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191.
Michele Zappalorto Paolo Lazzarin 《International Journal of Solids and Structures》2011,48(6):953-961
The paper deals with high order elastic singular terms at cracks and re-entrant corners (sharp V-notches), which are commonly omitted in linear elastic analyses by the argument that the strain energy and displacements in the near-tip region should be bounded. The present analysis proves that these terms are fully included in the elastic part of complete elastic–plastic stress and strain solutions.The intensities of high order singular terms are found to be linked to the linear elastic stress intensity factor and the extension of the plastic zone along the crack bisector line. The smaller the plastic radius, the smaller the intensities of high order singular terms are.A physical justification of the existence of high order singular terms is provided on the basis of the strain energy density distribution detected along the crack bisector line. Finally, the influence of the V-notch opening angle is made explicit, discussing also the relationship between the singularity orders and the solution of a Williams’ type sinusoidal eigen-equation. 相似文献
192.
The constitutive equation and the fatigue of anelastic media are described by using fractional order derivatives. The stress–strain
relation, based on a generalization of the Kelvin–Voigt model, describes typical hysteresis cycles with the stress increasing
as the number of cycles increases, a phenomenon known as cyclic hardening and observed in many materials such as, for instance,
steel. Criteria are established to find the number of cycles which may cause fatigue for a strain with a given amplitude and
frequency. They are based on the yield and fatigue stresses, on the melting temperature through the dissipated energy, and
on the strain energy. In all the cases, it is seen that the number of cycles to failure is inversely proportional to the amplitude
and to the frequency of the applied strain. Comparison to experimental data indicates that the model satisfies, at least qualitatively,
the behavior of real materials under cyclic loading. 相似文献
193.
Michele Benzi Eldad Haber Lauren Taralli 《Advances in Computational Mathematics》2011,35(2-4):149-173
We investigate the use of a preconditioning technique for solving linear systems of saddle point type arising from the application of an inexact Gauss?CNewton scheme to PDE-constrained optimization problems with a hyperbolic constraint. The preconditioner is of block triangular form and involves diagonal perturbations of the (approximate) Hessian to insure nonsingularity and an approximate Schur complement. We establish some properties of the preconditioned saddle point systems and we present the results of numerical experiments illustrating the performance of the preconditioner on a model problem motivated by image registration. 相似文献
194.
Raffaele Carlone Michele Correggi Lorenzo Tentarelli 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2019,36(1):257-294
We consider a two-dimensional nonlinear Schrödinger equation with concentrated nonlinearity. In both the focusing and defocusing case we prove local well-posedness, i.e., existence and uniqueness of the solution for short times, as well as energy and mass conservation. In addition, we prove that this implies global existence in the defocusing case, irrespective of the power of the nonlinearity, while in the focusing case blowing-up solutions may arise. 相似文献
195.
Michele Baglioni Giovanna Poggi David Chelazzi Piero Baglioni 《Molecules (Basel, Switzerland)》2021,26(13)
Cultural Heritage is a crucial socioeconomic resource; yet, recurring degradation processes endanger its preservation. Serendipitous approaches in restoration practice need to be replaced by systematically addressing conservation issues through the development of advanced materials for the preservation of the artifacts. In the last few decades, materials and colloid science have provided valid solutions to counteract degradation, and we report here the main highlights in the formulation and application of materials and methodologies for the cleaning, protection and consolidation of works of art. Several types of artifacts are addressed, from murals to canvas paintings, metal objects, and paper artworks, comprising both classic and modern/contemporary art. Systems, such as nanoparticles, gels, nanostructured cleaning fluids, composites, and other functional materials, are reviewed. Future perspectives are also commented, outlining open issues and trends in this challenging and exciting field. 相似文献
196.
197.
Michele Di Cristo Luca Rondi Sergio Vessella 《Annali di Matematica Pura ed Applicata》2006,185(2):223-255
We treat the stability issue for an inverse problem arising from non-destructive evaluation by thermal imaging. We consider
the determination of an unknown portion of the boundary of a thermic conducting body by overdetermined boundary data for a
parabolic initial-boundary value problem. We obtain that when the unknown part of the boundary is a priori known to be smooth,
the data are as regular as possible and all possible measurements are taken into account, the problem is exponentially ill-posed.
Then, we prove that a single measurement with some a priori information on the unknown part of the boundary and minimal assumptions
on the data, in particular on the thermal conductivity, is enough to have stable determination of the unknown boundary. Given
the exponential ill-posedness, the stability estimate obtained is optimal.
AMS 2000 Mathematics Subject Classification. Primary 35R30, Secondary 35B60, 33C90 相似文献
198.
The behaviour of an array of photonic crystal waveguides is numerically investigated. It is shown that high dispersion may
be achieved in the telecommunication window around 1550 nm, with a device whose dimensions are in the order of half a mm2. 相似文献
199.
We present the results of numerical experiments aimed at comparing two recently proposed sparse approximate inverse preconditioners
from the point of view of robustness, cost, and effectiveness. Results for a standard ILU preconditioner are also included.
The numerical experiments were carried out on a Cray C98 vector processor.
This work was partially supported by the GA AS CR under grant 2030706 and by the grant GA CR 205/96/0921. 相似文献