• 소성∙가공
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• 제30권6호
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• pp.311-322
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• 2021

• Archives of Plastic Surgery
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• 제46권5호
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• pp.405-413
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• 2019

Background Face transplantation has naturally evolved from reconstructive procedures. However, few institutions perform face transplantations, because it is time-consuming and it is necessary to justify non-vital organ transplantation. We investigated the process of organ donation from brain-dead patients and the possibility of incorporating face transplantation into the donation process. Methods A retrospective review was performed of 1,074 brain-dead patients from January 2015 to December 2016 in Korea. We analyzed the time intervals from admission to brain death decisions (first, second, and final), the causes of brain death, and the state of the transplanted organs. Results The patient base (n=1,074) was composed of 747 males and 327 females. The average period between admission to the first brain death decision was 8.5 days (${\pm}15.3$). The average time intervals between the first brain death decision and medical confirmation using electroencephalography and between the first brain death decision and the final determination of brain death were 16 hours 58 minutes (${\pm}14hours$ 50 minutes) and 22 hours 57 minutes (${\pm}16hours$ 16 minutes), respectively. The most common cause of brain death was cerebral hemorrhage/stroke (42.3%), followed by hypoxia (30.1%), and head trauma (25.2%). Conclusions When face transplantation is performed, the transplantation team has 22 hours 57 minutes on average to prepare after the first brain death decision. The cause of brain death was head trauma in approximately one-fourth of cases. Although head trauma does not always imply facial trauma, surgeons should be aware that the facial tissue may be compromised in such cases.

• 한국수산과학회지
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• 제33권6호
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• pp.524-528
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• 2000

식품중에 오염된 Listeria monocytogenes의 열감수성에 미치는 각종 첨가물의 영향과 식품의 처리 가공시에 수반되는 조리기구 수세나 염소, 자외선, 열탕 등 각종 소독처리의 효율성을 확인하였다. 키토산, 솔빈산칼륨 둥은 시험균주 L. monocytogenes H-12의 열 감수성 증대에 유의할 만한 영향을 미치지 못하였으나, 명태 연육에 중합인산염을 $1{\%}$ 첨가할 경우 시험균주의 열감수성은 뚜렷히 증가되었다. 시험균주 L. monocytogenes H-12가 $약 10^4{\~}10^5/cm^2$ 되도록 오염시킨 나무, 플라스틱, 스테인레스 재질의 도마를 흐르는 수도수로 세척하였을 때 스테인레스 도마나 플라스틱 도마의 경우 각각 10초 및 1분 후에는 균이 검출되지 않았으나, 나무 도마에서는 거의 제균효과가 없었다. 스테인레스 및 플라스틱 재질의 도마를 $5{\~}50 ppm$의 염소용액에 10초간 침지하고 수세할 경우 오염균의 제거가 가능하였으나, 나무 도마의 경우 100ppm 염소용액으로 처리하여도 균 수의 감소는 거의 없었다. 15W의 자외선을 30cm 거리에서 시험균주로 오염된 각 재질의 도마에 조사할 경우 스테인레스 및 플라스틱 도마의 경우 5분간 조사 후에는 균이 검출되지 않았으나, 나무 도마에서는 60분 처리 후에도 균이 검출되었다. 각종재질의 조리용 도마에 오염된 시험균주 L. monocytogenes H-12의 열탕처리에 의한 제균조건은 $70^{\circ}C$, 10초 이상으로 확인되었다.

• 한국분말재료학회지
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• 제17권3호
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• pp.190-196
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• 2010

In this paper, rapid solidified Mg-4.3Zn-0.7Y (at.%) alloy powders were prepared using an inert gas atomizer, followed by a severe plastic deformation technique of high pressure torsion (HPT) for consolidation of the powders. The gas atomized powders were almost spherical in shape, and grain size was as fine as less than $5\;{\mu}m$ due to rapid solidification. Plastic deformation responses during HPT were simulated using the finite element method, which shows in good agreement with the analytical solutions of a strain expression in torsion. Varying the HPT processing temperature from ambient to 473 K, the behavior of powder consolidation, matrix microstructural evolution and mechanical properties of the compacts was investigated. The gas atomized powders were deformed plastically as well as fully densified, resulting in effective grain size refinements and enhanced microhardness values.

• 자원리싸이클링
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• 제33권1호
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• pp.48-57
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• 2024

본 연구는 농촌에서 발생되는 C급 폐비닐의 활용률 개선을 목적으로 아임계 열수를 거쳐 생성된 에코 파우더(Eco-powder)를 플라스틱 원재료로 활용하기 위한 기초연구이다. 생성된 에코 파우더의 회분함량 제어를 위한 선가공 처리의 효율과 생성된 에코 파우더의 회분함량에 따른 플라스틱으로서의 기초 특성을 평가하였다. 기초 특성으로서는 수준별 에코 파우더 활용 압축성형 시험체의 회분함량, 충격강도, 굴곡강도, 인장강도를 평가하였다. 실험 결과, 선가공으로 물리적인 충격을 통한 토사분과 폐비닐 부분의 분리 효율이 개선되는 것을 확인하였다. 또한 회분함량에 따른 충격강도, 굴곡강도, 인장강도 평가 결과, 회분함량 26% 이하 수준의 에코 파우더에서 목표로 하는 성능을 만족하는 것으로 나타났다. 이로써 기존 활용도 및 회수율이 낮던 C급 폐비닐을 아임계 열수 처리 후 물리적 가공 처리를 통해 최적 조건을 설정하여 플라스틱 원료로서 활용이 가능한 것을 확인하였다.

