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This paper studies the coupled vehicle-pedestrian delay problem, taking into account the interactions between vehicles and pedestrians. In a previous paper, we found that for a large pedestrian arrival probability, coupled inefficient oscillations of pedestrian and vehicle flows emerge when pedestrians cross the street with a small time gap to approaching cars (aggressive pedestrians), while both pedestrians and vehicles benefit, when they keep some overcritical time gap (careful pedestrians). In this paper, we take into account the fact that the crossing time of a pedestrian group increases with its size. Our simulations show that when the crossing time of the pedestrian group is considered, the situation of careful pedestrians changes qualitatively. While vehicle and pedestrian flows for a low vehicle flow rate and small pedestrian arrival probability are efficient, oscillations occur when the vehicle flow rate and/or the pedestrian arrival probability increase. We propose a variable speed limit implemented by a LED display to avoid the inefficiency of vehicle and pedestrian flows for careful pedestrians. [ABSTRACT FROM AUTHOR]

Using vehicle trajectories for a motorway collected from a helicopter, and a newly developed approach to parameter identification, this paper provides new empirical evidence of multi-anticipative car-following by estimating the driver-specific parameters of the different multi-anticipative car-following models. We investigate the nature of the multi-leader stimuli, providing insight into the number of vehicles ahead to which drivers react and the kind of stimuli drivers respond to. The paper also shows that there is large inter-driver variability in multi-leader driving behavior. The implications of our research findings for microscopic modeling are discussed as well. [ABSTRACT FROM AUTHOR]

Insights into pedestrian behavior, and tools to predict this behavior, are essential in the planning and design of public pedestrian facilities, such as transfer stations, shopping malls, and airports. Both macroscopic features of pedestrian flows and microscopic walking behavior underlying these features are important. This paper discusses findings from an experiment with crossing pedestrian flows, and in particular the free speed distribution of the participating pedestrians. Available free speed estimation methods developed for car traffic appear to be not suited for pedestrian traffic. This paper presents a dedicated adaptation of a method used for car traffic, with satisfactory results in pedestrian crossing flows. [ABSTRACT FROM AUTHOR]

The paper analyses traffic flow data collected in the Lefortovo tunnel (Moscow) in 2004/05. First, it shows the presence of cooperative traffic dynamics in this tunnel and, second, studies the phase portrait of the vehicle ensemble in the velocity-density plane. In particular, the regions of regular and stochastic dynamics are found and the presence of dynamical traps is demonstrated. [ABSTRACT FROM AUTHOR]

Detection, identification and tracking of multiple moving targets have important applications in transportation and vehicle control areas. In this paper we present our approach to detect, recognize and track the vehicles within the detection region of a moving probe vehicle, based on the data collected by multiple sensors, including LIDAR and GPS. This paper develops a methodology to group the LIDAR measurements into targets, classify the targets as vehicles or fixed objects, and track the vehicular targets within lanes using a Kalman-filter. One important feature of this approach is that we track all of the observations in world coordinates, allowing us to average over many samples and ideally many runs to differentiate between the fixed objects (road boundaries) and moving objects (vehicles). [ABSTRACT FROM AUTHOR]

This paper shows that including the effects of lane-changing activity in kinematic wave theory reveals the physical mechanisms and reproduces the main empirical features that motivated Kerner's three-phase theory. This is shown using a hybrid representation of traffic flow where lane-changing vehicles are treated as discrete particles with realistic accelerations embedded in a continuous multilane kinematic wave stream. We show that this parsimonious four-parameter model reproduces the three phases identified by Kerner, including phase transitions and jam formation. We conclude that synchronized flow and wide-moving jams differ only in their lane-changing spatiotemporal patterns, but obey the same conservation laws and boundary conditions. Freeway segments with one, two and three junctions are analyzed. [ABSTRACT FROM AUTHOR]

