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Wave Component (wave + component)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Neural Correlates of Encoding Predict Infants' Memory in the Paired-Comparison Procedure

INFANCY, Issue 3 2010
Kelly A. Snyder
The present study used event-related potentials (ERPs) to monitor infant brain activity during the initial encoding of a previously novel visual stimulus, and examined whether ERP measures of encoding predicted infants' subsequent performance on a visual memory task (i.e., the paired-comparison task). A late slow wave component of the ERP measured at encoding predicted infants' immediate performance in the paired-comparison task: amplitude of the late slow wave at right-central and temporal leads decreased with stimulus repetition, and greater decreases at right-anterior-temporal leads during encoding were associated with better memory performance at test. By contrast, neither the amplitude nor latency of the negative central (Nc) component predicted infants' subsequent performance in the paired-comparison task. These findings are discussed with respect to a biased competition model of visual attention and memory. [source]

Supplement to ,Third-order transport due to internal waves and non-local turbulence in the stably stratified surface layer'

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 581 2002
Tarmo Soomere
Abstract A linear theory of internal gravity waves (IGWs) is applied to consider the IGW-induced vertical fluxes of kinetic energy, pressure and squared density (or buoyancy) in non-turbulent stably stratified fluid characterized by the Brunt,Väisälä frequency, N. These fluxes are required in modelling distant links and non-local transports in the atmosphere. Investigations of the vertical flux of kinetic energy have shown that this flux, caused by the wave component performing the most efficient vertical transport, is proportional to N3. As far as the authors know, the flux of the squared density fluctuations was not systematically investigated. It is shown to be proportional to N5. Copyright © 2002 Royal Meteorological Society. [source]

A Maslov-propagator seismogram for weakly anisotropic media

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2002
Georg Rümpker
Summary We introduce a formalism to calculate shear-wave seismograms for weakly-anisotropic and inhomogeneous media. The method is based on the combination of the forward-propagator method, which accounts for shear-wave interaction along a single reference ray, and the Maslov ray-summation, which incorporates amplitude and phase information from neighbouring rays to account for waveform and diffraction effects at caustics and in shadow regions. The approach is based on the assumption that the multiply split shear waves, on the way to a given receiver, travel along a common ray path that can by obtained from ray tracing in an isotropic reference medium (i.e. the common-ray approximation). The forward propagator and the Maslov amplitude are expressed with respect to radial and transverse coordinates (perpendicular to the ray propagation direction) that are defined uniquely by the initial conditions. Local polarizations and slownesses of the fast and slow shear-waves in the direction of propagation are obtained from the eikonal equation. The Maslov-propagator phase is given by the average shear-wave traveltime along the reference ray. Phase advances and delays of individual shear wave components are accounted for by the propagator. The geometrical-spreading information required for the Maslov integration is supplied by dynamic ray tracing in the isotropic reference medium. In the high-frequency limit effective phase functions are defined to assess the validity of the Maslov propagator phase information. For a homogeneous isotropic reference medium, we find good agreement with exact Maslov phase functions for anisotropic perturbations of up to 20 per cent. As a numerical application we consider effects of inhomogeneous anisotropy in a shear-wave cross-hole survey. The variations of the transversely-isotropic medium require 2-D slowness integrals. The method can handle discontinuities of the fast polarization along the ray path and also for neighbouring rays which is important for the slowness integration. Smooth transitions between isotropic and anisotropic regions along the ray path can be accounted for without the need to switch between numerical formulations. [source]

Comparison of decoupling methods for analyzing pressure fluctuations in gas-fluidized beds

AICHE JOURNAL, Issue 4 2010
Yongmin Zhang
Abstract Two methods of decoupling pressure fluctuations in fluidized beds by using the incoherent part (IOP) of absolute pressure (AP) and differential pressure (DP) fluctuations are evaluated in this study. Analysis is conducted first to demonstrate their similarities, differences, and drawbacks. Then, amplitudes, power spectral densities, mean frequencies, coherence functions, and filtering indices of the IOP of AP and DP fluctuations are calculated and compared based on experimental data from a two-dimensional fluidized column of FCC particles. Derived bubble sizes are also compared with the sizes of bubbles viewed in the two-dimensional bed. The results demonstrate the similarity of these two methods in filtering out global compression wave components from absolute pressure fluctuations, especially those generated from oscillations of fluidized particles and gas flow rate fluctuations. However, both methods are imperfect. Neither can filter out all the compression wave components and retain all the useful bubble-related wave components. Their amplitudes can be used to characterize global bubble property and quality of gas,solids contacting in bed, but they do not give accurate measurement of bubble sizes. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]