후막 스피커 응용을 위한 Pb(Zr₁Ti)O₃-PVDF 복합체의 압전 특성 평가

손용호,김성진,김영민,정준석,류성림,권순용,Son Yong-Ho,Kim Sung-Jin,Kim Young-Min,Jeong Joon-Seok,Ryu Sung-Lim,Kweon Soon-Yong 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.10

We reported on characteristics of the piezoelectric ceramic-polymer composite for the application of the thick-film speaker. The PVDF-PZT composites were fabricated to incorporate the advantages of both ceramic and polymer with various mixing ratios by 3-roll mill mixer. The composite solutions were coated by the conventional screen-printing method on ITO electrode coated PET (Polyethylene terephthalate) polymer film. After depositing the top-electrode of silver-paste, 4 kV/mm of DC field was applied at $120^{\circ}C$ for 30 min to poling the composite films. The value of $d_{33}$ (piezoelectric charge constant) was increased when the PZT weight percent was increased. The maximum value of the $d_{33}$ was 24 pC/N at 70 wt% PZT. But the $g{33}$ (piezoelectric voltage constant) showed the maximum value of $32mV{\cdot}m/N$ at 65 wt% of PZT powder. The SPL (sound pressure level) of the speaker fabricated with the 65:35 composite film was about 68 dB at 1 kHz.

Glass Frit의 첨가에 따른 BaTiO₃ 소결체의 유전 특성 및 미세구조 변화

우덕현,윤만순,손용호,류성림,어순철,권순용,Woo, Duck-Hyun,Yoon, Man-Soon,Son, Yong-Ho,Ryu, Sung-Lim,Ur, Soon-Chul,Kweon, Soon-Yong 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.3

$BaTiO_3$ dielectric ceramics are widely used to multi-layer ceramic capacitor. The $BaTiO_3$ powder was synthesized at $950^{\circ}C$ by using a solid state reaction and grinded by using a high-energy mill. And then, 2.53 wt% glass frit was added to the synthesized $BaTiO_3$ powders for lowering the sintering temperature. The mixed powders were sintered at various temperatures of $1170^{\circ}C$, $1200^{\circ}C$, $1230^{\circ}C$. Microstructures of the sintered $BaTiO_3$ ceramics were inspected by SEM and crystal structures were analyzed by XRD method. The relative dielectric constant was measured by using a impedance/gain phase analyzer. The synthesized $BaTiO_3$ powder had the tetragonal perovskite structure without secondary phase and the particle size was below 200 nm. The relative densities measured at the samples sintered at the temperature above $1200^{\circ}C$ were about 95%. The relative dielectric constant showed maximum value of 2310, which was measured in the specimen sintered at $1200^{\circ}C$. From these results, we could know that the added glass frit had effects on both lowering the sintering temperature and improving the dielectric property.

연구보문 : 사회과학 ; 캄보디아에서 한국산 주요 채소의 차광 효과

방진기 ( Jin Ki Bang ),동용호 ( Yong Ho Dong ),류민재 ( Min Jae Ryu ),김지은 ( Ji Eun Kim ),이윤호 ( Yun Ho Lee ),박병용 ( Byeong Yong Park ) 한국국제농업개발학회 2014 韓國國際農業開發學會誌 Vol.26 No.1

한국에서 개발한 고추 9품종, 토마토 5품종을 대상으로 캄보디아의 고온 조건에서 차광재배를 통하여 적응품종을 선발하고 그 품종과 함께 재배기술을 수요자에게 보급함으로서 소득향상에 기여할 기초자료를 얻고자 본 연구를 수행한 바 그 결과를 요약하면 다음과 같다. 1. 고추 품종의 과폭은 최대 1.35 cm (60%차광 Internet), 최소 0.56 cm(10%차광 Chili9) 로 나타났다 2. 고추 품종의 과장은 Asia Dan 4를 제외한 모든 품종에서 10%, 60% 차광의 경우 무차광에 비하여 커지는 경향이었다. 3. 고추의 과중은 0.9 g (무차광 Asia Dan)에서 7.3 g (60% Hot Asia)의 범위로 품종별, 차광별로 차이를 보였다. 4. Chili 9를 제외한 고추품종에서 차광재배보다 무차광에서 주당 과실수가 많았다. 특히 무차광일 경우 Asia Dan 2, Asia Dan 4, Asia Dan 24 등은 각각 55개, 40개, 41개 등으로 차광처리구 보다 많았다. Hot Asia, Hot Pia, Internet 품종 등은 차광재배가 더 유리한 것으로 보였다. Asia Dan 2, Asia Dan 4, Asia Dan 24 등은 노지재배가 더 유리할 것으로 보였다. 5. 토마토의 경우 10%와 60%차광의 과실수는 품종에 따라 10개 ~ 36개의 범위를 보였다. 반면 무차광의 경우는 품종에 따라 46 ~ 81개로 많았다. 특히 Hero110 과 Hera110의 경우 10%차광, 60%차광처리에 비해 무차광일 경우 4배 이상 높은 수확량을 보였다. 6. 토마토의 당도는 Asia Rio를 제외한 나머지는 무차광에서 높았다. 특히 Hero80은 다른 품종에 비하여 6.1 brix°를 보여 월등하게 높았다. This study was conducted to evaluate the effect of shade on growth and yield of Korean red pepper and tomato varieties in Cambodia. The shade levels were 10% and 60% of full sunlight, respectively. The width of fruits was measured maximum which is 1.35cm (60% shade, cv : Internet), and minimum is 0.56cm (10% shade, cv : Chili 9) in red pepper. The number of fruits per red pepper plant in unshaded full sunlight was more than shading condition. Especially in unshaded full sunlight, the number of fruits per plant for Asia Dan 2, Asia Dan 4 and Asia Dan 24 were better than shading condition. Shading condition should be selected for red pepper varieties such as Hot Pia, Hot Asia and Internet. Red pepper varieties such as Asia Dan 2, Asia Dan 4 and Asia Dan 24 have been shown better performance when they are provided unshaded full sunlight. The number of fruits per tomato plant ranged from 10 to 36 in 10% and 60% shade, and unshaded full sunlight showed from 46 to 81. Sugar content of selected tomato variety such as Hero 80 was more than 6.1 brix°.

