The problems of field evaporation (FE) and field desorption (FD) from surface of oxide high-temperature superconductors (HTSC) of 123, 2212 and 2223 type are discussed. Wide-angle atom probe, usual time-of-flight atom probe and field ionization magnet mass-spectrometer have been used in these experiments. The main purpose of the investigation was to search for effects connected with phase transition. Therefore, the experiments were carried out over a wide range of temperatures: from T of solid nitrogen to room T.
Composition of pure, contaminated and deep corroded surface and typical species of FE and FD spectra have been studied. The bond energies between some atoms (or clusters) and the surface have been estimated on the basis of experimental results and FE theory. From these estimations, and from discovering of correlated ion pairs, it was concluded that the redistribution of local bonds should be taken into consideration in this case. The increase of FE rate was observed at cryogenic temperatures. Various versions are discussed to explain these effects. Some of them are connected with phase transition.
A detailed study of FD of water protonized clusters is performed and the catalytic activity of HTSC crystal surfaces is discussed. 相似文献
The spectral decomposition for the square of the classical Riemann zeta function ζ2(s) is generalized to the case of the product of two such functions ζ(s1) · ζ(s2) of different arguments. Bibliography: 6 titles.
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Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 322, 2005, pp. 17–44. 相似文献
We consider a four-dimensional generalization of Hess–Appel’rot system and costruct its Lax pair. Both classical and algebro-geometric integration procedure are proceeded. The algebro-geometric integration is based on deep facts from geometry of Prym varieties such as the Mumford relation and Mumford-Dalalyan theory. The integration is similar to the integration of Lagrange bitop which has recetly been performed by the authors. 相似文献
Mathematical Diagnostics (MD) deals with identification problems arising in different practical areas. Some of these problems
can be described by mathematical models where it is required to identify points belonging to two or more sets of points. Most
of the existing tools provide some identification rule (a classifier) by means of which a given point is assigned (attributed)
to one of the given sets. Each classifier can be viewed as a virtual expert. If there exist several classifiers (experts),
the problem of evaluation of experts’ conclusions arises. In the paper for the case of supervised classification the method
of virtual experts (the VE-method) is described. Based on this method, a generalized VE method is proposed where each of the
classifiers can be chosen from a given family of classifiers. As a result, a new optimization problem with a discontinuous
functional is stated. Examples illustrating the proposed approach are provided.
The work of the second author was supported by the Russian Foundation for Fundamental Studies (RFFI) under Grant No 03-01-00668. 相似文献
Kadomtsev-Pogutse equations are of great interest from the viewpoint of the theory of symmetries and conservation laws and, in particular, enable us to demonstrate their potentials in action. This paper presents, firstly, the results of computations of symmetries and conservation laws for these equations and the methods of obtaining these results. Apparently, all the local symmetries and conservation laws admitted by the considered equations are exhausted by those enumerated in this paper. Secondly, we point out some reductions of Kadomtsev-Pogutse equations to more simpler forms which have less independent variables and which, in some cases, allow us to construct exact solutions. Finally, the technique of solution deformation by symmetries and their physical interpretation are demonstrated. 相似文献
The novel vanadium thiobromide, V4S9Br4, with a square-planar metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic properties and the heat capacity, and DFT calculations of the electronic structure. At the room temperature, the compound displays paramagnetic properties with an independent spin on each V atom and with a weak exchange constant (J approximately 10 cm(-1)). The paramagnetic state is transformed into a low-spin state (AF-type ordering) at low temperatures. This change is accompanied by a heat-capacity anomaly. The observed magnetic and heat-capacity anomalies can be explained by the thermal excitation of electrons on the closely spaced molecular energy levels in the presence of the Jahn-Teller effect. 相似文献
Conclusions The kinetics of the reaction of the butyraldehyde with 1-heptene in acetic acid by the action of Mn(III) acetate (in an inert atmosphere) supports the previously proposed mechanism for the catalytic alkylation of aldehydes by olefins. In accord with this mechanism, the selectivity in the formation of -alkyl-substituted aldehydes is attributed to the reaction proceeding in the coordination sphere of the metal.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 384–388, February, 1984. 相似文献