3,302 research outputs found
The self-energy of a charged particle in the presence of a topological defect distribution
In this work we study a charged particle in the presence of both a continuous
distribution of disclinations and a continuous distribution of edge
dislocations in the framework of the geometrical theory of defects. We obtain
the self-energy for a single charge both in the internal and external regions
of either distribution. For both distributions the result outside the defect
distribution is the self-energy that a single charge experiments in the
presence of a single defect.Comment: 12 pages, Revtex4, two figures,to appear in Int. Joun. Mod. Phys.
Validation of the Lower Tagus Valley velocity and structural model using ambient noise broadband measurements
Along his history the Lower Tagus Valley (LTV) region was shaken by several earthquakes, some of them were
produced in large ruptures of offshore structures located southwest of the Portuguese coastline, among these we
the Lisbon earthquake of 1 November 1755; other moderates earthquakes were produced by local sources such as
the 1344, 1531 and the 1909 Benavente earthquake.
In order to promote an improved assessment of the seismic hazard in this region, we propose the introduction
of realistic methods on the prediction of ground motion produced by moderate to large earthquakes in LTV.
This process involves the establishment of a structural 3D model based on all the available geophysical and
geotechnical data on the area (seismic, gravimetric, deep wells and geological outcrops) and the determination of
wave propagation from a finite difference method: by applying the E3D program [1,2].
To confirm this model we use broadband ambient noise measurements collected in two profiles with azimuth
perpendicular to the basin axis and we applied the horizontal to vertical (H/V) spectral ratio method [3] to the
recordings in order to estimate the amplification of the basin. The H/V curves obtained reveals the existence of two
low frequency peaks centered on 0.2 a 1 Hz frequencies[4]. These peaks are strongly related with the thickness
of Cenozoic and alluvial sediments. By inversion of the H/V curve, we obtain a more detailed velocity model for
the region where the profile were determined, which is in good agreement with borehole data and other results
obtained with magnetic and seismic reflection methods
Gravitational Geometric Phase in the Presence of Torsion
We investigate the relativistic and non-relativistic quantum dynamics of a
neutral spin-1/2 particle submitted an external electromagnetic field in the
presence of a cosmic dislocation. We analyze the explicit contribution of the
torsion in the geometric phase acquired in the dynamic of this neutral
spinorial particle. We discuss the influence of the torsion in the relativistic
geometric phase. Using the Foldy-Wouthuysen approximation, the non-relativistic
quantum dynamics are studied and the influence of the torsion in the
Aharonov-Casher and He-McKellar-Wilkens effects are discussed.Comment: 14 pages, no figur
Teste de avaliação do metabolismo espermático em ovinos.
Apresenta técnicas adotadas para avaliação da qualidade do sêmen, uma que seja de alta precisão, de simples adoção e que não requeira treinamento especializado, favorecendo as atividades de veterinários e de criadores de ovinos.bitstream/CNPC/20247/1/cot71.pd
Image Subtraction Reduction of Open Clusters M35 & NGC 2158 In The K2 Campaign-0 Super-Stamp
Observations were made of the open clusters M35 and NGC 2158 during the
initial K2 campaign (C0). Reducing these data to high-precision photometric
time-series is challenging due to the wide point spread function (PSF) and the
blending of stellar light in such dense regions. We developed an
image-subtraction-based K2 reduction pipeline that is applicable to both
crowded and sparse stellar fields. We applied our pipeline to the data-rich C0
K2 super-stamp, containing the two open clusters, as well as to the neighboring
postage stamps. In this paper, we present our image subtraction reduction
pipeline and demonstrate that this technique achieves ultra-high photometric
precision for sources in the C0 super-stamp. We extract the raw light curves of
3960 stars taken from the UCAC4 and EPIC catalogs and de-trend them for
systematic effects. We compare our photometric results with the prior
reductions published in the literature. For detrended, TFA-corrected sources in
the 12--12.25 magnitude range, we achieve a best 6.5 hour window
running rms of 35 ppm falling to 100 ppm for fainter stars in the 14--14.25 magnitude range. For stars with , our detrended and
6.5 hour binned light curves achieve the highest photometric precision.
Moreover, all our TFA-corrected sources have higher precision on all time
scales investigated. This work represents the first published image subtraction
analysis of a K2 super-stamp. This method will be particularly useful for
analyzing the Galactic bulge observations carried out during K2 campaign 9. The
raw light curves and the final results of our detrending processes are publicly
available at \url{http://k2.hatsurveys.org/archive/}.Comment: Accepted for publication in PASP. 14 pages, 5 figures, 2 tables.
Light curves available from http://k2.hatsurveys.org/archive
Sistema automático para inspecção visual de defeitos em tecidos
Pretende-se com esta comunicação apresentar o trabalho desenvolvido no âmbito da Campanha Têxtil do IDICT, onde se aplicaram algoritmos de processamento de imagem à inspecção de defeitos em tecidos. Devido à complexidade do problema em estudo foi necessário construir um sistema de iluminação estruturada para garantir luminosidade constante no tecido a inspeccionar. Um sistema de captura e processamento de imagens a cores foi desenvolvido, para o sistema operativo Windows 98, tendo por base a placa de aquisição Matrox Meteor II e o software Microsoft Visual C++. Após a conversão de imagens a cores em níveis de cinzento foram desenvolvidos algoritmos de binarização, baseados em análise estatística e morfologia matemática. Os algoritmos desenvolvidos abrangem os seguintes defeitos em tecidos: falta de fio, fio grosso, fio duplo, borboto, mancha e nódoa. Para cada tecido a inspecionar é necessário um período de treino do sistema de forma a identificar os parâmetros estatísticos que o caracterizam, média e desvio padrão dos níveis de cinzento. O sistema inspecciona de forma automática os defeitos descritos em tecidos penteados de uma só cor, tendo sido obtidos resultados bastante satisfatórios para o número de tecidos disponibilisados pelas empresas da região
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