Pramana最新文献

This article aims to derive optical soliton solutions for the ((4+1))-dimensional Davey–Stewartson–Kadomtsev–Petviashvili (DSKP) problem using the generalised exponential rational function method and the ((m+F))-expansion method. Both techniques yield various soliton solutions, including bright and dark solitons. The behaviour of these solitons may be further analysed using three-dimensional, two-dimensional and contour graphs. The effect of temporal parameter on the obtained soliton solutions is illustrated using two-dimensional graphs. The study emphasises the significance of solitons in optical fibre technology, signal processing and quantum systems, while also paving the way for applying the proposed techniques to more complex nonlinear models, such as fractional and higher-order systems. These findings contribute to a deeper theoretical understanding of soliton dynamics and support their practical implementation in advanced nonlinear optics and engineering applications.

This paper analyses the performance of a new fin field-effect transistor (FinFET) for two undesirable effects, such as self-heating and hot carrier effects. Two effects often degrade the device performance. This paper proposes a new FinFET architecture as dual gate dielectrics heterodielectric buried-oxide (HDB) FinFET. The HDB consists of SiO₂ and HfO₂ dielectrics, placed laterally. The use of HfO₂ with SiO₂ in the buried-oxide (BOX) increases the thermal conductivity, due to which the introduced structure demonstrates less self-heating effect on device characteristics. Similarly, the incorporation of HfO₂ beneath the drain lowers the band gap narrowing in the channel(/)drain region, resulting in reduced hot carrier degradation effect. To analyse the performance, the self-heating effect and the hot carrier effect is compared between the conventional and HDB FinFET. The proposed HDB FinFET is found to be better than the conventional FinFET and hence, a detailed analysis on self-heating and the hot carrier effects is performed by varying the different dimensions of the BOX, fin and work function of gate material.

The flow of a non-Newtonian Jeffrey fluid over a pulsating plate in a rotating frame is analysed. The effects of the Coriolis force and a constant magnetic field are also studied. The velocity of the plate is periodically pulsed, while the remaining part of the rotating fluid exhibits unsteady motion. Exact solutions for each case are obtained using the Laplace transform method with Mallin’s integral inversion formula. The graphical analysis shows how rotation, elasticity and magnetic field influence the fluid velocity during plate pulsation. It is found that the longitudinal component of velocity decreases with higher values of the Jeffrey parameter and magnetic field, while the transverse component of velocity shows the opposite behaviour.

Particle tracking passive microrheology in the 8CB liquid crystals is used to redefine the precessional motion of the orientation of nematic director in liquid crystals. Physical origin of the tumbling director in the presence of presmectic clusters under zero shear conditions is discussed. Different structural properties (pure nematic phase, presmectic (smectic C and smectic A clusters)) were differentiated with characteristic dependence of (G') on (omega ) in the nematic phase of the 8CB liquid crystals. Also, dynamic viscosity is observed with a cross-over between parallel and perpendicular components as the smectic A phase is approached.

Nanotechnology offers innovative and sustainable solutions for environmental remediation. However, enhancing photocatalytic efficiency remains a significant challenge. In this study, we developed a cost-effective method for synthesising carbon quantum dot (CQD)-incorporated cerium oxide (CeO₂) nanocomposites for efficient methyl orange (MO) degradation under direct sunlight. CeO₂ nanosols and CQDs were synthesised via sol–gel and hydrothermal processes, respectively, and combined using a hydrothermal route with sonication-assisted mixing. The nanocomposites were calcinated at 600 °C and characterised using XRD, FTIR, Raman, PL spectroscopy, SEM and EDX to analyse their structural, morphological and surface properties. The specific surface area of the CQDs(/)CeO₂ composites was determined to be 72.3 m²(/)g from the sol–gel method and 96.7 m²(/)g from the hydrothermal method, as measured by Brunauer–Emmett–Teller (BET) analysis. The optimised CQDs(/)CeO₂ (1:100 ratio) exhibited enhanced MO degradation, with the MO degradation rate constant for the hydrothermal composite. The energy band gap of the sol–gel composite was found to be 2.78 eV, while the hydrothermal composite showed a band gap of 2.73 eV, facilitating improved light absorption. The degradation efficiency was further influenced by MO concentration, pH and catalyst loading. Additionally, CQDs(/)CeO₂ demonstrated excellent catalytic stability over multiple cycles. These findings highlight the potential of CQDs(/)CeO₂ nanocomposites for cost-effective water purification and disinfection applications.