The multi-phase signal control method is one of the important measures to enhance intersection capacities and alleviate urban traffic problems. This paper employs the stopping-line-method to study the capacity model of cross multi-phase signalized intersections and analyses the relevant change of the intersection capacity and cycle length. It studies the intersection capacity in detail under two normal situations, one with one straight lane and one left-turn lane, and the other with two straight lanes and one left-turn lane. Finally, a practical intersection is chosen and its phase design is improved by the method proposed in the paper. [ABSTRACT FROM AUTHOR]

Agent-based and cellular automata models have been widely used in an efficient and effective way for studying granular traffic, but rarely considering the combined effect and interactions of pedestrians and vehicles in urban networks. So from this point of view an attempt has been made to develop a virtual urban environment which considers both vehicular and pedestrian traffic and the interactions arising from their behavior. This paper presents details of the model we have developed. For vehicular traffic a cellular automata model, combining and appropriately modifying (e.g. to account for the pedestrian movement) BML, NaSch and ChSch models, is considered. Pedestrian traffic is simulated using simple behavioral rules combined with an agent-based approach. Different constraints affecting the mobility of the whole system are considered, which can be seen and even changed by the user in the simulated environment. The model belongs to the microscopic category where pedestrians/vehicles behave in their environment by making a sequence of decisions. The interactions among vehicles and pedestrians are also incorporated which signifies various effects, ranging from accident risk of pedestrians to the generation of traffic jams. NetLogo which is a multi-agent based modeling language is used as the programming platform for the simulation. [ABSTRACT FROM AUTHOR]

This paper is concerned with a fluidodynamic model for traffic flow. More precisely, we consider a single conservation law, deduced from the conservation of the number of cars, defined on a road network that is a collection of roads with junctions. The evolution problem is underdetermined at junctions, hence we choose to have some fixed rules for the distribution of traffic plus an optimization criteria for the flux. We prove existence of solutions to the Cauchy problem and we show that the Lipschitz continuous dependence by initial data does not hold. Our method is based on wave front tracking approach, see [4]. [ABSTRACT FROM AUTHOR]

This paper discusses the validity of first-order traffic flow theory to describe two-dimensional pedestrian flow operations in case of an oversaturated bottleneck upstream of which a large high-density region has formed. Pedestrians passing the same cross-section inside of the congested region appear to encounter different flow conditions. In the lateral center, high densities and low speeds are observed. However, on the boundary of the congested region, pedestrians may walk in nearly free flow conditions. Visualising pedestrian flow data in the flow-density plane results in a large scatter of points having similar flows (bottleneck capacity), but different densities. Observations on congestion of pedestrian traffic over the total width of the cross-section are found to belong to a set of different fundamental diagrams instead of a single one. This has consequences for the estimation of the fundamental diagram describing pedestrian traffic. [ABSTRACT FROM AUTHOR]

This paper deals with the numerical approximation of the solutions of a macroscopic model for the description of the flow of pedestrians. Solutions of the associated Riemann problem are known to be possibly nonclassical in the sense that the underlying discontinuities may well violate Oleinik inequalities, which makes their numerical approximation very sensitive. This study proposes to apply the Transport-Equilibrium strategy proposed in [2] for computing nonclassical solutions of scalar conservation laws to this framework. Numerical evidences are proposed. [ABSTRACT FROM AUTHOR]

In a recent paper (Phys. Rev. E 72, 035102 (2005)) we have proposed a stochastic optimal velocity model which includes two exactly solvable stochastic models. It can be regarded as a stochastic version of the optimal velocity model. We find that the model shows striking metastability (i.e. long-lived metastable states, dynamical phase transition, and sharp spontaneous metastability breaking) as well as solvability. In this work, we present additional explanations of the solvability and metastability, which are helpful in understanding the traffic dynamics of the model. [ABSTRACT FROM AUTHOR]

