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Volume 03

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Polymer coated quartz crystal microbalance sensors for the detection of volatile organic compounds

In this work, plasma polymerization of tetraethoxysilane (TEOS) has been used for producing QCM chemical sensors. The sensor was exposed towards the methanol and chloroform molecules. The measured isotherms on modified QCM electrode
showed a good reproducibility and reversibility. Generally, the frequency shift (Δf) of QCM increases linearly with the vapor concentration. The evolution of sensor response showed clearly an improvement of the QCM sensibility. However, the film
elaborated from 50% of TEOS and 50% of O2 was found to be significantly more sensitive than film deposited from high proportion of oxygen due to dense structure. Concerning the selectivity, the results revealed a good affinity of the layer to methanol molecules. Fourier transform infrared spectroscopy (FTIR) analysis showed that VOCs molecules interact via hydrogen bonding due to the presence of the –OH group in the elaborated layers.

A comprehensive nonlinear model for GaAs MESFET transistor

An analytical two-dimensional (2D) model to accurately predict the channel potential and electric field distribution in sub-micron GaAs MESFET based on (2D) analytical solution of Poisson’s equation using superposition principle is presented. The results so obtained for current voltage characteristics, Transconductance and drain conductance, are presented and validated against both experimental I-V curves and various Models of the submicron MESFET GaAs. The model is then extended to predict the effects of parasitic resistances Rs and Rd, carriers mobility according to the electric fields and the edges effects on the performance. This model will allow more significant simulation of the component characteristics, with a precision improved for various conditions of Schottky barrier.

Detection of the Corrosion of Aluminium Alloy by Optical Method

The Speckle effect is a discipline with whole share. It is exploited in various scientific fields. On the application plan, it became a very powerful tool for the characterization and the non destructive testing. This technique which makes it possible to control and quantify in real time several parameters such as : the roughness of surface, the vibrations, the constraints, microphonedisplacements, the microstructure of surfaces, can be applied, at the same time, with the objects transparent and diffusing, solidor liquids. The development of flexible tools of capture of images to high resolution (camera CCD) coupled to information processing systems, nowadays makes the techniques speckle particularly important and interesting for industrial control. Ourwork consists in controlling qualitatively and quantitatively the variation thickness extracted the surface of the Duralumin sample (Aluminium alloy) immersed in a Salt water (to 3.5%), by using a camera CCD connected to a computer equipped with a software of image processing PRO-PLUS.

Downstream physico-chemical and bacteriological investigation of wastewater of Oued Athmania treatment plant

Wastewater treatment is a very important process that consists of applying modern and new technology to improve or upgrade the quality of a wastewater because its disposal whether by surface, subsurface methods or dilution, is dependent on its treatment. In the present work a full study has been carried out dealing with the physicochemical and bacteriological properties of wastewaters after being treated in Oued Athmania Wastewater Treatment Plant. The results revealed that the findings are in conformity with the international standards.

A new drain current I–V model for MESFET with submicron gate

In this work we present a new nonlinear approach for the calculation of the static characteristics of MESFET GaAs with submicron gate. First, we compare the results of the numerical simulations of the three main models for the MESFETs with submicron gate : Ahmed [1], Islam [2] and Memon [3] with experimental results. Then we propose a new approach that takes into account the surface states of the Schottky junction through a new mobility law for the determination of the output characteristics. The thermal effect is also represented in the mobility law. The comparison of our model with the three previous models referring to the experimental data shows that our approach gives the most accuracy result. Also, the proposed model can be used in the case of logic or analog circuits based on submicron GaAs MESFET.

New Approach to Modeling a planar flexible continuum robot simulating elephant trunkt

Research on the modeling of continuum robots is focused on ways to construct the geometric models, while maintaining maximum specificities and mechanical properties of the robot. This paper presents a new approach of geometric modeling of continuum planar multi- sections robots, assuming that each section is curved in a circular arc, while having inextensible central axis of the structure. The direct geometric model is calculated analytically, whereas the extreme points (used in calculating the inverse geometric model) of each section are calculated numerically using a particle swarm optimization (PSO) method. One advantage of this method is to simplify the mathematical calculations and transform the complex problem into a simple numerical function ; which allows the knowledge of the form of the central axis of the robot. Simulation examples using this method are carried to validate the proposed approach.

Effect of surfactants in the synthesis of NiO nanoparticles bycolloidal thermal assisted reflux condensation method

Nickel oxide (NiO) nanoparticles were prepared by colloidal thermal assisted reflux condensation method using nickel acetate (precursor salt) and N, N - Dimethylformamide - DMF (solvent) with or without the addition of surfactants such as cetyl trimethyl ammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and sodium monododecyl sulphate (SDS) respectively. Finally, the prepared samples products were calcined at different temperatures systematically such as at 200oC, 400oC, 600oC, 800oC for 2 hrs each to get the phase pure product. The calcined nanoparticles were characterized by X-Ray Diffraction (XRD), Energy Dispersive X-ray Analysis (EDAX), Fourier Transform Infrared (FTIR) Spectroscopy, Particle Size Analysis, Scanning Electron Microscopy (SEM), Diffuse Reflectance Spectroscopy (DRS) and Photo Luminescence (PL) Spectroscopy techniques. All the samples were crystallized in cubic structure. Effect of surfactants in the synthesis of nickel oxide (NiO) particles is discussed and reported.

Nd:Yag Laser Ablation of Recuperated and Industrial Aluminum Alloys. Study of Threshold Ablation

In this work, we used a nanosecond Nd : Yag laser (=532 nm) with a pulse duration of 15 ns, and an energy of 50 mJ and, therefore, we studied the threshold ablation of industrial aluminum alloy. The composition of the recuperated aluminum (% mass) is (72.02 Al, Si 13.05, 6.34 Zn, 4.28 O, 2.08 Mg, 1.75 Cu, 0.48 Ni) and the industrial aluminum is (83.10 Al, 1.66 Si, 4.12 Fe 2.17 O, 1.20 Mg, 5.47 Cu, 1.74 Mn, 1.79 Pb). For nanosecond lasers, the primary energy is lost by thermal diffusion in the irradiated target, because there is enough time to convert optical energy into thermal energy and heat spread. Fusion and / or evaporation may take place if the surface temperature exceeds the critical point when the energy of radiation is above the ablation threshold. The results shows that the threshold ablation of the recuperated aluminum is lower than that of the aluminum industry, it is about 5 J.cm-2 for the recovered aluminum and 10 J.cm-2 for the industrial aluminum. The threshold ablation is shifted towards the low values when the number of pulses increases.

Irradiance and temperature impact on thin film materials I-V curves

The thin-film solar cells are becoming increasingly used in various applications ; this is mainly due to the continued high cost of mono or polycrystalline silicon. In addition, the thin film technology offers the most diverse applications including uses low solar irradiance. The main fields of thin film solar cells are : the chain of amorphous silicon (a-Si), the chain of cadmium telluride (CdTe) and chalcopyrite sector (CIS and CIGS material). In this paper, a study on the influence of light and temperature on the characteristics I (V) of different thin film photovoltaic cells (a-Si:H single, a-Si:H tandem a-Si:H tripple, CdTe and CIS) is detailed. Under standard conditions (illumination of 1000W/m2 and cell temperature 25° C), we see that the CdTe is the closest that the monocrystalline silicon which has a maximum value of short circuit current material (3,26A).

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