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 77 for “"Acoustic measurements"”.
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High Resolution Acoustic Measurements of Musical Instruments
… work undertaken while carrying out research into acoustic measurement techniques for 3-dimensional acoustic radiation data for musical instruments, specifically when the instruments are being played by musicians. The original contribution to knowledge that is presented includes the development of …
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Compressible Flow Characterization Using Non-Intrusive Acoustic Measurements
Non-intrusive acoustic instruments that measure fluid velocity and temperature have been restricted to low subsonic Mach number applications due to increased complexities associated with acoustic refraction, low signal-to-noise ratios, and a limited range of practical applications. In the current …
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Acoustic measurements of flowing and quasi-static particulate suspensions
… satisfactorily resolved. This thesis explores acoustic techniques to measure the particle concentration. Controlled suspensions -- both flowing and quasi-static - were generated in cylindrical tubes, and their acoustic properties were measured over three frequency ranges, requiring a variety of …
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Heterogeneous acoustic measurements and multiple classifiers for speech recognition
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.
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A comparison of logging while drilling (LWD) and wireline acoustic measurements
The instruments used to measure borehole acoustic data can be classified as either wireline or logging while drilling (LWD). The wireline tool measures formation speeds after the borehole is drilled, and the LWD tool measures formation speeds while the borehole is drilled. This thesis focuses on …
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Effects of tool positions on borehole acoustic measurements : a stretched grid finite difference approach
… to numerical simulation and borehole acoustic logging. The first one is a novel finite difference time domain algorithm that features non- uniform grid, wavelet-based difference operator and anisotropic perfectly matched layer. This algorithm reduces numerical reflections and wave …
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Non-invasive assessment of bacterial biofilm in the middle ear using low-coherence interferometry/optical coherence tomography and acoustic measurements
… (LCI)/optical coherent tomography (OCT) and acoustic measurements. Portable systems were constructed by integrating LCI/OCT techniques with a standard video otoscope to provide depth-resolved optical scattering properties of the middle ear. An automatic algorithm was written to classify the …
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Investigation of the Relationships Between Geotechnical Sediment Properties and Sediment Dynamics Using Geotechnical and Geophysical Field Measurements
… and uppermost sediment layer investigation. Acoustic methods have been used to assess seabed layering, scour evolution, and seabed morphology. However, there still exist major limitations in using these methods for classification and characterization of seabed sediment surface layers in the …
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Aeroacoustic measurement and analysis of transient supersonic hot nozzle flows
… free jet to reach a quasi-steady-state before acoustic measurements can be made. However, if this constraint is met, the short run times become advantageous. The test articles are only exposed to the high temperature flow for a fraction of a second, and can be constructed of relatively …
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Seasonal and Mesoscale Variability in the Distribution of Antarctic Krill, <i>Euphausia superba</i>, West of the Antarctic Peninsula
… in selected environmental parameters. Acoustic measurements of krill were made each season at designated locations to estimate the abundance of krill, in terms of vertically-integrated krill biomass and the number of aggregations, characterize the depth distribution of krill, and …
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Moment analysis methods of ultrasonic waveforms to characterize the internal temperature and melt transition boundary for materials with irregular porosity.
The utilization of acoustic measurements occurs frequently in a multitude of industries. Monitoring the internal thermal and phase states of materials is of particular interest to the petro-chemical, food, and polymer processing industries, and ultrasound has found limited investigation within the …
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Inversion for subbottom sound velocity profiles in the deep and shallow ocean
This thesis investigates the application of acoustic measurements in the deep and shallow ocean to infer the sound velocity profile (svp) in the seabed. For the deep water ocean, an exact method based on the Gelfand-Levitan integral equation is evaluated. The input data is the complex plane-wave …
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A study of seismoelectric signals in measurement while drilling
An LWD acoustic wave can move the excess charge in the electric double layer along the borehole wall to generate a streaming electric field. This thesis is an experimental and theoretical investigation of the electric field induced by the multipole LWD acoustic wave. The main goal of this thesis is …
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Aeroacoustics of the bifurcated 2D supersonic inlet
… was performed to determine the aerodynamic and acoustic performance of the bifurcated 2D supersonic inlet during takeoff and approach flight conditions, and to compare these results indirectly to those of the axisymmetric supersonic inlet. The comparison is not direct since the centerbody …
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Fiber inline pressure and acoustic sensor fabricated with femtosecond laser
"Pressure and acoustic measurements are required in many industrial applications such as down-hole oil well monitoring, structural heath monitoring, engine monitoring, study of aerodynamics, etc. Conventional sensors are difficult to apply due to the high temperature, electromagnetic-interference …
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Acoustic scattering by axisymmertic finite-length bodies with application to fish : measurement and modeling
This thesis investigates the complexities of acoustic scattering by finite bodies in general and by fish in particular through the development of an advanced acoustic scattering model and detailed laboratory acoustic measurements. A general acoustic scattering model is developed that is accurate …
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Fan noise reduction from a supersonic inlet
… due to the choking effect. Both aerodynamic and acoustic measurements are taken in the experiments. The results show that when compared to the original design, the modified auxiliary inlet doors are successful in reducing distortion to the fan face, and that the blade passing frequency tone has …
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Multi-modal and inertial sensor solutions for navigation-type factor graphs
… front-end processes to deal with non-Gaussian measurements. Instead, our approach allows the front-end to defer ambiguities with non-Gaussian measurement models. We retain the acyclic Bayes tree (and incremental update strategy) from the predecessor iSAM2 maxproduct algorithm [Kaess et al., …
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ACCELERATED NOISE INTERFEROMETRY-BASED PASSIVE ACOUSTIC CHARACTERIZATION OF THE LITTORAL OCEAN
Acoustic remote sensing of the ocean traditionally relies on controlled sound sources and active sonars. Alternatively, the seabed and the water column can be characterized acoustically in a surreptitious and environmentally friendly way using noise interferometry. Noise interferometry exploits …
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Synthesis and characterization of metal-polyaniline thin films and membranes
… metals and polyaniline at the interfaces. Acoustic transmission properties of metal-polyaniline membranes were characterized by measuring the insertion loss as a function of acoustic frequencies and membrane geometry in various testing environments. Results indicated that the type of metal …
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