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Dissertationen zum Thema „Wave mechanics“
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1
Cornett, Andrew Malcolm. „Short-crested wave forces on a rigid segmented vertical cylinder“. Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26688.
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This thesis investigates water particle kinematics and the wave forces exerted on a slender rigid vertical cylinder in regular bidirectional
wave fields. The instrumented portion of this cylinder is partitioned into nine independent segments enabling measurement of the vertical profile of hydrodynamic loading both in-line and transverse to the direction of wave propagation. Experiments conducted at the Hydraulics Laboratory of the National Research Council in Ottawa are described and some results are compared with the predictions of a wave force model based on the Morison equation and linear fluid kinematics. The influence of the crossing angle between the two wave components on the forces experienced by the column is determined.
These experiments consider short-crested wave behavior in intermediate
and deep water resulting from the interaction of two identical regular wave trains crossing at angles of 30, 60 and 90 degrees. The limit corresponding to unidirectional monochromatic waves is also investigated to provide a reference condition for comparison with the short-crested results. Conditions at the location of maximum short-crested wave height are of primary interest, however, forces at locations between the anti-node and node of the flow are also examined. In all, water surface elevations, flow velocities, and wave forces were measured in 24 short-crested and 8 different long-crested wave conditions
spanning the range of Keulegan-Carpenter number between 4 and 24.
The results of this study confirm the findings of previous researchers that short -crested waves with a certain period travel faster and rise higher before breaking than do their long-crested counterparts, but that in-line wave forces are not necessarily increased.
Lift force maxima equal to half the maximum in-line force were measured; these forces can contribute significantly to the magnitude and direction of the total force resultant.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
2
Judd, Thomas Edward. „The wave mechanics of cold atoms“. Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490985.
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This thesis presents theoretical investigations on a range of topics in cold atom physics, primarily by means of wave mechanical simulations, implemented on High-Performance computers. Two particular concerns are the interaction of Bose-Einstein condensates with microfabricated surfaces, and the behaviour of strongly interacting Fermi atoms. In the course of this work. we have developed new theoretical models and computational techniques to handle problems which were beyond the scope of previous calculations.
3
Kil, Hyun-Gwon. „Propagation of elastic waves on thin-walled circular cylinders“. Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/15967.
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4
Jafari, Alireza. „Analysis and Prediction of Wave Transformation from Offshore into the Surfzone under Storm Condition“. Thesis, Griffith University, 2013. http://hdl.handle.net/10072/366745.
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Surfzone wave transformation under storm conditions is investigated through field and laboratory
measurements in this study. The observations have been used to examine currently available
models of wave energy dissipation.
Detailed field data has been collected by means of a novel method which was first introduced by
Nielsen (1988). This method has been utilised through a common program between Griffith
University and The University of Queensland at The Spit on the Gold Coast in Southeast
Queensland. The facility primarily consists of a manometer tube array with 12 different manometer
tube lengths varying from 60 m to 500 m offshore and a concrete manhole excavated into the dune
system to house the monitoring station. Accordingly, this system has enabled the monitoring of a
detailed wave height profile across the surfzone under any conditions from the safety of the
“bunker” on land.
The findings of new laboratory experiments on the frequency response of the semi-rigid
manometer tubes are also presented which extend and improve upon the previous work of Nielsen
et al. (1993). Testing was conducted over a range of frequencies (0.0067 Hz< f <2 Hz) and tube
lengths (10 m< L <900 m). New frequency response factors are determined by fitting the semiempirical
gain function of Nielsen et al. (1993) to the observed gain data. As a result, new
predictive formulas for the empirical coefficients as a function of tube parameters are provided in
this study.
Wave induced pore pressure in the surfzone seabed is investigated based on the recorded field data.
Two well-known models, i.e. Hsu and Jeng (1994) and Sleath (1970), are assessed against the
field measurements. The findings validate the accuracy of the models and indicate that the extent of
energy dissipation due to the overlying sand is less than 5% and depends on the incident wave
length.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text
5
Puckett, Anthony. „An Experimental and Theoretical Investigation fo Axially Symmetric Wave Propagation In Thick Cylindrical Waveguides“. Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/PuckettA2004.pdf.
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6
Mudge, Damien. „High power scalable diode-laser-pumped CW Nd:YAG laser using a stable-unstable resonator“. Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phm9438.pdf.
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7
Bell, James Andrew, und andrew bell@anu edu au. „The Underwater Piano: A Resonance Theory of Cochlear Mechanics“. The Australian National University. Research School of Biological Sciences, 2006. http://thesis.anu.edu.au./public/adt-ANU20080706.141018.
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This thesis takes a fresh approach to cochlear mechanics. Over the last
quarter of a century, we have learnt that the cochlea is active and highly tuned,
observations suggesting that something may be resonating. Rather than accepting the standard traveling wave interpretation, here I investigate whether a resonance theory of some kind can be applied to this remarkable behaviour.¶
A historical survey of resonance theories is first conducted, and advantages
and drawbacks examined. A corresponding look at the traveling wave theory
includes a listing of its short-comings.¶
A new model of the cochlea is put forward that exhibits inherently high
tuning. The surface acoustic wave (SAW) model suggests that the three rows of outer hair cells (OHCs) interact in a similar way to the interdigital transducers of an
electronic SAW device. Analytic equations are developed to describe the conjectured interactions between rows of active OHCs in which each cell is treated as a point source of expanding wavefronts. Motion of a cell launches a wave that is sensed by the stereocilia of neighbouring cells, producing positive feedback. Numerical calculations confirm that this arrangement provides sharp tuning when the feedback gain is set just below oscillation threshold.¶
A major requirement of the SAW model is that the waves carrying the feedback have slow speed (5-200 mm/s) and high dispersion. A wave type with the
required properties is identified - a symmetric Lloyd-Redwood wave (or squirting wave) - and the physical properties of the organ of Corti are shown to well match those required by theory.¶
The squirting wave mechanism may provide a second filter for a primary
traveling wave stimulus, or stand-alone tuning in a pure resonance model. In both, cyclic activity of squirting waves leads to standing waves, and this provides a physical rendering of the cochlear amplifier.
