855 resultados para Algoritmos e Meta-heurísticas


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Resumen en inglés. Resumen basado en el de la publicación. Capítulo incluido en el monográfico número 8 de la revista 'Tejuelo. Didáctica de la lengua y la literatura. Educación', titulado 'Comunicación social y educación'

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Resumen basado en el de la publicación.

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Resumen tomado de la publicaci??n

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Resumen basado en el de la publicaci??n

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Resumen basado en el de la publicaci??n

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The objective of this paper is to introduce a diVerent approach, called the ecological-longitudinal, to carrying out pooled analysis in time series ecological studies. Because it gives a larger number of data points and, hence, increases the statistical power of the analysis, this approach, unlike conventional ones, allows the complementation of aspects such as accommodation of random effect models, of lags, of interaction between pollutants and between pollutants and meteorological variables, that are hardly implemented in conventional approaches. Design—The approach is illustrated by providing quantitative estimates of the short-termeVects of air pollution on mortality in three Spanish cities, Barcelona,Valencia and Vigo, for the period 1992–1994. Because the dependent variable was a count, a Poisson generalised linear model was first specified. Several modelling issues are worth mentioning. Firstly, because the relations between mortality and explanatory variables were nonlinear, cubic splines were used for covariate control, leading to a generalised additive model, GAM. Secondly, the effects of the predictors on the response were allowed to occur with some lag. Thirdly, the residual autocorrelation, because of imperfect control, was controlled for by means of an autoregressive Poisson GAM. Finally, the longitudinal design demanded the consideration of the existence of individual heterogeneity, requiring the consideration of mixed models. Main results—The estimates of the relative risks obtained from the individual analyses varied across cities, particularly those associated with sulphur dioxide. The highest relative risks corresponded to black smoke in Valencia. These estimates were higher than those obtained from the ecological-longitudinal analysis. Relative risks estimated from this latter analysis were practically identical across cities, 1.00638 (95% confidence intervals 1.0002, 1.0011) for a black smoke increase of 10 μg/m3 and 1.00415 (95% CI 1.0001, 1.0007) for a increase of 10 μg/m3 of sulphur dioxide. Because the statistical power is higher than in the individual analysis more interactions were statistically significant,especially those among air pollutants and meteorological variables. Conclusions—Air pollutant levels were related to mortality in the three cities of the study, Barcelona, Valencia and Vigo. These results were consistent with similar studies in other cities, with other multicentric studies and coherent with both, previous individual, for each city, and multicentric studies for all three cities

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La aparición de terminales de telefonía móvil cada vez más potentes abre un nuevo abanico de posibilidades en cuanto a usos y aplicaciones. Sin embargo, y dadas las limitaciones tanto de memoria como de CPU que tienen estos dispositivos, algunas de las aplicaciones potenciales resultan muy difíciles o incluso imposibles de llevar a la práctica. Este es el caso, por ejemplo, de aplicaciones de cálculo de rutas. En el contexto del proyecto Itiner@, un asistente para rutas turísticas completamente autónomo que debe funcionar incluso sin conexión a Internet, todos los procesos deben ejecutarse íntegramente de forma local en el dispositivo móvil. Dado que es un proyecto orientado al ocio, es importante que la experiencia del usuario sea satisfactoria, por lo que además de poder ejecutar el algoritmo de cálculo de rutas, el sistema debe hacerlo de forma rápida. En este sentido, los algoritmos recursivos habituales son demasiado costosos o lentos para su uso en Itiner@ y ha sido necesario reinventar este tipo de algoritmos en función de las limitaciones que tienen estos dispositivos. En el presente trabajo se presenta el proceso seguido y las dificultades encontradas para implementar un algoritmo recursivo de cálculo de rutas que se ejecute íntegramente en un dispositivo móvil Android de forma eficiente. Así, finalmente se llega a un algoritmo recursivo de cálculo de rutas para dispositivos móviles que se ejecuta de forma más eficiente frente a algoritmos directamente portados a dispositivos móviles. La principal contribución del trabajo es doble: por un lado ofrece algunas guías útiles al desarrollo de algoritmos más eficientes para dispositivos móviles; y por el otro, muestra un algoritmo de cálculo de rutas que funciona con un tiempo de respuesta aceptable, en un entorno exigente, como es el de las aplicaciones de turismo en móviles

