회원작품 - 레인보우 유치원

최재형,Choi, Jae-hyeong 대한건축사협회 2015 建築士 Vol.2015 No.6

고온가압소결을 이용한 YSZ-TiC 세라믹스 복합체의 제조와 특성

최재형,최지영,김성원,Choi, Jae-Hyung,Choi, Ji-Young,Kim, Seongwon 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.5

Zirconia has excellent mechanical properties, such as high fracture toughness, wear resistance, and flexural strength, which make it a candidate for application in bead mills as milling media as well as a variety of components. In addition, enhanced mechanical properties can be attained by adding oxide or non-oxide dispersing particles to zirconia ceramics. In this study, the densification and mechanical properties of YSZ-TiC ceramic composites with different TiC contents and sintering temperatures are investigated. YSZ - x vol.% TiC (x=10, 20, 30) system is selected as compositions of interest. The mixed powders are sintered using hot pressing (HP) at different temperatures of 1300, 1400, and 1500℃. The densification behavior and mechanical properties of sintered ceramics, such as hardness and fracture toughness, are examined.

SiAlON 원료분말제조를 위한 분무건조 과립분말의 형상과 크기에 미치는 공정변수효과

최재형,이소율,한윤수,이성민,남산,김성원,Choi, Jae-Hyeong,Lee, Soyul,Han, Yoonsoo,Lee, Sung-Min,Nahm, Sahn,Kim, Seongwon 한국재료학회 2017 한국재료학회지 Vol.27 No.12

SiAlON-based ceramics are some of the most typical ceramic materials used as cutting tools for HRSA(Heat Resistant Super-Alloys). SiAlON can be fabricated using ceramic processing, such as mixing, granulation, compaction, and sintering. Spray drying is a widely-used method for producing a granular powder of controlled morphology and size with flowability. In this study, we report a systematic investigation aimed at optimizing spherical granule morphology by controlling spray-drying parameters such as gas flow and feed rate. Before spray drying, the viscosities of the raw material slurries were also optimized with the amount of dispersant added.

위암조직에서의 MAGE 유전자 발현

최재형,이상호,Choi, Jae-Young,Lee, Sang-Ho 대한위암학회 2005 대한위암학회지 Vol.5 No.3

목적: 정상세포와는 달리 종양세포에서만 비교적 특이적으로 발현되는 것을 tumor specific antigens이라고 하며 대표적인 것은 악성흑색종에서 처음 발견된 MAGE (melanoma antigen)가 있다. 위암조직에서의 MAGE subtype의 발현율은 약 $20{\sim}40%$ 정도로 알려져 있는데 진행성 위암은 전체적으로 예후가 불량하기 때문에 면역치료법과 같은 새로운 치료법을 고려해 볼 수 있다. 본 연구에서는 술 후에 얻은 정상 및 암 조직에서의 MAGE의 발현정도를 각 subtypes에 공통으로 존재하는 유전자를 Primers로 이용하여 조사하였다. 대상 및 방법: 내시경에서 진행성 암으로 진단된 후 수술받은 환자 53명을 대상으로 하였으며, 수술 중 절제된 위에서 정상조직과 암 조직을 얻어 $-70^{\circ}C$에서 보관하였다. 환자는 남자가 35명, 여자가 18명이었고 이들의 평균 연령은 57세였다. 보관된 조직에서 m-RNA를 분리한 후 RT-PCR과 nested PCR로 MAGE의 발현여부를 알아보았다. 기존에 알려진 MAGE gene의 subtypes에 공통으로 존재하는 oligonucleotides를 일차 primers로 이용하여 증폭시켰다. 그 후 또 다른 primers를 이용한 nested RT-PCR을 시행하여 각 조직에서의 발현율을 조사하였다. 결과: 위암환자에서 53예의 암조직 중 13개(24.5%)에서 MAGE gene이 양성으로 나왔고 정상조직에서는 MAGE gene이 모두 음성이었다. 위암의 조직형, ABO type, CEA, CA19-9와 cancer의 위치와는 상관관계가 없었다. 결론: 위암환자의 $20{\sim}30%$에서 MAGE gene이 발현되었으며, 이에 MAGE gene을 이용한 면역치료법의 시도가 필요 할 것으로 생각한다. Purpose: Among tumor-associated antigens, MAGE (melanoma antigen) was named as cancer/testis specific antigens because they are detected exclusively in the testis or cancer cells, including gastric carcinomas. Due to the elicitation of autoimmunitiy to tumors by these antigens either in vitro or in vivo and their tumor specificity, these antigens, thus, appear to be potential targets for tumor-specific immunotherapy. Materials and Methods: The fresh tumor tissue and normal gastric tissue samples were obtained from resected surgical specimens in 53 patients with gastric carcinomas. From the obtained cells, total cellular mRNA was extracted, and RT-PCR and nested PCR were run in 30 and 35 cycles respectively, with two different kinds of primers specially designed to detect six subtypes of MAGE DNA simultaneously. Results: In the 53 normal tissue, there was no expression of MAGE, but in the 53 cancer tissues, MAGE was expressed in 13 tissues (24.5%). Our data did not exhibit any correlation with the expression of the MAGE gene and clinicopathological factors. Conclusion: In our data, since 24.5% of gastric cancer tissues expressed MAGE, it should become possible to immunize a significant proportion of patients with advanced gastric carcinomas against the antigens encoded by these genes, provided that more antigenic peptides encoded by the genes of the MAGE family can be identified in the near future. (J Korean Gastric Cancer Assoc 2005;5:180-185)

