Trivalent chromium sorption on alginate beads

The applicability of trivalent chromium removal from aqueous solutions using calcium alginate beads was studied. The equilibrium isotherms were plotted at two temperatures. The relationship between the chromium sorbed and the calcium released was determined as well as the effect of alginate amount and initial pH on the equilibrium results. Chromium sorption kinetics were evaluated as a function of chromium initial concentration and temperature. Transport properties of trivalent chromium on alginate beads were characterised by calculating chromium diffusion coeffkients-the Linear Absorption Model and the Shrinking Core Model were assayed. Trivalent chromium removal from aqueous solutions, that made chromium alginate beads by directly dispensing the sodium alginate solution on chromium solutions, was also tested. Finally, a methodology for trivalent chromium removal with alginate is proposed. This method includes two steps: in the first, chromium is removed by using it as an agent for alginate bead formation (for chromium concentrations above 400 mg L-1); afterwards, the obtained solution is placed in contact with previously formed alginate beads for removal of the remaining chromium

Decomposição e liberação de nitrogênio, fósforo e potássio de resíduos da cultura do feijoeiro.

Este trabalho teve como objetivo mensurar a velocidade de decomposição e de liberação de nutrientes in situ de resíduos da cultura do feijoeiro (Phaseolus vulgaris L.). Em condições de campo, foram coletadas as folhas senescentes durante o ciclo da cultura, bem como os caules e a palhada de vagens após trilhagem dos grãos, de cultivares de feijoeiro. Esses resíduos continham 2,3 Mg ha-l de massa, 31 kg ha-l de N e 2,4 kg ha-1 de P, que correspondiam a 63, 41 e 28 % do total de massa, N e P, respectivamente, acumulados durante 0 ciclo da cultura. Foram realizados dois ensaios, nos períodos de inverno-primavera e primavera-verão, quando os caules, as vagens e as folhas senescentes foram colocados separadamente em litterbags, dispostos sobre 0 solo, e coletados entre 2 e 120 dias. As quantidades de matéria seca e nutrientes remanescentes em cada tipo de resíduo foram ajustadas a um modelo exponencial simples. O tempo de meia-vida dos resíduos foi de, no primeiro e segundo ensaios, respectivamente, 133 e 179 dias para caules, 70 e 80 dias para folhas e 64 dias para vagens. A relativamente lenta decomposição dos resíduos pode ser associada a sua alta relação C:N - acima de 60 para caule e palhada de vagens. A liberação de N e P pelos resíduos foi similar á dinâmica de decomposição, enquanto a liberação de K foi mais rápida. Os resultados indicam que as folhas senescentes e os resíduos produzidos após trilhagem dos grãos podem restituir parte da demanda de nutrientes do feijoeiro, assumindo relevância para sistemas de agricultura sustentável. The objective of this study was to measure the speed of decomposition and nutrient release in situ from residues of common bean (Phaseolus vulgaris L.) crop. In field conditions, leaves of common bean cultivars senesced during the growth cycle and stems and podwal ls after pod threshing were collected. These residues contained 2.3 Mg ha-l of mass, 31 kg ha-l of Nand 2.4 kg ha-l of P that corresponded to 63, 41 and 28 % of total mass, Nand P, respectively accumulated during the crop growth cycle. Two experiments were conducted, during winter-spring and spring-summer. Stems, podwalls and sene seed leaves were placed separately in litterbags on the ground and collected, from the 2nd to the 120th day. The dry matter and nutrient amounts found in each residue type were adjusted to a simple exponential model. The half-life of the residues was, in the first and second trial respectively, 133 and 179 days for stems, 70 and 80 days for leaves, and 64 days for podwalls. The relatively slow residue decomposition may be associated with the high C:N ratio (C:N> ao in stems and podwalls). Nitrogen and P release by residues was similar to the decomposition pattern, while K release was faster. The results indicate that senescent leaves and residues produced after pod threshing can cover part of the nutrient demand of common bean crop, which is relevant for sustainable agricultural systems.Parceria: IDAF; UFRRJ

Integrating social concerns into electricity planning

This paper deals with the complexity of the social issues surrounding electricity planning. A methodology is presented establishing a possible way of allocating weights to the most important social impacts of the electricity generation options and extending these results to the evaluation of future electricity plans. The process combined Delphi method with the Analytic Hierarchy Process, for the pairwise comparison of the electricity generation technologies against the social criteria. A social impact score was then derived and assigned to each technology. In order to obtain a final ranking of future feasible plans, these overall social scores of the electricity generation alternatives were aggregated using an additive function. The final output of the social analysis is an Average Social Index of each possible electricity generation mix

