A planar magneto-inductive lens for three-dimensional subwavelength imaging

A planar near-field magnetoinductive lens operating in the microwave range is presented. The proposed device consists of two parallel planar arrays of metallic broadside coupled (BC-) split ring resonators (SRRs), or BC-SRRs. Power coming from a point-like source located in front of the lens is focused into a receiver located in free space behind the device. This focus is clearly removed from the back side of the lens, and has a size which is an order of magnitude smaller than the free space wavelength of the incoming radiation. The imaging properties of the device mainly relies on the excitation of magnetoinductive surface waves on the BC-SRR arrays. By simply scaling the BC-SRRs size, as well as the arrays periodicity, the frequency of operation of the device can be tuned over a wide frequency range. Thus the proposed design is potentially useful for many applications ranging from megahertzs to terahertzs.Comment: 14 pages, 3 figures, submitted to Applied Physics Letter

New self-dual solutions of SU(2) Yang-Mills theory in Euclidean Schwarzschild space

We present a systematic study of spherically symmetric self-dual solutions of SU(2) Yang-Mills theory on Euclidean Schwarzschild space. All the previously known solutions are recovered and a new one-parameter family of instantons is obtained. The newly found solutions have continuous actions and interpolate between the classic Charap and Duff instantons. We examine the physical properties of this family and show that it consists of dyons of unit (magnetic and electric) charge.Comment: 12 pages, 5 figures. To appear in Phys Rev

the role of intercultural mediation

Migration is generally described as a process that is nationally specific and that have features common to several countries. This has been shown by several authors through comparative research that compares the migration process of the same immigrant group to several countries (among others, Engbersen, Snel, & de Boom, 2010) or which scrutinises the migration realities of different countries (Zimmermann, 2005). Most of these studies are about geographically near countries, which are part of the same political system (the EU), and that have an established (albeit differentiated) welfare system. These proximities (geographical, but also political and social) allowed the authors of these studies to conceptualise the existence of several migration models or regimes: the southern European model (Baldwin-Edwards, 2012), the Iberian model of Migration (Malheiros, 2012); the intra-EU mobility regime (Engbersen et al., 2017). These migratory regimes are intertwined by migrant integration models or by different approaches to increasingly diverse populations. Although these are often identified as ‘national models of integration’, they do not fail to integrate the developments that have been recorded in the last decades in the international contexts in which the countries are inserted. Throughout the present text, the Portuguese experience in dealing with immigrant integration is used to reflect on the development of intercultural policies and practices, and on the role of intercultural mediation. The article is structured in the following way: in the introductory section we will review the discussion on interculturalism; in a second section the Portuguese immigration context will be presented; in a third section the integration of immigrants in the country will be analysed, given special attention to the development of policies that support immigrants’ integration process. In the fourth section, the role of intercultural mediation for the integration of immigrants will be considered.info:eu-repo/semantics/publishedVersio

Inconsistency and non-additive Choquet integration in the Analytic Hierarchy Process

We propose to extend the aggregation scheme of Saaty’s AHP, from the stan- dard weighted averaging to the more general Choquet integration. In our model, a measure of inconsistency between criteria is derived from the main pairwise comparison matrix and it is used to construct a non-additive capacity, whose associated Choquet integral reduces to the standard weighted mean in the con- sistency case. In the general inconsistency case, however, the new aggregation scheme based on Choquet integration tends to attenuate (resp. emphasize) the priority values of the criteria with higher (resp. lower) average inconsistency with the remaining criteria.Aggregation Functions, Multiple Criteria Analysis, AHP, Inconsintency, non-additive measures, Choquet integral, and Shapley values.

