Pramana最新文献

The current paper focusses on the heat transfer characteristics in nanofluid MHD flow across a decelerated rotating disk with uniform suction. It is concerned with conventional von Karman flow pumping, but unlike a typical Newtonian fluid, it uses water-based nanofluids made up of TiO(_2), Al(_2)O(_3), Ag, CuO and Cu nanoparticles. The thermal energy equation was added to the classic von Karman flow problem in three dimensions. After employing the similarity transformations used by Watson and Wang, the leading equations transformed into a set of ordinary differential equations were numerically solved by using bvp4c MATLAB solver. Graphs were used to evaluate the behavioural study of heat transfer for various parameters. Furthermore, it can be stated that for a smaller Prandtl number Pr, the heat transfer rate is highest for all types of naofluids. The rate of heat transmission reduces as suction parameter A increases. The local Nusselt numbers are calculated and analysed and the path to enhance heat transfer is also proposed.

Hybrid entangled states are necessary for quantum information processing within heterogeneous quantum networks. We develop an entanglement mechanism between continuous variable (CV) states of definite parity and delocalized photon (discrete variable (DV) state) leading to deterministic generation of the hybrid entangled states. The mechanism is realized by means of mixing of the input states on beam splitter (BS) with arbitrary transmission and reflection coefficients followed by measurement of the number of photons in the measurement mode by photon number resolving (PNR) detector. The scheme under study allows for one to partially control hybrid entanglement by change of the transmission/reflection coefficients of the BS. There are wide domains of values which guarantee the generation of maximum hybrid entanglement. The mechanism of the CV–DV entanglement can be used for controllable entangled state distribution in hybrid optical network.

The paper aims to construct optical solitons and travelling wave solutions to two birefringent nonlinear models which consist of two-component form of vector solitons in optical fibre: the Biswas–Arshed model with Kerr-type nonlinearity and without four-wave mixing terms and the nonlinear Schrödinger equation with quadratic-cubic law of refractive index along with four-wave mixing terms. These nonlinear Schrödinger equations are applied in many physical and engineering fields. Optical solitons are considered in the context of photonic crystal fibres, couplers, polarisation-preserving fibres, metamaterials, birefringent fibres, and so on. Two reliable integration architectures, namely, the extended simplest equation method and the generalised sub-ODE approach, are adopted. As a result, bright soliton, kink and dark soliton, singular soliton, hyperbolic wave, a periodic wave, elliptic function solutions of Weierstrass and Jacobian types, and other travelling wave solutions, such as breather solutions and optical rogons, are derived, together with the existence conditions. In addition, the amplitude and intensity diagrams are portrayed by taking appropriate values for a few selected solutions. Furthermore, based on linear stability analysis, the modulation instability was explored for the obtained steady-state solutions. The reported results of this paper can enrich the dynamical behaviours of the two considered nonlinear models and can be useful in many scientific fields, such as mathematical physics, mathematical biology, telecommunications, engineering and optical fibres. This study confirms that the proposed approaches are sufficiently effective in extracting a variety of analytical solutions to other nonlinear models in both engineering and science.

The unstable nonlinear Schrödinger equation (UNLSE) characterises the time evolution of disturbances through unstable or marginally stable media. We study the stochastic UNLSE and stochastic modified UNLSE (mUNLSE). We apply the unified solver to provide some new stochastic solutions via Rayleigh distribution. The gained stochastic solutions play a crucial role in nonlinear sciences. Rayleigh distribution is used to depict the dispersion random input. In light of description of the behaviour of stochastic solutions, their mean and variance are illustrated. We show the influence of random parameters on the gained stochastic solutions. With the aid of Maple software, various profile pictures are introduced to exhibit the dynamical behaviour of the stochastic solutions.

