Journal articles on the topic 'Distributed oscillatory system'
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1
Astakhov, Oleg V., Sergey V. Astakhov, Natalia S. Fadeeva, and Vladimir V. Astakhov. "Dynamics of the generator with three circuits in the feedback loop. Multistability formation and transition to chaos." Izvestiya of Saratov University. New series. Series: Physics 21, no. 1 (March 24, 2021): 21–28. http://dx.doi.org/10.18500/1817-3020-2021-21-1-21-28.
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Background and Objectives: Studying the dynamical mechanisms of the emergence of nonlinear phenomena that are characteristic for multimode self-oscillating systems consisting of interacting oscillators and an ensemble of passive oscillators or representing active nonlinear systems with complex feedback channels is an important urgent task. The simplest example of a self-oscillating system with a complex feedback is the well-known classical van der Pol oscillator with an additional linear oscillatory circuit included in the feedback channel. We investigate the behavior of the multimode system increasing the number of oscillatory circuits in the oscillator’s feedback loop. The research in this paper can help to better understand the mechanisms of multistability formation in infinite-dimensional self-oscillating systems such as a generator with delayed feedback and a generator with distributed feedback. Materials and Methods: The system equations were derived for the electronic scheme of the self-oscillating system. To describe the existing dynamic modes by numerical simulation methods, the projections of the phase portraits and the Poincare sections were obtained. To study the mechanisms of formation of multistable states, the bifurcation analysis methods were used. Results: It was found that the mechanism underlying the multistability formation is based on a sequence of two supercritical Andronov – Hopf bifurcations and a subcritical Neymark – Saker bifurcation. Therefore, the multistability emerges as a result of gaining stability by the unstable limit set that existed before the multistability appears. Conclusion: The discovered mechanism of multistability formation opens up wide possibilities for managing the multistability, which are inaccessible for systems in which the multistability is realized through tangential bifurcations. In contrast to the tangential bifurcation, the subcritical Neymark – Sacker bifurcation assumes the existence of a limit cycle both before and after the bifurcation. Thus, it is possible to use a wide range of methods and tools to stabilize saddle limit cycles in order to control the boundaries of the multistability region in the space of control parameters of the system.
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Akulenko, L. D. "Boundary kinematic control of a distributed oscillatory system." Journal of Applied Mathematics and Mechanics 71, no. 6 (January 2007): 862–68. http://dx.doi.org/10.1016/j.jappmathmech.2007.12.005.
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Bublik, B. N. "Stabilization problem for a two-dimensional oscillatory distributed system." Cybernetics and Systems Analysis 33, no. 4 (July 1997): 589–92. http://dx.doi.org/10.1007/bf02733116.
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Tayar, Alexandra M., Eyal Karzbrun, Vincent Noireaux, and Roy H. Bar-Ziv. "Synchrony and pattern formation of coupled genetic oscillators on a chip of artificial cells." Proceedings of the National Academy of Sciences 114, no. 44 (October 16, 2017): 11609–14. http://dx.doi.org/10.1073/pnas.1710620114.
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Understanding how biochemical networks lead to large-scale nonequilibrium self-organization and pattern formation in life is a major challenge, with important implications for the design of programmable synthetic systems. Here, we assembled cell-free genetic oscillators in a spatially distributed system of on-chip DNA compartments as artificial cells, and measured reaction–diffusion dynamics at the single-cell level up to the multicell scale. Using a cell-free gene network we programmed molecular interactions that control the frequency of oscillations, population variability, and dynamical stability. We observed frequency entrainment, synchronized oscillatory reactions and pattern formation in space, as manifestation of collective behavior. The transition to synchrony occurs as the local coupling between compartments strengthens. Spatiotemporal oscillations are induced either by a concentration gradient of a diffusible signal, or by spontaneous symmetry breaking close to a transition from oscillatory to nonoscillatory dynamics. This work offers design principles for programmable biochemical reactions with potential applications to autonomous sensing, distributed computing, and biomedical diagnostics.
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Jezzini, Sami H., Andrew A. V. Hill, Pavlo Kuzyk, and Ronald L. Calabrese. "Detailed Model of Intersegmental Coordination in the Timing Network of the Leech Heartbeat Central Pattern Generator." Journal of Neurophysiology 91, no. 2 (February 2004): 958–77. http://dx.doi.org/10.1152/jn.00656.2003.
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To address the general problem of intersegmental coordination of oscillatory neuronal networks, we have studied the leech heartbeat central pattern generator. The core of this pattern generator is a timing network that consists of two segmental oscillators, each of which comprises two identified, reciprocally inhibitory oscillator interneurons. Intersegmental coordination between the segmental oscillators is mediated by synaptic interactions between the oscillator interneurons and identified coordinating interneurons. The small number of neurons (8) and the distributed structure of the timing network have made the experimental analysis of the segmental oscillators as discrete, independent units possible. On the basis of this experimental work, we have made conductance-based models to explore how intersegmental phase and cycle period are determined. We show that although a previous simple model, which ignored many details of the living system, replicated some essential features of the living system, the incorporation of specific cellular and network properties is necessary to capture the behavior of the system seen under different experimental conditions. For example, spike frequency adaptation in the coordinating interneurons and details of asymmetries in intersegmental connectivity are necessary for replicating driving experiments in which one segmental oscillator was injected with periodic current pulses to entrain the activity of the entire network. Nevertheless, the basic mechanisms of phase and period control demonstrated here appear to be very general and could be used by other networks that produce coordinated segmental motor outflow.
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Kyrychko, Y. N., K. B. Blyuss, and E. Schöll. "Amplitude and phase dynamics in oscillators with distributed-delay coupling." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1999 (September 28, 2013): 20120466. http://dx.doi.org/10.1098/rsta.2012.0466.
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This paper studies the effects of distributed-delay coupling on the dynamics in a system of non-identical coupled Stuart–Landau oscillators. For uniform and gamma delay distribution kernels, the conditions for amplitude death are obtained in terms of average frequency, frequency detuning and the parameters of the coupling, including coupling strength and phase, as well as the mean time delay and the width of the delay distribution. To gain further insights into the dynamics inside amplitude death regions, the eigenvalues of the corresponding characteristic equations are computed numerically. Oscillatory dynamics of the system is also investigated, using amplitude and phase representation. Various branches of phase-locked solutions are identified, and their stability is analysed for different types of delay distributions.
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Baetov, A. K., Zh T. Beksultanov, Zh K. Asanova, and Zh M. Soltohkulova. "OPTIMUM CONTROL OF A QUASILINEAR OSCILLATORY SYSTEM WITH DISTRIBUTED PARAMETERS." Современные наукоемкие технологии (Modern High Technologies), no. 10 2020 (2020): 9–16. http://dx.doi.org/10.17513/snt.38247.
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Du, Lili, Wei Fu, and Mingshu Fan. "Oscillatory solutions of delay hyperbolic system with distributed deviating arguments." Applied Mathematics and Computation 154, no. 2 (July 2004): 521–29. http://dx.doi.org/10.1016/s0096-3003(03)00732-x.
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Agaoglou, Makrina, Michal Fečkan, Michal Pospíšil, Vassilis Rothos, and Alexander Vakakis. "Periodically Forced Nonlinear Oscillatory Acoustic Vacuum." Axioms 7, no. 4 (September 22, 2018): 69. http://dx.doi.org/10.3390/axioms7040069.
