곡률을 갖는 셀프-피어싱 리벳 접합시편의 피로수명 평가

김민건,조석수,김동열,Kim, Min-Gun,Cho, Seok-Swoo,Kim, Dong-Youl 한국생산제조학회 2010 한국생산제조학회지 Vol.25 No.3

One of methods that accomplish fuel-efficient vehicle is to reduce the overall vehicle weight by using aluminum structure typically for cross members, rails and panels in body and chassis. For aluminum structures, the use of Self Piercing Rivet(SPR) is a relatively new joining technique in automotive manufacture. To predict SPR fatigue life, fatigue behavior of SPR connections needs to be investigated experimentally and numerically. Tests and simulations on lap-shear specimen with various material combinations are performed to obtain the joining strength and the fatigue life of SPR connections. A Finite element model of the SPR specimen is developed by using a FEMFAT SPR pre-processor. The fatigue lives of SPR specimens with the curvature are predicted using a FEMFAT 4.4e based on the liner finite element analysis.

동(銅) 표면(表面)의 화학부식(腐蝕)에 의한 식각(蝕刻) 패턴 연구

김민건,서봉원,Kim, Min-Gun,Seo, Bong-Won 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.1

In order to observe the pattern forming of copper plate and chemical corrosion reaction, a study on the effect of the process parameters on the formation of micro-pattern by a photochemical etching of copper plate was carried out. The results are as follows : 1) Etching rate increases as the concentration of etchant increases under the regular condition of the temperature by the increasing of diffusion rate to surface. 2) Etching rate increases as the temperature of etchant increases by the fast acting of the material delivery of diffusion to surface under the regular condition of concentration. 3) It was found that etching speed increases as the material delivery of convection rising increased when the aeration speed of etchant increases. This result was from the fact acted by the material delivery of convection rising rather than material delivery of diffusion to the surface.

황련해독탕가감방(黃連解毒湯加減方)으로 치료한 지루성 피부염 치험 3례

김민건,황문제,Kim, Min-Gun,Hwang, Moon-Je 대한한방안이비인후피부과학회 2014 한방안이비인후피부과학회지 Vol.27 No.1

Objectives : The purpose of this study is to report the effect of Hwangryuhaedok-tang gagambang on seborrheic dermatitis. Methods : The clinical study was done on 3 cases of seborrheic dermatitis patients with symptoms of flare, scales, pricking and itching. An author prescribed Hwangryuhaedok-tang gagambang for these patients and checked VAS(Visual Analogue Scale) scores depending on the patient's evaluation. Photographies were taken before and after the treatment. Results : VAS scores of all patients decreased from 10 to 1,2. Judging by photographies, patients noticeably improved in facial skin. As a result of examining VAS scores and photographies, Hwangryuhaedok-tang gagambang was effective on seborrheic dermatitis. Conclusions : From these results, Hwangryuhaedok-tang gagambang may be considered as a basic prescription for seborrheic dermatitis. And an author consider that continuous clinical study will be needed in Korean medical dermatology.

유동상로를 이용한 질화처리티타늄의 피로강도 특성

김민건,지정근,Kim, Min-Gun,Ji, Jueng-Keun 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1

Rotary bending fatigue tests were carried out on the nitrided titanium in order to investigate the effect of nitriding layer on fatigue limit. Main results obtained are as follows. (1) The fatigue limit of nitrided pure titanium is remarkably reduced because of enlargement of grain size at high heat treating temperature and high stress field created from the elastic interaction in the compound layer. (2) Further test using specimen which was removed nitrified layer gradually, were also conducted and it was found that by removing the compound layer the fatigue limit recovered as the level of basic material and rather increased by coming of a diffusion layer. Therefore it is concluded that the surface compound layer generated by nitriding treatment reduced the fatigue limit but diffusion layer increased it.

