Dynamic coupling of plasmonic resonators
Lee, Suyeon; Park, Q-Han
2016-01-01
We clarify the nature of dynamic coupling in plasmonic resonators and determine the dynamic coupling coefficient using a simple analytic model. We show that plasmonic resonators, such as subwavelength holes in a metal film which can be treated as bound charge oscillators, couple to each other through the retarded interaction of oscillating screened charges. Our dynamic coupling model offers, for the first time, a quantitative analytic description of the fundamental symmetric and anti-symmetric modes of coupled resonators which agrees with experimental results. Our model also reveals that plasmonic electromagnetically induced transparency arises in any coupled resonators of slightly unequal lengths, as confirmed by a rigorous numerical calculation and experiments. PMID:26911786
The Challenges to Coupling Dynamic Geospatial Models
Goldstein, N
2006-06-23
Many applications of modeling spatial dynamic systems focus on a single system and a single process, ignoring the geographic and systemic context of the processes being modeled. A solution to this problem is the coupled modeling of spatial dynamic systems. Coupled modeling is challenging for both technical reasons, as well as conceptual reasons. This paper explores the benefits and challenges to coupling or linking spatial dynamic models, from loose coupling, where information transfer between models is done by hand, to tight coupling, where two (or more) models are merged as one. To illustrate the challenges, a coupled model of Urbanization and Wildfire Risk is presented. This model, called Vesta, was applied to the Santa Barbara, California region (using real geospatial data), where Urbanization and Wildfires occur and recur, respectively. The preliminary results of the model coupling illustrate that coupled modeling can lead to insight into the consequences of processes acting on their own.
Coupling Dynamics in Aircraft: A Historical Perspective
NASA Technical Reports Server (NTRS)
Day, Richard E.
1997-01-01
Coupling dynamics can produce either adverse or beneficial stability and controllability, depending on the characteristics of the aircraft. This report presents archival anecdotes and analyses of coupling problems experienced by the X-series, Century series, and Space Shuttle aircraft. The three catastrophic sequential coupling modes of the X-2 airplane and the two simultaneous unstable modes of the X-15 and Space Shuttle aircraft are discussed. In addition, the most complex of the coupling interactions, inertia roll coupling, is discussed for the X-2, X-3, F-100A, and YF-102 aircraft. The mechanics of gyroscopics, centrifugal effect, and resonance in coupling dynamics are described. The coupling modes discussed are interacting multiple degrees of freedom of inertial and aerodynamic forces and moments. The aircraft are assumed to be rigid bodies. Structural couplings are not addressed. Various solutions for coupling instabilities are discussed.
Designing the Dynamics of Globally Coupled Oscillators
NASA Astrophysics Data System (ADS)
Orosz, G.; Moehlis, J.; Ashwin, P.
2009-09-01
A method for designing cluster states with prescribed stability is presented for coupled phase oscillator systems with all-to-all coupling. We determine criteria for the coupling function that ensure the existence and stability of a large variety of clustered configurations. We show that such criteria can be satisfied by choosing Fourier coefficients of the coupling function. We demonstrate that using simple trigonometric and localized coupling functions one can realize arbitrary patterns of stable clusters and that the designed systems are capable of performing finite state computation. The design principles may be relevant when engineering complex dynamical behavior of coupled systems, e.g. the emergent dynamics of artificial neural networks, coupled chemical oscillators and robotic swarms.
Dynamic mode coupling in terahertz metamaterials
Su, Xiaoqiang; Ouyang, Chunmei; Xu, Ningning; Tan, Siyu; Gu, Jianqiang; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Yan, Fengping; Han, Jiaguang; Zhang, Weili
2015-01-01
The near and far field coupling behavior in plasmonic and metamaterial systems have been extensively studied over last few years. However, most of the coupling mechanisms reported in the past have been passive in nature which actually fail to control the coupling mechanism dynamically in the plasmonic metamaterial lattice array. Here, we demonstrate a dynamic mode coupling between resonators in a hybrid metal-semiconductor metamaterial comprised of metallic concentric rings that are physically connected with silicon bridges. The dielectric function of silicon can be instantaneously modified by photodoped carriers thus tailoring the coupling characteristics between the metallic resonators. Based on the experimental results, a theoretical model is developed, which shows that the optical responses depend on mode coupling that originates from the variation of the damping rate and coupling coefficient of the resonance modes. This particular scheme enables an in-depth understanding of the fundamental coupling mechanism and, therefore, the dynamic coupling enables functionalities and applications for designing on-demand reconfigurable metamaterial and plasmonic devices. PMID:26035057
Dynamic mode coupling in terahertz metamaterials.
Su, Xiaoqiang; Ouyang, Chunmei; Xu, Ningning; Tan, Siyu; Gu, Jianqiang; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Yan, Fengping; Han, Jiaguang; Zhang, Weili
2015-01-01
The near and far field coupling behavior in plasmonic and metamaterial systems have been extensively studied over last few years. However, most of the coupling mechanisms reported in the past have been passive in nature which actually fail to control the coupling mechanism dynamically in the plasmonic metamaterial lattice array. Here, we demonstrate a dynamic mode coupling between resonators in a hybrid metal-semiconductor metamaterial comprised of metallic concentric rings that are physically connected with silicon bridges. The dielectric function of silicon can be instantaneously modified by photodoped carriers thus tailoring the coupling characteristics between the metallic resonators. Based on the experimental results, a theoretical model is developed, which shows that the optical responses depend on mode coupling that originates from the variation of the damping rate and coupling coefficient of the resonance modes. This particular scheme enables an in-depth understanding of the fundamental coupling mechanism and, therefore, the dynamic coupling enables functionalities and applications for designing on-demand reconfigurable metamaterial and plasmonic devices. PMID:26035057
Coupled dynamics analysis of wind energy systems
NASA Technical Reports Server (NTRS)
Hoffman, J. A.
1977-01-01
A qualitative description of all key elements of a complete wind energy system computer analysis code is presented. The analysis system addresses the coupled dynamics characteristics of wind energy systems, including the interactions of the rotor, tower, nacelle, power train, control system, and electrical network. The coupled dynamics are analyzed in both the frequency and time domain to provide the basic motions and loads data required for design, performance verification and operations analysis activities. Elements of the coupled analysis code were used to design and analyze candidate rotor articulation concepts. Fundamental results and conclusions derived from these studies are presented.
Novel coupling scheme to control dynamics of coupled discrete systems
NASA Astrophysics Data System (ADS)
Shekatkar, Snehal M.; Ambika, G.
2015-08-01
We present a new coupling scheme to control spatio-temporal patterns and chimeras on 1-d and 2-d lattices and random networks of discrete dynamical systems. The scheme involves coupling with an external lattice or network of damped systems. When the system network and external network are set in a feedback loop, the system network can be controlled to a homogeneous steady state or synchronized periodic state with suppression of the chaotic dynamics of the individual units. The control scheme has the advantage that its design does not require any prior information about the system dynamics or its parameters and works effectively for a range of parameters of the control network. We analyze the stability of the controlled steady state or amplitude death state of lattices using the theory of circulant matrices and Routh-Hurwitz criterion for discrete systems and this helps to isolate regions of effective control in the relevant parameter planes. The conditions thus obtained are found to agree well with those obtained from direct numerical simulations in the specific context of lattices with logistic map and Henon map as on-site system dynamics. We show how chimera states developed in an experimentally realizable 2-d lattice can be controlled using this scheme. We propose this mechanism can provide a phenomenological model for the control of spatio-temporal patterns in coupled neurons due to non-synaptic coupling with the extra cellular medium. We extend the control scheme to regulate dynamics on random networks and adapt the master stability function method to analyze the stability of the controlled state for various topologies and coupling strengths.
Dynamical robustness of coupled heterogeneous oscillators
NASA Astrophysics Data System (ADS)
Tanaka, Gouhei; Morino, Kai; Daido, Hiroaki; Aihara, Kazuyuki
2014-05-01
We study tolerance of dynamic behavior in networks of coupled heterogeneous oscillators to deterioration of the individual oscillator components. As the deterioration proceeds with reduction in dynamic behavior of the oscillators, an order parameter evaluating the level of global oscillation decreases and then vanishes at a certain critical point. We present a method to analytically derive a general formula for this critical point and an approximate formula for the order parameter in the vicinity of the critical point in networks of coupled Stuart-Landau oscillators. Using the critical point as a measure for dynamical robustness of oscillator networks, we show that the more heterogeneous the oscillator components are, the more robust the oscillatory behavior of the network is to the component deterioration. This property is confirmed also in networks of Morris-Lecar neuron models coupled through electrical synapses. Our approach could provide a useful framework for theoretically understanding the role of population heterogeneity in robustness of biological networks.
Dynamical Coupling of Pygmy and Giant Resonances
NASA Astrophysics Data System (ADS)
Bertulani, Carlos; Brady, Nathan; Aumann, Thomas; Thomas, James
2016-03-01
One of the effects overseen in studies of excitation of pygmy resonances is the fact that both pygmy and giant resonances are strongly coupled. This coupling leads to dynamical effects such as the modification of transition probabilities and and cross sections. We make an assessment of such effects by means of the relativistic coupled channels equations developed by our group. Supported by the U.S. NSF Grant No. 1415656 and the U.S. DOE Grant No. DE-FG02-08ER41533.
Coupled dislocation and martensitic phase transformation dynamics
NASA Astrophysics Data System (ADS)
Barros, Kipton; Acharya, Amit; Lookman, Turab
2013-03-01
We present a field theoretic model that couples dislocation dynamics and plasticity with martensitic phase transformation. Dislocations produce long-range stress via incompatibility of the elastic-distortion field. Phase transformations are modeled with a non-convex elastic potential that contains the crystal symmetries of austenite and martensite phases. We discuss the effects of dislocation dynamics on material microstructure produced under extreme conditions.
Synchronization Dynamics of Coupled Chemical Oscillators
NASA Astrophysics Data System (ADS)
Tompkins, Nathan
The synchronization dynamics of complex networks have been extensively studied over the past few decades due to their ubiquity in the natural world. Prominent examples include cardiac rhythms, circadian rhythms, the flashing of fireflies, predator/prey population dynamics, mammalian gait, human applause, pendulum clocks, the electrical grid, and of the course the brain. Detailed experiments have been done to map the topology of many of these systems and significant advances have been made to describe the mathematics of these networks. Compared to these bodies of work relatively little has been done to directly test the role of topology in the synchronization dynamics of coupled oscillators. This Dissertation develops technology to examine the dynamics due to topology within networks of discrete oscillatory components. The oscillatory system used here consists of the photo-inhibitable Belousov-Zhabotinsky (BZ) reaction water-in-oil emulsion where the oscillatory drops are diffusively coupled to one another and the topology is defined by the geometry of the diffusive connections. Ring networks are created from a close-packed 2D array of drops using the Programmable Illumination Microscope (PIM) in order to test Turing's theory of morphogenesis directly. Further technology is developed to create custom planar networks of BZ drops in more complicated topologies which can be individually perturbed using illumination from the PIM. The work presented here establishes the validity of using the BZ emulsion system with a PIM to study the topology induced effects on the synchronization dynamics of coupled chemical oscillators, tests the successes and limitations of Turing's theory of morphogenesis, and develops new technology to further probe the effects of network topology on a system of coupled oscillators. Finally, this Dissertation concludes by describing ongoing experiments which utilize this new technology to examine topology induced transitions of synchronization
Dynamics of strongly-coupled spiking neurons.
Bressloff, P C; Coombes, S
2000-01-01
We present a dynamical theory of integrate-and-fire neurons with strong synaptic coupling. We show how phase-locked states that are stable in the weak coupling regime can destabilize as the coupling is increased, leading to states characterized by spatiotemporal variations in the interspike intervals (ISIs). The dynamics is compared with that of a corresponding network of analog neurons in which the outputs of the neurons are taken to be mean firing rates. A fundamental result is that for slow interactions, there is good agreement between the two models (on an appropriately defined timescale). Various examples of desynchronization in the strong coupling regime are presented. First, a globally coupled network of identical neurons with strong inhibitory coupling is shown to exhibit oscillator death in which some of the neurons suppress the activity of others. However, the stability of the synchronous state persists for very large networks and fast synapses. Second, an asymmetric network with a mixture of excitation and inhibition is shown to exhibit periodic bursting patterns. Finally, a one-dimensional network of neurons with long-range interactions is shown to desynchronize to a state with a spatially periodic pattern of mean firing rates across the network. This is modulated by deterministic fluctuations of the instantaneous firing rate whose size is an increasing function of the speed of synaptic response. PMID:10636934
Dynamic coupling of three hydrodynamic models
NASA Astrophysics Data System (ADS)
Hartnack, J. N.; Philip, G. T.; Rungoe, M.; Smith, G.; Johann, G.; Larsen, O.; Gregersen, J.; Butts, M. B.
2008-12-01
The need for integrated modelling is evidently present within the field of flood management and flood forecasting. Engineers, modellers and managers are faced with flood problems which transcend the classical hydrodynamic fields of urban, river and coastal flooding. Historically the modeller has been faced with having to select one hydrodynamic model to cover all the aspects of the potentially complex dynamics occurring in a flooding situation. Such a single hydrodynamic model does not cover all dynamics of flood modelling equally well. Thus the ideal choice may in fact be a combination of models. Models combining two numerical/hydrodynamic models are becoming more standard, typically these models combine a 1D river model with a 2D overland flow model or alternatively a 1D sewer/collection system model with a 2D overland solver. In complex coastal/urban areas the flood dynamics may include rivers/streams, collection/storm water systems along with the overland flow. The dynamics within all three areas is of the same time scale and there is feedback in the system across the couplings. These two aspects dictate a fully dynamic three way coupling as opposed to running the models sequentially. It will be shown that the main challenges of the three way coupling are time step issues related to the difference in numerical schemes used in the three model components and numerical instabilities caused by the linking of the model components. MIKE FLOOD combines the models MIKE 11, MIKE 21 and MOUSE into one modelling framework which makes it possible to couple any combination of river, urban and overland flow fully dynamically. The MIKE FLOOD framework will be presented with an overview of the coupling possibilities. The flood modelling concept will be illustrated through real life cases in Australia and in Germany. The real life cases reflect dynamics and interactions across all three model components which are not possible to reproduce using a two-way coupling alone. The
Modeling coupled avulsion and earthquake timescale dynamics
NASA Astrophysics Data System (ADS)
Reitz, M. D.; Steckler, M. S.; Paola, C.; Seeber, L.
2014-12-01
River avulsions and earthquakes can be hazardous events, and many researchers work to better understand and predict their timescales. Improvements in the understanding of the intrinsic processes of deposition and strain accumulation that lead to these events have resulted in better constraints on the timescales of each process individually. There are however several mechanisms by which these two systems may plausibly become linked. River deposition and avulsion can affect the stress on underlying faults through differential loading by sediment or water. Conversely, earthquakes can affect river avulsion patterns through altering the topography. These interactions may alter the event recurrence timescales, but this dynamic has not yet been explored. We present results of a simple numerical model, in which two systems have intrinsic rates of approach to failure thresholds, but the state of one system contributes to the other's approach to failure through coupling functions. The model is first explored for the simplest case of two linear approaches to failure, and linearly proportional coupling terms. Intriguing coupling dynamics emerge: the system settles into cycles of repeating earthquake and avulsion timescales, which are approached at an exponential decay rate that depends on the coupling terms. The ratio of the number of events of each type and the timescale values also depend on the coupling coefficients and the threshold values. We then adapt the model to a more complex and realistic scenario, in which a river avulses between either side of a fault, with parameters corresponding to the Brahmaputra River / Dauki fault system in Bangladesh. Here the tectonic activity alters the topography by gradually subsiding during the interseismic time, and abruptly increasing during an earthquake. The river strengthens the fault by sediment loading when in one path, and weakens it when in the other. We show this coupling can significantly affect earthquake and avulsion
Dynamical coupled-channel analysis at EBAC.
Lee, T.-S. H.; Physics
2008-01-01
In this contribution, the author reports on the dynamical coupled-channels analysis being pursued at the Excited Baryon Analysis Center (EBAC) of Jefferson Laboratory. EBAC was established in January 2006. Its objective is to extract the parameters associated with the excited states (N*) of the nucleon from the world data of meson production reactions, and to also develop theoretical interpretations of the extracted N* parameters.
Coupling dynamic of twin supersonic jets
NASA Astrophysics Data System (ADS)
Kuo, Ching-Wen; Cluts, Jordan; Samimy, Mo
2015-11-01
In a supersonic shock-containing jet, the interaction of large-scale structures in the jet's shear layer with the shock waves generates acoustic waves. The waves propagate upstream, excite the jet initial shear layer instability, establish a feedback loop at certain conditions, and generate screech noise. The screech normally contains different modes of various strengths. Similarly, twin-jet plumes contain screech tones. If the dynamics of the two jet plumes are synchronized, the screech amplitude could be significantly amplified. There is a proposed analytical model in the literature for screech synchronization in twin rectangular jets. This model shows that with no phase difference in acoustic waves arriving at neighboring nozzle lips, twin-jet plumes feature a strong coupling with a significant level of screech tones. In this work the maximum nozzle separation distance for sustained screech synchronization and strong coupling is analytically derived. This model is used with our round twin-jet experiments and the predicted coupling level agrees well with the experimental results. Near-field microphone measurements and schlieren visualization along with the analytical model are used to investigate the coupling mechanisms of twin supersonic jets. Supported by ONR.
Dynamics of coupled human-landscape systems
NASA Astrophysics Data System (ADS)
Werner, B. T.; McNamara, D. E.
2007-11-01
A preliminary dynamical analysis of landscapes and humans as hierarchical complex systems suggests that strong coupling between the two that spreads to become regionally or globally pervasive should be focused at multi-year to decadal time scales. At these scales, landscape dynamics is dominated by water, sediment and biological routing mediated by fluvial, oceanic, atmospheric processes and human dynamics is dominated by simplifying, profit-maximizing market forces and political action based on projection of economic effect. Also at these scales, landscapes impact humans through patterns of natural disasters and trends such as sea level rise; humans impact landscapes by the effect of economic activity and changes meant to mitigate natural disasters and longer term trends. Based on this analysis, human-landscape coupled systems can be modeled using heterogeneous agents employing prediction models to determine actions to represent the nonlinear behavior of economic and political systems and rule-based routing algorithms to represent landscape processes. A cellular model for the development of New Orleans illustrates this approach, with routing algorithms for river and hurricane-storm surge determining flood extent, five markets (home, labor, hotel, tourism and port services) connecting seven types of economic agents (home buyers/laborers, home developers, hotel owners/ employers, hotel developers, tourists, port services developer and port services owners/employers), building of levees or a river spillway by political agents and damage to homes, hotels or port services within cells determined by the passage or depth of flood waters. The model reproduces historical aspects of New Orleans economic development and levee construction and the filtering of frequent small-scale floods at the expense of large disasters.
Dynamic optical coupled system employing Dammann gratings
NASA Astrophysics Data System (ADS)
Di, Caihui; Zhou, Changhe; Ru, Huayi
2004-10-01
With the increasing of the number of users in optical fiber communications, fiber-to-home project has a larger market value. Then the need of dynamic optical couplers, especially of N broad-band couplers, becomes greater. Though some advanced fiber fusion techniques have been developed, they still have many shortcomings. In this paper we propose a dynamic optical coupled system employing even-numbered Dammann gratings, which have the characteristic that the phase distribution in the first half-period accurately equals to that in the second-period with π phase inversion. In our experiment, we divide a conventional even-numbered Dammann grating into two identical gratings. The system can achieve the beam splitter and combiner as the switch between them according to the relative shift between two complementary gratings. When there is no shift between the gratings, the demonstrated 1×8 dynamic optical coupler achieves good uniformity of 0.06 and insertion loss of around 10.8 dB for each channel as a splitter. When the two gratings have an accurate shift of a half-period between them, our system has a low insertion loss of 0.46 dB as a combiner at a wavelength of 1550 nm.
Coupling geodynamic earthquake cycles and dynamic ruptures
NASA Astrophysics Data System (ADS)
van Zelst, Iris; van Dinther, Ylona; Gabriel, Alice-Agnes; Heuret, Arnauld
2016-04-01
Studying the seismicity in a subduction zone and its effects on tsunamis requires diverse modelling methods that span spatial and temporal scales. Hundreds of years are necessary to build the stresses and strengths on a fault, while consequent earthquake rupture propagation is determined by both these initial fault conditions and the feedback of seismic waves over periods of seconds up to minutes. This dynamic rupture displaces the sea floor, thereby causing tsunamis. The aim of the ASCETE (Advanced Simulations of Coupled Earthquake and Tsunami Events) project is to study all these aspects and their interactions. Here, we present preliminary results of the first aspects in this modelling chain: the coupling of a seismo-thermo-mechanical (STM) code to the dynamic rupture model SeisSol. STM models of earthquake cycles have the advantage of solving multiple earthquake events in a self-consistent manner concerning stress, strength and geometry. However, the drawback of these models is that they often lack in spatial or temporal resolution and do not include wave propagation. In contrast, dynamic rupture models solve for frictional failure coupled to seismic wave propagation. We use the software package SeisSol (www.seissol.org) based on an ADER-DG discretization allowing high-order accuracy in space and time as well as flexible tetrahedral meshing. However, such simulations require assumptions on the initial fault stresses and strengths and its geometry, which are hard to constrain due to the lack of near-field observations and the complexity of coseismic conditions. By adapting the geometry as well as the stress and strength properties of the self-consistently developing non-finite fault zones from the geodynamic models as initial conditions for the dynamic rupture models, the advantages of both methods are exploited and modelling results may be compared. Our results show that a dynamic rupture can be triggered spontaneously and that the propagating rupture is
G-protein-coupled receptor heteromer dynamics
Vilardaga, Jean-Pierre; Agnati, Luigi F.; Fuxe, Kjell; Ciruela, Francisco
2010-01-01
G-protein-coupled receptors (GPCRs) represent the largest family of cell surface receptors, and have evolved to detect and transmit a large palette of extracellular chemical and sensory signals into cells. Activated receptors catalyze the activation of heterotrimeric G proteins, which modulate the propagation of second messenger molecules and the activity of ion channels. Classically thought to signal as monomers, different GPCRs often pair up with each other as homo- and heterodimers, which have been shown to modulate signaling to G proteins. Here, we discuss recent advances in GPCR heteromer systems involving the kinetics of the early steps in GPCR signal transduction, the dynamic property of receptor–receptor interactions, and how the formation of receptor heteromers modulate the kinetics of G-protein signaling. PMID:21123619
Restoration of rhythmicity in diffusively coupled dynamical networks
Zou, Wei; Senthilkumar, D. V.; Nagao, Raphael; Kiss, István Z.; Tang, Yang; Koseska, Aneta; Duan, Jinqiao; Kurths, Jürgen
2015-01-01
Oscillatory behaviour is essential for proper functioning of various physical and biological processes. However, diffusive coupling is capable of suppressing intrinsic oscillations due to the manifestation of the phenomena of amplitude and oscillation deaths. Here we present a scheme to revoke these quenching states in diffusively coupled dynamical networks, and demonstrate the approach in experiments with an oscillatory chemical reaction. By introducing a simple feedback factor in the diffusive coupling, we show that the stable (in)homogeneous steady states can be effectively destabilized to restore dynamic behaviours of coupled systems. Even a feeble deviation from the normal diffusive coupling drastically shrinks the death regions in the parameter space. The generality of our method is corroborated in diverse non-linear systems of diffusively coupled paradigmatic models with various death scenarios. Our study provides a general framework to strengthen the robustness of dynamic activity in diffusively coupled dynamical networks. PMID:26173555
Restoration of rhythmicity in diffusively coupled dynamical networks.
Zou, Wei; Senthilkumar, D V; Nagao, Raphael; Kiss, István Z; Tang, Yang; Koseska, Aneta; Duan, Jinqiao; Kurths, Jürgen
2015-01-01
Oscillatory behaviour is essential for proper functioning of various physical and biological processes. However, diffusive coupling is capable of suppressing intrinsic oscillations due to the manifestation of the phenomena of amplitude and oscillation deaths. Here we present a scheme to revoke these quenching states in diffusively coupled dynamical networks, and demonstrate the approach in experiments with an oscillatory chemical reaction. By introducing a simple feedback factor in the diffusive coupling, we show that the stable (in)homogeneous steady states can be effectively destabilized to restore dynamic behaviours of coupled systems. Even a feeble deviation from the normal diffusive coupling drastically shrinks the death regions in the parameter space. The generality of our method is corroborated in diverse non-linear systems of diffusively coupled paradigmatic models with various death scenarios. Our study provides a general framework to strengthen the robustness of dynamic activity in diffusively coupled dynamical networks. PMID:26173555
Restoration of rhythmicity in diffusively coupled dynamical networks
NASA Astrophysics Data System (ADS)
Zou, Wei; Senthilkumar, D. V.; Nagao, Raphael; Kiss, István Z.; Tang, Yang; Koseska, Aneta; Duan, Jinqiao; Kurths, Jürgen
2015-07-01
Oscillatory behaviour is essential for proper functioning of various physical and biological processes. However, diffusive coupling is capable of suppressing intrinsic oscillations due to the manifestation of the phenomena of amplitude and oscillation deaths. Here we present a scheme to revoke these quenching states in diffusively coupled dynamical networks, and demonstrate the approach in experiments with an oscillatory chemical reaction. By introducing a simple feedback factor in the diffusive coupling, we show that the stable (in)homogeneous steady states can be effectively destabilized to restore dynamic behaviours of coupled systems. Even a feeble deviation from the normal diffusive coupling drastically shrinks the death regions in the parameter space. The generality of our method is corroborated in diverse non-linear systems of diffusively coupled paradigmatic models with various death scenarios. Our study provides a general framework to strengthen the robustness of dynamic activity in diffusively coupled dynamical networks.
Dynamics of strongly coupled spatially distributed logistic equations with delay
NASA Astrophysics Data System (ADS)
Kashchenko, I. S.; Kashchenko, S. A.
2015-04-01
The dynamics of a system of two logistic delay equations with spatially distributed coupling is studied. The coupling coefficient is assumed to be sufficiently large. Special nonlinear systems of parabolic equations are constructed such that the behavior of their solutions is determined in the first approximation by the dynamical properties of the original system.
Average dynamics of a finite set of coupled phase oscillators
Dima, Germán C. Mindlin, Gabriel B.
2014-06-15
We study the solutions of a dynamical system describing the average activity of an infinitely large set of driven coupled excitable units. We compared their topological organization with that reconstructed from the numerical integration of finite sets. In this way, we present a strategy to establish the pertinence of approximating the dynamics of finite sets of coupled nonlinear units by the dynamics of its infinitely large surrogate.
Dynamics of dark energy with a coupling to dark matter
Boehmer, Christian G.; Caldera-Cabral, Gabriela; Maartens, Roy; Lazkoz, Ruth
2008-07-15
Dark energy and dark matter are the dominant sources in the evolution of the late universe. They are currently only indirectly detected via their gravitational effects, and there could be a coupling between them without violating observational constraints. We investigate the background dynamics when dark energy is modeled as exponential quintessence and is coupled to dark matter via simple models of energy exchange. We introduce a new form of dark sector coupling, which leads to a more complicated dynamical phase space and has a better physical motivation than previous mathematically similar couplings.
Phase dynamics of coupled oscillators reconstructed from data
NASA Astrophysics Data System (ADS)
Rosenblum, Michael; Kralemann, Bjoern; Pikovsky, Arkady
2013-03-01
We present a technique for invariant reconstruction of the phase dynamics equations for coupled oscillators from data. The invariant description is achieved by means of a transformation of phase estimates (protophases) obtained from general scalar observables to genuine phases. Staring from the bivariate data, we obtain the coupling functions in terms of these phases. We discuss the importance of the protophase-to-phase transformation for characterization of strength and directionality of interaction. To illustrate the technique we analyse the cardio-respiratory interaction on healthy humans. Our invariant approach is confirmed by high similarity of the coupling functions obtained from different observables of the cardiac system. Next, we generalize the technique to cover the case of small networks of coupled periodic units. We use the partial norms of the reconstructed coupling functions to quantify directed coupling between the oscillators. We illustrate the method by different network motifs for three coupled oscillators. We also discuss nonlinear effects in coupling.
CHARACTERIZING COUPLED CHARGE TRANSPORT WITH MULTISCALE MOLECULAR DYNAMICS
Swanson, Jessica
2011-08-31
This is the final progress report for Award DE-SC0004920, entitled 'Characterizing coupled charge transport with multi scale molecular dynamics'. The technical abstract will be provided in the uploaded report.
Effective quantum dynamics of interacting systems with inhomogeneous coupling
Lopez, C. E.; Retamal, J. C.; Christ, H.; Solano, E.
2007-03-15
We study the quantum dynamics of a single mode (particle) interacting inhomogeneously with a large number of particles and introduce an effective approach to find the accessible Hilbert space, where the dynamics takes place. Two relevant examples are given: the inhomogeneous Tavis-Cummings model (e.g., N atomic qubits coupled to a single cavity mode, or to a motional mode in trapped ions) and the inhomogeneous coupling of an electron spin to N nuclear spins in a quantum dot.
Dynamics of symmetry breaking in strongly coupled QED
Bardeen, W.A.
1988-10-01
I review the dynamical structure of strong coupled QED in the quenched planar limit. The symmetry structure of this theory is examined with reference to the nature of both chiral and scale symmetry breaking. The renormalization structure of the strong coupled phase is analysed. The compatibility of spontaneous scale and chiral symmetry breaking is studied using effective lagrangian methods. 14 refs., 3 figs.
Nonadiabatic multichannel dynamics of a spin-orbit-coupled condensate
NASA Astrophysics Data System (ADS)
Xiong, Bo; Zheng, Jun-hui; Wang, Daw-wei
2015-06-01
We investigate the nonadiabatic dynamics of a driven spin-orbit-coupled Bose-Einstein condensate in both weak and strong driven force. It is shown that the standard Landau-Zener (LZ) tunneling fails in the regime of weak driven force and/or strong spin-orbital coupling, where the full nonadiabatic dynamics requires a new mechanism through multichannel effects. Beyond the semiclassical approach, our numerical and analytical results show an oscillating power-law decay in the quantum limit, different from the exponential decay in the semiclassical limit of the LZ effect. Furthermore, the condensate density profile is found to be dynamically fragmented by the multichannel effects and enhanced by interaction effects. Our work therefore provides a complete picture to understand the nonadiabatic dynamics of a spin-orbit coupled condensate, including various ranges of driven force and interaction effects through multichannel interference. The experimental indication of these nonadiabatic dynamics is also discussed.
Superlinearly scalable noise robustness of redundant coupled dynamical systems
NASA Astrophysics Data System (ADS)
Kohar, Vivek; Kia, Behnam; Lindner, John F.; Ditto, William L.
2016-03-01
We illustrate through theory and numerical simulations that redundant coupled dynamical systems can be extremely robust against local noise in comparison to uncoupled dynamical systems evolving in the same noisy environment. Previous studies have shown that the noise robustness of redundant coupled dynamical systems is linearly scalable and deviations due to noise can be minimized by increasing the number of coupled units. Here, we demonstrate that the noise robustness can actually be scaled superlinearly if some conditions are met and very high noise robustness can be realized with very few coupled units. We discuss these conditions and show that this superlinear scalability depends on the nonlinearity of the individual dynamical units. The phenomenon is demonstrated in discrete as well as continuous dynamical systems. This superlinear scalability not only provides us an opportunity to exploit the nonlinearity of physical systems without being bogged down by noise but may also help us in understanding the functional role of coupled redundancy found in many biological systems. Moreover, engineers can exploit superlinear noise suppression by starting a coupled system near (not necessarily at) the appropriate initial condition.
