2,268 research outputs found
Looking through the eyes of the painter: from visual perception to non-photorealistic rendering
In this paper we present a brief overview of the processing in the primary visual cortex, the multi-scale line/edge
and keypoint representations, and a model of brightness perception. This model, which is being extended from
1D to 2D, is based on a symbolic line and edge interpretation: lines are represented by scaled Gaussians and
edges by scaled, Gaussian-windowed error functions. We show that this model, in combination with standard
techniques from graphics, provides a very fertile basis for non-photorealistic image rendering
Cortical 3D Face Recognition Framework
Empirical studies concerning face recognition suggest that faces may be stored in memory by a few canonical representations. In cortical area V1 exist double-opponent colour blobs, also simple, complex and end-stopped cells which provide input for a multiscale line/edge representation, keypoints for dynamic routing and saliency maps for Focus-of-Attention. All these combined allow us to segregate faces. Events of different facial views are stored in memory and combined in order to identify the view and recognise the face including facial expression. In this paper we show that with five 2D views and their cortical representations it is possible to determine the left-right and frontal-lateral-profile views and to achieve view-invariant recognition of 3D faces
Artistic rendering of the visual cortex
In this paper we explain the processing in the
first layers of the visual cortex by simple, complex and endstopped
cells, plus grouping cells for line, edge, keypoint and
saliency detection. Three visualisations are presented: (a) an
integrated scheme that shows activities of simple, complex
and end-stopped cells, (b) artistic combinations of selected
activity maps that give an impression of global image
structure and/or local detail, and (c) NPR on the basis of a
2D brightness model. The cortical image representations
offer many possibilities for non-photorealistic rendering
Cortical multiscale line-edge disparity model
Most biological approaches to disparity extraction rely on
the disparity energy model (DEM). In this paper we present an alternative
approach which can complement the DEM model. This approach
is based on the multiscale coding of lines and edges, because surface
structures are composed of lines and edges and contours of objects often
cause edges against their background. We show that the line/edge approach
can be used to create a 3D wireframe representation of a scene
and the objects therein. It can also significantly improve the accuracy of
the DEM model, such that our biological models can compete with some
state-of-the-art algorithms from computer vision
Constructing and Visualizing High-Quality Classifier Decision Boundary Maps dagger
Visualizing decision boundaries of machine learning classifiers can help in classifier design, testing and fine-tuning. Decision maps are visualization techniques that overcome the key sparsity-related limitation of scatterplots for this task. To increase the trustworthiness of decision map use, we perform an extensive evaluation considering the dimensionality-reduction (DR) projection techniques underlying decision map construction. We extend the visual accuracy of decision maps by proposing additional techniques to suppress errors caused by projection distortions. Additionally, we propose ways to estimate and visually encode the distance-to-decision-boundary in decision maps, thereby enriching the conveyed information. We demonstrate our improvements and the insights that decision maps convey on several real-world datasets
Building the what and where systems: multi-scale lines, edges and keypoints
Computer vision for realtime applications requires tremendous computational
power because all images must be processed from the first to the last pixel. Ac
tive vision by probing specific objects on the basis of already acquired context
may lead to a significant reduction of processing. This idea is based on a few
concepts from our visual cortex (Rensink, Visual Cogn. 7, 17-42, 2000): (1) our
physical surround can be seen as memory, i.e. there is no need to construct
detailed and complete maps, (2) the bandwidth of the what and where systems
is limited, i.e. only one object can be probed at any time, and (3) bottom-up,
low-level feature extraction is complemented by top-down hypothesis testing, i.e.
there is a rapid convergence of activities in dendritic/axonal connections
Stimulated Brillouin scattering by surface acoustic waves in lithium niobate waveguides
We numerically demonstrate that Lithium Niobate on Insulator (LNOI)
waveguides may support confined short-wavelength surface acoustic waves that
interact strongly with optical fields through backward stimulated Brillouin
scattering in both and -cut orientation. We conduct fully anisotropic
simulations that consider not only moving boundary and photoelastic forces, but
also roto-optic forces for the Brillouin interaction. Our results indicate that
photoelasticity dominates the Brillouin gain and can reach as high as
= 0.43 Wm in standard ridge waveguide
Influence of physical exercise and sodium intake on arterial pressure and cardiac hypertrophy in rats
Há evidências de que a hipertrofia cardíaca (HC) seja um fator de risco para várias doenças cardiovasculares. Uma variedade de estímulos pode levar à HC, entre os quais estão condições que gerem sobrecarga de volume ou pressão, como o exercício físico e a dieta rica em cloreto de sódio (NaCl). Com o objetivo de verificar a possibilidade de o exercício físico e a ingestão de dieta rica em NaCl influenciarem na pressão arterial e trofismo miocárdico, realizou-se o presente estudo. Foram utilizados 36 ratos Holtzman, do sexo feminino, pesando entre 200 e 300 gramas, e divididos nos seguintes grupos (n=6): Grupo I (dieta com água sem NaCl), Grupo II (dieta com água sem NaCl), Grupo III (dieta com solução de NaCl a 2,5%), Grupo IV (dieta com solução de NaCl a 5%), Grupo V (dieta com solução de NaCl a 2,5%), Grupo VI (dieta com solução de NaCl a 5%). Os animais dos grupos II, III e IV praticaram natação durante 100 minutos ao dia, por cinco semanas, após as quais foram mortos e seus corações pesados. As medidas de pressão arterial (PA) e de peso durante o experimento foram comparadas. Houve diminuição do peso dos grupos submetidos a exercício físico e / ou dieta salina: Grupo I (229,0 g), Grupo II (201,17 g), Grupo III (207,0 g), Grupo IV (149,17 g) e Grupo V (156,17 g). Ao final do experimento, o grupo que foi submetido à dieta mais rica em sódio juntamente com exercício mostrou uma PA significativamente maior (102,67 mmHg) que o Grupo I (88,83 mmHg), sem fatores de risco. Houve uma maior relação peso do coração/peso corporal nos grupos III (0,452 %) e IV (0,417 %), em comparação com o Grupo I (0,337%). Concluindo, houve indícios de hipertrofia cardíaca e aumento da pressão arterial nos animais que ingeriram solução salina e realizaram exercício físico.Evidence shows that cardiac hypertrophy (CH) is a risk factor for many cardiovascular diseases. Several stimuli may cause CH-like manifestations and promote volume or pressure overload. Exercise-induced cardiac hypertrophy is an expected adaptation to regular exercise training. Salt intake has been shown to be the most important determinant of blood pressure in different populations. The purpose of the present work was to verify the influence of physical exercise and sodium intake on the blood pressure and myocardium. The study was performed on 36 rats divided into six groups: Group I (diet without salt overload), Group II (diet without salt overload and swimming), Group III (diet with 2.5% NaCl solution and swimming), Group IV (diet with 5% NaCl solution and swimming), Group V (diet with 2.5% NaCl solution without exercise), Group VI (diet with 5% NaCl solution without exercise). The arterial pressure was significantly lower in Group I when compared with Group IV. The ratio of cardiac mass/body mass was increased in Groups III and IV. In conclusion, there was evidence that exercise training and NaCl intake promotes arterial hypertension and cardiac hypertrophy
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