Aperçu sur le système d’exploitation Linux et les logiciels libres

La 11ième école de Linux et les logiciels libres organisés par l’université Mouloud Mammeri de Tizi-Ouzou du 26 au 29 mars 2006 a permis de réunir autour de ce thème, les personnes utilisatrices du système d’exploitation Linux. Outre la vulgarisation de ce système, cette formation a pour objectif de promouvoir le système d’exploitation Linux et le concept de Logiciels libres dans la vie scientifique et économique. Cet article donne un aperçu sur le système Linux et les logiciels libres

Quantifying time-dependent structural and mechanical properties of UV-aged LDPE power cables insulations

This paper reports effects of ultraviolet (UV) light radiation on the physicochemical, electrical and mechanical properties of low-density polyethylene (LDPE) cable insulating materials. Changes in structural and morphological properties of UV-aged samples were characterized by various analytical methods such as attenuated total reflection Fourier transform infrared spectroscopy (ATRFTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Additionally, elongation at break, tensile strength, dielectric strength, and optical properties were also evaluated. Changes in some physical properties of LDPE after exposing to UV irradiation clearly highlighted that the polymer underwent the structural degradation. In addition, it was also found that such degradation yielded both crosslinking and chain scission as two competing processes during UV aging

Modelling the Formation of Periodic Nanostructures on Solid Surface Induced by Femtosecond Laser Ablation by Particle-In- Cell Method,

International audienc

Mesure et interprétation de spectres de lanthanides faiblement ionisés dans l'ultraviolet (cas du néodyme et du thulium)

Le spectre d émission d éléments de lanthanides ionisés est observé et mesuré sur des spectrographes en incidence normale dans l ultraviolet(70-275nm). Les récepteurs sont des plaques argentiques ou des écrans photostimulables. Pour le néodyme, les raies de Nd III, IV et V sont discriminées expérimentalement en faisant varier les conditions d excitation de l étincelle. L étude des configurations électroniques selon les méthodes de Racah-Slater au moyen des programmes de Cowan conduit à trouver les niveaux des ions libres Nd3+ et Nd4+. Les 41 niveaux de 4f3 (Nd IV) et les 12 niveaux de 4f2 (Nd V) sont interprétés paramétriquement en tenant compte des interactions de configuration au 3 ordre de perturbation électrostatique et au 2 ordre pour les interactions du spin (écart quadratique moyen = 1/13000 du domaine d énergie interprété). Pour Nd IV, on rapporte 1426 raies avec leur classification, et les probabilités de transition gA calculées. Pour la première fois, le rôle des configurations de cœur excité sur les transitions de résonance 4f N+1-4fN5d, via l interaction 5p64f N-15d-5p54f n5d, est mis en évidence. Les méthodes sont appliquée au spectre, totalement inconnu auparavant de Tm IV, pour lequel 760 raies sont classées et les probabilités de transitions calculées. Dans le cas de Nd V, la comparaison des intensités calculées à l ETL et observées conduit à une température effective Teff=3,6(3)eV dans l étincelle.The emission spectrum of lanthanide elements is observed an measured on normal incidence spectrographs (70-275nm). Argentic plates or phosphor image plates are used as receptors. In the case of neodymium, spark excitation conditions are varied to discriminate Nd III, IV and V spectral lines. The electronic configurations of the Cowan codes. The 41 levels of 4f3 (Nd IV) and 12 levels of 4f2(Nd V) are interpreted parametrically by taking into account the configuration interaction effects at the 3rd order of perturbation and all spin dependent effects at the 2nd order , with a root mean square deviation of 1/13000 of the interpreted energy range. In Nd IV, 1426 lines are reported with the combining levels, the calculated transition probabilities gA. For the first time the importance of the interaction 5p64f N-15d-5p54fN5d on the resonance transitions 4f N+1-4fN5d is evidenced. The same methods are applied to the formely unknown spectrum of Tm IV, that comprises now 760 classified lines (with calculated transition probabilities), involving 209 energy levels. In the case of Nd V, the comparison of ETL computed versus measured intensities leads to Teff=3,6(3)eV in the spark.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Electrical ageing effects on dielectric properties of polymethyl methacrylate

