International Journal of Modern Physics C

The molecular organization of a nematic film sandwiched between two planar randomly aligned surfaces is studied by means of detailed Monte Carlo simulations. The formation as well as the evolution of topological defects induced by these particular boundary conditions are investigated. The resulting defect structure is compared with the one induced by hybrid aligned surfaces. The observation of such defects and some features of their structures can be associated with geometric parameters of the film and with properties of the confining surfaces.

A theoretical model on MHD hybrid nanofluid flow in accordance with non-uniform heat flux and solar energy radiation has been studied in our work. Also, the impact of multiple slip conditions is presumed at the boundary. Comparative flow analyses for hybrid nanofluid (Al₂O₃/Cu–H₂O) and single nanoparticle-based nanofluid (Cu–H₂O) are addressed here with graphs and charts. The leading partial differential equations with boundary conditions have been converted into ordinary differential equations with the aid of similarity transformation. The final system is tackled via the fifth-order Runge–Kutta–Felberg method with shooting procedure and the computation is done using Maple 17. One of the interesting results shows that with the growth of thermal radiation, the Nusselt number for Cu–H₂O is reduced by 26.16%, whereas for the same, Nusselt number for Al₂O₃/Cu–H₂O is lessened by 27.38%. Fallout shows that with the growing values of velocity slip parameter, the thermal boundary layer thickness enlarges faster for Al₂O₃/Cu–H₂O in comparison to Cu–H₂O.

The firefly algorithm and cuckoo search are the meta-heuristic algorithms efficient to determine the solution for the searching and optimization problems. The current work proposes an integrated concept of quantum-inspired firefly algorithm with cuckoo search (IQFACS) that adapts both algorithms’ expedient attributes to optimize the solution set. In the IQFACS algorithm, the quantum-inspired firefly algorithm (QFA) ensures the diversification of fireflies-based generated solution set using the superstitions quantum states of the quantum computing concept. The cuckoo search (CS) algorithm uses the Lévy flight attribute to escape the QFA from the premature convergence and stagnation stage more effectively than the quantum principles. Here, the proposed algorithm is applied for the application of optimal path planning. Before using the proposed algorithm for path planning, the algorithm is tested on different optimization benchmark functions to determine the efficacy of the proposed IQFACS algorithm than the firefly algorithm (FA), CS, and hybrid FA and CS algorithm. Using the proposed IQFACS algorithm, path planning is performed on the satellite images with vegetation as the focused region. These satellite images are captured from Google Earth and belong to the different areas of India. Here, satellite images are converted into morphologically processed binary images and considered as maps for path planning. The path planning process is also executed with the FA, CS, and QFA algorithms. The performance of the proposed algorithm and other algorithms are accessed with the evaluation of simulation time and the number of cycles to attain the shortest path from defined source to destination. The error rate measure is also incorporated to analyze the overall performance of the proposed IQFACS algorithm over the other algorithms.

During any unique crisis, panic sell-off leads to a massive stock market crash that may continue for more than a day, termed as mainshock. The effect of a mainshock in the form of aftershocks can be felt throughout the recovery phase of stock price. As the market remains in stress during recovery, any small perturbation leads to a relatively smaller aftershock. The duration of the recovery phase has been estimated using structural break analysis. We have carried out statistical analyses of 1987 stock market crash, 2008 financial crisis and 2020 COVID-19 pandemic considering the actual crash times of the mainshock and aftershocks. Earlier, such analyses were done considering absolute one-day return, which cannot capture a crash properly. The results show that the mainshock and aftershock in the stock market follow the Gutenberg–Richter (GR) power law. Further, we obtained higher $\beta$ value for the COVID-19 crash compared to the financial-crisis-2008 from the GR law. This implies that the recovery of stock price during COVID-19 may be faster than the financial-crisis-2008. The result is consistent with the present recovery of the market from the COVID-19 pandemic. The analysis shows that the high-magnitude aftershocks are rare, and low-magnitude aftershocks are frequent during the recovery phase. The analysis also shows that the inter-occurrence times of the aftershocks follow the generalized Pareto distribution, i.e. $P({\tau }_i)\propto \frac{1}{[1+\lambda (q-1){\tau }_i{]}^{\frac{1}{(q-1)}}}$, where $\lambda$ and $q$ are constants and ${\tau }_i$ is the inter-occurrence time. This analysis may help investors to restructure their portfolio during a market crash.

