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Laminated Tubular-channel Ferroelectret Systems from Low-density Polyethylene Films and from Fluoroethylene-propylene Copolymer Films - A Comparison

Altafim, Ruy Alberto Pisani; Rychkov, Dmitry; Wirges, Werner; Gerhard, Reimund; Basso, Heitor Cury; Altafim, Ruy Alberto Corrêa; Melzer, Martin
Fonte: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC; PISCATAWAY Publicador: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC; PISCATAWAY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.95%
A template-based lamination technique for the manufacture of ferroelectrets from uniform electret films was recently reported. In the present work, this technique is used to prepare similar ferroelectret structures from low-density polyethylene (LDPE) films and from fluoro-ethylene-propylene (FEP) copolymer films. A comparative analysis of the pressure-, temperature-, and frequency-dependent piezoelectric properties has been performed on the two ferroelectret systems. It is observed that the FEP ferroelectrets exhibit better piezoelectric responses and are thermally more stable. The difference between the piezoelectric d(33) coefficients of the two ferroelectret systems is partially explained here by their different elastic moduli. The anti-resonance peaks of both structures have been investigated by means of dielectric resonance spectroscopy and electroacoustic sound-pressure measurements. A difference of more than 10 kHz is observed between the anti-resonance frequencies of the two ferroelectret systems.; CAPES; CAPES; DAAD [PROBRAL D/08/11608]; DAAD; European Union; European Union

O uso do GPS como instrumento de controle de deslocamentos dinâmicos de obras civis - aplicação na área de transportes; The use of GPS as control instrument of dynamic displacements of civil structures

Larocca, Ana Paula Camargo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/06/2004 PT
Relevância na Pesquisa
25.95%
Este trabalho apresenta o desenvolvimento de metodologia para avaliar a utilização do Sistema de Posicionamento Global (GPS) como ferramenta de pesquisa no estudo do comportamento dinâmico de obras viárias. Para ser caracterizado como um instrumento de medição, foi estudada a potencialidade de um método, que se fundamenta numa forma específica de coleta e processamento de dados GPS; análise dos resíduos resultantes do processamento da dupla diferença de fase e aplicação de análise espectral para filtragem de informações indesejáveis (multicaminhamento dos sinais GPS). A coleta envolve um oscilador eletro-mecânico, especialmente projetado, que permite calibrar as medidas de amplitude e freqüência das oscilações mensuráveis pela obra sob teste. Inúmeros experimentos foram realizados em ambientes de reflexões e difrações variáveis e com diversos tipos de receptores e antenas GPS. Alguns ensaios foram realizados utilizando, simultaneamente, equipamentos como transdutores de deslocamento, acelerômetros e estações totais. Comparando os resultados obtidos, mesmo com valores prescritos em normas e códigos, afirma-se que o GPS, sob o método de coleta de dados testado, é um instrumento confiável para detecção e caracterização do comportamento dinâmico de estruturas...

Projeto de transdutor de corrente elétrica para alta tensão com nova abordagem de detecção magnetostritiva e sensoriamento óptico, utilizando Terfenol-D e grade de Bragg em fibra óptica; High voltage electric current transducer project, with innovative approach for magnetostrictive modulation and optical sensing using Terfenol-D and fiber Bragg gratings

Alcides Oliveira Cremonezi
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/08/2011 PT
Relevância na Pesquisa
26.18%
Os sensores a fibra óptica são imunes à interferência eletromagnética (EMI), eles são normalmente encontrados em ambientes eletricamente ruidosos, especialmente em linhas de transmissão de alta voltagem. Essa é a característica principal que faz desse tipo de sensores ideais para empresas de Energia Elétrica. Esse trabalho apresenta uma nova abordagem, de precisão moderada, robusta e de baixo custo, para a fabricação de um transdutor de corrente elétrica para alta tensão, com detecção magnetostritiva utilizando material inteligente, Terfenol-D, e sensoriamento óptico através de grade de Bragg em fibra óptica (FBG). O núcleo magnético foi desenvolvido em formato toroidal e construído utilizando usinagem através de eletro-erosão, o que resultou em uma peça única com projeto mecânico robusto. Aplicando compressão mecânica ao sensor toroidal e fazendo sua resposta ficar muito próxima a uma função quadrática, foi possível calcular o valor RMS da corrente diretamente do sinal de saída do sensor, e com isso, eliminar qualquer polarização magnética DC utilizada em técnicas anteriores reportadas na literatura. Foi utilizada com sucesso, uma nova técnica de circuito eletrônico de interrogação que permite a medida de sinais AC e mantém o ponto de operação DC da FBG. Resultados experimentais medidos com o transdutor óptico desenvolvido mostraram que entre correntes de aproximadamente 200 a 900A o erro observado foi de apenas 1...

