Semnan University PressProgress in Physics of Applied Materials2783-47947220270701Transfer Matrix Method Analysis of Graphene-Loaded Circular Waveguide181093510.22075/ppam.2026.41033.1219ENAlirezaDolatabadyDepartment of Electrical Engineering, Faculty of Engineering, Ayatollah Boroujerdi University, Boroujerd, Iran.BahramRashidiDepartment of Electrical Engineering, Faculty of Engineering, Ayatollah Boroujerdi University, Boroujerd, Iran.Journal Article20260428Graphene, owing to its electrically tunable surface conductivity and favorable electromagnetic properties, has attracted considerable attention for microwave and terahertz applications. In this paper, the transfer matrix method is employed to analyze the transmission, reflection, and absorption characteristics of graphene-loaded circular waveguides. Single-layer and periodically arranged non-interacting graphene layers are investigated by incorporating the graphene surface conductivity into the electromagnetic boundary conditions for both TE and TM modes. The effects of the graphene chemical potential and the incident angle on the reflection characteristics are examined for different dielectric configurations. The results show that the electromagnetic response depends on both the polarization and the graphene chemical potential, with the TE mode exhibiting a higher degree of electrical tunability than the TM mode. In addition, the periodic arrangement of graphene layers gives rise to a photonic band gap, whose characteristics are influenced by the graphene chemical potential and the structural parameters. The proposed analytical formulation provides a convenient approach for studying graphene-loaded circular waveguides and may be useful in the analysis and design of tunable microwave and terahertz waveguide components.https://ppam.semnan.ac.ir/article_10935_a0a40b610afc7e41298f3ebd55c60ded.pdfSemnan University PressProgress in Physics of Applied Materials2783-47947220270701Optimization of the Magnetothermal Properties of LGSMO–MXene–Based Nanocomposite for Magnetic Refrigeration Applications9151095410.22075/ppam.2026.41822.1245ENArtemy IgorevichKagramanianMoscow Institute of Physics and Technology (MIPT), Institutskiy per. 9, Dolgoprudny, 141701, Moscow Region, RussiaEgor AlexandrovichKanareykinMoscow Institute of Physics and Technology (MIPT), Institutskiy per. 9, Dolgoprudny, 141701, Moscow Region, RussiaYury IvanovichSpichkinMoscow Institute of Physics and Technology (MIPT), Institutskiy per. 9, Dolgoprudny, 141701, Moscow Region, RussiaLomonosov Moscow State University (MSU), Faculty of Physics, Leninskie Gory, 1, Moscow, 119991, RussiaMohammad HosseinEhsaniFaculty of Physics, Semnan University, Semnan 35195-363, Iran0000-0002-7169-7496Alexander MettalinovichTishinMoscow Institute of Physics and Technology (MIPT), Institutskiy per. 9, Dolgoprudny, 141701, Moscow Region, RussiaLomonosov Moscow State University (MSU), Faculty of Physics, Leninskie Gory, 1, Moscow, 119991, RussiaJournal Article20260630The optimization of magnetocaloric heat transfer efficiency in a La0.5Gd0.1Sr0.4MnO3 (LGSMO)/Ti3С2Tx MXene composite for solid-state magnetic refrigeration was performed. The effect of the orientation angle α of ellipsoidal LGSMO inclusions relative to the anisotropic MXene matrix and the inclusion aspect ratio λ on the heat removal rate, characterized by the target function J=∆T_ad/τ, where ∆T_ad is the adiabatic temperature rise and τ is the thermal relaxation time, was investigated using the finite element method. For a single grain, the optimal orientation was found at α = 90°, with the major axis aligned in the high-conductivity plane of MXene, and β = 0°, where β is the angle between the major axis and the external magnetic field direction, minimizing the demagnetization factor and maximizing the internal field H_{int}. The analysis was further extended to a fractal hexagonal packing of ellipsoidal grains by introducing an effective target function J_eff = J⋅η, which accounts for the volume fraction η of LGSMO in the composite. The optimal aspect ratio for the packed system was found at λ ≈ 5, balancing the competing effects of improved single-grain heat transfer and reduced packing density at higher λ. The model was further augmented by introducing cylindrical isothermal channels aligned along the high-conductivity direction of the MXene matrix as distributed heat sinks, which shifted the optimal aspect ratio to λ* ≈ 2.3, reflecting the dominant role of grain-to-channel thermal resistance in determining the heat removal efficiency of the active composite.https://ppam.semnan.ac.ir/article_10954_19ae449792fac7866a7d551fc38c08ed.pdfSemnan University PressProgress in Physics of Applied Materials2783-47947220270701Mechanical Strengthening Enhancement in PMMA/MWCNT/Co₃O₄ Hybrid Nanocomposites: A Comprehensive Study of Compression, Hardness, and Microstructural Properties17301098310.22075/ppam.2026.41215.1228ENNoor H.MajeedCollege of Science, Department of Physics, Wasit University, Wasit, IraqAli K.HattabCollege of Science, Department of Physics, Wasit University, Wasit, IraqAhmed A.ThamerCollege of Science, Department of Physics, Wasit University, Wasit, IraqReem HusseinAbdullahCollege of Science, Department of Physics, Wasit University, Wasit, IraqJournal Article20260515Hybrid nanocomposites of poly(methyl methacrylate) (PMMA) and multi-walled carbon nanotubes (MWCNTs) with cobalt oxide (Co₃O₄) nanoparticles were synthesized and systematically characterized in terms of their mechanical and microstructural properties. The nanocomposites were fabricated by a hand lay-up molding route with equal weight fractions (total loading ranging from 0.5 to 3.0 wt%) of the two nanofillers. Comprehensive characterization was carried out using compression testing (ASTM D695-15), Shore D hardness testing (ASTM D2240), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS/EDX). One-way analysis of variance (ANOVA) was applied to evaluate the statistical significance of the variations in the measured properties. The mechanical properties gradually improved with increasing filler concentration up to 2.0 wt% (1.0 wt% MWCNT + 1.0 wt% Co₃O₄); a further increase in filler concentration led to a deterioration in mechanical properties due to nanoparticle agglomeration. At the optimum composition, the compressive strength increased by 31.3% (from 85.6 ± 2.8 to 112.4 ± 3.2 MPa), the compressive modulus by 29.1% (from 2.85 ± 0.12 to 3.68 ± 0.15 GPa), and the Shore D hardness by 11.3% (from 82.5 ± 1.2 to 91.8 ± 1.0). All of these improvements were statistically significant (p < 0.05). The incorporation of cobalt and the reasonably uniform elemental distribution at lower loadings and increasing heterogeneity at higher filler content has been confirmed by the EDX point analysis and elemental mapping. The improvement is said to be due to the efficient load transfer along the MWCNTs, and to the Co₃O₄ nanoparticles, which are thought to inhibit re-agglomeration of the nanotubes, but since samples with one filler only were not prepared, the inferred synergistic effect is presented as a hypothesis. The results show that PMMA/MWCNT/Co₃O₄ hybrid nanocomposites are an interesting material for structural and protective-coating applications where high mechanical properties are required.https://ppam.semnan.ac.ir/article_10983_76b605730bd2606bbcb290f1244dac9a.pdf