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마찰교반점접합한 5454-O 알루미늄합금 판재의 접합부 거시조직 및 기계적 특성에 미치는 접합인자의 영향
최원호,권용재,윤성욱,강명수,임창용,서종덕,홍성태,박동환,이광학,Choi, Won-Ho,Kwon, Yong-Jai,Yoon, Sung-Ook,Kang, Myoung-Soo,Lim, Chang-Yong,Seo, Jong-Dock,Hong, Sung-Tae,Park, Dong-Hwan,Lee, Kwang-Hak 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.6
Friction stir spot welding between 5454 aluminum alloy sheets with the different thicknesses of 1.4 and 1.0 mm was performed. In the welding process, the tool for welding was rotated ranging from 500 to 2500, and plunged to the depth of 1.8 mm under a constant tool plunge speed of 100 mm/min. And then, the rotating tool was maintained at the plunge depth during the dwell time ranging from 0 to 7 sec. The pull-out speed of the rotating tool was 100 mm/min. The increase of tool rotation speed resulted in the change of the macrostructure of friction-stir-spot-welded zone, especially the geometry of welding interface. The results of the tensile shear test showed that the total displacement and toughness of the welds were increased with the increase of the tool rotation speed, although the maximum tensile shear load was decreased. However, the change in the dwell time at the plunge depth of the tool did not produce the remarkable variation in the macrostructure and mechanical properties of the welds. In all cases, the average hardness in friction-stir-spot-welded zone was higher than that of the base metal zone. By the friction stir spot welding technique, the welds with the excellent mechanical properties than the mechanically-clinched joints could be obtained.
열전도성 플라스틱을 이용한 21 W급 LED Light Engine의 방열설계
최원호,최두호,이진열,박대희,Choi, Won-Ho,Choi, Doo-Ho,Lee, Jin-Yeol,Park, Dae-Hee 한국전기전자재료학회 2015 전기전자재료학회논문지 Vol.28 No.3
This study will design the structural optimization of 21 W LED heat sink using the thermal conductive plastic materials. The thermal conductive plastic heat sink is inferior to aluminum heat sinks in thermal properties. This study will solve this problem using formability of thermal conductive plastic heat sink. A heat sink was optimized in terms of the number, and the thickness of fins and the base thickness of the heat sink, using the Heatsinkdesigner software. Also by using SolidWorks Flow simulation and thermal analysis software, the thermal characteristics of the heat sink were analyzed. As the result, the optimized heat sink has 17 fins, which are 1.5 mm thick and a 3.7 mm-thick base. The highest and the lowest temperature were $51.65^{\circ}C$ and $46.24^{\circ}C$ respectively. Based on these results, The thermal conductive plastic heat sink is considered possible to overcome heating problem when designing in complex structure.
예비 과학 교사의 화학 개념에 대한 이해도와 문제 해결 능력 조사
최원호,윤혜선,Choi, Won-Ho,Yoon, Hyeo-Seon 대한화학회 2012 대한화학회지 Vol.56 No.5
본 연구에서는 사범대학 과학교육과에 재학 중인 예비 과학 교사들을 대상으로 고등학교 교육과정에 해당하는 화학 개념의 이해도와 문제 해결 능력을 관련 문항을 이용하여 조사하였다. 연구 결과, 오답을 선택하며 문제 해결에 필요한 정확한 개념을 가지지 못하는 예비 과학 교사들이 모든 문항에서 발견되었다. 이 결과의 원인을 찾기 위한 심층 질문을 통해 일부 예비 과학 교사에게서 나타난 몇 가지 사실을 확인할 수 있었다. 첫째, 예비 과학 교사들은 고등학생들에 비해 상대적으로 정확한 개념을 가지고 있었지만 몇몇 개념들에 대해서 고등학생들과 동일한 오개념을 가지고 있었다. 둘째, 과학개념의 일반적 정의나 의미는 알고 있었지만 교육과정 상 강조하는 내용을 정확히 이해하지 못하였으며, 시각적으로 인지된 정보로 문제를 해결하려는 경향이 있었다. 셋째, 문제 해결과 관련된 일반적 개념의 필요성은 인식하는 반면 탐구와 관련하여 문제 해결에 필수적인 능력을 간과하거나 문제 해결에 도움이 되지 않는 상위 교육과정의 필요성을 제안하는 경향이 있었다. We investigated pre-service science teachers' understanding of and problem-solving ability with regard to chemistry concepts in the high school curriculum. For this purpose, we used related certain items and analyzed the results. We found that in the case of all items, some pre-service science teachers, who do not have clear concepts, selected incorrect answers. The in-depth interviews we conducted with the participants revealed some of the causes for the results obtained. First, although pre-service science teachers have better concepts as compared to high school students, they have the same misconceptions as students with regard to some concepts. Second, although they are familiar with the general definitions or meanings of scientific concepts, they do not understand the specific content that is emphasized in the curriculum. Moreover, they tend to solve problems by the information visually conceived. Third, although they know the necessity of general concepts related to problem solving, they sometimes fail to apply inquiry skills and tend to suggest concepts from the higher education curriculum that are not helpful for solving problems.
