1,061 research outputs found
Effect of ferromagnetic film thickness on magnetoresistance of thin-film superconductor-ferromagnet hybrids
We study the influence of the thickness Df of the plain ferromagnetic (F)
film on the electrical resistance of the flux-coupled hybrids, consisting of
superconducting (S) Al film and multilayer [Co/Pt] F film with out-of-plain
magnetization. The behavior of such hybrids at high and low temperatures is
found to be different: the nucleation of superconductivity at high temperatures
is governed mainly by the typical lateral dimensions of the magnetic domains,
while low temperature properties are determined by topology of the magnetic
template. We show that an increase in the Df value leads to a broadening of the
field- and temperature intervals where non-monotonous dependence of the
superconducting critical temperature Tc on the applied magnetic field H is
observed (for demagnetized F films). Further increase in the Df value results
in a global suppression of superconductivity. Thus, we determined an optimal
thickness, when the non-monotonous dependence Tc(H) can be observed in rather
broad T and H range, what can be interesting for further studies of the
localized superconductivity in planar Al-based S/F hybrids and for development
of the devices which can exploit the localized superconductivity.Comment: 10 pages, 9 figure
Bistability and Hysteresis of Intersubband Absorption in Strongly Interacting Electrons on Liquid Helium
We study nonlinear inter-subband microwave absorption of electrons bound to
the liquid helium surface. Already for a comparatively low radiation intensity,
resonant absorption due to transitions between the two lowest subbands is
accompanied by electron overheating. The overheating results in a significant
population of higher subbands. The Coulomb interaction between electrons causes
a shift of the resonant frequency, which depends on the population of the
excited states and thus on the electron temperature . The latter is
determined experimentally from the electron photoconductivity. The
experimentally established relationship between the frequency shift and
is in reasonable agreement with the theory. The dependence of the shift on the
radiation intensity introduces nonlinearity into the rate of the inter-subband
absorption resulting in bistability and hysteresis of the resonant response.
The hysteresis of the response explains the behavior in the regime of frequency
modulation, which we observe for electrons on liquid He and which was
previously seen for electrons on liquid He
High order approximation for the coverage probability by a confident set centered at the positive-part James-Stein estimator
In this paper we continue our investigation connected with the new approach developed in Ahmed et al. [Ahmed, S.E., Saleh, A.K.Md.E., Volodin, A., Volodin, I., 2006. Asymptotic expansion of the coverage probability of James-Stein estimators. Theory Probab. Appl. 51 (4) 1-14] for asymptotic expansion construction of coverage probabilities, for confidence sets centered at James-Stein and positive-part James-Stein estimators. The coverage probabilities for these confidence sets depend on the noncentrality parameter τ2, the same as the risks of these estimators. In this paper we consider only the confidence set centered at the positive-part James-Stein estimator. As is shown in the above-mentioned reference, the new approach provides a method to obtain for the given confidence set, an asymptotic expansion of the coverage probability as one formula for both cases τ → 0 and τ → ∞. We obtain the third terms of the asymptotic expansion for both mentioned cases, that is, the coefficients at τ2 and τ- 2. Numerical illustrations show that the third term has only a small influence on the accuracy of the asymptotic estimation of coverage probability. Crown Copyright © 2009
Confidence intervals for a ratio of binomial proportions based on direct and inverse sampling schemes
© 2016, Pleiades Publishing, Ltd.A general problem of the interval estimation for a ratio of two proportions p1/p2 according to data from two independent samples is considered. Each sample may be obtained in the framework of direct or inverse binomial sampling. Asymptotic confidence intervals are constructed in accordance with different types of sampling schemes with an application, where it is possible, of unbiased estimations of success probabilities and also their logarithms. Since methods of constructing confidence intervals in the situations when values for the both samples are obtained for identical sample schemes (for only direct or only inverse binomial sampling) are already developed and well known, the main purpose of this paper is the investigation of constructing confidence intervals in two cases that correspond