Strong stochastic stability for non-uniformly expanding maps

We consider random perturbations of discrete-time dynamical systems. We give sufficient conditions for the stochastic stability of certain classes of maps, in a strong sense. This improves the main result in J. F. Alves, V. Araujo, Random perturbations of non-uniformly expanding maps, Asterisque 286 (2003), 25--62, where it was proved the convergence of the stationary measures of the random process to the SRB measure of the initial system in the weak* topology. Here, under slightly weaker assumptions on the random perturbations, we obtain a stronger version of stochastic stability: convergence of the densities of the stationary measures to the density of the SRB measure of the unperturbed system in the L1-norm. As an application of our results we obtain strong stochastic stability for two classes of non-uniformly expanding maps. The first one is an open class of local diffeomorphisms introduced in J. F. Alves, C. Bonatti, M. Viana, SRB measures for partially hyperbolic systems whose central direction is mostly expanding, Invent. Math. 140 (2000), 351--398, and the second one the class of Viana maps.Comment: 43 page

Small sized pilot scale experiments on the recovery cooper and nickel hydroxide from galvanic sludge

The present work, carried out within the project VALMETAIS, proposes a hydrometallurgical process for copper and nickel recovery from galvanic sludges produced by Ni/Cr plating plants. The procedure has been developed on laboratory scale and the results validation was verified in a small sized pilot scale. The project starts with a leaching process of sludge in sulphuric acid solution in three stages followed by copper cementation step, using iron scrap as precipitating agent. It was found that metals dissolution was almost completed for the three stages of leaching process. Extraction rates of 99% for Cu and Ni were achieved under the leaching. The solid residue separated from the leaching solution is mostly constituted by gypsum (CaSO4), and presents heavy metal content below 1%. Copper cementation process was performed at a pH of 2. Such pH level led to insignificant precipitation of other metals present in the leaching solution, particularly chromium. The recovery rate of copper is about 99% with a purity grade of 99% which enables its application as a commercial product. Nickel hydroxide precipitation was performed by adding sodium hydroxide solution. Results showed a successfully nickel hydroxide extraction obtaining 99% with a purity grade of more than 98%. These evidences demonstrate the high potential of this methodology to treat and derive economic benefits from galvanic sludge. The end products cooper and nickel can be applied as a commercial product generating a profit and the gypsum based sludge from the leaching process can be reutilized as component of construction materials.QREN (NORTE-01-0202-FEDER-005509

Gestão de resíduos industriais por incorporação em materiais para construção civil

Nesta apresentação abordar-se-á a problemática da gestão de resíduos industriais da indústria metalúrgica e de processamento de materiais, por via da sua inertização durante o processo de fabricação de materiais para a construção civil. Referir-se-á, em particular, a experiência de valorização de resíduos da indústria metalúrgica no processo de fabricação de cerâmicos, de clinquer, de misturas cimentosas e de agregados betuminosos. Todos estes materiais, largamente utilizados pela indústria de construção civil, constituem boas opções para o escoamento de resíduos industriais, de forma ambientalmente correcta. Cada um dos materiais de construção civil testados apresenta características físicas, químicas e de processamento distintas. Esta especificidade implica diferentes aptidões para a inertização de resíduos, o que, globalmente, se apresenta como vantajoso. Os resultados obtidos até ao presente apontam genericamente para a elevada capacidade de valorização de resíduos das indústrias metalúrgicas e de processamento de materiais, por via da sua incorporação na produção de materiais para construção civil.In this presentation, the management of metal and materials processing industrial wastes, by its incorporation in civil construction products will be reviewed. In particular, the incorporation of metallurgical wastes in the fabrication of red ceramics, clincker, cement mortars and bituminous aggregates will be presented. All these materials are commonly used by construction industry and are hence good options for the management of industrial wastes, in a environmentally correct way. Each of the construction materials shows different and specific physical characteristics and properties. This is an important factor for wastes management, taking into account the variability of physical properties of the wastes themselves. Results obtained in research, both at laboratory and industrial environment, show that this is a very promising way of giving value to wastes from metallurgical and materials processing activitie

Influence of chemical composition and volume fraction of phases on the dezincification resistance of brasses

Although brasses are resistant to several forms of corrosion, they are susceptible to dezincification – selective dissolution of zinc – which may be responsible for failures in service of casting brass products. The effect of the chemical composition on dezincification resistance of brasses has been investigated. This study includes both commercial alloys and alloys prepared in laboratory in order to evaluate the specific effect of alloying elements such as lead, silicon, aluminium, iron, tin, nickel and arsenic upon the dezincification resistance. The effect of the volume fraction of α phase in the dezincification behaviour has also been studied. Dezincification tests have been carried out according to the ISO 6509 standard. The influence of the various alloying elements in the depth of the dezincificated layer, has been evaluated. The statistic treatment of results enable to the establishment of correlationship between the studied properties and the contents of some elements present in the chemical composition of brasses

Phase equilibria of the Al-Cu-Zn system for compositions close to brass alloys

The effect of aluminium in the equilibrium phases of the Cu-Zn alloys, within the range ofchemical compositions of interest to brass producers, has been studied. Ternary alloys werecasted by melting two Cu-Zn base alloys (with ~59.5% and ~61.2 wt.% of Cu) followed by theaddition of aluminium up to 3.68 wt.%. Isothermal homogenization, followed by rapid cooling,has been employed to determine the equilibrium phases at different temperatures. The alloys have been observed by scanning electron microscopy (SEM) and the respective chemicalanalysis determined by electron probe microanalysis (EPMA). The statistical analysis of theobtained results enable to correlate the chemical composition of equilibrium phases withtemperature, for the range of compositions studied

Adaptabilidade e estabilidade de linhagens de feijão-caupi de porte ereto em Roraima: safras 2004 e 2005.

Vinte linhagens de feijão-caupi de porte ereto foram avaliadas em dois locais durante dois anos consecutivos no Estado de Roraima com a finalidade de identificar aquelas com ampla adaptabilidade e estabilidade de produção. A linhagem mais produtiva foi a 23, com 1441 kg ha-1, e foi também a linhagem que apresentou o maior índice de recomendação sendo, portanto, a mais indicada para utilização comercial ou para ser empregada em programas de melhoramento em Roraima

Giving value to wastes : development of new technological routes to waste management

Apresentação de tecnologias para a valorização de resíduos.Centro para a Valorização de Resíduos (CVR