Showing papers in "International Journal of Modern Physics C in 2014"
TL;DR: In this paper, a car-following model for a non-lane-based system taking lateral separation into account is developed. But the authors do not consider the effect of lane width on the stability of the system.
Abstract: We develop a heterogeneous continuum model based upon a car-following model for a nonlane-based system taking lateral separation into account. The criterion for linear stability analysis and traveling wave solution of the homogeneous case is studied. The consideration of the lateral separation not only stabilizes the flow but also shrinks the critical region. For heterogeneous case, the fundamental diagram is examined for two different equilibrium speed-density functions and the effect of lane width is investigated for different compositions of heterogeneous traffic. The theoretical findings agree well with the results of numerical simulation which justifies the applicability of the model to a nonlane-based system.
93 citations
TL;DR: In this paper, the suitability of the Large Eddy Simulation (LES) turbulence modeling for the accurate simulation of the shock train phenomena in a convergent-divergent nozzle was discussed.
Abstract: This paper discusses the suitability of the Large Eddy Simulation (LES) turbulence modeling for the accurate simulation of the shock train phenomena in a convergent-divergent nozzle To this aim, we selected an experimentally tested geometry and performed LES simulation for the same geometry The structure and pressure recovery inside the shock train in the nozzle captured by LES model are compared with the experimental data, analytical expressions and numerical solutions obtained using various alternative turbulence models, including k–e RNG, k–ω SST, and Reynolds stress model (RSM) Comparing with the experimental data, we observed that the LES solution not only predicts the "locations of the first shock" precisely, but also its results are quite accurate before and after the shock train After validating the LES solution, we investigate the effects of the inlet total pressure on the shock train starting point and length The effects of changes in the back pressure, nozzle inlet angle (NIA) and wall temperature on the behavior of the shock train are investigated by details
49 citations
TL;DR: In this paper, an event-based simulation approach which reproduces the statistical distributions of wave theory is presented, by generating detection events one-by-one according to an unknown distribution.
Abstract: We review an event-based simulation approach which reproduces the statistical distributions of wave theory not by requiring the knowledge of the solution of the wave equation of the whole system but by generating detection events one-by-one according to an unknown distribution. We illustrate its applicability to various single photon and single neutron interferometry experiments and to two Bell-test experiments, a single-photon Einstein–Podolsky–Rosen experiment employing post-selection for photon pair identification and a single-neutron Bell test interferometry experiment with nearly 100% detection efficiency.
47 citations
TL;DR: In this article, a set of fundamental conditions required for the formulation of a thermohydrodynamic lattice Boltzmann model at an arbitrary Prandtl number is demonstrated, and a specific collision operator form is proposed that is in compliance with these conditions.
Abstract: In this paper, we demonstrate a set of fundamental conditions required for the formulation of a thermohydrodynamic lattice Boltzmann model at an arbitrary Prandtl number. A specific collision operator form is then proposed that is in compliance with these conditions. It admits two independent relaxation times, one for viscosity and another for thermal conductivity. But more importantly, the resulting thermohydrodynamic equations based on such a collision operator form is theoretically shown to remove the well-known non-Galilean invariant artifact at nonunity Prandtl numbers in previous thermal lattice Boltzmann models with multiple relaxation times.
36 citations
TL;DR: In this paper, a hybrid feedback control method is designed to achieve the projective lag synchronization (PLS) behavior between chaotic systems in drive-response dynamical networks (DRDNs) model with nonidentical nodes.
Abstract: This paper investigates projective lag synchronization (PLS) behavior between chaotic systems in drive-response dynamical networks (DRDNs) model with nonidentical nodes. A hybrid feedback control method is designed to achieve the PLS with and without mismatched terms. Specially, the coupling matrix in this model is not assumed to be symmetric, diffusive or irreducible. The stability of the error dynamics is proven theoretically using the Lyapunov stability theory. Finally, analytical results show that the states of the dynamical network with non-delayed coupling can be asymptotically synchronized onto a desired scaling factor under the designed controller. Moreover, the numerical simulations results demonstrate the validity of the proposed method.
