MASS TRANSFER CORRELATION FOR THE REMOVAL OF COPPER IONS FROM WASTEWATER

One of the biggest problems with ore processing in extractive metallurgical industries is the high toxicity of the heavy metals waste content (e.g., copper, lead, nickel and chrome). This work investigates the copper (II) íons removal from aqueous solutions in concentrations up to 1000 ppm. Therefore, a fluidized bed electrolytic reactor was used with flow-by configuration considered as a hopeful method due to the large specific surface area and the high mass transfer rate. The performance of the electrochemical reactor was investigated by using different porosities. Dimensionless Sherwood and Reynolds numbers were correlated to characterize the mass transport properties of the reactor, and they were fitted to the equation Sh = a.Reb.Sc1/3

EXPERIMENTAL METHOD FOR SPRAY VELOCITY FIELD PREDICTION MODEL IN PRESSURE SWILL ATOMIZERS

Pressure swill atomizers are widely used in engineering as an effective device for vaporization and liquid mass transfer in physical or chemical processes. Among many applications those atomizers are used in modern fuel injection systems for spark engines. An even fuel and air mixture may increase the overall engine performance by higher efficiency and low flue gas emissions. In applied atomization, one of the most important characteristics is the spray velocity field prediction. Droplet sizing models are also important, but they are relatively popular on books and papers. By the other hand spray velocity field prediction and profile is relatively rare. This work focus on the prediction of the velocity field of pressure swirl atomize by means of an experimental approach and applied statistics. For the spray measurements this study used a non-intrusive, quantitative method by Laser Doppler Interpherometry (LDI) for the spray velocity field and droplet sizing. Also four models for the film thickness calculation at atomizer discharge are compared considering their statistical significance

Preparação das discussões matemáticas no ensino da Álgebra: o caso da professora Ana

As discussões matemáticas podem ser uma atividade importante para promover a aprendizagem dos alunos, criando oportunidades para a partilha, justificação e argumentação de ideias matemáticas resultantes do seu trabalho com tarefas. No entanto, a sua realização constitui um desafio exigente para o professor, tanto na sua preparação como na sua condução tendo em vista a aprendizagem dos alunos. Nesta comunicação, procuramos compreender as práticas de discussão de Ana, professora do 3.º ciclo do Ensino Básico (EB), na preparação da discussão coletiva no trabalho com a Álgebra, em articulação com o seu conhecimento didático. Os resultados mostram que a professora, apoiada no seu conhecimento da Matemática, da prática letiva e dos alunos e da aprendizagem, identifica (antes e durante a aula) as ideias matemáticas que pretende que os alunos discutam a partir do seu trabalho com tarefas selecionadas para o efeito. Antecipa, também, possíveis estratégias de resolução e pensa como pode levar os alunos atingir os objetivos definidos. Na aula, e perante o trabalho dos alunos, reconhece as ideias mais importantes para discutir e estabelece uma ordem de apresentação tendo em vista promover a generalização dessas ideias

Modeling Heterogeneous Materials via Two-Point Correlation Functions: I. Basic Principles

Heterogeneous materials abound in nature and man-made situations. Examples include porous media, biological materials, and composite materials. Diverse and interesting properties exhibited by these materials result from their complex microstructures, which also make it difficult to model the materials. In this first part of a series of two papers, we collect the known necessary conditions on the standard two-point correlation function S2(r) and formulate a new conjecture. In particular, we argue that given a complete two-point correlation function space, S2(r) of any statistically homogeneous material can be expressed through a map on a selected set of bases of the function space. We provide new examples of realizable two-point correlation functions and suggest a set of analytical basis functions. Moreover, we devise an efficient and isotropy- preserving construction algorithm, namely, the Lattice-Point algorithm to generate realizations of materials from their two- point correlation functions based on the Yeong-Torquato technique. Subsequent analysis can be performed on the generated images to obtain desired macroscopic properties. These developments are integrated here into a general scheme that enables one to model and categorize heterogeneous materials via two-point correlation functions.Comment: 37 pages, 26 figure

Las dificultades de clasificación diagnóstica en Atención Temprana. La experiencia en dos unidades de Galicia

En este artículo se ofrecen los resultados de aplicar un modelo de categorización diagnóstica a la población atendida en dos centros de atención temprana durante un período de 5 años. Se atendieron 411 niños y niñas con diversos tipos de trastornos del desarrollo, siendo los de comunicación y lenguaje los más frecuentemente diagnosticados (39,1%), seguidos de los conductuales (25,9%) y los afectivos (19,3%). Cabe destacar la escasa presencia de los trastornos motores (6,6%) y de los de espectro autista (7%). Los resultados del estudio muestran la complejidad de los problemas asistenciales y de procedimiento que en la actualidad enfrenta la atención temprana