This work investigates the effect of rare earth substitution at the A-site of La0.6- xEuxCa0.4MnO3 (x = 0, 0.1) on the structural, magnetic, and magnetocaloric properties, with focus on the influence of ionic radius reduction on cooling performance. Polycrystalline samples synthesized via standard solid-state reaction were structurally characterized using X-ray diffraction, confirming single-phase formation with orthorhombic symmetry (Pnma space group). Magnetic characterization reveals a pronounced paramagnetic-ferromagnetic transition whose temperature exhibits strong dependence on lanthanide substitution. The Curie temperature () demonstrates significant reduction from 260 K for the parent compound (x = 0) to 135.5 K for the europium-doped variant (x = 0.1), attributable to decreased ionic radius at the A-site. Critical analysis of the phase transition through universal curve construction consistently confirms second-order magnetic behavior. Comprehensive evaluation of magnetocaloric parameters reveals exceptional cooling performance, with the europium-doped compound exhibiting a magnetic entropy change (||) of 3.33 J.kg-1.K-1 under 5 T applied field. The full-width at half-maximum of spans 102 K, yielding a substantial refrigerant capacity of 157 J & centerdot;kg- 1. Most notably, the relative cooling power demonstrates remarkable enhancement from 210 to 340 J & centerdot;kg- 1 at 50 kOe, representing a 60% improvement over the undoped compound. Additional thermodynamic parameters including adiabatic temperature change (), temperature-span averaged entropy change, and the field-normalized refrigerant capacity were quantified to establish comprehensive structure property relationships. These findings suggest that rare earth substitution at the A-site can effectively modify the magnetocaloric response in perovskite manganites, indicating their potential for magnetic refrigeration applications.
We revisit the Banach space PAP(ℝ,X,μ ,ν ) of pseudo almost periodic functions with respect to two measures μ and ν introduced in [22]. Using the Banach–Steinhaus theorem, we give a detailed study of the relationship between the ergodic spaces ℰ(ℝ,X,μ ) and ℰ(ℝ,X,μ ,ν ) . Moreover, we correct a claim of the uniqueness of the decomposition PAP(ℝ,X,μ ,ν )=AP(ℝ,X)⊕ℰ(ℝ,X,μ ,ν ) into almost periodic and ergodic parts by showing that the asymptotic joint growth condition r→∞lim supμ ([-r,r])/ν ([-r,r])>0 is necessary and sufficient for this unique decomposition to hold. Furthermore, we provide a sufficient condition on the nonlinearity which ensures the existence and uniqueness of a solution within this class of functions for certain evolution equations. This result is proved using Bielecki-type weighted norms.
Strategic mine planning decisions- particularly cut-off grades (COGs) and production capacities- strongly influence both the economic and environmental performance of mining projects. Conventional approaches typically optimize these variables independently, overlooking their interdependence and limiting opportunities for value creation. This study introduces a two-stage optimization framework that simultaneously optimizes COGs and production capacities across mining, pre-concentration, and processing stages while explicitly incorporating sustainability trade-offs. The model extends Lane’s opportunity-cost approach to accommodate multiple processing pathways, spatial grade variability, economies of scale, capital recovery, and monetized environmental impacts. In the first stage, dynamic COGs and capacities are optimized at the increment level to capture local geological conditions. In the second stage, aggregated strategic capacities are imposed and COGs are re-optimized under fixed infrastructure constraints. Applied to a copper deposit case study, the framework yields a consistent net present value improvement of over 5
Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are among the most promising clean energy conversion technologies due to their high efficiency, rapid dynamic response, and near-zero emissions. To improve performance and durability, it is essential to understand the complex coupling between electrochemical reactions, mass transport, and heat transfer occurring within the cell. In this study, a detailed three-dimensional (3D) nonisothermal Computational Fluid Dynamics (CFD) model was developed to investigate the coupled electrochemical and thermal transport phenomena in a PEMFC equipped with a branched serpentine flow field. The model captures the spatial distributions of electric potential, oxygen concentration, water vapor, temperature, and current density across the membrane-electrode assembly (MEA). Simulation results revealed pronounced temperature gradients within the MEA, significantly influencing water management, current density uniformity, and proton conductivity. The branched serpentine geometry improved reactant distribution and reduced pressure drop by approximately 18 %, while enhancing current-density uniformity by 6 % compared to a conventional serpentine layout. The model predicted a maximum temperature difference of 7.4 degrees C across the MEA, corresponding to a thermal regulation efficiency of 91 %. Furthermore, simulated polarization curves showed strong agreement with experimental data, with less than 4 % deviation, validating the model's predictive accuracy. These findings highlight the critical importance of effective thermal management and controlled water transport in maintaining membrane hydration and achieving high energy-conversion efficiency. The developed CFD framework provides a reliable platform for optimizing PEMFC design under realistic operating conditions and offers quantitative insights for improving hydrothermal regulation, enhancing material durability, and guiding the development of next-generation high-performance fuel cell systems. All simulations were performed using COMSOL Multiphysics 6.2, with user-defined electrochemical and heat-transfer equations implemented to capture the coupled non-isothermal behavior.
Meeting global food demands by 2050 requires a 45–60
