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Showing 1 to 20 of 51 for “"Sommerfeld"”.
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Uniformly valid asymptotic solutions of the Orr-Sommerfeld equation and their application to plane Poiseuille flow
Thesis: M.S., Massachusetts Institute of Technology, Department of Mathematics, 1961
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A numerical investigation of the linear hydrodynamic stability of Newtonian and weakly non-Newtonian channel flows as described by the Orr-Sommerfeld equation
The Orr-Sommerfeld equation describes the growth of infinitesimal disturbances to laminar solutions of the Newtonaian Navier-Stokes equations. In this dissertation we consides in part idealised flows between two parallel planes of infinite extent and a finite distance apart. They are referred to as …
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A STUDY FOR THE PROPAGATION OF ELECTROMAGNETIC WAVES OVER IMPERFECT GROUND PLANES BASED ON SCHELKUNOFF INTEGRALS
… for the analysis of this problem uses the Sommerfeld formulation. In Sommerfeld formulation, the wave function corresponding to a point source is expanded in terms of the propagation constants of the various waves in the radial direction from the source. This gives rise to the well-known …
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Constraint preserving boundary conditions for the linearized Einstein equations
… domain: the Neumann, Dirichlet, and Sommerfeld cases. In addition to the situation in which the boundary is aligned with a coordinate surface, we examine the presence of corners in the computational domain. We find that, at a corner, there are compatibility conditions which the …
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Low order models for hybrid gas bearings
… coefficients taken from a short width Full-Sommerfeld solution. The equations of motion are then modified, and rewritten in matrix form using variables relevant to the bearing literature. By studying the eigenvalues of the linear model, it is possible to determine at any operating point: 1) …
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Fast estimation model of pressure-temperature response for planning focused ultrasound surgery
… a numerical simulation model, known as Rayleigh-Sommerfeld method, is used. As the Rayleigh-Sommerfeld method is applicable only with homogenous media, a modified computation method that can deal with scattering and refractions from multiple tissue layers is developed to simulate the pressure …
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Efficient integral equation solution of electromagnetic scattering by arbitrarily shaped objects in planar, multilayered media
… formulations, this is due to the presence of the Sommerfeld integrals required for obtaining the Green's functions in spatial form.
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The Effects of Variable Parameters on the Behavior of Initial Wind Waves
… by integrating a transformed version of the Orr-Sommerfeld equation, subject to the boundary conditions at a two-fluid interface. Unbounded growth problems usually encountered in a direct numerical integration of the Orr-Sommerfeld equation were avoided by the use of the compound matrix method, …
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A study on computational electromagnetics problems with applications to casimir force calculations
… DGLM requires the evaluation of semi-infinite Sommerfeld integrals which prove to be a costly venture. An interpolation scheme is proposed here to allow for more efficient calculations of the Sommerfeld integrals. The interpolation is unique by its reuse of the same interpolation matrix to …
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Phase-Space Distributions of Galactic Dark Matter Halos and Implications for Detection
… in the self-annihilation cross-section from the Sommerfeld effect is considered in indirect detection; we derive an upper limit on the local velocity dispersion and examine the significance of local anisotropy in the local dark matter distribution in direct detection efforts.</p>
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Efficient Techniques for Near-Field Computation and Subreflector Analysis
… the radiating near field is expressed via the Sommerfeld-Wilcox expansion. For field computation, the series method of the modified Jacobi polynomials is employed. Advantages of this method over other existing methods are shown, and details for implementing the method for both planar aperture …
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Nichtlineare Stabilitätsanalyse der3D-Couette-Strömung unter Berücksichtigung derEnergietransfererhaltung
… 108-dimensionalen Galerkindarstellung in Orr-Sommerfeld- und Squire-Moden untersucht. Im Reynoldzahlbereich 325<= R <= 350 wird ein deutliches Übergangsverhalten gefunden; des weiteren wird auch die sensitive Abhängigkeit von den Anfangsbedingungen im Intermittenzbereich bestätigt, die …
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Unconventional Superconductivity in the Layered Iron Germanide YFe2Ge2
… system YFe$_2$Ge$_2$ exhibits an unusually high Sommerfeld coefficient of $\approx \SI{100}{\milli\joule/\mole\kelvin^2}$, signalling strong electronic correlations. Its low-temperature normal-state resistivity displays a $T^{1.5}$ power-law temperature dependence, which is an indication of …
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Hydrodynamic Stability of the boundary layer beneath a Stokes wave
… Chebyshev collocation methods to solve the Orr-Sommerfeld eigenvalue problem, we examine the stability of the flow across a broader parameter space. Our findings suggest that, while the laminar boundary layer remains stable for the momentary stability criterion against infinitesimal disturbances …
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Thermische Tieftemperatureigenschaften von Seltenerd-Übergangsmetall-Borkarbiden
… transition temperature Tc, of the Sommerfeld value gamma, of the upper critical magnetic field Hc2(0), of the negative curvature of the H-dependence of the T-linear specific heat contribution gamma(H), and in the reduction of the positive curvature of Hc2(T) near Tc. But …
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Analysis of Fabry-Pérot laser resonators stabilized by microlenses and applications in speckle-free imaging
… Gaussian optics as well as numerical Rayleigh-Sommerfeld diffraction results. It was found that the beams are generally uncoupled in this arrangement, and therefore do not produce interference. The resulting emission from large arrays of lasers has a moderate degree of coherence. Therefore, …
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Sparse signal representation based algorithms with application to ultrasonic array imaging
… effect using Huygens principle and Rayleigh-Sommerfeld diffraction formula. We then use this model to develop a sparse signal representation based imaging technique for a test sample immersed in water. Moreover, we develop a new sparse Bayesian technique. In the model that we develop, the …
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Quantification of internal variability of the arctic summer atmosphere based on HIRHAM5 ensemble simulations
The non-linear behaviour of the atmospheric dynamics is not well understood and makes the evaluation and usage of regional climate models (RCMs) difficult. Due to these non-linearities, chaos and internal variability (IV) within the RCMs are induced, leading to a sensitivity of RCMs to their …
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Predictions and Constraints of Cosmological Correlators
… we use the same data to constrain how much Sommerfeld enhancement of dark matter annihilation could have occurred, with the analysis being insensitive to the details of the annihilation. Finally, we propose a new method to detect the so-called CMB anomalies in a more general manner than is …
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Computational electromagnetics for microstrip and MEMS structures
… which is represented in terms of only two Sommerfeld integrals and is suitable for developing fast algorithms. The path deformation technique and the multipole-based acceleration are used to expedite the matrix-vector multiplication. Both the computation time per iteration and the memory …
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