Applications of Structure Preserving Wavelet Decompositions to Intermittent Turbulence: A Case Study

Hagelberg, C. R.; Gamage, Nimal

doi:10.1016/b978-0-08-052087-2.50008-6

Cited by 34 publications

(28 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…vs. local) gave identical results with the global method expressing less scatter due to the larger number of wavelet coecients employed in the technique. Since Hagelberg and Gamage 22 demonstrated that anti-symmetric wavelets are more sensitive in detecting zones of sharp transitions connected to coherent structures, the use of anti-symmetric basis functions is perhaps better suited to the present eort.…”

Section: Donoho and Johnstone's Local Methodsmentioning

confidence: 99%

“…The application of the so derived threshold value was presented in the local method. However, since the nonstructure component of atmospheric turbulent signals cannot be considered to be pure white noise due to the signi®cant slope of the corresponding non-structure energy spectrum 21,22,42 , the near-optimal behavior of the local method in these cases might not be guaranteed.…”

Section: Donoho and Johnstone's Local Methodsmentioning

confidence: 99%

See 1 more Smart Citation

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

Szilágyi

Parlange

Katul

et al. 1999

Advances in Water Resources

View full text Add to dashboard Cite

A new, parameter-free method, based on orthonormal wavelet expansions is proposed for calculating the principal time scale of coherent structures in atmospheric surface layer measurements. These organized events play an important role in the exchange of heat, mass, and momentum between the land and the atmosphere. This global technique decomposes the energy contribution at each scale into organized and random eddy motion. The method is demonstrated on vertical wind velocity measurements above bare and vegetated surfaces. It is found to give nearly identical results to a local thresholding approach developed for signal de-noising that assigns the wavelet coecients to organized and random motion. The eect of applying anti-and/or near-symmetrical wavelet basis functions is also investigated. Ó

show abstract

Section: Donoho and Johnstone's Local Methodsmentioning

confidence: 99%

Section: Donoho and Johnstone's Local Methodsmentioning

confidence: 99%

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

Szilágyi

Parlange

Katul

et al. 1999

Advances in Water Resources

View full text Add to dashboard Cite

show abstract

“…Finally, a wavelet transform (WT) analysis [13][14][15]22] was applied to further explore the evolution of variability (frequency, periods) over time (Figure 4). The twodimensional continuous WTs were calculated from the time series to represent the change of spectral power (time-frequency distribution of variations) and describe structures of different time scales by the application of Morlet mother wavelet.…”

Section: Statistical Analysesmentioning

confidence: 99%

“…The twodimensional continuous WTs were calculated from the time series to represent the change of spectral power (time-frequency distribution of variations) and describe structures of different time scales by the application of Morlet mother wavelet. This function is symmetric and very useful in identifying regions of maximum/minimum curvature [22].…”

Section: Statistical Analysesmentioning

confidence: 99%

Cyclic patterns of malaria incidence in Burundi

et al. 2010

View full text Add to dashboard Cite

Best available descriptions of malaria incidence and mortality dynamics are important to improve and evaluate the implementation of programs to monitor (e.g., remote sensing) and control disease, especially in endemic zones. High-frequency (e.g., semi-annual and seasonal) cycles in malaria incidence have been observed in various countries and they coincide with cycles in the natural environment (e.g., temperature, heliogeophysical activity, etc.). However, neither trend nor cyclical oscillations beyond a 6-month (0.5-year) period for this vector-borne disease were reported in a recent analysis on monthly notifications in Burundi for the years 1997-2003. Since the examination of graphical plots indicated an eventual existence of trans-year (multiannual) variations, we further analyzed the same data in more detail. Here we explore whether low-frequency cycles (beyond seasonality) might exist (e.g., trans-year cycles with periods of 13-24 months or longer). Monthly incidence rate per 100 inhabitants from the Province of Karuzi, Burundi, over the years 1997-2003 was analysed. The exploration of underlying chronomes (time structures) was done by linear and non-linear parametric regression models, autocorrelation, spectral analysis (e.g., fast Fourier transforms) , periodogram regression analysis (PRA) and wavelet transform (WT). By using a periodogram regression analysis, we describe a multicomponent cyclic chronome with periods T>12 months (19 and 86 months, all at P<0.05). Notably, the strongest cyclic pattern in the periodogram of the detrended malaria rates (whereas the peak was suppressed and beyond the semi-annual cycle of 6 months) was ≈1.5-1.6 years (T=19.0 months, R=0.32). A dynamic pattern of "shortening" of the length (period) of the cycles was observed during the pre-epidemic interval (from 8-9 to 5-6 months and from 20-22 to 16-18 months in years 1997-2000) that can be used to anticipate a forthcoming incidence increase and epidemic levels of malaria at a regional level. Indeed, these cycles in malaria incidence correspond to cyclic components of heliogeophysical activity (HGA) such as the sunspot cycle impulses of 0.5-2.0 years as well as the quasi-biennial solar magnetic cycle of 1.5-2.5 years and further, detailed analyses are warranted to investigate such relationships. A multicomponent dynamic cyclical pattern of malaria incidence variations in Burundi (1997Burundi ( -2003 exists thus allowing further, more specific analyses and modelling as well as correlations with similar environmental cycles to be explored. These results might also contribute to better estimates for forecasting, prevention and understanding of malaria dynamics and aetiology.

show abstract

“…The selection depends on the studied problem. For border detection, for example, a symmetric wavelet gives large coefficients at each sides of the transition and an antisymmetric wavelet gives large coefficients at the center of the transition [Hagelberg and Gamage, 1994]. It is better to use an irregular wavelet such as the simple Haar wavelet when the signal presents sharp variations, and a regular wavelet for smoother signal.…”

Section: The Mexican Hat Waveletmentioning

confidence: 99%

Analysis of gravity and magnetic fields in the Canadian Shield using standard and wavelet-based methods

Bourlon¹

2004

View full text Add to dashboard Cite

Applications of Structure Preserving Wavelet Decompositions to Intermittent Turbulence: A Case Study

Cited by 34 publications

References 21 publications

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

Cyclic patterns of malaria incidence in Burundi

Analysis of gravity and magnetic fields in the Canadian Shield using standard and wavelet-based methods

Contact Info

Product

Resources

About