International Journal of Modern Physics C

The focus in this study is to examine the flow formation of Taylor–Couette (T–C) for some fluids exhibiting non-Newtonian properties in a region of cylindrical annulus due to the effect of imposed stresses on the periphery of the inner cylinder while the outer cylinder is hanging around inert. This tangential shear will be liable for the motion of the fluid through the annulus. It is very often when researchers in different fields like engineering, mathematics and physics come across the complexity that the given mathematical model cannot be solved in the existing space and requires to be transformed in the space in which it can be easily solved. Thus, transforms are being used as a key tool for solving many dominant problems in different fields. Many transformations have been introduced by researchers but for solving problems in this study, we will make use of Hankel transform and Laplace transform to obtain the velocity field and the corresponding shear stresses (SS) for the fractional Oldroyd-B fluid (O-B fluid). In the end, a graphical presentation is given for the comparison of the effect on fluid motion due to different parameters like fractional parameters, relaxation and retardation times.

In urban traffic systems, alleviating traffic congestion originated from left-turn/U-turn lanes at highly demanded intersections plays an important role in enhancing the traffic efficiency. For a typical intersection, the layout with double left-turn (DLT) lanes is a relatively common geometric feature. However, the effect of DLT scheme on the performance of the entire traffic system is not clear. This paper compares the performance of urban traffic system with different lane function schemes with extended cellular automaton (CA) model considering the car-following, lane-changing, intersection-traversing and route-choice behavior of vehicles. Using the flow-density relation, three macroscopic parameters (average trip completion rate, average traffic flow and average velocity) are examined to evaluate the system performance. With the wide application of DLT scheme, the vehicles can be distributed more evenly among the lanes. As a result, the traffic flow and the trip completion rate will be higher, especially at high density. Case studies of realistic Hefei city network and Sioux Falls networks are also carried out. The results show that the performance of traffic network will be better if more intersections adopt the DLT scheme.

We study an extension of the Bornholdt spin-market model using configurable network topology. The distribution of returns was studied using the probability plot correlation coefficient and indicates three different behaviors for the tails of the distribution of returns. The price volatility was studied by fitting the magnetization with a Wiener process and a power-law behavior was found for the volatility as a function of the levels of randomness and connectivity of the network. Both parameters have opposing effects on the risk as inferred from the Shannon entropy of the magnetization. Also, we show that trading can spatially auto-organize depending on the conditions of the control space. Finally, we show that there is a range of values of the control space that renders a model that reproduces real-market data.

Herein, we propose new efficient spectral algorithms for handling the fractional diffusion wave equation (FDWE) and fractional diffusion wave equation with damping (FDWED). In these algorithms, we employ new basis functions of the shifted fifth-kind Chebyshev polynomials that satisfy all the initial and boundary conditions of the equation. The key idea of the presented algorithms depends on transforming the FDWE and FDWED with their underlying conditions into systems of algebraic equations in the unknown expansion coefficients. Our study is supported by a careful convergence analysis of the suggested shifted fifth-kind Chebyshev expansion. Finally, some numerical examples are presented to confirm the accuracy and efficiency of the proposed algorithms.

We have developed a software library that simulates noisy quantum logic circuits. We represent quantum states by their density matrices in the Pauli basis, and incorporate possible errors in initialization, logic gates, memory and measurement using simple models. Our quantum simulator is implemented as a new backend on IBM’s open-source Qiskit platform. In this paper, we provide its description, and illustrate it with some simple examples.

The aim of this work is to provide an efficient technique for numerical solutions of the reaction–dispersion equations including convection and diffusion. The Chebyshev spectral collocation method (ChSCM) is used in both space and time to exhibit anti-kink-type waves that appear as the result of the proposed model equations. It is shown that the revealed solutions are promising to efficiently catch such challenging physical behavior. Quantitative convergence results in both time and space are illustrated for the reaction–dispersion problems.

Community detection in signed networks has become a research hotspot in the area of network science recently. Since the classical problem has great significance for theoretical analysis and practical application, many heuristics or metaheuristics have been presented. Despite some progress and results that have been achieved, it remains an open challenge to identify community structure in large signed networks. In this paper, we propose a simple and effective iterated local search algorithm coupled with a powerful local search mechanism to solve the community detection problem. Due to the limitation of modularity in resolution, the modularity density criterion is adopted to find communities in signed networks. Extensive experiments have been conducted on synthetic and real-world networks. The statistical analyses demonstrate that the proposed algorithm can provide high-quality solutions compared to the state-of-the-art algorithms.

The thermal properties of three diatomic molecules such as hydrogen (H₂), carbon monoxide (CO) and iodine (I₂) are theoretically predicted. To this end, two different potential models are considered, Morse potential and improved deformed exponential-type potential (IDEP). The Schrödinger equation is analytically solved to obtain energy levels. For the Morse and IDEP potential models, the Laplace transformation and the Greene–Aldrich approximation and appropriate coordinate transformation are employed, respectively. In the former potential model, we have obtained energy eigenvalues by considering position-dependent effective mass. Using the energy levels of two models, the partition function is first determined. Second, thermal functions of the molecules such as heat capacity, enthalpy and entropy are obtained and compared with the available results. The calculated enthalpy using the two models for CO and I₂ molecules is in excellent agreement in comparison with the available data in a wide temperature range. But, the obtained enthalpy of H₂ molecule using the Morse potential at high temperatures does not agree excellently with the experimental data. The entropy of H₂, CO and I₂ using the two models is tin good agreement in comparison with the available data in a wide temperature range whereas the entropy of H₂ at low temperatures does not agree excellently with the experimental data. Our theoretical results using the two potential models do not show a suitable prediction about the heat capacity at a constant pressure of H₂, CO and I₂ molecules, But the IDEP shows more agreement compared to the Morse potential.

