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- Schulte, Peter, et al.
(författare)
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Cretaceous Extinctions: Evidence Overlooked Response
- 2010
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 328:5981, s. 975-976
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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- Correnty, Siobhán
(författare)
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Numerical methods for parameterized linear systems
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Solving linear systems of equations is a fundamental problem in engineering. Moreover, applications involving the solution to linear systems arise in the social sciences, business, and economics. Specifically, the research conducted in this dissertation explores solutions to linear systems where the system matrix depends nonlinearly on a parameter. The parameter can be a scalar or a vector, and a change in the parameter results in a change in the solution. Such a setting arises in the study of partial differential equations and time-delay systems, and we are interested in obtaining solutions corresponding to many values of the parameter simultaneously. The methods developed in this thesis can also be used to solve parameter estimation problems. Furthermore, software has been developed and is available online. This thesis consists of four papers and presents both algorithms and theoretical analysis. In Paper A, a linearization based on an infinite Taylor series expansion is considered. Specifically, the linearized system is a shifted parameterized system, and the parameter is a scalar. The GMRES method is used to solve the systems corresponding to many values of the parameter, and only one Krylov subspace basis matrix is required. Convergence analysis is based on solutions to a nonlinear eigenvalue problem and the magnitude of the parameter. Notably, the algorithm is carried out in a finite number of computations. The approach in Paper B is based on a preconditioned linearized system solved using the inexact GMRES method. In this setting, the linearization incorporates all terms in an infinite Taylor series expansion, and the preconditioner is applied approximately using iterative methods. Solutions corresponding to many values of the scalar parameter are generated from one subspace, and this is done in a finite number of linear algebra operations. Theoretical analysis, based on the error in the application of the preconditioner and the magnitude of the parameter, leads to a bound on the residual. Paper C proposes a short recurrence Krylov subspace method for solving linear systems that depend on a scalar parameter. In particular, a Chebyshev approximation is used to construct a linearization, and the linearized system is solved in a Bi-CG setting. Additionally, shift-and-invert preconditioning leads to fast convergence of the Krylov method for many different values of the parameter. An inexact variant of the method is also derived and analyzed. In Paper D, a reduced order model is constructed from snapshots to solve parameterized linear systems. Specifically, the parameter is a vector of dimension 2, and the sampling is performed on a sparse grid using the method proposed in Paper C. A tensor decomposition is utilized to build the model. Approaches of this kind are not always successful, and it is not known a priori if a decomposition will converge on a given set of snapshots. This work offers a novel way to generate a new set of snapshots in the same parameter space, to be used if the decomposition does not converge, with little extra computation.
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- Eriksson, Erik J., et al.
(författare)
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Acoustic impact on decoding of semantic emotions
- 2007
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Ingår i: Speaker classification II. - Berlin : Springer. - 9783540741213 ; , s. 57-69
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This paper examines the interaction between the emotion indicated by the content of an utternance and the emotion indicated by the acoustic of an utterance, and considers whether a speaker can hide their emotional state by acting an emotion even though being semantically honest. Three female and two male speakers of Swedish were recorded saying the sentences “Jag har vunnit en miljon pa° lotto” (I have won a million on the lottery), “Det finns böcker i bokhyllan” (There are books on the bookshelf) and “Min mamma har just dött” (my mother just died) as if they were happy, neutral (indifferent), angry or sad. Thirty-nine experimental participants (19 female and 20 male) heard 60 randomly selected stimuli randomly coupled with the question “Do you consider this speaker to be emotionally X?”, where X could be angry, happy, neutral or sad. They were asked to respond yes or no; the listeners’ responses and reaction times were collected. The results show that semantic cues to emotion play little role in the decoding process. Only when there are few specific acoustic cues to an emotion do semantic cues come into play. However, longer reaction times for the stimuli containing mismatched acoustic and semantic cues indicate that the semantic cues to emotion are processed even if they impact little on the perceived emotion.
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- Eriksson, Erik J, et al.
(författare)
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Dialect recognition in a noisy environment : preliminary data
- 2007
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Ingår i: Proceedings from Fonetik 2007. ; , s. 101-104
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The ability to identify the dialect spoken by an individual by voice alone has beenwidely investigated for many languages. The studies suggest a large degree of individualvariation in dialect recognition ability and that factors such as perceptualdistance and competence in the language interact with this variation. Trained listenershave also been shown to be unstable in their judgements of dialect. In the studypresented here naïve listeners attending a trade fair in Umeå were asked to selectbetween eight given dialects when identifying two dialects. The test environment wasnoisey. The level of the background noise changed with the flow of people and activitiesassociated with the trade fair. The noisy environment did not appear to affectthe listeners responses.
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