Liste des documents
Characterization of diatomitefrom Sig region (West Algeria)for industrial application
Diatomite also known Kieselguhr, is a non-metallic mineral composed of the skeletalremains of microscopic single-celled aquatic algae called diatoms. The purpose of this paper is to testand to evaluate the diatomite of Sig region (West Algeria) to substitute the main mould powder used incontinuous casting of steel for thermal insulation and lubrication.Design/methodology/approach – To assess the behavior of diatomite at different temperatures,a combination of simultaneous scanning calorimetric and thermogravimetric testing was used and toevaluate the structure of diatomite, the scanning microscopy method was applied.Findings – The results showed different endothermic and exothermic peaks, mainly at 84.7°C and783.5°C for endothermic peaks and 894.9°C for exothermic peak. The scanning microscopy methodwas used and a large porosity was observed. The trial industrial in continuous casting of steel showeda weak loss temperature of steel.Originality/value – This product may be used for thermal insulation in continuous casting of steel.Also the characterization showed the hot behavior of this product with the various transformationsand could give the possibility to other use Voir les détails
Mots clés : diatomite, fluorine, lubrication, Mould fluxes, thermal insulation
Evaluation and Chemical Analysis of Particulate Pollution in the Ironworks Site of El-Hadjar
The air that we breathe today is a mixture more or less polluted by location where we are. This mixture of pollutants generating significant and sustainable threats to human health, especially respiratory problems .The environmental concern is becoming increasingly strong, driven in particular by the current debate on sustainable development that is mirrored various international conferences [1] .Also theeffectson a global scale are warming the atmosphere and therefore the Earth, or the destruction of the ozone layer. The air quality management contributes to the mastery of a better knowledge of the pollution generated by the steel industrial activity. This investigation is the first national enterprise approach to the management of environmental problems on an industrial scale, more particularly in the steel sector. Taking into account these principles, it is appropriate to follow the pollution by suspended particles in and around the steel complex of El Hadjar.The objectives of this work are:Knowledge Of highest concentration level of dust inside and outside the workplace. Evaluation Compared to WHO limits values [2] and European Directives [3];[4]. Determination Of heavy metals in dust fallout.For the choice of measurement sites, a clipping entire surface of the steel complex was carried out by a method called mesh. This method we devoted 19 measurement sites. The sampling method used is that of BERGHEROFF. Indicators are the overall amount of dusts deposited chemical analysis elements such as Cr, Cu, Zn, Ni, Pb and Mn [4]. The quantities of dust are analytically weighed and then analyzed atomic absorption analytical chemistrySuspended particles that contaminate the air are the main carriers carry in the wind various polluting compounds (SO2, Cu, Pb, H2SO4, NH3 ...) [3]. At PMA 2, calculations show is discharged 4509 m3 per ton of fumes sinter. The results showed measurement sites S2, S3, S4, S5 and S18 are large emissions dusts. These sites except S18 represent the hot zone of complex. According Opair,the incidence of values of the measured dust on the sites is all above the limit value. For heavy metals in the dusts, there is a high concentration of zinc in all sites. Knowing that is neurotoxic and carcinogenic Pb is present in large quantities with a peak in S3. For S11 and S17 its value is close to the norm. The chromium and nickel both carcinogenic move in the same direction with alarming values. Voir les détails
Mots clés : Air pollution, dust emission, particulate fallout, TPS, method Bergeroff, heavy metals.
