Biblio

SummaryIn this study, the propagation and resonance properties of shear-horizontal surface acoustic waves (SH SAWs) on a rotated Y-cut 90°X propagating Ca3TaGa3Si2O14 (CTGS) with a Au- or Al-interdigital transducer (IDT) were investigated theoretically and experimentally. It was found that not only a high-density Au-IDT but also a conventional Al-IDT enables the energy trapping of SH SAW in the vicinity of the surface. For both IDTs, the effective electromechanical coupling factor of about 1.2% and the zero temperature coefficient of frequency can be simultaneously obtained by adjusting the cut angle of CTGS and the electrode film thickness.

Waveguided air-coupled ultrasonic phased arrays offer grating-lobe-free beam forming for many applications such as obstacle detection, non-destructive testing, flow metering or tactile feedback. However, for industrial applications, the open output ports of the waveguide can be clogged due to dust, liquids or dirt leading to additional acoustic attenuation. In previous work, we presented the effectiveness of hydrophobic fabrics as a protection layer for acoustic waveguides. In this work, we created a numerical model of the waveguide including the hydrophobic fabric allowing the prediction of the insertion loss (IL). The numerical model uses the boundary element method (BEM) and the finite element method (FEM) in the frequency domain including the waveguide, the hydrophobic fabric and the finite-sized rigid baffle used in the measurements. All walls are assumed as ideal sound hard and the transducers are ideal piston transducers. The specific flow resistivity of the hydrophobic fabric, which is required for the simulation, is analyzed using a 3D-printed flow pipe. The simulations are validated with a calibrated microphone in an anechoic chamber. The IL of the simulations are within the uncertainties of the measurements. In addition, both the measurements and the simulations have no significant influence on the beamforming capabilities.

This paper reports high frequency surface acoustic wave (SAW) devices developed on Sc doped (30%) AlN on high resistivity Si for demonstrating surface acoustic wave – spin wave coupling. Enhanced Q-factors were found for both propagation modes – Rayleigh (4.7 GHz) and Sezawa (8 GHz). SAW/SW (spin wave) coupling is proven for two-ports SAW structures having a magnetostrictive layer of Ni between the two interdigitated transducers (IDTs). A decrease of 3.42 dB was observed in the amplitude of the transmission parameter, at resonance, when the magnetic field was applied. The angle between the applied magnetic field and the SAW propagation direction is π/4.

Acoustic tomography experiments for ocean observation require low-frequency, broadband, high power, small size underwater acoustic transducer, but there are contradictions between the performance of the transducer, therefore a longitudinal-bending fluid-cavity coupled broadband underwater acoustic transducer is presented. The difference between the transducer and the traditional JH transducer is that the opening position of the Helmholtz resonant cavity is arranged between the radiation cover plate and the cylindrical cavity. Based on the optimization results of the finite element software ANSYS produced a transducer test prototype. The test results show that the simulation results and experimental results are basically consistent, and the transmitting voltage response can reach 136dB, the transmitting voltage response fluctuation shall no more than 6dB through the range of 700-1200Hz in the horizontal direction, verified the longitudinal-bending mode and the fluid-cavity mode of the transducer are well coupled, and the transducer is an ideal low-frequency, broadband, high power, small size underwater acoustic transducer.

The fingerprint sensor based on pMUTs was reported [1]. Spatial resolution of the image depends on the size of the acoustic source when a plane wave is used. If the size of the acoustic source is smaller, piezoelectric films with high dielectric constant are required. In this study, in order to obtain small acoustic source, we proposed Pb(Zrx Th-x)O3 (PZT) epitaxial transducers with high dielectric constant. PbTiO3 (PTO) epitaxial films were grown on conductive La-SrTiO3 (STO) substrate by RF magnetron sputtering. Longitudinal wave conversion loss of PTO transducers was measured by a network analyzer. The thermoplastic elastomer was used instead of real fingerprint. We confirmed that conversion loss of piezoelectric film/substrate structure was increased by contacting the elastomer due the change of reflection coefficient of the substrate bottom/elastomer interface. Minimum conversion loss images were obtained by mechanically scanning the soft probe on the transducer surface. We achieved the detection of the fingerprint phantom based on the elastomer in the GHz.

