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Rotation effect on geodesic and zonal flow modes in tokamak plasmas with isothermal magnetic surfaces

Elfimov, Artour; Galvao, Ricardo Magnus Osorio; Sgalla, Reneé Jordashe Franco
Fonte: IOP PUBLISHING LTD Publicador: IOP PUBLISHING LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.35%
The electrostatic geodesic mode oscillations are investigated in rotating large aspect ratio tokamak plasmas with circular isothermal magnetic surfaces. The analysis is carried out within the magnetohydrodynamic model including heat flux to compensate for the non-adiabatic pressure distribution along the magnetic surfaces in plasmas with poloidal rotation. Instead of two standard geodesic modes, three geodesic continua are found. The two higher branches of the geodesic modes have a small frequency up-shift from ordinary geodesic acoustic and sonic modes due to rotation. The lower geodesic continuum is a newzonal flowmode (geodesic Doppler mode) in plasmas with mainly poloidal rotation. Limits to standard geodesic modes are found. Bifurcation of Alfven continuum by geodesic modes at the rational surfaces is also discussed. Due to that, the frequency of combined geodesic continuum extends from the poloidal rotation frequency to the ion-sound band that can have an important role in suppressing plasma turbulence.; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq (National Council of Brazil for Science and Technology Development); Financiadora de Estudos e Projetos (FINEP); FINEP (Financiadora de Estudos e Projetos)

Impacto da hierarquia viária orientada para o automóvel no nível de serviço de modos não motorizados; Impacts of the auto-oriented street hierarchy on the level of service of non-motorized modes

Yuassa, Vanessa Naomi
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
Publicado em 03/04/2008 PT
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O objetivo desse trabalho é a verificação da hipótese de que, ao se basear na hierarquia viária direcionada ao automóvel, as estratégias de planejamento urbano e de transportes vigentes produzem impactos negativos no nível de serviço de outros modos de transporte, sobretudo os modos não motorizados. O método proposto, aplicado em um estudo de caso realizado na cidade de São Carlos, no estado de São Paulo, envolveu três etapas: (1) caracterização dos níveis de serviço das redes urbanas em análise para os modos a pé, bicicleta e automóvel; (2) análise exploratória dos resultados obtidos na etapa inicial através de geração de mapas e gráficos; e (3) comparação detalhada dos valores obtidos. Foram selecionadas cinco áreas de diferentes níveis de renda para o estudo de caso. Em cada uma delas foram identifi-cados diferentes tipos de vias (local, coletora, radial, estrutural e perimetral), e sele-cionados segmentos para compor uma amostra de 30% da extensão total das vias. A primeira atividade exigiu o desenvolvimento e adaptação de metodologias para a avaliação do nível de serviço dos modos considerados no estudo. Mais de trezentos e cinqüenta segmentos de vias foram examinados. Os resultados obtidos na análise exploratória apontaram que inúmeros segmentos com altos valores de NS para o modo automóvel tinham baixos valores de NS para o modo a pé...

Modos não-lineares de vibração e controle ativo de risers.; Non-linear vibration modes and active control of risers.

Sanches, César Tarabay
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
Publicado em 12/03/2009 PT
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36.35%
Este trabalho tem por objetivos: o estudo do comportamento dinâmico nãolinear de risers oceânicos, utilizando modos não-lineares de vibração, e o controle ativo das vibrações neles induzidas. Uma formulação não-linear do método dos elementos finitos é utilizada para a modelagem dos sistemas estruturais com vários graus de liberdade. Pela aplicação do método das variedades invariantes ao modelo de elementos finitos, determinam-se os modos normais não-lineares. Para o caso de ressonâncias internas, pode ser necessário determinar multi-modos não-lineares, o que se faz pela aplicação do método das múltiplas escalas. Apreciável esforço científico ainda é necessário para uma compreensão profunda da dinâmica de risers. Muitas das questões em aberto estão relacionadas a aplicações em águas ultraprofundas. Recentemente, novas reservas de óleo e gás foram descobertas no mar brasileiro em águas ultraprofundas, com lâminas dágua superiores a 2500m. Assim, a indústria offshore se depara com um novo conjunto de problemas e desafios relacionados à dinâmica não-linear de risers. Desta forma, a análise modal não-linear pode ter um importante papel na modelagem de Riser- Towers, SCRs (Steel Catenary Riser)...

