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소아 두부외상 환자에서의 반복적인 두부 CT 검사의 유용성
조호준 ( Ho Jun Jo ),임용수 ( Yong Su Lim ),김진주 ( Jin Joo Kim ),조진성 ( Jin Seong Cho ),현성열 ( Sung Youl Hyun ),양혁준 ( Hyuk Jun Yang ),이근 ( Gun Lee ) 대한외상학회 2015 大韓外傷學會誌 Vol.28 No.3
Purpose: Traumatic brain injury (TBI) is the most common cause of pediatric trauma patients came to the emergency department. Without guidelines, many of these children underwent repeat brain computed tomography (CT). The purpose of this study was to evaluate the value of repeat brain CT in children with TBI. Methods: We conducted a retrospective study of TBI in children younger than 19 years of age who visited the emergency department (ED) from January 2011 to December 2012. According to the Glasgow Coma Scale (GCS) and Pediatric Glasgow Coma Scale score of the patients, study population divided in three groups. Clinical data collected included age, mechanism of injury, type of TBI, and outcome. Results: A Total 83 children with TBI received repeat brain CT. There were no need for neurosurgical intervention in mild TBI (GCS score 13-15) group who underwent routine repeat CT. 4 patients of mild TBI group, received repeat brain CT due to neurological deterioration, and one patient underwent neurosurgical intervention. Routine repeat CT identified 12 patients with radiographic progression. One patient underwent neurosurgical intervention based on the second brain CT finding, who belonged to the moderate TBI (GCS score 9-12) group. Conclusion: Our study showed that children with mild TBI can be observed without repeat brain CT when there is no evidence of neurologic deterioration. Further study is needed for establish indication for repetition of CT scan in order to avoid unnecessary radiation exposure of children. [ J Trauma Inj 2015; 28: 149-157 ]
LPS법에 의한 카본코팅 Tyranno-SA 섬유 보강한 복합재료의 굽힘 강도 특성
조호준(Ho-Jun Cho),문승현(Seung-Hyun Moon),윤한기(Han-Ki Yoon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A recently developed SiC fiber, Tyranno-SA (2D plain-woven), was used as the reinforcemnet in several SiC<SUB>f</SUB>/SiC composites. The composites were fabricated by liquid phase sintering (LPS) process. The mechanical properties and fracture behaviors of LPS-SiC<SUB>f</SUB>/SiC composites, with the fiber volume fraction, were investigated in conjunction with a detailed analysis of their microstructure. The fiber preforms were prepared to keep a fiber volume fraction of about 20%, 30% and 40%, respectively. The flexural strength of LPS-SiC<SUB>f</SUB>/SiC composites were also carried out at room temperature thought three point bending test. A decrease in the fiber volume fraction led to an increase in the flexural strength of the LPS-SiC<SUB>f</SUB>/SiC composites, accompanying nearly full-density and a highly dense matrix with fiber bundle.
차세대 원자력 구조용 고온 SiC<SUB>f</SUB>/SiC 복합재료의 기계적 특성
조호준(Ho-Jun Cho),윤한기(Han-Ki Yoon) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
SiC<SUB>f</SUB>/SiC composites are well-known materials for high temperature structural applications because of their intrinsic properties using fusion power reactors such as shield and divertor coolant channel. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC<SUB>f</SUB>/SiC composite can be considered as a promising for structural materials because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the fiber. Therefore, an improvement of the coating fiber is key requirements for fabrication of SiC<SUB>f</SUB>/SiC composites by LPS method. In this paper, The SiC<SUB>f</SUB>/SiC composites were fabricated by the LPS method and investigated effects of SiC fiber coating. The SiC<SUB>f</SUB>/SiC composites were fabricated with coated and uncoated Tyranno-SA fibers. The thickness of the coating fiber was 0.25 ㎛ and 0.5 ㎛. In order to investigate effects of coating, the flexural strength were carried out at room temperature, respectively. The densification and microstructure of LPS-SiC<SUB>f</SUB>/SiC composites were observed by FE-SEM.
CVI법에 의한 SiC<SUB>f</SUB>/SiC 복합재료 제조와 기계적 강도
조호준(Ho-Jun Cho),문승현(Seung-Hyun Moon),윤한기(Han-Ki Yoon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Silicon carbide fiber-reinforced silicon carbide matrix composites (SiC<SUB>f</SUB>/SiC composites) are attractive materials for the blankets and divertors of nuclear fusion power reactors. Strength reliability of SiC<SUB>f</SUB>/SiC composites are important as structural candidates because of their properties. A recently developed SiC fiber, Tyranno-SA (2D plain-woven), was used as the reinforcement in several SiC<SUB>f</SUB>/SiC composites. The SiC<SUB>f</SUB>/SiC composites were fabricated by chemical vapor infiltration (CVI) process. Several pyrolytic carbons (PyC) with SiC interlayer coatings were applied to the composites for improvement of the mechanical properties at the interface. The mechanical properties and fracture behaviors were investigated using three-point bending test. The interlayers were deposited by isothermal CVI process. The test results showed a close PyC layer dependence on the strength of the composites. The flexural strength increased with the increasing of the PyC layer.
