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Lopez, Guiomar. "Evaluation, analysis, and application of HF radar wave and current measurements." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/9291.
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This study investigates the accuracy of the wave products retrieved by a 12-MHz high-frequency (HF) phased-array radar, and establishes their potential to characterise wave-current interactions. The two stations composing the system were deployed in 2011 to overlook the Wave Hub, a test site for marine renewable energy devices located on the south-western coast of the United Kingdom. The system was conceived and configured to reduce the inaccuracies introduced by short time averaging and minimal overlap between stations, both associated with the most traditional HF radar deployments, whose primary activity is current measurement. Wave spectra were retrieved by two independent inversion algorithms, which were evaluated both independently and relative to each other. This process helped determining the errors associated to the algorithm used, and differentiated them from those inherent to the radar technology itself. The first method investigated was a semi-empirical algorithm distributed with Wellen Radars (WERA), which was calibrated using in situ measurements collected within the radar footprint. Evaluated through comparison against measurements acquired by three in situ devices, the results revealed estimates of significant wave height with biases below 9 cm, Pearson correlations higher than 0.9, and RMS errors that range from 29 to 44 cm. The relative error of wave energy period comparisons was within 10% for periods between 8 and 13 s, while both under- and overestimations were observed above and below that range, respectively. The validation demonstrated that when locally calibrated, the algorithm performs better than in its original form in all metrics considered. Observed discrepancies were mainly attributable to single-site estimations, antenna sidelobes, and the effect of the second-harmonic peaks of the Doppler spectrum. As opposed to the semi-empirical inversion, the second method evaluated in this work provides estimates of the full directional spectrum. Compared against the in situ measurements, the radar spectra were more spread over frequencies and directions, and had a lower energy content at the peak of the spectrum. In terms of parameter estimation, this was generally translated in a slight underestimation of wave periods, but accurate estimates of significant wave heights. Pearson correlations between these parameters and the in situ measurements for the bulk of the spectrum were higher than 0.9, and both types of measurements resulted in similar standard deviations. The inversion algorithm showed a high skill estimating mean wave directions, which revealed linear correlations higher than 0.8, when compared to the in situ devices. Overall, the inversion algorithm has shown to be capable of providing accurate estimates of directional spectra and the parameters derived from them, and at present the main drawback of the method is the data return, which due to the high data quality requirements of the algorithm, did not exceed 55% over the 8-month period studied here. In the second part of this work, the validated measurements were examined to determine their ability to reproduce the effects of wave-current interactions. The fine structure of the surface current was first evaluated, and revealed a circulation dominated by tides. The residual flow was seen to respond to the wind, as well as to the stratification present in the area during the spring and summer months. These data were then used to assess their contribution to wave refraction over the radar domain. The results show modulations in the wave phase parameters, which resulted from both the temporal and spatial derivatives of the surface current velocities. The evaluation of HF radar wave measurements provided in this work has shown that, properly configured, this technology can produce accurate estimates of several statistical descriptors of the wave field. Together with the highly accurate surface currents also measured by this device, the spatial wave data obtained has proved to have great potential for studying wave-current interactions; a skill that can be of support to coastal wave modelling.
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Zomorodian, Seyed Mohammad Ali. "Shear wave velocity of soils by the spectral analysis of surface waves (SASW) method." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10395.
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Spectral analysis of surface waves (SASW) method is an in-situ seismic method used for determining the thickness and elastic properties of soil and pavement. The SASW method is fast and economical to perform since no boreholes are required. The method is suitable for sites where the use of large equipment is difficult or where sublayer conditions make it difficult to perform other seismic tests. The SASW method is also ideal for preliminary field investigations to be conducted prior to more detailed site investigation, and for quality control and monitoring of ground improvement. The purpose of this research was to improve the SASW method by incorporating multi-mode propagation in the backcalculation procedure. In order to facilitate the investigation carried out in this study, two computer programs were developed to simulate SASW tests (and also Steady-State surface wave tests) and to calculate theoretical dispersion curves. The program for calculating theoretical dispersion curves was based on the root-searching procedure used in existing backcalculation methods. The computer programs developed in this study were used in a case study to demonstrate difficulties encountered by existing methods in dealing with multi-mode situations. It was shown that: (i) wavelength filtering criteria used by existing methods yield inconsistent (i.e. erroneous) dispersion curves when more than one propagation mode participate in the wave field, and (ii) backcalculation procedures based on root-searching cannot identify predominant propagation modes and hence fail to yield accurate results in the case of multi-mode propagation. Two developments were made in the present study to overcome the above difficulties. First, a new wavelength filtering criterion was adopted. In this criterion, the dispersion data point for a particular frequency is rejected (i.e. filtered out) if the values of phase velocity obtained from two different receiver-to-receiver spacings are not in close agreement. In this manner, inconsistencies that might result in the dispersion due to multi-mode propagation are avoided. Second, a new procedure to calculate the theoretical dispersion curve was developed. This procedure is based on the maximum vertical flexibility coefficient (at each frequency) of the theoretical layered model. Unlike root-searching methods, the maximum vertical flexibility coefficient method easily identifies predominant propagation modes. A computer program was developed in this study for backcalculation of SASW data based on the flexibility coefficient method. Least-squares optimization using the down-hill simplex method was also implemented in this program to automate the backcalculation process. The accuracy of the above proposed procedures was demonstrated using SASW field tests. The shear wave velocity profiles obtained using the procedures developed in this study are in good agreement with those obtained from other in-situ seismic tests. (Abstract shortened by UMI.)
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Liu, Siyu. "Shear Wave Velocity Analysis by Surface Wave Methods in the Boston Area:." Thesis, Boston College, 2017. http://hdl.handle.net/2345/bc-ir:107367.
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Thesis advisor: John E. EbelThesis advisor: Alan L. Kafka
As the best seismic indicator of shear modulus, shear-wave velocity is an important property in engineering problems in near-surface site characterization. Several surface-wave methods have been developed to obtain the subsurface shear-wave velocity structure. This thesis compared three surface-wave methods, Spectral Analysis of Surface Waves (SASW) (Nazarian et al., 1983), Multichannel Analysis of Surface Waves (MASW) (Park et al., 1999), and Refraction Microtremor (ReMi) (Louie, 2001), to determine which method gives the best estimation of the 1-D shear-wave velocity profile of near-surface soils. We collected seismic data at three sites in the greater Boston area where there are direct measurements of shear-wave velocities for comparison. The three methods were compared in terms of accuracy and precision. Overall, the MASW and the ReMi methods have comparable quality of accuracy, whereas the SASW method is the least accurate method with the highest percentage differences with direct measurements. The MASW method is the most precise method among the three methods with the smallest standard deviations. In general, the MASW method is concluded to be the best surface-wave method in determining the shear-wave velocities of the subsurface structure in the greater Boston area
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Yoon, Sungsoo. "Array-Based Measurements of Surface Wave Dispersion and Attenuation Using Frequency-Wavenumber Analysis." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7246.
