Failure analysis of compressed earth block using numerical plastic damage model

In the last decade, several studies have been introduced to the development and use of compressed earth blocks in green building construction. Studying the evaluation of existing cracks in construction builders by these blocks is an important industrial and safety subject in recent research. This objective opens a new field in building construction where we describe the mechanical behavior of compressed earth solid blocks. In addition, we offer a solution to rupture damages presented by the propagation of masonry cracks. This paper aims to explore a numerical study in ABAQUS where we analyze the mechanical properties of this block. We started by investigating the elastic phase for this material and it has been generalized to a study in the plastic regime and rupture for the studied block. The different results of numerical simulation of the studied shape are presented, compared, and criticized

FANO resonances in solid-fluid one and two dimensional systems

The gaol of this paper is to demonstrate that the propagation of acoustic waves in a single slab made of a homogeneous one dimensional (1D) solid embedded in a fluid at oblique incidence on a slab made of two dimensional (2D) rectangular rods immersed in a fluid, can exhibit transmission zeros near resonances the so-called Fano resonances

Photonic Localization of Interface Modes at the Boundary between Metal and Fibonacci Quasi-Periodic Structure

We investigated on the interface modes in a heterostructure consisting of a semi-infinite metallic layer and a semi-infinite Fibonacci quasi-periodic structure. Various properties of the interface modes, such as their spatial localizations, self-similarities, and multifractal properties are studied. The interface modes decay exponentially in different ways and the modes in the lower stable gap possess highest spatial localization. A localization index is introduced to understand the localization properties of the interface modes. We found that the localization index of the interface modes in the upper stable gap will converge to two slightly different constants according to the parity of the Fibonacci generation. In addition, the localization-delocalization transition is also found in the interface modes of the transient gap.Comment: 20 pages, 5figure

Multifractal analysis of the electronic states in the Fibonacci superlattice under weak electric fields

Influence of the weak electric field on the electronic structure of the Fibonacci superlattice is considered. The electric field produces a nonlinear dynamics of the energy spectrum of the aperiodic superlattice. Mechanism of the nonlinearity is explained in terms of energy levels anticrossings. The multifractal formalism is applied to investigate the effect of weak electric field on the statistical properties of electronic eigenfunctions. It is shown that the applied electric field does not remove the multifractal character of the electronic eigenfunctions, and that the singularity spectrum remains non-parabolic, however with a modified shape. Changes of the distances between energy levels of neighbouring eigenstates lead to the changes of the inverse participation ratio of the corresponding eigenfunctions in the weak electric field. It is demonstrated, that the local minima of the inverse participation ratio in the vicinity of the anticrossings correspond to discontinuity of the first derivative of the difference between marginal values of the singularity strength. Analysis of the generalized dimension as a function of the electric field shows that the electric field correlates spatial fluctuations of the neighbouring electronic eigenfunction amplitudes in the vicinity of anticrossings, and the nonlinear character of the scaling exponent confirms multifractality of the corresponding electronic eigenfunctions.Comment: 10 pages, 9 figure

Transverse Acoustic Waves In Finite Piezoelectric-Metal Superlattices

In this communication, we study the propagation of transverse acoustic waves in a finite superlattice (SL) constituted of alternating piezoelectric and metal layers. Our objective is to determine: i) the transmission and reflection coefficients through a finite SL, ii) the confined modes related to the finite size of the SL and iii) the possibility of existence of the acoustic Brewster angle in these systems.In this communication, we study the propagation of transverse acoustic waves in a finite superlattice (SL) constituted of alternating piezoelectric and metal layers. Our objective is to determine: i) the transmission and reflection coefficients through a finite SL, ii) the confined modes related to the finite size of the SL and iii) the possibility of existence of the acoustic Brewster angle in these systems

Contribution à l'étude des structures phononiques et photoniques unidimensionnelles périodiques et quasi-périodiques (super-réseaux solide-fluide et guides monomodes)

