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차체 판넬 스템핑 공정에서 동적-외연적 유한요소법을 이용한 성형해석에 관한 연구
정동원,황재신,Jung, Dong-Won,Hwang, Jae-Sin 한국기계가공학회 2004 한국기계가공학회지 Vol.3 No.4
In this paper, a finite element formulation using dynamic-explicit time integration scheme is used for numerical analysis of auto-body panel stamping processes. The lumping scheme is employed for the diagonal mass matrix and dynamic explicit formulation. Auto-body panel forming is analyzed by using dynamic-explicit finite element method. Further, the simulated results of the auto-body panel stamping processes are shown and discussed. Its application is being increased especially in the stamping industrial area for the cost reduction, weight saving, and improvement of strength.
탄소나노튜브에 담지된 PtCo 촉매 제조 및 PEMFC Cathode 전극 특성
정동원,박순,강정탁,김준범,Jung, Dong-Won,Park, Soon,Kang, Jung-Tak,Kim, Jun-Bom 한국재료학회 2009 한국재료학회지 Vol.19 No.5
The electrocatalytic behavior of the PtCo catalyst supported on the multi-walled carbon nanotubes (MWNTs) has been evaluated and compared with commercial Pt/C catalyst in a polymer electrolyte membrane fuel cell(PEMFC). A PtCo/MWNTs electrocatalyst with a Pt:Co atomic ratio of 79:21 was synthesized and applied to a cathode of PEMFC. The structure and morphology of the synthesized PtCo/MWNTs electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. As a result of the X-ray studies, the crystal structure of a PtCo particle was determined to be a face-centered cubic(FCC) that was the same as the platinum structure. The particle size of PtCo in PtCo/MWNTs and Pt in Pt/C were 2.0 nm and 2.7 nm, respectively, which were calculated by Scherrer's formula from X-ray diffraction data. As a result we concluded that the specific surface activity of PtCo/MWNTs is superior to Pt/C's activity because of its smaller particle size. From the electrochemical impedance measurement, the membrane electrode assembly(MEA) fabricated with PtCo/MWNTs showed smaller anodic and cathodic activation losses than the MEA with Pt/C, although ohmic loss was the same as Pt/C. Finally, from the evaluation of cyclic voltammetry(CV), the unit cell using PtCo/MWNTs as the cathode electrocatalyst showed slightly higher fuel cell performance than the cell with a commercial Pt/C electrocatalyst.
다중벽 탄소 나노 튜브에 담지한 Pt<sub>x</sub>M<sub>(1-x)</sub>(M = Co, Cu, Ni) 합금촉매의 제조 및 고분자 전해질 연료전지에서 산소환원 특성
정동원,박순,안치영,최성호,김준범,Jung, Dong-Won,Park, Soon,Ahn, Chi-Yeong,Choi, Seong-Ho,Kim, Jun-Bom 한국재료학회 2009 한국재료학회지 Vol.19 No.12
The electrocatalytic characteristics of oxygen reduction reaction of the $PtxM_{(1-x)}$ (M = Co, Cu, Ni) supported on multi-walled carbon nanotubes (MWNTs) have been evaluated in a Polymer Electrolyte Membrane Fuel Cell (PEMFC). The $Pt_xM_{(1-x)}$/MWNTs catalysts with a Pt : M atomic ratio of about 3 : 1 were synthesized and applied to the cathode of PEMFC. The crystalline structure and morphology images of the $Pt_xM_{(1-x)}$ particles were characterized by X-ray diffraction and transmission electron microscopy, respectively. The results showed that the crystalline structure of the Pt alloy particles in Pt/MWNTs and $Pt_xM_{(1-x)}$/MWNTs catalysts are seen as FCC, and synthesized $Pt_xM_{(1-x)}$ crystals have lattice parameters smaller than the pure Pt crystal. According to the electrochemical surface area (ESA) calculated with cyclic voltammetry analysis, $Pt_{0.77}Co_{0.23}$/MWNTs catalyst has higher ESA than the other catalysts. The evaluation of a unit cell test using Pt/MWNTs or $Pt_xM_{(1-x)}$/MWNTs as the cathode catalysts demonstrated higher cell performance than did a commercial Pt/C catalyst. Among the MWNTs-supported Pt and $Pt_xM_{(1-x)}$ (M = Co, Cu, Ni) catalysts, the $Pt_{0.77}Co_{0.23}$/MWNTs shows the highest performance with the cathode catalyst of PEMFC because they had the largest ESA.
