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2015
Tschopp, Emanuel, Octávio Mateus, and Roger B. J. Benson. "A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)." PeerJ. 3 (2015): e857. Abstracttschopp_et_al_2015_brontosaurus_peerj-857.pdfWebsite

Diplodocidae are among the best known sauropod dinosaurs. Several species were described in the late 1800s or early 1900s from the Morrison Formation of North America. Since then, numerous additional specimens were recovered in the USA, Tanzania, Portugal, and Argentina, as well as possibly Spain, England, Georgia, Zimbabwe, and Asia. To date, the clade includes about 12 to 15 nominal species, some of them with questionable taxonomic status (e.g., ‘\textit{Diplodocus}’ \textit{hayi} or \textit{Dyslocosaurus polyonychius}), and ranging in age from Late Jurassic to Early Cretaceous. However, intrageneric relationships of the iconic, multi-species genera \textit{Apatosaurus} and \textit{Diplodocus} are still poorly known. The way to resolve this issue is a specimen-based phylogenetic analysis, which has been previously implemented for \textit{Apatosaurus}, but is here performed for the first time for the entire clade of Diplodocidae.The analysis includes 81 operational taxonomic units, 49 of which belong to Diplodocidae. The set of OTUs includes all name-bearing type specimens previously proposed to belong to Diplodocidae, alongside a set of relatively complete referred specimens, which increase the amount of anatomically overlapping material. Non-diplodocid outgroups were selected to test the affinities of potential diplodocid specimens that have subsequently been suggested to belong outside the clade. The specimens were scored for 477 morphological characters, representing one of the most extensive phylogenetic analyses of sauropod dinosaurs. Character states were figured and tables given in the case of numerical characters.The resulting cladogram recovers the classical arrangement of diplodocid relationships. Two numerical approaches were used to increase reproducibility in our taxonomic delimitation of species and genera. This resulted in the proposal that some species previously included in well-known genera like \textit{Apatosaurus} and \textit{Diplodocus} are generically distinct. Of particular note is that the famous genus \textit{Brontosaurus} is considered valid by our quantitative approach. Furthermore, “\textit{Diplodocus}” hayi represents a unique genus, which will herein be called \textit{Galeamopus} gen. nov. On the other hand, these numerical approaches imply synonymization of “\textit{Dinheirosaurus}” from the Late Jurassic of Portugal with the Morrison Formation genus \textit{Supersaurus}. Our use of a specimen-, rather than species-based approach increases knowledge of intraspecific and intrageneric variation in diplodocids, and the study demonstrates how specimen-based phylogenetic analysis is a valuable tool in sauropod taxonomy, and potentially in paleontology and taxonomy as a whole.

Biscaia, Hugo C., Carlos Chastre, and André Viegas. "A new discrete method to model unidirectional FRP-to-parent material bonded joints subjected to mechanical loads." Composite Structures. 121 (2015): 280-295. AbstractWebsite

Nowadays fiber reinforced polymer (FRP) composites play an important role in the strengthening of structures. Different methods can be used to apply these materials: the externally bonded reinforcement (EBR), and the near surface mounted (NSM) using strips and NSM rods. There are only a few studies comparing these methods or presenting an efficient model to simulate these strengthening techniques. This study looks mainly at the analysis of the interface between FRP-to-parent material bonded joints. The paper examines, through a new discrete model based on axial and shear springs, the performance of FRP-to-parent material bonded joints for EBR or NSM techniques using strips or composite rods. In order to implement the model a routine in MATLAB was developed and several bond–slip curves were assumed. The results revealed that load–slip curves or bond stresses, strains or slippages along the bonded length obtained from several bond–slip curves are similar to the analytical and other numerical solutions found in literature. In what concerns the adhesion between two different materials, and assuming the same bond characteristics for the three fiber strengthening techniques, the NSM system using FRP strips had the highest maximum load transmitted to the FRP strip combined with the lowest effective bond length. The results obtained from the proposed model were also very accurate with that obtained from an analytical solution found in literature that simulates the debonding phenomenon of FRP-to-concrete interfaces between to adjacent cracks.

