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noise-analysis
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Asymptotic eigenvectors, topological patterns and recurrent networks
, Article Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science ; Volume 14, Issue 2 , 2013 , Pages 95-100 ; 14549069 (ISSN) ; Sharif University of Technology
2013
Abstract
The notions of asymptotic eigenvectors and asymptotic eigenvalues are defined. Based on these notions a special probability rule for pattern selection in a Hopfield type dynamics is introduced. The underlying network is considered to be a d-regular graph, where d is an integer denoting the number of nodes connected to each neuron. It is shown that as far as the degree d is less than a critical value dc, the number of stored patterns with m μ = O(1) can be much larger than that in a standard recurrent network with Bernouill random patterns. As observed in [4] the probability rule we study here turns out to be related to the spontaneous activity of the network. So our result might be an...
General noise considerations of amplified photons in lightwave systems with optically bistable elements
, Article Proceedings - 10th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2010, 12 September 2010 through 14 September 2010 ; 2010 , Pages 93-95 ; 9781424469970 (ISBN) ; Naqavi, A ; Mehrany, K ; Mousavi, S. M ; Aliakbar, J ; Mousavi, S. M ; Sharif University of Technology
Abstract
An optical amplifier followed by a bistable element has been statistically analyzed before [1]. In this manuscript, output noise analysis represents, then signal to noise ratios (SNR) are calculated either for input or output. It will be shown that noise reduction, can be achieved by a proper selection of parameters
A new simple method for analysing of thermal noise in switched-capacitor filters
, Article International Journal of Electronics ; Volume 99, Issue 12 , Feb , 2012 , Pages 1729-1737 ; 00207217 (ISSN) ; Hemmatyar, A. M. A ; Hashemipour, O ; Sharif University of Technology
2012
Abstract
Thermal noise is one of the most important challenges in analogue integrated circuits design. This problem is more crucial in switched-capacitor (SC) filters due to the aliasing effect of wide-band thermal noise. In this article, a new simple method is proposed for estimating the power spectrum density of output thermal noise in SC filters, which have acceptable accuracy and short running time. In the proposed method, first using HSPICE simulator, accurate value of accumulated sampled noise on sampler capacitors in each clock state is achieved. Next, using difference equations of the SC filter, frequency response of the SC filter is shaped by time domain analysis. Based on the proposed...
Electrochemical potential noise analysis of Cu-BTA system using wavelet transformation
, Article Journal of Electroanalytical Chemistry ; Volume 633, Issue 1 , 2009 , Pages 240-245 ; 15726657 (ISSN) ; Roshan, M. S ; Norouzi, S ; Sadrnezhaad, S. K ; Jafari, A ; Sharif University of Technology
Elsevier
2009
Abstract
Electrochemical potential noise analysis was used to investigate corrosion behavior of copper electrodes in presence of 0.001, 0.005, 0.01 and 0.02 M benzotriazole (BTA) inhibitor. Energy distribution of the potential noise was obtained from wavelet transformation using the 4th order Daubechies pattern. Two lowest frequencies were added-up and fitted to the impulse response of the first order circuit to achieve the time-constant vs. concentration (T-C) diagram. T-C diagram can be used either as a conventional diagram of inhibition efficiency or a tool for evaluation of the surface film dielectric constant. The assumptions made in this treatment were confirmed by EIS method. © 2009 Elsevier...
Prediction of the noise spectrum in optoelectronic oscillators: An analytical conversion matrix approach
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 8 , August , 2014 , p. 1915-1925 ; ISSN: 07403224 ; Hosseini, S. E ; Banai, A ; Sharif University of Technology
Abstract
In this paper an analytical formulation based on the conversion matrix approach for characterizing the oscillator noise spectra as well as the phase and amplitude noise spectra for a single-loop optoelectronic oscillator (OEO) is presented. The validity of this approach is verified by comparing our results regarding the noise spectra of the OEO against the results of two references in the literature. The first reference presents simulation results, and the second reference presents both simulation and measurement results, and good agreement is seen between the results of the new method and those of the references. The advantage of the new approach is the simplicity of the theory as well as...
Computing all the Floquet eigenfunctions of oscillators using harmonic balance Jacobian matrices
, Article IET Circuits, Devices and Systems ; Volume 5, Issue 4 , July , 2011 , Pages 257-266 ; 1751858X (ISSN) ; Farzaneh, F ; Sharif University of Technology
2011
Abstract
Floquet eigenfunctions and Floquet exponents are encountered in stability and noise analysis of circuits operating at large signal periodic regime. It is analytically verified that the spectrum vectors of the left-hand and right-hand Floquet eigenfunctions and the Floquet exponents (Floquet eigenpairs) are members of the harmonic balance eigenvalues and eigenvectors (HB eigenpairs). The relationships between other HB eigenpairs with the Floquet eigenpairs are discussed. This discussion leads to a practical algorithm for computing the Floquet eigenpairs through HB eigenpairs. Furthermore, it is analytically verified that the main arguments of the study are consistent with the...
