19 resultados para special functions

em Repositório Científico do Instituto Politécnico de Lisboa - Portugal


Relevância:

30.00% 30.00%

Publicador:

Resumo:

As it is widely known, in structural dynamic applications, ranging from structural coupling to model updating, the incompatibility between measured and simulated data is inevitable, due to the problem of coordinate incompleteness. Usually, the experimental data from conventional vibration testing is collected at a few translational degrees of freedom (DOF) due to applied forces, using hammer or shaker exciters, over a limited frequency range. Hence, one can only measure a portion of the receptance matrix, few columns, related to the forced DOFs, and rows, related to the measured DOFs. In contrast, by finite element modeling, one can obtain a full data set, both in terms of DOFs and identified modes. Over the years, several model reduction techniques have been proposed, as well as data expansion ones. However, the latter are significantly fewer and the demand for efficient techniques is still an issue. In this work, one proposes a technique for expanding measured frequency response functions (FRF) over the entire set of DOFs. This technique is based upon a modified Kidder's method and the principle of reciprocity, and it avoids the need for modal identification, as it uses the measured FRFs directly. In order to illustrate the performance of the proposed technique, a set of simulated experimental translational FRFs is taken as reference to estimate rotational FRFs, including those that are due to applied moments.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We calculate the equilibrium thermodynamic properties, percolation threshold, and cluster distribution functions for a model of associating colloids, which consists of hard spherical particles having on their surfaces three short-ranged attractive sites (sticky spots) of two different types, A and B. The thermodynamic properties are calculated using Wertheim's perturbation theory of associating fluids. This also allows us to find the onset of self-assembly, which can be quantified by the maxima of the specific heat at constant volume. The percolation threshold is derived, under the no-loop assumption, for the correlated bond model: In all cases it is two percolated phases that become identical at a critical point, when one exists. Finally, the cluster size distributions are calculated by mapping the model onto an effective model, characterized by a-state-dependent-functionality (f) over bar and unique bonding probability (p) over bar. The mapping is based on the asymptotic limit of the cluster distributions functions of the generic model and the effective parameters are defined through the requirement that the equilibrium cluster distributions of the true and effective models have the same number-averaged and weight-averaged sizes at all densities and temperatures. We also study the model numerically in the case where BB interactions are missing. In this limit, AB bonds either provide branching between A-chains (Y-junctions) if epsilon(AB)/epsilon(AA) is small, or drive the formation of a hyperbranched polymer if epsilon(AB)/epsilon(AA) is large. We find that the theoretical predictions describe quite accurately the numerical data, especially in the region where Y-junctions are present. There is fairly good agreement between theoretical and numerical results both for the thermodynamic (number of bonds and phase coexistence) and the connectivity properties of the model (cluster size distributions and percolation locus).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We derive a set of differential inequalities for positive definite functions based on previous results derived for positive definite kernels by purely algebraic methods. Our main results show that the global behavior of a smooth positive definite function is, to a large extent, determined solely by the sequence of even-order derivatives at the origin: if a single one of these vanishes then the function is constant; if they are all non-zero and satisfy a natural growth condition, the function is real-analytic and consequently extends holomorphically to a maximal horizontal strip of the complex plane.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Seismic recordings of IRIS/IDA/GSN station CMLA and of several temporary stations in the Azores archipelago are processed with P and S receiver function (PRF and SRF) techniques. Contrary to regional seismic tomography these methods provide estimates of the absolute velocities and of the Vp/Vs ratio up to a depth of similar to 300 km. Joint inversion of PRFs and SRFs for a few data sets consistently reveals a division of the subsurface medium into four zones with a distinctly different Vp/Vs ratio: the crust similar to 20 km thick with a ratio of similar to 1.9 in the lower crust, the high-Vs mantle lid with a strongly reduced VpNs velocity ratio relative to the standard 1.8, the low-velocity zone (LVZ) with a velocity ratio of similar to 2.0, and the underlying upper-mantle layer with a standard velocity ratio. Our estimates of crustal thickness greatly exceed previous estimates (similar to 10 km). The base of the high-Vs lid (the Gutenberg discontinuity) is at a depth of-SO km. The LVZ with a reduction of S velocity of similar to 15% relative to the standard (IASP91) model is terminated at a depth of similar to 200 km. The average thickness of the mantle transition zone (TZ) is evaluated from the time difference between the S410p and SKS660p, seismic phases that are robustly detected in the S and SKS receiver functions. This thickness is practically similar to the standard IASP91 value of 250 km. and is characteristic of a large region of the North Atlantic outside the Azores plateau. Our data are indicative of a reduction of the S-wave velocity of several percent relative to the standard velocity in a depth interval from 460 to 500 km. This reduction is found in the nearest vicinities of the Azores, in the region sampled by the PRFs, but, as evidenced by SRFs, it is missing at a distance of a few hundred kilometers from the islands. We speculate that this anomaly may correspond to the source of a plume which generated the Azores hotspot. Previously, a low S velocity in this depth range was found with SRF techniques beneath a few other hotspots.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