Souza, Luiz A. S., Carlos Chastre, Válter J. G. LUCIO, and Sueli T. M. Souza. "Comportamento Dinâmico de Torres Treliçadas em Concreto Armado para Turbinas Eólicas Offshore." Congresso de Métodos Numéricos em Engenharia. Lisboa, Portugal 2015. 18. Abstractsouza2015chlusu.pdf

A demanda de energia, faz com que o homem esteja sempre a procura de novas soluções para a sua produção. Uma opção é a energia eólica, por se tratar de uma energia limpa, renovável e inesgotável. Para se evitar a ocupação das terras férteis, é natural a busca de soluções no mar. Portanto, neste trabalho é estudado o comportamento estrutural dinâmico de uma torre treliçada em concreto armado pós-tensionado por tirantes externos idealizada para uso offshore com a finalidade de suporte para turbinas eólicas de eixo horizontal. A torre está sujeita às ações gravitacionais, aerodinâmicas e hidrodinâmicas. Para considerar estas ações desenvolveu-se um código computacional específico usando a linguagem MATLAB. É proposto um modelo simplificado para análise bi-dimensional, utilizando-se elementos de pórtico plano com a finalidade de contornar as dificuldades de uma análise tridimensional. Embora específico para este tipo de torre, o codigo permite variar geometrias, carregamentos e alterações do nível do mar. Nas cargas aerodinâmicas élevado em conta o espectro de Von Karman. As cargas hidrodinâmicas são avaliadas pela equação de Morison. As cargas nodais equivalentes são determinadas por integração ao longo do elemento estrutural de acordo com o proposto por Souza. Os tirantes pós-tensionados são monitorados para não sofrerem esforços de compressão. A análise é realizada no domínio do tempo utilizando-se o algoritmo de integração de Newmark.. Através dos procedimentos adotados foi possível obter resultados para as freqüências, deslocamentose esforços, que se mostraram coerentes com os obtidos por modelos tri dimensionais mais complexos. O código desenvolvido permitiu a análise de forma simples, eficiente e confiável de torres treliçadas de concreto armado.

Störrle, Harald, Michel R. V. Chaudron, Vasco Amaral, and Miguel Goulão First International Workshop on Human Factors in Modeling (HuFaMo 2015) @ MODELS 2015 - Preface. First International Workshop on Human Factors in Modeling (HuFaMo 2015) @ MODELS 2015. Ottawa, Canada, 2015.
Ameller, David, Xavier Franch, Cristina Gómez, João Araújo, Richard Berntsson Svensson, Stefan Biffl, Jordi Cabot, Vittorio Cortellessa, Maya Daneva, Daniel Mendez Fernández, Ana Moreira, Henry Muccini, Antonio Vallecillo, Manuel Wimmer, Vasco Amaral, Hugo Brunelière, Loli Burgueño, Miguel Goulão, Bernhard Schätz, and Sabine Teufl. "Handling Non-Functional Requirements in Model-Driven Development: An Ongoing Industrial Survey." 23rd International Conference on Requirements Engineering (RE'15) - RE: Next! Ottawa, Canada: IEEE Computer Society, 2015.
Souza, Luiz A. S., Carlos Chastre, Válter J. G. LUCIO, and Sueli T. M. Souza. "Modelo simplificado para análise do comportamento dinâmico de torres treliçadas em concreto armado para turbinas eólicas offshore." CILAMCE 2015 - XXXVI Ibero-Latin American Congress on Computational Methods in Engineering. Rio de Janeiro, Brasil 2015. 16p. Abstractsouza2015chlusu-cilamce2015paper327.pdf

