• 한국산업융합학회 논문집
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• 제9권4호
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• pp.277-283
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• 2006

As the products such as HDD, Notebook, PDA, and Mobile Phone become smaller and thinner, the radius of threads as well as holes for assembling those products become smaller, even down to 1mm. To produce such small holes and thread efficiently, multi tapping is highly necessitated. However the multi tapping characteristics is not well known because its complicated cutting mechanism and thus the quality of the produced holes and threads is not well studied yet. In this paper, experiments have been conducted for small-radius threads using M2 and M2.6 and M3 cold forming tap to investigate multi tapping process using several useful signal such as torque and Z-axis encoder pulse. The surface and profile of the machined threads have been magnified and observed through a SEM.

• 소성∙가공
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• 제22권3호
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• pp.133-142
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• 2013

Recently, electric vehicles and hybrid cars are being promoted as alternatives to reduce automobile emissions. Generally, thin sheet materials such as aluminum alloy AA300X and cold-rolled steel sheet such as JIS-G-3141 are used for the container for the lithium-ion secondary batteries. In this study, a multi-stage deep drawing process is used to produce a rectangular cup from thin stainless steel sheet material, SUS409L, with an initial blank thickness of 0.4mm for the battery container application. Numerical simulations of the first through the fifth stages for the multi-stage deep drawing with thin SUS409L sheet were conducted using LS-Dyna3D Implicit/Explicit. Special consideration was given to the deformation characteristics due to the normal anisotropy of the sheet material. The numerical simulations were conducted with both isotropic properties and the anisotropic properties of the initial blank material. An unexpected forming failure, barreling in the bottom region of the deep drawn rectangular cup, was observed. This failure mode can be avoided by additional ironing thickness control during the process.

• 대한조선학회논문집
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• 제50권3호
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• pp.167-174
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• 2013

Model ice forming process in ice tank needs several steps of seeding, freezing, tempering. In those process, one of the most important factors to affect the accuracy of experiment is the homogeneity of the ice thickness and the temperature. This paper investigated a computational and statistical method to assess the uniformity of the model ice. In addition, the different configurations of freezing systems were considered to improve the uniformity. Qualitative assessment using streamlines from the cooling units was carried out by computational fluid dynamics (CFD) and the quantitative evaluations of the homogeneity were compared using the temperature distribution on the ice surface. In addition, multi species transport analysis is introduced to understand the circulation efficiency of cold air from the cooling units. As the results, optimized configurations were determined by adjusting the angles of vane in the cooling units.

• 한국정밀공학회지
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• 제21권7호
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• pp.136-144
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• 2004

Optimal process and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from a cold rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

• Asian-Australasian Journal of Animal Sciences
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• 제32권5호
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• pp.721-733
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• 2019

Objective: The objectives of this study were to investigate the thermal gelation properties and molecular forces of actomyosin extracted from two classes of chicken breast meat qualities (normal and pale, soft and exudative [PSE]-like) during heating process to further improve the understanding of the variations of functional properties between normal and PSE-like chicken breast meat. Methods: Actomyosin was extracted from normal and PSE-like chicken breast meat and the gel strength, water-holding capacity (WHC), protein loss, particle size and distribution, dynamic rheology and protein thermal stability were determined, then turbidity, active sulfhydryl group contents, hydrophobicity and molecular forces during thermal-induced gelling formation were comparatively studied. Results: Sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed that protein profiles of actomyosin extracted from normal and PSE-like meat were not significantly different (p>0.05). Compared with normal actomyosin, PSE-like actomyosin had lower gel strength, WHC, particle size, less protein content involved in thermal gelation forming (p<0.05), and reduced onset temperature ($T_o$), thermal transition temperature ($T_d$), storage modulus (G') and loss modulus (G"). The turbidity, reactive sulfhydryl group of PSE-like actomyosin were higher when heated from $40^{\circ}C$ to $60^{\circ}C$. Further heating to $80^{\circ}C$ had lower transition from reactive sulfhydryl group into a disulfide bond and surface hydrophobicity. Molecular forces showed that hydrophobic interaction was the main force for heat-induced gel formation while both ionic and hydrogen bonds were different significantly between normal and PSE-like actomyosin (p<0.05). Conclusion: These changes in chemical groups and inter-molecular bonds affected protein-protein interaction and protein-water interaction and contributed to the inferior thermal gelation properties of PSE-like meat.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.60-60
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• 2010

Since the curved hull plate was made by a series of manufacturing process including cold bending, manual local heating and correction work, the accuracy of curved plate strongly depends on the proficiency of worker. So the demands on the automatic local heating system for curved hull plate have continuously increased and the various researches relevant to it have been performed. Generally, the heat sources used for local heating were flame and induction heat. In terms of initial cost, flame heating is in a better favorable position than induction heating. However, from the viewpoint of the control of heat, induction heating has more advantage. So the various researches related to apply the induction heating to the automatic forming system has been performed. The purpose of this study is to establish the proper capacity of high frequency induction heating system for forming the curved hull plate. In order to do it, the proper coil shape for local heating was designed and the efficiency of induction heating system was determined by comparing of temperature results obtained by FEA and experiment. With the results, the extensive FEA was performed to identify the effect of heated plate dimension, cooling method and the capacity of induction heating system on the amount of heat loss introduced by induction heating. Based on the results, the proper capacity of high frequency induction heating system was proposed.

