• Smart Structures and Systems
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• 제12권2호
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• pp.97-119
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• 2013

This paper presents numerical and experimental results on the use of guided waves for structural health monitoring (SHM) of crack growth during a fatigue test in a thick steel plate used for civil engineering application. Numerical simulation, analytical modeling, and experimental tests are used to prove that piezoelectric wafer active sensor (PWAS) can perform active SHM using guided wave pitch-catch method and passive SHM using acoustic emission (AE). AE simulation was performed with the multi-physic FEM (MP-FEM) approach. The MP-FEM approach permits that the output variables to be expressed directly in electric terms while the two-ways electromechanical conversion is done internally in the MP-FEM formulation. The AE event was simulated as a pulse of defined duration and amplitude. The electrical signal measured at a PWAS receiver was simulated. Experimental tests were performed with PWAS transducers acting as passive receivers of AE signals. An AE source was simulated using 0.5-mm pencil lead breaks. The PWAS transducers were able to pick up AE signal with good strength. Subsequently, PWAS transducers and traditional AE transducer were applied to a 12.7-mm CT specimen subjected to accelerated fatigue testing. Active sensing in pitch catch mode on the CT specimen was applied between the PWAS transducers pairs. Damage indexes were calculated and correlated with actual crack growth. The paper finishes with conclusions and suggestions for further work.

• 대한전기학회논문지
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• 제41권8호
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• pp.858-868
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• 1992

0.085Ba(LaS11/2TNbS11/2T)OS13T-0.915Pb(ZrS1yTTiS11-yT)OS13T (0.45$\leq$y$\leq$0.65) transparent electrooptic ceramics were fabricated by two-stage sintering method. The structural, ferroelectric and electrooptic properties were investigated varying composition and second sintering time. Also the possibility of application to electrooptic device was studied. If we increase the PbZrOS13T contents, dielectric constants were increased and Curie temperature was decreased. In the composition of 0.55[mol] PbZrOS13T, electromechanical coupling factor and piezoelectric charge constant were the highest values of 43[%] and 173x10S0-12T[C/N], respectively. Mechanical quality factors were decreased with the increasing PbZrOS13T contents. Light transmittance was increased with wavelength when measured from 300[nm] to 900[nm], and with PbZrOS13T contents in the range of 0.50[mol]-0.65[mol], and had the highest value of 67[%] in the composition of 0.65[mol] PbZrOS13T. From the results of ferroelectric hysteresis loop and transmitted light intensity with electric field, the specimens with compositions of 0.65,0.60,0.55[mol] PbZrOS13T were applicable to electrooptic memory device and those with compositions of 0.50,0.45[mol] PbZrOS13T were applicable to linear electrooptic device.

• 한국전기전자재료학회논문지
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• 제13권3호
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• pp.214-219
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• 2000

In this paper the structural dielectric and piezoelectric properties of Pb［(M $g_{1}$2// $W_{1}$2/)$_{x}$-(N $i_{1}$3//N $b_{2}$3/)$_{0.15-x-(Zr_{0.5})}$ $Ti_{0.5}$)$_{0.85}$］ $O_3$ (x=0.0~0.10) ceramic were investigated with the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$. According to the substitution of Pb(M $g_{1}$2//W/1/2/) $O_3$ curie temperatures were slightly decrease due to the decrease of the tetrag-onality of crystal structure and coercive fields were decreased. Up to the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ 3mol%,remnant polarization dielectric constant piezoelectric constant were increased. Dielectric constant and electro-mechanical coupling factor( $k_{p}$, $k_{31}$ ) were appeared the highest value of 2230, 0.64, and 0.38 and piezoelectric constant( $d_{33}$ , $d_{31}$ ) was the largest value of 418, 202($\times$10$^{-12}$ /C/N), respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/N) respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ was 3mol%.s 3mol%.%.

• 한국전기전자재료학회논문지
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• 제24권9호
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• pp.728-732
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• 2011

In this study, piezoelectric and dielectric properties of Lead-free $0.97[(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3]+0.03[(Bi_{0.5}K_{0.5})TiO_3]$ (abbreviated as 0.97NKNS-0.03BKT)ceramics synthesized by conventional solid-state reaction process were investigated as a function of $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition. The results indicated that the $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition significantly improved the sinterability, grain growth and piezoelctric properties of 0.97NKNS-0.03BKT ceramics. The optimum values as planar piezoelectric coupling coefficient ($k_p$= 0.355), piezoelectric constant ($d_{33}$= 207 pC/N) and mechanical quality factor ($Q_m$= 128) were obtained when 0.009KCT was added. The electromechanical coupling factor($k_p$) was slightly decreased according to the increasing temperature.

• 센서학회지
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• 제5권3호
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• pp.1-8
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• 1996

LVDT는 독립적으로 움직일 수 있는 코어의 변위에 비례하여 전기적 출력을 나타내는 전기기계적 트랜스듀서이다. 기존의 일반적 LVDT는 구조적으로 측정범위에 대해 크기의 비가 작은 단점을 가지고 있다. 이러한 단점을 개선하기 위하여, 새로운 형태의 LVDT를 제안하였고 동일한 치수와 코어를 가진 두가지 형태의 LVDT에 대하여 FEM 해석을 통하여 시뮬레이션하였다. 시뮬레이션 한 결과를 토대로 이들을 제작하여 그 특성을 비교하였으며 시험결과 측정범위${\pm}5\;mm$ 에서 일반 LVDT는 ${\pm}3\;%$의 선형도를 나타내었으며, 본 연구에서 제안한 LVDT는 ${\pm}0.5\;%$의 선형특성을 나타내었다. 따라서 이론적 결과와 실험적 결과를 통하여 기존의 LVDT보다 제안된 LVDT의 특성이 우수함을 확인할 수 있었다.

