2,137 research outputs found
Multiscale Fractal Descriptors Applied to Nanoscale Images
This work proposes the application of fractal descriptors to the analysis of
nanoscale materials under different experimental conditions. We obtain
descriptors for images from the sample applying a multiscale transform to the
calculation of fractal dimension of a surface map of such image. Particularly,
we have used the}Bouligand-Minkowski fractal dimension. We applied these
descriptors to discriminate between two titanium oxide films prepared under
different experimental conditions. Results demonstrate the discrimination power
of proposed descriptors in such kind of application
Characterization of nanostructured material images using fractal descriptors
This work presents a methodology to the morphology analysis and
characterization of nanostructured material images acquired from FEG-SEM (Field
Emission Gun-Scanning Electron Microscopy) technique. The metrics were
extracted from the image texture (mathematical surface) by the volumetric
fractal descriptors, a methodology based on the Bouligand-Minkowski fractal
dimension, which considers the properties of the Minkowski dilation of the
surface points. An experiment with galvanostatic anodic titanium oxide samples
prepared in oxalyc acid solution using different conditions of applied current,
oxalyc acid concentration and solution temperature was performed. The results
demonstrate that the approach is capable of characterizing complex morphology
characteristics such as those present in the anodic titanium oxide.Comment: 8 pages, 5 figures, accepted for publication Physica
Automated algorithm for carotid lumen segmentation and 3D reconstruction in B-mode images
The B-mode image system is one of the most popular systems used in the medical area; however it imposes several difficulties in the image segmentation process due to low contrast and noise. Although these difficulties, this image mode is often used in the study and diagnosis of the carotid artery diseases.In this paper, it is described the a novel automated algorithm for carotid lumen segmentation and 3-D reconstruction in B- mode images
A constitutive three-dimensional interface model for masonry walls subjected to high strain rates
Investigation of the dynamic properties of construction materials is critical for structural engineering. The strain rate effect influences the properties of most constructions materials and this effect on materials such as concrete or steel has been intensively investigated. However, such studies on masonry materials are scarce.
Understanding the strain rate effect on masonry materials is important for proper modelling and design of masonry structures under high velocity impacts or blast loads. The work, described in this paper, aims to study the behaviour of masonry at different strain rates. First, a drop weight impact machine is used at different heights and weights introducing different levels of strain rate.
Then, a dynamic constitutive material interface model that includes an non-associated flow rule and high strain rate effects is proposed. The model capability is validated with numerical simulations of unreinforced block work
masonry walls subjected to impact.(undefined
On the nature of the (de)coupling of the magnetostructural transition in ErSi
In this report, a successful thermodynamical model was employed to understand
the structural transition in ErSi, able to explain the decoupling of
the magnetic and structural transition. This was achieved by the DFT
calculations which were used to determine the energy differences at 0 K, using
a LSDA+U approximation. It was found that the M structure as the stable phase
at low temperatures as verified experimentally with a 0.262 eV.
Finally, it was achieved a variation of Seebeck coefficient ( 6 V)
at the structural transition which allow to conclude that the electronic
entropy variation is negligible in the transition.Comment: 17 pages, 3 figures, 1 tabl
Computational Diagnosis of Skin Lesions from Dermoscopic Images using Combined Features
There has been an alarming increase in the number of skin cancer cases worldwide in recent years, which has raised interest in computational systems for automatic diagnosis to assist early diagnosis and prevention. Feature extraction to describe skin lesions is a challenging research area due to the difficulty in selecting meaningful features. The main objective of this work is to find the best combination of features, based on shape properties, colour variation and texture analysis, to be extracted using various feature extraction methods. Several colour spaces are used for the extraction of both colour- and texture-related features. Different categories of classifiers were adopted to evaluate the proposed feature extraction step, and several feature selection algorithms were compared for the classification of skin lesions. The developed skin lesion computational diagnosis system was applied to a set of 1104 dermoscopic images using a cross-validation procedure. The best results were obtained by an optimum-path forest classifier with very promising results. The proposed system achieved an accuracy of 92.3%, sensitivity of 87.5% and specificity of 97.1% when the full set of features was used. Furthermore, it achieved an accuracy of 91.6%, sensitivity of 87% and specificity of 96.2%, when 50 features were selected using a correlation-based feature selection algorithm
Evapotranspiration from a Mediterranean evergreen oak savannah: The role of trees and pasture
Mediterranean evergreen oak woodlands of southern Portugal (montados) are savannah-type ecosystems
with a widely sparse tree cover, over extensive grassland. Therefore, ecosystem water fluxes derive from
two quite differentiated sources: the trees and the pasture. Partitioning of fluxes according to these different
sources is necessary to quantify overall ecosystem water losses as well as to improve knowledge
on its functional behaviour. In southern Iberia, these woodlands are subjected to recurrent droughts.
