1,342 research outputs found
Il Mediterraneo, teatro delle incertezze
No full textIn questo saggio vengono individuati cinque temi per la interpretazione del volume: il ruolo dell'Ue nel Mediterraneo; l'Ue e la Nato, la sicurezza e le ingiustizie sociali; l'Italia nel Mediterraneo; l'Africa
Two-to-one resonant multi-modal dynamics of horizontal/inclined cables. Part I : theoretical formulation and model validation
No full textThis paper is first of the two papers dealingwith analytical investigation of resonant multimodal dynamics due to 2:1 internal resonances in the finite-amplitude free vibrations of horizontal/inclined cables. Part I deals with theoretical formulation and validation of the general cable model. Approximate nonlinear partial differential equations of 3-D coupled motion of small sagged cables - which account for both spatio-temporal variation of nonlinear dynamic tension and system asymmetry due to inclined sagged configurations - are presented. A multidimensional Galerkin expansion of the solution ofnonplanar/planar motion is performed, yielding a complete set of system quadratic/cubic coefficients. With the aim of parametrically studying the behavior of horizontal/inclined cables in Part II [25], a second-order asymptotic analysis under planar 2:1 resonance is accomplished by the method of multiple scales. On accounting for higher-order effectsof quadratic/cubic nonlinearities, approximate closed form solutions of nonlinear amplitudes, frequencies and dynamic configurations of resonant nonlinear normal modes reveal the dependence of cable response on resonant/nonresonant modal contributions. Depending on simplifying kinematic modeling and assigned system parameters, approximate horizontal/inclined cable models are thoroughly validated by numerically evaluating statics and non-planar/planar linear/non-linear dynamics against those of the exact model. Moreover, the modal coupling role and contribution of system longitudinal dynamics are discussed for horizontal cables, showing some meaningful effects due to kinematic condensation
Experimental and numerical studies of inclined cables: free and parametrically-forced vibrations
No full textBecause of few experimental studies in the inclined cable literature, this paper is aimed at experimental modelling and investigating the linear free and nonlinear forced vibrations of sagged inclined cables, by discussing the relevant outcomes in the background of theoretical and numerical achievements. Attention is paid to the identification of cable hybrid modes due to system asymmetry, which gives rise to an avoidance phenomenon in the natural frequency spectrum, and to the investigation of some typical 3-D nonlinear dynamics involving the simultaneous parametric/external excitation due to a harmonically time-varying support movement. Large-amplitude out-of-plane/in-plane multi-modal interactions due to non-planar/planar internal resonances are experimentally observed and complemented by space-time numerical simulation of the associated, geometrically nonlinear, partial-differential equations of parametrically-forced cable motion. Overall, the experimental and numerical results highlight the fundamental linear/nonlinear dynamic characteristics of inclined cables, and the crucial role played by the asymmetry induced by cable inclination, in addition to the significant effects of cable sag and dynamic extensibility
EU-Texte mit Kontaktfunktion in multilingualer und multikultureller Hinisicht
No full textL'articolo tematizza i concetti di localizzazione e di europeizzazione, prende quindi in esame alcuni problemi della riformulazione nelle lingue della UE (appellativi, titoli di articoli delle varie stampe nazionali, culturemi) sul sito della UE. La conclusione è che le strategie di localizzazione impiegate per il sito ufficiale UE riguardano in particolare il microlivello e preferiscono mantenere effetti di straniamento - non da ultimo probabilmente proprio al fine di promuovere il processo di conoscenza autentica dell'UE nei suoi cittadini
Implementation and validation of DFT-D for molecular vibrations and dynamics: The benzene dimer as a case study
No full textSemi-empirical correction to density functional theory for dispersion (DFT-D) has been implemented for energies, analytical gradients, and Hessians in order to explore potential energy surfaces by means of a complete set of first-principle methods. The impact of nonbonding interactions on structures, binding energies and zero-point energy contributions as well as on ab initio molecular dynamics trajectories have been investigated for the well known case of benzene dimer. While the static results are in remarkable agreement with the most sophisticated post-Hartree-Fock approaches, the low cost of DFT-D allows to unravel dynamical aspects too, which are mandatory for situations ruled by weak interactions
Mediterraneo teatro delle incertezze. L'Unione Europea, l'Africa, il Medio Oriente, l'Italia, la Nato alla prova dei tempi
No full textGli attori di questa storia mediterranea sono l'Unione Europea, l'Africa, il Medio Oriente, l'Italia e la Nato e a cascata, questioni quali il concetto di sicurezza, le relazioni politiche, gli affari economici, l'immigrazione, le missioni militari, le problematiche ambientali ed energetiche
Deteção remota aplicada à rega dos espaços verdes urbanos
No full textA nova cultura da água visa a conservação dos recursos naturais e o aumento do rendimento
produtivo da água nos espaços verdes públicos e privados. Estes espaços assumem uma
