냉간압출에 의한 새로운 헬리컬기어의 제조에 관한 연구

崔載燦,趙海龍,權赫洪 부산대학교 공과대학 1991 工大論文集 Vol.42 No.-

A new helical gear forming process by cold extrusion was proposed and its numerical solution program based on the upper bound method was developed. In the analysis the involute curve was used as a shape of die and the upper bound method was used to calculate energy dissipation rate. By this method the power requirement and optimum conditions necessary for extruding helical gear were successfully calculated. These numerical solutions were in good agreement with experimental data. In the experiment, die life of a new was greatly improved compared with hat of Samanta process and 4~5 class helical gear of KS standard for automobile transmission was successfully manufactured.

冷間押出 헬리컬기어의 精密度 向上에 관한 硏究

崔載燦,權赫洪 부산대학교 공과대학 1992 工大論文集 Vol.44 No.-

A new extrusion process of helical gear was proposed and developed. For the manufacturing of extrusion die, and electrical discharge machining was applied, where an electrode for E.D.M has been designed by a developed CAD program. The precision of cold extruded gear is associated with the over-burn in E.D.M, lapping and elastic expansion of die etc., so it can be improved by proper compensation about them in die manufacturing. In the experiment, tolerances of shaved gears after extruded fell within 4~5 class KS standard. Therefore, the cold extrusion process can be used as an advanced technique to replace the conventional hobbing process.

장애인 엘리트체육의 실태 분석

최승권,이인경,문준혁,임찬규,한동기,김권일 한국특수체육학회 2005 한국특수체육학회지 Vol.13 No.1

The purposes of this study are to analyze actual status of elite sports for athletes with disabilities through investigating factors such as athletes constitutions, levels of game performance, and administrative and supporting organizations, which are critical bases for establishing the policy of elite sports for athletes with disabilities. The contents and scopes are as followings. First, analyzing composition of elite athletes with disabilities and current status of sports associations/federations. Second, analyzing the levels of game performance of elite sports for athletes with disabilities(Far East and South Pacific Games for the disabled, and Paralympics). Third, analyzing the support system such as administrative organization and support for athletes, leadership training, and financial support. Forth, analyzing survey on attitude and needs for elite sports of athletes with disabilities. Literature reviews, site visits, and survey were used to analyze the current status of elite sports for athletes with disabilities in Korea. The following outcomes were driven. First, this study revealed fewer numbers of sports federations, unbalanced composition of athletes in events, sex, and ages, and aging compared to international events and games. Second, this study revealed low performance level in team sports overall, and international competitive abilities but shooting, weight lifting, and archery were shown to be low. Third, this study revealed the weak establishment of administrative and financial supporting system.

冷間押出用 헬리컬기어 金型의 强度解析

崔載燦,權赫洪,辛榮柱 부산대학교 공과대학 1992 工大論文集 Vol.44 No.-

In forging die design, pre-stressing is useful in preventing excessive tensile circumferential stresses which may cause die failure during forming. The finite element analysis (F.E.A.) package ANSYS reversion 4.4 A was used to this study. F.E.A., that is, static analysis was accomplished for insert-dies of helical gear. Die model was constructed with 8 node isoparametric solid finite elements. Static load analysis was performed for internal and outer pressure. Also, stress distribution and deformed shapes are shown. To assure durability and reliability, failure analysis was calculated by maximum normal stress theory and distortion energy theory. Results of the F.E. analysis and failure analysis for Samanta and new process dies were compared. The results of F.E. Analysis were in good agreement with that of experimental results. It is expected that the results of this study can be applied to designing various kinds of extrusion gear die.

부분입체선택적 Zwitterionic Claisen 전위반응

柳燦模,崔夏洵,李宗昊,鄭元爀 성균관대학교 기초과학연구소 1995 論文集 Vol.46 No.2

Aza-Claisen rearrangement through the zwitterionic intermediate is described. This reaction was able to carry out at low temperature(-78∼0℃) and also exhibited high diastereoselectivities. The formation of zwitterionic intermediate was realized by addition of t-crotylamine to the ketene formed from deprotonation of corresponding acyl halide. The electronically neutral product was achieved through the [3,3]-sigmatropic rearrangement of self-promoted zwitterionic intermediate in high diastereoselectivity due to lower reaction temperature. Treatment of N-crotylpiperidine with propionyl chloride in the presence of K_2CO_3 at 0℃ for 1 h gave threo selective(97 : 3) amide in 41% isolated yield.

