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 40 for “"Ill-conditioning"”.
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Spectral approach for improving the Ill-conditioning of the method of fundamental solutions
O método das soluções fundamentais, em inglês, method of fundamental solutions (MFS), é um método para solução de problemas de valor de fronteira de equações diferenciais com derivadas parciais. O método pertence à classe dos métodos que não necessitam de discretização do domínio, evitando, dessa …
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Multiple Reference Active Noise Control
… This approach suffers from the problem of ill-conditioning when the reference signals are correlated. The problem of ill-conditioning results in slow convergence rate and high sensitivity to measurement error especially when the FXLMS algorithm is applied. To handle this particular problem, …
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An investigation into aspects of rate-independent single crystal plasticity
… significant numerical challenges such as ill-conditioning and non-smoothness. The majority of the algorithms in the literature are heuristic and their accuracy, stability and performance not immediately clear. Other algorithms are more mathematically sound but computationally inefficient. …
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Ill-conditioned information matrices and the generalized linear model: an asymptotically biased estimation approach
… involves a key matrix, the information matrix. Ill-conditioning of the information matrix can be responsible for making many desirable properties of the parameter estimates unattainable. Some asymptotically biased alternatives to maximum likelihood estimation are put forth which alleviate the …
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A Bayesian statistics approach to updating finite element models with frequency response data
… problem that reduces the effects of numerical ill-conditioning. Model updates are performed with a simulated free-free beam, a simple steel frame, and a cantilever beam. Improved finite element models of the structures are obtained and several statistical tests are used to ensure that the …
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Numerical solutions to Poisson's equation using radial basis functions
… method that has resulted in some problems with ill-conditioning of the matrix used in the problem solving and a remedy has been examined in this paper. The second approximation method is new to this study and has revealed to have excellent results thus far for the problems researched in this …
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Image reconstruction on electrical resistance tomography measurements in a settling process
… detail and highlights several issues, including ill-conditioning, and regularisation as a method to improve the conditioning of the data. The results contain images of successful reconstruction of a settling process.
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Fast Magnetic Resonance Imaging by Data Sharing: Generalized Series Imaging and Parallel Imaging
… regression method is developed to overcome the ill-conditioning of the model matrix. An adaptive scheme for choosing the regularization parameters is also proposed. Experimental results show that the proposed algorithm can reconstruct images with fewer artifacts and higher signal-to-noise …
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Contributions to the anisotropic elasto-plastic analysis of shells
… The element formulation avoids instabilities and ill-conditioning. We also develop a triangular 6-node shell element that represents an important improvement over a recently published element. The element is spatially isotropic, passes the membrane and bending patch tests, contains no spurious …
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A finite element method and the method of finite spheres enriched for analysis of wave propagations
… similarly), a scheme is given to overcome ill-conditioning, the method is presented for time-dependent problems, and focus is on the solution of problems in solids and structures using real arithmetic only. The method combines advantages of finite element and spectral techniques, but an …
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Improved conditioning and accuracy of a two-scale generalized finite element method for fracture mechanics
… much lower than available FEMs. The issue of ill-conditioning of the system of equations obtained with the GFEM/XFEM has been well known since the inception of these methods more than a decade ago. The Stable GFEM (SGFEM) provides a robust, yet simple solution to this ill-conditioning. The …
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Modelling the star formation histories of nearby elliptical galaxies
… observed Lick indices lead to mathematical ill-conditioning: small variations in observations can lead to very large differences in population synthesis models attempting to recreate the observed values. As such, limited reliance should be placed on any results currently or historically in …
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Model simplification and robust control in deterministic and stochastic systems using singular perturbation methods
… performance and to alleviate the numerical ill-conditioning associated with the computation of the full-order solution. Third, we must obtain ""reliable"" reduced-order models for large-scale systems that exhibit two or multi time-scale behavior, such that the solution to the reduced-order …
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Model parameter estimation of atherosclerotic plaque mechanical properties : calculus-based and heuristic algorithms
… is globally convergent, shows immunity to ill-conditioning, and is expandable to more complex material models
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Techniques for robust source separation and localization in adverse environments: Issues and performance of a new framework of emerging techniques for frequency-domain convolutive blind/semi-blind separation and localization of acoustic sources
… In spite of recent developments many issues still need to be address to make such techniques robust in adverse conditions, such as high reverberation, ill-conditioning and occurrence of permutations. Furthermore, most of the proposed BSS methods are computationally expensive and not feasible …
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Stable Sparse Orthogonal Factorization of Ill-Conditioned Banded Matrices for Parallel Computing
… in the problems of computation with large-scale ill-conditioned banded matrices. Great concerns on existing methods include ill-conditioning, sparsity of factor matrices, computational complexity, and scalability. In this dissertation, we study a sparse orthogonal factorization of a banded matrix …
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Numerical analysis of cables in the offshore environment
… of their inherent flexibility which causes ill-conditioning of the stiffness matrices. Furthermore, the cable winding configuration causes a nonlinear stress-strain relationship, it's sagged geometry results in nonlinear strain-displacement relations, and the immersion in water leads to …
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Homotopy algorithms for the H² and the combined H²/H<sup>∞</sup> model order reduction problems
… However, they can fail to exist or be very ill conditioned. The conditions under which the input normal form and the Ly form become ill conditioned are examined. The over-parametrization formulation solves the ill conditioning issue, and usually is more efficient than the approach based on …
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Two-dimensional simulation of quantum well lasers including energy transport
… are included in the analysis. Sources of ill-conditioning in the simulation of thermal flow in semiconductor devices are considered, and a new conditioning scheme which gives a satisfactory convergence for the Newton method is also described. The boundary conditions for the energy flow …
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Advanced modeling and computational methods for distribution system state estimation
… a reliable state estimate while avoiding the ill-conditioning issues that plague the traditional iterative methods. Numerical tests have been successfully performed on the IEEE 13-bus and 123-bus case studies.
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