Critical dynamics in population vaccinating behavior.

Science.gov (United States)

Pananos, A Demetri; Bury, Thomas M; Wang, Clara; Schonfeld, Justin; Mohanty, Sharada P; Nyhan, Brendan; Salathé, Marcel; Bauch, Chris T

2017-12-26

Vaccine refusal can lead to renewed outbreaks of previously eliminated diseases and even delay global eradication. Vaccinating decisions exemplify a complex, coupled system where vaccinating behavior and disease dynamics influence one another. Such systems often exhibit critical phenomena-special dynamics close to a tipping point leading to a new dynamical regime. For instance, critical slowing down (declining rate of recovery from small perturbations) may emerge as a tipping point is approached. Here, we collected and geocoded tweets about measles-mumps-rubella vaccine and classified their sentiment using machine-learning algorithms. We also extracted data on measles-related Google searches. We find critical slowing down in the data at the level of California and the United States in the years before and after the 2014-2015 Disneyland, California measles outbreak. Critical slowing down starts growing appreciably several years before the Disneyland outbreak as vaccine uptake declines and the population approaches the tipping point. However, due to the adaptive nature of coupled behavior-disease systems, the population responds to the outbreak by moving away from the tipping point, causing "critical speeding up" whereby resilience to perturbations increases. A mathematical model of measles transmission and vaccine sentiment predicts the same qualitative patterns in the neighborhood of a tipping point to greatly reduced vaccine uptake and large epidemics. These results support the hypothesis that population vaccinating behavior near the disease elimination threshold is a critical phenomenon. Developing new analytical tools to detect these patterns in digital social data might help us identify populations at heightened risk of widespread vaccine refusal. Copyright © 2017 the Author(s). Published by PNAS.

A highly accurate dynamic contact angle algorithm for drops on inclined surface based on ellipse-fitting.

Science.gov (United States)

Xu, Z N; Wang, S Y

2015-02-01

To improve the accuracy in the calculation of dynamic contact angle for drops on the inclined surface, a significant number of numerical drop profiles on the inclined surface with different inclination angles, drop volumes, and contact angles are generated based on the finite difference method, a least-squares ellipse-fitting algorithm is used to calculate the dynamic contact angle. The influences of the above three factors are systematically investigated. The results reveal that the dynamic contact angle errors, including the errors of the left and right contact angles, evaluated by the ellipse-fitting algorithm tend to increase with inclination angle/drop volume/contact angle. If the drop volume and the solid substrate are fixed, the errors of the left and right contact angles increase with inclination angle. After performing a tremendous amount of computation, the critical dimensionless drop volumes corresponding to the critical contact angle error are obtained. Based on the values of the critical volumes, a highly accurate dynamic contact angle algorithm is proposed and fully validated. Within nearly the whole hydrophobicity range, it can decrease the dynamic contact angle error in the inclined plane method to less than a certain value even for different types of liquids.

Dynamics of quantum discord in a quantum critical environment

International Nuclear Information System (INIS)

Xi Zhengjun; Li Yongming; Lu Xiaoming; Sun Zhe

2011-01-01

We study the dynamics of quantum discord (QD) of two qubits independently coupled to an Ising spin chain in a transverse field, which exhibits a quantum phase transition. For this model, we drive the corresponding Kraus operators, obtain the analytic results of QD and compare the dynamics of QD with the dynamics of relative entropy of entanglement nearby the critical point. It is shown that the impact of the quantum criticality environment on QD can be concentrated in a very narrow region nearby the critical point, so it supplies an efficient way to detect the critical points. In the vicinity of the critical point, the evolution of QD is shown to be more complicated than that of entanglement. Furthermore, we find that separable states can also be used to reflect the quantum criticality of the environment.

Surface water acidification and critical loads: exploring the F-factor

Directory of Open Access Journals (Sweden)

K. Bishop

2009-11-01

Full Text Available As acid deposition decreases, uncertainties in methods for calculating critical loads become more important when judgements have to be made about whether or not further emission reductions are needed. An important aspect of one type of model that has been used to calculate surface water critical loads is the empirical F-factor which estimates the degree to which acid deposition is neutralised before it reaches a lake at any particular point in time relative to the pre-industrial, steady-state water chemistry conditions.

In this paper we will examine how well the empirical F-functions are able to estimate pre-industrial lake chemistry as lake chemistry changes during different phases of acidification and recovery. To accomplish this, we use the dynamic, process-oriented biogeochemical model SAFE to generate a plausible time series of annual runoff chemistry for ca. 140 Swedish catchments between 1800 and 2100. These annual hydrochemistry data are then used to generate empirical F-factors that are compared to the "actual" F-factor seen in the SAFE data for each lake and year in the time series. The dynamics of the F-factor as catchments acidify, and then recover are not widely recognised.

Our results suggest that the F-factor approach worked best during the acidification phase when soil processes buffer incoming acidity. However, the empirical functions for estimating F from contemporary lake chemistry are not well suited to the recovery phase when the F-factor turns negative due to recovery processes in the soil. This happens when acid deposition has depleted the soil store of BC, and then acid deposition declines, reducing the leaching of base cations to levels below those in the pre-industrial era. An estimate of critical load from water chemistry during recovery and empirical F functions would therefore result in critical loads that are too low. Therefore, the empirical estimates of the F-factor are a significant source of

Effects of surface modification on the critical behaviour in multiple-surface-layer ferroelectric thin films

International Nuclear Information System (INIS)

Lu, Z X

2013-01-01

Using the usual mean-field theory approximation, the critical behaviour (i.e. the Curie temperature T c and the critical surface transverse field Ω sc ) in a multiple-surface-layer ferroelectric thin film is studied on the basis of the spin- 1/2 transverse Ising model. The dependence of the Curie temperature T c on the surface transverse field Ω s and the surface layer number N s are discussed in detail. Meanwhile the dependence of the critical surface transverse field Ω sc on the surface layer number N s is also examined. The numerical results indicate that the critical behaviour of ferroelectric thin films is obviously affected by modifications of the surface transverse field Ω s and surface layer number N s .

Molecular dynamics simulation of potentiometric sensor response: the effect of biomolecules, surface morphology and surface charge.

Science.gov (United States)

Lowe, B M; Skylaris, C-K; Green, N G; Shibuta, Y; Sakata, T

2018-05-10

The silica-water interface is critical to many modern technologies in chemical engineering and biosensing. One technology used commonly in biosensors, the potentiometric sensor, operates by measuring the changes in electric potential due to changes in the interfacial electric field. Predictive modelling of this response caused by surface binding of biomolecules remains highly challenging. In this work, through the most extensive molecular dynamics simulation of the silica-water interfacial potential and electric field to date, we report a novel prediction and explanation of the effects of nano-morphology on sensor response. Amorphous silica demonstrated a larger potentiometric response than an equivalent crystalline silica model due to increased sodium adsorption, in agreement with experiments showing improved sensor response with nano-texturing. We provide proof-of-concept that molecular dynamics can be used as a complementary tool for potentiometric biosensor response prediction. Effects that are conventionally neglected, such as surface morphology, water polarisation, biomolecule dynamics and finite-size effects, are explicitly modelled.

Self-regulated dynamical criticality in human ECoG

Directory of Open Access Journals (Sweden)

Guillermo eSolovey

2012-07-01

Full Text Available Mounting experimental and theoretical results indicate that neural systems are poised near a critical state. In human subjects, however, most evidence comes from functional MRI studies, an indirect measurement of neuronal activity with poor temporal resolution. Electrocorticography (ECoG provides a unique window into human brain activity: each electrode records, with high temporal resolution, the activity resulting from the sum of the local field potentials of sim 10^5 neurons. We show that the human brain ECoG recordings display features of self-regulated dynamical criticality: dynamical modes of activation drift around the critical stability threshold, moving in and out of the unstable region and equilibrating the global dynamical state at a very fast time scale. Moreover, the analysis also reveals differences between the resting state and a motor task, associated with increased stability of a fraction of the dynamical modes.

Bursting and critical layer frequencies in minimal turbulent dynamics and connections to exact coherent states

Science.gov (United States)

Park, Jae Sung; Shekar, Ashwin; Graham, Michael D.

2018-01-01

The dynamics of the turbulent near-wall region is known to be dominated by coherent structures. These near-wall coherent structures are observed to burst in a very intermittent fashion, exporting turbulent kinetic energy to the rest of the flow. In addition, they are closely related to invariant solutions known as exact coherent states (ECS), some of which display nonlinear critical layer dynamics (motions that are highly localized around the surface on which the streamwise velocity matches the wave speed of ECS). The present work aims to investigate temporal coherence in minimal channel flow relevant to turbulent bursting and critical layer dynamics and its connection to the instability of ECS. It is seen that the minimal channel turbulence displays frequencies very close to those displayed by an ECS family recently identified in the channel flow geometry. The frequencies of these ECS are determined by critical layer structures and thus might be described as "critical layer frequencies." While the bursting frequency is predominant near the wall, the ECS frequencies (critical layer frequencies) become predominant over the bursting frequency at larger distances from the wall, and increasingly so as Reynolds number increases. Turbulent bursts are classified into strong and relatively weak classes with respect to an intermittent approach to a lower branch ECS. This temporally intermittent approach is closely related to an intermittent low drag event, called hibernating turbulence, found in minimal and large domains. The relationship between the strong burst and the instability of the lower branch ECS is further discussed in state space. The state-space dynamics of strong bursts is very similar to that of the unstable manifolds of the lower branch ECS. In particular, strong bursting processes are always preceded by hibernation events. This precursor dynamics to strong turbulence may aid in development of more effective control schemes by a way of anticipating dynamics

Data collapse and critical dynamics in neuronal avalanche data

Science.gov (United States)

Butler, Thomas; Friedman, Nir; Dahmen, Karin; Beggs, John; Deville, Lee; Ito, Shinya

2012-02-01

The tasks of information processing, computation, and response to stimuli require neural computation to be remarkably flexible and diverse. To optimally satisfy the demands of neural computation, neuronal networks have been hypothesized to operate near a non-equilibrium critical point. In spite of their importance for neural dynamics, experimental evidence for critical dynamics has been primarily limited to power law statistics that can also emerge from non-critical mechanisms. By tracking the firing of large numbers of synaptically connected cortical neurons and comparing the resulting data to the predictions of critical phenomena, we show that cortical tissues in vitro can function near criticality. Among the most striking predictions of critical dynamics is that the mean temporal profiles of avalanches of widely varying durations are quantitatively described by a single universal scaling function (data collapse). We show for the first time that this prediction is confirmed in neuronal networks. We also show that the data have three additional features predicted by critical phenomena: approximate power law distributions of avalanche sizes and durations, samples in subcritical and supercritical phases, and scaling laws between anomalous exponents.

Photochemical dynamics of surface oriented molecules

International Nuclear Information System (INIS)

Ho, W.

1992-01-01

The period 8/01/91-7/31/92 is the first year of a new project titled ''Photochemical Dynamics of Surface Oriented Molecules'', initiated with DOE Support. The main objective of this project is to understand the dynamics of elementary chemical reactions by studying photochemical dynamics of surface-oriented molecules. In addition, the mechanisms of photon-surface interactions need to be elucidated. The strategy is to carry out experiments to measure the translational energy distribution, as a function of the angle from the surface normal, of the photoproducts by time-of-flight (TOF) technique by varying the photon wavelength, intensity, polarization, and pulse duration. By choosing adsorbates with different bonding configuration, the effects of adsorbate orientation on surface photochemical dynamics can be studied

Probing Ultrafast Electron Dynamics at Surfaces Using Soft X-Ray Transient Reflectivity Spectroscopy

Science.gov (United States)

Baker, L. Robert; Husek, Jakub; Biswas, Somnath; Cirri, Anthony

The ability to probe electron dynamics with surface sensitivity on the ultrafast time scale is critical for understanding processes such as charge separation, injection, and surface trapping that mediate efficiency in catalytic and energy conversion materials. Toward this goal, we have developed a high harmonic generation (HHG) light source for femtosecond soft x-ray reflectivity. Using this light source we investigated the ultrafast carrier dynamics at the surface of single crystalline α-Fe2O3, polycrystalline α-Fe2O3, and the mixed metal oxide, CuFeO2. We have recently demonstrated that CuFeO2 in particular is a selective catalyst for photo-electrochemical CO2 reduction to acetate; however, the role of electronic structure and charge carrier dynamics in mediating catalytic selectivity has not been well understood. Soft x-ray reflectivity measurements probe the M2,3, edges of the 3d transition metals, which provide oxidation and spin state resolution with element specificity. In addition to chemical state specificity, these measurements are also surface sensitive, and by independently simulating the contributions of the real and imaginary components of the complex refractive index, we can differentiate between surface and sub-surface contributions to the excited state spectrum. Accordingly, this work demonstrates the ability to probe ultrafast carrier dynamics in catalytic materials with element and chemical state specificity and with surface sensitivity.

Phase space barriers and dividing surfaces in the absence of critical points of the potential energy: Application to roaming in ozone

Energy Technology Data Exchange (ETDEWEB)

Mauguière, Frédéric A. L., E-mail: frederic.mauguiere@bristol.ac.uk; Collins, Peter, E-mail: peter.collins@bristol.ac.uk; Wiggins, Stephen, E-mail: stephen.wiggins@mac.com [School of Mathematics, University of Bristol, Bristol BS8 1TW (United Kingdom); Kramer, Zeb C., E-mail: zebcolterkramer@gmail.com; Ezra, Gregory S., E-mail: gse1@cornell.edu [Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853 (United States); Carpenter, Barry K., E-mail: carpenterb1@cardiff.ac.uk [School of Chemistry, Cardiff University, Cardiff CF10 3AT (United Kingdom); Farantos, Stavros C., E-mail: farantos@iesl.forth.gr [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, and Department of Chemistry, University of Crete, Iraklion 711 10, Crete (Greece)

2016-02-07

We examine the phase space structures that govern reaction dynamics in the absence of critical points on the potential energy surface. We show that in the vicinity of hyperbolic invariant tori, it is possible to define phase space dividing surfaces that are analogous to the dividing surfaces governing transition from reactants to products near a critical point of the potential energy surface. We investigate the problem of capture of an atom by a diatomic molecule and show that a normally hyperbolic invariant manifold exists at large atom-diatom distances, away from any critical points on the potential. This normally hyperbolic invariant manifold is the anchor for the construction of a dividing surface in phase space, which defines the outer or loose transition state governing capture dynamics. We present an algorithm for sampling an approximate capture dividing surface, and apply our methods to the recombination of the ozone molecule. We treat both 2 and 3 degrees of freedom models with zero total angular momentum. We have located the normally hyperbolic invariant manifold from which the orbiting (outer) transition state is constructed. This forms the basis for our analysis of trajectories for ozone in general, but with particular emphasis on the roaming trajectories.

Ab initio lattice dynamics of metal surfaces

International Nuclear Information System (INIS)

Heid, R.; Bohnen, K.-P.

2003-01-01

Dynamical properties of atoms on surfaces depend sensitively on their bonding environment and thus provide valuable insight into the local geometry and chemical binding at the boundary of a solid. Density-functional theory provides a unified approach to the calculation of structural and dynamical properties from first principles. Its high accuracy and predictive power for lattice dynamical properties of semiconductor surfaces has been demonstrated in a previous article by Fritsch and Schroeder (Phys. Rep. 309 (1999) 209). In this report, we review the state-of-the-art of these ab initio approaches to surface dynamical properties of metal surfaces. We give a brief introduction to the conceptual framework with focus on recent advances in computational procedures for the ab initio linear-response approach, which have been a prerequisite for an efficient treatment of surface dynamics of noble and transition metals. The discussed applications to clean and adsorbate-covered surfaces demonstrate the high accuracy and reliability of this approach in predicting detailed microscopic properties of the phonon dynamics for a wide range of metallic surfaces

Dynamical speckles in watery surfaces

International Nuclear Information System (INIS)

Llovera-Gonzalez, J.J.; Moreno-Yeras, A.; Garcia-Diaz, M.; Alvarez-Salgado, Y.

2009-01-01

Recovery of watery surfaces with monolayer of surfactant substances is of interest in diverse technological applications. The format ion and study of molecular monolayer deposited in these surfaces require the application of measurements techniques that allow evaluating the recovery grade locally without modifying practically the studied surface. In this paper the preliminary results obtained by the authors it plows exposed applying the technique of dynamic speckle interferometry in watery surfaces and their consideration like to possible resource to measure the grade of local recovery of these surfaces on the it bases that the speckles pattern dog reveal the dynamics of evaporation that takes place in the same ones. (Author)

Slow dynamics at critical points: the field-theoretical perspective

International Nuclear Information System (INIS)

Gambassi, Andrea

2006-01-01

The dynamics at a critical point provides a simple instance of slow collective evolution, characterised by aging phenomena and by a violation of the fluctuation-dissipation relation even for long times. By virtue of the universality in critical phenomena it is possible to provide quantitative predictions for some aspects of these behaviours by field-theoretical methods. We review some of the theoretical results that have been obtained in recent years for the relevant (universal) quantities, such as the fluctuation-dissipation ratio, associated with the non-equilibrium critical dynamics

Universal Critical Dynamics in High Resolution Neuronal Avalanche Data

Science.gov (United States)

Friedman, Nir; Ito, Shinya; Brinkman, Braden A. W.; Shimono, Masanori; DeVille, R. E. Lee; Dahmen, Karin A.; Beggs, John M.; Butler, Thomas C.

2012-05-01

The tasks of neural computation are remarkably diverse. To function optimally, neuronal networks have been hypothesized to operate near a nonequilibrium critical point. However, experimental evidence for critical dynamics has been inconclusive. Here, we show that the dynamics of cultured cortical networks are critical. We analyze neuronal network data collected at the individual neuron level using the framework of nonequilibrium phase transitions. Among the most striking predictions confirmed is that the mean temporal profiles of avalanches of widely varying durations are quantitatively described by a single universal scaling function. We also show that the data have three additional features predicted by critical phenomena: approximate power law distributions of avalanche sizes and durations, samples in subcritical and supercritical phases, and scaling laws between anomalous exponents.

Critical Dynamics of Burst Instabilities in the Portevin-Le Chatelier Effect

International Nuclear Information System (INIS)

D'Anna, Gianfranco; Nori, Franco

2000-01-01

We investigate the Portevin-Le Chatelier effect (PLC), by compressing Al-Mg alloys in a very large deformation range, and interpret the results from the viewpoint of phase transitions and critical phenomena. The system undergoes two dynamical phase transitions between intermittent (or ''jerky'') and ''laminar'' plastic dynamic phases. Near these two dynamic critical points, the order parameter 1/τ of the PLC effect exhibits large fluctuations, and ''critical slowing down'' (i.e., the number τ of bursts, or plastic instabilities, per unit time slows down considerably)

Surface-Assisted Dynamic Search Processes.

Science.gov (United States)

Shin, Jaeoh; Kolomeisky, Anatoly B

2018-03-01

Many chemical and biological systems exhibit intermittent search phenomena when participating particles alternate between dynamic regimes with different dimensionalities. Here we investigate theoretically a dynamic search process of finding a small target on a two-dimensional surface starting from a bulk solution, which is an example of such an intermittent search process. Both continuum and discrete-state stochastic descriptions are developed. It is found that depending on the scanning length λ, which describes the area visited by the reacting molecule during one search cycle, the system can exhibit three different search regimes: (i) For small λ values, the reactant finds the target mostly via three-dimensional bulk diffusion; (ii) for large λ values, the reactant molecule associates to the target mostly via surface diffusion; and (iii) for intermediate λ values, the reactant reaches the target via a combination of three-dimensional and two-dimensional search cycles. Our analysis also shows that the mean search times have different scalings as a function of the size of the surface segment depending on the nature of the dynamic search regime. Search dynamics are also sensitive to the position of the target for large scanning lengths. In addition, it is argued that the continuum description underestimates mean search times and does not always correctly describe the most optimal conditions for the surface-assisted dynamic processes. The importance of our findings for real natural systems is discussed.

Role of the surface in the critical behavior of finite systems

Energy Technology Data Exchange (ETDEWEB)

Duflot, V.; Chomaz, Ph. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France); Gulminelli, F. [Laboratoire de Physique Corpusculaire, LPC-ISMRa, CNRS-IN2P3, 14 - Caen (France)

2000-07-01

The role of surfaces in a finite system undergoing a critical phenomenon is discussed in a canonical lattice-gas model. Surfaces are constrained by a mean volume defined via a La grange multiplier. We show that critical fragment size distributions are conserved even in very small systems with surfaces. This implies that critical signals are still relevant in the study of phase transitions in finite systems. (authors)

Dynamics of Wetting of Ultra Hydrophobic Surfaces

Science.gov (United States)

Mohammad Karim, Alireza; Kim, Jeong-Hyun; Rothstein, Jonathan; Kavehpour, Pirouz; Mechanical and Industrial Engineering, University of Massachusetts, Amherst Collaboration

2013-11-01

Controlling the surface wettability of hydrophobic and super hydrophobic surfaces has extensive industrial applications ranging from coating, painting and printing technology and waterproof clothing to efficiency increase in power and water plants. This requires enhancing the knowledge about the dynamics of wetting on these hydrophobic surfaces. We have done experimental investigation on the dynamics of wetting on hydrophobic surfaces by looking deeply in to the dependency of the dynamic contact angles both advancing and receding on the velocity of the three-phase boundary (Solid/Liquid/Gas interface) using the Wilhelmy plate method with different ultra-hydrophobic surfaces. Several fluids with different surface tension and viscosity are used to study the effect of physical properties of liquids on the governing laws.

Pinning effect on critical dynamics in Tl2Ba2CaCu2O8 films before and after introducing columnar defects

International Nuclear Information System (INIS)

Kim, J.-T.

1998-01-01

The effect of columnar defects on the critical dynamics of superconducting Tl 2 Ba 2 CaCu 2 O 8 (Tl-2212) film has been investigated. The Tl-2212 film was irradiated at 0 C by 1.3 GeV U-ions along the normal of the film surface. The dose of 6.0 x 10 10 ions/cm 2 of the U-ion irradiation corresponds to a matching field of 1.2 T. The in-plane longitudinal resistivity of the irradiated Tl-2212 has been measured as a function of magnetic field H and temperature T. The extracted fluctuation part of the conductivity σ xx (T, H) of the unirradiated sample exhibits 3D-XY scaling behavior that reveals dynamic critical exponent z = 1.8 ± 0.1 and static critical exponent v ∼ 1.338. The results indicate that the weak interlayer coupling along the c-axis of Tl-2212 significantly influences static critical exponent v and does not change dynamical critical exponent. After the irradiation, the fluctuation conductivities are enhanced by the strong pinnings and do not exhibit the same 3D-XY scaling behavior as for the unirradiated Tl-2212. Particularly at the low magnetic field values near the matching field of 1.2 T, the fluctuation conductivities show a clear deviation from the critical dynamics, suggesting that the pinning effect on the critical dynamics is significant

On the concept of critical surface excess of micellization.

Science.gov (United States)

Talens-Alesson, Federico I

2010-11-16

The critical surface excess of micellization (CSEM) should be regarded as the critical condition for micellization of ionic surfactants instead of the critical micelle concentration (CMC). There is a correspondence between the surface excesses Γ of anionic, cationic, and zwitterionic surfactants at their CMCs, which would be the CSEM values, and the critical association distance for ionic pair association calculated using Bjerrum's correlation. Further support to this concept is given by an accurate method for the prediction of the relative binding of alkali cations onto dodecylsulfate (NaDS) micelles. This method uses a relative binding strength parameter calculated from the values of surface excess Γ at the CMC of the alkali dodecylsulfates. This links both the binding of a given cation onto micelles and the onset for micellization of its surfactant salt. The CSEM concept implies that micelles form at the air-water interface unless another surface with greater affinity for micelles exists. The process would start when surfactant monomers are close enough to each other for ionic pairing with counterions and the subsequent assembly of these pairs becomes unavoidable. This would explain why the surface excess Γ values of different surfactants are more similar than their CMCs: the latter are just the bulk phase concentrations in equilibrium with chemicals with different hydrophobicity. An intriguing implication is that CSEM values may be used to calculate the actual critical distances of ionic pair formation for different cations, replacing Bjerrum's estimates, which only discriminate by the magnitude of the charge.

Structure, biomimetics, and fluid dynamics of fish skin surfaces*

Science.gov (United States)

Lauder, George V.; Wainwright, Dylan K.; Domel, August G.; Weaver, James C.; Wen, Li; Bertoldi, Katia

2016-10-01

The interface between the fluid environment and the surface of the body in swimming fishes is critical for both physiological and hydrodynamic functions. The skin surface in most species of fishes is covered with bony scales or toothlike denticles (in sharks). Despite the apparent importance of fish surfaces for understanding aquatic locomotion and near-surface boundary layer flows, relatively little attention has been paid to either the nature of surface textures in fishes or possible hydrodynamic effects of variation in roughness around the body surface within an individual and among species. Fish surfaces are remarkably diverse and in many bony fishes scales can have an intricate surface texture with projections, ridges, and comblike extensions. Shark denticles (or scales) are toothlike and project out of the skin to form a complexly textured surface that interacts with free-stream flow. Manufacturing biomimetic foils with fishlike surfaces allows hydrodynamic testing and we emphasize here the importance of dynamic test conditions where the effect of surface textures is assessed under conditions of self-propulsion. We show that simple two-dimensional foils with patterned cuts do not perform as well as a smooth control surface, but that biomimetic shark skin foils can swim at higher self-propelled speeds than smooth controls. When the arrangement of denticles on the foil surface is altered, we find that a staggered-overlapped pattern outperforms other arrangements. Flexible foils made of real shark skin outperform sanded controls when foils are moved with a biologically realistic motion program. We suggest that focus on the mechanisms of drag reduction by fish surfaces has been too limiting and an additional role of fish surface textures may be to alter leading edge vortices and flow patterns on moving surfaces in a way that enhances thrust. Analysis of water flow over an artificial shark skin foil under both static and dynamic conditions shows that a shear layer

Surface and finite size effect on fluctuations dynamics in nanoparticles with long-range order

Science.gov (United States)

Morozovska, A. N.; Eliseev, E. A.

2010-02-01

The influence of surface and finite size on the dynamics of the order parameter fluctuations and critical phenomena in the three-dimensional (3D)-confined systems with long-range order was not considered theoretically. In this paper, we study the influence of surface and finite size on the dynamics of the order parameter fluctuations in the particles of arbitrary shape. We consider concrete examples of the spherical and cylindrical ferroic nanoparticles within Landau-Ginzburg-Devonshire phenomenological approach. Allowing for the strong surface energy contribution in micro and nanoparticles, the analytical expressions derived for the Ornstein-Zernike correlator of the long-range order parameter spatial-temporal fluctuations, dynamic generalized susceptibility, relaxation times, and correlation radii discrete spectra are different from those known for bulk systems. Obtained analytical expressions for the correlation function of the order parameter spatial-temporal fluctuations in micro and nanosized systems can be useful for the quantitative analysis of the dynamical structural factors determined from magnetic resonance diffraction and scattering spectra. Besides the practical importance of the correlation function for the analysis of the experimental data, derived expressions for the fluctuations strength determine the fundamental limits of phenomenological theories applicability for 3D-confined systems.

Molecular-dynamics theory of the temperature-dependent surface phonons of W(001)

International Nuclear Information System (INIS)

Wang, C.Z.; Fasolino, A.; Tosatti, E.

1987-04-01

We study the temperature-dependent zone-boundary surface phonons across the c(2x2)→1x1 reconstruction phase transition of the clean W(001) surface. Velocity-velocity correlations and hence the phonon spectral densities are calculated by molecular dynamics for the surface atoms of a finite thickness (001) slab, with interatomic potentials established in a previous study of the surface statics. Our calculated k = (1/2,1/2)(2π/a) surface phonon are dominated by three main low-frequency modes. Of these, the longitudinal and the shear horizontal are reconstruction-related and display critical broadening and softening at the phase transition, while the third, the shear vertical, is basically unaffected. The reconstruction phase mode, shear horizontal, appears to be responsible for the phase fluctuations which destroy long-range order at the transition. (author). 30 refs, 12 figs

Quench dynamics across quantum critical points

International Nuclear Information System (INIS)

Sengupta, K.; Powell, Stephen; Sachdev, Subir

2004-01-01

We study the quantum dynamics of a number of model systems as their coupling constants are changed rapidly across a quantum critical point. The primary motivation is provided by the recent experiments of Greiner et al. [Nature (London) 415, 39 (2002)] who studied the response of a Mott insulator of ultracold atoms in an optical lattice to a strong potential gradient. In a previous work, it had been argued that the resonant response observed at a critical potential gradient could be understood by proximity to an Ising quantum critical point describing the onset of density wave order. Here we obtain numerical results on the evolution of the density wave order as the potential gradient is scanned across the quantum critical point. This is supplemented by studies of the integrable quantum Ising spin chain in a transverse field, where we obtain exact results for the evolution of the Ising order correlations under a time-dependent transverse field. We also study the evolution of transverse superfluid order in the three-dimensional case. In all cases, the order parameter is best enhanced in the vicinity of the quantum critical point

Characterizing heterogeneous dynamics at hydrated electrode surfaces

Science.gov (United States)

Willard, Adam P.; Limmer, David T.; Madden, Paul A.; Chandler, David

2013-05-01

In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

Characterizing heterogeneous dynamics at hydrated electrode surfaces.

Science.gov (United States)

Willard, Adam P; Limmer, David T; Madden, Paul A; Chandler, David

2013-05-14

In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

The Dynamics of Agile Practices for Safety-Critical Software Development

DEFF Research Database (Denmark)

Nielsen, Peter Axel; Tordrup Heeager, Lise

2017-01-01

This short paper reports from a case study of the agile development of safety-critical software. It utilizes a framework of dynamic relationships between agile practices with the purpose of demonstrating the utility of the framework to understand a case in its context, and it shows significant...... dynamics. The study is concluded by pointing at which further research on the framework is required to use the framework in managing the agile development of safety-critical software....

Collective motion of macroscopic spheres floating on capillary ripples: dynamic heterogeneity and dynamic criticality.

Science.gov (United States)

Sanlı, Ceyda; Saitoh, Kuniyasu; Luding, Stefan; van der Meer, Devaraj

2014-09-01

When a densely packed monolayer of macroscopic spheres floats on chaotic capillary Faraday waves, a coexistence of large scale convective motion and caging dynamics typical for glassy systems is observed. We subtract the convective mean flow using a coarse graining (homogenization) method and reveal subdiffusion for the caging time scales followed by a diffusive regime at later times. We apply the methods developed to study dynamic heterogeneity and show that the typical time and length scales of the fluctuations due to rearrangements of observed particle groups significantly increase when the system approaches its largest experimentally accessible packing concentration. To connect the system to the dynamic criticality literature, we fit power laws to our results. The resultant critical exponents are consistent with those found in densely packed suspensions of colloids.

Assessments of the kinetic and dynamic transient behavior of sub-critical systems (ADS) in comparison to critical reactor systems

International Nuclear Information System (INIS)

Schikorr, W.M.

2001-01-01

The neutron kinetic and the reactor dynamic behavior of Accelerator Driven Systems (ADS) is significantly different from those of conventional power reactor systems currently in use for the production of power. It is the objective of this study to examine and to demonstrate the intrinsic differences of the kinetic and dynamic behavior of accelerator driven systems to typical plant transient initiators in comparison to the known, kinetic and dynamic behavior of critical thermal and fast reactor systems. It will be shown that in sub-critical assemblies, changes in reactivity or in the external neutron source strength lead to an asymptotic power level essentially described by the instantaneous power change (i.e. prompt jump). Shutdown of ADS operating at high levels of sub-criticality, (i.e. k eff ∼0.99), without the support of reactivity control systems (such as control or safety rods), may be problematic in case the ability of cooling of the core should be impaired (i.e. loss of coolant flow). In addition, the dynamic behavior of sub-critical systems to typical plant transients such as protected or unprotected loss of flow (LOF) or heat sink (LOH) transients are not necessarily substantially different from the plant dynamic behavior of critical systems if the reactivity feedback coefficients of the ADS design are unfavorable. As expected, the state of sub-criticality and the temperature feedback coefficients, such as Doppler and coolant temperature coefficient, play dominant roles in determining the course and direction of plant transients. Should the combination of these safety coefficients be very unfavorable, not much additional margin in safety may be gained by making a critical system only sub-critical (i.e. k eff ∼0.95). A careful optimization procedure between the selected operating level of sub-criticality, the safety reactivity coefficients and the possible need for additional reactivity control systems seems, therefore, advisable during the early

He atom-surface scattering: Surface dynamics of insulators, overlayers and crystal growth

International Nuclear Information System (INIS)

Safron, S.A.; Skofronick, J.G.

1994-01-01

This progress report describes work carried out in the study of surface structure and dynamics of ionic insulators, the microscopic interactions controlling epitaxial growth and the formation of overlayers, and energy exchange in multiphonon surface scattering. The approach used is to employ high resolution helium atom scattering to study the geometry and structural features of the surfaces. Experiments have been carried out on the surface dynamics of RbCl and preliminary studies done on CoO and NiO. Epitaxial growth and overlayer dynamics experiments on the systems NaCl/NaCl(001), KBr/NaCl(001), NaCl/KBr(001) and KBr/RbCl(001) have been performed. They have collaborated with two theoretical groups to explore models of overlayer dynamics with which to compare and to interpret their experimental results. They have carried out extensive experiments on the multiphonon scattering of helium atoms from NaCl and, particularly, LiF. Work has begun on self-assembling organic films on gold and silver surfaces (alkyl thiols/Au(111) and Ag(111))

Quantum critical dynamics for a prototype class of insulating antiferromagnets

Science.gov (United States)

Wu, Jianda; Yang, Wang; Wu, Congjun; Si, Qimiao

2018-06-01

Quantum criticality is a fundamental organizing principle for studying strongly correlated systems. Nevertheless, understanding quantum critical dynamics at nonzero temperatures is a major challenge of condensed-matter physics due to the intricate interplay between quantum and thermal fluctuations. The recent experiments with the quantum spin dimer material TlCuCl3 provide an unprecedented opportunity to test the theories of quantum criticality. We investigate the nonzero-temperature quantum critical spin dynamics by employing an effective O (N ) field theory. The on-shell mass and the damping rate of quantum critical spin excitations as functions of temperature are calculated based on the renormalized coupling strength and are in excellent agreement with experiment observations. Their T lnT dependence is predicted to be dominant at very low temperatures, which will be tested in future experiments. Our work provides confidence that quantum criticality as a theoretical framework, which is being considered in so many different contexts of condensed-matter physics and beyond, is indeed grounded in materials and experiments accurately. It is also expected to motivate further experimental investigations on the applicability of the field theory to related quantum critical systems.

Avoided critical behavior in dynamically forced wetting.

Science.gov (United States)

Snoeijer, Jacco H; Delon, Giles; Fermigier, Marc; Andreotti, Bruno

2006-05-05

A solid object can be coated by a nonwetting liquid since a receding contact line cannot exceed a critical speed. In this Letter we study the dynamical wetting transition at which a liquid film gets deposited by withdrawing a vertical plate out of a liquid reservoir. It has recently been predicted that this wetting transition is critical with diverging time scales and coincides with the disappearance of stationary menisci. We demonstrate experimentally and theoretically that the transition is due to the formation of a solitary wave, well below the critical point. As a consequence, relaxation times remain finite at threshold. The structure of the liquid deposited on the plate involves a capillary ridge that does not trivially match the Landau-Levich film.

Effects of surface and bulk transverse fields on critical behaviour of ferromagnetic films

International Nuclear Information System (INIS)

Saber, A.; Lo Russo, S.; Mattei, G.

2002-02-01

The influence of surface and bulk transverse fields on the critical behaviour of a ferromagnetic Ising film is studied using the effective field theory based on a single-site cluster method. Surface exchange enhancement is considered and a critical value is obtained. The dependence of the critical uniform transverse field on film thickness, phase diagrams in the fields, critical surface transverse field versus the bulk one, and exchange coupling ratio are presented. (author)

Pulsed laser stereophotography of plasmas and dynamically moving surfaces

International Nuclear Information System (INIS)

Paisley, D.L.

1987-01-01

A pulsed laser is used as a light source for illuminating the surface of a dynamic event of 3 mm//μs. At a predetermined time during the dynamic action, a stereo camera is used to record a pair of images of the dynamically moving surface. The stereoimage pair can be quantified for surface contour

Summing Feynman graphs by Monte Carlo: Planar φ3-theory and dynamically triangulated random surfaces

International Nuclear Information System (INIS)

Boulatov, D.V.

1988-01-01

New combinatorial identities are suggested relating the ratio of (n-1)th and nth orders of (planar) perturbation expansion for any quantity to some average over the ensemble of all planar graphs of the nth order. These identities are used for Monte Carlo calculation of critical exponents γ str (string susceptibility) in planar φ 3 -theory and in the dynamically triangulated random surface (DTRS) model near the convergence circle for various dimensions. In the solvable case D=1 the exact critical properties of the theory are reproduced numerically. (orig.)

Dynamical Response near Quantum Critical Points.

Science.gov (United States)

Lucas, Andrew; Gazit, Snir; Podolsky, Daniel; Witczak-Krempa, William

2017-02-03

We study high-frequency response functions, notably the optical conductivity, in the vicinity of quantum critical points (QCPs) by allowing for both detuning from the critical coupling and finite temperature. We consider general dimensions and dynamical exponents. This leads to a unified understanding of sum rules. In systems with emergent Lorentz invariance, powerful methods from quantum field theory allow us to fix the high-frequency response in terms of universal coefficients. We test our predictions analytically in the large-N O(N) model and using the gauge-gravity duality and numerically via quantum Monte Carlo simulations on a lattice model hosting the interacting superfluid-insulator QCP. In superfluid phases, interacting Goldstone bosons qualitatively change the high-frequency optical conductivity and the corresponding sum rule.

