949 resultados para Delaunay, Triangulació de
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Collection : Archives de la linguistique française ; 100
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In order to compare coronary magnetic resonance angiography (MRA) data obtained with different scanning methodologies, adequate visualization and presentation of the coronary MRA data need to be ensured. Furthermore, an objective quantitative comparison between images acquired with different scanning methods is desirable. To address this need, a software tool ("Soap-Bubble") that facilitates visualization and quantitative comparison of 3D volume targeted coronary MRA data was developed. In the present implementation, the user interactively specifies a curved subvolume (enclosed in the 3D coronary MRA data set) that closely encompasses the coronary arterial segments. With a 3D Delaunay triangulation and a parallel projection, this enables the simultaneous display of multiple coronary segments in one 2D representation. For objective quantitative analysis, frequently explored quantitative parameters such as signal-to-noise ratio (SNR); contrast-to-noise ratio (CNR); and vessel length, sharpness, and diameter can be assessed. The present tool supports visualization and objective, quantitative comparisons of coronary MRA data obtained with different scanning methods. The first results obtained in healthy adults and in patients with coronary artery disease are presented.
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Collection : Archives de la linguistique française ; 128
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This thesis deals with distance transforms which are a fundamental issue in image processing and computer vision. In this thesis, two new distance transforms for gray level images are presented. As a new application for distance transforms, they are applied to gray level image compression. The new distance transforms are both new extensions of the well known distance transform algorithm developed by Rosenfeld, Pfaltz and Lay. With some modification their algorithm which calculates a distance transform on binary images with a chosen kernel has been made to calculate a chessboard like distance transform with integer numbers (DTOCS) and a real value distance transform (EDTOCS) on gray level images. Both distance transforms, the DTOCS and EDTOCS, require only two passes over the graylevel image and are extremely simple to implement. Only two image buffers are needed: The original gray level image and the binary image which defines the region(s) of calculation. No other image buffers are needed even if more than one iteration round is performed. For large neighborhoods and complicated images the two pass distance algorithm has to be applied to the image more than once, typically 3 10 times. Different types of kernels can be adopted. It is important to notice that no other existing transform calculates the same kind of distance map as the DTOCS. All the other gray weighted distance function, GRAYMAT etc. algorithms find the minimum path joining two points by the smallest sum of gray levels or weighting the distance values directly by the gray levels in some manner. The DTOCS does not weight them that way. The DTOCS gives a weighted version of the chessboard distance map. The weights are not constant, but gray value differences of the original image. The difference between the DTOCS map and other distance transforms for gray level images is shown. The difference between the DTOCS and EDTOCS is that the EDTOCS calculates these gray level differences in a different way. It propagates local Euclidean distances inside a kernel. Analytical derivations of some results concerning the DTOCS and the EDTOCS are presented. Commonly distance transforms are used for feature extraction in pattern recognition and learning. Their use in image compression is very rare. This thesis introduces a new application area for distance transforms. Three new image compression algorithms based on the DTOCS and one based on the EDTOCS are presented. Control points, i.e. points that are considered fundamental for the reconstruction of the image, are selected from the gray level image using the DTOCS and the EDTOCS. The first group of methods select the maximas of the distance image to new control points and the second group of methods compare the DTOCS distance to binary image chessboard distance. The effect of applying threshold masks of different sizes along the threshold boundaries is studied. The time complexity of the compression algorithms is analyzed both analytically and experimentally. It is shown that the time complexity of the algorithms is independent of the number of control points, i.e. the compression ratio. Also a new morphological image decompression scheme is presented, the 8 kernels' method. Several decompressed images are presented. The best results are obtained using the Delaunay triangulation. The obtained image quality equals that of the DCT images with a 4 x 4
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Aquest estudi analitza quatre zones del municipi català de Badia del Vallès, tres de les quals, d’acord amb les dades, constitueixen punts calents en matèria de delinqüència i incivisme (robatoris amb força en interior de domicili, robatoris en interior de vehicle i queixes veïnals per consum de drogues a la via pública i incivisme) i l’altre té gran importància estratègica, en tractar-se de la principal zona d’activitat comercial del municipi. La informació ha estat obtinguda a partir de quatre fonts: bases de dades policials, revisió de documents d’altres autors i institucions, entrevistes i observació participant. Posteriorment, s’ha comparat i sotmès a triangulació aquesta informació, i s’ha analitzat amb la perspectiva d’un marc teòric, amb l’objectiu d’establir un seguit de propostes d’intervenció urbanística adreçades,d’una banda, a la prevenció i a la disminució de la delinqüència als punts calents analitzats, però també a aconseguir una millor convivència. Entre les propostes d’intervenció hi ha la millora de l’enllumenat, la poda de l’arbrat que permeti el control informal, el manteniment i neteja dels espais i el mobiliari urbà, l’adequació dels espais i introducció d’equipaments,etc. Per últim s’ha definit una breu guia de recomanacions, aplicable a l’hora de dissenyar o recuperar espais públics, en la línea dels objectius esmentats: la prevenció i la reducció de la delinqüència i el foment de la convivència i el benestar de la població.
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1873/01/01 (N1)-1873/12/05 (N12).
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1873/05/05 (N5).
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1873/07/05 (N7).
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1873/09/05 (N9).
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1873/11/05 (N11).
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1873/01/01 (N1).
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Périodicité : Mensuel
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1873/06/05 (N6).