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Surface wave methods have been used to determine dynamic properties of near-surface soils in geotechnical engineering for the past 50 years. Although the capabilities of engineering surface wave methods have improved in recent years due to several advances, several issues including (1) near-field effects, (2) combined active and passive measurements, and (3) accurate measurements of surface wave attenuation still require study to further improve the capabilities of modern surface wave methods.
Near-field effects have been studied for traditional surface wave methods with two receivers and several filtering criteria to mitigate the effects have been recommended. However, these filtering criteria are not applicable to surface wave methods with multiple receivers. Moreover, the criteria are not quantitatively based and do not account for different types of soil profiles, which strongly influence near-field effects. A new study of near-field effects on surface wave methods with multiple receivers was conducted with numerical and experimental methods. Two normalized parameters were developed to capture near-field effects. Quantitatively based near-field effect criteria for an ideal homogeneous half-space and three typical soil profiles are presented.
Combining active and passive surface wave measurements allows developing a shear wave velocity profile to greater depth without sacrificing the near-surface resolution offered by active measurements. Generally, active and passive measurements overlap in the frequency range from approximately 4 to 10 Hz, and there are often systematic differences between the two measurements. The systematic errors in active and passive surface wave methods were explored to explain and resolve the differences, allowing for a more accurate composite dispersion curve.
The accuracy of measured surface wave attenuation is improved by properly accounting for (1) geometric spreading, (2) near-field effects, and (3) ambient noise. In this study, a traditional estimation method and a frequency-wavenumber method utilizing sub-arrays were investigated using displacement data from numerical simulations, focusing on near-field and ambient noise effects. Detailed procedures for the frequency-wavenumber estimation method are developed based on a study of the primary factors affecting attenuation estimates. The two methods are also evaluated using experimental displacement data obtained from surface wave field measurements with three different arrays.
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Fan, Yichao. "The analysis of surface defects using the ultrasonic Rayleigh surface wave." Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495017.
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Surface defects, such as rolling contact fatigue (RCF) cracking, can be a difficult class of surface defects for existing on-line non-destructive testing techniques to detect and size accurately at high speed. Gauge corner cracking on the running surface of the railway track is a type of RCF defect. There are economic and safety benefits to have an accurate, fast and reliable NDT technique to detect such defects. The EMAT pitch-catch ultrasonic testing technique, using the Rayleigh surface wave developed at the laser ultrasound group, has been shown to be able to detect and size surface defects. The pitch-catch geometry also allows this technique to be used at high speed, for on-line NDT applications.
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McAllister, Mark Laing. "Analysis of laboratory and field measurements of directionally spread nonlinear ocean waves." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28762.
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Surface gravity waves exist in the oceans as multi-directional nonlinear phenomena. Understanding how these two properties interact is intrinsically important in itself. Furthermore, an understanding of this relationship may be used to gain insight into other oceanic phenomena. This thesis first describes an experimental investigation into the relationship between directionality and non-linearity (Part I). This relationship was then used as a tool to estimate the directional spreading of field data (Part II). Experiments have been conducted in which directionally spread focused wave groups were created in a wave tank. The relationship between the degree of directional spreading and the second-order bound harmonics of the wave groups was examined, in particular the formation of a `set-up'. These measurements were then compared to predictions from second-order theories, finding good agreement. The two-dimensional structure of the bound waves was explored giving new insight into the underlying physics. Experiments were then carried out for directionally spread crossing wave groups. It is believed that the crossing of two sufficiently separated wave groups may be the cause of an anomalous set-up in the second-order bound waves observed for some extreme and potentially freak waves. This set-up is reproduced experimentally. Again, the results of these test agreed very well when compared to second-order theory. The insight gained from the foregoing experiments was then utilised in the analysis of field data. A method, which requires only a single measurement to estimate the observed degree of directional spreading, was applied to a large dataset of field measurements from the North Alwyn platform in the North Sea. This method was then compared to conventional approaches, which require multiple concurrent measurements. The method that requires only a single measurement was shown to be effective, and presents a promising approach to gaining additional insight about the directional spreading of point observations.
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Wijekoon, Wijekoon Mudiyanselage Kapila Piyasena. "Waveguide Surface Coherent anti-Stokes Raman Scattering Spectroscopy and optical second harmonic generation spectroscopy of molecules adsorbed on metal oxide surfaces." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184444.
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This dissertation reports the application of nonlinear optical effects for the investigation of vibrational and electronic spectroscopy of molecules adsorbed on thin film metal oxide surfaces and metal oxide surfaces. The main emphasis of the experiments cited here is to introduce the recently developed multi-photon technique, Waveguide Surface Coherent anti-Stokes Raman Scattering Spectroscopy (WSCARS), to the scientific community. Planar optical waveguides have been utilized to generate large optical field enhancements on metal oxide surfaces. Guided waves have been employed to obtain the surface coherent anti-Stokes Raman scattering spectra of pyridine, phenol, benzene, methanol, CD₃OD, 2,4-pentadione, oxygen, ammonia and ND₃ adsorbed onto a ZnO (0001) surface. Vibrational spectra of transient species (O₂⁻) adsorbed on ZnO (0001) surface are also presented. Furthermore, the WSCARS has been used to monitor catalytic hydrogenation of ethylene adsorbed on ZnO (0001) surface. The WSCARS technique is compared with the other vibrational surface probes. Future directions and limitations of the technique are also discussed. Electronic spectra of surface bound species have been examined by resonantly enhanced surface second harmonic generation (SSHG). SHG spectra of trans-cinnamic acid adsorbed on optically cleaned fused silica have been obtained at room temperature and at 4 K. Surface second harmonic generation has been applied to study the adsorption of water and acetone onto thermally grown silicon dioxide/silicon surface. SSHG has been successfully applied to monitor photo-oxidation and photo-reduction of a rutile (110) surface. Experiments are described, data are presented, and surface-adsorbate binding modes are discussed.
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Lowery, Kristen Mary. "Dynamic Analysis of an Inflatable Dam Subjected to a Flood." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35802.