Recent empirical observations at freeway merge bottlenecks have revealed (i) a drop in the bottleneck discharge rate when queues form upstream, (ii) an increase in lane-changing maneuvers simultaneous with this "capacity drop", and (iii) a reversal of the drop when the ramp is metered. This paper shows that a simple vehicle lane-changing theory, which has been shown to explain related phenomena at lane-drops and moving bottlenecks, also explains the new phenomena at merges. In this theory, lane-changing vehicles are modeled as discrete particles endowed with realistic accelerations, and are embedded in a multilane stream where each lane obeys the kinematic wave model. This theory is parsimonious: only one of its four parameters has to be calibrated by running the model. Our simulations show that the theory predicts surprisingly well the cumulative flows at all locations, the vehicle trip times, the number of lane-changing maneuvers, the capacity drop, its recovery upon metering, and the distribution of these measures across lanes and over time. Applications are discussed. [ABSTRACT FROM AUTHOR]

Traffic breakdowns are described by a balance equation that models the dynamics of jam formation by the following two contributions. There are discharge rate depending on the length of the congestion and an adhesion rate mainly depending on the traffic volume of the considered road section. With this balance equation it is feasible to calculate the dynamics of traffic pattern formation especially the first passage time for a transition from free flow condition to congested traffic including the influence of the parameters affecting the discharge and adhesion rates. As a simple approximation we consider constant attachment rate as well as constant detachment rate. Starting with the probability density and furtheron with the cumulative probability for breakdowns the change in the incident duration distribution is calculated and qualitatively given. The paper concludes with recommendations for a comprehensive operation improvement and provides necessary steps for a long lasting stabilization of traffic for a given vehicular flow time series pattern. [ABSTRACT FROM AUTHOR]

The problems of traffic flow forecasting on complex traffic networks are still almost not explored. However these problems are very actual for scientists as well as for traffic engineers. In this paper we consider problems of stability of particle (car) flows on networks. The definitions of critical, stable and unstable flow states on networks are obtained as properties of solutions of nonlinear differential equations on graphs. For networks with different geometry the necessary and sufficient conditions of flow stability on networks are found. The perspective problems of exploration of qualitative properties of flows on networks are formulated. [ABSTRACT FROM AUTHOR]

In this article, we show two examples for the application of pedestrian flow simulation and analysis: the World Youth Day 2005 (WYD) in Cologne and the (non-emergency) egress from a football stadium. Various circumstances are specific for religious events. The persons might perform rituals and therefore the patterns of movement or gathering are governed by rules that go beyond simple necessity or comfort. Furthermore, the persons are usually very much attracted by the (idealistic) aim of their pilgrimage. The final service at the WYD in Cologne, celebrated by the Pope, was the major event during the WYD. The paper is divided into three parts: The first section is concerned with the World Youth Day and the second with the egress from a football stadium. The final section summarizes the results, provides recommendations and concludes with the most important implications for the field of crowd dynamics simulation. [ABSTRACT FROM AUTHOR]

We present results of a statistical analysis of empirical floating-car data. Our investigations are based on analyzing the time series of four basic quantities namely velocity, velocity difference, spatial gap and the acceleration associated to some instrumented cars. We try to identify the moving phases of the instrumented vehicle according to the statistical properties of its velocity time series. Moreover, by exploring the two-point joint probabilities, we propose a new approach for modelling vehicular dynamics based on the floating car data. [ABSTRACT FROM AUTHOR]

The random shuffle update method for the asymmetric exclusion process (ASEP) is introduced and the cluster dynamics technique is extended in order to analyse its dynamics. A sequence of approximate models is introduced, the first element of which corresponds to the classical parallel update rule whose two-cluster dynamics is reviewed. It is then shown how the argument may be extended inductively to solve for the two-cluster probabilities for each element of the sequence of approximate models. A formal limit is then taken, and macroscopic velocities and flow rates are derived. [ABSTRACT FROM AUTHOR]

