International Journal of Modern Physics C

This paper was aimed to study of the wetting angle ($\mathrm{\Theta }$) of Sn–Ag–Cu, Sn–($3-x$)Ag–0.5Cu–($x$)Bi and Sn–($3-x$)Ag–0.5Cu–($x$)In ($x=0.5$, 1 and 2 in wt.%) Pb-free solder alloy systems at various temperatures (250, 280 and 310^∘C) on Cu substrate in Ar atmosphere. The new Sn–($3-x$)Ag–0.5Cu–xBi and Sn–($3-x$)Ag–0.5Cu$-$($x$) In systems, low Ag content quaternary Pb-free solder alloys, were produced by adding 0.5%, 1% and 2% Bi and In separately to the near-eutectic Sn-3wt.%Ag–0.5wt.%Cu (SAC305) alloy. The wetting angles of new alloys, Sn$-$2.5wt.%Ag$-$0.5wt.%Cu$-$0.5wt.%Bi (SAC-0.5Bi), Sn$-$2wt.%Ag$-$0.5wt.%Cu$-$1wt.%Bi(SAC-1Bi), Sn$-$1wt.%Ag$-$0.5wt.%Cu$-$2wt.%Bi(SAC-2Bi), Sn$-$2.5wt.%Ag$-$0.5wt.%Cu$-$0.5wt.%In (SAC-0.5In), Sn$-$2wt.%Ag$-$0.5wt.%Cu$-$1wt.%In (SAC-1In) and Sn$-$1wt.%Ag$-$0.5wt%.Cu$-$2wt.%In (SAC-2In) were measured by sessile drop method. Experimental results showed that additions of Bi and In separately to SAC305 resulted in a continuous decrease in the $\mathrm{\Theta }$ up to 1wt.% above which the $\mathrm{\Theta }$ value was increased and it is appeared that a correlation among the $\mathrm{\Theta }$, alloys compositions and the test temperatures exists which recommended an empirical model to estimate the $\mathrm{\Theta }$ at a given Bi and In content and temperature for a given alloy systems. The numerical model estimates the $\mathrm{\Theta }$ understandably well with the present work.

Pedestrian counter flows widely exist in public pedestrian facilities such as corridors, sidewalks, signalized crossings and so on. There is one specific flow in real life, namely counter flow with conflicting walking preference which often occurs in the case of presence of one-sidedly asymmetry due to shadows, light, snow and so on. It is often overlooked in practice and the related studies are still limited. In this study, to better understand the flow dynamics of pedestrian flow with various walking preference, a simple lattice-based model was proposed in which position exchange and walking preference were simultaneously considered. Specifically, simulations including pedestrian counter flow with preference (Case A), with conflicting preference (Case B), and without preference (Basic case) were performed. Results show that the presented model can capture some essential features of pedestrian counter flow with various walking preference. It is not always necessary to intervene the behavior of pedestrians ’ conflicting preference, since appropriate degree of preference is sometimes beneficial to movement of pedestrians. In addition, with the significant influence of position exchange, the flow in Case A with more orderly motion is more efficient in the context of low density, while the flow in Case B with more frequent interactions is more efficient in the case of high density. The findings in this study will be helpful in crowd management as well as the design and operation of pedestrian facilities.

As an effective method to remove fine particulate matter (FPM) in coal-fired industries, the aerodynamic agglomeration has recently received increasing attention due to its application value. In this paper, a CFD–PBM coupled model of the particle agglomeration for industrial application was developed to predict the particle size distributions (PSDs) using Eulerian multiphase approach and Population Balance Model. Three kinds of particles with different inertia (i.e. inertialess, finite inertial, and inertial) and Brownian motion were considered, and a collision efficiency was induced to modify the kernel functions. Furthermore, the impacts of inlet velocity, initial particle concentration and flow field on the PSDs and the agglomeration efficiency were investigated. The results show that the agglomeration efficiencies of particulate matters with aerodynamic diameter $\le$ 2.5$\mu$m and $\le$ 10$\mu$m (i.e. PM${}_{2.5}$ and PM${}_{10}$) both present logarithmic curves with the inlet velocity or the initial particle concentration. Under the working condition of the calculation, the optimal inlet velocity is in the range of 11–15m$\cdot$s${}^{-1}$, and the optimal agglomeration efficiency of $\mathrm{\text{P}}{\text{M}}_{2.5}$ and $\mathrm{\text{P}}{\text{M}}_{10}$ is about 40%. The aerodynamic agglomerator is suitable for the traditional coal-fired power plants and cement plants, but it is not recommended when the initial particle concentration is less than 16.9g$\cdot$m${}^{-3}$. The analysis of the flow field shows that the longitudinal edge of the vortex and the windward side of the vortex generator are the main regions where particles agglomerate.

