http://hdl.handle.net/2117/3560 2013-06-19T11:18:56Z http://hdl.handle.net/2117/14392 Title: Origin and modelling of cold dark matter halo properties: IV. Triaxial ellipticity Authors: Salvador-Solé, Eduard; Serra, Sinué; Manrique, Alberto; González Casado, Guillermo Abstract: In the three preceding papers in the series, we presented a model dealing with the global and small-scale structure and kinematics of hierarchically assembled, virialised, collisionless systems, which correctly accounted for the typical properties of simulated cold darkmatter (CDM) haloes. This model relied, however, on the spherical symmetry assumption. Here we show that the foundations of the model hold equally well for triaxial systems and extend it in a fully accurate way to objects that satisfy the latter more general symmetry. The master equations in the new version take the same form as in the version for spherically symmetric objects, but the profiles of all the physical quantities are replaced by their respective spherical averages. All the consequences of the model drawn under the spherical symmetry assumption continue to hold. In addition, the new version allows one to infer the axial ratios of virialised ellipsoids from those of the corresponding protoobjects. The present results generalise and validate those obtained in Papers I, II and III for CDM haloes. In particular, they confirm that all halo properties are the natural consequence of haloes evolving through accretion and major mergers from triaxial peaks (secondary maxima) in the primordial density field. 2012-01-02T12:38:30Z http://hdl.handle.net/2117/12477 Title: A technique to composite a modified Newton's method for solving nonlinear equations Authors: Grau Sánchez, Miguel; Díaz Barrero, José Luis Abstract: A zero-finding technique for solving nonlinear equations more efficiently than they usually are with traditional iterative methods in which the order of convergence is improved is presented. The key idea in deriving this procedure is to compose a given iterative method with a modified Newton’s method that introduces just one evaluation of the function. To carry out this procedure some classical methods with different orders of convergence are used to obtain root-finders with higher efficiency index. Description: Nova tècnica que permet construir mètodes iteratius d'ordre alt. 2011-05-05T11:44:52Z http://hdl.handle.net/2117/12475 Title: On computational order of convergence of some multi-precision solvers of nonlinear systems of equations Authors: Grau Sánchez, Miguel; Grau Gotés, Mª Ángela; Díaz Barrero, José Luis Abstract: In this paper the local order of convergence used in iterative methods to solve nonlinear systems of equations is revisited, where shorter alternative analytic proofs of the order based on developments of multilineal functions are shown. Most important, an adaptive multi-precision arithmetics is used hereof, where in each step the length of the mantissa is defined independently of the knowledge of the root. Furthermore, generalizations of the one dimensional case to m-dimensions of three approximations of computational order of convergence are defined. Examples illustrating the previous results are given. Description: Report d'un treball de recerca on es presenten noves tècniques de càlcul de l'ordre de convergència amb una aritmètica adaptativa. 2011-05-05T11:25:05Z http://hdl.handle.net/2117/12013 Title: Estudi de la transformació de l'espai de color RGB a l'espai de color HSV Authors: Grau Gotés, Mª Ángela; Grau Sánchez, Miguel; Montseny Masip, Eduard; Sobrevilla Frisón, Pilar Abstract: S’apliquen les tècniques clàssiques de propagació de l’error a la transformació de l’espai de color RGB en l’espai de color HSV a un conjunt de 1098 imatges test. El conjunt d’imatges test són 183 paletes de color i sis nivells d’il·luminació diferents. Els resultats que es presenten indiquen com varien la mitjana i la variància per la transformació. 2011-03-22T10:51:28Z