Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 74 for “"plane waves"”.
-
Contrast-enhanced Doppler Ultrasound Imaging using Plane Waves
… estimates. However, recent breakthroughs in plane-wave synthetic ultrasound considerably increased the maximal imaging frame rate, enabling new imaging trade-off previously unavailable. In this thesis, we first implement pulse inversion Doppler using plane-wave ultrasound and demonstrate the …
-
The nonlinear differential semblance algorithm for plane waves in layered media
This thesis proposes an alternative approach to the output least-squares (OLS) seismic inversion for layered-media. The latter cannot guarantee a reliable solution for either synthetic or field data, because of the existence of many spurious local minima of the objective function for typical data, …
-
SCATTERING OF ELECTROMAGNETIC PLANE WAVES FROM TWO INFINITELY LONG PARALLEL CYLINDERS OF ARBITRARY MATERIALS AT OBLIQUE INCIDENCE.
… for the scattering of an electromagnetic plane wave from two infinitely long, parallel, circular cylinders at oblique incidence are derived. Each cylinder can be of arbitrary materials (any refractive index). The incident wave can be in any polarization state. To find the scattering …
-
Spectroscopy of Discrete Breathers
… state (discrete breather) and small amplitude plane waves is studied.
-
Discrete Nonlinear Wave Propagation In Kerr Nonlinear Media
… factors in the formation of such nonlinear waves is discussed. The reversal of the sign of diffraction over a range of propagation angles leads to the stability of plane waves in a material with positive nonlinearity. This behavior can not be found in continuous self-focusing materials where …
-
Oblique reflections of internal gravity wave beams
… variation along the direction of the flow field, plane waves are exact nonlinear solutions of the governing equations. In general, energy is carried in the form of a wave beam, which is a superposition of plane waves having parallel wavevectors. However, beams incident upon a surface interact with …
-
Acoustic Response Validation of a Finite Cylindrical Shell with Multiple Loading Conditions
… also ignore complex loading conditions such as plane waves in favor of point forces or free vibration models. This work expands on the capabilities of these models by examining the acoustic response of a finite length cylinder with flat plate endcaps to multiple types of distributed loading …
-
Cyclostationary statistical optics
… pulsed fields that are either beam-like or plane waves are examined in the context of interferometric and spectroscopic measurements. Propagation of fields from more general sources is considered in relation to the spectral or polarimetric properties observed. A new scheme for measuring …
-
Fractality and topology of optical singularities
… The interference between three, four and five waves is investigated and inequalities are given which establish the topology of the singularity lines in fields composed of four plane waves. Beyond several waves, numerical simulations are used, supported by experiments, to establish that optical …
-
Asmptotically Plane Wave Spacetimes
In this thesis we study aspects of plane wave spacetimes in the hope of shedding light of the nature of holography for plane waves. In particular, we would like to understand better the space of asymptotically plane wave solutions. We first review the necessary background on plane waves, …
-
Modeling and detection of delaminations in laminated plates
… that is the tool we use to model scattering of waves by cracks in elastic media. A critical step in the TBEM is the evaluation of integrals with hypersingular kernels; we propose a novel approach to evaluate analytically these integrals for the plane-strain cases (antiplane and in-plane). …
-
On strain wave propagation in thermoelastic media
A complete solution of thermoelastic dilatational waves in an elastic, heat conducting, homogeneous, and isotropic medium has been obtained for both the steady and unsteady states. Discussions of the solution for a wide range of frequencies and various values of the coefficient of rise (or decay) …
-
Parametric subharmonic instability of internal gravity wave beams
Internal gravity wave beams are time-harmonic plane waves with general spatial pro- le that arise in continuously stratified fluids owing to the anisotropy of this wave motion. In the last decade, these wave disturbances have been at the forefront of research, both from a fundamental perspective …
-
Acoustic scattering analysis for remote sensing of manganese nodules
The theory of the scattering of plane waves in a fluid medium by an isotropic elastic sphere representing a manganese nodule is developed. Scattering cross sections were computed using the theory and the results are presented graphically. The scattering cross section and the reflectivity factor …
-
2-D Modeling of Electromagnetic Waves with Vibrating Conducting and Dielectric Objects
… include total-field scattered-field incident plane wave source conditions, a frequency domain near-to-far-field transformation, convolutional perfectly matched layer boundary conditions and an advanced surface boundary condition that accommodates the surface perturbations of the vibrating …
-
Revisiting the theory of alloy thermal conductivity
… modes in a material are assumed to be plane-waves, hence they can be modeled as a gas of particles that exchange energy through scattering events. During the last 100 years, the PGM has provided great insights into thermal transport in pure homogeneous crystals. However, when one …
-
Studies on Low Frequency Fast Multipole Algorithms
… second part. A low frequency fast inhomogeneous plane wave algorithm (LF-FIPWA) is developed to overcome this issue with the transition region around 0.1 wavelength. Evanescent waves and propagating waves are both used to compensate for the accuracy lost in the conventional translation process. …
-
Instabilities of finite-width internal wave beams
Internal gravity waves are fundamental to the dynamics of density stratified fluids and the instability mechanisms by which these waves dissipate their energy are a potentially significant factor that underlies the distribution of energy and momentum in the natural environment. Recently, it has …
-
Optimization of Plane Wave Directions in Plane Wave Discontinuous Galerkin Methods for the Helmholtz Equation
… In particular, for the 2D Helmholtz equation, plane waves have been used to derive an Interior Penalty (IP) type Plane Wave DG (PWDG) method and to provide an a priori error analysis of its p-version with respect to equidistributed plane wave directions. However, the dependence on the …
-
Amplified Total Internal Reflection at the Surface of Gain Medium
… In this thesis, reflectioncoefficients for plane waves are calculated by satisfying boundary conditions fromMaxwell’s equations at the reflecting surface for both optically lossy and gainy me-dia. Plane wave reflectivity is found to exhibit is discontinuous jump from belowunity to above as …
Page 1 of 4