This paper designed a longitudinal bending coupled piezoelectric transducer. The transducer is composed of a rear metal block, a longitudinally polarized piezoelectric ceramic piece and a slotted round front cover. The longitudinal vibration of the piezoelectric oscillators drive the front cover to generate bending vibration to widen the operating frequency band while reducing the fluctuation of transmission voltage response. In this paper, the design method of this multimode coupled transducer is given, and the method is verified by numerical simulation. The results show that the analytical theory and numerical simulation results have good consistency. This longitudinal-flexural coupled vibration transducer widens the bandwidth while preserving the emission voltage response.

According to the technical difficulties of the air-coupled piezoelectric ultrasonic transducer, 1-3 type piezoelectric composites and double matching layers structure are adopted in order to solve the acoustic impedance mismatch at the interface between the piezoelectric materials and air. The optimal design of the matching layer thickness for double matching layers structure air-coupled ultrasonic transducer is also completed through experiments. Based on this, 440 kHz flat-plate and focused air-coupled piezoelectric ultrasonic transducer are designed, fabricated and characterized. Finally, surface cracks are detected using the focused air-coupled piezoelectric ultrasonic transducer.

Wireless transmission of power has been in research for over a century. Our project aims at transmitting electric power over a distance of room. Various methods using microwaves, lasers, inductive coupling, capacitive coupling and acoustic medium have been used. In our project, we are majorly focusing on acoustic method of transferring power. Previous attempts of transferring power using acoustic methods have employed the usage of ultrasonic sound. In our project, we are using infrasonic sound as a medium to transfer electrical power. For this purpose, we are using suitable transducers and converters to transmit electric power from the 220V AC power supply to a load over a considerable distance. This technology can be used to wirelessly charge various devices more effectively.

In this work, a measurement system is developed based on acoustic resonance which can be used for classification of materials. Basically, the inspection methods based on acoustic, utilized for containers screening in the field, identification of defective pills hold high significance in the fields of health, security and protection. However, such techniques are constrained by costly instrumentation, offline analysis and complexities identified with transducer holder physical coupling. So a simple, non-destructive and amazingly cost effective technique in view of acoustic resonance has been formulated here for quick data acquisition and analysis of acoustic signature of liquids for their constituent identification and classification. In this system, there are two ceramic coated piezoelectric transducers attached at both ends of V-shaped glass, one is act as transmitter and another as receiver. The transmitter generates sound with the help of white noise generator. The pick up transducer on another end of the V-shaped glass rod detects the transmitted signal. The recording is being done with arduino interfaced to computer. The FFTs of recorded signals are being analyzed and the resulted resonant frequency observed for water, water+salt and water+sugar are 4.8 KHz, 6.8 KHz and 3.2 KHz respectively. The different resonant frequency in case different sample is being observed which shows that the developed prototype model effectively classifying the materials.

One of the primary motivations for using ultrasound reflectometry for fingerprint imaging is the promise of increased spoof resistance over conventional optical or capacitive sensing approaches due to the ability for ultrasound to determine the elastic impedance of the imaged material. A fake 3D printed plastic finger can therefore be easily distinguished from a real finger. However, ultrasonic sensors are still vulnerable to materials that are similar in impedance to tissue, such as water or rubber. Previously we demonstrated an ultrasonic fingerprint reader operating with 1.3GHz ultrasound based on pulse echo impedance imaging on the backside silicon interface. In this work, we utilize the large bandwidth of these sensors to differentiate between a finger and materials with similar impedances using the frequency response of elastic impedance obtained by transducer excitation with a wideband RF chirp signal. The reflected signal is a strong function of impedance mismatch and absorption [Hoople 2015].

