Maximal stability region of a perturbed nonnegative matrix

For a class of positive matrices A + K with a stable positive nominal part A and a structured positive perturbation part K, we address the problem of finding the largest set of admissible perturbations such that the global matrix remains stable. Theoretical bounds are derived and an algorithm for constructing this set is presented. As an example, this algorithm is applied to the regulation of water flow in open channels

Modelling and control of road traffic networks

Road traffic networks offer a particularly challenging research subject to the control community. The traffic congestion around big cities is constantly increasing and is now becoming a major problem. However, the dynamics of a road network exhibit some complex behaviours such as nonlinearities, delays and saturation effects that prevent the use of some classical control algorithms. This thesis presents different models and control algorithms used for road traffic networks. The dynamics are represented using a "fluid-flow" approach. This leads to a system of quasi-linear hyperbolic partial differential equations which represents the behaviour of the drivers on each road. The boundary conditions are represented by a set of algebraic relations describing the behaviour of the drivers at the junctions. Two models with different complexities are introduced and their properties analysed. Different control algorithms are presented. One method is focused on the steady state case and intends to minimise a "sustainable cost" function. This function takes into account a time cost, the pollution and the accident risk. Two other methods which are able to deal with transient effects are also presented. The first one is a routing strategy expressing how to spread the traffic flow between two paths leading to the same destination. The second one is a ramp metering strategy using linear feedback.(FSA 3)--UCL, 200

A second order model of road junctions in fluid models of traffic networks

This article deals with the modeling of junctions in a road network from a macroscopic point of view. After reviewing the Aw & Rascle second order model, a compatible junction model is proposed. The properties of this model and particularly the stability are analyzed. It turns out that this model presents physically acceptable solutions, is able to represent the capacity drop phenomenon and can be used to simulate the traffic evolution on a network

Accelerated and Localized Newton Schemes for Faster Dynamic Simulation of Large Power Systems

This paper proposes two methods to speed up the demanding time-domain simulations of large power system models. First, the sparse linear system to solve at each Newton iteration is decomposed according to its bordered block diagonal structure, in order to solve only those parts that need to be solved, and update only sub-matrices of the Jacobian that need to be updated. This brings computational savings without degradation of accuracy. Next, the Jacobian structure is further exploited to localize the system response, i.e. involve only the components identified as active, with an acceptable and controllable decrease in accuracy. The accuracy and computational savings are assessed on a large-scale test system

Experimental characterization and modelling of Baker’s yeast activity and viability during conventional drying

info:eu-repo/semantics/nonPublishe

Radioactive characterization of gas-solid flows in a conical spouted bed

info:eu-repo/semantics/nonPublishe

Lyapunov stability analysis of networks of scalar conservation laws

It is shown how an entropy-based Lyapunov function can be used for the stability analysis of equilibria in networks of scalar conservation laws. The analysis gives a sufficient stability condition which is weaker than the condition which was previously known in the literature. Various extensions and generalisations are briefly discussed. The approach is illustrated with an application to ramp-metering control of road traffic networks