The Experts below are selected from a list of 381972 Experts worldwide ranked by ideXlab platform
Imre Pázsit - One of the best experts on this subject based on the ideXlab platform.
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numerical tools applied to power reactor Noise Analysis
Progress in Nuclear Energy, 2009Co-Authors: Christophe Demaziere, Imre PázsitAbstract:In order to be able to calculate the space- and frequency-dependent neutron Noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor Noise Analysis are then described, including the unfolding of the parameters of the Noise source from the induced neutron Noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the Noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor Noise Analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.
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numerical tools applied to power reactor Noise Analysis
Proc. 5th Int. Topl. Mtg. Nuclear Plant Instrumentation Controls and Human Machine Interface Technology (NPIC&HMIT 2006) Albuquerque New Mexico USA No, 2006Co-Authors: Christophe Demaziere, Imre PázsitAbstract:In this paper, the development of numerical tools allowing the determination of the neutron Noise in power reactors is reported. These tools give the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the 2-group diffusion approximation and in a 2-dimensional representation of heterogeneous systems. Some applications of these tools to power reactor Noise Analysis are then described. These applications include the unfolding of the Noise source from the resulting neutron Noise measured at a few discrete locations throughout the core, the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the Noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of shell-mode core barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems.
Parthasarathy A - One of the best experts on this subject based on the ideXlab platform.
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Noise Analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search
'Oxford University Press (OUP)', 2022Co-Authors: Chalumeau A, Babak S, Petiteau A, Chen S, Samajdar A, Caballero R N, Theureau G, Guillemot L, Desvignes G, Parthasarathy AAbstract:Chalumeau A, Babak S, Petiteau A, et al. Noise Analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search. Monthly Notices of the Royal Astronomical Society. 2022;509(4):5538-5558.**ABSTRACT** The European Pulsar Timing Array (EPTA) collaboration has recently released an extended data set for six pulsars (DR2) and reported evidence for a common red Noise signal. Here we present a Noise Analysis for each of the six pulsars. We consider several types of Noise: (i) radio frequency independent, ‘achromatic’, and time-correlated red Noise; (ii) variations of dispersion measure and scattering; (iii) system and band Noise; and (iv) deterministic signals (other than gravitational waves) that could be present in the PTA data. We perform Bayesian model selection to find the optimal combination of Noise components for each pulsar. Using these custom models we revisit the presence of the common uncorrelated red Noise signal previously reported in the EPTA DR2 and show that the data still supports it with a high statistical significance. Next, we confirm that there is no preference for or against the Hellings–Downs spatial correlations expected for the stochastic gravitational-wave background. The main conclusion of the EPTA DR2 paper remains unchanged despite a very significant change in the Noise model of each pulsar. However, modelling the Noise is essential for the robust detection of gravitational waves and its impact could be significant when analysing the next EPTA data release, which will include a larger number of pulsars and more precise measurements
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Noise Analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background search
HAL CCSD, 2021Co-Authors: Chalumeau A, Babak S, Petiteau A, Chen S, Samajdar A, Theureau G, Guillemot L, Desvignes G, Caballero R.n., Parthasarathy AAbstract:The European Pulsar Timing Array (EPTA) collaboration has recently released an extended data set for six pulsars (DR2) and reported evidence for a common red Noise signal. Here we present a Noise Analysis for each of the six pulsars. We consider several types of Noise: (i) radio frequency independent, "achromatic", and time-correlated red Noise; (ii) variations of dispersion measure and scattering; (iii) system and band Noise; and (iv) deterministic signals (other than gravitational waves) that could be present in the PTA data. We perform Bayesian model selection to find the optimal combination of Noise components for each pulsar. Using these custom models we revisit the presence of the common uncorrelated red Noise signal previously reported in the EPTA DR2 and show that the data still supports it with a high statistical significance. Next, we confirm that there is no preference for or against the Hellings-Downs spatial correlations expected for the stochastic gravitational-wave background. The main conclusion of the EPTA DR2 paper remains unchanged despite a very significant change in the Noise model of each pulsar. However, modelling the Noise is essential for the robust detection of gravitational waves and its impact could be significant when analysing the next EPTA data release, which will include a larger number of pulsars and more precise measurements
Margaret Lin Veruki - One of the best experts on this subject based on the ideXlab platform.
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studying properties of neurotransmitter receptors by non stationary Noise Analysis of spontaneous postsynaptic currents and agonist evoked responses in outside out patches
Nature Protocols, 2007Co-Authors: Espen Hartveit, Margaret Lin VerukiAbstract:Chemical synaptic transmission depends on neurotransmitter-gated ion channels concentrated in the postsynaptic membrane of specialized synaptic contacts. The functional characteristics of these neurotransmitter receptor channels are important for determining the properties of synaptic transmission. Whole-cell recording of postsynaptic currents (PSCs) and outside-out patch recording of transmitter-evoked currents are important tools for estimating the single-channel conductance and the number of receptors contributing to the PSC activated by a single transmitter quantum. When single-channel activity cannot be directly resolved, non-stationary Noise Analysis is a valuable tool for determining these parameters. Peak-scaled non-stationary Noise Analysis can be used to compensate for quantal variability in synaptic currents. Here, we present detailed protocols for conventional and peak-scaled non-stationary Noise Analysis of spontaneous PSCs and responses in outside-out patches. In addition, we include examples of computer code for individual functions used in the different stages of non-stationary Noise Analysis. These Analysis procedures require 3-8 h.