Desenvolvimento de um protótipo para a simulação do sistema cardíaco humano

Lemos, Diogo Gonçalves
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2013 POR
Relevância na Pesquisa
16.36%
Dissertação de mestrado integrado em Engenharia Mecânica; O sistema cardiovascular é um dos sistemas mais importantes do corpo humano e tem sido alvo de vários estudos biomédicos. A simulação de diferentes sistemas fisiológicos pode ser muito útil quando utilizada como ferramenta pedagógica, pois permite uma melhor observação e compreensão dos papéis desempenhados por cada mecanismo em vários processos. O desenvolvimento de um simulador do sistema cardiovascular possibilita reinterpretar todo o sistema fisiológico, com a vantagem de se usar os mesmos transdutores e sensores que, normalmente, são utilizados para monitorizar vários parâmetros hemodinâmicos, durante o diagnóstico e tratamento de doenças cardiovasculares. A presente dissertação tem como objetivo o desenvolvimento de um protótipo capaz de simular o sistema cardiovascular humano, também denominado como duplicador de pulsos, e de reproduzir os diversos parâmetros fisiológicos envolvidos no processo. Este trabalho divide-se em duas partes. Inicialmente, descreve-se a simulação do sistema cardiovascular realizada com recurso ao software Automation Studio™, geralmente utilizado em projetos de circuitos hidráulicos. A segunda parte refere-se ao projeto mecânico do protótipo do simulador cardiovascular...

Design and Analysis of MEMS Based PVDF Ultrasonic Transducers for Vascular Imaging

Chandrana, Chaitanya; Talman, James; Pan, Tao; Roy, Shuvo; Fleischman, Aaron
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 21/09/2010 EN
Relevância na Pesquisa
36.25%
Polyvinilidene fluoride (PVDF) single-element transducers for high-frequency (>30 MHz) ultrasound imaging applications have been developed using MEMS (Micro-electro-Mechanical Systems) compatible techniques. Performance of these transducers has been investigated by analyzing the sources and effects of on-chip parasitic capacitances on the insertion-loss of the transducers. Modeling and experimental studies showed that on-chip parasitic capacitances degraded the performance of the transducers and an improved method of fabrication was suggested and new devices were built. New devices developed with minimal parasitic effects were shown to improve the performance significantly. A 1-mm aperture PVDF device developed with minimal parasitic effects has resulted in a reduction of insertion loss of 21 dB compared with devices fabricated using a previous method.

Thermal-Mechanical Noise Based CMUT Characterization and Sensing

Gurun, Gokce; Hochman, Michael; Hasler, Paul; Degertekin, F. Levent
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/2012 EN
Relevância na Pesquisa
26.11%
When capacitive micromachined ultrasonic transducers (CMUTs) are monolithically integrated with custom-designed low-noise electronics, the output noise of the system can be dominated by the CMUT thermal-mechanical noise both in air and in immersion even for devices with low capacitance. Since the thermal-mechanical noise can be related to the electrical admittance of the CMUTs, this provides an effective means of device characterization. This approach yields a novel method to test the functionality and uniformity of CMUT arrays and the integrated electronics where a direct connection to CMUT array element terminals is not available. These measurements can be performed in air at the wafer level, suitable for batch manufacturing and testing. We demonstrate this method on the elements of an 800-μm diameter CMUT-on-CMOS array designed for intravascular imaging in the 10-20 MHz range. Noise measurements in air show the expected resonance behavior and spring softening effects. Noise measurements in immersion for the same array provide useful information on both the acoustic cross talk and radiation properties of the CMUT array elements. The good agreement between a CMUT model based on finite difference and boundary element method and the noise measurements validates the model and indicates that the output noise is indeed dominated by thermal-mechanical noise. The measurement method can be exploited to implement CMUT based passive sensors to measure immersion medium properties...

