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Search Results: 1 - 10 of 9296 matches for " Ahmed Ayadi "
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Energy-Efficient and Reliable Transport Protocols for Wireless Sensor Networks: State-of-Art  [PDF]
Ahmed Ayadi
Wireless Sensor Network (WSN) , 2011, DOI: 10.4236/wsn.2011.33011
Abstract: New wireless sensor network applications (e.g., military surveillance) require higher reliability than a simple best effort service could provide. Classical reliable transport protocols like Transmission Control Protocol (TCP) are not well suited for wireless sensor networks due to both the characteristics of the network nodes (low computing power, strong energy constraints) and those of the main applications running on those nodes (low data rates). Recent researches present new transport protocols for wireless sensor networks providing various type of reliability and using new mechanisms for loss detection and recovery, and congestion control. This paper presents a survey on reliable transport protocol for WSNs.
Numerical solutions for a Timoshenko-type system with thermoelasticity with second sound
Ahmed Bchatnia,Makram Hamouda,Mohamed Ali Ayadi
Mathematics , 2015,
Abstract: In this work, we consider a nonlinear vibrating Timoshenko system with thermoelasticity with second sound. We recall first the results of well-posdness and regularity and the asymptotic behavior of the energy obtained in \cite{Ayadi}. Then, we use a fourth order finite difference scheme to compute the numerical solutions and thus we show the energy decay in several cases depending on the stability number. R\'esum\'e : Dans ce travail, on consid\`ere le syst\`eme de Timoshenko non-lin\'eaire avec Thermo-\'elasticit\'e et deuxi\`eme son. On rappelle d'abord les r\'esultats d'existence, de r\'egularit\'e et du comportement asymptotique de l'\'energie obtenus dans \cite{Ayadi}. Ensuite, on valide num\'eriquement ces r\'esultats th\'eoriques. Pour cela, on utilise une m\'ethode de diff\'erences finies d'ordre $4$. Ainsi la solution num\'erique obtenue permet de valider la d\'ecroissance de l'\'energie dans plusieurs cas selon la valeur du param\`etre de stabilit\'e.
TCP over low-power and lossy networks: tuning the segment size to minimize energy consumption
Ahmed Ayadi,Patrick Maillé,David Ros
Computer Science , 2010,
Abstract: Low-power and Lossy Networks (LLNs), like wireless networks based upon the IEEE 802.15.4 standard, have strong energy constraints, and are moreover subject to frequent transmission errors, not only due to congestion but also to collisions and to radio channel conditions. This paper introduces an analytical model to compute the total energy consumption in an LLN due to the TCP protocol. The model allows us to highlight some tradeoffs as regards the choice of the TCP maximum segment size, of the Forward Error Correction (FEC) redundancy ratio, and of the number of link-layer retransmissions, in order to minimize the total energy consumption.
Variation of chemical composition of essential oils in wild populations of Thymus algeriensis Boiss. et Reut., a North African endemic Species
Nacim Zouari, Imen Ayadi, Nahed Fakhfakh, Ahmed Rebai, Sami Zouari
Lipids in Health and Disease , 2012, DOI: 10.1186/1476-511x-11-28
Abstract: The essential oil composition of Thymus algeriensis was determined mainly by GC/FID and GC/MS. The chemical differentiation among populations performed on all compounds was assessed by linear discriminate analysis and cluster analysis based on Euclidean distance.A total of 71 compounds, representing 88.99 to 99.76% of the total oil, were identified. A significant effect of the population location on the chemical composition variability of T. algeriensis oil was observed. Only 18 out of 71 compounds showed a statistically significant variation among population locations and phenological stages. Chemical differentiation among populations was high. Minor compounds play an important role to distinguish between chemical groups. Five chemotypes according to the major compounds have been distinguished. Chemotypes distribution is linked to the population location and not to bioclimate, indicating that local selective environmental factors acted on the chemotype diversity.The major compounds at the species level were α-pinene (7.41-13.94%), 1,8-cineole (7.55-22.07%), cis-sabinene hydrate (0.10-12.95%), camphor (6.8-19.93%), 4-terpineol (1.55-11.86%), terpenyl acetate (0-14.92%) and viridiflorol (0-11.49%). Based on major compounds, the populations were represented by (α-pinene/1,8-cineole/cis-sabinene hydrate/camphor/viridiflorol), (1,8-cineole/camphor/terpenyl acetate), (α-pinene/1,8-cineole/camphor), (1,8-cineole/camphor/4-terpineol) and (α-pinene/1,8-cineole/cis-sabinene hydrate/camphor/4-terpineol) chemotypes. Variation of phenological stage did not have a statistically significant effect on the yield and metal chelating activity of the essential oil. These results can be used to investigate the geographical location and the harvesting time of this plant for relevant industries.In the last few years, there has been an increasing concern regarding the safety and potentially adverse effects of synthetic chemicals used for food preservation or in medicine. Therefore, the co
Molecular modeling of the TSR domain of R-spondin 4
Leila Ayadi
Bioinformation , 2008,
Abstract: R-spondin 4 is a secreted protein mainly associated with embryonic nail development. R-spondins have been recently identified as heparin-binding proteins with high affinity. Proteoglycan binding has been associated with both the TSR and the C terminal basic amino acid rich domains. In this paper, molecular modeling techniques were used to construct the model of R-spondin 4 TSR domain based on the structure of the F-spondin TSR domain 4 (30-40% sequence identity). Beside a positively charged surface in the TSR domain, presence of the basic amino acid rich domain which could forms a continuous heparin binding surface may explain the high affinity of R-spondins for heparin. Our results provide a framework for understanding the possible regulatory role of heparin in R-spondins signalling.
