Digital archives : comparative study and interoperability framework

Estágio realizado na ParadigmaXis e orientado pelo Eng.º Filipe CorreiaTese de mestrado integrado. Engenharia Informátca e Computação. Faculdade de Engenharia. Universidade do Porto. 200

Exact General Relativistic Perfect Fluid Disks with Halos

Using the well-known ``displace, cut and reflect'' method used to generate disks from given solutions of Einstein field equations, we construct static disks made of perfect fluid based on vacuum Schwarzschild's solution in isotropic coordinates. The same method is applied to different exactsolutions to the Einstein'sequations that represent static spheres of perfect fluids. We construct several models of disks with axially symmetric perfect fluid halos. All disks have some common features: surface energy density and pressures decrease monotonically and rapidly with radius. As the ``cut'' parameter $a$ decreases, the disks become more relativistic, with surface energy density and pressure more concentrated near the center. Also regions of unstable circular orbits are more likely to appear for high relativistic disks. Parameters can be chosen so that the sound velocity in the fluid and the tangential velocity of test particles in circular motion are less then the velocity of light. This tangential velocity first increases with radius and reaches a maximum.Comment: 22 pages, 25 eps.figs, RevTex. Phys. Rev. D to appea

Experimental mnd Modeling Investigation of The Performance Characteristics on Diesel Hcci with Hydrogen Additive- A Review

Homogeneous charge compression ignition (HCCI) combustion has been attracting considerable attention due to higher efficiency with lower nitrogen oxide (NOx) and particulate matter (PM) emissions. The combustion process in dual fuel systems in HCCI engines is very complex due to the interactions of mixing and chemistry inside the combustion chamber during the late stages of the compression stroke and the ignition process. The ignition process is very critical with significant heat release from chemical reactions occurs and the timing is difficult to predict. Controlling auto ignition was considered as the significant problem to HCCI especially in tackling the sudden pressure rise in-cylinder. Thus, it will affect the performance and emission that varies with the operating engine condition and fuel properties. The sudden pressure is due to heterogeneous which result in flame propagation.This paper mainly reviewson dual fuels in internal combustion engine, with a particular focus on using hydrogen as a fuel additive

Web service composition: A survey of techniques and tools

Web services are a consolidated reality of the modern Web with tremendous, increasing impact on everyday computing tasks. They turned the Web into the largest, most accepted, and most vivid distributed computing platform ever. Yet, the use and integration of Web services into composite services or applications, which is a highly sensible and conceptually non-trivial task, is still not unleashing its full magnitude of power. A consolidated analysis framework that advances the fundamental understanding of Web service composition building blocks in terms of concepts, models, languages, productivity support techniques, and tools is required. This framework is necessary to enable effective exploration, understanding, assessing, comparing, and selecting service composition models, languages, techniques, platforms, and tools. This article establishes such a framework and reviews the state of the art in service composition from an unprecedented, holistic perspective

Core regulatory network motif underlies the ocellar complex patterning in Drosophila melanogaster

arXiv:1404.4554v5During organogenesis, developmental programs governed by Gene Regulatory Networks (GRN) define the functionality, size and shape of the different constituents of living organisms. Robustness, thus, is an essential characteristic that GRNs need to fulfill in order to maintain viability and reproducibility in a species. In the present work we analyze the robustness of the patterning for the ocellar complex formation in Drosophila melanogaster fly. We have systematically pruned the GRN that drives the development of this visual system to obtain the minimum pathway able to satisfy this pattern. We found that the mechanism underlying the patterning obeys to the dynamics of a 3-nodes network motif with a double negative feedback loop fed by a morphogenetic gradient that triggers the inhibition in a French flag problem fashion. A Boolean modeling of the GRN confirms robustness in the patterning mechanism showing the same result for different network complexity levels. Interestingly, the network provides a steady state solution in the interocellar part of the patterning and an oscillatory regime in the ocelli. This theoretical result predicts that the ocellar pattern may underlie oscillatory dynamics in its genetic regulation.This work is partially financed by Junta de Andalucía (FQM-122) to A. Córdoba and by the Spanish Ministry for Science and Innovation (MICINN/MINECO) and Feder Funds through grants BFU2012-34324 to F. Casares (CABD, Seville, Spain) and Consolider Ingenio-2010 ‘From Genes to Shape’ (CSD 2007-008), of which F. Casares was a participant researcher.Peer Reviewe

Análise geométrica e capacidade de carga de pontes em arco de alvenaria do Noroeste Peninsular

Neste trabalho apresenta-se os resultados de um levantamento geométrico realizado em 59 pontes em arco de alvenaria das áreas geográficas do Norte de Portugal e Noroeste de Espanha. Com base na discussão dos resultados geométricos, foram definidas oito pontes de referência, representativas da amostra. Posteriormente, o artigo trata a avaliação da capacidade de carga das pontes de referência. Verificou-se que a espessura do arco e as propriedades físicas do material de enchimento são de primordial importância em termos de capacidade de carga. Além disso, os resultados indicaram que as pontes da amostra são estruturalmente seguras em relação à legislação aplicável

Geometric issues and ultimate load capacity of masonry arch bridges from the Northwest Iberian Peninsula

This paper reports the results from a geometrical survey carried out on 59 segmental masonry arch bridges from Portugal and Spain, with a focus on the adjacent geographical areas of northern Portugal and north-western Spain. Historical empirical rules are briefly presented and further compared against the bridges’ geometrical data. Departing from a detailed discussion of the geometrical results, eight reference bridges were defined as representative of the sample. Subsequently, the paper deals with a parametric assessment of the load-carrying capacity of the reference bridges and a discussion of results. It was found that arch thickness and physical properties of the fill are of paramount importance in terms of ultimate load-carrying capacity. Furthermore, the results indicate that the bridges from the sample are structurally safe with respect to applicable legislation