This study focuses on a steady two-dimensional laminar boundary-layer flow of a chemically reactive Casson nanofluid over a linearly stretched sheet in the presence of Brownian motion, thermophoresis, uniform heat generation, porous medium effects, and chemical reaction. The governing nonlinear partial differential equations for momentum, energy, and concentration transport are converted into a set of coupled nonlinear ordinary differential equations using appropriate similarity transformations. The resulting equations are numerically solved with the Keller Box method. The effects of key physical parameters, such as the Casson fluid parameter, Brownian motion parameter, thermophoresis parameter, Prandtl number, Lewis number, porous medium parameter, heat generation parameter, wall injection parameter, and chemical reaction parameter, on the velocity, temperature, and concentration fields are thoroughly investigated. The findings show that raising the Brownian motion and thermophoresis parameters boosts the thermal field and dramatically thickens the thermal boundary layer. In contrast, greater Prandtl and Lewis numbers diminish the thickness of the thermal boundary layer. As thermophoresis, Lewis number, and chemical reaction parameters increase, the concentration distribution reduces due to increased nanoparticle diffusion and species consumption. Furthermore, increasing porous medium resistance reduces fluid velocity and promotes thermal energy retention inside the boundary layer. Quantitative analysis shows that increasing the thermophoresis parameter from Nt = 0.1 to Nt = 0.5 increases the local Nusselt number from 2.1294 to 3.0351, a 42.53% increase, while decreasing the local Sherwood number from 0.9523 to 0.3211, a 66.28% reduction. The computed findings are in great agreement with previously published benchmark solutions, proving the correctness, stability, and dependability of the Keller Box numerical technique. The current findings provide light on the mechanisms that accelerate heat and mass transfer in chemically reactive Casson nanofluid flows across porous media, as well as the possible engineering applications.
Purpose There is a growing demand for lightweight and flexible alternatives to traditional lead-based radiation shields. This trend is driving interest in high atomic number (high-Z) nanoparticle-reinforced polymer composites. This study examines the photon attenuation of polyvinyl alcohol/polyethylene glycol (PVA/PEG) matrices containing tungsten trioxide (WO3; 0-40% v/v). These composites are tested across the diagnostic X-ray energy range of 20-150 kiloelectronvolts (keV). Materials and Methods Five PVA/PEG-WO3 composites were modeled in the GAMOS 6.2.0 Monte Carlo framework. The mass attenuation coefficient (MAC) was derived from transmitted fluence under monoenergetic, narrow-beam irradiation. From the simulated data, for each energy and composition, the following were calculated: the linear attenuation coefficient (LAC), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP). Results Attenuation improved with increasing tungsten trioxide (WO3) content. The 40% v/v composite exhibited the strongest performance at low energies, where photoelectric interactions are dominant. HVL decreased markedly compared to the undoped matrix, reaching sub-centimeter values over the 20-60 keV interval. MFP displayed similar reductions. This suggests an increased probability of photon interaction in WO3-rich formulations. Conclusion The attenuation trends predicted in this study are fully consistent with previously reported Monte Carlo and experimental investigations on tungsten-based flexible shielding materials, confirming the suitability of the GAMOS-based approach for evaluating and optimizing lead-free polymer composites in the diagnostic X-ray energy range.
In this study, the proton-induced increase in dark current and the production of random telegraph signal (RTS) in InGaAs infrared focal plane array (IR FPA) are investigated. We note that InGaAs FPA has a high sensitivity to proton-induced displacement damage. After 1 & times; 1011 p+/cm2 proton irradiation, the dark current distribution with a Gaussian shape and a universal damage factor (UDF) of 1136 e-/s/& micro;m3/(TeV/g) is obtained. The statistical distribution results of the RTS at different proton fluences, integration time and temperatures are also summarized. In addition, a special class of spine-RTS is discussed with respect to its characteristics and causes. The annealing trend of FPA dark current and the RTS evolution of several pixels indicate complex changes in cluster defects.
