Dynamics symmetries of Hamiltonian system on time scales

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Peng, Keke, E-mail: pengkeke88@126.com; Luo, Yiping, E-mail: zjstulyp@126.com [Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

2014-04-15

In this paper, the dynamics symmetries of Hamiltonian system on time scales are studied. We study the symmetries and quantities based on the calculation of variation and Lie transformation group. Particular focus lies in: the Noether symmetry leads to the Noether conserved quantity and the Lie symmetry leads to the Noether conserved quantity if the infinitesimal transformations satisfy the structure equation. As the new application of result, at end of the article, we give a simple example of Noether symmetry and Lie symmetry on time scales.

Decoding the Mobility and Time Scales of Protein Loops.

Science.gov (United States)

Gu, Yina; Li, Da-Wei; Brüschweiler, Rafael

2015-03-10

The flexible nature of protein loops and the time scales of their dynamics are critical for many biologically important events at the molecular level, such as protein interaction and recognition processes. In order to obtain a predictive understanding of the dynamic properties of loops, 500 ns molecular dynamics (MD) computer simulations of 38 different proteins were performed and validated using NMR chemical shifts. A total of 169 loops were analyzed and classified into three types, namely fast loops with correlation times Web server (http://spin.ccic.ohio-state.edu/index.php/loop). The results demonstrate that loop dynamics with their time scales can be predicted rapidly with reasonable accuracy, which will allow the screening of average protein structures to help better understand the various roles loops can play in the context of protein-protein interactions and binding.

Multiple time step integrators in ab initio molecular dynamics

International Nuclear Information System (INIS)

Luehr, Nathan; Martínez, Todd J.; Markland, Thomas E.

2014-01-01

Multiple time-scale algorithms exploit the natural separation of time-scales in chemical systems to greatly accelerate the efficiency of molecular dynamics simulations. Although the utility of these methods in systems where the interactions are described by empirical potentials is now well established, their application to ab initio molecular dynamics calculations has been limited by difficulties associated with splitting the ab initio potential into fast and slowly varying components. Here we present two schemes that enable efficient time-scale separation in ab initio calculations: one based on fragment decomposition and the other on range separation of the Coulomb operator in the electronic Hamiltonian. We demonstrate for both water clusters and a solvated hydroxide ion that multiple time-scale molecular dynamics allows for outer time steps of 2.5 fs, which are as large as those obtained when such schemes are applied to empirical potentials, while still allowing for bonds to be broken and reformed throughout the dynamics. This permits computational speedups of up to 4.4x, compared to standard Born-Oppenheimer ab initio molecular dynamics with a 0.5 fs time step, while maintaining the same energy conservation and accuracy

Qualitative aspects of Volterra integro-dynamic system on time scales

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Vasile Lupulescu

2013-01-01

Full Text Available This paper deals with the resolvent, asymptotic stability and boundedness of the solution of time-varying Volterra integro-dynamic system on time scales in which the coefficient matrix is not necessarily stable. We generalize at time scale some known properties about asymptotic behavior and boundedness from the continuous case. Some new results for discrete case are obtained.

Interaction of fast and slow dynamics in endocrine control systems with an application to β-cell dynamics.

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Wang, Yi-Fang; Khan, Michael; van den Berg, Hugo A

2012-01-01

Endocrine dynamics spans a wide range of time scales, from rapid responses to physiological challenges to with slow responses that adapt the system to the demands placed on it. We outline a non-linear averaging procedure to extract the slower dynamics in a way that accounts properly for the non-linear dynamics of the faster time scale and is applicable to a hierarchy of more than two time scales, although we restrict our discussion to two scales for the sake of clarity. The procedure is exact if the slow time scale is infinitely slow (the dimensionless ε-quantity is the period of the fast time scale fluctuation times an upper bound to the slow time scale rate of change). However, even for an imperfect separation of time scales we find that this construction provides an excellent approximation for the slow-time dynamics at considerably reduced computational cost. Besides the computation advantage, the averaged equation provided a qualitative insight into the interaction of the time scales. We demonstrate the procedure and its advantages by applying the theory to the model described by Tolić et al. [I.M. Tolić, E. Mosekilde, J. Sturis, Modeling the insulin-glucose feedback system: the significance of pulsatile insulin secretion, J. Theor. Biol. 207 (2000) 361-375.] for ultradian dynamics of the glucose-insulin homeostasis feedback system, extended to include β-cell dynamics. We find that the dynamics of the β-cell mass are dependent not only on the glycemic load (amount of glucose administered to the system), but also on the way this load is applied (i.e. three meals daily versus constant infusion), effects that are lost in the inappropriate methods used by the earlier authors. Furthermore, we find that the loss of the protection against apoptosis conferred by insulin that occurs at elevated levels of insulin has a functional role in keeping the β-cell mass in check without compromising regulatory function. We also find that replenishment of β-cells from a

Off-Policy Reinforcement Learning: Optimal Operational Control for Two-Time-Scale Industrial Processes.

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Li, Jinna; Kiumarsi, Bahare; Chai, Tianyou; Lewis, Frank L; Fan, Jialu

2017-12-01

Industrial flow lines are composed of unit processes operating on a fast time scale and performance measurements known as operational indices measured at a slower time scale. This paper presents a model-free optimal solution to a class of two time-scale industrial processes using off-policy reinforcement learning (RL). First, the lower-layer unit process control loop with a fast sampling period and the upper-layer operational index dynamics at a slow time scale are modeled. Second, a general optimal operational control problem is formulated to optimally prescribe the set-points for the unit industrial process. Then, a zero-sum game off-policy RL algorithm is developed to find the optimal set-points by using data measured in real-time. Finally, a simulation experiment is employed for an industrial flotation process to show the effectiveness of the proposed method.

Revealing Hidden Structural Order Controlling Both Fast and Slow Glassy Dynamics in Supercooled Liquids

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Hua Tong

2018-03-01

Full Text Available The dynamics of a supercooled liquid near the glass transition is characterized by two-step relaxation, fast β and slow α relaxations. Because of the apparently disordered nature of glassy structures, there have been long debates over whether the origin of drastic slowing-down of the α relaxation accompanied by heterogeneous dynamics is thermodynamic or dynamic. Furthermore, it has been elusive whether there is any deep connection between fast β and slow α modes. To settle these issues, here we introduce a set of new structural order parameters characterizing sterically favored structures with high local packing capability, and then access structure-dynamics correlation by a novel nonlocal approach. We find that the particle mobility is under control of the static order parameter field. The fast β process is controlled by the instantaneous order parameter field locally, resulting in short-time particle-scale dynamics. Then the mobility field progressively develops with time t, following the initial order parameter field from disorder to more ordered regions. As is well known, the heterogeneity in the mobility field (dynamic heterogeneity is maximized with a characteristic length ξ_{4}, when t reaches the relaxation time τ_{α}. We discover that this mobility pattern can be predicted solely by a spatial coarse graining of the initial order parameter field at t=0 over a length ξ without any dynamical information. Furthermore, we find a relation ξ∼ξ_{4}, indicating that the static length ξ grows coherently with the dynamic one ξ_{4} upon cooling. This further suggests an intrinsic link between τ_{α} and ξ: the growth of the static length ξ is the origin of dynamical slowing-down. These we confirm for the first time in binary glass formers both in two and three spatial dimensions. Thus, a static structure has two intrinsic characteristic lengths, particle size and ξ, which control dynamics in local and nonlocal manners, resulting

Revealing Hidden Structural Order Controlling Both Fast and Slow Glassy Dynamics in Supercooled Liquids

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Tong, Hua; Tanaka, Hajime

2018-01-01

The dynamics of a supercooled liquid near the glass transition is characterized by two-step relaxation, fast β and slow α relaxations. Because of the apparently disordered nature of glassy structures, there have been long debates over whether the origin of drastic slowing-down of the α relaxation accompanied by heterogeneous dynamics is thermodynamic or dynamic. Furthermore, it has been elusive whether there is any deep connection between fast β and slow α modes. To settle these issues, here we introduce a set of new structural order parameters characterizing sterically favored structures with high local packing capability, and then access structure-dynamics correlation by a novel nonlocal approach. We find that the particle mobility is under control of the static order parameter field. The fast β process is controlled by the instantaneous order parameter field locally, resulting in short-time particle-scale dynamics. Then the mobility field progressively develops with time t , following the initial order parameter field from disorder to more ordered regions. As is well known, the heterogeneity in the mobility field (dynamic heterogeneity) is maximized with a characteristic length ξ4, when t reaches the relaxation time τα. We discover that this mobility pattern can be predicted solely by a spatial coarse graining of the initial order parameter field at t =0 over a length ξ without any dynamical information. Furthermore, we find a relation ξ ˜ξ4, indicating that the static length ξ grows coherently with the dynamic one ξ4 upon cooling. This further suggests an intrinsic link between τα and ξ : the growth of the static length ξ is the origin of dynamical slowing-down. These we confirm for the first time in binary glass formers both in two and three spatial dimensions. Thus, a static structure has two intrinsic characteristic lengths, particle size and ξ , which control dynamics in local and nonlocal manners, resulting in the emergence of the two

The multiple time scales of sleep dynamics as a challenge for modelling the sleeping brain.

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Olbrich, Eckehard; Claussen, Jens Christian; Achermann, Peter

2011-10-13

A particular property of the sleeping brain is that it exhibits dynamics on very different time scales ranging from the typical sleep oscillations such as sleep spindles and slow waves that can be observed in electroencephalogram (EEG) segments of several seconds duration over the transitions between the different sleep stages on a time scale of minutes to the dynamical processes involved in sleep regulation with typical time constants in the range of hours. There is an increasing body of work on mathematical and computational models addressing these different dynamics, however, usually considering only processes on a single time scale. In this paper, we review and present a new analysis of the dynamics of human sleep EEG at the different time scales and relate the findings to recent modelling efforts pointing out both the achievements and remaining challenges.

Decay of surface nanostructures via long-time-scale dynamics

International Nuclear Information System (INIS)

Voter, A.F.; Stanciu, N.

1998-01-01

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have developed a new approach for extending the time scale of molecular dynamics simulations. For infrequent-event systems, the category that includes most diffusive events in the solid phase, this hyperdynamics method can extend the simulation time by a few orders of magnitude compared to direct molecular dynamics. The trajectory is run on a potential surface that has been biased to raise the energy in the potential basins without affecting the transition state region. The method is described and applied to surface and bulk diffusion processes, achieving microsecond and millisecond simulation times. The authors have also developed a new parallel computing method that is efficient for small system sizes. The combination of the hyperdynamics with this parallel replica dynamics looks promising as a general materials simulation tool

Time scales of the stick–slip dynamics of the peeling of an adhesive tape

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Mishra, Nachiketa; Parida, Nigam Chandra; Raha, Soumyendu

2015-01-01

The stick–slip dynamics of the peeling of an adhesive tape is characterized by bifurcations that have been experimentally well studied. In this work, we investigate the time scale in which the the stick–slips happen leading to the bifurcations. This is fundamental to understanding the triboluminescence and acoustic emissions associated with the bifurcations. We establish a relationship between the time scale of the bifurcations and the inherent mathematical structure of the peeling dynamics by studying a characteristic time quantity associated with the dynamics. PMID:25663802

A Fast Mellin and Scale Transform

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Davide Rocchesso

2007-01-01

Full Text Available A fast algorithm for the discrete-scale (and β-Mellin transform is proposed. It performs a discrete-time discrete-scale approximation of the continuous-time transform, with subquadratic asymptotic complexity. The algorithm is based on a well-known relation between the Mellin and Fourier transforms, and it is practical and accurate. The paper gives some theoretical background on the Mellin, β-Mellin, and scale transforms. Then the algorithm is presented and analyzed in terms of computational complexity and precision. The effects of different interpolation procedures used in the algorithm are discussed.

A Fast Mellin and Scale Transform

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Rocchesso Davide

2007-01-01

Full Text Available A fast algorithm for the discrete-scale (and -Mellin transform is proposed. It performs a discrete-time discrete-scale approximation of the continuous-time transform, with subquadratic asymptotic complexity. The algorithm is based on a well-known relation between the Mellin and Fourier transforms, and it is practical and accurate. The paper gives some theoretical background on the Mellin, -Mellin, and scale transforms. Then the algorithm is presented and analyzed in terms of computational complexity and precision. The effects of different interpolation procedures used in the algorithm are discussed.

Reduced linear noise approximation for biochemical reaction networks with time-scale separation: The stochastic tQSSA+

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Herath, Narmada; Del Vecchio, Domitilla

2018-03-01

Biochemical reaction networks often involve reactions that take place on different time scales, giving rise to "slow" and "fast" system variables. This property is widely used in the analysis of systems to obtain dynamical models with reduced dimensions. In this paper, we consider stochastic dynamics of biochemical reaction networks modeled using the Linear Noise Approximation (LNA). Under time-scale separation conditions, we obtain a reduced-order LNA that approximates both the slow and fast variables in the system. We mathematically prove that the first and second moments of this reduced-order model converge to those of the full system as the time-scale separation becomes large. These mathematical results, in particular, provide a rigorous justification to the accuracy of LNA models derived using the stochastic total quasi-steady state approximation (tQSSA). Since, in contrast to the stochastic tQSSA, our reduced-order model also provides approximations for the fast variable stochastic properties, we term our method the "stochastic tQSSA+". Finally, we demonstrate the application of our approach on two biochemical network motifs found in gene-regulatory and signal transduction networks.

Dynamics of fast ions in Tokamaks

International Nuclear Information System (INIS)

Helander, P.

1994-01-01

Fast ions play a prominent role in the heating of tokamak plasmas by, e.g. neutral-beam injection, ion-cyclotron-resonance heating, and alpha-particle heating. In this thesis, a number of physical and mathematical problems concerning the dynamics of fast ions in tokamaks are addressed. First, the motion under adiabatic perturbations is studied. The frequencies of instabilities excited in tokamaks sometimes vary slowly with time. The existence of an adiabatic invariant of particle motion in such circumstances is shown to lead to a rapid convection of particles in the radial direction. Generalized adiabatic invariants are constructed for systems where the slowly varying parameter is subjected to small, but rapidly varying, fluctuations. Second, the onset of stochastic motion under resonant perturbations is considered. It is shown that the finite width of fast-ion drift orbits significantly affects the threshold for stochastic motion caused by magnetic field ripple or ion-cyclotron-resonance heating. Finite-orbit-width effects are also shown to reduce the strength of resonant interaction between alpha particles and internal kink modes. Third, the diffusive motion in the stochastic regime is analysed mathematically. Monte Carlo operators for the motion on long time-scales are constructed, and the validity of the quasilinear diffusion coefficient is examined. Finally, the effects of close ion collisions are investigated. It is demonstrated that close encounters with fast ions produce a high-energy tail in the distribution functions of impurity ions, and that close collisions between fusion-generated alpha particles give rise to a population of such particles with energies extending up to twice the birth energy. 44 refs

Versatile synchronized real-time MEG hardware controller for large-scale fast data acquisition

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Sun, Limin; Han, Menglai; Pratt, Kevin; Paulson, Douglas; Dinh, Christoph; Esch, Lorenz; Okada, Yoshio; Hämäläinen, Matti

2017-05-01

Versatile controllers for accurate, fast, and real-time synchronized acquisition of large-scale data are useful in many areas of science, engineering, and technology. Here, we describe the development of a controller software based on a technique called queued state machine for controlling the data acquisition (DAQ) hardware, continuously acquiring a large amount of data synchronized across a large number of channels (>400) at a fast rate (up to 20 kHz/channel) in real time, and interfacing with applications for real-time data analysis and display of electrophysiological data. This DAQ controller was developed specifically for a 384-channel pediatric whole-head magnetoencephalography (MEG) system, but its architecture is useful for wide applications. This controller running in a LabVIEW environment interfaces with microprocessors in the MEG sensor electronics to control their real-time operation. It also interfaces with a real-time MEG analysis software via transmission control protocol/internet protocol, to control the synchronous acquisition and transfer of the data in real time from >400 channels to acquisition and analysis workstations. The successful implementation of this controller for an MEG system with a large number of channels demonstrates the feasibility of employing the present architecture in several other applications.

Fast exposure time decision in multi-exposure HDR imaging

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Piao, Yongjie; Jin, Guang

2012-10-01

Currently available imaging and display system exists the problem of insufficient dynamic range, and the system cannot restore all the information for an high dynamic range (HDR) scene. The number of low dynamic range(LDR) image samples and fastness of exposure time decision impacts the real-time performance of the system dramatically. In order to realize a real-time HDR video acquisition system, this paper proposed a fast and robust method for exposure time selection in under and over exposure area which is based on system response function. The method utilized the monotony of the imaging system. According to this characteristic the exposure time is adjusted to an initial value to make the median value of the image equals to the middle value of the system output range; then adjust the exposure time to make the pixel value on two sides of histogram be the middle value of the system output range. Thus three low dynamic range images are acquired. Experiments show that the proposed method for adjusting the initial exposure time can converge in two iterations which is more fast and stable than average gray control method. As to the exposure time adjusting in under and over exposed area, the proposed method can use the dynamic range of the system more efficiently than fixed exposure time method.

Bounds of Double Integral Dynamic Inequalities in Two Independent Variables on Time Scales

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S. H. Saker

2011-01-01

Full Text Available Our aim in this paper is to establish some explicit bounds of the unknown function in a certain class of nonlinear dynamic inequalities in two independent variables on time scales which are unbounded above. These on the one hand generalize and on the other hand furnish a handy tool for the study of qualitative as well as quantitative properties of solutions of partial dynamic equations on time scales. Some examples are considered to demonstrate the applications of the results.

Neural Computations in a Dynamical System with Multiple Time Scales.

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Mi, Yuanyuan; Lin, Xiaohan; Wu, Si

2016-01-01

Neural systems display rich short-term dynamics at various levels, e.g., spike-frequency adaptation (SFA) at the single-neuron level, and short-term facilitation (STF) and depression (STD) at the synapse level. These dynamical features typically cover a broad range of time scales and exhibit large diversity in different brain regions. It remains unclear what is the computational benefit for the brain to have such variability in short-term dynamics. In this study, we propose that the brain can exploit such dynamical features to implement multiple seemingly contradictory computations in a single neural circuit. To demonstrate this idea, we use continuous attractor neural network (CANN) as a working model and include STF, SFA and STD with increasing time constants in its dynamics. Three computational tasks are considered, which are persistent activity, adaptation, and anticipative tracking. These tasks require conflicting neural mechanisms, and hence cannot be implemented by a single dynamical feature or any combination with similar time constants. However, with properly coordinated STF, SFA and STD, we show that the network is able to implement the three computational tasks concurrently. We hope this study will shed light on the understanding of how the brain orchestrates its rich dynamics at various levels to realize diverse cognitive functions.

Existence and global exponential stability of periodic solutions for n-dimensional neutral dynamic equations on time scales.

Science.gov (United States)

Li, Bing; Li, Yongkun; Zhang, Xuemei

2016-01-01

In this paper, by using the existence of the exponential dichotomy of linear dynamic equations on time scales and the theory of calculus on time scales, we study the existence and global exponential stability of periodic solutions for a class of n-dimensional neutral dynamic equations on time scales. We also present an example to illustrate the feasibility of our results. The results of this paper are completely new and complementary to the previously known results even in both the case of differential equations (time scale [Formula: see text]) and the case of difference equations (time scale [Formula: see text]).

Principal and nonprincipal solutions of symplectic dynamic systems on time scales

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Ondrej Dosly

2000-01-01

Full Text Available We establish the concept of the principal and nonprincipal solution for the so-called symplectic dynamic systems on time scales. We also present a brief survey of the history of these concept for differential and difference equations.

Linearly scaling and almost Hamiltonian dielectric continuum molecular dynamics simulations through fast multipole expansions

Energy Technology Data Exchange (ETDEWEB)

Lorenzen, Konstantin; Mathias, Gerald; Tavan, Paul, E-mail: tavan@physik.uni-muenchen.de [Lehrstuhl für BioMolekulare Optik, Ludig–Maximilians Universität München, Oettingenstr. 67, 80538 München (Germany)

2015-11-14

Hamiltonian Dielectric Solvent (HADES) is a recent method [S. Bauer et al., J. Chem. Phys. 140, 104103 (2014)] which enables atomistic Hamiltonian molecular dynamics (MD) simulations of peptides and proteins in dielectric solvent continua. Such simulations become rapidly impractical for large proteins, because the computational effort of HADES scales quadratically with the number N of atoms. If one tries to achieve linear scaling by applying a fast multipole method (FMM) to the computation of the HADES electrostatics, the Hamiltonian character (conservation of total energy, linear, and angular momenta) may get lost. Here, we show that the Hamiltonian character of HADES can be almost completely preserved, if the structure-adapted fast multipole method (SAMM) as recently redesigned by Lorenzen et al. [J. Chem. Theory Comput. 10, 3244-3259 (2014)] is suitably extended and is chosen as the FMM module. By this extension, the HADES/SAMM forces become exact gradients of the HADES/SAMM energy. Their translational and rotational invariance then guarantees (within the limits of numerical accuracy) the exact conservation of the linear and angular momenta. Also, the total energy is essentially conserved—up to residual algorithmic noise, which is caused by the periodically repeated SAMM interaction list updates. These updates entail very small temporal discontinuities of the force description, because the employed SAMM approximations represent deliberately balanced compromises between accuracy and efficiency. The energy-gradient corrected version of SAMM can also be applied, of course, to MD simulations of all-atom solvent-solute systems enclosed by periodic boundary conditions. However, as we demonstrate in passing, this choice does not offer any serious advantages.

A note on the theory of fast money flow dynamics

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Sokolov, A.; Kieu, T.; Melatos, A.

2010-08-01

The gauge theory of arbitrage was introduced by Ilinski in [K. Ilinski, preprint arXiv:hep-th/9710148 (1997)] and applied to fast money flows in [A. Ilinskaia, K. Ilinski, preprint arXiv:cond-mat/9902044 (1999); K. Ilinski, Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)]. The theory of fast money flow dynamics attempts to model the evolution of currency exchange rates and stock prices on short, e.g. intra-day, time scales. It has been used to explain some of the heuristic trading rules, known as technical analysis, that are used by professional traders in the equity and foreign exchange markets. A critique of some of the underlying assumptions of the gauge theory of arbitrage was presented by Sornette in [D. Sornette, Int. J. Mod. Phys. C 9, 505 (1998)]. In this paper, we present a critique of the theory of fast money flow dynamics, which was not examined by Sornette. We demonstrate that the choice of the input parameters used in [K. Ilinski, Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)] results in sinusoidal oscillations of the exchange rate, in conflict with the results presented in [K. Ilinski, Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)]. We also find that the dynamics predicted by the theory are generally unstable in most realistic situations, with the exchange rate tending to zero or infinity exponentially.

Modeling fast and slow earthquakes at various scales.

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Ide, Satoshi

2014-01-01

Earthquake sources represent dynamic rupture within rocky materials at depth and often can be modeled as propagating shear slip controlled by friction laws. These laws provide boundary conditions on fault planes embedded in elastic media. Recent developments in observation networks, laboratory experiments, and methods of data analysis have expanded our knowledge of the physics of earthquakes. Newly discovered slow earthquakes are qualitatively different phenomena from ordinary fast earthquakes and provide independent information on slow deformation at depth. Many numerical simulations have been carried out to model both fast and slow earthquakes, but problems remain, especially with scaling laws. Some mechanisms are required to explain the power-law nature of earthquake rupture and the lack of characteristic length. Conceptual models that include a hierarchical structure over a wide range of scales would be helpful for characterizing diverse behavior in different seismic regions and for improving probabilistic forecasts of earthquakes.

Antipersistent dynamics in short time scale variability of self-potential signals

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M. Ragosta

2000-06-01

Full Text Available Time scale properties of self-potential signals are investigated through the analysis of the second order structure function (variogram, a powerful tool to investigate the spatial and temporal variability of observational data. In this work we analyse two sequences of self-potential values measured by means of a geophysical monitoring array located in a seismically active area of Southern Italy. The range of scales investigated goes from a few minutes to several days. It is shown that signal fluctuations are characterised by two time scale ranges in which self-potential variability appears to follow slightly different dynamical behaviours. Results point to the presence of fractal, non stationary features expressing a long term correlation with scaling coefficients which are the clue of stabilising mechanisms. In the scale ranges in which the series show scale invariant behaviour, self-potentials evolve like fractional Brownian motions with anticorrelated increments typical of processes regulated by negative feedback mechanisms (antipersistence. On scales below about 6 h the strength of such an antipersistence appears to be slightly greater than that observed on larger time scales where the fluctuations are less efficiently stabilised.

Hybrid approximations via second order combined dynamic derivatives on time scales

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Qin Sheng

2007-09-01

Full Text Available This article focuses on the approximation of conventional second order derivative via the combined (diamond-$\\alpha$ dynamic derivative on time scales with necessary smoothness conditions embedded. We will show the constraints under which the second order dynamic derivative provides a consistent approximation to the conventional second derivative; the cases where the dynamic derivative approximates the derivative only via a proper modification of the existing formula; and the situations in which the dynamic derivative can never approximate consistently even with the help of available structure correction methods. Constructive error analysis will be given via asymptotic expansions for practical hybrid modeling and computational applications.

CFD modeling of space-time evolution of fast pyrolysis products in a bench-scale fluidized-bed reactor

International Nuclear Information System (INIS)

Boateng, A.A.; Mtui, P.L.

2012-01-01

A model for the evolution of pyrolysis products in a fluidized bed has been developed. In this study the unsteady constitutive transport equations for inert gas flow and decomposition kinetics were modeled using the commercial computational fluid dynamics (CFD) software FLUENT-12. The Eulerarian-Eulerian multiphase model system described herein is a fluidized bed of sand externally heated to a predetermined temperature prior to introduction of agricultural biomass. We predict the spontaneous emergence of pyrolysis vapors, char and non-condensable (permanent) gases and confirm the observation that the kinetics are fast and that bio-oil vapor evolution is accomplished in a few seconds, and occupying two-thirds of the spatial volume of the reactor as widely reported in the open literature. The model could be advantageous in the virtual design of fast pyrolysis reactors and their optimization to meet economic scales required for distributed or satellite units. - Highlights: ► We model the evolution of pyrolysis products in a fluidized bed via CFD. ► We predict the spontaneous emergence of pyrolysis products. ► We confirm the experimental observation that the kinetics are fast. ► And that bio-oil vapor evolution is accomplished in a few seconds. ► The model is advantageous in the virtual design of fast pyrolysis reactors.

Non-monotonicity and divergent time scale in Axelrod model dynamics

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Vazquez, F.; Redner, S.

2007-04-01

We study the evolution of the Axelrod model for cultural diversity, a prototypical non-equilibrium process that exhibits rich dynamics and a dynamic phase transition between diversity and an inactive state. We consider a simple version of the model in which each individual possesses two features that can assume q possibilities. Within a mean-field description in which each individual has just a few interaction partners, we find a phase transition at a critical value qc between an active, diverse state for q < qc and a frozen state. For q lesssim qc, the density of active links is non-monotonic in time and the asymptotic approach to the steady state is controlled by a time scale that diverges as (q-qc)-1/2.

Fast Simulation of Large-Scale Floods Based on GPU Parallel Computing

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Qiang Liu

2018-05-01

Full Text Available Computing speed is a significant issue of large-scale flood simulations for real-time response to disaster prevention and mitigation. Even today, most of the large-scale flood simulations are generally run on supercomputers due to the massive amounts of data and computations necessary. In this work, a two-dimensional shallow water model based on an unstructured Godunov-type finite volume scheme was proposed for flood simulation. To realize a fast simulation of large-scale floods on a personal computer, a Graphics Processing Unit (GPU-based, high-performance computing method using the OpenACC application was adopted to parallelize the shallow water model. An unstructured data management method was presented to control the data transportation between the GPU and CPU (Central Processing Unit with minimum overhead, and then both computation and data were offloaded from the CPU to the GPU, which exploited the computational capability of the GPU as much as possible. The parallel model was validated using various benchmarks and real-world case studies. The results demonstrate that speed-ups of up to one order of magnitude can be achieved in comparison with the serial model. The proposed parallel model provides a fast and reliable tool with which to quickly assess flood hazards in large-scale areas and, thus, has a bright application prospect for dynamic inundation risk identification and disaster assessment.

Timing coincidence studies with fast photomultipliers

International Nuclear Information System (INIS)

Raoof, M.A.; Raoof, S.A.

1981-01-01

The time response of RCA C70045D photomultipliers was studied using a subnanosecond light flasher. The tubes, which have an output rise time of approximately 0.5 ns, were used in coincidence to study the variations in the fwhm of the time spectrum over a certain dynamic range of pulse amplitudes for both leading edge and constant fraction discrimination. A comparison has also been made for the measured time resolutions with some of the other fast photomultipliers. (orig.)

Modeling ramp compression experiments using large-scale molecular dynamics simulation.

Energy Technology Data Exchange (ETDEWEB)

Mattsson, Thomas Kjell Rene; Desjarlais, Michael Paul; Grest, Gary Stephen; Templeton, Jeremy Alan; Thompson, Aidan Patrick; Jones, Reese E.; Zimmerman, Jonathan A.; Baskes, Michael I. (University of California, San Diego); Winey, J. Michael (Washington State University); Gupta, Yogendra Mohan (Washington State University); Lane, J. Matthew D.; Ditmire, Todd (University of Texas at Austin); Quevedo, Hernan J. (University of Texas at Austin)

2011-10-01

Molecular dynamics simulation (MD) is an invaluable tool for studying problems sensitive to atomscale physics such as structural transitions, discontinuous interfaces, non-equilibrium dynamics, and elastic-plastic deformation. In order to apply this method to modeling of ramp-compression experiments, several challenges must be overcome: accuracy of interatomic potentials, length- and time-scales, and extraction of continuum quantities. We have completed a 3 year LDRD project with the goal of developing molecular dynamics simulation capabilities for modeling the response of materials to ramp compression. The techniques we have developed fall in to three categories (i) molecular dynamics methods (ii) interatomic potentials (iii) calculation of continuum variables. Highlights include the development of an accurate interatomic potential describing shock-melting of Beryllium, a scaling technique for modeling slow ramp compression experiments using fast ramp MD simulations, and a technique for extracting plastic strain from MD simulations. All of these methods have been implemented in Sandia's LAMMPS MD code, ensuring their widespread availability to dynamic materials research at Sandia and elsewhere.

OSCILLATION CRITERIA FOR A FOURTH ORDER SUBLINEAR DYNAMIC EQUATION ON TIME SCALE

Institute of Scientific and Technical Information of China (English)

无

2011-01-01

Some new criteria for the oscillation of a fourth order sublinear and/or linear dynamic equation on time scale are established. Our results are new for the corresponding fourth order differential equations as well as difference equations.

Global fast dynamic terminal sliding mode control for a quadrotor UAV.

Science.gov (United States)

Xiong, Jing-Jing; Zhang, Guo-Bao

2017-01-01

A control method based on global fast dynamic terminal sliding mode control (TSMC) technique is proposed to design the flight controller for performing the finite-time position and attitude tracking control of a small quadrotor UAV. Firstly, the dynamic model of the quadrotor is divided into two subsystems, i.e., a fully actuated subsystem and an underactuated subsystem. Secondly, the dynamic flight controllers of the quadrotor are formulated based on global fast dynamic TSMC, which is able to guarantee that the position and velocity tracking errors of all system state variables converge to zero in finite-time. Moreover, the global fast dynamic TSMC is also able to eliminate the chattering phenomenon caused by the switching control action and realize the high precision performance. In addition, the stabilities of two subsystems are demonstrated by Lyapunov theory, respectively. Lastly, the simulation results are given to illustrate the effectiveness and robustness of the proposed control method in the presence of external disturbances. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Fast Dynamic Simulation-Based Small Signal Stability Assessment and Control

Energy Technology Data Exchange (ETDEWEB)

Acharya, Naresh [General Electric Company, Fairfield, CT (United States); Baone, Chaitanya [General Electric Company, Fairfield, CT (United States); Veda, Santosh [General Electric Company, Fairfield, CT (United States); Dai, Jing [General Electric Company, Fairfield, CT (United States); Chaudhuri, Nilanjan [General Electric Company, Fairfield, CT (United States); Leonardi, Bruno [General Electric Company, Fairfield, CT (United States); Sanches-Gasca, Juan [General Electric Company, Fairfield, CT (United States); Diao, Ruisheng [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wu, Di [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Huang, Zhenyu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhang, Yu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jin, Shuangshuang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zheng, Bin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chen, Yousu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2014-12-31

Power grid planning and operation decisions are made based on simulation of the dynamic behavior of the system. Enabling substantial energy savings while increasing the reliability of the aging North American power grid through improved utilization of existing transmission assets hinges on the adoption of wide-area measurement systems (WAMS) for power system stabilization. However, adoption of WAMS alone will not suffice if the power system is to reach its full entitlement in stability and reliability. It is necessary to enhance predictability with "faster than real-time" dynamic simulations that will enable the dynamic stability margins, proactive real-time control, and improve grid resiliency to fast time-scale phenomena such as cascading network failures. Present-day dynamic simulations are performed only during offline planning studies, considering only worst case conditions such as summer peak, winter peak days, etc. With widespread deployment of renewable generation, controllable loads, energy storage devices and plug-in hybrid electric vehicles expected in the near future and greater integration of cyber infrastructure (communications, computation and control), monitoring and controlling the dynamic performance of the grid in real-time would become increasingly important. The state-of-the-art dynamic simulation tools have limited computational speed and are not suitable for real-time applications, given the large set of contingency conditions to be evaluated. These tools are optimized for best performance of single-processor computers, but the simulation is still several times slower than real-time due to its computational complexity. With recent significant advances in numerical methods and computational hardware, the expectations have been rising towards more efficient and faster techniques to be implemented in power system simulators. This is a natural expectation, given that the core solution algorithms of most commercial simulators were developed

Optimal dynamic voltage scaling for wireless sensor nodes with real-time constraints

Science.gov (United States)

Cassandras, Christos G.; Zhuang, Shixin

2005-11-01

Sensors are increasingly embedded in manufacturing systems and wirelessly networked to monitor and manage operations ranging from process and inventory control to tracking equipment and even post-manufacturing product monitoring. In building such sensor networks, a critical issue is the limited and hard to replenish energy in the devices involved. Dynamic voltage scaling is a technique that controls the operating voltage of a processor to provide desired performance while conserving energy and prolonging the overall network's lifetime. We consider such power-limited devices processing time-critical tasks which are non-preemptive, aperiodic and have uncertain arrival times. We treat voltage scaling as a dynamic optimization problem whose objective is to minimize energy consumption subject to hard or soft real-time execution constraints. In the case of hard constraints, we build on prior work (which engages a voltage scaling controller at task completion times) by developing an intra-task controller that acts at all arrival times of incoming tasks. We show that this optimization problem can be decomposed into two simpler ones whose solution leads to an algorithm that does not actually require solving any nonlinear programming problems. In the case of soft constraints, this decomposition must be partly relaxed, but it still leads to a scalable (linear in the number of tasks) algorithm. Simulation results are provided to illustrate performance improvements in systems with intra-task controllers compared to uncontrolled systems or those using inter-task control.

Atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

Science.gov (United States)

Pabst, Stefan

2013-04-01

Time-resolved investigations of ultrafast electronic and molecular dynamics were not possible until recently. The typical time scale of these processes is in the picosecond to attosecond realm. The tremendous technological progress in recent years made it possible to generate ultrashort pulses, which can be used to trigger, to watch, and to control atomic and molecular motion. This tutorial focuses on experimental and theoretical advances which are used to study the dynamics of electrons and molecules in the presence of ultrashort pulses. In the first part, the rotational dynamics of molecules, which happens on picosecond and femtosecond time scales, is reviewed. Well-aligned molecules are particularly suitable for angle-dependent investigations like x-ray diffraction or strong-field ionization experiments. In the second part, the ionization dynamics of atoms is studied. The characteristic time scale lies, here, in the attosecond to few-femtosecond regime. Although a one-particle picture has been successfully applied to many processes, many-body effects do constantly occur. After a broad overview of the main mechanisms and the most common tools in attosecond physics, examples of many-body dynamics in the attosecond world (e.g., in high-harmonic generation and attosecond transient absorption spectroscopy) are discussed.

Molecular dynamics on diffusive time scales from the phase-field-crystal equation.

Science.gov (United States)

Chan, Pak Yuen; Goldenfeld, Nigel; Dantzig, Jon

2009-03-01

We extend the phase-field-crystal model to accommodate exact atomic configurations and vacancies by requiring the order parameter to be non-negative. The resulting theory dictates the number of atoms and describes the motion of each of them. By solving the dynamical equation of the model, which is a partial differential equation, we are essentially performing molecular dynamics simulations on diffusive time scales. To illustrate this approach, we calculate the two-point correlation function of a fluid.

Fast and Cache-Oblivious Dynamic Programming with Local Dependencies

DEFF Research Database (Denmark)

Bille, Philip; Stöckel, Morten

2012-01-01

are widely used in bioinformatics to compare DNA and protein sequences. These problems can all be solved using essentially the same dynamic programming scheme over a two-dimensional matrix, where each entry depends locally on at most 3 neighboring entries. We present a simple, fast, and cache......-oblivious algorithm for this type of local dynamic programming suitable for comparing large-scale strings. Our algorithm outperforms the previous state-of-the-art solutions. Surprisingly, our new simple algorithm is competitive with a complicated, optimized, and tuned implementation of the best cache-aware algorithm...

Suppression of chaos at slow variables by rapidly mixing fast dynamics

Science.gov (United States)

Abramov, R.

2012-04-01

One of the key questions about chaotic multiscale systems is how the fast dynamics affects chaos at the slow variables, and, therefore, impacts uncertainty and predictability of the slow dynamics. Here we demonstrate that the linear slow-fast coupling with the total energy conservation property promotes the suppression of chaos at the slow variables through the rapid mixing at the fast variables, both theoretically and through numerical simulations. A suitable mathematical framework is developed, connecting the slow dynamics on the tangent subspaces to the infinite-time linear response of the mean state to a constant external forcing at the fast variables. Additionally, it is shown that the uncoupled dynamics for the slow variables may remain chaotic while the complete multiscale system loses chaos and becomes completely predictable at the slow variables through increasing chaos and turbulence at the fast variables. This result contradicts the common sense intuition, where, naturally, one would think that coupling a slow weakly chaotic system with another much faster and much stronger mixing system would result in general increase of chaos at the slow variables.

Probing Photoinduced Structural Phase Transitions by Fast or Ultra-Fast Time-Resolved X-Ray Diffraction

Science.gov (United States)

Cailleau, Hervé Collet, Eric; Buron-Le Cointe, Marylise; Lemée-Cailleau, Marie-Hélène Koshihara, Shin-Ya

A new frontier in the field of structural science is the emergence of the fast and ultra-fast X-ray science. Recent developments in time-resolved X-ray diffraction promise direct access to the dynamics of electronic, atomic and molecular motions in condensed matter triggered by a pulsed laser irradiation, i.e. to record "molecular movies" during the transformation of matter initiated by light pulse. These laser pump and X-ray probe techniques now provide an outstanding opportunity for the direct observation of a photoinduced structural phase transition as it takes place. The use of X-ray short-pulse of about 100ps around third-generation synchrotron sources allows structural investigations of fast photoinduced processes. Other new X-ray sources, such as laser-produced plasma ones, generate ultra-short pulses down to 100 fs. This opens the way to femtosecond X-ray crystallography, but with rather low X-ray intensities and more limited experimental possibilities at present. However this new ultra-fast science rapidly progresses around these sources and new large-scale projects exist. It is the aim of this contribution to overview the state of art and the perspectives of fast and ultra-fast X-ray scattering techniques to study photoinduced phase transitions (here, the word ultra-fast is used for sub-picosecond time resolution). In particular we would like to largely present the contribution of crystallographic methods in comparison with optical methods, such as pump-probe reflectivity measurements, the reader being not necessary familiar with X-ray scattering. Thus we want to present which type of physical information can be obtained from the positions of the Bragg peaks, their intensity and their shape, as well as from the diffuse scattering beyond Bragg peaks. An important physical feature is to take into consideration the difference in nature between a photoinduced phase transition and conventional homogeneous photoinduced chemical or biochemical processes where

Distributed solar radiation fast dynamic measurement for PV cells

Science.gov (United States)

Wan, Xuefen; Yang, Yi; Cui, Jian; Du, Xingjing; Zheng, Tao; Sardar, Muhammad Sohail

2017-10-01

To study the operating characteristics about PV cells, attention must be given to the dynamic behavior of the solar radiation. The dynamic behaviors of annual, monthly, daily and hourly averages of solar radiation have been studied in detail. But faster dynamic behaviors of solar radiation need more researches. The solar radiation random fluctuations in minute-long or second-long range, which lead to alternating radiation and cool down/warm up PV cell frequently, decrease conversion efficiency. Fast dynamic processes of solar radiation are mainly relevant to stochastic moving of clouds. Even in clear sky condition, the solar irradiations show a certain degree of fast variation. To evaluate operating characteristics of PV cells under fast dynamic irradiation, a solar radiation measuring array (SRMA) based on large active area photodiode, LoRa spread spectrum communication and nanoWatt MCU is proposed. This cross photodiodes structure tracks fast stochastic moving of clouds. To compensate response time of pyranometer and reduce system cost, the terminal nodes with low-cost fast-responded large active area photodiode are placed besides positions of tested PV cells. A central node, consists with pyranometer, large active area photodiode, wind detector and host computer, is placed in the center of the central topologies coordinate to scale temporal envelope of solar irradiation and get calibration information between pyranometer and large active area photodiodes. In our SRMA system, the terminal nodes are designed based on Microchip's nanoWatt XLP PIC16F1947. FDS-100 is adopted for large active area photodiode in terminal nodes and host computer. The output current and voltage of each PV cell are monitored by I/V measurement. AS62-T27/SX1278 LoRa communication modules are used for communicating between terminal nodes and host computer. Because the LoRa LPWAN (Low Power Wide Area Network) specification provides seamless interoperability among Smart Things without the

Theoretical restrictions on longest implicit time scales in Markov state models of biomolecular dynamics

Science.gov (United States)

Sinitskiy, Anton V.; Pande, Vijay S.

2018-01-01

Markov state models (MSMs) have been widely used to analyze computer simulations of various biomolecular systems. They can capture conformational transitions much slower than an average or maximal length of a single molecular dynamics (MD) trajectory from the set of trajectories used to build the MSM. A rule of thumb claiming that the slowest implicit time scale captured by an MSM should be comparable by the order of magnitude to the aggregate duration of all MD trajectories used to build this MSM has been known in the field. However, this rule has never been formally proved. In this work, we present analytical results for the slowest time scale in several types of MSMs, supporting the above rule. We conclude that the slowest implicit time scale equals the product of the aggregate sampling and four factors that quantify: (1) how much statistics on the conformational transitions corresponding to the longest implicit time scale is available, (2) how good the sampling of the destination Markov state is, (3) the gain in statistics from using a sliding window for counting transitions between Markov states, and (4) a bias in the estimate of the implicit time scale arising from finite sampling of the conformational transitions. We demonstrate that in many practically important cases all these four factors are on the order of unity, and we analyze possible scenarios that could lead to their significant deviation from unity. Overall, we provide for the first time analytical results on the slowest time scales captured by MSMs. These results can guide further practical applications of MSMs to biomolecular dynamics and allow for higher computational efficiency of simulations.

Communications overlapping in fast multipole particle dynamics methods

International Nuclear Information System (INIS)

Kurzak, Jakub; Pettitt, B. Montgomery

2005-01-01

In molecular dynamics the fast multipole method (FMM) is an attractive alternative to Ewald summation for calculating electrostatic interactions due to the operation counts. However when applied to small particle systems and taken to many processors it has a high demand for interprocessor communication. In a distributed memory environment this demand severely limits applicability of the FMM to systems with O(10 K atoms). We present an algorithm that allows for fine grained overlap of communication and computation, while not sacrificing synchronization and determinism in the equations of motion. The method avoids contention in the communication subsystem making it feasible to use the FMM for smaller systems on larger numbers of processors. Our algorithm also facilitates application of multiple time stepping techniques within the FMM. We present scaling at a reasonably high level of accuracy compared with optimized Ewald methods

A hierarchy of time-scales and the brain.

Science.gov (United States)

Kiebel, Stefan J; Daunizeau, Jean; Friston, Karl J

2008-11-01

In this paper, we suggest that cortical anatomy recapitulates the temporal hierarchy that is inherent in the dynamics of environmental states. Many aspects of brain function can be understood in terms of a hierarchy of temporal scales at which representations of the environment evolve. The lowest level of this hierarchy corresponds to fast fluctuations associated with sensory processing, whereas the highest levels encode slow contextual changes in the environment, under which faster representations unfold. First, we describe a mathematical model that exploits the temporal structure of fast sensory input to track the slower trajectories of their underlying causes. This model of sensory encoding or perceptual inference establishes a proof of concept that slowly changing neuronal states can encode the paths or trajectories of faster sensory states. We then review empirical evidence that suggests that a temporal hierarchy is recapitulated in the macroscopic organization of the cortex. This anatomic-temporal hierarchy provides a comprehensive framework for understanding cortical function: the specific time-scale that engages a cortical area can be inferred by its location along a rostro-caudal gradient, which reflects the anatomical distance from primary sensory areas. This is most evident in the prefrontal cortex, where complex functions can be explained as operations on representations of the environment that change slowly. The framework provides predictions about, and principled constraints on, cortical structure-function relationships, which can be tested by manipulating the time-scales of sensory input.

A hierarchy of time-scales and the brain.

Directory of Open Access Journals (Sweden)

Stefan J Kiebel

2008-11-01

Full Text Available In this paper, we suggest that cortical anatomy recapitulates the temporal hierarchy that is inherent in the dynamics of environmental states. Many aspects of brain function can be understood in terms of a hierarchy of temporal scales at which representations of the environment evolve. The lowest level of this hierarchy corresponds to fast fluctuations associated with sensory processing, whereas the highest levels encode slow contextual changes in the environment, under which faster representations unfold. First, we describe a mathematical model that exploits the temporal structure of fast sensory input to track the slower trajectories of their underlying causes. This model of sensory encoding or perceptual inference establishes a proof of concept that slowly changing neuronal states can encode the paths or trajectories of faster sensory states. We then review empirical evidence that suggests that a temporal hierarchy is recapitulated in the macroscopic organization of the cortex. This anatomic-temporal hierarchy provides a comprehensive framework for understanding cortical function: the specific time-scale that engages a cortical area can be inferred by its location along a rostro-caudal gradient, which reflects the anatomical distance from primary sensory areas. This is most evident in the prefrontal cortex, where complex functions can be explained as operations on representations of the environment that change slowly. The framework provides predictions about, and principled constraints on, cortical structure-function relationships, which can be tested by manipulating the time-scales of sensory input.

