Theoretical confirmation of Feynman's hypothesis on the creation of circular vortices in Bose-Einstein condensates: III

In two preceding papers (Infeld and Senatorski 2003 J. Phys.: Condens. Matter 15 5865, and Senatorski and Infeld 2004 J. Phys.: Condens. Matter 16 6589) the authors confirmed Feynman's hypothesis on how circular vortices can be created from oppositely polarized pairs of linear vortices (first paper), and then gave examples of the creation of several different circular vortices from one linear pair (second paper). Here in part III, we give two classes of examples of how the vortices can interact. The first confirms the intuition that the reconnection processes which join two interacting vortex lines into one, practically do not occur. The second shows that new circular vortices can also be created from pairs of oppositely polarized coaxial circular vortices. This seems to contradict the results for such pairs given in Koplik and Levine 1996 Phys. Rev. Lett. 76 4745.Comment: 10 pages, 7 figure

Evolution of rarefaction pulses into vortex rings

The two-dimensional solitary waves of the Gross-Pitaevskii equation in the Kadomtsev-Petviashvili limit are unstable with respect to three-dimensional perturbations. We elucidate the stages in the evolution of such solutions subject to perturbations perpendicular to the direction of motion. Depending on the energy (momentum) and the wavelength of the perturbation different types of three-dimensional solutions emerge. In particular, we present new periodic solutions having very small energy and momentum per period. These solutions also become unstable and this secondary instability leads to vortex ring nucleation.Comment: 5 pages, 5 figure

Numerical study of oscillatory regimes in the Kadomtsev-Petviashvili equation

The aim of this paper is the accurate numerical study of the KP equation. In particular we are concerned with the small dispersion limit of this model, where no comprehensive analytical description exists so far. To this end we first study a similar highly oscillatory regime for asymptotically small solutions, which can be described via the Davey-Stewartson system. In a second step we investigate numerically the small dispersion limit of the KP model in the case of large amplitudes. Similarities and differences to the much better studied Korteweg-de Vries situation are discussed as well as the dependence of the limit on the additional transverse coordinate.Comment: 39 pages, 36 figures (high resolution figures at http://www.mis.mpg.de/preprints/index.html

A new approach to the theory of fully developed turbulence

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Tribological properties of hybrid layers produced in combining the diffusion chromizing process and PVD treatment

W pracy omówiono wyniki badań dotyczących budowy i właściwości tribologicznych warstw hybrydowych typu CrC+CrN wytwarzanych na powierzchni stali X210Cr12 w procesach chromowania dyfuzyjnego, wykonywanego metodą proszkową, połączonych z obróbką PVD. Przeprowadzono porównanie warstw hybrydowych typu CrC+CrN z pojedynczymi warstwami węglikowymi typu CrC, wytwarzanymi na powierzchni stali, bez powłoki CrN. Właściwości tribologiczne (zużycie liniowe) otrzymanych warstw oceniano przy wykorzystaniu metody trzy wałeczki-stożek. Wykazano, że odporność na zużycie przez tarcie warstw hybrydowych typu CrC+CrN jest prawie dwa razy większa od odporności pojedynczych warstw węglikowych typu CrC.Tribological properties of the CrC+CrN type hybrid layers, produced on X210Cr12 steel in chromizing process by the pack powder method combined with arc evaporation PVD treatment, have been investigated. A comparison of the CrC+CrN type hybrid layers with the CrC single carbide layers, produced on steel surface without CrN coating, has been performed. Tribological properties of the layers were performed by means of taper-three rolls test. It has been proved that the resistance to abrasive wear of hybrid CrC+CrN type layers is almost two times higher than that for the single CrC carbide layers

Tribological Properties of AISI 316L Steel Surface Layer Implanted with Rare Earth Element

Stainless steels with their very good corrosion resistance are used in nuclear, petrochemical, chemical, pulp and paper chemical industries as well as in food processing and others. Unfortunately, poor tribological properties of this kind of steel can be the limitation in the situations in which wear can be responsible for material degradation, like corrosion-erosion. Improvement of the wear resistance of austenitic stainless steels can be achieved using different methods of surface modification, for example: enrichment of the surface layer with reactive elements. Rare earth elements were implanted to AISI 316L austenitic stainless steel using the MEVVA type implanter (65 kV). Different rare earth elements implanted doses: 10¹⁵, 5×10¹⁵, and 5×10¹⁶ ion/cm² were applied. Initial and modified surfaces were investigated using scanning electron microscopy, elemental analysis with the energy dispersive spectroscopy method, X-ray diffraction analysis and the Rutherford backscattered spectroscopy. Tribological properties were investigated using the Amsler method. The most important result was that the surface layers of AISI 316L steel implanted with rare earth elements showed improvement of tribological properties as compared with the initial material