Université Mustapha Stambouli de Mascara

Ball balancers are nonlinear, electromechanical, multivariable, open-loop unstable systems widely used in research laboratories, aerospace, military, and automotive industries to evaluate control mechanism effectiveness. The inherent difficulty in precisely managing ball position, combined with actuator saturation and system sensitivity to disturbances, makes trajectory tracking a persistent challenge. Conventional controllers often exhibit oscillatory responses with steady-state errors exceeding acceptable limits. Sliding mode control (SMC) offers robustness against model uncertainties; however, chattering finite-frequency, finite-amplitude oscillations near the sliding surface caused by switching imperfections, time delays, and actuator dynamics remain a significant limitation. This study addresses chattering through explicit vibration model compensation integrated into the SMC design for a 2-DOF ball balancer system using a visual servoing approach. A double-loop control architecture is implemented, where the inner loop handles servo angular position control and the outer loop manages ball position tracking through visual servoing feedback. The sliding mode controller is designed with a power rate reaching law, synthesizing two control laws: one with explicit vibration model compensation incorporating damping and stiffness terms, and one without. Experimental validation confirmed that SMC with compensation achieved significantly reduced steady-state error (0.034 mm vs. 0.386 mm) and lower overshoot (3.95% vs. 13.81%) compared to the uncompensated variant, with chattering amplitude reduced by approximately 72%.

Abstract The increasing presence of contaminants from aqueous solutions involves significant environmental and public health risks, necessitating the development of efficient adsorbents for their removal. This study explores the potential of polyaniline‐embedded montmorillonite‐type clay modified titanium dioxide which was designed via an in situ polymerization technique for removal of malachite green (MG) dye from water. Characterization was conducted using XRD, Fourier transform infrared spectroscopy, X‐ray fluorescence, X‐ray photoelectron spectroscopy, TEM, SEM coupled with energy dispersive X‐ray spectroscopy and a Brunauer–Emmett–Teller study. Significant findings for optimal conditions for MG adsorption were identified as pH 6.0, 50 mg adsorbent mass, 120 min contact time, 200 mg L −1 initial concentration and 298 K, achieving an adsorption capacity of 172.69 and 238.32 mg g −1 for Mt‐TiO 2 (Mt, natural montmorillonite‐type clay) and PAni@Mt‐TiO 2 (PAni, polyaniline), respectively. Kinetic studies followed a pseudo second order model, and equilibrium data best fitted the Langmuir isotherm for PAni@Mt‐TiO 2 ( R 2 = 0.924) and the Freundlich model for Mt‐TiO 2 ( R 2 = 0.817). The Gibbs free energy (Δ G 0 ) was negative for the adsorption process in the range 298–328 K, indicating that the process was spontaneous. In addition, the enthalpy parameter (Δ H 0 ) was determined for the adsorption process using PAni@Mt‐TiO 2 and Mt‐TiO 2 at 1.906 kJ mol −1 and 4.506 kJ mol −1 , respectively. A positive Δ H 0 indicates that the process is endothermic in the range 298–328 K using both adsorbents. The potential reusability of the adsorbent materials was confirmed for five adsorption–desorption cycles. These results highlight the potential of a conducting polymer matrix as a strategy to develop high‐performance, sustainable clay‐modified adsorbents for environmental uses, especially water treatment. © 2026 Society of Chemical Industry.

Introduction/purpose: The structural integrity of pressurized pipelines is often threatened by surface cracks, especially in welded regions. This study evaluates the effectiveness of composite wrap reinforcement in repairing longitudinal semi-elliptical cracks in welded steel pipelines subjected to internal pressure. Although environmental effects such as temperature, moisture, and chemical exposure were not modeled, they are acknowledged as key factors influencing the long-term durability of composite repairs. Methods: A three-dimensional finite element model was developed for a welded pipeline (outer diameter = 1016 mm, thickness = 12.8 mm) containing an external semi-elliptical crack (2c = 10.24 mm, a = 2.56 mm). The Virtual Crack Closure Technique (VCCT) was applied to compute Mode I Stress Intensity Factors (SIFs) under internal pressures of 2-12 MPa. A parametric study assessed the influence of patch length (100-400 mm), thickness (6-12 mm), and circumferential coverage angle (30°-360°), as well as adhesive shear modulus, thickness, and debonding effects. Results: Increasing patch length, thickness, and coverage angle reduced SIFs, improving crack-tip stress attenuation. A higher adhesive shear modulus enhanced interfacial load transfer, while excessive adhesive thickness impaired efficiency. Localized adhesive debonding significantly increased SIFs under pressure, highlighting the sensitivity of repair performance to bonding quality. Conclusions: This study provides design insights for optimizing composite reinforcement in welded pipeline repairs. Although a rectangular patch was analyzed, future work should investigate alternative geometries to mitigate edge stress concentrations and incorporate fatigue and environmental effects to better predict long-term service performance.

This paper examines the free vibration behavior of functionally graded (FG) hexagonal honeycomb sandwich cylindrical shells using a quasi-3D theory. The material properties are assumed to vary continuously through the thickness, following a power-law distribution that ranges from zero at the inner surface to one at the outer surface. Shear deformation and thickness stretching effects are captured by modeling all displacement fields with a hyperbolic distribution through the thickness. The governing equations are derived using Hamilton’s principle, and natural frequencies are calculated via the Navier technique. The accuracy of the hybrid quasi-3D theory is validated through comparisons with existing literature. Additionally, the influence of material and geometric parameters on natural frequencies is investigated within this framework.

Research on Algeria’s diplomatic sphere during the Ottoman period continues to attract scholars. This interest stems from the decisive role played by the Algerian navy in the western Mediterranean, a role that often led to confrontation or peace. Yet this field still requires more studies that deepen understanding, clarify its features, and shed light on hidden aspects of the era. One of the most important of these aspects is the diplomatic environment. Ottoman Algeria was a major diplomatic hub. It received envoys and consuls and concluded several treaties and agreements due to its position and influence in the region at the time. Consuls enjoyed many privileges to ensure their safety and the protection of their property. However, these immunities were frequently violated, which strained relations between Algeria and European states and at times led to the suspension of diplomatic ties.

There is a growing interest in the application of natural and waste-derived biofillers for reinforcing thermoplastic polymers, as their utilization helps to reduce the carbon footprint and therefore enhances sustainable development. The aim of this study is to synthesize and characterize a biocomposite based on PP reinforced with OS particles derived from biomass in order to reduce plastic shrinkage after injection molding and to assess their viability as environmentally sustainable materials. The addition of OS particles (10 wt.% and 30 wt.%) significantly reduces the crystallinity of the PP, thereby improving its rigidity, its tensile strength, and its thermal stability. DSC analysis and TGA validated superior thermal properties, whereas mechanical and dynamic mechanical assessments indicated augmented stiffness and energy storage capacity with increasing filler content. The utilization of OS waste, abundant in CaCO3, facilitates a circular economy model, minimizing environmental impact and enhancing waste valorization. The findings underscore the viability of PP/OS biocomposites as sustainable substitutes for traditional mineral-filled polymers in engineering applications.