Ferromagnetic order in aged Co-doped TiO2 anatase nanopowders

Oxide based diluted magnetic semiconductor (DMS) materials have been a subject of increasing interest due to reports of room temperature ferromagnetism in several systems and their potential use in the development of spintronic devices. However, concerns on the stability of the magnetic properties of different DMS systems have been raised. Their magnetic moment is often unstable, vanishing with a characteristic decay time of weeks or months, which precludes the development of real applications. This paper reports on the ferromagnetic properties of two-year-aged Ti1-xCoxO2-δ reduced anatase nanopowders with different Co contents (0.03≤x≤0.10). Aged samples retain rather high values of magnetization, remanence and coercivity which provide strong evidence for a quite preserved long-range ferromagnetic order. In what concern Co segregation, some degree of metastability of the diluted Co doped anatase structure could be inferred in the case of the sample with the higher Co content.

Complex fluids at complex surfaces simply complicated

We study wetting and filling of patterned surfaces by a nematic liquid crystal. We focus on three important classes of periodic surfaces: triangular, sinusoidal and rectangular. The results highlight the similarities and differences of nematic wetting of these surfaces and wetting by simple fluids. The interplay of geometry, surface and elastic energies can lead to the suppression of either filling or wetting. The periodic rectangular surface displays re-entrant transitions, with a sequence dry-filled-wet-filled, in the relevant region of parameter space.

On the monoids of transformations that preserve the order and a uniform partition

In this article we consider the monoid O(mxn) of all order-preserving full transformations on a chain with mn elements that preserve a uniformm-partition and its submonoids O(mxn)(+) and O(mxn)(-) of all extensive transformations and of all co-extensive transformations, respectively. We determine their ranks and construct a bilateral semidirect product decomposition of O(mxn) in terms of O(mxn)(-) and O(mxn)(+).

Wind turbines equipped with fractional-order controllers: Stress on the mechanical drive train due to a converter control malfunction

This paper is on variable-speed wind turbines with permanent magnet synchronous generator (PMSG). Three different drive train mass models and three different topologies for the power-electronic converters are considered. The three different topologies considered are respectively a matrix, a two-level and a multilevel converter. A novel control strategy, based on fractional-order controllers, is proposed for the wind turbines. Simulation results are presented to illustrate the behaviour of the wind turbines during a converter control malfunction, considering the fractional-order controllers. Finally, conclusions are duly drawn. Copyright (C) 2010 John Wiley & Sons, Ltd.

Research on using the decision tree method in order to select the best alternative for the pharmacies supply

Introduction / Aims: Adopting the important decisions represents a specific task of the manager. An efficient manager takes these decisions during a sistematic process with well-defined elements, each with a precise order. In the pharmaceutical practice and business, in the supply process of the pharmacies, there are situations when the medicine distributors offer a certain discount, but require payment in a shorter period of time. In these cases, the analysis of the offer can be made with the help of the decision tree method, which permits identifying the decision offering the best possible result in a given situation. The aims of the research have been the analysis of the product offers of many different suppliers and the establishing of the most advantageous ways of pharmacy supplying. Material / Methods: There have been studied the general product offers of the following medical stores: A&G Med, Farmanord, Farmexim, Mediplus, Montero and Relad. In the case of medicine offers including a discount, the decision tree method has been applied in order to select the most advantageous offers. The Decision Tree is a management method used in taking the right decisions and it is generally used when one needs to evaluate the decisions that involve a series of stages. The tree diagram is used in order to look for the most efficient means to attain a specific goal. The decision trees are the most probabilistic methods, useful when adopting risk taking decisions. Results: The results of the analysis on the tree diagrams have indicated the fact that purchasing medicines with discount (1%, 10%, 15%) and payment in a shorter time interval (120 days) is more profitable than purchasing without a discount and payment in a longer time interval (160 days). Discussion / Conclusion: Depending on the results of the tree diagram analysis, the pharmacies would purchase from the selected suppliers. The research has shown that the decision tree method represents a valuable work instrument in choosing the best ways for supplying pharmacies and it is very useful to the specialists from the pharmaceutical field, pharmaceutical management, to medicine suppliers, pharmacy practitioners from the community pharmacies and especially to pharmacy managers, chief – pharmacists.

Será que as empresas portuguesas seguem a pecking order na escolha das alternativas de financiamento?