Este trabalho apresenta o desenvolvimento de um software para análise de torres treliçadas em concreto armado, pós-tensionada por tirantes externos, com a finalidade de suporte para turbinas eólicas de eixo horizontal, em ambiente offshore. A torre está sujeita às ações gravitacionais, aerodinâmicas, hidrodinâmicas. Desenvolveu-se um código computacional, em linguagem MATLAB, específico para este tipo de torre. As dificuldades de uma análise tridimensional mais complexa foram reduzidas propondo-se um modelo simplificado bi-dimensional utilizando-se elementos de pórtico plano. As cargas de vento são variadas segundo o espectro de von Karman. Para as ondas marítimas e correntes são implementados o espectro de Pierson-Moskowitz e o de JONSWAP. As cargas hidrodinâmicas são avaliadas pela equação de Morison. Estas cargas são integradas ao longo dos elementos estruturais e transformadas em cargas nodais equivalentes, de acordo com o proposto por Souza. A análise é realizada no domínio do tempo com algoritmo de Newmark. Este software, por ser específico para este tipo de torre, possui facilidades na introdução de dados e na modelagem da estrutura. Com estas estratégias o modelo apresentou bons resultados para a avaliação de cargas, cálculo de freqüências naturais, resposta de deslocamentos, esforços e reações.

Caeiro, Frederico, Ana P. Martins, and Inês J. Sequeira. "Finite sample behaviour of classical and quantile regression estimators for the Pareto distribution." Proceedings of the International Conference on Numerical Analysis and Applied Mathematics 2014, ICNAAM 2014. Vol. 1648. American Institute of Physics Inc., 2015. Abstract

The Pareto distribution is a well known and important model in Statistics. It has been used to study large incomes, city population size, size of losses, stock price fluctuations, number of citations received by papers and other similar phenomena. In this work we compare the finite sample performance of several estimation methods, namely the Moment, Maximum Likelihood and Quantile Regression methods. The comparison will be made through a Monte-Carlo simulation study.The Pareto distribution is a well known and important model in Statistics. It has been used to study large incomes, city population size, size of losses, stock price fluctuations, number of citations received by papers and other similar phenomena. In this work we compare the finite sample performance of several estimation methods, namely the Moment, Maximum Likelihood and Quantile Regression methods. The comparison will be made through a Monte-Carlo simulation study.

Caeiro, Frederico, and Dora Susana Raposo Prata Gomes. "Adaptive estimation of a tail shape second order parameter." International Conference of Computational Methods in Sciences and Engineering 2015 (ICCMSE 2015). AIP Conference Proceedings. American Institute of Physics Inc., 2015. Abstract

In Statistics of Extremes, the tail shape second order parameter is a relevant parameter whenever we want to improve the estimation of first order parameters. We shall consider two semi-parametric estimators of the shape second order parameter, parameterized with a tuning parameter. We provide a Monte Carlo comparative simulation study of several algorithms for the choice of such tuning parameter and for an adaptive estimation of the shape second order parameter.In Statistics of Extremes, the tail shape second order parameter is a relevant parameter whenever we want to improve the estimation of first order parameters. We shall consider two semi-parametric estimators of the shape second order parameter, parameterized with a tuning parameter. We provide a Monte Carlo comparative simulation study of several algorithms for the choice of such tuning parameter and for an adaptive estimation of the shape second order parameter.

Caeiro, Frederico. "Preface of the "2nd Symposium on Computational Statistical Methods"." AIP Conference ProceedingsAIP Conference Proceedings. 1702 (2015). AbstractWebsite
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Caeiro, Frederico, and Ivette M. Gomes. "Revisiting the maximum likelihood estimation of a positive extreme value index." Journal Of Statistical Theory And PracticeJournal Of Statistical Theory And Practice. 9.1 (2015): 200-218. AbstractWebsite

In this article, we revisit Feuerverger and Halls maximum likelihood estimation of the extreme value index. Based on those estimators we propose new estimators that have the smallest possible asymptotic variance, equal to the asymptotic variance of the Hill estimator. The full asymptotic distributional properties of the estimators are derived under a general third-order framework for heavy tails. Applications to a real data set and to simulated data are also presented.In this article, we revisit Feuerverger and Halls maximum likelihood estimation of the extreme value index. Based on those estimators we propose new estimators that have the smallest possible asymptotic variance, equal to the asymptotic variance of the Hill estimator. The full asymptotic distributional properties of the estimators are derived under a general third-order framework for heavy tails. Applications to a real data set and to simulated data are also presented.

