A symplectic extension map and a new Shubin class of pseudo-differential operators

For an arbitrary pseudo-differential operator $A:\mathcal{S}(\mathbb{R}^{n})\longrightarrow\mathcal{S}^{\prime}(\mathbb{R}^{n})$ with Weyl symbol $a\in\mathcal{S}^{\prime}(\mathbb{R}^{2n})$, we consider the pseudo-differential operators $\widetilde{A}:\mathcal{S}(\mathbb{R}^{n+k})\longrightarrow\mathcal{S}^{\prime}(\mathbb{R}^{n+k})$ associated with the Weyl symbols $\widetilde{a}=(a\otimes1_{2k})\circ{s}$, where $1_{2k}(x)=1$ for all $x\in\mathbb{R}^{2k}$ and ${s}$ is a linear symplectomorphism of $\mathbb{R}^{2(n+k)}$. We call the operators $\widetilde{A}$ symplectic dimensional extensions of $A$. In this paper we study the relation between $A$ and $\widetilde{A}$ in detail, in particular their regularity, invertibility and spectral properties. We obtain an explicit formula allowing to express the eigenfunctions of $\widetilde{A}$ in terms of those of $A$. We use this formalism to construct new classes of pseudo-differential operators, which are extensions of the Shubin classes $HG_{\rho}^{m_{1},m_{0}}$ of globally hypoelliptic operators. We show that the operators in the new classes share the invertibility and spectral properties of the operators in $HG_{\rho }^{m_{1},m_{0}}$ but not the global hypoellipticity property. Finally, we study a few examples of operators that belong to the new classes and which are important in mathematical physics.Comment: 28 pages, new version, accepted for publication in JF

Time dependent transformations in deformation quantization

We study the action of time dependent canonical and coordinate transformations in phase space quantum mechanics. We extend the covariant formulation of the theory by providing a formalism that is fully invariant under both standard and time dependent coordinate transformations. This result considerably enlarges the set of possible phase space representations of quantum mechanics and makes it possible to construct a causal representation for the distributional sector of Wigner quantum mechanics.Comment: 16 pages, to appear in the J. Math. Phy

CFRP group effect and interaction between stirrups and strips on the NSM-shear strengthening of RC beams

Available experimental research shows that the technique based on installing Carbon Fibre Reinforced Polymer (CFRP) strips into slits opened on the cover concrete of the beam’s lateral faces, designated as Near Surface Mounted (NSM), is very effective to increase the shear resistance of reinforced concrete (RC) beams. However, recent research has revealed that, in terms of NSM shear strengthening effectiveness, a detrimental effect can occur between existing steel stirrups and applied strips, as well as amongst the strips when the distance between strips, sf, is lower than a certain limit. In the present work, a test setup was developed and an experimental program was carried out to assess the influence of both sf and interaction between existing steel stirrups and strips on the shear strengthening of RC beams. The experimental program is described and the main results are presented and analyzed.(13-05-04-FDR-00031

Solutions for vehicular communications: a review

Vehicular networks experience a number of unique challenges due to the high mobility of vehicles and highly dynamic network topology, short contact durations, disruption intermittent connectivity, significant loss rates, node density, and frequent network fragmentation. All these issues have a profound impact on routing strategies in these networks. This paper gives an insight about available solutions on related literature for vehicular communications. It overviews and compares the most relevant approaches for data communication in these networks, discussing their influence on routing strategies. It intends to stimulate research and contribute to further advances in this rapidly evolving area where many key open issues that still remain to be addressed are identified.Part of this work has been supported by the Instituto de Telecomunicações, Next Generation Networks and Applications Group (NetGNA), Portugal, in the framework of the Project VDTN@Lab, and by the Euro-NF Network of Excellence of the Seventh Framework Programme of EU, in the framework of the Specific Joint Research Project VDTN

Aplicação de novos materiais e de modelos de análise não linear material no desenvolvimento de sistemas estruturais pré-fabricados para edifícios industriais

No presente trabalho é descrita a investigação efectuada no âmbito do dimensionamento de viga pré-fabricada para vencer vãos de 20 m de coberturas de edifícios industriais, denominada VMC20. Para tal utilizou-se betão reforçado com fibras de aço e recorreu-se a métodos avançados de análise de estruturas

Analytical and numerical analysis of the behaviour of RC beams flexural strengthened with CFRP

Experimental research regarding the flexural strengthening of reinforced concrete (RC) structures with Carbon Fibre Reinforced (CFRP) systems using the Externally Bonded Reinforcing (EBR) and the Near Surface Mounted (NSM) techniques has been carried out at the University of Minho. Considering the experimental results of this research, the performance of the ACI and fib formulations for the EBR flexural strengthening was appraised in this paper. The same was done in terms of NSM technique adopting for the CFRP debonding strain a value that is 70% of the CFRP ultimate strain, according to the recommendations of the ACI Committee 440. However, the experimental results show that the CFRP debonding strain is dependent on the CFRP percentage and existing longitudinal steel reinforcement ratio. To estimate an equation for the prediction of the CFRP debonding strain, which takes into account these parameters, a numerical model was applied to the simulation of the tests carried out.(undefined

Phytochemical and antioxidant characterization of Hypericum perforatum alcoholic extracts

The antioxidant potentials of a total ethanolic extract of Hypericum perforatum (TE) and fractions were evaluated and correlated with their phenolic contents. The extracts were fully characterised by HPLC-DAD-MS-MS. Kaempferol 3-rutinoside and rutin-acetyl were identified for the first time in TE extracts. The free radical-scavenging properties of TE (EC50=21 [mu]g dwb/ml) and fractions were studied using DPPH. Fractions containing flavonoids and/or caffeoylquinic acids were found to be the main contributors to the free radical-scavenging activity of the TE. Lipid peroxidation, induced with ascorbate/Fe2+, was significantly reduced in the presence of the TE (EC50=26 [mu]g dwb/ml) and fractions containing flavonoids and/or caffeoylquinic acids. The fraction containing flavonoid aglycones was found to be responsible for a major part of the TE protection against lipid peroxidation. Hypericins and hyperforins made no significant contributions to the antioxidant properties of TE. Human consumption of H. perforatum extract or fractions could be beneficial.http://www.sciencedirect.com/science/article/B6T6R-4CG2JK5-3/1/ae503f0537dcaaab2ede0770605a66c