1,721,149 research outputs found
Unsteady inflow conditions: A variationally based solution to the insurgence of pressure fluctuations
Full text linkThe application of unsteady inflow conditions represents an important aspect when scale resolving turbulence models are adopted in Computational Fluid Dynamics (CFD) analyses. In such context, with reference to Wind Engineering applications, the main concern is often represented by the generation of a synthetic velocity field representative of the turbulent fluctuations impinging on the studied body. Once such synthetic field has been generated, it is applied at the inflow patch. Unfortunately, such operation is not trivial: undesired pressure fluctuations are often generated due to the incompatibility between the applied inflow condition and the flow field found inside the computational domain. In this paper, a procedure able to guarantee a correct application of synthetically generated velocity fields to CFD simulations is described. The procedure, which relies on a variational background, is simple and can be readily implemented in existing codes. Numerical results confirm that, by adopting the proposed corrections, pressure fluctuations are strongly reduced, so confirming the soundness of the proposed approach. An OpenFoam implementation of the method is available for download at https://site.unibo.it/cwe-lamc/en
Consistency and recovery in electroelasticity Part I: Standard finite elements
No full textDeveloping finite elements for electroelastic analysis requires a special care as the coupling in the discrete equations depends on the matching between the approximations assumed for mechanical and electrical variables. To provide a formal basis to this intuitive remark, a notion of consistency is established and a rigorous consistency analysis is presented for the standard finite element model based on assumed displacement and electric potential. In this way, specific analytical requirements are obtained which serve as a guide to select the interpolation functions for primary variables. Moreover, the analysis shows that violating consistency can be reflected as spurious outcomes upsetting the local distributions of secondary variables. Indeed, this undesirable effect is shown to be typical of the standard approach if stress and electric flux density are computed via the constitutive equations. To cure the trouble, an alternative recovery procedure is devised based on the consistency analysis. The procedure is variationally correct and reconstitutes in a consistent manner the distributions of stress and electric flux density. © 2002 Elsevier Science B.V. All rights reserved
Recovery of consistent stresses for compatible finite elements
No full textIn displacement based finite element models, stresses deduced directly from the constitutive relationship can show local erratic behaviour. This occurs in problems involving initial stresses or strains, or varying rigidities over the element domain, when local stresess do not meet a specific consistency requirement. In this context, an integrated procedure for recovering consisten stresses, that is stresses riddled of spurious outcomes, is proposed. The procedure is developed within a general weighted residual approach, suitably specialized for the purpose. The relationship between the proposed procedure and those based on the Hu-Washizu formulation is also elucidated. For illustration purpose, some numerical tests are included. © 2002 Elsevier Science B.V. All rights reserved
On the consistency of finite element models in thermoelastic analysis
No full textIn thermoelastic analysis, compatible finite elements may predict oscillating stresses if the temperature distribution is not coherent with the element strain coming from the assumed displacement approximation. Modelling the stress field as an independent variable could be a viable alternative to avoid these spurious outcomes. To this purpose, the behavior of mixed, hybrid stress and equilibrium finite element models in the presence of initial strains due to temperature is investigated and compared with the usually employed displacement approach. The consistency requirement for each model is established and the spurious outcomes due to inconsistent temperature fields are discussed, examining also the effects of element geometry distortions. The analysis, illustrated through some numerical tests, shows that a direct approximation for the stress field can eliminate, or at least reduce, the generation of spurious stress modes, although this is not a priori guaranteed by a mixed approach. © 2001 Elsevier Science B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Environmentally-induced loss of performance in FRP strengthening systems bonded to full-scale masonry structures
Full text linkThe issue of building materials deterioration due to environmental actions, which are expected to worsen in the future according to climate change predictions, is recognized as high-priority by the scientific community. However, the impact of material deterioration on the structural and seismic performances of masonry and historical structures strengthened with composites has not been investigated in detail, even though potentially significant. This paper aims to evaluate the environmentally-induced loss of performance in fiber reinforced polymer (FRP) strengthening systems bonded to masonry structures. An efficient damaging block-based modelling strategy, recently developed by the authors, is used to model masonry. FRP strips are originally introduced in the model and bonded to masonry blocks through a contact-based formulation with cohesion. This novel numerical approach is validated through FRP-strengthened masonry wall benchmarks. Numerical analyses are performed on FRP-strengthened in- and out-of-plane loaded masonry full-scale walls and houses with non-degraded material properties to predict the structural response at design conditions. Then, degraded material properties are deduced from accelerated ageing laboratory tests which investigated environmental degradation in FRP-strengthened masonry and are adopted in the same numerical analysis framework to predict the structural response at degraded conditions. Therefore, the environmentally-induced loss of performance in FRP strengthening systems bonded to masonry structures is deduced by comparing the structural response at degraded conditions with the one at design conditions