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A dynamic simulation of the response of an inflatable dam subjected to a flood was carried out to determine the survivability envelope of the dam where it can operate without rupture, or overflow. A fully nonlinear free-surface flow was applied in two dimensions using a mixed Eulerian-Lagrangian formulation.
An ABAQUS finite element model was used to determine the dynamic structural response of the dam. The problem was solved in the time domain which allows the prediction of a number of transient phenomena such as the generation of upstream advancing waves, and dynamic structural collapse. Stresses in the dam material were monitored to determine when rupture occurs. An iterative study was performed to find the service envelope of the dam in terms of the internal pressure and the flood Froude number for two flood depths. It was found that the driving parameter governing failure of the dam was the internal pressure. If this pressure is too low, the dam overflows; if this pressure is too high, the dam ruptures. The fully nonlinear free-surface flow over a semi-circular bottom obstruction was studied numerically in two dimensions using a similar solution formulation as that used in the previous study. A parametric study was performed for a range of values of the depth-based Froude number up to 2.5 and non-dimensional obstacle heights up to 0.9. When wave breaking does not occur, three distinct flow regimes were identified: subcritical, transcritical and supercritical. When breaking occurs it may be of any type: spilling, plunging or surging. In addition, for values of the Froude number close to 1, the upstream solitary waves break. A systematic study was undertaken, to define the boundaries of each type of breaking and non-breaking pattern, and to determine the drag and lift coefficients, free surface profile characteristics and transient behavior.
Master of Science
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Cameron, Thomas P. (Thomas Philip) Carleton University Dissertation Engineering Electrical. "Circuit factor compensation for saw filters using modal analysis." Ottawa, 1988.
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Williams, Duncan Paul. "Scattering by wave-bearing surfaces under fluid loading." Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/14370/.
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Wave-bearing surfaces and compressible fluids are often adjacent, the subsequent interactions are of substantial interest in structural acoustics, acoustic microscopy, seismology and many other fields. Here we take a broad view and discuss a variety of problems, both time harmonic and transient, which are amenable to exact solution. These in turn highlight physical effects and can additionally form the basis of asymptotic solutions. In structural acoustics the interaction of plate waves with defects is Cl major source of underwater noise. A model problem of two semi-infinite elastic plates (made of different material) joined in a variety of ways is considered for obliquely incident flexural plate waves. Asymptotic results for 'light' and 'heavy' fluid loading are extracted. In addition reciprocity and power flow relations, besides being of independent interest, provide a useful check on the results. There are many closely related problems involving a fluid loaded elastic solid. The situation here is somewhat similar, but often more complicated, due to the number of waves that an elastic solid supports, mode conversion at interfaces, and interfacial waves. We first address the scattering effects of low frequency waves by very small interfacial defects, that is, small relative to a typical wavelength. In this limit, and in related water wave or acoustic work, matched asymptotic expansions are used. An important aspect, that has not been noticed before, is the natural separation that occurs in the inner problem into fluid and solid pieces. A matching argument may now be used to give a useful physical interpretation of these defects and far field directivity patterns show the distinctive beaming that occurs along the Rayleigh angles in the light fluid loading limit. In many areas of interest embedded defects are imaged by pulses and we therefore require a transient analysis. In this case our problem involves a combination of compressional and shear source loadings beneath a fluid-solid interface. The exact solution is found and a full asymptotic analysis of this solution is performed with an emphasis upon wavefront expansions and leaky waves, and in particular, for 'light' and 'moderate' fluid loading. In some situations, when the sources are near the interface, a pseudo-compressional wavefront is generated and the limit as the loading approaches the interface is investigated. These non-geometric wave arrivals may be important in seismology and elastic wave studies related to the non-destructive evaluation of structures. This study is generalised to investigate the dynamic stress loading of subsurface cracks in either homogeneous or non-homogeneous media. An iterative method of solution based on physical considerations is developed and quantities of interest such as the scattered displacement fields and the stress intensity factors are determined. The problems considered here are ideally suited to analysis by transform methods and the Wiener-Hopf and Cagniard-de Hoop techniques.
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Harvey, Alan Paul. "Nonlinear surface acoustic waves and applications." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.255827.
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Hughes, Adrian. "Transduction and guidance by narrow aperture surface acoustic wave structures." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236172.
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Orozco, M. Catalina (Maria Catalina). "Inversion Method for Spectral Analysis of Surface Waves (SASW)." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5124.
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This research focuses on estimating the shear wave velocity (Vs) profile based on the dispersion curve obtained from SASW field test data (i.e., inversion of SASW data). It is common for the person performing the inversion to assume the prior information required to constrain the problem based on his/her own judgment. Additionally, the Vs profile is usually shown as unique without giving a range of possible solutions. For these reasons, this work focuses on: (i) studying the non-uniqueness of the solution to the inverse problem; (ii) implementing an inversion procedure that presents the estimated model parameters in a way that reflects their uncertainties; and (iii) evaluating tools that help choose the appropriate prior information.
One global and one local search procedures were chosen to accomplish these purposes: a pure Monte Carlo method and the maximum likelihood method, respectively. The pure Monte Carlo method was chosen to study the non-uniqueness by looking at the range of acceptable solutions (i.e., Vs profiles) obtained with as few constraints as possible. The maximum likelihood method was chosen because it is a statistical approach, which enables us to estimate the uncertainties of the resulting model parameters and to apply tools such as the Bayesian criterion to help select the prior information objectively.
The above inversion methods were implemented for synthetic data, which was produced with the same forward algorithm used during inversion. This implies that all uncertainties were caused by the nature of the SASW inversion problem (i.e., there were no uncertainties added by experimental errors in data collection, analysis of the data to create the dispersion curve, layered model to represent a real 3-D soil stratification, or wave propagation theory). At the end of the research, the maximum likelihood method of inversion and the tools for the selection of prior information were successfully used with real experimental data obtained in Memphis, Tennessee.
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Kalinski, Michael E. "Determination of in situ V[subscript s] and G[subscript max] using surface wave measurements in cased and uncased boreholes /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Blake, Christina Diane. "Narrow apperture surface acoustic wave transducers and their application in spectrum analysis." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329903.
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Ogilvy, J. A. "On the theory of ultrasonic wave scattering from rough surfaces." Thesis, University of Bath, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378884.
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Thorvaldsson, Thor. "Design and analysis of surface acoustic wave resonators and resonator filters /." [S.l.] : [s.n.], 1988. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8471.