Dynamics of chaotic systems with attractive and repulsive couplings.
Chen, Yuehua; Xiao, Jinghua; Liu, Weiqing; Li, Lixiang; Yang, Yixian
2009-10-01
Together with attractive couplings, repulsive couplings play crucial roles in determining important evolutions in natural systems, such as in learning and oscillatory processes of neural networks. The complex interactions between them have great influence on the systems. A detailed understanding of the dynamical properties under this type of couplings is of practical significance. In this paper, we propose a model to investigate the dynamics of attractive and repulsive couplings, which give rise to rich phenomena, especially for amplitude death (AD). The relationship among various dynamics and possible transitions to AD are illustrated. When the system is in the maximally stable AD, we observe the transient behavior of in-phase (high frequency) and out-of-phase (low frequency) motions. The mechanism behind the phenomenon is given. PMID:19905414
Molecular Dynamics Study of Naturally Existing Cavity Couplings in Proteins
Barbany, Montserrat; Meyer, Tim; Hospital, Adam; Faustino, Ignacio; D'Abramo, Marco; Morata, Jordi; Orozco, Modesto; de la Cruz, Xavier
2015-01-01
Couplings between protein sub-structures are a common property of protein dynamics. Some of these couplings are especially interesting since they relate to function and its regulation. In this article we have studied the case of cavity couplings because cavities can host functional sites, allosteric sites, and are the locus of interactions with the cell milieu. We have divided this problem into two parts. In the first part, we have explored the presence of cavity couplings in the natural dynamics of 75 proteins, using 20 ns molecular dynamics simulations. For each of these proteins, we have obtained two trajectories around their native state. After applying a stringent filtering procedure, we found significant cavity correlations in 60% of the proteins. We analyze and discuss the structure origins of these correlations, including neighbourhood, cavity distance, etc. In the second part of our study, we have used longer simulations (≥100ns) from the MoDEL project, to obtain a broader view of cavity couplings, particularly about their dependence on time. Using moving window computations we explored the fluctuations of cavity couplings along time, finding that these couplings could fluctuate substantially during the trajectory, reaching in several cases correlations above 0.25/0.5. In summary, we describe the structural origin and the variations with time of cavity couplings. We complete our work with a brief discussion of the biological implications of these results. PMID:25816327
Coupled intertwiner dynamics: A toy model for coupling matter to spin foam models
NASA Astrophysics Data System (ADS)
Steinhaus, Sebastian
2015-09-01
The universal coupling of matter and gravity is one of the most important features of general relativity. In quantum gravity, in particular spin foams, matter couplings have been defined in the past, yet the mutual dynamics, in particular if matter and gravity are strongly coupled, are hardly explored, which is related to the definition of both matter and gravitational degrees of freedom on the discretization. However, extracting these mutual dynamics is crucial in testing the viability of the spin foam approach and also establishing connections to other discrete approaches such as lattice gauge theories. Therefore, we introduce a simple two-dimensional toy model for Yang-Mills coupled to spin foams, namely an Ising model coupled to so-called intertwiner models defined for SU (2 )k. The two systems are coupled by choosing the Ising coupling constant to depend on spin labels of the background, as these are interpreted as the edge lengths of the discretization. We coarse grain this toy model via tensor network renormalization and uncover an interesting dynamics: the Ising phase transition temperature turns out to be sensitive to the background configurations and conversely, the Ising model can induce phase transitions in the background. Moreover, we observe a strong coupling of both systems if close to both phase transitions.
Stochastic dynamics of coupled active particles in an overdamped limit
NASA Astrophysics Data System (ADS)
Ann, Minjung; Lee, Kong-Ju-Bock; Park, Pyeong Jun
2015-10-01
We introduce a model for Brownian dynamics of coupled active particles in an overdamped limit. Our system consists of several identical active particles and one passive particle. Each active particle is elastically coupled to the passive particle and there is no direct coupling among the active particles. We investigate the dynamics of the system with respect to the number of active particles, viscous friction, and coupling between the active and passive particles. For this purpose, we consider an intracellular transport process as an application of our model and perform a Brownian dynamics simulation using realistic parameters for processive molecular motors such as kinesin-1. We determine an adequate energy conversion function for molecular motors and study the dynamics of intracellular transport by multiple motors. The results show that the average velocity of the coupled system is not affected by the number of active motors and that the stall force increases linearly as the number of motors increases. Our results are consistent with well-known experimental observations. We also examine the effects of coupling between the motors and the cargo, as well as of the spatial distribution of the motors around the cargo. Our model might provide a physical explanation of the cooperation among active motors in the cellular transport processes.
Dynamics of coupled vortices in perpendicular field
Jain, Shikha; Novosad, Valentyn Fradin, Frank Y.; Pearson, John E.; Bader, Samuel D.
2014-02-24
We explore the coupling mechanism of two magnetic vortices in the presence of a perpendicular bias field by pre-selecting the polarity combinations using the resonant-spin-ordering approach. First, out of the four vortex polarity combinations (two of which are degenerate), three stable core polarity states are achieved by lifting the degeneracy of one of the states. Second, the response of the stiffness constant for the vortex pair (similar polarity) in perpendicular bias is found to be asymmetric around the zero field, in contrast to the response obtained from a single vortex core. Finally, the collective response of the system for antiparallel core polarities is symmetric around zero bias. The vortex core whose polarization is opposite to the bias field dominates the response.
The dynamics of strong coupling gravity
NASA Astrophysics Data System (ADS)
Niedermaier, Max
2015-01-01
In the limit of infinite Newton constant, the 1+d dimensional vacuum Einstein equations reduce to their ‘velocity dominated’ counterparts. We construct all solutions with generic initial data and spatially closed sections by employing the constant mean curvature (CMC) gauge [1]. The latter is a nonlinearly admissible gauge in which the evolution equations are integrable ordinary differential equations and the diffeomorphism constraint decouples from the Hamiltonian constraint. The dynamical fields in this gauge are invariant under all gauge transformations but time independent spatial diffeomorphisms. The decoupled constraints are solved using a lapse-weighted conformal-traceless decomposition and produce equivalence classes of physical configurations modulo spatial diffeomorphisms. The CMC gauge can be augmented by a gauge condition {{χ }a} on the unimodular part of the spatial metric to provide a complete gauge fixing. Based on it a complete set of fully gauge invariant dynamical fields (observables) is constructed. By utilizing an algebraic gauge condition {{χ }a} a variant of the construction is found that isolates the physical degrees of freedoms algebraically.
Dynamic plasticity in coupled avian midbrain maps
NASA Astrophysics Data System (ADS)
Atwal, Gurinder Singh
2004-12-01
Internal mapping of the external environment is carried out using the receptive fields of topographic neurons in the brain, and in a normal barn owl the aural and visual subcortical maps are aligned from early experiences. However, instantaneous misalignment of the aural and visual stimuli has been observed to result in adaptive behavior, manifested by functional and anatomical changes of the auditory processing system. Using methods of information theory and statistical mechanics a model of the adaptive dynamics of the aural receptive field is presented and analyzed. The dynamics is determined by maximizing the mutual information between the neural output and the weighted sensory neural inputs, admixed with noise, subject to biophysical constraints. The reduced costs of neural rewiring, as in the case of young barn owls, reveal two qualitatively different types of receptive field adaptation depending on the magnitude of the audiovisual misalignment. By letting the misalignment increase with time, it is shown that the ability to adapt can be increased even when neural rewiring costs are high, in agreement with recent experimental reports of the increased plasticity of the auditory space map in adult barn owls due to incremental learning. Finally, a critical speed of misalignment is identified, demarcating the crossover from adaptive to nonadaptive behavior.
Dynamics of the Phase Oscillators with Plastic Couplings
NASA Astrophysics Data System (ADS)
Kasatkin, D. V.; Nekorkin, V. I.
2016-05-01
We study the dynamical regimes in the system of two identical interacting phase oscillators with plastic couplings. The joint evolution of the states of the elements and the interelement couplings is a feature of the system studied. It is shown that the introduction of plastic couplings leads to a multistable behavior of the system and emergence of the asynchronous regimes which are not observed for the considered parameter values in the case of static couplings. The parameter plane is divided into regions with different dynamic regimes of the system. In particular, the regions in which the system demonstrates bistable synchronous behavior and the region in which the coexistence of many various asynchronous regimes is observed are singled out.
Molecular dynamics with coupling to an external bath
NASA Astrophysics Data System (ADS)
Berendsen, H. J. C.; Postma, J. P. M.; van Gunsteren, W. F.; DiNola, A.; Haak, J. R.
1984-10-01
In molecular dynamics (MD) simulations the need often arises to maintain such parameters as temperature or pressure rather than energy and volume, or to impose gradients for studying transport properties in nonequilibrium MD. A method is described to realize coupling to an external bath with constant temperature or pressure with adjustable time constants for the coupling. The method is easily extendable to other variables and to gradients, and can be applied also to polyatomic molecules involving internal constraints. The influence of coupling time constants on dynamical variables is evaluated. A leap-frog algorithm is presented for the general case involving constraints with coupling to both a constant temperature and a constant pressure bath.
Pinning impulsive directed coupled delayed dynamical network and its applications
NASA Astrophysics Data System (ADS)
Lin, Chunnan; Wu, Quanjun; Xiang, Lan; Zhou, Jin
2015-01-01
The main objective of the present paper is to further investigate pinning synchronisation of a complex delayed dynamical network with directionally coupling by a single impulsive controller. By developing the analysis procedure of pinning impulsive stability for undirected coupled dynamical network previously, some simple yet general criteria of pinning impulsive synchronisation for such directed coupled network are derived analytically. It is shown that a single impulsive controller can always pin a given directed coupled network to a desired homogenous solution, including an equilibrium point, a periodic orbit, or a chaotic orbit. Subsequently, the theoretical results are illustrated by a directed small-world complex network which is a cellular neural network (CNN) and a directed scale-free complex network with the well-known Hodgkin-Huxley neuron oscillators. Numerical simulations are finally given to demonstrate the effectiveness of the proposed control methodology.
Synchronization in complex dynamical networks coupled with complex chaotic system
NASA Astrophysics Data System (ADS)
Wei, Qiang; Xie, Cheng-Jun; Wang, Bo
2015-11-01
This paper investigates synchronization in complex dynamical networks with time delay and perturbation. The node of complex dynamical networks is composed of complex chaotic system. A complex feedback controller is designed to realize different component of complex state variable synchronize up to different scaling complex function when complex dynamical networks realize synchronization. The synchronization scaling function is changed from real field to complex field. Synchronization in complex dynamical networks with constant delay and time-varying coupling delay are investigated, respectively. Numerical simulations show the effectiveness of the proposed method.
A dynamical stochastic coupled model for financial markets
NASA Astrophysics Data System (ADS)
Govindan, T. E.; Ibarra-Valdez, Carlos; Ruiz de Chávez, J.
2007-07-01
A model coupling a deterministic dynamical system which represents trading, with a stochastic one that represents asset prices evolution is presented. Both parts of the model have connections with well established dynamic models in mathematical economics and finance. The main objective is to represent the double feedback between trading dynamics (the demand/supply interaction) and price dynamics (assumed as largely random). We present the model, and address to some extent existence and uniqueness, continuity with respect to initial conditions and stability of solutions. The non-Lipschitz case is briefly considered as well.
Collective dynamics in strongly coupled dusty plasma medium
NASA Astrophysics Data System (ADS)
Das, Amita; Dharodi, Vikram; Tiwari, Sanat; Tiwari
2014-12-01
A simplified description of dynamical response of strongly coupled medium is desirable in many contexts of physics. The dusty plasma medium can play an important role in this regard due to its uniqueness, as its dynamical response typically falls within the perceptible grasp of human senses. Furthermore, even at room temperature and normal densities it can be easily prepared to be in a strongly coupled regime. A simplified phenomenological fluid model based on the visco - elastic behaviour of the medium is often invoked to represent the collective dynamical response of a strongly coupled dusty plasma medium. The manuscript reviews the role of this particular Generalized Hydrodynamic (GHD) fluid model in capturing the collective properties exhibited by the medium. In addition the paper also provides new insights on the collective behaviour predicted by the model for the medium, in terms of coherent structures, instabilities, transport and mixing properties.
Dynamic Plasticity of Coupled Cortical Maps
NASA Astrophysics Data System (ADS)
Atwal, G. S.
2003-03-01
Spatiotemporal location of an object may be achieved by inference from a combination of different noisy stimuli such as in the case of barn owls which locate prey using both aural and visual stimuli. The symbolic representation of an event is carried out using the receptive fields of neurons in the cortex, and in a normal barn owl the aural and visual receptive fields are aligned from early experiences. However, misalignment induced by the wearing of prismatic glasses may result in adaptive behavior, manifested by physical modification of the receptive fields. A model of this dynamic plasticity is presented and analyzed by maximising the weighted information of both sensory neural outputs, demonstrating a transition from adaptive to non-adaptive behavior as the rate of misalignment increases.
Invisible RNA state dynamically couples distant motifs
Lee, Janghyun; Dethoff, Elizabeth A.; Al-Hashimi, Hashim M.
2014-01-01
Using on- and off-resonance carbon and nitrogen R1ρ NMR relaxation dispersion in concert with mutagenesis and NMR chemical shift fingerprinting, we show that the transactivation response element RNA from the HIV-1 exists in dynamic equilibrium with a transient state that has a lifetime of ∼2 ms and population of ∼0.4%, which simultaneously remodels the structure of a bulge, stem, and apical loop. This is accomplished by a global change in strand register, in which bulge residues pair up with residues in the upper stem, causing a reshuffling of base pairs that propagates to the tip of apical loop, resulting in the creation of three noncanonical base pairs. Our results show that transient states can remodel distant RNA motifs and possibly give rise to mechanisms for rapid long-range communication in RNA that can be harnessed in processes such as cooperative folding and ribonucleoprotein assembly. PMID:24979799
Nonadiabatic dynamics of two strongly coupled nanomechanical resonator modes.
Faust, Thomas; Rieger, Johannes; Seitner, Maximilian J; Krenn, Peter; Kotthaus, Jörg P; Weig, Eva M
2012-07-20
The Landau-Zener transition is a fundamental concept for dynamical quantum systems and has been studied in numerous fields of physics. Here, we present a classical mechanical model system exhibiting analogous behavior using two inversely tunable, strongly coupled modes of the same nanomechanical beam resonator. In the adiabatic limit, the anticrossing between the two modes is observed and the coupling strength extracted. Sweeping an initialized mode across the coupling region allows mapping of the progression from diabatic to adiabatic transitions as a function of the sweep rate. PMID:22861892
Time-delayed coupled logistic capacity model in population dynamics
NASA Astrophysics Data System (ADS)
Cáceres, Manuel O.
2014-08-01
This study proposes a delay-coupled system based on the logistic equation that models the interaction of a population with its varying environment. The integro-diferential equations of the model are presented in terms of a distributed time-delayed coupled logistic-capacity equation. The model eliminates the need for a prior knowledge of the maximum saturation environmental carrying capacity value. Therefore the dynamics toward the final attractor in a distributed time-delayed coupled logistic-capacity model is studied. Exact results are presented, and analytical conclusions have been done in terms of the two parameters of the model.
Nuclear Hybrid Energy System Modeling: RELAP5 Dynamic Coupling Capabilities
Piyush Sabharwall; Nolan Anderson; Haihua Zhao; Shannon Bragg-Sitton; George Mesina
2012-09-01
The nuclear hybrid energy systems (NHES) research team is currently developing a dynamic simulation of an integrated hybrid energy system. A detailed simulation of proposed NHES architectures will allow initial computational demonstration of a tightly coupled NHES to identify key reactor subsystem requirements, identify candidate reactor technologies for a hybrid system, and identify key challenges to operation of the coupled system. This work will provide a baseline for later coupling of design-specific reactor models through industry collaboration. The modeling capability addressed in this report focuses on the reactor subsystem simulation.
Coupled dynamics of translation and collapse of acoustically driven microbubbles.
Reddy, Anil J; Szeri, Andrew J
2002-10-01
Pressure gradients drive the motion of microbubbles relative to liquids in which they are suspended. Examples include the hydrostatic pressure due to a gravitational field, and the pressure gradients in a sound field, useful for acoustic levitation. In this paper, the equations describing the coupled dynamics of radial oscillation and translation of a microbubble are given. The formulation is based on a recently derived expression for the hydrodynamic force on a bubble of changing size in an incompressible liquid [J. Magnaudet and D. Legendre, Phys. Fluids 10, 550-556 (1998)]. The complex interaction between radial and translation dynamics is best understood by examination of the added momentum associated with the liquid motion caused by the moving bubble. Translation is maximized when the bubble collapses violently. The new theory for coupled collapse and translation dynamics is compared to past experiments and to previous theories for decoupled translation dynamics. Special attention is paid to bubbles of relevance in biomedical applications. PMID:12398441
An elementary mode coupling theory of random heteropolymer dynamics.
Takada, S; Portman, J J; Wolynes, P G
1997-03-18
The Langevin dynamics of a random heteropolymer and its dynamic glass transition are studied using elementary mode coupling theory. Contrary to recent reports using a similar framework, a discontinuous ergodic-nonergodic phase transition is predicted for all Rouse modes at a finite temperature T(A). For sufficiently long chains, T(A) is almost independent of chain length and is in good agreement with the value previously estimated by a static replica theory. PMID:9122192
Dynamic regimes of hydrodynamically coupled self-propelling particles
NASA Astrophysics Data System (ADS)
Llopis, I.; Pagonabarraga, I.
2006-09-01
We analyze the collective dynamics of self-propelling particles (spps) which move at small Reynolds numbers including the hydrodynamic coupling to the suspending solvent through numerical simulations. The velocity distribution functions show marked deviations from Gaussian behavior at short times, and the mean-square displacement at long times shows a transition from diffusive to ballistic motion for appropriate driving mechanism at low concentrations. We discuss the structures the spps form at long times and how they correlate to their dynamic behavior.
Inductive-dynamic magnetosphere-ionosphere coupling via MHD waves
NASA Astrophysics Data System (ADS)
Tu, Jiannan; Song, Paul; Vasyliūnas, Vytenis M.
2014-01-01
In the present study, we investigate magnetosphere-ionosphere/thermosphere (M-IT) coupling via MHD waves by numerically solving time-dependent continuity, momentum, and energy equations for ions and neutrals, together with Maxwell's equations (Ampère's and Faraday's laws) and with photochemistry included. This inductive-dynamic approach we use is fundamentally different from those in previous magnetosphere-ionosphere (M-I) coupling models: all MHD wave modes are retained, and energy and momentum exchange between waves and plasma are incorporated into the governing equations, allowing a self-consistent examination of dynamic M-I coupling. Simulations, using an implicit numerical scheme, of the 1-D ionosphere/thermosphere system responding to an imposed convection velocity at the top boundary are presented to show how magnetosphere and ionosphere are coupled through Alfvén waves during the transient stage when the IT system changes from one quasi steady state to another. Wave reflection from the low-altitude ionosphere plays an essential role, causing overshoots and oscillations of ionospheric perturbations, and the dynamical Hall effect is an inherent aspect of the M-I coupling. The simulations demonstrate that the ionosphere/thermosphere responds to magnetospheric driving forces as a damped oscillator.
The dynamical correlation in spacer-mediated electron transfer couplings
Yang, C.-H.; Hsu, C.-P.
2006-06-28
The dynamical correlation effect in electron transfer (ET) coupling was studied in this work, for cases where electrons tunnel through a many-electron environment. The ET couplings for three different bridge-mediated model systems were calculated: (I) trans-alkyl chains [H{sub 2}C-(CH{sub 2}){sub n}-CH{sub 2}, n=2-10], (II) two isomers of trans-1,4-dimethylenecyclohexane, and (III) two ethylenes spaced by a saturated ethane molecule. The couplings were calculated as half energy gaps of the two lowest adiabatic states. The dynamical correlation was included with spin-flip (SF) and ionization potential or electron affinity coupled-cluster singles and doubles (SF-CCSD and IP/EA-CCSD) and a {delta}CCSD scheme. The direct coupling (DC) scheme is also used as a way to obtain a solution with nondynamical correlation, since DC uses approximated eigenstates that are symmetry-restoring linear combinations of two symmetry-broken unrestricted Hartree-Fock configurations. For all cases tested except for one, results from the DC scheme closely follow the CCSD data, indicating that the dual-configuration solutions can be a good approximation of wave functions with nondynamical correlation included, but there exist exceptions. Comparing the DC results with SF-CCSD and IP or EA-CCSD data, we concluded that the dynamical correlation effect is small for most of the cases we tested.
Coupling Dynamics Interlip Coordination in Lower Lip Load Compensation
ERIC Educational Resources Information Center
van Lieshout, Pascal; Neufeld, Chris
2014-01-01
Purpose: To study the effects of lower lip loading on lower and upper lip movements and their coordination to test predictions on coupling dynamics derived from studies in limb control. Method: Movement data were acquired using electromagnetic midsagittal articulography under 4 conditions: (a) without restrictions, serving as a baseline; (b) with…
SOLITONS: Dynamics of strong coupling formation between laser solitons
NASA Astrophysics Data System (ADS)
Rosanov, Nikolai N.; Fedorov, S. V.; Shatsev, A. N.
2005-03-01
The dynamics of the strong coupling formation between two solitons with the unit topological charge is studied in detail for a wide-aperture class A laser. The sequence of bifurcations of the vector field of energy fluxes in the transverse plane was demonstrated during the formation of a soliton complex.
Analysis of the numerics of physics-dynamics coupling
NASA Astrophysics Data System (ADS)
Staniforth, Andrew; Wood, Nigel; Côté, Jean
2002-10-01
A methodology for analysing the numerical properties of schemes for coupling physics parametrizations to a dynamical core is presented. As an example of its application, the methodology is used to study four coupling schemes ('explicit', 'implicit', 'split-implicit' and 'symmetrized split-implicit') in the context of a semi-implicit semi-Lagrangian dynamical core. Each coupling scheme is assessed in terms of its numerical stability and of the accuracy of both its transient and steady-state responses. Additionally, the occurrence of spurious, computational resonance is analysed and discussed. It is found that in this respect all four schemes behave similarly.In particular, in the absence of any damping mechanism to control resonance, the time-step restriction needed to avoid spurious resonance is twice as restrictive for time-dependent forcing as for stationary forcing.
Dynamics of Coupled Cell Networks: Synchrony, Heteroclinic Cycles and Inflation
NASA Astrophysics Data System (ADS)
Aguiar, M.; Ashwin, P.; Dias, A.; Field, M.
2011-04-01
We consider the dynamics of small networks of coupled cells. We usually assume asymmetric inputs and no global or local symmetries in the network and consider equivalence of networks in this setting; that is, when two networks with different architectures give rise to the same set of possible dynamics. Focussing on transitive (strongly connected) networks that have only one type of cell (identical cell networks) we address three questions relating the network structure to dynamics. The first question is how the structure of the network may force the existence of invariant subspaces (synchrony subspaces). The second question is how these invariant subspaces can support robust heteroclinic attractors. Finally, we investigate how the dynamics of coupled cell networks with different structures and numbers of cells can be related; in particular we consider the sets of possible "inflations" of a coupled cell network that are obtained by replacing one cell by many of the same type, in such a way that the original network dynamics is still present within a synchrony subspace. We illustrate the results with a number of examples of networks of up to six cells.
Quantum emitters dynamically coupled to a quantum field
Acevedo, O. L.; Quiroga, L.; Rodríguez, F. J.; Johnson, N. F.
2013-12-04
We study theoretically the dynamical response of a set of solid-state quantum emitters arbitrarily coupled to a single-mode microcavity system. Ramping the matter-field coupling strength in round trips, we quantify the hysteresis or irreversible quantum dynamics. The matter-field system is modeled as a finite-size Dicke model which has previously been used to describe equilibrium (including quantum phase transition) properties of systems such as quantum dots in a microcavity. Here we extend this model to address non-equilibrium situations. Analyzing the system’s quantum fidelity, we find that the near-adiabatic regime exhibits the richest phenomena, with a strong asymmetry in the internal collective dynamics depending on which phase is chosen as the starting point. We also explore signatures of the crossing of the critical points on the radiation subsystem by monitoring its Wigner function; then, the subsystem can exhibit the emergence of non-classicality and complexity.
Magnetization dynamics in exchange coupled antiferromagnet spin superfluids
NASA Astrophysics Data System (ADS)
Liu, Yizhou; Barlas, Yafis; Yin, Gen; Zang, Jiadong; Lake, Roger
Antiferromagnets (AFMs) are commonly used as the exchange bias layer in magnetic recording and spintronic devices. Recently, several studies on the spin transfer torque and spin pumping in AFMs reveal much more interesting physics in AFMs. Properties of AFMs such as the ultrafast switching within picoseconds and spin superfluidity demonstrate the potential to build AFM based spintronic devices. Here, we study the magnetization dynamics in an exchange coupled AFM systems. Beginning from the Landau-Lifshitz-Gilbert equation, we derive a Josephson-like equation for the exchange coupled system. We investigate the detailed magnetization dynamics by employing spin injection and spin pumping theory. We also propose a geometry that could be used to measure this magnetization dynamics. This work was supported as part of the Spins and Heat in Nanoscale Electronic Systems (SHINES) an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #SC0012670.
Quench dynamics of two coupled zig-zag ion chains
NASA Astrophysics Data System (ADS)
Klumpp, Andrea; Liebchen, Benno; Schmelcher, Peter
2016-08-01
We explore the non-equilibrium dynamics of two coupled zig-zag chains of trapped ions in a double well potential. Following a quench of the potential barrier between both wells, the induced coupling between both chains due to the long-range interaction of the ions leads to the complete loss of order in the radial direction. The resulting dynamics is however not exclusively irregular but leads to phases of motion during which various ordered structures appear with ions arranged in arcs, lines and crosses. We quantify the emerging order by introducing a suitable measure and complement our analysis of the ion dynamics using a normal mode analysis showing a decisive population transfer between only a few distinguished modes.
Dynamics of the excitonic coupling in organic crystals.
Aragó, Juan; Troisi, Alessandro
2015-01-16
We show that the excitonic coupling in molecular crystals undergoes a very large fluctuation at room temperature as a result of the combined thermal motions of the nuclei. This observation dramatically affects the description of exciton transport in organic crystals and any other phenomenon (like singlet fission or exciton dissociation) that originates from an exciton in a molecular crystal or thin film. This unexpected result is due to the predominance of the short-range excitonic coupling mechanisms (exchange, overlap, and charge-transfer mediated) over the Coulombic excitonic coupling for molecules in van der Waals contact. To quantify this effect we develop a procedure to evaluate accurately the short-range excitonic coupling (via a diabatization scheme) along a molecular dynamics trajectory of the representative molecular crystals of anthracene and tetracene. PMID:25635554
Dynamics of the Excitonic Coupling in Organic Crystals
NASA Astrophysics Data System (ADS)
Aragó, Juan; Troisi, Alessandro
2015-01-01
We show that the excitonic coupling in molecular crystals undergoes a very large fluctuation at room temperature as a result of the combined thermal motions of the nuclei. This observation dramatically affects the description of exciton transport in organic crystals and any other phenomenon (like singlet fission or exciton dissociation) that originates from an exciton in a molecular crystal or thin film. This unexpected result is due to the predominance of the short-range excitonic coupling mechanisms (exchange, overlap, and charge-transfer mediated) over the Coulombic excitonic coupling for molecules in van der Waals contact. To quantify this effect we develop a procedure to evaluate accurately the short-range excitonic coupling (via a diabatization scheme) along a molecular dynamics trajectory of the representative molecular crystals of anthracene and tetracene.
Reduction of Additive Colored Noise Using Coupled Dynamics
NASA Astrophysics Data System (ADS)
Kohar, Vivek; Kia, Behnam; Lindner, John F.; Ditto, William L.
We study the effect of additive colored noise on the evolution of maps and demonstrate that the deviations caused by such noise can be reduced using coupled dynamics. We consider both Ornstein-Uhlenbeck process as well as 1/fα noise in our numerical simulations. We observe that though the variance of deviations caused by noise depends on the correlations in the noise, under optimal coupling strength, it decreases by a factor equal to the number of coupled elements in the array as compared to the variance of deviations in a single isolated map. This reduction in noise levels occurs in chaotic as well as periodic regime of the maps. Lastly, we examine the effect of colored noise in chaos computing and find that coupling the chaos computing elements enhances the robustness of chaos computing.
Coupled Polarization/magnetization Dynamics in Composite Multiferroics: AN Overview
NASA Astrophysics Data System (ADS)
Sukhov, A.; Chotorlishvili, L.; Jia, C. L.; Berakdar, J.
In this chapter we present a theoretical approach for modeling the coupled polarization-magnetization dynamics in composite multiferroic nanostructures. The free energy functional is based on coupling established expressions for the the Ginzburg-Landau-Devonshire polarization free energy density with the Landau-Ginzburg magnetization free energy density. The polarization/magnetization coupling term depends on the nature of the underlying magnetoelectric interaction. As an example we inspect the role of an emerging non-collinear spin order at the ferroelectric/magnetic interface and discuss how this mechanism is reflected in the total free energy density. We present and analyze numerical results for the coupled polarization and magnetization dynamics driven by external electric and magnetic fields and show how this dynamics can be accessed experimentally via ferromagnetic resonance in nanostructured multiferroic BaTiO3/Fe or BaTiO3/Co composites. As a way for robust signal transmission and conversion, solitonic excitations are envisaged. The finding is that initially prepared magnetic (electric) solitonic signals propagate towards the interface where they are efficiently converted into electric (magnetic) signals. In a further section we explore the potential of multiferroics for quantum information applications.
The Coupled Chemical and Physical Dynamics Model of MALDI.
Knochenmuss, Richard
2016-06-12
The coupled physical and chemical dynamics model of ultraviolet matrix-assisted laser desorption/ionization (MALDI) has reproduced and explained a wide variety of MALDI phenomena. The rationale behind and elements of the model are reviewed, including the photophysics, kinetics, and thermodynamics of primary and secondary reaction steps. Experimental results are compared with model predictions to illustrate the foundations of the model, coupling of ablation and ionization, differences between and commonalities of matrices, secondary charge transfer reactions, ionization in both polarities, fluence and concentration dependencies, and suppression and enhancement effects. PMID:27070182
Dynamic Jahn-Teller coupling and high T c superconductivity
NASA Astrophysics Data System (ADS)
Clougherty, Dennis P.; Johnson, Keith H.; McHenry, Michael E.
1989-12-01
Based on the cooperative dynamic Jahn-Teller effect, a universal model of superconductivity is sketched which accounts for many aspects of conventional BCS and high T c superconductors. Within the quasi-molecular approximation, a real space vibronic coupling of degenerate (or nearly degenerate) electronic states to anharmonically mixed nuclear distortions is shown to lead to electron pairing. The crossover from electron-phonon behavior to electronic behavior as a function of Jahn-Teller coupling and anharmonic mixing is illustrated for the case of a CuO 4 cluster having D 4 h symmetry.
Multimode dynamics in a network with resource mediated coupling
NASA Astrophysics Data System (ADS)
Postnov, D. E.; Sosnovtseva, O. V.; Scherbakov, P.; Mosekilde, E.
2008-03-01
The purpose of this paper is to study the special forms of multimode dynamics that one can observe in systems with resource-mediated coupling, i.e., systems of self-sustained oscillators in which the coupling takes place via the distribution of primary resources that controls the oscillatory state of the individual unit. With this coupling, a spatially inhomogenous state with mixed high and low-amplitude oscillations in the individual units can arise. To examine generic phenomena associated with this type of interaction we consider a chain of resistively coupled electronic oscillators connected to a common power supply. The two-oscillator system displays antiphase synchronization, and it is interesting to note that two-mode oscillations continue to exist outside of the parameter range in which oscillations occur for the individual unit. At low coupling strengths, the multi-oscillator system shows high dimensional quasiperiodicity with little tendency for synchronization. At higher coupling strengths, one typically observes spatial clustering involving a few oscillating units. We describe three different scenarios according to which the cluster can slide along the chain as the bias voltage changes.