상황 인지(Situation-Aware) RFID 시스템 아키텍처
정동원,인호,Jung, Dong-Won,In, Ho 한국통신학회 2004 정보와 통신 Vol.21 No.6
RFID(Radio Frequency IDentification)는 무선주파수를 이용하여 비접촉 정보 액세스(읽기)를 가능하게 하며 인간의 개입 없이 원거리 모니터링 및 트랜잭션 처리를 지원해 준다. 이러한 RFID는 현재 교통, 전자화폐, 물류 등의 분야에서 다양한 용도로 사용되고 있다[1, 2, 8]. 향후 컴퓨팅 패러다임의 변화와 기술의 발전은 현재의 RFID 시스템에 대한 보다 광범위하고 폭넓은 활용성을 요구하게 될 것이다.(중략)
무선 센서 네트워크에서 신뢰성 향상을 위한 효율적인 체크포인트 프로토콜
정동원,최창열,김성수,Jung, Dong-Won,Choi, Chang-Yeol,Kim, Sung-Soo 한국정보처리학회 2006 정보처리학회논문지 C : 정보통신,정보보안 Vol.13 No.5
유비쿼터스 환경에서 정확한 데이터를 얻기 위해, 무선 센서 네트워크의 신뢰성은 필수적이다. 이것을 위해, 롤백 기술을 통한 자가 치유는 신뢰성 향상에 도움을 준다. 하지만, 로컬 시스템만을 고려한 기존 롤백 기술은 무선 센서 네트워크에서 자칫 전체 시스템 차원의 결함을 발생시킨다. 따라서, 롤백 기술을 무선 네트워크 차원으로 지원하기 위해 체크포인트 프로토콜이 제시되었다. 하지만, 무선 센서 네트워크가 가지고 있는 특유의 제한 조건 때문에 각각의 프로토콜들은 메모리, 성능, 그리고 전력 소모 효율에 있어서 상충관계가 존재한다. 따라서, 본 논문에서는 주소 기록 기반 프로토콜(address log based protocol, ALBP)이라 불리는 새로운 프로토콜을 제시한다. 이 기법은 비동기 방식을 지원하는 플랫폼 기반의 프로토콜로, 무선 센서 네트워크에서 중요한 고려사항인 전력 소모량, 메모리 사용량, 그리고 마감시간을 맞추기 위한 빠른 응답시간을 만족시킬 수 있다. The reliability concept of wireless sensor network is essential to get exactly actual data from the ubiquitous environment. A rollback technique for the self-healing helps to increase it. However, a fault can occur in wireless sensor network when to use a previous rollback technique because it is designed just for the local system. So, checkpoint protocols are suggested in order to use a rollback technique in the network without the fault. However, there is trade-off among performance overhead, power consumption, and memory overhead for each of protocols. Hence, we suggest a novel global checkpoint protocol, so called address log based protocol(ALBP), based on an asynchronous protocol. It is a platform based protocol to reduce power consumption, performance overhead, and memory overhead which are the most of consideration in wireless sensor network.
정동원,임세영,Jung, Dong-Won,Lim, Sae-Young 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.11
A finite element anlaysis is performed for large deformations of a felxible beam. The total Lagrangian formulation for a general large deformation, which involves finite rotations, is chosen and the exponential map is used to treat finite rotations from the Eulerian point of view. The finite elements results are confirmed for several cases of deformations through comparison to a first order elasticity solution obtained by numerical integration, and the agreement between the two is found to be excellent. For lateral buckling, the point of vanishing determinant of the resulting unsymmetric tangent stiffness is traced to examine its relationship to bifurcation points. It is found that the points of vanishing determinant is not corresponding to bifurcation points for large deformation in general, which suggests that the present unsymmetric tangent stiffness is not an exact first derivative of internal forces with respect to displacement.
