Production of metallic nanoparticles, from industrial residues, by the use of different types of reduction gases

The need to enhance and reuse existing materials on secondary sources of metals has had quite an impact in recent times. Several processes and technologies had being studied for recovery of raw materials from industrial waste generated. This study focuses on the possibility of waste reducing, from the galvanic floor covering industry, with the aim of obtaining micro or nano-particles of nickel or a nickel based alloy. Sludges from one galvanic treatment plant were used as base material in two conditions: as produced and after a hydrometallurgical treatment for metal concentration. Several reducing agents were used in this study: a synthesis gas from a polymer pyrolysis and solid polymer agents (PVC, HDPE and PP residues). Obtained products were characterised in terms of metallic particles production during the reduction treatment and by SEM/EDS analysis on the final products. A simultaneous differential thermal and thermogravimetric equipment (DSC/TGA) was used for the study of the reduction process with a reduction gas obtained from the pyrolysis of chlorine free PVC derived char. The obtained results show that it is possible to obtain small metallic particles, in the range of 60 to 240 nm, at 800 ºC. Reduction tests, by the use of a solid residue, were made in a laboratorial furnace with two independent heating zones. Best results were obtained with de-chlorinated PVC as a reduction agent with the production of metallic particles, in the range of 150 to 600 nm, at 800 ºC. For all the tested conditions the metallic particles were constituted by Ni and Cu with variable chemical composition

Descoberta da jazida da Idade do bronze na Tapada da Ajuda

Separata de "Setúbal Arqueológica". Vol. VI-VII, de 1980-81Un «hameau» pré-historique, localisé dans l'aire urbaine de Lisbonne (Tapada da Ajuda) est étudié. Du point de vue géologique et géomorphologique, il est situé sur un versant du Complexe Basaltique de Lisbonne (5ième coulée lavique), de déclive doux et sans défenses naturelles. Parmi les industries recueillies, presque exclusivement à la surface, on peut remarquer l'abondance d'élèments de faucille, sur éclats, en silex (134 exemplaires), quartzite (1 exemplaire) et calcédoine (1 exemplaire), associés à d'autre matériel lithique dont la chronologie fût impossible d'être précisée, vu l'inexistence d'indications stratigraphiques, et d'une abondante céramique e l'Âge du Bronze, dont une partie est de fabrication locale (la présence de mineraux ferromagnésiens dans les pâtes en est témoin). La réalisation d'un talu d'excavation destiné à un terrassement (qui a détruit une partie importante de la station), a permi l'observation d'une coupe ou se concentraient des résidus de cuisine, en particulier de la faune malacologique (surtout Ostrea edule). Des éclats résiduels y ont été recueillis, et aussi un racloir lateral denticulé, deux élèments de faucille sur éclats et des morceaux céramiques typologiquement caraetéristiques du Bronze final. Une analyse camparative des objects étudiés a permit de conclure sur l'exclusivité des élèments de faucille sur éclats en stations de l'Âge du Bronze, au contraire des époques antérieures, où ces élèments étaient surtout façonnés sur lâmes. La rareté des faucilles en bronze (dont on a récemment inventarié seulement 19 exemplaires pour le Portugal), à une époque si tardive de l'Âge du Bronze, peut done s'expliquer par l'efficacité de celles de sílex, très abondants, surtout dans les «habitats-hameaux» de la Péninsule de Lisbonne. Ce modèle d'organisation sociale, qui correspond une à dispersion du peuplement semble caractériser, à cette époque, la fertile région que nous venons de mentioner et pourrait done correspondre à une soeiété au pouvoir centralisé, administrant tout une région, semblablé à ceIui preconisé pour le Bas Alentejo, à la même époque (C. Tavares da Silva e J. Soares, 1978).info:eu-repo/semantics/publishedVersio

