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 “"Periodic systems"”.
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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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Control of Periodic Systems Governed by Partial Differential Equations Using Averaging
… 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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Wave transport in parity-time symmetric, time-varying, and quasi-periodic systems
… in the fields of artificial materials and systems, in particular in the areas of parity-time symmetric systems, time-varying systems and quasi-periodic systems. These newly developed material platforms have been enabling many exotic wave-matter interaction phenomena unavailable in nature. …
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Wavefunction-based method for excited-state electron correlations in periodic systems - application to polymers
… determining correlated wavefunctions of extended systems in the ground state as well as in excited states is presented. It allows to fully exploit the power of quantum-chemical programs designed for correlation calculations of finite molecules. Using localized Hartree-Fock (HF) orbitals (both …
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Application of the Filtered-X LMS Algorithm for Disturbance Rejection in Time-Periodic Systems
… 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 aperiodic systems by …
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Quantum-mechanics simulations of bi and tridimensional periodic systems. Thermal models, friction and self-assembly
Esta tesis, titulada "Simulaciones Mecánico-Cuánticas de Sistemas Periódicos Bi y Tridimensionales. Modelos térmicos, fricción y auto ensamblado", aborda desde la perspectiva de la química teórica y computacional la explicación detallada y el entendimiento de diferentes fenómenos de alto interés …
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Response of periodic systems to electromagnetic fields: multipole expansion, microscopic charge-current density, polarization and magnetization
… treat polarization and magnetization fields in periodic structures and I analyze the radiation spectrum emitted by them. The methods are based on the multipole expansion of charge-current distributions and on its extensions to account for the motion of charges between lattice sites. In the first …
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Analytical amd experimental aspects of nonlinear normal modes and nonlinear mode localization
… for two classes of conservative nonlinear systems; namely (i) periodic systems composed of repeated sub-structural elements and (ii) systems possessing internal resonances. For coupled repetitive systems, NNMs are shown to provide an excellent framework by which to study the nonlinear mode …
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ΚΒΑΝΤΙΚΗ ΤΡΙΒΗ ΣΕ ΠΕΡΙΟΔΙΚΟ ΔΥΝΑΜΙΚΟ
… USING THE HAMILTONIAN C-K(CALDIROLA-KANAI) FOR PERIODIC MATIEU-TYPE POTENTIALS. FURTHERMORE THIS IS EXTENDED TO SPACE AND TIME DEPENDED PERIODIC SYSTEMS. THEN THE PROBLEM IS CONSIDERED FOR UNIFORM MAGNETIC FIELD AND THE QUESTION OF QUANTUM STATISTICS IS ANALYSED AND WELL KNOWN THERMODYNAMICS …
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On Exponentially Localized Wannier Functions in Non-Periodic Insulators
… in space. When a material is insulating and periodic, conditions which guarantee the existence of ELWFs in dimensions one, two, and three are well-known and methods for constructing ELWFs numerically are well-developed. In this dissertation, we consider the case where the material is …
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Semi-Analytical Model to Study Vibrations of High-Speed, Rotating Axisymmetric Bodies Coupled to Other Rotating/ Stationary Structures
The vibration of complex mechanical systems that include coupled rotating and stationary bodies motivates this work. A semi-analytical model is developed for high-speed, compliant, rotating bodies. Exploiting the axisymmetry of the rotating body, the developed semi-analytical model only discretizes …
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Parallel multigrid for large-scale least squares sensitivity
… (long- time average) sensitivities for dynamical systems. Computing these sensitivities is essential to performing engineering analysis and design. The first technique is a novel approach to solving the "climate" sensitivity problem for periodic systems. A small change to the traditional adjoint …
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Nonperturbative renormalization in classical φ4 theory
… to study nonrelativistic quartic interacting systems. The model studied is that of classical real scalar φ4 theory. A variety of techniques are used including a rescaling of a nonlinear complete basis, a limit of finite periodic systems, and an analytic calculation of RG equations using a …
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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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Novel applications of Maxwell's equations to quantum and thermal phenomena
… techniques to compute photonic bandstructures in periodic systems can be extended to certain types of quasi-periodic structures, termed photonic-quasicrystals (PQCs).
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Simulation and Analysis of Behavioral Analog Systems
Periodic circuits and systems which are stiff pose special problems to traditional simulators like SPICE due to the wide separation in time constants characterizing them. Examples of such systems include power electronic circuits, phase-locked loops and RF circuits such as narrow-band amplifiers …
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Stability optimization of open-loop controlled walking robots
… control is applicable to a much wider range of systems than was conceived before. An open-loop stable control strategy does not use any feedback nor does it take any active measures to respond to perturbations but entirely relies on the mechanical system's natural kinematics and dynamics to …
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