Processing of titanium aluminides by ceramic crucible induction melting

This work describes the processing results of TiAl alloys melted in controlled atmosphere induction furnace, using crucibles made of calcia and zirconia stabilised with yttria, calcia and magnesia, solidified and inside the crucible, in order to simulate the worst situation using this processing. In the results are presented segregation profiles of residual elements and its relation with micro hardness and “alpha-case” extension, in the microconstituents present at room temperatur

The production of TiAl by foundry processes

This paper describes a foundry technique that enables the production of TiAl employing an adapted melting procedure that uses an induction furnace with suitable refractory crucibles, inside a controlled atmosphere chamber. The developed technique allows the production of samples with a low and controlled amount of residual elements, with a thin superficial hard skin – known as “alpha-case” – and allows the use of higher superheating temperatures, when compared with alternative melting procedures. The micro-hardness and the residual contamination profiles, from the outside to the interior of samples, are presented and correlated to crucible refractory material and foundry practice.(undefined

Aspect oriented pluggable support for parallel computing

In this paper, we present an approach to develop parallel applications based on aspect oriented programming. We propose a collection of aspects to implement group communication mechanisms on parallel applications. In our approach, parallelisation code is developed by composing the collection into the application core functionality. The approach requires fewer changes to sequential applications to parallelise the core functionality than current alternatives and yields more modular code. The paper presents the collection and shows how the aspects can be used to develop efficient parallel applicationsFundação para a Ciência e a Tecnologia (FCT) - PPC-VM (Portable Parallel Computing based on Virtual Machines) Project POSI/CHS/47158/2002; SOFTAS (POSI/EIA/60189/2004).Fundo Europeu de Desenvolvimento Regional (FEDER)

Reusable aspect-oriented implementations of concurrency patterns and mechanisms

In this paper, we present a collection of well-known high-level concurrency patterns and mechanisms, coded in AspectJ. We discuss benefits of these implementations relative to plain Java implementations of the same concerns. We detect benefits from using AspectJ in all the cases presented, in the form of higher modularity, reuse, understandability and unpluggability. For most of the implementations, two alternatives can be used: one based on traditional pointcut interfaces and one based on annotations.Fundo Europeu de Desenvolvimento Regional (FEDER).Fundação para a Ciência e a Tecnologia (FCT) - PPC-VM Project POSI/CHS/47158/2002; Project SOFTAS (POSI/EIA/60189/2004)

Baseline assessment of the reef fish assemblage from Cagarras Archipelago, Rio de Janeiro, southeastern Brazil

The extensive Brazilian coast comprises diverse reef fish communities. Here, we report a pioneer study on the reef fish community composition of the Cagarras Archipelago. This rocky reef system consists of a small group of coastal islands 5 km south off Ipanema Beach, Rio de Janeiro city, Brazil. A relatively diverse and disturbed fish community (99 species from 39 families) was found in this archipelago. Two different visual census techniques were utilized and a large difference was observed in the number of species compared to other Brazilian reef sites. Trophic structure and biogeographical affinities are discussed. The absence of some reef fish species, mainly top predators, suggests severe environmental impact in this area and exhorts the Brazilian authorities to create a marine protected area. Results obtained in this study will serve to future environmental studies in Cagarras.A extensa costa brasileira abriga uma grande diversidade de peixes recifais. Este trabalho é um estudo pioneiro no que diz respeito à composição de espécies de peixes recifais do Arquipélago das Cagarras. Este sistema recifal é formado por um grupo de ilhas costeiras, distantes 5 km ao sul da Praia de Ipanema no estado do Rio de Janeiro, Brasil. Uma comunidade relativamente diversa e impactada, com 99 espécies pertencentes a 39 famílias de peixes recifais, foi encontrada. A utilização de duas técnicas de censo visual mostrou uma grande diferença nos dados obtidos, quando comparados a outras regiões recifais brasileiras. São discutidos dados da estrutura trófica e a distribuição biogeográfica da ictiofauna da região. A ausência de algumas espécies, principalmente grandes predadores, sugere que a região está sofrendo grande impacto ambiental, e torna urgente a criação de uma área de proteção marinha pelas autoridades Brasileiras. Os resultados obtidos poderão servir como base para futuros estudos ambientais nas Cagarras

Model predictive current control of a proposed single-switch three-level active rectifier applied to EV battery chargers

This paper presents a model predictive current control applied to a proposed new topology of single-switch three-level (SSTL) active rectifier, which is exemplified in an application of single-phase battery charger for electric vehicles (EVs). During each sampling period, this current control scheme selects the state of the SSTL active rectifier that minimizes the error between the grid current and its reference. Using this strategy it is possible to obtain sinusoidal grid currents with low total harmonic distortion and unitary power factor, which is one of the main requirements for EVs chargers. The paper presents in detail the principle of operation of the SSTL active rectifier, the digital control algorithm and the EV battery charger (where is incorporated the SSTL active rectifier) that was used in the experimental verification. The obtained experimental results confirm the correct application of the model predictive current control applied to the proposed SSTL active rectifier.This work was supported in part by the FCT–Fundação para a Ciência e Tecnologia in the scope of the project: PEst UID/CEC/00319/2013. Vítor Monteiro was supported by the scholarship SFRH/BD/80155/2011 granted by the FCT agency

Mudanças no padrão de alimentação da população urbana brasileira (1962-1988)

