Results 11  20
of
347
SelfOrganization in PeertoPeer Systems
 In Proceedings of the 2002 SIGOPS European Workshop, St. Emilion
, 2002
"... This paper addresses the problem of forming groups in peertopeer (P2P) systems and examines what dependability means in decentralized distributed systems. Much of the literature in this field assumes that the participants form a local picture of global state, yet little research has been done disc ..."
Abstract

Cited by 27 (2 self)
 Add to MetaCart
This paper addresses the problem of forming groups in peertopeer (P2P) systems and examines what dependability means in decentralized distributed systems. Much of the literature in this field assumes that the participants form a local picture of global state, yet little research has been done discussing how this state remains stable as nodes enter and leave the system. We assume that nodes remain in the system long enough to benefit from retaining state, but not sufficiently long that the dynamic nature of the problem can be ignored. We look at the components that describe a system's dependability and argue that nextgeneration decentralized systems must explicitly delineate the information dispersal mechanisms (e.g., probe, eventdriven, broadcast), the capabilities assumed about constituent nodes (bandwidth, uptime, reentry distributions), and distribution of information demands (needles in a haystack vs. hay in a haystack [13]). We evaluate two systems based on these criteria: Chord [22] and a heterogeneousnode hierarchical grouping scheme [11]. The former gives a failed request rate under normal P2P conditions and a prototype of the latter a similar rate under more strenuous conditions with an order of magnitude more organizational messages. This analysis suggests several methods to greatly improve the prototype.
ON THE MODELLING CROWD DYNAMICS FROM SCALING TO HYPERBOLIC MACROSCOPIC MODELS
, 2008
"... This paper, that deals with the modelling of crowd dynamics, is the first one of a project finalized to develop a mathematical theory refereing to the modelling of the complex systems constituted by several interacting individuals in bounded and unbounded domains. The first part of the paper is devo ..."
Abstract

Cited by 25 (0 self)
 Add to MetaCart
This paper, that deals with the modelling of crowd dynamics, is the first one of a project finalized to develop a mathematical theory refereing to the modelling of the complex systems constituted by several interacting individuals in bounded and unbounded domains. The first part of the paper is devoted to scaling and related representation problems, then the macroscopic scale is selected and a variety of models are proposed according to different approximations of the pedestrian strategies and interactions. The second part of the paper deals with a qualitative analysis of the models with the aim of analyzing their properties. Finally, a critical analysis is proposed in view of further development of the modelling approach. Additional reasonings are devoted to understanding the conceptual differences between crowd and swarm modelling.
Pedestrian, Crowd and Evacuation Dynamics
 in Encyclopedia of Complexity and System Science
, 2009
"... This contribution describes efforts to model the behavior of individual pedestrians and their interactions in crowds, which generate certain kinds of selforganized patterns of motion. Moreover, this article focusses on the dynamics of crowds in panic or evacuation situations, methods to optimize b ..."
Abstract

Cited by 24 (3 self)
 Add to MetaCart
This contribution describes efforts to model the behavior of individual pedestrians and their interactions in crowds, which generate certain kinds of selforganized patterns of motion. Moreover, this article focusses on the dynamics of crowds in panic or evacuation situations, methods to optimize building designs for egress, and factors potentially causing the breakdown of orderly motion. 2
Cooperative SelfOrganization in a Heterogeneous Swarm Robotic System
"... We study how a swarm robotic system consisting of two different types of robots can solve a foraging task. The first type of robots are small wheeled robots, called footbots, and the second type are flying robots that can attach to the ceiling, called eyebots. While the footbots perform the actual ..."
Abstract

Cited by 24 (6 self)
 Add to MetaCart
(Show Context)
We study how a swarm robotic system consisting of two different types of robots can solve a foraging task. The first type of robots are small wheeled robots, called footbots, and the second type are flying robots that can attach to the ceiling, called eyebots. While the footbots perform the actual foraging, i.e. they move back and forth between a source and a target location, the eyebots are deployed in stationary positions against the ceiling, with the goal of guiding the footbots. The key component of our approach is a process of mutual adaptation, in which footbots execute instructions given by eyebots, and eyebots observe the behavior of footbots to adapt the instructions they give. Through a simulation study, we show that this process allows the system to find a path for foraging in a cluttered environment. Moreover, it is able to converge onto the shortest of two paths, and spread over different paths in case of congestion. Since our approach involves mutual adaptation between two subswarms of different robots, we refer to it as cooperative self
The Virtues and Vices of Equilibrium and the future of financial economics
, 2009
"... The use of equilibrium models in economics springs from the desire for parsimonious models of economic phenomena that take human reasoning into account. This approach has been the cornerstone of modern economic theory. We explain why this is so, extolling the virtues of equilibrium theory; then we p ..."
Abstract

