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.

scholarly journals The seismic signatures of the 2009 Shiaolin landslide in Taiwan

2011 ◽  
Vol 11 (5) ◽  
pp. 1559-1569 ◽  
Author(s):  
Z. Feng
Keyword(s):  
Surface Wave ◽  
Seismic Waves ◽  
Frequency Spectra ◽  
Hilbert Huang Transform ◽  
Time Frequency ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Mode Function ◽  
Mode Decomposition ◽  
Weak Surface

Abstract. The Shiaolin landslide occurred on 9 August 2009 after Typhoon Morakot struck Taiwan, claiming over 400 lives. The seismic signals produced by the landslide were recorded by broadband seismic stations in Taiwan. The time-frequency spectra for these signals were obtained by the Hilbert-Huang transform (HHT) and were analyzed to obtain the seismic characteristics of the landslide. Empirical mode decomposition (EMD) was applied to differentiate weak surface-wave signals from noise and to estimate the surface-wave velocities in the region. The surface-wave velocities were estimated using the fifth intrinsic mode function (IMF 5) obtained from the EMD. The spectra of the earthquake data were compared. The main frequency content of the seismic waves caused by the Shiaolin landslide were in the range of 0.5 to 1.5 Hz. This frequency range is smaller than the frequency ranges of other earthquakes. The spectral analysis of surface waves (SASW) method is suggested for characterizing the shear-wave velocities of the strata in the region.

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 Single Frame Fringe Pattern Analysis for Phase Recovery with Analytic Signal

ISRN Optics ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
Khalid Assid ◽  
Vamara Dembele ◽  
Faiçal Alaoui ◽  
Abdel Karim Nassim
Keyword(s):  
Fringe Pattern ◽  
Good Accuracy ◽  
Phase Distribution ◽  
Analytic Signal ◽  
One Dimensional ◽  
Hilbert Huang Transform ◽  
Mode Function ◽  
Single Frame ◽  
Mode Decomposition ◽  
Fringe Pattern Analysis

We consider a new application of the normalized Hilbert-Huang transform to extract directly the phase from a single fringe pattern. We present a technique to provide, with good accuracy, the phase distribution from a single interferogram without unwrapping step and this by a new exploitation of the analytic signal corresponding to each intrinsic mode function, resulting from one-dimensional empirical mode decomposition of the fringe pattern. A theoretical analysis was carried out for this technique, followed by computer simulations and a real experimental fringe pattern for verification.

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 Application of Hilbert-Huang Transform in Structural Health Monitoring: A State-of-the-Art Review

2014 ◽  
Vol 2014 ◽  
pp. 1-22 ◽  
Author(s):  
Bo Chen ◽  
Sheng-lin Zhao ◽  
Peng-yun Li
Keyword(s):  
System Identification ◽  
Health Monitoring ◽  
Structural Damage ◽  
State Of The Art ◽  
Theoretical Method ◽  
Future Trends ◽  
Structural Damage Detection ◽  
Engineering Structures ◽  
Hilbert Huang Transform ◽  
Mode Function

This paper reviews the development and application of HHT in the field of SHM in the last two decades. The challenges and future trends in the development of HHT based techniques for the SHM of civil engineering structures are also put forward. It also reviews the basic principle of the HHT method, which contains the extraction of the intrinsic mode function (IMF), mechanism of the EMD, and the features of HT; shows the application of HHT in the system identification, which contains the introduction of theoretical method, the identification of modal parameters, and the system identification on real structures; and discusses the structural damage detection using HHT based approaches, which includes the detection of common damage events, sudden damage events, and cracks and flaws.

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.

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.

Characterisation of the Instantaneous Velocity and Mixture Field Issuing From a Lean Premixed Module (LPM)

2003 ◽  
Author(s):  
J. F. Carrotte ◽  
C. Batchelor-Wylam
Keyword(s):  
Velocity Field ◽  
Flow Field ◽  
Swirling Flow ◽  
Spectral Characteristics ◽  
Gaseous Fuel ◽  
Constant Current ◽  
Reacting Flow ◽  
Lean Premixed ◽  
Velocity Spectra ◽  
The Individual

Measurements have been made on the non-reacting flow field issuing from a Lean Premixed module (LPM) that incorporates a radial swirler, mixing duct section and nozzle. The geometry contains many features that are thought typical of LPM systems in which gaseous fuel is introduced into a swirling flow at a discrete number of locations. Hot wire anemometry measurements have been used to define the velocity field issuing from the module whilst additional experiments have utilised heated air to simulate gaseous fuel. In this way temperature measurements, using Constant Current Anemometry, have been used to infer the fuel-air mixture field issuing from the module. The velocity data indicates a highly turbulent flow field and the basic spectral characteristics of this velocity field are defined. In addition, within certain regions a strong periodic flow component is observed and is indicative of the instabilities typically associated with swirling flows. The spectral characteristics of the mixture field are also presented and the method by which the mixture and velocity spectra should be compared is outlined. Using this method the measurements indicate the basic spectral characteristics are virtually identical and, furthermore, a periodic fluctuation in the mixture field is also observed. For these types of LPM systems fluctuations in the mixture and velocity fields are therefore strongly correlated. In addition it is shown that the flow fields are dominated by the relatively large time and length scales associated with the main velocity field rather than, say, the much smaller velocity and mixing scales associated with the individual fuel jets.

Vibration-Based Damage Detection of Composite Wingbox Structures Using Improved Hilbert-Huang Transform

2006 ◽  
Vol 324-325 ◽  
pp. 539-542 ◽  
Author(s):  
Huan Guo Chen ◽  
Yun Ju Yan ◽  
Jie Sheng Jiang
Keyword(s):  
Structural Damage ◽  
Wavelet Packet ◽  
Dynamic Responses ◽  
Structural Dynamic ◽  
Hilbert Huang Transform ◽  
Mode Function ◽  
Index Vector ◽  
Selection For ◽  
Instantaneous Energy ◽  
Composite Wing

A vibration-based approach to detect crack damage in a cantilever composite wingbox is studied using the improved Hilbert-Huang Transform (HHT). The improved HHT is composed of HHT with Wavelet Packet Transform (WPT) and a simple but effective method for intrinsic mode function (IMF) selection. For different damage status, in order to obtain structural dynamic responses, which imply plentiful damage information, the composite wing boxes were excited by a contrived square wave signal. Then, the dynamic responses of intact wingbox and damaged wingbox are disposed using improved HHT. Finally, a feature index vector of structural damage, i.e. the ariation quantity of instantaneous energy, is constructed. The obtained results show that the proposed damage feature index vector is more sensitive to small damage than those in traditional signal processing.

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