35 citations
TL;DR: In this paper, the authors used the lattice Boltzmann method (LBM) for the analysis of a two-dimensional flow physics produced by a symmetric wedge entering vertically a weakly-compressible fluid at a constant velocity.
Abstract: This paper deals with the simulation of water entry problems using the lattice Boltzmann method (LBM). The dynamics of the free surface is treated through the mass and momentum fluxes across the interface cells. A bounce-back boundary condition is utilized to model the contact between the fluid and the moving object. The method is implemented for the analysis of a two-dimensional flow physics produced by a symmetric wedge entering vertically a weakly-compressible fluid at a constant velocity. The method is used to predict the wetted length, the height of water pile-up, the pressure distribution and the overall force on the wedge. The accuracy of the numerical results is demonstrated through comparisons with data reported in the literature.
33 citations
TL;DR: In this paper, a stable finite volume (FV) formulation of the thermal lattice Boltzmann method (LBM) was used to investigate fluid flows with enhanced heat transfer in porous channels.
Abstract: In this paper, fluid flows with enhanced heat transfer in porous channels are investigated through a stable finite volume (FV) formulation of the thermal lattice Boltzmann method (LBM). Temperature field is tracked through a double distribution function (DDF) model, while the porous media is modeled using Brinkman–Forchheimer assumptions. The method is tested against flows in channels partially filled with porous media and parametric studies are conducted to evaluate the effects of various parameters, highlighting their influence on the thermo-hydrodynamic behavior.
28 citations
TL;DR: In this paper, a system of self-propelled dumbbells interacting by a Weeks-Chandler-Anderson potential is considered, and the kinetics of the cluster formation and the growth law for the average cluster size are analyzed.
Abstract: A systems of self-propelled dumbbells interacting by a Weeks–Chandler–Anderson potential is considered. At sufficiently low temperatures the system phase separates into a dense phase and a gas-like phase. The kinetics of the cluster formation and the growth law for the average cluster size are analyzed.
28 citations
TL;DR: In this paper, the synchronization and anti-synchronization problem of N different coupled chaotic systems with ring connections was considered and some simple stability criteria were derived for reaching the synchronization in such systems.
Abstract: This paper considers the synchronization and anti-synchronization problem of N different coupled chaotic systems with ring connections. Employing the direct design method to design the synchronization and anti-synchronization controllers which can transform the error systems into a stable system with special anti-symmetric structure. Some simple stability criteria are then derived for reaching the synchronization in such systems. It is proved that these criteria not only are easily verified, but also improve and generalize previously known results. Finally, numerical examples are provided to demonstrate the effectiveness of the theoretical.
27 citations
TL;DR: Simulation results show that the proposed strategy to enhance the network transport efficiency by adding links to the existing networks can bring better traffic capacity and shorter average shortest path length than the low-degree-first (LDF) strategy and theLow-betweenness- first (LBF) strategy.
Abstract: In this paper, we propose an efficient strategy to enhance the network transport efficiency by adding links to the existing networks. In our proposed strategy, we consider both the node betweenness centrality (BC) and the shortest path length (L) as two important factors. The overall traffic capacity of a network system can be evaluated by the critical packet generating rate Rc. Simulation results show that the proposed strategy can bring better traffic capacity and shorter average shortest path length than the low-degree-first (LDF) strategy and the low-betweenness-first (LBF) strategy. This work is helpful for designing and optimizing of realistic networks.
20 citations
CERN1
TL;DR: The various components that are necessary for an effective solution that ensures the storage, the long term preservation, and the worldwide distribution of large quantities of data that is necessary in a large scientific research project are reviewed.
Abstract: In recent years, intense usage of computing has been the main strategy of investigations in several scientific research projects. The progress in computing technology has opened unprecedented opportunities for systematic collection of experimental data and the associated analysis that were considered impossible only few years ago. This paper focuses on the strategies in use: it reviews the various components that are necessary for an effective solution that ensures the storage, the long term preservation, and the worldwide distribution of large quantities of data that are necessary in a large scientific research project. The paper also mentions several examples of data management solutions used in High Energy Physics for the CERN Large Hadron Collider (LHC) experiments in Geneva, Switzerland which generate more than 30,000 terabytes of data every year that need to be preserved, analyzed, and made available to a community of several tenth of thousands scientists worldwide.