Preoperative fasting times: Prescribed and actual fasting times at ...

African Journals Online (AJOL)

The current international guidelines for preoperative fasting for elective surgery are 6 ... to determine whether this policy was being followed and patients were being starved ..... recommended fasting time, so that autonomous patients take care.

Scaling criteria for rock dynamic experiments

Energy Technology Data Exchange (ETDEWEB)

Crowley, Barbara K [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

1970-05-01

A set of necessary conditions for performing scaled rock dynamics experiments is derived from the conservation equations of continuum mechanics. Performing scaled experiments in two different materials is virtually impossible because of the scaling restrictions imposed by two equations of state. However, performing dynamically scaled experiments in the same material is possible if time and distance use the same scaling factor and if the effects of gravity are insignificant. When gravity becomes significant, dynamic scaling is no longer possible. To illustrate these results, example calculations of megaton and kiloton experiments are considered. (author00.

Reduced α-stable dynamics for multiple time scale systems forced with correlated additive and multiplicative Gaussian white noise

Science.gov (United States)

Thompson, William F.; Kuske, Rachel A.; Monahan, Adam H.

2017-11-01

Stochastic averaging problems with Gaussian forcing have been the subject of numerous studies, but far less attention has been paid to problems with infinite-variance stochastic forcing, such as an α-stable noise process. It has been shown that simple linear systems driven by correlated additive and multiplicative (CAM) Gaussian noise, which emerge in the context of reduced atmosphere and ocean dynamics, have infinite variance in certain parameter regimes. In this study, we consider the stochastic averaging of systems where a linear CAM noise process in the infinite variance parameter regime drives a comparatively slow process. We use (semi)-analytical approximations combined with numerical illustrations to compare the averaged process to one that is forced by a white α-stable process, demonstrating consistent properties in the case of large time-scale separation. We identify the conditions required for the fast linear CAM process to have such an influence in driving a slower process and then derive an (effectively) equivalent fast, infinite-variance process for which an existing stochastic averaging approximation is readily applied. The results are illustrated using numerical simulations of a set of example systems.

Hardy inequality on time scales and its application to half-linear dynamic equations

Directory of Open Access Journals (Sweden)

Řehák Pavel

2005-01-01

Full Text Available A time-scale version of the Hardy inequality is presented, which unifies and extends well-known Hardy inequalities in the continuous and in the discrete setting. An application in the oscillation theory of half-linear dynamic equations is given.

Revealing the fast atomic motion of network glasses.

Science.gov (United States)

Ruta, B; Baldi, G; Chushkin, Y; Rufflé, B; Cristofolini, L; Fontana, A; Zanatta, M; Nazzani, F

2014-05-19

Still very little is known on the relaxation dynamics of glasses at the microscopic level due to the lack of experiments and theories. It is commonly believed that glasses are in a dynamical arrested state, with relaxation times too large to be observed on human time scales. Here we provide the experimental evidence that glasses display fast atomic rearrangements within a few minutes, even in the deep glassy state. Following the evolution of the structural relaxation in a sodium silicate glass, we find that this fast dynamics is accompanied by the absence of any detectable aging, suggesting a decoupling of the relaxation time and the viscosity in the glass. The relaxation time is strongly affected by the network structure with a marked increase at the mesoscopic scale associated with the ion-conducting pathways. Our results modify the conception of the glassy state and asks for a new microscopic theory.

Internal motion time scales of a small, highly stable and disulfide-rich protein: A 15N, 13C NMR and molecular dynamics study

International Nuclear Information System (INIS)

Guenneugues, Marc; Gilquin, Bernard; Wolff, Nicolas; Menez, Andre; Zinn-Justin, Sophie

1999-01-01

Motions of the backbone CαHα and threonine CβHβ bonds of toxin α were investigated using natural abundance 13C NMR and molecular dynamics. Measurement of the 13C longitudinal and transverse relaxation rates employed ACCORDION techniques together with coherence selection by pulsed field gradients and sensitivity enhancement through the use of preservation of equivalent pathway, thus allowing a considerable reduction of the required spectrometer time. 13C R1, R2, 1H → 13C NOE were obtained, as well as the variations of R1ρ(90 deg.) as a function of the rf field strength. These data were compared to those recorded by 1H and 15N NMR on a labelled sample of the toxin [Guenneugues et al. (1997) Biochemistry, 36, 16097-16108]. Both sets of data showed that picosecond to nanosecond time scale motions are well correlated to the secondary structure of the protein. This was further reinforced by the analysis of a 1 ns molecular dynamics simulation in water. Several CαHα and threonine CβHβ experimentally exhibit fast motions with a correlation time longer than 500 ps, that cannot be sampled along the simulation. In addition, the backbone exhibits motions on the microsecond to millisecond time scale on more than half of its length. Thus, toxin α, a highly stable protein (Tm=75 deg. C at acidic pH) containing 61 amino acids and 4 disulfides, shows important internal motions on time scales ranging from 0.1-0.5 ps, to 10-100 ps, 1 ns, and about 30 μs to 10 ms

Efficiency optimization of a fast Poisson solver in beam dynamics simulation

Science.gov (United States)

Zheng, Dawei; Pöplau, Gisela; van Rienen, Ursula

2016-01-01

Calculating the solution of Poisson's equation relating to space charge force is still the major time consumption in beam dynamics simulations and calls for further improvement. In this paper, we summarize a classical fast Poisson solver in beam dynamics simulations: the integrated Green's function method. We introduce three optimization steps of the classical Poisson solver routine: using the reduced integrated Green's function instead of the integrated Green's function; using the discrete cosine transform instead of discrete Fourier transform for the Green's function; using a novel fast convolution routine instead of an explicitly zero-padded convolution. The new Poisson solver routine preserves the advantages of fast computation and high accuracy. This provides a fast routine for high performance calculation of the space charge effect in accelerators.

Synchronization and Causality Across Time-scales: Complex Dynamics and Extremes in El Niño/Southern Oscillation

Science.gov (United States)

Jajcay, N.; Kravtsov, S.; Tsonis, A.; Palus, M.

2017-12-01

A better understanding of dynamics in complex systems, such as the Earth's climate is one of the key challenges for contemporary science and society. A large amount of experimental data requires new mathematical and computational approaches. Natural complex systems vary on many temporal and spatial scales, often exhibiting recurring patterns and quasi-oscillatory phenomena. The statistical inference of causal interactions and synchronization between dynamical phenomena evolving on different temporal scales is of vital importance for better understanding of underlying mechanisms and a key for modeling and prediction of such systems. This study introduces and applies information theory diagnostics to phase and amplitude time series of different wavelet components of the observed data that characterizes El Niño. A suite of significant interactions between processes operating on different time scales was detected, and intermittent synchronization among different time scales has been associated with the extreme El Niño events. The mechanisms of these nonlinear interactions were further studied in conceptual low-order and state-of-the-art dynamical, as well as statistical climate models. Observed and simulated interactions exhibit substantial discrepancies, whose understanding may be the key to an improved prediction. Moreover, the statistical framework which we apply here is suitable for direct usage of inferring cross-scale interactions in nonlinear time series from complex systems such as the terrestrial magnetosphere, solar-terrestrial interactions, seismic activity or even human brain dynamics.

A Bayesian method for construction of Markov models to describe dynamics on various time-scales.

Science.gov (United States)

Rains, Emily K; Andersen, Hans C

2010-10-14

The dynamics of many biological processes of interest, such as the folding of a protein, are slow and complicated enough that a single molecular dynamics simulation trajectory of the entire process is difficult to obtain in any reasonable amount of time. Moreover, one such simulation may not be sufficient to develop an understanding of the mechanism of the process, and multiple simulations may be necessary. One approach to circumvent this computational barrier is the use of Markov state models. These models are useful because they can be constructed using data from a large number of shorter simulations instead of a single long simulation. This paper presents a new Bayesian method for the construction of Markov models from simulation data. A Markov model is specified by (τ,P,T), where τ is the mesoscopic time step, P is a partition of configuration space into mesostates, and T is an N(P)×N(P) transition rate matrix for transitions between the mesostates in one mesoscopic time step, where N(P) is the number of mesostates in P. The method presented here is different from previous Bayesian methods in several ways. (1) The method uses Bayesian analysis to determine the partition as well as the transition probabilities. (2) The method allows the construction of a Markov model for any chosen mesoscopic time-scale τ. (3) It constructs Markov models for which the diagonal elements of T are all equal to or greater than 0.5. Such a model will be called a "consistent mesoscopic Markov model" (CMMM). Such models have important advantages for providing an understanding of the dynamics on a mesoscopic time-scale. The Bayesian method uses simulation data to find a posterior probability distribution for (P,T) for any chosen τ. This distribution can be regarded as the Bayesian probability that the kinetics observed in the atomistic simulation data on the mesoscopic time-scale τ was generated by the CMMM specified by (P,T). An optimization algorithm is used to find the most

Connection between slow and fast dynamics of molecular liquids around the glass transition

International Nuclear Information System (INIS)

Niss, Kristine; Dalle-Ferrier, Cecile; Frick, Bernhard; Russo, Daniela; Dyre, Jeppe; Alba-Simionesco, Christiane

2010-01-01

The mean-square displacement (MSD) was measured by neutron scattering at various temperatures and pressures for a number of molecular glass-forming liquids. The MSD is invariant along the glass-transition line at the pressure studied, thus establishing an 'intrinsic' Lindemann criterion for any given liquid. A one-to-one connection between the MSD's temperature dependence and the liquid's fragility is found when the MSD is evaluated on a time scale of ∼4 ns, but does not hold when the MSD is evaluated at shorter times. The findings are discussed in terms of the elastic model and the role of relaxations, and the correlations between slow and fast dynamics are addressed.

Phenomenology of local scale invariance: from conformal invariance to dynamical scaling

International Nuclear Information System (INIS)

Henkel, Malte

2002-01-01

Statistical systems displaying a strongly anisotropic or dynamical scaling behaviour are characterized by an anisotropy exponent θ or a dynamical exponent z. For a given value of θ (or z), we construct local scale transformations, which can be viewed as scale transformations with a space-time-dependent dilatation factor. Two distinct types of local scale transformations are found. The first type may describe strongly anisotropic scaling of static systems with a given value of θ, whereas the second type may describe dynamical scaling with a dynamical exponent z. Local scale transformations act as a dynamical symmetry group of certain non-local free-field theories. Known special cases of local scale invariance are conformal invariance for θ=1 and Schroedinger invariance for θ=2. The hypothesis of local scale invariance implies that two-point functions of quasi primary operators satisfy certain linear fractional differential equations, which are constructed from commuting fractional derivatives. The explicit solution of these yields exact expressions for two-point correlators at equilibrium and for two-point response functions out of equilibrium. A particularly simple and general form is found for the two-time auto response function. These predictions are explicitly confirmed at the uniaxial Lifshitz points in the ANNNI and ANNNS models and in the aging behaviour of simple ferromagnets such as the kinetic Glauber-Ising model and the kinetic spherical model with a non-conserved order parameter undergoing either phase-ordering kinetics or non-equilibrium critical dynamics

Fast ignition breakeven scaling

International Nuclear Information System (INIS)

Slutz, Stephen A.; Vesey, Roger Alan

2005-01-01

A series of numerical simulations have been performed to determine scaling laws for fast ignition break even of a hot spot formed by energetic particles created by a short pulse laser. Hot spot break even is defined to be when the fusion yield is equal to the total energy deposited in the hot spot through both the initial compression and the subsequent heating. In these simulations, only a small portion of a previously compressed mass of deuterium-tritium fuel is heated on a short time scale, i.e., the hot spot is tamped by the cold dense fuel which surrounds it. The hot spot tamping reduces the minimum energy required to obtain break even as compared to the situation where the entire fuel mass is heated, as was assumed in a previous study [S. A. Slutz, R. A. Vesey, I. Shoemaker, T. A. Mehlhorn, and K. Cochrane, Phys. Plasmas 7, 3483 (2004)]. The minimum energy required to obtain hot spot break even is given approximately by the scaling law E T = 7.5(ρ/100) -1.87 kJ for tamped hot spots, as compared to the previously reported scaling of E UT = 15.3(ρ/100) -1.5 kJ for untamped hotspots. The size of the compressed fuel mass and the focusability of the particles generated by the short pulse laser determines which scaling law to use for an experiment designed to achieve hot spot break even

Fluctuation-Response Relation and modeling in systems with fast and slow dynamics

Directory of Open Access Journals (Sweden)

G. Lacorata

2007-10-01

Full Text Available We show how a general formulation of the Fluctuation-Response Relation is able to describe in detail the connection between response properties to external perturbations and spontaneous fluctuations in systems with fast and slow variables. The method is tested by using the 360-variable Lorenz-96 model, where slow and fast variables are coupled to one another with reciprocal feedback, and a simplified low dimensional system. In the Fluctuation-Response context, the influence of the fast dynamics on the slow dynamics relies in a non trivial behavior of a suitable quadratic response function. This has important consequences for the modeling of the slow dynamics in terms of a Langevin equation: beyond a certain intrinsic time interval even the optimal model can give just statistical prediction.

Cardiorespiratory Dynamic Response to Mental Stress: A Multivariate Time-Frequency Analysis

Directory of Open Access Journals (Sweden)

Devy Widjaja

2013-01-01

out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3 s than unrelated to (30 s respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales.

Fast-forward of quantum adiabatic dynamics in electro-magnetic field

OpenAIRE

Masuda, Shumpei; Nakamura, Katsuhiro

2010-01-01

We show a method to accelerate quantum adiabatic dynamics of wavefunctions under electro-magnetic field by developing the previous theory (Masuda & Nakamura 2008 and 2010). Firstly we investigate the orbital dynamics of a charged particle. We derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states except for the spatially uniform phase such as the adiabatic phase in any desired short time. Fast-forward of adiabatic squeezing and tran...

Accuracy of single photoelectron time spread measurement of fast photomultipliers

International Nuclear Information System (INIS)

Leskovar, B.

1975-01-01

The accuracy of time spread measurements of fast photomultipliers was investigated, using single photoelectrons. The effect of the finite light pulse width on the measurement accuracy was determined and discussed. Experimental data were obtained on a special measuring system for light pulse widths ranging from 200 psec to 10 nsec, using fast photomultipliers 8850 and C31024 with optimized operating conditions for minimum transit time spread. A modified exponential function expression and curve-fitting parameters are given, which fit closely the experimentally obtained data over a wide dynamic range of light pulse widths. (U.S.)

Quasi-potential and Two-Scale Large Deviation Theory for Gillespie Dynamics

KAUST Repository

Li, Tiejun; Li, Fangting; Li, Xianggang; Lu, Cheng

2016-01-01

theory for Gillespie-type jump dynamics. In the application to a typical genetic switching model, the two-scale large deviation theory is developed to take into account the fast switching of DNA states. The comparison with other proposals are also

Fast engineering optimization: A novel highly effective control parameterization approach for industrial dynamic processes.

Science.gov (United States)

Liu, Ping; Li, Guodong; Liu, Xinggao

2015-09-01

Control vector parameterization (CVP) is an important approach of the engineering optimization for the industrial dynamic processes. However, its major defect, the low optimization efficiency caused by calculating the relevant differential equations in the generated nonlinear programming (NLP) problem repeatedly, limits its wide application in the engineering optimization for the industrial dynamic processes. A novel highly effective control parameterization approach, fast-CVP, is first proposed to improve the optimization efficiency for industrial dynamic processes, where the costate gradient formulae is employed and a fast approximate scheme is presented to solve the differential equations in dynamic process simulation. Three well-known engineering optimization benchmark problems of the industrial dynamic processes are demonstrated as illustration. The research results show that the proposed fast approach achieves a fine performance that at least 90% of the computation time can be saved in contrast to the traditional CVP method, which reveals the effectiveness of the proposed fast engineering optimization approach for the industrial dynamic processes. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Nonadiabatic dynamics of electron transfer in solution: Explicit and implicit solvent treatments that include multiple relaxation time scales

International Nuclear Information System (INIS)

Schwerdtfeger, Christine A.; Soudackov, Alexander V.; Hammes-Schiffer, Sharon

2014-01-01

The development of efficient theoretical methods for describing electron transfer (ET) reactions in condensed phases is important for a variety of chemical and biological applications. Previously, dynamical dielectric continuum theory was used to derive Langevin equations for a single collective solvent coordinate describing ET in a polar solvent. In this theory, the parameters are directly related to the physical properties of the system and can be determined from experimental data or explicit molecular dynamics simulations. Herein, we combine these Langevin equations with surface hopping nonadiabatic dynamics methods to calculate the rate constants for thermal ET reactions in polar solvents for a wide range of electronic couplings and reaction free energies. Comparison of explicit and implicit solvent calculations illustrates that the mapping from explicit to implicit solvent models is valid even for solvents exhibiting complex relaxation behavior with multiple relaxation time scales and a short-time inertial response. The rate constants calculated for implicit solvent models with a single solvent relaxation time scale corresponding to water, acetonitrile, and methanol agree well with analytical theories in the Golden rule and solvent-controlled regimes, as well as in the intermediate regime. The implicit solvent models with two relaxation time scales are in qualitative agreement with the analytical theories but quantitatively overestimate the rate constants compared to these theories. Analysis of these simulations elucidates the importance of multiple relaxation time scales and the inertial component of the solvent response, as well as potential shortcomings of the analytical theories based on single time scale solvent relaxation models. This implicit solvent approach will enable the simulation of a wide range of ET reactions via the stochastic dynamics of a single collective solvent coordinate with parameters that are relevant to experimentally accessible

Adaptive dynamics on an environmental gradient that changes over a geological time-scale.

Science.gov (United States)

Fortelius, Mikael; Geritz, Stefan; Gyllenberg, Mats; Toivonen, Jaakko

2015-07-07

The standard adaptive dynamics framework assumes two timescales, i.e. fast population dynamics and slow evolutionary dynamics. We further assume a third timescale, which is even slower than the evolutionary timescale. We call this the geological timescale and we assume that slow climatic change occurs within this timescale. We study the evolution of our model population over this very slow geological timescale with bifurcation plots of the standard adaptive dynamics framework. The bifurcation parameter being varied describes the abiotic environment that changes over the geological timescale. We construct evolutionary trees over the geological timescale and observe both gradual phenotypic evolution and punctuated branching events. We concur with the established notion that branching of a monomorphic population on an environmental gradient only happens when the gradient is not too shallow and not too steep. However, we show that evolution within the habitat can produce polymorphic populations that inhabit steep gradients. What is necessary is that the environmental gradient at some point in time is such that the initial branching of the monomorphic population can occur. We also find that phenotypes adapted to environments in the middle of the existing environmental range are more likely to branch than phenotypes adapted to extreme environments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Geometrical shock dynamics for magnetohydrodynamic fast shocks

KAUST Repository

Mostert, W.; Pullin, D. I.; Samtaney, Ravi; Wheatley, V.

2016-01-01

We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press

Geometrical shock dynamics for magnetohydrodynamic fast shocks

KAUST Repository

Mostert, W.

2016-12-12

We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press

A fast dynamic mode in rare earth based glasses

Energy Technology Data Exchange (ETDEWEB)

Zhao, L. Z.; Xue, R. J.; Zhu, Z. G.; Wang, W. H.; Bai, H. Y., E-mail: hybai@iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Ngai, K. L. [Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa (Italy)

2016-05-28

Metallic glasses (MGs) usually exhibit only slow β-relaxation peak, and the signature of the fast dynamic is challenging to be observed experimentally in MGs. We report a general and unusual fast dynamic mode in a series of rare earth based MGs manifested as a distinct fast β′-relaxation peak in addition to slow β-relaxation and α-relaxation peaks. We show that the activation energy of the fast β′-relaxation is about 12RT{sub g} and is equivalent to the activation of localized flow event. The coupling of these dynamic processes as well as their relationship with glass transition and structural heterogeneity is discussed.

Temporal Gillespie Algorithm: Fast Simulation of Contagion Processes on Time-Varying Networks.

Science.gov (United States)

Vestergaard, Christian L; Génois, Mathieu

2015-10-01

Stochastic simulations are one of the cornerstones of the analysis of dynamical processes on complex networks, and are often the only accessible way to explore their behavior. The development of fast algorithms is paramount to allow large-scale simulations. The Gillespie algorithm can be used for fast simulation of stochastic processes, and variants of it have been applied to simulate dynamical processes on static networks. However, its adaptation to temporal networks remains non-trivial. We here present a temporal Gillespie algorithm that solves this problem. Our method is applicable to general Poisson (constant-rate) processes on temporal networks, stochastically exact, and up to multiple orders of magnitude faster than traditional simulation schemes based on rejection sampling. We also show how it can be extended to simulate non-Markovian processes. The algorithm is easily applicable in practice, and as an illustration we detail how to simulate both Poissonian and non-Markovian models of epidemic spreading. Namely, we provide pseudocode and its implementation in C++ for simulating the paradigmatic Susceptible-Infected-Susceptible and Susceptible-Infected-Recovered models and a Susceptible-Infected-Recovered model with non-constant recovery rates. For empirical networks, the temporal Gillespie algorithm is here typically from 10 to 100 times faster than rejection sampling.

Rapid-mixing studies on the time-scale of radiation damage in cells

International Nuclear Information System (INIS)

Adams, G.E.; Michael, B.D.; Asquith, J.C.; Shenoy, M.A.; Watts, M.E.; Whillans, D.W.

1975-01-01

Rapid mixing studies were performed to determine the time scale of radiation damage in cells. There is evidence that the sensitizing effects of oxygen and other chemical dose-modifying agents on the response of cells to ionizing radiation involve fast free-radical processes. Fast response technique studies in bacterial systems have shown that extremely fast processes occur when the bacteria are exposed to oxygen or other dose-modifying agents during irradiation. The time scales observed were consistent with the involvement of fast free-radical reactions in the expression of these effects

Coupled slow and fast surface dynamics in an electrocatalytic oscillator: Model and simulations

International Nuclear Information System (INIS)

Nascimento, Melke A.; Nagao, Raphael; Eiswirth, Markus; Varela, Hamilton

2014-01-01

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 fast ions during sawtooth oscillations in the TEXTOR tokamak measured by collective Thomson scattering

DEFF Research Database (Denmark)

Nielsen, Stefan Kragh; Salewski, Mirko; Bindslev, Henrik

2011-01-01

Experimental investigations of sawteeth interaction with fast ions measured by collective Thomson scattering on TEXTOR are presented. Time-resolved measurements of localized 1D fast-ion distribution functions allow us to study fast-ion dynamics during several sawtooth cycles. Sawtooth oscillation...

Fast-forward scaling theory for phase imprinting on a BEC: creation of a wave packet with uniform momentum density and loading to Bloch states without disturbance

Science.gov (United States)

Masuda, Shumpei; Nakamura, Katsuhiro; Nakahara, Mikio

2018-02-01

We study phase imprinting on Bose-Einstein condensates (BECs) with the fast-forward scaling theory revealing a nontrivial scaling property in quantum dynamics. We introduce a wave packet with uniform momentum density (WPUM) which has peculiar properties but is short-lived. The fast-forward scaling theory is applied to derive the driving potential for creation of the WPUMs in a predetermined time. Fast manipulation is essential for the creation of WPUMs because of the instability of the state. We also study loading of a BEC into a predetermined Bloch state in the lowest band from the ground state of a periodic potential. Controlled linear potential is not sufficient for creation of the Bloch state with large wavenumber because the change in the amplitude of the order parameter is not negligible. We derive the exact driving potential for creation of predetermined Bloch states using the obtained theory.

Temperature dependence of fluctuation time scales in spin glasses

DEFF Research Database (Denmark)

Kenning, Gregory G.; Bowen, J.; Sibani, Paolo

2010-01-01

Using a series of fast cooling protocols we have probed aging effects in the spin glass state as a function of temperature. Analyzing the logarithmic decay found at very long time scales within a simple phenomenological barrier model, leads to the extraction of the fluctuation time scale of the s...

Hardy type inequalities on time scales

CERN Document Server

Agarwal, Ravi P; Saker, Samir H

2016-01-01

The book is devoted to dynamic inequalities of Hardy type and extensions and generalizations via convexity on a time scale T. In particular, the book contains the time scale versions of classical Hardy type inequalities, Hardy and Littlewood type inequalities, Hardy-Knopp type inequalities via convexity, Copson type inequalities, Copson-Beesack type inequalities, Liendeler type inequalities, Levinson type inequalities and Pachpatte type inequalities, Bennett type inequalities, Chan type inequalities, and Hardy type inequalities with two different weight functions. These dynamic inequalities contain the classical continuous and discrete inequalities as special cases when T = R and T = N and can be extended to different types of inequalities on different time scales such as T = hN, h > 0, T = qN for q > 1, etc.In this book the authors followed the history and development of these inequalities. Each section in self-contained and one can see the relationship between the time scale versions of the inequalities and...

Suppression of chaos at slow variables by rapidly mixing fast dynamics through linear energy-preserving coupling

Science.gov (United States)

Abramov, R. V.

2011-12-01

Chaotic multiscale dynamical systems are common in many areas of science, one of the examples being the interaction of the low-frequency dynamics in the atmosphere with the fast turbulent weather dynamics. One of the key questions about chaotic multiscale systems is how the fast dynamics affects chaos at the slow variables, and, therefore, impacts uncertainty and predictability of the slow dynamics. Here we demonstrate that the linear slow-fast coupling with the total energy conservation property promotes the suppression of chaos at the slow variables through the rapid mixing at the fast variables, both theoretically and through numerical simulations. A suitable mathematical framework is developed, connecting the slow dynamics on the tangent subspaces to the infinite-time linear response of the mean state to a constant external forcing at the fast variables. Additionally, it is shown that the uncoupled dynamics for the slow variables may remain chaotic while the complete multiscale system loses chaos and becomes completely predictable at the slow variables through increasing chaos and turbulence at the fast variables. This result contradicts the common sense intuition, where, naturally, one would think that coupling a slow weakly chaotic system with another much faster and much stronger chaotic system would result in general increase of chaos at the slow variables.

Stochastic time scale for the Universe

International Nuclear Information System (INIS)

Szydlowski, M.; Golda, Z.

1986-01-01

An intrinsic time scale is naturally defined within stochastic gradient dynamical systems. It should be interpreted as a ''relaxation time'' to a local potential minimum after the system has been randomly perturbed. It is shown that for a flat Friedman-like cosmological model this time scale is of order of the age of the Universe. 7 refs. (author)

Overview of fast algorithm in 3D dynamic holographic display

Science.gov (United States)

Liu, Juan; Jia, Jia; Pan, Yijie; Wang, Yongtian

2013-08-01

3D dynamic holographic display is one of the most attractive techniques for achieving real 3D vision with full depth cue without any extra devices. However, huge 3D information and data should be preceded and be computed in real time for generating the hologram in 3D dynamic holographic display, and it is a challenge even for the most advanced computer. Many fast algorithms are proposed for speeding the calculation and reducing the memory usage, such as:look-up table (LUT), compressed look-up table (C-LUT), split look-up table (S-LUT), and novel look-up table (N-LUT) based on the point-based method, and full analytical polygon-based methods, one-step polygon-based method based on the polygon-based method. In this presentation, we overview various fast algorithms based on the point-based method and the polygon-based method, and focus on the fast algorithm with low memory usage, the C-LUT, and one-step polygon-based method by the 2D Fourier analysis of the 3D affine transformation. The numerical simulations and the optical experiments are presented, and several other algorithms are compared. The results show that the C-LUT algorithm and the one-step polygon-based method are efficient methods for saving calculation time. It is believed that those methods could be used in the real-time 3D holographic display in future.

Fast Simulation of Large-Scale Floods Based on GPU Parallel Computing

OpenAIRE

Qiang Liu; Yi Qin; Guodong Li

2018-01-01

Computing speed is a significant issue of large-scale flood simulations for real-time response to disaster prevention and mitigation. Even today, most of the large-scale flood simulations are generally run on supercomputers due to the massive amounts of data and computations necessary. In this work, a two-dimensional shallow water model based on an unstructured Godunov-type finite volume scheme was proposed for flood simulation. To realize a fast simulation of large-scale floods on a personal...

Fast rise times and the physical mechanism of deep earthquakes

Science.gov (United States)

Houston, H.; Williams, Q.

1991-01-01

A systematic global survey of the rise times and stress drops of deep and intermediate earthquakes is reported. When the rise times are scaled to the seismic moment release of the events, their average is nearly twice as fast for events deeper than about 450 km as for shallower events.

Fast-forward Langevin dynamics with momentum flips

Science.gov (United States)

Hijazi, Mahdi; Wilkins, David M.; Ceriotti, Michele

2018-05-01

Stochastic thermostats based on the Langevin equation, in which a system is coupled to an external heat bath, are popular methods for temperature control in molecular dynamics simulations due to their ergodicity and their ease of implementation. Traditionally, these thermostats suffer from sluggish behavior in the limit of high friction, unlike thermostats of the Nosé-Hoover family whose performance degrades more gently in the strong coupling regime. We propose a simple and easy-to-implement modification to the integration scheme of the Langevin algorithm that addresses the fundamental source of the overdamped behavior of high-friction Langevin dynamics: if the action of the thermostat causes the momentum of a particle to change direction, it is flipped back. This fast-forward Langevin equation preserves the momentum distribution and so guarantees the correct equilibrium sampling. It mimics the quadratic behavior of Nosé-Hoover thermostats and displays similarly good performance in the strong coupling limit. We test the efficiency of this scheme by applying it to a 1-dimensional harmonic oscillator, as well as to water and Lennard-Jones polymers. The sampling efficiency of the fast-forward Langevin equation thermostat, measured by the correlation time of relevant system variables, is at least as good as the traditional Langevin thermostat, and in the overdamped regime, the fast-forward thermostat performs much better, improving the efficiency by an order of magnitude at the highest frictions we considered.

Stability and periodicity of solutions for delay dynamic systems on time scales

Directory of Open Access Journals (Sweden)

Zhi-Qiang Zhu

2014-04-01

Full Text Available This article concerns the stability and periodicity of solutions to the delay dynamic system $$ x^{\\triangle}(t=A(t x(t + F(t, x(t, x(g(t+C(t $$ on a time scale. By the inequality technique for vectors, we obtain some stability criteria for the above system. Then, by using the Horn fixed point theorem, we present some conditions under which our system is asymptotically periodic and its periodic solution is unique. In particular, the periodic solution is positive under proper assumptions.

Model based analysis of the time scales associated to pump start-ups

Energy Technology Data Exchange (ETDEWEB)

Dazin, Antoine, E-mail: antoine.dazin@lille.ensam.fr [Arts et métiers ParisTech/LML Laboratory UMR CNRS 8107, 8 bld Louis XIV, 59046 Lille cedex (France); Caignaert, Guy [Arts et métiers ParisTech/LML Laboratory UMR CNRS 8107, 8 bld Louis XIV, 59046 Lille cedex (France); Dauphin-Tanguy, Geneviève, E-mail: genevieve.dauphin-tanguy@ec-lille.fr [Univ Lille Nord de France, Ecole Centrale de Lille/CRISTAL UMR CNRS 9189, BP 48, 59651, Villeneuve d’Ascq cedex F 59000 (France)

2015-11-15

Highlights: • A dynamic model of a hydraulic system has been built. • Three periods in a pump start-up have been identified. • The time scales of each period have been estimated. • The parameters affecting the rapidity of a pump start-up have been explored. - Abstract: The paper refers to a non dimensional analysis of the behaviour of a hydraulic system during pump fast start-ups. The system is composed of a radial flow pump and its suction and delivery pipes. It is modelled using the bond graph methodology. The prediction of the model is validated by comparison to experimental results. An analysis of the time evolution of the terms acting on the total pump pressure is proposed. It allows for a decomposition of the start-up into three consecutive periods. The time scales associated with these periods are estimated. The effects of parameters (angular acceleration, final rotation speed, pipe length and resistance) affecting the start-up rapidity are then explored.

Multi-Time Scale Model Order Reduction and Stability Consistency Certification of Inverter-Interfaced DG System in AC Microgrid

Directory of Open Access Journals (Sweden)

Xiaoxiao Meng

2018-01-01

Full Text Available AC microgrid mainly comprise inverter-interfaced distributed generators (IIDGs, which are nonlinear complex systems with multiple time scales, including frequency control, time delay measurements, and electromagnetic transients. The droop control-based IIDG in an AC microgrid is selected as the research object in this study, which comprises power droop controller, voltage- and current-loop controllers, and filter and line. The multi-time scale characteristics of the detailed IIDG model are divided based on singular perturbation theory. In addition, the IIDG model order is reduced by neglecting the system fast dynamics. The static and transient stability consistency of the IIDG model order reduction are demonstrated by extracting features of the IIDG small signal model and using the quadratic approximation method of the stability region boundary, respectively. The dynamic response consistencies of the IIDG model order reduction are evaluated using the frequency, damping and amplitude features extracted by the Prony transformation. Results are applicable to provide a simplified model for the dynamic characteristic analysis of IIDG systems in AC microgrid. The accuracy of the proposed method is verified by using the eigenvalue comparison, the transient stability index comparison and the dynamic time-domain simulation.

Fast Optimal Replica Placement with Exhaustive Search Using Dynamically Reconfigurable Processor

Directory of Open Access Journals (Sweden)

Hidetoshi Takeshita

2011-01-01

Full Text Available This paper proposes a new replica placement algorithm that expands the exhaustive search limit with reasonable calculation time. It combines a new type of parallel data-flow processor with an architecture tuned for fast calculation. The replica placement problem is to find a replica-server set satisfying service constraints in a content delivery network (CDN. It is derived from the set cover problem which is known to be NP-hard. It is impractical to use exhaustive search to obtain optimal replica placement in large-scale networks, because calculation time increases with the number of combinations. To reduce calculation time, heuristic algorithms have been proposed, but it is known that no heuristic algorithm is assured of finding the optimal solution. The proposed algorithm suits parallel processing and pipeline execution and is implemented on DAPDNA-2, a dynamically reconfigurable processor. Experiments show that the proposed algorithm expands the exhaustive search limit by the factor of 18.8 compared to the conventional algorithm search limit running on a Neumann-type processor.

Waiting Time Dynamics in Two-Dimensional Infrared Spectroscopy

NARCIS (Netherlands)

Jansen, Thomas L. C.; Knoester, Jasper

We review recent work on the waiting time dynamics of coherent two-dimensional infrared (2DIR) spectroscopy. This dynamics can reveal chemical and physical processes that take place on the femto- and picosecond time scale, which is faster than the time scale that may be probed by, for example,

Recovery time after localized perturbations in complex dynamical networks

International Nuclear Information System (INIS)

Mitra, Chiranjit; Kittel, Tim; Kurths, Jürgen; Donner, Reik V; Choudhary, Anshul

2017-01-01

Maintaining the synchronous motion of dynamical systems interacting on complex networks is often critical to their functionality. However, real-world networked dynamical systems operating synchronously are prone to random perturbations driving the system to arbitrary states within the corresponding basin of attraction, thereby leading to epochs of desynchronized dynamics with a priori unknown durations. Thus, it is highly relevant to have an estimate of the duration of such transient phases before the system returns to synchrony, following a random perturbation to the dynamical state of any particular node of the network. We address this issue here by proposing the framework of single-node recovery time (SNRT) which provides an estimate of the relative time scales underlying the transient dynamics of the nodes of a network during its restoration to synchrony. We utilize this in differentiating the particularly slow nodes of the network from the relatively fast nodes, thus identifying the critical nodes which when perturbed lead to significantly enlarged recovery time of the system before resuming synchronized operation. Further, we reveal explicit relationships between the SNRT values of a network, and its global relaxation time when starting all the nodes from random initial conditions. Earlier work on relaxation time generally focused on investigating its dependence on macroscopic topological properties of the respective network. However, we employ the proposed concept for deducing microscopic relationships between topological features of nodes and their respective SNRT values. The framework of SNRT is further extended to a measure of resilience of the different nodes of a networked dynamical system. We demonstrate the potential of SNRT in networks of Rössler oscillators on paradigmatic topologies and a model of the power grid of the United Kingdom with second-order Kuramoto-type nodal dynamics illustrating the conceivable practical applicability of the proposed

Recovery time after localized perturbations in complex dynamical networks

Science.gov (United States)

Mitra, Chiranjit; Kittel, Tim; Choudhary, Anshul; Kurths, Jürgen; Donner, Reik V.

2017-10-01

Maintaining the synchronous motion of dynamical systems interacting on complex networks is often critical to their functionality. However, real-world networked dynamical systems operating synchronously are prone to random perturbations driving the system to arbitrary states within the corresponding basin of attraction, thereby leading to epochs of desynchronized dynamics with a priori unknown durations. Thus, it is highly relevant to have an estimate of the duration of such transient phases before the system returns to synchrony, following a random perturbation to the dynamical state of any particular node of the network. We address this issue here by proposing the framework of single-node recovery time (SNRT) which provides an estimate of the relative time scales underlying the transient dynamics of the nodes of a network during its restoration to synchrony. We utilize this in differentiating the particularly slow nodes of the network from the relatively fast nodes, thus identifying the critical nodes which when perturbed lead to significantly enlarged recovery time of the system before resuming synchronized operation. Further, we reveal explicit relationships between the SNRT values of a network, and its global relaxation time when starting all the nodes from random initial conditions. Earlier work on relaxation time generally focused on investigating its dependence on macroscopic topological properties of the respective network. However, we employ the proposed concept for deducing microscopic relationships between topological features of nodes and their respective SNRT values. The framework of SNRT is further extended to a measure of resilience of the different nodes of a networked dynamical system. We demonstrate the potential of SNRT in networks of Rössler oscillators on paradigmatic topologies and a model of the power grid of the United Kingdom with second-order Kuramoto-type nodal dynamics illustrating the conceivable practical applicability of the proposed

Scaling properties in time-varying networks with memory

Science.gov (United States)

Kim, Hyewon; Ha, Meesoon; Jeong, Hawoong

2015-12-01

The formation of network structure is mainly influenced by an individual node's activity and its memory, where activity can usually be interpreted as the individual inherent property and memory can be represented by the interaction strength between nodes. In our study, we define the activity through the appearance pattern in the time-aggregated network representation, and quantify the memory through the contact pattern of empirical temporal networks. To address the role of activity and memory in epidemics on time-varying networks, we propose temporal-pattern coarsening of activity-driven growing networks with memory. In particular, we focus on the relation between time-scale coarsening and spreading dynamics in the context of dynamic scaling and finite-size scaling. Finally, we discuss the universality issue of spreading dynamics on time-varying networks for various memory-causality tests.

Existence of positive solutions for semipositone dynamic system on time scales

Directory of Open Access Journals (Sweden)

You-Wei Zhang

2008-08-01

Full Text Available In this paper, we study the following semipositone dynamic system on time scales $$displaylines{ -x^{DeltaDelta}(t=f(t,y+p(t, quad tin(0,T_{mathbb{T}},cr -y^{DeltaDelta}(t=g(t,x, quad tin(0,T_{mathbb{T}},cr x(0=x(sigma^{2}(T=0, cr alpha{y(0}-eta{y^{Delta}{(0}}= gamma{y(sigma(T}+delta{y^{Delta}(sigma(T}=0. }$$ Using fixed point index theory, we show the existence of at least one positive solution. The interesting point is the that nonlinear term is allowed to change sign and may tend to negative infinity.

Fast timing discriminator

International Nuclear Information System (INIS)

Lo, C.C.

1977-01-01

The processing of pulses with very fast risetimes for timing purposes involves many problems because of the large equivalent bandwidths involved. For pulses with risetimes in the 150 ps range (and full widths at half maximum (FWHM) of 400 ps) bandwidths in excess of 1GHz are required. Furthermore, these very narrow pulses with current amplitudes as small as 1 mA carry very small charges ( -12 coulomb), therefore, requiring very sensitive trigger circuits. The difficulty increases when timing characteristics in the picosecond range are sought especially when a wide input signal amplitude range causes a time-walk problem. The fast timing discriminator described has a time-walk of approximately +-75 ps over the input signal range from 80 mV to 3V. A schematic of the discriminator is included, and operation and performance are discussed

Fast-ion dynamics in the TEXTOR tokamak measured by collective Thomson scattering

DEFF Research Database (Denmark)

Bindslev, H.; Nielsen, S.K.; Porte, L.

2006-01-01

Here we present the first measurements by collective Thomson scattering of the evolution of fast-ion populations in a magnetically confined fusion plasma. 150 kW and 110 Ghz radiation from a gyrotron were scattered in the TEXTOR tokamak plasma with energetic ions generated by neutral beam injection...... and ion cyclotron resonance heating. The temporal behavior of the spatially resolved fast-ion velocity distribution is inferred from the received scattered radiation. The fast-ion dynamics at sawteeth and the slowdown after switch off of auxiliary heating is resolved in time. The latter is shown...

The scale-free dynamics of eukaryotic cells.

Directory of Open Access Journals (Sweden)

Miguel A Aon

Full Text Available Temporal organization of biological processes requires massively parallel processing on a synchronized time-base. We analyzed time-series data obtained from the bioenergetic oscillatory outputs of Saccharomyces cerevisiae and isolated cardiomyocytes utilizing Relative Dispersional (RDA and Power Spectral (PSA analyses. These analyses revealed broad frequency distributions and evidence for long-term memory in the observed dynamics. Moreover RDA and PSA showed that the bioenergetic dynamics in both systems show fractal scaling over at least 3 orders of magnitude, and that this scaling obeys an inverse power law. Therefore we conclude that in S. cerevisiae and cardiomyocytes the dynamics are scale-free in vivo. Applying RDA and PSA to data generated from an in silico model of mitochondrial function indicated that in yeast and cardiomyocytes the underlying mechanisms regulating the scale-free behavior are similar. We validated this finding in vivo using single cells, and attenuating the activity of the mitochondrial inner membrane anion channel with 4-chlorodiazepam to show that the oscillation of NAD(PH and reactive oxygen species (ROS can be abated in these two evolutionarily distant species. Taken together these data strongly support our hypothesis that the generation of ROS, coupled to redox cycling, driven by cytoplasmic and mitochondrial processes, are at the core of the observed rhythmicity and scale-free dynamics. We argue that the operation of scale-free bioenergetic dynamics plays a fundamental role to integrate cellular function, while providing a framework for robust, yet flexible, responses to the environment.

Fast Responding Voltage Regulator and Dynamic VAR Compensator

Energy Technology Data Exchange (ETDEWEB)

Divan, Deepak [Varentec, Incorporated, San Jose, CA (United States); Moghe, Rohit [Varentec, Incorporated, San Jose, CA (United States); Tholomier, Damien [Varentec, Incorporated, San Jose, CA (United States)

2014-12-31

The objectives of this project were to develop a dynamic VAR compensator (DVC) for voltage regulation through VAR support to demonstrate the ability to achieve greater levels of voltage control on electricity distribution networks, and faster response compared to existing grid technology. The goal of the project was to develop a prototype Fast Dynamic VAR Compensator (Fast DVC) hardware device, and this was achieved. In addition to developing the dynamic VAR compensator device, Varentec in partnership with researchers at North Carolina State University (NCSU) successfully met the objectives to model the potential positive impact of such DVCs on representative power networks. This modeling activity validated the ability of distributed dynamic VAR compensators to provide fast voltage regulation and reactive power control required to respond to grid disturbances under high penetration of fluctuating and intermittent distributed energy resources (DERs) through extensive simulation studies. Specifically the following tasks were set to be accomplished: 1) Development of dynamic VAR compensator to support dynamic voltage variations on the grid through VAR control 2) Extensive testing of the DVC in the lab environment 3) Present the operational DVC device to the DOE at Varentec’s lab 4) Formulation of a detailed specification sheet, unit assembly document, test setup document, unit bring-up plan, and test plan 5) Extensive simulations of the DVC in a system with high PV penetration. Understanding the operation with many DVC on a single distribution system 6) Creation and submittal of quarterly and final reports conveying the design documents, unit performance data, modeling simulation charts and diagrams, and summary explanations of the satisfaction of program goals. This report details the various efforts that led to the development of the Fast DVC as well as the modeling & simulation results. The report begins with the introduction in Section II which outlines the

Dynamic structural analysis of a fast shutter with a pneumatic actuator

Energy Technology Data Exchange (ETDEWEB)

Nemov, A., E-mail: nemov@compmechlab.com [St. Petersburg State Polytechnical University, Mechanics and Control Processes Department, Computational Mechanichs Laboratory, Polytechnicheskaya, 29, 195251 St. Petersburg (Russian Federation); Panin, A. [Institut fuer Energieforschung – Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Member of Trilateral Euregio Cluster, 52425 Juelich (Germany); Borovkov, A.; Khovayko, M.; Zhuravskaya, E. [St. Petersburg State Polytechnical University, Mechanics and Control Processes Department, Computational Mechanichs Laboratory, Polytechnicheskaya, 29, 195251 St. Petersburg (Russian Federation); Krasikov, Yu.; Biel, W.; Neubauer, O. [Institut fuer Energieforschung – Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Member of Trilateral Euregio Cluster, 52425 Juelich (Germany)

2013-10-15

Highlights: ► The dynamical simulations of cCXRS shutter with the use of the LS-DYNA explicit solver are presented and discussed. ► The results of the implicit and explicit solvers are compared; their pros and cons are pointed out. ► The simplified LS-DYNA shutter model for parametric studies has been built up and benchmarked against the full model. ► Oscillations of the shutter arms for different actuator flood times were studied. -- Abstract: Fast shutters can play important role for the ITER diagnostics. They protect diagnostic mirrors, especially the first ones closest to the plasma, between measurements, during dwell time and baking. In a nominal mode, as it is assumed, for example, for the ITER upper port plug no. 3 diagnostics, its shutter stays open ∼1 s and closed ∼21 s. The principal idea of the shutter concept is its ability to make fast transitions between the open and closed positions within fractions of second. A pneumatic actuator produces a pressure force to open or close the shutter. Due to the fast transient nature of the shutter operation, complicated by the parts’ impact interaction, the FE codes using the explicit time integration scheme have an advantage over the implicit ones. The shutter operation is modeled using the explicit solver. Since the shutter dynamic behavior strongly depends on the actuator flood time, different time profiles of the actuator pressure rise (drop) has been verified, including a fast transient with duration of ∼0.1 s. The results of the implicit and explicit solvers are compared. Their pros and cons are pointed out. The system damping, estimations of energy loss and ways to specify damping in FE models are discussed in the paper.