• 한국분말재료학회지
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• 제15권1호
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• pp.31-36
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• 2008

In this study, the bottom-up powder metallurgy and the top-down severe plastic deformation (SPD) techniques for manufacturing bulk nanomaterials were combined in order to achieve both full density and grain refinement without grain growth of rapidly solidified Al-20 wt% Si alloy powders during consolidation processing. Continuous equal channel multi-angular processing (C-ECMAP) was proposed to improve low productivity of conventional ECAP, one of the most promising method in SPD. As a powder consolidation method, C-ECMAP was employed. A wide range of experimental studies were carried out for characterizing mechanical properties and microstructures of the ECMAP processed materials. It was found that effective properties of high strength and full density maintaining nanoscale microstructure are achieved. The proposed SPD processing of powder materials can be a good method to achieve fully density and nanostructured materials.

• 한국분말재료학회지
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• 제13권6호
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• pp.415-420
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• 2006

Nanostructured metallic materials are synthesized by bottom-up processing which starts with powders for assembling bulk materials or top-down processing starting with a bulk solid. A representative bottom-up and top-down paths for bulk nanostructured/ultrafine grained metallic materials are powder consolidation and severe plastic deformation (SPD) methods, respectively. In this study, the bottom-up powder and top-down SPD approaches were combined in order to achieve both full density and grain refinement without grain growth, which were considered as a bottle neck of the bottom-up method using conventional powder metallurgy of compaction and sintering. For the powder consolidation, equal channel angular pressing (ECAP), one of the most promising method in SPD, was used. The ECAP processing associated with stress developments was investigated. ECAP for powder consolidation were numerically analyzed using the finite element method (FEM) in conjunction with pressure and shear stress.

• 소성∙가공
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• 제31권6호
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• pp.365-375
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• 2022

The microstructure and high-temperature plastic deformation behavior of the modified Al-0.7Mn alloy were investigated and compared with the conventional Al-0.3Mn (Al3102) alloy. α-Al (matrix) and Al₆(Mn, Fe) phases were identified in both alloys. As a result of microstructure observation, both alloys showed equiaxed grains, and Al-0.7Mn alloy showed larger grain size and higher Al₆(Mn, Fe) fraction than Al-0.3Mn alloy. High temperature compressive tests, the deformation temperatures of 410℃, 450℃, 490℃, 530℃ and strain rats of 10^-2/s, 10^-1/s, 1/s, 10/s, were conducted using Gleeble equipment. The flow stress values of Al-0.7Mn alloy were higher than that of Al-0.3Mn alloy at all strain rates and temperature conditions. Constitutive equations were presented using the flow stresses obtained from experimental results and the Zener-Hollomon parameter. In the true stress-true strain curves of the two alloys, the experimental and predicted values were in good agreement with each other. Based on the dynamic material model, eutectic deformation maps of Al-0.7Mn and Al-0.3Mn alloys were suggested, and the plastic instability region was presented. The modified Al-0.7Mn alloy showed a wider plastic instability region than that Al-0.3Mn alloy. Based on the process deformation maps, the MPE tube parts could be manufactured through the actual extrusion process using the suggested conditions.

• 소성∙가공
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• 제31권3호
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• pp.124-128
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• 2022

NdFeB magnets have been positioned as the core materials in advanced technologies such as MRI (magnetic resonance imaging), FA (factory automation system), robot, motors, and so on based on the highest magnetic properties. To effectively improve the refined microstructure, the plastic deformation has been known as the good alternatives by the recrystallization. However, it has been regarded as being impossible because of the few slip systems in the RE-Fe-B magnets at room temperature. The purpose of this study was to investigate the possibility of control of grain refinement and magnetic anisotropy of NdFeB alloy powder by the severe plastic deformation. The NdFeB magnet powder was fabricated by gas atomization process, and the powder was pre-compacted at high temperature. The pre-compacted billets were deformed by HPT (high pressure torsion), and then the deformed billets were observed microstructure and magnetic properties. After the HPT process at room temperature, the grain size decreased with increasing because of the melted Nd-rich phase, and the anisotropy of Nd₂Fe₁₄B phase was formed after the HPT process.

• 소성∙가공
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• 제16권5호통권95호
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• pp.406-411
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• 2007

The microstructure and the hardness of interstitial free steel processed by equal channel angular pressing (ECAP) was investigated experimentally. ECAP processing of route A and route C was compared with regard to grain refinement by transmission electron micrographs. Micro hardness evolution was correlated with the gram structure produced by ECAP. Especially, the effects of the ECAP processing temperature and the number of processing passes were discussed in terms of grain refinement.