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송영기,서성재 ( Y . K . Song,S . Suh ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.3
Laser hardening for the piston ring groove of ductile cast iron was tried. Mechanical and microstructural investigation for the hardened area indicated that the laser heating technique could replace conventional induction hardening process completely and further showed that post grinding process would be eliminated by minimizing bulging of heat treated area. In laser hardening, the volume increase caused by martensitic phase transformation proved to be less than 10㎛, which insures no post machining on the hardened surface. As expected, the depth of hardening was inversely proportional to the beam scanning velocity and the highest surface hardness was obtained at the beam velocity of 0.75m/min. Heat treatment using phosphate coating demonstrated quite comparable result to the case of graphite suscepter.
류주현,서성재,Ryu, Ju-Hyeon,Seo, Seong-Jae The Korean Institute of Electrical Engineers 1999 전기학회논문지C Vol.48 No.9
Piezoelectric properties of PMN-PZT ceramics with $CeO_2$ impurity were investigated. Mechanical quality factor, $Q_m$ of 1792, 1285 and the electromechanical coupling coefficient, $k_p$ of 0.52, 0.54 were obtained from the specimen with 0.25 and 0.5 mole % $CeO_2$ respectively. Curie temperature was decreased with the addition of $CeO_2$ while the electric coercive field was proportional to the amount of impurity. Based on the system ceramics with 0.5 mole % cerium oxide, a Rosen type piezoelectric transformer was fabricated and tested. Voltage step-up ratios of 230 and 13 were obtained from the transformer at no load and $100 k\Omega$ resistance, respectively. Experimental results showed a potential of the transformer for the practical use coupled with the expected strength increase by the grain size refinement.
조현수,서성재 대한용접접합학회 1997 대한용접·접합학회지 Vol.15 No.6
Friction welding technique was studied to weld the turbine wheel and shaft of a turbocharger. The welding parameters were selected to investigate the effects of variables on welding quality of Inconel 713C and SCM 440. Experimental results showed that the turbine wheel and shaft could be successfully welded by friction welding. The heat affected zone was identified to be 2 mm from the weld seam. After welding, the hardness profile was found to have sudden increase and decrease for inconel 713C and SCM 440 respectively. Tensile strength of welded specimens was higher than the required strength for all of the studied welding parameters. The central portion of fracture surfaces by bending had no defects such as crack.
결정립 조대화된 기계적 합금화 ODS NiAl의 Creep 성질
어순철,서성재,Eo, Sun-Cheol,Seo, Seong-Jae 한국재료학회 1997 한국재료학회지 Vol.7 No.11
NiAI기 산화물 분산강화(Oxide Dispersion Strengthende:ODS)합금을 기계적 합금화 (Mechanical Alloying: MA)방법으로 제조하였으며, 열간압축방법으로 성형하였다. 연이어 단순항온처리에 의한 정상결정립성장과 특성조건에서의 thermomechanical treatment 에 의한 이차재결정화를 유도하였다. 결정립 조대화된 ODSD MA NiAI의 creep 성질 및 이에 조대화된 미세조직은 creep 성질이 저하된 반면, 이차재결정화된 MA NiAI의 creep성질은 크게 향상되었다. 이 creep 성질의 향상은 이차재결정화의 특성인 급격한 결정립의 조대화, 분산상의 성장억제 및 grain aspect ratio의 증가에 기인한 것으로 사료되었다. 이차재결정화된 ODS MA NiAI의 creep또는 glide controlled dislocation creep임을 제시하지만, 전체 creep속도가 결정립 크기 및 grain aspect ratio의 영향을 크게 받은 것을 볼 때, 결정립계 미끄럼기구가 주 creep 기구와 조합되어 MA NiAI의 전체 creep기구에 영향을 준 것으로 추정할 수 있었다.
