Wave equation depth migration using complex Pad�� approximation

Propomos um novo m��todo de migra����o em profundidade baseado na solu����o da equa����o da onda com densidade constante no dom��nio da freq����ncia. Uma aproxima����o de Pad�� complexa �� usada para aproximar o operador de evolu����o aplicado na extrapola����o do campo de ondas. Esse m��todo reduz as imprecis��es e instabilidades devido ��s ondas evanescentes e produz imagens com menos ru��dos num��ricos que aquelas obtidas usando-se a aproxima����o de Pad�� real para o operador exponencial, principalmente em meios com fortes varia����es de velocidades. Testes em dados de afastamento nulo do modelo de sal SEG/EAGE e nos dados de tiro comum 2-D Marmousi foram realizados. Os resultados obtidos mostram que o m��todo de migra����o proposto consegue lidar com fortes varia����es laterais e tamb��m tem uma boa resposta para refletores com mergulhos ��ngremes. Os resultados foram comparados ��queles resultados obtidos com os m��todos split-step Fourier (SSF), phase shift plus interpolarion (PSPI) e Fourier diferen��as-finitas (FFD).

Empilhamento pelo m��todo superf��cie de reflex��o comum 2-D com topografia e introdu����o ao caso 3-D

O m��todo de empilhamento s��smico CRS simula se����es s��smicas ZO a partir de dados de cobertura m��ltipla, independente do macro-modelo de velocidades. Para meios 2-D, a fun����o tempo de tr��nsito de empilhamento depende de tr��s par��metros, a saber: do ��ngulo de emerg��ncia do raio de reflex��o normal (em rela����o �� normal da superf��cie) e das curvaturas das frentes de onda relacionadas ��s ondas hipot��ticas, denominadas NIP e Normal. O empilhamento CRS consiste na soma das amplitudes dos tra��os s��smicos em dados de m��ltipla cobertura, ao longo da superf��cie definida pela fun����o tempo de tr��nsito do empilhamento CRS, que melhor se ajusta aos dados. O resultado do empilhamento CRS �� assinalado a pontos de uma malha pr��-definida na se����o ZO. Como resultado tem-se a simula����o de uma se����o s��smica ZO. Isto significa que para cada ponto da se����o ZO deve-se estimar o trio de par��metros ��timos que produz a m��xima coer��ncia entre os eventos de reflex��o s��smica. Nesta Tese apresenta-se f��rmulas para o m��todo CRS 2-D e para a velocidade NMO, que consideram a topografia da superf��cie de medi����o. O algoritmo �� baseado na estrat��gia de otimiza����o dos par��metros de f��rmula CRS atrav��s de um processo em tr��s etapas: 1) Busca dos par��metros, o ��ngulo de emerg��ncia e a curvatura da onda NIP, aplicando uma otimiza����o global, 2) busca de um par��metro, a curvatura da onda N, aplicando uma otimiza����o global, e 3) busca de tr��s par��metros aplicando uma otimiza����o local para refinar os par��metros estimados nas etapas anteriores. Na primeira e segunda etapas �� usado o algoritmo Simulated Annealing (SA) e na terceira etapa �� usado o algoritmo Variable Metric (VM). Para o caso de uma superf��cie de medi����o com varia����es topogr��ficas suaves, foi considerada a curvatura desta superf��cie no algoritmo do m��todo de empilhamento CRS 2-D, com aplica����o a dados sint��ticos. O resultado foi uma se����o ZO simulada, de alta qualidade ao ser comparada com a se����o ZO obtida por modelamento direto, com uma alta raz��o sinal-ru��do, al��m da estimativa do trio de par��metros da fun����o tempo de tr��nsito. Foi realizada uma n��lise de sensibilidade para a nova fun����o de tempo de tr��nsito CRS em rela����o �� curvatura da superf��cie de medi����o. Os resultados demonstraram que a fun����o tempo de tr��nsito CRS �� mais sens��vel nos pontos-m��dios afastados do ponto central e para grandes afastamentos. As express��es da velocidade NMO apresentadas foram aplicadas para estimar as velocidades e as profundidades dos refletores para um modelo 2-D com topografia suave. Para a invers��o destas velocidades e profundidades dos refletores, foi considerado o algoritmo de invers��o tipo Dix. A velocidade NMO para uma superf��cie de medi����o curva, permite estimar muito melhor estas velocidades e profundidades dos refletores, que as velocidades NMO referidas as superf��cies planas. Tamb��m apresenta-se uma abordagem do empilhamento CRS no caso 3-D. neste caso a fun����o tempo de tr��nsito depende de oito par��metros. S��o abordadas cinco estrat��gias de busca destes par��metros. A combina����o de duas destas estrat��gias (estrat��gias das tr��s aproxima����es dos tempos de tr��nsito e a estrat��gia das configura����es e curvaturas arbitr��rias) foi aplicada exitosamente no empilhamento CRS 3-D de dados sint��ticos e reais.

