Pramana最新文献

Hybrid nanomaterials have different applications and scientists have presented different methods to enhance the thermal efficiencies of cooling and heating systems, improving energy resources, thermal managements, extrusion processes, chemical reactions, etc. Current investigation reports a thermal study based on hybrid nanofluid model via fractional approach. The hybrid nanofluid contains molybdenum disulphide (MoS(_2)) and graphene oxide (GO) nanoparticles. Engine oil is used as a base liquid for which thermal properties need to be enhanced. Additionally, the impact of magnetic force is studied for electrically conducting hybrid nanofluid. Fractional computations are performed using Atanangana–Balenau (AB) fractional derivative, followed by the Laplace technique for integration assessment. The role of physical flow parameters is tested graphically. It is observed that the heat transfer phenomenon enhances due to nanoparticle volume fraction, the velocity profile declines due to Grashof number and skin friction coefficient increases due to fractional parameter and Grashof number.

Bolts are utilised extensively in machinery and often bear large loads. Reliable connection of bolts is related to the effective functioning of machinery. Therefore, it is of utmost importance to detect bolt looseness in time. However, the identification of bolt looseness is typically challenging due to the strong background noise. Compared with Gaussian white noise, only few researches were conducted on Poisson white noise. To detect the looseness of the bolt in the presence of strong Poisson white noise, we propose a novel method based on sub-harmonic resonance, time-domain averaging and adaptive stochastic resonance. The disadvantages of damaging characteristic frequencies that exist in a majority of approaches are overcome. In addition, the looseness is assessed by the quality factor derived from physical science. To verify the efficacy of the method, we propose numerical simulations and experimental validations. The results demonstrate that the proposed method has effectively detected bolt looseness under strong Poisson white noise. The detection of bolt looseness might benefit greatly by adopting the suggested approach.

Motivated by recent studies on non-local integrable models, we consider a non-local inhomogeneous linear differential equation model of Newtonian type:

where (lambda ) and (mu ) are real constants and f is continuous. Through decomposing functions into their even and odd parts, we transform the non-local model into a local model, and then with the classical ODE technique, solve the resulting local model under the even and odd constraints. The general solution involving two arbitrary constants is presented in nine cases of the coefficients.

This paper aims to propose a material-independent novel locally-active memristor (LAM) model, which is applied to the fourth-order autonomous chaotic oscillation circuit to investigate the phenomena and mechanisms of chaos and hyperchaos. Under different parameter configurations, the LAM-based system can exhibit rich dynamic behaviours and multistability, such as multi-equilibrium points, period, chaos and hyperchaos attractors. The phase diagram, bifurcation diagram, Lyapunov exponential spectrum, basins of attraction and dynamics map are used to analyse the complex dynamics of the system. In addition, we find many types of coexisting attractors, including periodic attractors with multiple different periods, hyperchaotic attractors with multiple different scrolls, a double-scroll chaotic attractor with a shock wave orbit and so on. This work fills the gap by theoretical analysis and numerical simulation. And proves that the local activity and non-volatility of memristors are two important reasons for the generation of complex and coexisting attractors.

Fluid mechanics has been linked to a wide range of disciplines, such as atmospheric science, oceanography and astrophysics. In this paper, we focus our attention on a ((3+1))-dimensional variable-coefficient Kadomtsev-Petviashvili-like equation in a fluid. Through the Hirota method, we derive a bilinear form. We obtain an auto-Bäcklund transformation based on the truncated Painlev(acute{textrm{e}}) expansion and a bilinear Bäcklund transformation based on the bilinear form. With the variable coefficients (alpha (t)), (beta (t)), (gamma (y,t)), (delta (t)) and (mu (t)) taken as certain constraints, one- and two-kink solutions are shown. Based on the one-kink solutions, we take (gamma (y,t)) as the linear and trigonometric functions of y, and then give the ring-type and periodic-type one-kink waves, where t and y are the independent variables. According to the two-kink solutions, we obtain the parabolic-type, linear-type and periodic-type kink waves.

