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Search Results: 1 - 10 of 4115 matches for " Alain Goupil "
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A product of integer partitions
Alain Goupil
Mathematics , 2009,
Abstract: I present a bijection on integer partitions that leads to recursive expressions, closed formulae and generating functions for the cardinality of certain sets of partitions of a positive integer $n$. The bijection leads also to a product on partitions that is associative with a natural grading thus defining a free associative algebra on the set of integer partitions. As an outcome of the computations, certain sets of integers appear that I call difference sets and the product of the integers in a difference set is an invariant for a family of sets of partitions. The main combinatorial objects used in these constructions are the central hooks of the Ferrers diagrams of partitions.
3D Polyominoes inscribed in a rectangular prism
Goupil Alain,Cloutier Hugo
Mathematics , 2010,
Abstract: We introduce a family of 3D combinatorial objects that we define as minimal 3D polyominoes inscribed in a rectanglar prism. These objects are connected sets of unitary cubic cells inscribed in a given rectangular prism and of minimal volume under this condition. They extend the concept of 2D polyominoes inscribed in a rectangle defined in a previous work. Using their geometric structure and elementary combinatorial arguments, we construct generating functions of minimal 3D polyominoes in the form of rational functions. We also obtain a number of exact formulas and recurrences for sub-families of these polyominoes.
Combinatorial operators for Kronecker powers of representations of $§_n$
Alain Goupil,Cedric Chauve
Mathematics , 2005,
Abstract: We present combinatorial operators for the expansion of the Kronecker product of irreducible representations of the symmetric group. These combinatorial operators are defined in the ring of symmetric functions and act on the Schur functions basis. This leads to a combinatorial description of the Kronecker powers of the irreducible representations indexed with the partition (n-1,1) which specializes the concept of oscillating tableaux in Young's lattice previously defined by S. Sundaram. We call our specialization {\it Kronecker tableaux}. Their combinatorial analysis leads to enumerative results for the multiplicity of any irreducible representation in the Kronecker powers of the form ${\c^{(n-1,1)}}^{\otimes k}$.
The vortex depinning transition in untwinned YBaCuO using complex impedance measurements
Alain Pautrat,Christophe Goupil,Charles Simon,Bart Andrewjewski,A. I. Rykov,S. Tajima
Physics , 2003, DOI: 10.1016/j.physc.2004.03.034
Abstract: We present surface impedance measurement of the vortex linear response in a large untwinned YBCO crystal. The depinning spectra obtained over a broad frequency range (100 Hz- 30 MHz) are those of a surface pinned vortex lattice with a free flux flow resistivity (two modes response). The critical current in the "Campbell" like regime and the flux flow resistivity in the dissipative regime are extracted. Those two parameters are affected by the first order transition, showing that this transition may be related to the electronic state of vortices.
Partially Directed Snake Polyominoes
Alain Goupil,Marie-Eve Pellerin,Jér?me de Wouters d'Oplinter
Mathematics , 2013,
Abstract: The goal of this paper is to study the family of snake polyominoes. More precisely, we focus our attention on the class of partially directed snakes. We establish functional equations and length generating functions of two dimensional, three dimensional and then $N$ dimensional partially directed snake polyominoes. We then turn our attention to partially directed snakes inscribed in a $b\times k$ rectangle and we establish two-variable generating functions, with respect to height $k$ and length $n$ of the snakes. We include observations on the relationship between snake polyominoes and self-avoiding walks. We conclude with a discussion on inscribed snakes polyominoes of maximal length which lead us to the formulation of a conjecture encountered in the course of our investigations.
Why pinning by surface irregularities can explain the peak effect in transport properties and neutron diffraction results in NbSe2 and Bi-2212 crystals?
Charles Simon,Alain Pautrat,Christophe Goupil,Joseph Scola,Patrice Mathieu,Annie Brulet,Antoine Ruyter,M. J. Higgins,Shobo Battacharya
Physics , 2006, DOI: 10.1007/BF02704939
Abstract: The existence of a peak effect in transport properties (a maximum of the critical current as function of magnetic field) is a well-known but still intriguing feature of type II superconductors such as NbSe2 and Bi-2212. Using a model of pinning by surface irregularities in anisotropic superconductors, we have developed a calculation of the critical current which allows estimating quantitatively the critical current in both the high critical current phase and in the low critical current phase. The only adjustable parameter of this model is the angle of the vortices at the surface. The agreement between the measurements and the model is really very impressive. In this framework, the anomalous dynamical properties close to the peak effect is due to co-existence of two different vortex states with different critical currents. Recent neutron diffraction data in NbSe2 crystals in presence of transport current support this point of view.
Quantitative analysis of the critical current due to vortex pinning by surface corrugation
Alain Pautrat,J. Scola,C. Goupil,Ch. Simon,C. Villard,B. Domenges,Y. Simon,Ch. Guilpin,L. Mechin
Physics , 2004, DOI: 10.1103/PhysRevB.69.224504
Abstract: The transport critical current of a Niobium (Nb) thick film has been measured for a large range of magnetic field. Its value and variation are quantitatively described in the framework of the pinning of vortices due to boundary conditions at the rough surface, with a contact angle well explained by the spectral analysis of the surface roughness. Increasing the surface roughness using a Focused Ion Beam results also in an increase of the superficial critical current.
Seismic diagnostics for rotating massive main sequence stars
Mariejo Goupil
Physics , 2011, DOI: 10.1007/978-3-642-19928-8_8
Abstract: Effects of stellar rotation on adiabatic oscillation frequencies of $\beta$ Cephei star are discussed. Methods to evaluate them are briefly described and some of the main results for four specific stars are presented.
Trouble déficitaire de l’attention à l’université
France Landry,Georgette Goupil
Revue Internationale de Pédagogie de l’Enseignement Supérieur , 2011,
Abstract: Cet article présente un portrait du trouble déficitaire de l’attention avec ou sans hyperactivité (TDA/H) chez les adultes et, plus particulièrement, chez les étudiants universitaires. Après avoir défini le TDA/H, le texte expose les défis de ces étudiants et la situation des universités québécoises sur cette question. La deuxième partie illustre un exemple d’intervention auprès de ces étudiants, soit un programme de tutorat appliqué à l’Université du Québec à Montréal. This article presents a descriptive portrait of Attention Deficit Hyperactivity Disorder (ADHD) in adults, more particularly in university students. After describing ADHD, we will look at the many challenges those students may encounter during their university studies. Moreover, we will present a tutoring program that is currently taking place at the University of Québec in Montréal (UQAM).
La construction de l’identité alimentaire campagnarde dans les comédies d’Aristophane
Sébastien Goupil
Cahiers des études Anciennes , 2010,
Abstract: Les recherches en histoire de l’alimentation ont montré à quel point la nourriture participe activement aux constructions identitaires. Pour l’Antiquité grecque, on conna t bien le r le du sacrifice et des banquets dans la construction des identités religieuses et civiques. On sait aussi que les pratiques de commensalité se sont révélées de puissants vecteurs identitaires et ont servi à cristalliser les différences entre Grecs et barbares, la frugalité orgueilleuse et civilisatrice des premie...
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