Caeiro, Frederico, and Ivette M. Gomes. "Bias reduction in the estimation of a shape second-order parameter of a heavy-tailed model." Journal Of Statistical Computation And SimulationJournal Of Statistical Computation And Simulation. 85.17 (2015): 3405-3419. AbstractWebsite

In extreme value theory, the shape second-order parameter is a quite relevant parameter related to the speed of convergence of maximum values, linearly normalized, towards its limit law. The adequate estimation of this parameter is vital for improving the estimation of the extreme value index, the primary parameter in statistics of extremes. In this article, we consider a recent class of semi-parametric estimators of the shape second-order parameter for heavy right-tailed models. These estimators, based on the largest order statistics, depend on a real tuning parameter, which makes them highly flexible and possibly unbiased for several underlying models. In this article, we are interested in the adaptive choice of such tuning parameter and the number of top order statistics used in the estimation procedure. The performance of the methodology for the adaptive choice of parameters is evaluated through a Monte Carlo simulation study.In extreme value theory, the shape second-order parameter is a quite relevant parameter related to the speed of convergence of maximum values, linearly normalized, towards its limit law. The adequate estimation of this parameter is vital for improving the estimation of the extreme value index, the primary parameter in statistics of extremes. In this article, we consider a recent class of semi-parametric estimators of the shape second-order parameter for heavy right-tailed models. These estimators, based on the largest order statistics, depend on a real tuning parameter, which makes them highly flexible and possibly unbiased for several underlying models. In this article, we are interested in the adaptive choice of such tuning parameter and the number of top order statistics used in the estimation procedure. The performance of the methodology for the adaptive choice of parameters is evaluated through a Monte Carlo simulation study.

Baltazar, Luis G., Fernando MA Henriques, and Maria Teresa Cidade. "Contribution to the design of hydraulic lime-based grouts for masonry consolidation." 21.6 (2015): 698-709. Abstract
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Mateus, Ayana Maria Xavier Furtado, and Frederico Almeida Gião Gonçalves Caeiro. "The difference-sign randomness test." NTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2015. Vol. 1702. AIP Conference Proceedings, 1702. American Institute of Physics Inc., 2015. Abstract

In this paper we review the properties of the difference-sign randomness test. First we analyse the exact andasymptotic distribution of the test statistic and provide a table with values for the exact distribution function, for samples ofsize n ≤ 32. Then, we also present several moments of the statistic test, under the null hypothesis of randomness and underthe hypothesis of the existence of a linear trend. Finally, we present an illustration of the test difference-sign to a real data set.In this paper we review the properties of the difference-sign randomness test. First we analyse the exact andasymptotic distribution of the test statistic and provide a table with values for the exact distribution function, for samples ofsize n ≤ 32. Then, we also present several moments of the statistic test, under the null hypothesis of randomness and underthe hypothesis of the existence of a linear trend. Finally, we present an illustration of the test difference-sign to a real data set.

Brehm, Tiago, Gonçalo Pereira, C. R. Leal, Clara Gonçalves, João P. Borges, and Maria Teresa Cidade. "Electrorheological characterization of dispersions in silicone oil of encapsulated liquid crystal 4-n-penthyl-4′-cyanobiphenyl in polyvinyl alcohol and in silica." 90.3 (2015): 035802. Abstract
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Baltazar, Luis G., Fernando MA Henriques, and Maria Teresa Cidade. "Experimental Study and Modeling of Rheological and Mechanical Properties of NHL Grouts." 27.12 (2015): 04015055. Abstract
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Caeiro, Frederico Almeida Gião Gonçalves, Ayana Maria Xavier Furtado Mateus, and Luís Pedro Carneiro Ramos. "Extreme value analysis of the sea levels in Venice." PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014. AIP Conference Proceedings. American Institute of Physics Inc., 2015. Abstract

The number of floods in the city of Venice has increased substantially in the last decades and can be explained bythe sea level rise and land subsidence. Using Statistics of Extremes we shall model the extreme behaviour of the sea level inVenice and quantify risk through the estimation of important parameters such as return periods of high levels.The number of floods in the city of Venice has increased substantially in the last decades and can be explained bythe sea level rise and land subsidence. Using Statistics of Extremes we shall model the extreme behaviour of the sea level inVenice and quantify risk through the estimation of important parameters such as return periods of high levels.