Combined Molecular Dynamics Simulation-Molecular-Thermodynamic Theory Framework for Predicting Surface Tensions.

Science.gov (United States)

Sresht, Vishnu; Lewandowski, Eric P; Blankschtein, Daniel; Jusufi, Arben

2017-08-22

A molecular modeling approach is presented with a focus on quantitative predictions of the surface tension of aqueous surfactant solutions. The approach combines classical Molecular Dynamics (MD) simulations with a molecular-thermodynamic theory (MTT) [ Y. J. Nikas, S. Puvvada, D. Blankschtein, Langmuir 1992 , 8 , 2680 ]. The MD component is used to calculate thermodynamic and molecular parameters that are needed in the MTT model to determine the surface tension isotherm. The MD/MTT approach provides the important link between the surfactant bulk concentration, the experimental control parameter, and the surfactant surface concentration, the MD control parameter. We demonstrate the capability of the MD/MTT modeling approach on nonionic alkyl polyethylene glycol surfactants at the air-water interface and observe reasonable agreement of the predicted surface tensions and the experimental surface tension data over a wide range of surfactant concentrations below the critical micelle concentration. Our modeling approach can be extended to ionic surfactants and their mixtures with both ionic and nonionic surfactants at liquid-liquid interfaces.

Critical properties of Sudden Quench Dynamics in the anisotropic XY Model

OpenAIRE

Guo, Hongli; Liu, Zhao; Fan, Heng; Chen, Shu

2010-01-01

We study the zero temperature quantum dynamical critical behavior of the anisotropic XY chain under a sudden quench in a transverse field. We demonstrate theoretically that both quench magnetic susceptibility and two-particle quench correlation can be used to describe the dynamical quantum phase transition (QPT) properties. Either the quench magnetic susceptibility or the derivative of correlation functions as a function of initial magnetic field $a$ exhibits a divergence at the critical poin...

Anomalous quantum critical spin dynamics in YFe2Al10

Science.gov (United States)

Huang, K.; Tan, C.; Zhang, J.; Ding, Z.; MacLaughlin, D. E.; Bernal, O. O.; Ho, P.-C.; Baines, C.; Wu, L. S.; Aronson, M. C.; Shu, L.

2018-04-01

We report results of a muon spin relaxation (μ SR ) study of YFe2Al10 , a quasi-two-dimensional (2D) nearly ferromagnetic metal in which unconventional quantum critical behavior is observed. No static Fe2 + magnetism, with or without long-range order, is found down to 19 mK. The dynamic muon spin relaxation rate λ exhibits power-law divergences in temperature and magnetic field, the latter for fields that are too weak to affect the electronic spin dynamics directly. We attribute this to the proportionality of λ (ωμ,T ) to the dynamic structure factor S (ωμ,T ) , where ωμ≈105-107s-1 is the muon Zeeman frequency. These results suggest critical divergences of S (ωμ,T ) in both temperature and frequency. Power-law scaling and a 2D dissipative quantum XY model both yield forms for S (ω ,T ) that agree with neutron scattering data (ω ≈1012s-1 ). Extrapolation to μ SR frequencies agrees semiquantitatively with the observed temperature dependence of λ (ωμ,T ) , but predicts frequency independence for ωμ≪T , in extreme disagreement with experiment. We conclude that the quantum critical spin dynamics of YFe2Al10 is not well understood at low frequencies.

Molecular Dynamics Simulations of Slip on Curved Surfaces

Directory of Open Access Journals (Sweden)

Ross D.A.

2016-07-01

Full Text Available We present Molecular Dynamics (MD simulations of liquid water confined within nanoscale geometries, including slit-like and cylindrical graphitic pores. These equilibrium results are used for calculating friction coefficients, which in turn can be used to calculate slip lengths. The slip length is a material property independent of the fluid flow rate. It is therefore a better quantity for study than the fluid velocity at the wall, also known as the slip velocity. Once the slip length has been found as a function of surface curvature, it can be used to parameterise Lattice Boltzmann (LB simulations. These larger scale simulations are able to tell us about how fluid transport is affected by slip in complex geometries; not just limited to single pores. Applications include flow and transport in nano-porous engine valve deposits and gas shales. The friction coefficient is found to be a function of curvature and is higher for fluid on convex surfaces and lower for concave surfaces. Both concave and convex surfaces approach the same value of the friction coefficient, which is constant above some critical radius of curvature, here found to be 7.4 ± 2.9 nm. The constant value of the friction coefficient is 10,000 ± 600 kg m−2 s−1, which is equivalent to a slip length of approximately 67 ± 4 nm.

Static and Dynamic Criticality: Are They Different?

International Nuclear Information System (INIS)

Cullen, D E; Clouse, C J; Procassini, R; Little, R C

2003-01-01

Let us start by stating that this paper does not contain anything new. It only contains material that has been known for decades, but which is periodically forgotten. As such this paper is intended merely to refresh people's memories. We will also mention that this paper is an example of the occasional discrepancy between textbook methodologies and real world applications, in the sense that the conclusions reached here contradict what it says in most textbooks, i.e., most textbooks incorrectly interpret the methods presented here, particularly with respect to the use of importance sampling to maintain population control. This paper is not intended as a general tutorial on criticality calculations. It is intended only to clarify the accuracy of various methods for solving criticality problems, such as a true time dependent dynamic calculation, versus an alpha or K static calculation. In particular, we address the long standing controversy between users of the TART code [1] with the dynamic method, and users of the MCNP code [2] with the alpha static method. In this paper we will prove which methods are accurate and inaccurate

Peak load-impulse characterization of critical pulse loads in structural dynamics

International Nuclear Information System (INIS)

Abrahamson, G.R.; Lindberg, H.E.

1975-01-01

In presenting the characterization scheme, some general features are described first. A detailed analysis is given for the rigid-plastic system of one degree of freedom to illustrate the calculation of critical load curves in terms of peak load and impulse. This is followed by the presentation of critical load curves for uniformly loaded rigid-plastic beams and plates and for dynamic buckling of cylindrical shells under uniform lateral loads. The peak load-impulse characterization of critical pulse loads is compared with the dynamic load factor characterization, and some aspects of the history of the peak load-pulse scheme are presented. (orig./HP) [de

Effects of stressor characteristics on early warning signs of critical transitions and "critical coupling" in complex dynamical systems.

Science.gov (United States)

Blume, Steffen O P; Sansavini, Giovanni

2017-12-01

Complex dynamical systems face abrupt transitions into unstable and catastrophic regimes. These critical transitions are triggered by gradual modifications in stressors, which push the dynamical system towards unstable regimes. Bifurcation analysis can characterize such critical thresholds, beyond which systems become unstable. Moreover, the stochasticity of the external stressors causes small-scale fluctuations in the system response. In some systems, the decomposition of these signal fluctuations into precursor signals can reveal early warning signs prior to the critical transition. Here, we present a dynamical analysis of a power system subjected to an increasing load level and small-scale stochastic load perturbations. We show that the auto- and cross-correlations of bus voltage magnitudes increase, leading up to a Hopf bifurcation point, and further grow until the system collapses. This evidences a gradual transition into a state of "critical coupling," which is complementary to the established concept of "critical slowing down." Furthermore, we analyze the effects of the type of load perturbation and load characteristics on early warning signs and find that gradient changes in the autocorrelation provide early warning signs of the imminent critical transition under white-noise but not for auto-correlated load perturbations. Furthermore, the cross-correlation between all voltage magnitude pairs generally increases prior to and beyond the Hopf bifurcation point, indicating "critical coupling," but cannot provide early warning indications. Finally, we show that the established early warning indicators are oblivious to limit-induced bifurcations and, in the case of the power system model considered here, only react to an approaching Hopf bifurcation.

Dynamic air layer on textured superhydrophobic surfaces

KAUST Repository

Vakarelski, Ivan Uriev

2013-09-03

We provide an experimental demonstration that a novel macroscopic, dynamic continuous air layer or plastron can be sustained indefinitely on textured superhydrophobic surfaces in air-supersaturated water by a natural gas influx mechanism. This type of plastron is an intermediate state between Leidenfrost vapor layers on superheated surfaces and the equilibrium Cassie-Baxter wetting state on textured superhydrophobic surfaces. We show that such a plastron can be sustained on the surface of a centimeter-sized superhydrophobic sphere immersed in heated water and variations of its dynamic behavior with air saturation of the water can be regulated by rapid changes of the water temperature. The simple experimental setup allows for quantification of the air flux into the plastron and identification of the air transport model of the plastron growth. Both the observed growth dynamics of such plastrons and millimeter-sized air bubbles seeded on the hydrophilic surface under identical air-supersaturated solution conditions are consistent with the predictions of a well-mixed gas transport model. © 2013 American Chemical Society.

Voltage Imaging of Waking Mouse Cortex Reveals Emergence of Critical Neuronal Dynamics

Science.gov (United States)

Scott, Gregory; Fagerholm, Erik D.; Mutoh, Hiroki; Leech, Robert; Sharp, David J.; Shew, Woodrow L.

2014-01-01

Complex cognitive processes require neuronal activity to be coordinated across multiple scales, ranging from local microcircuits to cortex-wide networks. However, multiscale cortical dynamics are not well understood because few experimental approaches have provided sufficient support for hypotheses involving multiscale interactions. To address these limitations, we used, in experiments involving mice, genetically encoded voltage indicator imaging, which measures cortex-wide electrical activity at high spatiotemporal resolution. Here we show that, as mice recovered from anesthesia, scale-invariant spatiotemporal patterns of neuronal activity gradually emerge. We show for the first time that this scale-invariant activity spans four orders of magnitude in awake mice. In contrast, we found that the cortical dynamics of anesthetized mice were not scale invariant. Our results bridge empirical evidence from disparate scales and support theoretical predictions that the awake cortex operates in a dynamical regime known as criticality. The criticality hypothesis predicts that small-scale cortical dynamics are governed by the same principles as those governing larger-scale dynamics. Importantly, these scale-invariant principles also optimize certain aspects of information processing. Our results suggest that during the emergence from anesthesia, criticality arises as information processing demands increase. We expect that, as measurement tools advance toward larger scales and greater resolution, the multiscale framework offered by criticality will continue to provide quantitative predictions and insight on how neurons, microcircuits, and large-scale networks are dynamically coordinated in the brain. PMID:25505314

Coherent inflationary dynamics for Bose-Einstein condensates crossing a quantum critical point

Science.gov (United States)

Feng, Lei; Clark, Logan W.; Gaj, Anita; Chin, Cheng

2018-03-01

Quantum phase transitions, transitions between many-body ground states, are of extensive interest in research ranging from condensed-matter physics to cosmology1-4. Key features of the phase transitions include a stage with rapidly growing new order, called inflation in cosmology5, followed by the formation of topological defects6-8. How inflation is initiated and evolves into topological defects remains a hot topic of debate. Ultracold atomic gas offers a pristine and tunable platform to investigate quantum critical dynamics9-21. We report the observation of coherent inflationary dynamics across a quantum critical point in driven Bose-Einstein condensates. The inflation manifests in the exponential growth of density waves and populations in well-resolved momentum states. After the inflation stage, extended coherent dynamics is evident in both real and momentum space. We present an intuitive description of the quantum critical dynamics in our system and demonstrate the essential role of phase fluctuations in the formation of topological defects.

The Role of Electronic Excitations on Chemical Reaction Dynamics at Metal, Semiconductor and Nanoparticle Surfaces

Energy Technology Data Exchange (ETDEWEB)

Tully, John C. [Yale Univ., New Haven, CT (United States)

2017-06-10

Chemical reactions are often facilitated and steered when carried out on solid surfaces, essential for applications such as heterogeneous catalysis, solar energy conversion, corrosion, materials processing, and many others. A critical factor that can determine the rates and pathways of chemical reactions at surfaces is the efficiency and specificity of energy transfer; how fast does energy move around and where does it go? For reactions on insulator surfaces energy transfer generally moves in and out of vibrations of the adsorbed molecule and the underlying substrate. By contrast, on metal surfaces, metallic nanoparticles and semiconductors, another pathway for energy flow opens up, excitation and de-excitation of electrons. This so-called “nonadiabatic” mechanism often dominates the transfer of energy and can directly impact the course of a chemical reaction. Conventional computational methods such as molecular dynamics simulation do not account for this nonadiabatic behavior. The current DOE-BES funded project has focused on developing the underlying theoretical foundation and the computational methodology for the prediction of nonadiabatic chemical reaction dynamics at surfaces. The research has successfully opened up new methodology and new applications for molecular simulation. In particular, over the last three years, the “Electronic Friction” theory, pioneered by the PI, has now been developed into a stable and accurate computational method that is sufficiently practical to allow first principles “on-the-fly” simulation of chemical reaction dynamics at metal surfaces.

Phase transitions, nonequilibrium dynamics, and critical behavior of strongly interacting systems

International Nuclear Information System (INIS)

Mottola, E.; Bhattacharya, T.; Cooper, F.

1998-01-01

This is the final report of a three-year, Laboratory Directed Research and Development project at Los Alamos National Laboratory. In this effort, large-scale simulations of strongly interacting systems were performed and a variety of approaches to the nonequilibrium dynamics of phase transitions and critical behavior were investigated. Focus areas included (1) the finite-temperature quantum chromodynamics phase transition and nonequilibrium dynamics of a new phase of matter (the quark-gluon plasma) above the critical temperature, (2) nonequilibrium dynamics of a quantum fields using mean field theory, and (3) stochastic classical field theoretic models with applications to spinodal decomposition and structural phase transitions in a variety of systems, such as spin chains and shape memory alloys

Phase transitions, nonequilibrium dynamics, and critical behavior of strongly interacting systems

Energy Technology Data Exchange (ETDEWEB)

Mottola, E.; Bhattacharya, T.; Cooper, F. [and others

1998-12-31

This is the final report of a three-year, Laboratory Directed Research and Development project at Los Alamos National Laboratory. In this effort, large-scale simulations of strongly interacting systems were performed and a variety of approaches to the nonequilibrium dynamics of phase transitions and critical behavior were investigated. Focus areas included (1) the finite-temperature quantum chromodynamics phase transition and nonequilibrium dynamics of a new phase of matter (the quark-gluon plasma) above the critical temperature, (2) nonequilibrium dynamics of a quantum fields using mean field theory, and (3) stochastic classical field theoretic models with applications to spinodal decomposition and structural phase transitions in a variety of systems, such as spin chains and shape memory alloys.

Quantum critical point revisited by dynamical mean-field theory

Science.gov (United States)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

2017-03-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. We use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. By comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

The dynamics of nucleation and growth of a particle in the ternary alloy melt with anisotropic surface tension.

Science.gov (United States)

Chen, Ming-Wen; Li, Lin-Yan; Guo, Hui-Min

2017-08-28

The dynamics of nucleation and growth of a particle affected by anisotropic surface tension in the ternary alloy melt is studied. The uniformly valid asymptotic solution for temperature field, concentration field, and interface evolution of nucleation and particle growth is obtained by means of the multiple variable expansion method. The asymptotic solution reveals the critical radius of nucleation in the ternary alloy melt and an inward melting mechanism of the particle induced by the anisotropic effect of surface tension. The critical radius of nucleation is dependent on isotropic surface tension, temperature undercooling, and constitutional undercooling in the ternary alloy melt, and the solute diffusion melt decreases the critical radius of nucleation. Immediately after a nucleus forms in the initial stage of solidification, the anisotropic effect of surface tension makes some parts of its interface grow inward while some parts grow outward. Until the inward melting attains a certain distance (which is defined as "the melting depth"), these parts of interface start to grow outward with other parts. The interface of the particle evolves into an ear-like deformation, whose inner diameter may be less than two times the critical radius of nucleation within a short time in the initial stage of solidification. The solute diffusion in the ternary alloy melt decreases the effect of anisotropic surface tension on the interface deformation.

Seasonal dynamics of surface chlorophyll concentration and sea surface temperature, as indicator of hydrological structure of the ocean (by satellite data)

Science.gov (United States)

Shevyrnogov, Anatoly; Vysotskaya, Galina

Continuous monitoring of phytopigment concentrations and sea surface temperature in the ocean by space-borne methods makes possible to estimate ecological condition of biocenoses in critical areas. Unlike land vegetation, hydrological processes largely determine phytoplank-ton dynamics, which may be either recurrent or random. The types of chlorophyll concentration dynamics and sea surface temperature can manifest as zones quasistationary by seasonal dynamics, quasistationary areas (QSA). In the papers of the authors (A. Shevyrnogov, G. Vysotskaya, E. Shevyrnogov, A study of the stationary and the anomalous in the ocean surface chlorophyll distribution by satellite data. International Journal of Remote Sensing, Vol. 25, No.7-8, pp. 1383-1387, April 2004 & A. P. Shevyrnogov, G. S. Vysotskaya, J. I. Gitelson, Quasistationary areas of chlorophyll concentra-tion in the world ocean as observed satellite data Advances in Space Research, Volume 18, Issue 7, Pages 129-132, 1996) existence of zones, which are quasi-stationary with similar seasonal dynamics of chlorophyll concentration at surface layer of ocean, was shown. Results were obtained on the base of processing of time series of satellite images SeaWiFS. It was shown that fronts and frontal zones coincide with dividing lines between quasi-stationary are-as, especially in areas of large oceanic streams. To study the dynamics of the ocean for the period from 1985 through 2012 we used data on the temperature of the surface layer of the ocean and chlorophyll concentration (AVHRR, SeaWiFS and MODIS). Biota of surface oceanic layer is more stable in comparison with quickly changing surface tem-perature. It gives a possibility to circumvent influence of high-frequency component (for exam-ple, a diurnal cycle) in investigation of dynamics of spatial distribution of surface streams. In addition, an analyses of nonstable ocean productivity phenomena, stood out time series of satellite images, showed existence of areas with

Electrostatic cloaking of surface structure for dynamic wetting

Science.gov (United States)

Shiomi, Junichiro; Nita, Satoshi; Do-Quang, Minh; Wang, Jiayu; Chen, Yu-Chung; Suzuki, Yuji; Amberg, Gustav

2017-11-01

Dynamic wetting problems are fundamental to the understanding of the interaction between liquids and solids. Even in a superficially simple experimental situation, such as a droplet spreading over a dry surface, the result may depend not only on the liquid properties but also strongly on the substrate-surface properties; even for macroscopically smooth surfaces, the microscopic geometrical roughness can be important. In addition, as surfaces may often be naturally charged, or electric fields are used to manipulate fluids, electric effects are crucial components that influence wetting phenomena. Here we investigate the interplay between electric forces and surface structures in dynamic wetting. While surface microstructures can significantly hinder the spreading, we find that the electrostatics can ``cloak'' the microstructures, i.e. deactivate the hindering. We identify the physics in terms of reduction in contact-line friction, which makes the dynamic wetting inertial force dominant and insensitive to the substrate properties. This work was financially supported in part by, the Japan Society for the Promotion of Science, Swedish Governmental Agency for Innovation Systems, and the Japan Science and Technology Agency.

A Dynamic Hydrology-Critical Zone Framework for Rainfall-triggered Landslide Hazard Prediction

Science.gov (United States)

Dialynas, Y. G.; Foufoula-Georgiou, E.; Dietrich, W. E.; Bras, R. L.

2017-12-01

Watershed-scale coupled hydrologic-stability models are still in their early stages, and are characterized by important limitations: (a) either they assume steady-state or quasi-dynamic watershed hydrology, or (b) they simulate landslide occurrence based on a simple one-dimensional stability criterion. Here we develop a three-dimensional landslide prediction framework, based on a coupled hydrologic-slope stability model and incorporation of the influence of deep critical zone processes (i.e., flow through weathered bedrock and exfiltration to the colluvium) for more accurate prediction of the timing, location, and extent of landslides. Specifically, a watershed-scale slope stability model that systematically accounts for the contribution of driving and resisting forces in three-dimensional hillslope segments was coupled with a spatially-explicit and physically-based hydrologic model. The landslide prediction framework considers critical zone processes and structure, and explicitly accounts for the spatial heterogeneity of surface and subsurface properties that control slope stability, including soil and weathered bedrock hydrological and mechanical characteristics, vegetation, and slope morphology. To test performance, the model was applied in landslide-prone sites in the US, the hydrology of which has been extensively studied. Results showed that both rainfall infiltration in the soil and groundwater exfiltration exert a strong control on the timing and magnitude of landslide occurrence. We demonstrate the extent to which three-dimensional slope destabilizing factors, which are modulated by dynamic hydrologic conditions in the soil-bedrock column, control landslide initiation at the watershed scale.

Critical reflection activation analysis - a new near-surface probe

International Nuclear Information System (INIS)

Gunn, J.M.F.; Trohidou, K.N.

1988-09-01

We propose a new surface analytic technique, Critical Reflection Activation Analysis (CRAA). This technique allows accurate depth profiling of impurities ≤ 100A beneath a surface. The depth profile of the impurity is simply related to the induced activity as a function of the angle of reflection. We argue that the technique is practical and estimate its accuracy. (author)

Quantum critical point revisited by dynamical mean-field theory

International Nuclear Information System (INIS)

Xu, Wenhu; Kotliar, Gabriel; Rutgers University, Piscataway, NJ; Tsvelik, Alexei M.

2017-01-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

Report on Microgravity Experiments of Dynamic Surface Deformation Effects on Marangoni Instability in High-Prandtl-Number Liquid Bridges

Science.gov (United States)

Yano, Taishi; Nishino, Koichi; Matsumoto, Satoshi; Ueno, Ichiro; Komiya, Atsuki; Kamotani, Yasuhiro; Imaishi, Nobuyuki

2018-04-01

This paper reports an overview and some important results of microgravity experiments called Dynamic Surf, which have been conducted on board the International Space Station from 2013 to 2016. The present project mainly focuses on the relations between the Marangoni instability in a high-Prandtl-number (Pr= 67 and 112) liquid bridge and the dynamic free surface deformation (DSD) as well as the interfacial heat transfer. The dynamic free surface deformations of large-scale liquid bridges (say, for diameters greater than 10 mm) are measured with good accuracy by an optical imaging technique. It is found that there are two causes of the dynamic free surface deformation in the present study: the first is the time-dependent flow behavior inside the liquid bridge due to the Marangoni instability, and the second is the external disturbance due to the residual acceleration of gravity, i.e., g-jitter. The axial distributions of DSD along the free surface are measured for several conditions. The critical parameters for the onset of oscillatory Marangoni convection are also measured for various aspect ratios (i.e., relative height to the diameter) of the liquid bridge and various thermal boundary conditions. The characteristics of DSD and the onset conditions of instability are discussed in this paper.

Investigating the dynamics of surface-immobilized DNA nanomachines

Science.gov (United States)

Dunn, Katherine E.; Trefzer, Martin A.; Johnson, Steven; Tyrrell, Andy M.

2016-07-01

Surface-immobilization of molecules can have a profound influence on their structure, function and dynamics. Toehold-mediated strand displacement is often used in solution to drive synthetic nanomachines made from DNA, but the effects of surface-immobilization on the mechanism and kinetics of this reaction have not yet been fully elucidated. Here we show that the kinetics of strand displacement in surface-immobilized nanomachines are significantly different to those of the solution phase reaction, and we attribute this to the effects of intermolecular interactions within the DNA layer. We demonstrate that the dynamics of strand displacement can be manipulated by changing strand length, concentration and G/C content. By inserting mismatched bases it is also possible to tune the rates of the constituent displacement processes (toehold-binding and branch migration) independently, and information can be encoded in the time-dependence of the overall reaction. Our findings will facilitate the rational design of surface-immobilized dynamic DNA nanomachines, including computing devices and track-based motors.

Inferring Ice Thickness from a Glacier Dynamics Model and Multiple Surface Datasets.

Science.gov (United States)

Guan, Y.; Haran, M.; Pollard, D.

2017-12-01

The future behavior of the West Antarctic Ice Sheet (WAIS) may have a major impact on future climate. For instance, ice sheet melt may contribute significantly to global sea level rise. Understanding the current state of WAIS is therefore of great interest. WAIS is drained by fast-flowing glaciers which are major contributors to ice loss. Hence, understanding the stability and dynamics of glaciers is critical for predicting the future of the ice sheet. Glacier dynamics are driven by the interplay between the topography, temperature and basal conditions beneath the ice. A glacier dynamics model describes the interactions between these processes. We develop a hierarchical Bayesian model that integrates multiple ice sheet surface data sets with a glacier dynamics model. Our approach allows us to (1) infer important parameters describing the glacier dynamics, (2) learn about ice sheet thickness, and (3) account for errors in the observations and the model. Because we have relatively dense and accurate ice thickness data from the Thwaites Glacier in West Antarctica, we use these data to validate the proposed approach. The long-term goal of this work is to have a general model that may be used to study multiple glaciers in the Antarctic.

Dynamic Defrosting on Scalable Superhydrophobic Surfaces

International Nuclear Information System (INIS)

Murphy, Kevin R.; McClintic, William T.; Lester, Kevin C.; Collier, C. Patrick; Boreyko, Jonathan B.

2017-01-01

Recent studies have shown that frost can grow in a suspended Cassie state on nanostructured superhydrophobic surfaces. During defrosting, the melting sheet of Cassie frost spontaneously dewets into quasi-spherical slush droplets that are highly mobile. Promoting Cassie frost would therefore seem advantageous from a defrosting standpoint; however, nobody has systematically compared the efficiency of defrosting Cassie ice versus defrosting conventional surfaces. Here, we characterize the defrosting of an aluminum plate, one-half of which exhibits a superhydrophobic nanostructure while the other half is smooth and hydrophobic. For thick frost sheets (>1 mm), the superhydrophobic surface was able to dynamically shed the meltwater, even at very low tilt angles. In contrast, the hydrophobic surface was unable to shed any appreciable meltwater even at a 90° tilt angle. For thin frost layers (≲1 mm), not even the superhydrophobic surface could mobilize the meltwater. We attribute this to the large apparent contact angle of the meltwater, which for small amounts of frost serves to minimize coalescence events and prevent droplets from approaching the capillary length. Finally, we demonstrate a new mode of dynamic defrosting using an upside-down surface orientation, where the melting frost was able to uniformly detach from the superhydrophobic side and subsequently pull the frost from the hydrophobic side in a chain reaction. Treating surfaces to enable Cassie frost is therefore very desirable for enabling rapid and low-energy thermal defrosting, but only for frost sheets that are sufficiently thick.

Initial stages of Pt(111) electrooxidation: dynamic and structural studies by surface X-ray diffraction

International Nuclear Information System (INIS)

Drnec, Jakub; Ruge, Martin; Reikowski, Finn; Rahn, Björn; Carlà, Francesco; Felici, Roberto; Stettner, Jochim; Magnussen, Olaf M.; Harrington, David A.

2017-01-01

In-situ surface X-ray diffraction is used to characterize the surface oxides on a Pt(111) surface in 0.1 M HClO 4 . Detailed analysis at two potentials confirms that the surface restructuring in the initial oxidation stages is consistent with a place exchange process between Pt and O atoms, and the exchanged Pt atoms are located above their original positions in the Pt(111) lattice. The (1,1,1.5) reflection is used to dynamically study the surface during cyclic voltammetry. The restructuring associated with the place exchange initiates with the CV peak at 1.05 V, even though multiple cycles to 1.17 V lead to no changes in the CV. The restructuring is reversible below a critical coverage of place exchanged Pt atoms, which we estimate to be between 0.07 and 0.15 ML. Extensive cycling to potentials higher or equal to 1.17 V leads to progressive disordering of the surface.

An effective field study of the magnetic properties and critical behaviour at the surface Ising film

International Nuclear Information System (INIS)

Bengrine, M.; Benyoussef, A.; Ez-Zahraouy, H.; Mhirech, F.

1998-09-01

The influence of corrugation and disorder at the surface on the critical behaviour of a ferromagnetic spin-1/2 Ising film is investigated using mean-field theory and finite cluster approximation. It is found that the critical surface exponent β 1 follows closely the one of a perfect surface, in the two cases: corrugated surface and random equiprobable coupling surface. However, in the case of flat surface with random interactions the surface critical exponent β 1 depends on the concentration p of the strong interaction for p>p c =0,5, while for p≤p c , such critical exponent is independent on the value of p and is equal to the one of the perfect surface. Moreover, in the case of corrugated surface, the effective exponent for a layer z, β eff J(z,n), is calculated as a function of the number of steps at the surface. (author)

Nonlinear dynamics in the perceptual grouping of connected surfaces.

Science.gov (United States)

Hock, Howard S; Schöner, Gregor

2016-09-01

Evidence obtained using the dynamic grouping method has shown that the grouping of an object's connected surfaces has properties characteristic of a nonlinear dynamical system. When a surface's luminance changes, one of its boundaries is perceived moving across the surface. The direction of this dynamic grouping (DG) motion indicates which of two flanking surfaces has been grouped with the changing surface. A quantitative measure of overall grouping strength (affinity) for adjacent surfaces is provided by the frequency of DG motion perception in directions promoted by the grouping variables. It was found that: (1) variables affecting surface grouping for three-surface objects evolve over time, settling at stable levels within a single fixation, (2) how often DG motion is perceived when a surface's luminance is perturbed (changed) depends on the pre-perturbation affinity state of the surface grouping, (3) grouping variables promoting the same surface grouping combine cooperatively and nonlinearly (super-additively) in determining the surface grouping's affinity, (4) different DG motion directions during different trials indicate that surface grouping can be bistable, which implies that inhibitory interactions have stabilized one of two alternative surface groupings, and (5) when alternative surface groupings have identical affinity, stochastic fluctuations can break the symmetry and inhibitory interactions can then stabilize one of the surface groupings, providing affinity levels are not too high (which results in bidirectional DG motion). A surface-grouping network is proposed within which boundaries vary in salience. Low salience or suppressed boundaries instantiate surface grouping, and DG motion results from changes in boundary salience. Copyright © 2015 Elsevier Ltd. All rights reserved.

Critical assessment of Pt surface energy - An atomistic study

Science.gov (United States)

Kim, Jin-Soo; Seol, Donghyuk; Lee, Byeong-Joo

2018-04-01

Despite the fact that surface energy is a fundamental quantity in understanding surface structure of nanoparticle, the results of experimental measurements and theoretical calculations for the surface energy of pure Pt show a wide range of scattering. It is necessary to further ensure the surface energy of Pt to find the equilibrium shape and atomic configuration in Pt bimetallic nanoparticles accurately. In this article, we critically assess and optimize the Pt surface energy using a semi-empirical atomistic approach based on the second nearest-neighbor modified embedded-atom method interatomic potential. That is, the interatomic potential of pure Pt was adjusted in a way that the surface segregation tendency in a wide range of Pt binary alloys is reproduced in accordance with experimental information. The final optimized Pt surface energy (mJ/m2) is 2036 for (100) surface, 2106 for (110) surface, and 1502 for (111) surface. The potential can be utilized to find the equilibrium shape and atomic configuration of Pt bimetallic nanoparticles more accurately.

Studying the Effect of Roughness of Wet Road on Critical speed of Vehicle

Directory of Open Access Journals (Sweden)

Ali K. Mohammed

2018-01-01

Full Text Available Hydroplaning is one the most dangerous phenomena which effect on the safety of driving cars on wet roads, then, the critical speed of slipping cars is an important parameter in the hydroplaning ,and depends on the properties of  the following three  parameters: tires, water layer and  road surface. The road texture is the main property of road specifications which affect directly on the critical speed of the vehicle. In the present work, the properties of road roughness and influence of surface texture on critical speed of vehicle are studied with variation of the following parameters: thickness and dynamic viscosity of water on the road surface and the vehicle load. The results showed that increasing the road surface roughness and the vehicle load both has a appositive influence on the critical speed (increaseof the vehicle, while increasing the dynamic viscosity and thickness of the water layer on the road surface has a negative influence on the critical speed (decrease of the vehicle. DOI: http://dx.doi.org/10.25130/tjes.24.2017.24

Optimal system size for complex dynamics in random neural networks near criticality

Energy Technology Data Exchange (ETDEWEB)

Wainrib, Gilles, E-mail: wainrib@math.univ-paris13.fr [Laboratoire Analyse Géométrie et Applications, Université Paris XIII, Villetaneuse (France); García del Molino, Luis Carlos, E-mail: garciadelmolino@ijm.univ-paris-diderot.fr [Institute Jacques Monod, Université Paris VII, Paris (France)

2013-12-15

In this article, we consider a model of dynamical agents coupled through a random connectivity matrix, as introduced by Sompolinsky et al. [Phys. Rev. Lett. 61(3), 259–262 (1988)] in the context of random neural networks. When system size is infinite, it is known that increasing the disorder parameter induces a phase transition leading to chaotic dynamics. We observe and investigate here a novel phenomenon in the sub-critical regime for finite size systems: the probability of observing complex dynamics is maximal for an intermediate system size when the disorder is close enough to criticality. We give a more general explanation of this type of system size resonance in the framework of extreme values theory for eigenvalues of random matrices.

Optimal system size for complex dynamics in random neural networks near criticality

International Nuclear Information System (INIS)

Wainrib, Gilles; García del Molino, Luis Carlos

2013-01-01

In this article, we consider a model of dynamical agents coupled through a random connectivity matrix, as introduced by Sompolinsky et al. [Phys. Rev. Lett. 61(3), 259–262 (1988)] in the context of random neural networks. When system size is infinite, it is known that increasing the disorder parameter induces a phase transition leading to chaotic dynamics. We observe and investigate here a novel phenomenon in the sub-critical regime for finite size systems: the probability of observing complex dynamics is maximal for an intermediate system size when the disorder is close enough to criticality. We give a more general explanation of this type of system size resonance in the framework of extreme values theory for eigenvalues of random matrices

Dynamic Factor Models for the Volatility Surface

DEFF Research Database (Denmark)

van der Wel, Michel; Ozturk, Sait R.; Dijk, Dick van

The implied volatility surface is the collection of volatilities implied by option contracts for different strike prices and time-to-maturity. We study factor models to capture the dynamics of this three-dimensional implied volatility surface. Three model types are considered to examine desirable...

Rigorous lower bound on the dynamic critical exponent of some multilevel Swendsen-Wang algorithms

International Nuclear Information System (INIS)

Li, X.; Sokal, A.D.

1991-01-01

We prove the rigorous lower bound z exp ≥α/ν for the dynamic critical exponent of a broad class of multilevel (or ''multigrid'') variants of the Swendsen-Wang algorithm. This proves that such algorithms do suffer from critical slowing down. We conjecture that such algorithms in fact lie in the same dynamic universality class as the stanard Swendsen-Wang algorithm

msiDBN: A Method of Identifying Critical Proteins in Dynamic PPI Networks

Directory of Open Access Journals (Sweden)

Yuan Zhang

2014-01-01

Full Text Available Dynamics of protein-protein interactions (PPIs reveals the recondite principles of biological processes inside a cell. Shown in a wealth of study, just a small group of proteins, rather than the majority, play more essential roles at crucial points of biological processes. This present work focuses on identifying these critical proteins exhibiting dramatic structural changes in dynamic PPI networks. First, a comprehensive way of modeling the dynamic PPIs is presented which simultaneously analyzes the activity of proteins and assembles the dynamic coregulation correlation between proteins at each time point. Second, a novel method is proposed, named msiDBN, which models a common representation of multiple PPI networks using a deep belief network framework and analyzes the reconstruction errors and the variabilities across the time courses in the biological process. Experiments were implemented on data of yeast cell cycles. We evaluated our network construction method by comparing the functional representations of the derived networks with two other traditional construction methods. The ranking results of critical proteins in msiDBN were compared with the results from the baseline methods. The results of comparison showed that msiDBN had better reconstruction rate and identified more proteins of critical value to yeast cell cycle process.

Molecular-dynamics analysis of mobile helium cluster reactions near surfaces of plasma-exposed tungsten

Energy Technology Data Exchange (ETDEWEB)

Hu, Lin; Maroudas, Dimitrios, E-mail: maroudas@ecs.umass.edu [Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003-9303 (United States); Hammond, Karl D. [Department of Chemical Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Wirth, Brian D. [Department of Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

2015-10-28

We report the results of a systematic atomic-scale analysis of the reactions of small mobile helium clusters (He{sub n}, 4 ≤ n ≤ 7) near low-Miller-index tungsten (W) surfaces, aiming at a fundamental understanding of the near-surface dynamics of helium-carrying species in plasma-exposed tungsten. These small mobile helium clusters are attracted to the surface and migrate to the surface by Fickian diffusion and drift due to the thermodynamic driving force for surface segregation. As the clusters migrate toward the surface, trap mutation (TM) and cluster dissociation reactions are activated at rates higher than in the bulk. TM produces W adatoms and immobile complexes of helium clusters surrounding W vacancies located within the lattice planes at a short distance from the surface. These reactions are identified and characterized in detail based on the analysis of a large number of molecular-dynamics trajectories for each such mobile cluster near W(100), W(110), and W(111) surfaces. TM is found to be the dominant cluster reaction for all cluster and surface combinations, except for the He{sub 4} and He{sub 5} clusters near W(100) where cluster partial dissociation following TM dominates. We find that there exists a critical cluster size, n = 4 near W(100) and W(111) and n = 5 near W(110), beyond which the formation of multiple W adatoms and vacancies in the TM reactions is observed. The identified cluster reactions are responsible for important structural, morphological, and compositional features in the plasma-exposed tungsten, including surface adatom populations, near-surface immobile helium-vacancy complexes, and retained helium content, which are expected to influence the amount of hydrogen re-cycling and tritium retention in fusion tokamaks.

