• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.4
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• pp.214-217
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• 2017

An IGBT (insulated gate bipolar transistor) device has an excellent current-conducting capability. It has been widely employed as a switching device to use in power supplies, converters, solar inverters, and household appliances or the like, designed to handle high power. The aim with IGBT is to meet the requirements for use in ideal power semiconductor devices with a high breakdown voltage, an on-state voltage drop, a high switching speed, and high reliability for power-device applications. In general, the concentration of the drift region decreases when the breakdown voltage increases, but the on-resistance and other characteristics should be reduced to improve the breakdown voltage and on-state voltage drop characteristics by optimizing the design and structure changes. In this paper, using the T-CAD, we designed the NPT-IGBT (non punch-through IGBT) and FS-IGBT (field stop IGBT) and analyzed the electrical characteristics of those devices. Our analysis of the electrical characteristics showed that the FS-IGBT was superior to the NPT-IGBT in terms of the on-state voltage drop.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.332-337
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• 2009

Recently, boss and rib test based on backward extrusion process was proposed to quantitative evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and friction condition on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the heights of the boss and rib. In addition, the effect of flow stress was also investigated on the deformation patterns through FE simulations.

• Transactions of Materials Processing
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• v.18 no.8
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• pp.640-645
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• 2009

Recently, boss and rib test based on backward extrusion process was proposed to quantitatively evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and flow stress on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the calibration curves showing the heights of the boss and rib. In addition, the effect of flow stress on the calibration curves was investigated through FE simulations. It was found that there is no effect of strength coefficient of the workpiece on the calibration curves for estimation of friction condition. On the other hand, the strain-hardening exponent of the workpiece has a significant influence on the calibration curve.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.628-646
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• 2016

This paper proposes a novel channel assignment scheme that is based on finite projective plane (FPP) theory. The proposed scheme involves using a Markov chain model to allocate N channels to N users through intermixed channel group arrangements, particularly when channel resources are idle because of inefficient use. The intermixed FPP-based channel group arrangements successfully related Markov chain modeling to punch through ratio formulations proposed in this study, ensuring fair resource use among users. The simulation results for the proposed FPP scheme clearly revealed that the defined throughput increased, particularly under light traffic load conditions. Nevertheless, if the proposed scheme is combined with successive interference cancellation techniques, considerably higher throughput is predicted, even under heavy traffic load conditions.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.185-192
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• 2001

In order to obtain the optimal products in deep drawing process, elliptical deep drawing tests were carried out with several shape radii of the punch and die. As parameters on testing, shape radii of the punch and die were selected. In addition, the conventional shape radii have been determined by trial-and-error using industrial experience and post processing test, and only approximate shape radii of the punch and die have been presented. The optimal shape radii of the punch and die in elliptical deep drawing process with biaxisymmetric blank shape are proposed. In this study, we suggest the appropriate conditions to be applicable to the actual manufacturing processes through the experiment and finite element method.

• Transactions of Materials Processing
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• v.9 no.2
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• pp.120-127
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• 2000

Recently, most of researches for sheet metal deep drawing process have been performed on the formability of axisymmetric shape, but there are not any concrete reports on the formability of non-axisymmetric shape. In addition, the conventional shape radius of the punch and die has been determined by trial-and-error using industrial experience and post processing test, and only approximate shape radius of the punch and die has been presented. In this study, the optimal shape radius of the punch and die in deep drawing process with biaxisymmetric blank shape is proposed. Through the deep drawing experiment, especially it is found that in order to obtain the optimal products, and improvement of formability can be researched by selection of such punch and die shape radius that gives an adequate thickness distribution in all processes.

• Design & Manufacturing
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• v.9 no.2
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• pp.16-19
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• 2015

In this paper, The experimental study on the crack during press forming of the door latch assembly for a vehicle door is performed. Length to be inserted into the conventional mold upper die punch is 20 mm, wherein the cracks are generated on the product surface and causes a secondary quality problem. In this study, the length to be inserted in the mold upper die punch 0 mm, 10 mm, 20 mm, which was changed to perform the experiment. Through the experiment, the length inserted into the mold can be seen that the upper die punch of the press forming conditions optimized when the 0 mm.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.370-373
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• 2008

It is known that the temperatures of die, punch, holder and punch pad need to be kept different to get better formability in Mg sheet forming processes. Heating and cooling channels are usually equipped in each tool to assign different temperature. This study focused on the optimal design of the heating and cooling channels for a cross-shaped deep drawing die set. While the die and blankholder were heated to and kept at $250^{\circ}C$ by using heat cartridges, the punch and punch pad were kept at much lower temperature than that of the die and blankholder by water circulating through cooling channels. All the approaches were done by numerical analyses, aiming to maximize the cup height and to minimize the punch corner radius without any failure.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.2
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• pp.157-167
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• 2008

Six smooth flat tensile specimens and eighteen punch specimens with three different thicknesses were machined from steel of JIS G3131 SPHC. In addition to punch tests, incremental tensile tests were conducted to obtain average true flow stress - logarithmic true strain curves. Through parametric FE simulations for the tensile specimens, material parameters related to GTN model were identified. Using indenters with three kinds of radius, punch tests were carried out to obtain fracture characteristics of punch specimens. Numerical analyses using both fracture models, GTN and $J_2$ plasticity model, gave that the former estimated well the fracture of punch specimen but the latter did not. A new concept for critical size of plate elements was introduced based on minimum relative sharpness between contact structures. Consequently, a new criterion for critical element size was proposed to be less than 20% of minimum relative radius of interacting structures.

• Journal of Hydrogen and New Energy
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• v.21 no.4
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• pp.340-345
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• 2010

For the conversion into hydrogen society, not only studying facilities of hydrogen production, storage, transportation and charging system but also developing technique of ensuring safety are essentially needed. Hence, for the first step of that, evaluated the hydrogen embrittlement of Inconel alloy 617, Ni-based super heat-resisting alloy, by small punch test. Prepared the various specimens through changing electrochemical charging time and measured the toughness degradation of the specimens by small-punch test. The analysis of hydrogen embrittlement behavior were carried out by investigating the fractured surface of specimens. This study has significance on revealing mechanism of hydrogen embrittlement behavior and the factor affecting hydrogen embrittlement in the future study.