Um algoritmo para sintonia de controladores robustos para amortecimento de modos intra-planta em sistemas de potência; An algorithm for robust controller tuning to damp intra-plant modes in power systems

Borges, Rafael Cruz
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
Publicado em 06/07/2009 PT
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36.38%
O problema de modos intra-planta em sistemas de potência é caracterizado pela oscilação dos geradores de uma mesma usina uns contra os outros. Estes modos são geralmente bem amortecidos, mas uma sintonia inadequada dos parâmetros dos PSSs (Power System Stabilizers), visando fornecer um amortecimento aos modos locais, por exemplo, pode reduzir o amortecimento dos modos intra-planta. Esta possibilidade pode ser evitada por uma sintonia cuidadosa dos estabilizadores, em um modelo que seja capaz de representar os modos intra-planta. Este processo de sintonia pode ser tedioso e demorado, exigindo muitas horas de trabalho de um especialista. Neste trabalho, apresentamos um algoritmo computacional capaz de realizar esse processo, com uma intervenção mínima do projetista (reduzindo, portanto, o esforço do engenheiro projetista na sintonia do PSS e deixando que o computador faça de maneira eficiente) e aplicamos este algoritmo para encontrar uma sintonia adequada de PSSs para o amortecimento dos modos local e intra-planta coexistentes no mesmo sistema. Como mostrado neste trabalho, o algoritmo é capaz de sintonizar os PSSs para varias condições de operação de uma só vez, o que pode também resultar em uma melhor sintonia quando comparado com abordagens seqüenciais de projeto.; The problem of intra-plant modes is characterized by the oscillation of the machines within a power station against each other. These modes are usually well-damped...

A propriedade social como suporte da existência : a crise do individualismo moderno e os modos de subjetivação contemporâneos; Social property as support for existence: modern individualism crisis and contemporary modes of subjectification

Nardi, Henrique Caetano; Barbarini, Neuzi
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
POR
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36.32%
Este artigo discute o conceito de propriedade social (CASTEL, 1998; 2000) como possibilidade de problematização dos modos de subjetivação contemporâneos. A genealogia da sociedade salarial proposta por Robert Castel nos permite pensar a construção da propriedade social como suporte da existência e como garantia do gozo dos direitos de forma igualitária. As transformações dos modos de subjetivação associadas ao novo modelo de acumulação capitalista reinstaurou a desigualdade e a insegurança como forma de revitalizar a competição enquanto valor central da sociedade neoliberal. Propomos aqui utilizar o modelo compreensivo de Castel para pensar os análogos da propriedade social construídos na história brasileira e que marcam a relação entre os modos de subjetivação e o trabalho.; This article discusses the contribution of the concept of social property (CASTEL, 1998; 2000) for understanding contemporary modes of subjectification. The genealogy of a salaried society proposed by the author allows us to take social propriety as support for existence and as a guarantee of egalitarian rights. The transformations of the modes of subjectification that are associated with the new model of capitalistic accumulation has reinstalled inequality and insecurity as forms of revitalization of competition as a central value in liberal society. In this text we use Castel’s comprehensive model in order to analyse the corresponding modes of social propriety in Brazilian history and their impact on the relationship between work and the modes of subjectification.

Embedded crack elements with non-uniform discontinuity modes

Manzoli, O. L.; Shing, P. B.; KonstaGdoutos, M. S.
Fonte: Springer Publicador: Springer
Tipo: Conferência ou Objeto de Conferência Formato: 115-123
ENG
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The consequences of the use of embedded crack finite elements with uniform discontinuity modes (opening and sliding) to simulate crack propagation in concrete are investigated. It is shown the circumstances in which the consideration of uniform discontinuity modes is not suitable to accurately model the kinematics induced by the crack and must be avoided. It is also proposed a technique to embed cracks with non-uniform discontinuity modes into standard displacement-based finite elements to overcome the shortcomings of the uniform discontinuity modes approach.