Mestrado em Contabilidade e Análise Financeira

Synthesis of new Fe(II) and Ru(II) eta(5)-monocyclopentadienyl compounds showing significant second order NLO properties

A series of new ruthenium(II) complexes of the general formula [Ru(eta(5)-C5H5)(PP)(L)][PF6] (PP = DPPE or 2PPh(3), L = 4-butoxybenzonitrile or N-(3-cyanophenyl)formamide) and the binuclear iron(II) complex [Fe(eta(5)-C5H5)(PP)(mu-L)(PP)(eta(5)-C5H5)Fe][PF6](2) (L = (E)-2-(3-(4-nitrophenyl)allylidene)malononitrile, that has been also newly synthesized) have been prepared and studied to evaluate their potential in the second harmonic generation property. All the new compounds were fully characterized by NMR, IR and UV-Vis spectroscopies and their electrochemistry behaviour was studied by cyclic voltammetry. Quadratic hyperpolarizabilities (beta) of three of the complexes have been determined by hyper-Rayleigh scattering (HRS) measurements at fundamental wavelength of 1500 nm and the calculated static beta(0) values are found to fall in the range 65-212 x 10(-30) esu. Compound presenting beta(0) = 212 x 10(-30) esu has revealed to be 1.2 times more efficient than urea standard in the second harmonic generation (SHG) property, measured in the solid state by Kurtz powder technique, using a Nd:YAG laser (1064 nm). (C) 2013 Elsevier B.V. All rights reserved.

On the use of IEEE 802.15.4/Zigbee for time-sensitive wireless sensor network applications

Mestrado em Engenharia Electrotécnica e de Computadores

A model for heterogeneous networks management and Performance evaluation

In general, modern networks are analysed by taking several Key Performance Indicators (KPIs) into account, their proper balance being required in order to guarantee a desired Quality of Service (QoS), particularly, cellular wireless heterogeneous networks. A model to integrate a set of KPIs into a single one is presented, by using a Cost Function that includes these KPIs, providing for each network node a single evaluation parameter as output, and reflecting network conditions and common radio resource management strategies performance. The proposed model enables the implementation of different network management policies, by manipulating KPIs according to users' or operators' perspectives, allowing for a better QoS. Results show that different policies can in fact be established, with a different impact on the network, e.g., with median values ranging by a factor higher than two.

Avaliação da cinetica bacteriana na biolixiviação de calcopirita

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The gambin model provides a superior fit to species abundance distributions with a single free parameter : evidence, implementation and interpretation

The species abundance distribution (SAD) has been a central focus of community ecology for over fifty years, and is currently the subject of widespread renewed interest. The gambin model has recently been proposed as a model that provides a superior fit to commonly preferred SAD models. It has also been argued that the model's single parameter (α) presents a potentially informative ecological diversity metric, because it summarises the shape of the SAD in a single number. Despite this potential, few empirical tests of the model have been undertaken, perhaps because the necessary methods and software for fitting the model have not existed. Here, we derive a maximum likelihood method to fit the model, and use it to undertake a comprehensive comparative analysis of the fit of the gambin model. The functions and computational code to fit the model are incorporated in a newly developed free-to-download R package (gambin). We test the gambin model using a variety of datasets and compare the fit of the gambin model to fits obtained using the Poisson lognormal, logseries and zero-sum multinomial distributions. We found that gambin almost universally provided a better fit to the data and that the fit was consistent for a variety of sample grain sizes. We demonstrate how α can be used to differentiate intelligibly between community structures of Azorean arthropods sampled in different land use types. We conclude that gambin presents a flexible model capable of fitting a wide variety of observed SAD data, while providing a useful index of SAD form in its single fitted parameter. As such, gambin has wide potential applicability in the study of SADs, and ecology more generally.

Determinação da tensão interfacial do sistema Água - Tolueno - Acetona

Mestrado em Engenharia Química. Ramo de Optimização Energética na Indústria Química

Cluster analysis using affinity aoefficient in order to identify religious beliefs profiles

International Scientific Forum, ISF 2013, ISF 2013, 12-14 December 2013, Tirana.

Mapping stability : real rational maps of degree zero

In memory of our beloved Professor José Rodrigues Santos de Sousa Ramos (1948-2007), who João Cabral, one of the authors of this paper, had the honor of being his student between 2000 and 2006, we wrote this paper following the research by experimentation, using the new technologies to capture a new insight about a problem, as him so much love to do it. His passion was to create new relations between different fields of mathematics. He was a builder of bridges of knowledge, encouraging the birth of new ways to understand this science. One of the areas that Sousa Ramos researched was the iteration of maps and the description of its behavior, using the symbolic dynamics. So, in this issue of this journal, honoring his memory, we use experimental results to find some stable regions of a specific family of real rational maps, the ones that he worked with João Cabral. In this paper we describe a parameter space (a,b) to the real rational maps fa,b(x) = (x2 −a)/(x2 −b), using some tools of dynamical systems, as the study of the critical point orbit and Lyapunov exponents. We give some results regarding the stability of these family of maps when we iterate it, specially the ones connected to the order 3 of iteration. We hope that our results would help to understand better the behavior of these maps, preparing the ground to a more efficient use of the Kneading Theory on these family of maps, using symbolic dynamics.

