250 research outputs found
Novel Regime of Operation for Superconducting Quantum Interference Filters
A new operating regime of the Superconducting Quantum Interference Filter
(SQIF) is investigated. The voltage to magnetic field response function, V(H),
is determined by a Fraunhofer dependence of the critical current and magnetic
flux focusing effect in Josephson junctions (F-mode). For SQIF-arrays made of
high-Tc superconducting bicrystal Josephson junctions the F-mode plays a
predominant role in the voltage-field response V(H). The relatively large
superconducting loops of the SQIF are used for inductive coupling to the
external input circuit. It is shown that the output noise of a SQIF-array
measured with a cooled amplifier in the 1-2 GHz range is determined by the
slope of the V(H) characteristic. Power gain and saturation power were
evaluated using low frequency SQIF parameters. Finally, we consider the
influence of the spread in the parameters of Josephson junctions in the
SQIF-array on the V(H) characteristic of the whole structure.Comment: 7 pages, 4 figure
ON CALCULATING THE VALUE OF A DIFFERENTIAL GAME IN THE CLASS OF COUNTER STRATEGIES
For a linear dynamic system with control and disturbance, a feedback control problem is considered, in which the Euclidean norm of a set of deviations of the system’s motion from given targets at given times is optimized. The problem is formalized into a differential game in “strategy-counterstrategy” classes. A game value computing procedure, which reduces the problem to a recursive construction of upper convex hulls of auxiliary functions, is justified. Results of numerical simulations are presented
On Calculating the Value of a Differential Game in the Class of Counter Strategies
For a linear dynamic system with control and disturbance, a feedback control problem is considered, in which the Euclidean norm of a set of deviations of the system’s motion from given targets at given times is optimized. The problem is formalized into a differential game in “strategy-counterstrategy” classes. A game value computing procedure, which reduces the problem to a recursive construction of upper convex hulls of auxiliary functions, is justified. Results of numerical simulations are presented.This work was supported by Complex Program of Fundamental Research UrO RAN (project 15-16-1-13)
A combined theoretical and experimental study of the low temperature properties of BaZrO3
Low temperature properties of BaZrO3 are revealed by combining experimental
techniques (X-ray diffraction, neutron scattering and dielectric measurements)
with theoretical first-principles-based methods (total energy and linear
response calculations within density functional theory, and effective
Hamiltonian approaches incorporating/neglecting zero-point phonon vibrations).
Unlike most of the perovskite systems, BaZrO3 does not undergo any
(long-range-order) structural phase transition and thus remains cubic and
paraelectric down to 2 K, even when neglecting zero-point phonon vibrations. On
the other hand, these latter pure quantum effects lead to a negligible thermal
dependency of the cubic lattice parameter below ~ 40 K. They also affect the
dielectricity of BaZrO3 by inducing an overall saturation of the real part of
the dielectric response, for temperatures below ~ 40 K. Two fine structures in
the real part, as well as in the imaginary part, of dielectric response are
further observed around 50-65 K and 15 K, respectively. Microscopic origins
(e.g., unavoidable defects and oxygen octahedra rotation occurring at a local
scale) of such anomalies are suggested. Finally, possible reasons for the facts
that some of these dielectric anomalies have not been previously reported in
the better studied KTaO3 and SrTiO3 incipient ferroelectrics are also
discussed.Comment: 8 pages, 5 figures, submitted to Physical Review
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