International Journal of Modern Physics B

In this paper, we explore the use of opinion dynamics models to examine changes in opinions of lifelong learning, and to identify groups of people for targeted intervention to improve their reception to lifelong learning. This method has a multitude of potential applications related to clustering and segmentation. Singapore’s initiative for lifelong learning, SkillsFuture, serves as a case study for the application of the technique. We first found a positive correlation between how motivated people are to learn and a negative correlation between how much people know about SkillsFuture opportunities, with respect to their reception to SkillsFuture courses. Then, we used an opinion dynamics model to model the evolution of opinions to produce clusters of people whose opinions will converge. The clusters were then grouped into three groups: those with the largest increase, largest decrease and a middle group. Further examining the covariates of the people in each cluster (e.g., age, last drawn salary, etc.), we propose organizing sharing sessions for the group with the largest increase, intervention for the group with the largest decrease, and gathering more information about the motivations of the middle group.

There are several uses for bio-convection mechanisms, such as in sedimentary pools, fuel models, and microbially accelerated oil restoration. These are the basis of motile microorganisms which are applied to improve the mixability of fluid and tiny nanoparticles because they are accountable for biological transmission procedure. This work examines the bio-convective nanoparticles fluid flow and electrically conducting incompressible magneto-hydrodynamic flow of nanofluid towards a chemically reactive stretchable surface. Buongiorno model is considered here, which incorporates Brownian motion and thermophoretic diffusion, is employed in this study to explain how nanofluids improve heat transfer. The controlling boundary layer nonlinear PDEs are converted into ODEs by utilizing certain suitable similarity approaches. Numerical scheme is adopted to solve the transformed ordinary differential equations. The main findings of this research are that the magnetic field slows motion of the fluid when the thermal and mass buoyancy forces speed it up, and that thermophoretic diffusion increases the temperature and concentration of dimensionless fluids, resulting in stronger concentration and thermal boundary layers. The Brownian motion, concentration exponent, and chemical reaction parameters show an inverse relationship between temperature and concentration. Additionally, the first-order chemical reaction creates a lighter concentration boundary layer while the magnetic field’s presence due to impact of thermal and mass buoyancies helps to lower the heat transfer rate and shear stress. The findings show that while the Nusselt number and wall shear stress values are declining, the microorganism number is increasing.

Bound states in the continuum (BICs) are a special kind of resonant states that remain localized even though they coexist with a continuous spectrum of radiating waves. They have already emerged as an important design principle for creating systems with high-quality ($Q)$ factor states to enhance light–matter interaction. Many approaches have been proposed to achieve BICs, but it is still of great challenge to design multiple BICs simultaneously, and especially working at terahertz (THz) frequencies. In this paper, we propose an all-dielectric metamaterial, consisting of four hollow cylinders in each unit cell. We show dual BICs exist in such a simple structure, and as breaking the symmetry via varying the inner radius of two diagonal cylinders, they will turn to quasi-BICs with high yet finite Q-factor. These quasi-BICs are manifested themselves as two new dips in the transmission spectrum, of which the resonance shapes can be well described by the Fano formula with a few fitting parameters. We find the evolution of their Q-factors still follows the simple linear relationship with respect to the inverse square of the asymmetry parameter. Based on the multipole decomposition method, two BICs are further investigated to show different multipole components for them. Interestingly, the higher frequency BIC is closely related to the excitation of toroidal dipole (TD), which will split into two TDs as breaking the symmetry. The proposed metamaterial provides an alternative platform to merge the physics of BICs, Fano, and TD, and to pave the way for potential device applications (since the states of extremely high-Q factor).