A simple CA model (CA-184s2ss) is shown to reproduce, at freeway bottlenecks, elements of the observed phenomena of two-capacity flow, including both breakdown and recovery flows, and of wide moving jams. Notwithstanding that both of these phenomena are incompatible with classical kinematic-wave models (KWMs) of traffic flow, sufficiently coarsely time-aggregated CA-184s2ss simulations are shown to be approximated modestly well by the KWM, with a single suitable empirically determined capacity at the bottleneck. [ABSTRACT FROM AUTHOR]

A cellular automaton traffic model of cars on two single-lane roads crossing at one point is studied. At the crossing real-time traffic information is displayed and drivers determine the driving direction based on the information about the trip-time. The traffic flow and density of the cars on the roads oscillate between free flow and jam states, and their time-behavior is chaotic. The real-time traffic information lures the driver to a road with shorter trip-time and causes too much concentration of the traffic by the nonlinearity of the velocity-density relation. [ABSTRACT FROM AUTHOR]

A genetic algorithm approach is used to study the behaviour of agents in a simulation of a daily route choice. There are two roads to choose and we show that there is a welfare enhancing effect of an Advanced Traveller Information System (ATIS) in comparison to the standard case without an ATIS. In the first case it is remarkable that not all agents follow the recommendation of the ATIS and the equilibrium distribution is only approximately attained. [ABSTRACT FROM AUTHOR]

Adaptive-Cruise Control (ACC) automatically accelerates or decelerates a vehicle to maintain a selected time gap, to reach a desired velocity, or to prevent a rear-end collision. To this end, the ACC sensors detect and track the vehicle ahead for measuring the actual distance and speed difference. Together with the own velocity, these input variables are exactly the same as in car-following models. The focus of this contribution is: What will be the impact of a spreading of ACC systems on the traffic dynamics? Do automated driving strategies have the potential to improve the capacity and stability of traffic flow or will they necessarily increase the heterogeneity and instability? How does the result depend on the ACC equipment level? We discuss microscopic modeling aspects for human and automated (ACC) driving. By means of microscopic traffic simulations, we study how a variable percentage of ACC-equipped vehicles influences the stability of traffic flow, the maximum flow under free traffic conditions until traffic breaks down, and the dynamic capacity of congested traffic. Furthermore, we compare different percentages of ACC with respect to travel times in a specific congestion scenario. Remarkably, we find that already a small amount of ACC equipped cars and, hence, a marginally increased free and dynamic capacity, leads to a drastic reduction of traffic congestion. [ABSTRACT FROM AUTHOR]

In this talk I will review some very simple models of nonequilibrium systems known as the ‘Asymmetric Exclusion Process' and the ‘Zero-Range Process'. These involve particles hopping stochastically on a lattice and thus form stochastic models of flow. Systems driven out of equilibrium can often exhibit behaviour not seen in systems in thermal equilibrium - for example phase transitions in one-dimensional systems. I shall show how examples of such transitions may be interpreted as jamming transitions in the context of traffic flow. More generally I shall discuss other instances of the condensation transition which is the phenomenon of a finite fraction of the driven conserved quantity condensing into a small spatial region. Criteria for the occurrence of condensation may be formulated and the detailed properties of the condensate such as its fluctuations have recently been elucidated. [ABSTRACT FROM AUTHOR]

In dense vehicular traffic cars often drive at close distances, they form clusters or platoons. Within these platoons, time headways are observed, which are often even shorter than the reaction time of the drivers - a situation which is potentially dangerous. Here we propose a simple dynamical model for a platoon undergoing emergency braking, which takes into account the individual variations of the reaction time and braking capacities. We apply the model to real platoons, i.e. platoons which have been identified in large sets of single-vehicle traffic data. We use our results in order to compare the impact of different possible regulations (speed limit, minimum headway). [ABSTRACT FROM AUTHOR]