중풍 후 언어 장애에 대한 ☐☐의부집성(醫部集成)☐☐의 침구치료 고찰
정동원,민인규,문상관,나병조,홍진우,박성욱,정우상,박정미,고창남,조기호,배형섭,김영석,Jeong, Dong-won,Min, In-kyu,Moon, Sang-kwan,Na, Byong-jo,Hong, Jin-woo,Park, Seong-uk,Jung, Woo-sang,Park, Jung-mee,Ko, Chang-nam,Cho, Ki-ho,Bae, Hyung- 대한중풍순환신경학회 2007 대한중풍.순환신경학회지 Vol.8 No.1
Objectives and methods : The Euibujipsung is one of the huge-scale encyclopedias about Oriental Medicine. To search the most frequently used aupoints for dysarthria after stroke, we used Euibujipsung CD-ROM database with several chinese character keyword concerned with vernal function(語, 言, 音, 啞, 瘖, etc). Results : We found four popular acupoints(PC5, GV20, GV16, TE6), and five meridians (Governor vessel, Gall Bladder, Heart, Large Intestine and Triple Energizer). We also found that the extra meridians were used more frequently than other type of meridians. Conclusion : We think that these findings can give further ideas to clinical practice and research fields for stroke rehabilitation in Oriental medicine.
중풍 후 운동 장애에 대한 『의부집성(醫部集成)』의 침구치료 고찰
정동원,민인규,문상관,박성욱,정우상,박정미,고창남,조기호,배형섭,김영석,Jeong, Dong-won,Min, In-kyu,Moon, Sang-kwan,Park, Seong-uk,Jung, Woo-sang,Park, Jung-mee,Ko, Chang-nam,Cho, Ki-ho,Bae, Hyung-sup,Kim, Young-suk 대한중풍순환신경학회 2006 대한중풍.순환신경학회지 Vol.7 No.1
Objectives and methods : The Euibujipsung is the one of the huge-scale encyclopedias about Oriental Medicine. To investigate the most frequently used acupoints for hemiparesis after stroke, we used Euibujipsung CR-ROM database with several key words concerned with motor weakness (半身不遂 不遂不隨 癱瘓 中臟 中腑 風痱, etc.). Results : In the result, we found five popular acupoints (GV20, LI11, LI15, ST36 and GB39), and four meridians (Stomach, Gall bladder, Large intestine and Small intestine). We also found that the Yang meridians were cited more frequently than the Yin. Conclusion : Therefore we think that these findings can give further ideas to clinical practice and research fields for stroke rehabilitation in Oriental medicine.
차체판넬 스템핑공정의 동적 외연적해석과 동적해석에 미치는 영향인자 분석
정동원,Jung, Dong-Won 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.2
In the present work a finite element formulation using dynamic explicit time integration scheme is used for numerical analysis of auto-body panel stamping processes. The lumping scheme is employed for the diagonal mass matrix and linearizing dynamic formulation. A contact scheme is developed by combining the skew boundary condition and direct trial-and-error method. In this work, for economic analysis the faster punch velocity and the mass scaling method are introduced. To investigate the effects of punch velocity and mass scaling, the various values of punch velocity and the various mass scalings are used for numerical analysis. Computations are carried out for analysis of complicated auto-body panel stamping processes such as forming of an oil pan and a fuel tank.
Multi-Stage 조립품인 캔-용기 생산 공정에서 동적-외연적 유한요소법을 이용한 성형해석에 관한 연구
정동원,황재신,Jung, Dong-Won,Hwang, Jae-Sin 한국기계가공학회 2004 한국기계가공학회지 Vol.3 No.3
In the present work a finite element formulation using dynamic-explicit time integration scheme is used for numerical analysis of multi-stage stamping processes. The lumping scheme is employed for the diagonal mass matrix and dynamic explicit formulation Multi-Stage stamping is analyzed by using dynamic-explicit finite element method. Further, the simulated results for the panel stamping processes are shown and discussed. Its application is being increased especially in the stamping industrial area for the cost reduction, weight saving, and improvement of strength.