Response prevention and extinction of escape behavior: Duration, frequency, similarity, and retraining variables in rats.

Describes 3 experiments in which a total of 158 female hooded rats received escape training, response prevention, and then regular extinction. Following training, Ss in Exp I received 1 response-prevention trial lasting 0, 120, 240, or 400 sec, or multiple trials (6, 12, or 20) lasting 20 sec each. Extinction was faster as prevention duration or frequency increased. At each duration, extinction was faster following multiple- than following single-prevention trials. In Exp II Ss received "prevention" in the original escape situation or in similar or dissimilar situations. Extinction was faster as prevention and training situations increased in similarity. To evaluate the persistence of prevention effects, in Exp III Ss received shock retraining between prevention and regular extinction. Retraining attenuated but did not eradicate the effects of prevention. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bit error performance evaluation of double-differential QPSK infaded channels characterized by Gaussian plus impulsive noise andDoppler effects

A Fourier-Bessel series-based analysis that allows real-time symbol-to-symbol error performance evaluation for mobile radio direct-sequence code division multiple-access (DS-CDMA) systems is described. The technique analyzes mobile radio communication aeronautic links and generates average bit error rate (BER) and bit-to-bit patterns. Various communication systems parameters (e.g., modulation scheme, data rate, signal-to-noise ratio, and receive speed) as well as multiaccess interference (MAI) environments (i.e., Rayleigh-faded channels with Doppler frequency shift) may be specified and permit performance comparison. Additive white Gaussian (AWG) and impulsive ϵ-mixture type of noise are also considered to be present for the asynchronous and quasi-synchronous DS-CDMA configurations, with both schemes characterized by the incorporation of double-differential QPSK (DDQPSK) modulation. The obtained results demonstrate that the proposed combination in terms of multiplexing and digital modulation may be a suitable alternative solution for air-to-air and/or air-to-ground aeronautic communications for optimized BER versus signal-to-noise ratio system performance and, hence, for “best” channel capacity versus receiver complexity     

High-order discontinuous Galerkin computation of axisymmetric transonic flows in safety relief valves

This paper presents a discontinuous Galerkin (DG) discretization of the compressible RANS and k–ω turbulence model equations for two-dimensional axisymmetric flows. The developed code has been applied to investigate the transonic flow in safety relief valves.This new DG implementation has evolved from the DG method presented in [1]. An “exact” Riemann solver is used to compute the interface numerical inviscid flux while the viscous flux discterization relies on the BRMPS scheme [2] and [3]. Control of oscillations of high-order solutions around shocks is obtained by means of a shock-capturing technique developed and assessed within the EU ADIGMA project [4].The code has been applied to compute the flow in a spring loaded safety valve at several back pressures and different disk lifts. The predicted device flow capacity and the pressure inside its bonnet have been checked against experimental data. The CFD simulations allow to clarify the complex flow patterns occurring and to explain the measured trends.