This research aims to experimentally improve the overall efficiency of solar photovoltaic (PV) panels by coating them with hydrophobic SiO₂ nanomaterial. Also, an accurate mathematical model was used to estimate the parameters of the PV panel, which is a non-linear optimization problem. Based on the experimental data and using the particle swarm optimization (PSO) algorithm, the optimal five parameters of a single diode model of a PV panel were determined in this study. This experimental work was conducted and carried out in the Renewable Energy Laboratory of Assiut University, Egypt. A comparative analysis was completed for three identical solar PV panels; the first panel was coated with hydrophobic SiO₂ nanomaterial, so it was considered to be a self-cleaning panel; the second panel was uncoated and cleaned manually on a daily basis; and the third panel was kept dusty all the time through the experimental investigation, and was used as a reference. Experimentally, the output power of the PV panels was monitored for each panel in this study. Also, the anti-static and anti-reflection effects of coating solar PV panels with hydrophobic SiO₂ nanomaterial were investigated experimentally. According to the obtained experimental results, it was found that the use of SiO₂ coating for PV panels results in the better performance of the PV panels. The overall efficiency of the coated panel increased by 15% and 5%, compared to the dusty panel and the uncoated panel which was manually cleaned daily, respectively.

Objective: In this work, graphene (Gr) or/and Cu particles are used to improve the thermal and mechanical properties of epoxy resin. Methods: Various contents of Gr powder (0.1, 0.3, and 0.5 wt%), and Cu powder (10, 30, and 50 wt%) were loaded to epoxy to form Gr/epoxy and Cu/epoxy composites, respectively. In addition, hybrids epoxy/Cu/Gr samples were prepared with a selection of the lowest (0.1 and 10) and the highest (0.5 and 50) ratios of Gr, and Cu, respectively. Results: The thermal conductivity increased with the increasing weight ratio of Gr and Cu as compared to the pure epoxy. The thermogravimetric analysis (TGA) of epoxy composites and hybrid composites revealed an improvement in the thermal stability. In addition, the mechanical properties such as hardness shore D and the wear resistance were enhanced for both the epoxy composites and hybrids composites. However, the Ep+0.5wt%Gr+50wt%Cu hybrid composite was found to have the maximum hardness 84, with the thermal conductivity of 3.84 W/m.K. It showed the lowest wear resistance 2.7×10^-6 mm³/Nm at loading 10 N. Conclusion: The hybrid composite containing 0.5wt%Gr and 50wt%Cu shows the maximum hardness and thermal conductivity, as well as the lowest wear resistance when compared to other composites. The physical properties of the hybrid composite can be controlled by the host blend, and hence the morphology, and interfacial characteristics.

In this work, a phenomenological model (PM) is used to simulate the magnetocaloric effect (MCE) of GdMn_1-xCr_xO₃ (0 ≤x ≤0.4) (GMCO) samples through the modelling of experimental isofield thermo-magnetization curves. The results showed that the MCE of GMCO samples depends strongly on Cr content, achieving a conventional MCE for low Cr content (level of doping x ≤ 0.3). However, the MCE of a higher Cr content sample has an inverse MCE. The behaviour of MCE in GMCO samples indicated that GMCO compounds are interesting magnetocaloric materials and can fruitfully be functioned as cryogenic magnetic refrigerants below 40 K especially in radiation detectors for outer space research.

To simulate the magnetocaloric effect (MCE) of a HoCo₂ sample, a phenomenological model (PM) is used. MCE parameters are inferred from PM as the result of modelling for magnetization vs. temperature in 0.5 T. The HoCo₂ exhibits two consecutive conventional MCEs with cooling via adiabatic demagnetization. HoCo₂ exhibits double peak MCE behaviour. It is recommended that HoCo₂ use it as a useful MR material over a temperature range spanning a significant temperature range of 0–140 K. Consequently, HoCo₂ is appealing for MR because its MCE spans a wide temperature range, particularly liquefaction of nitrogen and hydrogen.

Nanocomposites of polyvinylidene fluoride (PVDF) with dimensional (1D) cobalt oxide (Co₃O₄) and f-MWCNTs were prepared successfully by the solution casting method. The impact of 1D Co₃O₄ filler and 1D Co₃O₄/f-MWCNTs co-fillers on the structural, thermal, and electrical behavior of PVDF were studied. The crystal structural properties of pure PVDF and its nanocomposite films were studied by XRD, which revealed a significant enhancement of β-phase PVDF in the resulting nanocomposite films. The increase in β-phase was further revealed by the FTIR spectroscopic analysis of the samples. TG, DTA, and DSC analyses confirmed an increase in thermal stability of PVDF with the addition of nano-fillers as well as their increasing wt.%. From impedance spectroscopic studies, it was found that the DC conductivity of PVDF increases insignificantly initially (up to 0.1 wt.% of nano-fillers addition), but a significant improvement in DC conductivity was found at higher concentrations of the nano-fillers. Furthermore, it was observed that the DC conductivity decreases with frequency. The increase in DC conductivity corresponded to the strong interactions of nano-fillers with PVDF polymer chains.

The magnetocaloric effect-(MCE) of MgB₂ is simulated, considering the effect of sintering temperature on MCE. The results show that MCE of MgB₂ samples is an inverse type in a temperature range of diamagnetic-paramagnetic transition. Moreover, the MCE for MgB₂ is improved with high sintering temperature. The comparison between MCE of MgB₂ samples and other some reported magnetic materials has been done, showing that MCE parameters of MgB₂ samples are larger than some MCE parameters of La_1-xCd_xMnO₃, La_1.25Sr_0.75MnCoO₆, Gd_1−xCa_xBaCo₂O_5.5, Ni₅₈Fe₂₆Ga₂₈, Ni_2+xMn_1−xGe, Ge_0.95Mn_0.05 film, and (001)-oriented MnAs film. It suggested that MgB₂ samples could be a promising sharing candidate for MR in cryogenic temperatures.