Página 17 dos resultados de 106770 itens digitais encontrados em 0.037 segundos

## Computational Method to Determine Reflected Ultrasonic Signals From Arbitrary-Geometry Targets

BUIOCHI, Flavio; BUIOCHI, Elaine B.; FORMIGONI, Paulo O.; ADAMOWSKI, Julio C.
Fonte: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC Publicador: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.04%
A computational method based on the impulse response and on the discrete representation computational concept is proposed for the determination of the echo responses from arbitrary-geometry targets. It is supposed that each point of the transducer aperture can be considered as a source radiating hemispherical waves to the reflector. The local interaction with each of the hemispherical waves at the reflector surface can be modeled as a plane wave impinging on a planar surface, using the respective reflection coefficient. The method is valid for all field regions and can be performed for any excitation waveform radiated from an arbitrary acoustic aperture. The effects of target geometry, position, and material on both the amplitude and the shape of the echo response are studied. The model is compared with experimental results obtained using broadband transducers together with plane and cylindrical concave rectangular reflectors (aluminum, brass, and acrylic), as well as a circular cavity placed on a plane surface, in a water medium. The method can predict the measured echoes accurately. This paper shows an improved approach of the method, considering the reflection coefficient for all incident hemispherical waves arriving at each point of the target surface.; FAPESP; CNPq; ANP; Petrobras

## Interactive geometry goes mobile with GeoTouch

Isotani, Seiji; Reis, Helena Macedo; Borges, Simone de Sousa; Lopes, Aparecida Maria Zem; Souza, João Paulo Tannus de; Brandão, Anarosa Alves Franco; Brandao, Leonidas de Oliveira
Fonte: Institute of Electrical and Electronics Engineers (IEEE); Athens Publicador: Institute of Electrical and Electronics Engineers (IEEE); Athens
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.04%
Interactive Geometry (IG) is a computational approach to teach geometry using interactive geometric objects. It is based on the learning-by-doing method where the representation and manipulation of geometric spaces can support students to construct their knowledge through experience. Several research findings indicate various benefits of using IG in classroom. Nevertheless, IG software developed to date has been based on the desktop model where the interaction between a user and the IG software occurs through the conventional inputs and outputs methods: keyboard, mouse, and a monitor. Currently, this model is being challenged by the widespread adoption and use of mobile devices. In this scenario before building an IG software that can be effectively used in mobile devices such as smartphones and tablets, where the input is based on touches and movements of fingers and the output is a small screen, there is a need to rethink the interface and what interaction methods should be employed. In response to this need, our paper examines the design and development of a GI application for mobile devices. In this study, we have proposed and implemented an interface and interaction model that is suitable for developing a GI software for mobile devices.

## Estudo da geometria de arestas de corte aplicadas em usinagem com altas velocidades de corte; Study of cutting edge geometry applied in high speed machining

Rodrigues, Alessandro Roger
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
36.04%

## Um método expedito de representação da geometria de uma rodovia na forma em que foi efetivamente construída; A rapid method of road geometry as built representation

Lotti, Cynthia Perpétua
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
36.04%

## Applets em ambientes de geometria dinâmica : ações para a formação de professores de matemática; Applets in dynamic geometry environments: actions for mathematics teacher eduaction

Barcelos, Gilmara Teixeira; Behar, Patrícia Alejandra; Passerino, Liliana Maria; Batista, Silvia Cristina Freitas
Tipo: Artigo de Revista Científica Formato: application/pdf
POR
Relevância na Pesquisa
36.04%
Na Matemática, os applets, em geral, permitem investigar, levantar e testar conjecturas e, assim, construir conhecimentos. Neste artigo destaca-se a importância da elaboração/modificação de applets, em ambientes de Geometria Dinâmica, desde a formação inicial de professores de Matemática. Em sentido mais amplo, defende-se que a formação inicial destes professores deve contemplar disciplinas relacionadas ao uso pedagógico das tecnologias digitais. Para tanto, relatam-se ações promovidas na disciplina Educação Matemática e Tecnologias (EMTs) e descreve-se o processo de elaboração/modificação de applets no GeoGebra (ambiente de Geometria Dinâmica). Finalizando, analisam-se dados de uma pesquisa qualitativa realizada com alunos da disciplina EMTs. A referida análise sinalizou que o uso e a elaboração/modificação de applets são importantes para a aprendizagem matemática.; Applets, in Mathematics learning, allow the user to investigate, make and test conjectures, which results in knowledge construction. This article emphasizes the importance of elaborating and modifying applets in Dynamic Geometry environments by Mathematics teachers. In a broader sense, it is argued that the initial teacher education should include disciplines related to the pedagogical use of digital technologies. In this context...

