scholarly journals THE DEPENDENCE OF SUSPENDED SAND CONCENTRATION ON THE DEGREE OF STORM DEVELOPMENT

2011 ◽  
Vol 1 (32) ◽  
pp. 19
Author(s):  
Ruben Kos'yan ◽  
Joachim Grüne ◽  
Boris Divinsky ◽  
Igor Podymov ◽  
Chris Vincent ◽  
...  
Keyword(s):  
Laboratory Experiment ◽  
Surface Waves ◽  
Spectral Characteristics ◽  
Water Environment ◽  
Basic Method ◽  
Spectral Energy ◽  
Dynamic Parameters ◽  
Bottom Deposits ◽  
Basic Purpose ◽  
Frequency Area

The basic purpose of the present research is the establishment of connections between surface waves’ spectral characteristics and laws of the bottom material suspension. The basic method is the laboratory experiment that allows controlling the interconnected dynamic parameters of the water environment and processes of bottom deposits transport. It is shown, that observed suspension laws physical preconditions are the nonlinear intrawave interactions and hence the redistribution of waves spectral energy in frequency area.

Localized and Distributed Energy in Wave–Current Flow

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Santosh Kumar Singh ◽  
Anatoliy Khait ◽  
Pankaj Kumar Raushan ◽  
Koustuv Debnath
Keyword(s):  
Velocity Field ◽  
Current Flow ◽  
Spectral Characteristics ◽  
Maximum Energy ◽  
Spectral Energy ◽  
Distributed Energy ◽  
Hilbert Huang Transform ◽  
Mode Function ◽  
Intrinsic Mean ◽  
The Imf

Abstract Evaluation of localized and distributed in time spectral energy in wave–current coexisting environment is investigated in this study. In order to understand the inherent characteristics of the flow under consideration, the Hilbert-Huang transform (HHT) is introduced to determine the instantaneous frequency corresponding to the maximum energy carrying by the velocity field. This frequency is associated with the timescale of the most energetic velocity fluctuations. The intrinsic mean frequency of the intrinsic mode function (IMF) is reduced with the increase in the IMF number. It was shown that the maximum energy is concentrated close to the center of the IMF series. The spectral characteristics obtained by the HHT are carefully compared with those obtained by more conventional Fourier and wavelet transform (FFT and WT, respectively). Addition of the surface wave component to the velocity field of the current-only case leads to the extension of the frequency range containing the dominant portion of the energy.

Spontaneous skin temperature oscillations in normal human subjects

1997 ◽  
Vol 273 (3) ◽  
pp. R1173-R1181 ◽  
Author(s):  
V. Shusterman ◽  
K. P. Anderson ◽  
O. Barnea
Keyword(s):  
Skin Temperature ◽  
Muscle Tone ◽  
Human Subjects ◽  
Spectral Characteristics ◽  
Peak Frequency ◽  
Temperature Variability ◽  
Spectral Energy ◽  
Temperature Oscillations ◽  
Normal Human ◽  
Vasomotor Activity

A noninvasive method based on high-resolution measurements and bandpass filtering of spontaneous skin temperature oscillations (approximately 4.0 x 10(-2) degrees C) in the low-frequency range (0.01-0.04 Hz) was investigated in normal human subjects. We hypothesized that the oscillations (temperature variability) originate from vasomotor activity of small arteries and arterioles in subcutaneous tissues. To test this hypothesis, continuous blood pressure waveforms were obtained with the use of an external piezoelectric sensor. The peak-to-peak envelope of the pressure signal (pressure variability) was used as an indicator of vasomotor activity. The variabilities of temperature and pressure were compared using cross-spectral and coherence analysis. The correlation between the peak frequency of the signals was 0.92, and the coherence was greater than 0.9. The signals demonstrated similar changes in spectral energy and peak frequency in response to mental stress. Reproducibility of the temperature variability in individual subjects was verified by repeating measurements 1-12 wk later. The differences in peak frequency were small (0.0155 +/- 0.001 Hz), and in each subject the signals exhibited similar patterns in response to stress. Correlation between spectral characteristics of the signals suggests that temperature variability can be attributed to changes in blood flow resulting from oscillations in vasomotor smooth muscle tone.