Investigating the propagation noise in PWRs via closed-loop neutron-kinetic/thermal-hydraulic noise calculations
, Article Annals of Nuclear Energy ; Volume 80 , 2015 , Pages 101-113 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Neutron noise induced by propagating thermal-hydraulic disturbances (propagation noise for short) in pressurized water reactors is investigated in this paper. A closed-loop neutron-kinetic/thermal-hydraulic noise simulator (named NOISIM) has been developed, with the capability of modeling the propagation noise in both Western-type and VVER-type pressurized water reactors. The neutron-kinetic/thermal-hydraulic noise equations are on the basis of the first-order perturbation theory. The spatial discretization among the neutron-kinetic noise equations is based on the box-scheme finite difference method (BSFDM) for rectangular-z, triangular-z and hexagonal-z geometries. Furthermore, the finite...
Neutronic Simulation of Generation IV Prismatic High Temperature Reactors and Noise Analysis
, Ph.D. Dissertation Sharif University of Technology ; Ghofrani, Mohammad Bagher (Supervisor)
Abstract
This thesis has been done with the goal of comprehensive neutronic calculation of a small size High Temperature Gas Cooled Reactor and HTTR was selected as a reference reactor for simulations. Calculations are divided into four parts of zero and full power stochastic calculations, deterministic calculations and noise analysis. In zero power calculations, an algorithm is proposed for modeling random arrangement of TRISO particles in the fuel compacts of HTTR. The effect of this arrangement on criticality calculations, i.e. effective multiplication factor and critical position of control rods, is then compared with regular arrangement. In the second part, full power calculations with the use...
Noise analysis in satellite attitude estimation using angular rate and a single vector measurement
, Article Proceedings of the IEEE Conference on Decision and Control, 12 December 2011 through 15 December 2011 ; December , 2011 , Pages 7476-7481 ; 01912216 (ISSN) ; 9781612848006 (ISBN) ; Namvar, M ; Sharif University of Technology
Abstract
This paper investigates the effect of noisy measurements of the angular rate in a nonlinear attitude estimator for satellites. The attitude estimator uses measurement of a single attitude sensor such as sun, earth horizon, star tracker or magnetometer together with a rate gyro, and guarantees exponential convergence of the attitude estimation error to zero under no noise condition. This paper presents stochastic and deterministic upper bounds for the attitude estimation error affected by the noise in gyro. A realistic simulation is presented to illustrate the results
Calculation and analysis of thermal-hydraulics fluctuations in pressurized water reactors
, Article Annals of Nuclear Energy ; Volume 76 , 2015 , Pages 75-84 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Analysis of thermal-hydraulics fluctuations in pressurized water reactors (e.g., local and global temperature or density fluctuations, as well as primary and charging pumps fluctuations) has various applications in calculation or measurement of the core dynamical parameters (temperature or density reactivity coefficients) in addition to thermal-hydraulics surveillance and diagnostics. In this paper, the thermal-hydraulics fluctuations in PWRs are investigated. At first, the single-phase thermal-hydraulics noise equations (in the frequency domain) are originally derived, without any simplifying assumptions. The fluctuations of all the coolant parameters, as well as the radial distribution of...
A simple time domain approach to noise analysis of switched capacitor circuits
, Article IEICE Electronics Express ; Volume 7, Issue 11 , Jun , 2010 , Pages 745-750 ; 13492543 (ISSN) ; Hashemipour, O ; Afshin Hemmatyar, A. M ; Sharif University of Technology
2010
Abstract
Thermal noise is one of the most important limiting factors on the performance of switched-capacitor (SC) circuit due to the aliasing effect of wide-band thermal noise. In this paper a new simple method for estimating the effect of thermal noise is presented. In the proposed technique only the discrete sampled noise is considered. HSPICE simulator and analytical analysis are used to estimate the sampled noise specification on each clock state. Next, using difference equations of the circuit, time domain simulation is done by MATLAB. Based on this method, a SC integrator is analyzed and results compared to the measured noise response
Spatiotemporal Modeling & Simulation of the Second Order Moments of the Transport Equation
, Ph.D. Dissertation Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
Precise knowledge of the laws which govern a system is of interest for two reasons. First, it paves the way to understand the subtle behaviors of the system, which are not understandable from simpler models of the system. Second, it helps in the design of experimental requirements needed to observe these behaviors. The behavior of neutrons in a system, which could be a reactor or a detector, is stochastic from two perspectives. First of all, since the place of the atoms of a medium are randomly sited, at least from a neutrons point of view, the collision sites are random places, which contributes to the stochasticity of the transport phenomena. This type of randomness is somewhat similar to...
Noise Analysis and Performance Improvement of Microwave Diode Mixers, and Improving the Method of Noise Figure Measurement
, Ph.D. Dissertation Sharif University of Technology ; Banai, Ali (Supervisor)
Abstract
In spite of developments in microwave mixers, reducing its noise figure is still a designers’ challenge in receiver applications. Due to generating intermodulations and saturating the following stages, the low noise amplifier cannot have a so much gain to decrease the noise of the following stages in a typical receiver. This problem is intensified in special applications because of low dynamic range of low noise amplifiers. Accordingly, the low noise amplifier is replaced sometimes by the mixer. Therefore, the design of a low noise mixer is an important issue in improving the noise performance of a total receiver.To this end, it is required to accurately analyse the nonlinear and noise...
