• Title/Summary/Keyword: vibrator

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Mechanical properties and adiabatic temperature rise of low heat concrete using ternary blended cement

  • Kim, Si-Jun;Yang, Keun-Hyeok;Lee, Kyung-Ho;Yi, Seong-Tae
    • Computers and Concrete
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    • v.17 no.2
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    • pp.271-280
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    • 2016
  • This study examined the mechanical properties and adiabatic temperature rise of low-heat concrete developed based on ternary blended cement using ASTM type IV (LHC) cement, ground fly ash (GFA) and limestone powder (LSP). To enhance reactivity of fly ash, especially at an early age, the grassy membrane was scratched through the additional vibrator milling process. The targeted 28-day strength of concrete was selected to be 42 MPa for application to high-strength mass concrete including nuclear plant structures. The concrete mixes prepared were cured under the isothermal conditions of $5^{\circ}C$, $20^{\circ}C$, and $40^{\circ}C$. Most concrete specimens gained a relatively high strength exceeding 10 MPa at an early age, achieving the targeted 28-day strength. All concrete specimens had higher moduli of elasticity and rupture than the predictions using ACI 318-11 equations, regardless of the curing temperature. The peak temperature rise and the ascending rate of the adiabatic temperature curve measured from the prepared concrete mixes were lower by 12% and 32%, respectively, in average than those of the control specimen made using 80% ordinary Portland cement and 20% conventional fly ash.

Directivity Characteristics Control of Ultrasonic Transducer Array Using Two-layered Piezoelectric Transducer (2층 구조 압전 트랜스듀서를 이용한 초음파 트랜스듀서 어레이의 지향 특성 가변)

  • 김정호;송인진;하강렬;김천덕;김무준
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.8
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    • pp.629-636
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    • 2003
  • It will be very convenient if the directivity characteristics of ultrasonic transducer array are controllable by the purpose of use in the fields of sonar system or ultrasonic diagnostic system, In this paper, a control method of the directivity characteristics was suggested. The transducer array was consisted of two-layered piezoelectric vibrators. Efficiency of each vibrator is controlled in 2nd harmonic mode by electrical capacitance. Therefore, the beam width of the transducer array can be controlled by changing the capacitance. The directivity characteristics of the array were analyzed experimentally and theoretically. As the results, it is confirmed that -3 dB beam width of main lobe can be controlled in the range of 7.6°∼16.2°.

Development of Vibration Assisted Hybrid Femtosecond Laser Ultra-precision Machining System and Cu-Zn alloy Application (진동자를 이용한 하이브리드 극초단 펄스 레이저 초정밀가공시스템 개발 및 Cu-Zn합금 응용)

  • Choi, Won-Suk;Yoon, Ji-Wook;Cho, Sung-Hak;Kang, Myung-Chang
    • Journal of Powder Materials
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    • v.20 no.4
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    • pp.308-312
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    • 2013
  • In this paper, we describe experiment results using a vibration assisted hybrid femtosecond laser (${\lambda}$:795 nm) ultra-precision machining system. The hybrid system we have developed is possible that optical focal point of the femtosecond laser constantly and frequently within the range of PZT(piezoactuator) vibrator working distance. Using the hybrid system, We have experimented on brass and studied about differences of result of hole aspect ratio compare to general experiment setup of femtosecond laser system. Aspect ratio of a micro hole on brass is increased as 54% with 100 Hz vibration frequency and surface roughness of the side wall also improved compare to non-vibration.

A Study on Cooling of Piezoelectric Element of Multifunction Equipment for Vacuum Exhaust and Ultrasonic Joining (진공 배기 및 초음파 접합 복합기 진동자 냉각에 관한 연구)

  • Park, Sang-Jun;Lee, Young-Lim
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.4
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    • pp.1511-1517
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    • 2012
  • Vacuum chamber or vacuum tube for the exhaust process of vacuum glazing is presently used, where excessive time and expenses are required to make the whole vacuum chamber or tube vacuum. To solve this problem, multifunction equipment for vacuum exhaust and ultrasonic joining at atmospheric pressure has been developed, in which a piezoelectric vibrator experiences excessive temperature rise resulting in optimizing the cooling of the equipment. Therefore, in this study, cooling effects of natural convection and forced convection methods were identified by numerical analysis and experiments, and cooling performance of the multifunction equipment was optimized.

A Proposal of Modulation Method and Vibrator Structure for the Improvement of Power Transfer Efficiency of the Implantable Middle Ear (이식형 인공중이의 전력전달효율 개선을 위한 변조방식 및 진동체 구조 제안)

  • Song, B.S.;Jung, Y.S.;Yoon, Y.H.;Won, C.H.;Kim, M.N.;Park, S.K.;Lee, S.H.;Cho, J.H.
    • Proceedings of the KOSOMBE Conference
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    • v.1997 no.05
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    • pp.136-140
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    • 1997
  • In this paper, we proposed a implantable middle ear system using FM transmission and receiving method which has higher detection efficiency than that of AM method. And a new shape of vibrating transducer which is more efficiently vibrate than the conventional type is designed. This tranducer consist of coil and small T-type cylindrical permanent magnet. We investigated and compared the differences between conventional methods and proposed methods by quantitive analysis. We proved them by experiment.

