Cohesive crack approach to debonding analysis

Debonding of coatings from substrate due to coating compression occurs in many engineering applications. A simplified analytical approach for the estimation of the ultimate coating compression leading to debonding is developed in this paper, assuming an assigned out-of-plane defect of the coating. The formulation is based on the solution of a beam on a Pasternak (two parameters) elastic foundation, and on the assumption of a Mode I cohesive failure of the coating-substrate interface. The resulting formulas are simple and require the knowledge of a limited number of parameters

Damage modelling in concrete subject to sulfate attack

In this paper, we consider the mechanical effect of the sulfate attack on concrete. The durability analysis of concrete structures in contact to external sulfate solutions requires the definition of a proper diffusion-reaction model, for the computation of the varying sulfate concentration and of the consequent ettringite formation, coupled to a mechanical model for the prediction of swelling and material degradation. In this work, we make use of a two-ions formulation of the reactive-diffusion problem and we propose a bi-phase chemo-elastic damage model aimed to simulate the mechanical response of concrete and apt to be used in structural analyses

The geometrical nature of optical resonances : from a sphere to fused dimer nanoparticles

We study the electromagnetic response of smooth gold nanoparticles with shapes varying from a single sphere to two ellipsoids joined smoothly at their vertices. We show that the plasmonic resonance visible in the extinction and absorption cross sections shifts to longer wavelengths and eventually disappears as the mid-plane waist of the composite particle becomes narrower. This process corresponds to an increase of the numbers of internal and scattering modes that are mainly confined to the surface and coupled to the incident field. These modes strongly affect the near field, and therefore are of great importance in surface spectroscopy, but are almost undetectable in the far field

The prescribed mean curvature equation in weakly regular domains

We show that the characterization of existence and uniqueness up to vertical translations of solutions to the prescribed mean curvature equation, originally proved by Giusti in the smooth case, holds true for domains satisfying very mild regularity assumptions. Our results apply in particular to the non-parametric solutions of the capillary problem for perfectly wetting fluids in zero gravity. Among the essential tools used in the proofs, we mention a \textit{generalized Gauss-Green theorem} based on the construction of the weak normal trace of a vector field with bounded divergence, in the spirit of classical results due to Anzellotti, and a \textit{weak Young's law} for $(\Lambda,r_{0})$-minimizers of the perimeter.Comment: 23 pages, 1 figure --- The results on the weak normal trace of vector fields have been now extended and moved in a self-contained paper available at: arXiv:1708.0139

A systematic review and meta-analyses of pregnancy and fetal outcomes in women with multiple sclerosis: a contribution from the IMI2 ConcePTION project.

Neurologists managing women with Multiple Sclerosis (MS) need information about the safety of disease modifying drugs (DMDs) during pregnancy. However, this knowledge is limited. The present study aims to summarize previous studies by performing a systematic review and meta-analyses. The terms "multiple sclerosis" combined with DMDs of interest and a broad profile for pregnancy terms were used to search Embase and Medline databases to identify relevant studies published from January 2000 to July 2019.1260 studies were identified and ten studies met our inclusion criteria. Pooled risk ratios (RR) of pregnancy and birth outcomes in pregnancies exposed to DMDs compared to those not exposed were calculated using a random effects model. For spontaneous abortion RR = 1.14, 95% CI 0.99-1.32, for preterm births RR = 0.93, 95% CI 0.72-1.21 and for major congenital malformations RR = 0.86, 95% CI 0.47-1.56. The most common major congenital malformations reported in MS patients exposed to MS drugs were atrial septal defect (ASD) (N = 4), polydactyly (N = 4) and club foot (N = 3), which are among the most prevalent birth defects observed in the general population. In conclusion, interferons, glatiramer acetate or natalizumab, do not appear to increase the risk for spontaneous abortions, pre-term birth or major congenital malformations. There were very few patients included that were exposed to fingolimod, azathioprine and rituximab; therefore, these results cannot be generalized across drugs. Future studies including internal comparators are needed to enable treating physicians and their patients to decide on the best treatment options

New extended high temperature series for the N-vector spin models on three-dimensional bipartite lattices

High temperature expansions for the susceptibility and the second correlation moment of the classical N-vector model (O(N) symmetric Heisenberg model) on the sc and the bcc lattices are extended to order $\beta^{19}$ for arbitrary N. For N= 2,3,4.. we present revised estimates of the critical parameters from the newly computed coefficients.Comment: 11 pages, latex, no figures, to appear in Phys. Rev.

High-Temperature series for the RPn−1RP^{n-1} lattice spin model (generalized Maier-Saupe model of nematic liquid crystals) in two space dimensions and with general spin dimensionality n

High temperature series expansions of the spin-spin correlation functions of the RP^{n-1} spin model on the square lattice are computed through order beta^{8} for general spin dimensionality n. Tables are reported for the expansion coefficients of the energy per site, the susceptibility and the second correlation moment.Comment: 6 pages, revtex, IFUM 419/FT, 2 figures not include

Critical specific heats of the N-vector spin models on the sc and the bcc lattices

We have computed through order $\beta^{21}$ the high-temperature expansions for the nearest-neighbor spin correlation function $G(N,\beta)$ of the classical N-vector model, with general N, on the simple-cubic and on the body-centered-cubic lattices. For this model, also known in quantum field theory as the lattice O(N) nonlinear sigma model, we have presented in previous papers extended expansions of the susceptibility, of its second field derivative and of the second moment of the correlation function. Here we study the internal specific energy and the specific heat $C(N,\beta)$, obtaining new estimates of the critical parameters and therefore a more accurate direct test of the hyperscaling relation $d \nu(N)=2 - \alpha(N)$ on a range of values of the spin dimensionality N, including N=0 [the self-avoiding walk model], N=1 [the Ising spin 1/2 model], N=2 [the XY model], N=3 [the classical Heisenberg model]. By the newly extended series, we also compute the universal combination of critical amplitudes usually denoted by $R^+_{\xi}(N)$, in fair agreement with renormalization group estimates.Comment: 15 pages, latex, no figure

A regularized damage model for structural analyses of concrete dams in the presence of alkali-silica reaction

Alkali-silica reaction is a chemical phenomenon that affects concrete structures built some decades ago and subject to a very wet environment, e.g. dams. The starting point of this work is a bi-phase damage model present in the literature. In general, finite element solutions with damage models for material having a softening behaviuor exhibit a sensitivity to the element size and do not converge to physically meaningful solutions as the mesh is refined. In literature, some regularization techniques have been proposed and the fracture energy one has been implemented in the bi-phase chemo-damage model. The limit of this approach is that the solution remains mesh-dependent, so if the mesh is refined the damage localizes in a band of width fixed by the element size. In this work the nonlocal formulation of this damage model has been developed, validated with simple examples and applied to an existing concrete gravity dam, subject to service loading and affected by the ASR. A comparison between fracture energy regularization approach and nonlocal formulation is performed