Coupled nonlinear dynamical systems
NASA Astrophysics Data System (ADS)
Sun, Hongyan
In this dissertation, we study coupled nonlinear dynamical systems that exhibit new types of complex behavior. We numerically and analytically examine a variety of dynamical models, ranging from systems of ordinary differential equations (ODE) with novel elements of feedback to systems of partial differential equations (PDE) that model chemical pattern formation. Chaos, dynamical uncertainty, synchronization, and spatiotemporal pattern formation constitute the primary topics of the dissertation. Following the introduction in Chapter 1, we study chaos and dynamical uncertainty in Chapter 2 with coupled Lorenz systems and demonstrate the existence of extreme complexity in high-dimensional ODE systems. In Chapter 3, we demonstrate that chaos synchronization can be achieved by mutual and multiplicative coupling of dynamical systems. Chapter 4 and 5 focus on pattern formation in reaction-diffusion systems, and we investigate segregation and integration behavior of populations in competitive and cooperative environments, respectively.
Coupling strength versus coupling impact in nonidentical bidirectionally coupled dynamics
NASA Astrophysics Data System (ADS)
Laiou, Petroula; Andrzejak, Ralph G.
2017-01-01
The understanding of interacting dynamics is important for the characterization of real-world networks. In general, real-world networks are heterogeneous in the sense that each node of the network is a dynamics with different properties. For coupled nonidentical dynamics symmetric interactions are not straightforwardly defined from the coupling strength values. Thus, a challenging issue is whether we can define a symmetric interaction in this asymmetric setting. To address this problem we introduce the notion of the coupling impact. The coupling impact considers not only the coupling strength but also the energy of the individual dynamics, which is conveyed via the coupling. To illustrate this concept, we follow a data-driven approach by analyzing signals from pairs of coupled model dynamics using two different connectivity measures. We find that the coupling impact, but not the coupling strength, correctly detects a symmetric interaction between pairs of coupled dynamics regardless of their degree of asymmetry. Therefore, this approach allows us to reveal the real impact that one dynamics has on the other and hence to define symmetric interactions in pairs of nonidentical dynamics.
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
Dynamic Coupling of Underactuated Manipulators
1994-08-01
using dynamic coupling. IEEE Transactions on Robotics and Automation, vol. 7, no. 4, Aug. 1991, pp. 528-534. [2] Bergerman, M.; Xu, Y. Robust control of...equilibrium manifolds. IEEE Transactions on Robotics and Automation, vol. 9, no. 5, Oct. 1993. [8] Nakamura, Y. Advanced robotics: Redundancy and
Vehicle systems: coupled and interactive dynamics analysis
NASA Astrophysics Data System (ADS)
Vantsevich, Vladimir V.
2014-11-01
This article formulates a new direction in vehicle dynamics, described as coupled and interactive vehicle system dynamics. Formalised procedures and analysis of case studies are presented. An analytical consideration, which explains the physics of coupled system dynamics and its consequences for dynamics of a vehicle, is given for several sets of systems including: (i) driveline and suspension of a 6×6 truck, (ii) a brake mechanism and a limited slip differential of a drive axle and (iii) a 4×4 vehicle steering system and driveline system. The article introduces a formal procedure to turn coupled system dynamics into interactive dynamics of systems. A new research direction in interactive dynamics of an active steering and a hybrid-electric power transmitting unit is presented and analysed to control power distribution between the drive axles of a 4×4 vehicle. A control strategy integrates energy efficiency and lateral dynamics by decoupling dynamics of the two systems thus forming their interactive dynamics.
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.
Nonlinear dynamics of coupled oscillator arrays
NASA Astrophysics Data System (ADS)
Mosher, David
1988-03-01
The phase-locked dynamics of large oscillator arrays is currently of interest because of possible microwave directed energy applications. Straight-forward integration of the coupled dynamical equations for such arrays is computationally costly for the associated multidimensional parameter space, long integration times, various initial conditions and system configurations. Finite difference analogs of the nonlinear differential equations can reproduce their complex dynamical behavior with a 2 to 3 order-of-magnitude improvement in computational time. Here, the applicability of the finite difference technique is demonstrated by solutions of the dynamical equations for 2 coupled oscillators and rings of larger numbers. Parameter studies for these configurations suggest the values of the coupler length and coupling strength required to provide robust phase-locked operation. The finite difference technique can be extended to model large oscillator arrays with other coupling geometries, amplifier arrays, and additional physical phenomena.
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.
Dynamic effects of magnetic multilayer interlayer coupling
Pechan, M.J.; Xu, J. . Dept. of Physics); Kelly, D.M.; Schuller, I.K. . Dept. of Physics)
1993-11-01
Coupling between magnetic layers in multilayer samples gives rise to dynamic effects which are manifest as anomalous modes in ferromagnetic resonance (FMR) spectra. According to the model presented, antiferromagnetic (ferromagnetic) coupling would produce such modes on the high (low) field side of the uniform FMR mode. Anomalous modes, observed in Fe/Cu and Fe/Cr multilayer samples, are analyzed to obtain coupling constants as a function of nonmagnetic layer thickness. The modes are shown to arise from 180 out-of-phase interlayer magnetization precession. The coupling is observed to be antiferromagnetic in all samples and to be an order of magnitude greater in the Cr system than in the Cu.
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.
Dynamical localization of coupled relativistic kicked rotors
NASA Astrophysics Data System (ADS)
Rozenbaum, Efim B.; Galitski, Victor
2017-02-01
A periodically driven rotor is a prototypical model that exhibits a transition to chaos in the classical regime and dynamical localization (related to Anderson localization) in the quantum regime. In a recent work [Phys. Rev. B 94, 085120 (2016), 10.1103/PhysRevB.94.085120], A. C. Keser et al. considered a many-body generalization of coupled quantum kicked rotors, and showed that in the special integrable linear case, dynamical localization survives interactions. By analogy with many-body localization, the phenomenon was dubbed dynamical many-body localization. In the present work, we study nonintegrable models of single and coupled quantum relativistic kicked rotors (QRKRs) that bridge the gap between the conventional quadratic rotors and the integrable linear models. For a single QRKR, we supplement the recent analysis of the angular-momentum-space dynamics with a study of the spin dynamics. Our analysis of two and three coupled QRKRs along with the proved localization in the many-body linear model indicate that dynamical localization exists in few-body systems. Moreover, the relation between QRKR and linear rotor models implies that dynamical many-body localization can exist in generic, nonintegrable many-body systems. And localization can generally result from a complicated interplay between Anderson mechanism and limiting integrability, since the many-body linear model is a high-angular-momentum limit of many-body QRKRs. We also analyze the dynamics of two coupled QRKRs in the highly unusual superballistic regime and find that the resonance conditions are relaxed due to interactions. Finally, we propose experimental realizations of the QRKR model in cold atoms in optical lattices.
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
Ultrastrong coupling dynamics with a transmon qubit
NASA Astrophysics Data System (ADS)
Kraglund Andersen, Christian; Blais, Alexandre
2017-02-01
The interaction of light and matter is often described by the exchange of single excitations. When the coupling strength is a significant fraction of the system frequencies, the number of excitations are no longer preserved and that simple picture breaks down. This regime is known as the ultrastrong coupling regime and is characterized by non-trivial light–matter eigenstates and by complex dynamics. In this work, we propose to use an array Josephson junctions to increase the impedance of the light mode enabling ultrastrong coupling to a transmon qubit. We show that the resulting dynamics can be generated and probed by taking advantage of the multi-mode structure of the junction array. This proposal relies on the frequency tunability of the transmon and, crucially, on the use of a low frequency mode of the array, which allows for non-adiabatic changes of the ground state.
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
Structure and dynamics of coupled viscous liquids
NASA Astrophysics Data System (ADS)
Ninarello, Andrea; Berthier, Ludovic; Coslovich, Daniele
2015-09-01
We perform Monte-Carlo simulations to analyse the structure and microscopic dynamics of a viscous Lennard-Jones liquid coupled to a quenched reference configuration of the same liquid. The coupling between the two replicas is introduced via a field ɛ conjugate to the overlap Q between the two particle configurations. This allows us to study the evolution of various static and dynamic correlation functions across the (ɛ, T) equilibrium phase diagram. As the temperature is decreased, we identify increasingly marked precursors of a first-order phase transition between a low-Q and a high-Q phase induced by the field ɛ. We show in particular that both static and dynamic susceptibilities have a maximum at a temperature-dependent value of the coupling field, which defines a 'Widom line'. We also show that, in the high-overlap regime, diffusion and structural relaxation are strongly decoupled because single-particle motion mostly occurs via discrete hopping on the sites defined by the reference configuration. These results, obtained using conventional numerical tools, provide encouraging signs that an equilibrium phase transition exists in coupled viscous liquids, but also demonstrate that important numerical challenges must be overcome to obtain more conclusive numerical evidence.
Dynamics of mobile coupled phase oscillators
NASA Astrophysics Data System (ADS)
Uriu, Koichiro; Ares, Saúl; Oates, Andrew C.; Morelli, Luis G.
2013-03-01
We study the transient synchronization dynamics of locally coupled phase oscillators moving on a one-dimensional lattice. Analysis of spatial phase correlation shows that mobility speeds up relaxation of spatial modes and leads to faster synchronization. We show that when mobility becomes sufficiently high, it does not allow spatial modes to form and the population of oscillators behaves like a mean-field system. Estimating the relaxation timescale of the longest spatial mode and comparing it with systems with long-range coupling, we reveal how mobility effectively extends the interaction range.
Complex mode dynamics of coupled wave oscillators
NASA Astrophysics Data System (ADS)
Alexander, T. J.; Yan, D.; Kevrekidis, P. G.
2013-12-01
We explore how nonlinear coherent waves localized in a few wells of a periodic potential can act analogously to a chain of coupled oscillators. We identify the small-amplitude oscillation modes of these “coupled wave oscillators” and find that they can be extended into the large amplitude regime, where some “ring” for long times. We also reveal the appearance of complex behavior such as the breakdown of Josephson-like oscillations, the destabilization of fundamental oscillation modes, and the emergence of chaotic oscillations for large amplitude excitations. We show that the dynamics may be accurately described by a discrete model with nearest-neighbor coupling, in which the lattice oscillators bear an effective mass.
Magnetization dynamics of coupled ferromagnetic disks
Heinonen, Olle
2015-08-10
The magnetization configuration in two stacked micron-size ferromagnetic disks can assume different equilibrium states depending on the interfacial coupling between the disks. In this paper, I examine the magnetization dynamics in response to an out-of-plane field pulse for different equilibrium states. For antiferromagnetic coupling, the response spectrum generally consists of a lower-frequency part and a higher-frequency part. The former is related to the response of the core region, which has a significant in-plane response coupled to the out-of-plane one; the latter is related to spin waves generated at the edges of the disk. Finally, for a meron structure the responsemore » in the two disks to an out-of-plane pulse is also asymmetric.« less
Magnetization dynamics of coupled ferromagnetic disks
Heinonen, Olle
2015-08-10
The magnetization configuration in two stacked micron-size ferromagnetic disks can assume different equilibrium states depending on the interfacial coupling between the disks. In this paper, I examine the magnetization dynamics in response to an out-of-plane field pulse for different equilibrium states. For antiferromagnetic coupling, the response spectrum generally consists of a lower-frequency part and a higher-frequency part. The former is related to the response of the core region, which has a significant in-plane response coupled to the out-of-plane one; the latter is related to spin waves generated at the edges of the disk. Finally, for a meron structure the response in the two disks to an out-of-plane pulse is also asymmetric.
Dynamics of weakly coupled parametrically forced oscillators.
Salgado Sánchez, P; Porter, J; Tinao, I; Laverón-Simavilla, A
2016-08-01
The dynamics of two weakly coupled parametric oscillators are studied in the neighborhood of the primary subharmonic instability. The nature of both primary and secondary instabilities depends in a critical way on the permutation symmetries, if any, that remain after coupling is considered, and this depends on the relative phases of the parametric forcing terms. Detailed bifurcation sets, revealing a complex series of transitions organized in part by Bogdanov-Takens points, are calculated for representative sets of parameters. In the particular case of out-of-phase forcing the predictions of the coupled oscillator model are compared with direct numerical simulations and with recent experiments on modulated cross waves. Both the initial Hopf bifurcation and the subsequent saddle-node heteroclinic bifurcation are confirmed.
Coupling of protein dynamics with the solvent
NASA Astrophysics Data System (ADS)
Caliskan, Gokhan; Sauzan, Azzam; Mehtani, Disha; Sokolov, Alexei
2003-03-01
Glycerol and trehalose are among the many viscous solvents that are widely used for biostabilization and controlling the dynamics of proteins. It is believed that the suppression of the structural relaxations by high viscosity of solvent is responsible for improved stability in proteins. However, results of [1] and [2] demonstrate stronger suppression of biochemical activity and dynamics of proteins by liquid glycerol than by solid trehalose in a wide temperature range. The authors tried to explain the counterintuitive observations by a possible decoupling of the dynamics of the protein from trehalose. In order to test the validity of this assumption and to investigate the influence of the fast dynamics in proteins, the low frequency Raman scattering spectroscopy technique is used. Both relaxational and vibrational dynamics of glycerol, trehalose, and lysozyme in glycerol and in trehalose are studied in a wide temperature range. Dynamics of lysozyme in glycerol follows the strong temperature dependence of relaxational and vibrational dynamics of the bulk glycerol. On the other hand, the weak temperature dependence of dynamics of lysozyme in trehalose follows exactly the behavior of pure trehalose. This proves that there is a strong dynamic coupling between the protein and the solvents used. Interestingly, stronger relaxations in solid trehalose as compared to liquid glycerol are observed in the GHz region at low temperatures. This could be the reason for the enhanced protein activity observed in trehalose, compared to that in glycerol in this temperature range. Suppression of these fast relaxations should be the key for providing long-term stability to proteins. 1. Sastry, G.M. and N. Agmon, Trehalose prevents myoglobin collapse and preserves its internal mobility. BIOCHEMISTRY, 1997, 36(23): p. 7097-108. 2. Caliskan, G., et al., Influence of solvent on dynamics and stability of a protein. Journal of Non-Crystalline Solids, 2002, 307-310: p. 887-893.
Chaotic itinerancy in coupled dynamical recognizers.
Ikegami, Takashi; Morimoto, Gentaro
2003-09-01
We argue that chaotic itinerancy in interaction between humans originates in the fluctuation of predictions provided by the nonconvergent nature of learning dynamics. A simple simulation model called the coupled dynamical recognizer is proposed to study this phenomenon. Daily cognitive phenomena provide many examples of chaotic itinerancy, such as turn taking in conversation. It is therefore an interesting problem to bridge two chaotic itinerant phenomena. A clue to solving this is the fluctuation of prediction, which can be translated as "hot prediction" in the context of cognitive theory. Hot prediction is simply defined as a prediction based on an unstable model. If this approach is correct, the present simulation will reveal some dynamic characteristics of cognitive interactions.
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.
Dynamically Coupled Oscillators: Cooperative Behavior via Dynamical Interaction
NASA Astrophysics Data System (ADS)
Aonishi, Toru; Okada, Masato
2003-06-01
We propose a theoretical framework for studying the cooperative behavior of dynamically coupled oscillators (DCOs) that possess dynamical interactions. Then, to clarify synchronization phenomena in networks of interneurons which possess inhibitory interactions, we propose a DCO model with dynamics of interactions that tend to cause 180^\\circ phase lags. Employing the approach developed here, we demonstrate that although our model displays synchronization at high frequencies, it does not exhibit synchronization at low frequencies because this dynamical interaction does not cause a phase lag sufficiently large to cancel the effect of the inhibition. We interpret the disappearance of synchronization in our model with decreasing frequency as describing the breakdown of synchronization in the interneuron network of the CA1 area below the critical frequency of 20 Hz.
Exciton dynamics in paracyclophane coupled dimers
NASA Astrophysics Data System (ADS)
Maddox, Jeremy; Kim, Jeongho; Moran, Andrew; Hong, Janice; Bazan, Guillermo; Scherer, Norbert; Mukamel, Shaul
2005-03-01
Understanding and manipulating through-space electronic communication within aggregates of organic fragments with delocalized bonding structures can impact a range of nanotechnology applications. However, interrogating aggregates of this type has encountered multiple difficulties in the past, ranging from heterogeneity of environments in the solid to the ill-defined geometry of intermolecular contacts in solution. These difficulties are circumvented by designing aggregates which contain [2.2]paracyclophane contacts among molecular units with well-defined architectures and dimensions. These offer excellent control over the distance and relative orientation of the participating units and provide a model system for detailed examination of the molecular structure-function relationship of conducting polymeric materials. We present a comparative experimental and theoretical study of a model complex consisting of two (oligo)phenylenevinylene chromophores that are strongly coupled through a paracyclophane junction. Ultrafast pump-probe anisotropy measurements are compared with numerical simulations to investigate the nature of exciton dynamics in strongly coupled chromophores.
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
Dynamic aperture effects due to linear coupling
Parzen, G.
1991-01-01
The coupling introduced by the random a{sub 1} can produce considerable distortion of the betatron motion. For a given initial x{sub o}, x{sub o}{prime}, y{sub o}, y{sub o}{prime}, the maximum x and the maximum y for the subsequent motion can be considerably larger when coupling is present. The maximum x and y can be used as a measure of the betatron distortion. One effect of this betatron distortion shows up in the dynamic aperture, in a loss in the stability limit, A{sub SL}, found by tracking. The betatron distortion causes the particle to move further out in the magnets, where it sees stronger non-linear fields. Previous tracking showed a loss in A{sub SL} due to random a{sub 1} and b{sub 1}. It was noticed then that the loss in A{sub SL} was associated with a betatron motion distortion which was primarily a linear effect. For a given initial x, x{prime}, y, y{prime} the x{sub max} and y{sub max} in the high-{Beta} magnets were considerably larger for those random a{sub 1} distributions which produced the smaller A{sub SL}. The studies described in this report show that the stability limit, A{sub SL}, depends on the starting location around the ring. This variation in A{sub SL} around the ring can be correlated with the variation in the betatron distortion for particles starting at different places around the ring. It is proposed that the average of the A{sub SL} found by starting at each of the QF, the focusing quadrupoles in the arcs, can be taken as a measure of the dynamic aperture. It is found that the average A{sub SL} is reduced by about 15% by the random a{sub 1} multipoles expected in RHIC.
Dynamic nonlinear thermal optical effects in coupled ring resonators
NASA Astrophysics Data System (ADS)
Huang, Chenguang; Fan, Jiahua; Zhu, Lin
2012-09-01
We investigate the dynamic nonlinear thermal optical effects in a photonic system of two coupled ring resonators. A bus waveguide is used to couple light in and out of one of the coupled resonators. Based on the coupling from the bus to the resonator, the coupling between the resonators and the intrinsic loss of each individual resonator, the system transmission spectrum can be classified by three different categories: coupled-resonator-induced absorption, coupled-resonator-induced transparency and over coupled resonance splitting. Dynamic thermal optical effects due to linear absorption have been analyzed for each category as a function of the input power. The heat power in each resonator determines the thermal dynamics in this coupled resonator system. Multiple "shark fins" and power competition between resonators can be foreseen. Also, the nonlinear absorption induced thermal effects have been discussed.
Wang, Zhengxin; Duan, Zhisheng; Cao, Jinde
2012-03-01
This paper aims to investigate the synchronization problem of coupled dynamical networks with nonidentical Duffing-type oscillators without or with coupling delays. Different from cluster synchronization of nonidentical dynamical networks in the previous literature, this paper focuses on the problem of complete synchronization, which is more challenging than cluster synchronization. By applying an impulsive controller, some sufficient criteria are obtained for complete synchronization of the coupled dynamical networks of nonidentical oscillators. Furthermore, numerical simulations are given to verify the theoretical results.
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
2015-07-15
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.
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
Coupled dynamic systems and Le Chatelier's principle in noise control
NASA Astrophysics Data System (ADS)
Maidanik, G.; Becker, K. J.
2004-05-01
Investigation of coupling an externally driven dynamic system-a master dynamic system-to a passive one-an adjunct dynamic system-reveals that the response of the adjunct dynamic system affects the precoupled response of the master dynamic system. The responses, in the two dynamic systems when coupled, are estimated by the stored energies (Es) and (E0), respectively. Since the adjunct dynamic system, prior to coupling, was with zero (0) stored energy, E0s=0, the precoupled stored energy (E00) in the master dynamic system is expected to be reduced to (E0) when coupling is instituted; i.e., one expects E0
Photon Dynamics in Coherently Coupled Optical Resonators
NASA Technical Reports Server (NTRS)
Smith, David D.; Chang, Hong-Rok; Fuller, K. A.
2004-01-01
The temporal response of coupled resonators is investigated using a linear systems analysis and coupled mode theory. Damped Rabi oscillations, slow and fast light, and coherent photon transfer techniques are demonstrated in these systems.
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.
Dynamical spin-spin coupling of quantum dots
NASA Astrophysics Data System (ADS)
Grigoryan, Vahram; Xiao, Jiang; A spintronics Group Team
2014-03-01
We carried out a nested Schrieffer-Wolff transformation of an Anderson two-impurity Hamiltonian to study the spin-spin coupling between two dynamical quantum dots under the influence of rotating transverse magnetic field. As a result of the rotating field, we predict a novel Ising type spin-spin coupling mechanism between quantum dots, whose strength is tunable via the magnitude of the rotating field. Due to its dynamical origin, this new coupling mechanism is qualitatively different from the all existing static couplings such as RKKY, while the strength could be comparable to the strength of the RKKY coupling. The dynamical coupling with the intristic RKKY coupling enables to construct a four level system of maximally entangled Bell states in a controllable manner. This work was supported by the special funds for the Major State Basic Research Project of China (No. 2011CB925601) and the National Natural Science Foundation of China (Grants No. 11004036 and No. 91121002).
An approach for characterizing coupling in dynamical systems
NASA Astrophysics Data System (ADS)
Janjarasjitt, S.; Loparo, K. A.
2008-10-01
The study of coupling in dynamical systems dates back to Christian Hyugens who, in 1665, discovered that pendulum clocks with the same length pendulum synchronize when they are near to each other. In that case the observed synchronous motion was out of phase. In this paper we propose a new approach for measuring the degree of coupling and synchronization of a dynamical system consisting of interacting subsystems. The measure is based on quantifying the active degrees of freedom (e.g. correlation dimension) of the coupled system and the constituent subsystems. The time-delay embedding scheme is extended to coupled systems and used for attractor reconstruction of the coupled dynamical system. We use the coupled Lorenz, Rossler and Hénon model systems with a coupling strength variable for evaluation of the proposed approach. Results show that we can measure the active degrees of freedom of the coupled dynamical systems and can quantify and distinguish the degree of synchronization or coupling in each of the dynamical systems studied. Furthermore, using this approach the direction of coupling can be determined.
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.
Influence of electronic—nuclear coupling on dynamics
NASA Astrophysics Data System (ADS)
Longo, Ricardo; Diz, Agustín; Deumens, Erik; Öhrn, Yngve
1994-04-01
Electronic nuclear dynamics (END), a recently developed explicitly time-dependent theory treats fully the electronic—nuclear coupling. The END theory at the level of a model that employs a single complex spin-unrestricted determinantal wavefunction for the electrons and classical nuclei has been implemented in the computer code ENDyne. It permits comparisons of the full dynamics at this level of treatment with one where the electronic—nuclear coupling is neglected. The neglect of coupling terms is shown to have quite drastic influence on the detailed dynamics of ion—atom and ion—molecule collisions.
Quark dynamics and pion-nucleon coupling
NASA Astrophysics Data System (ADS)
Weise, W.; Werner, E.
1981-05-01
In the framework of nonperturbative QCD phenomenology we discuss: (1) The elementary process for the creation of color-singlet qq-pairs inside a hadron. (2) The interaction of the qq-pair with the surrounding quark-gluon medium. An important consequence of these discussions is that meson emission takes place preferentially, if the primary qq-pair is created in the surface region of the hadron. For the case of pseudoscalar coupling we employ PCAC to obtain the coupling of the qq-pair to the pion. The resulting form and coupling strength of the πNN vertex is consistent with the phenomenological OPEP.
Dynamics of Attractively and Repulsively Coupled Elementary Chaotic Systems
NASA Astrophysics Data System (ADS)
Trinschek, Sarah; Linz, Stefan J.
We investigate an elementary model for doubly coupled dynamical systems that consists of two identical, mutually interacting minimal chaotic flows in the form of jerky dynamics. The coupling mechanisms allow for the simultaneous presence of attractive and repulsive interactions between the systems. Despite its functional simplicity, the model is capable of exhibiting diverse types of dynamical phenomena induced by the presence of the couplings. We provide an in-depth numerical investigation of the dynamics depending on the coupling strengths and the autonomous dynamical behavior of the subsystems. Partly, the dynamics of the system can be analytically understood using the Poincaré-Lindstedt method. An approximation of periodic orbits is carried out in the vicinity of a phase-flip transition that leads to deeper insights into the organization of the appearing dynamics in the parameter space. In addition, we propose a circuit that enables an electronic implementation of the model. A variation of the coupling mechanism to a coupling in conjugate variables leads to a regime of amplitude death.
Heteroclinic dynamics of coupled semiconductor lasers with optoelectronic feedback.
Shahin, S; Vallini, F; Monifi, F; Rabinovich, M; Fainman, Y
2016-11-15
Generalized Lotka-Volterra (GLV) equations are important equations used in various areas of science to describe competitive dynamics among a population of N interacting nodes in a network topology. In this Letter, we introduce a photonic network consisting of three optoelectronically cross-coupled semiconductor lasers to realize a GLV model. In such a network, the interaction of intensity and carrier inversion rates, as well as phases of laser oscillator nodes, result in various dynamics. We study the influence of asymmetric coupling strength and frequency detuning between semiconductor lasers and show that inhibitory asymmetric coupling is required to achieve consecutive amplitude oscillations of the laser nodes. These studies were motivated primarily by the dynamical models used to model brain cognitive activities and their correspondence with dynamics obtained among coupled laser oscillators.
Dynamical behavior of hydrodynamic Lyapunov modes in coupled map lattices.
Yang, Hong-liu; Radons, Günter
2006-01-01
In our previous study of hydrodynamic Lyapunov modes (HLMs) in coupled map lattices, we found that there are two classes of systems with different lambda-k dispersion relations. For coupled circle maps we found the quadratic dispersion relations lambda approximately k2 and lambda approximately k for coupled standard maps. Here, we carry out further numerical experiments to investigate the dynamic Lyapunov vector (LV) structure factor which can provide additional information on the Lyapunov vector dynamics. The dynamic LV structure factor of coupled circle maps is found to have a single peak at omega=0 and can be well approximated by a single Lorentzian curve. This implies that the hydrodynamic Lyapunov modes in coupled circle maps are nonpropagating and show only diffusive motion. In contrast, the dynamic LV structure factor of coupled standard maps possesses two visible sharp peaks located symmetrically at +/- omega. The spectrum can be well approximated by the superposition of three Lorentzian curves centered at omega=0 and +/-omegau, respectively. In addition, the omega-k dispersion relation takes the form omegau=cuk for k --> 2pi/L. These facts suggest that the hydrodynamic Lyapunov modes in coupled standard maps are propagating. The HLMs in the two classes of systems are shown to have different dynamical behavior besides their difference in spatial structure. Moreover, our simulations demonstrate that adding damping to coupled standard maps turns the propagating modes into diffusive ones alongside a change of the lambda-k dispersion relation from lambda approximately k to lambda approximately k2. In cases of weak damping, there is a crossover in the dynamic LV structure factors; i.e., the spectra with smaller k are akin to those of coupled circle maps while the spectra with larger k are similar to those of coupled standard maps.
Dynamics of a network of phase oscillators with plastic couplings
Nekorkin, V. I.; Kasatkin, D. V.
2016-06-08
The processes of synchronization and phase cluster formation are investigated in a complex network of dynamically coupled phase oscillators. Coupling weights evolve dynamically depending on the phase relations between the oscillators. It is shown that the network exhibits several types of behavior: the globally synchronized state, two-cluster and multi-cluster states, different synchronous states with a fixed phase relationship between the oscillators and chaotic desynchronized state.
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.
Cooperative Phase Dynamics in Coupled Nephrons
NASA Astrophysics Data System (ADS)
Postnov, D. E.; Sosnovtseva, O. V.; Mosekilde, E.; Holstein-Rathlou, N.-H.
The individual functional unit of the kidney (the nephron) displays oscillations in its pressure and flow regulation at two different time scales: Relatively fast oscillations associated with the myogenic dynamics of the afferent arteriole, and slower oscillations related with a delay in the tubuloglomerular feedback. Neighboring nephrons interact via vascularly propagated signals. We study the appearance of various forms of coherent behavior in a model of two such interacting nephrons. Among the observed phenomena are in-phase and anti-phase synchronization of chaotic dynamics, multistability, and partial phase synchronization in which the nephrons attain a state of chaotic phase synchronization with respect to their slow dynamics, but the fast dynamics remains desynchronized.
Time-delayed conjugate coupling in dynamical systems
NASA Astrophysics Data System (ADS)
Sharma, Amit; Shrimali, Manish Dev; Prasad, Awadhesh; Ramaswamy, Ram
2017-06-01
We study the effect of time-delay when the coupling between nonlinear systems is "conjugate", namely through dissimilar variables. This form of coupling can induce anomalous transitions such as the emergence of oscillatory dynamics between regimes of amplitude death and oscillation death. The specific cases of coupled Landau-Stuart oscillators as well as a predator-prey model system with cross-predation are discussed. The dynamical behaviour is analyzed numerically and the regions corresponding to different asymptotic states are identified in parameter space.
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 (≥100 ns) 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.
Dynamical aspects of coupled Rossler systems: effects of noise
NASA Astrophysics Data System (ADS)
Pravitha, R.; Indic, P.; Nampoori, V. P. N.
2002-02-01
Nonlinear time series analysis is employed to study the complex behaviour exhibited by a coupled pair of Rossler systems. Dimensional analysis with emphasis on the topological correlation dimension and the Kolmogorov entropy of the system is carried out in the coupling parameter space. The regime of phase synchronization is identified and the extent of synchronization between the systems constituting the coupled system is quantified by the phase synchronization index. The effect of noise on the coupling between the systems is also investigated. An exhaustive study of the topological, dynamical and synchronization properties of the nonlinear system under consideration in its characteristic parameter space is attempted.
Noise reduction by recycling dynamically coupled time series.
Mera, M Eugenia; Morán, Manuel
2011-12-01
We say that several scalar time series are dynamically coupled if they record the values of measurements of the state variables of the same smooth dynamical system. We show that much of the information lost due to measurement noise in a target time series can be recovered with a noise reduction algorithm by crossing the time series with another time series with which it is dynamically coupled. The method is particularly useful for reduction of measurement noise in short length time series with high uncertainties.
Driven Nonlinear Dynamics of Two Coupled Exchange-Only Qubits
NASA Astrophysics Data System (ADS)
Pal, Arijeet; Rashba, Emmanuel I.; Halperin, Bertrand I.
2014-01-01
Inspired by the creation of a fast exchange-only qubit [Medford et al., Phys. Rev. Lett. 111, 050501 (2013)], we develop a theory describing the nonlinear dynamics of two such qubits that are capacitively coupled, when one of them is driven resonantly at a frequency equal to its level splitting. We include conditions of strong driving, where the Rabi frequency is a significant fraction of the level splitting, and we consider situations where the splitting for the second qubit may be the same as or different than the first. We demonstrate that coupling between qubits can be detected by reading the response of the second qubit, even when the coupling between them is only of about 1% of their level splittings, and we calculate entanglement between qubits. Patterns of nonlinear dynamics of coupled qubits and their entanglement are strongly dependent on the geometry of the system, and the specific mechanism of interqubit coupling deeply influences dynamics of both qubits. In particular, we describe the development of irregular dynamics in a two-qubit system, explore approaches for inhibiting it, and demonstrate the existence of an optimal range of coupling strength maintaining stability during the operational time.
Quantification of causal couplings via dynamical effects: a unifying perspective.
Smirnov, Dmitry A
2014-12-01
Quantitative characterization of causal couplings from time series is crucial in studies of complex systems of different origin. Various statistical tools for that exist and new ones are still being developed with a tendency to creating a single, universal, model-free quantifier of coupling strength. However, a clear and generally applicable way of interpreting such universal characteristics is lacking. This work suggests a general conceptual framework for causal coupling quantification, which is based on state space models and extends the concepts of virtual interventions and dynamical causal effects. Namely, two basic kinds of interventions (state space and parametric) and effects (orbital or transient and stationary or limit) are introduced, giving four families of coupling characteristics. The framework provides a unifying view of apparently different well-established measures and allows us to introduce new characteristics, always with a definite "intervention-effect" interpretation. It is shown that diverse characteristics cannot be reduced to any single coupling strength quantifier and their interpretation is inevitably model based. The proposed set of dynamical causal effect measures quantifies different aspects of "how the coupling manifests itself in the dynamics," reformulating the very question about the "causal coupling strength."
Coupling between evolutionary and population dynamics in experimental microbial populations
NASA Astrophysics Data System (ADS)
Sanchez, Alvaro; Gore, Jeff
2012-02-01
It has been often been assumed that population dynamics and evolutionary dynamics occur at such different timescales that they are effectively de-coupled. This view has been challenged recently, due to observations of evolutionary changes occurring in short timescales. This has led to a growing interest in understanding eco-evolutionary dynamics of populations. In this context, recent theoretical models have predicted that coupling between population dynamics and evolutionary dynamics can have important effects for the evolution and stability of cooperation, and lead to extremely rich and varied dynamics. Here, we report our investigation of the eco-evolutionary dynamics of a cooperative social behavior, sucrose metabolism, in experimental yeast populations. We have devised an experimental strategy to visualize trajectories in the phase space formed by the population size (N) and the fraction of cooperator cells in the population (f). Our measurements confirm a strong coupling between evolutionary and population dynamics, and allowed us to characterize the bifurcation plots. We used this approach to investigate how sudden environmental changes affect the stability and recovery of populations, and therefore the stability of cooperation.
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.
Dynamics of coupled vortices in perpendicular field
Jain, Shikha; Novosad, Valentyn; Fradin, Frank Y.; Pearson, John E.; Bader, Samuel D.
2014-02-27
In this paper, 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. Finally, the vortex core whose polarization is opposite to the bias field dominates the response.
Dynamics of coupled vortices in perpendicular field
Jain, Shikha; Novosad, Valentyn; Fradin, Frank Y.; ...
2014-02-27
In this paper, 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 themore » system for antiparallel core polarities is symmetric around zero bias. Finally, the vortex core whose polarization is opposite to the bias field dominates the response.« less
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.
The dynamics of large-scale arrays of coupled resonators
NASA Astrophysics Data System (ADS)
Borra, Chaitanya; Pyles, Conor S.; Wetherton, Blake A.; Quinn, D. Dane; Rhoads, Jeffrey F.
2017-03-01
This work describes an analytical framework suitable for the analysis of large-scale arrays of coupled resonators, including those which feature amplitude and phase dynamics, inherent element-level parameter variation, nonlinearity, and/or noise. In particular, this analysis allows for the consideration of coupled systems in which the number of individual resonators is large, extending as far as the continuum limit corresponding to an infinite number of resonators. Moreover, this framework permits analytical predictions for the amplitude and phase dynamics of such systems. The utility of this analytical methodology is explored through the analysis of a system of N non-identical resonators with global coupling, including both reactive and dissipative components, physically motivated by an electromagnetically-transduced microresonator array. In addition to the amplitude and phase dynamics, the behavior of the system as the number of resonators varies is investigated and the convergence of the discrete system to the infinite-N limit is characterized.
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.
Coupling Dynamical And Collisional Evolution Of Dust In Protoplanetary Disks
NASA Astrophysics Data System (ADS)
Charnoz, Sebastien
2010-10-01
Gaseous circumstellar disks are rich in dust and are thought to be both accretionaly and dynamically active. Unfortunately large bodies that could be embedded in these disks are still difficult to observe and their putative properties are indirectly inferred from the observable small dust content. It is why constraining the size distribution coupled with dust-dynamics is so critical. Unfortunately, coupling effects such as a realistic time-dependant dynamics, fragmentation and coagulation, has been recognized as numerically challenging and almost no attempt really succeeded with a generic approach. In these disks, the dust dynamics is driven by a variety of processes (gravity, gas drag, radiation pressure..) inducing a size-dependant dynamics, and, at the same time collisional evolution changes the local size distributions. These two effects are intimately coupled because the local dynamics and size-distribution determines the local collision rates, that, in-turn, determines the size-distribution and modifies the particle's dynamics. Here we report on a new algorithm that overcomes these difficulties by using a hybrid approach extending the work of Charnoz & Morbidelli (Icarus, 2004, 2007). We will briefly present the method and focus on gaseous protoplanetary disks either laminar or turbulent (the time dependant transport and dust evolution will be shown) . We will show how the taking into account of a 3D dynamics helps to determine disantengle the dust size-distribution in the disk's photosphere and in the midplane and thus may provide observational signatures of accretion. We will show how the coupling of turbulence with fragmentation may significantly affect the dust/ratio for the smallest bodies. Finally, we will show that an accurate description of the time dependant dynamics of larger dusts (those with Stokes numbers >= 1) may provide a possible path to the formation of bodies larger than the accretion barrier, through accretion in a transitory regime.
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.
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.
Tinamit: Making coupled system dynamics models accessible to stakeholders
NASA Astrophysics Data System (ADS)
Malard, Julien; Inam Baig, Azhar; Rojas Díaz, Marcela; Hassanzadeh, Elmira; Adamowski, Jan; Tuy, Héctor; Melgar-Quiñonez, Hugo
2017-04-01
Model coupling is increasingly used as a method of combining the best of two models when representing socio-environmental systems, though barriers to successful model adoption by stakeholders are particularly present with the use of coupled models, due to their high complexity and typically low implementation flexibility. Coupled system dynamics - physically-based modelling is a promising method to improve stakeholder participation in environmental modelling while retaining a high level of complexity for physical process representation, as the system dynamics components are readily understandable and can be built by stakeholders themselves. However, this method is not without limitations in practice, including 1) inflexible and complicated coupling methods, 2) difficult model maintenance after the end of the project, and 3) a wide variety of end-user cultures and languages. We have developed the open-source Python-language software tool Tinamit to overcome some of these limitations to the adoption of stakeholder-based coupled system dynamics - physically-based modelling. The software is unique in 1) its inclusion of both a graphical user interface (GUI) and a library of available commands (API) that allow users with little or no coding abilities to rapidly, effectively, and flexibly couple models, 2) its multilingual support for the GUI, allowing users to couple models in their preferred language (and to add new languages as necessary for their community work), and 3) its modular structure allowing for very easy model coupling and modification without the direct use of code, and to which programming-savvy users can easily add support for new types of physically-based models. We discuss how the use of Tinamit for model coupling can greatly increase the accessibility of coupled models to stakeholders, using an example of a stakeholder-built system dynamics model of soil salinity issues in Pakistan coupled with the physically-based soil salinity and water flow 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.
Mutual synchronization and clustering in randomly coupled chaotic dynamical networks.
Manrubia, S C; Mikhailov, A S
1999-08-01
We introduce and study systems of randomly coupled maps where the relevant parameter is the degree of connectivity in the system. Global (almost-) synchronized states are found (equivalent to the synchronization observed in globally coupled maps) until a certain critical threshold for the connectivity is reached. We further show that not only the average connectivity, but also the architecture of the couplings is responsible for the cluster structure observed. We analyze the different phases of the system and use various correlation measures in order to detect ordered nonsynchronized states. Finally, it is shown that the system displays a dynamical hierarchical clustering which allows the definition of emerging graphs.
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.
An elementary mode coupling theory of random heteropolymer dynamics
Takada, Shoji; Portman, John J.; Wolynes, Peter G.
1997-01-01
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 TA. For sufficiently long chains, TA is almost independent of chain length and is in good agreement with the value previously estimated by a static replica theory. PMID:9122192
Dynamics of a pulsed inductively coupled oxygen plasma
NASA Astrophysics Data System (ADS)
Zaka-ul-Islam, Mujahid
2016-11-01
Inductively coupled plasma system (ICPs) is extensively used for a wide range of nanofabrication applications. The ICPs operated in a pulsed or power modulated mode has shown several advantages compared to the continuous discharge. In this work, the plasma dynamics in a planar coil pulsed inductively coupled plasma system (ICPs) operated in oxygen has been investigated, using phase and space resolved optical emission spectroscopy. It is well-known that the ICPs operates in two distinct operational modes as a function of power known as E and H modes, generated dominantly by capacitive and inductive couplings, respectively. The measurements show that the discharge ignites due a capacitive coupling (in the E-mode) and later transits to the H-mode as a function of time. The inductive coupling, however, starts during the E-mode along with capacitive coupling. The relative contribution of inductive coupling increases until the discharge reaches the E-H transition where the growth rate of inductive coupling becomes much faster. It is found that the time to reach E-H transition decreases with the pressure. At the E-H transition, the total emission has a spike-like feature (i.e., it first achieves a peak emission which later decreases and finally settles to a lower value). The 2D images of the discharge show that at the time of peak total-emission, the discharge structure is sharp and bright, which later decreases in brightness and becomes diffusive.
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.
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…
Methodologies for launcher-payload coupled dynamic analysis
NASA Astrophysics Data System (ADS)
Fransen, S. H. J. A.
2012-06-01
An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain, also referred to as coupled loads analysis (CLA). The objective of such analyses is the computation of the dynamic environment of the spacecraft (payload) in terms of interface accelerations, interface forces, center of gravity (CoG) accelerations as well as the internal state of stress. In order to perform an efficient, fast and accurate launcher-payload coupled dynamic analysis, various methodologies have been applied and developed. The methods are related to substructuring techniques, data recovery techniques, the effects of prestress and fluids and time integration problems. The aim of this paper was to give an overview of these methodologies and to show why, how and where these techniques can be used in the process of launcher-payload coupled dynamic analysis. In addition, it will be shown how these methodologies fit together in a library of procedures which can be used with the MSC.Nastran™ solution sequences.
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…
A review of substructure coupling methods for dynamic analysis
NASA Technical Reports Server (NTRS)
Craig, R. R., Jr.; Chang, C. J.
1976-01-01
The state of the art is assessed in substructure coupling for dynamic analysis. A general formulation, which permits all previously described methods to be characterized by a few constituent matrices, is developed. Limited results comparing the accuracy of various methods are presented.
Dynamical regimes of four oscillators with excitatory pulse coupling.
Safonov, Dmitry A; Klinshov, Vladimir V; Vanag, Vladimir K
2017-05-17
The dynamical regimes of four almost identical oscillators with pulsatile excitatory coupling have been studied theoretically with two models: a kinetic model of the Belousov-Zhabotinsky reaction and a phase-reduced model. Unidirectional coupling on a ring and all-to-all coupling have been considered. The time delay τ between the moments of a spike in one oscillator and a pulse perturbation of the other(s) plays a crucial role in the emergence of the dynamical modes, which are classified as regular, complex, and OS (oscillation-suppression)-modes. The regular modes, in which each oscillator gives only one spike during the period T, consist of the modes in which the period T is linearly dependent on τ and modes in which T is almost independent of τ. The τ-dependent and τ-independent modes alternate if τ increases. A unique sequence of modes observed at growing τ is the same for all types of connectivity and even for both excitatory and inhibitory coupling. For unidirectional coupling, the analytical dependence of T on τ is found for all regular modes. Multirhythmicity is observed at large values of the coupling strength Cex. The effect of small frequency dispersion (within a few percents) on the stability of the regular modes has been studied. Unusual modes like bursting or heteroclinic switching are found in narrow regions of the Cex-τ plane between the regular modes.
Effect of Coriolis coupling in chemical reaction dynamics.
Chu, Tian-Shu; Han, Ke-Li
2008-05-14
It is essential to evaluate the role of Coriolis coupling effect in molecular reaction dynamics. Here we consider Coriolis coupling effect in quantum reactive scattering calculations in the context of both adiabaticity and nonadiabaticity, with particular emphasis on examining the role of Coriolis coupling effect in reaction dynamics of triatomic molecular systems. We present the results of our own calculations by the time-dependent quantum wave packet approach for H + D2 and F(2P3/2,2P1/2) + H2 as well as for the ion-molecule collisions of He + H2 +, D(-) + H2, H(-) + D2, and D+ + H2, after reviewing in detail other related research efforts on this issue.
Coriolis coupling and nonadiabaticity in chemical reaction dynamics.
Wu, Emilia L
2010-12-01
The nonadiabatic quantum dynamics and Coriolis coupling effect in chemical reaction have been reviewed, with emphasis on recent progress in using the time-dependent wave packet approach to study the Coriolis coupling and nonadiabatic effects, which was done by K. L. Han and his group. Several typical chemical reactions, for example, H+D(2), F+H(2)/D(2)/HD, D(+)+H(2), O+H(2), and He+H(2)(+), have been discussed. One can find that there is a significant role of Coriolis coupling in reaction dynamics for the ion-molecule collisions of D(+)+H(2), Ne+H(2)(+), and He+H(2)(+) in both adiabatic and nonadiabatic context.
Synchronization in complex dynamical networks with nonsymmetric coupling
NASA Astrophysics Data System (ADS)
Wu, Jianshe; Jiao, Licheng
2008-10-01
Based on the work of Nishikawa and Motter, who have extended the well-known master stability framework to include non-diagonalizable cases, we develop another extension of the master stability framework to obtain criteria for global synchronization. Several criteria for global synchronization are provided which generalize some previous results. The Jordan canonical transformation method is used in stead of the matrix diagonalization method. Especially, we show clearly that, the synchronizability of a dynamical network with nonsymmetric coupling is not always characterized by its second-largest eigenvalue, even though all the eigenvalues of the nonsymmetric coupling matrix are real. Furthermore, the effects of the asymmetry of coupling on synchronizability of networks with different structures are analyzed. Numerical simulations are also done to illustrate and verify the theoretical results on networks in which each node is a dynamical limit cycle oscillator consisting of a two-cell cellular neural network.
Coupled Elastic-Thermal Dynamics of Deployable Mesh Reflectors
NASA Technical Reports Server (NTRS)
Shi, H.; Yang, B.; Thomson, M.; Fang, H.
2011-01-01
This paper presents a coupled elastic-thermal dynamic model and a quasi-static strategy on the analysis of the reflector dynamics in the space mission. The linearized model, its natural frequencies and mode shapes are then derived upon the nonlinear static equilibrium of the structure. The numerical example is provided to fully adapt the strategy and investigate the dynamic behaviors of the structure. Finally the proposed method is applied on the sample of the deployable mesh reflector and the simulation results are presented. The research work delivered in the paper will be used to design the feedback surface in future.
Coupled Elastic-Thermal Dynamics of Deployable Mesh Reflectors
NASA Technical Reports Server (NTRS)
Shi, H.; Yang, B.; Thomson, M.; Fang, H.
2011-01-01
This paper presents a coupled elastic-thermal dynamic model and a quasi-static strategy on the analysis of the reflector dynamics in the space mission. The linearized model, its natural frequencies and mode shapes are then derived upon the nonlinear static equilibrium of the structure. The numerical example is provided to fully adapt the strategy and investigate the dynamic behaviors of the structure. Finally the proposed method is applied on the sample of the deployable mesh reflector and the simulation results are presented. The research work delivered in the paper will be used to design the feedback surface in future.
Flexible dynamics of two quorum-sensing coupled repressilators.
Hellen, Edward H; Volkov, Evgeny
2017-02-01
Genetic oscillators play important roles in cell life regulation. The regulatory efficiency usually depends strongly on the emergence of stable collective dynamic modes, which requires designing the interactions between genetic networks. We investigate the dynamics of two identical synthetic genetic repressilators coupled by an additional plasmid which implements quorum sensing (QS) in each network thereby supporting global coupling. In a basic genetic ring oscillator network in which three genes inhibit each other in unidirectional manner, QS stimulates the transcriptional activity of chosen genes providing for competition between inhibitory and stimulatory activities localized in those genes. The "promoter strength", the Hill cooperativity coefficient of transcription repression, and the coupling strength, i.e., parameters controlling the basic rates of genetic reactions, were chosen for extensive bifurcation analysis. The results are presented as a map of dynamic regimes. We found that the remarkable multistability of the antiphase limit cycle and stable homogeneous and inhomogeneous steady states exists over broad ranges of control parameters. We studied the antiphase limit cycle stability and the evolution of irregular oscillatory regimes in the parameter areas where the antiphase cycle loses stability. In these regions we observed developing complex oscillations, collective chaos, and multistability between regular limit cycles and complex oscillations over uncommonly large intervals of coupling strength. QS coupling stimulates the appearance of intrachaotic periodic windows with spatially symmetric and asymmetric partial limit cycles which, in turn, change the type of chaos from a simple antiphase character into chaos composed of pieces of the trajectories having alternating polarity. The very rich dynamics discovered in the system of two identical simple ring oscillators may serve as a possible background for biological phenotypic diversification, as well
Flexible dynamics of two quorum-sensing coupled repressilators
NASA Astrophysics Data System (ADS)
Hellen, Edward H.; Volkov, Evgeny
2017-02-01
Genetic oscillators play important roles in cell life regulation. The regulatory efficiency usually depends strongly on the emergence of stable collective dynamic modes, which requires designing the interactions between genetic networks. We investigate the dynamics of two identical synthetic genetic repressilators coupled by an additional plasmid which implements quorum sensing (QS) in each network thereby supporting global coupling. In a basic genetic ring oscillator network in which three genes inhibit each other in unidirectional manner, QS stimulates the transcriptional activity of chosen genes providing for competition between inhibitory and stimulatory activities localized in those genes. The "promoter strength", the Hill cooperativity coefficient of transcription repression, and the coupling strength, i.e., parameters controlling the basic rates of genetic reactions, were chosen for extensive bifurcation analysis. The results are presented as a map of dynamic regimes. We found that the remarkable multistability of the antiphase limit cycle and stable homogeneous and inhomogeneous steady states exists over broad ranges of control parameters. We studied the antiphase limit cycle stability and the evolution of irregular oscillatory regimes in the parameter areas where the antiphase cycle loses stability. In these regions we observed developing complex oscillations, collective chaos, and multistability between regular limit cycles and complex oscillations over uncommonly large intervals of coupling strength. QS coupling stimulates the appearance of intrachaotic periodic windows with spatially symmetric and asymmetric partial limit cycles which, in turn, change the type of chaos from a simple antiphase character into chaos composed of pieces of the trajectories having alternating polarity. The very rich dynamics discovered in the system of two identical simple ring oscillators may serve as a possible background for biological phenotypic diversification, as well
Quantum emitters dynamically coupled to a quantum field
NASA Astrophysics Data System (ADS)
Acevedo, O. L.; Quiroga, L.; Rodríguez, F. J.; Johnson, N. F.
