• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1337-1338
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• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, 0.07Pb$(Mn_{1/3}Nb_{2/3})O_{3}-xPb(Ni_{1/3}Nb_{2/3})O_{3}-(0.93-x)Pb(Zr,Ti)O_{3}$ ceramics system were fabricated using $Li_{2}CO_{3}-Bi_{2}O_{3}$-CuO sintering aids and the specimens were sintered at $930^{\circ}C$. Thereafter their piezoelectric and dielectric characteristics were investigated with the amount of PNN substitution. At 9[mol%] PNN substitution, electromechanical coupling factor (kp), mechanical quality factor (Qm) and piezoelectric constant ($d_{33}$) showed the optimum value of 0.60, 1323 and 387pC/N, respectively.

• ETRI Journal
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• 제44권2호
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• pp.260-273
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• 2022

This study presents a novel multilayer structure of parallel coupled-line bandpass filtercentered at 2.42 GHz with a fractional bandwidth value of approximately 19.4%. The designed filter can suppress harmonics with an appropriate frequency response by incorporating different techniques based on the multilayer technique. A combination of different techniques such as radial microstrip stubs and defected ground structure (DGS) and defected microstrip structure techniques are employed to suppress harmonics up to 5f₀. These techniques are used in two layers to suppress up to 5f₀. In addition, in this study, the effects of different parameters, such as the width of slot-line DGS, the angle of diagonal line slots in the upper layer, and the air gap between the two layers on the filter performance, are investigated. To verify the correct circuit operation, the designed filter is implemented and tested. The measurement results of the proposed filter are compared with the simulation results.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.174-176
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• 2012

Piezoelectric 0.93(Na0.5K0.5)NbO3-0.07BiTiO3 (NKN-BTO) ceramics were fabricated by the mixed-oxide method and their structural and dielectric properties was investigated with the variation of sintering temperature. All specimens were crystallized in the perovskite single phase without any formation of a second phase such as pyrochlore. The average grain size of the NKN-BTO specimen sintered at 1130 ℃ is 0.32 ㎛. The specimen sintered at 1100 ℃ showed the highest relative density of 98%. Electromechanical coupling factor, relative dielectric constant and dielectric loss of the NKN-BTO specimens sintered at 1110 ℃ were 0.31, 1222 and 0.02, respectively. Curie temperature of the specimen sintered at 1110 ℃ was 445 ℃.

• Structural Monitoring and Maintenance
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• 제11권2호
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• pp.149-171
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• 2024

Drive-by monitoring (also known as indirect monitoring or mobile sensing) of bridges has obvious advantages when compared to other approaches of Structural Health Monitoring. The underlying concept involves leveraging the coupling between the vertical vibrations of the bridge and those generated in the passing vehicle. In this scenario, the vehicle serves as both the initiator and recipient of the vibrations, which can provide information on the structural condition of the bridge. In the literature, a wide range of methods has been proposed, primarily focused on highway bridges. However, limited research has been published to assess the suitability of indirect methods for monitoring railway bridges, bounded to numerical studies based on theoretical simulations and, rarely, on experimental investigations. The aim of this work is to contribute to filling this gap and explore the feasibility of implementing drive-by monitoring for railway bridges using in-service vehicles and discuss its potential applicability, from theoretical and practical point of view, with illustration through real case studies from the Moroccan railway network.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.174-174
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• 2000

A strong antiferromagnetic coupling in Fe/Si multilayered films (MLF) had been recently discovered and much consideration has been given to whether the coupling in the Fe/Si MLF system has the same origin as the metal/metal MLF. Nevertheless, the nature of the interfacial ron silicide is still controversial. On one hand, a metal/ semiconductor structure was suggested with a narrow band-gap semiconducting $\varepsilon$-FeSi spacer that mediates the coupling. However, some features show that the nature of coupling can be well understood in terms of the conventional metal/metal multilayered system. It is well known that both magneto-optical (MO) and optical properties of a metal depend strongly on their electronic structure that is also correlated with the atomic and chemical ordering. In this study, the nature of the interfacial regions is the Fe/Si multilayers has been investigated by the experimental and computer-simulated MO and optical spectroscopies. The Fe/Si MLF were prepared by rf-sputtering onto glass substrates at room temperature with the number of repetition N=50. The thickness of Fe sublayer was fixed at 3.0nm while the Si sublayer thickness was varied from 1.0 to 2.0 nm. The topmost layer of all the Fe/Si MLF is Fe. In order to carry out the computer simulations, the information on the MO and optical parameters of the materials that may constitute a real multilayered structure should be known in advance. For this purpose, we also prepared Fe, Si, FeSi2 and FeSi samples. The structural characterization of Fe/Si MLF was performed by low- and high -angle x-ray diffraction with a Cu-K$\alpha$ radiation and by transmission electron microscopy. A bulk $\varepsilon$-FeSi was also investigated. The MO and optical properties were measured at room temperature in the 1.0-4.7 eV energy range. The theoretical simulations of MO and optical properties for the Fe/Si MLF were performed by solving exactly a multireflection problem using the scattering matrix approach assuming various stoichiometries of a nonmagnetic spacer separating the antiferromagnetically coupled Fe layers. The simulated spectra of a model structure of FeSi2 or $\varepsilon$-FeSi as the spacer turned out to fail in explaining the experimental spectra of the Fe/Si MLF in both intensity and shape. Thus, the decisive disagreement between experimental and simulated MO and optical properties ruled out the hypothesis of FeSi2 and $\varepsilon$-FeSi as the nonmagnetic spacer. By supposing the spontaneous formation of a metallic ζ-FeSi, a reasonable agreement between experimental and simulated MO and optical spectra was obtained.

