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Benmouiza K.,Abou Bekr Belkaid University Tlemcen | Cheknane A.,University of Laghouat
Energy Conversion and Management | Year: 2013

In this paper, we review our work for forecasting hourly global horizontal solar radiation based on the combination of unsupervised k-means clustering algorithm and artificial neural networks (ANN). k-Means algorithm focused on extracting useful information from the data with the aim of modeling the time series behavior and find patterns of the input space by clustering the data. On the other hand, nonlinear autoregressive (NAR) neural networks are powerful computational models for modeling and forecasting nonlinear time series. Taking the advantage of both methods, a new method was proposed combining k-means algorithm and NAR network to provide better forecasting results. © 2013 Elsevier Ltd. All rights reserved. Source


Houari A.,Abou Bekr Belkaid University Tlemcen
European Journal of Physics | Year: 2013

In this paper, using the Lambert W function, I derive closed-form analytical expressions for the decay constant of an exponentially decaying process and the time constant of a process subject to a linear resistive force. Similarly, I derive closed-form analytical formulae for the electrical resistivity of a metal and the temperature of a thermionic emitter material. Besides their theoretical importance, the results obtained will be of interest to teachers involved in undergraduate physics experiments. © 2013 IOP Publishing Ltd. Source


Houari A.,Abou Bekr Belkaid University Tlemcen
European Journal of Physics | Year: 2013

I show that one can obtain an exact analytical expression for the viscosity of a liquid by solving the equation of motion for a spherical ball falling through it. I also deduce an approximate analytical relationship suitable for an experimental determination of the viscosity of liquids. © 2013 IOP Publishing Ltd. Source


Houmat A.,Abou Bekr Belkaid University Tlemcen
Composite Structures | Year: 2012

The geometrically nonlinear free vibration of a composite rectangular plate with variable fiber spacing is investigated. The investigation is limited to a single ply composite having straight and parallel fibers. The fibers are distributed more densely in the central region where high stiffness is needed than in other regions. The assumptions of von Karman's nonlinear thin plate theory are made. The problem is solved numerically using the hierarchical finite element method. The nonlinear equations of free motion are mapped from the time domain to the frequency domain using the harmonic balance method. The resultant nonlinear equations are solved iteratively using the linearized updated mode method. Results for the fundamental linear and nonlinear frequencies are obtained for simply supported and clamped composite square plates with three variable distributions of E-Glass, Graphite, and Boron fibers in Epoxy matrices. The efficiency of the hierarchical finite element procedure is demonstrated through convergence and comparison with published data. The variable fiber spacing, fiber volume fraction, type of fiber material, and boundary conditions are shown to influence the hardening behavior. © 2012 Elsevier Ltd. Source


Houmat A.,Abou Bekr Belkaid University Tlemcen
Composite Structures | Year: 2013

The geometrically nonlinear free vibration of laminated composite rectangular plates with curvilinear fibers is investigated. The assumptions of Von Kármán's nonlinear thin plate theory are made. The problem is solved numerically using the hierarchical finite element method. The nonlinear equations of free motion are mapped from the time domain to the frequency domain using the harmonic balance method. The resultant nonlinear equations are solved iteratively using the linearized updated mode method. Results for the fundamental linear and nonlinear frequencies and associated mode shapes are obtained for fully clamped laminated composite square plates composed of shifted curvilinear fibers. The efficiency and accuracy of the hierarchical finite element technique is demonstrated through convergence and comparison studies. Contour plots of fundamental linear and nonlinear frequencies as a function of fiber orientation angles are presented. The fiber orientation angles and layup sequence are shown to affect the degree of hardening and mode shapes. © 2013 Elsevier Ltd. Source

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