Prediction of flexural drift capacity in masonry walls through a nonlinear truss-based model
Full text linkIn this paper, the in-plane flexural drift capacity of masonry walls is numerically investigated. In particular, a nonlinear truss-based model is specifically developed to predict the monotonic response of in-plane horizontally-loaded masonry walls undergoing flexural failure, so that to investigate their deformation capacity. This novel modelling strategy assumes a band of nonlinear truss elements at the wall toe to account for flexural failure. The truss elements are supposed no-tension with plastic-softening behaviour in compression. This simple and original model is easily and fully characterizable by experimentally-based compressive stress–strain relationships available in the literature for different masonry types. The modelling strategy is validated against two different pier-scale experimental tests which experienced flexural failure. The model is then used to predict the flexural drift capacity of walls with different masonry types and geometrical features, subjected to a full-range of axial load ratios. As a result, drift capacity is found to nonlinearly decrease while increasing the axial load ratio, and to be sensibly dependent on the wall width (i.e. drift capacity diminishes while increasing wall width), for any masonry type. Finally, a simple analytic expression based on numerical results is deduced for the flexural drift capacity of masonry walls, function of axial load ratio, masonry type, and wall size. Accordingly, this analytic expression could be implemented in any structural analysis masonry-oriented commercial code to account for a consistent description of the flexural drift capacity of masonry walls
Sá de Miranda\'s classical comedy and the intertextual dialogue with its literary paradigms
No full textEsta dissertação tem como objetivo examinar o método de composição das comédias de Sá de Miranda e a maneira como o autor utilizou o processo de recriação poética denominado imitatio para promover o diálogo intertextual com seus paradigmas. Trata-se aqui de analisar intertextualmente textos gerados dentro de um contexto histórico-literário específico, em que o imitar era a regra. O autor tem como primeira intenção ao compor esse tipo de obra inserir-se numa tradição poética que aceita e pressupõe a alusão a textos precedentes, ou seja, uma tradição poética autônoma, em que as relações intertextuais se dão de maneira consciente e técnica e a obra de imitação resulta da reelaboração criativa de modelos. O primeiro capítulo vem situar a obra cômica mirandina no contexto histórico-cultural em que foi gerada. O segundo capítulo trata de imitatio e intertextualidade, estabelecendo terminologia e métodos para a análise intertextual, especificamente, de obras que têm a apropiação intencional de textos como princípio de criação literária. O terceiro capítulo apresenta um breve histórico do teatro latino, das origens até o surgimento da fabula palliata, adaptação latina da Comédia Nova Grega, que foi o modelo de comédia imitado pelos poetas renascentistas italianos, cujas obras se tornaram também paradigmas para o poeta português. O último capítulo é dedicado à análise intertextual das comédias de Sá de Miranda.The objective of this dissertation is to examine the method of composition of Sá de Miranda?s comedies and the way the author made use of the poetic recreation process denominated imitatio to promote the intertextual dialogue with their paradigms. It concerns to the intertextual analysis of texts produced within a specific historical and literary context in which imitating was the rule. The author who composes literary works under this rule has as his first intention to get into a poetic tradition which accepts and presupposes the alusion to preceding texts, i. e., an autonomous poetic tradition in which the intertextual relations take place in a conscious and technical manner and the work of imitation results of the creative re-elaboration of the patterns. The first chapter comes to situate Sá de Miranda?s comic work in the historical and cultural context in which it was generated. The second chapter deals with imitatio and intertextuality, establishing terminology and methodology for intertextual analysis of specifically literary works which have the intentional appropriation of texts as literary creation principle. The third chapter presents a brief history of the Roman theater, from its origins up to the arising of the fabula palliata, the Roman adaptation of the Greek New Comedy, which was the model of comedy imitated by the Italian poets of the Renaissance, whose works became paradigms to the Portuguese poet too. The last chapter is dedicated to the intertextual analysis of Sá de Miranda?s Comedy
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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