The current work is concerned with some novel solutions of the new extended (3 + 1)-dimensional Boiti–Leon–Manna–Pempinelli equation (BLMPE) that plays a key role in the incompressible fluid. The N-soliton solutions (NSSs) are extracted by virtue of the Hirota form which is developed using the Cole–Hopf transform. Based on the NSSs, we elaborate the resonance conditions of the soliton molecules and derive the soliton molecules of the 2-solitons, 3-solitons and 4-solitons on the (x, y)-, (x, z)- and (y, z)-planes. Additionally, we also explore some novel hybrid interaction solutions including the interaction between the soliton molecule and solitons and the interaction between the breather solution and the solitons. Correspondingly, the dynamic properties of the solutions are depicted graphically. The derived solutions in this study are all new and can enlarge the exact solutions of the new extended (3 + 1)-dimensional BLMPE. Besides, they can enable us to understand nonlinear dynamic behaviours better.

The spherical tokamak (ST) operates in a steady state with a high fusion gain. The 0-dimensional power balance model, including radiation losses to determine Q value as an inductive fusion gain, and the current balance model for determining (Q_{textrm{CD}}) as a non-inductive fusion gain, is used to investigate the viability of D–(^{3})He fuel for a steady-state operation. The spherical tokamak’s geometry, including the magnetic field (B_{t}) and (beta _{textrm{th}}) as a ratio of its kinetic pressure to the magnetic pressure, is used to analyse the impact of the confinement enhancement factor (H_{y2}) and the impurity density fraction (f_{textrm{I}}) on (Q_{textrm{CD}}). By comparing the obtained values with the device data, plasma characteristics, such as the safety factor (q_{textrm{I}}) and Greenwald density limit (N_{textrm{G}}) are examined to determine the optimum density limit and safety factor for an assurance about (Qapprox Q_{textrm{CD}}) as the aim of steady-state operation. A comparison with ARIES-III performance is also made. The overall plant power balance equation is included. Furthermore, the desirable plant thermal efficiency value (eta _{textrm{th}}) and normalised beta value (beta _{N}) for producing net electric power (P_{textrm{NET}}>) 1 GW for the ST are achieved. Therefore, ST’s capability of having a lower aspect ratio A and higher elongation (kappa _{s}) than ARIES-III in generating more significant fusion power with lower (H_{y2}) and higher energy confinement time (tau _{E}) is approved.

A comparison of the vorticity field tensor with the electromagnetic tensor is done. An attempt is made to express the vorticity and its dual in the language of geometric algebra using bivectors. In the language of geometric algebra, all four fluid Maxwell’s equations are reduced to a single equation in two ways, i.e., using a bivector (textbf{F}) and also its Hodge dual (mathbf {F^*}), and these are analogous to the corresponding results in electromagnetism. The complex structure (textbf{F}=textbf{L}-Itextbf{W}) in fluid dynamics is a novel approach in this work. A multivector representation of Maxwell’s equations and an expression for the Poynting vector are also obtained.

Physical parameters are necessary to determine the suitability of the chalcogenide materials for specific applications. The present study reports the physical characteristics of the multicomponent GeTe_2-x(SeSb)_x (x = 0, 0.2, 0.4, 0.6) chalcogenide glasses synthesised by the melt-quench technique. The differential scanning calorimetric (DSC) technique has been used at separate heating rates β = 5, 10, 15, 20 °C(/)min. XRD and SEM–EDX studies have been carried out for structural and morphological analyses. The average coordination number and constraints of the compound have been calculated which indicates that the composition forms a glassy system. Lone pair electrons present in the composition have been evaluated. R parameter has a value greater than 1, indicating that the composition has sufficient chalcogen, chalcogen–chalcogen and heteropolar bonds. The overall bond energy of the compound has been calculated using the chemical bonding approach to understand the fine-structure properties of the compound. Cohesive energy has been observed to increase with composition. Thermal stability, glass transition temperature and glass forming ability of the compound have been calculated using different relations like Saad and Poulin relation, Dieztal relation, Hurby parameter (H_r) and reduced glass transition temperature (T_rg) and studied theoretically to examine the thermal stability of the composition that shows that the prepared samples are suitable for data storage.