This paper presents an accurate numerical algorithm to solve the space fractional-order Fisher’s equation where the derivative operator is described in the Caputo derivative sense. In the presented discretization process, first, we use the compact finite difference (CFD) for a semi-discrete occurrence in time derivative and implement the Chebyshev spectral collocation method (CSCM) of the third-kind to discretize the spatial fractional derivative. The presented method converts the problem understudy to be a system of algebraic equations which can be easily solved. To study the convergence and stability analysis, some theorems are given with their proofs. A numerical simulation is outputted to test the accuracy and applicability of our presented algorithm.

To avoid social and economic losses, governments need to control rumor propagation by releasing official rumor-refuting information (ORI) to dispel the rumors. Therefore, understanding the complex competition mechanism between ORI and rumors is key to successfully refuting rumors. This paper presents an in-depth analysis of the function of ORI in suppressing and quashing rumors. First, the influencing factors were determined from which a competition model was constructed and the quenched mean-field method employed to determine the rumor outbreak threshold. It was found that public cognition could affect the rumor threshold and lead to rumor depletion, which was confirmed in a model simulation. The simulation results also indicated that government credibility and the release time of ORI played a critical role in controlling rumors. Specifically, it was found that when government credibility was high, the ORI release was able to quash the rumor spread. And it is shown that the government should release the ORI as soon as possible, and ensure the continuous dissemination of ORI to dispel rumors effectively.

In this work, we have performed Monte Carlo simulations to study phase transitions in a mixed spin-1 and spin-3/2 Ising ferrimagnetic system on the square and cubic lattices and with two different single-ion anisotropies. These lattices are divided in two interpenetrating sublattices with spins $S^A=1$ (states $\pm 1$ and 0) on the sublattice $A$ and $S^B=3∕2$ (states $\pm 3∕2$, $\pm 1∕2$) on the sublattice $B$. We have used single-ion anisotropies $D_A$ and $D_B$ acting on the sites of the sublattice $A$ and $B$, respectively. We have determined the phase diagrams of the model in the temperature $T$ vs. the single-ion anisotropies strength $D_A$ and $D_B$ plane and shown that the system exhibits both second- and first-order phase transitions. This system also displays compensation points for some values of the anisotropies.

MHD viscoelastic (Walters’-B) fluid flow close to the stagnation point region along an extending plate with the changeable fluid properties’ influences has been debated. Heat transfer’s features are scrutinized via Cattaneo–Christov (CC) theory. The mathematical model for the physical problem is tackled numerically via Chebyshev pseudospectral (CPS) technique. The existing outcomes are supported by recent research and have acquired a suitable agreement. The numerical outcomes reveal that temperature fields are more pronounced for Fourier’s law case. Further, the opposite behavior is noticed with the heat transfer rate. Higher values of the conjugate parameter result in an increment of the heat transfer rate and temperature field. Fluid flow’s features, as well as physical quantities, are substantially varied via variable fluid properties.

Linux operating system (LOS) represents one of the most complex human-made systems, and it acts as an important function between software and hardware. In recent years, a large number of related works treat Linux operating system as a complex network and explore some of the unique characteristics of the network. However, there is little research on the execution process of LOS in terms of networks. In this paper, the run-time behaviors of execution process are traced by system calls of LOS kernel, and the run-time behaviors networks (RTBNs) are constructed, in which the nodes of RTBN represent the functions, and the edges of RTBN represent the function call relations. On this basis, the statistical characteristics of the RTBNs are investigated, and some features of the RTBNs are revealed. The result shows that some of the network characteristics remain relatively stable without obvious changes, showing the characteristics of consistency. However, some of the network characteristics tend to be random and uncertain, showing the feature of polymorphism.

The paper modeled a leader’s opinion transmission in a population. The proposed model develops the cooperation agent-based continuous model in which the cooperation of individuals is based on the similarity of evolved “tags” which are relative to evolved tag-difference tolerances. In proposed model, an individual’s opinion and the individual’s tolerance are specified as variables in the model. During communication with each other and with a leader, the resources of individuals are incremented, if they are tolerable to the opinions of their opponents. An opinion formation in population is established by a cooperative process — changing individual’s opinion, if the individual is tolerable to the opinions of opponents, and by a competitive process — copying opinions and tolerances of successful individuals who have higher resource. Numerical experiments have proven that the public opinion reached a consensus followed the leader’s opinion.