relevância no bem-estar e na qualidade de vida das populações urbanas. No entanto, o aumento
da área verde em climas mediterrâneos estará inevitavelmente associado ao aumento do
consumo em água. A rega surge com a finalidade de fazer face às necessidades hídricas das
plantas em função das caraterísticas climáticas da região. Esta situação é mais relevante quando a
escolha das plantas não recai sobre as autóctones e a água para a rega tem origem na rede de
distribuição de água potável. Nos últimos anos, alguns municípios em Portugal têm vindo a
implementar a instalação de dois tipos distintos de contadores de água: consumo doméstico e
rega. Assim, garante-se água para rega com tarifário de menor custo, visto não incluir tratamento
de água residual. Desde 2012, que a vila de São Brás de Alportel implementou este sistema de
rega para os jardins privados. O presente trabalho tem como objetivos o estudo da evolução dos
consumos de água na rega dos espaços verdes privados que aderiram a este sistema e a monitorização da rega nos espaços verdes públicos, para uma gestão sustentável da água. A
monitorização será realizada pela avaliação da qualidade dos espaços verdes através da deteção
remota, integrada com a informação dos dados climáticos e dos consumos de água.info:eu-repo/semantics/publishedVersio
The effects of kinematic condensation on internally resonant forced vibrations of shallow horizontal cables
No full textThis study aims at comparing non-linear modal interactions in shallow horizontal cables with kinematically non-condensed vs. condensed modeling, under simultaneous primary external and internal resonances. Planar 1:1 or 2:1 internal resonance is considered. The governing partial-differential equations of motion of non-condensed model account for spatio-temporal modification of dynamic tension, and explicitly capture non-linear coupling of longitudinal/ vertical displacements. On the contrary, in the condensed model, a single integro-differential equation is obtained by eliminating the longitudinal inertia according to a quasi-static cable stretching assumption, which entails spatially uniform dynamic tension. This model is largely considered in the literature. Based on a multi-modal discretization and a second-order multiple scales solution accounting for higher-order quadratic effects of a infinite number of modes, coupled/uncoupled dynamic responses and the associated stability are evaluated by means of frequency- and force-response diagrams. Direct numerical integrations confirm the occurrence of amplitude-steady or -modulated responses. Non-linear dynamic configurations and tensions are also examined. Depending on internal resonance condition, system elasto-geometric and control parameters, the condensed model may lead to significant quantitative and/or qualitative discrepancies, against the non-condensed model, in the evaluation of resonant dynamic responses, bifurcations and maximal/minimal stresses. Results of even shallow cables reveal meaningful drawbacks of the kinematic condensation and allow us to detect cases where the more accurate non-condensed model has to be used
INVESTIGATION OF VOLVOX CARTERI CELL DIFFERENTIATION AND ITS EVOLUTION THROUGH FUNCTIONAL ANALYSIS OF REGA AND REGA HOMOLOGUES
No full textMulticellularity and cell differentiation have evolved multiple times in the history of life on this planet, but they evolved so long ago in most lineages that it has been difficult to learn the genetic mechanisms behind their evolution. The family of volvocine green algae comprise an excellent system to study this process, because it contains unicellular, colonial, and multicellular lineages with a relatively recent transition to multicellularity. V. carteri possess two different cell types, reproductive gonidia and motile somatic cells. The somatic regenerator A (regA) gene is essential for maintaining differentiation of the somatic cells, by repressing cell growth and reproduction. regA encodes a nuclear protein with a ~110-amino acid region known as the Volvocine Algal regA like (VARL) domain, which is present in several regA-like sequence (rls) genes in V. carteri and in other volvocine genomes. rlsA-D are the closest regA paralogs, but their functions are unknown. To help pursue my goal of understanding the evolution of cell differentiation in V. carteri, I developed new selectable markers for transformation and a new CRISPR/Cas9 genome editing system for V. carteri. To test the functional equivalency of VARL domains, I used chimeric regA genes encoding VARL domains derived from RegA paralogs�RlsA-D, or RegA homologs from Pandorina morum, Eudorina elegans (colonial) or Pleodorina japonica (cell differentiation). Only the chimeric protein with P. japonica RegA VARL domain rescued the cell differentiation phenotype of a regA mutant, suggesting a unique RegA VARL domain function in cell differentiation. To test the function of the close regA paralogs, I used RNAi (hairpin RNA) and genomic clones to manipulate expression of rlsA-D. rlsA-C RNAi transgene recipients did not express vegetative phenotypes. rlsD knockdown and overexpression have negative effects on growth during asexual life cycle. Interestingly, light deprivation increased levels of rlsD expression. This work reveals that the RegA VARL domain has a unique and specialized functions for somatic cell differentiation, and that rlsD might have a stress adaptation function, suggesting that cell differentiation might have evolved when a regulator of cell growth in response to stress was co-opted and modified to repress growth in somatic cells
- …