Dynamic structural analysis of a fast shutter with a pneumatic actuator

International Nuclear Information System (INIS)

Nemov, A.; Panin, A.; Borovkov, A.; Khovayko, M.; Zhuravskaya, E.; Krasikov, Yu.; Biel, W.; Neubauer, O.

2013-01-01

Highlights: ► The dynamical simulations of cCXRS shutter with the use of the LS-DYNA explicit solver are presented and discussed. ► The results of the implicit and explicit solvers are compared; their pros and cons are pointed out. ► The simplified LS-DYNA shutter model for parametric studies has been built up and benchmarked against the full model. ► Oscillations of the shutter arms for different actuator flood times were studied. -- Abstract: Fast shutters can play important role for the ITER diagnostics. They protect diagnostic mirrors, especially the first ones closest to the plasma, between measurements, during dwell time and baking. In a nominal mode, as it is assumed, for example, for the ITER upper port plug no. 3 diagnostics, its shutter stays open ∼1 s and closed ∼21 s. The principal idea of the shutter concept is its ability to make fast transitions between the open and closed positions within fractions of second. A pneumatic actuator produces a pressure force to open or close the shutter. Due to the fast transient nature of the shutter operation, complicated by the parts’ impact interaction, the FE codes using the explicit time integration scheme have an advantage over the implicit ones. The shutter operation is modeled using the explicit solver. Since the shutter dynamic behavior strongly depends on the actuator flood time, different time profiles of the actuator pressure rise (drop) has been verified, including a fast transient with duration of ∼0.1 s. The results of the implicit and explicit solvers are compared. Their pros and cons are pointed out. The system damping, estimations of energy loss and ways to specify damping in FE models are discussed in the paper

Accelerated dynamic EPR imaging using fast acquisition and compressive recovery.

Science.gov (United States)

Ahmad, Rizwan; Samouilov, Alexandre; Zweier, Jay L

2016-12-01

Electron paramagnetic resonance (EPR) allows quantitative imaging of tissue redox status, which provides important information about ischemic syndromes, cancer and other pathologies. For continuous wave EPR imaging, however, poor signal-to-noise ratio and low acquisition efficiency limit its ability to image dynamic processes in vivo including tissue redox, where conditions can change rapidly. Here, we present a data acquisition and processing framework that couples fast acquisition with compressive sensing-inspired image recovery to enable EPR-based redox imaging with high spatial and temporal resolutions. The fast acquisition (FA) allows collecting more, albeit noisier, projections in a given scan time. The composite regularization based processing method, called spatio-temporal adaptive recovery (STAR), not only exploits sparsity in multiple representations of the spatio-temporal image but also adaptively adjusts the regularization strength for each representation based on its inherent level of the sparsity. As a result, STAR adjusts to the disparity in the level of sparsity across multiple representations, without introducing any tuning parameter. Our simulation and phantom imaging studies indicate that a combination of fast acquisition and STAR (FASTAR) enables high-fidelity recovery of volumetric image series, with each volumetric image employing less than 10 s of scan. In addition to image fidelity, the time constants derived from FASTAR also match closely to the ground truth even when a small number of projections are used for recovery. This development will enhance the capability of EPR to study fast dynamic processes that cannot be investigated using existing EPR imaging techniques. Copyright © 2016 Elsevier Inc. All rights reserved.

Scaling and Universality at Dynamical Quantum Phase Transitions.

Science.gov (United States)

Heyl, Markus

2015-10-02

Dynamical quantum phase transitions (DQPTs) at critical times appear as nonanalyticities during nonequilibrium quantum real-time evolution. Although there is evidence for a close relationship between DQPTs and equilibrium phase transitions, a major challenge is still to connect to fundamental concepts such as scaling and universality. In this work, renormalization group transformations in complex parameter space are formulated for quantum quenches in Ising models showing that the DQPTs are critical points associated with unstable fixed points of equilibrium Ising models. Therefore, these DQPTs obey scaling and universality. On the basis of numerical simulations, signatures of these DQPTs in the dynamical buildup of spin correlations are found with an associated power-law scaling determined solely by the fixed point's universality class. An outlook is given on how to explore this dynamical scaling experimentally in systems of trapped ions.

Hybrid parallel strategy for the simulation of fast transient accidental situations at reactor scale

International Nuclear Information System (INIS)

Faucher, V.; Galon, P.; Beccantini, A.; Crouzet, F.; Debaud, F.; Gautier, T.

2015-01-01

Highlights: • Reference accidental situations for current and future reactors are considered. • They require the modeling of complex fluid–structure systems at full reactor scale. • EPX software computes the non-linear transient solution with explicit time stepping. • Focus on the parallel hybrid solver specific to the proposed coupled equations. - Abstract: This contribution is dedicated to the latest methodological developments implemented in the fast transient dynamics software EUROPLEXUS (EPX) to simulate the mechanical response of fully coupled fluid–structure systems to accidental situations to be considered at reactor scale, among which the Loss of Coolant Accident, the Core Disruptive Accident and the Hydrogen Explosion. Time integration is explicit and the search for reference solutions within the safety framework prevents any simplification and approximations in the coupled algorithm: for instance, all kinematic constraints are dealt with using Lagrange Multipliers, yielding a complex flow chart when non-permanent constraints such as unilateral contact or immersed fluid–structure boundaries are considered. The parallel acceleration of the solution process is then achieved through a hybrid approach, based on a weighted domain decomposition for distributed memory computing and the use of the KAAPI library for self-balanced shared memory processing inside subdomains

Parallel Fast Multipole Boundary Element Method for crustal dynamics

International Nuclear Information System (INIS)

Quevedo, Leonardo; Morra, Gabriele; Mueller, R Dietmar

2010-01-01

Crustal faults and sharp material transitions in the crust are usually represented as triangulated surfaces in structural geological models. The complex range of volumes separating such surfaces is typically three-dimensionally meshed in order to solve equations that describe crustal deformation with the finite-difference (FD) or finite-element (FEM) methods. We show here how the Boundary Element Method, combined with the Multipole approach, can revolutionise the calculation of stress and strain, solving the problem of computational scalability from reservoir to basin scales. The Fast Multipole Boundary Element Method (Fast BEM) tackles the difficulty of handling the intricate volume meshes and high resolution of crustal data that has put classical Finite 3D approaches in a performance crisis. The two main performance enhancements of this method: the reduction of required mesh elements from cubic to quadratic with linear size and linear-logarithmic runtime; achieve a reduction of memory and runtime requirements allowing the treatment of a new scale of geodynamic models. This approach was recently tested and applied in a series of papers by [1, 2, 3] for regional and global geodynamics, using KD trees for fast identification of near and far-field interacting elements, and MPI parallelised code on distributed memory architectures, and is now in active development for crustal dynamics. As the method is based on a free-surface, it allows easy data transfer to geological visualisation tools where only changes in boundaries and material properties are required as input parameters. In addition, easy volume mesh sampling of physical quantities enables direct integration with existing FD/FEM code.

Towards a Unified Formulation of Dynamics and Thermodynamics I. From Microscopic to Macroscopic Time Scales

Czech Academy of Sciences Publication Activity Database

Durand, P.; Paidarová, Ivana

2011-01-01

Roč. 111, č. 2 (2011), s. 225-236 ISSN 0020-7608 R&D Projects: GA AV ČR IAA100400501; GA AV ČR IAA401870702 Institutional research plan: CEZ:AV0Z40400503 Keywords : Liouville equation * time scales * chemical kinetics and dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.357, year: 2011

Fast dynamics perturbation analysis for prediction of protein functional sites

Directory of Open Access Journals (Sweden)

Cohn Judith D

2008-01-01

Full Text Available Abstract Background We present a fast version of the dynamics perturbation analysis (DPA algorithm to predict functional sites in protein structures. The original DPA algorithm finds regions in proteins where interactions cause a large change in the protein conformational distribution, as measured using the relative entropy Dx. Such regions are associated with functional sites. Results The Fast DPA algorithm, which accelerates DPA calculations, is motivated by an empirical observation that Dx in a normal-modes model is highly correlated with an entropic term that only depends on the eigenvalues of the normal modes. The eigenvalues are accurately estimated using first-order perturbation theory, resulting in a N-fold reduction in the overall computational requirements of the algorithm, where N is the number of residues in the protein. The performance of the original and Fast DPA algorithms was compared using protein structures from a standard small-molecule docking test set. For nominal implementations of each algorithm, top-ranked Fast DPA predictions overlapped the true binding site 94% of the time, compared to 87% of the time for original DPA. In addition, per-protein recall statistics (fraction of binding-site residues that are among predicted residues were slightly better for Fast DPA. On the other hand, per-protein precision statistics (fraction of predicted residues that are among binding-site residues were slightly better using original DPA. Overall, the performance of Fast DPA in predicting ligand-binding-site residues was comparable to that of the original DPA algorithm. Conclusion Compared to the original DPA algorithm, the decreased run time with comparable performance makes Fast DPA well-suited for implementation on a web server and for high-throughput analysis.

Dynamic critical behaviour and scaling

International Nuclear Information System (INIS)

Oezoguz, B.E.

2001-01-01

Traditionally the scaling is the property of dynamical systems at thermal equilibrium. In second order phase transitions scaling behaviour is due to the infinite correlation length around the critical point. In first order phase transitions however, the correlation length remains finite and a different type of scaling can be observed. For first order phase transitions all singularities are governed by the volume of the system. Recently, a different type of scaling, namely dynamic scaling has attracted attention in second order phase transitions. In dynamic scaling, when a system prepared at high temperature is quenched to the critical temperature, it exhibits scaling behaviour. Dynamic scaling has been applied to various spin systems and the validity of the arguments are shown. Firstly, in this thesis project the dynamic scaling is applied to 4-dimensional using spin system which exhibits second order phase transition with mean-field critical indices. Secondly, it is shown that although the dynamic is quite different, first order phase transitions also has a different type of dynamic scaling

Mode coupling theory analysis of electrolyte solutions: Time dependent diffusion, intermediate scattering function, and ion solvation dynamics.

Science.gov (United States)

Roy, Susmita; Yashonath, Subramanian; Bagchi, Biman

2015-03-28

A self-consistent mode coupling theory (MCT) with microscopic inputs of equilibrium pair correlation functions is developed to analyze electrolyte dynamics. We apply the theory to calculate concentration dependence of (i) time dependent ion diffusion, (ii) intermediate scattering function of the constituent ions, and (iii) ion solvation dynamics in electrolyte solution. Brownian dynamics with implicit water molecules and molecular dynamics method with explicit water are used to check the theoretical predictions. The time dependence of ionic self-diffusion coefficient and the corresponding intermediate scattering function evaluated from our MCT approach show quantitative agreement with early experimental and present Brownian dynamic simulation results. With increasing concentration, the dispersion of electrolyte friction is found to occur at increasingly higher frequency, due to the faster relaxation of the ion atmosphere. The wave number dependence of intermediate scattering function, F(k, t), exhibits markedly different relaxation dynamics at different length scales. At small wave numbers, we find the emergence of a step-like relaxation, indicating the presence of both fast and slow time scales in the system. Such behavior allows an intriguing analogy with temperature dependent relaxation dynamics of supercooled liquids. We find that solvation dynamics of a tagged ion exhibits a power law decay at long times-the decay can also be fitted to a stretched exponential form. The emergence of the power law in solvation dynamics has been tested by carrying out long Brownian dynamics simulations with varying ionic concentrations. The solvation time correlation and ion-ion intermediate scattering function indeed exhibit highly interesting, non-trivial dynamical behavior at intermediate to longer times that require further experimental and theoretical studies.

Evaluation of Fast-Time Wake Vortex Models using Wake Encounter Flight Test Data

Science.gov (United States)

Ahmad, Nashat N.; VanValkenburg, Randal L.; Bowles, Roland L.; Limon Duparcmeur, Fanny M.; Gloudesman, Thijs; van Lochem, Sander; Ras, Eelco

2014-01-01

This paper describes a methodology for the integration and evaluation of fast-time wake models with flight data. The National Aeronautics and Space Administration conducted detailed flight tests in 1995 and 1997 under the Aircraft Vortex Spacing System Program to characterize wake vortex decay and wake encounter dynamics. In this study, data collected during Flight 705 were used to evaluate NASA's fast-time wake transport and decay models. Deterministic and Monte-Carlo simulations were conducted to define wake hazard bounds behind the wake generator. The methodology described in this paper can be used for further validation of fast-time wake models using en-route flight data, and for determining wake turbulence constraints in the design of air traffic management concepts.

Dynamically controlled energy dissipation for fast magnetic vortex switching

Science.gov (United States)

Badea, R.; Berezovsky, J.

2017-09-01

Manipulation of vortex states in magnetic media provides new routes towards information storage and processing technology. The typical slow relaxation times (˜100 ns) of magnetic vortex dynamics may present an obstacle to the realization of these applications. Here, we investigate how a vortex state in a ferromagnetic microdisk can be manipulated in a way that translates the vortex core while enhancing energy dissipation to rapidly damp the vortex dynamics. We use time-resolved differential magneto-optical Kerr effect microscopy to measure the motion of the vortex core in response to applied magnetic fields. We first map out how the vortex core becomes sequentially trapped by pinning sites as it translates across the disk. After applying a fast magnetic field step to translate the vortex from one pinning site to another, we observe long-lived dynamics of the vortex as it settles to the new equilibrium. We then demonstrate how the addition of a short (<10 ns) magnetic field pulse can induce additional energy dissipation, strongly damping the long-lived dynamics. A model of the vortex dynamics using the Thiele equation of motion explains the mechanism behind this effect.

Correlated continuous time random walks: combining scale-invariance with long-range memory for spatial and temporal dynamics

International Nuclear Information System (INIS)

Schulz, Johannes H P; Chechkin, Aleksei V; Metzler, Ralf

2013-01-01

Standard continuous time random walk (CTRW) models are renewal processes in the sense that at each jump a new, independent pair of jump length and waiting time are chosen. Globally, anomalous diffusion emerges through scale-free forms of the jump length and/or waiting time distributions by virtue of the generalized central limit theorem. Here we present a modified version of recently proposed correlated CTRW processes, where we incorporate a power-law correlated noise on the level of both jump length and waiting time dynamics. We obtain a very general stochastic model, that encompasses key features of several paradigmatic models of anomalous diffusion: discontinuous, scale-free displacements as in Lévy flights, scale-free waiting times as in subdiffusive CTRWs, and the long-range temporal correlations of fractional Brownian motion (FBM). We derive the exact solutions for the single-time probability density functions and extract the scaling behaviours. Interestingly, we find that different combinations of the model parameters lead to indistinguishable shapes of the emerging probability density functions and identical scaling laws. Our model will be useful for describing recent experimental single particle tracking data that feature a combination of CTRW and FBM properties. (paper)

Status review of large fast reactor core designs and their dynamics related features

International Nuclear Information System (INIS)

Spenke, H.; Kiefhaber, E.

1982-01-01

Since several years conventional and unconventional concepts of large fast reactor cores have been investigated in the Federal Republic of Germany at INTERATOM and Kernforschungszentrum Karlsruhe. The work was performed jointly with Belgonucleaire (Belgium). Basically, the studies were aimed at the determination of the performance potential of different core concepts for large fast reactors. Thus the following points were considered: power distribution, neutron fluence and residence time, doubling time, uranium ore consumption, dynamics and safety related features, economics, cooling strategy, core element bowing behaviour. In this paper, the state of the analysis will be presented with emphasis on those points relevant for this meeting. However, we have to make clear, that dynamic and accident studies are still under way and that we are not yet able to cover these aspects in a quantitative manner. This is due to the fact, that the efforts in the DeBeNe-countries have been concentrated on the work necessary for being granted the different licenses for SNR 300, fast breeder prototype reactor near Kalkar. As we expect to obtain these important licenses at the beginning of 1982, an increased man power can be devoted to studies of dynamic and safety problems of large fast cores from that time on. These studies have to fit into the planning recently announced by the utility ESK who will be ordering SNR 2, the first demonstration breeder reactor of Germany, Belgium, Netherlands and France. The planning calls for concept decisions in 1983, leading to an engineering contract for SNR 2 in 1983/1984. Accordingly we shall have to complete and evaluate the ongoing core concept Investigations till 1983 resulting in a subsequent final choice

Decoherence recuperating fast environmental dynamics

International Nuclear Information System (INIS)

Cetinbas, Murat

2010-01-01

We examine the exact internal decoherence dynamics of a qubit in an isolated Josephson charge-qubit quantum computer in the presence of one- and two-body static internal imperfections. By help of open system dynamics quantifiers, i.e. purity, fidelity, covariance and Loschmidt echo, we distinguish between non-unitary and unitary components of internal decoherence dynamics and show that the non-unitary component consists of two processes: system-environment entanglement and incoherence. Our results indicate that the incoherence process is the major source of internal decoherence rather than system-environment entanglement. We find that strong one-body intra-environmental interactions, which generate fast environmental dynamics, result in a rapid suppression of decoherence induced by both system-environment entanglement and incoherence processes. We explain the mechanisms of suppression of decoherence for these two processes and discuss our results.

A CMOS integrated timing discriminator circuit for fast scintillation counters

International Nuclear Information System (INIS)

Jochmann, M.W.

1998-01-01

Based on a zero-crossing discriminator using a CR differentiation network for pulse shaping, a new CMOS integrated timing discriminator circuit is proposed for fast (t r ≥ 2 ns) scintillation counters at the cooler synchrotron COSY-Juelich. By eliminating the input signal's amplitude information by means of an analog continuous-time divider, a normalized pulse shape at the zero-crossing point is gained over a wide dynamic input amplitude range. In combination with an arming comparator and a monostable multivibrator this yields in a highly precise timing discriminator circuit, that is expected to be useful in different time measurement applications. First measurement results of a CMOS integrated logarithmic amplifier, which is part of the analog continuous-time divider, agree well with the corresponding simulations. Moreover, SPICE simulations of the integrated discriminator circuit promise a time walk well below 200 ps (FWHM) over a 40 dB input amplitude dynamic range

A scheme for recording a fast process at nanosecond scale by using digital holographic interferometry with continuous wave laser

Science.gov (United States)

Wang, Jun; Zhao, Jianlin; Di, Jianglei; Jiang, Biqiang

2015-04-01

A scheme for recording fast process at nanosecond scale by using digital holographic interferometry with continuous wave (CW) laser is described and demonstrated experimentally, which employs delayed-time fibers and angular multiplexing technique and can realize the variable temporal resolution at nanosecond scale and different measured depths of object field at certain temporal resolution. The actual delay-time is controlled by two delayed-time fibers with different lengths. The object field information in two different states can be simultaneously recorded in a composite hologram. This scheme is also suitable for recording fast process at picosecond scale, by using an electro-optic modulator.

Application of Fast Dynamic Allan Variance for the Characterization of FOGs-Based Measurement While Drilling.

Science.gov (United States)

Wang, Lu; Zhang, Chunxi; Gao, Shuang; Wang, Tao; Lin, Tie; Li, Xianmu

2016-12-07

The stability of a fiber optic gyroscope (FOG) in measurement while drilling (MWD) could vary with time because of changing temperature, high vibration, and sudden power failure. The dynamic Allan variance (DAVAR) is a sliding version of the Allan variance. It is a practical tool that could represent the non-stationary behavior of the gyroscope signal. Since the normal DAVAR takes too long to deal with long time series, a fast DAVAR algorithm has been developed to accelerate the computation speed. However, both the normal DAVAR algorithm and the fast algorithm become invalid for discontinuous time series. What is worse, the FOG-based MWD underground often keeps working for several days; the gyro data collected aboveground is not only very time-consuming, but also sometimes discontinuous in the timeline. In this article, on the basis of the fast algorithm for DAVAR, we make a further advance in the fast algorithm (improved fast DAVAR) to extend the fast DAVAR to discontinuous time series. The improved fast DAVAR and the normal DAVAR are used to responsively characterize two sets of simulation data. The simulation results show that when the length of the time series is short, the improved fast DAVAR saves 78.93% of calculation time. When the length of the time series is long ( 6 × 10 5 samples), the improved fast DAVAR reduces calculation time by 97.09%. Another set of simulation data with missing data is characterized by the improved fast DAVAR. Its simulation results prove that the improved fast DAVAR could successfully deal with discontinuous data. In the end, a vibration experiment with FOGs-based MWD has been implemented to validate the good performance of the improved fast DAVAR. The results of the experience testify that the improved fast DAVAR not only shortens computation time, but could also analyze discontinuous time series.

Application of Fast Dynamic Allan Variance for the Characterization of FOGs-Based Measurement While Drilling

Directory of Open Access Journals (Sweden)

Lu Wang

2016-12-01

Full Text Available The stability of a fiber optic gyroscope (FOG in measurement while drilling (MWD could vary with time because of changing temperature, high vibration, and sudden power failure. The dynamic Allan variance (DAVAR is a sliding version of the Allan variance. It is a practical tool that could represent the non-stationary behavior of the gyroscope signal. Since the normal DAVAR takes too long to deal with long time series, a fast DAVAR algorithm has been developed to accelerate the computation speed. However, both the normal DAVAR algorithm and the fast algorithm become invalid for discontinuous time series. What is worse, the FOG-based MWD underground often keeps working for several days; the gyro data collected aboveground is not only very time-consuming, but also sometimes discontinuous in the timeline. In this article, on the basis of the fast algorithm for DAVAR, we make a further advance in the fast algorithm (improved fast DAVAR to extend the fast DAVAR to discontinuous time series. The improved fast DAVAR and the normal DAVAR are used to responsively characterize two sets of simulation data. The simulation results show that when the length of the time series is short, the improved fast DAVAR saves 78.93% of calculation time. When the length of the time series is long ( 6 × 10 5 samples, the improved fast DAVAR reduces calculation time by 97.09%. Another set of simulation data with missing data is characterized by the improved fast DAVAR. Its simulation results prove that the improved fast DAVAR could successfully deal with discontinuous data. In the end, a vibration experiment with FOGs-based MWD has been implemented to validate the good performance of the improved fast DAVAR. The results of the experience testify that the improved fast DAVAR not only shortens computation time, but could also analyze discontinuous time series.

Short-time dynamics of phenylene-rings in bisphenol based engineering thermoplastics

International Nuclear Information System (INIS)

Arrese-Igor, S.; Arbe, A.; Alegria, A.; Colmenero, J.; Frick, B.

2003-01-01

We have recently performed one of the first approaches by means of quasielastic neutron scattering (QENS) to the problem of identifying the molecular motions giving rise to the secondary relaxations of engineering thermoplastics. Preliminary results point to phenylene ring π-flips as the main motion causing the observed quasielastic broadening in the ∼10 -10 -10 -9 s time scale below the glass transition temperature T g . Continuing our study of sub-T g dynamics in these systems by QENS, measurements on polycarbonate (PC) and polysulfone (PSF) with deuterated methyl groups (d6) in the ∼10 -13 -10 -11 s time scale have been performed. The intermediate scattering function shows a smooth second decay in addition to that of vibrations and 'fast dynamics' at T > or approx. 200 K. The extrapolation of phenylene π-flip motion to faster times does not explain the decay observed. However, a non-negligible contribution of π-flips at T≥350 K in PCd6 is noticeable, whereas for PSFd6 some effect can be inferred above ∼450 K. In the temperature region where the π-flips do not contribute to the spectra we have characterised the signal by assuming a temperature dependent distribution of small angle oscillations of phenylene rings leading to an activation energy of 0.18 eV

Some New Inequalities of Opial's Type on Time Scales

Directory of Open Access Journals (Sweden)

Samir H. Saker

2012-01-01

Full Text Available We will prove some new dynamic inequalities of Opial's type on time scales. The results not only extend some results in the literature but also improve some of them. Some continuous and discrete inequalities are derived from the main results as special cases. The results can be applied on the study of distribution of generalized zeros of half-linear dynamic equations on time scales.

Movable shark scales act as a passive dynamic micro-roughness to control flow separation

International Nuclear Information System (INIS)

Lang, Amy W; Bradshaw, Michael T; Smith, Jonathon A; Wheelus, Jennifer N; Motta, Philip J; Habegger, Maria L; Hueter, Robert E

2014-01-01

Shark scales on fast-swimming sharks have been shown to be movable to angles in excess of 50°, and we hypothesize that this characteristic gives this shark skin a preferred flow direction. During the onset of separation, flow reversal is initiated close to the surface. However, the movable scales would be actuated by the reversed flow thereby causing a greater resistance to any further flow reversal and this mechanism would disrupt the process leading to eventual flow separation. Here we report for the first time experimental evidence of the separation control capability of real shark skin through water tunnel testing. Using skin samples from a shortfin mako Isurus oxyrinchus, we tested a pectoral fin and flank skin attached to a NACA 4412 hydrofoil and separation control was observed in the presence of movable shark scales under certain conditions in both cases. We hypothesize that the scales provide a passive, flow-actuated mechanism acting as a dynamic micro-roughness to control flow separation. (paper)

Liquidity crises on different time scales

Science.gov (United States)

Corradi, Francesco; Zaccaria, Andrea; Pietronero, Luciano

2015-12-01

We present an empirical analysis of the microstructure of financial markets and, in particular, of the static and dynamic properties of liquidity. We find that on relatively large time scales (15 min) large price fluctuations are connected to the failure of the subtle mechanism of compensation between the flows of market and limit orders: in other words, the missed revelation of the latent order book breaks the dynamical equilibrium between the flows, triggering the large price jumps. On smaller time scales (30 s), instead, the static depletion of the limit order book is an indicator of an intrinsic fragility of the system, which is related to a strongly nonlinear enhancement of the response. In order to quantify this phenomenon we introduce a measure of the liquidity imbalance present in the book and we show that it is correlated to both the sign and the magnitude of the next price movement. These findings provide a quantitative definition of the effective liquidity, which proves to be strongly dependent on the considered time scales.

Ultra-fast relaxation, decoherence, and localization of photoexcited states in π-conjugated polymers

Science.gov (United States)

Mannouch, Jonathan R.; Barford, William; Al-Assam, Sarah

2018-01-01

The exciton relaxation dynamics of photoexcited electronic states in poly(p-phenylenevinylene) are theoretically investigated within a coarse-grained model, in which both the exciton and nuclear degrees of freedom are treated quantum mechanically. The Frenkel-Holstein Hamiltonian is used to describe the strong exciton-phonon coupling present in the system, while external damping of the internal nuclear degrees of freedom is accounted for by a Lindblad master equation. Numerically, the dynamics are computed using the time evolving block decimation and quantum jump trajectory techniques. The values of the model parameters physically relevant to polymer systems naturally lead to a separation of time scales, with the ultra-fast dynamics corresponding to energy transfer from the exciton to the internal phonon modes (i.e., the C-C bond oscillations), while the longer time dynamics correspond to damping of these phonon modes by the external dissipation. Associated with these time scales, we investigate the following processes that are indicative of the system relaxing onto the emissive chromophores of the polymer: (1) Exciton-polaron formation occurs on an ultra-fast time scale, with the associated exciton-phonon correlations present within half a vibrational time period of the C-C bond oscillations. (2) Exciton decoherence is driven by the decay in the vibrational overlaps associated with exciton-polaron formation, occurring on the same time scale. (3) Exciton density localization is driven by the external dissipation, arising from "wavefunction collapse" occurring as a result of the system-environment interactions. Finally, we show how fluorescence anisotropy measurements can be used to investigate the exciton decoherence process during the relaxation dynamics.

Network Dynamics with BrainX3: A Large-Scale Simulation of the Human Brain Network with Real-Time Interaction

OpenAIRE

Xerxes D. Arsiwalla; Riccardo eZucca; Alberto eBetella; Enrique eMartinez; David eDalmazzo; Pedro eOmedas; Gustavo eDeco; Gustavo eDeco; Paul F.M.J. Verschure; Paul F.M.J. Verschure

2015-01-01

BrainX3 is a large-scale simulation of human brain activity with real-time interaction, rendered in 3D in a virtual reality environment, which combines computational power with human intuition for the exploration and analysis of complex dynamical networks. We ground this simulation on structural connectivity obtained from diffusion spectrum imaging data and model it on neuronal population dynamics. Users can interact with BrainX3 in real-time by perturbing brain regions with transient stimula...

Network dynamics with BrainX3: a large-scale simulation of the human brain network with real-time interaction

OpenAIRE

Arsiwalla, Xerxes D.; Zucca, Riccardo; Betella, Alberto; Martínez, Enrique, 1961-; Dalmazzo, David; Omedas, Pedro; Deco, Gustavo; Verschure, Paul F. M. J.

2015-01-01

BrainX3 is a large-scale simulation of human brain activity with real-time interaction, rendered in 3D in a virtual reality environment, which combines computational power with human intuition for the exploration and analysis of complex dynamical networks. We ground this simulation on structural connectivity obtained from diffusion spectrum imaging data and model it on neuronal population dynamics. Users can interact with BrainX3 in real-time by perturbing brain regions with transient stimula...

Steffensen's Integral Inequality on Time Scales

Directory of Open Access Journals (Sweden)

Ozkan Umut Mutlu

2007-01-01

Full Text Available We establish generalizations of Steffensen's integral inequality on time scales via the diamond- dynamic integral, which is defined as a linear combination of the delta and nabla integrals.

Stochastic partial differential fluid equations as a diffusive limit of deterministic Lagrangian multi-time dynamics.

Science.gov (United States)

Cotter, C J; Gottwald, G A; Holm, D D

2017-09-01

In Holm (Holm 2015 Proc. R. Soc. A 471 , 20140963. (doi:10.1098/rspa.2014.0963)), stochastic fluid equations were derived by employing a variational principle with an assumed stochastic Lagrangian particle dynamics. Here we show that the same stochastic Lagrangian dynamics naturally arises in a multi-scale decomposition of the deterministic Lagrangian flow map into a slow large-scale mean and a rapidly fluctuating small-scale map. We employ homogenization theory to derive effective slow stochastic particle dynamics for the resolved mean part, thereby obtaining stochastic fluid partial equations in the Eulerian formulation. To justify the application of rigorous homogenization theory, we assume mildly chaotic fast small-scale dynamics, as well as a centring condition. The latter requires that the mean of the fluctuating deviations is small, when pulled back to the mean flow.

Use of soil moisture dynamics and patterns at different spatio-temporal scales for the investigation of subsurface flow processes

Directory of Open Access Journals (Sweden)

T. Blume

2009-07-01

Full Text Available Spatial patterns as well as temporal dynamics of soil moisture have a major influence on runoff generation. The investigation of these dynamics and patterns can thus yield valuable information on hydrological processes, especially in data scarce or previously ungauged catchments. The combination of spatially scarce but temporally high resolution soil moisture profiles with episodic and thus temporally scarce moisture profiles at additional locations provides information on spatial as well as temporal patterns of soil moisture at the hillslope transect scale. This approach is better suited to difficult terrain (dense forest, steep slopes than geophysical techniques and at the same time less cost-intensive than a high resolution grid of continuously measuring sensors. Rainfall simulation experiments with dye tracers while continuously monitoring soil moisture response allows for visualization of flow processes in the unsaturated zone at these locations. Data was analyzed at different spacio-temporal scales using various graphical methods, such as space-time colour maps (for the event and plot scale and binary indicator maps (for the long-term and hillslope scale. Annual dynamics of soil moisture and decimeter-scale variability were also investigated. The proposed approach proved to be successful in the investigation of flow processes in the unsaturated zone and showed the importance of preferential flow in the Malalcahuello Catchment, a data-scarce catchment in the Andes of Southern Chile. Fast response times of stream flow indicate that preferential flow observed at the plot scale might also be of importance at the hillslope or catchment scale. Flow patterns were highly variable in space but persistent in time. The most likely explanation for preferential flow in this catchment is a combination of hydrophobicity, small scale heterogeneity in rainfall due to redistribution in the canopy and strong gradients in unsaturated conductivities leading to

Self-excited vibration control for axially fast excited beam by a time delay state feedback

International Nuclear Information System (INIS)

Hamdi, Mustapha; Belhaq, Mohamed

2009-01-01

This work examines the control of self-excited vibration of a simply-supported beam subjected to an axially high-frequency excitation. The investigation of the resonant cases are not considered in this paper. The control is implemented via a corrective position feedback with time delay. The objective of this control is to eliminate the undesirable self-excited vibrations with an appropriate choice of parameters. The issue of stability is also addressed in this paper. Using the technique of direct partition of motion, the dynamic of discretized equations is separated into slow and fast components. The multiple scales method is then performed on the slow dynamic to obtain a slow flow for the amplitude and phase. Analysis of this slow flow provides analytical approximations locating regions in parameters space where undesirable self-excited vibration can be eliminated. A numerical study of these regions is performed on the original discretized system and compared to the analytical prediction showing a good agreement.

Effect of core burnup on the dynamic behavior of fast reactors

International Nuclear Information System (INIS)

Ilberg, D.; Saphier, D.; Yiftah, S.

1977-01-01

Performance of a dynamic analysis, taking burnup changes into account, requires fission-product nuclear data of relatively small uncertainty, suitable burnup calculation models, and dynamic computer programs. These were prepared and used with the following results: (1) Significant changes in static and dynamic parameters were observed when investigating the effect of burnup. These changes were found to be larger than differences introduced by the uncertainty of the fission-product nuclear data. (2) A one-dimensional burnup computer program was prepared. It was found that a burnup model based on the generalized radioactive decay scheme is suitable for accurate fast reactor calculations. (3) Space-time dynamic calculations of fast reactors having different burnup levels were performed. The stability difference between ''clean'' and high burnup cores is greater when local rather than uniform perturbations are inserted along the entire core length. The magnitude by which the ''end-of-life'' core increases the transient excursion over that of the clean core depends on the particular region in which the perturbation is inserted. The end-of-life core will magnify the transient excursion more than the clean core whenever the perturbation is inserted into a region having a higher adjoint flux level than that of the clean core. However, when a reactor safety system operates successfully, the difference in the temperature transient of the clean and end-of-life cores will be relatively small. It is suggested that only the analysis of large local perturbations be performed for end-of-life cores as well as for clean cores in the safety evaluation of fast reactors

Real-Time linux dynamic clamp: a fast and flexible way to construct virtual ion channels in living cells.

Science.gov (United States)

Dorval, A D; Christini, D J; White, J A

2001-10-01

We describe a system for real-time control of biological and other experiments. This device, based around the Real-Time Linux operating system, was tested specifically in the context of dynamic clamping, a demanding real-time task in which a computational system mimics the effects of nonlinear membrane conductances in living cells. The system is fast enough to represent dozens of nonlinear conductances in real time at clock rates well above 10 kHz. Conductances can be represented in deterministic form, or more accurately as discrete collections of stochastically gating ion channels. Tests were performed using a variety of complex models of nonlinear membrane mechanisms in excitable cells, including simulations of spatially extended excitable structures, and multiple interacting cells. Only in extreme cases does the computational load interfere with high-speed "hard" real-time processing (i.e., real-time processing that never falters). Freely available on the worldwide web, this experimental control system combines good performance. immense flexibility, low cost, and reasonable ease of use. It is easily adapted to any task involving real-time control, and excels in particular for applications requiring complex control algorithms that must operate at speeds over 1 kHz.

Instability in time-delayed switched systems induced by fast and random switching

Science.gov (United States)

Guo, Yao; Lin, Wei; Chen, Yuming; Wu, Jianhong

2017-07-01

In this paper, we consider a switched system comprising finitely or infinitely many subsystems described by linear time-delayed differential equations and a rule that orchestrates the system switching randomly among these subsystems, where the switching times are also randomly chosen. We first construct a counterintuitive example where even though all the time-delayed subsystems are exponentially stable, the behaviors of the randomly switched system change from stable dynamics to unstable dynamics with a decrease of the dwell time. Then by using the theories of stochastic processes and delay differential equations, we present a general result on when this fast and random switching induced instability should occur and we extend this to the case of nonlinear time-delayed switched systems as well.

Universal Linear Scaling of Permeability and Time for Heterogeneous Fracture Dissolution

Science.gov (United States)

Wang, L.; Cardenas, M. B.

2017-12-01

Fractures are dynamically changing over geological time scale due to mechanical deformation and chemical reactions. However, the latter mechanism remains poorly understood with respect to the expanding fracture, which leads to a positively coupled flow and reactive transport processes, i.e., as a fracture expands, so does its permeability (k) and thus flow and reactive transport processes. To unravel this coupling, we consider a self-enhancing process that leads to fracture expansion caused by acidic fluid, i.e., CO2-saturated brine dissolving calcite fracture. We rigorously derive a theory, for the first time, showing that fracture permeability increases linearly with time [Wang and Cardenas, 2017]. To validate this theory, we resort to the direct simulation that solves the Navier-Stokes and Advection-Diffusion equations with a moving mesh according to the dynamic dissolution process in two-dimensional (2D) fractures. We find that k slowly increases first until the dissolution front breakthrough the outbound when we observe a rapid k increase, i.e., the linear time-dependence of k occurs. The theory agrees well with numerical observations across a broad range of Peclet and Damkohler numbers through homogeneous and heterogeneous 2D fractures. Moreover, the theory of linear scaling relationship between k and time matches well with experimental observations of three-dimensional (3D) fractures' dissolution. To further attest to our theory's universality for 3D heterogeneous fractures across a broad range of roughness and correlation length of aperture field, we develop a depth-averaged model that simulates the process-based reactive transport. The simulation results show that, regardless of a wide variety of dissolution patterns such as the presence of dissolution fingers and preferential dissolution paths, the linear scaling relationship between k and time holds. Our theory sheds light on predicting permeability evolution in many geological settings when the self

Slow speed—fast motion: time-lapse recordings in physics education

Science.gov (United States)

Vollmer, Michael; Möllmann, Klaus-Peter

2018-05-01

Video analysis with a 30 Hz frame rate is the standard tool in physics education. The development of affordable high-speed-cameras has extended the capabilities of the tool for much smaller time scales to the 1 ms range, using frame rates of typically up to 1000 frames s-1, allowing us to study transient physics phenomena happening too fast for the naked eye. Here we want to extend the range of phenomena which may be studied by video analysis in the opposite direction by focusing on much longer time scales ranging from minutes, hours to many days or even months. We discuss this time-lapse method, needed equipment and give a few hints of how to produce respective recordings for two specific experiments.

Time Scale in Least Square Method

Directory of Open Access Journals (Sweden)

Özgür Yeniay

2014-01-01

Full Text Available Study of dynamic equations in time scale is a new area in mathematics. Time scale tries to build a bridge between real numbers and integers. Two derivatives in time scale have been introduced and called as delta and nabla derivative. Delta derivative concept is defined as forward direction, and nabla derivative concept is defined as backward direction. Within the scope of this study, we consider the method of obtaining parameters of regression equation of integer values through time scale. Therefore, we implemented least squares method according to derivative definition of time scale and obtained coefficients related to the model. Here, there exist two coefficients originating from forward and backward jump operators relevant to the same model, which are different from each other. Occurrence of such a situation is equal to total number of values of vertical deviation between regression equations and observation values of forward and backward jump operators divided by two. We also estimated coefficients for the model using ordinary least squares method. As a result, we made an introduction to least squares method on time scale. We think that time scale theory would be a new vision in least square especially when assumptions of linear regression are violated.

Multiple dynamical time-scales in networks with hierarchically

Indian Academy of Sciences (India)

Modular networks; hierarchical organization; synchronization. ... we show that such a topological structure gives rise to characteristic time-scale separation ... This suggests a possible functional role of such mesoscopic organization principle in ...

Quasi-potential and Two-Scale Large Deviation Theory for Gillespie Dynamics

KAUST Repository

Li, Tiejun

2016-01-07

The construction of energy landscape for bio-dynamics is attracting more and more attention recent years. In this talk, I will introduce the strategy to construct the landscape from the connection to rare events, which relies on the large deviation theory for Gillespie-type jump dynamics. In the application to a typical genetic switching model, the two-scale large deviation theory is developed to take into account the fast switching of DNA states. The comparison with other proposals are also discussed. We demonstrate different diffusive limits arise when considering different regimes for genetic translation and switching processes.

Dynamic response of materials on subnanosecond time scales, and beryllium properties for inertial confinement fusion

International Nuclear Information System (INIS)

Swift, Damian C.; Tierney, Thomas E.; Luo Shengnian; Paisley, Dennis L.; Kyrala, George A.; Hauer, Allan; Greenfield, Scott R.; Koskelo, Aaron C.; McClellan, Kenneth J.; Lorenzana, Hector E.; Kalantar, Daniel; Remington, Bruce A.; Peralta, Pedro; Loomis, Eric

2005-01-01

During the past few years, substantial progress has been made in developing experimental techniques capable of investigating the response of materials to dynamic loading on nanosecond time scales and shorter, with multiple diagnostics probing different aspects of the behavior. These relatively short time scales are scientifically interesting because plastic flow and phase changes in common materials with simple crystal structures--such as iron--may be suppressed, allowing unusual states to be induced and the dynamics of plasticity and polymorphism to be explored. Loading by laser-induced ablation can be particularly convenient: this technique has been used to impart shocks and isentropic compression waves from ∼1 to 200 GPa in a range of elements and alloys, with diagnostics including line imaging surface velocimetry, surface displacement (framed area imaging), x-ray diffraction (single crystal and polycrystal), ellipsometry, and Raman spectroscopy. A major motivation has been the study of the properties of beryllium under conditions relevant to the fuel capsule in inertial confinement fusion: magnetically driven shock and isentropic compression shots at Z were used to investigate the equation of state and shock melting characteristics, complemented by laser ablation experiments to investigate plasticity and heterogeneous response from the polycrystalline microstructure. These results will help to constrain acceptable tolerances on manufacturing, and possible loading paths, for inertial fusion ignition experiments at the National Ignition Facility. Laser-based techniques are being developed further for future material dynamics experiments, where it should be possible to obtain high quality data on strength and phase changes up to at least 1 TPa

A critical oscillation constant as a variable of time scales for half-linear dynamic equations

Czech Academy of Sciences Publication Activity Database

Řehák, Pavel

2010-01-01

Roč. 60, č. 2 (2010), s. 237-256 ISSN 0139-9918 R&D Projects: GA AV ČR KJB100190701 Institutional research plan: CEZ:AV0Z10190503 Keywords : dynamic equation * time scale * half-linear equation * (non)oscillation criteria * Hille-Nehari criteria * Kneser criteria * critical constant * oscillation constant * Hardy inequality Subject RIV: BA - General Mathematics Impact factor: 0.316, year: 2010 http://link.springer.com/article/10.2478%2Fs12175-010-0009-7

Computational challenges of large-scale, long-time, first-principles molecular dynamics

International Nuclear Information System (INIS)

Kent, P R C

2008-01-01

Plane wave density functional calculations have traditionally been able to use the largest available supercomputing resources. We analyze the scalability of modern projector-augmented wave implementations to identify the challenges in performing molecular dynamics calculations of large systems containing many thousands of electrons. Benchmark calculations on the Cray XT4 demonstrate that global linear-algebra operations are the primary reason for limited parallel scalability. Plane-wave related operations can be made sufficiently scalable. Improving parallel linear-algebra performance is an essential step to reaching longer timescales in future large-scale molecular dynamics calculations

In-situ materials characterization across spatial and temporal scales

CERN Document Server

Graafsma, Heinz; Zhang, Xiao; Frenken, Joost

2014-01-01

The behavior of nanoscale materials can change rapidly with time either because the environment changes rapidly, or because the influence of the environment propagates quickly across the intrinsically small dimensions of nanoscale materials. Extremely fast time resolution studies using X-rays, electrons and neutrons are of very high interest to many researchers and is a fast-evolving and interesting field for the study of dynamic processes. Therefore, in situ structural characterization and measurements of structure-property relationships covering several decades of length and time scales (from atoms to millimeters and femtoseconds to hours) with high spatial and temporal resolutions are crucially important to understand the synthesis and behavior of multidimensional materials. The techniques described in this book will permit access to the real-time dynamics of materials, surface processes, and chemical and biological reactions at various time scales. This book provides an interdisciplinary reference for res...

Thermodynamics, maximum power, and the dynamics of preferential river flow structures at the continental scale

Directory of Open Access Journals (Sweden)

A. Kleidon

2013-01-01

Full Text Available The organization of drainage basins shows some reproducible phenomena, as exemplified by self-similar fractal river network structures and typical scaling laws, and these have been related to energetic optimization principles, such as minimization of stream power, minimum energy expenditure or maximum "access". Here we describe the organization and dynamics of drainage systems using thermodynamics, focusing on the generation, dissipation and transfer of free energy associated with river flow and sediment transport. We argue that the organization of drainage basins reflects the fundamental tendency of natural systems to deplete driving gradients as fast as possible through the maximization of free energy generation, thereby accelerating the dynamics of the system. This effectively results in the maximization of sediment export to deplete topographic gradients as fast as possible and potentially involves large-scale feedbacks to continental uplift. We illustrate this thermodynamic description with a set of three highly simplified models related to water and sediment flow and describe the mechanisms and feedbacks involved in the evolution and dynamics of the associated structures. We close by discussing how this thermodynamic perspective is consistent with previous approaches and the implications that such a thermodynamic description has for the understanding and prediction of sub-grid scale organization of drainage systems and preferential flow structures in general.

Hybrid parallel strategy for the simulation of fast transient accidental situations at reactor scale

International Nuclear Information System (INIS)

Faucher, V.; Galon, P.; Beccantini, A.; Crouzet, F.; Debaud, F.; Gautier, T.

2013-01-01

This contribution is dedicated to the latest methodological developments implemented in the fast transient dynamics software EUROPLEXUS (EPX) to simulate the mechanical response of fully coupled fluid-structure systems to accidental situations to be considered at reactor scale, among which the Loss of Coolant Accident, the Core Disruptive Accident and the Hydrogen Explosion. Time integration is explicit and the search for reference solutions within the safety framework prevents any simplification and approximations in the coupled algorithm: for instance, all kinematic constraints are dealt with using Lagrange Multipliers, yielding a complex flow chart when non-permanent constraints such as unilateral contact or immersed fluid-structure boundaries are considered. The parallel acceleration of the solution process is then achieved through a hybrid approach, based on a weighted domain decomposition for distributed memory computing and the use of the KAAPI library for self-balanced shared memory processing inside sub-domains. (authors)

A Lagrangian dynamic subgrid-scale model turbulence

Science.gov (United States)

Meneveau, C.; Lund, T. S.; Cabot, W.