Therefore, reaction/resilience to water stress becomes an essential feature of vegetation on these ecosystems.
Long-term tree transpiration was recorded for 6 years from a sample of holm oak (Quercus ilex ssp.
rotundifolia) trees, using the Granier sap flow method. Ecosystem transpiration was measured by the eddy
covariance technique for an 11-month period (February to December 2005), partly coincident with a
drought year. Pasture transpiration was estimated as the difference between ecosystem (eddy covariance)
and tree (sap flow) transpiration. Pasture transpiration stopped during the summer, when the surface
soil dried up. In the other seasons, pasture transpiration showed a strong dependence on rainfall
occurrence and on top soil water. Conversely, trees were able to maintain transpiration throughout the
summer due to the deep root access to groundwater. Q. ilex trees showed a high resilience to both seasonal
and annual drought. Tree transpiration represented more than half of ecosystem transpiration, in
spite of the low tree density (30 trees ha 1) and crown cover fraction (21%). Tree evapotranspiration
was dominated by transpiration (76%), and interception loss represented only 24% of overall tree
evaporatio
Essential tremor: clinical observations
The authors have studied 53 patients with essential tremor, focusing its clinical and epidemiological aspects. There were familial history in 37.70% of all cases, prevailing in females (56.60%) and white people (69.80%); nevertheless this difference can not be assured from the statistical point of view due to lack of population data. We agreed that the main incidence of this syndrome occurred beyond the 5th decade, specially during the 6th and 7th decades. Topographically, we could observe that the hand tremor predominated, with an incidence of 96.20% of the total number of cases, followed by head tremor (28.30%), voice tremor (16.99%), leg tremor (11.30%), tongue tremor (3.78%) and trunk tremor (1.88%). These focal tremors were seldom observed alone and we noted frequent association with hand tremor.Foram analisados 53 casos de tremor essencial (TE) do Ambulatório de Distúrbios do Movimento da Disciplina de Neurologia do Hospital Universitário Pedro Ernesto - UERJ, quanto a história familiar, sexo, idade e áreas de acometimento corporal. Dos pacientes avaliados, somente 37,70% apresentavam história familiar para TE. Observa-se predomínio do sexo feminino (56,60%) em relação ao masculino (43,40%) e da raça branca (69,80%) sobre as demais, entretanto, não se pode afirmar que esta diferença seja estatisticamente significativa, por não se dispor de dados populacionais. Nossos achados mostraram maior incidência após os 50 anos de idade, predominando nas 6ª e 7ª décadas, principalmente nesta última. O acometimento das mãos (96,20%) prevaleceu sobre as demais áreas corporais: cefálico (28,30%), de voz (16,99%), de pernas (11,30%), de língua (3,78%) e de tronco (1,88%). Estes dificilmente se apresentavam isolados e ocorriam, em sua maioria, associados ao tremor de mãos.EPMUniversidade do Estado do Rio de Janeiro Hospital Universitário Pedro Ernesto Ambulatório de Distúrbios do MovimentoUNIFESP, EPMSciEL
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