무도장 교량에 사용되는 내후성강재의 부식 및 피로거동에 미치는 산성안개의 영향

김민건(Min-Gun Kim) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.1

The purpose of this study is to investigate the effect of acid fog on the rust formation behavior of weathering steel (SMA50) which is used in un-coated bridges. Weathering steel didn't form the passive film under the environment of acid fog(pH5,6), whereas the environment of distilled water formed the protective oxide film. Therefore, the construction of weathering steel under the environment extremely exposed to SOx and NOx which are the main compositions of acid fog is not adequate. Fatigue limits of weathering steel under acid fog environment are remarkably decreased as compared with environment of distilled water. The corrosive constituents in acid fog has piled up the corrosion products on specimen surface and generated the corrosion pits. Because of the high stress concentration arising at this corrosion pit, relatively low fatigue limits were obtained for acid fog specimens.

리드스크루에 사용되는 베어링 스크루의 전산내구해석

김민건(Min-gun Kim),조석수(Seok-swoo Cho),김동열(Dong-youl Kim),김요셉(Yo-seb Kim) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.12

리드스크루에 사용되는 베어링 스크루의 강성을 평가하기 위해서, 먼저 베어링의 응력과 피로수명의 유한요소해석을 수행하였다. 해석결과의 값을 바탕으로 베어링 스크루의 피로수명이 향상된 모델을 제안하였다. 이 개선된 모델은 베어링 스크루 응력집중부의 응력을 분산시키기 위한 필릿을 도입한 것이다. 또한, W사에서 제작된 베어링 스크루가 단층촬영기에 사용되었을 때 강도측면에서의 적합성 여부를 검토하였다. In order to assess the stiffness of bearing screw used for lead screw, finite element analysis on stress and fatigue life of bearing screw has been performed. Based on these analysis, fatigue life dominant model of bearing screw was proposed. This improved model introduces a fillet to release the concentrated stress generated in the vicinity of bearing screw hole. This paper also considered the strength suitability when the bearing screw manufactured in W company was applied to X-ray CT.

국제경영 : 아시아 시장에서의 환율과 주가간의 변동성 전이효과

김민건 ( Min Gun Kim ),강상훈 ( Sang Hoon Kang ) 국제지역학회 2013 국제지역연구 Vol.17 No.1

본 연구는 주요 아시아 국가(호주, 홍콩, 인도, 인도네시아, 일본, 한국, 싱가포르)의 주가지수 수익률과 환율 변화율에 대한 가격 및 변동성 전이효과를 분석하였다. 이변량 VAR-EGARCH 모형을 중심으로 아시아 주식시장과 환율시장 간의 가격전이효과와 변동성 전이효과, 상관관계를 추정하였고, 또한 글로벌 금융위기가 전이효과에 어떠한 변화를 주었는지 알고자 글로벌 금융위기 전후 기간을 나누어 결과 값을 추정하였다. 실증분석 결과 가격전이효과는 호주, 홍콩, 일본, 한국, 싱가포르에서는 양방향으로, 인도와 인도네시아는 단방향으로 주가지수 수익률이 환율 변화율에 영향을 주고 있었으며 전반적으로 환율이 주가 수익률에 영향을 주는 것으로 분석 되었다. 그리고 글로벌 금융위기를 겪으며 이러한 현상은 더욱 두드러짐을 알 수 있었다. 또한, 변동성 전이효과는 환율 변화율과 주가지수 수익률 간에 한국과 싱가포르를 제외하고 양방향으로 전이되어 지는 것을 발견하였다. 그리고 금융위기 전후를 비교한 결과, 변동성 전이효과 역시 두 지수의 상호의존성에 많은 변화가 일어났음을 발견하였다. 고정조건부 상관관계 분석에서 호주와 일본의 경우 양(+)의 상관계수를, 홍콩, 인도, 인도네시아, 한국, 싱가포르는 음(-)의 상관계수를 지니고 있었으며 금융위기를 지나며 음(-)의 상관계수를 지닌 국가는 더욱 강한 음(-)의 상관계수로, 양(+)의 상관계수를 지닌 국가는 더욱 강한 양(+)의 상관계수로 변화함을 발견하였다. This study investigates the return and volatility spillover effects and correlation between the exchange rate and stock price in asian markets(Australia, Hong Kong, India, Indonesia, Japan, Korea, Singapore) using the Bivariate VAR-EGARCH model and CCC method. The main results of this study can be summarized as follows. First, the returns spillover effects have influenced bi-directionally Australia, Hong Kong, Japan, Korea and Singapore, but directionally India and Indonesia. After the 2008 Global Financial Crisis, this phenomenon was strongly prominent in the return spillover effect. Second, volatility spillover effects have an effect on countries bi-directionally except for Korea and Singapore. Comparing the empirical results of the pre- and post Global Financial Crisis, it is observed that volatility spillover effects are also a lot of changes in the relation of the exchange rates and equity prices. Finally, countries with a positive correlations are strengthened as positive values. Also, Countries with negative correlations are strengthened as negative one.