This work has studied some nonlinear optical properties of Al_0.3Ga_0.7As/GaAs quantum dot system with tangent-square potential (TSP), with special emphasis on the role of second harmonic generation (SHG) coefficient under hydrostatic pressure and temperature. Due to the strain of external application conditions, the changes of the energy level and wave function of the neutron band in the system structure provide valuable insights into the optical properties of the quantum dot structure. In this paper, we report the effects of structural parameters, temperature and hydrostatic pressure on the SHG coefficient. According to the results obtained in the work, it can be reported that the nonlinear optical properties of the quantum dot system can be improved by adjusting the hydrostatic pressure and temperature. At the same time, the interaction of various parameters has produced some interesting observations, which are relevant in relevant research fields.

This work presents an innovative platform of a multi-channel one-dimensional photonic crystal (1-DPC) based on blood refractive index data of different patients in the aspect of the main protein components like hemoglobin. This photonic crystal (PC) contains a defect center infiltrated with plasma using a microorder size syringe. When binary silica and III–V semiconductor (InSb) materials are combined, they increase the refractive index difference between the alternate layers of the composite material, resulting in a wide photonic band gap (PBG). We use the well-known transfer matrix method (TMM) to observe the reflectance of various blood samples that were previously published. We assess and contrast the influence of different refractive index data on the dynamic shift in PBG calculation for novel superior and resourceful sensor in the prevention of microscopic organisms such as SARS-CoV-2, the virus linked with COVID-19. Yet, the performance of this PC has more moral content and unlimited casting efficacy in the face of an incurable virus.

Experimental studies have shown that many natural and artificial systems need to maintain stable oscillations during application, but the occurrence of oscillation quenching phenomenon will destroy the oscillation activity of the system and hinder the normal operation of the system. In this paper, to solve the important problem of oscillation quenching leading to system paralysis, the weighted average function of oscillators is applied to each oscillator as an external feedback, which is an extension of the mean-field feedback [N. Zhao and Z. Sun, Int. J. Bifurcation Chaos 30, 2050094 (2020)]. Taking the Stuart–Landau oscillators with the identical and nonidentical frequencies as examples, respectively, we find that the weighted average feedback is better than the previously proposed mean-field feedback in eliminating oscillation quenching with different coupling scenarios. Especially, when the weight is 0 or 1, that is, when a single oscillator is used as the feedback, the weighted average feedback is highly efficient in reviving oscillation. Our results provide a more convenient method to overcome these quenching states of coupled systems, and broaden the practical applications with respect to revoking rhythmic oscillations via external feedback in nature and real life.

It was precisely because LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode material had many advantages, including high voltage, high power, no pollution, low cost, etc., that it became a research hotspot for lithium-ion cathode materials. Although LiNi${}_{0.5}$Mn${}_{1.5}$O₄ has a three-dimensional Li${}^{+}$ diffusion channel, there are still some problems that lead to capacity decay and reduced cycling stability, limiting its commercial application. In this paper, the LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode material was prepared by the freezing precipitation method. We studied the effects of different drying methods, such as blast drying, water bath drying and freeze-drying on the structure, morphology and electrochemical properties of LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode materials. The study found that the LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode material prepared by the precipitation-freeze-drying method had a complete crystal form, a stable structure and no Li_xNi${}_{1-x}$O impurity peak. The SEM image showed that the particles were smaller and had a smooth surface. The initial discharge-specific capacity at 0.1C was 105.2mAh⋅g${}^{-1}$. After 50 cycles, its specific discharge capacity was 99.4mAh⋅g${}^{-1}$ and the capacity retention rate was 94.5%. Compared with LiNi${}_{0.5}$Mn${}_{1.5}$O₄ materials prepared by other methods, it had better electrochemical performance.

This research uses the Sinc Collocation method to numerically examine the Degasperis–Procesi and Benjamin–Bona–Mahony equations, achieving a high level of precision and accuracy on computational grounds with a variety of mesh points. The proposed technique involves global collocation using Sinc bases function (SBF) as an activation function. Initially, the time derivative discretization has been performed through finite difference scheme and the remaining spatial derivatives are approximated by $\theta$-weighted scheme to minimize the complexity in numerical computations. The main contribution of research is in modifying the proposed scheme to overcome the complexity involved in the whole process of finding solutions with a cardinal expansion of Sinc functions in nonlinear and singular systems. The solutions of Degasperis–Procesi and Benjamin–Bona–Mahony stiff nonlinear systems are illustrated numerically and graphically and the validation and verification of the obtained results are examined through stability analysis by calculating the spectral radius by bounding the value of $\theta$. A comparative study is presented with some of the well-known numerical techniques, which assured the accuracy and reliability of our technique.

