Implementation of onboard watermarking for satellite images

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Implementation of onboard watermarking for satellite images.

Digital representation of data has many advantages over analogue formats; however these advantages present serious problems of copyright violation, illegal copying and distribution. Consequently, protection for multimedia distribution against piracy is needed. A part of the solution is to use a watermark indicating content owner or distribution route, which is transparently and robustly embedded into the material. The thesis presents work addressing specific issues of concern for satellite images. These include complexity of implementation and reversibility of the insertion as well as the obvious robustness issues. Methods have been defined and tested to reduce the complexity of finding appropriate insertion positions in DCT-based watermarking. However, to further reduce the implementation complexity, the final selected method is based on the fast Hadamard transform which has been shown to be suitable and robust. In addition, using predefined positions of insertion, the reversibility property is achieved. Finally, the hardware implementation of the above method is described; the simulations have proven that the hardware design has delivered the same functionality as the software algorithm. Most important is that we have demonstrated the feasibility of performing real time watermarking onboard satellites, using reconfigurable logic devices. The first hardware watermarking design for onboard micro satellite imaging system is presented. The design can be run at 50 Megapixels/second which will ensure the real time processing of the watermarking process with accordance of the process flow of the data handling payload

Influence des ajouts d'argiles gréseuses ou/et vaseuses sur les propriétés des matériaux cimentaires

Ce travail s'inscrit dans le cadre général de la valorisation des matériaux locaux, ayant pour intérêt l'amélioration des caractéristiques physico-chimiques et mécaniques des produits issus de la récupération entrant dans la confection des éléments de structures et de construction. Le but principal porte sur la valorisation des boues de dragage du barrage Ksob – Algérie. La vase et la marne argileuse rouge abondante dans la région, contiennent de la kaolinite et de l'illite. Ces argiles sont calcinées respectivement à 750 et 780 °C et mélangées au clinker afin d'étudier leurs influences sur les propriétés des matériaux cimentaires. Comparé à un ciment portland, on constate, avec chaque augmentation du taux d'ajout, une diminution dans le taux d'oxyde de calcium et une croissance du taux de silice. Les différents résultats des essais de compression montrent que le ciment type R10 présente une bonne résistance en compression, à 28 jours, elle est de l'ordre de 42 à 43 MPa, celle du ciment portland est de 44 MPa alors que, pour les bétons, les résistances en compression observées dépassent les 50 MPa. Ces résultats mettent en exergue l'influence des ajouts d'argiles gréseuses et vaseuses, sur les propriétés des matériaux cimentaires, montrant ainsi l'intérêt économique et environnemental de la substitution du clinker par les argiles calcinées

Antireflection Coating of TiO2_2 Study and Deposition by the Screen Printing Method

We are developing the Screen Printing technique for depositing a single layer quarter wavelength thick antireflection coating of titanium dioxide on silicon substrate. The ink is composed by the titanium ethoxide as the organometallic compound, terpineol as the solvent and the octyphenoxy polyethoxy as the vehicle. It has been applied to 4 inch polished silicon wafers, dried then fired and characterized. The objective of our work was to control the deposition parameters and the ink viscosity to determine their effects on the layer properties. The thicknesses of the TiO$_2$ films were measured by the stylus technique using a Profilometer. AES, RBS and X-Ray diffraction are used to analyse the layer and to determine its structure and composition according to firing temperatures. The reflection coefficient is measured as a function of the wavelength. As a result, we obtain TiO$_2$ coating thicknesses between 600 and 800 Å and a minimum reflection near 600nm