A multi-zone model of the CFR engine : investigating cascading autoignition and octane rating

Includes abstract.Includes bibliographical references (p. 103-109).The CFR engine is the standardised research engine used for the measurement of knock resistance of fuels through the Research Octane Number (RON) and Motor Octane Number(MON) tests. In standard production engines, knock manifests as an almost instantaneous pressure rise followed by knock ringing" pressure oscillations of similar magnitude. However, knock in the CFR engine is characterised, and measured by, a steep, but more gradual pressure rise, followed by ringing of much lesser magnitude. It has been previously proposed that a cascading autoignition", resulting from an in-cylinder temperature gradient, is responsible for this unique pressure development

Sun-symbolism and cosmology in Michelangelo's Last Judgment

A Dissertation submitted to the Faculty of Arts University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy, 1991Although the perception of the design of Michelangelo's Last Judgment as dependent upon a basically circular composition around the figure of Christ has generally been observed in the literature, no sailsfactory explanation of this has been presented. In the following hypothesis, a cosmological interpretation of Michelangelo's Last Judgment proposes new sources for the circular design of the fresco around a central Apollonian Sun-Christ. After. an outline of the basic nature of the problem, an examination of earlier examples of the Last Judgment demonstrates the cosmological associations of the traditional iconography of the subject, primarily related to the hierarchical implications! of the 'flat-earth theory,' which places Heaven above and Hell beneath the earth's surface. Close formal analysis of Michelangelo's own version of the Last Judgment, which emphasizes the innovative aspects of its organisation, is then followed by an assessment of various existing interpretations of the work. In then examining the type of Sources which appear likely to have contributed to the final programme of the work, different areas of religious, literary and philosophical material are brought under consideration. In order to resolve the meaning of the fresco's iconography and composition, the influences upon Michelangelo of the Catholic religion and Reform thought, of the writings of Dante, and of Florentine Neoplatonism have been examined in an entirely new way, from a cosmologicalpoint of view, which brings to light their common emphasis on the Sun as a eymbol of the Deity. A new area of potential source material, that of contemporary scientific cosmology, has also been considered. Prevailing knowledge of Copernicus' theory of the Sun-centred universe, hitherto dismissed as a possible direct influence by renowned writers like Charles de Tolnay, on the grounds of chronology, is specifically discussed and found to be securely documented in Vatican circles at the time of the commission. Thus the sources finally proposed for the overall theme of Sun-symbolism and Cosmologyin the fresco are found to 'be dependent upon the common. ground shared between the Catholic Reformation revival of the traditional Christian analogy between the Deity and the Sun, the Neoplatonic cult of Sun-symholism, literary sources in Dante and the scientific theory of heliocentricity, as developed by Copernicus. Against this background of the History of Ideas in the Renaissance period, consideration of art historical methods leads to the suggestion of a newly proposed Biblical source for the fresco and, finally)l discussion of the deductive method of art historical intterpretation suggests the broader implications of the hypothesls, Ii both for the life and work at Michelangelo himself as well as for the/! sixteenth-century 'context of the fresco's creation.MT201

Vision 3D multi-images (contribution à l'obtention de solutions globales par optimisation polynomiale et théorie des moments)

L objectif général de cette thèse est d appliquer une méthode d optimisation polynomiale basée sur la théorie des moments à certains problèmes de vision artificielle. Ces problèmes sont en général non convexes et classiquement résolus à l aide de méthodes d optimisation locales Ces techniques ne convergent généralement pas vers le minimum global et nécessitent de fournir une estimée initiale proche de la solution exacte. Les méthodes d optimisation globale permettent d éviter ces inconvénients. L optimisation polynomiale basée sur la théorie des moments présente en outre l avantage de prendre en compte des contraintes. Dans cette thèse nous étendrons cette méthode aux problèmes de minimisation d une somme d un grand nombre de fractions rationnelles. De plus, sous certaines hypothèses de "faible couplage" ou de "parcimonie" des variables du problème, nous montrerons qu il est possible de considérer un nombre important de variables tout en conservant des temps de calcul raisonnables. Enfin nous appliquerons les méthodes proposées aux problèmes de vision par ordinateur suivants : minimisation des distorsions projectives induites par le processus de rectification d images, estimation de la matrice fondamentale, reconstruction 3D multi-vues avec et sans distorsions radiales.The overall objective of this thesis is to apply a polynomial optimization method, based on moments theory, on some vision problems. These problems are often nonconvex and they are classically solved using local optimization methods. Without additional hypothesis, these techniques don t converge to the global minimum and need to provide an initial estimate close to the exact solution. Global optimization methods overcome this drawback. Moreover, the polynomial optimization based on moments theory could take into account particular constraints. In this thesis, we extend this method to the problems of minimizing a sum of many rational functions. In addition, under particular assumptions of "sparsity", we show that it is possible to deal with a large number of variables while maintaining reasonable computation times. Finally, we apply these methods to particular computer vision problems: minimization of projective distortions due to image rectification process, Fundamental matrix estimation, and multi-view 3D reconstruction with and without radial distortions.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF

Vision 3D multi-images : contribution à l’obtention de solutions globales par optimisation polynomiale et théorie des moments

L’objectif général de cette thèse est d’appliquer une méthode d’optimisation polynomiale basée sur la théorie des moments à certains problèmes de vision artificielle. Ces problèmes sont en général non convexes et classiquement résolus à l’aide de méthodes d’optimisation locales Ces techniques ne convergent généralement pas vers le minimum global et nécessitent de fournir une estimée initiale proche de la solution exacte. Les méthodes d’optimisation globale permettent d’éviter ces inconvénients. L’optimisation polynomiale basée sur la théorie des moments présente en outre l’avantage de prendre en compte des contraintes. Dans cette thèse nous étendrons cette méthode aux problèmes de minimisation d’une somme d’un grand nombre de fractions rationnelles. De plus, sous certaines hypothèses de "faible couplage" ou de "parcimonie" des variables du problème, nous montrerons qu’il est possible de considérer un nombre important de variables tout en conservant des temps de calcul raisonnables. Enfin nous appliquerons les méthodes proposées aux problèmes de vision par ordinateur suivants : minimisation des distorsions projectives induites par le processus de rectification d’images, estimation de la matrice fondamentale, reconstruction 3D multi-vues avec et sans distorsions radiales. ABSTRACT : The overall objective of this thesis is to apply a polynomial optimization method, based on moments theory, on some vision problems. These problems are often nonconvex and they are classically solved using local optimization methods. Without additional hypothesis, these techniques don’t converge to the global minimum and need to provide an initial estimate close to the exact solution. Global optimization methods overcome this drawback. Moreover, the polynomial optimization based on moments theory could take into account particular constraints. In this thesis, we extend this method to the problems of minimizing a sum of many rational functions. In addition, under particular assumptions of "sparsity", we show that it is possible to deal with a large number of variables while maintaining reasonable computation times. Finally, we apply these methods to particular computer vision problems: minimization of projective distortions due to image rectification process, Fundamental matrix estimation, and multi-view 3D reconstruction with and without radial distortions