Coupled disease-behavior dynamics on complex networks: A review.
Wang, Zhen; Andrews, Michael A; Wu, Zhi-Xi; Wang, Lin; Bauch, Chris T
2015-12-01
It is increasingly recognized that a key component of successful infection control efforts is understanding the complex, two-way interaction between disease dynamics and human behavioral and social dynamics. Human behavior such as contact precautions and social distancing clearly influence disease prevalence, but disease prevalence can in turn alter human behavior, forming a coupled, nonlinear system. Moreover, in many cases, the spatial structure of the population cannot be ignored, such that social and behavioral processes and/or transmission of infection must be represented with complex networks. Research on studying coupled disease-behavior dynamics in complex networks in particular is growing rapidly, and frequently makes use of analysis methods and concepts from statistical physics. Here, we review some of the growing literature in this area. We contrast network-based approaches to homogeneous-mixing approaches, point out how their predictions differ, and describe the rich and often surprising behavior of disease-behavior dynamics on complex networks, and compare them to processes in statistical physics. We discuss how these models can capture the dynamics that characterize many real-world scenarios, thereby suggesting ways that policy makers can better design effective prevention strategies. We also describe the growing sources of digital data that are facilitating research in this area. Finally, we suggest pitfalls which might be faced by researchers in the field, and we suggest several ways in which the field could move forward in the coming years. PMID:26211717
Coupled disease-behavior dynamics on complex networks: A review
NASA Astrophysics Data System (ADS)
Wang, Zhen; Andrews, Michael A.; Wu, Zhi-Xi; Wang, Lin; Bauch, Chris T.
2015-12-01
It is increasingly recognized that a key component of successful infection control efforts is understanding the complex, two-way interaction between disease dynamics and human behavioral and social dynamics. Human behavior such as contact precautions and social distancing clearly influence disease prevalence, but disease prevalence can in turn alter human behavior, forming a coupled, nonlinear system. Moreover, in many cases, the spatial structure of the population cannot be ignored, such that social and behavioral processes and/or transmission of infection must be represented with complex networks. Research on studying coupled disease-behavior dynamics in complex networks in particular is growing rapidly, and frequently makes use of analysis methods and concepts from statistical physics. Here, we review some of the growing literature in this area. We contrast network-based approaches to homogeneous-mixing approaches, point out how their predictions differ, and describe the rich and often surprising behavior of disease-behavior dynamics on complex networks, and compare them to processes in statistical physics. We discuss how these models can capture the dynamics that characterize many real-world scenarios, thereby suggesting ways that policy makers can better design effective prevention strategies. We also describe the growing sources of digital data that are facilitating research in this area. Finally, we suggest pitfalls which might be faced by researchers in the field, and we suggest several ways in which the field could move forward in the coming years.
Dynamic model of neural networks with asymmetric diluted couplings
NASA Astrophysics Data System (ADS)
Choi, M. Y.; Choi, Meekyoung
1990-06-01
We study an asymmetric diluted version of the dynamic model for neural networks proposed recently, which explicitly takes into account the existence of several time scales without discretizing the time. The dynamics is neither totally synchronous nor totally asynchronous, and the couplings in the neural networks are asymmetric. These considerations may be regarded as more biologically realistic. We obtain the phase diagram as a function of the temperature ɛ-1, the capacity α, and the ratio a of the refractory period to the action potential duration.
Nonlinearly coupled dynamics of irregularities in the equatorial electrojet
NASA Astrophysics Data System (ADS)
Atul, J. K.; Sarkar, S.; Singh, S. K.
2016-04-01
Kinetic wave description is used to study the nonlinear influence of background Farley Buneman (FB) modes on the Gradient Drift (GD) modes in the equatorial electrojet ionosphere. The dominant nonlinearity is mediated through the electron flux term in the governing fluid equation which further invokes a turbulent current into the system. Electron dynamics reveals the modification in electron collision frequency and inhomogeneity scale length. It is seen that the propagation and growth rate of GD modes get modified by the background FB modes. Also, a new quasimode gets excited through the quadratic dispersion relation. Physical significance of coupled dynamics between the participating modes is also discussed.
Sequential dynamics in the motif of excitatory coupled elements
NASA Astrophysics Data System (ADS)
Korotkov, Alexander G.; Kazakov, Alexey O.; Osipov, Grigory V.
2015-11-01
In this article a new model of motif (small ensemble) of neuron-like elements is proposed. It is built with the use of the generalized Lotka-Volterra model with excitatory couplings. The main motivation for this work comes from the problems of neuroscience where excitatory couplings are proved to be the predominant type of interaction between neurons of the brain. In this paper it is shown that there are two modes depending on the type of coupling between the elements: the mode with a stable heteroclinic cycle and the mode with a stable limit cycle. Our second goal is to examine the chaotic dynamics of the generalized three-dimensional Lotka-Volterra model.
Integrable order parameter dynamics of globally coupled oscillators
NASA Astrophysics Data System (ADS)
Pritula, G. M.; Prytula, V. I.; Usatenko, O. V.
2016-02-01
We study the nonlinear dynamics of globally coupled nonidentical oscillators in the framework of two order parameter (mean field and amplitude-frequency correlator) reduction. The main result of the paper is the exact solution of a corresponding nonlinear system on a two-dimensional invariant manifold. We present a complete classification of phase portraits and bifurcations, obtain explicit expressions for invariant manifolds (a limit cycle among them) and derive analytical solutions for arbitrary initial data and different regimes.
Pinning synchronization of discrete dynamical networks with delay coupling
NASA Astrophysics Data System (ADS)
Cheng, Ranran; Peng, Mingshu; Zuo, Jun
2016-05-01
The purpose of this paper is to investigate the pinning synchronization analysis for nonlinear coupled delayed discrete dynamical networks with the identical or nonidentical topological structure. Based on the Lyapunov stability theory, pinning control method and linear matrix inequalities, several adaptive synchronization criteria via two kinds of pinning control method are obtained. Two examples based on Rulkov chaotic system are included to illustrate the effectiveness and verification of theoretical analysis.
Relationship dynamics around depression in gay and lesbian couples.
Thomeer, Mieke Beth; Reczek, Corinne; Umberson, Debra
2015-12-01
Research on intimate relationship dynamics around depression has primarily focused on heterosexual couples. This body of work shows that wives are more likely than husbands to offer support to a depressed spouse. Moreover, when wives are depressed, they are more likely than husbands to try and shield their spouse from the stress of their own depression. Yet, previous research has not examined depression and relationship dynamics in gay and lesbian couples. We analyze in-depth interviews with 26 gay and lesbian couples (N = 52 individuals) in which one or both partners reported depression. We find evidence that dominant gender scripts are both upheld and challenged within gay and lesbian couples, providing important insight into how gender operates in relation to depression within same-sex contexts. Our results indicate that most gay and lesbian partners offer support to a depressed partner, yet lesbian couples tend to follow a unique pattern in that they provide support both as the non-depressed and depressed partner. Support around depression is sometimes viewed as improving the relationship, but if the support is intensive or rejected, it is often viewed as contributing to relationship strain. Support is also sometimes withdrawn by the non-depressed partner because of caregiver exhaustion or the perception that the support is unhelpful. This study points to the importance of considering depression within gay and lesbian relational contexts, revealing new ways support sustains and strains intimate partnerships. We emphasize the usefulness of deploying couple-level approaches to better understand depression in sexual minority populations. PMID:26523788
The coupled nonlinear dynamics of a lift system
Crespo, Rafael Sánchez E-mail: stefan.kaczmarczyk@northampton.ac.uk E-mail: huijuan.su@northampton.ac.uk; Kaczmarczyk, Stefan E-mail: stefan.kaczmarczyk@northampton.ac.uk E-mail: huijuan.su@northampton.ac.uk; Picton, Phil E-mail: stefan.kaczmarczyk@northampton.ac.uk E-mail: huijuan.su@northampton.ac.uk; Su, Huijuan E-mail: stefan.kaczmarczyk@northampton.ac.uk E-mail: huijuan.su@northampton.ac.uk
2014-12-10
Coupled lateral and longitudinal vibrations of suspension and compensating ropes in a high-rise lift system are often induced by the building motions due to wind or seismic excitations. When the frequencies of the building become near the natural frequencies of the ropes, large resonance motions of the system may result. This leads to adverse coupled dynamic phenomena involving nonplanar motions of the ropes, impact loads between the ropes and the shaft walls, as well as vertical vibrations of the car, counterweight and compensating sheave. Such an adverse dynamic behaviour of the system endangers the safety of the installation. This paper presents two mathematical models describing the nonlinear responses of a suspension/ compensating rope system coupled with the elevator car / compensating sheave motions. The models accommodate the nonlinear couplings between the lateral and longitudinal modes, with and without longitudinal inertia of the ropes. The partial differential nonlinear equations of motion are derived using Hamilton Principle. Then, the Galerkin method is used to discretise the equations of motion and to develop a nonlinear ordinary differential equation model. Approximate numerical solutions are determined and the behaviour of the system is analysed.
The coupled nonlinear dynamics of a lift system
NASA Astrophysics Data System (ADS)
Crespo, Rafael Sánchez; Kaczmarczyk, Stefan; Picton, Phil; Su, Huijuan
2014-12-01
Coupled lateral and longitudinal vibrations of suspension and compensating ropes in a high-rise lift system are often induced by the building motions due to wind or seismic excitations. When the frequencies of the building become near the natural frequencies of the ropes, large resonance motions of the system may result. This leads to adverse coupled dynamic phenomena involving nonplanar motions of the ropes, impact loads between the ropes and the shaft walls, as well as vertical vibrations of the car, counterweight and compensating sheave. Such an adverse dynamic behaviour of the system endangers the safety of the installation. This paper presents two mathematical models describing the nonlinear responses of a suspension/ compensating rope system coupled with the elevator car / compensating sheave motions. The models accommodate the nonlinear couplings between the lateral and longitudinal modes, with and without longitudinal inertia of the ropes. The partial differential nonlinear equations of motion are derived using Hamilton Principle. Then, the Galerkin method is used to discretise the equations of motion and to develop a nonlinear ordinary differential equation model. Approximate numerical solutions are determined and the behaviour of the system is analysed.
Coarse-Grained Clustering Dynamics of Heterogeneously Coupled Neurons.
Moon, Sung Joon; Cook, Katherine A; Rajendran, Karthikeyan; Kevrekidis, Ioannis G; Cisternas, Jaime; Laing, Carlo R
2015-12-01
The formation of oscillating phase clusters in a network of identical Hodgkin-Huxley neurons is studied, along with their dynamic behavior. The neurons are synaptically coupled in an all-to-all manner, yet the synaptic coupling characteristic time is heterogeneous across the connections. In a network of N neurons where this heterogeneity is characterized by a prescribed random variable, the oscillatory single-cluster state can transition-through [Formula: see text] (possibly perturbed) period-doubling and subsequent bifurcations-to a variety of multiple-cluster states. The clustering dynamic behavior is computationally studied both at the detailed and the coarse-grained levels, and a numerical approach that can enable studying the coarse-grained dynamics in a network of arbitrarily large size is suggested. Among a number of cluster states formed, double clusters, composed of nearly equal sub-network sizes are seen to be stable; interestingly, the heterogeneity parameter in each of the double-cluster components tends to be consistent with the random variable over the entire network: Given a double-cluster state, permuting the dynamical variables of the neurons can lead to a combinatorially large number of different, yet similar "fine" states that appear practically identical at the coarse-grained level. For weak heterogeneity we find that correlations rapidly develop, within each cluster, between the neuron's "identity" (its own value of the heterogeneity parameter) and its dynamical state. For single- and double-cluster states we demonstrate an effective coarse-graining approach that uses the Polynomial Chaos expansion to succinctly describe the dynamics by these quickly established "identity-state" correlations. This coarse-graining approach is utilized, within the equation-free framework, to perform efficient computations of the neuron ensemble dynamics. PMID:26458901
Vanag, Vladimir K; Smelov, Pavel S; Klinshov, Vladimir V
2016-02-21
The dynamic regimes in networks of four almost identical spike oscillators with pulsatile coupling via inhibitor are systematically studied. We used two models to describe individual oscillators: a phase-oscillator model and a model for the Belousov-Zhabotinsky reaction. A time delay τ between a spike in one oscillator and the spike-induced inhibitory perturbation of other oscillators is introduced. Diagrams of all rhythms found for three different types of connectivities (unidirectional on a ring, mutual on a ring, and all-to-all) are built in the plane C(inh)-τ, where C(inh) is the coupling strength. It is shown analytically and numerically that only four regular rhythms are stable for unidirectional coupling: walk (phase shift between spikes of neighbouring oscillators equals the quarter of the global period T), walk-reverse (the same as walk but consecutive spikes take place in the direction opposite to the direction of connectivity), anti-phase (any two neighbouring oscillators are anti-phase), and in-phase oscillations. In the case of mutual on the ring coupling, an additional in-phase-anti-phase mode emerges. For all-to-all coupling, two new asymmetrical patterns (two-cluster and three-cluster modes) have been found. More complex rhythms are observed at large C(inh), when some oscillators are suppressed completely or generate smaller number of spikes than others. PMID:26863079
Phase response curves elucidating the dynamics of coupled oscillators.
Granada, A; Hennig, R M; Ronacher, B; Kramer, A; Herzel, H
2009-01-01
Phase response curves (PRCs) are widely used in circadian clocks, neuroscience, and heart physiology. They quantify the response of an oscillator to pulse-like perturbations. Phase response curves provide valuable information on the properties of oscillators and their synchronization. This chapter discusses biological self-sustained oscillators (circadian clock, physiological rhythms, etc.) in the context of nonlinear dynamics theory. Coupled oscillators can synchronize with different frequency ratios, can generate toroidal dynamics (superposition of independent frequencies), and may lead to deterministic chaos. These nonlinear phenomena can be analyzed with the aid of a phase transition curve, which is intimately related to the phase response curve. For illustration purposes, this chapter discusses a model of circadian oscillations based on a delayed negative feedback. In a second part, the chapter provides a step-by-step recipe to measure phase response curves. It discusses specifications of this recipe for circadian rhythms, heart rhythms, neuronal spikes, central pattern generators, and insect communication. Finally, it stresses the predictive power of measured phase response curves. PRCs can be used to quantify the coupling strength of oscillations, to classify oscillator types, and to predict the complex dynamics of periodically driven oscillations. PMID:19216921
Self-organized network evolution coupled to extremal dynamics
NASA Astrophysics Data System (ADS)
Garlaschelli, Diego; Capocci, Andrea; Caldarelli, Guido
2007-11-01
The interplay between topology and dynamics in complex networks is a fundamental but widely unexplored problem. Here, we study this phenomenon on a prototype model in which the network is shaped by a dynamical variable. We couple the dynamics of the Bak-Sneppen evolution model with the rules of the so-called fitness network model for establishing the topology of a network; each vertex is assigned a `fitness', and the vertex with minimum fitness and its neighbours are updated in each iteration. At the same time, the links between the updated vertices and all other vertices are drawn anew with a fitness-dependent connection probability. We show analytically and numerically that the system self-organizes to a non-trivial state that differs from what is obtained when the two processes are decoupled. A power-law decay of dynamical and topological quantities above a threshold emerges spontaneously, as well as a feedback between different dynamical regimes and the underlying correlation and percolation properties of the network.
Phase and amplitude dynamics of nonlinearly coupled oscillators
NASA Astrophysics Data System (ADS)
Cudmore, P.; Holmes, C. A.
2015-02-01
This paper addresses the amplitude and phase dynamics of a large system of nonlinearly coupled, non-identical damped harmonic oscillators, which is based on recent research in coupled oscillation in optomechanics. Our goal is to investigate the existence and stability of collective behaviour which occurs due to a play-off between the distribution of individual oscillator frequency and the type of nonlinear coupling. We show that this system exhibits synchronisation, where all oscillators are rotating at the same rate, and that in the synchronised state the system has a regular structure related to the distribution of the frequencies of the individual oscillators. Using a geometric description, we show how changes in the non-linear coupling function can cause pitchfork and saddle-node bifurcations which create or destroy stable and unstable synchronised solutions. We apply these results to show how in-phase and anti-phase solutions are created in a system with a bi-modal distribution of frequencies.
Photoexcitation dynamics of coupled semiconducting carbon nanotube thin films.
Mehlenbacher, Randy D; Wu, Meng-Yin; Grechko, Maksim; Laaser, Jennifer E; Arnold, Michael S; Zanni, Martin T
2013-04-10
Carbon nanotubes are a promising means of capturing photons for use in solar cell devices. We time-resolved the photoexcitation dynamics of coupled, bandgap-selected, semiconducting carbon nanotubes in thin films tailored for photovoltaics. Using transient absorption spectroscopy and anisotropy measurements, we found that the photoexcitation evolves by two mechanisms with a fast and long-range component followed by a slow and short-range component. Within 300 fs of optical excitation, 20% of nanotubes transfer their photoexcitation over 5-10 nm into nearby nanotube fibers. After 3 ps, 70% of the photoexcitation resides on the smallest bandgap nanotubes. After this ultrafast process, the photoexcitation continues to transfer on a ~10 ps time scale but to predominantly aligned tubes. Ultimately the photoexcitation hops twice on average between fibers. These results are important for understanding the flow of energy and charge in coupled nanotube materials and light-harvesting devices. PMID:23464618
Bell states and entanglement dynamics on two coupled quantum molecules
Oliveira, P.A.; Sanz, L.
2015-05-15
This work provides a complete description of entanglement properties between electrons inside coupled quantum molecules, nanoestructures which consist of two quantum dots. Each electron can tunnel between the two quantum dots inside the molecule, being also coupled by Coulomb interaction. First, it is shown that Bell states act as a natural basis for the description of this physical system, defining the characteristics of the energy spectrum and the eigenstates. Then, the entanglement properties of the eigenstates are discussed, shedding light on the roles of each physical parameters on experimental setup. Finally, a detailed analysis of the dynamics shows the path to generate states with a high degree of entanglement, as well as physical conditions associated with coherent oscillations between separable and Bell states.
Fractional dynamics of coupled oscillators with long-range interaction
Tarasov, Vasily E.; Zaslavsky, George M.
2006-06-15
We consider a one-dimensional chain of coupled linear and nonlinear oscillators with long-range powerwise interaction. The corresponding term in dynamical equations is proportional to 1/|n-m|{sup {alpha}}{sup +1}. It is shown that the equation of motion in the infrared limit can be transformed into the medium equation with the Riesz fractional derivative of order {alpha}, when 0<{alpha}<2. We consider a few models of coupled oscillators and show how their synchronization can appear as a result of bifurcation, and how the corresponding solutions depend on {alpha}. The presence of a fractional derivative also leads to the occurrence of localized structures. Particular solutions for fractional time-dependent complex Ginzburg-Landau (or nonlinear Schroedinger) equation are derived. These solutions are interpreted as synchronized states and localized structures of the oscillatory medium.
Calcium dynamics in astrocyte processes during neurovascular coupling
Otsu, Yo; Couchman, Kiri; Lyons, Declan G; Collot, Mayeul; Agarwal, Amit; Mallet, Jean-Maurice; Pfrieger, Frank W; Bergles, Dwight E; Charpak, Serge
2015-01-01
Enhanced neuronal activity in the brain triggers a local increase in blood flow, termed functional hyperemia, via several mechanisms, including calcium (Ca2+) signaling in astrocytes. However, recent in vivo studies have questioned the role of astrocytes in functional hyperemia because of the slow and sparse dynamics of their somatic Ca2+ signals and the absence of glutamate metabotropic receptor 5 in adults. Here, we reexamined their role in neurovascular coupling by selectively expressing a genetically encoded Ca2+ sensor in astrocytes of the olfactory bulb. We show that in anesthetized mice, the physiological activation of olfactory sensory neuron (OSN) terminals reliably triggers Ca2+ increases in astrocyte processes but not in somata. These Ca2+ increases systematically precede the onset of functional hyperemia by 1–2 s, reestablishing astrocytes as potential regulators of neurovascular coupling. PMID:25531572
Cheung, Nicole W T
2015-02-01
Knowledge of the influence of couple dynamics on gender differences in gambling behavior remains meager. Building on general strain theory from the sociology of deviance and stress crossover theory from social psychology, we argue that the strain encountered by one partner in a social setting may affect his or her spouse. For instance, the wife of a man under more social strain may experience more strain in turn and thus be at a higher risk of developing disordered gambling than the wife of a man under less social strain. Using community survey data of 1620 Chinese married couples, we performed multilevel dyad analyses to address social strain and couple dynamics, in addition to their roles as predictors of gambling behavior in both spouses. This was a community survey of Hong Kong and therefore was not representative of China. Based on the DSM-IV screen, the rates of probable problem gambling and pathological gambling among male partners (12.8% vs. 2.5%) were twice those among female partners (5.2% vs. 0.3%). We also found that the social strain experienced by a male partner significantly predicted both his and his wife's likelihood of developing gambling problems. Although a female partner's exposure to social strain was a significant correlate of her gambling problem, it had no significant association with her husband's gambling behavior. These results suggest that the cross-spouse transference of social strain may be a gendered process. PMID:25452063
Coupled Dynamic Modeling of Floating Wind Turbine Systems: Preprint
Wayman, E. N.; Sclavounos, P. D.; Butterfield, S.; Jonkman, J.; Musial, W.
2006-03-01
This article presents a collaborative research program that the Massachusetts Institute of Technology (MIT) and the National Renewable Energy Laboratory (NREL) have undertaken to develop innovative and cost-effective floating and mooring systems for offshore wind turbines in water depths of 10-200 m. Methods for the coupled structural, hydrodynamic, and aerodynamic analysis of floating wind turbine systems are presented in the frequency domain. This analysis was conducted by coupling the aerodynamics and structural dynamics code FAST [4] developed at NREL with the wave load and response simulation code WAMIT (Wave Analysis at MIT) [15] developed at MIT. Analysis tools were developed to consider coupled interactions between the wind turbine and the floating system. These include the gyroscopic loads of the wind turbine rotor on the tower and floater, the aerodynamic damping introduced by the wind turbine rotor, the hydrodynamic damping introduced by wave-body interactions, and the hydrodynamic forces caused by wave excitation. Analyses were conducted for two floater concepts coupled with the NREL 5-MW Offshore Baseline wind turbine in water depths of 10-200 m: the MIT/NREL Shallow Drafted Barge (SDB) and the MIT/NREL Tension Leg Platform (TLP). These concepts were chosen to represent two different methods of achieving stability to identify differences in performance and cost of the different stability methods. The static and dynamic analyses of these structures evaluate the systems' responses to wave excitation at a range of frequencies, the systems' natural frequencies, and the standard deviations of the systems' motions in each degree of freedom in various wind and wave environments. This article in various wind and wave environments. This article explores the effects of coupling the wind turbine with the floating platform, the effects of water depth, and the effects of wind speed on the systems' performance. An economic feasibility analysis of the two concepts
Simulating the Dynamic Coupling of Market and Physical System Operations
Widergren, Steven E.; Roop, Joseph M.; Guttromson, Ross T.; Huang, Zhenyu
2004-06-01
Abstract-As energy trading products cover shorter time periods and demand response programs move toward real-time pricing, financial market-based activity impacts ever more directly the physical operation of the system. To begin to understand the complex interactions between the market-driven operation signals, the engineered controlled schemes, and the laws of physics, new system modeling and simulation techniques must be explored. This discussion describes requirements for new simulation tools to address such market transaction control interactions and an approach to capture the dynamic coupling between energy markets and the physical operation of the power system appropriate for dispatcher reaction time frames.
Dynamic Binding of Driven Interfaces in Coupled Ultrathin Ferromagnetic Layers
NASA Astrophysics Data System (ADS)
Metaxas, P. J.; Stamps, R. L.; Jamet, J.-P.; Ferré, J.; Baltz, V.; Rodmacq, B.; Politi, P.
2010-06-01
We demonstrate experimentally dynamic interface binding in a system consisting of two coupled ferromagnetic layers. While domain walls in each layer have different velocity-field responses, for two broad ranges of the driving field H, walls in the two layers are bound and move at a common velocity. The bound states have their own velocity-field response and arise when the isolated wall velocities in each layer are close, a condition which always occurs as H→0. Several features of the bound states are reproduced using a one-dimensional model, illustrating their general nature.
Dynamic binding of driven interfaces in coupled ultrathin ferromagnetic layers.
Metaxas, P J; Stamps, R L; Jamet, J-P; Ferré, J; Baltz, V; Rodmacq, B; Politi, P
2010-06-11
We demonstrate experimentally dynamic interface binding in a system consisting of two coupled ferromagnetic layers. While domain walls in each layer have different velocity-field responses, for two broad ranges of the driving field H, walls in the two layers are bound and move at a common velocity. The bound states have their own velocity-field response and arise when the isolated wall velocities in each layer are close, a condition which always occurs as H→0. Several features of the bound states are reproduced using a one-dimensional model, illustrating their general nature. PMID:20867268
Non-stationary resonance dynamics of weakly coupled pendula
NASA Astrophysics Data System (ADS)
Manevitch, L. I.; Romeo, F.
2015-11-01
In this letter we fill the gap in understanding the non-stationary Hamiltonian dynamics of the weakly coupled pendula model having significant applications in numerous fields of physics. While common knowledge of this model is predominantly based on the stationary theory and quasi-linear approach to non-stationary dynamics, we consider a strongly nonlinear system without any polynomial approximation of the anharmonic potential. In the adopted asymptotics only closeness to any inter-pendulum resonance frequency is assumed. Being able to explore the whole diapason of initial conditions, two key nonlinear features are revealed by means of the Limiting Phase Trajectories concept: the conditions of intense energy exchange between the pendula and transition to energy localization. The roots and the domain of chaotic behavior are clarified as they are associated with the latter, purely non-stationary, topological transition.
Dynamic stabilization of a coupled ultracold atom-molecule system
NASA Astrophysics Data System (ADS)
Li, Sheng-Chang; Ye, Chong
2015-12-01
We numerically demonstrate the dynamic stabilization of a strongly interacting many-body bosonic system which can be realized by coupled ultracold atom-molecule gases. The system is initialized to an unstable equilibrium state corresponding to a saddle point in the classical phase space, where subsequent free evolution gives rise to atom-molecule conversion. To control and stabilize the system, periodic modulation is applied that suddenly shifts the relative phase between the atomic and the molecular modes and limits their further interconversion. The stability diagram for the range of modulation amplitudes and periods that stabilize the dynamics is given. The validity of the phase diagram obtained from the time-average calculation is discussed by using the orbit tracking method, and the difference in contrast with the maximum absolute deviation analysis is shown as well. A brief quantum analysis shows that quantum fluctuations can put serious limitations on the applicability of the mean-field results.
Dynamic stabilization of a coupled ultracold atom-molecule system.
Li, Sheng-Chang; Ye, Chong
2015-12-01
We numerically demonstrate the dynamic stabilization of a strongly interacting many-body bosonic system which can be realized by coupled ultracold atom-molecule gases. The system is initialized to an unstable equilibrium state corresponding to a saddle point in the classical phase space, where subsequent free evolution gives rise to atom-molecule conversion. To control and stabilize the system, periodic modulation is applied that suddenly shifts the relative phase between the atomic and the molecular modes and limits their further interconversion. The stability diagram for the range of modulation amplitudes and periods that stabilize the dynamics is given. The validity of the phase diagram obtained from the time-average calculation is discussed by using the orbit tracking method, and the difference in contrast with the maximum absolute deviation analysis is shown as well. A brief quantum analysis shows that quantum fluctuations can put serious limitations on the applicability of the mean-field results. PMID:26764672
Emerging dynamics in neuronal networks of diffusively coupled hard oscillators.
Ponta, L; Lanza, V; Bonnin, M; Corinto, F
2011-06-01
Oscillatory networks are a special class of neural networks where each neuron exhibits time periodic behavior. They represent bio-inspired architectures which can be exploited to model biological processes such as the binding problem and selective attention. In this paper we investigate the dynamics of networks whose neurons are hard oscillators, namely they exhibit the coexistence of different stable attractors. We consider a constant external stimulus applied to each neuron, which influences the neuron's own natural frequency. We show that, due to the interaction between different kinds of attractors, as well as between attractors and repellors, new interesting dynamics arises, in the form of synchronous oscillations of various amplitudes. We also show that neurons subject to different stimuli are able to synchronize if their couplings are strong enough. PMID:21411276
Coupled Radiative-Dynamical GCM Simulations of Hot Jupiters
NASA Astrophysics Data System (ADS)
Showman, Adam P.; Fortney, J. J.; Lian, Y.; Marley, M. S.
2007-10-01
The stellar flux incident on hot Jupiters is expected to drive an atmospheric circulation that shapes the day-night temperature difference, infrared lightcurve, spectra, albedo, and atmospheric composition. Recent Spitzer lightcurve observations show that on some hot Jupiters, including HD189733b and HD209458b, the circulation efficiently homogenizes the temperature, whereas other planets such as Ups And b may exhibit large day-night temperature differences. Moreover, Spitzer infrared photometry and spectra constrain the vertical temperature structure in the atmosphere, which may deviate strongly from radiative equilibrium. Several groups have investigated the atmospheric circulation with a variety of 2D and 3D models (Showman and Guillot 2002; Cho et al. 2003, 2006; Langton and Laughlin 2007; Cooper and Showman 2005, 2006; Dobbs-Dixon and Lin 2007). However, all of these models drive the dynamics with simplified heating/cooling schemes that preclude robust predictions for the 3D temperature patterns, spectra, and lightcurves. Here, we present the first simulations of cloud-free hot Jupiters from a 3D general circulation model (GCM) that couples the atmospheric dynamics to a realistic representation of radiative transfer. For the dynamics, we adopt the MITgcm, which is a state-of-the-art circulation model that solves the 3D primitive equations of meteorology. Our radiation model is that of Marley and McKay (1999), which solves the two-stream radiative-transfer equations using the correlated-k method for the opacities; this radiative-transfer model has been extensively applied to brown dwarfs and extrasolar planets by Marley, Fortney, and collaborators. By coupling these components, the GCM provides a much more realistic representation of the radiative-dynamical interaction than possible with previous models. Here, we will present simulations of HD209458b and HD189733b, compare the predicted temperatures, spectra, and lightcurves with existing data, and make
Nonlinear dynamic analysis of hydrodynamically-coupled stainless steel structures
Zhao, Y.
1996-12-01
Spent nuclear fuel is usually stored temporarily on the site of nuclear power plants. The spent fuel storage racks are nuclear-safety-related stainless steel structures required to be analyzed for seismic loads. When the storage pool is subjected to three-dimensional (3-D) floor seismic excitations, rack modules, stored fuel bundles, adjacent racks and pool walls, and surrounding water are hydrodynamically coupled. Hydrodynamic coupling (HC) significantly affects the dynamic responses of the racks that are free-standing and submerged in water within the pool. A nonlinear time-history dynamic analysis is usually needed to describe the motion behavior of the racks that are both geometrically nonlinear and material nonlinear in nature. The nonlinearities include the friction resistance between the rack supporting legs and the pool floor, and various potential impacts of fuel-rack, rack-rack, and rack-pool wall. The HC induced should be included in the nonlinear dynamic analysis using the added-hydrodynamic-mass concept based on potential theory per the US Nuclear Regulatory Commission (USNRC) acceptance criteria. To this end, a finite element analysis constitutes a feasible and effective tool. However, most people perform somewhat simplified 1-D, or 2-D, or 3-D single rack and 2-D multiple rack analyses. These analyses are incomplete because a 3-D single rack model behaves quite differently from a 2-D mode. Furthermore, a 3-D whole pool multi-rack model behaves differently than a 3-D single rack model, especially when the strong HC effects are unsymmetrical. In this paper 3-D nonlinear dynamic time-history analyses were performed in a more quantitative manner using sophisticated finite element models developed for a single rack as well as all twelve racks in the whole-pool. Typical response results due to different HC effects are determined and discussed.