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FEM Analysis on the Characteristics of Piezoelectric Ceramics Using $L_{1}-B_{4}$ Vibration mode ($L_{1}-B_{4}$ 진동모드를 이용하는 압전 세라믹스의 유한요소 해석)

  • 김범진;정동석;김태열;박태곤;김명호
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.393-397
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    • 2001
  • A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramics element as a driving element. That is, L$_1$-B$_4$ linear ultrasonic motor can be constructed using a multi-mode vibrator of longitudinal and bending modes. The simulation with variation of material characteristics of piezoceramic were performed as use of finite element analysis ANSYS 5.5, such as elastic compliance, piezoelectric constant, electro-mechanical coupling coefficient, poisson's ratio and density. The results of simulation, elastic compliance constant s$_{11}$ and piezoelectric constant d$_{31}$ had the most of influence on the elliptic-motion. This results consist with using transverse effect of material. The used motor were piezoceramics of 4 layers, and the dimensions were 65$\times$5$\times$3.5mm(LxWxt).).

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Effect of ZnO on Low Temperature Sintering of PMN-PNN-PZT Ceramics (ZnO가 PMN-PNN-PZT 세라믹스의 저온소결에 미치는 영향)

  • Lee, Sang-Ho;Yoo, Ju-Hyun;Hong, Jae-Il;Ryu, Sung-Lim
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.11a
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    • pp.32-33
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    • 2006
  • In this study, in order to develop multilayer ceramic actuator for ultrasonic nozzle and ultrasonic vibrator, PMN-PNN-PZT ceramics were fabricated using $Li_2CO_3$. $Na_2CO_3$ and ZnO as sintering aids. And then, their piezoelectric and dielectric properties according to the amount of ZnO addition were investigated. The addition of ZnO improved density, dielectric constant, electromechanical coupling factor, mechanical quality factor and piezoelectric d constant of PMN-PNN-PZT ceramics due to the increase of sinterability and accepter doping effect. Electromechanical coupling factor and mechanical quality factor of PMN-PNN-PZT ceramics increased with ZnO amount up to 0.4wt% and then decreased. At the sintering temperature of $900^{\circ}C$ and 0.4wt% ZnO addition, density, dielectric constant, electromechanical coupling factor, mechanical quality factor and piezoelectric d constant showed the optimum value of 7.876g/$cm^2$, 1299, 0.612, 1151 and 369pC/N, respectively.

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A Stable Threshold Linear Current Pulse Discriminator (안정한계 선형전류펄스변별기)

  • 김병찬
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.5 no.2
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    • pp.8-14
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    • 1968
  • A linear current-pulse discriminator consisting: of a transistor monostable multivibrator and a Si tunnel diode is described. The input currant pulse range is about 50$\mu$A~5.23mA. The measured maximum linearity deviation is $\pm$0.75% in the input current pulse range mentioned above. The pulse resolving ability of the discriminator measured depends upon the bias current through the T, D. ; and, under the reverse bias current of 3mA, the resolving time is 2rs if allow the excess pulse amplitude of 5%. The threshold stability of the discriminator depends mainly upon the stability of the peak current Ip of the T. D. ; and, under the ambient temperature variation from $0^{\circ}C$ to 5$0^{\circ}C$, no bigger threshold variation than the maximum linearity deviation, i. e. $\pm$ 0.75%, was observed.

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A Study on the Surface Air-Void Reduction of High Performance Concrete (고성능 콘크리트의 표면기포 저감에 관한 연구)

  • Park, Sang-Joon
    • Journal of the Korea Institute of Building Construction
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    • v.9 no.1
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    • pp.49-55
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    • 2009
  • In this study, reduction methods of surface air void were examined for high performance concrete having high viscosity. The effects of assumed influencing factors such as form types, form-coating materials, tamping equipments and methods were examined based on the tests on mock-up specimens made of high performance concrete. The test results can be summarized as follows: As for form types, the most favorable results were obtained when coated plywood form was used with panel-shape tamping equipments at the contact region with concrete, the second and the third being the water/air-permeable sheets and steel with coated plywood, respectively. As for tamping equipments, a vibrator with 6.5cm diameter was most effective. Finally, the shorter the tamping intervals, the better the reduction effect of surface air void. As a conclusion, an improved method was proposed to reduce surface air void and it was verified with the test result that only four air voids as large as $5{\sim}10mm$ are found in the are of $1m^2$.

A Study on the Accelerometer for the Acceleration and Inclination Estimation of Structures using Double-FBG Optical Sensors (이중 FBG 광섬유센서를 이용한 구조물 가속도 및 기울기 측정 장치에 관한 연구)

  • Lee, Geum-Suk;Ahn, Soo-Hong;Shon, Su-Deok;Lee, Seung-Jae
    • Journal of Korean Association for Spatial Structures
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    • v.16 no.1
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    • pp.85-94
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    • 2016
  • In this study, an acceleration sensor that has optical fibers to measure the inclination and acceleration of a structure through contradictory changes in two-component FBG sensors was examined. The proposed method was to ensure precise measurement through the unification of the deformation rate sensor and the angular displacement sensor. A high sensitivity three-axis accelerometer was designed and prepared using this method. To verify the accuracy of the accelerometer, the change in wavelength according to temperature and tension was tested. Then, the change in wavelength of the prepared accelerometer according to the sensor angle, and that of the sensor according to the change in ambient temperature were measured. According to the test results on the FBG-based vibration sensor that was developed using a high-speed vibrator, the range in measurement was 0.7 g or more, wavelength sensitivity, 2150 pm/g or more, and the change in wavelength change, $9.5pm/^{\circ}C$.