Stable knots in the trapped Bose-Einstein condensates

The knot of spin texture is studied within the two-component Bose-Einstein condensates which are described by the nonlinear Gross-Pitaevskii equations. We start from the non-interacting equations including an axisymmetric harmonic trap to obtain an exact solution, which exhibits a non-trivial topological structure. The spin-texture is a knot with an integral Hopf invariant. The stability of the knot is verified by numerically evolving the nonlinear Gross-Pitaevskii equations along imaginary time.Comment: 4 pages, 5 figure

Interplay between Quantum Size Effect and Strain Effect on Growth of Nanoscale Metal Thin Film

We develop a theoretical framework to investigate the interplay between quantum size effect (QSE) and strain effect on the stability of metal nanofilms. The QSE and strain effect are shown to be coupled through the concept of "quantum electronic stress. First-principles calculations reveal large quantum oscillations in the surface stress of metal nanofilms as a function of film thickness. This adds extrinsically additional strain-coupled quantum oscillations to surface energy of strained metal nanofilms. Our theory enables a quantitative estimation of the amount of strain in experimental samples, and suggests strain be an important factor contributing to the discrepancies between the existing theories and experiments

Kinetics of mesa overlayer growth: climbing of adatoms onto the mesa top

Journal ArticleWe have calculated the energy barriers for an adatom climbing up onto a Pb mesa top either over a facet-facet edge or through a facet-step joint, using a modified embedded atom method. We found that the second process is not only thermodynamically more favorable than the first one but also much faster with a diminishing barrier. Our results provide a plausible explanation for the experimentally observed intriguing growth behavior of a Pb mesa. The underlying mechanisms can be generally applicable to other systems

Dynamic simulation analysis of elastic overpressure fluctuation on silo wall for the arch action

In this research, the concept of elastic overpressure fluctuation is introduced on the basis of the overpressure theory in the arch action, the formation of overpressure in the arch action is investigated with the elastic fluctuation on the silo wall. The formation and elastic fluctuation of overpressure in arch action is analyzed systematically with the laboratory experiment and the PFC simulation which were established on the basic of a project example, the models achieve the arch action by changing factors such as the physical parameters of grain and cone half angle of the silo hopper. The results obtained indicate that the increment of pressure and the overpressure coefficient all decrease with height. And the overpressure started from the arch feet, propagated upward in the form of fluctuation on the silo wall. In addition, the overpressure fluctuations propagate uniformly which is illustrated by observing the time step of when the pressure fluctuations amplitude occur at each monitoring points. The results reveal the formation mechanism of the overpressure in arching, and the relevant research conclusions would be of great reference significance for the design of silo