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자동차 개발과정에서 적용될 수 있는 Virtual Engineering 기술
최원철(Woncheol Choi) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_2
Virtual engineering is simulations of engineering activity performed in virtual environment to assist engineering decisions and controls. Virtual engineering can help bringing the detailed design to the early stage of product development. Thus, virtual engineering can be a critical tool for shortening product development schedule. Currently some advanced automobile companies such as chrysler have been actively employ virtual engineering in their product development, and reported a drastic improvement in product development time. In order to complete in the world market, Korean automaobile companies also need to employ virtual engineering. There are several obstacles for Korean automobile to overcome in the Processes of reaching to virtual engineering .The most important one is that they need to employ a master CAD model that can be used for geometric design, CAE analysis, and simulations.<br/>
최원철(Woncheol Choi),김정섭(Jungsub Kim),정판근(Pankeun Jeong),천건희(Geonhee Cheon),홍종빈(Jongbin Hong) 한국자동차공학회 2017 한국자동차공학회 학술대회 및 전시회 Vol.2017 No.11
The purpose of this study is that the optimal bead structure is apply for cowl cross member have steel material to increase the stiffness performance through the optimization analysis. Firstly, to determine the bead shape, modal and structural analysis of many bead shape types were carried out and the optimal bead shape was selected. Secondly, in order to analyze the influence of the design factors about selected bead shape, bead optimization analysis was carried out considering main effect of each design factors such as bead height and width. In addition, the bead shape has optimal design factors was applied in the stiffness weak areas of the conventional type. Finally, to check reliability about increase the stiffness performance, modal and structural analysis of cowl cross members were carried out and it was possible to check increase the stiffness performance and the same level of weight as the conventional type.
Choi, Yoon Jin,Kim, Nayoung,Jang, Woncheol,Seo, Bochang,Oh, Sooyeon,Shin, Cheol Min,Lee, Dong Ho,Jung, Hyun Chae Williams & Wilkins Co 2016 Medicine Vol.95 No.20
<▼1><P>Supplemental Digital Content is available in the text</P></▼1><▼2><P><B>Abstract</B></P><P>This comprehensive cross-sectional study aimed to identify factors contributing to familial aggregation of gastric cancer (GC). A total of 1058 GC patients and 1268 controls were analyzed separately according to the presence or absence of a first-degree relative of GC (GC-relative). Logistic regression analysis adjusted for age, gender, residence during childhood, smoking, alcohol intake, monthly income, spicy food ingestion, <I>Helicobacter pylori</I> status and host cytokine polymorphisms was performed. Cytotoxin-associated gene A (<I>cagA</I>) positivity was a distinctive risk factor for GC in the family history (FH)-positive group (odds ratio [OR], 2.39; 95% confidence interval [CI], 1.42–4.00), while current/ex-smoker, moderate to strong spicy food ingestion, and non-B blood types were more closely associated with GC in the FH-negative group. Among the FH-positive group, alcohol consumption showed a synergistic carcinogenic effect in the at least 2 GC-relatives group compared to the 1 GC-relative group (1.71 vs. 9.58, <I>P</I> for interaction = 0.026), and this was dose-dependent. In the subjects with ≥2 GC-relatives, <I>TGFB1</I>-509T/T was a risk factor for GC (OR 23.74; 95% CI 1.37–410.91), as were rural residency in childhood, alcohol consumption, spicy food ingestion, and <I>cagA</I> positivity. These results suggest that subjects with FH may be a heterogeneous group in terms of gastric cancer susceptibility. Especially, subjects with ≥2 GC-relatives should undergo risk stratification including <I>TGFB1</I>-509T/T and alcohol consumption.</P></▼2>
Purification and Biocompatibility of Fermented Hyaluronic Acid for Its Applications to Biomaterials
최성철,Woncheol Choi,Sekweon Kim,Su Yeon Lee,노인섭,김찬화 한국생체재료학회 2014 생체재료학회지 Vol.18 No.2
Background: Hyaluronic acid (HA) is of importance due to its diverse applications in pharmaceuticals and medical devices such as dermal filler, adhesion barriers, carrier for cells and bioactive molecules as well as scaffold biomaterials for tissue engineering. Evaluations of purification and biocompatibility of HA are required for its applications to biomaterials. Methods: After synthesizing HA by fermentation of streptococcus zooepidemicus for 25 hr, extensively purification of the fermented broth was performed to remove impurities using a filtration process for insoluble components and cells, and diverse adsorbents for soluble impurities. Its in vitro biocompatibility has been evaluated by measurement of cell counting and assay of cell live and dead. Results: 60% yield of white HA powder was obtained, having 15-17 dL/g intrinsic viscosity with a molecular weight of approximately 1,000 kDa. While low molecular weight impurities and insoluble impurities were successfully removed using a ultrafiltration membrane with 50 KDa molecular weight cut, endotoxins, high molecular weight proteins and nucleic acids were removed from the broth by employing adsorbents such as alumina and activated carbons. Alumina showed the best results for the removal of endotoxins, all of the activated carbons were very effective in the removal of high molecular weight proteins and nucleic acids. The purified HA solution showed excellent cell compatibility with no cell damages as observed by both measurement of cell proliferation and observation of cell viability. Conclusions: We obtained high molecular weight HA with excellent biocompatibility as judged by both measurement of cell proliferation and viability, indicating high possibility of its applications to biomaterials.