Resolving Turbulent Wakes

2003 ◽  
Vol 125 (5) ◽  
pp. 823-834 ◽  
Author(s):  
Stephen A. Jordan
Keyword(s):  
Fourth Order ◽  
Incompressible Flows ◽  
Spectral Characteristics ◽  
The Body ◽  
Scale Model ◽  
Inertial Subrange ◽  
Spectral Energy ◽  
Turbulent Statistics ◽  
Convective Derivative ◽  
Fifth Order

Resolving the turbulent statistics of bluff-body wakes is a challenging task. Frequently, the streamwise grid point spacing approaching the vortex exit boundary is sacrificed to gain near full resolution of the turbulent scales neighboring the body surface. This choice favors the solution strategies of direct numerical and large-eddy simulations (DNS and LES) that house spectral-like resolving characteristics with inherent dissipation. Herein, two differencing stencils are tested for approximating four forms of the convective derivative in the DNS and LES formulations for incompressible flows. The wake spectral characteristics and conventional parameters are computed for Reynolds numbers Re=200 (laminar wake) and Re=3900. These tests demonstrated reliable stability and spectral-like accuracy of compact fifth-order upwinding for the advective derivative and fourth-order cell-centered Pade´ (with fourth-order upwinding interpolation) for the Arakawa form of the convective derivative. Specifically, observations of the DNS computations suggest that best results of the wake properties are acquired when the inertial subrange of the spectral energy is fully resolved at the grid-scale level. The LES solutions degraded dramatically only when the fifth-order upwind stencil resolved the spanwise periodic turbulence. Although the dynamic subgrid-scale model showed strong participation on the instantaneous level, its spectral contributions were negligible regardless of the chosen grid-scale scheme.

scholarly journals Multiwavelength analysis as a probe of accretion and radiative processes in LINERs

2012 ◽  
Vol 8 (S290) ◽  
pp. 355-356
Author(s):  
George Younes ◽  
Delphine Porquet
Keyword(s):  
Black Hole ◽  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Spectral Characteristics ◽  
Spectral Energy ◽  
X Ray ◽  
Radiative Processes ◽  
Central Engine ◽  
Galactic Black Hole ◽  
X Ray Binaries

AbstractWe study the multiwavelength properties of an optically selected sample of Low Ionization Nuclear Emission-line Regions (LINERs), in an attempt to determine the accretion mechanism powering their central engine. We show how their X-ray spectral characteristics, and their spectral energy distribution compare to luminous AGN, and briefly discuss their connection to their less massive counter-parts galactic black-hole X-ray binaries.

scholarly journals The effect of jaw position on perceptual and acoustic characteristics of speech

2016 ◽  
Vol 42 (1) ◽  
pp. 15-24
Author(s):  
Nancy Solomon ◽  
◽  
Matthew Makashay ◽  
Benjamin Munson ◽  
Keyword(s):  
Young Adults ◽  
Spectral Characteristics ◽  
Systematic Difference ◽  
Spectral Energy ◽  
Formant Frequency ◽  
Bite Block ◽  
Acoustic Characteristics ◽  
Spectral Kurtosis ◽  
Second Formant ◽  
Jaw Position

