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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

On a class of one-parameter operator semigroups with state space Rn x Zm generated by pseudo-differential operators

Morris, Owen Christopher January 2013 (has links)
The thesis shows that, under suitable conditions, a pseudo-differential operator, defined on some "nice" set of functions on Rn x Zm, with continuous negative definite symbol q(x,xi,o) extends to a generator of a Feller semigroup. Sections 1-5 are the preliminary sections, these sections discuss some harmonic analysis concerning locally compact Abelian groups. The essence of this thesis are Sections 6-13, which deals with obtaining the estimates required for the fulfilment of the conditions of the Hille-Yosida-Ray theorem.
182

The Effect of Procedural Injustice on Cooperation with 911 Operators and Criminal Justice Authorities: A Factorial Vignette-Based Study

January 2018 (has links)
abstract: Prior research looking at procedural justice has largely focused on legal authorities, such as the police. There is a gap in the research regarding the influence of procedurally-just treatment of other criminal justice professionals, including 911 operators. These individuals are often the first contact citizens have when initiating police services, and it is likely that 911 operators set the stage for how police encounters with the public unfold. Using a factorial vignette design, this study tests the causal links between procedural injustice and several outcome measures, including cooperation, satisfaction, callback likelihood, and willingness to testify in court. Data from a university-based sample (n=488) were used to estimate a series of ordinal regression models. The results show that participants who received the injustice stimuli were generally less likely to report they would call 911 in the future, cooperate with the 911 operator if asked additional questions, cooperate with the police once they arrived on the scene, and had lower levels of satisfaction with the how the operator handled the call. These results were significant across two different scenarios (i.e., breaking and entering and traffic accident). Seriousness of the encounter also varied across these outcomes, but the magnitude of the effect was more modest. The results demonstrate the effect non-sworn personnel, such as 911 operators, can have on the outcome of police-citizen encounters. / Dissertation/Thesis / Masters Thesis Criminology and Criminal Justice 2018
183

Local spectral asymptotics and heat kernel bounds for Dirac and Laplace operators

Li, Liangpan January 2016 (has links)
In this dissertation we study non-negative self-adjoint Laplace type operators acting on smooth sections of a vector bundle. First, we assume base manifolds are compact, boundaryless, and Riemannian. We start from the Fourier integral operator representation of half-wave operators, continue with spectral zeta functions, heat and resolvent trace asymptotic expansions, and end with the quantitative Wodzicki residue method. In particular, all of the asymptotic coefficients of the microlocalized spectral counting function can be explicitly given and clearly interpreted. With the auxiliary pseudo-differential operators ranging all smooth endomorphisms of the given bundle, we obtain certain asymptotic estimates about the integral kernel of heat operators. As applications, we study spectral asymptotics of Dirac type operators such as characterizing those for which the second coefficient vanishes. Next, we assume vector bundles are trivial and base manifolds are Euclidean domains, and study non-negative self-adjoint extensions of the Laplace operator which acts component-wise on compactly supported smooth functions. Using finite propagation speed estimates for wave equations and explicit Fourier Tauberian theorems obtained by Yuri Safarov, we establish the principle of not feeling the boundary estimates for the heat kernel of these operators. In particular, the implied constants are independent of self-adjoint extensions. As a by-product, we affirmatively answer a question about upper estimate for the Neumann heat kernel. Finally, we study some specific values of the spectral zeta function of two-dimensional Dirichlet Laplacians such as spectral determinant and Casimir energy. For numerical purposes we substantially improve the short-time Dirichlet heat trace asymptotics for polygons. This could be used to measure the spectral determinant and Casimir energy of polygons whenever the first several hundred or one thousand Dirichlet eigenvalues are known with high precision by other means.
184

