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P Hauptmann - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Compressional-Wave influence on thickness-shear-mode resonators in liquids
Sensors and Actuators A: Physical, 1997Co-Authors: Ralf Lucklum, Stefan Schranz, Frank Eichelbaum, Charles Behling, P HauptmannAbstract:The operation of a thickness-shear-mode (TSM) resonator contacting a finite liquid layer has been analysed to investigate the effect of Compressional-Wave generation. This effect is mainly related to the non-uniform shear velocity profile across the surface of a TSM device. Hydrophone measurements show two coils of longitudinal Waves. Their influence on the TSM resonator response is studied with impedance analysis, varying the spacing between resonator and reflector as well as the reflecting conditions on the top side of the liquid layer. A characteristic response with a periodicity of λ/2 is observed when the spacing of the liquid cavity or the liquid layer thickness is changed. It indicates standing longitudinal Waves in the cavity. Their influence can be modelled with an additional complex impedance in the motional arm of the Butterworth-van-Dyke equivalent circuit representing an own (Compressional) transmission line.
Stephen J. Martin - One of the best experts on this subject based on the ideXlab platform.
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Influence of Compressional Wave generation on thickness-shear mode resonator response in a fluid
Analytical Chemistry, 1995Co-Authors: Thomas Schneider, Stephen J. MartinAbstract:Acoustic interferometry was performed with thickness-shear mode (TSM) resonators to investigate the effect of Compressional Wave generation on the response (resonant frequency and damping). Resonator response was measured while the spacing between the resonator and adjacent solid was filled with fluid and the spacing was varied. A characteristic resonance response was observed whenever the spacing reached a multiple of λ c /2, where λ c is the Compressional Wavelength in the fluid. Compressional Wave generation arises from a gradient in the inplane surface displacement. A model is proposed to predict the resonator response that arises from combined shear Wave and Compressional Wave generation. Experimental data fit to this model determine device coupling to shear and Compressional Waves. The model also relates resonator response to the surface displacement profile. By measuring this displacement profile, Compressional Wave generation can be estimated. The effect of surface roughness and device geometry on shear and Compressional Wave coupling is examined. The results indicate that even in a semiinfinite fluid, Compressional Wave generation contributes significantly to device damping (motional resistance) but not to the frequency shift.
Ralf Lucklum - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Compressional-Wave influence on thickness-shear-mode resonators in liquids
Sensors and Actuators A: Physical, 1997Co-Authors: Ralf Lucklum, Stefan Schranz, Frank Eichelbaum, Charles Behling, P HauptmannAbstract:The operation of a thickness-shear-mode (TSM) resonator contacting a finite liquid layer has been analysed to investigate the effect of Compressional-Wave generation. This effect is mainly related to the non-uniform shear velocity profile across the surface of a TSM device. Hydrophone measurements show two coils of longitudinal Waves. Their influence on the TSM resonator response is studied with impedance analysis, varying the spacing between resonator and reflector as well as the reflecting conditions on the top side of the liquid layer. A characteristic response with a periodicity of λ/2 is observed when the spacing of the liquid cavity or the liquid layer thickness is changed. It indicates standing longitudinal Waves in the cavity. Their influence can be modelled with an additional complex impedance in the motional arm of the Butterworth-van-Dyke equivalent circuit representing an own (Compressional) transmission line.
Thomas Schneider - One of the best experts on this subject based on the ideXlab platform.
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Influence of Compressional Wave generation on thickness-shear mode resonator response in a fluid
Analytical Chemistry, 1995Co-Authors: Thomas Schneider, Stephen J. MartinAbstract:Acoustic interferometry was performed with thickness-shear mode (TSM) resonators to investigate the effect of Compressional Wave generation on the response (resonant frequency and damping). Resonator response was measured while the spacing between the resonator and adjacent solid was filled with fluid and the spacing was varied. A characteristic resonance response was observed whenever the spacing reached a multiple of λ c /2, where λ c is the Compressional Wavelength in the fluid. Compressional Wave generation arises from a gradient in the inplane surface displacement. A model is proposed to predict the resonator response that arises from combined shear Wave and Compressional Wave generation. Experimental data fit to this model determine device coupling to shear and Compressional Waves. The model also relates resonator response to the surface displacement profile. By measuring this displacement profile, Compressional Wave generation can be estimated. The effect of surface roughness and device geometry on shear and Compressional Wave coupling is examined. The results indicate that even in a semiinfinite fluid, Compressional Wave generation contributes significantly to device damping (motional resistance) but not to the frequency shift.
Gary Benjamin O'neill Robb - One of the best experts on this subject based on the ideXlab platform.
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measurement of the in situ Compressional Wave properties of marine sediments
IEEE Journal of Oceanic Engineering, 2007Co-Authors: Gary Benjamin O'neill Robb, Justin K. Dix, Angus I. Best, Jonathan M. Bull, Timothy G. Leighton, Paul R. White, A HarrisAbstract:Geoacoustic inversion requires a generic knowledge of the frequency dependence of Compressional Wave properties in marine sediments, the nature of which is still under debate. The use of in situ probes to measure sediment acoustic properties introduces a number of experimental difficulties that must be overcome. To this end, a series of well-constrained in situ acoustic transmission experiments were undertaken on intertidal sediments using a purpose-built in situ device, the Sediment Probing Acoustic Detection Equipment (SPADE). Compressional Wave speed and attenuation coefficient were measured from 16 to 100 kHz in medium to fine sands and coarse to medium silts. Spreading losses, which were adjusted for sediment type, were incorporated into the data processing, as were a thorough error analysis and an examination of the repeatability of both the acoustic Wave emitted by the source and the coupling between probes and sediment. Over the experimental frequency range and source-to-receiver (S-R) separations of 0.99-8.1 m, resulting speeds are accurate to between 1.1% and 4.5% in sands and less than 1.9% in silts, while attenuation coefficients are accurate to between 1 and 7 dBm in both sands and silts. Preliminary results indicate no speed dispersion and an attenuation coefficient that is proportional to frequency.
