13 research outputs found
Leak identification in saturated unsteady flow via a Cauchy problem
No full textThis work is an initial study of a numerical method for identifying multiple leak zones in saturated unsteady flow. Using the conventional saturated groundwater flow equation, the leak identification problem is modelled as a Cauchy problem for the heat equation and the aim is to find the regions on the boundary of the solution domain where the solution vanishes, since leak zones correspond to null pressure values. This problem is ill-posed and to reconstruct the solution in a stable way, we therefore modify and employ an iterative regularizing method proposed in [1] and [2]. In this method, mixed well-posed problems obtained by changing the boundary conditions are solved for the heat operator as well as for its adjoint, to get a sequence of approximations to the original Cauchy problem. The mixed problems are solved using a Finite element method (FEM), and the numerical results indicate that the leak zones can be identified with the proposed method
On the characterizations of third-degree semiclassical forms via polynomial mappings
No full textThe aim of this contribution is the study of orthogonal polynomials via polynomial mappings in the framework of the third-degree semiclassical linear forms. Let u and v be two regular forms and let denote by {pn}n≥0 and {qn}n≥0 the corresponding sequences of monic orthogonal polynomials such that there exists a monic polynomial θm of degree m, with 0 ≤ m ≤ k − 1 and r ∈ C, in such a way (...)The work of the first author (Francisco Marcellán) has been supported by [grant number PGC2018-096504-B-C31] by FEDER/ Spanish Ministry of Science and Innovation – Agencia Estatal de Investigación (AEI) of Spain
Stability of Third Degree Linear Functionals and Rational Spectral Transformations
No full textIn this paper, we consider linear forms of the third degree class. This means that the Stieltjes function associated with the corresponding moment sequence satisfies a cubic equation with polynomial coefficients. We introduce the notion of a primitive triple of a strict third degree form. A simplification criterion of the corresponding cubic algebraic equation is given. Moreover, we show that the class of third degree linear forms is closed under rational spectral transformations. Several consequences of this fact are deduced. In particular, we illustrate with several examples the set of third degree linear forms is stable for the most standard algebraic operations in the linear space of linear forms.The work of the second author (Francisco Marcellán) has been supported by Agencia Estatal de Investigación (AEI) of Spain, grant PGC2018-096504-B-C31 and FEDER
Second Degree Linear Forms and Semiclassical Forms of Class One. A Case Study
No full textAbstract. Based on their second degree character, in this contribution we study new characterizations of families of symmetric and quasi-symmetric semiclassical linear forms of class one. In fact, by using the Stieltjes function and the moments of those forms, we give necessary and sufficient conditions for a regular form to be at the same time of the second degree, symmetric (resp. quasi-symmetric) and semiclassical of class one. We focus our attention on the link between these forms and the Jacobi forms Tp,q = J(p − 1/2, q − 1/2), p, q ∈ Z, p + q ≥ 0. All of them are rational transformations of the first kind Chebychev form T = J (−1/2, −1/2). Finally, we study a family of second degree linear forms which are semiclassical of class one and are not included in the above families.The work of the second author (Francisco Marcellán) has been supported by Agencia Estatal de Investigación (AEI) of Spain, grant PGC2018-096504-B-C31 and FEDER
Influence of the characteristics of the experimental data set used to identify anisotropy parameters
No full textThis work presents an investigation into the effect of the number and type of experimental
input data used in parameter identification of Hill’48, Barlat’91 (Yld91) and Cazacu and
Barlat’2001 (CB2001) yield criteria on the accuracy of the finite element simulation results.