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In this work, we study the in-plane oscillations of a finite lattice of particles coupled by linear springs under distributed harmonic excitation. Melnikov-type analysis is applied for the persistence of periodic oscillations of a reduced system.
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Ghazanfar, Asif A., and Donald B. Katz. "Distributed neural substrates and the evolution of speech production." Behavioral and Brain Sciences 21, no. 4 (August 1998): 516–17. http://dx.doi.org/10.1017/s0140525x9828126x.
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There is evidence of reciprocal connectivity, similarity of oscillatory responses to stimulation of multiple motor and somatosensory cortices, whole system oscillation, and short- latency responses to behavioral perturbation. These suggest that frame/content may be instantiated by overlapping neural populations, and that the genesis of frame oscillations may be profitably thought of as an emergent property of a distributed neural system.
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Ryskin, N. M., and A. M. Shigaev. "Complex dynamics of a simple distributed self-oscillatory model system with delay." Technical Physics 47, no. 7 (July 2002): 795–802. http://dx.doi.org/10.1134/1.1495037.
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Lanets, O. S., V. T. Dmytriv, V. M. Borovets, I. A. Derevenko, and I. M. Horodetskyy. "Analytical Model of the Two-Mass Above Resonance System of the Eccentric-Pendulum Type Vibration Table." International Journal of Applied Mechanics and Engineering 25, no. 4 (December 1, 2020): 116–29. http://dx.doi.org/10.2478/ijame-2020-0053.
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AbstractThe article deals with atwo-mass above resonant oscillatory system of an eccentric-pendulum type vibrating table. Based on the model of a vibrating oscillatory system with three masses, the system of differential equations of motion of oscillating masses with five degrees of freedom is compiled using generalized Lagrange equations of the second kind. For given values of mechanical parameters of the oscillatory system and initial conditions, the autonomous system of differential equations of motion of oscillating masses is solved by the numerical Rosenbrock method. The results of analytical modelling are verified by experimental studies. The two-mass vibration system with eccentric-pendulum drive in resonant oscillation mode is characterized by an instantaneous start and stop of the drive without prolonged transient modes. Parasitic oscillations of the working body, as a body with distributed mass, are minimal at the frequency of forced oscillations.
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Kubyshkin, E. P. "The Effect of Domain Deformation on the Behavior of a Distributed Kinetic System." Modeling and Analysis of Information Systems 20, no. 1 (March 18, 2015): 99–106. http://dx.doi.org/10.18255/1818-1015-2013-1-99-106.
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The behavior of a distributed kinetic system, which is in homogeneous equilibrium within a flat circular reactor, under circular domain deformation is studied. We show that the deformation of domain may lead to appearance of stable spatially inhomogeneous oscillatory solutions, including chaotic oscillations (strange attractors), in the neighborhood of homogeneous equilibrium. We also speak about mechanisms of initiation of chaotic attractors and calculate Lyapunov exponents and Lyapunov dimension for these regimes. We call this mechanism of appearance of spatially inhomogeneous nonlinear oscillations in distributed kinetic system the domain effect.
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Xu, Tianqi, Jing Huo, Shuai Shao, Michelle Po, Taizo Kawano, Yangning Lu, Min Wu, Mei Zhen, and Quan Wen. "Descending pathway facilitates undulatory wave propagation in Caenorhabditis elegans through gap junctions." Proceedings of the National Academy of Sciences 115, no. 19 (April 23, 2018): E4493—E4502. http://dx.doi.org/10.1073/pnas.1717022115.
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Descending signals from the brain play critical roles in controlling and modulating locomotion kinematics. In the Caenorhabditis elegans nervous system, descending AVB premotor interneurons exclusively form gap junctions with the B-type motor neurons that execute forward locomotion. We combined genetic analysis, optogenetic manipulation, calcium imaging, and computational modeling to elucidate the function of AVB-B gap junctions during forward locomotion. First, we found that some B-type motor neurons generate rhythmic activity, constituting distributed oscillators. Second, AVB premotor interneurons use their electric inputs to drive bifurcation of B-type motor neuron dynamics, triggering their transition from stationary to oscillatory activity. Third, proprioceptive couplings between neighboring B-type motor neurons entrain the frequency of body oscillators, forcing coherent bending wave propagation. Despite substantial anatomical differences between the motor circuits of C. elegans and higher model organisms, converging principles govern coordinated locomotion.
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Khadem Abbasi, Alireza, and Mohd Wazir Mustafa. "Mathematical Model and Stability Analysis of Inverter-Based Distributed Generator." Mathematical Problems in Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/195038.
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This paper presents a mathematical (small-signal) model of an electronically interfaced distributed generator (DG) by considering the effect of voltage and frequency variations of the prime source. Dynamic equations are found by linearization about an operating point. In this study, the dynamic of DC part of the interface is included in the model. The stability analysis shows with proper selection of system parameters; the system is stable during steady-state and dynamic situations, and oscillatory modes are well damped. The proposed model is useful to study stability analysis of a standalone DG or a Microgrid.
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Chaban, Andriy, Marek Lis, Andrzej Szafraniec, and Radoslaw Jedynak. "Application of Genetic Algorithm Elements to Modelling of Rotation Processes in Motion Transmission Including a Long Shaft." Energies 14, no. 1 (December 28, 2020): 115. http://dx.doi.org/10.3390/en14010115.
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Genetic algorithms are used to parameter identification of the model of oscillatory processes in complicated motion transmission of electric drives containing long elastic shafts as systems of distributed mechanical parameters. Shaft equations are generated on the basis of a modified Hamilton–Ostrogradski principle, which serves as the foundation to analyse the lumped parameter system and distributed parameter system. They serve to compute basic functions of analytical mechanics of velocity continuum and rotational angles of shaft elements. It is demonstrated that the application of the distributed parameter method to multi-mass rotational systems, that contain long elastic elements and complicated control systems, is not always possible. The genetic algorithm is applied to determine the coefficients of approximation the system of Rotational Transmission with Elastic Shaft by equivalent differential equations. The fitness function is determined as least-square error. The obtained results confirm that application of the genetic algorithms allow one to replace the use of a complicated distributed parameter model of mechanical system by a considerably simpler model, and to eliminate sophisticated calculation procedures and identification of boundary conditions for wave motion equations of long elastic elements.
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Sammon, M. "Symmetry, bifurcations, and chaos in a distributed respiratory control system." Journal of Applied Physiology 77, no. 5 (November 1, 1994): 2481–95. http://dx.doi.org/10.1152/jappl.1994.77.5.2481.
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A multivariate model is outlined for a distributed respiratory central pattern generator (RCPG) and its afferent control. Oscillatory behavior of the system depends on structure and symmetry of a matrix of phase-switching functions (F omega, phi) that control distribution of central excitation (CE) and inhibition (CI) within the circuit. The matrix diagonal (F omega) controls activation of CI variables as excitatory inputs are altered (e.g., central and afferent contributions to inspiratory off switch); off-diagonal terms (F phi) distribute excitations within the CI system and produce complex eigenvalues at the switching points between inspiration and expiration. For null F phi, phase switchings of saddle equilibria located at end expiration and end inspiration are overdamped all-or-nothing events; graded control of CI is seen for phi > 0. When coupling is significant (phi >> 0), CI dynamics become underdamped, admitting a domain of inputs where chaotic behavior is predictably observed. For the homogeneous RCPG (symmetric F omega, phi), CE oscillations are one-dimensional limit cycles (D = 1) or weakly chaotic (D approximately equal to 1). When perturbations from symmetry are significant, the distributed RCPG becomes partitioned where strongly chaotic oscillations (D > or = 2) and central apnea (D = 0) are seen more frequently. The equations provide means for mapping Silnikov bifurcations that alter the geometry and dimension of the breathing pattern and formalisms for discussing RCPG processing of afferent information.
