• Electrical & Electronic Materials
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• v.1 no.2
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• pp.162-167
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• 1988

본 논문에서는 Pb(Sn$_{1}$7/Mn$_{2}$7/Nb$_{4}$7/)O$_{3}$- Pb(Zr, Ti)O$_{3}$계에 La$_{2}$O$_{3}$를 첨가하여 그양에 따른 압전일 전기력 성질의 변화를 고찰하였다. La$_{2}$O$_{3}$ 첨가량의 증가에 따라 유전상수, 압전 d상수, 유전손실, 비저항 등은 증가하였으나 경시 변화량은 오히려 감소하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.716-722
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• 2003

ZnO thin films were deposited on Al and Pt electrodes by an RF reactive sputtering system for the fabrication of FBAR (film bulk acoustic wave resonator), and the effect of thermal treatment temperature on their c-axis preferred orientation was investigated. SEM experiments show that columnar structure of ZnO thin films were grown with c-axis normal to electrode material, and XRD experiments show that both ZnO films were grown with (002) plane preferred orientation, but larger diffraction peak was observed with Pt electrode. The peak intensity increased with higher thermal treatment temperature, but c-axis preferred orientation was diminished. The surface roughness of Al thin film was higher than that of Pt, and these affect the surface roughness of ZnO film deposited on the electrode. Though the preferred orientation with respect to Pt(111) plane was improved with higher thermal treatment temperature, this could not improve the c-axis orientation of ZnO film.

• Coupled systems mechanics
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• v.6 no.4
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• pp.465-485
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• 2017

In this paper, free vibration and static response of magneto-electro-elastic (MEE) beams has been investigated. To this end, a 3D finite element formulation has been derived by minimization the total potential energy and linear constitutive equation. The coupling between elastic, electric and magnetic fields can have a significant influence on the stiffness and in turn on the static behaviour of MEE beam. Further, different Barium Titanate ($BaTiO_3$) and Cobalt Ferric oxide ($CoFe_2O_4$) volume fractions results in indifferent coupled response. Therefore, through the numerical examples the influence of volume fractions and boundary conditions on the natural frequencies of MEE beam is illustrated. The study is extended to evaluate the static response of MEE beam under various forms of mechanical loading. It is seen from the numerical evaluation that the volume fractions, loading and boundary conditions have a significant effect on the structural behaviour of MEE structures. The observations made here may serve as benchmark solutions in the optimum design of MEE structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.202-207
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• 2007

In order to understand the phenomena of combustion instability, an experimental study was conducted at the moderate pressure and ambient temperature conditions. The flame behavior and the pressure fluctuations were measured in a dump combustor. Various types of combustion modes occurred in accordance with the equivalence ratio and the fuel supplying conditions. The fluctuation of pressure, heat release and equivalence ratio were measured by piezoelectric pressure sensor, high speed Intensified Charge Coupled Device (HICCD) camera and gas chromatography respectively. Two representative modes were self-excited pressure oscillations at the resonance of combustion chamber (200Hz) and instabilities related to the modulated fuel flow rate through the fuel holes (10Hz). It is found that, especially in an unchoked fuel flow condition, the modulation of the fuel flow rate affects the characteristics of flame behavior and pressure fluctuations in a lean premixed flame.

• Journal of the Semiconductor & Display Technology
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• v.4 no.2 s.11
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• pp.21-24
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• 2005

Ink-jetting characteristics of pulse width and pulse amplitude for a piezoelectric ink jet printer driver have been mapped with various polymer EL ink. In this study, the jetting characteristics have been classified into 4 regime; no Jetting, unstable jetting, stable jetting, and spraying, and the importance of fluid viscosity on the scope of the stable jetting regime has been emphasized. The relation between jetting speed and the width and amplitude of driving signal has also been investigated and the effect of the speed on the jetting characteristics has been discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.713-716
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• 2010

본 논문에서는 코리올리 효과를 가진 압전-구조 시스템의 주파수응답 해석을 효율적으로 수행하기 위한 크리로프 부공간 모델차수축소법을 제안하였다. 이 방법은 초기 유한요소모델과 축소모델의 전달함수의 계수인 모멘트를 일치시키는 방법을 이용하는 축소기법으로 이미 대형 유한요소모델의 주파수응답 해석에 효과적으로 이용되고 있다. 예제로 고려된 압전형 미소 각속도계의 해석에는 압전구동 하중과 구조체의 회전에 따른 원심력이 동시에 입력하중으로 고려되는 다중입력의 경우이므로 변환행렬 V의 생성시, block Arnoldi 과정을 이용하여 두 하중의 효과를 축소모델에 함께 고려한다. 본 문제에 제안된 축소기법을 이용한 결과, 축소모델을 이용하여 원래 시스템의 관심영역의 주파수응답을 작은 차수의 모델로도 정확하게 계산할 수 있음을 확인하였다. 본 논문에서 제안된 방법을 이용하면 다양한 가진조건과 각속도 입력 하에서의 주파수응답을 정확하고 더욱 효율적으로 계산할 수 있을 것이다.

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.225-228
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• 2003

A Bender typed Multilayer Actuator(BMA) for decreasing the depolarization effect was designed and fabricated. Unlike bimorph and multimorph actuators in which depolarization occurred, the BMA did not generate depolarization because the polarization and the electric field directions are the same. The simulated results indicate that higher displacement of the BMA can be achieved by increasing input voltage. Compared with the multimorph actuator, the proposed actuator is expected to extend a life time as well as acceptable voltage range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.446-450
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• 2001

In this study, microstructural and electrical properties of (Pb)(La,Nd)TiO$_3$ ceramics were investigated as a function of CuO addition. Taking into consideration Tc of 3$25^{\circ}C$, dynamic range of 49dB( at the wafer form) and density of 7.71g/㎤, it can be concluded that the specimen S2 sintered at 120$0^{\circ}C$ is the best for the resonator application. Dynamic characteristics of energy-trapped 20MHz SMD type resonator as a function of internal dot size variation were also investigated. Dynamic range characteristics showed the highest value of 60.72dB at S2-4(dot size 1.13mm).

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.209-210
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• 2006

Organic binders are usually pre-mixed with ceramic powders to enhance the formability during the shape forming process. These binders, however, must be eliminated before sintering in order to avoid pore formation and unusual grain growth during sintering. The present work was performed to investigate the effects of residual binder on grain growth behavior during sintering of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ piezoelectric ceramics. The microstructures of sintered samples were examined for various thermal processes and atmosphere at debinding. Addition of binder seems to promote abnormal grain growth especially in incompletely debinded regions and to make the grain shape change from corner-rounded to faceted.

• Journal of the Korean Society of Combustion
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• v.1 no.2
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• pp.21-29
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• 1996

Flame propagation characteristics of propane-air mixtures were experimentally investigated in constant-volume combustion chambers. Flame propagation process was observed as a function of mixture strength, initial mixture temperature and initial mixture pressure in quiescent mixtures. A cylindrical combustion chamber and a spherical combustion chamber contain a pair of parallel windows through which optical access into the chamber can be provided. Laser two beam deflection method was adopted to measure the local flame propagation, which gave information on the flame size and flame propagation speed. Pressure development was also measured by a piezoelectric pressure transducer to characterize combustion in quiescent mixtures. Burning velocity was calculated from flame propagation and pressure measurements. The effect of flow on flame propagation was also investigated under flowing mixture conditions. Laser two beam method was found to be feasible in measuring flame propagation of quiescent mixtures. Flame was observed to propagate faster with higher initial mixture temperature and lower initial pressure. Combustion duration was shortened in the highly turbulent flowing mixtures.