• 소성∙가공
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• 제11권3호
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• pp.246-254
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• 2002

A simple method to derive an optimal pressure curve, characterized by initial pressure, final pressure and pressure path, has been proposed. The initial pressure has been determined from the condition to prevent recoiling phenomenon in the early stage, while the final pressure is from the FE analysis and pressure path is from the punch penetration volume. In order to realize the pressure curve, an open loop control system based on a proportional relief valve has been developed for the renovated CNC hydroforming press. Through the comparison of experiment and analysis, the predicted pressure curve has been verified optimal curve since no defect has been observed.

• Journal of Chest Surgery
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• 제12권1호
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• pp.61-66
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• 1979

This is a report of a case of tuberculous esophageal perforation, which was surgically treated.. The patient was 32-year-old Korean female patient, who complained swallowing difficulty for` 4 weeks duration. Esophagogram was shown irregular filling defects in the upper one third of esophagus, about 4 cm in length. It was noticed that a small amount of contrast media was leaked out from the involved area of esophagus into the right mediastinum. It was highly suggested that abscess formation was due to perforation of esophageal cancer. Esophagoscopy revealed no definitive evidence of perforation of esophagus, but punch biopsy specimen of esophageal mucosa was shown acute and chronic inflammatory changes. Operation was performed under impression of esophageal cancer. In the right-sided upper mediastinum, a walnut-sized abscess cavity which was connected with esophagus through a fistulous tract was noted. A portion of cavity submitted for frozen section was shown tuberculous inflammation. The abscess cavity, fistula tract, and involved esophageal wall were removed. The perforated esophagus was closed layer by layer. The tuberculous changes were confirmed by histopathologic examination postoperatively. The postoperative course was uneventful.

• Nuclear Engineering and Technology
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• 제38권5호
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• pp.405-410
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• 2006

Microstructural features and their related mechanical property changes in the 309L cladding and the heat affected zone (HAZ) of SA508 cl.3 steel were investigated through the use of TEM, tensile and small punch (SP) tests. The specimens were irradiated at 563 K up to the neutron fluences of $5.79{\times}10^{19}n/cm^2$ (>1MeV). The microstructure of the clad was mainly composed of a fcc ${\gamma}-phase$, a low percentage of bcc ${\delta}-ferrite$, and a brittle ${\sigma}-phase$. Along the weld fusion line there formed a heavy carbide precipitation with a width of $20{\sim}40{\mu}m$, showing preferential cracking during plastic deformation. The yield stress and ductile-to-brittle transition temperature (DBTT) of the irradiated clads increased. The origin of the hardening and the shift of the DBTT are discussed in terms of the irradiation-produced defect clusters of a fine size and brittle ${\sigma}-phase$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.232-235
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• 1995

A side-extrusion model, meant for deeper understanding of the material flow in the CONFORM (continuous extrusion forming) of trub shaped aluminum profiles is presented. In order to get the desirded straight shape of the extrudate,every part of its cross-section must exit the die with the same velocity. Problem is assumed by plane strain UBET-model to analyze it in a simplified way. This has been done by studying the side-extrusion through a two -hole die face. The flow is balanced by determining the optimum lengths of the bearing lands, i.e., those lengths which result in equal exit velocities of the extrudates. Furthermore, the material flow, as influenced by the punch velocity, has been investigated.

• 소성∙가공
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• 제10권6호
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• pp.500-508
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• 2001

The integration of Rapid prototyping (RP) and Rapid Tooling (RT) has the potential for rapid net shaping of thee-dimensional parts, which have a geometrical complexity. In this study, a new R)P process, (VLM-SP), was proposed to manufacture net shapes of three-dimensional prototypes and it was shown that VLM-SP is an effective and economic process through the comparison of building time, building cost and dimensional accuracy for the test parts with the commercial RP processes ; LOM and FDM. In addition, the metal parts, which are a spanner shape and a clover punch, were produced by the plaster casting as one of RT using the prototypes of VLM-SP.

• 한국전기전자재료학회논문지
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• 제23권4호
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• pp.273-279
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• 2010

In this paper, we proposed 2500 V Non punch-through(NPT) Insulated gate bipolar transistor(IGBT) for high voltage industry application. we carried out optimal simulation for high efficiency of 2500 V NPT IGBT according to size of device. In results, we obtaind design parameter with 375 um n-drift thickness, 15 um gate length, and 8um emitter windows. After we simulate with optimal parameter, we obtained 2840 V breakdown voltage and 3.4V Vce,sat. These design and process parameter will be used designing of more 2000 V NPT IGBT devices.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.563-564
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• 2008

This paper presents a new Insulated Gate Bipolar Transistor(IGBT) for power switching device based on Non Punch Through(NPT) IGBT structure. The proposed structure has adding N+ beside the P-base region of the conventional IGBT structure. The proposed device has faster turn-off time and lower forward conduction loss than the conventional IGBT structure.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1270-1279
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• 2002

Residual stress is a dominant obstacle to efficient production and safe usage of device by deteriorating the mechanical strength and failure properties. Therefore, we proposed a new thin film stress-analyzing technique using a nanoindentation method. For this aim, the shape change in the indentation load-depth curve during the stress-relief in film was theoretically modeled. The change in indentation depth by load-controlled stress relaxation process was related to the increase or decrease in the applied load using the elastic flat punch theory. Finally, the residual stress in thin film was calculated from the changed applied load based on the equivalent stress interaction model. The evaluated stresses for diamond-like carbon films from this nanoindentation analysis were consistent with the results from the conventional curvature method.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1366-1375
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• 2002

In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. The model experiment results are in good agreement with the FE simulation ones.

• 한국생산제조학회지
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• 제7권4호
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• pp.14-20
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• 1998

This paper describes a computer-aided die design system of progressive die for making CPT grid. An approach to the development of the automatic design system is based on knowledge-based rules. The developed system is designed by considering several factors, such as grid geometry and punch profile. Grid, a key component of electronic gun, is formed through a sequence of many operations, among which the pilot piercing, beading, notching, bending, swaging and slotting etc. Using the developed system, design parameters are determined and output is generated in graphic forms. Therefore the developed system provides part drawing and the assembly drawing of die set.