Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 39 for “"Time harmonic"”.
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Computation of multiscale time-harmonic electromagnetic radiation
The effect of installation for an antenna is key to understanding its performance in the intended operating environments. While existing formulations support such analysis, their mapping of calculations to distributed computing hardware does not support simulating installation environments of …
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Domain decomposition methods for time-harmonic elastic waves
The construction of optimal solvers for high frequency Helmholtz-type equations is highly problematic. After discretisation of the previous equations by a finite element method,the underlying linear systems are usually large and difficult to solve both by direct and iterative methods. Domain …
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Studies of non-diffusive heat conduction through spatially periodic and time-harmonic thermal excitations
… We explore both spatially periodic and time-harmonic thermal excitations as a means for probing the non-diffusive transport regime, where the Fourier heat diffusion law breaks down. Boltzmann transport equation calculations of one-dimensional (1D) spatially sinusoidal thermal excitations …
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High-Fidelity Modeling of eVTOL Rotor Unsteady Aerodynamic and Aeroacoustic Response to Time-Harmonic Gust
… of a representative eVTOL rotor subjected to time-harmonic inflow disturbances, providing a detailed numerical framework to quantify how periodic gusts influence rotor performance, unsteady loading, and sound radiation.</p> <p>The study employs a three-stage computational methodology using the …
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On finite element solutions for bounded time-harmonic scattering problems with an exact nonlocal boundary condition.
Time-harmonic scattering problems in partial differential equations have been thoroughly analyzed for many years. These problems are originally posed in an unbounded domain, but to easily discretize the domain, we will instead restrict to a finite, bounded domain and utilize the finite element …
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A study of node-based finite elements for the solution of the time-harmonic Maxwell equations
… by means of numerical examples in this thesis. Time-harmonic source problems and eigen-problems are analyzed using mixed node-based finite elements. The results are compared to results obtained with vector finite elements.
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A Dynamical Study of the Evolution of Pressure Waves Propagating through a Semi-Infinite Region of Homogeneous Gas Combustion Subject to a Time-Harmonic Signal at the Boundary
… the evolution of a pressure wave driven by a harmonic signal on the boundary during gas combustion is studied. The problem is modeled by a nonlinear, hyperbolic partial differential equation. Steady-state behavior is investigated using the perturbation method to ensure that enough time has …
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Analytic model for matched-filtered scattered intensity of volume inhomogeneities in an ocean waveguide calibrated to measured seabed reverberation
… and provide a computationally efficient time harmonic approximation to the matched filtered model. Following the approach developed by Galinde et al 16], the expressions are derived from first principles, by applying Green's theorem and the Born approximation. The scattered field and the …
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The Polarimetric Impulse Response and Convolutional Model for the Remote Sensing of Layered Vegetation
… however, these models often rely on purely time-harmonic formulations and approximations to integrals. Forms of VRT models have recently been developed which account for a Gaussian pulse incident waveform, however, these models often rely heavily on very specific and obfuscated …
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Numerical Modeling of Synthetic Vortical Disturbance Interactions Using OpenFOAM
… upstream synthetic disturbance field (such as a time-harmonic gust or turbulence with required characteristics) is employed. Validation test studies are conducted to examine and compare with previous results for the benchmark case of 2D time-harmonic gust interaction with NACA0012 airfoil, and …
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Optimal Control for an Impedance Boundary Value Problem
… the scattering problem. Assume that an incoming time harmonic wave is scattered by a surface of an impenetrable obstacle. The reflected wave is determined by the surface impedance of the obstacle. In this paper we will investigate the problem of choosing the surface impedance so that a desired …
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Parametric Viscous Analysis of Gust Interaction with Stationary and Elastically Mounted Airfoil
… models are developed to introduce sharp-edge and time-harmonic gust perturbations with specified amplitude, frequency and duration inside the computational domain through the source terms in the governing momentum equations. Parametric analysis of gust-airfoil interactions for different steady …
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Analisys and Syntesys of Thin-Film Solar Cells with Metallic Nanoparticles
… applied to the analysis of the scattering of time-harmonic electromagnetic waves at optical frequencies from metallic nanoparticles of arbitrary shape. Moreover, the optimization of a thin solar cell with metallic nanoparticles is performed by means of Genetic Algorithms and the Finite Element …
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A coupled thermal-magnetic finite element model for high frequency transformers
… of the soft-ferrite core material permits a time-harmonic transformation of the electromagnetic equations. This eliminates the need to step through time while maintaining the effects of hysteresis losses. Also, a quasi-steady formulation of the heat-conduction equation eliminates the time …
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Oscillatory oseenlets
… far-field flowconsists of both steady and time periodic components. The time periodic component canbe decomposed into a Fourier expansion series of time harmonic terms. The form of thesteady terms given by the steady oseenlets are well-known. However, the time-harmonicterms given by the …
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Electromagnetic scattering and induction models for spheroidal geometries
… from a conducting and permeable spheroid under time harmonic excitation is demonstrated. Analytical electromagnetic solutions for spheroidal geometries are desirable because of their versatility in modeling manmade and natural shapes includ- ing solid and hollow needles, spheres, and disks, …
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The theory and design of switched-mode power transformers for minimum conductor loss
… their usefulness and range of validity. The time-harmonic treatment is generalized to arbitrary periodic exoitation by means of Fourier analysis, resulting in a powerful extension of its applicability to any possible converter topology. Results for several representative waveshapes are …
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Stochastic turning point problem
… medium is considered in an acoustic context. A time harmonic plane wave emitted by a source is incident upon it and generates totally reflected fields which consist of "signal" and "noise". The statistical properties, i.e., mean and correlation functions, of these fields are to be obtained. The …
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Three-dimensional pulsed disturbances in a plane mixing layer.
… via amplitude modulation of a spanwise uniform time-harmonic wave train which provides a clear phase reference for the phase-locked velocity measurements. The evolution of the pulsed disturbance depends critically on the time delay between the modulation pulse and the carrier wave train, the …
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Influence of higher time harmonics on the electrical and mechanical performance of an inverter-fed squirrel cage induction motor
… quite non-sinusoidal and polluted with higher time harmonic components. The higher time harmonics affect the electrical and mechanical performance significantly, and adverse effects are investigated. Literature on the effect of higher time harmonics is reviewed. Recommendations referring to …
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