2013-12-01
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.
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.
Dynamic signaling cascades: reversible covalent reaction-coupled molecular switches.
Ren, Yulong; You, Lei
2015-11-11
The research of systems chemistry exploring complex mixtures of interacting synthetic molecules has been burgeoning recently. Herein we demonstrate for the first time the coupling of molecular switches with a dynamic covalent reaction (DCR) and the modulation of created chemical cascades with a variety of inputs, thus closely mimicking a biological signaling system. A novel Michael type DCR of 10-methylacridinium perchlorate and monothiols exhibiting excellent regioselectivity and tunable affinity was discovered. A delicate balance between the unique reactivity of the reactant and the stability of the adduct leads to the generation of a strong acid in a thermodynamically controlled system. The dynamic cascade was next created via coupling of the DCR and a protonation-induced configurational switch (E/Z isomerization) through a proton relay. Detailed examination of the interdependence of the equilibrium enabled us to rationally optimize the cascade and also shed light on the possible intermediate of the switching process. Furthermore, relative independence of the coupled reactions was verified by the identification of stimuli that are able to facilitate one reaction but suppress the other. To further enhance systematic complexity, a second DCR of electrophilic aldehydes and thiols was employed for the reversible inhibition of the binary system, thus achieving the interplay of multiple equilibria. Finally, a fluorescence switch was turned on through coupling with the DCR, showcasing the versatility of our strategy. The results described herein should pave the way for the exploitation of multifunctional dynamic covalent cascades.
The Coupled Chemical and Physical Dynamics Model of MALDI
NASA Astrophysics Data System (ADS)
Knochenmuss, Richard
2016-06-01
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.
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.
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.
Non-equilibrium dynamics of coupled Luttinger liquids
NASA Astrophysics Data System (ADS)
Foini, Laura; Giamarchi, Thierry
2015-03-01
We consider the dynamics of two tunnel coupled chains after a quench in the tunneling strength is performed and the two systems are let evolve independently. We describe the form of the initial state comparing with previous results concerning the dynamics after the splitting of a one-dimensional gas of bosons into two phase coherent systems. We compute different correlation functions, among which those that are relevant for interference measurements, and discuss the emergence of effective temperatures also in connection with previous works. This work was supported in part by the Swiss NSF under Division II and ARO-MURI W911NF-14-1-0003
Dynamic energy release rate in couple-stress elasticity
NASA Astrophysics Data System (ADS)
Morini, L.; Piccolroaz, A.; Mishuris, G.
2013-07-01
This paper is concerned with energy release rate for dynamic steady state crack problems in elastic materials with microstructures. A Mode III semi-infinite crack subject to loading applied on the crack surfaces is considered. The micropolar behaviour of the material is described by the theory of couple-stress elasticity developed by Koiter. A general expression for the dynamic J-integral including both traslational and micro-rotational inertial contributions is derived, and the conservation of this integral on a path surrounding the crack tip is demonstrated.
Collective Rabi dynamics of electromagnetically coupled quantum-dot ensembles
NASA Astrophysics Data System (ADS)
Glosser, Connor; Shanker, B.; Piermarocchi, Carlo
2017-09-01
Rabi oscillations typify the inherent nonlinearity of optical excitations in quantum dots. Using an integral kernel formulation to solve the three-dimensional Maxwell-Bloch equations in ensembles of up to 104 quantum dots, we observe features in Rabi oscillations due to the interplay of nonlinearity, nonequilibrium excitation, and electromagnetic coupling between the dots. This approach allows us to observe the dynamics of each dot in the ensemble without resorting to spatial averages. Our simulations predict synchronized multiplets of dots that exchange energy, dots that dynamically couple to screen the effect of incident external radiation, localization of the polarization due to randomness and interactions, as well as wavelength-scale regions of enhanced and suppressed polarization.
Dynamic positive feedback source-coupled logic (D-PFSCL)
NASA Astrophysics Data System (ADS)
Gupta, Kirti; Pandey, Neeta; Gupta, Maneesha
2016-10-01
This paper presents dynamic positive feedback source-coupled logic (D-PFSCL) style which is derived from positive feedback source-coupled logic (PFSCL). The proposed logic style uses dynamic current source in contrast to constant current source of PFSCL to attain lower power consumption. Two techniques for D-PFSCL style-based multistage applications are suggested. Several D-PFSCL gates are simulated and compared with the respective PFSCL counterparts through SPICE simulations by using Taiwan semiconductor manufacturing company 0.18 µm CMOS technology parameters. A maximum power reduction of 84% is achieved for D-PFSCL gates. The effect of process variation on the power consumption of the D-PFSCL gates shows a maximum variation factor of 1.5 between the best and the worst cases.
Isochronous dynamics in pulse coupled oscillator networks with delay
NASA Astrophysics Data System (ADS)
Li, Pan; Lin, Wei; Efstathiou, Konstantinos
2017-05-01
We consider a network of identical pulse-coupled oscillators with delay and all-to-all coupling. We demonstrate that the discontinuous nature of the dynamics induces the appearance of isochronous regions—subsets of the phase space filled with periodic orbits having the same period. For each fixed value of the network parameters, such an isochronous region corresponds to a subset of initial states on an appropriate surface of section with non-zero dimensions such that all periodic orbits in this set have qualitatively similar dynamical behaviour. We analytically and numerically study in detail such an isochronous region, give proof of its existence, and describe its properties. We further describe other isochronous regions that appear in the system.
Coupled Ultrafast Lattice and Polarization Dynamics in Ferroelectric Nanolayers
Korff Schmising, C. v.; Bargheer, M.; Kiel, M.; Zhavoronkov, N.; Woerner, M.; Elsaesser, T.; Vrejoiu, I.; Hesse, D.; Alexe, M.
2007-06-22
We report the first analysis of the polarization and lattice dynamics in a metal/ferroelectric/metal nanolayer system by femtosecond x-ray diffraction. Two Bragg reflections provide information on the coupled dynamics of the two relevant phonon modes for ferroelectricity in perovskites, the tetragonal distortion and the soft mode. Optical excitation of the SrRuO{sub 3} metal layers generates giant stress (>1 GPa) compressing the PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} layers by up to 2%. The resulting change of tetragonality reaches a maximum after 1.3 ps. As a result, the ferroelectric polarization P is reduced by up to 100% with a slight delay that is due to the anharmonic coupling of the two modes.
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.
Quench dynamics of a disordered array of dissipative coupled cavities
Creatore, C.; Fazio, R.; Keeling, J.; Türeci, H. E.
2014-01-01
We investigate the mean-field dynamics of a system of interacting photons in an array of coupled cavities in the presence of dissipation and disorder. We follow the evolution of an initially prepared Fock state, and show how the interplay between dissipation and disorder affects the coherence properties of the cavity emission, and show that these properties can be used as signatures of the many-body phase of the whole array. PMID:25197253
Dynamics of false vacuum bubbles with nonminimal coupling
Lee, Bum-Hoon; Lee, Chul H.; Lee, Wonwoo; Nam, Siyoung; Park, Chanyong
2008-03-15
We study the dynamics of false vacuum bubbles. A nonminimally coupled scalar field gives rise to the effect of negative tension. The mass of a false vacuum bubble from an outside observer's point of view can be positive, zero, or negative. The interior false vacuum has de Sitter geometry, while the exterior true vacuum background can have geometry depending on the vacuum energy. We show that there exist expanding false vacuum bubbles without the initial singularity in the past.
Dynamical coupled channel approach to omega meson production
Mark Paris
2007-09-10
The dynamical coupled channel approach of Matsuyama, Sato, and Lee is used to study the $\\omega$--meson production induced by pions and photons scattering from the proton. The parameters of the model are fixed in a two-channel (\\omega N,\\pi N) calculation for the non-resonant and resonant contributions to the $T$ matrix by fitting the available unpolarized differential cross section data. The polarized photon beam asymmetry is predicted and compared to existing data.
Coupled jump rotational dynamics in aqueous nitrate solutions.
Banerjee, Puja; Yashonath, Subramanian; Bagchi, Biman
2016-12-21
A nitrate ion (NO3(-)) with its trigonal planar geometry and charges distributed among nitrogen and oxygen atoms can couple to the extensive hydrogen bond network of water to give rise to unique dynamical characteristics. We carry out detailed atomistic simulations and theoretical analyses to investigate these aspects and report certain interesting findings. We find that the nitrate ions in aqueous potassium nitrate solution exhibit large amplitude rotational jump motions that are coupled to the hydrogen bond rearrangement dynamics of the surrounding water molecules. The jump motion of nitrate ions bears certain similarities to the Laage-Hynes mechanism of rotational jump motions of tagged water molecules in neat liquid water. We perform a detailed atomic-level investigation of hydrogen bond rearrangement dynamics of water in aqueous KNO3 solution to unearth two distinct mechanisms of hydrogen bond exchange that are instrumental to promote these jump motions of nitrate ions. As observed in an earlier study by Xie et al., in the first mechanism, after breaking a hydrogen bond with nitrate ion, water forms a new hydrogen bond with a water molecule, whereas the second mechanism involves just a switching of hydrogen bond between the two oxygen atoms of the same nitrate ion (W. J. Xie et al., J. Chem. Phys. 143, 224504 (2015)). The magnitude as well as nature of the reorientational jump of nitrate ion for the two mechanisms is different. In the first mechanism, nitrate ion predominantly undergoes out-of-plane rotation, while in the second mechanism, in-plane reorientation of NO3(-) is favourable. These have been deduced by computing the torque on the nitrate ion during the hydrogen bond switching event. We have defined and computed the time correlation function for coupled reorientational jump of nitrate and water and obtained the associated relaxation time which is also different for the two mechanisms. These results provide insight into the relation between the
Coupled jump rotational dynamics in aqueous nitrate solutions
NASA Astrophysics Data System (ADS)
Banerjee, Puja; Yashonath, Subramanian; Bagchi, Biman
2016-12-01
A nitrate ion (NO3-) with its trigonal planar geometry and charges distributed among nitrogen and oxygen atoms can couple to the extensive hydrogen bond network of water to give rise to unique dynamical characteristics. We carry out detailed atomistic simulations and theoretical analyses to investigate these aspects and report certain interesting findings. We find that the nitrate ions in aqueous potassium nitrate solution exhibit large amplitude rotational jump motions that are coupled to the hydrogen bond rearrangement dynamics of the surrounding water molecules. The jump motion of nitrate ions bears certain similarities to the Laage-Hynes mechanism of rotational jump motions of tagged water molecules in neat liquid water. We perform a detailed atomic-level investigation of hydrogen bond rearrangement dynamics of water in aqueous KNO3 solution to unearth two distinct mechanisms of hydrogen bond exchange that are instrumental to promote these jump motions of nitrate ions. As observed in an earlier study by Xie et al., in the first mechanism, after breaking a hydrogen bond with nitrate ion, water forms a new hydrogen bond with a water molecule, whereas the second mechanism involves just a switching of hydrogen bond between the two oxygen atoms of the same nitrate ion (W. J. Xie et al., J. Chem. Phys. 143, 224504 (2015)). The magnitude as well as nature of the reorientational jump of nitrate ion for the two mechanisms is different. In the first mechanism, nitrate ion predominantly undergoes out-of-plane rotation, while in the second mechanism, in-plane reorientation of NO3- is favourable. These have been deduced by computing the torque on the nitrate ion during the hydrogen bond switching event. We have defined and computed the time correlation function for coupled reorientational jump of nitrate and water and obtained the associated relaxation time which is also different for the two mechanisms. These results provide insight into the relation between the coupled
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
2015-01-01
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
Coupled spin-light dynamics in cavity optomagnonics
NASA Astrophysics Data System (ADS)
Viola Kusminskiy, Silvia; Tang, Hong X.; Marquardt, Florian
2016-09-01
Experiments during the past 2 years have shown strong resonant photon-magnon coupling in microwave cavities, while coupling in the optical regime was demonstrated very recently for the first time. Unlike with microwaves, the coupling in optical cavities is parametric, akin to optomechanical systems. This line of research promises to evolve into a new field of optomagnonics, aimed at the coherent manipulation of elementary magnetic excitations in solid-state systems by optical means. In this work we derive the microscopic optomagnonic Hamiltonian. In the linear regime the system reduces to the well-known optomechanical case, with remarkably large coupling. Going beyond that, we study the optically induced nonlinear classical dynamics of a macrospin. In the fast-cavity regime we obtain an effective equation of motion for the spin and show that the light field induces a dissipative term reminiscent of Gilbert damping. The induced dissipation coefficient, however, can change sign on the Bloch sphere, giving rise to self-sustained oscillations. When the full dynamics of the system is considered, the system can enter a chaotic regime by successive period doubling of the oscillations.
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.
Adaptive resolution simulations coupling atomistic water to dissipative particle dynamics
NASA Astrophysics Data System (ADS)
Zavadlav, Julija; Praprotnik, Matej
2017-09-01
Multiscale methods are the most efficient way to address the interlinked spatiotemporal scales encountered in soft matter and molecular liquids. In the literature reported hybrid approaches span from quantum to atomistic, coarse-grained, and continuum length scales. In this article, we present the hybrid coupling of the molecular dynamics (MD) and dissipative particle dynamics (DPD) methods, bridging the micro- and mesoscopic descriptions. The interfacing is performed within the adaptive resolution scheme (AdResS), which is a linear momentum conserving coupling technique. Our methodology is hence suitable to simulate fluids on the micro/mesoscopic scale, where hydrodynamics plays an important role. The presented approach is showcased for water at ambient conditions. The supramolecular coupling is enabled by a recently developed clustering algorithm SWINGER that assembles, disassembles, and reassembles clusters as needed during the course of the simulation. This allows for a seamless coupling between standard atomistic MD and DPD models. The developed framework can be readily applied to various applications in the fields of materials and life sciences, e.g., simulations of phospholipids and polymer melts, or to study the red blood cells behavior in normal and disease states.
A computational fluid dynamics model of viscous coupling of hairs.
Lewin, Gregory C; Hallam, John
2010-06-01
Arrays of arthropod filiform hairs form highly sensitive mechanoreceptor systems capable of detecting minute air disturbances, and it is unclear to what extent individual hairs interact with one another within sensor arrays. We present a computational fluid dynamics model for one or more hairs, coupled to a rigid-body dynamics model, for simulating both biological (e.g., a cricket cercal hair) and artificial MEMS-based systems. The model is used to investigate hair-hair interaction between pairs of hairs and quantify the extent of so-called viscous coupling. The results show that the extent to which hairs are coupled depends on the mounting properties of the hairs and the frequency at which they are driven. In particular, it is shown that for equal length hairs, viscous coupling is suppressed when they are driven near the natural frequency of the undamped system and the damping coefficient at the base is small. Further, for certain configurations, the motion of a hair can be enhanced by the presence of nearby hairs. The usefulness of the model in designing artificial systems is discussed.
Adaptive resolution simulations coupling atomistic water to dissipative particle dynamics.
Zavadlav, Julija; Praprotnik, Matej
2017-09-21
Multiscale methods are the most efficient way to address the interlinked spatiotemporal scales encountered in soft matter and molecular liquids. In the literature reported hybrid approaches span from quantum to atomistic, coarse-grained, and continuum length scales. In this article, we present the hybrid coupling of the molecular dynamics (MD) and dissipative particle dynamics (DPD) methods, bridging the micro- and mesoscopic descriptions. The interfacing is performed within the adaptive resolution scheme (AdResS), which is a linear momentum conserving coupling technique. Our methodology is hence suitable to simulate fluids on the micro/mesoscopic scale, where hydrodynamics plays an important role. The presented approach is showcased for water at ambient conditions. The supramolecular coupling is enabled by a recently developed clustering algorithm SWINGER that assembles, disassembles, and reassembles clusters as needed during the course of the simulation. This allows for a seamless coupling between standard atomistic MD and DPD models. The developed framework can be readily applied to various applications in the fields of materials and life sciences, e.g., simulations of phospholipids and polymer melts, or to study the red blood cells behavior in normal and disease states.
Dynamical Coupled-channels Effects on Pion Photoproduction
Julia-Diaz, B; Lee, T -S. H.; Matsuyama, A; Sato, T; Smith, L C
2007-12-18
The electromagnetic pion production reactions are investigated within the dynamical coupled-channels model developed in {\\bf Physics Reports, 439, 193 (2007)}. The meson-baryon channels included in this study are $\\gamma N$, $\\pi N$, $\\eta N$, and the $\\pi\\Delta$, $\\rho N$ and $\\sigma N$ resonant components of the $\\pi\\pi N$ channel. With the hadronic parameters of the model determined in a recent study of $\\pi N$ scattering, we show that the pion photoproduction data up to the second resonance region can be described to a very large extent by only adjusting the bare $\\gamma N \\rightarrow N^*$ helicity amplitudes, while the non-resonant electromagnetic couplings are taken from previous works. It is found that the coupled-channels effects can contribute about 10 - 20 $\\%$ of the production cross sections in the $\\Delta$ (1232) resonance region, and can drastically change the magnitude and shape of the cross sections in the second resonance region. The importance of the off-shell effects in a dynamical approach is also demonstrated. The meson cloud effects as well as the coupled-channels contributions to the $\\gamma N \\rightarrow N^*$ form factors are found to be mainly in the low $Q^2$ region. For the magnetic M1 $\\gamma N \\rightarrow \\Delta$ (1232) form factor, the results are close to that of the Sato-Lee Model. Necessary improvements to the model and future developments are discussed.
Nonlinear coupled dynamics analysis of a truss spar platform
NASA Astrophysics Data System (ADS)
Li, Cheng-xi; Zhang, Jun
2016-12-01
Accurate prediction of the offshore structure motion response and associate mooring line tension is important in both technical applications and scientific research. In our study, a truss spar platform, operated in Gulf of Mexico, is numerically simulated and analyzed by an in-house numerical code `COUPLE'. Both the platform motion responses and associated mooring line tension are calculated and investigated through a time domain nonlinear coupled dynamic analysis. Satisfactory agreement between the simulation and corresponding field measurements is in general reached, indicating that the numerical code can be used to conduct the time-domain analysis of a truss spar interacting with its mooring and riser system. Based on the comparison between linear and nonlinear results, the relative importance of nonlinearity in predicting the platform motion response and mooring line tensions is assessed and presented. Through the coupled and quasi-static analysis, the importance of the dynamic coupling effect between the platform hull and the mooring/riser system in predicting the mooring line tension and platform motions is quantified. These results may provide essential information pertaining to facilitate the numerical simulation and design of the large scale offshore structures.
Synchronization in complex delayed dynamical networks with nonsymmetric coupling
NASA Astrophysics Data System (ADS)
Wu, Jianshe; Jiao, Licheng
2007-12-01
A new general complex delayed dynamical network model with nonsymmetric coupling is introduced, and then we investigate its synchronization phenomena. Several synchronization criteria for delay-independent and delay-dependent synchronization are provided which generalize some previous results. The matrix Jordan canonical formalization method is used instead of the matrix diagonalization method, so in our synchronization criteria, the coupling configuration matrix of the network does not required to be diagonalizable and may have complex eigenvalues. Especially, we show clearly that the synchronizability of a delayed dynamical network is not always characterized by the second-largest eigenvalue even though all the eigenvalues of the coupling configuration matrix are real. Furthermore, the effects of time-delay on synchronizability of networks with unidirectional coupling are studied under some typical network structures. The results are illustrated by delayed networks in which each node is a two-dimensional limit cycle oscillator system consisting of a two-cell cellular neural network, numerical simulations show that these networks can realize synchronization with smaller time-delay, and will lose synchronization when the time-delay increase larger than a threshold.
Ryanodine Receptor Allosteric Coupling and the Dynamics of Calcium Sparks
Groff, Jeffrey R.; Smith, Gregory D.
2008-01-01
Puffs and sparks are localized intracellular Ca2+ elevations that arise from the cooperative activity of Ca2+-regulated inositol 1,4,5-trisphosphate receptors and ryanodine receptors clustered at Ca2+ release sites on the surface of the endoplasmic reticulum or the sarcoplasmic reticulum. While the synchronous gating of Ca2+-regulated Ca2+ channels can be mediated entirely though the buffered diffusion of intracellular Ca2+, interprotein allosteric interactions also contribute to the dynamics of ryanodine receptor (RyR) gating and Ca2+ sparks. In this article, Markov chain models of Ca2+ release sites are used to investigate how the statistics of Ca2+ spark generation and termination are related to the coupling of RyRs via local [Ca2+] changes and allosteric interactions. Allosteric interactions are included in a manner that promotes the synchronous gating of channels by stabilizing neighboring closed-closed and/or open-open channel pairs. When the strength of Ca2+-mediated channel coupling is systematically varied (e.g., by changing the Ca2+ buffer concentration), simulations that include synchronizing allosteric interactions often exhibit more robust Ca2+ sparks; however, for some Ca2+ coupling strengths the sparks are less robust. We find no evidence that the distribution of spark durations can be used to distinguish between allosteric interactions that stabilize closed channel pairs, open channel pairs, or both in a balanced fashion. On the other hand, the changes in spark duration, interspark interval, and frequency observed when allosteric interactions that stabilize closed channel pairs are gradually removed from simulations are qualitatively different than the changes observed when open or both closed and open channel pairs are stabilized. Thus, our simulations clarify how changes in spark statistics due to pharmacological washout of the accessory proteins mediating allosteric coupling may indicate the type of synchronizing allosteric interactions exhibited
Human seizures couple across spatial scales through travelling wave dynamics.
Martinet, L-E; Fiddyment, G; Madsen, J R; Eskandar, E N; Truccolo, W; Eden, U T; Cash, S S; Kramer, M A
2017-04-04
Epilepsy-the propensity toward recurrent, unprovoked seizures-is a devastating disease affecting 65 million people worldwide. Understanding and treating this disease remains a challenge, as seizures manifest through mechanisms and features that span spatial and temporal scales. Here we address this challenge through the analysis and modelling of human brain voltage activity recorded simultaneously across microscopic and macroscopic spatial scales. We show that during seizure large-scale neural populations spanning centimetres of cortex coordinate with small neural groups spanning cortical columns, and provide evidence that rapidly propagating waves of activity underlie this increased inter-scale coupling. We develop a corresponding computational model to propose specific mechanisms-namely, the effects of an increased extracellular potassium concentration diffusing in space-that support the observed spatiotemporal dynamics. Understanding the multi-scale, spatiotemporal dynamics of human seizures-and connecting these dynamics to specific biological mechanisms-promises new insights to treat this devastating disease.
Human seizures couple across spatial scales through travelling wave dynamics
Martinet, L-E; Fiddyment, G.; Madsen, J. R.; Eskandar, E. N.; Truccolo, W.; Eden, U. T.; Cash, S. S.; Kramer, M. A.
2017-01-01
Epilepsy—the propensity toward recurrent, unprovoked seizures—is a devastating disease affecting 65 million people worldwide. Understanding and treating this disease remains a challenge, as seizures manifest through mechanisms and features that span spatial and temporal scales. Here we address this challenge through the analysis and modelling of human brain voltage activity recorded simultaneously across microscopic and macroscopic spatial scales. We show that during seizure large-scale neural populations spanning centimetres of cortex coordinate with small neural groups spanning cortical columns, and provide evidence that rapidly propagating waves of activity underlie this increased inter-scale coupling. We develop a corresponding computational model to propose specific mechanisms—namely, the effects of an increased extracellular potassium concentration diffusing in space—that support the observed spatiotemporal dynamics. Understanding the multi-scale, spatiotemporal dynamics of human seizures—and connecting these dynamics to specific biological mechanisms—promises new insights to treat this devastating disease. PMID:28374740
Human seizures couple across spatial scales through travelling wave dynamics
NASA Astrophysics Data System (ADS)
Martinet, L.-E.; Fiddyment, G.; Madsen, J. R.; Eskandar, E. N.; Truccolo, W.; Eden, U. T.; Cash, S. S.; Kramer, M. A.
2017-04-01
Epilepsy--the propensity toward recurrent, unprovoked seizures--is a devastating disease affecting 65 million people worldwide. Understanding and treating this disease remains a challenge, as seizures manifest through mechanisms and features that span spatial and temporal scales. Here we address this challenge through the analysis and modelling of human brain voltage activity recorded simultaneously across microscopic and macroscopic spatial scales. We show that during seizure large-scale neural populations spanning centimetres of cortex coordinate with small neural groups spanning cortical columns, and provide evidence that rapidly propagating waves of activity underlie this increased inter-scale coupling. We develop a corresponding computational model to propose specific mechanisms--namely, the effects of an increased extracellular potassium concentration diffusing in space--that support the observed spatiotemporal dynamics. Understanding the multi-scale, spatiotemporal dynamics of human seizures--and connecting these dynamics to specific biological mechanisms--promises new insights to treat this devastating disease.
Dynamic heterogeneity above and below the mode-coupling temperature
NASA Astrophysics Data System (ADS)
Flenner, Elijah; Szamel, Grzegorz
2012-02-01
We study the temperature dependence of the spatial extend of the dynamic heterogeneity in a soft sphere system near the so-called mode-coupling temperature Tc. We utilize a recently introduced procedureootnotetextE. Flenner and G. Szamel, Phys. Rev. Lett. 105, 217801 (2010) to calculate the ensemble independent dynamic susceptibility χ4(τα) and the dynamic correlation length ξ(τα) at the alpha relaxation time τα. Above Tc, we find that χ4(τα) ˜ξ(τα)^3 and ξ(τα) ˜(τα), which is the same behavior found in a binary hard-sphere system. We track these relationships below Tc to examine the recently reported non-monotonic temperature dependence of dynamic correlations found in the same systemootnotetextW. Kob, S. Roland-Vargas and L. Berthier, Nat. Phys. DOI:10.1038/NPHYS2133. Finally, we examine the relationship between dynamic susceptibilities that can be determined from experiments and the dynamic correlation length ξ(τα).
Dynamics of exciton transfer in coupled polymer chains
NASA Astrophysics Data System (ADS)
Zhang, Y. L.; Liu, X. J.; Sun, Z.; An, Z.
2013-05-01
The dynamics of singlet and triplet exciton transfer in coupled polymer chains are investigated within the Su-Schrieffer-Heeger+Pariser-Parr-Pople model including both electron-phonon (e-p) coupling and electron-electron (e-e) interactions, using a multi-configurational time-dependent Hartree-Fock dynamic method. In order to explain the processes involved, the effects of on-site and long-range e-e interactions on the locality of the singlet and triplet excitons are first investigated on an isolated chain. It is found that the locality of the singlet exciton decreases, while the locality of the triplet exciton increases with an increase in the on-site e-e interactions. On the other hand, an increase in the long-range e-e interaction results in a more localized singlet exciton and triplet exciton. In coupled polymer chains, we then quantitatively show the yields of singlet and triplet exciton transfer products under the same interchain coupling. It is found that the yield of singlet interchain excitons is much higher than that of triplet interchain excitons, that is to say, singlet exciton transfer is significantly easier than that for triplet excitons. This results from the fact that the singlet exciton is more delocalized than the triplet exciton. In addition, hopping of electrons with opposite spins between the coupled chains can facilitate the transfer of singlet excitons. The results are of great significance for understanding the photoelectric conversion process and developing high-power organic optoelectronic applications.
Inflationary dynamics of kinetically-coupled gauge fields
Ferreira, Ricardo Z.; Ganc, Jonathan E-mail: ganc@cp3.dias.sdu.dk
2015-04-01
We investigate the inflationary dynamics of two kinetically-coupled massless U(1) gauge fields with time-varying kinetic-term coefficients. Ensuring that the system does not have strongly coupled regimes shrinks the parameter space. Also, we further restrict ourselves to systems that can be quantized using the standard creation, annihilation operator algebra. This second constraint limits us to scenarios where the system can be diagonalized into the sum of two decoupled, massless, vector fields with a varying kinetic-term coefficient. Such a system might be interesting for magnetogenesis because of how the strong coupling problem generalizes. We explore this idea by assuming that one of the gauge fields is the Standard Model U(1) field and that the other dark gauge field has no particles charged under its gauge group. We consider whether it would be possible to transfer a magnetic field from the dark sector, generated perhaps before the coupling was turned on, to the visible sector. We also investigate whether the simple existence of the mixing provides more opportunities to generate magnetic fields. We find that neither possibility works efficiently, consistent with the well-known difficulties in inflationary magnetogenesis.
Dynamics of finite-size networks of coupled oscillators
NASA Astrophysics Data System (ADS)
Buice, Michael; Chow, Carson
2010-03-01
Mean field models of coupled oscillators do not adequately capture the dynamics of large but finite size networks. For example, the incoherent state of the Kuramoto model of coupled oscillators exhibits marginal modes in mean field theory. We demonstrate that corrections due to finite size effects render these modes stable in the subcritical case, i.e. when the population is not synchronous. This demonstration is facilitated by the construction of a non-equilibrium statistical field theoretic formulation of a generic model of coupled oscillators. This theory is consistent with previous results. In the all-to-all case, the fluctuations in this theory are due completely to finite size corrections, which can be calculated in an expansion in 1/N, where N is the number of oscillators. The N -> infinity limit of this theory is what is traditionally called mean field theory for the Kuramoto model. We also demonstrate this approach with a system of pulse coupled theta neurons and describe the stability of the population activity.
Modeling the network dynamics of pulse-coupled neurons
NASA Astrophysics Data System (ADS)
Chandra, Sarthak; Hathcock, David; Crain, Kimberly; Antonsen, Thomas M.; Girvan, Michelle; Ott, Edward
2017-03-01
We derive a mean-field approximation for the macroscopic dynamics of large networks of pulse-coupled theta neurons in order to study the effects of different network degree distributions and degree correlations (assortativity). Using the ansatz of Ott and Antonsen [Chaos 18, 037113 (2008)], we obtain a reduced system of ordinary differential equations describing the mean-field dynamics, with significantly lower dimensionality compared with the complete set of dynamical equations for the system. We find that, for sufficiently large networks and degrees, the dynamical behavior of the reduced system agrees well with that of the full network. This dimensional reduction allows for an efficient characterization of system phase transitions and attractors. For networks with tightly peaked degree distributions, the macroscopic behavior closely resembles that of fully connected networks previously studied by others. In contrast, networks with highly skewed degree distributions exhibit different macroscopic dynamics due to the emergence of degree dependent behavior of different oscillators. For nonassortative networks (i.e., networks without degree correlations), we observe the presence of a synchronously firing phase that can be suppressed by the presence of either assortativity or disassortativity in the network. We show that the results derived here can be used to analyze the effects of network topology on macroscopic behavior in neuronal networks in a computationally efficient fashion.
Coupled nucleotide covariations reveal dynamic RNA interaction patterns.
Gultyaev, A P; Franch, T; Gerdes, K
2000-01-01
Evolutionarily conserved structures in related RNA molecules contain coordinated variations (covariations) of paired nucleotides. Analysis of covariations is a very powerful approach to deduce phylogenetically conserved (i.e., functional) conformations, including tertiary interactions. Here we discuss conserved RNA folding pathways that are revealed by covariation patterns. In such pathways, structural requirements for alternative pairings cause some nucleotides to covary with two different partners. Such "coupled" covariations between three or more nucleotides were found in various types of RNAs. The analysis of coupled covariations can unravel important features of RNA folding dynamics and improve phylogeny reconstruction in some cases. Importantly, it is necessary to distinguish between multiple covariations determined by mutually exclusive structures and those determined by tertiary contacts. PMID:11105748
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.
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
An investigation of helicopter dynamic coupling using an analytical model
NASA Technical Reports Server (NTRS)
Keller, Jeffrey D.
1995-01-01
Many attempts have been made in recent years to predict the off-axis response of a helicopter to control inputs, and most have had little success. Since physical insight is limited by the complexity of numerical simulation models, this paper examines the off-axis response problem using an analytical model, with the goal of understanding the mechanics of the coupling. A new induced velocity model is extended to include the effects of wake distortion from pitch rate. It is shown that the inclusion of these results in a significant change in the lateral flap response to a steady pitch rate. The proposed inflow model is coupled with the full rotor/body dynamics, and comparisons are made between the model and flight test data for a UH-60 in hover. Results show that inclusion of induced velocity variations due to shaft rate improves correlation in the pitch response to lateral cycle inputs.
Chaotic transients and fractal structures governing coupled swing dynamics
Ueda, Y.; Enomoto, T. ); Stewart, H.B. )
1990-01-01
Numerical simulations are used to study coupled swing equations modeling the dynamics of two electric generators connected to an infinite bus by a simple transmission network. In particular, the effect of varying parameters corresponding to the input power supplied to each generator is studied. In addition to stable steady operating conditions, which should correspond to synchronized, normal operation, the coupled swing model has other stable states of large amplitude oscillations which, if realized, would represent non-synchronized motions: the phase space boundary separating their basins of attraction is fractal, corresponding to chaotic transient motions. These fractal structures in phase space and the associated fractal structures in parameter space will be of primary concern to engineers in predicting system behavior.
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. Copyright © 2014 Elsevier Ltd. All rights reserved.
Dynamic optimization of metabolic networks coupled with gene expression.
Waldherr, Steffen; Oyarzún, Diego A; Bockmayr, Alexander
2015-01-21
The regulation of metabolic activity by tuning enzyme expression levels is crucial to sustain cellular growth in changing environments. Metabolic networks are often studied at steady state using constraint-based models and optimization techniques. However, metabolic adaptations driven by changes in gene expression cannot be analyzed by steady state models, as these do not account for temporal changes in biomass composition. Here we present a dynamic optimization framework that integrates the metabolic network with the dynamics of biomass production and composition. An approximation by a timescale separation leads to a coupled model of quasi-steady state constraints on the metabolic reactions, and differential equations for the substrate concentrations and biomass composition. We propose a dynamic optimization approach to determine reaction fluxes for this model, explicitly taking into account enzyme production costs and enzymatic capacity. In contrast to the established dynamic flux balance analysis, our approach allows predicting dynamic changes in both the metabolic fluxes and the biomass composition during metabolic adaptations. Discretization of the optimization problems leads to a linear program that can be efficiently solved. We applied our algorithm in two case studies: a minimal nutrient uptake network, and an abstraction of core metabolic processes in bacteria. In the minimal model, we show that the optimized uptake rates reproduce the empirical Monod growth for bacterial cultures. For the network of core metabolic processes, the dynamic optimization algorithm predicted commonly observed metabolic adaptations, such as a diauxic switch with a preference ranking for different nutrients, re-utilization of waste products after depletion of the original substrate, and metabolic adaptation to an impending nutrient depletion. These examples illustrate how dynamic adaptations of enzyme expression can be predicted solely from an optimization principle.
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
Predictability and Coupled Dynamics of MJO During DYNAMO
2013-09-30
00-2013 to 00-00-2013 4 . TITLE AND SUBTITLE Predictability and Coupled Dynamics of MJO During DYNAMO 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...during DYNAMO, large number of vertical layers are allocated in the upper ocean to allow 4 - 5 layers in the upper 1-meter and 33 layers in the upper...whereas CF24 lacks the diurnal variation. While the mean SST appears to be slightly warmer in CF24 than 4 CF1, due to the large range of diurnal
Predictability and Coupled Dynamics of MJO During DYNAMO
2013-09-30
2013 2. REPORT TYPE 3. DATES COVERED 00-00-2013 to 00-00-2013 4 . TITLE AND SUBTITLE Predictability and Coupled Dynamics of MJO During DYNAMO 5a...allocated in the upper ocean to allow 4 - 5 layers in the upper 1-meter and 33 layers in the upper 55 meters. WRF and ROMS share the identical grids and...SST appears to be slightly warmer in CF24 than 4 CF1, due to the large range of diurnal variation in temperature, higher SST is achieved on
Dynamic Homogenization of Acoustic Metamaterials with Coupled Field Response
NASA Astrophysics Data System (ADS)
Sieck, C. F.; Alù, A.; Haberman, M. R.
Acoustic metamaterials (AMM) are heterogeneous materials with dynamic subwavelength structures that can generate useful effective responses of interest to ultrasonic imaging applications such as negative refraction and zero index. Traditional effective medium models fail to capture details of frequency dependent AMM response and can give non-causal properties. This work derives non-local expressions for effective properties for an infinite periodic lattice of heterogeneities in an isotropic fluid using conservation of mass and momentum and the equation of state. The resulting model correctly predicts a causal effective material response by considering coupling between the ensemble-averaged volume strain and momentum fields.
Coupling lattice Boltzmann and molecular dynamics models for dense fluids
NASA Astrophysics Data System (ADS)
Dupuis, A.; Kotsalis, E. M.; Koumoutsakos, P.
2007-04-01
We propose a hybrid model, coupling lattice Boltzmann (LB) and molecular dynamics (MD) models, for the simulation of dense fluids. Time and length scales are decoupled by using an iterative Schwarz domain decomposition algorithm. The MD and LB formulations communicate via the exchange of velocities and velocity gradients at the interface. We validate the present LB-MD model in simulations of two- and three-dimensional flows of liquid argon past and through a carbon nanotube. Comparisons with existing hybrid algorithms and with reference MD solutions demonstrate the validity of the present approach.
Coupling lattice Boltzmann and molecular dynamics models for dense fluids.
Dupuis, A; Kotsalis, E M; Koumoutsakos, P
2007-04-01
We propose a hybrid model, coupling lattice Boltzmann (LB) and molecular dynamics (MD) models, for the simulation of dense fluids. Time and length scales are decoupled by using an iterative Schwarz domain decomposition algorithm. The MD and LB formulations communicate via the exchange of velocities and velocity gradients at the interface. We validate the present LB-MD model in simulations of two- and three-dimensional flows of liquid argon past and through a carbon nanotube. Comparisons with existing hybrid algorithms and with reference MD solutions demonstrate the validity of the present approach.
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.
Optically Resolving the Dynamic Walking of a Plasmonic Walker Couple.
Urban, Maximilian J; Zhou, Chao; Duan, Xiaoyang; Liu, Na
2015-12-09
Deterministic placement and dynamic manipulation of individual plasmonic nanoparticles with nanoscale precision feature an important step toward active nanoplasmonic devices with prescribed levels of performance and functionalities at optical frequencies. In this Letter, we demonstrate a plasmonic walker couple system, in which two gold nanorod walkers can independently or simultaneously perform stepwise walking powered by DNA hybridization along the same DNA origami track. We utilize optical spectroscopy to resolve such dynamic walking with nanoscale steps well below the optical diffraction limit. We also show that the number of walkers and the optical response of the system can be correlated. Our studies exemplify the power of plasmonics, when integrated with DNA nanotechnology for realization of advanced artificial nanomachinery with tailored optical functionalities.
Vortex dynamics and frequency splitting in vertically coupled nanomagnets
Stebliy, M. E.; Jain, S.; Kolesnikov, A. G.; ...
2017-04-25
Here, we explored the dynamic response of a vortex core in a circular nanomagnet by manipulating its dipole-dipole interaction with another vortex core confined locally on top of the nanomagnet. A clear frequency splitting is observed corresponding to the gyrofrequencies of the two vortex cores. The peak positions of the two resonance frequencies can be engineered by controlling the magnitude and direction of the external magnetic field. Both experimental and micromagnetic simulations show that the frequency spectra for the combined system is significantly dependent on the chirality of the circular nanomagnet and is asymmetric with respect to the external biasmore » field. We attribute this result to the strong dynamic dipole-dipole interaction between the two vortex cores, which varies with the distance between them. The possibility of having multiple states in a single nanomagnet with vertical coupling could be of interest for magnetoresistive memories.« less
Quantum dynamics of impurities coupled to a Fermi sea
NASA Astrophysics Data System (ADS)
Parish, Meera M.; Levinsen, Jesper
2016-11-01
We consider the dynamics of an impurity atom immersed in an ideal Fermi gas at zero temperature. We focus on the coherent quantum evolution of the impurity following a quench to strong impurity-fermion interactions, where the interactions are assumed to be short range like in cold-atom experiments. To approximately model the many-body time evolution, we use a truncated basis method, where at most two particle-hole excitations of the Fermi sea are included. When the system is initially noninteracting, we show that our method exactly captures the short-time dynamics following the quench, and we find that the overlap between initial and final states displays a universal nonanalytic dependence on time in this limit. We further demonstrate how our method can be used to compute the impurity spectral function, as well as describe many-body phenomena involving coupled impurity spin states, such as Rabi oscillations in a medium or highly engineered quantum quenches.
Vortex dynamics and frequency splitting in vertically coupled nanomagnets.
Stebliy, M E; Jain, S; Kolesnikov, A G; Ognev, A V; Samardak, A S; Davydenko, A V; Sukovatitcina, E V; Chebotkevich, L A; Ding, J; Pearson, J; Khovaylo, V; Novosad, V
2017-04-25
We explored the dynamic response of a vortex core in a circular nanomagnet by manipulating its dipole-dipole interaction with another vortex core confined locally on top of the nanomagnet. A clear frequency splitting is observed corresponding to the gyrofrequencies of the two vortex cores. The peak positions of the two resonance frequencies can be engineered by controlling the magnitude and direction of the external magnetic field. Both experimental and micromagnetic simulations show that the frequency spectra for the combined system is significantly dependent on the chirality of the circular nanomagnet and is asymmetric with respect to the external bias field. We attribute this result to the strong dynamic dipole-dipole interaction between the two vortex cores, which varies with the distance between them. The possibility of having multiple states in a single nanomagnet with vertical coupling could be of interest for magnetoresistive memories.
Coupling in goshawk and grouse population dynamics in Finland.
Tornberg, Risto; Lindén, Andreas; Byholm, Patrik; Ranta, Esa; Valkama, Jari; Helle, Pekka; Lindén, Harto
2013-04-01
Different prey species can vary in their significance to a particular predator. In the simplest case, the total available density or biomass of a guild of several prey species might be most relevant to the predator, but behavioural and ecological traits of different prey species can alter the picture. We studied the population dynamics of a predator-prey setting in Finland by fitting first-order log-linear vector autoregressive models to long-term count data from active breeding sites of the northern goshawk (Accipiter gentilis; 1986-2009), and to three of its main prey species (1983-2010): hazel grouse (Bonasa bonasia), black grouse (Tetrao tetrix) and capercaillie (T. urogallus), which belong to the same forest grouse guild and show synchronous fluctuations. Our focus was on modelling the relative significance of prey species and estimating the tightness of predator-prey coupling in order to explain the observed population dynamics, simultaneously accounting for effects of density dependence, winter severity and spatial correlation. We established nine competing candidate models, where different combinations of grouse species affect goshawk dynamics with lags of 1-3 years. Effects of goshawk on grouse were investigated using one model for each grouse species. The most parsimonious model for goshawk indicated separate density effects of hazel grouse and black grouse, and different effects with lags of 1 and 3 years. Capercaillie showed no effects on goshawk populations, while the effect of goshawk on grouse was clearly negative only in capercaillie. Winter severity had significant adverse effects on goshawk and hazel grouse populations. In combination, large-scale goshawk-grouse population dynamics are coupled, but there are no clear mutual effects for any of the individual guild members. In a broader context, our study suggests that pooling data on closely related, synchronously fluctuating prey species can result in the loss of relevant information, rather than
Desynchronization in networks of globally coupled neurons with dendritic dynamics.
Majtanik, Milan; Dolan, Kevin; Tass, Peter A
2006-10-01
Effective desynchronization can be exploited as a tool for probing the functional significance of synchronized neural activity underlying perceptual and cognitive processes or as a mild treatment for neurological disorders like Parkinson's disease. In this article we show that pulse-based desynchronization techniques, originally developed for networks of globally coupled oscillators (Kuramoto model), can be adapted to networks of coupled neurons with dendritic dynamics. Compared to the Kuramoto model, the dendritic dynamics significantly alters the response of the neuron to the stimulation. Under medium stimulation amplitude a bistability of the response of a single neuron is observed. When stimulated at some initial phases, the neuron displays only modulations of its firing, whereas at other initial phases it stops oscillating entirely. Significant alterations in the duration of stimulation-induced transients are also observed. These transients endure after the end of the stimulation and cause maximal desynchronization to occur not during the stimulation, but with some delay after the stimulation has been turned off. To account for this delayed desynchronization effect, we have designed a new calibration procedure for finding the stimulation parameters that result in optimal desynchronization. We have also developed a new desynchronization technique by low frequency entrainment. The stimulation techniques originally developed for the Kuramoto model, when using the new calibration procedure, can also be applied to networks with dendritic dynamics. However, the mechanism by which desynchronization is achieved is substantially different than for the network of Kuramoto oscillators. In particular, the addition of dendritic dynamics significantly changes the timing of the stimulation required to obtain desynchronization. We propose desynchronization stimulation for experimental analysis of synchronized neural processes and for the therapy of movement disorders.
Dynamic Brazilian Tests of Granite Under Coupled Static and Dynamic Loads
NASA Astrophysics Data System (ADS)
Zhou, Zilong; Li, Xibing; Zou, Yang; Jiang, Yihui; Li, Guonan
2014-03-01
Rocks in underground projects at great depth, which are under high static stresses, may be subjected to dynamic disturbance at the same time. In our previous work (Li et al. Int J Rock Mech Min Sci 45(5):739-748, 2008), the dynamic compressive behaviour of pre-stressed rocks was investigated using coupled-load equipment. The current work is devoted to the investigation of the dynamic tensile behaviour of granite rocks under coupled loads using the Brazilian disc (BD) method with the aid of a high-speed camera. Through wave analyses, stress measurements and crack photography, the fundamental problems of BD tests, such as stress equilibrium and crack initiation, were investigated by the consideration of different loading stresses with abruptly or slowly rising stress waves. The specially shaped striker method was used for the coupled-load test; this generates a slowly rising stress wave, which allows gradual stress accumulation in the specimen, whilst maintaining the load at both ends of the specimen in an equilibrium state. The test results showed that the tensile strength of the granite under coupled loads decreases with increases in the static pre-stresses, which might lead to modifications of the blasting design or support design in deep underground projects. Furthermore, the failure patterns of specimens under coupled loads have been investigated.
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.
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.
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.
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
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.
Local dynamics of gap-junction-coupled interneuron networks
NASA Astrophysics Data System (ADS)
Lau, Troy; Gage, Gregory J.; Berke, Joshua D.; Zochowski, Michal
2010-03-01
Interneurons coupled by both electrical gap-junctions (GJs) and chemical GABAergic synapses are major components of forebrain networks. However, their contributions to the generation of specific activity patterns, and their overall contributions to network function, remain poorly understood. Here we demonstrate, using computational methods, that the topological properties of interneuron networks can elicit a wide range of activity dynamics, and either prevent or permit local pattern formation. We systematically varied the topology of GJ and inhibitory chemical synapses within simulated networks, by changing connection types from local to random, and changing the total number of connections. As previously observed we found that randomly coupled GJs lead to globally synchronous activity. In contrast, we found that local GJ connectivity may govern the formation of highly spatially heterogeneous activity states. These states are inherently temporally unstable when the input is uniformly random, but can rapidly stabilize when the network detects correlations or asymmetries in the inputs. We show a correspondence between this feature of network activity and experimental observations of transient stabilization of striatal fast-spiking interneurons (FSIs), in electrophysiological recordings from rats performing a simple decision-making task. We suggest that local GJ coupling enables an active search-and-select function of striatal FSIs, which contributes to the overall role of cortical-basal ganglia circuits in decision-making.
Vibrational dynamics of DNA. I. Vibrational basis modes and couplings
NASA Astrophysics Data System (ADS)
Lee, Chewook; Park, Kwang-Hee; Cho, Minhaeng
2006-09-01
Carrying out density functional theory calculations of four DNA bases, base derivatives, Watson-Crick (WC) base pairs, and multiple-layer base pair stacks, we studied vibrational dynamics of delocalized modes with frequency ranging from 1400to1800cm-1. These modes have been found to be highly sensitive to structure fluctuation and base pair conformation of DNA. By identifying eight fundamental basis modes, it is shown that the normal modes of base pairs and multilayer base pair stacks can be described by linear combinations of these vibrational basis modes. By using the Hessian matrix reconstruction method, vibrational coupling constants between the basis modes are determined for WC base pairs and multilayer systems and are found to be most strongly affected by the hydrogen bonding interaction between bases. It is also found that the propeller twist and buckle motions do not strongly affect vibrational couplings and basis mode frequencies. Numerically simulated IR spectra of guanine-cytosine and adenine-thymine bases pairs as well as of multilayer base pair stacks are presented and described in terms of coupled basis modes. It turns out that, due to the small interlayer base-base vibrational interactions, the IR absorption spectrum of multilayer base pair system does not strongly depend on the number of base pairs.
Wave Dynamical Coupling of Atmospheres During Sudden Stratospheric Warming Events
NASA Astrophysics Data System (ADS)
Laskar, F. I.; Duggirala, P. R.
2015-12-01
The electrodynamic and neutral dynamic behavior of the low-latitude upper atmosphere during sudden stratospheric warming (SSW) events has been investigated. The equatorial electrojet (EEJ) strength and the total electron content (TEC) data from low latitudes, over Indian longitudes, during the mid-winter season in the years 2005 to 2013 are used in this study. Five major and three minor SSW events occurred in the observation duration, wherein the solar activity had varied from minimum (almost no sunspots) to mini-maximum (approximately 50 sunspots of the solar cycle 24). Spectral powers of the quasi-16-day waves in the EEJ and the TEC have been found to be dominant and varying with solar activity and SSW strengths. Specifically, the spectral powers of quasi-16-day type variations during the three dramatic strong SSW events in the years 2006, 2009, and 2013 were found to be very high in comparison with those of other years. For these major events, the amplitudes of the semi-diurnal tides and quasi-16-day waves were found to be highly correlated and were maximum around the peak of SSW, suggesting a strong interaction between the two waves. However, this correlation was poor and the quasi-16-day spectral power was low for the minor events. A strong vertical coupling of atmospheres was noted in spite of the solar activity being relatively higher during 2013, which was, however, explained to be due to the occurrence of a strong SSW event. These results suggest that the wave dynamical vertical coupling of atmospheres is stronger during strong major SSW events and weaker during minor events. Also, SSW events play an important role in enabling the upward coupling of atmospheres even during high solar activity.
