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김정훈(Jeong Hun Kim),황성주(Sung Joo Hwang),안정환(Jung Hwan Ahn),홍성광(Seong Kwang Hong),김선중(Sun Jung Kim),송예원(Yewon song),성태현(Tae Hyun Sung) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
Nowadays, enhancement of output power of piezoelectric energy harvesting is actively conducted. We study strain of piezoelectric energy harvester induced by magnets. We supply constant input using a function generator and a vibration exciter. Under a constant mechanical vibration input, we match impedance between piezoelectric material and the load resistor. Thereafter we measure electrical output of piezoelectric cantilever beam. We measure the resonance frequency and the output voltage of an open circuit while the distance between the magnets changes; 2, 5, 8, 10, 15 mm. As the distance between the magnets decreases it shows a higher resonance frequency and output voltage. In the case of an open circuit and vibration frequency of 71 Hz, output voltage was measured 16.6 Voc. Load impedance was matched at 17 kΩ, in such conditions the output voltage and power were measured to be 10.9 Vrms and 6.98 mW.
내구수명 100년 확보를 위한 해양환경 콘크리트의 배합 특성 연구
장봉석 ( Jang Bong-seok ),안정환 ( Ahn Jeong-hwan ) 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.11 No.2
This study examins the some experimental works to distinguish the characteristics of concrete mixtures using blended cement; slag cement and ternary cement. In this study, 40%, 50% and 60% replacement ratio of blast furnace slag(BSF) to OPC are used, also 35:45:20, 30:35:35, 30:40:30 and 35:40:25 ratio of OPC:BSF:FA are used. The characteristics tests include slump, air content, compressive strength and thermal properties of concrete. The compressive strength tests are executed at the age of 3, 7, 28, 56, and 91 days. The coefficient of chloride diffusion is determined by NT Build 492 method. The purpose of this study is to shows the characteristics of concrete mixtures according to the type of blended cement. Finally the best mixing design is adapted to the construction site of S-project. Also, this study results can be usefully applied to the other project.
부하연결에 따른 외팔보 압전에너지 하베스터의 공진주파수 변화 해석
황성주(Sung Joo Hwang),안정환(Jung Hwan Ahn),김선중(Sun Jung Kim),김정훈(Jeong Hun Kim),송예원(Yewon Song),성태현(Tae Hyun Sung) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
Piezoelectric cantilever beam is used in conversion of mechanical energy to electrical energy, and vice versa. But, when an external load connected to piezoelectric material, mechanical characteristic of cantilever beam is changed. We study resonance frequency shift of the piezoelectric cantilever beam according to load connection. When the external circuit changed from open to short, resonance frequency of the piezoelectric cantilever beam is changed from 40 Hz to 39 Hz. Also, displacement of the free end of the piezoelectric cantilever beam increased 2.4%. After then, we optimize resistive impedance matching for maximum power transfer. In matching case, resonance frequency is located between open and short circuit connection. Free end displacement also 21.4% decreased. This result shows that electrical load connection results in changing of mechanical characteristic like stiffness, resonance frequency, displacement.