In keeping with pure resonance, this thesis proposes that OHCs react to the
fast pressure wave rather than to bending of stereocilia induced by a traveling wave. Investigation of literature on OHC ultrastructure reveals anatomical features consistent with them being pressure detectors: they possess a cuticular pore (a small compliant spot in an otherwise rigid cell body) and a spherical body within (Hensens
body) that could be compressible. I conclude that OHCs are dual detectors, sensing displacement at high intensities and pressure at low. Thus, the conventional traveling wave could operate at high levels and resonance at levels dominated by the cochlear
amplifier. ¶
The latter picture accords with the description due to Gold (1987) that the cochlea is an underwater piano - a bank of strings that are highly tuned despite immersion in liquid.¶
An autocorrelation analysis of the distinctive outer hair cell geometry shows
trends that support the SAW model. In particular, it explains why maximum
distortion occurs at a ratio of the two primaries of about 1.2. This ratio also produces near-integer ratios in certain hair-cell alignments, suggesting that music may have a cochlear basis.¶
The thesis concludes with an evaluation and proposals to experimentally test
its validity.
8
Hosoglu, Selcuk. „Cellular automata an approach to wave propagation and fracture mechanics problems“. Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FHosoglu.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Young W. Kwon. "December 2006." Includes bibliographical references (p. 63-64). Also available in print.
9
Thomson, Edward Andrew. „Schrodinger wave-mechanics and large scale structure“. Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2976/.
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In recent years various authors have developed a new numerical approach to cosmological simulations that formulates the equations describing large scale structure (LSS) formation within a quantum mechanical framework. This method couples the Schrodinger and Poisson equations. Previously, work has evolved mainly along two different strands of thought: (1) solving the full system of equations as Widrow & Kaiser attempted, (2) as an approximation to the full set of equations (the Free Particle Approximation developed by Coles, Spencer and Short). It has been suggested that this approach can be considered in two ways: (1) as a purely classical system that includes more physics than just gravity, or (2) as the representation of a dark matter field, perhaps an Axion field, where the de Broglie wavelength of the particles is large. In the quasi-linear regime, the Free Particle Approximation (FPA) is amenable to exact solution via standard techniques from the quantum mechanics literature. However, this method breaks down in the fully non-linear regime when shell crossing occurs (confer the Zel'dovich approximation). The first eighteen months of my PhD involved investigating the performance of illustrative 1-D and 3-D ``toy" models, as well as a test against the 3-D code Hydra. Much of this work is a reproduction of the work of Short, and I was able to verify and confirm his results. As an extension to his work I introduced a way of calculating the velocity via the probability current rather than using a phase unwrapping technique. Using the probability current deals directly with the wavefunction and provides a faster method of calculation in three dimensions. After working on the FPA I went on to develop a cosmological code that did not approximate the Schrodinger-Poisson system. The final code considered the full Schrodinger equation with the inclusion of a self-consistent gravitational potential via the Poisson equation. This method follows on from Widrow & Kaiser but extends their method from 2D to 3D, it includes periodic boundary conditions, and cosmological expansion. Widrow & Kaiser provided expansion via a change of variables in their Schrodinger equation; however, this was specific only to the Einstein-de Sitter model. In this thesis I provide a generalization of that approach which works for any flat universe that obeys the Robertson-Walker metric. In this thesis I aim to provide a comprehensive review of the FPA and of the Widrow-Kaiser method. I hope this work serves as an easy first point of contact to the wave-mechanical approach to LSS and that this work also serves as a solid reference point for all future research in this new field.
10
Coughtrie, David James. „Gaussian wave packets for quantum statistical mechanics“. Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682558.
