Band 80, Heft 6

The heat transfer analysis from the mixture flow of Carreau fluid in infinite horizontal parallel plates under the impact of the magnetic field is proposed in this theoretical analysis. The flow and heat transfer analysis through parallel plates offers various applications in nuclear reactors, microfluidic devices, lubrication systems, chemical, industrial and biological systems, etc. With motivation of current non-Newtonian fluids (Carrreau fluid) used in industries and chemical engineering, the goal of this research is to develop a mathematical model based on fluid phase and particulate phase to control the temperature of fluid and increase the convective heat transfer in considered non-Newtonian fluids under the suitable range of the physical parameters including magnetic field parameter, Darcy number, Power-law index, slip boundary conditions, volume fraction density and Weissenberg number. The nonlinear mathematical model is established with the contribution of the stress tensor and solved through the perturbation series technique. The computational results are discussed through plots and tables. From the calculated data it is perceived that volume fraction density improved the velocity and temperature distributions. It is also noted that the contribution of the magnetic field declines the flow and thermal field. The slip parameters and Darcy number upsurge the velocity and temperature fields. The comparative analysis between mixture phase flow and simple phase flow is also discussed and observed that the mixture phase flow gives more heat transfer in Carreau fluid as compared to simple phase fluid. The present research will help to understand the basic research of the mixture-phase flow of highly viscous fluid through the porous medium when the uniform magnetic field is applied transversely. Further, applications of the present study are found in medical treatment with wound healing and hyperthermia, heat exchangers, nuclear reactors, etc. This research can also be useful in petroleum industries for cleaning and purifying immiscible oils.

Discrete nonlinear systems involving memristors have been extensively studied in recent years. In this work, we combine the nonlinearity of a discrete memristor with a sinusoidal transformation scheme to construct a new 3D discrete hyperchaotic circuit, which is useful for image encryption. Firstly, we perform a dynamical analysis of the proposed system. Using analytical and numerical tools, we find that the model exhibits rich and complex dynamics, including fixed-point planes, hidden attractors, hyperchaos, periodicity, and multistability. To demonstrate its practical implementation, the proposed oscillator is integrated into a microcontroller-based laboratory setup, and the experimental results closely match the numerical findings. Secondly, hyperchaotic sequences generated by the new model are used to build a simple 8 × 8 S-box for secure image encryption. The hyperchaotic sequences are first used to shuffle the columns and rows of the original image, which is then substituted using the 8 × 8 substitution box and finally encrypted through nonlinear diffusion. To validate the performance of our protocol, we conduct standard security analyses, including correlation coefficient evaluation, pixel change rate, information entropy, time complexity, and key space analysis. The results are in perfect agreement with those in the literature.

The flow of non-Newtonian fluids is commonly used in many biological systems such as the transport of foods through the digestive sector, circulations of the blood, and motion of the urine from the bladder to the kidney, etc. Motivated by the applications of non-Newtonian fluids in various biological systems, the objective of this research is to examine the comparative analysis of ciliated and non-ciliated walls in a two-phase flow of Ellis fluid model through a horizontal tube under the impact of the thermal radiation and viscous dissipation by using the WOLFRAM MATHEMATICA 14.1. The fluid and particle suspension models are developed in terms of conservation of mass, momentum, and energy equations with the help of the Ellis fluid model. The dimensionless quantities are utilized to convert the problem into dimensionless form. The assumption of long-wavelength approximation and low-Reynolds number are employed to simplify and generate the exact solution through WOLFRAM MATHEMATICA. The calculated results revealed that the heat transfer rate is increased by 12 % and 25 % against the variation in volume concentration of particle and Brinkman number, respectively, and the thermal radiation parameter drops the heat transfer rate up to 27 %. The wall shear stress is increased by 18 % and 31 % for Ellis’s fluid parameter and amplitude ratio, respectively. The size of the bolus is increased and decreased at the upper and lower wall of the tube respectively against the Ellis fluid parameter. The calculated results of the present study can be useful in understanding the role of ciliated and non-ciliated walls in peristaltic flows and how these are important in flow and heat transfer mechanisms.

