638 research outputs found
The finite section method in the space of essentially bounded functions: An approach using limit operators
No full textWe present an approach to the finite section method for band-dominated operators - the norm-limits of band operators on L∞(ℝn). We hereby show that the sequence of finite sections is stable if and only if some associated operator is invertible at infinity. By means of the theory in Lindner and Silbermann (Lindner, M., Silbermann, B. (2003). Invertibility at infinity of band-dominated operators in the space of essentially bounded functions, (accepted at) Integral Equations and Operator Theory.) and Lindner (Lindner, M. (2003). Classes of multiplication operators and their limit operators (submitted to) Zeitschrift für Analysis und ihre Anwendungen), we study this invertibility at infinity using limit operators. Having the mentioned criterion at our disposal, we will give some applications in an algebra of convolution and multiplication operators: one for the usual finite section method and one for an approximation method of operators on the space of continuous functions
Über einige neuseeländische Stratiomyiiden Osten-Sackens im Deutschen Entomologischen Institut in Berlin (Diptera).
No full textDer Verfasser berichtet über 11 Arten der Dipteren-Familie Stratiomyiidae. Er gibt Neubeschreibungen von 2 Gattungen und 6 Arten.Nomenklatorische Handlungenamoena Lindner, 1958 (Australoberis), spec. n.parvula Lindner, 1958 (Dysbiota), spec. n.osten-sackeni Lindner, 1958 (Neoexaireta), spec. n.smaragdina Lindner, 1958 (Neoexaireta), spec. n.venusta Lindner, 1958 (Neoexaireta), spec. n.Australoberis Lindner, 1958 (Stratiomyiidae), gen. n.Dysbiota Lindner, 1958 (Stratiomyiidae), gen. n.The author deals with 11 species of Stratiomyiidae (Diptera). He dercribes as new 2 genera and 6 species. Nomenclatural Actsamoena Lindner, 1958 (Australoberis), spec. n.parvula Lindner, 1958 (Dysbiota), spec. n.osten-sackeni Lindner, 1958 (Neoexaireta), spec. n.smaragdina Lindner, 1958 (Neoexaireta), spec. n.venusta Lindner, 1958 (Neoexaireta), spec. n.Australoberis Lindner, 1958 (Stratiomyiidae), gen. n.Dysbiota Lindner, 1958 (Stratiomyiidae), gen. n
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Convergence and numerics of a multisection method for scattering by three-dimensional rough surfaces
No full textWe introduce a novel multisection method for the solution of integral equations on unbounded domains. The method is applied to the rough surface scattering problem in three dimensions, in particular to a Brakhage-Werner-type integral equation for acoustic scattering by an unbounded rough surface with Dirichlet boundary condition, where the fundamental solution is replaced by some appropriate half-space Green's function. The basic idea of the multisection method is to solve an integral equation A phi = f by approximately solving the equation P(rho)AP(tau phi) = P(rho)f for some positive constants rho,tau. Here P(rho) is a projection operator that truncates a function to a ball with radius rho > 0. For a very general class of operators A, for which the Brakhage-Werner equation from acoustic scattering is a particular example, we will show existence of approximate solutions to the multisection equation and show that approximate solutions to the multisection equation approximate the true solution phi(0) of the operator equation A(phi) = f. Finally, we describe a numerical implementation of the multisection algorithm and provide numerical examples for the case of rough surface scattering in three dimensions
An insider's guide to working for the federal government: navigating all levels of government as a civil servant or contractor/ Dan Lindner.
No full textIncludes bibliographical references and index.With simple, to-the-point, explanations of the different branches and agencies of government, insider Dan Lindner guides prospective employees and contractors through the halls of bureaucracy, giving readers everything they need to know to excel in the federal environment.Preface -- 1. The Tricameral Form of Government -- 2. Departments and Agencies -- 3. The Civil Service -- 4. How to Get a Job -- 5. Retirement -- 6. Classified Work -- 7. Contractors -- 8. Staff Work -- 9. Excellence on the Job: Employee Dos and Don'ts -- 10. Managing-Supervision -- 11. Communication -- 12. Meetings and Presentations -- 13. Some Historical Case Studies -- Bibliography -- Index -- About the Author.1 online resource (viii, 196 pages
New records of Stratiomyidae (Diptera) from the Near East with a key to the species of Israel, Sinai and the Golan
No full textA supplement is given to the publications of the senior author (Lindner, 1974 and 1975) on the Stratiomyidae of the Near East. Pachygaster atra Panzer and Aspidacantha atra Kertesz (Pachygastrinae) are recorded from the area for the first time. The male of Heradina galeata Lindner is described for the first time. New synonyms are established, and a key is given to all the species recorded so far from the area
Researching the characteristics of stalkers
No full textDiplomska naloga Raziskovanje značilnosti zalezovalcev se osredotoča na pregled metodologije nekaterih obstoječih raziskav, ki se navezujejo na zalezovalce. Zalezovanje predstavlja kompleksen problem sodobnega časa, ki se dotika tako pravnih in psiholoških vidikov kot tudi družbe same. Velja za zapleteno obliko človeškega vedenja, ki ga je zaradi velikega obsega dejavnikov in zavedanja žrtve težko predvideti ter preprečevati. Raziskovalci se pri raziskovanju pogosto srečujejo s težavami, povezanimi z merjenjem občutljivih vedenj in motivacij zalezovalcev, zato je ustreznost merskih instrumentov in njihova izbira ključna za učinkovitejše razvijanje preventivnih in intervencijskih ukrepov. V diplomskem delu smo preverili, kako so značilnosti zalezovalcev raziskovali v obstoječi znanstveni literaturi s poudarkom na uporabljenih raziskovalnih pristopih, metodologiji in kakovosti zbranih podatkov. Glavni cilj je bil ugotoviti prednosti in pomanjkljivosti uporabljenih vprašalnikov. Analizirali smo vsebine 36 člankov, ki smo jih pridobili v podatkovni bazi Web Of