• 대한기계학회논문집A
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• 제24권3호
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• pp.676-684
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• 2000

In this study, behavior of $C_t$ which is a well-known fracture parameter characterizing creep crack growth rate, is investigated for weld interface cracks. Finite element analyses were per formed for a C(T) specimen under constant loading condition for elastic-plastic-creeping materials. In modeling C(T) geometry, an interface was employed along the crack plane which simulated the interface between weld and base metals. The $C_t$ versus time relations were obtained under various creep constant combinations and plastic constant combinations for weld and base metals, respectively. A unified $C_t$ versus time curve is obtained by normalizing $C_t$ with $C^*$ and t with $t_T$ for all the cases of material constant variations.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.159-162
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• 1999

This study has been performed to investigate forming limit of PCM(Pre-Coated Metal) widely using appliances. Die set was made for deep drawing test and some PCMs were inrectangular deep drawing test in no-lubricant 20% clearance some die materials(STD11(TiCN) STD11(HrC60) STD11(TD) AMOCO and 6mm/sec punch speed. and Ericshen test was performed in regular conditions In this experiment forming limit forming characteistics superior die materials and fracture of PCMs been investigated. In results tested PCMs have lower forming limit than base material because lower elongation ultimate strength than base material And two-fracture types - occurring band and flaking - of PCMs have been investiqated.

• Journal of Welding and Joining
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• 제13권3호
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• pp.125-133
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• 1995

Rene80 superalloy was liquid phase diffusion bonded by using pure boron (B) as an insert material. As a basic study for the possibility of practical application of this bonding method, hardness and high temperature tensile strength of the bonded joint and metallurgical analysis were investigated. As experimental results, hardness of the bonded joint was homogenized after bonding and the tensile strength at 1144K was obtained to 90% of that of base metal. But there were some problems to be improved also, that means the joint was hardened after bonding due to increase of B content and elongation was much lower than that of base metal. Flat area and (Mo, Cr, W) boride, which should be harmful for bonding strength, were observed on the fractured surface of the tensile tested specimen.

• 상하수도학회지
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• 제24권4호
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• pp.413-423
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• 2010

Eutrophication caused by the excessive supply of phosphorus to water has been considered as one of the most important environmental problems. In this study, the titanium mesostrcture, which was prepared with the template of different surfactant, was tested to confirm the applicability as an adsorbent for phosphorus removal and evaluate the phosphorus removal efficiency. X-ray diffraction analysis, phosphorus adsorption istotherm and kinetic test were performed for the titanium mesostructure, synthesized at various base material/surfactant molar ratio and with different surfactant templates. From the results, we found that mesostructure was synthesized at the base material/surfactant molar ratio of 1/0.25 was most uniformly and clearly formed and thus the adsorption capacity was also maximized.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.357-360
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• 2003

In this paper, we designed 4.5kV/1.5kA IGCT devices. GCT thyristor has many superior characteristics compared with GTO thyristor, for examples; snubberless turn-off capability, short storage time, high turn-on capability, small turn-off gate charge and low total power loss of the application system containing device and peripheral parts such as anode reactor and snubber capacitance. In this paper we designed GCT thyristor devices, and analyzed static and dynamic characteristics of GCT thyristor depending on the minority carrier lifetime, n-base thickness and doping concentration of n-base region, respectively. Especially, turn-on and turn-off characteristics are very important characteristics for GCT thyristor devices. So, we considered above characteristic for design and analysis of GCT devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.374-377
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• 2003

In this paper, turn on characteristics of (Punch-Through Insulated Gate Bipolar Transistor) PT-IGBT has been studied. Based on the transient power loss, turn on charges first base to collector capacitance. Furthermore we present the charge variation in the base including n+ buffer layer to express the transient turn-on characteristics of the device.

• 한국표면공학회지
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• 제42권1호
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• pp.34-40
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• 2009

In the study, it was carried out dissimilar metal welding on materials for Al ship. The electrochemical and mechanical characteristics evaluated for specimen welded by ROBOT. The hardness of welding zone is lower than those of heat affected zone and base metal. At the result of tensile test, the specimen welded with ER5183 welding material presented excellent property compared with ER5556. The polarization trend for the base metal and welding metal showed the effects of concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation. At the Tafel experiments result, the corrosion density in welded with ER5183 welding material presented the lowest value.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.83-84
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• 2018

3D printing technology can be applied to various industries, and is trapped by major technologies that change existing manufacturing processes. 3D printing materials must satisfy designability, economy and productivity, and building materials are required to have strength and economy secured technology. 3D printing technology of construction field can be divided into structural materials and internal and external materials, and is mainly done by extruding and adapting. Particularly when it is applied as an exterior materials, it is mainly applied to an unstructured exterior materials and high accuracy is required. The exterior materials can be used as a cement composite materials, it is suitable also for a lamination type, and the role of a cement base bonding material is important. In this research, we developed a cementitious base binder applicable as a 3D printing exterior materials, confirmed density and strength characteristics for application as an exterior materials, a flame retardancy test for improving the fire resistance of buildings and confirmed its possibility.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.10-12
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• 1996

AlGaAs/GaAs Heterojunotion Bipolar Transistors (HBTs) with various emitter areas were fabricated and the device size dependence on the current gain was examined. With the different emitter areas, the passivated devices having the same peripheral length were fabricated and measured. The measured base current density in the Gummel plots shows an ideality factor of nearly 2. It is found that as the emitter area becomes small, the base current density with the ideality factor of 2 increases linearly, and as the emitter perimeter/area ratio becomes large, the surface recombination current density component increases. The current gain performance in AlGaAs/GaAs HBTs is mainly determined by either the larger emitter area or the smaller ratio of the emitter perimeter to the emitter area. These results will be compared with experimental works for GaInP/GaAs HBTs

• 소성∙가공
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• 제18권1호
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• pp.73-79
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• 2009

In order to investigate the formability of friction stir welded(FSW) tailor welded blanks(TWB) with respect to the base material's directional combination, aluminum alloy AA6111-T4 sheets were welded with three different conjoining types: RD-RD, TD-RD and TD-TD. Here, RD and TD represent rolling and transverse directions, respectively. For experimental formability study, three tests with gradual complexity were performed: the simple tension test with various weld line directions for uni-axial elongation, the hemisphere dome stretching test for biaxial stretching and the cylindrical cup deep drawing test. As a result, all three forming tests showed that RD-RD type samples exhibited the best formability, while TD-TD type sheets showed the least formability performance.