TL;DR: A pseudo-random bit generator (PRBG) based on two lag time series of the logistic map using positive and negative values in the bifurcation parameter giving satisfactory results for use in stream ciphers.
Abstract: In this paper, we present a pseudo-random bit generator (PRBG) based on two lag time series of the logistic map using positive and negative values in the bifurcation parameter. In order to hidden the map used to build the pseudo-random series we have used a delay in the generation of time series. These new series when they are mapped xn against xn+1 present a cloud of points unrelated to the logistic map. Finally, the pseudo-random sequences have been tested with the suite of NIST giving satisfactory results for use in stream ciphers.
TL;DR: The regularized lattice BGK (RLBGK) is validated against high-accuracy spectral Chebyshev methods for lid-driven cavity flows and shows significant enhancement of numerical stability at a very moderate computational extra-cost.
Abstract: The regularized lattice BGK (RLBGK) is validated against high-accuracy spectral Chebyshev methods for lid-driven cavity flows. RLBGK is shown to provide a viable alternative to standard lattice BGK schemes, with significant enhancement of numerical stability at a very moderate computational extra-cost.
TL;DR: Eight prevalent strategies on an asymmetric two-route traffic network with different slowdown behaviors on alternative routes show that only mean velocity feedback strategy (MVFS) is able to equalize travel time, i.e. approximate user optimality (UO); while the others fail due to incapability of establishing relations between the feedback parameters and travel time.
Abstract: To alleviate traffic congestion, a variety of route guidance strategies have been proposed for intelligent transportation systems. A number of strategies are introduced and investigated on a symmetric two-route traffic network over the past decade. To evaluate the strategies in a more general scenario, this paper conducts eight prevalent strategies on an asymmetric two-route traffic network with different slowdown behaviors on alternative routes. The results show that only mean velocity feedback strategy (MVFS) is able to equalize travel time, i.e. approximate user optimality (UO); while the others fail due to incapability of establishing relations between the feedback parameters and travel time. The paper helps better understand these strategies, and suggests MVFS if the authority intends to achieve user optimality.
TL;DR: In this paper, the authors compare two families of Lattice Boltzmann (LB) models derived by means of Gauss quadratures in the momentum space, and order themselves according to the maximum order N of the moments of the equilibrium distribution function that are exactly recovered.
Abstract: In this paper, we compare two families of Lattice Boltzmann (LB) models derived by means of Gauss quadratures in the momentum space. The first one is the HLB(N;Qx,Qy,Qz) family, derived by using the Cartesian coordinate system and the Gauss–Hermite quadrature. The second one is the SLB(N;K,L,M) family, derived by using the spherical coordinate system and the Gauss–Laguerre, as well as the Gauss–Legendre quadratures. These models order themselves according to the maximum order N of the moments of the equilibrium distribution function that are exactly recovered. Microfluidics effects (slip velocity, temperature jump, as well as the longitudinal heat flux that is not driven by a temperature gradient) are accurately captured during the simulation of Couette flow for Knudsen number (kn) up to 0.25.
TL;DR: In this paper, nonequilibrium thermal transpiration flow is numerically analyzed by an extended thermodynamic approach, a high-order moment method, and the captured velocity profiles of temperature-driven flow in a p...
Abstract: Nonequilibrium thermal transpiration flow is numerically analyzed by an extended thermodynamic approach, a high-order moment method. The captured velocity profiles of temperature-driven flow in a p...
TL;DR: The robustness of interdependent Erdos–Renyi (ER) networks and interdependent scale-Free (SF) networks coupled by two sub-networks with different average degree are investigated, and it is found that interdependent networks with differentAverage degree are significantly different from those inter dependent networks with equal average degree.
Abstract: Most of modern systems are coupled by two sub-networks and therefore should be modeled as interdependent networks. The study towards robustness of interdependent networks becomes interesting and significant. In this paper, mainly by numerical simulations, the robustness of interdependent Erdos–Renyi (ER) networks and interdependent scale-Free (SF) networks coupled by two sub-networks with different average degree are investigated. First, we study the robustness of interdependent networks under random attack. Second, we study the robustness of interdependent networks under targeted attack on high or low degree nodes, and find that interdependent networks with different average degree are significantly different from those interdependent networks with equal average degree.
