Discrepância posterior e sua relação com o padrão de crescimento facial hiperdivergente

Poster apresentado na XXVII Reunião Científica Anual da SPODF. Figueira da Foz, 23-25 Abril 201

Propagation of cracks and dislocations in 2D quasicrystals

A closed-form solution is provided for the stress, strain and velocity fields due to a planar crack steadily propagating in an elastic quasicrystal with fivefold symmetry at speed lower than the bulk wave-speeds. The cases of a semi-infinite rectilinear crack and a Griffith crack which propagates maintaining a constant length, according to the Yoffe model, are considered. Crack face loading and remote loading conditions are taken into consideration. The dynamic theory of quasicrystal with inertia forces, but neglecting dissipative phonon activity, is assumed to govern the motion of the medium. The phonon and phason stress fields turn out to be square-root singular at crack tip. The energy release rate is positive for subsonic and subRayleigh crack propagation

On the automated learning of air pollution prediction models from data collected by mobile sensor networks

This paper addresses the problem of automated learning of air pollution predictive models that were trained using information gathered by a set of mobile low-cost sensors. Concretely, fast to compute machine learning methods (Decision Trees and Support Vector Machines) were used to build regression models that predict air pollution levels for a given location. The models were trained using the data collected by the OpenSense project, in particular, number of particulate matter, particle diameter, and lung deposited surface area (LDSA). We examined two different sets of attributes: one based on a geographical description of the location under analysis (e.g. distribution of households and roads), and another based on a time series of past air pollution observations in that location. Overall, we have found out that past measures lead to better pollution predictions. The best R2 score was 0.751 obtained with the model that predicts LDSA and was trained with the data set with time series attributes, while the worst R2 was 0.009 obtained with the geographical data set to predict number of particles. The performance of the best model is on par with similar air pollution systems. Moreover it can be used in a production system that requires frequent updates.info:eu-repo/semantics/acceptedVersio

Acoustic analogues of black hole singularities

We search for acoustic analogues of a spherical symmetric black hole with a pointlike source. We show that the gravitational system has a dynamical counterpart in the constrained, steady motion of a fluid with a planar source. The equations governing the dynamics of the gravitational system can be exactly mapped in those governing the motion of the fluid. The different meaning that singularities and sources have in fluid dynamics and in general relativity is also discussed. Whereas in the latter a pointlike source is always associated with a (curvature) singularity in the former the presence of sources does not necessarily imply divergences of the fields.Comment: 9 pages, no figure

Lagrangian Formalism for nonlinear second-order Riccati Systems: one-dimensional Integrability and two-dimensional Superintegrability

The existence of a Lagrangian description for the second-order Riccati equation is analyzed and the results are applied to the study of two different nonlinear systems both related with the generalized Riccati equation. The Lagrangians are nonnatural and the forces are not derivable from a potential. The constant value $E$ of a preserved energy function can be used as an appropriate parameter for characterizing the behaviour of the solutions of these two systems. In the second part the existence of two--dimensional versions endowed with superintegrability is proved. The explicit expressions of the additional integrals are obtained in both cases. Finally it is proved that the orbits of the second system, that represents a nonlinear oscillator, can be considered as nonlinear Lissajous figuresComment: 25 pages, 7 figure

Thickness of the buccal bone wall and root angulation in the maxilla and mandible: an approach to cone beam computed tomography

Background: The objective of this paper is to anatomically describe the bone morphology in the maxillary and mandibular tooth areas, which might help in planning post-extraction implants. Methods: CBCT images (Planmeca ProMax 3D) of 403 teeth (208 upper teeth and 195 lower teeth) were obtained from 49 patients referred to the Dental School of Seville from January to December 2014. The thickness of the facial wall was measured at the crest, point A, 4mm below, point B, and at the apex, point C. The second parameter was the angle formed between the dental axis and the axis of the basal bone. Results: A total of 403 teeth were measured. In the maxilla, 89.4% of incisors, 93.94% of canines, 78% of premolars and 70.5% of molars had a buccal bone wall thickness less than the ideal 2mm. In the mandible, 73.5% of incisors, 49% of canines, 64% of premolars and 53% of molars had <1mm buccal bone thickness as measured at point B. The mean angulation in the maxilla was 11.67±6.37° for incisors, 16.88±7.93° for canines, 13.93±8.6° for premolars, and 9.89±4.8° for molars. In the mandible, the mean values were 10.63±8.76° for incisors, 10.98±7.36° for canines, 10.54±5.82° for premolars and 16.19±11.22° for molars. Conclusions: The high incidence of a buccal wall thickness of less than 2mm in over 80% of the assessed sites indicates the need for additional regeneration procedures, and several locations may also require custom abutments to solve the angulation problems for screw-retained crowns

Non-perturbative approach to backscattering off a dynamical impurity in 1D Fermi systems

We investigate the problem of backscattering off a time-dependent impurity in a one-dimensional electron gas. By combining the Schwinger-Keldysh method with an adiabatic approximation in order to deal with the corresponding out of equilibrium Dirac equation, we compute the total energy density (TED) of the system. We show how the free fermion TED is distorted by the backscattering amplitude and the geometry of the impurity.Comment: 5 pages, 2 figures, RevTex4. Appendix and some text added. Results and conclusions did not change. Version accepted for publication in Phys. Rev.

A graphical tool for eliciting knowledge of air pollution sources

With tens of thousands of air quality monitoring stations installed in the world, this source of information has become the standard in air quality measuring. Air pollution becoming a growing concern for decades now, the need for an easy way to visualise pollution data arose. Extensive maps have been created to represent air pollution using data collected from monitoring stations, as well as other sources of information, such as traffic density or weather forecasts. This paper introduces a complementary source: direct environmental expert knowledge. By using the developed tool, the goal is to allow experts to express their knowledge about air pollution emission and diffusion as a function of the presence of key topological elements in a map, such as buildings or roads. The results of the usability tests performed with a sample of 30 participants are promising. Participants provided useful feedback regarding key application features to be implemented in future iterations.info:eu-repo/semantics/acceptedVersio

Saturation effect for dependence of the electrical conductivity of planar oriented nematic liquid crystal 6CB on the concentration of Cu7PS6 nanoparticles

The influence of Cu7PS6 nanoparticles with the average size 117 nm on the dielectric properties of planar oriented nematic liquid crystal 6CB has been investigated within the frequency range 10(1) ...10(6) Hz and at the temperature 293 K. It has been shown that when changing the concentration of nanoparticles within the range 0 to 1 wt.%, the conductivity of the liquid crystal changes stronger than its dielectric permittivity. It has been shown that the electrical conductivity increases monotonously with increasing the concentration of nanoparticles. However, for this dependence a saturation effect is observed. The mechanism of this effect was proposed.info:eu-repo/semantics/publishedVersio