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Thermal (canonical) condensed-phase systems are of considerable interest in computational science, and include for example reactions in solution. Time-independent properties of these systems include free energies and thermally averaged geometries - time-dependent properties include correlation functions and thermal reaction rates. Accounting for quantum effects in such simulations remains a considerable challenge, especially for large systems, due to the quantum nature and high dimensionality of the phase space. Additionally time-dependent properties require treatment of quantum dynamics. Most current methods rely on semi-classical trajectories, path integrals or imaginary-time propagation of wave packets. Trajectory based approaches use continuous phase-space trajectories, similar to classical molecular dynamics, but lack a direct link to a wave packet and so the time-dependent schrodinger equation. Imaginary time propagation methods retain the wave packet, however the imaginary-time trajectory cannot be used as an approximation for real-time dynamics. We present a new approach that combines aspects of both. Using a generalisation of the coherent-state basis allows for mapping of the quantum canonical statistical average onto a phase-space average of the centre and width of thawed Gaussian wave packets. An approximate phase-space density that is exact in the low-temperature harmonic limit, and is a direct function of the phase space is proposed, defining the Gaussian statistical average. A novel Nose-Hoover looped chain thermostat is developed to generate the Gaussian statistical average via the ergodic principle, in conjunction with variational thawed Gaussian wave-packet dynamics. Numerical tests are performed on simple model systems, including quartic bond stretching modes and a double well potential. The Gaussian statistical average is found to be accurate to around 10% for geometric properties at room temperature, but gives energies two to three times too large. An approach to correct the Gaussian statistical average and ensure classical statistics is retrieved at high temperature is then derived, called the switched statistical average. This involves transitioning the potential surface upon which the Gaussian wave packet propagates, and the system property being averaged. Switching functions designed to perform these tasks are derived and tested on model systems. Bond lengths and their uncertainties calculated using the switched statistical average were found to be accurate to within 1% relative to exact results, and similarly for energies. The switched statistical average, calculated with Nose- Hoover looped chain thermostatted Gaussian dynamics, forms a new platform for evaluating statistical properties of quantum condensed-phase systems using an explicit real-time wave packet, whilst retaining appealing features of trajectory based approaches.
11
Poon, Chun-Kin. „Numerical simulation of coupled long wave-short wave system with a mismatch in group velocities“. Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B35381334.
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12
Kowalski, Benjamin John. „Transient SH-Wave Interaction with a Cohesive Interface“. The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417706326.
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13
Lennon, Francis. „Shock wave propagation in water“. Thesis, Manchester Metropolitan University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240559.
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14
Smith, Brian John. „Photon wave mechanics and experimental quantum state determination /“. view abstract or download file of text, 2007. http://proquest.umi.com/pqdweb?did=1324388721&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2007.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 231-242). Also available for download via the World Wide Web; free to University of Oregon users.
15
Weaver, P. M. „Shock wave interactions with aqueous foams“. Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292434.
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16
Lee, Man-yip Mark, und 李文業. „Wave transformation due to vertical barriers in fluids“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B29812781.
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17
Lee, Man-yip Mark. „Wave transformation due to vertical barriers in fluids /“. Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19669264.
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18
Poon, Chun-Kin, und 潘俊健. „Numerical simulation of coupled long wave-short wave system with a mismatch in group velocities“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B35381334.
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19
Shaarawi, Amr Mohamed. „Nondispersive wave packets“. Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54417.
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In this work, nondispersive wave packet solutions to linear partial differential equations are investigated. These solutions are characterized by infinite energy content; otherwise, they are continuous, nonsingular and propagate in free space without spreading out. Examples of such solutions are Berry and Balazs’ Airy packet, MacKinnon’s wave packet and Brittingham’s Focus Wave Mode (FWM). It is demonstrated in this thesis that the infinite energy content is not a basic problem per se and that it can be dealt with in two distinct ways. First these wave packets can be used as bases to construct highly localized, slowly decaying, time-limited pulsed solutions. In the case of the FWMs, this path leads to the formulation of the bidirectional representation, a technique that provides the most natural basis for synthesizing Brittingham-like solutions. This representation is used to derive new exact solutions to the 3-D scalar wave equation. It is also applied to problems involving boundaries, in particular to the propagation of a localized pulse in an infinite acoustic waveguide and to the launch ability of such a pulse from the opening of a semi-infinite waveguide. The second approach in dealing with the infinite energy content utilizes the bump-like structure of nondispersive solutions. With an appropriate choice of parameters, these bump fields have very large amplitudes around the centers, in comparison to their tails. In particular, the FWM solutions are used to model massless particles and are capable of providing an interesting interpretation to the results of Young’s two slit experiment and to the wave-particle duality of light. The bidirectional representation provides, also, a systematic way of deriving packet solutions to the Klein-Gordon, the Schrodinger and the Dirac equations. Nondispersive solutions of the former two equations are compared to previously derived ones, e.g., the Airy packet and MacKinnon's wave packet.Ph. D.
20
Ayanle, Hassan Shiekh-Ali. „Mode competition in cross-waves“. Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184872.
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Cross-waves generated by an oscillating wavemaker in a rectangular wave tank are examined when two or more modes are simultaneously unstable. The partial differential equations governing the evolution of the complex amplitude of inviscid cross-waves are shown to be two coupled nonlinear Schrodinger equations with transverse modulations. Energy dissipation in the system is taken into account by the inclusion of a linear viscous damping term into the amplitude equations. A linearized stability analysis is performed on these equations to determine the critical modes, the growth rates and the stability curves. A center manifold analysis is used to reduce the PDE's to a system of ODE's in the neighborhood of a codimension two point where two adjacent spanwise modes are simultaneously nearly marginal. Four possible steady states of the system are found, one of which is a mixed mode state. A Hopf bifurcation from the mixed mode is predicted for a certain region of the parameter plane, suggesting the possibility of energy interchange between the two modes. The stability of the Hopf bifurcation is determined by studying a fifth order problem, where the quintic contributions come from the higher modes as well as the perturbations of damping and detuning.
21
Li, Dongli. „Computational and experimental study of shock wave interactions with cells“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:38beffe8-06c9-4b49-89f8-f5318c527800.
