Acoustical modeling study of the open test section of the NASA Langley V/STOL wind tunnel

An acoustic model study was carried out to identify effective sound absorbing treatment of strategically located surfaces in an open wind tunnel test section. Also an aerodynamic study done concurrently, sought to find measures to control low frequency jet pulsations which occur when the tunnel is operated in its open test section configuration. The acoustical modeling study indicated that lining of the raised ceiling and the test section floor immediately below it, results in a substantial improvement. The aerodynamic model study indicated that: (1) the low frequency jet pulsations are most likely caused or maintained by coupling of aerodynamic and aeroacoustic phenomena in the closed tunnel circuit, (2) replacing the hard collector cowl with a geometrically identical but porous fiber metal surface of 100 mks rayls flow resistance does not result in any noticable reduction of the test section noise caused by the impingement of the turbulent flow on the cowl

New limits for neutrinoless tau decays

Neutrinoless 3-prong tau lepton decays into a charged lepton and either two charged particles or one neutral meson have been searched for using 4.79 fb-1 of data collected with the CLEO II detector at Cornell Electron Storage Ring. This analysis represents an update of a previous study and the addition of six decay channels. In all channels the numbers of events found are compatible with background estimates and branching fraction upper limits are set for 28 different decay modes. These limits are either more stringent than those set previously or represent the first attempt to find these decays

Large area silicon sheet by EFG

Progress in a program to produce high speed, thin, wide silicon sheets for fabricating 10% efficient solar cells is reported. An EFG ribbon growth system was used to perform growth rate and ribbon thickness experiments. A new, wide ribbon growth system was developed. A theoretical study of stresses in ribbons was also conducted. The EFG ribbons were observed to exhibit a characteristic defect structure which is orientation dependent in the early stages of growth

The geology, geochemistry, and petrogenesis of the Huckleberry Cu-Ni-PGE prospect in the Labrador Trough, Canada: Perspectives for regional prospectivity

The Palaeoproterozoic Huckleberry Cu-Ni-(PGE) prospect in the Labrador Trough, northern Québec, represents a ∼ 400-m-thick, out-of-sequence sill complex that comprises a ∼ 200-m-thick glomeroporphyritic gabbro, intruded in its centre by a ∼ 200-m-thick differentiated gabbro-peridotite sill and in its gabbroic footwall, several thinner ( 10,000) suggest sulphide melt saturation was attained before their final emplacement in magma feeder conduits or staging chambers at relatively low R factors (1,000-5,000). Downward decreasing concentrations of chalcophile elements in the drill cores suggests that sulphide melt percolated downward from the ultramafic cumulate units into the glomeroporphyritic gabbro footwall. We propose that the footwall ultramafic sills represent downward injections of olivine + sulphide melt from the overlying gabbro-peridotite sill, which mechanically concentrated high volumes of sulphide in narrow sills

Preliminary Grade and Volume Model of Alluvial Sn-Au Placers

Summary The following preliminary points are made during this study of Sn-Au placer deposits: Grade and volume model of Sn-Au placers is developed from 63 deposits found worldwide The model is preliminary because: (1) it includes some highly uncertain data, (2) most S.E. Asia deposits are absent, (3) significant departure from the expected lognormal distribution in volume is found, and (4) data are from deposits worked using small-volume and large-volume methods The model is for use in mineral resource assessment Sn grades and deposit volumes are not significantly correlated

Stability of Negative Image Equilibria in Spike-Timing Dependent Plasticity

We investigate the stability of negative image equilibria in mean synaptic weight dynamics governed by spike-timing dependent plasticity (STDP). The neural architecture of the model is based on the electrosensory lateral line lobe (ELL) of mormyrid electric fish, which forms a negative image of the reafferent signal from the fish's own electric discharge to optimize detection of external electric fields. We derive a necessary and sufficient condition for stability, for arbitrary postsynaptic potential functions and arbitrary learning rules. We then apply the general result to several examples of biological interest.Comment: 13 pages, revtex4; uses packages: graphicx, subfigure; 9 figures, 16 subfigure