Controlo de águas do processo e optimização da produção de papel

Na Fábrica de Papel da Ponte Redonda fabricam-se sacos de papel multi-folhas e papel reciclado do tipo Kraft. Tendo em consideração a primeira actividade, é de grande interesse optimizar o processo de fabrico de papel com vista a incorporara a máxima taxa de papel produzido internamente nas diferentes camadas dos sacos de papel. Os papéis de maior interesse são os do tipo Fluting e Liners, tendo sido produzidos em 2010 um total de 4,9 mil toneladas, ou seja 90% de todo o papel fabricado em 2010, correspondendo a a 4 mil toneladas de papéis do tipo Liners e 0,9 mil toneladas para os papéis do tipo Fluting. Nos papéis do tipo Liners incluem-se os papéis do tipo Test-Liner e Kraft-Liner, representando em termos produtivos valores idênticos. No âmbito deste trabalho, em que se pretendeu controlar as águas do processo e optimizar a produção de papel, foram introduzidos uma unidade de flutuação e um sistema que permitisse regular a consistência da suspensão fibrosa à entrada da máquina do papel, e foram ainda estudadas as possibilidades de adição de produtos químicos para melhorar as características da pasta assim como um tratamento microbiológico mais eficaz para todo o processo. Para se avaliar se as medidas implementadas teriam um impacto positivo na qualidade desses dois tipos de papéis, desenvolveu-se o trabalho em duas fases: a primeira envolve a introdução de um sistema de flutuação e de um sistema de controlo de consistência da pasta, assim como a selecção de produtos químicos a adicionar ao processo. A segunda fase consistiu na avaliação do efeito destas medidas nas características do papel fabricado. Para o efeito foram escolhidos dois tipos de papel e de diferentes gramagens, nomeadamente Test-Liner de 80 g/m2 e Fluting de 110 g/m2. Introduziu-se um flutuador com o objectivo de tratar parte das águas do processo de fabrico com vista a serem reutilizadas em determinadas aplicações possíveis para a qualidade da água obtida (lavagens e água do processo), de modo a conseguir-se uma poupança de água, assim como aproveitar-se as lamas resultantes, ricas em fibra de celulose, para utilizá-las como matéria-prima. Foi introduzido um regulador de consistência no processo da Ponte Redonda com o objectivo de alimentar de uma forma constante a consistência da pasta à entrada da máquina do papel proporcionando uma melhor formação da folha, devido à ligação entre fibras, na direcção máquina e direcção transversal. Esse sistema inovador é um Regulador de Consistência que vem proporcionar à máquina do papel uma alimentação em fibra mais constante. O fabrico de papel apenas a partir de fibras de celulose não permitirá obter um papel com as características desejadas para a sua utilização. Para corrigir estas deficiências, são adicionados produtos químicos para atribuir ou melhorar as propriedades dos papéis. Desta forma considerou-se interessante introduzir no processo um agente de retenção numa fase posterior à preparação da pasta e antes da chegada à máquina de papel, de forma a melhorar as características da suspensão fibrosa. Assim foi implementado um sistema cuja eficácia foi avaliada. Concluiu-se que com a sua implementação a máquina de papel apresentou melhores resultados na drenagem e na turbidez da água removida, significando uma água com menor teor de matéria suspensa e dissolvida, devido à melhor agregação das fibras dispersas na suspensão fibrosa, levando a um aumento da drenagem e consequentemente melhor eficiência das prensas e secaria. Foi também elaborado um estudo para introdução de um sistema de tratamento microbiológico em todo o processo de fabrico de papel, devido à existência de microorganismos prejudiciais ao seu fabrico. Concluiu-se que a água clarificada proveniente do flutuador apresentou qualidade aceitável para os objectivos pretendidos. No entanto, considerando a eficiência de 26,5% na remoção de sólidos suspensos será necessário mais algum tempo de utilização da água clarificada, cerca de um ano, para avaliar se esta terá algum efeito prejudicial nos equipamentos. Verificou-se que devido à existência de microrganismos em todo o processo de fabrico de papel será necessário efectuar lavagens aos tinões, tanques e circuitos com alguma regularidade, aproveitando-se as paragens do processo assim como implementar um sistema de tratamento microbiológico mais eficaz. Em resultado das medidas implementadas concluiu-se que os papéis produzidos apresentaram melhorias, tendo-se obtido melhores resultados em todos os ensaios de resistência. No papel do tipo Test-Liner destacam-se os bons resultados nos ensaios de superfície, Cobb60 e rebentamento. No caso do parâmetro do Cobb60, foi um resultado surpreendente visto que por norma este tipo de papéis reciclados não suportam este ensaio. Concluiu-se também que as medidas implementadas proporcionaram uma melhor agregação e ligação entre fibras, e melhor formação da folha na máquina do papel proporcionando aos papéis propriedades físico-mecânicas mais interessantes.