Some results on thermal stress of layered plates and shells by using Unified Formulation

This work presents some results on two-dimensional modelling of thermal stress problems in multilayered structures. The governing equations are written by referring to the Unified Formulation (UF) introduced by the first author. These equations are obtained in a compact form, that doesn't depend on the order of expansion of variables in the thickness direction or the variable description (layer-wise models and equivalent single layers models). Classical and refined theories based on the Principle of Virtual Displacements (PVD) and advanced mixed theories based on the Reissner Mixed Variational Theorem (RMVT) are both considered. As a result, a large variety of theories are derived and compared. The temperature profile along the thickness of the plate/shell is calculated by solving the Fourier's heat conduction equation. Alternatively, thermo-mechanical coupling problems can be considered, in which the thermal variation is influenced by mechanical loading. Exact closed-form solutions are provided for plates and shells, but also the applications of the Ritz method and the Finite Element Method (FEM) are presented

Submm-bright QSOs at z~2: signposts of co-evolution at high z

We have assembled a sample of 5 X-ray and submm-luminous z~2 QSOs which are therefore both growing their central black holes through accretion and forming stars copiously at a critical epoch. Hence, they are good laboratories to investigate the co-evolution of star formation and AGN. We have performed a preliminary analysis of the AGN and SF contributions to their UV-to-FIR SEDs, fitting them with simple direct (disk), reprocessed (torus) and star formation components. All three are required by the data and hence we confirm that these objects are undergoing strong star formation in their host galaxies at rates 500-2000 Msun/y. Estimates of their covering factors are between about 30 and 90%. In the future, we will assess the dependence of these results on the particular models used for the components and relate their observed properties to the intrinsice of the central engine and the SF material, as well as their relevance for AGN-galaxy coevolution.Comment: 6 pages, 2 figures, contributed talk to "Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation" November 6-8, 2012. MPIfR, Bonn, Germany. Po

Submm-bright X-ray absorbed QSOs at z~2: insights into the co-evolution of AGN and star-formation

We have assembled a sample of 5 X-ray-absorbed and submm-luminous type 1 QSOs at $z \sim 2$ which are simultaneously growing their central black holes through accretion and forming stars copiously. We present here the analysis of their rest-frame UV to submm Spectral Energy Distributions (SEDs), including new Herschel data. Both AGN (direct and reprocessed) and Star Formation (SF) emission are needed to model their SEDs. From the SEDs and their UV-optical spectra we have estimated the masses of their black holes $M_{BH}\sim 10^{9}-10^{10}\,M_{\odot}$, their intrinsic AGN bolometric luminosities $L_{BOL}\sim(0.8 - 20)\times 10^{13} L_{\odot}$, Eddington ratios $L_{BOL}/L_{Edd}\sim 0.1 - 1.1$ and bolometric corrections $L_{BOL}/L_{X,2-10}\sim 30 - 500$. These values are common among optically and X-ray-selected type 1 QSOs (except for RX~J1249), except for the bolometric corrections, which are higher. These objects show very high far-infrared luminosities $L_{FIR}\sim$ (2 - 8)$\times10^{12}\,M_{\odot}$ and Star Formation Rates SFR$\sim 1000 M_{\odot}/$y. From their $L_{FIR}$ and the shape of their FIR-submm emission we have estimated star-forming dust masses of $M_{DUST}\sim 10^9\,M_\odot$. We have found evidence of a tentative correlation between the gas column densities of the ionized absorbers detected in X-ray (N$_{H_{ion}}$) and $SFR$. Our computed black hole masses are amongst the most massive known.Comment: Accepted for publication in MNRAS, December 22, 2014, 17 pages, 5 figure

X-ray absorbed QSOs and the QSO evolutionary sequence

Unexpected in the AGN unified scheme, there exists a population of broad-line z~2 QSOs which have heavily absorbed X-ray spectra. These objects constitute 10% of the population at luminosities and redshifts characteristic of the main producers of QSO luminosity in the Universe. Our follow up observations in the submm show that these QSOs are often embedded in ultraluminous starburst galaxies, unlike most QSOs at the same redshifts and luminosities. The radically different star formation properties between the absorbed and unabsorbed QSOs implies that the X-ray absorption is unrelated to the torus invoked in AGN unification schemes. Instead, these results suggest that the objects represent a transitional phase in an evolutionary sequence relating the growth of massive black holes to the formation of galaxies. The most puzzling question about these objects has always been the nature of the X-ray absorber. We present our study of the X-ray absorbers based on deep (50-100ks) XMM-Newton spectroscopy. We show that the absorption is most likely due to a dense ionised wind driven by the QSO. This wind could be the mechanism by which the QSO terminates the star formation in the host galaxy, and ends the supply of accretion material, to produce the present day black hole/spheroid mass ratio.Comment: 4 pages, to appear in conference proceedings "Studying Galaxy Evolution with Spitzer and Herschel