Reproductive modes in frogs and their unexpected diversity in the Atlantic forest of Brazil

Haddad, Célio F. B.; Prado, Cynthia P. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 207-217
ENG
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Amphibians, and especially the anurans (frogs and toads), exhibit a greater diversity of reproductive modes than other tetrapod vertebrates. Twenty-nine reproductive modes have been recognized for the anurans; we propose 10 more, elevating by more than 34% the number of reproductive modes known for anurans worldwide. These newly recognized reproductive modes for the frogs elevate by almost 48% the number of anuran reproductive modes known for the Neotropics. The highly complex topography of the Atlantic forest, breaking up the biome into many small microhabitats, and the high humidity, which reduces desiccation risks, have enabled the evolution of reproductive specializations such as eggs or tadpoles that develop out of water. Nearly 90% of the Atlantic forest has been cleared, and because several anurans are endemic to this region or have specialized reproductive modes dependent on the forest, this partly explains the generalized population declines and large numbers of species that have disappeared in the last few decades. © 2005 American Institute of Biological Sciences.

Selection of elementary modes for bioprocess control

Soons, Zita; Ferreira, E. C.; Rocha, I.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /07/2010 ENG
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The lack of model-based information in bioreactor monitoring and control can have a profound impact on biological systems. We therefore aim to develop a model using elementary modes (EMs) that represents the observed phenotype in given environmental conditions suited for bioprocess control. Challenges in the model development were the high number of possible phenotypes of stoichiometric models and the high computational intensity. Two methods were compared to reduce the number of EMs to match the observed cellular phenotype. The first method is based on ranking modes and the second is a controlled random search (CRS) algorithm. Since we wish to obtain a biologically realistic subset of EMs, the objective function to be minimized is a trade-off between the error, efficiency of the modes, and model size. The case study considered the central carbon metabolism of Escherichia coli. The original model containing 2706 modes for case 1 and 11718 for case 2 was reduced to a system of one for case 1 and three modes for case 2 giving a good correlation with the measured data. Furthermore, considering also intracellular besides extracellular metabolites, results in a better fit of the measured rates. Finally, the CRS outperformed the ranking algorithm.

Probing the Existence of a Dark Matter Isothermal Core Using Gravity Modes

Lopes, I; Silk, J
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.32%
Although helioseismology has been used as an effective tool for studying the physical mechanisms acting in most of the solar interior, the microscopic level and the dynamics of the deep core are still not well understood. Helioseismological anomalies may be partially resolved if the Sun captures light, non-annihilating dark matter particles, a currently discussed dark matter candidate that is motivated by recent direct detection limits. Once trapped, such particles (4-10 GeV) naturally fill the solar core. With the use of a well-defined stellar evolution code that takes into account an accurate description of the capture of dark matter particles by the Sun, we investigate the impact of such particles in its inner core. Even a relatively small amount of dark matter particles in the solar core will leave an imprint on the absolute frequency values of gravity modes as well as the equidistant spacing between modes of the same degree. The period separation for gravity modes could reveal changes of up to 3% for annihilating dark matter and of up to 20% for non-annihilating dark matter. This effect is most pronounced in the case of the gravity dipole (l = 1) modes.

Firm Performance and Modes of Innovation

Nunes, S.; Lopes, R.; Dias, José G.
Fonte: Instituto Universitário de Lisboa Publicador: Instituto Universitário de Lisboa
Tipo: Trabalho em Andamento
Publicado em 14/04/2014 ENG
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It has been shown that firms tend to develop different modes of innovation, based on the relationship between the different types of underlying knowledge and learning processes. This paper seeks to identify different modes of business innovation, relating them to firms’ innovative and economic performance, and to analyze the relationship between the different innovation modes and the economic impact of the crisis on firms’ performance. These hypotheses are tested by regression and latent class models for the Portuguese population of firms, using a sample of 397 firms, classified according to technological intensity, firm size and region. Our results show three different modes of innovation in terms of the relationship between economic and innovative performance, with significant differences in terms of resilience in the face of the economic crisis. These findings lead to a reflection on innovation, competitiveness and regional policy.

