Дисертації з теми "MEMS Piezoelectric Acoustic Transducers"
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Tabrizian, Roozbeh. "Temperature-compensated silicon-based bulk acoustic resonators." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52929.
Повний текст джерелаSenesi, Matteo. "Frequency steerable acoustic transducers." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44819.
Повний текст джерелаSharapov, V. M., K. V. Bazilo, and R. V. Trembovetskaya. "Electro-Acoustic System with Piezoelectric Sensor." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/41006.
Повний текст джерелаLarson, Gregg D. "The analysis and realization of a state switched acoustic transducer." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/16008.
Повний текст джерелаClark, Robert L. "Advanced sensing techniques for active structural acoustic control /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-05222007-091351/.
Повний текст джерелаJenne, Kirk E. "Acoustic cymbal transducers-design, hydrostatic pressure compensation, and acoustic performance." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FJenne.pdf.
Повний текст джерелаThesis advisor(s): Thomas R. Howarth, Dehua Huang. Includes bibliographical references (p. 67-69). Also available online.
Dhar, Romit. "Growth and optimization of piezoelectric single crystal transducers for energy harvesting from acoustic sources." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Spring2009/R_Dhar_031309.pdf.
Повний текст джерелаCortes, Correales Daniel H. "Elastic guided wave dispersion in layered piezoelectric plates application to ultrasound transducers and acoustic sensors /." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10206.
Повний текст джерелаTitle from document title page. Document formatted into pages; contains vi, 84 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 79-84).
Clark, Robert L. Jr. "Advanced sensing techniques for active structural acoustic control." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/37880.
Повний текст джерелаPh. D.
Naeli, Kianoush. "Optimization of piezoresistive cantilevers for static and dynamic sensing applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28247.
Повний текст джерелаCommittee Chair: Brand, Oliver; Committee Member: Adibi, Ali; Committee Member: Allen, Mark G.; Committee Member: Bottomley, Lawrence A.; Committee Member: Degertekin, F. Levent.
Nascimento, Valéria Monteiro do 1974. "Simulação do campo acústico de transdutores ultrassônicos de alta frequência do tipo array anular com e sem espaçamento entre anéis." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261168.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-22T22:55:05Z (GMT). No. of bitstreams: 1 Nascimento_ValeriaMonteirodo_D.pdf: 6068450 bytes, checksum: 537e820daa45af6d8d50ccee4ad135e5 (MD5) Previous issue date: 2013
Resumo: Para observar o efeito no campo acústico dos diversos parâmetros de configuração do projeto de um transdutor ultrassônico, foram simuladas várias configurações de transdutor de alta frequência (5 a 50 MHz), tipo array anular, com kerf e kerfless, de cerâmica PZT-5H e de filme de PVDF. Transdutores com configurações de três, quatro, cinco e seis anéis, em que os anéis possuíam a mesma largura foram simulados com elemento ativo de cerâmica. E transdutores com cinco, seis, sete, oito e dez anéis de mesma área, com separação física entre os elementos (kerf) e sem separação física entre os elementos (kerfless) foram simulados com elementos piezoelétricos de cerâmica PZT-5H e filme de PVDF. Também foram testados materiais de diferentes impedâncias acústicas nas camadas de retaguarda (epóxi, epóxi e Araldite, ferro, tungstênio, alumina e madeira), foram usadas diversas funções de excitação dos elementos piezoelétricos (Blackman, Wavelet, Gauss, Seno, Step) em frequências variadas, além de se acionar os diversos elementos anelares isoladamente, em grupos e com atraso temporal. O objetivo das simulações realizadas foi determinar a melhor configuração de um transdutor array anular, quanto