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Rosenblad, Brent Lyndon. "Experimental and theoretical studies in support of implementing the spectral-analysis-of-surface-wave (SASW) method offshore /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Venkata, Pradeep Kumar Garudadri. "SURFACE WAVE SCATTERING FROM METALLIC NANO PARTICLES: THEORETICAL FRAMEWORK AND NUMERICAL ANALYSIS." Lexington, Ky. : [University of Kentucky Libraries], 2006. http://lib.uky.edu/ETD/ukymeen2006t00408/Thesis%5FPGV%5FFinal%5Fn.pdf.
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Thesis (M.S.)--University of Kentucky, 2006.Title from document title page (viewed on June 1, 2006). Document formatted into pages; contains ix, 94 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 91-93).
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Bertel, Jeffrey D. "Analytical study of the spectral-analysis-of-surface-waves method at complex geotechnical sites." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4625.
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Thesis (M.S.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 21, 2007) Includes bibliographical references.
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Godwin, Melinda Dee. "Continuous curved near wake analysis for a lifting surface." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/42517.
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Fisher, Brian. "Surface Acoustic Wave (SAW) Cryogenic Liquid and Hydrogen Gas Sensors." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5208.
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This research was born from NASA Kennedy Space Center's (KSC) need for passive, wireless and individually distinguishable cryogenic liquid and H2 gas sensors in various facilities. The risks of catastrophic accidents, associated with the storage and use of cryogenic fluids may be minimized by constant monitoring. Accidents involving the release of H2 gas or LH2 were responsible for 81% of total accidents in the aerospace industry. These problems may be mitigated by the implementation of a passive (or low-power), wireless, gas detection system, which continuously monitors multiple nodes and reports temperature and H2 gas presence. Passive, wireless, cryogenic liquid level and hydrogen (H2) gas sensors were developed on a platform technology called Orthogonal Frequency Coded (OFC) surface acoustic wave (SAW) radio frequency identification (RFID) tag sensors. The OFC-SAW was shown to be mechanically resistant to failure due to thermal shock from repeated cycles between room to liquid nitrogen temperature. This suggests that these tags are ideal for integration into cryogenic Dewar environments for the purposes of cryogenic liquid level detection. Three OFC-SAW H2 gas sensors were simultaneously wirelessly interrogated while being exposed to various flow rates of H2 gas. Rapid H2 detection was achieved for flow rates as low as 1ccm of a 2% H2, 98% N2 mixture. A novel method and theory to extract the electrical and mechanical properties of a semiconducting and high conductivity thin-film using SAW amplitude and velocity dispersion measurements were also developed. The SAW device was shown to be a useful tool in analysis and characterization of ultrathin and thin films and physical phenomena such as gas adsorption and desorption mechanisms.?Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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Lee, Seung-Woo. "Computational electromagnetic approaches for the analysis of rough surface scattering and artificial composite materials /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/5997.
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Onen, Onursal. "Analytical Modeling, Perturbation Analysis and Experimental Characterization of Guided Surface Acoustic Wave Sensors." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4555.
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In this dissertation, guided surface acoustic wave sensors were investigated theoretically and experimentally in detail for immunosensing applications. Shear horizontal polarized guided surface acoustic wave propagation for mass loading sensing applications was modeled using analytical modeling and characterized by perturbation analysis. The model verification was performed experimentally and a surface acoustic wave immunosensor case study was presented. The results of the immunosensing were also investigated using the perturbation analysis.
Guided surface acoustic wave propagation problem was investigated in detail for gravimetric (or mass loading) guided wave sensors, more specifically for immunosensors. The analytical model was developed for multilayer systems taking viscoelasticity into account. The closed form algebraic solutions were obtained by applying appropriate boundary conditions. A numerical approach was used to solve dispersion equation. Detailed parametric investigation of dispersion curves was conducted using typical substrate materials and guiding layers. Substrate types of ST-cut quartz, 41° YX lithium Niobate and 36° YX lithium tantalate with guiding layers of silicon dioxide, metals (chromium and gold), and polymers (Parylene-C and SU-8) were investigated. The effects of frequency and degree of viscoelasticity were also studied. The results showed that frequency only has effect on thickness with same shaped dispersion curves. Dispersion curves were found to be unaffected by the degree of viscoelasticity. It was also observed that when there was a large shear velocity difference between substrate and guiding layer, a transition region with a gradual decrease in phase velocity was obtained. However, when shear velocities were close, a smooth transition was observed. Furthermore, it was observed that, large density differences between substrate and guiding layer resulted in sharp and with nearly constant slope transition. Smooth transition was observed for the cases of minimal density differences. Experimental verification of the model was done using multi-layer photoresists. It was shown that with modifications, the model was able to represent the cases studied.
Perturbation equations were developed with first order approximations by relating the slope of the dispersion curves with sensitivity. The equations were used to investigate the sensitivity for material selection (substrate, guiding layer, and mass perturbing layer) and degree of viscoelasticity. The investigations showed that the sensitivity was increased by using guiding layers with lower shear velocities and densities. Among the guiding layers investigated, Parylene C showed the highest sensitivity followed by gold and chrome. The perturbation investigations were also extended to viscoelasticity and to protein layers for immunosensing applications. It was observed that, viscous behavior resulted in slightly higher sensitivity; and sensitivity to protein layers was very close to sensitivity for polymers. The optimum case is found to be ST-cut quartz with Parylene-C guiding layer for protein layer sensing.
Finally, an immunosensing case study was presented for selective capture of protein B-cell lymphoma 2 (Bcl-2), which is elevated in many cancer types including ovarian cancer. The immunosensor was designed, fabricated, and experimentally characterized. An application-specific surface functionalization scheme with monoclonal antibodies, ODMS, Protein A/G and Pluronic F127 was developed and applied. Characterization was done using the oscillation frequency shift of with sensor used as the feedback element of an oscillator circuit. Detection of Bcl-2 with target sensitivity of 0.5 ng/ml from buffer solutions was presented. A linear relation between frequency shift and Bcl-2 concentration was observed. The selectivity was shown with experiments by introducing another protein, in addition to Bcl-2, to the buffer. It was seen that similar detection performance of Bcl-2 was obtained even with presence of control protein in very high concentrations. The results were also analyzed with perturbation equations.
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Shen, Yangfei. "Coupled Wave Analysis of Two-Dimensional Second Order Surface-Emitting Distributed Feedback Lasers." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461713975.
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Tufekci, Sinan. "Combined Surface-Wave and Resistivity Imaging for Shallow Subsurface Characterization." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1250891786.
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Rahman, Shubeur. "A finite element analysis of semiconductor quantum dot structures and surface acoustic wave devices." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613835.