Entanglement dynamics in critical random quantum Ising chain with perturbations

Energy Technology Data Exchange (ETDEWEB)

Huang, Yichen, E-mail: ychuang@caltech.edu

2017-05-15

We simulate the entanglement dynamics in a critical random quantum Ising chain with generic perturbations using the time-evolving block decimation algorithm. Starting from a product state, we observe super-logarithmic growth of entanglement entropy with time. The numerical result is consistent with the analytical prediction of Vosk and Altman using a real-space renormalization group technique. - Highlights: • We study the dynamical quantum phase transition between many-body localized phases. • We simulate the dynamics of a very long random spin chain with matrix product states. • We observe numerically super-logarithmic growth of entanglement entropy with time.

Surface dynamics of micellar diblock copolymer films

Science.gov (United States)

Song, Sanghoon; Cha, Wonsuk; Kim, Hyunjung; Jiang, Zhang; Narayanan, Suresh

2011-03-01

We studied the structure and surface dynamics of poly(styrene)-b-poly(dimethylsiloxane) (PS-b-PDMS) diblock copolymer films with micellar PDMS surrounded by PS shells. By `in-situ' high resolution synchrotron x-ray reflectivity and diffuse scattering, we obtained exact thickness, electron density and surface tension. A segregation layer near the top surface was appeared with increasing temperature Surface dynamics were measured as a function of film thickness and temperature by x-ray photon correlation spectroscopy. The best fit to relaxation time constants as a function of in-plane wavevectors were analyzed with a theory based on capillary waves with hydrodynamics with bilayer model Finally the viscosities for the top segregated layer as well as for the bottom layer are obtained at given temperatures This work was supported by National Research Foundation of Korea (R15-2008-006-01001-0), Seoul Research and Business Development Program (10816), and Sogang University Research Grant (2010).

Cinematic Operation of the Cerebral Cortex Interpreted via Critical Transitions in Self-Organized Dynamic Systems.

Science.gov (United States)

Kozma, Robert; Freeman, Walter J

2017-01-01

Measurements of local field potentials over the cortical surface and the scalp of animals and human subjects reveal intermittent bursts of beta and gamma oscillations. During the bursts, narrow-band metastable amplitude modulation (AM) patters emerge for a fraction of a second and ultimately dissolve to the broad-band random background activity. The burst process depends on previously learnt conditioned stimuli (CS), thus different AM patterns may emerge in response to different CS. This observation leads to our cinematic theory of cognition when perception happens in discrete steps manifested in the sequence of AM patterns. Our article summarizes findings in the past decades on experimental evidence of cinematic theory of cognition and relevant mathematical models. We treat cortices as dissipative systems that self-organize themselves near a critical level of activity that is a non-equilibrium metastable state. Criticality is arguably a key aspect of brains in their rapid adaptation, reconfiguration, high storage capacity, and sensitive response to external stimuli. Self-organized criticality (SOC) became an important concept to describe neural systems. We argue that transitions from one AM pattern to the other require the concept of phase transitions, extending beyond the dynamics described by SOC. We employ random graph theory (RGT) and percolation dynamics as fundamental mathematical approaches to model fluctuations in the cortical tissue. Our results indicate that perceptions are formed through a phase transition from a disorganized (high entropy) to a well-organized (low entropy) state, which explains the swiftness of the emergence of the perceptual experience in response to learned stimuli.

Bayesian inversion analysis of nonlinear dynamics in surface heterogeneous reactions.

Science.gov (United States)

Omori, Toshiaki; Kuwatani, Tatsu; Okamoto, Atsushi; Hukushima, Koji

2016-09-01

It is essential to extract nonlinear dynamics from time-series data as an inverse problem in natural sciences. We propose a Bayesian statistical framework for extracting nonlinear dynamics of surface heterogeneous reactions from sparse and noisy observable data. Surface heterogeneous reactions are chemical reactions with conjugation of multiple phases, and they have the intrinsic nonlinearity of their dynamics caused by the effect of surface-area between different phases. We adapt a belief propagation method and an expectation-maximization (EM) algorithm to partial observation problem, in order to simultaneously estimate the time course of hidden variables and the kinetic parameters underlying dynamics. The proposed belief propagation method is performed by using sequential Monte Carlo algorithm in order to estimate nonlinear dynamical system. Using our proposed method, we show that the rate constants of dissolution and precipitation reactions, which are typical examples of surface heterogeneous reactions, as well as the temporal changes of solid reactants and products, were successfully estimated only from the observable temporal changes in the concentration of the dissolved intermediate product.

Quantum wavepacket ab initio molecular dynamics: an approach for computing dynamically averaged vibrational spectra including critical nuclear quantum effects.

Science.gov (United States)

Sumner, Isaiah; Iyengar, Srinivasan S

2007-10-18

We have introduced a computational methodology to study vibrational spectroscopy in clusters inclusive of critical nuclear quantum effects. This approach is based on the recently developed quantum wavepacket ab initio molecular dynamics method that combines quantum wavepacket dynamics with ab initio molecular dynamics. The computational efficiency of the dynamical procedure is drastically improved (by several orders of magnitude) through the utilization of wavelet-based techniques combined with the previously introduced time-dependent deterministic sampling procedure measure to achieve stable, picosecond length, quantum-classical dynamics of electrons and nuclei in clusters. The dynamical information is employed to construct a novel cumulative flux/velocity correlation function, where the wavepacket flux from the quantized particle is combined with classical nuclear velocities to obtain the vibrational density of states. The approach is demonstrated by computing the vibrational density of states of [Cl-H-Cl]-, inclusive of critical quantum nuclear effects, and our results are in good agreement with experiment. A general hierarchical procedure is also provided, based on electronic structure harmonic frequencies, classical ab initio molecular dynamics, computation of nuclear quantum-mechanical eigenstates, and employing quantum wavepacket ab initio dynamics to understand vibrational spectroscopy in hydrogen-bonded clusters that display large degrees of anharmonicities.

Assessing the dynamic material criticality of infrastructure transitions: A case of low carbon electricity

International Nuclear Information System (INIS)

Roelich, Katy; Dawson, David A.; Purnell, Phil; Knoeri, Christof; Revell, Ruairi; Busch, Jonathan; Steinberger, Julia K.

2014-01-01

Highlights: • We present a method to analyse material criticality of infrastructure transitions. • Criticality is defined as the potential for, and exposure to, supply disruption. • Our method is dynamic reducing the probability of lock-in to at-risk technologies. • We show that supply disruption potential is reducing but exposure is increasing. - Abstract: Decarbonisation of existing infrastructure systems requires a dynamic roll-out of technology at an unprecedented scale. The potential disruption in supply of critical materials could endanger such a transition to low-carbon infrastructure and, by extension, compromise energy security more broadly because low carbon technologies are reliant on these materials in a way that fossil-fuelled energy infrastructure is not. Criticality is currently defined as the combination of the potential for supply disruption and the exposure of a system of interest to that disruption. We build on this definition and develop a dynamic approach to quantifying criticality, which monitors the change in criticality during the transition towards a low-carbon infrastructure goal. This allows us to assess the relative risk of different technology pathways to reach a particular goal and reduce the probability of being ‘locked in’ to currently attractive but potentially future-critical technologies. To demonstrate, we apply our method to criticality of the proposed UK electricity system transition, with a focus on neodymium. We anticipate that the supply disruption potential of neodymium will decrease by almost 30% by 2050; however, our results show the criticality of low carbon electricity production increases ninefold over this period, as a result of increasing exposure to neodymium-reliant technologies

Influence of the hydrostatic stress component on critical surface expansion in forging compound products

DEFF Research Database (Denmark)

Vorm, T; Bay, Niels; Wanheim, Tarras

1974-01-01

of a superimposed hydrostatic pressure on the critical surface expansion during a forging process. The critical surface expansion appears to decrease with increasing hydrostatic pressure. This may be due to the fact that the close contact between the materials necessary to obtain bonding is created by a micro...

Dynamic Recrystallization Behavior and Critical Conditions of SiCp/A1-Cu Composite

Directory of Open Access Journals (Sweden)

HAO Shiming

2017-08-01

Full Text Available Using the Gleeble-1500D simulator, the high temperature plastic deformation behavior of 40%SiCP/Al-Cu composite were investigated at 350-500℃ with the strain rate of 0.01-10 s-1. The stress-strain curves were obtained during the tests. The critical conditions of dynamic recrystallization for onset of DRX during deformation of 40%SiCP/Al-Cu composite was obtained by computation of the strain hardening rate (θ from initial stress-strain data and introduction of the inflection point criterion of ln θ-ε curves and the minimum value criterion of (-∂(ln θ/∂ε-ε curves. The results indicate that the softening mechanism of the dynamic recrystallization is a feature of high-temperature flow stress strain curves of the composites, and the peak stress increases with the decrease of deformation temperature or the increase of strain rate. The inflection point in the ln θ-ε curve appears, and the minimum value of the (-∂(ln θ/∂ε-ε curve is presented when the critical state is attained for this composite. The critical strain decreases with the decrease of strain rate and the increase of deformation temperature. There is linear relationship between critical strain and peak strain, i.e. εc=0.528εp. The predicting model of critical strain is described by the function of εc=4.58×10-3Z0.09. Electron microscopic analysis show that the dynamic recrystallization occurs when the strain is 0.06 (T=400℃, ε=10 s-1, and the dynamic recrystallization grains fully grow up when the strain is 0.2.

Experimental studies of photon-surface interaction dynamics in the alkali halides

International Nuclear Information System (INIS)

Haglund, R.F. Jr.; Tolk, N.H.

1986-01-01

We describe recent measurements which have provided, in unprecedented detail, insights into the electronic mechanisms through which energy carried into a material by photon irradiation is absorbed, localized and rechanneled to produce desorption, surface modification, erosion and damage. The specific object of these studies has been desorption induced by electronic transition in alkali halide crystals, with particular emphasis on the dynamics of changes in the surface and near-surface regions. In our experiments, the irradiating ultraviolet photons are provided by a synchrotron storage ring, and the dynamical information about desorption products is obtained from optical measurements of the quantum states, yields and velocity distributions of neutral ground-state and excited-state atoms ejected from the surface of the irradiating material. These studies have shown that the dominant exit channels in photon-induced particle emission are those producing ground-state and excited-state neutral atoms. Using dynamical information about these desorbing neutral species, obtained, for example, by laser-induced fluorescence and laser Doppler spectroscopy, we are generating an increasingly comprehensive picture of the dynamics of electronic energy flow into and out of pure crystalline surfaces in these prototypical dielectrics. We are also beginning to be able to relate desorption dynamics to specific materials properties, and to discriminate between pure surface and near-surface effects in these materials. Applications of these techniques to the problem of photon-induced surface damage and to analysis of surface dynamics in dielectric materials are discussed, and the relationships between these nearly ideal model materials and the non-crystalline, covalently bonded materials more typical of real optical elements are pointed out. 19 refs., 13 figs

The complex dynamics of wishful thinking: the critical positivity ratio.

Science.gov (United States)

Brown, Nicholas J L; Sokal, Alan D; Friedman, Harris L

2013-12-01

We examine critically the claims made by Fredrickson and Losada (2005) concerning the construct known as the "positivity ratio." We find no theoretical or empirical justification for the use of differential equations drawn from fluid dynamics, a subfield of physics, to describe changes in human emotions over time; furthermore, we demonstrate that the purported application of these equations contains numerous fundamental conceptual and mathematical errors. The lack of relevance of these equations and their incorrect application lead us to conclude that Fredrickson and Losada's claim to have demonstrated the existence of a critical minimum positivity ratio of 2.9013 is entirely unfounded. More generally, we urge future researchers to exercise caution in the use of advanced mathematical tools, such as nonlinear dynamics, and in particular to verify that the elementary conditions for their valid application have been met. PsycINFO Database Record (c) 2013 APA, all rights reserved.

Sub-nanometer glass surface dynamics induced by illumination

International Nuclear Information System (INIS)

Nguyen, Duc; Nienhaus, Lea; Haasch, Richard T.; Lyding, Joseph; Gruebele, Martin

2015-01-01

Illumination is known to induce stress and morphology changes in opaque glasses. Amorphous silicon carbide (a-SiC) has a smaller bandgap than the crystal. Thus, we were able to excite with 532 nm light a 1 μm amorphous surface layer on a SiC crystal while recording time-lapse movies of glass surface dynamics by scanning tunneling microscopy (STM). Photoexcitation of the a-SiC surface layer through the transparent crystal avoids heating the STM tip. Up to 6 × 10 4 s, long movies of surface dynamics with 40 s time resolution and sub-nanometer spatial resolution were obtained. Clusters of ca. 3-5 glass forming units diameter are seen to cooperatively hop between two states at the surface. Photoexcitation with green laser light recruits immobile clusters to hop, rather than increasing the rate at which already mobile clusters hop. No significant laser heating was observed. Thus, we favor an athermal mechanism whereby electronic excitation of a-SiC directly controls glassy surface dynamics. This mechanism is supported by an exciton migration-relaxation-thermal diffusion model. Individual clusters take ∼1 h to populate states differently after the light intensity has changed. We believe the surrounding matrix rearranges slowly when it is stressed by a change in laser intensity, and clusters serve as a diagnostic. Such cluster hopping and matrix rearrangement could underlie the microscopic mechanism of photoinduced aging of opaque glasses

Dynamic surface properties of poly(methylalkyldiallylammonium chloride) solutions

Czech Academy of Sciences Publication Activity Database

Novikova, A. A.; Vlasov, P. S.; Lin, S.-Y.; Sedláková, Zdeňka; Noskov, B. A.

2017-01-01

Roč. 80, November (2017), s. 122-127 ISSN 1876-1070 Institutional support: RVO:61389013 Keywords : polymer solutions * dynamic surface tension * dilational surface rheology Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 4.217, year: 2016

Dynamical modeling of surface tension

International Nuclear Information System (INIS)

Brackbill, J.U.; Kothe, D.B.

1996-01-01

In a recent review it is said that free-surface flows ''represent some of the difficult remaining challenges in computational fluid dynamics''. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin. This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin are discussed

Smooth perfluorinated surfaces with different chemical and physical natures: their unusual dynamic dewetting behavior toward polar and nonpolar liquids.

Science.gov (United States)

Cheng, Dalton F; Masheder, Benjamin; Urata, Chihiro; Hozumi, Atsushi

2013-09-10

The effects of surface chemistry and the mobility of surface-tethered functional groups of various perfluorinated surfaces on their dewetting behavior toward polar (water) and nonpolar (n-hexadecane, n-dodecane, and n-decane) liquids were investigated. In this study, three types of common smooth perfluorinated surfaces, that is, a perfluoroalkylsilane (heptadecafluoro-1,1,2,2-tetrahydrooctyl-dimethylchlorosilane, FAS17) monomeric layer, an amorphous fluoropolymer film (Teflon AF 1600), and a perfluorinated polyether (PFPE)-terminated polymer brush film (Optool DSX), were prepared and their static/dynamic dewetting characteristics were compared. Although the apparent static contact angles (CAs) of these surfaces with all probe liquids were almost identical to each other, the ease of movement of liquid drops critically depended on the physical (solidlike or liquidlike) natures of the substrate surface. CA hysteresis and substrate tilt angles (TAs) of all probe liquids on the Optool DSX surface were found to be much lower than those of Teflon AF1600 and FAS17 surfaces due to its physical polymer chain mobility at room temperature and the resulting liquidlike nature. Only 6.0° of substrate incline was required to initiate movement for a small drop (5 μL) of n-decane, which was comparable to the reported substrate TA value (5.3°) for a superoleophobic surface (θ(S) > 160°, textured perfluorinated surface). Such unusual dynamic dewetting behavior of the Optool DSX surface was also markedly enhanced due to the significant increase in the chain mobility of PFPE by moderate heating (70 °C) of the surface, with substrate TA reducing to 3.0°. CA hysteresis and substrate TAs rather than static CAs were therefore determined to be of greater consequence for the estimation of the actual dynamic dewetting behavior of alkane probe liquids on these smooth perfluorinated surfaces. Their dynamic dewettability toward alkane liquids is in the order of Optool DSX > Teflon AF1600 �

Monitoring peptide-surface interaction by means of molecular dynamics simulation

Energy Technology Data Exchange (ETDEWEB)

Nonella, Marco, E-mail: mnonella@pci.uzh.ch [Physikalisch-Chemisches Institut, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Seeger, Stefan, E-mail: sseeger@pci.uzh.ch [Physikalisch-Chemisches Institut, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)

2010-12-09

Graphical abstract: Protein-surface interactions play a crucial role in a wide field of research areas like biology, biotechnology, or pharmacology. Only recently, it has been shown that not only peptide adsorption represents an important process but also spreading and clustering of adsorbed proteins. By means of classical molecular dynamics, peptide adsorption as well as the dynamics of adsorbed peptides have been investigated in order to gain deeper insight into such processes. The picture shows a snapshot of an adsorbed peptide on a silica surface showing strong direct hydrogen bonding. Research highlights: {yields} Simulation of peptide surface interaction. {yields} Dynamics of hydrogen bond formation and destruction. {yields} Internal flexibility of adsorbed peptides. - Abstract: Protein adsorption and protein surface interactions have become an important research topic in recent years. Very recently, for example, it has been shown that protein clusters can undergo a surface-induced spreading after adsorption. Such phenomena emphasize the need of a more detailed insight into protein-silica interaction at an atomic level. Therefore, we have studied a model system consisting of a short peptide, a silica slab, and water molecules by means of classical molecular dynamics simulations. The study reveals that, besides of electrostatic interactions caused by the chosen charge distribution, the peptide interacts with the silica surface through formation of direct peptide-surface hydrogen bonds as well as indirect peptide-water-surface hydrogen bonds. The number of created hydrogen bonds varies considerably among the simulated structures. The strength of hydrogen bonding determines the mobility of the peptide on the surface and the internal flexibility of the adsorbed peptide.

Dynamic surface tension measurements of ionic surfactants using maximum bubble pressure tensiometry

Science.gov (United States)

Ortiz, Camilla U.; Moreno, Norman; Sharma, Vivek

Dynamic surface tension refers to the time dependent variation in surface tension, and is intimately linked with the rate of mass transfer of a surfactant from liquid sub-phase to the interface. The diffusion- or adsorption-limited kinetics of mass transfer to interfaces is said to impact the so-called foamability and the Gibbs-Marangoni elasticity of surfaces. Dynamic surface tension measurements carried out with conventional methods like pendant drop analysis, Wilhelmy plate, etc. are limited in their temporal resolution (>50 ms). In this study, we describe design and application of maximum bubble pressure tensiometry for the measurement of dynamic surface tension effects at extremely short (1-50 ms) timescales. Using experiments and theory, we discuss the overall adsorption kinetics of charged surfactants, paying special attention to the influence of added salt on dynamic surface tension.

Quantum Critical Point revisited by the Dynamical Mean Field Theory

Science.gov (United States)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei

Dynamical mean field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low energy kink and the high energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high energy antiferromagnetic paramagnons. We use the frequency dependent four-point correlation function of spin operators to calculate the momentum dependent correction to the electron self energy. Our results reveal a substantial difference with the calculations based on the Spin-Fermion model which indicates that the frequency dependence of the the quasiparitcle-paramagnon vertices is an important factor. The authors are supported by Center for Computational Design of Functional Strongly Correlated Materials and Theoretical Spectroscopy under DOE Grant DE-FOA-0001276.

Critical heat flux (CHF) phenomenon on a downward facing curved surface

Energy Technology Data Exchange (ETDEWEB)

Cheung, F.B.; Haddad, K.H.; Liu, Y.C. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering

1997-06-01

This report describes a theoretical and experimental study of the boundary layer boiling and critical heat flux phenomena on a downward facing curved heating surface, including both hemispherical and toroidal surfaces. A subscale boundary layer boiling (SBLB) test facility was developed to measure the spatial variation of the critical heat flux and observe the underlying mechanisms. Transient quenching and steady-state boiling experiments were performed in the SBLB facility under both saturated and subcooled conditions to obtain a complete database on the critical heat flux. To complement the experimental effort, an advanced hydrodynamic CHF model was developed from the conservation laws along with sound physical arguments. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel. Based upon the CHF model, a scaling law was established for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water. The scaling law, which compares favorably with all the available local CHF data obtained for various vessel sizes, can be used to predict the local CHF limits on large commercial-size vessels. This technical information represents one of the essential elements that is needed in assessing the efficacy of external cooling of core melt by cavity flooding as a severe accident management strategy. 83 figs., 3 tabs.

Critical heat flux (CHF) phenomenon on a downward facing curved surface

International Nuclear Information System (INIS)

Cheung, F.B.; Haddad, K.H.; Liu, Y.C.

1997-06-01

This report describes a theoretical and experimental study of the boundary layer boiling and critical heat flux phenomena on a downward facing curved heating surface, including both hemispherical and toroidal surfaces. A subscale boundary layer boiling (SBLB) test facility was developed to measure the spatial variation of the critical heat flux and observe the underlying mechanisms. Transient quenching and steady-state boiling experiments were performed in the SBLB facility under both saturated and subcooled conditions to obtain a complete database on the critical heat flux. To complement the experimental effort, an advanced hydrodynamic CHF model was developed from the conservation laws along with sound physical arguments. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel. Based upon the CHF model, a scaling law was established for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water. The scaling law, which compares favorably with all the available local CHF data obtained for various vessel sizes, can be used to predict the local CHF limits on large commercial-size vessels. This technical information represents one of the essential elements that is needed in assessing the efficacy of external cooling of core melt by cavity flooding as a severe accident management strategy. 83 figs., 3 tabs

Critical dynamics of an interacting magnetic nanoparticle system

DEFF Research Database (Denmark)

Hansen, Mikkel Fougt; Jonsson, P.E.; Nordblad, P.

2002-01-01

Effects of dipole-dipole interactions on the magnetic relaxation have been investigated for three Fe-C nanoparticle samples with volume concentrations of 0.06, 5 and 17 vol%. While both the 5 and 17 vol% samples exhibit collective behaviour due to dipolar interactions, only the 17 vol% sample dis...... displays critical behaviour close to its transition temperature. The behaviour of the 5 vol% sample can be attributed to a mixture of collective and single-particle dynamics....

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.

Critical dynamics a field theory approach to equilibrium and non-equilibrium scaling behavior

CERN Document Server

Täuber, Uwe C

2014-01-01

Introducing a unified framework for describing and understanding complex interacting systems common in physics, chemistry, biology, ecology, and the social sciences, this comprehensive overview of dynamic critical phenomena covers the description of systems at thermal equilibrium, quantum systems, and non-equilibrium systems. Powerful mathematical techniques for dealing with complex dynamic systems are carefully introduced, including field-theoretic tools and the perturbative dynamical renormalization group approach, rapidly building up a mathematical toolbox of relevant skills. Heuristic and qualitative arguments outlining the essential theory behind each type of system are introduced at the start of each chapter, alongside real-world numerical and experimental data, firmly linking new mathematical techniques to their practical applications. Each chapter is supported by carefully tailored problems for solution, and comprehensive suggestions for further reading, making this an excellent introduction to critic...

The magnetic flux dynamics in the critical state of one-dimensional discrete superconductor

International Nuclear Information System (INIS)

Ginzburg, S.L.; Nakin, A.V.; Savitskaya, N.E.

2006-01-01

We give a theoretical description of avalanche-like dynamics of magnetic flux in the critical state of discrete superconductors using a one-dimensional model of a multijunction SQUID. We show that the system under consideration demonstrates the self-organized criticality. The avalanches of vortices manifest themselves as jumps of the total magnetic flux in the sample. The sizes of these jumps have a power-law distribution. We argue that similarities in the behavior of discrete and usual type-II superconductors allows to extend our results for description of avalanche-like dynamics in type-II superconductors with strong pinning

Dynamic interactions of Leidenfrost droplets on liquid metal surface

Science.gov (United States)

Ding, Yujie; Liu, Jing

2016-09-01

Leidenfrost dynamic interaction effects of the isopentane droplets on the surface of heated liquid metal were disclosed. Unlike conventional rigid metal, such conductive and deformable liquid metal surface enables the levitating droplets to demonstrate rather abundant and complex dynamics. The Leidenfrost droplets at different diameters present diverse morphologies and behaviors like rotation and oscillation. Depending on the distance between the evaporating droplets, they attract and repulse each other through the curved surfaces beneath them and their vapor flows. With high boiling point up to 2000 °C, liquid metal offers a unique platform for testing the evaporating properties of a wide variety of liquid even solid.

Reaction dynamics of molecular hydrogen on silicon surfaces

DEFF Research Database (Denmark)

Bratu, P.; Brenig, W.; Gross, A.

1996-01-01

of the preexponential factor by about one order of magnitude per lateral degree of freedom. Molecular vibrations have practically no effect on the adsorption/desorption dynamics itself, but lead to vibrational heating in desorption with a strong isotope effect. Ab initio calculations for the H-2 interaction...... between the two surfaces. These results indicate that tunneling, molecular vibrations, and the structural details of the surface play only a minor role for the adsorption dynamics. Instead, they appear to be governed by the localized H-Si bonding and Si-Si lattice vibrations. Theoretically, an effective......Experimental and theoretical results on the dynamics of dissociative adsorption and recombinative desorption of hydrogen on silicon are presented. Using optical second-harmonic generation, extremely small sticking probabilities in the range 10(-9)-10(-5) could be measured for H-2 and D-2 on Si(111...

Atomic probes of surface structure and dynamics

International Nuclear Information System (INIS)

Heller, E.J.; Jonsson, H.

1992-01-01

Progress for the period Sept. 15, 1992 to Sept. 14, 1993 is discussed. Semiclassical methods that will allow much faster and more accurate three-dimensional atom--surface scattering calculations, both elastic and inelastic, are being developed. The scattering of He atoms from buckyballs is being investigated as a test problem. Somewhat more detail is given on studies of He atom scattering from defective Pt surfaces. Molecular dynamics simulations of He + and Ar + ion sputtering of Pt surfaces are also being done. He atom scattering from Xe overlayers on metal surfaces and the thermalized dissociation of H 2 on Cu(110) are being studied. (R.W.R.) 64 refs

Firm Size, a Self-Organized Critical Phenomenon: Evidence from the Dynamical Systems Theory

Science.gov (United States)

Chandra, Akhilesh

This research draws upon a recent innovation in the dynamical systems literature called the theory of self -organized criticality (SOC) (Bak, Tang, and Wiesenfeld 1988) to develop a computational model of a firm's size by relating its internal and the external sub-systems. As a holistic paradigm, the theory of SOC implies that a firm as a composite system of many degrees of freedom naturally evolves to a critical state in which a minor event starts a chain reaction that can affect either a part or the system as a whole. Thus, the global features of a firm cannot be understood by analyzing its individual parts separately. The causal framework builds upon a constant capital resource to support a volume of production at the existing level of efficiency. The critical size is defined as the production level at which the average product of a firm's factors of production attains its maximum value. The non -linearity is inferred by a change in the nature of relations at the border of criticality, between size and the two performance variables, viz., the operating efficiency and the financial efficiency. The effect of breaching the critical size is examined on the stock price reactions. Consistent with the theory of SOC, it is hypothesized that the temporal response of a firm breaching the level of critical size should behave as a flicker noise (1/f) process. The flicker noise is characterized by correlations extended over a wide range of time scales, indicating some sort of cooperative effect among a firm's degrees of freedom. It is further hypothesized that a firm's size evolves to a spatial structure with scale-invariant, self-similar (fractal) properties. The system is said to be self-organized inasmuch as it naturally evolves to the state of criticality without any detailed specifications of the initial conditions. In this respect, the critical state is an attractor of the firm's dynamics. Another set of hypotheses examines the relations between the size and the

Gauge dependence of the critical dynamics at the superconducting phase transition

Directory of Open Access Journals (Sweden)

M.Dudka

2007-01-01

Full Text Available The critical dynamics of superconductors in the charged regime is reconsidered within field-theory. For the dynamics, the Ginzburg-Landau model with complex order parameter coupled to the gauge field suggested earlier [Lannert et al. Phys. Rev. Lett. 92, 097004 (2004] is used. Assuming relaxational dynamics for both quantities, the renormalization group functions within one loop approximation are recalculated for different choices of the gauge. A gauge independent result for the divergence of the melectric conductivity is obtained only at the weak scaling fixed point unstable in one loop order where the timescales of the order parameter and the gauge field are different.

Bulk-mediated surface diffusion: non-Markovian desorption dynamics

International Nuclear Information System (INIS)

Revelli, Jorge A; Budde, Carlos E; Prato, Domingo; Wio, Horacio S

2005-01-01

Here we analyse the dynamics of adsorbed molecules within the bulk-mediated surface diffusion framework, when the particle's desorption mechanism is characterized by a non-Markovian process, while the particle's adsorption as well as its motion in the bulk is governed by Markovian dynamics. We study the diffusion of particles in both semi-infinite and finite cubic lattices, analysing the conditional probability to find the system on the reference absorptive plane as well as the surface dispersion as functions of time. The results are compared with known Markovian cases showing the differences that can be exploited to distinguish between Markovian and non-Markovian desorption mechanisms in experimental situations

Critical dynamics

International Nuclear Information System (INIS)

Dekker, H.

1980-01-01

It is shown how to solve the master equation for a Markov process including a critical point by means of successive approximations in terms of a small parameter. A critical point occurs if, by adjusting an externally controlled quantity, the system shows a transition from normal monostable to bistable behaviour. The fundamental idea of the theory is to separate the master equation into its proper irreducible part and a corrective remainder. The irreducible or zeroth order stochastic approximation will be a relatively simple Fokker-Planck equation that contains the essential features of the process. Once the solution of this irreducible equation is known, the higher order corrections in the original master equation can be incorporated in a systematic manner. (Auth.)

Geometrical critical phenomena on a random surface of arbitrary genus

International Nuclear Information System (INIS)

Duplantier, B.; Kostov, I.K.

1990-01-01

The statistical mechanics of self-avoiding walks (SAW) or of the O(n)-loop model on a two-dimensional random surface are shown to be exactly solvable. The partition functions of SAW and surface configurations (possibly in the presence of vacuum loops) are calculated by planar diagram enumeration techniques. Two critical regimes are found: a dense phase where the infinite walks and loops fill the infinite surface, the non-filled part staying finite, and a dilute phase where the infinite surface singularity on the one hand, and walk and loop singularities on the other, merge together. The configuration critical exponents of self-avoiding networks of any fixed topology G, on a surface with arbitrary genus H, are calculated as universal functions of G and H. For self-avoiding walks, the exponents are built from an infinite set of basic conformal dimensions associated with central charges c = -2 (dense phase) and c = 0 (dilute phase). The conformal spectrum Δ L , L ≥ 1 associated with L-leg star polymers is calculated exactly, for c = -2 and c = 0. This is generalized to the set of L-line 'watermelon' exponents Δ L of the O(n) model on a random surface. The divergences of the partition functions of self-avoiding networks on the random surface, possibly in the presence of vacuum loops, are shown to satisfy a factorization theorem over the vertices of the network. This provides a proof, in the presence of a fluctuating metric, of a result conjectured earlier in the standard plane. From this, the value of the string susceptibility γ str (H,c) is extracted for a random surface of arbitrary genus H, bearing a field theory of central charge c, or equivalently, embedded in d=c dimensions. Lastly, by enumerating spanning trees on a random lattice, we solve the similar problem of hamiltonian walks on the (fluctuating) Manhattan covering lattice. We also obtain new results for dilute trees on a random surface. (orig./HSI)

Structure and dynamics at the liquid surface of benzyl alcohol

International Nuclear Information System (INIS)

Dietter, J.; Morgner, H.

1999-01-01

A molecular dynamics simulation of a liquid layer of benzyl alcohol has been performed in order to compare the results with those obtained in experimental studies of our group. The main result of the experimental work was a strong orientational ordering of the benzyl alcohol molecules in the surface as well as an exceptionally large surface potential of ca. 0.6 V. According to the experiments the surface molecules orientate in such a way that the benzene ring points toward the vapor phase while the CH 2 group and the OH group are directed towards the bulk of the liquid. The simulation confirms this orientation of the surface molecules. The surface potential resulting from the simulation is 350 mV. The simulation reveals that the rather large surface potential can be understood as a consequence of the mean orientation of the molecular dipole moment in the surface region. The mean orientation of the molecules themselves in the surface is due to the tendency of the system to maintain the hydrogen bonding structure of the bulk in the surface region as well. The preferential orientation of the surface molecules causes a change of the dynamics of the individual components of the molecules when switching from bulk to surface which depends on the separation of these components from the polar group. This becomes most obvious in case of the reorientation dynamics of the molecular axes, e.g. the reorientation of the benzene ring is faster than the reorientation of the OH group. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

CSDMS2.0: Computational Infrastructure for Community Surface Dynamics Modeling

Science.gov (United States)

Syvitski, J. P.; Hutton, E.; Peckham, S. D.; Overeem, I.; Kettner, A.

2012-12-01

The Community Surface Dynamic Modeling System (CSDMS) is an NSF-supported, international and community-driven program that seeks to transform the science and practice of earth-surface dynamics modeling. CSDMS integrates a diverse community of more than 850 geoscientists representing 360 international institutions (academic, government, industry) from 60 countries and is supported by a CSDMS Interagency Committee (22 Federal agencies), and a CSDMS Industrial Consortia (18 companies). CSDMS presently distributes more 200 Open Source models and modeling tools, access to high performance computing clusters in support of developing and running models, and a suite of products for education and knowledge transfer. CSDMS software architecture employs frameworks and services that convert stand-alone models into flexible "plug-and-play" components to be assembled into larger applications. CSDMS2.0 will support model applications within a web browser, on a wider variety of computational platforms, and on other high performance computing clusters to ensure robustness and sustainability of the framework. Conversion of stand-alone models into "plug-and-play" components will employ automated wrapping tools. Methods for quantifying model uncertainty are being adapted as part of the modeling framework. Benchmarking data is being incorporated into the CSDMS modeling framework to support model inter-comparison. Finally, a robust mechanism for ingesting and utilizing semantic mediation databases is being developed within the Modeling Framework. Six new community initiatives are being pursued: 1) an earth - ecosystem modeling initiative to capture ecosystem dynamics and ensuing interactions with landscapes, 2) a geodynamics initiative to investigate the interplay among climate, geomorphology, and tectonic processes, 3) an Anthropocene modeling initiative, to incorporate mechanistic models of human influences, 4) a coastal vulnerability modeling initiative, with emphasis on deltas and

Critical heat flux for downward-facing pool boiling on CANDU calandria tube surface

Energy Technology Data Exchange (ETDEWEB)

Behdadi, Azin, E-mail: behdada@mcmaster.ca; Talebi, Farshad; Luxat, John

2017-04-15

Highlights: • Pressure tube-calandria tube contact may challenge fuel channel integrity in CANDU. • Critical heat flux variation is predicted on the outer surface of CANDU calandria tube. • A two-phase boundary layer flow driven by buoyancy is modeled on the surface. • Different slip ratios and flow regimes are considered inside the boundary layer. • Subcooling effects are added to the model using wall heat flux partitioning. - Abstract: One accident scenario in CANDU reactors that can challenge the integrity of the primary pressure boundary is a loss of coolant accident, referred to as critical break LOCA, in which the pressure tube (PT) can undergo thermal creep strain deformation and contact its calandria tube (CT). In such case, rapid redistribution of stored heat from PT to CT, leads to a large spike in heat flux to the moderator which can cause bubble accumulation and dryout on the CT surface. A challenge to fuel channel integrity is posed if critical heat flux occurs on the surface of the CT and results in sustained film boiling. If the post-dryout temperature becomes sufficiently high then continued creep strain of the PT and CT may lead to fuel channel failure. In this study, a mechanistic model is developed to predict the critical heat flux variations along the downward facing outer surface of CT. The hydrodynamic model considers a liquid macrolayer beneath an elongated vapor slug on the surface. Local dryout is postulated to occur whenever the fresh liquid supply to the macrolayer is not sufficient to compensate for the liquid depletion. A boundary layer analysis is performed, treating the two phase motion as an external buoyancy driven flow. The model shows good agreement with the available experimental data and has been modified to take into account the effect of subcooling.

Improved High Resolution Models of Subduction Dynamics: Use of transversely isotropic viscosity with a free-surface

Science.gov (United States)

Liu, X.; Gurnis, M.; Stadler, G.; Rudi, J.; Ratnaswamy, V.; Ghattas, O.

