177 research outputs found
Circle and Popov Criterion for Output Feedback Stabilization of Uncertain Systems
In this paper, we address the problem of output feedback stabilization for a class of uncertain dynamical systems. An asymptotically stabilizing controller is proposed under the assumption that the nominal system is absolutely stable
Zeros of polynomials orthogonal with respect to a signed weight
AbstractIn this paper we consider the monic polynomial sequence (Pnα,q(x)) that is orthogonal on [−1,1] with respect to the weight function x2q+1(1−x2)α(1−x),α>−1,q∈N; we obtain the coefficients of the tree-term recurrence relation(TTRR) by using a different method from the one derived in Atia et al. (2002) [2]; we prove that the interlacing property does not hold properly for (Pnα,q(x)); and we also prove that, if xn,nα+i,q+j is the largest zero of Pnα+i,q+j(x), x2n−2j,2n−2jα+j,q+j<x2n−2i,2n−2iα+i,q+i,0≤i<j≤n−1
Magnetic field induced control of breather dynamics in a single plaquette of Josephson junctions
We present a theoretical study of inhomogeneous dynamic (resistive) states in
a single plaquette consisting of three Josephson junctions. Resonant
interactions of such a breather state with electromagnetic oscillations
manifest themselves by resonant current steps and voltage jumps in the
current-voltage characteristics. An externally applied magnetic field leads to
a variation of the relative shift between the Josephson current oscillations of
two resistive junctions. By making use of the rotation wave approximation
analysis and direct numerical simulations we show that this effect allows to
effectively control the breather instabilities, e. g. to increase (decrease)
the height of the resonant steps and to suppress the voltage jumps in the
current-voltage characteristics.Comment: 4 pages, 3 figure
Revised structural phase diagram of (Ba0.7Ca0.3TiO3)-(BaZr0.2Ti0.8O3)
The temperature-composition phase diagram of barium calcium titanate zirconate (x(Ba0.7Ca0.3TiO3)(1-x)(BaZr0.2Ti0.8O3); BCTZ) has been reinvestigated using high-resolution synchrotron x-ray powder diffraction. Contrary to previous reports of an unusual rhombohedral-tetragonal phase transition in this system, we have observed an intermediate orthorhombic phase, isostructural to that present in the parent phase, BaTiO3, and we identify the previously assigned T-R transition as a T-O transition. We also observe the O-R transition coalescing with the previously observed triple point, forming a phase convergence region. The implication of the orthorhombic phase in reconciling the exceptional piezoelectric properties with the surrounding phase diagram is discussed
The Kalman condition for the boundary controllability of coupled parabolic systems. Bounds on biorthogonal families to complex matrix exponentials
International audienceThis paper is devoted to prove the controllability to trajectories of a system of one-dimensional parabolic equations when the control is exerted on a part of the boundary by means of controls. We give a general \textit{Kalman condition} (necessary and sufficient) and also present a construction and sharp estimates of a biothorgonal family in L^{2}(0,T; \C) to .Cet article a pour but de démontrer la contrôlabilité des trajectoires d’un système de équations paraboliques en une dimension d’espace par contrôles exercés sur une partie du bord. On obtient une condition de Kalman (nécessaire et suffisante). La démonstration passe par la construction dans L^{2}(0,T; \C) d’une famille biorthogonale de la suite et par une estimation de la norme de ses éléments
Kink propagation in a two-dimensional curved Josephson junction
We consider the propagation of sine-Gordon kinks in a planar curved strip as
a model of nonlinear wave propagation in curved wave guides. The homogeneous
Neumann transverse boundary conditions, in the curvilinear coordinates, allow
to assume a homogeneous kink solution. Using a simple collective variable
approach based on the kink coordinate, we show that curved regions act as
potential barriers for the wave and determine the threshold velocity for the
kink to cross. The analysis is confirmed by numerical solution of the 2D
sine-Gordon equation.Comment: 8 pages, 4 figures (2 in color
Experimental investigation of flux motion in exponentially shaped Josephson junctions
We report experimental and numerical analysis of expontentially shaped long
Josephson junctions with lateral current injection. Quasi-linear flux flow
branches are observed in the current-voltage characteristic of the junctions in
the absence of magnetic field. A strongly asymmetric response to an applied
magnetic field is also exhibited by the junctions. Experimental data are found
in agreement with numerical predictions and demonstrate the existence of a
geometry-induced potential experienced by the flux quanta in nonuniform width
junctions.Comment: 16 pg, 8 figures, Submitted in PRB March
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