Browsing by Issue Date, starting with "2007-11"
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- An evolutionary approach for performing structural unit-testing on third-party object-oriented Java softwarePublication . Ribeiro, José Carlos Bregieiro; Zenha-Rela, Mário Alberto; Fernandéz de Vega, FranciscoEvolutionary Testing is an emerging methodology for automatically generating high quality test data. The focus of this paper is on presenting an approach for generating test cases for the unit-testing of object-oriented programs, with basis on the information provided by the structural analysis and interpretation of Java bytecode and on the dynamic execution of the instrumented test object. The rationale for working at the bytecode level is that even when the source code is unavailable, insight can still be obtained and used to guide the search-based test case generation process. Test cases are represented using the Strongly Typed Genetic Programming paradigm, which effectively mimics the polymorphic relationships, inheritance dependences and method argument constraints of object-oriented programs.
- Evaluation of dry protonated calcium alginate beads for biosorption applications and studies of lead uptakePublication . Lagoa, Ricardo; Rodrigues, Joaquim RuiAlginate polysaccharide is a promising biosorbent for metal uptake. Dry protonated calcium alginate beads for biosorption applications were prepared, briefly characterized and tested for lead uptake. Several advantages of this biosorbent are reported and discussed in comparison with other alginate-based sorbents. The alginate beads contained 4.7 mmol/g of COOH groups, which suffered hydrolysis near pH 4. The Weber and Morris model, applied to kinetic results of lead uptake, showed that intraparticle diffusion was the rate-controlling step in lead sorption by dry alginate beads. Equilibrium experiments were performed and the data were fitted with different isotherm models. The Langmuir equation was the most adequate to model lead sorption. The maximum uptake capacity (qmax) was estimated as 339 mg/g and the Langmuir constant (b) as 0.84 l/mg. These values were compared with that of other sorbents found in the literature, indicating that dry protonated calcium alginate beads are among the best biosorbents for the treatment and recovery of heavy metals from aqueous streams.
- An efficient time-domain simulation method for multirate RF nonlinear circuitsPublication . Oliveira, Jorge dos Santos Freitas de; Pedro, José CarlosThis paper describes a new computer-aided design tool especially conceived for the efficient time-domain simulation of highly heterogeneous nonlinear wireless communication circuits, i.e., combining RF and baseband analog circuitry and digital components. Using multirate Runge–Kutta algorithms within a multitime framework, to benefit from the different rates of variation of slowly varying (latent) and fast-varying (active) currents and voltages (state variables), we managed to solve the envelope transient regime of circuits excited by AM and PM RF carriers, in a highly efficient way. Indeed, with the adoption of convenient sampling rates for the multiple time representations of the slowly varying and fast-varying state variables, gains of more than one order of magnitude in simulation time are reported, even for an illustrative circuit example of very small size.
- Internal and external factors on firms' transfer pricing decisions: insights from organization studiesPublication . Li, Dan; Ferreira, Manuel PortugalWell understood in economics, accounting, finance, and legal research, transfer pricing has rarely been comprehensively explored in organization management literature. This paper explores some theoretical explanations of transfer pricing within multidivisional firms drawing insights from various organizational theories - primarily institutional theory, transaction cost economics, and social networks - to develop a conceptual model of transfer pricing. This model focuses on the nature of multidivisional firms' internal transfers, internal and external technological environments, and internal and external social environments. We highlight the importance of transfer pricing as a key strategic dimension to understand intra-firm flows and their associated costs.
- Visualização de espaços arqueológicos usando High Dynamic RangePublication . Gonçalves, Alexandrino José Marques; Magalhães, Luís Gonzaga; Moura, João Paulo; Chalmers, AlanÉ hoje amplamente reconhecido que os sistemas informáticos desempenham um papel fundamental no estudo e interpretação de espaços arqueológicos. Uma das suas principais áreas de aplicação é, seguramente, a reconstrução virtual de ambientes históricos, em particular os que já não existem. Neste domínio, a forma como visualizamos tais ambientes é particularmente importante para uma correcta interpretação arqueológica do espaço em causa, seja ele qual for. No entanto, a busca pelo perfeccionismo na representação visual de um qualquer cenário, está estritamente relacionada com a tecnologia de visualização usada para o efeito. O Sistema Visual Humano tem, na realidade, uma capacidade extraordinária e consegue captar valores de intensidade e cromaticidade verdadeiramente astronómicos. No entanto, grande parte dessa amplitude dinâmica não tem representação possível no modelo RGB, usado praticamente na totalidade dos dispositivos de visualização actuais. High Dynamic Range (HDR) é uma área de investigação que se dedica ao estudo de formas e métodos que visam suprir essa lacuna. Para atingir tal intento, têm sido desenvolvidas novas técnicas para a geração, armazenamento e representação de imagens que consigam preservar a (elevada) amplitude dinâmica captada pelo Sistema Visual Humano. Neste artigo apresentamos uma metodologia de trabalho que utiliza este novo paradigma de visualização onde o seu potencial se apropria verdadeiramente, a arqueologia. Desse modo propomo-nos gerar imagens de um dos mais belos e imponentes espaços existente nas ruínas da antiga cidade Romana de Conimbriga, a Casa dos Repuxos. Para tal, iremos simular a visualização, com recurso a imagens HDR, dos frescos e mosaicos lá existentes usando luminárias da época.