2017-12-01

Dynamic topography, or uncompensated topography, is controlled by internal dynamics, and provide constraints on the buoyancy structure and rheological parameters in the mantle. Compared with other surface manifestations such as the geoid, dynamic topography is very sensitive to shallower and more regional mantle structure. For example, the significant dynamic topography above the subduction zone potentially provides a rich mine for inferring the rheological and mechanical properties such as plate coupling, flow, and lateral viscosity variations, all critical in plate tectonics. However, employing subduction zone topography in the inversion study requires that we have a better understanding of the topography from forward models, especially the influence of the viscosity formulation, numerical resolution, and other factors. One common approach to formulating a fault between the subducted slab and the overriding plates in viscous flow models assumes a thin weak zone. However, due to the large lateral variation in viscosity, topography from free-slip numerical models typically has artificially large magnitude as well as high-frequency undulations over subduction zone, which adds to the difficulty in making comparisons between model results and observations. In this study, we formulate a weak zone with the transversely isotropic viscosity (TI) where the tangential viscosity is much smaller than the viscosity in the normal direction. Similar with isotropic weak zone models, TI models effectively decouple subducted slabs from the overriding plates. However, we find that the topography in TI models is largely reduced compared with that in weak zone models assuming an isotropic viscosity. Moreover, the artificial `tooth paste' squeezing effect observed in isotropic weak zone models vanishes in TI models, although the difference becomes less significant when the dip angle is small. We also implement a free-surface condition in our numerical models, which has a smoothing

Towards a dynamic assessment of raw materials criticality: Linking agent-based demand — With material flow supply modelling approaches

International Nuclear Information System (INIS)

Knoeri, Christof; Wäger, Patrick A.; Stamp, Anna; Althaus, Hans-Joerg; Weil, Marcel

2013-01-01

Emerging technologies such as information and communication-, photovoltaic- or battery technologies are expected to increase significantly the demand for scarce metals in the near future. The recently developed methods to evaluate the criticality of mineral raw materials typically provide a ‘snapshot’ of the criticality of a certain material at one point in time by using static indicators both for supply risk and for the impacts of supply restrictions. While allowing for insights into the mechanisms behind the criticality of raw materials, these methods cannot account for dynamic changes in products and/or activities over time. In this paper we propose a conceptual framework intended to overcome these limitations by including the dynamic interactions between different possible demand and supply configurations. The framework integrates an agent-based behaviour model, where demand emerges from individual agent decisions and interaction, into a dynamic material flow model, representing the materials' stocks and flows. Within the framework, the environmental implications of substitution decisions are evaluated by applying life-cycle assessment methodology. The approach makes a first step towards a dynamic criticality assessment and will enhance the understanding of industrial substitution decisions and environmental implications related to critical metals. We discuss the potential and limitation of such an approach in contrast to state-of-the-art methods and how it might lead to criticality assessments tailored to the specific circumstances of single industrial sectors or individual companies. - Highlights: ► Current criticality assessment methods provide a ‘snapshot’ at one point in time. ► They do not account for dynamic interactions between demand and supply. ► We propose a conceptual framework to overcomes these limitations. ► The framework integrates an agent-based behaviour model with a dynamic material flow model. ► The approach proposed makes

Characterization of neutron leakage probability, k /SUB eff/ , and critical core surface mass density of small reactor assemblies through the Trombay criticality formula

International Nuclear Information System (INIS)

Kumar, A.; Rao, K.S.; Srinivasan, M.

1983-01-01

The Trombay criticality formula (TCF) has been derived by incorporating a number of well-known concepts of criticality physics to enable prediction of changes in critical size or k /SUB eff/ following alterations in geometrical and physical parameters of uniformly reflected small reactor assemblies characterized by large neutron leakage from the core. The variant parameters considered are size, shape, density and diluent concentration of the core, and density and thickness of the reflector. The effect of these changes (except core size) manifests, through sigma /SUB c/ the critical surface mass density of the ''corresponding critical core,'' that sigma, the massto-surface-area ratio of the core,'' is essentially a measure of the product /rho/ extended to nonspherical systems and plays a dominant role in the TCF. The functional dependence of k /SUB eff/ on sigma/sigma /SUB c/ , the system size relative to critical, is expressed in the TCF through two alternative representations, namely the modified Wigner rational form and, an exponential form, which is given

Dynamics of the contact between a ruthenium surface with a single nanoasperity and a flat ruthenium surface: Molecular dynamics simulations

International Nuclear Information System (INIS)

Barros de Oliveira, Alan; Fortini, Andrea; Buldyrev, Sergey V.; Srolovitz, David

2011-01-01

We study the dynamics of the contact between a pair of surfaces (with properties designed to mimic ruthenium) via molecular dynamics simulations. In particular, we study the contact between a ruthenium surface with a single nanoasperity and a flat ruthenium surface. The results of such simulations suggest that contact behavior is highly variable. The goal of this study is to investigate the source and degree of this variability. We find that during compression, the behavior of the contact force displacement curves is reproducible, while during contact separation, the behavior is highly variable. Examination of the contact surfaces suggests that two separation mechanisms are in operation and give rise to this variability. One mechanism corresponds to the formation of a bridge between the two surfaces that plastically stretches as the surfaces are drawn apart and eventually separate in shear. This leads to a morphology after separation in which there are opposing asperities on the two surfaces. This plastic separation/bridge formation mechanism leads to a large work of separation. The other mechanism is a more brittle-like mode in which a crack propagates across the base of the asperity (slightly below the asperity/substrate junction) leading to most of the asperity on one surface or the other after separation and a slight depression facing this asperity on the opposing surface. This failure mode corresponds to a smaller work of separation. This failure mode corresponds to a smaller work of separation. Furthermore, contacts made from materials that exhibit predominantly brittle-like behavior will tend to require lower work of separation than those made from ductile-like contact materials.

Surface critical behavior and scaling functions for the three-dimensional mean spherical model

Energy Technology Data Exchange (ETDEWEB)

Amin, Magdy E. [Mathematics Department, Ar' ar Teacher College, Kingdom of Saudi Arabia (Saudi Arabia) and Mathematics Department, Faculty of Science, Minia University (Egypt)]. E-mail: aminmagdy@yahoo.com

2006-10-09

The d-dimensional mean spherical model on a fully finite L{sup d} simple cubic lattice with Neumann-Dirichlet boundary conditions is considered in the presence of a surface external fields acting at the surfaces bounding the system. Exact calculations are evaluated for the fully finite system and in the case of a film geometry Lx{approx}{sup d-1}. Critical finite-size scaling functions both for the specific heat and the mean-square magnetization are derived and investigated close to and below the bulk critical temperature K{sub c}.

Critical heat flux on micro-structured zircaloy surfaces for flow boiling of water at low pressures

International Nuclear Information System (INIS)

Haas, C.; Miassoedov, A.; Schulenberg, T.; Wetzel, T.

2012-01-01

The influence of surface structure on critical heat flux for flow boiling of water was investigated for Zircaloy tubes in a vertical annular test section. The objectives were to find suitable surface modification processes for Zircaloy tubes and to test their critical heat flux performance in comparison to the smooth tube. Surface structures with micro-channels, porous layer, oxidized layer, and elevations in micro- and nano-scale were produced on a section of a Zircaloy cladding tube. These modified tubes were tested in an internally heated vertical annulus with a heated length of 326 mm and an inner and outer diameter of 9.5 and 18 mm. The experiments were performed with mass fluxes of 250 and 400 kg/(m 2 s), outlet pressures between 120 and 300 kPa, and constant inlet subcooling enthalpy of 167 kJ/kg. Only a small influence of modified surface structures on critical heat flux was observed for the pressure of 120 kPa in the present test section geometry. However, with increasing pressure the critical heat flux could increase up to 29% using the surface structured tubes with micro-channels, porous and oxidized layers. Capillary effects and increased nucleation site density are assumed to improve the critical heat flux performance. (authors)

Validation of a laboratory method for evaluating dynamic properties of reconstructed equine racetrack surfaces.

Directory of Open Access Journals (Sweden)

Jacob J Setterbo

Full Text Available Racetrack surface is a risk factor for racehorse injuries and fatalities. Current research indicates that race surface mechanical properties may be influenced by material composition, moisture content, temperature, and maintenance. Race surface mechanical testing in a controlled laboratory setting would allow for objective evaluation of dynamic properties of surface and factors that affect surface behavior.To develop a method for reconstruction of race surfaces in the laboratory and validate the method by comparison with racetrack measurements of dynamic surface properties.Track-testing device (TTD impact tests were conducted to simulate equine hoof impact on dirt and synthetic race surfaces; tests were performed both in situ (racetrack and using laboratory reconstructions of harvested surface materials. Clegg Hammer in situ measurements were used to guide surface reconstruction in the laboratory. Dynamic surface properties were compared between in situ and laboratory settings. Relationships between racetrack TTD and Clegg Hammer measurements were analyzed using stepwise multiple linear regression.Most dynamic surface property setting differences (racetrack-laboratory were small relative to surface material type differences (dirt-synthetic. Clegg Hammer measurements were more strongly correlated with TTD measurements on the synthetic surface than the dirt surface. On the dirt surface, Clegg Hammer decelerations were negatively correlated with TTD forces.Laboratory reconstruction of racetrack surfaces guided by Clegg Hammer measurements yielded TTD impact measurements similar to in situ values. The negative correlation between TTD and Clegg Hammer measurements confirms the importance of instrument mass when drawing conclusions from testing results. Lighter impact devices may be less appropriate for assessing dynamic surface properties compared to testing equipment designed to simulate hoof impact (TTD.Dynamic impact properties of race surfaces

Simulation Based Exploration of Critical Zone Dynamics in Intensively Managed Landscapes

Science.gov (United States)

Kumar, P.

2017-12-01

The advent of high-resolution measurements of topographic and (vertical) vegetation features using areal LiDAR are enabling us to resolve micro-scale ( 1m) landscape structural characteristics over large areas. Availability of hyperspectral measurements is further augmenting these LiDAR data by enabling the biogeochemical characterization of vegetation and soils at unprecedented spatial resolutions ( 1-10m). Such data have opened up novel opportunities for modeling Critical Zone processes and exploring questions that were not possible before. We show how an integrated 3-D model at 1m grid resolution can enable us to resolve micro-topographic and ecological dynamics and their control on hydrologic and biogeochemical processes over large areas. We address the computational challenge of such detailed modeling by exploiting hybrid CPU and GPU computing technologies. We show results of moisture, biogeochemical, and vegetation dynamics from studies in the Critical Zone Observatory for Intensively managed Landscapes (IMLCZO) in the Midwestern United States.

New model for surface fracture induced by dynamical stress

OpenAIRE

Andersen, J. V.; Lewis, L. J.

1997-01-01

We introduce a model where an isotropic, dynamically-imposed stress induces fracture in a thin film. Using molecular dynamics simulations, we study how the integrated fragment distribution function depends on the rate of change and magnitude of the imposed stress, as well as on temperature. A mean-field argument shows that the system becomes unstable for a critical value of the stress. We find a striking invariance of the distribution of fragments for fixed ratio of temperature and rate of ch...

Molecular dynamics simulation of a binary mixture near the lower critical point

Energy Technology Data Exchange (ETDEWEB)

Pousaneh, Faezeh; Edholm, Olle, E-mail: oed@kth.se [Theoretical Biological Physics, Department of Theoretical Physics, Royal Institute of Technology (KTH), AlbaNova University Center, SE-106 91 Stockholm (Sweden); Maciołek, Anna [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Max-Planck-Institut für Intelligente Systeme, Heisenbergstrasse 3, D-70569 Stuttgart (Germany)

2016-07-07

2,6-lutidine molecules mix with water at high and low temperatures but in a wide intermediate temperature range a 2,6-lutidine/water mixture exhibits a miscibility gap. We constructed and validated an atomistic model for 2,6-lutidine and performed molecular dynamics simulations of 2,6-lutidine/water mixture at different temperatures. We determined the part of demixing curve with the lower critical point. The lower critical point extracted from our data is located close to the experimental one. The estimates for critical exponents obtained from our simulations are in a good agreement with the values corresponding to the 3D Ising universality class.

Dynamical effects and the critical behavior of random-field systems

International Nuclear Information System (INIS)

Shapir, Y.

1985-01-01

A variety of phenomena is observed experimentally in random-field (RF) systems realized by the application of an external field to diluted antiferromagnets. At low temperatures, infinitely long hysteretic effects are manifested by the history dependence of the final states: long-range order is observed if the field is applied after cooling, while domain states are reached when field cooled. While no indications for critical fluctuations are detected in 2-D systems, scaling behavior, for both the correlation length and the specific heat, is observed in 3-D systems over an intermediate range of temperatures. The related critical properties seem to be well described by the corresponding ones in the 2-D pure Ising model. The renormalization-group approach, which yields for the equilibrium critical exponents their values of the pure model in d-2 dimensions, is reviewed. A generalization of the dimensional-reduction approach, which accounts self-consistently for renormalized responses of the RF system, is presented. The dynamical effects are implicitly incorporated through the variation in the critical response between the local and the global regimes, associated with short- and long-time scales, respectively. In both regimes the lower critical dimension is found to be d = 2 in accordance with stability arguments. The short-time critical behavior indicates a dimensional reduction by one for the 3-D thermal exponents, in agreement with the experimental results. 37 references

General Critical Properties of the Dynamics of Scientific Discovery

Energy Technology Data Exchange (ETDEWEB)

Bettencourt, L. M. A. (LANL); Kaiser, D. I. (MIT)

2011-05-31

Scientific fields are difficult to define and compare, yet there is a general sense that they undergo similar stages of development. From this point of view it becomes important to determine if these superficial similarities can be translated into a general framework that would quantify the general advent and subsequent dynamics of scientific ideas. Such a framework would have important practical applications of allowing us to compare fields that superficially may appear different, in terms of their subject matter, research techniques, typical collaboration size, etc. Particularh' important in a field's history is the moment at which conceptual and technical unification allows widespread exchange of ideas and collaboration, at which point networks of collaboration show the analog of a percolation phenomenon, developing a giant connected component containing most authors. Here we investigate the generality of this topological transition in the collaboration structure of scientific fields as they grow and become denser. We develop a general theoretical framework in which each scientific field is an instantiation of the same large-scale topological critical phenomenon. We consider whether the evidence from a variety of specific fields is consistent with this picture, and estimate critical exponents associated with the transition. We then discuss the generality of the phenomenon and to what extent we may expect other scientific fields — including very large ones — to follow the same dynamics.

A non-critical string approach to black holes, time and quantum dynamics

CERN Document Server

Ellis, John R.; Nanopoulos, Dimitri V.

1994-01-01

We review our approach to time and quantum dynamics based on non-critical string theory, developing its relationship to previous work on non-equilibrium quantum statistical mechanics and the microscopic arrow of time. We exhibit specific non-factorizing contributions to the {\

THE INFLUENCE OF AEROSOL GAS-DYNAMIC SUSPENSION CLEANING ON SURFACE OF THE AIRCRAFT PARTS

Directory of Open Access Journals (Sweden)

Vitaly D. Hizhko

2008-02-01

Full Text Available  The specificity of the surface microgeometry formation under the influence of aerosol gas-dynamic suspension flow was considered. The composition and character of metallic surface layer formation of aircraft parts was investigated. The possibility of surface material composition and properties adjustment changing aerosol gas-dynamic suspension flow parameters was determined. The hypothesis about the possibility of using aerosol gas-dynamic suspension flow to form corrosion-resistant coating on the detail metallic surfaces was set up.

Elasto-dynamic analysis of spinning nanodisks via a surface energy-based model

Science.gov (United States)

Kiani, Keivan

2016-07-01

Using the surface elasticity theory of Gurtin and Murdoch, in-plane vibrations of annular nanodisks due to their rotary motion are explored. By the imposition of non-classical boundary conditions on the innermost and outermost surfaces and employing Hamilton’s principle, the unknown elasto-dynamic fields of the bulk zone are determined via the finite element method. The roles of both nanodisk geometry and surface effect on the natural frequencies are addressed. Subsequently, forced vibrations of spinning nanodisks with fixed-free and free-free boundary conditions are comprehensively examined. The obtained results show that the maximum dynamic elastic fields grow in a parabolic manner as the steady angular velocity increases. By increasing the outermost radius, the maximum dynamic elastic field is magnified and the influence of the surface effect on the results reduced. This work can be considered as a pivotal step towards optimal design and dynamic analysis of nanorotors with disk-like parts, which are one of the basic building blocks of the upcoming advanced nanotechnologies.

Effect of surface modification and hybridization on dynamic ...

Indian Academy of Sciences (India)

Epoxy; Roystonea regia; glass; surface modification; hybridization; dynamic mechanical ... other advantages such as light weight, low cost, high specific ... ful technique to study the mechanical behaviour of mate- ... The test reveals response.

A power law of order 1/4 for critical mean field Swendsen-Wang dynamics

CERN Document Server

Long, Yun; Ning, Weiyang; Peres, Yuval

2014-01-01

The Swendsen-Wang dynamics is a Markov chain widely used by physicists to sample from the Boltzmann-Gibbs distribution of the Ising model. Cooper, Dyer, Frieze and Rue proved that on the complete graph K_n the mixing time of the chain is at most O(\\sqrt{n}) for all non-critical temperatures. In this paper the authors show that the mixing time is \\Theta(1) in high temperatures, \\Theta(\\log n) in low temperatures and \\Theta(n^{1/4}) at criticality. They also provide an upper bound of O(\\log n) for Swendsen-Wang dynamics for the q-state ferromagnetic Potts model on any tree of n vertices.

Static and Dynamic Verification of Critical Software for Space Applications

Science.gov (United States)

Moreira, F.; Maia, R.; Costa, D.; Duro, N.; Rodríguez-Dapena, P.; Hjortnaes, K.

Space technology is no longer used only for much specialised research activities or for sophisticated manned space missions. Modern society relies more and more on space technology and applications for every day activities. Worldwide telecommunications, Earth observation, navigation and remote sensing are only a few examples of space applications on which we rely daily. The European driven global navigation system Galileo and its associated applications, e.g. air traffic management, vessel and car navigation, will significantly expand the already stringent safety requirements for space based applications Apart from their usefulness and practical applications, every single piece of onboard software deployed into the space represents an enormous investment. With a long lifetime operation and being extremely difficult to maintain and upgrade, at least when comparing with "mainstream" software development, the importance of ensuring their correctness before deployment is immense. Verification &Validation techniques and technologies have a key role in ensuring that the onboard software is correct and error free, or at least free from errors that can potentially lead to catastrophic failures. Many RAMS techniques including both static criticality analysis and dynamic verification techniques have been used as a means to verify and validate critical software and to ensure its correctness. But, traditionally, these have been isolated applied. One of the main reasons is the immaturity of this field in what concerns to its application to the increasing software product(s) within space systems. This paper presents an innovative way of combining both static and dynamic techniques exploiting their synergy and complementarity for software fault removal. The methodology proposed is based on the combination of Software FMEA and FTA with Fault-injection techniques. The case study herein described is implemented with support from two tools: The SoftCare tool for the SFMEA and SFTA

Surface water retardation around single-chain polymeric nanoparticles: critical for catalytic function?

Science.gov (United States)

Stals, Patrick J M; Cheng, Chi-Yuan; van Beek, Lotte; Wauters, Annelies C; Palmans, Anja R A; Han, Songi; Meijer, E W

2016-03-01

A library of water-soluble dynamic single-chain polymeric nanoparticles (SCPN) was prepared using a controlled radical polymerisation technique followed by the introduction of functional groups, including probes at targeted positions. The combined tools of electron paramagnetic resonance (EPR) and Overhauser dynamic nuclear polarization (ODNP) reveal that these SCPNs have structural and surface hydration properties resembling that of enzymes.

Observation of dynamic water microadsorption on Au surface

Energy Technology Data Exchange (ETDEWEB)

Huang, Xiaokang, E-mail: xiaokang.huang@tqs.com; Gupta, Gaurav; Gao, Weixiang; Tran, Van; Nguyen, Bang; McCormick, Eric; Cui, Yongjie; Yang, Yinbao; Hall, Craig; Isom, Harold [TriQuint Semiconductor, Inc., 500 W Renner Road, Richardson, Texas 75080 (United States)

2014-05-15

Experimental and theoretical research on water wettability, adsorption, and condensation on solid surfaces has been ongoing for many decades because of the availability of new materials, new detection and measurement techniques, novel applications, and different scales of dimensions. Au is a metal of special interest because it is chemically inert, has a high surface energy, is highly conductive, and has a relatively high melting point. It has wide applications in semiconductor integrated circuitry, microelectromechanical systems, microfluidics, biochips, jewelry, coinage, and even dental restoration. Therefore, its surface condition, wettability, wear resistance, lubrication, and friction attract a lot of attention from both scientists and engineers. In this paper, the authors experimentally investigated Au{sub 2}O{sub 3} growth, wettability, roughness, and adsorption utilizing atomic force microscopy, scanning electron microscopy, reflectance spectrometry, and contact angle measurement. Samples were made using a GaAs substrate. Utilizing a super-hydrophilic Au surface and the proper surface conditions of the surrounding GaAs, dynamic microadsorption of water on the Au surface was observed in a clean room environment. The Au surface area can be as small as 12 μm{sup 2}. The adsorbed water was collected by the GaAs groove structure and then redistributed around the structure. A model was developed to qualitatively describe the dynamic microadsorption process. The effective adsorption rate was estimated by modeling and experimental data. Devices for moisture collection and a liquid channel can be made by properly arranging the wettabilities or contact angles of different materials. These novel devices will be very useful in microfluid applications or biochips.

Non-linear quantum critical dynamics and fluctuation-dissipation ratios far from equilibrium

Energy Technology Data Exchange (ETDEWEB)

Zamani, Farzaneh [Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden (Germany); Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden (Germany); Ribeiro, Pedro [CeFEMA, Instituto Superior Tcnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Russian Quantum Center, Novaya Street 100 A, Skolkovo, Moscow Area, 143025 (Russian Federation); Kirchner, Stefan, E-mail: stefan.kirchner@correlated-matter.com [Center for Correlated Matter, Zhejiang University, Hangzhou, Zhejiang 310058 (China)

2016-02-15

Non-thermal correlations of strongly correlated electron systems and the far-from-equilibrium properties of phases of condensed matter have become a topical research area. Here, an overview of the non-linear dynamics found near continuous zero-temperature phase transitions within the context of effective temperatures is presented. In particular, we focus on models of critical Kondo destruction. Such a quantum critical state, where Kondo screening is destroyed in a critical fashion, is realized in a number of rare earth intermetallics. This raises the possibility of experimentally testing for the existence of fluctuation-dissipation relations far from equilibrium in terms of effective temperatures. Finally, we present an analysis of a non-interacting, critical reference system, the pseudogap resonant level model, in terms of effective temperatures and contrast these results with those obtained near interacting quantum critical points. - Highlights: • Critical Kondo destruction explains the unusual properties of quantum critical heavy fermion compounds. • We review the concept of effective temperatures in models of critical Kondo destruction. • We compare effective temperatures found near non-interacting and fully interacting fixed points. • A comparison with non-interacting quantum impurity models is presented.

The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

DEFF Research Database (Denmark)

Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

2004-01-01

Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding......-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time...

Dynamical simulation of a linear sigma model near the critical point

Energy Technology Data Exchange (ETDEWEB)

Wesp, Christian; Meistrenko, Alex; Greiner, Carsten [Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt (Germany); Hees, Hendrik van [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt (Germany)

2014-07-01

The intention of this study is the search for signatures of the chiral phase transition. To investigate the impact of fluctuations, e.g. of the baryon number, on the transition or a critical point, the linear sigma model is treated in a dynamical 3+1D numerical simulation. Chiral fields are approximated as classical fields, quarks are described by quasi particles in a Vlasov equation. Additional dynamic is implemented by quark-quark and quark-sigma-field interaction. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.

Atmospheric stability analysis over statically and dynamically rough surfaces

Science.gov (United States)

Maric, Emina; Metzger, Meredith; Singha, Arindam; Sadr, Reza

2011-11-01

The ratio of buoyancy flux to turbulent kinetic energy production in the atmospheric surface layer is investigated experimentally for air flow over two types of surfaces characterized by static and dynamic roughness. In this study, ``static'' refers to the time-invariant nature of naturally-occurring roughness over a mud/salt playa; while, ``dynamic'' refers to the behavior of water waves along an air-water interface. In both cases, time-resolved measurements of the momentum and heat fluxes were acquired from synchronized 3D sonic anemometers mounted on a vertical tower. Field campaigns were conducted at two sites, representing the ``statically'' and ``dynamically'' rough surfaces, respectively: (1) the SLTEST facility in Utah's western desert, and (2) the new Doha airport in Qatar under construction along the coast of the Persian Gulf. Note, at site 2, anemometers were located directly above the water by extension from a tower secured to the end of a 1 km-long pier. Comparisons of the Monin-Obukhov length, flux Richardson number, and gradient Richardson number are presented, and discussed in the context of the observed evolution of the turbulent spectra in response to diurnal variations of atmospheric stability. Supported by the Qatar National Research Fund.

Dynamic contact angle cycling homogenizes heterogeneous surfaces.

Science.gov (United States)

Belibel, R; Barbaud, C; Mora, L

2016-12-01

In order to reduce restenosis, the necessity to develop the appropriate coating material of metallic stent is a challenge for biomedicine and scientific research over the past decade. Therefore, biodegradable copolymers of poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) were prepared in order to develop a new coating exhibiting different custom groups in its side chain and being able to carry a drug. This material will be in direct contact with cells and blood. It consists of carboxylic acid and hexylic groups used for hydrophilic and hydrophobic character, respectively. The study of this material wettability and dynamic surface properties is of importance due to the influence of the chemistry and the potential motility of these chemical groups on cell adhesion and polymer kinetic hydrolysis. Cassie theory was used for the theoretical correction of contact angles of these chemical heterogeneous surfaces coatings. Dynamic Surface Analysis was used as practical homogenizer of chemical heterogeneous surfaces by cycling during many cycles in water. In this work, we confirmed that, unlike receding contact angle, advancing contact angle is influenced by the difference of only 10% of acidic groups (%A) in side-chain of polymers. It linearly decreases with increasing acidity percentage. Hysteresis (H) is also a sensitive parameter which is discussed in this paper. Finally, we conclude that cycling provides real information, thus avoiding theoretical Cassie correction. H(10)is the most sensible parameter to %A. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of water table dynamics on land surface hydrologic memory

Science.gov (United States)

Lo, Min-Hui; Famiglietti, James S.

2010-11-01

The representation of groundwater dynamics in land surface models has received considerable attention in recent years. Most studies have found that soil moisture increases after adding a groundwater component because of the additional supply of water to the root zone. However, the effect of groundwater on land surface hydrologic memory (persistence) has not been explored thoroughly. In this study we investigate the effect of water table dynamics on National Center for Atmospheric Research Community Land Model hydrologic simulations in terms of land surface hydrologic memory. Unlike soil water or evapotranspiration, results show that land surface hydrologic memory does not always increase after adding a groundwater component. In regions where the water table level is intermediate, land surface hydrologic memory can even decrease, which occurs when soil moisture and capillary rise from groundwater are not in phase with each other. Further, we explore the hypothesis that in addition to atmospheric forcing, groundwater variations may also play an important role in affecting land surface hydrologic memory. Analyses show that feedbacks of groundwater on land surface hydrologic memory can be positive, negative, or neutral, depending on water table dynamics. In regions where the water table is shallow, the damping process of soil moisture variations by groundwater is not significant, and soil moisture variations are mostly controlled by random noise from atmospheric forcing. In contrast, in regions where the water table is very deep, capillary fluxes from groundwater are small, having limited potential to affect soil moisture variations. Therefore, a positive feedback of groundwater to land surface hydrologic memory is observed in a transition zone between deep and shallow water tables, where capillary fluxes act as a buffer by reducing high-frequency soil moisture variations resulting in longer land surface hydrologic memory.

Thermodiffusion as a means to manipulate liquid film dynamics on chemically patterned surfaces.

Science.gov (United States)

Kalpathy, Sreeram K; Shreyes, Amrita Ravi

2017-06-07

The model problem examined here is the stability of a thin liquid film consisting of two miscible components, resting on a chemically patterned solid substrate and heated from below. In addition to surface tension gradients, the temperature variations also induce gradients in the concentration of the film by virtue of thermodiffusion/Soret effects. We study the stability and dewetting behaviour due to the coupled interplay between thermal gradients, Soret effects, long-range van der Waals forces, and wettability gradient-driven flows. Linear stability analysis is first employed to predict growth rates and the critical Marangoni number for chemically homogeneous surfaces. Then, nonlinear simulations are performed to unravel the interfacial dynamics and possible locations of the film rupture on chemically patterned substrates. Results suggest that appropriate tuning of the Soret parameter and its direction, in conjunction with either heating or cooling, can help manipulate the location and time scales of the film rupture. The Soret effect can either potentially aid or oppose film instability depending on whether the thermal and solutal contributions to flow are cooperative or opposed to each other.

DYNAMIC SURFACE BOUNDARY-CONDITIONS - A SIMPLE BOUNDARY MODEL FOR MOLECULAR-DYNAMICS SIMULATIONS

NARCIS (Netherlands)

JUFFER, AH; BERENDSEN, HJC

1993-01-01

A simple model for the treatment of boundaries in molecular dynamics simulations is presented. The method involves the positioning of boundary atoms on a surface that surrounds a system of interest. The boundary atoms interact with the inner region and represent the effect of atoms outside the

Mapping Carrier Dynamics on Material Surfaces in Space and Time using Scanning Ultrafast Electron Microscopy

KAUST Repository

Sun, Jingya; Adhikari, Aniruddha; Shaheen, Basamat; Yang, Haoze; Mohammed, Omar F.

2016-01-01

Selectively capturing the ultrafast dynamics of charge carriers on materials surfaces and at interfaces is crucial to the design of solar cells and optoelectronic devices. Despite extensive research efforts over the past few decades, information and understanding about surface-dynamical processes, including carrier trapping and recombination remains extremely limited. A key challenge is to selectively map such dynamic processes, a capability that is hitherto impractical by time-resolved laser techniques, which are limited by the laser’s relatively large penetration depth and consequently they record mainly bulk information. Such surface dynamics can only be mapped in real space and time by applying four-dimensional (4D) scanning ultrafast electron microscopy (S-UEM), which records snapshots of materials surfaces with nanometer spatial and sub-picosecond temporal resolutions. In this method, the secondary electron (SE) signal emitted from the sample’s surface is extremely sensitive to the surface dynamics and is detected in real time. In several unique applications, we spatially and temporally visualize the SE energy gain and loss, the charge carrier dynamics on the surface of InGaN nanowires and CdSe single crystals and its powder film. We also provide the mechanisms for the observed dynamics, which will be the foundation for future potential applications of S-UEM to a wide range of studies on material surfaces and device interfaces.

Mapping Carrier Dynamics on Material Surfaces in Space and Time using Scanning Ultrafast Electron Microscopy

KAUST Repository

Sun, Jingya

2016-02-25

Selectively capturing the ultrafast dynamics of charge carriers on materials surfaces and at interfaces is crucial to the design of solar cells and optoelectronic devices. Despite extensive research efforts over the past few decades, information and understanding about surface-dynamical processes, including carrier trapping and recombination remains extremely limited. A key challenge is to selectively map such dynamic processes, a capability that is hitherto impractical by time-resolved laser techniques, which are limited by the laser’s relatively large penetration depth and consequently they record mainly bulk information. Such surface dynamics can only be mapped in real space and time by applying four-dimensional (4D) scanning ultrafast electron microscopy (S-UEM), which records snapshots of materials surfaces with nanometer spatial and sub-picosecond temporal resolutions. In this method, the secondary electron (SE) signal emitted from the sample’s surface is extremely sensitive to the surface dynamics and is detected in real time. In several unique applications, we spatially and temporally visualize the SE energy gain and loss, the charge carrier dynamics on the surface of InGaN nanowires and CdSe single crystals and its powder film. We also provide the mechanisms for the observed dynamics, which will be the foundation for future potential applications of S-UEM to a wide range of studies on material surfaces and device interfaces.

Dynamic modeling method of the bolted joint with uneven distribution of joint surface pressure

Science.gov (United States)

Li, Shichao; Gao, Hongli; Liu, Qi; Liu, Bokai

2018-03-01

The dynamic characteristics of the bolted joints have a significant influence on the dynamic characteristics of the machine tool. Therefore, establishing a reasonable bolted joint dynamics model is helpful to improve the accuracy of machine tool dynamics model. Because the pressure distribution on the joint surface is uneven under the concentrated force of bolts, a dynamic modeling method based on the uneven pressure distribution of the joint surface is presented in this paper to improve the dynamic modeling accuracy of the machine tool. The analytic formulas between the normal, tangential stiffness per unit area and the surface pressure on the joint surface can be deduced based on the Hertz contact theory, and the pressure distribution on the joint surface can be obtained by the finite element software. Futhermore, the normal and tangential stiffness distribution on the joint surface can be obtained by the analytic formula and the pressure distribution on the joint surface, and assigning it into the finite element model of the joint. Qualitatively compared the theoretical mode shapes and the experimental mode shapes, as well as quantitatively compared the theoretical modal frequencies and the experimental modal frequencies. The comparison results show that the relative error between the first four-order theoretical modal frequencies and the first four-order experimental modal frequencies is 0.2% to 4.2%. Besides, the first four-order theoretical mode shapes and the first four-order experimental mode shapes are similar and one-to-one correspondence. Therefore, the validity of the theoretical model is verified. The dynamic modeling method proposed in this paper can provide a theoretical basis for the accurate dynamic modeling of the bolted joint in machine tools.

He atom surface scattering: Surface dynamics of insulators, overlayers and crystal growth

International Nuclear Information System (INIS)

1992-01-01

Investigations have focused primarily on surface structure and dynamics of ionic insulators, epitaxial growth onto alkali halide crystals and multiphoton studies. The surface dynamics of RbCl has been re-examined. We have developed a simple force constant model which provides insight into the dynamics of KBr overlayers on NaCl(001), a system with a large lattice mismatch. The KBr/NaCl(001) results are compared to Na/Cu(001) and NaCl/Ge(001). We have completed epitaxial growth experiments for KBr onto RbCl(001). Slab dynamics calculations using a shell model for this system with very small lattice mismatch are being carried out in collaboration with Professor Manson of Clemson University and with Professor Schroeder in Regensburg, Germany. Extensive experiments on multiphoton scattering of helium atoms onto NaCl and, particularly, LiF have been carried out and the theory has been developed to a rather advanced stage by Professor Manson. This work will permit the extraction of more information from time-of-flight spectra. It is shown that the theoretical model provides a very good description of the multiphoton scattering from organic films. Work has started on self-assembling organic films on gold (alkyl thiols/Au(111)). We have begun to prepare and characterize the gold crystal; one of the group members has spent two weeks at the Oak Ridge National Laboratory learning the proper Au(111) preparation techniques. One of our students has carried out neutron scattering experiments on NiO, measuring both bulk phonon and magnon dispersion curves

Critical Dynamics of the Xy-Model on the One-Dimensional Superlattice by Position Space Renormalization Group

Science.gov (United States)

Lima, J. P. De; Gonçalves, L. L.

The critical dynamics of the isotropic XY-model on the one-dimensional superlattice is considered in the framework of the position space renormalization group theory. The decimation transformation is introduced by considering the equations of motion of the operators associated to the excitations of the system, and it corresponds to an extension of the procedure introduced by Stinchcombe and dos Santos (J. Phys. A18, L597 (1985)) for the homogeneous lattice. The dispersion relation is obtained exactly and the static and dynamic scaling forms are explicitly determined. The dynamic critical exponent is also obtained and it is shown that it is identical to the one of the XY-model on the homogeneous chain.

Unstable dynamics, nonequilibrium phases, and criticality in networked excitable media

International Nuclear Information System (INIS)

Franciscis, S. de; Torres, J. J.; Marro, J.

2010-01-01

Excitable systems are of great theoretical and practical interest in mathematics, physics, chemistry, and biology. Here, we numerically study models of excitable media, namely, networks whose nodes may occasionally be dormant and the connection weights are allowed to vary with the system activity on a short-time scale, which is a convenient and realistic representation. The resulting global activity is quite sensitive to stimuli and eventually becomes unstable also in the absence of any stimuli. Outstanding consequences of such unstable dynamics are the spontaneous occurrence of various nonequilibrium phases--including associative-memory phases and one in which the global activity wanders irregularly, e.g., chaotically among all or part of the dynamic attractors--and 1/f noise as the system is driven into the phase region corresponding to the most irregular behavior. A net result is resilience which results in an efficient search in the model attractor space that can explain the origin of some observed behavior in neural, genetic, and ill-condensed matter systems. By extensive computer simulation we also address a previously conjectured relation between observed power-law distributions and the possible occurrence of a ''critical state'' during functionality of, e.g., cortical networks, and describe the precise nature of such criticality in the model which may serve to guide future experiments.

Molecular dynamics simulation of annealed ZnO surfaces

Energy Technology Data Exchange (ETDEWEB)

Min, Tjun Kit; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

2015-04-24

The effect of thermally annealing a slab of wurtzite ZnO, terminated by two surfaces, (0001) (which is oxygen-terminated) and (0001{sup ¯}) (which is Zn-terminated), is investigated via molecular dynamics simulation by using reactive force field (ReaxFF). We found that upon heating beyond a threshold temperature of ∼700 K, surface oxygen atoms begin to sublimate from the (0001) surface. The ratio of oxygen leaving the surface at a given temperature increases as the heating temperature increases. A range of phenomena occurring at the atomic level on the (0001) surface has also been explored, such as formation of oxygen dimers on the surface and evolution of partial charge distribution in the slab during the annealing process. It was found that the partial charge distribution as a function of the depth from the surface undergoes a qualitative change when the annealing temperature is above the threshold temperature.

Ti and Zr surfaces studied by molecular dynamics

International Nuclear Information System (INIS)

Pascuet, Maria I.; Passianot, Roberto C.; Monti, Ana M.

2003-01-01

The interaction between point defects technique and the (0001), (1-210), (10-10) surfaces in Ti and Zr is studied by the molecular dynamics technique. Both of metals are in the hexagonal structure and within a temperature range of 100 to 900 K. The atomic interactions are modeled by EAM-type many-body potentials, that were used previously in static simulations. New migration mechanisms are unraveled and others are verified with respect to those already proposed in the static studies. Also included is an analysis of the vacancy stability in the sub-surface layers of the prismatic surfaces. (author)

Towards a dynamic assessment of raw materials criticality: linking agent-based demand--with material flow supply modelling approaches.

