Application of the wavelet transform in the laminar turbulent transition for a flow in a mixed convection phenomenon

The aim of this paper is to show the effect of secondary flows caused by natural convection on the laminar-turbulent hydrodynamic transition. It is not a question of measuring a critical threshold value of Reynolds number of transition but only to estimate the degree of turbulence in the transition regime, i.e. weak turbulence in the case of superposition (mixed convection) or not (forced convection) of secondary flows on the forced flow. This is possible thanks to the application of the wavelet transform. The calculation of the H?lder exponent, associated with the maximum value of the singularity spectrum for two configurations, vertical (forced convection) and horizontal (mixed convection) allows the degree of turbulence to be measured in both cases. The variation of the H?lder exponent versus the Reynolds number has enabled it to be shown that the secondary flows stabilise the main flow and stifle the beginnings of the turbulence during the regime of transition to turbulence; these kinds of results have also been shown in literature. Generally, large-sized secondary flows (for example Dean's flows) stabilise the turbulence. Our work confirms this, through an experiment carried out in identical conditions for mixed convection (horizontal flow) and forced convection (vertical flow). Received 30 March 1998 and Received in final form 28 April 1999     

Coalescing points for eigenvalues of banded matrices depending on parameters with application to banded random matrix functions

Numerical Algorithms - In this work, we develop and implement new numerical methods to locate generic degeneracies (i.e., isolated parameters’ values where the eigenvalues coalesce) of banded...     

The lattice-theoretic structure of the sets of triangular norms and semi-copulas

The lattice-theoretic structure of the set of semi-copulas and some of its subsets is investigated. As a relevant case, we obtain that the set of commutative semi-copulas is a lattice completion of the set of triangular norms.     

Measurement of the high-energy electron and positron spectrum in the PAMELA experiment

The PAMELA magnetic spectrometer onboard the Resurs DK1 satellite no. 1 was put into (Earth) orbit on June 15, 2006; measurements continue at the present time. The scientific objective of the spectrometer is the study of antiproton, proton, positron, electron and light nucleus fluxes in cosmic rays. In this paper, we present the technique for measuring electron and positron spectra in the energy range from 20 to 800 GeV.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

Some remarks on the intersection of embedded sets

We study certain connections between a parameter characterizing the intersection of embedded sets and the Jung constant. We also define the critical value of the parameter for a certain product space and prove that, in reflexive spaces, the intersection of embedded sets is nonempty for the critical value of the parameter.     

Distance Types in Banach Spaces

We introduce and study the notion of a distance type, on a Banach space, defined by a nested sequence of convex sets. Among other things, we show that there always exist distance types that are not types in the classical sense. Then, we recover the notion of the flat nested sequence of Milman and Milman and show that distance types defined by flat nested sequences coincide with the bidual types of Farmaki. These results are applied to show that a flat nested sequence of convex sets is Wijsman convergent to the intersection of their weak*-closures in bidual space.     

Antipodal pairs and the geometry of Banach spaces

In this paper we define and study, in Banach spaces, a new function. We indicate a few relations with some geometric properties of the space (such as uniform convexity) and we calculate the expression of that function in some classical spaces.