Reconstruction of 3D Object Meshes from Silhouette Images

In this work we propose a method for computing mesh representations of 3D objects reconstructed from a set of silhouette images. Our method is based on the polygonization of volumetric reconstructions by using a modified version of the dual contouring method. In order to apply dual contouring on volumetric reconstruction from silhouettes we devised a method that is able to determine the discrete topology of the surface in relation to the octree cells. We also developed a new scheme for computing hermitian data representing the intersections of conic volumes with the octree cells and their corresponding normals with subpixel accuracy. Due to the discrete and extremely noisy nature of the data used in the reconstruction we had to devise a different criterion for mesh simplification that applies topological consistency tests only when the geometric error measure is beyond a given tolerance. We present results of the application of the proposed method in the extraction of a mesh corresponding to the surface of objects of a real scene.     

Evolution of neural networks for classification and regression

Although Artificial Neural Networks (ANNs) are importantdata mining techniques, the search for the optimal ANN is a challenging task: the ANN should learn the input–output mapping without overfitting the data and training algorithms may get trapped in local minima. The use of Evolutionary Computation (EC) is a promising alternative for ANN optimization. This work presents two hybrid EC/ANN algorithms: the first evolves neural topologies while the latter performs simultaneous optimization of architectures and weights. Sixteen real-world tasks were used to test these strategies. Competitive results were achieved when compared with a heuristic model selection and other Data Mining algorithms.     

Contracting agents: legal personality and representation

The combined use of computers and telecommunications and the latest evolution in the field of Artificial Intelligence brought along new ways of contracting and of expressing will and declarations. The question is, how far we can go in considering computer intelligence and autonomy, how can we legally deal with a new form of electronic behaviour capable of autonomous action? In the field of contracting, through Intelligent Electronic Agents, there is an imperious need of analysing the question of expression of consent, and two main possibilities have been proposed: considering electronic devices as mere machines or tools, or considering electronic devices as legal persons. Another possibility that has been frequently mentioned consists in the application of the rules of agency to electronic transactions. Meanwhile, the question remains: would it possible, under a Civil Law framework, to apply the notions of “legal personhood” and “representation” to electronic agents? It is obvious that existing legal norms are not fit for such an endeavouring challenge. Yet, the virtual world exists and it requires a new but realistic legal approach on software agents, in order to enhance the use of electronic commerce in a global world.     

DW-RBAC: A formal security model of delegation and revocation in workflow systems

One reason workflow systems have been criticized as being inflexible is that they lack support for delegation. This paper shows how delegation can be introduced in a workflow system by extending the role-based access control (RBAC) model. The current RBAC model is a security mechanism to implement access control in organizations by allowing users to be assigned to roles and privileges to be associated with the roles. Thus, users can perform tasks based on the privileges possessed by their own role or roles they inherit by virtue of their organizational position. However, there is no easy way to handle delegations within this model. This paper tries to treat the issues surrounding delegation in workflow systems in a comprehensive way. We show how delegations can be incorporated into the RBAC model in a simple and straightforward manner. The new extended model is called RBAC with delegation in a workflow context (DW-RBAC). It allows for delegations to be specified from a user to another user, and later revoked when the delegation is no longer required. The implications of such specifications and their subsequent revocations are examined. Several formal definitions for assertion, acceptance, execution and revocation are provided, and proofs are given for the important properties of our delegation framework.     