Science.gov (United States)

Knoeri, Christof; Wäger, Patrick A; Stamp, Anna; Althaus, Hans-Joerg; Weil, Marcel

2013-09-01

Emerging technologies such as information and communication-, photovoltaic- or battery technologies are expected to increase significantly the demand for scarce metals in the near future. The recently developed methods to evaluate the criticality of mineral raw materials typically provide a 'snapshot' of the criticality of a certain material at one point in time by using static indicators both for supply risk and for the impacts of supply restrictions. While allowing for insights into the mechanisms behind the criticality of raw materials, these methods cannot account for dynamic changes in products and/or activities over time. In this paper we propose a conceptual framework intended to overcome these limitations by including the dynamic interactions between different possible demand and supply configurations. The framework integrates an agent-based behaviour model, where demand emerges from individual agent decisions and interaction, into a dynamic material flow model, representing the materials' stocks and flows. Within the framework, the environmental implications of substitution decisions are evaluated by applying life-cycle assessment methodology. The approach makes a first step towards a dynamic criticality assessment and will enhance the understanding of industrial substitution decisions and environmental implications related to critical metals. We discuss the potential and limitation of such an approach in contrast to state-of-the-art methods and how it might lead to criticality assessments tailored to the specific circumstances of single industrial sectors or individual companies. Copyright © 2013 Elsevier B.V. All rights reserved.

Biofilm attachment reduction on bioinspired, dynamic, micro-wrinkling surfaces

International Nuclear Information System (INIS)

Epstein, Alexander K; Hong, Donggyoon; Kim, Philseok; Aizenberg, Joanna

2013-01-01

Most bacteria live in multicellular communities known as biofilms that are adherent to surfaces in our environment, from sea beds to plumbing systems. Biofilms are often associated with clinical infections, nosocomial deaths and industrial damage such as bio-corrosion and clogging of pipes. As mature biofilms are extremely challenging to eradicate once formed, prevention is advantageous over treatment. However, conventional surface chemistry strategies are either generally transient, due to chemical masking, or toxic, as in the case of leaching marine antifouling paints. Inspired by the nonfouling skins of echinoderms and other marine organisms, which possess highly dynamic surface structures that mechanically frustrate bio-attachment, we have developed and tested a synthetic platform based on both uniaxial mechanical strain and buckling-induced elastomer microtopography. Bacterial biofilm attachment to the dynamic substrates was studied under an array of parameters, including strain amplitude and timescale (1–100 mm s −1 ), surface wrinkle length scale, bacterial species and cell geometry, and growth time. The optimal conditions for achieving up to ∼ 80% Pseudomonas aeruginosa biofilm reduction after 24 h growth and ∼ 60% reduction after 48 h were combinatorially elucidated to occur at 20% strain amplitude, a timescale of less than ∼ 5 min between strain cycles and a topography length scale corresponding to the cell dimension of ∼ 1 μm. Divergent effects on the attachment of P. aeruginosa, Staphylococcus aureus and Escherichia coli biofilms showed that the dynamic substrate also provides a new means of species-specific biofilm inhibition, or inversely, selection for a desired type of bacteria, without reliance on any toxic or transient surface chemical treatments. (paper)

Biofilm attachment reduction on bioinspired, dynamic, micro-wrinkling surfaces

Science.gov (United States)

Epstein, Alexander K.; Hong, Donggyoon; Kim, Philseok; Aizenberg, Joanna

2013-09-01

Most bacteria live in multicellular communities known as biofilms that are adherent to surfaces in our environment, from sea beds to plumbing systems. Biofilms are often associated with clinical infections, nosocomial deaths and industrial damage such as bio-corrosion and clogging of pipes. As mature biofilms are extremely challenging to eradicate once formed, prevention is advantageous over treatment. However, conventional surface chemistry strategies are either generally transient, due to chemical masking, or toxic, as in the case of leaching marine antifouling paints. Inspired by the nonfouling skins of echinoderms and other marine organisms, which possess highly dynamic surface structures that mechanically frustrate bio-attachment, we have developed and tested a synthetic platform based on both uniaxial mechanical strain and buckling-induced elastomer microtopography. Bacterial biofilm attachment to the dynamic substrates was studied under an array of parameters, including strain amplitude and timescale (1-100 mm s-1), surface wrinkle length scale, bacterial species and cell geometry, and growth time. The optimal conditions for achieving up to ˜ 80% Pseudomonas aeruginosa biofilm reduction after 24 h growth and ˜ 60% reduction after 48 h were combinatorially elucidated to occur at 20% strain amplitude, a timescale of less than ˜ 5 min between strain cycles and a topography length scale corresponding to the cell dimension of ˜ 1 μm. Divergent effects on the attachment of P. aeruginosa, Staphylococcus aureus and Escherichia coli biofilms showed that the dynamic substrate also provides a new means of species-specific biofilm inhibition, or inversely, selection for a desired type of bacteria, without reliance on any toxic or transient surface chemical treatments.

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

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.

Non-equilibrium dynamics of single polymer adsorption to solid surfaces

NARCIS (Netherlands)

Panja, D.; Barkema, G.T.; Kolomeisky, A.B.

2009-01-01

The adsorption of polymers to surfaces is crucial for understanding many fundamental processes in nature. Recent experimental studies indicate that the adsorption dynamics is dominated by non-equilibrium effects. We investigate the adsorption of a single polymer of length N to a planar solid surface

Spherical harmonics analysis of surface density fluctuations of spherical ionic SDS and nonionic C12E8 micelles: A molecular dynamics study.

Science.gov (United States)

Yoshii, Noriyuki; Nimura, Yuki; Fujimoto, Kazushi; Okazaki, Susumu

2017-07-21

The surface structure and its fluctuation of spherical micelles were investigated using a series of density correlation functions newly defined by spherical harmonics and Legendre polynomials based on the molecular dynamics calculations. To investigate the influence of head-group charges on the micelle surface structure, ionic sodium dodecyl sulfate and nonionic octaethyleneglycol monododecylether (C 12 E 8 ) micelles were investigated as model systems. Large-scale density fluctuations were observed for both micelles in the calculated surface static structure factor. The area compressibility of the micelle surface evaluated by the surface static structure factor was tens-of-times larger than a typical value of a lipid membrane surface. The structural relaxation time, which was evaluated from the surface intermediate scattering function, indicates that the relaxation mechanism of the long-range surface structure can be well described by the hydrostatic approximation. The density fluctuation on the two-dimensional micelle surface has similar characteristics to that of three-dimensional fluids near the critical point.

Network Randomization and Dynamic Defense for Critical Infrastructure Systems

Energy Technology Data Exchange (ETDEWEB)

Chavez, Adrian R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Mitchell Tyler [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hamlet, Jason [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stout, William M.S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lee, Erik [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-04-01

Critical Infrastructure control systems continue to foster predictable communication paths, static configurations, and unpatched systems that allow easy access to our nation's most critical assets. This makes them attractive targets for cyber intrusion. We seek to address these attack vectors by automatically randomizing network settings, randomizing applications on the end devices themselves, and dynamically defending these systems against active attacks. Applying these protective measures will convert control systems into moving targets that proactively defend themselves against attack. Sandia National Laboratories has led this effort by gathering operational and technical requirements from Tennessee Valley Authority (TVA) and performing research and development to create a proof-of-concept solution. Our proof-of-concept has been tested in a laboratory environment with over 300 nodes. The vision of this project is to enhance control system security by converting existing control systems into moving targets and building these security measures into future systems while meeting the unique constraints that control systems face.

Dynamic bioactive stimuli-responsive polymeric surfaces

Science.gov (United States)

Pearson, Heather Marie

This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and Φ11 bacteriophages (phages) on PE and PTFE surface. This was accomplished by carbodiimide coupling between --COOH

Dynamic data-driven integrated flare model based on self-organized criticality

Science.gov (United States)

Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M. K.

2013-05-01

Context. We interpret solar flares as events originating in active regions that have reached the self-organized critical state. We describe them with a dynamic integrated flare model whose initial conditions and driving mechanism are derived from observations. Aims: We investigate whether well-known scaling laws observed in the distribution functions of characteristic flare parameters are reproduced after the self-organized critical state has been reached. Methods: To investigate whether the distribution functions of total energy, peak energy, and event duration follow the expected scaling laws, we first applied the previously reported static cellular automaton model to a time series of seven solar vector magnetograms of the NOAA active region 8210 recorded by the Imaging Vector Magnetograph on May 1 1998 between 18:59 UT and 23:16 UT until the self-organized critical state was reached. We then evolved the magnetic field between these processed snapshots through spline interpolation, mimicking a natural driver in our dynamic model. We identified magnetic discontinuities that exceeded a threshold in the Laplacian of the magnetic field after each interpolation step. These discontinuities were relaxed in local diffusion events, implemented in the form of cellular automaton evolution rules. Subsequent interpolation and relaxation steps covered all transitions until the end of the processed magnetograms' sequence. We additionally advanced each magnetic configuration that has reached the self-organized critical state (SOC configuration) by the static model until 50 more flares were triggered, applied the dynamic model again to the new sequence, and repeated the same process sufficiently often to generate adequate statistics. Physical requirements, such as the divergence-free condition for the magnetic field, were approximately imposed. Results: We obtain robust power laws in the distribution functions of the modeled flaring events with scaling indices that agree well

Random surfaces: A non-perturbative regularization of strings?

International Nuclear Information System (INIS)

Ambjoern, J.

1989-12-01

I review the basic properties of the theory of randum surfaces. While it is by now well known that the theory of (discretized) random surfaces correctly describes the (perturbative) aspects of non-critical strings in d 1. In these lectures I intend to show that the theory of dynamical triangulated random surfaces provides us with a lot of information about the dynamics of both the bosonic string and the superstring even for d>1. I also briefly review recent attempts to define a string field theory (sum over all genus) in this approach. (orig.)

Dynamical effects and the critical behavior of random-field systems (invited)

International Nuclear Information System (INIS)

Shapir, Y.

1985-01-01

A variety of phenomena is observed experimentally in random-field (RF) systems realized by the application of an external field to diluted antiferromagnets. At low temperatures, infinitely long hysteretic effects are manifested by the history dependence of the final states: long-range order is observed if the field is applied after cooling, while domain states are reached when field cooled. While no indications for critical fluctuations are detected in 2-D systems, scaling behavior, for both the correlation length and the specific heat, is observed in 3-D systems over an intermediate range of temperatures. The related critical properties seem to be well described by the corresponding ones in the 2-D pure Ising model. The renormalization-group approach, which yields for the equilibrium critical exponents their values of the pure model in d-2 dimensions, is reviewed. A generalization of the dimensional-reduction approach, which accounts self-consistently for renormalized responses of the RF system, is presented. The dynamical effects are implicitly incorporated through the variation in the critical response between the local and the global regimes, associated with short- and long-time scales, respectively. In both regimes the lower critical dimension is found to be d = 2 in accordance with stability arguments. The short-time critical behavior indicates a dimensional reduction by one for the 3-D thermal exponents, in agreement with the experimental results

Identification of an evolutionarily conserved extracellular threonine residue critical for surface expression and its potential coupling of adjacent voltage-sensing and gating domains in voltage-gated potassium channels.

Science.gov (United States)

Mckeown, Lynn; Burnham, Matthew P; Hodson, Charlotte; Jones, Owen T

2008-10-31

The dynamic expression of voltage-gated potassium channels (Kvs) at the cell surface is a fundamental factor controlling membrane excitability. In exploring possible mechanisms controlling Kv surface expression, we identified a region in the extracellular linker between the first and second of the six (S1-S6) transmembrane-spanning domains of the Kv1.4 channel, which we hypothesized to be critical for its biogenesis. Using immunofluorescence microscopy, flow cytometry, patch clamp electrophysiology, and mutagenesis, we identified a single threonine residue at position 330 within the Kv1.4 S1-S2 linker that is absolutely required for cell surface expression. Mutation of Thr-330 to an alanine, aspartate, or lysine prevented surface expression. However, surface expression occurred upon co-expression of mutant and wild type Kv1.4 subunits or mutation of Thr-330 to a serine. Mutation of the corresponding residue (Thr-211) in Kv3.1 to alanine also caused intracellular retention, suggesting that the conserved threonine plays a generalized role in surface expression. In support of this idea, sequence comparisons showed conservation of the critical threonine in all Kv families and in organisms across the evolutionary spectrum. Based upon the Kv1.2 crystal structure, further mutagenesis, and the partial restoration of surface expression in an electrostatic T330K bridging mutant, we suggest that Thr-330 hydrogen bonds to equally conserved outer pore residues, which may include a glutamate at position 502 that is also critical for surface expression. We propose that Thr-330 serves to interlock the voltage-sensing and gating domains of adjacent monomers, thereby yielding a structure competent for the surface expression of functional tetramers.

Dynamics of gas-surface interactions atomic-level understanding of scattering processes at surfaces

CERN Document Server

Díez Muniño, Ricardo

2013-01-01

This book gives a representative survey of the state of the art of research on gas-surface interactions. It provides an overview of the current understanding of gas surface dynamics and, in particular, of the reactive and non-reactive processes of atoms and small molecules at surfaces. Leading scientists in the field, both from the theoretical and the experimental sides, write in this book about their most recent advances. Surface science grew as an interdisciplinary research area over the last decades, mostly because of new experimental technologies (ultra-high vacuum, for instance), as well as because of a novel paradigm, the ‘surface science’ approach. The book describes the second transformation which is now taking place pushed by the availability of powerful quantum-mechanical theoretical methods implemented numerically. In the book, experiment and theory progress hand in hand with an unprecedented degree of accuracy and control. The book presents how modern surface science targets the atomic-level u...

A novel critical infrastructure resilience assessment approach using dynamic Bayesian networks

Science.gov (United States)

Cai, Baoping; Xie, Min; Liu, Yonghong; Liu, Yiliu; Ji, Renjie; Feng, Qiang

2017-10-01

The word resilience originally originates from the Latin word "resiliere", which means to "bounce back". The concept has been used in various fields, such as ecology, economics, psychology, and society, with different definitions. In the field of critical infrastructure, although some resilience metrics are proposed, they are totally different from each other, which are determined by the performances of the objects of evaluation. Here we bridge the gap by developing a universal critical infrastructure resilience metric from the perspective of reliability engineering. A dynamic Bayesian networks-based assessment approach is proposed to calculate the resilience value. A series, parallel and voting system is used to demonstrate the application of the developed resilience metric and assessment approach.

The approximate determination of the critical temperature of a liquid by measuring surface tension versus the temperature

International Nuclear Information System (INIS)

Maroto, J A; Nieves, F J de las; Quesada-Perez, M

2004-01-01

A classical experience in a physics student laboratory is to determine the surface tension of a liquid versus the temperature and to check the linear appearance of the obtained graph. In this work we show a simple method to estimate the critical temperature of three liquids by using experimental data of surface tension at different temperatures. By a logarithm fitting between surface tension and temperature, the critical temperature can be determined and compared with data from the literature. For two liquids (butanol and nitrobenzene) the comparison is acceptable but the differences are too high for the third liquid (water). By discussing the results it seems to be clear that the difference between the critical temperature of the liquid and the maximum temperature of the surface tension measurements is the determining factor in obtaining acceptable results. From this study it is possible to obtain more information on the liquid characteristics from surface tension measurements that are currently carried out in a student laboratory. Besides, in this paper it is shown how to select the most suitable liquids which provide both acceptable values for the critical temperature and measurements of the surface tension at moderate temperatures. The complementary use of numerical methods permits us to offer a complete experience for the students with a simple laboratory experiment which we recommend for physics students in advanced university courses

Dynamic Eigenvalue Problem of Concrete Slab Road Surface

Science.gov (United States)

Pawlak, Urszula; Szczecina, Michał

2017-10-01

The paper presents an analysis of the dynamic eigenvalue problem of concrete slab road surface. A sample concrete slab was modelled using Autodesk Robot Structural Analysis software and calculated with Finite Element Method. The slab was set on a one-parameter elastic subsoil, for which the modulus of elasticity was separately calculated. The eigen frequencies and eigenvectors (as maximal vertical nodal displacements) were presented. On the basis of the results of calculations, some basic recommendations for designers of concrete road surfaces were offered.

System Dynamics Approach for Critical Infrastructure and Decision Support. A Model for a Potable Water System.

Science.gov (United States)

Pasqualini, D.; Witkowski, M.

2005-12-01

The Critical Infrastructure Protection / Decision Support System (CIP/DSS) project, supported by the Science and Technology Office, has been developing a risk-informed Decision Support System that provides insights for making critical infrastructure protection decisions. The system considers seventeen different Department of Homeland Security defined Critical Infrastructures (potable water system, telecommunications, public health, economics, etc.) and their primary interdependencies. These infrastructures have been modeling in one model called CIP/DSS Metropolitan Model. The modeling approach used is a system dynamics modeling approach. System dynamics modeling combines control theory and the nonlinear dynamics theory, which is defined by a set of coupled differential equations, which seeks to explain how the structure of a given system determines its behavior. In this poster we present a system dynamics model for one of the seventeen critical infrastructures, a generic metropolitan potable water system (MPWS). Three are the goals: 1) to gain a better understanding of the MPWS infrastructure; 2) to identify improvements that would help protect MPWS; and 3) to understand the consequences, interdependencies, and impacts, when perturbations occur to the system. The model represents raw water sources, the metropolitan water treatment process, storage of treated water, damage and repair to the MPWS, distribution of water, and end user demand, but does not explicitly represent the detailed network topology of an actual MPWS. The MPWS model is dependent upon inputs from the metropolitan population, energy, telecommunication, public health, and transportation models as well as the national water and transportation models. We present modeling results and sensitivity analysis indicating critical choke points, negative and positive feedback loops in the system. A general scenario is also analyzed where the potable water system responds to a generic disruption.

Linking seasonal surface water dynamics with methane emissions and export from small, forested wetlands

Science.gov (United States)

Hondula, K. L.; Palmer, M.

2017-12-01

One of the biggest uncertainties about global methane sources and sinks is attributed to uncertainties regarding wetland area and its dynamics. This is exacerbated by confusion over the role of small, shallow water bodies like Delmarva bay wetlands that could be categorized as both wetlands and ponds. These small inland water bodies are often poorly quantified due to their size, closed forest canopies, and inter- and intra-annual variability in surface water extent. We are studying wetland-rich areas on the Delmarva Peninsula in the U.S. mid-Atlantic to address this uncertainty at the scale of individual wetland ecosystems ( 1m depth). We estimated the size and temporal variability of the methane emissions source area by combining these measurements with daily estimates of the extent of surface water inundation derived from water level monitoring and a high-resolution digital elevation model. This knowledge is critical for informing land use decisions (e.g. restoring wetlands specifically for climate mitigation), the jurisdiction of environmental policies in the US, and for resolving major outstanding discrepancies in our understanding of the global methane budget.

Condensation and Wetting Dynamics on Micro/Nano-Structured Surfaces

Science.gov (United States)

Olceroglu, Emre

Because of their adjustable wetting characteristics, micro/nanostructured surfaces are attractive for the enhancement of phase-change heat transfer where liquid-solid-vapor interactions are important. Condensation, evaporation, and boiling processes are traditionally used in a variety of applications including water harvesting, desalination, industrial power generation, HVAC, and thermal management systems. Although they have been studied by numerous researchers, there is currently a lack of understanding of the underlying mechanisms by which structured surfaces improve heat transfer during phase-change. This PhD dissertation focuses on condensation onto engineered surfaces including fabrication aspect, the physics of phase-change, and the operational limitations of engineered surfaces. While superhydrophobic condensation has been shown to produce high heat transfer rates, several critical issues remain in the field. These include surface manufacturability, heat transfer coefficient measurement limitations at low heat fluxes, failure due to surface flooding at high supersaturations, insufficient modeling of droplet growth rates, and the inherent issues associated with maintenance of non-wetted surface structures. Each of these issues is investigated in this thesis, leading to several contributions to the field of condensation on engineered surfaces. A variety of engineered surfaces have been fabricated and characterized, including nanostructured and hierarchically-structured superhydrophobic surfaces. The Tobacco mosaic virus (TMV) is used here as a biological template for the fabrication of nickel nanostructures, which are subsequently functionalized to achieve superhydrophobicity. This technique is simple and sustainable, and requires no applied heat or external power, thus making it easily extendable to a variety of common heat transfer materials and complex geometries. To measure heat transfer rates during superhydrophobic condensation in the presence of non

Dynamic characterisation of the specific surface area for fracture networks

Science.gov (United States)

Cvetkovic, V.

2017-12-01

One important application of chemical transport is geological disposal of high-level nuclear waste for which crystalline rock is a prime candidate for instance in Scandinavia. Interconnected heterogeneous fractures of sparsely fractured rock such as granite, act as conduits for transport of dissolved tracers. Fluid flow is known to be highly channelized in such rocks. Channels imply narrow flow paths, adjacent to essentially stagnant water in the fracture and/or the rock matrix. Tracers are transported along channelised flow paths and retained by minerals and/or stagnant water, depending on their sorption properties; this mechanism is critical for rocks to act as a barrier and ultimately provide safety for a geological repository. The sorbing tracers are retained by diffusion and sorption on mineral surfaces, whereas non-sorbing tracers can be retained only by diffusion into stagnant water of fractures. The retention and transport properties of a sparsely fractured rock will primarily depend on the specific surface area (SSA) of the fracture network which is determined by the heterogeneous structure and flow. The main challenge when characterising SSA on the field-scale is its dependence on the flow dynamics. We first define SSA as a physical quantity and clarify its importance for chemical transport. A methodology for dynamic characterisation of SSA in fracture networks is proposed that relies on three sets of data: i) Flow rate data as obtained by a flow logging procedure; ii) transmissivity data as obtained by pumping tests; iii) fracture network data as obtained from outcrop and geophysical observations. The proposed methodology utilises these data directly as well as indirectly through flow and particle tracking simulations in three-dimensional discrete fracture networks. The methodology is exemplified using specific data from the Swedish site Laxemar. The potential impact of uncertainties is of particular significance and is illustrated for radionuclide

Reactive surface organometallic complexes observed using dynamic nuclear polarization surface enhanced NMR spectroscopy

KAUST Repository

Pump, Eva; Viger-Gravel, Jasmine; Abou-Hamad, Edy; Samantaray, Manoja; Hamzaoui, Bilel; Gurinov, Andrei; Anjum, Dalaver H.; Gajan, David; Lesage, Anne; Bendjeriou-Sedjerari, Anissa; Emsley, Lyndon; Basset, Jean-Marie

2016-01-01

Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) is an emerging technique that allows access to high-sensitivity NMR spectra from surfaces. However, DNP SENS usually requires the use of radicals as an exogenous source of polarization, which has so far limited applications for organometallic surface species to those that do not react with the radicals. Here we show that reactive surface species can be studied if they are immobilized inside porous materials with suitably small windows, and if bulky nitroxide bi-radicals (here TEKPol) are used as the polarization source and which cannot enter the pores. The method is demonstrated by obtaining significant DNP enhancements from highly reactive complelxes [(equivalent to Si-O-)W(Me)(5)] supported on MCM-41, and effects of pore size (6.0, 3.0 and 2.5 nm) on the performance are discussed.

Reactive surface organometallic complexes observed using dynamic nuclear polarization surface enhanced NMR spectroscopy

KAUST Repository

Pump, Eva

2016-08-15

Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) is an emerging technique that allows access to high-sensitivity NMR spectra from surfaces. However, DNP SENS usually requires the use of radicals as an exogenous source of polarization, which has so far limited applications for organometallic surface species to those that do not react with the radicals. Here we show that reactive surface species can be studied if they are immobilized inside porous materials with suitably small windows, and if bulky nitroxide bi-radicals (here TEKPol) are used as the polarization source and which cannot enter the pores. The method is demonstrated by obtaining significant DNP enhancements from highly reactive complelxes [(equivalent to Si-O-)W(Me)(5)] supported on MCM-41, and effects of pore size (6.0, 3.0 and 2.5 nm) on the performance are discussed.

Accelerated sampling by infinite swapping of path integral molecular dynamics with surface hopping

Science.gov (United States)

Lu, Jianfeng; Zhou, Zhennan

2018-02-01

To accelerate the thermal equilibrium sampling of multi-level quantum systems, the infinite swapping limit of a recently proposed multi-level ring polymer representation is investigated. In the infinite swapping limit, the ring polymer evolves according to an averaged Hamiltonian with respect to all possible surface index configurations of the ring polymer and thus connects the surface hopping approach to the mean-field path-integral molecular dynamics. A multiscale integrator for the infinite swapping limit is also proposed to enable efficient sampling based on the limiting dynamics. Numerical results demonstrate the huge improvement of sampling efficiency of the infinite swapping compared with the direct simulation of path-integral molecular dynamics with surface hopping.

Global observations and modeling of atmosphere-surface exchange of elemental mercury: a critical review

Science.gov (United States)

Zhu, Wei; Lin, Che-Jen; Wang, Xun; Sommar, Jonas; Fu, Xuewu; Feng, Xinbin

2016-04-01

Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East

Switch of Sensitivity Dynamics Revealed with DyGloSA Toolbox for Dynamical Global Sensitivity Analysis as an Early Warning for System's Critical Transition

Science.gov (United States)

Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas

2013-01-01

Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA – a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits. PMID:24367574

Switch of sensitivity dynamics revealed with DyGloSA toolbox for dynamical global sensitivity analysis as an early warning for system's critical transition.

Science.gov (United States)

Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas

2013-01-01

Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA - a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits.

The estimation of dynamic contact angle of ultra-hydrophobic surfaces using inclined surface and impinging droplet methods

Science.gov (United States)

Jasikova, Darina; Kotek, Michal

2014-03-01

The development of industrial technology also brings with optimized surface quality, particularly where there is contact with food. Application ultra-hydrophobic surface significantly reduces the growth of bacteria and facilitates cleaning processes. Testing and evaluation of surface quality are used two methods: impinging droplet and inclined surface method optimized with high speed shadowgraphy, which give information about dynamic contact angle. This article presents the results of research into new methods of measuring ultra-hydrophobic patented technology.

Surface wettability effects on critical heat flux of boiling heat transfer using nanoparticle coatings

KAUST Repository

Hsu, Chin-Chi

2012-06-01

This study investigates the effects of surface wettability on pool boiling heat transfer. Nano-silica particle coatings were used to vary the wettability of the copper surface from superhydrophilic to superhydrophobic by modifying surface topography and chemistry. Experimental results show that critical heat flux (CHF) values are higher in the hydrophilic region. Conversely, CHF values are lower in the hydrophobic region. The experimental CHF data of the modified surface do not fit the classical models. Therefore, this study proposes a simple model to build the nexus between the surface wettability and the growth of bubbles on the heating surface. © 2012 Elsevier Ltd. All rights reserved.

Analytical description of critical dynamics for two-dimensional dissipative nonlinear maps

International Nuclear Information System (INIS)

Méndez-Bermúdez, J.A.; Oliveira, Juliano A. de; Leonel, Edson D.

2016-01-01

The critical dynamics near the transition from unlimited to limited action diffusion for two families of well known dissipative nonlinear maps, namely the dissipative standard and dissipative discontinuous maps, is characterized by the use of an analytical approach. The approach is applied to explicitly obtain the average squared action as a function of the (discrete) time and the parameters controlling nonlinearity and dissipation. This allows to obtain a set of critical exponents so far obtained numerically in the literature. The theoretical predictions are verified by extensive numerical simulations. We conclude that all possible dynamical cases, independently on the map parameter values and initial conditions, collapse into the universal exponential decay of the properly normalized average squared action as a function of a normalized time. The formalism developed here can be extended to many other different types of mappings therefore making the methodology generic and robust. - Highlights: • We analytically approach scaling properties of a family of two-dimensional dissipative nonlinear maps. • We derive universal scaling functions that were obtained before only approximately. • We predict the unexpected condition where diffusion and dissipation compensate each other exactly. • We find a new universal scaling function that embraces all possible dissipative behaviors.

Critical behavior of ferromagnetic Ising thin films

International Nuclear Information System (INIS)

Cossio, P.; Mazo-Zuluaga, J.; Restrepo, J.

2006-01-01

In the present work, we study the magnetic properties and critical behavior of simple cubic ferromagnetic thin films. We simulate LxLxd films with semifree boundary conditions on the basis of the Monte Carlo method and the Ising model with nearest neighbor interactions. A Metropolis dynamics was implemented to carry out the energy minimization process. For different film thickness, in the nanometer range, we compute the temperature dependence of the magnetization, the magnetic susceptibility and the fourth order Binder's cumulant. Bulk and surface contributions of these quantities are computed in a differentiated fashion. Additionally, according to finite size scaling theory, we estimate the critical exponents for the correlation length, magnetic susceptibility, and magnetization. Results reveal a strong dependence of critical temperature and critical exponents on the film thickness. The obtained critical exponents are finally compared to those reported in literature for thin films

Dynamic Bubble Surface Tension Measurements in Northwest Atlantic Seawater

Science.gov (United States)

Kieber, D. J.; Long, M. S.; Keene, W. C.; Kinsey, J. D.; Frossard, A. A.; Beaupre, S. R.; Duplessis, P.; Maben, J. R.; Lu, X.; Chang, R.; Zhu, Y.; Bisgrove, J.

2017-12-01

Numerous reports suggest that most organic matter (OM) associated with newly formed primary marine aerosol (PMA) originates from the sea-surface microlayer. However, surface-active OM rapidly adsorbs onto bubble surfaces in the water column and is ejected into the atmosphere when bubbles burst at the air-water interface. Here we present dynamic surface tension measurements of bubbles produced in near surface seawater from biologically productive and oligotrophic sites and in deep seawater collected from 2500 m in the northwest Atlantic. In all cases, the surface tension of bubble surfaces decreased within seconds after the bubbles were exposed to seawater. These observations demonstrate that bubble surfaces are rapidly saturated by surfactant material scavenged from seawater. Spatial and diel variability in bubble surface evolution indicate corresponding variability in surfactant concentrations and/or composition. Our results reveal that surface-active OM is found throughout the water column, and that at least some surfactants are not of recent biological origin. Our results also support the hypothesis that the surface microlayer is a minor to negligible source of OM associated with freshly produced PMA.

Dynamic critical phenomena in two-dimensional fully frustrated Coulomb gas model with disorder

International Nuclear Information System (INIS)

Zhang Wei; Luo Mengbo

2008-01-01

The dynamic critical phenomena near depinning transition in two-dimensional fully frustrated square lattice Coulomb gas model with disorders was studied using Monte Carlo technique. The ground state of the model system with disorder σ=0.3 is a disordered state. The dependence of charge current density J on electric field E was investigated at low temperatures. The nonlinear J-E behavior near critical depinning field can be described by a scaling function proposed for three-dimensional flux line system [M.B. Luo, X. Hu, Phys. Rev. Lett. 98 (2007) 267002]. We evaluated critical exponents and found an Arrhenius creep motion for field region E c /2 c . The scaling law of the depinning transition is also obtained from the scaling function

Phase dynamics of low critical current density YBCO Josephson junctions

Energy Technology Data Exchange (ETDEWEB)

Massarotti, D., E-mail: dmassarotti@na.infn.it [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Stornaiuolo, D. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); Rotoli, G. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy); Carillo, F. [Nest, Scuola Normale Superiore, Piazza San Silvestro 12, 56126 Pisa (Italy); Galletti, L. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Longobardi, L. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy); American Physical Society, 1 Research Road, Ridge, NY 11961 (United States); Beltram, F. [Nest, Scuola Normale Superiore, Piazza San Silvestro 12, 56126 Pisa (Italy); Tafuri, F. [CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy)

2014-08-15

Highlights: • We study the phase dynamics of YBaCuO Josephson junctions using various tools. • We derive information on the dissipation in a wide range of transport parameters. • Dissipation in such devices can be described by a frequency dependent damping model. • The use of different substrates allows us to tune the shell circuit. - Abstract: High critical temperature superconductors (HTS) based devices can have impact in the study of the phase dynamics of Josephson junctions (JJs) thanks to the wide range of junction parameters they offer and to their unconventional properties. Measurements of current–voltage characteristics and of switching current distributions constitute a direct way to classify different regimes of the phase dynamics and of the transport, also in nontrivial case of the moderately damped regime (MDR). MDR is going to be more and more common in JJs with advances in nanopatterning superconductors and synthesizing novel hybrid systems. Distinctive signatures of macroscopic quantum tunneling and of thermal activation in presence of different tunable levels of dissipation have been detected in YBCO grain boundary JJs. Experimental data are supported by Monte Carlo simulations of the phase dynamics, in a wide range of temperatures and dissipation levels. This allows us to quantify dissipation in the MDR and partially reconstruct a phase diagram as guideline for a wide range of moderately damped systems.

A novel approach to locomotion learning: Actor-Critic architecture using central pattern generators and dynamic motor primitives.

Science.gov (United States)

Li, Cai; Lowe, Robert; Ziemke, Tom

2014-01-01

In this article, we propose an architecture of a bio-inspired controller that addresses the problem of learning different locomotion gaits for different robot morphologies. The modeling objective is split into two: baseline motion modeling and dynamics adaptation. Baseline motion modeling aims to achieve fundamental functions of a certain type of locomotion and dynamics adaptation provides a "reshaping" function for adapting the baseline motion to desired motion. Based on this assumption, a three-layer architecture is developed using central pattern generators (CPGs, a bio-inspired locomotor center for the baseline motion) and dynamic motor primitives (DMPs, a model with universal "reshaping" functions). In this article, we use this architecture with the actor-critic algorithms for finding a good "reshaping" function. In order to demonstrate the learning power of the actor-critic based architecture, we tested it on two experiments: (1) learning to crawl on a humanoid and, (2) learning to gallop on a puppy robot. Two types of actor-critic algorithms (policy search and policy gradient) are compared in order to evaluate the advantages and disadvantages of different actor-critic based learning algorithms for different morphologies. Finally, based on the analysis of the experimental results, a generic view/architecture for locomotion learning is discussed in the conclusion.

A Novel Approach to Locomotion Learning: Actor-Critic Architecture using Central Pattern Generators and Dynamic Motor Primitives

Directory of Open Access Journals (Sweden)

Cai eLi

2014-10-01

Full Text Available In this article, we propose an architecture of a bio-inspired controller that addresses the problem of learning different locomotion gaits for different robot morphologies. The modelling objective is split into two: baseline motion modelling and dynamics adaptation. Baseline motion modelling aims to achieve fundamental functions of a certain type of locomotion and dynamics adaptation provides a ``reshaping function for adapting the baseline motion to desired motion. Based on this assumption, a three-layer architecture is developed using central pattern generators (CPGs, a bio-inspired locomotor center for the the baseline motion and dynamic motor primitives (DMPs, a model with universal ``reshaping functions. In this article, we use this architecture with the actor-critic algorithms for finding a good ``reshaping function. In order to demonstrate the learning power of the actor-critic based architecture, we tested it on two experiments: 1 learning to crawl on a humanoid and, 2 learning to gallop on a puppy robot. Two types of actor-critic algorithms (policy search and policy gradient are compared in order to evaluate the advantages and disadvantages of different actor-critic based learning algorithms for different morphologies. Finally, based on the analysis of the experimental results, a generic view/architecture for locomotion learning is discussed in the conclusion.

Influence of surface oxidation on ion dynamics and capacitance in porous and nonporous carbon electrodes

Energy Technology Data Exchange (ETDEWEB)

Dyatkin, Boris [Drexel Univ., Philadelphia, PA (United States); Zhang, Yu [Vanderbilt Univ., Nashville, TN (United States); Mamontov, Eugene [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kolesnikov, Alexander I. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cheng, Yongqiang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Meyer, III, Harry M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cummings, Peter T. [Vanderbilt Univ., Nashville, TN (United States); Gogotsi, Yury G. [Drexel Univ., Philadelphia, PA (United States)

2016-04-07

Here, we investigate the influence of surface chemistry and ion confinement on capacitance and electrosorption dynamics of room-temperature ionic liquids (RTILs) in supercapacitors. Using air oxidation and vacuum annealing, we produced defunctionalized and oxygen-rich surfaces of carbide-derived carbons (CDCs) and graphene nanoplatelets (GNPs). While oxidized surfaces of porous CDCs improve capacitance and rate handling abilities of ions, defunctionalized nonporous GNPs improve charge storage densities on planar electrodes. Quasi-elastic neutron scattering (QENS) and inelastic neutron scattering (INS) probed the structure, dynamics, and orientation of RTIL ions confined in divergently functionalized pores. Oxidized, ionophilic surfaces draw ions closer to pore surfaces and enhance potential-driven ion transport during electrosorption. Molecular dynamics (MD) simulations corroborated experimental data and demonstrated the significance of surface functional groups on ion orientations, accumulation densities, and capacitance.

Critical Domain Problem for the Reaction–Telegraph Equation Model of Population Dynamics

Directory of Open Access Journals (Sweden)

Weam Alharbi

2018-04-01

Full Text Available A telegraph equation is believed to be an appropriate model of population dynamics as it accounts for the directional persistence of individual animal movement. Being motivated by the problem of habitat fragmentation, which is known to be a major threat to biodiversity that causes species extinction worldwide, we consider the reaction–telegraph equation (i.e., telegraph equation combined with the population growth on a bounded domain with the goal to establish the conditions of species survival. We first show analytically that, in the case of linear growth, the expression for the domain’s critical size coincides with the critical size of the corresponding reaction–diffusion model. We then consider two biologically relevant cases of nonlinear growth, i.e., the logistic growth and the growth with a strong Allee effect. Using extensive numerical simulations, we show that in both cases the critical domain size of the reaction–telegraph equation is larger than the critical domain size of the reaction–diffusion equation. Finally, we discuss possible modifications of the model in order to enhance the positivity of its solutions.