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This thesis presents a combined numerical and experimental study on the response of kidney cells to shock waves. The motivation was to develop a mechanistic model of cell deformation in order to improve the clinical use of shock waves, by either enhancing their therapeutic action against target cells or minimising their impact on healthy cells. An ultra-high speed camera was used to visualise individual cells, embedded in tissue-mimicking gel, in order to measure their deformation when subject to a shock wave from a clinical shock wave source. Advanced image processing was employed to extract the contour of the cell from the images. The evolution of the observed cell contour revealed a relatively small deformation during the compressional phase and a much larger deformation during the tensile phases of a shock wave. The experimental observations were captured by a numerical model which describes the volumetric cell response with a bilinear Equation of State and the deviatoric cell response with a viscoelastic framework. Experiments using human kidney cancer cells (CAKI-2) and noncancerous kidney cells (HRE and HK-2) were compared to the model in order to determine their mechanical properties. The differences between cancerous and noncancerous cells were exploited to demonstrate a design process by which shock waves may be able to improve the specificity on targeted cancer cells while having minimal effect on normal cells. The cell response to shock waves was studied in a more biophysically realistic environment to include influence of cell size, shape and orientation, and the presence of neighbouring cells. The most significant difference was predicted when cells were in a cluster in which case the presence of neighbouring cells resulted in a four-fold increase on the von Mises stress and the membrane strain. Finally the numerical model was extended to capture the effect of cell damage using one of two paradigms. In the first paradigm the model captured microdamage during one shock wave but then assumed that the cell recovered by the time the next shock wave arrived. The second model allowed microdamage to accumulate with increasing number of shock waves. These models may be able to explain the strong effect that shock wave loading rate has on tissue damage. In conclusion a validated numerical model has been developed which provides a mechanistic understanding of how cells respond to shock waves. The model has application in suggesting improved strategies for current uses of shock waves, e.g., lithotripsy, as well as opening up new indications such as cancer treatment.
22
Masiello, David John. „On the canonical formulation of electrodynamics and wave mechanics“. [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004333.
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23
Aldridge, Christopher John. „Density-wave oscillations in two-phase flows“. Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260741.
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24
Lee-Young, James S. „Bed mechanics in combined steady and oscillatory flow“. Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276189.
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25
Leonard, Kevin Raymond. „Ultrasonic guided wave tomography of pipes: A development of new techniques for the nondestructive evaluation of cylindrical geometries and guided wave multi-mode analysis“. W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1539616737.
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This dissertation concentrates on the development of two new tomographic techniques that enable wide-area inspection of pipe-like structures. By envisioning a pipe as a plate wrapped around upon itself, the previous Lamb Wave Tomography (LWT) techniques are adapted to cylindrical structures. Helical Ultrasound Tomography (HUT) uses Lamb-like guided wave modes transmitted and received by two circumferential arrays in a single crosshole geometry. Meridional Ultrasound Tomography (MUT) creates the same crosshole geometry with a linear array of transducers along the axis of the cylinder. However, even though these new scanning geometries are similar to plates, additional complexities arise because they are cylindrical structures. First, because it is a single crosshole geometry, the wave vector coverage is poorer than in the full LWT system. Second, since waves can travel in both directions around the circumference of the pipe, modes can also constructively and destructively interfere with each other. These complexities necessitate improved signal processing algorithms to produce accurate and unambiguous tomographic reconstructions. Consequently, this work also describes a new algorithm for improving the extraction of multi-mode arrivals from guided wave signals. Previous work has relied solely on the first arriving mode for the time-of-flight measurements. In order to improve the LWT, HUT and MUT systems reconstructions, improved signal processing methods are needed to extract information about the arrival times of the later arriving modes. Because each mode has different through-thickness displacement values, they are sensitive to different types of flaws, and the information gained from the multi-mode analysis improves understanding of the structural integrity of the inspected material. Both tomographic frequency compounding and mode sorting algorithms are introduced. It is also shown that each of these methods improve the reconstructed images both qualitatively and quantitatively.
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Crossley, Peter Simon. „On spectral methods for shock wave calculations“. Thesis, Manchester Metropolitan University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361577.
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Dominy, Robert Gerald. „Rarefied hypersonic shock wave and blunt body flows“. Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47034.
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Bowman, S. B. „Mathematical aspects of wave motions in stratified fluids“. Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370240.
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Brewer, Cerian Sara. „Wave propagation and complexity : a transfer operator approach“. Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/53874/.
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We consider wave dynamics on networks of beams/plates coupled along 1D joints. This set-up can be mapped onto the wave dynamics on graphs and is introduced here as an extension to generic wave graph systems such as studied in quantum graph theory. In particular, we consider the elastic case which entails different mode-types (bending, longitudinal and shear waves) which propagate at different wave speeds and can mix at interfaces. The bending modes are described in terms of 4th order equations introducing an always evanescent wave component into the system. The scattering matrices describing reflection/transmission at interfaces thus contain both propagating (open) and evanescent (closed) channels. As a result, the scattering matrices and the transfer operator are no longer unitary; the consequences of this non-unitaritiness on secular equations and the Weyl law will be discussed. The findings are of relevance to describing complex engineering structures. We note that existing methods used to solve wave propagation problems often provide average solutions. As well as the aforementioned extension of quantum graphs to the elastic case, we consider fluctuations about this mean solution. This is done by propagating correlation functions on graphs; it turns out that this provides a suitable wave analogue of ray methods. This approach allows us to investigate response statistics and distributions; these properties are of real significance in, for example, the automotive industry.
30
Rubbo, Louis Joseph. „Gravitational wave astronomy using spaceborne detectors“. Diss., Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/rubbo/RubboL0805.pdf.
