전두부 골간단 이형성증의 광범위한 수술적 치료

장의석,문구현,임소영,현원석,방사익,오갑성,변재경 대한성형외과학회 2006 Archives of Plastic Surgery Vol.33 No.3

Frontometaphyseal dysplasia is a rare genetic syndrome first described by Gorlin and Cohen in 1969. This disease affects the skeletal system and connective tissue, and could be characterized by hyperostosis of the skull, prominence of supraorbital ridges, additional skeletal and extraskeletal abnormalities. It is believed that the condition is an X-linked dominant trait with severe manifextations in males and extreme variability in females.We described a case of 15-year-old boy manifested a pronounced supraorbital ridge associated with exorbitism. He also had bilateral progressive hearing deficit, thoracic spine scoliosis, chest wall deformity, bilateral maxillary sinusitis and both 5th finger arachnodactyly.The patient underwent a fronto-temporo-orbital cranioplasty through a coronal incision. The frontal bone including supraorbital region, orbital lateral rim and temporal bone were extensively contoured with burr. And then, burring of the medial aspect of lateral orbital wall was made to increase both orbital volume for correction of exorbitism.Postoperative results show well corrected prominent supraorbital ridge, hyperostosis of frontotemporal bone and exorbitism. The patient was satisfied with the improved appearance. No recurrence occurred during the 6 months of follow-up period. We report this case as it shows esthetically good result without any complication.

페놀수지 기반 복합재료의 마찰 마모 특성

홍의석(Ui Seok Hong),정소라(So La Jung),장호(Ho Jang),김성진(Seong Jin Kim) 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.11

Tribological properties of phenolic resins in the friction materials for C-SiC brake systems were investigated. Boron-phosphorus modified resin, silicon modified resin, and straight resin were used as binders of friction materials. A simple formulation containing aramid pulp, potassium titanate, zircon silicate, and phenolic resin was used to investigate the effect of the resins at elevated temperatures up to 400℃. Friction stability and wear rate of the three friction materials were compared as a function of temperature and the activation energy for the wear rate of the three phenolic resins were obtained from Arrhenius type plot. It was found that the composite materials clearly exhibit different wear mechanisms below and above the critical temperatures. The friction materials with B-P modified resin showed good wear resistance and friction stability compared with the others.

레이저유도 플라즈마 분광법을 이용한 폐금속 분류를 위한 추정 연성정보 기반의 최빈 분류 기술

김에덴,장혜민,신성호,정성호,황의석,Kim, Eden,Jang, Hyemin,Shin, Sungho,Jeong, Sungho,Hwang, Euiseok 한국자원리싸이클링학회 2018 資源 리싸이클링 Vol.27 No.1

In this study, a novel soft information based most probable classification scheme is proposed for sorting recyclable metal alloys with laser induced breakdown spectroscopy (LIBS). Regression analysis with LIBS captured spectrums for estimating concentrations of common elements can be efficient for classifying unknown arbitrary metal alloys, even when that particular alloy is not included for training. Therefore, partial least square regression (PLSR) is employed in the proposed scheme, where spectrums of the certified reference materials (CRMs) are used for training. With the PLSR model, the concentrations of the test spectrum are estimated independently and are compared to those of CRMs for finding out the most probable class. Then, joint soft information can be obtained by assuming multi-variate normal (MVN) distribution, which enables to account the probability measure or a prior information and improves classification performance. For evaluating the proposed schemes, MVN soft information is evaluated based on PLSR of LIBS captured spectrums of 9 metal CRMs, and tested for classifying unknown metal alloys. Furthermore, the likelihood is evaluated with the radar chart to effectively visualize and search the most probable class among the candidates. By the leave-one-out cross validation tests, the proposed scheme is not only showing improved classification accuracies but also helpful for adaptive post-processing to correct the mis-classifications.