A new software environment (NETSIM) is presented that can be used for interactive experimental studies concerning the route-choice behaviour of human actors in different scenarios. It is also possible to create scenarios in which human actors interact with software agents. Since the treatments in laboratory experiments are well controlled, the behaviour of subjects in situations of economically relevant decision-making can be analysed more thoroughly. We describe an experimental setup in which the Nagel Schreckenberg Algorithm for vehicle dynamics is used. [ABSTRACT FROM AUTHOR]

We present analytical and numerical results of modeling of flows represented as correlated non-Poissonian point process and as Poissonian sequence of pulses of different size. Both models may generate signals with power-law distributions of the intensity of the flow and power-law spectral density. Furthermore, different distributions of the interevent time of the point process and different statistics of the size of pulses may result in 1/fβ noise with 0.5 ≲ β ≲ 2. A combination of the models is applied for modeling Internet traffic. [ABSTRACT FROM AUTHOR]

We describe a new model of vehicular traffic flow with phase transitions. The model is obtained by coupling the classical Lighthill-Whitham-Richards equation with the 2 × 2 system proposed by Aw and Rascle. We show an application to the modeling of a bottleneck, and compare the results with those obtained using other models. [ABSTRACT FROM AUTHOR]

The Optimal-Velocity (OV) model is posed on an inhomogeneous ring- road and the consequent spatial traffic patterns are described and analysed. Parameters are chosen throughout for which all uniform flows are linearly stable, and a simple model for a bottleneck is used in which the OV function is scaled down on a subsection of the road. The large-time behaviour of this system is stationary and it is shown that there are three types of macroscopic traffic pattern, each consisting of plateaus joined together by sharp fronts. These patterns solve simple flow and density balances, which in some cases have non-unique solutions. It is shown how the theory of characteristics for the classical Lighthill-Whitham PDE model may be used to explain qualitatively which solutions the OV model selects. However, fine details of the OV model solution structure may only be explained by higher order PDE modelling. [ABSTRACT FROM AUTHOR]

We investigate the adaptation of the time headways in car-following models as a function of the local velocity variance, which is a measure of the inhomogeneity of traffic flows. We apply our meta-model to several car-following models and simulate traffic breakdowns in open systems with an on-ramp bottleneck. Single-vehicle data generated by ‘virtual detectors' show a semi-quantitative agreement with microscopic data from the Dutch freeway A9. This includes the observed distributions of the net time headways and times-to-collisions for free and congested traffic, and the velocity variance as a function of traffic density. Macroscopic properties such as the observed wide scattering of flow-density data are reproduced as well, even for deterministic simulations. We explain these phenomena by a self-organized variance-driven process that leads to the spontaneous formation and decay of long-lived platoons. [ABSTRACT FROM AUTHOR]

A bottleneck simulation of road traffic on a loop, using the cellular automata Nagel-Schreckenberg model (with p = 0), reveals three types of stationary wave solutions. They consist of i) two shock waves at the bottleneck boundaries, ii) one shock wave at the boundary and one on the "open" road and iii) the trivial solution, i.e. homogeneous, uniform flow. These solutions are selected dynamically from a range of stationary wave solutions, similar in fashion to the wave selection in a bottleneck simulation of the optimal-velocity model. This is yet another indication that CA and OV models share certain underlying dynamics, although the former are discrete in space and time while the latter are continuous. [ABSTRACT FROM AUTHOR]

We introduce cellular automaton models for both cars alone [1] and mixed traffic (cars and buses) on motorways in Bogotá. Our model includes three elements: hysteresis between acceleration and braking gaps, a delay time in the acceleration, and instantaneous braking. In addition, we include a lane changing rule and the disordered behavior of Bogotan bus drivers. The parameters of our model were obtained from direct measurements on a car and a bus in this city. We use this model to simulate the flux-density fundamental diagram for a singlelane road with car traffic and a two-lane road with mixed traffic, and compare the results with experimental data. Our simulations are in very good agreement with experimental measurements, and reproduce both the shape and the value of the maximal flux. Moreover, they show that the causes of the measured high fluxes are the short gaps that the Bogotan drivers are used to maintain to the car ahead (the agressive driving that is typical for this city). [ABSTRACT FROM AUTHOR]