## Further investigation of the initial fission-track length and geometry factor in apatite fission-track thermochronology

Soares, Cleber J.; Guedes, Sandro; Tello, Carlos A.; Lixandrão Filho, Arnaldo L.; Osório, Ana M.; Alencar, Igor; Dias, Airton N.C.; Hadler, Julio
Tipo: Artigo de Revista Científica Formato: 1381-1392
ENG
Relevância na Pesquisa
36.04%
The external detector method (EDM) is a widely used technique in fission track thermochronology (FTT) in which two different minerals are concomitantly employed: spontaneous tracks are observed in apatite and induced ones in the muscovite external detector. They show intrinsic differences in detection and etching properties that should be taken into account. In this work, new geometry factor values, g, in apatite, were obtained by directly measuring the ρed/ρis ratios and independently determined [GQR]ed/is values through the measurement of projected lengths. Five mounts, two of which were large area prismatic sections and three samples composed of random-orientation pieces have been used to determine the g-values. A side effect of applying EDM is that the value of the initial confined induced fission track, L0, is not measured in routine analyses. The L 0-value is an important parameter to quantify with good confidence the degree of annealing of the spontaneous fission tracks in unknown-age samples, and is essential for accurate thermal history modeling. The impact of using arbitrary L0-values on the inference of sample thermal history is investigated and discussed. The measurement of the L0-value for each sample to be dated using an extra irradiated apatite mount is proposed. This extra mount can be also used for determining the g value as an extension of the ρed/ρis ratio method. Eight apatite samples from crystalline basement...

## Formação de professores leigos em serviço : um estudo sobre saberes e praticas docentes em geometria; Education of lay teachers during teaching practice: a study of teaching knowledge and practice in geometry

Maria Elidia Teixeira Reis
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
36.04%

## Geometria dos caminhos em grupos de Lie; Path geometry in Lie groups

Luciano Vianna Felix
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
36.04%
Neste trabalho estudamos a geometria dos caminhos em grupos de Lie usando a exponencial estocástica e o logaritmo estocástico. Apresentamos as construções geométricas do espaço tangente, uma métrica e uma conexão natural as caminhos em grupos de Lie. Finalmente apresentamos uma situação em que essa conexão é Levi-Civita e outra que não é; In this work, we study the path geometry in Lie groups using the stochastic exponential and the stochastic logarithm. We show the geometric constructions of tangent space, one metric and one natural conection of Lie groups valued path. Finelly we show one situation that this conection is Levi-Civita and another one that is not

## Geometria de Weyl e materia escura; Weyl geometry and dark matter

Ronaldo Savioli Sume Vieira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
36.04%
Neste trabalho fazemos um estudo de métricas lorentzianas e da teoria de conexões lineares em variedades diferenciáveis, focando em variedades de Weyl com métricas lorentzianas e conexões de Weyl. Também analisamos algumas teorias físicas baseadas nessa geometria, estendendo a essas teorias o modelo de Kuzmin para um disco fino de matéria. A partir desse estudo e do limite newtoniano das teorias, investigamos se esses resultados suprem a necessidade da presença de matéria escura em galáxias espirais para explicar as curvas de rotação observadas; In this work we study Lorentzian metrics and the theory of linear connections on smooth manifolds, focusing on Weyl manifolds with lorentzian metrics and Weyl connections. We also analyze some physical theories based on this geometry, extending to these theories the Kuzmin model for a thin disk of matter. From this study and from the newtonian limit of the theories, we examine if these results supply the necessity of the presence of dark matter in spiral galaxies to explain the observed rotation curves

## Sobre álgebras de Clifford, geometria projetiva e visão computacional; On Clifford algebras, projective geometry and computer vision

Eduardo Souza Mattos
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
36.04%
Atualmente, o estudo das Álgebras de Clifford é utilizado em inúmeras áreas de pesquisa. Uma delas é na área de Visão Computacional. O objetivo central dessa dissertação consiste em exibir noções sobre Álgebras de Clifford e sua utilização na formulação dos conceitos e definições de operações entre objetos da Geometria Projetiva e na formulação algébrica de câmeras virtuais, que é um dos assuntos tratados na área de Visão Computacional. Para isso são expostos de forma gradual e coerente os principais aspectos teóricos necessários para atingir os objetivos citados. Como resultado, as Álgebras de Clifford proporcionam uma excelente descrição da Geometria Projetiva e das câmeras virtuais.; Currently, the study of Clifford algebras are used in many research areas. One is in the area of Computer Vision. The main objective of this dissertation is to display notions of Clifford algebras and their use in formulating the concepts and definitions of transactions between objects of Projective Geometry and algebraic formulation of virtual cameras, which is one of the topics covered in Computer Vision. For it is exposed gradually and consistently the main theoretical aspects needed to achieve the goals mentioned. As a result...