Physical Modeling of Dynamic Coupling between Chromosomal Loci.
Lampo, Thomas J; Kennard, Andrew S; Spakowitz, Andrew J
2016-01-19
The motion of chromosomal DNA is essential to many biological processes, including segregation, transcriptional regulation, recombination, and packaging. Physical understanding of these processes would be dramatically enhanced through predictive, quantitative modeling of chromosome dynamics of multiple loci. Using a polymer dynamics framework, we develop a prediction for the correlation in the velocities of two loci on a single chromosome or otherwise connected by chromatin. These predictions reveal that the signature of correlated motion between two loci can be identified by varying the lag time between locus position measurements. In general, this theory predicts that as the lag time interval increases, the dual-loci dynamic behavior transitions from being completely uncorrelated to behaving as an effective single locus. This transition corresponds to the timescale of the stress communication between loci through the intervening segment. This relatively simple framework makes quantitative predictions based on a single timescale fit parameter that can be directly compared to the in vivo motion of fluorescently labeled chromosome loci. Furthermore, this theoretical framework enables the detection of dynamically coupled chromosome regions from the signature of their correlated motion. PMID:26789757
Coupling a geodynamic seismic cycling model to rupture dynamic simulations
NASA Astrophysics Data System (ADS)
Gabriel, Alice; van Dinther, Ylona
2014-05-01
The relevance and results of dynamic rupture scenarios are implicitly linked to the geometry and pre-existing stress and strength state on a fault. The absolute stresses stored along faults during interseismic periods, are largely unquantifiable. They are, however, pivotal in defining coseismic rupture styles, near-field ground motion, and macroscopic source properties (Gabriel et al., 2012). Obtaining these in a physically consistent manner requires seismic cycling models, which directly couple long-term deformation processes (over 1000 year periods), the self-consistent development of faults, and the resulting dynamic ruptures. One promising approach to study seismic cycling enables both the generation of spontaneous fault geometries and the development of thermo-mechanically consistent fault stresses. This seismo-thermo-mechanical model has been developed using a methodology similar to that employed to study long-term lithospheric deformation (van Dinther et al., 2013a,b, using I2ELVIS of Gerya and Yuen, 2007). We will innovatively include the absolute stress and strength values along physically consistent evolving non-finite fault zones (regions of strain accumulation) from the geodynamic model into dynamic rupture simulations as an initial condition. The dynamic rupture simulations will be performed using SeisSol, an arbitrary high-order derivative Discontinuous Galerkin (ADER-DG) scheme (Pelties et al., 2012). The dynamic rupture models are able to incorporate the large degree of fault geometry complexity arising in naturally evolving geodynamic models. We focus on subduction zone settings with and without a splay fault. Due to the novelty of the coupling, we first focus on methodological challenges, e.g. the synchronization of both methods regarding the nucleation of events, the localization of fault planes, and the incorporation of similar frictional constitutive relations. We then study the importance of physically consistent fault stress, strength, and
Model of bound interface dynamics for coupled magnetic domain walls
NASA Astrophysics Data System (ADS)
Politi, P.; Metaxas, P. J.; Jamet, J.-P.; Stamps, R. L.; Ferré, J.
2011-08-01
A domain wall in a ferromagnetic system will move under the action of an external magnetic field. Ultrathin Co layers sandwiched between Pt have been shown to be a suitable experimental realization of a weakly disordered 2D medium in which to study the dynamics of 1D interfaces (magnetic domain walls). The behavior of these systems is encapsulated in the velocity-field response v(H) of the domain walls. In a recent paper [P. J. Metaxas , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.237206 104, 237206 (2010)] we studied the effect of ferromagnetic coupling between two such ultrathin layers, each exhibiting different v(H) characteristics. The main result was the existence of bound states over finite-width field ranges, wherein walls in the two layers moved together at the same speed. Here we discuss in detail the theory of domain wall dynamics in coupled systems. In particular, we show that a bound creep state is expected for vanishing H and we give the analytical, parameter free expression for its velocity which agrees well with experimental results.
A first analysis regarding matter-dynamical diffeomorphism coupling
NASA Astrophysics Data System (ADS)
Aldaya, V.; Jaramillo, J. L.
2000-12-01
A first attempt at adding matter degrees of freedom to the two-dimensional `vacuum' gravity model presented in Aldaya and Jaramillo (2000 Class. Quantum Grav. 17 1649) is analysed in this paper. Just as in the previous pure gravity case, quantum diffeomorphism operators (constructed from a Virasoro algebra) possess a dynamical content; their gauge nature is recovered only after the classical limit. Emphasis is placed on the new physical modes modelled on an SU(1,1)-Kac-Moody algebra. The non-trivial coupling to `gravity' is a consequence of the natural semi-direct structure of the entire extended algebra. A representation associated with the discrete series of the rigid SU(1,1) algebra is revisited in the light of previously neglected crucial global features which imply the appearance of an SU(1,1)-Kac-Moody fusion rule, determining the rather entangled quantum structure of the physical system. In the classical limit, an action which explicitly couples gravity and matter modes governs the dynamics.
Dynamics of learning in coupled oscillators tutored with delayed reinforcements
NASA Astrophysics Data System (ADS)
Trevisan, M. A.; Bouzat, S.; Samengo, I.; Mindlin, G. B.
2005-07-01
In this work we analyze the solutions of a simple system of coupled phase oscillators in which the connectivity is learned dynamically. The model is inspired by the process of learning of birdsongs by oscine birds. An oscillator acts as the generator of a basic rhythm and drives slave oscillators which are responsible for different motor actions. The driving signal arrives at each driven oscillator through two different pathways. One of them is a direct pathway. The other one is a reinforcement pathway, through which the signal arrives delayed. The coupling coefficients between the driving oscillator and the slave ones evolve in time following a Hebbian-like rule. We discuss the conditions under which a driven oscillator is capable of learning to lock to the driver. The resulting phase difference and connectivity are a function of the delay of the reinforcement. Around some specific delays, the system is capable of generating dramatic changes in the phase difference between the driver and the driven systems. We discuss the dynamical mechanism responsible for this effect and possible applications of this learning scheme.
Cavity-coupled molecular vibrational spectra and dynamics
NASA Astrophysics Data System (ADS)
Owrutsky, Jeffrey; Dunkelberger, Adam; Long, James; Fears, Kenan; Dressick, Walter; Compton, Ryan; Spann, Bryan; Simpkins, Blake
Coherent coupling between an optical transition and confined optical mode, when sufficiently strong, gives rise to new modes separated by the vacuum Rabi splitting. Such systems have been investigated for electronic-state transitions, for quantum wells and dots, however, only very recently have vibrational transitions been explored. Both static and dynamic results are described for vibrational bands strongly coupled to optical cavities. First, we experimentally and numerically describe coupling between a Fabry-Perot cavity and carbonyl stretch (~1730 cm1) in poly-methylmethacrylate as a function of several parameters of the system including absorber strength and concentration as well as cavity length. Similar studies are carried out for anions both in solution and exchanged into cationic polymers. Ultrafast pump-probe studies are performed on W(CO)6 in solution which reveals changes to the transient spectra and modified relaxation rates. We believe these modified relaxation rates are a consequence of the energy separation between the vibration-cavity polariton modes and excited state transitions. Cavity-modified vibrational states and energy transfer may provide a new avenue for systematic control of molecular processes and chemistry. The work supported by the Office of Naval Research through the Naval Research Laboratory.
Feedbacks between coupled subglacial hydrology and glacier dynamics
NASA Astrophysics Data System (ADS)
Hoffman, Matthew; Price, Stephen
2014-03-01
On most glaciers and ice sheet outlets the majority of motion is due to basal slip, a combination of basal sliding and bed deformation. The importance of basal water in controlling sliding is well established, with increased sliding generally related to high basal water pressure, but the details of the interactions between the ice and water systems has not received much study when there is coupling between the systems. Here we use coupled subglacial hydrology and ice dynamics models within the Community Ice Sheet Model to investigate feedbacks between the ice and water systems. The dominant feedback we find is negative: sliding over bedrock bumps opens additional cavity space, which lowers water pressure and, in turn, sliding. We also find two small positive feedbacks: basal melt increases through frictional heat during sliding, which raises water pressure, and strain softening of basal ice during localized speedup causes cavities to close more quickly and maintain higher water pressures. Our coupled modeling demonstrates that a sustained input of surface water to a distributed drainage system can lead to a speedup event that decays even in the absence of channelization, due to increased capacity of the system through opening of cavities, which is enhanced through the sliding-opening feedback. We find that the negative feedback resulting from sliding-opening is robust across a wide range of parameter values. However, our modeling also argues that subglacial channelization is required to terminate speedup events over timescales that are commensurate with observations of late summer slowdown on mountain glaciers.
CIDGA - Coupling of Interior Dynamic models with Global Atmosphere models
NASA Astrophysics Data System (ADS)
Noack, Lena; Plesa, Ana-Catalina; Breuer, Doris
2010-05-01
Atmosphere temperatures and in particular the surface temperatures mostly depend on the solar heat flux and the atmospheric composition. The latter can be influenced by interior processes of the planet, i.e. volcanism that releases greenhouse gases such as H2O, CO2 and methane into the atmosphere and plate tectonics through which atmospheric CO2 is recycled via carbonates into the mantle. An increasing concentration of greenhouse gases in the atmosphere results in an increase of the surface temperature. Changes in the surface temperature on the other hand may influence the cooling behaviour of the planet and hence influence its volcanic activity [Phillips et al., 2001]. This feedback relation between mantle convection and atmosphere is not very well understood, since until now mostly either the interior dynamic of a planet or its atmosphere was investigated separately. 2D or 3D mantle convection models to the authors' knowledge haven't been coupled to the atmosphere so far. We have used the 3D spherical simulation code GAIA [Hüttig et al., 2008] including partial melt production and coupled it with the atmosphere module CIDGA using a gray greenhouse model for varying H2O concentrations. This way, not only the influence of mantle dynamics on the atmosphere can be investigated, but also the recoupling effect, that the surface temperature has on the mantle dynamics. So far, we consider one-plate planets without crustal and thus volatile recycling. Phillips et al. [2001] already investigated the coupling effect of the surface temperature on mantle dynamics by using simple parameterized convection models for Venus. In their model a positive feedback mechanism has been observed, i.e., an increase of the surface temperature leads to an increase of partial melt and hence an increase of atmosphere density and surface temperature. Applying our model to Venus, we show that an increase of surface temperature leads not only to an increase of partial melt in the mantle; it also
Charge dynamics in capacitively coupled radio frequency discharges
NASA Astrophysics Data System (ADS)
Schulze, J.; Schüngel, E.; Donkó, Z.; Czarnetzki, U.
2010-06-01
In a capacitively coupled radio frequency (CCRF) discharge the number of positive and negative charges lost to each electrode must balance within one RF period to ensure a constant total uncompensated charge in the discharge, Qtot, on time average. This balance is the result of a compensation of electron and ion fluxes at each electrode within one RF period. Although Qtot is constant on temporal average, it is time dependent on time scales shorter than one RF period, since it results from a balance of the typically constant ion flux and the strongly time dependent electron flux at each electrode. Nevertheless, Qtot is assumed to be constant in various models. Here the dynamics of Qtot is investigated in a geometrically symmetric CCRF discharge operated in argon at 13.56 and 27.12 MHz with variable phase shift θ between the driving voltages by a PIC simulation and an analytical model. Via the electrical asymmetry effect (EAE) a variable dc self-bias is generated as a function of θ. It is found that Qtot is not temporally constant within the low frequency period, but fluctuates by about 10% around its time average value. This modulation is understood by an analytical model. It is demonstrated that this charge dynamics leads to a phase shift of the dc self-bias not captured by models neglecting the charge dynamics. This dynamics is not restricted to dual frequency discharges. It is a general phenomenon in all CCRF discharges and can generally be described by the model introduced here. Finally, Qtot is split into the uncompensated charges in each sheath. The sheath charge dynamics and the self-excitation of non-linear plasma series resonance oscillations of the RF current via the EAE at low pressures of a few pascals are discussed.
Coupled climate network analysis of multidecadal dynamics in the Arctic
NASA Astrophysics Data System (ADS)
Wiedermann, M.; Donges, J. F.; Heitzig, J.; Kurths, J.
2012-04-01
Climate network analysis provides a powerful tool for investigating the correlation structure of the dynamical system Earth. Elements of time series analysis and the theory of complex networks are combined to give new insights into the dynamics of the climate system by delivering a spatially resolved image of the underlying correlation structure from which the network is constructed. Recent results have indicated a possible correlation between the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) with a time lag of 15 to 30 years. However, identifying the involved physical mechanisms remains an open problem of ocean science and atmospheric research. We perform a climate network analysis aiming at assessing the importance of the Arctic for this connection between North Atlantic and North Pacific. As storm tracks were suggested to play a role and the large delay between AMO and PDO points to oceanic processes at work, we focus on analyzing the coupling structure between oceanic sea surface temperature (SST) and atmospheric sea level pressure (SAP) as well as geopotential height (GPH) fields. We employ the recently developed theory of interacting networks, with the corresponding statistical cross-network measures, that enables us to study the properties of a coupled climate network that divides into several subnetworks representing horizontal fields of different observables. As the analysis is performed in a region close to the north pole one has to bear in mind that climatological datasets are often arranged on a rectangular grid such that the density of nodes increases rapidly towards the poles. To correct for the distortions in our results resulting from this inhomogenous node density, we refine the cross-network measures in a way that enables us to assign every node with an individual weight according to the area that the node represents on the Earth's surface. This method has already been applied to the standard set of measures
Large mass hierarchies from strongly-coupled dynamics
NASA Astrophysics Data System (ADS)
Athenodorou, Andreas; Bennett, Ed; Bergner, Georg; Elander, Daniel; Lin, C.-J. David; Lucini, Biagio; Piai, Maurizio
2016-06-01
Besides the Higgs particle discovered in 2012, with mass 125 GeV, recent LHC data show tentative signals for new resonances in diboson as well as diphoton searches at high center-of-mass energies (2 TeV and 750 GeV, respectively). If these signals are confirmed (or other new resonances are discovered at the TeV scale), the large hierarchies between masses of new bosons require a dynamical explanation. Motivated by these tentative signals of new physics, we investigate the theoretical possibility that large hierarchies in the masses of glueballs could arise dynamically in new strongly-coupled gauge theories extending the standard model of particle physics. We study lattice data on non-Abelian gauge theories in the (near-)conformal regime as well as a simple toy model in the context of gauge/gravity dualities. We focus our attention on the ratio R between the mass of the lightest spin-2 and spin-0 resonances, that for technical reasons is a particularly convenient and clean observable to study. For models in which (non-perturbative) large anomalous dimensions arise dynamically, we show indications that this mass ratio can be large, with R>5. Moreover,our results suggest that R might be related to universal properties of the IR fixed point. Our findings provide an interesting step towards understanding large mass ratios in the non-perturbative regime of quantum field theories with (near) IR conformal behaviour.
Coupled nonlinear aeroelasticity and flight dynamics of fully flexible aircraft
NASA Astrophysics Data System (ADS)
Su, Weihua
This dissertation introduces an approach to effectively model and analyze the coupled nonlinear aeroelasticity and flight dynamics of highly flexible aircraft. A reduced-order, nonlinear, strain-based finite element framework is used, which is capable of assessing the fundamental impact of structural nonlinear effects in preliminary vehicle design and control synthesis. The cross-sectional stiffness and inertia properties of the wings are calculated along the wing span, and then incorporated into the one-dimensional nonlinear beam formulation. Finite-state unsteady subsonic aerodynamics is used to compute airloads along lifting surfaces. Flight dynamic equations are then introduced to complete the aeroelastic/flight dynamic system equations of motion. Instead of merely considering the flexibility of the wings, the current work allows all members of the vehicle to be flexible. Due to their characteristics of being slender structures, the wings, tail, and fuselage of highly flexible aircraft can be modeled as beams undergoing three dimensional displacements and rotations. New kinematic relationships are developed to handle the split beam systems, such that fully flexible vehicles can be effectively modeled within the existing framework. Different aircraft configurations are modeled and studied, including Single-Wing, Joined-Wing, Blended-Wing-Body, and Flying-Wing configurations. The Lagrange Multiplier Method is applied to model the nodal displacement constraints at the joint locations. Based on the proposed models, roll response and stability studies are conducted on fully flexible and rigidized models. The impacts of the flexibility of different vehicle members on flutter with rigid body motion constraints, flutter in free flight condition, and roll maneuver performance are presented. Also, the static stability of the compressive member of the Joined-Wing configuration is studied. A spatially-distributed discrete gust model is incorporated into the time simulation
Dynamics of magnetosphere-ionosphere coupling including turbulent transport
NASA Technical Reports Server (NTRS)
Lysak, R. L.; Dum, C. T.
1982-01-01
A two dimensional two-fluid MHD model including anomalous resistivity was used to investigate the dynamics of magnetosphere-ionosphere coupling. When a field-aligned current is generated on auroral field lines, the disturbance propagates towards the ionosphere in the form of a kinetic Alfven wave. When the current exceeds a critical value, microscopic turbulence is produced, which modifies the propagation of the Alfven wave. This process is modeled by a nonlinear collision frequency, which increases with the excess of the drift velocity over the critical value. Turbulence leads to absorption and reflection of the Alfven wave, partially decoupling the generator from the ionosphere. The approach to a steady-state is strongly dependent on the presence or absence of the turbulence. The current is self-limiting, since a current in excess of critical causes a diffusion of the magnetic field perturbation and a reduction of current.
Dynamical coupled channel calculation of pion and omega meson production
Paris, Mark
2009-01-01
A dynamical coupled channel approach is used to study $\\pi$ and $\\omega$--meson production induced by pions and photons scattering from the proton. Six-channels are used to fit unpolarized and polarized scattering data including $\\pi N$, $\\eta N$, $\\pi\\Delta$, $\\sigma N$, $\\rho N$, $\\omega N$. Bare parameters in an effective hadronic Lagrangian are fixed in $\\chi^2$-fits to data from $\\pi N \\to \\pi N$, $\\gamma N \\to \\pi N$, $\\pi^- p \\to \\omega n$, and $\\gamma p \\to \\omega p$ reactions at center-of-mass energies from threshold to $E < 2.0$ GeV. The $T$ matrix determined in these fits is used to calculate the photon beam asymmetry for $\\omega$-meson production and the $\\omega N \\to \\omega N$ total cross section and scattering lengths.
Hybrid dynamics in delay-coupled swarms with ``mothership'' networks
NASA Astrophysics Data System (ADS)
Hindes, Jason; Schwartz, Ira
Swarming behavior continues to be a subject of immense interest because of its centrality in many naturally occurring systems in biology and physics. Moreover, the development of autonomous mobile agents that can mimic the behavior of swarms and can be engineered to perform complex tasks without constant intervention is a very active field of practical research. Here we examine the effects on delay-coupled swarm pattern formation from the inclusion of a small fraction of highly connected nodes, ``motherships'', in the swarm interaction network. We find a variety of new behaviors and bifurcations, including new hybrid motions of previously analyzed patterns. Both numerical and analytic techniques are used to classify the dynamics and construct the phase diagram. The implications for swarm control and robustness from topological heterogeneity are also discussed. This research was funded by the office of Naval Research (ONR), and was performed while JH held a National Research Council Research Associateship Award.
Particle dynamics in a strongly-coupled dusty plasma
NASA Astrophysics Data System (ADS)
Goree, J.; Pieper, J. B.
1996-11-01
We have used video imaging to study the dynamics of 9 μ m plastic spheres suspended in low-power Krypton discharges. The spheres, which are highly charged and levitated by the electrode sheath, form a strongly-coupled system. Using a digitized series of images, we tracked individual particles and measured collective and random particle motions.footnote J. B. Pieper and J. Goree, submitted to PRL Dust acoustic waves were excited at <= 10 Hz and their dispersion relation verified. Fitting the measured and theoretical dispersion relations also give a measurement of the particle charge and the "linearized" Debye length. The temperature of random particle motion in the horizontal plane (parallel to the electrode) was measured to be 2-10 times room temperature and about 2 times the temperature in the vertical plane. It is proposed that the particles are heated by low-frequency (kHz) electrostatic plasma fluctuations. Work supported by NSF and NASA
Particle dynamics in a strongly-coupled dusty plasma
NASA Astrophysics Data System (ADS)
Quinn, R. A.; Goree, J.; Pieper, J. B.
1996-10-01
We have used video imaging to study the dynamics of 9 μ m plastic spheres in low-power Krypton discharges. The spheres, which are highly charged and levitated by the electrode sheath, form a strongly-coupled system. Using a digitized series of images, we tracked individual particles and measured collective and random particle motions.footnote Pieper and Goree, submitted to PRL Dust acoustic waves were excited at <= 10 Hz and their dispersion relation verified. The temperature of random particle motion in the horizontal plane (parallel to the electrode) was measured to be 2-10 times room temperature and about 2 times the temperature in the vertical plane. It is proposed that the particles are heated by low-frequency (kHz) electrostatic plasma fluctuations.
Viscoplasticity with dynamic yield surface coupled to damage
NASA Astrophysics Data System (ADS)
Johansson, M.; Runesson, K.
1997-07-01
A formulation of viscoplasticity theory, with kinetic coupling to damage, is presented. The main purpose is to describe rate-dependent material behavior and failure processes, including creep-rupture (for constant load) and creep-fatigue (for cyclic load). The Duvaut-Lions' formulation of viscoplasticity is adopted with quite general hardening of the quasistatic yield surface. The formulation is thermodynamically consistent, i.e. the dissipation inequality is satisfied. Like in the classical viscoplasticity formulations, the rate-independent response is activated at a very small loading rate. In addition, an (unconventional) dynamic yield surface is introduced, and this is approached asymptotically at infinite loading rate. Explicit constitutive relations are established for a quasistatic yield surface of von Mises type with nonlinear hardening. The resulting model is assessed for a variety of loading situations.
Probing cell membrane dynamics using plasmon coupling microscopy
NASA Astrophysics Data System (ADS)
Rong, Guoxin
The plasma membrane of mammalian cells is depicted as a two-dimensional hybrid material which is compartmentalized into submicron-sized domains. These membrane domains play a pivotal role in cellular signaling processes due to selective recruitment of specific cell surface receptors. The structural dynamics of the membrane domains and their exact biological functions are, however, still unclear, partially due to the wave nature of light, which limits the optical resolution in the visible light to approximately 400 nm in conventional optical microscopy. Here, we provide a non-fluorescence based approach for monitoring distance changes on subdiffraction limit length scales in a conventional far-field optical microscope. This approach, which is referred to as plasmon coupling microscopy (PCM), utilizes the distance dependent near-field coupling between noble metal nanoparticle (NP) labels to resolve close contacts on the length scale of approximately one NP diameter. We firstly utilize this PCM strategy to resolve interparticle separations during individual encounters of gold NP labeled fibronectin-integrin complexes in living HeLa cells. We then further refine this ratiometric detection methodology by augmenting it with a polarization-sensitive detection, which enables simultaneous monitoring of the distance and conformation changes in NP dimers and clusters. We apply this polarization resolved PCM approach to characterize the structural lateral heterogeneity of cell membranes on sub-micron length scales. Finally, we demonstrate that PCM can provide quantitative information about the structural dynamics of individual epidermal growth factor receptor (ErbB1)-enriched membrane domains in living cells.
Ultrafast electron relaxation dynamics in coupled metal nanoparticles in aggregates.
Jain, Prashant K; Qian, Wei; El-Sayed, Mostafa A
2006-01-12
We report the effect of aggregation in gold nanoparticles on their ultrafast electron-phonon relaxation dynamics measured by femtosecond transient absorption pump-probe spectroscopy. UV-visible extinction and transient absorption of the solution-stable aggregates of gold nanoparticles show a broad absorption in the 550-700-nm region in addition to the isolated gold nanoparticle plasmon resonance. This broad red-shifted absorption can be attributed to contributions from gold nanoparticle aggregates with different sizes and/or different fractal structures. The electron-phonon relaxation, reflected as a fast decay component of the transient bleach, is found to depend on the probe wavelength, suggesting that each wavelength interrogates one particular subset of the aggregates. As the probe wavelength is changed from 520 to 635 nm across the broad aggregate absorption, the rate of electron-phonon relaxation increases. The observed trend in the hot electron lifetimes can be explained on the basis of an increased overlap of the electron oscillation frequency with the phonon spectrum and enhanced interfacial electron scattering, with increasing extent of aggregation. The experimental results strongly suggest the presence of intercolloid electronic coupling within the nanoparticle aggregates, besides the well-known dipolar plasmon coupling. PMID:16471511
Vibrational Dynamics and Guest-Host Coupling in Clathrate Hydrates
NASA Astrophysics Data System (ADS)
Koza, Michael M.; Schober, Helmut
Clathrate hydrates may turn out either a blessing or a curse for mankind. On one hand, they constitute a huge reservoir of fossil fuel. On the other hand, their decomposition may liberate large amounts of green house gas and have disastrous consequences on sea floor stability. It is thus of paramount importance to understand the formation and stability of these guest-host compounds. Neutron diffraction has successfully occupied a prominent place on the stage of these scientific investigations. Complete understanding, however, is not achieved without an explanation for the thermal properties of clathrates. In particular, the thermal conductivity has a large influence on clathrate formation and conservation. Neutron spectroscopy allows probing the microscopic dynamics of clathrate hydrates. We will show how comparative studies of vibrations in clathrate hydrates give insight into the coupling of the guest to the host lattice. This coupling together with the anharmonicity of the vibrational modes is shown to lay the foundations for the peculiar thermodynamic properties of clathrate hydrates. The results obtained reach far beyond the specific clathrate system. Similar mechanisms are expected to be at work in any guest-host complex.
Finite-amplitude dynamics of coupled cylindrical menisci.
Cox, B L; Steen, P H
2011-10-01
The cylindrical meniscus is a liquid/gas interface of circular-cap cross-section constrained along its axis and bounded by end-planes. The inviscid motions of coupled cylindrical menisci are studied here. Motions result from the competition between inertia and surface tension forces. Restriction to shapes that are of circular-cap cross-section leads to an ordinary differential equation (ode) model, with the advantage that finite-amplitude stability can be examined. The second-order nonlinear ode model has a Hamiltonian structure, showing dynamical behavior like the Duffing-oscillator. The energy landscape has either a single- or double-welled potential depending on the extent of volume overfill. Total liquid volume is a bifurcation parameter, as in the corresponding problem for coupled spherical-cap droplets. Unlike the spherical-cap problem, however, axial disturbances can also destabilize, depending on overfill. For large volumes, previously known axial stability results are applied to find the limit at which axial symmetry is lost and comparison is made to the Plateau-Rayleigh limit. PMID:21723560
Dynamical equivalence of networks of coupled dynamical systems: I. Asymmetric inputs
NASA Astrophysics Data System (ADS)
Agarwal, N.; Field, M.
2010-06-01
We give a simple necessary and sufficient condition for the dynamical equivalence of two coupled cell networks. The results are applicable to both continuous and discrete dynamical systems and are framed in terms of what we term input and output equivalence. We also give an algorithm that allows explicit construction of the cells in a system with a given network architecture in terms of the cells from an equivalent system with different network architecture. Details of proofs are provided for the case of cells with asymmetric inputs—details for the case of symmetric inputs are provided in a companion paper.
Coupled-Cluster Dynamic Polarizabilities Including Triple Excitations
Hammond, Jeffrey R.; De Jong, Wibe A.; Kowalski, Karol
2008-06-10
Dynamic polarizabilities for open- and closed-shell molecules were obtained using coupled-cluster (CC) linear response theory with full treatment of singles, doubles and triples (CCSDT-LR) with large basis sets utilizing the NWChem software suite. Using four approximate CC methods in conjunction with augmented cc-pVNZ basis sets, we are able to evaluate the convergence in both many-electron and one-electron spaces. For systems with primarily dynamic correlation, the results for CC3 and CCSDT are almost indistinguishable. For systems with more static correlation, the PS(T) approximation [J. Chem. Phs. 127, 164105 (2007) performs better that CC3. Additionally, the PS(T) approach separates the triples contribution to the poles of the response function from the triples amplitudes themselves, and demonstrates that the latter are less important than originally thought Lastly, our results show that the choice of reference (ROHF versus UHF) can have a significant impact on the accuracy of polarizabilities for open-shell systems.
Dynamic Coupling among Protein Binding, Sliding, and DNA Bending Revealed by Molecular Dynamics.
Tan, Cheng; Terakawa, Tsuyoshi; Takada, Shoji
2016-07-13
Protein binding to DNA changes the DNA's structure, and altered DNA structure can, in turn, modulate the dynamics of protein binding. This mutual dependency is poorly understood. Here we investigated dynamic couplings among protein binding to DNA, protein sliding on DNA, and DNA bending by applying a coarse-grained simulation method to the bacterial architectural protein HU and 14 other DNA-binding proteins. First, we verified our method by showing that the simulated HU exhibits a weak preference for A/T-rich regions of DNA and a much higher affinity for gapped and nicked DNA, consistent with biochemical experiments. The high affinity was attributed to a local DNA bend, but not the specific chemical moiety of the gap/nick. The long-time dynamic analysis revealed that HU sliding is associated with the movement of the local DNA bending site. Deciphering single sliding steps, we found the coupling between HU sliding and DNA bending is akin to neither induced-fit nor population-shift; instead they moved concomitantly. This is reminiscent of a cation transfer on DNA and can be viewed as a protein version of polaron-like sliding. Interestingly, on shorter time scales, HU paused when the DNA was highly bent at the bound position and escaped from pauses once the DNA spontaneously returned to a less bent structure. The HU sliding is largely regulated by DNA bending dynamics. With 14 other proteins, we explored the generality and versatility of the dynamic coupling and found that 6 of the 15 assayed proteins exhibit the polaron-like sliding. PMID:27309278
Drift dynamics in a coupled model initialized for decadal forecasts
NASA Astrophysics Data System (ADS)
Sanchez-Gomez, Emilia; Cassou, Christophe; Ruprich-Robert, Yohan; Fernandez, Elodie; Terray, Laurent
2016-03-01
Drifts are always present in models when initialized from observed conditions because of intrinsic model errors; those potentially affect any type of climate predictions based on numerical experiments. Model drifts are usually removed through more or less sophisticated techniques for skill assessment, but they are rarely analysed. In this study, we provide a detailed physical and dynamical description of the drifts in the CNRM-CM5 coupled model using a set of decadal retrospective forecasts produced within CMIP5. The scope of the paper is to give some physical insights and lines of approach to, on one hand, implement more appropriate techniques of initialisation that minimize the drift in forecast mode, and on the other hand, eventually reduce the systematic biases of the models. We first document a novel protocol for ocean initialization adopted by the CNRM-CERFACS group for forecasting purpose in CMIP5. Initial states for starting dates of the predictions are obtained from a preliminary integration of the coupled model where full-field ocean surface temperature and salinity are restored everywhere to observations through flux derivative terms and full-field subsurface fields (below the prognostic ocean mixed layer) are nudged towards NEMOVAR reanalyses. Nudging is applied only outside the 15°S-15°N band allowing for dynamical balance between the depth and tilt of the tropical thermocline and the model intrinsic biased wind. A sensitivity experiment to the latitudinal extension of no-nudging zone (1°S-1°N instead of 15°, hereafter referred to as NOEQ) has been carried out. In this paper, we concentrate our analyses on two specific regions: the tropical Pacific and the North Atlantic basins. In the Pacific, we show that the first year of the forecasts is characterized by a quasi-systematic excitation of El Niño-Southern Oscillation (ENSO) warm events whatever the starting dates. This, through ocean-to-atmosphere heat transfer materialized by diabatic heating
Dynamically reconfigurable nanoscale modulators utilizing coupled hybrid plasmonics.