SOLUTION OF 1D AND 2D POISSON'S EQUATION BY USING WAVELET SCALING FUNCTIONS

The use of multiresolution techniques and wavelets has become increasingly popular in the development of numerical schemes for the solution of partial differential equations (PDEs). Therefore, the use of wavelet scaling functions as a basis in computational analysis holds some promise due to their compact support, orthogonality and localization properties. Daubechies and Deslauriers-Dubuc functions have been successfully used as basis functions in several schemes like the Wavelet- Galerkin Method (WGM) and the Wavelet Finite Element Method (WFEM). Another possible advantage of their use is the fact that the calculation of integrals of inner products of wavelet scaling functions and their derivatives can be made by solving a linear system of equations, thus avoiding the problem of using approximations by some numerical method. These inner products were defined as connection coefficients and they are employed in the calculation of stiffness matrices and load vectors. In this work, some mathematical foundations regarding wavelet scaling functions, their derivatives and connection coefficients are reviewed. A scheme based on the Galerkin Method is proposed for the direct solution of Poisson's equation (potential problems) in a meshless formulation using interpolating wavelet scaling functions (Interpolets). The applicability of the proposed method and some convergence issues are illustrated by means of a few examples

Solving problems through engineering design: An exploratory study with pre-service teachers

A possible pathway to achieve disciplinary integration is through the use of the Engineering Design (ED) process, starting with problems in a real context that enable the mobilization of concepts from various disciplinary areas. The study reported in this paper aims to analyze the performance underlying the use of the ED process in solving authentic problems in a STEAM perspective, with future teachers of elementary education. We adopted a qualitative and interpretative methodology, with an exploratory design, where data were collected through participant observation, documents, artefacts and photographic records. The results are discussed, taking into account previous research and the data collected throughout the classes, where future teachers solved a problem task and created an artefact and a poster. Preliminary results show that the participants valued the experience and were actively engaged, showing persistence and motivation in solving the problem in a collaborative way, through the different steps of the ED cycle. This approach constituted an opportunity to favor the establishment of connections between different areas, such as mathematics, sciences or arts, detecting the possibility of integrating previously learned concepts. Difficulties were evidenced in the identification of some underlying mathematical and physical sciences concepts, particularly in the mobilization of an adequate scientific language while arguing and making decisions, or in accurately justifying the need to improve the designed plan.0D1E-4824-1244 | Ana Cristina Coelho Barbosainfo:eu-repo/semantics/publishedVersio

Solving authentic problems through engineering design

The importance of STEAM education in pre- paring students to deal with societal challenges is nowa- days an international recommendation. We may find different perspectives concerning STEAM education and the integration of its disciplines. A possible pathway to achieve a balanced integration is through Engineering Design (ED), starting from problems of reality that enable the articulated mobilization of concepts from various dis- ciplinary areas, promoting interdisciplinary where team- work and context play a fundamental role. This article reports a study with primary preservice teachers (6?12 years old) that aims to analyze the learning displayed and the difficulties underlying the usage of ED in solving STEAM problems. The participants were 45 preservice teachers. We adopted a qualitative methodology, and data were collected through observation, documents, artifacts, and photos. The preliminary results show a very positive reaction of the participants to the experi- ence of solving real context problems collaboratively and mobilizing mathematical and physical science concepts in an integrated way. We identified active engagement, persistence, and motivation in the creation of a model that fulfilled the requested conditions. Difficulties were evidenced in the identification of some concepts and the mobilization of adequate scientific language in the argumentation of decisions.0D1E-4824-1244 | Ana Cristina Coelho Barbosainfo:eu-repo/semantics/publishedVersio

The Network of Epicenters of the Olami-Feder-Christensen Model of Earthquakes

We study the dynamics of the Olami-Feder-Christensen (OFC) model of earthquakes, focusing on the behavior of sequences of epicenters regarded as a growing complex network. Besides making a detailed and quantitative study of the effects of the borders (the occurrence of epicenters is dominated by a strong border effect which does not scale with system size), we examine the degree distribution and the degree correlation of the graph. We detect sharp differences between the conservative and nonconservative regimes of the model. Removing border effects, the conservative regime exhibits a Poisson-like degree statistics and is uncorrelated, while the nonconservative has a broad power-law-like distribution of degrees (if the smallest events are ignored), which reproduces the observed behavior of real earthquakes. In this regime the graph has also a unusually strong degree correlation among the vertices with higher degree, which is the result of the existence of temporary attractors for the dynamics: as the system evolves, the epicenters concentrate increasingly on fewer sites, exhibiting strong synchronization, but eventually spread again over the lattice after a series of sufficiently large earthquakes. We propose an analytical description of the dynamics of this growing network, considering a Markov process network with hidden variables, which is able to account for the mentioned properties.Comment: 9 pages, 10 figures. Smaller number of figures, and minor text corrections and modifications. For version with full resolution images see http://fig.if.usp.br/~tpeixoto/cond-mat-0602244.pd