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Search Results: 1 - 10 of 35 matches for " Libdry Belkhir "
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Police in the Islamic Maghreb
Libdry Belkhir
Historical Kan Periodical , 2010,
Abstract: " " . . . . . . . : . :
Quantum and Many-Body Effects on the Capacitance of a Quantum Dot
Lotfi Belkhir
Physics , 1994, DOI: 10.1103/PhysRevB.50.8885
Abstract: We calculate exactly, using finite size techniques, the quantum mechanical and many-body effects to the self-capacitance of a spherical quantum dot in the regime of extreme confinement, where the radius of the sphere is much smaller than the effective Bohr radius. We find that the self-capacitance oscillates as a function of the number of electrons close to its classical value. We also find that the electrostatic energy extrapolates to zero when $N=1$, suggesting that the energy scales like $e^{2}N(N-1)$. This establishes, at least for this configuration, that the semiclassical description of Coulomb charging effects in terms of capacitances holds to a good approximation even at very small scales.
The Star Height Hierarchy Vs. The Variable Hierarchy
Walid Belkhir
Computer Science , 2009,
Abstract: The star height hierarchy (resp. the variable hierarchy) results in classifying $\mu$-terms into classes according to the nested depth of fixed point operators (resp. to the number of bound variables). We prove, under some assumptions, that the variable hierarchy is a proper refinement of the star height hierarchy. We mean that the non collapse of the variable hierarchy implies the non collapse of the star height hierarchy. The proof relies on the combinatorial characterization of the two hierarchies.
Closure Under Minors of Undirected Entanglement
Walid Belkhir
Computer Science , 2009,
Abstract: Entanglement is a digraph complexity measure that origins in fixed-point theory. Its purpose is to count the nested depth of cycles in digraphs. In this paper we prove that the class of undirected graphs of entanglement at most $k$, for arbitrary fixed $k \in \mathbb{N}$, is closed under taking minors. Our proof relies on the game theoretic characterization of entanglement in terms of Robber and Cops games.
Undirected Graphs of Entanglement 3
Walid Belkhir
Computer Science , 2009,
Abstract: Entanglement is a complexity measure of digraphs that origins in fixed-point logics. Its combinatorial purpose is to measure the nested depth of cycles in digraphs. We address the problem of characterizing the structure of graphs of entanglement at most $k$. Only partial results are known so far: digraphs for $k=1$, and undirected graphs for $k=2$. In this paper we investigate the structure of undirected graphs for $k=3$. Our main tool is the so-called \emph{Tutte's decomposition} of 2-connected graphs into cycles and 3-connected components into a tree-like fashion. We shall give necessary conditions on Tutte's tree to be a tree decomposition of a 2-connected graph of entanglement 3.
From Causal Semantics To Duration Timed Models
Walid Belkhir
Computer Science , 2009,
Abstract: The interleaving semantics is not compatible with both action refinement and durational actions. Since many true concurrency semantics are congruent w.r.t. action refinement, notably the causality and the maximality ones, this has challenged us to study the dense time behavior - where the actions are of arbitrary fixed duration - within the causality semantics of Da Costa. We extend the causal transition systems with the clocks and the timed constraints, and thus we obtain an over class of timed automata where the actions need not to be atomic. We define a real time extension of the formal description technique CSP, called duration-CSP, by attributing the duration to actions. We give the operational timed causal semantics of duration-CSP as well as its denotational semantics over the class of timed causal transition systems. Afterwards, we prove that the two semantics are equivalent. Finally we extend the duration-CSP language with a refinement operator $\rho$ - that allows to replace an action with a process - and prove that it preserves the timed causal bisimulation.
A Service Discovery Approach Based on a Quantitative Similarity Measure for M-Tourism Platforms  [PDF]
Fay?al M’hamed Bouyakoub, Abdelkader Belkhir
Communications and Network (CN) , 2012, DOI: 10.4236/cn.2012.43027
Abstract: This paper presents a localization architecture for an m-tourism services delivery platform. The aim of the system is to deliver services for nomads (e-tourists) according to their localization and according to the results given by the search engine. This engine is based on a quantitative similarity measure. The discovered services are presented via a Web Map Service. Moreover, the platform integrates an adaptation sub-system for heterogeneous environments and an e-negotiation module.
DEVELOPPEMENT D’UN ATTENUATEUR DE LUMIERE BASE SUR DES REFLEXIONS VITREUSES
K. Ferria,N. Belkhir
Journal of Fundamental and Applied Sciences , 2012,
Abstract: The light intensity control of a luminous source is a very important operation in many optical applications. Several types of light attenuator exploiting different optical phenomena like diffraction, absorption, and reflection exist and they differ principally in the maximum attenuation rate, the control range, the sensitivity and the spectral band. In the presented work, we have developed and designed a light attenuator based on the progressive decrease of the transmitted light intensity, when it undergoes multiple vitreous reflections across eight plates glasses arranged in a roof shape. Several tests were carried out using a laser light as a source. We have shown that the attenuation rate can be controlled by the choice of the incidence angle on the glasses slides, in addition we have confirmed, for the case of perpendicular polarization of the laser light, that the attenuation obeys to a linear function. The obtained results are very close to those predicted theoretically.
Lazy AC-Pattern Matching for Rewriting
Walid Belkhir,Alain Giorgetti
Electronic Proceedings in Theoretical Computer Science , 2012, DOI: 10.4204/eptcs.82.3
Abstract: We define a lazy pattern-matching mechanism modulo associativity and commutativity. The solutions of a pattern-matching problem are stored in a lazy list composed of a first substitution at the head and a non-evaluated object that encodes the remaining computations. We integrate the lazy AC-matching in a strategy language: rewriting rule and strategy application produce a lazy list of terms.
From Cooper Pairs to Composite Bosons: A Generalized RPA Analysis of Collective Excitations
Lotfi Belkhir,Mohit Randeria
Physics , 1993, DOI: 10.1103/PhysRevB.49.6829
Abstract: The evolution of the ground state and the excitation spectrum of the two and three dimensional attractive Hubbard model is studied as the system evolves from a Cooper pair regime for weak attraction to a composite boson regime for a strong attraction.
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