1994-01-01

A new formulation of the dynamic subgrid-scale model is tested in which the error associated with the Germano identity is minimized over flow pathlines rather than over directions of statistical homogeneity. This procedure allows the application of the dynamic model with averaging to flows in complex geometries that do not possess homogeneous directions. The characteristic Lagrangian time scale over which the averaging is performed is chosen such that the model is purely dissipative, guaranteeing numerical stability when coupled with the Smagorinsky model. The formulation is tested successfully in forced and decaying isotropic turbulence and in fully developed and transitional channel flow. In homogeneous flows, the results are similar to those of the volume-averaged dynamic model, while in channel flow, the predictions are superior to those of the plane-averaged dynamic model. The relationship between the averaged terms in the model and vortical structures (worms) that appear in the LES is investigated. Computational overhead is kept small (about 10 percent above the CPU requirements of the volume or plane-averaged dynamic model) by using an approximate scheme to advance the Lagrangian tracking through first-order Euler time integration and linear interpolation in space.

Dynamically Scaled Model Experiment of a Mooring Cable

Directory of Open Access Journals (Sweden)

Lars Bergdahl

2016-01-01

Full Text Available The dynamic response of mooring cables for marine structures is scale-dependent, and perfect dynamic similitude between full-scale prototypes and small-scale physical model tests is difficult to achieve. The best possible scaling is here sought by means of a specific set of dimensionless parameters, and the model accuracy is also evaluated by two alternative sets of dimensionless parameters. A special feature of the presented experiment is that a chain was scaled to have correct propagation celerity for longitudinal elastic waves, thus providing perfect geometrical and dynamic scaling in vacuum, which is unique. The scaling error due to incorrect Reynolds number seemed to be of minor importance. The 33 m experimental chain could then be considered a scaled 76 mm stud chain with the length 1240 m, i.e., at the length scale of 1:37.6. Due to the correct elastic scale, the physical model was able to reproduce the effect of snatch loads giving rise to tensional shock waves propagating along the cable. The results from the experiment were used to validate the newly developed cable-dynamics code, MooDy, which utilises a discontinuous Galerkin FEM formulation. The validation of MooDy proved to be successful for the presented experiments. The experimental data is made available here for validation of other numerical codes by publishing digitised time series of two of the experiments.

Double dynamic scaling in human communication dynamics

Science.gov (United States)

Wang, Shengfeng; Feng, Xin; Wu, Ye; Xiao, Jinhua

2017-05-01

In the last decades, human behavior has been deeply understanding owing to the huge quantities data of human behavior available for study. The main finding in human dynamics shows that temporal processes consist of high-activity bursty intervals alternating with long low-activity periods. A model, assuming the initiator of bursty follow a Poisson process, is widely used in the modeling of human behavior. Here, we provide further evidence for the hypothesis that different bursty intervals are independent. Furthermore, we introduce a special threshold to quantitatively distinguish the time scales of complex dynamics based on the hypothesis. Our results suggest that human communication behavior is a composite process of double dynamics with midrange memory length. The method for calculating memory length would enhance the performance of many sequence-dependent systems, such as server operation and topic identification.

Dynamic scaling in natural swarms

Science.gov (United States)

Cavagna, Andrea; Conti, Daniele; Creato, Chiara; Del Castello, Lorenzo; Giardina, Irene; Grigera, Tomas S.; Melillo, Stefania; Parisi, Leonardo; Viale, Massimiliano

2017-09-01

Collective behaviour in biological systems presents theoretical challenges beyond the borders of classical statistical physics. The lack of concepts such as scaling and renormalization is particularly problematic, as it forces us to negotiate details whose relevance is often hard to assess. In an attempt to improve this situation, we present here experimental evidence of the emergence of dynamic scaling laws in natural swarms of midges. We find that spatio-temporal correlation functions in different swarms can be rescaled by using a single characteristic time, which grows with the correlation length with a dynamical critical exponent z ~ 1, a value not found in any other standard statistical model. To check whether out-of-equilibrium effects may be responsible for this anomalous exponent, we run simulations of the simplest model of self-propelled particles and find z ~ 2, suggesting that natural swarms belong to a novel dynamic universality class. This conclusion is strengthened by experimental evidence of the presence of non-dissipative modes in the relaxation, indicating that previously overlooked inertial effects are needed to describe swarm dynamics. The absence of a purely dissipative regime suggests that natural swarms undergo a near-critical censorship of hydrodynamics.

Simulating Biomass Fast Pyrolysis at the Single Particle Scale

Energy Technology Data Exchange (ETDEWEB)

Ciesielski, Peter [National Renewable Energy Laboratory (NREL); Wiggins, Gavin [ORNL; Daw, C Stuart [ORNL; Jakes, Joseph E. [U.S. Forest Service, Forest Products Laboratory, Madison, Wisconsin, USA

2017-07-01

Simulating fast pyrolysis at the scale of single particles allows for the investigation of the impacts of feedstock-specific parameters such as particle size, shape, and species of origin. For this reason particle-scale modeling has emerged as an important tool for understanding how variations in feedstock properties affect the outcomes of pyrolysis processes. The origins of feedstock properties are largely dictated by the composition and hierarchical structure of biomass, from the microstructural porosity to the external morphology of milled particles. These properties may be accounted for in simulations of fast pyrolysis by several different computational approaches depending on the level of structural and chemical complexity included in the model. The predictive utility of particle-scale simulations of fast pyrolysis can still be enhanced substantially by advancements in several areas. Most notably, considerable progress would be facilitated by the development of pyrolysis kinetic schemes that are decoupled from transport phenomena, predict product evolution from whole-biomass with increased chemical speciation, and are still tractable with present-day computational resources.

Exploiting Fast-Variables to Understand Population Dynamics and Evolution

Science.gov (United States)

Constable, George W. A.; McKane, Alan J.

2017-11-01

We describe a continuous-time modelling framework for biological population dynamics that accounts for demographic noise. In the spirit of the methodology used by statistical physicists, transitions between the states of the system are caused by individual events while the dynamics are described in terms of the time-evolution of a probability density function. In general, the application of the diffusion approximation still leaves a description that is quite complex. However, in many biological applications one or more of the processes happen slowly relative to the system's other processes, and the dynamics can be approximated as occurring within a slow low-dimensional subspace. We review these time-scale separation arguments and analyse the more simple stochastic dynamics that result in a number of cases. We stress that it is important to retain the demographic noise derived in this way, and emphasise this point by showing that it can alter the direction of selection compared to the prediction made from an analysis of the corresponding deterministic model.

Fast wave current drive in reactor scale tokamaks

International Nuclear Information System (INIS)

Moreau, D.

1992-01-01

The IAEA Technical Committee Meeting on Fast Wave Current Drive in Reactor Scale Tokamaks, hosted by the Commissariat a l'Energie Atomique (CEA), Departement de Recherches sur la Fusion Controlee (Centres d'Etudes de Cadarache, under the Euratom-CEA Association for fusion) aimed at discussing the physics and the efficiency of non-inductive current drive by fast waves. Relevance to reactor size tokamaks and comparison between theory and experiment were emphasized. The following topics are described in the summary report: (i) theory and modelling of radiofrequency current drive (theory, full wave modelling, ray tracing and Fokker-Planck calculations, helicity injection and ponderomotive effects, and alternative radio-frequency current drive effects), (ii) present experiments, (iii) reactor applications (reactor scenarios including fast wave current drive; and fast wave current drive antennas); (iv) discussion and summary. 32 refs

Intermediate length scale dynamics of polyisobutylene

International Nuclear Information System (INIS)

Farago, B.; Arbe, A.; Colmenero, J.; Faust, R.; Buchenau, U.; Richter, D.

2002-01-01

We report on a neutron spin echo investigation of the intermediate scale dynamics of polyisobutylene studying both the self-motion and the collective motion. The momentum transfer (Q) dependences of the self-correlation times are found to follow a Q -2/β law in agreement with the picture of Gaussian dynamics. In the full Q range of observation, their temperature dependence is weaker than the rheological shift factor. The same is true for the stress relaxation time as seen in sound wave absorption. The collective times show both temperature dependences; at the structure factor peak, they follow the temperature dependence of the viscosity, but below the peak, one finds the stress relaxation behavior

Fast reactor safety and computational thermo-fluid dynamics approaches

International Nuclear Information System (INIS)

Ninokata, Hisashi; Shimizu, Takeshi

1993-01-01

This article provides a brief description of the safety principle on which liquid metal cooled fast breeder reactors (LMFBRs) is based and the roles of computations in the safety practices. A number of thermohydraulics models have been developed to date that successfully describe several of the important types of fluids and materials motion encountered in the analysis of postulated accidents in LMFBRs. Most of these models use a mixture of implicit and explicit numerical solution techniques in solving a set of conservation equations formulated in Eulerian coordinates, with special techniques included to specific situations. Typical computational thermo-fluid dynamics approaches are discussed in particular areas of analyses of the physical phenomena relevant to the fuel subassembly thermohydraulics design and that involve describing the motion of molten materials in the core over a large scale. (orig.)

Nano-scale measurement of sub-micrometer MEMS in-plane dynamics using synchronized illumination

International Nuclear Information System (INIS)

Warnat, S; Forbrigger, C; Kujath, M; Hubbard, T

2015-01-01

A method for measuring the sub-micrometer in-plane dynamics of MEMS devices with nano-scale precision using a CCD camera and synchronized pulsating illumination is presented. Typical MEMS actuators have fast responses (generally in the 1–200 kHz range), much faster than typical cameras which record a time averaged motion. Under constant illumination the average displacement is steady state and independent of dynamic amplitude or phase. Methods such as strobe illumination use short light pulses to freeze the motion. This paper develops the use of longer pulses of illumination that do not freeze the image, but make the average displacement depend on dynamic amplitude and phase; thus allowing both properties to be extracted. The expected signal is derived as a function of light pulse width and delay, and short versus longer pulses are compared. Measurements using a conventional microscope with replacement of the lamp with LEDs confirmed the derived equations. The system was used to measure sub-micrometer motion of MEMS actuators with ∼5 nm precision. The time constant of a thermal actuator was measured and found to be 48 µs. A resonant peak of a MEMS device was measured at 123.30 kHz with an amplitude of 238 nm. (paper)

Multiscale functions, scale dynamics, and applications to partial differential equations

Science.gov (United States)

Cresson, Jacky; Pierret, Frédéric

2016-05-01

Modeling phenomena from experimental data always begins with a choice of hypothesis on the observed dynamics such as determinism, randomness, and differentiability. Depending on these choices, different behaviors can be observed. The natural question associated to the modeling problem is the following: "With a finite set of data concerning a phenomenon, can we recover its underlying nature? From this problem, we introduce in this paper the definition of multi-scale functions, scale calculus, and scale dynamics based on the time scale calculus [see Bohner, M. and Peterson, A., Dynamic Equations on Time Scales: An Introduction with Applications (Springer Science & Business Media, 2001)] which is used to introduce the notion of scale equations. These definitions will be illustrated on the multi-scale Okamoto's functions. Scale equations are analysed using scale regimes and the notion of asymptotic model for a scale equation under a particular scale regime. The introduced formalism explains why a single scale equation can produce distinct continuous models even if the equation is scale invariant. Typical examples of such equations are given by the scale Euler-Lagrange equation. We illustrate our results using the scale Newton's equation which gives rise to a non-linear diffusion equation or a non-linear Schrödinger equation as asymptotic continuous models depending on the particular fractional scale regime which is considered.

Dynamic analysis of fast-acting solenoid valves using finite element method

International Nuclear Information System (INIS)

Kwon, Ki Tae; Han, Hwa Taik

2001-01-01

It is intended to develop an algorithm for dynamic simulation of fast-acting solenoid valves. The coupled equations of the electric, magnetic, and mechanical systems should be solved simultaneously in a transient nonlinear manner. The transient nonlinear electromagnetic field is analyzed by the Finite Element Method (FEM), which is coupled with nonlinear electronic circuitry. The dynamic movement of the solenoid valve is analyzed at every time step from the force balances acting on the plunger, which include the electromagnetic force calculated from the finite element analysis as well as the elastic force by a spring and the hydrodynamic pressure force along the flow passage. Dynamic responses of the solenoid valves predicted by this algorithm agree well the experimental results including bouncing effects

Photoluminescence decay dynamics in γ-Ga2O3 nanocrystals: The role of exclusion distance at short time scales

Science.gov (United States)

Fernandes, Brian; Hegde, Manu; Stanish, Paul C.; Mišković, Zoran L.; Radovanovic, Pavle V.

2017-09-01

We developed a comprehensive theoretical model describing the photoluminescence decay dynamics at short and long time scales based on the donor-acceptor defect interactions in γ-Ga2O3 nanocrystals, and quantitatively determined the importance of exclusion distance and spatial distribution of defects. We allowed for donors and acceptors to be adjacent to each other or separated by different exclusion distances. The optimal exclusion distance was found to be comparable to the donor Bohr radius and have a strong effect on the photoluminescence decay curve at short times. The importance of the exclusion distance at short time scales was confirmed by Monte Carlo simulations.

Super-transient scaling in time-delay autonomous Boolean network motifs

Energy Technology Data Exchange (ETDEWEB)

D' Huys, Otti, E-mail: otti.dhuys@phy.duke.edu; Haynes, Nicholas D. [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Lohmann, Johannes [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Gauthier, Daniel J. [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

2016-09-15

Autonomous Boolean networks are commonly used to model the dynamics of gene regulatory networks and allow for the prediction of stable dynamical attractors. However, most models do not account for time delays along the network links and noise, which are crucial features of real biological systems. Concentrating on two paradigmatic motifs, the toggle switch and the repressilator, we develop an experimental testbed that explicitly includes both inter-node time delays and noise using digital logic elements on field-programmable gate arrays. We observe transients that last millions to billions of characteristic time scales and scale exponentially with the amount of time delays between nodes, a phenomenon known as super-transient scaling. We develop a hybrid model that includes time delays along network links and allows for stochastic variation in the delays. Using this model, we explain the observed super-transient scaling of both motifs and recreate the experimentally measured transient distributions.

Scaling symmetry, renormalization, and time series modeling: the case of financial assets dynamics.

Science.gov (United States)

Zamparo, Marco; Baldovin, Fulvio; Caraglio, Michele; Stella, Attilio L

2013-12-01

We present and discuss a stochastic model of financial assets dynamics based on the idea of an inverse renormalization group strategy. With this strategy we construct the multivariate distributions of elementary returns based on the scaling with time of the probability density of their aggregates. In its simplest version the model is the product of an endogenous autoregressive component and a random rescaling factor designed to embody also exogenous influences. Mathematical properties like increments' stationarity and ergodicity can be proven. Thanks to the relatively low number of parameters, model calibration can be conveniently based on a method of moments, as exemplified in the case of historical data of the S&P500 index. The calibrated model accounts very well for many stylized facts, like volatility clustering, power-law decay of the volatility autocorrelation function, and multiscaling with time of the aggregated return distribution. In agreement with empirical evidence in finance, the dynamics is not invariant under time reversal, and, with suitable generalizations, skewness of the return distribution and leverage effects can be included. The analytical tractability of the model opens interesting perspectives for applications, for instance, in terms of obtaining closed formulas for derivative pricing. Further important features are the possibility of making contact, in certain limits, with autoregressive models widely used in finance and the possibility of partially resolving the long- and short-memory components of the volatility, with consistent results when applied to historical series.

Scaling symmetry, renormalization, and time series modeling: The case of financial assets dynamics

Science.gov (United States)

Zamparo, Marco; Baldovin, Fulvio; Caraglio, Michele; Stella, Attilio L.

2013-12-01

We present and discuss a stochastic model of financial assets dynamics based on the idea of an inverse renormalization group strategy. With this strategy we construct the multivariate distributions of elementary returns based on the scaling with time of the probability density of their aggregates. In its simplest version the model is the product of an endogenous autoregressive component and a random rescaling factor designed to embody also exogenous influences. Mathematical properties like increments’ stationarity and ergodicity can be proven. Thanks to the relatively low number of parameters, model calibration can be conveniently based on a method of moments, as exemplified in the case of historical data of the S&P500 index. The calibrated model accounts very well for many stylized facts, like volatility clustering, power-law decay of the volatility autocorrelation function, and multiscaling with time of the aggregated return distribution. In agreement with empirical evidence in finance, the dynamics is not invariant under time reversal, and, with suitable generalizations, skewness of the return distribution and leverage effects can be included. The analytical tractability of the model opens interesting perspectives for applications, for instance, in terms of obtaining closed formulas for derivative pricing. Further important features are the possibility of making contact, in certain limits, with autoregressive models widely used in finance and the possibility of partially resolving the long- and short-memory components of the volatility, with consistent results when applied to historical series.

The generalized centroid difference method for picosecond sensitive determination of lifetimes of nuclear excited states using large fast-timing arrays

Energy Technology Data Exchange (ETDEWEB)

Régis, J.-M., E-mail: regis@ikp.uni-koeln.de [Institut für Kernphysik der Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany); Mach, H. [Departamento de Física Atómica y Nuclear, Universidad Complutense, 28040 Madrid (Spain); Simpson, G.S. [Laboratoire de Physique Subatomique et de Cosmologie Grenoble, 53, rue des Martyrs, 38026 Grenoble Cedex (France); Jolie, J.; Pascovici, G.; Saed-Samii, N.; Warr, N. [Institut für Kernphysik der Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany); Bruce, A. [School of Computing, Engineering and Mathematics, University of Brighton, Lewes Road, Brighton BN2 4GJ (United Kingdom); Degenkolb, J. [Institut für Kernphysik der Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany); Fraile, L.M. [Departamento de Física Atómica y Nuclear, Universidad Complutense, 28040 Madrid (Spain); Fransen, C. [Institut für Kernphysik der Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany); Ghita, D.G. [Horia Hulubei National Institute for Physics and Nuclear Engineering, 77125 Bucharest (Romania); and others

2013-10-21

A novel method for direct electronic “fast-timing” lifetime measurements of nuclear excited states via γ–γ coincidences using an array equipped with N∈N equally shaped very fast high-resolution LaBr{sub 3}(Ce) scintillator detectors is presented. Analogous to the mirror symmetric centroid difference method, the generalized centroid difference method provides two independent “start” and “stop” time spectra obtained by a superposition of the N(N−1)γ–γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ–γ cascade. Provided that the energy response and the electronic time pick-off of the detectors are almost equal, a mean prompt response difference between start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing arrays mean γ–γ time-walk characteristics can be determined for 40keVdynamic range is mainly determined by the statistics. The setup of an N=4 detector fast-timing array delivered an absolute time resolving power of 3 ps for 10 000 γ–γ events per total fast timing array start and stop time spectrum. The new method is tested over the total dynamic range by the measurements of known picosecond lifetimes in standard γ-ray sources.

Rotation invariant fast features for large-scale recognition

Science.gov (United States)

Takacs, Gabriel; Chandrasekhar, Vijay; Tsai, Sam; Chen, David; Grzeszczuk, Radek; Girod, Bernd

2012-10-01

We present an end-to-end feature description pipeline which uses a novel interest point detector and Rotation- Invariant Fast Feature (RIFF) descriptors. The proposed RIFF algorithm is 15× faster than SURF1 while producing large-scale retrieval results that are comparable to SIFT.2 Such high-speed features benefit a range of applications from Mobile Augmented Reality (MAR) to web-scale image retrieval and analysis.

Interactive exploration of large-scale time-varying data using dynamic tracking graphs

KAUST Repository

Widanagamaachchi, W.

2012-10-01

Exploring and analyzing the temporal evolution of features in large-scale time-varying datasets is a common problem in many areas of science and engineering. One natural representation of such data is tracking graphs, i.e., constrained graph layouts that use one spatial dimension to indicate time and show the "tracks" of each feature as it evolves, merges or disappears. However, for practical data sets creating the corresponding optimal graph layouts that minimize the number of intersections can take hours to compute with existing techniques. Furthermore, the resulting graphs are often unmanageably large and complex even with an ideal layout. Finally, due to the cost of the layout, changing the feature definition, e.g. by changing an iso-value, or analyzing properly adjusted sub-graphs is infeasible. To address these challenges, this paper presents a new framework that couples hierarchical feature definitions with progressive graph layout algorithms to provide an interactive exploration of dynamically constructed tracking graphs. Our system enables users to change feature definitions on-the-fly and filter features using arbitrary attributes while providing an interactive view of the resulting tracking graphs. Furthermore, the graph display is integrated into a linked view system that provides a traditional 3D view of the current set of features and allows a cross-linked selection to enable a fully flexible spatio-temporal exploration of data. We demonstrate the utility of our approach with several large-scale scientific simulations from combustion science. © 2012 IEEE.

Real-time high dynamic range laser scanning microscopy

Science.gov (United States)

Vinegoni, C.; Leon Swisher, C.; Fumene Feruglio, P.; Giedt, R. J.; Rousso, D. L.; Stapleton, S.; Weissleder, R.

2016-04-01

In conventional confocal/multiphoton fluorescence microscopy, images are typically acquired under ideal settings and after extensive optimization of parameters for a given structure or feature, often resulting in information loss from other image attributes. To overcome the problem of selective data display, we developed a new method that extends the imaging dynamic range in optical microscopy and improves the signal-to-noise ratio. Here we demonstrate how real-time and sequential high dynamic range microscopy facilitates automated three-dimensional neural segmentation. We address reconstruction and segmentation performance on samples with different size, anatomy and complexity. Finally, in vivo real-time high dynamic range imaging is also demonstrated, making the technique particularly relevant for longitudinal imaging in the presence of physiological motion and/or for quantification of in vivo fast tracer kinetics during functional imaging.

Scale-dependent intrinsic entropies of complex time series.

Science.gov (United States)

Yeh, Jia-Rong; Peng, Chung-Kang; Huang, Norden E

2016-04-13

Multi-scale entropy (MSE) was developed as a measure of complexity for complex time series, and it has been applied widely in recent years. The MSE algorithm is based on the assumption that biological systems possess the ability to adapt and function in an ever-changing environment, and these systems need to operate across multiple temporal and spatial scales, such that their complexity is also multi-scale and hierarchical. Here, we present a systematic approach to apply the empirical mode decomposition algorithm, which can detrend time series on various time scales, prior to analysing a signal's complexity by measuring the irregularity of its dynamics on multiple time scales. Simulated time series of fractal Gaussian noise and human heartbeat time series were used to study the performance of this new approach. We show that our method can successfully quantify the fractal properties of the simulated time series and can accurately distinguish modulations in human heartbeat time series in health and disease. © 2016 The Author(s).

Current scaling of axially radiated power in dynamic hohlraums and dynamic hohlraum load design for ZR

International Nuclear Information System (INIS)

Mock, Raymond Cecil; Nash, Thomas J.; Sanford, Thomas W. L.

2007-01-01

We present designs for dynamic hohlraum z-pinch loads on the 28 MA, 140 ns driver ZR. The scaling of axially radiated power with current in dynamic hohlraums is reviewed. With adequate stability on ZR this scaling indicates that 30 TW of axially radiated power should be possible. The performance of the dynamic hohlraum load on the 20 MA, 100 ns driver Z is extensively reviewed. The baseline z-pinch load on Z is a nested tungsten wire array imploding onto on-axis foam. Data from a variety of x-ray diagnostics fielded on Z are presented. These diagnostics include x-ray diodes, bolometers, fast x-ray imaging cameras, and crystal spectrometers. Analysis of these data indicates that the peak dynamic radiation temperature on Z is between 250 and 300 eV from a diameter less than 1 mm. Radiation from the dynamic hohlraum itself or from a radiatively driven pellet within the dynamic hohlraum has been used to probe a variety of matter associated with the dynamic hohlraum: the tungsten z-pinch itself, tungsten sliding across the end-on apertures, a titanium foil over the end aperture, and a silicon aerogel end cap. Data showing the existence of asymmetry in radiation emanating from the two ends of the dynamic hohlraum is presented, along with data showing load configurations that mitigate this asymmetry. 1D simulations of the dynamic hohlraum implosion are presented and compared to experimental data. The simulations provide insight into the dynamic hohlraum behavior but are not necessarily a reliable design tool because of the inherently 3D behavior of the imploding nested tungsten wire arrays

Computational Fluid Dynamics Study on the Effects of RATO Timing on the Scale Model Acoustic Test

Science.gov (United States)

Nielsen, Tanner; Williams, B.; West, Jeff

2015-01-01

The Scale Model Acoustic Test (SMAT) is a 5% scale test of the Space Launch System (SLS), which is currently being designed at Marshall Space Flight Center (MSFC). The purpose of this test is to characterize and understand a variety of acoustic phenomena that occur during the early portions of lift off, one being the overpressure environment that develops shortly after booster ignition. The SLS lift off configuration consists of four RS-25 liquid thrusters on the core stage, with two solid boosters connected to each side. Past experience with scale model testing at MSFC (in ER42), has shown that there is a delay in the ignition of the Rocket Assisted Take Off (RATO) motor, which is used as the 5% scale analog of the solid boosters, after the signal to ignite is given. This delay can range from 0 to 16.5ms. While this small of a delay maybe insignificant in the case of the full scale SLS, it can significantly alter the data obtained during the SMAT due to the much smaller geometry. The speed of sound of the air and combustion gas constituents is not scaled, and therefore the SMAT pressure waves propagate at approximately the same speed as occurs during full scale. However, the SMAT geometry is much smaller allowing the pressure waves to move down the exhaust duct, through the trench, and impact the vehicle model much faster than occurs at full scale. To better understand the effect of the RATO timing simultaneity on the SMAT IOP test data, a computational fluid dynamics (CFD) analysis was performed using the Loci/CHEM CFD software program. Five different timing offsets, based on RATO ignition delay statistics, were simulated. A variety of results and comparisons will be given, assessing the overall effect of RATO timing simultaneity on the SMAT overpressure environment.

A Fast Dynamic 64-bit Comparator with Small Transistor Count

Directory of Open Access Journals (Sweden)

Chua-Chin Wang

2002-01-01

Full Text Available In this paper, we propose a 64-bit fast dynamic CMOS comparator with small transistor count. Major features of the proposed comparator are the rearrangement and re-ordering of transistors in the evaluation block of a dynamic cell, and the insertion of a weak n feedback inverter, which helps the pull-down operation to ground. The simulation results given by pre-layout tools, e.g. HSPICE, and post-layout tools, e.g. TimeMill, reveal that the delay is around 2.5 ns while the operating clock rate reaches 100 MHz. A physical chip is fabricated to verify the correctness of our design by using UMC (United Microelectronics Company 0.5 μm (2P2M technology.

A High-Speed Vision-Based Sensor for Dynamic Vibration Analysis Using Fast Motion Extraction Algorithms

Directory of Open Access Journals (Sweden)

Dashan Zhang

2016-04-01

Full Text Available The development of image sensor and optics enables the application of vision-based techniques to the non-contact dynamic vibration analysis of large-scale structures. As an emerging technology, a vision-based approach allows for remote measuring and does not bring any additional mass to the measuring object compared with traditional contact measurements. In this study, a high-speed vision-based sensor system is developed to extract structure vibration signals in real time. A fast motion extraction algorithm is required for this system because the maximum sampling frequency of the charge-coupled device (CCD sensor can reach up to 1000 Hz. Two efficient subpixel level motion extraction algorithms, namely the modified Taylor approximation refinement algorithm and the localization refinement algorithm, are integrated into the proposed vision sensor. Quantitative analysis shows that both of the two modified algorithms are at least five times faster than conventional upsampled cross-correlation approaches and achieve satisfactory error performance. The practicability of the developed sensor is evaluated by an experiment in a laboratory environment and a field test. Experimental results indicate that the developed high-speed vision-based sensor system can extract accurate dynamic structure vibration signals by tracking either artificial targets or natural features.

Discontinuity in Fast Dynamics at the Glass Transition of ortho-Terphenyl.

Science.gov (United States)

Hoffman, David J; Fayer, Michael D

2017-11-16

The dynamics of the molecular glass former ortho-terphenyl through the glass transition were observed with two-dimensional infrared vibrational spectroscopy measurements of spectral diffusion using the small probe molecule phenylselenocyanate. Although the slow diffusive motions were not visible on the experimental time scale, a picosecond-scale exponential relaxation was observed at temperatures from above to well below the glass transition temperature. The characteristic time scale has a smooth temperature dependence from the liquid into the glass phase, but the range of vibrational frequencies the probe samples displayed a discontinuity at the glass transition temperature. Complementary pump-probe experiments associate the observed motion with density fluctuations. The key features of the dynamics are reproduced with a simple corrugated well potential energy surface model. In addition, the temperature dependence of the homogeneous vibrational dephasing was found to have a T 2 functional form, where T is the absolute temperature.

The Field Assessment Stroke Triage for Emergency Destination (FAST-ED): a Simple and Accurate Pre-Hospital Scale to Detect Large Vessel Occlusion Strokes

Science.gov (United States)

Lima, Fabricio O.; Silva, Gisele S.; Furie, Karen L.; Frankel, Michael R.; Lev, Michael H.; Camargo, Érica CS; Haussen, Diogo C.; Singhal, Aneesh B.; Koroshetz, Walter J.; Smith, Wade S.; Nogueira, Raul G.

2016-01-01

Background and Purpose Patients with large vessel occlusion strokes (LVOS) may be better served by direct transfer to endovascular capable centers avoiding hazardous delays between primary and comprehensive stroke centers. However, accurate stroke field triage remains challenging. We aimed to develop a simple field scale to identify LVOS. Methods The FAST-ED scale was based on items of the NIHSS with higher predictive value for LVOS and tested in the STOPStroke cohort, in which patients underwent CT angiography within the first 24 hours of stroke onset. LVOS were defined by total occlusions involving the intracranial-ICA, MCA-M1, MCA-2, or basilar arteries. Patients with partial, bi-hemispheric, and/or anterior + posterior circulation occlusions were excluded. Receiver operating characteristic (ROC) curve, sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of FAST-ED were compared with the NIHSS, Rapid Arterial oCclusion Evaluation (RACE) scale and Cincinnati Prehospital Stroke Severity Scale (CPSSS). Results LVO was detected in 240 of the 727 qualifying patients (33%). FAST-ED had comparable accuracy to predict LVO to the NIHSS and higher accuracy than RACE and CPSS (area under the ROC curve: FAST-ED=0.81 as reference; NIHSS=0.80, p=0.28; RACE=0.77, p=0.02; and CPSS=0.75, p=0.002). A FAST-ED ≥4 had sensitivity of 0.60, specificity 0.89, PPV 0.72, and NPV 0.82 versus RACE ≥5 of 0.55, 0.87, 0.68, 0.79 and CPSS ≥2 of 0.56, 0.85, 0.65, 0.78, respectively. Conclusions FAST-ED is a simple scale that if successfully validated in the field may be used by medical emergency professionals to identify LVOS in the pre-hospital setting enabling rapid triage of patients. PMID:27364531

Towards denoising XMCD movies of fast magnetization dynamics using extended Kalman filter.

Science.gov (United States)

Kopp, M; Harmeling, S; Schütz, G; Schölkopf, B; Fähnle, M

2015-01-01

The Kalman filter is a well-established approach to get information on the time-dependent state of a system from noisy observations. It was developed in the context of the Apollo project to see the deviation of the true trajectory of a rocket from the desired trajectory. Afterwards it was applied to many different systems with small numbers of components of the respective state vector (typically about 10). In all cases the equation of motion for the state vector was known exactly. The fast dissipative magnetization dynamics is often investigated by x-ray magnetic circular dichroism movies (XMCD movies), which are often very noisy. In this situation the number of components of the state vector is extremely large (about 10(5)), and the equation of motion for the dissipative magnetization dynamics (especially the values of the material parameters of this equation) is not well known. In the present paper it is shown by theoretical considerations that - nevertheless - there is no principle problem for the use of the Kalman filter to denoise XMCD movies of fast dissipative magnetization dynamics. Copyright © 2014 Elsevier B.V. All rights reserved.

Analysis methods for fast impurity ion dynamics data

International Nuclear Information System (INIS)

Den Hartog, D.J.; Almagri, A.F.; Prager, S.C.; Fonck, R.J.

1994-08-01

A high resolution spectrometer has been developed and used on the MST reversed-field pinch (RFP) to measure passively impurity ion temperatures and flow velocities with 10 μs temporal resolution. Such measurements of MHD-scale fluctuations are particularly relevant in the RFP because the flow velocity fluctuation induced transport of current (the ''MHD dynamo'') may produce the magnetic field reversal characteristic of an RFP. This instrument will also be used to measure rapid changes in the equilibrium flow velocity, such as occur during locking and H-mode transition. The precision of measurements made to date is <0.6 km/s. The authors are developing accurate analysis techniques appropriate to the reduction of this fast ion dynamics data. Moment analysis and curve-fitting routines have been evaluated for noise sensitivity and robustness. Also presented is an analysis method which correctly separates the flux-surface average of the correlated fluctuations in u and B from the fluctuations due to rigid shifts of the plasma column

Neural Computations in a Dynamical System with Multiple Time Scales

Directory of Open Access Journals (Sweden)

Yuanyuan Mi

2016-09-01

Full Text Available Neural systems display rich short-term dynamics at various levels, e.g., spike-frequencyadaptation (SFA at single neurons, and short-term facilitation (STF and depression (STDat neuronal synapses. These dynamical features typically covers a broad range of time scalesand exhibit large diversity in different brain regions. It remains unclear what the computationalbenefit for the brain to have such variability in short-term dynamics is. In this study, we proposethat the brain can exploit such dynamical features to implement multiple seemingly contradictorycomputations in a single neural circuit. To demonstrate this idea, we use continuous attractorneural network (CANN as a working model and include STF, SFA and STD with increasing timeconstants in their dynamics. Three computational tasks are considered, which are persistent activity,adaptation, and anticipative tracking. These tasks require conflicting neural mechanisms, andhence cannot be implemented by a single dynamical feature or any combination with similar timeconstants. However, with properly coordinated STF, SFA and STD, we show that the network isable to implement the three computational tasks concurrently. We hope this study will shed lighton the understanding of how the brain orchestrates its rich dynamics at various levels to realizediverse cognitive functions.

Slow-fast stochastic diffusion dynamics and quasi-stationarity for diploid populations with varying size.

Science.gov (United States)

Coron, Camille

2016-01-01

We are interested in the long-time behavior of a diploid population with sexual reproduction and randomly varying population size, characterized by its genotype composition at one bi-allelic locus. The population is modeled by a 3-dimensional birth-and-death process with competition, weak cooperation and Mendelian reproduction. This stochastic process is indexed by a scaling parameter K that goes to infinity, following a large population assumption. When the individual birth and natural death rates are of order K, the sequence of stochastic processes indexed by K converges toward a new slow-fast dynamics with variable population size. We indeed prove the convergence toward 0 of a fast variable giving the deviation of the population from quasi Hardy-Weinberg equilibrium, while the sequence of slow variables giving the respective numbers of occurrences of each allele converges toward a 2-dimensional diffusion process that reaches (0,0) almost surely in finite time. The population size and the proportion of a given allele converge toward a Wright-Fisher diffusion with stochastically varying population size and diploid selection. We insist on differences between haploid and diploid populations due to population size stochastic variability. Using a non trivial change of variables, we study the absorption of this diffusion and its long time behavior conditioned on non-extinction. In particular we prove that this diffusion starting from any non-trivial state and conditioned on not hitting (0,0) admits a unique quasi-stationary distribution. We give numerical approximations of this quasi-stationary behavior in three biologically relevant cases: neutrality, overdominance, and separate niches.

Ignoring detailed fast-changing dynamics of land use overestimates regional terrestrial carbon sequestration

Directory of Open Access Journals (Sweden)

S. Q. Zhao

2009-08-01

Full Text Available Land use change is critical in determining the distribution, magnitude and mechanisms of terrestrial carbon budgets at the local to global scales. To date, almost all regional to global carbon cycle studies are driven by a static land use map or land use change statistics with decadal time intervals. The biases in quantifying carbon exchange between the terrestrial ecosystems and the atmosphere caused by using such land use change information have not been investigated. Here, we used the General Ensemble biogeochemical Modeling System (GEMS, along with consistent and spatially explicit land use change scenarios with different intervals (1 yr, 5 yrs, 10 yrs and static, respectively, to evaluate the impacts of land use change data frequency on estimating regional carbon sequestration in the southeastern United States. Our results indicate that ignoring the detailed fast-changing dynamics of land use can lead to a significant overestimation of carbon uptake by the terrestrial ecosystem. Regional carbon sequestration increased from 0.27 to 0.69, 0.80 and 0.97 Mg C ha⁻¹ yr⁻¹ when land use change data frequency shifting from 1 year to 5 years, 10 years interval and static land use information, respectively. Carbon removal by forest harvesting and prolonged cumulative impacts of historical land use change on carbon cycle accounted for the differences in carbon sequestration between static and dynamic land use change scenarios. The results suggest that it is critical to incorporate the detailed dynamics of land use change into local to global carbon cycle studies. Otherwise, it is impossible to accurately quantify the geographic distributions, magnitudes, and mechanisms of terrestrial carbon sequestration at the local to global scales.

Palaeoclimate dynamics : a voyage through scales

Science.gov (United States)

Crucifix, Michel; Mitsui, Takahito

2015-04-01

Our knowledge of climate dynamics depends on indirect observations of past climate evolution, as well as on what can be inferred from theoretical arguments. At the scale of the Cenozoic, it is common to define a framework of nested time scales, the longest time scale of interest being related to the slow tectonic evolution, then variability associated with or controlled by the astronomical forcing, and finally the fastest dynamics associated with the natural modes of variability of the ocean and the atmosphere. For example, in a model, the astronomical modes of variability may be simulated with deterministic equations under fixed boundary conditions representing the tectonic state, and associated with stochastic parameterisations of the ocean-atmosphere (chaotic) modes of motion. Bifurcations or, more generally, qualitative changes in climate dynamics may be scanned by changing slowly the tectonic state, in order to provide explanations to observed changes in regimes such as the appearance of ice ages and their changes in length or amplitude. The above framework, largely theorized by B. Saltzman, may still be partly justified but is in need of a review. We address here specifically three questions: To what extent astronomical variability interacts with natural modes of ocean - atmosphere variability ? Specifically, how does millennial variability (e.g.: Dansgaard-Oeschger events) fit the Saltzman scheme ? The astronomical forcing is quasi-periodic, and we recently showed that it may produce somewhat counter-intuitive dynamics associated with the emergence of strange non-chaotic attractors. What are the consequences on the spectrum of climate variability ? What are the effects of centennial climate variability on the slow variability of climate ? These three questions are addressed by reference to recently published material, with the objective of emphasising research questions to be explored in the near future.

Fast evaluation of protein dynamics from deficient 15N relaxation data

KAUST Repository

Jaremko, Łukasz

2018-03-28

Simple and convenient method of protein dynamics evaluation from the insufficient experimental N relaxation data is presented basing on the ratios, products, and differences of longitudinal and transverse N relaxation rates obtained at a single magnetic field. Firstly, the proposed approach allows evaluating overall tumbling correlation time (nanosecond time scale). Next, local parameters of the model-free approach characterizing local mobility of backbone amide N–H vectors on two different time scales, S and R, can be elucidated. The generalized order parameter, S, describes motions on the time scale faster than the overall tumbling correlation time (pico- to nanoseconds), while the chemical exchange term, R, identifies processes slower than the overall tumbling correlation time (micro- to milliseconds). Advantages and disadvantages of different methods of data handling are thoroughly discussed.

Fast evaluation of protein dynamics from deficient 15N relaxation data

KAUST Repository

Jaremko, Łukasz; Jaremko, Mariusz; Ejchart, Andrzej; Nowakowski, Michał

2018-01-01

Simple and convenient method of protein dynamics evaluation from the insufficient experimental N relaxation data is presented basing on the ratios, products, and differences of longitudinal and transverse N relaxation rates obtained at a single magnetic field. Firstly, the proposed approach allows evaluating overall tumbling correlation time (nanosecond time scale). Next, local parameters of the model-free approach characterizing local mobility of backbone amide N–H vectors on two different time scales, S and R, can be elucidated. The generalized order parameter, S, describes motions on the time scale faster than the overall tumbling correlation time (pico- to nanoseconds), while the chemical exchange term, R, identifies processes slower than the overall tumbling correlation time (micro- to milliseconds). Advantages and disadvantages of different methods of data handling are thoroughly discussed.

BE-FAST (Balance, Eyes, Face, Arm, Speech, Time): Reducing the Proportion of Strokes Missed Using the FAST Mnemonic.

Science.gov (United States)

Aroor, Sushanth; Singh, Rajpreet; Goldstein, Larry B

2017-02-01

The FAST algorithm (Face, Arm, Speech, Time) helps identify persons having an acute stroke. We determined the proportion of patients with acute ischemic stroke not captured by FAST and evaluated a revised mnemonic. Records of all patients admitted to the University of Kentucky Stroke Center between January and December 2014 with a discharge International Classification of Diseases, Ninth Revision, Clinical Modification code for acute ischemic stroke were reviewed. Those misclassified, having missing National Institutes of Health Stroke Scale data, or were comatose or intubated were excluded. Presenting symptoms, demographics, and examination findings based on the National Institutes of Health Stroke Scale data were abstracted. Of 858 consecutive records identified, 736 met inclusion criteria; 14.1% did not have any FAST symptoms at presentation. Of these, 42% had gait imbalance or leg weakness, 40% visual symptoms, and 70% either symptom. With their addition, the proportion of stroke patients not identified was reduced to 4.4% (Pface weakness, arm weakness, or speech impairment on admission examination were considered in addition to a history of FAST symptoms, the proportion missed was reduced to 9.9% (P=0.0010). The proportion of stroke patients not identified was also reduced (2.6%) with the addition of a history of gait imbalance/leg weakness or visual symptoms (P<0.0001). Of patients with ischemic stroke with deficits potentially amenable to acute intervention, 14% are not identified using FAST. The inclusion of gait/leg and visual symptoms leads to a reduction in missed strokes. If validated in a prospective study, a revision of public educational programs may be warranted. © 2017 American Heart Association, Inc.

Almost Automorphic Functions on the Quantum Time Scale and Applications

Directory of Open Access Journals (Sweden)

Yongkun Li

2017-01-01

Full Text Available We first propose two types of concepts of almost automorphic functions on the quantum time scale. Secondly, we study some basic properties of almost automorphic functions on the quantum time scale. Then, we introduce a transformation between functions defined on the quantum time scale and functions defined on the set of generalized integer numbers; by using this transformation we give equivalent definitions of almost automorphic functions on the quantum time scale; following the idea of the transformation, we also give a concept of almost automorphic functions on more general time scales that can unify the concepts of almost automorphic functions on almost periodic time scales and on the quantum time scale. Finally, as an application of our results, we establish the existence of almost automorphic solutions of linear and semilinear dynamic equations on the quantum time scale.

Initial Study of An Effective Fast-Time Simulation Platform for Unmanned Aircraft System Traffic Management

Science.gov (United States)

Xue, Min; Rios, Joseph

2017-01-01

Small Unmanned Aerial Vehicles (sUAVs), typically 55 lbs and below, are envisioned to play a major role in surveilling critical assets, collecting important information, and delivering goods. Large scale small UAV operations are expected to happen in low altitude airspace in the near future. Many static and dynamic constraints exist in low altitude airspace because of manned aircraft or helicopter activities, various wind conditions, restricted airspace, terrain and man-made buildings, and conflict-avoidance among sUAVs. High sensitivity and high maneuverability are unique characteristics of sUAVs that bring challenges to effective system evaluations and mandate such a simulation platform different from existing simulations that were built for manned air traffic system and large unmanned fixed aircraft. NASA's Unmanned aircraft system Traffic Management (UTM) research initiative focuses on enabling safe and efficient sUAV operations in the future. In order to help define requirements and policies for a safe and efficient UTM system to accommodate a large amount of sUAV operations, it is necessary to develop a fast-time simulation platform that can effectively evaluate requirements, policies, and concepts in a close-to-reality environment. This work analyzed the impacts of some key factors including aforementioned sUAV's characteristics and demonstrated the importance of these factors in a successful UTM fast-time simulation platform.

Suppression of chaos at slow variables by rapidly mixing fast dynamics through linear energy-preserving coupling

OpenAIRE

Abramov, Rafail V.

2011-01-01

Chaotic multiscale dynamical systems are common in many areas of science, one of the examples being the interaction of the low-frequency dynamics in the atmosphere with the fast turbulent weather dynamics. One of the key questions about chaotic multiscale systems is how the fast dynamics affects chaos at the slow variables, and, therefore, impacts uncertainty and predictability of the slow dynamics. Here we demonstrate that the linear slow-fast coupling with the total energy conservation prop...

Collisionless magnetic reconnection in large-scale electron-positron plasmas

International Nuclear Information System (INIS)

Daughton, William; Karimabadi, Homa

2007-01-01

One of the most fundamental questions in reconnection physics is how the dynamical evolution will scale to macroscopic systems of physical relevance. This issue is examined for electron-positron plasmas using two-dimensional fully kinetic simulations with both open and periodic boundary conditions. The resulting evolution is complex and highly dynamic throughout the entire duration. The initial phase is distinguished by the coalescence of tearing islands to larger scale while the later phase is marked by the expansion of diffusion regions into elongated current layers that are intrinsically unstable to plasmoid generation. It appears that the repeated formation and ejection of plasmoids plays a key role in controlling the average structure of a diffusion region and preventing the further elongation of the layer. The reconnection rate is modulated in time as the current layers expand and new plasmoids are formed. Although the specific details of this evolution are affected by the boundary and initial conditions, the time averaged reconnection rate remains fast and is remarkably insensitive to the system size for sufficiently large systems. This dynamic scenario offers an alternative explanation for fast reconnection in large-scale systems

Initial Report of the Fast Timing Working Group

CERN Document Server

CMS Collaboration

2016-01-01

A preliminary set of results highlighting the unique capabilities of fast-timing for resolving information from individual collisions at the High-Luminosity LHC (HL- LHC) is presented. These results explore the possibilities made available by using fast timing to enhance the reconstruction and physics capabilities of the CMS detector in terms of pileup mitigation and searches for new physics. Fast timing applications in calorimetry, for electromagnetic showers, and for MIPs, to time-tag tracks, are demonstrated as are first examples of what is possible with their combination.

Multi-resolution and multi-scale simulation of the thermal hydraulics in fast neutron reactor assemblies

International Nuclear Information System (INIS)

Angeli, P.-E.