• 공업화학
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• 제25권5호
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• pp.487-496
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• 2014

본 연구에서는 phenothiazine과 benzothiadiazole을 기반으로 하고, phenothiazine의 질소 위치에 다양한 side-chain을 치환한 고분자를 합성하였다. 합성된 고분자는 광학적, 전기화학적 분석 결과 300~700 nm에서 흡수를 보였고, -5.4 eV 정도의 이상적인 HOMO energy level를 갖는 특성을 확인하였다. 고분자와 $PC_{71}BM$을 광활성층으로 사용한 소자를 제작하였고, 측정결과 branched side-chain을 가지며 탄소수가 많은 P2HDPZ-bTP-OBT가 2.4%로 최대 광전변환효율을 갖는 것으로 확인되었다($V_{OC}$ : 0.74 V, $J_{SC}$ : $6.9mA/cm^2$, FF : 48.0%).

• 대한전자공학회논문지
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• 제11권6호
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• pp.1-15
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• 1974

본 연구는 탄성파 지연선에 이용되는 탄성표면파중에서 SH표면파 모우드에 대하여 이론적 해석을 하였으며 그 결과 전기-기계적 결합계수가 크며 또한 여전 매질내 깊이 방향으로 아주 작은 감쇠률을 갖고 표면을 따라 전파됨을 알았단. 예로서 PZT-4인 경우 에너지의 80%가 감쇠되는 깊이는 190파장이 된다. 또한 탄성표면파 지연선을 하나의 계단자강으로서 취급하여 삽입손실를 구하였으며 특히 SH표면파 모우드와 같이 전기-기계론 결합계수가 큰 경우는 인터디지탈 트랜스듀셔의 전극폭과 윤극간 간격 사이의 비에 따라 중심 주파수가 현저히 달라진다. 그리고 탄성파 지연선의 온도계수를 벌크파인 종파, 횡파에 대하여 구하였으며 LiTaO2 Z축방향 전파의 횡파는 지연시간의 온도계수가 5.4X10-6/℃로 아주 작아짐을 알았다. 또한 LiNbO3의 130°, 64° 로테이트 Y캇트, X전파의 탄성표면파의 온도계수가 이론치와 잘 일치함을 실험적으로 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1487-1488
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• 2011

Electrical properties and microstructure were investigated on the effects of $MnO_2$ and the lead-free $(Na_{0.44}K_{0.52}Li_{0.04})(Nb_{0.83}Sb_{0.07}Ta_{0.1})O_3$ ceramics with the addition of $MnO_2$ were fabricated by a conventional mixed oxide method. A gradual change in the crystal and microstructure was observed with the increase of $MnO_2$ addition. For the NKN-LST-xmol%$MnO_2$ sintered at $1100^{\circ}C$, bulk density increased with the addition of $MnO_2$ and showed maximum value at addition 1.0mol% of $MnO_2$. Curie temperature of the NKN-LST ceramics slightly decreased with adding $MnO_2$. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased below 0.25mol% of $MnO_2$ addition, which might be due to the increase in density. The high piezoelectric properties = 145 pC/N, electromechanical coupling factor = 0.421 and dielectric constant = 2883 were obtained for the NKN-LST-0.25mol%$MnO_2$ sintered at $1100^{\circ}C$ for 4h.

• 한국전기전자재료학회논문지
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• 제25권7호
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• pp.506-510
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• 2012

In this study, lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics were fabricated by conventional mixed oxide method. Structural and electrical properties of lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics with the variation of sintering temperature were investigated. As results of x-ray diffraction analysis, all specimens showed a typical polycrystalline perovskite structure without presence of the second phase. Sintered density increased with an increases of sintering temperature and the specimen sintered at $1,020^{\circ}C$ showed the maximum value of 4.5 $g/cm^3$. The average grain size of the $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimen sintered at $1,020^{\circ}C$ is about 0.83 ${\mu}m$. Electromechanical coupling factor, relative dielectric constant and dielectric loss of $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimens sintered at $1,020^{\circ}C$ were 0.252, 741 and 0.043% respectively.

• Progress in Superconductivity
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• 제8권2호
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• pp.143-151
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• 2007

Accurate measurements of the microwave surface resistance (Rs) of high temperature superconductor (HTS) films are important with regard to applications of HTS materials for wireless communications. As the surface resistance values of HTS films are usually extracted from the measured unloaded quality factor ($Q_0$) of resonators made of HTS films, it is essential to measure the resonator $Q_0$ with accuracy. The $TE_{011}\;mode\;Q_0$ of sapphire resonators with the endplates made of $YBa_2Cu_3O_{7-{\delta}}$(YBCO) film on $LaAlO_3$ is measured by using the S-parameter circle-fit method at a frequency of about 19.6 GHz and temperatures of 30 K to 90 K, which is compared with the measured values by using the Lorentzian-fit method. Good agreements are found between the two sets of $Q_0$ values measured by using the two different methods whether the resonator is used in a weak-coupling scheme or a strong-coupling scheme, showing reliability of both methods fur measuring the resonator $Q_0$ accurately. The $Q_0$ of sapphire resonators with a gap between the top plate and the rest of the resonator is also discussed.