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Synthesis and visible light photocatalytic activity of porous CeO2-TiO2 composite powders
한재길,고준빈,Sung-Min Choi,강인철 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.1
Porous CeO2-20 wt.%TiO2 composite powders having a homogeneous distribution and nanocrystalline were successfully synthesized by a sol-gel process using titanium iso-propoxide and Ce(NO3)3·6H2O as precursors. The particle sizes of the asreceived porous CeO2-20 wt.%TiO2 composite powders were measured in the range from 0.3 to 10 μm by SEM. As the calcination temperature was increased up to 1050 oC, the porous composite powders having pores ranging from 0.1 nm to 3 μm in pore size were obtained. The pore frames of CeO2-20 wt.%TiO2 composite powders were less than 500 nm thick and they were nanocrystalline with a dense structure. From a comparison of the photocatalytic activity, the porous CeO2-20 wt.%TiO2composite powders calcined at 900 oC showed an excellent efficiency for the removal of phenol under UV light. However, in the powders calcined at 600 oC, there was a relatively higher photocatalytic activity than that of other powders under visible light. Hence this sample had a strong edge band at a blue-green wavelength range.
마이크로파-수열 합성법을 이용한 나노 수산화아파타이트 합성과 특성평가
한재길,이치우,이병택,Han, Jae-Kil,Lee, Chi-Woo,Lee, Byong-Taek 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.2
Nano-sized hydroxyapatite (HAp) powders were synthesized by a microwave-hydrothermal method using $H_3PO_4\;and\;Ca(OH)_2$ as starting materials. The applied microwave powers and mole ratio of Ca/P were served as powerful factors in the synthesis of calcium phosphate. In the case of relatively low microwave power of 450 Wand Ca/P ratio of 1.57, the mixed calcium phosphate compounds were detected in the synthesized powders. But in the case of running at 550 Wand 1.67(Ca/P), the synthesized powder showed the monophase of HAp having two kinds of morphologies. One was a needle shape with $5\~15\;nm$ in width and $20\~50\;nm$ in length, and the other was a spherical shape of $10\~40\;nm$ in diameter.
한재오(Jae-Oh Han),이수영(Soo-Young Lee),유승훈(Seung-Hun Yu),이재권(Jai-Kwon Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper was a study about noise reduction through flow stabilization in duct using experimental method and numerical analysis at the same time. To determine the fan's type three kinds of fans(axial fan, centrifugal fan, and axial fan with centrifugal type blades) was examined to investigate the suitability for in-line duct. As a result, under the equal number of rotation 2000 RPM, performance of an axial fan with centrifugal type blades was the most superior by 55㏈A at 4.3CMM among other fans. After this, analyzed the results of the numerical analysis to find out the optimum design of pitch angle such as 0°, 10°, 15° and 20°. The intensity of turbulence was low when pitch angle was 15° and air volume became peak by 5.08 CMM. It was observed that axis component of velocity increased gradually when pitch angle increased from 0° to 20°, and embodied noise reduction and improvement of air flow rate through flow stabilization.
Development of Auxiliary Wheel Unit Mechanism for Overcoming Obstacles
한재오,염광욱 한국인터넷방송통신학회 2019 Journal of Advanced Smart Convergence Vol.8 No.2
Recently, the spread of personal mobility has been rapidly increasing due to the development of environmentally friendly alternative transportation means. In addition, the level of battery technology is also rapidly developing, accelerating the popularization of personal mobility. Such personal mobility has convenience of location transfer, amusement, and high portability compared to other transportation devices. Most personal mobility, however, is made up of small wheels, which cannot overcome obstacles such as rugged roads or obstacles on the road. In this paper, to solve these problems, we tried to devise a device that can easily overcome obstacles by combining wheels with small moving means. The wheel size can be mounted on the front wheel of the small moving means in a protruding manner so that obstacles can be encountered before the front wheels and the safety and ride comfort of the running can be improved
CaAl<sub>2</sub>O<sub>4</sub>-CaAl<sub>4</sub>O<sub>7</sub>의 비율에 따른 시멘트 모르타르의 물리, 화학적 특성에 대한 연구
한재도 ( Han Jae-doh ),이한승 ( Lee Han-seung ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.2
콘크리트 내에서 염소이온을 고정 및 침투 억제할 수 있는 CA계 클링커의 상호간의 영향을 파악하기 위하여 CA(CaAl<sub>2</sub>O<sub>4</sub>)와 CA<sub>2</sub>(CaAl<sub>4</sub>O<sub>7</sub>)을 혼입하여 실험체를 제작하였다. 실험수준은 W/C 50%로 28일간 수중양생 진행되었고 클링커는 시멘트 중량대비 10%로 설정되었다. 평가결과 CA의 혼입율이 증가 할수록 초결이 빨랐지만 장기강도 발현이 감소했고, 시멘트 매트릭스 내부 공긍률이 증가했다. XRD분석결과 CA계 클링커를 혼입한 실험체에서 하이드로 칼루마이트 생성이 증가 한 것으로 보아 염소이온고정능력이 향상될 것 이라고 판단된다
공동현상을 고려한 유공압 방식 착륙장치의 낙하특성에 관한 연구
한재도(Jae-Do Han),이영신(Young-Sin Lee),강연식(Yeon-Sik Kang),안오성(Oh-Sung Ahn),공정표(Jeong-Pya Kong) 한국항공우주학회 2009 韓國航空宇宙學會誌 Vol.37 No.2
본 논문에서는 소형항공기용 유-공압 방식(oleo pneumatic type) 착륙장치의 낙하특성을 연구하였다. 본 연구대상의 착륙장치의 방식은 미터링 핀이 없는 단순 유-공압 방식댐퍼 이다. 일반적으로 유-공압 방식의 착륙장치는 단순한 구조로 되어 있어 무게가 가볍고 좋은 충격흡수 효율을 가진다. 낙하해석을 위하여 상용 코드인 MSC ADAMS를 이웅하여 모델링 하였다. 모델링한 후에 해석과 시험결과의 상사성을 검증하기 위하여 일련의 시험이 수햄되었다. 시험과 해석결과의 보다 좋은 일치성을 얻기 위하여 해석 모델에 공동현상 효과가 고려되었다. 공동현상을 고려한 착륙장치의 동적 거동 시뮬레이션 결과들이 현저하게 개선되었으며 시험결과와 보다 잘 일치함을 확인하였다. 이러한 과정을 통해 신뢰성이 검증된 해석모델을 이용하여 경사면에 대해서 해석적 방법을 통해 낙하특성을 예측하였다. This paper investigated the drop characteristics of oleo pneumatic type landing gear for small aircraft and the effects of cavitations in modeling the landing gear system. The landing gear system employed a simple oleo pneumatic type damper without a metering pin. In general, oleo-pneumatic type landing gears are light-weighted because of it's simplicity, yet they offer excellent impact absorption characteristics. In this study, the landing gear system was modeled using MSC ADAMS, which offers a drop simulation module. After modeling the system, a series of testing was conducted, using a prototype landing gear system, to validate the analysis model and simulation results. The effect of cavitation was considered in the simulation model to obtain a better correlation between the test and simulation results. The results show that adding the cavitation effect in the simulation model significantly improved the simulation model and better captured the dynamic behaviors of the landing system. Using the 'cavitation' model, dynamics characteristics of the landing gear were further evaluated for other landing conditions, such as landing in various angles of slopes.