10,461 research outputs found
A fast subspace optimization method for nonlinear inverse problems in Banach spaces with an application in parameter identification
No full textWald(vertrags)naturschutz aus Sicht der Nachfrager
Full text linkZiel des WaVerNa-Arbeitspakets „Ökonomische Analysen zur Nachfrageseite“ war die transaktionskostentheoretische Untersuchung von Instrumenten des Wald(vertrags)naturschutzes der Nachfrager. Hierfür wurden der Umsetzungsstand des Wald(vertrags)naturschutzes erhoben und die aktuell eingesetzten Instrumente untersucht. Für die vergleichende Analyse erfolgte eine Kategorisierung der Instrumente nach der
Ausprägung ihrer Merkmale auf Grundlage einer transaktionskostentheoretisch weiterentwickelten Systematik zu Zahlungen für Ökosystemleistungen. Die systematisierten Instrumente wurden anschließend anhand von Befunden aus Fallstudien sowie wissenschaftlichen Veröffentlichungen im Hinblick auf Kontinuität, Flexibilität, Rechtssicherheit und Akzeptanz bewertet
On parameter identification problems for elliptic boundary value problems in divergence form, Part I: An abstract framework
No full textParameter identification problems for partial differential equations are an important subclass of inverse problems. The parameter-to-state map, which maps the parameter of interest to the respective solution of the PDE or state of the system, plays the central role in the (usually nonlinear) forward operator. Consequently, one is interested in well-definedness and further analytic properties such as continuity and differentiability of this operator w.r.t. the parameter in order to make sure that techniques from inverse problems theory may be successfully applied to solve the inverse problem. In this work, we present a general functional analytic framework suited for the study of a huge class of parameter identification problems including a variety of elliptic boundary value problems (in divergence form) with Dirichlet, Neumann, Robin or mixed boundary conditions. In particular, we show that the corresponding parameter-to-state operators fulfil, under suitable conditions, the tangential cone condition, which is often postulated for numerical solution techniques. This framework particularly covers the inverse medium problem and an inverse problem that arises in terahertz tomography
On parameter identification problems for elliptic boundary value problems in divergence form, Part I: An abstract framework
No full textParameter identification problems for partial differential equations are an important subclass of inverse problems. The parameter-to-state map, which maps the parameter of interest to the respective solution of the PDE or state of the system, plays the central role in the (usually nonlinear) forward operator. Consequently, one is interested in well-definedness and further analytic properties such as continuity and differentiability of this operator w.r.t. the parameter in order to make sure that techniques from inverse problems theory may be successfully applied to solve the inverse problem. In this work, we present a general functional analytic framework suited for the study of a huge class of parameter identification problems including a variety of elliptic boundary value problems (in divergence form) with Dirichlet, Neumann, Robin or mixed boundary conditions. In particular, we show that the corresponding parameter-to-state operators fulfil, under suitable conditions, the tangential cone condition, which is often postulated for numerical solution techniques. This framework particularly covers the inverse medium problem and an inverse problem that arises in terahertz tomography
Patrick Wald Lasowski (éd.) :Romanciers libertins du 18e siècle. Avec la collaboration d'A. Clairval, J.-P. Dubost, M. Hénaff, P. Saint-Amand, R. Wald Lasowski, tome 1, 2000
No full textDeneys-Tunney Anne. Patrick Wald Lasowski (éd.) :Romanciers libertins du 18e siècle. Avec la collaboration d'A. Clairval, J.-P. Dubost, M. Hénaff, P. Saint-Amand, R. Wald Lasowski, tome 1, 2000. In: Dix-huitième Siècle, n°35, 2003. L'épicurisme des Lumières, sous la direction de Anne Deneys-Tunney et Pierre-François Moreau. pp. 573-574
Anne as Pagan, Anne as Queer
No full text‘Anne as Pagan, Anne as Queer’ is a critical and creative answer to the question: How do we construct Anne Shirley, and what does she mean to us? This creative research submission is a work of fanfiction, specifically a mash up based on Anne of the Island, L.M.M. Montgomery’s sequel to Anne of Green Gables. In this short work of fiction (under 4 thousand words) Anne is revealed as a changeling, one of the Faerie Folk, and also a being not strictly male or female; sometimes neither, sometimes both. The mash up is based on the last two chapters of Anne of the Island, the scenes in which Gilbert Blythe is seriously ill and Anne realises she loves him. This realisation causes Anne, in this version, to reveal to Gilbert that she is both non-human and not a girl, and to use Faerie magic to save Gilbert’s life. Anne’s revelation causes Gilbert a great relief, as he has been keeping a secret also - that he too is queer. The piece has an accompanying research statement and reflection, that reflects on the ways the contributor/author interprets Anne, as a being troubled by gender, and not strictly gender conforming. The much-loved scene from Anne of Green Gables in which Anne realises she is not wanted by the Cuthberts because she is not a boy is inserted into the mash up (as a memory) as this scene is the principal cause for the contributor’s identification with Anne as a gender non-conforming figure who resists gender expectations. Overall, this creative and critical work and reflection queers both Anne as a character and the Anne of the Island novel.Book chapter - work of fiction with a critical reflective essa