This article presents a study of the performance decrease caused by blocking one link. We predict which types of links are important for the well functioning of the network as a whole. Traffic is simulated on a regional network in which the links are blocked sequentially. Each of these outcomes is compared to the outcome of the fully operational network. We argue that traffic dynamics including spillback are important in the reduction of performance. We assessed the performance decrease for two situations, one in which people stick to their everyday routes and one in which they will adapt their routes to the new situation. A blocking of motorways turns out to influence the traffic flow most. In the situation that people stick to their everyday routes, urban roads close to the motorway are equally important: spillback effects causes delays also for through traffic on the motorway. [ABSTRACT FROM AUTHOR]

We analyse the effects of agents' decisions on the creation of, and reaction to, congestion on a centralised network with ring-and-hub topology. The system dynamics are driven by an interplay between the creation of, and the transition between, particular stable states which arise as the network is varied. Our results show that the existence of congestion in a network is a dynamic process which is as much dependent on the agents' decisions as it is on the structure of the network itself. [ABSTRACT FROM AUTHOR]

The relation between the fundamental quantities flow, density, and speed is well studied empirically in "undistorted" traffic, i.e. traffic on highways or major non-urban roads. The situation on urban roads is more complicated since urban traffic is influenced by a number of effects. Especially, the situation at intersections (traffic lights, merging traffic) is of striking importance. While the flow between two intersections can be considered as roughly constant, the density and the speed are quantities that vary rapidly along the road. By analyzing data from stationary sensors (measuring flow and local speed) as well as Floating Car Data (measuring travel time, i.e. averaged speed) we found that the speed on many urban roads does not depend on the corresponding flow (respectively the density) alone. For a given flow, the speeds at different times of the day may differ. This effect can be observed for local speeds as well as for speeds averaged along edges or over an area. Very often the maximum in the flow at morning peak precedes the speed minimum. The time difference between these two events is up to one hour varying from road to road. Similar observations have been found in averages over an urban area. A possible explanation for the observed relation between flow and speed is — besides the influence of traffic signalling — that a more heterogeneous traffic (with a higher fraction of vehicles merging into different directions) leads to slower speeds. [ABSTRACT FROM AUTHOR]

This contribution proposes a new approach to estimate model parameters of microscopic pedestrian models using individual pedestrian trajectory data. To this end, a generic approach is proposed that enables parameter identification for microscopic models in general and in particular for walker models. The application results provide new insight into the behavior of individual pedestrians, inter-pedestrian differences, as well as the resulting pedestrian flow characteristics. By comparing different models of increasing complexity, it is investigated which of the model amendments are significant from a statistical point of view and which are not. It is shown that besides anisotropy, finite reaction times play an important role in correctly describing microscopic walking behavior. The implications of these findings in the microscopic description of pedestrians flows are considered by studying the predicted flow operations at a narrow bottleneck. It turns out that the finite reaction times have a significant effect on the pedestrian flow operations. [ABSTRACT FROM AUTHOR]

The goal of our study is to make use of the (fractally-defined) harmonicmean criterion (HMC) as an indicator of proper/improper matter nucleation-transportation and matter-(non)densification tasks realized over certain thermodynamickinetic pathways in d-dimensional environments. We investigate three dynamic processes: self-avoiding random walk (SAW), cluster-cluster aggregation (CCA) and diffusion-limited aggregation (DLA). They are all considered as dispersive systems characteristic of excluded-volume effect (EVE). From our mean-field investigation it turns out that the HMC shows that SAW and CCA belong to the same kinetic (or, dispersive chemical kinetics) class, whereas DLA does not since it is realized over a mixed (non-homogeneous) thermodynamic-kinetic pathway. Our findings clearly reveal that the dimension two appears to be kinetically optimal for SAW and CCA but cast again some serious doubts on whether the so-called DLA 2D "paradigm" is here a well-posed problem. [ABSTRACT FROM AUTHOR]