TL;DR: In this article, the authors used the finite volume lattice Boltzmann method (FVLBM) to simulate the transient heat conduction from macro-to nano-scales corresponding to Kn = 0.01-10.
Abstract: This paper uses the finite volume lattice Boltzmann method (FVLBM) to simulate the transient heat conduction from macro- to nano-scales corresponding to Kn = 0.01–10. This model is used for two dimensional (2D) transient hotspot modeling. The results of the diffusive regime are compared with those of the Fourier law as a model of continuum mechanics and an excellent agreement is found in this regime. After the validation of model for the case of Kn = 0.01, it has been used for high-Knudsen number simulations and a test case with Kn = 10 is studied. By increasing the Knudsen number from 0.01 up to 10, the transition from totally diffusive to totally ballistic behavior has been discussed and the wave-feature of heat transport through the solid material has been investigated.
TL;DR: These networks are constructed and the numerical results show that when the networks are of a power-law distribution, a stronger community structure will result in the failure of fewer nodes, while the RCN, however, display a different result.
Abstract: Much empirical evidence shows that when attacked with cascading failures, scale-free or even random networks tend to collapse more extensively when the initially deleted node has higher betweenness. Meanwhile, in networks with strong community structure, high-betweenness nodes tend to be bridge nodes that link different communities, and the removal of such nodes will reduce only the connections among communities, leaving the networks fairly stable. Understanding what will affect cascading failures and how to protect or attack networks with strong community structure is therefore of interest. In this paper, we have constructed scale-free Community Networks (SFCN) and Random Community Networks (RCN). We applied these networks, along with the Lancichinett–Fortunato–Radicchi (LFR) benchmark, to the cascading-failure scenario to explore their vulnerability to attack and the relationship between cascading failures and the degree distribution and community structure of a network. The numerical results show that when the networks are of a power-law distribution, a stronger community structure will result in the failure of fewer nodes. In addition, the initial removal of the node with the highest betweenness will not lead to the worst cascading, i.e. the largest avalanche size. The Betweenness Overflow (BOF), an index that we developed, is an effective indicator of this tendency. The RCN, however, display a different result. In addition, the avalanche size of each node can be adopted as an index to evaluate the importance of the node.
TL;DR: In this paper, the authors deal with the molecular dynamics simulation (MDS) of nanofluid under Poiseuille flow in a model nanochannel, where the flow is simulated by molecules with the Lennard-Jones (LJ) intermolecular potential function.
Abstract: This paper deals with the molecular dynamics simulation (MDS) of nanofluid under Poiseuille flow in a model nanochannel. The nanofluid is created by exerting four solid nanoparticles dispersed in Argon (Ar), as base fluid, between two parallel solid walls. The flow is simulated by molecules with the Lennard-Jones (LJ) intermolecular potential function. Different simulations are done with two different types of solid particles and two cut-off radii. In each case, Copper (Cu) and Platinum (Pt) LJ parameters are applied for the nanoparticles and solid walls particles with cut-off ratios of 2.2σ and 2.5σ. The microstructure of the system at different time steps is investigated to describe the aggregation kinetics of nanofluid on Poiseuille flow. When a few nanoparticles or a cluster of them reach each other, they stick together and the interaction surface of the solid–fluid interface reduces, so the potential energy of the system decreases at these time steps. Therefore, the system enthalpy reduces at the aggregation time steps. Results show that the simulations with cut-off radius 2.5σ indicate minimum clustering effect at the same time. Based on the obtained results, the system with Cu nanoparticles makes it to aggregate later than that of Pt nanoparticles which is due to differences in potential interaction of two materials. The new simulation results enhance our understanding of cluster morphology and aggregation mechanisms.
TL;DR: An original traffic flow model with a consideration of signal effect based on Bando's optimal velocity model was proposed and the mathematical expression for energy dissipation was derived.