Bite blocks are used to stabilize the jaw and to isolate tongue and lip movements from that of the mandible during speech and nonspeech activities. Ten normally speaking young adults produced sentences with an unconstrained jaw and with unilateral placement of 2-mm and 5-mm bite blocks. Six listeners rated sentences spoken without either bite block as the most natural sounding. Spectral characteristics of /s/, /J/ and /t/ (sibilant frication and stop bursts) differed significantly with than without bite blocks, such that mean spectral energy decreased, and variation and skew of spectral energy increased. Spectral kurtosis did not change for the group, but 2 participants exhibited highly kurtotic /s/ spectra without a bite block that normalized with bite blocks. The second formant frequency for the high vowel /i/ was lower with bite blocks; there was no systematic difference in F2 slope for diphthongs. Segmental and suprasegmental timing of speech articulation was not affected significantly by these small bite blocks. This study provides support for using small bite blocks to isolate the tongue from the jaw without large effects on speech, but cautions that speech is likely to sound less natural than when produced with an unconstrained jaw.

scholarly journals The γ-ray spectrum of the core of Centaurus A as observed with H.E.S.S. and Fermi-LAT

2018 ◽  
Vol 619 ◽  
pp. A71 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Exposure Time ◽  
Statistical Significance ◽  
Spectral Energy Distribution ◽  
Spectral Characteristics ◽  
Physical Nature ◽  
High Energy ◽  
Spectral Energy ◽  
The Core ◽  
Advanced Analysis ◽  
Centaurus A

Centaurus A (Cen A) is the nearest radio galaxy discovered as a very-high-energy (VHE; 100 GeV–100 TeV) γ-ray source by the High Energy Stereoscopic System (H.E.S.S.). It is a faint VHE γ-ray emitter, though its VHE flux exceeds both the extrapolation from early Fermi-LAT observations as well as expectations from a (misaligned) single-zone synchrotron-self Compton (SSC) description. The latter satisfactorily reproduces the emission from Cen A at lower energies up to a few GeV. New observations with H.E.S.S., comparable in exposure time to those previously reported, were performed and eight years of Fermi-LAT data were accumulated to clarify the spectral characteristics of the γ-ray emission from the core of Cen A. The results allow us for the first time to achieve the goal of constructing a representative, contemporaneous γ-ray core spectrum of Cen A over almost five orders of magnitude in energy. Advanced analysis methods, including the template fitting method, allow detection in the VHE range of the core with a statistical significance of 12σ on the basis of 213 hours of total exposure time. The spectrum in the energy range of 250 GeV–6 TeV is compatible with a power-law function with a photon index Γ = 2.52 ± 0.13stat ± 0.20sys. An updated Fermi-LAT analysis provides evidence for spectral hardening by ΔΓ ≃ 0.4 ± 0.1 at γ-ray energies above 2.8+1.0−0.6 GeV at a level of 4.0σ. The fact that the spectrum hardens at GeV energies and extends into the VHE regime disfavour a single-zone SSC interpretation for the overall spectral energy distribution (SED) of the core and is suggestive of a new γ-ray emitting component connecting the high-energy emission above the break energy to the one observed at VHE energies. The absence of significant variability at both GeV and TeV energies does not yet allow disentanglement of the physical nature of this component, though a jet-related origin is possible and a simple two-zone SED model fit is provided to this end.

scholarly journals What makes a galaxy radio-loud?

2011 ◽  
Vol 7 (S284) ◽  
pp. 221-223
Author(s):  
R. A. Ortega-Minakata ◽  
J. P. Torres-Papaqui ◽  
H. Andernach ◽  
R. Coziol ◽  
J. M. Islas-Islas ◽  
...  
Keyword(s):  
Black Holes ◽  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Spectral Characteristics ◽  
Spectral Energy ◽  
Isolated Galaxies ◽  
Accretion Rates ◽  
The Masses ◽  
Lower Luminosity ◽  
Eddington Limit

AbstractWe compare the Spectral Energy Distribution (SED) of radio-loud and radio-quiet AGNs in three different samples observed with SDSS: radio-loud AGNs (RLAGNs), Low Luminosity AGNs (LLAGNs) and AGNs in isolated galaxies (IG-AGNs). All these galaxies have similar optical spectral characteristics. The median SED of the RLAGNs is consistent with the characteristic SED of quasars, while that of the LLAGNs and IG-AGNs are consistent with the SED of LINERs, with a lower luminosity in the IG-AGNs than in the LLAGNs. We infer the masses of the black holes (BHs) from the bulge masses. These increase from the IG-AGNs to the LLAGNs and are highest for the RLAGNs. All these AGNs show accretion rates near or slightly below 10% of the Eddington limit, the differences in luminosity being solely due to different BH masses. Our results suggests there are two types of AGNs, radio quiet and radio loud, differing only by the mass of their bulges or BHs.