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
NASA Astrophysics Data System (ADS)
Blanco, Joaquín. E.; Nolan, David S.; Mapes, Brian E.
2016-10-01
This second part of a two-part study uses Weather Research and Forecasting simulations with aquachannel and aquapatch domains to investigate the time evolution of convectively coupled Kelvin waves (CCKWs). Power spectra, filtering, and compositing are combined with object-tracking methods to assess the structure and phase speed propagation of CCKWs during their strengthening, mature, and decaying phases. In this regard, we introduce an innovative approach to more closely investigate the wave (Kelvin) versus entity (super cloud cluster or "SCC") dualism. In general, the composite CCKW structures represent a dynamical response to the organized convective activity. However, pressure and thermodynamic fields in the boundary layer behave differently. Further analysis of the time evolution of pressure and low-level moist static energy finds that these fields propagate eastward as a "moist" Kelvin wave (MKW), faster than the envelope of organized convection or SCC. When the separation is sufficiently large the SCC dissipates, and a new SCC generates to the east, in the region of strongest negative pressure perturbations. We revisit the concept itself of the "coupling" between convection and dynamics, and we also propose a conceptual model for CCKWs, with a clear distinction between the SCC and the MKW components.
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
Quantum dynamics in strong fields with Fermion Coupled Coherent States
NASA Astrophysics Data System (ADS)
Kirrander, Adam; Shalashilin, Dmitrii V.
2012-06-01
We present a new version of the Coupled Coherent State method, specifically adapted for solving the time-dependent Schr"odinger equation for multi-electron dynamics in atoms and molecules. This new theory takes explicit account of the exchange symmetry of fermion particles, and 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 10^14 - 10^16 W/cm^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 1.5 10^15 W/cm^2, in order to compare to the detailed experiments by Rudenko et al. For this more challenging task, full convergence is not achieved, but however major effects such as the finger-like structures in the momentum distribution are reproduced.
Coriolis-coupled wave packet dynamics of H + HLi reaction.
Padmanaban, R; Mahapatra, S
2006-05-11
We investigated the effect of Coriolis coupling (CC) on the initial state-selected dynamics of H+HLi reaction by a time-dependent wave packet (WP) approach. Exact quantum scattering calculations were obtained by a WP propagation method based on the Chebyshev polynomial scheme and ab initio potential energy surface of the reacting system. Partial wave contributions up to the total angular momentum J=30 were found to be necessary for the scattering of HLi in its vibrational and rotational ground state up to a collision energy approximately 0.75 eV. For each J value, the projection quantum number K was varied from 0 to min (J, K(max)), with K(max)=8 until J=20 and K(max)=4 for further higher J values. This is because further higher values of K do not have much effect on the dynamics and also because one wishes to maintain the large computational overhead for each calculation within the affordable limit. The initial state-selected integral reaction cross sections and thermal rate constants were calculated by summing up the contributions from all partial waves. These were compared with our previous results on the title system, obtained within the centrifugal sudden and J-shifting approximations, to demonstrate the impact of CC on the dynamics of this system.
Stability of power systems coupled with market dynamics
NASA Astrophysics Data System (ADS)
Meng, Jianping
This Ph.D. thesis presented here spans two relatively independent topics. The first part, Chapter 2 is self-contained, and is dedicated to studies of new algorithms for power system state estimation. The second part, encompassing the remaining chapters, is dedicated to stability analysis of power system coupled with market dynamics. The first part of this thesis presents improved Newton's methods employing efficient vectorized calculations of higher order derivatives in power system state estimation problems. The improved algorithms are proposed based on an exact Newton's method using the second order terms. By efficiently computing an exact gain matrix, combined with a special optimal multiplier method, the new algorithms show more reliable convergence compared with the existing methods of normal equations, orthogonal decomposition, and Hachtel's sparse tableau. Our methods are able to handle ill-conditioned problems, yet show minimal penalty in computational cost for well-conditioned cases. These claims are illustrated through the standard IEEE 118 and 300 bus test examples. The second part of the thesis focuses on stability analysis of market/power systems. The work presented is motivated by an emerging problem. As the frequency of market based dispatch updates increases, there will inevitably be interaction between the dynamics of markets determining the generator dispatch commands, and the physical response of generators and network interconnections, necessitating the development of stability analysis for such coupled systems. We begin with numeric tests using different market models, with detailed machine/exciter/turbine/governor dynamics, in the New England 39 bus test system. A progression of modeling refinements are introduced, including such non-ideal effects as time delays. Electricity market parameter identification algorithms are also studied based on real time data from the PJM electricity market. Finally our power market model is augmented by optimal
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
NASA Astrophysics Data System (ADS)
Romera, M.; Lacoste, B.; Ebels, U.; Buda-Prejbeanu, L. D.
2016-09-01
The general concepts of spin wave theory are adapted to the spin torque driven dynamics of a self-polarized system based on two layers coupled via interlayer exchange (conservative coupling) and mutual spin torque (dissipative coupling). An analytical description of the nonlinear dynamics is proposed and validated through numerical simulations. In contrast to the single layer model, the phase equation of the coupled system has a contribution coming from the dissipative part of the LLGS equation. It is shown that this is a major contribution to the frequency mandatory to describe well the most basic features of the dynamics of this coupled system. Using the proposed model a specific feature of coupled dynamics is addressed: the redshift to blueshift transition observed in the frequency current dependence of this kind of exchange coupled systems upon increasing the applied field. It is found that the blueshift regime can only occur in a region of field where the two linear eigenmodes contribute equally to the steady state mode (i.e., high mode hybridization). Finally, a general perturbed Hamiltonian equation for the coupled system is proposed.
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.
Molecular dynamics techniques for modeling G protein-coupled receptors.
McRobb, Fiona M; Negri, Ana; Beuming, Thijs; Sherman, Woody
2016-10-01
G protein-coupled receptors (GPCRs) constitute a major class of drug targets and modulating their signaling can produce a wide range of pharmacological outcomes. With the growing number of high-resolution GPCR crystal structures, we have the unprecedented opportunity to leverage structure-based drug design techniques. Here, we discuss a number of advanced molecular dynamics (MD) techniques that have been applied to GPCRs, including long time scale simulations, enhanced sampling techniques, water network analyses, and free energy approaches to determine relative binding free energies. On the basis of the many success stories, including those highlighted here, we expect that MD techniques will be increasingly applied to aid in structure-based drug design and lead optimization for GPCRs.
Computational model for amoeboid motion: Coupling membrane and cytosol dynamics.
Moure, Adrian; Gomez, Hector
2016-10-01
A distinguishing feature of amoeboid motion is that the migrating cell undergoes large deformations, caused by the emergence and retraction of actin-rich protrusions, called pseudopods. Here, we propose a cell motility model that represents pseudopod dynamics, as well as its interaction with membrane signaling molecules. The model accounts for internal and external forces, such as protrusion, contraction, adhesion, surface tension, or those arising from cell-obstacle contacts. By coupling the membrane and cytosol interactions we are able to reproduce a realistic picture of amoeboid motion. The model results are in quantitative agreement with experiments and show how cells may take advantage of the geometry of their microenvironment to migrate more efficiently.
Computational model for amoeboid motion: Coupling membrane and cytosol dynamics
NASA Astrophysics Data System (ADS)
Moure, Adrian; Gomez, Hector
2016-10-01
A distinguishing feature of amoeboid motion is that the migrating cell undergoes large deformations, caused by the emergence and retraction of actin-rich protrusions, called pseudopods. Here, we propose a cell motility model that represents pseudopod dynamics, as well as its interaction with membrane signaling molecules. The model accounts for internal and external forces, such as protrusion, contraction, adhesion, surface tension, or those arising from cell-obstacle contacts. By coupling the membrane and cytosol interactions we are able to reproduce a realistic picture of amoeboid motion. The model results are in quantitative agreement with experiments and show how cells may take advantage of the geometry of their microenvironment to migrate more efficiently.
Coupled Simulation of Wetland Hydrology, Nutrient and Vegetation Dynamics
NASA Astrophysics Data System (ADS)
Yang, L.; Campbell, K. L.; Graham, W. D.; Kiker, G. A.
2004-12-01
Ecohydrological variations such as altered hydrologic regime, invasion of exotic flora, and nutrient enrichment in the Kissimmee-Okeechobee-Everglades aquatic ecosystem in south Florida have been observed. It is important to study the dynamics of wetland hydrology, nutrient and vegetation communities and their interactions over multiple spatial and temporal scales so that wetland restoration, ecological protection, and best management policy decision-making can be effectively accomplished. Hydrologic models are important tools in these decision-making processes. Hydrological components capable of multi-directional overland flow and lateral groundwater flow simulation within the Java-based, object-oriented framework of the ACRU2000 model were developed to make the existing hydrologic model in ACRU2000 more applicable in the Lake Okeechobee Basin where flat topography, high-water-table and sandy soils define the very unique hydrology. In addition nutrient components capable of multi-directional transport and transformation of nitrogen and phosphorus were modified to make the current nutrient model in ACRU2000 more applicable in the Lake Okeechobee Basin. Observed data in the Lake Okeechobee Basin were used to validate the coupled hydrologic and nutrient cycling model's predictions of the spatial and temporal distribution of flow and nutrient concentrations. The simulated results indicate that the coupled model is capable of simulating nutrient, overland, and lateral groundwater flows over a watershed that incorporates wetlands. Future work will focus on the development of a new wetland vegetation model to be integrated into this coupled hydrological and nutrient model. The new model will then be applied in the Lake Okeechobee Basin to simulate the ecohydrological variations due to the implementation of alternative water and land management practices. (More information regarding ACRU2000 and its modification for use in the Southeastern Coastal Plain can be found at
Dynamical Recurrence and the Quantum Control of Coupled Oscillators
NASA Astrophysics Data System (ADS)
Genoni, Marco G.; Serafini, Alessio; Kim, M. S.; Burgarth, Daniel
2012-04-01
Controllability—the possibility of performing any target dynamics by applying a set of available operations—is a fundamental requirement for the practical use of any physical system. For finite-dimensional systems, such as spin systems, precise criteria to establish controllability, such as the so-called rank criterion, are well known. However, most physical systems require a description in terms of an infinite-dimensional Hilbert space whose controllability properties are poorly understood. Here, we investigate infinite-dimensional bosonic quantum systems—encompassing quantum light, ensembles of bosonic atoms, motional degrees of freedom of ions, and nanomechanical oscillators—governed by quadratic Hamiltonians (such that their evolution is analogous to coupled harmonic oscillators). After having highlighted the intimate connection between controllability and recurrence in the Hilbert space, we prove that, for coupled oscillators, a simple extra condition has to be fulfilled to extend the rank criterion to infinite-dimensional quadratic systems. Further, we present a useful application of our finding, by proving indirect controllability of a chain of harmonic oscillators.
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.
Dynamic coupling of ferromagnets via spin Hall magnetoresistance
NASA Astrophysics Data System (ADS)
Taniguchi, Tomohiro
2017-03-01
The synchronized magnetization dynamics in ferromagnets on a nonmagnetic heavy metal caused by the spin Hall effect is investigated theoretically. The direct and inverse spin Hall effects near the ferromagnetic/nonmagnetic interface generate longitudinal and transverse electric currents. The phenomenon is known as the spin Hall magnetoresistance effect, whose magnitude depends on the magnetization direction in the ferromagnet due to the spin transfer effect. When another ferromagnet is placed onto the same nonmagnet, these currents are again converted to the spin current by the spin Hall effect and excite the spin torque to this additional ferromagnet, resulting in the excitation of the coupled motions of the magnetizations. The in-phase or antiphase synchronization of the magnetization oscillations, depending on the value of the Gilbert damping constant and the field-like torque strength, is found in the transverse geometry by solving the Landau-Lifshitz-Gilbert equation numerically. On the other hand, in addition to these synchronizations, the synchronization having a phase difference of a quarter of a period is also found in the longitudinal geometry. The analytical theory clarifying the relation among the current, frequency, and phase difference is also developed, where it is shown that the phase differences observed in the numerical simulations correspond to that giving the fixed points of the energy supplied by the coupling torque.
A global coupled model of the lithosphere and mantle dynamics
NASA Astrophysics Data System (ADS)
Iaffaldano, G.; Bunge, H.
2004-12-01
Understanding the dynamics of global lithospheric motion is one of the most important problems in geodynamics today. Mantle convection is commonly accepted as the driving force for plate motion but, while the kinematics of plate movement is well known from space geodetic and paleomagnetic observations, we lack a rigorous description of the coupled mantle convection-plate motion system. Here we present first results from a coupled mantle convection-global lithosphere motion model following a similar effort by Lithgow-Bertelloni and Guynn. Our plate motion code is SHELLS, a thinsheet FEM code developed by Bird which computes global plate motion and explicitly accounts for faults. The global mantle convection code is TERRA, a high-resolution 3-D FEM code developed and parallelized by Bunge and Baumgardner. We perform simple modeling experiments in which the shear tractions applied to the bottom of the lithosphere arise directly from the mantle circulation model. Our mantle circulation model includes a history of subduction and accounts, among others, for variations in mantle viscosity and strong bottom heating from the core. We find that our results are sensitive to the amount of core heating, an inference that has received renewed attention lately, and that models with stronger core heating overall are in better agreement with observations of intraplate stresses derived from the World Stress Map.
Coupled-cluster methods for core-hole dynamics
NASA Astrophysics Data System (ADS)
Picon, Antonio; Cheng, Lan; Hammond, Jeff R.; Stanton, John F.; Southworth, Stephen H.
2014-05-01
Coupled cluster (CC) is a powerful numerical method used in quantum chemistry in order to take into account electron correlation with high accuracy and size consistency. In the CC framework, excited, ionized, and electron-attached states can be described by the equation of motion (EOM) CC technique. However, bringing CC methods to describe molecular dynamics induced by x rays is challenging. X rays have the special feature of interacting with core-shell electrons that are close to the nucleus. Core-shell electrons can be ionized or excited to a valence shell, leaving a core-hole that will decay very fast (e.g. 2.4 fs for K-shell of Ne) by emitting photons (fluorescence process) or electrons (Auger process). Both processes are a clear manifestation of a many-body effect, involving electrons in the continuum in the case of Auger processes. We review our progress of developing EOM-CC methods for core-hole dynamics. Results of the calculations will be compared with measurements on core-hole decays in atomic Xe and molecular XeF2. This work is funded by the Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, under Contract No. DE-AC02-06CH11357.
Coupled electron-nuclear wavepacket dynamics in potassium dimers
NASA Astrophysics Data System (ADS)
Braun, Hendrike; Bayer, Tim; Sarpe, Cristian; Siemering, Robert; de Vivie-Riedle, Regina; Baumert, Thomas; Wollenhaupt, Matthias
2014-06-01
Recently we have demonstrated control of valence-bond excitation of a molecule due to the interplay of the induced charge oscillation with the precisely tailored phase of the driving laser field (Bayer et al 2013 Phys. Rev. Lett. 110 123003). In this contribution we describe in more detail the two-colour experiment—a control pulse sequence followed by an ionizing probe pulse of a different wavelength. We provide details on the quantum dynamics simulations carried out to reproduce and to analyse the experimental results. The procedure for averaging over the focal intensity distribution in the interaction region and the method for orientation averaging, which are both crucial for the reproduction of our strong-field measurements, are also described in detail. The analysis of the temporal evolution of the expectation values of the wavepackets on the relevant potentials, the induced energetic shifts in the molecule and the modulation in the charge oscillation provides further insights into the interplay of the coupled nuclear-electron dynamics. Because the measured photoelectron spectra reveal the population of the target states we describe the quantum mechanical approach to calculate the photoelectron spectra and rationalize the results using Mulliken's difference potential method.
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.
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
2015-07-20
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.
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
Dynamical Dark Matter from strongly-coupled dark sectors
NASA Astrophysics Data System (ADS)
Dienes, Keith R.; Huang, Fei; Su, Shufang; Thomas, Brooks
2017-02-01
Dynamical Dark Matter (DDM) is an alternative framework for dark-matter physics in which the dark sector comprises a vast ensemble of particle species whose Standard-Model decay widths are balanced against their cosmological abundances. Previous studies of this framework have focused on a particular class of DDM ensembles—motivated primarily by Kaluza-Klein towers in theories with extra dimensions—in which the density of dark states scales roughly as a polynomial of the mass. In this paper, by contrast, we study the properties of a different class of DDM ensembles in which the density of dark states grows exponentially with mass. Ensembles with this Hagedorn-like property arise naturally as the "hadronic" resonances associated with the confining phase of a strongly-coupled dark sector; they also arise naturally as the gauge-neutral bulk states of Type I string theories. We study the dynamical properties of such ensembles, and demonstrate that an appropriate DDM-like balancing between decay widths and abundances can emerge naturally—even with an exponentially rising density of states. We also study the effective equations of state for such ensembles, and investigate some of the model-independent observational constraints on such ensembles that follow directly from these equations of state. In general, we find that such constraints tend to introduce correlations between various properties of these DDM ensembles such as their associated mass scales, lifetimes, and abundance distributions. For example, we find that these constraints allow DDM ensembles with energy scales ranging from the GeV scale all the way to the Planck scale, but that the total present-day cosmological abundance of the dark sector must be spread across an increasing number of different states in the ensemble as these energy scales are dialed from the Planck scale down to the GeV scale. Numerous other correlations and constraints are also discussed.
NASA Astrophysics Data System (ADS)
Fukuyama, T.; Okugawa, M.
2017-03-01
We have experimentally investigated the dynamic behavior of coupled nonlinear oscillators, including chaos caused by the instability of ionization waves in a glow discharge plasma. We studied the phase synchronization process of coupled asymmetric oscillators with increasing coupling strength. Coherence resonance and phase synchronization were observed in the coupled systems. The phase synchronization process revealed scaling laws with a tendency of Type-I intermittency in the relationships between the coupling strength and the average duration of successive laminar states interrupted by a phase slip. Coupled periodic oscillators changed from a periodic state to chaos caused by the interaction of nonlinear periodic waves at increasing coupling strength.
Space-Time Correlations and Dynamic Coupling in Turbulent Flows
NASA Astrophysics Data System (ADS)
He, Guowei; Jin, Guodong; Yang, Yue
2017-01-01
Space-time correlation is a staple method for investigating the dynamic coupling of spatial and temporal scales of motion in turbulent flows. In this article, we review the space-time correlation models in both the Eulerian and Lagrangian frames of reference, which include the random sweeping and local straining models for isotropic and homogeneous turbulence, Taylor's frozen-flow model and the elliptic approximation model for turbulent shear flows, and the linear-wave propagation model and swept-wave model for compressible turbulence. We then focus on how space-time correlations are used to develop time-accurate turbulence models for the large-eddy simulation of turbulence-generated noise and particle-laden turbulence. We briefly discuss their applications to two-point closures for Kolmogorov's universal scaling of energy spectra and to the reconstruction of space-time energy spectra from a subset of spatial and temporal signals in experimental measurements. Finally, we summarize the current understanding of space-time correlations and conclude with future issues for the field.
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.
NASA Astrophysics Data System (ADS)
Mohanam, L. N.; Ong, S. W.; Tok, E. S.; Kang, H. C.
2015-02-01
Even though the Car-Parrinello molecular dynamics (CPMD) method provides excellent sampling for thermal equilibrium, coupling between ionic motion and the fictitious orbital dynamics leads to an underestimation of ionic vibration frequencies In this letter we examine how this coupling affects calculated rates of energy-barrier crossing. Simulating double-well potentials in 'toy' models based on H3O2- and H5O2+ complexes, we demonstrate that barrier crossing rates can be dramatically affected depending upon how orbitals evolve at the top of the reaction barrier. Thus, it is important that calculated dynamical quantities such as chemical reaction rates be assessed for this coupling effect.
Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics.
Erban, Radek
2016-02-01
Molecular dynamics (MD) simulations of ions (K(+), Na(+), Ca(2+) 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.
Landucci, Jennifer; Foley, Gretchen N
2014-03-01
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.
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
Dynamics of hydration water and coupled protein sidechains around a polymerase protein surface
NASA Astrophysics Data System (ADS)
Qin, Yangzhong; Yang, Yi; Wang, Lijuan; Zhong, Dongping
2017-09-01
Water-protein coupled interactions are essential to the protein structural stability, flexibility and dynamic functions. The ultimate effects of the hydration dynamics on the protein fluctuations remain substantially unexplored. Here, we investigated the dynamics of both hydration water and protein sidechains at 13 different sites around the polymerase β protein surface using a tryptophan scan with femtosecond spectroscopy. Three types of hydration-water relaxations and two types of protein sidechain motions were determined, reflecting a highly dynamic water-protein interactions fluctuating on the picosecond time scales. The hydration-water dynamics dominate the coupled interactions with higher flexibility.
Energy Band and Josephson Dynamics of Spin-Orbit Coupled Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Zhang, Xin; Yu, Zi-Fa; Xue, Ju-Kui
2015-10-01
We theoretically investigate the energy band structure and Josephson dynamics of a spin-orbit coupled Bose-Einstein condensate in a double-well potential. We study the energy band structure and the corresponding tunneling dynamics of the system by properly adjusting the SO coupling, Raman coupling, Zeeman field and atomic interactions. The coupled effects of SO coupling, Raman coupling, Zeeman field and atomic interactions lead to the appearance of complex energy band structure including the loop structure. Particularly, the emergence of the loop structure in energy band also depends on SO coupling, Raman coupling, Zeeman field and atomic interactions. Correspondingly, the Josephson dynamics of the system are strongly related to the energy band structure. Especially, the emergence of the loop structure results in complex tunneling dynamics, including suppression-revival transitions and self-trapping of atoms transfer between two spin states and two wells. This engineering provides a possible means for studying energy level and corresponding dynamics of two-species SO coupled BECs. Supported by the National Natural Science Foundation of China under Grant Nos. 11274255 and 11305132, by Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20136203110001, by the Natural Science Foundation of Gansu province under Grant No. 2011GS04358, and by Creation of Science and Technology of Northwest Normal University under Grant Nos. NWNU-KJCXGC-03-48, NWNU-LKQN-12-12
Transportation dynamics on coupled networks with limited bandwidth
Li, Ming; Hu, Mao-Bin; Wang, Bing-Hong
2016-01-01
The communication networks in real world often couple with each other to save costs, which results in any network does not have a stand-alone function and efficiency. To investigate this, in this paper we propose a transportation model on two coupled networks with bandwidth sharing. We find that the free-flow state and the congestion state can coexist in the two coupled networks, and the free-flow path and congestion path can coexist in each network. Considering three bandwidth-sharing mechanisms, random, assortative and disassortative couplings, we also find that the transportation capacity of the network only depends on the coupling mechanism, and the fraction of coupled links only affects the performance of the system in the congestion state, such as the traveling time. In addition, with assortative coupling, the transportation capacity of the system will decrease significantly. However, the disassortative coupling has little influence on the transportation capacity of the system, which provides a good strategy to save bandwidth. Furthermore, a theoretical method is developed to obtain the bandwidth usage of each link, based on which we can obtain the congestion transition point exactly. PMID:27966624
Transportation dynamics on coupled networks with limited bandwidth
NASA Astrophysics Data System (ADS)
Li, Ming; Hu, Mao-Bin; Wang, Bing-Hong
2016-12-01
The communication networks in real world often couple with each other to save costs, which results in any network does not have a stand-alone function and efficiency. To investigate this, in this paper we propose a transportation model on two coupled networks with bandwidth sharing. We find that the free-flow state and the congestion state can coexist in the two coupled networks, and the free-flow path and congestion path can coexist in each network. Considering three bandwidth-sharing mechanisms, random, assortative and disassortative couplings, we also find that the transportation capacity of the network only depends on the coupling mechanism, and the fraction of coupled links only affects the performance of the system in the congestion state, such as the traveling time. In addition, with assortative coupling, the transportation capacity of the system will decrease significantly. However, the disassortative coupling has little influence on the transportation capacity of the system, which provides a good strategy to save bandwidth. Furthermore, a theoretical method is developed to obtain the bandwidth usage of each link, based on which we can obtain the congestion transition point exactly.
Transportation dynamics on coupled networks with limited bandwidth.
Li, Ming; Hu, Mao-Bin; Wang, Bing-Hong
2016-12-14
The communication networks in real world often couple with each other to save costs, which results in any network does not have a stand-alone function and efficiency. To investigate this, in this paper we propose a transportation model on two coupled networks with bandwidth sharing. We find that the free-flow state and the congestion state can coexist in the two coupled networks, and the free-flow path and congestion path can coexist in each network. Considering three bandwidth-sharing mechanisms, random, assortative and disassortative couplings, we also find that the transportation capacity of the network only depends on the coupling mechanism, and the fraction of coupled links only affects the performance of the system in the congestion state, such as the traveling time. In addition, with assortative coupling, the transportation capacity of the system will decrease significantly. However, the disassortative coupling has little influence on the transportation capacity of the system, which provides a good strategy to save bandwidth. Furthermore, a theoretical method is developed to obtain the bandwidth usage of each link, based on which we can obtain the congestion transition point exactly.
Synchronization and local convergence analysis of networks with dynamic diffusive coupling
NASA Astrophysics Data System (ADS)
Burbano Lombana, Daniel Alberto; di Bernardo, Mario
2016-11-01
In this paper, we address the problem of achieving synchronization in networks of nonlinear units coupled by dynamic diffusive terms. We present two types of couplings consisting of a static linear term, corresponding to the diffusive coupling, and a dynamic term which can be either the integral or the derivative of the sum of the mismatches between the states of neighbouring agents. The resulting dynamic coupling strategy is a distributed proportional-integral (PI) or a proportional-derivative (PD) law that is shown to be effective in improving the network synchronization performance, for example, when the dynamics at nodes are nonidentical. We assess the stability of the network by extending the classical Master Stability Function approach to the case where the links are dynamic ones of PI/PD type. We validate our approach via a set of representative examples including networks of chaotic Lorenz and networks of nonlinear mechanical systems.
Entanglement dynamics of quantum oscillators nonlinearly coupled to thermal environments
NASA Astrophysics Data System (ADS)
Voje, Aurora; Croy, Alexander; Isacsson, Andreas
2015-07-01
We study the asymptotic entanglement of two quantum harmonic oscillators nonlinearly coupled to an environment. Coupling to independent baths and a common bath are investigated. Numerical results obtained using the Wangsness-Bloch-Redfield method are supplemented by analytical results in the rotating wave approximation. The asymptotic negativity as function of temperature, initial squeezing, and coupling strength, is compared to results for systems with linear system-reservoir coupling. We find that, due to the parity-conserving nature of the coupling, the asymptotic entanglement is considerably more robust than for the linearly damped cases. In contrast to linearly damped systems, the asymptotic behavior of entanglement is similar for the two bath configurations in the nonlinearly damped case. This is due to the two-phonon system-bath exchange causing a suppression of information exchange between the oscillators via the bath in the common-bath configuration at low temperatures.
Dynamics of phase oscillators with generalized frequency-weighted coupling
NASA Astrophysics Data System (ADS)
Xu, Can; Gao, Jian; Xiang, Hairong; Jia, Wenjing; Guan, Shuguang; Zheng, Zhigang
2016-12-01
Heterogeneous coupling patterns among interacting elements are ubiquitous in real systems ranging from physics, chemistry to biology communities, which have attracted much attention during recent years. In this paper, we extend the Kuramoto model by considering a particular heterogeneous coupling scheme in an ensemble of phase oscillators, where each oscillator pair interacts with different coupling strength that is weighted by a general function of the natural frequency. The Kuramoto theory for the transition to synchronization can be explicitly generalized, such as the expression for the critical coupling strength. Also, a self-consistency approach is developed to predict the stationary states in the thermodynamic limit. Moreover, Landau damping effects are further revealed by means of linear stability analysis and resonance poles theory below the critical threshold, which turns to be far more generic. Our theoretical analysis and numerical results are consistent with each other, which can help us understand the synchronization transition in general networks with heterogenous couplings.
Coupled Dynamics for Superfluid (4) {He} 4 He in a Channel
NASA Astrophysics Data System (ADS)
Khomenko, D.; Mishra, P.; Pomyalov, A.
2017-06-01
We study the coupled dynamics of normal and superfluid components of superfluid ^4{He} in a channel considering the counterflow turbulence with laminar normal component. In particular, we calculated profiles of the normal velocity, the mutual friction, the vortex line density and other flow properties and compared them to the case where the dynamic of the normal component is "frozen." We have found that the coupling between the normal and superfluid components leads to flattening of the normal velocity profile, increasingly more pronounced with temperature, as the mutual friction, and therefore, coupling becomes stronger. The commonly measured flow properties also change when the coupling between the two components is taken into account.
Routes to complex dynamics in a ring of unidirectionally coupled systems.
Perlikowski, P; Yanchuk, S; Wolfrum, M; Stefanski, A; Mosiolek, P; Kapitaniak, T
2010-03-01
We study the dynamics of a ring of unidirectionally coupled autonomous Duffing oscillators. Starting from a situation where the individual oscillator without coupling has only trivial equilibrium dynamics, the coupling induces complicated transitions to periodic, quasiperiodic, chaotic, and hyperchaotic behavior. We study these transitions in detail for small and large numbers of oscillators. Particular attention is paid to the role of unstable periodic solutions for the appearance of chaotic rotating waves, spatiotemporal structures, and the Eckhaus effect for a large number of oscillators. Our analytical and numerical results are confirmed by a simple experiment based on the electronic implementation of coupled Duffing oscillators.
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.
NASA Astrophysics Data System (ADS)
Wen, Sun; Chen, Shihua; Guo, Wanli
2008-10-01
This Letter investigates the global synchronization of a general complex dynamical network with non-delayed and delayed coupling. Based on Lasalle's invariance principle, adaptive global synchronization criteria is obtained. Analytical result shows that under the designed adaptive controllers, a general complex dynamical network with non-delayed and delayed coupling can globally asymptotically synchronize to a given trajectory. What is more, the node dynamic need not satisfy the very strong and conservative uniformly Lipschitz condition and the coupling matrix is not assumed to be symmetric or irreducible. Finally, numerical simulations are presented to verify the effectiveness of the proposed synchronization criteria.
Coupling between inter-helical hydrogen bonding and water dynamics in a proton transporter.
del Val, Coral; Bondar, Luiza; Bondar, Ana-Nicoleta
2014-04-01
Long-distance proton transfers by proton pumps occurs in discrete steps that may involve the direct participation of protein sidechains and water molecules, and coupling of protonation changes to structural rearrangements of the protein matrix. Here we explore the role of inter-helical hydrogen bonding in long-distance protein conformational coupling and dynamics of internal water molecules. From molecular dynamics simulations of wild type and nine different bacteriorhodopsin mutants we find that both intra- and inter-helical hydrogen bonds are important determinants of the local protein structure, dynamics, and water interactions. Based on molecular dynamics and bioinformatics analyses, we identify an aspartate/threonine inter-helical hydrogen-bonding motif involved in controlling the local conformational dynamics. Perturbation of inter-helical hydrogen bonds can couple to rapid changes in water dynamics.
Dynamics of non-minimally coupled perfect fluids
Bettoni, Dario; Liberati, Stefano E-mail: liberati@sissa.it
2015-08-01
We present a general formulation of the theory for a non-minimally coupled perfect fluid in which both conformal and disformal couplings are present. We discuss how such non-minimal coupling is compatible with the assumptions of a perfect fluid and derive both the Einstein and the fluid equations for such model. We found that, while the Euler equation is significantly modified with the introduction of an extra force related to the local gradients of the curvature, the continuity equation is unaltered, thus allowing for the definition of conserved quantities along the fluid flow. As an application to cosmology and astrophysics we compute the effects of the non-minimal coupling on a Friedmann-Lemaȋtre-Robertson-Walker metric at both background and linear perturbation level and on the Newtonian limit of our theory.
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.
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.
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.
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
Adaptive synchronization of two nonlinearly coupled complex dynamical networks with delayed coupling
NASA Astrophysics Data System (ADS)
Zheng, Song; Wang, Shuguo; Dong, Gaogao; Bi, Qinsheng
2012-01-01
This paper investigates the adaptive synchronization between two nonlinearly delay-coupled complex networks with the bidirectional actions and nonidentical topological structures. Based on LaSalle's invariance principle, some criteria for the synchronization between two coupled complex networks are achieved via adaptive control. To validate the proposed methods, the unified chaotic system as the nodes of the networks are analyzed in detail, and numerical simulations are given to illustrate the theoretical results.
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
Collective dynamics of a spin-orbit-coupled Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Hu, Fang-Qi; Wang, Jian-Jun; Yu, Zi-Fa; Zhang, Ai-Xia; Xue, Ju-Kui
2016-02-01
We study the collective dynamics of the spin-orbit coupled two pseudospin components of a Bose-Einstein condensate trapped in a quasi-one-dimensional harmonic potential, by using variational and directly numerical approach of binary mean-field Gross-Pitaevskii equations. The results show that, because of strong coupling of spin-orbit coupling (SOC), Rabi coupling, and atomic interaction, the collective dynamics of the system behave as complex characters. When the Rabi coupling is absent, the density profiles of the system preserve the Gauss type and the wave packets do harmonic oscillations. The amplitude of the collective oscillations increases with SOC. Furthermore, when the SOC strength increases, the dipole oscillations of the two pseudospin components undergo a transition from in-phase to out-of-phase oscillations. When the Rabi coupling present, there will exist a critical value of SOC strength (which depends on the Rabi coupling and atomic interaction). If the SOC strength is less than this critical value, the density profiles of the system can preserve the Gauss type and the wave packets do anharmonic (the frequency of dipole oscillations depends on SOC) oscillations synchronously (i.e., in-phase oscillations). However, if the SOC strength is larger than this critical value, the wave packets are dynamically fragmented and the stable dipole oscillations of the system can not exist. The collective dynamics of the system can be controlled by adjusting the atomic interaction, SOC, and Rabi-coupling strength.
Collective dynamics of a spin-orbit-coupled Bose-Einstein condensate.
Hu, Fang-Qi; Wang, Jian-Jun; Yu, Zi-Fa; Zhang, Ai-Xia; Xue, Ju-Kui
2016-02-01
We study the collective dynamics of the spin-orbit coupled two pseudospin components of a Bose-Einstein condensate trapped in a quasi-one-dimensional harmonic potential, by using variational and directly numerical approach of binary mean-field Gross-Pitaevskii equations. The results show that, because of strong coupling of spin-orbit coupling (SOC), Rabi coupling, and atomic interaction, the collective dynamics of the system behave as complex characters. When the Rabi coupling is absent, the density profiles of the system preserve the Gauss type and the wave packets do harmonic oscillations. The amplitude of the collective oscillations increases with SOC. Furthermore, when the SOC strength increases, the dipole oscillations of the two pseudospin components undergo a transition from in-phase to out-of-phase oscillations. When the Rabi coupling present, there will exist a critical value of SOC strength (which depends on the Rabi coupling and atomic interaction). If the SOC strength is less than this critical value, the density profiles of the system can preserve the Gauss type and the wave packets do anharmonic (the frequency of dipole oscillations depends on SOC) oscillations synchronously (i.e., in-phase oscillations). However, if the SOC strength is larger than this critical value, the wave packets are dynamically fragmented and the stable dipole oscillations of the system can not exist. The collective dynamics of the system can be controlled by adjusting the atomic interaction, SOC, and Rabi-coupling strength.
Function of dynamic membrane in self-forming dynamic membrane coupled bioreactor.
Wu, Y; Huang, X; Wen, X; Chen, F
2005-01-01
The Self-Forming Dynamic Membrane Coupled Bioreactor (SFDMBR), which uses coarse pore-sized material to separate solid and liquid in bioreactors, has some advantages compared with MBR using micro-/ultra-filtration membranes, for example, low module cost and high flux. The cake layer and gel layer formed on the surface and in the pores of the material during filtration played an important role, called self-forming dynamic membrane (DM), which mainly consisted of activated sludge. In this study, the function of DM in pollutant removal was investigated. It was found that DM could remove some organic matter (12.6 mg L(-1) on average) and total nitrogen (3.01 mg L(-1) on average) in the supernatant. Colloids and organic nitrogen were partly removed by DM while DOC, ammonia nitrogen and nitrate nitrogen removal by DM varied from negative to positive, which resulted from the combination of various biological activities, e.g. nitrification, biological utilization and so on. DO concentration in DM decreased with the depth and reached zero at about 1.5-2.5 mm depth. The organic degradation activity and nitrification activity of the biomass suspended in the bioreactor were higher than those of the biomass in the cake layer, which might be caused by the low DO concentration and low organic pollutant content in DM.
Time-varying coupling functions: Dynamical inference and cause of synchronization transitions
NASA Astrophysics Data System (ADS)
Stankovski, Tomislav
2017-02-01
Interactions in nature can be described by their coupling strength, direction of coupling, and coupling function. The coupling strength and directionality are relatively well understood and studied, at least for two interacting systems; however, there can be a complexity in the interactions uniquely dependent on the coupling functions. Such a special case is studied here: synchronization transition occurs only due to the time variability of the coupling functions, while the net coupling strength is constant throughout the observation time. To motivate the investigation, an example is used to present an analysis of cross-frequency coupling functions between delta and alpha brain waves extracted from the electroencephalography recording of a healthy human subject in a free-running resting state. The results indicate that time-varying coupling functions are a reality for biological interactions. A model of phase oscillators is used to demonstrate and detect the synchronization transition caused by the varying coupling functions during an invariant coupling strength. The ability to detect this phenomenon is discussed with the method of dynamical Bayesian inference, which was able to infer the time-varying coupling functions. The form of the coupling function acts as an additional dimension for the interactions, and it should be taken into account when detecting biological or other interactions from data.
Time-varying coupling functions: Dynamical inference and cause of synchronization transitions.
Stankovski, Tomislav
2017-02-01
Interactions in nature can be described by their coupling strength, direction of coupling, and coupling function. The coupling strength and directionality are relatively well understood and studied, at least for two interacting systems; however, there can be a complexity in the interactions uniquely dependent on the coupling functions. Such a special case is studied here: synchronization transition occurs only due to the time variability of the coupling functions, while the net coupling strength is constant throughout the observation time. To motivate the investigation, an example is used to present an analysis of cross-frequency coupling functions between delta and alpha brain waves extracted from the electroencephalography recording of a healthy human subject in a free-running resting state. The results indicate that time-varying coupling functions are a reality for biological interactions. A model of phase oscillators is used to demonstrate and detect the synchronization transition caused by the varying coupling functions during an invariant coupling strength. The ability to detect this phenomenon is discussed with the method of dynamical Bayesian inference, which was able to infer the time-varying coupling functions. The form of the coupling function acts as an additional dimension for the interactions, and it should be taken into account when detecting biological or other interactions from data.
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.
Collective Dynamics in a Binary Mixture of Hydrodynamically Coupled Microrotors
NASA Astrophysics Data System (ADS)
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.
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
Dynamics of globally coupled oscillators: Progress and perspectives
NASA Astrophysics Data System (ADS)
Pikovsky, Arkady; Rosenblum, Michael
2015-09-01
In this paper, we discuss recent progress in research of ensembles of mean field coupled oscillators. Without an ambition to present a comprehensive review, we outline most interesting from our viewpoint results and surprises, as well as interrelations between different approaches.
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.
Mitochondrial Dynamics: Coupling Mitochondrial Fitness with Healthy Aging.
Sebastián, David; Palacín, Manuel; Zorzano, Antonio
2017-03-01
Aging is associated with a decline in mitochondrial function and the accumulation of abnormal mitochondria. However, the precise mechanisms by which aging promotes these mitochondrial alterations and the role of the latter in aging are still not fully understood. Mitochondrial dynamics is a key process regulating mitochondrial function and quality. Altered expression of some mitochondrial dynamics proteins has been recently associated with aging and with age-related alterations in yeast, Caenorhabditis elegans, mice, and humans. Here, we review the link between alterations in mitochondrial dynamics, aging, and age-related impairment. We propose that the dysregulation of mitochondrial dynamics leads to age-induced accumulation of unhealthy mitochondria and contributes to alterations linked to aging, such as diabetes and neurodegeneration.
NASA Astrophysics Data System (ADS)
Proskurkin, I. S.; Vanag, V. K.
2015-02-01
Resonance regimes of two frequency different chemical oscillators coupled via pulsed inhibitory coupling with time delay τ have been studied theoretically and experimentally. The Belousov-Zhabotinsky reaction is used as a chemical oscillator. Regions of the 1: 1, 2: 3, 1: 2, 2: 5, and 1: 3 resonances, as well as complex oscillations and a regime in which one oscillator is suppressed have been found in the parameter plane "the ratio between the T 2/ T 1-τ." For the 1: 2 resonance, a sharp transition from one synchronized regime (called "0/0.5") to the other one (called "0.2/0.7") has been found. This transition (reminiscent to the transition between in-phase and anti-phase oscillations in case of the 1: 1 resonance) is controlled by time delay τ and the coupling strength.
NASA Astrophysics Data System (ADS)
Xu, Yuhua; Zhou, Wuneng; Fang, Jian'an; Sun, Wen
2010-04-01
This Letter investigates the synchronization of a general complex dynamical network with non-derivative and derivative coupling. Based on LaSalle's invariance principle, adaptive synchronization criteria are obtained. Analytical result shows that under the designed adaptive controllers, a general complex dynamical network with non-derivative and derivative coupling can asymptotically synchronize to a given trajectory, and several useful criteria for synchronization are given. What is more, the coupling matrix is not assumed to be symmetric or irreducible. Finally, simulations results show the method is effective.
Switching dynamics of single and coupled VO2-based oscillators as elements of neural networks
NASA Astrophysics Data System (ADS)
Velichko, Andrey; Belyaev, Maksim; Putrolaynen, Vadim; Pergament, Alexander; Perminov, Valentin
2017-01-01
In the present paper, we report on the switching dynamics of both single and coupled VO2-based oscillators, with resistive and capacitive coupling, and explore the capability of their application in oscillatory neural networks. Based on these results, we further select an adequate SPICE model to describe the modes of operation of coupled oscillator circuits. Physical mechanisms influencing the time of forward and reverse electrical switching, that determine the applicability limits of the proposed model, are identified. For the resistive coupling, it is shown that synchronization takes place at a certain value of the coupling resistance, though it is unstable and a synchronization failure occurs periodically. For the capacitive coupling, two synchronization modes, with weak and strong coupling, are found. The transition between these modes is accompanied by chaotic oscillations. A decrease in the width of the spectrum harmonics in the weak-coupling mode, and its increase in the strong-coupling one, is detected. The dependences of frequencies and phase differences of the coupled oscillatory circuits on the coupling capacitance are found. Examples of operation of coupled VO2 oscillators as a central pattern generator are demonstrated.
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.
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.
Observer-based synchronization in complex dynamical networks with nonsymmetric coupling
NASA Astrophysics Data System (ADS)
Wu, Jianshe; Jiao, Licheng
2007-12-01
Based on a general complex dynamical network model with nonsymmetric coupling, some criteria for synchronization are proposed based on the approach of state observer design. Unlike the nonobserver-based dynamical networks, where the coupling between two connected nodes is defined by an inner coupling matrix and full state coupling is typically needed, in this paper, smaller amount of coupling variables or even only a scalar output signal of each node is needed to synchronize the network. Unlike the commonly researched complex network model, where the coupling between nodes is symmetric, here, in our network model, the coupling configuration matrix is not assumed to be symmetric and may have complex eigenvalues. The matrix Jordan canonical formalization method is used instead of the matrix diagonalization method, so in our synchronization criteria, the coupling configuration matrix is not required to be diagonalizable. Especially, the proposed step-by-step approach is simpler in computation than the existent ones, which usually rely heavily on numerical toolbox, and may be done by hand completely. An example is given to illustrate the step-by-step approach, in which each node is a two-dimensional dynamical limit cycle oscillator system consisting of a two-cell cellular neural network, and numerical simulations are also done to verify the results of design.
Simulation of transient dynamic behavior in laterally coupled VCSEL arrays
NASA Astrophysics Data System (ADS)
Riyopoulos, Spilios
2002-06-01
A novel, fast simulation tool for transient response is developed to study jitter and noise caused by lateral cavity interactions in VCSEL arrays. The cavity mode profiles, obtained from a paraxial eigenmode analysis, are used to derive fast 1-D rate equations that implement gain confinement, edge clipping, wide angle scattering and diffraction (self-interference) losses. These equations are augmented by lateral coupling terms describing the interactions among nearest neighbor cavities. Slow time scale coupling describes interactions of phase-shifted cavities via mutually induced electric polarization, cross-hole burning and cross-cavity gain due to optical fringe-field interactions. The tool is used to study cavity cross-talk, lateral bit pattern error effects, and the possibility of excitation of long range modulations over the array. Conclusions relating VCSEL packing density to BER, bit suppression by neighboring cavities, and array phase locking are given.
Solitons and dynamics for a general integrable nonlocal coupled nonlinear Schrödinger equation
NASA Astrophysics Data System (ADS)
Song, Cai-Qin; Xiao, Dong-Mei; Zhu, Zuo-Nong
2017-04-01
In this paper, we investigate a general integrable nonlocal coupled nonlinear Schrödinger (NLS) system with the parity-time (PT) symmetry, which contains not only the nonlocal self-phase modulation and the nonlocal cross-phase modulation, but also the nonlocal four-wave mixing terms. This nonlocal coupled NLS system is a nonlocal version of a coupled NLS system. The general N-th Darboux transformation for the nonlocal coupled NLS equation is constructed. By using the Darboux transformation, its soliton solutions are obtained. Dynamics and interactions of different kinds of soliton solutions are discussed.
Influence of coupling on thermal forces and dynamic friction in plasmas with multiple ion species
NASA Astrophysics Data System (ADS)
Kagan, Grigory; Baalrud, Scott D.; Daligault, Jérôme
2017-07-01
The recently proposed effective potential theory [Phys. Rev. Lett. 110, 235001 (2013)] is used to investigate the influence of coupling on inter-ion-species diffusion and momentum exchange in multi-component plasmas. Thermo-diffusion and the thermal force are found to diminish rapidly as strong coupling onsets. For the same coupling parameters, the dynamic friction coefficient is found to tend to unity. These results provide an impetus for addressing the role of coupling on diffusive processes in inertial confinement fusion experiments.
Dynamic phase response and amplitude-phase coupling of self-assembled semiconductor quantum dots
NASA Astrophysics Data System (ADS)
Lingnau, Benjamin; Herzog, Bastian; Kolarczik, Mirco; Woggon, Ulrike; Lüdge, Kathy; Owschimikow, Nina
2017-06-01
The optical excitation of semiconductor gain media introduces both gain and refractive index changes, commonly referred to as amplitude-phase coupling. Quantum-confined structures with an energetically well separated carrier reservoir usually exhibit a decreased amplitude-phase coupling compared to bulk materials. However, its magnitude and definition is still controversially discussed. We investigate the fundamental processes influencing the amplitude-phase coupling in semiconductor quantum-dot media using a coupled-carrier rate-equation model. We are able to analyze the dependence on the electronic structure and suggest routes towards an optimization of the dynamic phase response of the gain material.
Boundary in the dynamic phase of globally coupled oscillatory and excitable units
NASA Astrophysics Data System (ADS)
Daido, Hiroaki
2017-07-01
There is a crucial boundary between dynamic phase 1 and dynamic phase 2 of globally coupled oscillatory and excitable units, where the mean field is constant and oscillates in the former and the latter, respectively. This boundary is theoretically derived here for a large population of dynamical units, each having only a phase variable, where it is assumed that both the coupling strength and the distribution width of bifurcation parameters are equally small. This theory, which is applicable only if all or most of the units are intrinsically oscillatory, is confirmed to agree with simulation results for two different distribution densities.
Dynamic coupling of magnetic resonance modes in pairs of mesoscopic rectangles
NASA Astrophysics Data System (ADS)
Swoboda, Christian; Kuhlmann, Nils; Martens, Michael; Vogel, Andreas; Meier, Guido
2013-07-01
We investigate the magnetization dynamics in pairs of mesoscopic permalloy (Ni80Fe20) rectangles by means of broadband-ferromagnetic resonance measurements and micromagnetic simulations. Each pair consists of two rectangles that differ in their geometry. The local effective field at each element is significantly affected by the stray field of its neighbor for small center-to-center distances between the rectangles. In antiparallel magnetization alignment, this dynamic dipolar coupling becomes prominent and anticrossing between ferromagnetic resonance modes and higher-order spin-wave modes is observed. Combination of the experimental and the simulational findings provides a comprehensive understanding of dynamically coupled rectangles.
Dynamics for a two-atom two-mode intensity-dependent Raman coupled model
Singh, S. E-mail: sudhhasingh@gmail.com; Gilhare, K.
2016-06-15
We study the quantum dynamics of a two-atom Raman coupled model interacting with a quantized bimodal field with intensity-dependent coupling terms in a lossless cavity. The unitary transformation method used to solve the time-dependent problem also gives the eigensolutions of the interaction Hamiltonian. We study the atomic-population dynamics and dynamics of the photon statistics in the two cavity modes, and present evidence of cooperative effects in the production of antibunching and anticorrelations between the modes. We also investigate the effect of detuning on the evolution of second-order correlation functions and observe that the oscillations become more rapid for large detuning.
Exploring Dynamics of Land surface-Subsurface Coupling Under Change
NASA Astrophysics Data System (ADS)
Ajami, Hoori; McCabe, Matthew F.; Evans, Jason P.
2013-04-01
The degree of land surface-subsurface coupling is controlled by complex interactions between the atmosphere, land surface condition and subsurface hydrologic characteristics. Global climate models project increases in temperature and changes in precipitation rates and patterns which in turn alter terrestrial water and energy budgets impacting water resources. However, the degree of land surface-subsurface coupling under scenarios of land cover and climate change has not been fully explored. In this study, we used an integrated groundwater-surface water-land surface model (ParFlow.CLM) across a semi-arid catchment located in the central west New South Wales, Australia to assess variability in water and energy fluxes under historic condition and scenarios of climate and land cover change. The Baldry hydrological observatory situated in a topographically flat terrain has the area of 2 km2 and contains two distinct land cover types of pasture and a regenerated Eucalyptus forest. High resolution groundwater level measurements in the site reveal differences in groundwater connectivity in wet versus dry periods in pasture and Eucalyptus forest for the historic condition. Using downscaled climate forcing obtained from a regional climate model for eastern Australia, the degree of land surface-subsurface coupling within the catchment was examined under various scenarios of climate and changes in land cover types. It is expected that a fully integrated hydrologic model like ParFlow.CLM improve predictions in land-atmospheric feedback processes under changes in hydrologic conditions.
