistant outer shell and inner layers. The inner layers are generally composed of a moisture barrier and a thermal barrier. On performing the task in fire place the heat and perspiration generated from the body become trapped inside the protective clothing. Those heat and moisture result into heat-stress and physical fatigue of fire fighter, which hinder the work. Therefore, the system of clothing designs and material layers must be chosen carefully to balance protection and comfort. 3 kinds of protective clothing of 3 layer structure were used in the experiment of physiological comfort. From the comparison of wear trials with the 3 kinds of layers in firefighters clothing, it indicates that the moisture dissipation of A+B2+C was highest, following A+BI+C andA+B3+C. And the heat dissipation of A+BI+C and A+B2+C were better than A+B3+C. In the protective clothing with A+B3+C, heat and perspiration generated through exercise remained in clothing system long and caused discomfort.