In this thesis, we consider three fundamental problems of transducers theory. The containment problem asks, given two transducers,whether the relation defined by the first is included into the relation defined by the second. The equivalence problem asks, given two transducers,whether they define the same relation. Finally, the sequential uniformisation problem,corresponding to the synthesis problem in the setting of transducers,asks, given a transducer, whether it is possible to deterministically pick an output correspondingto each input of its domain. These three decision problems are undecidable in general. As a first step, we consider different manners of recovering the decidability of the three problems considered.First, we characterise a family of classes of transducers, called controlled by effective languages, for which the containment and equivalence problems are decidable. Second, we add structural constraints to the problems considered: for instance, instead of only asking that two transducers define the same relation, we require that this relation is defined by both transducers in a similar way. This `similarity' is formalised through the notion of delay,used to measure the difference between the output production of two transducers. This allows us to introduce stronger decidable versions of our three decision problems, which we use to prove the decidability of the original problems in the setting of finite-valued transducers. In the second part, we study extensions of the automaton model,together with the adaptation of the sequential uniformisation problems to these new settings.Weighted automata are automata which,along each transition, output a weight in Z. Then, whereas a transducer preserves all the output mapped to a given input, weighted automata only preserve the maximal weight. In this setting, the sequential uniformisation problem turns into the determinisation problem: given a weighted automaton, is it possible to deterministically pick the maximal output mapped to each input? The decidability of this problem is open.The notion of delay allows us to devise a complete semi-algorithm deciding it. Finally, we consider two-way transducers, that are allowed to move back and forth over the input tape. These transducers enjoy good properties with respect to the sequential uniformisation problem: every transducer admits a sequential two-way uniformiser. We strengthen this result by showing that every transducer admits a reversible two-way uniformiser, i.e. a uniformiser that is both sequential and cosequential (backward sequential). / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Compact, autonomous computing systems with integrated transducers are imperative to deliver advances in healthcare, navigation, livestock monitoring, point of care diagnostics, remote sensing, internet-of-things applications, smart cities etc. Reflecting this need, there has been sustained growth in the market for transducers. Polymer based transducers, which meld highly desirable properties such as low cost, light weight, high manufacturability, biocompatibility and flexibility, are quite attractive. Doping polymers with magnetic materials results in the formation of magnetic composite polymers, enhancing the attractive traits of polymer transducers with magnetic properties. This dissertation is dedicated to the development of magnetic polymer transducers, which are suitable for energy harvesting and saline fluid transduction. The first-ever magnetic composite energy harvester capable of converting vibrations from the practically relevant low-frequency range into electrical energy was fabricated and tested. The harvester was realized by fabricating an array of PDMS-iron nanowire nanocomposite cilia on a planar coil array and exhibits a linear frequency response. This energy harvester design was further improved by increasing the doping concentration of the composite, adding a composite proof mass and improving the microfabricated coil. These changes manifest in an energy harvester that not only increases the power density by 4 orders of magnitude over the previous design but also possesses large operational bandwidth. The composite structure, comprising of the cilia and the proof mass has a frequency response comprised of two closely spaced resonant peaks facilitating the desirable broadband behavior at low frequency.A polymer-based magneto hydrodynamic pump prototype capable of actuating saline fluids was developed. The benefit of this pumping concept to operate without any moving parts is combined with simple and cheap fabrication methods and a magnetic composite material, enabling a high level of integration together with the advantages of mechanical flexibility. The pump electrodes are created by laser printing of graphene on polyimide, while the permanent magnet is molded from an NdFeB powder - polydimethylsiloxane (PDMS) composite. These materials were leveraged to fabricate an integrated, low profile magneto hydrodynamic pump, suitable for deployment in lab on chip systems.

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This thesis presents an introduction into surface acoustics wave (SAW) unidirectional transducer (UDT) technologies and identifies advantages and disadvantages of various approaches. A complete model of the three-phase unidirectional structure is presented for the purpose of design analysis. This model incorporates the effects of the electrodes and transducer pattern along with the equivalent circuit model of the transducer structure. The model, when included with the appropriate peripheral components for transducer phasing and matching, can be used to determine accurately the frequency response of a given transducer structure. Such a model is well suited for implementation on a digital computer. With this in mind, the necessary FORTRAN 77 software was developed and is presented which is an addition part of the SAW computer aided design (CAD) facilities at UCF-COE. An analysis example is given and the results are compared to published data.