Alguns resultados sobre a teoria de restrição da transformada de Fourier

Aquino, Junielson Pantoja de January 2016 (has links)
A análise harmônica e o ramo da matemática que estuda a representação de funções ou sinais como a sobreposição de ondas base. Ela investiga e generaliza as noções das séries de Fourier e da transformação de Fourier. Neste trabalho, investigou-se um teorema de restrição da transformada de Fourier devido a Mitsis e Mockenhaupt (uma generalização do teorema de Stein-Tomas). Foram realizados estudos analíticos sobre o método para operadores integrais oscilatórios, baseado na fase estacionária. Os resultados permitem deduzir o teorema de restrição no plano (em seu caso geral) e o teorema de Carleson-Sjölin. / Harmonic analysis is the mathematical branch that studies the function or signals representation as a base wave overlay. It investigates and generalizes the notions of Fourier series and of the Fourier transform. In this work, was investigated a restriction theorem of the Fourier transform due to Mitsis and Mockenhaupt (a generalization of Stein-Tomas theorem) . Were performed analytic studies on the method for oscillating integral operators, based in the stationary phase. The results allow deducing the restriction theorem on the plane (in the general case) and the Carleson-Sjölin theorem.
185

A study on a calculus for the Tk,x,y,z-operator

Khan, Mumtaz Ahmad, Rouhi, Bijan 25 September 2017 (has links)
The present paper deals with the calculus of Tk,x,y,z - operator. The operator is a three variable analogue of the operator given earlier by W. A. Al-Salam [1] and H. B. Mittal [10]. The operator is useful for finding operational representations and generating functions of polynomials of three variables and will be dealt in a separate communication.
186

Substitution operators

Vanessa Rocha, Andréa 31 January 2009 (has links)
Made available in DSpace on 2014-06-12T18:28:46Z (GMT). No. of bitstreams: 2 arquivo4238_1.pdf: 678788 bytes, checksum: 1a19da235845c146881443f4bbcb79b9 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2009 / Nós estudamos um novo tipo de processo estocástico a tempo discreto, que nós chamamos de processos de substituição. Como o tempo é discreto, nós podemos definir este processo através de um operador que transforma uma medida de probabilidade (em um certo espaço) em outra. Vale a pena notar que a maioria dos estudos de processos de partículas interagentes se baseia na suposição de que o conjunto de sítios, também chamado de espaço, não muda ao longo da interação. Existem apenas poucos trabalhos onde os sítios podem aparecer e desaparecer durante a realização do processo, e este trabalho é um deles. Considere então um conjunto finito não-vazio A chamado de alfabeto, cujos elementos são chamados de letras. Sequências finitas de letras são chamadas de palavras e o comprimento de uma palavra é o número de letras que existe nela. Os elementos de AZ (sequências bi-infinitas de letras) são chamados de configurações. Denotamos por M o conjunto de medidas de probabilidade invariantes por translação. Nós podemos definir um operador de substituição genérico como um operador de M em M que substitui cada ocorrência de uma palavra G (onde G precisa satisfazer uma certa condição) em uma configuração por outra palavra H com probabilidade ρ, onde ρ pertence a [0; 1], independentemente das outras ocorrências. A nossa maior contribuição é dada pela definição e estudo dos operadores de substituição em geral. O caso mais interessante do operador de substituição, na nossa opinião, é o caso em que G e H têm comprimentos diferentes; a própria definição do operador neste caso é não-trivial. De fato, foi preciso desenvolver uma teoria de aproximação de medidas por sequências de palavras para lidar com este caso. Uma dificuldade com este caso é que os operadores de substituição não são lineares. No entanto, foi possível provar que todos eles são finos, que nos parece ser a melhor propriedade depois da linearidade. Nós também provamos que todos os operadores de substituição são contínuos e nós utilizamos este fato para obter conclusões a respeito da existência de medidas invariantes por estes operadores, o que nos ajuda a estudar ergodicidade do processo de substituição. Por fim, nós esperamos que estas propriedades possam ser relacionadas com certas necessidades de ciências aplicadas
187

Normal Spectrum of a Subnormal Operator

Kumar, Sumit January 2013 (has links) (PDF)
Let H be a separable Hilbert space over the complex field. The class S := {N|M : N is normal on H and M is an invariant subspace for Ng of subnormal operators. This notion was introduced by Halmos. The minimal normal extension Ň of a subnormal operator S was introduced by σ (S) and then Bram proved that Halmos. Halmos proved that σ(Ň) (S) is obtained by filling certain number of holes in the spectrum (Ň) of the minimal normal extension Ň of a subnormal operator S. Let σ (S) := σ (Ň) be the spectrum of the minimal normal extension Ň of S; which is called the normal spectrum of a subnormal operator S: This notion is due to Abrahamse and Douglas. We give several well-known characterization of subnormality. Let C* (S1) and C* (S2) be the C*- algebras generated by S1 and S2 respectively, where S1 and S2 are bounded operators on H: Next we give a characterization for subnormality which is purely C - algebraic. We also establish an intrinsic characterization of the normal spectrum for a subnormal operator, which enables us to answer the fol-lowing two questions. Let II be a *- representation from C* (S1) onto C* (S2) such that II(S1) = S2. If S1 is subnormal, then does it follow that S2 is subnormal? What is the relation between σ (S1) and σ (S2)? The first question was asked by Bram and second was asked by Abrahamse and Douglas. Answers to these questions were given by Bunce and Deddens.
188

Normal Spectrum of a Subnormal Operator

Kumar, Sumit January 2013 (has links) (PDF)
Let H be a separable Hilbert space over the complex field. The class S := {N|M : N is normal on H and M is an invariant subspace for Ng of subnormal operators. This notion was introduced by Halmos. The minimal normal extension Ň of a subnormal operator S was introduced by σ (S) and then Bram proved that Halmos. Halmos proved that σ(Ň) (S) is obtained by filling certain number of holes in the spectrum (Ň) of the minimal normal extension Ň of a subnormal operator S. Let σ (S) := σ (Ň) be the spectrum of the minimal normal extension Ň of S; which is called the normal spectrum of a subnormal operator S: This notion is due to Abrahamse and Douglas. We give several well-known characterization of subnormality. Let C* (S1) and C* (S2) be the C*- algebras generated by S1 and S2 respectively, where S1 and S2 are bounded operators on H: Next we give a characterization for subnormality which is purely C - algebraic. We also establish an intrinsic characterization of the normal spectrum for a subnormal operator, which enables us to answer the fol-lowing two questions. Let II be a *- representation from C* (S1) onto C* (S2) such that II(S1) = S2. If S1 is subnormal, then does it follow that S2 is subnormal? What is the relation between σ (S1) and σ (S2)? The first question was asked by Bram and second was asked by Abrahamse and Douglas. Answers to these questions were given by Bunce and Deddens.
189

Continuity of generalized inverses in Banach algebras

Behrendt, Darren Robin 24 January 2012 (has links)
M.Sc.
190

The role of secondary education in operator employability in the automotive industry

Puchert, Juliet January 2014 (has links)
This study was designed to assess the role of secondary education in the employability of operators in the South African automotive industry. Five types of secondary education are referred to, namely, a secondary education including Mathematics and Science as subjects; a matriculation with Mathematics as a subject; a secondary education inclusive of Science as a subject; a technical type Grade 12 qualification and a general form of secondary education. A two-phase aptitude testing selection process, employing three sub-tests from the Differential Aptitude Test (DAT-K) and five from the Trade Aptitude Test (TRAT) batteries, was utilised to assess whether there were significant differences in aptitude test scores of applicants with different types of secondary education. These aptitude measures were administered to 2 463 preselected respondents. Descriptive statistics such as median, mode and frequency distribution graphs were used. Statistical analysis was also carried out, using the Chi-square test of independence, to determine the differences in aptitude test results obtained by the groups in the study. The study‟s findings revealed that the type of Grade 12 qualification held by applicants is an important criterion to be considered in the selection of automotive operators. The findings specifically indicated that a secondary education that included Mathematics and/or Science as subjects resulted in notable performance in the aptitude instruments employed in this study. The findings are broadly relevant to the South African automotive industry and are of value to human resource practitioners, educators, social scientists and other researchers.

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