ao número de anéis, espaçamento entre eles e necessidade ou não de separação física entre os elementos, levando-se em conta a complexidade de construção e as características do campo acústico gerado. Para isso, os parâmetros observados no campo acústico foram à amplitude do pico, a amplitude média de pressão, a profundidade do campo, a colimação do feixe principal e a presença de lóbulos laterais. Outros parâmetros observados foram à tensão e a carga nos elementos. Os resultados obtidos nas simulações dos transdutores arrays circulares, feitas com o programa PZFlex®, foram processados no Matlab® para visualização do campo acústico e extração de parâmetros. As funções de transferência do sinal de excitação e da resposta à estimulação foram calculadas com os dados obtidos. O transdutor kerfless foi simulado no PZFlex® e seus resultados processados no Matlab®, para comparar com os resultados do transdutor com kerf de mesma configuração. Os resultados das simulações mostraram que o campo acústico neste tipo de transdutor, array anular, tem a região de campo distante começando bem próximo à face do transdutor. A camada de retaguarda de epóxi e Araldite® apresentaram valores mais elevados de amplitude do campo acústico. A função de excitação foi Wavelet na frequência de 30 MHz devido às restrições da relação diâmetro / espessura da cerâmica PZT-5H. O transdutor kerfless apresentou um campo acústico com as mesmas características do transdutor com kerf, com a vantagem de sua construção ser mais simples
Abstract: In order to observe the effect of ultrasound transducers parameters configurations in an acoustic field, simulations were made in some different configuration of an annular array ultrasound transducer in high frequency (5 to 50 MHz), kerf and kerfless, with active element of PZT - 5H ceramic or PVDF. The transducers configurations simulated were three, four, five and six annulus, with the same width, and the active element was PZT-5H. And transducers with five, six, seven, eight and ten annulus, with the same area, with and without physical separation between the elements had been simulated with active element of PZT-5H ceramics or PVDF. The materials of backing layer (epoxy, epoxy and Araldite, iron, tungsten, alumina and wood dust) with different impedance were also be tested, and a variety of excited functions (Blackman, Wavelet, Gauss, Sine, Step), in different frequencies, and also with time delay in active elements. The objective of this simulation was to find out the better configuration of an annular array ultrasound transducer in high frequency, the number of annulus, spacing between them, the area, the transducer is kerf or kerfless, considering the build complexity and the characteristics of acoustic field. To do this, the peak amplitude, the depth and the average amplitude of the acoustic field was measured. The charge and the voltage in the elements were also observed. The results obtained in simulations in PZFlex® software were run in Matlab® to visualize the acoustic field and to extract parameter. The ultrasound kerfless transducer was simulated in PZFlex® and the data obtained runs in Matlab®, the results were compared with the results of a transducer with kerf in the same configuration. The simulation results showed that the acoustic field of this kind of transducer has Fraunhofer zone began near the transducer's face. The backing layer with epoxy and Araldite® showed high amplitude of acoustic field. The frequency 30 MHz was choice due to diameter/thickness relations. The excitation function was wavelet, as this present high values response in acoustic field. Kerfless transducer showed acoustic field characteristics the same as the kerf transducers, with the advantage of a simple construction
Doutorado
Engenharia Biomedica
Doutora em Engenharia Elétrica
Tuloup, Corentin. "Process and structural health monitoring of Polymer-Matrix Composites (PMC) using embedded piezoelectric transducers." Thesis, Compiègne, 2020. https://bibliotheque.utc.fr/Default/doc/SYRACUSE/2020COMP2593.
