• Journal of the Korean Ceramic Society
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• v.22 no.2
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• pp.17-24
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• 1985

In the composition of $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ the effect of particle size on PbO vaporization were measured, . The initial step of discontinuous vaporization of unreated PbO during the calcining process was depended on the particle size. All additives $La_2O_3Nb_2O_5$ and $Al_2O_3$ inhibited the grain growth of the composition $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ +2wt% excess PbO. The dielectric and piezoelectric properties of the composition $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ were improved by the addition of 2wt% excess PbO and proper additive. The electromechanical planar coupling factor of 0.65 and mechnical quality factor of 390 could be obtained by adding 5wt% $Nb_2O_5$ to the composition 2wt% excess PbO+$Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.6
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• pp.429-436
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• 2014

Most mechanical systems are now operating consistently and getting faster due to the development of automation systems. Peoples' dependence on machines have increased as when problems occur within the mechanical system, personal injury and production loss may come as a result, as most of the mechanical system's malfunctions are caused by the failure of the rotational bearing. What we need now is a maintenance system that can warn us when it detects abnormal conditions before significant damage occurs to the bearing. In this study, we have developed an acoustic emissions sensor that can figure if the bearing works under the normal condition. With this acoustic emissions sensor, we can inspect the bearing for defects by using the Heterodyne technique, which converts the ultrasound signal into audio, as a signal conditioning process.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.6
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• pp.88-95
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• 1996

The ultrasonic motor(USM) has good characteristics such as compact size, silent motion, high speed responce, low speed and high torque. The USM is driven by 2-phase AC electricity. The control parameters of USM are voltage, phase, and frequency of input powers, etc. In this paper, a voltage difference control is proposed. The voltage difference control has more advantage than phase difference control. Specially, current and power is lower than that of phase difference control. For this voltage diffrence control, we designed USM controller to adjust volatage and phase using PLSI(Programmable Large Scale Integration).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1453-1459
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• 2012

The dual stage manipulator is composed of the voice coil motor (VCM) and piezoelectric ceramics transducer (PZT), which can produce the high precise displacement and express a well dynamic performance. However, inaccurate modeling of the dual stage will exacerbate the positioning accuracy. This paper presents an approach to model the dual stage system by using bond graph theory. And the state space equations can be derived through the bond graph straightforwardly, which can be used in computing simulations. Through designing the compensators for the dual stage system and simulating, the dual stage performs better dynamics characteristic than the single actuator system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.972-975
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• 2001

The effect of Cr$_2$O$_3$(0 to 0.5 wt%) doping on the microstructure and electrical properties of ternary Pb(Zr,Ti)O$_3$-Pb(Ni,Nb)O$_3$piezoelectric ceramic has been investigated. Abnormal grain growth (grain size 3.3 to 11.2 $\mu$m) and densification are found. Minor additives of $\leq$0.1 wt% improve the mechanical coupling factor, but with more additives of $\geq$0.2 wt% electrical properties deteriorate. Thus, these phenomna can be ascribed mainly to anomalous developed microstructure. The large grains were composed of a core region that is free of Cr and a surrounding shell region rich in Cr. The interfaces between the core and the shell were composed of misfit dislocations. The mechanical properties of the specimens were strongly influenced by this microstructural change. The microstrutural and compositonal evolution of the specimens containing different amounts of Cr$_2$O$_3$were monitored. Electrical properties were measured and related to the variations in the microstructure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.324-324
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• 2010

최근에는 압전체의 환경오염 문제의 해결 및 가격경쟁력을 갖추기 위해서 비납계 압전체에 대한 연구가 활발히 진행되고 있다. (Na,K)$NbO_3$ 계는 페로브스카이트 구조를 가지는 비납계 세라믹스로 현재 가장 많이 연구되고 있는 물질 중의 하나이다. 본 연구에서는 압전성이 우수한 $(Na_{0.44}K_{0.52}Li_{0.04})(Nb_{0.9}Ta_{0.04}Sb_{0.06})O_3$ 조성에 CuO, $Cu_2O$ 등의 Cu 산화물을 첨가하였을 때의 전기기계결합계수, 기계적품질계수, 비유전율, 압전전하상수, 문극-전계 이력곡선 (P-E hysteresis curve) 등을 변화를 평가하고자 하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.224-227
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• 1999

A high power deep-water sonar transducer of FFR (Free Flooded Ring) type has been designed using a coupled FE-BEM. The present sonar transducer is composed of rectangular piezoelectric ceramics and pie-shaped steels (or the advantage of simple fabrication. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Different results are available such as steady-state frequency response for TX and RX displacement modes, directivity patterns, back-scattering patterns, bandwidths, transmitting voltage responses and receiving sensitivity responses. The TV response shows a very high acoustic pressure of 150 dB/lV (ref $1{\mu}Pa$ at 1m) at 1900 Hz. This ultra high power response of the sonar transducer indicates a new possibility of the sonar transducer development.

• The Journal of the Acoustical Society of Korea
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• v.16 no.5
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• pp.12-17
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• 1997

In this work, we developed a new type ultrasonic dehumidifier with piezoelectric ceramics, which and efficiently repel waterdrops on outdoor glass plates exposed to raindrops. Through finite element analysis of a certain type of glass plates to analyze its dynamic behavior, the structure of the ultrasonic device we determined to get the optimal performance. A supplemental metal plate was attached to the glass plate for uniform cleaning. Based on the theoretical results, experimental samples were fabricated and evaluated with various dimensions of the glass plate and the piezoceramic vibrator. Driving circuit for the dehumidifier made use of the frequency sweeping technique to keep track of the resonant frequency of the glass plate that was variant with environmental conditions.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.299-303
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• 2005

The crystal structure and ferroelectricity of the $(1-x)BiFeO_3\;(BF)-xPbTiO_3$ (PT) ceramic system with the addition of $DyFeO_3$ (DF) have been investigated for attaining a high temperature piezoelectric material. This study is focused on the relation between crystal structure and ferroelectric property with the addition of DF over the phase boundary in the (1-x)BF-xPT system. Hysteresis curves of polarization-electric field at room temperature have been measured. The X-ray and neutron diffraction data were analyzed by the rietveld refinement method. The addition of 0.1 mole DF into BF-PT system greatly increases the ferroelectric remanant polarization Pr values, e.g. 17 ${\mu}C/cm^2$ in 0.6BF-yDF-(0.4-y)PT and 31${\mu}C/cm^2$ in 0.5BF-yDF-(0.5.y)PT, respectively. The improved Pr value has been discussed in relation with crystal structure and electrical property.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.60-66
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• 1986

The effect of composition size of sintered body and electrode on resonant characteristics of the system $Pb(Mn_{1/3}Nb_{2/3})O_3 PbTiO_3-PbZrO_3$ has been decribed. Composition ranged from X=40 to X=55 diameter of sintered body ranged from D=6.5 to D=12.5(mm) and diameter of electrode ranged from De=5.5 to De=11 (mm) In the composition of morphotropic phase boundary antiresonant frequency (fa) dcreased slowly whereas resonant frequency (fr) decreased rapidly on the ground of this Δf(fa-fr) and electromechanical coupling fractor Kp increased and Qm showed low value. On the contrary in toward the composition of tetragonal and rhombo-hedral fa increased slowly whereas fr increased rapidly on the ground of this Δf and Kp decreased and Qm increased abruptly. Substance of the above statements have no concern with size of sintered body and ele-ctrode. The other side as the size of electrode decreased Qm fr, fa and Δf increased. Cm and Co dominantly affect the resonant frequency and antiresonant frequency.