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형상기억합금으로 능동구속된 콘크리트 기둥의 해석모델 개발
정동혁 ( Jung¸ Donghyuk ),정새벽 ( Jeong¸ Sae-beyok ) 한국복합신소재구조학회 2021 복합신소재구조학회논문집 Vol.12 No.5
지난 수십 년간 발생한 강진으로 인해 철근의 내부 구속력이 부족한 철근 콘크리트(RC) 기둥에 수많은 심각한 피해가 발생하였다. 다양한 보수공법 중 형상기억합금(SMA)을 이용한 능동구속 기법은 지진에 취약한 RC기둥의 휨 연성을 높이는데 유의미한 결과를 보였다. SMA로 구속된 RC기둥의 동적거동에 관한 연구는 선행 연구자들에 의해 실험적으로 수행되었지만 구조적인 모델 개발은 거의 수행되지 않았다. 따라서 본 연구에서는 다양한 조건에서 능동구속된 RC기둥의 지진 시 거동을 확보하기 위해 SMA와이어로 보강된 RC 기둥의 진동대 실험 결과를 바탕으로 한 능동구속된 RC 기둥의 해석 모델을 제안한다. 제안된 해석모델은 양방향 지진력에 의한 SMA- RC기둥의 동적 거동 및 손상 정도를 확인할 수 있는 것으로 나타났다. Several reinforced concrete (RC) columns have been severely damaged by prior earthquakes because of the lack of sufficient internal steel confinement. Among various retrofitting methods, active confinement technique using shape memory alloy (SMA) showed promising results in improving the flexural ductility of seismically deficient RC columns. Although previous studies have experimentally investigated the seismic responses of SMA-confined RC columns, their structural models were rarely developed. This study develops analytical models of actively confined RC columns based on the shake table testing of RC columns retrofitted with SMA wires to estimate the seismic responses of actively confined RC columns under various conditions. It is demonstrated that the proposed analytical models can capture the dynamic behavior and damage status of SMA-confined RC columns under bidirectional seismic excitations.
GeoMapApp 자료를 이용한 화산과 지진 학습에서 초등학생의 공간 능력에 따른 공간적 사고의 발현 양상
송동혁 ( Song¸ Donghyuk ),맹승호 ( Maeng¸ Seungho ) 한국초등과학교육학회 2021 초등과학교육 Vol.40 No.3
이 연구는 화산과 지진 단원의 수업에 GeoMapApp을 활용한 학습 자료를 적용하고, 공간 능력이 서로 다른 초등학생들이 인지한 공간 개념, 표현한 공간적 표상의 도구, 지형 구조를 표현하는 데 적용한 공간적 추론을 추출하여 공간적 사고의 과정을 분석하였다. 공간 능력 상위 집단 학생들은 인지한 공간 개념 정보를 수평 거리에 따라 구간을 나누어 화산과 지진의 지형 구조에 관한 심리적 이미지를 형성하는 내적 공간 표상을 활용하거나, 인식한 공간 개념을 그대로 연결하는 공간적 추론의 사례를 보였다. 또한, 지진 자료를 보고 공간 개념을 변형하여 공간적 추론을 수행하는 예도 있었다. 공간 능력 하위 집단 학생들은 공간 개념을 직접 지형 구조로 연결하는 공간적 추론을 보이거나, 공간 개념을 부분적으로 인식하여 지형을 파악하는 공간적 추론 사례를 보였다. 연구 결과를 근거로 초등학생들이 GeoMapApp 자료에서 거리, 높이, 깊이와 같은 공간 개념을 정확히 인식해야 더 나은 공간적 사고를 구현할 수 있음을 밝혔다. This study investigated how elementary students with different spatial ability constructed spatial thinking process about on volcanoes and earthquakes with GeoMapApp-based materials. Students’ spatial thinking process was analyzed in terms of spatial concept recognized, tools of spatial representation, and their spatial reasoning to construct topographic structure. The student group with high-scored spatial ability showed the spatial reasoning based on internal representation of building mental images through sectional division of horizontal distance, directly connected with spatial concept, or distorting spatial concept. The student group with low-scored spatial ability built the spatial reasoning directly connected with spatial concept instead of transforming into internal representation, and partially recognized spatial concept on either distance or depth. Based on the results, we argued identifying spatial concepts such as distance, height, or depth from the GeoMapApp data would be fundamental for the better spatial thinking.
Three-Dimensional Theoretical Study on Flow Characteristics of a Spiral-Channel Viscous Micropump
Donghyuk Kang,Koichi Nishibe,Kotaro Sato,Kazuhiko Yokota 한국유체기계학회 2019 International journal of fluid machinery and syste Vol.12 No.2
Technological developments have led to micropumps playing an ever-greater role at the heart of micro total analysis systems. Spiral-channel viscous micropumps have been studied theoretically, numerically, and experimentally. However, high-accuracy performance predictions have not been achieved over a wide range of operating conditions. The present study proposes three-dimensional and quasi-three-dimensional theoretical expressions for predicting the pressure performance of spiral-channel viscous micropumps in low-Reynolds-number environments. The theoretical analysis is validated through a series of comparisons with numerical simulation results for the pressure performance curves, velocity distributions, velocity gradient distributions, and channel internal pressure distributions. Furthermore, the influence of the channel aspect ratio on the performance characteristics is investigated.
Holographic Data Storage Channel Model With Intensity Factor
Donghyuk Park,Jaejin Lee IEEE 2009 IEEE transactions on magnetics Vol.45 No.5
<P>We consider the holographic data storage channel model which includes intensity factor. We define the intensity factor as the degree of the diminishing phenomenon of the read page and model the diminishing phenomenon using a simple page masking filter. Thus, the page masking filter coefficients are determined by the intensity factor. We discuss the performance of the channel model employing one-dimensional (1-D) PRML with two-dimensional (2-D) PR equalizer when the degree of blur is 1.7.</P>
Evaluation of photocatalytic activity of carbon-doped TiO2 films under solar irradiation
Donghyuk Jung,Byung Woo Kim,Gyusun Kim,Moon-Sun Kim 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.6
We proposed a method to obtain carbon-doped TiO2 (C-TiO2) with a higher photocatalytic activity for degradation of toluene. Solar radiation was used as a visible light source for photocatalytic oxidation. An optical fiber reactor (OFR) was used to investigate the photocatalytic oxidation of toluene in air. All C-TiO2 films used as catalysts were synthesized by a modified sol-gel and combustion method using carbon nanoparticles. The performance of the OFR using C-TiO2 was evaluated under various experimental conditions. The effects of solar flux, surface sensitization, inlet concentration of toluene and concentration of carbon nanopowder in C-TiO2 were examined.