By combining the techniques of dielectric relaxation spectroscopy (DRS), measurement of both ac and dc conductivities, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), we have explored the effect of electrical ageing on poly (methyl methacrylate) (PMMA) films at temperature between 0 °C and 80 °C in the frequency range of 1 Hz–107 Hz. These results are discussed and correlated to FTIR and SEM observations

Numerical study of an efficient light focusing nano-coupler based on C-shaped waveguides

International audienceWe present an FDTD simulation study of a new design of light focusing nano-coupler consisting of a tapered succession of C-shaped silver waveguides. Its operation is based on the use of the fundamental guided mode <span class="mathjax-tex"&gt<span class="MathJax_Preview" style=""&gt</span&gt<span class="MathJax" id="MathJax-Element-1-Frame" tabindex="0" style="position: relative;" data-mathml="<math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt<mi&gtT</mi&gt<msub&gt<mi&gtE</mi&gt<mrow class=&quot;MJX-TeXAtom-ORD&quot;&gt<mn&gt10</mn&gt</mrow&gt</msub&gt</math&gt" role="presentation"&gt<nobr aria-hidden="true"&gt<span class="math" id="MathJax-Span-1" style="width: 2.455em; display: inline-block;"&gt<span style="display: inline-block; position: relative; width: 2.202em; height: 0px; font-size: 111%;"&gt<span style="position: absolute; clip: rect(1.422em, 1002.2em, 2.568em, -1000em); top: -2.252em; left: 0em;"&gt<span class="mrow" id="MathJax-Span-2"&gt<span class="mi" id="MathJax-Span-3" style="font-family: MathJax_Math; font-style: italic;"&gtT<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.12em;"&gt</span&gt</span&gt<span class="msubsup" id="MathJax-Span-4"&gt<span style="display: inline-block; position: relative; width: 1.52em; height: 0px;"&gt<span style="position: absolute; clip: rect(3.174em, 1000.76em, 4.154em, -1000em); top: -4.004em; left: 0em;"&gt<span class="mi" id="MathJax-Span-5" style="font-family: MathJax_Math; font-style: italic;"&gtE<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.026em;"&gt</span&gt</span&gt<span style="display: inline-block; width: 0px; height: 4.004em;"&gt</span&gt</span&gt<span style="position: absolute; top: -3.854em; left: 0.738em;"&gt<span class="texatom" id="MathJax-Span-6"&gt<span class="mrow" id="MathJax-Span-7"&gt<span class="mn" id="MathJax-Span-8" style="font-size: 70.7%; font-family: MathJax_Main;"&gt10</span&gt</span&gt</span&gt<span style="display: inline-block; width: 0px; height: 4.004em;"&gt</span&gt</span&gt</span&gt</span&gt</span&gt<span style="display: inline-block; width: 0px; height: 2.252em;"&gt</span&gt</span&gt</span&gt<span style="display: inline-block; overflow: hidden; vertical-align: -0.239em; border-left: 0px solid; width: 0px; height: 1.05em;"&gt</span&gt</span&gt</nobr&gt</span&gt</span&gt<span class="mathjax-tex"&gt</span&gt. Thanks to the optimization of the structural design parameters, we have demonstrated numerically that this compact coupler enables a sub-wavelength light focusing with a transmission coefficient of 65% and a coupling efficiency of 77% that have higher values than the optimized designs reported in the literature. We also show that our structure is an efficient functional coupler at multiple wavelengths when used in a periodic grating as well as an isolated device. This could pave the way for the development of a new generation of metamaterials for guidance and detection applications

Critical issues in XLPE-based polymer nanocomposites and their blends

Thanks to its excellent properties, cross-linked polyethylene (XLPE) is widely used in the insulation of medium and high voltage cables. However, under service conditions, the insulation of XLPE encounters several problems such as space charge accumulation, water trees, electrical trees, and partial discharges. Recently, research for cable insulating material has shown that nano-size filler added to XLPE may help reducing these problems. Currently, XLPE-based nanocomposites can be used as reliable insulation materials due to its excellent mechanical, thermal, and electrical properties. However, although it offers a number of advantages including its usage as insulator in power cables, some other issues remain to be addressed. In this chapter, the critical issues in XLPE-based nanocomposites are discussed. It includes significant tutorial elements as well as some analyses