압전 PZT 변환자의 과도응답 특성

이종규,하강열 釜山水産大學校 1992 釜山水産大學 硏究報告 Vol.32 No.2

The transient responses of piezoelectric PZT transducers were observed at the epicenter of a glass plate(thickness=43.7 ㎜ and diameter=290 ㎜) during glass capillary breakage. The piezoelectric PZT transducers with air-backing composed of the front material of a white alumina and a EC-65 PZT ceramics(Supplied by Edo Co. USA) with the same diameter and different thickness. The 1st pulse observed at ??sec may be considered as the arrival of the longitudinal wave propagating on the front face of the PZT ceramic since the measurements and the calculations were in agreement. The 1st pulse voltages increased linearly with an increase of load and exp(-dt/RC), where dt, R, and C are the sampling time of 10 nsec, the resistance of 50 ohm and the capacitance of the PZT transducer, respectively, and it may be considered that the 1st pulse voltages depend on the particle velocity and the time constant, ??. The full-width at half-maximum of the 1st pulse voltage with the different thickness of the white alumina, i.e., 0.66 and 0.13 ㎜ were about 240 and 190 nsec, respectively, then the longer full-width at half-maximum of the 1st pulse voltage on the thicker thickness of the front material may be considered as the longer propagation time of the thicker thickness. Furthermore, due to the agreement of the measurements and calculations, the voltage pulses observed at ??, ?? and ??sec may be considered as the arrival of 1P, 3P and 5P, respectively, where nP represents the arrival of the longitudinal wave propagating n times through the glass plate. The next pulse after the 1st pulse observed at ??sec may be considered as the arrival of the longitudinal wave propagating on the rear face the PZT ceramic. Therefore the velocity of the longitudinal wave on the PZT ceramic is 4,615m/sec.

LiTaO_3 단결정을 사용한 압전변압기의 개발

황성필,김무준,하강열,강갑중 한국센서학회 2002 센서학회지 Vol.11 No.3

본 연구에서는 온도에 따른 압전특성이 매우 안정적인 LiTaO_3(x-112°y) 단결정을 이용하여 압전변압기를 제작하고 그 특성을 분석하였다. 제작시 LiTaO_3 단결정의 변환효율이 낮은 단점을 보완하기 위해 Lame'-mode를 이용하여 길이와 폭의 비가 2:1인 압전변압기를 제작하고 PSpice를 이용하여 진동 모드 해석, 입력전압에 따른 출력전압특성 및 진동속도특성을 분석하였다. 제작한 압전변압기는 길이방향의 제 2차 고조파 주파수와 폭방향의 기본공진주파수가 결합된 290.83(㎑)에서 입력전압에 대한 최대출력전압이 나타났으며, 약 10배 정도의 승압비를 얻을 수 있었다. The single crystal of LiTaO_3(x-112°y) has very stable thermal characteristics in a piezoelectric transformer. In this paper, a piezoelectric transformer made of the crystal is newly designed and its operating characteristics are analyzed. The length of the transformer is determined as twice as its width for Lame'-mode because the single crystal of LiTaO_3 has low electro-acoustic efficiency. The electric and vibrational characteristics of the transformer is simulated by the PSpice program, and its results are compared to experimental ones. As the results, the ratio of output voltage to input shows large than 10 at 290.83(㎑), which is the frequency coupled the 2nd harmonic for length and the fundamental for width of the Lame'-mode transformer.

Estimation and measurement of forward propagated ultrasonic fields in layered fluid media

Ha, Kang-lyeol,Kim, Moo-joon,Hyun, Byung-gook 부경대학교 음향진동공학연구소 2000 音響振動工學硏究所 硏究報告 Vol.5 No.-

A Basic Study on Application of Acoustic Microscopy to Dental Research Field

Ha, Kang-Lyeol 釜山水産大學校 1992 釜山水産大學 硏究報告 Vol.32 No.2

초음파현미경(Scanning Acoustic Microscope : SAM)은 물질의 미세영역의 탄성적 성질을 超音波畵像, 또는 漏泄彈性表面波(leaky surface acoustic wave : LSAW)의 음속 및 감쇄계수에 의한 정량적인 계측치로 나타내는 장치이다. 개발초기의 초음파현미경에 관한 연구는 주로 空間分解能을 향상시키기 위한 방법을 모색하는 것이었다. 그후, 漏泄彈性表面波에 의한 V(z)곡선이 발견되고, 그 곡선의 해석에 의한 각종 mode의 LSAW의 음속 및 감쇄계수의 定量計測法이 확립되자, 고체물성 연구등에 활발히 응용되기 시작하였다. 生體硬組織(齒牙나 骨등)은 초음파현미경이 갖는 두가지 계측법 즉, 畵像計測法과 定量計測法이 동시에 적용될 수 있는 가장 적합한 대상 중의 하나이다. 본 논문에서는 高分解能의 超音波畵像을 얻을 수 있는 중심주파수 400㎒의 點集束빔 초음파 集束素子와 高精度의 정량계측치를 얻을 수 있는 중심주파수 225㎒의 直線集束빔 초음파 集束素子를 사용하여 화상계측과 정량계측의 두가지 복합기능을 갖춘 초음파현미경 시스템을 구성한 후, 齒學分野에 도입시켜, 1) 一次우식(primary caries)의 탐지 및 그 疾患의 상태 평가를 위해 畵像計測法을, 2) 齒牙 및 齒科材料의 탄성적 성질 평가를 위해 定量計測法을 적용하고, 그 결과로부터 齒學硏究에 있어서의 초음파현미경의 有用性을 보인다.