We present a mathematical model for self-driven particles (2-D Optimal Velocity Model), which can reproduce a big variety of patterns in group formation and phase transition physics, by changing only two control-parameters and the number of particles. We show the formation of several typical patterns and their phase diagrams. The model can be applied to the study of group formation of collective bio-motions such as schools of fish. [ABSTRACT FROM AUTHOR]

Molecular motors perform active movements along cytoskeletal filaments and drive the traffic of organelles and other cargo particles in cells. In contrast to the macroscopic traffic of cars, however, the traffic of molecular motors is characterized by a finite walking distance (or run length) after which a motor unbinds from the filament along which it moves. Unbound motors perform Brownian motion in the surrounding aqueous solution until they rebind to a filament. We use variants of driven lattice gas models to describe the interplay of their active movements, the unbound diffusion, and the binding/unbinding dynamics. If the motor concentration is large, motor-motor interactions become important and lead to a variety of cooperative traffic phenomena such as traffic jams on the filaments, boundary-induced phase transitions, and spontaneous symmetry breaking in systems with two species of motors. If the filament is surrounded by a large reservoir of motors, the jam length, i.e., the extension of the traffic jams, is of the order of the walking distance. Much longer jams can be found in confined geometries such as tube-like compartments. [ABSTRACT FROM AUTHOR]

We develop a theoretical model of intra-cellular transport by mutually interacting molecular motors KIF1A that takes into account the hydrolysis of ATP explicitly. A remarkable feature of this model is that all its parameters can be directly determined from experimental data. Our results are in excellent quantitative agreement with the empirical data, and we also provide experimental evidence for the existence of domain walls in our in-vitro experiment. [ABSTRACT FROM AUTHOR]

Motor proteins are key players in intracellular transport processes and biological motion. Theoretical modeling of these systems has been achieved by the use of step processes on one-dimensional lattices. After a comprehensive introduction to the total asymmetric exclusion process and some analytical tools, we will give a review on different lines of research attracted to the aspects of this systems. We will focus on the generic properties of a coupling between the exclusion process and Langmuir bulk kinetics that induce topological changes in the phase diagram and multi-phase coexistence. [ABSTRACT FROM AUTHOR]

The particle discharge process from a vertical open-top pipe with a capillary outlet reveals some exceptions to the common belief that the outflux oscillation results solely from dynamic arching of beads at the orifice and that the outflux is not sensitive to the filling height. With beads of a particular size range, the outflux fluctuates greatly with time and the bulk dense granular flow in the pipe shows stop-and-go motion when the filling height is above a threshold. When the filling height falls to the threshold, led by a transitional stage, the outflux and the bulk movement become stable. The dropping velocity variation of the upper surface is measured to study the bulk motion in the pipe. With a heuristic theory, we find that the granular compaction and interstitial air pressure effect are responsible for the stop-and-go oscillation and the transitional behavior. [ABSTRACT FROM AUTHOR]

In suspensions with charged particles, electrostatic forces and hydrodynamic interactions are both important to describe the system. We study different models of hydrodynamic interaction for monopolarly charged particles in a nonpolar liquid. In this case, there is no screening of the Coulomb repulsion, so the repulsion between all pairs must be taken into account. For some selected systems we examine different models of hydrodynamic interaction, and we show that anomalies and unphysical behaviour in many cases result. We propose a way to model the interaction which does not suffer from these problems. [ABSTRACT FROM AUTHOR]

We present and analyze a cellular automaton model for granular surface flow along piles and inclines. It is based on the intuitive idea that granular surface flow happens via successive excitation of small-scale avalanches. We show that this model reproduces several essential experimental results for granular surface flow and give a continuum approximation of its spatio-temporal evolution. [ABSTRACT FROM AUTHOR]

