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 50 for “"Method of multiple scales"”.
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Non-linear response of a fluid valve
The method of multiple scales is used to study the nonlinear response of a relief valve under a constant static pressure and a sinusoidal dynamic pressure that can be generated by variations in the pneumatic transmission lines. Under certain conditions, large vibrations may occur, causing …
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Modeling and Analysis of a Cantilever Beam Tip Mass System
We model the nonlinear dynamics of a cantilever beam with tip mass system subjected to different excitation and exploit the nonlinear behavior to perform sensitivity analysis and propose a parameter identification scheme for nonlinear piezoelectric coefficients. First, the distributed parameter …
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Response of a parametrically-excited system to a nonstationary excitation
The response of a parametrically-excited system to a deterministic nonstationary excitation is studied. The system, which has a cubic nonlinearity, has one focus and two saddle points and can be used as a simple model of a ship in the head or follower seas. The method of multiple scales is applied …
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Parameter Identification of Nonlinear Systems Using Perturbation Methods and Higher-Order Statistics
… procedure is proposed that combines the method of multiple scales and higher-order statistics to efficiently and accurately model nonlinear systems. A theoretical background for the method of multiple scales and higher-order statistics is given. Validation of the procedure is performed …
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Nonlinear resonances in systems having many degrees of freedom
An analysis is presented of the main, superharmonic, subharmonic, combination and internal resonances in a weakly nonlinear system having many degrees of freedom. The system has cubic nonlinearities, modal linear viscous damping and is subject to harmonic excitations. The method of multiple scales, …
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Non-linear propagation of waves on two-dimensional liquid sheets
The long time behavior of antisymmetric as well as symmetric waves on a two-dimensional liquid sheet is studied, the effects of the surrounding fluid being taken into account. The non-linear Schrödinger equation governing the wave motion is derived by the method of multiple scales. Modulatory …
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Long waves in water over a visco-elastic muddy seabed
The propagation of surface waves over a flat muddy seabed are studied. Mud is first considered as a Newtonian fluid. Water and mud equations are derived in order to obtain governing equation for surface and interface waves. By the method of multiple scales. nonlinear evolution equations are derived …
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Effect of compressibility, suction, and heat transfer on the nonparallel stability of boundary-layer flows
We present an analysis of the effects of heating, suction, and compressibility on the stability characteristics of boundary-layer flows within the framework of a complete nonparallel, linear, spatial stability theory. Included in the theory are disturbances due to velocity, Pressure, temperature, …
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Forced, nonlinear, planar and nonplanar oscillations of a cantilvered beam including static deflection
In this dissertation, the response of a slender, elastic, cantilevered beam to a simple harmonic excitation is investigated. The effects of nonlinear curvature, nonlinear inertia, viscous damping and static load are included. The nonlinear equations governing the motion of the beam are derived by …
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Nonlinear Vibrations of Doubly Curved Cross-PLy Shallow Shells
The objective of this work is to study the local and global nonlinear vibrations of isotropic single-layered and multi-layered cross-ply doubly curved shallow shells with simply supported boundary conditions. The study is based-on the full nonlinear partial-differential equations of motion for …
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Experimental Identification of Nonlinear Systems
… identifying the nonlinear parameters of a model approximating the response of a cantilevered beam by a single mode. The model accounts for cubic inertia and stiffness nonlinearities and quadratic damping. The method of multiple scales is used to determine the frequency-response …
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Wave interactions in three-dimensional boundary layers
The roles of weakly nonlinear triad interactions and the self-interaction of primary instabilities in the transition-to-turbulence process in three-dimensional boundary layers are investigated. Resonant triad interactions are studied in the boundary layer on the leading edge of a swept wing under …
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Identification of nonlinear ship motion using perturbation techniques
… an identification scheme for the dynamic model of a ship at sea. We determine the form of the governing differential equations for a ship which is free to pitch and roll, but constrained in all other degrees of freedom, using a perturbation-energy technique. This technique approximates energy …
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Parameter Estimation of Structural Systems Possessing One or Two Nonlinear Normal Modes
In this Dissertation, we develop, and provide proof of principle for, parameter identification techniques for structural systems that can be described in terms of one or two nonlinear normal modes. We model the dynamics of these modes by second-order ordinary-differential equations based on the …
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Nonlinear dynamics in power systems
We use a perturbation analysis to predict some of the instabilities in a single-machine quasi-infinite busbar system. The system’s behavior is described by the so-called swing equation, which is a nonlinear second-order ordinary-differential equation with additive and multiplicative harmonic terms …
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Receptivity to free stream acoustic disturbances due to a roughness element on a flat plate
… a forcing at a wave number equal to that of the Tollmien-Schlichting (TS) eigenmode and a frequency equal to that of the free-stream acoustic disturbance. The basic (mean) flow is calculated using an interacting boundary layer (IBL) scheme that accounts for viscous/inviscid interactions. …
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Nonlinear oscillations under multifrequency parametric excitation
A second-order system of differential equations containing a multifrequency parametric excitation and weak quadratic and cubic nonlinearities is investigated. The method of multiple scales is used to carry out a general analysis, and three resonance conditions are considered in detail. First, the …
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Parametric identification of nonlinear structural dynamic systems
The identification of linear structural dynamic systems has been dealt with extensively in past studies. Identification methods for nonlinear structures have also been introduced in previous articles, including procedures based on the method of multiple scales, iterative and noniterative direct …
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Nonlinear oscillations of self-excited systems under multifrequency parametric excitation
… excitation is investigated in this study. The method of multiple scales is used to analyze the system under four different resonances relating parametric excitation frequencies with the natural frequencies. In the first case, the parametric excitation frequency is approximately equal to twice …
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Nonlinear Forced Vibration of an Unsymmetrically Laminated Composite Beam
<p>The purpose of this thesis is to study the nonlinear forced vibration of an unsymmetrically laminated composite beam. Two cases are considered: unsymmetrical angle-ply and unsymmetrical cross-ply composite beams. The nonlinear governing partial differential equations of motion are obtained by …
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