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Hobiger, Manuel. "Polarisation des ondes de surface : caractérisation, inversion et application à l'étude de l'aléa sismique." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00577887.
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L'aléa sismique d'un site donné peut être largement influencé par des effets de site. Afin d'évaluer ces effets, la structure locale du sous-sol ainsi que les propriétés du champ d'onde doivent être étudiées. Les ondes de surface (ondes de Love et de Rayleigh) s'avèrent utiles, leurs propriétés (courbes de dispersion, ellipticité des ondes de Rayleigh) étant directement liées à la structure du sous-sol. Le paramètre clé pour l'identification du type d'onde est la polarisation. Dans la première partie de la thèse, de nouvelles méthodes pour l'estimation de paramètres de polarisation d'ondes de surface sont développées. Deux méthodes, DELFI et RayDec, estiment l'ellipticité des ondes de Rayleigh à partir d'enregistrements d'un seul capteur sismique. La troisième méthode, MUSIQUE, est basée sur la méthode MUSIC et utilise les enregistrements multi-composantes de réseaux sismiques afin de distinguer ondes de Love et ondes de Rayleigh et d'estimer leurs propriétés. Dans la deuxième partie de la thèse, une étude théorique de l'inversion de courbes d'ellipticité montre quelles parties de ces courbes véhiculent les informations importantes sur la structure du sol et comment l'inversion peut être améliorée. Le schéma d'inversion résultant est alors testé en l'appliquant à des données réelles mesurées pour 14 sites européens. Finalement, 22 séismes enregistrés par un réseau de capteurs dans la vallée de Santa Clara en Californie sont analysés par MUSIQUE. La répartition azimutale, les courbes de dispersion, la courbe d'ellipticité et les énergies des différents types d'ondes sont analysées et soulignent l'importance des ondes de surface diffractées dans le champ d'ondes enregistré.
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McEnaney, Kevin Bernard. "Magneto-absorption of surface acoustic waves by a 2-dimensional electron gas." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293651.
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Casey, Thomas J. "Shear wave data collection in mid America using an automated surface source during seismic cone testing." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/32804.
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Pethiyagoda, Ravindra. "Mathematical and computational analysis of Kelvin ship wave patterns." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/101167/1/Ravindra_Pethiyagoda_Thesis.pdf.
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This thesis concerns the form of water wave patterns generated by an idealised ship moving steadily through still water. An efficient numerical scheme for computing these waves with much finer detail than ever before is developed, and the results are used to determine the effect that certain properties, such as the ship's speed and dimensions, have on ship wakes. Two features are used to characterise the ship wave: the ship's apparent wake angle, the half-angle of the characteristic v-pattern of a ship wave, and a spectrogram produced by applying time-frequency analysis to a cross-section of the ship wave.
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Moueddene, Kada. "Analyse d'images en sismique : pretraitement et extraction d'informations par la morphologie mathematique." Toulouse 3, 1987. http://www.theses.fr/1987TOU30006.
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Techniques de traitement d'images appliquees aux diagraphies sismiques. En particulier, utilisation des operateurs de morphologie mathematique pour les problemes de pretraitement et d'extraction d'informations. Deux exemples d'application sont presentes: tir de bruits pour l'extraction des spectres de vitesses et tir au centre pour le filtrage des ondes de surface et des arrivees refractees
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Sritharan, Kumudesh. "Applications of surface acoustic waves (SAW) for chemical and biological analysis." kostenfrei, 2008. http://d-nb.info/994505051/34.
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Zywicki, Daren Joseph. "Advanced signal processing methods applied to engineering analysis of seismic surface waves." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20232.
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Dowaikh, Mohammad Abdulghani. "Surface and interfacial waves and deformations in pre-stressed elastic materials." Thesis, Connect to e-thesis, 1990. http://theses.gla.ac.uk/709/.
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Neal, Thomas C. "Analysis of Monterey Bay CODAR-derived surface currents, March to May 1992." Monterey, Calif. : Naval Postgraduate School, 1992. http://catalog.hathitrust.org/api/volumes/oclc/52761036.html.
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Sodeify, Kamran. "Modelling for response analysis of earth dams subjected to travelling surface waves." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295725.
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Marchioreto, Adriano. "Implementação, testes e avaliação do método SASW (Spectral Analysis of Surface Waves)." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/44/44133/tde-07082015-110048/.
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O SASW (\"Spectral Analysis of Surface Waves\") é um método geofísico de ensaio não destrutivo, baseado na geração e detecção de ondas elásticas de superfície (Rayleigh), e o estudo da natureza dispersiva desta onda. A aplicação desse método em geotecnia objetiva, a partir da determinação das velocidades de propagação das ondas S, definir os parâmetros elásticos dinâmicos dos diferentes materiais em subsuperfície. Este trabalho visou o desenvolvimento de um sistema instrumental para registro de ondas sísmicas e sua utilização na implementação, teste e avaliação do método SASW. O método SASW envolve a detecção de ondas superficiais do tipo Rayleigh e é realizado na superfície do terreno, não necessitando de furos de sondagem ou qualquer outra infraestrutura, tornando-se assim mais econômico do que os dois métodos sísmicos mais usados para o estudo de parâmetros elásticos do solo (\"crosshole\" e \"downhole\"), pois ambos métodos medem as velocidades de propagação de ondas de corpo P e S, e requerem a perfuração e revestimento de furos de sondagem. Como a natureza dispersiva da onda se dá em termos de freqüência, todo o processamento dos sinais é realizado no domínio da freqüência. A metodologia para execução dos ensaios SASW envolve três etapas: a) aquisição dos dados de campo; b) determinação da curva de dispersão das ondas Rayleigh e c) Inversão da curva de dispersão para obter um perfil de velocidade da onda S. Para cada uma das etapas foi feita uma descrição dos procedimentos adotados, com especial ênfase ao tópico b, uma vez que no processo de cálculo das curvas de dispersão ocorrem os maiores problemas do método. Foram escolhidos para apresentação e descrição três estudos de caso que permitiram discutir e avaliar em detalhe a aplicabilidade, vantagens e desvantagens do método. No primeiro caso, considerado como bom, as curvas de dispersão obtidas para diferentes espaçamentos de geofones se sobrepuseram numa ) determinada faixa de freqüências. No segundo exemplo, classificado como de qualidade intermediária, as curvas variaram pouco de uma para outra. No terceiro exemplo, considerado ruim, as curvas para diferentes espaçamentos entre geofones não convergiram, tendo sido necessário tentar uma nova estratégia para confeccionar a curva de dispersão representativa da área. A terceira etapa do método consiste na inversão da curva de dispersão. Diversos modelos iniciais foram gerados e todos eles, após algumas dezenas de iterações, apresentaram a mesma tendência. Para os ensaios no campus da USP obtiveram-se as curvas de dispersão coincidentes que permitiram a obtenção de um modelo de velocidade consistente. No caso do campus da UNICAMP os valores concordaram bem até 4 metros de profundidade com os valores de velocidade obtidos pelo ensaio \"crosshole\", porém para profundidades maiores do que 4 metros