International Journal of Modern Physics C

The objective of this study was to investigate the impact of connected and autonomous vehicles (CAVs) on traffic flow under various parameters. For this purpose, we propose a mixed CAV and conventional vehicle (CV) model to investigate a bidirectional two-lane traffic flow under the periodic boundary condition. The traffic flux and the phase diagrams of the system in the (${\rho }_1,{\rho }_2$) area are constructed in both cases: with and without CAVs. The overtaking frequency is also calculated. The simulation findings show that the traffic capacity is greatly enhanced with the increase in the CAV penetration ratio. Owing to the cooperative driving strategy, with the increase in penetration ratio of the CAV, the portion of smooth overtaking is boosted. Furthermore, it is found that the traffic throughput is positively correlated to the speed limit of the fast vehicle where the flux increases as $V_{\mathrm{\text{max}}-F}$ increases. Also, even if there is a low rate of slow moving vehicles in the system, it will have an appreciable and a significant negative influence.

The centralized lubrication system is an important mechanism required in most industries where the pumps provide the lubricant. This study is aimed to design a variable displacement pump that will replace the existing pump and reduce the cost of the operations required to provide the lubrication as per the requirement. A novel design of variable displacement pump is proposed with different components providing the variable discharge. Initially, the design of the variable displacement pump is evaluated, and analytical solutions are validated numerically. Numerical simulations are performed for the forces obtained in the analytical calculations, and the design proposed is safe within the permissible limit. The novel variable displacement pump proposed will reduce the wastage of fluid.

This paper investigates the phenomena of heat transfer and entropy generation on time-dependent electro-magnetohydrodynamic boundary layer flow of viscous fluid past a curved oscillatory stretchable Riga surface. Also, the impacts of thermal radiation and Joule heating are accounted for in the energy equation. To develop the flow model in mathematical form, curvilinear coordinates system is followed. The series solution of the governing nonlinear partial differential equations is attained with the help of the homotopy analysis method (HAM). The impacts of various involved parameters like dimensionless radius of curvature, modified magnetic parameter, the proportion of frequency of oscillation of the sheet to its stretchable rate parameter, magnetic parameter, Prandtl number, Eckert number, radiation parameter and Brinkman number on entropy generation, Bejan number, temperature and flow equations are comprehensively examined and results are displayed through graphs. Numerical variation in the magnitude of surface drag force and local Nusselt number under the influence of aforesaid parameters are presented through the tables. Entropy generation is enhanced with an enhancement in a radius of curvature and Brinkman number, while the Bejan number shows opposite behavior for both parameters. The amplitude of velocity distribution shows growing behavior with modified magnetic parameter.

A solid immersion Fresnel zone plate (SI-FZP) is designed, and its near-field diffraction characteristics are analyzed using the vector angular spectrum (VAS) method. The analytical VAS model of formulism for the electric field vector transmitted from a binary amplitude and/or phase circular SI-FZP is obtained for any polarization of incidence. Numerical calculations show that, when the solid film immersing a high-numerical-aperture FZP is truncated close to the FZP’s focus in a single homogeneous medium, the focusing intensity in the vicinity of the SI-FZP–air interface can be improved dozens of times in magnitude for radially polarized incidence, compared with the FZP’s far-field focusing in the single medium without an interface. The validity of the proposed analytical VAS model of formulism to analyze SI-FZP’s diffraction problems has been affirmed by comparison with numerical results obtained by the finite-difference time-domain simulation.

The ultra-high significances of thermal radiation, magnetic field and activation energy in thermal enhancement processes allow significant applications in chemical and mechanical engineering, modern technology and various thermal engineering eras. The improvement in energy resources and production became one of the major challenges for researchers and scientists for sustained development in industrial growths. Beside this, the bioconvection assessment in nanomaterials conveys prestigious applications in biotechnology like bio-sensors, enzymes, petroleum industry, bio-fuels and many more. In view of such renewable applications, present exploration discloses unsteady two-dimensional flow of third-grade nanomaterial accommodating gyrotactic microorganisms induced by unsteady stretched Riga sheet in porous medium. The formulated flow problem is further scrutinized by utilizing the chemical reaction, activation energy, thermal radiation and magnetic aspects. The convective Nield constraints are further subjected in the current investigation. Apposite transformations are used to condense the nonlinear developed problem into dimensionless ordinary form. The numerical solution of such similar flow problem is presented via shooting technique. The detailed graphical illustrations of the dimensionless temperature, nanoparticles concentration, velocity and motile microorganisms for physical significance of diverse relevant parameters are deliberated. Furthermore, numerical data of local Sherwood, Nusselt and motile density numbers is designated in tabular form. Study accentuated that velocity increases for higher modified Hartmann and material constants, while the effects of buoyancy ratio and bioconvected Rayleigh numbers are rather opposite. The temperature, microorganism and concentration distributions were enhanced for unsteady parameter. It is also acknowledged that the concentration distribution is enhanced for activating the energy number. Moreover, the microorganism distribution enhances for concentration difference and magneto-porous constants, while bioconvected Lewis and Peclet numbers show conflicting trend.

