João Pedro Cardoso | Universidade Federal de Sergipe (original) (raw)
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Papers by João Pedro Cardoso
The lack of competitiveness of the Portuguese construction industry has been recurrently mentione... more The lack of competitiveness of the Portuguese construction industry has been recurrently mentioned in the press and in technical literature. Some symptoms of this have been stressed by several parties and their causes often related to the lack of accomplishment of essential management functions in construction projects. In view of this, a research project has been launched to help clarity causes and find possible solutions for the problem. Parallel to the project development, a PhD thesis on construction delays has been undertaken by the first author. In the scope of the latter, a large survey to Portuguese construction stakeholders has been conducted. This paper briefly reports the results of this, providing some information on the survey and commenting results in the shape of preventive measures highlighted by respondents.
Journal of Applied Physics, 2009
The magnetic and transport properties of Co80Fe20(t)/Al2O3(4 nm) multilayers with low nominal thi... more The magnetic and transport properties of Co80Fe20(t)/Al2O3(4 nm) multilayers with low nominal thicknesses t=0.7 and 0.9 nm of Co80Fe20 granular layers are studied. Magnetic studies find a superparamagnetic state above the blocking temperature Tb (of field-cooled/zero-field-cooled splitting) that grows with t and decreases with H. The low-voltage Ohmic tunnel transport passes to non-Ohmic I~V3/2 law for applied fields above ~500 V/cm. At fixed V, the temperature dependence of conductance reveals an anomalous dip around ~220 K, which can be attributed to the effect of surface contamination by supercooled water. Current-in-plane tunnel magnetoresistance (MR) ratio tends, at lower t, to higher maximum values (~8% at room temperature) but to lower field sensitivity. This may indicate growing discorrelation effect (e.g., between shrinking areas of correlated moments) in this regime and corroborates the deficit of granule magnetization estimated from the Inoue-Maekawa MR fit, compared to that from direct magnetization measurements. MR displays a mean-field-like critical behavior when t approaches the point of superparamagnetic/superferromagnetic transition (tc~1.3 nm at room temperature) from below, different from the formerly reported percolationlike behavior at approaching it from above. With growing temperature, MR reveals, beyond the common decrease, an anomalous plateau from Tb~30-50 K up to some higher value T*~150-200 K, not seen at higher t.
Review of Scientific Instruments, 2011
Magneto-optical Kerr effect (MOKE) magnetometry is an indispensable, reliable, and one of the mos... more Magneto-optical Kerr effect (MOKE) magnetometry is an indispensable, reliable, and one of the most widely used techniques for the characterization of nanostructured magnetic materials. Information, such as the magnitude of coercive fields or anisotropy strengths, can be readily obtained from MOKE measurements. We present a description of our state-of-the-art vectorial MOKE magnetometer, being an extremely versatile, accurate, and sensitivity unit with a low cost and comparatively simple setup. The unit includes focusing lenses and an automatized stepper motor stage for angular dependent measurements. The performance of the magnetometer is demonstrated by hysteresis loops of Co thin films displaying uniaxial anisotropy induced on growth, MnIr/CoFe structures exhibiting the so called exchange bias effect, spin valves, and microfabricated flux guides produced by optical lithography.
The study and understanding of the social behavior of insects has contributed to the definition o... more The study and understanding of the social behavior of insects has contributed to the definition of some algorithms that are capable of solving several types of optimization problems. In 1997 Di Caro and Dorigo developed the first routing algorithm for wired networks, called AntNet, using an approach which was inspired in the behavior of ant colonies. At each node, AntNet, similar to others Ant Colony Optimization (ACO) based algorithms, forward ants based in the amount of pheromones present in the links and in response to the node's queue lengths. In this paper, an adaptation of the ϵ-DANTE algorithm for discrete problems, as an IP based routing mechanism, was implemented. We also propose the inclusion of a new parameter for the computation of paths for both the AntNet and the newly proposed algorithm: the available bandwith. Those methods were tested in ns-2 using two dense network architectures and their efficiency is compared with the original AntNet and a Link-State routing algorithm, when considering the transmission of competing traffic flows between distinct nodes.
A abordagem do planeamento da construção repetitiva iniciou-se com os métodos tradicionais de pro... more A abordagem do planeamento da construção repetitiva iniciou-se com os métodos tradicionais de programação. Porém, dadas as suas limitações no tratamento do problema desenvolveram-se métodos específicos para este tipo de construção, e mais recentemente introduziu-se o conceito de aprendizagem. Neste trabalho apresenta-se um novo método de programação dos trabalhos repetitivos, dotado dos atributos das metodologias tradicionais e das vantagens que resultam da utilização de métodos específicos na programação daquele tipo de trabalhos e que inclui a consideração do efeito da aprendizagem.