A New Calculation Mathod of Radiation Impedance for Vibrating Surfaces with an A

Ha, Kang Lyeol 부경대학교 기초과학연구소 2000 부경대 기초과학연구논문집 Vol.3 No.-

Estimation and Measurement of Forward Propagated Ultrasonic Fields in Layered Fluid Media

Ha, Kang-Lyeol,Kim, Moo-Joon,Hyun, Byung-Gook The Acoustical Society of Korea 2000 韓國音響學會誌 Vol.19 No.e2

The forward propagated ultrasonic fields resulting from a circular plane or a concave transducer in layered fluid media as well as in homogeneous water are theoretically estimated by the angular spectrum method(ASMJ) combined with Rayleigh-Sommerfeld diffraction theory(RSDT), and measured by a precision 3-D scanning system with a needle-point hydrophone. To make the aliasing error negligible on the 2-D FFT in the theoretical estimation, the spatial discretization in the ASM are carefully considered for optimal selection of spatial sampling intervals and the size of discretization area. It is shown that the estimated fields agree reasonably with the measured ones.

A $PbTiO_{3}$ Transmitting/P(VDF-TrFE) Receiving Wideband Ultrasonic Transducer in VHF Band

Ha, Kang-Lyeol,Kim, Moo-Joon,Kim, Jung-Ho,Kim, Jung-Soon The Acoustical Society of Korea 2004 韓國音響學會誌 Vol.23 No.e4

A new type of high frequency wideband ultrasonic transducer with a separation between a transmitter and a receiver was proposed and its characteristics were simulated using a PSpice model. The piezoelectric ceramic $PbTiO_{3}$ as a transmitter and the piezoelectric copolymer P(VDF- TrFE) as a receiver were used for high sensitivity and wide bandwidth, respectively. The characteristics of the focusing transducer with center frequency of approximately 35MHz fabricated in this study showed very wide bandwidth, which could give an axial spatial resolution better than $30{\mu}m$ in B-mode image for biological tissues.

물리센서 - 2 차원 배열 수증청음기의 제작과 초음파 음장 측정에의 응용

하강열(Kang Lyeol Ha),김무준(Moo Joon Kim),강갑중(Gab Joong Kang),현병국(Byung Gook Hyun),채민구(Min Ku Chae),금야 화언(Gazuhiko Imano) 한국센서학회 2001 센서학회지 Vol.10 No.5

N/A Two-dimensional array hydrophones with 8 x 8 elements were designed and fabricated using the PVDF(Polyvinylidene fluoride) piezoelectric film, and the method and system for ultrasonic field measurement in several MHz ∼ tens of MHz band using the hydrophones was established. The characteristics of frequency response relating to the backing materials were analyzed with the Mason equivalent circuit for design, and the accuracy of ultrasonic field measurement relating to the sizes and kerfs of piezoelectric elements was discussed. Good results of the measurement of ultrasonic field formed by a circular plane transducer of 2.25MHz in water were obtained by the system with the array hydrophones.

압전고분자 초음파 트랜스듀서와 생의학적 응용

하강렬(Kang-Lyeol Ha),曹永剛(Yonggang Cao) 한국비파괴검사학회 2012 한국비파괴검사학회지 Vol.32 No.5

PVDF와 P(VDF-TrFE)로 대별되는 압전고분자는 종래의 대표적인 압전재료인 PZT에 비해 전기음향변환효율이 떨어지며 내부손실이 큰 단점은 있으나, 음향임피던스가 물 또는 생체와 비슷하고 수신효율이 우수하며 광대역 특성을 나타내는 등의 장점을 가진 재료이다. 또한 다른 압전재료에 비해 얇은 막으로의 제작이 쉽고, 그 막은 유연하므로 복잡한 곡면을 갖는 고주파 초음파 트랜스듀서 재료로 유용하다. 그러한 특성은 생의학적 응용에 적합한바, 다양한 형태의 초음파 트랜스듀서가 연구 개발되어져 왔다. 본 논문에서는 먼저, 압전고분자막을 이용하여 초음파 트랜스듀서를 설계 제작하는데 있어서 고려해야할 몇 가지 주요사항을 기술하고, KLM 모델을 사용한 해석을 통하여 그 고려사항들이 트랜스듀서의 동작에 미치는 영향을 파악하였다. 다음으로, 의학적 또는 생물학적 응용을 목적으로 초음파 영상을 얻고 있는 몇몇 주요 응용분야에서 사용되는 압전고분자 트랜스듀서의 구조와 그것을 이용하여 얻은 영상의 특징에 대하여 간략히 해설하였다. PVDF(poly vinylidene fluoride) and P(VDF-TrFE)(poly vinylidene fluoride-tetrafluoroethylene) are the typical piezoelectric polymers with unique properties. Even they are inferior to conventional piezoelectric ceramics PZT in electromechanical conversion efficiency and interior loss, though they are superior in receiving sensitivity and frequency bandwidth. Their acoustic impedances are relatively close to water or biological tissue and it is easier to make thin film than other piezoelectric materials. Futhermore, the film is so flexible that it is easy to attach on a complex surface. Those properties are suitable for the ultrasound transducers which are useful for medical and biological application, so that various types of polymer transducers have been developed. In this paper, several important considerations for design and fabrication of piezoelectric polymer transducers were described and their effect on the transducer performance were demonstrated through the KLM model analysis. Then, it was briefly reviewed about the structures of the polymer transducers developed for obtaining images as well as the characteristics of the images in several important medical and biological application fields.

해양에서의 수평적 수온변화가 음파전달에 미치는 영향에 대한 기초적 연구

하강열 ( Kang Lyeol Ha ),김무준 ( Moo Joon Kim ) 한국어업기술학회 1996 수산해양기술연구 Vol.32 No.4