First-principles Investigations on Polytypes of BaTiO3:Hybrid Calculations and Pressure Dependences

서유성,안재석 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.11

We report our first-principles investigations on three polytypes of BaTiO3 (BTO): a paraelectric phase with cubic Pm−3m structure and two ferroelectric (FE) phases with tetragonal P4mm and rhombohedral R3m structures. We compared the structural and the electrical properties of BTO obtained by using various approaches: e.g., the Hartree-Fock (HF) theory, the density functional theory (DFT) with the local density approximation (LDA) or with the two generalized gradient approximations (two GGAs: PWGGA and PBE), and three hybrid functionals of the HF and the DFT (B3LYP, B3PW, and PBE0). For the P4mm structure, the two GGAs and the hybrid functionals reproduced the cell volumes, but slightly overestimated the c/a ratio. The hybrid functionals provided accurate predictions for the experimental energy gaps, but slightly underestimated the experimental dielectric constants. The calculated dielectric constants were inversely proportional to the c/a ratios for the P4mm structure (or the cH/aH ratio for the R3m structure), irrespective of the functional choice. Also, the over-estimated polarization could be ascribed to a super-tetragonality in the GGA/hybrid functionals. The pressure dependences for the cell parameters, fractional atomic displacements, energy gaps, dielectric constants, and FE polarizations were calculated by using the B3PW hybrid functional. As pressure was increased, the polarization decreased monotonically until it reached zero at a critical pressure of ∼ 20 GPa for both the P4mm and the R3m structures. Anomalous behaviors were also observed in the atomic movements and the polarizations for the P4mm structure: δTi, the fractional coordinate of Ti, showed a sign reversal at pressures below −8 GPa while the polarization showed a maximum at −2 GPa and then decreased with decreasing pressure. However, such effects were not observed for the R3m structure: the polarization monotonically increased with decreasing pressure. Such behaviors of the polarizations, together with super-tetragonality/super-trigonality, are discussed.

Combination of Spectroscopic Ellipsometry and Transmittance for Measuring the Optical Constants of Transparent Layers: Application to a Pyrochlore PbZr_(0.2)Ti_(0.8)O₃Thin Film on a SrTiO₃ Substrate

서유성,권대영,김복기,안재석,정일경 한국물리학회 2011 새물리 Vol.61 No.8

We describe the combination of spectroscopic ellipsometry (SE) and transmittance (T) measurements in determining the optical constants of a transparent thin film on a non-absorbing substrate. The conjoined method, SE-emph{T}, was applied to a pyrochlore PbZr_(0.2)Ti_(0.8)O₃ (PZT) thin film on a SrTiO₃substrate. The SE-T analysis provided the best results, with minimum uncertainty, compared with conventional SE analyses. The optical constants of pyrochlore PZT were successfully determined with a modified three-phase model by assuming an additional rough surface layer.

다소성 골괴사

서유성,박형근,최형석,김연일,이병일 순천향의학연구소 2002 Journal of Soonchunhyang Medical Science Vol.8 No.2

In case of the occurrence of osteonecrosis at three or more anatomical location, it is defined as multifocal osteonecrosis, but still any king of study with references hasn't been reported in Korea. The patient who had admitted due to the pain in both knee joints, both hip joints and left ankle joint and we diagnosed as multifocal osteonecrosis by using bone scan and magnetic resonance imaging. To relieve right knee joint and left hip joint pain, we perfomed arthroplasty. Here we present one case report of multifocal osteonecrosis through analysis by patient's history and hematologic examination and provide a review of the literature.

저주파 자극 및 근적외선을 활용한 요실금 예방 및 관리 훈련기기가 골반 바닥근에 미치는 영향

서유성,강태석,강수정,손주영,홍다빈,최정현,김경 한국운동재활복지협회 2025 운동재활·복지 Vol.6 No.1

본 연구에서는 건강한 성인을 대상으로 전기자극과 근적외선이 조합된 골반바닥근 강화 운동기 사용이 골반바닥근에 미치는 영향을 알아보고자 한다. 건강한 성인 남성 13명을 대상으로, 골반바닥근 강화 운동기 사용 전후에 케겔 운동 시의 큰볼기근의 근활성도를 비교하였다. 연구 결과, 큰볼기근의 세 근육군 모두 근활성도가 감소하였으며, 큰볼기근 Lower part의 근활성도에서 유의한 차이가 나타났다. 이는 골반바닥근 강화 운동기 사용은 골반바닥근을 간접적으로 자극하는데 효과적이며, 지속적인 사용은 골반바닥근 강화에 도움이 될 것으로 예상된다. This study evaluated a pelvic floor muscle strengthening device that combines electrical stimulation and near-infrared light. The device was tested on 13 healthy adult males, and muscle activation of the three gluteus muscle groups was compared before and after treatment. The results showed a decrease in muscle activation across all three muscle groups, with a statistically specifically observed particularly in the lower muscle group. Therefore, the application of the pelvic floor muscle strengthening device is effective in stimulating and activating the pelvic floor muscles. Continuous application of the device is expected to contribute to the strengthening of the pelvic floor muscles.

Multilock 대퇴삽입물을 이용한 고관절 치환술의 단기결과

서유성,황재영,나수균,최창욱 최신의학사 1995 最新醫學 Vol.38 No.8

Clinical and Radiologic Outcomes among Bipolar Hemiarthroplasty, Compression Hip Screw and Proximal Femur Nail Antirotation in Treating Comminuted Intertrochanteric Fractures

서유성,노재휘,김성민,홍시전,최형석,박종석 대한고관절학회 2015 Hip and Pelvis Vol.27 No.1

Purpose: In comminuted intertrochanteric fractures, various operative options have been introduced. The purpose of this study was to determine whether there were differences in clinical and radiologic outcomes among bipolar hemiarthroplasty (BH), compression hip screw (CHS) and proximal femur nail antirotation (PFNA) in treating comminuted intertrochanteric fractures (AO/OTA classification, A2 [22, 23])Materials and Methods: We retrospectively evaluated total 150 patients (BH, 50; CHS, 50; PFNA, 50) who were operated due to intertrochanteric fractures from March 2010 to December 2012 and were older than 65 years at the time of surgery. We compared these three groups for radiologic and clinical outcomes at 12 months postoperatively, including Harris Hip Score, mobility (Koval stage), visual analogue scale and radiologic limb length discrepancy (shortening). Results: There was no statistical significance among three groups in clinical outcomes including Harris Hip Score, mobility (Koval stage), visual analogue scale. However, there was significant differences in radiologic limb discrepancy in plain radiographs at 12 months postoperatively (radiologic shortening: BH, 2.3 mm; CHS, 5.1 mm; PFNA, 3.0 mm; P=0.000). Conclusion: There were no clinical differences among BH, PFNA, and CHS in this study. However, notable limb length shortening could be originated during fracture healing in osteosynthesis, compared to arthroplasty (BH<PFNA<CHS).

정형외과 수술의 무수혈적 환자혈액관리 프로토콜

서유성,이정재,노재휘,정하란,이원석,장병웅,김용범,천동일,최성우,이재철,최형석 대한수혈학회 2019 大韓輸血學會誌 Vol.30 No.1

We developed a new blood management protocol that allows patients to not undergo transfusion during major orthopaedic surgery. Here, we report the safety of or our protocol. The preoperative pharmacological protocol consisted of the administration of 40 g of recombinant erythropoietin subcutaneously and 100 mg of iron supplements intravenously. During the operation, reinfusion of drainage blood using a cell saver and plasma expander was used. The cell saver device passed the collected blood through a filter, which washed the blood, removing the hemolyzed cells and other impurities. Intravenous tranexamic acid 1 g is given just before the operation, except high-risk patients for venous thromboembolism. Postoperatively, recombinant erythropoietin and iron supplements were administered in the same manner with the preoperative protocol and continued until a hemoglobin level reached 10 g/dL.

제7회 연수강좌 : 총론 및 기초 ; 고관절 진단학

서유성 대한고관절학회 2005 Hip and Pelvis Vol.17 No.3

샌드위치 세라믹 라이너의 골절 : 1예 보고 One Case Report

서유성,임강철 순천향의학연구소;Soonchunhyang Medical Research Institute 2004 Journal of Soonchunhyang Medical Science Vol.10 No.2

In Alumina-Alumina Artificial Hip joints with a sandwich ceramic liner, liner fracture and dissociation is rare. In December 2001, a 58-year-old man underwent a right total hip arthroplasty because of avascular necrosis of femoral head. 3.8 years after surgery, he felt click and squeak in the groin and had thigh and inguinal pain. Radiographs shows a fracture of the ceramic acetabular insert. At sergery, we found the fracture of the insert, which had become detached from the polyethylene backing, the greatly worn polyethylene backing and the ceramic head that was discolored from contact with the metal shell. The patient was treated by revisional total hip arthroplasty and a new polyethylene liner and a metal head were fitted. We describe this one rare case and review the literature.

고관절 전 치환 성형술 후 탈구에 관한 치험 및 연구

서유성,김동진,박종석,임수재,나수균,최창욱 순천향의학연구소 1998 Journal of Soonchunhyang Medical Science Vol.4 No.2

Dislocation is one of the serious complications in total hip replacement arthroplasties. The purpose of this study is to evaluate the risk factors of dislocation, including age, sex, preoperative diagnosis and bilaterality, history of previous hip surgery, positioning of component, soft tissue tension, treatment after dislocation or redislocation. Authors reviewed 190 patients of total hip replacement arthroplasty, which were performed from Jan. 1990 to Dec. 1996. 15 cases developed dislocation after surgery. Incidence of dislocation was 7.89%(15 of 190 cases). Dislocation after revision was not happened(0 of 18 cases). Inclination of acetabular cup was average 37.5° (range: 31° - 43° ). Average anteversion of the acetabular component was 18.1" by Woo and Morrey method, 11.4° by Hassan method. They were normal range except 3 cases. Dislocation was not prevented even though inclination and anteversion of acetabular cup were within normal range. Soft tissue tension is determined by change of limb and femoral neck length. Average limb length difference was -0.2mm(range; -l0mm - +10mm) and average offset difference was +1.7mm(range;-4mm - +18mm). Revision must be accomplished as soon as possible when limb shortening happen by upward migration of the acetabular component. In conclusion, anteversion of acetabular cup may be most important factor in our cases, so cup position must be fixed in proper position during operation.