Enhancing and preserving the atomic correlation and entanglement is of significant utility in quantum information. To this aim, we study the temporal evolution of uncertainty-induced nonlocality (${𝒰}$) and logarithmic negativity (${ℒ}{𝒩}$) as measures of quantum correlations (QCs) and quantum entanglement (QE) between two effective atoms coupled to a bosonic reservoir in the absence of thermal fluctuations and in the presence of Kerr medium (KM) and Stark shift (SS) under which n-photon transitions are permitted. We explore how Markovian and non-Markovian regimes affect the temporal dynamics of atomic correlation and entanglement and its limitations. Our findings indicate that by adjusting the KM and SS parameters, the quantum correlations between the two atoms can be enhanced and maintained while displaying similar qualitative behavior. Notably, it was observed that the QCs and QE quantities are at their highest magnitudes in the non-Markovian regime when the strengths of both SS and KM are increased, implying that QCs and QE are well protected. In contrast to the typical view that protecting the QCs from decoherence that may be observed owing to environmental noise, we proposed a gainful way to reduce the atomic decoherence by adjusting the number of n-photon transitions. Our investigation reveals that in the non-Markovian regime, the considered system exhibits better resistance against decoherence in comparison to the Markovian regime, as evidenced by the significant amount of quantum correlations detected among the two effective atoms at a specific point in time.

In this paper, the thermal behavior of cylindrical and conical pin fin structures operating in a convective–radiative environment has been examined. The fully wet porous fin structures are assumed to be mounted with a stretching/shrinking mechanism similar to a conveyer belt. The conical pin fin has been comparatively analyzed with the cylindrical one for three distinct cases of stretching, stagnant, and shrinking. Further, the Darcy model has been employed to analyze the fluid–solid interactions. The differential transformation method (DTM) has been used to solve the resulting second-order nonlinear ordinary differential equations. On the thermal performance of conical and cylindrical pin fin structures, the effects of the stretching/shrinking parameter, Peclet number, wet porous parameter, convective parameter, and radiative parameter have been established graphically. The conical pin fin is found to aid the heat transmission process better than the cylindrical one. The work is also helpful in the realm of microelectronics, particularly in the development of micro-pin-fin structures.

Optical birefringence measurements were performed on Ising-spin antiferromagnets with the chemical formula ACo$X_3$. The temperature dependences of the birefringences of CsCoCl₃ and CsCoBr₃ reflect the thermal shrinkage of the crystal lattice and the development of magnetic short-range correlation in Ising spin chains. Moreover, the temperature dependences of the birefringences of RbCoBr₃ and TlCoCl₃ show marked anomalies at structural phase transition points. We demonstrate a method of numerically analyzing the birefringence in magnetic compounds that undergo structural phase transitions.

