Running characteristics of aerodynamic bearing with self-lifting capability at low rotational speed

This article has been made available through the Brunel Open Access Publishing Fund - Copyright @ 2011 Tadeusz Adam Stolarski.An aerodynamic journal bearing that is capable of self-generating squeeze-film pressure is presented and its dynamic characteristics investigated numerically and experimentally. A numerical method based on a time-marching static model was applied to assess the orbit trajectory path of the rotor upon a perturbation. Experimental results were obtained to validate the effect of the self-generated squeeze-film pressure on the stability of the rotor. Analyzing the Fast Fourier Transform (FFT) responses of the rotor orbits enabled identification of self-excited whirling instabilities. Both numerical and experimental results showed that increasing the squeeze-film effect of the bearing could raise the threshold speed of instability

Classical c=1 Tachyon Scattering and 1/2-BPS Correlators

We study the correlator of chiral primary operators in \Ncal=4 super Yang-Mills theory in large $N$ limit. Through the free fermion picture, we map the gauge group rank and R-charges in SYM to the Fermi level and tachyon momenta, respectively, in the c=1 matrix model. By doing so, it is seen that half-BPS correlators are reproduced by tree-level tachyon scattering amplitudes.Comment: 7 pages, v2: typos corrected and a reference added, v3: PTP versio

Short seed extractors against quantum storage

Some, but not all, extractors resist adversaries with limited quantum storage. In this paper we show that Trevisan's extractor has this property, thereby showing an extractor against quantum storage with logarithmic seed length