고속전철용 소결 복합재의 마찰 특성평가

정소라(So La Jung),홍의석(Ui Seok Hong),박형철(Hyoung Chul Park),유병관(Byung Kwan Ryu),장호(Ho Jang) 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.11

The friction performance of sintered Friction materials for the high speed train was studied. In this study, newly developed sintered materials based on copper were compared with the commercial products for high speed trains. They were tested on a 1/5 scale dynamometer using low carbon steel disks. Effectiveness, fade, and recovery tests were carried out to examine friction performance and the change of disk thickness variation (DTV) during brake applications and noise propensity were also evaluated. Results showed that the two sintered friction materials exhibit similar friction coefficients and braking performance, whereas the newly developed friction material was superior in terms of DTV generation and noise propensity to the commercial friction material. The improvement of the newly developed friction material was attributed to the high graphite content which reduced the stick-slip phenomena and prevented uneven disk wear by friction films on the counter disk.

세라믹 디스크의 표면 개질에 따른 마찰 마모 특성

김기정(Ki Jung Kim),홍의석(Ui Seok Hong),장호(Ho Jang),김성진(Seong Jin Kim),박홍식(Hong Sik Park) 한국트라이볼로지학회 2006 한국트라이볼로지학회 학술대회 Vol.2006 No.6

Tribological properties of ceramic brake discs were investigated using a commercial friction material. The discs were manufactured by liquid silicon infiltration (LSI) into a C-C preform. The disc surface was modified by two different methods, producing sliding surfaces with chopped carbon fibers and carbon felt. In addition, the composition of the surface was also changed. Friction characteristics of the discs were examined using a 1/5 scale dynamometer with a rigid caliper. Dynamometer tests comprised burnishing, effectiveness tests, fade-recovery tests. A gray iron disc was also tested with the same friction material to compare with ceramic discs. Results showed that the type and composition of the disc surface significantly affected the level of braking effectiveness and high temperature brake performance. The discs with felt surfaces showed higher friction levels than those with chopped fiber surface and SiC tended to increase the friction level while C lowered the friction coefficient. The ceramic disc was more sensitive to the deceleration rate than gray iron, showing high speed sensitivity.

고속전철용 소결 복합재의 마찰 특성평가

정소라(Sola Chung),홍의석(Uiseok Hong),장호(Ho Jang) 한국트라이볼로지학회 2007 한국윤활학회지(윤활학회지) Vol.23 No.6

The brake performance of sintered friction materials for the high speed train was studied. In this study, newly developed sintered materials based on copper were compared with the commercial products for high speed trains. They were tested on a 1/5 scale dynamometer using low carbon steel disks. Effectiveness, fade, and recovery tests were carried out to examine friction performance and the change of disk thickness variation (DTV) during brake applications and noise propensity were also evaluated. Results showed that the two sintered friction materials exhibit similar friction coefficients and braking performance, whereas the newly developed friction material was superior in terms of DTV generation and noise propensity to the commercial friction material. The improvement of the newly developed friction material was attributed to the high graphite content which reduced the stick-slip phenomena and prevented uneven disk wear by producing friction films on the counter disk.

나노스크래칭 시 모재의 방위 및 입계가 마찰특성에 미치는 영향에 관한 분자 동역학 모사

조민형(Min Hyung Cho),조근형(Keun Hyung Cho),홍의석(Ui Seok Hong),이강선(Kang Sun Lee),장호(Ho Jang) 한국트라이볼로지학회 2006 한국트라이볼로지학회 학술대회 Vol.2006 No.11

Friction force fluctuation during scratching of a Cu {100} surface by a nano-size spherical asperity was studied by molecular dynamics simulation using embedded atom potentials. The scratching simulation was performed at different directions ([100] and [101]), and crystal geometries (single crystal and bi-crystal substrates). Results showed that the friction force oscillated during the scratching and the oscillation changed into repetitive stick-slip patterns when it involved dislocation nucleation and propagation, exhibiting slow elastic deformation followed by an abrupt friction force drop due to plastic yielding of the Cu substrate. The level and the periodicity of friction force were changed with sliding directions and this was related with the shear stress along the slip direction. The presence of grain boundaries strongly affected the friction force oscillation due to the interaction between dislocations and grain boundaries and the interaction produced non-periodic stick-slip behaviour.