os valores divergem. No caso da UNESP (Bauru) os valores de ambos os métodos divergiram totalmente. Concluiu-se que, apesar do sistema instrumental desenvolvido ter se comportado bem, a completa automatização do ensaio é impossível pois no método de geração de curvas de dispersão, a intervenção do intérprete é fundamental. Isto é devido, em grande parte à dificuldade de geração de ondas de baixa frequência.The Spectral Analysis of Surface Waves (SASW) is a non-destructive test based on the generation and detection of elastic surface waves (Rayleigh), and the study of the dispersion behavior of these waves. The application of this method to geotechnical problems aims at defining the elastic parameters of the different materials from the determination of the S wave propagation velocity. The objective of this thesis was to develop an instrumental system to record seismic waves and its utilization in the implementation, test and evaluation of the SASW method. The SASW method consists in the detection of Rayleigh surface waves and do not require boreholes or any other infrastructure since it is performed from thesurface. This allows it to be more economical than the crosshole or downhole tests that require the perforation and casing of boreholes to measure the P and S propagation velocities. The processing is carried out in frequency domain since the dispersive nature of the wave is in terms of frequency. The SASW methodology consists in three steps: a) data acquisition; b) determination of the dispersion curve of the Rayleigh wave and c) the inversion of the dispersion curve to obtain an S wave profile. It is presented a description of the adopted procedure for each step of the processing. Care was taken with the b) item since the major problems of the method appear during the calculation of the dispersion curve. Three case studies were presented. This allowed discussing and evaluating in detail the applicability, advantages and disadvantages of the method. The first case, classified as good, the dispersion curves, calculated from different geophone spacing, overlapped in a certain frequency window. In the second study, classified as intermediate quality, the dispersion curves presented some variations. The third example, classified as bad, the dispersion curves from different geophone spacing did not converge and it was necessary to try a new methodology to generate the dispersion curve of the area. The third step of the method consists in the inversion of the dispersion curve. Several initial models were generated and, after few dozens of iterations, presented the same trend. For the experiments in the USP campus very coincident dispersion curves were obtained and, consequently, a very consistent model was generated. In the UNICAMP campus case study the values agreed well, up to 4 meters of depth, with the crosshole results but diverge for higher depths. In the UNESP campus case study the results diverge completely. It was concluded that the instrument developed was appropriate to perform SASW tests. The automation of the tests is not possible due to the need of a high degree of interpret intervention. It is due mainly to the difficult to generate low frequencies.
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Yang, Ming. "Development and analysis of a multiple beam laser system for measurement of surface vibrations." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/17685.
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Liu, Chuan-Chang. "Design, Analysis and Implementation of Fully-Integrated Millimeter-Wave Coupled-Oscillator Antenna Array." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452240824.
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Shinall, Brian Darnell. "Using surface plasmon resonance spectroscopy to characterize thin composite films." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/10157.
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Retaureau, Ghislain J. "Detection of Surface Corrosion by Ultrasonic Backscattering." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11498.
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Corrosion often occurs in the inner aluminum lining of the HB-53 helicopter external fuel tank, resulting in fuel leaks. This project centers on developing an in-situ ultrasonic inspection technique to detect corroded areas inside the fuel tank. Due to the complexity of the composite structure of the tank, the ultrasonic inspection is carried out from inside the tank using a monostatic backscattering technique. The backscattered field contains information related to the insonified surface properties (surface roughness scales). Numerical predictions are implemented with a simplified model of backscattered intensity (Ogilvy, 1991). Experimental results are obtained on artificially corroded plates, and on the actual fuel tank of the HB-53 helicopter. Signal processing techniques (Envelope Correlation and Inverse Technique) are used to detect corroded surfaces with data obtained with a focused 10 MHz pulsed transducer.
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Silvestri, Lorenzo. "Numerical study of wind-wave interfacial phenomena." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14643/.
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A DNS simulation has been performed in order to study the wind-wave interaction, especially focusing the attention on the interfacial phenomena. The numerical model is founded to reproduce gravity waves generation under the action of a turbulent wind. The VOF (volume of fraction) method is used in order to capture and model the free surface, while the wind is generated by imposing an external pressure gradient. This last choice, in contrast with the usual ways of simulating wind by a moving wall, turned out to be very effective from both the computational and the physical point of view.
The simulation can be described by two fundamental parameters: the friction Reynolds number is about 330 and the wave age is 35. The wave age has been calculated by a spectral analysis of the free surface: through this analysis the wavelength of the main ripple is found to be about 5 cm, while its phase speed results to be 0.7 m/s. This wavelength and phase speed seems reasonable by comparing it with experiments and observations.
The turbulent boundary layer is significantly modified by waves in a way that resembles rough turbulence. The spatially and time averaged mean velocity profile is affected by the roughness of waves as much as the fluctuating field. In this study a sea surface roughness of 0.017 is founded by observing the behaviour of the wind close to the free surface. This similarity between a rough wall and waves, can be relevant for modelling flows over wavy walls or predicting wind and wave currents, especially in the Geophysical fluid dynamic field.
Finally, the Phillips mechanism (turbulent pressure fluctuations along the free surface) and the sheltering mechanism (positive and negative pressure fluctuations respectively in front and on the leeside of the wave due to the boundary layer separation) have been clearly observed.
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Hicks, Malcolm Andrew. "Geotechnical Investigations of Wind Turbine Foundations Using Multichannel Analysis of Surface Waves (MASW)." Thesis, University of Canterbury. Geological Sciences, 2011. http://hdl.handle.net/10092/6519.
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The geophysical technique known as Multichannel Analysis of Surface Waves, or MASW (Park et al., 1999) is a relatively new seismic characterisation method which utilises Rayleigh waves propagation. With MASW, the frequency dependent, planar travelling Rayleigh waves are created by a seismic source and then measured by an array of geophone receivers. The recorded data is used to image characteristics of the subsurface.
This thesis explains how MASW was used as a geotechnical investigation tool on windfarms in the lower North Island, New Zealand, to determine the stiffness of the subsurface at each wind turbine site. Shear‐wave velocity (VS) profiles at each site were determined through the processing of the MASW data, which were then used to determine physical properties of the underlying, weathered greywacke.