Повний текст джерелаThis innovative work studies the interest of integrating piezoelectric transducers (ceramic and/or polymer-based) within Polymer- Matrix Composite materials (PMC) to perform real-time and in-situ monitoring of their manufacturing process (Process Monitoring PM) as well as their lifespan (Structural Health Monitoring SHM). To do this, the piezoelectric transducers were integrated into the heart of the fibrous stacks using an innovative methodology developed within the "Materials and Surfaces" research team at the Roberval laboratory. The Liquid Resin Infusion (LRI) manufacturing system used (PM campaign), as well as the resulting samples tested mechanically (SHM campaign), were multi-instrumented using several Non-Destructive Testing devices (NDT: Acoustic Emission (AE), Infrared Thermography (IRT), Digital Image Correlation (DIC), etc.) in order to establish multi-physical couplings between the signals of external NDT techniques and the internal signature (electrical capacitance) coming from the transducers integrated into the heart of the material. In PM, the piezoceramic (PZT) transducers were found to be sensitive to the various key steps of the LRI process (flow front passing, impregnation, end of injection, chemo-physical transitions during curing and associated consolidation rates) achieved at different hardener rates, and able to detect manufacturing defects. These results showed great potential, worthy of future use on an industrial scale. In SHM, after verification of the non-intrusiveness of the ceramic and polymer-based transducers integrated into the heart of the mechanical test specimens, the polymer transducers allowed a real-time evaluation of the triaxial strain state and the rigidity loss experienced by the host PMC during its mechanical loading. However, despite a Non-Working Threshold (NWT) linked to the brittleness of their constitutive material, the piezoceramic transducers have shown a high sensitivity to the detection and monitoring of damage in real-time when they are positioned intelligently with respect to the mechanical stress. These thesis works ended with a first attempt aimed at transposing the knowledge acquired on PM and SHM of in-situ piezoelectric transducers from a 2D “laboratory” scale to a 3D structural one closer to industrial realities. The multi-instrumented manufacturing of an “Omega” stiffener PMC structure integrating 14 piezoelectric transducers (PZT and P(VDF-TrFE) copolymer) and reinforced through-the-thickness by a carbon tuft thread allowed confirming the previously evidenced PM abilities of the PZT, and showed a difference between how the electrical capacitance signals of PZT and copolymers react to the whole manufacturing process
Haghighattalab, Armin. "Finite Element Modeling of Spiral Frequency Steerable Acoustic Transducers (FSATs) for guided waves based Structural Health Monitoring of plate-like structures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
Знайти повний текст джерелаBakhtiari, Nejad Marjan. "Dynamics of Multi-functional Acoustic Holograms in Contactless Ultrasonic Energy Transfer Systems." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/102414.
Повний текст джерелаDoctor of Philosophy
This dissertation presents several techniques to enhance the wireless transfer of ultrasonic energy in which the sound wave is generated by an acoustic source or transmitter, transferred through an acoustic medium such as water or human tissue to a sensor or receiver. The receiver transducer then converts the vibrational energy into electricity and delivers to an electrical load in which the electrical power output from the system can be determined. The first enhancement technique presented in this dissertation is using a pre-designed and simple structured plate called an acoustic hologram in conjunction with a transmitter transducer to arbitrarily pattern and shape ultrasound fields at a particular distance from the hologram mounted on the transmitter. The desired wavefront such as single or multi-focal pressure fields or an arbitrary image such as a VT image pattern can simply be encoded in the thickness profile of this hologram plate by removing some of the hologram material based on the desired shape. When the sound wave from the transmitter passes this structured plate, it is locally delayed in proportion to the hologram thickness due to the different speed of sound in the hologram material compared to water. In this dissertation, various hologram types are designed numerically to implement in the ultrasonic power transfer (UPT) systems for powering receivers located at the predetermined focal points more significantly and finally, their functionality and performances are verified in several experiments. Current UPT systems suffer from significant acoustic losses through the transmission from a transmitter to an acoustic medium and then to a receiver due to the different acoustic impedance (defined as the product of density and sound speed) between the medium and transducers material, which reflects most of the incident pressure wave at the boundary layers. The second enhancement technology addressed in this dissertation is using intermediate materials, called acoustic impedance matching layers, bonded to the front side of the transmitter and receiver face to alleviate the acoustic impedance mismatch. Experiments are performed to identify the input acoustic pressure from a transmitter to a receiver. Using a two-layer matching structure, significant enhancements are observed in terms of the receiver's electrical power output. A design platform is also developed that can facilitate the construction of high-fidelity acoustically matched transducers, that is, the material layers' selection and determination of their thicknesses. Furthermore, this dissertation presents a numerical analysis for the dynamical motions of a microbubble exposed to a high-intensity focused ultrasound (HIFU) field, which entails the problem of several biomedical ultrasound applications such as microbubble-mediated ultrasound therapy or targeted drug delivery. Finally, an enhancement technique involving the design and use of acoustic holograms in microfluidic channels is addressed which opens the door of acoustic patterning in particle and cell sorting for medical ultrasound systems.
Silva, Emilio Carlos Nelli. "Modelagem vibracional de transdutores de ultra-som piezoelétricos pelo método de elementos finitos." Universidade de São Paulo, 1993. http://www.teses.usp.br/teses/disponiveis/3/3132/tde-11072017-091843/.