2011-01-01

The present work is devoted to a multi-scale numerical simulation of an assembly of fast neutron reactor. In spite of the rapid growth of the computer power, the fine complete CFD of a such system remains out of reach in a context of research and development. After the determination of the thermalhydraulic behaviour of the assembly at the macroscopic scale, we propose to carry out a local reconstruction of the fine scale information. The complete approach will require a much lower CPU time than the CFD of the entire structure. The macro-scale description is obtained using either the volume averaging formalism in porous media, or an alternative modeling historically developed for the study of fast neutron reactor assemblies. It provides some information used as constraint of a down-scaling problem, through a penalization technique of the local conservation equations. This problem lean on the periodic nature of the structure by integrating periodic boundary conditions for the required microscale fields or their spatial deviation. After validating the methodologies on some model applications, we undertake to perform them on 'industrial' configurations which demonstrate the viability of this multi-scale approach. (author) [fr

Lifetime, turnover time, and fast magnetic field regeneration in random flows

International Nuclear Information System (INIS)

Tanner, S. E. M.

2007-01-01

The fast dynamo is thought to be relevant in the regeneration of magnetic fields in astrophysics where the value of the magnetic Reynolds number (Rm) is immense. The fast dynamo picture is one in which chaotic flows provide a mechanism for the stretching of magnetic field lines. Furthermore, a cascade of energy down to small scales results in intermittent regions of a small-scale, intense magnetic field. Given this scenario it is natural to invoke the use of kinematic random flows in order to understand field regeneration mechanisms better. Here a family of random flows is used to study the effects that L, the lifetime of the cell, and τ, the turnover time of the cell, may have on magnetic field regeneration. Defining the parameter Γ=L/τ, it has been varied according to Γ>1, Γ<1, Γ∼O(1). In the kinematic regime, dynamo growth rates and Lyapunov exponents are examined at varying values of Rm. The possibility of fast dynamo action is considered. In the nonlinear regime, magnetic and kinetic energies are examined. Results indicate that there does appear to be a relationship between Γ and dynamo efficiency. In particular, the most efficient dynamos seem to operate at lower values of Γ

Temporal changes in vegetation of a virgin beech woodland remnant: stand-scale stability with intensive fine-scale dynamics governed by stand dynamic events

Directory of Open Access Journals (Sweden)

Tibor Standovár

2017-03-01

Full Text Available The aim of this resurvey study is to check if herbaceous vegetation on the forest floor exhibits overall stability at the stand-scale in spite of intensive dynamics at the scale of individual plots and stand dynamic events (driven by natural fine scale canopy gap dynamics. In 1996, we sampled a 1.5 ha patch using 0.25 m² plots placed along a 5 m × 5 m grid in the best remnant of central European montane beech woods in Hungary. All species in the herbaceous layer and their cover estimates were recorded. Five patches representing different stand developmental situations (SDS were selected for resurvey. In 2013, 306 plots were resurveyed by using blocks of four 0.25 m² plots to test the effects of imperfect relocation. We found very intensive fine-scale dynamics in the herbaceous layer with high species turnover and sharp changes in ground layer cover at the local-scale (< 1 m2. A decrease in species richness and herbaceous layer cover, as well as high species turnover, characterized the closing gaps. Colonization events and increasing species richness and herbaceous layer cover prevailed in the two newly created gaps. A pronounced decrease in the total cover, but low species turnover and survival of the majority of the closed forest specialists was detected by the resurvey at the stand-scale. The test aiming at assessing the effect of relocation showed a higher time effect than the effect of imprecise relocation. The very intensive fine-scale dynamics of the studied beech forest are profoundly determined by natural stand dynamics. Extinction and colonisation episodes even out at the stand-scale, implying an overall compositional stability of the herbaceous vegetation at the given spatial and temporal scale. We argue that fine-scale gap dynamics, driven by natural processes or applied as a management method, can warrant the survival of many closed forest specialist species in the long-run. Nomenclature: Flora Europaea (Tutin et al. 2010 for

Identification of low order models for large scale processes

NARCIS (Netherlands)

Wattamwar, S.K.

2010-01-01

Many industrial chemical processes are complex, multi-phase and large scale in nature. These processes are characterized by various nonlinear physiochemical effects and fluid flows. Such processes often show coexistence of fast and slow dynamics during their time evolutions. The increasing demand

Fast Timing for Collider Detectors

CERN Multimedia

CERN. Geneva

2017-01-01

Advancements in fast timing particle detectors have opened up new possibilities to design collider detectors that fully reconstruct and separate event vertices and individual particles in the time domain. The applications of these techniques are considered for the physics at HL-LHC.

Ultra-fast dynamics in the nonlinear optical response of silver nanoprism ordered arrays.

Science.gov (United States)

Sánchez-Esquivel, Héctor; Raygoza-Sanchez, Karen Y; Rangel-Rojo, Raúl; Kalinic, Boris; Michieli, Niccolò; Cesca, Tiziana; Mattei, Giovanni

2018-03-15

In this work we present the study of the ultra-fast dynamics of the nonlinear optical response of a honeycomb array of silver triangular nanoprisms, performed using a femtosecond pulsed laser tuned with the dipolar surface plasmon resonance of the nanoarray. Nonlinear absorption and refraction, and their time-dependence, were explored using the z-scan and time-resolved excite-probe techniques. Nonlinear absorption is shown to change sign with the input irradiance and the behavior was explained on the basis of a three-level model. The response time was determined to be in the picosecond regime. A technique based on a variable frequency chopper was also used in order to discriminate the thermal and electronic contributions to the nonlinearity, which were found to have opposite signs. All these findings propel the investigated nanoprism arrays as good candidates for applications in advanced ultra-fast nonlinear nanophotonic devices.

Static and Dynamic Electron Microscopy Investigations at the Atomic and Ultrafast Scales

Science.gov (United States)

Suri, Pranav Kumar

Advancements in the electron microscopy capabilities - aberration-corrected imaging, monochromatic spectroscopy, direct-electron detectors - have enabled routine visualization of atomic-scale processes with millisecond temporal resolutions in this decade. This, combined with progress in the transmission electron microscopy (TEM) specimen holder technology and nanofabrication techniques, allows comprehensive experiments on a wide range of materials in various phases via in situ methods. The development of ultrafast (sub-nanosecond) time-resolved TEM with ultrafast electron microscopy (UEM) has further pushed the envelope of in situ TEM to sub-nanosecond temporal resolution while maintaining sub-nanometer spatial resolution. A plethora of materials phenomena - including electron-phonon coupling, phonon transport, first-order phase transitions, bond rotation, plasmon dynamics, melting, and dopant atoms arrangement - are not yet clearly understood and could be benefitted with the current in situ TEM capabilities having atomic-level and ultrafast precision. Better understanding of these phenomena and intrinsic material dynamics (e.g. how phonons propagate in a material, what time-scales are involved in a first-order phase transition, how fast a material melts, where dopant atoms sit in a crystal) in new-generation and technologically important materials (e.g. two-dimensional layered materials, semiconductor and magnetic devices, rare-earth-element-free permanent magnets, unconventional superconductors) could bring a paradigm shift in their electronic, structural, magnetic, thermal and optical applications. Present research efforts, employing cutting-edge static and dynamic in situ electron microscopy resources at the University of Minnesota, are directed towards understanding the atomic-scale crystallographic structural transition and phonon transport in an iron-pnictide parent compound LaFeAsO, studying the mechanical stability of fast moving hard-drive heads in heat

Large Deviations for Two-Time-Scale Diffusions, with Delays

International Nuclear Information System (INIS)

Kushner, Harold J.

2010-01-01

We consider the problem of large deviations for a two-time-scale reflected diffusion process, possibly with delays in the dynamical terms. The Dupuis-Ellis weak convergence approach is used. It is perhaps the most intuitive and simplest for the problems of concern. The results have applications to the problem of approximating optimal controls for two-time-scale systems via use of the averaged equation.

How fast are the ultra-fast nano-scale solid-liquid phase transitions induced by energetic particles in solids?

International Nuclear Information System (INIS)

Lopasso, E.M.; Caro, A.; Caro, M.

2003-01-01

We study the thermodynamic forces acting on the evolution of the nanoscale regions excited by collisions of energetic particles into solid targets. We analyze the role of diffusion, thermo-migration, and the liquidus-solidus two-phase field crossing, as the system cools down from the collision-induced melt under different conditions of energy deposition. To determine the relevance of these thermodynamic forces, solute redistribution is evaluated using molecular dynamics simulations of equilibrium Au-Ni solid solutions. At low collision energies, our results show that the quenching of spherical cascades is too fast to allow for solute redistribution according to equilibrium solidification as determined from the equilibrium phase diagram (zone refining effect), and only thermo-migration is observed. At higher energies instead, in the cylindrical symmetry of ion tracks, quenching rate is in a range that shows the combined effects of thermo-migration and solute redistribution that, depending on the material, can reinforce or cancel each other. These results are relevant for the interpretation of the early stage of radiation damage in alloys, and show that the combination of ultra-fast but nano-scale characteristics of these processes can still be described in terms of linear response of the perturbed system

Bat Dynamics of Female Fast Pitch Softball Batters.

Science.gov (United States)

Messier, Stephen P.; Owen, Marjorie G.

1984-01-01

Female fast pitch softball batters served in an examination of the dynamic characteristics of the bat during the swing through the use of three-dimensional cinematographic analysis techniques. These results were compared with those from previous studies of baseball batting. Findings are listed. (Author/DF)

Temporal dynamics of Bose-condensed gases

Energy Technology Data Exchange (ETDEWEB)

Trujillo Martinez, Mauricio

2014-03-19

We perform a detailed quantum dynamical study of non-equilibrium trapped, interacting Bose-condensed gases. We investigate Josephson oscillations between interacting Bose-Einstein condensates confined in a finite size double-well trap and the non-trivial time evolution of a coherent state placed at the center of a two dimensional optical lattice. For the Josephson oscillations three time scales appear. We find that Josephson junction can sustain multiple undamped oscillations up to a characteristic time scale τ{sub c} without exciting atoms out of the condensates. Beyond the characteristic time scale τ{sub c} the dynamics of the junction are governed by fast, non-condensed particles assisted Josephson tunnelling as well as the collisions between non-condensed particles. In the non-condensed particles dominated regime we observe strong damping of the oscillations due to inelastic collisions, equilibrating the system leading to an effective loss of details of the initial conditions. In addition, we predict that an initially self-trapped BEC state will be destroyed by these fast dynamics. The time evolution of a coherent state released at the center of a two dimensional optical lattice shows a ballistic expansion with a decreasing expansion velocity for increasing two-body interactions strength and particle number. Additionally, we predict that if the two-body interactions strength exceeds a certain value, a forerunner splits up from the expanding coherent state. We also observe that this system, which is prepared far from equilibrium, can evolve to a quasistationary non-equilibrium state.

Emergence of scaling in human-interest dynamics

Science.gov (United States)

Zhao, Zhi-Dan; Yang, Zimo; Zhang, Zike; Zhou, Tao; Huang, Zi-Gang; Lai, Ying-Cheng

2013-01-01

Human behaviors are often driven by human interests. Despite intense recent efforts in exploring the dynamics of human behaviors, little is known about human-interest dynamics, partly due to the extreme difficulty in accessing the human mind from observations. However, the availability of large-scale data, such as those from e-commerce and smart-phone communications, makes it possible to probe into and quantify the dynamics of human interest. Using three prototypical “Big Data” sets, we investigate the scaling behaviors associated with human-interest dynamics. In particular, from the data sets we uncover fat-tailed (possibly power-law) distributions associated with the three basic quantities: (1) the length of continuous interest, (2) the return time of visiting certain interest, and (3) interest ranking and transition. We argue that there are three basic ingredients underlying human-interest dynamics: preferential return to previously visited interests, inertial effect, and exploration of new interests. We develop a biased random-walk model, incorporating the three ingredients, to account for the observed fat-tailed distributions. Our study represents the first attempt to understand the dynamical processes underlying human interest, which has significant applications in science and engineering, commerce, as well as defense, in terms of specific tasks such as recommendation and human-behavior prediction. PMID:24326949

Fast monitoring of motor exhaust components by resonant multi-photon ionisation and time-of-flight mass spectrometry

Science.gov (United States)

Franzen, Jochen; Frey, Rüdiger; Nagel, Holger

1995-03-01

A new analytical procedure is provided by the combination of two types of spectroscopy. Resonant ionization of selected compounds by multiphoton ionization is based on results of absorption spectroscopy for the compound molecules of interest and time-of-flight mass spectrometry serves for the unambigious detection of these compounds. An interesting application of this method is the fast exhaust gas analysis. In the development of future combustion engines, the management of dynamic motor processes becomes predominant because by more than 90 % of all the dangerous exhaust pollutions are produced in instationary motor phases such as fast speed or load changes. The investigation of dynamic processes however, requires fast analytical procedures with millisecond time resolution together with the capability to measure individual components in a very complex gas mixture The objectives for a development project of such an instrument were set by the Research Association for Combustion Engines (Forschungsvereinigung Verbrennungskraftmaschinen, FVV, Germany): Up to ten substances should be monitored synchroneously with a time resolution of about 10 milliseconds, with concentration limits of 1 part per million and with a precision better than 10 % relative standard deviation. Such a laser mass spectrometer for fast multi-component automotive exhaust analyses has been developed in a joint research project by Bruker-Franzen Analytik GmbH, Dornier GmbH and the Technical University of Munich. The system has been applied at a motor test facility to investigate the emissions of the aromatic hydrocarbons benzene, toluene and xylene, of nitric oxide and acetaldehyde in stationary and dynamic engine operation. These measurements demonstrate that strong emission of these pollutants takes place at instationary engine operation and in particular that these compounds are emitted at different times, giving new information about the processes in the combustion chamber and in the exhaust pipe.

FAST - A multiprocessed environment for visualization of computational fluid dynamics

International Nuclear Information System (INIS)

Bancroft, G.V.; Merritt, F.J.; Plessel, T.C.; Kelaita, P.G.; Mccabe, R.K.

1991-01-01

The paper presents the Flow Analysis Software Toolset (FAST) to be used for fluid-mechanics analysis. The design criteria for FAST including the minimization of the data path in the computational fluid-dynamics (CFD) process, consistent user interface, extensible software architecture, modularization, and the isolation of three-dimensional tasks from the application programmer are outlined. Each separate process communicates through the FAST Hub, while other modules such as FAST Central, NAS file input, CFD calculator, surface extractor and renderer, titler, tracer, and isolev might work together to generate the scene. An interprocess communication package making it possible for FAST to operate as a modular environment where resources could be shared among different machines as well as a single host is discussed. 20 refs

Scale relativity: from quantum mechanics to chaotic dynamics.

Science.gov (United States)

Nottale, L.

Scale relativity is a new approach to the problem of the origin of fundamental scales and of scaling laws in physics, which consists in generalizing Einstein's principle of relativity to the case of scale transformations of resolutions. We recall here how it leads one to the concept of fractal space-time, and to introduce a new complex time derivative operator which allows to recover the Schrödinger equation, then to generalize it. In high energy quantum physics, it leads to the introduction of a Lorentzian renormalization group, in which the Planck length is reinterpreted as a lowest, unpassable scale, invariant under dilatations. These methods are successively applied to two problems: in quantum mechanics, that of the mass spectrum of elementary particles; in chaotic dynamics, that of the distribution of planets in the Solar System.

Fast time- and frequency-domain finite-element methods for electromagnetic analysis

Science.gov (United States)

Lee, Woochan

Fast electromagnetic analysis in time and frequency domain is of critical importance to the design of integrated circuits (IC) and other advanced engineering products and systems. Many IC structures constitute a very large scale problem in modeling and simulation, the size of which also continuously grows with the advancement of the processing technology. This results in numerical problems beyond the reach of existing most powerful computational resources. Different from many other engineering problems, the structure of most ICs is special in the sense that its geometry is of Manhattan type and its dielectrics are layered. Hence, it is important to develop structure-aware algorithms that take advantage of the structure specialties to speed up the computation. In addition, among existing time-domain methods, explicit methods can avoid solving a matrix equation. However, their time step is traditionally restricted by the space step for ensuring the stability of a time-domain simulation. Therefore, making explicit time-domain methods unconditionally stable is important to accelerate the computation. In addition to time-domain methods, frequency-domain methods have suffered from an indefinite system that makes an iterative solution difficult to converge fast. The first contribution of this work is a fast time-domain finite-element algorithm for the analysis and design of very large-scale on-chip circuits. The structure specialty of on-chip circuits such as Manhattan geometry and layered permittivity is preserved in the proposed algorithm. As a result, the large-scale matrix solution encountered in the 3-D circuit analysis is turned into a simple scaling of the solution of a small 1-D matrix, which can be obtained in linear (optimal) complexity with negligible cost. Furthermore, the time step size is not sacrificed, and the total number of time steps to be simulated is also significantly reduced, thus achieving a total cost reduction in CPU time. The second contribution

Dynamic measurements at THz frequencies with a fast rotary delay line

Science.gov (United States)

Guerboukha, Hichem; Markov, Andrey; Qu, Hang; Skorobogatiy, Maksim

2016-02-01

Fabrication, characterization, and applications of a fast rotary linear optical delay line (FRLODL) for THz time-domain spectroscopy are presented. The FRLODL features two reflective surfaces with spatially separated incoming and outgoing beams. It has been manufactured using CNC machining. A linear dependence of the optical delay on the rotation angle allows a straightforward extraction of the conversion factor between the acquisition time (in ms) and the terahertz pulse time (in ps). The FRLODL has been tested using rotation speeds of up to 48 Hz, corresponding to an acquisition rate of up to 192 Hz with four blades incorporated on the same disk. At high speeds we observe a decrease of the bandwidth due to the limitations of the electronics, in particular, the transimpedance amplifier. An error analysis is performed by experimentally evaluating the signal-to-noise ratio and the dynamic range. With regard to the applications of the FRLODL, we first present observation of the evaporation of liquids, namely water, acetone and methanol. We then demonstrate monitoring of the spray painting process. Finally, detection of fast moving objects at 1 m/s and their thickness characterization are presented.

New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

International Nuclear Information System (INIS)

Pabst, Stefan Ulf

2013-04-01

The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO 2 is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the

New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

Energy Technology Data Exchange (ETDEWEB)

Pabst, Stefan Ulf

2013-04-15

The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO{sub 2} is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the

Improving predictions of large scale soil carbon dynamics: Integration of fine-scale hydrological and biogeochemical processes, scaling, and benchmarking

Science.gov (United States)

Riley, W. J.; Dwivedi, D.; Ghimire, B.; Hoffman, F. M.; Pau, G. S. H.; Randerson, J. T.; Shen, C.; Tang, J.; Zhu, Q.

2015-12-01

Numerical model representations of decadal- to centennial-scale soil-carbon dynamics are a dominant cause of uncertainty in climate change predictions. Recent attempts by some Earth System Model (ESM) teams to integrate previously unrepresented soil processes (e.g., explicit microbial processes, abiotic interactions with mineral surfaces, vertical transport), poor performance of many ESM land models against large-scale and experimental manipulation observations, and complexities associated with spatial heterogeneity highlight the nascent nature of our community's ability to accurately predict future soil carbon dynamics. I will present recent work from our group to develop a modeling framework to integrate pore-, column-, watershed-, and global-scale soil process representations into an ESM (ACME), and apply the International Land Model Benchmarking (ILAMB) package for evaluation. At the column scale and across a wide range of sites, observed depth-resolved carbon stocks and their 14C derived turnover times can be explained by a model with explicit representation of two microbial populations, a simple representation of mineralogy, and vertical transport. Integrating soil and plant dynamics requires a 'process-scaling' approach, since all aspects of the multi-nutrient system cannot be explicitly resolved at ESM scales. I will show that one approach, the Equilibrium Chemistry Approximation, improves predictions of forest nitrogen and phosphorus experimental manipulations and leads to very different global soil carbon predictions. Translating model representations from the site- to ESM-scale requires a spatial scaling approach that either explicitly resolves the relevant processes, or more practically, accounts for fine-resolution dynamics at coarser scales. To that end, I will present recent watershed-scale modeling work that applies reduced order model methods to accurately scale fine-resolution soil carbon dynamics to coarse-resolution simulations. Finally, we

Multiple time scale analysis of pressure oscillations in solid rocket motors

Science.gov (United States)

Ahmed, Waqas; Maqsood, Adnan; Riaz, Rizwan

2018-03-01

In this study, acoustic pressure oscillations for single and coupled longitudinal acoustic modes in Solid Rocket Motor (SRM) are investigated using Multiple Time Scales (MTS) method. Two independent time scales are introduced. The oscillations occur on fast time scale whereas the amplitude and phase changes on slow time scale. Hopf bifurcation is employed to investigate the properties of the solution. The supercritical bifurcation phenomenon is observed for linearly unstable system. The amplitude of the oscillations result from equal energy gain and loss rates of longitudinal acoustic modes. The effect of linear instability and frequency of longitudinal modes on amplitude and phase of oscillations are determined for both single and coupled modes. For both cases, the maximum amplitude of oscillations decreases with the frequency of acoustic mode and linear instability of SRM. The comparison of analytical MTS results and numerical simulations demonstrate an excellent agreement.

Network Dynamics with BrainX3: A Large-Scale Simulation of the Human Brain Network with Real-Time Interaction

Directory of Open Access Journals (Sweden)

Xerxes D. Arsiwalla

2015-02-01

Full Text Available BrainX3 is a large-scale simulation of human brain activity with real-time interaction, rendered in 3D in a virtual reality environment, which combines computational power with human intuition for the exploration and analysis of complex dynamical networks. We ground this simulation on structural connectivity obtained from diffusion spectrum imaging data and model it on neuronal population dynamics. Users can interact with BrainX3 in real-time by perturbing brain regions with transient stimulations to observe reverberating network activity, simulate lesion dynamics or implement network analysis functions from a library of graph theoretic measures. BrainX3 can thus be used as a novel immersive platform for real-time exploration and analysis of dynamical activity patterns in brain networks, both at rest or in a task-related state, for discovery of signaling pathways associated to brain function and/or dysfunction and as a tool for virtual neurosurgery. Our results demonstrate these functionalities and shed insight on the dynamics of the resting-state attractor. Specifically, we found that a noisy network seems to favor a low firing attractor state. We also found that the dynamics of a noisy network is less resilient to lesions. Our simulations on TMS perturbations show that even though TMS inhibits most of the network, it also sparsely excites a few regions. This is presumably, due to anti-correlations in the dynamics and suggests that even a lesioned network can show sparsely distributed increased activity compared to healthy resting-state, over specific brain areas.

Dynamics of glass-forming liquids

DEFF Research Database (Denmark)

Hansen, Henriette Wase

on alpha relaxation dynamics, and for the two van der Waals liquids, also when we have separation of timescales, i.e. the alpha relaxation is not contributing to the picosecond dynamics. The concept of isomorphs is observed to break down in two cases for the hydrogen bonding system: in density scaling......The overall theme of this work has been to experimentally test the shoving model and isomorph theory related to the dynamics of glass-forming liquids, both of which, rather than being universal explanations, are expected to work in the simplest case. We test the connection between fast and slow...... dynamics in light of the shoving model from the temperature dependence of the mean-squared displacement from neutron scattering at nanosecond timescale and the elastic modulus from shear mechanics. We find the fast dynamics to correlate with the alpha relaxation time and fragility in agreement...

Cycles, scaling and crossover phenomenon in length of the day (LOD) time series

Science.gov (United States)

Telesca, Luciano

2007-06-01

The dynamics of the temporal fluctuations of the length of the day (LOD) time series from January 1, 1962 to November 2, 2006 were investigated. The power spectrum of the whole time series has revealed annual, semi-annual, decadal and daily oscillatory behaviors, correlated with oceanic-atmospheric processes and interactions. The scaling behavior was analyzed by using the detrended fluctuation analysis (DFA), which has revealed two different scaling regimes, separated by a crossover timescale at approximately 23 days. Flicker-noise process can describe the dynamics of the LOD time regime involving intermediate and long timescales, while Brownian dynamics characterizes the LOD time series for small timescales.

Monitoring vegetation dynamics with medium resolution MODIS-EVI time series at sub-regional scale in southern Africa

Science.gov (United States)

Dubovyk, Olena; Landmann, Tobias; Erasmus, Barend F. N.; Tewes, Andreas; Schellberg, Jürgen

2015-06-01

Currently there is a lack of knowledge on spatio-temporal patterns of land surface dynamics at medium spatial scale in southern Africa, even though this information is essential for better understanding of ecosystem response to climatic variability and human-induced land transformations. In this study, we analysed vegetation dynamics across a large area in southern Africa using the 14-years (2000-2013) of medium spatial resolution (250 m) MODIS-EVI time-series data. Specifically, we investigated temporal changes in the time series of key phenometrics including overall greenness, peak and timing of annual greenness over the monitoring period and study region. In order to specifically capture spatial and per pixel vegetation changes over time, we calculated trends in these phenometrics using a robust trend analysis method. The results showed that interannual vegetation dynamics followed precipitation patterns with clearly differentiated seasonality. The earliest peak greenness during 2000-2013 occurred at the end of January in the year 2000 and the latest peak greenness was observed at the mid of March in 2012. Specifically spatial patterns of long-term vegetation trends allowed mapping areas of (i) decrease or increase in overall greenness, (ii) decrease or increase of peak greenness, and (iii) shifts in timing of occurrence of peak greenness over the 14-year monitoring period. The observed vegetation decline in the study area was mainly attributed to human-induced factors. The obtained information is useful to guide selection of field sites for detailed vegetation studies and land rehabilitation interventions and serve as an input for a range of land surface models.

Chaos and dynamics on 0.5--300 ps time scales in vibrationally excited acetylene: Fourier transform of stimulated-emission pumping spectrum

International Nuclear Information System (INIS)

Pique, J.P.; Chen, Y.; Field, R.W.; Kinsey, J.L.

1987-01-01

A recently proposed technique based on the Fourier transform of the spectrum is applied to the stimulated-emission pumping spectrum of acetylene at --26 500 cm/sup -1/ above the vibrational ground state. Correlations on two different time scales (--3 and --45 ps) were found from analysis of low-resolution (0.3 cm/sup -1/) and high-resolution (0.05 cm/sup -1/) spectra, respectively. Additional structure produced dynamic information on a wider (0.5--300 ps) time scale. The results show that acetylene at 26 500 cm/sup -1/ is in the transition from the regular to the chaotic regime

Time scales of supercooled water and implications for reversible polyamorphism

Science.gov (United States)

Limmer, David T.; Chandler, David

2015-09-01

Deeply supercooled water exhibits complex dynamics with large density fluctuations, ice coarsening and characteristic time scales extending from picoseconds to milliseconds. Here, we discuss implications of these time scales as they pertain to two-phase coexistence and to molecular simulations of supercooled water. Specifically, we argue that it is possible to discount liquid-liquid criticality because the time scales imply that correlation lengths for such behaviour would be bounded by no more than a few nanometres. Similarly, it is possible to discount two-liquid coexistence because the time scales imply a bounded interfacial free energy that cannot grow in proportion to a macroscopic surface area. From time scales alone, therefore, we see that coexisting domains of differing density in supercooled water can be no more than nanoscale transient fluctuations.

Multi-time, multi-scale correlation functions in turbulence and in turbulent models

NARCIS (Netherlands)

Biferale, L.; Boffetta, G.; Celani, A.; Toschi, F.

1999-01-01

A multifractal-like representation for multi-time, multi-scale velocity correlation in turbulence and dynamical turbulent models is proposed. The importance of subleading contributions to time correlations is highlighted. The fulfillment of the dynamical constraints due to the equations of motion is

Dynamical scales for multi-TeV top-pair production at the LHC

Energy Technology Data Exchange (ETDEWEB)

Czakon, Michał [Institut für Theoretische Teilchenphysik und Kosmologie, RWTH Aachen University,Aachen, D-52056 (Germany); Heymes, David; Mitov, Alexander [Cavendish Laboratory, University of Cambridge,Cambridge, CB3 0HE (United Kingdom)

2017-04-12

We calculate all major differential distributions with stable top-quarks at the LHC. The calculation covers the multi-TeV range that will be explored during LHC Run II and beyond. Our results are in the form of high-quality binned distributions. We offer predictions based on three different parton distribution function (pdf) sets. In the near future we will make our results available also in the more flexible fastNLO format that allows fast re-computation with any other pdf set. In order to be able to extend our calculation into the multi-TeV range we have had to derive a set of dynamic scales. Such scales are selected based on the principle of fastest perturbative convergence applied to the differential and inclusive cross-section. Many observations from our study are likely to be applicable and useful to other precision processes at the LHC. With scale uncertainty now under good control, pdfs arise as the leading source of uncertainty for TeV top production. Based on our findings, true precision in the boosted regime will likely only be possible after new and improved pdf sets appear. We expect that LHC top-quark data will play an important role in this process.

Nonlinear MHD dynamics of tokamak plasmas on multiple time scales

International Nuclear Information System (INIS)

Kruger, S.E.; Schnack, D.D.; Brennan, D.P.; Gianakon, T.A.; Sovinec, C.R.

2003-01-01

Two types of numerical, nonlinear simulations using the NIMROD code are presented. In the first simulation, we model the disruption occurring in DIII-D discharge 87009 as an ideal MHD instability driven unstable by neutral-beam heating. The mode grows faster than exponential, but on a time scale that is a hybrid of the heating rate and the ideal MHD growth rate as predicted by analytic theory. The second type of simulations, which occur on a much longer time scale, focus on the seeding of tearing modes by sawteeth. Pressure effects play a role both in the exterior region solutions and in the neoclassical drive terms. The results of both simulations are reviewed and their implications for experimental analysis is discussed. (author)

Dynamic simulation of a pilot scale vacuum gas oil hydrocracking unit by the space-time CE/SE method

Energy Technology Data Exchange (ETDEWEB)

Sadighi, S.; Ahmad, A. [Institute of Hydrogen Economy, Universiti Teknologi Malaysia, Johor Bahru (Malaysia); Shirvani, M. [Faculty of Chemical Engineering, University of Science and Technology, Tehran (Iran, Islamic Republic of)

2012-05-15

This work introduces a modified space-time conservation element/solution element (CE/SE) method for the simulation of the dynamic behavior of a pilot-scale hydrocracking reactor. With this approach, a four-lump dynamic model including vacuum gas oil (VGO), middle distillate, naphtha and gas is solved. The proposed method is capable of handling the stiffness of the partial differential equations resulting from the hydrocracking reactions. To have a better judgment, the model is also solved by the finite difference method (FDM), and the results from both approaches are compared. Initially, the absolute average deviation of the cold dynamic simulation using the CE/SE approach is 8.98 %, which is better than that obtained using the FDM. Then, the stability analysis proves that for achieving an appropriate response from the dynamic model, the Courant number, which is a function of the time step size, mesh size and volume flow rate through the catalytic bed, should be less than 1. Finally, it is found that, following a careful selection of these parameters, the CE/SE solutions to the hydrocracking model can produce higher accuracy than the FDM results. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Reducing preoperative fasting time: A trend based on evidence.

Science.gov (United States)

de Aguilar-Nascimento, José Eduardo; Dock-Nascimento, Diana Borges

2010-03-27

Preoperative fasting is mandatory before anesthesia to reduce the risk of aspiration. However, the prescribed 6-8 h of fasting is usually prolonged to 12-16 h for various reasons. Prolonged fasting triggers a metabolic response that precipitates gluconeogenesis and increases the organic response to trauma. Various randomized trials and meta-analyses have consistently shown that is safe to reduce the preoperative fasting time with a carbohydrate-rich drink up to 2 h before surgery. Benefits related to this shorter preoperative fasting include the reduction of postoperative gastrointestinal discomfort and insulin resistance. New formulas containing amino acids such as glutamine and other peptides are being studied and are promising candidates to be used to reduce preoperative fasting time.

Fast electrostatic force calculation on parallel computer clusters

International Nuclear Information System (INIS)

Kia, Amirali; Kim, Daejoong; Darve, Eric

2008-01-01

The fast multipole method (FMM) and smooth particle mesh Ewald (SPME) are well known fast algorithms to evaluate long range electrostatic interactions in molecular dynamics and other fields. FMM is a multi-scale method which reduces the computation cost by approximating the potential due to a group of particles at a large distance using few multipole functions. This algorithm scales like O(N) for N particles. SPME algorithm is an O(NlnN) method which is based on an interpolation of the Fourier space part of the Ewald sum and evaluating the resulting convolutions using fast Fourier transform (FFT). Those algorithms suffer from relatively poor efficiency on large parallel machines especially for mid-size problems around hundreds of thousands of atoms. A variation of the FMM, called PWA, based on plane wave expansions is presented in this paper. A new parallelization strategy for PWA, which takes advantage of the specific form of this expansion, is described. Its parallel efficiency is compared with SPME through detail time measurements on two different computer clusters

An assessment of prompt neutron reproduction time in a reflector dominated fast critical system: ELECTRA

International Nuclear Information System (INIS)

Suvdantsetseg, E.; Wallenius, J.

2014-01-01

Highlights: • Prompt neutron reproduction time of ELECTRA is evaluated. • Static and dynamic reproduction times are distinguished for ELECTRA. • Avery-Cohn’s two-region prompt neutron theory is applied. - Abstract: In this paper, an accurate method to evaluate the prompt neutron reproduction time for a reflector dominated fast critical reactor, ELECTRA, is discussed. To adequately handle the problem, explicit time dependent Monte Carlo calculations with MCNP, applying repeated time cut-off technique, are used and compared against the σ∼1/v time dependent absorber method, applying artificial cross-section data in the Monte Carlo code SERPENT. The results show that when a reflector plays a major role in criticality for fast neutron reactor, the two methods predict different physical parameters (Λ=69±2 ns and Λ=83±1 ns for time cut-off and the 1/v method respectively). The reason is explained by applying Avery-Cohn’s two-region prompt neutron model

Dynamic modelling of heavy metals - time scales and target loads

NARCIS (Netherlands)

Posch, M.; Vries, de W.

2009-01-01

Over the past decade steady-state methods have been developed to assess critical loads of metals avoiding long-term risks in view of food quality and eco-toxicological effects on organisms in soils and surface waters. However, dynamic models are needed to estimate the times involved in attaining a

Structural relaxation dynamics and annealing effects of sodium silicate glass.

Science.gov (United States)

Naji, Mohamed; Piazza, Francesco; Guimbretière, Guillaume; Canizarès, Aurélien; Vaills, Yann

2013-05-09

Here we report high-precision measurements of structural relaxation dynamics in the glass transition range at the intermediate and short length scale for a strong sodium silicate glass during long annealing times. We evidence for the first time the heterogeneous dynamics at the intermediate range order by probing the acoustic longitudinal frequency in the GHz region by Brillouin light scattering spectroscopy. Or, from in-situ Raman measurements, we show that relaxation is indeed homogeneous at the interatomic length scale. Our results show that the dynamics at the intermediate range order contains two distinct relaxation time scales, a fast and a slow component, differing by about a 10-fold factor below Tg and approaching to one another past the glass transition. The slow relaxation time agrees with the shear relaxation time, proving that Si-O bond breaking constitutes the primary control of structural relaxation at the intermediate range order.

Applying System Dynamics Approach to the Fast Fashion Supply Chain: Case Study of an SME in Indonesia

Directory of Open Access Journals (Sweden)

Mariany W Lidia

2012-09-01

Full Text Available The fashion industry is the biggest contributor among the 14 creative industries in Indonesia. Nowadays many apparel companies are shifting toward the vertical integration. Since speed is everything to be successful in the apparel industry, fast fashion retailers must quickly respond to the market demand. This papers aims to develop a model of the supply chain of a small and medium scale enterprise (SME of an apparel company in Indonesia and to propose a decision support system using System Dynamics (SD and helps the management to identify the best business strategy. Simulated scenarios can help the management to identify the most appropriate policy to be applied in the future. Case study method was used in this research where data were collected from a typical fast fashion firm in Indonesia that produces its own wares ranging from raw materials to be ready-to-wear clothes, has three stores, a warehouse and is running online sales system. We analyses the result of many simulations in a fashion company from an operational point of view and from them we derive suggestions about the future business strategy in a small and medium fashion company in Indonesia. Keywords: system dynamics, fast fashion, supply chain management, SME, Indonesia

MyDTW - Dynamic Time Warping program for stratigraphical time series

Science.gov (United States)

Kotov, Sergey; Paelike, Heiko

2017-04-01

One of the general tasks in many geological disciplines is matching of one time or space signal to another. It can be classical correlation between two cores or cross-sections in sedimentology or marine geology. For example, tuning a paleoclimatic signal to a target curve, driven by variations in the astronomical parameters, is a powerful technique to construct accurate time scales. However, these methods can be rather time-consuming and can take ours of routine work even with the help of special semi-automatic software. Therefore, different approaches to automate the processes have been developed during last decades. Some of them are based on classical statistical cross-correlations such as the 'Correlator' after Olea [1]. Another ones use modern ideas of dynamic programming. A good example is as an algorithm developed by Lisiecki and Lisiecki [2] or dynamic time warping based algorithm after Pälike [3]. We introduce here an algorithm and computer program, which are also stemmed from the Dynamic Time Warping algorithm class. Unlike the algorithm of Lisiecki and Lisiecki, MyDTW does not lean on a set of penalties to follow geological logics, but on a special internal structure and specific constrains. It differs also from [3] in basic ideas of implementation and constrains design. The algorithm is implemented as a computer program with a graphical user interface using Free Pascal and Lazarus IDE and available for Windows, Mac OS, and Linux. Examples with synthetic and real data are demonstrated. Program is available for free download at http://www.marum.de/Sergey_Kotov.html . References: 1. Olea, R.A. Expert systems for automated correlation and interpretation of wireline logs // Math Geol (1994) 26: 879. doi:10.1007/BF02083420 2. Lisiecki L. and Lisiecki P. Application of dynamic programming to the correlation of paleoclimate records // Paleoceanography (2002), Volume 17, Issue 4, pp. 1-1, CiteID 1049, doi: 10.1029/2001PA000733 3. Pälike, H. Extending the

Collisionally induced stochastic dynamics of fast ions in solids

International Nuclear Information System (INIS)

Burgdoerfer, J.

1989-01-01

Recent developments in the theory of excited state formation in collisions of fast highly charged ions with solids are reviewed. We discuss a classical transport theory employing Monte-Carlo sampling of solutions of a microscopic Langevin equation. Dynamical screening by the dielectric medium as well as multiple collisions are incorporated through the drift and stochastic forces in the Langevin equation. The close relationship between the extrinsically stochastic dynamics described by the Langevin and the intrinsic stochasticity in chaotic nonlinear dynamical systems is stressed. Comparison with experimental data and possible modification by quantum corrections are discussed. 49 refs., 11 figs

Real-time Holographic Display Based on a Super Fast Response Thin Film

International Nuclear Information System (INIS)

Gao, Hongyue; Li, Xiao; He, Zhenghong; Su, Yikai; Poon, Ting-Chung

2013-01-01

Real-time dynamic holographic display is obtained with super fast response in a thin film without any applied electric field. Holograms can be refreshed in the order of a millisecond and there is no cross talk between the recorded holograms because the hologram formed in the film is transient and can be completely self erased, and the hologram formation time and self-erasure time are both ∼1 ms. Holographic video display is achieved, which shows the real-time holographic image display capability of the thin film, and its much higher resolution than those of commercially available spatial light modulators. Furthermore, multiplexed hologram display using two polarization directions of a recorded light and multiple color holographic display at different laser wavelengths are presented, which demonstrate the feasibility of a RGB color holographic three-dimensional display with the thin film. Because the sample is easy to be fabricated into a large size screen and needs no external applied electric field, we think that the film can be developed into a large-size, dynamic, and color holographic three-dimensional display in the future.

Slow dynamics in translation-invariant quantum lattice models

Science.gov (United States)

Michailidis, Alexios A.; Žnidarič, Marko; Medvedyeva, Mariya; Abanin, Dmitry A.; Prosen, Tomaž; Papić, Z.

2018-03-01

Many-body quantum systems typically display fast dynamics and ballistic spreading of information. Here we address the open problem of how slow the dynamics can be after a generic breaking of integrability by local interactions. We develop a method based on degenerate perturbation theory that reveals slow dynamical regimes and delocalization processes in general translation invariant models, along with accurate estimates of their delocalization time scales. Our results shed light on the fundamental questions of the robustness of quantum integrable systems and the possibility of many-body localization without disorder. As an example, we construct a large class of one-dimensional lattice models where, despite the absence of asymptotic localization, the transient dynamics is exceptionally slow, i.e., the dynamics is indistinguishable from that of many-body localized systems for the system sizes and time scales accessible in experiments and numerical simulations.

Time-dependent scaling patterns in high frequency financial data

Science.gov (United States)

Nava, Noemi; Di Matteo, Tiziana; Aste, Tomaso

2016-10-01

We measure the influence of different time-scales on the intraday dynamics of financial markets. This is obtained by decomposing financial time series into simple oscillations associated with distinct time-scales. We propose two new time-varying measures of complexity: 1) an amplitude scaling exponent and 2) an entropy-like measure. We apply these measures to intraday, 30-second sampled prices of various stock market indices. Our results reveal intraday trends where different time-horizons contribute with variable relative amplitudes over the course of the trading day. Our findings indicate that the time series we analysed have a non-stationary multifractal nature with predominantly persistent behaviour at the middle of the trading session and anti-persistent behaviour at the opening and at the closing of the session. We demonstrate that these patterns are statistically significant, robust, reproducible and characteristic of each stock market. We argue that any modelling, analytics or trading strategy must take into account these non-stationary intraday scaling patterns.

The risk of shorter fasting time for pediatric deep sedation.

Science.gov (United States)

Clark, Mathew; Birisci, Esma; Anderson, Jordan E; Anliker, Christina M; Bryant, Micheal A; Downs, Craig; Dalabih, Abdallah

2016-01-01

Current guidelines adopted by the American Academy of Pediatrics calls for prolonged fasting times before performing pediatric procedural sedation and analgesia (PSA). PSA is increasingly provided to children outside of the operating theater by sedation trained pediatric providers and does not require airway manipulation. We investigated the safety of a shorter fasting time compared to a longer and guideline compliant fasting time. We tried to identify the association between fasting time and sedation-related complications. This is a prospective observational study that included children 2 months to 18 years of age and had an American Society of Anesthesiologists physical status classification of I or II, who underwent deep sedation for elective procedures, performed by pediatric critical care providers. Procedures included radiologic imaging studies, electroencephalograms, auditory brainstem response, echocardiograms, Botox injections, and other minor surgical procedures. Subjects were divided into two groups depending on the length of their fasting time (4-6 h and >6 h). Complication rates were calculated and compared between the three groups. In the studied group of 2487 subjects, 1007 (40.5%) had fasting time of 4-6 h and the remaining 1480 (59.5%) subjects had fasted for >6 h. There were no statistically significant differences in any of the studied complications between the two groups. This study found no difference in complication rate in regard to the fasting time among our subjects cohort, which included only healthy children receiving elective procedures performed by sedation trained pediatric critical care providers. This suggests that using shorter fasting time may be safe for procedures performed outside of the operating theater that does not involve high-risk patients or airway manipulation.

Mobile Charge Generation Dynamics in P3HT:PCBM Observed by Time-Resolved Terahertz Spectroscopy

DEFF Research Database (Denmark)

Cooke, D. G.; Krebs, Frederik C; Jepsen, Peter Uhd

2012-01-01

Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale.......Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale....

Mobile charge generation dynamics in P3HT: PCBM observed by time-resolved terahertz spectroscopy

DEFF Research Database (Denmark)

Cooke, D. G.; Krebs, Frederik C; Jepsen, Peter Uhd

2012-01-01

Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale.......Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale....

Thermodynamic modeling, energy equipartition, and nonconservation of entropy for discrete-time dynamical systems

Directory of Open Access Journals (Sweden)

Chellaboina Vijaysekhar

2005-01-01

Full Text Available We develop thermodynamic models for discrete-time large-scale dynamical systems. Specifically, using compartmental dynamical system theory, we develop energy flow models possessing energy conservation, energy equipartition, temperature equipartition, and entropy nonconservation principles for discrete-time, large-scale dynamical systems. Furthermore, we introduce a new and dual notion to entropy; namely, ectropy, as a measure of the tendency of a dynamical system to do useful work and grow more organized, and show that conservation of energy in an isolated thermodynamic system necessarily leads to nonconservation of ectropy and entropy. In addition, using the system ectropy as a Lyapunov function candidate, we show that our discrete-time, large-scale thermodynamic energy flow model has convergent trajectories to Lyapunov stable equilibria determined by the system initial subsystem energies.

Fast response of electron-scale turbulence to auxiliary heating cessation in National Spherical Torus Experiment

Energy Technology Data Exchange (ETDEWEB)

Ren, Y.; Wang, W. X.; LeBlanc, B. P.; Guttenfelder, W.; Kaye, S. M.; Ethier, S.; Mazzucato, E.; Bell, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Lee, K. C. [National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Domier, C. W. [University of California at Davis, Davis, California 95616 (United States); Smith, D. R. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yuh, H. [Nova Photonics, Inc., Princeton, New Jersey 08540 (United States)

2015-11-15

In this letter, we report the first observation of the fast response of electron-scale turbulence to auxiliary heating cessation in National Spherical Torus eXperiment [Ono et al., Nucl. Fusion 40, 557 (2000)]. The observation was made in a set of RF-heated L-mode plasmas with toroidal magnetic field of 0.55 T and plasma current of 300 kA. It is observed that electron-scale turbulence spectral power (measured with a high-k collective microwave scattering system) decreases significantly following fast cessation of RF heating that occurs in less than 200 μs. The large drop in the turbulence spectral power has a short time delay of about 1–2 ms relative to the RF cessation and happens on a time scale of 0.5–1 ms, much smaller than the energy confinement time of about 10 ms. Power balance analysis shows a factor of about 2 decrease in electron thermal diffusivity after the sudden drop of turbulence spectral power. Measured small changes in equilibrium profiles across the RF cessation are unlikely able to explain this sudden reduction in the measured turbulence and decrease in electron thermal transport, supported by local linear stability analysis and both local and global nonlinear gyrokinetic simulations. The observations imply that nonlocal flux-driven mechanism may be important for the observed turbulence and electron thermal transport.

