Modern Physics Letters B

When a rod is vertically withdrawn from a granular layer, oblique force chains can be developed by effective shearing. In this study, the force-chain structure in a rod-withdrawn granular layer was experimentally investigated using a photoelastic technique. The rod is vertically withdrawn from a two-dimensional granular layer consisting of bidisperse photoelastic disks. During the withdrawal, the development process of force chains is visualized by the photoelastic effect. By systematic analysis of photoelastic images, force chain structures newly developed by the rod withdrawing are identified and analyzed. In particular, the relation between the rod-withdrawing force $F_{\mathrm{\text{w}}}$, total force-chains force $F_{\mathrm{\text{t}}}$, and their average orientation $𝜃$ are discussed. We find that the oblique force chains are newly developed by withdrawing. The force-chain angle $𝜃$ is almost constant (approximately $20^{\circ }$ from the horizontal), and the total force $F_{\mathrm{\text{t}}}$ gradually increases by the withdrawal. In addition, $F_{\mathrm{\text{t}}}sin𝜃$ shows a clear correlation with $F_{\mathrm{\text{w}}}$.

Bus and metro are the two most important public transport modes in many metropolises in China, and they both have experienced rapid growth and meanwhile coexisted for decades. However, little is known on how the metro and bus interacted with each other during their rapid growths. This study was proposed to investigate the growth and interaction of bus-metro from the macro perspective. The passenger volume data for metro and bus were collected from seven central cities to represent the development of the two public transport modes, and the Logistic model and Lotka–Volterra model were employed to model the growth as well as the interaction of bus-metro, respectively. The modeling results show that the development of bus conforms to the Logistic model (i.e. S-shaped curve), while the bus-metro interaction conforms to the Lotka–Volterra model with interaction modes of competition (Shanghai city from 2000–2009, Shanghai city from 2009–2018, Guangzhou city from 2009–2017, Nanjing city from 2008–2018), and mutualism (Guangzhou city from 2000–2009). The further analysis indicates that urban characteristics and policies determine the interaction, and the parameters of the Lotka–Volterra model could be used to judge the bus-metro interaction type.

In this paper, a windmill-like phononic crystal (PC) structure with optimal locally resonant bandgaps (LRBGs) is proposed. By analyzing the variation trend of BGs, three geometric parameters (the side length and height of cuboid scatterer, and the width of elastic beams) are found to be key factors for the determination of BGs. Using response surface methodology (RSM), 3-factor and 7-level experiment are designed to obtain experimental data with the help of finite element simulations. Three relationships (fitting equations) between the three factors and the second BGs terminating frequency, the first BGs bandwidth, and the second BGs bandwidth, are further obtained by fitting the simulation data. Based on the three fitting equations, the optimal LRBGs are finally obtained using a simple optimization method. The proposed windmill-like structure PC is demonstrated to possess an optimal range of BG.

In this paper, the fractional reduced differential transform method (FRDTM) is used to obtain the series solution of time-fractional seventh-order Sawada–Kotera (SSK) and Lax’s KdV (LKdV) equations under initial conditions (ICs). Here, the fractional derivatives are considered in the Caputo sense. The results obtained are contrasted with other previous techniques for a specific case, $\alpha =1$ revealing that the presented solutions agree with the existing solutions. Further, convergence analysis of the present results with an increasing number of terms of the solution and absolute error has also been studied. The behavior of the FRDTM solution and the effects on different values $\alpha$ are illustrated graphically. Also, CPU-time taken to obtain the solutions of the title problems using FRDTM has been demonstrated.

New artificial Negative index materials (NIMs) or metamaterials have rapidly attracted researchers and industry due to their unusual properties. Applications of various NIMs have been found to be used in manufacturing and design some nano devices such as optical sensors and solar cells. The concept of solar cells depends on the maximizing the light transmission and minimizing the reflection. We propose solar cell structure model based on NIMs to enhance the light efficiency in solar cells. The proposed structure consists of four layers including two NIMs layers called Double NIMs. The simulation of the proposed model has been done utilizing the Transfer Matrix Method (TMM). High transmission and low reflection have been obtained. Solar cells based on double NIMs show promising future and could successfully be used to design highly efficient solar cells.