The work zone with lane closure will be an active bottleneck due to vehicles’ mandatory lane-changing conflicts. The emerging Connected Autonomous Vehicle (CAV) technology provides opportunities for vehicle motion planning to improve traffic performance. However, the literature using CAV technology mainly focuses on single-lane lane-changing control in the merging area. The algorithm dealing with multi-lane lane-changing control is absent. In this paper, a simulation system with a lane-changing optimal strategy embedded for the multi-lane work zone is presented under the heterogeneous traffic flow. First, the road upstream of the work zone is divided into several segments, and an optimal multi-lane lane-changing algorithm is designed. It is recommended that CAVs, on the closure lane and the merged lane, change lanes on each segment to balance traffic distribution and minimize traffic delay. Second, to validate the algorithm proposed, a typical three-lane freeway with one-lane closed for the work zone is researched, and the simulation platform based on cellular automata is developed. Third, the advantages of multi-lane control strategies are studied and discussed in traffic efficiency improvement and collision risk reduction by comparing previous lane-changing control algorithms.

Employing the Hybrid Reverse Monte Carlo (HRMC) simulation, we compute, using the obtained three-dimensional configurations, the orientational correlations of water molecules in the supercooled 9.26 molal LiCl aqueous solution. This study aims to add relevant structural properties to those obtained in our latest studies and further support our findings. The Li/Cl pair ions hydration shells and the water molecules distribution studied using the Radial Pair Distribution Functions (RPDF), ($g_{\mathrm{\text{Li/Cl}},i}(r);i=\mathrm{\text{O,H}}$) and ($g_{jk}(r);j,k=\mathrm{\text{O,H}}$) are further described using the Orientational Pair Correlation Functions (OPCF), $g(r,{\mathrm{\Omega }}_1,{\mathrm{\Omega }}_2)$ which describes the probability of a water molecule oriented by the Euler angles ${\mathrm{\Omega }}_2$, being located at the position $r$, with respect to another water molecule oriented ${\mathrm{\Omega }}_1$ placed at the origin. The high dimensionality of the orientational correlation functions has not presented a calculation disability, as known with several simulations, in the face of the efficiency of the HRMC and the water–water orientational correlation functions showed the dominant impact of ions on the water molecular dipole orientations within the hydration shells and in the hydrogen bonded molecules network.

In this paper, an improved multianticipative cooperative adaptive cruise control (CACC) model is proposed based on fully utilizing multivehicle information obtained by vehicle-to-vehicle communication. More flexible, effective and practical spacing strategy is embedded into the model. We design a new lane-changing rule for CACC vehicles on the freeway. The rule considers that CACC vehicles are more inclined to form a platoon for coordinated control. Furthermore, we investigate the effect of CACC vehicles on two-lane traffic flow. The results demonstrate that introducing CACC vehicles into mixed traffic and forming CACC platoon to cooperative control can improve traffic efficiency and enhance road capacity to a certain extent.

In this study, numerical simulations are conducted to investigate droplet breakup in an asymmetric $T$-junction microchannel with different cross-section ratios. To this approach, a two-phase model based on the volume of fluid (VOF) method is adopted to study the three-dimensional feature of droplet motion inside $T$-junctions. The comparison reveals that the present results are in good agreement with previous studies. The effects of the capillary number (Ca), the non-dimensional droplet length ($L^{\ast }$), and the non-dimensional width ratio ($W^{\ast }$) on the breakup time and splitting ratio of daughter droplets are studied. Five distinct regimes are observed involving the non-breakup, breakup with tunnel, breakup without tunnel, asymmetric breakup, and sorting. Achieved results indicate that the time of breakup ($t_{\mathrm{\text{breakup}}}^{\ast }$) increases about 15% when the Ca is increased from 0.0134 to 0.0268 (about 100%). It is also found that the mass center of the mother droplet in the primary channel is shifted to a larger wide branch, which facilitates the asymmetric breakup of the droplet in a $T$-junction microchannel.

In this paper, He’s homotopy perturbation method (HPM) is used, which is an approximate analytical method for solving numerically the problem of Newtonian fluid flow past a porous exponentially stretching sheet with Joule heating and convective boundary condition. 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 proposed method is very effective, convenient, and quite accurate to systems of nonlinear differential equations. Results of this study shed light on the accuracy and efficiency of the HPM in solving these types of nonlinear boundary layer equations.

In this work, to rectify the equation of state (EOS) of a recently introduced constant speed entropic kinetic model (CSKM), a virtual force method is proposed. The CSKM, as shown in Zadehgol and Ashrafizaadeh [J. Comp. Phys. 274, 803 (2014)] and Zadehgol [Phys. Rev. E 91, 063311 (2015)], is an entropic kinetic model with unconventional entropies of Burg and Tsallis. The dependence of the pressure on the velocity, in the CSKM, was addressed and it was shown that it can be rectified by inserting rest particles into the model. This work shows that this dependence can also be removed by treating the pressure gradient as a pseudo force term, expanding the source term using the Fourier series, and applying the modified method of Khazaeli et al. [Phys. Rev. E 98, 053303 (2018)]. The proposed method can potentially be used to remove other pseudo-force error terms of the CSKM, e.g. the residual error terms which become significant at high Mach numbers, ensuring thermodynamic consistency of the entropic model, at the compressible flow regimes. The accuracy of the method is verified by simulating benchmark flows.