Migra����o 3-D Kirchhoff-Gaussian-Beam (KGB) pr��-empilhamento no dom��nio da profundidade

O Feixe Gaussiano (FG) �� uma solu����o assint��tica da equa����o da elastodin��mica na vizinhan��a paraxial de um raio central, a qual se aproxima melhor do campo de ondas do que a aproxima����o de ordem zero da Teoria do Raio. A regularidade do FG na descri����o do campo de ondas, assim como a sua elevada precis��o em algumas regi��es singulares do meio de propaga����o, proporciona uma forte alternativa na solu����o de problemas de modelagem e imageamento s��smicos. Nesta Tese, apresenta-se um novo procedimento de migra����o s��smica pr��-empilhamento em profundidade com amplitudes verdadeiras, que combina a flexibilidade da migra����o tipo Kirchhoff e a robustez da migra����o baseada na utiliza����o de Feixes Gaussianos para a representa����o do campo de ondas. O algoritmo de migra����o proposto �� constitu��do por dois processos de empilhamento: o primeiro �� o empilhamento de feixes (���beam stack���) aplicado a subconjuntos de dados s��smicos multiplicados por uma fun����o peso definida de modo que o operador de empilhamento tenha a mesma forma da integral de superposi����o de Feixes Gaussianos; o segundo empilhamento corresponde �� migra����o Kirchhoff tendo como entrada os dados resultantes do primeiro empilhamento. Pelo exposto justifica-se a denomina����o migra����o Kirchhoff-Gaussian-Beam (KGB). As principais caracter��sticas que diferenciam a migra����o KGB, durante a realiza����o do primeiro empilhamento, de outros m��todos de migra����o que tamb��m utilizam a teoria dos Feixes Gaussianos, s��o o uso da primeira zona de Fresnel projetada para limitar a largura do feixe e a utiliza����o, no empilhamento do feixe, de uma aproxima����o de segunda ordem do tempo de tr��nsito de reflex��o. Como exemplos s��o apresentadas aplica����es a dados sint��ticos para modelos bidimensionais (2-D) e tridimensionais (3-D), correspondentes aos modelos Marmousi e domo de sal da SEG/EAGE, respectivamente.

Expression of receptors for BMP15 is differentially regulated in dominant and subordinate follicles during follicle deviation in cattle

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Search for gravitational wave ringdowns from perturbed intermediate mass black holes in LIGO-Virgo data from 2005-2010

We report results from a search for gravitational waves produced by perturbed intermediate mass black holes ( IMBH) in data collected by LIGO and Virgo between 2005 and 2010. The search was sensitive to astrophysical sources that produced damped sinusoid gravitational wave signals, also known as ringdowns, with frequency 50 <= f(0)/Hz <= 2000 and decay timescale 0.0001 less than or similar to tau/s less than or similar to 0.1 characteristic of those produced in mergers of IMBH pairs. No significant gravitational wave candidate was detected. We report upper limits on the astrophysical coalescence rates of IMBHs with total binary mass 50 <= M/ M circle dot <= 450 and component mass ratios of either 1: 1 or 4: 1. For systems with total mass 100 <= M/M circle dot <= 150, we report a 90% confidence upper limit on the rate of binary IMBH mergers with nonspinning and equal mass components of 6.9 x 10(-8) Mpc(-3) yr(-1). We also report a rate upper limit for ringdown waveforms from perturbed IMBHs, radiating 1% of their mass as gravitational waves in the fundamental, l = m = 2, oscillation mode, that is nearly three orders of magnitude more stringent than previous results.

Statistical properties for a dissipative model of relativistic particles in a wave packet: A parameter space investigation

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Reconstruction of the gravitational wave signal h(t) during the Virgo science runs and independent validation with a photon calibrator

The Virgo detector is a kilometer-scale interferometer for gravitational wave detection located near Pisa (Italy). About 13 months of data were accumulated during four science runs (VSR1, VSR2, VSR3 and VSR4) between May 2007 and September 2011, with increasing sensitivity. In this paper, the method used to reconstruct, in the range 10 Hz-10 kHz, the gravitational wave strain time series h(t) from the detector signals is described. The standard consistency checks of the reconstruction are discussed and used to estimate the systematic uncertainties of the h(t) signal as a function of frequency. Finally, an independent setup, the photon calibrator, is described and used to validate the reconstructed h(t) signal and the associated uncertainties. The systematic uncertainties of the h(t) time series are estimated to be 8% in amplitude. The uncertainty of the phase of h(t) is 50 mrad at 10 Hz with a frequency dependence following a delay of 8 mu s at high frequency. A bias lower than 4 mu s and depending on the sky direction of the GW is also present.