Nonergodic dynamics of the two-dimensional random-phase sine-Gordon model: Applications to vortex-glass arrays and disordered-substrate surfaces

International Nuclear Information System (INIS)

Cule, D.; Shapir, Y.

1995-01-01

The dynamics of the random-phase sine-Gordon model, which describes two-dimensional vortex-glass arrays and crystalline surfaces on disordered substrates, is investigated using the self-consistent Hartree approximation. The fluctuation-dissipation theorem is violated below the critical temperature T c for large time t>t * where t * diverges in the thermodynamic limit. While above T c the averaged autocorrelation function diverges as Tln(t), for T c it approaches a finite value q * ∼1/(T c -T) as q(t)=q * -c(t/t * ) -ν (for t→t * ) where ν is a temperature-dependent exponent. On larger time scales t>t * the dynamics becomes nonergodic. The static correlations behave as ∼Tln|rvec x| for T>T c and for T c when x * with ξ * ∼exp{A/(T c -T)}. For scales x>ξ * , they behave as ∼m -1 Tln|rvec x| where m∼T/T c near T c , in general agreement with the variational replica-symmetry breaking approach and with recent simulations of the disordered-substrate surface. For strong coupling the transition becomes first order

Modeling Apple Surface Temperature Dynamics Based on Weather Data

Directory of Open Access Journals (Sweden)

Lei Li

2014-10-01

Full Text Available The exposure of fruit surfaces to direct sunlight during the summer months can result in sunburn damage. Losses due to sunburn damage are a major economic problem when marketing fresh apples. The objective of this study was to develop and validate a model for simulating fruit surface temperature (FST dynamics based on energy balance and measured weather data. A series of weather data (air temperature, humidity, solar radiation, and wind speed was recorded for seven hours between 11:00–18:00 for two months at fifteen minute intervals. To validate the model, the FSTs of “Fuji” apples were monitored using an infrared camera in a natural orchard environment. The FST dynamics were measured using a series of thermal images. For the apples that were completely exposed to the sun, the RMSE of the model for estimating FST was less than 2.0 °C. A sensitivity analysis of the emissivity of the apple surface and the conductance of the fruit surface to water vapour showed that accurate estimations of the apple surface emissivity were important for the model. The validation results showed that the model was capable of accurately describing the thermal performances of apples under different solar radiation intensities. Thus, this model could be used to more accurately estimate the FST relative to estimates that only consider the air temperature. In addition, this model provides useful information for sunburn protection management.

Modeling apple surface temperature dynamics based on weather data.

Science.gov (United States)

Li, Lei; Peters, Troy; Zhang, Qin; Zhang, Jingjin; Huang, Danfeng

2014-10-27

The exposure of fruit surfaces to direct sunlight during the summer months can result in sunburn damage. Losses due to sunburn damage are a major economic problem when marketing fresh apples. The objective of this study was to develop and validate a model for simulating fruit surface temperature (FST) dynamics based on energy balance and measured weather data. A series of weather data (air temperature, humidity, solar radiation, and wind speed) was recorded for seven hours between 11:00-18:00 for two months at fifteen minute intervals. To validate the model, the FSTs of "Fuji" apples were monitored using an infrared camera in a natural orchard environment. The FST dynamics were measured using a series of thermal images. For the apples that were completely exposed to the sun, the RMSE of the model for estimating FST was less than 2.0 °C. A sensitivity analysis of the emissivity of the apple surface and the conductance of the fruit surface to water vapour showed that accurate estimations of the apple surface emissivity were important for the model. The validation results showed that the model was capable of accurately describing the thermal performances of apples under different solar radiation intensities. Thus, this model could be used to more accurately estimate the FST relative to estimates that only consider the air temperature. In addition, this model provides useful information for sunburn protection management.

Critical Assessment of the Surface Tension determined by the Maximum Pressure Bubble Method

OpenAIRE

Benedetto, Franco Emmanuel; Zolotucho, Hector; Prado, Miguel Oscar

2015-01-01

The main factors that influence the value of surface tension of a liquid measured with the Maximum Pressure Bubble Method are critically evaluated. We present experimental results showing the effect of capillary diameter, capillary depth, bubble spheroidicity and liquid density at room temperature. We show that the decrease of bubble spheroidicity due to increase of capillary immersion depth is not sufficient to explain the deviations found in the measured surface tension values. Thus, we pro...

Non-equilibrium dynamics of single polymer adsorption to solid surfaces

International Nuclear Information System (INIS)

Panja, Debabrata; Barkema, Gerard T; Kolomeisky, Anatoly B

2009-01-01

The adsorption of polymers to surfaces is crucial for understanding many fundamental processes in nature. Recent experimental studies indicate that the adsorption dynamics is dominated by non-equilibrium effects. We investigate the adsorption of a single polymer of length N to a planar solid surface in the absence of hydrodynamic interactions. We find that for weak adsorption energies the adsorption timescales ∼N (1+2ν)/(1+ν) , where ν is the Flory exponent for the polymer. We argue that in this regime the single chain adsorption is closely related to a field-driven polymer translocation through narrow pores. Surprisingly, for high adsorption energies the adsorption time becomes longer, as it scales as ∼N 1+ν , which is explained by strong stretching of the unadsorbed part of the polymer close to the adsorbing surface. These two dynamic regimes are separated by an energy scale that is characterized by non-equilibrium contributions during the adsorption process. (fast track communication)

Fluorescence quenching studies of potential-dependent DNA reorientation dynamics at glassy carbon electrode surfaces.

Science.gov (United States)

Li, Qin; Cui, Chenchen; Higgins, Daniel A; Li, Jun

2012-09-05

The potential-dependent reorientation dynamics of double-stranded DNA (ds-DNA) attached to planar glassy carbon electrode (GCE) surfaces were investigated. The orientation state of surface-bound ds-DNA was followed by monitoring the fluorescence from a 6-carboxyfluorescein (FAM6) fluorophore covalently linked to the distal end of the DNA. Positive potentials (i.e., +0.2 V vs open circuit potential, OCP) caused the ds-DNA to align parallel to the electrode surface, resulting in strong dipole-electrode quenching of FAM6 fluorescence. Switching of the GCE potential to negative values (i.e., -0.2 V vs OCP) caused the ds-DNA to reorient perpendicular to the electrode surface, with a concomitant increase in FAM6 fluorescence. In addition to the very fast (submilliseconds) dynamics of the initial reorientation process, slow (0.1-0.9 s) relaxation of FAM6 fluorescence to intermediate levels was also observed after potential switching. These dynamics have not been previously described in the literature. They are too slow to be explained by double layer charging, and chronoamperometry data showed no evidence of such effects. Both the amplitude and rate of the dynamics were found to depend upon buffer concentration, and ds-DNA length, demonstrating a dependence on the double layer field. The dynamics are concluded to arise from previously undetected complexities in the mechanism of potential-dependent ds-DNA reorientation. The possible origins of these dynamics are discussed. A better understanding of these dynamics will lead to improved models for potential-dependent ds-DNA reorientation at electrode surfaces and will facilitate the development of advanced electrochemical devices for detection of target DNAs.

Assessing the Nano-Dynamics of the Cell Surface

Energy Technology Data Exchange (ETDEWEB)

Bae, Chil Man [Dept. of Physiology and Biophysics, State University of New York, Buffalo (United States); Park, Ik Keun [Mechanical Engineering, Seoul National University of Technology, Seoul (Korea, Republic of); Bulter, Peter J. [Dept. of Bioengineering, The Pennsylvania State University, University Park (United States)

2012-06-15

It is important to know the mechanism of cell membrane fluctuation because it can be readout for the nanomechanical interaction between cytoskeleton and plasma membrane. Traditional techniques, however, have drawbacks such as probe contact with the cell surface, complicate analysis, and limit spatial and temporal resolution. In this study, we developed a new system for non-contact measurement of nano-scale localized-cell surface dynamics using modified-scanning ion-conductance microscopy. With 2 nm resolution, we determined that endothelial cells have local membrane fluctuations of -20 nm, actin depolymerization causes increase in fluctuation amplitude, and ATP depletion abolishes all membrane fluctuations.

Dust Dynamics Near Planetary Surfaces

Science.gov (United States)

Colwell, Joshua; Hughes, Anna; Grund, Chris

Observations of a lunar "horizon glow" by several Surveyor spacecraft in the 1960s opened the study of the dynamics of charged dust particles near planetary surfaces. The surfaces of the Moon and other airless planetary bodies in the solar system (asteroids, and other moons) are directly exposed to the solar wind and ionizing solar ultraviolet radiation, resulting in a time-dependent electric surface potential. Because these same objects are also exposed to bombardment by micrometeoroids, the surfaces are usually characterized by a power-law size distribution of dust that extends to sub-micron-sized particles. Individual particles can acquire a charge different from their surroundings leading to electrostatic levitation. Once levitated, particles may simply return to the surface on nearly ballistic trajectories, escape entirely from the moon or asteroid if the initial velocity is large, or in some cases be stably levitated for extended periods of time. All three outcomes have observable consequences. Furthermore, the behavior of charged dust near the surface has practical implications for planned future manned and unmanned activities on the lunar surface. Charged dust particles also act as sensitive probes of the near-surface plasma environment. Recent numerical modeling of dust levitation and transport show that charged micron-sized dust is likely to accumulate in topographic lows such as craters, providing a mechanism for the creation of dust "ponds" observed on the asteroid 433 Eros. Such deposition can occur when particles are supported by the photoelectron sheath above the dayside and drift over shadowed regions of craters where the surface potential is much smaller. Earlier studies of the lunar horizon glow are consistent with those particles being on simple ballistic trajectories following electrostatic launching from the surface. Smaller particles may be accelerated from the lunar surface to high altitudes consistent with observations of high altitude

Movement, demographics, and occupancy dynamics of a federally-threatened salamander: evaluating the adequacy of critical habitat

Directory of Open Access Journals (Sweden)

Nathan F. Bendik

2016-03-01

Full Text Available Critical habitat for many species is often limited to occupied localities. For rare and cryptic species, or those lacking sufficient data, occupied habitats may go unrecognized, potentially hindering species recovery. Proposed critical habitat for the aquatic Jollyville Plateau salamander (Eurycea tonkawae and two sister species were delineated based on the assumption that surface habitat is restricted to springs and excludes intervening stream reaches. To test this assumption, we performed two studies to understand aspects of individual, population, and metapopulation ecology of E. tonkawae. First, we examined movement and population demographics using capture-recapture along a spring-influenced stream reach. We then extended our investigation of stream habitat use with a study of occupancy and habitat dynamics in multiple headwater streams. Indications of extensive stream channel use based on capture-recapture results included frequent movements of >15 m, and high juvenile abundance downstream of the spring. Initial occupancy of E. tonkawae was associated with shallow depths, maidenhair fern presence and low temperature variation (indicative of groundwater influence, although many occupied sites were far from known springs. Additionally, previously dry sites were three times more likely to be colonized than wet sites. Our results indicate extensive use of stream habitats, including intermittent ones, by E. tonkawae. These areas may be important for maintaining population connectivity or even as primary habitat patches. Restricting critical habitat to occupied sites will result in a mismatch with actual habitat use, particularly when assumptions of habitat use are untested, thus limiting the potential for recovery.

Measurement of Dynamic Friction Coefficient on the Irregular Free Surface

International Nuclear Information System (INIS)

Yeom, S. H.; Seo, K. S.; Lee, J. H.; Lee, K. H.

2007-01-01

A spent fuel storage cask must be estimated for a structural integrity when an earthquake occurs because it freely stands on ground surface without a restriction condition. Usually the integrity estimation for a seismic load is performed by a FEM analysis, the friction coefficient for a standing surface is an important parameter in seismic analysis when a sliding happens. When a storage cask is placed on an irregular ground surface, measuring a friction coefficient of an irregular surface is very difficult because the friction coefficient is affected by the surface condition. In this research, dynamic friction coefficients on the irregular surfaces between a concrete cylinder block and a flat concrete slab are measured with two methods by one direction actuator

Critical realism in supply chain research: Understanding the dynamics of a seasonal goods supply chain

OpenAIRE

Adamides, E. D.; Papachristos, G.; Pomonis, N.

2012-01-01

Purpose – The purpose of this paper is to show how a critical realist paradigmatic stance and its associated research methodology can contribute to supply‐chain research by providing explanations for specific supply‐chain‐ and logistics‐related dynamic phenomena. / Design/methodology/approach – Initially, the case for a critical realist research paradigm is made, and then a retroductive pluralistic research methodology is used for demonstrating its application. Starting from an observation in...

Dynamic analysis of the photoenhancement process of colloidal quantum dots with different surface modifications

Energy Technology Data Exchange (ETDEWEB)

Valledor Llopis, Marta; Campo Rodriguez, Juan Carlos; Ferrero Martin, Francisco J [Departamento de Ingenieria Electrica, Electronica, C y S Universidad de Oviedo, Campus de Gijon s/n, 33204 Gijon, Asturias, (Spain); Coto, Ana Maria; Fernandez-Argueelles, Maria T; Costa-Fernandez, J M; Sanz-Medel, A [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, Campus del Cristo, 33006 Oviedo, Asturias (Spain)

2011-09-23

Photoinduced fluorescence enhancement of colloidal quantum dots (QDs) is a hot topic addressed in many studies due to its great influence on the bioanalytical performance of such nanoparticles. However, understanding of this process is not a simple task, and it cannot be explained by a general mechanism as it greatly depends on the QDs' nature, solubilization strategies, surrounding environment, etc. In this vein, we have critically compared the behavior of CdSe QDs (widely used in bioanalytical applications) with different surface modifications (ligand exchange and polymer coating), in different controlled experimental conditions, in the presence-absence of the ZnS layer and in different media when exposed for long times to intense UV irradiation. Thus six different types of colloidal QDs were finally studied. This research was carried out from a novel perspective, based on the analysis of the dynamic behavior of the photoactivation process (of great interest for further applications of QDs as labels in biomedical applications). The results showed a different behavior of the studied colloidal QDs after UV irradiation in terms of their photoluminescence characteristics, potential toxicity due to metal release to the environment, nanoparticle stability and surface coating degradation.

Dynamic analysis of the photoenhancement process of colloidal quantum dots with different surface modifications

International Nuclear Information System (INIS)

Valledor Llopis, Marta; Campo Rodriguez, Juan Carlos; Ferrero Martin, Francisco J; Coto, Ana Maria; Fernandez-Argueelles, Maria T; Costa-Fernandez, J M; Sanz-Medel, A

2011-01-01

Photoinduced fluorescence enhancement of colloidal quantum dots (QDs) is a hot topic addressed in many studies due to its great influence on the bioanalytical performance of such nanoparticles. However, understanding of this process is not a simple task, and it cannot be explained by a general mechanism as it greatly depends on the QDs' nature, solubilization strategies, surrounding environment, etc. In this vein, we have critically compared the behavior of CdSe QDs (widely used in bioanalytical applications) with different surface modifications (ligand exchange and polymer coating), in different controlled experimental conditions, in the presence-absence of the ZnS layer and in different media when exposed for long times to intense UV irradiation. Thus six different types of colloidal QDs were finally studied. This research was carried out from a novel perspective, based on the analysis of the dynamic behavior of the photoactivation process (of great interest for further applications of QDs as labels in biomedical applications). The results showed a different behavior of the studied colloidal QDs after UV irradiation in terms of their photoluminescence characteristics, potential toxicity due to metal release to the environment, nanoparticle stability and surface coating degradation.

Study on dynamic deformation synchronized measurement technology of double-layer liquid surfaces

Science.gov (United States)

Tang, Huiying; Dong, Huimin; Liu, Zhanwei

2017-11-01

Accurate measurement of the dynamic deformation of double-layer liquid surfaces plays an important role in many fields, such as fluid mechanics, biomechanics, petrochemical industry and aerospace engineering. It is difficult to measure dynamic deformation of double-layer liquid surfaces synchronously for traditional methods. In this paper, a novel and effective method for full-field static and dynamic deformation measurement of double-layer liquid surfaces has been developed, that is wavefront distortion of double-wavelength transmission light with geometric phase analysis (GPA) method. Double wavelength lattice patterns used here are produced by two techniques, one is by double wavelength laser, and the other is by liquid crystal display (LCD). The techniques combine the characteristics such as high transparency, low reflectivity and fluidity of liquid. Two color lattice patterns produced by laser and LCD were adjusted at a certain angle through the tested double-layer liquid surfaces simultaneously. On the basis of the refractive indexes difference of two transmitted lights, the double-layer liquid surfaces were decoupled with GPA method. Combined with the derived relationship between phase variation of transmission-lattice patterns and out-of plane heights of two surfaces, as well as considering the height curves of the liquid level, the double-layer liquid surfaces can be reconstructed successfully. Compared with the traditional measurement method, the developed method not only has the common advantages of the optical measurement methods, such as high-precision, full-field and non-contact, but also simple, low cost and easy to set up.

Analysis of neutronics and dynamic characteristics with reactivity injection in LBE cooled sub-critical reactor

International Nuclear Information System (INIS)

Chen Sen; Wu Yican; Jin Ming; Chen Zhibin; Bai Yunqing; Zhao Zhumin

2014-01-01

Accelerator Driven Sub-critical System (ADS) has particular neutronics behaviors compared with the critical system. Prompt jump approximation point reactor kinetics equations taken external source into account have been deduced using an approach of prompt jump approximation. And the relationship between injection reactivity and power ampliation has been achieved. In addition, based on the RELAP5 code the prolong development of point reactor kinetics code used into assessing sub-critical system have been promoted. Different sub-criticality (k eff = 0.90, 0.95, 0.97, 0.98 and 0.99) have been assessed in preliminary design of a type of natural circulation cooling sub-critical reactor under conditions of reactivity injection +1 β in one second. It shows that the external source prompt transient approximation method has an accurate solution after injecting reactivity around short time and has a capacity to solve the dynamic equation, and the sub-critical system has an inner stability while the deeper sub-criticality the less impact on the sub-critical system. (authors)

Optimizing critical heat flux enhancement through nano-particle-based surface modifications

International Nuclear Information System (INIS)

Truong, B.; Hu, L. W.; Buongiorno, J.

2008-01-01

Colloidal dispersions of nano-particles, also known as nano-fluids, have shown to yield significant Critical Heat Flux (CHF) enhancement. The CHF enhancement mechanism in nano-fluids is due to the buildup of a porous layer of nano-particles upon boiling. Unlike microporous coatings that had been studied extensively, nano-particles have the advantages of forming a thin layer on the substrate with surface roughness ranges from the sub-micron to several microns. By tuning the chemical properties it is possible to coat the nano-particles in colloidal dispersions onto the desired surface, as has been demonstrated in engineering thin film industry. Building on recent work conducted at MIT, this paper illustrates the maximum CHF enhancement that can be achieved based on existing correlations. Optimization of the CHF enhancement by incorporation of key factors, such as the surface wettability and roughness, will also be discussed. (authors)

The Ramifications of Meddling with Systems Governed by Self-organized Critical Dynamics

Science.gov (United States)

Carreras, B. A.; Newman, D. E.; Dobson, I.

2002-12-01

Complex natural, well as man-made, systems often exhibit characteristics similar to those seen in self-organized critical (SOC) systems. The concept of self-organized criticality brings together ideas of self-organization of nonlinear dynamical systems with the often-observed near critical behavior of many natural phenomena. These phenomena exhibit self-similarities over extended ranges of spatial and temporal scales. In those systems, scale lengths may be described by fractal geometry and time scales that lead to 1/f-like power spectra. Natural applications include modeling the motion of tectonics plates, forest fires, magnetospheric dynamics, spin glass systems, and turbulent transport. In man-made systems, applications have included traffic dynamics, power and communications networks, and financial markets among many others. Simple cellular automata models such as the running sandpile model have been very useful in reproducing the complexity and characteristics of these systems. One characteristic property of the SOC systems is that they relax through what we call events. These events can happen over all scales of the system. Examples of these events are: earthquakes in the case of plate tectonic; fires in forest evolution extinction in the co evolution of biological species; and blackouts in power transmission systems. In a time-averaged sense, these systems are subcritical (that is, they lie in an average state that should not trigger any events) and the relaxation events happen intermittently. The time spent in a subcritical state relative to the time of the events varies from one system to another. For instance, the chance of finding a forest on fire is very low with the frequency of fires being on the order of one fire every few years and with many of these fires small and inconsequential. Very large fires happen over time periods of decades or even centuries. However, because of their consequences, these large but infrequent events are the important ones

Great differences in the critical erosion threshold between surface and subsurface sediments: A field investigation of an intertidal mudflat, Jiangsu, China

Science.gov (United States)

Shi, Benwei; Wang, Ya Ping; Wang, Li Hua; Li, Peng; Gao, Jianhua; Xing, Fei; Chen, Jing Dong

2018-06-01

Understanding of bottom sediment erodibility is necessary for the sustainable management and protection of coastlines, and is of great importance for numerical models of sediment dynamics and transport. To investigate the dependence of sediment erodibility on degree of consolidation, we measured turbidity, waves, tidal currents, intratidal bed-level changes, and sediment properties on an exposed macrotidal mudflat during a series of tidal cycles. We estimated the water content of surface sediments (in the uppermost 2 cm of sediment) and sub-surface sediments (at 2 cm below the sediment surface). Bed shear stress values due to currents (τc), waves (τw), and combined current-wave action (τcw) were calculated using a hydrodynamic model. In this study, we estimate the critical shear stress for erosion using two approaches and both of them give similar results. We found that the critical shear stress for erosion (τce) was 0.17-0.18 N/m2 in the uppermost 0-2 cm of sediment and 0.29 N/m2 in sub-surface sediment layers (depth, 2 cm), as determined by time series of τcw values and intratidal bed-level changes, and values of τce, obtained using the water content of bottom sediments, were 0.16 N/m2 in the uppermost 2 cm and 0.28 N/m2 in the sub-surface (depth, 2 cm) sediment. These results indicate that the value of τce for sub-surface sediments (depth, 2 cm) is much greater than that for the uppermost sediments (depth, 0-2 cm), and that the τce value is mainly related to the water content, which is determined by the extent of consolidation. Our results have implications for improving the predictive accuracy of models of sediment transport and morphological evolution, by introducing variable τce values for corresponding sediment layers, and can also provide a mechanistic understanding of bottom sediment erodibility at different sediment depths on intertidal mudflats, as related to differences in the consolidation time.

Structural dynamics of surfaces by ultrafast electron crystallography: experimental and multiple scattering theory.

Science.gov (United States)

Schäfer, Sascha; Liang, Wenxi; Zewail, Ahmed H

2011-12-07

Recent studies in ultrafast electron crystallography (UEC) using a reflection diffraction geometry have enabled the investigation of a wide range of phenomena on the femtosecond and picosecond time scales. In all these studies, the analysis of the diffraction patterns and their temporal change after excitation was performed within the kinematical scattering theory. In this contribution, we address the question, to what extent dynamical scattering effects have to be included in order to obtain quantitative information about structural dynamics. We discuss different scattering regimes and provide diffraction maps that describe all essential features of scatterings and observables. The effects are quantified by dynamical scattering simulations and examined by direct comparison to the results of ultrafast electron diffraction experiments on an in situ prepared Ni(100) surface, for which structural dynamics can be well described by a two-temperature model. We also report calculations for graphite surfaces. The theoretical framework provided here allows for further UEC studies of surfaces especially at larger penetration depths and for those of heavy-atom materials. © 2011 American Institute of Physics

Urban Land: Study of Surface Run-off Composition and Its Dynamics

Science.gov (United States)

Palagin, E. D.; Gridneva, M. A.; Bykova, P. G.

2017-11-01

The qualitative composition of urban land surface run-off is liable to significant variations. To study surface run-off dynamics, to examine its behaviour and to discover reasons of these variations, it is relevant to use the mathematical apparatus technique of time series analysis. A seasonal decomposition procedure was applied to a temporary series of monthly dynamics with the annual frequency of seasonal variations in connection with a multiplicative model. The results of the quantitative chemical analysis of surface wastewater of the 22nd Partsjezd outlet in Samara for the period of 2004-2016 were used as basic data. As a result of the analysis, a seasonal pattern of variations in the composition of surface run-off in Samara was identified. Seasonal indices upon 15 waste-water quality indicators were defined. BOD (full), suspended materials, mineralization, chlorides, sulphates, ammonium-ion, nitrite-anion, nitrate-anion, phosphates (phosphorus), iron general, copper, zinc, aluminium, petroleum products, synthetic surfactants (anion-active). Based on the seasonal decomposition of the time series data, the contribution of trends, seasonal and accidental components of the variability of the surface run-off indicators was estimated.

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

Directory of Open Access Journals (Sweden)

W. Zhu

2016-04-01

Full Text Available Reliable quantification of air–surface fluxes of elemental Hg vapor (Hg0 is crucial for understanding mercury (Hg global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc. in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere–surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air–surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.. However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann–Whitney U test. The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia. The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0

Incorporating human-water dynamics in a hyper-resolution land surface model

Science.gov (United States)

Vergopolan, N.; Chaney, N.; Wanders, N.; Sheffield, J.; Wood, E. F.

2017-12-01

The increasing demand for water, energy, and food is leading to unsustainable groundwater and surface water exploitation. As a result, the human interactions with the environment, through alteration of land and water resources dynamics, need to be reflected in hydrologic and land surface models (LSMs). Advancements in representing human-water dynamics still leave challenges related to the lack of water use data, water allocation algorithms, and modeling scales. This leads to an over-simplistic representation of human water use in large-scale models; this is in turn leads to an inability to capture extreme events signatures and to provide reliable information at stakeholder-level spatial scales. The emergence of hyper-resolution models allows one to address these challenges by simulating the hydrological processes and interactions with the human impacts at field scales. We integrated human-water dynamics into HydroBlocks - a hyper-resolution, field-scale resolving LSM. HydroBlocks explicitly solves the field-scale spatial heterogeneity of land surface processes through interacting hydrologic response units (HRUs); and its HRU-based model parallelization allows computationally efficient long-term simulations as well as ensemble predictions. The implemented human-water dynamics include groundwater and surface water abstraction to meet agricultural, domestic and industrial water demands. Furthermore, a supply-demand water allocation scheme based on relative costs helps to determine sectoral water use requirements and tradeoffs. A set of HydroBlocks simulations over the Midwest United States (daily, at 30-m spatial resolution for 30 years) are used to quantify the irrigation impacts on water availability. The model captures large reductions in total soil moisture and water table levels, as well as spatiotemporal changes in evapotranspiration and runoff peaks, with their intensity related to the adopted water management strategy. By incorporating human-water dynamics in

Dynamics of ice nucleation on water repellent surfaces.

Science.gov (United States)

Alizadeh, Azar; Yamada, Masako; Li, Ri; Shang, Wen; Otta, Shourya; Zhong, Sheng; Ge, Liehui; Dhinojwala, Ali; Conway, Ken R; Bahadur, Vaibhav; Vinciquerra, A Joseph; Stephens, Brian; Blohm, Margaret L

2012-02-14

Prevention of ice accretion and adhesion on surfaces is relevant to many applications, leading to improved operation safety, increased energy efficiency, and cost reduction. Development of passive nonicing coatings is highly desirable, since current antiicing strategies are energy and cost intensive. Superhydrophobicity has been proposed as a lead passive nonicing strategy, yet the exact mechanism of delayed icing on these surfaces is not clearly understood. In this work, we present an in-depth analysis of ice formation dynamics upon water droplet impact on surfaces with different wettabilities. We experimentally demonstrate that ice nucleation under low-humidity conditions can be delayed through control of surface chemistry and texture. Combining infrared (IR) thermometry and high-speed photography, we observe that the reduction of water-surface contact area on superhydrophobic surfaces plays a dual role in delaying nucleation: first by reducing heat transfer and second by reducing the probability of heterogeneous nucleation at the water-substrate interface. This work also includes an analysis (based on classical nucleation theory) to estimate various homogeneous and heterogeneous nucleation rates in icing situations. The key finding is that ice nucleation delay on superhydrophobic surfaces is more prominent at moderate degrees of supercooling, while closer to the homogeneous nucleation temperature, bulk and air-water interface nucleation effects become equally important. The study presented here offers a comprehensive perspective on the efficacy of textured surfaces for nonicing applications.

Integrated Surface/subsurface flow modeling in PFLOTRAN

Energy Technology Data Exchange (ETDEWEB)

Painter, Scott L [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-10-01

Understanding soil water, groundwater, and shallow surface water dynamics as an integrated hydrological system is critical for understanding the Earth’s critical zone, the thin outer layer at our planet’s surface where vegetation, soil, rock, and gases interact to regulate the environment. Computational tools that take this view of soil moisture and shallow surface flows as a single integrated system are typically referred to as integrated surface/subsurface hydrology models. We extend the open-source, highly parallel, subsurface flow and reactive transport simulator PFLOTRAN to accommodate surface flows. In contrast to most previous implementations, we do not represent a distinct surface system. Instead, the vertical gradient in hydraulic head at the land surface is neglected, which allows the surface flow system to be eliminated and incorporated directly into the subsurface system. This tight coupling approach leads to a robust capability and also greatly simplifies implementation in existing subsurface simulators such as PFLOTRAN. Successful comparisons to independent numerical solutions build confidence in the approximation and implementation. Example simulations of the Walker Branch and East Fork Poplar Creek watersheds near Oak Ridge, Tennessee demonstrate the robustness of the approach in geometrically complex applications. The lack of a robust integrated surface/subsurface hydrology capability had been a barrier to PFLOTRAN’s use in critical zone studies. This work addresses that capability gap, thus enabling PFLOTRAN as a community platform for building integrated models of the critical zone.

Predicting critical transitions in dynamical systems from time series using nonstationary probability density modeling.

Science.gov (United States)

Kwasniok, Frank

2013-11-01

A time series analysis method for predicting the probability density of a dynamical system is proposed. A nonstationary parametric model of the probability density is estimated from data within a maximum likelihood framework and then extrapolated to forecast the future probability density and explore the system for critical transitions or tipping points. A full systematic account of parameter uncertainty is taken. The technique is generic, independent of the underlying dynamics of the system. The method is verified on simulated data and then applied to prediction of Arctic sea-ice extent.

Synthesis, surface properties and oil solubilisation capacity of cationic gemini surfactants

NARCIS (Netherlands)

Dam, Th.; Engberts, J.B.F.N.; Karthäuser, J.; Karaborni, S.; Os, N.M. van

1996-01-01

The critical micelle concentration (CMC) and the surface tension at the CMC have been determined for the gemini surfactants alkanediyl-u,w-bis(dimethyla1kylammoniubmr omide) by means of dynamic surface tension measurements. For the same number of carbon atoms in the hydrophobic chain per hydrophilic

He-atom surface scattering apparatus for studies of crystalline surface dynamics. Progress report, May 1, 1985-April 30, 1986

International Nuclear Information System (INIS)

1986-01-01

The primary goal of this grant is the construction of a state-of-the-art He atom-crystal surface scattering apparatus which will be capable of measuring both elastic and inelastic scattering of He atoms from crystal surfaces of metals, semiconductors and insulators. First, the apparatus will be constructed and characterized, after which a program of studies on the surface dynamics of a variety of crystal surfaces will be started. 6 refs., 2 figs

Critical Thresholds in Earth-System Dynamics

Science.gov (United States)

Rothman, D.

2017-12-01

The history of the Earth system is a story of change. Some changesare gradual and benign, but others, especially those associated withcatastrophic mass extinction, are relatively abrupt and destructive.What sets one group apart from the other? Here I hypothesize thatperturbations of Earth's carbon cycle lead to mass extinction if theyexceed either a critical rate at long time scales or a critical sizeat short time scales. By analyzing 31 carbon-isotopic events duringthe last 542 million years, I identify the critical rate with a limitimposed by mass conservation. Further analysis identifies thecrossover timescale separating fast from slow events with thetimescale of the ocean's homeostatic response to a change in pH. Theproduct of the critical rate and the crossover timescale then yieldsthe critical size. The modern critical size for the marine carboncycle is roughly similar to the mass of carbon that human activitieswill likely have added to the oceans by the year 2100.

Nonuniversal critical behaviour in a model for charge density wave dynamics

International Nuclear Information System (INIS)

Ritala, R.K.; Hertz, J.A.

1986-02-01

We have studied short range fluctuations around the infinite-range model of charge density wave (CDW) dynamics. We find that the inhomogeneity of the local field, which is neglected in the infinite-range approximation has a dramatic effect on the transition. In the Bethe approximation the critical behaviour is nonuniversal. In particular, the current exponent is ζ = 3/2 log(z-1)/[log(z)]+log(1+f/J)], where z is the number of neighbors, f the pinning strength, and J the elastic coupling. (orig.)

The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

Science.gov (United States)

Nguyen, Duc; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Girolami, Gregory S.; Lyding, Joseph; Gruebele, Martin

2014-11-01

Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB2 glass surface, two-state hopping of 1-2 nm diameter cooperatively rearranging regions or "clusters" occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how "mixed" features can show up in surface dynamics of glasses.

Dynamical Quantum Phase Transitions in Spin Chains with Long-Range Interactions: Merging Different Concepts of Nonequilibrium Criticality

Science.gov (United States)

Žunkovič, Bojan; Heyl, Markus; Knap, Michael; Silva, Alessandro

2018-03-01

We theoretically study the dynamics of a transverse-field Ising chain with power-law decaying interactions characterized by an exponent α , which can be experimentally realized in ion traps. We focus on two classes of emergent dynamical critical phenomena following a quantum quench from a ferromagnetic initial state: The first one manifests in the time-averaged order parameter, which vanishes at a critical transverse field. We argue that such a transition occurs only for long-range interactions α ≤2 . The second class corresponds to the emergence of time-periodic singularities in the return probability to the ground-state manifold which is obtained for all values of α and agrees with the order parameter transition for α ≤2 . We characterize how the two classes of nonequilibrium criticality correspond to each other and give a physical interpretation based on the symmetry of the time-evolved quantum states.

Molecular Structure and Dynamics in Thin Water Films at the Silica and Graphite Surfaces

Energy Technology Data Exchange (ETDEWEB)

Argyris, Dr. Dimitrios [University of Oklahoma; Tummala, Dr. Naga Rajesh [University of Oklahoma; StrioloDr., A [Vanderbilt University; Cole, David R [ORNL

2008-01-01

The structure and dynamic properties of interfacial water at the graphite and silica solid surfaces were investigated using molecular dynamics simulations. The effect of surface properties on the characteristics of interfacial water was quantified by computing density profiles, radial distribution functions, surface density distributions, orientation order parameters, and residence and reorientation correlation functions. In brief, our results show that the surface roughness, chemical heterogeneity, and surface heterogeneous charge distribution affect the structural and dynamic properties of the interfacial water molecules, as well as their rate of exchange with bulk water. Most importantly, our results indicate the formation of two distinct water layers at the SiO2 surface covered by a large density of hydroxyl groups. Further analysis of the data suggests a highly confined first layer where the water molecules assume preferential hydrogen-down orientation and a second layer whose behavior and characteristics are highly dependent on those of the first layer through a well-organized hydrogen bond network. The results suggest that water-water interactions, in particular hydrogen bonds, may be largely responsible for macroscopic interfacial properties such as adsorption and contact angle.

Theoretical Studies of the Structure and the Dynamics on Clean and Chemisorbed Metal Surfaces

Science.gov (United States)

Yang, Liqiu

Molecular dynamics (MD) and lattice dynamics (LD) techniques are employed to investigate several phenomena related to the structure and vibrations at metal surfaces. The MD simulations are performed with the many-body interaction potentials obtained using the Embedded-Atom Method (EAM). As specific examples, we present the results for Ag(100) at 300 K and Cu(100) at 150 K, 300 K, and 600 K. The calculated frequencies and polarizations of all surface modes and resonances at the high-symmetry points in the two-dimensional Brillouin zone are in good agreement with available data, as well as, existing lattice dynamics results with force constants obtained from first-principles calculations. Our calculated surface relaxation is also in reasonable agreement with the data. We also test a much simpler lattice dynamics model with nearest neighbor central force interactions, and conclude that it can reproduce the main features of the phonon modes, but only when adjustable surface parameters are used. Additionally, the temperature dependent studies of the phonon line-widths and the mean-square displacement (MSD) of surface atoms are indicative of enhanced surface anharmonicity. On several chemisorbed metal surfaces, for which force constants are not available from first-principles calculations or the EAM, we perform lattice dynamics studies of phonon dispersion curves using simple force-constant models. These studies provide reliable mean-square displacement of surface atoms and can distinguish between possible reconstruction patterns, the results being insensitive to the exact values of the surface parameters. On c(2 times 2)S-Ni(100), it is found that the parallel component of the mean-square displacement for sulfur is around 50% larger than the vertical component, but for the mean-square displacement of oxygen atoms in the system c(2 times 2)O-Ni(100), the opposite is the case. As regards surface reconstruction, for both p(2 times 1)O-Ag(110) and p(2 times 1)O-Ni(110

Sustainability from the Occurrence of Critical Dynamic Power System Blackout Determined by Using the Stochastic Event Tree Technique

Directory of Open Access Journals (Sweden)

Muhammad Murtadha Othman

2017-06-01

Full Text Available With the advent of advanced technology in smart grid, the implementation of renewable energy in a stressed and complicated power system operation, aggravated by a competitive electricity market and critical system contingencies, this will inflict higher probabilities of the occurrence of a severe dynamic power system blackout. This paper presents the proposed stochastic event tree technique used to assess the sustainability against the occurrence of dynamic power system blackout emanating from implication of critical system contingencies such as the rapid increase in total loading condition and sensitive initial transmission line tripping. An extensive analysis of dynamic power system blackout has been carried out in a case study of the following power systems: IEEE RTS-79 and IEEE RTS-96. The findings have shown that the total loading conditions and sensitive transmission lines need to be given full attention by the utility to prevent the occurrence of dynamic power system blackout.