Ce travail de thèse présente une contribution à l'étude de la propagation et la localisation des ondes acoustiques et électromagnétiques dans les cristaux phononiques et photoniques unidimensionnels. Notre intérêt a porté principalement sur la propagation des ondes acoustiques dans les matériaux multicouches périodiques de type solide-fluide et les ondes électromagnétiques dans les guides d'ondes monomodes quasipériodiques. L'objectif étant de chercher de nouveaux matériaux avec des bandes interdites larges et étudier l'effet de la présence des inhomogénéités (défaut) dans ces structures telles que : la surface libre, l'interface avec un substrat homogène ou l'existence d'une cavité. Ces résultats sont obtenus à partir d'un calcul analytique détaillé des fonctions de Green qui nous a permis de déterminer les relations de dispersion, les densités d'états locale et totale et les différents coefficients de transmission et de réflexion ainsi que les temps de phase correspondants. Dans le cas des ondes acoustiques de polarisation sagittale dans les super-réseaux solide-fluide, nous avons mis en évidence l'existence et le comportement des modes de surface et d'interface ainsi qu'une règle générale sur l'existence de ces modes. Aussi, nous avons montré que ces systèmes peuvent présenter des gaps omnidirectionnels qui réfléchissent les ondes quelque soit l'angle d'incidence (miroirs acoustiques) ainsi qu'une transmission sélective à travers les modes de défaut et d'interface (filtres acoustiques). Dans le cas des ondes électromagnétiques dans les guides d'ondes monomodes quasi-périodiques (de type Fibonacci) à base de câbles coaxiaux, nous avons mis en évidence certaines propriétés liées à ces systèmes telles que l'auto-similarité avec un facteur d'échelle dans le cas d'une seule séquence de Fibonacci. Aussi, II a été montré que ces systèmes peuvent présenter dans certaines régions de fréquences, des vitesses subluminiques et superluminiques. Dans le cas des séquences périodiques de Fibonacci, nous avons montré des propriétés liées aux bandes permises telles que la fragmentation des spectres de fréquences selon une loi en puissance ainsi que deux types de modes de surface. Les modes de volume et de surface dans ces structures peuvent présenter des comportements liés aux systèmes multifractals. Tous ces résultats sont obtenus à partir de la mesure de l'amplitude et la phase de la transmission à travers ces cristaux photoniques placés soit horizontalement entre deux guides soit verticalement sur un guide. Les résultats expérimentaux sont en bon accord avec les résultats théoriques.LILLE1-BU (590092102) / SudocSudocFranceF

A non-linear backstepping control of Permanent Magnet Synchronous Motor (PMSM)

In the industry, the permanent magnet synchronous motors are one of the most widely used motors and have superior performance compared to the other types of motors. The principal objective of this paper is to ameliorate the performance of PMSMs by implementing a robust non-linear backstepping control. The first part deals with the vector control of mechanical sensors using PI controller. In the second part, we shed the light on the non-linear backstepping control, using Lyapunov function, of PMSM from the point of view of stability and robustness. The results are validated by MALTAB/SIMULINK. The results obtained show the good stability and good dynamic of PMSM’s control by backstepping controller, also the PI is very sensitive to parameter’s machine variation compared with the backstepping controller

A non-linear backstepping control of Permanent Magnet Synchronous Motor (PMSM)

In the industry, the permanent magnet synchronous motors are one of the most widely used motors and have superior performance compared to the other types of motors. The principal objective of this paper is to ameliorate the performance of PMSMs by implementing a robust non-linear backstepping control. The first part deals with the vector control of mechanical sensors using PI controller. In the second part, we shed the light on the non-linear backstepping control, using Lyapunov function, of PMSM from the point of view of stability and robustness. The results are validated by MALTAB/SIMULINK. The results obtained show the good stability and good dynamic of PMSM’s control by backstepping controller, also the PI is very sensitive to parameter’s machine variation compared with the backstepping controller

Two types of modes in finite size one-dimensional coaxial photonic crystals : general rules and experimental evidence

We demonstrate analytically and experimentally the existence and behavior of two types of modes in finite size one-dimensional coaxial photonic crystals made of N cells with vanishing magnetic field on both sides. We highlight the existence of N−1 confined modes in each band and one mode by gap associated to either one or the other of the two surfaces surrounding the structure. The latter modes are independent of N. These results generalize our previous findings on the existence of surface modes in two semi-infinite superlattices obtained from the cleavage of an infinite superlattice between two cells. The analytical results are obtained by means of the Green’s function method, whereas the experiments are carried out using coaxial cables in the radio-frequency regime

Sagittal acoustic waves in finite solid-fluid superlattices: band-gap structure, surface and confined modes, and omnidirectional reflection and selective transmission

Using a Green’s function method, we present a comprehensive theoretical analysis of the propagation of sagittal acoustic waves in superlattices (SLs) made of alternating elastic solid and ideal fluid layers. This structure may exhibit very narrow pass bands separated by large stop bands. In comparison with solid-solid SLs, we show that the band gaps originate both from the periodicity of the system (Bragg-type gaps) and the transmission zeros induced by the presence of the solid layers immersed in the fluid. The width of the band gaps strongly depends on the thickness and the contrast between the elastic parameters of the two constituting layers. In addition to the usual crossing of subsequent bands, solid-fluid SLs may present a closing of the bands, giving rise to large gaps separated by flat bands for which the group velocity vanishes. Also, we give an analytical expression that relates the density of states and the transmission and reflection group delay times in finite-size systems embedded between two fluids. In particular, we show that the transmission zeros may give rise to a phase drop of π in the transmission phase, and therefore, a negative delta peak in the delay time when the absorption is taken into account in the system. A rule on the confined and surface modes in a finite SL made of N cells with free surfaces is demonstrated, namely, there are always N−1 modes in the allowed bands, whereas there is one and only one mode corresponding to each band gap. Finally, we present a theoretical analysis of the occurrence of omnidirectional reflection in a layered media made of alternating solid and fluid layers. We discuss the conditions for such a structure to exhibit total reflection of acoustic incident waves in a given frequency range for all incident angles. Also, we show how this structure can be used as an acoustic filter that may transmit selectively certain frequencies within the omnidirectional gaps. In particular, we show the possibility of filtering assisted either by cavity modes (in particular sharp Fano resonances) or by interface resonances