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31
Kwok, Loong-Piu. „Viscous cross-waves: Stability and bifurcation“. Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184441.
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In the first part of this thesis, the nonlinear Schrodinger equation for inviscid cross-waves near onset is found to be modified by viscous linear damping and detuning. The accompanying boundary condition at the wavemaker is also modified by damping from the wavemaker meniscus. The relative contributions of the free-surface, sidewalls, bottom, and wavemaker viscous boundary layers are computed. It is shown that viscous dissipation due to the wavemaker meniscus breaks the symmetry of the neutral curve. In the second part, existence and stability of steady solutions to the nonlinear Schrodinger equation are examined numerically. It is found that at forcing frequency above a critical value, f(c), only one solution exists. However, below f(c), multiple steady solutions, the number of which is determined, are possible. This multiplicity leads to hysteresis for f < f(c), in agreement with observation. A Hopf bifurcation of the steady solutions is found. This bifurcation is compared with the transition from unmodulated to periodically modulated cross-waves observed experimentally.
32
Petch, Jason Charles. „Resonant four-wave mixing in krypton“. Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243502.
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33
Pack, Jeong-Ki. „A wave-kinetic numerical method for the propagation of optical waves“. Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104527.
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34
Jiang, Feng. „The development of linear wave packets in unbounded shear flows“. Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385425.
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35
Dong, Xiaobo. „Characterization of soil behavior using electromagnetic wave-based technique /“. View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20DONG.
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McKeon, James Christopher P. „Tomography applied to Lamb wave contact scanning nondestructive evaluation“. W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539623370.
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The aging world-wide aviation fleet requires methods for accurately predicting the presence of structural flaws that compromise airworthiness in aircraft structures. Nondestructive Evaluation (NDE) provides the means to assess these structures quickly, quantitatively, and noninvasively. Ultrasonic guided waves, Lamb waves, are useful for evaluating the plate and shell structures common in aerospace applications. The amplitude and time-of-flight of Lamb waves depend on the material properties and thickness of a medium, and so they can be used to detect any areas of differing thickness or material properties which indicate flaws. By scanning sending and receiving transducers over an aircraft, large sections can be evaluated after a single pass. However, while this technique enables the detection of areas of structural deterioration, it does not allow for the quantification of the extent of that deterioration. Tomographic reconstruction with Lamb waves allows for the accurate reconstruction of the variation of quantities of interest, such as thickness, throughout the investigated region, and it presents the data as a quantitative map. The location, shape, and extent of any flaw region can then be easily extracted from this Tomographic image. Two Lamb wave tomography techniques using Parallel Projection tomography (PPT) and Cross Borehole tomography (CBT), are shown to accurately reconstruct flaws of interest to the aircraft industry. A comparison of the quality of reconstruction and practicality is then made between these two methods, and their limitations are discussed and shown experimentally. Higher order plate theory is used to derive analytical solutions for the scattering of the lowest order symmetric Lamb wave from a circular inclusion, and these solutions are used to explain the scattering effects seen in the Tomographic reconstructions. Finally, the means by which this scattering theory can be used to develop Lamb wave Tomographic algorithms that are more generally applicable in-the-field, is presented.
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Johnston, Rebecca Rae. „Wave-mechanical representations of cosmological fluid dynamics“. Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608280.
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38
Katsidoniotaki, Eirini. „Extreme wave conditions and the impact on wave energy converters“. Licentiate thesis, Uppsala universitet, Elektricitetslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-441043.
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The amount of energy enclosed in ocean waves has been classified as one of the most promising renewable energy sources. Nowadays, different wave energy conversion (WEC) systems are being investigated, but only a few concepts have been operated in a sea environment. One of the largest challenges is to guarantee the offshore survivability of the devices in extreme wave conditions. However, there are large uncertainties related to the prediction of extreme wave loads on WECs. Highfidelity computational fluid dynamics (CFD) simulations can resolve nonlinear hydrodynamic effects associated with wave-structure interaction (WSI). This thesis explores the point-absorbing WEC developed by Uppsala University in extreme wave conditions. The dynamic response and the forces on key components (mooring line, buoy, generator's end-stop spring) of the device are studied and compared. The high nonlinear phenomena accompany the steep and high waves, i.e., breaking behavior, slamming loads can be well-captured by the highfidelity CFD simulations. A commonly used methodology for extreme waves selection, recommended by technical specifications and guidelines, is the environmental contour approach. The 100-year contour in Hamboldt Bay site in California and the 50-year contour in the Dowsing site, outside the UK, are utilized to extract the extreme waves examined in the present thesis. Popular methodologies and data from different sources (observational and hindcast data) are examined for the environmental contour generation providing useful insights. Moreover, two popular approaches for the numerical representation of the extreme sea states, either as focused wave or as equivalent regular wave, were examined and compared. A midfidelity model of the WEC is successfully verified, as the utilization of lower fidelity tools in the design stage would reduce the computational cost. Last but not least, in CFD simulations the computational grid is sensitive in large motions, something often occurs during extreme-WSI. The solution of this issue for the open source CFD software OpenFOAM is provided here.
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Sivapuratharasu, Mithilan. „Inertial effects on thin-film wave structures with imposed surface shear“. Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/42569/.
