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전계 인가에 따른 PLZT 강유전체의 유전특성 및 전기열량 효과
김유석,류주현,정영호,Kim, You-Seok,Yoo, Ju-Hyun,Jeong, Yeong-Ho 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.3
In this study, in order to develop relaxor ferroelectric ceramics for refrigeration device application with large electrocaloric effect, PLZT(8/65/35) composition was fabricated using conventional solid-state method. The Curi temperature of this composition PLZT ceramics was $230^{\circ}C$, and the P-E hysteresis loops of the PLZT ceramics as a fuction of temperature became slim by degrees with higher temperatures. The maximum value of ${\Delta}T$ of $0.243^{\circ}C$ in ambient temperature of $215^{\circ}C$ with 30 kV/cm was appeared. It is considered that PLZT ceramics possess the possibility of refrigeration device application.
PLZT(8/65/35) 세라믹스의 소결온도에 따른 유전 및 전기열량 특성
김유석,한종대,류주현,정영호,Kim, You-Seok,Han, Jong-Dae,Yoo, Ju-Hyun,Jeong, Yeong-Ho 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.10
In this study, in order to develop relaxor ferroelectric ceramics for refrigeration device application with large electrocaloric effect and low sintering temperature, PLZT(8/65/35) ceramics was fabricated using conventional solid-state method with the variation of sintering temperature ($1,050^{\circ}C$, $1,100^{\circ}C$, $1,200^{\circ}C$). The XRD pattern of all specimens indicated general perovskite structure with secondary phase. From the results of temperature dependence of dielectric constant, the $T_C$ (ferroelectric-paraelectric phase transition temperature) was shifted toward high temperature with increasing sintering temperature. When the specimen was sintered at $1,100^{\circ}C$, the optimal value of ${\Delta}T{\sim}0.349^{\circ}C$ in ambient temperature of $215^{\circ}C$ was appeared. It is considered that PLZT(8/65/35) ceramics possess the possibility of refrigeration device application.
김유석,방동하,김민규,서경원,주민석,박정현,최을수,정주현,최은화,윤정희,윤화영,최민철,이창우,한홍율,황철용 한국임상수의학회 2005 한국임상수의학회지 Vol.22 No.3
Five dogs at the age of 2-13 years, with variant respiratory signs like as dry cough, dyspnea, exercise intorelance and lameness were presented. On thoracic radiographs, all dogs had abnormalities such as soft tissue density, round mass image, increased pulmonary infiltration and pleural effusion. All dogs were diagnosed as adenocarcinoma on cytopathologic examinations by fine needle aspiration with ultrasound guidance. Computed tomography was performed in three cases to evaluate clinical stage. Primary papillary adenocarcinoma was confirmed after necropsy in one case.
김유석,황규영,정승우 조선대학교 구강생물학연구소 2003 Oral Biology Research (Oral Biol Res) Vol.27 No.1
The free gingival graft has proven to be a predictable procedure for obtaining an increased width of attached gingiva, concomitantly increasing vestibular depth and eliminating the tension of an abnormal frenulum, and root coverage. The free gingival grafts is needed when the patient experiences discomfort during toothbrushing due to gingival recession and chewing due to an interfering lining mucosa and/or when the margin of restoration is placed in a subgingival position at sites with a thin gingiva that may favor an inflammatory tissue reaction in the presence of subgingival plaque. In this study, two patients were treated by the free gingiva1 grafts. One patient had no attached gingiva at lower left 2nd premolar, 2nd molar which were treated subgingival restoration and more inflammatory. The free gingival grafts were performed in this sites. The 1-2㎜ attached gingiva were obtained and maintained after 4monthes. The other had 3-4㎜ gingival recession at lower left 1st, 2nd premolar and experiences discomfort during toothbrushing, cold hypersensitivity. The free gingival grafts were performed in this sites. The 2-3㎜ root coverage were obtained and maintained after 30 months. The free gingival graft for increasing width and thickness of gingiva can be performed in case of subgingival restorations , gingival recession.
혈압조절을 위한 모선 제어되는 체내 이식형 전기 자극기의 개발 및 체외 성능 평가
김유석,박성민,심은보,최성욱,Kim, Yoo-Seok,Park, Seong-Min,Shim, Eun-Bo,Choi, Seong-Wook 대한의용생체공학회 2010 의공학회지 Vol.31 No.5
Hypertension is the chronic disease that the 16% of total population are suffering, and it needs to be studied to find alternative treatment because of the tolerance and side effect of medications that may bother some patients. in this paper, we verified practicality of implantable electrical stimulator that can readily change stimulus magnitude and frequency. And this device is possible to stimulate baroreflex or parasympathetic nerve. Therefore we performed in vitro tests and animal experiment for device's operating conditions. This device consist of implantable electrical stimulator and extracorporeal control/monitoring system. Stimulator was designed to make 1Hz~100Hz pulses and it can change continuous or periodic pulse train type. And this device can control stimulator's function and monitor stimulator's status and patients' blood pressure at exterior of body using ZigBee module as wireless telecommunication. We verified that stimulator have error rate under 5% at 50mm depth of organs and, stimulator makes high-efficiency energy with closer position of two electrodes. Also we can confirm the performance of device that decreasing blood pressure and heart rate of a rat by electrical stimulation.
소성 온도가 (Na,K,Li)(Nb,Sb,Ta)O<sub>3</sub> 세라믹스의 유전 및 압전 특성에 미치는 영향
김유석,류주현,홍재일,이지영,Kim, You-Seok,Yoo, Ju-Hyun,Hong, Jae-Il,Lee, Jie-Young 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.11
In this study, $(Na_{0.525}K_{0.443}Li_{0.037})(Nb_{0.883}Sb_{0.08}Ta_{0.037})O_3+0.10\;wt%Bi_2O_3+0.35\;wt%B_2O_3$ ceramics were prepared by conventional soild-state sintering process. The specimens were sintered at temperature range from $1,060^{\circ}C$ to $1,100^{\circ}C$. XRD (X-ray diffractron), SEM (scanning electron microscope) were used to analyze the crystal structure and microstructural sproperties of specimens. And also, $T_{O-T}$, TC were observed by the mesurement of temperature dependence of dielectric constant. Excellect physical properties of the piezoelectric constant $d_{33}$= 170 pC/N, electromechanical coupling factor kp= 0.312, Tc= $315^{\circ}C$ were obtained, respectively, from the specimen sintered at $1,080^{\circ}C$.