Vortex dynamics in coherently coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Calderaro, Luca; Fetter, Alexander L.; Massignan, Pietro; Wittek, Peter
2017-02-01
In classical hydrodynamics with uniform density, vortices move with the local fluid velocity. This description is rewritten in terms of forces arising from the interaction with other vortices. Two such positive straight vortices experience a repulsive interaction and precess in a positive (anticlockwise) sense around their common centroid. A similar picture applies to vortices in a two-component, two-dimensional uniform Bose-Einstein condensate (BEC) coherently coupled through rf Rabi fields. Unlike the classical case, however, the rf Rabi coupling induces an attractive interaction and two such vortices with positive signs now rotate in the negative (clockwise) sense. Pairs of counter-rotating vortices are instead found to translate with uniform velocity perpendicular to the line joining their cores. This picture is extended to a single vortex in a two-component trapped BEC. Although two uniform vortex-free components experience familiar Rabi oscillations of particle-number difference, such behavior is absent for a vortex in one component because of the nonuniform vortex phase. Instead the coherent Rabi coupling induces a periodic vorticity transfer between the two components.
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.
Tandem strip mill's multi-parameter coupling dynamic modeling based on the thickness control
NASA Astrophysics Data System (ADS)
Peng, Yan; Zhang, Yang; Sun, Jianliang; Zang, Yong
2015-03-01
The rolling process is determined by the interaction of a number of different movements, during which the relative movement occurs between the vibrating roll system and the rolled piece, and the roll system's vibration interacts with the strip's deformation and rigid movement. So many parameters being involved leads to a complex mechanism of this coupling effect. Through testing and analyzing the vibration signals of the mill in the rolling process, the rolling mill's coupled model is established with comprehensive consideration of the coupling interaction between the mill's vertical vibration, its torsional vibration and the working roll's horizontal vibration, and vibration characteristics of different forms of rolling mill's vibration are analyzed under the coupling effect. With comprehensive attention to the relationship between the roll system, the moving strip and the rolling parameters' dynamic properties, and also from the strip thickness control point of view, further research is done on the coupling mechanism between the roll system's movement and the moving strip's characteristics in the rolling process. As a result, the law of inertial coupling and the stiffness coupling effect caused by different forms of the roll system's vibration is determined and the existence of nonlinear characteristics caused by the elastic deformation of moving strip is also found. Furthermore, a multi-parameter coupling-dynamic model is established which takes the tandem strip mill as its research object by making a detailed kinematics analysis of the roll system and using the principle of virtual work. The coupling-dynamic model proposes the instruction to describe the roll system's movement, and analyzes its dynamic response and working stability, and provides a theoretical basis for the realization of the strip thickness' dynamic control.
Variational Dynamic Coupled-Loads Analysis within the Frame of Launcher Upper Stage Development
NASA Astrophysics Data System (ADS)
Meitzner, R.; Abdoly, K.; Beuchel, W.; Stellino, W.
2014-06-01
During development the definition of realistic mechanical loads is a major challenge and milestone for space launcher programs. Especially the definition of dynamic loads for large structures, e.g. cryogenic tanks, and equipments, based on multi-variational payload configurations is a key element in the frame of new launcher upper stage developments.This paper presents a methodology to define realistic dynamic loads based on multi-variational dynamic coupled- loads analyses in the global launcher system up to equipment level.The complex challenge towards this task is to perform about 256000 complete coupled-loads analyses for the entire launcher upper stage including various recovery items within two weeks.The shown example describes multi-variational dynamic coupled-loads analyses and their post processing for the complete Ariane 5 Midlife Evolution launcher including the new upper stage using Nastran and PUMA3D software.
Dynamic Magneto-optic Coupling in a Ferromagnetic Nematic Liquid Crystal
NASA Astrophysics Data System (ADS)
Potisk, Tilen; Svenšek, Daniel; Brand, Helmut R.; Pleiner, Harald; Lisjak, Darja; Osterman, Natan; Mertelj, Alenka
2017-09-01
Hydrodynamics of complex fluids with multiple order parameters is governed by a set of dynamic equations with many material constants, of which only some are easily measurable. We present a unique example of a dynamic magneto-optic coupling in a ferromagnetic nematic liquid, in which long-range orientational order of liquid crystalline molecules is accompanied by long-range magnetic order of magnetic nanoplatelets. We investigate the dynamics of the magneto-optic response experimentally and theoretically and find out that it is significantly affected by the dissipative dynamic cross-coupling between the nematic and magnetic order parameters. The cross-coupling coefficient determined by fitting the experimental results with a macroscopic theory is of the same order of magnitude as the dissipative coefficient (rotational viscosity) that governs the reorientation of pure liquid crystals.
NASA Astrophysics Data System (ADS)
Hwang, G. Y.; Kim, K. T.; Chung, S. U.; Hwang, S. M.; Kang, B. S.; Hwang, I. C.
2002-05-01
With the advent of 3G mobile phones, a combined laptop personal computer and mobile phone can be realized that enables multimedia data communication such as TV streaming, web searching, music play, etc. A dynamic speaker is an essential part to generate high quality sound in the next generation mobile phones. Noting that characteristics of a dynamic speaker are a coupled phenomenon of mechanical, electrical, and magnetic system, a systematic analysis must be implemented to fully consider the coupling effects for an improved design. This paper presents a complete analysis of a dynamic speaker by considering mechanical, electrical and magnetic coupling effects. Results of the analysis are confirmed by the experiments. An improved design of a dynamic speaker is also proposed with enhanced performance.
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.
Dynamical transition between weak and strong coupling in Brillouin laser pulse amplification
Schluck, F.; Lehmann, G.; Müller, C.; Spatschek, K. H.
2016-08-15
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.
Nonlinear dynamic analysis for coupled vehicle-bridge vibration system on nonlinear foundation
NASA Astrophysics Data System (ADS)
Zhou, Shihua; Song, Guiqiu; Wang, Rongpeng; Ren, Zhaohui; Wen, Bangchun
2017-03-01
In this paper, the nonlinear dynamics of a parametrically excited coupled vehicle-bridge vibration system (CVBVS) is investigated, and the coupled system is subjected to a time-dependent transverse load including a constant value together with a harmonic time-variant component. The dynamic equations of the CVBVS are established by using the generalized Lagrange's equation. With the Galerkin truncation method, a set of nonlinear ordinary differential equations are derived by discretizing the continuous governing equation. The influences of parametric excitation with nonlinear support stiffness, mass ratio, excitation amplitude and position relation on the dynamic behaviors are studied for the interaction between vehicle and the bridge. The analysis results indicate that the nonlinear dynamic characteristics are strongly attributed to the interaction of the coupled system. Nonlinear support stiffness of foundation and mass ratio can lead to complex dynamic behaviors such as jump discontinuous phenomenon, periodic, quasi-periodic and chaotic motions. Vibration amplitude increases depending on the position, where the maximum vibration displacement does not occur at the center of the bridge. The excitation amplitude has an obvious influence on the nonlinear dynamic behaviors and the increase of the excitation amplitude makes the vibration strengthen. The bifurcation diagram and 3-D frequency spectrum are used to analyze the complex nonlinear dynamic behaviors of the CVBVS. The presented results can provide an insight to the understanding of the vibration characteristics of the coupled vehicle-bridge vibration system in engineering.
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
Recovering classical dynamics from coupled quantum systems through continuous measurement
Ghose, Shohini; Alsing, Paul; Deutsch, Ivan; Bhattacharya, Tanmoy; Habib, Salman; Jacobs, Kurt
2003-05-01
We study the role of continuous measurement in the quantum to classical transition for a system with coupled internal (spin) and external (motional) degrees of freedom. Even when the measured motional degree of freedom can be treated classically, entanglement between spin and motion causes strong measurement back action on the quantum spin subsystem so that classical trajectories are not recovered in this mixed quantum-classical regime. The measurement can extract localized quantum trajectories that behave classically only when the internal action also becomes large relative to ({Dirac_h}/2{pi})
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.
Locally coupled coherent states and Herman-Kluk dynamics
NASA Astrophysics Data System (ADS)
Child, M. S.; Shalashilin, D. V.
2003-02-01
An exact analysis of coupled coherent state (CCS) theory in the moving locally quadratic Hamiltonian approximation is shown to reproduce both the linearized coherent state matrix element of the Herman-Kluk propagator and the coherent state overlap with Heller's thawed Gaussian wave function. The derivation is applicable to anharmonic as well as harmonic systems, because the quadratic approximation is taken to apply only in the vicinity of a particular classical trajectory. New compact expressions for the linearized Herman-Kluk coherent state matrix element are given, and improvements for the practical application of CCS theory are discussed.
NASA Astrophysics Data System (ADS)
Pelle, G.; Ohayon, J.; Oddou, C.
1994-06-01
We report here preliminary results in the development of a computational model in cardiac mechanics which takes into account the coupled effects of ventricular mechanics and intracardiac hemodynamics. In this first work, complex geometrical, architectural and rheological properties of the organ have been strongly simplified in order to propose a “quasi-analytical” model. We assume axisymmetrical geometry of the ventricle and myocardium material to be made of a sheath of a composite, collagenic, fibrous and active muscle medium inside which the blood dynamics is dominated by unsteady inertial effects. Moreover, we have made grossly simplifying assumptions concerning rather stringent and unusual functioning conditions about the mechanical behavior of the input and output valvular and vascular impedances as well as the biochemical action of the fiber. By imposing the time variation of the input and output flow rate and activation function, it is possible, assuming uniformity of the pressure stresses applied to the internal wall surface at every instant of the cardiac cycle, to calculate the overall distribution of fluid pressure and velocity inside the cavity as well as the distributions of stresses and strains inside the wall. It was shown that under the action of a given biochemical activation function, both kinematics of the wall and induced motion of the fluid are such that the boundary conditions concerning normal pressure stresses conservation was constantly satisfied. Moreover, the results concerning the dynamics of the blood flow, as viewed through the human clinical investigations using velocimetric technology based upon color doppler ultrasound, are in accordance with those obtained from such a model, at least during the ejection phase. In particular, contrarily to the filling phase processes, the ejection dynamics is such that the time evolution of the blood velocity measured along the cavity axis does not display any phase shift characterizing an
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
Modeling TGF-mediated flow dynamics in a system of three coupled nephrons.
Bayram, Saziye
2012-03-01
This paper focuses on a mathematical model of a system of three closely coupled nephrons and accompanying analytical and computational analysis. In our previous modeling efforts, we have shown how coupling magnifies the tendency of many coupled identical nephrons to oscillate owing to tubuloglomerular feedback (TGF) mechanism. However, in this study, our focus is on the coupled nonidentical nephrons and their dynamics due to the TGF system. Our detailed analytical and computational results suggest that systems of three nonidentical nephrons coupled to their nearest neighbors are prone to be found in an oscillatory state, relative to a single-nephron case with the same properties; however, their steady-state regions are not necessarily as small as it was predicted from the system of many coupled identical nephrons cases.
Magnetization reversal dynamics in antiferromagnetically coupled magnetic recording media
NASA Astrophysics Data System (ADS)
Schabes, Manfred
2002-03-01
Antiferromagnetically coupled (AFC) media have been shown to provide an important extension of longitudinal magnetic data storage at high bit densities.[1,2] In this work we report the results of micromagnetic calculations to examine the magnetization reversal mechanism in two-layer AFC media as a function of bottom layer thickness and interfacial exchange coupling. It is shown that the magnetization reversal in the top and bottom layers can proceed at rather different time scales, if the interfacial energy density is small or the bottom layer thickness is large. In this case the reversal of the bottom layer may involve spin wave like oscillations that require time periods for damping that are large compared to the reversal time of the top layer. Detailed solutions of the Landau-Lifshitz-Langevin[2] equations are discussed to study these novel oscillatory excitations in AFC media at a temperature of 350 K. [1] E.E. Fullerton et al., Appl. Phys. Lett., vol.77, (2000),3806. [2] M.E. Schabes et al., IEEE Trans. Mag. MAG-37, (2001), 1432.
Coupling of lipid membrane elasticity and in-plane dynamics
NASA Astrophysics Data System (ADS)
Tsang, Kuan-Yu; Lai, Yei-Chen; Chiang, Yun-Wei; Chen, Yi-Fan
2017-07-01
Biomembranes exhibit liquid and solid features concomitantly with their in-plane fluidity and elasticity tightly regulated by cells. Here, we present experimental evidence supporting the existence of the dynamics-elasticity correlations for lipid membranes and propose a mechanism involving molecular packing densities to explain them. This paper thereby unifies, at the molecular level, the aspects of the continuum mechanics long used to model the two membrane features. This ultimately may elucidate the universal physical principles governing the cellular phenomena involving biomembranes.
On the coupling between the dynamics of protein and water.
Gavrilov, Yulian; Leuchter, Jessica D; Levy, Yaakov
2017-03-09
Interactions between water and biomolecules can significantly change the former's structural, dynamic, and thermodynamic properties relative to the bulk. Experimental, theoretical, and computational studies show that changes in water properties can be observed at distances of more than 10 Å from a biomolecule. The effects of biopolymers on hydration water molecules can be attributed to several factors: the chemical nature of the amino acid residues involved, the spatial arrangement of the biomolecule, and its conformational flexibility. In the current study, we concentrate on the effect of protein chain flexibility on the properties of hydration water, using short peptides as a model. We constructed 18 linear peptides with the sequence (XXGG) × 5, where X represents one of the common amino acids, other than glycine and proline. Using molecular dynamics (MD) simulations, we studied how restricting the chain flexibility can affect the structural, dynamic, and thermodynamic properties of hydration water. We found that restricting the peptide dynamics can slow down the translational motions of water molecules to a distance of at least 12-13 Å. Analysis of the 'slow' water molecules (residence time ≥ 100 ps) together with a thermodynamic analysis of water within 4.5 Å of the peptide revealed significant differences between the hydration properties of the peptides. The balance between the entropic and enthalpic solvation effects defines the final contribution to the hydration free energy of the restricted system. Our study implies that different regions of the proteins that have different configurational entropies may also have different solvation entropies and therefore different contributions to the overall thermodynamic stability. Therefore, mutations of a solvent exposed residue may modify the thermodynamic stability depending solely on the flexibility of the mutated sites due to their different solvation characteristics.
Proton Dynamics on Goethite Nanoparticles and Coupling to Electron Transport
Zarzycki, Piotr P.; Smith, Dayle MA; 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.
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
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.
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
2012-08-10
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.
Dynamics-dependent synchronization in on-chip coupled semiconductor lasers
NASA Astrophysics Data System (ADS)
Ohara, Shoma; Dal Bosco, Andreas Karsaklian; Ugajin, Kazusa; Uchida, Atsushi; Harayama, Takahisa; Inubushi, Masanobu
2017-09-01
Synchronization properties of chaotic dynamics in two mutually coupled semiconductor lasers with optical feedback embedded in a photonic integrated circuit are investigated from the point of view of their dynamical content. A phenomenon in which the two lasers can show qualitatively different synchronization properties according to the frequency range of investigation and their nonlinear dynamics is identified and termed dynamics-dependent synchronization. In-phase synchronization is observed for original signals and antiphase synchronization is observed for low-pass filtered signals in the case where one of the lasers shows chaotic oscillations while the other laser exhibits low-frequency fluctuations dynamics. The experimental conditions causing the synchronization states to vary according to the considered frequency interval are studied and the key roles of asymmetric coupling strength and injection currents are clarified.
NASA Astrophysics Data System (ADS)
Kim, Pilkee; Nguyen, Minh Sang; Kwon, Ojin; Kim, Young-Jin; Yoon, Yong-Jin
2016-09-01
A system of magnetically coupled oscillators has been recently considered as a promising compact structure to integrate multiple bistable energy harvesters (BEHs), but its design is not straightforward owing to its varying potential energy pattern, which has not been understood completely yet. This study introduces the concept of phase-dependent dynamic potential in a magnetically coupled BEH system with two degrees of freedom (DOFs) to explain the underlying principle of the complicated dynamics of the system. Through theoretical simulations and analyses, two distinct dynamic regimes, called the out-of-phase and in-phase mode regimes in this report, are found to exist in the frequency regions of the 1st and 2nd primary intrawell resonances. For the out-of-phase mode regime, the frequency displacement (and output power) responses of the 2-DOF BEH system exhibit typical double-well dynamics, whereas for the in-phase mode regime, only single-well dynamics is observed though the system is statically bistable. These dynamic regimes are also revealed to be caused by the difference in the dynamic potential energy trajectories propagating on a high-dimensional potential energy surface. The present approach to the dynamics of the 2-DOF BEH system can be extended and applied to higher-DOF systems, which sheds light on compact and efficient designs of magnetically coupled BEH chain structures.
Kim, Pilkee; Nguyen, Minh Sang; Kwon, Ojin; Kim, Young-Jin; Yoon, Yong-Jin
2016-09-28
A system of magnetically coupled oscillators has been recently considered as a promising compact structure to integrate multiple bistable energy harvesters (BEHs), but its design is not straightforward owing to its varying potential energy pattern, which has not been understood completely yet. This study introduces the concept of phase-dependent dynamic potential in a magnetically coupled BEH system with two degrees of freedom (DOFs) to explain the underlying principle of the complicated dynamics of the system. Through theoretical simulations and analyses, two distinct dynamic regimes, called the out-of-phase and in-phase mode regimes in this report, are found to exist in the frequency regions of the 1(st) and 2(nd) primary intrawell resonances. For the out-of-phase mode regime, the frequency displacement (and output power) responses of the 2-DOF BEH system exhibit typical double-well dynamics, whereas for the in-phase mode regime, only single-well dynamics is observed though the system is statically bistable. These dynamic regimes are also revealed to be caused by the difference in the dynamic potential energy trajectories propagating on a high-dimensional potential energy surface. The present approach to the dynamics of the 2-DOF BEH system can be extended and applied to higher-DOF systems, which sheds light on compact and efficient designs of magnetically coupled BEH chain structures.
Doshi, Urmi; Holliday, Michael J; Eisenmesser, Elan Z; Hamelberg, Donald
2016-04-26
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.
Kim, Pilkee; Nguyen, Minh Sang; Kwon, Ojin; Kim, Young-Jin; Yoon, Yong-Jin
2016-01-01
A system of magnetically coupled oscillators has been recently considered as a promising compact structure to integrate multiple bistable energy harvesters (BEHs), but its design is not straightforward owing to its varying potential energy pattern, which has not been understood completely yet. This study introduces the concept of phase-dependent dynamic potential in a magnetically coupled BEH system with two degrees of freedom (DOFs) to explain the underlying principle of the complicated dynamics of the system. Through theoretical simulations and analyses, two distinct dynamic regimes, called the out-of-phase and in-phase mode regimes in this report, are found to exist in the frequency regions of the 1st and 2nd primary intrawell resonances. For the out-of-phase mode regime, the frequency displacement (and output power) responses of the 2-DOF BEH system exhibit typical double-well dynamics, whereas for the in-phase mode regime, only single-well dynamics is observed though the system is statically bistable. These dynamic regimes are also revealed to be caused by the difference in the dynamic potential energy trajectories propagating on a high-dimensional potential energy surface. The present approach to the dynamics of the 2-DOF BEH system can be extended and applied to higher-DOF systems, which sheds light on compact and efficient designs of magnetically coupled BEH chain structures. PMID:27677356
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
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.
Dynamics, Structure, and Function are Coupled in the Mitochondrial Matrix
NASA Astrophysics Data System (ADS)
Scalettar, Bethe A.; Abney, James R.; Hackenbrock, Charles R.
1991-09-01
The coupling between molecular diffusion and the structure and function of the rat liver mitochondrial matrix was explored using fluorescence anisotropy techniques and electron microscopy. The results confirm that matrix ultrastructure and the concentration of matrix protein are influenced by the respiratory state of mitochondria and the osmolarity of the external medium. At physiological osmolarity, a fluorescent metabolite-sized probe was found to diffuse slowly in the mitochondrial matrix but not to be completely immobile. In addition, significant differences in diffusion rates were found to exist between different mitochondrial respiratory states, with the slowest diffusion occurring in states with the highest matrix protein concentration. These data support the concept of a matrix structure in which diffusion is considerably hindered due to limited probe-accessible water and further suggest that volume-dependent regulation of matrix protein packing may modulate metabolite diffusion and, in turn, mitochondrial metabolism.
Noncompact dynamical symmetry of a spin-orbit-coupled oscillator
NASA Astrophysics Data System (ADS)
Haaker, S. M.; Bais, F. A.; Schoutens, K.
2014-03-01
We explain the finite as well as infinite degeneracy in the spectrum of a particular system of spin-1/2 fermions with spin-orbit coupling in three spatial dimensions. Starting from a generalized Runge-Lenz vector, we explicitly construct a complete set of symmetry operators, which span a noncompact SO(3,2) algebra. The degeneracy of the physical spectrum only involves an infinite, so-called singleton representation. In the branch where orbital and spin angular momentum are aligned, the full representation appears, constituting a three-dimensional analog of Landau levels. Antialigning the spin leads to a finite degeneracy due to a truncation of the singleton representation. We conclude the paper by constructing the spectrum generating algebra of the problem.
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.
Non-Markovian dynamics of fully coupled fermionic and bosonic oscillators
NASA Astrophysics Data System (ADS)
Sargsyan, V. V.; Lacroix, D.; Adamian, G. G.; Antonenko, N. V.
2017-03-01
The non-Markovian Langevin approach is applied to study the dynamics of fermionic (bosonic) oscillator linearly coupled to a fermionic (bosonic) environment. The analytical expressions for occupation numbers in two different types of couplings (rotating-wave approximation and fully coupled) are compared and discussed. The weak-coupling and high- and low-temperature limits are considered as well. The conditions under which the environment imposes its thermal equilibrium on the collective subsystem are discussed. The sameness of the results, obtained with both the Langevin approach and the discretized environment method are shown. Short- and long-time nonequilibrium dynamics of fermionic and bosonic open quantum systems are analyzed both analytically and numerically.
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
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.
NASA Astrophysics Data System (ADS)
Wu, Xiangjun; Lu, Hongtao
2010-08-01
In this Letter, generalized projective synchronization (GPS) between two different complex dynamical networks with delayed coupling is investigated. Two complex networks are distinct if they have diverse node dynamics, or different number of nodes, or different topological structures. By using the adaptive control scheme, a sufficient synchronization criterion for this GPS is derived based on the LaSalle invariance principle. Three corollaries are also obtained. It is noticed that the synchronization speed sensitively depends on the adjustable positive constants μ. Furthermore, the coupling configuration matrix is not necessary to be symmetric or irreducible, and the inner coupling matrix need not be symmetric. In addition, the node dynamic need not satisfy the very strong and conservative uniformly Lipschitz condition. Numerical simulations further demonstrate the feasibility and effectiveness of the theoretical results.
Turbulent coronal heating mechanisms: coupling of dynamics and thermodynamics
NASA Astrophysics Data System (ADS)
Dahlburg, R. B.; Einaudi, G.; Rappazzo, A. F.; Velli, M.
2012-08-01
Context. Photospheric motions shuffle the footpoints of the strong axial magnetic field that threads coronal loops, which gives rise to turbulent nonlinear dynamics that are characterized by the continuous formation and dissipation of field-aligned current sheets in which energy is deposited at small-scales and the heating occurs. Previous studies showed that the current sheet thickness is several orders of magnitude smaller than present-day state-of-the-art observational resolution (~700 km). Aims: To understand coronal heating and correctly interpret observations it is crucial to study the thermodynamics of such a system in which energy is deposited at unresolved small-scales. Methods: Fully compressible three-dimensional magnetohydrodynamic simulations were carried out to understand the thermodynamics of coronal heating in the magnetically confined solar corona. Results: We show that temperature is highly structured at scales below observational resolution. It is also nonhomogeneously distributed so that only a fraction of the coronal mass and volume is heated at each time. Conclusions: This is a multi-thermal system in which hotter and cooler plasma strands are also found next to each other at sub-resolution scales and exhibit a temporal dynamics.
NEW ACTIVE MEDIA AND ELEMENTS OF LASER SYSTEMS: Laser with resonators coupled by a dynamic hologram
NASA Astrophysics Data System (ADS)
Gerasimov, V. B.; Golyanov, A. V.; Luk'yanchuk, B. S.; Ogluzdin, Valerii E.; Rubtsova, I. L.; Sugrobov, V. A.; Khizhnyak, A. I.
1987-11-01
The nature of operation of a laser with a phase-conjugate mirror utilizing multibeam interaction was found to have a considerable influence on the coupling of its resonator to the resonator of a laser used to pump the mirror. A system of this kind with resonators coupled by a dynamic hologram exhibited "soft" lasing in the presence of a self-pumped phase-conjugate mirror.
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.
A dynamical mechanism for large volumes with consistent couplings
NASA Astrophysics Data System (ADS)
Abel, Steven
2016-11-01
A mechanism for addressing the "decompactification problem" is proposed, which consists of balancing the vacuum energy in Scherk-Schwarzed theories against contributions coming from non-perturbative physics. Universality of threshold corrections ensures that, in such situations, the stable minimum will have consistent gauge couplings for any gauge group that shares the same N = 2 beta function for the bulk excitations as the gauge group that takes part in the minimisation. Scherk-Schwarz compactification from 6D to 4D in heterotic strings is discussed explicitly, together with two alternative possibilities for the non-perturbative physics, namely metastable SQCD vacua and a single gaugino condensate. In the former case, it is shown that modular symmetries gives various consistency checks, and allow one to follow soft-terms, playing a similar role to R-symmetry in global SQCD. The latter case is particularly attractive when there is nett Bose-Fermi degeneracy in the massless sector. In such cases, because the original Casimir energy is generated entirely by excited and/or non-physical string modes, it is completely immune to the non-perturbative IR physics. Such a separation between UV and IR contributions to the potential greatly simplifies the analysis of stabilisation, and is a general possibility that has not been considered before.
Dynamically Active Compartments Coupled by a Stochastically Gated Gap Junction
NASA Astrophysics Data System (ADS)
Bressloff, Paul C.; Lawley, Sean D.
2017-03-01
We analyze a one-dimensional PDE-ODE system representing the diffusion of signaling molecules between two cells coupled by a stochastically gated gap junction. We assume that signaling molecules diffuse within the cytoplasm of each cell and then either bind to some active region of the cell's membrane (treated as a well-mixed compartment) or pass through the gap junction to the interior of the other cell. We treat the gap junction as a randomly fluctuating gate that switches between an open and a closed state according to a two-state Markov process. This means that the resulting PDE-ODE is stochastic due to the presence of a randomly switching boundary in the interior of the domain. It is assumed that each membrane compartment acts as a conditional oscillator, that is, it sits below a supercritical Hopf bifurcation. In the ungated case (gap junction always open), the system supports diffusion-induced oscillations, in which the concentration of signaling molecules within the two compartments is either in-phase or anti-phase. The presence of a reflection symmetry (for identical cells) means that the stochastic gate only affects the existence of anti-phase oscillations. In particular, there exist parameter choices where the gated system supports oscillations, but the ungated system does not, and vice versa. The existence of oscillations is investigated by solving a spectral problem obtained by averaging over realizations of the stochastic gate.
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.
Street Canyon Atmospheric Composition: Coupling Dynamics and Chemistry
NASA Astrophysics Data System (ADS)
Bright, V.; Bloss, W. J.; Cai, X.
2010-12-01
Atmospheric composition within the urban environment, particularly within street canyons (formed by a road running between two rows of buildings), has a direct effect on the air quality of an environment in which a large majority of people live and work. The composition of air within a street canyon is determined by the composition of background air mixed in from above, advection of air into and out of the canyon, vehicle exhaust and other emissions from within the street, together with the mixing and chemical processing of pollutants within the canyon. This occurs on a timescale of a few seconds to minutes and as a result, within-canyon atmospheric processes can have a significant effect on atmospheric composition on such timescales. This paper outlines a modelling study of street canyon atmospheric composition, integrating the combined effects of emissions, dynamics and chemistry. This work builds upon an existing dynamical model of canyon atmospheric motion (Large Eddy Simulation (LES) model) by adding a detailed chemical reaction scheme. Previous studies have considered basic NOx-O3 cycles with only a small number of chemical reactions included. Initially, a zero-dimensional box model was used to develop and assess the accuracy of a suitable reduced chemical scheme to be included within the LES. The reduced chemical scheme, based upon a subset of the Master Chemical Mechanism (MCM), includes 51 chemical species and 136 reactions. Vehicle emissions taken from the UK National Atmospheric Emissions Inventory (NAEI) were subsequently added to the box model. These elements were then combined with the canyon dynamics simulated by the Large Eddy Simulation (LES) model. Results demonstrate that the enhanced model is a suitable tool to be used to further investigate the combined effects of mixing and chemical processing upon air quality within the street canyon. Subsequently, a number of key questions relating to urban atmospheric composition are addressed using the
Dynamics and bifurcations of a coupled column-pendulum oscillator
NASA Astrophysics Data System (ADS)
Mustafa, G.; Ertas, A.
1995-05-01
This study deals with the dynamics of a large flexible column with a tip mass-pendulum arrangement. The system is a conceptualization of a vibration-absorbing device for flexible structures with tip appendages. The bifurcation diagrams of the averaged system indicate that the system loses stability via two distinct routes; one leading to a saddle-node bifurcation, and the other to the Hopf bifurcation, indicating the existence of an invariant torus. Under the change of forcing amplitude, these bifurcations coalesce. This phenomenon has important global ramifications, in the sense that the periodic modulations associated with the Hopf bifurcation tend to have an infinite period, a strong indicator of existence of homoclinic orbits. The system also possesses isolated solutions (the so-called "isolas") that form isolated loops bounded away from zero. As the forcing amplitude is varied, the isolas appear, disappear or coalesce with the regular solution branches. The response curves indicate that the column amplitude shows saturation and the pendulum acts as a vibration absorber. However, there is also a frequency range over which a reverse flow of energy occurs, where the pendulum shows reduced amplitude at the cost of large amplitudes of the column. The experimental dynamics shows that the periodic motion gives rise to a quasi-periodic response, confirming the existence of tori. Within the quasi-periodic region, there are windows containing intricate webs of mode-locked periodic responses. An increase in the force amplitude causes the tori to break up, a phenomenon similar to the onset of turbulence in hydrodynamics.
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.
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.
NASA Astrophysics Data System (ADS)
Grooms, Ian; Julien, Keith; Fox-Kemper, Baylor
2010-11-01
The planetary geostrophic (PG) equations for large-scale oceanic flow are linked to the quasigeostrophic (QG) equations for mesoscale flow in a multiple-scales asymptotic expansion. The model describes the coupling of planetary-scale and mesoscale dynamics: eddy kinetic energy is generated by baroclinic instability of the planetary flow, and the resulting eddy buoyancy fluxes feed back on the planetary flow. Anisotropy of the planetary flow is seen to play a key role in allowing the two-way coupling. The resulting equations are amenable to theoretical and computational investigation of the interaction of mesoscale and planetary scale dynamics.
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
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.
New coupling limits, dynamical symmetries and microscopic operators of IBM/TQM
Paar, V.
1985-01-15
A new particle-core basis having approximate supersymmetric (SUSY) features associated with SU(3) dynamical symmetry is introduced. The SUSY and CO-SUSY limits of IBFM/PTQM appear for the characteristic intermediate coupling strengths GAMMA/delta = +- (GAMMA/delta)/sub SUSY/. The CO-SUSY limit is a truncated analog of the Stephens rotation-aligned scheme. A paradox was found in the relation of the SUSY and truncated strong coupling (TSC) limits to the strong coupling limit of the Bohr-Mottelson model.
Coupling dynamics of Nb/Nb2O5 relaxation oscillators.
Li, Shuai; Liu, Xinjun; Nandi, Sanjoy Kumar; Venkatachalam, Dinesh Kumar; Elliman, Robert Glen
2017-03-24
The coupling dynamics of capacitively coupled Nb/Nb2O5 relaxation oscillators are shown to exhibit rich collective behaviour depending on the negative differential resistance response of the individual devices, the operating voltage and the coupling capacitance. These coupled oscillators are shown to exhibit stable frequency and phase locking states at source voltages as low as 2.2 V, with frequency control in the range from 0.85 to 16.2 MHz and frequency tunability of ∼8 MHz V(-1). The experimental realisation of such compact, scalable and low power coupled-oscillator systems is of particular significance for the development and implementation of large oscillator networks in non-Boolean computing architectures.
Coupling dynamics of Nb/Nb2O5 relaxation oscillators
NASA Astrophysics Data System (ADS)
Li, Shuai; Liu, Xinjun; Nandi, Sanjoy Kumar; Venkatachalam, Dinesh Kumar; Elliman, Robert Glen
2017-03-01
The coupling dynamics of capacitively coupled Nb/Nb2O5 relaxation oscillators are shown to exhibit rich collective behaviour depending on the negative differential resistance response of the individual devices, the operating voltage and the coupling capacitance. These coupled oscillators are shown to exhibit stable frequency and phase locking states at source voltages as low as 2.2 V, with frequency control in the range from 0.85 to 16.2 MHz and frequency tunability of ∼8 MHz V–1. The experimental realisation of such compact, scalable and low power coupled-oscillator systems is of particular significance for the development and implementation of large oscillator networks in non-Boolean computing architectures.
Dynamic interactions mediated by nonredundant signaling mechanisms couple circadian clock neurons.
Evans, Jennifer A; Leise, Tanya L; Castanon-Cervantes, Oscar; Davidson, Alec J
2013-11-20
Interactions among suprachiasmatic nucleus (SCN) neurons are required for robust circadian rhythms entrained to local time. To investigate these signaling mechanisms, we developed a functional coupling assay that uniquely captures the dynamic process by which SCN neurons interact. As a population, SCN neurons typically display synchronized rhythms with similar peak times, but will peak 6-12 hr apart after in vivo exposure to long days. Once they are removed from these conditions, SCN neurons resynchronize through a phase-dependent coupling process mediated by both vasoactive intestinal polypeptide (VIP) and GABAA signaling. Notably, GABAA signaling contributes to coupling when the SCN network is in an antiphase configuration, but opposes synchrony under steady-state conditions. Further, VIP acts together with GABAA signaling to couple the network in an antiphase configuration, but promotes synchrony under steady-state conditions by counteracting the actions of GABAA signaling. Thus, SCN neurons interact through nonredundant coupling mechanisms influenced by the state of the network.
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.
NASA Astrophysics Data System (ADS)
Tchakui, Murielle Vanessa; Woafo, Paul
2016-11-01
This work deals with the dynamics of three unidirectionally coupled Duffing oscillators and that of three coupled piezoelectric actuators, considering the special case of inchworm motors. Two configurations of the network are studied: ring configuration and chain configuration. The effects of the coupling coefficient and the time delay are analyzed through different bifurcation diagrams and phase difference variation. It is shown that varying the coupling coefficient and the time delay leads to the appearance of different dynamical behaviors: steady states, periodic and quasiperiodic oscillations, chaos, and phase synchronization.
Tchakui, Murielle Vanessa; Woafo, Paul
2016-11-01
This work deals with the dynamics of three unidirectionally coupled Duffing oscillators and that of three coupled piezoelectric actuators, considering the special case of inchworm motors. Two configurations of the network are studied: ring configuration and chain configuration. The effects of the coupling coefficient and the time delay are analyzed through different bifurcation diagrams and phase difference variation. It is shown that varying the coupling coefficient and the time delay leads to the appearance of different dynamical behaviors: steady states, periodic and quasiperiodic oscillations, chaos, and phase synchronization.
Dynamical strong coupling and parametric amplification of mechanical modes of graphene drums
NASA Astrophysics Data System (ADS)
Mathew, John P.; Patel, Raj N.; Borah, Abhinandan; Vijay, R.; Deshmukh, Mandar M.
2016-09-01
Mechanical resonators are ubiquitous in modern information technology. With the possibility of coupling them to electromagnetic and plasmonic modes, they hold promise as the key building blocks in future quantum information technology. Graphene-based resonators are of interest for technological applications due to their high resonant frequencies, multiple mechanical modes and low mass. The tension-mediated nonlinear coupling between various modes of the resonator can be excited in a controllable manner. Here we engineer a graphene resonator with large frequency tunability at low temperatures, resulting in a large intermodal coupling strength. We observe the emergence of new eigenmodes and amplification of the coupled modes using red and blue parametric excitation, respectively. We demonstrate that the dynamical intermodal coupling is tunable. A cooperativity of 60 between two resonant modes of ∼100 MHz is achieved in the strong coupling regime. The ability to dynamically control the coupling between the high-frequency eigenmodes of a mechanical system opens up the possibility of quantum mechanical experiments at low temperatures.
Dynamical strong coupling and parametric amplification of mechanical modes of graphene drums.
Mathew, John P; Patel, Raj N; Borah, Abhinandan; Vijay, R; Deshmukh, Mandar M
2016-09-01
Mechanical resonators are ubiquitous in modern information technology. With the possibility of coupling them to electromagnetic and plasmonic modes, they hold promise as the key building blocks in future quantum information technology. Graphene-based resonators are of interest for technological applications due to their high resonant frequencies, multiple mechanical modes and low mass. The tension-mediated nonlinear coupling between various modes of the resonator can be excited in a controllable manner. Here we engineer a graphene resonator with large frequency tunability at low temperatures, resulting in a large intermodal coupling strength. We observe the emergence of new eigenmodes and amplification of the coupled modes using red and blue parametric excitation, respectively. We demonstrate that the dynamical intermodal coupling is tunable. A cooperativity of 60 between two resonant modes of ∼100 MHz is achieved in the strong coupling regime. The ability to dynamically control the coupling between the high-frequency eigenmodes of a mechanical system opens up the possibility of quantum mechanical experiments at low temperatures.
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
Local Dynamics and Global Size Coupling during Magnetic Reconnection
NASA Astrophysics Data System (ADS)
Jacobson, C. M.; Breslau, J. A.; Jardin, S. C.; Ji, H.
2008-11-01
Magnetic reconnection is an important physical process not only in small systems such as laboratory plasmas, but also in large systems such as solar flares. The reconnection rate increases with resistivity η and decreases with the current sheet length L. Recent experimental results suggest that these parameters are not independent, but anti-correlate such that ηL is kept roughly constant; thus the reconnection rate is a function of both local dynamics and global size [1]. In order to verify these results and further extend the system size, a numerical MHD model [2] is used. This code allows simulation of either two-fluid or single-fluid resistive MHD reconnection of colliding flux tubes on a 2D grid. The resistivity and system size are systematically varied, and scalings of the ion skin depth, collisionality, and reconnection rate due to these quantities are presented. Results are compared to experimental data, and findings are projected to solar flare scales. [1] A. Kuritsyn et al. Geophys. Res. Lett. 34, L16106 (2007) [2] J. A. Breslau and S. C. Jardin, Comput. Phys. Commun. 151, 8 (2003)
Investigations Into Internal and External Aspects of Dynamic Agent-Environment Couplings
NASA Astrophysics Data System (ADS)
Dautenhahn, Kerstin
This paper originates from my work on `social agents'. An issue which I consider important to this kind of research is the dynamic coupling of an agent with its social and non-social environment. I hypothesize `internal dynamics' inside an agent as a basic step towards understanding. The paper therefore focuses on the internal and external dynamics which couple an agent to its environment. The issue of embodiment in animals and artifacts and its relation to `social dynamics' is discussed first. I argue that embodiment is linked to a concept of a body and is not necessarily given when running a control program on robot hardware. I stress the individual characteristics of an embodied cognitive system, as well as its social embeddedness. I outline the framework of a physical-psychological state space which changes dynamically in a self-modifying way as a holistic approach towards embodied human and artificial cognition. This framework is meant to discuss internal and external dynamics of an embodied, natural or artificial agent. In order to stress the importance of a dynamic memory I introduce the concept of an `autobiographical agent'. The second part of the paper gives an example of the implementation of a physical agent, a robot, which is dynamically coupled to its environment by balancing on a seesaw. For the control of the robot a behavior-oriented approach using the dynamical systems metaphor is used. The problem is studied through building a complete and co-adapted robot-environment system. A seesaw which varies its orientation with one or two degrees of freedom is used as the artificial `habitat'. The problem of stabilizing the body axis by active motion on a seesaw is solved by using two inclination sensors and a parallel, behavior-oriented control architecture. Some experiments are described which demonstrate the exploitation of the dynamics of the robot-environment system.
Emergent Dynamics of Sustainability and Resource Equity in Coupled Human Coastline Systems
NASA Astrophysics Data System (ADS)
McNamara, D.; Lazarus, E.; Murray, A. B.; Smith, M.; Gopalakrishnan, S.
2010-12-01
Human influence in the form of dynamical landscape alterations continues to increase on marginal landscapes. A prominent example of this occurs along developed coastlines as humans alter natural coastal processes in an attempt to stabilize eroding shorelines by periodically taking sediment from outside the local coastal system and placing it on the coastline. As this process of beach nourishment alters natural coastal processes, and these alterations affect subsequent beach nourishment decisions along the coast, human and natural dynamics are coupled along developed coastlines. Understanding how long-time scale aspects of the coupled human-coastal system, such as the sustainability of coastline defense and sediment-resource equity, respond to changes in external driving forces, like the rate of sea level rise or storminess, requires an understanding of emergent dynamics that might result from feedbacks in the coupled human-coastal dynamical system. We use a coupled coastal-economic model that simulates erosion from sea level rise, alongshore sediment transport and beach nourishment decisions, to explore a range of feedbacks between human and coastal processes and the resulting emergent dynamics. Results suggest that when the relatively fast time scale processes of diffusive alongshore sediment transport and spatially myopic nourishment decision-making are coupled, increases in the rate of sea level rise can cause feedbacks that destabilize economically optimal nourishment practices into a regime characterized by the emergence of chaotic shoreline evolution. Results also show how feedbacks between slower scale patterns of shoreline change along a cuspate coast similar to North Carolina and large-scale patterns of property value can significantly alter resource equity and sustainability, as the coupled system responds to changing storminess.
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
Cosmological dynamics with non-minimally coupled scalar field and a constant potential function
Hrycyna, Orest; Szydłowski, Marek E-mail: marek.szydlowski@uj.edu.pl
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.
Kong, Xiangrong; Wang, Mei-Cheng; Gray, Ronald
2014-01-01
We consider a specific situation of correlated data where multiple outcomes are repeatedly measured on each member of a couple. Such multivariate longitudinal data from couples may exhibit multi-faceted correlations which can be further complicated if there are polygamous partnerships. An example is data from cohort studies on human papillomavirus (HPV) transmission dynamics in heterosexual couples. HPV is a common sexually transmitted disease with 14 known oncogenic types causing anogenital cancers. The binary outcomes on the multiple types measured in couples over time may introduce inter-type, intra-couple, and temporal correlations. Simple analysis using generalized estimating equations or random effects models lacks interpretability and cannot fully utilize the available information. We developed a hybrid modeling strategy using Markov transition models together with pairwise composite likelihood for analyzing such data. The method can be used to identify risk factors associated with HPV transmission and persistence, estimate difference in risks between male-to-female and female-to-male HPV transmission, compare type-specific transmission risks within couples, and characterize the inter-type and intra-couple associations. Applying the method to HPV couple data collected in a Ugandan male circumcision (MC) trial, we assessed the effect of MC and the role of gender on risks of HPV transmission and persistence. PMID:26195849
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
Bright soliton dynamics in spin orbit-Rabi coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Vinayagam, P. S.; Radha, R.; Bhuvaneswari, S.; Ravisankar, R.; Muruganandam, P.
2017-09-01
We investigate the dynamics of a spin-orbit (SO) coupled BECs in a time dependent harmonic trap and show the dynamical system to be completely integrable by constructing the Lax pair. We then employ gauge transformation approach to witness the rapid oscillations of the condensates for a relatively smaller value of SO coupling in a time independent harmonic trap compared to their counterparts in a transient trap. Keeping track of the evolution of the condensates in a transient trap during its transition from confining to expulsive trap, we notice that they collapse in the expulsive trap. We further show that one can manipulate the scattering length through Feshbach resonance to stretch the lifetime of the confining trap and revive the condensate. Considering a SO coupled state as the initial state, the numerical simulation indicates that the reinforcement of Rabi coupling on SO coupled BECs generates the striped phase of the bright solitons and does not impact the stability of the condensates despite destroying the integrability of the dynamical system.
NASA Astrophysics Data System (ADS)
Butts, Michael; Drews, Martin; Larsen, Morten A. D.; Lerer, Sara; Rasmussen, Søren H.; Grooss, Jesper; Overgaard, Jesper; Refsgaard, Jens C.; Christensen, Ole B.; Christensen, Jens H.
2014-12-01
To improve our understanding of the impacts of feedback between the atmosphere and the terrestrial water cycle including groundwater and to improve the integration of water resource management modelling for climate adaption we have developed a dynamically coupled climate-hydrological modelling system. The OpenMI modelling interface is used to couple a comprehensive hydrological modelling system, MIKE SHE running on personal computers, and a regional climate modelling system, HIRHAM running on a high performance computing platform. The coupled model enables two-way interaction between the atmosphere and the groundwater via the land surface and can represent the lateral movement of water in both the surface and subsurface and their interactions, not normally accounted for in climate models. Meso-scale processes are important for climate in general and rainfall in particular. Hydrological impacts are assessed at the catchment scale, the most important scale for water management. Feedback between groundwater, the land surface and the atmosphere occurs across a range of scales. Recognising this, the coupling was developed to allow dynamic exchange of water and energy at the catchment scale embedded within a larger meso-scale modelling domain. We present the coupling methodology used and describe the challenges in representing the exchanges between models and across scales. The coupled model is applied to one-way and two-way coupled simulations for a managed groundwater-dominated catchment, the Skjern River, Denmark. These coupled model simulations are evaluated against field observations and then compared with uncoupled climate and hydrological model simulations. Exploratory simulations show significant differences, particularly in the summer for precipitation and evapotranspiration the coupled model including groundwater and the RCM where groundwater is neglected. However, the resulting differences in the net precipitation and the catchment runoff in this groundwater
Altered dynamic coupling of lateral occipital complex during visual perception in schizophrenia
Harvey, Philippe-Olivier; Lee, Junghee; Cohen, Mark S.; Engel, Stephen A.; Glahn, David C.; Nuechterlein, Keith H.; Wynn, Jonathan K.; Green, Michael F.
2011-01-01
Introduction There is mounting evidence that visual perception abnormalities in schizophrenia are partly explained by a dysfunction of the lateral occipital complex (LO). We previously demonstrated that schizophrenia patients had broader topography and reduced magnitude of activity of LO. However, the functional connectivity of LO with other brain regions during visual perception has not been directly investigated in schizophrenia. Material and Methods Eighteen patients with schizophrenia and eighteen matched controls performed a backward masking task during functional magnetic resonance imaging (fMRI). Stimulus onset asynchronies were manipulated to change the level of target visibility. To examine connectivity with LO function we conducted psychophysiological interactions (PPI) analyses using: 1) a region of interest (ROI) approach and 2) a whole brain analysis. ROIs were defined based on a contrast of trials on which a target was presented versus null trials in which no stimuli were presented. Results Eleven ROIs were identified. Both groups showed similar strength of coupling between LO and the 11 ROIs when visibility was not taken into account. Healthy controls showed clear changes in coupling between LO and prefrontal and parietal regions as a function of target visibility (higher coupling with more visible targets). In comparison, patients showed reduced dynamic coupling with LO in the right superior frontal gyrus (significant after correcting for multiple comparisons) and a trend for reduced coupling in the left precuneus and left inferior frontal regions. Whole brain analysis identified additional regions that showed dynamic coupling with LO in healthy controls, but not in patients. Discussion The increased coupling between LO and higher-level parietal and prefrontal regions during visual awareness in healthy controls likely reflects visual reentrant processing. The lack of modulation of coupling between LO and key prefrontal and parietal regions found in
NASA Astrophysics Data System (ADS)
Ngai, K. L.; Wang, Li-Min
2011-11-01
Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past tc = 1-2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others had proposed the random Rouse model (RRM) in which each monomer has different mobility taken from a broad log-normal distribution. Despite the success of the RRM, Diddens et al. [Eur. Phys. Lett. 95, 56003 (2011)] extracted the distribution of friction coefficients from the MD simulations of a PEO/PMMA blend and found that the distribution is much narrower than expected from the RRM. We propose a simpler alternative explanation of the data by utilizing alone the observed crossover of PEO chain dynamics at tc. The present problem is just a special case of a general property of relaxation in interacting systems, which is the crossover from independent relaxation to coupled many-body relaxation at some tc determined by the interaction potential and intermolecular coupling/constraints. The generality is brought out vividly by pointing out that the crossover also had been observed by neutron scattering from entangled chains relaxation in monodisperse homopolymers, and from the segmental α-relaxation of PEO in blends with PMMA. The properties of all the relaxation processes in connection with the crossover are similar, despite the length scales of the relaxation in these systems are widely different.
Ngai, K L; Wang, Li-Min
2011-11-21
Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past t(c) = 1-2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others had proposed the random Rouse model (RRM) in which each monomer has different mobility taken from a broad log-normal distribution. Despite the success of the RRM, Diddens et al. [Eur. Phys. Lett. 95, 56003 (2011)] extracted the distribution of friction coefficients from the MD simulations of a PEO/PMMA blend and found that the distribution is much narrower than expected from the RRM. We propose a simpler alternative explanation of the data by utilizing alone the observed crossover of PEO chain dynamics at t(c). The present problem is just a special case of a general property of relaxation in interacting systems, which is the crossover from independent relaxation to coupled many-body relaxation at some t(c) determined by the interaction potential and intermolecular coupling/constraints. The generality is brought out vividly by pointing out that the crossover also had been observed by neutron scattering from entangled chains relaxation in monodisperse homopolymers, and from the segmental α-relaxation of PEO in blends with PMMA. The properties of all the relaxation processes in connection with the crossover are similar, despite the length scales of the relaxation in these systems are widely different.