Invited article: The fast readout low noise camera as a versatile x-ray detector for time resolved dispersive extended x-ray absorption fine structure and diffraction studies of dynamic problems in materials science, chemistry, and catalysis

International Nuclear Information System (INIS)

Labiche, Jean-Claude; Mathon, Olivier; Pascarelli, Sakura; Newton, Mark A.; Ferre, Gemma Guilera; Curfs, Caroline; Vaughan, Gavin; Homs, Alejandro; Carreiras, David Fernandez

2007-01-01

Originally conceived and developed at the European Synchrotron Radiation Facility (ESRF) as an 'area' detector for rapid x-ray imaging studies, the fast readout low noise (FReLoN) detector of the ESRF [J.-C. Labiche, ESRF Newsletter 25, 41 (1996)] has been demonstrated to be a highly versatile and unique detector. Charge coupled device (CCD) cameras at present available on the public market offer either a high dynamic range or a high readout speed. A compromise between signal dynamic range and readout speed is always sought. The parameters of the commercial cameras can sometimes be tuned, in order to better fulfill the needs of specific experiments, but in general these cameras have a poor duty cycle (i.e., the signal integration time is much smaller than the readout time). In order to address scientific problems such as time resolved experiments at the ESRF, a FReLoN camera has been developed by the Instrument Support Group at ESRF. This camera is a low noise CCD camera that combines high dynamic range, high readout speed, accuracy, and improved duty cycle in a single image. In this paper, we show its application in a quasi-one-dimensional sense to dynamic problems in materials science, catalysis, and chemistry that require data acquisition on a time scale of milliseconds or a few tens of milliseconds. It is demonstrated that in this mode the FReLoN can be applied equally to the investigation of rapid changes in long range order (via diffraction) and local order (via energy dispersive extended x-ray absorption fine structure) and in situations of x-ray hardness and flux beyond the capacity of other detectors

The length and time scales of water's glass transitions

Science.gov (United States)

Limmer, David T.

2014-06-01

Using a general model for the equilibrium dynamics of supercooled liquids, I compute from molecular properties the emergent length and time scales that govern the nonequilibrium relaxation behavior of amorphous ice prepared by rapid cooling. Upon cooling, the liquid water falls out of equilibrium whereby the temperature dependence of its relaxation time is predicted to change from super-Arrhenius to Arrhenius. A consequence of this crossover is that the location of the apparent glass transition temperature depends logarithmically on cooling rate. Accompanying vitrification is the emergence of a dynamical length-scale, the size of which depends on the cooling rate and varies between angstroms and tens of nanometers. While this protocol dependence clarifies a number of previous experimental observations for amorphous ice, the arguments are general and can be extended to other glass forming liquids.

The length and time scales of water's glass transitions.

Science.gov (United States)

Limmer, David T

2014-06-07

Using a general model for the equilibrium dynamics of supercooled liquids, I compute from molecular properties the emergent length and time scales that govern the nonequilibrium relaxation behavior of amorphous ice prepared by rapid cooling. Upon cooling, the liquid water falls out of equilibrium whereby the temperature dependence of its relaxation time is predicted to change from super-Arrhenius to Arrhenius. A consequence of this crossover is that the location of the apparent glass transition temperature depends logarithmically on cooling rate. Accompanying vitrification is the emergence of a dynamical length-scale, the size of which depends on the cooling rate and varies between angstroms and tens of nanometers. While this protocol dependence clarifies a number of previous experimental observations for amorphous ice, the arguments are general and can be extended to other glass forming liquids.

Feedback-Based Admission Control for Firm Real-Time Task Allocation with Dynamic Voltage and Frequency Scaling

Directory of Open Access Journals (Sweden)

Piotr Dziurzanski

2018-04-01

Full Text Available Feedback-based mechanisms can be employed to monitor the performance of Multiprocessor Systems-on-Chips (MPSoCs and steer the task execution even if the exact knowledge of the workload is unknown a priori. In particular, traditional proportional-integral controllers can be used with firm real-time tasks to either admit them to the processing cores or reject in order not to violate the timeliness of the already admitted tasks. During periods with a lower computational power demand, dynamic voltage and frequency scaling (DVFS can be used to reduce the dissipation of energy in the cores while still not violating the tasks’ time constraints. Depending on the workload pattern and weight, platform size and the granularity of DVFS, energy savings can reach even 60% at the cost of a slight performance degradation.

The magnetic monopole and the separation between fast and slow magnetic degrees of freedom.

Science.gov (United States)

Wegrowe, J-E; Olive, E

2016-03-16

The Landau-Lifshitz-Gilbert (LLG) equation that describes the dynamics of a macroscopic magnetic moment finds its limit of validity at very short times. The reason for this limit is well understood in terms of separation of the characteristic time scales between slow degrees of freedom (the magnetization) and fast degrees of freedom. The fast degrees of freedom are introduced as the variation of the angular momentum responsible for the inertia. In order to study the effect of the fast degrees of freedom on the precession, we calculate the geometric phase of the magnetization (i.e. the Hannay angle) and the corresponding magnetic monopole. In the case of the pure precession (the slow manifold), a simple expression of the magnetic monopole is given as a function of the slowness parameter, i.e. as a function of the ratio of the slow over the fast characteristic times.

The magnetic monopole and the separation between fast and slow magnetic degrees of freedom

International Nuclear Information System (INIS)

Wegrowe, J-E; Olive, E

2016-01-01

The Landau–Lifshitz–Gilbert (LLG) equation that describes the dynamics of a macroscopic magnetic moment finds its limit of validity at very short times. The reason for this limit is well understood in terms of separation of the characteristic time scales between slow degrees of freedom (the magnetization) and fast degrees of freedom. The fast degrees of freedom are introduced as the variation of the angular momentum responsible for the inertia. In order to study the effect of the fast degrees of freedom on the precession, we calculate the geometric phase of the magnetization (i.e. the Hannay angle) and the corresponding magnetic monopole. In the case of the pure precession (the slow manifold), a simple expression of the magnetic monopole is given as a function of the slowness parameter, i.e. as a function of the ratio of the slow over the fast characteristic times. (paper)

Cardiorespiratory dynamic response to mental stress: a multivariate time-frequency analysis.

Science.gov (United States)

Widjaja, Devy; Orini, Michele; Vlemincx, Elke; Van Huffel, Sabine

2013-01-01

Mental stress is a growing problem in our society. In order to deal with this, it is important to understand the underlying stress mechanisms. In this study, we aim to determine how the cardiorespiratory interactions are affected by mental arithmetic stress and attention. We conduct cross time-frequency (TF) analyses to assess the cardiorespiratory coupling. In addition, we introduce partial TF spectra to separate variations in the RR interval series that are linearly related to respiration from RR interval variations (RRV) that are not related to respiration. The performance of partial spectra is evaluated in two simulation studies. Time-varying parameters, such as instantaneous powers and frequencies, are derived from the computed spectra. Statistical analysis is carried out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3 s) than unrelated to (30 s) respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales.

Detection of fast oscillating magnetic fields using dynamic multiple TR imaging and Fourier analysis.

Directory of Open Access Journals (Sweden)

Ki Hwan Kim

Full Text Available Neuronal oscillations produce oscillating magnetic fields. There have been trials to detect neuronal oscillations using MRI, but the detectability in in vivo is still in debate. Major obstacles to detecting neuronal oscillations are (i weak amplitudes, (ii fast oscillations, which are faster than MRI temporal resolution, and (iii random frequencies and on/off intervals. In this study, we proposed a new approach for direct detection of weak and fast oscillating magnetic fields. The approach consists of (i dynamic acquisitions using multiple times to repeats (TRs and (ii an expanded frequency spectral analysis. Gradient echo echo-planar imaging was used to test the feasibility of the proposed approach with a phantom generating oscillating magnetic fields with various frequencies and amplitudes and random on/off intervals. The results showed that the proposed approach could precisely detect the weak and fast oscillating magnetic fields with random frequencies and on/off intervals. Complex and phase spectra showed reliable signals, while no meaningful signals were observed in magnitude spectra. A two-TR approach provided an absolute frequency spectrum above Nyquist sampling frequency pixel by pixel with no a priori target frequency information. The proposed dynamic multiple-TR imaging and Fourier analysis are promising for direct detection of neuronal oscillations and potentially applicable to any pulse sequences.

Scaling Laws in the Transient Dynamics of Firefly-like Oscillators

International Nuclear Information System (INIS)

Rubido, N; Cabeza, C; Marti, A; Ramirez Avila, G M

2011-01-01

Fireflies constitute a paradigm of pulse-coupled oscillators. In order to tackle the problems related to synchronisation transients of pulse-coupled oscillators, a Light-Controlled Oscillator (LCO) model is presented. A single LCO constitutes a one-dimensional relaxation oscillator described by two distinct time-scales meant to mimic fireflies in the sense that: it is capable of emitting light in a pulse-like fashion and detect the emitted by others in order to adjust its oscillation. We present dynamical results for two interacting LCOs in the torus for all possible coupling configurations. Transient times to the synchronous limit cycle are obtained experimentally and numerically as a function of initial conditions and coupling strengths. Scaling laws are found based on dimensional analysis and critical exponents calculated, thus, global dynamic is restricted. Furthermore, an analytical orthogonal transformation that allows to calculate Floquet multipliers directly from the time series is presented. As a consequence, local dynamics is also fully characterized. This transformation can be easily extended to a system with an arbitrary number of interacting LCOs.

Focusing light through dynamical samples using fast continuous wavefront optimization.

Science.gov (United States)

Blochet, B; Bourdieu, L; Gigan, S

2017-12-01

We describe a fast continuous optimization wavefront shaping system able to focus light through dynamic scattering media. A micro-electro-mechanical system-based spatial light modulator, a fast photodetector, and field programmable gate array electronics are combined to implement a continuous optimization of a wavefront with a single-mode optimization rate of 4.1 kHz. The system performances are demonstrated by focusing light through colloidal solutions of TiO 2 particles in glycerol with tunable temporal stability.

Geosynchronous magnetic field responses to fast solar wind dynamic pressure enhancements: MHD field model

Directory of Open Access Journals (Sweden)

T. R. Sun

2012-08-01

Full Text Available We performed global MHD simulations of the geosynchronous magnetic field in response to fast solar wind dynamic pressure (Pd enhancements. Taking three Pd enhancement events in 2000 as examples, we found that the main features of the total field B and the dominant component Bz can be efficiently predicted by the MHD model. The predicted B and Bz varies with local time, with the highest level near noon and a slightly lower level around mid-night. However, it is more challenging to accurately predict the responses of the smaller component at the geosynchronous orbit (i.e., Bx and By. In contrast, the limitations of T01 model in predicting responses to fast Pd enhancements are presented.

Near scale-free dynamics in neural population activity of waking/sleeping rats revealed by multiscale analysis.

Directory of Open Access Journals (Sweden)

Leonid A Safonov

Full Text Available A neuron embedded in an intact brain, unlike an isolated neuron, participates in network activity at various spatial resolutions. Such multiple scale spatial dynamics is potentially reflected in multiple time scales of temporal dynamics. We identify such multiple dynamical time scales of the inter-spike interval (ISI fluctuations of neurons of waking/sleeping rats by means of multiscale analysis. The time scale of large non-Gaussianity in the ISI fluctuations, measured with the Castaing method, ranges up to several minutes, markedly escaping the low-pass filtering characteristics of neurons. A comparison between neural activity during waking and sleeping reveals that non-Gaussianity is stronger during waking than sleeping throughout the entire range of scales observed. We find a remarkable property of near scale independence of the magnitude correlations as the primary cause of persistent non-Gaussianity. Such scale-invariance of correlations is characteristic of multiplicative cascade processes and raises the possibility of the existence of a scale independent memory preserving mechanism.

Numerical studies of fast ion slowing down rates in cool magnetized plasma using LSP

Science.gov (United States)

Evans, Eugene S.; Kolmes, Elijah; Cohen, Samuel A.; Rognlien, Tom; Cohen, Bruce; Meier, Eric; Welch, Dale R.

2016-10-01

In MFE devices, rapid transport of fusion products from the core into the scrape-off layer (SOL) could perform the dual roles of energy and ash removal. The first-orbit trajectories of most fusion products from small field-reversed configuration (FRC) devices will traverse the SOL, allowing those particles to deposit their energy in the SOL and be exhausted along the open field lines. Thus, the fast ion slowing-down time should affect the energy balance of an FRC reactor and its neutron emissions. However, the dynamics of fast ion energy loss processes under the conditions expected in the FRC SOL (with ρe code, to examine the effects of SOL density and background B-field on the slowing-down time of fast ions in a cool plasma. As we use explicit algorithms, these simulations must spatially resolve both ρe and λDe, as well as temporally resolve both Ωe and ωpe, increasing computation time. Scaling studies of the fast ion charge (Z) and background plasma density are in good agreement with unmagnetized slowing down theory. Notably, Z-scaling represents a viable way to dramatically reduce the required CPU time for each simulation. This work was supported, in part, by DOE Contract Number DE-AC02-09CH11466.

Improved scaling of temperature-accelerated dynamics using localization

Energy Technology Data Exchange (ETDEWEB)

Shim, Yunsic; Amar, Jacques G. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States)

2016-07-07

While temperature-accelerated dynamics (TAD) is a powerful method for carrying out non-equilibrium simulations of systems over extended time scales, the computational cost of serial TAD increases approximately as N{sup 3} where N is the number of atoms. In addition, although a parallel TAD method based on domain decomposition [Y. Shim et al., Phys. Rev. B 76, 205439 (2007)] has been shown to provide significantly improved scaling, the dynamics in such an approach is only approximate while the size of activated events is limited by the spatial decomposition size. Accordingly, it is of interest to develop methods to improve the scaling of serial TAD. As a first step in understanding the factors which determine the scaling behavior, we first present results for the overall scaling of serial TAD and its components, which were obtained from simulations of Ag/Ag(100) growth and Ag/Ag(100) annealing, and compare with theoretical predictions. We then discuss two methods based on localization which may be used to address two of the primary “bottlenecks” to the scaling of serial TAD with system size. By implementing both of these methods, we find that for intermediate system-sizes, the scaling is improved by almost a factor of N{sup 1/2}. Some additional possible methods to improve the scaling of TAD are also discussed.

Improved scaling of temperature-accelerated dynamics using localization

International Nuclear Information System (INIS)

Shim, Yunsic; Amar, Jacques G.

2016-01-01

While temperature-accelerated dynamics (TAD) is a powerful method for carrying out non-equilibrium simulations of systems over extended time scales, the computational cost of serial TAD increases approximately as N 3 where N is the number of atoms. In addition, although a parallel TAD method based on domain decomposition [Y. Shim et al., Phys. Rev. B 76, 205439 (2007)] has been shown to provide significantly improved scaling, the dynamics in such an approach is only approximate while the size of activated events is limited by the spatial decomposition size. Accordingly, it is of interest to develop methods to improve the scaling of serial TAD. As a first step in understanding the factors which determine the scaling behavior, we first present results for the overall scaling of serial TAD and its components, which were obtained from simulations of Ag/Ag(100) growth and Ag/Ag(100) annealing, and compare with theoretical predictions. We then discuss two methods based on localization which may be used to address two of the primary “bottlenecks” to the scaling of serial TAD with system size. By implementing both of these methods, we find that for intermediate system-sizes, the scaling is improved by almost a factor of N 1/2 . Some additional possible methods to improve the scaling of TAD are also discussed.

A data-driven prediction method for fast-slow systems

Science.gov (United States)

Groth, Andreas; Chekroun, Mickael; Kondrashov, Dmitri; Ghil, Michael

2016-04-01

In this work, we present a prediction method for processes that exhibit a mixture of variability on low and fast scales. The method relies on combining empirical model reduction (EMR) with singular spectrum analysis (SSA). EMR is a data-driven methodology for constructing stochastic low-dimensional models that account for nonlinearity and serial correlation in the estimated noise, while SSA provides a decomposition of the complex dynamics into low-order components that capture spatio-temporal behavior on different time scales. Our study focuses on the data-driven modeling of partial observations from dynamical systems that exhibit power spectra with broad peaks. The main result in this talk is that the combination of SSA pre-filtering with EMR modeling improves, under certain circumstances, the modeling and prediction skill of such a system, as compared to a standard EMR prediction based on raw data. Specifically, it is the separation into "fast" and "slow" temporal scales by the SSA pre-filtering that achieves the improvement. We show, in particular that the resulting EMR-SSA emulators help predict intermittent behavior such as rapid transitions between specific regions of the system's phase space. This capability of the EMR-SSA prediction will be demonstrated on two low-dimensional models: the Rössler system and a Lotka-Volterra model for interspecies competition. In either case, the chaotic dynamics is produced through a Shilnikov-type mechanism and we argue that the latter seems to be an important ingredient for the good prediction skills of EMR-SSA emulators. Shilnikov-type behavior has been shown to arise in various complex geophysical fluid models, such as baroclinic quasi-geostrophic flows in the mid-latitude atmosphere and wind-driven double-gyre ocean circulation models. This pervasiveness of the Shilnikow mechanism of fast-slow transition opens interesting perspectives for the extension of the proposed EMR-SSA approach to more realistic situations.

Nonequilibrium dynamic critical scaling of the quantum Ising chain.

Science.gov (United States)

Kolodrubetz, Michael; Clark, Bryan K; Huse, David A

2012-07-06

We solve for the time-dependent finite-size scaling functions of the one-dimensional transverse-field Ising chain during a linear-in-time ramp of the field through the quantum critical point. We then simulate Mott-insulating bosons in a tilted potential, an experimentally studied system in the same equilibrium universality class, and demonstrate that universality holds for the dynamics as well. We find qualitatively athermal features of the scaling functions, such as negative spin correlations, and we show that they should be robustly observable within present cold atom experiments.

Fast switching of bistable magnetic nanowires through collective spin reversal

Science.gov (United States)

Vindigni, Alessandro; Rettori, Angelo; Bogani, Lapo; Caneschi, Andrea; Gatteschi, Dante; Sessoli, Roberta; Novak, Miguel A.

2005-08-01

The use of magnetic nanowires as memory units is made possible by the exponential divergence of the characteristic time for magnetization reversal at low temperature, but the slow relaxation makes the manipulation of the frozen magnetic states difficult. We suggest that finite-size segments can show a fast switching if collective reversal of the spins is taken into account. This mechanism gives rise at low temperatures to a scaling law for the dynamic susceptibility that has been experimentally observed for the dilute molecular chain Co(hfac)2NitPhOMe. These results suggest a possible way of engineering nanowires for fast switching of the magnetization.

A massively parallel algorithm for the solution of constrained equations of motion with applications to large-scale, long-time molecular dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Fijany, A. [Jet Propulsion Lab., Pasadena, CA (United States); Coley, T.R. [Virtual Chemistry, Inc., San Diego, CA (United States); Cagin, T.; Goddard, W.A. III [California Institute of Technology, Pasadena, CA (United States)

1997-12-31

Successful molecular dynamics (MD) simulation of large systems (> million atoms) for long times (> nanoseconds) requires the integration of constrained equations of motion (CEOM). Constraints are used to eliminate high frequency degrees of freedom (DOF) and to allow the use of rigid bodies. Solving the CEOM allows for larger integration time-steps and helps focus the simulation on the important collective dynamics of chemical, biological, and materials systems. We explore advances in multibody dynamics which have resulted in O(N) algorithms for propagating the CEOM. However, because of their strictly sequential nature, the computational time required by these algorithms does not scale down with increased numbers of processors. We then present the new constraint force algorithm for solving the CEOM and show that this algorithm is fully parallelizable, leading to a computational cost of O(N/P+IogP) for N DOF on P processors.

Current-driven dynamics in molecular-scale devices

International Nuclear Information System (INIS)

Seideman, Tamar

2003-01-01

We review recent theoretical work on current-triggered processes in molecular-scale devices - a field at the interface between solid state physics and chemical dynamics with potential applications in diverse areas, including artificial molecular machines, unimolecular transport, surface nanochemistry and nanolithography. The qualitative physics underlying current-triggered dynamics is first discussed and placed in context with several well-studied phenomena with which it shares aspects. A theory for modelling these dynamics is next formulated within a time-dependent scattering approach. Our end result provides useful insight into the system properties that determine the reaction outcome as well as a computationally convenient framework for numerical realization. The theory is applied to study single-molecule surface reactions induced by a scanning tunnelling microscope and current-triggered dynamics in single-molecule transistors. We close with a discussion of several potential applications of current-induced dynamics in molecular devices and several opportunities for future research. (topical review)

Mouse Activity across Time Scales: Fractal Scenarios

Science.gov (United States)

Lima, G. Z. dos Santos; Lobão-Soares, B.; do Nascimento, G. C.; França, Arthur S. C.; Muratori, L.; Ribeiro, S.; Corso, G.

2014-01-01

In this work we devise a classification of mouse activity patterns based on accelerometer data using Detrended Fluctuation Analysis. We use two characteristic mouse behavioural states as benchmarks in this study: waking in free activity and slow-wave sleep (SWS). In both situations we find roughly the same pattern: for short time intervals we observe high correlation in activity - a typical 1/f complex pattern - while for large time intervals there is anti-correlation. High correlation of short intervals ( to : waking state and to : SWS) is related to highly coordinated muscle activity. In the waking state we associate high correlation both to muscle activity and to mouse stereotyped movements (grooming, waking, etc.). On the other side, the observed anti-correlation over large time scales ( to : waking state and to : SWS) during SWS appears related to a feedback autonomic response. The transition from correlated regime at short scales to an anti-correlated regime at large scales during SWS is given by the respiratory cycle interval, while during the waking state this transition occurs at the time scale corresponding to the duration of the stereotyped mouse movements. Furthermore, we find that the waking state is characterized by longer time scales than SWS and by a softer transition from correlation to anti-correlation. Moreover, this soft transition in the waking state encompass a behavioural time scale window that gives rise to a multifractal pattern. We believe that the observed multifractality in mouse activity is formed by the integration of several stereotyped movements each one with a characteristic time correlation. Finally, we compare scaling properties of body acceleration fluctuation time series during sleep and wake periods for healthy mice. Interestingly, differences between sleep and wake in the scaling exponents are comparable to previous works regarding human heartbeat. Complementarily, the nature of these sleep-wake dynamics could lead to a better

Transition Manifolds of Complex Metastable Systems: Theory and Data-Driven Computation of Effective Dynamics.

Science.gov (United States)

Bittracher, Andreas; Koltai, Péter; Klus, Stefan; Banisch, Ralf; Dellnitz, Michael; Schütte, Christof

2018-01-01

We consider complex dynamical systems showing metastable behavior, but no local separation of fast and slow time scales. The article raises the question of whether such systems exhibit a low-dimensional manifold supporting its effective dynamics. For answering this question, we aim at finding nonlinear coordinates, called reaction coordinates, such that the projection of the dynamics onto these coordinates preserves the dominant time scales of the dynamics. We show that, based on a specific reducibility property, the existence of good low-dimensional reaction coordinates preserving the dominant time scales is guaranteed. Based on this theoretical framework, we develop and test a novel numerical approach for computing good reaction coordinates. The proposed algorithmic approach is fully local and thus not prone to the curse of dimension with respect to the state space of the dynamics. Hence, it is a promising method for data-based model reduction of complex dynamical systems such as molecular dynamics.

Network dynamics with BrainX(3): a large-scale simulation of the human brain network with real-time interaction.

Science.gov (United States)

Arsiwalla, Xerxes D; Zucca, Riccardo; Betella, Alberto; Martinez, Enrique; Dalmazzo, David; Omedas, Pedro; Deco, Gustavo; Verschure, Paul F M J

2015-01-01

BrainX(3) is a large-scale simulation of human brain activity with real-time interaction, rendered in 3D in a virtual reality environment, which combines computational power with human intuition for the exploration and analysis of complex dynamical networks. We ground this simulation on structural connectivity obtained from diffusion spectrum imaging data and model it on neuronal population dynamics. Users can interact with BrainX(3) in real-time by perturbing brain regions with transient stimulations to observe reverberating network activity, simulate lesion dynamics or implement network analysis functions from a library of graph theoretic measures. BrainX(3) can thus be used as a novel immersive platform for exploration and analysis of dynamical activity patterns in brain networks, both at rest or in a task-related state, for discovery of signaling pathways associated to brain function and/or dysfunction and as a tool for virtual neurosurgery. Our results demonstrate these functionalities and shed insight on the dynamics of the resting-state attractor. Specifically, we found that a noisy network seems to favor a low firing attractor state. We also found that the dynamics of a noisy network is less resilient to lesions. Our simulations on TMS perturbations show that even though TMS inhibits most of the network, it also sparsely excites a few regions. This is presumably due to anti-correlations in the dynamics and suggests that even a lesioned network can show sparsely distributed increased activity compared to healthy resting-state, over specific brain areas.

Network dynamics with BrainX3: a large-scale simulation of the human brain network with real-time interaction

Science.gov (United States)

Arsiwalla, Xerxes D.; Zucca, Riccardo; Betella, Alberto; Martinez, Enrique; Dalmazzo, David; Omedas, Pedro; Deco, Gustavo; Verschure, Paul F. M. J.

2015-01-01

BrainX3 is a large-scale simulation of human brain activity with real-time interaction, rendered in 3D in a virtual reality environment, which combines computational power with human intuition for the exploration and analysis of complex dynamical networks. We ground this simulation on structural connectivity obtained from diffusion spectrum imaging data and model it on neuronal population dynamics. Users can interact with BrainX3 in real-time by perturbing brain regions with transient stimulations to observe reverberating network activity, simulate lesion dynamics or implement network analysis functions from a library of graph theoretic measures. BrainX3 can thus be used as a novel immersive platform for exploration and analysis of dynamical activity patterns in brain networks, both at rest or in a task-related state, for discovery of signaling pathways associated to brain function and/or dysfunction and as a tool for virtual neurosurgery. Our results demonstrate these functionalities and shed insight on the dynamics of the resting-state attractor. Specifically, we found that a noisy network seems to favor a low firing attractor state. We also found that the dynamics of a noisy network is less resilient to lesions. Our simulations on TMS perturbations show that even though TMS inhibits most of the network, it also sparsely excites a few regions. This is presumably due to anti-correlations in the dynamics and suggests that even a lesioned network can show sparsely distributed increased activity compared to healthy resting-state, over specific brain areas. PMID:25759649

Dynamic relations between fast-food restaurant and body weight status: a longitudinal and multilevel analysis of Chinese adults.

Science.gov (United States)

Xu, Hongwei; Short, Susan E; Liu, Tao

2013-03-01

Mixed findings have been reported on the association between Western fast-food restaurants and body weight status. Results vary across study contexts and are sensitive to the samples, measures and methods used. Most studies have failed to examine the temporally dynamic associations between community exposure to fast-food restaurants and weight changes. Bayesian hierarchical regressions are used to model changes in body mass index, waist-to-height ratio (WHtR) and waist-to-hip ratio (WHpR) as a function of changes in Western fast-food restaurants in 216 communities for more than 9000 Chinese adults followed up multiple times between 2000 and 2009. Number of Western fast-food restaurants is positively associated with subsequent increases in WHtR and WHpR among rural population. More fast-food restaurants are positively associated with a future increase in WHpR for urban women. Increased availability of fast food between two waves is related to increased WHtR for urban men over the same period. A past increase in number of fast-food restaurants is associated with subsequent increases in WHtR and WHpR for rural population. The associations between community exposure to Western fast food and weight changes are temporally dynamic rather than static. Improved measures of exposure to community environment are needed to achieve more precise estimates and better understanding of these relationships. In light of the findings in this study and China's rapid economic growth, further investigation and increased public health monitoring is warranted since Western fast food is likely to be more accessible and affordable in the near future.

Dynamic gas flow during plasma operation in TMX-U

International Nuclear Information System (INIS)

Pickles, W.L.; Carter, M.R.; Clower, C.A.; Drake, R.P.; Hunt, A.L.; Simonen, T.C.; Turner, W.C.

1982-01-01

Control of the neutral density outside of the plasma radius is essential for proper operation of the various plasma configurations in TMX-U. TMX-U excess-beam, stream-gun, gas-box, and beam-reflux gases are pumped internally in regions defined by 73 0 Ti-gettered liners and warm Ti-gettered plasma liners. The array of fast and slow ion gauges - a large TMX-U diagnostic - has been used to measure the dynamic pressure in many of the liner-defined regions on three time scales. The natural divertor action, or plasma pump effect, of mirror plasmas has been measured using the ion gauge diagnostics on a fast time scale during operation of TMX-U with ECRH start-up. Routine operation of TMX-U is enhanced by the ability to verify the effectiveness of gettering and to locate leaks using pressure data collected on the two slow time scales. A computer code, DYNAVAC 6, which treats TMX-U as a set of conductance-coupled regions with pumping and sources in each region, has been used to successfully model the overall gas dynamics during all phases of TMX-U operation

An ultrafast programmable electrical tester for enabling time-resolved, sub-nanosecond switching dynamics and programming of nanoscale memory devices

Science.gov (United States)

Shukla, Krishna Dayal; Saxena, Nishant; Manivannan, Anbarasu

2017-12-01

Recent advancements in commercialization of high-speed non-volatile electronic memories including phase change memory (PCM) have shown potential not only for advanced data storage but also for novel computing concepts. However, an in-depth understanding on ultrafast electrical switching dynamics is a key challenge for defining the ultimate speed of nanoscale memory devices that demands for an unconventional electrical setup, specifically capable of handling extremely fast electrical pulses. In the present work, an ultrafast programmable electrical tester (PET) setup has been developed exceptionally for unravelling time-resolved electrical switching dynamics and programming characteristics of nanoscale memory devices at the picosecond (ps) time scale. This setup consists of novel high-frequency contact-boards carefully designed to capture extremely fast switching transient characteristics within 200 ± 25 ps using time-resolved current-voltage measurements. All the instruments in the system are synchronized using LabVIEW, which helps to achieve various programming characteristics such as voltage-dependent transient parameters, read/write operations, and endurance test of memory devices systematically using short voltage pulses having pulse parameters varied from 1 ns rise/fall time and 1.5 ns pulse width (full width half maximum). Furthermore, the setup has successfully demonstrated strikingly one order faster switching characteristics of Ag5In5Sb60Te30 (AIST) PCM devices within 250 ps. Hence, this novel electrical setup would be immensely helpful for realizing the ultimate speed limits of various high-speed memory technologies for future computing.

Impact of Stock Market Structure on Intertrade Time and Price Dynamics

Science.gov (United States)

Ivanov, Plamen Ch.; Yuen, Ainslie; Perakakis, Pandelis

2014-01-01

We analyse times between consecutive transactions for a diverse group of stocks registered on the NYSE and NASDAQ markets, and we relate the dynamical properties of the intertrade times with those of the corresponding price fluctuations. We report that market structure strongly impacts the scale-invariant temporal organisation in the transaction timing of stocks, which we have observed to have long-range power-law correlations. Specifically, we find that, compared to NYSE stocks, stocks registered on the NASDAQ exhibit significantly stronger correlations in their transaction timing on scales within a trading day. Further, we find that companies that transfer from the NASDAQ to the NYSE show a reduction in the correlation strength of transaction timing on scales within a trading day, indicating influences of market structure. We also report a persistent decrease in correlation strength of intertrade times with increasing average intertrade time and with corresponding decrease in companies' market capitalization–a trend which is less pronounced for NASDAQ stocks. Surprisingly, we observe that stronger power-law correlations in intertrade times are coupled with stronger power-law correlations in absolute price returns and higher price volatility, suggesting a strong link between the dynamical properties of intertrade times and the corresponding price fluctuations over a broad range of time scales. Comparing the NYSE and NASDAQ markets, we demonstrate that the stronger correlations we find in intertrade times for NASDAQ stocks are associated with stronger correlations in absolute price returns and with higher volatility, suggesting that market structure may affect price behavior through information contained in transaction timing. These findings do not support the hypothesis of universal scaling behavior in stock dynamics that is independent of company characteristics and stock market structure. Further, our results have implications for utilising transaction timing

Impact of stock market structure on intertrade time and price dynamics.

Science.gov (United States)

Ivanov, Plamen Ch; Yuen, Ainslie; Perakakis, Pandelis

2014-01-01

We analyse times between consecutive transactions for a diverse group of stocks registered on the NYSE and NASDAQ markets, and we relate the dynamical properties of the intertrade times with those of the corresponding price fluctuations. We report that market structure strongly impacts the scale-invariant temporal organisation in the transaction timing of stocks, which we have observed to have long-range power-law correlations. Specifically, we find that, compared to NYSE stocks, stocks registered on the NASDAQ exhibit significantly stronger correlations in their transaction timing on scales within a trading day. Further, we find that companies that transfer from the NASDAQ to the NYSE show a reduction in the correlation strength of transaction timing on scales within a trading day, indicating influences of market structure. We also report a persistent decrease in correlation strength of intertrade times with increasing average intertrade time and with corresponding decrease in companies' market capitalization-a trend which is less pronounced for NASDAQ stocks. Surprisingly, we observe that stronger power-law correlations in intertrade times are coupled with stronger power-law correlations in absolute price returns and higher price volatility, suggesting a strong link between the dynamical properties of intertrade times and the corresponding price fluctuations over a broad range of time scales. Comparing the NYSE and NASDAQ markets, we demonstrate that the stronger correlations we find in intertrade times for NASDAQ stocks are associated with stronger correlations in absolute price returns and with higher volatility, suggesting that market structure may affect price behavior through information contained in transaction timing. These findings do not support the hypothesis of universal scaling behavior in stock dynamics that is independent of company characteristics and stock market structure. Further, our results have implications for utilising transaction timing

Relaxation dynamics following transition of solvated electrons

International Nuclear Information System (INIS)

Barnett, R.B.; Landman, U.; Nitzan, A.

1989-01-01

Relaxation dynamics following an electronic transition of an excess solvated electron in clusters and in bulk water is studied using an adiabatic simulation method. In this method the solvent evolves classically and the electron is constrained to a specified state. The coupling between the solvent and the excess electron is evaluated via the quantum expectation value of the electron--water molecule interaction potential. The relaxation following excitation (or deexcitation) is characterized by two time scales: (i) a very fast (/similar to/20--30 fs) one associated with molecular rotations in the first solvation shell about the electron, and (ii) a slower stage (/similar to/200 fs), which is of the order of the longitudinal dielectric relaxation time. The fast relaxation stage exhibits an isotope effect. The spectroscopical consequences of the relaxation dynamics are discussed

Nonlinear analysis of pupillary dynamics.

Science.gov (United States)

Onorati, Francesco; Mainardi, Luca Tommaso; Sirca, Fabiola; Russo, Vincenzo; Barbieri, Riccardo

2016-02-01

Pupil size reflects autonomic response to different environmental and behavioral stimuli, and its dynamics have been linked to other autonomic correlates such as cardiac and respiratory rhythms. The aim of this study is to assess the nonlinear characteristics of pupil size of 25 normal subjects who participated in a psychophysiological experimental protocol with four experimental conditions, namely “baseline”, “anger”, “joy”, and “sadness”. Nonlinear measures, such as sample entropy, correlation dimension, and largest Lyapunov exponent, were computed on reconstructed signals of spontaneous fluctuations of pupil dilation. Nonparametric statistical tests were performed on surrogate data to verify that the nonlinear measures are an intrinsic characteristic of the signals. We then developed and applied a piecewise linear regression model to detrended fluctuation analysis (DFA). Two joinpoints and three scaling intervals were identified: slope α0, at slow time scales, represents a persistent nonstationary long-range correlation, whereas α1 and α2, at middle and fast time scales, respectively, represent long-range power-law correlations, similarly to DFA applied to heart rate variability signals. Of the computed complexity measures, α0 showed statistically significant differences among experimental conditions (pnonlinear dynamics, (b) three well-defined and distinct long-memory processes exist at different time scales, and (c) autonomic stimulation is partially reflected in nonlinear dynamics. (c) autonomic stimulation is partially reflected in nonlinear dynamics.

Fast optical measurements and imaging of flow mixing

DEFF Research Database (Denmark)

Clausen, Sønnik; Fateev, Alexander; Nielsen, Karsten Lindorff

Project is focused on fast time-resolved infrared measurements of gas temperature and fast IR-imagining of flames in various combustion environments. The infrared spectrometer system was developed in the project for fast infrared spectral measurements on industrial scale using IR-fibre- optics. F...... engine and visualisation of gas flow behaviour in cylinder.......Project is focused on fast time-resolved infrared measurements of gas temperature and fast IR-imagining of flames in various combustion environments. The infrared spectrometer system was developed in the project for fast infrared spectral measurements on industrial scale using IR-fibre- optics....... Fast time-and spectral-resolved measurements in 1.5-5.1 μm spectral range give information about flame characteristics like gas and particle temperatures, eddies and turbulent gas mixing. Time-resolved gas composition in that spectral range (H2O, CH4, CO2, CO) which is one of the key parameters...

Overcoming time scale and finite size limitations to compute nucleation rates from small scale well tempered metadynamics simulations

Science.gov (United States)

Salvalaglio, Matteo; Tiwary, Pratyush; Maggioni, Giovanni Maria; Mazzotti, Marco; Parrinello, Michele

2016-12-01

Condensation of a liquid droplet from a supersaturated vapour phase is initiated by a prototypical nucleation event. As such it is challenging to compute its rate from atomistic molecular dynamics simulations. In fact at realistic supersaturation conditions condensation occurs on time scales that far exceed what can be reached with conventional molecular dynamics methods. Another known problem in this context is the distortion of the free energy profile associated to nucleation due to the small, finite size of typical simulation boxes. In this work the problem of time scale is addressed with a recently developed enhanced sampling method while contextually correcting for finite size effects. We demonstrate our approach by studying the condensation of argon, and showing that characteristic nucleation times of the order of magnitude of hours can be reliably calculated. Nucleation rates spanning a range of 10 orders of magnitude are computed at moderate supersaturation levels, thus bridging the gap between what standard molecular dynamics simulations can do and real physical systems.

JY1 time scale: a new Kalman-filter time scale designed at NIST

International Nuclear Information System (INIS)

Yao, Jian; Parker, Thomas E; Levine, Judah

2017-01-01

We report on a new Kalman-filter hydrogen-maser time scale (i.e. JY1 time scale) designed at the National Institute of Standards and Technology (NIST). The JY1 time scale is composed of a few hydrogen masers and a commercial Cs clock. The Cs clock is used as a reference clock to ease operations with existing data. Unlike other time scales, the JY1 time scale uses three basic time-scale equations, instead of only one equation. Also, this time scale can detect a clock error (i.e. time error, frequency error, or frequency drift error) automatically. These features make the JY1 time scale stiff and less likely to be affected by an abnormal clock. Tests show that the JY1 time scale deviates from the UTC by less than  ±5 ns for ∼100 d, when the time scale is initially aligned to the UTC and then is completely free running. Once the time scale is steered to a Cs fountain, it can maintain the time with little error even if the Cs fountain stops working for tens of days. This can be helpful when we do not have a continuously operated fountain or when the continuously operated fountain accidentally stops, or when optical clocks run occasionally. (paper)

Measuring Fast Calcium Fluxes in Cardiomyocytes

Science.gov (United States)

Golebiewska, Urszula; Scarlata, Suzanne

2011-01-01

Cardiomyocytes have multiple Ca2+ fluxes of varying duration that work together to optimize function 1,2. Changes in Ca2+ activity in response to extracellular agents is predominantly regulated by the phospholipase Cβ- Gαq pathway localized on the plasma membrane which is stimulated by agents such as acetylcholine 3,4. We have recently found that plasma membrane protein domains called caveolae5,6 can entrap activated Gαq7. This entrapment has the effect of stabilizing the activated state of Gαq and resulting in prolonged Ca2+ signals in cardiomyocytes and other cell types8. We uncovered this surprising result by measuring dynamic calcium responses on a fast scale in living cardiomyocytes. Briefly, cells are loaded with a fluorescent Ca2+ indicator. In our studies, we used Ca2+ Green (Invitrogen, Inc.) which exhibits an increase in fluorescence emission intensity upon binding of calcium ions. The fluorescence intensity is then recorded for using a line-scan mode of a laser scanning confocal microscope. This method allows rapid acquisition of the time course of fluorescence intensity in pixels along a selected line, producing several hundreds of time traces on the microsecond time scale. These very fast traces are transferred into excel and then into Sigmaplot for analysis, and are compared to traces obtained for electronic noise, free dye, and other controls. To dissect Ca2+ responses of different flux rates, we performed a histogram analysis that binned pixel intensities with time. Binning allows us to group over 500 traces of scans and visualize the compiled results spatially and temporally on a single plot. Thus, the slow Ca2+ waves that are difficult to discern when the scans are overlaid due to different peak placement and noise, can be readily seen in the binned histograms. Very fast fluxes in the time scale of the measurement show a narrow distribution of intensities in the very short time bins whereas longer Ca2+ waves show binned data with a broad

Analytical dynamic modeling of fast trilayer polypyrrole bending actuators

International Nuclear Information System (INIS)

Amiri Moghadam, Amir Ali; Moavenian, Majid; Tahani, Masoud; Torabi, Keivan

2011-01-01

Analytical modeling of conjugated polymer actuators with complicated electro-chemo-mechanical dynamics is an interesting area for research, due to the wide range of applications including biomimetic robots and biomedical devices. Although there have been extensive reports on modeling the electrochemical dynamics of polypyrrole (PPy) bending actuators, mechanical dynamics modeling of the actuators remains unexplored. PPy actuators can operate with low voltage while producing large displacement in comparison to robotic joints, they do not have friction or backlash, but they suffer from some disadvantages such as creep and hysteresis. In this paper, a complete analytical dynamic model for fast trilayer polypyrrole bending actuators has been proposed and named the analytical multi-domain dynamic actuator (AMDDA) model. First an electrical admittance model of the actuator will be obtained based on a distributed RC line; subsequently a proper mechanical dynamic model will be derived, based on Hamilton's principle. The purposed modeling approach will be validated based on recently published experimental results

Thermal quantum time-correlation functions from classical-like dynamics

Science.gov (United States)

Hele, Timothy J. H.

2017-07-01

Thermal quantum time-correlation functions are of fundamental importance in quantum dynamics, allowing experimentally measurable properties such as reaction rates, diffusion constants and vibrational spectra to be computed from first principles. Since the exact quantum solution scales exponentially with system size, there has been considerable effort in formulating reliable linear-scaling methods involving exact quantum statistics and approximate quantum dynamics modelled with classical-like trajectories. Here, we review recent progress in the field with the development of methods including centroid molecular dynamics , ring polymer molecular dynamics (RPMD) and thermostatted RPMD (TRPMD). We show how these methods have recently been obtained from 'Matsubara dynamics', a form of semiclassical dynamics which conserves the quantum Boltzmann distribution. We also apply the Matsubara formalism to reaction rate theory, rederiving t → 0+ quantum transition-state theory (QTST) and showing that Matsubara-TST, like RPMD-TST, is equivalent to QTST. We end by surveying areas for future progress.

Flow immune photoacoustic sensor for real-time and fast sampling of trace gases

Science.gov (United States)

Petersen, Jan C.; Balslev-Harder, David; Pelevic, Nikola; Brusch, Anders; Persijn, Stefan; Lassen, Mikael

2018-02-01

A photoacoustic (PA) sensor for fast and real-time gas sensing is demonstrated. The PA cell has been designed for flow noise immunity using computational fluid dynamics (CFD) analysis. PA measurements were conducted at different flow rates by exciting molecular C-H stretch vibrational bands of hexane (C6H14) in clean air at 2950cm-1 (3.38 μm) with a custom made mid-infrared interband cascade laser (ICL). The PA sensor will contribute to solve a major problem in a number of industries using compressed air by the detection of oil contaminants in high purity compressed air. We observe a (1σ, standard deviation) sensitivity of 0.4 +/-0.1 ppb (nmol/mol) for hexane in clean air at flow rates up to 2 L/min, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 2.5×10-9 W cm-1 Hz1/2, thus demonstrating high sensitivity and fast and real-time gas analysis. The PA sensor is not limited to molecules with C-H stretching modes, but can be tailored to measure any trace gas by simply changing the excitation wavelength (i.e. the laser source) making it useful for many different applications where fast and sensitive trace gas measurements are needed.

Scaling aspects of the sea-ice-drift dynamics and pack fracture

Directory of Open Access Journals (Sweden)

A. Chmel

2007-05-01

Full Text Available A study of the sea-ice dynamics in the periods of time prior to and during the cycles of basin-wide fragmentation of the ice cover in the Arctic Ocean is presented. The fractal geometry of the ice-sheets limited by leads and ridges was assessed using the satellite images, while the data on the correlated sea-ice motion were obtained in the research stations "North Pole 32" and "North Pole 33" established on the ice pack. The revealed decrease of the fractal dimension as a result of large-scale fragmentation is consistent with the localization of the fracture process (leads propagation. At the same time, the scaling properties of the distribution of amplitudes of ice-fields accelerations were insensitive to the event of sea-ice fragmentation. The temporal distribution of the accelerations was scale-invariant during "quiet" periods of sea-ice drift but disordered in the period of mechanical perturbation. The period of decorrelated (in time ice-field motion during the important fracture event was interpreted as an inter-level transition in the hierarchic dynamical system. The mechanism of the long-range correlations in the sea-ice cover, including the fracture process, is suggested to be in relation with the self-organized oscillation dynamics inherent in the ice pack.

Large-scale micromagnetics simulations with dipolar interaction using all-to-all communications

Directory of Open Access Journals (Sweden)

Hiroshi Tsukahara

2016-05-01

Full Text Available We implement on our micromagnetics simulator low-complexity parallel fast-Fourier-transform algorithms, which reduces the frequency of all-to-all communications from six to two times. Almost all the computation time of micromagnetics simulation is taken up by the calculation of the magnetostatic field which can be calculated using the fast Fourier transform method. The results show that the simulation time is decreased with good scalability, even if the micromagentics simulation is performed using 8192 physical cores. This high parallelization effect enables large-scale micromagentics simulation using over one billion to be performed. Because massively parallel computing is needed to simulate the magnetization dynamics of real permanent magnets composed of many micron-sized grains, it is expected that our simulator reveals how magnetization dynamics influences the coercivity of the permanent magnet.

A predator-2 prey fast-slow dynamical system for rapid predator evolution

DEFF Research Database (Denmark)

Piltz, Sofia Helena; Veerman, Frits; Maini, Philip K.

2017-01-01

We consider adaptive change of diet of a predator population that switches its feeding between two prey populations. We develop a novel 1 fast-3 slow dynamical system to describe the dynamics of the three populations amidst continuous but rapid evolution of the predator's diet choice. The two ext...

Radiation assisted thermonuclear burn wave dynamics in heavy ion fast ignition of cylindrical deuterium-tritium fuel target

International Nuclear Information System (INIS)

Rehman, S.; Kouser, R.; Nazir, R.; Manzoor, Z.; Tasneem, G.; Jehan, N.; Nasim, M.H.; Salahuddin, M.