Multiple Indices of the ‘Bounce’ Phenomenon Obtained from the Same Human Ears

Drexl, M.; Überfuhr, M.; Weddell, T. D.; Lukashkin, A. N.; Wiegrebe, L.; Krause, E.; Gürkov, R.
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
35.95%
Loud low-frequency sounds can induce temporary oscillatory changes in cochlear sensitivity, which have been termed the ‘bounce’ phenomenon. The origin of these sensitivity changes has been attributed to slow fluctuations in cochlear homeostasis, causing changes in the operating points of the outer hair cell mechano-electrical and electro-mechanical transducers. Here, we acquired three objective and subjective measures resulting in a comprehensive dataset of the bounce phenomenon in each of 22 normal-hearing human subjects. We analysed the level and phase of cubic and quadratic distortion product otoacoustic emissions and the auditory thresholds before and after presentation of a low-frequency stimulus (30 Hz sine wave, 120 dB SPL, 90 s) as a function of time. In addition, the perceived loudness of temporary, tinnitus-like sensations occurring in all subjects after cessation of the low-frequency stimulus was tracked over time. The majority of the subjects (70 %) showed a significant, biphasic change of quadratic, but not cubic, distortion product otoacoustic emissions of about 3–4 dB. Eighty-six percent of the tested subjects showed significant alterations of hearing thresholds after low-frequency stimulation. Four different types of threshold changes were observed...

MEMS Microphone Array Sensor for Air-Coupled Impact-Echo

Groschup, Robin; Grosse, Christian U.
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 25/06/2015 EN
Relevância na Pesquisa
25.95%
Impact-Echo (IE) is a nondestructive testing technique for plate like concrete structures. We propose a new sensor concept for air-coupled IE measurements. By using an array of MEMS (micro-electro-mechanical system) microphones, instead of a single receiver, several operational advantages compared to conventional sensing strategies in IE are achieved. The MEMS microphone array sensor is cost effective, less sensitive to undesired effects like acoustic noise and has an optimized sensitivity for signals that need to be extracted for IE data interpretation. The proposed sensing strategy is justified with findings from numerical simulations, showing that the IE resonance in plate like structures causes coherent surface displacements on the specimen under test in an area around the impact location. Therefore, by placing several MEMS microphones on a sensor array board, the IE resonance is easier to be identified in the recorded spectra than with single point microphones or contact type transducers. A comparative measurement between the array sensor, a conventional accelerometer and a measurement microphone clearly shows the suitability of MEMS type microphones and the advantages of using these microphones in an array arrangement for IE. The MEMS microphone array will make air-coupled IE measurements faster and more reliable.

2.141 Modeling and Simulation of Dynamic Systems, Fall 2002; Modeling and Simulation of Dynamic Systems

Hogan, Neville John
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
EN-US
Relevância na Pesquisa
66.43%
Mathematical modeling of complex engineering systems at a level of detail compatible with the design and implementation of modern control systems. Wave-like and diffusive energy transmission systems. Multiport energy storing fields and dissipative fields; consequences of symmetry and asymmetry. Nonlinear mechanics and canonical transformation theory. Examples will include mechanisms, electromechanical transducers, electronic systems, fluid systems, thermal systems, compressible flow processes, chemical processes. Description from course home page: This course deals with modeling multi-domain engineering systems at a level of detail suitable for design and control system implementation. Topics covered include network representation, state-space models; multi-port energy storage and dissipation, Legendre transforms, nonlinear mechanics, transformation theory, Lagrangian and Hamiltonian forms and control-relevant properties. Application examples may include electro-mechanical transducers, mechanisms, electronics, fluid and thermal systems, compressible flow, chemical processes, diffusion, and wave transmission.

The application of Tikhonov regularised inverse filtering to digital communication through multi-channel acoustic systems.

Dumuid, Pierre Marc
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
16.23%
Communication between underwater vessels such as submarines is difficult to achieve over long distances using radio waves because of their high rate of absorption by water. Using underwater acoustic wave propagation for digital communication has the potential to overcome this limitation. In the last 30 years, there have been numerous papers published on the design of communication systems for shallow underwater acoustic environments. Shallow underwater acoustic environments have been described as extremely difficult media in which to achieve high data rates. The major performance limitations arise from losses due to geometrical spreading and absorption, ambient noise, Doppler spread and reverberation from surface and seafloor reflections (multi-path), with the latter being the primary limitation. The reverberation from multi-path in particular has been found to be very problematic when using the general communication systems that have been developed for radio wave communication systems. In the early 1990s, the principal means of combating multi-path in the shallow underwater environment was to use non-coherent modulation techniques. Coherent of obtaining a phase-lock and also that the environment was subject to fading. Designs have since been presented that addressed both of these problems by using a complex receiver design that involved a joint update of the phase-lock loop and the taps of the decision feedback filter (DFE). In recent years a technique known as time-reversal has been investigated for use in underwater acoustic communication systems. A major benefit of using the time-reversal filter in underwater acoustic communication systems is that it can provide a fast and simple method to provide a receiver design of low complexity. A technique that can be related to time-reversal and possibly used in underwater acoustics is Tikhonov regularised inverse filtering. The Tikhonov regularised inverse filter is a fast method of obtaining a stable inverse filter design by calculating the filter in the frequency domain using the fast Fourier transform...

