A counterexample to De Pierro's conjecture on the convergence of under-relaxed cyclic projections

The convex feasibility problem consists in finding a point in the intersection of a finite family of closed convex sets. When the intersection is empty, a best compromise is to search for a point that minimizes the sum of the squared distances to the sets. In 2001, de Pierro conjectured that the limit cycles generated by the $\varepsilon$-under-relaxed cyclic projection method converge when $\varepsilon\downarrow 0$ towards a least squares solution. While the conjecture has been confirmed under fairly general conditions, we show that it is false in general by constructing a system of three compact convex sets in $\mathbb{R}^3$ for which the $\varepsilon$-under-relaxed cycles do not converge

GIS-Based Identification of Topographic Sites in Italy with Significant Ground Motion Amplification Effects

Surface topography can significantly affect earthquake ground motions, as suggested by many examples of unexpected damage suffered by buildings located on the top of hills, on ridges or along slopes. European and Italian seismic codes suggest topographic aggravation factors in the 1 – 1.4 range to be applied to seismic actions, depending not only on simple morphologic parameters (average slope angle, width and height of the relief) but also on the type of relief (isolated cliff or ridge) and on the location of the site relative to the relief. Furthermore, strongly irregular topographies should be dealt with by a specific study. To provide a practical tool for the identification of critical topographic sites, analyses of high resolution digital elevation models (DEM), with the support of Geographic Information Systems (GIS), are presented in this paper. Simple GIS functions are used to classify critical ranges of inclination, while the identification of valleys and ridges requires more complex procedures. A comparison of different methods for their identification is presented in this work, aiming at finding the most suitable ones for seismic microzonation analyses. Once the critical conditions are synthesized into GIS layers, their proximity to inhabited centres or strategic structures are checked. The resulting maps can be used for topography-related seismic risk assessment at large scale. We present two examples of application of this procedure, with particular attention to the small historical centres located on the Apennine mountains in Central and Southern Italy

Evaluation of the influence of texture and microstructure of titanium substrates on TiO2 anodic coatings at 60 V

The current paper analyzes the influence of texture and microstructure of Ti substrates on morphology and color of titanium dioxide coatings obtained by anodic oxidation. Substrates of Ti grade 2 and Ti grade 5 with different thermo-mechanical histories were used in the shape of cylindrical bars cut in both longitudinal and transversal directions, and laminated sheets. The crystalline orientation of the surface grains in the substrate before oxidation, were determined by electron backscatter diffraction. The oxide coatings were analyzed by optical and scanning electron microscopy. The results show that different substrate grain orientations produce oxides with different colors, because of different thickness depending on their orientations. An oxide grown on a basal hcp plane, with higher atomic density is thinner than an oxide grown on a transversal hcp plane with lower atomic density. This effect is more pronounced on elongated grains. Different anodic oxidation process parameters and heat treatments of the substrate were applied in order to obtain a more uniform oxide thickness. A specific heat treatment of the substrate was the most efficient, starting from a favorable orientation of crystals, characteristic of rolling texture.Fil: Vera, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Avalos, Martina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rosenberger, Mario Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Schvezov, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Ares, Alicia Esther. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; Argentin

Estudio comparativo in vitro de la película de cementación en incrustaciones posteriores con cemento de resina dual versus termoplastificadas

Tesis (Cirujano Dentista)En este estudio se realizó una comparación in vitro entre el espesor y homogeneidad de la película de cementación obtenida en incrustaciones posteriores para el cemento de resina termoplastificada y cemento de resina foto independiente. Esto se obtuvo mediante dos cavidades oclusoproximales de profundidad estandarizada para 10 dientes recolectados. Luego, mediante método indirecto, se confeccionó dos incrustaciones por diente. A y B fueron cementadas con resina termoplastificada y Relyx U200 respectivamente. Posterior a esto, se realizó un corte mesiodistal, de oclusal a apical, pasando por el centro de cada restauración, se regularizó la superficie con discos softlex para eliminar rayas e impurezas y se llevó al microscopio electrónico de barrido. Se midió en micras el espesor en cuatro puntos de cada restauración. Se realizaron comparaciones entre los puntos de cada muestra para estudiar homogeneidad y luego se promediaron y compararon entre ambos grupos para analizar espesor. Los resultados fueron analizados estadísticamente mediante el test de comparación de U Mann-Whitney, para lo cual no se encontraron diferencias significativas. La mayor parte de las muestras de ambos grupos analizados no logró los espesores adecuados recomendados en su película de cementación ni se presentó homogénea en sus puntos analizados. Se considera que el cemento de resina termoplastificada es el material de elección para la cementación de incrustaciones posteriores, ya que presenta mejores propiedades mecánicas y menor contracción de polimerización