Spectra and energy transfer in stably stratified turbulence

1989 ◽  
Vol 207 ◽  
pp. 419-452 ◽  
Author(s):  
E. C. Itsweire ◽  
K. N. Helland
Keyword(s):  
Energy Transfer ◽  
Spectral Characteristics ◽  
Water Channel ◽  
Three Dimensional ◽  
Density Fluctuations ◽  
Buoyancy Flux ◽  
Spectral Energy ◽  
Small Scale ◽  
Two Dimensional ◽  
Buoyancy Forces

The influence of stabilizing buoyancy forces on the spectral characteristics and spectral energy transfer of grid-generated turbulence was studied in a ten-layer closed-loop stratified water channel. The results are compared to the limiting ideal cases of the three-dimensional turbulence and two-dimensional turbulence theories. The velocity power spectra evolve from a classical isotropic shape to a shape of almost k−2 after the suppression of the net vertical mixing. This final spectral shape is rather different from the k−3 to k−4 predicted by the theory of two-dimensional turbulence and could result from the interaction between small-scale internal waves and quasi-two-dimensional turbulent structures as well as some Doppler shift of advected waves. Several lengthscales are derived from the cospectra of the vertical velocity and density fluctuations and compared with the buoyancy, overturning and viscous lengthscales measured in previous studies, e.g. Stillinger, Helland & Van Atta (1983) and Itsweire, Helland & Van Atta (1986). The smallest turbulent scale, defined when the buoyancy flux goes to zero, can be related to the peak of the cospectra of the buoyancy flux. This new relationship can be used to provide a measure of the smallest turbulent scale in cases where the buoyancy flux never goes to zero, i.e. a growing turbulent stratified shear flow. Finally, the one-dimensional energy transfer term computed from the bispectra shows evidence of a reverse energy cascade from the small scales to the large scales far from the grid where buoyancy forces dominate inertial forces. The observed reverse energy transfer could be produced by the development of quasi-two-dimensional eddies as the original three-dimensional turbulence collapses.

scholarly journals Inter-annual variations in wave spectral characteristics at a location off the central west coast of India

2015 ◽  
Vol 33 (2) ◽  
pp. 159-167 ◽  
Author(s):  
V. Sanil Kumar ◽  
M. Anjali Nair
Keyword(s):  
West Coast ◽  
Spectral Characteristics ◽  
Wave Spectrum ◽  
Spectral Energy ◽  
Monsoon Period ◽  
West Coast Of India ◽  
Annual Variations ◽  
The Indian Ocean ◽  
Wind Sea ◽  
Two Peaks

Abstract. The inter-annual variations in wave spectrum are examined based on the wave data measured at 9 m water depth off the central west coast of India from 2009 to 2012 using a wave rider buoy. The temporal variation of the spectral energy density over a calendar year indicates similar variation in all the four years studied. The inter-annual variations in wave spectrum are observed in all months with larger variations during January to February, May and October to November due to the changes in wind-sea. The seasonal average wave spectrum during the monsoon (June–September) is single-peaked and the swell component is high in 2011 compared to other years. The annual averaged wave spectrum had higher peak energy during 2011 due to the higher spectral energy present during the monsoon period. During the non-monsoon period, two peaks are predominantly observed in the wave spectra; with the average peak at 0.07 Hz corresponding to the swells from the Indian Ocean and another at 0.17 Hz due to the local wind field.

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