Different sets of experimental data are used to identify the anisotropy parameters of two
metal sheets, exhibiting different anisotropic behaviour and hardening characteristics: a
mild steel (DC06) and an aluminium alloy (AA6016-T4). Although it has been shown that
the CB2001 yield criterion can lead to an accurate description of anisotropic behaviour of
metallic sheets, its calibration requires a large set of experimental input data. A calibration
procedure is proposed for CB2001 based on a reduced set of experimental data, i.e. where
the results are limited to three uniaxial tensile tests, combined with artificial data obtained
using the Barlat’91 yield criterion. Evaluation of the predictive capacity of the studied yield
criteria, calibrated using different sets of experimental data, is made by comparing finite
element simulation results with experimental results for the deep drawing of a crossshaped
part. A satisfying agreement is observed between experimental and numerical
thickness distributions, with a negligible effect of the number and type of experimental
data for the Hill’48 and Yld91 yield criteria. On the contrary, CB2001 calibration is quite
sensitive to the experimental data available, particularly biaxial values. Nevertheless,
CB2001 calibration based on the combination of effective and artificial experimental data
achieves satisfying results, which in the worst case are similar to the ones obtained with
the Yld91.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT)
via the projects PTDC/EMS-TEC/1805/2012 and PEst-C/EME/UI0285/2013 and by FEDER funds through the program
COMPETE – Programa Operacional Factores de Competitividade, under the project CENTRO-07-0224-FEDER-002001
(MT4MOBI). The first author is also grateful for the Post-Doc grant.info:eu-repo/semantics/publishedVersio
Mechanical characterization and constitutive parameter identification of anisotropic tubular materials for hydroforming applications
No full textThis paper aims to identify the constitutive parameters of anisotropic tubular materials and to verify the
accuracy of models' prediction. The identification of the constitutive parameters is based on information
obtained from tensile tests, performed on samples cut from the tubes, and from the free tubular bulge
test, using a home-developed bulge forming machine. Two tubular materials exhibiting different anisotropic
behaviour and work hardening characteristics are investigated: a mild steel S235 seamed tube
and an aluminium alloy AA6063 extruded tube. It is shown that advanced phenomenological yield
functions, including a large number of anisotropy parameters, can accurately describe the plastic flow of
highly anisotropic tubular materials during the tube hydroforming process. However, parameter identification
procedure of advanced yield criteria requires a high number of experimental tests. Thus, in
order to enable the parameter identification of these yield criteria when using a reduced set of experimental
results, the present study develops a method that combines tensile tests with (i) a free bulge test,
which is used to characterize the biaxial stress state experienced by the tube during the bulge testing,
and (ii) some generated artificial input data. Finally, the proposed method shows an excellent agreement
between numerical predictions and experimental results.The authors gratefully acknowledge the financial support of the
Portuguese Foundation for Science and Technology (FCT) via the
projects PTDC/EMS-TEC/1805/2012 and PEst-C/EME/UI0285/2013
and by FEDER funds through the program COMPETE – Programa
Operacional Factores de Competitividade, under the project CENTRO-07-0224-FEDER-002001
(MT4MOBI). The first author is also
grateful for the Post-Doc grant.info:eu-repo/semantics/publishedVersio
Nucleic Acids Res
No full textFragile X syndrome (FXS), the most common form of inherited intellectual disability, is caused by the silencing of the FMR1 gene encoding an RNA-binding protein (FMRP) mainly involved in translational control. We characterized the interaction between FMRP and the mRNA of GRK4, a member of the guanine nucleotide-binding protein (G protein)-coupled receptor kinase super-family, both in vitro and in vivo. While the mRNA level of GRK4 is unchanged in the absence or in the presence of FMRP in different regions of the brain, GRK4 protein level is increased in Fmr1-null cerebellum, suggesting that FMRP negatively modulates the expression of GRK4 at the translational level in this brain region. The C-terminal region of FMRP interacts with a domain of GRK4 mRNA, that we called G4RIF, that is folded in four stem loops. The SL1 stem loop of G4RIF is protected by FMRP and is part of the S1/S2 sub-domain that directs translation repression of a reporter mRNA by FMRP. These data confirm the role of the G4RIF/FMRP complex in translational regulation. Considering the role of GRK4 in GABAB receptors desensitization, our results suggest that an increased GRK4 levels in FXS might contribute to cerebellum-dependent phenotypes through a deregulated desensitization of GABAB receptors
Descriptive epidemiology of 30,223 histopathologically confirmed meningiomas in France: 2006–2015
No full textInternational audienc