The impacts of wind power on power systems operation

The wind power sector is growing rapidly in Portugal and the National objectives for energy include a significant increase of wind power during the next years. The large penetration of wind power in Portugal will influence significantly the energy system cost, but it seems also essential to materialize the international energetic and environmental commitments. This paper focuses on the impact of large scale wind scenarios on the power system operation. CO2 abatement potential is estimated along with the effects on the operating costs of thermal power plants. Simulations for different wind scenarios were run for 2016, assuming the possibility of exports. According to the results, it seems that about 20% of wind power penetration may be achieved in Portugal with minor losses of efficiency of the global system

Influence of the microstructure on the creep behaviour of Tin-Silver-Copper solder

A common failure mode of electronic printed circuit boards (PCB’s) is the appearance of cold solder joints between the component and PCB, during product life. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. With today’s solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. As fatigue life decreases with increasing plastic strain, creep occurrence should have significant impact, especially during thermal cycles and, thus, should be studied. Through the cooling phase, on the production of PCB assembly’s by the reflow technology, the hoven atmosphere temperature is adjusted in order to control the cooling rate. Narrow criteria is used so as to control the inter-metallic compounds (IMC) thickness, PCB assembly distortion and defects due to thermal shock. The cooling rate also affects solder microstructure, which has direct impact on creep behaviour and, thus, on the soldered joint reliability. In this paper, a dynamic mechanical analyser (DMA) is used to study the influence of the solder cooling rate on its creep behaviour. SAC405 samples with two distinct cooling rates were produced: inside a hoven cooling and by water quenching. Creep tests were made on three-point-bending clamp configuration, isothermally at 25 °C, 50 °C and 75 °C and under three separate levels of stress, 3, 5 and 9 MPa. The results show that creep behaviour has a noticeable cooling rate dependence. It was also noticed that creep propensity is exacerbated by the temperature at which stresses are applied, especially for the slower cooling rates. Creep mechanisms were related to the solder microstructural constituents, namely by the amount of phases ant their morphology.The authors would like to express his acknowledgments for the support given by the Portugal Incentive System for Research and Technological Development. Project in co-promotion This research is sponsored by the Portugal Incentive System for Research and Technological Development. This work is supported by: European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project nº 002814; Funding Reference: POCI-01-0247-FEDER-002814]. This work was financed by FCT, under the Strategic Project UID/SEM/04077/2013; PEst2015-2020 with the reference UID/CEC/00319/2013 and UID/FIS/04650/2013

Electricity power planning: the role of wind energy

Combining energy efficiency with renewable energy sources constitutes a key strategy for a sustainable future. The wind power sector stands out as a fundamental element for the achievement of the European renewable objectives and Portugal is no exception to the increase of the wind energy for the electricity generation. This work proposes an optimization model for the long range electricity power planning in a system similar to the Portuguese one, where the expected impacts of the increasing installed wind power on the operating performance of thermal power plants are taken into account. The main results indicate that the increasing penetration of wind power in the electricity system will have significant effects on the combined cycle gas power plants operation and on the theoretically expected cost reduction and environmental gains. This research demonstrated the need to address the impact that energy sources with variable output may have, not only on the short-term operational planning, but especially on the medium to long range planning activities, in order to meet the strategic objectives for the energy sector.Fundação para a Ciência e Tecnologia (FCT)COMPETE – Programa Operacional Factores de Competitividade under Research Project PTDC/SEN-ENR/099578/200

An overview of the Portuguese wind power sector

In the following paper the present situation of the electricity production from Renewable energy Sources (RES) in Portugal is analysed, giving particular attention to the wind power sector due to its increasing importance. The evolution of the electricity system is presented along with the strategies for the sector, and future prospects for the RES. Although the high interest of private companies in the wind sector the administrative and grid barriers represent major obstacles to the wind power development. The problem of the wind intermittency and uncertainty is also discussed. The improvement of interconnection capacity and the increase of power reserve are identified as key requirements for ensuring the security of supply. A clear comprehension of all these aspects is fundamental to aim for an integrated multidimensional wind power planning.(undefined

Carbono orgânico em solos sob floresta na Amazônia Central.