Graphical abstract

The purpose of this paper is to study the trajectory controllability (which is said to be the strongest notion rather than other controllabilities) and null controllability of a control system commanded by fractional-order composite relaxation semi-linear differential equation. The linear control system under consideration addresses a classical problem in fluid dynamics, specifically focussing on the dynamics of a particle experiencing unsteady movement within a viscous fluid while subjected to gravitational forces. Initially, we derive the mild solution of the considered control system employing the results on (a, k)-regularised families of bounded linear operator (matrices). Under some appropriate assumptions regarding non-linear terms and by utilising the Gronwall’s inequality, we establish the trajectory controllability and null controllability with constrained controls via fixed point technique. Finally, a few examples are shown to illustrate and explore the applications of the obtained findings.

Precision observables are well known for constraining most of the beyond standard model (BSM) scenarios tightly, among which the electroweak precision observables (EWPO) play a significant role. Recent measurement of the W boson mass ((M_W)) at CDF-II has put a renewed focus on the EWPO and its ensuing constraints. In this study, we look at the scenarios where these BSM effects are encoded primarily in ten dimension-6 standard model effective field theory (SMEFT) operators (in the Warsaw basis) which contribute to the EWPO at tree-level. After presenting the fitting procedure and testing it on the S, T and V parameters, we go on to fit various BSM scenarios consisting of different well-motivated subsets of the 10 operators of our interest. To constrain these scenarios further, we augment the EWPO with (Delta _{textrm{CKM}}) measurement using 1-loop matching of the low-energy effective field theory to SMEFT operators at the Z-pole. We show that the inclusion of the (Delta _{textrm{CKM}}) constraint indeed results in stronger bounds on our Wilson coefficients. One of our operator subsets caters to the models of vector-like leptons, where we find out that such a minimal extension is in tension with the forward–backward asymmetry in the b-sector ((A_b^{textrm{FB}})) and (M_W). Finally, we also include the LEP-II observables pertaining to the WW production, thereby lifting the two associated blind directions, helping us present the results for the full fit.

This paper investigates the geodesic motion and circular motion of particles around a linear Maxwell (f(R)) black hole in a modified gravity black hole field, using a specific metric. It focusses on framing the effective potential function for photon-like as well as massive particles, revealing differences in the behaviour of coordinate and proper time relative to radial distance in the space–time geometry. The analysis focusses on effective potential curves obtained from specific equations, examining the dynamics of massless and massive particles in different scenarios. Moreover, it examines the stability of particle orbits using the Lyapunov exponent and explains how the circular orbit of a particle moving under the influence of gravitational field of the black hole is conditionally stabilised. This paper examines how the cosmological constant and gravitational modification parameter influence the circular and geodesic motion of the particle. Finally, this paper provides a graphical analysis of the radius of the innermost stable circular orbit and outermost stable circular orbit of the particles moving in the field of modified gravity.

Current biosocial theories, such as the influence of neurotransmitters on the behaviour, ecological perspectives that consider cultural, political, and institutional factors and interpersonal views like attachment, have shaped our understanding of romantic and interpersonal relationships as typical social experiences. However, these theories fail to offer a comprehensive framework for the relationship dynamics and a fully integrated theoretical approach is still missing. Here, we have developed a mathematical model to investigate the dynamics of romantic and interpersonal relationships between male, female, child and society via a system of fractional differential equations (SFDEs) to provide insight into the love/hate behaviour. The model comprises four classes describing the love/hate of males, females, children and society. The modified operational matrix of integration (OMI) of the Legendre wavelets is presented and used to solve the SFDEs. The model is solved using RK4, NDSolve and the Legendre wavelet collocation method (LWCM) for numerical analysis and comparison of the solutions. Numerical and graphical study of fractional order is done for different values of (gamma ). The pictorial analysis of various values of parameters to show the variation of classes is done. The Mathematica software has been used for numerical computations. This study reveals how the internal relationship and status affect the status of the society.

This paper constructs a spreading model driven by positive and negative feedback interactions to study the impact of inter-individual feedback interaction on message spreading in online social networks. By analysing the network topology and the social attributes of the propagators, we introduce feedback interaction rules. In addition, the individual’s spreading motivation comes from the direct feedback interactions of multilevel neighbours and the group-level pressure of the social environment. Therefore, we established a feedback efficiency function. Experimental results show that the model is effective in promoting the positive spread of messages. Meanwhile, it is found that the increased social distance between individuals weakens the feedback strength, the group feedback rate enhances the expected spreading ability of the upline nodes and the group feedback has a more significant incentive effect than the neighbour feedback. Finally, the reasonableness of the model is verified by comparing with real cases.