New Iterative Method for Fractional Gas Dynamics and Coupled Burger's Equations
2015-01-01
This paper presents the approximate analytical solutions to solve the nonlinear gas dynamics and coupled Burger's equations with fractional time derivative. By using initial values, the explicit solutions of the equations are solved by using a reliable algorithm. Numerical results show that the new iterative method is easy to implement and accurate when applied to time-fractional partial differential equations. PMID:25884018
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.
New iterative method for fractional gas dynamics and coupled Burger's equations.
Al-Luhaibi, Mohamed S
2015-01-01
This paper presents the approximate analytical solutions to solve the nonlinear gas dynamics and coupled Burger's equations with fractional time derivative. By using initial values, the explicit solutions of the equations are solved by using a reliable algorithm. Numerical results show that the new iterative method is easy to implement and accurate when applied to time-fractional partial differential equations.
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…
Light-Quark Baryon Spectroscopy from ANL-Osaka Dynamical Coupled-Channels Analysis
NASA Astrophysics Data System (ADS)
Kamano, Hiroyuki
We review our recent efforts for determining resonance parameters associated with light-quark baryons (N*,Δ *,Λ *,Σ *) through comprehensive analyses of various meson production reactions off the nucleon within the ANL-Osaka dynamical coupled-channels approach.
The Dynamics of Small-Sized Ensembles of the Phase-Locked Loops with Unidirectional Couplings
NASA Astrophysics Data System (ADS)
Aleshin, K. N.; V. Matrosov, V.; Shalfeev, V. D.
2016-06-01
We study collective dynamics of a small-sized chain of the unidirectionally coupled phase-locked loop. The conditions for the synchronous-regime existence are found, the asynchronous selfoscillation regimes and the transitions among them are studied, and the property of inheriting the structure of the parameter space of the chain when a new element is added to it is established.
NASA Astrophysics Data System (ADS)
Strickler, Trevor; McQuillen, Patrick; Langin, Thomas; Killian, Thomas; Bannasch, Georg; Pohl, Thomas
2014-05-01
Collision rates in weakly-coupled plasmas are well-described by the Landau-Spitzer formula. In the regime of strong coupling, however, the formula breaks down. This has motivated much theoretical and experimental work to study collision rates in strongly-coupled plasmas. In previous work, we have demonstrated direct measurements of thermalization rates in strongly-coupled ultracold neutral plasmas (UCNPs) created by photoionizing strontium atoms in magneto-optical trap. Our technique used optical pumping to create spin ``tagged'' subpopulations of ions having skewed velocity distributions. With LIF imaging, we measured the equilibration of the skewed velocity profiles to extract ion collision rates. We are now using these techniques to explore the early time dynamics of these skewed ion velocity distributions in the first 100ns after optical pumping. Molecular dynamics simulations of strongly coupled plasmas predict deviations from the exponential decay of average skewed velocity that is expected for weakly coupled plasmas. We use probe laser pulses on the order of 30ns to measure the relaxation of the skewed velocity profiles to test the theoretical predictions. This work was supported by the United States National Science Foun- dation and Department of Energy Partnership in Basic Plasma Science and Engineering (PHY-1102516) and the Air Force Office of Scientific Research (FA9550-12-1-0267).
NASA Astrophysics Data System (ADS)
Meng, Deshan; Wang, Xueqian; Xu, Wenfu; Liang, Bin
2017-05-01
For a space robot with flexible appendages, vibrations of flexible structure can be easily excited during both orbit and/or attitude maneuvers of the base and the operation of the manipulators. Hence, the pose (position and attitude) of the manipulator's end-effector will greatly deviate from the desired values, and furthermore, the motion of the manipulator will trigger and exacerbate vibrations of flexible appendages. Given lack of the atmospheric damping in orbit, the vibrations will last for quite a while and cause the on-orbital tasks to fail. We derived the rigid-flexible coupling dynamics of a space robot system with flexible appendages and established a coupling model between the flexible base and the space manipulator. A specific index was defined to measure the coupling degree between the flexible motion of the appendages and the rigid motion of the end-effector. Then, we analyzed the dynamic coupling for different conditions, such as modal displacements, joint angles (manipulator configuration), and mass properties. Moreover, the coupling map was adopted and drawn to represent the coupling motion. Based on this map, a trajectory planning method was addressed to suppress structure vibration. Finally, simulation studies of typical cases were performed, which verified the proposed models and method. This work provides a theoretic basis for the system design, performance evaluation, trajectory planning, and control of such space robots.
Tang, Jinghua; McGrath, Michael; Laszczak, Piotr; Jiang, Liudi; Bader, Dan L; Moser, David; Zahedi, Saeed
2015-12-01
Design and fitting of artificial limbs to lower limb amputees are largely based on the subjective judgement of the prosthetist. Understanding the science of three-dimensional (3D) dynamic coupling at the residuum/socket interface could potentially aid the design and fitting of the socket. A new method has been developed to characterise the 3D dynamic coupling at the residuum/socket interface using 3D motion capture based on a single case study of a trans-femoral amputee. The new model incorporated a Virtual Residuum Segment (VRS) and a Socket Segment (SS) which combined to form the residuum/socket interface. Angular and axial couplings between the two segments were subsequently determined. Results indicated a non-rigid angular coupling in excess of 10° in the quasi-sagittal plane and an axial coupling of between 21 and 35 mm. The corresponding angular couplings of less than 4° and 2° were estimated in the quasi-coronal and quasi-transverse plane, respectively. We propose that the combined experimental and analytical approach adopted in this case study could aid the iterative socket fitting process and could potentially lead to a new socket design.
Mean-field dynamics of spin-orbit coupled Bose-Einstein condensates.
Zhang, Yongping; Mao, Li; Zhang, Chuanwei
2012-01-20
Spin-orbit coupling (SOC), the interaction between the spin and momentum of a quantum particle, is crucial for many important condensed matter phenomena. The recent experimental realization of SOC in neutral bosonic cold atoms provides a new and ideal platform for investigating spin-orbit coupled quantum many-body physics. In this Letter, we derive a generic Gross-Pitaevskii equation as the starting point for the study of many-body dynamics in spin-orbit coupled Bose-Einstein condensates. We show that different laser setups for realizing the same SOC may lead to different mean-field dynamics. Various ground state phases (stripe, phase separation, etc.) of the condensate are found in different parameter regions. A new oscillation period induced by the SOC, similar to the Zitterbewegung oscillation, is found in the center-of-mass motion of the condensate.
Exact non-Markovian dynamics of qubits coupled to two interacting environments
NASA Astrophysics Data System (ADS)
Shen, H. Z.; Li, D. X.; Su, Shi-Lei; Zhou, Y. H.; Yi, X. X.
2017-09-01
As the memory effect may be helpful in quantum information processing, non-Markovian dynamics plays an important role in the description of many-body open systems. Among these topics, the system consisting of independent qubits interacting with several coupled environments is of particular interest. In this paper, we study the exact non-Markovian dynamics of two independent qubits. Each of the qubits interacts individually with its environment, and these two environments coupled with each other. We investigate the non-Markovianity measure of the system for the whole parameter regime without the rotating-wave approximation (RWA) and compare the results with that under the RWA. We find that the non-Markovianity measure for two qubits manifests a transition from a non-Markovian to Markovian regime regardless of the coupling strength between the environments. The physical origin of this transition is revealed, and a possible observation of the prediction in superconducting quantum interference devices is discussed.
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.
Male Same Sex Couple Dynamics and Received Social Support for HIV Medication Adherence
Wrubel, Judith; Stumbo, Scott; Johnson, Mallory O.
2010-01-01
This qualitative study examines received social support by analyzing relationship dynamics concerning antiretroviral therapy (ART) adherence among HIV+ seroconcordant and serodiscordant male couples. Using narrative data from forty participants (20 couples interviewed separately), we describe patterns of relationship dynamics and support preferences. One group viewed adherence as a Personal Responsibility. A second group viewed adherence as a Couple Responsibility and integrated support for medication adherence into the relationship. A third group was in the process of ending their relationships and adherence support was one-sided or withdrawn altogether. Examining support exchanges contexts at cultural, situational, relational, and personal levels illuminated adherence processes. Qualitative methods provided a framework for investigating these complex relationships and their associations with HIV treatment adherence. PMID:20651943
Stable collective dynamics of two-level systems coupled by dipole interactions
NASA Astrophysics Data System (ADS)
Parmee, C. D.; Cooper, N. R.
2017-03-01
We study the dynamics of a set of two-level systems coupled by dipolar interactions under a resonant external Rabi drive. The two-level systems are prepared initially in a coherent product state, and we ask how the nonequilibrium conditions caused by the drive affect this coherence. We study the full nonlinear dynamics of the coupled two-level systems within a classical approximation by analyzing numerically the equations of motion and determining the stability of the collective coherent state within classical Floquet theory. We establish the behavior analytically in the high Rabi coupling limit by employing a Magnus expansion and spin-wave analysis. Our results show that, typically, the dipole interactions between the two-level systems lead to instabilities that cause a breakdown of the collective Rabi oscillations. However, we identify parameter regimes for which the two-level systems undergo collective coherent Rabi oscillations even in the presence of the dipole interactions.
From synchronous to one-time delayed dynamics in coupled maps
NASA Astrophysics Data System (ADS)
Anteneodo, Celia; González-Avella, Juan Carlos; Vallejos, Raúl O.
2017-06-01
We study the completely synchronized states (CSSs) of a system of coupled logistic maps as a function of three parameters: interaction strength (ɛ ), range of the interaction (α ), that can vary from first neighbors to global coupling, and a parameter (β ) that allows one to scan continuously from nondelayed to one-time delayed dynamics. In the α -ɛ plane we identify periodic orbits, limit cycles, and chaotic trajectories, and describe how these structures change with delay. These features can be explained by studying the bifurcation diagrams of a two-dimensional nondelayed map. This allows us to understand the effects of one-time delays on CSSs, e.g., regularization of chaotic orbits and synchronization of short-range coupled maps, observed when the dynamics is moderately delayed. Finally, we substitute the logistic map with cubic and logarithmic maps, in order to test the robustness of our findings.
Mean-Field Dynamics of Spin-Orbit Coupled Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Zhang, Yongping; Mao, Li; Zhang, Chuanwei
2012-01-01
Spin-orbit coupling (SOC), the interaction between the spin and momentum of a quantum particle, is crucial for many important condensed matter phenomena. The recent experimental realization of SOC in neutral bosonic cold atoms provides a new and ideal platform for investigating spin-orbit coupled quantum many-body physics. In this Letter, we derive a generic Gross-Pitaevskii equation as the starting point for the study of many-body dynamics in spin-orbit coupled Bose-Einstein condensates. We show that different laser setups for realizing the same SOC may lead to different mean-field dynamics. Various ground state phases (stripe, phase separation, etc.) of the condensate are found in different parameter regions. A new oscillation period induced by the SOC, similar to the Zitterbewegung oscillation, is found in the center-of-mass motion of the condensate.
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.
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.
Dynamically Maintained Spike Timing Sequences in Networks of Pulse-Coupled Oscillators with Delays
NASA Astrophysics Data System (ADS)
Gong, Pulin; van Leeuwen, Cees
2007-01-01
We demonstrate the widespread occurrence of dynamically maintained spike timing sequences in recurrent networks of pulse-coupled spiking neurons with large time delays. The sequences occur in transient, quasistable phase-locking states. The system spontaneously jumps between these states. This collective dynamics enables the system to generate a large number of distinct precise spike timing sequences. Distributed time delays play a constructive role by enhancing the dominance in parameter space of the dynamics responsible for producing the large variety of spike timing sequences.
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.
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
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.
Molecular dynamics simulation with weak coupling to heat and material baths
NASA Astrophysics Data System (ADS)
Eslami, Hossein; Mojahedi, Fatemeh; Moghadasi, Jalil
2010-08-01
A method for performing molecular dynamics simulation in the grand canonical ensemble is developed. The molecular dynamics, with coupling to an external bath, simulation method of [Berendsen et al., J. Chem. Phys. 81, 3684 (1984)] is extended for this purpose. Here the physical system of interest consists of real indistinguishable particles plus one fractional particle, whose potential energy of interaction with the rest of particles is scaled by a coupling parameter, ranging dynamically between zero and one. This coupling changes the number of particles in the system gradually and dynamically, depending on the target values of the excess chemical potential, temperature, and volume. A nonlinear scaling scheme has been adopted to scale the potential energy of interaction of the fractional particle with the rest of the system. The method has been employed to predict the density of compressed Lennard-Jones fluid, compatible with the target values of temperature and the excess chemical potential, over a wide range of temperatures and densities. The method has further been applied to do molecular dynamics simulation in the grand canonical ensemble for water and to predict its vapor-liquid phase coexistence point. The results obtained using this method are in complete agreement with previously reported results in the literature.
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.
Horikawa, Yo
2016-04-01
Metastable dynamical transient patterns in arrays of bidirectionally coupled neurons with self-coupling and asymmetric output were studied. First, an array of asymmetric sigmoidal neurons with symmetric inhibitory bidirectional coupling and self-coupling was considered and the bifurcations of its steady solutions were shown. Metastable dynamical transient spatially nonuniform states existed in the presence of a pair of spatially symmetric stable solutions as well as unstable spatially nonuniform solutions in a restricted range of the output gain of a neuron. The duration of the transients increased exponentially with the number of neurons up to the maximum number at which the spatially nonuniform steady solutions were stabilized. The range of the output gain for which they existed reduced as asymmetry in a sigmoidal output function of a neuron increased, while the existence range expanded as the strength of inhibitory self-coupling increased. Next, arrays of spiking neuron models with slow synaptic inhibitory bidirectional coupling and self-coupling were considered with computer simulation. In an array of Class 1 Hindmarsh-Rose type models, in which each neuron showed a graded firing rate, metastable dynamical transient firing patterns were observed in the presence of inhibitory self-coupling. This agreed with the condition for the existence of metastable dynamical transients in an array of sigmoidal neurons. In an array of Class 2 Bonhoeffer-van der Pol models, in which each neuron had a clear threshold between firing and resting, long-lasting transient firing patterns with bursting and irregular motion were observed.
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)
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
Chaotic dynamics of a Bose-Einstein condensate coupled to a qubit.
Martin, J; Georgeot, B; Shepelyansky, D L
2009-06-01
We study numerically the coupling between a qubit and a Bose-Einstein condensate (BEC) moving in a kicked optical lattice using Gross-Pitaevskii equation. In the regime where the BEC size is smaller than the lattice period, the chaotic dynamics of the BEC is effectively controlled by the qubit state. The feedback effects of the nonlinear chaotic BEC dynamics preserve the coherence and purity of the qubit in the regime of strong BEC nonlinearity. This gives an example of an exponentially sensitive control over a macroscopic state by internal qubit states. At weak nonlinearity quantum chaos leads to rapid dynamical decoherence of the qubit. The realization of such coupled systems is within reach of current experimental techniques.
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.
Microtubule dynamic instability: A new model with coupled GTP hydrolysis and multistep catastrophe
Bowne-Anderson, Hugo; Zanic, Marija; Kauer, Monika; Howard, Jonathon
2013-01-01
A key question in understanding microtubule dynamics is how GTP hydrolysis leads to catastrophe, the switch from slow growth to rapid shrinkage. We first provide a review of the experimental and modeling literature, and then present a new model of microtubule dynamics. We demonstrate that vectorial, random, and coupled hydrolysis mechanisms are not consistent with the dependence of catastrophe on tubulin concentration and show that, although single-protofilament models can explain many features of dynamics, they do not describe catastrophe as a multistep process. Finally, we present a new combined (coupled plus random hydrolysis) multiple-protofilament model that is a simple, analytically solvable generalization of a single-protofilament model. This model accounts for the observed lifetimes of growing microtubules, the delay to catastrophe following dilution and describes catastrophe as a multistep process. PMID:23532586
Automatic network coupling analysis for dynamical systems based on detailed kinetic models.
Lebiedz, Dirk; Kammerer, Julia; Brandt-Pollmann, Ulrich
2005-10-01
We introduce a numerical complexity reduction method for the automatic identification and analysis of dynamic network decompositions in (bio)chemical kinetics based on error-controlled computation of a minimal model dimension represented by the number of (locally) active dynamical modes. Our algorithm exploits a generalized sensitivity analysis along state trajectories and subsequent singular value decomposition of sensitivity matrices for the identification of these dominant dynamical modes. It allows for a dynamic coupling analysis of (bio)chemical species in kinetic models that can be exploited for the piecewise computation of a minimal model on small time intervals and offers valuable functional insight into highly nonlinear reaction mechanisms and network dynamics. We present results for the identification of network decompositions in a simple oscillatory chemical reaction, time scale separation based model reduction in a Michaelis-Menten enzyme system and network decomposition of a detailed model for the oscillatory peroxidase-oxidase enzyme system.
Probing the equilibrium dynamics of colloidal hard spheres above the mode-coupling glass transition.
Brambilla, G; El Masri, D; Pierno, M; Berthier, L; Cipelletti, L; Petekidis, G; Schofield, A B
2009-02-27
We use dynamic light scattering and computer simulations to study equilibrium dynamics and dynamic heterogeneity in concentrated suspensions of colloidal hard spheres. Our study covers an unprecedented density range and spans seven decades in structural relaxation time, tau(alpha0, including equilibrium measurements above phi(c), the location of the glass transition deduced from fitting our data to mode-coupling theory. Instead of falling out of equilibrium, the system remains ergodic above phi(c) and enters a new dynamical regime where tau(alpha) increases with a functional form that was not anticipated by previous experiments, while the amplitude of dynamic heterogeneity grows slower than a power law with tau(alpha), as found in molecular glass formers close to the glass transition.
NASA Astrophysics Data System (ADS)
Qu, K.; Tang, H.
2012-12-01
In order to study many emerging coastal problems such as tidal power generation and its environmental impact, it is urgently needed to develop our capabilities to predict small-scale, fully three dimensional (3D) phenomena in coastal ocean flows, especially those in nearshore regions. A feasible as well as effective approach for the development is a hybrid method that couples different models designed for physics at different scales; a fully 3D fluid dynamics (FDE) model is used to capture local flows, and it is coupled with a geophysical physics fluid dynamics (GFD) model that is employed to predict large-scale background currents. A crucial issue in realizing such coupling is to correctly as well as accurately exchange solutions of the FDE and GFD models at their interfaces. It has been found that frequently artificial oscillations occur at the interfaces, and they may pollute the overall solution for the problems. It is desirable for the coupling algorithms to assure seamless transition between solutions of the two models and no artifacts at the interfaces. In this study, we investigate different treatments including direct interpolation to exchange solutions of the two models at the interfaces, and analyze solution quality and other aspects associated with different algorithms when they are applied to test flows. Discussion will be made on how to improve solution quality towards seamless solution transition at the model interfaces.
Chaotic dynamics of cardioventilatory coupling in humans: effects of ventilatory modes.
Mangin, Laurence; Clerici, Christine; Similowski, Thomas; Poon, Chi-Sang
2009-04-01
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
Synchronization and time shifts of dynamical patterns for mutually delay-coupled fiber ring lasers.
Shaw, Leah B; Schwartz, Ira B; Rogers, Elizabeth A; Roy, Rajarshi
2006-03-01
A pair of coupled erbium doped fiber ring lasers is used to explore the dynamics of coupled spatiotemporal systems. The lasers are mutually coupled with a coupling delay less than the cavity round-trip time. We study synchronization between the two lasers in the experiment and in a delay differential equation model of the system. Because the lasers are internally perturbed by spontaneous emission, we include a noise source in the model to obtain stochastic realizations of the deterministic equations. Both amplitude synchronization and phase synchronization are considered. We use the Hilbert transform to define the phase variable and compute phase synchronization. We find that synchronization increases with coupling strength in the experiment and the model. When the time series from two lasers are time shifted in either direction by the delay time, approximately equal synchronization is frequently observed, so that a clear leader and follower cannot be identified. We define an algorithm to determine which laser leads the other when the synchronization is sufficiently different with one direction of time shift, and statistics of switches in leader and follower are studied. The frequency of switching between leader and follower increases with coupling strength, as might be expected since the lasers mutually influence each other more effectively with stronger coupling.
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.
NASA Astrophysics Data System (ADS)
Lai, Pik-Yin
2017-02-01
Reconstructing network connection topology and interaction strengths solely from measurement of the dynamics of the nodes is a challenging inverse problem of broad applicability in various areas of science and engineering. For a discrete-time step network under noises whose noise-free dynamics is stationary, we derive general analytic results relating the weighted connection matrix of the network to the correlation functions obtained from time-series measurements of the nodes for networks with one-dimensional intrinsic node dynamics. Information about the intrinsic node dynamics and the noise strengths acting on the nodes can also be obtained. Based on these results, we develop a scheme that can reconstruct the above information of the network using only the time-series measurements of node dynamics as input. Reconstruction formulas for higher-dimensional node dynamics are also derived and illustrated with a two-dimensional node dynamics network system. Furthermore, we extend our results and obtain a reconstruction scheme even for the cases when the noise-free dynamics is periodic. We demonstrate that our method can give accurate reconstruction results for weighted directed networks with linear or nonlinear node dynamics of various connection topologies, and with linear or nonlinear couplings.
Mirroring and beyond: coupled dynamics as a generalized framework for modelling social interactions.
Hasson, Uri; Frith, Chris D
2016-05-05
When people observe one another, behavioural alignment can be detected at many levels, from the physical to the mental. Likewise, when people process the same highly complex stimulus sequences, such as films and stories, alignment is detected in the elicited brain activity. In early sensory areas, shared neural patterns are coupled to the low-level properties of the stimulus (shape, motion, volume, etc.), while in high-order brain areas, shared neural patterns are coupled to high-levels aspects of the stimulus, such as meaning. Successful social interactions require such alignments (both behavioural and neural), as communication cannot occur without shared understanding. However, we need to go beyond simple, symmetric (mirror) alignment once we start interacting. Interactions are dynamic processes, which involve continuous mutual adaptation, development of complementary behaviour and division of labour such as leader-follower roles. Here, we argue that interacting individuals are dynamically coupled rather than simply aligned. This broader framework for understanding interactions can encompass both processes by which behaviour and brain activity mirror each other (neural alignment), and situations in which behaviour and brain activity in one participant are coupled (but not mirrored) to the dynamics in the other participant. To apply these more sophisticated accounts of social interactions to the study of the underlying neural processes we need to develop new experimental paradigms and novel methods of data analysis.
Coupled Attitude-Orbit Dynamics and Control for an Electric Sail in a Heliocentric Transfer Mission
Huo, Mingying; Zhao, Jun; Xie, Shaobiao; Qi, Naiming
2015-01-01
The paper discusses the coupled attitude-orbit dynamics and control of an electric-sail-based spacecraft in a heliocentric transfer mission. The mathematical model characterizing the propulsive thrust is first described as a function of the orbital radius and the sail angle. Since the solar wind dynamic pressure acceleration is induced by the sail attitude, the orbital and attitude dynamics of electric sails are coupled, and are discussed together. Based on the coupled equations, the flight control is investigated, wherein the orbital control is studied in an optimal framework via a hybrid optimization method and the attitude controller is designed based on feedback linearization control. To verify the effectiveness of the proposed control strategy, a transfer problem from Earth to Mars is considered. The numerical results show that the proposed strategy can control the coupled system very well, and a small control torque can control both the attitude and orbit. The study in this paper will contribute to the theory study and application of electric sail. PMID:25950179
Coupled attitude-orbit dynamics and control for an electric sail in a heliocentric transfer mission.
Huo, Mingying; Zhao, Jun; Xie, Shaobiao; Qi, Naiming
2015-01-01
The paper discusses the coupled attitude-orbit dynamics and control of an electric-sail-based spacecraft in a heliocentric transfer mission. The mathematical model characterizing the propulsive thrust is first described as a function of the orbital radius and the sail angle. Since the solar wind dynamic pressure acceleration is induced by the sail attitude, the orbital and attitude dynamics of electric sails are coupled, and are discussed together. Based on the coupled equations, the flight control is investigated, wherein the orbital control is studied in an optimal framework via a hybrid optimization method and the attitude controller is designed based on feedback linearization control. To verify the effectiveness of the proposed control strategy, a transfer problem from Earth to Mars is considered. The numerical results show that the proposed strategy can control the coupled system very well, and a small control torque can control both the attitude and orbit. The study in this paper will contribute to the theory study and application of electric sail.
NASA Astrophysics Data System (ADS)
Addari, D.; Aglietti, G. S.; Remedia, M.
2017-01-01
Microvibrations of a satellite reaction wheel assembly are commonly analysed in either hard-mounted or coupled boundary conditions, though coupled wheel-to-structure disturbance models are more representative of the real environment in which the wheel operates. This article investigates the coupled microvibration dynamics of a cantilever configured reaction wheel assembly mounted on either a stiff or flexible platform. Here a method is presented to cope with modern project necessities: (i) need of a model which gives accurate estimates covering a wide frequency range; (ii) reduce the personnel and time costs derived from the test campaign, (iii) reduce the computational effort without affecting the quality of the results. The method involves measurements of the disturbances induced by the reaction wheel assembly in a hard-mounted configuration and of the frequency and speed dependent dynamic mass of the reaction wheel. In addition, it corrects the approximation due to missing speed dependent dynamic mass in conventional reaction wheel assembly microvibration analysis. The former was evaluated experimentally using a previously designed and validated platform. The latter, on the other hand, was estimated analytically using a finite element model of the wheel assembly. Finally, the validation of the coupled wheel-structure disturbance model is presented, giving indication of the level of accuracy that can be achieved with this type of analyses.
Mirroring and beyond: coupled dynamics as a generalized framework for modelling social interactions
Hasson, Uri; Frith, Chris D.
2016-01-01
When people observe one another, behavioural alignment can be detected at many levels, from the physical to the mental. Likewise, when people process the same highly complex stimulus sequences, such as films and stories, alignment is detected in the elicited brain activity. In early sensory areas, shared neural patterns are coupled to the low-level properties of the stimulus (shape, motion, volume, etc.), while in high-order brain areas, shared neural patterns are coupled to high-levels aspects of the stimulus, such as meaning. Successful social interactions require such alignments (both behavioural and neural), as communication cannot occur without shared understanding. However, we need to go beyond simple, symmetric (mirror) alignment once we start interacting. Interactions are dynamic processes, which involve continuous mutual adaptation, development of complementary behaviour and division of labour such as leader–follower roles. Here, we argue that interacting individuals are dynamically coupled rather than simply aligned. This broader framework for understanding interactions can encompass both processes by which behaviour and brain activity mirror each other (neural alignment), and situations in which behaviour and brain activity in one participant are coupled (but not mirrored) to the dynamics in the other participant. To apply these more sophisticated accounts of social interactions to the study of the underlying neural processes we need to develop new experimental paradigms and novel methods of data analysis PMID:27069044
Spatiotemporal dynamics of a digital phase-locked loop based coupled map lattice system
Banerjee, Tanmoy Paul, Bishwajit; Sarkar, B. C.
2014-03-15
We explore the spatiotemporal dynamics of a coupled map lattice (CML) system, which is realized with a one dimensional array of locally coupled digital phase-locked loops (DPLLs). DPLL is a nonlinear feedback-controlled system widely used as an important building block of electronic communication systems. We derive the phase-error equation of the spatially extended system of coupled DPLLs, which resembles a form of the equation of a CML system. We carry out stability analysis for the synchronized homogeneous solutions using the circulant matrix formalism. It is shown through extensive numerical simulations that with the variation of nonlinearity parameter and coupling strength the system shows transitions among several generic features of spatiotemporal dynamics, viz., synchronized fixed point solution, frozen random pattern, pattern selection, spatiotemporal intermittency, and fully developed spatiotemporal chaos. We quantify the spatiotemporal dynamics using quantitative measures like average quadratic deviation and spatial correlation function. We emphasize that instead of using an idealized model of CML, which is usually employed to observe the spatiotemporal behaviors, we consider a real world physical system and establish the existence of spatiotemporal chaos and other patterns in this system. We also discuss the importance of the present study in engineering application like removal of clock-skew in parallel processors.
Spatiotemporal dynamics of a digital phase-locked loop based coupled map lattice system.
Banerjee, Tanmoy; Paul, Bishwajit; Sarkar, B C
2014-03-01
We explore the spatiotemporal dynamics of a coupled map lattice (CML) system, which is realized with a one dimensional array of locally coupled digital phase-locked loops (DPLLs). DPLL is a nonlinear feedback-controlled system widely used as an important building block of electronic communication systems. We derive the phase-error equation of the spatially extended system of coupled DPLLs, which resembles a form of the equation of a CML system. We carry out stability analysis for the synchronized homogeneous solutions using the circulant matrix formalism. It is shown through extensive numerical simulations that with the variation of nonlinearity parameter and coupling strength the system shows transitions among several generic features of spatiotemporal dynamics, viz., synchronized fixed point solution, frozen random pattern, pattern selection, spatiotemporal intermittency, and fully developed spatiotemporal chaos. We quantify the spatiotemporal dynamics using quantitative measures like average quadratic deviation and spatial correlation function. We emphasize that instead of using an idealized model of CML, which is usually employed to observe the spatiotemporal behaviors, we consider a real world physical system and establish the existence of spatiotemporal chaos and other patterns in this system. We also discuss the importance of the present study in engineering application like removal of clock-skew in parallel processors.
In-situ coupling between kinase activities and protein dynamics within single focal adhesions
NASA Astrophysics Data System (ADS)
Wu, Yiqian; Zhang, Kaiwen; Seong, Jihye; Fan, Jason; Chien, Shu; Wang, Yingxiao; Lu, Shaoying
2016-07-01
The dynamic activation of oncogenic kinases and regulation of focal adhesions (FAs) are crucial molecular events modulating cell adhesion in cancer metastasis. However, it remains unclear how these events are temporally coordinated at single FA sites. Therefore, we targeted fluorescence resonance energy transfer (FRET)-based biosensors toward subcellular FAs to report local molecular events during cancer cell adhesion. Employing single FA tracking and cross-correlation analysis, we quantified the dynamic coupling characteristics between biochemical kinase activities and structural FA within single FAs. We show that kinase activations and FA assembly are strongly and sequentially correlated, with the concurrent FA assembly and Src activation leading focal adhesion kinase (FAK) activation by 42.6 ± 12.6 sec. Strikingly, the temporal coupling between kinase activation and individual FA assembly reflects the fate of FAs at later stages. The FAs with a tight coupling tend to grow and mature, while the less coupled FAs likely disassemble. During FA disassembly, however, kinase activations lead the disassembly, with FAK being activated earlier than Src. Therefore, by integrating subcellularly targeted FRET biosensors and computational analysis, our study reveals intricate interplays between Src and FAK in regulating the dynamic life of single FAs in cancer cells.
Self-Diffusion and Non-Markovian Dynamics in Strongly Coupled Ultracold Neutral Plasmas
NASA Astrophysics Data System (ADS)
Strickler, Trevor; Langin, Thomas; McQuillen, Patrick; Killian, Thomas
2015-05-01
Collisional processes in weakly coupled plasmas are well-described by the Landau-Spitzer formalism. Classical plasma theory breaks down, however, in strongly coupled systems because of the non-perturbative nature of particle interactions, and improving our understanding of this regime is an important fundamental challenge. We present experimental measurements of the self-diffusion constant and observation of non-Markovian equilibration for strongly coupled ions in an ultracold neutral plasma (UCNP) created by photoionizing strontium atoms in a magneto-optical trap. Our diagnostic uses optical pumping to create ``spin-tagged'' subpopulations of ions having skewed velocity distributions that then relax back to equilibrium. A Green-Kubo relation is used to extract the self-diffusion constant from the equilibration curves. With improved time resolution (down to 30 ns), we have explored the early time dynamics of these skewed ion distributions within 100 ns after the optical pumping, where molecular dynamics simulations predict non-Markovian deviations from the exponential velocity damping expected for weakly coupled systems. At longer times, we observe oscillations of the average velocity during the relaxation, which indicate coupling of single-particle motion to collective modes. This work was supported by the United States National Science Foundation and the Department of Energy (PHY-0714603), and the Air Force Office of Scientific Research (FA9550-12-1-0267).
Numerical study on air-structure coupling dynamic characteristics of the axial fan blade
NASA Astrophysics Data System (ADS)
Chen, Q. G.; Xie, B.; Li, F.; Gu, W. G.
2013-12-01
In order to understand the dynamic characteristics of the axial-flow fan blade due to the effect of rotating stress and the action of unsteady aerodynamic forces caused by the airflow, a numerical simulation method for air-structure coupling in an axial-flow fan with fixed rear guide blades was performed. The dynamic characteristics of an axial-flow fan rotating blade were studied by using the two-way air-structure coupling method. Based on the standard k-ε turbulence model, and using weak coupling method, the preceding six orders modal parameters of the rotating blade were obtained, and the distributions of stress and strain on the rotating blade were presented. The results show that the modal frequency from the first to the sixth order is 3Hz higher than the modal frequency without considering air-structure coupling interaction; the maximum stress and the maximum strain are all occurred in the vicinity of root area of the blade no matter the air-structure coupling is considered or not, thus, the blade root is the dangerous location subjected to fatigue break; the position of maximum deformation is at the blade tip, so the vibration of the blade tip is significant. This study can provide theoretical references for the further study on the strength analysis and mechanical optimal design.
Nichols, J.M.; Moniz, L.; Nichols, J.D.; Pecora, L.M.; Cooch, E.
2005-01-01
A number of important questions in ecology involve the possibility of interactions or ?coupling? among potential components of ecological systems. The basic question of whether two components are coupled (exhibit dynamical interdependence) is relevant to investigations of movement of animals over space, population regulation, food webs and trophic interactions, and is also useful in the design of monitoring programs. For example, in spatially extended systems, coupling among populations in different locations implies the existence of redundant information in the system and the possibility of exploiting this redundancy in the development of spatial sampling designs. One approach to the identification of coupling involves study of the purported mechanisms linking system components. Another approach is based on time series of two potential components of the same system and, in previous ecological work, has relied on linear cross-correlation analysis. Here we present two different attractor-based approaches, continuity and mutual prediction, for determining the degree to which two population time series (e.g., at different spatial locations) are coupled. Both approaches are demonstrated on a one-dimensional predator?prey model system exhibiting complex dynamics. Of particular interest is the spatial asymmetry introduced into the model as linearly declining resource for the prey over the domain of the spatial coordinate. Results from these approaches are then compared to the more standard cross-correlation analysis. In contrast to cross-correlation, both continuity and mutual prediction are clearly able to discern the asymmetry in the flow of information through this system.
Applications of time-domain spectroscopy to electron-phonon coupling dynamics at surfaces.
Matsumoto, Yoshiyasu
2014-10-01
Photochemistry is one of the most important branches in chemistry to promote and control chemical reactions. In particular, there has been growing interest in photoinduced processes at solid surfaces and interfaces with liquids such as water for developing efficient solar energy conversion. For example, photoinduced charge transfer between adsorbates and semiconductor substrates at the surfaces of metal oxides induced by photogenerated holes and electrons is a core process in photovoltaics and photocatalysis. In these photoinduced processes, electron-phonon coupling plays a central role. This paper describes how time-domain spectroscopy is applied to elucidate electron-phonon coupling dynamics at metal and semiconductor surfaces. Because nuclear dynamics induced by electronic excitation through electron-phonon coupling take place in the femtosecond time domain, the pump-and-probe method with ultrashort pulses used in time-domain spectroscopy is a natural choice for elucidating the electron-phonon coupling at metal and semiconductor surfaces. Starting with a phenomenological theory of coherent phonons generated by impulsive electronic excitation, this paper describes a couple of illustrative examples of the applications of linear and nonlinear time-domain spectroscopy to a simple adsorption system, alkali metal on Cu(111), and more complex photocatalyst systems.
NASA Astrophysics Data System (ADS)
Xu, Guangping; Wang, Jiasong
2017-10-01
Two dynamical models, the traditional method of moments coupled model (MCM) and Taylor-series expansion method of moments coupled model (TECM) for particle dispersion distribution and gravitation deposition are developed in three-dimensional ventilated environments. The turbulent airflow field is modeled with the renormalization group (RNG) k-ε turbulence model. The particle number concentration distribution in a ventilated room is obtained by solving the population balance equation coupled with the airflow field. The coupled dynamical models are validated using experimental data. A good agreement between the numerical and experimental results can be achieved. Both models have a similar characteristic for the spatial distribution of particle concentration. Relative to the MCM model, the TECM model presents a more close result to the experimental data. The vortex structure existed in the air flow makes a relative large concentration difference at the center region and results in a spatial non-uniformity of concentration field. With larger inlet velocity, the mixing level of particles in the room is more uniform. In general, the new dynamical models coupled with computational fluid dynamics (CFD) in the current study provide a reasonable and accurate method for the temporal and spatial evolution of particles effected by the deposition and dispersion behaviors. In addition, two ventilation modes with different inlet velocities are proceeded to study the effect on the particle evolution. The results show that with the ceiling ventilation mode (CVM), the particles can be better mixed and the concentration level is also higher. On the contrast, with the side ceiling ventilation mode (SVM), the particle concentration has an obvious stratified distribution with a relative lower level and it makes a much better environment condition to the human exposure.
Evidence of coupling in ocean-atmosphere dynamics over the North Atlantic
NASA Astrophysics Data System (ADS)
Vannitsem, Stéphane; Ghil, Michael
2017-04-01
The investigation of low-frequency variability (LFV) in the mid-latitude atmosphere, for instance of the North Atlantic Oscillation (NAO), is currently attracting considerable interest. One of the main reasons is LFV's potential to enable predictions beyond the generally accepted upper bound of weather forecasting skill of 10-15 days in mid-latitudes. To understand the development of the LFV in the atmosphere, it is necessary to clarify how it interacts with the other components of the climate system, in particular the ocean. The usual strategy to clarify the coupling between the ocean and the atmosphere is to analyze the one-way sensitivity of either component to forcing by the other. In the present work, we adopt a different strategy by investigating the projections of atmospheric and oceanic fields, based on reanalysis datasets, onto a reduced phase space. The latter ocean-atmosphere subspace is dynamically defined here by relying on the leading modes of the Vannitsem et al. (2015) idealized low-order model. This approach allows one to isolate the dominant modes of the coupled system's observed variability. The coupled projection is then analyzed using multichannel singular spectrum analysis (M-SSA). The results suggest that a dominant low-frequency signal with a 25-30-yr period already mentioned in the literature is a common mode of variability of the atmosphere and the ocean. A new score for evaluating the internal nature of the common variability is then introduced and it confirms the presence of coupled dynamics in the ocean-atmosphere system that includes a significant large-scale atmospheric component. The physical nature of this coupled dynamics is also discussed. Reference Vannitsem S., J. Demaeyer, L. de Cruz, and M. Ghil, Low-frequency variability and heat transport in a low-order nonlinear coupled ocean-atmosphere model, Physica D, 309, 71-85, 2015.
Collective dynamics of identical phase oscillators with high-order coupling
Xu, Can; Xiang, Hairong; Gao, Jian; Zheng, Zhigang
2016-01-01
In this paper, we propose a framework to investigate the collective dynamics in ensembles of globally coupled phase oscillators when higher-order modes dominate the coupling. The spatiotemporal properties of the attractors in various regions of parameter space are analyzed. Furthermore, a detailed linear stability analysis proves that the stationary symmetric distribution is only neutrally stable in the marginal regime which stems from the generalized time-reversal symmetry. Moreover, the critical parameters of the transition among various regimes are determined analytically by both the Ott-Antonsen method and linear stability analysis, the transient dynamics are further revealed in terms of the characteristic curves method. Finally, for the more general initial condition the symmetric dynamics could be reduced to a rigorous three-dimensional manifold which shows that the neutrally stable chaos could also occur in this model for particular parameters. Our theoretical analysis and numerical results are consistent with each other, which can help us understand the dynamical properties in general systems with higher-order harmonics couplings. PMID:27491401
The effect of temperature on the coupled slow and fast dynamics of an electrochemical oscillator
Zülke, Alana A.; Varela, Hamilton
2016-01-01
The coupling among disparate time-scales is ubiquitous in many chemical and biological systems. We have recently investigated the effect of fast and, long-term, slow dynamics in surface processes underlying some electrocatalytic reactions. Herein we report on the effect of temperature on the coupled slow and fast dynamics of a model system, namely the electro-oxidation of formic acid on platinum studied at five temperatures between 5 and 45 °C. The main result was a turning point found at 25 °C, which clearly defines two regions for the temperature dependency on the overall kinetics. In addition, the long-term evolution allowed us to compare reaction steps related to fast and slow evolutions. Results were discussed in terms of the key role of PtO species, which chemically couple slow and fast dynamics. In summary we were able to: (a) identify the competition between two reaction steps as responsible for the occurrence of two temperature domains; (b) compare the relative activation energies of these two steps; and (c) suggest the role of a given reaction step on the period-increasing set of reactions involved in the oscillatory dynamics. The introduced methodology could be applied to other systems to uncover the temperature dependence of complex chemical networks. PMID:27079514
The effect of temperature on the coupled slow and fast dynamics of an electrochemical oscillator
NASA Astrophysics Data System (ADS)
Zülke, Alana A.; Varela, Hamilton
2016-04-01
The coupling among disparate time-scales is ubiquitous in many chemical and biological systems. We have recently investigated the effect of fast and, long-term, slow dynamics in surface processes underlying some electrocatalytic reactions. Herein we report on the effect of temperature on the coupled slow and fast dynamics of a model system, namely the electro-oxidation of formic acid on platinum studied at five temperatures between 5 and 45 °C. The main result was a turning point found at 25 °C, which clearly defines two regions for the temperature dependency on the overall kinetics. In addition, the long-term evolution allowed us to compare reaction steps related to fast and slow evolutions. Results were discussed in terms of the key role of PtO species, which chemically couple slow and fast dynamics. In summary we were able to: (a) identify the competition between two reaction steps as responsible for the occurrence of two temperature domains; (b) compare the relative activation energies of these two steps; and (c) suggest the role of a given reaction step on the period-increasing set of reactions involved in the oscillatory dynamics. The introduced methodology could be applied to other systems to uncover the temperature dependence of complex chemical networks.
Dynamical effects of Stark-shifted quantum dots strongly coupled to photonic crystal cavities
NASA Astrophysics Data System (ADS)
Roy Choudhury, Kaushik; Bose, Ranojoy; Waks, Edo
2013-03-01
Single semiconductor quantum-dots (QDs) strongly coupled to photonic crystal cavities are a strong candidate for single photon generation, ultra-fast all optical switching and quantum information processing. Recent experiments on coupled-cavity quantum dot systems show possible manipulation of emission wavelength of the dot through optical Stark effect. Interesting dynamical features arise when the Stark pulse duration is comparable to QD-cavity interaction time. Here, we present a theoretical treatment of these dynamical effects and investigate dynamical emission spectrum, energy transfer and single photon generation. We study these effects through numerical solution of the full master equation. We demonstrate that dynamic Stark effects can be used to generate ultra-fast indistinguishable single photons using rapid Stark tuning of the quantum dot. The theoretical limit for the speed is shown to be faster than adiabatic rapid passage technique used for microwave photon generation in circuit QED. A systematic study of role of device parameters such as pulse-shape, dot-cavity coupling and incoherent losses on the efficiency and speed of single photon generation is also presented for possible experimental realization.
Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots.
Nichol, John M; Harvey, Shannon P; Shulman, Michael D; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I; Halperin, Bertrand I; Yacoby, Amir
2015-07-17
The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems.
NASA Astrophysics Data System (ADS)
Tu, Jiannan; Song, Paul; Vasyliūnas, Vytenis M.
2011-09-01
Ionosphere/thermosphere heating driven by magnetospheric convection is investigated through a three-fluid inductive (including Faraday's law) approach to describing magnetosphere-ionosphere/thermosphere coupling, for a 1-D stratified ionosphere/thermosphere in this initial study. It is shown that the response of the ionosphere/thermosphere and thus the heating is dynamic and height-dependent. The heating is essentially frictional in nature rather than Joule heating as commonly assumed. The heating rate reaches a quasi-steady state after about 25 Alfvén travel times. During the dynamic period, the heating can be enhanced and displays peaks at multiple times due to wave reflections. The dynamic heating rate can be more than twice greater than the quasi-steady state value. The heating is strongest in the E-layer but the heating rate per unit mass is concentrated around the F-layer peak height. This implies a potential mechanism of driving O+ upflow from O+ rich F-layer. It is shown that the ionosphere/thermosphere heating caused by the magnetosphere-ionosphere coupling can be simply evaluated through the relative velocity between the plasma and neutrals without invoking field-aligned currents, ionospheric conductance, and electric field. The present study provides understanding of the dynamic magnetosphere-ionosphere/thermosphere coupling from the ionospheric/thermospheric view in addition to magnetospheric perspectives.
Collective dynamics of identical phase oscillators with high-order coupling
NASA Astrophysics Data System (ADS)
Xu, Can; Xiang, Hairong; Gao, Jian; Zheng, Zhigang
2016-08-01
In this paper, we propose a framework to investigate the collective dynamics in ensembles of globally coupled phase oscillators when higher-order modes dominate the coupling. The spatiotemporal properties of the attractors in various regions of parameter space are analyzed. Furthermore, a detailed linear stability analysis proves that the stationary symmetric distribution is only neutrally stable in the marginal regime which stems from the generalized time-reversal symmetry. Moreover, the critical parameters of the transition among various regimes are determined analytically by both the Ott-Antonsen method and linear stability analysis, the transient dynamics are further revealed in terms of the characteristic curves method. Finally, for the more general initial condition the symmetric dynamics could be reduced to a rigorous three-dimensional manifold which shows that the neutrally stable chaos could also occur in this model for particular parameters. Our theoretical analysis and numerical results are consistent with each other, which can help us understand the dynamical properties in general systems with higher-order harmonics couplings.
Quenching of dynamic nuclear polarization by spin–orbit coupling in GaAs quantum dots
Nichol, John M.; Harvey, Shannon P.; Shulman, Michael D.; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I.; Halperin, Bertrand I.; Yacoby, Amir
2015-01-01
The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin–orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron–nuclear system, despite weak spin–orbit coupling in GaAs. Using Landau–Zener sweeps to measure static and dynamic properties of the electron spin–flip probability, we observe that the size of the spin–orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin–orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin–orbit coupling in central-spin systems. PMID:26184854
The effect of quenched disorder on dynamical transitions in systems of coupled cells
NASA Astrophysics Data System (ADS)
Xu, Jinshan; Singh, Rajeev; Garnier, Nicolas B.; Sinha, Sitabhra; Pumir, Alain
2013-09-01
Non-equilibrium systems are characterized by a rich variety of dynamical behaviors, which may sensitively depend on control parameters. Here, we investigate and provide a quantitative analysis of the role of disorder on the transitions between different dynamical regimes in extended heterogeneous systems of excitable and passive cells, induced by varying the strength of the coupling between cells. The random distribution of passive cells provides a quenched disorder in important biological contexts, such as the appearance of contractions in the pregnant uterus. We observe a large variability between different realizations of the disorder (replicas) in a lattice of excitable cells, each cell being coupled to a random number of passive cells. The statistics of these large disorder-induced fluctuations are related to the properties of the coarse-grained distribution of passive cells, in particular, to its extreme values. We show that these fluctuations can be characterized by a simple scaling relation, involving the strength of the coupling between excitable cells, the mean passive cell density and the logarithm of the system size. Our results provide a quantitative understanding of the important effect of a quenched disorder in the transition between dynamical regimes in extended dynamical systems.
Chaotic dynamics of coupled transverse-longitudinal plasma oscillations in magnetized plasmas.
Teychenné, D; Bésuelle, E; Oloumi, A; Salomaa, R R
2000-12-25
The propagation of intense electromagnetic waves in cold magnetized plasma is tackled through a relativistic hydrodynamic approach. The analysis of coupled transverse-longitudinal plasma oscillations is performed for traveling plane waves. When these waves propagate perpendicularly to a static magnetic field, the model is describable in terms of a nonlinear dynamical system with 2 degrees of freedom. A constant of motion is obtained and the powerful classical mechanics methods can be used. A new class of solutions, i.e., the chaotic solutions, is discovered by the Poincaré surface of sections. As a result, coupled transverse-longitudinal plasma oscillations become aperiodically modulated.
Dynamic dipole polarizabilities of H- and Ps- in weakly coupled plasmas
NASA Astrophysics Data System (ADS)
Kar, Sabyasachi; Li, H. W.; Jiang, Pinghui
2013-08-01
The effects of weakly coupled plasmas on the dynamic dipole polarizabilities of the H- and Ps- ions are investigated using highly correlated exponential wave functions. The Debye-Hückel shielding approach of plasma modeling is used to represent weakly coupled plasma environments. In free-atomic cases, results obtained from the present study for H- are in agreement with the available calculations and results for Ps- are reported for the first time. Frequency-dependent polarizabilities of H- and Ps- as functions of screening parameter are also presented for the first time.
Lax Representation of the Hyperbolic van Diejen Dynamics with Two Coupling Parameters
NASA Astrophysics Data System (ADS)
Pusztai, B. G.; Görbe, T. F.
2017-09-01
In this paper, we construct a Lax pair for the classical hyperbolic van Diejen system with two independent coupling parameters. Built upon this construction, we show that the dynamics can be solved by a projection method, which in turn allows us to initiate the study of the scattering properties. As a consequence, we prove the equivalence between the first integrals provided by the eigenvalues of the Lax matrix and the family of van Diejen's commuting Hamiltonians. Also, at the end of the paper, we propose a candidate for the Lax matrix of the hyperbolic van Diejen system with three independent coupling constants.
Hope, J J; Olsen, M K
2001-04-09
We show that in certain parameter regimes there is a macroscopic dynamical breakdown of the Gross-Pitaevskii equation. Stochastic field equations for coupled atomic and molecular condensates are derived using the functional positive- P representation. These equations describe the full quantum state of the coupled condensates and include the commonly used Gross-Pitaevskii equation as the noiseless limit. The full quantum theory includes the spontaneous processes which will become significant when the atomic population is low. The experimental signature of the quantum effects will be the time scale of the revival of the atomic population after a near total conversion to the molecular condensate.