선인장 양심실 보조장치의 설계 및 임상적용을 위한 평가

민병구,박찬영,최재순,이혁수,황창모,김삼성,윤걸중,김종원,선경,이경갑,정종태,김원곤 제주대학교 인공심장이식연구소 2001 인공심장 연구 Vol.2 No.1

현재 개발되고 있는 맥동형 이식형 인공심장은 완전이식형 인공심장과 좌심실보조장치 뿐이다. 좌심실보조장치를 장착한 환자의 10~15%가 우심실의 보조를 필요로하고 완전이식형 인공심장의 장착을 위해서는 자연심장을 제거해야하는 상황에서 이식형 양심실보조장치에 대한 필요성이 대두되고 있다. 본 연구진은 완전이식형 인공심장으로 개발된 한국형 인공심장을 개선하여 양심 실 보조장치를 개발하였다. 양심실보조장치는 이동형 작동기식 미케니즘을 이용하고 있으며 에너지 변환장치와 감속기로 구성된 작동기와 혈액주머니, 그리고 내장형 제어기로 구성되어 있다. 선인장 펌프로 명명된 KAH350은 캐뉼라의 연결을 위한 커넥터를 포함하여 길이 177mm, 폭 164mm, 높이 67 이고 무게 780g이며 최대 심박출량은 5L/min 이다. 양심실보조장치로 개발된 선인장펌프는 좌심실보조장치로도 응용이 가능하다. 이식적합성과 생체적합성을 평가하기 위하여 좌심실보조장치로 5회, 양싱실보조장치로 6회의 동물실험을 수행하였다. 각각 최장 28일간 생존하였으며 11회의 동물실험중 장치의 결함에 의한 것이 3회 있었는데 이들은 모두 전자장치의 결함과 방수처리문제였다. 현재 이식적합성과 일박출량을 향상시킨 KAH400모델이 개발중이다. The types of pulsatile implantable artificial hearts that are on the way of development and have been developed are totally implantable artificial heart and implantable left ventricular assist device (LVAD). Approximately 10% to 15% of all patients Implanted with wearable VADs have required right heart support with another device. And it is reluctant to patient who should remove his or her own heart to be implanted with total artificial heart. These situations drive the development of implantable bi-ventricular assist device (BVAD). The Korean BVAD was develophed by modifying the moving actuator type Korean artificial heart. This electro-mechanical BVAD comprises actuator including energy converter and reduction gear train, blood sacs, and internal motor and energy controllers. The KAH350 which is named as 'Cactus Pump' is 177mm in length, 164mm in width, and 67mm in thickness including connectors and nuts. The weight and maximum cardiac output of Cactus Pump is 780g and 5L/min, respectively. The Cactus Pump that was developed as BVAD could be used as LVAD by attaching compliance caps on the 2 ports of one ventricle. The animal experiments were undergone 5 times for LVAD, and 6 times for BVAD. The best records were 28 days survival in both applications. There were 3 times of device failure and they were all associated with electrical connection and hermetic sealing. The KAH400 that has improved anatomical fitting characterisitcs and stroke volume is on development.

지속성 외래복막투석 환자들의 예후에 영향을 미치는 요인들에 관한 고찰

권혁만,김찬덕,조지형,장민화,최혁준,이현철,박자용,박선희,김용림 대한신장학회 2004 대한신장학회잡지 Vol.23 No.2

Effect of Pulsing on SiO₂ Etching using C₄H₂F<SUB>6</SUB> and C₄F<SUB>8</SUB> in CCP System

Chan-hyuk Choi,Hyunwoo Tak,Dain Sung,Seongbae Kim,Seulki Kim,Sangyeob Lee,Mincheol Park,Donghyun Park,Dongwoo Kim,Geunyoung Yeom 한국표면공학회 2023 한국표면공학회 학술발표회 초록집 Vol.2023 No.11-1

Clinical practice guideline for endoscopic resection of early gastrointestinal cancer

( Chan Hyuk Park ),( Dong-hoon Yang ),( Jong Wook Kim ),( Jie-hyun Kim ),( Ji Hyun Kim ),( Yang Won Min ),( Si Hyung Lee ),( Jung Ho Bae ),( Hyunsoo Chung ),( Kee Don Choi ),( Jun Chul Park ),( Hyuk L 대한장연구학회 2021 Intestinal Research Vol.19 No.2