We show here that a direct application of resummation-based quantum Monte Carlo (QMC) — implemented recently for sign-problem-free SU(2)-symmetric spin Hamiltonians in the stochastic series expansion (SSE) framework — does not reduce the sign problem for frustrated SU(2)-symmetric (S=frac{1}{2}) Heisenberg antiferromagnets on canonical geometrically frustrated lattices composed of triangular motifs such as the triangular lattice. In the process, we demonstrate that resummation-based updates do provide an ergodic sampling of the SSE-based QMC configurations which can be an issue when using the standard SSE updates, however, severely limited by the sign problem as previously mentioned. The notions laid out in these notes may be useful in the design of better algorithms for geometrically frustrated magnets.

The aim of this study is to discuss viable anisotropic solutions of self-gravitating system through a minimal geometric deformation approach in the perspective of (f(R, T^{2})) gravity. In this regard, we assume two sources (seed and additional) for the static sphere. The seed source is considered to be isotropic, while the additional source induces anisotropy. The field equations are decoupled into two sets by deforming the radial metric function. The metric potentials of the Krori–Barua solution are employed to obtain exact solution of the field equations while three different constraints are used to find the solutions corresponding to the anisotropic source. Junction conditions are utilised to determine the values of unknown constants at the hypersurface. Finally, we check the viability and stability of the obtained solutions using the star candidate PSR J1614-2230. We show that all the three solutions satisfy the viability conditions. It is found that solution I is stable using both Herrara’s cracking as well as squared sound speed approach while solutions II and III are stable using only Herrara’s cracking approach.

The pulse-shaped explosion (abbreviated as PSE) behavior, represented as the system roots pulse-shaped quantitative changing sharply, is a new way to the bursting oscillations proposed recently. In the present paper, the complex bursting oscillation patterns triggered by the PSE and integer frequency ratios are considered based on a Rayleigh–van der Pol system (abbreviated as RVDPS) excited by the parametrical and external forces. Two cascade bursting oscillations, the cascade supHopf/supHopf bursting oscillations induced by the integer frequency ratios and the cascade supHopf/supHopf bursting oscillations with multiple PSE/PSE hysteresis loops induced by the integer frequency ratios and PSEs, are investigated. We show that the PSEs occur when the system solution curve approaches to infinity at some certain values and the PSEs do not change the stabilities of the attractors. In addition, we find that the frequency and period of the cascade bursting oscillation patterns equal to that of the external force. Our study proposes a new PSE type to the bursting oscillations named the cascade PSEs and increases two cascade bursting oscillation patterns.

With the aid of the reciprocal transformation between the modified short pulse (mSP) equation and the sine-Gordon (sG) equation, certain periodic solutions of the mSP equation are constructed. Both one-phase and two-phase periodic solutions are presented. Taking the proper limits of those periodic solutions, various solitary wave solutions such as one-cuspon, two-cuspon and one-breather solutions are recovered. In addition, three novel standing wave solutions for the mSP equation are obtained.

In this study, the behaviour of the triple product ((n_itau _E T_i)) and height of the saddle point are investigated on the basis of the particle and power balance equations by considering primary reaction and side reactions among all product and reactant species in a spherical torus nuclear fusion reactor. For this purpose, a set of equations are coupled and solved numerically. Ignition capability is investigated and compared for different types of side reactions and other features like, the ratio between particle and energy confinement time and hot ion modes. Finally, the results are compared with each other to improve future research.

This research presents the simulation, fabrication, and measurement of a new terahertz (THz) metamaterial absorber (MMA). Copper and polyimide are the materials used in this project. The polyimide substrate is sandwiched between the two copper conductor layers. Theoretical results reveal that the absorber has five distinct and significant absorption peaks at 0.994, 0.97, 0.947, 0.904 and 0.892 THz, respectively, with absorption rates of 94%, 99.9%, 99.9%, 97%, and 92%. The electric field, magnetic field, and surface current distributions are used to investigate the structure’s physical mechanism. The incident and polarisation angles of the structure are modified from 0 to 90 degrees to examine the insensitive behaviour of the incident angle and polarisation angle. Laser micromachining and terahertz time-domain spectroscopy are used to build and examine the structure. This work is compared with previous works. It has numerous scientific and sensory applications.