• Transactions on Electrical and Electronic Materials
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• 제9권3호
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• pp.91-95
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• 2008

In this study, in order to develop the composition ceramics for low loss multilayer piezoelectric actuator application, $Pb(Zn_{1/2}W_{1/2})O_3-Pb(Mn_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3$ (abbreviated as PZW-PMN-PZT)ceramics according to the amount of $MnO_2$ addition were fabricated using two-stage calcinations method. And also, their dielectric and piezoelectric properties were investigated. At the 0.2 wt% $MnO_2$ added PZW-PMN-PZT ceramics sintered at $930^{\circ}C$, density, electromechanical coupling factor $k_p$, dielectric constant ${\varepsilon}_r$, piezoelectric $d_{33}$ constant and mechanical quality factor $Q_m$ showed the optimum value of $7.84g/cm^3$, 0.543, 1,392, 318.7 pC/N, 1,536, respectively for low loss multilayer ceramics actuator application.

• Transactions on Electrical and Electronic Materials
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• 제3권3호
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• pp.25-28
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• 2002

In this study, microstructural, dielectric and electrical properties of (Pb$\sub$0.83/) (La$\sub$0.2/Ce$\sub$0.8/)$\sub$0.08/TiO$_3$(PCT) ceramics as a function of MnO$_2$ addition and electrode size variation were investigated for 30 MHz high frequency ceramic resonator application. Grain size was gradually increased according to the increase of MnO$_2$ addition amount. Moreover, the density showed a constant value with increasing MnO$_2$ addition amount. Dielectric constant was decreased with increasing MnO$_2$ addition amount. Curie temperature of all the composition ceramics was nearly constant around 330$^{\circ}C$. The maximum D.R.of 50.5 dB and maximum Q$\sub$mt3/ of 1842 in the 3$\^$rd/ overtone vibration mode were appeared at the composition of 0.3wt% MnO$_2$, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.248-251
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• 1999

The microwave dielectric properties of The Dielectric Properties of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ (A = Sr, Ca, x = 0, 0.2 ,0.4 ,0.6, 0.8, 1.0) were investigated. In composition of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O, densities are decreased with increasing x values. Grain sizes are decreased with Sr content and Increased with Ca content. The hexagonally ordered superstructure was observed in $Ba_{1-x}$Sr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the intensity of superlattice increased with x value. In $Ba_{1-x}$Cr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the additional diffraction patterns were shown. The highest value of $\varepsilon$$_{r}$ was shown in x=0.2 of BCMN systems and the value was 41.9. The highest Q$\times$f was shown in x=0.2 of BSMN systems and the value was 68,000. $\tau$$_{f}$ were shown 0 ppm/$^{\circ}C$ near x=0.8.TEX> near x=0.8.0.8.

• 한국지반환경공학회 논문집
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• 제3권3호
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• pp.5-13
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• 2002

본 연구에서는 수도권 근처의 터널설계시 대심도 탄성파 토모그래피 탐사에 의한 탄성파 속도와 Q 값과의 상관관계를 도출하고 이를 통한 정확한 암반분류로 공사비 절감효과에 대하여 고찰하였다. 터널전구간 지표면에서 탐사를 수행하여 대심도 구간의 자료를 얻어 암반분류를 수행하였으며, 이상대 구간에서는 VSP를 통한 자료를 추가하여 보다 상세한 자료를 얻어 신뢰성 향상을 얻을 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.756-757
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• 2008

Interior permanent magnet synchronous motor (IPMSM) which has high power density is usually applied to traction motor for hybrid electric vehicle. In order to analyze characteristics of IPMSM, d- and q-axis equivalent circuit analysis is generally used. However, the line current of IPMSM calculated by d- and q-axis equivalent circuit analysis differ from measured value. This error is mainly appeared under the flux weakening control. In order to reduce the error between calculated and measured line current, no-load linkage flux which is calculated with considering saturation of magnetic core and armature reaction is applied to characteristic analysis. The result of line current calculated by the method dealt with in this paper is verified by comparison with experimental results.

• Current Optics and Photonics
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• 제1권2호
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• pp.118-124
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• 2017

Color rendering index (CRI) and luminous efficacy (LE) are two key performance factors of white LEDs (WLED). While most recent works in optics focus on methodology to improve these factors, little attention has been dedicated to chemical composition of materials. This paper studies the effect of $Sr_{2.4}1F_{2.59}B_{20.03}O_{74.8}:Eu_{0.12},Sm_{0.048}$ phosphor (SrSm), in terms of concentration and particle size on CRI and LE of 8500 K - WLEDs. Importantly, the molar mass of the componential ions in SrSm are calculated to shed light on the connection between the chemical composition of the material of interest and the performance of WLEDs. Results show that CRI can be improved to a value of around 86 by boosting red-light components in WLEDs, for all 3 major configurations: conformal, in-cup, and remote phosphor. CRI value tends to decrease with larger size of particles, while LE value goes in the reverse direction. On the other hand, both CRI and LE appear to be reduced at higher concentration of SrSm. This light attenuation is analyzed by using the Lambert-Beer law and Mie-scattering theory.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.143-148
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• 2001

