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.

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.

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.

소성 온도가 (Na,K,Li)(Nb,Sb,Ta)O₃ 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 $1,080^{\circ}C$.

무연 강유전 (Ba_0.85Ca_0.15)(Ti_0.92Zr_0.08)O₃ 세라믹스의 전기열량 효과 및 강유전 이력 특성

김유석,류주현,정영호,이지영,Kim, You-Seok,Yoo, Ju-Hyun,Jeong, Yeong-Ho,Lee, Jie-Young 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.11

In this study, electrocaloric effects of Pb-free $(Ba_{0.85}Ca_{0.15})(Ti_{0.92}Zr_{0.08})O_3$ ferroelectric ceramics were investigated and discussed using the characteristics of P-E hysteresis loops at wide temperature range from room temperature to $140^{\circ}C$. The remnant polarization $P_r$ and coercive field $E_c$ were decreased with increasing temperature. The temperature change ${\Delta}T$ by the electrcaloric effect was calculated by Maxwell's relations, and reached the maximum of ~0.15 at $120^{\circ}C$ under applied electric field of 30 kV/cm.

한쪽 엽에 국한된 고분화 갑상선암에서 갑상선 엽절제술의 의의

김유석,김권천,Yoo Seok Kim,Kweon Cheon Kim 대한갑상선-내분비외과학회 2013 The Koreran journal of Endocrine Surgery Vol.13 No.2

Purpose: There has been controversy of the lobectomy for well differentiated thyroid cancer (WDTC). Current guidelines recommend total thyroidectomy for the cancer over 1cm, despite previous report suggesting that the lobectomy provides similar excellent outcomes. The purpose of our study is to report our experience of WDTC treated by thyroid lobectomy. Methods: We retrospectively analyzed 284 patients with WDTC treated by thyroid lobectomy at department of Surgery in Chosun University Hospital from January 2002 to December 2010. Overall survival (OS) and disease-free survival (DFS) were determined by the Kaplan-Meier method. Factors predictive of recurrence by univariate and multivariate analysis were determined using the ՗<SUP>2 </SUP>test and Cox proportional hazard model respectively. Results: With a mean follow-up of 60.4 months, OS and RFS for all patients were 97.9% and 96.5% respectively. No patient died due to WDTC. Univariate analysis showed statistically significant differences in recurrence by tumor size (P=0.013) and presence of invasion (P=0.039). However, Multivariate analysis showed no significant difference in local recurrence. Conclusion: Patients with WDTC confined to one lobe can be safely treated by lobectomy.

4기 위암 환자의 임상적 특성

김유석,김성수,민영돈,Kim, Yoo Seok,Kim, Sung Soo,Min, Young Don 대한위암학회 2008 대한위암학회지 Vol.8 No.2

목적: 최근 내시경 및 각종 영상진단 기술의 발달로 위암의 조기 발견 및 수술 전 병기의 진단율이 높아지고 있으나 여전히 초진 시 진행 위암 상태로 진단되는 경우가 많고 개복 수술 후 병리조직 검사에서 4기 위암으로 진단이 되는 경우도 있다. 4기 위암은 예후가 극히 불량하지만 임상 분석을 통해 적극적인 치료 효과에 대한 의의를 찾아 보고자 본 연구를 시행하였다. 대상 및 방법: 1994년 1월부터 2006년 12월까지 위암으로 진단되어 개복수술을 받은 1,376명의 환자들 중 4기 위암으로 진단된 150명의 환자를 대상으로 후향적 연구를 시행하였다. 결과: 개복술을 시행 받은 4기 위암환자 150명의 평균 나이는 57.8세(28~93세)였으며 이 중 남자가 104명, 여자가 46명이었다. 119명은 위아전절제술 또는 위전절제술을 시행하였으며 31명은 절제 불가하였다. 절제술을 시행한 환자의 생존기간은 평균 722일(14일~4,559일)로 그렇지 않은 환자의 173일(16일~374일)과 통계적으로 유의한 차이를 보였다. 위절제술을 시행한 4기 위암 환자를 TNM 병기로 세분하였을 때 T4 환자들은 33명으로 평균 생존일은 534일(17일~3,378일)이었으며, N3 환자들은 63명으로 평균 생존일은 521일(14일~4,190일)이었으나 통계적 의미는 없었다. 항암화학요법을 시행한 환자는 98명이었고 52명에 대해서는 항암화학요법을 시행하지 않았으며 생존기간은 각각 792일, 243일로 통계적으로 의미 있는 차이를 보였다. 결론: 4기 위암에 대해서도 원격 장기 전이의 증거가 없는 한 확대 림프절제술을 포함한 근치적 위절제술과 항암화학요법 등 적극적인 치료를 시도함으로써 생존율의 향상을 기대할 수 있다. Purpose: The early detection of gastric cancer and accuracy of preoperative staging has currently been on the increase due to the development of endoscopy and imaging techniques, but there are still many cases of advanced gastric cancer detected at the first diagnosis and there are also many cases of stage IV gastric cancer diagnosed after a postoperative pathological examination. Although the prognosis of stage IV gastric cancer is very poor, this study was performed to determine the value of the use of aggressive treatment determined after a clinical analysis. Materials and Methods: We retrospectively analyzed 150 patients that were diagnosed with stage IV gastric cancer among 1376 patients who underwent a laparotomy for gastric cancer from January 1994 to December 2006. Results: Of the 150 patients with stage IV gastric cancer who underwent a laparotomy, there were 104 men and 46 women. The mean patient age was 57.8 years (age range, 28~93 years). A subtotal gastrectomy or total gastrectomy was performed in 119 patients and 31 patients underwent an explorative laparotomy. The mean survival time of patients that underwent a gastrectomy and patients that did not undergo a gastrectomy was 722 days (range, 14~4,559 days) and 173 days (range, 16~374 days), respectively this result was statistically significant. When patients that underwent a gastrectomy were classified according to the TNM stage, the mean survival time of 33 patients with stage T4 disease was 534 days (range, 17~3,378 days) and the mean survival time of 63 patients with stage N3 disease was 521 days (range, 14~4,190 days), but there was no statistical significance. Chemotherapy was administered to 98 patients and 52 patients did not receive chemotherapy. The mean survival time of patients that received chemotherapy was 792 days (range, 36~4,559 days) and the mean survival time of patients that did not receive chemotherapy was 243 days (range, 14~2,413 days), with statistical significance. Conclusion: If there is no evidence of distant metastasis in stage IV gastric cancer, one can expect improvement of the survival rate by the use of aggressive treatment, including curative gastric resection with radical lymph node dissection and chemotherapy.