Cited by 24 (1 self)
 Add to MetaCart
(Show Context)
The use of equilibrium models in economics springs from the desire for parsimonious models of economic phenomena that take human reasoning into account. This approach has been the cornerstone of modern economic theory. We explain why this is so, extolling the virtues of equilibrium theory; then we present a critique and describe why this approach is inherently limited, and why economics needs to move in new directions if it is to continue to make progress. We stress that this shouldn’t be a question of dogma, and should be resolved empirically. There are situations where equilibrium models provide useful predictions and there are situations where they can never provide useful predictions. There are also many situations where the jury is still out,i.e.,where so far they fail to provide a good description of the world, but where proper extensions might change this. Our goal is to convince the skeptics that equilibrium models can be useful, but also to make traditional economists more aware of the limitations of equilibrium models.We sketch some alternative approaches and discuss why they should play an important role in
Enhanced intelligent driver model to access the impact of driving strategies on traffic capacity
 Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
, 1928
"... ar ..."
MISTUNINGBASED CONTROL DESIGN TO IMPROVE CLOSEDLOOP STABILITY OF VEHICULAR PLATOONS
, 2008
"... We consider a decentralized bidirectional control of a platoon of N identical vehicles moving in a straight line. The control objective is for each vehicle to maintain a constant velocity and intervehicular separation using only the local information from itself and its two nearest neighbors. Eac ..."
Abstract

Cited by 20 (1 self)
 Add to MetaCart
We consider a decentralized bidirectional control of a platoon of N identical vehicles moving in a straight line. The control objective is for each vehicle to maintain a constant velocity and intervehicular separation using only the local information from itself and its two nearest neighbors. Each vehicle is modeled as a double integrator. To aid the analysis, we use continuous approximation to derive a partial differential equation (PDE) approximation of the discrete platoon dynamics. The PDE model is used to explain the progressive loss of closedloop stability with increasing number of vehicles, and to devise ways to combat this loss of stability. If every vehicle uses the same controller, we show that the least stable closedloop eigenvalue approaches zero as O ( 1 N 2) in the limit of a large number (N) of vehicles. We then show how to ameliorate this loss of stability margin by small amounts of “mistuning”, i.e., changing the controller gains from their nominal values. We prove that with arbitrary small amounts of mistuning, the asymptotic behavior of the least stable closed loop eigenvalue can be improved to O ( 1 N). All the conclusions drawn from analysis of the PDE model are corroborated via numerical calculations of the statespace platoon model.
The spatial variability of vehicle densities as determinant of urban network capacity
, 2010
"... ..."
Large scale dynamics of the Persistent Turning Walker Model of fish behavior
 Journal of Statistical Physics
"... This paper considers a new model of individual displacement, based on fish motion, the socalled Persistent Turning Walker (PTW) model, which involves an OrnsteinUhlenbeck process on the curvature of the particle trajectory. The goal is to show that its large time and space scale dynamics is of dif ..."
Abstract

Cited by 19 (9 self)
 Add to MetaCart
(Show Context)
This paper considers a new model of individual displacement, based on fish motion, the socalled Persistent Turning Walker (PTW) model, which involves an OrnsteinUhlenbeck process on the curvature of the particle trajectory. The goal is to show that its large time and space scale dynamics is of diffusive type, and to provide an analytic expression of the diffusion coefficient. Two methods are investigated. In the first one, we compute the large time asymptotics of the variance of the individual stochastic trajectories. The second method is based on a diffusion approximation of the kinetic formulation of these stochastic trajectories. The kinetic model is a FokkerPlanck type equation posed in an extended phasespace involving the curvature among the kinetic variables. We show that both methods lead to the same value of the diffusion constant. We present some numerical simulations to illustrate the theoretical results. Acknowledgements: The authors wish to thank Guy Théraulaz and Jacques Gautrais of the ’Centre de Recherches sur la Cognition Animale ’ in Toulouse, for introducing them to the model and for stimulating discussions.