2015-01-01

Dynamics of thermonuclear burn wave propagation assisted by thermal radiation precursor in a heavy ion fast ignition of cylindrical deuterium-tritium (DT) fuel target are studied by two dimensional radiation hydrodynamic simulations using Multi-2D code. Thermal radiations, as they propagate ahead of the burn wave, suffer multiple reflections and preheat the fuel, are found to play a vital role in burn wave dynamics. After fuel ignition, the burn wave propagates in a steady state manner for some time. Multiple reflection and absorption of radiation at the fuel-tamper interface, fuel ablation and radial implosion driven by ablative shock and fast fusion rates on the fuel axis, at relatively later times, result into filamentary wave front. Strong pressure gradients are developed and sausage like structures behind the front are appeared. The situation leads to relatively reduced and non-uniform radial fuel burning and burn wave propagation. The fuel burning due to DD reaction is also taken into account and overall fusion energy and fusion power density, due to DT and DD reactions, during the burn wave propagation are determined as a function of time. (authors)

A limit set trichotomy for order-preserving systems on time scales

Directory of Open Access Journals (Sweden)

Christian Poetzsche

2004-04-01

Full Text Available In this paper we derive a limit set trichotomy for abstract order-preserving 2-parameter semiflows in normal cones of strongly ordered Banach spaces. Additionally, to provide an example, Muller's theorem is generalized to dynamic equations on arbitrary time scales and applied to a model from population dynamics.

Fractal differential equations and fractal-time dynamical systems

Indian Academy of Sciences (India)

like fractal subsets of the real line may be termed as fractal-time dynamical systems. Formulation ... involving scaling and memory effects. But most of ..... begin by recalling the definition of the Riemann integral in ordinary calculus [33]. Let g: [a ...

Interactions of district electricity and heating systems considering time-scale characteristics based on quasi-steady multi-energy flow

International Nuclear Information System (INIS)

Pan, Zhaoguang; Guo, Qinglai; Sun, Hongbin

2016-01-01

Highlights: • Interaction mechanisms of district electricity and heating systems are analyzed. • The interaction process is divided into four quasi-steady stages. • A quasi-steady multi-energy flow model is proposed and calculated. • A heating network node type transformation technique is developed. • Attention should be paid on the fast hydraulic process and slow thermal process. - Abstract: Integrated energy systems (IESs) are under development for a variety of benefits. District electricity and heating systems (DEHSs) deliver electricity and heat, the most common energy demands, to end-users. This paper studies the interactions in a DEHS considering the time-scale characteristics. Interaction mechanisms of a DEHS are analyzed. A disturbance in one system influences another system through coupling components, depending on the disturbance, operating characteristics, and control strategies. A model of the main components in DEHSs is presented. The time scale characteristics are studied based on a dynamic comparison of the different components. Then the interaction process is divided into four stages; each is a quasi-steady state. A quasi-steady multi-energy flow model is proposed and calculated, with a heating network node type transformation technique developed. A case study with detailed results and discussion of 3 types of disturbance is presented to verify the methods. The results present the interactions between the electricity and the system. It is suggested that attention should be paid both on the fast hydraulic process and slow thermal process for system security and economic operation.

The Role of Fast Carrier Dynamics in SOA Based Devices

DEFF Research Database (Denmark)

Mørk, Jesper; Berg, Tommy Winther; Nielsen, Mads Lønstrup

2004-01-01

and the properties of schemes relying on cross-gain as well as cross-phase modulation are discussed. The possible benefits of using SOAs with quantum dot active regions are theoretically analyzed. The bandfilling characteristics and the presence of fast capture processes may allow to reach bitrates in excess of 100......We describe the characteristics of all-optical switching schemes based on semiconductor optical amplifiers (SOAs), with particular emphasis on the role of the fast carrier dynamics. The SOA response to a single short pulse as well as to a data-modulated pulse train is investigated...

A two-time-scale dynamic-model approach for magnetic and kinetic profile control in advanced tokamak scenarios on JET

International Nuclear Information System (INIS)

Moreau, D.; Mazon, D.; Ariola, M.; Tommasi, G. De; Laborde, L.; Piccolo, F.; Sartori, F.; Zabeo, L.; Boboc, A.; Brix, M.; Challis, C.D.; Felton, R.; Hawkes, N.; Tala, T.; Bouvier, E.; Cordoliani, V.; Brzozowski, J.; Cocilovo, V.; Crisanti, F.; Luna, E. de la

2008-01-01

Real-time simultaneous control of several radially distributed magnetic and kinetic plasma parameters is being investigated on JET, in view of developing integrated control of advanced tokamak scenarios. This paper describes the new model-based profile controller which has been implemented during the 2006-2007 experimental campaigns. The controller aims to use the combination of heating and current drive (H and CD) systems-and optionally the poloidal field (PF) system-in an optimal way to regulate the evolution of plasma parameter profiles such as the safety factor, q(x), and gyro-normalized temperature gradient, ρ Te *(x). In the first part of the paper, a technique for the experimental identification of a minimal dynamic plasma model is described, taking into account the physical structure and couplings of the transport equations, but making no quantitative assumptions on the transport coefficients or on their dependences. To cope with the high dimensionality of the state space and the large ratio between the time scales involved, the model identification procedure and the controller design both make use of the theory of singularly perturbed systems by means of a two-time-scale approximation. The second part of the paper provides the theoretical basis for the controller design. The profile controller is articulated around two composite feedback loops operating on the magnetic and kinetic time scales, respectively, and supplemented by a feedforward compensation of density variations. For any chosen set of target profiles, the closest self-consistent state achievable with the available actuators is uniquely defined. It is reached, with no steady state offset, through a near-optimal proportional-integral control algorithm. Conventional optimal control is recovered in the limiting case where the ratio of the plasma confinement time to the resistive diffusion time tends to zero. Closed-loop simulations of the controller response have been performed in preparation for

Transcription factor assisted loading and enhancer dynamics dictate the hepatic fasting response

Science.gov (United States)

Goldstein, Ido; Baek, Songjoon; Presman, Diego M.; Paakinaho, Ville; Swinstead, Erin E.; Hager, Gordon L.

2017-01-01

Fasting elicits transcriptional programs in hepatocytes leading to glucose and ketone production. This transcriptional program is regulated by many transcription factors (TFs). To understand how this complex network regulates the metabolic response to fasting, we aimed at isolating the enhancers and TFs dictating it. Measuring chromatin accessibility revealed that fasting massively reorganizes liver chromatin, exposing numerous fasting-induced enhancers. By utilizing computational methods in combination with dissecting enhancer features and TF cistromes, we implicated four key TFs regulating the fasting response: glucocorticoid receptor (GR), cAMP responsive element binding protein 1 (CREB1), peroxisome proliferator activated receptor alpha (PPARA), and CCAAT/enhancer binding protein beta (CEBPB). These TFs regulate fuel production by two distinctly operating modules, each controlling a separate metabolic pathway. The gluconeogenic module operates through assisted loading, whereby GR doubles the number of sites occupied by CREB1 as well as enhances CREB1 binding intensity and increases accessibility of CREB1 binding sites. Importantly, this GR-assisted CREB1 binding was enhancer-selective and did not affect all CREB1-bound enhancers. Single-molecule tracking revealed that GR increases the number and DNA residence time of a portion of chromatin-bound CREB1 molecules. These events collectively result in rapid synergistic gene expression and higher hepatic glucose production. Conversely, the ketogenic module operates via a GR-induced TF cascade, whereby PPARA levels are increased following GR activation, facilitating gradual enhancer maturation next to PPARA target genes and delayed ketogenic gene expression. Our findings reveal a complex network of enhancers and TFs that dynamically cooperate to restore homeostasis upon fasting. PMID:28031249

Space-Time Dynamics of Soil Moisture and Temperature: Scale issues

Science.gov (United States)

Mohanty, Binayak P.; Miller, Douglas A.; Th.vanGenuchten, M.

2003-01-01

The goal of this project is to gain further understanding of soil moisture/temperature dynamics at different spatio-temporal scales and physical controls/parameters.We created a comprehensive GIS database, which has been accessed extensively by NASA Land Surface Hydrology investigators (and others), is located at the following URL: http://www.essc.psu.edu/nasalsh. For soil moisture field experiments such as SGP97, SGP99, SMEX02, and SMEX03, cartographic products were designed for multiple applications, both pre- and post-mission. Premission applications included flight line planning and field operations logistics, as well as general insight into the extent and distribution of soil, vegetation, and topographic properties for the study areas. The cartographic products were created from original spatial information resources that were imported into Adobe Illustrator, where the maps were created and PDF versions were made for distribution and download.

Fasting, circadian rhythms, and time restricted feeding in healthy lifespan

Science.gov (United States)

Longo, Valter D.; Panda, Satchidananda

2016-01-01

Summary Feeding in most animals is confined to a defined period, leaving short periods of fasting that coincide with sleep. Fasting enables organisms to enter alternative metabolic phases, which rely less on glucose and more on ketone body-like carbon sources. Both intermittent and periodic fasting result in benefits ranging from prevention to the enhanced treatment of diseases. Similarly, time-restricted feeding (TRF), in which feeding time is restricted to certain hours of the day, allows the daily fasting period to last >12 h, thus imparting pleiotropic benefits in multiple organisms. Understanding the mechanistic link between nutrients and the fasting benefits is leading to the identification of fasting mimicking diets (FMDs) that achieve changes similar to those caused by fasting. Given the pleiotropic and sustained benefits of TRF and FMD, both basic science and translational research are warranted to develop fasting-associated interventions into effective and inexpensive treatments with the potential to improve healthspan. PMID:27304506

Antipersistent dynamics in short time scale variability of self-potential signals

OpenAIRE

Cuomo, V.; Lanfredi, M.; Lapenna, V.; Macchiato, M.; Ragosta, M.; Telesca, L.

2000-01-01

Time scale properties of self-potential signals are investigated through the analysis of the second order structure function (variogram), a powerful tool to investigate the spatial and temporal variability of observational data. In this work we analyse two sequences of self-potential values measured by means of a geophysical monitoring array located in a seismically active area of Southern Italy. The range of scales investigated goes from a few minutes to several days. It is shown that signal...

Elucidating dynamic metabolic physiology through network integration of quantitative time-course metabolomics

DEFF Research Database (Denmark)

Bordbar, Aarash; Yurkovich, James T.; Paglia, Giuseppe

2017-01-01

The increasing availability of metabolomics data necessitates novel methods for deeper data analysis and interpretation. We present a flux balance analysis method that allows for the computation of dynamic intracellular metabolic changes at the cellular scale through integration of time-course ab......The increasing availability of metabolomics data necessitates novel methods for deeper data analysis and interpretation. We present a flux balance analysis method that allows for the computation of dynamic intracellular metabolic changes at the cellular scale through integration of time...

Fast regional readout CMOS Image Sensor for dynamic MLC tracking

Science.gov (United States)

Zin, H.; Harris, E.; Osmond, J.; Evans, P.

2014-03-01

Advanced radiotherapy techniques such as volumetric modulated arc therapy (VMAT) require verification of the complex beam delivery including tracking of multileaf collimators (MLC) and monitoring the dose rate. This work explores the feasibility of a prototype Complementary metal-oxide semiconductor Image Sensor (CIS) for tracking these complex treatments by utilising fast, region of interest (ROI) read out functionality. An automatic edge tracking algorithm was used to locate the MLC leaves edges moving at various speeds (from a moving triangle field shape) and imaged with various sensor frame rates. The CIS demonstrates successful edge detection of the dynamic MLC motion within accuracy of 1.0 mm. This demonstrates the feasibility of the sensor to verify treatment delivery involving dynamic MLC up to ~400 frames per second (equivalent to the linac pulse rate), which is superior to any current techniques such as using electronic portal imaging devices (EPID). CIS provides the basis to an essential real-time verification tool, useful in accessing accurate delivery of complex high energy radiation to the tumour and ultimately to achieve better cure rates for cancer patients.

Fast regional readout CMOS image sensor for dynamic MLC tracking

International Nuclear Information System (INIS)

Zin, H; Harris, E; Osmond, J; Evans, P

2014-01-01

Advanced radiotherapy techniques such as volumetric modulated arc therapy (VMAT) require verification of the complex beam delivery including tracking of multileaf collimators (MLC) and monitoring the dose rate. This work explores the feasibility of a prototype Complementary metal-oxide semiconductor Image Sensor (CIS) for tracking these complex treatments by utilising fast, region of interest (ROI) read out functionality. An automatic edge tracking algorithm was used to locate the MLC leaves edges moving at various speeds (from a moving triangle field shape) and imaged with various sensor frame rates. The CIS demonstrates successful edge detection of the dynamic MLC motion within accuracy of 1.0 mm. This demonstrates the feasibility of the sensor to verify treatment delivery involving dynamic MLC up to ∼400 frames per second (equivalent to the linac pulse rate), which is superior to any current techniques such as using electronic portal imaging devices (EPID). CIS provides the basis to an essential real-time verification tool, useful in accessing accurate delivery of complex high energy radiation to the tumour and ultimately to achieve better cure rates for cancer patients.

Chimeric β-Lactamases: Global Conservation of Parental Function and Fast Time-Scale Dynamics with Increased Slow Motions

Science.gov (United States)

Clouthier, Christopher M.; Morin, Sébastien; Gobeil, Sophie M. C.; Doucet, Nicolas; Blanchet, Jonathan; Nguyen, Elisabeth; Gagné, Stéphane M.; Pelletier, Joelle N.

2012-01-01

Enzyme engineering has been facilitated by recombination of close homologues, followed by functional screening. In one such effort, chimeras of two class-A β-lactamases – TEM-1 and PSE-4 – were created according to structure-guided protein recombination and selected for their capacity to promote bacterial proliferation in the presence of ampicillin (Voigt et al., Nat. Struct. Biol. 2002 9:553). To provide a more detailed assessment of the effects of protein recombination on the structure and function of the resulting chimeric enzymes, we characterized a series of functional TEM-1/PSE-4 chimeras possessing between 17 and 92 substitutions relative to TEM-1 β-lactamase. Circular dichroism and thermal scanning fluorimetry revealed that the chimeras were generally well folded. Despite harbouring important sequence variation relative to either of the two ‘parental’ β-lactamases, the chimeric β-lactamases displayed substrate recognition spectra and reactivity similar to their most closely-related parent. To gain further insight into the changes induced by chimerization, the chimera with 17 substitutions was investigated by NMR spin relaxation. While high order was conserved on the ps-ns timescale, a hallmark of class A β-lactamases, evidence of additional slow motions on the µs-ms timescale was extracted from model-free calculations. This is consistent with the greater number of resonances that could not be assigned in this chimera relative to the parental β-lactamases, and is consistent with this well-folded and functional chimeric β-lactamase displaying increased slow time-scale motions. PMID:23284969

Petascale molecular dynamics simulation using the fast multipole method on K computer

KAUST Repository

Ohno, Yousuke; Yokota, Rio; Koyama, Hiroshi; Morimoto, Gentaro; Hasegawa, Aki; Masumoto, Gen; Okimoto, Noriaki; Hirano, Yoshinori; Ibeid, Huda; Narumi, Tetsu; Taiji, Makoto

2014-01-01

In this paper, we report all-atom simulations of molecular crowding - a result from the full node simulation on the "K computer", which is a 10-PFLOPS supercomputer in Japan. The capability of this machine enables us to perform simulation of crowded cellular environments, which are more realistic compared to conventional MD simulations where proteins are simulated in isolation. Living cells are "crowded" because macromolecules comprise ∼30% of their molecular weight. Recently, the effects of crowded cellular environments on protein stability have been revealed through in-cell NMR spectroscopy. To measure the performance of the "K computer", we performed all-atom classical molecular dynamics simulations of two systems: target proteins in a solvent, and target proteins in an environment of molecular crowders that mimic the conditions of a living cell. Using the full system, we achieved 4.4 PFLOPS during a 520 million-atom simulation with cutoff of 28 Å. Furthermore, we discuss the performance and scaling of fast multipole methods for molecular dynamics simulations on the "K computer", as well as comparisons with Ewald summation methods. © 2014 Elsevier B.V. All rights reserved.

Petascale molecular dynamics simulation using the fast multipole method on K computer

KAUST Repository

Ohno, Yousuke

2014-10-01

In this paper, we report all-atom simulations of molecular crowding - a result from the full node simulation on the "K computer", which is a 10-PFLOPS supercomputer in Japan. The capability of this machine enables us to perform simulation of crowded cellular environments, which are more realistic compared to conventional MD simulations where proteins are simulated in isolation. Living cells are "crowded" because macromolecules comprise ∼30% of their molecular weight. Recently, the effects of crowded cellular environments on protein stability have been revealed through in-cell NMR spectroscopy. To measure the performance of the "K computer", we performed all-atom classical molecular dynamics simulations of two systems: target proteins in a solvent, and target proteins in an environment of molecular crowders that mimic the conditions of a living cell. Using the full system, we achieved 4.4 PFLOPS during a 520 million-atom simulation with cutoff of 28 Å. Furthermore, we discuss the performance and scaling of fast multipole methods for molecular dynamics simulations on the "K computer", as well as comparisons with Ewald summation methods. © 2014 Elsevier B.V. All rights reserved.

Characterizing Motif Dynamics of Electric Brain Activity Using Symbolic Analysis

Directory of Open Access Journals (Sweden)

Massimiliano Zanin

2014-10-01

Full Text Available Motifs are small recurring circuits of interactions which constitute the backbone of networked systems. Characterizing motif dynamics is therefore key to understanding the functioning of such systems. Here we propose a method to define and quantify the temporal variability and time scales of electroencephalogram (EEG motifs of resting brain activity. Given a triplet of EEG sensors, links between them are calculated by means of linear correlation; each pattern of links (i.e., each motif is then associated to a symbol, and its appearance frequency is analyzed by means of Shannon entropy. Our results show that each motif becomes observable with different coupling thresholds and evolves at its own time scale, with fronto-temporal sensors emerging at high thresholds and changing at fast time scales, and parietal ones at low thresholds and changing at slower rates. Finally, while motif dynamics differed across individuals, for each subject, it showed robustness across experimental conditions, indicating that it could represent an individual dynamical signature.

Reducing preoperative fasting time: A trend based on evidence

OpenAIRE

de Aguilar-Nascimento, José Eduardo; Dock-Nascimento, Diana Borges

2010-01-01

Preoperative fasting is mandatory before anesthesia to reduce the risk of aspiration. However, the prescribed 6-8 h of fasting is usually prolonged to 12-16 h for various reasons. Prolonged fasting triggers a metabolic response that precipitates gluconeogenesis and increases the organic response to trauma. Various randomized trials and meta-analyses have consistently shown that is safe to reduce the preoperative fasting time with a carbohydrate-rich drink up to 2 h before surgery. Benefits re...

Parametric control of structural vibrations and sound radiation by fast time-space variation of distributed stiffness parameters

International Nuclear Information System (INIS)

Krylov, V.I.; Sorokin, S.V.

1998-01-01

The dynamics of a Euler-Bernoulli beam with a time-and-space dependent bending stiffness is studied. The , problem is considered in connection with the application of noise control using smart structures. It is shown that a control for the vibrations of the beam can be achieved by varying the bending stiffness. The technique of direct separation of fast and slow motion coupled with a Green's function method is used to analyze the dynamics of the beam with high-frequency modulation of the stiffness

Dynamic Modeling and Real-Time Monitoring of Froth Flotation

Directory of Open Access Journals (Sweden)

Khushaal Popli

2015-08-01

Full Text Available A dynamic fundamental model was developed linking processes from the microscopic scale to the equipment scale for batch froth flotation. State estimation, fault detection, and disturbance identification were implemented using the extended Kalman filter (EKF, which reconciles real-time measurements with dynamic models. The online measurements for the EKF were obtained through image analysis of froth images that were captured and analyzed using the commercial package VisioFroth (Metsor Minerals. The extracted image features were then correlated to recovery using principal component analysis and partial least squares regression. The performance of real-time state estimation and fault detection was validated using batch flotation of pure galena at various operating conditions. The image features that were strongly representative of recovery were identified, and calibration and validation were performed against off-line measurements of recovery. The EKF successfully captured the dynamics of the process by updating the model states and parameters using the online measurements. Finally, disturbances in the air flow rate and impeller speed were introduced into the system, and the dynamic behavior of the flotation process was successfully tracked and the disturbances were identified using state estimation.

Sensory information in local field potentials and spikes from visual and auditory cortices: time scales and frequency bands.

Science.gov (United States)

Belitski, Andrei; Panzeri, Stefano; Magri, Cesare; Logothetis, Nikos K; Kayser, Christoph

2010-12-01

Studies analyzing sensory cortical processing or trying to decode brain activity often rely on a combination of different electrophysiological signals, such as local field potentials (LFPs) and spiking activity. Understanding the relation between these signals and sensory stimuli and between different components of these signals is hence of great interest. We here provide an analysis of LFPs and spiking activity recorded from visual and auditory cortex during stimulation with natural stimuli. In particular, we focus on the time scales on which different components of these signals are informative about the stimulus, and on the dependencies between different components of these signals. Addressing the first question, we find that stimulus information in low frequency bands (50 Hz), in contrast, is scale dependent, and is larger when the energy is averaged over several hundreds of milliseconds. Indeed, combined analysis of signal reliability and information revealed that the energy of slow LFP fluctuations is well related to the stimulus even when considering individual or few cycles, while the energy of fast LFP oscillations carries information only when averaged over many cycles. Addressing the second question, we find that stimulus information in different LFP bands, and in different LFP bands and spiking activity, is largely independent regardless of time scale or sensory system. Taken together, these findings suggest that different LFP bands represent dynamic natural stimuli on distinct time scales and together provide a potentially rich source of information for sensory processing or decoding brain activity.

Time Scale Analysis of Interest Rate Spreads and Output Using Wavelets

Directory of Open Access Journals (Sweden)

Marco Gallegati

2013-04-01

Full Text Available This paper adds to the literature on the information content of different spreads for real activity by explicitly taking into account the time scale relationship between a variety of monetary and financial indicators (real interest rate, term and credit spreads and output growth. By means of wavelet-based exploratory data analysis we obtain richer results relative to the aggregate analysis by identifying the dominant scales of variation in the data and the scales and location at which structural breaks have occurred. Moreover, using the “double residuals” regression analysis on a scale-by-scale basis, we find that changes in the spread in several markets have different information content for output at different time frames. This is consistent with the idea that allowing for different time scales of variation in the data can provide a fruitful understanding of the complex dynamics of economic relationships between variables with non-stationary or transient components, certainly richer than those obtained using standard time domain methods.

Scale and size effects in dynamic fracture of concretes and rocks

Directory of Open Access Journals (Sweden)

Petrov Y.

2015-01-01

Full Text Available Structural-temporal approach based on the notion of incubation time is used for interpretation of strain-rate effects in the fracture process of concretes and rocks. It is established that temporal dependences of concretes and rocks are calculated by the incubation time criterion. Experimentally observed different relations between ultimate stresses of concrete and mortar in static and dynamic conditions are explained. It is obtained that compressive strength of mortar at a low strain rate is greater than that of concrete, but at a high strain rate the opposite is true. Influence of confinement pressure on the mechanism of dynamic strength for concretes and rocks is discussed. Both size effect and scale effect for concrete and rocks samples subjected to impact loading are analyzed. Statistical nature of a size effect contrasts to a scale effect that is related to the definition of a spatio-temporal representative volume determining the fracture event on the given scale level.

Modeling and control of a large nuclear reactor. A three-time-scale approach

Energy Technology Data Exchange (ETDEWEB)

Shimjith, S.R. [Indian Institute of Technology Bombay, Mumbai (India); Bhabha Atomic Research Centre, Mumbai (India); Tiwari, A.P. [Bhabha Atomic Research Centre, Mumbai (India); Bandyopadhyay, B. [Indian Institute of Technology Bombay, Mumbai (India). IDP in Systems and Control Engineering

2013-07-01

Recent research on Modeling and Control of a Large Nuclear Reactor. Presents a three-time-scale approach. Written by leading experts in the field. Control analysis and design of large nuclear reactors requires a suitable mathematical model representing the steady state and dynamic behavior of the reactor with reasonable accuracy. This task is, however, quite challenging because of several complex dynamic phenomena existing in a reactor. Quite often, the models developed would be of prohibitively large order, non-linear and of complex structure not readily amenable for control studies. Moreover, the existence of simultaneously occurring dynamic variations at different speeds makes the mathematical model susceptible to numerical ill-conditioning, inhibiting direct application of standard control techniques. This monograph introduces a technique for mathematical modeling of large nuclear reactors in the framework of multi-point kinetics, to obtain a comparatively smaller order model in standard state space form thus overcoming these difficulties. It further brings in innovative methods for controller design for systems exhibiting multi-time-scale property, with emphasis on three-time-scale systems.

Slope-scale dynamic states of rockfalls

Science.gov (United States)

Agliardi, F.; Crosta, G. B.

2009-04-01

Rockfalls are common earth surface phenomena characterised by complex dynamics at the slope scale, depending on local block kinematics and slope geometry. We investigated the nature of this slope-scale dynamics by parametric 3D numerical modelling of rockfalls over synthetic slopes with different inclination, roughness and spatial resolution. Simulations were performed through an original code specifically designed for rockfall modeling, incorporating kinematic and hybrid algorithms with different damping functions available to model local energy loss by impact and pure rolling. Modelling results in terms of average velocity profiles suggest that three dynamic regimes (i.e. decelerating, steady-state and accelerating), previously recognized in the literature through laboratory experiments on granular flows, can set up at the slope scale depending on slope average inclination and roughness. Sharp changes in rock fall kinematics, including motion type and lateral dispersion of trajectories, are associated to the transition among different regimes. Associated threshold conditions, portrayed in "phase diagrams" as slope-roughness critical lines, were analysed depending on block size, impact/rebound angles, velocity and energy, and model spatial resolution. Motion in regime B (i.e. steady state) is governed by a slope-scale "viscous friction" with average velocity linearly related to the sine of slope inclination. This suggest an analogy between rockfall motion in regime B and newtonian flow, whereas in regime C (i.e. accelerating) an analogy with a dilatant flow was observed. Thus, although local behavior of single falling blocks is well described by rigid body dynamics, the slope scale dynamics of rockfalls seem to statistically approach that of granular media. Possible outcomes of these findings include a discussion of the transition from rockfall to granular flow, the evaluation of the reliability of predictive models, and the implementation of criteria for a

Fast sparsely synchronized brain rhythms in a scale-free neural network.

Science.gov (United States)

Kim, Sang-Yoon; Lim, Woochang

2015-08-01

We consider a directed version of the Barabási-Albert scale-free network model with symmetric preferential attachment with the same in- and out-degrees and study the emergence of sparsely synchronized rhythms for a fixed attachment degree in an inhibitory population of fast-spiking Izhikevich interneurons. Fast sparsely synchronized rhythms with stochastic and intermittent neuronal discharges are found to appear for large values of J (synaptic inhibition strength) and D (noise intensity). For an intensive study we fix J at a sufficiently large value and investigate the population states by increasing D. For small D, full synchronization with the same population-rhythm frequency fp and mean firing rate (MFR) fi of individual neurons occurs, while for large D partial synchronization with fp>〈fi〉 (〈fi〉: ensemble-averaged MFR) appears due to intermittent discharge of individual neurons; in particular, the case of fp>4〈fi〉 is referred to as sparse synchronization. For the case of partial and sparse synchronization, MFRs of individual neurons vary depending on their degrees. As D passes a critical value D* (which is determined by employing an order parameter), a transition to unsynchronization occurs due to the destructive role of noise to spoil the pacing between sparse spikes. For Ddynamics to population synchronization change depending on their degrees, unlike in the case of full synchronization. Consequently, dynamics of individual neurons reveal the inhomogeneous network structure for the case of partial and sparse synchronization, which is in contrast to the case of

Fast sparsely synchronized brain rhythms in a scale-free neural network

Science.gov (United States)

Kim, Sang-Yoon; Lim, Woochang

2015-08-01

We consider a directed version of the Barabási-Albert scale-free network model with symmetric preferential attachment with the same in- and out-degrees and study the emergence of sparsely synchronized rhythms for a fixed attachment degree in an inhibitory population of fast-spiking Izhikevich interneurons. Fast sparsely synchronized rhythms with stochastic and intermittent neuronal discharges are found to appear for large values of J (synaptic inhibition strength) and D (noise intensity). For an intensive study we fix J at a sufficiently large value and investigate the population states by increasing D . For small D , full synchronization with the same population-rhythm frequency fp and mean firing rate (MFR) fi of individual neurons occurs, while for large D partial synchronization with fp> ( : ensemble-averaged MFR) appears due to intermittent discharge of individual neurons; in particular, the case of fp>4 is referred to as sparse synchronization. For the case of partial and sparse synchronization, MFRs of individual neurons vary depending on their degrees. As D passes a critical value D* (which is determined by employing an order parameter), a transition to unsynchronization occurs due to the destructive role of noise to spoil the pacing between sparse spikes. For D dynamics to population synchronization change depending on their degrees, unlike in the case of full synchronization. Consequently, dynamics of individual neurons reveal the inhomogeneous network structure for the case of partial and sparse synchronization, which is in contrast to the case of statistically homogeneous

Noise Induced Dissipation in Discrete-Time Classical and Quantum Dynamical Systems

OpenAIRE

Wolowski, Lech

2004-01-01

We introduce a new characteristics of chaoticity of classical and quantum dynamical systems by defining the notion of the dissipation time which enables us to test how the system responds to the noise and in particular to measure the speed at which an initially closed, conservative system converges to the equilibrium when subjected to noisy (stochastic) perturbations. We prove fast dissipation result for classical Anosov systems and ...

Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics.

Science.gov (United States)

Davis, Caitlin M; Reddish, Michael J; Dyer, R Brian

2017-05-05

Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of jump induced difference spectrum from 50ns to 0.5ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics. Copyright © 2017 Elsevier B.V. All rights reserved.

A Fast Time-to-Pulse Height Converter

Energy Technology Data Exchange (ETDEWEB)

Aspelund, O

1962-12-15

A fast time-to-pulse height converter representing a development of Green and Bell's gated beam converter is described. The converter is compatible with 2 input pulses in the stop channel and exhibits excellent linearity and time resolution properties. High stability and large output pulses are obtained by using a large time constant in the converting network.

Fasting, circadian rhythms, and time restricted feeding in healthy lifespan

OpenAIRE

Longo, Valter D.; Panda, Satchidananda

2016-01-01

Feeding in most animals is confined to a defined period, leaving short periods of fasting that coincide with sleep. Fasting enables organisms to enter alternative metabolic phases, which rely less on glucose and more on ketone body-like carbon sources. Both intermittent and periodic fasting result in benefits ranging from prevention to the enhanced treatment of diseases. Similarly, time-restricted feeding (TRF), in which feeding time is restricted to certain hours of the day, allows the daily...

Twin Positive Solutions of a Nonlinear m-Point Boundary Value Problem for Third-Order p-Laplacian Dynamic Equations on Time Scales

Directory of Open Access Journals (Sweden)

Wei Han

2008-01-01

Full Text Available Several existence theorems of twin positive solutions are established for a nonlinear m-point boundary value problem of third-order p-Laplacian dynamic equations on time scales by using a fixed point theorem. We present two theorems and four corollaries which generalize the results of related literature. As an application, an example to demonstrate our results is given. The obtained conditions are different from some known results.

Non-dimensional scaling of impact fast ignition experiments

International Nuclear Information System (INIS)

Farley, D R; Shigemori, K; Murakami, M; Azechi, H

2008-01-01

Recent experiments at the Osaka University Institute for Laser Engineering (ILE) showed that 'Impact Fast Ignition' (IFI) could increase the neutron yield of inertial fusion targets by two orders of magnitude [1]. IFI utilizes the thermal and kinetic energy of a laser-accelerated disk to impact an imploded fusion target. ILE researchers estimate a disk velocity of 10 8 cm/sec is needed to ignite the fusion target [2]. To be able to study the IFI concept using lasers different from that at ILE, appropriate non-dimensionalization of the flow should be done. Analysis of the rocket equation gives parameters needed for producing similar IFI results with different lasers. This analysis shows that a variety of laboratory-scale commercial lasers could produce results useful to full-scale ILE experiments

Dynamics of proteins aggregation. II. Dynamic scaling in confined media

Science.gov (United States)

Zheng, Size; Shing, Katherine S.; Sahimi, Muhammad

2018-03-01

In this paper, the second in a series devoted to molecular modeling of protein aggregation, a mesoscale model of proteins together with extensive discontinuous molecular dynamics simulation is used to study the phenomenon in a confined medium. The medium, as a model of a crowded cellular environment, is represented by a spherical cavity, as well as cylindrical tubes with two aspect ratios. The aggregation process leads to the formation of β sheets and eventually fibrils, whose deposition on biological tissues is believed to be a major factor contributing to many neuro-degenerative diseases, such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis diseases. Several important properties of the aggregation process, including dynamic evolution of the total number of the aggregates, the mean aggregate size, and the number of peptides that contribute to the formation of the β sheets, have been computed. We show, similar to the unconfined media studied in Paper I [S. Zheng et al., J. Chem. Phys. 145, 134306 (2016)], that the computed properties follow dynamic scaling, characterized by power laws. The existence of such dynamic scaling in unconfined media was recently confirmed by experiments. The exponents that characterize the power-law dependence on time of the properties of the aggregation process in spherical cavities are shown to agree with those in unbounded fluids at the same protein density, while the exponents for aggregation in the cylindrical tubes exhibit sensitivity to the geometry of the system. The effects of the number of amino acids in the protein, as well as the size of the confined media, have also been studied. Similarities and differences between aggregation in confined and unconfined media are described, including the possibility of no fibril formation, if confinement is severe.

Is Earth F**ked? Dynamical Futility of Global Environmental Management and Possibilities for Sustainability via Direct Action Activism

Science.gov (United States)

wErnEr, B.

2012-12-01

Environmental challenges are dynamically generated within the dominant global culture principally by the mismatch between short-time-scale market and political forces driving resource extraction/use and longer-time-scale accommodations of the Earth system to these changes. Increasing resource demand is leading to the development of two-way, nonlinear interactions between human societies and environmental systems that are becoming global in extent, either through globalized markets and other institutions or through coupling to global environmental systems such as climate. These trends are further intensified by dissipation-reducing technological advances in transactions, communication and transport, which suppress emergence of longer-time-scale economic and political levels of description and facilitate long-distance connections, and by predictive environmental modeling, which strengthens human connections to a short-time-scale virtual Earth, and weakens connections to the longer time scales of the actual Earth. Environmental management seeks to steer fast scale economic and political interests of a coupled human-environmental system towards longer-time-scale consideration of benefits and costs by operating within the confines of the dominant culture using a linear, engineering-type connection to the system. Perhaps as evidenced by widespread inability to meaningfully address such global environmental challenges as climate change and soil degradation, nonlinear connections reduce the ability of managers to operate outside coupled human-environmental systems, decreasing their effectiveness in steering towards sustainable interactions and resulting in managers slaved to short-to-intermediate-term interests. In sum, the dynamics of the global coupled human-environmental system within the dominant culture precludes management for stable, sustainable pathways and promotes instability. Environmental direct action, resistance taken from outside the dominant culture, as in

A Hierarchical and Dynamic Seascape Framework for Scaling and Comparing Ocean Biodiversity Observations

Science.gov (United States)

Kavanaugh, M.; Muller-Karger, F. E.; Montes, E.; Santora, J. A.; Chavez, F.; Messié, M.; Doney, S. C.

2016-02-01

The pelagic ocean is a complex system in which physical, chemical and biological processes interact to shape patterns on multiple spatial and temporal scales and levels of ecological organization. Monitoring and management of marine seascapes must consider a hierarchical and dynamic mosaic, where the boundaries, extent, and location of features change with time. As part of a Marine Biodiversity Observing Network demonstration project, we conducted a multiscale classification of dynamic coastal seascapes in the northeastern Pacific and Gulf of Mexico using multivariate satellite and modeled data. Synoptic patterns were validated using mooring and ship-based observations that spanned multiple trophic levels and were collected as part of several long-term monitoring programs, including the Monterey Bay and Florida Keys National Marine Sanctuaries. Seascape extent and habitat diversity varied as a function of both seasonal and interannual forcing. We discuss the patterns of in situ observations in the context of seascape dynamics and the effect on rarefaction, spatial patchiness, and tracking and comparing ecosystems through time. A seascape framework presents an effective means to translate local biodiversity measurements to broader spatiotemporal scales, scales relevant for modeling the effects of global change and enabling whole-ecosystem management in the dynamic ocean.

Dynamics of Phenanthrenequinone on Carbon Nano-Onion Surfaces Probed by Quasielastic Neutron Scattering

International Nuclear Information System (INIS)

Mamontov, Eugene; Brown, Gilbert M.; Overbury, Steven H.; Mavila Chathoth, Suresh

2012-01-01

We used quasielastic neutron scattering (QENS) to study the dynamics of phenanthrenequinone (PQ) on the surface of onion-like carbon (OLC), or so called carbon onions, as a function of surface coverage and temperature. For both the high- and low-coverage samples, we observed two diffusion processes; a faster process and nearly an order of magnitude slower process. On the high-coverage surface, the slow diffusion process is of long-range translational character, whereas the fast diffusion process is spatially localized on the length scale of ∼ 4.7. On the low-coverage surface, both diffusion processes are spatially localized; on the same length scale of ∼ 4.7 for the fast diffusion and a somewhat larger length scale for the slow diffusion. Arrhenius temperature dependence is observed except for the long-range diffusion on the high-coverage surface. We attribute the fast diffusion process to the generic localized in-cage dynamics of PQ molecules, and the slow diffusion process to the long-range translational dynamics of PQ molecules, which, depending on the coverage, may be either spatially restricted, or long-range. On the low-coverage surface, uniform surface coverage is not attained, and the PQ molecules experience the effect of spatial constraints on their long-range translational dynamics. Unexpectedly, the dynamics of PQ molecules on OLC as a function of temperature and surface coverage bears qualitative resemblance to the dynamics of water molecules on oxide surfaces, including practically temperature-independent residence times for the low-coverage surface. The dynamics features that we observed may be universal across different classes of surface adsorbates.

Coherent structures at ion scales in fast and slow solar wind: Cluster observations

Science.gov (United States)

Perrone, D.; Alexandrova, O.; Zouganelis, Y.; Roberts, O.; Lion, S.; Escoubet, C. P.; Walsh, A. P.; Maksimovic, M.; Lacombe, C.

2017-12-01

Spacecraft measurements generally reveal that solar wind electromagnetic fluctuations are in a state of fully-developed turbulence. Turbulence represents a very complex problem in plasmas since cross-scale coupling and kinetic effects are present. Moreover, the intermittency phenomenon, i.e. the manifestation of the non-uniform and inhomogeneous energy transfer and dissipation in a turbulent system, represents a very important aspect of the solar wind turbulent cascade. Here, we study coherent structures responsible for solar wind intermittency around ion characteristic scales. We find that, in fast solar wind, intermittency is due to Alfvén vortex-like structures and current sheets. In slow solar wind, we observe as well compressive structures like magnetic solitons, holes and shocks. By using high-time resolution magnetic field data of multi-point measurements of Cluster spacecraft, we characterize the observed coherent structures in terms of topology and propagation speed. We show that all structures around ion characteristic scales, both in fast and slow solar wind, are characterized by a strong wave-vector anisotropy in the perpendicular direction with respect to the local magnetic field. Moreover, some of them propagate in the plasma rest frame in the direction perpendicular to the local field. Finally, a further analysis on the electron and ion velocity distributions shows a high variability; in particular, close to coherent structures the electron and ion distribution functions appear strongly deformed and far from the thermodynamic equilibrium. Possible interpretations of the observed structures and their role in the heating process of the plasma are also discussed.

Parareal in Time for Dynamic Simulations of Power Systems

Energy Technology Data Exchange (ETDEWEB)

Gurrala, Gurunath [ORNL; Dimitrovski, Aleksandar D [ORNL; Pannala, Sreekanth [ORNL; Simunovic, Srdjan [ORNL; Starke, Michael R [ORNL

2015-01-01

In recent years, there have been significant developments in parallel algorithms and high performance parallel computing platforms. Parareal in time algorithm has become popular for long transient simulations (e.g., molecular dynamics, fusion, reacting flows). Parareal is a parallel algorithm which divides the time interval into sub-intervals and solves them concurrently. This paper investigates the applicability of the parareal algorithm to power system dynamic simulations. Preliminary results on the application of parareal for multi-machine power systems are reported in this paper. Two widely used test systems, WECC 3-generator 9-bus system, New England 10-generator 39- bus system, is used to explore the effectiveness of the parareal. Severe 3 phase bus faults are simulated using both the classical and detailed models of multi-machine power systems. Actual Speedup of 5-7 times is observed assuming ideal parallelization. It has been observed that the speedup factors of the order of 20 can be achieved by using fast coarse approximations of power system models. Dependency of parareal convergence on fault duration and location has been observed.

Computational issues in complex water-energy optimization problems: Time scales, parameterizations, objectives and algorithms

Science.gov (United States)

Efstratiadis, Andreas; Tsoukalas, Ioannis; Kossieris, Panayiotis; Karavokiros, George; Christofides, Antonis; Siskos, Alexandros; Mamassis, Nikos; Koutsoyiannis, Demetris

2015-04-01

Modelling of large-scale hybrid renewable energy systems (HRES) is a challenging task, for which several open computational issues exist. HRES comprise typical components of hydrosystems (reservoirs, boreholes, conveyance networks, hydropower stations, pumps, water demand nodes, etc.), which are dynamically linked with renewables (e.g., wind turbines, solar parks) and energy demand nodes. In such systems, apart from the well-known shortcomings of water resources modelling (nonlinear dynamics, unknown future inflows, large number of variables and constraints, conflicting criteria, etc.), additional complexities and uncertainties arise due to the introduction of energy components and associated fluxes. A major difficulty is the need for coupling two different temporal scales, given that in hydrosystem modeling, monthly simulation steps are typically adopted, yet for a faithful representation of the energy balance (i.e. energy production vs. demand) a much finer resolution (e.g. hourly) is required. Another drawback is the increase of control variables, constraints and objectives, due to the simultaneous modelling of the two parallel fluxes (i.e. water and energy) and their interactions. Finally, since the driving hydrometeorological processes of the integrated system are inherently uncertain, it is often essential to use synthetically generated input time series of large length, in order to assess the system performance in terms of reliability and risk, with satisfactory accuracy. To address these issues, we propose an effective and efficient modeling framework, key objectives of which are: (a) the substantial reduction of control variables, through parsimonious yet consistent parameterizations; (b) the substantial decrease of computational burden of simulation, by linearizing the combined water and energy allocation problem of each individual time step, and solve each local sub-problem through very fast linear network programming algorithms, and (c) the substantial

Modelling Protein Dynamics on the Microsecond Time Scale

DEFF Research Database (Denmark)

Siuda, Iwona Anna

Recent years have shown an increase in coarse-grained (CG) molecular dynamics simulations, providing structural and dynamic details of large proteins and enabling studies of self-assembly of biological materials. It is not easy to acquire such data experimentally, and access is also still limited...... in atomistic simulations. During her PhD studies, Iwona Siuda used MARTINI CG models to study the dynamics of different globular and membrane proteins. In several cases, the MARTINI model was sufficient to study conformational changes of small, purely alpha-helical proteins. However, in studies of larger......ELNEDIN was therefore proposed as part of the work. Iwona Siuda’s results from the CG simulations had biological implications that provide insights into possible mechanisms of the periplasmic leucine-binding protein, the sarco(endo)plasmic reticulum calcium pump, and several proteins from the saposin-like proteins...

Dynamic Modeling, Optimization, and Advanced Control for Large Scale Biorefineries

DEFF Research Database (Denmark)

Prunescu, Remus Mihail

with a complex conversion route. Computational fluid dynamics is used to model transport phenomena in large reactors capturing tank profiles, and delays due to plug flows. This work publishes for the first time demonstration scale real data for validation showing that the model library is suitable...

Time-slice analysis of the Australian summer monsoon during the late Quaternary using the Fast Ocean Atmosphere Model

Science.gov (United States)

Marshall, A. G.; Lynch, A. H.

2006-10-01

We use the Fast Ocean Atmosphere Model (FOAM) to investigate the variation in the Australian summer monsoon over the last 55 000 years. A synthesis of palaeoenvironmental observations is used to constrain the model for six time slices: 55, 35, 21, 11, 6 and 0 ka. Both inter-hemispheric forcing and the seasonal timing of local insolation changes play key, and interacting, roles on the evolution and intensity of the monsoon.During the onset to the monsoon, a heat low develops to the west of Australia over the Indian Ocean in all time slices, but with varying strengths. Divergent outflow from Asia converges with the cyclonic flow to bring increased rainfall to northern Australia and the maritime continent. The relative importance of a low pressure pull and the high pressure push varies according to the strength of the pressure anomalies. Only in the middle Holocene is the low pressure pull the dominant forcing mechanism. At 21 ka, the climate shift to colder mean temperatures determines the large-scale dynamics of the monsoon.The general picture that emerges from these results is consistent with available palaeodata but highlights the importance of a broad regional perspective to ascribe the driving mechanisms at different times. Copyright

A Study on Time-Scales Ratio and Turbulent Prandtl Number in Ducts of Industrial Applications

DEFF Research Database (Denmark)

Rokni, Masoud

2006-01-01

is solved using a two-equation heat flux model. The computed results compare satisfactory with the available experimental data. The time-scale ratio R is defined as the ratio between the dynamic time-scale (k/ε) and the scalar time-scale(0.5θθ/εθ). Based on existing DNS data and calculations in this work...... of heat exchangers for various applications area....

The dynamic current-voltage characteristic as a powerful tool to analyze fast phenomena in plasma

International Nuclear Information System (INIS)

Ivan, L. M.; Mihai-Plugaru, M.; Amarandei, G.; Aflori, M.; Dimitriu, D. G.

2006-01-01

The static current-voltage characteristic of an electrode immersed in plasma is obtained by slowly increasing and subsequently decreasing the potential on the electrode with respect to the plasma potential or the ground. This characteristic can give us important information about the phenomena that take place in front of the electrode. Current jumps can be evidenced which were often associated with an hysteresis effect, regions with S-type or N-type negative differential resistance, etc. The method is always used when we investigate the appearance of complex space charge configurations (CSCC) in front of an electrode immersed in plasma. However, to investigate the dynamics of such structures or other fast phenomena (like instabilities) which take place in plasma devices with frequencies of tenth, hundred kHz or more, complex investigation techniques must be used. One of the most efficient methods to investigate fast phenomena in plasma devices is the dynamic current-voltage characteristic. This is obtained by recording the time series of the current collected by the electrode when the voltage applied on it is very fast modified (most likely increased) by using a signal generator. In this way, very fast oscillations of the current can be recorded and new phenomena can be evidenced. We used this technique to study the phenomena which take place at the onset of electrostatic instabilities in Q-machine plasma, namely the potential relaxation instability (PRI) and the electrostatic ion-cyclotron instability (EICI). The obtained experimental results prove that the negative differential resistance region in the static current-voltage characteristic is the result of a nonlinear dynamics of a CSCC in form of a double layer (DL) which takes place just before the onset of the instabilities. In the case of the PRI we emphasized current jumps related with the DL appearance, which are not present in the static current-voltage characteristic at high plasma density. (authors)

Implementation of a fast 16-Bit dynamic clamp using LabVIEW-RT.

