Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 39 for “"Ultrasonic transducers"”.
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Ultrasonic transducers for wideband attenuation measurements
… (typically 3 dB/cm) require therefore that the ultrasonic transducers exhibit efficient wideband characteristics. Piezoceramic transducers vibrating in thickness-mode are the most suitable to generate ultrasound at these frequencies. However, their high acoustic impedances relative to their …
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Gesture sensing with flexural ultrasonic transducers
… on the development of an array of flexural ultrasonic transducers to allow sensing through a fully metal substrate. An analytical model, finite element simulations, and experiments are presented to characterize and optimize the transducers, and a prototype is developed as a proof of concept …
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The design of high power ultrasonic transducers
… design and construction of high power ultrasound transducers as well as some of the effects of high power ultrasound. The two design approaches that are researched and applied are the equivalent circuit method and Finite Element Method (FEM). These methods are used in conjunction with each other …
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Passive materials for high frequency piezocomposite ultrasonic transducers
… mean there is great potential for commercial transducers far superior to conventional devices currently in clinical use. This Thesis reports the fabrication and characterisation of passive materials suitable for use in high frequency piezocomposite transducer devices. Epoxy composites have …
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Piezoelectric micro-machined ultrasonic transducers for medical imaging
… of cost effective and array compatible transducers making piezoelectric micro-machined ultrasonic transducers (pMUTs) an attractive alternative to the current bulk piezoelectric technology. This thesis aims to realize pMUT potential starting with the development of an effective single …
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Minimally invasive capacitive micromachined ultrasonic transducers array For biomedical applications
… to medical diagnosis and treatment. The ultrasonic transducer plays an important role in determining the resolution, sensitivity, as well as other critical diagnostic capabilities of an ultrasonic detection or imaging system. Currently piezoelectric ultrasonic transducers dominate the …
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Mathematical Modelling of Novel Ultrasonic Transducers with Fractal-Like Geometries
Piezoelectric ultrasonic transducers have the potential to operate as both a sensor and as an actuator of ultrasonic waves. Standard designed transducers have a regular structure and therefore operate effectively over narrow bandwidths due to their single length scale. Biological transducers of …
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Novel ultrasonic transducers and array designs using self-similar fractal geometries
Wider operational bandwidth is an important requirement of an ultrasound transducer across many applications. Naturally occurring resonating systems utilise structures containing a range of length scales to produce a broad operating bandwidth. In this work, a novel concept of designing a …
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Design, construction, and testing of ultrasonic transducers with modified radial velocity profiles
… of modified far field patterns of an ultrasonic transducer, it is desirable to use a transducer which produces a beam with a Gaussian profile. A transducer with a velocity profile which is Gaussian as a function of radius and independent of angle is described. The transducer has been …
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Design and characterization of variable acoustic field amplitude and focusing ultrasonic transducers
Ultrasonic transducers with concentric annular ring electrodes can be used to generate various circularly symmetric acoustic field profiles. These transducers can also electronically simulate a circular phased array and generate a focused ultrasonic beam. A model which predicts the acoustic …
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Photoacoustic Microscopy and Photoacoustic Computed Tomography Using High-frequency Linear Array Ultrasonic Transducers
… centimeters imaging depth in tissue by employing ultrasonic array detectors and inverse algorithms. This dissertation aims to improve the functionality of OR-PAM using a high-frequency linear ultrasonic array, and to advance the performance of linear-array PACT to full view angle capability and …
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Nonlinear Dynamics of Circular Plates under Electrical Loadings for Capacitive Micromachined Ultrasonic Transducers (CMUTs)
… for applications in capacitive micromachined ultrasonic transducers (CMUTs). After establishing the equations governing the plate, we discretized the system by using a Galerkin approach. The distributed-parameter equations were then reduced to a finite system of ordinary-differential equations …
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Modeling ultrasonic transducer in homogeneous and non-homogeneous media using DPSM method
Modeling ultrasonic transducers is an important aspect of research in nondestructive evaluation and testing. In most nondestructive evaluation applications, the ultrasonic transducers are traditionally modeled as: (1) point sources generating spherical wave fronts (2) line sources generating …
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Dual-Use Strain Sensors for Simultaneous Strain Measurement and Acoustic Source Location
The use of metal strain gauges and ultrasonic transducers have long been studied in the field of Nondestructive Evaluation (NDE) as a part of structural health monitoring (SHM). Strain gauges use electrical resistance to monitor strains during the loading of a component. Ultrasonic transducers are …
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Slurry flowmetering using correlation techniques
… to model the flowmeter consisting of the two transducers a known distance apart. A review of transducers for converting time-varying spatial flow patterns into electrical signals is undertaken and leads to ultrasonic transducers being chosen as most suitable for slurry flowrate measurements. …
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Stiffness characterization of mechanically-compressed cohesive soils using wave propagation
… shear waves through soft cohesive soils with ultrasonic transducers, bender elements are typically used, which couple to the soft clay. Unfortunately, the stress limitation of bender elements precludes it from testing above 1.5 MPa. A novel setup using ultrasonic transducers, with electronic …
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Data Rate Enhancement in Ultrasonic Data Telemetry Links
… of data rate in wireless data transfer through ultrasonic telemetry links. Referred to as INtervened-Timing, Enhanced-Rate Interval Modulation (INTERIM), the proposed technique is an isochronous pulse-based modulation technique, which embeds the telemetered symbol in the time interval between …
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Time and frequency domain modelling of the piezoelectric transducer
A new model for piezoelectric ultrasonic transducers is proposed. Using a systems engineering approach, the concept of feedback is used to explain secondary piezoelectric effects and to clearly describe electro-mechanical interaction. The model is derived from the fundamental piezoelectric …
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Real-time, Software-based Ultrasound Image Formation for Array Transducer Systems
… in medical ultrasound rely on multichannel ultrasonic transducers requiring expensive, dedicated hardware to perform beamforming. This dissertation explores the reduction of hardware requirements for multi-channel ultrasound image formation through the use of software-based …
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Development of Ultrasonic Devices for Microparticle and Cell Manipulation
… chemistry has driven recent development of ultrasonic manipulation technology. Compared to the other major technologies used for cell and particle manipulation, such as magnetic tweezing, optical tweezing and dielectrophoresis, ultrasonic manipulation has shown excellent capabilities and …
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