250 research outputs found

    Novel Regime of Operation for Superconducting Quantum Interference Filters

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    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

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    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

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    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

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    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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