Повний текст джерелаThe theoretical basis of piezoelectric finite element method (FEM), and its application in piezoelectric ultrasonic transducer modelling is presented. Among these applications we have the calculation of resonance and antiresonance frequencies, vibration modes, piezoelectric coupling coefficient, admittance curve and transient analysis of piezoelectric structure excited by a short pulse. By means of piezoelectric FEM the influence of variation of piezoelectric constant with radius is analysed. It is discussed three kind of functions (linear, cosinoidal and Gaussian). This technique is called apodization. The acoustic filed generated by the transducer operating in continuous wave (CW) was calculated by using FEM applied to acoustic, considering the fluid-structure coupling. The study of wave propagation in liquids is started by using FEM, analyzing the waves generated by a plane piston in contact with the fluid, excited by a short pulse. For each case discussed above, all boundary conditions and hypothesis assumed in the construction of finite element models are discussed. Although the models considered are circular transducers, the concepts acquired can be expanded to other geometries. The vibrational modes were visualized by means of a laser interferometry technique (ESPI), and the admittance curves were measured by using an impedometer. These results were compared with the FEM results, and the models precision was discussed.
Sorenson, Logan D. "Design and analysis of microelectromechanical resonators with ultra-low dissipation." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52910.
Повний текст джерелаLi, Yifeng. "Développement d’outils de simulation numérique pour l’élastodynamique non linéaire : application à l’imagerie acoustique de défauts à l’aide de transducteur à cavité chaotique." Thesis, Ecole centrale de Lille, 2009. http://www.theses.fr/2009ECLI0014/document.
Повний текст джерелаIn this thesis we propose the development of an innovative micro-damage imaging system based on a combination of Nonlinear Elastic Wave Spectroscopy techniques and “chaotic cavity transducer” concept. It consists of a combination of a PZT ceramic glued to a cavity of chaotic shape with the time reversal principle. The feasibility and capabilities of these new ideas is explored by numerical simulations, and optimal operational parameters for experimental implementation are suggested based on the modelling support. A large part of the research work conducted in this thesis is concentrated on the development of numerical simulation tools to help the improvement of such nonlinear imaging methods. A nodal Discontinuous Galerkin Finite Element Method (DG-FEM) scheme is extended to nonlinear elasto-dynamic including source terms. A Perfectly Matched Layer absorbing boundary condition well adapted to the DG-FEM scheme, called Nearly Perfectly Matched Layer (NPML), is also developed. In the case of orthotropic material as stability problems appear, a mixture of NPML and sponge layer, with a controllable ratio of these two kinds of absorbing layers, is introduced. The experimental validation of “chaotic cavity transducer” to focalize in reverberant and non-reverberant solid media with only one source is made. Classical time reversal, inverse filter and 1 Bit time reversal process are discussed and compared. The experimental demonstration of the use of a “chaotic cavity transducer”, in combination with the pulse inversion and 1-bit methods, to obtain an image of localized nonlinearity is made. This opens the possibility for high resolution imaging of nonlinear defects
Du, Sijun. "Energy-efficient interfaces for vibration energy harvesting." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270359.
Повний текст джерелаChou, Derrick Ren-yu. "Piezoelectric Micromachined Ultrasound Transducers for Medical Imaging." Diss., 2011. http://hdl.handle.net/10161/4978.
Повний текст джерелаPiezoelectric micromachined ultrasound transducer (pMUT) two-dimensional (2D) arrays have been proposed as an alternative to conventional bulk-PZT thickness-mode transducers for high frequency, forward-looking, catheter-based ultrasound imaging of the cardiovascular system. The appeal of pMUTs is based on several key advantages over conventional transducer technologies, including high operational frequencies, small element size, and low cost due to their microelectromechanical system (MEMS) silicon-based fabrication. While previous studies have demonstrated acoustic performance characteristics suitable for ultrasound image formation, pulse-echo B-mode imaging of tissue and tissue-like phantoms using 2D pMUT arrays small enough for forward-looking catheter-based applications have been demonstrated only at Duke University by Dausch et al.
Having demonstrated the suitability of 2D pMUT arrays for tissue imaging, an important step is to demonstrate effective design control. The frequency of operation is a fundamental component of transducer design. Previous modeling efforts for pMUT vibration have used classical/Kirchoff thin plate theory (CPT) or Mindlin thick plate theory, however pMUTs with geometric dimensions similar to those explored here, have not been modeled with experimental comparison to physical devices.