Lin, Charles; Helmy, Amr S
2015-01-01
The balance between extinction ratio (ER) and insertion loss (IL) dictates strict trade-off when designing travelling-wave electro-optic modulators. This in turn entails significant compromise in device footprint (L3dB) or energy consumption (E). In this work, we report a nanoscale modulator architecture that alleviates this trade-off while providing dynamic reconfigurability that was previously unattainable. This is achieved with the aide of three mechanisms: (1) Utilization of epsilon-near-zero (ENZ) effect, which maximizes the attainable attenuation that an ultra-thin active material can inflict on an optical mode. (2) Non-resonant coupled-plasmonic structure which supports modes with athermal long-range propagation. (3) Triode-like biasing scheme for flexible manipulation of field symmetry and subsequently waveguide attributes. By electrically inducing indium tin oxide (ITO) to be in a local ENZ state, we show that a Si/ITO/HfO2/Al/HfO2/ITO/Si coupled-plasmonic waveguide can provide amplitude modulation with ER = 4.83 dB/μm, IL = 0.03 dB/μm, L3dB = 622 nm, and E = 14.8 fJ, showing at least an order of magnitude improvement in modulator figure-of-merit and power efficiency compared to other waveguide platforms. Employing different biasing permutations, the same waveguide can then be reconfigured for phase and 4-quadrature-amplitude modulation, with actively device length of only 5.53 μm and 17.78 μm respectively. PMID:26189813
Thermomechanical coupling and dynamic strain ageing in ductile fracture
NASA Astrophysics Data System (ADS)
Delafosse, David
1995-01-01
This work is concerned with plastic deformation at the tip of a ductile tearing crack during propagation. Two kinds of effects are investigated: the thermomechanical coupling at the tip of a mobile ductile crack, and the influence of Dynamic Strain Aging (DSA) on ductile fracture. Three alloys are studied: a nickel based superalloy (N18), a soft carbon steel, and an Al-Li light alloy (2091). The experimental study of the thermo mechanical coupling effects by means of infrared thermography stresses the importance of plastic dissipation in the energy balance of ductile fracture. Numerical simulations involving plastic deformation as the only dissipation mechanism account for the main part of the measured heating. The effects of DSA on ductile tearing are investigated in the 2091 Al-Li alloy. Based on the strain rate/temperature dependence predicted by the standard model of DSA, an experimental procedure is set up for this purpose. Three main effects are evidenced. A maximum in tearing resistance is shown to be associated with the minimum of strain rate sensitivity. Through a simple model, this peak in tearing resistance is attributed to an increase in plastic dissipation as the strain rate sensitivity is decreased. Heterogenous plastic deformation is observed in the crack tip plastic zone. Comparison with uniaxial testing allows us to identify the observed strain heterogeneities as Portevin-Le Chatelier instabilities in the crack tip plastic zone. We perform a simplified numerical analysis of the effect of strain localization on crack tip screening. Finally, small crack propagation instabilities appear at temperatures slightly above that of the tearing resistance peak. These are interpreted as resulting from a positive feed-back between the local heating at the tip of a moving crack and the decrease in tearing resistance with increasing temperature.
Dynamically reconfigurable nanoscale modulators utilizing coupled hybrid plasmonics
Lin, Charles; Helmy, Amr S.
2015-01-01
The balance between extinction ratio (ER) and insertion loss (IL) dictates strict trade-off when designing travelling-wave electro-optic modulators. This in turn entails significant compromise in device footprint (L3dB) or energy consumption (E). In this work, we report a nanoscale modulator architecture that alleviates this trade-off while providing dynamic reconfigurability that was previously unattainable. This is achieved with the aide of three mechanisms: (1) Utilization of epsilon-near-zero (ENZ) effect, which maximizes the attainable attenuation that an ultra-thin active material can inflict on an optical mode. (2) Non-resonant coupled-plasmonic structure which supports modes with athermal long-range propagation. (3) Triode-like biasing scheme for flexible manipulation of field symmetry and subsequently waveguide attributes. By electrically inducing indium tin oxide (ITO) to be in a local ENZ state, we show that a Si/ITO/HfO2/Al/HfO2/ITO/Si coupled-plasmonic waveguide can provide amplitude modulation with ER = 4.83 dB/μm, IL = 0.03 dB/μm, L3dB = 622 nm, and E = 14.8 fJ, showing at least an order of magnitude improvement in modulator figure-of-merit and power efficiency compared to other waveguide platforms. Employing different biasing permutations, the same waveguide can then be reconfigured for phase and 4-quadrature-amplitude modulation, with actively device length of only 5.53 μm and 17.78 μm respectively. PMID:26189813
Dynamically reconfigurable nanoscale modulators utilizing coupled hybrid plasmonics
NASA Astrophysics Data System (ADS)
Lin, Charles; Helmy, Amr S.
2015-07-01
The balance between extinction ratio (ER) and insertion loss (IL) dictates strict trade-off when designing travelling-wave electro-optic modulators. This in turn entails significant compromise in device footprint (L3dB) or energy consumption (E). In this work, we report a nanoscale modulator architecture that alleviates this trade-off while providing dynamic reconfigurability that was previously unattainable. This is achieved with the aide of three mechanisms: (1) Utilization of epsilon-near-zero (ENZ) effect, which maximizes the attainable attenuation that an ultra-thin active material can inflict on an optical mode. (2) Non-resonant coupled-plasmonic structure which supports modes with athermal long-range propagation. (3) Triode-like biasing scheme for flexible manipulation of field symmetry and subsequently waveguide attributes. By electrically inducing indium tin oxide (ITO) to be in a local ENZ state, we show that a Si/ITO/HfO2/Al/HfO2/ITO/Si coupled-plasmonic waveguide can provide amplitude modulation with ER = 4.83 dB/μm, IL = 0.03 dB/μm, L3dB = 622 nm, and E = 14.8 fJ, showing at least an order of magnitude improvement in modulator figure-of-merit and power efficiency compared to other waveguide platforms. Employing different biasing permutations, the same waveguide can then be reconfigured for phase and 4-quadrature-amplitude modulation, with actively device length of only 5.53 μm and 17.78 μm respectively.
Dynamics of magnetosphere-ionosphere coupling including turbulent transport
NASA Technical Reports Server (NTRS)
Lysak, R. L.; Dum, C. T.
1983-01-01
The dynamics of magnetosphere-ionosphere coupling has been investigated by means of a two-dimensional two-fluid MHD model including anomalous resistivity. When field-aligned current is generated on auroral field lines, the disturbance propagates toward the ionosphere in the form of a kinetic Alfven wave. When the current exceeds a critical value, microscopic turbulence is produced, which modifies the propagation of the Alfven wave. This process is modeled by a nonlinear collision frequency, which increases with the excess of the drift velocity over the critical value. The system evolves toward an electrostatic structure, with the perpendicular electric field having a shorter scale than the field-aligned current. The approach to a steady state is strongly dependent on the presence or absence of the turbulence and on the boundary conditions imposed in the generator. As current is increased or scale size is decreased, the turbulent region reflects and absorbs most of the Alfven wave energy, decoupling the generator from the ionosphere.
Dynamical coupled channels calculation of pion and omega meson production
Paris, Mark W.
2009-02-15
The dynamical coupled-channels approach developed at the Excited Baryon Analysis Center is extended to include the {omega}N channel to study {pi}- and {omega}-meson production induced by scattering pions and photons from the proton. Six intermediate channels, including {pi}N, {eta}N, {pi}{delta}, {sigma}N, {rho}N, and {omega}N, are employed to describe unpolarized and polarized data. Bare parameters in an effective hadronic Lagrangian are determined in a fit to the data for {pi}N{yields}{pi}N, {gamma}N{yields}{pi}N, {pi}{sup -}p{yields}{omega}n, and {gamma}p{yields}{omega}p reactions at center-of-mass energies from threshold to W<2.0 GeV. The T matrix determined in these fits is used to calculate the photon beam asymmetry for {omega}-meson production and the {omega}N{yields}{omega}N total cross section and {omega}N-scattering lengths. The calculated beam asymmetry is in good agreement with the observed in the range of energies near threshold to W < or approx. 2.0 GeV.
Wealth distribution of simple exchange models coupled with extremal dynamics
NASA Astrophysics Data System (ADS)
Bagatella-Flores, N.; Rodríguez-Achach, M.; Coronel-Brizio, H. F.; Hernández-Montoya, A. R.
2015-01-01
Punctuated Equilibrium (PE) states that after long periods of evolutionary quiescence, species evolution can take place in short time intervals, where sudden differentiation makes new species emerge and some species extinct. In this paper, we introduce and study the effect of punctuated equilibrium on two different asset exchange models: the yard sale model (YS, winner gets a random fraction of a poorer player's wealth) and the theft and fraud model (TF, winner gets a random fraction of the loser's wealth). The resulting wealth distribution is characterized using the Gini index. In order to do this, we consider PE as a perturbation with probability ρ of being applied. We compare the resulting values of the Gini index at different increasing values of ρ in both models. We found that in the case of the TF model, the Gini index reduces as the perturbation ρ increases, not showing dependence with the agents number. While for YS we observe a phase transition which happens around ρc = 0.79. For perturbations ρ <ρc the Gini index reaches the value of one as time increases (an extreme wealth condensation state), whereas for perturbations greater than or equal to ρc the Gini index becomes different to one, avoiding the system reaches this extreme state. We show that both simple exchange models coupled with PE dynamics give more realistic results. In particular for YS, we observe a power low decay of wealth distribution.
Numerical simulations of coupled sea waves and boundary layer dynamics
NASA Astrophysics Data System (ADS)
Chalikov, D.
2009-04-01
Wind-wave dynamic and thermodynamic interaction belongs to one of the most important problems of geophysical fluid dynamics. At present this interaction in a parameterized form is taken into account for formulation of boundary conditions in atmospheric and oceanic models, weather forecast models, coupled ocean-atmosphere climate models and wave forecasting models. However, the accuracy of this parameterization is mostly unknown. The main difficulty in experimental and theoretical investigation of small-scale ocean-atmosphere interaction is the presence of a multi-mode (and, occasionally, non- single-valued) nonstationary interface. It makes impossible many types of measurements in close vicinity of the physical surface, and highly complicates construction of numerical models. Existing approaches on the wind-wave interaction problem are based on assumptions that a wave field can be represented as superposition of linear waves whilst the process of wind-wave interaction is a superposition of elementary processes. This assumption is acceptable only for very small amplitude waves due to: (1) wave surface cannot be represented as superposition of linear waves with random phases as a result of nonlinearity leading to formation of ‘bound' waves, focusing energy in physical space and wave breaking; (2) dynamic interactions of waves with the air (for example, long waves modify the local flow, which influences energy input into short waves, while short waves create local drag that affects the flow over large waves). In general, all waves "spring, burgeon and fall" in the environment provided by the entire spectrum; (3) energy input into waves of even moderate steepness is concentrated rather in physical space than in Fourier space. Hence, a Fourier image of the input is often not quite representative. The new approach to the problem is based on coupled 2-D modeling of waves and boundary layer in joint conformal surface-following coordinates. The wave model is based on full
Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics
2016-01-01
Molecular dynamics (MD) simulations of ions (K+, Na+, Ca2+ and Cl−) in aqueous solutions are investigated. Water is described using the SPC/E model. A stochastic coarse-grained description for ion behaviour is presented and parametrized using MD simulations. It is given as a system of coupled stochastic and ordinary differential equations, describing the ion position, velocity and acceleration. The stochastic coarse-grained model provides an intermediate description between all-atom MD simulations and Brownian dynamics (BD) models. It is used to develop a multiscale method which uses all-atom MD simulations in parts of the computational domain and (less detailed) BD simulations in the remainder of the domain. PMID:27118886
Coupled Radiative-Dynamical GCM Simulations of Hot Jupiters
NASA Astrophysics Data System (ADS)
Showman, Adam P.; Fortney, J. J.; Lian, Y.; Marley, M. S.; Knutson, H. A.; Charbonneau, D.
2008-09-01
The stellar flux incident on hot Jupiters -- gas giants within 0.1 AU of their stars -- is expected to drive an atmospheric circulation that shapes the day-night temperature difference, infrared lightcurves, spectrum, albedo, and atmospheric composition. Although several atmospheric-dynamics models of these objects have been published, all adopt simplified heating/cooling schemes that preclude robust predictions for the 3D temperature patterns, spectra, and lightcurves. Here, we present cloud-free simulations of hot Jupiters from the first 3D general circulation model (GCM) that couples the atmospheric dynamics to a realistic representation of radiative transfer. We emphasize HD189733b and HD209458b, which are the best observationally constrained hot Jupiters and which represent an interesting pair because one (HD209458b) appears to have a dayside stratosphere while the other (HD189733b) does not. Our simulations develop large day-night temperature contrasts and winds reaching speeds of several km/sec. A prograde equatorial jet forms with retrograde flows at higher latitudes, which leads to an eastward displacement of the hottest regions from the substellar point and coldest regions from the antistellar point. For HD189733b, our predicted lightcurves compare favorably with lightcurves observed at 8 and 24 microns with the Spitzer Space Telescope, including the modest day-night flux variation and offset of the flux peak from the time of secondary eclipse. The simulated temperatures decrease with altitude, leading to a spectrum dominated by absorption features. For HD209458b, inclusion of TiO and VO opacity leads to a dayside thermal inversion layer (stratosphere) where temperatures rise above 2000 K, consistent with suggestions offered to explain the observed secondary-eclipse spectrum. Interestingly, however, our 3D models do not match the observed spectrum, which suggests that our simulated stratosphere does not yet have the correct properties (e.g., altitude and
Couples Therapy: Treating Selected Personality-disordered Couples Within a Dynamic Therapy Framework
Foley, Gretchen N.
2014-01-01
Personality disordered couples present unique challenges for couples therapy. Novice therapists may feel daunted when taking on such a case, especially given the limited literature available to guide them in this specific area of therapy. Much of what is written on couples therapy is embedded in the larger body of literature on family therapy. While family therapy techniques may apply to couples therapy, this jump requires a level of understanding the novice therapist may not yet have. Additionally, the treatment focus within the body of literature on couples therapy tends to be situation-based (how to treat couples dealing with divorce, an affair, illness), neglecting how to treat couples whose dysfunction is not the product of a crisis, but rather a longstanding pattern escalated to the level of crisis. This is exactly the issue in therapy with personality disordered couples, and it is an important topic, as couples with personality pathology often do present for treatment. This article strives to present practical techniques, modeled in case vignettes, that can be applied directly to couples therapy— specifically therapy with personality disordered couples. PMID:24800131
Subotnik, Joseph E; Alguire, Ethan C; Ou, Qi; Landry, Brian R; Fatehi, Shervin
2015-05-19
Electronically photoexcited dynamics are complicated because there are so many different relaxation pathways: fluorescence, phosphorescence, radiationless decay, electon transfer, etc. In practice, to model photoexcited systems is a very difficult enterprise, requiring accurate and very efficient tools in both electronic structure theory and nonadiabatic chemical dynamics. Moreover, these theoretical tools are not traditional tools. On the one hand, the electronic structure tools involve couplings between electonic states (rather than typical single state energies and gradients). On the other hand, the dynamics tools involve propagating nuclei on multiple potential energy surfaces (rather than the usual ground state dynamics). In this Account, we review recent developments in electronic structure theory as directly applicable for modeling photoexcited systems. In particular, we focus on how one may evaluate the couplings between two different electronic states. These couplings come in two flavors. If we order states energetically, the resulting adiabatic states are coupled via derivative couplings. Derivative couplings capture how electronic wave functions change as a function of nuclear geometry and can usually be calculated with straightforward tools from analytic gradient theory. One nuance arises, however, in the context of time-dependent density functional theory (TD-DFT): how do we evaluate derivative couplings between TD-DFT excited states (which are tricky, because no wave function is available)? This conundrum was recently solved, and we review the solution below. We also discuss the solution to a second, pesky problem of origin dependence, whereby the derivative couplings do not (strictly) satisfy translation variance, which can lead to a lack of momentum conservation. Apart from adiabatic states, if we order states according to their electronic character, the resulting diabatic states are coupled via electronic or diabatic couplings. The couplings
Suppression of dynamics and frequency synchronization in coupled slow and fast dynamical systems
NASA Astrophysics Data System (ADS)
Gupta, Kajari; Ambika, G.
2016-06-01
We present our study on the emergent states of two interacting nonlinear systems with differing dynamical time scales. We find that the inability of the interacting systems to fall in step leads to difference in phase as well as change in amplitude. If the mismatch is small, the systems settle to a frequency synchronized state with constant phase difference. But as mismatch in time scale increases, the systems have to compromise to a state of no oscillations. We illustrate this for standard nonlinear systems and identify the regions of quenched dynamics in the parameter plane. The transition curves to this state are studied analytically and confirmed by direct numerical simulations. As an important special case, we revisit the well-known model of coupled ocean-atmosphere system used in climate studies for the interactive dynamics of a fast oscillating atmosphere and slowly changing ocean. Our study in this context indicates occurrence of multi stable periodic states and steady states of convection coexisting in the system, with a complex basin structure.
Kirrander, Adam; Shalashilin, Dmitrii V.
2011-09-15
We present an alternate version of the coupled-coherent-state method, specifically adapted for solving the time-dependent Schroedinger equation for multielectron dynamics in atoms and molecules. This theory takes explicit account of the exchange symmetry of fermion particles, and it uses fermion molecular dynamics to propagate trajectories. As a demonstration, calculations in the He atom are performed using the full Hamiltonian and accurate experimental parameters. Single- and double-ionization yields by 160-fs and 780-nm laser pulses are calculated as a function of field intensity in the range 10{sup 14}-10{sup 16} W/cm{sup 2}, and good agreement with experiments by Walker et al. is obtained. Since this method is trajectory based, mechanistic analysis of the dynamics is straightforward. We also calculate semiclassical momentum distributions for double ionization following 25-fs and 795-nm pulses at 1.5x10{sup 15} W/cm{sup 2}, in order to compare them with the detailed experiments by Rudenko et al. For this more challenging task, full convergence is not achieved. However, major effects such as the fingerlike structures in the momentum distribution are reproduced.
Dynamical couplings, dynamical vacuum energy and confinement/deconfinement from R2-gravity
NASA Astrophysics Data System (ADS)
Guendelman, Eduardo; Kaganovich, Alexander; Nissimov, Emil; Pacheva, Svetlana
2013-01-01
We study within Palatini formalism an f (R)-gravity with f (R) = R + αR2 interacting with a dilaton and a special kind of nonlinear gauge field system containing a square-root of the standard Maxwell term, which is known to produce confinement in flat space-time. Reformulating the model in the physical Einstein frame we find scalar field effective potential with a flat region where the confinement dynamics disappears, while in other regions it remains intact. The effective gauge couplings as well as the induced cosmological constant become dynamical. In particular, a conventional Maxwell kinetic term for the gauge field is dynamically generated even if absent in the original theory. We find few interesting classes of explicit solutions: (i) asymptotically (anti-)de Sitter black holes of non-standard type with additional confining vacuum electric potential even for the electrically neutral ones; (ii) non-standard Reissner-Nordström black holes with additional constant vacuum electric field and having non-flat-space-time "hedgehog" asymptotics; (iii) generalized Levi-Civita-Bertotti-Robinson "tube-like" space-times.
Dynamic analysis of pretwisted elastically-coupled rotor blades
NASA Technical Reports Server (NTRS)
Nixon, Mark W.; Hinnant, Howard E.
1994-01-01
The accuracy of using a one-dimensional analysis to predict frequencies of elastically-coupled highly-twisted rotor blades is addressed. Degrees of freedom associated with shear deformation are statically condensed from the formulation, so the analysis uses only those degrees of freedom associated with classical beam theory. The effects of cross section deformation (warping) are considered, and are shown to become significant for some types of elastic coupling. Improved results are demonstrated for highly-coupled blade structures through account of warping in a local cross section analysis, without explicit inclusion of these effects in the beam analysis. A convergence study is also provided which investigates the potential for improving efficiency of elastically-coupled beam analysis through implementation of a p-version beam finite element.
Dynamic properties of one-component strongly coupled plasmas: The sum-rule approach
Arkhipov, Yu. V.; Askaruly, A.; Davletov, A. E.; Ballester, D.; Tkachenko, I. M.
2010-02-15
The dynamic characteristics of strongly coupled one-component plasmas are studied within the moment approach. Our results on the dynamic structure factor and the dynamic local-field correction satisfy the sum rules and other exact relations automatically. A quantitative agreement is obtained with numerous simulation data on the plasma dynamic properties, including the dispersion and decay of collective modes. Our approach allows us to correct and complement the results previously found with other treatments.
Experimental and Mathematical Evaluation of Dynamic Behaviour of AN Oil-Air Coupling Shock Absorber
NASA Astrophysics Data System (ADS)
PING, Y.
2003-11-01
The physical mechanism of the actual shock absorber with multi-types of damping and non-linear stiffness through coupling the oil, air, rubber and spring by ingenious devices is systematically investigated. The experimental results of the key-model machine in multi-parameter coupling dynamic test show complex non-linearity dynamic characteristics. Based on this, the non-linear dynamic model for the shock absorber is presented by analysing the internal fluid dynamic phenomenon with respect to the shock absorber. Comparisons with experimental data confirm the validity of the model. Using the model, it is possible to evaluate the importance of different factors for designing the shock absorber.
Li Xiantao Yang, Jerry Z. E, Weinan
2010-05-20
We present a multiscale model for numerical simulations of dynamics of crystalline solids. The method combines the continuum nonlinear elasto-dynamics model, which models the stress waves and physical loading conditions, and molecular dynamics model, which provides the nonlinear constitutive relation and resolves the atomic structures near local defects. The coupling of the two models is achieved based on a general framework for multiscale modeling - the heterogeneous multiscale method (HMM). We derive an explicit coupling condition at the atomistic/continuum interface. Application to the dynamics of brittle cracks under various loading conditions is presented as test examples.
Wide dynamic range microwave planar coupled ring resonator for sensing applications
NASA Astrophysics Data System (ADS)
Zarifi, Mohammad Hossein; Daneshmand, Mojgan
2016-06-01
A highly sensitive, microwave-coupled ring resonator with a wide dynamic range is studied for use in sensing applications. The resonator's structure has two resonant rings and, consequently, two resonant frequencies, operating at 2.3 and 2.45 GHz. Inductive and capacitive coupling mechanisms are explored and compared to study their sensing performance. Primary finite element analysis and measurement results are used to compare the capacitive and inductive coupled ring resonators, demonstrating sensitivity improvements of up to 75% and dynamic range enhancement up to 100% in the capacitive coupled structure. In this work, we are proposing capacitive coupled planar ring resonators as a wide dynamic range sensing platform for liquid sensing applications. This sensing device is well suited for low-cost, real-time low-power, and CMOS compatible sensing technologies.
Nonequilibrium Spin Dynamics: from Protons in Water to a Gauge Theory of Spin-Orbit Coupling
NASA Astrophysics Data System (ADS)
Tokatly, I. V.; Sherman, E. Ya.
Nonequilibrium dynamics of spin degrees of freedom in condensed matter, ranging from classical liquids to solids and ultracold atomic gases, is one of the focus topics in physics. Here we present a gauge theory of spin dynamics in spinorbit coupled gases for a "pure" gauge realization of the spin-orbit coupling field. This approach allows one to describe the spin dynamics in fermionic systems in terms of exact general response functions and to map it on the density dynamics in a dual system without spin-orbit coupling. We apply this approach to electrons in disordered two-dimensional structures and to cold atomic gases of interacting fermions with synthetic spin-orbit coupling at very low temperatures.
Dynamical coupled-channels study of meson production reactions from EBAC@Jlab
Hiroyuki Kamano
2011-10-01
We present the current status of a combined and simultaneous analysis of meson production reactions based on a dynamical coupled-channels (DCC) model, which is conducted at Excited Baryon Analysis Center (EBAC) of Jefferson Lab.
Dynamical coupled-channels study of meson production reactions from EBACatJLab
Kamano, Hiroyuki
2011-10-24
We present the current status of a combined and simultaneous analysis of meson production reactions based on a dynamical coupled-channels (DCC) model, which is conducted at Excited Baryon Analysis Center (EBAC) of Jefferson Lab.
NASA Astrophysics Data System (ADS)
Carpenter, Michael
Almost any change that occurs in a crystal structure results in some lattice strain and it is inevitable that this will appear also as a change in elastic properties. It follows that one of the most characteristic features of phase transitions, whether driven by structural, magnetic or electronic effects, will be variations of elastic constants. In addition, transformation microstructures such as ferroelastic twins may be mobile under some conditions of temperature and stress and will give characteristic patterns of acoustic loss when measured by dynamical methods. Thanks substantially to the pioneering work of Dr Albert Migliori in developing the technique of Resonant Ultrasound Spectroscopy (RUS), it has been possible to follow the elastic and anelastic behaviour associated with phase transitions quantitatively as a function of temperature through the interval 2-1600 K. It is also possible to add magnetic and electric fields. The frequency window 0.1-2 MHz and inherently small strains of RUS appear to be particularly sensitive for observing the consequences of strain coupling and microstructure relaxation dynamics. Recent collaborative work carried out using the RUS facilities in Cambridge will be presented, relating to phase transitions in multiferroic perovskites, such as PbZr0.53Ti0.47O3-PbFe0.5Nb0.5O3 and Sr2FeMoO6, the ferroelectric/improper ferroelastic transition in GeTe, and magnetoelastic behaviour of EuTiO3. A common feature of these is softening of the shear modulus ahead of the transition that is not expected on the basis of linear/quadratic coupling between strain and the driving order parameter (improper ferroelastic). This appears to be due to coupling of acoustic modes with unseen central modes which are related to collective motions of domains with short range order. In some cases the ferroelastic twin walls have a well defined freezing interval (GeTe) whereas anelastic loss and stiffening over a wide temperature interval appears to be diagnostic
Beougher, Sean C.; Mandic, Carmen Gómez; Darbes, Lynae A.; Chakravarty, Deepalika; Neilands, Torsten B.; Garcia, Carla C.; Hoff, Colleen C.
2013-01-01
Discordant couples are unique because neither partner shares the same serostatus. Yet research overlooks how they became discordant, mistakenly assuming that they have always been that way and, by extension, that being discordant impacts the relationship in a similar manner. This study examines HIV infection history and its impact on relationship dynamics using qualitative data from 35 discordant gay male couples. Most couples met discordant (69%); however, many did not (31%). Those couples that met discordant felt being discordant had a lesser impact on their sexual and relational satisfaction, while those that did not meet discordant felt it had a greater impact, reporting sexual frustration and anxiety over seroconverting. This suggests that relationship dynamics may differ for discordant couples depending on HIV infection history. HIV prevention and counseling services for discordant couples can be better tailored and more effective when differences in HIV infection history are recognized. PMID:24244082
Dynamic acousto-optic control of a strongly coupled photonic molecule
Kapfinger, Stephan; Reichert, Thorsten; Lichtmannecker, Stefan; Müller, Kai; Finley, Jonathan J.; Wixforth, Achim; Kaniber, Michael; Krenner, Hubert J.
2015-01-01
Strongly confined photonic modes can couple to quantum emitters and mechanical excitations. To harness the full potential in quantum photonic circuits, interactions between different constituents have to be precisely and dynamically controlled. Here, a prototypical coupled element, a photonic molecule defined in a photonic crystal membrane, is controlled by a radio frequency surface acoustic wave. The sound wave is tailored to deliberately switch on and off the bond of the photonic molecule on sub-nanosecond timescales. In time-resolved experiments, the acousto-optically controllable coupling is directly observed as clear anticrossings between the two nanophotonic modes. The coupling strength is determined directly from the experimental data. Both the time dependence of the tuning and the inter-cavity coupling strength are found to be in excellent agreement with numerical calculations. The demonstrated mechanical technique can be directly applied for dynamic quantum gate operations in state-of-the-art-coupled nanophotonic, quantum cavity electrodynamic and optomechanical systems. PMID:26436203
Beougher, Sean C; Mandic, Carmen Gómez; Darbes, Lynae A; Chakravarty, Deepalika; Neilands, Torsten B; Garcia, Carla C; Hoff, Colleen C
2013-10-01
Discordant couples are unique because neither partner shares the same serostatus. Yet research overlooks how they became discordant, mistakenly assuming that they have always been that way and, by extension, that being discordant impacts the relationship in a similar manner. This study examines HIV infection history and its impact on relationship dynamics using qualitative data from 35 discordant gay male couples. Most couples met discordant (69%); however, many did not (31%). Those couples that met discordant felt being discordant had a lesser impact on their sexual and relational satisfaction, while those that did not meet discordant felt it had a greater impact, reporting sexual frustration and anxiety over seroconverting. This suggests that relationship dynamics may differ for discordant couples depending on HIV infection history. HIV prevention and counseling services for discordant couples can be better tailored and more effective when differences in HIV infection history are recognized. PMID:24244082
Choi, Bumkyoo; Lee, Seung-Yop; Kim, Taekhyun; Baek, Seog Soon
2008-01-01
In a vertical type, vibratory gyroscope, the coupled motion between reference (driving) and sensing vibrations causes the zero-point output, which is the unwanted sensing vibration without angular velocity. This structural coupling leads to an inherent discrepancy between the natural frequencies of the reference and the sensing oscillations, causing curve veering in frequency loci. The coupled motion deteriorates sensing performance and dynamic stability. In this paper, the dynamic characteristics associated with the coupling phenomenon are theoretically analyzed. The effects of reference frequency and coupling factor on the rotational direction and amplitude of elliptic oscillation are determined. Based on the analytical studies on the coupling effects, we propose and fabricate a vertically decoupled vibratory gyroscope with the frequency matching.
A Dynamic Coupled Magnetosphere-Ionosphere-Ring Current Model
NASA Astrophysics Data System (ADS)
Pembroke, Asher
In this thesis we describe a coupled model of Earth's magnetosphere that consists of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM). We report some results of the coupled model using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field-line averaged plasma-beta ¡=1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand-alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region-1 and region-2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region-2 currents shielded the low-latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low-entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging. Finally, we introduce several new methods for magnetospheric visualization and analysis, including a fluid-spatial volume for RCM and a field-aligned analysis mesh for the LFM. The latter allows us to construct novel visualizations of flux tubes, drift surfaces, topological boundaries, and bursty-bulk flows.
NASA Astrophysics Data System (ADS)
Pahlavani, H.; Kolur, E. Rahmanpour
2016-08-01
Based on the electrical charge discreteness, the Hamiltonian operator for the mutual inductance coupled quantum mesoscopic LC circuits has been found. The persistent current on two driven coupled mesoscopic electric pure L circuits (two quantum loops) has been obtained by using algebraic quantum dynamic approach. The influence of the mutual inductance on energy spectrum and quantum fluctuations of the charge and current for two coupled quantum electric mesoscopic LC circuits have been investigated.
Coupled Thermo-Mechanical Analyses of Dynamically Loaded Rubber Cylinders
NASA Technical Reports Server (NTRS)
Johnson, Arthur R.; Chen, Tzi-Kang
2000-01-01
A procedure that models coupled thermo-mechanical deformations of viscoelastic rubber cylinders by employing the ABAQUS finite element code is described. Computational simulations of hysteretic heating are presented for several tall and short rubber cylinders both with and without a steel disk at their centers. The cylinders are compressed axially and are then cyclically loaded about the compressed state. The non-uniform hysteretic heating of the rubber cylinders containing a steel disk is presented. The analyses performed suggest that the coupling procedure should be considered for further development as a design tool for rubber degradation studies.
