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황지훈,설철환,박병윤 대한성형외과학회 2005 Archives of Plastic Surgery Vol.32 No.5
Orthognathic surgery for Class III malocclusion requires an elaborate preoperative planning using cephalometries or Mock surgery models which enable the surgeon to anticipate postoperative skeletal changes of maxilla and mandible as well as dentition. After surgery, patient's satisfaction is greatly influenced by appearance of soft tissue change. Therefore, it is imperative to predict a relatively accurate soft tissue change prior to surgery. A 5 year retrospective study was designed to evaluate the soft tissue change after sagittal split osteotomy of ramus(SSRO) for class III malocclusion. Analyses of preoperative and postoperative anthropometric measurements were performed. Patients who were treated only by SSRO for class III malocclusion and could follow up for 6 months were studied. Among them, the patients who had history of cleft palate and lip or hemifacial microsomia were excluded. Soft tissue changes were estimated by using the frontal and lateral photographs. Skeletal changes were observed by measuring amount of set back and angular changes of mandible to the reference line by using cephalometries. Relapses were also measured 6 months after the operation. We could observe skeletal changes were more profound than soft tissue changes concerning amount of set back, but soft tissue changes were also profound in angle. Relapse was more profound in skeleton than soft tissue but the amount was not significant. In spite of the variables which may affect proper assessment of the soft tissue change after skeletal relocation, this study can serve as a guide for exact prediction of the postoperative change of soft tissue and skeleton.
황지훈,이영철,이욱진 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.1
Sapphire single crystals have been highlighted for epitaxial of gallium nitride films in high-power laser and lightemitting diode industries. In this study, the evolution of thermally induced stress in sapphire during the verticalBridgman crystal growth process was investigated using a finite element model that simplified the real Bridgmanprocess. A vertical Bridgman process of cylindrical sapphire crystal with a diameter of 50 mm was considered forthe model. The solidification history effect during the growth was modeled by the quite element technique. Theeffects of temperature gradient, seeding interface shape and seeding position on the thermal stress during the processwere discussed based on the finite element analysis results.
유리 피판을 이용한 다양한 하지 연부 조직 결손의 재건
황지훈,이건창,유원민,탁관철,노태석,Hwang, Jee-Hoon,Lee, Kun-Chang,Yoo, Won-Min,Tark, Kwan-Chul,Roh, Tai-Suk 대한미세수술학회 2004 Archives of reconstructive microsurgery Vol.13 No.2
Lower extremity injuries are frequently accompanied with large soft-tissue defects. Such Injuries are difficult to manage for its poor vascularity, rigid tissue distensibility, easy infectability and a relatively long healing period. Also, osteomyelitis, and/or non-union of the fractured bones are relatively common in lower extremity injuries and its weight-bearing role should be considered. Therefore, it is important to select appropriate reconstruction method of the lower extremities, which is applicable to a variety of surgical techniques according to these considerations. The goal of flap coverage in the lower extremity should not only be satisfactory wound coverage, but also acceptable appearance and minimal donor site morbidity. In this article, we have tried to establish a reconstruction method in the lower extremity based on our experiences and clinical analysis of soft tissue reconstruction using free muscle flap transfer in 27 cases from Jan. 2000 to Dec. 2002. The results showed 96% flap survival, and flap failure noted in one of the cases due to vascular insufficiency. In conclusion, we believe that in cases of lower extremity soft-tissue defects especially with open comminuted fractures and infections, muscle free flaps should be considered as the first line of treatment.
황지훈,장정현,양경석,최재혁,Hwang, Ji-Hoon,Jang, Jeong-Hyun,Yang, Kyeong-Seok,Choi, Jae-Hyouk 한국교육시설학회 2012 敎育施設 Vol.19 No.4
Recently large scale earthquake s are occurred around the world following the damage of buildings. So the interest of preparing for earthquake seismic design and seismic performance has becoming high. School buildings are though used for educational purpose; they are also used as emergency shelter for local residents during earthquake disaster. However, the current seismic design ratio of our country (Korea) is 3.7% and if massive earthquake is occurred it follows a serious damage. In order to overcome this situation, seismic performance evaluation is carried out for existing school building and an accurate and appropriate seismic retrofit is required based on performance evaluation to upgrade the existing school buildings. In this paper, nonlinear static analysis on existing school buildings for ATC-40 and FEMA-356 are carried out using the capacity spectrum method to evaluate seismic performance and to determine the need for retrofitting. In addition, after reinforcement to verify the effect of retrofit enhance the seismic performance is applied the seismic performance evaluation is carried out to verify the effect of seismic retrofit time history analysis using nonlinear dynamic analysis is also performed and nonlinear behavior of earthquake load of seismic retrofit of structures was also investigated.
Development of analysis technique to predict the material behavior of blowing agent
황지훈,이성기,황소영,김낙수 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.4
In order to numerically simulate the foaming behavior of mastic sealer containing the blowing agent, afoaming and driving force model are needed which incorporate the foaming characteristics. Also, the elasticstress model is required to represent the material behavior of co-existing phase of liquid state and the curedpolymer. It is important to determine the thermal properties such as thermal conductivity and specific heatbecause foaming behavior is heavily influenced by temperature change. In this study, three models are proposedto explain the foaming process and material behavior during and after the process. To obtain thematerial parameters in each model, following experiments and the numerical simulations are performed:thermal test, simple shear test and foaming test. The error functions are defined as differences between theexperimental measurements and the numerical simulation results, and then the parameters are determinedby minimizing the error functions. To ensure the validity of the obtained parameters, the confirmation simulationfor each model is conducted by applying the determined parameters. The cross-verification is performedby measuring the foaming/shrinkage force. The results of cross-verification tended to follow theexperimental results. Interestingly, it was possible to estimate the micro-deformation occurring in automobileroof surface by applying the proposed model to oven process analysis. The application of developedanalysis technique will contribute to the design with minimized micro-deformation.