Improved Upper Limits on the Stochastic Gravitational-Wave Background from 2009-2010 LIGO and Virgo Data

Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the Universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the Universe. We carry out a search for the stochastic background with the latest data from the LIGO and Virgo detectors. Consistent with predictions from most stochastic gravitational-wave background models, the data display no evidence of a stochastic gravitational-wave signal. Assuming a gravitational-wave spectrum of Omega(GW)(f) = Omega(alpha)(f/f(ref))(alpha), we place 95% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.5-1726 Hz. In the frequency band of 41.5-169.25 Hz for a spectral index of alpha = 0, we constrain the energy density of the stochastic background to be Omega(GW)(f) < 5.6 x 10(-6). For the 600-1000 Hz band, Omega(GW)(f) < 0.14(f/900 Hz)(3), a factor of 2.5 lower than the best previously reported upper limits. We find Omega(GW)(f) < 1.8 x 10(-4) using a spectral index of zero for 170-600 Hz and Omega(GW)(f) < 1.0(f/1300 Hz)(3) for 1000-1726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the possible evidence for inflationary gravitational waves.

Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data

In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational-wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed assuming both that polarization parameters are completely unknown and that they are known with some uncertainty, as derived from x-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of 2 below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.

Synthesis of Bi-based superconductor by microwave-assisted hydrothermal method

In this work we studied the synthesis of BSCCO-2212 superconducting phase associating a quite similar method developed by Pechini with the microwave-assisted hydrothermal method. To study the influence of the microwaves on the properties of BSCCO system, we synthesized two samples by such method. For one sample we used carbonates and for the other one we used nitrates as chemical reagents. We also produced a reference sample just using carbonates by Pechini&apos;s method to compare their morphological and superconducting properties. The structural properties of the samples were analyzed by scanning electron microscopy and X-ray diffraction. The Bi-2212 phase is predominant in all samples and despites the nitrates-like sample has a broader distribution of grain size in comparison with the reference sample, its magnetic behaviour is closer to that presented by the reference one.

On the equivalence between the wave-packet phase space representation (WPPSR) and the phase space generated by the squeezed states

We show that the parametrized Wave-Packet Phase Space representation, which has been studied earlier by one of the authors, is equivalent to a Squeezed States Phase Space Representation of quantum mechanics. �� 1988.

Aortic distensibility measured by pulse-wave velocity is not modified in patients with Chagas' disease

Abstract Background Experimental studies demonstrate that infection with trypanosoma cruzi causes vasculitis. The inflammatory lesion process could hypothetically lead to decreased distensibility of large and small arteries in advanced Chagas' disease. We tested this hypothesis. Methods and results We evaluated carotid-femoral pulse-wave velocity (PWV) in 53 Chagas' disease patients compared with 31 healthy volunteers (control group). The 53 patients were classified into 3 groups: 1) 16 with indeterminate form of Chagas' disease; 2) 18 with Chagas' disease, electrocardiographic abnormalities, and normal systolic function; 3) 19 with Chagas' disease, systolic dysfunction, and mild-to-moderate congestive heart failure. No difference was noted between the 4 groups regarding carotid-femoral PWV (8.4 �� 1.1 vs 8.2 �� 1.5 vs 8.2 �� 1.4 vs 8.7 �� 1.6 m/s, P = 0.6) or pulse pressure (39.5 �� 7.6 vs 39.3 �� 8.1 vs 39.5 �� 7.4 vs 39.7 �� 6.9 mm Hg, P = 0.9). A positive, significant, similar correlation occurred between PWV and age in patients with Chagas' disease (r = 0.42, P = 0.002), in controls (r = 0.48, P = 0.006), and also between PWV and systolic blood pressure in both groups (patients with Chagas' disease, r = 0.38, P = 0.005; healthy subjects, r = 0.36, P = 0.043). Conclusion Carotid femoral pulse-wave velocity is not modified in patients with Chagas' disease, suggesting that elastic properties of large arteries are not affected in this disorder.

Caratterizzazione e generazione di segnali PWM per amplificatori in classe D ad alta efficienza

The convergence of information technology and consumer electronics towards battery powered portable devices has increased the interest in high efficiency, low dissipation amplifiers. Class D amplifiers are the state of the art in low power consumption and high performance amplification. In this thesis we explore the possibility of exploiting nonlinearities introduced by the PWM modulation, by designing an optimized modulation law which scales its carrier frequency adaptively with the input signal's average power while preserving the SNR, thus reducing power consumption. This is achieved by means of a novel analytical model of the PWM output spectrum, which shows how interfering harmonics and their bandwidth affect the spectrum. This allows for frequency scaling with negligible aliasing between the baseband spectrum and its harmonics. We performed low noise power spectrum measurements on PWM modulations generated by comparing variable bandwidth, random test signals with a variable frequency triangular wave carrier. The experimental results show that power-optimized frequency scaling is both feasible and effective. The new analytical model also suggests a new PWM architecture that can be applied to digitally encoded input signals which are predistorted and compared with a cosine carrier, which is accurately synthesized by a digital oscillator. This approach has been simulated in a realistic noisy model and tested in our measurement setup. A zero crossing search on the obtained PWM modulation law proves that this approach yields an equivalent signal quality with respect to traditional PWM schemes, while entailing the use of signals whose bandwidth is remarkably smaller due to the use of a cosine instead of a triangular carrier.