Abstract: We proposed an original traffic flow model with a consideration of signal effect based on Bando's optimal velocity model The optimal velocity function was improved more realistically in describing the motion process of vehicles moving on a road with signals Based on the improved model, we derived the mathematical expression for energy dissipation Simulations are conducted to verify the energy dissipation laws in traffic flow with signals Numerical results show that energy dissipation (rate) can be affected not only by traffic density, but also traffic signal control parameters: split and cycle
TL;DR: Random multiple snowball with Cohen (RMSC) process sampling which combines the advantages of random sampling and snowball sampling is proposed in this paper and indicates that this novel sampling method could keep the similarity between sampling subnet and original network on degree distribution, connectivity rate and average shortest path.
Abstract: Sampling subnet is an important topic of complex network research. Sampling methods influence the structure and characteristics of subnet. Random multiple snowball with Cohen (RMSC) process sampling which combines the advantages of random sampling and snowball sampling is proposed in this paper. It has the ability to explore global information and discover the local structure at the same time. The experiments indicate that this novel sampling method could keep the similarity between sampling subnet and original network on degree distribution, connectivity rate and average shortest path. This method is applicable to the situation where the prior knowledge about degree distribution of original network is not sufficient.
TL;DR: Self-time-delay synchronization (STDS) of complex chaotic systems implies that the synchronization between the time-delay system and the original system while maintaining the structure and parameters of systems unchanged, thus these various problems produced by time- delay in practice are avoided.
Abstract: Considering the time lag produced by the transmission in chaos-communication, we present self-time-delay synchronization (STDS) of complex chaotic systems. STDS implies that the synchronization between the time-delay system (the receiver) and the original system (the transmitter) while maintaining the structure and parameters of systems unchanged, thus these various problems produced by time-delay in practice are avoided. It is more suitable to simulate real communication situation. Aimed to time-delay coupled complex chaotic systems, the control law is derived by active control technique. Based on STDS, a novel communication scheme is further designed according to chaotic masking. In simulation, we take time-delay coupled complex Lorenz system transmitting actual speech signal (analog signal) and binary signal as examples. The speech signal contains two components, which are transmitted by the real part and imaginary part of one complex state variable. Two sequences of binary bits are converted into anal...
TL;DR: In this paper, a flexible forcing immersed boundary and lattice Boltzmann method (IB-LBM) is introduced to produce unphysical streamline penetration into the solid object, where the force density is obtained from the unknown velocity correction with a unique single Lagrangian velocity correction term.
Abstract: A novel flexible forcing immersed boundary and lattice Boltzmann method (IB-LBM) is introduced in this paper In the conventional IB-LBM scheme, explicit calculation of the force density term may not guarantee exact satisfaction of the no-slip boundary condition This produces unphysical streamline penetration into the solid object In this study, an implicit approach is followed where the force density is obtained from the unknown velocity correction with a unique single Lagrangian velocity correction term and flexible number of forcing steps The proposed algorithm is computationally efficient and easy for new code development Also the algorithm is found advantageous for unsteady flow case where no-slip condition is accurately satisfied Flow past circular cylinder is studied for both steady and unsteady flow cases to validate the proposed scheme
TL;DR: This work presents a fully resolved two-dimensional model for blood suspension flow, employing a discrete element model (DEM) for RBCs and coupling it to a lattice Boltzmann method (LBM) fluid solver using the immersed boundary method (IBM).
Abstract: Many rheological properties of blood, along with transport properties of blood cells can be captured by means of modeling blood through its main constituents, red blood cells (RBCs) and plasma. In the current work, we present a fully resolved two-dimensional model for blood suspension flow, employing a discrete element model (DEM) for RBCs and coupling it to a lattice Boltzmann method (LBM) fluid solver using the immersed boundary method (IBM). We identify an efficient computationally reduced mesoscopic representation of cells and flow, still able to recover essential physics and physiological phenomena. Our model is found to agree quantitatively with experimental findings. The Fahraeus–Lindqvist effect and shear thinning is recovered, while the thickness of the cell-free layer (CFL) matches the observations. In addition, we investigate the tank-treading frequency of a single RBC in shear flow along with the transition from tumbling to tank-treading, also matching experimental data.
