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Hajji M.,Institute Superieur Delectronique Et Of Communication Of Sfax
Applied Surface Science | Year: 2013

This paper presents a new method to produce porous silicon which derived from the conventional stain etching (SE) method. But instead of one etching step that leads to formation of porous layer, the substrate is subjected to an initial etching step with a duration Δt0 followed by a number of supplementary short steps that differs from a layer to another. The duration of the initial step is just the necessary time to have a homogenous porous layer on the whole surface of the substrate. It was found that this duration is largely dependent of the doping type and level of the silicon substrate. The duration of supplementary steps was kept as short as possible to prevent the formation of bubbles on the silicon surface during silicon dissolution which leads generally to inhomogeneous porous layers. It is found from surface investigation by atomic force microscopy (AFM) that multistep stain etching (MS-SE) method allows to produce homogeneous porous silicon nanostructures compared to the conventional SE method. The chemical composition of the obtained porous layers has been evaluated using Fourier transform infrared spectroscopy (FTIR). Photoluminescence (PL) measurement shows that porous layers produced by SE and MS-SE methods have comparable spectra indicating that those layers are composed of nanocrystallites with comparable sizes. But the intensity of photoluminescence of layer elaborated by MS-SE method is higher than that elaborated by the SE method. Total reflectance characteristics show that the presented method allows the production of porous silicon layers with controllable thicknesses and optical properties. Results for porous silicon layers elaborated on heavily doped n-type silicon show that the reflectance can be reduced to values less than 3% in the major part of the spectrum. © 2013 Elsevier B.V. All rights reserved.

Widlowski J.-L.,European Commission - Joint Research Center Ispra | Pinty B.,European Commission - Joint Research Center Ispra | Lopatka M.,European Commission - Joint Research Center Ispra | Atzberger C.,University of Natural Resources and Life Sciences, Vienna | And 18 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2013

The radiation transfer model intercomparison (RAMI) activity aims at assessing the reliability of physics-based radiative transfer (RT) models under controlled experimental conditions. RAMI focuses on computer simulation models that mimic the interactions of radiation with plant canopies. These models are increasingly used in the development of satellite retrieval algorithms for terrestrial essential climate variables (ECVs). Rather than applying ad hoc performance metrics, RAMI-IV makes use of existing ISO standards to enhance the rigor of its protocols evaluating the quality of RT models. ISO-13528 was developed "to determine the performance of individual laboratories for specific tests or measurements." More specifically, it aims to guarantee that measurement results fall within specified tolerance criteria from a known reference. Of particular interest to RAMI is that ISO-13528 provides guidelines for comparisons where the true value of the target quantity is unknown. In those cases, "truth" must be replaced by a reliable "conventional reference value" to enable absolute performance tests. This contribution will show, for the first time, how the ISO-13528 standard developed by the chemical and physical measurement communities can be applied to proficiency testing of computer simulation models. Step by step, the pre-screening of data, the identification of reference solutions, and the choice of proficiency statistics will be discussed and illustrated with simulation results from the RAMI-IV "abstract canopy" scenarios. Detailed performance statistics of the participating RT models will be provided and the role of the accuracy of the reference solutions as well as the choice of the tolerance criteria will be highlighted. Key Points ISO-13528 can be applied to the verification of computer simulation models. Model comparisons require detailed definitions on acceptable bias levels. Operator choices/errors are likely cause for most observed biases in RAMI-IV. ©2013. American Geophysical Union. All Rights Reserved.

Khalifa M.,Center de Biotechnologie de la Technopole de Borj-Cedria | Hajji M.,Center de Biotechnologie de la Technopole de Borj-Cedria | Hajji M.,Institute Superieur Delectronique Et Of Communication Of Sfax | Ezzaouia H.,Center de Biotechnologie de la Technopole de Borj-Cedria
Bulletin of Materials Science | Year: 2013

This work investigates the photothermal treatment of silica sand to reduce impurities to a low level suitable for the production of acceptable solar grade silicon for photovoltaic application. It describes experiment carried out by using a tungsten lamp furnace to purify silica under controlled atmosphere. This process enables to attract impurities to the surface of silica grains where they can be easily extracted by partial dissolution in an acid mixture. Thus obtained silica was investigated by inductively coupled plasma atomic emission spectrometry (ICP-AES) method. Major impurities present in silica sand were Al, K, Fe, Na, Ca, Mg and B. Among the new products, almost major impurities were removed effectively. Indeed purity degree, given by characterization of ICP-AES, passes from 99.76 to 99.96% and the average impurity removal efficiency is 83.33%. © 2013 Indian Academy of Sciences.

Degardin V.,Lille University of Science and Technology | Kilani K.,Institute Superieur Delectronique Et Of Communication Of Sfax | Kone L.,Lille University of Science and Technology | Lienard M.,Lille University of Science and Technology | Degauque P.,Lille University of Science and Technology
IEEE Transactions on Industrial Electronics | Year: 2014

In the aerospace domain, more electrical aircraft will have to face a drastic issue in the future, in relation to an increase in the number of wires and connectors, which impact weight and system reliability. A possible solution could be using power-line communications (PLC). In this paper, we focus our attention on the feasibility of communication between a pulsewidth modulation inverter and a motor, using a three-phase cable as a physical support for the data transmission, with a transmitting frequency band extending from 1 to 30 MHz. The required raw bit rate is on the order of 5 to 20 Mbits/s. Noise measurements, in both the time and frequency domains, were performed to extract the main characteristics of the impulsive noise generated by the inverter. Channel transfer functions were measured for an inductive coupling to the motor cable. A software tool simulating the communication link was developed, which is based on recent signal specifications for PLC. Furthermore, noise processing techniques are also proposed, to decrease the impact of the impulsive noise on the received signals. By introducing both the measured transfer functions and noise in the simulation tool, performances of the link, in terms of bit error rate, are presented. © 1982-2012 IEEE.

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