Although surgery was the standard treatment for early gastrointestinal cancers, endoscopic resection is now a standard treatment for early gastrointestinal cancers without regional lymph node metastasis. High-definition white light endoscopy, chromoendoscopy, and image-enhanced endoscopy such as narrow band imaging are performed to assess the edge and depth of early gastrointestinal cancers for delineation of resection boundaries and prediction of the possibility of lymph node metastasis before the decision of endoscopic resection. Endoscopic mucosal resection and/or endoscopic submucosal dissection can be performed to remove early gastrointestinal cancers completely by en bloc fashion. Histopathological evaluation should be carefully made to investigate the presence of risk factors for lymph node metastasis such as depth of cancer invasion and lymphovascular invasion. Additional treatment such as radical surgery with regional lymphadenectomy should be considered if the endoscopically resected specimen shows risk factors for lymph node metastasis. This is the first Korean clinical practice guideline for endoscopic resection of early gastrointestinal cancer. This guideline was developed by using mainly de novo methods and encompasses endoscopic management of superficial esophageal squamous cell carcinoma, early gastric cancer, and early colorectal cancer. This guideline will be revised as new data on early gastrointestinal cancer are collected. (Intest Res 2021;19:127-157)

Effect of αGal on corneal xenotransplantation in a mouse model

Choi, Hyuk Jin,Kim, Mee Kum,Lee, Hyun Ju,Jeong, So Hee,Kang, Hee Jung,Park, Chan‐,Sik,Park, Chung‐,Gyu,Joon Kim, Sang,Wee, Won Ryang Blackwell Publishing Ltd 2011 Xenotransplantation Vol.18 No.3

<P>Choi HJ, Kim MK, Lee HJ, Jeong SH, Kang HJ, Park C‐S, Park C‐G, Kim SJ, Wee WR. Effect of αGal on corneal xenotransplantation in a mouse model. Xenotransplantation 2011; 18: 176–182. © 2011 John Wiley & Sons A/S.</P><P><B>Abstract: </B><B> Background: </B> It has been reported that hyperacute rejection (HAR) does not occur after pig‐to‐nonhuman corneal xenotransplantation. However, considering that immune privilege is already disrupted in most human corneal recipients, and the expression of αGal can be gradually reduced after pig‐to‐rat corneal transplantation, the long‐term survival of corneal grafts from wild‐type pigs cannot be guaranteed. Accordingly, we aimed to investigate the effect of αGal on the change in anti‐Gal antibodies, using sensitized α1,3‐galactosyltransferase gene‐knockout (GTKO) mice recipients.</P><P><B>Methods: </B> C57BL/6 (B6) and GTKO mice were divided into 5 groups and underwent orthotopically full thickness cormeal transplantation as follows (n=4 for each group): (1) group 1: B6 to B6; (2) group 2: fresh porcine posterior corneal lamella to B6; (3) fresh porcine posterior corneal lamella to GTKO; (4) group 4: decellularized porcine posterior corneal lamella to GTKO, and (5) group 5: B6 to GTKO. Before transplantation, all GTKO recipients were sensitized using intraperitoneal injections of rabbit blood cells. Median survival times (MST) for the corneal grafts of the different groups were compared and plasma concentrations of IgG/IgM anti‐Gal antibodies were evaluated at 1 week, 2 weeks and 3 weeks post‐transplantation.</P><P><B>Results: </B> There were no differences in MSTs between groups. Although there was no HAR of fresh porcine posterior corneal grafts even in sensitized GTKO recipients, αGal expression was induced in the transplanted fresh porcine corneal grafts and plasma concentration of IgG anti‐Gal antibody was gradually increased in fresh porcine cornea‐grafted GTKO recipients. On the contrary, αGal expression did not increase in the grafts and plasma concentration of anti‐Gal antibodies did not change after transplantation using decellularized porcine corneas.</P><P><B>Conclusions: </B> Our findings suggest that αGal may affect the long‐term survival of porcine corneal xenografts via antibody‐mediated rejection, although αGal does not have an effect on acute rejection and decellularized porcine corneas may enable the long‐term survival of porcine corneal xenografts.</P>