Chaos analysis and delayed-feedback control in a discrete dynamic coupled map traffic model
NASA Astrophysics Data System (ADS)
Fang, Yaling; Shi, Zhongke
2015-03-01
The presence of chaos in traffic flow is studied using a modified discrete dynamic coupled map model which is derived from both the flow-density-speed fundamental diagram and Del Castillo's speed-density model. The modified model employs occupancy as its new variable and introduces a coupling strength with the consideration of effect of the front adjacent vehicle. And we analyze its stability of the control system and provide a procedure to design the decentralized delayed-feedback controllers for the traffic control system. These theoretical results are illustrated by numerical simulations.
The dynamics of a symmetric coupling of three modified quadratic maps
NASA Astrophysics Data System (ADS)
Paulo, C. Rech
2013-08-01
We investigate the dynamical behavior of a symmetric linear coupling of three quadratic maps with exponential terms, and identify various interesting features as a function of two control parameters. In particular, we investigate the emergence of quasiperiodic states arising from Naimark—Sacker bifurcations of stable period-1, period-2, and period-3 orbits. We also investigate the multistability in the same coupling. Lyapunov exponents, parameter planes, phase space portraits, and bifurcation diagrams are used to investigate transitions from periodic to quasiperiodic states, from quasiperiodic to mode-locked states and to chaotic states, and from chaotic to hyperchaotic states.
Dynamics of two arbitrary qubits strongly coupled to a quantum oscillator
NASA Astrophysics Data System (ADS)
Dong, Kun
2016-12-01
Using adiabatic approximation, a two arbitrary qubits Rabi model has been studied in ultra-strong coupling. The analytical expressions of the eigenvalues and the eigenvalues are obtained. They are in accordance with the numerical determined results. The dynamical behavior of the system and the evolution of entanglement have also been discussed. The collapse and revival phenomena has garnered particular attention. The influence of inconsistent coupling strength on them is studied. These results will be applied in quantum information processing. Project supported by the National Natural Science Foundation of China (Grant No. 10875018).
The electronic nonadiabatic coupling term: can it be ignored in dynamic calculations?
Halász, G J; Vibók, A; Suhai, S; Baer, M
2007-12-28
Whereas the search for the degeneracy points which are better known as conical intersections (or ci-points) is usually carried out with a lot of devotion, the nonadiabatic coupling terms (NACTs) which together with the adiabatic potential energy surfaces appear in the nuclear Born-Oppenheimer-Schrodinger equation are ignored in most dynamical calculations. In the present article we consider two well known frameworks, namely, the semiclassical surface hopping method and the vibrational coupling model Hamiltonian that avoid the NACTs and examine to what extent, this procedure is justified.
Topological effects on dynamics in complex pulse-coupled networks of integrate-and-fire type
NASA Astrophysics Data System (ADS)
Shkarayev, Maxim S.; Kovačič, Gregor; Cai, David
2012-03-01
For a class of integrate-and-fire, pulse-coupled networks with complex topology, we study the dependence of the pulse rate on the underlying architectural connectivity statistics. We derive the distribution of the pulse rate from this dependence and determine when the underlying scale-free architectural connectivity gives rise to a scale-free pulse-rate distribution. We identify the scaling of the pairwise coupling between the dynamical units in this network class that keeps their pulse rates bounded in the infinite-network limit. In the process, we determine the connectivity statistics for a specific scale-free network grown by preferential attachment.
The situated HKB model: how sensorimotor spatial coupling can alter oscillatory brain dynamics
Aguilera, Miguel; Bedia, Manuel G.; Santos, Bruno A.; Barandiaran, Xabier E.
2013-01-01
Despite the increase of both dynamic and embodied/situated approaches in cognitive science, there is still little research on how coordination dynamics under a closed sensorimotor loop might induce qualitatively different patterns of neural oscillations compared to those found in isolated systems. We take as a departure point the Haken-Kelso-Bunz (HKB) model, a generic model for dynamic coordination between two oscillatory components, which has proven useful for a vast range of applications in cognitive science and whose dynamical properties are well understood. In order to explore the properties of this model under closed sensorimotor conditions we present what we call the situated HKB model: a robotic model that performs a gradient climbing task and whose “brain” is modeled by the HKB equation. We solve the differential equations that define the agent-environment coupling for increasing values of the agent's sensitivity (sensor gain), finding different behavioral strategies. These results are compared with two different models: a decoupled HKB with no sensory input and a passively-coupled HKB that is also decoupled but receives a structured input generated by a situated agent. We can precisely quantify and qualitatively describe how the properties of the system, when studied in coupled conditions, radically change in a manner that cannot be deduced from the decoupled HKB models alone. We also present the notion of neurodynamic signature as the dynamic pattern that correlates with a specific behavior and we show how only a situated agent can display this signature compared to an agent that simply receives the exact same sensory input. To our knowledge, this is the first analytical solution of the HKB equation in a sensorimotor loop and qualitative and quantitative analytic comparison of spatially coupled vs. decoupled oscillatory controllers. Finally, we discuss the limitations and possible generalization of our model to contemporary neuroscience and
Alvarez-Paggi, Damián; Martín, Diego F; DeBiase, Pablo M; Hildebrandt, Peter; Martí, Marcelo A; Murgida, Daniel H
2010-04-28
Direct electron transfer (ET) of redox proteins immobilized on biomimetic or biocompatible electrodes represents an active field of fundamental and applied research. In this context, several groups have reported for a variety of proteins unexpected distance dependencies of the ET rate, whose origin remains largely speculative and controversial, but appears to be a quite general phenomenon. Here we have employed molecular dynamics (MD) simulations and electron pathway analyses to study the ET properties of cytochrome c (Cyt) electrostatically immobilized on Au coated by carboxyl-terminated alkylthiols. The MD simulations and concomitant binding energy calculations allow identification of preferred binding configurations of the oxidized and reduced Cyt which are established via different lysine residues and, thus, correspond to different orientations and dipole moments. Calculations of the electronic coupling matrices for the various Cyt/self-assembled monolayer (SAM) complexes indicate that the thermodynamically preferred protein orientations do not coincide with the orientations of optimum coupling. These findings demonstrate that the ET of the immobilized Cyt is controlled by an interplay between protein dynamics and tunneling probabilities. Protein dynamics exerts two level of tuning on the electronic coupling via reorientation (coarse) and low amplitude thermal fluctuations (fine). Upon operating the Au support as an electrode, electric-field-dependent alignment of the protein dipole moment becomes an additional determinant for the protein dynamics and thus for the overall ET rate. The present results provide a consistent molecular description of previous (spectro)electrochemical data and allow conclusions concerning the coupling of protein dynamics and ET of Cyt in physiological complexes.
Dynamics of AV coupling during human atrial fibrillation: role of atrial rate.
Masè, M; Marini, M; Disertori, M; Ravelli, F
2015-07-01
The causal relationship between atrial and ventricular activities during human atrial fibrillation (AF) is poorly understood. This study analyzed the effects of an increase in atrial rate on the link between atrial and ventricular activities during AF. Atrial and ventricular time series were determined in 14 patients during the spontaneous acceleration of the atrial rhythm at AF onset. The dynamic relationship between atrial and ventricular activities was quantified in terms of atrioventricular (AV) coupling by AV synchrogram analysis. The technique identified n:m coupling patterns (n atrial beats in m ventricular cycles), quantifying their percentage, maximal length, and conduction ratio (= m/n). Simulations with a difference-equation AV model were performed to correlate the observed dynamics to specific atrial/nodal properties. The atrial rate increase significantly affected AV coupling and ventricular response during AF. The shortening of atrial intervals from 185 ± 32 to 165 ± 24 ms (P < 0.001) determined transitions toward AV patterns with progressively decreasing m/n ratios (from conduction ratio = 0.34 ± 0.09 to 0.29 ± 0.08, P < 0.01), lower occurrence (from percentage of coupled beats = 27.1 ± 8.0 to 21.8 ± 6.9%, P < 0.05), and higher instability (from maximal length = 3.9 ± 1.5 to 2.8 ± 0.7 s, P < 0.01). Advanced levels of AV block and coupling instability at higher atrial rates were associated with increased ventricular interval variability (from 123 ± 52 to 133 ± 55 ms, P < 0.05). AV pattern transitions and coupling instability in patients were predicted, assuming the filtering of high-rate irregular atrial beats by the slow recovery of nodal excitability. These results support the role of atrial rate in determining AV coupling and ventricular response and may have implications for rate control in AF.
Limits on variations in protein backbone dynamics from precise measurements of scalar couplings.
Vögeli, Beat; Ying, Jinfa; Grishaev, Alexander; Bax, Ad
2007-08-01
3JHN,Halpha, 3JHN,Cbeta, and 3JHN,C' couplings, all related to the backbone torsion angle phi, were measured for the third immunoglobulin binding domain of protein G, or GB3. Measurements were carried out using both previously published methods and novel sequences based on the multiple-quantum principle, which limit attenuation of experimental couplings caused by finite lifetimes of the spin states of passive spins. High reproducibility between the multiple-quantum and conventional approaches confirms the accuracy of the measurements. With few exceptions, close agreement between 3JHN,Halpha, 3JHN,Cbeta, and 3JHN,C' and values predicted by their respective Karplus equations is observed. For the three types of couplings, up to 20% better agreement is obtained when fitting the experimental couplings to a dynamic ensemble NMR structure, which has a phi angle root-mean-square spread of 9 +/- 4 degrees and was previously calculated on the basis of a very extensive set of residual dipolar couplings, than for any single static NMR structure. Fits of 3J couplings to a 1.1-A X-ray structure, with hydrogens added in idealized positions, are 40-90% worse. Approximately half of the improvement when fitting to the NMR structures relates to the amide proton deviating from its idealized, in-peptide-plane position, indicating that the positioning of hydrogens relative to the backbone atoms is one of the factors limiting the accuracy at which the backbone torsion angle phi can be extracted from 3J couplings. Introducing an additional, residue-specific variable for the amplitude of phi angle fluctuations does not yield a statistically significant improvement when fitting to a set of dynamic Karplus curves, pointing to a homogeneous behavior of these amplitudes.
Electron dynamics in graphene with spin–orbit couplings and periodic potentials
NASA Astrophysics Data System (ADS)
Seshadri, Ranjani; Sen, Diptiman
2017-04-01
We use both continuum and lattice models to study the energy-momentum dispersion and the dynamics of a wave packet for an electron moving in graphene in the presence of spin–orbit couplings and either a single potential barrier or a periodic array of potential barriers. Both Kane–Mele and Rashba spin–orbit couplings are considered. A number of special things occur when the Kane–Mele and Rashba couplings are equal in magnitude. In the absence of a potential, the dispersion then consists of both massless Dirac and massive Dirac states. A periodic potential is known to generate additional Dirac points; we show that spin–orbit couplings generally open gaps at all those points, but if the two spin–orbit couplings are equal, some of the Dirac points remain gapless. We show that the massless and massive states respond differently to a potential barrier; the massless states transmit perfectly through the barrier at normal incidence while the massive states reflect from it. In the presence of a single potential barrier, we show that there are states localized along the barrier. Finally, we study the time evolution of a wave packet in the presence of a periodic potential. We discover special points in momentum space where there is almost no spreading of a wave packet; there are six such points in graphene when the spin–orbit couplings are absent.
Electron dynamics in graphene with spin-orbit couplings and periodic potentials.
Seshadri, Ranjani; Sen, Diptiman
2017-04-20
We use both continuum and lattice models to study the energy-momentum dispersion and the dynamics of a wave packet for an electron moving in graphene in the presence of spin-orbit couplings and either a single potential barrier or a periodic array of potential barriers. Both Kane-Mele and Rashba spin-orbit couplings are considered. A number of special things occur when the Kane-Mele and Rashba couplings are equal in magnitude. In the absence of a potential, the dispersion then consists of both massless Dirac and massive Dirac states. A periodic potential is known to generate additional Dirac points; we show that spin-orbit couplings generally open gaps at all those points, but if the two spin-orbit couplings are equal, some of the Dirac points remain gapless. We show that the massless and massive states respond differently to a potential barrier; the massless states transmit perfectly through the barrier at normal incidence while the massive states reflect from it. In the presence of a single potential barrier, we show that there are states localized along the barrier. Finally, we study the time evolution of a wave packet in the presence of a periodic potential. We discover special points in momentum space where there is almost no spreading of a wave packet; there are six such points in graphene when the spin-orbit couplings are absent.
Dynamic matrix controller design for performance study of an interacting coupled tank MIMO process
NASA Astrophysics Data System (ADS)
Rani, L. Thillai; Sivakumar, D.; Rathikarani, D.
2017-07-01
Model predictive control (MPC) is the class of advanced control techniques. A primary advantage to this approach is the explicit handling of constraints. MPC utilizes an internal model to predict system dynamic behaviour over a finite horizon. MPC is a discrete-time form of control, so inaccuracies in predicted behavior are corrected at the next control interval. This technique makes the control of processes to become more efficient and cost effective. Most of its applications are in the refining, petrochemical industries and in other chemical plants. Dynamic Matrix Control(DMC) is a kind of model predictive control technique based on step response model of the process. In this paper, the dynamic matrix control algorithm is implemented on coupled tank system and control quality has been analyzed using a simulation model with different setting parameters. From the simulation results it has been observed that dynamic matrix control algorithm can achieve good results with accuracy.
Tiana-Alsina, Jordi; Buldú, Javier M; Torrent, M C; García-Ojalvo, Jordi
2010-01-28
We quantify the level of stochasticity in the dynamics of two mutually coupled semiconductor lasers. Specifically, we concentrate on a regime in which the lasers synchronize their dynamics with a non-zero lag time, and the leader and laggard roles alternate irregularly between the lasers. We analyse this switching dynamics in terms of the number of forbidden patterns of the alternate time series. The results reveal that the system operates in a stochastic regime, with the level of stochasticity decreasing as the lasers are pumped further away from their lasing threshold. This behaviour is similar to that exhibited by a single semiconductor laser subject to external optical feedback, as its dynamics shifts from the regime of low-frequency fluctuations to coherence collapse. This journal is © 2010 The Royal Society
Coupling of dynamics and contact mechanics of artificial hip joints in a pendulum model.
Liu, H; Ellison, P J; Xu, H; Jin, Z
2010-01-01
To date, fully coupled dynamics and contact mechanics analysis is still limited by expensive computational cost and long computing time and has not been addressed comprehensively, particularly in the hip joint. To understand the influence of different parameters on the biomechanics of the total hip replacement (THR) and improve its design, two numerical approaches were developed and implemented in finite element models to investigate the coupling between the dynamics response and the contact mechanics for three different THR configurations, metal-on-polyethylene (MOP), metal-on-metal (MOM), and ceramic-on-ceramic (COC). The dynamic force and the contact pressure distribution at the bearing surfaces from the two methods were predicted and compared. The influences of various parameters (motion angle, load applied in the pendulum, friction coefficient, geometry, and material properties) were subsequently investigated. From the comparisons, the decoupled method, based on the rigid-body dynamics and the quasi-static elastic contact mechanics, was adequate to predict the performance of the THRs efficiently. The load had the greatest influence on the dynamics/contact mechanics among other factors.
Dynamics of Disordered Network of Coupled Hindmarsh-Rose Neuronal Models
NASA Astrophysics Data System (ADS)
Dtchetgnia Djeundam, S. R.; Yamapi, R.; Filatrella, G.; Kofane, T. C.
We investigate the effects of disorder on the synchronized state of a network of Hindmarsh-Rose neuronal models. Disorder, introduced as a perturbation of the neuronal parameters, destroys the network activity by wrecking the synchronized state. The dynamics of the synchronized state is analyzed through the Kuramoto order parameter, adapted to the neuronal Hindmarsh-Rose model. We find that the coupling deeply alters the dynamics of the single units, thus demonstrating that coupling not only affects the relative motion of the units, but also the dynamical behavior of each neuron; Thus, synchronization results in a structural change of the dynamics. The Kuramoto order parameter allows to clarify the nature of the transition from perfect phase synchronization to the disordered states, supporting the notion of an abrupt, second order-like, dynamical phase transition. We find that the system is resilient up to a certain disorder threshold, after that the network abruptly collapses to a desynchronized state. The loss of perfect synchronization seems to occur even for vanishingly small values of the disorder, but the degree of synchronization (as measured by the Kuramoto order parameter) gently decreases, and the completely disordered state is never reached.
Tunneling dynamics and band structures of three weakly coupled Bose-Einstein condensates.
Guo, Qiuyi; Chen, XuZong; Wu, Biao
2014-08-11
We study the tunneling dynamics and energy bands of three Bose-Einstein condensates which are coupled weakly with each other. The study is carried out with both the mean-filed model and the second-quantized model. The results from these two models are compared and found to agree with each other when the particle number is large. Without interaction, this system possesses a Dirac point in its energy band. This Dirac point is immediately destroyed and develops into a loop structure with arbitrary small interaction. This loop structure has a strong effect on the tunneling dynamics. We find that the tunneling dynamics in this system is very sensitive to the system parameter, e.g., the interaction strength. This sensitivity is found to be caused by the chaos in the mean-field model and the avoided energy crossings with tiny gaps in the second-quantized model. This result gives a certain indication on how the classical dynamics and quantum dynamics are connected in the semi-classical limit. Our mean-field results are also valid for three mutually coupled optical nonlinear waveguides.
Eddy current and coupled landscapes for nonadiabatic and nonequilibrium complex system dynamics
Zhang, Kun; Sasai, Masaki; Wang, Jin
2013-01-01
Physical and biological systems are often involved with coupled processes of different time scales. In the system with electronic and atomic motions, for example, the interplay between the atomic motion along the same energy landscape and the electronic hopping between different landscapes is critical: the system behavior largely depends on whether the intralandscape motion is slower (adiabatic) or faster (nonadiabatic) than the interlandscape hopping. For general nonequilibrium dynamics where Hamiltonian or energy function is unknown a priori, the challenge is how to extend the concepts of the intra- and interlandscape dynamics. In this paper we establish a theoretical framework for describing global nonequilibrium and nonadiabatic complex system dynamics by transforming the coupled landscapes into a single landscape but with additional dimensions. On this single landscape, dynamics is driven by gradient of the potential landscape, which is closely related to the steady-state probability distribution of the enlarged dimensions, and the probability flux, which has a curl nature. Through an example of a self-regulating gene circuit, we show that the curl flux has dramatic effects on gene regulatory dynamics. The curl flux and landscape framework developed here are easy to visualize and can be used to guide further investigation of physical and biological nonequilibrium systems. PMID:23980160
Dynamic coupling and allosteric behavior in a non-allosteric protein†
Clarkson, Michael W.; Gilmore, Steven A.; Edgell, Marshall H.; Lee, Andrew L.
2008-01-01
Long-range intraprotein interactions give rise to many important protein behaviors. Understanding how energy is transduced through protein structures to either transmit a signal or elicit conformational changes is therefore a current challenge in structural biology. In an effort to understand such linkages, multiple V→A mutations were made in the small globular protein eglin c. The physical responses, as mapped by NMR spin relaxation, residual dipolar couplings (RDCs), and scalar couplings, illustrate that the interior of this non-allosteric protein forms a dynamic network and that local perturbations are transmitted as dynamic and structural changes to distal sites as far as 16 Å away. Two basic types of propagation responses were observed: contiguous pathways of enhanced (attenuated) dynamics with no change in structure; and dispersed (non-contiguous) changes in methyl rotation rates that appear to result from subtle deformation of backbone structure. In addition, energy transmission is found to be unidirectional. In one mutant, an allosteric conformational change of a side chain is seen in the context of a pathway of propagated changes in ps-ns dynamics. The observation of so many long-range interactions in a small, rigid system lends experimental weight to the idea that all well-folded proteins inherently possess allosteric features [Gunasekaran et al. (2004) Proteins 57, 433−443], and that dynamics are a rich source of information for mapping and gaining mechanistic insight into communication pathways in individual proteins. PMID:16784220
Mode-coupling approach for the slow dynamics of a liquid on a spherical substrate.
Vest, Julien-Piera; Tarjus, Gilles; Viot, Pascal
2015-08-28
We study the dynamics of a one-component liquid constrained on a spherical substrate, a 2-sphere, and investigate how the mode-coupling theory (MCT) can describe the new features brought by the presence of curvature. To this end we have derived the MCT equations in a spherical geometry. We find that, as seen from the MCT, the slow dynamics of liquids in curved space at low temperature does not qualitatively differ from that of glass-forming liquids in Euclidean space. The MCT predicts the right trend for the evolution of the relaxation slowdown with curvature but is dramatically off at a quantitative level.
Dynamical coupling of pygmy and giant resonances in relativistic Coulomb excitation
Brady, N. S.; Aumann, T.; Bertulani, C. A.; ...
2016-04-20
We study the Coulomb excitation of pygmy dipole resonances (PDR) in heavy ion reactions at 100 MeV/nucleon and above. The reactions Ni-68 + Au-197 and Ni-68 + Pb-208 are taken as practical examples. Our goal is to address the question of the influence of giant resonances on the PDR as the dynamics of the collision evolves. We show that the coupling to the giant resonances affects considerably the excitation probabilities of the PDR, a result that indicates the need of an improved theoretical treatment of the reaction dynamics at these bombarding energies. (C) 2016 The Authors. Published by Elsevier B.V.
Coexistence of Regular and Irregular Dynamics in Complex Networks of Pulse-Coupled Oscillators
NASA Astrophysics Data System (ADS)
Timme, Marc; Wolf, Fred; Geisel, Theo
2002-11-01
For general networks of pulse-coupled oscillators, including regular, random, and more complex networks, we develop an exact stability analysis of synchronous states. As opposed to conventional stability analysis, here stability is determined by a multitude of linear operators. We treat this multioperator problem exactly and show that for inhibitory interactions the synchronous state is stable, independent of the parameters and the network connectivity. In randomly connected networks with strong interactions this synchronous state, displaying regular dynamics, coexists with a balanced state exhibiting irregular dynamics. External signals may switch the network between qualitatively distinct states.
Supercurrent and dynamical instability of spin-orbit-coupled ultracold Bose gases
NASA Astrophysics Data System (ADS)
Ozawa, Tomoki; Pitaevskii, Lev P.; Stringari, Sandro
2013-06-01
We investigate the stability of supercurrents in a Bose-Einstein condensate with one-dimensional spin-orbit and Raman couplings. The consequence of the lack of Galilean invariance is explicitly discussed. We show that in the plane-wave phase, characterized by a uniform density, the supercurrent state can become dynamically unstable, the instability being associated with the occurrence of a complex sound velocity, in a region where the effective mass is negative. We also discuss the emergence of energetic instability in these supercurrent states. We argue that both the dynamical and the energetic instabilities in these systems can be generated experimentally through excitation of the collective dipole oscillation.
Coupling between amino acid and water dynamics by broadband dielectric spectroscopy
NASA Astrophysics Data System (ADS)
Saiz, Luciana; Cerveny, Silvina
2014-05-01
The dynamics of proline aqueous solution was investigated for water concentrations from 40 to 60 wt% by dielectric spectroscopy (106 - 109 Hz) in the temperature range from 230 to 300 K, where the solutions remain amorphous. We found two relaxation processes, related with the reorientation of proline and water as previously observed in a higher frequency range at room temperature [1]. We found that both dynamics are strongly coupled, as previously observed in hydrated proteins powders, in spite of the fact that a single amino acid is a molecule much simpler than a protein.
Spin-Orbit Coupling Drives Femtosecond Nonadiabatic Dynamics in a Transition Metal Compound.
Carbery, William P; Verma, Archana; Turner, Daniel B
2017-03-16
Transient absorption measurements conducted using broadband, 6 fs laser pulses reveal unexpected femtosecond dynamics in the [IrBr6](2-) model system. Vibrational spectra and the X-ray crystal structure indicate that these dynamics are not induced by a Jahn-Teller distortion, a type of conical intersection typically associated with the spectral features of transition metal compounds. Two-dimensional electronic spectra of [IrBr6](2-) contain 23 cross peaks, which necessarily arise from spin-orbit coupling. Real-valued 2D spectra support a spectroscopic basis where strong nonadiabatic coupling, ascribed to multiple conical intersections, mediates rapid energy relaxation to the lowest-energy excited state. Subsequent analysis gives rise to a more generalized description of a conical intersection as a degeneracy between two adiabatic states having the same total angular momentum.
Switch programming of reflectivity control devices for the coupled dynamics of a solar sail
NASA Astrophysics Data System (ADS)
Hu, Tianjian; Gong, Shengping; Mu, Junshan; Li, Junfeng; Wang, Tianshu; Qian, Weiping
2016-03-01
As demonstrated in the Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS), reflectivity control devices (RCDs) are switched on or off independently with each other, which has nevertheless been ignored by many previous researches. This paper emphasizes the discrete property of RCDs, and aims to obtain an appropriate switch law of RCDs for a rigid spinning solar sail. First, the coupled attitude-orbit dynamics is derived from the basic solar force and torque model into an underdetermined linear system with a binary set constraint. Subsequently, the coupled dynamics is reformulated into a constrained quadratic programming and a basic gradient projection method is designed to search for the optimal solution. Finally, a circular sail flying in the Venus rendezvous mission demonstrates the model and method numerically, which illustrates approximately 103 km terminal position error and 0.5 m/s terminal velocity error as 80 independent RCDs are switched on or off appropriately.
Coupled dipole method for radiation dynamics in finite photonic crystal structures.
Bordas, Frédéric; Louvion, Nicolas; Callard, Ségolène; Chaumet, Patrick C; Rahmani, Adel
2006-05-01
We present a coupled-dipole treatment of radiation dynamics in the weak-coupling regime in a finite three-dimensional photonic crystal structure. The structure is discretized in real space and the self-consistent local field is computed. We illustrate the computation of radiation dynamics by calculating the spontaneous emission rate for a source located in a defect cavity inside a slab photonic crystal structure. We compute the cavity spectral response, the near-field modal structure, and the far-field radiation pattern of the microcavity. We also discuss our results in light of the recent experimental near-field observations of the optical modes of a photonic crystal microcavity.
Strong nonlocal coupling stabilizes localized structures: an analysis based on front dynamics.
Fernandez-Oto, C; Clerc, M G; Escaff, D; Tlidi, M
2013-04-26
We investigate the effect of strong nonlocal coupling in bistable spatially extended systems by using a Lorentzian-like kernel. This effect through front interaction drastically alters the space-time dynamics of bistable systems by stabilizing localized structures in one and two dimensions, and by affecting the kinetics law governing their behavior with respect to weak nonlocal and local coupling. We derive an analytical formula for the front interaction law and show that the kinetics governing the formation of localized structures obeys a law inversely proportional to their size to some power. To illustrate this mechanism, we consider two systems, the Nagumo model describing population dynamics and nonlinear optics model describing a ring cavity filled with a left-handed material. Numerical solutions of the governing equations are in close agreement with analytical predictions.
Song, Wan-lu; Yang, Wan-li; Yin, Zhang-qi; Chen, Chang-yong; Feng, Mang
2016-01-01
We explore controllable quantum dynamics of a hybrid system, which consists of an array of mutually coupled superconducting resonators (SRs) with each containing a nitrogen-vacancy center spin ensemble (NVE) in the presence of inhomogeneous broadening. We focus on a three-site model, which compared with the two-site case, shows more complicated and richer dynamical behavior, and displays a series of damped oscillations under various experimental situations, reflecting the intricate balance and competition between the NVE-SR collective coupling and the adjacent-site photon hopping. Particularly, we find that the inhomogeneous broadening of the spin ensemble can suppress the population transfer between the SR and the local NVE. In this context, although the inhomogeneous broadening of the spin ensemble diminishes entanglement among the NVEs, optimal entanglement, characterized by averaging the lower bound of concurrence, could be achieved through accurately adjusting the tunable parameters. PMID:27627994
Coupling Osmolarity Dynamics within Human Tear Film on an Eye-Shaped Domain
NASA Astrophysics Data System (ADS)
Li, Longfei; Braun, R. J.; Driscoll, T. A.; Henshaw, W. D.; Banks, J. W.; King-Smith, P. E.
2013-11-01
The concentration of ions in the tear film (osmolarity) is a key variable in understanding dry eye symptoms and disease. We derived a mathematical model that couples osmolarity (treated as a single solute) and fluid dynamics within the tear film on a 2D eye-shaped domain. The model concerns the physical effects of evaporation, surface tension, viscosity, ocular surface wettability, osmolarity, osmosis and tear fluid supply and drainage. We solved the governing system of coupled nonlinear PDEs using the Overture computational framework developed at LLNL, together with a new hybrid time stepping scheme (using variable step BDF and RKC) that was added to the framework. Results of our numerical simulations show good agreement with existing 1D models (for both tear film and osmolarity dynamics) and provide new insight about the osmolarity distribution over the ocular surface during the interblink.
Dynamic Coupling and Allosteric Networks in the α Subunit of Heterotrimeric G Proteins*
Yao, Xin-Qiu; Malik, Rabia U.; Griggs, Nicholas W.; Skjærven, Lars; Traynor, John R.; Sivaramakrishnan, Sivaraj; Grant, Barry J.
2016-01-01
G protein α subunits cycle between active and inactive conformations to regulate a multitude of intracellular signaling cascades. Important structural transitions occurring during this cycle have been characterized from extensive crystallographic studies. However, the link between observed conformations and the allosteric regulation of binding events at distal sites critical for signaling through G proteins remain unclear. Here we describe molecular dynamics simulations, bioinformatics analysis, and experimental mutagenesis that identifies residues involved in mediating the allosteric coupling of receptor, nucleotide, and helical domain interfaces of Gαi. Most notably, we predict and characterize novel allosteric decoupling mutants, which display enhanced helical domain opening, increased rates of nucleotide exchange, and constitutive activity in the absence of receptor activation. Collectively, our results provide a framework for explaining how binding events and mutations can alter internal dynamic couplings critical for G protein function. PMID:26703464
Shape memory alloy nanostructures with coupled dynamic thermo-mechanical effects
NASA Astrophysics Data System (ADS)
Dhote, R. P.; Gomez, H.; Melnik, R. N. V.; Zu, J.
2015-07-01
Employing the Ginzburg-Landau phase-field theory, a new coupled dynamic thermo-mechanical 3D model has been proposed for modeling the cubic-to-tetragonal martensitic transformations in shape memory alloy (SMA) nanostructures. The stress-induced phase transformations and thermo-mechanical behavior of nanostructured SMAs have been investigated. The mechanical and thermal hysteresis phenomena, local non-uniform phase transformations and corresponding non-uniform temperatures and deformations' distributions are captured successfully using the developed model. The predicted microstructure evolution qualitatively matches with the experimental observations. The developed coupled dynamic model has provided a better understanding of underlying martensitic transformation mechanisms in SMAs, as well as their effect on the thermo-mechanical behavior of nanostructures.
Cosmological implications of Nambu-Jona-Lasinio model with a dynamical coupling
NASA Astrophysics Data System (ADS)
Quintanar, G. Leonardo; de La Macorra, Axel
We study the cosmological implications of the Nambu-Jona-Lasinio (NJL) model when the coupling constant is field dependent. The NJL model has a four-fermion interaction describing two different phases due to quantum interaction effects and determined by the strength of the coupling constant g. It describes massless fermions for weak coupling and a massive fermions and strong coupling, where a fermion condensate is formed. In the original NJL model, the coupling constant g is indeed constant, and in this work we consider a modified version of the NJL model by introducing a dynamical field dependent coupling motivated by string theory. The effective potential as a function of the varying coupling (aimed to implement a natural phase transition) is seen to develop a negative divergence, i.e. becomes a “bottomless well” in certain limit region. Although we explain how an lower unbounded potential is not necessarily unacceptable in a cosmological context, the divergence can be removed if we consider a mass term for the coupling like field. We found that for a proper set of parameters, the total potential obtained has two minima, one located at the origin (the trivial solution, in which the fluid associated with the fields behave like matter); and the other related to the nontrivial solution. This last solution has three possibilities: (1) if the minimum is positive Vmin > 0, the system behaves as a cosmological constant, thus leading eventually to an accelerated universe; (2) if the minimized potential vanishes Vmin = 0, then we have matter with no acceleration; (3) finally a negative minimum Vmin < 0 leads an eventually collapsing universe with a flat geometry. Therefore, a possible interpretation as dark matter (DM) or dark energy (DE) is allowed among the behaviors implicated in the model.
NASA Astrophysics Data System (ADS)
Kiselev, Egor I.; Scheurer, Mathias S.; Wölfle, Peter; Schmalian, Jörg
2017-03-01
An ordered state in the spin sector that breaks parity without breaking time-reversal symmetry, i.e., that can be considered dynamically generated spin-orbit coupling, was proposed to explain puzzling observations in a range of different systems. Here, we derive severe restrictions for such a state that follow from a Ward identity related to spin conservation. It is shown that l =1 spin-Pomeranchuk instabilities are not possible in nonrelativistic systems since the response of spin-current fluctuations is entirely incoherent and nonsingular. This rules out relativistic spin-orbit coupling as an emergent low-energy phenomenon. We illustrate the exotic physical properties of the remaining higher-angular-momentum analogs of spin-orbit coupling and derive a geometric constraint for spin-orbit vectors in lattice systems.
Real-time dynamic coupling of GPC-enhanced diffraction-limited focal spots
NASA Astrophysics Data System (ADS)
Villangca, Mark; Bañas, Andrew; Kopylov, Oleksii; Palima, Darwin; Glückstad, Jesper
2015-03-01
We have previously demonstrated on-demand dynamic coupling of an optically manipulated wave-guided optical waveguide (WOW) using diffractive techniques on a "point and shoot" approach. In this work, the generation of the coupling focal spots is done in real-time following the position of the WOW. Object-tracking routine has been added in the trapping program to get the position of the WOW. This approach allows continuous coupling of light through the WOWs which may be useful in some application. In addition, we include a GPC light shaper module in the holography setup to efficiently illuminate the spatial light modulator (SLM). The ability to switch from on-demand to continuous addressing with efficient illumination leverages our WOWs for potential applications in stimulation and nonlinear optics.
NASA Astrophysics Data System (ADS)
Farinha, Maria Luísa Braga; Azevedo, Nuno Monteiro; Candeias, Mariline
2017-02-01
The explicit formulation of a small displacement model for the coupled hydro-mechanical analysis of concrete gravity dam foundations based on joint finite elements is presented. The proposed coupled model requires a thorough pre-processing stage in order to ensure that the interaction between the various blocks which represent both the rock mass foundation and the dam is always edge to edge. The mechanical part of the model, though limited to small displacements, has the advantage of allowing an accurate representation of the stress distribution along the interfaces, such as rock mass joints. The hydraulic part and the mechanical part of the model are fully compatible. The coupled model is validated using a real case of a dam in operation, by comparison of the results with those obtained with a large displacement discrete model. It is shown that it is possible to assess the sliding stability of concrete gravity dams using small displacement models under both static and dynamic conditions.
Dynamics of High-Order Spin-Orbit Couplings about Linear Momenta in Compact Binary Systems*
NASA Astrophysics Data System (ADS)
Huang, Li; Wu, Xin; Mei, Li-Jie; Huang, Guo-Qing
2017-09-01
This paper relates to the post-Newtonian Hamiltonian dynamics of spinning compact binaries, consisting of the Newtonian Kepler problem and the leading, next-to-leading and next-to-next-to-leading order spin-orbit couplings as linear functions of spins and momenta. When this Hamiltonian form is transformed to a Lagrangian form, besides the terms corresponding to the same order terms in the Hamiltonian, several additional terms, third post-Newtonian (3PN), 4PN, 5PN, 6PN and 7PN order spin-spin coupling terms, yield in the Lagrangian. That means that the Hamiltonian is nonequivalent to the Lagrangian at the same PN order but is exactly equivalent to the full Lagrangian without any truncations. The full Lagrangian without the spin-spin couplings truncated is integrable and regular. Whereas it is non-integrable and becomes possibly chaotic when any one of the spin-spin terms is dropped. These results are also supported numerically.
Equilibrium dynamics of the Dean-Kawasaki equation: Mode-coupling theory and its extension
NASA Astrophysics Data System (ADS)
Kim, Bongsoo; Kawasaki, Kyozi; Jacquin, Hugo; van Wijland, Frédéric
2014-01-01
We extend a previously proposed field-theoretic self-consistent perturbation approach for the equilibrium dynamics of the Dean-Kawasaki equation presented in [Kim and Kawasaki, J. Stat. Mech. (2008) P02004, 10.1088/1742-5468/2008/02/P02004]. By taking terms missing in the latter analysis into account we arrive at a set of three new equations for correlation functions of the system. These correlations involve the density and its logarithm as local observables. Our new one-loop equations, which must carefully deal with the noninteracting Brownian gas theory, are more general than the historic mode-coupling one in that a further approximation corresponding to Gaussian density fluctuations leads back to the original mode-coupling equation for the density correlations alone. However, without performing any further approximation step, our set of three equations does not feature any ergodic-nonergodic transition, as opposed to the historical mode-coupling approach.
Equilibrium dynamics of the Dean-Kawasaki equation: mode-coupling theory and its extension.
Kim, Bongsoo; Kawasaki, Kyozi; Jacquin, Hugo; van Wijland, Frédéric
2014-01-01
We extend a previously proposed field-theoretic self-consistent perturbation approach for the equilibrium dynamics of the Dean-Kawasaki equation presented in [Kim and Kawasaki, J. Stat. Mech. (2008) P02004]. By taking terms missing in the latter analysis into account we arrive at a set of three new equations for correlation functions of the system. These correlations involve the density and its logarithm as local observables. Our new one-loop equations, which must carefully deal with the noninteracting Brownian gas theory, are more general than the historic mode-coupling one in that a further approximation corresponding to Gaussian density fluctuations leads back to the original mode-coupling equation for the density correlations alone. However, without performing any further approximation step, our set of three equations does not feature any ergodic-nonergodic transition, as opposed to the historical mode-coupling approach.
Anisotropic dynamics of a spin-orbit-coupled Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Martone, Giovanni I.; Li, Yun; Pitaevskii, Lev P.; Stringari, Sandro
2012-12-01
By calculating the density response function we identify the excitation spectrum of a Bose-Einstein condensate with equal Rashba and Dresselhaus spin-orbit coupling. We find that the velocity of sound along the direction of spin-orbit coupling is deeply quenched and vanishes when one approaches the second-order phase transition between the plane-wave and the zero momentum quantum phases. We also point out the emergence of a roton minimum in the excitation spectrum for small values of the Raman coupling, providing the onset of the transition to the stripe phase. Our findings point out the occurrence of a strong anisotropy in the dynamic behavior of the gas. A hydrodynamic description accounting for the collective oscillations in both uniform and harmonically trapped gases is also derived.
Eliasson, B; Shukla, P K
2006-10-01
We consider nonlinear interactions between two colliding laser beams in an electron plasma, accounting for the relativistic electron mass increase in the laser fields and radiation pressure driven electron-acoustic (EA) perturbations that are supported by hot and cold electrons. By using the hydrodynamic and Maxwell equations, we obtain the relevant equations for nonlinearly coupled laser beams and EA perturbations. The coupled equations are then Fourier analyzed to obtain a nonlinear dispersion relation. The latter is numerically solved to show the existence of new classes of the parametric instabilities in the presence of two colliding laser beams in a two-electron plasma. The dynamics of nonlinearly coupled laser beams in our electron plasma is also investigated. The results should be useful in understanding the nonlinear propagation characteristics of multiple electromagnetic beams in laser-produced plasmas as well as in space plasmas.
Three-Dimensional Molecular Theory of Solvation Coupled with Molecular Dynamics in Amber
Luchko, T.; Simmerling, C.; Gusarov, S.; Roe, D.R., Case, D.A.; Tuszynski, J.; Kovalenko, A.
2010-02-01
We present the three-dimensional molecular theory of solvation (also known as 3D-RISM) coupled with molecular dynamics (MD) simulation by contracting solvent degrees of freedom, accelerated by extrapolating solvent-induced forces and applying them in large multiple time steps (up to 20 fs) to enable simulation of large biomolecules. The method has been implemented in the Amber molecular modeling package and is illustrated here on alanine-dipeptide and protein-G.
Dynamical Coupled-Channel Model of Meson Production Reactions in the Nucleon Resonance Region
T.-S. H. Lee; A. Matsuyama; T. Sato
2006-11-15
A dynamical coupled-channel model is presented for investigating the nucleon resonances (N*) in the meson production reactions induced by pions and photons. Our objective is to extract the N* parameters and to investigate the meson production reaction mechanisms for mapping out the quark-gluon substructure of N* from the data. The model is based on an energy-independent Hamiltonian which is derived from a set of Lagrangians by using a unitary transformation method.
Light-Quark Baryon Spectroscopy within ANL-Osaka Dynamical Coupled-Channels Approach
NASA Astrophysics Data System (ADS)
Kamano, Hiroyuki
2016-10-01
Recent results on the study of light-quark baryons with the ANL-Osaka dynamical coupled-channels (DCC) approach are presented, which contain the N^* and Δ ^* spectroscopy via the analysis of π N and γ N reactions and the Λ ^* and Σ ^* spectroscopy via the analysis of K^- p reactions. A recent application of our DCC approach to neutrino-nucleon reactions in the resonance region is also presented.
Synchronization Dynamics in the Presence of Coupling Delays and Phase Shifts
NASA Astrophysics Data System (ADS)
Jörg, David J.; Morelli, Luis G.; Ares, Saúl; Jülicher, Frank
2014-05-01
In systems of coupled oscillators, the effects of complex signaling can be captured by time delays and phase shifts. Here, we show how time delays and phase shifts lead to different oscillator dynamics and how synchronization rates can be regulated by substituting time delays by phase shifts at a constant collective frequency. For spatially extended systems with time delays, we show that the fastest synchronization can occur for intermediate wavelengths, giving rise to novel synchronization scenarios.
NASA Astrophysics Data System (ADS)
Sato, T.
2007-12-01
A dynamical approach of the meson production reaction for extracting nucleon resonance parameters has been developed. We report on the γ N Δ form factors extracted from the recent pion electroproduction data and the coupled-channels model of π N scattering up to W ≤ 2 GeV. An analysis of the resonance poles extracted using the speed-plot and time-delay methods is briefly discussed.
Dynamically coupled plasmon-phonon modes in GaP: An indirect-gap polar semiconductor
NASA Astrophysics Data System (ADS)
Ishioka, Kunie; Brixius, Kristina; Höfer, Ulrich; Rustagi, Avinash; Thatcher, Evan M.; Stanton, Christopher J.; Petek, Hrvoje
2015-11-01
The ultrafast coupling dynamics of coherent optical phonons and the photoexcited electron-hole plasma in the indirect gap semiconductor GaP are investigated by experiment and theory. For below-gap excitation and probing by 800-nm light, only the bare longitudinal optical (LO) phonons are observed. For above-gap excitation with 400-nm light, the photoexcitation creates a high density, nonequilibrium e -h plasma, which introduces an additional, faster decaying oscillation due to an LO phonon-plasmon coupled (LOPC) mode. The LOPC mode frequency exhibits very similar behavior for both n - and p -doped GaP, downshifting from the LO to the transverse optical (TO) phonon frequency limits with increasing photoexcited carrier density. We assign the LOPC mode to the LO phonons coupled with the photoexcited multicomponent plasma. For the 400-nm excitation, the majority of the photoexcited electrons are scattered from the Γ valley into the satellite X valley, while the light and spin-split holes are scattered into the heavy hole band, within 30 fs. The resulting mixed plasma is strongly damped, leading to the LOPC frequency appearing in the reststrahlen gap. Due to the large effective masses of the X electrons and heavy holes, the coupled mode appears most distinctly at carrier densities ≳5 ×1018cm-3 . We perform theoretical calculations of the nuclear motions and the electronic polarizations following an excitation with an ultrashort optical pulse to obtain the transient reflectivity responses of the coupled modes. We find that, while the longitudinal diffusion of photoexcited carriers is insignificant, the lateral inhomogeneity of the photoexcited carriers due to the laser intensity profile should be taken into account to reproduce the major features of the observed coupled mode dynamics.
NASA Astrophysics Data System (ADS)
Simpkins, Blake S.; Fears, Kenan P.; Dressick, Walter J.; Dunkelberger, Adam D.; Spann, Bryan T.; Owrutsky, Jeffrey C.
2016-09-01
Coherent coupling between an optical transition and confined optical mode have been investigated for electronic-state transitions, however, only very recently have vibrational transitions been considered. Here, we demonstrate both static and dynamic results for vibrational bands strongly coupled to optical cavities. We experimentally and numerically describe strong coupling between a Fabry-Pérot cavity and carbonyl stretch ( 1730 cm 1) in poly-methylmethacrylate and provide evidence that the mixed-states are immune to inhomogeneous broadening. We investigate strong and weak coupling regimes through examination of cavities loaded with varying concentrations of a urethane monomer. Rabi splittings are in excellent agreement with an analytical description using no fitting parameters. Ultrafast pump-probe measurements reveal transient absorption signals over a frequency range well-separated from the vibrational band, as well as drastically modified relaxation rates. We speculate these modified kinetics are a consequence of the energy proximity between the vibration-cavity polariton modes and excited state transitions and that polaritons offer an alternative relaxation path for vibrational excitations. Varying the polariton energies by angle-tuning yields transient results consistent with this hypothesis. Furthermore, Rabi oscillations, or quantum beats, are observed at early times and we see evidence that these coherent vibration-cavity polariton excitations impact excited state population through cavity losses. Together, these results indicate that cavity coupling may be used to influence both excitation and relaxation rates of vibrations. Opening the field of polaritonic coupling to vibrational species promises to be a rich arena amenable to a wide variety of infrared-active bonds that can be studied in steady state and dynamically.
Role of protein dynamics in ion selectivity and allosteric coupling in the NaK channel
Brettmann, Joshua B.; Urusova, Darya; Tonelli, Marco; Silva, Jonathan R.; Henzler-Wildman, Katherine A.
2015-01-01
Flux-dependent inactivation that arises from functional coupling between the inner gate and the selectivity filter is widespread in ion channels. The structural basis of this coupling has only been well characterized in KcsA. Here we present NMR data demonstrating structural and dynamic coupling between the selectivity filter and intracellular constriction point in the bacterial nonselective cation channel, NaK. This transmembrane allosteric communication must be structurally different from KcsA because the NaK selectivity filter does not collapse under low-cation conditions. Comparison of NMR spectra of the nonselective NaK and potassium-selective NaK2K indicates that the number of ion binding sites in the selectivity filter shifts the equilibrium distribution of structural states throughout the channel. This finding was unexpected given the nearly identical crystal structure of NaK and NaK2K outside the immediate vicinity of the selectivity filter. Our results highlight the tight structural and dynamic coupling between the selectivity filter and the channel scaffold, which has significant implications for channel function. NaK offers a distinct model to study the physiologically essential connection between ion conduction and channel gating. PMID:26621745
Role of protein dynamics in ion selectivity and allosteric coupling in the NaK channel.
Brettmann, Joshua B; Urusova, Darya; Tonelli, Marco; Silva, Jonathan R; Henzler-Wildman, Katherine A
2015-12-15
Flux-dependent inactivation that arises from functional coupling between the inner gate and the selectivity filter is widespread in ion channels. The structural basis of this coupling has only been well characterized in KcsA. Here we present NMR data demonstrating structural and dynamic coupling between the selectivity filter and intracellular constriction point in the bacterial nonselective cation channel, NaK. This transmembrane allosteric communication must be structurally different from KcsA because the NaK selectivity filter does not collapse under low-cation conditions. Comparison of NMR spectra of the nonselective NaK and potassium-selective NaK2K indicates that the number of ion binding sites in the selectivity filter shifts the equilibrium distribution of structural states throughout the channel. This finding was unexpected given the nearly identical crystal structure of NaK and NaK2K outside the immediate vicinity of the selectivity filter. Our results highlight the tight structural and dynamic coupling between the selectivity filter and the channel scaffold, which has significant implications for channel function. NaK offers a distinct model to study the physiologically essential connection between ion conduction and channel gating.
Modeling of synchronization behavior of bursting neurons at nonlinearly coupled dynamical networks.
Çakir, Yüksel
2016-01-01
Synchronization behaviors of bursting neurons coupled through electrical and dynamic chemical synapses are investigated. The Izhikevich model is used with random and small world network of bursting neurons. Various currents which consist of diffusive electrical and time-delayed dynamic chemical synapses are used in the simulations to investigate the influences of synaptic currents and couplings on synchronization behavior of bursting neurons. The effects of parameters, such as time delay, inhibitory synaptic strengths, and decay time on synchronization behavior are investigated. It is observed that in random networks with no delay, bursting synchrony is established with the electrical synapse alone, single spiking synchrony is observed with hybrid coupling. In small world network with no delay, periodic bursting behavior with multiple spikes is observed when only chemical and only electrical synapse exist. Single-spike and multiple-spike bursting are established with hybrid couplings. A decrease in the synchronization measure is observed with zero time delay, as the decay time is increased in random network. For synaptic delays which are above active phase period, synchronization measure increases with an increase in synaptic strength and time delay in small world network. However, in random network, it increases with only an increase in synaptic strength.
A multiscale model on hospital infections coupling macro and micro dynamics
NASA Astrophysics Data System (ADS)
Wang, Xia; Tang, Sanyi
2017-09-01
A multiscale model of hospital infections coupling the micro model of the growth of bacteria and the macro model describing the transmission of the bacteria among patients and health care workers (HCWs) was established to investigate the effects of antibiotic treatment on the transmission of the bacteria among patients and HCWs. The model was formulated by viewing the transmission rate from infected patients to HCWs and the shedding rate of bacteria from infected patients to the environment as saturated functions of the within-host bacterial load. The equilibria and the basic reproduction number of the coupled system were studied, and the global dynamics of the disease free equilibrium and the endemic equilibrium were analyzed in detail by constructing two Lyapunov functions. Furthermore, effects of drug treatment in the within-host model on the basic reproduction number and the dynamics of the coupled model were studied by coupling a pharmacokinetics model with the within-host model. Sensitive analysis indicated that the growth rate of the bacteria, the maximum drug effect and the dosing interval are the three most sensitive parameters contributing to the basic reproduction number. Thus, adopting ;wonder; drugs to decrease the growth rate of the bacteria or to increase the drug's effect is the most effective measure but changing the dosage regime is also effective. A quantitative criterion of how to choose the best dosage regimen can also be obtained from numerical results.
Darbes, Lynae A.; Chakravarty, Deepalika; Neilands, Torsten B.; Beougher, Sean C.; Hoff, Colleen C.
