16,462 research outputs found
KNbO3 single crystal growth by the radio frequency heating Czochralski method
A radio frequency heating Czochralski technique to obtain single crystal KNbO3 is first presented. The technological parameters of KNbO3 crystal growth by the Czochralski technique and its pulling conditions were studied in detail. The experiments on second harmonic generation using 1.06 micrometer Nd:YAG laser in KNbO3 have been conducted. The second harmonic efficiency for upconversion of KNbO3 is found to be as high as that of NaBa2Nb5O15. An automatic scanning measurement for the optical homogeneity of KNbO crystal is also described. KNbO3 is revealed to be a potentially useful nonlinear material for optical device applications
The impact of a wave farm on large scale sediment transport
This study investigates the interactions of waves and tides at a wave farm in the southwest of England, in particular their effects on radiation stress, bottom stress, and consequently on the sediment transport and the coast adjacent to the wave-farm (the Wave Hub). In this study, an integrated complex numerical modelling system is setup at the Wave Hub site and is used to compute the wave and current fields by taking into account the wave-current interaction, as well as the sediment transport. Results show that tidal elevation and tidal currents have a significant effect on the wave height and direction predictions; tidal forcing and wind waves have a significant effect on the bed shear-stress, relevant to sediment transport; waves via radiation stresses have an important effect on the longshore and cross-shore velocity components, particularly during the spring tides. Waves can impact on bottom boundary layer and mixing in the water column. The results highlight the importance of the interactions between waves and tides when modelling coastal morphology with presence of wave energy devices
Subthreshold rho contribution in J/psi decay to omega pion pion and Kaon anti-Kaon pion
We carry out a theoretical and Monte Carlo study on the decays into
and through intermediate subthreshold meson
by using SU(3)-symmetric Lagrangian approach. It is found that the subthreshold
contribution is not negligible and may have significant influence on
partial wave analysis of resonances in these channels, especially near the
and thresholds.Comment: 12 pages, 5 figure
Ergodicity for the -type Markov Chain
Ergodicity is a fundamental issue for a stochastic process. In this paper, we
refine results on ergodicity for a general type of Markov chain to a specific
type or the -type Markov chain, which has many interesting and
important applications in various areas. It is of interest to obtain conditions
in terms of system parameters or the given information about the process, under
which the chain has various ergodic properties. Specifically, we provide
necessary and sufficient conditions for geometric, strong and polynomial
ergodicity, respectively.Comment: 16 page
Understanding I=2 pi-pi Interaction
A correct understanding and description of the I=2 pi-pi S-wave interaction
is important for the extraction of the I=0 pi-pi S-wave interaction from
experimental data and for understanding the I=0 pi-pi S-wave interaction
theoretically. With t-channel rho, f2(1270) exchange and the pi pi -> rho rho
-> pi pi box diagram contribution, we reproduce the pi-pi isotensor S-wave and
D-wave scattering phase shifts and inelasticities up to 2.2 GeV quite well in a
K-matrix formalism.Comment: Talk given at Hadron 03: 10th International Conference on Hadron
Spectroscopy, Aschaffenburg, Germany, 31 Aug - 6 Sep 200
Efficient and reliable hierarchical error estimates for the discretization error of elliptic obstacle problems
We present and analyze novel hierarchical a posteriori error estimates for self-adjoint elliptic obstacle problems. Our approach differs from straightforward, but nonreliable estimators by an additional extra term accounting for the deviation of the discrete free boundary in the localization step. We prove efficiency and reliability on a saturation assumption and a regularity condition on the underlying grid. Heuristic arguments suggest that the extra term is of higher order and preserves full locality. Numerical computations confirm our theoretical findings
Electronic States and Magnetism of Mn Impurities and Dimers in Narrow-Gap and Wide-Gap III-V Semiconductors
Electronic states and magnetic properties of single impurity and dimer
doped in narrow-gap and wide-gap - semiconductors have been studied
systematically. It has been found that in the ground state for single
impurity, - complex is antiferromagnetic (AFM) coupling when -
hybridization is large and both the hole level and the
impurity level are close to the midgap; or very weak ferromagnetic (FM)
when is small and both and are deep in the valence band.
In dimer situation, the spins are AFM coupling for half-filled or
full-filled orbits; on the contrast, the Mn spins are double-exchange-like
FM coupling for any -orbits away from half-filling. We propose the strong
{\it p-d} hybridized double exchange mechanism is responsible for the FM order
in diluted - semiconductors
- …