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The present work concerns the study of the great solar proton events during the solar cycle 23. For this purpose, the temporal behavior of six solar indices during these great events will be studied. These indices are the radio flux (10.7cm) intensity, the sunspot no., the sunspot area, the GEOS X-ray background flux intensity, and the intensity of the X-ray flares and optical flares.

The paper concerns on the satellite laser ranging (SLR) in Egypt. The three generations which can be loosely defined by their single shot root mean square precision, are discussed. The laser generators used at the Helwan half automatic and full automatic stations are described. The equipments used for the operation of the satellite laser ranging and their upgrading are presented. The observations carried out from Helwan-SLR stations are mentioned. The importance of the satellite laser ranging from Egypt and their contributions to the SLR network are explained. The modification requested for increasing the performance of the Helwan-SLR station is given. ª 2015 Production and hosting by Elsevier B.V. on behalf

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In different fields in space researches, Scientists are in need to deal with the product of matrices. In this paper, we develop conditions under which a product  of matrices chosen from a possibly infinite set of matricesThere exists a vector norm such that all matrices in M are no expansive with respect to this norm and also a subsequence of the sequence of nonnegative integers such that the corresponding sequence of operators converges to an operator which is paracontracting with respect to this norm. The continuity of the limit of the product of matrices as a function of the sequencesThe results are applied to the convergence of inner-outer iteration schemes for solving singular consistent linear systems of equations, where the outer splitting is regular and the inner splitting is weak regular.