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This thesis provides a depth-averaged analytical and numerical approach to the mathematical simulation of thin-film flow on a flat inclined plane relevant to gravity-driven flows subject to high surface shear. Motivated by modelling thin-film structures within an industrial context, wave structures are investigated for flows with moderate inertial effects and small film depth aspect ratio e. Approximations are made assuming a Reynolds number, Re ~O (1/e) and a depth-averaged approach used to simplify the governing Navier-Stokes equations. A classical, parallel, Stokes flow is expected in the absence of any wave disturbance based on a local quadratic profile; in this work a generalised approach, which includes inertial effects, is solved. Flow structures are identified and compared with studies for Stokes flow in the limit of negligible inertial effects. Both two-tier and three-tier wave disturbances are constructed to study film profile evolution subject to shear at the free surface. An evaluation of film profiles is given from a paramet- ric study for wave disturbances with increasing film Reynolds number. An evaluation of standing wave and transient film profiles is undertaken which identifies new profiles not previously predicted when inertial effects are neglected. A revised integral boundary layer model incorporating a more general cubic velocity profile is also introduced, to better capture fluid re- circulation associated with a capillary region, and is developed to provide a better understanding of the internal flow dynamics within the thin-film layer. Notably, the wavelength and amplitude of the capillary ripples are analysed. The effect of the boundary conditions between the fluid and the plane is undertaken to simulate slip properties of various substrates over which the fluid may flow. A Navier slip condition is proposed at this boundary and its effect on the wave structure is examined both with and without the inclusion of inertia. The corresponding film dynamics are analysed with increased slip at the fluid-plane boundary and the effect on the wave structures formed are discussed. In a subsequent chapter solitary wave structures are investigated through a study of gravity-driven flow structures as associated with an oscillating inlet. The effects of increasing the film Reynolds number of these flows is evaluated together with an investigation of the stability characteristics relevant to inlet frequency and inertial effects. The effect of surface shear on solitary waves is examined, both as a stabilising and a destabilising factor on perturbations introduced at the inlet. A final section provides an overview of the outcomes from this study.
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Hatifi, Mohamed. „Beyond pilot wave dynamics : non-linearity and non-equilibrium in quantum mechanics“. Thesis, Ecole centrale de Marseille, 2019. http://www.theses.fr/2019ECDM0006.
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La mécanique quantique a modifié notre façon d'interpréter ce que jadis l'on appelait communément "réalité physique". A titre d'exemple, selon l'interprétation standard de la mécanique quantique (dite interprétation probabiliste de Copenhague) les propriétés d’un objet quantique n'ont pas de réalité physique, du moins, pas avant que l’observateur ne les mesure. De plus, tout semble se passer comme s'il y avait un indéterminisme intrinsèque à la dynamique quantique qui ne permettrait pas de prédire avec certitude le résultat d'une mesure. Dès lors, plusieurs interprétations physiques et philosophiques ont vu naissance afin de décrire (notre connaissance de) cette réalité.C'est au cours de la conférence de Solvay en 1927 que Louis de Broglie, un opposant à l'interprétation probabiliste, proposa une solution alternative qui permettait d'une part de restaurer le déterminisme (ainsi que le réalisme) et d'autre part de remettre au premier plan la notion de trajectoire. Par la suite cette théorie fut redécouverte et complétée par David Bohm pour donner naissance à la théorie connue aujourd'hui sous l'appellation de théorie de l'onde pilote. John Bell a dit à propos de cette interprétation : " En 1952, l'impossible a été rendu possible. C'était dans l'article de David Bohm. Bohm a montré explicitement comment une description indéterministe pouvait être transformée en théorie déterministe."Les travaux présentés dans ce manuscrit de thèse s'inscrivent dans la continuité de la vision de de Broglie et consistent en deux parties, chacune d'elles ayant pour but de répondre à une problématique particulière. Dans la première, on considère deux formalismes du type onde pilote, une version déterministe (dynamique de de Broglie-Bohm chapitre 2) ainsi qu'une de ses extensions stochastiques (dynamique de Bohm-Hiley-Nelson chapitre 3). On s'attardera notamment sur l’émergence de la probabilité quantique à partir de ces dynamiques dans l’approche dite du "Quantum Non-Equilibrium". Cette approche permet entre autres de s'affranchir du statut axiomatique de la distribution de probabilité mais aussi de la justifier par des arguments similaires à ceux que l'on retrouve en mécanique statistique. Parmi ces arguments on retrouvera à titre d’exemple la notion d’ergodicité, de chaos, de mixing ainsi que d’autres propriétés qui feront l’objet d’une étude approfondie (chapitre 4). En particulier, l’émergence de l’équilibre s'accompagne d'un processus de relaxation que nous allons caractériser dans chacune de ces dynamiques (dans le chapitre 3 nous dériverons un théorème H qui décrit quantitativement ce processus dans le cas stochastique). Par ailleurs, nous nous efforcerons, dans une approche phénoménologique, d’appliquer ces théories quantiques d'onde pilote à la dynamique macroscopique des gouttes d'huile rebondissantes dans un bain (chapitre 5).La deuxième problématique quant à elle, repose sur une hypothétique généralisation non-linéaire de la mécanique quantique. En particulier, nous considérerons l'équation de Schrodinger Newton comme une première proposition a cette généralisation. Cette équation non-linéaire découle d’une approximation semi-classique de la gravité et a été entre autres proposée par Roger Penrose pour expliquer le collapse de la fonction d’onde. Nous montrerons dans un premier temps comment le programme de la double solution de Louis de Broglie se développe dans ce contexte (chapitre 6). Par la suite nous verrons comment tester cette généralisation non-linéaire par deux propositions expérimentales (chapitre 7). En particulier, l’une de ces propositions nous conduira à étudier des effets de décohérence lors du refroidissement laser (Doppler cooling, chapitre 8). Pour