O conceito de poesia uma forma de arte e traduz-se como um espelho do pensamento do homem realizado na palavra oral e escrita. A poesia poder ensinar o homem no estudo da palavra, atravs do seu significado nos valores denotativo e/ou conotativo. A aplicao destes conceitos faz sentido, a partir da ideia de que a palavra no contexto da poesia pode produzir emoes e sensaes nas pessoas a quem ela transmitida. A poesia tem funes multissensoriais que podem definir o input lingustico como forma de desenvolver a linguagem. Vrios so os estudos que apontam para as principais competncias deficitrias nos indivduos com Trissomia 21, mas poucas so as investigaes que se debruam sobre a influncia da poesia nas vrias competncias lingusticas. Uma perceo mais ampla e visionria da Arte na voz da poesia pela parte da escola, professores e, em particular, professores de Educao Especial permitir adotar estratgias de interveno inovadoras. Pretende este estudo investigar e analisar a forma como a poesia pode influenciar o desenvolvimento da linguagem oral numa aluna com Trissomia 21. Neste projeto, a partir da identificao do caso-problema e da constatao da ausncia da poesia no currculo da aluna, procurou-se intervir, no sentido de melhorar as suas competncias lingusticas, utilizando para tanto a poesia. A implementao do projeto aconteceu ao longo de seis meses durante quinze sesses de interveno individuais. Os resultados do projeto mostram que, em todas as competncias lingusticas, houve um processo evolutivo, sendo particularmente significativo o desenvolvimento da competncia fonolgica, aumento de vocabulrio e uma maior noo da palavra em contexto. Estes dados levam-nos a crer que a utilizao da poesia poder, tambm, constituir uma forma de promover a socializao e a autonomia, revelando os efeitos colaterais que podero decorrer deste tipo de interveno. - Abstract The concept of poetry is a form of art, showing the man's thought held in the spoken and written word. Poetry can teach man in the study of the word, its meaning through denotative and/or connotative values. The application of these concepts makes sense, from the idea that the word in the context of poetry can stir emotions and feelings in the people to whom it is transmitted. Poetry has multisensory functions that can set the linguistic input as a way to develop language at phonological, lexical, semantics, pragmatic and morfosyntactic skills. There are several studies that point out to the key skills deficit in individuals with Trisomy 21, but there are few investigations that focus on the influence of poetry in various language skills. A broader perception and vision of poetry as art given by school, and teachers, and, particularly teachers of Special Education will allow a more effective intervention strategies. This study aims to investigate and analyze how poetry can influence the development of oral language in a student with Trisomy 21. In this project, we tried to intervene, improving the language skills of the student, using poetry from the identification case-problem and confirmation of the absence of poetry in her curriculum. The implementation of the project took place throughout six months for fifteen individual intervention sessions. The project results show that, in all language skills, there was a progressive process, being particularly significant the development of the phonological skills, increased vocabulary and a greater sense of the word into context. These data lead us to believe that the use of poetry can also be a way to promote socialization and autonomy, revealing the side effects that may result from this type of intervention.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Dissertao apresentada Escola Superior de Educao de Lisboa para a obteno do grau de mestre em Cincias da Educao - Especializao em Educao Especial

Relevância:

20.00% 20.00%

Publicador:

Resumo:

WDM multilayered SiC/Si devices based on a-Si:H and a-SiC:H filter design are approached from a reconfigurable point of view. Results show that the devices, under appropriated optical bias, act as reconfigurable active filters that allow optical switching and optoelectronic logic functions development. Under front violet irradiation the magnitude of the red and green channels are amplified and the blue and violet reduced. Violet back irradiation cuts the red channel, slightly influences the magnitude of the green and blue ones and strongly amplifies de violet channel. This nonlinearity provides the possibility for selective removal of useless wavelengths. Particular attention is given to the amplification coefficient weights, which allow taking into account the wavelength background effects when a band needs to be filtered from a wider range of mixed signals, or when optical active filter gates are used to select and filter input signals to specific output ports in WDM communication systems. A truth table of an encoder that performs 8-to-1 multiplexer (MUX) function is presented.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Dissertao apresentada Escola Superior de Educao de Lisboa para obteno do grau de Mestre em Interveno Precoce

