128,345 research outputs found
Analyse des signaux multicomposante à modulation de fréquence linéaire par la transformation de Teager-Huang-Hough
No full textA novel detection approach of linear FM (LFM) signals, with single or multiple components, in the time-frequency plane of Teager-Huang (TH) transform is presented. The detection scheme that combines TH transform and Hough transform is referred to as Teager-Huang-Hough (THH) transform. The input signal is mapped into the time-frequency plane by using TH transform followed by the application of Hough transform to recognize time-frequency components. LFM components are detected and their parameters are estimated from peaks and their locations in the Hough space. Advantages of THH transform over Hough transform of Wigner-Ville distribution (WVD) are: 1) cross-terms free detection and estimation, and 2) good time and frequency resolutions. No assumptions are made about the number of components of the LFM signals and their models. THH transform is illustrated on multicomponent LFM signals in free and noisy environments and the results compared with WVD-Hough and pseudo-WVD-Hough transforms
L estimates for degenerate non-local Kolmogorov operators
No full textLet , with . We prove a priori estimates of the following type :
\|\Delta_x^\frac \alpha 2 v \|_L^p(\R^N) \le
c_p
\Big \| L_x v + \sum_i,j=1^Na_ijz_i\partial_z_j v \Big \|_L^p(\R^N),
\;\; 1
for ,
where is a non-local operator comparable with the -fractional Laplacian in terms of symbols, .
We require that when is replaced by the classical -Laplacian , i.e., in the limit local case , the operator
\Delta_x + \sum_i,j=1^Na_ijz_i\partial_z_j satisfy
a weak type H\"ormander condition with invariance by suitable dilations. Such estimates were only known
for .
This is
one of the first results on estimates for degenerate non-local operators under H\"ormander type conditions.
We complete our result on -regularity for L_x + \sum_i,j=1^Na_ijz_i\partial_z_j by proving
estimates like
\beginequation* \labelnew
\|\Delta_y_i^\frac \alpha_i 2 v \|_L^p(\R^N) \le
c_p
\Big \| L_x v + \sum_i,j=1^Na_ijz_i\partial_z_j v \Big \|_L^p(\R^N),
\endequation*
involving fractional Laplacians in the degenerate directions (here depends on and on the numbers of commutators needed to obtain the -direction). The last estimates are new even in the local limit case which is also considered
Letter from Carl Hayden to L. S. Williams
No full textLetter from Carl Hayden to L. S. Williams about the potential to expand the park boundaries
Mystery Author Stan Jones and Sepculative Fiction Authors Sterling Emmal and L. S. Goulet
No full textSterling Emmal is author of the sci-fi fantasy The Executioner of Rawule and L. S. Goulet is author of the fantasy book Sword of Dragonblood. Tundra Kill is Stan Jones' latest Nathan Active mystery. His other books include White Sky, Black Ice; Shaman Pass, Frozen Sun; Village of the Ghost Bears, and the nonfiction classic, The Spill: Personal Stories from the Exxon Valdez Disaster, coauthored with Sharon Bushell
Letter from L. S. Williams to Carl Hayden
No full textLetter from L. S. Williams to Carl Hayden suggesting a boundary amendment to the national park bill
Letter from L. S. Williams to Carl Hayden
No full textLetter from L. S. Williams to Carl Hayden about visiting Mr. Buggeln to discuss proposed park boundary changes
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