TL;DR: An extended cellular automaton model is proposed to simulate the complex characteristics of traffic flow and the probability of the occurrence of traffic accidents by considering the modified conditions for determining whether traffic accidents happen and the effect of multi-slowdown sections on a highway, and results show that the multi- slowdown sections can lead to multiphase coexistences in traffic system.
Abstract: In this paper, an extended cellular automaton model is proposed to simulate the complex characteristics of traffic flow and the probability of the occurrence of traffic accidents by considering the modified conditions for determining whether traffic accidents happen and the effect of multi-slowdown sections on a highway. The simulation results show that the multi-slowdown sections can lead to multiphase coexistences (i.e. free flow phase, congestion phase and saturation phase) in traffic system. The fundamental diagram shows that the number of slowdown section does not influence the mean velocity and the mean flow under the periodic boundary condition, but the existence of slowdown sections can effectively reduce the occurrence of traffic accident. In particular, it is found that the probability of car accidents to occur is the largest at the joint of the normal-speed section and slowdown section, and the underlying mechanism is analyzed. In addition, to design the appropriate limited speed and reduce the differences between the normal speed and limited speed will alleviate traffic congestion and reduce the occurrence of traffic accidents obviously.
TL;DR: In this article, a simpler derivation of the Fokker-Planck equation is presented, which is very similar in form to Pareto's well-known law.
Abstract: The so-called "Yard-Sale Model" of wealth distribution posits that wealth is transferred between economic agents as a result of transactions whose size is proportional to the wealth of the less wealthy agent. In recent work [B. M. Boghosian, Phys. Rev. E89, 042804 (2014)], it was shown that this results in a Fokker–Planck equation governing the distribution of wealth. With the addition of a mechanism for wealth redistribution, it was further shown that this model results in stationary wealth distributions that are very similar in form to Pareto's well-known law. In this paper, a much simpler derivation of that Fokker–Planck equation is presented.
TL;DR: This paper carries out the image encryption with a revised and modified cryptosystem based on a rule-90 cellular automaton using an appropriate and convenient matrix approach to implement the main components of the encryption system, two indexed families of permutations and a pseudo-random bit generator.
Abstract: This paper carries out the image encryption with a revised and modified cryptosystem based on a rule-90 cellular automaton. For this purpose, we used an appropriate and convenient matrix approach to implement the main components of the encryption system, two indexed families of permutations and a pseudo-random bit generator. Furthermore, we modify the encryption scheme for improving its security. This makes our encryption proposal resist some common attacks, e.g. chosen plain-text attack, and the encryption and decryption processes are performed in a flexible way. Also, some security aspects of the cryptosystem are evaluated with a series of statistical tests exhibiting good results. It is believed that this proposal fits naturally in the present digital technology and is capable of achieving high levels of performance.
TL;DR: In this paper, the correlation between the velocity of two successive vehicles as a function of time headway is studied in the one-dimensional cellular automata (CA) NaSch model within parallel dynamic update.
Abstract: The correlation between the velocity of two successive vehicles as a function of time headway is studied in the one-dimensional cellular automata (CA) NaSch model within parallel dynamic update. It is found that a strong correlation occurs in short time headway. The behavior of the correlation velocity as a function of the car density in different traffic states is also investigated. Moreover, our study is also extended to a more complicated situation where the two vehicles are separated by a number n of other vehicles. It is shown that the velocity correlation coefficient depends strongly on the number n of vehicles in between and on their positions.
TL;DR: Numerical simulations can be used to explain future process window scenarios and find the best parameter set for a good surface quality and dense products and justifies simulations for future improvements of the EBM processes.
Abstract: This paper validates three-dimensional (3D) simulation results of electron beam melting (EBM) processes by comparing experimental and numerical data. The physical setup is presented which is discretized by a 3D thermal lattice Boltzmann method (LBM). An experimental process window is used for the validation depending on the line energy injected into the metal powder bed and the scan velocity of the electron beam. In the process window, the EBM products are classified into the categories, porous, good and swelling, depending on the quality of the surface. The same parameter sets are used to generate a numerical process window. A comparison of numerical and experimental process windows shows a good agreement. This validates the EBM model and justifies simulations for future improvements of the EBM processes. In particular, numerical simulations can be used to explain future process window scenarios and find the best parameter set for a good surface quality and dense products.