Science.gov (United States)

Kullmann, Paul H M; Wheeler, Diek W; Beacom, Joshua; Horn, John P

2004-01-01

The dynamic-clamp method provides a powerful electrophysiological tool for creating virtual ionic conductances in living cells and studying their influence on membrane potential. Here we describe G-clamp, a new way to implement a dynamic clamp using the real-time version of the Lab-VIEW programming environment together with a Windows host, an embedded microprocessor that runs a real-time operating system and a multifunction data-acquisition board. The software includes descriptions of a fast voltage-dependent sodium conductance, delayed rectifier, M-type and A-type potassium conductances, and a leak conductance. The system can also read synaptic conductance waveforms from preassembled data files. These virtual conductances can be reliably implemented at speeds < or =43 kHz while simultaneously saving two channels of data with 16-bit precision. G-clamp also includes utilities for measuring current-voltage relations, synaptic strength, and synaptic gain. Taking an approach built on a commercially available software/hardware platform has resulted in a system that is easy to assemble and upgrade. In addition, the graphical programming structure of LabVIEW should make it relatively easy for others to adapt G-clamp for new experimental applications.

Dynamic Beam Solutions for Real-Time Simulation and Control Development of Flexible Rockets

Science.gov (United States)

Su, Weihua; King, Cecilia K.; Clark, Scott R.; Griffin, Edwin D.; Suhey, Jeffrey D.; Wolf, Michael G.

2016-01-01

In this study, flexible rockets are structurally represented by linear beams. Both direct and indirect solutions of beam dynamic equations are sought to facilitate real-time simulation and control development for flexible rockets. The direct solution is completed by numerically integrate the beam structural dynamic equation using an explicit Newmark-based scheme, which allows for stable and fast transient solutions to the dynamics of flexile rockets. Furthermore, in the real-time operation, the bending strain of the beam is measured by fiber optical sensors (FOS) at intermittent locations along the span, while both angular velocity and translational acceleration are measured at a single point by the inertial measurement unit (IMU). Another study in this paper is to find the analytical and numerical solutions of the beam dynamics based on the limited measurement data to facilitate the real-time control development. Numerical studies demonstrate the accuracy of these real-time solutions to the beam dynamics. Such analytical and numerical solutions, when integrated with data processing and control algorithms and mechanisms, have the potential to increase launch availability by processing flight data into the flexible launch vehicle's control system.

Challenges in transferring knowledge between scales in coastal sediment dynamics

Directory of Open Access Journals (Sweden)

Shari L Gallop

2015-10-01

Full Text Available ‘Packaging’ coastal sediment transport into discrete temporal and spatial scale bands is necessary for measurement programs, modelling, and design. However, determining how to best measure and parameterize information, to transfer between scales, is not trivial. An overview is provided of the major complexities in transferring information on coastal sediment transport between scales. Key considerations that recur in the literature include: interaction between sediment transport and morphology; the influence of biota; episodic sediment transport; and recovery time-scales. The influence of bedforms and landforms, as well as sediment-biota interactions, varies with spatio-temporal scale. In some situations, episodic sediment dynamics is the main contributor to long-term sediment transport. Such events can also significantly alter biogeochemical and ecological processes, which interact with sediments. The impact of such episodic events is fundamentally influenced by recovery time-scales, which vary spatially. For the various approaches to scaling (e.g., bottom-up, aggregation, spatial hierarchies, there is a need for fundamental research on the assumptions inherent in each approach.

Linear Dynamics Model for Steam Cooled Fast Power Reactors

Energy Technology Data Exchange (ETDEWEB)

Vollmer, H

1968-04-15

A linear analytical dynamic model is developed for steam cooled fast power reactors. All main components of such a plant are investigated on a general though relatively simple basis. The model is distributed in those parts concerning the core but lumped as to the external plant components. Coolant is considered as compressible and treated by the actual steam law. Combined use of analogue and digital computer seems most attractive.

A multiple-time-scale approach to the control of ITBs on JET

International Nuclear Information System (INIS)

Laborde, L.; Mazon, D.; Moreau, D.; Moreau, D.; Ariola, M.; Cordoliani, V.; Tala, T.

2005-01-01

The simultaneous real-time control of the current and temperature gradient profiles could lead to the steady state sustainment of an internal transport barrier (ITB) and so to a stationary optimized plasma regime. Recent experiments in JET have demonstrated significant progress in achieving such a control: different current and temperature gradient target profiles have been reached and sustained for several seconds using a controller based on a static linear model. It's worth noting that the inverse safety factor profile evolves on a slow time scale (resistive time) while the normalized electron temperature gradient reacts on a faster one (confinement time). Moreover these experiments have shown that the controller was sensitive to rapid plasma events such as transient ITBs during the safety factor profile evolution or MHD instabilities which modify the pressure profiles on the confinement time scale. In order to take into account the different dynamics of the controlled profiles and to better react to rapid plasma events the control technique is being improved by using a multiple-time-scale approximation. The paper describes the theoretical analysis and closed-loop simulations using a control algorithm based on two-time-scale state-space model. These closed-loop simulations using the full dynamic but linear model used for the controller design to simulate the plasma response have demonstrated that this new controller allows the normalized electron temperature gradient target profile to be reached faster than the one used in previous experiments. (A.C.)

A multiple-time-scale approach to the control of ITBs on JET

Energy Technology Data Exchange (ETDEWEB)

Laborde, L.; Mazon, D.; Moreau, D. [EURATOM-CEA Association (DSM-DRFC), CEA Cadarache, 13 - Saint Paul lez Durance (France); Moreau, D. [Culham Science Centre, EFDA-JET, Abingdon, OX (United Kingdom); Ariola, M. [EURATOM/ENEA/CREATE Association, Univ. Napoli Federico II, Napoli (Italy); Cordoliani, V. [Ecole Polytechnique, 91 - Palaiseau (France); Tala, T. [EURATOM-Tekes Association, VTT Processes (Finland)

2005-07-01

The simultaneous real-time control of the current and temperature gradient profiles could lead to the steady state sustainment of an internal transport barrier (ITB) and so to a stationary optimized plasma regime. Recent experiments in JET have demonstrated significant progress in achieving such a control: different current and temperature gradient target profiles have been reached and sustained for several seconds using a controller based on a static linear model. It's worth noting that the inverse safety factor profile evolves on a slow time scale (resistive time) while the normalized electron temperature gradient reacts on a faster one (confinement time). Moreover these experiments have shown that the controller was sensitive to rapid plasma events such as transient ITBs during the safety factor profile evolution or MHD instabilities which modify the pressure profiles on the confinement time scale. In order to take into account the different dynamics of the controlled profiles and to better react to rapid plasma events the control technique is being improved by using a multiple-time-scale approximation. The paper describes the theoretical analysis and closed-loop simulations using a control algorithm based on two-time-scale state-space model. These closed-loop simulations using the full dynamic but linear model used for the controller design to simulate the plasma response have demonstrated that this new controller allows the normalized electron temperature gradient target profile to be reached faster than the one used in previous experiments. (A.C.)

Vibrational dynamics of aqueous hydroxide solutions probed using broadband 2DIR spectroscopy

International Nuclear Information System (INIS)

Mandal, Aritra; Tokmakoff, Andrei

2015-01-01

We employed ultrafast transient absorption and broadband 2DIR spectroscopy to study the vibrational dynamics of aqueous hydroxide solutions by exciting the O–H stretch vibrations of the strongly hydrogen-bonded hydroxide solvation shell water and probing the continuum absorption of the solvated ion between 1500 and 3800 cm −1 . We observe rapid vibrational relaxation processes on 150–250 fs time scales across the entire probed spectral region as well as slower vibrational dynamics on 1–2 ps time scales. Furthermore, the O–H stretch excitation loses its frequency memory in 180 fs, and vibrational energy exchange between bulk-like water vibrations and hydroxide-associated water vibrations occurs in ∼200 fs. The fast dynamics in this system originate in strong nonlinear coupling between intra- and intermolecular vibrations and are explained in terms of non-adiabatic vibrational relaxation. These measurements indicate that the vibrational dynamics of the aqueous hydroxide complex are faster than the time scales reported for long-range transport of protons in aqueous hydroxide solutions

Neutron dynamics of fast-spectrum dedicated cores for waste transmutation

International Nuclear Information System (INIS)

Massara, S.

2002-04-01

Among different scenarios achieving minor actinide transmutation, the possibility of double strata scenarios with critical, fast spectrum, dedicated cores must be checked and quantified. In these cores, the waste fraction has to be at the highest level compatible with safety requirements during normal operation and transient conditions. As reactivity coefficients are poor in such critical cores (low delayed neutron fraction and Doppler feed-back, high coolant void coefficient), their dynamic behaviour during transient conditions must be carefully analysed. Three nitride-fuel configurations have been analysed: two liquid metal-cooled (sodium and lead) and a particle-fuel helium-cooled one. A dynamic code, MAT4 DYN, has been developed during the PhD thesis, allowing the study of loss of flow, reactivity insertion and loss of coolant accidents, and taking into account two fuel geometries (cylindrical and spherical) and two thermal-hydraulics models for the coolant (incompressible for liquid metals and compressible for helium). Dynamics calculations have shown that if the fuel nature is appropriately chosen (letting a sufficient margin during transients), this can counterbalance the bad state of reactivity coefficients for liquid metal-cooled cores, thus proving the interest of this kind of concept. On the other side, the gas-cooled core dynamics is very badly affected by the high value of the helium void coefficient (which is a consequence of the choice of a hard spectrum), this effect being amplified by the very low thermal inertia of particle-fuel design. So, a new kind of concept should be considered for a helium-cooled fast-spectrum dedicated core. (authors)

Singular perturbation methods for nonlinear dynamic systems with time delays

International Nuclear Information System (INIS)

Hu, H.Y.; Wang, Z.H.

2009-01-01

This review article surveys the recent advances in the dynamics and control of time-delay systems, with emphasis on the singular perturbation methods, such as the method of multiple scales, the method of averaging, and two newly developed methods, the energy analysis and the pseudo-oscillator analysis. Some examples are given to demonstrate the advantages of the methods. The comparisons with other methods show that these methods lead to easier computations and higher accurate prediction on the local dynamics of time-delay systems near a Hopf bifurcation.

Fast Simulation of Dynamic Ultrasound Images Using the GPU.

Science.gov (United States)

Storve, Sigurd; Torp, Hans

2017-10-01

Simulated ultrasound data is a valuable tool for development and validation of quantitative image analysis methods in echocardiography. Unfortunately, simulation time can become prohibitive for phantoms consisting of a large number of point scatterers. The COLE algorithm by Gao et al. is a fast convolution-based simulator that trades simulation accuracy for improved speed. We present highly efficient parallelized CPU and GPU implementations of the COLE algorithm with an emphasis on dynamic simulations involving moving point scatterers. We argue that it is crucial to minimize the amount of data transfers from the CPU to achieve good performance on the GPU. We achieve this by storing the complete trajectories of the dynamic point scatterers as spline curves in the GPU memory. This leads to good efficiency when simulating sequences consisting of a large number of frames, such as B-mode and tissue Doppler data for a full cardiac cycle. In addition, we propose a phase-based subsample delay technique that efficiently eliminates flickering artifacts seen in B-mode sequences when COLE is used without enough temporal oversampling. To assess the performance, we used a laptop computer and a desktop computer, each equipped with a multicore Intel CPU and an NVIDIA GPU. Running the simulator on a high-end TITAN X GPU, we observed two orders of magnitude speedup compared to the parallel CPU version, three orders of magnitude speedup compared to simulation times reported by Gao et al. in their paper on COLE, and a speedup of 27000 times compared to the multithreaded version of Field II, using numbers reported in a paper by Jensen. We hope that by releasing the simulator as an open-source project we will encourage its use and further development.

The question is: are fast-moving scales contracted or elongated?

International Nuclear Information System (INIS)

Strel'tsov, V.N.

1991-01-01

The traditional definition of the length of a fast-moving scale and the concept of relativistic length are considered from the point of view of the condition of relativistic covariance. It is shown that the latter concept satisfies this condition whereas the traditional definition is in contrast with it ('synchronous length' is not a 4-vector). It is stressed that the light and retarded distances and the relativistic length introduced in fact on their base serve as the basis for the space-time picture of the radar formulation of relativistic theory. The consequence of this approach is lengthening (and not contraction) of longitudinal sizes of relativistic objects. It is noted that the use of radar length (instead of 'instantaneous' one) in the known interpretation of the Michelson-Morley experiment leads to the elongation formula for a longitudinal arm of the interferometer. 16 refs.; 1 fig

Chaos anticontrol and synchronization of three time scales brushless DC motor system

International Nuclear Information System (INIS)

Ge Zhengming; Cheng Juiwen; Chen Yensheng

2004-01-01

Chaos anticontrol of three time scale brushless dc motors and chaos synchronization of different order systems are studied. Nondimensional dynamic equations of three time scale brushless DC motor system are presented. Using numerical results, such as phase diagram, bifurcation diagram, and Lyapunov exponent, periodic and chaotic motions can be observed. By adding constant term, periodic square wave, the periodic triangle wave, the periodic sawtooth wave, and kx vertical bar x vertical bar term, to achieve anticontrol of chaotic or periodic systems, it is found that more chaotic phenomena of the system can be observed. Then, by coupled terms and linearization of error dynamics, we obtain the partial synchronization of two different order systems, i.e. brushless DC motor system and rate gyroscope system

Efficient graph-based dynamic load-balancing for parallel large-scale agent-based traffic simulation

NARCIS (Netherlands)

Xu, Y.; Cai, W.; Aydt, H.; Lees, M.; Tolk, A.; Diallo, S.Y.; Ryzhov, I.O.; Yilmaz, L.; Buckley, S.; Miller, J.A.

2014-01-01

One of the issues of parallelizing large-scale agent-based traffic simulations is partitioning and load-balancing. Traffic simulations are dynamic applications where the distribution of workload in the spatial domain constantly changes. Dynamic load-balancing at run-time has shown better efficiency

Boost-invariant early time dynamics from AdS/CFT

International Nuclear Information System (INIS)

Beuf, Guillaume; Peschanski, Robi; Heller, Michal P.; Janik, Romuald A.

2009-01-01

Boost-invariant dynamics of a strongly-coupled conformal plasma is studied in the regime of early proper-time using the AdS/CFT correspondence. It is shown, in contrast with the late-time expansion, that a scaling solution does not exist. The boundary dynamics in this regime depends on initial conditions encoded in the bulk behavior of a Fefferman-Graham metric coefficient at initial proper-time. The relation between the early-time expansion of the energy density and initial conditions in the bulk of AdS is provided. As a general result it is proven that a singularity of some metric coefficient in Fefferman-Graham frame exists at all times. Requiring that this singularity at τ = 0 is a mere coordinate singularity without the curvature blow-up gives constraints on the possible boundary dynamics. Using a simple Pade resummation for solutions satisfying the regularity constraint, the features of a transition to local equilibrium, and thus to the hydrodynamical late-time regime, have been observed. The impact of this study on the problem of thermalization is discussed.

Space-Time Dynamics of Membrane Currents Evolve to Shape Excitation, Spiking, and Inhibition in the Cortex at Small and Large Scales

DEFF Research Database (Denmark)

Roland, Per E.

2017-01-01

positions. After transition to active spiking states, larger structured zones with active spiking neurons appear, propagating through the cortical network, driving it into various forms of widespread excitation, and engaging the network from microscopic scales to whole cortical areas. At each engaged...... cortical site, the amount of excitation in the network, after a delay, becomes matched by an equal amount of space-time fine-tuned inhibition that might be instrumental in driving the dynamics toward perception and action....

Fast and Practical Head Tracking in Brain Imaging with Time-of-Flight Camera

DEFF Research Database (Denmark)

Wilm, Jakob; Olesen, Oline Vinter; Jensen, Rasmus Ramsbøl

2013-01-01

scanners. Particularly in MRI and PET, the newest generation of TOF cameras could become a method of tracking small and large scale patient movement in a fast and user friendly way required in clinical environments. We present a novel methodology for fast tracking from TOF point clouds without the need...

Objective assessment of drowsiness and reaction time during intermittent Ramadan fasting in young men: a case-crossover study.

Science.gov (United States)

Bahammam, Ahmed S; Nashwan, Samar; Hammad, Omeima; Sharif, Munir M; Pandi-Perumal, Seithikurippu R

2013-08-12

Ramadan fasting and its attendant lifestyle changes induce changes in the circadian rhythm and in associated physiological and metabolic functions. Previous studies that have assessed psychomotor performance during Ramadan fasting have reported conflicting results. Therefore, we designed this study to objectively assess the effects of intermittent fasting during and outside Ramadan (to control for lifestyle changes) on drowsiness, blink total duration and mean reaction time (MRT) test while controlling for potential confounders. Eight healthy volunteers with a mean age of 25.3 ± 2.9 years and a mean body mass index (BMI) of 23.4 ± 3.2 kg/m2 reported to the sleep laboratory on four occasions for polysomnography (PSG) and drowsiness and psychomotor assessments as follows: 1) adaptation; 2) 4 weeks before Ramadan while performing the Islamic fasting for 1 week (baseline fasting) (BLF); 3) 1 week before Ramadan (non-fasting baseline) (BL); and 4) during the second week of Ramadan while fasting (Ramadan). OPTALERT™ was used to objectively assess daytime drowsiness using the Johns Drowsiness Scale (JDS), and blink total duration and a visual reaction time test were used to assess MRT. Rapid eye movement (REM) sleep percentage was significantly lower at BLF (17.7 ± 8.1%) and at Ramadan (18.6 ± 10.7%) compared with BL (25.6 ± 4.8%) (p intermittent fasting has no impact on drowsiness and vigilance as measured by the JDS, total blink duration and MRT.

Verification and Validation of the New Dynamic Mooring Modules Available in FAST v8

DEFF Research Database (Denmark)

Wendt, Fabian F.; Andersen, Morten Thøtt; Robertson, Amy N.

2016-01-01

The open-source, aero-hydro-servo-elastic wind turbine simulation software FAST v8 (created by the National Renewable Energy Laboratory) was recently coupled to two newly developed mooring dynamics modules: MoorDyn and FEAMooring. MoorDyn is a lumped-mass-based mooring dynamics module developed b...

A simple and fast representation space for classifying complex time series

International Nuclear Information System (INIS)

Zunino, Luciano; Olivares, Felipe; Bariviera, Aurelio F.; Rosso, Osvaldo A.

2017-01-01

In the context of time series analysis considerable effort has been directed towards the implementation of efficient discriminating statistical quantifiers. Very recently, a simple and fast representation space has been introduced, namely the number of turning points versus the Abbe value. It is able to separate time series from stationary and non-stationary processes with long-range dependences. In this work we show that this bidimensional approach is useful for distinguishing complex time series: different sets of financial and physiological data are efficiently discriminated. Additionally, a multiscale generalization that takes into account the multiple time scales often involved in complex systems has been also proposed. This multiscale analysis is essential to reach a higher discriminative power between physiological time series in health and disease. - Highlights: • A bidimensional scheme has been tested for classification purposes. • A multiscale generalization is introduced. • Several practical applications confirm its usefulness. • Different sets of financial and physiological data are efficiently distinguished. • This multiscale bidimensional approach has high potential as discriminative tool.

A simple and fast representation space for classifying complex time series

Energy Technology Data Exchange (ETDEWEB)

Zunino, Luciano, E-mail: lucianoz@ciop.unlp.edu.ar [Centro de Investigaciones Ópticas (CONICET La Plata – CIC), C.C. 3, 1897 Gonnet (Argentina); Departamento de Ciencias Básicas, Facultad de Ingeniería, Universidad Nacional de La Plata (UNLP), 1900 La Plata (Argentina); Olivares, Felipe, E-mail: olivaresfe@gmail.com [Instituto de Física, Pontificia Universidad Católica de Valparaíso (PUCV), 23-40025 Valparaíso (Chile); Bariviera, Aurelio F., E-mail: aurelio.fernandez@urv.cat [Department of Business, Universitat Rovira i Virgili, Av. Universitat 1, 43204 Reus (Spain); Rosso, Osvaldo A., E-mail: oarosso@gmail.com [Instituto de Física, Universidade Federal de Alagoas (UFAL), BR 104 Norte km 97, 57072-970, Maceió, Alagoas (Brazil); Instituto Tecnológico de Buenos Aires (ITBA) and CONICET, C1106ACD, Av. Eduardo Madero 399, Ciudad Autónoma de Buenos Aires (Argentina); Complex Systems Group, Facultad de Ingeniería y Ciencias Aplicadas, Universidad de los Andes, Av. Mons. Álvaro del Portillo 12.455, Las Condes, Santiago (Chile)

2017-03-18

In the context of time series analysis considerable effort has been directed towards the implementation of efficient discriminating statistical quantifiers. Very recently, a simple and fast representation space has been introduced, namely the number of turning points versus the Abbe value. It is able to separate time series from stationary and non-stationary processes with long-range dependences. In this work we show that this bidimensional approach is useful for distinguishing complex time series: different sets of financial and physiological data are efficiently discriminated. Additionally, a multiscale generalization that takes into account the multiple time scales often involved in complex systems has been also proposed. This multiscale analysis is essential to reach a higher discriminative power between physiological time series in health and disease. - Highlights: • A bidimensional scheme has been tested for classification purposes. • A multiscale generalization is introduced. • Several practical applications confirm its usefulness. • Different sets of financial and physiological data are efficiently distinguished. • This multiscale bidimensional approach has high potential as discriminative tool.

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization

International Nuclear Information System (INIS)

Thoen, D. J.; Bongers, W. A.; Westerhof, E.; Baar, M. R. de; Berg, M. A. van den; Beveren, V. van; Goede, A. P. H.; Graswinckel, M. F.; Schueller, F. C.; Oosterbeek, J. W.; Buerger, A.; Hennen, B. A.

2009-01-01

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

Localized diffusive motion on two different time scales in solid alkane nanoparticles

International Nuclear Information System (INIS)

Wang, S.-K.; Mamontov, Eugene; Bai, M.; Hansen, F.Y.; Taub, H.; Copley, J.R.D.; Garcia Sakai, V.; Gasparovic, Goran; Jenkins, Timothy; Tyagi, M.; Herwig, Kenneth W.; Neumann, D.A.; Montfrooij, W.; Volkmann, U.G.

2010-01-01

High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nano- to bulk-sized particles of the alkane n-C32H66. The crystalline-to-plastic and plastic-to-fluid phase transition temperatures are observed to decrease as the particle size decreases. In all samples, localized molecular diffusive motion in the plastic phase occurs on two different time scales: a 'fast' motion corresponding to uniaxial rotation about the long molecular axis; and a 'slow' motion attributed to conformational changes of the molecule. Contrary to the conventional interpretation in bulk alkanes, the fast uniaxial rotation begins in the low-temperature crystalline phase.

The role of large-scale, extratropical dynamics in climate change

Energy Technology Data Exchange (ETDEWEB)

Shepherd, T.G. [ed.

1994-02-01

The climate modeling community has focused recently on improving our understanding of certain processes, such as cloud feedbacks and ocean circulation, that are deemed critical to climate-change prediction. Although attention to such processes is warranted, emphasis on these areas has diminished a general appreciation of the role played by the large-scale dynamics of the extratropical atmosphere. Lack of interest in extratropical dynamics may reflect the assumption that these dynamical processes are a non-problem as far as climate modeling is concerned, since general circulation models (GCMs) calculate motions on this scale from first principles. Nevertheless, serious shortcomings in our ability to understand and simulate large-scale dynamics exist. Partly due to a paucity of standard GCM diagnostic calculations of large-scale motions and their transports of heat, momentum, potential vorticity, and moisture, a comprehensive understanding of the role of large-scale dynamics in GCM climate simulations has not been developed. Uncertainties remain in our understanding and simulation of large-scale extratropical dynamics and their interaction with other climatic processes, such as cloud feedbacks, large-scale ocean circulation, moist convection, air-sea interaction and land-surface processes. To address some of these issues, the 17th Stanstead Seminar was convened at Bishop`s University in Lennoxville, Quebec. The purpose of the Seminar was to promote discussion of the role of large-scale extratropical dynamics in global climate change. Abstracts of the talks are included in this volume. On the basis of these talks, several key issues emerged concerning large-scale extratropical dynamics and their climatic role. Individual records are indexed separately for the database.

The role of large-scale, extratropical dynamics in climate change

International Nuclear Information System (INIS)

Shepherd, T.G.

1994-02-01

The climate modeling community has focused recently on improving our understanding of certain processes, such as cloud feedbacks and ocean circulation, that are deemed critical to climate-change prediction. Although attention to such processes is warranted, emphasis on these areas has diminished a general appreciation of the role played by the large-scale dynamics of the extratropical atmosphere. Lack of interest in extratropical dynamics may reflect the assumption that these dynamical processes are a non-problem as far as climate modeling is concerned, since general circulation models (GCMs) calculate motions on this scale from first principles. Nevertheless, serious shortcomings in our ability to understand and simulate large-scale dynamics exist. Partly due to a paucity of standard GCM diagnostic calculations of large-scale motions and their transports of heat, momentum, potential vorticity, and moisture, a comprehensive understanding of the role of large-scale dynamics in GCM climate simulations has not been developed. Uncertainties remain in our understanding and simulation of large-scale extratropical dynamics and their interaction with other climatic processes, such as cloud feedbacks, large-scale ocean circulation, moist convection, air-sea interaction and land-surface processes. To address some of these issues, the 17th Stanstead Seminar was convened at Bishop's University in Lennoxville, Quebec. The purpose of the Seminar was to promote discussion of the role of large-scale extratropical dynamics in global climate change. Abstracts of the talks are included in this volume. On the basis of these talks, several key issues emerged concerning large-scale extratropical dynamics and their climatic role. Individual records are indexed separately for the database

Diffusive real-time dynamics of a particle with Berry curvature

Science.gov (United States)

Misaki, Kou; Miyashita, Seiji; Nagaosa, Naoto

2018-02-01

We study theoretically the influence of Berry phase on the real-time dynamics of the single particle focusing on the diffusive dynamics, i.e., the time dependence of the distribution function. Our model can be applied to the real-time dynamics of intraband relaxation and diffusion of optically excited excitons, trions, or particle-hole pair. We found that the dynamics at the early stage is deeply influenced by the Berry curvature in real space (B ), momentum space (Ω ), and also the crossed space between these two (C ). For example, it is found that Ω induces the rotation of the wave packet and causes the time dependence of the mean square displacement of the particle to be linear in time t at the initial stage; it is qualitatively different from the t3 dependence in the absence of the Berry curvature. It is also found that Ω and C modify the characteristic time scale of the thermal equilibration of momentum distribution. Moreover, the dynamics under various combinations of B ,Ω , and C shows singular behaviors such as the critical slowing down or speeding up of the momentum equilibration and the reversals of the direction of rotations. The relevance of our model for time-resolved experiments in transition metal dichalcogenides is also discussed.

Examining a scaled dynamical system of telomere shortening

Science.gov (United States)

Cyrenne, Benoit M.; Gooding, Robert J.

2015-02-01

A model of telomere dynamics is proposed and examined. Our model, which extends a previously introduced model that incorporates stem cells as progenitors of new cells, imposes the Hayflick limit, the maximum number of cell divisions that are possible. This new model leads to cell populations for which the average telomere length is not necessarily a monotonically decreasing function of time, in contrast to previously published models. We provide a phase diagram indicating where such results would be expected via the introduction of scaled populations, rate constants and time. The application of this model to available leukocyte baboon data is discussed.

Multiple Positive Symmetric Solutions to p-Laplacian Dynamic Equations on Time Scales

Directory of Open Access Journals (Sweden)

You-Hui Su

2009-01-01

two examples are given to illustrate the main results and their differences. These results are even new for the special cases of continuous and discrete equations, as well as in the general time-scale setting.

Heterogeneous dynamics of ionic liquids: A four-point time correlation function approach

Science.gov (United States)

Liu, Jiannan; Willcox, Jon A. L.; Kim, Hyung J.

2018-05-01

Many ionic liquids show behavior similar to that of glassy systems, e.g., large and long-lasted deviations from Gaussian dynamics and clustering of "mobile" and "immobile" groups of ions. Herein a time-dependent four-point density correlation function—typically used to characterize glassy systems—is implemented for the ionic liquids, choline acetate, and 1-butyl-3-methylimidazolium acetate. Dynamic correlation beyond the first ionic solvation shell on the time scale of nanoseconds is found in the ionic liquids, revealing the cooperative nature of ion motions. The traditional solvent, acetonitrile, on the other hand, shows a much shorter length-scale that decays after a few picoseconds.

Fast fission phenomenon, deep inelastic reactions and compound nucleus formation described within a dynamical macroscopic model

International Nuclear Information System (INIS)

Gregoire, C.; Ngo, C.; Remaud, B.

1982-01-01

We present a dynamical model to describe dissipative heavy ion reactions. It treats explicitly the relative motion of the two ions, the mass asymmetry of the system and the projection of the isospin of each ion. The deformations, which are induced during the collision, are simulated with a time-dependent interaction potential. This is done by a time-dependent transition between a sudden interaction potential in the entrance channel and an adiabatic potential in the exit channel. The model allows us to compute the compound-nucleus cross section and multidifferential cross-sections for deep inelastic reactions. In addition, for some systems, and under certain conditions which are discussed in detail, a new dissipative heavy ion collision appears: fast-fission phenomenon which has intermediate properties between deep inelastic and compound nucleus reactions. The calculated properties concerning fast fission are compared with experimental results and reproduce some of those which could not be understood as belonging to deep inelastic or compound-nucleus reactions. (orig.)

Uncertainty quantification of fast sodium current steady-state inactivation for multi-scale models of cardiac electrophysiology.

Science.gov (United States)

Pathmanathan, Pras; Shotwell, Matthew S; Gavaghan, David J; Cordeiro, Jonathan M; Gray, Richard A

2015-01-01

Perhaps the most mature area of multi-scale systems biology is the modelling of the heart. Current models are grounded in over fifty years of research in the development of biophysically detailed models of the electrophysiology (EP) of cardiac cells, but one aspect which is inadequately addressed is the incorporation of uncertainty and physiological variability. Uncertainty quantification (UQ) is the identification and characterisation of the uncertainty in model parameters derived from experimental data, and the computation of the resultant uncertainty in model outputs. It is a necessary tool for establishing the credibility of computational models, and will likely be expected of EP models for future safety-critical clinical applications. The focus of this paper is formal UQ of one major sub-component of cardiac EP models, the steady-state inactivation of the fast sodium current, INa. To better capture average behaviour and quantify variability across cells, we have applied for the first time an 'individual-based' statistical methodology to assess voltage clamp data. Advantages of this approach over a more traditional 'population-averaged' approach are highlighted. The method was used to characterise variability amongst cells isolated from canine epi and endocardium, and this variability was then 'propagated forward' through a canine model to determine the resultant uncertainty in model predictions at different scales, such as of upstroke velocity and spiral wave dynamics. Statistically significant differences between epi and endocardial cells (greater half-inactivation and less steep slope of steady state inactivation curve for endo) was observed, and the forward propagation revealed a lack of robustness of the model to underlying variability, but also surprising robustness to variability at the tissue scale. Overall, the methodology can be used to: (i) better analyse voltage clamp data; (ii) characterise underlying population variability; (iii) investigate

Model validation of solar PV plant with hybrid data dynamic simulation based on fast-responding generator method

Directory of Open Access Journals (Sweden)

Zhao Dawei

2016-01-01

Full Text Available In recent years, a significant number of large-scale solar photovoltaic (PV plants have been put into operation or been under planning around the world. The model accuracy of solar PV plant is the key factor to investigate the mutual influences between solar PV plants and a power grid. However, this problem has not been well solved, especially in how to apply the real measurements to validate the models of the solar PV plants. Taking fast-responding generator method as an example, this paper presents a model validation methodology for solar PV plant via the hybrid data dynamic simulation. First, the implementation scheme of hybrid data dynamic simulation suitable for DIgSILENT PowerFactory software is proposed, and then an analysis model of solar PV plant integration based on IEEE 9 system is established. At last, model validation of solar PV plant is achieved by employing hybrid data dynamic simulation. The results illustrate the effectiveness of the proposed method in solar PV plant model validation.

Scaling of a fast spherical discharge

Energy Technology Data Exchange (ETDEWEB)

Antsiferov, P. S., E-mail: Ants@isan.troitsk.ru; Dorokhin, L. A. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)

2017-02-15

The influence of the discharge cavity dimensions on the properties of the spherical plasma formed in a fast discharge was studied experimentally. The passage of a current pulse with an amplitude of 30–40 kA and a rise rate of ~10{sup 12} A/s (a fast discharge) through a spherical ceramic (Al{sub 2}O{sub 3}) cavity with an inner diameter of 11 mm filled with argon at a pressure of 80 Pa results in the formation of a 1- to 2-mm-diameter spherical plasma with an electron temperature of several tens of electronvolts and a density of 10{sup 18}–10{sup 19} cm{sup –3}. It is shown that an increase in the inner diameter of the discharge cavity from 11 to 21 mm leads to the fourfold increase in the formation time of the spherical plasma and a decrease in the average ion charge. A decrease in the cavity diameter to 7 mm makes the spherical plasma unstable.

Dynamics of polymers in a good solvent - a molecular dynamics study using the Connection Machine

International Nuclear Information System (INIS)

Shannon, S.R.; Choy, T.C.

1996-01-01

In recent times the use of molecular dynamics simulations has become an important tool in modelling and understanding the dynamics of interacting many-body systems. With recent advances in computing power it is now feasible to perform modelling of systems which contain a large number of interacting particles, and thus to simulate the behaviour of real systems reasonably. Our earlier discoveries of anomalous corrections to scaling behaviour of the Edward's polymer were applied to study the dynamical behaviour of two dimensional polymer systems - either a single chain immersed in a fluid, a pure polymer melt, or with any concentration of polymers in the fluid. By choosing a suitable interaction potential between the fluid particles and the monomers, we are able to study the experimentally observable time dependent structure factor of polymers in a good solvent. Simulations were performed using the Connection Machine CM5 supercomputer at the Australian National University which due to its fast multi- processor nearest neighbour communications facility, enables us to easily model large systems of at least 3000 fluid plus monomer particles. Our study is based on a finite difference solution of Newton's equations of motion i.e. the Verlet algorithm, and the results are used to test current theories of polymer dynamics, which were based primarily on the earlier models proposed by Rouse (1953) and Zimm (1956). In particular dynamical scaling predictions is scrutinised to examine the effects due to the anomalous corrections-to-scaling behaviour found in an earlier work using finite-size scaling analysis of Monte-Carlo data and now understood via a new perturbation concept

Fast time-resolved aerosol collector: proof of concept

Science.gov (United States)

Yu, X.-Y.; Cowin, J. P.; Iedema, M. J.; Ali, H.

2010-10-01

Atmospheric particles can be collected in the field on substrates for subsequent laboratory analysis via chemically sensitive single particle methods such as scanning electron microscopy with energy dispersive x-ray analysis. With moving substrates time resolution of seconds to minutes can be achieved. In this paper, we demonstrate how to increase the time resolution when collecting particles on a substrate to a few milliseconds to provide real-time information. Our fast time-resolved aerosol collector ("Fast-TRAC") microscopically observes the particle collection on a substrate and records an on-line video. Particle arrivals are resolved to within a single frame (4-17 ms in this setup), and the spatial locations are matched to the subsequent single particle analysis. This approach also provides in-situ information on particle size and number concentration. Applications are expected in airborne studies of cloud microstructure, pollution plumes, and surface long-term monitoring.

Return times dynamics: role of the Poincare section in numerical analysis

International Nuclear Information System (INIS)

Pavlov, Alexey N.; Dumsky, Dmitry V.

2003-01-01

We study how different measures estimated from return time sequences are sensitive to choice of the Poincare section in the case of chaotic dynamics. We show that scaling characteristics of point processes are highly dependent on the secant plane. We focus on dynamical properties of a chaotic regime being more stable to displacements of the section than metrical characteristics

Timing, timing, timing: Fast decoding of object information from intracranial field potentials in human visual cortex

Science.gov (United States)

Liu, Hesheng; Agam, Yigal; Madsen, Joseph R.; Kreiman, Gabriel

2010-01-01

Summary The difficulty of visual recognition stems from the need to achieve high selectivity while maintaining robustness to object transformations within hundreds of milliseconds. Theories of visual recognition differ in whether the neuronal circuits invoke recurrent feedback connections or not. The timing of neurophysiological responses in visual cortex plays a key role in distinguishing between bottom-up and top-down theories. Here we quantified at millisecond resolution the amount of visual information conveyed by intracranial field potentials from 912 electrodes in 11 human subjects. We could decode object category information from human visual cortex in single trials as early as 100 ms post-stimulus. Decoding performance was robust to depth rotation and scale changes. The results suggest that physiological activity in the temporal lobe can account for key properties of visual recognition. The fast decoding in single trials is compatible with feed-forward theories and provides strong constraints for computational models of human vision. PMID:19409272

Dynamical basis for Koba-Nielsen-Olesen scaling and its violation

International Nuclear Information System (INIS)

Hinz, D.C.; Lam, C.S.

1986-01-01

We discuss a class of dynamical models motivated by Koba-Nielsen-Olesen (KNO) scaling and phase-space considerations. These modified phase-space models (MPSM's) generalize some of the existing models and provide them with a dynamical basis. Multiplicity distributions in MPSM's can be obtained by solving an appropriate evolution equation, from which kinematical KNO-scaling violations before the asymptotic scaling energy is reached can be calculated. Possible causes for dynamical KNO-scaling violations are also discussed

Space-time modeling of soil moisture

Science.gov (United States)

Chen, Zijuan; Mohanty, Binayak P.; Rodriguez-Iturbe, Ignacio

2017-11-01

A physically derived space-time mathematical representation of the soil moisture field is carried out via the soil moisture balance equation driven by stochastic rainfall forcing. The model incorporates spatial diffusion and in its original version, it is shown to be unable to reproduce the relative fast decay in the spatial correlation functions observed in empirical data. This decay resulting from variations in local topography as well as in local soil and vegetation conditions is well reproduced via a jitter process acting multiplicatively over the space-time soil moisture field. The jitter is a multiplicative noise acting on the soil moisture dynamics with the objective to deflate its correlation structure at small spatial scales which are not embedded in the probabilistic structure of the rainfall process that drives the dynamics. These scales of order of several meters to several hundred meters are of great importance in ecohydrologic dynamics. Properties of space-time correlation functions and spectral densities of the model with jitter are explored analytically, and the influence of the jitter parameters, reflecting variabilities of soil moisture at different spatial and temporal scales, is investigated. A case study fitting the derived model to a soil moisture dataset is presented in detail.

Deviations from uniform power law scaling in nonstationary time series

Science.gov (United States)

Viswanathan, G. M.; Peng, C. K.; Stanley, H. E.; Goldberger, A. L.

1997-01-01

A classic problem in physics is the analysis of highly nonstationary time series that typically exhibit long-range correlations. Here we test the hypothesis that the scaling properties of the dynamics of healthy physiological systems are more stable than those of pathological systems by studying beat-to-beat fluctuations in the human heart rate. We develop techniques based on the Fano factor and Allan factor functions, as well as on detrended fluctuation analysis, for quantifying deviations from uniform power-law scaling in nonstationary time series. By analyzing extremely long data sets of up to N = 10(5) beats for 11 healthy subjects, we find that the fluctuations in the heart rate scale approximately uniformly over several temporal orders of magnitude. By contrast, we find that in data sets of comparable length for 14 subjects with heart disease, the fluctuations grow erratically, indicating a loss of scaling stability.

Nonreciprocity in the dynamics of coupled oscillators with nonlinearity, asymmetry, and scale hierarchy

Science.gov (United States)

Moore, Keegan J.; Bunyan, Jonathan; Tawfick, Sameh; Gendelman, Oleg V.; Li, Shuangbao; Leamy, Michael; Vakakis, Alexander F.

2018-01-01

In linear time-invariant dynamical and acoustical systems, reciprocity holds by the Onsager-Casimir principle of microscopic reversibility, and this can be broken only by odd external biases, nonlinearities, or time-dependent properties. A concept is proposed in this work for breaking dynamic reciprocity based on irreversible nonlinear energy transfers from large to small scales in a system with nonlinear hierarchical internal structure, asymmetry, and intentional strong stiffness nonlinearity. The resulting nonreciprocal large-to-small scale energy transfers mimic analogous nonlinear energy transfer cascades that occur in nature (e.g., in turbulent flows), and are caused by the strong frequency-energy dependence of the essentially nonlinear small-scale components of the system considered. The theoretical part of this work is mainly based on action-angle transformations, followed by direct numerical simulations of the resulting system of nonlinear coupled oscillators. The experimental part considers a system with two scales—a linear large-scale oscillator coupled to a small scale by a nonlinear spring—and validates the theoretical findings demonstrating nonreciprocal large-to-small scale energy transfer. The proposed study promotes a paradigm for designing nonreciprocal acoustic materials harnessing strong nonlinearity, which in a future application will be implemented in designing lattices incorporating nonlinear hierarchical internal structures, asymmetry, and scale mixing.

Synaptic scaling enables dynamically distinct short- and long-term memory formation.

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Christian Tetzlaff

2013-10-01

Full Text Available Memory storage in the brain relies on mechanisms acting on time scales from minutes, for long-term synaptic potentiation, to days, for memory consolidation. During such processes, neural circuits distinguish synapses relevant for forming a long-term storage, which are consolidated, from synapses of short-term storage, which fade. How time scale integration and synaptic differentiation is simultaneously achieved remains unclear. Here we show that synaptic scaling - a slow process usually associated with the maintenance of activity homeostasis - combined with synaptic plasticity may simultaneously achieve both, thereby providing a natural separation of short- from long-term storage. The interaction between plasticity and scaling provides also an explanation for an established paradox where memory consolidation critically depends on the exact order of learning and recall. These results indicate that scaling may be fundamental for stabilizing memories, providing a dynamic link between early and late memory formation processes.

Synaptic scaling enables dynamically distinct short- and long-term memory formation.

Science.gov (United States)

Tetzlaff, Christian; Kolodziejski, Christoph; Timme, Marc; Tsodyks, Misha; Wörgötter, Florentin

2013-10-01

Memory storage in the brain relies on mechanisms acting on time scales from minutes, for long-term synaptic potentiation, to days, for memory consolidation. During such processes, neural circuits distinguish synapses relevant for forming a long-term storage, which are consolidated, from synapses of short-term storage, which fade. How time scale integration and synaptic differentiation is simultaneously achieved remains unclear. Here we show that synaptic scaling - a slow process usually associated with the maintenance of activity homeostasis - combined with synaptic plasticity may simultaneously achieve both, thereby providing a natural separation of short- from long-term storage. The interaction between plasticity and scaling provides also an explanation for an established paradox where memory consolidation critically depends on the exact order of learning and recall. These results indicate that scaling may be fundamental for stabilizing memories, providing a dynamic link between early and late memory formation processes.

Communication: Time-dependent optimized coupled-cluster method for multielectron dynamics

Science.gov (United States)

Sato, Takeshi; Pathak, Himadri; Orimo, Yuki; Ishikawa, Kenichi L.

2018-02-01

Time-dependent coupled-cluster method with time-varying orbital functions, called time-dependent optimized coupled-cluster (TD-OCC) method, is formulated for multielectron dynamics in an intense laser field. We have successfully derived the equations of motion for CC amplitudes and orthonormal orbital functions based on the real action functional, and implemented the method including double excitations (TD-OCCD) and double and triple excitations (TD-OCCDT) within the optimized active orbitals. The present method is size extensive and gauge invariant, a polynomial cost-scaling alternative to the time-dependent multiconfiguration self-consistent-field method. The first application of the TD-OCC method of intense-laser driven correlated electron dynamics in Ar atom is reported.

TIME-VARYING DYNAMICAL STAR FORMATION RATE

Energy Technology Data Exchange (ETDEWEB)

Lee, Eve J.; Chang, Philip; Murray, Norman, E-mail: evelee@berkeley.edu [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON M5S 3H8 (Canada)

2015-02-10

We present numerical evidence of dynamic star formation in which the accreted stellar mass grows superlinearly with time, roughly as t {sup 2}. We perform simulations of star formation in self-gravitating hydrodynamic and magnetohydrodynamic turbulence that is continuously driven. By turning the self-gravity of the gas in the simulations on or off, we demonstrate that self-gravity is the dominant physical effect setting the mass accretion rate at early times before feedback effects take over, contrary to theories of turbulence-regulated star formation. We find that gravitational collapse steepens the density profile around stars, generating the power-law tail on what is otherwise a lognormal density probability distribution function. Furthermore, we find turbulent velocity profiles to flatten inside collapsing regions, altering the size-line width relation. This local flattening reflects enhancements of turbulent velocity on small scales, as verified by changes to the velocity power spectra. Our results indicate that gas self-gravity dynamically alters both density and velocity structures in clouds, giving rise to a time-varying star formation rate. We find that a substantial fraction of the gas that forms stars arrives via low-density flows, as opposed to accreting through high-density filaments.

Scale-invariant entropy-based theory for dynamic ordering

International Nuclear Information System (INIS)

Mahulikar, Shripad P.; Kumari, Priti

2014-01-01

Dynamically Ordered self-organized dissipative structure exists in various forms and at different scales. This investigation first introduces the concept of an isolated embedding system, which embeds an open system, e.g., dissipative structure and its mass and/or energy exchange with its surroundings. Thereafter, scale-invariant theoretical analysis is presented using thermodynamic principles for Order creation, existence, and destruction. The sustainability criterion for Order existence based on its structured mass and/or energy interactions with the surroundings is mathematically defined. This criterion forms the basis for the interrelationship of physical parameters during sustained existence of dynamic Order. It is shown that the sufficient condition for dynamic Order existence is approached if its sustainability criterion is met, i.e., its destruction path is blocked. This scale-invariant approach has the potential to unify the physical understanding of universal dynamic ordering based on entropy considerations

Multi-Scale Entropy Analysis as a Method for Time-Series Analysis of Climate Data