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961.
Transition between layered and filamentary types of anisotropy in layered superconducting structures
D. A. Kuptsov 《Annalen der Physik》1992,504(4):296-301
A model of layered superconducting structure consisting of alternating anisotropic superconducting layers S1 and S2 with different transition temperatures is considered. It is shown that due to competition between two origins of anisotropy - effective-mass anisotropy of individual layers and proximity-induced anisotropy the effective anisotropy of the whole system signficiantly varies temperature. The components of the effective-mass tensor mc (along the anisotropy axis) and ma (perpendicular to the anisotropy axis) strongly depend upon temperature. This may lead to transition between layered (mc > ma) and quasi one-dimensional (mc < ma) types of anisotropy as well as to biaxial-type anisotropy which is also temperature dependent. The field distribution in a tilted vortex in a biaxial superconductor is calculated. The change in the properties of the vortex lattice with temperature in such systems is also investigated. The properties of YBa2Cu3Ox/PrBa2Cu3Oy multilayers are discussed in this connection. 相似文献
962.
E.P. Yelsukov Yu.N. Vorobyov T.I. Arbusova I.B. Smolyak 《Journal of magnetism and magnetic materials》1994,130(1-3):44-50
We have measured the concentration dependence of the average magnetic moment per Fe atom
Fe(x) in microcrystalline and amorphous Fe-P alloys obtained over a wide concentration range using electrochemical deposition. The model of local magnetic moments has been used to described
Fe(x). On the basis of this model the effects of phosphorus on the value
Fe are explained in terms of the parameters of the local environment of the Fe atom. 相似文献
963.
E. Gantner U. Kuhnes H. J. Ache 《Journal of Radioanalytical and Nuclear Chemistry》1992,161(2):561-574
The application, the advantage and limits of neutron monitoring techniques, such as Hf-monitors, fissile material accumulation and concentration monitors are being discussed. The active neutron counting technique applied to emptied pulsed extraction columns containing Hf-sieve plates allows conclusive answers as to the position of the plates in the columns. Pu-accumulations on Hf-sieve plates in pulsed extraction columns can be estimated within a factor of two, whereby the detection limit is about equal to or less than 1 g Pu/plate. Fissile material concentration changes of 1.1 g/l can be detected in the case of235U in solution and of 0.4 Pu/l if a239Pu/240Pu ratio of 4 to 1 is assumed. 相似文献
964.
A. A. van der Horst A. M. van der Kraan J. J. van Loef D. J. Lieftink C. Joosten 《Hyperfine Interactions》1994,91(1):613-618
Mössbauer spectroscopy has been applied to two rattle stones found in the Netherlands, which have been formed under different pedoenvironment conditions in the past. Ultrafine particles of goethite are dominantly present in both core and mantle of these stones. The latter differs in both composition and mean particle size; this is related to the distinct manner of their formation. 相似文献
965.
The paper deals with the global minimization of a differentiable cost function mapping a ball of a finite dimensional Euclidean space into an interval of real numbers. It is established that a suitable random perturbation of the gradient method with a fixed parameter generates a bounded minimizing sequence and leads to a global minimum: the perturbation avoids convergence to local minima. The stated results suggest an algorithm for the numerical approximation of global minima: experiments are performed for the problem of fitting a sum of exponentials to discrete data and to a nonlinear system involving about 5000 variables. The effect of the random perturbation is examined by comparison with the purely deterministic gradient method. 相似文献
966.
Room temperature transmission Mössbauer spectra of Fe62Ni16B14Si8 ribbons, annealed in vacuum for time periods ranging from 5 to 60 minutes at the crystallization temperatureT
x=720 K, have been used to investigate the crystallization mechanism by isothermal annealing. Reorientation of the magnetic anisotropy almost normal to the ribbon plane was observed and correlated to the annealing time dependence of the mean hyperfine field (HF) of the amorphous component. Crystallization started at the surface before the bulk and was found to occur in two steps: a metastable equilibrium of the amorphous phase with (FeNi), (FeNi)Si and t-(FeNi)3B, followed by the decomposition of t-(FeNi)3B into t-(FeNi)2B and (FeNi). The increase of the mean magnetic moment at the Fe sites as compared to related iron-based alloys was attributed to compositional small Ni additions. 相似文献
967.
D. Yu. Grigor'ev 《Journal of Mathematical Sciences》1992,59(3):823-841
This paper presents an algorithm of polynomial complexity for finding greatest common (right) divisors of families of linear ordinary differential operators. An algorithm is presented for factorization of operators into the product of irreducible operators with complexity significantly better than that of previously known algorithms. Estimates are given for the coefficients of the expansion of the fundamental solution of the corresponding linear differential equation.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akademii Nauk SSSR, Vol. 176, pp. 68–103, 1989. 相似文献
968.
969.
I. D. Protasov 《Theoretical and Mathematical Physics》1995,105(3):1581-1592
State equations for simple lattice systems are constructed by extending the Gibbs method to a non-equilibrium system.In memory of D. N. Zubarev, teacher and scientist, whose advice and attention are gratefully remembered.The idea of constructing such a model (on the basis of the vacancy model of condensed matter proposed by the author) belongs to D. N. Zubarev.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 105, No. 3, pp. 478–490, December, 1995. 相似文献
970.
The morphology of blends of styrenic polymers in a matrix of 75% Nylon-6 prepared in a Brabender Plasti-Corder was examined by scanning electron microscopy. Styrene/acrylonitrile copolymers (SAN) form smaller particles as the AN level increases owing to the corresponding decrease in the SAN–polyamide interfacial tension. Various styrenic polymers containing functional groups, maleic anhydride or oxazoline type, that can react with Nylon-6 during melt processing were added to the SAN phase which also led to a decrease in the particle size owing to the graft copolymer formed in situ. The effects of functional group type, amount of functional groups per chain, amount of functional polymer added, and the miscibility of the styrene/maleic anhydride (SMA) and SAN copolymers on the morphology of the styrenic phase in the Nylon-6 matrix are described. © 1992 John Wiley & Sons, Inc. 相似文献