The noise emitted from an axial fan has become one of the primary concerns for many industrial applications. This paper presents the work to predict the noise generation and investigate sound sources in a low speed axial fan. Computational fluid dynamics modeling is conducted using Scale Adaptive Simulation for the unsteady flow field. The sound predictions by the acoustic analogy are in good agreement with the experimental data. The results from this study show that the aerodynamic interaction between the blades and outlet vanes has a major contribution to the radiated noise spectrum. Two types of sources of narrowband humps are identified in the axial fan. The first is found at the leading edge of the blade tip, which is related to the interaction of coherent flow structures in the blade tip region. The second is found in the vicinity of the blade hub, which can be attributed to the recirculating flow and hub vortex. The noise below the frequency of 1500 Hz is mainly due to the blade-outlet vane aerodynamic interaction, manifested as the tonal sound at BPF and its harmonics, whereas above 1500 Hz the broadband component of sound is mainly related to the turbulent boundary layers.

In this paper, we propose a cellular automaton model to investigate the traffic flow characteristics in the traffic circle system with adaptive traffic lights control. The traffic flow in the circulating lane was evaluated and depending on it the traffic lights lit red in the entry lanes to reduce the coming traffic. The density and the satisfaction rate were used as feedback to control the traffic flow in the circulating lane. It is found that both parameters (i.e. the density and the satisfaction rate in the circulating lane), if they are used as a criterion to control the coming traffic from entry lanes, promote the throughput in the traffic circle system. Traffic flow for the traffic circle system without using the traffic lights was investigated. In this case, we find that the traffic flow in the system is characterized by three phases, namely, gridlock, congestion, and free flow. The gridlock phase is predominant over the other phases. Furthermore, with the use of the adaptive traffic lights, the gridlock phase has vanished and the maximum current, jammed, and congestion phases take place. The density criterion shows good performance as compared with the satisfaction rate criterion in terms of the lengths of the red cycle. The capacity is also investigated. The space-time configurations were given to understand the microscopic interaction between vehicles.

This study focuses on the asymptotic properties of quenching solutions for the quasilinear parabolic electrostatic micro-electro-mechanical system with singular logarithm boundary flux. Under some assumptions on initial data, quenching in finite time, blowup phenomenon of a time derivative, lower and upper bounds of quenching rate are studied theoretically, and the asymptotic behaviors near quenching time are verified numerically.

The external random magnetic field $(H_i)$ with three nodes, i.e. acting up and down along the $z$-axis and zero, effective on the spins in the Blume-Capel model is analyzed on the Bethe lattice in terms of the exact recursion relations. All the nodes are assumed to have the same probability, $p=1/3$, so that the model could give various kinds of phase transitions. As a mapping of the phase transitions, the phase diagrams are constructed on two different planes which present very rich and interesting phase diagrams. In addition to the second- and first-order phase transitions, a few critical points, reentrant and double reentrant behaviors are also observed.

This paper presents dynamic behavior of a fractional-order memristive time-delay system and its application in image encryption. First, a fractional-order memristive time-delay system is proposed, and the stability and bifurcation behaviors of the system are theoretically analyzed. Some limited conditions for describing the stability interval and switching between different dynamic behaviors are derived. Second, the dynamic characteristics of the system are analyzed through the coexisting attractors, coexisting bifurcation diagrams, the Largest Lyapunov exponents (LLE), the 0-1 test. When parameters change, such as time delay and fractional order, the system transits from steady state to periodic state, single scroll chaotic state, double scroll chaotic state. Furthermore, an image encryption scheme based on the fractional-order memristive time-delay system is introduced, and some statistical features are analyzed. Finally, numerical simulations verify the validity of the theoretical analysis and safety of the image encryption scheme based on the fractional-order delayed memristive chaotic system.

