Modelling laser-atom interactions in the strong field regime

We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states.Comment: 11 pages, 5 figure

Interarea oscillations in power systems

To highlight the basic nature of interarea oscillations, power systems are modeled by a chain of identical areas, linked by tie lines. The steady state analysis exhibit locus of eigenvalues, characteristic of the dynamics of the areas, but independent of their number, size or distances. The interarea modes are basically an interaction between the mechanical parts of the generating plants through the electrical part of the system. Therefore, the transmittance of the electrical part of the areas has a significant influence, especially on the damping. Simple analytical expressions of the low frequency modes are obtained from an active power model.Anglai

Loop flows in a ring AC power system

The interconnection of AC power systems surrounding a sea or a chain of mountains may lead to a structure having a ring shape. An example is the projected Mediterranean ring, planned to be operational within a few years. In the past, large circulating power flows of about 1000 MW were recorded in the ring power systems around the lake Erie and around the Rocky Mountains in North America. This paper shows that a stable power flow may circulate in a ring AC power system and corresponds to a total phase shift of 2pi (or a multiple of 2pi) radians along the ring. The various power flow solutions of a theoretical system are shown as a function of the power transfer between two areas. Simulations of the system dynamic behaviour show the presence of a loop flow due to a line tripping. The reclosure of the tripped line does not always restore the original power flow. The easiest way to get rid of it is to increase the equivalent impedance of a well-chosen path of the ring power system by opening one or several tie lines. The subsequent reclosure of these lines keeps the system in the normal state. (C) 2003 Elsevier Science Ltd. All rights reserved

Chiral imidate ligands : synthesis and applications in asymmetric catalysis

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Rigorous Definition of the Transformation Ratio in the Presence of Magnetic Saturation and Leakages

This paper proposes a new method for modelling multi-winding devices with non-linear magnetic core. This method is founded on rigorous theoretical bases. It is successfully applied to the study of a voltage transformer for 245 kV network