The compressibility effect and transport motion in highspeed turbulent boundary layer (TBL) is a fundamental problem because they dominate the average and statistical characteristics. Using the statistical methods and flow visualization technology, flat-plate TBLs at ${Ma}_{\infty }=8$ with high- and low-wall temperatures, $T_w∕T_{\infty }=10.03$ and 1.9, are investigated based on the direct numerical simulation (DNS) datasets. Compared with previous studies, this study considers relative higher Mach number and strong cold wall temperature condition at the same time. First, the turbulent Mach number and turbulent intensity show that the compressibility effects are enhanced by the cooling process. Second, the high-order statistical moments and structure parameters confirm cold wall that causes stronger compressibility and the corresponding increased intensities of local streamwise and wall-normal transport motions. Finally, for uncovering the relationship between the compressibility effect and turbulent transport, more in-depth visualization analyses of velocity streaks are performed. It is found that ‘knot-like’ structures are generated when cooling the wall, and they lead to stronger intermittent, which results in the rapid increase of local compressibility effect and the wall-normal transport motion. Our research sheds light on providing a theoretical basis for further understanding the compressibility effects of TBL at high Mach number.

Different epidemiological compartmental models have been presented to predict the transmission dynamics of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, we have proposed a fuzzy rule-based Susceptible-Exposed-Infectious-Recovered-Death ($SEIRD$) compartmental model considering a new dynamic transmission possibility variable as a function of time and three different fuzzy linguistic intervention variables to delineate the intervention and transmission heterogeneity on SARS-CoV-2 viral infection. We have analyzed the datasets of active cases and total death cases of China and Bangladesh. Using our model, we have predicted active cases and total death cases for China and Bangladesh. We further presented the correspondence of different intervention measures in relaxing the transmission possibility. The proposed model delineates the correspondence between the intervention measures as fuzzy subsets and the predicted active cases and total death cases. The prediction made by our system fitted the collected dataset very well while considering different fuzzy intervention measures. The integration of fuzzy logic in the classical compartmental model also produces more realistic results as it generates a dynamic transmission possibility variable. The proposed model could be used to control the transmission of SARS-CoV-2 as it deals with the intervention and transmission heterogeneity on SARS-CoV-2 transmission dynamics.

The objective of this work is to analyze the Indice de Precios y Cotizaciones (IPC), which is the Mexican stock market index, by using several statistical tools in order to study the tendencies that can shed light on the evolution of the IPC towards a more efficient market. The methodology used is to apply the statistical tools to the Mexican index and compare the results with a mature and well-known market index such as the Dow Jones Industrial Average (DJIA). We employ an autocorrelation analysis, and the volatility of the indexes, applied to the daily returns of the closing price on a moving time window during the studied period (1980–2018). Additionally, we perform an order three permutation entropy analysis, which can quantify the disorder present in the time series. Our results show that there is evidence that the IPC has become more mature since its creation and that it can be considered an efficient market since around year 2000. The behavior of the several techniques used shows a similar behavior to the DJIA which is not observed before that year. There are some limitations mainly because there is no high frequency data that would permit a more detailed analysis, specifically in the periods before and after a crisis is located. Our conclusion is that since around the year 2000, the Mexican stock index displays the typical behavior of other mature markets and can be considered as one.

In this paper, an improved car-following model is raised by taking the preceding vehicle’s velocity feedback and desired inter-vehicle distance into account. The asymptotic and local stability criteria are obtained via control theory method to analyze the effect of the preceding vehicle’s velocity feedback and desired inter-vehicle distance on dynamic characteristics of traffic flow. In addition, numerical simulations are constructed on vehicle starting and traffic flow evolution processes, which show that the proposed car-following model can better present the characteristics of traffic flow. The preceding vehicle’s velocity feedback and desired inter-vehicle distance play a vital role on vehicle starting process and the stability of traffic flow.

The results of Kermack–McKendrick SIR model are planned to be reproduced by cellular automata (CA) lattice model. The CA algorithms are proposed to study the model of an epidemic, systematically. The basic goal is to capture the effects of spreading of infection over a scale of length. This CA model can provide the rate of growth of the infection over the space which was lacking in the mean-field like susceptible-infected-removed (SIR) model. The motion of the circular front of an infected cluster shows a linear behavior in time. The correlation of a particular site to be infected with respect to the central site is also studied. The outcomes of the CA model are in good agreement with those obtained from SIR model. The results of vaccination have been also incorporated in the CA algorithm with a satisfactory degree of success. The advantage of the present model is that it can shed a considerable amount of light on the physical properties of the spread of a typical epidemic in a simple, yet robust way.