We present two experimental studies on the flow of model granular media made of nearly elastic spherical particles. Experiments are performed in microgravity conditions inside an airplane undergoing parabolic flights. We first investigate the rheological behaviour of the medium in a cylindrical Couette geometry. The curves, shear stress versus shear rate, are presented and the quadratic dependence on the shear rate is clearly shown. The second series of experiments investigate the behaviour of a vibrated monolayer of spherical particles. A high speed camera is used to record the motion of particles. With an image analysis tracking technique we determine the velocities of the particles from which we retrieve the temperature. The density profiles show the persistence of clusters of particles at the centre of the cell which coexist with a gas phase at the edges of the cell. We conclude by comparing experiments performed in microgravity and in normal gravity. [ABSTRACT FROM AUTHOR]

Experiments on bidisperse dry granular flows on an inclined rough plane were made in order to better understand the rheology of this kind of material. Flows, created by a localised input of a granular matter onto the plane, propagate and spread laterally, being unconfined by the experimental set-up. Because of size segregation, the lateral and vertical inhomogeneous repartitions of particles lead to several effects causing the main difference between bidisperse and monodisperse flow: the outline effect and the interfaces effects. The outline effect is due to the large beads at the front, and at the borders of the flow. It can be interpreted using the relative frictions of the two types of beads on the rough plane. The relative friction has been quantified with experiments on monodisperse granular flows. The interfaces effects deal with the interaction between the layers of large and small beads and with the interaction between the small beads and the plane. It combines friction, dragging and longitudinal separation of th etwo superposed layers of beads. [ABSTRACT FROM AUTHOR]

Vibratory conveyors are well established in routine industrial production for controlled transport of bulk solids. Because of the complicated interactions between the vibrating trough and the particles both glide and throw movements frequently appear within one oscillation cycle. Apart from the amplitude and frequency, the form of the trajectory of the conveyor's motion also exerts an influence. The goal of our project is a systematic investigation of the dependence of the transport behavior on the three principle oscillation forms: linear, circular and elliptic. For circular oscillations of the shaking trough a non-monotonous dependence of the transport velocity on the normalized acceleration is observed. Two maxima are separated by a regime, where the granular flow is much slower and, in a certain driving range, even reverses its direction. In addition, standing waves oscillating at half the forcing frequency are observed within a certain range of the driving acceleration. The dominant wavelength of the pattern is measured for various forcing frequencies at constant amplitude. These waves are not stationary, but drift with a velocity equal to the transport velocity of the granular material, determined by means of a tracer particle. Finally, the fluidization of a monolayer of glass beads is studied. At peak forcing accelerations between 1.1 g and 1.5 g a solid-like and a gas-like domain coexist. It is found that the number density in the solid phase is several times that in the gas, while its granular temperature is orders of magnitude lower. [ABSTRACT FROM AUTHOR]

We present and study lattice and off-lattice microscopic models in which particles interact via a local anisotropic rule. The rule induces preferential hopping along one direction, so that a net current sets in if allowed by boundary conditions. This may be viewed as an oversimplification of the situation concerning certain traffic and flow problems. The emphasis in our study is on the influence of dynamic details on the resulting (non-equilibrium) steady state. In particular, we shall discuss on the similarities and differences between a lattice model and its continuous counterpart, namely, a Lennard-Jones analogue in which the particles' coordinates vary continuously. Our study, which involves a large series of computer simulations, in particular reveals that spatial discretization will often modify the resulting morphological properties and even induce a different phase diagram and criticality. [ABSTRACT FROM AUTHOR]

We study the geometry of forces in some simple models for granular stackings. The information contained in geometry is complementary to that in the distribution of forces in a single inter-particle contact, which is more widely studied. We present a method which focuses on fractal features of the force network and find good evidence of scale invariance of patterns of large forces. The method enables us to distinguish universality classes characterized by critical exponents. Our approach can be applied to force networks in other athermal jammed systems. [ABSTRACT FROM AUTHOR]