Technological and organizational preconditions to Internet Banking implementation: Case of a Tunisian bank
Achraf AYADI
Journal of Internet Banking and Commerce , 2006,
Abstract: This paper explores the importance of some prerequisite factors in developing Internet Banking (IB) services. According to the emergent case of Web services in the Tunisian banking sector, two types of preconditions are investigated: technological preconditions and organizational preconditions. Based on a case study, a set of qualitative and quantitative research methods were carried out beside the bank direction, the commercial staff and subscribed customers to IB services. The research illustrates that centralised architectures, fragmented Information Systems (IS), organizational rigidity and disregarding user's implication could be factors of slowness (or failure) in implementing IB.
Equipartition of energy for the wave equation associated to the Dunkl-Cherednik Laplacian
Fatma Ayadi
Mathematics , 2008,
Abstract: This paper is concerned with energy properties of the wave equation associated to the Dunkl-Cherednik Laplacian. We establish the conservation of the total energy, the strict equipartition of energy under suitable assumptions and the asymptotic equipartition in the general case.
Hypercyclic Abelian Affine Groups
Adlene Ayadi
Mathematics , 2010,
Abstract: In this paper, we give a characterization of hypercyclic abelian affine group G. If G is finitely generated, this characterization is explicit. We prove in particular that no abelian group generated by n affine maps on C^n has a dense orbit.
Semicircle Law for Random Matrices of Long-Range Percolation Model
Ayadi Slim
Mathematics , 2008,
Abstract: We study the normalized eigenvalue counting measure d\sigma of matrices of long-range percolation model. These are (2n+1)\times (2n+1) random real symmetric matrices H=\{H(i,j)\}_{i,j} whose elements are independent random variables taking zero value with probability 1-\psi [(i-j)/b], b\in \mathbb{R}^{+}, where \psi is an even positive function \psi(t)\le{1} vanishing at infinity. It is shown that if the third moment of \sqrt{b}H(i,j), i\leq{j} is uniformly bounded then the measure d\sigma:=d\sigma_{n,b} weakly converges in probability in the limit n,b\to\infty, b=o(n) to the semicircle (or Wigner) distribution. The proof uses the resolvent technique combined with the cumulant expansions method. We show that the normalized trace of resolvent g_{n,b}(z) converges in average and that the variance of g_{n,b}(z) vanishes. In the second part of the paper, we estimate the rate of decreasing of the variance of g_{n,b}(z), under further conditions on the moments of \sqrt{b}H(i,j), \ i\le{j}.
Asymptotic Properties of Random Matrices of Long-Range Percolation Model
Slim Ayadi
Mathematics , 2009,
Abstract: We study the spectral properties of matrices of long-range percolation model. These are N\times N random real symmetric matrices H=\{H(i,j)\}_{i,j} whose elements are independent random variables taking zero value with probability 1-\psi((i-j)/b), b\in \mathbb{R}^{+}, where $\psi$ is an even positive function with \psi(t)\le{1} and vanishing at infinity. We study the resolvent G(z)=(H-z)^{-1}, Imz\neq{0} in the limit N,b\to\infty, b=O(N^{\alpha}), 1/3<\alpha<1 and obtain the explicit expression T(z_{1},z_{2}) for the leading term of the correlation function of the normalized trace of resolvent g_{N,b}(z)=N^{-1}Tr G(z). We show that in the scaling limit of local correlations, this term leads to the expression (Nb)^{-1}T(\lambda+r_{1}/N+i0,\lambda+r_{2}/N-i0)= b^{-1}\sqrt{N}|r_{1}-r_{2}|^{-3/2}(1+o(1)) found earlier by other authors for band random matrix ensembles. This shows that the ratio $b^{2}/N$ is the correct scale for the eigenvalue density correlation function and that the ensemble we study and that of band random matrices belong to the same class of spectral universality.
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