This paper contains natural convection of Ag–MgO/water micropolar hybrid nanofluid in a hollow hot square enclosure equipped by four cold obstacles on the walls. The simulations were performed by the lattice Boltzmann method (LBM). The influences of Rayleigh number and volume fraction of nanoparticle on the fluid flow and heat transfer performance were studied. Moreover, the effects of some geometric parameters, such as cold obstacle height and aspect ratio, were also considered in this study. The results showed that when the aspect ratio is not large ($\mathrm{\text{AR}}=0.2$ or 0.4), at low Rayleigh number (10³), the two secondary vortices are established in each main vortex and this kind of secondary vortex does not form at high Rayleigh number (10⁶). However, at $\mathrm{\text{Ra}}=10^6$, these secondary vortices occur again in the middle two vortices at $\mathrm{\text{AR}}=0.6$, which is similar to that at $\mathrm{\text{Ra}}=10^3$. At $\mathrm{\text{AR}}=0.2$, the critical Rayleigh number, when the dominated mechanism of heat transfer changes from conduction to convection, is 10⁴. However, the critical Rayleigh number becomes 10⁵ at $\mathrm{\text{AR}}=0.4$ or 0.6. When the cold obstacle height increases, the shape of the vortices inside the enclosure changes due to the different spaces. Besides, at $\mathrm{\text{Ra}}=10^6$, for different cold obstacle heights, the location of the thermal plume is different, owing to the different shapes of vortices. Accordingly, the average Nusselt number increases by increment of the Rayleigh number, nanoparticle volume fraction, cold obstacle height and aspect ratio.

In any legal chess position, we define an attacked-square entropy $S$ for either Black or White pieces in terms of the square occupation probability $p_i=m_i∕M$, where $m$ is the number of all possible movements to square $i$ (free or occupied by an opponent’s piece) and $M$ is the total mobility defined as the sum of all possible movements. Thus, each attacked square contributes to the entropy according to its received “firepower” concentration. A simpler nonsquare-dependant equiprobable entropy $S_e$ in terms of equal probabilities $p_e=1∕M$ always yields $S_e-S\ge 0$. On average, the difference $S_e-S$ is very large in the Opening phase and $S$ decreases faster for lower ranked players after move 25. A major cause of the reduction of $S$ during a game is material loss, which is an irreversible process. By game outcome, gaps in average $〈S〉$ among winners, draws and losers are larger for Amateur players than for Elite players, both in the Middlegame and Endgame. Statistically, Elite players exhibit narrower dispersions in $S$. Also, the entropy rates of the Elite level fluctuate much less than the entropies of other levels. Density of attacks in the four-square central zone is very high in the Opening, specially for Elite players.

Bone scaffolds are porous structures that are used to repair, regenerate and restore the functions of damaged bone tissue. Scaffolds should have sufficient mechanical strength since they are subjected to different mechanical loadings as implanted in the defect site. Recently, there has been growing interest in the application of micromechanical approaches to estimate the effective mechanical properties of these structures. However, most of the micromechanical methods are originally proposed for dilute concentration condition in which all of the pores are isolated and they are not suitable for the structures like scaffolds with an interconnected network of pores. This paper presents the modified version of the Mori–Tanaka approach which is able to consider the interconnectivity between the pores and is completely appropriate for investigation of the mechanical behavior of the scaffolds. The validity of the developed relations is investigated via statistical finite element analysis. The effective moduli of the numerous scaffolds available in the literature are also computed using the suggested modifications. Comparison between the findings of this paper and published empirical studies shows that for the scaffolds with interconnected pore networks, using these modifications significantly improves the results in comparison with the case of using the classical Mori–Tanaka scheme.

This paper put forward a new discrete-time lattice hydrodynamic model with a steady flow control strategy. The controlled discrete-time lattice hydrodynamic model is theoretically studied by the discrete-time Lyapunov stability theory, and a sufficient stable condition to suppress traffic congestion is given in the form of linear matrix inequality. Also, the traffic flow evolution rules under different conditions of control gain are exhibited through numerical simulation, and the stabilization effect of the steady flow control strategy on traffic flow is verified intuitively.