Motivated by recent research works on the flat-band correlated electron systems, we construct a plaquette-Lieb lattice, which exhibits nearly flat bands close to the Fermi level around half-filling, when the inter-plaquette hopping integral is much smaller than the intra-plaquette one. A detailed comparison study with the well-known checkerboard lattice indicates that there exist significant differences for the pairing property between the two lattices, and the nearly flat bands on the plaquette-Lieb lattice strongly enhance the $d$-wave pairing correlation for repulsive on-site Hubbard interaction and $s$-wave pairing correlation for attractive on-site Hubbard interaction. Our study not only provides a new lattice with nearly flat bands, but also deepens the understanding of electronic structure on superconductivity.

In this work, an approximate analytical solution for the problem of non-Newtonian Casson fluid flow past a porous exponentially stretching sheet with Joule heating and convective boundary condition is obtained using a relatively new technique; He’s homotopy perturbation (HPM). The major feature of HPM is that it does not need the small parameters in the equations, and hence the determination of classical perturbation can be discarded. Due to the complete efficiency of the HPM, it becomes practically well suited for use in this field of study. Also, the obtained solutions for both the velocity and temperature field are graphically sketched. The results reveal that the method is very effective, convenient and quite accurate to systems of nonlinear equations.

The present investigation set out to assess the influence of the surface roughness on the flow and thermal mean quantities, around the heated corrugated cylinder in the laminar steady flow. The current investigation has been devoted to a numerical analysis of a two-dimensional steady flow and forced convection heat transfer characteristics over a heated longitudinal sinusoidal shape grooved cylinder, immersed in an unconfined Newtonian fluid. The number of the grooved cavities was chosen to be 10, 20 and 30 grooves, equally distributed around the cylinder circumference with wavelength and wave amplitude of 1/50 and 1, respectively. Moreover, the thermal boundary condition effect has been analyzed by imposing a uniform heat flux and constant temperature on the cylinder periphery as a thermal boundary condition, over a Reynolds number range of ($0.1\le \mathrm{\text{Re}}\le 40$) and a fixed Prandtl number of 0.715. The numerical procedure is based on the finite volume method. The findings indicate that with increasing groove number, the total drag coefficient of the grooved cylinder reduces markedly compared to the smooth one. This trend is more pronounced as the Reynolds number increases. The effect of the groove number on the pressure coefficients is limited, where the profiles of the grooved cylinder coincide with that of the smooth one over the Reynolds number range. When the Reynolds number varies from 0.1 to 40, the average Nusselt number enhances noticeably by about 86% for the smooth and grooved cylinders. Moreover, the groove number affects significantly the average Nusselt number, where the increased groove number results in a gradual reduction in the average Nusselt number. This attenuation is more pronounced as the Reynolds number increases. To predict the average Nusselt number, a correlation has been proposed.

In this study, the flow pattern and scouring around the submerged sharp edge weir, with different slope angles, have been numerically simulated using the Flow-3D model. After validating the results of the numerical model in simulating the flow pattern and scour around the weir with a 90^∘ angle, the effect of the weir angles relative to the upstream and downstream on the flow and scour field had been investigated. The results showed upstream and downstream of the weir, vortex flows were formed and by taking an angle of 90^∘, the vortex flows were weakened. In addition, the downstream slope of the weir had little effect on the upstream water level and most changes occurred in the downstream flow depth with a 90^∘ angle. The downstream scour depth was independent of the upstream slope angle and the upstream scour depth was independent of the downstream slope. When the upstream angle became closer to the horizon, scouring was reduced in this area. The depth of scour downstream was greater than the depth of scouring upstream. Angles of 50^∘, 70^∘, 110^∘ and 130^∘ had slight changes in the depth of the downstream scour, but compared to the angle of 90^∘, the depth of the downstream scour for these angles decreased significantly.

As COVID-19 spread globally in 2020, the interaction between the traffic dynamics and the spread of the epidemic has attracted much attention. However, controlling the spread of the epidemic remains a challenging issue. In this paper, we have investigated the relationships between link-closure strategies and the traffic-driven epidemic spreading. It is found that the epidemic spreading can be suppressed by the targeted closing of links between small-degree nodes. In contrast, closing links between large-degree nodes can accelerate the outbreak of the epidemic. These findings have significance for controlling the spread of the epidemic.

In this study, two-dimensional incompressible steady and time-dependent magnetohydrodynamic (MHD) flows around a cylinder were simulated by applying a finite volume method. The method was first validated through fair agreement of its results with the analytical solution for MHD flows inside the channels. It was then applied to simulate the MHD flows around a cylinder at Reynolds (Re) numbers varying from 100 to 1000 and Hartmann (Ha) numbers varying from 10 to 100. According to the results, although the increase in Re number strengthens the flow instability, the magnetic field suppresses this effect. The evidence for this claim is that the increase in Ha number leads to reduce in the separation angle for each Re number. This was in such a way that no flow separation was observed at Ha number equal to 50 and above for any considered Re number. Instability and therefore unsteady flows were seen only for the cases where Ha number was equal to 10 (the minimum considered value) and Re number was 500 or above. The drag coefficient (as a constant value for steady flows) or its average value (for unsteady flows) was enhanced by increasing the Ha number. The amplitude of the drag and lift coefficient fluctuations for unsteady cases were grown up by increasing the Re number. The Strouhal number was also found as a parameter that is dependent on both Re and Ha numbers.