WAVELETS AND PRINCIPAL COMPONENT ANALYSIS METHOD FOR VIBRATION MONITORING OF ROTATING MACHINERY
Fault diagnosis is playing today a crucial role in industrial systems. To improve the reliability, safety and efficiency advanced monitoring methods become increasingly important for many systems. Vibration analysis method is essential in improving condition monitoring and fault diagnosis of rotating machinery. Effective utilization of the vibration signals depends upon the effectiveness of the applied signal processing techniques. In this paper, fault diagnosis is performed using a combination between Wavelet Transform (WT) and Principal Component Analysis (PCA). The WT is employed to decompose the vibration signal of measurements data in different frequency bands. The obtained decomposition levels are used as input to the PCA method for fault identification using respectively, the Q-statistic, it is also called Squared Prediction Error (SPE), and the Q-contribution. Clearly, useful information about the fault can be contained in some levels of wavelet decomposition. For this purpose, Q-contribution is used as an evaluation criterion to select the optimal level, which contains the maximum information. Associated to spectral analysis and envelope analysis, it allows clear visualization of fault frequencies. The objective of this method is to obtain the information contained in the measured data. The monitoring results using real sensor measurements from a pilot scale are presented and discussed. Voir les détails
Mots clés : vibration, Fault Diagnosis, Wavelet Analysis, principal component analysis, squared prediction error
First-principles investigation of the optical properties for rocksalt mixed metal oxide MgxZn1-xO
In this paper, we have presented a theoretical study of the optical properties for the cubic MgxZn1-xO(x = 0.0, 0.125, 0.375, 0.625, 0.875 and 1.0) alloys using the full-potential linearized augmented planewave (FP-LAPW) method based on the density functional theory (DFT). The local density approximation(LDA) was applied to calculate the structural properties. In order to explore the desired properties, the MgxZn1-xO alloys were modeled at various x compositions from 0.0 to 1.0 by step of 0.125. The recentlymodified semi-local Becke-Johnson potential with LDA correlation in the form of mBJ-LDA was used topredict the energy band gap, optical dielectric function, refractive index, absorption coefficient, reflectivity,optical conductivity and the electron energy loss of MgxZn1-xO alloys. The obtained results show good agreement with the experimental data, which indicate that the investigated ternary alloys areamong promising material for the fabrication of electronic, optoelectronic devices and their applications. Voir les détails
Mots clés : alloys, Electronic materials, Optical materials, Ab initio calculations, Band-structure
A Comparative Study of Various Methodsof Bearing Faults Diagnosis Using the CaseWestern Reserve University Data.
Bearing is probably one of the most criticalcomponents of rotating machinery. They are employed toguide and support the shafts in rotating machinery.Therefore, any fault in the bearings can lead to losses onthe level of production and equipments as well as potentiallyunsafe. For these reasons, the bearing fault diagnosishas received considerable attention from the research andengineering communities in recent years. The purpose ofthis study is to review the vibration analysis techniques andto explore their capabilities, advantages, and disadvantagein monitoring rolling element bearings. Voir les détails
Mots clés : Vibration analysis, bearing Fault diagnosis, Temporal analysis, Cepstrum analysis
Full-potential calculations of structural and optoelectronic properties of cubic indium gallium arsenide semiconductor alloys
In this work, the first-principle calculations have been performed to predict the structural,electronic and optical properties of cubic InxGa1−xAs for 0≤x≤1, using 16-atom within the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method based on Density Functional Theory (DFT) as implemented in WIEN2k computational code. The Local Density Approximation (LDA) and Wu–Cohen Generalized Gradient Approximation (WC–GGA)were employed as the exchange–correlation term to calculate the structural and electronic properties. Moreover, the Engel–Vosko GGA (EV-GGA) and the recently modified semi–local Becke–Johnson (mBJ) functional were also used to compute the electronic and optical properties in order to get some better degree of precision. The real and the imaginary parts ofthe dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient and optical conductivity were calculated to discuss the linear optical properties ofInxGa1−xAs alloys. The achieved results show a great potential utilization in optoelectronic devices especially in infrared applications. Voir les détails
Mots clés : Ab inition, DFT, Cubic, InxGa1-xAs alloys, structural parameters, Optoelectronic properties
Structural, electronic, optical and elastic properties of the complex K2PtCl6-structure hydrides ARuH6 (A = Mg, Ca, Sr and Ba): first-principles study