Ghisolfi, A., F. Condello, C. Fliedel, V. Rosa, and P. Braunstein. "Facile and Room-Temperature Activation of Csp3-Cl Bonds by Cheap and Air-Stable Nickel(II) Complexes of (N-Thioether) DPPA-Type Ligands." Organometallics. 34.11 (2015): 2255-2260. AbstractWebsite
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Micaelo, R., A. Pereira, L. Quaresma, and M. T. Cidade. "Fatigue resistance of asphalt binders: assessment of the analysis methods in strain-controlled tests." 98 (2015): 703-712. Abstract
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Caeiro, Frederico, and Dora Susana Raposo Prata Gomes. "A log probability weighted moment estimator of extreme quantiles." Theory and Practice of Risk Assessment - ICRA5 2013. Vol. 136. Springer New York LLC, 2015. 293-303. Abstract

In this paper we consider the semi-parametric estimation of extreme quantiles of a right heavy-tail model. We propose a new Probability Weighted Moment estimator for extreme quantiles, which is obtained from the estimators of the shape and scale parameters of the tail. Under a second-order regular variation condition on the tail, of the underlying distribution function, we deduce the non degenerate asymptotic behaviour of the estimators under study and present an asymptotic comparison at their optimal levels. In addition, the performance of the estimators is illustrated through an application to real data.In this paper we consider the semi-parametric estimation of extreme quantiles of a right heavy-tail model. We propose a new Probability Weighted Moment estimator for extreme quantiles, which is obtained from the estimators of the shape and scale parameters of the tail. Under a second-order regular variation condition on the tail, of the underlying distribution function, we deduce the non degenerate asymptotic behaviour of the estimators under study and present an asymptotic comparison at their optimal levels. In addition, the performance of the estimators is illustrated through an application to real data.

Foth, Christian, Serjoscha Evers, Ben Pabst, Octávio Mateus, Alexander Flisch, Mike Patthey, and Oliver W. M. Rauhut. "New insights into the lifestyle of Allosaurus (Dinosauria: Theropoda) based on another specimen with multiple pathologies." PeerJ PrePrints. 3 (2015): e824v1. Abstractfoth_et_al_2015_peerj-preprints-824.pdfWebsite

Adult large-bodied theropods are often found with numerous pathologies. A large, almost complete, probably adult Allosaurus specimen from the Howe Stephens Quarry, Morrison Formation (Late Kimmeridgian–Early Tithonian), Wyoming, shows multiple pathologies. Pathologic bones include the left dentary, two cervical vertebrae, one cervical and several dorsal ribs, the left scapula, the left humerus, right ischium, and two left pedal phalanges. These pathologies can be classified as follows: the fifth cervical vertebra, the scapula, several ribs and the ischium are traumatic, and a callus on the shaft of the left pedal phalanx II-2 is traumatic-infectious. Traumatically fractured elements exposed to frequent movement (e.g. the scapula and the ribs) show a tendency to develop pseudarthroses instead of callus healing. The pathologies in the lower jaw and a reduced flexor tubercle of the left pedal phalanx II-2 are most likely traumatic or developmental in origin. The pathologies on the fourth cervical are most likely developmental in origin or idiopathic, that on the left humerus is infectious or idiopathic, whereas left pedal phalanx IV-1 is classified as idiopathic. With exception of the ischium, all traumatic / traumatic-infectious pathologic elements show unambiguous evidences of healing, indicating that the respective pathologies did not cause the death of this individual. Alignment of the scapula and rib pathologies from the left side suggests that all may have been caused by a single traumatic event. The ischial fracture may have been fatal. The occurrence of multiple traumatic pathologies again underlines that large-bodied theropods experienced frequent injuries during life, indicating an active predatory lifestyle, and their survival perhaps supports a gregarious behavior for Allosaurus. Signs of infections are scarce and locally restricted, indicating a successful prevention of the spread of pathogens, as it is the case in extant reptiles (including birds).

