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김정중(Kim Jung-Joong),손장열(Sohn Jang-Yeul) 한국생활환경학회 2009 한국생활환경학회지 Vol.16 No.2
Recently sports stadiums have been built not only for athletic sports but also for various events such as live concerts and recitals. The number of the stadiums which are covered by a half dome have been increasing. Therefore it is very important to solve the sound obstacle problem caused by the half dome. But sound designs of most of stadiums, with only a few as an exception, have not been planned properly and the proper sound absorption materials have not been used. This study investigates four World Cup stadiums (Seoul, Incheon, Daegu, Busan). First, sound factors according to the location in the stadium were compared by the design standard through field measurement. Then architectural sound absorption structure was analyzed and in turn the sound factors were considered totally for obtaining the proper reverberation time, RASTI, and sound pressure level. The average reverberation time for dome stadiums Busan were 6.03 seconds, longer than arch(Daegu) stadiums which were 3.8 seconds. However, the variance of the reverberation time at low frequencies(125 ㎐ and 250 ㎐) between the lower tiers(tier 1, 2) and the higher tiers(tier 4, 5) was larger in arch stadiums Daegu by about 2 seconds. The RASTI values for shield kite stadiums Seoul and dome stadiums Busan were between 0.38 and 0.50 indicating that audibility was ‘Poor’ to ‘Fair’. But otherwise, cone stadiums incheon achieved a RASTI value of 0.50 for all spectator seats and arch stadiums Daegu satisfy audibility standards for all areas except the playing field.
산화 이리듐의 물의 산화반응에 대한 버블 과전압 현상과 촉매 특성 연구
김정중,최용수,권성중,Kim, Jeong Joong,Choi, Yong Soo,Kwon, Seong Jung 한국전기화학회 2013 한국전기화학회지 Vol.16 No.2
Iridium oxide is well known as an electrocatalyst for the water oxidation. Recently, Dr. Bard's group observed the electrocatalytic behavior of individual nanoparticle of Iridium oxide using the electrochemical amplification method by detecting the single nanoparticle collisions at the ultramicroelectrode (UME). However, the electrocatalytic current is decayed as a function of time. In this study, we investigated that the reason of electrocatalytic current decay of water oxidation at Iridium oxide nanoparticles. We identified it is due to the bubble overpotential because the cyclic current decay and recovery were synchronized to the oxygen bubble growth and coming away from an Iridium disk electrode. 산화 이리듐은 물의 산화반응에 대해 좋은 전기촉매 물질로서 많은 연구가 이루어 지고 있다. 최근 전기화학적 증폭방법을 이용하여 산화 이리듐 나노입자의 개별적인 촉매특성을 연구한 결과를 보면 촉매반응에 의한 전류가 지속적으로 유지되지 않고 시간에 따라 감소하는 결과가 얻어 졌다. 이러한 촉매특성의 사라짐에 대한 원인을 규명하고자 사이즈가 큰 이리듐전극을 산화시킨 산화이리듐 전극에서 물의 산화반응을 진행시켰다. 그 결과 나노입자에서와 유사하게 전류가 감소하는 현상이 관찰되었다. 큰 전극에서의 실험에서는 발생하는 산소방울을 관찰 할 수 있었는데 산소방울의 발생 주기가 전류의 증감주기와 일치하는 것으로 보아 전류의 감소는 산소방울에 의한 버블 과전압 때문으로 생각된다.
FRP-UHPC 복합 보강기법으로 보강된 RC 슬라브의 휨 파괴를 위한 설계 조건
김정중 ( Jung Joong Kim ),노혁천 ( Hyuk Chun Noh ),마흐무드레다타하 ( Reda Taha,Mahmoud ) 한국복합신소재구조학회 2012 복합신소재학회논문집 Vol.3 No.2
This study proposes flexural failure design criteria of continuous slabs enhanced by a hybrid system of fiber reinforced polymer (FRP) and ultra high performance concrete (UHPC). The proposed hybrid retrofit system is designed to be placed at the top surface of the slabs for flexural strengthening of the sections in both positive and negative moment zones. The enhancing mechanisms of the proposed system for both positive and negative moment regions are presented. The neutral axis of the enhanced sections in positive moment zone at flexural failure is enforced to be in UHPC overlay for preventing the compression in FRP. From this condition, a relationship between design parameters of FRP and UHPC is established. Although the capacity of the proposed retrofit system to enhance flexural strength and ductility is confirmed through experiments of one-way RC slabs having two continuous spans, the retrofitted slabs failed in shear. To prevent this shear failure, a design criteria of flexural failure is proposed.
실리케이트 연결구조를 고려하여 포졸란 물질을 포함한 시멘트 바인더의 반응도를 결정하는 방법
김정중(Kim Jung Joong) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.6
본 논문에서는 ²⁹Si MAS (Magic Angle Spinning) NMR (Nuclear Magnetic Resonance) 실험을 통하여 시멘트 구성물질의 반응도를 결정하는 방법을 소개한다. 시멘트 구성물질의 반응도를 중량비에 따른 가중치로 평균하여 시멘트의 수화도를 결정한다. 구성물질의 반응도는 아브라미(Avrami) 방정식을 따르는 것으로 가정한다. 또한, 포졸란 물질을 사용한 시멘트에 대해서는 ²⁹Si MAS NMR 결과를 활용하여 포졸란의 변환율을 결정하는 방법도 소개한다. 사례연구와 함께 제안된 방법에 대한 계산과정을 실었다. In this study, a methodology to determine the degree of reactivity for compositions of cements was introduced. The degree of hydration can be determined by the weighted average of the degree of reactivity for major compositions of cements. It is assumed that the degree of reactivity for major compositions of cements follows Avrami equation. Moreover, the conversion fraction of pozzolan materials for pozzolan blended cement pastes can be extracted from the results of ²⁹Si nuclear magnetic resonance (NMR) experiments. The calculation procedures for the proposed methodology are presented with case studies.