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 transducer output for a given scaled voltage input has been developed. Several transducers have been designed using this model. Special attention has been given to the unique case of the two-dimensional radially Gaussian amplitude profile. Fabrication techniques for these transducers have been developed and are discussed. A microprocessor-based data acquisition system is described which will characterize the two-dimensional transducer profile as well as the propagation profile along one radial axis. Example tests of some of these transducers are presented. / M.S.

In ultrasonic processing, it has been a practice to measure intensity of ultrasonics as a product of plate current and voltage as indicated on ultra sonic generator. At low frequencies the standard equipment is available, such as the sound level meter, to measure the absolute intensity, but at higher frequencies the problem becomes complicated by the diffraction effects on account of the size of the measuring device. In this investigation an attempt has been made to construct a measuring device (called the probe) to measure intensity. A small barium titanate cylindrical element (1/16 inch in diameter and 1/16 inch length) was used as a detector-convertor of sonic pressures. The alternating voltages thus produced were indicated by a vacuum tube voltmeter. This element was cemented in a hypodermic needle in turn was held in a lucite rod (1/2 inch in diameter and five inches in length) which served as a holder. This arrangement was used to probe the sonic fields of cylindrical and bowl shaped transducers. / Ph. D.

In this dissertation, two nonlinear regressive models, the forward model and the inverse model, have been developed to determine the pose (position and orientation) of the scanning laser Doppler vibrometer (SLDV) with respect to a structural coordinate system. The parameters in the forward model include the pose and the ranges. The parameters in the inverse model include the pose only. The parameters of those models are obtained by using the least squares technique. A geometrical method is developed to get an estimation of the pose and the ranges. This estimation is used as an initial solution in the iterative procedure for determining the parameters in the nonlinear regressive models. The statistical inferences are made about the inverse model by the linear approximation. The nonlinearity of the inverse modal is measured in order to verify the validity of the linear approximation. Included along with the development of the models, are the implementation of the algorithm (geometrical method and inverse model), the assessment of the inverse model, the calibration of the scanner, and the accuracy evaluation of the algorithm. / Ph. D.

In materials evaluation applications requiring the interrogation 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 constructed by depositing a circularly symmetric metallic multiple electrode array on a 12. 7 mm diameter x-cut quartz disk. Each electrode is independently connected to an impedance network optimized to produce the Gaussian distribution with less than two percent maximum error. A computer aided electrode design and normalized three dimensional ultrasonic measurements of the far field distribution are presented. / Master of Science

The objective of this thesis is to develop an analysis approach for formulation of transduction or input/output representations for magnetostrictive actuators. This transduction model is developed through application of an electro-magneto-mechanical impedance modeling approach which combines both the mechanical dynamics and coupled behavior of the actuator device. Lumped and continuous mechanical impedance elements model the actuator dynamics and the constitutive relationships for Terfenol-D characterize the electro-magneto-mechanical interaction. Experimental analysis of a Terfenol-D actuator serves to verify the developed models and provides an indication of actuator non-linearity. The developed transduction model allows for various device behavior analysis including dissipative power consumption, force and stroke output, and efficiency as a transducer. An actuator design strategy based upon the dynamics of the actuator and a driven external system is presented and allows for analysis of various actuator behaviors in terms of device parameters. The Terfenol-D actuator as a collocated actuator/sensor is also made possible with the transduction model. / Master of Science

Health monitoring of aeronautic structures and human beings is becoming crucial because of the human safety issues. In this thesis integrated (IUTs) and flexible ultrasonic transducers (FUTs) have been developed using a sol-gel spray piezoelectric film fabrication technology. IUTs can be fabricated directly onto the structures with curved surfaces even on-site. FUTs were made using membrane substrates of thickness less than 75 mum. In-situ monitoring of AI airframe thickness was carried out and the thickness measurement accuracy was better than 36 mum and 41 mum for IUT and FUT, respectively. The thickness of the ice on top of the AI airframe was also measured. Two crucial piezoelectric constants d33 and d31 of the composite film were measured with laser interferometer and optical coherence tomography system, respectively. Pulse and breath of a human being were also monitored using flexible piezoelectric membrane sensors. In addition, bones in human body were observed using FUTs as well and their performance is comparable to that of commercial ultrasonic transducers.