Sequentielle Unterraum-Optimierung für nichtlineare inverse Probleme mit einer Anwendung in der Terahertz-Tomographie
No full textWe introduce a sequential subspace optimization (SESOP) method for the iterative solution of nonlinear inverse problems in Hilbert spaces, based on the well-known methods for linear problems. The key idea is to use multiple search directions per iteration. Their length is determined by the nonlinearity and the local character of the forward operator. This choice admits a geometric interpretation after which the method is originally named: The current iterate is projected sequentially onto (intersections of) stripes, which emerge from affine hyperplanes whose respective normal vectors are given by the search directions and contain the solution set of the unperturbed inverse problem. We prove convergence and regularization properties and present a fast method using two search directions, which is evaluated by solving a simple nonlinear problem. Furthermore, we extend our methods for complex Hilbert spaces and apply it to solve the inverse problem of terahertz tomography, a nonlinear parameter identification problem based on the Helmholtz equation, which consists in the nondestructive testing of dielectric media. The tested object is illuminated by an electromagnetic Gaussian beam and the goal is the reconstruction of the complex refractive index from measurements of the electric field. We conclude with some numerical reconstructions from synthetic data.In der vorliegenden Arbeit stellen wir eine Erweiterung der sequentiellen Unterraum-Optimierung (SESOP) zur Lösung nichtlinearer inverser Probleme in Hilberträumen vor, welche auf den bereits bekannten Verfahren für lineare Probleme basiert. Dabei handelt es sich um eine iterative Methode, bei der in jedem Schritt mehrere Suchrichtungen verwendet werden. Die Berechnung der Schrittweite berücksichtigt die Nichtlinearität des Vorwärtsoperators und lässt eine anschauliche geometrische Interpretation zu, welche dem Verfahren ursprünglich ihren Namen gab: Die aktuelle Iterierte wird sequentiell auf (den Schnitt von) Streifen projiziert. Diese Streifen gehen aus affinen Hyperebenen hervor und enthalten die Lösungsmenge des inversen Problems bei exakten Daten. Wir zeigen Konvergenz- und Regularisierungseigenschaften des Verfahrens. Insbesondere geben wir ein schnelles Verfahren mit zwei Suchrichtungen an und evaluieren die Methode anhand eines einfachen Beispiels. Anschließend weiten wir die Methode auf komplexe Hilberträume aus und verwenden diese zur Lösung des inversen Problems der Terahertz-Tomographie. Dabei wird ein nichtleitendes, nichtmagnetisches Objekt mithilfe eines elektromagnetischen Gaußstrahls abgetastet. Das Ziel ist die Rekonstruktion des komplexen Brechungsindex aus Messungen des elektrischen Feldes. Dieses inverse Problem modellieren wir als Parameteridentifikationsproblem mithilfe der Helmholtzgleichung. Schließlich erzeugen wir für verschiedene Objekte synthetische Daten und rekonstruieren daraus den komplexen Brechungsindex
Umsetzung von Vertragsnaturschutz im deutschen Wald
Full text linkMit dem WaVerNa-Projekt sollte ein bundesweiter Überblick zur Umsetzung von Vertragsnaturschutz im deutschen Wald gewonnen werden. Hierzu wurden von den Verbundprojektpartnern bundesweite Erhebungen zum Status quo sowie vertiefende Fallstudien durchgeführt. Da diese Erhebungen zentrale Datengrundlage für die weiteren Analysen der Teilprojekte waren, werden nachfolgend das Vorgehen und zentrale Ergebnisse dieser Arbeitsschritte vorgestellt
Parameter identification for elliptic boundary value problems: an abstract framework and applications
No full textAbstractParameter identification problems for partial differential equations are an important subclass of inverse problems. The parameter-to-state map, which maps the parameter of interest to the respective solution of the PDE or state of the system, plays the central role in the (usually nonlinear) forward operator. Consequently, one is interested in well-definedness and further analytic properties such as continuity and differentiability of this operator w.r.t. the parameter in order to make sure that techniques from inverse problems theory may be successfully applied to solve the inverse problem. In this work, we present a general functional analytic framework suited for the study of a huge class of parameter identification problems including a variety of elliptic boundary value problems with Dirichlet, Neumann, Robin or mixed boundary conditions in Hilbert and Banach spaces and possibly complex-valued parameters. In particular, we show that the corresponding parameter-to-state operators fulfill, under suitable conditions, the tangential cone condition, which is often postulated for numerical solution techniques. This framework particularly covers the inverse medium problem and an inverse problem that arises in terahertz tomography
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