동적 유한요소 해석을 통한 일체형 원자로 안전주입 노즐 이종금속 용접부의 잔류응력에 미치는 레이저 피닝 변수의 영향 고찰

서중현(Joong Hyun Seo),김종성(Jong Sung Kim),정명조(Myung Jo Jhung),류용호(Yong Ho Ryu) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

In this study, the effect of the laser peening variable that it reaches to the welding residual stress mitigation through the dynamic finite-element analysis tries to be considered. In case of applying the integrated nuclear reactor safety injection nozzle dissimilar welds in which inner the repair welding is performed to the laser peening, it faced and by using ABAQUS, that is the commercial finite element analysis program, the dynamic finite-element analysis was practiced. Consequently, it confirmed that the tension residual stress at the Alloy 690 series alloy inner surface contacted with the high temperature chemistry primary water was considerably mitigated. In addition, the more the maximum impact pressure, impact pressure duration and laser spot diameter increases, the more the inner surface tension residual stress mitigation decreases, but the more the depth of the mitigated area increases. Also, the laser peening direction can know that an effect is nearly not at the residual stress mitigation.

일체형 원자로 안전주입 노즐 이종금속 용접부에 대한 레이저 피닝 적용의 수치 해석적 연구

서중현(Joong Hyun Seo),김종성(Jong Sung Kim),정명조(Myung Jo Jhung),류용호(Yong Ho Ryu) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.6

일체형 원자로의 안전주입 노즐 이종금속 용접부의 잔류응력에 대한 레이저 피닝의 효과를 고찰하기 위해 상용 프로그램인 ABAQUS를 이용하여 implicit 동적 유한요소 해석을 통해 연구를 수행하였다. implicit 동적 유한요소 해석은 기존의 실험 결과와의 비교에 따르면 레이저 피닝을 통한 잔류응력 이완에 대해 타당하다고 확인된다. 한편 내부 보수용접이 수행된 이종금속 용접부에 대해 해석이 수행되며 그 결과는 축방향 및 원환 잔류응력 모두 내부 보수용접에 기인하여 노즐의 내표면에서 인장임을 나타낸다. 또한 용접 잔류응력 이완에 대한 최대 충격 압력, 압력 지속 시간, 스폿 직경 및 피닝 방향과 같은 여러 변수의 효과를 고찰하기 위해 변수 해석 또한 수행하였다. 결과적으로, 레이저 피닝은 내표면 근처 영역의 잔류응력을 주로 이완시키는 예방정비 효과가 있음을 확인하였다. A numerical analysis has been performed through implicit dynamic finite element analysis using the commercial package, ABAQUS in order to investigate effect of laser peening on welding residual stress mitigation of dissimilar metal welds in a safety injection nozzle of integral reactor. The implicit dynamic finite element analysis are compared with the previous experimental results. By comparison, it is identified that the implicit dynamic finite element analysis is valid for residual stress mitigation via laser peening. Implicit static finite element residual stress analysis has been performed for the dissimilar metal welds subject to inner repair welding. The analysis results represent that both axial and hoop residual stresses are tensile on inner surface of safety injection nozzle due to inner repair welding. Also Parametric study has performed to investigate effect of laser peening variables such as maximum impact pressure, duration time of pressure, spot diameter and peening direction on the welding residual stress mitigation. As a result, it is found that laser peening has the preventive maintenance effect to mitigate mainly residual stresses of region near inner surface.

기구학적 구속 연계 유한요소 해석을 통한 원자로 압력용기노즐 용접부의 잔류응력에 미치는 배관 상호작용의 영향 고찰

김종성(Jong Sung Kim),정명조(Myung Jo Jhung),류용호(Yong Ho Ryu) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4

In this study, residual stress distributions of the welds in reactor pressure vessel nozzle are calculated by using three-dimensional finite element analysis. The effect of piping interaction on the welding residual stresses is investigated via the kinematic constraint coupling method between continuum finite element and shell finite element. As a result of the investigation, it is found that the piping interaction has a meaningful effect on the residual stress distributions on the inner surface of weld.

매입형 영구자석 동기전동기의 약계자 제어를 위한 최대전압 선정에 관한 연구

김수열,김장목,임익헌,류호선,안용호,윤기갑,전향식 한국산업안전학회 2000 한국안전학회지 Vol.15 No.2

The constraint conditions are the stator voltage and the stator current to operate the motor in the flux weakening region. The maximum current is limited by the inverter current rating and the machine thermal rating. Given DC link voltage to control the motor in the flux weakening the maximum voltage is determined by considering PWM strategy, dead time, voltage drop of the inverter switching device, and the margin of the voltage for current forcing. In this paper, the new method to determine the available maximum voltage is derived by the quantitative method and by considering the factors of the voltage drop. The proposed method to determine the maximum voltage is very useful to improve the stability of the motor system and to enlarge the speed operation region in the flux weakening operation. Therefore the utility of the maximum voltage is increased