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 66 for “"Acoustic impedance"”.
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The acoustic impedance of the glottis. Measurements and modeling
Contains fulltext : 132973.pdf (Publisher’s version ) (Open Access)
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Three-dimensional acoustic impedance map analysis of soft tissue
Three-dimensional impedance maps (3DZMs) are virtual volumes of acoustic impedance values constructed from histology to represent tissue microstructure acoustically. From the 3DZM, the ultrasonic backscattered power spectrum can be predicted and model based scatterer properties, such as effective …
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Smartphone acoustic impedance sensing based on additive sum mixing technique
We have developed a method to perform impedance measurement using general purpose smartphones that will not require the presence of external power source. The need for battery-less impedance sensing methods is greatly demanded given recent years’ advancements in impedance based sensing …
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Acoustic impedance inversion for static and dynamic characterization of a CO₂ EOR project, Postle field, Oklahoma
Includes bibliographical references (leaves 86-89).
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Fluid content effect on acoustic impedance and limits of direct detection capability : illustrated on an offshore prospect
The presence of gas and oil in some sand formations decreases the seismic velocity and density to such an extent that anomalously large reflections coefficients are encountered at fluid contacts. Geerstma and Gassmann's theories are equivalent and provide a good way to study the physical properties …
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Survey of free-field methods to measure the normal specific acoustic impedance of ground surfaces in situ at low frequencies
… techniques for measuring the normal specific acoustic impedance of the ground in situ and at low frequencies are examined. These techniques include the use of a spherical wave model, plane wave model, boundary conditions method, and the ANSI S1.18-2010 standard. Experiments are performed with …
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Influence of low frequencies on seismic impedance inversion
Acoustic impedance is a rock property that can be derived from seismic data and contains important information about subsurface properties. Mathematically, the acoustic impedance can be calculated from earth’s reflectivity function and this function can be estimated from seismic data. However, …
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Interpretation and Fracture Characterization of Early-Cretaceous Buda Limestone Formation Using Post-Stack 3D Seismic Data in Zavala County, Texas
… based on well log analysis tied to seismic acoustic impedance (AI) inversion to locate areas of probable natural fractures. Acoustic impedance inversion was performed across a 42 square mile 3D seismic survey. The AI data shows low AI shadow zones on the down thrown side of faults. Post …
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Interpretation of Vibroseis reflections from within the Catoctin Formation of central Virginia
… Virginia are interpreted to originate from acoustically thin beds of interlayered metabasalts and metasediments. Large acoustic impedance contrasts exist between epidotised layers ( epidosites and volcanic breccia) and non-epidotised layers (greenstones and phyllites) within the Catoctin …
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Passive materials for high frequency piezocomposite ultrasonic transducers
… filler material with volume fractions up to 0.4. Acoustic impedance and attenuation has been determined for different filler volume fractions to provide data for modelling to aid transducer design and also determine the filler volume fraction required to provide optimal results. Acoustic impedance …
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Dynamic reservoir characterization using 4D multicomponent seismic data and rock physics modeling at Delhi field, Louisiana
… data to jointly invert for Vp/Vs ratio and acoustic impedance. This technique has the advantage of adding more information to the non-unique inversion problem. Combining the inversion results from the monitor surveys of June 2010 and August 2011 provides acoustic impedance and Vp/Vs …
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A comparison of analytical models and experimental results for the acoustic response in a non-rigid-wall enclosure
… need for an accurate modeling approach for the acoustic response in a non-rigid-wall enclosure. The acoustic response in any enclosure is determined by the boundary conditions at the interior surface of the enclosure walls, and the types of sources present. The analyses presented in this thesis …
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Tubos de impedância e suas aplicações na determinação de propriedades acústicas de meios porosos
Acoustic impedances and absortion coefficients in fluid-saturated porous solids are experimentally determined in air and water in impedance tubes. An experimental methodology is developed for the measurements in water. A study is made of the ways in which the experimentally measured parameters …
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Ultrasonic wave reflection measurements on stiffening and setting of cement paste
… impact resistance polystyrene or HIPS) with acoustic impedance that is close to that of cement paste. The use of the HIPS buffer together with a new signal compensating method provide sensitive, accurate and reliable measurements on the stiffening and setting of early-age cement paste. In …
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Investigation of a radially vibrating, oil filled cylindrical ceramic transducer with a variable internal impedance and devoid of all forms of pressure release
… this type, which was constructed with a variable acoustic impedance in the oil filled interior. The results were compared with theoretical computations, which proved helpful in analyzing and interpreting the resonances of the transducer. Additional measurements were made on the transducer and were …
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The Dynamics of Single and Double Cavitation Bubbles and Interaction Between Bubbles and Different Materials
… aiming to quantify the impacts of material acoustic impedance and thickness on single laser-induced cavitation bubble dynamics with measurements of exerted pressure on a specific material in order to identify the primary sources most responsible for material damages is presented in this …
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Seismic attribute analysis and CO2 monitoring within the Mississippian reservoir, Wellington field, Sumner County, Kansas
… was used to evaluate Mississippian reservoir acoustic property changes due to CO2 saturation changes. CO2 saturation levels of 10%, 25%, and 50% displayed a decrease (larger absolute value) in normal-incidence acoustic impedance of up to 2.4%, 6.1%, and 13.3% with increasing CO2 saturation, …
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Ultrasonic transducers for wideband attenuation measurements
… at these frequencies. However, their high acoustic impedances relative to their liquid loads make them inherently narrowband and inefficient. To overcome these undesirable features, impedance matching techniques are used whereby the impedance mismatch between a transducer and its load is …
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Analyzing Skid Resistance and Tire/Road Noise on Porous Pavement Using Numerical Modeling
… drainage and reduces tire/road noise through acoustic absorption. This study attempts to explore the development of numerical models in predicting skid resistance and tire/road noise on porous pavements. The drainage capacity of a porous surface is modeled by a simplified pore structure. This …
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Reservoir characterization using seismic reflectivity and attributes
… procedure is followed. First, reflectivity and acoustic impedance profiles are obtained from the inversion of post-stack seismic data. Second, a multi-attribute analysis, calibrated using well logs, is used to obtain porosity. This procedure is applied to a 40x40 sq. km field data set from the …
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