• Book : 604()
• Pub. Date : 2025
• Page : pp.155479
• Keyword :

• Book : 228()
• Pub. Date : 2025
• Page : pp.112410
• Keyword :

• Book : 179()
• Pub. Date : 2025
• Page : pp.105532
• Keyword :

In this study, our primary focus lies in meticulously exploring the intricacies of the universe by employing a flat Friedmann-Lemaître-Robertson-Walker (FLRW) model within the framework of $ f(R,G)$ gravity. In our analysis, the $ f(R,G)$ function is delineated as the sum of two distinct components, commencing with a quadratic correction of the geometric term denoted by $ f(R)$, structured as $ f(R) = R + \xi R^{2}$, alongside a matter term denoted by $ f(G) = \lambda G^{2}$, where $ R$ and $ G$ symbolize the Ricci scalar and Gauss-Bonnet invariant, respectively. In the pursuit of solutions to the gravitational field equations within the $ f(R,G)$ formalism, we embrace a specific expression for the scale factor, represented as $ a =\sinh ^{ \frac{1}{\alpha }}(\beta t)$ [D. Rabha and R. R. Baruah, The dynamics of a hyperbolic solution in $ f(R,G)$ gravity, Astron. Comput. 45 (2023) 100761]. In this context, the parameters $ \alpha $ and $ \beta $ intricately shape the scale factor’s behavior. The model posits the intriguing prospect of perpetual cosmic acceleration when $ 0 @@\symbol{'3C} @@ \alpha @@\symbol{'3C} @@ 1.19$, signifying a continuous expansion of the universe. Conversely, for $ \alpha \geq 1.19$, the model proposes a pivotal transition from an early deceleration phase to the present accelerated epoch, a transformative shift in line with our understanding of cosmic evolution. Furthermore, the model demonstrates its credibility by satisfying Jean’s instability condition during the shift from a radiation-dominated era to a matter-dominated era, substantiating the formation of cosmic structures. In our analysis, a central focus is directed toward scrutinizing the equation of state parameter $ \omega $ within our model. We delve into a comprehensive examination of the scalar field and meticulously assess the energy conditions surrounding the derived solution. To establish the robustness of our model, we deploy an array of diagnostic tools, including the Jerk, Snap, and Lerk parameters, along with the Om diagnostic, Classical stability of the model, and statefinder diagnostic tools, Observational Constraints on the Model Parameters. The outcomes, intertwined with a detailed analysis of both the results and the inherent intricacies of the model, are diligently clarified and presented.

• Book : 22(1)
• Pub. Date : 2025
• Page : pp.2450259
• Keyword :

This study presents a simplified semi-analytical model to analyze the dynamic behavior of a plate with shark skin biomimetic surface modifications. The base plate is considered to be thin isotropic homogeneous and modeled using a Kirchhoff-Love plate theory, whereas the dermal denticles are modeled as a distributed array of point mass and replicated using a Dirac delta function. A semi-analytical formulation, which takes into account closed-form beam mode shapes, with the Galerkin technique to minimize errors is utilized to study the free and forced vibration response of modified plates. Harmonic analysis is carried out to understand the dynamic behavior of the modified plate both quantitatively as well as qualitatively. A parametric study varying the array spacing and the boundary conditions is carried out to understand the effect of surface modification on power radiation characteristics. It appears that adding dermal denticles reduces the peak velocity amplitude and peak radiated power at all resonance frequencies. A separate study by varying the base plate material reveals that a higher reduction in the dynamic response and the radiated power can be achieved by increasing the mass ratio. Hence, surface modification using such a shark skin layer may prove beneficial to reduce acoustic radiation and dynamic response and to optimize the design.

• Book : 25(2)
• Pub. Date : 2025
• Page : pp.2440013
• Keyword :

The study of magnetic nanostructures is interesting because of its applications. Some of them are the development of magnetic refrigerators, ferrofluids, drug delivery systems, fabrication of devices with giant magnetoresistance effects, and high-frequency transformers. The physical and chemical properties of metal changes due to silica coating. The interaction potential can be manipulated using surface coatings and also the particle shape can be controlled. Nanoparticles with a proper surface coating are of interest for several other applications in optoelectronic devices and in the biomedical field. Thus, developing a new synthetic route for these particles and investigating the stability of magnetic materials are of great importance. Silica coating improves the chemical stability and electrical resistivity of the material. In this study, Ni₃Fe (core) nanoparticles were prepared and the silica shell for this core was synthesized. The as-prepared X-ray diffraction (XRD) patterns and 300°C annealed sample of Ni₃Fe/SiO₂ shows a characteristic hump in the low angle range confirming the presence of amorphous cristobalite phase of SiO₂. The size of the Ni₃Fe cluster in the Ni₃Fe/SiO₂ composite was estimated to be 8$ \,$nm and 9$ \,$nm, respectively, for the as-prepared and annealed samples. Vibrating sample magnetometer (VSM) measurements show the Ni₃Fe to silica ratio to be 59:41. A small decrease in the coercivity value, is probably due to morphological changes associated with the coating. Scanning electron microscope (SEM) studies of the as-prepared and annealed Ni₃Fe/SiO₂ powder particles are of flowerlike morphology and in agglomeration. The impedance spectra were found at room temperature for the as-prepared samples.

• Book : 13(1)
• Pub. Date : 2025
• Page : pp.2440019
• Keyword :

• Book : 342()
• Pub. Date : 2025
• Page : pp.120946
• Keyword :

• Book : 324()
• Pub. Date : 2025
• Page : pp.119237
• Keyword :

• Book : 379()
• Pub. Date : 2025
• Page : pp.137646
• Keyword :

• Book : 77(1)
• Pub. Date : 2025
• Page : pp.26-50
• Keyword :