스퍼터링 타겟용 저온 분사 Cu-15 at.%Ga 코팅 소재의 특성에 미치는 열처리 분위기의 영향

최병철,박동용,김형준,오익현,이기안,Choi, Byung-Chul,Park, Dong-Yong,Kim, Hyung-Jun,Oh, Ik-Hyun,Lee, Kee-Ahn 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.6

This study attempted to manufacture a Cu-15 at.%Ga coating layer via the cold spray process and investigated the effect of heat treatment environment on the properties of cold sprayed coating material. Three kinds of heat treatment environments, $5%H_2$+argon, pure argon, and vacuum were used in this study. Annealing treatments were conducted at $200{\sim}800^{\circ}C$/1 hr. With the cold sprayed coating layer, pure ${\alpha}$-Cu and small amounts of $Ga_2O_3$ were detected in the XRD, EDS, EPMA analyses. Porosity significantly decreased and hardness also decreased with increasing annealing temperature. The inhomogeneous dendritic microstructure of cold sprayed coating material changed to the homogeneous and dense one (microstructural evolution) with annealing heat treatment. Oxides near the interface of particles could be reduced by heat treatment especially in vacuum and argon environments. Vacuum environment during heat treatment was suggested to be most effective one to improve the densification and purification properties of cold sprayed Cu-15 at.%Ga coating material.

u-IT 기술혁신과 산업변화

최병철,박기식,Choi, B.C.,Park, K.S. 한국전자통신연구원 2006 전자통신동향분석 Vol.21 No.2

최근 컨버전스가 하나의 트렌드로 정착해 감에 따라, 그 동안 기기 및 기능 중심으로진행되던 디지털컨버전스가 이제는 인간, 사물, 공간을 유기적으로 통합하는 차원에서인간과 사물, 그리고 공간과 IT가 한데 어우러지는 유비쿼터스 양상으로까지 발전하고있다. 유비쿼터스 컴퓨팅 기술의 발달과 더불어 이제 유비쿼터스는 단순한 개념정립단계를 넘어 u-City, u-Health, u-교통, u-교육, u-유통/물류 등 수많은 분야에서 현실에 접목되면서 점점 더 구체화되고 있다. 유비쿼터스 기술이 가져오게 될 소위 유비쿼터스 IT 혁명은 소리없이 우리에게 다가오고 있으나, 그것이 몰고 올 변화는 우리 생활양식의 변화를 포함하여 실로 막대할 것으로 예측되고 있다. 이에 본 고에서는 u-IT시대를 향한 기술발전의 방향과 함께 그에 따른 관련 산업의 변화되는 모습을 예측해보고, 나아가서는 u-IT 사회를 조기에 구현하기 위해 해결되어야 할 주요한 과제들은 무엇인지를 간단하게 살펴보고자 한다.

향사양위탕(香砂養胃湯) 전탕액이 노화주의 비장, 췌장, 위장 세포의 항산화능에 미치는 영향

최병철,안택원,Choi, Byoung-Chol,Ahn, Taek-Won 사상체질의학회 2008 사상체질의학회지 Vol.20 No.2

1. Objectives The purpose of this study was to observe the anti-oxidant effects of Hyangsayangyi-tang(HY) in SD rats. 2. Methods This experiment was used the tissue of stomach, spleen and pancreas cells of 6, 52 and 68 weeks old SD rats. Each age group was again divided into three groups. One group, as normal group, was not-treated cells, another group, as control group, was saline-treated cells, and the last group, as experimental group, was HY-treated cells. After culture for 48 hours, each groups measured the level of SOD, GSH, MDA and NO in the tissue of stomach, spleen and pancreas cells. 3. Results and Conclusions The activity of SOD were significantly increased in spleen cell of 52, 68 w-HY group, pancreas cell of 68 w-HY group and in stomach cell of 52, 68 w-HY group compared with those of the normal and the control groups. The level of GSH were significantly increased in spleen cell of 52, 68w-HY group and in pancreas cell of 68w-HY group compared with those of the normal and the control groups. The level of MDA were significantly decreased in pancreas cell of 68 w-HY group compared with those of the normal and the control groups. The level of NO were significantly decreased in spleen cell of 68 w-HY group, pancreas cell of 52, 68w-HGD groups compared with those of the control groups. According to results, HY showed anti-oxidant effect. Investigation into the clinical use of the HY is suggested for future research.

