1,763 research outputs found
Consensus-based control for a network of diffusion PDEs with boundary local interaction
In this paper the problem of driving the state of a network of identical
agents, modeled by boundary-controlled heat equations, towards a common
steady-state profile is addressed. Decentralized consensus protocols are
proposed to address two distinct problems. The first problem is that of
steering the states of all agents towards the same constant steady-state
profile which corresponds to the spatial average of the agents initial
condition. A linear local interaction rule addressing this requirement is
given. The second problem deals with the case where the controlled boundaries
of the agents dynamics are corrupted by additive persistent disturbances. To
achieve synchronization between agents, while completely rejecting the effect
of the boundary disturbances, a nonlinear sliding-mode based consensus protocol
is proposed. Performance of the proposed local interaction rules are analyzed
by applying a Lyapunov-based approach. Simulation results are presented to
support the effectiveness of the proposed algorithms
On the constrained KP hierarchy
An explanation for the so-called constrained hierarhies is presented by
linking them with the symmetries of the KP hierarchy. While the existence of
ordinary symmetries (belonging to the hierarchy) allows one to reduce the KP
hierarchy to the KdV hierarchies, the existence of additional symmetries allows
to reduce KP to the constrained KP.Comment: 7pp, LaTe
Negative high-frequency differential conductivity in semiconductor superlattices
We examine the high-frequency differential conductivity response properties
of semiconductor superlattices having various miniband dispersion laws. Our
analysis shows that the anharmonicity of Bloch oscillations (beyond
tight-binding approximation) leads to the occurrence of negative high-frequency
differential conductivity at frequency multiples of the Bloch frequency. This
effect can arise even in regions of positive static differential conductivity.
The influence of strong electron scattering by optic phonons is analyzed. We
propose an optimal superlattice miniband dispersion law to achieve
high-frequency field amplification
Visualization of the 3-dimensional flow around a model with the aid of a laser knife
A method for visualizing the three-dimensional flow around models of various shapes in a wind tunnel at a Mach number of 5 is described. A laser provides a planar light flux such that any plane through the model can be selectively illuminated. The shape of shock waves and separation regions is then determined by the intensity of light scattered by soot particles in the flow
Derived Categories of Coherent Sheaves and Triangulated Categories of Singularities
In this paper we establish an equivalence between the category of graded
D-branes of type B in Landau-Ginzburg models with homogeneous superpotential W
and the triangulated category of singularities of the fiber of W over zero. The
main result is a theorem that shows that the graded triangulated category of
singularities of the cone over a projective variety is connected via a fully
faithful functor to the bounded derived category of coherent sheaves on the
base of the cone. This implies that the category of graded D-branes of type B
in Landau-Ginzburg models with homogeneous superpotential W is connected via a
fully faithful functor to the derived category of coherent sheaves on the
projective variety defined by the equation W=0.Comment: 26 pp., LaTe
Combined Backstepping/Second-Order Sliding-Mode Boundary Stabilization of an Unstable Reaction-Diffusion Process
In this letter we deal with a class of open-loop unstable reaction-diffusion PDEs with boundary control and Robin-type boundary conditions. A second-order sliding mode algorithm is employed along with the backstepping method to asymptotically stabilize the controlled plant while providing at the same time the rejection of an external persistent boundary disturbance. A constructive Lyapunov analysis supports the presented synthesis, and simulation results are presented to validate the developed approach
Tunable subpicosecond electron bunch train generation using a transverse-to-longitudinal phase space exchange technique
We report on the experimental generation of a train of subpicosecond electron
bunches. The bunch train generation is accomplished using a beamline capable of
exchanging the coordinates between the horizontal and longitudinal degrees of
freedom. An initial beam consisting of a set of horizontally-separated beamlets
is converted into a train of bunches temporally separated with tunable bunch
duration and separation. The experiment reported in this Letter unambiguously
demonstrates the conversion process and its versatility.Comment: 4 pages, 5 figures, 1 table; accepted for publication in PR
Generation of Relativistic Electron Bunches with Arbitrary Current Distribution via Transverse-to-Longitudinal Phase Space Exchange
We propose a general method for tailoring the current distribution of
relativistic electron bunches. The technique relies on a recently proposed
method to exchange the longitudinal phase space emittance with one of the
transverse emittances. The method consists of transversely shaping the bunch
and then converting its transverse profile into a current profile via a
transverse-to-longitudinal phase-space-exchange beamline. We show that it is
possible to tailor the current profile to follow, in principle, any desired
distributions. We demonstrate, via computer simulations, the application of the
method to generate trains of microbunches with tunable spacing and
linearly-ramped current profiles. We also briefly explore potential
applications of the technique.Comment: 13 pages, 17 figure
Fermionic approach to the evaluation of integrals of rational symmetric functions
We use the fermionic construction of two-matrix model partition functions to
evaluate integrals over rational symmetric functions. This approach is
complementary to the one used in the paper ``Integrals of Rational Symmetric
Functions, Two-Matrix Models and Biorthogonal Polynomials'' \cite{paper2},
where these integrals were evaluated by a direct method.Comment: 34 page
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