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the frequency dependence of Compressional Wave velocity and attenuation coefficient of intertidal marine sediments
Journal of the Acoustical Society of America, 2006Co-Authors: Gary Benjamin O'neill Robb, Justin K. Dix, Angus I. Best, Jonathan M. Bull, Timothy G. Leighton, Paul R. WhiteAbstract:To advance the present understanding of the frequency dependence of Compressional Wave velocity and attenuation in marine sediments a series of well-constrained in situ acoustic transmission experiments (16 to 100kHz) were performed on intertidal sediments. The processing techniques incorporated in situ spreading losses, sediment to transducer coupling and thorough error analyses. Significant variations in velocity and attenuation were observed over scales of tens of meters within the same sediment type. Velocity was generally nondispersive in sands, while highly variable silt velocities prevented any meaningful dispersion estimates from being determined. The attenuation coefficient was proportional to frequency for 75% of the experimental sites. The measured Compressional Wave properties were compared to predictions from the Grain-Shearing model. For the sandy sites, the phase velocities predicted by the Grain Shearing model exceed those measured, while predicted phase velocities agreed with measured gro...
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The Compressional Wave and physical properties of inter-tidal marine sediments
2005Co-Authors: Gary Benjamin O'neill Robb, Justin K. Dix, Angus I. Best, Jonathan M. Bull, Timothy G. Leighton, Paul R. White, A. SealAbstract:New quadratic regression equations for inter-tidal sediments are presented, which relate Compressional Wave properties (velocity ratio and proportionality constant) to porosity, bulk density and mean grain size. The Compressional Wave properties were derived from Compressional Wave velocities and attenuation coefficients measured on inter-tidal sediments from 16 - 100 kHz using common experimental and processing techniques. The regression equations are more robust for velocity ratio than proportionality constant. Discrepancies between the new regression equations and those derived for submerged sediments support the conclusion that the sediment structure of inter-tidal sediments differs from that of submerged sediments. This is attributed to the different physical processes which govern the supply, deposition and dynamics of the sediment in each environment.
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The in situ Compressional Wave properties of marine sediments
2004Co-Authors: Gary Benjamin O'neill RobbAbstract:The inversion of Compressional Wave properties is presently emerging as a technique for determining the geotechnical properties of marine sediments. However, the relationships required to perform such an inversion are still under debate, with further research required to resolve the dependence of Compressional Wave properties on both frequency and geotechnical properties. Though the use of in situ probes provides the most promising manner of examining these relationships, previous work in this field has encountered a number of experimental difficulties. This work presents a series of well-constrained in situ transmission experiments. These were undertaken on inter-tidal sediments using a purpose built in situ device, the Sediment Probing Acoustic Detection Equipment (SPADE). Compressional Wave properties were measured from 16 to 100 kHz in a range of sediment types (medium to fine sands and medium to fine silts), with several closely spaced locations examined at each general site to assess the local variability in Compressional Wave properties. Spreading losses, which were adjusted for sediment type, were incorporated into the data processing. Also included were a thorough error analysis and an examination of the repeatability of both the acoustic Wave emitted by the source and the coupling between the probes and the sediment. The results indicate that sands possess greater group velocities, greater effective attenuation coefficients and lower quality factors than silts, while the low velocities measured in silts imply that the bulk moduli of the silt sites examined are lower than expected owing to a considerable fraction of organic matter. Significant variations were observed in Compressional Wave properties, which were more reliably related to variations in geotechnical properties in sands than in silts. Group velocities were observed to be independent of frequency in sands within 95 % confidence limits, with no reliable frequency-dependence being determined in silts owing to variability in the measured values. Effective attenuation coefficients were proportional to frequency within 95 % confidence limits for the majority of the sand and silt locations examined. Results indicate that Compressional Wave properties can be used to determine porosity, bulk density and sand fraction, while the reliable determination of mean grain diameter from Compressional Wave properties in inhibited by the scatter in the data. The results from this study were also used to assess the effectiveness of Biot Theory to predict the Compressional Wave properties of these sediment types. In sands, the Biot phase velocities agreed with measured group velocities, while Biot absorption coefficients were less than measured effective attenuation coefficients, owing to scattering or squirt flow not accounted for in the Biot Theory. In silts, Biot phase velocities are greater than measured group velocities, while Biot absorption coefficients generally agree with or are greater than measured effective attenuation coefficients. In silts, predicted velocities are greater than those measured, while absorption coefficients generally agree with or are greater than measured attenuation coefficients. The discrepancy between the measured attenuation coefficients and predicted absorption coefficients can be explained through the over-estimation of in situ porosities by the geotechnical measurement techniques adopted.