A catalyst layer optimisation approach using electrochemical impedance spectroscopy for PEM fuel cells operated with pyrolysed transition metal-N-C catalysts

AbstractThe effect of the ionomer to carbon (I/C) ratio on the performance of single cell polymer electrolyte fuel cells is investigated for three different types of non-precious metal cathodic catalysts. Polarisation curves as well as impedance spectra are recorded at different potentials in the presence of argon or oxygen at the cathode and hydrogen at the anode. It is found that a optimised ionomer content is a key factor for improving the performance of the catalyst. Non-optimal ionomer loading can be assessed by two different factors from the impedance spectra. Hence this observation could be used as a diagnostic element to determine the ideal ionomer content and distribution in newly developed catalyst-electrodes. An electrode morphology based on the presence of inhomogeneous resistance distribution within the porous structure is suggested to explain the observed phenomena. The back-pressure and relative humidity effect on this feature is also investigated and supports the above hypothesis. We give a simple flowchart to aid optimisation of electrodes with the minimum number of trials

A influência do design na valorização de marcas: construção de posicionamentos de marcas com foco no público

Anualmente, empresas como a Interbrand anunciam um ranking das marcas mais valiosas. Nesta análise, a empresa leva em consideração factos como a capacidade de a marca influenciar e fidelizar o consumidor. Neste sendo percebe-se o design como um gerador de diferenciação e valor de marcas, por meio da gestão da idendade de marca com foco no consumidor. Neste contexto, notam-se mudanças no comportamento, tanto das empresas que passam a ver no design um meio de alavancar o potencial competitivo, como no consumidor que passa a interagir de modo diferente com as empresas e suas marcas, assim como na atuação do design. Assim, por meio de uma pesquisa exploratória com base em procedimentos bibliográficos, busca-se compreender como o papel do design evoluiu junto as mudanças na sociedade, a fim de proporcionar valor superior as empresas, por meio da identidade de suas marcas.ABSTRACT: Every year companies such as Interbrand announce a ranking of the most valuable brands. In this analysis the company takes into consideration facts such as the ability to influence brand loyalty and consumers. In this way it’s possible to noce design as a generator of differential on and brand value through the management of brand identity with a focus on the consumer. In this context will be noticed changes in the behavior of both companies now see the design a means to leverage the competitive potential, as the consumer starts to interact with different companies and brands so as well as the performance of the design. Thus, through an exploratory research based on published procedures, we seek to understand how the role of design has evolved with the changes in society in order to provide superior value to companies through the identity of its brands.info:eu-repo/semantics/publishedVersio

Renewable energy support policy based on contracts for difference and bilateral negotiation

ABSTRACT: The European Union has been one of the major drivers of the development of renewable energy. The energy policies of most European countries have involved subsidized tariffs, such as the feed-in tariff in Portugal, the regulated tariff and the market price plus premium in Spain, and the Renewables Obligation in UK, that came into effect in 2002. Recently, UK has made some reforms and started to consider contracts for difference (CfDs) as a key element of the energy policy. This paper presents a support policy based on CfDs and bilateral negotiation. The first phase consists in a CfD auction and the second phase involves a bilateral negotiation between a Government and each of the selected investors. The paper also presents a case-study to analyze the potential benefits of the support policy. It was performed with the help of the MATREM system. The preliminary results indicate some advantages for the Government (and, in some cases, for the investors as well).info:eu-repo/semantics/publishedVersio

A neuronal network model of interictal and recurrent ictal activity

We propose a neuronal network model which undergoes a saddle-node bifurcation on an invariant circle as the mechanism of the transition from the interictal to the ictal (seizure) state. In the vicinity of this transition, the model captures important dynamical features of both interictal and ictal states. We study the nature of interictal spikes and early warnings of the transition predicted by this model. We further demonstrate that recurrent seizures emerge due to the interaction between two networks.Comment: 9 pages, 7 figure

Level Sets and Stable Manifold Approximations for Perceptually Driven Nonholonomically Constrained Navigation

This paper addresses problems of robot navigation with nonholonomic motion constraints and perceptual cues arising from onboard visual servoing in partially engineered environments. We focus on a unicycle motion model and a variety of artificial beacon constellations motivated by relevance to the autonomous hexapod, RHex. We propose a general hybrid procedure that adapts to the constrained motion setting the standard feedback controller arising from a navigation function in the fully actuated case by switching back and forth between moving down and across the associated gradient field toward the stable manifold it induces in the constrained dynamics. Guaranteed to avoid obstacles in all cases, we provide some reasonably general sufficient conditions under which the new procedure guarantees convergence to the goal. Simulations are provided for perceptual models previously introduced by other authors

Spatial patterns of mango malformation in irrigated areas of the brazilian semi-arid.

There are over 18.000 ha of irrigated mango in the São Francisco River Valley, and 90% of the fruit produced in this semi-arid region is exported to the european and american markets. With the expansion of the mango areas in the last decade, the intensity of malformation has been increasing, and there are many unresolved questions on the dynamics of the disease in the region, such as the role of the mango bud mite (Aceria mangiferae) or mechanical transmission in the dissemination of the disease. This study aimed to characterize the spatial patterns of mango malformation in commercial orchards, of the brazilian semi-arid

Enriched elderly virtual profiles by means of a multidimensional integrated assessment platform

The pressure over Healthcare systems is increasing in most developed countries. The generalized aging of the population is one of the main causes. This situation is even worse in underdeveloped, sparsely populated regions like Extremadura in Spain or Alentejo in Portugal. The authors propose to use the Situational-Context, a technique to seamlessly adapt Internet of Things systems to the needs and preferences of their users, for virtually modeling the elderly. These models could be used to enhance the elderly experience when using those kind of systems without raising the need for technical skills or the costs of implementing such systems by the regional healthcare systems. In this paper, the integration of a multidimensional integrated assessment platform with such virtual profiles is presented. The assessment platform provides and additional source of information for the virtual profiles that is used to better adapt existing systems to the elders needs

Visual Registration and Navigation using Planar Features

This paper addresses the problem of registering the hexapedal robot RHex, relative to a known set of beacons, by real-time visual servoing. A suitably constructed navigation function represents the task, in the sense that for a completely actuated machine in the horizontal plane, the gradient dynamics guarantee convergence to the visually cued goal without ever losing sight of the beacons that define it. Since the horizontal plane behavior of RHex can be represented as a unicycle, feeding back the navigation function gradient avoids loss of beacons, but does not yield an asymptotically stable goal. We address new problems arising from the configuration of the beacons and present preliminary experimental results that illustrate the discrepancies between the idealized and physical robot actuation capabilities

Participation of wind power producers in intra-day markets : a case-study

ABSTRACT: The evolution of renewable energy has increased substantially over the past decade. Wind power producers (WPPs) can submit bids to energy markets, making short-term commitments to produce specific quantities of energy. This article presents a case-study to analyze the benefits of the active participation of wind power producers in energy markets, particularly intra-day markets. The case-study is carried out with the help of the MATREM system. The preliminary results indicate a reduction of the deviations of WPPs, but also a decreasing in their remuneration. Thus, the results highlight to some extent the importance of new market mechanisms to enable the active participation of WPPs in markets, without support policies.info:eu-repo/semantics/publishedVersio