It is hypothesized that the frequency of vibration of pMUTs can be predictively modeled based on experimental data from various pMUT configurations. Experimental frequency results were acquired and used to develop an empirical model based on a modified Mindlin thick plate theory. This dissertation presents the development of the frequency design theory culminating in a set of predictive design equations for the frequency of vibration of 2D pMUT arrays aimed at improving their use in high-frequency, forward-looking, catheter-based ultrasound imaging applications.
Dissertation
"Thin Film Transistor Control Circuitry for MEMS Acoustic Transducers." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15984.
Повний текст джерелаDissertation/Thesis
M.S. Electrical Engineering 2012
Dangi, Ajay. "Piezoelectric Micromachined Ultrasound Transducers : From Design to Applications." Thesis, 2016. http://etd.iisc.ernet.in/2005/3737.
Повний текст джерелаChen, San-Pen, and 陳三本. "Analysis of the Acoustic Field of Phase Array Piezoelectric Transducers." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/23383056498542116481.
Повний текст джерела國立交通大學
機械工程系
88
This thesis presents an investigation of the acoustic field induced by linear array piezoelectric transducers using transient finite element analysis. Ultrasonic inspection of defects near roots of turbine blades was numerically studied by assuming that the ultrasound were transmitted simultaneously and received individually by the phase array transducers. The influences of various inspection parameters are also discussed and used as a reference for design of an array transducer and planning of an inspection. Conventional B-scan can only provide time-of-flight information of the reflected/diffracted signals from internal discontinuities in specimens. The spatial relations among those discontinuities can not be directly interpreted from B-scan images. The interpretation results in a need of well-experienced inspectors. However, the echoes reflected from complex dovetails of the blades usually have greater amplitudes than those diffracted signals from the crack tips. The inspectors were often confused with signals of geometric reflection. This research applied an angular-spectrum-based synthetic aperture imaging technique to reconstruct images of the defects and geometric boundaries of the dovetails. The present study provides a promising method to improve the capability of ultrasonic inspection for the defects and their orientations in turbine blade dovetails.
Ozevin, Didem. "Capacitive MEMS transducers for acoustic emission testing of materials and structures /." Diss., 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3188504.
Повний текст джерелаKo, Chung-Ting, and 柯忠廷. "Design and Characterization of Acoustic Matching Layers for Piezoelectric Ultrasonic Transducers." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/69843913545092115562.
Повний текст джерела國立臺灣大學
材料科學與工程學研究所
95
A novel active matching layer made of lead zirconate titanate (PZT) plate has been developed as an “impedance matching layer” for high-intensity focused ultrasound (HIFU) applications. The PZT matching layer redistributes the frequency spectrum of an original broadband ultrasonic probe, and acts as a frequency filter without reducing the wave amplitude. These behaviors are contributed to electromechanical and mechanical properties at the PZT matching layer, and are investigated in this study by a series of experiments on PZT matching plates with different electromechanical properties and polarization and surface charge conditions. Traditional passive matching layers, such as ceramic-polymer composites, are also studied. Three different ceramic-epoxy composite are developed and their impedance properties studied. Among the three, the zirconium oxide-epoxy composite exhibits a tolerable attenuation level and an optimum impedance value. It is then integrated on to a home-made HIFU transducer to test its effectiveness. The beam profile of the matched HIFU transducer is characterized by a hydrophone, and an in-vivo experiment is carried out to gauge its performance. In this study, structure materials such as porous ceramics and porous ceramic-epoxy composites are also proposed as candidate materials for impedance matching for water and human tissues due to their low attenuations and impedances.
Ko, Chung-Ting. "Design and Characterization of Acoustic Matching Layers for Piezoelectric Ultrasonic Transducers." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2307200715501100.
Повний текст джерелаKwan, Chi-Hang. "Acoustic Streaming Pump for Microfluidic Applications." Thesis, 2011. http://hdl.handle.net/1807/29585.
Повний текст джерелаGross, Jonah M. "Development of acoustic transducers for use in the parametric pumping of spin waves." Thesis, 2013. http://hdl.handle.net/1957/37905.