In a recent article, we proposed an example suggesting a possible link between the Heisenberg–Euler (HE) model of nonlinear electrodynamics (NLED) and relativistic type-II superconductivity, drawing parallels with the Ginzburg–Landau (GL) theory. In cylindrical coordinates, we considered a concrete static electromagnetic (EM) four-potential in vacuum with Gaussian-like behavior in the radial coordinate. This work extends our analysis to a time-dependent EM potential with a Gaussian-like radial profile and a time-dependent harmonic sinusoidal angular behavior. By deriving nonlinear Maxwell’s equations from the HE Lagrangian, we determine the four-current density. Concurrently, we investigate relativistic type-II superconductivity in analogy with the GL theory. This leads us to propose a specific form for the relativistic vortex’s supercurrent density and to establish a connection between this current and the HE current. As a result, we deduce a relation that allows us to obtain the relativistic order parameter that characterizes the macroscopic quantum state of the superconductor. Thereafter, we present a discussion on possible corrections to our results in relation to the extended GL (EGL) formalism. This formalism provides a more sophisticated description of vortex dynamics in type-II superconductors. Additionally, we briefly comment on high-temperature condensates in intense EM fields where relativistic effects may become prominent. This scenario is particularly relevant to neutron stars, where the formation of superconducting protons and superfluid neutrons in neutron-star outer cores can lead to coupled multiband-like effects.

In this study, we present a modified quantum theory, denoted as QT *, which introduces mass-dependent decoherence effects. These effects are derived by averaging the influence of a proposed global quantum fluctuation in position and velocity. While QT * is initially conceived as a conceptual framework – a “toy theory” – to demonstrate the internal consistency of specific perspectives in the measurement process debate, it also exhibits physical features worthy of serious consideration. The introduced decoherence effects create a distinction between micro- and macrosystems, determined by a characteristic mass-dependent decoherence timescale, τ ( m ). For macrosystems, QT * can be approximated by classical statistical mechanics (CSM), while for microsystems, the conventional quantum theory QT remains applicable. The quantum measurement process is analyzed within the framework of QT *, where Galilean decoherence enables the transition from entangled states to proper mixtures. This transition supports an ignorance-based interpretation of measurement outcomes, aligning with the ensemble interpretation of quantum states. To illustrate the theory’s application, the Stern–Gerlach spin measurement is explored. This example demonstrates that internal consistency can be achieved despite the challenges of modeling interactions with macroscopic detectors.

Research into tunable broadband absorbers has recently grown in popularity due to the terahertz technology’s spectacular development. This article proposes and analyzes a metamaterial structure based on vanadium dioxide (VO 2 ) that can be used as a broadband terahertz absorber, which is tuned dynamically. The upper layer of the absorber is made of VO 2 , the ground is composed of gold, and middle dielectric substrate is made of polyimide. The prescribed design provides more than 95 % of absorption with 4 THz bandwidth from 3.3 to 7.3 THz. Moreover, absorption peak intensity can be constantly enhanced from 5 % to 97 % when the VO 2 ’s conductivity varies from 200 to 2 × 10 5  S/m. This transition enables dynamic control between high absorption and high reflection states. This research endeavours to thoroughly investigate VO 2 -based THz Metamaterial Absorber (MMA), encompassing all aspects of the design validation and modelling using an electronic equivalent lumped design. The conductive phenomena of VO 2 radiating patch to achieve a high percentage absorption for the relevant absorption frequency band is very useful to understand. Additionally, it has been verified that the polarization angle has no effect on the absorptance. The prescribed absorber has potential applications including terahertz imaging, sensing, detection, electromagnetic cloaking, and optoelectronic switches.

The present theoretical analysis elaborates on the thermal entrance problem using the Cattaneo–Cristov heat flux model. The modified heat equation for the Cattaneo–Cristov model is solved via an integral transform technique. The entering fluid has a uniform velocity and constant physical characteristics. Temperature jump boundary conditions and axial conduction are also considered. A hybrid scheme is utilized to achieve the solution of the modified heat equation with the aid of Mathematica 13 platform. The results of bulk temperature, local, and mean Nussetle number are plotted for different embedded parameters. Applications for this type of study include heat exchangers, plug flow reactors, low Prandtl number liquid flows, and duct-flowing liquid metals with low Reynolds numbers.