SACS2: Dynamic and Formal Safety Analysis Method for Complex Safety Critical System

International Nuclear Information System (INIS)

Koh, Kwang Yong; Seong, Poong Hyun

2009-01-01

Fault tree analysis (FTA) is one of the most widely used safety analysis technique in the development of safety critical systems. However, over the years, several drawbacks of the conventional FTA have become apparent. One major drawback is that conventional FTA uses only static gates and hence can not capture dynamic behaviors of the complex system precisely. Although several attempts such as dynamic fault tree (DFT), PANDORA, formal fault tree (FFT) and so on, have been made to overcome this problem, they can not still do absolute or actual time modeling because they adapt relative time concept and can capture only sequential behaviors of the system. Second drawback of conventional FTA is its lack of rigorous semantics. Because it is informal in nature, safety analysis results heavily depend on an analyst's ability and are error-prone. Finally reasoning process which is to check whether basic events really cause top events is done manually and hence very labor-intensive and timeconsuming for the complex systems. In this paper, we propose a new safety analysis method for complex safety critical system in qualitative manner. We introduce several temporal gates based on timed computational tree logic (TCTL) which can represent quantitative notion of time. Then, we translate the information of the fault trees into UPPAAL query language and the reasoning process is automatically done by UPPAAL which is the model checker for time critical system

Interplay between magnetic quantum criticality, Fermi surface and unconventional superconductivity in UCoGe, URhGe and URu2Si2

International Nuclear Information System (INIS)

Bastien, Gael

2017-01-01

This thesis is concentrated on the ferromagnetic superconductors UCoGe and URhGe and on the hidden order state in URu 2 Si 2 . In the first part the pressure temperature phase diagram of UCoGe was studied up to 10.5 GPa. Ferromagnetism vanishes at the critical pressure pc≅1 GPa. Unconventional superconductivity and non Fermi liquid behavior can be observed in a broad pressure range around pc. The superconducting upper critical field properties were explained by the suppression of the magnetic fluctuations under field. In the second part the Fermi surfaces of UCoGe and URhGe were investigated by quantum oscillations. In UCoGe four Fermi surface pockets were observed. Under magnetic field successive Lifshitz transitions of the Fermi surface have been detected. The observed Fermi surface pockets in UCoGe evolve smoothly with pressure up to 2.5 GPa and do not show any Fermi surface reconstruction at the critical pressure pc. In URhGe, three heavy Fermi surface pockets were detected by quantum oscillations. In the last part the quantum oscillation study in the hidden order state of URu 2 Si 2 shows a strong g factor anisotropy for two Fermi surface pockets, which is compared to the macroscopic g factor anisotropy extracted from the upper critical field study. (author) [fr

Near Space Hypersonic Unmanned Aerial Vehicle Dynamic Surface Backstepping Control Design

Directory of Open Access Journals (Sweden)

Jinyong YU

2014-07-01

Full Text Available Compared with traditional aircraft, the near space hypersonic unmanned aerial vehicle control system design must deal with the extra prominent dynamics characters, which are differ from the traditional aircrafts control system design. A new robust adaptive control design method is proposed for one hypersonic unmanned aerial vehicle (HSUAV uncertain MIMO nonaffine block control system by using multilayer neural networks, feedback linearization technology, and dynamic surface backstepping. Multilayer neural networks are used to compensate the influence from the uncertain, which designs the robust terms to solve the problem from approach error. Adaptive backstepping is adopted designed to ensure control law, the dynamic surface control strategy to eliminate “the explosion of terms” by introducing a series of first order filters to obtain the differentiation of the virtual control inputs. Finally, nonlinear six-degree-of-freedom (6-DOF numerical simulation results for a HSUAV model are presented to demonstrate the effectiveness of the proposed method.

Implementation of surface hopping molecular dynamics using semiempirical methods

International Nuclear Information System (INIS)

Fabiano, E.; Keal, T.W.; Thiel, W.

2008-01-01

A molecular dynamics driver and surface hopping algorithm for nonadiabatic dynamics has been implemented in a development version of the MNDO semiempirical electronic structure package. The required energies, gradients and nonadiabatic couplings are efficiently evaluated on the fly using semiempirical configuration interaction methods. The choice of algorithms for the time evolution of the nuclear motion and quantum amplitudes is discussed, and different schemes for the computation of nonadiabatic couplings are analysed. The importance of molecular orbital tracking and electronic state following is underlined in the context of configuration interaction calculations. The method is applied to three case studies (ethylene, methaniminium ion, and methanimine) using the orthogonalization corrected OM2 Hamiltonian. In all three cases decay times and dynamics paths similar to high-level ab initio results are obtained

Renormalization group and instantons in stochastic nonlinear dynamics, from self-organized criticality to thermonuclear reactors

International Nuclear Information System (INIS)

Volchenkov, D.

2009-01-01

Stochastic counterparts of nonlinear dynamics are studied by means of nonperturbative functional methods developed in the framework of quantum field theory (QFT). In particular, we discuss fully developed turbulence, including leading corrections on possible compressibility of fluids, transport through porous media, theory of waterspouts and tsunami waves, stochastic magnetohydrodynamics, turbulent transport in crossed fields, self-organized criticality, and dynamics of accelerated wrinkled flame fronts advancing in a wide canal. This report would be of interest to the broad auditorium of physicists and applied mathematicians, with a background in nonperturbative QFT methods or nonlinear dynamical systems, having an interest in both methodological developments and interdisciplinary applications. (author)

Renormalization group and instantons in stochastic nonlinear dynamics, from self-organized criticality to thermonuclear reactors

Energy Technology Data Exchange (ETDEWEB)

Volchenkov, D. [Bielefeld Univ., Center of Excellence Cognitive Interaction Technology (CITEC) (Germany)

2009-03-15

Stochastic counterparts of nonlinear dynamics are studied by means of nonperturbative functional methods developed in the framework of quantum field theory (QFT). In particular, we discuss fully developed turbulence, including leading corrections on possible compressibility of fluids, transport through porous media, theory of waterspouts and tsunami waves, stochastic magnetohydrodynamics, turbulent transport in crossed fields, self-organized criticality, and dynamics of accelerated wrinkled flame fronts advancing in a wide canal. This report would be of interest to the broad auditorium of physicists and applied mathematicians, with a background in nonperturbative QFT methods or nonlinear dynamical systems, having an interest in both methodological developments and interdisciplinary applications. (author)

Dynamical analysis of surface-insulated planar wire array Z-pinches

Science.gov (United States)

Li, Yang; Sheng, Liang; Hei, Dongwei; Li, Xingwen; Zhang, Jinhai; Li, Mo; Qiu, Aici

2018-05-01

The ablation and implosion dynamics of planar wire array Z-pinches with and without surface insulation are compared and discussed in this paper. This paper first presents a phenomenological model named the ablation and cascade snowplow implosion (ACSI) model, which accounts for the ablation and implosion phases of a planar wire array Z-pinch in a single simulation. The comparison between experimental data and simulation results shows that the ACSI model could give a fairly good description about the dynamical characteristics of planar wire array Z-pinches. Surface insulation introduces notable differences in the ablation phase of planar wire array Z-pinches. The ablation phase is divided into two stages: insulation layer ablation and tungsten wire ablation. The two-stage ablation process of insulated wires is simulated in the ACSI model by updating the formulas describing the ablation process.

Dynamic Surface Adaptive Robust Control of Unmanned Marine Vehicles with Disturbance Observer

Directory of Open Access Journals (Sweden)

Pengchao Zhang

2018-01-01

Full Text Available This paper presents a dynamic surface adaptive robust control method with disturbance observer for unmanned marine vehicles (UMV. It uses adaptive law to estimate and compensate the disturbance observer error. Dynamic surface is introduced to solve the “differential explosion” caused by the virtual control derivation in traditional backstepping method. The final controlled system is proved to be globally uniformly bounded based on Lyapunov stability theory. Simulation results illustrate the effectiveness of the proposed controller, which can realize the three-dimensional trajectory tracking for UMV with the systematic uncertainty and time-varying disturbances.

Molecular dynamics simulations of diffusion and clustering along critical isotherms of medium-chain n-alkanes.

Science.gov (United States)

Mutoru, J W; Smith, W; O'Hern, C S; Firoozabadi, A

2013-01-14

Understanding the transport properties of molecular fluids in the critical region is important for a number of industrial and natural systems. In the literature, there are conflicting reports on the behavior of the self diffusion coefficient D(s) in the critical region of single-component molecular systems. For example, D(s) could decrease to zero, reach a maximum, or remain unchanged and finite at the critical point. Moreover, there is no molecular-scale understanding of the behavior of diffusion coefficients in molecular fluids in the critical regime. We perform extensive molecular dynamics simulations in the critical region of single-component fluids composed of medium-chain n-alkanes-n-pentane, n-decane, and n-dodecane-that interact via anisotropic united-atom potentials. For each system, we calculate D(s), and average molecular cluster sizes κ(cl) and numbers N(cl) at various cluster lifetimes τ, as a function of density ρ in the range 0.2ρ(c) ≤ ρ ≤ 2.0ρ(c) at the critical temperature T(c). We find that D(s) decreases with increasing ρ but remains finite at the critical point. Moreover, for any given τ critical point.

A dynamic modelling approach for estimating critical loads of nitrogen based on plant community changes under a changing climate

International Nuclear Information System (INIS)

Belyazid, Salim; Kurz, Dani; Braun, Sabine; Sverdrup, Harald; Rihm, Beat; Hettelingh, Jean-Paul

2011-01-01

A dynamic model of forest ecosystems was used to investigate the effects of climate change, atmospheric deposition and harvest intensity on 48 forest sites in Sweden (n = 16) and Switzerland (n = 32). The model was used to investigate the feasibility of deriving critical loads for nitrogen (N) deposition based on changes in plant community composition. The simulations show that climate and atmospheric deposition have comparably important effects on N mobilization in the soil, as climate triggers the release of organically bound nitrogen stored in the soil during the elevated deposition period. Climate has the most important effect on plant community composition, underlining the fact that this cannot be ignored in future simulations of vegetation dynamics. Harvest intensity has comparatively little effect on the plant community in the long term, while it may be detrimental in the short term following cutting. This study shows: that critical loads of N deposition can be estimated using the plant community as an indicator; that future climatic changes must be taken into account; and that the definition of the reference deposition is critical for the outcome of this estimate. - Research highlights: → Plant community changes can be used to estimate critical loads of nitrogen. → Climate change is decisive for future changes of geochemistry and plant communities. → Climate change cannot be ignored in estimates of critical loads. → The model ForSAFE-Veg was successfully used to set critical loads of nitrogen. - Plant community composition can be used in dynamic modelling to estimate critical loads of nitrogen deposition, provided the appropriate reference deposition, future climate and target plant communities are defined.

Critical current densities and vortex dynamics in FeTexSe1-x single crystals

International Nuclear Information System (INIS)

Taen, T.; Tsuchiya, Y.; Nakajima, Y.; Tamegai, T.

2010-01-01

The critical current density and the normalized relaxation rate are reported in FeTe 0.59 Se 0.41 single crystal. Critical current density is of order of 10 5 A/cm 2 , which is comparable to that in Co-doped BaFe 2 As 2 . In low temperature and low field region, the vortex dynamics of this system is well defined by the collective creep theory, which is quite similar to Co-doped BaFe 2 As 2 reported before. We also discuss the origin of the anomaly in the field dependence of the relaxation rate.

Criticality meets learning: Criticality signatures in a self-organizing recurrent neural network.

Science.gov (United States)

Del Papa, Bruno; Priesemann, Viola; Triesch, Jochen

2017-01-01

Many experiments have suggested that the brain operates close to a critical state, based on signatures of criticality such as power-law distributed neuronal avalanches. In neural network models, criticality is a dynamical state that maximizes information processing capacities, e.g. sensitivity to input, dynamical range and storage capacity, which makes it a favorable candidate state for brain function. Although models that self-organize towards a critical state have been proposed, the relation between criticality signatures and learning is still unclear. Here, we investigate signatures of criticality in a self-organizing recurrent neural network (SORN). Investigating criticality in the SORN is of particular interest because it has not been developed to show criticality. Instead, the SORN has been shown to exhibit spatio-temporal pattern learning through a combination of neural plasticity mechanisms and it reproduces a number of biological findings on neural variability and the statistics and fluctuations of synaptic efficacies. We show that, after a transient, the SORN spontaneously self-organizes into a dynamical state that shows criticality signatures comparable to those found in experiments. The plasticity mechanisms are necessary to attain that dynamical state, but not to maintain it. Furthermore, onset of external input transiently changes the slope of the avalanche distributions - matching recent experimental findings. Interestingly, the membrane noise level necessary for the occurrence of the criticality signatures reduces the model's performance in simple learning tasks. Overall, our work shows that the biologically inspired plasticity and homeostasis mechanisms responsible for the SORN's spatio-temporal learning abilities can give rise to criticality signatures in its activity when driven by random input, but these break down under the structured input of short repeating sequences.

Approximate critical surface of the bond-mixed square-lattice Ising model

International Nuclear Information System (INIS)

Levy, S.V.F.; Tsallis, C.; Curado, E.M.F.

1979-09-01

The critical surface of the quenched bond-mixed square-lattice spin-1/2 first-neighbour-interaction ferromagnetic Ising model (with exchange interactions J 1 and J 2 ) has been investigated. Through renormalization group and heuristical procedures, a very accurate (error inferior to 3x10 -4 in the variables t sub(i) = th (J sub(i)/k sub(b)T)) approximate numerical proposal for all points of this surface is presented. This proposal simultaneously satisfies all the available exact results concerning the surface, namely P sub(c) = 1/2, t sub(c) = √2 - 1, both limiting slopes in these points, and t 2 = (1-t 1 )/(1+t 1 ) for p = 1/2. Furthemore an analytic approximation (namely (1 - p) 1n(1 + t 1 ) + p 1n(1 + t 2 ) =(1/2)1n 2) is also proposed. In what concerns the available exact results, it only fails in reproducing one of the two limiting slopes, where there is an error of 1% in the derivative: these facts result in an estimated error less than 10 -3 (in the t-variables) for any points in the surface. (Author) [pt

Influence of the heater material on the critical heat load at boiling of liquids on surfaces with different sizes

Science.gov (United States)

Anokhina, E. V.

2010-05-01

Data on critical heat loads q cr for the saturated and unsaturated pool boiling of water and ethanol under atmospheric pressure are reported. It is found experimentally that the critical heat load does not necessarily coincide with the heat load causing burnout of the heater, which should be taken into account. The absolute values of q cr for the boiling of water and ethanol on copper surfaces 65, 80, 100, 120, and 200 μm in diameter; tungsten surface 100 μm in diameter; and nichrome surface 100 μm in diameter are obtained experimentally.

Real-Space Imaging of Carrier Dynamics of Materials Surfaces by Second-Generation Four-Dimensional Scanning Ultrafast Electron Microscopy

KAUST Repository

Sun, Jingya

2015-09-14

In the fields of photocatalysis and photovoltaics, ultrafast dynamical processes, including carrier trapping and recombination on material surfaces, are among the key factors that determine the overall energy conversion efficiency. A precise knowledge of these dynamical events on the nanometer (nm) and femtosecond (fs) scales was not accessible until recently. The only way to access such fundamental processes fully is to map the surface dynamics selectively in real space and time. In this study, we establish a second generation of four-dimensional scanning ultrafast electron microscopy (4D S-UEM) and demonstrate the ability to record time-resolved images (snapshots) of material surfaces with 650 fs and ∼5 nm temporal and spatial resolutions, respectively. In this method, the surface of a specimen is excited by a clocking optical pulse and imaged using a pulsed primary electron beam as a probe pulse, generating secondary electrons (SEs), which are emitted from the surface of the specimen in a manner that is sensitive to the local electron/hole density. This method provides direct and controllable information regarding surface dynamics. We clearly demonstrate how the surface morphology, grains, defects, and nanostructured features can significantly impact the overall dynamical processes on the surface of photoactive-materials. In addition, the ability to access two regimes of dynamical probing in a single experiment and the energy loss of SEs in semiconductor-nanoscale materials will also be discussed.

Surface conductivity dependent dynamic behaviour of an ultrafine atmospheric pressure plasma jet for microscale surface processing

Energy Technology Data Exchange (ETDEWEB)

Abuzairi, Tomy [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electrical Engineering, Faculty of Engineering, Universitas Indonesia, Depok 16424 (Indonesia); Okada, Mitsuru [Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Bhattacharjee, Sudeep [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Nagatsu, Masaaki, E-mail: nagatsu.masaaki@shizuoka.ac.jp [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan)

2016-12-30

Highlights: • Spatio-temporal behaviors of capillary APPJs are studied for various substrates. • Plasma irradiation area depended on the substrate conductivity and permittivity. • Surface irradiation area was significantly broadened in polymer-like substrate. • Effect of applying a substrate bias on the APPJ irradiation area was investigated. - Abstract: An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5–4.2 km/s and 2–7 × 10{sup 17} m{sup −3}. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from −900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.

Surface conductivity dependent dynamic behaviour of an ultrafine atmospheric pressure plasma jet for microscale surface processing

International Nuclear Information System (INIS)

Abuzairi, Tomy; Okada, Mitsuru; Bhattacharjee, Sudeep; Nagatsu, Masaaki

2016-01-01

Highlights: • Spatio-temporal behaviors of capillary APPJs are studied for various substrates. • Plasma irradiation area depended on the substrate conductivity and permittivity. • Surface irradiation area was significantly broadened in polymer-like substrate. • Effect of applying a substrate bias on the APPJ irradiation area was investigated. - Abstract: An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5–4.2 km/s and 2–7 × 10"1"7 m"−"3. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from −900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.

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

Impact of dynamic vegetation phenology on the simulated pan-Arctic land surface state

Science.gov (United States)

Teufel, Bernardo; Sushama, Laxmi; Arora, Vivek K.; Verseghy, Diana

2018-03-01

The pan-Arctic land surface is undergoing rapid changes in a warming climate, with near-surface permafrost projected to degrade significantly during the twenty-first century. Vegetation-related feedbacks have the potential to influence the rate of degradation of permafrost. In this study, the impact of dynamic phenology on the pan-Arctic land surface state, particularly near-surface permafrost, for the 1961-2100 period, is assessed by comparing two simulations of the Canadian Land Surface Scheme (CLASS)—one with dynamic phenology, modelled using the Canadian Terrestrial Ecosystem Model (CTEM), and the other with prescribed phenology. These simulations are forced by atmospheric data from a transient climate change simulation of the 5th generation Canadian Regional Climate Model (CRCM5) for the Representative Concentration Pathway 8.5 (RCP8.5). Comparison of the CLASS coupled to CTEM simulation to available observational estimates of plant area index, spatial distribution of permafrost and active layer thickness suggests that the model captures reasonably well the overall distribution of vegetation and permafrost. It is shown that the most important impact of dynamic phenology on the land surface occurs through albedo and it is demonstrated for the first time that vegetation control on albedo during late spring and early summer has the highest potential to impact the degradation of permafrost. While both simulations show extensive near-surface permafrost degradation by the end of the twenty-first century, the strong projected response of vegetation to climate warming and increasing CO2 concentrations in the coupled simulation results in accelerated permafrost degradation in the northernmost continuous permafrost regions.

Memory effects in nonadiabatic molecular dynamics at metal surfaces

DEFF Research Database (Denmark)

Olsen, Thomas; Schiøtz, Jakob

2010-01-01

We study the effect of temporal correlation in a Langevin equation describing nonadiabatic dynamics at metal surfaces. For a harmonic oscillator, the Langevin equation preserves the quantum dynamics exactly and it is demonstrated that memory effects are needed in order to conserve the ground state...... energy of the oscillator. We then compare the result of Langevin dynamics in a harmonic potential with a perturbative master equation approach and show that the Langevin equation gives a better description in the nonperturbative range of high temperatures and large friction. Unlike the master equation......, this approach is readily extended to anharmonic potentials. Using density functional theory, we calculate representative Langevin trajectories for associative desorption of N-2 from Ru(0001) and find that memory effects lower the dissipation of energy. Finally, we propose an ab initio scheme to calculate...

Accelerating solving the dynamic multi-objective nework design problem using response surface methods

NARCIS (Netherlands)

Wismans, Luc Johannes Josephus; van Berkum, Eric C.; Bliemer, Michiel C.J.; Viti, F.; Immers, B.; Tampere, C.

2011-01-01

Multi objective optimization of externalities of traffic solving a network design problem in which Dynamic Traffic Management measures are used, is time consuming while heuristics are needed and solving the lower level requires solving the dynamic user equilibrium problem. Use of response surface

Surface science principles and current applications

CERN Document Server

Taglauer, E; Wandelt, K

1996-01-01

Modern technologies increasingly rely on low-dimensional physics at interfaces and in thin-films and nano-structures. Surface science holds a key position in providing the experimental methods and theoretical models for a basic understanding of these effects. This book includes case studies and status reports about research topics such as: surface structure determination by tensor-LEED and surface X-ray diffraction; the preparation and detection of low-dimensional electronic surface states; quantitative surface compositional analysis; the dynamics of adsorption and reaction of adsorbates, e.g. kinetic oscillations; the characterization and control of thin-film and multilayer growth including the influence of surfactants; a critical assessment of the surface physics approach to heterogeneous catalysis.

Effect of colored noise on the critical dynamics of the Time-Dependent Landau-Ginzburg Model A

International Nuclear Information System (INIS)

Korutcheva, E.; Rubia, J. de la

1999-08-01

By using the dynamical renormalization-group method, we show that the introduction of an additive colored noise with weak long-range correlations in the Time-Dependent Landau-Ginzburg Model A, does not give perturbative corrections for the dynamical critical exponent at least up to order O(ε 2 ). This result differs for a system with random quenched impurities, where a similar type of impurity correlation leads to corrections even of order O(ε). (author)

The dynamics of marginality and self-organized criticality as a paradigm for turbulent transport

International Nuclear Information System (INIS)

Newman, D.E.; Carreras, B.A.; Diamond, P.H.; Hahm, T.S.

1995-01-01

A general paradigm, based on the concept of self-organized criticality (SOC), for turbulent transport in magnetically confined plasmas has been recently suggested as an explanation for some of the apparent discrepancies between most theoretical models of turbulent transport and experimental observations of the transport in magnetically confined plasmas. This model describes the dynamics of the transport without relying on the underlying local fluctuation mechanisms. Computations based on a cellular automata realization of such a model have found that noise driven SOC systems can maintain average profiles that are linearly stable (submarginal) and yet are able to sustain active transport dynamics. It is also found that the dominant scales in the transport dynamics in the absence of sheared flow are system scales rather than the underlying local fluctuation scales. The addition of sheared flow into the dynamics leads to a large reduction of the system-scale transport events and a commensurate increase in the fluctuation-scale transport events needed to maintain the constant flux. The dynamics of these models and the potential ramifications for transport studies are discussed

Dynamic Leidenfrost temperature on micro-textured surfaces: Acoustic wave absorption into thin vapor layer

Science.gov (United States)

Jerng, Dong Wook; Kim, Dong Eok

2018-01-01

The dynamic Leidenfrost phenomenon is governed by three types of pressure potentials induced via vapor hydrodynamics, liquid dynamic pressure, and the water hammer effect resulting from the generation of acoustic waves at the liquid-vapor interface. The prediction of the Leidenfrost temperature for a dynamic droplet needs quantitative evaluation and definition for each of the pressure fields. In particular, the textures on a heated surface can significantly affect the vapor hydrodynamics and the water hammer pressure. We present a quantitative model for evaluating the water hammer pressure on micro-textured surfaces taking into account the absorption of acoustic waves into the thin vapor layer. The model demonstrates that the strength of the acoustic flow into the liquid droplet, which directly contributes to the water hammer pressure, depends on the magnitude of the acoustic resistance (impedance) in the droplet and the vapor region. In consequence, the micro-textures of the surface and the increased spacing between them reduce the water hammer coefficient ( kh ) defined as the ratio of the acoustic flow into the droplet to total generated flow. Aided by numerical calculations that solve the laminar Navier-Stokes equation for the vapor flow, we also predict the dynamic Leidenfrost temperature on a micro-textured surface with reliable accuracy consistent with the experimental data.

Ocean current surface measurement using dynamic elevations obtained by the GEOS-3 radar altimeter

Science.gov (United States)

Leitao, C. D.; Huang, N. E.; Parra, C. G.

1977-01-01

Remote Sensing of the ocean surface from the GEOS-3 satellite using radar altimeter data has confirmed that the altimeter can detect the dynamic ocean topographic elevations relative to an equipotential surface, thus resulting in a reliable direct measurement of the ocean surface. Maps of the ocean dynamic topography calculated over a one month period and with 20 cm contour interval are prepared for the last half of 1975. The Gulf Stream is observed by the rapid slope change shown by the crowding of contours. Cold eddies associated with the current are seen as roughly circular depressions.

The global distribution and dynamics of surface soil moisture

Science.gov (United States)

McColl, Kaighin A.; Alemohammad, Seyed Hamed; Akbar, Ruzbeh; Konings, Alexandra G.; Yueh, Simon; Entekhabi, Dara

2017-01-01

Surface soil moisture has a direct impact on food security, human health and ecosystem function. It also plays a key role in the climate system, and the development and persistence of extreme weather events such as droughts, floods and heatwaves. However, sparse and uneven observations have made it difficult to quantify the global distribution and dynamics of surface soil moisture. Here we introduce a metric of soil moisture memory and use a full year of global observations from NASA's Soil Moisture Active Passive mission to show that surface soil moisture--a storage believed to make up less than 0.001% of the global freshwater budget by volume, and equivalent to an, on average, 8-mm thin layer of water covering all land surfaces--plays a significant role in the water cycle. Specifically, we find that surface soil moisture retains a median 14% of precipitation falling on land after three days. Furthermore, the retained fraction of the surface soil moisture storage after three days is highest over arid regions, and in regions where drainage to groundwater storage is lowest. We conclude that lower groundwater storage in these regions is due not only to lower precipitation, but also to the complex partitioning of the water cycle by the surface soil moisture storage layer at the land surface.

Water pollution abatement programme. The Czech Republic. Project 4.2. Assessing critical loads of acidity to surface waters in the Czech Republic. Critical loads of acidity to surface waters, north-eastern Bohemia and northern Moravia, The Czech Republic

Energy Technology Data Exchange (ETDEWEB)

Lien, L.; Raclavsky, K.; Raclavska, H.; Matysek, D.; Hovind, H.

1996-01-01

This report discusses estimates of critical loads of acidity to surface waters and their exceedances, for north-eastern Bohemia and Moravia in The Czech Republic. The survey covers 13 400 km{sup 2}, or 17% of the area of the country. Varying critical loads were observed within the examined region. 19% of the examined area showed exceedance of critical load and another 11% was close to exceedance. The survey should continue in Bohemia. 24 refs., 20 figs., 4 tabs.

Dynamics of H2 on Ti/Al(100) surfaces

NARCIS (Netherlands)

Chen, Jian-Cheng

2011-01-01

What is the catalytic role played by titanium in the hydrogen storage material NaAlH4? This thesis aims at unraveling the dynamics of an elementary reaction: H2 dissociation on Ti/Al(100) surfaces. Although this reaction is not the rate limiting step in the hydrogen storage of NaAlH4, it is an

Nanoparticles dynamics on a surface: fractal pattern formation and fragmentation

DEFF Research Database (Denmark)

Dick, Veronika V.; Solov'yov, Ilia; Solov'yov, Andrey V.

2010-01-01

In this paper we review our recent results on the formation and the post-growth relaxation processes of nanofractals on surface. For this study we developed a method which describes the internal dynamics of particles in a fractal and accounts for their diffusion and detachment. We demonstrate...... that these kinetic processes determine the final shape of the islands on surface after post-growth relaxation. We consider different scenarios of fractal relaxation and analyze the time evolution of the island's morphology....

Solid surface vs. liquid surface: nanoarchitectonics, molecular machines, and DNA origami.

Science.gov (United States)

Ariga, Katsuhiko; Mori, Taizo; Nakanishi, Waka; Hill, Jonathan P

2017-09-13

The investigation of molecules and materials at interfaces is critical for the accumulation of new scientific insights and technological advances in the chemical and physical sciences. Immobilization on solid surfaces permits the investigation of different properties of functional molecules or materials with high sensitivity and high spatial resolution. Liquid surfaces also present important media for physicochemical innovation and insight based on their great flexibility and dynamicity, rapid diffusion of molecular components for mixing and rearrangements, as well as drastic spatial variation in the prevailing dielectric environment. Therefore, a comparative discussion of the relative merits of the properties of materials when positioned at solid or liquid surfaces would be informative regarding present-to-future developments of surface-based technologies. In this perspective article, recent research examples of nanoarchitectonics, molecular machines, DNA nanotechnology, and DNA origami are compared with respect to the type of surface used, i.e. solid surfaces vs. liquid surfaces, for future perspectives of interfacial physics and chemistry.

Euler Strut: A Mechanical Analogy for Dynamics in the Vicinity of a Critical Point

Science.gov (United States)

Bobnar, Jaka; Susman, Katarina; Parsegian, V. Adrian; Rand, Peter R.; Cepic, Mojca; Podgornik, Rudolf

2011-01-01

An anchored elastic filament (Euler strut) under an external point load applied to its free end is a simple model for a second-order phase transition. In the static case, a load greater than the critical load causes a Euler buckling instability, leading to a change in the filament's shape. The analysis of filament dynamics with an external point…

Basement to surface expressions and critical factors in the genesis of unconformity-related deposits

International Nuclear Information System (INIS)

Potter, Eric

2014-01-01

Two subprojects: 1) Basement to surface expressions of deep mineralization and refinement of critical factors leading to the genesis of unconformity-related uranium deposits; and 2) Recognition of uranium ore system alteration signatures in complex terranes: IOCG vs albite-hosted uranium vs volcanic-hosted uranium.

National implementation of the UNECE convention on long-range transboundary air pollution (effects). Pt. 2. Impacts and risk estimation, critical loads, biodiversity, dynamic modelling, critical level violation, material corrosion; Nationale Umsetzung UNECE-Luftreinhaltekonvention (Wirkungen). T. 2. Wirkungen und Risikoabschaetzungen Critical Loads, Biodiversitaet, Dynamische Modellierung, Critical Levels Ueberschreitungen, Materialkorrosion

Energy Technology Data Exchange (ETDEWEB)

Gauger, Thomas [Bundesforschungsanstalt fuer Landwirtschaft, Braunschweig (DE). Inst. fuer Agraroekologie (FAL-AOE); Stuttgart Univ. (Germany). Inst. fuer Navigation; Haenel, Hans-Dieter; Roesemann, Claus [Bundesforschungsanstalt fuer Landwirtschaft, Braunschweig (DE). Inst. fuer Agraroekologie (FAL-AOE); Nagel, Hans-Dieter; Becker, Rolf; Kraft, Philipp; Schlutow, Angela; Schuetze, Gudrun; Weigelt-Kirchner, Regine [OeKO-DATA Gesellschaft fuer Oekosystemanalyse und Umweltdatenmanagement mbH, Strausberg (Germany); Anshelm, Frank [Geotechnik Suedwest Frey Marx GbR, Bietigheim-Bissingen (Germany)

2008-09-15

The report on the implementation of the UNECE convention on long-range transboundary air pollution Pt.2 covers the following issues: The tasks of the NFC (National Focal Center) Germany including the ICP (international cooperative program) modeling and mapping and the expert panel for heavy metals. Results of the work for the multi-component protocol cover the initial data for the calculation of the critical loads following the mass balance method, critical loads for acid deposition, critical loads for nitrogen input, critical load violations (sulfur, nitrogen). The results of work for the heavy metal protocol cover methodology development and recommendations for ICO modeling and mapping in accordance with international development, contributions of the expert group/ task force on heavy metals (WGSR), data sets on the critical loads for lead, cadmium and mercury, and critical load violations (Pb, Cd, Hg). The results of work on the inclusion of biodiversity (BERN) cover data compilation, acquisition and integration concerning ecosystems, model validation and verification and the possible interpretation frame following the coupling with dynamic modeling. The future development and utilization of dynamic modeling covers model comparison, applicability, the preparation of a national data set and preparations concerning the interface to the BERN model.

Analysis of critical neutron- scattering data from iron and dynamical scaling theory

DEFF Research Database (Denmark)

Als-Nielsen, Jens Aage

1970-01-01

Experimental three- axis spectrometer data of critical neutron- scattering data from Fe are reanalyzed and compared with the recent theoretical prediction by P. Resibois and C. Piette. The reason why the spin- diffusion parameter did not obey the prediction of dynamical scaling theory is indicated....... Double- axis spectrometer data have previously been interpreted in terms of a non- Lorentzian susceptibility. It is shown that with proper corrections for the inelasticity of the scattering the data are consistent with a Lorentzian form of susceptibility....

Ultrafast surface carrier dynamics in the topological insulator Bi₂Te₃.

Science.gov (United States)

Hajlaoui, M; Papalazarou, E; Mauchain, J; Lantz, G; Moisan, N; Boschetto, D; Jiang, Z; Miotkowski, I; Chen, Y P; Taleb-Ibrahimi, A; Perfetti, L; Marsi, M

2012-07-11

We discuss the ultrafast evolution of the surface electronic structure of the topological insulator Bi(2)Te(3) following a femtosecond laser excitation. Using time and angle-resolved photoelectron spectroscopy, we provide a direct real-time visualization of the transient carrier population of both the surface states and the bulk conduction band. We find that the thermalization of the surface states is initially determined by interband scattering from the bulk conduction band, lasting for about 0.5 ps; subsequently, few picoseconds are necessary for the Dirac cone nonequilibrium electrons to recover a Fermi-Dirac distribution, while their relaxation extends over more than 10 ps. The surface sensitivity of our measurements makes it possible to estimate the range of the bulk-surface interband scattering channel, indicating that the process is effective over a distance of 5 nm or less. This establishes a correlation between the nanoscale thickness of the bulk charge reservoir and the evolution of the ultrafast carrier dynamics in the surface Dirac cone.

A Lagrangian cylindrical coordinate system for characterizing dynamic surface geometry of tubular anatomic structures.

Science.gov (United States)

Lundh, Torbjörn; Suh, Ga-Young; DiGiacomo, Phillip; Cheng, Christopher

2018-03-03

Vascular morphology characterization is useful for disease diagnosis, risk stratification, treatment planning, and prediction of treatment durability. To quantify the dynamic surface geometry of tubular-shaped anatomic structures, we propose a simple, rigorous Lagrangian cylindrical coordinate system to monitor well-defined surface points. Specifically, the proposed system enables quantification of surface curvature and cross-sectional eccentricity. Using idealized software phantom examples, we validate the method's ability to accurately quantify longitudinal and circumferential surface curvature, as well as eccentricity and orientation of eccentricity. We then apply the method to several medical imaging data sets of human vascular structures to exemplify the utility of this coordinate system for analyzing morphology and dynamic geometric changes in blood vessels throughout the body. Graphical abstract Pointwise longitudinal curvature of a thoracic aortic endograft surface for systole and diastole, with their absolute difference.

Nano hydroxyapatite-blasted titanium surface affects pre-osteoblast morphology by modulating critical intracellular pathways.

Science.gov (United States)

Bezerra, Fábio; Ferreira, Marcel R; Fontes, Giselle N; da Costa Fernandes, Célio Jr; Andia, Denise C; Cruz, Nilson C; da Silva, Rodrigo A; Zambuzzi, Willian F

2017-08-01

Although, intracellular signaling pathways are proposed to predict the quality of cell-surface relationship, this study addressed pre-osteoblast behavior in response to nano hydroxyapatite (HA)-blasted titanium (Ti) surface by exploring critical intracellular pathways and pre-osteoblast morphological change. Physicochemical properties were evaluated by atomic force microscopy (AFM) and wettability considering water contact angle of three differently texturized Ti surfaces: Machined (Mac), Dual acid-etching (DAE), and nano hydroxyapatite-blasted (nHA). The results revealed critical differences in surface topography, impacting the water contact angle and later the osteoblast performance. In order to evaluate the effect of those topographical characteristics on biological responses, we have seeded pre-osteoblast cells on the Ti discs for up to 4 h and subjected the cultures to biological analysis. First, we have observed pre-osteoblasts morphological changes resulting from the interaction with the Ti texturized surfaces whereas the cells cultured on nHA presented a more advanced spreading process when compared with the cells cultured on the other surfaces. These results argued us for analyzing the molecular machinery and thus, we have shown that nHA promoted a lower Bax/Bcl2 ratio, suggesting an interesting anti-apoptotic effect, maybe explained by the fact that HA is a natural element present in bone composition. Thereafter, we investigated the potential effect of those surfaces on promoting pre-osteoblast adhesion and survival signaling by performing crystal violet and immunoblotting approaches, respectively. Our results showed that nHA promoted a higher pre-osteoblast adhesion supported by up-modulating FAK and Src activations, both signaling transducers involved during eukaryotic cell adhesion. Also, we have shown Ras-Erk stimulation by the all evaluated surfaces. Finally, we showed that all Ti-texturing surfaces were able to promote osteoblast differentiation

[Importance of cleaning and disinfection of critical surfaces in dental health services. Impact of an intervention program].