The development of lightweight, flexible, and non-toxic radiation shielding materials has become increasingly important for modern medical, industrial, and portable radiation applications, where conventional shielding materials pose limitations. In the present study, gamma-ray attenuation behaviour and photon interaction characteristics of seven low-Z polymers-Polyisobutylene (PIB), Poly (vinyl acetate) (PVAc), Poly (methyl acrylate) (PMA), Poly (tetrafluoroethylene) (PTFE), Poly (methyl methacrylate) (PMMA), Poly (phenylene sulfide) (PPS), and Poly (ethyl methacrylate) (PEMA)-have been systematically investigated over the photon energy range of 122-1330 keV using a NaI(Tl) detector under narrow-beam geometry. The experimentally determined mass attenuation coefficients (& micro;/rho) and derived parameters, including total atomic cross-sections (sigma t), electronic cross-sections (sigma e), effective atomic numbers (Zeff), effective electron densities (Neff), and molar extinction coefficients (epsilon), provide detailed insight into photon-matter interaction mechanisms within polymeric systems. The observed decrease in & micro;/rho, sigma t, and sigma e with increasing photon energy reflects the reduced probability of photon absorption and the growing dominance of Compton scattering in the intermediate energy region. Similarly, the variation in Zeff and Neff indicates that photon interaction is strongly governed by the effective electron distribution and elemental composition of the polymers. Polymers containing relatively higher atomic constituents, such as fluorine and sulfur in PTFE and PPS, exhibit comparatively enhanced attenuation behavior, highlighting the role of molecular composition in radiation shielding efficiency. The experimental results are in good agreement with theoretical predictions, confirming the reliability of the measurements. This study establishes a comprehensive experimental understanding of structure-dependent radiation interaction in pure polymers, providing a scientific basis for the design of efficient, low-cost, and environmentally safe polymer-based shielding materials.
This study investigates the stagnation-point flow of a micropolar nanofluid over a Riga plate in the presence of Soret-Dufour effects and bioconvection induced by motile microorganisms. The mathematical model incorporates the influences of electromagnetic forcing, thermal radiation, heat generation/absorption and chemical reaction on the transport phenomena. By employing suitable similarity transformations, the governing partial differential equations are reduced to a system of coupled nonlinear ordinary differential equations, which are solved numerically using the Runge-Kutta fourth-order method combined with a shooting technique. Furthermore, the graphical and tabular representations analyze the impacts of several relevant parameters on velocity, microrotation, temperature, concentration profiles and the engineering quantities such as skin friction, couple stress, Nusselt number, Sherwood number and motile density fields. The results reveal that the modified Hartmann number significantly enhances the fluid velocity, whereas the Riga plate decay parameter suppresses it. Temperature is found to increase with radiation, Dufour number, heat generation parameter, and Biot number, while it decreases with increasing Prandtl number. Furthermore, the Soret number enhances nanoparticle concentration, whereas higher Schmidt number and chemical reaction parameter reduce it. The density of motile microorganisms decreases with increasing bioconvection Lewis number, P & eacute;clet number and microorganism difference parameters. The numerical scheme's correctness is verified with the previously published literature and shows excellent agreement. The novelty is that it presents a unified mathematical framework that captures the coupled interactions among momentum, heat, mass and microorganism transport mechanisms. The findings of this study provide valuable insights into the control of heat, mass and microorganism transport in electromagnetically driven micropolar nanofluid systems with potential applications in biotechnology, microfluidics and advanced thermal management technologies.
This work examines neutron-induced damage in nanocrystalline Zn1-xCuxFe2O4 to understand how the material degrades under high-radiation environments. The samples were synthesised via the sol-gel method and irradiated with a D-D neutron generator at doses of 2.4 and 7.2 Sv, with the required dose levels estimated using PHITS simulations. Neutron irradiation-induced defects, as well as structural, morphological, and electrical modifications, were examined using Doppler-broadening positron annihilation spectroscopy (DB-PAS), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), and dielectric measurements. XRD results revealed the formation and growth of CuO and ZnO secondary phases with increasing dose. DB-PAS measurements showed an increase in the S-parameter, indicating the generation of open-volume defects, while the linear S-W correlation suggested a stable chemical environment for positron annihilation. PL spectra (lambda(exc) = 400 nm) exhibited red-orange emissions, and SEM imaging confirmed irradiation-induced morphological changes. Dielectric measurements demonstrated a frequency-dependent decrease in the dielectric constant, with enhanced low-frequency polarisation attributed to radiation effects.