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Wu, Hui, and Dongwook Kim. "Distribution of Order Parameter for Kuramoto Model." International Journal for Innovation Education and Research 3, no. 9 (September 30, 2015): 52–68. http://dx.doi.org/10.31686/ijier.vol3.iss9.432.
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The synchronization in large populations of interacting oscillators has been observed abundantly in nature, emergining in fields such as physical, biological and chemical system. For this reason, many scientists are seeking to understand the underlying mechansim of the generation of synchronous patterns in oscillatory system. The synchronization is analyzed in one of the most representative models of coupled phase oscillators, the Kuramoto model. The Kuramoto model can be used to understand the emergence of synchronization in nextworks of coupled, nonlinear oscillators. In particular, this model presents a phase transition from incoherence to synchronization. In this paper, we investigated the distribution of order parameter γ which describes the strength of synchrony of these oscillators. The larger the order parameter γ is, the more extent the oscillators are synchronized together. This order parameter γ is a critical parameter in the Kuramoto model. Kuramoto gave a initial estimate equation for the value of the order parameter by giving the value of the coupling constant. But our numerical results show that the distribution of the order parameter is slightly different from Kuramoto’s estimation. We gave an estimation for the distribution of order parameter for different values of initial conditions. We discussed how the numerical result will be distributed around Kuramoto’s analytical equation.
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GORYACHEV, ANDREI, RAYMOND KAPRAL, and HUGUES CHATÉ. "SYNCHRONIZATION DEFECT LINES." International Journal of Bifurcation and Chaos 10, no. 07 (July 2000): 1537–64. http://dx.doi.org/10.1142/s0218127400000992.
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Spatially distributed reaction–diffusion media where the local dynamics exhibits complex oscillatory or chaotic dynamics are investigated. Spiral waves in such complex-oscillatory or excitable media contain synchronization defect lines which separate domains of different oscillation phases and across which the phase changes by multiples of 2π. Such synchronization defect lines arise from the need to reconcile the rotation period of a one-armed spiral wave with the oscillation period of the local dynamics. We analyze synchronization defect lines and show how to classify them and enumerate their types. In certain parameter regions the spatially distributed system exhibits line defect turbulence arising from the nucleation, growth and destruction of defect lines. The transitions to line defect turbulence may be characterized by power law behavior of order parameters and may be described as nonequilibrium phase transitions.
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Vukelić, Mathias, Katharina Lingelbach, Kathrin Pollmann, and Matthias Peissner. "Oscillatory EEG Signatures of Affective Processes during Interaction with Adaptive Computer Systems." Brain Sciences 11, no. 1 (December 31, 2020): 35. http://dx.doi.org/10.3390/brainsci11010035.
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Affect monitoring is being discussed as a novel strategy to make adaptive systems more user-oriented. Basic knowledge about oscillatory processes and functional connectivity underlying affect during naturalistic human–computer interactions (HCI) is, however, scarce. This study assessed local oscillatory power entrainment and distributed functional connectivity in a close-to-naturalistic HCI-paradigm. Sixteen participants interacted with a simulated assistance system which deliberately evoked positive (supporting goal-achievement) and negative (impeding goal-achievement) affective reactions. Electroencephalography (EEG) was used to examine the reactivity of the cortical system during the interaction by studying both event-related (de-)synchronization (ERD/ERS) and event-related functional coupling of cortical networks towards system-initiated assistance. Significantly higher α-band and β-band ERD in centro-parietal and parieto-occipital regions and β-band ERD in bi-lateral fronto-central regions were observed during impeding system behavior. Supportive system behavior activated significantly higher γ-band ERS in bi-hemispheric parietal-occipital regions. This was accompanied by functional coupling of remote β-band and γ-band activity in the medial frontal, left fronto-central and parietal regions, respectively. Our findings identify oscillatory signatures of positive and negative affective processes as reactions to system-initiated assistance. The findings contribute to the development of EEG-based neuroadaptive assistance loops by suggesting a non-obtrusive method for monitoring affect in HCI.
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Sekar, R., and D. Murugan. "Linear Stability Effect of Densely Distributed Porous Medium and Coriolis Force on Soret Driven Ferrothermohaline Convection." International Journal of Applied Mechanics and Engineering 23, no. 4 (November 1, 2018): 911–28. http://dx.doi.org/10.2478/ijame-2018-0051.
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Abstract The effect of Coriolis force on the Soret driven ferrothermohaline convection in a densely packed porous medium has been studied. A linear stability analysis is carried out using normal mode technique. It is found that stationary convection is favorable for the Darcy model, therefore oscillatory instability is studied. A small thermal perturbation is applied to the basic state and linear stability analysis is used for which the normal mode technique is applied. It is found that the presence of a porous medium favours the onset of convection. The porous medium is assumed to be variable and the effect of the permeable parameter is to destabilize the system. The present work has been carried out both for oscillatory as well as stationary instabilities. The results are depicted graphically.
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YUAN, YUEYANG, CHONGCHANG YANG, ZHE LI, ZHIXIN CAO, SIMON ZHANG, and JASON SUN. "OSCILLATORY FLOW OF HFV DISTRIBUTED IN LEFT AND RIGHT LUNGS: A MODEL-BASED EXPERIMENT AND INVESTIGATION." Journal of Mechanics in Medicine and Biology 14, no. 06 (December 2014): 1440015. http://dx.doi.org/10.1142/s0219519414400156.
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The human respiratory system is not entirely symmetric, and regional respiratory diseases can further enlarge this difference in most cases. Therefore, the lungs perform differently. This paper explored the possibilities of suppressing and enhancing the performance of a diseased lung with different high-frequency ventilation (HFV) frequencies by experimenting, as well as modeling, the oscillatory airflow distribution between the left and right lungs. The experimental setup mainly consisted of a physical respiratory model, a signal acquisition device, and a high-frequency oscillation ventilator. This ventilator outputs a positive sinusoidal air-pressure during inspiration. On these bases, a series of experiments were also conducted with different compliances and resistances in the left and the right lungs. The experiments demonstrated that the oscillatory flow distribution is primarily correlated with the oscillation frequency and the regional lung compliance.
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RYBALKO, SERGEI, and EKATERINA ZHUCHKOVA. "A GENERALIZED MODEL OF ACTIVE MEDIA WITH A SET OF INTERACTING PACEMAKERS: APPLICATION TO THE HEART BEAT ANALYSIS." International Journal of Bifurcation and Chaos 19, no. 01 (January 2009): 263–79. http://dx.doi.org/10.1142/s0218127409022865.
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We propose a fairly general model of active media by considering of the interaction between pacemakers via their phase response curves. This model describes a network of pulse oscillators coupled by their response to the internal depolarization of mutual stimulations. First, a macroscopic level corresponding to an arbitrary large number of oscillatory elements coupled globally is considered. As a specific and important case of the proposed model, the bidirectional interaction of two cardiac nodes is described. This case is generalized by means of an additional pacemaker, which can be expounded as an external stimulator. The behavior of such a system is analyzed. Second, the microscopic level corresponding to the representation of cardiac nodes by two-dimensional lattices of pulse oscillators coupled via the nearest neighbors is described. The model is a universal one in the sense that on its basis one can easily construct discrete distributed media of active elements, which interact via phase response curves.