Investigating the lateral mobility of outer hair cell plasma membrane constituents by fluorescence recovery after photobleaching

Organ, Louise E.
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
36.21%
Mammalian hearing exhibits exquisite sensitivity and frequency selectivity attributed to the unique properties of cochlear outer hair cells (OHCs). These sensory epithelial cells are electro-mechanical transducers, capable of converting sound-induced electrical signals into mechanical forces which provide feedback via a mechanism known as the cochlear amplifier. In a process aptly termed electromotility, electro-mechanical transduction manifests as whole-cell axial length changes in OHCs that occur in response to changes in the transmembrane potential. The polytopic motor protein prestin functions as the voltage sensor and molecular motor, both in OHCs and when expressed in heterologous systems. As the molecular mechanism(s) of electromotility remain unknown, examining the structure and function of prestin is a major focus of ongoing research. Since changes in membrane composition and biophysical properties affect protein function and organization, we are particularly interested in membrane-protein interactions. Recent studies suggest that manipulations in membrane cholesterol levels reversibly shift the membrane microdomain distribution of prestin, modulate prestin oligomerization states, and alter prestin function, thus regulating electromotility through membrane-protein interactions. Measurements of protein and lipid lateral mobility provide a powerful tool to dynamically examine such interactions. We hypothesize that OHC plasma membrane cholesterol levels affect electromotility either through microdomain-mediated mechanisms that cluster or segregate prestin molecules or via alterations in the material properties of the membrane...

An electro-mechanical acoustic imaging scanner assembly.

Pearson, John Davis
Fonte: Monterey, California ; Naval Postgraduate School Publicador: Monterey, California ; Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
46.17%
The design of "a combined electro-mechanical acoustic image scanning assembly is described. Various acoustic imaging system techniques have demonstrated an ability to form underwater images at distances greater than those obtained by optical means. The scanning assembly -utilizes a sixteen element linear transducer array mounted on the radius of an eight inch diameter circle at the focal plane of an acoustic lens. The line array is rotated at a constant speed of 400 RPM. Acoustic signals at 250 KHZ of approximately 26 db re 1 ubar at the transducers were sufficient to produce satisfactory detection.

A Low-Noise DC Seismic Accelerometer Based on a Combination of MET/MEMS Sensors

Neeshpapa, Alexander; Antonov, Alexander; Agafonov, Vadim
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 26/12/2014 EN
Relevância na Pesquisa
26.04%
Molecular-electronic transducers (MET) have a high conversion coefficient and low power consumption, and do not require precision mechanical components thus allowing the construction of cost- and power-efficient seismic accelerometers. Whereas the instrumental resolution of a MET accelerometer within the 0.1–100 Hz frequency range surpasses that of the best Micro-Electro Mechanical Systems (MEMS) and even some force-balanced accelerometers, the fundamental inability to register gravity or, in other words, zero frequency acceleration, significantly constrains the further spread of MET-based accelerometers. Ways of obviating this inherent zero frequency insensitivity within MET technology have so far, not been found. This article explores a possible approach to the construction of a hybrid seismic accelerometer combining the superb performance of a MET sensor in the middle and high frequency range with a conventional on chip MEMS accelerometer covering the lower frequencies and gravity. Though the frequency separation of a signal is widely used in various applications, the opposite task, i.e., the combining of two signals with different bandwidths is less common. Based on theoretical research and the analysis of actual sensors' performance...