The primary research site, the Te Rere Hau Windfarm in the Tararua Ranges of the North Island, is situated within the Esk Head Belt of Torlesse greywacke (Lee & Begg, 2002). Due to the high level of tectonic activity in the area, along with the high rates of weathering, the greywacke material onsite is highly fractured and weathering grades vary significantly, both vertically and laterally. MASW was performed to characterise the physical properties at each turbine site through the weathering profile. The final dataset included 1‐dimensional MASW shear‐wave evaluations from 100 turbine sites. In addition, Poisson’s ratio and density values were characterised through the weathering profile for the weathered greywacke. During the geotechnical foundation design at the Te Rere Hau Windfarm site, a method of converting shear wave velocity profiles was utilised. MASW surveying was used to determine VS profiles with depth, which were converted to elastic modulus profiles, with the input parameters of Poisson’s ratio and density.
This study focuses on refining and improving the current method used for calculating elastic modulus values from shear‐wave velocities, primarily by improving the accuracy of the input parameters used in the calculation.
Through the analysis of both geotechnical and geophysical data, the significant influence of overburden pressure, or depth, on the shear wave velocity was identified. Through each of the weathering grades, there was a non‐linear increase in shear wave velocity with depth. This highlights the need for overburden pressure conditions to be considered before assigning characteristic shear wave velocity values to different lithologies.
Further to the dataset analysis of geotechnical and geophysical information, a multiple variant non‐linear regression analysis was performed on the three variables of shear wave velocity, depth and weathering grade. This produced a predictive equation for determining shear wave
velocity within the Esk Head belt ‘greywacke’ when depth and weathering data are known. If the insitu geological conditions are not comparable to that of the windfarm sites in this study, a set of guidelines have been developed, detailing the most efficient and cost effective method of
using MASW surveying to calculate the elastic modulus through the depth profile of an
investigation site.
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Jamali, Mirmosadegh. "Aymptotic analysis of interaction of a surface wave with two internal waves." Thesis, 2000. http://hdl.handle.net/2429/10441.
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The motion of a surface wave in a two-layer fluid can lead to generation of two internal
waves through a resonance mechanism under certain circumstances. Two subjects related to
this interaction are studied theoretically here. These are the behavior of the waves in threedimensional
interaction when the density difference between the two layers is small, and the
effect of a diffuse interface on the interaction.
In the first study, the three-dimensional interaction of a surface wave with two oblique
internal waves is analyzed asymptotically in an attempt to obtain simple approximate
expressions for the growth rate as well as the kinematic properties of the internal waves. The
non-dimensional density difference 8 is taken as a perturbation parameter, and the first few
terms in the expansions of the desired quantities are derived. The results indicate that the
internal-wave numbers are O(δ⁻¹), one order larger than the surface-wave number. Also, at
leading order the internal wave frequencies are equal to ω₀/2, and the directions of the two
internal waves differ by 180 . An important finding is that an immediate consequence of
taking δ as a small parameter is that the internal waves become deep-water waves in both
layers. According to the asymptotic analysis, the interaction coefficients α₁ and α₂ are 0(l)
and are equal at leading order.
The second study concerns the generation of two internal waves by a surface wave on a
thin diffuse interface. As in the first analysis, the non-dimensional density difference δ is
taken as a small perturbation parameter. In addition, it is assumed that the diffuse interface is
small compared to the internal wavelengths by taking it to be order δ². A three-layer system
admits two modes of internal wave motion, and similarly two modes of interaction are found
possible through the analysis. These are interaction between a surface wave and two first
mode internal waves, and interaction between a surface wave, a first-mode and a secondmode
internal wave. It is shown that, contrary to the first mode, in the second mode of
interaction the waves are not sub-harmonic to the surface wave. An important finding is that
the growth rate in the first mode is higher than in the second. This implies that in a real
situation the interaction between a surface wave and two first-mode internal waves has more
chance to occur.
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Schorer, Jan. "Theoretical evaluation, analysis and design of surface-mounted waveguide (SMW) components for on-substrate integrated microwave applications." Thesis, 2016. http://hdl.handle.net/1828/7098.
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This dissertation presents the research on a novel combination of well proven concepts for passive electromagnetic wave-guiding components. The goal of this work is to overcome and minimize losses occurring in frequency-selective structures. The work aims to contribute to an improvement in the application of conventional and Substrate Integrated Waveguide (SIW). It is proposed to mount conventional waveguide structures on the surface of printed circuit boards containing substrate integrated waveguides. The crossover technology is referred to as Surface Mounted Waveguide (SMW). Theoretical investigations are performed, proving the validity and superiority of the proposed structure focusing on the elimination of losses, while maintaining low space consumption and printed circuit board technology compatible manufacturing processes. Additionally, a mode matching technique is developed and successfully applied to prototype such components. The validation of this method reveals superior computational speed when compared to commercial available electromagnetic field solvers. The proposed structures are validated by measurements of several prototypes, including coupled SMW resonator filters, combined SMW and SIW resonator filters, a SMW triple-layer diplexer and single individual SMW resonator filters. The experimental verification shows good agreement between theory and measurements.
Moreover, the comparison to other technologies proves the superiority of the proposed structures.Graduate
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Naskar, Tarun. "Testing of Ground Subsurface using Spectral and Multichannel Analysis of Surface Waves." Thesis, 2017. http://etd.iisc.ernet.in/2005/3775.
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Two surface wave testing methods, namely, (i) the spectral analysis of surface waves (SASW), and (ii) the multi-channel analysis of surface waves (MASW), form non-destructive and non-intrusive techniques for predicting the shear wave velocity profile of different layers of ground and pavement. These field testing tools are based on the dispersive characteristics of Rayleigh waves, that is, different frequency components of the surface wave travel at different velocities in layered media. The SASW and MASW testing procedure basically comprises of three different components: (i) field measurements by employing geophones/accelerometers, (ii) generating dispersion plots, and (iii) predicting the shear wave velocity profile based on an inversion analysis.
For generating the field dispersion plot, the complexities involved while doing the phase unwrapping calculations for the SASW technique, while performing the spectral calculations on the basis of two receivers’ data, makes it difficult to automate since it requires frequent manual judgment. In the present thesis, a new method, based on the sliding Fourier transform, has been introduced. The proposed method has been noted to be quite accurate, computationally economical and it generally overcomes the difficulties associated with the unwrapping of the phase difference between the two sensors’ data. In this approach, the unwrapping of the phase can be carried out without any manual intervention. As a result, an automation of the entire computational process to generate the dispersion plot becomes feasible. The method has been thoroughly validated by including a number of examples on the basis of surface wave field tests as well as synthetic test data.