• 대한기계학회논문집A
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• 제34권4호
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• pp.423-430
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• 2010

표면의 균열, 겹침결함, 금형의 코너반경이 작아 재료의 유동성이 낮을 때 발생하는 콜드셧, 부분충진등의 단조결함이 없는 자동차용 단조 플랜지를 생산하기 위해서 열전달, 단류선 흐름, 응력분포를 고려하여 형단조 공정과 금형에 대한 해석을 수행하였다. 축박기(up-set) 단조, 예비성형, 최종성형, 단조압력으로 구성된 단조과정은 유한요소법으로 해석되었다. 예비성형과 상하 금형의 높이비율이 단조공정과 금형에 미치는 영향을 평가하여 예비금형의 각 $10^{\circ}$와 최종 금형의 상하비율 1.5:1이 단조결함이 없는 결과를 나타내었다. 이를 반영한 새로 설계된 금형은 재료강도, 완전충진, 하중한계 13,000 KN 이라는 공정변수를 모두 만족시켰다. 이론 입증을 위해서 개선된 금형과 플랜지가 제작되었으며, 단조결함이 발견되지 않았다.

• 소성∙가공
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• 제23권7호
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• pp.405-412
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• 2014

As a major type of heat exchanger, the steam generator (SG) produces steam from heat energy of a nuclear power plant reactor. The steam produced by the steam generator flows into a turbine, and plays an important role in electric power generation. The heat transfer tubes in the steam generator consist of approximately 10,000 U-shaped tubes, which perform a structural role and act as thermal boundaries. The heat transfer tubes conduct the thermal energy between the primary coolant (about $320^{\circ}C$, $157kgf/cm^2$) obtained from the reactor and the secondary coolant (about $260^{\circ}C$, $60kgf/cm^2$) as part of the secondary system. Recently, the heat transfer tubes in the steam generator of the pressurized water reactor (PWR) are primarily produced from Alloy 600 and Alloy 690 seamless tubes. As a pilot study to find process parameters for the cold U-bending process using rotary draw bending, numerical and experimental investigations were conducted to produce U-shaped tubes from long straight SUS304L seamless tubes. 3D finite element simulations were run using ABAQUS Explicit with consideration of the elastic recovery. The process parameters studied were the angular speed, the operation period and the bending angle. Experimental verifications were conducted to insure the suitability of the final U-shaped configurations with respect to both ovality and wall thickness.

• 동의생리병리학회지
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• 제33권5호
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• pp.249-254
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• 2019

This study is aimed to refute against medical opponent's claim that Korean medicine does not conform to the conditions of science. Analyses and refutations against a journal treatise and a Facebook column formally written for a logical criticism and attack were conducted. As an example of the logic of the knowledge production process in Chinese medicine, 8 principle theory was exemplified in the Han danasty Classics "Neijing" and "Shanghanlun" at first. The knowledge was continuously revised and accumulated historically and then completed through Ming、Cheng period. The differential diagnosis and treatment theory is a logical process of forming knowledge through the process of abduction, deduction and induction begun from "Shanghanlun" succeeded to nowadays and it is essentially equaled with the process of experimental inference by Claude Bernard. Examples of normal science status based on Kuhn's scientific standards include the theory of 8 principle, differntial diagnosis of viscera and bowel, 3 yang and 3 yin diseases of "Shanghanlun" and warm disease theory. Examples of science lost or get its normal status by refutation following Popper's standards were cold damage theory and warm disease theory respectively. This allowed Chinese medicine to follow the general principles of science that form scientific knowledge and to correspond with the demarcation standards and concepts of science. However, as one of the conditions for becoming a science, Chinese medicine is partially lacking in terms of the interpretation of text language or the accordance with modern knowledge. Therefore methods are required to supplement this lack through multi-faceted research such as literature-based, theoretical and clinical studies.

• 한국결정성장학회지
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• 제8권2호
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• pp.356-364
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• 1998

$ZTA:\;Al_2O_3/\;15\;vol{%}\;ZrO_2$ (Zirconia Toughened Alumina : ZTA)를 상압소결에 의해 제조시 분무건조한 granule의 특성에 따른 성형밀도 및 소결밀도의 변화를 고찰하여, 소결밀도의 재현성을 향상시킬 수 있는 성령 공정 조건을 제시하였다. 결합제의 첨가 유무에 따라 granule의 구형도, 평균크기, granule 내의 hollow의 생성정도, 수분함유량 등이 다름을 확인하였다. granule의 물성 차이가 성형거동에 미치는 영향을 성형압(80~120MPa)과 성형방법(일축성형과 정수압 성형)에 따른 성형밀도의 변화를 통하여 조사하였다. granule의 특성 변화에 의한 밀도의 낮은 재현성은 성형압과 성형방법의 최적화를 통하여 극복될 수 있음을 확인하였다. 즉 가능한 낮은 압력(80MPa)에서 일축성형한 후 고압(500MPa)에서 정수압 성형하였을 때 소결후 밀도변화는 1%이내에서 조절되었다.