Повний текст джерелаGraduation date: 2013
Chen, Guan Lin, and 陳冠霖. "Piezoelectric Polymer Micromachined Acoustic Transducers and Their Applications to Rapid Screening of Drug Residue in Foods." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ws4rzr.
Повний текст джерела國立清華大學
動力機械工程學系
105
In recent years, people pay more attention to food safety. Traditional detection technology is expensive, complicated and time-consuming, so that it is impossible to do the real-time and on-site detection for the irregular additives in food samples. This study further investigate and improve the droplet-based piezoelectric polymer deposition. In addition, the deposited piezoelectric polymer deivces are integrated on a biochip for rapid detection of drug residue in foods. First, we changed the wire width of electrode to design and choose different area ratio of P(VDF-TrFE). In the electrodeposition process, we discussed the optimization parameter, including electrodeposition time, volume of droplet, supplying voltage, and the pre-treatment of relative humidity. In the examination of acoustic property, the maximum output power was 86.31 μW (10 kHz). Compare of past study, the signal strengthen was enhanced by 62 % (10 kHz), the output power was enhanced by 37 %, the efficiency was enhanced by 220 %. In the property of acoustic transceiver, the signal coefficient of variation was reduced to 0.38 % from 17.79 % by the pre-tunable treatment. The developed acoustic transceiver was applied to the detection of animal drugs residue in meat samples after the optimization process and pre-tunable treatment. The detection frequency was 10 kHz, and the target drugs were ractopamine、benzylpenicillin、doxycycline. The response, including fluid disturbance and steady tim) was 80 sec, and the SNR of steady signal was up to 29.03 dB. Linear range was 0 ~ 100 ppb, and sensitivity was up to 2.4 mV/ppb and the detection limit was 2.06 ppb (3 dB). Finally, the acoustic transceiver was integrated with MIP films on microfluidic chip, and 20 ppb pork sample was applied to our chip for drugs residue detection. The detection result was up to 23.7±1.15 ppb. The detection time was 4 min, including fluid operation and dynamic signal measurement. In this study, the developed high-sensitivity piezoelectric acoustic transceiver presented the advantages of low cost, simple steps and high integration. Besides the drugs residue detection, it also was applied as others biosensor in the future.
Weber, Jan [Verfasser]. "Investigation of the physical properties, performance and application of MEMS sensors based on bulk acoustic waves excited in piezoelectric thin film devices / Jan Weber." 2007. http://d-nb.info/985347880/34.
Повний текст джерела(10285355), Matthew J. Storey. "Lithium Niobate Acoustoelectric Platforms for Integrated Non-Reciprocal RF MEMS Devices." Thesis, 2021.
Знайти повний текст джерелаMalhi, Charanjeet Kaur. "Studies on the Design of Novel MEMS Microphones." Thesis, 2014. http://hdl.handle.net/2005/3125.
Повний текст джерелаΒογιατζή, Ελένη. "Αυτόματος διαχωρισμός ακουστικών σημάτων που διαδίδονται στο ανθρώπινο σώμα και λαμβάνονται από πιεζοκρυστάλλους κατά την διάρκεια ύπνου". Thesis, 2013. http://hdl.handle.net/10889/6418.
Повний текст джерелаIn this particular thesis, analysis and application of separation of acoustic signals is carried out. These signals have been taken from the human body in a sleeping state. They are obtained by means of a piezocrystallic device and their separation is achieved by the method of Independent Component Analysis (ICA). The main purpose of all this is to use this methodology in order to diagnose the Obstructive Sleep Apnea (OSA). The first chapter presents the method of ICA and the mathematical model that describes it as well as all the pre-processing steps. Then it analyses, in detail, the algorithm FastICA, which is used in the experimental part of this thesis and its properties. The second chapter studies the disease of obstructive sleep apnea (OSA), its factors and its pathology and the major diagnostic symptom: snoring. Then, it discusses the diagnosis and the best known ways of treating this disease and eventually the method of Snoring Detection. The third chapter is an introduction to piezoelectricity and a study of the piezoelectric effect and its mathematical description. This is followed by a reference to the types of piezoelectric sensors which are used to obtain the signals used in this paper. In chapter five we have listed some examplesapplications of the FastICA algorithm with random signals, which are designed to test the performance. Section six is where the experimental procedure takes place. The signals derived from the human body are separated by the algorithm FastICA and the implementation is done in Matlab. In addition, some conclusions regarding the performance of the algorithm. At the end of this paper, all the MATLAB codes used for the completion of the experimental part of the chapters five and six are listed in an Annex.