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Singer, Wolf. "The Brain, a Complex Self-organizing System." European Review 17, no. 2 (May 2009): 321–29. http://dx.doi.org/10.1017/s1062798709000751.
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Our intuition assumes that there is a centre in our brain in which all relevant information converges and where all decisions are reached. To neurobiologists, the brain presents itself as a highly distributed system in which a very large number of processes occur simultaneously and in parallel without requiring coordination by a central convergence centre. The specific architecture resembles, in many respects, small world networks and raises the question of how the multiple operations occurring in parallel are bound together in order to give rise to coherent perception and action. Based on data obtained with massive parallel recordings, the hypothesis will be forwarded that temporal coherence serves as an important organizing principle and that this coherence is achieved by the synchronization of oscillatory activity in distinct frequency bands.
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Prakash, J., P. Kumar, S. Manan, and K. R. Sharma. "The Effect of Magnetic Field Dependent Viscosity on Ferromagnetic Convection in a Rotating Sparsely Distributed Porous Medium - Revisited." International Journal of Applied Mechanics and Engineering 25, no. 1 (March 1, 2020): 142–58. http://dx.doi.org/10.2478/ijame-2020-0010.
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AbstractThe effect of magnetic field dependent (MFD) viscosity on the thermal convection in a ferrofluid layer saturating a sparsely distributed porous medium has been investigated by using the Darcy-Brinkman model in the simultaneous presence of a uniform vertical magnetic field and a uniform vertical rotation. A correction is applied to the study of Vaidyanathan et al. [11] which is very important in order to predict the correct behavior of MFD viscosity. A linear stability analysis has been carried out for stationary modes and oscillatory modes separately. The critical wave number and critical Rayleigh number for the onset of instability, for the case of free boundaries, are determined numerically for sufficiently large values of the magnetic parameter M1. Numerical results are obtained and are illustrated graphically. It is shown that magnetic field dependent viscosity has a destabilizing effect on the system for the case of stationary mode and a stabilizing effect for the case of oscillatory mode, whereas magnetization has a destabilizing effect.
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Tkachova, S. A., A. S. Maltsev, A. A. Fedotov, A. S. Gunkina, and O. Ja Kravets. "Optimal control of pulse compensators of oscillatory phenomena in a network oil and gas pipeline system." Journal of Physics: Conference Series 2094, no. 5 (November 1, 2021): 052024. http://dx.doi.org/10.1088/1742-6596/2094/5/052024.
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Abstract Within the framework of oil and gas engineering, the problem of optimal control of pulse compensators that counteract harmful oscillatory phenomena in a continuous medium during transportation via network gas-hydraulic carriers is considered. Powerful compressor units that create high pressure in the carrier of a continuous medium, to a large extent contribute to the formation of undesirable oscillatory phenomena (pulsations) that occur at the output of these compressors. These ripples are transmitted to the network carrier environment, which significantly reduces the efficiency of compressor units and even causes accidents in the networks of gas and hydraulic carriers. The latter means that the software engineering of the oil and gas industry should include research in the direction of improving the reliability of operation of compressor units and gas-hydraulic carriers. In the presented study, the mathematical description of the oscillatory process of a continuous medium is carried out by formalisms of a differential-difference system of hyperbolic equations with distributed parameters on a graph. At the same time, the mathematical model contains a fairly accurate mathematical description of controlled pulse compensators. The problem of controlling pulse compensators of an oscillatory process is considered as the problem of a point control action on a controlled differential-difference system at the places where continuous medium vibration dampers are connected to a network carrier. This is a characteristic feature of the presented study, which is quite often used in practice when engineering the processes of transporting various kinds of continuous media through network oil and gas carriers. The study essentially uses the conjugate state and the conjugate system for a differential-difference system - the relations determining the optimal point control are obtained. The results of the work are applicable in the framework of oil and gas engineering to the study of issues of stabilization and parametric optimization.
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Wang, Zhipeng, Davit A. Potoyan, and Peter G. Wolynes. "Stochastic resonances in a distributed genetic broadcasting system: the NF κ B/I κ B paradigm." Journal of The Royal Society Interface 15, no. 138 (January 2018): 20170809. http://dx.doi.org/10.1098/rsif.2017.0809.
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Gene regulatory networks must relay information from extracellular signals to downstream genes in an efficient, timely and coherent manner. Many complex functional tasks such as the immune response require system-wide broadcasting of information not to one but to many genes carrying out distinct functions whose dynamical binding and unbinding characteristics are widely distributed. In such broadcasting networks, the intended target sites are also often dwarfed in number by the even more numerous non-functional binding sites. Taking the genetic regulatory network of NF κ B as an exemplary system we explore the impact of having numerous distributed sites on the stochastic dynamics of oscillatory broadcasting genetic networks pointing out how resonances in binding cycles control the network's specificity and performance. We also show that active kinetic regulation of binding and unbinding through molecular stripping of DNA bound transcription factors can lead to a higher coherence of gene-co-expression and synchronous clearance.
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Begum, Mahmuda, Mohsen Eskandari, Mohammad Abuhilaleh, Li Li, and Jianguo Zhu. "Fuzzy-Based Distributed Cooperative Secondary Control with Stability Analysis for Microgrids." Electronics 10, no. 4 (February 7, 2021): 399. http://dx.doi.org/10.3390/electronics10040399.
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This research suggests a novel distributed cooperative control methodology for a secondary controller in islanded microgrids (MGs). The proposed control technique not only brings back the frequency/voltage to its reference values, but also maintains precise active and reactive power-sharing among distributed generation (DG) units by means of a sparse communication system. Due to the dynamic behaviour of distributed secondary control (DSC), stability issues are a great concern for a networked MG. To address this issue, the stability analysis is undertaken systematically, utilizing the small-signal state-space linearized model of considering DSC loops and parameters. As the dynamic behaviour of DSC creates new oscillatory modes, an intelligent fuzzy logic-based parameter-tuner is proposed for enhancing the system stability. Accurate tuning of the DSC parameters can develop the functioning of the control system, which increases MG stability to a greater extent. Moreover, the performance of the offered control method is proved by conducting a widespread simulation considering several case scenarios in MATLAB/Simscape platform. The proposed control method addresses the dynamic nature of the MG by supporting the plug-and-play functionality, and working even in fault conditions. Finally, the convergence and comparison study of the offered control system is shown.
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Noori, Rabiya, Daniel Park, John D. Griffiths, Sonya Bells, Paul W. Frankland, Donald Mabbott, and Jeremie Lefebvre. "Activity-dependent myelination: A glial mechanism of oscillatory self-organization in large-scale brain networks." Proceedings of the National Academy of Sciences 117, no. 24 (June 1, 2020): 13227–37. http://dx.doi.org/10.1073/pnas.1916646117.