Ensino e aprendizagem de línguas : em tempos de reflexão e de mudança

Livro de homenagem à professora Maria Laura Bettencourt Pire

Segurança ao derrubamento e ao deslizamento de barragens gravidade de betão

As barragens são estruturas que, em caso de acidente grave que origine uma rotura, podem ocasionar danos severos no vale a jusante, quer no que se refere ao número de vítimas, quer no que se refere a bens económicos e ambientais. Neste sentido, são obras onde as preocupações com a segurança assumem particular importância. As barragens gravidade de betão constituem um número significativo de obras, cujos principais cenários de rotura se relacionam com a possibilidade de ocorrência de derrubamento de blocos e de deslizamentos ao longo de superfícies de baixa resistência existentes na fundação, no corpo da barragem ou, mais frequentemente na ligação betão/fundação. O estudo destes cenários está, assim, previsto no Regulamento de Segurança de Barragens de Portugal, bem como em documentos regulamentares de outros países. Nesta dissertação procedeu-se à apresentação deste tipo de estudos, incluindo a aplicação a um caso de estudo. Foi utilizado um programa já elaborado e procedeu-se ao estudo comparativo das disposições regulamentares existentes em alguns países de referência. Foram ainda apresentados dois estudos paramétricos de características diferentes com o objectivo de determinar o valor mínimo que cada parâmetro pode assumir garantindo a segurança da barragem

Application-Driven design to extend WSN lifetime

he lifetime of a WSN depends on the energy of the nodes. As soon as nodes run out of energy, they get disconnected from the WSN. This paper proposes an Application Driven solution that increases the WSN lifetime by limiting the routing and forwarding functions of the network mainly to nodes running the same applications. The solution is evaluated against AODV, and the results obtained show gains of about 30%info:eu-repo/semantics/publishedVersio

A cidade: territórios, linguagens, identidades

peerreviewe

The effects of health on wages

Mestrado em Decisão Económica e EmpresarialEsta tese examina o efeito da saúde sobre os salários, utilizando um conjunto de dados longitudinais provenientes do British Household Panel Survey. Uma estimativa credível para este efeito só pode ser obtida após ter em conta a potencial endogeniedade do regressor que representa o estado de saúde. Desta forma, com o intuito de encontrar uma estimativa segura para o efeito da saúde sobre salário, um modelo linear relacionando estas duas variáveis foi posto em pratica. Neste, o salário será a nossa variável dependente e o estado de saúde um dos regressores independentes. O erro da regressão do modelo não é observável, e assim sendo irá conter todas as variáveis que não estão incluídas no modelo como regressores. No presente caso, este erro irá incluir indicadores não observáveis que estão relacionados com o estilo de vida dos indivíduos. Como o estilo de vida de cada individuo estará também provavelmente relacionado com o salário, esta pesquisa depara-se com o problema das variáveis omitidas. Deste modo, podemos concluir que a variável que representa o estado de saúde será possivelmente endógena no nosso modelo. Devido a esta endogeneidade, vários estimadores conhecidos são inúteis e as estimativas obtidas por estes estimadores apenas levarão a conclusões incorrectas. Assim, de modo a lidar com este problema de endogeneidade, estimadores provenientes dos Dados de Painel são introduzidos. Estes, estarão muito mais propensos a obter resultados de confiança.This thesis examines the effect of health on wages using a longitudinal data from the British Household Panel Survey. A credible estimate of this effect can only be obtained after considering the potential endogeneity of the regressor that represents health. Therefore, in order to find a credible estimate of the effect of health on wage a linear model to describe the relationship is used, where the dependent variable is wage and one of the regressors is an indicator of health. The disturbance in this regression model is unobserved, and will contain all the variables that cannot be included as regressors because there is no data available on them. In the present case, this disturbance will include unobserved indicators that are related to the life-style of the subject. As the life-style of the subject will likely be related to wage as well, this research encounters the so-called omitted variables problem. Consequently, the health regressor is possibly endogenous in our model, because the employer may perceive health to be correlated with unobservable attributes of an individual which affect productivity and accordingly over higher wages to healthier employees. It is assumed that these unobservable attributes are constant over time, and therefore part of the unobserved heterogeneity term. Due to this endogeneity, several well-known estimators are useless. Estimates obtained by using these estimators will lead to conclusions that are misleading. Thus, panel data estimators are introduced to deal with this endogeneity problem. They are more likely to lead to credible estimation results