PSN-PZT계 세라믹스를 이용한 고출력 압전 트랜스포머의 전기적 특성
이용우,류주현,윤광희,정회승,서성재,김종선 한국전기전자재료학회 2000 전기전자재료학회논문지 Vol.13 No.4
In this paper we investigated the structural dielectric and piezoelectric properties of 0.03Pb(Sb$\_$1/2//Nb$\_$1/2/)-0.97Pb(Zr$\_$0.495//Ti$\_$0.505/)O$_3$+0.5 wt% excess PbO + wt% MnO(X=0, 0.1, 0.3, 0.5, 0.7) ceramics to develop the high-power piezoelectric transformer. The piezoelectric transformers with dimension of 27.5$\times$27.5$\times$2.5[mm$^3$]were fabricated and their electrical properties were measured. Maxima of piezoelectric properties such as electro-mechanical coupling factor of 0.534 and mechanical quality factor of 1487 were obtained for the PSN-PZT with 0.3wt% MnO. voltage step-up ratios of piezoelectric transformers at 500[Ω]and no load were 0.78, 12.82, respectively. The maximum efficiency of piezoelectric transformer was 98.6% at 800[Ω]. While the 14W fluorescent lamp were driven by the piezoelectric transformer for more than 20[min], increment of temperature in the piezoelectric transformer was 7[$\^{C}$].
PSN-PMN-PZT 세라믹스의 Zr/Ti 비에 따른 전기적 특성과 공진주파수의 온도안정성
류주현,윤광희,민석규,이명수,서성재 한국전기전자재료학회 2000 전기전자재료학회논문지 Vol.13 No.8
In this study the temperature coefficient of resonant frequency(TC $F_{r}$) dielectric and piezoelectric properties of Pb[(S $b_{1}$2//N $b_{1}$2/)$_{0.065}$)-(Z $r_{x}$, $Ti_{1-x}$ )$_{0.90}$] $O_3$ceramics were investigated with Zr/Ti ratio. The compositions near the morphotropic phase boundary (MPB) appeared when Zr/Ti ratio was 49.5/50.5 The dielectric constant and electromechanical coupling factor( $k_{p}$) also showed the highest values of 1,257, 0.653 respectively when the Zr/Ti ratio was 49.5/50.5 Moreover the mechanical quality factor( $Q_{m}$) showed th lowest value of 713 when the Zr/Ti ratio. The temperature coefficient of resonant frequency(TC $F_{r}$) abruptly change at the morphotropic phase boundary(MPB) which existed between the rhombohedral phase with highly negative TC $F_{r}$ of -106ppm/$^{\circ}C$ and the tetragonal phase with highly positive TC $F_{r}$ of +64pp $m^{\circ}C$ as Zr/Ti ratio varied from 50/50 to 49.5/50.5.50.5..50.5.
뇌졸중 후 편마비 환자에게 적용된 과제지향훈련 효과의 체계고찰 연구
송보경 ( Bo-kyung Song ),김아란 ( Ah-ran Kim ),김준수 ( Jun-soo Kim ),서성재 ( Sung-jae Seo ),손준희 ( Jun-hee Son ),신희덕 ( Hee-duck Shin ),정지원 ( Ji-won Jung ),양병일 ( Byung-il Yang ) 대한신경치료학회 2019 신경치료 Vol.23 No.2
Purpose The purpose of this study is to analyze the functional improvement through task-oriented training of stroke patients and to suggest the clinical application effect of task-oriented training through systematic review. Methods From the period of 2011 to 2016, we searched the papers which received the original text downloading service among domestic journals and theses published in e-journals. Major search terms were “task-oriented” by searching “stroke” A total of 108 papers were searched by using appropriate combinations of the words “upper extremity”, “lower extremity”, “gait”, “mental”, “sense” and “Seventeen papers were selected for inclusion and exclusion criteria. Results A total of 17 studies were classified according to body function and task performance included in the framework of occupational therapy execution system. The results were as follows: 10 studies (58.8%) on neuromuscular movement, 2 (11.8%), and 5 (29.4%) were related to daily life activities. The results of the study showed that task-oriented training was effective in improving the function of stroke patients. Conclusion Task-oriented training showed a positive change in functional recovery of stroke patients, suggesting that task-oriented training is needed for stroke patients. Therefore, in future research, it is necessary to study the task-oriented training development of stroke patients. Based on this, we will give how clinicians help occupational performance and body functions through more systemic review, and will be able to suggest evidences future intervention direction for patients following intervention effect.