Contemporary changes in food consumption patterns in urban areas of Brazil are described. The main data sources are two national food expenditure surveys undertaken in the early 60's and late 80's (1961-62 and 1987-88) and one national food intake survey undertaken in the mid-70' s (1974-75). The analysis is restricted to the seven metropolitan areas represented in the three surveys. Food patterns are described on the basis of the relative consumption of different food groups, proportion of energy from carbohydrates, protein and lipids, proportion of animal and vegetable protein and fats, proportion of complex and simple carbohydrates, ratio between poly-unsaturated and saturated fatty acids and relative consumption of cholesterol. Main food changes were similar in the Northeastern and Southeastern cities and involved: 1) reduction in the relative consumption of cereals, beans, roots and tubercles; 2) replacement of lard, bacon and butter by vegetable oils and margarine: and 3) increase in the relative consumption of eggs, milk and dairy products. As a net result of these changes there was, simultaneously, a decrease in the carbohydrate content of the Brazilian diet and an increase in its fat content. Total protein content of the diet remained at around 12% in the three surveys but animal protein increased. Changes in the fat content of the diet involved an increased proportion of vegetable fat, an increased ratio of poly-unsaturated/saturated fatty acids and a reduction in cholesterol intake. Health implications of dietary changes are discussed based on the World Health Organization's dietary guidelines.Objetivou-se avaliar o comportamento do padrão alimentar da população urbana brasileira ao longo das três últimas décadas. As fontes de dados foram duas pesquisas nacionais de orçamentos familiares realizadas no início da década de 60 (1961-63) e no final da década de 80 (1987-88) e um inquérito nacional sobre consumo alimentar realizado em meados da década de 70 (1974-75), restringindo-se a análise a sete áreas metropolitanas estudadas em comum pelas três pesquisas. O padrão alimentar foi caracterizado a partir da participação relativa de diferentes alimentos na dieta e do consumo relativo de nutrientes específicos. As mudanças principais mostraram-se semelhantes nas regiões Nordeste e Sudeste e envolveram: 1) redução no consumo relativo de cereais, feijão, raízes e tubérculos; 2) substituição de banha, toucinho e manteiga por óleos e margarinas; e 3) aumento no consumo relativo de leite e derivados e ovos. Essas mudanças deterninaram diminuição na participação relativa de carboidratos na dieta e aumento na participação de lipídios. A proporção total de proteínas manteve-se estável entre as pesquisas (ao redor de 12%), crescendo, entretanto, a participação específica de proteínas de origem animal na dieta. Situação inversa foi observada com os lipídios, registrando-se aumento da fração correspondente aos lipídios de origem vegetal, o que levou ao predomínio dos ácidos graxos poli-insaturados sobre os saturados e à redução do consumo relativo de colesterol. As implicações das mudanças no padrão alimentar da população urbana do país são discutidas à luz de recomendações dietéticas enunciadas pela Organização Mundial de Saúde

Fuzzy Method for in Control Acetaldehyde Generation in Resin Pet in the Process of Packaging Pre-Forms of Plastic Injection

In order to control the drying temperature of the PET resin in the silo of the plastic injection molding machine, during the plastic injection process in the industries producing preforms for the manufacture of beverage bottles, care is taken in the ideal temperature regulation for the better performance in controlling the generation of Acetaldehyde (AA), which alters the taste of carbonated or non-carbonated drinks, providing a citrus nuance to the palate and questioning the quality of the packaged products The objective of this work is to develop a tool based on Fuzzy logic to support the control of the drying temperature of PET resin, allowing specialists to make the ideal temperature control decisions necessary to control the generation of Acetaldehyde (AA). For the development of the proposed Fuzzy inference model, we used the Matlab Fuzzy toolbox tool, where the input variables, the fuzzyfication rules and the output variable were implemented based on the data collected from the preform injection process. From the inference model, we obtained a more precise management of the variables that influence the generation of AA, estimating a reduction of $ 240,044.00 in annual costs in the production of preforms

Evaluation of Y2O3 as front layer of ceramic crucibles for vaccum induction melting of tial based alloys

During the last decades titanium alloys were found to be valuable engineering materials for many different applications. Formerly used in critical applications like aerospace, aeronautic and military equipment, where the factor cost is not relevant, titanium alloys are finding now new and different markets. However, the development of such new markets will depend on an effective cost reduction of titanium parts, in order to achieve a selling cost suitable with its application in consumer goods. A possible solution to decrease production costs might be the use of traditional casting techniques to produce near net shape functional parts. During the last years, the authors have developed extensive research work on this field, and a new technique both for melting and moulding, using ceramic multi-layered crucibles and investment casting shells was developed. This paper presents some of the results obtained during that research work: Ti-48Al alloy were melted and cooled inside CaO, MgO and Y2O3 stabilized ZrO2 crucibles with inside layer of Y2O3. The chemical composition, hardness and microstructure at the metal-crucible interface, studied by secondary ion mass spectrometry, SEM/EDS and XRS are presented. On a second step, the same alloy was melted on the same crucibles, and poured into graphite moulds, and the crucibles wall was characterized by SEM/EDS and XRS.(undefined

NEEM: network-friendly epidemic multicast

Epidemic, or probabilistic, multicast protocols have emerged as a viable mechanism to circumvent the scalabil- ity problems of reliable multicast protocols. However, most existing epidemic approaches use connectionless transport protocols to exchange messages and rely on the intrinsic robustness of the epidemic dissemination to mask network omissions. Unfortunately, such an approach is not network- friendly, since the epidemic protocol makes no effort to re- duce the load imposed on the network when the system is congested. In this paper, we propose a novel epidemic protocol whose main characteristic is to be network-friendly. This property is achieved by relying on connection-oriented transport connections, such as TCP/IP, to support the com- munication among peers. Since during congestion mes- sages accumulate in the border of the network, the pro- tocol uses an innovative buffer management scheme, that combines different selection techniques to discard messages upon overflow. This technique improves the quality of the information delivered to the application during periods of network congestion. The protocol has been implemented and the benefits of the approach are illustrated using a com- bination of experimental and simulation results