Connivence et non connivence : les modes d’intervention des professionnels auprès d’aidants familiaux ayant un proche atteint de la maladie d’Alzheimer

Contreras, Ricardo
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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Ce mémoire a pour objectif de retracer les modes d’intervention qu’entretiennent les intervenants de la santé vis-à-vis des aidants familiaux ayant un proche atteint d’une maladie cognitive de type Alzheimer. À l’aide de l’analyse de contenu, nous allons explorer quels sont les modes d’intervention qu’ils privilégient dans un contexte d’impératifs technocratiques. Pour ce faire, nous avons étudié les entrevues menées auprès de 12 intervenants provenant de diverses professions du champ de la santé et des services sociaux, qui ont un rapport direct avec les aidants familiaux. Les résultats indiquent deux types de mode d’intervention : soit, des rapports de connivence ou de non connivence. Ces deux modes d’intervention se distinguent principalement par le recours aux savoirs pratiques.; This thesis will portray the intervention modes which health professionals maintain with respect to helping caregivers having an ill relative affected by Alzheimer-type cognitive disease. Using a qualitative approach, we explore which are the intervention modes that experts privilege, in a context of technocratic requirements. Thus, using content analysis, we explored the interviews of 12 practitioners from several professional fields and having a direct relationship with caregivers. Results indicate that there are two types of intervention. On one hand...

Coupled fracture modes in three-dimensional fracture mechanics

Kotooussov, A.; Lazzarin, P.; Berto, F.
Fonte: Engineers Australia; CDROM / DVDROM Publicador: Engineers Australia; CDROM / DVDROM
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
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Shear and anti-plane loadings of an elastic plate with a through-the-thickness crack generate various singular stress states: primary fracture modes (conventional fracture mode II and III), corner singularities, and coupled fracture modes. Two latter 3D singular states are largely ignored in theoretical and experimental investigations as well as in the current standards and failure assessment codes. It is often implicitly assumed that all three-dimensional effects are negligible and the actual three-dimensional stress state can be adequately approximated by stress components found, for example, from the corresponding classical solutions of the plane theory of elasticity. In this paper we provide an overview of recent 3D studies carried out by the authors, which demonstrate that the account for these coupled modes can totally change the classical view of many fracture phenomena. In particular, this relates to a generation of the coupled fracture modes by shear and anti-plane loading with KII = 0 and KIII = 0, respectively. In these cases the coupled fracture modes dominate the near crack tip stress field and are capable to initiate brittle fracture. In addition, the intensities of the coupled modes are significantly influenced by the thickness of the plate...

Normal modes of oscillation of the VULCAN PHALANX close-in weapon system

MacNeil, Donald P.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: 166 p.
EN_US
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Approved for public release; distribution is unlimited.; A study of the PHALANX CLOSE-IN WEAPON SYSTEM's (CIWS) Mkl49 round and the M6lAl Gatling gun focused on modeling the various design factors that influence projectile trajectory and accuracy. The PHALANX currently experiences random and variable dispersion values which can diminish the PHALANX' ability to destroy incoming targets. The focus of the analysis was on determining and understanding the dynamical modes of oscillation and forced response dynamics. A model of the PHALANX' M6lAl Gatling gun was developed in great detail and its normal modes of vibration and natural frequencies were computed. Because dynamic response is comprised of modal responses, it is critical that the modes of the gun are understood. Various. excitation forces were applied, simulating a range of firing bursts, and displacements of the firing barrel were recorded in all translational directions. Animation of the normal modes of vibration indicate that PHALANX' six-barrel system plays a significant role in the lower order normal modes, and possibly the most significant contribution to dispersion. Also, results of the dynamic response reveal barrel tip displacements, that are consistent with well documented dispersion values. The FEM provides a timely method to evaluate proposed design modifications and subsequent analysis. This model will be valuable as part of the Optimized Barrel Design project currently underway.; Lieutenant...

