1,626 research outputs found
Anisotropic diffusion for noise removal of band pass signals
No full textA noise removal method for band pass signals based on anisotropic diffusion algorithm is proposed in this paper. This anisotropic smoothing algorithm is for band pass signals with a constant frequency and is an extension of the anisotropic diffusion method proposed by Perona and Malik. Band pass signals are considered as complex valued vectors here. To this end, real valued band pass signals are therefore converted to complex valued signals by using Hilbert transform. An appropriate linear operator is considered here for such complex valued signals to form an anisotropic diffusion algorithm. A partial differential equation to smooth band pass noisy signals is therefore driven. The propagator of this differential equation is a complex valued Gabor filter. The algorithm proposed here demonstrates better performance for band pass noisy signals containing discontinuities in comparison with the traditional Perona-Malik (PM) algorithm and is robust at the presence of excessive noise with SNR less than unit
Birth and Early History of Nonlinear Dynamics in Economics
No full textDesde comienzos de los ’80, la elaboración de modelos no lineales se está volviendo una metodología cada vez más popular en economía. Sin embargo, no es tan novedosa como muchos investigadores parecen creer. Antes de que el enfoque lineal dominara a la teoría económica alrededor de los ’50, muchos economistas se encontraban comprometidos con el desarrollo de modelos no lineales, especialmente durante el período 1930-1950. El principal objetivo de este ensayo es proporcionar una revisión sistemática de los desarrollos pioneros en dinámica no lineal en economía, desde el modelo original de impulso y propagación de Frisch en 1933, hasta la formalización de Goodwin del ciclo límite en 1951. Since the 1980s, nonlinear dynamic modelling is becoming a popular methodology in economics. However, it is not as new as many researchers seem to believe. Before the linear approach dominated economic theory around the 1950s, many economists were actively involved in the development of nonlinear models, this tendency being particularly strong during the period 1930-1950. The main objective of this essay is to offer a systematic and comprehensive survey of the early developments in nonlinear dynamics in economics, ranging form Frisch’s original impulse and propagation model in 1933, to Goodwin’s formalisation of the limit cycle in 1951.modelos no lineales, ciclos económicos, macrodinámica, fluctuaciones endógenas/exógenas, historia del pensamiento 1930-1950, nonlinear modelling, economic cycles, macrodynamics, endogeneous/exogenous fluctuations, history of thought 1930-1950
Deformable kernels for early vision
No full textCaption title.Includes bibliographical references (p. 22-24).Research supported by the U.S. Army Research Office. DAAL01-86-K-0171Pietro Perona
Detecting and localizing edges composed of steps, peaks and roofs
No full textCaption title.Includes bibliographical references (p. 17-18).Research supported by the U.S. Army Research Office. DAAL01-86-K-0171Pietro Perona and Jitendra Malik
A simple experimental equation for the bursting cycle
No full textThis Brief Communication presents a simple second-order differential equation extracted from experimental data, which can mimic the velocity fluctuations that are typical of bursting. The starting time series concerns the longitudinal component of turbulent velocity measured near the wall in a hydraulically smooth pipe flow. By means of standard conditional sampling techniques, we found the typical behavior of velocity fluctuations during the bursting events, to which we then applied the trajectory method in order to extract the equation of motion. The resulting equation, containing quadratic and cubic nonlinearities, follows the original time series very well, and may represent a useful starting point for the construction of more complex models of this phenomenon
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