A Method for Accurate in silico modeling of Ultrasound Transducer Arrays

Guenther, Drake A.; Walker, William F.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.09%
This paper presents a new approach to improve the in silico modeling of ultrasound transducer arrays. While current simulation tools accurately predict the theoretical element spatio-temporal pressure response, transducers do not always behave as theorized. In practice, using the probe's physical dimensions and published specifications in silico, often results in unsatisfactory agreement between simulation and experiment. We describe a general optimization procedure used to maximize the correlation between the observed and simulated spatio-temporal response of a pulsed single element in a commercial ultrasound probe. A linear systems approach is employed to model element angular sensitivity, lens effects, and diffraction phenomena. A numerical deconvolution method is described to characterize the intrinsic electro-mechanical impulse response of the element. Once the response of the element and optimal element characteristics are known, prediction of the pressure response for arbitrary apertures and excitation signals is performed through direct convolution using available tools. We achieve a correlation of 0.846 between the experimental emitted waveform and simulated waveform when using the probe's physical specifications in silico. A far superior correlation of 0.988 is achieved when using the optimized in silico model. Electronic noise appears to be the main effect preventing the realization of higher correlation coefficients. More accurate in silico modeling will improve the evaluation and design of ultrasound transducers as well as aid in the development of sophisticated beamforming strategies.

Effect of laser phase noise on the fidelity of optomechanical quantum memory

Farman, Farnaz; Bahrampour, Alireza
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
25.95%
Optomechanical and electromechanical cavities have been widely used in quantum memories and quantum transducers. We theoretically investigate the robustness of opto(electro)-mechanical quan- tum memories against the noise of the control laser. By solving the Langevin equations and using the covariance matrix formalism in the presence of laser noise, the storing fidelity of Gaussian states is obtained. It is shown that, the destructive effect of phase noise is more significant in higher values of coupling laser amplitude and optomechanical coupling strength G. However, by further increasing coupling coefficient, the interaction time between photons and phonons decreases below the coherence time of laser frequency noise and the destructive effect of laser phase noise on the storing fidelity drops as well.

Complete model of a spherical gravitational wave detector with capacitive transducers. Calibration and sensitivity optimization

Gottardi, Luciano
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.3%
We report the results of a detailed numerical analysis of a real resonant spherical gravitational wave antenna operating with six resonant two-mode capacitive transducers read out by superconducting quantum interference devices (SQUID) amplifiers. We derive a set of equations to describe the electro-mechanical dynamics of the detector. The model takes into account the effect of all the noise sources present in each transducer chain: the thermal noise associated with the mechanical resonators, the thermal noise from the superconducting impedance matching transformer, the back-action noise and the additive current noise of the SQUID amplifier. Asymmetries in the detector signal-to-noise ratio and bandwidth, coming from considering the transducers not as point-like objects but as sensor with physically defined geometry and dimension, are also investigated. We calculate the sensitivity for an ultracryogenic, 30 ton, 2 meter in diameter, spherical detector with optimal and non-optimal impedance matching of the electrical read-out scheme to the mechanical modes. The results of the analysis is useful not only to optimize existing smaller mass spherical detector like MiniGrail, in Leiden, but also as a technological guideline for future massive detectors. Furthermore we calculate the antenna patterns when the sphere operates with one...

Force sensors based on piezoresistive and MOSFET cantilevers for biomolecular sensing

Tosolini, Giordano
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2014 ENG
Relevância na Pesquisa
26.25%
Los procesos de reconocimiento biomolecular entre receptores y ligandos son muy importantes en biología. Estas biomoléculas pueden desarrollar complejos muy específicos y tener una variedad de funciones como replicación y transcripción genómica, actividad enzimática, respuesta inmune, señalamiento celular, etc. La complementariedad inequívoca mostrada por estos componentes biológicos es ampliamente utilizada para desarrollar biosensores. Dependiendo de la naturaleza de las señales que se convierten, los biosensores pueden ser clasificados en ópticos, eléctricos o mecánicos. Entre los sensores mecánicos, los microcantilevers son los más comunes. Han sido utilizados como sensores de estrés superficial o como sensores de masa en detección de biomoléculas, desde hace más de 10 años. El enlace de las moléculas a sus superficies funcionalizadas se puede detectar midiendo la deflexión en modo estático o la variación de la frecuencia de resonancia en modo dinámico. Para lograr la máxima resolución, la deflexión es medida por un láser y un fotodetector. Este método limita las medidas en fluidos transparentes, la portabilidad del instrumento, e incrementa la complejidad de medición multiplexada. El desarrollo de cantilevers sensibles a la deflexión mediante la integración de piezoresistores o transistores de efecto de campo (MOSFET) implementados en el mismo voladizo...

Micro-Electro-Mechanical-Systems (MEMS) and Fluid Flows

Ho, Chih-Ming; Tai, Yu-Chong
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /01/1998
Relevância na Pesquisa
46.21%
The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electro-mechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research.