Browsing by Issue Date, starting with "2007-09"
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- Environmental life cycle assessment of concrete made with fine recycled concrete aggregatesPublication . Evangelista, Luis; De Brito, JorgeThe majority of worldwide structures use concrete as its main material. This happens because concrete is economically feasible, due to its undemanding production technology and case Of use. However, it is widely recognized that concrete production has a strong environmental impact in the planet. Natural aggregates use is one of the most important problems of concrete production nowadays, since they are obtained from limited, and in some countries scarce, resources. In Portugal, although there are enough stone quarries to cover coarse aggregates needs for several more years, Supplies of fine aggregates are becoming scarcer, especially in the northern part of the country. On the other hand, as concrete structures' life cycle comes to an end, an urgent need emerges to establish technically and economically viable solutions for demolition debris, other than for use as road base and quarry fill. This paper presents a partial life cycle assessment (LCA) of concrete made with fine recycled concrete aggregates performed with EcoConcrete tool. EcoConcrete is a tailor-made, interactive, learning and communications tool promoted by the Joint Project Group (JPG) on the LCA of concrete, to qualify and quantify the overall environment impact of concrete products. It consists of an interactive Excel-spreadsheet in which several environmental inputs (material quantities, distances from origin to production Site, production processes) and outputs (material, energy, emissions to air, water, soil or waste) are collected in a life cycle inventory, and are then processed to determine the environmental impact (assessment) of the analysed concrete, in terms of ozone layer depletion, smog or "greenhouse" effect.
- Blind hyperspectral unmixingPublication . Nascimento, Jose; Bioucas-Dias, José M.Hyperspectral unmixing methods aim at the decomposition of a hyperspectral image into a collection endmember signatures, i.e., the radiance or reflectance of the materials present in the scene, and the correspondent abundance fractions at each pixel in the image. This paper introduces a new unmixing method termed dependent component analysis (DECA). This method is blind and fully automatic and it overcomes the limitations of unmixing methods based on Independent Component Analysis (ICA) and on geometrical based approaches. DECA is based on the linear mixture model, i.e., each pixel is a linear mixture of the endmembers signatures weighted by the correspondent abundance fractions. These abundances are modeled as mixtures of Dirichlet densities, thus enforcing the non-negativity and constant sum constraints, imposed by the acquisition process. The endmembers signatures are inferred by a generalized expectation-maximization (GEM) type algorithm. The paper illustrates the effectiveness of DECA on synthetic and real hyperspectral images.
- Os antropólogos portugueses, nos últimos anos do século XXPublication . Cavaleiro Rodrigues, JoséA partir de dados recolhidos pelo Inquérito à Situação dos Antropólogos em Portugal, o texto pretende traçar um perfil evolutivo dos antropólogos portugueses entre 1989-99, os seus percursos académicos, científicos e profissionais.
- A luz do desejo: a fotografia publicitáriaPublication . Pina, Helena FigueiredoEste ensaio reflete sobre os fatores que presidem à distinção da Fotografia Publicitária face às categorias da Fotografia Artística e da Fotografia Jornalística. As diferentes formas de utilizar a fotografia podem traduzir-se em várias categorias cujas fronteiras são muitas vezes ténues e extremamente difíceis de situar. No entanto, a existência destas categorias é comummente aceite e reconhecida, dando origem a uma classificação hierarquizada que acarreta uma diferença de estatutos. A Fotografia Publicitária serve um fim muito particular: o de promover comercialmente os bens, serviços ou instituições dos quais depende a economia de consumo em que as sociedades actuais se baseiam. Embora as imagens da Publicidade sejam um tema corrente na investigação da comunicação das últimas décadas, a Fotografia Publicitária, em si mesma, não parece ter sido palco de discussão ou reflexão muito alargadas. Os anos de exercício em diversas funções da Publicidade, a par da prática de investigação académica, permitiram uma análise realista do “lugar” ocupado por esta categoria a partir de uma interrogação acerca das diferenças de estatuto subjacentes às diversas categorias em análise. Ainda que não seja expressamente assumido, e portanto podendo ser considerado um julgamento de “senso comum”, a verdade é que as diferenças de estatuto impregnam os discursos. Assim, sendo considerada por muitos como uma atividade marginal, que não pertence ao domínio das artes e não possui os atributos de «informação pura», a Fotografia Publicitária possui uma conotação marcadamente mercantil que a coloca numa espécie de categoria à parte, mas que numa situação de pós-modernidade importa ser analisada. Eis porque, e apesar de não ser tarefa fácil construir uma análise adequada, me proponho interrogar ao longo deste trabalho acerca dos eventuais pontos de contacto entre a Fotografia Publicitária, a Fotografia Artística e a Fotografia Jornalística, para então determinar possíveis fatores que presidem à sua distinção. Igualmente, como forma de “testar” as conclusões, apresenta-se um conjunto de exercícios que visam provar a tese defendida.
- James Carey and the legacy of Chicago school of sociology on communication and media studiesPublication . Subtil, Filipa Mónica de Brito GonçalvesAlthough the communication issue has won intellectual status in modern thought and in the social research through the sociological school of Chicago, the communication and media studies have tended to neglect, with some exceptions, that crucial contribution. This paper will focus on the way James Carey, one of the most influent American theorists of media and journalism in the second half of XX century, considered, discussed, and critically embodied the reflection about communication in the Chicago School of sociology. By questioning the “standard” history of mass communication research confined to the functionalist and empiricist paradigm of mass communication, Carey points out the importance of reconsidering an argumentative, civic and universalistic conception of communication which was a legacy of Dewey, Cooley, Mead, and Park. Firstly, this paper proposes to show how Carey recovers and re-elaborates this notion to argue that communication is more than transmission of signals and signs. Supported by the Chicago tradition, he defines communication as a life experience found on human quality of intimacy, conversation, and on the understanding that comes from shared experience. Secondly, it presents Carey’s critique to the utopic features of this tradition, especially to the excessive expectations on communication technologies to improve the quality of culture and civic life. Finally, it discusses how Carey brings back the sociological communication concept of Chicago to confront it with a technical conception of communication that distinguishes the present media industry, showing how communication has lost its dimension of communion and sharing, and definitively tangled in a world of sophisticated economical and political strategies.
- The spin polarization of CrO2 revisitedPublication . Yates, Karen A.; Branford, W. R.; Magnus, F.; Miyoshi, Y.; Morris, B.; Cohen, L. F.; Sousa, P. M.; Conde, O.; Silvestre, António JorgeHere, we use Andreev reflection spectroscopy to study the spin polarization of high quality CrO2 films. We study the spin polarization as a function of growth temperature, resulting in grain size and electrical resistivity. In these films low temperature growth appears to be a necessary but not sufficient condition to guarantee the observation of high spin polarization, and this is only observed in conjunction with suppressed superconducting gap values and anomalously low interface properties. We suggest that this combination of observations is a manifestation of the long range spin triplet proximity effect. (C) 2007 American Institute of Physics.