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.

In this study, DyCrO3 orthochromite was synthesized via the sol–gel method and its structural and optical properties were examined. Rietveld refinement of X-ray diffraction confirmed an orthorhombic structure with the Pbnm space group. UV–Vis absorption spectroscopy revealed a direct optical band gap of about 3.3 eV, together with estimates of the Urbach energy and refractive index. The observed absorption features were further interpreted using crystal field theory to assign the Cr3⁺ electronic transitions. These findings highlight the promising potential of DyCrO3 as a wide-bandgap perovskite oxide for future optoelectronic applications.

This paper proposes an adaptive hybrid estimation framework combining a Long Short-Term Memory (LSTM) network and an Extended Kalman Filter (EKF) for simultaneous robot state estimation and actuator fault detection in mobile robots operating under uncertain conditions. The LSTM network learns temporal patterns and nonlinear relationships from sensor data, while the EKF provides model-based filtering with uncertainty quantification. A novel adaptive fusion mechanism dynamically balances these complementary approaches using a weighting factor derived from the estimation uncertainties of both components. The proposed method was extensively evaluated on a differential-drive robot model subject to various noise conditions and fault profiles, including progressive drift faults and abrupt jump faults. Simulation results demonstrate that our hybrid approach significantly outperforms standalone EKF and LSTM estimators, achieving up to 74.6% improvement in fault estimation accuracy and 34.5% reduction in position error under challenging high-noise conditions. The framework maintains consistent performance across diverse fault types, showing particular effectiveness in detecting gradual fault progression while remaining responsive to sudden fault events. These findings confirm that the adaptive LSTM-EKF fusion provides enhanced accuracy, robustness, and generalization capability compared to conventional approaches.

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.