조호준(Ho-Jun Cho),정제평(Je-Pyong Jeong) 한국콘크리트학회 2021 한국콘크리트학회 학술대회 논문집 Vol.33 No.1
철근콘크리트 구조물에 균열이 발생하면 실제 휨모멘트는 선형탄성해석 결과와 다르게 나타난다. 휨모멘트의 분포는 지점부에서 균열이 발생하면 달라지기 시작한다. 철근콘크리트 보에 균열이 발생하면 강성변화가 일어난다. 따라서, 본 연구는 모멘트분배 과정의 매트리스 구조해석을 하였다. When a crack occurs in a reinforced concrete structure, the actual bending moment appears different from the results of the linear elastic analysis. The distribution of the bending moment starts to change when a crack occurs at the point. When cracks occur in reinforced concrete beams, stiffness changes occur. Therefore, this study performed a matrix structure analysis of the moment distribution process.
조호준(Ho-Jun Cho),윤한기(Han-Ki Yoon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Silicon carbide (SiC) ceramics have been fabricated by Nano-Infiltration Transient Eutectic Phase (NITE) process, using Hot pressing (HP) with SiC nano-powder. Al₂O₃ and Y₂O₃ particles were used for NITE-SiC ceramics as sintering additive materials. The mixed powders were sintered for 1 hr at 1760, 1780, 1800 and 1820 ℃ under a pressure of 20 ㎫. Composition of sintering additive materials with a ratio of 10 wt.% were controlled to be 0.4, 0.7, 1.5 and 2.3 wt.% (Al₂O₃/Y₂O₃) to investigate the effect on sintering additives. Mechanical properties and microstructures of NITE-SiC ceramics were evaluated by SEM, XRD and three point bending test. NITE-SiC ceramics sintered at 1800 ℃ with sintering additive of 1.5 wt.% was effective for improving the flexural strength of monolithic SiC material.
조호준(Cho, Ho-Jun),정제평(Jeong, Je-Pyong) 한국콘크리트학회 2021 한국콘크리트학회 학술대회 논문집 Vol.33 No.2
본연구는 PSC연속교의 하중횡분배 영향을 유한요소해석 하였다. 가로보의 개수에 따른 L/2, L/3, L/5 형태로 배치하여 검토한다. 또한 PSC연속교의 격자해석법 및 Solid요소 해석을 비교한다. 그 결과, 격자해석보다 Solid요소 해석이 완만한 처짐이 발생한다. 두 해석 방법에 따라 모멘트도의 차이도 발생한다. This study is perfomed finite element analysis on the effect of load lateral distribution of continous PSC bridge. Cross beam is arranged in the form of L/2, L/3, and L/5 to examine the effect. In addition, The grid analysis method and the Solid element analysis of continuos PSC bridge are compared. As a result, a more gentle deflection occurs in the solid element analysis than in the grid analysis. There is also a difference in moment diagram between the two analysis methods.
NITE 방법에 의한 SiC<SUB>f</SUB>/SiC 복합재료의 인장강도 특성
조호준(Ho-Jun Cho),이영주(Young-Ju Lee),윤한기(Han-Ki Yoon) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
This paper concerns the nano-infiltration transient eutectic-phase (NITE) method for the fabrication of SiC based ceramic materials and effect of SiC fiber coating. The submicron SiC powder was also utilized for the improvement of NITE-SiC materials. A mixture powder of Al₂O₃ and Y₂O₃ was used as an additive in the NITE process. NITE-SiC materials were fabricated by various sintering parameters such as sintering temperature, additive composition ratio (Al₂O₃/Y₂O₃) and additive amount (Al₂O₃+Y₂O₃). The materials have been sintered for 1 hour at 1800℃ under the pressure of 20㎫. The SiC fiber of SiC<SUB>f</SUB>/SiC composite was important to improve mechanical properties of SiC composite. Effect of fiber coating was examined to improve their ductility. Therefore, In order to investigate mechanical properties, The tensile strength of NITE-SiC materials was carried out at room temperature using a tensile test to evaluate effect of SiC Fiber coating.
선박엔진용 Crankcase Relief Valve의 구조 해석 및 역설계
조호준(Ho-Jun Cho),이영주(Young-Ju Lee),박수건(Su-Kun Park),윤한기(Han-Ki Yoon) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The relief valve is the important equipment used to protect the pressure vessel, the steam generator and the other pressure facility from overpressure by discharging the operating medium when the pressure of system is reaching the design pressure of the system. But we are depending on technology of a foreign country to the present time because we don't have our own technology. Therefore, we have developed a new relief valve which is a safety device for the domestic crankcase relief valve.