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 45 for “"time-periodic"”.
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Model Reduction of Linear Time-Periodic Dynamical Systems
… for dynamical systems whose parameters vary with time. We have particular interest here in linear time-periodic dynamical systems; we seek a structure-preserving algorithm for model reduction of linear time-periodic (LTP) dynamical systems of large scale that generalizes from the linear …
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Harmonic and Narrowband Disturbance Rejection for Linear Time-Periodic Plants
… disturbance rejection problem for linear time-periodic (LTP) systems. The consequence of disturbances on LTP systems is similar to their linear time-invariant (LTI) counterparts, but is complicated by the interaction of the disturbance and plant acting at different frequencies, which …
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A Problem From Hamiltonian Mechanics With Time -Periodic Coefficients, Small Noise, and Degeneracy
… weakly dissipative dynamical system with time-periodic co-efficients. Their time average is governed by a degenerate Hamiltonian whose set of critical points has an interior. The dynamics of the system is studied in the presence of three time scales. The periodic fluctuations of the …
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Application of the Filtered-X LMS Algorithm for Disturbance Rejection in Time-Periodic Systems
… rejection methods have been established for time-invariant systems. However, the development of these techniques has not focused on application to time-periodic systems in particular until recently. The filtered-X LMS algorithm is regarded as the best disturbance rejection technique for …
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Periodic Solutions of Chaotic Partial Differential Equations With Symmetries
We consider the problem of finding relative time-periodic solutions of chaotic partial differential equations with symmetries. Relative time-periodic solutions are solutions which are periodic in time, up to a transformation by an element of the equations' symmetry group. First, we work with the …
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An Analytical Investigation of Flapping Wing Structures for Micro Air Vehicles
… analytical model addresses this need. A time-periodic assumed-modes beam analysis of a flapping, flexible wing undergoing linear deformations is developed from a beam analysis of a helicopter blade. The resultant structural model includes bending and torsion degrees of freedom. The model …
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Reduction of periodic systems with partial Floquet transforms
Input-output systems with time periodic parameters are commonly found in nature (e.g., oceanic movements) and engineered systems (e.g., vibrations due to gyroscopic forces in vehicles). In a broader sense, periodic behaviors can arise when there is a dynamic equi- librium between inertia and …
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Identification of the harmonic transfer functions of a helicopter rotor
Identification of the time periodic dynamics of a helicopter rotor system is necessary for effective controller design and analysis. The transfer properties of a linear time periodic (LTP) system can be described by harmonic transfer functions (HTF) that give the input-output relationship between …
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Spectroscopy of Discrete Breathers
… the interaction between a spatial localized and time periodic state (discrete breather) and small amplitude plane waves is studied.
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Investigation of chaotic mixing in laminar fluid systems by the use of computational fluid dynamics
… development into chaotic mixing induced through periodic boundaries and twisting flows. Three-dimensional closed and throughput domains are shown to exhibit chaotic motion under both time periodic and time independent boundary motions, A property is developed originating from a signature of …
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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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Generic planar lattice patterns in liquid crystals
… set of steady states and go on to calculate the time periodic solutions resulting from Hopf bifurcations in the same planar layer of liquid crystal. We describe the possible symmetries of the system by the group ?L x S1, (or just ?L in the steady states), ?L = (H n T2) x Z2, where H is the …
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Model Reduction for Linear Time-Varying Systems
The thesis treats model reduction for linear time-varying systems. Time-varying models appear in many fields, including power systems, chemical engineering, aeronautics, and computational science. They can also be used for approximation of time-invariant nonlinear models. Model reduction is a topic …
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ADIABATIC PUMPING IN THE FLOQUET TOPOLOGICAL SYSTEMS
… have no static counterparts have emerged in the time periodic(Floquet) quantum system. It is natural to ask: Can we use the Floquet topological systems to perform quantum information tasks which can benefit from the topological robustness? Can we use the Floquet formalism to engineer the band …
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Periodic driving and nonreciprocity in cavity optomechanics
… with cavity optomechanical systems subject to periodic driving. We develop a Floquet approach to solve time-periodic quantum Langevin equations in the steady state, show that two-time correlation functions of system operators can be expanded in a Fourier series, and derive a generalized …
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Floquet theory of electronic stopping processes of projectiles in solids
… projectile following a direction of crystalline periodicity, which allows a treatment based on Floquet theory for time-periodic systems. Floquet theory allows to find the solutions of time-periodic Hamiltonians through the same techniques used in time-independent problems: this provides the new …
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Molecular simulation of liquid crystal polymer flow : a wavelet-finite element analysis
… S vs. concentration parameter N, beyond which time-periodic solutions are the only stable solutions. At low De, the time-periodic solutions onset as tumbling states at a global bifurcation. At high De, they onset as wagging states at a Hopf bifurcation, with a subsequent second transition to …
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Control of Periodic Systems Governed by Partial Differential Equations Using Averaging
… is a mathematical tool for dynamic analysis of time-periodic and space-periodic dynamical systems, including those governed by partial differential equations. The control design procedure presented in this work uses averaging techniques, the well-developed linear control strategies, and finite …
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Light-induced States and Phase Transitions in Quantum Materials investigated by Photoemission Spectroscopy and Epitaxial Synthesis
… in graphene. These states are generated by a time-periodic potential of light, closely related to the topic of Floquet engineering. (2) A light-induced insulator-to-metal transition was observed in Sr₂IrO₄, providing valuable insights into the fundamental characteristics of its ground states. …
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Theoretical and Experimental Study of a Continuous Hydrodynamically-Enhanced Separation System Paradigm
… field in SHV is reconstructed for the first time from coarse Magnetic Resonance Imaging (MRI) data. A novel reconstruction approach is introduced to process the point-wise MRI velocity measurements such that fluid mechanical constraints are strictly enforced, rather than performing simple …
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