L'art public : les nouveaux modes d'expression artistique et le processus d'intégration en milieu urbain

Ricard, Marjolaine
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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36.4%
L’art public se présente sous divers modes d’expression artistique dans l’espace public. Qu’il soit permanent, temporaire ou éphémère, qu’il soit singulier, interactif ou participatif, qu’il soit traditionnel ou numérique, l’œuvre intégrée ou insérée dans ce contexte tente d’interpeller le public. Cette recherche examine l’évolution des modes d’expression artistique dans l’espace public, dans l’espoir de trouver une définition de l’art public. L’étude de cas de la Ville de Montréal est la base de cette recherche pour examiner les nombreuses manifestations de l’art dans l’espace public et ses périmètres. Dans une perspective conceptuelle et transdisciplinaire, sous lesquels nous considérons les approches artistiques, paysagères et politiques dans l’analyse du sujet, nous nous intéressons aux frontières des modes d’expression artistique et les moyens de les représenter. En somme, nous souhaitons saisir ce que l’on considère comme l’art public dans l’aménagement urbain montréalais et générer des connaissances plus générales. Notre revue de littérature et les observations faites sur le terrain révèlent de nouveaux enjeux qui influencent les pratiques artistiques et la perception que peut susciter une œuvre d’art public aujourd’hui. Nous examinons les facteurs qui les influencent à ce jour. En étudiant la question...

Climate indices modes and relationship with Brazilians rivers flow

Cardoso, A. O.; Dias, Pedro Leite da Silva
Fonte: Florianópolis Publicador: Florianópolis
Tipo: Conferência ou Objeto de Conferência
ENG
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36.38%
There are indications that the Brazil's rivers flows have significant relationships with climate pattems with different time scales (from interannual to decadallmultidecadal), whose influence may vary with the location of the river and the time of year. The goal of this study is identify pattems of several climate indices and their relationship with rivers flow time series, in order to further understand the main modes of adjustment of climate pattems that have significant relationships with the flow. We used monthly data of natural flows at 16 locations of hydroelectric plants in main Brazilians basins, available through the National Electric System Operator, and the following monthly climatic indices, provided by NOAA: Southem Oscillation Index - SOl; North Atlantic Oscillation - NAO; Pacific North America Pattem - PNA; Atlantic Multidecadal Oscillation - AMO; Tropical Southem Atlantic - TSA; Tropical North Atlantic - TNA; Pacific Decadal Oscillation - PDO; SST anomalies in the Nino 3.4 region (N3.4); Quasi-Biennal Oscillation - QBO; Atlantic Meridional Mode - AMM; Arctic Oscillation - AO; Antarctic Oscillation - AAO. The period of study was from 1979 to 2011. The principal component analysis (PCA) was applied to the climate indices set...

Depth of cure of dental composites submitted to different light-curing modes

Monte Alto,Raphael Vieira; Guimarães,José Guilherme Antunes; Poskus,Laiza Tatiana; Silva,Eduardo Moreira da
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2006 EN
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36.32%
OBJECTIVE: This study evaluated the depth of cure of five dental composites submitted to different light-curing modes. MATERIAL AND METHODS: Canal-shaped cavities with 5mm of length were prepared on the buccal surfaces of extracted third molars, and restored using P-60, A-110, Admira, Z-250 and Supreme resin composites. Materials were light-cured from the top, according to three modes (Group 1- Conventional (C): 500 mW/cm² / 40 s; Group 2 - Soft-Start (SS): 250 mW/cm²/ 20 s + 500 mW/cm²/ 20 s + 500 mW/cm²/ 10 s and Group 3 - LED: 250 mW/cm²/ 40 s). After that, cavity longitudinal surfaces were polished and marked with a millimeter scale of 4mm of length. Depth of cure was evaluated by means of Knoop hardness number (KHN), so that five indentations were performed at each millimeter. Original data were submitted to three-way ANOVA and Fisher's LSD test (alpha = 0.01). RESULTS: All materials presented a significant reduction on KHN from first to third millimeter. Regarding depth of cure, the results obtained for Conventional and Soft-Start modes were similar, but statistically superiors to those found for group 3 (LED). CONCLUSION: This performance may be related to the differences among energy densities obtained with different light-curing modes.