We report a systematic study of the structural, electronic, optical and elastic properties of the ternary ruthenium-based hydrides A2RuH6 (A = Mg, Ca, Sr and Ba) within two complementary first-principles approaches. We describe the properties of the A2RuH6 systems looking for trends on different properties as a function of the A sublattice. Our results are in agreement with experimental ones when the latter are available. In particular, our theoretical lattice parameters obtained using the GGA-PBEsol to include the exchange-correlation functional are in good agreement with experiment. Analysis of the calculated electronic band structure diagrams suggests that these hydrides are wide nearly direct band semiconductors, with a very slight deviation from the ideal direct-band gap behaviour and they are expected to have a poor hole-type electrical conductivity. The TB-mBJ potential has been used to correct the deficiency of the standard GGA for predicting the optoelectronic properties. The calculated TB-mBJ fundamental band gaps are about 3.53, 3.11, 2.99 and 2.68 eV for Mg2RuH6, Ca2RuH6, Sr2RuH6 and Ba2RuH6, respectively. Calculated density of states spectra demonstrates that the topmost valence bands consist of d orbitals of the Ru atoms, classifying these materials as d-type hydrides. Analysis of charge density maps tells that these systems can be classified as mixed ionic-covalent bonding materials. Optical spectra in a wide energy range from 0 to 30 eV have been provided and the origin of the observed peaks and structures has been assigned. Optical spectra in the visible range of solar spectrum suggest these hydrides for use as antireflection coatings. The single-crystal and polycrystalline elastic moduli and their related properties have been numerically estimated and analysed for the first time. Voir les détails
Mots clés : Ruthenium-based hydrides; first-principles calculations; elastic constants; optical properties; electronic
Adsorption of the copper in solution by the kaolin
The physico-chemical characterization showed that this adsorbent is mostly silica and alumina and. The specific surface area measured is more important for purified. The proposed disposal is in batch system. The results of investigations carried out show that the equilibrium is reached after 30 minutes. This sorption is maximum at 20°C, for stirring speed of 200 tr/min a size of between 150 and 200 µm and at pH 4. The maximum amount adsorbed at equilibrium per gram is 46.18 mg/g. The model of adsorption obeys to the Langmuir equation. The plot of the sorption isotherm is confirmed by the presence of a slow landing. The kinetics is pseudo first order. The external transport of metal ions considered in the solution towards the adsorbent seems a step controlling the overall speed of the process. Therefore internal transport in the pores is not the only mechanism limiting the kinetics of sorption. The probably other mechanisms involved. This adsorption is divided into two zones: a diffusion region and a kinetic area controlled by the reaction. The thermodynamic parameters show that the sorption is spontaneous (ΔG <0), exothermic (ΔH <0) and no changes have been made in its structure (ΔS <0). Measured activation energy is 24.45 kj/mol Voir les détails
Mots clés : Kaolin, copper, adsorption, water, depollution
Computer Code for Materials Diagnosis Using Monte CarloMethod and Neural Networks
Non-destructive testing (NDT) is a highlyvaluable technique in evaluation and evolution of materialsand products. X-ray imaging is an important NDT techniquethat is used widely in the metal industry in order tocontrol the quality of materials. Sometimes it may be difficultto get a measurement. The simulation of X-rayimaging is often performed using computer codes. Thispaper presents a new simulation method for materialsdiagnosis. The simulation is based primarily on the X-rayattenuation law and it is performed using a combinationbetween Monte Carlo method and multi-layer perceptronneural network. The main goal of the proposed method isto obtain more detailed information about the state of thematerials. Voir les détails
Mots clés : Non-Destructive testing, X-ray imaging, Materials diagnosis, Monte Carlo, Neural Network
Diagnosis and Detection of Eccentricity Faults in a Doubly-Fed Induction Generator
Doubly-fed induction generators are being used extensively in wind energy conversion systems. Efforts are being made to effectively adopt existing condition monitoring and fault diagnostic techniques for these systems. We consider in this paper to take account of the specificities and characteristics of the doubly-fed induction generator, for develop an analytical model that describes as precisely as possible the machine performance in healthy and machine with different eccentricity faults types. In this paper, we propose a method for the eccentricity diagnosis fault based on the stator current analysis during the start-up using this wavelet method enables faults eccentricity detection and isolation of this fault in rotor by analysing the frequency spectrum. This study showed that the application of this technique offered reliable and acceptable results for diagnosis detection and faults. Voir les détails
Mots clés : diagnosis, Detection, faults, doubly-fed indduction generator, eccentricity, modeling, simulation