The study of advection–diffusion equation has relatively became an active research topic in the field of uncertainty quantification (UQ) due to its numerous real life applications. In this paper, Hermite polynomial chaos is united with summation-by-parts (SBP) – simultaneous approximation terms (SATs) technique to solve the advection–diffusion equations with random Dirichlet boundary conditions (BCs). Polynomial chaos expansion (PCE) with Hermite basis is employed to separate the randomness, then SBP operators are used to approximate the differential operators and SATs are used to enforce BCs by ensuring the stability. For each chaos coefficient, time integration is performed using Runge–Kutta method of fourth order (RK4). Statistical moments namely mean and variance are computed using polynomial chaos coefficients without any extra computational effort. The method is applied on three test problems for validation. The first two test problems are stochastic advection equations on $ℝ$ without any boundary and third problem is stochastic advection–diffusion equation on [0,2] with Dirichlet BCs. In case of third problem, we have obtained a range of permissible parameters for a stable numerical solution.

We introduce a minesweeper percolation model, in which the system configuration is obtained via an automatic minesweeper process. For a variety of candidate networks with different lattice configurations, our process gives rise to a second-order phase transition. Using Monte Carlo simulation, we identify the critical points implied by giant components. A set of critical exponents are extracted to characterize the nature of the minesweeper percolation transition. The determined universality class shows a clear difference from the traditional percolation transition. A proper mine density of the minesweeper game should be set around the critical density.

We study the estimated investigative answers for one of the popular models in biomathematics, in particular, the nonlinear Anopheles mosquito model numerically. The optimal control (OC) for nonlinear Anopheles mosquito model is examined. Important and adequate conditions to ensure the presence and singularity of the arrangements of the control issue are assumed. Two control factors are suggested to limit the normal measure of eggs laid per treated female every day. The signal stream chart and Simulink$\setminus$Matlab of this model are constructed. The framework is designed utilizing the MULTISIM simulation program. We utilize the homotopy disruption strategy (HPM) to examine the logical surmised answer for the nonlinear control issue. We utilize the mathematical programming bundles, for example, Maple, to emphasize while ascertaining the rough arrangement. Results are displayed graphically and introduced to delineate the conduct of obtained inexact arrangements.

We aim to compute the discrete energy spectrum for two-body scattering in a three-dimensional box under periodic boundary conditions. The spectrum in the center of mass is obtained by solving the Schödinger equation in a test potential using the Fourier basis. The focus is on how to project the spectrum into the various irreducible representations of the symmetry groups of the box. Four examples are given to show how the infinite-volume spectrum (including both bound and scattering states) is resolved in cubic or elongated boxes, and in systems with integer or half-integer total spin. Such a demonstration is a crucial step in relating the discrete spectrum in the box to the infinite-volume scattering phaseshifts via the Lüscher method.

Cooperate epidemic spreading dynamics has attracted much attention from the field of network science. In this paper, we study the cooperate epidemic spreading dynamics on multiplex networks with heterogeneous populations, which induces the heterogeneous coinfection susceptibility. We propose a spreading model to describe the evolution mechanisms. To predict the final state of the epidemic outbreak size, a generalized bond percolation theory is suggested. Through numerical simulations and theoretical analyses, we find that the system exhibits a discontinuous phase transition for large average and small variance of the distribution of coinfection susceptibility on ER–ER multiplex networks, while the phase transition is continuous on SF–SF networks. In addition, the final outbreak size increases with the average coinfection susceptibility and decreases with the variance of the coinfection susceptibility. Our suggested bond percolation theory can well predict the numerical simulations.

In this work, the structural, electronic and absorption properties of 2-methyl-2H-naphtho-[1,8-de]triazine in the pressure ranges of 0–250GPa are studied in detail (hereinafter referred to as 2-methyl crystal). Density functional theory (DFT) is used to calculate the lattice constants, bond lengths and bond angles of 2-methyl under different pressures. The results show that the crystals undergo complex transformations under compression, and the major structural transformations occur at pressures of 90GPa and 210GPa with repeated formations and disconnections. In addition, the $a$- and $c$-directions of the 2-methyl are stiffer than the $b$-direction, which indicates that the compressibility of the crystal is anisotropic. From the specific analysis of the bandgaps of 2-methyl, we can know that the crystal is converted from semiconductor to metal at 90GPa. The absorption spectrum of the crystal also indicates that 2-methyl has a relatively high optical activity with the increasing pressure.

Based on first-principles calculations, we studied the magnetic properties of ultrathin Fe film on a nonmagnetic substrate Ta(001). We found that the perpendicular magnetocrystalline anisotropy (PMA) of Fe/Ta(001) system with only one or two Fe atomic layer(s) can be enhanced significantly, and the corresponding magnetocrystalline anisotropy energy is enlarged tos about 3 times of that in pure ultrathin Fe film. Analysis of electronic properties demonstrates that the magnetic proximity effect at the Fe/Ta interface plays an important role in the enhancement of the PMA. Alternative arrangement of Ta and Fe layers with more Fe/Ta interfaces may further strengthen the PMA.