Coupling dynamic analysis of spacecraft with multiple cylindrical tanks and flexible appendages
NASA Astrophysics Data System (ADS)
Wu, Wen-Jun; Yue, Bao-Zeng; Huang, Hua
2016-02-01
This paper is mainly concerned with the coupling dynamic analysis of a complex spacecraft consisting of one main rigid platform, multiple liquid-filled cylindrical tanks, and a number of flexible appendages. Firstly, the carrier potential function equations of liquid in the tanks are deduced according to the wall boundary conditions. Through employing the Fourier-Bessel series expansion method, the dynamic boundaries conditions on a curved free-surface under a low-gravity environment are transformed to general simple differential equations and the rigid-liquid coupled sloshing dynamic state equations of liquid in tanks are obtained. The state vectors of rigid-liquid coupled equations are composed with the modal coordinates of the relative potential function and the modal coordinates of wave height. Based on the Bernoulli-Euler beam theory and the D'Alembert's principle, the rigid-flexible coupled dynamic state equations of flexible appendages are directly derived, and the coordinate transform matrixes of maneuvering flexible appendages are precisely computed as time-varying. Then, the coupling dynamics state equations of the overall system of the spacecraft are modularly built by means of the Lagrange's equations in terms of quasi-coordinates. Lastly, the coupling dynamic performances of a typical complex spacecraft are studied. The availability and reliability of the presented method are also confirmed.
Collective dynamics in a binary mixture of hydrodynamically coupled microrotors.
Yeo, Kyongmin; Lushi, Enkeleida; Vlahovska, Petia M
2015-05-01
We study, numerically, the collective dynamics of self-rotating nonaligning particles by considering a monolayer of spheres driven by constant clockwise or counterclockwise torques. We show that hydrodynamic interactions alter the emergence of large-scale dynamical patterns compared to those observed in dry systems. In dilute suspensions, the flow stirred by the rotors induces clustering of opposite-spin rotors, while at higher densities same-spin rotors phase separate. Above a critical rotor density, dynamic hexagonal crystals form. Our findings underscore the importance of inclusion of the many-body, long-range hydrodynamic interactions in predicting the phase behavior of active particles. PMID:26001020
Cerebrospinal Fluid Mechanics and Its Coupling to Cerebrovascular Dynamics
NASA Astrophysics Data System (ADS)
Linninger, Andreas A.; Tangen, Kevin; Hsu, Chih-Yang; Frim, David
2016-01-01
Cerebrospinal fluid (CSF) is not stagnant but displays fascinating oscillatory flow patterns inside the ventricular system and reversing fluid exchange between the cranial vault and spinal compartment. This review provides an overview of the current knowledge of pulsatile CSF motion. Observations contradicting classical views about its bulk production and clearance are highlighted. A clinical account of diseases of abnormal CSF flow dynamics, including hydrocephalus, syringomyelia, Chiari malformation type 1, and pseudotumor cerebri, is also given. We survey medical imaging modalities used to observe intracranial dynamics in vivo. Additionally, we assess the state of the art in predictive models of CSF dynamics. The discussion addresses open questions regarding CSF dynamics as they relate to the understanding and management of diseases.
Comparing Effects of Cluster-Coupled Patterns on Opinion Dynamics
NASA Astrophysics Data System (ADS)
Liu, Yun; Si, Xia-Meng; Zhang, Yan-Chao
2012-07-01
Community structure is another important feature besides small-world and scale-free property of complex networks. Communities can be coupled through specific fixed links between nodes, or occasional encounter behavior. We introduce a model for opinion evolution with multiple cluster-coupled patterns, in which the interconnectivity denotes the coupled degree of communities by fixed links, and encounter frequency controls the coupled degree of communities by encounter behaviors. Considering the complicated cognitive system of people, the CODA (continuous opinions and discrete actions) update rules are used to mimic how people update their decisions after interacting with someone. It is shown that, large interconnectivity and encounter frequency both can promote consensus, reduce competition between communities and propagate some opinion successfully across the whole population. Encounter frequency is better than interconnectivity at facilitating the consensus of decisions. When the degree of social cohesion is same, small interconnectivity has better effects on lessening the competence between communities than small encounter frequency does, while large encounter frequency can make the greater degree of agreement across the whole populations than large interconnectivity can.
Dynamics of globally delay-coupled neurons displaying subthreshold oscillations.
Masoller, Cristina; Torrent, M C; García-Ojalvo, Jordi
2009-08-28
We study an ensemble of neurons that are coupled through their time-delayed collective mean field. The individual neuron is modelled using a Hodgkin-Huxley-type conductance model with parameters chosen such that the uncoupled neuron displays autonomous subthreshold oscillations of the membrane potential. We find that the ensemble generates a rich variety of oscillatory activities that are mainly controlled by two time scales: the natural period of oscillation at the single neuron level and the delay time of the global coupling. When the neuronal oscillations are synchronized, they can be either in-phase or out-of-phase. The phase-shifted activity is interpreted as the result of a phase-flip bifurcation, also occurring in a set of globally delay-coupled limit cycle oscillators. At the bifurcation point, there is a transition from in-phase to out-of-phase (or vice versa) synchronized oscillations, which is accompanied by an abrupt change in the common oscillation frequency. This phase-flip bifurcation was recently investigated in two mutually delay-coupled oscillators and can play a role in the mechanisms by which the neurons switch among different firing patterns. PMID:19620122
Dynamic Coupling of Alaska Based Ecosystem and Geophysical Models into an Integrated Model
NASA Astrophysics Data System (ADS)
Bennett, A.; Carman, T. B.
2012-12-01
As scientific models and the challenges they address have grown in complexity and scope, so has interest in dynamically coupling or integrating these models. Dynamic model coupling presents software engineering challenges stemming from differences in model architectures, differences in development styles between modeling groups, and memory and run time performance concerns. The Alaska Integrated Ecosystem Modeling (AIEM) project aims to dynamically couple three independently developed scientific models so that each model can exchange run-time data with each of the other models. The models being coupled are a stochastic fire dynamics model (ALFRESCO), a permafrost model (GIPL), and a soil and vegetation model (DVM-DOS-TEM). The scientific research objectives of the AIEM project are to: 1) use the coupled models for increasing our understanding of climate change and other stressors on landscape level physical and ecosystem processes, and; 2) provide support for resource conservation planning and decision making. The objectives related to the computer models themselves are modifiability, maintainability, and performance of the coupled and individual models. Modifiability and maintainability are especially important in a research context because source codes must be continually adapted to address new scientific concepts. Performance is crucial to delivering results in a timely manner. To achieve the objectives while addressing the challenges in dynamic model coupling, we have designed an architecture that emphasizes high cohesion for each individual model and loose coupling between the models. Each model will retain the ability to run independently, or to be available as a linked library to the coupled model. Performance is facilitated by parallelism in the spatial dimension. With close collaboration among modeling groups, the methodology described here has demonstrated the feasibility of coupling complex ecological and geophysical models to provide managers with more
ERIC Educational Resources Information Center
Gerstorf, Denis; Hoppmann, Christiane A.; Kadlec, Kelly M.; McArdle, John J.
2009-01-01
This study examined dyadic interrelations between episodic memory and depressive symptom trajectories of change in old and advanced old age. The authors applied dynamic models to 10-year incomplete longitudinal data of initially 1,599 married couples from the study of Asset and Health Dynamics Among the Oldest Old (M[subscript age] = 75 years at…
Dynamics of two coupled semiconductor spin qubits in a noisy environment
NASA Astrophysics Data System (ADS)
Das Sarma, S.; Throckmorton, Robert E.; Wu, Yang-Le
2016-07-01
We theoretically consider the temporal dynamics of two coupled spin qubits (e.g., semiconductor quantum dots) driven by the interqubit spin-spin coupling. The presence of environmental noise (e.g., charge traps, nuclear spins, random magnetic impurities) is accounted for by including random magnetic field and random interqubit coupling terms in the Hamiltonian. Both Heisenberg coupling and Ising coupling between the spin qubits are considered, corresponding respectively to exchange and capacitive gates as appropriate for single spin and singlet-triplet semiconductor qubit systems, respectively. Both exchange (Heisenberg) and capacitive (Ising) coupling situations can be solved numerically exactly even in the presence of noise, leading to the key findings that (i) the steady-state return probability to the initial state remains close to unity in the presence of strong noise for many, but not all, starting spin configurations, and (ii) the return probability as a function of time is oscillatory with a characteristic noise-controlled decay toward the steady-state value. We also provide results for the magnetization dynamics of the coupled two-qubit system. Our predicted dynamics can be directly tested in the already existing semiconductor spin qubit setups providing insight into their coherent interaction dynamics. Retention of the initial state spin memory even in the presence of strong environmental noise has important implications for quantum computation using spin qubits.
Dynamics of an ion coupled to a parametric superconducting circuit
NASA Astrophysics Data System (ADS)
Kafri, Dvir; Adhikari, Prabin; Taylor, Jacob M.
2016-01-01
Superconducting circuits and trapped ions are promising architectures for quantum information processing. However, the natural frequencies for controlling these systems—radio-frequency ion control and microwave domain superconducting qubit control—make direct Hamiltonian interactions between them weak. In this paper we describe a technique for coupling a trapped ion's motion to the fundamental mode of a superconducting circuit, by applying to the circuit a carefully modulated external magnetic flux. In conjunction with a nonlinear element (Josephson junction), this gives the circuit an effective time-dependent inductance. We then show how to tune the external flux to generate a resonant coupling between the circuit and ion's motional mode and discuss the limitations of this approach compared to using a time-dependent capacitance.
Delay model for dynamically switching coupled RLC interconnects
NASA Astrophysics Data System (ADS)
Sharma, Devendra Kumar; Kaushik, Brajesh Kumar; Sharma, Rajender Kumar
2014-04-01
With the evolution of integrated circuit technology, the interconnect parasitics can be the limiting factor in high speed signal transmission. With increasing frequency of operation, length of interconnect and fast transition time of the signal, the RC models are not sufficient to estimate the delay accurately. To mitigate this problem, accurate delay models for coupled interconnects are very much required. This paper proposes an analytical model for estimating propagation delay in lossy coupled RLC interconnect lines for simultaneously switching scenario. To verify the proposed model, the analytical results are compared with those of FDTD and SPICE results for the two cases of inputs switching under consideration. An average error of 2.07% is observed which shows an excellent agreement with SPICE simulation and FDTD computations.
Observation of chaotic dynamics of coupled nonlinear oscillators
NASA Astrophysics Data System (ADS)
van Buskirk, R.; Jeffries, C.
1985-05-01
Experimental data are employed as bases for theoretically modelling the behavior of a finite number of driven nonlinear coupled oscillators. Attention is focused on Si p-n junction resonators exposed to an external inductance. A junction oscillator displays period doubling, Hopf figuracions to quasi-periodicity, entrainment horns and breakup of the invariant torus. Calculated and measured data are compared, with favorable results, by means of Poincare' sections, bifurcation diagrams and parameter phase space diagrams for the drive voltage and frequency. Fractal dimensions 2.03 and 2.33 are expressed in Poincare' sections to illustrate the behavior of single and dual coupled resonators which experience a breakup of the strange attractor.
Ab initio quantum dynamics using coupled-cluster.
Kvaal, Simen
2012-05-21
The curse of dimensionality (COD) limits the current state-of-the-art ab initio propagation methods for non-relativistic quantum mechanics to relatively few particles. For stationary structure calculations, the coupled-cluster (CC) method overcomes the COD in the sense that the method scales polynomially with the number of particles while still being size-consistent and extensive. We generalize the CC method to the time domain while allowing the single-particle functions to vary in an adaptive fashion as well, thereby creating a highly flexible, polynomially scaling approximation to the time-dependent Schrödinger equation. The method inherits size-consistency and extensivity from the CC method. The method is dubbed orbital-adaptive time-dependent coupled-cluster, and is a hierarchy of approximations to the now standard multi-configurational time-dependent Hartree method for fermions. A numerical experiment is also given. PMID:22612082
NASA Astrophysics Data System (ADS)
Megam Ngouonkadi, Elie B.; Nono, Martial Kabong; Tamba, Victor Kamdoum; Fotsin, Hilaire B.
2015-11-01
Diffusive electrical connections in neuronal networks are instantaneous, while excitatory or inhibitory couplings through chemical synapses contain a transmission time-delay. Moreover, chemical synapses are nonlinear dynamical systems whose behavior can be described by nonlinear differential equations. In this work, neuronal networks with diffusive electrical couplings and time-delayed dynamic chemical couplings are considered. We investigate the effects of distributed time delays on phase synchronization of bursting neurons. We observe that in both excitatory and Inhibitory chemical connections, the phase synchronization might be enhanced when time-delay is taken into account. This distributed time delay can induce a variety of phase-coherent dynamical behaviors. We also study the collective dynamics of network of bursting neurons. The network model presents the so-called Small-World property, encompassing neurons whose dynamics have two time scales (fast and slow time scales). The neuron parameters in such Small-World network, are supposed to be slightly different such that, there may be synchronization of the bursting (slow) activity if the coupling strengths are large enough. Bounds for the critical coupling strengths to obtain burst synchronization in terms of the network structure are given. Our studies show that the network synchronizability is improved, as its heterogeneity is reduced. The roles of synaptic parameters, more precisely those of the coupling strengths and the network size are also investigated.
Sediment dynamics in the Adriatic Sea investigated with coupled models
Sherwood, Christopher R.; Book, Jeffrey W.; Carniel, Sandro; Cavaleri, Luigi; Chiggiato, Jacopo; Das, Himangshu; Doyle, James D.; Harris, Courtney K.; Niedoroda, Alan W.; Perkins, Henry; Poulain, Pierre-Marie; Pullen, Julie; Reed, Christopher W.; Russo, Aniello; Sclavo, Mauro; Signell, Richard P.; Traykovski, Peter A.; Warner, John C.
2004-01-01
Several large research programs focused on the Adriatic Sea in winter 2002-2003, making it an exciting place for sediment dynamics modelers (Figure 1). Investigations of atmospheric forcing and oceanic response (including wave generation and propagation, water-mass formation, stratification, and circulation), suspended material, bottom boundary layer dynamics, bottom sediment, and small-scale stratigraphy were performed by European and North American researchers participating in several projects. The goal of EuroSTRATAFORM researchers is to improve our ability to understand and simulate the physical processes that deliver sediment to the marine environment and generate stratigraphic signatures. Scientists involved in the Po and Apennine Sediment Transport and Accumulation (PASTA) experiment benefited from other major research programs including ACE (Adriatic Circulation Experiment), DOLCE VITA (Dynamics of Localized Currents and Eddy Variability in the Adriatic), EACE (the Croatian East Adriatic Circulation Experiment project), WISE (West Istria Experiment), and ADRICOSM (Italian nowcasting and forecasting) studies.
Generic behavior of master-stability functions in coupled nonlinear dynamical systems
NASA Astrophysics Data System (ADS)
Huang, Liang; Chen, Qingfei; Lai, Ying-Cheng; Pecora, Louis M.
2009-09-01
Master-stability functions (MSFs) are fundamental to the study of synchronization in complex dynamical systems. For example, for a coupled oscillator network, a necessary condition for synchronization to occur is that the MSF at the corresponding normalized coupling parameters be negative. To understand the typical behaviors of the MSF for various chaotic oscillators is key to predicting the collective dynamics of a network of these oscillators. We address this issue by examining, systematically, MSFs for known chaotic oscillators. Our computations and analysis indicate that it is generic for MSFs being negative in a finite interval of a normalized coupling parameter. A general scheme is proposed to classify the typical behaviors of MSFs into four categories. These results are verified by direct simulations of synchronous dynamics on networks of actual coupled oscillators.
NASA Astrophysics Data System (ADS)
Su, Jianbin; Xiao, Dingbang; Wu, Xuezhong; Hou, Zhanqiang; Chen, Zhihua
2013-07-01
We present a dynamic electrical balancing of coupling stiffness for improving the bias stability of micromachined gyroscopes, which embeds the coupling stiffness in a closed-loop system to make the micromachined gyroscope possess more robust bias stability by suppressing the variation of coupling stiffness. The effect of the dynamic electrical balancing control is theoretically analyzed and implemented using a silicon micromachined gyroscope as an example case. It has been experimentally shown that, comparing with open loop detection, the proposed method increased the stability of the amplitude of the mechanical quadrature signal by 38 times, and therefore improved the bias stability by 5.2 times from 89 to 17 deg/h, and the temperature stability of scale factor by 2.7 times from 622 to 231 ppm/°C. Experimental results effectively indicated the theoretical model of dynamic electrical balancing of coupling stiffness.
Dynamical spin-density waves in a spin-orbit-coupled Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Li, Yan; Qu, Chunlei; Zhang, Yongsheng; Zhang, Chuanwei
2015-07-01
Synthetic spin-orbit (SO) coupling, an important ingredient for quantum simulation of many exotic condensed matter physics, has recently attracted considerable attention. The static and dynamic properties of a SO-coupled Bose-Einstein condensate (BEC) have been extensively studied in both theory and experiment. Here we numerically investigate the generation and propagation of a dynamical spin-density wave (SDW) in a SO-coupled BEC using a fast moving Gaussian-shaped barrier. We find that the SDW wavelength is sensitive to the barrier's velocity while varies slightly with the barrier's peak potential or width. We qualitatively explain the generation of SDW by considering a rectangular barrier in a one-dimensional system. Our results may motivate future experimental and theoretical investigations of rich dynamics in the SO-coupled BEC induced by a moving barrier.
Dynamics of the locomotor-respiratory coupling at different frequencies.
Hoffmann, Charles P; Bardy, Benoît G
2015-05-01
The locomotor-respiratory coupling (LRC) is a universal phenomenon reported for various forms of rhythmic exercise. In this study, we investigated the effect of movement and respiratory frequencies on LRC. Participants were instructed to cycle or breath in synchrony with a periodic auditory stimulation at preferred and non-preferred frequencies. LRC stability was assessed by frequency and phase coupling indexes using the theory of nonlinear coupled oscillators through the sine circle map model, and the Farey tree. Results showed a stabilizing effect of sound on LRC for all frequencies and for the two systems paced. The sound-induced effect was more prominent when the rhythm of the stimulation corresponded to the preferred frequencies. The adoption of cycling or respiratory frequencies far off preferential ones led to a loss of stability in LRC. Contrary to previous findings, our results suggest that LRC is not unidirectional-from locomotion onto respiration-but bidirectional between the two systems. They also suggest that auditory information plays an important role in the modulation of LRC. PMID:25796188
Ultrafast Polariton-Phonon Dynamics of Strongly Coupled Quantum Dot-Nanocavity Systems
NASA Astrophysics Data System (ADS)
Müller, Kai; Fischer, Kevin A.; Rundquist, Armand; Dory, Constantin; Lagoudakis, Konstantinos G.; Sarmiento, Tomas; Kelaita, Yousif A.; Borish, Victoria; Vučković, Jelena
2015-07-01
We investigate the influence of exciton-phonon coupling on the dynamics of a strongly coupled quantum dot-photonic crystal cavity system and explore the effects of this interaction on different schemes for nonclassical light generation. By performing time-resolved measurements, we map out the detuning-dependent polariton lifetime and extract the spectrum of the polariton-to-phonon coupling with unprecedented precision. Photon-blockade experiments for different pulse-length and detuning conditions (supported by quantum optical simulations) reveal that achieving high-fidelity photon blockade requires an intricate understanding of the phonons' influence on the system dynamics. Finally, we achieve direct coherent control of the polariton states of a strongly coupled system and demonstrate that their efficient coupling to phonons can be exploited for novel concepts in high-fidelity single-photon generation.
On the use of attachment modes in substructure coupling for dynamic analysis
NASA Technical Reports Server (NTRS)
Craig, R. R., Jr.; Chang, C.-J.
1977-01-01
Substructure coupling or component-mode synthesis may be employed in the solution of dynamics problems for complex structures. Although numerous substructure-coupling methods have been devised, little attention has been devoted to methods employing attachment modes. In the present paper the various mode sets (normal modes, constraint modes, attachment modes) are defined. A generalized substructure-coupling procedure is described. Those substructure-coupling methods which employ attachment modes are described in detail. One of these methods is shown to lead to results (e.g., system natural frequencies) comparable to or better than those obtained by the Hurty (1965) method.
The effect of inertial coupling in the dynamics and control of flexible robotic manipulators
NASA Technical Reports Server (NTRS)
Tesar, Delbert; Curran, Carol Cockrell; Graves, Philip Lee
1988-01-01
A general model of the dynamics of flexible robotic manipulators is presented, including the gross motion of the links, the vibrations of the links and joints, and the dynamic coupling between the gross motions and vibrations. The vibrations in the links may be modeled using lumped parameters, truncated modal summation, a component mode synthesis method, or a mixture of these methods. The local link inertia matrix is derived to obtain the coupling terms between the gross motion of the link and the vibrations of the link. Coupling between the motions of the links results from the kinematic model, which utilizes the method of kinematic influence. The model is used to simulate the dynamics of a flexible space-based robotic manipulator which is attached to a spacecraft, and is free to move with respect to the inertial reference frame. This model may be used to study the dynamic response of the manipulator to the motions of its joints, or to externally applied disturbances.
Quantum-Classical Nonadiabatic Dynamics: Coupled- vs Independent-Trajectory Methods.
Agostini, Federica; Min, Seung Kyu; Abedi, Ali; Gross, E K U
2016-05-10
Trajectory-based mixed quantum-classical approaches to coupled electron-nuclear dynamics suffer from well-studied problems such as the lack of (or incorrect account for) decoherence in the trajectory surface hopping method and the inability of reproducing the spatial splitting of a nuclear wave packet in Ehrenfest-like dynamics. In the context of electronic nonadiabatic processes, these problems can result in wrong predictions for quantum populations and in unphysical outcomes for the nuclear dynamics. In this paper, we propose a solution to these issues by approximating the coupled electronic and nuclear equations within the framework of the exact factorization of the electron-nuclear wave function. We present a simple quantum-classical scheme based on coupled classical trajectories and test it against the full quantum mechanical solution from wave packet dynamics for some model situations which represent particularly challenging problems for the above-mentioned traditional methods. PMID:27030209
Coupling Eruptive Dynamics Models to Multi-fluid Plasma Dynamic Simulations at Enceladus
NASA Astrophysics Data System (ADS)
Paty, C. S.; Dufek, J.; Waite, J. H.; Tokar, R. L.
2011-12-01
The interaction of Saturn's magnetosphere with Enceladus provides an exciting natural laboratory for expanding our understanding of charge-neutral-dust interactions and their impact on mass and momentum loading of the system and the associated magnetic perturbations. However, one of the more challenging questions regarding the Enceladus plume relates to the subsurface eruptive mechanism responsible for generating the observed jets of material that compose the plume, and the three-dimensional distribution of neutral gas and dust in the plume. In this work we implement a multiphase eruptive dynamics model [cf. Dufek & Bergantz, 2007; Dufek and Bergantz, 2005] to examine the evolution of the plume morphology for a given eruption. We model the eruptive mechanism in a two-part, coupled domain including a fissure model and a plume model. A high resolution, multiphase, fissure model examines eruptive processes in a fissure from fragmentation to the surface. The fissure model is two-dimensional and provides spatial and temporal information about the dust/ice grains and gas. The depth to the fragmentation surface is currently treated as a free parameter and we examine a range of fissure morphologies. We do not explicitly force choked conditions at the vent, but rather due to the geometry, the velocities of the particle and gas mixture approach the sound speed for a 'dusty' gas mixture. The fissure model provides a source for the 3D plume model which examines the morphology of the plume resulting from different fissure configurations and provides a self-consistent physical basis to link concentrations in different regions of the plume to an eruptive mechanism. These initial models describing the resulting gas and dust grain distribution will be presented in the context of existing observations. We will also demonstrate the first stages of integration of these results into the existing multi-fluid plasma dynamic simulations of Enceladus' interaction with Saturn
Dynamical transition between weak and strong coupling in Brillouin laser pulse amplification
NASA Astrophysics Data System (ADS)
Schluck, F.; Lehmann, G.; Müller, C.; Spatschek, K. H.
2016-08-01
Short laser pulse amplification via stimulated Brillouin backscattering in plasma is considered. Previous work distinguishes between the weakly and strongly coupled regime and treats them separately. It is shown here that such a separation is not generally applicable because strong and weak coupling interaction regimes are entwined with each other. An initially weakly coupled amplification scenario may dynamically transform into strong coupling. This happens when the local seed amplitude grows and thus triggers the strongly driven plasma response. On the other hand, when in a strong coupling scenario, the pump pulse gets depleted, and its amplitude might drop below the strong coupling threshold. This may cause significant changes in the final seed pulse shape. Furthermore, experimentally used pump pulses are typically Gaussian-shaped. The intensity threshold for strong coupling may only be exceeded around the maximum and not in the wings of the pulse. Also here, a description valid in both strong and weak coupling regimes is required. We propose such a unified treatment which allows us, in particular, to study the dynamic transition between weak and strong coupling. Consequences for the pulse forms of the amplified seed are discussed.
Dynamic simulation of kinematic Stirling engines: Coupled and decoupled analysis
Fischer, K.; Lemrani, H.; Stouffs, P.
1995-12-31
A coupled analysis modelling method of Stirling engines is presented. The main feature of this modelling method is the use of a software package combining the capabilities of a pre-/post-processor with a differential algebraic equations solver. As a result, modelling is merely a matter of linking appropriate objects from a model library and the outcoming tool is very flexible and powerful. Some simulation results are presented and compared with those obtained from a decoupled analysis. It clearly appears that the main imperfection of the model does not come from the modelling process itself but from their incomplete knowledge of the physics behind the Stirling engine operation.
The dynamics of a coupled soilscape-landscape evolution model
NASA Astrophysics Data System (ADS)
Welivitiya, Dimuth; Willgoose, Garry; Hancock, Greg
2016-04-01
In this study we present results obtained from a landform evolution model coupled with SSSPAM5D soilscape evolution model. This presentation will show a number of computer animations with this coupled model using a range of widely accepted soil profile weathering models, and erosion/armouring models. The animations clearly show that subtle changes in process can result in dramatic changes in long-term equilibrium hillslope and soilscape form. We will discuss the reasons for these differences, arguing from the various mathematical and physical assumptions modelled, and infer how observed hillslope form may provide identifiable (and perhaps quantifiable) landform and soilscape signatures of landscape and soilscape process, and in particular the coupling between the landscape and the soilscape. Specifically we have simulated soilscapes using 3 depth dependent weathering functions: 1) Exponential, 2) Humped and 3) Reversed exponential. The Exponential weathering function simulates physical weathering due to thermal effects, and the weathering rate exponentially decreases with depth. The Humped function simulates chemical and/or physical weathering with moisture feedbacks, where the highest weathering rate is at a finite depth below the surface and exponentially declines with depth. The Reversed exponential function simulates chemical weathering, and the highest weathering rate is at the soil-saprolite interface and exponentially decreases both above and below the interface. Both the Humped and Reversed exponential functions can be used as approximations to chemical weathering as they can be derived analytically by solving widely accepted geochemical weathering equations. The Humped function can arise where the weathering fluid is introduced at the top of the soil profile (e.g. rainfall equilibrated with carbon dioxide in the atmosphere), while the Reversed exponential can be derived when carbon dioxide is generated within the profile (e.g. by biodegradation of soil
GENERAL: Bistability in Coupled Oscillators Exhibiting Synchronized Dynamics
NASA Astrophysics Data System (ADS)
Olusola, O. I.; Vincent, U. E.; Njah, A. N.; Olowofela, J. A.
2010-05-01
We report some new results associated with the synchronization behavior of two coupled double-well Duffing oscillators (DDOs). Some sufficient algebraic criteria for global chaos synchronization of the drive and response DDOs via linear state error feedback control are obtained by means of Lyapunov stability theory. The synchronization is achieved through a bistable state in which a periodic attractor co-exists with a chaotic attractor. Using the linear perturbation analysis, the prevalence of attractors in parameter space and the associated bifurcations are examined. Subcritical and supercritical Hopf bifurcations and abundance of Arnold tongues — a signature of mode locking phenomenon are found.
Coupling dynamic blow down and pool evaporation model for LNG.
Woodward, John L
2007-02-20
Treating the dynamic effects of accidental discharges of liquefied natural gas (LNG) is important for realistic predictions of pool radius. Two phenomena have important influence on pool spread dynamics, time-varying discharge (blow down) and pool ignition. Time-varying discharge occurs because a punctured LNG tanker or storage tank drains with a decreasing liquid head and decreasing head-space pressure. Pool ignition increases the evaporation rate of a pool and consequently decreases the ultimate pool area. This paper describes an approach to treat these phenomena in a dynamic pool evaporation model. The pool evaporation model developed here has two separate regimes. Early in the spill, momentum forces dominate and the pool spreads independently of pool evaporation rate and the corresponding heat transfer rate. After the average pool depth drops below a minimum value, momentum forces are largely dissipated and the thin edges of the pool completely evaporate, so pool area is established by the heat transfer rate. The maximum extent of a burning pool is predicted to be significantly less than that of an unignited pool because the duration of the first regime is reduced by higher heat transfer rates. The maximum extent of an LNG pool is predicted to be larger upon accounting for blow down compared with using a constant average discharge rate. However, the maximum pool extent occurs only momentarily before retreating. PMID:17184912
Collective Dynamics of Elastically Coupled Myosin V Motors*
Lu, Hailong; Efremov, Artem K.; Bookwalter, Carol S.; Krementsova, Elena B.; Driver, Jonathan W.; Trybus, Kathleen M.; Diehl, Michael R.
2012-01-01
Characterization of the collective behaviors of different classes of processive motor proteins has become increasingly important to understand various intracellular trafficking and transport processes. This work examines the dynamics of structurally-defined motor complexes containing two myosin Va (myoVa) motors that are linked together via a molecular scaffold formed from a single duplex of DNA. Dynamic changes in the filament-bound configuration of these complexes due to motor binding, stepping, and detachment were monitored by tracking the positions of different color quantum dots that report the position of one head of each myoVa motor on actin. As in studies of multiple kinesins, the run lengths produced by two myosins are only slightly larger than those of single motor molecules. This suggests that internal strain within the complexes, due to asynchronous motor stepping and the resultant stretching of motor linkages, yields net negative cooperative behaviors. In contrast to multiple kinesins, multiple myosin complexes move with appreciably lower velocities than a single-myosin molecule. Although similar trends are predicted by a discrete state stochastic model of collective motor dynamics, these analyses also suggest that multiple myosin velocities and run lengths depend on both the compliance and the effective size of their cargo. Moreover, it is proposed that this unique collective behavior occurs because the large step size and relatively small stalling force of myoVa leads to a high sensitivity of motor stepping rates to strain. PMID:22718762
Proton Dynamics on Goethite Nanoparticles and Coupling to Electron Transport.