• 센서학회지
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• 제6권5호
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• pp.392-399
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• 1997

본 연구에서는 $0.125Pb(Mg_{1/2}Nb_{2/3})O_{3}-0.435PbTiO_{3}-0.44PbZrO_{3}$의 조성을 갖는 hard계 압전 재료에 0.5 wt%의 $MnO_{2}$를 첨가하였으며, 이 시편으로 초음파 전동기를 제작하고자, 소결 온도에 따른 시편의 유전 및 압전특성에 대하여 연구하였다. 실험 결과, $1270^{\circ}C$의 소결 온도에서 다음과 같이 가장 우수한 압전특성을 나타냈다. 즉 시편의 밀도는 $7.72\;g/cm^{3}$ 유전상수는 570, 유전손실은 0.82 %f, 잔류분극 Pr은 $19.18{\mu}C/cm^{2}$ 항전계 Ec는 9.63 kW/cm, 전기기계 결합계수 kp는 55.1%, 기계적 품질계수 Qm은 886이 되었다. 또한 $1270^{\circ}C$ 에서 소결된 시편의 유전상수 및 유전손실을 주파수 변화와 온도 변화에 따라 조사하였다.

• 대한한의정보학회지
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• 제14권1호
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• pp.81-106
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• 2008

The ECG which used for this paper, is analysis result from alogrisms of arrythmia, and we have studied that how we could certain Cold(寒 )type or Heat(熱) type and that Deficiency(虛) type or Excess(實)type of organs from various special diseases, and we obtained like these results. 1. we depend on our examination about Pulse(脈) because we can't discriminate arrythmia using EKG analysis instruments. 2. We obtained that Cold(寒) type diseases had wave that prolonged above normal baseline and ST wave which had downward aptitude. 3. We obtained that Heat(熱) type diseases had the fibrillation which had shortend wave that compare to normal and had downward aptitude or negative aptitude. 4. We obtained that Respiratory system (肺) diseases had wave that is within normal or is short of normal range and had much fluctuation in potential difference or trans on P wave. 5. The character of EKG which presented about diseases of gastric systems is prolonged above narmal range of wave, and the EKG had represented mixed wave with Heat(熱) type when accompany inflammatory in gastric system. 6. The wave of Blood Stasis(瘀血) type had upward aptitude of QRS wave, and the wave of anemia or blood loss type(少血 ) had downward aptitude of QRS wave, the wave which had both Cold(寒) and Heat (熱) represented mixed waves. 7. The Knotted Pulse(結脈) and Intermittent Pulse(代脈) is corresponded with sinus brady cardia, and the Swift Pulsle(疾脈) is corresponded with fibrillation. 8. We pay attention to the relations of formations about pressures pulse from formations of EMD( electromechanical dissociation ). From these results, we will have to study about EKG which using in tests of change of Parkinsons disease.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.280-280
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• 2007

Lead oxide-based ferroelectrics are the most widely used materials for piezoelectric actuators, sensors and transducers due to their excellent piezoelectric properties. Considering lead toxicity, there is great interest in developing lead-free piezoelectric materials, which are biocompatible and environmentally friendlier. Recently alkali oxide materials, including sodium - potassium niobate (NKN), have been given attention in view of their ultrasonic application and also as promising candidates for piezoelectric lead-free system. However, it is difficult to sinter such NKN-based materials via conventional sintering process. In this reason, many researchers have investigated hot press, hot isostatic press or spark-plasma sintering of NKN-based ceramics. In this study, as candidates for lead-free piezoelectric materials, dense (Na,K,Li)(Nb,Sb)$O_3$ systems were developed by conventional sintering process. The microstructures and piezoelectric properties of the (Na,K,Li)(Nb,Sb)$O_3$ systems were investigated as a function of variable compositions. The excellent piezoelectric and electromechanical properties indicate that this system is potentially good candidate as lead-free material for a wide range of electro-mechanical transducer applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.306-306
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• 2007

최근, LED 구동 인버터, DC-DC 컨버터, AC-DC 컨버터 및 형광등 ballaster 등의 고전압전원장치등에 압전변압기를 적용하고자 하는 연구가 활발히 진행되고 있다. 순수한 $PbTiO_3$는 큐리온도($490^{\circ}C$)가 높고, 기계적강도가 크며, 비유전율(약 200 정도)이 작다. 또한, 두께방향 진동의 전기기계 결합계수 ($K_t$)가 윤곽진동의 전기기계 결합계수($K_p$)보다 크므로 두께방향의 진동모드를 이용한 벌크파 진동자의 경우 윤곽진동방향으로 불요신호(spurious signal)가 적고, 작은 grain size($1\;{\mu}m$정도)로 미세가공이 가능하여 고주파 재료로 이용되고 있다. 압전변압기의 출력 전력을 향상시키기 위해서는 적층으로 제작하여야 하는데 적층 압전변압기 제작시 층간의 내부 전극이 도포된 상태에서 소결하여야 한다. 이때 소걸 온도가 높으면 Pd 함랑이 높은 전극을 사용하여야 하는데 Pd 전극의 가격이 비싸 소자의 경제성이 떨어지게 된다. 따라서 순수한 Ag 전극을 내부전극으로 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결이 가능하여야 한다. 따라서 본 연구에서는 $(Pb,Ca,Sr)Ti(Mn,Sb)O_3$ 조성을 이용하여 $900^{\circ}C$ 이하의 저온소결이 가능한 두께방향진동모드 적층 압전변암기를 제작하여 그에 대한 전기적 특성을 조사하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.261-261
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• 2007

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to- electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen. Under an external vibration acceleration of 0.1G at 120 Hz, the device exhibited a peak-to-peak voltage of 2.8 V and a power of 0.5 mw in resonance mode.