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Communication and oscillatory synchrony between distributed neural populations are believed to play a key role in multiple cognitive and neural functions. These interactions are mediated by long-range myelinated axonal fiber bundles, collectively termed as white matter. While traditionally considered to be static after development, white matter properties have been shown to change in an activity-dependent way through learning and behavior—a phenomenon known as white matter plasticity. In the central nervous system, this plasticity stems from oligodendroglia, which form myelin sheaths to regulate the conduction of nerve impulses across the brain, hence critically impacting neural communication. We here shift the focus from neural to glial contribution to brain synchronization and examine the impact of adaptive, activity-dependent changes in conduction velocity on the large-scale phase synchronization of neural oscillators. Using a network model based on primate large-scale white matter neuroanatomy, our computational and mathematical results show that such plasticity endows white matter with self-organizing properties, where conduction delay statistics are autonomously adjusted to ensure efficient neural communication. Our analysis shows that this mechanism stabilizes oscillatory neural activity across a wide range of connectivity gain and frequency bands, making phase-locked states more resilient to damage as reflected by diffuse decreases in connectivity. Critically, our work suggests that adaptive myelination may be a mechanism that enables brain networks with a means of temporal self-organization, resilience, and homeostasis.
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Berman, N., H. F. Chou, A. Berman, and E. Ipp. "A mathematical model of oscillatory insulin secretion." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 264, no. 5 (May 1, 1993): R839—R851. http://dx.doi.org/10.1152/ajpregu.1993.264.5.r839.
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Insulin is secreted in sustained oscillatory fashion from isolated islets of Langerhans. This finding has led to the assumption of an underlying synchronizing process that coordinates insulin oscillations. This assumption was tested by developing a mathematical model of oscillatory insulin secretion in which we included degree of synchrony as a parameter. We first evaluated insulin oscillations in perifused isolated rat islets, using spectral analysis to determine their regularity and frequency. A parsimonious mathematical model was developed to account for these characteristics. The model postulates a group of secretory units discharging at discrete intervals with the same underlying period. Variation from two sources, phase differences between units (synchrony) and regularity within units, is introduced by adding two normally distributed random variables with standard deviations (Sg and Si, respectively) to the secretory period. Sets of 100 simulations for different values of Sg and Si were run. Results of the simulations suggest that the system tolerates a relatively large degree of asynchrony yet still demonstrates regularity of oscillations on spectral analysis. Comparison with perifusion data suggests that a moderate degree of asynchrony between islets can best account for the pattern of insulin oscillations observed. This model provides a theoretical basis for the study of mechanisms for insulin oscillations.
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Korzhik, Oleksii Volodymyrovych, Oleh Mykolaiovych Petrishchev, and N. Yu Filippova. "Axisymmetric vibrations of a cylindrical final height piezoceramic shell." Electronics and Communications 16, no. 6 (May 29, 2012): 25–29. http://dx.doi.org/10.20535/2312-1807.2011.16.6.240459.
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A new approach to describing the formation of an electric field in a material is proposed electroelastic transducer, which presented in the form of a cylindrical circular thin-walled radial polarized shell. The problem was solved by the "end-to-end" method, which involves a joint solution equations for acoustic, mechanical and electric fields taking into account physical properties of the emitting transducer. The general analytical solution "end-to-end" problem in the form of a system of resulting equations for the considered electroelastic oscillatory system in vacuum with distributed parameters written with respect to axial and radial displacement
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Priezjev, Nikolai V. "Shear Band Formation in Amorphous Materials under Oscillatory Shear Deformation." Metals 10, no. 3 (February 26, 2020): 300. http://dx.doi.org/10.3390/met10030300.
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The effect of periodic shear on strain localization in disordered solids is investigated using molecular dynamics simulations. We consider a binary mixture of one million atoms annealed to a low temperature with different cooling rates and then subjected to oscillatory shear deformation with a strain amplitude slightly above the critical value. It is found that the yielding transition occurs during one cycle but the accumulation of irreversible displacements and initiation of the shear band proceed over larger number of cycles for more slowly annealed glasses. The spatial distribution and correlation function of nonaffine displacements reveal that their collective dynamics changes from homogeneously distributed small clusters to a system-spanning shear band. The analysis of spatially averaged profiles of nonaffine displacements indicates that the location of a shear band in periodically loaded glasses can be identified at least several cycles before yielding. These insights are important for the development of novel processing methods and prediction of the fatigue lifetime of metallic glasses.
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Schoof, C., C. A. Rada, N. J. Wilson, G. E. Flowers, and M. Haseloff. "Oscillatory subglacial drainage in the absence of surface melt." Cryosphere 8, no. 3 (May 22, 2014): 959–76. http://dx.doi.org/10.5194/tc-8-959-2014.
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Abstract. The presence of strong diurnal cycling in basal water pressure records obtained during the melt season is well established for many glaciers. The behaviour of the drainage system outside the melt season is less well understood. Here we present borehole observations from a surge-type valley glacier in the St Elias Mountains, Yukon Territory, Canada. Our data indicate the onset of strongly correlated multi-day oscillations in water pressure in multiple boreholes straddling a main drainage axis, starting several weeks after the disappearance of a dominant diurnal mode in August 2011 and persisting until at least January 2012, when multiple data loggers suffered power failure. Jökulhlaups provide a template for understanding spontaneous water pressure oscillations not driven by external supply variability. Using a subglacial drainage model, we show that water pressure oscillations can also be driven on a much smaller scale by the interaction between conduit growth and distributed water storage in smaller water pockets, basal crevasses and moulins, and that oscillations can be triggered when water supply drops below a critical value. We suggest this in combination with a steady background supply of water from ground water or englacial drainage as a possible explanation for the observed wintertime pressure oscillations.
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Schoof, C., C. A. Rada, N. J. Wilson, G. E. Flowers, and M. Haseloff. "Oscillatory subglacial drainage in the absence of surface melt." Cryosphere Discussions 7, no. 6 (November 20, 2013): 5613–57. http://dx.doi.org/10.5194/tcd-7-5613-2013.
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Abstract. The presence of strong diurnal cycling in basal water pressure records obtained during the melt season is well-established for many glaciers. The behaviour of the drainage system outside the melt season is less well understood. Here we present borehole observations from a surge-type valley glacier in the St Elias Mountains, Yukon Territory, Canada. These indicate the onset of strongly correlated multi-day oscillations in water pressure in multiple boreholes straddling a main drainage axis, starting several weeks after the disappearance of a dominant diurnal mode in August 2011 and persisting until at least January 2012, when multiple data loggers suffered power failure. Jökulhlaups provide a template for understanding spontaneous water pressure oscillations not driven by external supply variability. Using a subglacial drainage model, we show that water pressure oscillations can also be driven on a much smaller scale by the interaction between conduit growth and distributed water storage in smaller water pockets, basal crevasses and moulins, and that oscillations can be triggered when water supply drops below a critical value. We suggest this in combination with a steady background supply of water from groundwater or englacial drainage as a possible explanation for the observed wintertime pressure oscillations.
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Kim, Sang H., and Vladimir Hlavacek. "Qualitative Properties of Autocatalytic Reactions Occurring in a Flow System." Zeitschrift für Naturforschung A 40, no. 7 (July 1, 1985): 736–47. http://dx.doi.org/10.1515/zna-1985-0715.
