Understanding the key parameters for the rational design of layered oxide materials by composite sol-gel procedures

Previous works have well demonstrated that particle size of the filler used in layered oxide formulation is the first important parameter and must be decreased below 5 μm (Agrafiotis, 1999-2000 [10]). But once the particle size is set what are the next formulation parameters to highlight as critical? How do we improve cohesion and adhesion of the coatings? To highlight the key parameters driving the quality of coating, a model layered oxide material was prepared inside a pan granulator. The model composite sol gel formulation is based on boehmite nanoparticles (binder) and amonomodal two micrometer grain size gamma alumina (filler) which is applied onto alpha alumina beads substrate. The influences of the wetting method and relative amount of filler and binderwere investigated. Extensive characterization and imaging of the layered materials (SEM, Cryo-SEM, EPMA, Washburn test, mechanical tests, Hg-porosimetry) were used in order to follow the microstructure evolution of coating during and at the end of drying. Several crack propagation schemes were observed and explained qualitatively. Overall quality of coating is mainly related to the sol-gel transition of the binder. It defines if prior to shaping, the binder primer will be able to improve the coating adhesion and it defines also the nature and extent of damages that the coating undergoes during drying. The mechanical properties of layered oxide materials obtained using composite sol-gel formulation are definitely correlated with the binder gel shrinkage during drying

ANALYSE LES PERFORMANCES D’UN SYSTÈME DS-OCDMA EN UTILISANT LES CODES OPTIQUE ORTHOGONAUX (OOC)

In a DS-OCDMA system, the MAI is one of the major limitations due to the unipolarity of the codes used. To mitigate the MAI, several techniques are developed for receptions eliminate the contribution of unwanted users. In this work, we studied the characteristics of correlations OOC codes, and we presented three structures of receptors that are well placed to estimate the information bits. For this, we have developed the theoretical BER expressions error probability

Optimum design and control of hydraulic systems driven by swash plate pumps using vibration based diagnosis

Swash plate pumps are widely used to drive hydraulic systems, especially because they offer high specific power. In order to improve their performance and make them more reliable, it is necessary to reduce the flow fluctuations, incorporate a control system that is more responsive, and minimize vibration levels. Furthermore, the flow should be controlled according to load requirements and pipe response at the design level. Moreover, there is a need to monitor the health of the system by analysing its vibration signatures. A novel port plate design is used with a pair of deep silencing grooves on the edges of delivery and suction ports, which reduces the flow fluctuations and improves the pump output. In addition to the load information, the pipe dynamics are also used as a control input. Hence, pipe instabilities with different boundary conditions are studied, where simple, accurate and comprehensive expressions to describe the pipe instabilities are produced, solved, and plotted. In swash plate pumps, the control unit changes the pump output according to the load requirements. The current pump design is equipped with a double negative feedback strategy. The inner loop controls the spool position, and the outer loop controls the swash plate angle. Since this design has a high rise time, it was suggested to equip the pump with a single feedback PD controller. Although this reduced the rise time, it introduced high levels of vibration. The present research proposes a new control strategy with a single feedback PID controller that minimizes vibration levels. Results are obtained experimentally. The control strategy is generalized to control the pump flow according to load requirements and pipe vibration levels. A compensation factor is introduced to moderate the negative impact of the pipe vibrations, and to generate a new set value for the inclination angle. For timely detection of faults, the application of wavelet analysis to detect different defects is examined. Some defects are produced, such as pipe flutter, pump dynamic instability, and voltage unbalance in the driving electric motor. Continuous wavelet and discrete wavelet analyses are used to analyze the vibration signature by using Debauches' mother wavelet. The data is collected experimentally. The results show that wavelet analysis is very efficient at identifying defects in the pipe or pump. The results are discussed and appropriate conclusions are drawn based on the present research. Suggestions for future extensions of the research are propose

Analyse Des réseaux De Bragg Superposés Pour l’encodage OCDMA. Utilisation Des Codes à Séquences premières

Cet article présente une nouvelle méthode de codage fréquentielle pour le CDMA optique à base de réseaux de Bragg superposés travaillant en réflexion. Des codes à séquences premières PS non cohérent, générées et décodées de manière « tout optique» par un composant spécifique. Le composant consiste en une succession de réseaux de Bragg inscrits sur une fibre optique à différentes longueurs d’onde et à des positions bien définis sur la fibre prédéfinie. L’ordre, ainsi que le choix des longueurs d’onde de ces réseaux de Bragg déterminent le code. La méthode des matrices de transfert a été retenue pour étudier et modéliser un réseau unique ou des réseaux superposés

STABILITE ELASTOPLASTIQUE DES BARRES COMPRIME-FLECHIES A IMPERFECTIONS INITIALES

La sédimentation des barrages dans les pays de l’Afrique du nord est très élevée et même spectaculaire. Elle est due directement aux forts taux d’érosion des bassins versants, dont les particules solides sont drainées directement par les cours d’eau et provoqueront à l’entrée des retenues des courants de densité. Cette sédimentation pose d’énormes problèmes à savoir ; la réduction de la capacité, l’obturation des organes de vidange, la sécurité de l’ouvrage, la sédimentation des canaux d’irrigation et elle a même un impact sur la qualité de l’eau

Modélisation des composants à base des réseaux de bragg particulier. Application: les lasers accordables

La principale fonction d’un réseau de Bragg est le filtrage. On peut le rencontrer dans les composants à base de fibres optiques ou bien à base de semi- conducteurs passifs ou actifs. Dans ce travail, on présente les principaux résultats obtenus lors de l’analyse des différents types de réseaux de Bragg par la méthode des modes couplés. Nous présentons par la suite le fonctionnement des DBR sont accordables. L’utilisation de réseaux de Bragg dans un laser permet d’obtenir des sources monomodes, agiles en longueur d’ondes. L’utilisation de réseau échantillonné permet d’augmenter la gamme d’accord

Class II phosphoinositide 3-kinase C2 beta regulates a novel signaling pathway involved in breast cancer progression

It is now well established that the enzymes phosphoinositide 3-kinases (PI3Ks) have a key role in the development and progression of many cancer types and indeed PI3Ks inhibitors are currently being tested in clinical trials. Although eight distinct PI3K isoforms exist, grouped into three classes, most of the evidence currently available are focused on one specific isoform with very little known about the potential role of the other members of this family in cancer. Here we demonstrate that the class II enzyme PI3K-C2β is overexpressed in several human breast cancer cell lines and in human breast cancer specimens. Our data indicate that PI3K-C2β regulates breast cancer cell growth in vitro and in vivo and that PI3K-C2β expression in breast tissues is correlated with the proliferative status of the tumor. Specifically we show that downregulation of PI3K-C2β in breast cancer cell lines reduces colony formation, induces cell cycle arrest and inhibits tumor growth, in particular in an estrogen-dependent in vivo xenograft. Investigation of the mechanism of the PI3K-C2β-dependent regulation of cell cycle progression and cell growth revealed that PI3K-C2β regulates cyclin B1 protein levels through modulation of microRNA miR-449a levels. Our data further demonstrate that downregulation of PI3K-C2β inhibits breast cancer cell invasion in vitro and breast cancer metastasis in vivo. Consistent with this, PI3K-C2β is highly expressed in lymph-nodes metastases compared to matching primary tumors. These data demonstrate that PI3K-C2β plays a pivotal role in breast cancer progression and in metastasis development. Our data indicate that PI3K-C2β may represent a key molecular switch that regulates a rate-limiting step in breast tumor progression and therefore it may be targeted to limit breast cancer spread