갑상선 수술 후 응급상황 및 대처방법

김유석(KIM YOO SEOK) 대한갑상선-내분비외과학회 2017 대한갑상선-내분비외과학회 학술대회 논문집 Vol.- No.-

암의 혈관생성과 혈류역학에 대한 수치적 연구

김유석(Yoo Seok Kim),심은보(Eun Bo Shim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

Cancer hemodynamics in vascular state was numerically simulated using a pressure node equation. The cancer angiogenesis pattern in our previous study was used for the geometry of vessel networks. For cancer angiogenesis, the equation that governed angiogenesis comprises a cancer angiogenesis factor (TAF) conservation equation in time and space, which is solved numerically using the Galerkin finite element method. A stochastic process model is used to simulate vessel formation and vessel. In this study, we used a two-dimensional model with planar vessel structure. Hemodynamics in angiogenesis vessel was assumed as incompressible steady flow with Newtonian fluid properties. In parent vessel, arterial pressure is assigned as a boundary condition whereas a constant terminal pressure is specified in cancer inside. Kirchhoff’s law is applied to each pressure node to simulate the pressure distribution in vessel networks. Transient pressure distribution along with angiogenesis pattern was presented to investigate the effect of cancer growth on hemodynamics.

전례 분석을 통한 도시지역 공격작전 발전방안 연구 -소부대급 공지합동작전을 중심으로-

김유석 ( Yoo-seok Kim ) 미래군사학회 2015 한국군사학논총 Vol.4 No.1

The effectiveness of Air Ground Joint Operations was analysed for the ‘Seoul Recapture Operation’ in the Korean War and the ‘Thunder Run Operations’ during the Iraq War. From the analysis, CAS(Close Air Support) was found to be very effective for offense operations on urban terrain even for small units at company-level and below. Especially noteworthy were the operation accomplishments during the Iraq War where the ground operation forces showed very high effectiveness through Air Ground Joint Operations using Precision Guidance Missiles. Five issues for consideration were derived from the analysis. First, Air Ground Joint Operations on urban terrain should be more heavily employed in future battlefields because the importance of Military Operations on urban terrain and the utility of Air Ground Joint Operations have been heightened by increasing urbanization. Second, this study suggests four ‘prerequisites of Joint Forces’ for effective Air to Ground Joint Operations on urban terrain such as sharing information between friendly forces in the urban area on carefully selected objectives. Third, as part of ‘performance of proper role of ground troops’ and acquisition of necessary abilities for effective Air to Ground Joint Operations, four factors including the fulfillment of communication skills of acknowledging same information of enemy with air force were researched. Fourth, despite the importance of offense operations of air support, this research suggests that Ground Troops nonetheless have a crucial role to play as final victory ultimately depends on them. Finally, three training factors including the education contents for field grade officers were analysed to foster ability to conduct Air to Ground Joint Operations.