국가수준 학업성취도 평가에서 중학생의 성취수준별 특징 분석: 화학 영역을 중심으로
최원호,Choi, Won-Ho 대한화학회 2013 대한화학회지 Vol.57 No.1
우리나라 중학교 3학년 학생들을 대상으로 실시한 2009, 2010년 국가수준 학업성취도 평가 결과를 이용하여 학생들의 성취수준별 특징을 조사하였다. 성취수준별 대표 문항 분석을 통하여 다음과 같은 내용을 알았다. 우수학력 학생들은 현상의 변화를 물질의 특징과 모형을 함께 이용하여 설명할 수 있고, 보통학력 학생들은 단순한 상황에 한정하여 모형을 활용하여 현상을 설명할 수 있으며, 기초학력 학생들은 모형의 의미를 이해하지 못하여 물질 현상을 모형을 이용하여 설명하지 못했다. We investigated student's characteristics in each educational achievement level using the results of the NAEA (National Assessment of Educational Achievement) in 2009 and 2010 for Grade 9 students. The analysis of representative items of each educational achievement level revealed that (a) advanced level students could explain the change in phenomena with both the characteristics of matter and the model, (b) proficient level students could explain only simple phenomena with the model, and (c) basic level students did not understand the model and were therefore unable to use it to explain phenomena.
최원호,양보석,주호진,Choi, Won-Ho,Yang, Bo-Suk,Joo, Ho-Jin 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.6
This paper present the claculating method of optimum correction mass within permissible vibration linits for ratating machinery in two-plane field balancing. Basic technique of this method is based on influence coefficient method, and grphic vector composition that the resultant of two influence vectors obtained by trial mass have to be equilibrium with initial vibration vector in the each correction plane. Genetic algorithm which is a search algorithm based on the mechanism of natural selection and natural genetics is sued for vector composition, and SUMT method is used to objective function which seeks optimum correction mass for balancing a rotor.
최원호(Choi Wonn Ho) 한국경영학회 2015 한국경영학회 통합학술발표논문집 Vol.2015 No.08
가계부채와 부채가 없는 가계의 포트폴리오 구성은 재정적 목표와 자산의 선호에 따라 달라진다. 특히 국내가계는 실물자산을 금융자산보다 두 배 넘게 보유하고 있어, 두 가계집단간에 포트폴리오 구성과 포트폴리오 구성에 어느 요인이 영향을 미치는 분석하였다. 본 논문에서는 2010-2012 가계금융조사 설문조사자료를 분석하여 다음과 같은 결과를 얻었다. 우선, 순자산 수준이 높으면 부채가구는 부채가 없는 가구에 비하여 금융자산을 보유하려는 경향이 두드러졌다. 둘째, 순자산 수준이 낮은 부채가구는 실물자산을 꺼려했으나 순자산 수준이 높은 부채가구는 실물자산보유를 선호했다. 반면, 부채가 없는 가구의 순자산은 정반대의 결과를 나타내 극명한 대조를 보였다. 셋째, 부채가구는 부동산, 거주주택, 자동차등 내구재를 선호하나 보험과 채권이외의 금융자산은 선호하기 않았다. 또한, 부채가구의 원금과 이자상환은 예상과는 달리 실물자산 수요를 감소시키는 요인으로 작용하지 않았다. 넷째, 부채가 있는 노년세대나 중년세대는 부채가 없는 동일세대보다 주식을 선호하는 현상이 나타났으며 청년세대보다 주식선호현상이 더 두드러졌다.
양송이 수확 후 배지로부터 분리한 Bacillus subtilis AB-55가 생산하는 xylanase의 특성
최원호(Won-Ho Choi),최용수(Yong-Su Choi),장갑열(Kab-Yeul Jang),윤민호(Min-Ho Yoon) 충남대학교 농업과학연구소 2012 농업과학연구 Vol.39 No.2
A bacterium AB-55, isolated from waste mushroom bed of Agaricus bisporus in Sukseong-myeon, Buyeo-gun, Chungcheongnam-do, Korea, was screened onto xylan agar congo-red plate by the xylanolysis method and was used to produce an xylanase in shaker buffle flask cultures containing oat spelt xylans. The phylogenetic analysis using 16S rRNA gene sequence data showed that the strain AB-55 had the highest homology (99.0%) with Bacillus subtilis and it was named as Bacillus subtilis AB-55. A xylanase was purified by ammonium sulfate precipitation (50∼80%), gel filtration on sephacryl S-300, and ion exchange chromatography on DEAE sepharose FF. The molecular weight of the xylanase was estimated as 44 kDa by SDS-PAGE. Optimal pH and temperature for the xylanase activity was pH 7 and 50℃, respectively. N-terminal amino acid sequence of the enzyme was identified as Ser-Ala-Val-Lys-His-Gly-Ala-Ile-Val-Phe. The substrate specificity of the enzyme exhibited that it hydrolyzed efficiently oat spelt xylan as well as beechwood xylan, but showed no activity against Avicel and carboxymethyl clellulose (CMC). The enzyme activity was enhanced by Fe<SUP>2+</SUP> and Mn<SUP>2+</SUP>whereas was entirely inhibited by Hg?.
레이저 원격 용접기술 적용을 위한 차체 설계기술 및 용접지그 개발
최원호(Wonho Choi),이재수(Jaesoo Lee),김대근(Daegeun Kim),박기영(Kiyoung Park) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
The objective of the research which it sees applies Laser Remote Welding technique in mass production line to be, from data base securities against the material variable, a process variable from Laser welding processes and the mechanical quality of the welding region it leads and body plan techniques and welding jig techniques of optimum about under establishing site to apply. And to keep up the body parts quality of top, simultaneously decrease of the material and weight because decrease of welding places, the mobile path of the robot against the assembly parts of complicated form, the product and the welding gun avoid with each other interference cause by reduced a production cycle time, also to diminish the duplication investment of body assembly equipment and the increase of assembly line caused by, it confront in a strategy module of productivity improvement and the automobile part, with the result that it strengthens the competitive power of the enterprise.