2015-01-01
While the relationship context itself is increasingly being examined to understand sexual risk behavior among gay male couples, few studies have examined relationship dynamics and HIV risk longitudinally. We aimed to investigate relationship dynamics and psychosocial predictors of unprotected anal intercourse (UAI) with outside partners of serodiscordant or unknown HIV serostatus (UAIOUT) over time as well as UAI with primary partner in serodiscordant couples (UAIPP). We recruited a sample of 566 ethnically diverse, seroconcordant and serodiscordant couples and interviewed them six times over the course of three years. The surveys encompassed relationship dynamics between the partners and sexual behavior with primary and outside partners. We fit generalized linear mixed models for both the UAI outcomes with time and relationship dynamics as predictors while controlling for relationship length. Analyses of the longitudinal data revealed that, in both categories of couples, those with higher levels of positive relationship dynamics (e.g., commitment, satisfaction) were less likely to engage in UAIOUT. Higher investment in sexual agreement and communication were among the factors that significantly predicted less UAI for seroconcordant couples, but not for serodiscordant couples. For serodiscordant couples, greater levels of attachment and intimacy were associated with greater odds of UAIPP while increased HIV-specific social support was associated with lower odds of UAIPP. These results underscore the importance of creating and tailoring interventions for gay couples that help maintain and strengthen positive relationship dynamics as they have the potential to produce significant changes in HIV risk behavior and thereby in HIV transmission. PMID:24233329
Dynamically Coupled Food-web and Hydrodynamic Modeling with ADH-CASM
NASA Astrophysics Data System (ADS)
Piercy, C.; Swannack, T. M.
2012-12-01
Oysters and freshwater mussels are "ecological engineers," modifying the local water quality by filtering zooplankton and other suspended particulate matter from the water column and flow hydraulics by impinging on the near-bed flow environment. The success of sessile, benthic invertebrates such as oysters depends on environmental factors including but not limited to temperature, salinity, and flow regime. Typically food-web and other types of ecological models use flow and water quality data as direct input without regard to the feedback between the ecosystem and the physical environment. The USACE-ERDC has developed a coupled hydrodynamic-ecological modeling approach that dynamically couples a 2-D hydrodynamic and constituent transport model, Adaptive Hydraulics (ADH), with a bioenergetics food-web model, the Comprehensive Aquatics Systems Model (CASM), which captures the dynamic feedback between aquatic ecological systems and the environment. We present modeling results from restored oyster reefs in the Great Wicomico River on the western shore of the Chesapeake Bay, which quantify ecosystem services such as the influence of the benthic ecosystem on water quality. Preliminary results indicate that while the influence of oyster reefs on bulk flow dynamics is limited due to the localized influence of oyster reefs, large reefs and the associated benthic ecosystem can create measurable changes in the concentrations of nitrogen, phosphorus, and carbon in the areas around reefs. We also present a sensitivity analysis to quantify the relative sensitivity of the coupled ADH-CASM model to both hydrodynamic and ecological parameter choice.
The coupling of fluids, dynamics, and controls on advanced architecture computers
NASA Technical Reports Server (NTRS)
Atwood, Christopher
1995-01-01
This grant provided for the demonstration of coupled controls, body dynamics, and fluids computations in a workstation cluster environment; and an investigation of the impact of peer-peer communication on flow solver performance and robustness. The findings of these investigations were documented in the conference articles.The attached publication, 'Towards Distributed Fluids/Controls Simulations', documents the solution and scaling of the coupled Navier-Stokes, Euler rigid-body dynamics, and state feedback control equations for a two-dimensional canard-wing. The poor scaling shown was due to serialized grid connectivity computation and Ethernet bandwidth limits. The scaling of a peer-to-peer communication flow code on an IBM SP-2 was also shown. The scaling of the code on the switched fabric-linked nodes was good, with a 2.4 percent loss due to communication of intergrid boundary point information. The code performance on 30 worker nodes was 1.7 (mu)s/point/iteration, or a factor of three over a Cray C-90 head. The attached paper, 'Nonlinear Fluid Computations in a Distributed Environment', documents the effect of several computational rate enhancing methods on convergence. For the cases shown, the highest throughput was achieved using boundary updates at each step, with the manager process performing communication tasks only. Constrained domain decomposition of the implicit fluid equations did not degrade the convergence rate or final solution. The scaling of a coupled body/fluid dynamics problem on an Ethernet-linked cluster was also shown.
Ganzenmüller, Georg C.; Hiermaier, Stefan; Steinhauser, Martin O.
2012-01-01
We propose a thermodynamically consistent and energy-conserving temperature coupling scheme between the atomistic and the continuum domain. The coupling scheme links the two domains using the DPDE (Dissipative Particle Dynamics at constant Energy) thermostat and is designed to handle strong temperature gradients across the atomistic/continuum domain interface. The fundamentally different definitions of temperature in the continuum and atomistic domain – internal energy and heat capacity versus particle velocity – are accounted for in a straightforward and conceptually intuitive way by the DPDE thermostat. We verify the here-proposed scheme using a fluid, which is simultaneously represented as a continuum using Smooth Particle Hydrodynamics, and as an atomistically resolved liquid using Molecular Dynamics. In the case of equilibrium contact between both domains, we show that the correct microscopic equilibrium properties of the atomistic fluid are obtained. As an example of a strong non-equilibrium situation, we consider the propagation of a steady shock-wave from the continuum domain into the atomistic domain, and show that the coupling scheme conserves both energy and shock-wave dynamics. To demonstrate the applicability of our scheme to real systems, we consider shock loading of a phospholipid bilayer immersed in water in a multi-scale simulation, an interesting topic of biological relevance. PMID:23300586
Polaron dynamics with off-diagonal coupling: beyond the Ehrenfest approximation.
Huang, Zhongkai; Wang, Lu; Wu, Changqin; Chen, Lipeng; Grossmann, Frank; Zhao, Yang
2017-01-04
Treated traditionally by the Ehrenfest approximation, the dynamics of a one-dimensional molecular crystal model with off-diagonal exciton-phonon coupling is investigated in this work using the Dirac-Frenkel time-dependent variational principle with the multi-D2Ansatz. It is shown that the Ehrenfest method is equivalent to our variational method with the single D2Ansatz, and with the multi-D2Ansatz, the accuracy of our simulated dynamics is significantly enhanced in comparison with the semi-classical Ehrenfest dynamics. The multi-D2Ansatz is able to capture numerically accurate exciton momentum probability and help clarify the relation between the exciton momentum redistribution and the exciton energy relaxation. The results demonstrate that the exciton momentum distributions in the steady state are determined by a combination of the transfer integral and the off-diagonal coupling strength, independent of the excitonic initial conditions. We also probe the effect of the transfer integral and the off-diagonal coupling on exciton transport in both real and reciprocal space representations. Finally, the variational method with importance sampling is employed to investigate temperature effects on exciton transport using the multi-D2Ansatz, and it is demonstrated that the variational approach is valid in both low and high temperature regimes.
PERK regulates Gq protein-coupled intracellular Ca(2+) dynamics in primary cortical neurons.
Zhu, Siying; McGrath, Barbara C; Bai, Yuting; Tang, Xin; Cavener, Douglas R
2016-10-01
PERK (EIF2AK3) is an ER-resident eIF2α kinase required for behavioral flexibility and metabotropic glutamate receptor-dependent long-term depression via its translational control. Motivated by the recent discoveries that PERK regulates Ca(2+) dynamics in insulin-secreting β-cells underlying glucose-stimulated insulin secretion, and modulates Ca(2+) signals-dependent working memory, we explored the role of PERK in regulating Gq protein-coupled Ca(2+) dynamics in pyramidal neurons. We found that acute PERK inhibition by the use of a highly specific PERK inhibitor reduced the intracellular Ca(2+) rise stimulated by the activation of acetylcholine, metabotropic glutamate and bradykinin-2 receptors in primary cortical neurons. More specifically, acute PERK inhibition increased IP3 receptor mediated ER Ca(2+) release, but decreased receptor-operated extracellular Ca(2+) influx. Impaired Gq protein-coupled intracellular Ca(2+) rise was also observed in genetic Perk knockout neurons. Taken together, our findings reveal a novel role of PERK in neurons, which is eIF2α-independent, and suggest that the impaired working memory in forebrain-specific Perk knockout mice may stem from altered Gq protein-coupled intracellular Ca(2+) dynamics in cortical pyramidal neurons.
2015-09-01
extended for computation of free-flight aerodynamics and flight dynamics of a finned projectile with pulse jet control21 and is being extended for...Dynamics ( CFD )-based Simulation Technique: Free Motion by Jubaraj Sahu and Frank Fresconi Approved for public release...US Army Research Laboratory Flight Behaviors of a Complex Projectile Using a Coupled Computational Fluid Dynamics ( CFD )-based Simulation
Park, Jihoon; Mori, Hiroki; Okuyama, Yuji; Asada, Minoru
2017-01-01
Chaotic itinerancy is a phenomenon in which the state of a nonlinear dynamical system spontaneously explores and attracts certain states in a state space. From this perspective, the diverse behavior of animals and its spontaneous transitions lead to a complex coupled dynamical system, including a physical body and a brain. Herein, a series of simulations using different types of non-linear oscillator networks (i.e., regular, small-world, scale-free, random) with a musculoskeletal model (i.e., a snake-like robot) as a physical body are conducted to understand how the chaotic itinerancy of bodily behavior emerges from the coupled dynamics between the body and the brain. A behavior analysis (behavior clustering) and network analysis for the classified behavior are then applied. The former consists of feature vector extraction from the motions and classification of the movement patterns that emerged from the coupled dynamics. The network structures behind the classified movement patterns are revealed by estimating the "information networks" different from the given non-linear oscillator networks based on the transfer entropy which finds the information flow among neurons. The experimental results show that: (1) the number of movement patterns and their duration depend on the sensor ratio to control the balance of strength between the body and the brain dynamics and on the type of the given non-linear oscillator networks; and (2) two kinds of information networks are found behind two kinds movement patterns with different durations by utilizing the complex network measures, clustering coefficient and the shortest path length with a negative and a positive relationship with the duration periods of movement patterns. The current results seem promising for a future extension of the method to a more complicated body and environment. Several requirements are also discussed.
Mori, Hiroki; Okuyama, Yuji; Asada, Minoru
2017-01-01
Chaotic itinerancy is a phenomenon in which the state of a nonlinear dynamical system spontaneously explores and attracts certain states in a state space. From this perspective, the diverse behavior of animals and its spontaneous transitions lead to a complex coupled dynamical system, including a physical body and a brain. Herein, a series of simulations using different types of non-linear oscillator networks (i.e., regular, small-world, scale-free, random) with a musculoskeletal model (i.e., a snake-like robot) as a physical body are conducted to understand how the chaotic itinerancy of bodily behavior emerges from the coupled dynamics between the body and the brain. A behavior analysis (behavior clustering) and network analysis for the classified behavior are then applied. The former consists of feature vector extraction from the motions and classification of the movement patterns that emerged from the coupled dynamics. The network structures behind the classified movement patterns are revealed by estimating the “information networks” different from the given non-linear oscillator networks based on the transfer entropy which finds the information flow among neurons. The experimental results show that: (1) the number of movement patterns and their duration depend on the sensor ratio to control the balance of strength between the body and the brain dynamics and on the type of the given non-linear oscillator networks; and (2) two kinds of information networks are found behind two kinds movement patterns with different durations by utilizing the complex network measures, clustering coefficient and the shortest path length with a negative and a positive relationship with the duration periods of movement patterns. The current results seem promising for a future extension of the method to a more complicated body and environment. Several requirements are also discussed. PMID:28796797
Schüler, D; Alonso, S; Torcini, A; Bär, M
2014-12-01
Pattern formation often occurs in spatially extended physical, biological, and chemical systems due to an instability of the homogeneous steady state. The type of the instability usually prescribes the resulting spatio-temporal patterns and their characteristic length scales. However, patterns resulting from the simultaneous occurrence of instabilities cannot be expected to be simple superposition of the patterns associated with the considered instabilities. To address this issue, we design two simple models composed by two asymmetrically coupled equations of non-conserved (Swift-Hohenberg equations) or conserved (Cahn-Hilliard equations) order parameters with different characteristic wave lengths. The patterns arising in these systems range from coexisting static patterns of different wavelengths to traveling waves. A linear stability analysis allows to derive a two parameter phase diagram for the studied models, in particular, revealing for the Swift-Hohenberg equations, a co-dimension two bifurcation point of Turing and wave instability and a region of coexistence of stationary and traveling patterns. The nonlinear dynamics of the coupled evolution equations is investigated by performing accurate numerical simulations. These reveal more complex patterns, ranging from traveling waves with embedded Turing patterns domains to spatio-temporal chaos, and a wide hysteretic region, where waves or Turing patterns coexist. For the coupled Cahn-Hilliard equations the presence of a weak coupling is sufficient to arrest the coarsening process and to lead to the emergence of purely periodic patterns. The final states are characterized by domains with a characteristic length, which diverges logarithmically with the coupling amplitude.
NASA Astrophysics Data System (ADS)
Schüler, D.; Alonso, S.; Torcini, A.; Bär, M.
2014-12-01
Pattern formation often occurs in spatially extended physical, biological, and chemical systems due to an instability of the homogeneous steady state. The type of the instability usually prescribes the resulting spatio-temporal patterns and their characteristic length scales. However, patterns resulting from the simultaneous occurrence of instabilities cannot be expected to be simple superposition of the patterns associated with the considered instabilities. To address this issue, we design two simple models composed by two asymmetrically coupled equations of non-conserved (Swift-Hohenberg equations) or conserved (Cahn-Hilliard equations) order parameters with different characteristic wave lengths. The patterns arising in these systems range from coexisting static patterns of different wavelengths to traveling waves. A linear stability analysis allows to derive a two parameter phase diagram for the studied models, in particular, revealing for the Swift-Hohenberg equations, a co-dimension two bifurcation point of Turing and wave instability and a region of coexistence of stationary and traveling patterns. The nonlinear dynamics of the coupled evolution equations is investigated by performing accurate numerical simulations. These reveal more complex patterns, ranging from traveling waves with embedded Turing patterns domains to spatio-temporal chaos, and a wide hysteretic region, where waves or Turing patterns coexist. For the coupled Cahn-Hilliard equations the presence of a weak coupling is sufficient to arrest the coarsening process and to lead to the emergence of purely periodic patterns. The final states are characterized by domains with a characteristic length, which diverges logarithmically with the coupling amplitude.
A Statistical Approach for the Concurrent Coupling of Molecular Dynamics and Finite Element Methods
NASA Technical Reports Server (NTRS)
Saether, E.; Yamakov, V.; Glaessgen, E.
2007-01-01
Molecular dynamics (MD) methods are opening new opportunities for simulating the fundamental processes of material behavior at the atomistic level. However, increasing the size of the MD domain quickly presents intractable computational demands. A robust approach to surmount this computational limitation has been to unite continuum modeling procedures such as the finite element method (FEM) with MD analyses thereby reducing the region of atomic scale refinement. The challenging problem is to seamlessly connect the two inherently different simulation techniques at their interface. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the typical boundary value problem used to define a coupled domain. The method uses statistical averaging of the atomistic MD domain to provide displacement interface boundary conditions to the surrounding continuum FEM region, which, in return, generates interface reaction forces applied as piecewise constant traction boundary conditions to the MD domain. The two systems are computationally disconnected and communicate only through a continuous update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM) as opposed to a direct coupling method where interface atoms and FEM nodes are individually related. The methodology is inherently applicable to three-dimensional domains, avoids discretization of the continuum model down to atomic scales, and permits arbitrary temperatures to be applied.
Schüler, D.; Alonso, S.; Bär, M.; Torcini, A.
2014-12-15
Pattern formation often occurs in spatially extended physical, biological, and chemical systems due to an instability of the homogeneous steady state. The type of the instability usually prescribes the resulting spatio-temporal patterns and their characteristic length scales. However, patterns resulting from the simultaneous occurrence of instabilities cannot be expected to be simple superposition of the patterns associated with the considered instabilities. To address this issue, we design two simple models composed by two asymmetrically coupled equations of non-conserved (Swift-Hohenberg equations) or conserved (Cahn-Hilliard equations) order parameters with different characteristic wave lengths. The patterns arising in these systems range from coexisting static patterns of different wavelengths to traveling waves. A linear stability analysis allows to derive a two parameter phase diagram for the studied models, in particular, revealing for the Swift-Hohenberg equations, a co-dimension two bifurcation point of Turing and wave instability and a region of coexistence of stationary and traveling patterns. The nonlinear dynamics of the coupled evolution equations is investigated by performing accurate numerical simulations. These reveal more complex patterns, ranging from traveling waves with embedded Turing patterns domains to spatio-temporal chaos, and a wide hysteretic region, where waves or Turing patterns coexist. For the coupled Cahn-Hilliard equations the presence of a weak coupling is sufficient to arrest the coarsening process and to lead to the emergence of purely periodic patterns. The final states are characterized by domains with a characteristic length, which diverges logarithmically with the coupling amplitude.
Ultrafast XUV spectroscopy: Unveiling the nature of electronic couplings in molecular dynamics
NASA Astrophysics Data System (ADS)
Timmers, Henry Robert
Molecules are traditionally treated quantum mechanically using the Born-Oppenheimer formalism. In this formalism, different electronic states of the molecule are treated independently. However, most photo-initiated phenomena occurring in nature are driven by the couplings between different electronic states in both isolated molecules and molecular aggregates, and therefore occur beyond the Born-Oppenheimer formalism. These couplings are relevant in reactions relating to the perception of vision in the human eye, the oxidative damage and repair of DNA, the harvesting of light in photosynthesis, and the transfer of charge across large chains of molecules. While these reaction dynamics have traditionally been studied with visible and ultraviolet spectroscopy, attosecond XUV pulses formed through the process of high harmonic generation form a perfect tool for probing coupled electronic dynamics in molecules. In this thesis, I will present our work in using ultrafast, XUV spectroscopy to study these dynamics in molecules of increasing complexity. We begin by probing the relaxation dynamics of superexcited states in diatomic O 2. These states can relax via two types of electronic couplings, either through autoionization or neutral dissociation. We find that our pump-probe scheme can disentangle the two relaxation mechanisms and independently measure their contributing lifetimes. Next, we present our work in observing a coherent electron hole wavepacket initiated by the ionization of polyatomic CO 2 near a conical intersection. The electron-nuclear couplings near the conical intersection drive the electron hole between different orbital configurations. We find that we can not only measure the lifetime of quantum coherence in the electron hole wavepacket, but also control its evolution with a strong, infrared probing field. Finally, we propose an experiment to observe the migration of an electron hole across iodobenzene on the few-femtosecond timescale. We present
Dynamics of atom-field probability amplitudes in a coupled cavity system with Kerr non-linearity
Priyesh, K. V.; Thayyullathil, Ramesh Babu
2014-01-28
We have investigated the dynamics of two cavities coupled together via photon hopping, filled with Kerr non-linear medium and each containing a two level atom in it. The evolution of various atom (field) state probabilities of the coupled cavity system in two excitation sub space are obtained numerically. Detailed analysis has been done by taking different initial conditions of the system, with various coupling strengths and by varying the susceptibility of the medium. The role of susceptibility factor, on the dynamics atom field probability has been examined. In a coupled cavity system with strong photon hopping it is found that the susceptibility factor modifies the behaviour of probability amplitudes.
Dynamics and predictability of a low-order wind-driven ocean-atmosphere coupled model
NASA Astrophysics Data System (ADS)
Vannitsem, Stéphane
2014-04-01
The dynamics of a low-order coupled wind-driven ocean-atmosphere system is investigated with emphasis on its predictability properties. The low-order coupled deterministic system is composed of a baroclinic atmosphere for which 12 dominant dynamical modes are only retained (Charney and Straus in J Atmos Sci 37:1157-1176, 1980) and a wind-driven, quasi-geostrophic and reduced-gravity shallow ocean whose field is truncated to four dominant modes able to reproduce the large scale oceanic gyres (Pierini in J Phys Oceanogr 41:1585-1604, 2011). The two models are coupled through mechanical forcings only. The analysis of its dynamics reveals first that under aperiodic atmospheric forcings only dominant single gyres (clockwise or counterclockwise) appear, while for periodic atmospheric solutions the double gyres emerge. In the present model domain setting context, this feature is related to the level of truncation of the atmospheric fields, as indicated by a preliminary analysis of the impact of higher wavenumber ("synoptic" scale) modes on the development of oceanic gyres. In the latter case, double gyres appear in the presence of a chaotic atmosphere. Second the dynamical quantities characterizing the short-term predictability (Lyapunov exponents, Lyapunov dimension, Kolmogorov-Sinaï (KS) entropy) displays a complex dependence as a function of the key parameters of the system, namely the coupling strength and the external thermal forcing. In particular, the KS-entropy is increasing as a function of the coupling in most of the experiments, implying an increase of the rate of loss of information about the localization of the system on its attractor. Finally the dynamics of the error is explored and indicates, in particular, a rich variety of short term behaviors of the error in the atmosphere depending on the (relative) amplitude of the initial error affecting the ocean, from polynomial ( at 2 + bt 3 + ct 4) up to exponential-like evolutions. These features are explained
Adaptive spacetime method using Riemann jump conditions for coupled atomistic-continuum dynamics
Kraczek, B. Miller, S.T. Haber, R.B. Johnson, D.D.
2010-03-20
We combine the Spacetime Discontinuous Galerkin (SDG) method for elastodynamics with the mathematically consistent Atomistic Discontinuous Galerkin (ADG) method in a new scheme that concurrently couples continuum and atomistic models of dynamic response in solids. The formulation couples non-overlapping continuum and atomistic models across sharp interfaces by weakly enforcing jump conditions, for both momentum balance and kinematic compatibility, using Riemann values to preserve the characteristic structure of the underlying hyperbolic system. Momentum balances to within machine-precision accuracy over every element, on each atom, and over the coupled system, with small, controllable energy dissipation in the continuum region that ensures numerical stability. When implemented on suitable unstructured spacetime grids, the continuum SDG model offers linear computational complexity in the number of elements and powerful adaptive analysis capabilities that readily bridge between atomic and continuum scales in both space and time. A special trace operator for the atomic velocities and an associated atomistic traction field enter the jump conditions at the coupling interface. The trace operator depends on parameters that specify, at the scale of the atomic spacing, the position of the coupling interface relative to the atoms. In a key finding, we demonstrate that optimizing these parameters suppresses spurious reflections at the coupling interface without the use of non-physical damping or special boundary conditions. We formulate the implicit SDG-ADG coupling scheme in up to three spatial dimensions, and describe an efficient iterative solution scheme that outperforms common explicit schemes, such as the Velocity Verlet integrator. Numerical examples, in 1dxtime and employing both linear and nonlinear potentials, demonstrate the performance of the SDG-ADG method and show how adaptive spacetime meshing reconciles disparate time steps and resolves atomic-scale signals in
An Embedded Statistical Method for Coupling Molecular Dynamics and Finite Element Analyses
NASA Technical Reports Server (NTRS)
Saether, E.; Glaessgen, E.H.; Yamakov, V.
2008-01-01
The coupling of molecular dynamics (MD) simulations with finite element methods (FEM) yields computationally efficient models that link fundamental material processes at the atomistic level with continuum field responses at higher length scales. The theoretical challenge involves developing a seamless connection along an interface between two inherently different simulation frameworks. Various specialized methods have been developed to solve particular classes of problems. Many of these methods link the kinematics of individual MD atoms with FEM nodes at their common interface, necessarily requiring that the finite element mesh be refined to atomic resolution. Some of these coupling approaches also require simulations to be carried out at 0 K and restrict modeling to two-dimensional material domains due to difficulties in simulating full three-dimensional material processes. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the standard boundary value problem used to define a coupled domain. The method replaces a direct linkage of individual MD atoms and finite element (FE) nodes with a statistical averaging of atomistic displacements in local atomic volumes associated with each FE node in an interface region. The FEM and MD computational systems are effectively independent and communicate only through an iterative update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM). ESCM provides an enhanced coupling methodology that is inherently applicable to three-dimensional domains, avoids discretization of the continuum model to atomic scale resolution, and permits finite temperature states to be applied.
A New Concurrent Multiscale Methodology for Coupling Molecular Dynamics and Finite Element Analyses
NASA Technical Reports Server (NTRS)
Yamakov, Vesselin; Saether, Erik; Glaessgen, Edward H/.
2008-01-01
The coupling of molecular dynamics (MD) simulations with finite element methods (FEM) yields computationally efficient models that link fundamental material processes at the atomistic level with continuum field responses at higher length scales. The theoretical challenge involves developing a seamless connection along an interface between two inherently different simulation frameworks. Various specialized methods have been developed to solve particular classes of problems. Many of these methods link the kinematics of individual MD atoms with FEM nodes at their common interface, necessarily requiring that the finite element mesh be refined to atomic resolution. Some of these coupling approaches also require simulations to be carried out at 0 K and restrict modeling to two-dimensional material domains due to difficulties in simulating full three-dimensional material processes. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the standard boundary value problem used to define a coupled domain. The method replaces a direct linkage of individual MD atoms and finite element (FE) nodes with a statistical averaging of atomistic displacements in local atomic volumes associated with each FE node in an interface region. The FEM and MD computational systems are effectively independent and communicate only through an iterative update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM). ESCM provides an enhanced coupling methodology that is inherently applicable to three-dimensional domains, avoids discretization of the continuum model to atomic scale resolution, and permits finite temperature states to be applied.
NASA Astrophysics Data System (ADS)
Shevliakova, E.; Pacala, S. W.; Malyshev, S.; Hurtt, G. C.; Caspersen, J. P.
2003-12-01
Modeling global interactions between the atmosphere, hydrosphere and biosphere continues to pose a significant challenge, because of the tight and complex coupling of flows of water, energy, greenhouse gases, and ecosystem dynamics. We developed a comprehensive dynamic land surface model (LM3) able to simulate carbon and vegetation dynamics on time scales from minutes to centuries, as well as the exchange of water and energy among the land, LM3 predicts carbon dynamics in vegetation and soil in response to environmental conditions (weather, climate and soil type), ambient concentration of CO2, natural disturbances (e.g. fire), and anthropogenic land use changes (e.g. deforestation, agricultural cropland abandonment and forest management). A suite of the historical 300 years land cover change scenarios (developed at University of New Hampshire) is used to represent direct anthropogenic forcing on the terrestrial carbon system. Here we analyze the behavior of LM3 forced with observed atmospheric data and coupled with GFDL atmospheric circulation model AM2. The series of experiments indicates that our model adequately simulates climatic gradients of net primary productivity (NPP), leaf area index (LAI), biomass accumulation, evapotranspiration, and runoff. Additionally, analysis of the simulations suggests that anthropogenic land use has been a major forcing on the terrestrial carbon cycle, with large sources of CO2 caused primarily by deforestation and timber harvesting in the current tropics and past north temperate zone, and large current north temperate sinks caused primarily by secondary forest growth.
Coherent dynamic structure factors of strongly coupled plasmas: A generalized hydrodynamic approach
Luo, Di; Hu, GuangYue; Gong, Tao; Xia, YuQing; Zhao, Bin; Zheng, Jian
2016-05-15
A generalized hydrodynamic fluctuation model is proposed to simplify the calculation of the dynamic structure factor S(ω, k) of non-ideal plasmas using the fluctuation-dissipation theorem. In this model, the kinetic and correlation effects are both included in hydrodynamic coefficients, which are considered as functions of the coupling strength (Γ) and collision parameter (kλ{sub ei}), where λ{sub ei} is the electron-ion mean free path. A particle-particle particle-mesh molecular dynamics simulation code is also developed to simulate the dynamic structure factors, which are used to benchmark the calculation of our model. A good agreement between the two different approaches confirms the reliability of our model.
Spin dynamics and magneto-optical response in charge-neutral tunnel-coupled quantum dots
NASA Astrophysics Data System (ADS)
Gawełczyk, Michał; Machnikowski, Paweł
2017-04-01
We model the electron and hole spin dynamics in an undoped double quantum dot structure, considering the carrier tunneling between quantum dots. Taking the presence of an additional in-plane or tilted magnetic field into account, we enable the simulation of magneto-optical experiments, like the time-resolved Kerr rotation measurement, which are currently performed on such structures to probe the temporal spin dynamics. With our model, we reproduce the experimentally observed effect of the extension of the spin polarization lifetime caused by spatial charge separation, which may occur in structures of this type. Moreover, we provide a number of qualitative predictions concerning the necessary conditions for observation of this effect as well as about possible channels of its suppression, including the spin-orbit coupling, which leads to tunneling of carriers accompanied by a spin flip. We also consider the impact of the magnetic field tilting, which results in an interesting spin polarization dynamics.
Physics and Dynamics Coupling Across Scales in the Next Generation CESM. Final Report
Bacmeister, Julio T.
2015-06-12
This project examines physics/dynamics coupling, that is, exchange of meteorological profiles and tendencies between an atmospheric model’s dynamical core and its various physics parameterizations. Most model physics parameterizations seek to represent processes that occur on scales smaller than the smallest scale resolved by the dynamical core. As a consequence a key conceptual aspect of parameterizations is an assumption about the subgrid variability of quantities such as temperature, humidity or vertical wind. Most existing parameterizations of processes such as turbulence, convection, cloud, and gravity wave drag make relatively ad hoc assumptions about this variability and are forced to introduce empirical parameters, i.e., “tuning knobs” to obtain realistic simulations. These knobs make systematic dependences on model grid size difficult to quantify.
Universal transport dynamics in a quenched tunnel-coupled Luttinger liquid
NASA Astrophysics Data System (ADS)
Gambetta, F. M.; Cavaliere, F.; Citro, R.; Sassetti, M.
2016-07-01
The transport dynamics of a quenched Luttinger liquid tunnel-coupled to a fermionic reservoir is investigated. In the transient dynamics, we show that for a sudden quench of the electron interaction universal power-law decay in time of the tunneling current occurs, ascribed to the presence of entangled compound excitations created by the quench. In sharp contrast to the usual nonuniversal power-law behavior of a zero-temperature nonquenched Luttinger liquid, the steady-state tunneling current is Ohmic and can be explained in terms of an effective quench-activated heating of the system. Our study unveils an unconventional dynamics for a quenched Luttinger liquid that could be identified in quenched cold Fermi gases.
Detecting event-related changes of multivariate phase coupling in dynamic brain networks.
Canolty, Ryan T; Cadieu, Charles F; Koepsell, Kilian; Ganguly, Karunesh; Knight, Robert T; Carmena, Jose M
2012-04-01
Oscillatory phase coupling within large-scale brain networks is a topic of increasing interest within systems, cognitive, and theoretical neuroscience. Evidence shows that brain rhythms play a role in controlling neuronal excitability and response modulation (Haider B, McCormick D. Neuron 62: 171-189, 2009) and regulate the efficacy of communication between cortical regions (Fries P. Trends Cogn Sci 9: 474-480, 2005) and distinct spatiotemporal scales (Canolty RT, Knight RT. Trends Cogn Sci 14: 506-515, 2010). In this view, anatomically connected brain areas form the scaffolding upon which neuronal oscillations rapidly create and dissolve transient functional networks (Lakatos P, Karmos G, Mehta A, Ulbert I, Schroeder C. Science 320: 110-113, 2008). Importantly, testing these hypotheses requires methods designed to accurately reflect dynamic changes in multivariate phase coupling within brain networks. Unfortunately, phase coupling between neurophysiological signals is commonly investigated using suboptimal techniques. Here we describe how a recently developed probabilistic model, phase coupling estimation (PCE; Cadieu C, Koepsell K Neural Comput 44: 3107-3126, 2010), can be used to investigate changes in multivariate phase coupling, and we detail the advantages of this model over the commonly employed phase-locking value (PLV; Lachaux JP, Rodriguez E, Martinerie J, Varela F. Human Brain Map 8: 194-208, 1999). We show that the N-dimensional PCE is a natural generalization of the inherently bivariate PLV. Using simulations, we show that PCE accurately captures both direct and indirect (network mediated) coupling between network elements in situations where PLV produces erroneous results. We present empirical results on recordings from humans and nonhuman primates and show that the PCE-estimated coupling values are different from those using the bivariate PLV. Critically on these empirical recordings, PCE output tends to be sparser than the PLVs, indicating fewer
Dynamic localization in optical and Zeeman lattices in the presence of spin-orbit coupling
NASA Astrophysics Data System (ADS)
Kartashov, Yaroslav V.; Konotop, Vladimir V.; Zezyulin, Dmitry A.; Torner, Lluis
2016-12-01
The dynamic localization of a two-level atom in a periodic potential under the action of spin-orbit coupling and a weak harmonically varying linear force is studied. We consider optical and Zeeman potentials that are either in phase or out of phase in two spinor components, respectively. The expectation value for the position of the atom after one oscillation period of the linear force is recovered in authentic resonances or in pseudoresonances. The frequencies of the linear force corresponding to authentic resonances are determined by the band structure of the periodic potential and are affected by the spin-orbit coupling. The width or dispersion of the wave packet in authentic resonances is usually minimal. The frequencies corresponding to pseudoresonances do not depend on the type of potential and on the strength of the spin-orbit coupling, while the evolution of excitations at the corresponding frequencies is usually accompanied by significant dispersion. Pseudoresonances are determined by the initial phase of the linear force and by the quasimomentum of the wave packet. Due to the spinor nature of the system, the motion of the atom is accompanied by periodic, but not harmonic, spin oscillations. Under the action of spin-orbit coupling the oscillations of the wave packet can be nearly completely suppressed in optical lattices. Dynamic localization in Zeeman lattices is characterized by doubling of the resonant oscillation periods due to band crossing at the boundary of the Brillouin zone. We also show that higher harmonics in the Fourier expansion of the energy band lead to effective dispersion, which can be strong enough to prevent dynamic localization of the Bloch wave packet.
Medial Prefrontal-Medial Temporal Theta Phase Coupling in Dynamic Spatial Imagery.
Kaplan, Raphael; Bush, Daniel; Bisby, James A; Horner, Aidan J; Meyer, Sofie S; Burgess, Neil
2017-03-01
Hippocampal-medial prefrontal interactions are thought to play a crucial role in mental simulation. Notably, the frontal midline/medial pFC (mPFC) theta rhythm in humans has been linked to introspective thought and working memory. In parallel, theta rhythms have been proposed to coordinate processing in the medial temporal cortex, retrosplenial cortex (RSc), and parietal cortex during the movement of viewpoint in imagery, extending their association with physical movement in rodent models. Here, we used noninvasive whole-head MEG to investigate theta oscillatory power and phase-locking during the 18-sec postencoding delay period of a spatial working memory task, in which participants imagined previously learned object sequences either on a blank background (object maintenance), from a first-person viewpoint in a scene (static imagery), or moving along a path past the objects (dynamic imagery). We found increases in 4- to 7-Hz theta power in mPFC when comparing the delay period with a preencoding baseline. We then examined whether the mPFC theta rhythm was phase-coupled with ongoing theta oscillations elsewhere in the brain. The same mPFC region showed significantly higher theta phase coupling with the posterior medial temporal lobe/RSc for dynamic imagery versus either object maintenance or static imagery. mPFC theta phase coupling was not observed with any other brain region. These results implicate oscillatory coupling between mPFC and medial temporal lobe/RSc theta rhythms in the dynamic mental exploration of imagined scenes.
Mosha, Idda; Ruben, Ruerd; Kakoko, Deodatus
2013-05-30
Contraceptive use is low in developing countries which are still largely driven by male dominated culture and patriarchal values. This study explored family planning (FP) decisions, perceptions and gender dynamics among couples in Mwanza region of Tanzania. Twelve focus group discussions and six in-depth interviews were used to collect information from married or cohabiting males and females aged 18-49. The participants were purposively selected. Qualitative methods were used to explore family planning decisions, perceptions and gender dynamics among couples. A guide with questions related to family planning perceptions, decisions and gender dynamics was used. The discussions and interviews were tape-recorded, transcribed verbatim and analyzed manually and subjected to content analysis. Four themes emerged during the study. First, "risks and costs" which refer to the side effects of FP methods and the treatment of side -effects as well as the costs inherit in being labeled as an unfaithful spouse. Second, "male involvement" as men showed little interest in participating in family planning issues. However, the same men were mentioned as key decision-makers even on the number of children a couple should have and the child spacing of these children. Third, "gender relations and communication" as participants indicated that few women participated in decision-making on family planning and the number of children to have. Fourth, "urban-rural differences", life in rural favoring having more children than urban areas therefore, the value of children depended on the place of residence. Family Planning programs should adapt the promotion of communication as well as joint decision-making on FP among couples as a strategy aimed at enhancing FP use.
Impact of Dynamical Downscaling on Model Representation of Land-Atmosphere Coupling Strength
NASA Astrophysics Data System (ADS)
Santanello, J. A., Jr.; Roundy, J. K.; Ferguson, C. R.
2015-12-01
Extremes in the water cycle, such as drought and flood, threaten the sustainability of water resources and cause significant impacts on society that will likely increase due to growing populations and a changing climate. Reducing the impact of extreme events requires preparations enabled by reliable and relevant predictions of the climate. Climate predictions are made using Global Climate Models (GCMs) that typically have spatial resolutions that are too course for application at the local level where the prediction is needed to ensure a society resilient to extremes. Therefore, a common practice is to dynamically downscale results from GCM's using a regional model that can provide predictions at scales consistent with the application. Downscaled predictions are dependent on model physics and model setup (e.g. boundary conditions, nudging) and as a result the overall validity of dynamically downscaling has not been fully demonstrated to date. NASA has recently sponsored an intra-agency downscaling project to better understand the validity of dynamical downscaling. As part of this project, several 10-year simulations of the NASA Unified Weather Research and Forecast (NU-WRF) model that vary in resolution and large scale nudging were used to downscale MERRA-2 reanalyses over the continental U.S. This work leverages these model runs in order to understand the impact of model resolution and nudging on the representation of land-atmosphere coupling strength and its impact on downscaled predictions of the water cycle. The representation of land-atmosphere coupling strength is analyzed through a suite of local land-atmosphere coupling (LoCo) metrics that are compared across downscaling runs as well as coarse scale predictions from GEOS-5 and MERRA-2. The impact of downscaling approaches and resolution on the representation of land-atmosphere coupling is presented and the implications for future downscaling applications are discussed.
2013-01-01
Background Contraceptive use is low in developing countries which are still largely driven by male dominated culture and patriarchal values. This study explored family planning (FP) decisions, perceptions and gender dynamics among couples in Mwanza region of Tanzania. Methods Twelve focus group discussions and six in-depth interviews were used to collect information from married or cohabiting males and females aged 18–49. The participants were purposively selected. Qualitative methods were used to explore family planning decisions, perceptions and gender dynamics among couples. A guide with questions related to family planning perceptions, decisions and gender dynamics was used. The discussions and interviews were tape-recorded, transcribed verbatim and analyzed manually and subjected to content analysis. Results Four themes emerged during the study. First, “risks and costs” which refer to the side effects of FP methods and the treatment of side -effects as well as the costs inherit in being labeled as an unfaithful spouse. Second, “male involvement” as men showed little interest in participating in family planning issues. However, the same men were mentioned as key decision-makers even on the number of children a couple should have and the child spacing of these children. Third, “gender relations and communication” as participants indicated that few women participated in decision-making on family planning and the number of children to have. Fourth, “urban–rural differences”, life in rural favoring having more children than urban areas therefore, the value of children depended on the place of residence. Conclusion Family Planning programs should adapt the promotion of communication as well as joint decision-making on FP among couples as a strategy aimed at enhancing FP use. PMID:23721196
NASA Technical Reports Server (NTRS)
Shia, Run-Lie; Zhou, Shuntai; Ko, Malcolm K. W.; Sze, Nien-Dak; Salstein, David; Cady-Pereira, Karen
1997-01-01
A zonal mean chemistry transport model (2-D CTM) coupled with a semi-spectral dynamical model is used to simulate the distributions of trace gases in the present day atmosphere. The zonal-mean and eddy equations for the velocity and the geopotential height are solved in the semi-spectral dynamical model. The residual mean circulation is derived from these dynamical variables and used to advect the chemical species in the 2- D CTM. Based on a linearized wave transport equation, the eddy diffusion coefficients for chemical tracers are expressed in terms of the amplitude, frequency and growth rate of dynamical waves; local chemical loss rates; and a time constant parameterizing small scale mixing. The contributions to eddy flux are from the time varying wave amplitude (transient eddy), chemical reactions (chemical eddy) and small scale mixing. In spite of the high truncation in the dynamical module (only three longest waves are resolved), the model has simulated many observed characteristics of stratospheric dynamics and distribution of chemical species including ozone. Compared with the values commonly used in 2-D CTMs, the eddy diffusion coefficients for chemical species calculated in this model are smaller, especially in the subtropics. It is also found that the chemical eddy diffusion has only a small effects in determining the distribution of most slow species, including ozone in the stratosphere.
Coupled Dynamics and Entropic Contribution to the Allosteric Mechanism of Pin1.
Barman, Arghya; Hamelberg, Donald
2016-08-25
Allosteric communication in proteins regulates a plethora of downstream processes in subcellular signaling pathways. Describing the effects of cooperative ligand binding on the atomic level is a key to understanding many regulatory processes involving biomolecules. Here, we use microsecond-long molecular dynamics simulations to investigate the allosteric mechanism of Pin1, a potential therapeutic target and a phosphorylated-Ser/Thr dependent peptidyl-prolyl cis-trans isomerase that regulates several subcellular processes and has been implicated in many diseases, including cancer and Alzheimer's. Experimental studies suggest that the catalytic domain and the noncatalytic WW domain are allosterically coupled; however, an atomic level description of the dynamics associated with the interdomain communication is lacking. We show that binding of the substrate to the WW domain is directly coupled to the dynamics of the catalytic domain, causing rearrangement of the residue-residue contact dynamics from the WW domain to the catalytic domain. The binding affinity of the substrate in the catalytic domain is also enhanced upon binding of the substrate to the WW domain. Modulation of the dynamics of the catalytic domain upon binding of the substrate to the WW domain leads to prepayment of the entropic cost of binding the substrate to the catalytic domain. This study shows that Ile 28 at the interfacial region between the catalytic and WW domains is certainly one of the residues responsible for bridging the communication between the two domains. The results complement previous experiments and provide valuable atomistic insights into the role of dynamics and possible entropic contribution to the allosteric mechanism of proteins.
NASA Astrophysics Data System (ADS)
Gueven, I.; Steeb, H.; Luding, S.
2014-12-01
Electrokinetic waves describe the coupling between seismic and electromagnetic waves that exist in porous media. The coupling between them arise from an electrochemical boundary layer between grain and fluid interface of saturated porous media. Acoustical waves cause a disturbance of the electrical fluid charge within the double layer, which therefore creates an electric streaming current (seismoelectric effect). Inversely, electromagnetic waves can generate mechanical signals (electroseismic effect). Electrokinetic conversion potentially combines high seismic resolution with good electromagnetic hydrocarbon sensitivity. The (stationary and frequency-dependent) streaming potential coefficient is a key property, which gives rise to the coupling between electromagnetic and acoustical waves. It depends strongly on the fluid conductivity, porosity, tortuosity, permeability, pore throat and zeta potential of porous media. We examine experimentally both, the stationary and dynamic permeabilities and coupling coefficients of sintered glass bead systems. For this purpose a multi-purpose measuring cell was developed which allows us to carry out - besides common ultrasound experiments - also to perform stationary and frequency-dependent permeability and coupling coefficient measurements. For the experiments sintered mono- and slightly polydisperse glass bead samples with different glass bead diameters between 0.4 and 8mm and porosities ranging between 21 and 39% were used. The stationary and dynamic permeability and streaming potential measurements are supported by μCT scans which enable us a deeper insight into the porous medium. Based on the μCT scans of the produced sintered glass bead samples essential influence parameters, like tortuosity, porosity, effective particle diameters and pore throats in different regions of the entire scanned region have been analyzed in detail to understand the laboratory experiments, cf. Illustration 1. In addition lattice Boltzmann
NASA Astrophysics Data System (ADS)
Tu, J.; Song, P.
2016-12-01
We have developed a new numerical simulation model of the ionosphere/thermosphere by using an inductive-dynamic approach (including self-consistent solutions of Faraday's law and retaining inertia terms in ion momentum equations), that is, based on magnetic field B and plasma velocity v (B, v paradigm), which is distinctive from the conventional modeling based on electric field E and current j. The model solves self-consistently time-dependent continuity, momentum, and energy equations for multiple species of ions and neutrals including photochemistry, and Maxwell's equations. The governing equations solved in the model are a set of multifluid-collisional-Hall MHD equations which are one of unique features of our ionosphere/thermosphere model. With such an inductive-dynamic approach, not only sound wave mode but also all possible MHD wave modes are retained in the solutions of the governing equations so that the dynamic coupling between the magnetosphere and ionosphere and among different regions of the ionosphere can be self-consistently investigated. In the present study, we demonstrate dynamic propagation of field-aligned currents and ionospheric electric field carried by Alfven waves, as well as formation of closure horizontal currents (Pedersen currents in the E-region), indicating that the M-I coupling is via the Alfven waves instead of the field-aligned currents or electric field mapping. The simulation results also show that the Poynting flux and strongest energy dissipation in the ionosphere/thermosphere is in the regions of the largest ion velocities and not necessarily in the auroral oval where the field-aligned currents reside. The frictional heating increases plasma temperature and thus drives ion upflows. The frictional heating also increase neutral temperature and produces neutral upflows but in a much longer time scale. Furthermore, the coupling of high-to-low latitude ionosphere is investigated in terms of propagation of fast MHD waves.
A two-dimensional global simulation study of inductive-dynamic magnetosphere-ionosphere coupling
NASA Astrophysics Data System (ADS)
Tu, Jiannan; Song, Paul
2016-12-01
We present the numerical methods and results of a global two-dimensional multifluid-collisional-Hall magnetohydrodynamic (MHD) simulation model of the ionosphere-thermosphere system, an extension of our one-dimensional three-fluid MHD model. The model solves, self-consistently, Maxwell's equations, continuity, momentum, and energy equations for multiple ion and neutral species incorporating photochemistry, collisions among the electron, ion and neutral species, and various heating sources in the energy equations. The inductive-dynamic approach (solving self-consistently Faraday's law and retaining inertia terms in the plasma momentum equations) used in the model retains all possible MHD waves, thus providing faithful physical explanation (not merely description) of the magnetosphere-ionosphere/thermosphere (M-IT) coupling. In the present study, we simulate the dawn-dusk cross-polar cap dynamic responses of the ionosphere to imposed magnetospheric convection. It is shown that the convection velocity at the top boundary launches velocity, magnetic, and electric perturbations propagating with the Alfvén speed toward the bottom of the ionosphere. Within the system, the waves experience reflection, penetration, and rereflection because of the inhomogeneity of the plasma conditions. The reflection of the Alfvén waves may cause overshoot (stronger than the imposed magnetospheric convection) of the plasma velocity in some regions. The simulation demonstrates dynamic propagation of the field-aligned currents and ionospheric electric field carried by the Alfvén waves, as well as formation of closure horizontal currents (Pedersen currents in the E region), indicating that in the dynamic stage the M-I coupling is via the Alfvén waves instead of field-aligned currents or electric field mapping as described in convectional M-I coupling models.
Coupled nonlinear flight dynamics, aeroelasticity, and control of very flexible aircraft
NASA Astrophysics Data System (ADS)
Shearer, Christopher M.
Flight dynamics and control of rigid aircraft motion coupled with linearized structural dynamics has been studied for several decades. However, new requirements for very flexible aircraft are challenging the validity of most rigid body coupled linearized structural motion formulations, due to the presence of large elastic motions. This dissertation presents, the flight dynamics, integration, and control of the six degree-of-freedom equations of motion of a reference point on a very flexible aircraft coupled with the aeroelastic equations which govern the geometrically nonlinear structural response of the vehicle. A low-order strain-based nonlinear structural analysis coupled with unsteady finite-state potential flow aerodynamics form the basis for the aeroelastic formulation. The nonlinear beam structural model is based upon the finite strain approach. Kinematic differential equations are used to provide orientation and position of the fixed reference point. The resulting governing differential equations are non-linear, first- and second-order differential algebraic equations and provide a low-order complete nonlinear aircraft formulation. The resulting equations are integrated using an implicit Modified Newmark Method. The method incorporates both first- and second-order nonlinear equations without the necessity of transforming second-order equations to first-order form. The method also incorporates a Newton-Raphson sub-iteration scheme to reduce residual error. Due to the inherent flexibility of these aircraft, the low order structural modes couple directly with the rigid body modes. This creates a system which cannot be separated as in traditional control schemes. Trajectory control techniques are developed based upon a combination of linear and nonlinear inner-loop tracking and an outer-loop nonlinear transformation from desired trajectories to reference frame velocities. Numerical simulations are presented validating the proposed integration scheme and the
Dynamic coupling of regulated binding sites and cycling myosin heads in striated muscle.
Campbell, Kenneth S
2014-03-01
In an activated muscle, binding sites on the thin filament and myosin heads switch frequently between different states. Because the status of the binding sites influences the status of the heads, and vice versa, the binding sites and myosin heads are dynamically coupled. The functional consequences of this coupling were investigated using MyoSim, a new computer model of muscle. MyoSim extends existing models based on Huxley-type distribution techniques by incorporating Ca(2+) activation and cooperative effects. It can also simulate arbitrary cross-bridge schemes set by the researcher. Initial calculations investigated the effects of altering the relative speeds of binding-site and cross-bridge kinetics, and of manipulating cooperative processes. Subsequent tests fitted simulated force records to experimental data recorded using permeabilized myocardial preparations. These calculations suggest that the rate of force development at maximum activation is limited by myosin cycling kinetics, whereas the rate at lower levels of activation is limited by how quickly binding sites become available. Additional tests investigated the behavior of transiently activated cells by driving simulations with experimentally recorded Ca(2+) signals. The unloaded shortening profile of a twitching myocyte could be reproduced using a model with two myosin states, cooperative activation, and strain-dependent kinetics. Collectively, these results demonstrate that dynamic coupling of binding sites and myosin heads is important for contractile function.
Modulation of spin dynamics via voltage control of spin-lattice coupling in multiferroics
Zhu, Mingmin; Zhou, Ziyao; Peng, Bin; ...