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The dynamic behavior of an autocatalytic reaction with a product inhibition term is studied in a flow system. A unique steady state exists in the continuous tank reactor. Linear stability analysis predicts either a stable node, a focus or an unstable saddle-focus. Sustained oscillations around the unstable focus can occur for high values of the Damköhler number (Da). In the distributed system, travelling, standing or complex oscillatory waves are detected. For a low value of Da, travelling waves with a pseudo-constant pattern are observed. With an intermediate value of Da, single or multiple standing waves are obtained. The temporal behavior indicates also the appearance of retriggering or echo waves. For a high value of Da, both single peak and complex multipeak oscillations are found. In the cell model, both regular oscillations near the inlet and chaotic behavior downstream are observed. In the dispersion model, higher Peclet numbers (Pe) eliminate the oscillations. The spatial profile shows a train of pulsating waves for the discrete model and a single pulsating or solitary wave for the continuous model.
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Boehmer, Tyler, and Sven Bilén. "Low-Power GPS-Disciplined Oscillator Module for Distributed Wireless Sensor Nodes." Electronics 10, no. 6 (March 18, 2021): 716. http://dx.doi.org/10.3390/electronics10060716.
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Many sensor systems, such as distributed wireless sensor arrays, require high-accuracy timing while maintaining low power consumption. Although the capabilities of chip-scale atomic clocks have advanced significantly, their cost continues to be prohibitive for many applications. GPS signals are commonly used to discipline local oscillators in order to inherit the long-term stability of GPS timing; however, commercially available GPS-disciplined oscillators typically use temperature-controlled oscillators and take an extended period of time to reach their stated accuracy, resulting in a large power consumption, usually over a watt. This has subsequently limited their adoption in low-power applications. Modern temperature-compensated crystal oscillators now have stabilities that enable the possibility of duty cycling a GPS receiver and intermittently correcting the oscillator for drift. Based on this principle, a design for a GPS-disciplined oscillator is presented that achieves an accuracy of 5 μs rms in its operational environment, while consuming only 45 mW of average power. The circuit is implemented in a system called geoPebble, which uses a large grid of wireless sensors to perform glacial reflectometry.
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Chen, Cheng-Wu. "Modeling and Fuzzy PDC Control and Its Application to an Oscillatory TLP Structure." Mathematical Problems in Engineering 2010 (2010): 1–13. http://dx.doi.org/10.1155/2010/120403.
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An analytical solution is derived to describe the wave-induced flow field and surge motion of a deformable platform structure controlled with fuzzy controllers in an oceanic environment. In the controller design procedure, a parallel distributed compensation (PDC) scheme is utilized to construct a global fuzzy logic controller by blending all local state feedback controllers. The Lyapunov method is used to carry out stability analysis of a real system structure. The corresponding boundary value problems are then incorporated into scattering and radiation problems. These are analytically solved, based on the separation of variables, to obtain a series of solutions showing the harmonic incident wave motion and surge motion. The dependence of the wave-induced flow field and its resonant frequency on wave characteristics and structural properties including platform width, thickness and mass can thus be drawn with a parametric approach. The wave-induced displacement of the surge motion is determined from these mathematical models. The vibration of the floating structure and mechanical motion caused by the wave force are also discussed analytically based on fuzzy logic theory and the mathematical framework to find the decay in amplitude of the surge motion in the tension leg platform (TLP) system. The expected effects of the damping in amplitude of the surge motion due to the control force on the structural response are obvious.
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Markenscoff, X., Luqun Ni, and J. Dundurs. "The Interface Anticrack and Green’s Functions for Interacting Anticracks and Cracks/Anticracks." Journal of Applied Mechanics 61, no. 4 (December 1, 1994): 797–802. http://dx.doi.org/10.1115/1.2901559.
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Solution is obtained for an anticrack-a bonded rigid lamella inclusion-at the interface between two isotropic elastic solids. The problem is formulated in terms of distributed line-loads at the anticrack which constitute the Green’s functions and the system of the governing coupled integral equations is solved analytically in closed form for the cases of uniform biaxial tension and of anticracks loaded by concentrated forces or moment. Solutions are also obtained by the interaction of an interface anticrack with a first-order singularity (concentrated force and dislocation) and second-order singularity (doublet of forces) at the interface. In the latter case the limit as the second-order singularity approaches the tip of the anticrack does not exist, but neither can a finite limit be obtained by reseating as in the homogeneous material. The solution of the interface anticrack exhibits the oscillatory singularities that appear at interface cracks which indicates that the overlapping of the displacement on the crack faces is not’the reason for this anomalous behavior. Moreover, it should be pointed out that the material condition that the stress does not exhibit oscillatory behavior is not the same as for interface cracks: for anticracks it is κ1 (1−β) = κ2 (1 + β) while for cracks it is β = 0.
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Alayi, Reza, Farhad Zishan, Seyed Reza Seyednouri, Ravinder Kumar, Mohammad Hossein Ahmadi, and Mohsen Sharifpur. "Optimal Load Frequency Control of Island Microgrids via a PID Controller in the Presence of Wind Turbine and PV." Sustainability 13, no. 19 (September 27, 2021): 10728. http://dx.doi.org/10.3390/su131910728.
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This article studied the load frequency control (LFC) of a multi-source microgrid with the presence of renewable energy sources. To maintain a sustainable power supply, the frequency of the system must be kept constant. A Proportional–Integral–Derivative (PID) controller is presented as a secondary controller to control the frequency of the microgrid in island mode, and the integral of squared time multiplied by error squared (ISTES) is used as a performance index. The use of the Craziness-Based Particle Swarm Optimization (CRPSO), which is an improved version of Particle Swarm Optimization (PSO), improves the convergence speed in optimizing the nonlinear problem of load and frequency controller design. The test microgrid is composed of the load and distributed generation units such as diesel generators, photovoltaics and wind turbines. The proposed controller provided the desired response to adjusting the microgrid frequency, achieving the final response after a short time and making it more stable and less oscillatory compared with the conventional system.
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Oppermann, Frank, Uwe Hassler, Jörg D. Jescheniak, and Thomas Gruber. "The Rapid Extraction of Gist—Early Neural Correlates of High-level Visual Processing." Journal of Cognitive Neuroscience 24, no. 2 (February 2012): 521–29. http://dx.doi.org/10.1162/jocn_a_00100.
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The human cognitive system is highly efficient in extracting information from our visual environment. This efficiency is based on acquired knowledge that guides our attention toward relevant events and promotes the recognition of individual objects as they appear in visual scenes. The experience-based representation of such knowledge contains not only information about the individual objects but also about relations between them, such as the typical context in which individual objects co-occur. The present EEG study aimed at exploring the availability of such relational knowledge in the time course of visual scene processing, using oscillatory evoked gamma-band responses as a neural correlate for a currently activated cortical stimulus representation. Participants decided whether two simultaneously presented objects were conceptually coherent (e.g., mouse–cheese) or not (e.g., crown–mushroom). We obtained increased evoked gamma-band responses for coherent scenes compared with incoherent scenes beginning as early as 70 msec after stimulus onset within a distributed cortical network, including the right temporal, the right frontal, and the bilateral occipital cortex. This finding provides empirical evidence for the functional importance of evoked oscillatory activity in high-level vision beyond the visual cortex and, thus, gives new insights into the functional relevance of neuronal interactions. It also indicates the very early availability of experience-based knowledge that might be regarded as a fundamental mechanism for the rapid extraction of the gist of a scene.
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Wang, Wen-Qin, and Huaizong Shao. "Performance Prediction of a Synchronization Link for Distributed Aerospace Wireless Systems." Scientific World Journal 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/159742.