Nonlinear localized modes in complex chains and carbon nanotubes

Savin, Alexander V; Kivshar, Yuri
Fonte: Institute for Low Temperature Physics and Engineering Publicador: Institute for Low Temperature Physics and Engineering
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.32%
We discuss the existence of spatially localized nonlinear modes in carbon nanotubes with different chiralities, and demonstrate that in nanotubes with the chirality index (m, 0) three types of localized modes can exist, namely longitudinal, radial, and tw

Profundidade de polimerização de compósitos restauradores submetidos a diferentes métodos de fotoativação; Depth of cure of dental composites submitted to different light-curing modes

Monte Alto, Raphael Vieira; Guimarães, José Guilherme Antunes; Poskus, Laiza Tatiana; Silva, Eduardo Moreira da
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Formato: application/pdf
Publicado em 01/04/2006 ENG
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36.32%
OBJETVO: Este estudo avaliou a profundidade de polimerização de cinco compósitos fotopolimerizáveis submetidos a diferentes métodos de fotoativação. MATERIAL E MÉTODO: Cavidades em forma de canaleta com 5 mm de comprimento, preparadas nas faces vestibulares de terceiros molares, foram restauradas com os compósitos P-60, A-110, Admira, Z-250 e Supreme. Os materiais foram fotoativados pelo topo das cavidades com três técnicas (Grupo 1 - Convencional (C): 500 mW / cm² / 40 s; Grupo 2 - Soft-Start (SS): 250 mW / cm² / 20 s + 500 mW / cm² / 20 s + 500 mW / cm² / 10 s e Grupo 3 - LED: 250 mW / cm² / 40 s). Após a fotoativação, as superfícies longitudinais dos materiais foram polidas e marcadas com uma escala milimetrada com 4 mm de comprimento. A profundidade de polimerização foi avaliada através do número de dureza Knoop (NDK), com cinco indentações a cada milímetro. Os dados originais foram submetidos à Análise de Variância de três fatores e teste de Fisher para comparações entre médias (alfa = 0,01). RESULTADOS: Todos os materiais apresentaram diminuição do NDK do primeiro para o terceiro milímetro (p < 0,01). Os resultados obtidos com os Grupos Convencional e Soft-Start foram similares e superiores ao Grupo LED (p < 0...

An electron diffraction, XRD and lattice dynamical investigation of the average structure and rigid unit mode (RUM) modes of distortion of microporous AlPO4-5

Liu, Yun; Withers, Raymond; Noren, Lasse
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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Electron diffraction is used to investigate the unit cell and space group symmetry of the average structure of AlPO4-5 as well as the zero frequency rigid unit mode (RUM) modes of distortion thereof. Despite recent reports to the contrary, absolutely no evidence could be found to justify the lowering of the average structure space group symmetry of AlPO4-5 from P6cc. Direct experimental evidence (in the form of a highly structured, characteristic diffuse intensity distribution) is found, however, for the (presumably dynamic) excitation of numerous zero frequency RUM modes of distortion of the ideal AlPO4-5 tetrahedral framework structure. The lattice dynamic program CRUSH is used to confirm the existence of these zero frequency RUM modes of distortion as well as to show that they are an intrinsic, predictable property of the AlPO4-5 tetrahedral framework structure. Six zero frequency RUM modes of distortion are predicted to exist for modulation wave-vectors of the form [hk0]*, 4 for wave-vectors of the form [00]* and a single RUM for wave-vectors falling on a curved (hyperbolic) distribution. These RUM modes of distortion involve tetrahedral rotation about in-plane rotation axes. Their simultaneous (presumably dynamic) excitation is necessary to understand the apparent linear Al-O-P angles in average structure refinements.

High-resolution analysis of the gravest seismic normal modes after the 2004 Mw = 9 Sumatra earthquake using superconducting gravimeter data

Rosat, S; Sato, Tadahiro; Imanishi, Yuichi; Hinderer, J; Tamura, Yoshiaki; McQueen, Herbert; Ohashi, M
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Artigo de Revista Científica
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The Mw > 9 Sumatra-Andaman earthquake on December 26, 2004 has strongly excited the low-frequency seismic modes and is a unique opportunity to improve the frequency and damping measurements of the gravest seismic modes. The precise estimation of the frequency splitting of the seismic modes below 1 mHz is needed to improve 1D-density models of the Earth. From this event, 2S1 is observed for the first time without any stacking on both SG (Superconducting Gravimeter) and seismic records. We report here analyses of SG data obtained from 11 sites. The spectra of SG records clearly show the splitting of 0S2 into 5 completely resolved singlets and the splitting of 0S3 into 7 singlets at individual stations. The present results demonstrate that SGs provide high quality data for a precise analysis of the low-frequency seismic modes.