to different sampling schemes (one is direct, another is inverse). In this situation it is possible to plan the sample size for the second sample according to the number of successes in the first sample. This, as it is shown by the results of statistical modeling, provides the intervals with confidence level which closer to the nominal value. Our goal is to show that the normal approximations (which are relatively simple) for estimates of p1/p2 and their logarithms are reliable for a construction of confidence intervals. The main criterion of our judgment is the closeness of the confidence coefficient to the nominal confidence level. It is proved theoretically and shown by statistically modeled data that the scheme of inverse binomial sampling with planning of the size in the second sample is preferred. Main probability characteristics of intervals corresponding to all possible combinations of sampling schemes are investigated by the Monte-Carlo method. Estimations of coverage probability, expectation and standard deviation of interval widths are collected in tables and some recommendations for an application of each of the intervals obtained are presented. Finally, a sufficient and complete review of the literature for the problem is also presented
Sonoluminescence and collapse dynamics of multielectron bubbles in helium
Multielectron bubbles (MEBs) differ from gas-filled bubbles in that it is the
Coulomb repulsion of a nanometer thin layer of electrons that forces the bubble
open rather than the pressure of an enclosed gas. We analyze the implosion of
MEBs subjected to a pressure step, and find that despite the difference in the
underlying processes the collapse dynamics is similar to that of gas-filled
bubbles. When the MEB collapses, the electrons inside it undergo strong
accelerations, leading to the emission of radiation. This type of
sonoluminescence does not involve heating and ionisation of any gas inside the
bubble. We investigate the conditions necessary to obtain sonoluminescence from
multielectron bubbles and calculate the power spectrum of the emitted
radiation.Comment: 6 figure
Equilibrium properties of the mixed state in superconducting niobium in a transverse magnetic field: Experiment and theoretical model
Equilibrium magnetic properties of the mixed state in type-II superconductors
were measured with high purity bulk and film niobium samples in parallel and
perpendicular magnetic fields using dc magnetometry and scanning Hall-probe
microscopy. Equilibrium magnetization data for the perpendicular geometry were
obtained for the first time. It was found that none of the existing theories is
consistent with these new data. To address this problem, a theoretical model is
developed and experimentally validated. The new model describes the mixed state
in an averaged limit, i.e. %without detailing the samples' magnetic structure
and therefore ignoring interactions between vortices. It is quantitatively
consistent with the data obtained in a perpendicular field and provides new
insights on properties of vortices. % and the entire mixed state. At low values
of the Ginzburg-Landau parameter, the model converts to that of Peierls and
London for the intermediate state in type-I superconductors. It is shown that
description of the vortex matter in superconductors in terms of a 2D gas is
more appropriate than the frequently used crystal- and glass-like scenarios.Comment: 8 pages, 9 figure
BUSINESS FINANCES, FINANCINAL TECHNOLOGY, AND CAPITAL STRUCTURE
We distinguish the theoretical issues of the Category business finance. Considered some problems of the nature and definition of finance role of the financial strategy in the overall strategy of the enterprise. The main thing was shown is a technique to identify the impact of the capital structure on the company’s profitability of its own funds
BUSINESS FINANCES, FINANCINAL TECHNOLOGY, AND CAPITAL STRUCTURE
We distinguish the theoretical issues of the Category business finance. Considered some problems of the nature and definition of finance role of the financial strategy in the overall strategy of the enterprise. The main thing was shown is a technique to identify the impact of the capital structure on the company’s profitability of its own funds
On Complete Convergence of the Sum of a Random Number of Stable Type P Random Elements
Complete convergence for randomly indexed normalized sums of random elements of the form [Formula Omitted] is established. The random elements {Xn} belong to a type p stable space and are assumed to be independent, but not necessarily identically distributed. No assumptions are placed on the joint distributions of the stopping times {Tn}. © 1995, Hindawi Publishing Corporation. All rights reserved
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