Real time prelocalization of underground single-phase cable insulation failure by using the sheath behavior at fault point

This article presents a prelocalization approach of insulation faults affecting single-phase cables by using electrical measurements of voltage and current available in one substation. This approach is based on the theory of distributed parameters for modeling the faults to the ground. The specificity of this approach is the introduction of a resistance modeling the sheath-ground insulation allowing us to study the various types of faults to the ground (frankly and resistive). The fault distance and resistances are determined by two methods numerical and analytical. Many fault scenarios applied to the 150 kV underground cable connecting HTB sub-stations of Tyna-Taparoura-Sidimansour in Sfax, show a good agreement between the two methods. A simulation of the global system using the software Simulink-SimPowerSystems of Matlab is carried out giving us the voltages and currents on the source side necessary to the execution of the developed methods and the validation of the obtained results.     

Detoxification of Tunisian landfill leachates by selected fungi

Young landfill leachates (LFL) collected from Djebel Chekir (Tunisia) discharge area were found to be highly loaded with organic matter, ammonia, salts, heavy metals, phenols and hydrocarbons. Despite the possibility of their biodegradability, they represent a threat to the environment and show some resistance to conventional wastewater treatment processes. For these reasons, this study attempted to develop a biological process for the treatment of LFL using selected strains of Trametes trogii, Phanerochaete chrysosporium, Lentinus tigrinus and Aspergillus niger. Experiments were undertaken at different concentrations of the effluent up to 100%. COD removal efficiencies for P. chrysosporium, T. trogii and L. tigrinus were of 68, 79 and 90%, respectively, when LFL underwent a two-fold dilution. COD abatements were accompanied with an important enzyme secretion and a high reduction in the toxicity, expressed as percent bioluminescence inhibition (%BI < 20%). Above 50% of LFL, the effluent was toxic to these strains and caused growth inhibition indicating the sensitivity of these strains to concentrated LFL. Comparatively to the other tested strains, A. niger showed to tolerate raw LFL since it grew at 100% of LFL. However, this strain is inefficient in removing phenols and hydrocarbons. Consequently, toxicity abatement was very low (%BI > 70%).     

Reduction of petroleum hydrocarbons content from an engine oil refinery wastewater using a continuous stirred tank reactor monitored by spectrometry tools

BACKROUND: Hydrocarbon contamination of groundwater resources has become a major environmental and human health concern in many parts of the world. Microbial degradation of hydrocarbons, through either naturally occurring processes or engineered systems, has been successfully used to reduce concentrations of these pollutants. In order to develop an aerobic bioreactor tailored for this purpose, the present study aims to investigate petroleum contaminated wastewater remediation and toxicity reduction by acclimated microbial consortium enriched in a continuous stirred tank bioreactor (CSTR). Characterization and quantification of refinery wastewater components were performed by gas chromatography mass spectrometry (GC/MS) and Fourier transform infrared (FTIR) spectroscopy. RESULTS: The petroleum hydrocarbons were significantly degraded (97%) by the microbial consortium. After continuous aerobic treatment in the CSTR, the COD_effluent and BOD_5effluent average removals were high reaching 97% and 78%, respectively. Also, strong degradation of C10? C35 n‐alkanes was observed. The concomitant use of GC/MS and FTIR proved to be a useful complementary tool to assess the impact of treatment strategies on hydrocarbon‐contaminated wastewater. In addition, the toxicity of the contaminated wastewater decreased drastically after bioremediation. CONCLUSION: This work shows the ability of this consortium to degrade hydrocarbons and reduce toxicity, which makes them useful candidates for environmental restoration applications at other hydrocarbon‐contaminated environments. Copyright © 2011 Society of Chemical Industry     

Influence of fractures and karstification on the development of a quarry at Jebel Feriana,Tunisia

At Jebel Feriana in western Tunisia the Maastrichtian limestones are particularly white and hence have been exploited for dimension stone, glass, paint and pharmaceutical products. The paper assesses the geometry of the discontinuities in the quarry and proposes an exploitation plan for the future development of this quarry, which is only 1 km from the town of Feriana. The white limestones have experienced significant karstification, particularly along fractures trending N60° and N90°. This karstification is not only significant in the quarry development, mainly its influence on air pressures during blasting, but is also important when the site is considered as a potential landfill.      

