16:30
16:30
16:15
Robust numerical methods for computer aided process plant design
Abstract
The process industries are one of the UK's major sectors and include
petrochemicals, pharmaceuticals, water, energy and the food industry,
amongst others. The design of a processing plant is a difficult task. This
is due to both the need to cater for multiple criteria (such as economics,
environmental and safety) and the use highly complex nonlinear models to
describe the behaviour of individual unit operations in the process. Early
in the design stages, an engineer may wish to use automated design tools to
generate conceptual plant designs which have potentially positive attributes
with respect to the main criteria. Such automated tools typically rely on
optimization for solving large mixed integer nonlinear programming models.
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This talk presents an overview of some of the work done in the Computer
Aided Process Engineering group at UCL. Primary emphasis will be given to
recent developments in hybrid optimization methods, including the use of
graphical interfaces based on problem specific visualization techniques to
allow the engineer to interact with embedded optimization procedures. Case
studies from petrochemical and water industries will be presented to
demonstrate the complexities involved and illustrate the potential benefits
of hybrid approaches.
17:00
17:00
17:00
15:30
14:15
14:15
A use of non-commutative formal power series in stochastic processes
16:30
Piecewise-holonomic mechanics, hybrid dynamical systems and escaping cockroaches
Preconditioning for 3D sedimentary basin simulations
Abstract
The simulation of sedimentary basins aims at reconstructing its historical
evolution in order to provide quantitative predictions about phenomena
leading to hydrocarbon accumulations. The kernel of this simulation is the
numerical solution of a complex system of time dependent, three
dimensional partial differential equations of mixed parabolic-hyperbolic
type in highly heterogeneous media. A discretisation and linearisation of
this system leads to large ill-conditioned non-symmetric linear systems
with three unknowns per mesh element.
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In the seminar I will look at different preconditioning approaches for
these systems and at their parallelisation. The most effective
preconditioner which we developed so far consists in three stages: (i) a
local decoupling of the equations which (in addition) aims at
concentrating the elliptic part of the system in the "pressure block'';
(ii) an efficient preconditioning of the pressure block using AMG; (iii)
the "recoupling'' of the equations. Numerical results on real case
studies, exhibit (i) a significant reduction of sequential CPU times, up
to a factor 5 with respect to the current ILU(0) preconditioner, (ii)
robustness with respect to physical and numerical parameters, and (iii) a
speedup of up to 4 on 8 processors.
17:00
Grothendieck's Problems Concerning Profinite Completions and Representations of Groups
17:00
17:00