In various systems of energy, such as turbo-machinery and viscous-lock system, squeeze film plays a crucial role for improving transport systems. The importance of the aforementioned applications led us to explore the physical behavior of Rabinowitsch fluid flow for several values of viscosity, $Q\in [0-1]$, load capacity $(W^{\ast })$, nonlinear factor, $\omega =[-2\times 10^{-4},0,2\times 10^{-4}]$, dimensionless film thickness $(h^{\ast })$, dimensionless radius of the capillary tube $(R_0^{\ast })$, dimensionless thickness of porous pad $(H_0^{\ast }=0,0.1,0.2$), inner and outer radius ratio $(\mathrm{\Omega }=0,0.2,0.4)$, roughness parameter $(c^{\ast }=0,0.1,0.2,0.3,0.4)$ through a squeeze film with two rough porous annular discs. Five-point Gauss quadrature integral formula has been used to examine the characteristics of annular discs, and small perturbation method has been used to discretize the governing Rabinowitsch fluid flow (RFF) equations. The modified Reynolds equation for rough, porous and viscosity change with film thickness is developed using Christensen’s stochastic theory, modified Darcy’s theory and the association between viscosity and film thickness agreement. The impacts of $\omega$ on the behavior of porosity and viscosity variability of RFF have been visually depicted in terms of film pressure, load capacity and squeeze reaction time of annular discs. It has been determined that for RFF with variable viscosity and roughness parameter on a porous media, the performance of the annular disks enhances for $\omega =-2\times 10^{-4}$ (dilatant lubricant), and diminishes for $\omega =2\times 10^{-4}$ (pseudo-plastic lubricant). It has been found that the film pressure in case of dilatant lubricant is increased by the influence of Rabinowitsch fluids on porous walls, but the behavior of pseudo-plastic lubricants has an opposite tendency relative to Newtonian lubricants. It has also been found that the impact of variability in porosity, roughness and viscosity diminishes the load-carrying capacity (LCC) with increased film thickness than the case of nonporous, smooth surface and constant viscosity of Rabinowitsch fluid.

Ferroelectric ceramics are highly desired for applications in energy storage devices due to their fast charge-discharge capability. However, electric field-driven gradual degradation of ferroelectric polarization (i.e., fatigue) inevitably results in a decrease in energy efficiency and energy storage density. Therefore, improving fatigue endurance is one challenge for their practical applications in energy storage devices. Here, we provide a strategy to modulate the strain response to the external electric field, and thus, increase the fatigue endurance by employing hybrid improper ferroelectricc Ca₃Ti₂O₇ ceramic that exhibits a negative piezoelectric effect. We synthesized $(1-x)$ BaTiO${}_3-x$ Ca₃Ti₂O₇ (BT-xCT) ceramics, in which the strain response of ceramics to the electric field gradually decreases with the increasing proportion of Ca₃Ti₂O₇. For BT-0.3CT ceramic, the energy density storage efficiency is improved to 74.95% which is much higher than that of BT-0.1CT (48.07%). The strain response to the external electric field of BT-0.3CT is substantially lowered and almost reaches zero, leading to excellent fatigue endurance ability. This research work paves a route for designing ferroelectric ceramics with smaller strain response and enhanced fatigue endurance ability, which is expected to benefit a wide range of applications of ferroelectric ceramics in various electric capacitors and electric storage devices.

We propose a simplified 2D effective scalar electrodynamics model of relativistic type-II superconductivity. Within this framework, we discuss possible electromagnetic (EM) behaviors of superconductivity along the lines of the nonrelativistic Ginzburg–Landau (GL) theory. This model may be of significance to study very diverse physical phenomena such as a nonlinear version of the electron–hole conversion by a superconductor and electron-positron dynamics around neutron stars. We briefly comment on extending the model to study the 3D dynamics of vortex–vortex interactions and Abrikosov fluxonics.

Rahman et al. [International Journal of Mod. Phys. B 30, 1650199 (2016)] found that MgCu intermetallic compound with CsCl-type (B2) structure becomes unstable under pressure at about 15GPa. This prediction has been made using an elastic instability condition for second-order elastic constants given by Born. They determined the elastic constants using Hooke’s law for the linear stress–strain relationship which does not hold good at high pressures. It has been shown here that the values of elastic constants for MgCu at high pressures determined by Rahman et al. are not consistent with the values of bulk modulus computed from the Birch–Murnaghan equation of state (BM-EOS). We have used the Tallon formulation based on the thermodynamics of elastic deformation to estimate elastic constants which yields results for the bulk modulus of MgCu at different pressures in good agreement with those determined from the BM-EOS. It has been found that MgCu remains stable up to about 20 GPa which is significantly higher than the limit of elastic stability predicted by Rahman et al.