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Singil Kang,Hojun Cha,Seungcheol Ryu,Kiwhan Kim,Seungmin Jeon,Jaesun Lee,Seokho Kim 한국초전도저온학회 2022 한국초전도저온공학회논문지 Vol.24 No.1
Recently, research on applying composite materials to various industrial fields is being actively conducted. In particular, composite materials fabricated by Fused Deposition Modeling 3D printers have more advantages than existing materials as they have fewer restrictions on manufacturing shape, reduce the time required, weight. With these advantages, it is possible to consider utilizing composite materials in cryogenic environments such as the application of liquid oxygen and liquid hydrogen, which are mainly used in an aerospace and mobility. However, FDM composite materials are not verified in cryogenic environments less than 150K. This study evaluates the characteristics of composite materials such as tensile strength and strain using a UTM (Universal Testing Machine). The specimen is immersed in liquid nitrogen (77 K) to cool down during the test. The specimen is fabricated using 3D print, and can be manufactured by stacking reinforced fibers such as carbon fiber, fiber glass, and aramid fiber (Kevlar) with base material (Onyx). For the experimental method and specimen shape, international standards ASTM D638 and ASTM D3039 for tensile testing of composite materials were referenced.
김승철(Seungcheol Kim),최재섭(Jaeseob Choi),강병영(Byungyoung Kang),김원식(Wonsik Kim),김병조(Byungjo Kim) 한국자동차공학회 2019 한국자동차공학회 학술대회 및 전시회 Vol.2019 No.11
본 연구에서는 토출구 상하폭이 15㎜ 이하인 초슬림 에어벤트의 풍향성을 확보하기 위한 구조에 대해 논하고자 한다. 제한된 공간에 공조성능이 기존 대비 떨어지지 않는 에어벤트를 적용하기 위한 실험적 분석 및 설계를 진행하였다. 15㎜ 이하의 좁은 틈에서 바람이 나올 경우 코안다 효과가 크래시패드의 상측 혹은 하측 스킨면을 타고 형성되는 것이 실험적으로 관찰되었다. 코안다 효과의 영향도를 분석할 실험을 진행하기 위해 에어벤트, 스킨면 그리고 코안다 효과와의 관계를 정의하고 그에 부합하는 설계인자를 설정하였다. 설계 인자 기준으로 제작된 간이 모델과 Fog 유동 가시화 장비를 이용하여 코안다 효과로 인한 풍향 변화를 측정하였다. 그 결과 상하 스킨면의 각도 차이와 길이 차이가 커질수록, 코안다 효과가 더 커지는 것이 확인되었다. 또한, 설계인자의 조절을 통해 바람이 한 쪽 스킨면으로만 흘러 상향풍, 하향풍만 형성할 수 있는 것이 아닌 중간 영역의 바람도 형성할 수 있다는 것을 발견하였다. 실험적 분석을 기반으로 코안다 효과를 응용한 초슬림 에어벤트의 신규 구조를 설계하였고, 해석 및 시험 평가를 통해 공조성능을 검증하였다. 또한, 초슬림 에어벤트를 적용하기 위한 제약 조건을 정의하고 코안다 효과가 극대화 될 수 있는 상하 스킨면의 조건을 정의하였다. 이와 같은 과정을 통해 초슬림 에어벤트의 풍향 조절을 위한 구조를 제안하고자 한다.
Jae Hee Choi,Seungcheol Kang,Hyojune Kim,Euisop Lee,Yu Na Lee,In Kyong Shim,Kyoung Hwan Koh 대한견주관절의학회 2021 대한견주관절학회 학술대회논문집 Vol.2021 No.3
Introduction and Background Stem cells are an effective method of biologic healing and can be used to enhance the natural enthesis of the tendon-to-bone junction in rotator cuff repair. This study investigated whether the application of engineered stem cell sheets using adipose-derived stem cells (ASCs) was effective in regenerating natural enthesis and, whether there was a difference in the result of repair depending on the applied location. Material and Method A chronic rotator cuff tear model was induced for 2 weeks, and rat ASC-derived cell sheets were transplanted into the tendon-to-bone junction during surgical repair. Based on the transplant location of the cell sheets, the difference in rotator cuff healing level between the overlay group and the interposition group was compared with the surgical repair only group. The samples were obtained based on the tendon-to-bone junction, and analysis of gross morphology, histology staining, and biomechanical analysis were performed. Results The differentiation potentials of ASCs as stem cells were confirmed, as was the potential for tenogenic differentiation by growth factors. ASCs were prepared as a sheet form to maintain the shape at the target site and attach easily. Green fluorescent protein-expressing ASCs were proliferated in vivo and observed at the transplantation site. The overall healing level was better in the cell sheet transplanted groups than the surgical repair only group. In addition, differences in healing level were observed based on the cell sheet location regarding morphological, histological, and biomechanical perspectives. Histological results showed that the interposition transplantation group had better fibrocartilage formation and collagen orientation at the junction than the overlay group. Conclusions In the chronic rotator cuff repair model, the engineered stem cell sheets enhanced the regeneration of the tendon-to-bone junction. This regeneration was more effective when the stem cell sheet was interpositioned at the tendon-to-bone interface.
