7 research outputs found

    Triple decomposition technique in air-water flows: application to instationary flows on a stepped spillway

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    Self-sustained instabilities and pseudo-periodic motion may be observed in hydraulic structures and industrial flows. Documented examples include the hydraulic jump, sloshing motion in a reservoir and surging waves in pooled stepped spillways. The instabilities may generate some very large turbulence levels and integral turbulent scales, combining the contributions of both slow fluctuations and fast turbulent fluctuations. Herein a triple decomposition of phase-detection probe signals was developed to identify the turbulent contributions of the slow and fast velocity components in highly aerated free-surface flows. The raw probe signals were split into slow and fast signal components and the air-water flow properties of each component were calculated. The method was applied to a new data set collected down a stepped spillway channel with two stepped configurations (flat and pooled). The latter configuration experienced some self-sustained pseudo-periodic instabilities. The data analysis results showed that the fast turbulent velocity fluctuations of the decomposed signal were close to the turbulence levels on the flat stepped spillway (i.e. in absence of instability). And the largest turbulent energy was contained in the slow fluctuating velocity component. The findings showed a new implementation of a triple decomposition technique to instationary air-water flows. (C) 2013 Elsevier Ltd. All rights reserved

    “Polyaural ” Array Processing for Automatic Speech Recognition in Degraded Environments

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    In this paper we present a new method of signal processing for robust speech recognition using multiple microphones. The method, loosely based on the human binaural hearing system, consists of passing the speech signals detected by multiple microphones through bandpass filtering and nonlinear halfwave rectification operations, and then cross-correlating the outputs from each channel within each frequency band. These operations provide rejection of off-axis interfering signals. These operations are repeated (in a non-physiological fashion) for the negative of the signal, and an estimate of the desired signal is obtained by combining the positive and negative outputs. We demonstrate that the use of this approach provides substantially better recognition accuracy than delay-and-sum beamforming using the same sensors for target signals in the presence of additive broadband and speech maskers. Improvements in reverberant environments are tangible but more modest. Index Terms: robust speech recognition, binaural hearing, auditory processing, speech enhancemen
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