University of Zakho

This study investigates quasi-consensus in fractional-order multi-agent systems (FOMASs) with three time-varying delays, unknown nonlinear dynamics, bounded disturbances, and intermittent Denial-of-Service (DoS) attacks. A dual-channel adaptive Radial Basis Function Neural Network (RBFNN) is developed to estimate unknown nonlinearities online. An adaptive impulsive pinning strategy dynamically selects agents according to their consensus errors, concentrating control effort on agents with larger deviations. A Lyapunov-Razumikhin-based framework is established to derive sufficient conditions for quasi-consensus under delayed and attacked communication. A DoS-aware impulsive contraction factor is introduced to capture the effects of adaptive pinning and attack frequency-duration characteristics. An explicit quasi-consensus error bound is derived to quantify the effects of disturbances, neural approximation errors, fractional-order dynamics, and impulsive intervals. Numerical results demonstrate accurate leader-following tracking, rapid convergence, and strong resilience against intermittent DoS attacks, confirming the effectiveness of the proposed approach for secure coordination of uncertain FOMASs.

Diels–Alder (DA) cycloadditions are potent atom-economical transformations for the formation of six-membered cycloadducts with excellent regio- and stereoselectivity. The DA 4 + 2 cycloaddition between furan-2-ylmethanol and N-phenylmaleimides with para-substituents (X = H, F, Cl, Br) is studied using MEDT and density functional theory calculations at the M06‑2X(D3)/6‑311G(d,p) level. The polarity of the studied cycloaddition reaction was determined using conceptual DFT (CDFT) indices, natural population analysis (NPA), and global electron density-transfer (GEDT) values to quantify the electronic properties of the reagents and track the expected flow of electron density. In all substitution patterns, exo path is projected to be more favorable than endo path. The transition states’ polarity is corroborated by high GEDT values (≈ 0.26–0.28 e), showing electron density transfer from the furan-derived diene to the maleimide framework. Electron localization function (ELF) topological analysis for reactants and transition states was combined with bonding evolution theory (BET) along intrinsic reaction coordinates (IRC) to better understand chemical bond formation and how substituents affect it. These analyses suggest a two-stage, one-step (asynchronous) cycloaddition in which the new C–C bond is formed earlier at the transition state than the second bond involving the heteroatom-containing fragment, indicating a polar, nonsynchronous bonding reorganization rather than a perfectly coordinated event. Additional QTAIM and NCI descriptions show developing interactions at the forming bond critical points and weak stabilizing noncovalent contacts that favor exo transition structures. Electron-withdrawing substituents enhance electrophilicity of dienophile and subtly modulate energetics and electron density redistribution along the exo path, explaining the impact of phenyl-ring halogen substitution.

Co-contamination of paddy soils with antimony (Sb) and nickel (Ni) poses significant risks to soil quality, crop productivity, and food safety. This study evaluated the effectiveness of iron-titanium oxide-engineered biochar (Fe-Ti-BC) in mitigating Sb and Ni mobility in contaminated paddy soil and examined associated changes in soil carbon dynamics and microbial communities. Compared with the control, Fe-Ti-BC application reduced CaCl2-extractable Sb and DTPA-extractable Ni by 20.31-34.31% and 39.87-79.67%, respectively. Amendment with Fe-Ti-BC and unmodified biochar enhanced the carbon pool management index (CPMI) and labile organic carbon fractions, indicating improved carbon sequestration potential and nutrient cycling capacity. Rice biomass significantly increased following biochar treatments. Iron and titanium concentrations in root Fe plaque were approximately 20-fold and twofold higher, respectively, in Fe-Ti-BC-amended soils than in the control, suggesting enhanced plaque-mediated immobilization of trace elements. Consequently, Sb and Ni concentrations in rice grains decreased by 20.02-78.18% and 60.17-69.79%, respectively. High-throughput sequencing revealed that Fe-Ti-BC reshaped soil bacterial community composition and metabolic activity, promoting keystone taxa including Actinobacteria, Proteobacteria, and Firmicutes. Partial least squares path modeling (PLS-PM) identified CaCl2-extractable Sb, DTPA-extractable Ni, and Fe-Ti plaque formation as key determinants governing trace element accumulation in rice grains. Overall, Fe-Ti-BC effectively stabilized Sb and Ni through coupled geochemical and biological mechanisms, thereby reducing metal transfer to edible tissues while enhancing soil carbon functionality and productivity. These findings highlight the potential of engineered biochar as a sustainable remediation strategy for multi-metal contaminated paddy systems with direct implications for environmental health and food security.

This study investigates the fabrication and characterization of microwaves assisted Bismuth-doped graphitic carbon nitride (Bi@g-C3N4)composite into TiO2 as a photoanode material, for dye-sensitized solar cells (DSSC). The effect of Bi@g-C3N4/TiO2 was evaluated through photovoltaic performance measurements, revealing significant increases in power conversion efficiency (PCE) from 2.70

This paper investigates the Lie symmetry structure, conservation laws, and novel soliton solutions of a nonlinear Schro & uml;dinger equation. We determine the admitted Lie point symmetries and establish the associated Lie algebra generated by Gamma(1 )= partial derivative(x), Gamma(2) = partial derivative(t), and Gamma(3) = x partial derivative(x) +2t partial derivative(t). The algebraic structure is explored through the commutator table, adjoint representation, and classification of the optimal system of subalgebras. Corresponding similarity reductions transform the PDE system into reduced ordinary differential equations, for which approximate solutions are constructed using power series methods. In addition, conservation laws are systematically derived via conservation theorem, linking the symmetries to physically meaningful invariants. Novel soliton solutions have been established using the modified generalized Riccati equation mapping method (MGREMM). The results provide a comprehensive symmetry-based framework for the system under study, contributing to the broader understanding of nonlinear coupled PDEs and their analytical properties.