Browsing by Issue Date, starting with "2011-06"
Now showing 1 - 10 of 10
Results Per Page
Sort Options
- As nanopartículas em ambientes ocupacionaisPublication . Matos, Maria Luísa Ferreira; Santos, Paula; Barbosa, Fernando
- Scale-up of a system for hydrocarbon production by electrochemical reduction of CO2Publication . Fernandes, T. R. C.; Machado, Ana; Condeço, J.; Rangel, C. M.; Pardal, T.This work addresses the scaling up of a system for electrochemical reduction of CO2 to produce hydrocarbons that can be used as fuel for a regenerative energy storage cycle. Challenges involved in such a task are mentioned. Scalingup results of a system based on electrodes of high surface area with modified copper deposits are described. Current densities around 100 mA/cm2 were obtained. This corresponds to the current density threshold that enables technological applications. At potentials as negative as -1.6 V it was observed that CO2 reduction still dominated over hydrogen evolution reaction.
- Bem utilizar madeiras portuguesas na construção / reabilitaçãoPublication . Santos, José António dos; Duarte, M. Carlota; Santos, Joana; Pestana, Luís
- Networks and the organisation of knowledge intensive sectorsPublication . Salavisa, Isabel; Sousa, Cristina; Fontes, MargaridaThis paper addresses the role of networks in the organisation of two different knowledge intensive sectors - biotechnology and software. Its main aim is to identify and explain the differences in the architecture of the networks, formal and informal, mobilised to access resources and competences by young entrepreneurial firms in those two sectors in Portugal. Then it discusses the diversity of the actual network topologies in the light of their contribution to the organisation of those sectors, taking into account their specific environment. For this purpose, it applies a methodology that permits to assemble a vast array of data capturing the nature and contents of the range of relationships through which key innovation resources flow into the firms. The results show that, when a detailed analysis is carried out, significant inter-sectoral differences emerge, both in the network diagrams and in the measures of composition and structure. We argue that those different topologies make sense regarding the empirical literature and shed light on the specific organisation of the sectors, with their strengths, weaknesses and policy-driven influences.
- Mineralization of olive mill wastewater over DSAPublication . Gonçalves, M. R.; Correia, J. P.; Marques, Isabel PaulaBioenergy recovery from olive mill wastewater (OMW) has been effectively accomplished by anaerobic digestion [1]. Nevertheless, a post treatment is required to attain the discharge limit values. After the anaerobic treatment of OMW, the main issues are related to the remaining organic matter (COD), recalcitrant phenolic compounds (40-50%) and effluent dark-brown colour. The electrochemical treatment is proposed in this work as a final step to mineralise the OMW non-biodegradable fraction. The electrochemical oxidation of OMW anaerobically digested was investigated over DSAs. The performance of RuO2 and IrO2 based DSAs was studied by cyclic voltammetry and bulk electrolysis. The experiments were carried out with alkaline samples from the anaerobic reactor comprising 1 to 10 g COD/L, depending to the digester operational conditions. KNO3 was used as electrolyte, alternatively to the preferred NaCl [2], to avoid obtaining an effluent with higher toxicity than the initial one. It was found that RuO2 based anode was significantly more efficient than IrO2, mainly for the COD removal (Figure 1). With an electrolysis charge of Q=1517 C it was obtained COD removals of 9 and 52%, phenols removals of 72 and 98% and colour removal of 61 and 98%, for IrO2 and RuO2 type DSAs, respectively. The exclusion of the centrifugation/filtration step before the electrochemical treatment was considered, since the anaerobic treatment step reduces considerably the solids fraction. It is concluded that the electrochemical oxidation over DSAs is a suitable second step treatment for OMW disposal after the recovery of its energetic potential. The outcome energy from biogas production can balance or reduce the costs of the electrochemical treatment.
- Modelling of the IPS buoy wave energy converter including the effect of non-uniform tube cross-sectionPublication . Falcão, António F. de O.; Cândido, José J.; Justino, Paulo Alexandre; Henriques, João C. C.An important class of floating wave energy converters (that includes the IPS buoy, the Wavebob and the PowerBuoy) comprehends devices in which the energy is converted from the relative (essentially heaving) motion between two bodies oscillating differently. The paper considers the case of the IPS buoy, consisting of a floater rigidly connected to a fully submerged vertical (acceleration) tube open at both ends. The tube contains a piston whose motion relative to the floater-tube system (motion originated by wave action on the floater and by the inertia of the water enclosed in the tube) drives a power take-off mechanism (PTO) (assumed to be a linear damper). To solve the problem of the end-stops, the central part of the tube, along which the piston slides, bells out at either end to limit the stroke of the piston. The use of a hydraulic turbine inside the tube is examined as an alternative to the piston. A frequency domain analysis of the device in regular waves is developed, combined with a one-dimensional unsteady flow model inside the tube (whose cross-section is in general nonuniform). Numerical results are presented for a cylindrical buoy in regular waves, including the optimization of the acceleration tube geometry and PTO damping coefficient for several wave periods.
- Progress in the catalysed hydrolysis of sodium borohydride as a gydrogen source for low power PEM Fuel CellsPublication . Fernandes, Vitor; Ferreira, M. J.; Esteves, M. Alexandra; Pinho, A. M. F. R.; Rangel, C. M.
- Influence of the support characteristics and their functionalization on the catalytic activity of Pt-Ru catalysts for PEM fuel cellsPublication . Calderon, J. C.; Figueiredo, J. L.; Mahata, N.; Pereira, M. F. R.; Fernandes, Vitor; Rangel, C. M.; Pastor, E.; Calvillo, L.; Lázaro, M. J.
- Degradation of a Lithium Iron Phosphate based Cathode in Lithium-ion Batteries after 2000 cyclesPublication . Plancha, Maria João; Rangel, C. M.; Rodrigues, B.; Azevedo, F.