238 research outputs found
Analytical calculation of the transition to complete phase synchronization in coupled oscillators
Here we present a system of coupled phase oscillators with nearest neighbors
coupling, which we study for different boundary conditions. We concentrate at
the transition to total synchronization. We are able to develop exact solutions
for the value of the coupling parameter when the system becomes completely
synchronized, for the case of periodic boundary conditions as well as for an
open chain with fixed ends. We compare the results with those calculated
numerically.Comment: 5 pages, 3 figure
VOICE RECOGNITION SECURITY SYSTEM USING MEL-FREQUENCY CEPSTRUM COEFFICIENTS
ABSTRACTObjective: Voice Recognition is a fascinating field spanning several areas of computer science and mathematics. Reliable speaker recognition is a hardproblem, requiring a combination of many techniques; however modern methods have been able to achieve an impressive degree of accuracy. Theobjective of this work is to examine various speech and speaker recognition techniques and to apply them to build a simple voice recognition system.Method: The project is implemented on software which uses different techniques such as Mel frequency Cepstrum Coefficient (MFCC), VectorQuantization (VQ) which are implemented using MATLAB.Results: MFCC is used to extract the characteristics from the input speech signal with respect to a particular word uttered by a particular speaker. VQcodebook is generated by clustering the training feature vectors of each speaker and then stored in the speaker database.Conclusion: Verification of the speaker is carried out using Euclidian Distance. For voice recognition we implement the MFCC approach using softwareplatform MatlabR2013b.Keywords: Mel-frequency cepstrum coefficient, Vector quantization, Voice recognition, Hidden Markov model, Euclidean distance
Dissipation-managed soliton in a quasi-one-dimensional Bose-Einstein condensate
We use the time-dependent mean-field Gross-Pitaevskii equation to study the
formation of a dynamically-stabilized dissipation-managed bright soliton in a
quasi-one-dimensional Bose-Einstein condensate (BEC). Because of three-body
recombination of bosonic atoms to molecules, atoms are lost (dissipated) from a
BEC. Such dissipation leads to the decay of a BEC soliton. We demonstrate by a
perturbation procedure that an alimentation of atoms from an external source to
the BEC may compensate for the dissipation loss and lead to a
dynamically-stabilized soliton. The result of the analytical perturbation
method is in excellent agreement with mean-field numerics. It seems possible to
obtain such a dynamically-stabilized BEC soliton without dissipation in
laboratory.Comment: 5 pages, 3 figure
PRABHA - A New Heuristic Approach For Machine Cell Formation Under Dynamic Production Environments
Over the past three decades, Cellular Manufacturing Systems (CMS) have attracted a lot of attention from manufacturers because of its positive impacts on analysis of batch-type production and also a wide range of potential application areas. Machine cell formation and part family creation are two important tasks of cellular manufacturing systems. Most of the current CMS design methods have been developed for a static production environment. This paper addresses the problem of machine cell formation and part family formation for a dynamic production requirement with the objective of minimizing the material handling cost, penalty for cell load variation and the machine relocation cost. The parameters considered include demand of parts in different period, routing sequences, processing time and machine capacities. In this work a new heuristic approach named PRABHA is proposed for machine cell formation and the part family formation. The computational results of the proposed heuristics approach were obtained and compared with the Genetic Algorithm approach and it was found that the proposed heuristics PRABHA outperforms the Genetic Algorithm
Suppression of extreme events and chaos in a velocity-dependent potential system with time-delay feedback
The foremost aim of this study is to investigate the influence of
time-delayed feedback on extreme events in a non-polynomial system with
velocity dependent potential. To begin, we investigate the effect of this
feedback on extreme events for four different values of the external forcing
parameter. Among these four values, in the absence of time-delayed feedback,
for two values, the system does not exhibit extreme events and for the other
two values, the system exhibits extreme events. On the introduction of
time-delayed feedback and varying the feedback strength, we found that extreme
events get suppressed as well as get induced. When the feedback is positive,
suppression occurs for a larger parameter region whereas in the case of
negative feedback it is restricted to the limited parameter region. We confirm
our results through Lyapunov exponents, probability density function of peaks,
plot and two parameter probability plot. Finally, we analyze the
changes in the overall dynamics of this system under the influence of
time-delayed feedback. We notice that complete suppression of chaos occurs in
the considered system for higher values of the time-delayed feedback.Comment: 28 pages, 16 figures, 1 table, Accepted for Publication Chaos,
Solitons & Fractal
Transition to complete synchronization in phase coupled oscillators with nearest neighbours coupling
We investigate synchronization in a Kuramoto-like model with nearest
neighbour coupling. Upon analyzing the behaviour of individual oscillators at
the onset of complete synchronization, we show that the time interval between
bursts in the time dependence of the frequencies of the oscillators exhibits
universal scaling and blows up at the critical coupling strength. We also bring
out a key mechanism that leads to phase locking. Finally, we deduce forms for
the phases and frequencies at the onset of complete synchronization.Comment: 6 pages, 4 figures, to appear in CHAO
Scaling and synchronization in a ring of diffusively coupled nonlinear oscillators
Chaos synchronization in a ring of diffusively coupled nonlinear oscillators
driven by an external identical oscillator is studied. Based on numerical
simulations we show that by introducing additional couplings at -th
oscillators in the ring, where is an integer and is the maximum
number of synchronized oscillators in the ring with a single coupling, the
maximum number of oscillators that can be synchronized can be increased
considerably beyond the limit restricted by size instability. We also
demonstrate that there exists an exponential relation between the number of
oscillators that can support stable synchronization in the ring with the
external drive and the critical coupling strength with a scaling
exponent . The critical coupling strength is calculated by numerically
estimating the synchronization error and is also confirmed from the conditional
Lyapunov exponents (CLEs) of the coupled systems. We find that the same scaling
relation exists for couplings between the drive and the ring. Further, we
have examined the robustness of the synchronous states against Gaussian white
noise and found that the synchronization error exhibits a power-law decay as a
function of the noise intensity indicating the existence of both noise-enhanced
and noise-induced synchronizations depending on the value of the coupling
strength . In addition, we have found that shows an
exponential decay as a function of the number of additional couplings. These
results are demonstrated using the paradigmatic models of R\"ossler and Lorenz
oscillators.Comment: Accepted for Publication in Physical Review
Self-trapping of a binary Bose-Einstein condensate induced by interspecies interaction
The problem of self-trapping of a Bose-Einstein condensate (BEC) and a binary
BEC in an optical lattice (OL) and double well (DW) is studied using the
mean-field Gross-Pitaevskii equation. For both DW and OL, permanent
self-trapping occurs in a window of the repulsive nonlinearity of the GP
equation: . In case of OL, the critical nonlinearities
and correspond to a window of chemical potentials
defining the band gap(s) of the periodic OL. The
permanent self-trapped BEC in an OL usually represents a breathing oscillation
of a stable stationary gap soliton. The permanent self-trapped BEC in a DW, on
the other hand, is a dynamically stabilized state without any stationary
counterpart. For a binary BEC with intraspecies nonlinearities outside this
window of nonlinearity, a permanent self trapping can be induced by tuning the
interspecies interaction such that the effective nonlinearities of the
components fall in the above window
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