cela on utilisera le modèle de Ghirardi–Rimini–Weber (GRW) comme modèle de décohérence. Ce qui nous permettra par la suite de généraliser les résultats obtenus auparavant par GRW dans leur modèleThe quantum theory has modified the way we interpret what in the past was commonly called "physical reality". As an example, according to the standard interpretation of quantum mechanics (the so-called probabilistic interpretation of Copenhagen), the properties of a quantum object have no physical reality, at least not before the observer measures them. Moreover, everything seems to happen as if there was an intrinsic indeterminism in the quantum dynamics that forbids to predict with certainty the result of a measurement. From then, several physical and philosophical interpretations were born to describe (our knowledge of) this reality.It is in 1927, during the Solvay conference, that Louis de Broglie, an opponent of the probabilistic interpretation, proposed an alternative solution to that problem. He proposed on the one hand to restore determinism (as well as realism) and on the other hand to bring back the notion of trajectory to the foreground. Subsequently this theory was rediscovered and supplemented by David Bohm to give birth to the theory known today as pilot wave theory. John Bell said about this interpretation: " In 1952, I saw the impossible done. It was in papers by David Bohm. Bohm showed explicitly how .... the indeterministic description could be transformed into a deterministic one."The works carried out in this manuscript are in continuity with de Broglie’s view and can be summed up in two main parts, each of them having the aim of answering a particular problem. In the first part, we consider two versions of the pilot wave theory: a deterministic version (de Broglie-Bohm dynamics in chapter 2) as well as one of its stochastic extensions (Bohm-Hiley-Nelson dynamics in chapter 3). In the framework of what is called the "Quantum non-equilibrium" approach we shall see how the quantum probability emerges from those dynamics. This approach makes it possible to get rid of the axiomatic status of the probability distribution but also to justify it by arguments similar to those found in statistical mechanics. Among these arguments we shall for instance find ergodicity, chaos, mixing and other properties that will be studied in depth (chapter 4). In particular, the emergence of the quantum probability is accompanied by a relaxation process that will be characterized for both dynamics (in chapter 3 we derive a strong H-theorem for the stochastic dynamics which quantitatively describes how this process occurs). In addition, we will try in a phenomenological approach to apply these quantum pilot wave theories to the macroscopic dynamics of bouncing oil droplets (chapter 5).The second problem is linked to a hypothetical nonlinear generalization of the quantum theory. In particular, we considered the Schrodinger Newton equation as a first proposal to this generalization. In a nutshell, this non-linear equation derives from a semi-classical approximation of gravity and has been proposed by Roger Penrose among others to explain the collapse of the wave function. We shall first show how it is related to the double solution program of Louis de Broglie (chapter 6). Subsequently we will see how to test this nonlinear generalization by considering two experimental proposals (chapter 7). In particular, one of these proposals will lead us to study the interplay between decoherence and Doppler cooling (chapter 8). To do this we shall use the model of Ghirardi-Rimini and Weber (GRW) as a decoherence model, which will allow us to generalize their original results
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Gao, Liping. „Seismotectonics, and the mechanics of faulting inferred from seismic body wave inversions“. Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186154.
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Seismotectonics plays a very important role in global and regional tectonic studies. The study of earthquakes as tectonic processes is known as seismotectonics. Seismotectonics integrates the earthquake process into the broader framework of tectonic geologic processes. Understanding the earthquake process can, in turn, provide valuable constraints on tectonic setting. In this dissertation, I have used three seismological examples to understand the regional tectonics. Although these examples are from very different tectonic settings, they all show that seismology provides us a quantitative view of the kinematic movement of a certain tectonic region. Also, seismology is a unique way to study nuclear explosions, very non-tectonic related events. One of the main interpretive tools in seismotectonics is focal mechanisms. I used broad band seismic body waves to retrieve the focal mechanisms and source time functions. The technique includes Joint inversion of body waves from a group of stations and single station moment tensor inversion. In Chapter II, the strike-slip earthquakes in Sudan sequence indicate shear movement of an intra-continental transform fault. The aftershocks of this event imply a more complicated interaction in the continent than typically observed on the ocean floor. Old structures in a continent can have significant influence in the faulting process. The 1990 Iranian earthquake sequence (Chapter III) demonstrates another significant phenomena when convergence is oblique to the geologic structure, slip partitioning could occur. In NW Iran, a region of compressional tectonics, most of the earthquakes display reverse or thrust faulting. However the strike-slip mechanism events in 1990 Iranian earthquake sequence (including the mainshock) occur because the slip vector of the convergence between the Eurasian and the Arab plates is very oblique to the general structure in NW Iran. In addition to the usual reverse faulting along NW fault plane, there is also left-lateral motion to accomplish this oblique movement. Chapter IV provides an example of seismotectonics providing understanding to a non-tectonic related phenomenon--nuclear explosions. Almost all the underground nuclear explosions show some sort of non-isotropic component and this non-isotropic component can be interpreted as tectonic release. The extensive studies around NTS (Nevada Test Site) show this tectonic release is related to the regional stress regime. Our studies on Lop Nor test site of Chinese nuclear explosions show strong evidence for tectonic release. The type of the tectonic release is based on the size or yield, of the explosions. Smaller explosions generate mainly thrust faulting, while larger explosions are associated with strike-slip faulting.