Fangueiro, Gil Mauro Cruz. "Desenvolvimento de sensor acústico para medição de corrente marítima." Master's thesis, 2019. http://hdl.handle.net/1822/69796.
Повний текст джерелаO objetivo deste trabalho é desenvolver um sensor acústico capaz de medir correntes marítimas. Este projeto surge da necessidade de recolher alguns dados de interesse marítimo com o objetivo de criar modelos de funcionamento dos ecossistemas. Neste projeto pretende-se colocar vários sensores georreferenciados, a diferentes profundidades, a fazer medições e a armazenar os dados respetivos. Este sensor será responsável por medir a velocidade da água que flui num determinado nó do sistema. Este deverá ser capaz de medir a intensidade da corrente e a direção independentemente da sua posição no espaço, necessitando por isso de um magnetómetro (bússola digital) para utilizar o norte geográfico como referência. O sensor de corrente marítima que é apresentado utiliza transdutores piezoelétricos ultrassónicos pretendendo com isso tornar o sistema mais fiável e com maior robustez devido à ausência de partes móveis. A propriedade dos ultrassons explorada neste trabalho para obtenção da velocidade da corrente é o tempo de voo. O tempo de voo é o tempo que um determinado sinal demora a propagar-se num determinado meio entre dois pontos. No desenvolvimento do sensor será estudado o formato da estrutura, a posição e a orientação dos transdutores, de forma a melhorar a qualidade das medições em diferentes condições. Tal deverá ter em conta a robustez, dimensões razoáveis e evitar fenómenos de turbulência no volume de água a ser medido. O processamento dos sinais enviados e recebidos pelos transdutores será executado por um circuito integrado capaz de executar rotinas de medição de tempo de voo e de temperatura. Esse circuito integrado irá comunicar com um microcontrolador que irá interpretar os tempos de voo e converter na velocidade do fluido. Para além da comunicação com este circuito integrado, o microcontrolador, terá que comunicar com um relógio de tempo real, para obtenção de uma referência temporal, com um cartão de memória, para armazenamento de dados num ficheiro e com um magnetómetro, para obter uma referência de orientação ao norte geográfico já que o sensor não estará fixo. Com vários sensores destes é possível entender fenómenos de transporte à escala costeira, graças aos dados que é possível obter com um instrumento de medição desta escala.
The objective of this work is to develop an acoustic sensor capable of measuring sea currents. This project arises from the need to collect some data of maritime interest with the aim of creating models for the functioning of ecosystems. In this project, we intend to place several georeferenced sensors at different depths to make measurements and store the respective data. This sensor will be responsible for measuring the velocity of the water flowing in a particular node of the system. It should be able to measure the intensity of the current and direction independently of its position in space, thus necessitating a magnetometer (digital compass) to establish geographic north as a reference. The marine current sensor which is shown utilizes ultrasonic piezoelectric transducers in order to make the system more reliable and more robust due to the absence of moving parts. The property of the ultrasound explored in this work to obtain the velocity of the current is the flight time. Flight time is the time that a given signal takes to propagate in a certain medium between two points. In the development of the sensor will be studied the structure format, the position and the orientation of the transducers, in order to improve the quality of the measurements under different conditions. This should take into account the robustness, reasonable dimensions and avoid phenomena of turbulence in the volume of water to be measured. The processing of the signals sent and received by the transducers will be performed by an integrated circuit capable of performing flight time and temperature measurement routines. This integrated circuit will communicate with a microcontroller that will interpret flight times and convert to fluid velocity. In addition to communicating with this integrated circuit, the microcontroller must communicate with a real-time clock, to obtain a time reference, with a memory card, to store data in a file and with a magnetometer, to obtain a reference geographic north since the sensor will not be static. With several sensors of these it is possible to understand transport phenomena to the scale of the coast, thanks to the data that can be obtained with a measurement instrument of this scale.