PbWO$_4$ can be densified at 85$0^{\circ}C$ and it shows fairy good microwave dielectric properties; dielectric constant($\varepsilon$$_{r}$) of 21.5, quality factor(Q $\times$f$_{0}$) of 37,224 GHz, and temperature coefficient of resonant frequency($\tau$/suf f/) of -31ppm/$^{\circ}C$. Due to its low sintering temperature, PbWO$_4$ can be used as a multilayered chip component at microwave frequency with high electrical performance by using high conductive electrode metals such as Ag and Cu. However, in order to use this material for microwave communication devices, the $\tau$$_{f}$ of PbWO$_4$ must be stabilized to near zero with high Q$\times$f$_{0}$. In present study, PbWO$_4$ was modified by adding TiO$_2$, B$_2$O$_3$, and CuO in order to improve the microwave dielectric properties without increasing the sintering temperature. The addition of TiO$_2$ increased the $\tau$$_{f}$ and $\varepsilon$$_{r}$, due to its high rr(200ppm/$^{\circ}C$) and $\varepsilon$$_{r}$(100). However, the addition of TiO$_2$ reduced the Q$\times$f$_{0}$ value. When the mot ratio of PbWO$_4$ and TiO$_2$ was 0.913:7.087, near zero $\tau$$_{f}$(0.2ppm/$^{\circ}C$) was obtaibed with $\varepsilon$$_{r}$=22.3, and Q$\times$f/$_{0}$=21,443GHz. With this composition, various amount of B$_2$O$_3$ and CuO were added in order to improve the quality factor. The addition, of B$_2$O$_3$ decreased the $\varepsilon$$_{r}$. However, increased Q$\times$f$_{0}$ and $\tau$$_{f}$. When 2.5 wt% of B$_2$O$_3$ was added to the 0.913PbWO$_4$-0.087TiO$_2$ ceramic, $\tau$$_{f}$ =8.2, $\varepsilon$$_{r}$=20.3, Q$\times$f$_{0}$=54784 GHz. When CuO added to the 0.913PbWO$_4$-0.087TiO$_2$ ceramic, $\tau$$_{f}$ was continuously decreased. And $\varepsilon$$_{r}$ . and Q$\times$f$_{0}$ were increased up to 1.0 wt% then decreased. At 0.1 wt% of CuO addition, the 0.913PbWO$_4$-7.087Ti0$_2$ Ceramic Showed $\varepsilon$$_{r}$=23.5, $\tau$$_{f}$=4.4ppm/$^{\circ}C$, and Q$\times$f$_{0}$=32,932 GHz.> 0/=32,932 GHz.X>=32,932 GHz.> 0/=32,932 GHz.

• Transactions on Electrical and Electronic Materials
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• 제13권5호
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• pp.233-236
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• 2012

The driving properties of a particle-insertion method that filters non-moving particles are analyzed, by measuring its optical and electrical properties. An area that is occupied by the moved particles is proposed, as a desirable evaluation method for a reflective display. To compare the driving property of the particle-moving method with that of the reported simple particle-loading method, two panels are fabricated, according to the different particle-insertion methods, in the same panel condition, of which the width of ribs is $30{\mu}m$, the cell size is $220{\mu}m{\times}220{\mu}m$, the cell gap is $116-120{\mu}m$, the q/m value of the black particles is $+1.8{\mu}C/g$ and that for the white particles is $-4.3{\mu}C/g$. The particle-moving method has a filtering effect which excludes the non-moving particles, inserting only movable particles into the respective cell, so that a panel fabricated by the particle-moving method can drive most of the particles in a cell. Also, most of the particles move at the threshold voltage of 40 V, with enhanced reflectivity. The driving property is also verified by measurement of the occupation rate of the moved particles.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권3호
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• pp.154-161
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• 2005

This paper proposes a speed-sensorless induction motor control system using a rotor speed compensation. To explain the proposed system, this paper describes an induction motor model in the synchronous reference frame for the vector control. The rotor flux is estimated by the rotor flux observer using the reduced-dimensional state estimator technique. The estimated rotor speed is directly obtained from the electrical frequency, the slip frequency, and the rotor speed compensation with the estimated q-axis rotor flux. The error of the rotor time constant is indirectly reflected in the rotor speed compensation using the compensation of the flux error angle. To precisely estimate the rotor flux, the actual value of the stator resistance, whose actual variation is reflected, is derived. An implementation of pulse-width modulation (PWM) pulses using an effective space vector modulation (SVM) is briefly mentioned. For fast calculation and improved performance of the proposed algorithm, all control functions are implemented in software using a digital signal processor (DSP) with its environmental circuits. Also, it is shown through experimental results that the proposed system gives good performance for the speed-sensorless induction motor control.

• 한국전기전자재료학회논문지
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• 제13권8호
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• pp.675-680
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• 2000

In this study the temperature coefficient of resonant frequency(TC $F_{r}$) dielectric and piezoelectric properties of Pb[(S $b_{1}$2//N $b_{1}$2/)$_{0.065}$)-(Z $r_{x}$, $Ti_{1-x}$ )$_{0.90}$] $O_3$ceramics were investigated with Zr/Ti ratio. The compositions near the morphotropic phase boundary (MPB) appeared when Zr/Ti ratio was 49.5/50.5 The dielectric constant and electromechanical coupling factor( $k_{p}$) also showed the highest values of 1,257, 0.653 respectively when the Zr/Ti ratio was 49.5/50.5 Moreover the mechanical quality factor( $Q_{m}$) showed th lowest value of 713 when the Zr/Ti ratio. The temperature coefficient of resonant frequency(TC $F_{r}$) abruptly change at the morphotropic phase boundary(MPB) which existed between the rhombohedral phase with highly negative TC $F_{r}$ of -106ppm/$^{\circ}C$ and the tetragonal phase with highly positive TC $F_{r}$ of +64pp $m^{\circ}C$ as Zr/Ti ratio varied from 50/50 to 49.5/50.5.50.5..50.5.