The lack of competitiveness of the Portuguese construction industry has been recurrently mentione... more The lack of competitiveness of the Portuguese construction industry has been recurrently mentioned in the press and in technical literature. Some symptoms of this have been stressed by several parties and their causes often related to the lack of accomplishment of essential management functions in construction projects. In view of this, a research project has been launched to help clarity causes and find possible solutions for the problem. Parallel to the project development, a PhD thesis on construction delays has been undertaken by the first author. In the scope of the latter, a large survey to Portuguese construction stakeholders has been conducted. This paper briefly reports the results of this, providing some information on the survey and commenting results in the shape of preventive measures highlighted by respondents.
Journal of Applied Physics, 2009
The magnetic and transport properties of Co80Fe20(t)/Al2O3(4 nm) multilayers with low nominal thi... more The magnetic and transport properties of Co80Fe20(t)/Al2O3(4 nm) multilayers with low nominal thicknesses t=0.7 and 0.9 nm of Co80Fe20 granular layers are studied. Magnetic studies find a superparamagnetic state above the blocking temperature Tb (of field-cooled/zero-field-cooled splitting) that grows with t and decreases with H. The low-voltage Ohmic tunnel transport passes to non-Ohmic I~V3/2 law for applied fields above ~500 V/cm. At fixed V, the temperature dependence of conductance reveals an anomalous dip around ~220 K, which can be attributed to the effect of surface contamination by supercooled water. Current-in-plane tunnel magnetoresistance (MR) ratio tends, at lower t, to higher maximum values (~8% at room temperature) but to lower field sensitivity. This may indicate growing discorrelation effect (e.g., between shrinking areas of correlated moments) in this regime and corroborates the deficit of granule magnetization estimated from the Inoue-Maekawa MR fit, compared to that from direct magnetization measurements. MR displays a mean-field-like critical behavior when t approaches the point of superparamagnetic/superferromagnetic transition (tc~1.3 nm at room temperature) from below, different from the formerly reported percolationlike behavior at approaching it from above. With growing temperature, MR reveals, beyond the common decrease, an anomalous plateau from Tb~30-50 K up to some higher value T*~150-200 K, not seen at higher t.
Review of Scientific Instruments, 2011
Magneto-optical Kerr effect (MOKE) magnetometry is an indispensable, reliable, and one of the mos... more Magneto-optical Kerr effect (MOKE) magnetometry is an indispensable, reliable, and one of the most widely used techniques for the characterization of nanostructured magnetic materials. Information, such as the magnitude of coercive fields or anisotropy strengths, can be readily obtained from MOKE measurements. We present a description of our state-of-the-art vectorial MOKE magnetometer, being an extremely versatile, accurate, and sensitivity unit with a low cost and comparatively simple setup. The unit includes focusing lenses and an automatized stepper motor stage for angular dependent measurements. The performance of the magnetometer is demonstrated by hysteresis loops of Co thin films displaying uniaxial anisotropy induced on growth, MnIr/CoFe structures exhibiting the so called exchange bias effect, spin valves, and microfabricated flux guides produced by optical lithography.
The study and understanding of the social behavior of insects has contributed to the definition o... more The study and understanding of the social behavior of insects has contributed to the definition of some algorithms that are capable of solving several types of optimization problems. In 1997 Di Caro and Dorigo developed the first routing algorithm for wired networks, called AntNet, using an approach which was inspired in the behavior of ant colonies. At each node, AntNet, similar to others Ant Colony Optimization (ACO) based algorithms, forward ants based in the amount of pheromones present in the links and in response to the node's queue lengths. In this paper, an adaptation of the ϵ-DANTE algorithm for discrete problems, as an IP based routing mechanism, was implemented. We also propose the inclusion of a new parameter for the computation of paths for both the AntNet and the newly proposed algorithm: the available bandwith. Those methods were tested in ns-2 using two dense network architectures and their efficiency is compared with the original AntNet and a Link-State routing algorithm, when considering the transmission of competing traffic flows between distinct nodes.
A abordagem do planeamento da construção repetitiva iniciou-se com os métodos tradicionais de pro... more A abordagem do planeamento da construção repetitiva iniciou-se com os métodos tradicionais de programação. Porém, dadas as suas limitações no tratamento do problema desenvolveram-se métodos específicos para este tipo de construção, e mais recentemente introduziu-se o conceito de aprendizagem. Neste trabalho apresenta-se um novo método de programação dos trabalhos repetitivos, dotado dos atributos das metodologias tradicionais e das vantagens que resultam da utilização de métodos específicos na programação daquele tipo de trabalhos e que inclui a consideração do efeito da aprendizagem.