Magnetoplasmon excitations in an array of periodically modulated quantum wires

Motivated by the recent experiment of Hochgraefe et al., we have investigated the magnetoplasmon excitations in a periodic array of quantum wires with a periodic modulation along the wire direction. The equilibrium and dynamic properties of the system are treated self-consistently within the Thomas-Fermi-Dirac-von Weizsaecker approximation. A calculation of the dynamical response of the system to a far-infrared radiation field reveals a resonant anticrossing between the Kohn mode and a finite-wavevector longitudinal excitation which is induced by the density modulation along the wires. Our theoretical calculations are found to be in excellent agreement with experiment.Comment: 9 pages, 8 figure

The internal structure of the WRISc

Abstract: Personality-based integrity tests are used in selection procedures to reduce the chance of hiring employees who are likely to engage in counterproductive work behaviour. The present study reports the internal psychometric properties of a new personality-based measure developed for this purpose. Data collected from 1353 working adults were used to investigate internal consistency reliability, and to examine construct validity with confirmatory factor analysis and Rasch analysis. Results showed that the reliability estimates for all the scales of the assessment were satisfactory. For the confirmatory factor analysis, inspection of the incremental (CFI and TLI) and absolute (RMSEA) goodness-of fit values found strong support for the construct validity of all the scales. Infit statistics from Rasch analysis provided further support for construct validity, with items from all the scales fitting the Rasch model. Combined the confirmatory and Rasch analysis demonstrated that unidimensional, coherent and meaningful latent constructs are being measured on the WRISc. Overall, results found excellent support for the internal psychometric properties of the instrument in a culturally diverse context

Exact first-order density matrix for a d-dimensional harmonically confined Fermi gas at finite temperature

We present an exact closed form expression for the {\em finite temperature} first-order density matrix of a harmonically trapped ideal Fermi gas in any dimension. This constitutes a much sought after generalization of the recent results in the literature, where exact expressions have been limited to quantities derived from the {\em diagonal} first-order density matrix. We compare our exact results with the Thomas-Fermi approximation (TFA) and demonstrate numerically that the TFA provides an excellent description of the first-order density matrix in the large-N limit. As an interesting application, we derive a closed form expression for the finite temperature Hartree-Fock exchange energy of a two-dimensional parabolically confined quantum dot. We numerically test this exact result against the 2D TF exchange functional, and comment on the applicability of the local-density approximation (LDA) to the exchange energy of an inhomogeneous 2D Fermi gas.Comment: 12 pages, 3 figures included in the text, RevTeX4. Text before Eq.(25) corrected. Additional equation following Eq.(25) has been adde

A Practical Solution for Locating the Source of Voltage Dips in HV/MV Interconnected Grids

Monitoring the technical performance of a power system is significantly enhanced when distributed instrumentation produces coherent field data, i.e., synchronized by GPS timestamping. In this paper a practical methodology is presented to improve the localisation of the source of a voltage dip on power grids. The proposed solution makes use of synchronised dip data provided by power quality meters. Field data reporting events occurred in an HV/MV interconnected system in South Africa are used to validate the results obtained by the improved method and compare with results of two alternative methods