## Algoritmos para problemas de geometria molecular; Algorithms for molecular geometry problems

Felipe Delfini Caetano Fidalgo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
36.04%
Neste trabalho, analisamos dois algoritmos da literatura para o "Molecular Distance Geometry Problem" (MDGP) e propomos um novo algoritmo que mantém a qualidade das soluções obtidas pelos dois anteriores e apresenta ganhos em termos de eficiência computacional. O MDGP consiste em determinar as posições dos átomos de uma molécula, no espaço tridimensional, a partir de um conjunto de distâncias entre eles. Quando todas as distâncias são conhecidas, o problema pode ser resolvido em tempo polinomial. Caso contrário, é um problema NP-difícil.; In this work, we analyse two algorithms from the bibliography to solve the so-called "Molecular Distance Geometry Problem" (MDGP). Then, we propose a new algorithm that keeps the quality on the solutions obtained by both the previous ones and shows gains regarding computacional efficiency. The MDGP consists on the determination of positions of atoms in a molecule, on the tridimensional space, from a set containing distances among them. When all the distances are known, the problem might be solved in polynomial time. Otherwise, it is an NP-hard problem.

## Geometria e topologia de cobordos; Geometry and topology of cobondaries

Llohann Dallagnol Sperança
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
36.04%
Nesse trabalho estudaremos a geometria e a topologia de algumas variedades homeomorfas, porém não difeomorfas, à esfera padrão Sn, chamadas esferas exóticas. Realizaremos duas dessas variedades como quocientes isométricos de fibrados principais com métricas de conexão sobre esferas de curvatura constante. Através disso, apresentaremos simetrias desses espaços e exemplos explícitos de difeomorfismos não isotópicos a identidade, usando-os para o cálculo de grupos de homotopia equivariante. Como mais uma aplicação dessa construção, provaremos que, se uma esfera homotópica de dimensão 15 é realizável como um fibrado linear sobre S8, então a mesma esfera é realizável como um fibrado linear sobre a esfera exótica de dimensão 8 com as mesmas funções de transição. No ultimo capítulo lidaremos com a geometria de fibrados induzidos, deduzindo uma condição necessária sobre a função indutora para que a métrica da conexão induzida tenha curvatura seccional não-negativa.; In this work we study the geometry and topology of manifolds homemorphic, but not diffeomorphic, to the standard sphere Sn, the so called exotic spheres. We realize two of these manifolds as isometric quotients of principal bundles with connection metrics over the constant curved sphere. Through this...

## Dividindo e conquistando com simetrias em geometria de distâncias; Divinding and conquering with symmetries in distance geometry

Felipe Delfini Caetano Fidalgo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
36.04%
Motivado por estudos em estruturas 3D de proteínas, biomoléculas imprescindíveis no estudo da vida, surgiu um problema chamado Discretizable Molecular Distance Geometry Problem (DMDGP) que provou ser NP-Difícil. Para resolvê-lo, existe um algoritmo da literatura, Branch & Prune (BP), que utiliza uma estratégia combinatória de exploração de uma árvore binária de soluções associada ao problema. Além disso, foram descobertas relações de simetria que permitem obter uma solução, a partir de outra, através de reflexões nos chamados vértices de simetria. Alguns pesquisadores passaram a realizar este trabalho em paralelo (ParallelBP), dividindo uma instância em sub-instâncias, resolvendo localmente com o BP (o que pode ser feito em duas direções) e unindo as sub-soluções com movimentos rígidos, com o intuito de determinar as soluções em menor tempo. Nossa proposta é fornecer uma estratégia Dividir-e-Conquistar para resolver o DMDGP, de modo a melhorar a abordagem em paralelo. Ela possui três estágios. Inicialmente, dividimos uma instância em sub-instâncias duas-a-duas sobrepostas através dos vértices de simetria. Depois, utiliza-se os chamados gaps para decidir a direção em que o BP deve fornecer a solução local. Por fim...

## Geometry of the moduli space of Higgs bundles

Hausel, Tamas
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.09%
This thesis contains work which appeared in several papers. Additionally to the results in the papers it contains a detailed introduction and some further proofs and remarks. The dissertation gives a description of the topology and symplectic and algebraic geometry of Hitchin's hyperkaehler moduli space M of rank 2 Higgs bundles with fixed determinant of odd degree over a fixed Riemann surface. After the long introduction it describes a compactification of M in great detail, using symplectic cutting (math.AG/9804083). Examining the downward Morse flow of a natural circle action on M it shows the vanishing of intersection numbers (math.AG/9805071). Examining the upward Morse flow it explains a set of generators of the cohomology ring and a conjectured explicit description of the cohomology ring (which was proven in math.AG/0003094). Then finally it introduces the resolution tower for M, and shows that its direct limit is homotopically equivalent with the classifying space of the gauge group. In turn it yields another proof of the generation theorem (as in math.AG/0003093) and also yields a purely algebraic geometric proof of the Mumford conjecture about the cohomology ring of the moduli space of rank 2 stable bundles on curves. It finishes by proving homotopy stabilizations in the resolution tower analogously to the Atiyah-Jones conjecture.; Comment: author's 1998 PhD thesis...