촉매 연소기용 촉매의 내구 성능 향상 연구

최병철,유진상,서용석,정필수,Choi, Byugchul,Yu, Jin sang,Seo, Yong seok,Jung, Pilsoo 한국교통대학교 융복합기술연구소 2019 융ㆍ복합기술연구소 논문집 Vol.9 No.1

The aim of this study is to improve the durability performance of catalysts for a catalytic combustor and to obtain operating conditions for stable combustion of the catalytic combustor. It was attempted to improve the durability of the catalysts by adding a promoter in order to reduce the cost of replacing Pt catalyst while maintaining stability. The main catalyst used in the study was Pt and the promoters were Ni and La. Pure Pt3/γ-Al₂O₃ catalyst without promoter was promoted to fast sintering states under harsh conditions and catalytic combustion was turned off, whereas the catalysts added La, Ni as promoter were showed relatively slow sintering states. It can be concluded that the promoter La, Ni effectively contributes to the improvement of the durability of the Pt catalyst, and it is possible to get longer durability and more stable duration than the conventional catalytic combustor.

촉매연소기용 귀금속 촉매와 조촉매의 열적 내구특성 연구

최병철,고병운,김명환,신혁,Choi, Byungchul,Ko, Byeongwoon,Kim, Myeonghwan,Sin, Hyeok 한국교통대학교 융복합기술연구소 2020 융ㆍ복합기술연구소 논문집 Vol.10 No.1

The purpose of the study is to investigate the thermal durability characteristics of the Pt catalyst and additives used in a catalytic combustor. The catalyst used in the experiment was based on Pt (3 wt%), and a total of 12 types were prepared using a combination of additives (Ni, La, Ce, Fe, and Co). From the results, In the fresh state, the two types of combination catalysts with the highest C₃H₈ conversion were Pt_Ce (79.9%) at 500℃, and in the three types of combination catalysts, Pt_La_Ni (93.4%) at 500℃ had the best performance. Among aged catalysts at 850℃ and 8 hours, Pt-La-Ni and Pt-Ni-Ce catalysts showed the highest C₃H₈ conversion of about 71% at 500℃.

다공성 TiO₂-SiO₂ 복합 단열재의 열전도율 평가

최병철,김종호,김종범,정우남,이상현,Choi, Byugchul,Kim, Jon-Ho,Kim, Jon Beom,Jung, Woonam,Lee, Sang-Hyun 한국교통대학교 융복합기술연구소 2018 융ㆍ복합기술연구소 논문집 Vol.8 No.1

We developed nano-porous $TiO_2-SiO_2$ composites (commercial name : PTI, porous titania insulator) with low thermal conductivity as thermal insulating material as well as function of photocatalyst. The objectives of this paper are, firstly, to evaluate of the thermal conductivity of the PTI powder in the temperature range from -160 to $250^{\circ}C$, secondly to evaluate of thermal conductivities of insulation materials that is applied PTI powder. The structure of the PTI powder that has the pores size of 20-30 nm and the particle diameter of 2-10 nm. The PTI had a high surface area of $400m^2/g$ and a mean pore size of $45{\AA}$, which was fairly uniform. The thermal conductivity was measured by GHP(guarded hot plate) method and HFM(heat flux method). The PTI structure is a three-dimensional network nano-structures composed by a pearl-necklace that involved a precious stone in the center of the necklace. The thermal conductivities of PTI-PX powder by the GHP and HFM were 0.0366 W/m.K, 0.0314 W/m.K at $20^{\circ}C$, respectively. This is similar to values that are proportional to the square of the absolute temperature of the thermal conductivity of static air. The thermal conductivities of insulating sheets coated with PTI powder were similar results with that of the PTI powder.

황사의 발생 및 예보

최병철,Choi Byeong-Cheol 대한설비공학회 2006 설비저널 Vol.35 No.4

인공심장판막 실패에 대한 재치환술의 임상적 고찰

최병철,유환국,안욱수,허용,김병열,이정호,유회성,Choi, B.C.,Yoo, H.K.,Ahn, W.S.,Hur, Y.,Kim, B.Y.,Yoo, H.S. 대한심장혈관흉부외과학회 1991 Journal of Chest Surgery (J Chest Surg) Vol.24 No.7

To evaluate risks, complications and mortality of reoperations on heart valve prosthesis, we reviewed clinical records of 53 patients who underwent reoperation because of prosthetic valve failure[PVF], from Jan 1959 through Jun. 1991. They had undergone 48 mitral, 10 aortic valve rereplacement Primary tissue failure was the main cause of reoperation : it occurred in 51 valves at a mean postoperative interval of 58 months. Calcification and collagen disruption of prosthesis were main causes of primary tissue failure in macro and micropathology, In 3 failing mechanical prostheses, paravalvular leak was in 2 cases, another one case had the thrombi at the hinge portion. If conditions such as emergency operation with or without endocarditis, thromboembolism and advanced NYHA functional class are prevented, we think that reoperative valve replacement has similar morbidity and mortality to initial valve replacement surgery. But our sturdy represents higher mortality [22.6%] because of late surgical intervention failing the prevention of conditions leading to myocardial damage. In conclusion if the tearing, calcification, and a new murmur were detected the early reoperation should be considered to increase late survival.

