University of Gabès

This study offers a complete analysis of the optical properties of La0.67 − xPrxBa0.33MnO3 (x = 0.1 and x = 0.2) polycrystalline materials prepared by sol–gel auto-combustion method. The FTIR results confirmed the formation of the rhombohedral perovskite phase of the prepared materials. The SEM micrographs of the prepared materials showed agglomerated nanoparticles of 0.76 µm (x = 0.1) and 0.97 µm (x = 0.2), respectively. Optical characterization using UV–Visible absorption and diffuse reflectance spectroscopy indicated direct band gap transitions of approximately 3.84 eV and 3.14 eV for x = 0.1 and 0.2, respectively, with values relatively comparable to those reported in the literature. The refractive index, skin depth, optical and electrical conductivity, Urbach energy, and optical extinction coefficient were all determined as functions of photon wavelength. These results demonstrate how promising these compounds are for use in solar cells as well as optoelectronic devices.

This paper develops an enhanced current control approach for a Three-Phase Four-Wire (3P4W) split-capacitor Shunt Active Power Filter (SAPF) to mitigate current harmonics produced by Compact Fluorescent Lamps (CFLs). A Fuzzy Hysteresis Current Controller (FHCC) and a Modulated Hysteresis Current Controller (MHCC) are proposed to provide the triggering signals for the Insulated-Gate Bipolar Transistors (IGBTs) of the SAPF to ensure improved switching performance and reduced steady-state error near the Shifted Zero-Crossing Area (S-ZCA). The Synchronous Reference Frame (SRF) power theory is adopted for reference current generation. The effectiveness of both techniques, FHCC and MHCC, is evaluated through simulations inMATLAB®/Simulink and validated in real time using the Hardware-in-the-Loop (HIL) platform, especially with the Typhoon HIL-402 device. As both techniques act exclusively for switching gate signal generation techniques and not reference-current extraction methods, the structures are general in nature and are not load-dependent. Comparative analysis with the conventional hysteresis current controller (HCC) demonstrates significant improvements in the reduction of Total Harmonic Distortion (THD) to 1.08% and the overall improvement of power quality without notches in waveforms near zero crossings. The results confirm the robustness and efficiency of the proposed MHCC strategy in the HIL implementation.

Mg0.7Zr0.3Cr2O4 spinel oxide was successfully synthesized via the sol-gel route in order to investigate the influence of aliovalent Zr4+ substitution on the structural, electrical, dielectric, and optical properties of magnesium chromite. X-ray diffraction combined with Rietveld refinement confirmed the formation of a single-phase cubic spinel structure with the Fd-3 m space group, indicating that Zr incorporation preserves the fundamental lattice symmetry while inducing slight lattice expansion. Microstructural analysis revealed nanometric crystallite dimensions with limited lattice strain, suggesting good crystallinity and structural homogeneity. Electrical conductivity measurements exhibited typical frequency-dependent behavior described by Jonscher's universal power law, where conductivity increases with both frequency and temperature, consistent with thermally activated hopping conduction. The nearly temperature-independent frequency exponent (s approximate to 0.8) indicates that the AC conduction mechanism is dominated by quantum mechanical tunneling between localized states. Arrhenius analysis of DC conductivity yielded a relatively high activation energy, reflecting enhanced carrier localization due to substitution-induced disorder. Dielectric investigations revealed strong dispersion at low frequencies governed by Maxwell-Wagner interfacial polarization and grain boundary effects, while impedance spectroscopy confirmed non-Debye relaxation behavior and thermally activated charge transport. Optical studies demonstrated significant band-gap narrowing compared with the parent MgCr2O4 spinel, accompanied by increased Urbach energy, highlighting the role of defect states and lattice distortion in modifying the electronic structure. The combined results emphasize that Zr4+ substitution effectively tailors charge dynamics and optical absorption in MgCr2O4-based spinels, making Mg0.7Zr0.3Cr2O4 a promising candidate for electronic and optoelectronic applications.

Olive mill wastewater (OMW), characterized by a high load of recalcitrant organic pollutants, presents a significant environmental burden due to its phytotoxicity and resistance to conventional treatment methods. This study investigates the development and application of a novel biochar-supported titanium dioxide (biochar/TiO₂) photocatalyst for the solar-driven degradation of organic contaminants in OMW. The biochar was synthesized via pyrolysis of palm waste, offering a sustainable support material. The photocatalyst's performance was evaluated with varying TiO₂ contents to determine the optimal composition for maximum pollutant removal efficiency. A composite containing 10

Natural processes and human-generated pollution have impacted the groundwater quality in several regions worldwide. Identifying the causes and processes of groundwater quality alteration in these regions is fundamental for proper planning and management of water resources. This research aimed to depict the origins of salinity and nitrate in the groundwater and to derive the principal mechanisms governing its chemistry in the agricultural plain of Sidi Smail (northwestern Tunisia). Groundwater samples (n = 28) taken at the end of the hot and dry summer season from 15 boreholes and 13 wells were assessed regarding their physicochemical properties and stable isotope composition (δ18O and δ2H). The nitrate pollution index (NPI) was used to evaluate the degree of groundwater pollution. The results of the statistical analyses indicate that 88