Search results for "Signal"

FDTD signal extrapolation using a finite impulse response neural network model

1999

An Improved Forecasting Model from Satellite Imagery Based on Optimum Wavelet Bases and Adam Optimized LSTM Methods

2021

This paper proposes a new hybrid approach I-WT-LSTM (i.e., Improved Wavelet Long Short-Term Memory (LSTM) Model) for forecasting non-stationary time series (TS) from satellite imagery. The proposed approach consists of two steps: The first step aims at decomposing TS using Multi-Resolution Analysis wavelet (MRA-WT) into inter-and intra-annual components using 18 different mother wavelets (MW). Then, the energy to Shannon entropy ratio criterion is calculated to select the best MW. The second step is based on the LSTM model using Adam optimizer to predict the future. The proposed approach is tested using TS derived from Moderate Resolution Imaging Spectroradiometer (MODIS) images from 2001 t…

Characterization of the human visual system threshold performance by a weighting function in the Gabor domain

1997

Abstract As evidenced by many physiological and psychophysical reports, the receptive fields of the first-stage set of mechanisms of the visual process fit to two-dimensional (2D) compactly supported harmonic functions. The application of this set of band-pass filter functions to the input signal implies that the visual system carries out some kind of conjoint space/spatial frequency transform. Assuming that a conjoint transform is carried out, we present in this paper a new characterization of the visual system performance by means of a weighting function in the conjoint domain. We have called this weighting function (in the particular case of the Gabor transform) the Gabor stimuli Sensiti…

Fast nonstationary preconditioned iterative methods for ill-posed problems, with application to image deblurring

2013

We introduce a new iterative scheme for solving linear ill-posed problems, similar to nonstationary iterated Tikhonov regularization, but with an approximation of the underlying operator to be used for the Tikhonov equations. For image deblurring problems, such an approximation can be a discrete deconvolution that operates entirely in the Fourier domain. We provide a theoretical analysis of the new scheme, using regularization parameters that are chosen by a certain adaptive strategy. The numerical performance of this method turns out to be superior to state-of-the-art iterative methods, including the conjugate gradient iteration for the normal equation, with and without additional precondi…

An electrical current smart transducer based on PSoC platform and integrated spin-valve sensor with embedded thin film Ruthenium temperature sensor

2011

This work presents an intelligent electrical current sensor that combines a programmable system on chip (PSoC) with a microfabrication of a giant magnetoresistance sensor (GMR) and resistive temperature detector (RTD). Four spin-valve GMR elements configured in a Wheatstone bridge sense the electrical current, while a thin film RTD based on Ruthenium measures the temperature for spin-valve bridge sensitivity thermal compensation. The mixed signal PSoC allows implement in a single chip all electronic circuits needed to design a smart transducer: the spin-valve biasing, conditioning signal, analog to digital converter, digital signal processing and ports for communications. In the experimenta…

Optical wireless communication systems

2017

Abstract The emerging field of optical wireless communication (OWC) systems is seen as potential complementary technology to the radio frequency wireless communications in certain applications. It is deemed as a possible technology in the future 5th Generation communication networks to address the spectrum congestion and improve the system’s capacity. More research and developments in OWC is still needed in order for it to be adopted in current and future communication systems. This special issue brings together research papers on OWC covering free space optic, visible communications and ultraviolet communications.

Alarm calling by individual willow tits, Parus montanus

1990

Abstract Alarm responses of wild-captured individual willow tits to model sparrowhawks, Accipiter nisus, flying over a test chamber were studied. Tits did not usually give alarm calls if the apparent predator was passing nearby (at a height of 10 m), while over half of the individuals responded by alarm calling for a more distant predator (40 m). This suggests that alarm calling involves a risk to the caller. Second, there was individual variation in the responses, with older males giving the call more frequently than females or young males. The greater responsiveness of adult males may indicate that different individuals in a flock gain different benefits by warning the others. The tendenc…

Wind Shear On-Line Identification for Unmanned Aerial Systems

2014

An algorithm to perform the on line identification of the wind shear components suitable for the UAS characteristics has been implemented. The mathematical model of aircraft and wind shear in the augmented state space has been built without any restrictive assumption on the dynamic of wind shear. Due to the severe accelerations on the aircraft induced by the strong velocity variation typical of wind shear, the wind shear effects have been modeled as external forces and moments applied on the aircraft. The identification problem addressed in this work has been solved by using the Filter error method approach. An Extended Kalman Filter has been developed to propagate state. It has been tuned …

Simultaneous ranging and self-positioning in unsynchronized wireless acoustic sensor networks

2016

Automatic ranging and self-positioning is a very desirable property in wireless acoustic sensor networks, where nodes have at least one microphone and one loudspeaker. However, due to environmental noise, interference, and multipath effects, audio-based ranging is a challenging task. This paper presents a fast ranging and positioning strategy that makes use of the correlation properties of pseudonoise sequences for estimating simultaneously relative time-of-arrivals from multiple acoustic nodes. To this end, a proper test signal design adapted to the acoustic node transducers is proposed. In addition, a novel self-interference reduction method and a peak matching algorithm are introduced, a…

Multi-Resolution error analysis of predicted absorption coefficients. Method and application to the infrared spectrum of methane at high temperature.

2010

La version V2 inclut les modifications proposées par les reviewers.; International audience; A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. Statistical numerical experiments are implemented to quantify the propagation of errors from line parameters to absorption coefficients or cross-sections as a function of the resolution. The method uses line parameter predictions (position and intensity) with estimated uncertainties derived from global polyad models. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high…