Gomes, Ivette M., Fátima M. Brilhante, Frederico Caeiro, and Dinis Pestana. "A new partially reduced-bias mean-of-order p class of extreme value index estimators." Computational Statistics & Data AnalysisComputational Statistics & Data Analysis. 82 (2015): 223-227. AbstractWebsite

A class of partially reduced-bias estimators of a positive extreme value index (EVI), related to a mean-of-order-p class of EVI-estimators, is introduced and studied both asymptotically and for finite samples through a Monte-Carlo simulation study. A comparison between this class and a representative class of minimum-variance reduced-bias (MVRB) EVI-estimators is further considered. The MVRB EVI-estimators are related to a direct removal of the dominant component of the bias of a classical estimator of a positive EVI, the Hill estimator, attaining as well minimal asymptotic variance. Heuristic choices for the tuning parameters p and k, the number of top order statistics used in the estimation, are put forward, and applied to simulated and real data.A class of partially reduced-bias estimators of a positive extreme value index (EVI), related to a mean-of-order-p class of EVI-estimators, is introduced and studied both asymptotically and for finite samples through a Monte-Carlo simulation study. A comparison between this class and a representative class of minimum-variance reduced-bias (MVRB) EVI-estimators is further considered. The MVRB EVI-estimators are related to a direct removal of the dominant component of the bias of a classical estimator of a positive EVI, the Hill estimator, attaining as well minimal asymptotic variance. Heuristic choices for the tuning parameters p and k, the number of top order statistics used in the estimation, are put forward, and applied to simulated and real data.

Brusatte, Stephen L., Richard J. Butler, Octávio Mateus, and Sébastien J. Steyer. "A new species of Metoposaurus from the Late Triassic of Portugal and comments on the systematics and biogeography of metoposaurid temnospondyls." Journal of Vertebrate PaleontologyJournal of Vertebrate Paleontology (2015): e912988. Abstractbrusatte_et_al2015metoposaurusportugal.pdfWebsite

ABSTRACTMetoposaurids are a group of temnospondyl amphibians that filled crocodile-like predatory niches in fluvial and lacustrine environments during the Late Triassic. Metoposaurids are common in the Upper Triassic sediments of North Africa, Europe, India, and North America, but many questions about their systematics and phylogeny remain unresolved. We here erect Metoposaurus algarvensis, sp. nov., the first Metoposaurus species from the Iberian Peninsula, based on several new specimens from a Late Triassic bonebed in Algarve, southern Portugal. We describe the cranial and pectoral anatomy of M. algarvensis and compare it with other metoposaurids (particularly other specimens of Metoposaurus from Germany and Poland). We provide a revised diagnosis and species-level taxonomy for the genus Metoposaurus, which is currently represented with certainty by three European species (M. diagnosticus, M. krasiejowensis, M. algarvensis). We also identify cranial characters that differentiate these three species, and may have phylogenetic significance. These include features of the braincase and mandible, which indicate that metoposaurid skulls are more variable than previously thought. The new Portuguese bonebed provides further evidence that metoposaurids congregated in fluvial and lacustrine settings across their geographic range and often succumbed to mass death events. We provide an updated paleogeographic map depicting all known metoposaurid occurrences, which shows that these temnospondyls were globally distributed in low latitudes during the Late Triassic and had a similar, but not identical, paleogeographic range as phytosaurs.http://zoobank.org/urn:lsid:zoobank.org:pub:083C80C6-0AB6-49E1-A636-6A8BDBC06A47ABSTRACTMetoposaurids are a group of temnospondyl amphibians that filled crocodile-like predatory niches in fluvial and lacustrine environments during the Late Triassic. Metoposaurids are common in the Upper Triassic sediments of North Africa, Europe, India, and North America, but many questions about their systematics and phylogeny remain unresolved. We here erect Metoposaurus algarvensis, sp. nov., the first Metoposaurus species from the Iberian Peninsula, based on several new specimens from a Late Triassic bonebed in Algarve, southern Portugal. We describe the cranial and pectoral anatomy of M. algarvensis and compare it with other metoposaurids (particularly other specimens of Metoposaurus from Germany and Poland). We provide a revised diagnosis and species-level taxonomy for the genus Metoposaurus, which is currently represented with certainty by three European species (M. diagnosticus, M. krasiejowensis, M. algarvensis). We also identify cranial characters that differentiate these three species, and may have phylogenetic significance. These include features of the braincase and mandible, which indicate that metoposaurid skulls are more variable than previously thought. The new Portuguese bonebed provides further evidence that metoposaurids congregated in fluvial and lacustrine settings across their geographic range and often succumbed to mass death events. We provide an updated paleogeographic map depicting all known metoposaurid occurrences, which shows that these temnospondyls were globally distributed in low latitudes during the Late Triassic and had a similar, but not identical, paleogeographic range as phytosaurs.http://zoobank.org/urn:lsid:zoobank.org:pub:083C80C6-0AB6-49E1-A636-6A8BDBC06A47

