Coupling of free surface and groundwater flows

In this paper we present some preliminary results about the coupling of shallow water equations for free surface flows and Darcy equation for groundwater flows. A suitable set of interface conditions is discussed: the Beavers and Joseph formula for the bottom stress is used. An iterative algorithm to solve the coupled problem is proposed and some numerical results are presented.     

Preparation of grids for simulations of groundwater flow in fractured porous media

This work presents an extension of grid generation techniques for finite-volume discretizations of density-driven flow in fractured porous media, in which fractures are considered as low-dimensional manifolds and are resolved by sides of grid elements. The proposed technique introduces additional degrees of freedom for the unknowns assigned to the fractures and thus allows to reconstruct jumps of the solution over a fracture. Through the concept of degenerated elements, the proposed technique can be used for arbitrary junctions of fractures but is sufficiently simple regarding the implementation and allows for the application of conventional numerical solvers. Numerical experiments presented at the end of the paper demonstrate the applicability of this technique in two and three dimensions for complicated fracture networks.     

Anelastic reorganisation of fibre-reinforced biological tissues

In this work, we contribute to the study of the structural reorganisation of biological tissues in response to mechanical stimuli. We specialise our investigation to a class of hydrated soft tissues, whose internal structure features reinforcing fibres. These are oriented statistically within the tissue, and their pattern of orientation is such that, at each material point, the tissue is anisotropic. From its natural, stress-free state, the tissue can be distorted anelastically into a global reference configuration, and then deformed under the action of external mechanical loads. The anelastic distortions are responsible for changing irreversibly the internal structure of the tissue, which, in the present context, occurs through both the rearrangement of the bonds among the tissue cells and the deformation-driven reorientation of the fibres. The anelastic strains, in addition, are assumed to model the onset and evolution of microcracks in the tissue, which may be triggered by the mechanical loads applied to the tissue in the case of traumatic events, or diseases. For our purposes, we formulate an anisotropic model of remodelling and we consider a fully isotropic model of structural reorganisation for comparison, with the aim to study if, how, and to what extent the evolution of anelastic distortions is influenced by the tissue’s anisotropy.

     

Safer asynchronous runtime monitoring using compensations

Asynchronous monitoring relieves the system from additional overheads induced through online runtime monitoring. The price paid with such monitoring approaches is that the system may proceed further despite having reached an anomalous state. Any actions performed by the system after the error occurring are undesirable, since for instance, an unchecked malicious user access may perform unauthorized actions. In this paper we investigate the use of compensations to enable the undoing of such undesired actions, thus enriching asynchronous monitoring with the ability to restore the system to the original state just after the anomaly had occurred. Furthermore, we show how adaptive synchronisation and desynchronisation of the monitor with the system can also be achieved and report on the use of the proposed approach on an industrial case study of a financial transaction handling system.     

“Greening Up” Cross-Coupling Chemistry

New methodologies that enable palladium catalyzed cross-coupling reactions to be performed under environmentally benign conditions (in water and/or at room temperature) have been developed. Described approaches involve in situ activation of carbon–halogen or carbon–hydrogen bonds using zinc metal, or cationic palladium, respectively.     

A Mathematical Approach in the Design of Arterial Bypass Using Unsteady Stokes Equations

In this paper we present an approach for the study of Aorto-Coronaric bypass anastomoses configurations using unsteady Stokes equations. The theory of optimal control based on adjoint formulation is applied in order to optimize the shape of the zone of the incoming branch of the bypass (the toe) into the coronary according to several optimality criteria.Dedicated to David Gottlieb on the occasion of his 60th birthdayValery Agoshkov: This work has been prepared when the first author was a visiting professor at Institut d’Analyse et Calcul Scientifique of the école Polytechnique Fédérale de Lausanne     

Editorial

The papers published in this issue of Computing and Visualisation in Science have been presented at the Second AMIF International Conference that was held at Il Ciocco in Tuscany (Italy) on 12-14 October 2000. AMIF stands for Applied Mathematics for Industrial Flows. It is an ESF scientific program, whose goal is to develop research contributions in the following areas: - development and analysis of mathematical modeling of fluid flows of practical (industrial) relevance, - their simulation by modern numerical methods, - set-up and analysis of effective numerical algorithms in the context of advanced parallel computing. The aim is to clarify and highlight the mathematical foundations of differential models and numerical methods, to achieve a better understanding of existing models and methods, as well as to enhance the development of new ones. Application of these tools to the simulation of flow problems of industrial interest is a constant concern of our action. Special attention is drawn on the coupling of heterogeneous models, at both physical and numerical levels: in this respect, the coupling between fluids and solids, between fluids at different regimes, or different numerical models, will be one of the qualifying aspects of this program. Our actions concern: - Organisation of specialized workshops; - Organisation of tutorials and training sessions for researchers including those in industries; - Organisation of a conference of general interest every two years; - Granting fellowships for young researchers; - Support of short visits of senior researchers. This program is supported by the funding Agencies of 12 European Countries. Information on AMIF and instructions for AMIF research fellowships and grants can be obtained at the following internet address: http://dmawww. epfl. ch/Quarteroni-Chaire/AMIF/ For this publication we would like to thank the Journal Editor Prof. G. Wittum, Dr. M. Peters from Springer-Verlag and Mrs. C. Werner from ESF. All papers accepted for publication have been peer reviewed according to the Journal guidelines. Pierre-Louis Lions Alfio Quarteroni     

Induction Motor Identification by a Microcomputer-Based Structure

The paper deals with the parameter estimation of an induction motor performed through a microcomputer-based data acquisition system and recursive identification algorithms (RLS and RGLS) implemented by means of a general purpose computer. The microcomputer-based data acquisition system is essentially made by connecting the Z80 CPU with its peripherals and auxiliary memories through a bus standard. The motor is represented by a classical fifth-order model linearized around a usual working point; an approximate third-order model, obtained via balanced realization, is in good correlation with the original one according to the identification aims and to the measurement set efficiency. An original CAD procedure is utilized to determine the electrical parameters.