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 42 for “"nonlinear problem"”.
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Bandwidth-limited robust nonlinear spacecraft control
… of multiaxial attitude dynamics is a highly nonlinear problem, which can be resolved by exact feedback linearization with respect to attitude variables. This requires exact measurements and perfect model parameters. However, spacecraft maneuvers in uncertain circumstances. Thus robust control …
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Applications of auction algorithms to complex problems with constraints
Linear and nonlinear assignment problems are addressed by the use of auction algorithms. The application of auction to the standard linear assignment problem is reviewed. The extension to nonlinear problems is introduced and illustrated with two examples. Techniques that are employed for model …
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The Numerical approximation of minimal surfaces with free boundaries by finite elements
… with free boundaries: Solution of the Plateau Problem corresponding to a supporting surface S, Solution of the Thread Problem. In both case, the problem is reformulated and the highly nonlinear problem (obtained) is discretized using piecewise linear finite elements. The convergence of the …
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Adaptive control of nonlinear systems
In the last few years, adaptive control of nonlinear systems has emerged as an important area of research, with possible applications in areas as diverse as robotic systems, electric motors, chemical processes, and automotive suspensions. Many of the existing results employ design methods and proof …
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Instabilidade de estruturas metálicas planas compostas de perfis de chapa dobrada
… behaviour is analyzed by means of a geometric nonlinear finit element model which takes also into account an additional nonlinearity due to local "U" section buckling effect. The solution of the nonlinear problem is obtained through a hibrid numerical scheme: incremental/iterative (tangent …
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Optimal cooperative power-limited rendezvous
… A direct method using direct collocation with nonlinear programming is used for the nonlinear problem. Solutions obtained are checked against the primer vector necessary conditions for optimality. The optimal solutions depend in a complicated way on the power-to-mass ratios of the two …
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A Time Integration Method of Approximate Particular Solutions for Nonlinear Ordinary Differential Equations
… method of fundamental solutions (MFS) to solve nonlinear ordinary differential equations. Firstly, we convert a nonlinear problem into a sequence of time-dependent non-homogeneous boundary value problems through a fictitious time integration method. The superposition principle is applied to …
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Array antenna synthesis including element and feed coupling
… for such coupling. Unfortunately, this is a nonlinear problem requiring special solution techniques. This report presents the solution techniques for determining feed network parameter values that compensate for antenna-feed network coupling. Scattering parameter representations of the …
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Galerkin Projections Between Finite Element Spaces
… PDEs with Galerkin finite element methods. For nonlinear PDEs, solving the nonlinear problem with Newton's method requires an initial guess of the solution on a refined space, which can be found by interpolating the solution from a previous refinement. Improving the accuracy of the …
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Least squares finite element methods for the Stokes and Navier-Stokes equations
… first order formulation for the Stokes problem. We show that for the Stokes equations there are two general types of boundary conditions. For the first type, practical least squares methods can be defined and analyzed in a fairly standard way, based on application of the Agmon, Douglis …
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A direct D-bar reconstruction algorithm for complex admittivities in W2,∞(Ω) for the 2-D EIT problem
… approach using D-bar methods to solve the full nonlinear problem for twice-differentiable conductivities and permittivities. In this thesis the necessary formulas to turn her proof into a direct D-bar reconstruction algorithm that solves the full nonlinear admittivity problem in 2-D are …
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Nonlinear Waves on Extremal Black Hole Spacetimes
… study of the global behaviour of solutions of nonlinear wave equations where the nonlinearity satisfies the null condition on extremal Reissner-Nordstrom black hole spacetimes.Under the assumption of spherical symmetry I show that solutions which arise from sufficiently small compactly …
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Structural Optimization Using Geometric Programming and the Integrated Formulation
… treated as explicit equality constraints and the problem solved as a large scale nonlinear mathematical programming problem. In contrast to current methods of optimization where analysis and design are separated into two distinct phases, the integrated approach does not distinguish between the two …
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Noniterative construction of optimal quadratically-nonlinear ODE models from time series
We consider the problem of constructing a quadratically nonlinear ordinary differential equation (ODE) system from time series, with the latter obtained either from experiment, or from computational simulation using a higher-dimensional mathematical model (e.g., one or more partial differential …
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Parameter optimization of atmospheric skip trajectories for use in minimum fuel usage transfer orbits
The problem of developing a generalized impulse as a function of a set of parameters is investigated. The proposed generalized impulse alters an existing orbit by producing, over some period of time, a change in velocity, ΔV, as well as a change in position, Δr. The generalized impulse is described …
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Development of hierarchical optimal control algorithms for interconnected nonlinear dynamical systems
… algorithms for optimal control of interconnected nonlinear systems. To achieve this, four basic hierarchical structures are developed by taking into account the manner in which real process measurements taken from interaction inputs are incorporated and utilized in the model-based optimal control …
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Structuring Optimal Control of Legged Locomotion with Learning-based Methods
… timings in an online fashion. This highly nonlinear problem is made tractable by collecting thousands of feasible trajectories offline from trajectory optimizations and learning to generate them from the initial falling conditions. By initializing the search for a solution with the …
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Stability analysis of spatially dependent nonlinear reactor systems
… behavior of a neutron distribution governed by nonlinear multigroup diffusion approximation is considered in this thesis. Stability criteria for equilibrium states of various reactor feedback models are determined by the methods of Liapunov, semigroup and comparison functions. Comparison of the …
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Reaction-Diffusion Models of Cancer Dispersion
… existing approaches.</p> <p>We conclude with a nonlinear problem of cancer dispersion in which an integral equation governing the propagation of the cancer front is obtained. A primary difference between this model and the previous models is the inclusion of another major transport process …
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Finite element analysis of 3D electric machine problems
… simulation tool to analyze electric machine problems. As one of the largest fossil energy consumers, electric machines have to be designed properly with robust simulation tools that are capable of handling the inherent complexity, such as multiple materials, complicated geometry, eddy …
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