Summary form only given. Strong light-matter coupling has been recently successfully explored in the GHz and THz [1] range with on-chip platforms. New and intriguing quantum optical phenomena have been predicted in the ultrastrong coupling regime [2], when the coupling strength Ω becomes comparable to the unperturbed frequency of the system ω. We recently proposed a new experimental platform where we couple the inter-Landau level transition of an high-mobility 2DEG to the highly subwavelength photonic mode of an LC meta-atom [3] showing very large Ω/ωc = 0.87. Our system benefits from the collective enhancement of the light-matter coupling which comes from the scaling of the coupling Ω ∝ √n, were n is the number of optically active electrons. In our previous experiments [3] and in literature [4] this number varies from 104-103 electrons per meta-atom. We now engineer a new cavity, resonant at 290 GHz, with an extremely reduced effective mode surface Seff = 4 × 10-14 m2 (FE simulations, CST), yielding large field enhancements above 1500 and allowing to enter the few ({\textbackslash}textless;100) electron regime. It consist of a complementary metasurface with two very sharp metallic tips separated by a 60 nm gap (Fig.1(a, b)) on top of a single triangular quantum well. THz-TDS transmission experiments as a function of the applied magnetic field reveal strong anticrossing of the cavity mode with linear cyclotron dispersion. Measurements for arrays of only 12 cavities are reported in Fig.1(c). On the top horizontal axis we report the number of electrons occupying the topmost Landau level as a function of the magnetic field. At the anticrossing field of B=0.73 T we measure approximately 60 electrons ultra strongly coupled (Ω/ω- {\textbackslash}textbar{\textbackslash}textbar

This scientific paper reveals an intelligent system for data acquisition for dam monitoring and diagnose. This system is built around the RS485 communication standard and uses its own communication protocol [2]. The aim of the system is to monitor all signal levels inside the communication bus, respectively to detect the out of action data loggers. The diagnose test extracts the following functional parameters: supply voltage and the absolute value and common mode value for differential signals used in data transmission (denoted with “A” and “B”). Analyzing this acquired information, it's possible to find short-circuits or open-circuits across the communication bus. The measurement and signal processing functions, for flaws, are implemented inside the system's central processing unit. The next testing step is finding the out of action data loggers and is being made by trying to communicate with every data logger inside the network. The lack of any response from a data logger is interpreted as an error and using the code of the data logger's microcontroller, it is possible to find its exact position inside the dam infrastructure. The novelty of this procedure is the fact that it completely automates the diagnose procedure, which, until now, was made visually by checking every data logger.
 

Acoustic microscopy is characterized by relatively long scanning time, which is required for the motion of the transducer over the entire scanning area. This time may be reduced by using a multi-channel acoustical system which has several identical transducers arranged as an array and is mounted on a mechanical scanner so that each transducer scans only a fraction of the total area. The resulting image is formed as a combination of all acquired partial data sets. The mechanical instability of the scanner, as well as the difference in parameters of the individual transducers causes a misalignment of the image fractures. This distortion may be partially compensated for by the introduction of constant or dynamical signal leveling and data shift procedures. However, a reduction of the random instability component requires more advanced algorithms, including auto-adjustment of processing parameters. The described procedure was implemented into the prototype of an ultrasonic fingerprint reading system. The specialized cylindrical scanner provides a helical spiral lens trajectory which eliminates repeatable acceleration, reduces vibration and allows constant data flow on maximal rate. It is equipped with an array of four spherically focused 50 MHz acoustic lenses operating in pulse-echo mode. Each transducer is connected to a separate channel including pulser, receiver and digitizer. The output 3D data volume contains interlaced B-scans coming from each channel. Afterward, data processing includes pre-determined procedures of constant layer shift in order to compensate for the transducer displacement, phase shift and amplitude leveling for compensation of variation in transducer characteristics. Analysis of statistical parameters of individual scans allows adaptive eliminating of the axial misalignment and mechanical vibrations. Further 2D correlation of overlapping partial C-scans will realize an interpolative adjustment which essentially improves the output image. Implementation of this adaptive algorithm into a data processing sequence allows us to significantly reduce misreading due to hardware noise and finger motion during scanning. The system provides a high quality acoustic image of the fingerprint including different levels of information: fingerprint pattern, sweat porous locations, internal dermis structures. These additional features can effectively facilitate fingerprint based identification. The developed principles and algorithm implementations allow improved quality, stability and reliability of acoustical data obtained with the mechanical scanner, accommodating several transducers. General principles developed during this work can be applied to other configurations of advanced ultrasonic systems designed for various biomedical and NDE applications. The data processing algorithm, developed for a specific biometric task, can be adapted for the compensation of mechanical imperfections of the other devices.