2017-02-03
Our work aims at magnonics manipulation by the magnetoelectric coupling effect and is motivated by the most recent progresses in both magnonics (spin dynamics) and multiferroics fields. Here, voltage control of magnonics, particularly the surface spin waves, is achieved in La0.7Sr0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 multiferroic heterostructures. With the electron spin resonance method, a large 135 Oe shift of surface spin wave resonance (≈7 times greater than conventional voltage-induced ferromagnetic resonance shift of 20 Oe) is determined. A model of the spin-lattice coupling effect, i.e., varying exchange stiffness due to voltage-induced anisotropic lattice changes, has been established to explain experiment results with good agreement.more » In addition, an “on” and “off” spin wave state switch near the critical angle upon applying a voltage is created. The modulation of spin dynamics by spin-lattice coupling effect provides a platform for realizing energy-efficient, tunable magnonics devices.« less
Intrinsic islet heterogeneity and gap junction coupling determine spatiotemporal Ca²⁺ wave dynamics.
Benninger, Richard K P; Hutchens, Troy; Head, W Steven; McCaughey, Michael J; Zhang, Min; Le Marchand, Sylvain J; Satin, Leslie S; Piston, David W
2014-12-02
Insulin is released from the islets of Langerhans in discrete pulses that are linked to synchronized oscillations of intracellular free calcium ([Ca(2+)]i). Associated with each synchronized oscillation is a propagating calcium wave mediated by Connexin36 (Cx36) gap junctions. A computational islet model predicted that waves emerge due to heterogeneity in β-cell function throughout the islet. To test this, we applied defined patterns of glucose stimulation across the islet using a microfluidic device and measured how these perturbations affect calcium wave propagation. We further investigated how gap junction coupling regulates spatiotemporal [Ca(2+)]i dynamics in the face of heterogeneous glucose stimulation. Calcium waves were found to originate in regions of the islet having elevated excitability, and this heterogeneity is an intrinsic property of islet β-cells. The extent of [Ca(2+)]i elevation across the islet in the presence of heterogeneity is gap-junction dependent, which reveals a glucose dependence of gap junction coupling. To better describe these observations, we had to modify the computational islet model to consider the electrochemical gradient between neighboring β-cells. These results reveal how the spatiotemporal [Ca(2+)]i dynamics of the islet depend on β-cell heterogeneity and cell-cell coupling, and are important for understanding the regulation of coordinated insulin release across the islet. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Intrinsic Islet Heterogeneity and Gap Junction Coupling Determine Spatiotemporal Ca2+ Wave Dynamics
Benninger, Richard K.P.; Hutchens, Troy; Head, W. Steven; McCaughey, Michael J.; Zhang, Min; Le Marchand, Sylvain J.; Satin, Leslie S.; Piston, David W.
2014-01-01
Insulin is released from the islets of Langerhans in discrete pulses that are linked to synchronized oscillations of intracellular free calcium ([Ca2+]i). Associated with each synchronized oscillation is a propagating calcium wave mediated by Connexin36 (Cx36) gap junctions. A computational islet model predicted that waves emerge due to heterogeneity in β-cell function throughout the islet. To test this, we applied defined patterns of glucose stimulation across the islet using a microfluidic device and measured how these perturbations affect calcium wave propagation. We further investigated how gap junction coupling regulates spatiotemporal [Ca2+]i dynamics in the face of heterogeneous glucose stimulation. Calcium waves were found to originate in regions of the islet having elevated excitability, and this heterogeneity is an intrinsic property of islet β-cells. The extent of [Ca2+]i elevation across the islet in the presence of heterogeneity is gap-junction dependent, which reveals a glucose dependence of gap junction coupling. To better describe these observations, we had to modify the computational islet model to consider the electrochemical gradient between neighboring β-cells. These results reveal how the spatiotemporal [Ca2+]i dynamics of the islet depend on β-cell heterogeneity and cell-cell coupling, and are important for understanding the regulation of coordinated insulin release across the islet. PMID:25468351
Interface dynamics and coupled growth in directional solidification in presence of bubbles
NASA Astrophysics Data System (ADS)
Jamgotchian, H.; Trivedi, R.; Billia, B.
1993-12-01
The formation and dynamics of gas bubbles in Bridgman growth of succinonitrile-acetone alloys is examined. The experimental results show for the first time the rich dynamics that are associated with the formation and propagation of bubbles during directional solidification of alloys. The strong coupling of bubbles with the solid-liquid interface is found to result in the growth of elongated bubbles, either attached to a flat solidification front or forming localized cellular as well as dendritic duplexes (bubbles wrapped by a solid envelope). The coupling of the bubble with the solidification front is shown to cause oscillations in the bubble, which are characterized by fast Fourier transforms. When several duplexes are formed, coupled growth and screening may occur. The basic factors that give rise to oscillations, namely competition between source and sink of acetone assisted by capillary convection at the bubble cap, are discussed qualitatively through the development of an internal oscillator model. Coherent sidebranching observed on dendritic duplexes is shown to be due to resonant modes between the bubble cap and the solid envelope.
New coupling limits, dynamical symmetries and microscopic operators of IBM/TQM
NASA Astrophysics Data System (ADS)
Paar, V.
1985-01-01
A new particle-core basis having approximate supersymmetric (SUSY) features associated with SU(3) dynamical symmetry is introduced. The SUSY and CO-SUSY limits of IBFM/PTQM appear for the characteristic intermediate coupling strengths Γ/δ=±(Γ/δ)SUSY. The CO-SUSY limit is a truncated analog of the Stephens rotation-aligned scheme. A paradox was found in the relation of the SUSY and truncated strong coupling (TSC) limits to the strong coupling limit of the Bohr-Mottelson model. Microscopic dyson and Holstein-Primakoff realizations of RPA collective quadrupole phonon operators are explicitly constructed. Employing this mapping procedure in conjunction with the leading RPA diagrams, various operators of IBM/TQM, IBFM/PTQM have been derived in the particle-hole channel: E2 operator, one-particle transfer operator, two-particle transfer operator etc. In addition to the standard terms, this derivation gives in the same diagrammatic order the additional terms also. A new model was introduced for the odd-odd nuclei in the framework of IBM/TQM. For the SU(3) core the truncated analog of Gallagher-Moszkowski bands appears as the approximate SUSY pattern, of the same intrinsic structure as in the odd-even system. The idea of boson-fermion dynamical symmetry and supersymmetry is extended to odd-odd nuclei and hypernuclei.
Dahirel, Vincent; Zhao, Xudong; Jardat, Marie
2016-08-01
We applied the multiparticle collision dynamics (MPC) simulation technique to highly asymmetric electrolytes in solution, i.e., charged nanoparticles and their counterions in a solvent. These systems belong to a domain of solute size which ranges between the electrolyte and the colloidal domains, where most analytical theories are expected to fail, and efficient simulation techniques are still missing. MPC is a mesoscopic simulation method which mimics hydrodynamics properties of a fluid, includes thermal fluctuations, and can be coupled to a molecular dynamics of solutes. We took advantage of the size asymmetry between nanoparticles and counterions to treat the coupling between solutes and the solvent bath within the MPC method. Counterions were coupled to the solvent bath during the collision step and nanoparticles either through a direct interaction force or with stochastic rotation rules which mimic stick boundary conditions. Moreover, we adapted the simulation procedure to address the issue of the strong electrostatic interactions between solutes of opposite charges. We show that the short-ranged repulsion between counterions and nanoparticles can be modeled by stochastic reflection rules. This simulation scheme is very efficient from a computational point of view. We have also computed the transport coefficients for various densities. The diffusion of counterions was found in one case to increase slightly with the volume fraction of nanoparticles. The deviation of the electric conductivity from the ideal behavior (solutes at infinite dilution without any direct interactions) is found to be strong.
NASA Astrophysics Data System (ADS)
Dahirel, Vincent; Zhao, Xudong; Jardat, Marie
2016-08-01
We applied the multiparticle collision dynamics (MPC) simulation technique to highly asymmetric electrolytes in solution, i.e., charged nanoparticles and their counterions in a solvent. These systems belong to a domain of solute size which ranges between the electrolyte and the colloidal domains, where most analytical theories are expected to fail, and efficient simulation techniques are still missing. MPC is a mesoscopic simulation method which mimics hydrodynamics properties of a fluid, includes thermal fluctuations, and can be coupled to a molecular dynamics of solutes. We took advantage of the size asymmetry between nanoparticles and counterions to treat the coupling between solutes and the solvent bath within the MPC method. Counterions were coupled to the solvent bath during the collision step and nanoparticles either through a direct interaction force or with stochastic rotation rules which mimic stick boundary conditions. Moreover, we adapted the simulation procedure to address the issue of the strong electrostatic interactions between solutes of opposite charges. We show that the short-ranged repulsion between counterions and nanoparticles can be modeled by stochastic reflection rules. This simulation scheme is very efficient from a computational point of view. We have also computed the transport coefficients for various densities. The diffusion of counterions was found in one case to increase slightly with the volume fraction of nanoparticles. The deviation of the electric conductivity from the ideal behavior (solutes at infinite dilution without any direct interactions) is found to be strong.
Complex dynamics analysis of impulsively coupled Duffing oscillators with ring structure
NASA Astrophysics Data System (ADS)
Jiang, Hai-Bo; Zhang, Li-Ping; Yu, Jian-Jiang
2015-02-01
Impulsively coupled systems are high-dimensional non-smooth systems that can exhibit rich and complex dynamics. This paper studies the complex dynamics of a non-smooth system which is unidirectionally impulsively coupled by three Duffing oscillators in a ring structure. By constructing a proper Poincaré map of the non-smooth system, an analytical expression of the Jacobian matrix of Poincaré map is given. Two-parameter Hopf bifurcation sets are obtained by combining the shooting method and the Runge-Kutta method. When the period is fixed and the coupling strength changes, the system undergoes stable, periodic, quasi-periodic, and hyper-chaotic solutions, etc. Floquet theory is used to study the stability of the periodic solutions of the system and their bifurcations. Project supported by the National Natural Science Foundation of China (Grant Nos. 11402224, 11202180, 61273106, and 11171290), the Qing Lan Project of the Jiangsu Higher Educational Institutions of China, and the Jiangsu Overseas Research and Training Program for University Prominent Young and Middle-aged Teachers and Presidents.
Le Gac, Stéphane; Fusaro, Luca; Roisnel, Thierry; Boitrel, Bernard
2014-05-07
A bis-strap porphyrin ligand (1), with an overhanging carboxylic acid group on each side of the macrocycle, has been investigated toward the formation of dynamic libraries of bimetallic complexes with Hg(II), Cd(II), and Pb(II). Highly heteroselective metalation processes occurred in the presence of Pb(II), with Hg(II) or Cd(II) bound out-of-plane to the N-core and "PbOAc" bound to a carboxylate group of a strap on the opposite side. The resulting complexes, 1(Hg)·PbOAc and 1(Cd)·PbOAc, display three levels of dynamics. The first is strap-level (interactional dynamics), where the PbOAc moiety swings between the left and right side of the strap owing to a second sphere of coordination with lateral amide functions. The second is ligand-level (motional dynamics), where 1(Hg)·PbOAc and 1(Cd)·PbOAc exist as two degenerate states in equilibrium controlled by a chemical effector (AcO(-)). The process corresponds to a double translocation of the metal ions according to an intramolecular migration of Hg(II) or Cd(II) through the N-core, oscillating between the two equivalent overhanging carbonyl groups, coupled to an intermolecular pathway for PbOAc exchanging between the two equivalent overhanging carboxylate groups (N-core(up) ⇆ N-core(down) coupled to strap(down) ⇆ strap(up), i.e., coupled motion #1 in the abstract graphic). The third is library-level (constitutional dynamics), where a dynamic constitutional evolution of the system was achieved by the successive addition of two chemical effectors (DMAP and then AcO(-)). It allowed shifting equilibrium forward and backward between 1(Hg)·PbOAc and the corresponding homobimetallic complexes 1(Hg2)·DMAP and 1(Pb)·PbOAc. The latter displays a different ligand-level dynamics, in the form of an intraligand coupled migration of the Pb(II) ions (N-core(up) ⇆ strap(up) coupled to strap(down) ⇆ N-core(down), i.e., coupled motion #2 in the abstract graphic). In addition, the neutral "bridged" complexes 1HgPb and 1Cd
Dynamical Coupling Between the Stratosphere and the Troposphere: The Influence of External Forcings
NASA Astrophysics Data System (ADS)
Hansen, Felicitas; Matthes, Katja
2013-04-01
The dynamical coupling between the stratosphere and the troposphere is dominated by planetary waves that are generated in the troposphere by orography and land-sea contrasts. These waves travel upward into the stratosphere where they either dissipate or are reflected downward to impact the troposphere again. Through the interaction with the zonal mean flow planetary waves can induce stratospheric sudden warmings (SSWs), i.e., conditions during NH winter where the stratospheric polar vortex is disturbed so that the zonal mean zonal wind in the NH stratospheric jet becomes easterly and the polar cap meridional temperature gradient reverses. Since strong major SSWs can propagate down into the troposphere and even affect surface weather, SSWs present a strong and clear manifestation of the dynamical coupling in the stratosphere-troposphere system. We will investigate the influence of some external forcings, namely sea surface temperatures (SSTs), anthropogenic greenhouse gases and the quasi-biennial oscillation (QBO), on these coupling processes. Thereby we are interested in how the distribution of SSWs in the winter months changes due to the different forcings, whether the events evolve differently, and whether they show differences in their preconditioning, e.g. a different wave geometry. We will also investigate whether and how vertical reflective surfaces in the stratosphere, which can reflect upward propagating planetary waves, influence the evolution of SSWs. To address these questions, we performed a set of model simulations with NCAR's Community Earth System Model (CESM), a coupled model system including an interactive ocean (POP2), land (CLM4), sea ice (CICE) and atmosphere (NCAR's Whole Atmosphere Community Climate Model (WACCM)) component. Our control experiment is a 140-year simulation with the fully coupled atmosphere-ocean version of CESM. A second experiment is a 55-year simulation with only CESM's atmospheric component WACCM, a fully interactive
Collective dynamics of time-delay-coupled phase oscillators in a frustrated geometry
NASA Astrophysics Data System (ADS)
Thakur, Bhumika; Sharma, Devendra; Sen, Abhijit; Johnston, George L.
2017-01-01
We study the effect of time delay on the dynamics of a system of repulsively coupled nonlinear oscillators that are configured as a geometrically frustrated network. In the absence of time delay, frustrated systems are known to possess a high degree of multistability among a large number of coexisting collective states except for the fully synchronized state that is normally obtained for attractively coupled systems. Time delay in the coupling is found to remove this constraint and to lead to such a synchronized ground state over a range of parameter values. A quantitative study of the variation of frustration in a system with the amount of time delay has been made and a universal scaling behavior is found. The variation in frustration as a function of the product of time delay and the collective frequency of the system is seen to lie on a characteristic curve that is common for all natural frequencies of the identical oscillators and coupling strengths. Thus time delay can be used as a tuning parameter to control the amount of frustration in a system and thereby influence its collective behavior. Our results can be of potential use in a host of practical applications in physical and biological systems in which frustrated configurations and time delay are known to coexist.
Modified relaxation dynamics and coherent energy exchange in coupled vibration-cavity polaritons
Dunkelberger, A. D.; Spann, B. T.; Fears, K. P.; Simpkins, B. S.; Owrutsky, J. C.
2016-01-01
Coupling vibrational transitions to resonant optical modes creates vibrational polaritons shifted from the uncoupled molecular resonances and provides a convenient way to modify the energetics of molecular vibrations. This approach is a viable method to explore controlling chemical reactivity. In this work, we report pump–probe infrared spectroscopy of the cavity-coupled C–O stretching band of W(CO)6 and the direct measurement of the lifetime of a vibration-cavity polariton. The upper polariton relaxes 10 times more quickly than the uncoupled vibrational mode. Tuning the polariton energy changes the polariton transient spectra and relaxation times. We also observe quantum beats, so-called vacuum Rabi oscillations, between the upper and lower vibration-cavity polaritons. In addition to establishing that coupling to an optical cavity modifies the energy-transfer dynamics of the coupled molecules, this work points out the possibility of systematic and predictive modification of the excited-state kinetics of vibration-cavity polariton systems. PMID:27874010
Three-mode coupling interference patterns in the dynamic structure factor of a relaxor ferroelectric
NASA Astrophysics Data System (ADS)
Manley, M. E.; Abernathy, D. L.; Sahul, R.; Stonaha, P. J.; Budai, J. D.
2016-09-01
A longstanding controversy for relaxor ferroelectrics has been the origin of the "waterfall" effect in the phonon dispersion curves, in which low-energy transverse phonons cascade into vertical columns. Originally interpreted as phonons interacting with polar nanoregions (PNRs), it was later explained as an interference effect of coupling damped optic and acoustic phonons. In light of a recently discovered PNR vibrational mode near the "waterfall" wave vector [M. E. Manley, J. W. Lynn, D. L. Abernathy, E. D. Specht, O. Delaire, A. R. Bishop, R. Sahul, and J. D. Budai, Nat. Commun. 5, 3683 (2014), 10.1038/ncomms4683], we have reexamined this feature using neutron scattering on [100]-poled PMN-30%PT [0.6 Pb (M g1 /3N b2 /3 ) O3-0.3 PbTi O3] . We find that the PNR mode couples to both optic and acoustic phonons and that this results in complex patterns in the dynamic structure factor, including intensity pockets and peaks localized in momentum-energy space. These features are fully explained by extending the mode-coupling model to include three coupled damped harmonic oscillators representing the transverse optic, acoustic, and PNR modes.
Income dynamics in couples and the dissolution of marriage and cohabitation.
Kalmijn, Matthijs; Loeve, Anneke; Manting, Dorien
2007-02-01
Several studies have shown that a wife's strong (socio)economic position is associated with an increase in the risk of divorce. Less is known about such effects for cohabiting relationships. Using a unique and large-scale sample of administrative records from The Netherlands, we analyze the link between couples' income dynamics and union dissolution for married and cohabiting unions over a 10-year period. We find negative effects of household income on separation and positive effects of the woman's relative income, in line with earlier studies. The shape of the effect of the woman's relative income, however, depends on the type of union. Movements away from income equality toward a male-dominant pattern tend to increase the dissolution risk for cohabiting couples, whereas they reduce the dissolution risk for married couples. Movements away from income equality toward a female-dominant pattern (reverse specialization) increase the dissolution risks for both marriage and cohabitation. The findings suggest that equality is more protective for cohabitation, whereas specialization is more protective for marriage, although only when it fits a traditional pattern. Finally, we find that the stabilizing effects of income equality are more pronounced early in the marriage and that income equality also reduces the dissolution risk for same-sex couples.
Three-mode coupling interference patterns in the dynamic structure factor of a relaxor ferroelectric
Manley, M. E.; Abernathy, D. L.; Sahul, R.; Stonaha, P. J.; Budai, J. D.
2016-09-22
A long-standing controversy for relaxor ferroelectrics has been the origin of the waterfall effect in the phonon dispersion curves, in which low-energy transverse phonons cascade into vertical columns. Originally interpreted as phonons interacting with polar nanoregions (PNRs), it was later explained as an interference effect of coupling damped optic and acoustic phonons. In light of a recently discovered PNR vibrational mode near the waterfall wavevector [M. E. Manley, J. W. Lynn, D. L. Abernathy, E. D. Specht, O. Delaire, A. R. Bishop, R. Sahul, and J. D. Budai, Nat. Commun. 5, 3683 (2014)] we have reexamined this feature using neutron scattering on [100]-poled PMN-30%PT (0.6Pb(Mg_{1/3}Nb_{2/3})O_{3} 0.3PbTiO_{3}). In addition, we find that the PNR mode couples to both optic and acoustic phonons, and that this results in complex patterns in the dynamic structure factor, including intensity pockets and peaks localized in momentum-energy space. These features are fully explained by extending the mode-coupling model to include three coupled damped harmonic oscillators representing the transverse optic, acoustic, and PNR modes.
Three-mode coupling interference patterns in the dynamic structure factor of a relaxor ferroelectric
Manley, M. E.; Abernathy, D. L.; Sahul, R.; ...
2016-09-22
A long-standing controversy for relaxor ferroelectrics has been the origin of the waterfall effect in the phonon dispersion curves, in which low-energy transverse phonons cascade into vertical columns. Originally interpreted as phonons interacting with polar nanoregions (PNRs), it was later explained as an interference effect of coupling damped optic and acoustic phonons. In light of a recently discovered PNR vibrational mode near the waterfall wavevector [M. E. Manley, J. W. Lynn, D. L. Abernathy, E. D. Specht, O. Delaire, A. R. Bishop, R. Sahul, and J. D. Budai, Nat. Commun. 5, 3683 (2014)] we have reexamined this feature using neutronmore » scattering on [100]-poled PMN-30%PT (0.6Pb(Mg1/3Nb2/3)O3 0.3PbTiO3). In addition, we find that the PNR mode couples to both optic and acoustic phonons, and that this results in complex patterns in the dynamic structure factor, including intensity pockets and peaks localized in momentum-energy space. These features are fully explained by extending the mode-coupling model to include three coupled damped harmonic oscillators representing the transverse optic, acoustic, and PNR modes.« less
Three-mode coupling interference patterns in the dynamic structure factor of a relaxor ferroelectric
Manley, M. E.; Abernathy, D. L.; Sahul, R.; Stonaha, P. J.; Budai, J. D.
2016-09-22
A long-standing controversy for relaxor ferroelectrics has been the origin of the waterfall effect in the phonon dispersion curves, in which low-energy transverse phonons cascade into vertical columns. Originally interpreted as phonons interacting with polar nanoregions (PNRs), it was later explained as an interference effect of coupling damped optic and acoustic phonons. In light of a recently discovered PNR vibrational mode near the waterfall wavevector [M. E. Manley, J. W. Lynn, D. L. Abernathy, E. D. Specht, O. Delaire, A. R. Bishop, R. Sahul, and J. D. Budai, Nat. Commun. 5, 3683 (2014)] we have reexamined this feature using neutron scattering on [100]-poled PMN-30%PT (0.6Pb(Mg_{1/3}Nb_{2/3})O_{3} 0.3PbTiO_{3}). In addition, we find that the PNR mode couples to both optic and acoustic phonons, and that this results in complex patterns in the dynamic structure factor, including intensity pockets and peaks localized in momentum-energy space. These features are fully explained by extending the mode-coupling model to include three coupled damped harmonic oscillators representing the transverse optic, acoustic, and PNR modes.
Coupled dynamics of Earth's geomagnetic westward drift and inner core super-rotation
NASA Astrophysics Data System (ADS)
Pichon, Guillaume; Aubert, Julien; Fournier, Alexandre
2016-03-01
The geomagnetic westward drift and the inner core differential rotation relative to the mantle are two components of the Earth's core rotational dynamics. We present a systematic study of their long-term relationship in convective numerical simulations of the geodynamo. All models comprise gravitational coupling between the inner core and the mantle, in addition to electromagnetic coupling at the inner core and core-mantle boundaries. We show that the strength of these couplings has no influence on the global shear available in the fluid shell, the amount of which is entirely governed by the vigor of convection. This shear is distributed between the long-term westward drift and the long-term differential rotation of the inner core, in proportions controlled by the relative magnitudes of the electromagnetic and gravitational couplings. A present-day estimate of this available shear predicts a magnitude of the westward drift close to that observed on average during the last 400 yrs, which then implies a non-existent long-term inner core differential rotation. Assuming a lower mantle conductance of order 108 S, this in turn sets a constraint on the minimum stiffness of the inner core, the viscosity of which should be larger than 2 ×1017 Pa s for the westward drift to dominate.
Study of the Ionization Dynamics and Equation of State of a Strongly Coupled Plasma
Shepherd, R; Audebert, P; Geindre, J P; Iglesias, C; Foord, M; Rogers, F; Gauthier, J C; Springer, P
2003-02-06
Preliminary experiments to study the ionization dynamics and equation of state of a strongly coupled plasma have been performed at the LLNL COMET laser facility. In these experiment, a 1.0 J, 500 fs, 532 nm laser was used to create a uniform, warm dense plasma.The primary diagnostic, Fourier Domain Interferometry (FDI), was used to provide information about the position of the critical density of the target and thus the expansion hydrodynamics, laying the ground work for the plasma characterization. The plasmas were determined to be strongly coupled. In addition work was performed characterizing the back-lighter. A von Hamos spectrograph coupled to a 500 fs X-ray streak camera (TREX-VHS) developed at LLNL was used for these measurements. This diagnostic combines high collection efficiency ({approx} 10{sup -4} steradians) with fast temporal response ({approx} 500 fs), allowing resolution of extremely transient spectral variations. The TREX-VHS will be used to determine the time history, intensity, and spectral content of the back-lighter resulting in absorption measurements that provide insight into bound states in strongly coupled conditions.
Dynamical coupled-channels study of {pi}N {right arrow} {pi pi}N reactions.
Kamano, H.; Julia-Diaz, B.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.; Physics; Jefferson Lab.; Univ. of Barcelona; Shizuoka Univ.; Osaka Univ.
2009-02-24
As a step toward performing a complete coupled-channels analysis of the world data of {pi}N,{gamma}*N {yields} {pi}N,{eta}N,{pi}{pi}N reactions, the {pi}N {yields} {pi}{pi}N reactions are investigated starting with the dynamical coupled-channels model developed in Phys. Rev. C 76, 065201 (2007). The channels included are {pi}N,{eta}N, and {pi}{pi}N which has {pi}{Delta},{rho}N, and {sigma}N resonant components. The nonresonant amplitudes are generated from solving a set of coupled-channels equations with the meson-baryon potentials defined by effective Lagrangians. The resonant amplitudes are generated from 16 bare excited nucleon (N*) states that are dressed by the nonresonant interactions as constrained by the unitarity condition. The data of total cross sections and {pi}N and {pi}{pi} invariant mass distributions of {pi} + p {yields} {pi} + {pi} + n, {pi} + {pi}0p and {pi} - p {yields} {pi} + {pi} - n, {pi} - {pi}0p,{pi}0{pi}0n reactions from threshold to the invariant mass W = 2 GeV can be described to a very large extent. We show the importance of the coupled-channels effects and the strong interference among the contributions from the {pi}{Delta},{sigma}N, and {rho}N channels. The large interference between the resonant and nonresonant amplitudes is also demonstrated. Possible future developments are discussed.
Kolmogorov flow in two dimensional strongly coupled Yukawa liquid: A molecular dynamics study
NASA Astrophysics Data System (ADS)
Gupta, Akanksha; Ganesh, Rajaraman; Joy, Ashwin
2015-10-01
The transition from laminar to turbulent flows in liquids remains a problem of great interest despite decades of intensive research. Here, we report an atomistic study of this transition in a model Yukawa liquid using molecular dynamics simulations. Starting from an thermally equilibrated Yukawa liquid, for a given value of coupling parameter Γ (defined as ratio of potential energy to kinetic energy per particle) and screening length κ, a subsonic flow of magnitude U0 is superposed and transition to an unstable regime is observed eventually leading to turbulent flow at sufficiently high Reynolds numbers. We have performed a parametric study for a range of Reynolds number R and found that the flow is neutrally stable for R
Dynamic coupling of complex brain networks and dual-task behavior.
Alavash, Mohsen; Thiel, Christiane M; Gießing, Carsten
2016-04-01
Multi-tasking is a familiar situation where behavioral performance is often challenged. To date, fMRI studies investigating the neural underpinning of dual-task interference have mostly relied on local brain activation maps or static brain connectivity networks. Here, based on task fMRI we explored how fluctuations in behavior during concurrent performance of a visuospatial and a speech task relate to alternations in the topology of dynamic brain connectivity networks. We combined a time-resolved functional connectivity and complex network analysis with a sliding window approach applied to the trial by trial behavioral responses to investigate the coupling between dynamic brain networks and dual-task behavior at close temporal proximity. Participants showed fluctuations in their dual-task behavior over time, with the accuracy in the component tasks being statistically independent from one another. On the global level of brain networks we found that dynamic changes of network topology were differentially coupled with the behavior in each component task during the course of dual-tasking. While momentary decrease in the global efficiency of dynamic brain networks correlated with subsequent increase in visuospatial accuracy, better speech performance was preceded by higher global network efficiency and was followed by an increase in between-module connectivity over time. Additionally, dynamic alternations in the modular organization of brain networks at the posterior cingulate cortex were differentially predictive for the visuospatial as compared to the speech accuracy over time. Our results provide the first evidence that, during the course of dual-tasking, each component task is supported by a distinct topological configuration of brain connectivity networks. This finding suggests that the failure of functional brain connectivity networks to adapt to an optimal topology supporting the performance in both component tasks at the same time contributes to the moment to
NASA Astrophysics Data System (ADS)
Dialynas, Y. G.; Bastola, S.; Billings, S. A.; Bras, R. L.
2014-12-01
Soil erosion and deposition play an important role in the global carbon (C) cycle, constituting an important driver of atmospheric CO2. Clarification of the net effect of landscape evolution on the C cycle may be achieved using coupled fully-distributed modelling of hydro-geomorphic and biogeochemical processes. We developed a distributed model of soil organic C (SOC) dynamics within an existing coupled physically-based hydro-geomorphic model (tRIBS - Erosion) to simulate the effects of soil erosion and deposition on C dynamics at basin scale. The SOC mass balance is analytically formulated at each cell using temporally variant, continuous vertical profiles of SOC content and SOC production and oxidation rate constants derived from SOC turnover characteristics. Landscape evolution feedbacks on C dynamics include the redistribution of eroded SOC, and the alteration of the SOC production and oxidation throughout the corresponding vertical profiles due to geomorphic perturbations. At each time step, model outputs include lateral and vertical C fluxes, and SOC content, at each soil column. We applied the model to the Calhoun Experimental Forest in South Carolina, which constitutes a forest recovering from agricultural land degradation prior to the mid-20th century. To test performance we carried out a point comparison against a spreadsheet-based model, SOrCERO (Soil Organic Carbon, Erosion, Replacement, and Oxidation) of SOC dynamics, which estimates effects of SOC erosion and altered SOC production and oxidation on CO2 release at an eroding profile. At a point, time integrated results from the two models were comparable. The proposed model has the additional advantage of being able to quantify C sinks and sources across the landscape in a spatially explicit manner, by systematically accounting for topographic controls on C dynamics. Sensitivity analysis suggested that the alteration of SOC production and oxidation due to landscape evolution and management practices
NASA Astrophysics Data System (ADS)
Warner, Thomas T.; Sheu, Rong-Shyang; Bowers, James F.; Sykes, R. Ian; Dodd, Gregory C.; Henn, Douglas S.
2002-05-01
Ensemble simulations made using a coupled atmospheric dynamic model and a probabilistic Lagrangian puff dispersion model were employed in a forensic analysis of the transport and dispersion of a toxic gas that may have been released near Al Muthanna, Iraq, during the Gulf War. The ensemble study had two objectives, the first of which was to determine the sensitivity of the calculated dosage fields to the choices that must be made about the configuration of the atmospheric dynamic model. In this test, various choices were used for model physics representations and for the large-scale analyses that were used to construct the model initial and boundary conditions. The second study objective was to examine the dispersion model's ability to use ensemble inputs to predict dosage probability distributions. Here, the dispersion model was used with the ensemble mean fields from the individual atmospheric dynamic model runs, including the variability in the individual wind fields, to generate dosage probabilities. These are compared with the explicit dosage probabilities derived from the individual runs of the coupled modeling system. The results demonstrate that the specific choices made about the dynamic-model configuration and the large-scale analyses can have a large impact on the simulated dosages. For example, the area near the source that is exposed to a selected dosage threshold varies by up to a factor of 4 among members of the ensemble. The agreement between the explicit and ensemble dosage probabilities is relatively good for both low and high dosage levels. Although only one ensemble was considered in this study, the encouraging results suggest that a probabilistic dispersion model may be of value in quantifying the effects of uncertainties in a dynamic-model ensemble on dispersion model predictions of atmospheric transport and dispersion.
NASA Astrophysics Data System (ADS)
Krönke, Sven; Knörzer, Johannes; Schmelcher, Peter
2015-05-01
We explore the correlated quantum dynamics of a single atom with a spatio-temporally localized coupling to a finite bosonic ensemble [arXiv:1410.8676]. The single atom is initially prepared in a coherent state of low energy and oscillates in a harmonic trap. An ensemble of NA interacting bosons is held in a displaced trap such that it is periodically penetrated by the single atom. The non-equilibrium quantum dynamics of the total system is simulated by means of an ab-initio method. Here, we focus on characterizing the impact of the peculiar inter-species coupling and the thereby induced inter-species correlations on the subsystem states: At instants of not too imbalanced excess energy distribution among the subsystems, inter-species correlations prove to be significant. A phase-space analysis for the single atom reveals that these correlations manifests themselves in short phases of strong deviations from a coherent state. In the bosonic ensemble, the single atom mainly induces singlet and delayed doublet excitations, for which we offer analytical insights with a stroboscopic time-dependent perturbation theory approach. When increasing the ensemble size, its maximal dynamical quantum depletion is shown to decrease faster than 1 /NA for a fixed excess energy.
First order coupled dynamic model of flexible space structures with time-varying configurations
NASA Astrophysics Data System (ADS)
Wang, Jie; Li, Dongxu; Jiang, Jianping
2017-03-01
This paper proposes a first order coupled dynamic modeling method for flexible space structures with time-varying configurations for the purpose of deriving the characteristics of the system. The model considers the first time derivative of the coordinate transformation matrix between the platform's body frame and the appendage's floating frame. As a result it can accurately predict characteristics of the system even if flexible appendages rotate with complex trajectory relative to the rigid part. In general, flexible appendages are fixed on the rigid platform or forced to rotate with a slow angular velocity. So only the zero order of the transformation matrix is considered in conventional models. However, due to neglecting of time-varying terms of the transformation matrix, these models introduce severe error when appendages, like antennas, for example, rotate with a fast speed relative to the platform. The first order coupled dynamic model for flexible space structures proposed in this paper resolve this problem by introducing the first time derivative of the transformation matrix. As a numerical example, a central core with a rotating solar panel is considered and the results are compared with those given by the conventional model. It has been shown that the first order terms are of great importance on the attitude of the rigid body and dynamic response of the flexible appendage.
Vertex coloring of graphs via phase dynamics of coupled oscillatory networks.
Parihar, Abhinav; Shukla, Nikhil; Jerry, Matthew; Datta, Suman; Raychowdhury, Arijit
2017-04-19
While Boolean logic has been the backbone of digital information processing, there exist classes of computationally hard problems wherein this paradigm is fundamentally inefficient. Vertex coloring of graphs, belonging to the class of combinatorial optimization, represents one such problem. It is well studied for its applications in data sciences, life sciences, social sciences and technology, and hence, motivates alternate, more efficient non-Boolean pathways towards its solution. Here we demonstrate a coupled relaxation oscillator based dynamical system that exploits insulator-metal transition in Vanadium Dioxide (VO2) to efficiently solve vertex coloring of graphs. Pairwise coupled VO2 oscillator circuits have been analyzed before for basic computing operations, but using complex networks of VO2 oscillators, or any other oscillators, for more complex tasks have been challenging in theory as well as in experiments. The proposed VO2 oscillator network harnesses the natural analogue between optimization problems and energy minimization processes in highly parallel, interconnected dynamical systems to approximate optimal coloring of graphs. We further indicate a fundamental connection between spectral properties of linear dynamical systems and spectral algorithms for graph coloring. Our work not only elucidates a physics-based computing approach but also presents tantalizing opportunities for building customized analog co-processors for solving hard problems efficiently.
Dynamic modeling and experiments on the coupled vibrations of building and elevator ropes
NASA Astrophysics Data System (ADS)
Yang, Dong-Ho; Kim, Ki-Young; Kwak, Moon K.; Lee, Seungjun
2017-03-01
This study is concerned with the theoretical modelling and experimental verification of the coupled vibrations of building and elevator ropes. The elevator ropes consist of a main rope which supports the cage and the compensation rope which is connected to the compensation sheave. The elevator rope is a flexible wire with a low damping, so it is prone to vibrations. In the case of a high-rise building, the rope length also increases significantly, so that the fundamental frequency of the elevator rope approaches the fundamental frequency of the building thus increasing the possibility of resonance. In this study, the dynamic model for the analysis of coupled vibrations of building and elevator ropes was derived by using Hamilton's principle, where the cage motion was also considered. An experimental testbed was built to validate the proposed dynamic model. It was found that the experimental results are in good agreement with the theoretical predictions thus validating the proposed dynamic model. The proposed model was then used to predict the vibrations of real building and elevator ropes.
Tian, Xiumei; Zeng, Dong; Zhang, Shanli; Huang, Jing; Zhang, Hua; He, Ji; Lu, Lijun; Xi, Weiwen; Ma, Jianhua; Bian, Zhaoying
2016-11-22
Dynamic cerebral perfusion x-ray computed tomography (PCT) imaging has been advocated to quantitatively and qualitatively assess hemodynamic parameters in the diagnosis of acute stroke or chronic cerebrovascular diseases. However, the associated radiation dose is a significant concern to patients due to its dynamic scan protocol. To address this issue, in this paper we propose an image restoration method by utilizing coupled dictionary learning (CDL) scheme to yield clinically acceptable PCT images with low-dose data acquisition. Specifically, in the present CDL scheme, the 2D background information from the average of the baseline time frames of low-dose unenhanced CT images and the 3D enhancement information from normal-dose sequential cerebral PCT images are exploited to train the dictionary atoms respectively. After getting the two trained dictionaries, we couple them to represent the desired PCT images as spatio-temporal prior in objective function construction. Finally, the low-dose dynamic cerebral PCT images are restored by using a general DL image processing. To get a robust solution, the objective function is solved by using a modified dictionary learning based image restoration algorithm. The experimental results on clinical data show that the present method can yield more accurate kinetic enhanced details and diagnostic hemodynamic parameter maps than the state-of-the-art methods.
Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators.
Driben, R; Konotop, V V; Malomed, B A; Meier, T
2016-07-01
The dynamics of a pair of harmonic oscillators represented by three-dimensional fields coupled with a repulsive cubic nonlinearity is investigated through direct simulations of the respective field equations and with the help of the finite-mode Galerkin approximation (GA), which represents the two interacting fields by a superposition of 3+3 harmonic-oscillator p-wave eigenfunctions with orbital and magnetic quantum numbers l=1 and m=1, 0, -1. The system can be implemented in binary Bose-Einstein condensates, demonstrating the potential of the atomic condensates to emulate various complex modes predicted by classical field theories. First, the GA very accurately predicts a broadly degenerate set of the system's ground states in the p-wave manifold, in the form of complexes built of a dipole coaxial with another dipole or vortex, as well as complexes built of mutually orthogonal dipoles. Next, pairs of noncoaxial vortices and/or dipoles, including pairs of mutually perpendicular vortices, develop remarkably stable dynamical regimes, which feature periodic exchange of the angular momentum and periodic switching between dipoles and vortices. For a moderately strong nonlinearity, simulations of the coupled-field equations agree very well with results produced by the GA, demonstrating that the dynamics is accurately spanned by the set of six modes limited to l=1.
Dynamic coupling of magnetic fields, thermal emissions, and zonal flows in ice giant planets
NASA Astrophysics Data System (ADS)
Soderlund, Krista M.; Heimpel, M. H.; King, E. M.; Aurnou, J. M.
2013-10-01
Magnetic fields are ubiquitous in the solar system, yet their characteristics are as diverse as the planets themselves. These fields are thought to result from dynamo action driven by thermochemical convection in electrically conducting fluid regions. The multipolar dynamos of Uranus and Neptune provide a unique opportunity to test hypotheses for magnetic field generation. Since no sharp structural boundaries in the ice giants between the ionic ocean and overlying molecular envelope are expected, it is possible that these regions are linked dynamically. Thus, an understanding of the coupling between magnetic fields, heat flow, and atmospheric winds is crucial to determine what controls the strength, morphology, and evolution of giant planet dynamos. Here we present numerical simulations of turbulent convection in spherical shells to test the hypothesis that poorly organized turbulence will generate ice giant-like magnetic fields, thermal emissions, and zonal flows. We find that this style of convection leads to small-scale, fluctuating dynamo action that generates a multipolar magnetic field, Hadley-like circulation cells that promote equatorial upwellings to create low latitude peaks in internal heat flux, and homogenized absolute angular momentum that drives three-jet zonal flows. This qualitative agreement with observations suggests that the internal dynamics of ice giant planets may be characterized by three-dimensional convective turbulence with dynamic coupling between the dynamo region and electrically insulating envelope above playing an important role as well.
Coupled slow and fast surface dynamics in an electrocatalytic oscillator: Model and simulations
Nascimento, Melke A.; Nagao, Raphael; Eiswirth, Markus; Varela, Hamilton
2014-12-21
The co-existence of disparate time scales is pervasive in many systems. In particular for surface reactions, it has been shown that the long-term evolution of the core oscillator is decisively influenced by slow surface changes, such as progressing deactivation. Here we present an in-depth numerical investigation of the coupled slow and fast surface dynamics in an electrocatalytic oscillator. The model consists of four nonlinear coupled ordinary differential equations, investigated over a wide parameter range. Besides the conventional bifurcation analysis, the system was studied by means of high-resolution period and Lyapunov diagrams. It was observed that the bifurcation diagram changes considerably as the irreversible surface poisoning evolves, and the oscillatory region shrinks. The qualitative dynamics changes accordingly and the chaotic oscillations are dramatically suppressed. Nevertheless, periodic cascades are preserved in a confined region of the resistance vs. voltage diagram. Numerical results are compared to experiments published earlier and the latter reinterpreted. Finally, the comprehensive description of the time-evolution in the period and Lyapunov diagrams suggests further experimental studies correlating the evolution of the system's dynamics with changes of the catalyst structure.
Dynamics of a mesoscopic qubit ensemble coupled to a cavity: Role of collective dark states
NASA Astrophysics Data System (ADS)
Zhukov, A. A.; Shapiro, D. S.; Pogosov, W. V.; Lozovik, Yu. E.
2017-09-01
We consider the dynamics of a disordered ensemble of qubits interacting with a single-mode photon field, which is described by an exactly solvable inhomogeneous Dicke model. In particular, we concentrate on the crossover from few-qubit systems to the system of many qubits and analyze how the collective behavior of a coupled qubit-cavity system emerges despite the broadening. We show that quantum interference effects survive in the mesoscopic regime—the dynamics of an entangled Bell state encoded into the qubit subsystem remains highly sensitive to the symmetry of the total wave function. Moreover, relaxation of these states is slowed down due to the formation of collective dark states weakly coupled to light. Dark states also significantly influence the dynamics of the excitations of a photon subsystem by absorbing them into the qubit subsystem and releasing quasiperiodically in time. We argue that the predicted phenomena can be useful in quantum technologies based on superconducting qubits. For instance, they provide tools to deeply probe both collective and quantum properties of such artificial macroscopic systems.
Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators
NASA Astrophysics Data System (ADS)
Driben, R.; Konotop, V. V.; Malomed, B. A.; Meier, T.
2016-07-01
The dynamics of a pair of harmonic oscillators represented by three-dimensional fields coupled with a repulsive cubic nonlinearity is investigated through direct simulations of the respective field equations and with the help of the finite-mode Galerkin approximation (GA), which represents the two interacting fields by a superposition of 3 +3 harmonic-oscillator p -wave eigenfunctions with orbital and magnetic quantum numbers l =1 and m =1 , 0, -1 . The system can be implemented in binary Bose-Einstein condensates, demonstrating the potential of the atomic condensates to emulate various complex modes predicted by classical field theories. First, the GA very accurately predicts a broadly degenerate set of the system's ground states in the p -wave manifold, in the form of complexes built of a dipole coaxial with another dipole or vortex, as well as complexes built of mutually orthogonal dipoles. Next, pairs of noncoaxial vortices and/or dipoles, including pairs of mutually perpendicular vortices, develop remarkably stable dynamical regimes, which feature periodic exchange of the angular momentum and periodic switching between dipoles and vortices. For a moderately strong nonlinearity, simulations of the coupled-field equations agree very well with results produced by the GA, demonstrating that the dynamics is accurately spanned by the set of six modes limited to l =1 .
NASA Astrophysics Data System (ADS)
Wang, Hai; Toma, Andrea; Wang, Haiyu; Sun, Hong-Bo; Proietti Zaccaria, Remo
2016-09-01
Strong coupling regime is reached when SPPs and matter exchange energy coherently and reversibly before losses take place, resulting in the formation of new hybrid exciton-plasmon states formed by lower and upper energy bands [1,2]. In this field most of the works focus on steady-state observations, indeed experiments on the dynamics of such hybrid systems are relatively scarce and their intrinsic photophysics is still far from being understood. Here, in order to improve our understanding of the dynamics of hybrid exciton-plasmon states, we have studied through ultrafast pump-probe approach, a hybrid system composed by gold hole arrays and J-aggregate molecules while modifying the lattice constant of the metallic array. Under upper hybrid band resonant excitation, transient absorption spectra provide the evidence that exciton-plasmon hybrid states are formed. Meanwhile, kinetics analysis led to the discovery of a remarkably long-lived upper band, at least one order of magnitude at 1/e than bare J-aggregate molecules. This result was explained with the identification, in the transient absorption spectra, of a trap state combined with the negligible relaxation effect from vibrational modes. The intrinsic long lifetime of hybrid states is of crucial importance both from a fundamental and applicative point of view, having implications in the use of exciton-plasmon states for technological purposes. The understanding of the dynamics on strong coupling systems can provide indeed a promising route towards novel ultrafast plasmonic devices with coherent functionalities.
Driben, R.; Konotop, V. V.; Meier, T.
2016-01-01
Nonlinearity is the driving force for numerous important effects in nature typically showing transitions between different regimes, regular, chaotic or catastrophic behavior. Localized nonlinear modes have been the focus of intense research in areas such as fluid and gas dynamics, photonics, atomic and solid state physics etc. Due to the richness of the behavior of nonlinear systems and due to the severe numerical demands of accurate three-dimensional (3D) numerical simulations presently only little knowledge is available on the dynamics of complex nonlinear modes in 3D. Here, we investigate the dynamics of 3D non-coaxial matter wave vortices that are trapped in a parabolic potential and interact via a repulsive nonlinearity. Our numerical simulations demonstrate the existence of an unexpected and fascinating nonlinear regime that starts immediately when the nonlinearity is switched-on and is characterized by a smooth dynamics representing torque-free precession with nutations. The reported motion is proven to be robust regarding various effects such as the number of particles, dissipation and trap deformations and thus should be observable in suitably designed experiments. Since our theoretical approach, i.e., coupled nonlinear Schrödinger equations, is quite generic, we expect that the obtained novel dynamical behavior should also exist in other nonlinear systems. PMID:26964759
Coupled turbulence and aerosol dynamics modeling of vehicle exhaust plumes using the CTAG model
NASA Astrophysics Data System (ADS)
Wang, Yan Jason; Zhang, K. Max
2012-11-01
This paper presents the development and evaluation of an environmental turbulent reacting flow model, the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model. CTAG is designed to simulate transport and transformation of multiple air pollutants, e.g., from emission sources to ambient background. For the on-road and near-road applications, CTAG explicitly couples the major turbulent mixing processes, i.e., vehicle-induced turbulence (VIT), road-induced turbulence (RIT) and atmospheric boundary layer turbulence with gas-phase chemistry and aerosol dynamics. CTAG's transport model is referred to as CFD-VIT-RIT. This paper presents the evaluation of the CTAG model in simulating the dynamics of individual plumes in the “tailpipe-to-road” stage, i.e., VIT behind a moving van and aerosol dynamics in the wake of a diesel car by comparing the modeling results against the respective field measurements. Combined with sensitivity studies, we analyze the relative roles of VIT, sulfuric acid induced nucleation, condensation of organic compounds and presence of soot-mode particles in capturing the dynamics of exhaust plumes as well as their implications in vehicle emission controls.
The coupling of mechanical dynamics and induced currents in plates and surfaces
Weissenburger, D.W.; Bialek, J.M.
1986-10-01
Significant mechanical reactions and deflections may be produced when electrical eddy currents induced in a conducting structure by transformer-like electromotive forces interact with background magnetic fields. Additional eddy currents induced by structural motion through the background fields modify both the mechanical and electrical dynamic behavior of the system. The observed effects of these motional eddy currents are sometimes referred to as magnetic damping and magnetic stiffness. This paper addresses the coupled structural deformation and eddy currents in flat plates and simple two-dimensional surfaces in three-space. A coupled system of equations has been formulated using finite element techniques for the mechanical aspects and a mesh network method for the electrical aspects of the problem.
NASA Astrophysics Data System (ADS)
Teodorescu, Razvan
2009-10-01
Systems of oscillators coupled non-linearly (stochastically or not) are ubiquitous in nature and can explain many complex phenomena: coupled Josephson junction arrays, cardiac pacemaker cells, swarms or flocks of insects and birds, etc. They are know to have a non-trivial phase diagram, which includes chaotic, partially synchronized, and fully synchronized phases. A traditional model for this class of problems is the Kuramoto system of oscillators, which has been studied extensively for the last three decades. The model is a canonical example for non-equilibrium, dynamical phase transitions, so little understood in physics. From a stochastic analysis point of view, the transition is described by the large deviations principle, which offers little information on the scaling behavior near the critical point. I will discuss a special case of the model, which allows a rigorous analysis of the critical properties of the model, and reveals a new, anomalous scaling behavior in the vicinity of the critical point.
Dynamically tunable plasmon-induced absorption in resonator-coupled graphene waveguide
NASA Astrophysics Data System (ADS)
Wen, Mengting; Wang, Lingling; Zhai, Xiang; Lin, Qi; Xia, Shengxuan
2016-11-01
We demonstrate plasmon-induced absorption (PIA) in an ultra-compact graphene waveguide system which is composed of a single graphene sheet with two air cavities side-coupled to a graphene nanoribbon. By designing two coherent optical pathways, the pronounced PIA can be achieved due to the extreme destructive interference between the radiant and subradiant modes supported by the two graphene nanoribbons. The resonant strength shows strong dependence on the coupling distance between the two graphene nanoribbons and the resonance wavelength can be dynamically tuned by varying their Fermi energy. Furthermore, the group delay time up to -0.14 ps can be reached at the PIA window, suggesting unique fast-light feature. In addition, the double PIA phenomenon is also analyzed by introducing another graphene nanoribbon. Our results may pave the way for controlling the transmission of a light signal in the design of ultra-compact plasmonic devices.