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For reasons of stealth and other operational advantages, distributed aerospace wireless systems have received much attention in recent years. In a distributed aerospace wireless system, since the transmitter and receiver placed on separated platforms which use independent master oscillators, there is no cancellation of low-frequency phase noise as in the monostatic cases. Thus, high accurate time and frequency synchronization techniques are required for distributed wireless systems. The use of a dedicated synchronization link to quantify and compensate oscillator frequency instability is investigated in this paper. With the mathematical statistical models of phase noise, closed-form analytic expressions for the synchronization link performance are derived. The possible error contributions including oscillator, phase-locked loop, and receiver noise are quantified. The link synchronization performance is predicted by utilizing the knowledge of the statistical models, system error contributions, and sampling considerations. Simulation results show that effective synchronization error compensation can be achieved by using this dedicated synchronization link.
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Ma, Leixin, Ke Hu, Shixiao Fu, Torgeir Moan, and Runpei Li. "A Hybrid Empirical-Numerical Method for Hydroelastic Analysis of a Floater-and-Net System." Journal of Ship Research 60, no. 01 (March 1, 2016): 14–29. http://dx.doi.org/10.5957/jsr.2016.60.1.14.
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Because of scale effects and inappropriate hydrodynamic models, the nonlinear hydroelastic response of net cages used for fish-farming cannot be analyzed precisely with traditional model testing or combinations of finite element methods (FEMs) and load models. In this study, an innovative hybrid method is proposed to determine the hydroelastic response of full-scale floater-and-net systems more accurately. In this method, the net for the fish cage was vertically and peripherally divided into similar interconnected sections with different hydrodynamic parameters, which were assumed to be uniformly distributed over each section. A model of a typical section was subjected to various towing velocities, oscillation periods, and amplitudes in a towing tank to simulate the potential motions of all sections in the net under various currents, waves, and floater movements. By analyzing the measured hydrodynamic force from this test section, a hydrodynamic force database for a typical net section under various currents, waves, and floater motions was built. Finally, based on an FEM, the modified Morison equation and the hydrodynamic force database, the hydroelastic behavior of the full-scale fish cage was calculated with an iterative scheme. It is demonstrated that this hybrid method is able to produce correct hydroelastic response for both steady and oscillatory flows. The hydroelastic response of a two-dimensional example of a full-length net panel with steady currents and floater oscillations was studied in detail.
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Chaban, Andriy, Marek Lis, and Andrzej Szafraniec. "Voltage Stabilisation of a Drive System Including a Power Transformer and Asynchronous and Synchronous Motors of Susceptible Motion Transmission." Energies 15, no. 3 (January 23, 2022): 811. http://dx.doi.org/10.3390/en15030811.
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A mathematical model is developed of the master circuit of an electric driver system including a power transformer and susceptible motion transmission of asynchronous and synchronous drives. Electric motors drive water pumps by means of motion transmission that comprises two elastic couplings of lumped mechanical parameters and a long shaft of distributed mechanical parameters. Differential equations for oscillatory processes for the long shaft and the elastic couplings are different. The shaft is described with partial derivative Euler–Poisson equations, which, combined with the boundary conditions, form mixed problems from the mathematical point of view. The elastic couplings, on the other hand, are described with the ordinary second type Lagrange equations. Based on the theory of electromagnetic field, the partial differential equations describe the skin effects across the rotor age bars. Vertical pumps are presented by means of a loading torque waveform as a function of the input shaft’s angular velocity. The complex mathematical model serves to analyse electromechanical transient processes across the integrated drive system. Starting from there, conditions of stabilisation of the drive system voltage are determined. Electromechanical state equations are presented in the normal Cauchy form and integrated using the fourth-order Runge–Kutta method. Results of computer simulations are shown with graphics, which are interpreted and described.
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Fábio Carmona Tirintan, Álvaro Henrique Borges, Jesus Djalma Pécora, Manoel dos Santos da Silva Neto, Matheus Gehrke Barbosa, and Cyntia Rodrigues de Araújo Estrela. "Verification of remaining filling materials in flattened/oval-shaped root canals after use of several endodontic retreatment protocols." RSBO 17, no. 2 (January 28, 2021): 72–78. http://dx.doi.org/10.21726/rsbo.v17i2.29.
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This study verified of remaining filling materials in flattened/oval-shaped root canals after use of several endodontic retreatment protocols. Material and methods: Seventy human mandibular incisors were selected. Sixty specimens received crown-apex preparation performed by ProTaper Next® system andwere filled with hybrid Tagger technique with gutta-percha and AH Plus®. Ten specimens were left unprepared (Control Group). The specimens were randomly distributed in six groups, according the different retreatment protocols: G1 – Clearsonic® + ProTaper Universal Retreatment® + Reciproc®; G2 – Reciproc®; G3 – Clearsonic® + ProTaper Universal Retreatment®; G4 – Clearsonic® + Reciproc®; G5 – Oscillatory EndoEze® + Manual files; G6 – ProTaper Universal Retreatment®. Presence of root canal filling material residual were evaluated using Scanning Electron Microscopy. The relative differences of remaining filling materials between the groups and root thirds were determined by Kolmogorov-Smirnov and Levene tests followed by Tukey post hoc test. The level of significance was set at α = 5%. Results: Regarding the presence residual, G1 (Clearsonic® + ProTaper Universal Retreatment® + Reciproc®), G2 (Reciproc®), G3(Clearsonic® + ProTaper Universal Retreatment®) and G6 (ProTaper Universal Retreatment®) protocols presented a lower amount (p<0.05). The highest values (p<0.05) of remaining filling materials were presented in the G5 (Oscillatory EndoEze® + Manual files) protocol. Intermediate values (p<0.05) were presented by G4 (Clearsonic® + Reciproc®) protocol. Conclusion: The endodontic retreatment protocols no showed effectiveness for complete removal of remaining sealing material from flattened/oval-shaped root canals.
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Li, Jacob, Richard L. Patterson, and Ahmad Hammoud. "Characterization of the Vectron PX-570 Crystal Oscillator for Use in Harsh Environments." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, HITEC (January 1, 2012): 000072–81. http://dx.doi.org/10.4071/hitec-2012-tp12.
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Computing hardware, data-acquisition systems, communications systems, and many electronic control systems require well-controlled timing signals for proper and accurate operation. These signals are, in most cases, provided by circuits that employ crystal oscillators due to availability, cost, ease of operation, and accuracy. In some cases, the electronic systems are expected to survive and operate under harsh conditions that include exposure to extreme temperatures. These applications exist in terrestrial systems as well as in aerospace products. Well-logging, geothermal systems, and industrial process control are examples of ground-based applications, while distributed jet engine control in aircraft, space-based observatories (such as the James Webb Space Telescope), satellites, and lunar and planetary landers are typical environments where electronics are exposed to harsh operating conditions. To ensure these devices produce reliable results, the digital heartbeat from the oscillator must deliver a stable signal that is not affected by external temperature or other conditions. One such solution is a recently introduced commercial-off-the-shelf (COTS) oscillator, the PX-570 series from Vectron International. The oscillator was designed for high-temperature applications and as proof, the crystal oscillator was subjected to a wide suite of tests to determine its ruggedness for operation in harsh environments. The tests performed by Vectron included electrical characterization under wide range of temperature, accelerated life test/aging, shock and vibration, internal moisture analysis, ESD threshold, and latch-up testing. The parametric evaluation was performed on the oscillator's frequency, output signal rise and fall times, duty cycle, and supply current over the temperature range of −125 °C to +230 °C. The evaluations also determined the effects of thermal cycling and the oscillator's re-start capability at extreme hot and cold temperatures. These thermal cycling and restart tests were performed at the NASA Glenn Research Center. Overall, the crystal oscillator performed well and demonstrated very good frequency stability. This paper will discuss the test procedures and present details of the performance results.
