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 15 of 15 for “"Eigenfrequency"”.
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Modeling and response analysis of thin-walled beam structures constructed of advanced composite materials
… modelled as thin-walled beams as well as the eigenfrequency problem of cantilevered composite thin-walled beams of closed cross-section are considered in the framework of a reformed theory incorporating non-classical effects. The numerical results reveal the great role played by non-classical …
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Development and applications of hypersingular boundary integral equations for three-dimensional acoustics and elastodynamics
… BIE's, are applied to overcome the fictitious eigenfrequency difficulty (nonunique solutions) existing in the conventional BIE formulations of exterior acoustic and elastic wave problems. Overhauser $C\sp1$ continuous boundary elements, which satisfy the smoothness requirement of the …
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A novel method to study the dynamic behavior of lattice structures
… the different coordinate directions at each eigenfrequency. This information is then used to identify the structural vibration mode associated with the wave propagation at that frequency. Further, the wave polarization is identified using an angle of propagation calculated with reference to …
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Stability of Topological States and Crystalline Solids
… efficiency and accuracy of atomic relaxation and eigenfrequency calculation. We test the performance on a diverse selection of case studies, with varying symmetries and mass distributions, and show that the proposed formalism outperforms existing restricted Hartree-Fock and density functional …
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Electromechanical Phenomena in Superconducting and Normal Nanostructures
… the frequency of the ac signal is close to the eigenfrequency of the mechanical subsystem. The parametrically excited mechanical oscillations result in a dc shuttle current in a certain direction due to spontaneous symmetry breaking, where the direction of the current is determined by the phase …
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Forced Capillary-Gravity Waves in a 2D Rectangular Basin
… that the frequency of the forcing is close to an eigenfrequency and the solution has an asymptotic expansion using a two time-scales approach. Under an edge condition, the first- and second-order approximations of the solution and a solvability condition from the third-order equations yield an …
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Tonalness and consonance of technical sounds
… problem is a cylindrical mode 2 vibration. The eigenfrequency of this mode is in the frequency range where the hearing system is most sensitive and the radial force excites mainly this mode.- One important component of the perceived annoyance of technical sounds is the tonalness.- The comparison …
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Windkanal-Freiflugmessungen zur Bestimmung flugmechanischer Kenngrößen
… be adapted until they fit most exactly to the eigenfrequency of the aircraft. The control algorithm has the function to reposition the aircraft after an identification manoeuvre and to trim. Additional, the algorithm takes control of the aircraft if it reaches the border of the free stream and …
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Atmospheric temperature structure in the RoAp stars
… a lot of information about these stars. The eigenfrequency spectra of roAp stars can potentially reveal information such as their rotation periods, rotational inclinations, magnetic geometries, internal magnetic field strengths, radii, masses, luminosities and ages. Matthews et al. (1990, …
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Ultra-low frequency wireless transmitter design using resonant oscillating permanent magnets
… show that the in-phase mode has the highest eigenfrequency, and optimum mode shape can be achieved by tuning the rotor-stator distance. Using these concepts, I design and demonstrate a range of multi-rotor prototypes that work in 400 - 1000 Hz range. In addition to generating a constant …
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Intentional nonlinearity in the small scale with applications to atomic force microscopy (AFM) and mass sensing
… the 2nd mode frequency (i.e., the out-of-phase eigenfrequency) coincides with an integer multiple of the fundamental mode frequency, providing the necessary conditions for realization of internal resonance. During tapping mode, the nonlinear tip-sample force activates the internal resonance and …
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High-throughput sensing of bulk fluids and freely flowing particles with opto-mechano-fluidics
… mechanical modes. A numerical setup for an eigenfrequency analysis of the OMFR system in the acoustic regime is developed. This model unifies the solid shell domain and the inner fluid domain by applying interactive boundary conditions on the shell-fluid interface. As a result, we can …
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Spectral Optimization Problems Controlling Wave Phenomena
… escape is governed by the complex scattering eigenfrequency which is closest to the real axis. We study the structural design problem: Find a refractive index profile n* within an admissible class which has a scattering frequency with minimal imaginary part. The admissible class is defined in …
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Thermomechanics of helical strands and helical-fiber-reinforced rods
Helical strands, or helically wound cables, are made of layers of individual wires wrapped around a common central axis. They are seen in ropes and power transmission cables. Similar structures are also present in biological tissues in the form of helical fiber reinforced composites. Regardless of …
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A Thousand Bells: Acoustical implementation of bell spectra using the finite element method and its compositional realization
This dissertation focuses primarily on the analysis of acoustical models of bell sounds and the modelling of virtual bell shapes and their spectra using the Finite Element Method (FEM) technique. The first chapter provides a brief introduction of pre and post-spectral music that is inspired by or …