To decrease the exergy drop, a new style of tape with an inset of the obstacle has been applied in the current utilized heat exchanger. Numerical technique was chosen to discover the solution of the equations for the current application. Hybrid nanopowders were added into a base fluid and an experimental formulation was utilized for involving the new working fluid. Addition of nanopowder and insertion of obstacle over the tape lead to augmentation of productivity of unit and help the system to minimize the irreversibility. Checking the correctness of the procedure in the modeling has been tested and proved to be in nice agreement. Two configurations for geometry of tube have been compared in two levels of Re. The regime of fluid is turbulent and the generation of grid has been done with considering the limitation of $Y^{+}$. With the insertion of obstacle in the lowest level of Re, the swirl flow increases and $S_{\mathrm{\text{gen}},f}$ augments about 252.6% while $S_{\mathrm{\text{gen}},h}$ reduces about 21.22%. The value of heating term is much higher than the friction term, so Xd declines by 21.21%. With the use of new configuration of turbulator, elevating $V_{\mathrm{\text{in}}}$ leads to elevation of $S_{\mathrm{\text{gen}},f}$ by 24.21% but $S_{\mathrm{\text{gen}},h}$ declines about 83.39%. Adding the turbulator with obstacle, $T_w$ decreases about 0.22% when Re $=$ 2e4.

In this paper, we present a Monte Carlo study of four explosive bond percolation models on the square lattice: (i) product rule which suppresses intrabonds (PR-SI), (ii) sum rule which suppresses intrabonds (SR-SI), (iii) product rule which enhances intrabonds (PR-EI) and (iv) sum rule which enhances intrabonds (SR-EI). By performing extensive simulations and finite-size scaling analysis of the wrapping probability $R^{(x)}$ and a ratio $Q$ for PR-SI, SR-SI, PR-EI, and the composite quantities $Z_R$ and $Z_Q$ for SR-EI (defined by $R^{(x)}$ and $Q$ corresponding to two different $p$-values, respectively), we determine the thresholds $p_c$ of all models with best precision. We also estimate the critical exponents $\beta ∕\nu$ and $\gamma ∕\nu$ for PR-SI, SR-SI and PR-EI by studying the critical behaviors of the size of the largest cluster $C_1$ and the second moment $M_2$ of sizes of all clusters. For SR-EI, from $C_1$ and $M_2$, we only obtain pseudo-critical exponents, which are nonphysical. Precisely at $p_c$, we study the critical cluster-size distribution $n(s,L)$ (number density of the clusters of size $s$) for all models and find that it can be described by $n(s,L)\sim s^{-{\tau }^{\prime }}ñ(s∕L^{d^{\prime }})$, where ${\tau }^{\prime }=1+d∕d^{\prime }$ with $d^{\prime }=d_{\mathrm{\text{F}}}$ (fractal dimension) for PR-SI, SR-SI, PR-EI, $d^{\prime }=d$ (spatial dimension) for SR-EI, and $ñ(x)$ with $x=s∕L^{d^{\prime }}$ is an universal scaling function. Based on critical cluster-size distribution, we conjecture the values of $\beta ∕\nu$ (and $\gamma ∕\nu$ with the help of a scaling relation) for SR-EI. It is found that the exponents for PR-SI and SR-SI are consistent with each other, but the ones for PR-EI and SR-EI are different. Our results disclose two facts: (1) all models investigated here undergo continuous phase transitions, since their behaviors can be described by typical scaling formulas for continuous phase transitions; (2) PR-SI and SR-SI belong to a same universality class, however, PR-EI and SR-EI belong to different universality classes, and all of them differ from which random percolation belongs to. This work provides a testing ground for future theoretical studies.

In this paper, we consider the spread of an epidemic on a changing network, specifically focusing on two phenomena. The first part of the paper investigates a possible mechanism of disease outbreaks on college campuses. We present a toy model, dividing students into extroverts (high-degree nodes with a large number of contacts) and introverts (low-degree nodes with a small number of contacts). In our model, the average degree of extroverts is evolving with time, and its dynamics is coupled with the current epidemic situation: extroverts tend to increase their number of contacts for low level of epidemic, but as more and more students get infected, they start decreasing their average degree. Another phenomenon analyzed in the paper is vaccination: how should the vaccine be allocated to best benefit the population? We consider two possible vaccination strategies: (1) vaccinating people starting from high risk groups (older people with a higher risk of mortality) or (2) prioritizing vaccination of people with a higher number of contacts (such as college students) to decrease the epidemic outbreak. Both phenomena show the importance of diversity in the number of contacts.

COVID-19 pandemic is one of the major disasters that humanity has ever faced. In this paper, we try to model the effect of vaccination in controlling the pandemic, particularly in context to the third wave which is predicted to hit globally. Here, we have modified the susceptible–exposed–infected–recovered–dead model by introducing a vaccination term. One of our main assumptions is that the infection rate ($\beta (t)$) is oscillatory. This oscillatory nature has been discussed earlier in literature with reference to the seasonality of epidemics. However, in our case, we invoke this nature of the infection rate ($\beta (t)$) to model the cyclical behavior of the COVID-19 pandemic within a short period. This study focuses on a minimalistic approach where we have logically deduced that the infection rate ($\beta (t)$) and the vaccination rate ($\lambda$) are the most important parameters while the other parameters can be assumed to be constants throughout the simulation. Finally, we have studied the rich interplay between the infection rate ($\beta (t)$) and the vaccination rate ($\lambda$) on the infectious cases of COVID-19 and made some robust conclusions regarding the global behavior of this pandemic in near future.