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O projeto que se apresenta tem por finalidade investigar processos de aperfeiçoamento da competência de escrita do texto argumentativo de alunos do Ensino Secundário. Considerou-se as contribuições convergentes das teorias e técnicas da psicologia cognitiva e de perspetivas sociais da linguagem. Em consequência, associou-se o modelo de revisão de Hayes e Flower (1983; 1980), e de Hayes, Flower, Schriver, Stratman e Carey (1987), ao modelo de análise do discurso de Bronckart (2004; 1996) e à proposta linguística de Adam (2006; 1992). A hipótese que sustenta a investigação é que a consciência (meta)linguística pode facilitar a revisão textual e o aperfeiçoamento da competência de escrita de textos argumentativos, em contexto de Oficina de Escrita. A investigação conjugou duas fases. Na fase intensiva do estudo de caso, os alunos do 11.º ano de Português de uma Escola do Porto progrediram, através de trabalho continuado em Oficina de Escrita. Após a experiência, mesmo alunos com dificuldades revelaram domínio de metalinguagem, mais consciência (meta)linguística na revisão e autorregulação da sua aprendizagem. Na fase extensiva, foi aplicado um inquérito por questionário a uma amostra probabilística de professores do Secundário, igualmente do Porto. Os docentes valorizaram os aspetos supracitados, bem como a leitura de textos argumentativos e o treino do conhecimento explícito da língua. Contudo, em triangulação, as respostas indiciam um ensino centrado no professor, pouco aberto a projetos de escrita, a novas tecnologias e à divulgação de textos à Escola e ao meio. Os resultados indicam que a competência de escrita de textos argumentativos é passível de aperfeiçoamento em Oficina de Escrita, através de interiorização do género textual e aprofundamento da competência (meta)linguística. No contexto do estudo, comprova-se a influência de um treino de escrita inserido em Projetos de Escola, tendo o aluno como sujeito da sua própria aprendizagem, em interação com o meio.

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This paper is organized in the following way. First I deal with Hardt’s and Negri’s Empire; the second section of the paper focuses on Beck´s World Risk Society; the third main section of this paper tackles the functional differentiation argument posed by Buzan and Albert. By way of conclusion, the final section of this paper briefly discusses alternatives to grand-narratives and master concepts.

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We run a standard income convergence analysis for the last decade and confirm an already established finding in the growth economics literature. EU countries are converging. Regions in Europe are also converging. But, within countries, regional disparities are on the rise. At the same time, there is probably no reason for EU Cohesion Policy to be concerned with what happens inside countries. Ultimately, our data shows that national governments redistribute well across regions, whether they are fiscally centralised or decentralised. It is difficult to establish if Structural and Cohesion Funds play any role in recent growth convergence patterns in Europe. Generally, macroeconomic simulations produce better results than empirical tests. It is thus possible that Structural Funds do not fully realise their potential either because they are not efficiently allocated or are badly managed or are used for the wrong investments, or a combination of all three. The approach to assess the effectiveness of EU funds should be consistent with the rationale behind the post-1988 EU Cohesion Policy. Standard income convergence analysis is certainly not sufficient and should be accompanied by an assessment of the changes in the efficiency of the capital stock in the recipient countries or regions as well as by a more qualitative assessment. EU funds for competitiveness and employment should be allocated by looking at each region’s capital efficiency to maximise growth generating effects or on a pure competitive.

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The paper considers meta-analysis of diagnostic studies that use a continuous score for classification of study participants into healthy or diseased groups. Classification is often done on the basis of a threshold or cut-off value, which might vary between studies. Consequently, conventional meta-analysis methodology focusing solely on separate analysis of sensitivity and specificity might be confounded by a potentially unknown variation of the cut-off value. To cope with this phenomena it is suggested to use, instead, an overall estimate of the misclassification error previously suggested and used as Youden’s index and; furthermore, it is argued that this index is less prone to between-study variation of cut-off values. A simple Mantel–Haenszel estimator as a summary measure of the overall misclassification error is suggested, which adjusts for a potential study effect. The measure of the misclassification error based on Youden’s index is advantageous in that it easily allows an extension to a likelihood approach, which is then able to cope with unobserved heterogeneity via a nonparametric mixture model. All methods are illustrated at hand of an example on a diagnostic meta-analysis on duplex doppler ultrasound, with angiography as the standard for stroke prevention.