A new elaboration concept of polypropylene/unmodified Montmorillonite nanocomposites by reactive extrusion based on direct injection of polypropylene aqueous suspensions

Nanocomposites based on polypropylene (PP) and unmodified Montmorillonite were prepared using a novel elaboration route based on a water‐assisted extrusion process. Unmodified Montmorillonite, high shear compounding together with injection of aqueous suspension and reactive processing technology were used. Different aqueous suspensions containing cationic or anionic surfactants, and a compatibilizer (PP‐g‐MA) were injected during extrusion to promote clay dispersion. For a comparison purpose, a commercial PP/clay masterbatch was melt mixed to PP. Structural, morphological, and rheological characterizations indicate clearly that the cationic suspensions ease the dispersion of clay platelets in the PP matrix. No full exfoliation is, however, obtained, and the system remains still less homogeneous than the nanocomposite based on the commercial masterbatch. Nevertheless, mechanical and thermal characterizations of the nanocomposites based on cationic surfactants demonstrate the efficiency to disperse clay in the polymer matrix, and the effect on the ductility compared to usual PP nanocomposites is promising. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Improved fuzzy sliding mode control for a class of MIMO nonlinear uncertain and perturbed systems

In this paper, a stable adaptive fuzzy sliding mode based tracking control is developed for a class of nonlinear MIMO systems that are represented by input output models involving system uncertainties and external disturbances. The main contribution of the proposed method is that the structure of the controller system is partially unknown and does not require the bounds of uncertainties and disturbance to be known. First, a fuzzy logic system is designed to estimate the unknown function. Secondly, in order to eliminate the chattering phenomenon brought by the conventional variable structure control, the signum function is replaced by an adaptive Proportional Derivative (PD) term in the proposed approach. All parameter adaptive laws and robustifying control terms are derived based on Lyapunov stability analysis, so that convergence to zero of tracking errors and boudedness of all signals in the closed-loop system can be guaranteed. Finally, a mass-spring-damper system is simulated to demonstrate the validity and the effectiveness of the proposed controller.     

Crystal structure and characterization of [2,5-(CH3O)2C6H3NH3]4P4O12·2H2O

The preparation, crystal structure, TG–DTA analysis and spectroscopy investigation are reported for the 2,5-dimethoxy phenyl ammonium cyclotetraphosphate dihydrate [2,5-(CH₃O)₂C₆H₃NH₃]₄P₄O₁₂·2H₂O. This new compound is triclinic P with unit cell dimensions: a = 7.438(5) Å, b = 11.841(7) Å, c = 12.354(4) Å,  = 96.61(4)°, β = 98.35(4)°, γ = 102.60(6)°, Z = 1 and V = 1038.0(1) Å³. Its crystal structure has been determined and refined to R = 0.049, with 5128 independant reflections. The structure can be described by rows of P₄O₁₂ ring anions along the a axis; between these rows are located the organic groups, connected to them by hydrogen bonds.     

Numerical and experimental study on the flow history effects of axial flow on the Couette–Taylor flow

In this research, experimental and numerical techniques are used to study the flow history effects of axial flow on the Couette–Taylor flow. For the experimental investigation, the flow is visualized using the PIV technique with reflective particles with a density of 1.62 g/cm³. Dispersed in a solution, the particles have a strong refraction index equal to 1.85. In this study, two protocols are adopted to study the effect of an axial flow superimposed on a Couette–Taylor flow, and of the history of the flow. The first one, the direct protocol, consists of imposing an azimuthal flow to the inner cylinder. In this case, when the regime is established, the axial flow is superimposed. The second protocol, the inverse protocol, consists of imposing first the axial flow in the gap of the system, after which an azimuthal flow is conveyed. The Couette–Taylor flow with axial flow is strongly dependent on the flow history (the protocol). Thus, the flow structures and development for different protocols are studied and analyzed here experimentally and numerically. In addition, from the numerical results, mathematical models for the two protocols are presented. For the direct protocol, a new relation between the axial Reynolds number, which stabilizes the Couette–Taylor flow, and the Taylor number is presented; for the inverse protocol, a new mathematical model for the critical Taylor number is developed as a function of the axial Reynolds number and also the first critical Taylor number without axial flow.     

Natural Antimicrobial Edible Coatings for Microbial Safety and Food Quality Enhancement

Natural antimicrobial agents have been investigated as alternatives to synthetic ones for ensuring food safety and quality. However, the practical use of these preservatives in the food industry is limited due to their negative impact on the odor and taste of food products, as well as the early loss of functionality due to their rapid diffusion and interaction with food components. The incorporation of natural antimicrobial agents into edible coatings has been investigated to control diffusion of active compounds and maintain their concentrations at a critical level on a food surface. Recently, nanoencapsulating and multilayered/nanolaminate delivery systems have emerged as promising tools to enhance the functionality of edible coatings. This review highlights the potential use of polymeric edible coatings for the incorporation of natural antimicrobial agents and the improvement of their controlled release in food systems. The methods used to assess the antimicrobial activity of encapsulated natural antimicrobial agents and the most recent findings regarding the application of nanoencapsulating and multilayered/nanolaminate delivery systems in food products are also discussed.