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최원창,윤현도,이재연 한국구조물진단유지관리공학회 2012 한국구조물진단유지관리공학회 논문집 Vol.16 No.3
바이오매스에서 얻어지는 바이오차는 토질 개량제와 탄소 격리제로 제한적인 분야에서 성공적으로 사용되고 있다. 현재 산업전반에서 CO2 에 의한 환경에 부정적인 영향을 완화시키고 지속가능성을 증진시키기 위한 연구가 활발히 진행되고 있다. 이에 본 연구에서는 고탄소 바이오차를 탄소 격리제 또는 시멘트의 혼화재로써 활용 가능성을 평가하고자 하였다. 견목재에서 얻어진 바이오차를 혼화재로 사용하여 시멘트 배합조건을 달리하면서 모타르의 압축강도, 마이크로구조, 압축강도, 유동성, 중량감소와 같은 화학적, 물리적 재료성질을 평가하였다. 또한 플리이애쉬를 사용한 모르타르의 역학적 특성과 비교 평가하였다. Bio-char, obtained from biomass as a by-product of the pyrolysis process, is used successfully as a soil amendment and carbon sequester in this limited study. Recent and active research from literatures has extended the application of bio-char in the industry to promote sustainability and help mitigate the negative environmental impacts caused by carbon emissions. This study aims to investigate the feasibility of high-carbon bio-char as a carbon sequester and/or admixture in mortar and concrete to improve the sustainability of concrete. This paper presents the experimental results of an initial attempt to develop a cement admixture using bio-char. In particular, the effects of the water retention capacity of bio-char in concrete are investigated. The chemical and mechanical properties (e.g., the chemical components, microstructure, concrete weight loss, compressive strength and mortar flow) are examined using sample mortar mixes with varying replacement rates of cement that contains hardwood bio-char. The experimental results also are compared with mortar mixes that contain fly ash as the cement substitute.
Spray Pyrolysis에 의한 Manganese Oxide 입자의 제조 및 전기화학적 특성
최원창,변동진,이중기,박달근,김현중,Choi, Won-Chang,Byun, Dong-Jin,Lee, Jung-Kee,Park, Dal-Keun,Kim, Hyeon-Joong 한국재료학회 2001 한국재료학회지 Vol.11 No.11
Spray pyrolysis is a favorable technique to form complex mixed-metal oxide powders with high purity in high temperature region. Manganese oxide powders were prepared by spray pyrolysis from an aqueous solution of $Mn(NO_3)_2$. Powders were formed in the temperature range of 500~$700^{\circ}C$ under the constant pressure of 300torr. All the powders have hydrous forms. When the temperature was increased, the size and the surface area of the particles decreased. An electrochemical capacitors were made with manganese oxide electrodes and KOH electrolyte. With the temperature decreased, capacitors showed high capacitance. Capacitor which was prepared with powders formed in the temperature $500^{\circ}C$ demonstrated specific capacitances as high as 83F/g.
Design of Feedback Control for Quadrotors Considering Signal Transmission Delays
최원창,Stephen K. Armah,Sun Yi 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.6
For quadrotor types of unmanned aerial vehicles (UAVs), existence of transmission delays caused bywireless communication is one of the critical challenges. Estimation of the delays and analysis of their effectsare not straightforward for designing controllers. An estimation method is introduced using experimental data andanalytical solutions of delay differential equations (DDEs). Collected altitude responses in the time domain arecompared to the predicted ones obtained from the analytical solutions. The Lambert W function-based approachfor first-order DDEs is used for such analysis. The dominant characteristic roots among infinite number of rootsare obtained in terms of coefficients and the delay. The effects of the time delay on the responses are analysedthrough the locations of the characteristic roots in the complex plane. Based on the estimation result, proportionalplus velocity controllers are proposed to improve transient altitude responses.