Publications Scientifiques

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    Gabriel graph-based connectivity and density for internal validity of clustering
    (Springer link, 2020) Boudane, Fatima; Berrichi, A.
    Clustering has an important role in data mining field. However, there is a large variety of clustering algorithms and each could generate quite different results depending on input parameters. In the research literature, several cluster validity indices have been proposed to evaluate clustering results and find the partition that best fits the input dataset. However, these validity indices may fail to achieve satisfactory results, especially in case of clusters with arbitrary shapes. In this paper, we propose a new cluster validity index for density-based, arbitrarily shaped clusters. Our new index is based on the density and connectivity relations extracted among the data points, based on the proximity graph, Gabriel graph. The incorporation of the connectivity and density relations allows achieving the best clustering results in the case of clusters with any shape, size or density. The experimental results on synthetic and real datasets, using the well-known neighborhood-based clustering (NBC) algorithm and the DBSCAN (density-based spatial clustering of applications with noise) algorithm, illustrate the superiority of the proposed index over some classical and recent indices and show its effectiveness for the evaluation of clustering algorithms and the selection of their appropriate parameters
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    Upper bounds for the forwarding indices of communication networks
    (Discrete Mathematics, 2004) El Haddad, M.; Manoussakis, Y.; Saad, R.
    The decision version of the forwarding index problem is, given a connected graph G and an integer ξ, to find a way of connecting each ordered pair of vertices by a path so that every vertex is an internal point of at most such paths. The optimization version of the problem is to find the smallest ξ for which a routing of this kind exists. Such a problem arises in the design of communication networks and distributed architectures. A model of parallel computation is represented by a network of processors, or machines processing and forwarding (synchronous) messages to each other, subject to physical constraints bearing on either the number of messages that can be processed by a single machine or the number of messages that can be sent through a connection. It was in this context that the problem was first introduced by Chung et al. (IEEE Trans. Inform. Theory 33 (1987) 224). The aim of this paper is to establish upper bounds for the optimal ξ as a function of the connectivity of the graph. © 2004 Published by Elsevier B.V
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    Properties of a hydrophone produced with porous PZT ceramic
    (2007) Boumchedda, K.; Hamadi, M.; Fantozzi, G.
    Interconnected piezoelectric porous ceramics PZT have been tested for possible use in hydrophone applications. These materials consisted of: (1) ceramics with fine porosity having pores from 50 to 100 μm and (2) cellular ceramics having cavities of the order of the millimeters. Porous ceramics are coated with flexible polymer standard polyurethane for the hydrostatics tests. The effect of the size of the pores and porous volume on the sensitivity of the sensor is studied and the performances of the hydrophones devices are presented