O carbono orgânico terrestre é alterado pelas interferências sobre o ambiente, sendo que a sua estabilidade ainda necessita de quantificações mais precisas para determinar seus teores e estoques. Este estudo quantificou os teores e estoques de carbono orgânico do solo sob floresta primária até 2 m de profundidade, em diferentes posições topográficas, na Reserva Biologica do Cueiras, Manaus/ZF2, km 34, na Amazônia Central. Coletaram-se amostras de solos ao longo de um transecto de 850 m num gradiente topográfico Latossolo (platô), Argissolo (vertente) e Espodossolo (baixio). Utilizaram-se 9 parcelas de 20 x 40 m, durante cinco anos consecutivos. Os estoques de carbono do solo foram obtidos multiplicando a concentração de carbono pela densidade do solo e espessura de camadas do solo. Delimitou-se uma microbacia hidrográfica, extrapolando-se os teores de carbono obtidos no transecto como forma de avaliar o potencial de estocagem de carbono em uma área de 2.678,68 ha. Entre os solos argilosos, os maiores estoques de carbono foram observados sob Latossolo tanto a nível de transecto (90 a 175,5 Mg ha-1de C) quanto a nível de área da microbacia (100,2 a 195,2 Mg ha-1de C). Os estoques de carbono sob solo arenoso (Espodossolo/baixio) foi superior aos solos argilosos ao longo do transecto (160 a 241 Mg ha-1de C) e próximo a eles na área delimitada da Microbacia do Igarapé Asu (96.90 a 146.01 Mg ha-1de C)

Analysis of sources of risk and uncertainties in the electricity system

Electricity power planning is a serious national task that encompasses not only forecasts but more importantly the evolution in short, medium and long term of each element that composes the assumptions, the constraints and/or the parameters of the planning model. Deterministic models can bring simplicity to the electricity power planning but do not consider the uncertainties and sources of risk of the electricity system. On the other hand, stochastic models tend to include the behaviour of one or more uncertain parameters that are critical to obtain a robust solution, being however more detailed and lengthy than deterministic models. The aim of this work was to identify the major sources of risk and uncertainties facing electricity system, representing valuable input for the electricity planner task. From this study it can be observed that several different behaviours for each uncertain parameter can be found along a time horizon. Thus, it is concluded that reeling on average lowers can represent a reductionist approach and in order to obtain more reliable scenarios for future electricity system, the statistical characteristics of each parameter should be considered in the electricity power planning.This research was supported by a Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Union Framework Programme, under project NETEP- European Brazilian Network on Energy Planning (PIRSES-GA-2013-612263)

Distribuição do carbono nas frações do solo sob área de floresta.

As transformações dos sistemas naturais nas regiões tropicais, geralmente cobertas por florestas com grande biomassa representam uma importante causa do aumento da concentração de CO2 atmosférico. Estimou-se a estocagem e a suscetibilidade potencial do carbono no solo do ecossistema sob floresta, até 2 m de profundidade, a partir da determinação da qualidade e a da quantidade do carbono orgânico nas diversas frações do solo em área de floresta primária na Amazônia Central. Fracionou-se a matéria orgânica do solo (MOS) por densidade e granulometria, obtendo-se: FLF (fração leve livre), FLIA (fração leve intra-agregada), F-areia (fração areia), F-argila (fração argila) e F-silte (fração silte). As amostras de solo para o fracionamento e análises físicas foram coletadas em posições topográficas distintas (platô, vertente e baixio), em parcelas de 20 m x 40 m, nas camadas entre 0-5, 5-10, 10-20, 20-40, 40-60, 60-80, 80-100, 100-160 e 160-200 cm de profundidade. Na superfície, o carbono está estocado na fração leve livre (FLF) e em profundidade na fração pesada (F-argila). A distribuição do carbono nas frações do solo foram de 112,6 Mg ha-1 (FLF), 2,5 Mg ha-1 (FLIA), 40,5 Mg ha-1 (F-silte), 56,2 Mg ha-1 (F-argila) e 28,3 Mg ha-1 (F-areia). O carbono orgânico do solo (COS) estocado no platô (Latossolo), vertente (Argissolo) e baixio (Espodossolo) foi de 86,1 Mg ha-1, 72,6 Mg ha-1 e 81,4 Mg ha-1, respectivamente, potencializando uma capacidade de emissão para a atmosfera de 240,1 Mg ha-1