Bragg spectroscopy of a superfluid Bose-Hubbard gas

Bragg spectroscopy is used to measure excitations of a trapped, quantum-degenerate gas of 87Rb atoms in a 3-dimensional optical lattice. The measurements are carried out over a range of optical lattice depths in the superfluid phase of the Bose-Hubbard model. For fixed wavevector, the resonant frequency of the excitation is found to decrease with increasing lattice depth. A numerical calculation of the resonant frequencies based on Bogoliubov theory shows a less steep rate of decrease than the measurements.Comment: 11 pages, 4 figure

Influence of mechanical uncertainties on dynamic responses of a full-scale all-FRP footbridge

This is the final version. Available on open access from Elsevier via the DOI in this recordThe data analysed in this paper can be reproduced using information provided in the paper.This paper aims to determine the effects of uncertainties in the mechanical properties of FRP composites on the dynamic responses of a full-scale all-FRP bridge. The novelty of the study is in determining the effects that the uncertainties have on the global structural scale properties rather than component properties often studied in literature. To achieve this aim, both uncertainty quantification and global sensitivity analysis are performed using a computationally cost-effective approach based on the polynomial chaos expansion. The results reveal that a coefficient of variation (COV) of 10% for four mechanical parameters can lead to COVs of 3.37%, 2.92% and 3.07% for natural frequencies, COVs of 2.98%, 0.04% and 0.61% for modal masses (corresponding to unity-scaled mode shapes) of the first lateral, first vertical and second vertical modes, and COV of 0.93% for the absolute peak acceleration. The effect of uncertainties, therefore, is very small for the considered excitation case and it could be neglected in the design. In addition, it was found that the longitudinal elastic modulus and shear modulus of the panel are the most influential mechanical parameters in dynamic analysis.Engineering and Physical Sciences Research Council (EPSRC

Growth and pyroelectric property of 0.2 mol % Fe-doped Pb(Mg[sub ⅓]Nb[sub ⅔])O₃-0.38PbTiO₃ single crystals measured by a dynamic technique

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe