All Years Seminars
[INMA] 2013-10-22 (14.00) : On-line river flow forecasting with "Hydromax"
At Euler building
Speaker :
Robert David (UCL)
Abstract :
"Hydromax" is the river flow forecasting system for the early warning of extreme hydrological events (floods as well as low waters) in the Meuse river basin and its tributaries. Hydromax provides in real-time short-term predictions of river flows based on past rainfall and river flow measurements, and long-term flood forecasting based on meteorological forecasts. It is now successfully in routine operation for more than eighteen years. The purpose of this communication is to give a general description of Hydromax and to report on its performance with typical experimental examples.
[INMA] 2013-10-18 (11.00) : Robust symmetrization - one algorithm, many applications
At Euler building
Speaker :
Sarlette, Alain
Abstract :
This talk generalizes the dynamics behind consensus algorithms towards a procedure to symmetrize the actions of a finite group. After
introducing the theoretical framework, most of the talk will review its various applications that range from extended agreement problems,
through uniform random state generation, and a Fourier transform, to open-loop disturbance rejection techniques.
[INMA] 2013-10-08 (14.00) : Barycentric Lagrange Interpolation and Rootfinding
At Euler building
Speaker :
Piers Lawrence (UCLouvain/KULeuven)
Abstract :
Polynomial approximations to functions arise in almost all areas of computational mathematics, since polynomial expressions can be manipulated in ways that the original function cannot. Polynomials are most often expressed in the monomial basis; however, in many applications polynomials are constructed by interpolating data at a series of points.
In many numerical analysis textbooks the Lagrange basis is quickly disposed of in favour of the Newton basis, due to the larger amount of work required for evaluation and questionable numerical stability of the Lagrange interpolation formula. However, a simple rearrangement yields the so called barycentric interpolation formula which can be shown to be numerically stable, and can be evaluated using the same number of operations as for the Newton basis.
To compute the roots of a polynomial expressed in barycentric form, we may linearize the polynomial, which is to say we convert the rootfinding problem into a generalized eigenvalue problem. This particular linearization is constructed directly from the coefficients in the Lagrange basis (that is, directly from function values). In this talk we show how the linearization can be reduced Hessenberg form in only O(n^2) operations by taking advantage of the structure of the matrices. Thus, we may compute all of the roots of a degree n polynomial in O(n^2) time and O(n) storage. We further show that computing the roots of polynomials via this linearization is backward stable, and give easily computable (and intelligible) bounds for the backward error.
[INMA] 2013-09-23 (14.00) : Modelling and Control for So-Called Smart Grids
At Euler building
Speaker :
Iven Mareels (University of Melbourne)
Abstract :
In today's power grid, the power generators are localised, and the consumers are distributed. In such circumstances the low voltage part of the electricity distribution grid poses as a mere disturbance on the grid. Consequently it is only poorly monitored. Moreover, in this scenario, electricity demand is king, and supply follows demand as there is no significant electrical energy storage.
Recent trends change this classic picture. Distributed power generation is becoming more attractive and is well suited to renewable sources like wind and PV. Also embedded generation, like co-generation is becoming economically attractive. Also, new loads such as electric vehicles pose significant challenges. Moreover, with climate change, the heating/cooling loads on the grid are becoming more variable and peakier.
Also, from a measurement and control point of view, it is now feasible to measure the electric power flow in near real time across an entire distribution network.
We argue that this conflux of technologies enables a new approach to resolve the demand-supply matching problem across the electricity grid. In our scenario we advocate a win-win-win. Consumers benefit from lower unit prices. Producers benefit from a better return on investment because of larger sales, and a greater utilisation of the available assets. Importantly, the environment wins by wasting less energy and integrating more renewable energy sources in the energy mix.
The main idea is that in a smart grid environment, demand and supply can be matched in energy terms rather than power terms. Indeed, by exploiting the significant energy storage in the end-user devices (fridges, air conditioned homes, freezers, batteries),
a new regime of power management is enabled.
To this end, we revisit the modeling and control of a low voltage distribution network, and in particular pose the problem of electric vehicle charging as a receding horizon control problem for a spatially distributed collection of cars, subject to the network's operational limits. Realistic models, validated against operational data (for local networks in Australia) will be presented. Our modelling tool, called POSSIM, is open software, maintained by our team, see http://www.possim.org/. In this context, we discuss the potential for adaptive model identification, centralised control options as well as decentralised and consensus based control options. Some early results on the potential penetration of electric vehicles in a managed smart grid environment are also presented.
The work as discussed is based on an Australian Research Council sponsored project "Integrating Electric Vehicles into a Smart Grid" at the University of Melbourne, School of Engineering, executed by Prof Iven Mareels, Prof Doreen Thomas, A/Prof Marcus Brazil, Dr Tansu Alpcan, Dr Julian de Hoog and PhD students Valentin Muenzel and Derek Jayasuriya; and involves collaboration with IBM's Smart Grid efforts around the nPlug idea introduced by Dr Shivkumar Kalyanaraman, a variant of which will be briefly discussed in this talk.
[INMA] 2013-09-17 (14.00) : Synchronizing automata
At Euler building
Speaker :
Vladimir Gusev (Ural Federal University)
Abstract : An automaton is called synchronizing if there is a word w and a state q such that w applied to an arbitrary state p leads to q. This
notion naturally appears in different areas of computer science, usually, as a model of error resistant system. In my talk I will tell about
applications of synchronizing automata and about two famous problems related to synchronizing automata: road coloring problem and Cerny conjecture.
Former was open for 37 years and was recently settled. Latter is widely open for already 48 years.
Seminars
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