3,631 research outputs found
Quantum Fluctuations in Josephson Junction Comparators
We have developed a method for calculation of quantum fluctuation effects, in
particular of the uncertainty zone developing at the potential curvature sign
inversion, for a damped harmonic oscillator with arbitrary time dependence of
frequency and for arbitrary temperature, within the Caldeira-Leggett model. The
method has been applied to the calculation of the gray zone width Delta Ix of
Josephson-junction balanced comparators driven by a specially designed
low-impedance RSFQ circuit. The calculated temperature dependence of Delta Ix
in the range 1.5 to 4.2K is in a virtually perfect agreement with experimental
data for Nb-trilayer comparators with critical current densities of 1.0 and 5.5
kA/cm^2, without any fitting parameters.Comment: 4 pages, 4 figures, submitted to Physical Review Letter
Algebraic Model for scattering in three-s-cluster systems. I. Theoretical Background
A framework to calculate two-particle matrix elements for fully
antisymmetrized three-cluster configurations is presented. The theory is
developed for a scattering situation described in terms of the Algebraic Model.
This means that the nuclear many-particle state and its asymptotic behaviour
are expanded in terms of oscillator states of the intra-cluster coordinates.
The Generating Function technique is used to optimize the calculation of matrix
elements. In order to derive the dynamical equations, a multichannel version of
the Algebraic Model is presented.Comment: 20 pages, 1 postscript figure, submitted to Phys. Rev.
Thin films flowing down inverted substrates: Three dimensional flow
We study contact line induced instabilities for a thin film of fluid under
destabilizing gravitational force in three dimensional setting. In the previous
work (Phys. Fluids, {\bf 22}, 052105 (2010)), we considered two dimensional
flow, finding formation of surface waves whose properties within the
implemented long wave model depend on a single parameter,
, where is the capillary number and is
the inclination angle. In the present work we consider fully 3D setting and
discuss the influence of the additional dimension on stability properties of
the flow. In particular, we concentrate on the coupling between the surface
instability and the transverse (fingering) instabilities of the film front. We
furthermore consider these instabilities in the setting where fluid viscosity
varies in the transverse direction. It is found that the flow pattern strongly
depends on the inclination angle and the viscosity gradient
Magnetic properties and magnetostructural phase transitions in Ni2+xMn1-xGa shape memory alloys
A systematic study of magnetic properties of Ni2+xMn1-xGa (0 \le x \le 0.19)
Heusler alloys undergoing structural martensite-austenite transformations while
in ferromagnetic state has been performed. From measurements of spontaneous
magnetization, Ms(T), jumps \Delta M at structural phase transitions were
determined. Virtual Curie temperatures of the martensite were estimated from
the comparison of magnetization in martensitic and austenitic phases. Both
saturation magnetic moments in ferromagnetic state and effective magnetic
moments in paramagnetic state of Mn and Ni atoms were estimated and the
influence of delocalization effects on magnetism in these alloys was discussed.
The experimental results obtained show that the shift of martensitic transition
temperature depends weakly on composition. The values of this shift are in good
correspondence with Clapeyron-Clausius formalism taking into account the
experimental data on latent heat at martensite-austenite transformations.Comment: 7 pages, 8 figure
Measuring microwave quantum states: tomogram and moments
Two measurable characteristics of microwave one-mode photon states are
discussed: a rotated quadrature distribution (tomogram) and
normally/antinormally ordered moments of photon creation and annihilation
operators. Extraction of these characteristics from amplified microwave signal
is presented. Relations between the tomogram and the moments are found and can
be used as a cross check of experiments. Formalism of the ordered moments is
developed. The state purity and generalized uncertainty relations are
considered in terms of moments. Unitary and non-unitary time evolution of
moments is obtained in the form of linear differential equations in contrast to
partial differential equations for quasidistributions. Time evolution is
specified for the cases of a harmonic oscillator and a damped harmonic
oscillator, which describe noiseless and decoherence processes, respectively.Comment: 10 pages, 1 figure, to appear in Phys. Rev.
Growth and Segregation of Intermenallic Phases in Zirconium Alloys
Relations between the processes of growth of intermetallic inclusions and their surface segregation in binary and ternary alloys of zirconium are presented. An increased surface concentration of iron atoms was observed, and is associated with intermetallic inclusion growth with increased annealing temperature of the deformed alloys. Modelling the asymmetric growth of these intermetallic inclusions, leading to their migration, have enabled the determination of the diffusion coefficient of iron in these intermetallics.
Keywords: Zirconium alloys, Iron state, Mössbauer effec
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