Science in Cobiss. Ugotovili smo, da so metodološke značilnosti raziskav pogosto pomanjkljivo napisane. Raziskovalci so uporabili predvsem kombinacije prilagojenih avtorskih vprašalnikov, narejenih po literaturi drugih avtorjev in ocenjevalne lestvice. Vprašalniki so bili pogosteje navedeni kot veljavni, vendar delno kakovostni. Najpogosteje so raziskovalci uporabili neverjetnostno priložnostno in namensko vzorčenje. Majhni vzorci, možnost subjektivnosti, uporaba hipotetičnih scenarijev, napake samoporočanja in neodzivnost udeležencev so predstavljali najpogostejše omejitve raziskav.The thesis, Researching the characteristics of stalkers, focuses on reviewing the methodologies of existing studies on stalking. Stalking represents a multifaceted issue in modern society, involving legal, psychological and social dimensions. It is considered a complex form of human behaviour, which, due to the multitude of influencing factors and the victim\u27s awareness, is difficult to predict and prevent. Researchers often face challenges when studying sensitive behaviours and the motivation of stalkers, which is why appropriate measurement instruments are crucial for the effective development of preventive and intervention strategies. This thesis examines how the characteristics of stalkers have been studied in the existing scientific literature, with a focus on research approaches, methodologies and quality of collected data. The main goal was to determine the advantages and limitations of the questionnaires used. We have done a content analysis of 36 research articles retrieved from Web of Science and Cobiss. We found that the reporting of the methodologies was often insufficiently described. Most researchers relied on adapted, author-designed questionnaires and rating scales. The questionnaires were more frequently cited as valid but partly of limited quality. The most commonly used sampling methods were non-probability sampling, such as convenience and purposive sampling. Small samples, the possibility of bias, the use of hypothetical scenarios, self-reporting errors and non-responsiveness of participants represented the most common limitations of the studies
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Gershgorin-type spectral inclusions for matrices
No full textIn this paper we derive sequences of Gershgorin-type inclusion sets for the spectra and pseudospectra of finite matrices. In common with previous generalisations of the classical Gershgorin bound for the spectrum, our inclusion sets are based on a block decomposition. In contrast to previous generalisations that treat the matrix as a perturbation of a block-diagonal submatrix, our arguments treat the matrix as a perturbation of a block-tridiagonal matrix, which can lead to sharp spectral bounds, as we show for the example of large Toeplitz matrices. Our inclusion sets, which take the form of unions of pseudospectra of square or rectangular submatrices, build on our own recent work on inclusion sets for bi-infinite matrices
[Chandler-Wilde, Chonchaiya, Lindner, J. Spectr. Theory 14, 719-804 (2024)]
Gershgorin-Type Spectral Inclusions for Matrices
No full textIn this paper we derive families of Gershgorin-type inclusion sets for the
spectra and pseudospectra of finite matrices. In common with previous
generalisations of the classical Gershgorin bound for the spectrum, our
inclusion sets are based on a block decomposition. In contrast to previous
generalisations that treat the matrix as a perturbation of a block-diagonal
submatrix, our arguments treat the matrix as a perturbation of a
block-tridiagonal matrix, which can lead to sharp spectral bounds, as we show
for the example of large Toeplitz matrices. Our inclusion sets, which take the
form of unions of pseudospectra of square or rectangular submatrices, build on
our own recent work on inclusion sets for bi-infinite matrices [Chandler-Wilde,
Chonchaiya, Lindner, {\em J. Spectr. Theory} {\bf 14}, 719--804 (2024)].Comment: 28 pages + 9 pages of Supplementary Informatio
A metric approach to limit operators
No full textWe extend the limit operator machinery of Rabinovich, Roch, and Silbermann from Z^N to (bounded geometry, strongly) discrete metric spaces. We do not assume the presence of any group structure or action on our metric spaces. Using this machinery and recent ideas of Lindner and Seidel, we show that if a metric space X has Yu's property A, then a band-dominated operator on X is Fredholm if and only if all of its limit operators are invertible. We also show that this always fails for metric spaces without property
Finiteness and children with specific language impairment: an exploratory study
No full textChildren with specific language impairment (SLI) are well known for their difficulties in mastering the inflectional paradigms; in the case of learning German they also have problems with the appropriate verb position, in particular with the verb in second position. This paper explores the possibilities of applying a broader concept of finiteness to data from children with SLI in order to put their deficits, or rather their skills, into a wider perspective. The concept, as developed by Klein (1998, 2000), suggests that finiteness is tied to the assertion that a certain state of affairs is valid with regard to some topic time; that is, finiteness relates the propositional content to the topic component. Its realization involves the interaction of various grammatical devices and, possibly, lexical means like temporal adverbs. Furthermore, in the acquisition of finiteness it has been found that scope particles play a major role in both first- and second-language learning. The purpose of this paper is to analyze to what extent three German-learning children with SLI have mastered these grammatical and lexical means and to pinpoint the phase in the development of finiteness they have reached. The data to be examined are mostly narrative and taken from conversations and experiments. It will be shown that each child chooses a different developmental path to come to grips with the interaction of these devices
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