Recommender Systems using SVD with Social Network Information

Min-Gun Kim(김민건),Kyoung-jae Kim(김경재) 한국지능정보시스템학회 2016 지능정보연구 Vol.22 No.4

협업필터링은 사용자의 선호도 평가자료를 이용하여 특정 사용자의 특정 상품에 대한 선호도를 예측하고 이를 이용하여 유사한 사용자에게 상품을 추천한다. 협업필터링은 전자상거래에서의 정보 과잉현상을 줄여 주기에 가장 인기 있는 개인화 기법이다. 그러나 협업필터링은 희소성과 확장성 문제 등을 가지고 있다. 본 연구에서는 희소성과 확장성 문제와 같은 협업필터링의 주요 한계점을 보완하고 추천과정에 사용자의 정성적이고 감성적인 정보를 반영하도록 하기 위하여 사회연결망 정보와 협업필터링을 접목하는 방안을 이용한다. 본 논문에서는 특이값 분해에 내재적인 정보를 반영할 수 있도록 확장한 SVD++에 사회연결망 정보를 고려할 수 있도록 한 Social SVD++ 알고리듬을 협업필터링에 접목한 새로운 추천 알고리듬을 이용한다. 특히, 본 연구는 추천과정에 실제 사용자의 사회연결망 정보를 반영하여 모형의 성과를 평가할 것이다. Collaborative Filtering (CF) predicts the focal user’s preference for particular item based on user’s preference rating data and recommends items for the similar users by using them. It is a popular technique for the personalization in e-commerce to reduce information overload. However, it has some limitations including sparsity and scalability problems. In this paper, we use a method to integrate social network information into collaborative filtering in order to mitigate the sparsity and scalability problems which are major limitations of typical collaborative filtering and reflect the user"s qualitative and emotional information in recommendation process. In this paper, we use a novel recommendation algorithm which is integrated with collaborative filtering by using Social SVD++ algorithm which considers social network information in SVD++, an extension algorithm that can reflect implicit information in singular value decomposition (SVD). In particular, this study will evaluate the performance of the model by reflecting the real-world user"s social network information in the recommendation process.

시간가변 장기기억 특성 분석: KOSPI 주요 산업지수 중심으로

김민건 ( Min Gun Kim ),강상훈 ( Sang Hoon Kang ) 한국금융공학회 2013 금융공학연구 Vol.12 No.1

구상흑연주철의 저주기 피로수명에 미치는 흑연입자수의 영향

김민건(Min Gun Kim),이병현(Byeong Hyeon Lee) 대한금속재료학회 ( 구 대한금속학회 ) 2002 대한금속·재료학회지 Vol.40 No.9

The behavior of crack nucleation and propagation during low cycle fatigue of ductile the cast irons with different nodule counts and similar nodule size have been compared. In spite of similar nodule size, the fatigue life of ductile cast iron with lower nodule count was longer than that with higher one. This fact shows that not only the nodule size but also the nodule count is the factor governing the fatigue life. Meanwhile, the crack nucleation density of the former was notably increased in the early stage of stress cycling, but the increasing rate was diminished greatly in the middle one. Therefore, difference in fatigue life of these specimens could not be explained with the crack nucleation behaviors only. The difference in fatigue life of these specimens can be explained by the easiness of crack coalescence which depends upon the nodule count. Consequently, the effect of the nodule count on the fatigue life was significant because of the importance of crack coalescence and propagation.