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COCCO, SUSANNA. „Empirical faithfulness and typicality: a pragmatic reading of Everett's pure wave mechanics“. Doctoral thesis, Università degli Studi di Cagliari, 2015. http://hdl.handle.net/11584/266372.
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Everett’s Relative State Formulation is one of the most famous and debated interpretations of Quantum Theory. Further deepening of the debates has been made possible by the discovery of his unpublished notes and manuscripts.
My purpose is to examine Everett’s ideas about physical theories, and show that his understanding of actual experience can be put into correspondence with the latest forms of constructive empiricism and empirical adequacy: the problem of ‘extra structure’, which is the reason for metaphysical interpretations, can be solved by using a pragmatic criterion to choose in which way the theory should correspond to empirical evidence.
A quantitative justification for probabilities in Everettian context is given in terms of typicality.
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Xu, Peng. „Turbulent flow control using spanwise travelling wave via Lorentz forcing“. Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10710/.
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Lorentz-forcing spanwise travelling wave actuation in the turbulent boundary layer has been studied in a water channel at various experimental conditions (St = 139.2, 186 and 232; T+ = 17, 42 and 82). At the Reynolds number of Reτ = 388, a maximum skin friction drag reduction of 30% is achieved in some cases, while up to 22.8% of viscous drag increase is also observed. The results of the turbulent boundary layer profiles show that the turbulence intensities for both the drag-reducing and the drag-increasing cases are reduced. The higher moments of turbulence statistics such as the skewness and the kurtosis increase near the wall when T+ = 42, St = 232 in the drag-reducing case. For the drag-increasing case (T+ = 17, St = 232), the skewness and the kurtosis are decreased when very close to the wall (y+ < 6), while they are increased for y+ > 6, similar to the drag-reducing case. The reduction in the turbulent intensities as well as the changes in VITA velocity profiles suggest that the drag changes are due to the modified near-wall activities by the Lorentz forcing. Flow visualisation shows that the low-speed streaks are twisted into the spanwise directions in both the drag-reducing and the drag-increasing cases. For the drag-reducing case, the low-speed streaks are clustered together to form a wide low-speed region similar to what Du et al (2002) have found. This low-speed region seems to act as the ‘storage’ of low-speed fluid to help reduce the skin friction drag. To achieve the drag reduction, the spanwise displacement of low-speed streaks must be greater than 115 wall units in the present configuration, which compares well with the average spacing of low-speed streaks in the turbulent boundary layer. When the drag increase occurs, only pseudo-local spanwise oscillation is observed without a formation of a wide low-speed region. The pseudo-local spanwise oscillation appears to produce converging and diverging motions around the forcing-activation area. The induced streamwise vorticity layers are believed to enhance the effect of the sweep motion, which results in the increasing skin-friction drag.
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Andre, Daniel Batista. „Weyl expansion for multicomponent wave equations“. Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310887.
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Hope, Sarah A. „Arterial pressure waves : waveform characteristics, their associations and factors influencing their propagation“. Monash University, Faculty of Medicine, Nursing and Health Sciences, 2003. http://arrow.monash.edu.au/hdl/1959.1/5566.
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Hughes, Michael G. „A field study of wave-sediment interaction in the swash zone“. Phd thesis, School of Geosciences, 1989. http://hdl.handle.net/2123/10464.
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Doyle, B. „Development of a numerical model of wave induced flow in a sea outfall“. Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269078.
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Hamlin, Simon Mark. „Body wave propagation in an analogue granular material in a cubical cell apparatus“. Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.683560.
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Shear and compression wave velocities are examined in assemblages of spherical glass beads in isotropic, triaxial and multiaxial stress states in the Cubical Cell Apparatus (CCA). The CCA enables application of non-rotational stress-states to a cube-shaped sample with independent control of the three principal stresses. Waves are transmitted using bender/extender elements (Lings & Greening 2001), the performance of which are assessed by laser vibrometry. Uncertainties in the analysis of wave velocities are examined in relation to the method of travel time assessment, extending to frequency and shape of the transmitted pulse waveform. Results suggest that uncertainties over wave travel time result largely from the mismatching of the transmitted waveform and the method by which its arrival is analysed. Methods based on cross-correlation are the most universally applicable and can be semi automated but still rely on the operator to correctly identify the wave arrival. Results for velocities in isotropic stress states are curve-fitted to a power law; the coefficients and exponents of these best fit curves appear to be related by an inverse power law, which is backed up by published data. How this may relate to material properties remains unclear. Additional laser vibrometry results from targets on the outside of a cubical sample enable examination of the propagation of the wavefront through the sample. The received traces for S-wave transmissions support the theory that the operation of the bender element produces sideways propagating P-wave 'lobes' (Lee and Santamarina 2005). The trend of their arrivals with distance between the bender and laser target supports the accepted use tip-to-tip travel distance for S-wave transmissions but suggests it may be too short for P-waves; this latter requires further experimental work.
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Skryabin, Dmitry Vladimirovich. „Modulational instability of optical solitary waves“. Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366995.
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Lee, Jong-eao John. „The inverse spectral solution, modulation theory and linearized stability analysis of N-phase, quasi-periodic solutions of the nonlinear Schrodinger equation /“. The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726601122429.
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