Nonhydrolytic sol-gel synthesis and characterization of YAG

Yttrium–aluminum oxides are interesting compounds, which are widely used as hosts for lasers and phosphors due to their stable physical and chemical properties. The manufacture of YAG has been investigated thoroughly. YAG powders are traditionally synthesized through the reaction of aluminum and yttrium powders at high temperatures. The work reported here involved an investigation into the preparation of YAG by a nonhydrolytic sol-gel route and the influence of heating time at low temperatures to obtain YAG from inorganic precursors (yttrium and aluminum chloride). AlCl₃, YCl₃ and ethanol were reflux reacted under an argon atmosphere. Europium III chloride was added as a structural probe. The powder was treated at 800 °C for 1, 2, 4, 8 and 16 h. The YAG structure was analyzed by X-ray diffraction (XRD), nuclear magnetic resonance (NMR), thermal analysis (TA) and photoluminescence (PL). The XRD revealed only peaks corresponding to the YAG phase. PL data showed that the YAG phase was formed in 2 min with samples pretreated at 50 °C. For the samples pretreated at 800 °C, the YAG phase appeared in 30 s. The excitation spectra presented a maximum of 394 nm corresponding to the ⁵L₆ level, while the emission spectra of Eu III ions showed characteristic transition bands arising from the ⁵D₀ → ⁷F _J (J = 1, 2, 3, 4) manifolds at maximum excitation. The magnetic dipole ⁵D₀ → ⁷F₁ transition exhibited greater intensity than the electric dipole ⁵D₀ → ⁷F₂ transition. This methodology proved efficient for obtaining YAG phase.     

Lessons learned from the testing of RC frames with masonry infills and proposals for new solutions / Untersuchungen an mit Mauerwerk ausgefachten Stahlbetonrahmen und neue Lösungsvorschläge

Past experience has shown that inadequate design of unreinforced masonry walls (URM) or inadequate selection of materials can lead to significant economic losses and fatalities in the case of a strong earthquake. In this context, this paper presents the experimental research that has been carried out with the aim of gaining a better insight into the traditional masonry infill walls commonly built in Portugal. The experimental research includes: (1) shaking table tests on reduced‐scale reinforced concrete (RC) buildings with masonry infills with distinct typologies, from traditional solutions to those with enhanced properties and solutions to improve the seismic behaviour; (2) in‐plane static cyclic tests on a representative one‐storey, one‐bay RC frame with masonry infills with distinct typologies but similar to the ones tested in the RC building models. It was concluded that the typology of masonry walls influences the global behaviour of RC buildings, particularly when there is no connection between masonry infill and RC frame. An appropriate design is necessary to prevent an unforeseen failure mechanism due to shear stresses in the RC columns induced by the infill. The in‐plane cyclic tests showed that render plays a central role in the lateral strength and stiffness. Additionally, it was observed that bed joint reinforcement and reinforced render are important measures for controlling damage but do not significantly influence the in‐plane lateral strength and stiffness.     

Integration of beamforming and uncertainty-of-observation techniques for robust ASR in multi-source environments

This paper presents a new approach for increasing the robustness of multi-channel automatic speech recognition in noisy and reverberant multi-source environments. The proposed method uses uncertainty propagation techniques to dynamically compensate the speech features and the acoustic models for the observation uncertainty determined at the beamforming stage. We present and analyze two methods that allow integrating classical multi-channel signal processing approaches like delay and sum beamformers or Zelinski-type Wiener filters, with uncertainty-of-observation techniques like uncertainty decoding or modified imputation. An analysis of the results on the PASCAL-CHiME task shows that this approach consistently outperforms conventional beamformers with a minimal increase in computational complexity. The use of dynamic compensation based on observation uncertainty also outperforms conventional static adaptation with no need of adaptation data.     

Biosynthesis and Site of Production of Sex Pheromone Components of the Cerambycid Beetle, Hedypathes betulinus

We determined the site of pheromone production tissues and a partial route for the biosynthesis of the sex pheromone in Hedypathes betulinus (Coleoptera: Cerambycidae: Lamiinae), Brazil’s main green maté pest. Pheromone was found predominantly in the prothorax of males, suggesting that this is the region of production of pheromones in this insect. Scanning electron microscopy revealed small pores that may be associated with pheromone release in males; these pores also were observed in females. A deuterium-labeled putative precursor (geranyl acetone-D₅) of the sex pheromone of H. betulinus was synthesized. When applied to the prothorax of males, label from the precursor was incorporated into the pheromone components, confirming that pheromone production occurs in the prothorax and that the pheromone components are biosynthesized from geranyl acetone.