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Relić, Filip, Predrag Marić, Hrvoje Glavaš, and Ivica Petrović. "Influence of FACTS Device Implementation on Performance of Distribution Network with Integrated Renewable Energy Sources." Energies 13, no. 20 (October 21, 2020): 5516. http://dx.doi.org/10.3390/en13205516.
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In the modern power system, Flexible Alternating Current Transmission System (FACTS) devices are widely used. An increased share of the distributed generation (DG) and the development of microgrids change the power flows in the existing distribution networks as well as a conventional power flow direction from the transmission to the distribution network level which may affect the overall stability aspects. The paper shows the FACTS devices’ implementation influence on the performance of the distribution network with integrated renewable energy sources (RES) observing the aspects of the oscillatory stability and the low-voltage motor starting. The FACTS devices, in particular the static var compensators (SVC), have been allocated according to a novel algorithm proposed in the paper. The algorithm uses an iterative process to determine an optimal location for implementation and rating power of SVC considering active power losses minimization, improvement of the voltage profile and maximizing return of investment (ROI) of FACTS devices. Novel constraints—transformer station construction constraint, SVC industrial nominal power value constraint and the constraint of distribution system operator (DSO) economic willingness to investment in the distribution network development are considered in the proposed algorithm. The analysis has been performed on 20 kV rural distribution network model in DIgSILENT PowerFactory software.
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Mishra, Debani Prasad, Amba Subhadarshini Nayak, Truptasha Tripathy, Surender Reddy Salkuti, and Sanhita Mishra. "A novel artificial neural network for power quality improvement in AC microgrid." International Journal of Power Electronics and Drive Systems (IJPEDS) 12, no. 4 (December 1, 2021): 2151. http://dx.doi.org/10.11591/ijpeds.v12.i4.pp2151-2159.
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The microgrid concept provides a flexible power supply to the utility where the conventional grid is unable to supply. The microgrid structure is based on renewable energy sources known as distributed generators (DGs) and the power network. Nevertheless, the power quality (PQ) is a great challenge in the microgrid concept. Particularly the inclusion of renewable energy sources into the conventional grids increases the problems in the quality of power, like voltage sag/swell, oscillatory transient, voltage flickering, and voltage notching which reduces the quality and reliability of the power supply. In this paper, a microgrid is considered which consists of PV cells as DG, battery energy storage system (BESS), and a novel control strategy known as the nonlinear autoregressive exogenous model (NARX). The proposed controller is an improved artificial neural network (ANN). The various case studies like sag/swell, unbalanced condition, and voltage deviation have been simulated with the model. The comprehensive simulation results are compared with the proportional-integral (PI) controller. Hence in this paper, the robustness of the proposed controller has been studied through different situations.
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Yuan, Jing, Maria Elektorowicz, and Zhi Chen. "Improved environmental multimedia modeling and its sensitivity analysis." Water Science and Technology 63, no. 10 (May 1, 2011): 2155–63. http://dx.doi.org/10.2166/wst.2011.343.
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Modeling of multimedia environmental issues is extremely complex due to the intricacy of the systems with the consideration of many factors. In this study, an improved environmental multimedia modeling is developed and a number of testing problems related to it are examined and compared with each other with standard numerical and analytical methodologies. The results indicate the flux output of new model is lesser in the unsaturated zone and groundwater zone compared with the traditional environmental multimedia model. Furthermore, about 90% of the total benzene flux was distributed to the air zone from the landfill sources and only 10% of the total flux emitted into the unsaturated, groundwater zones in non-uniform conditions. This paper also includes functions of model sensitivity analysis to optimize model parameters such as Peclet number (Pe). The analyses results show that the Pe can be considered as deterministic input variables for transport output. The oscillatory behavior is eliminated with the Pe decreased. In addition, the numerical methods are more accurate than analytical methods with the Pe increased. In conclusion, the improved environmental multimedia model system and its sensitivity analysis can be used to address the complex fate and transport of the pollutants in multimedia environments and then help to manage the environmental impacts.
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Wang, Chengen, and Keegan J. Moore. "Breaking reciprocity to realize extreme energy isolation in coupled oscillators." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A42. http://dx.doi.org/10.1121/10.0010595.
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This research investigates the isolation achieved by breaking the reciprocity of between two coupled oscillators. The two oscillators have equal mass and the first one is linearly grounded and called the linear oscillator (LO). The second oscillator is nonlinearly coupled to the LO and is termed the nonlinear oscillator (NO). By breaking dynamical reciprocity using asymmetry and nonlinearity, the LO–NO system is shown to exhibit regimes of extreme energy isolation in only one of the oscillators as well as regimes where energy is exchanged between them. These regimes are shown to arise under both impulsive and harmonic excitation. The resulting system is governed by two nonlinear normal modes (NNMs), which can interact with each other under internal resonance of different ratios. Under different loading scenarios, different energy isolations are illustrated. This research starts with analytical study using numerical simulations that assess how energy distributes in the structure under varying loads. The analytical predictions are validated experimentally for both impulsive and harmonic excitations. The results of this research demonstrate that there remains much to learn about energy transfer in general and the breaking of dynamic reciprocity may lead to new types of acoustic and vibrational metamaterials.
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Surovtsev, Ivan V., Manuel Campos, and Christine Jacobs-Wagner. "DNA-relay mechanism is sufficient to explain ParA-dependent intracellular transport and patterning of single and multiple cargos." Proceedings of the National Academy of Sciences 113, no. 46 (October 31, 2016): E7268—E7276. http://dx.doi.org/10.1073/pnas.1616118113.
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Spatial ordering of macromolecular components inside cells is important for cellular physiology and replication. In bacteria, ParA/B systems are known to generate various intracellular patterns that underlie the transport and partitioning of low-copy-number cargos such as plasmids. ParA/B systems consist of ParA, an ATPase that dimerizes and binds DNA upon ATP binding, and ParB, a protein that binds the cargo and stimulates ParA ATPase activity. Inside cells, ParA is asymmetrically distributed, forming a propagating wave that is followed by the ParB-rich cargo. These correlated dynamics lead to cargo oscillation or equidistant spacing over the nucleoid depending on whether the cargo is in single or multiple copies. Currently, there is no model that explains how these different spatial patterns arise and relate to each other. Here, we test a simple DNA-relay model that has no imposed asymmetry and that only considers the ParA/ParB biochemistry and the known fluctuating and elastic dynamics of chromosomal loci. Stochastic simulations with experimentally derived parameters demonstrate that this model is sufficient to reproduce the signature patterns of ParA/B systems: the propagating ParA gradient correlated with the cargo dynamics, the single-cargo oscillatory motion, and the multicargo equidistant patterning. Stochasticity of ATP hydrolysis breaks the initial symmetry in ParA distribution, resulting in imbalance of elastic force acting on the cargo. Our results may apply beyond ParA/B systems as they reveal how a minimal system of two players, one binding to DNA and the other modulating this binding, can transform directionally random DNA fluctuations into directed motion and intracellular patterning.