SiAlON의 절삭성능에 미치는 소결조제와 조성의 영향에 대한 연구

최재형,이성민,남산,김성원,Choi, Jae-Hyeong,Lee, Sung-Min,Nahm, Sahn,Kim, Seongwon 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.5

SiAlON ceramics are used as ceramic cutting tools for heat-resistant super alloys (HRSAs) due to their excellent fracture toughness and thermal properties. They are manufactured from nitride and oxide raw materials. Mixtures of nitrides and oxides are densified via liquid phase sintering by using gas pressure sintering. Rare earth oxides, when used as sintering additives, affect the color and mechanical properties of SiAlON. Moreover, these sintering additives influence the cutting performance. In this study, we have prepared $Yb_{m/3}Si_{12-(m+n)}Al_{m+n}O_nN_{16-n}$ (m = 0.5; n = 0.5, 1.0) ceramics and manufactured SiAlON ceramics, which resulted in different colors. In addition, the characteristics of the sintered SiAlON ceramics such as fracture toughness and microstructure have been investigated and results of the cutting test have been analyzed.

회전익 항공기 전륜착륙장치 단속거동 현상 개선연구

최재형,장민욱,이윤우,윤종진,Choi, Jae Hyung,Chang, Min Wook,Lee, Yoon-Woo,Yoon, Jong Jin 한국항공운항학회 2017 한국항공운항학회지 Vol.25 No.3

The Nose Landing Gear(NLG) of Rotary Wing Aircraft is an essential equipment in Landing System for pilot to perform a flight mission. It supports the fuselage at ground and absorbs the impact from the ground when landing, thereby, these functions sustain operational capability for pilot and crew. However, the A aircraft caused stick-slip behavior when it was stationed on the ground. Therefore, this paper summarizes pilot comment in operation which are classified by cause of occurrence and the troubleshooting process about each comment. It also describes design improvements which was derived from troubleshooting and suggests verification results of flight test.

전도냉각형 고온초전도 에너지저장장치의 전기적 특성

최재형,곽동순,천현권,김해종,김상현,Choi, Jae-Hyeong,Kwag, Dong-Soon,Cheon, Hyeon-Gweon,Kim, Hae-Jong,Kim, Sang-Hyun 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.2

The conduction-cooled HTS SMES is operated in cryogenic and high vacuum condition. Thus, Insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish miniaturization that is a big advantage of HTS SMES. However, the behaviors of insulators for cryogenic conditions in vacuum are virtually unknown. Therefore, we need active research and development of insulation concerning application of the conduction-cooled HTS SMES. Therefore, in this study, we experimented about insulation characteristic high vacuum and cryogenic similar to driving condition of SMES system. Also, investigated about insulation characteristic of suitable some materials to insulator for conduction-cooled HTS SMES. As this results, we possessed basis data for insulation materials selection and insulation design for development of 600 kJ class conduction-cooled HTS SMES.

해상풍력 기술개발 및 서남해 실증단지 공사 현황

최재형(jaehyung Choi),김동준(Dong-Joon Kim),김현일(hyunil Kim),최윤호(Yoonho Choi) 대한토목학회 2018 대한토목학회지 Vol.66 No.1

반응표면법과 유전자 알고리듬을 이용한 런플랫 타이어 최적화

최재형(Jaehyeong Choi),강남철(Namcheol Kang) 한국소음진동공학회 2015 한국소음진동공학회 논문집 Vol.25 No.4

Ride comfort is one of the major factors in evaluating the performance of the vehicle. Tire is closely related to the ride comfort of the vehicle as the only parts in contact with the road surface directly. Vertical stiffness which is one of the parameters to evaluate the tire performance is great influence on the ride comfort. In general, the lower the vertical stiffness, the ride comfort is improved. Research for improving the ride comfort has been mainly carried out by optimizing the shape of the pneumatic tire. However, demand for safety of the vehicle has been increased recently such as a run-flat tire which is effective in safety improvement. But a run-flat tire have trouble in practical use because of poor ride comfort than general tire. Therefore, In this paper, the research was carried out for improving the ride comfort through the optimization of the SIR shape inside a run-flat tire. Meta-model was generated by using the design of experiment and it was able to reduce the time for the finite element analysis of optimization. In addition, Shape optimization for improving the ride comfort was performed by using the genetic algorithm which is one of the global optimization techniques.

환경차폐코팅용 이터븀 실리케이트의 제조와 물성평가

최재형(Jae-Hyeong Choi),김성원(Seongwon Kim) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.6

Environmental barrier coatings(EBCs) are applied to the SiC/SiC ceramic matrix composites(CMCs) in order to protect CMCs from being corroded with water vapor by combustion gas in gas turbine engines. Ytterbium silicates, such as ytterbium monosilicate and ytterbium disilicate, are ones of the candidate materials for EBCs due to their excellent resistance to water vapor corrosion as well as thermal-expansion match with SiC. In this study, ytterbium silicates are fabricated with 2-step solid-state synthesis targeting ytterbium disilicate. After synthesizing ytterbium monosilicate, the mixtures of ytterbium monosilicate and SiO₂ are heat-treated and densified by using pressureless sintering or hot pressing with a variety of heating conditions. The phase formation, thermal expansion, and oxidation behavior are examined with fabricated specimens. The final densified bodies are found to be composites between ytterbium monosilicate and ytterbium disilicate with different ratios, which results in 4.43 to 6.72×10<SUP>-6</SUP>/K range of coefficients of thermal expansion. The probability of these ytterbium silicates for EBC applications is also discussed.