Pereira, Pedro, Fábio Passos, and Helena M. Fino. "Optimization-Based Design of RF-VCOs with Tapered Inductors." Performance Optimization Techniques in Analog, Mixed-Signal, and Radio-Frequency Circuit Design. Eds. Mourad Fakhfakh, Esteban Tlelo-Cuautle, and Maria Helena Fino. Hershey, PA, USA: IGI Global, 2015. 134-157. Abstract

Voltage-Controlled Oscillators (VCOs) are widely used in wireless transceivers. Due to the stringent specifications regarding phase-noise, LC-VCOs are usually adopted. The need for maximizing phase-noise as well as minimizing the power consumption makes imperious the adoption of optimization-based design methodologies. For the optimization of the LC-VCO characteristics, special attention must be paid to the integrated inductor design, since its quality factor may have a strong influence in the LC-VCO phase-noise. Furthermore, designers must ensure that the higher limit of VCO operating frequency is sufficiently below the inductor resonant frequency. In this chapter, a study on the influence of the quality factor of the inductors on the LC-VCO overall behavior is presented. Then, optimization of integrated inductors by exploring the inductor geometric layout is presented. Finally, results obtained for the design of an LC-VCO in 130nm Technology using a previously optimized inductor are presented.

Fliedel, C., V. Rosa, F. M. Alves, A. M. Martins, T. Avilés, and S. Dagorne. "P,O-Phosphinophenolate zinc(ii) species: Synthesis, structure and use in the ring-opening polymerization (ROP) of lactide, ε-caprolactone and trimethylene carbonate." Dalton Transactions. 44.27 (2015): 12376-12387. AbstractWebsite
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Nunes, D., A. Pimentel, JV Pinto, T. R. Calmeiro, S. Nandy, P. Barquinha, L. Pereira, P. A. Carvalho, E. Fortunato, and R. Martins. "Photocatalytic behavior of TiO2 films synthesized by microwave irradiation." Catalysis Today (2015). AbstractWebsite

Titanium dioxide was synthesized on glass substrates from titanium (IV)isopropoxide and hydrochloride acid aqueous solutions through microwave irradiation using as seed layer either fluorine-doped crystalline tin oxide (SnO2:F) or amorphous tin oxide (a-SnOx). Three routes have been followed with distinct outcome: (i) equimolar hydrochloride acid/water proportions (1HCl:1water) resulted in nanorod arrays for both seed layers; (ii) higher water proportion (1HCl:3water) originated denser films with growth yield dependent on the seed layer employed; while (iii) higher acid proportion (3HCl:1water) hindered the formation of TiO2. X-ray diffraction (XRD) showed that the materials crystallized with the rutile structure, possibly with minute fractions of brookite and/or anatase. XRD peak inversions observed for the materials synthesized on crystalline seeds pointed to preferred crystallographic orientation. Electron diffraction showed that the especially strong XRD peak inversions observed for TiO2 grown from the 1HCl:3water solution on SnO2:F originated from a [001] fiber texture. Transmittance spectrophotometry showed that the materials with finer structure exhibited significantly higher optical band gaps. Photocatalytic activity was assessed from methylene blue degradation, with the 1HCl:3water SnO2:F material showing remarkable degradability performance, attributed to a higher exposure of (001) facets, together with stability and reusability.