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We present the supersymmetric standard model three-loop beta-functions for gauge and Yukawa couplings and consider the effect of three-loop corrections on the standard running coupling analyses.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The purpose of this paper is the design of an optoelectronic circuit based on a-SiC technology, able to act simultaneously as a 4-bit binary encoder or a binary decoder in a 4-to-16 line configurations and show multiplexer-based logical functions. The device consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n multilayered structure produced by PECVD. To analyze it under information-modulated wave (color channels) and uniform irradiation (background) four monochromatic pulsed lights (input channels): red, green, blue and violet shine on the device. Steady state optical bias was superimposed separately from the front and the back sides, and the generated photocurrent was measured. Results show that the devices, under appropriate optical bias, act as reconfigurable active filters that allow optical switching and optoelectronic logic functions development providing the possibility for selective removal of useless wavelengths. The logic functions needed to construct any other complex logic functions are the NOT, and both or either an AND or an OR. Any other complex logic function that might be found can also be used as building blocks to achieve the functions needed for the retrieval of channels within the WDM communication link. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this paper we develop an appropriate theory of positive definite functions on the complex plane from first principles and show some consequences of positive definiteness for meromorphic functions.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Meshless methods are used for their capability of producing excellent solutions without requiring a mesh, avoiding mesh related problems encountered in other numerical methods, such as finite elements. However, node placement is still an open question, specially in strong form collocation meshless methods. The number of used nodes can have a big influence on matrix size and therefore produce ill-conditioned matrices. In order to optimize node position and number, a direct multisearch technique for multiobjective optimization is used to optimize node distribution in the global collocation method using radial basis functions. The optimization method is applied to the bending of isotropic simply supported plates. Using as a starting condition a uniformly distributed grid, results show that the method is capable of reducing the number of nodes in the grid without compromising the accuracy of the solution. (C) 2013 Elsevier Ltd. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We have conducted a P and S receiver functions [PRFs and SRFs] analysis for 19 seismic stations on the Iberia and western Mediterranean. In the transition zone [TZ] the PRFs analysis reveals a band [from Gibraltar to Balearic] increased by 10-20 km relative to the standard 250 km. The TZ thickness variations are strongly correlated with the P660s times in PRFs. We interpret the variable depth of the 660-km discontinuity as an effect of subduction. Over the anomalous TZ we found a reduced velocity zone in the upper mantle. Joint inversion of PRFs and SRFs reveals a subcrustal high S velocity lid and an underlying LVZ. A reduction of the S velocity in the LVZ is less than 10%. The Gutenberg discontinuity is located at 655 km, but in several models sampling the Mediterranean, the lid is missing or its thickness is reduced to ~30 km. In the Gibraltar and North Africa this boundary is located at ~100 km. The lid Vp/Vs beneath Betics is reduced relative to the standard 1.8. Another evidence of the Vp/Vs anomaly is provided by S410p phase late arrivals in the SRFs. The azimuthal anisotropy analysis with a new technology was conducted at 5 stations and at 2 groups of stations. The fast direction in the uppermost mantle layer is ~90 in Iberian Massif. In Balearic is in the azimuth of ~120. At a depth of ~60 km the direction becomes 90. Anisotropy in the upper layer can be interpreted as frozen, whereas anisotropy in the lower layer is active, corresponding to the present-day or recent flow. The effect of the asthenosphere in the SKS splitting is much larger than the effect of the subcrustal lithosphere.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Este artigo pretende descrever vrios aspetos da segregao, integrao e incluso dentro do sistema educativo obrigatrio austraco. Aps uma introduo que contm definies e um resumo internacional, ser brevemente descrito o sistema educativo da ustria. Subsequentemente, trs temas de interesse sero debatidos. Primeiro ser caracterizada a situao atual referente incluso de crianas com necessidades educativas especiais. Esta situao difere bastante entre estados federais. Sero descritos os desenvolvimentos que conduziram situao atual. Em segundo sero apresentados estudos empricos recentes relativos ao movimento austraco que almeja a incluso. Em terceiro e a ttulo exemplificativo sero apresentados em detalhe alguns desenvolvimentos recentes, alguns planos e vises futuras de trs estados federais austracos.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Mestrado em Fiscalidade