Bae Kunhyung,Park Soo-Sung,Park Jinhee,Kang Michael Seungcheol 대한의학회 2021 Journal of Korean medical science Vol.36 No.45
Background: In the Korean medical system, the severity classification for a specific disease depends primarily on its nationwide admission rate in tertiary hospitals. Inversely, one of the important designation criteria for a tertiary hospital is the hospital's treatment ratio of patients classified as having a specific severe disease. Most diseases requiring pediatric orthopaedic surgery (POS) are not currently classified as high severity in terms of disease severity. We investigated the admission rates for the representative POS diseases in tertiary hospitals and compared these rates with those for adult orthopaedic surgery (AOS) diseases. Methods: Seven POS diagnoses and three AOS diagnoses were selected based on frequency of admission. Nationwide sample data were used to investigate the admission rates for these representative diagnoses from 2008 to 2017. Results: Six of the seven frequent POS diagnoses presented high admission rates in tertiary hospitals (62.5–92.3%). In contrast, all frequent AOS diagnoses presented low admission rates in tertiary hospitals. Conclusion: The admission rates of frequent POS diagnoses in tertiary hospitals are high. Considering that these rates are the most important factors for the classification of disease severity, POS diseases seem to be underestimated in terms of severity. This may lead to a tendency for tertiary hospitals to intentionally reduce the admission of children with POS diseases. As a result, these children may not receive appropriate professional care. Therefore, for the disease severity, POS diseases should be classified differently from general AOS diseases by using different criteria reflecting the patient's age.
유찬호(Yoo Chanho),한연진(Han Yeonjin),강수용(Kang Sooyoung),백승철(Baek Seungcheol) 한국지반환경공학회 2012 한국지반환경공학회논문집 Vol.13 No.3
연약지반 개량공법에 있어서 대부분의 수평 배수층은 모래나 쇄석 등의 골재를 이용하고 있으나, 이러한 골재를 수평 배수층으로 사용하는 경우에는 종종 원지반의 침하불량을 유발하는 경우가 발생하고 있다. 이에 수평 배수층을 깔지 않고 수평 배수용 파이프를 이용하는 수평배수관망 시스템이 개발되어 적용되고 있다. 이러한 공법은 반복 성토과정으로 발생하는 과잉 간극수압을 수평 배수관망으로 직접 배수하는 시스템이다. 본 연구에서는 수평배수관망 시스템의 적용성과 시공성을 확인하고자 실 규모 현장시험 시공을 수행하여 수평배수관망 시스템의 적용성을 평가하였다. 현장시험시공을 통하여 수평 배수관망 시스템의 침하 거동특성을 살펴보았으며, 또한 수평배수관망 변형정도를 확인하여 일반적인 수평배수층을 이용하는 공법과 비교분석하여 그 효용성을 확인하였다. The most of horizontal drainages, which is composed of the aggregates made of sand and crushed stone, are used to improve the soft ground. However, where the aggregates are used as the horizontal drainage, it often brings about the delay of consolidation. For this reason, the horizontal drain pipe system is applied to properly improve the soft ground using a drainage pipe instead of horizontal drainage. This system is direct drain method for disappearing the excess porewater pressure which is caused by placing of fill on the soft ground. The large-scale field test was conducted in order to evaluate the applicability and constructability of the horizontal drain pipe system. The settlement characteristics of improved ground with horizontal drain pipe system was observed. It is also compared to the conventional soft ground improvement method to confirm its effectiveness.
Il-Yeong Hwang,Jinhee Park,Soo-Sung Park,Jinseok Yang,Michael Seungcheol Kang 대한정형외과학회 2021 Clinics in Orthopedic Surgery Vol.13 No.3
Background: Many studies have reported injury characteristics of individual traumatic situations. However, a comparative analysis of specific risks is meaningful to better understand injury characteristics and help establish injury-prevention measures. This study was conducted to investigate and compare injury characteristics in children and adolescents by various outdoor traumatic situations. Methods: Outdoor traumatic situations were determined and classified into physical activity-related injury (n = 3,983) and pedestrian (n = 784) and passenger (n = 1,757) injuries in traffic accidents. Home injury (n = 16,121) was used as the control group. Then, the characteristics of each outdoor trauma were compared with 1:1 matched indoor trauma (among home injuries); each outdoor traumatic situation’s predisposing risk for the injured body part, injury type, and injury severity were analyzed; and changes by age of frequency ranking among physical activity-related injuries were investigated. Results: Outdoor trauma showed higher risks for limb injuries (injured body part), fracture and muscle/tendon injuries (injury type), and severe injuries (severity) than indoor trauma. Various outdoor traumatic situations presented different predisposing effects on injury characteristics. Among physical activity-related injuries, bicycle injury was commonest across all ages, and playing activities were common causes for injury for individuals of age < 9 years, whereas sports activities overwhelmed the common causes thereafter. Conclusions: The findings would help to better understand the specific injury risk of various outdoor traumatic situations and may potentially facilitate the establishment of more effective injury-prevention measures.