Monte Carlo simulation of Feynman-α and Rossi-α techniques for calculation of kinetic parameters of Tehran research reactor
, Article Annals of Nuclear Energy ; Volume 38, Issue 10 , 2011 , Pages 2140-2145 ; 03064549 (ISSN) ; Vosoughi, N ; Hosseini, M ; Sharif University of Technology
Abstract
Noise analysis techniques including Feynman-α (variance-to-mean) and Rossi-α (correlation) have been simulated by MCNP computer code to calculate the prompt neutron decay constant (α0), effective delayed neutron fraction (βeff) and neutron generation time (Λ) in a subcritical condition for the first operating core configuration of Tehran Research Reactor (TRR). The reactor core is considered to be in zero power (reactor power is less than 1 W) in the entire simulation process. The effect of some key parameters such as detector efficiency, detector position and its dead time on the results of simulation has been discussed as well. The results of proposed method in the current study are...
Phase noise characterization of oscillators through Ito calculus
, Article International Journal of Circuit Theory and Applications ; Volume 43, Issue 11 , November , 2015 , Pages 1581-1596 ; 00989886 (ISSN) ; Farzaneh, F ; Sharif University of Technology
John Wiley and Sons Ltd
2015
Abstract
Recent phase noise analysis techniques of oscillators mainly rely on solving a stochastic differential equation governing the phase noise process. This equation has been solved in the literature using a number of mathematical tools from probability theory like deriving the Fokker-Planck equation governing the phase noise probability density function. Here, a completely different approach for solving this equation in presence of white noise sources is introduced that is based on the Ito calculus for stochastic differential equations. Time-domain analytical expressions for the correlation of the noisy variables of the oscillator are derived that in asymptotically large times give the...
Localization of a noise source in VVER-1000 reactor core using neutron noise analysis methods
, Article International Conference on Nuclear Engineering, Proceedings, ICONE, 17 May 2010 through 21 May 2010 ; Volume 2 , May , 2010 ; 9780791849309 (ISBN) ; Vosoughi, N ; Zahedinejad, E ; Nuclear Engineering Division ; Sharif University of Technology
2010
Abstract
In this paper, localization of a noise source from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The boxscheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. The dynamic state is assumed in the frequency domain which leads to discarding of the time disrcetisation. The developed 2-D 2- group neutron noise simulator calculates...
Phase noise degradation of varactor and BJT frequency multipliers in the presence of parametric instability
, Article IET Microwaves, Antennas and Propagation ; Volume 4, Issue 3 , 2010 , Pages 408-419 ; 17518725 (ISSN) ; Banai, A ; Farzaneh, F ; Sharif University of Technology
2010
Abstract
Varactor and bipolar junction transistor (BJT) frequency multipliers are a class of non-linear circuits that show parametric instability when the input drive is varied. If parametric oscillations are present in the circuit, output phase noise of the multiplier degrades remarkably in some specific driving levels. Phase noise analysis is performed by the conversion matrix method using generalised nodal analysis. The conversion method predicts the phase noise degradation precisely because it encompasses the effect of the noise sources that are modulated by the large signal drive. The added phase noise of a varactor and a BJT frequency doubler with subharmonic oscillation is calculated and the...
Effect of parametric instability on phase noise degradation in a varactor frequency multiplier
, Article Asia-Pacific Microwave Conference, APMC 2007, Bangkok, 11 December 2007 through 14 December 2007 ; 2007 ; 1424407494 (ISBN); 9781424407491 (ISBN) ; Banai, A ; Sharif University of Technology
2007
Abstract
Varactor frequency multipliers often show parametric instability with increasing RF input power. Examination of the added phase noise of the varactor frequency multipliers show that, if parametric oscillations are present in the circuit, output phase noise degrades remarkably in some specific driving levels. Phase noise analysis is done by the conversion matrix method. The conversion method predicts the phase noise degradation precisely because it encounters the noise conversion by large driving levels. The added phase noise of a varactor frequency doubler with subharmonic oscillation is calculated and the simulation results are compared with measurement results. Both simulation and...
Topological pattern selection in recurrent networks
, Article Neural Networks ; Volume 31 , 2012 , Pages 22-32 ; 08936080 (ISSN) ; Abbassian, A ; Sharif University of Technology
2012
Abstract
The impact of adding correlation to a population of neurons on the information and the activity of the population is one of the fundamental questions in recent system neuroscience. In this paper, we would like to introduce topology-based correlation at the level of storing patterns in a recurrent network. We then study the effects of topological patterns on the activity and memory capacity of the network. The general aim of the present work is to show how the repertoire of possible stored patterns is determined by the underlying network topology.Two topological probability rules for pattern selection in recurrent network are introduced. The first one selects patterns according to a...