817 research outputs found
Influence of the passive region on Zero Field Steps for window Josephson junctions
We present a numerical and analytic study of the influence of the passive
region on fluxon dynamics in a window junction. We examine the effect of the
extension of the passive region and its electromagnetic characteristics, its
surface inductance and capacitance. When the velocity in the passive region
is equal to the Swihart velocity (1) a one dimensional model describes
well the operation of the device. When is different from 1, the fluxon
adapts its velocity to . In both cases we give simple formulas for the
position of the limiting voltage of the zero field steps. Large values of
inductance and capacitance lead to different types of solutions which are
analyzed.Comment: 12 pages, 13 figure
Common features of vortex structure in long exponentially shaped Josephson junctions and Josephson junctions with inhomogeneities
We study vortex structure in three different models of long Josephson
junctions: exponentially shaped Josephson junction and Josephson junctions with
resistor and shunt inhomogeneities in barrier layer. Numerical calculations of
the possible magnetic flux distributions and corresponding bifurcation curves
have done. For these three models the critical curves ``critical
current-magnetic field'' are constructed. We develop an idea of the equivalence
of exponentially shaped Josephson junction and rectangular junction with
distributed inhomogeneity and demonstrate that at some parameters of shunt and
resistor inhomogeneities at the ends of the junction the corresponding critical
curves are very close to the exponentially shaped one.Comment: Presented for M2S, Dresden, July 9-14, 200
Inverse problem for a parabolic system with two components by measurements of one component
We consider a system of parabolic equations with first and zeroth
coupling and establish a Carleman estimate by extra data of only one component
without data of initial values. Then we apply the Carleman estimate to inverse
problems of determining some or all of the coefficients by observations in an
arbitrary subdomain over a time interval of only one component and data of two
components at a fixed positive time over the whole spatial domain. The
main results are Lipschitz stability estimates for the inverse problems. For
the Lipschitz stability, we have to assume some non-degeneracy condition at
for the two components and for it, we can approximately control the
two components of the system by inputs to only one component. Such
approximate controllability is proved also by our new Carleman estimate.
Finally we establish a Carleman estimate for a system for parabolic
equations with coupling of zeroth-order terms by one component to show the
corresponding approximate controllability with a control to one component
On the Practical Output Feedback Stabilization for Nonlinear Uncertain Systems
In this paper, we treat the problem of output feedback stabilization of nonlinear uncertain systems. We propose an output feedback controller that guarantees global uniform practical stability of the closed loop system
Quantitative Fattorini-Hautus test and minimal null control time for parabolic problems
This paper investigates the link between the null controllability property for some abstract parabolic problems and an inequality that can be seen as a quantified Fattorini-Hautus test. Depending on the hypotheses made on the abstract setting considered we prove that this inequality either gives the exact minimal null control time or at least gives the qualitative property of existence of such a minimal time. We also prove that for many known examples of minimal time in the parabolic setting, this inequality recovers the value of this minimal time.Dans cet article nous Ă©tudions le lien entre la contrĂ´labilitĂ© Ă zĂ©ro d'un problème parabolique abstrait et la validitĂ© d'une inĂ©galitĂ© qui est une version quantifiĂ©e du test de Fattorini–Hautus. Nous prouvons que cette inĂ©galitĂ© permet de caractĂ©riser l'existence d'un temps minimal pour le problème de contrĂ´labilitĂ© Ă zĂ©ro et, selon les hypothèses considĂ©rĂ©es, d'obtenir la valeur de ce temps minimal. Nous prouvons aussi que dans la plupart des exemples connus de problèmes paraboliques ayant un temps minimal de contrĂ´le Ă zĂ©ro, cette inĂ©galitĂ© est une condition nĂ©cessaire et suffisante de contrĂ´labilitĂ©.Ministerio de EconomĂa y Competitivida
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
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
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