In terms of reducing traffic congestion, it should be understood that traffic dynamics depend on network structure. Most of complex networks in the real world can be represented by multi-layer and community structures, that is, the connections within the community are relatively close, and the connections between the community are relatively sparse. There are generally strong and weak community networks in community networks. In this work, the strong and weak community networks are used to construct two-layer network models of different scales, and then the influence of community structure on traffic capacity is analyzed. The simulation results show that when the two-layer network model is composed of two strong community networks, the traffic capacity is the largest, followed by the two-layer network model composed of two weak community networks, the traffic capacity is also relatively large. When the two subnetworks are of different community strength, the traffic capacity is relatively small.

This paper utilized the methods of linear combination and unitary transformation to evaluate the vibrational frequency (VF) and ground state binding energy (GSBE) of a strong-coupling magnetopolaron in an asymmetrical Gaussian potential quantum well (AGPQW), and the effects of the temperature on these physical quantities were studied through quantum statistical theory. The changes of the VF and GSBE versus temperature and cyclotron frequency (CF) in a magnetic field were discussed. The numerical calculations revealed that with the increase of temperature, the VF and GSBE also increased. Meanwhile, the numerical results show that the VF increases with the increase of the CF. However, the GSBE versus the CF has different changing properties.

The oxidation behaviour of Ni8Al and Ni25Cr coatings produced by high velocity oxygen fuel spray (HVOF) which were deposited on Fe-based alloys (CB2) was investigated. We simulated the service environment of the steam generator unit, and put the samples in a thermostatic tube furnace at 650${}^{\circ }$ in air with 20 wt.% water vapor for 1000 hours of cyclic oxidation. The formation mechanism are explained using SEM, XRD, and EDX. There were no spallations and obvious cracks in both coatings. Ni25Cr coating generated a better protection oxides scale than that scale on Ni8Al. The behavior and mechanism of the oxide scale formation had an important influence in coatings and we have discussed these phenomenons in the study.

Unsteady aerodynamic interference between a rotorcraft and a ship occurs during shipboard launch and recovery operations and has a negative impact on the safety. An experiment of a reduced-scale model rotor and a CFD analysis in hover was carried out to investigate the performance and flow field of a rotor approaching a ship. In this paper, the thrust and pitching moment of the rotor hovering above the ground, deck were tested, and the influence of hangar door on the thrust, pitching moment, and flow field was also measured. A CFD method based on RANS and overset technology was used to investigate the flow field of the rotor operating on the model-scale ship. As the rotor approaches the deck, its thrust first decreases induced by a recirculation near the deck, and then increases induced by the effect of deck, and finally obviously decreases caused by the recirculation near hangar door. The deck and hangar door also affects the flow field to yield an intensive nose-down pitching moment. The status of the hangar door has a significant influence on the rotor thrust and pitching moment. The recirculation is weakened with an opened hangar door resulting in recovery of the rotor thrust and decrease of the nosed down pitching moment.

This paper presents the results of a study on the production of nanofiber anisotropic nanoporous materials based on silk fibroin and cotton cellulose by electrospinning using a rotating screen-receiver of nanofibers in the form of a thin material. The difference in the anisotropic properties of the nanofiber material is shown by the method of birefringence, sorption of water vapor and filtration of a liquid-phase mixture. The possibility of using nanofiber nanoporous fibroin and cotton cellulose materials as a nanofilter of gaseous and liquid-phase mixtures has been shown.

Current communication aims to examine the novel thermal consequences of thermal radiation, Joule heating and activation energy in bioconvection flow of tangent hyperbolic nanofluid. The flow is developed by a three-dimensional (3D) extending surface in presence of porous space. The heat and mass transfer inspection in non-Newtonian fluid flow is inspected in laws of modified flux relations. The Brownian movement and thermophoresis diffusions are also accounted for current analysis. The governing formulated frameworks are simplified by appropriate similarity transformations. A familiar shooting scheme for obtaining the numerical outcomes to the nonlinear system is carried out. The graphical results are obtained with the aid of shooting technique. Flow of fluid, thermal field, concentration of species and microorganism’s field are conducted for tangent hyperbolic fluid. Furthermore, the significance of various noteworthy variables on velocity field, thermal field, solutal field of nanomaterials, microorganisms’ profile, local skin friction coefficients, local heat flux rate, local Sherwood number and local microorganisms density number is scrutinized in graphical and tabular structure. The importance of current model is in the field of nanotechnology and bioengineering.