심활성도 압반사 제어 모델을 이용한 심혈관시스템 모델링 및 시뮬레이션

최병철,정도운,손정만,예수영,김호종,이현철,김윤진,정동근,이상훈,전계록,Choi Byeong Cheol,Jeong Do Un,Shon Jung Man,Yae Su Yung,Kim Ho Jong,Lee Hyun Cheol,Kim Yun Jin,Jung Dong keun,Yi Sang Hun,Jeon Gye Rok 대한의용생체공학회 2004 의공학회지 Vol.25 No.6

본 연구에서는 심혈관시스템 내의 압력 변화를 감지하는 압수용체 중 가장 대표적인 대동맥 압수용체의 시뮬레이션을 위한 심활성도 압반사 제어모델을 제안하였다. 그리고 제안된 모델은 압반사 조절, 시간지연을 포함한 전기회로 모델들로 구성하였으며, 대동맥동의 압반사 조절시 시간지연이 심주기와 일회 심박출량에 주는 영향을 관찰할 수 있도록 하였다. 심활성도 압수용체 제어 모델에서 시간지연의 기전은 대동맥동 압수용체에서 감지된 압력 정보가 구심성 신경으로 전달되고, 이 정보는 중추신경을 거쳐 원심성 신경으로 전달되어 제어 기능을 수행한다. 제안된 모델의 시뮬레이션 결과 시간지연에 따라 심혈관시스템 변이성의 세가지 패턴을 관찰할 수 있었다. 먼저 시간지연이 2.5초 이상일 경우에는 대동맥압, 일회심박출량, 심박동수가 비주기적으로 발생하고 불규칙인 것을 관찰할 수 있었고, 시간지연이 0.1초에서 2.5초 사이일 경우에는 주기적인 진동이 발생함을 관찰할 수 있었다. 그리고 시간지연이 0.1초 이하인 경우에는 심박동수와 동맥압-심박동수의 궤적은 안정상태를 유지함을 관찰할 수 있었다. In this paper, we proposed a heart activity control model for simulation of the aortic sinus baroreceptor, which was the most representative baroreceptor sensing the variance of pressure in the cardiovascular system. And then, the heart activity control model composed electric circuit model of the cardiovascular system with baroreflex control and time delay sub-model to observe the effect of time delay in heart period and stroke volume under the regulation of baroreflex in the aortic sinus. The mechanism of time delay in the heart activity baroreflex control model is as follows. A control function is conduct sensing pressure information in the aortic sinus baroreceptor to transmit the efferent nerve through central nervous system. As simulation results of the proposed model, we observed three patterns of the cardiovascular system variability by the time delay. First of all, if the time delay over 2.5 second, aortic pressure and stroke volume and heart rate was observed non-periodically and irregularly. However, if the time delay from 0.1 second to 0.25 second, the regular oscillation was observed. And then, if time delay under 0.1 second, then heart rate and aortic pressure-heart rate trajectory were maintained in stable state.

Ni, Ru-ZSM-5를 첨가한 NSR 촉매의 NOx 정화 특성

최병철,이춘희,정종우,Choi, Byung-Chul,Lee, Choon-Hee,Jeong, Jong-Woo 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.5

In this study, we investigated the conversion performance of de-NOx catalyst for lean-burn natural gas engine. As a de-NOx catalyst, NOx storage reduction catalyst was composed of Pt, Pd and Rh with washcoat including Ba and Ni, Ru-ZSM-5. Ni, Ru-ZSM-5, which was regarded as a NOx direct decomposition catalyst, was made up of ion exchanged ZSM-5 by 5wt.% Ni or Ru. The performance of de-NOx catalyst was evaluated by NOx storage capacity and catalytic reduction in air/fuel, $\lambda=1.6$. The catalytic reaction was also observed when the added fuel was supplied to fuel rich atmosphere by fuel spike period of 5 seconds. The NOx conversion of the catalysts with Ni-ZSM-5 or Ru-ZSM-5 was mainly caused by the effect of NOx adsorption of Ba rather than the catalytic reduction of Ni, Ru-ZSM-5. Ni, Ru-ZSM-5 catalysts can not use for the NSR catalyst because they have quick process in thermal deactivation.