Zarzycki, Piotr; Smith, Dayle M; Rosso, Kevin M
2015-04-14
The surface chemistry of metal oxide particles is governed by the charge that develops at the interface with aqueous solution. Mineral transformation, biogeochemical reactions, remediation, and sorption dynamics are profoundly affected in response. Here we report implementation of replica-exchange constant-pH molecular dynamics simulations that use classical molecular dynamics for exploring configurational space and Metropolis Monte Carlo walking through protonation space with a simulated annealing escape route from metastable configurations. By examining the archetypal metal oxide, goethite (α-FeOOH), we find that electrostatic potential gradients spontaneously arise between intersecting low-index crystal faces and across explicitly treated oxide nanoparticles at a magnitude exceeding the Johnson-Nyquist voltage fluctuation. Fluctuations in adsorbed proton density continuously repolarize the surface potential bias between edge-sharing crystal faces, at a rate slower than the reported electron-polaron hopping rate in goethite interiors. This suggests that these spontaneous surface potential fluctuations will control the net movement of charge carriers in the lattice. PMID:26574382
Doshi, Urmi; Holliday, Michael J.; Eisenmesser, Elan Z.; Hamelberg, Donald
2016-01-01
Detailed understanding of how conformational dynamics orchestrates function in allosteric regulation of recognition and catalysis remains ambiguous. Here, we simulate CypA using multiple-microsecond-long atomistic molecular dynamics in explicit solvent and carry out NMR experiments. We analyze a large amount of time-dependent multidimensional data with a coarse-grained approach and map key dynamical features within individual macrostates by defining dynamics in terms of residue–residue contacts. The effects of substrate binding are observed to be largely sensed at a location over 15 Å from the active site, implying its importance in allostery. Using NMR experiments, we confirm that a dynamic cluster of residues in this distal region is directly coupled to the active site. Furthermore, the dynamical network of interresidue contacts is found to be coupled and temporally dispersed, ranging over 4 to 5 orders of magnitude. Finally, using network centrality measures we demonstrate the changes in the communication network, connectivity, and influence of CypA residues upon substrate binding, mutation, and during catalysis. We identify key residues that potentially act as a bottleneck in the communication flow through the distinct regions in CypA and, therefore, as targets for future mutational studies. Mapping these dynamical features and the coupling of dynamics to function has crucial ramifications in understanding allosteric regulation in enzymes and proteins, in general. PMID:27071107
Dynamics of coupled maps with a conservation law
NASA Astrophysics Data System (ADS)
Grigoriev, R. O.; Cross, M. C.
1997-06-01
A particularly simple model belonging to a wide class of coupled maps which obey a local conservation law is studied. The phase structure of the system and the types of the phase transitions are determined. It is argued that the structure of the phase diagram is robust with respect to mild violations of the conservation law. Critical exponents possibly determining a new universality class are calculated for a set of independent order parameters. Numerical evidence is produced suggesting that the singularity in the density of Lyapunov exponents at λ=0 is a reflection of the singularity in the density of Fourier modes (a "Van Hove" singularity) and disappears if the conservation law is broken. Applicability of the Lyapunov dimension to the description of spatiotemporal chaos in a system with a conservation law is discussed.
Dynamics of coupled maps with a conservation law.
Grigoriev, R. O.; Cross, M. C.
1997-06-01
A particularly simple model belonging to a wide class of coupled maps which obey a local conservation law is studied. The phase structure of the system and the types of the phase transitions are determined. It is argued that the structure of the phase diagram is robust with respect to mild violations of the conservation law. Critical exponents possibly determining a new universality class are calculated for a set of independent order parameters. Numerical evidence is produced suggesting that the singularity in the density of Lyapunov exponents at lambda=0 is a reflection of the singularity in the density of Fourier modes (a "Van Hove" singularity) and disappears if the conservation law is broken. Applicability of the Lyapunov dimension to the description of spatiotemporal chaos in a system with a conservation law is discussed. (c) 1997 American Institute of Physics. PMID:12779659
Coupling surface and mantle dynamics: A novel experimental approach
NASA Astrophysics Data System (ADS)
Kiraly, Agnes; Faccenna, Claudio; Funiciello, Francesca; Sembroni, Andrea
2015-05-01
Recent modeling shows that surface processes, such as erosion and deposition, may drive the deformation of the Earth's surface, interfering with deeper crustal and mantle signals. To investigate the coupling between the surface and deep process, we designed a three-dimensional laboratory apparatus, to analyze the role of erosion and sedimentation, triggered by deep mantle instability. The setup is constituted and scaled down to natural gravity field using a thin viscous sheet model, with mantle and lithosphere simulated by Newtonian viscous glucose syrup and silicon putty, respectively. The surface process is simulated assuming a simple erosion law producing the downhill flow of a thin viscous material away from high topography. The deep mantle upwelling is triggered by the rise of a buoyant sphere. The results of these models along with the parametric analysis show how surface processes influence uplift velocity and topography signals.
The kinesin walk: a dynamic model with elastically coupled heads.
Derényi, I; Vicsek, T
1996-01-01
Recently individual two-headed kinesin molecules have been studied in in vitro motility assays revealing a number of their peculiar transport properties. In this paper we propose a simple and robust model for the kinesin stepping process with elastically coupled Brownian heads that show all of these properties. The analytic and numerical treatment of our model results in a very good fit to the experimental data and practically has no free parameters. Changing the values of the parameters in the restricted range allowed by the related experimental estimates has almost no effect on the shape of the curves and results mainly in a variation of the zero load velocity that can be directly fitted to the measured data. In addition, the model is consistent with the measured pathway of the kinesin ATPase. PMID:8692894
Energetic Consistency and Coupling of the Mean and Covariance Dynamics
NASA Technical Reports Server (NTRS)
Cohn, Stephen E.
2008-01-01
The dynamical state of the ocean and atmosphere is taken to be a large dimensional random vector in a range of large-scale computational applications, including data assimilation, ensemble prediction, sensitivity analysis, and predictability studies. In each of these applications, numerical evolution of the covariance matrix of the random state plays a central role, because this matrix is used to quantify uncertainty in the state of the dynamical system. Since atmospheric and ocean dynamics are nonlinear, there is no closed evolution equation for the covariance matrix, nor for the mean state. Therefore approximate evolution equations must be used. This article studies theoretical properties of the evolution equations for the mean state and covariance matrix that arise in the second-moment closure approximation (third- and higher-order moment discard). This approximation was introduced by EPSTEIN [1969] in an early effort to introduce a stochastic element into deterministic weather forecasting, and was studied further by FLEMING [1971a,b], EPSTEIN and PITCHER [1972], and PITCHER [1977], also in the context of atmospheric predictability. It has since fallen into disuse, with a simpler one being used in current large-scale applications. The theoretical results of this article make a case that this approximation should be reconsidered for use in large-scale applications, however, because the second moment closure equations possess a property of energetic consistency that the approximate equations now in common use do not possess. A number of properties of solutions of the second-moment closure equations that result from this energetic consistency will be established.
Coupling dynamics and chemistry in the air pollution modelling of street canyons: A review.
Zhong, Jian; Cai, Xiao-Ming; Bloss, William James
2016-07-01
Air pollutants emitted from vehicles in street canyons may be reactive, undergoing mixing and chemical processing before escaping into the overlying atmosphere. The deterioration of air quality in street canyons occurs due to combined effects of proximate emission sources, dynamical processes (reduced dispersion) and chemical processes (evolution of reactive primary and formation of secondary pollutants). The coupling between dynamics and chemistry plays a major role in determining street canyon air quality, and numerical model approaches to represent this coupling are reviewed in this article. Dynamical processes can be represented by Computational Fluid Dynamics (CFD) techniques. The choice of CFD approach (mainly the Reynolds-Averaged Navier-Stokes (RANS) and Large-Eddy Simulation (LES) models) depends on the computational cost, the accuracy required and hence the application. Simplified parameterisations of the overall integrated effect of dynamics in street canyons provide capability to handle relatively complex chemistry in practical applications. Chemical processes are represented by a chemical mechanism, which describes mathematically the chemical removal and formation of primary and secondary species. Coupling between these aspects needs to accommodate transport, dispersion and chemical reactions for reactive pollutants, especially fast chemical reactions with time scales comparable to or shorter than those of typical turbulent eddies inside the street canyon. Different approaches to dynamical and chemical coupling have varying strengths, costs and levels of accuracy, which must be considered in their use for provision of reference information concerning urban canopy air pollution to stakeholders considering traffic and urban planning policies. PMID:27149146
Meister, M; Caplan, S R; Berg, H C
1989-05-01
The bacterial flagellar motor is a molecular engine that couples the flow of protons across the cytoplasmic membrane to rotation of the flagellar filament. We analyze the steady-state behavior of an explicit mechanical model in which a fixed number of protons carries the filament through one revolution. Predictions of this model are compared with experimentally determined relationships between protonmotive force, proton flux, torque, and speed. All such tightly coupled mechanisms produce the same torque when the motor is stalled but vary greatly in their behavior at high speed. The speed at zero load predicted by our model is limited by the rates of association and dissociation of protons at binding sites on the rotor and by the mobility of force generators containing transmembrane channels that interact with these sites. Our analysis suggests that more could be learned about the motor if it were driven by an externally applied torque backwards (at negative speed) or forwards at speeds greater than the zero-load speed. PMID:2720081
Dynamic coupling of bulk chemistry, trace elements and mantle flow
NASA Astrophysics Data System (ADS)
Davies, J. H.; Heck, H. V.; Nowacki, A.; Wookey, J. M.; Elliott, T.; Porcelli, D.
2015-12-01
Fully dynamical models that not only track the evolution of chemical heterogeneities through the mantle, but also incorporate the effect of chemical heterogeneities on the dynamics of mantle convection are now emerging. Since in general analytical solutions to these complex problems are lacking, careful testing and investigations of the effect and usefulness of these models is needed. We extend our existing numerical mantle convection code that can track fluid flow in 3D spherical geometry and tracks both bulk chemical components (basal fraction) and different trace elements. The chemical components fractionate upon melting when and where the solidus is crossed. Now, the chemical information will effect the flow of the fluid in the following ways: The bulk composition will link to density and the (radioactive) trace element abundance to heat production. Results will be reported of the effect of different density structures; either starting with a primordial dense layer at the base of the mantle, having all density variation originate from melting (basalt production), or a combination between these two end-member scenarios. In particular we will focus on the connection between large scale bulk chemical structures in the (deep) mantle and the evolution of the distribution of noble gasses (He and Ar). The distribution of noble gasses depend upon 1) assumptions on the initial distributions in the mantle, 2) the mantle flow, 3) radioactive production and, 4) outgassing to the atmosphere upon melting close to the surface.
Asboth, J. K.; Domokos, P.
2007-11-15
In two recent articles [D. Meiser and P. Meystre, Phys. Rev. A 73, 033417 (2006); 74, 065801 (2006)], Meiser and Meystre describe the coupled dynamics of a dense gas of atoms and an optical cavity pumped by a laser field. They make two important simplifying assumptions: (i) The gas of atoms forms a regular lattice and can be replaced by a fictitious mirror and (ii) the atoms strive to minimize the dipole potential. We show that the two assumptions are inconsistent: The configuration of atoms minimizing the dipole potential is not a perfect lattice. Assumption (ii) is erroneous, as in the strong coupling regime the dipole force does not arise from the dipole potential. The real steady state, where the dipole forces vanish, is indeed a regular lattice. Furthermore, the bistability predicted by Meiser and Meystre does not occur in this system.
Hawke, B.C.
1963-02-26
This patent relates to a releasable coupling connecting a control rod to a control rod drive. This remotely operable coupling mechanism can connect two elements which are laterally and angviarly misaligned, and provides a means for sensing the locked condition of the elements. The coupling utilizes a spherical bayonet joint which is locked against rotation by a ball detent lock. (AEC)
Coupled attitude-orbit dynamics and control for displaced solar orbits
NASA Astrophysics Data System (ADS)
Gong, Shengping; Baoyin, Hexi; Li, Junfeng
2009-09-01
The paper discusses the coupled attitude-orbit dynamics of a solar sail. The equilibrium point of the coupled dynamical equations is obtained by designing the inertia of the sail. The stability of the equilibrium is analyzed through a linearization. It is found that the stability of the coupled equilibrium is determined by the stability of the attitude and orbital equilibrium point, respectively. For the sail discussed in this paper, the stability of the orbital equilibrium determines the stability of coupled system since the attitude is always marginally stable. Several numerical examples are employed to validate the conclusions. For unstable displaced orbits, active control is employed to stabilize the attitude and orbit. The results show that a small control torque can stabilize both the attitude and orbit.
Wind tunnel determination of dynamic cross-coupling derivatives - A new approach
NASA Technical Reports Server (NTRS)
Hanff, E. S.; Orlik-Rueckemann, J.
1980-01-01
The latest developments in the NAE ongoing dynamic stability research program are briefly summarized. Emphasis is placed on the recently developed wind-tunnel data reduction procedures used to obtain cross and cross-coupling derivatives due to an oscillatory motion. These procedures, which account for the dynamic behaviour of the model-balance subsystem, are described for the balance configurations currently in use. The principles on which they are based, however, are quite general and can therefore be applied to other balance configurations. Two full-model dynamic stability apparatuses are described and typical results, obtained from dynamic calibrations as well as from wind-tunnel experiments, are presented.
Lourderaj, Upakarasamy; Sun, Rui; De Jong, Wibe A.; Windus, Theresa L.; Hase, William L.
2014-03-01
The interface for VENUS and NWChem, and the resulting software package for direct dynamics simulations are described. The coupling of the two codes is considered to be a tight coupling. The two codes are compiled and linked together and act as one executable with data being passed between the two codes through routine calls. The advantages of this type of coupling are discussed. The interface has been designed to have as little interference as possible with the core codes of both VENUS and NWChem. VENUS is the code that propagates the direct dynamics trajectories and, therefore, is the program that drives the overall execution of VENUS/NWChem. VENUS has remained an essentially sequential code, which uses the highly parallel structure of NWChem. Subroutines of the interface which accomplish the data transmission and communication between the two computer programs are described. Recent examples of the use of VENUS/NWChem for direct dynamics simulations are summarized.
Rieffel, John A.; Valero-Cuevas, Francisco J.; Lipson, Hod
2010-01-01
Traditional engineering approaches strive to avoid, or actively suppress, nonlinear dynamic coupling among components. Biological systems, in contrast, are often rife with these dynamics. Could there be, in some cases, a benefit to high degrees of dynamical coupling? Here we present a distributed robotic control scheme inspired by the biological phenomenon of tensegrity-based mechanotransduction. This emergence of morphology-as-information-conduit or ‘morphological communication’, enabled by time-sensitive spiking neural networks, presents a new paradigm for the decentralized control of large, coupled, modular systems. These results significantly bolster, both in magnitude and in form, the idea of morphological computation in robotic control. Furthermore, they lend further credence to ideas of embodied anatomical computation in biological systems, on scales ranging from cellular structures up to the tendinous networks of the human hand. PMID:19776146
Northern Forest Ecosystem Dynamics Using Coupled Models and Remote Sensing
NASA Technical Reports Server (NTRS)
Ranson, K. J.; Sun, G.; Knox, R. G.; Levine, E. R.; Weishampel, J. F.; Fifer, S. T.
1999-01-01
Forest ecosystem dynamics modeling, remote sensing data analysis, and a geographical information system (GIS) were used together to determine the possible growth and development of a northern forest in Maine, USA. Field measurements and airborne synthetic aperture radar (SAR) data were used to produce maps of forest cover type and above ground biomass. These forest attribute maps, along with a conventional soils map, were used to identify the initial conditions for forest ecosystem model simulations. Using this information along with ecosystem model results enabled the development of predictive maps of forest development. The results obtained were consistent with observed forest conditions and expected successional trajectories. The study demonstrated that ecosystem models might be used in a spatial context when parameterized and used with georeferenced data sets.
Coupling Dynamical Quantum Diffeomorphisms to Matter Degrees of Freedom
NASA Astrophysics Data System (ADS)
Aldaya, V.; Jaramillo, J. L.
2002-12-01
We introduce matter degrees of freedom into a recently proposed 2D quantum gravity model based on the Virasoro group. Quantum diffeomorphisms have dynamical content in this model, thus spoiling their classical gauge nature. The algebra of observables is enlarged now with the inclusion of an ensemble of new operators closing the affine Kac-Moody algebra of the (non-compact) semi-simple group SL(2, R), and constituting the modes of a set of scalar fields. The gravity effect on those new fields is accomplished by the natural semi-direct action of the Virasoro group on the new subalgebra. While the model is rather entangled at the severe quantum regime, at the semi-classical level we recover the action of the scalar fields modified with an added gravitational interaction term...
NASA Astrophysics Data System (ADS)
Omrani, Nour-Eddine
2016-04-01
There is increasing evidence that the response to future anthropogenic climate changes in Northern hemisphere is characterized by weakening of high-latitude westerlies in the coupled stratosphere/troposphere-system and strengthening of mid-latitude tropospheric eddy-driven jet with strong impact on large-scale precipitation. Here we show using different model experiments and wave geometry diagnostics that the overall dynamics of this response can be understood in the framework of two competing atmospheric bridges. One bridge is located in the stratosphere and connect the tropical Sea Surface Temperature (SST) with the coupled high-latitude stratosphere/troposphere system through changes in the upper flank of subtropical jet and downward stratosphere/troposphere dynamical coupling. This bridge is responsible for the weakening of the westerlies in high latitude stratosphere/troposphere system. The second bridge is in the troposphere and connects the tropical ocean warming with the extra-tropics trough changes in the static stability. This bridge is responsible for the wave-induced strengthening of the tropospheric eddy-driven jet. It is shown that the large-scale precipitation response in mid-to-high latitudes results mainly from the dynamical adjustment to wave-driven changes in the tropospheric meridional overturning circulation. The competing interaction between the stratospheric and tropospheric pathway constitutes another aspect of stratosphere/troposphere dynamical coupling. Her we will show how that such coupling can help understanding model discrepancies in the Northern Hemisphere future climate change.
NASA Astrophysics Data System (ADS)
Kumar, P.; Grillot, F.
2013-07-01
We numerically investigate the complex nonlinear dynamics for two independently coupled laser systems consisting of (i) mutually delay-coupled edge emitting diode lasers and (ii) injection-locked quantum nanostructures lasers. A comparative study in dependence on the dynamical role of α parameter, which determine the phase-amplitude coupling of the optical field, in both the cases is probed. The variation of α lead to conspicuous changes in the dynamics of both the systems, which are characterized and investigated as a function of optical injection strength η for the fixed coupled-cavity delay time τ. Our analysis is based on the observation that the cross-correlation and bifurcation measures unveil the signature of enhancement of amplitude-death islands in which the coupled lasers mutually stay in stable phase-locked states. In addition, we provide a qualitative understanding of the physical mechanisms underlying the observed dynamical behavior and its dependence on α. The amplitude death and the existence of multiple amplitude death islands could be implemented for applications including diode lasers stabilization.
NASA Astrophysics Data System (ADS)
Vannitsem, Stéphane; Lucarini, Valerio
2016-04-01
We study the dynamics of the error in a simplified coupled atmosphere-ocean model using the formalism of covariant Lyapunov vectors (CLVs), which link physically-based directions of perturbations to growth/decay rates. The model is obtained via a severe truncation of quasi-geostrophic equations for the two fluids, and includes a simple yet physically meaningful representation of their dynamical/thermodynamical coupling. The model has 36 degrees of freedom, and the parameters are chosen so that a chaotic behaviour is observed. Furthermore, for some specific coupling strength a Low-Frequency Variability is developing reminiscent of the North Atlantic Oscillation. Different behaviors of the error were found depending on the specific norm chosen to measure the amplitude of the error. For the L2 norm, a super-exponential behavior is found, inducing a mean error amplification in the stable subspace described by the CLVs dominating the error dynamics within the ocean. This behavior disappears when the logarithmic norm is used, except for a few CLVs in the highly degenerate subspace defined by CLVs 6-10 for which complicate mixing and amplifications arise. Furthermore the long term dynamics of the error considerably changes when the LFV is developing in the system. When the LFV is not developing, the error saturation arises on different time scales associated to the variables under considerations, while once the LFV is present, the error along all variables of the model - and in particular of the atmosphere - is saturating on the longer time scales associated with the dynamics of the ocean. The implications of this error dynamics on the predictability of the coupled ocean-atmosphere system at short, medium and long term are discussed.
NASA Astrophysics Data System (ADS)
Wolfe, Michael; Kestner, Jason
Electrons confined in lateral quantum dots are promising candidates for scalable quantum bits. Particularly, singlet-triplet qubits can entangle electrostatically and offer long coherence times due to their weak interactions with the environment. However, fast two-qubit operations are challenging. We examine the dynamics of singlet triplet qubits capacitively coupled to a classical transmission line resonator driven near resonance. We numerically simulate the dynamics of the von Neumann entanglement entropy and investigate parameters of the coupling element that optimizes the operation time for the qubit.
Modeling dynamically coupled fluid-duct systems with finite line elements
NASA Technical Reports Server (NTRS)
Saxon, J. B.
1994-01-01
Structural analysis of piping systems, especially dynamic analysis, typically considers the duct structure and the contained fluid column separately. Coupling of these two systems, however, forms a new dynamic system with characteristics not necessarily described by the superposition of the two component system's characteristics. Methods for modeling the two coupled components simultaneously using finite line elements are presented. Techniques for general duct intersections, area or direction changes, long radius bends, hydraulic losses, and hydraulic impedances are discussed. An example problem and results involving time transients are presented. Additionally, a program to enhance post-processing of line element models is discussed.
On the coupling of fluid dynamics and electromagnetism at the top of the earth's core
NASA Technical Reports Server (NTRS)
Benton, E. R.
1985-01-01
A kinematic approach to short-term geomagnetism has recently been based upon pre-Maxwell frozen-flux electromagnetism. A complete dynamic theory requires coupling fluid dynamics to electromagnetism. A geophysically plausible simplifying assumption for the vertical vorticity balance, namely that the vertical Lorentz torque is negligible, is introduced and its consequences are developed. The simplified coupled magnetohydrodynamic system is shown to conserve a variety of magnetic and vorticity flux integrals. These provide constraints on eligible models for the geomagnetic main field, its secular variation, and the horizontal fluid motions at the top of the core, and so permit a number of tests of the underlying assumptions.
NASA Astrophysics Data System (ADS)
Misra, Gaurav; Izadi, Maziar; Sanyal, Amit; Scheeres, Daniel
2016-04-01
The effects of dynamical coupling between the rotational (attitude) and translational (orbital) motion of spacecraft near small Solar System bodies is investigated. This coupling arises due to the weak gravity of these bodies, as well as solar radiation pressure. The traditional approach assumes a point-mass spacecraft model to describe the translational motion of the spacecraft, while the attitude motion is considered to be completely decoupled from the translational motion. The model used here to describe the rigid-body spacecraft dynamics includes the non-uniform rotating gravity field of the small body up to second degree and order along with the attitude dependent terms, solar tide, and solar radiation pressure. This model shows that the second degree and order gravity terms due to the small body affect the dynamics of the spacecraft to the same extent as the orbit-attitude coupling due to the primary gravity (zeroth order) term. Variational integrators are used to simulate the dynamics of both the rigid spacecraft and the point mass. The small bodies considered here are modeled after Near-Earth Objects (NEO) 101955 Bennu, and 25143 Itokawa, and are assumed to be triaxial ellipsoids with uniform density. Differences in the numerically obtained trajectories of a rigid spacecraft and a point mass are then compared, to illustrate the impact of the orbit-attitude coupling on spacecraft dynamics in proximity of small bodies. Possible implications on the performance of model-based spacecraft control and on the station-keeping budget, if the orbit-attitude coupling is not accounted for in the model of the dynamics, are also discussed. An almost globally asymptotically stable motion estimation scheme based solely on visual/optical feedback that estimates the relative motion of the asteroid with respect to the spacecraft is also obtained. This estimation scheme does not require a model of the dynamics of the asteroid, which makes it perfectly suited for asteroids whose
Coupled Dynamic Modeling to Assess Human Impact on Watershed Hydrology
NASA Astrophysics Data System (ADS)
Mohammed, I. N.; Tsai, Y.; Turnbull, S.; Bomblies, A.; Zia, A.
2014-12-01
Humans are intrinsic to the hydrologic system, both as agents of change and as beneficiaries of ecosystem services. This connection has been underappreciated in hydrology. We present a modeling linkage framework of an agent-based land use change model with a physical-based watershed model. The coupled model framework presented constitutes part of an integrated assessment model that is being developed to study human-ecosystem interaction in Missisquoi Bay, spanning Vermont and Québec, which is experiencing high concentrations of nutrients from the Missisquoi River watershed. The integrated assessment approach proposed is comprised of linking two simulation models: the Interactive Land-Use Transition Agent-Based Model (ILUTABM) and a physically based process model, the Regional Hydro-Ecological Simulation System (RHESSys). The ILUTABM treats both landscape and landowners as agents and simulates annual land-use patterns resulting from landowners annual land-use decisions and Best Management Practices (BMPs) adaptations to landowners utilities, land productivity and perceived impacts of floods. The Missisquoi River at Swanton watershed RHESSys model (drainage area of 2,200 km2) driven by climate data was first calibrated to daily streamflows and water quality sensor data at the watershed outlet. Simulated land-use patterns were then processed to drive the calibrated RHESSys model to obtain streamflow nutrient loading realizations. Nutrients loading realizations are then examined and routed back to the ILUTAB model to obtain public polices needed to manage the Missisquoi watershed as well as the Lake Champlain in general. We infer that the applicability of this approach can be generalized to other similar watersheds. Index Terms: 0402: Agricultural systems; 1800: Hydrology; 1803: Anthropogenic effects; 1834 Human impacts; 6344: System operation and management; 6334: Regional Planning
Nonlinear dynamics of magnetically coupled beams for multi-modal vibration energy harvesting
NASA Astrophysics Data System (ADS)
Abed, I.; Kacem, N.; Bouhaddi, N.; Bouazizi, M. L.
2016-04-01
We investigate the nonlinear dynamics of magnetically coupled beams for multi-modal vibration energy harvesting. A multi-physics model for the proposed device is developed taking into account geometric and magnetic nonlinearities. The coupled nonlinear equations of motion are solved using the Galerkin discretization coupled with the harmonic balance method and the asymptotic numerical method. Several numerical simulations have been performed showing that the expected performances of the proposed vibration energy harvester are significantly promising with up to 130 % in term of bandwidth and up to 60 μWcm-3g-2 in term of normalized harvested power.
The coupled dynamics of fluids and spacecraft in low gravity and low gravity fluid measurement
NASA Technical Reports Server (NTRS)
Hansman, R. John; Peterson, Lee D.; Crawley, Edward F.
1987-01-01
The very large mass fraction of liquids stored on broad current and future generation spacecraft has made critical the technologies of describing the fluid-spacecraft dynamics and measuring or gauging the fluid. Combined efforts in these areas are described, and preliminary results are presented. The coupled dynamics of fluids and spacecraft in low gravity study is characterizing the parametric behavior of fluid-spacecraft systems in which interaction between the fluid and spacecraft dynamics is encountered. Particular emphasis is given to the importance of nonlinear fluid free surface phenomena to the coupled dynamics. An experimental apparatus has been developed for demonstrating a coupled fluid-spacecraft system. In these experiments, slosh force signals are fed back to a model tank actuator through a tunable analog second order integration circuit. In this manner, the tank motion is coupled to the resulting slosh force. Results are being obtained in 1-g and in low-g (on the NASA KC-135) using dynamic systems nondimensionally identical except for the Bond numbers.
Reed, Rebecca G; Barnard, Kobus; Butler, Emily A
2015-02-01
Well-regulated emotions, both within people and between relationship partners, play a key role in facilitating health and well-being. The present study examined 39 heterosexual couples' joint weight status (both partners are healthy-weight, both overweight, 1 healthy-weight, and 1 overweight) as a predictor of 2 interpersonal emotional patterns during a discussion of their shared lifestyle choices. The first pattern, coregulation, is one in which partners' coupled emotions show a dampening pattern over time and ultimately return to homeostatic levels. The second, codysregulation, is one in which partners' coupled emotions are amplified away from homeostatic balance. We demonstrate how a coupled linear oscillator (CLO) model (Butner, Amazeen, & Mulvey, 2005) can be used to distinguish coregulation from codysregulation. As predicted, healthy-weight couples and mixed-weight couples in which the man was heavier than the woman displayed coregulation, but overweight couples and mixed-weight couples in which the woman was heavier showed codysregulation. These results suggest that heterosexual couples in which the woman is overweight may face formidable coregulatory challenges that could undermine both partners' well-being. The results also demonstrate the importance of distinguishing between various interpersonal emotional dynamics for understanding connections between interpersonal emotions and health. PMID:25664951
NASA Astrophysics Data System (ADS)
Chen, Yonghong; Rangarajan, Govindan; Ding, Mingzhou
2006-12-01
In arbitrarily coupled dynamical systems (maps or ordinary differential equations), the stability of synchronized states (including equilibrium point, periodic orbit or chaotic attractor) and the formation of patterns from loss of stability of the synchronized states are two problems of current research interest. These two problems are often treated separately in the literature. Here, we present a unified framework in which we show that the eigenvalues of the coupling matrix determine the stability of the synchronized state, while the eigenvectors correspond to patterns emerging from desynchronization. Based on this simple framework three results are derived: First, general approaches are developed that yield constraints directly on the coupling strengths which ensure the stability of synchronized dynamics. Second, when the synchronized state becomes unstable spatial patterns can be selectively realized by varying the coupling strengths. Distinct temporal evolution of the spatial pattern can be obtained depending on the bifurcating synchronized state. Third, given a desired spatiotemporal pattern, one is able to design coupling schemes which give rise to that pattern as the coupled system evolves. Systems with specific coupling schemes are used as examples to illustrate the general methods.
Lattice Dynamics of EuO: Evidence for Giant Spin-Phonon Coupling
NASA Astrophysics Data System (ADS)
Pradip, R.; Piekarz, P.; Bosak, A.; Merkel, D. G.; Waller, O.; Seiler, A.; Chumakov, A. I.; Rüffer, R.; Oleś, A. M.; Parlinski, K.; Krisch, M.; Baumbach, T.; Stankov, S.
2016-05-01
Comprehensive studies of lattice dynamics in the ferromagnetic semiconductor EuO have been performed by a combination of inelastic x-ray scattering, nuclear inelastic scattering, and ab initio calculations. A remarkably large broadening of the transverse acoustic phonons was discovered at temperatures above and below the Curie temperature TC=69 K . This result indicates a surprisingly strong momentum-dependent spin-phonon coupling induced by the spin dynamics in EuO.
Coupling Ecology and River Dynamics using a Simplified Interaction Model
NASA Astrophysics Data System (ADS)
Longjas, A.; Czuba, J. A.; Schwenk, J.; Danesh Yazdi, M.; Hansen, A.; Foufoula-Georgiou, E.
2013-12-01
Quantifying how changes in streamflow and sediment affect riverine life is an important component of river basin management and stream restoration efforts, especially under human and climate-induced changes affecting many basins around the world. In the Midwestern US, drastic changes in mussel populations have been witnessed over the past decade begging quantitative understanding of cause and effect and attribution of these changes to the concurrent changes in streamflow and sediment loads to the rivers. Previous empirical analyses have attempted to explore mussel abundance with habitat associations and bulk hydrologic and geomorphic attributes as predictors but results showed relatively weak relationships and low predictive power. In this work, we developed a process-based model that incorporates water-sediment-mussel interactions using functional relationships and predicts the long-term trends of suspended-sediment, chlorophyll-a and mussel population using a daily streamflow record. We applied the model to the Minnesota River Basin, which has experienced significant changes in precipitation and runoff, increased sediment delivery, and decreasing mussel populations. Our model captures the general dynamics of the system and provides a better predictor of mussel populations than predictions based on geomorphic (e.g. upstream drainage area, slope) and hydraulic variables (e.g. 2-year recurrence interval peak streamflow, depth, width, cross sectional area, velocity, and Froude number) alone. To highlight the utility of our model, we tested possible scenarios that illustrate (1) how climate and land-use change may undermine the resilience of mussel populations and (2) how management efforts can allow mussel populations to recover.