Incubatori di impresa sociale, volano di sviluppo locale

L'articolo analizza le principali relazioni tra PA ed organizzazioni non profit, dedicando particolare attenzione al tema degli incubatori di impresa sociale. Dopo un confronto sulle principali esperienze a livello europeo e nazioanle gli autori esaminano le scelte strategiche, le logiche di funzionamento e le performance di Autopromozione sociale, incubatore di imprese sociali promosso dal Comune di Rom

Component-wise damage detection by neural networks and refined FEs training

Multilayer perceptrons are utilized in this work for vibration-based damage detection of multicomponent aerospace structures. A back-propagation algorithm is utilized along with Monte Carlo simulations and advanced structural theories for training Artificial Neural Networks (ANN’s), which are able to detect and classify local damages in structures given the natural frequencies and the associated vibrations modes. The latter ones are feed into the network in terms of Modal Assurance Criterion (MAC), which is a scalar representing the degree of consistency between undamaged and damaged modal vectors. Dataset and ANN training process is carried out by means of Carrera Unified Formulation (CUF), according to which refined finite elements with component-wise capabilities can be implemented in a hierarchical and unified manner. The proposed results demonstrate that CUF-trained ANNs can approximate complete mapping of the damage distribution, even in case of low damage intensities and local defects in localized components (stringers, spar caps, webs, etc.

Damage detection in composites by AI and high-order modelling surface-strain-displacement analysis

In the recent years, machine learning algorithms have been widely employed for structural health monitoring applications. As an example, Artificial Neu-ral Networks (ANN) could be useful in giving a precise and complete map-ping of damage distribution in a structure, including low-intensity or local-ized defects, which could be difficult to detected via traditional testing tech-niques. In this domain, Convolutional Neural Network (CNN) are employed in this work along with one-dimensional refined models based on the Carrera Unified formulation (CUF) for surface strain\displacement based damage detection in composite laminates. A layer-wise kinematic is adopted, while both an isotropic and orthotropic damage formulation is implemented. In de-tail, CUF-based finite element models have been exploited in combination with Monte Carlo simulations for the creation of a dataset of damage scenar-ios used for the training of the CNN. Therefore, the latter is fed with images of the strain or displacement field in a region of particular interest for each sample, which are subjected to the same boundary conditions. The trained ANN, given the strain\displacement mapping of an unknown structure, is therefore able to detect and classify all the damages within the structure, solving the so-called inverse problem

CUF-based Multiscale Analysis of Failure of Composite Laminates

The detection of failure onset and progression in composites requires the proper modeling of various mechanical behaviors at various scales. Furthermore, the necessity of virtual models of large structures and the nonlinear nature of failure demand computational efficiency without accuracy penalties. Over the last years, a set of modeling strategies based on refined structural theories has been developed via the Carrera Unified Formulation (CUF). Such developments range from Equivalent Single Layer (ESL) and Layer-Wise (LW) models for the macro- and mesoscale to the component-wise modeling of microscale. The computational efficiency and accuracy stem from the use of 1D or 2D models, node-dependent kinematics (NDK) and global-local strategies providing the complete 3D stress state necessary to capture failure in critical locations such as free-edges. The coupling with well-known models for micromechanics, progressive failure (including non-local methodologies based on peridynamics) and multiscale analyses led to promising outcomes with multifold reductions of computational times

Free vibration analysis of simply supported beams with solid and thin-walled cross-sections using higher-order theories based on displacement variables

Solutions for undamped free vibration of beams with solid and thin-walled cross-sections are provided by using refined theories based on displacement variables. In essence, higher-order displacement fields are developed by using the Carrera unified formulation (CUF), and by discretizing the cross-section kinematics with bilinear, cubic and fourth-order Lagrange polynomials. Subsequently, the differential equations of motion and the natural boundary conditions are formulated in terms of fundamental nuclei by using CUF and the strong form of the principle of virtual displacements. The second-order system of ordinary differential equations is then reduced into a classical eigenvalue problem by assuming simply supported boundary conditions. The proposed methodology is extensively assessed for different solid and thin-walled metallic beam structures and the results are compared with those appeared in published literature and also checked by finite element solutions. The research demonstrates that: (i) the innovative 1D closed form CUF represents a reliable and compact method to develop refined beam models with solely displacement variables; (ii) 3D-like numerically exact solutions of complex structures can be obtained with ease; and (iii) the numerical efficiency of the present method is uniquely robust when compared to other methods that provide similar accuracies