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[en] We investigated the utility of ICA for evaluation of fetal rhythm in five uncomplicated twin pregnancies and in five twin pregnancies complicated by fetal arrhythmia. Using objective and subjective criteria, we sought to determine how the signal-to-noise ratio, signal fidelity and interference rejection are affected when synthesizing the fetal signal using all the signal-containing ICA components (rank-p ICA) versus using the single dominant component (rank-1 ICA). The signal of each fetus was most commonly distributed over 1 or 2 ICA components, as previously observed in studies of singleton pregnancies; however, in 8 of 26 (31%) cases the signal of each fetus was distributed over 3, 4 or even 5 ICA components. Rank-1 ICA provided the highest SNR and interference rejection, but at the cost of reduced signal fidelity. Our results corroborate that in twin pregnancies, including twin pregnancies complicated by fetal arrhythmia, rank-1 ICA is very effective in isolating the QRS complexes of each fetus; however, it has some limitations when used for fetal rhythm evaluation due to signal distortion. Occasionally, rank-1 ICA completely separates the P-wave and the T-wave from the QRS complex, thus requiring the mixing of several ICA components to achieve acceptable signal fidelity
[en] The in-ice radio interferometric phased array technique for detection of high energy neutrinos looks for Askaryan emission from neutrinos interacting in large volumes of glacial ice, and is being developed as a way to achieve a low energy threshold and a large effective volume at high energies. The technique is based on coherently summing the impulsive Askaryan signal from multiple antennas, which increases the signal-to-noise ratio for weak signals. We report here on measurements and a simulation of thermal noise correlations between nearby antennas, beamforming of impulsive signals, and a measurement of the expected improvement in trigger efficiency through the phased array technique. We also discuss the noise environment observed with an analog phased array at Summit Station, Greenland, a possible site for an interferometric phased array for radio detection of high energy neutrinos.
[en] We propose to examine several points concerning the methods used for the measurements made in nuclear power plants. These methods can be divided into two groups: 1) those concerning measurements which will provide characteristic parameters, expressed in physical units: 2) those concerning the detection of any variation in deviations or faults. For the group 1 methods what are required are the greatest possible precision with the conditions of acquisition; for group 2, the methods should be sufficiently sensitive to the symptomatic variations and more or less insensitive to the others. The signals are processed either by analyzers, or by specialized systems, designed and manufactured for the application in question, or by microprocessors equipped with software developed for this purpose. We will deliberately restrict ourselves to systems using the periodogramme method for the evaluation of the PSD. We will refer to ideas which are already familiar, drawing particular attention to their practical use and certain delicate points
[en] Radio astronomy is a subfields of astronomy which is discovers the celestial objects at radio frequencies. Observation in radio astronomy is conducted using single antenna or array of antennas, known as radio telescope. Other than that, radio astronomy also holds an advantage over other alternatives to optical astronomy due to its capability of observing from the ground level. In this study, the effect of solar radiation that contributes the Radio Frequency Interferences (RFI) is reviewed. The low RFI level is required to set up the radio telescope for radio astronomy observation. The effect of solar radiation on radio signal was investigated by determining the RFI pattern using spectrum analyzer. The solar radiation data was obtained from weather station located at KUSZA Observatory, East Coast Environmental Research Institute (ESERI), UniSZA. We can conclude that the solar radiation factor give the minimum significant effect to radio signal. (author)
[en] An important issue in nonlinear dynamics is the optimal estimation and detection of the partially observed states of a system at low signal-to-noise ratios. In this paper, we will outline a Bayesian-based approach that allows for the optimal determination of the state probability density function in time as a function of the observations. This leads to optimal detector designs based on the notion of generalized innovation sequences. Here, the density functions are defined over a computational grid which is designed to capture the phase space dynamics of the nonlinear system. Partial measurements are used to update the projected system state and density function. Estimation and detection decisions are based on the propagated density functions. copyright 1996 American Institute of Physics
[en] Lorentzian signals are valuable information carriers on many science fields. Although well established procedures for nonlinear fitting exists, they tend to show slow performance when either a large number of bands or high resolution signals are involved. This work introduces a procedure that automatically makes an initial estimate of the band's parameters, which are subsequently improved by a routine called Simultaneous Height Adjust (SHA), designed for accounting neighbors' signal distortions, and a linear least square fitting procedure. As result, we obtain an easy to implement and fast procedure that, for the case of LIBS applications, never overestimates the peak's energy. - Highlights: • A fitting algorithm for signals composed by multiple Lorentzian shapes is proposed. • The execution time is linear when a high number of bands and/or points are employed. • Never overestimates peaks' energy. • Does not require user intervention
[en] Since a dispersion interferometer is free from mechanical vibrations, it does not need a vibration compensation system even if a wavelength of a probe beam is short (e.x. infrared and near infrared region). This paper describes a new signal processing of the dispersion interferometer using a ratio of modulation amplitudes with a photoelastic modulator. The proposed method is immune to changes in detected signal intensities and the signal processing system becomes simple. Designs of the optical system of the dispersion interferometer for proof of principle, especially specification of a nonlinear optical crystal, are also shown. (author)
[en] Defining the quantity K as the signal-to-noise ratio (SNR) and the normalized intensity fluctuation C(0) of a single-mode laser for bias signal modulation driven by color noises with colored correlation, the whole output properties of the laser system is described by K. It is found that there is a maximum in the curves of K versus D, Q, and i0 . The optimization parameters are gained.
[en] In part because of its universal role as a first approximation of more complicated behaviour and in part because of the depth and breadth of its principle paradigms, the study of linear systems continues to play a central role in control theory and its applications. Enhancing more traditional applications to aerospace and electronics, application areas such as econometrics, finance, and speech and signal processing have contributed to a renaissance in areas such as realization theory and classical automatic feedback control. Thus, the last few years have witnessed a remarkable research effort expended in understanding both new algorithms and new paradigms for modeling and realization of linear processes and in the analysis and design of robust control strategies. The papers in this volume reflect these trends in both the theory and applications of linear systems and were selected from the invited and contributed papers presented at the 8th International Symposium on the Mathematical Theory of Networks and Systems held in Phoenix on June 15-19, 1987