Conduction block and chaotic dynamics in an asymmetrical model of coupled cardiac cells.
Landau, M; Lorente, P
1997-05-01
The initiation and propagation of the cardiac impulse depends on intrinsic properties of cells, geometrical arrangements, and intercellular coupling resistances. To address the issue of the interplay between these factors in a simple way, we have used a system, based on the van Capelle and Dürrer model, including a pacemaker and a non-pacemaker cell linked by an ohmic coupling resistance. The influence of asymmetrical cell sizes and electronic load was investigated by using numerical simulations and continuation-bifurcation techniques. The loading of a small pacemaker cell by a large non-pacemaker one (pacemaker: non-pacemaker size ratio = 0.3) was expressed as a pronounced early repolarization in the pacemaker cell and a quite long latency for the impulse propagation. Using coupling resistance as the continuation parameter, three behavioral zones were detected from low to high coupling resistance values: a zone of total quiescence (0:0), a zone of effective entertainment (1:1), and a zone of total block (1:0 pattern). At the boundary between 1:1 and 1:0 patterns, for relatively high coupling resistance values, a cascade of period doubling bifurcations emerged, corresponding to discrete changes of propagation patterns leading into irregular dynamics. Another route to irregular dynamics was also observed in the parameter space. The high sensitivity of the detected irregular dynamics to initial conditions and the positive value of the maximum Lyapunov exponent allowed us to identify these dynamics as being chaotic. Since neither intermediate block patterns nor irregular dynamics were observed with larger size ratios, we suggest that the interplay between resting membrane conductance of the non-pacemaker cell and intercellular coupling may bring about these rhythmic disturbances. PMID:9176640
Cosmological dynamics with non-minimally coupled scalar field and a constant potential function
NASA Astrophysics Data System (ADS)
Hrycyna, Orest; Szydłowski, Marek
2015-11-01
Dynamical systems methods are used to investigate global behaviour of the spatially flat Friedmann-Robertson-Walker cosmological model in gravitational theory with a non-minimally coupled scalar field and a constant potential function. We show that the system can be reduced to an autonomous three-dimensional dynamical system and additionally is equipped with an invariant manifold corresponding to an accelerated expansion of the universe. Using this invariant manifold we find an exact solution of the reduced dynamics. We investigate all solutions for all admissible initial conditions using theory of dynamical systems to obtain a classification of all evolutional paths. The right-hand sides of the dynamical system depend crucially on the value of the non-minimal coupling constant therefore we study bifurcation values of this parameter under which the structure of the phase space changes qualitatively. We found a special bifurcation value of the non-minimal coupling constant which is distinguished by dynamics of the model and may suggest some additional symmetry in matter sector of the theory.
Proctor, Elizabeth A.; Kota, Pradeep; Aleksandrov, Andrei A.; He, Lihua; Riordan, John R.; Dokholyan, Nikolay V.
2014-01-01
Many cellular functions necessary for life are tightly regulated by protein allosteric conformational change, and correlated dynamics between protein regions has been found to contribute to the function of proteins not previously considered allosteric. The ability to map and control such dynamic coupling would thus create opportunities for the extension of current therapeutic design strategy. Here, we present an approach to determine the networks of residues involved in the transfer of correlated motion across a protein, and apply our approach to rescue disease-causative mutant cystic fibrosis transmembrane regulator (CFTR) ion channels, ΔF508 and ΔI507, which together constitute over 90% of cystic fibrosis cases. We show that these mutations perturb dynamic coupling within the first nucleotide-binding domain (NBD1), and uncover a critical residue that mediates trans-domain coupled dynamics. By rationally designing a mutation to this residue, we improve aberrant dynamics of mutant CFTR as well as enhance surface expression and function of both mutants, demonstrating the rescue of a disease mutation by rational correction of aberrant protein dynamics. PMID:25685315
NASA Astrophysics Data System (ADS)
Luo, Qing; Li, Dongxu; Jiang, Jianping
2014-01-01
Control moment gyros (CMGs) are widely used as actuators for attitude control in spacecraft. However, micro-vibrations produced by CMGs will degrade the pointing performance of high-sensitivity instruments on-board the spacecraft. This paper addresses dynamic modelling and performs an analysis on the micro-vibration isolation for a single gimbal CMG (SGCMG) cluster. First, an analytical model was developed to describe both the coupled SGCMG cluster and the multi-axis isolation system that can express the dynamic outputs. This analytical model accurately reflects the mass and inertia properties, the gyroscopic effects and flexible modes of the coupled system, which can be generalized for isolation applications of SGCMG clusters. Second, the analytical model was validated using MSC.NASTRAN software based on the finite element technique. The dynamic characteristics of the coupled system are affected by the mass distribution and the gyroscopic effects of the SGCMGs. The gyroscopic effects produced by the rotary flywheel will stiffen or soften several of the structural modes of the coupled system. In addition, the gyroscopic effect of each SGCMG can interact with or counteract that of others, which induce vibration modes coupled together. Finally, the performance of the passive isolation was analysed. It was demonstrated that the gyroscopic effects should be considered in isolation studies on SGCMG clusters; otherwise, the isolation performance will be underestimated if they are ignored.
Dynamics of Time Delay-Induced Multiple Synchronous Behaviors in Inhibitory Coupled Neurons
Gu, Huaguang; Zhao, Zhiguo
2015-01-01
The inhibitory synapse can induce synchronous behaviors different from the anti-phase synchronous behaviors, which have been reported in recent studies. In the present paper, synchronous behaviors are investigated in the motif model composed of reciprocal inhibitory coupled neurons with endogenous bursting and time delay. When coupling strength is weak, synchronous behavior appears at a single interval of time delay within a bursting period. When coupling strength is strong, multiple synchronous behaviors appear at different intervals of time delay within a bursting period. The different bursting patterns of synchronous behaviors, and time delays and coupling strengths that can induce the synchronous bursting patterns can be well interpreted by the dynamics of the endogenous bursting pattern of isolated neuron, which is acquired by the fast-slow dissection method, combined with the inhibitory coupling current. For an isolated neuron, when a negative impulsive current with suitable strength is applied at different phases of the bursting, multiple different bursting patterns can be induced. For a neuron in the motif, the inhibitory coupling current, of which the application time and strength is modulated by time delay and coupling strength, can cause single or multiple synchronous firing patterns like the negative impulsive current when time delay and coupling strength is suitable. The difference compared to the previously reported multiple synchronous behaviors that appear at time delays wider than a period of the endogenous firing is discussed. The results present novel examples of synchronous behaviors in the neuronal network with inhibitory synapses and provide a reasonable explanation. PMID:26394224
A block iterative LU solver for weakly coupled linear systems. [in fluid dynamics equations
NASA Technical Reports Server (NTRS)
Cooke, C. H.
1977-01-01
A hybrid technique, called the block iterative LU solver, is proposed for solving the linear equations resulting from a finite element numerical analysis of certain fluid dynamics problems where the equations are weakly coupled between distinct sets of variables. Either the block Jacobi iterative method or the block Gauss-Seidel iterative solver is combined with LU decomposition.
ERIC Educational Resources Information Center
Allison, Colleen J.; Bartholomew, Kim; Mayseless, Ofra; Dutton, Donald G.
2008-01-01
The authors explored the attachment dynamics of heterosexual couples identified for male partner violence. Based on semistructured interviews, participants were assessed for attachment orientations. Based on a thematic analysis of the interviews, two strategies for regulating distance within these relationships were identified: pursuit and…
Investigation on dynamic coupling between stay cable and magneto-rheological fluid (MR) damper
NASA Astrophysics Data System (ADS)
Liu, Min; Li, H.; Guan, X. Ch..; Li, J. H.; Ou, J. P.
2009-03-01
In this paper, experimental investigation on vibration control is carried out on a stay cable model incorporated with one small size magnetorheological fluid (MR) damper. The control efficiency of the MR dampers to reduce the cable vibration under sinusoidal excitation using passive control strategy is firstly tested. The dynamic coupling between the cable and MR damper with the passive control strategy is obviously observed. Dynamic coupling models between stay cable and MR damper with constant and fluctuating current input are proposed respectively. The proposed dynamic coupling model corresponding to the MR damper with constant current input is validated by the numerical simulations of the measured experimental data. Furthermore, using the proposed dynamic coupling corresponding to the MR damper with fluctuating current input, experimental investigation on the cable vibration control subjected to sinusoidal excitation using semi-active control strategy is then conducted. Experimental results demonstrate that the semi-active MR damper can achieve much better mitigation efficacy than the passive MR dampers with different constant current inputs due to negative stiffness provided by the semi-active MR damper.
NASA Astrophysics Data System (ADS)
Horikawa, Yo
2013-12-01
Transient patterns in a bistable ring of bidirectionally coupled sigmoidal neurons were studied. When the system had a pair of spatially uniform steady solutions, the instability of unstable spatially nonuniform steady solutions decreased exponentially with the number of neurons because of the symmetry of the system. As a result, transient spatially nonuniform patterns showed dynamical metastability: Their duration increased exponentially with the number of neurons and the duration of randomly generated patterns obeyed a power-law distribution. However, these metastable dynamical patterns were easily stabilized in the presence of small variations in coupling strength. Metastable rotating waves and their pinning in the presence of asymmetry in the direction of coupling and the disappearance of metastable dynamical patterns due to asymmetry in the output function of a neuron were also examined. Further, in a two-dimensional array of neurons with nearest-neighbor coupling, intrinsically one-dimensional patterns were dominant in transients, and self-excitation in these neurons affected the metastable dynamical patterns.
Dimensionality crossover in vortex dynamics of magnetically coupled F-S-F hybrids.
Karapetrov, G.; Belkin, A.; Iavarone, M.; Yefremenko, V.; Pearson, J. E.; Divan, R.; Cambel, V.; Novosad, V.; Slovak Academy of Sciences; Temple Univ.
2011-01-19
We report on the vortex dynamics in magnetically coupled F-S-F trilayers extracted from the analysis of the resistance-current isotherms. The superconducting thin film that is conventionally in the 2D vortex limit exhibits quite different behavior when sandwiched between ferromagnetic layers. The value of the dynamic critical exponent strongly increases in the F-S-F case due to screening of the stray vortex field by the adjacent ferromagnetic layers, leading to an effective dimensional crossover in vortex dynamics. Furthermore, the directional pinning by the magnetic stripe domains induces anisotropy in the vortex glass transition temperature and causes metastable avalanche behavior at strong driving currents.
Decoherence dynamics of two charge qubits in vertically coupled quantum dots
Ben Chouikha, W.; Bennaceur, R.; Jaziri, S.
2007-12-15
The decoherence dynamics of two charge qubits in a double quantum dot is investigated theoretically. We consider the quantum dynamics of two interacting electrons in a vertically coupled quantum dot driven by an external electric field. We derive the equations of motion for the density matrix, in which the presence of an electron confined in the double dot represents one qubit. A Markovian approach to the dynamical evolution of the reduced density matrix is adopted. We evaluate the concurrence of two qubits in order to study the effect of acoustic phonons on the entanglement. We also show that the disentanglement effect depends on the double dot parameters and increases with the temperature.
Hiroyuki Kamano
2012-04-01
We review a global analysis of meson production reactions off the nucleons by a collaboration at Excited Baryon Analysis Center of Jefferson Lab. The analysis is pursued with a dynamical coupled-channels approach, within which the dynamics of multi-channel reaction processes are taken into account in a fully consistent way with the two-body as well as three-body unitarity of the S-matrix. With this approach, new features of nucleon excitations are revealed as resonant particles originating from the non-trivial multi-channel reaction dynamics, which cannot be addressed by static hadron models where the nucleon excitations are treated as stable particles.
NASA Astrophysics Data System (ADS)
Wang, Zhen; Andrews, Michael A.; Wu, Zhi-Xi; Wang, Lin; Bauch, Chris T.
2015-12-01
We would like to begin this response by recognizing all the insightful and thought-provoking comments to our review "Coupled disease-behavior dynamics on complex networks" [1]. We find that, with their diverse expertise, all the commentators enrich the discussion on this topic, and also identify important, interesting questions [2-13], indicating how much space there still is for the development of the field. To give the readers a systematic understanding, these opinions and suggestions are roughly divided into two classes: (i) whether the coupled models could be closer to realistic observations, yet simpler [2-5,7-10,13]; and (ii) whether the hypothesis of network models could mimic the empirical networks more accurately [5-8,10-13].
Quantum dynamics of a vibronically coupled linear chain using a surrogate Hamiltonian approach.
Lee, Myeong H; Troisi, Alessandro
2016-06-01
Vibronic coupling between the electronic and vibrational degrees of freedom has been reported to play an important role in charge and exciton transport in organic photovoltaic materials, molecular aggregates, and light-harvesting complexes. Explicitly accounting for effective vibrational modes rather than treating them as a thermal environment has been shown to be crucial to describe the effect of vibronic coupling. We present a methodology to study dissipative quantum dynamics of vibronically coupled systems based on a surrogate Hamiltonian approach, which is in principle not limited by Markov approximation or weak system-bath interaction, using a vibronic basis. We apply vibronic surrogate Hamiltonian method to a linear chain system and discuss how different types of relaxation process, intramolecular vibrational relaxation and intermolecular vibronic relaxation, influence population dynamics of dissipative vibronic systems. PMID:27276944
Dynamic vibronic coupling in InGaAs quantum dots [Invited
NASA Astrophysics Data System (ADS)
Brash, A. J.; Martins, L. M. P. P.; Barth, A. M.; Liu, F.; Quilter, J. H.; Glässl, M.; Axt, V. M.; Ramsay, A. J.; Skolnick, M. S.; Fox, A. M.
2016-07-01
The electron-phonon coupling in self-assembled InGaAs quantum dots is relatively weak at low light intensities, which means that the zero-phonon line in emission is strong compared to the phonon sideband. However, the coupling to acoustic phonons can be dynamically enhanced in the presence of an intense optical pulse tuned within the phonon sideband. Recent experiments have shown that this dynamic vibronic coupling can enable population inversion to be achieved when pumping with a blue-shifted laser and for rapid de-excitation of an inverted state with red detuning. In this paper we con?rm the incoherent nature of the phonon-assisted pumping process and explore the temperature dependence of the mechanism. We also show that a combination of blue- and red-shifted pulses can create and destroy an exciton within a timescale ~20 ps determined by the pulse duration and ultimately limited by the phonon thermalisation time.
Dynamics in the Kuramoto model with a bi-harmonic coupling function
NASA Astrophysics Data System (ADS)
Yuan, Di; Cui, Haitao; Tian, Junlong; Xiao, Yi; Zhang, Yingxin
2016-09-01
We study a variant of the Kuramoto model with a bi-harmonic coupling function, in which oscillators with positive first harmonic coupling strength are conformists and oscillators with negative first harmonic coupling strength are contrarians. We show that the model displays different synchronous dynamics and different dynamics may be characterized by the phase distributions of oscillators. There exist stationary synchronous states, travelling wave states, π state and, most interestingly, another type of nonstationary state: an oscillating π state. The phase distribution oscillates in a confined region and the phase difference between conformists and contrarians oscillates around π with a constant amplitude and a constant period in oscillating π state. Finally, the bifurcation diagram of the model in the parameter space is presented.
The dynamics of the Schrödinger-Newton system with self-field coupling
NASA Astrophysics Data System (ADS)
Franklin, J.; Guo, Y.; Cole Newton, K.; Schlosshauer, M.
2016-04-01
We probe the dynamics of a modified form of the Schrödinger-Newton (SN) system of gravity coupled to single particle quantum mechanics. At the masses of interest here, the ones associated with the onset of ‘collapse’ (where the gravitational attraction is competitive with the quantum mechanical dissipation), we show that the Schrödinger ground state energies match the Dirac ones with an error of ˜ 10%. At the Planck mass scale, we predict the critical mass at which a potential collapse could occur for the self-coupled gravitational case, m≈ 3.3 Planck mass, and show that gravitational attraction opposes Gaussian spreading at around this value, which is a factor of two higher than the one predicted (and verified) for the SN system. Unlike the SN dynamics, we do not find that the self-coupled case tends to decay towards its ground state; there is no collapse in this case.
Dynamics of quantum Fisher information in a two-level system coupled to multiple bosonic reservoirs
NASA Astrophysics Data System (ADS)
Wang, Guo-You; Guo, You-Neng; Zeng, Ke
2015-11-01
We consider the optimal parameter estimation for a two-level system coupled to multiple bosonic reservoirs. By using quantum Fisher information (QFI), we investigate the effect of the Markovian reservoirs’ number N on QFI in both weak and strong coupling regimes for a two-level system surrounded by N zero-temperature reservoirs of field modes initially in the vacua. The results show that the dynamics of QFI non-monotonically decays to zero with revival oscillations at some time in the weak coupling regime depending on the reservoirs’ parameters. Furthermore, we also present the relations between the QFI flow, the flows of energy and information, and the sign of the decay rate to gain insight into the physical processes characterizing the dynamics. Project supported by the Hunan Provincial Innovation Foundation for Postgraduate, China (Grant No. CX2014B194) and the Scientific Research Foundation of Hunan Provincial Education Department, China (Grant No. 13C039).
NASA Astrophysics Data System (ADS)
Du, Peng; Li, Michael Y.
2014-10-01
The global dynamics of coupled systems of differential equations defined on an interaction network are investigated. Local dynamics at each vertex, when interactions are absent, are assumed to be simple: solutions to each vertex system are assumed to converge to an equilibrium, either on the boundary or in the interior of the feasible region. The interest is to investigate the collective behaviours of the coupled system when interactions among vertex systems are present. It was shown in Li and Shuai (2010) that, if the interaction network is strongly connected, then solutions to the coupled system synchronize at a single equilibrium. We focus on the case when the underlying network is not strongly connected and the coupled system may have mixed equilibria whose coordinates are in the interior at some vertices while on the boundary at others. We show that solutions on a strongly connected component of the network will synchronize. Considering a condensed digraph by collapsing each strongly connected component, we are able to introduce a partial order on the set P of all equilibria, and show that all solutions of the coupled system converge to a unique equilibrium P∗ that is the maximizer in P. We further establish that behaviours of the coupled system at minimal elements of the condensed digraph determine whether the global limit P∗ is a mixed equilibrium. The theory are applied to mathematical models from epidemiology and spatial ecology.
NASA Technical Reports Server (NTRS)
2001-01-01
Magnetospheric Constellation Dynamic Response and Coupling Observatory (DRACO) is the Solar Terrestrial Probe (STP) designed to understand the nonlinear dynamics, responses, and connections within the Earth's structured magnetotail, using a constellation of approximately 50 to 100 distributed vector measurement spacecraft. DRACO will reveal magnetotail processes operating within a domain extending 20 Earth radii (R(sub E)) across the tail and 40 R(sub E)down the tail, on spatial and time scales accessible to global circulation models, i.e., approximately 2 R(sub E) and 10 seconds.
Spatiotemporal Dynamics of a Network of Coupled Time-Delay Digital Tanlock Loops
NASA Astrophysics Data System (ADS)
Paul, Bishwajit; Banerjee, Tanmoy; Sarkar, B. C.
The time-delay digital tanlock loop (TDTLs) is an important class of phase-locked loop that is widely used in electronic communication systems. Although nonlinear dynamics of an isolated TDTL has been studied in the past but the collective behavior of TDTLs in a network is an important topic of research and deserves special attention as in practical communication systems separate entities are rarely isolated. In this paper, we carry out the detailed analysis and numerical simulations to explore the spatiotemporal dynamics of a network of a one-dimensional ring of coupled TDTLs with nearest neighbor coupling. The equation representing the network is derived and we carry out analytical calculations using the circulant matrix formalism to obtain the stability criteria. An extensive numerical simulation reveals that with the variation of gain parameter and coupling strength the network shows a variety of spatiotemporal dynamics such as frozen random pattern, pattern selection, spatiotemporal intermittency and fully developed spatiotemporal chaos. We map the distinct dynamical regions of the system in two-parameter space. Finally, we quantify the spatiotemporal dynamics by using quantitative measures like Lyapunov exponent and the average quadratic deviation of the full network.
Dynamical mass generation in strongly coupled quantum electrodynamics with weak magnetic fields
Ayala, Alejandro; Raya, Alfredo; Rojas, Eduardo; Bashir, Adnan
2006-05-15
We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of weak magnetic fields using Schwinger-Dyson equations. Contrary to the case where the magnetic field is strong, in the weak field limit the coupling should exceed certain critical value in order for the generation of masses to take place, just as in the case where no magnetic field is present. The weak field limit is defined as eB<
Mixed quantum-classical versus full quantum dynamics: Coupled quasiparticle-oscillator system
NASA Astrophysics Data System (ADS)
Schanz, Holger; Esser, Bernd
1997-05-01
The relation between the dynamical properties of a coupled quasiparticle-oscillator system in the mixed quantum-classical and fully quantized descriptions is investigated. The system is considered as a model for applying a stepwise quantization. Features of the nonlinear dynamics in the mixed description such as the presence of a separatrix structure or regular and chaotic motion are shown to be reflected in the evolu- tion of the quantum state vector of the fully quantized system. In particular, it is demonstrated how wave packets propagate along the separatrix structure of the mixed description, and that chaotic dynamics leads to a strongly entangled quantum state vector. Special emphasis is given to viewing the system from a dyn- amical Born-Oppenheimer approximation defining integrable reference oscillators, and elucidating the role of the nonadiabatic couplings which complement this approximation into a rigorous quantization scheme.
Deterministic escape dynamics of two-dimensional coupled nonlinear oscillator chains.
Fugmann, S; Hennig, D; Schimansky-Geier, L; Hänggi, P
2008-06-01
We consider the deterministic escape dynamics of a chain of coupled oscillators under microcanonical conditions from a metastable state over a cubic potential barrier. The underlying dynamics is conservative and noise free. We introduce a two-dimensional chain model and assume that neighboring units are coupled by Morse springs. It is found that, starting from a homogeneous lattice state, due to the nonlinearity of the external potential the system self-promotes an instability of its initial preparation and initiates complex lattice dynamics leading to the formation of localized large amplitude breathers, evolving in the direction of barrier crossing, accompanied by global oscillations of the chain transverse to the barrier. A few chain units accumulate locally sufficient energy to cross the barrier. Eventually the metastable state is left and either these particles dissociate or pull the remaining chain over the barrier. We show this escape for both linear rodlike and coil-like configurations of the chain in two dimensions. PMID:18643245
Auer, Benjamin; Soudackov, Alexander V; Hammes-Schiffer, Sharon
2012-07-01
Theoretical approaches for simulating the ultrafast dynamics of photoinduced proton-coupled electron transfer (PCET) reactions in solution are developed and applied to a series of model systems. These processes are simulated by propagating nonadiabatic surface hopping trajectories on electron-proton vibronic surfaces that depend on the solute and solvent nuclear coordinates. The PCET system is represented by a four-state empirical valence bond model, and the solvent is treated either as explicit solvent molecules or as a dielectric continuum, in which case the solvent dynamics is described in terms of two collective solvent coordinates corresponding to the energy gaps associated with electron and proton transfer. The explicit solvent simulations reveal two distinct solvent relaxation time scales, where the faster time scale relaxation corresponds to librational motions of solvent molecules in the first solvation shell, and the slower time scale relaxation corresponds to the bulk solvent dielectric response. The charge transfer dynamics is strongly coupled to both the fast and slow time scale solvent dynamics. The dynamical multistate continuum theory is extended to include the effects of two solvent relaxation time scales, and the resulting coupled generalized Langevin equations depend on parameters that can be extracted from equilibrium molecular dynamics simulations. The implicit and explicit solvent approaches lead to qualitatively similar charge transfer and solvent dynamics for model PCET systems, suggesting that the implicit solvent treatment captures the essential elements of the nonequilibrium solvent dynamics for many systems. A combination of implicit and explicit solvent approaches will enable the investigation of photoinduced PCET processes in a variety of condensed phase systems. PMID:22651684
Multiple coupled landscapes and non-adiabatic dynamics with applications to self-activating genes.
Chen, Cong; Zhang, Kun; Feng, Haidong; Sasai, Masaki; Wang, Jin
2015-11-21
Many physical, chemical and biochemical systems (e.g. electronic dynamics and gene regulatory networks) are governed by continuous stochastic processes (e.g. electron dynamics on a particular electronic energy surface and protein (gene product) synthesis) coupled with discrete processes (e.g. hopping among different electronic energy surfaces and on and off switching of genes). One can also think of the underlying dynamics as the continuous motion on a particular landscape and discrete hoppings among different landscapes. The main difference of such systems from the intra-landscape dynamics alone is the emergence of the timescale involved in transitions among different landscapes in addition to the timescale involved in a particular landscape. The adiabatic limit when inter-landscape hoppings are fast compared to continuous intra-landscape dynamics has been studied both analytically and numerically, but the analytical treatment of the non-adiabatic regime where the inter-landscape hoppings are slow or comparable to continuous intra-landscape dynamics remains challenging. In this study, we show that there exists mathematical mapping of the dynamics on 2(N) discretely coupled N continuous dimensional landscapes onto one single landscape in 2N dimensional extended continuous space. On this 2N dimensional landscape, eddy current emerges as a sign of non-equilibrium non-adiabatic dynamics and plays an important role in system evolution. Many interesting physical effects such as the enhancement of fluctuations, irreversibility, dissipation and optimal kinetics emerge due to non-adiabaticity manifested by the eddy current illustrated for an N = 1 self-activator. We further generalize our theory to the N-gene network with multiple binding sites and multiple synthesis rates for discretely coupled non-equilibrium stochastic physical and biological systems. PMID:26455835
Gender Dynamics Predict Changes in Marital Love Among African American Couples
Stanik, Christine E.; McHale, Susan M.; Crouter, Ann C.
2013-01-01
This study examined the implications of gender attitudes and spouses’ divisions of household labor, time with children, and parental knowledge for their trajectories of love in a sample of 146 African American couples. Multilevel modeling in the context of an accelerated longitudinal design accommodated 3 annual waves of data. The results revealed that traditionality in husbands’ gender attitudes was linked to lower levels of love. Furthermore, divisions of household labor and parental knowledge moderated changes in love such that couples with more egalitarian divisions exhibited higher and more stable patterns of love, whereas more traditional couples exhibited significant declines in love over time. Finally, greater similarity between spouses’ time with their children was linked to higher levels of marital love. The authors highlight the implications of gender dynamics for marital harmony among African American couples and discuss ways that this work may be applied and extended in practice and future research. PMID:23956462
Second-order quantized Hamilton dynamics coupled to classical heat bath
Heatwole, Eric M.; Prezhdo, Oleg V.
2005-06-15
Starting with a quantum Langevin equation describing in the Heisenberg representation a quantum system coupled to a quantum bath, the Markov approximation and, further, the closure approximation are applied to derive a semiclassical Langevin equation for the second-order quantized Hamilton dynamics (QHD) coupled to a classical bath. The expectation values of the system operators are decomposed into products of the first and second moments of the position and momentum operators that incorporate zero-point energy and moderate tunneling effects. The random force and friction as well as the system-bath coupling are decomposed to the lowest classical level. The resulting Langevin equation describing QHD-2 coupled to classical bath is analyzed and applied to free particle, harmonic oscillator, and the Morse potential representing the OH stretch of the SPC-flexible water model.
Chaotic dynamics of cardioventilatory coupling in humans: effects of ventilatory modes
Mangin, Laurence; Clerici, Christine; Similowski, Thomas; Poon, Chi-Sang
2009-01-01
Cardioventilatory coupling (CVC), a transient temporal alignment between the heartbeat and inspiratory activity, has been studied in animals and humans mainly during anesthesia. The origin of the coupling remains uncertain, whether or not ventilation is a main determinant in the CVC process and whether the coupling exhibits chaotic behavior. In this frame, we studied sedative-free, mechanically ventilated patients experiencing rapid sequential changes in breathing control during ventilator weaning during a switch from a machine-controlled assistance mode [assist-controlled ventilation (ACV)] to a patient-driven mode [inspiratory pressure support (IPS) and unsupported spontaneous breathing (USB)]. Time series were computed as R to start inspiration (RI) and R to the start of expiration (RE). Chaos was characterized with the noise titration method (noise limit), largest Lyapunov exponent (LLE) and correlation dimension (CD). All the RI and RE time series exhibit chaotic behavior. Specific coupling patterns were displayed in each ventilatory mode, and these patterns exhibited different linear and chaotic dynamics. When switching from ACV to IPS, partial inspiratory loading decreases the noise limit value, the LLE, and the correlation dimension of the RI and RE time series in parallel, whereas decreasing intrathoracic pressure from IPS to USB has the opposite effect. Coupling with expiration exhibits higher complexity than coupling with inspiration during mechanical ventilation either during ACV or IPS, probably due to active expiration. Only 33% of the cardiac time series (RR interval) exhibit complexity either during ACV, IPS, or USB making the contribution of the cardiac signal to the chaotic feature of the coupling minimal. We conclude that 1) CVC in unsedated humans exhibits a complex dynamic that can be chaotic, and 2) ventilatory mode has major effects on the linear and chaotic features of the coupling. Taken together these findings reinforce the role of
A spacetime, balance-law formulation of coupled atomistic and continuum dynamics for solids
NASA Astrophysics Data System (ADS)
Kraczek, Brent
Coupled dynamic atomistic and continuum computational methods for solids have received much interest recently, because many problems are not addressed well by either model alone. In most coupled methods more emphasis has been placed on damping spurious reflections than on balancing momentum and energy. I present a new method for concurrent coupling of dynamic atomistic and continuum simulations of solids that enforces these balance laws on the atom/element level while minimizing spurious reflections. The coupled formulation is composed of the continuum spacetime discontinuous Galerkin (SDG) method and the mathematically consistent, time finite element, atomistic discontinuous Galerkin (ADG) method. On the continuum side I develop a two- and three-field SDG formulations for linearized elastodynamics to illuminate the mathematical structure of the original one-field SDG formulation and to assist in making connections to the atomistic formulation. On the atomistic side I examine connections between the SDG and ADG methods, and then extend this to relationships with the Velocity Verlet integrator. The component SDG and ADG methods are coupled using the same Godunov flux solution as is used by the SDG method, to enforce weakly the jump conditions on momentum balance and kinematic compatibility. To obtain compatible fluxes on the atomistic side of the coupling boundary I define a boundary atomistic trace that can be optimized to minimize boundary reflections. The coupled SDG--ADG formulation preserves the characteristic structure of the hyperbolic problem, guarantees element/atom-wise momentum balance to machine precision and yields energy error that is small, dissipative and controllable. The flux-based coupling can also be used with the Velocity Verlet method in place of the ADG, although the SDG--VV method suffers from uncontrolled energy error for long-time simulations due to the mismatch in the mathematical models. I present the formulations in spacetime, with one
Frisch, E.; Johnson, C.G.
1962-05-15
A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)
Morrison, S; Cortes, N; Newell, K M; Kerr, G
2014-09-19
This study was designed to examine differences in the coupling dynamics between upper limb motion, physiological tremor and whole body postural sway in young healthy adults. Acceleration of the hand and fingers, forearm EMG activity and postural sway data were recorded. Estimation of the degree of bilateral and limb motion-postural sway coupling was determined by cross correlation, coherence and Cross-ApEn analyses. The results revealed that, under postural tremor conditions, there was no significant coupling between limbs, muscles or sway across all metrics of coupling. In contrast, performing a rapid alternating flexion/extension movement about the wrist joint (with one or both limbs) resulted in stronger coupling between limb motion and postural sway. These results support the view that, for physiological tremor responses, the control of postural sway is maintained independent to tremor in the upper limb. However, increasing the level of movement about a distal segment of one arm (or both) leads to increased coupling throughout the body. The basis for this increased coupling would appear to be related to the enhanced neural drive to task-specific muscles within the upper limb. PMID:25067826