## Statistical mechanics approach to some problems in conformal geometry

Kiessling, Michael K. -H.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.09%
A weak law of large numbers is established for a sequence of systems of N classical point particles with logarithmic pair potential in $\bbR^n$, or $\bbS^n$, $n\in \bbN$, which are distributed according to the configurational microcanonical measure $\delta(E-H)$, or rather some regularization thereof, where H is the configurational Hamiltonian and E the configurational energy. When $N\to\infty$ with non-extensive energy scaling $E=N^2 \vareps$, the particle positions become i.i.d. according to a self-consistent Boltzmann distribution, respectively a superposition of such distributions. The self-consistency condition in n dimensions is some nonlinear elliptic PDE of order n (pseudo-PDE if n is odd) with an exponential nonlinearity. When n=2, this PDE is known in statistical mechanics as Poisson-Boltzmann equation, with applications to point vortices, 2D Coulomb and magnetized plasmas and gravitational systems. It is then also known in conformal differential geometry, where it is the central equation in Nirenberg's problem of prescribed Gaussian curvature. For constant Gauss curvature it becomes Liouville's equation, which also appears in two-dimensional so-called quantum Liouville gravity. The PDE for n=4 is Paneitz' equation, and while it is not known in statistical mechanics...

## Noncommutative Geometry and Conformal Geometry. III. Vafa-Witten Inequality and Poincar\'e Duality

Ponge, Raphaël; Wang, Hang
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.09%
This paper is the the third part of a series of paper whose aim is to use of the framework of \emph{twisted spectral triples} to study conformal geometry from a noncommutive geometric viewpoint. In this paper we reformulate the inequality of Vafa-Witten \cite{VW:CMP84} in the setting of twisted spectral triples. This involves a notion of Poincar\'e duality for twisted spectral triples. Our main results have various consequences. In particular, we obtain a version in conformal geometry of the original inequality of Vafa-Witten, in the sense of an explicit control of the Vafa-Witten bound under conformal changes of metric. This result has several noncommutative manifestations for conformal deformations of ordinary spectral triples, spectral triples associated to conformal weights on noncommutative tori, and spectral triples associated to duals of torsion-free discrete cocompact subgroups satisfying the Baum-Connes conjecture.; Comment: Final version. 38 pages

## A Serre-Swan theorem for bundles of bounded geometry

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.09%
The Serre-Swan theorem in differential geometry establishes an equivalence between the category of smooth vector bundles over a smooth compact manifold and the category of finitely generated projective modules over the unital ring of smooth functions. This theorem is here generalized to manifolds of bounded geometry. In this context it states that the category of Hilbert bundles of bounded geometry is equivalent to the category of operator *-modules over the operator *-algebra of continuously differentiable functions which vanish at infinity. Operator *-modules are generalizations of Hilbert C*-modules where C*-algebras have been replaced by a more flexible class of involutive algebras of bounded operators: Operator *-algebras. They play an important role in the study of the unbounded Kasparov product.; Comment: 32 pages

## The odd side of torsion geometry

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.09%
We introduce and study a notion of Sasaki with torsion structure' (ST) as an odd-dimensional analogue of K\"ahler with torsion geometry (KT). These are normal almost contact metric manifolds that admit a unique compatible connection with 3-form torsion. Any odd-dimensional compact Lie group is shown to admit such a structure; in this case the structure is left-invariant and has closed torsion form. We illustrate the relation between ST structures and other generalizations of Sasaki geometry, and explain how some standard constructions in Sasaki geometry can be adapted to this setting. In particular, we relate the ST structure to a KT structure on the space of leaves, and show that both the cylinder and the cone over an ST manifold are KT, although only the cylinder behaves well with respect to closedness of the torsion form. Finally, we introduce a notion of G-moment map'. We provide criteria based on equivariant cohomology ensuring the existence of these maps, and then apply them as a tool for reducing ST structures.; Comment: 34 pages; v2: added a small generalization (Proposition 3.6) of the cone construction; two references added. To appear on Ann. Mat. Pura Appl

## Foundation phase teachers' (limited) knowledge of geometry

Luneta,Kakoma
Fonte: South African Journal of Childhood Education Publicador: South African Journal of Childhood Education
Tipo: Artigo de Revista Científica Formato: text/html