Differential space–time modulation has been recently proposed in the literature for multiple-antenna systems over Rayleigh-fading channels, where neither the transmitter nor the receiver knows the fading coefficients. For the practical success of differential space–time modulation, it has been shown critical to design unitary space–time signal constellations with large diversity product which i...

Satellite constellations ooer interesting perspectives for Internet traac routing, since they beneet from a worldwide coverage and do not have the main drawback of geosynchronous satellites : propagation delay. However, because of their low altitude, LEO satellites are in constant motion and exhibit speciic issues for routing. This article presents a general architecture applicable to the integ...

The discipline of Information Systems is often viewed as a social science. research and teaching pertain to the management sociological issues computing field. It also includes programming systems analysis, design development. is, therefore, challenging plot on continuum disciplinary clusters. Depending viewpoint held scientific world, groups disciplines take different forms. Although metaphors...

an extended star is a tree which has only one vertex with degree larger than two. the -center problem in a graph  asks to find a subset  of the vertices of  of cardinality  such that the maximum weighted distances from  to all vertices is minimized. in this paper we consider the -center problem on the unweighted extended stars, and present some properties to find solution.

stars valley is one of the tourism areas in the qeshm island and is located at the southwest of qeshm city, south eastern corner of the island. sediments forming this unique landscape are not completely lithified and is composed of marl and marly limestone which is formed by erosional and weathering processes. deposits of stars valley contain diverse assemblages of echinoids, bivalves, gastropo...

The enumeration of transitive ordered factorizations of a given permutation is a combinatorial problem related to singularity theory. Let n > 1, m > 2, and let 0 be a permutation of Sn having di cycles of length i, for i > 1. We prove that the number of m-tuples (1 ; : : : ; m) of permutations of Sn such that: A one-to-one correspondence relates these m-tuples to some rooted planar maps, which ...

introduction: students in elementary schools due to the physical and behavioral characteristics more than adults have exposed to environmental hazards. this study was conducted to examine the environmental health and safety indices in girls' elementary schools in ilam city. materials and methods: this cross-sectional study was carried out via census sampling method in girls' elementar...