While obtaining the dispersion image by using the MASW method, three different transformation techniques, namely, (i) the Park’s wavefield transform, (ii) the frequency (f) -wavenumber ( ) transform and (iii) the time intercept ( -phase slowness (p) transform have been utilized for generating the multimodal dispersion plots. The performance of these three different methods has been assessed by using synthetic as well as field data records obtained from a ground site by means of 48 geophones. Two-dimensional as well as three-dimensional dispersion plots were generated. The Park’s wavefield transformation method has been found to be especially advantageous since it neither requires a very high sampling rate nor an inclusion of the zero padding of the data in a wavenumber (distance) domain.
In the case of an irregular dispersive media, a proper analysis of the higher modes existing in the dispersion plots becomes essential for predicting the shear wave velocity profile of ground on the basis of surface wave tests. In such cases, the establishment of the predominant mode becomes quite significant. In the current investigation for Rayleigh wave propagation, the predominant mode has been computed by maximizing the normalized vertical displacements along the free surface. Eigenvectors computed from the thin layer approach (TLM) approach are analyzed to predict the corresponding predominant mode. It is noted that the establishment of the predominant mode becomes quite important where only two to six sensors are employed and the governing (predominant) modal dispersion curve is usually observed rather than several multiple modes which can otherwise be identified by using around 24 to 48 multiple sensors.
By using the TLM, it is, however, not possible to account for the exact contribution of the elastic half space in the dynamic stiffness matrix (DSM) approach. A method is suggested to incorporate the exact contribution of the elastic half space in the TLM. The numerical formulation is finally framed as a quadratic eigenvalue problem which can be easily solved by using the subroutine polyeig in MATLAB. The dispersion plots were generated for several chosen different ground profiles. The numerical results were found to match quite well with the data available from literature.
In order to address all the three different aspects of SASW and MASW techniques, a series of field tests were performed on five different ground sites. The ground vibrations were induced by means of (i) a 65 kg mass dropped freely from a height of 5 m, and (ii) by using a 20 pound sledge hammer. It was found that by using a 65 kg mass dropped from a height of 5 m, for stiffer sites, ground exploration becomes feasible even up to a depth of 50-80 m whereas for the softer sites the exploration depth is reduced to about 30 m. By using a 20 lb sledge hammer, the exploration depth is restricted to only 8-10 m due to its low impact energy.
Overall, it is expected that the work reported in the thesis will furnish useful guidelines for (i) performing the SASW and MASW field tests, (ii) generating dispersion plots/images, and (iii) predicting the shear wave velocity profile of the site based on an inversion analysis.
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Yen, Ta-Lung, and 嚴大龍. "Surface Wave Dispersion Analysis of Planar Corrugated Surfaces by Asymptotic Corrugations Boundary Conditions." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/13358769963814126866.
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碩士國立交通大學
電信工程研究所
100
Electromagnetic bandgap (EBG) structures had been widely investigated in literature in recent years, and the planar corrugated surface is one of them. In studying such structures, the dispersion and reflection phase diagrams are two of the most important characteristics. In this thesis, we will study how to retrieve the dispersion diagram of the corrugations accurately and rapidly. By an asymptotic method and the use of classical vector potentials, we can derive the characteristic equation, thereby obtaining the surface-wave dispersion diagram. To demonstrate its accuracy and quickness, the method we proposed will be compared to a full wave simulator and the transverse resonance technique (TRT), the latter being a traditional method for getting the dispersion diagram. Finally, we fabricated a corrugation, and measure its scattering parameters to indirectly verify the dispersion diagram obtained by the method we proposed. In traditional studies of corrugations, surface-wave propagations along only the two principal directions are considered, pertaining to the so-called soft and hard surfaces. In this thesis, we will further explore the situation whereby the wave propagates obliquely on the surface. By observing the dispersion diagram of the corrugations, we will notice its difference compared to normal periodic structures, and then explain the wave propagation properties on the corrugation surface. At the measurement stage, it is difficult to get the dispersion diagram directly, and usually the scattering parameters are used to explain the width and position in the frequency spectrum of the bandgaps. In the thesis, the relationship of the scattering parameters and wavenumbers are discussed, so that the measured scattering parameters can be transformed to the dispersion diagram effectively. So far we succeed in transforming the simulated scattering parameters to the dispersion diagram, and we hope this method can be applied to measured data in the future.
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Lee, Morjin, and 李昇峻. "A Surface Wave Analysis Technique for Crack Sizing." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/46571959700782239259.
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碩士大葉大學
電機工程學系碩士班
92
In this study, a method of surface wave inspection is approached to detect an object’s surface condition. Surface wave inspection is performed by emitting ultrasonic waves along the surface of the object, and then according to the acquired property values of wave reflection, to determine whether if there is an existence of abnormal surface condition, for example, a fissure.During the employment of ultrasonic wave aiming to detect possible fissure, multiple reflective signals are returned and recorded. By analyzing these signals, formation of path composition by various waves is then formulated. Furthermore, these signals are proved to be a useful tool to double check for accuracy of the fissure height. By combining the results drawn from the above analyses, mean and standard deviation for multiple estimates are derived, as well as the confidence level. In conclusion, it follows from what has been said that, accurate fissure height derived from surface wave inspection is an applicable index for equipment safety and maintenance analyses.
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Ming-Tien, Yang, and 楊明典. "Design and Analysis of Surface Acoustic Wave Oscillator." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/76897187795406565500.
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碩士義守大學
電機工程學系
89
A surface acoustic wave (SAW) oscillator consists of a high quality factor SAW resonator and an active circuit. A SAW resonator composes of Interdigital Transducers (IDT) and reflectors fabricated on a piezoelectric substrate. The properties of substrate, the modes of wave propagation, the geometry of IDT and reflecting grating determine the characteristics of a SAW resonator. In this thesis, the Mason’s equivalent circuit was applied to model the IDT. The Coupling of Modes (COM) was used for reflector. The cascade model and the theory of multiport connection were applied to simulate the frequency response. The ST-X quartz was chosen as the substrate for the reason of stable temperature coefficient in the room temperature. One-port SAW resonators were discussed in detail. First of all, self-developed program was used to simulate the frequency response and input impedance of the resonator. The simulating’s results were then put in the RF CAD design tool to design an oscillator. Finally, the performance of resonators and oscillators were compared with experimentation.