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 36 for “"Higher modes"”.
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Two methods for separating higher modes of seismic surface waves.
Massachusetts Institute of Technology. Dept. of Geology and Geophysics. Thesis. 1966. M.S.
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Modeling and control of flexible structures
… finite element convergence toward the natural modes and frequencies of a structure, it is found that two mechanisms limiting the accuracy of higher modes are, first, a decrease in the number of active degrees of freedom for higher mode approximations due to orthogonality constraints, and, …
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Spillover stabilization in the control of large flexible space structures
… implemented to control only a few known elastic modes. Linear Quadratic Regulators (LQR) and Kalman-Bucy Filter (KBF) observers are usually designed to control the desired modes of vibration. Higher modes, referred to as residual modes, are generally ignored in the analysis and may be excited by …
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Reduction of computational effort in structural dynamics calculations
… may have to include many degrees of freedom. The higher modes that are present may have very short periods, which require very short time intervals for stability and convergence of the calculation and for accuracy.
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Random vibrations of mistuned periodic structures
Nearly periodic structures exhibit localized modes of vibration depending upon the ex· tent of the coupling and the disorder between their periodic components. These localized modes may cause excessive vibration amplitudes resulting in significantly higher stresses than the ones the structures …
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Extracting damping ratios using wavelets
… damping ratios, added noisy data, separated modes and close modes. To achieve this goal, a simulated analytical signal is analyzed by estimating the modal parameters. The simulated analytic signal is useful because the exact values are known and the characteristic of the FRF can be varied in …
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The driven and stochastic dynamics of micro and nanoscale cantilevers in viscous fluid and near a solid boundary
… tip distribute energy differently to the higher flexural modes. The externally driven dynamics of microscale cantilevers in fluid are also considered. The driven dynamics are calculated using numerical simulations of the cantilever response to a force impulse. It is found that the driven …
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Macro-Fiber Composites for Sensing, Actuation and Power Generation
… interdigitated electrodes that capitalize on the higher d33 piezoelectric coupling coefficient that allow it to produce higher forces and strain than typical monolithic piezoceramic materials. The research presented in this thesis investigates some potential applications for the MFC as well as …
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Nonlinear stochastic vibration in geometrically varying beams
… deflection curve in terms of the undamped linear modes. Substituting this expansion into the partial differential equation yields a set of ordinary differential equations in terms of the modal response functions, which are coupled through the nonlinear terms. The normal modes are found by the …
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Optical micro- and nanofibres: Higher mode generation and particle manipulation studies
… fields of optical micro- and nanofibre research; higher mode generation/excitation and evanescent field optical manipulation. Standard, commercial, single-mode silica fibre is used throughout most of the experiments; this generally produces high-quality, single-mode, micro- or nanofibres when …
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Seismic performance, design and placement of multiple tuned mass dampers in building applications
… of the reasons is that both the fundamental and higher vibration modes may play important roles in the seismic responses of building structures while the conventional single TMD tuned to the fundamental mode has little effect on the responses of higher modes.</p> <p>In this study, a multiple …
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Stochastic and seismic design response of linear and nonlinear structures
… the pseudostatic contribution of the truncated modes without including them in the analysis. In particular, the modified mode displacement approach is a useful tool for the calculation of seismic design responses affected by the contributions or higher modes. It properly considers the modal …
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The Response of an Oil Rig Model to Dynamic Excitation
… end condition analysis were used later in the higher modes analysis of the model rig using sub-structuring techniques.
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Fluid mechanics of liquid drops and thin-films
… particular for drops with low contact angles and higher modes of vibration. The third topic is to find the underlying physics of filamentous structures formed when sticky pitcher fluids are dewetted on a substrate. By using polyethylene oxide (PEO) aqueous solutions on a polydimethyl siloxane …
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Very low frequency seismo-acoustic noise below the sea floor (0.2-10 Hz)
… (1959) and reveal two fundamental interface wave modes for short wavelength noise propagation in the crust: the Stoneley and pseudo-Rayleigh wave. For ocean sediments, where the shear wave velocity is less than the acoustic wave velocity of water, only the Stoneley interface wave can exist. For …
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Frequency dependent heat generation during vibrothermographic testing of composite materials
… during vibrothermographic testing results from higher stresses or strains due to local resonance. The heat generation was affected by the combination of the principal strains and shear strain for the lower modes of resonant vibration, and was dominated by the shear strain for the higher modes of …
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Anisotropy and the structural evolution of the oceanic upper mantle
… phase velocities of the fundamental and first higher Love modes have been simultaneously measured using a new technique. The squares of the difference between the observed phase and the predicted phase are sumed over 45 paths for a set of trial phase velocities. The trial velocities which give …
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The Effect of Waveform Shape on Dynamics and Kinematics of the Flow in Endovascular Stents
… is changed by systematically filtering out the higher modes of Fourier decomposition and the negative flowrate extension is reduced by shifting the waveform to the positive flowrate. The presence of the stent causes vortical structures to be created between stent struts. These vortices are …
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Confined wrinkling of thin elastic rods, sheets and cones
… but within a prescribed confinement to ensure higher-mode buckling and hence a reasonable post-buckling capacity. The main aim is to understand and predict this confined buckling behaviour of some simple thin-walled structural forms: a rod, rectangular sheet, trapezium, rectangle with a central …
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Analysis, Design, and Experimentation of Beam-Like Structures
… for a periodically supported beam using a higher order textit{k}-refinement. Next, an Integral Equation Approach (IEA) is implemented using EBT to obtain natural frequencies and buckling loads of periodically supported non-prismatic beams. Ill-conditioning errors were alleviated using …
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