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studying properties of neurotransmitter receptors by non stationary Noise Analysis of spontaneous synaptic currents
The Journal of Physiology, 2006Co-Authors: Espen Hartveit, Margaret Lin VerukiAbstract:The properties of neurotransmitter receptor channels are important for determining synaptic transmission in the nervous system. The presence of quantal variability complicates the use of conventional non-stationary Noise Analysis for determining the unitary conductance and number of channels involved in synaptic currents. Peak-scaled non-stationary Noise Analysis has been used to compensate for quantal variability, but there is evidence that the resulting variance versus mean relationships can be transformed from parabolic to skewed. We have used computer modelling based on experimentally derived kinetic schemes to investigate such relationships and demonstrate that their shape is a consequence of the temporal structure of the fluctuations during synaptic responses. Covariance Analysis showed that peak-scaling generates a skewed relationship when the covariance function decays rapidly (compared to the average response waveform), corresponding to a low correlation between fluctuations at the peak and in neighbouring regions of the decay phase. A parabolic relationship is obtained when the covariance function decays more slowly, corresponding to a higher correlation. Irrespective of a skewed or parabolic relationship, we demonstrate that the unitary current can be reliably estimated, with a coefficient of variation (CV) as low as 0.05 and bias as low as ±2% under ideal conditions. While the shape of the variance versus mean curve after peak-scaled non-stationary Noise Analysis is ultimately a consequence of the kinetic properties of the channels, inadequate alignment of individual waveforms can transform the relationship from parabolic to skewed, and low-pass filtering can transform the relationship from skewed to parabolic. These findings have important implications for Analysis of experimental data.
Christophe Demaziere - One of the best experts on this subject based on the ideXlab platform.
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numerical tools applied to power reactor Noise Analysis
Progress in Nuclear Energy, 2009Co-Authors: Christophe Demaziere, Imre PázsitAbstract:In order to be able to calculate the space- and frequency-dependent neutron Noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor Noise Analysis are then described, including the unfolding of the parameters of the Noise source from the induced neutron Noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the Noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor Noise Analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.
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numerical tools applied to power reactor Noise Analysis
Proc. 5th Int. Topl. Mtg. Nuclear Plant Instrumentation Controls and Human Machine Interface Technology (NPIC&HMIT 2006) Albuquerque New Mexico USA No, 2006Co-Authors: Christophe Demaziere, Imre PázsitAbstract:In this paper, the development of numerical tools allowing the determination of the neutron Noise in power reactors is reported. These tools give the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the 2-group diffusion approximation and in a 2-dimensional representation of heterogeneous systems. Some applications of these tools to power reactor Noise Analysis are then described. These applications include the unfolding of the Noise source from the resulting neutron Noise measured at a few discrete locations throughout the core, the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the Noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of shell-mode core barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems.
Amit Mehrotra - One of the best experts on this subject based on the ideXlab platform.
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Noise Analysis of phase locked loops
IEEE Transactions on Circuits and Systems I-regular Papers, 2002Co-Authors: Amit MehrotraAbstract:This work addresses the problem of Noise Analysis of phase-locked loops (PLLs). The problem is formulated as a stochastic differential equation and is solved in the presence of circuit white Noise sources yielding the spectrum of the PLL output. Specifically, the effect of loop filter characteristics, phase-frequency detector, and phase Noise of the open-loop voltage-controlled oscillator (VCO) on the PLL output spectrum is quantified. These results are derived using a full nonlinear Analysis of the VCO in the feedback loop and cannot be predicted using traditional linear analyses or the phase Noise Analysis of open-loop oscillators. The computed spectrum matches well with measured results; specifically, the shape of the output spectrum matches very well with measured PLL output spectra reported in the literature for different kinds of loop filters and phase detectors. The PLL output spectrum computation only requires the phase Noise of the VCO, loop filter and phase detector Noise, phase detector gain, and loop filter transfer function and does not require the transient simulation of the entire PLL which can be very expensive. The Noise Analysis technique is illustrated with some examples.
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Noise Analysis of phase locked loops
International Conference on Computer Aided Design, 2000Co-Authors: Amit MehrotraAbstract:This work addresses the problem of Noise Analysis of phase locked loops (PLLs). The problem is formulated as a stochastic differential equation and is solved in presence of circuit white Noise sources yielding the spectrum of the PLL output. Specifically, the effect of loop filter characteristics, phase-frequency detector and phase Noise of the open loop voltage controlled oscillator (VCO) on the PLL output spectrum is quantified. These results are derived using a full nonlinear Analysis of the VCO in the feedback loop and cannot be predicted using traditional linear analyses or the phase Noise Analysis of open loop oscillators. The computed spectrum matches well with measured results, specifically, the shape of the output spectrum matches very well with measured PLL output spectra reported in the literature for different kinds of loop filters and phase detectors. The PLL output spectrum computation only requires the phase Noise of the VCO, loop filter and phase detector Noise, phase detector gain and loop filter transfer function and does not require the transient simulation of the entire PLL which can be very expensive. The Noise Analysis technique is illustrated with some examples.