Science.gov (United States)

Véliz, Elena; Vergara, Teresa; Pearcy, Mercedes; Dabanch, Jeannette

Introduction Dental care has become a challenge for healthcare associated infection prevention programs, since the environment, within other factors, plays an important role in the transmission chain. Materials and Methods An intervention program was designed for the Dental Unit of Hospital Militar de Santiago, between years 2014 and 2015. The program contemplated 3 stages: diagnostic, intervention and evaluation stage. Objective To improve the safety of critical surfaces involved in dental healthcare. Results During the diagnostic stage, the cleaning and disinfection process was found to be deficient. The most contaminated critical surface was the instrument holder unit, then the clean area and lamp handle. The surfaces that significantly reduced their contamination, after the intervention, were the clean area and the instrument carrier unit. Conclusion Training in the processes of cleaning and disinfecting surfaces and dental equipment is one of the cost-effective strategies in preventing healthcare-associated infections (HCAI), with simple and easy-to-apply methods.

PREFACE: Vibrations at surfaces Vibrations at surfaces

Science.gov (United States)

Rahman, Talat S.

2011-12-01

This special issue is dedicated to the phenomenon of vibrations at surfaces—a topic that was indispensible a couple of decades ago, since it was one of the few phenomena capable of revealing the nature of binding at solid surfaces. For clean surfaces, the frequencies of modes with characteristic displacement patterns revealed how surface geometry, as well as the nature of binding between atoms in the surface layers, could be different from that in the bulk solid. Dispersion of the surface phonons provided further measures of interatomic interactions. For chemisorbed molecules on surfaces, frequencies and dispersion of the vibrational modes were also critical for determining adsorption sites. In other words, vibrations at surfaces served as a reliable means of extracting information about surface structure, chemisorption and overlayer formation. Experimental techniques, such as electron energy loss spectroscopy and helium-atom-surface scattering, coupled with infra-red spectroscopy, were continually refined and their resolutions enhanced to capture subtleties in the dynamics of atoms and molecules at surfaces. Theoretical methods, whether based on empirical and semi-empirical interatomic potential or on ab initio electronic structure calculations, helped decipher experimental observations and provide deeper insights into the nature of the bond between atoms and molecules in regions of reduced symmetry, as encountered on solid surfaces. Vibrations at surfaces were thus an integral part of the set of phenomena that characterized surface science. Dedicated workshops and conferences were held to explore the variety of interesting and puzzling features revealed in experimental and theoretical investigations of surface vibrational modes and their dispersion. One such conference, Vibrations at Surfaces, first organized by Harald Ibach in Juelich in 1980, continues to this day. The 13th International Conference on Vibrations at Surfaces was held at the University of

Experimental investigation of the discharge valve dynamics in a reciprocating compressor for trans-critical CO2 refrigeration cycle

International Nuclear Information System (INIS)

Ma Yuan; He Zhilong; Peng Xueyuan; Xing Ziwen

2012-01-01

The self-acting valve has a significant influence on the efficiency and reliability of the reciprocating compressor. In the trans-critical CO 2 cycle, the large density and high pressure difference across the valve cause serious bending and impact stresses in the valve, offering great challenges for successful valve design. Experimental investigation of the valve dynamics is required in order to design a self-acting valve with a high efficiency and long life span for the trans-critical CO 2 compressor. A semi-hermetic reciprocating compressor was developed for application in CO 2 refrigeration, and a test system was incorporated into the compressor performance test rig, with a focus on investigating the dynamics of the discharge valves. With the experimental results, the movement of the valve was discussed in detail for the trans-critical CO 2 compressor, allowing for the study of the thermodynamic performance of the compressor. While varying design parameters such as pressure ratio, valve lift, spring stiffness and compressor speed, the movement of the discharge valve in the reciprocating CO 2 compressor was measured in order to investigate the major factors that influence the valve dynamics. The average valve speed increased from 0.71 m/s to 0.81 m/s as the discharge pressure changed from 7.8 MPa to 12 MPa. The experimental methods and results discussed in this paper could provide useful information for both valve testing and the optimization of their reliability in trans-critical CO 2 compressors.

Dynamical properties of tertiarybutylarsine on GaAs(0 0 1) surface

CERN Document Server

Ozeki, M; Tanaka, Y

2002-01-01

The dynamical properties of tertiarybutylarsine (TBA) was studied on GaAs(0 0 1) surface using a supersonic molecular beam. The temperature and incident energy dependence of the reflected beam revealed a reaction channel of TBA on GaAs surface with a large decrease in the activation energy from 2.7 to 1.8 eV as the incident energy increases from 0.04 to 2.5 eV.

Image-based rendering of intersecting surfaces for dynamic comparative visualization

NARCIS (Netherlands)

Busking, S.; Botha, C.P.; Ferrarini, L.; Milles, J.; Post, F.H.

2010-01-01

Nested or intersecting surfaces are proven techniques for visualizing shape differences between static 3D objects (Weigle and Taylor II, IEEE Visualization, Proceedings, pp. 503–510, 2005). In this paper we present an image-based formulation for these techniques that extends their use to dynamic

External Thermal Insulation Composite Systems: Critical Parameters for Surface Hygrothermal Behaviour

Directory of Open Access Journals (Sweden)

Eva Barreira

2014-01-01

Full Text Available External Thermal Insulation Composite Systems (ETICS are often used in Europe. Despite its thermal advantages, low cost, and ease of application, this system has serious problems of biological growth causing the cladding defacement. Recent studies pointed that biological growth is due to high values of surface moisture content, which mostly results from the combined effect of exterior surface condensation, wind-driven rain, and drying process. Based on numerical simulation, this paper points the most critical parameters involved in hygrothermal behaviour of ETICS, considering the influence of thermal and hygric properties of the external rendering, the effect of the characteristics of the façade, and the consequences of the exterior and interior climate on exterior surface condensation, wind-driven rain, and drying process. The model used was previously validated by comparison with the results of an “in situ” campaign. The results of the sensitivity analyses show that relative humidity and temperature of the exterior air, atmospheric radiation, and emissivity of the exterior rendering are the parameters that most influence exterior surface condensation. Wind-driven rain depends mostly on horizontal rain, building’s height, wind velocity, and orientation. The drying capacity is influenced by short-wave absorbance, incident solar radiation, and orientation.

Optical Feather and Foil for Shape and Dynamic Load Sensing of Critical Flight Surfaces, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Future flight vehicles may comprise complex flight surfaces requiring coordinated in-situ sensing and actuation. Inspired by the complexity of the flight surfaces on...

He atom surface spectroscopy: Surface lattice dynamics of insulators, metals and metal overlayers

International Nuclear Information System (INIS)

1990-01-01

During the first three years of this grant (1985--1988) the effort was devoted to the construction of a state-of-the-art He atom scattering (HAS) instrument which would be capable of determining the structure and dynamics of metallic, semiconductor or insulator crystal surfaces. The second three year grant period (1988--1991) has been dedicated to measurements. The construction of the instrument went better than proposed; it was within budget, finished in the proposed time and of better sensitivity and resolution than originally planned. The same success has been carried over to the measurement phase where the concentration has been on studies of insulator surfaces, as discussed in this paper. The experiments of the past three years have focused primarily on the alkali halides with a more recent shift to metal oxide crystal surfaces. Both elastic and inelastic scattering experiments were carried out on LiF, NaI, NaCl, RbCl, KBr, RbBr, RbI, CsF, CsI and with some preliminary work on NiO and MgO

Dynamic analysis of a hollow cylinder subject to a dual traveling force imposed on its inner surface

Science.gov (United States)

Lee, Sooyoung; Seok, Jongwon

2015-03-01

The dynamic behavior of a hollow cylinder under a dual traveling force applied to the inner surface is investigated in this study. The cylinder is constrained at both the top and bottom surfaces not to move in the length direction but free in other directions. And a dual force travels at a constant velocity along the length direction on the inner surface of the hollow cylinder. The resulting governing field equations and the associated boundary conditions are ruled by the general Hooke's law. Due to the nature of the field equations, proper adjoint system of equations and biorthogonality conditions were derived in a precise and detailed manner. To solve these field equations in this study, the method of separation of variable is used and the method of Fro¨benius is employed for the differential equations in the radial direction. Using the field equations, the eigenanalyses on both the original and its adjoint system were performed with great care, which results in the eigenfunction sets of both systems. The biorthogonality conditions were applied to the field equations to obtain the discretized equation for each mode. Using the solutions of the discretized equations that account for the boundary forcing terms, the critical speed for a dual traveling force for each mode could be computed.

Quantum chemical molecular dynamical investigation of alkyl nitrite photo-dissociated on copper surfaces

International Nuclear Information System (INIS)

Wang Xiaojing; Wang Wei; Han Peilin; Kubo, Momoji; Miyamoto, Akira

2008-01-01

An accelerated quantum chemical molecular dynamical code 'Colors-Excite' was used to investigate the photolysis of alkyl nitrites series, RONO (R=CH 3 and C(CH 3 ) 3 ) on copper surfaces. Our calculations showed that the photo-dissociated processes are associated with the alkyl substituents of RONO when adsorbed on copper surfaces. For R=CH 3 , a two-step photolysis reaction occurred, yielding diverse intermediate products including RO radical, NO, and HNO, consistent with those reported in gas phase. While for R=C(CH 3 ) 3 , only one-step photolysis reaction occurred and gave intermediate products of RO radical and NO. Consequently, pure RO species were achieved to adsorb on metal surfaces by removing the NO species in photolysis reaction. The detailed photo-dissociated behaviors of RONO on copper surfaces with different alkyl substituents which are uncovered by the present simulation can be extended to explain the diverse dissociative mechanism experimentally observed. The quantum chemical molecular dynamical code 'Colors-Excite' is proved to be highly applicable to the photo-dissociations on metal surfaces

Desorption dynamics of deuterium molecules from the Si(100)-(3×1) dideuteride surface

OpenAIRE

Niida, T; Tsurumaki, Hiroshi; Namiki, Akira

2006-01-01

We measured polar angle ()-resolved time-of-flight spectra of D2 molecules desorbing from the Si(100)-(3×1) dideuteride surface. The desorbing D2 molecules exhibit a considerable translational heating with mean desorption kinetic energies of 0.25 eV, which is mostly independent of the desorption angles for 0°30°. The observed desorption dynamics of deuterium was discussed along the principle of detailed balance to predict their adsorption dynamics onto the monohydride Si surface.

Characterizing interstate vibrational coherent dynamics of surface adsorbed catalysts by fourth-order 3D SFG spectroscopy

Science.gov (United States)

Li, Yingmin; Wang, Jiaxi; Clark, Melissa L.; Kubiak, Clifford P.; Xiong, Wei

2016-04-01

We report the first fourth-order 3D SFG spectroscopy of a monolayer of the catalyst Re(diCN-bpy)(CO)3Cl on a gold surface. Besides measuring the vibrational coherences of single vibrational modes, the fourth-order 3D SFG spectrum also measures the dynamics of interstate coherences and vibrational coherences states between two vibrational modes. By comparing the 3D SFG to the corresponding 2D and third-order 3D IR spectroscopy of the same molecules in solution, we found that the interstate coherences exist in both liquid and surface systems, suggesting that the interstate coherence is not disrupted by surface interactions. However, by analyzing the 3D spectral lineshape, we found that the interstate coherences also experience non-negligible homogenous dephasing dynamics that originate from surface interactions. This unique ability of determining interstate vibrational coherence dynamics of the molecular monolayer can help in understanding of how energy flows within surface catalysts and other molecular monolayers.

The influence of the radiation pressure force on possible critical surfaces in binary systems

International Nuclear Information System (INIS)

Vanbeveren, D.

1978-01-01

Using a spherically symmetric approximation for the radiation pressure force to compute a possible critical surface for binary systems, previous authors found that the surface opens up at the far side of the companion. It is shown that this effect may be unreal, and could be a consequence of the simple approximation for the radiation pressure force, Due to the influence of the radiation force, mass will be lost over the whole surface of the star. In that way much mass could leave the system in massive binary systems. On the basis of evolutionary models, including mass loss by stellar wind, the results were applied on the X-ray binaries 3U 1700 - 37 and HD 77581. (Auth.)

An Optimization Method for Virtual Globe Ocean Surface Dynamic Visualization

Directory of Open Access Journals (Sweden)

HUANG Wumeng

2016-12-01

Full Text Available The existing visualization method in the virtual globe mainly uses the projection grid to organize the ocean grid. This special grid organization has the defects in reflecting the difference characteristics of different ocean areas. The method of global ocean visualization based on global discrete grid can make up the defect of the projection grid method by matching with the discrete space of the virtual globe, so it is more suitable for the virtual ocean surface simulation application.But the available global discrete grids method has many problems which limiting its application such as the low efficiency of rendering and loading, the need of repairing grid crevices. To this point, we propose an optimization for the global discrete grids method. At first, a GPU-oriented multi-scale grid model of ocean surface which develops on the foundation of global discrete grids was designed to organize and manage the ocean surface grids. Then, in order to achieve the wind-drive wave dynamic rendering, this paper proposes a dynamic wave rendering method based on the multi-scale ocean surface grid model to support real-time wind field updating. At the same time, considering the effect of repairing grid crevices on the system efficiency, this paper presents an efficient method for repairing ocean surface grid crevices based on the characteristics of ocean grid and GPU technology. At last, the feasibility and validity of the method are verified by the comparison experiment. The experimental results show that the proposed method is efficient, stable and fast, and can compensate for the lack of function of the existing methods, so the application range is more extensive.

Determination of the Critical Stress Associated with Dynamic Phase Transformation in Steels by Means of Free Energy Method

Directory of Open Access Journals (Sweden)

Clodualdo Aranas

2018-05-01

Full Text Available The double differentiation method overestimates the critical stress associated with the initiation of dynamic transformation (DT because significant amounts of the dynamic phase must be present in order for its effect on the work hardening rate to be detectable. In this work, an alternative method (referred to here as the free energy method is presented based on the thermodynamic condition that the driving force is equal to the total energy obstacle during the exact moment of transformation. The driving force is defined as the difference between the DT critical stress (measured in the single-phase austenite region and the yield stress of the fresh ferrite that takes its place. On the other hand, the energy obstacle consists of the free energy difference between austenite and ferrite, and the work of shear accommodation and dilatation associated with the phase transformation. Here, the DT critical stresses in a C-Mn steel were calculated using the free energy method at temperatures ranging from 870 °C to 1070 °C. The results show that the calculated critical stress using the present approach appears to be more accurate than the values measured by the double differentiation method.

Spin dynamics in the high-field phase of quantum-critical S =1/2 TlCuCl sub 3

CERN Document Server

Rueegg, C; Furrer, A; Krämer, K; Güdel, H U; Vorderwisch, P; Mutka, H

2002-01-01

An external magnetic field suppresses the spin-energy gap in singlet ground state S=1/2 TlCuCl sub 3. The system becomes quantum-critical at H sub c approx 5.7 T, where the energy of the lowest Zeeman-split triplet excitation crosses the nonmagnetic ground state. Antiferromagnetic ordering is reported above H sub c , which underlines the three-dimensional nature of the observed quantum phase transition. The intrinsic parameters of S=1/2 TlCuCl sub 3 allow us to access the critical region microscopically by neutron scattering. A substantial study of the spin dynamics in the high-field phase of TlCuCl sub 3 at T=1.5 K up to H=12 T was performed for the first time. The results possibly indicate two dynamical regimes, which can be understood within characteristically renormalized triplet modes and a low-lying dynamics of potentially collective origin. (orig.)

Instability and dynamics of volatile thin films

Science.gov (United States)

Ji, Hangjie; Witelski, Thomas P.

2018-02-01

Volatile viscous fluids on partially wetting solid substrates can exhibit interesting interfacial instabilities and pattern formation. We study the dynamics of vapor condensation and fluid evaporation governed by a one-sided model in a low-Reynolds-number lubrication approximation incorporating surface tension, intermolecular effects, and evaporative fluxes. Parameter ranges for evaporation-dominated and condensation-dominated regimes and a critical case are identified. Interfacial instabilities driven by the competition between the disjoining pressure and evaporative effects are studied via linear stability analysis. Transient pattern formation in nearly flat evolving films in the critical case is investigated. In the weak evaporation limit unstable modes of finite-amplitude nonuniform steady states lead to rich droplet dynamics, including flattening, symmetry breaking, and droplet merging. Numerical simulations show that long-time behaviors leading to evaporation or condensation are sensitive to transitions between filmwise and dropwise dynamics.

Computational multi-fluid dynamics predictions of critical heat flux in boiling flow

Energy Technology Data Exchange (ETDEWEB)

Mimouni, S., E-mail: stephane.mimouni@edf.fr; Baudry, C.; Guingo, M.; Lavieville, J.; Merigoux, N.; Mechitoua, N.

2016-04-01

Highlights: • A new mechanistic model dedicated to DNB has been implemented in the Neptune-CFD code. • The model has been validated against 150 tests. • Neptune-CFD code is a CFD tool dedicated to boiling flows. - Abstract: Extensive efforts have been made in the last five decades to evaluate the boiling heat transfer coefficient and the critical heat flux in particular. Boiling crisis remains a major limiting phenomenon for the analysis of operation and safety of both nuclear reactors and conventional thermal power systems. As a consequence, models dedicated to boiling flows have being improved. For example, Reynolds Stress Transport Model, polydispersion and two-phase flow wall law have been recently implemented. In a previous work, we have evaluated computational fluid dynamics results against single-phase liquid water tests equipped with a mixing vane and against two-phase boiling cases. The objective of this paper is to propose a new mechanistic model in a computational multi-fluid dynamics tool leading to wall temperature excursion and onset of boiling crisis. Critical heat flux is calculated against 150 tests and the mean relative error between calculations and experimental values is equal to 8.3%. The model tested covers a large physics scope in terms of mass flux, pressure, quality and channel diameter. Water and R12 refrigerant fluid are considered. Furthermore, it was found that the sensitivity to the grid refinement was acceptable.

Computational multi-fluid dynamics predictions of critical heat flux in boiling flow

International Nuclear Information System (INIS)

Mimouni, S.; Baudry, C.; Guingo, M.; Lavieville, J.; Merigoux, N.; Mechitoua, N.

2016-01-01

Highlights: • A new mechanistic model dedicated to DNB has been implemented in the Neptune_CFD code. • The model has been validated against 150 tests. • Neptune_CFD code is a CFD tool dedicated to boiling flows. - Abstract: Extensive efforts have been made in the last five decades to evaluate the boiling heat transfer coefficient and the critical heat flux in particular. Boiling crisis remains a major limiting phenomenon for the analysis of operation and safety of both nuclear reactors and conventional thermal power systems. As a consequence, models dedicated to boiling flows have being improved. For example, Reynolds Stress Transport Model, polydispersion and two-phase flow wall law have been recently implemented. In a previous work, we have evaluated computational fluid dynamics results against single-phase liquid water tests equipped with a mixing vane and against two-phase boiling cases. The objective of this paper is to propose a new mechanistic model in a computational multi-fluid dynamics tool leading to wall temperature excursion and onset of boiling crisis. Critical heat flux is calculated against 150 tests and the mean relative error between calculations and experimental values is equal to 8.3%. The model tested covers a large physics scope in terms of mass flux, pressure, quality and channel diameter. Water and R12 refrigerant fluid are considered. Furthermore, it was found that the sensitivity to the grid refinement was acceptable.

Influence of chemistry on wetting dynamics of nanotextured hydrophobic surfaces.

Science.gov (United States)

Di Mundo, Rosa; Palumbo, Fabio; d'Agostino, Riccardo

2010-04-06

In this work, the role of a chemical parameter, such as the degree of fluorination, on the wetting behavior of nanotextured hydrophobic surfaces is investigated. Texture and chemistry tuning of the surfaces has been accomplished with single batch radiofrequency low-pressure plasma processes. Polystyrene substrates have been textured by CF(4) plasma etching and subsequently covered by thin films with a tunable F-to-C ratio, obtained in discharges fed with C(4)F(8)-C(2)H(4). Measurements of wetting dynamics reveal a regime transition from adhesive-hydrophobic to slippery-superhydrophobic, i.e., from wet to non wet states, as the F-to-C rises at constant topography. Such achievements are strengthened by calculation of the solid fraction of surface water contact area applying Cassie-Baxter advancing and receding equations to water contact angle data of textured and flat reference surfaces.

He atom-surface scattering: Surface dynamics of insulators, overlayers and crystal growth

International Nuclear Information System (INIS)

1992-01-01

Investigations in this laboratory have focused on the surface structure and dynamics of ionic insulators and on epitaxial growth onto alkali halide crystals. In the later the homoepitaxial growth of NaCl/NaCl(001) and the heteroepitaxial growth of KBr/NaCl(001), NaCl/KBr(001) and KBr/RbCl(001) have been studied by monitoring the specular He scattering as a function of the coverage and by measuring the angular and energy distributions of the scattered He atoms. These data provide information on the surface structure, defect densities, island sizes and surface strain during the layer-by-layer growth. The temperature dependence of these measurements also provides information on the mobilities of the admolecules. He atom scattering is unique among surface probes because the low-energy, inert atoms are sensitive only to the electronic structure of the topmost surface layer and are equally applicable to all crystalline materials. It is proposed for the next year to exploit further the variety of combinations possible with the alkali halides in order to carry out a definitive study of epitaxial growth in the ionic insulators. The work completed so far, including measurements of the Bragg diffraction and surface dispersion at various stages of growth, appears to be exceptionally rich in detail, which is particularly promising for theoretical modeling. In addition, because epitaxial growth conditions over a wide range of lattice mismatches is possible with these materials, size effects in growth processes can be explored in great depth. Further, as some of the alkali halides have the CsCl structure instead of the NaCl structure, we can investigate the effects of the heteroepitaxy with materials having different lattice preferences. Finally, by using co-deposition of different alkali halides, one can investigate the formation and stability of alloys and even alkali halide superlattices

Dynamics and Instabilities of Free Surface and Vortex Flows

DEFF Research Database (Denmark)

Tophøj, Laust Emil Hjerrild

2012-01-01

This PhD thesis consists of two main parts. The first part describes the dynamics of an ideal fluid on a stationary free surface of a given shape. It turns out that one can formulate a set of self-contained equations of momentum conservation for the tangential flow, with no reference to the flow ......)]. Finally, an experimental work on elastic collisions of wet spheres is briefly discussed....

Modeling Coupled Landscape Evolution and Soil Organic Carbon Dynamics in Intensively Management Landscapes

Science.gov (United States)

Yan, Q.; Kumar, P.

2017-12-01

Soil is the largest reservoir of carbon in the biosphere but in agricultural areas it is going through rapid erosion due disturbance arising from crop harvest, tillage, and tile drainage. Identifying whether the production of soil organic carbon (SOC) from the crops can compensate for the loss due to erosion is critical to ensure our food security and adapt to climate change. In the U.S. Midwest where large areas of land are intensively managed for agriculture practices, predicting soil quantity and quality are critical for maintaining crop yield and other Critical Zone services. This work focuses on modeling the coupled landscape evolutions soil organic carbon dynamics in agricultural fields. It couples landscape evolution, surface water runoff, organic matter transformation, and soil moisture dynamics to understand organic carbon gain and loss due to natural forcing and farming practices, such as fertilizer application and tillage. A distinctive feature of the model is the coupling of surface ad subsurface processes that predicts both surficial changes and transport along with the vertical transport and dynamics. Our results show that landscape evolution and farming practices play dominant roles in soil organic carbon (SOC) dynamics both above- and below-ground. Contrary to the common assumption that a vertical profile of SOC concentration decreases exponentially with depth, we find that in many situations SOC concentration below-ground could be higher than that at the surface. Tillage plays a complex role in organic matter dynamics. On one hand, tillage would accelerate the erosion rate, on the other hand, it would improve carbon storage by burying surface SOC into below ground. Our model consistently reproduces the observed above- and below-ground patterns of SOC in the field sites of Intensively Managed Landscapes Critical Zone Observatory (IMLCZO). This model bridges the gaps between the landscape evolution, below- and above-ground hydrologic cycle, and

Dynamic Corneal Surface Mapping with Electronic Speckle Pattern Interferometry

Science.gov (United States)

Iqbal, S.; Gualini, M. M. S.

2013-06-01

In view of the fast advancement in ophthalmic technology and corneal surgery, there is a strong need for the comprehensive mapping and characterization techniques for corneal surface. Optical methods with precision non-contact approaches have been found to be very useful for such bio measurements. Along with the normal mapping approaches, elasticity of corneal surface has an important role in its characterization and needs to be appropriately measured or estimated for broader diagnostics and better prospective surgical results, as it has important role in the post-op corneal surface reconstruction process. Use of normal corneal topographic devices is insufficient for any intricate analysis since these devices operate at relatively moderate resolution. In the given experiment, Pulsed Electronic Speckle Pattern Interferometry has been utilized along with an excitation mechanism to measure the dynamic response of the sample cornea. A Pulsed ESPI device has been chosen for the study because of its micron-level resolution and other advantages in real-time deformation analysis. A bovine cornea has been used as a sample in the subject experiment. The dynamic response has been taken on a chart recorder and it is observed that it does show a marked deformation at a specific excitation frequency, which may be taken as a characteristic elasticity parameter for the surface of that corneal sample. It was seen that outside resonance conditions the bovine cornea was not that much deformed. Through this study, the resonance frequency and the corresponding corneal deformations are mapped and plotted in real time. In these experiments, data was acquired and processed by FRAMES plus computer analysis system. With some analysis of the results, this technique can help us to refine a more detailed corneal surface mathematical model and some preliminary work was done on this. Such modelling enhancements may be useful for finer ablative surgery planning. After further experimentation

Transmission-lattice based geometric phase analysis for evaluating the dynamic deformation of a liquid surface.

Science.gov (United States)

Shi, Wenxiong; Huang, Xianfu; Liu, Zhanwei

2014-05-05

Quantitatively measuring a dynamic liquid surface often presents a challenge due to high transparency, fluidity and specular reflection. Here, a novel Transmission-Lattice based Geometric Phase Analysis (TLGPA) method is introduced. In this method, a special lattice is placed underneath a liquid to be tested and, when viewed from above, the phase of the transmission-lattice image is modulated by the deformation of the liquid surface. Combining this with multi-directional Newton iteration algorithms, the dynamic deformation field of the liquid surface can be calculated from the phase variation of a series of transmission-lattice images captured at different moments. The developed method has the advantage of strong self-adaption ability to initial lattice rotational errors and this is discussed in detail. Dynamic 3D ripples formation and propagation was investigated and the results obtained demonstrated the feasibility of the method.

DNSC08 mean sea surface and mean dynamic topography models

DEFF Research Database (Denmark)

Andersen, Ole Baltazar; Knudsen, Per

2009-01-01

-2004. It is the first global MSS without a polar gap including all of the Arctic Ocean by including laser altimetry from the ICESat mission. The mean dynamic topography (MDT) is the quantity that bridges the geoid and the mean sea surface constraining large-scale ocean circulation. Here we present a new high...

Surface activation of cyclo olefin polymer by oxygen plasma discharge: a molecular dynamics study

International Nuclear Information System (INIS)

Soberon, Felipe

2014-01-01

Thermoplastic substrates made of cyclo olefin polymer (COP) are treated with oxygen plasma discharges to introduce polar groups at the surface. This is the first step in the process of surface functionalization of COP substrates used in biosensor devices. A molecular dynamics model of basic COP structure is implemented using the second-generation reactive empirical bond order (REBO) potentials for hydrocarbon–oxygen interactions. The model includes covalent bond and Van der Waals interactions. The bombardment of a COP surface with mono-energetic atomic oxygen ions, energy in the range 1-35 eV, is simulated and reported here. The dynamics of the substrate modification reveals that the substrate top layer is de-hydrogenated and subsequently builds up an oxygen–carbon matrix layer, ∼10 Å thick. Analysis of the modified substrates indicates that surface yield is predominantly peroxide groups. (paper)

Ultrafast electron dynamics at alkali/ice structures adsorbed on a metal surface

International Nuclear Information System (INIS)

Meyer, Michael

2011-01-01

mediated by tunneling through a potential barrier which is determined by the thickness of the ice layer. In the second system electron solvation at small alkali/water clusters directly prepared at the metal substrate is investigated. In these experiments the average number of water molecules in such a cluster can be controlled so that the population and stabilization dynamics of excess electrons can be investigated as a function of D 2 O coverage. Two main effects are observed: (i) the alkalis are solvated by a reorientation of the surrounding solvent molecules in the cluster; and (ii) above a critical number of water molecules per alkali excess electrons can localize at the clusters where they are energetically stabilized. This critical ratio depends on the type of alkali and is inversely proportional to the alkali-induced dipole moment. Finally, it is demonstrated that trapped electrons in crystalline ice adsorbed on Ru(001) can very efficiently mediate chemical reactions via dissociative electron attachment. When electronegative molecules like CFCl 3 are coadsorbed with crystalline ice a DEA process between trapped electrons and CFCl 3 molecules occurs, resulting in the formation of .CFCl 2 radicals and Cl - anions. These results suggest that photoexcited trapped electrons can play an important role in heterogeneous chemical processes on ice surfaces and could thus be relevant in the polar stratosphere chemistry.

Towards the Verification of Safety-critical Autonomous Systems in Dynamic Environments

Directory of Open Access Journals (Sweden)

Adina Aniculaesei

2016-12-01

Full Text Available There is an increasing necessity to deploy autonomous systems in highly heterogeneous, dynamic environments, e.g. service robots in hospitals or autonomous cars on highways. Due to the uncertainty in these environments, the verification results obtained with respect to the system and environment models at design-time might not be transferable to the system behavior at run time. For autonomous systems operating in dynamic environments, safety of motion and collision avoidance are critical requirements. With regard to these requirements, Macek et al. [6] define the passive safety property, which requires that no collision can occur while the autonomous system is moving. To verify this property, we adopt a two phase process which combines static verification methods, used at design time, with dynamic ones, used at run time. In the design phase, we exploit UPPAAL to formalize the autonomous system and its environment as timed automata and the safety property as TCTL formula and to verify the correctness of these models with respect to this property. For the runtime phase, we build a monitor to check whether the assumptions made at design time are also correct at run time. If the current system observations of the environment do not correspond to the initial system assumptions, the monitor sends feedback to the system and the system enters a passive safe state.

Applications of granular-dynamics numerical simulations to asteroid surfaces

Science.gov (United States)

Richardson, D. C.; Michel, P.; Schwartz, S. R.; Yu, Y.; Ballouz, R.-L.; Matsumura, S.

2014-07-01

Spacecraft images and indirect observations including thermal inertia measurements indicate most small bodies have surface regolith. Evidence of granular flow is also apparent in the images. This material motion occurs in very low gravity, therefore in a totally different gravitational environment than on the Earth. Upcoming sample-return missions to small bodies, and possible future manned missions, will involve interaction with the surface regolith, so it is important to develop tools to predict the surface response. We have added new capabilities to the N-body gravity tree code pkdgrav [1,2] that permit the simulation of granular dynamics, including multi-contact physics and friction forces, using the soft-sphere discrete-element method [3]. The numerical approach has been validated through comparison with laboratory experiments (e.g., [3,4]). (1) We carried out impacts into granular materials using different projectile shapes under Earth's gravity [5] and compared the results to laboratory experiments [6] in support of JAXA's Hayabusa 2 asteroid sample-return mission. We tested different projectile shapes and confirmed that the 90-degree cone was the most efficient at excavating mass when impacting 5-mm-diameter glass beads. Results are sensitive to the normal coefficient of restitution and the coefficient of static friction. Preliminary experiments in micro-gravity for similar impact conditions show both the amount of ejected mass and the timescale of the impact process increase, as expected. (2) It has been found (e.g., [7,8]) that ''fresh'' (unreddened) Q-class asteroids have a high probability of recent planetary encounters (˜1 Myr; also see [9]), suggesting that surface refreshening may have occurred due to tidal effects. As an application of the potential effect of tidal interactions, we carried out simulations of Apophis' predicted 2029 encounter with the Earth to see whether regolith motion might occur, using a range of plausible material parameters

Study on Dynamic Development of Three-dimensional Weld Pool Surface in Stationary GTAW

Science.gov (United States)

Huang, Jiankang; He, Jing; He, Xiaoying; Shi, Yu; Fan, Ding

2018-04-01

The weld pool contains abundant information about the welding process. In particular, the type of the weld pool surface shape, i. e., convex or concave, is determined by the weld penetration. To detect it, an innovative laser-vision-based sensing method is employed to observe the weld pool surface of the gas tungsten arc welding (GTAW). A low-power laser dots pattern is projected onto the entire weld pool surface. Its reflection is intercepted by a screen and captured by a camera. Then the dynamic development process of the weld pool surface can be detected. By observing and analyzing, the change of the reflected laser dots reflection pattern, for shape of the weld pool surface shape, was found to closely correlate to the penetration of weld pool in the welding process. A mathematical model was proposed to correlate the incident ray, reflected ray, screen and surface of weld pool based on structured laser specular reflection. The dynamic variation of the weld pool surface and its corresponding dots laser pattern were simulated and analyzed. By combining the experimental data and the mathematical analysis, the results show that the pattern of the reflected laser dots pattern is closely correlated to the development of weld pool, such as the weld penetration. The concavity of the pool surface was found to increase rapidly after the surface shape was changed from convex to concave during the stationary GTAW process.

Theory of the reaction dynamics of small molecules on metal surfaces

Energy Technology Data Exchange (ETDEWEB)

Jackson, Bret [Univ. of Massachusetts, Amherst, MA (United States)

2016-09-09

The objective of this project has been to develop realistic theoretical models for gas-surface interactions, with a focus on processes important in heterogeneous catalysis. The dissociative chemisorption of a molecule on a metal is a key step in many catalyzed reactions, and is often the rate-limiting step. We have explored the dissociative chemisorption of H₂, H₂O and CH₄ on a variety of metal surfaces. Most recently, our extensive studies of methane dissociation on Ni and Pt surfaces have fully elucidated its dependence on translational energy, vibrational state and surface temperature, providing the first accurate comparisons with experimental data. We have explored Eley-Rideal and hot atom reactions of H atoms with H- and C-covered metal surfaces. H atom interactions with graphite have also been explored, including both sticking and Eley-Rideal recombination processes. Again, our methods made it possible to explain several experiments studying these reactions. The sticking of atoms on metal surfaces has also been studied. To help elucidate the experiments that study these processes, we examine how the reaction dynamics depend upon the nature of the molecule-metal interaction, as well as experimental variables such as substrate temperature, beam energy, angle of impact, and the internal states of the molecules. Electronic structure methods based on Density Functional Theory are used to compute each molecule-metal potential energy surface. Both time-dependent quantum scattering techniques and quasi-classical methods are used to examine the reaction or scattering dynamics. Much of our effort has been directed towards developing improved quantum methods that can accurately describe reactions, as well as include the effects of substrate temperature (lattice vibration).

Anomalous water dynamics at surfaces and interfaces: synergistic effects of confinement and surface interactions

Science.gov (United States)

Biswas, Rajib; Bagchi, Biman

2018-01-01

In nature, water is often found in contact with surfaces that are extended on the scale of molecule size but small on a macroscopic scale. Examples include lipid bilayers and reverse micelles as well as biomolecules like proteins, DNA and zeolites, to name a few. While the presence of surfaces and interfaces interrupts the continuous hydrogen bond network of liquid water, confinement on a mesoscopic scale introduces new features. Even when extended on a molecular scale, natural and biological surfaces often have features (like charge, hydrophobicity) that vary on the scale of the molecular diameter of water. As a result, many new and exotic features, which are not seen in the bulk, appear in the dynamics of water close to the surface. These different behaviors bear the signature of both water-surface interactions and of confinement. In other words, the altered properties are the result of the synergistic effects of surface-water interactions and confinement. Ultrafast spectroscopy, theoretical modeling and computer simulations together form powerful synergistic approaches towards an understanding of the properties of confined water in such systems as nanocavities, reverse micelles (RMs), water inside and outside biomolecules like proteins and DNA, and also between two hydrophobic walls. We shall review the experimental results and place them in the context of theory and simulations. For water confined within RMs, we discuss the possible interference effects propagating from opposite surfaces. Similar interference is found to give rise to an effective attractive force between two hydrophobic surfaces immersed and kept fixed at a separation of d, with the force showing an exponential dependence on this distance. For protein and DNA hydration, we shall examine a multitude of timescales that arise from frustration effects due to the inherent heterogeneity of these surfaces. We pay particular attention to the role of orientational correlations and modification of the

Non-critical string theory formulation of microtubule dynamics and quantum aspects of brain function

CERN Document Server

Mavromatos, Nikolaos E

1995-01-01

Microtubule (MT) networks, subneural paracrystalline cytosceletal structures, seem to play a fundamental role in the neurons. We cast here the complicated MT dynamics in the form of a 1+1-dimensional non-critical string theory, thus enabling us to provide a consistent quantum treatment of MTs, including enviromental {\\em friction} effects. We suggest, thus, that the MTs are the microsites, in the brain, for the emergence of stable, macroscopic quantum coherent states, identifiable with the {\\em preconscious states}. Quantum space-time effects, as described by non-critical string theory, trigger then an {\\em organized collapse} of the coherent states down to a specific or {\\em conscious state}. The whole process we estimate to take {\\cal O}(1\\,{\\rm sec}), in excellent agreement with a plethora of experimental/observational findings. The {\\em microscopic arrow of time}, endemic in non-critical string theory, and apparent here in the self-collapse process, provides a satisfactory and simple resolution to the age...

A novel reformulation of the Theory of Critical Distances to design notched metals against dynamic loading

International Nuclear Information System (INIS)

Yin, T.; Tyas, A.; Plekhov, O.; Terekhina, A.; Susmel, L.

2015-01-01

Highlights: • The proposed method is successful in estimating dynamic strength of metals. • The critical distance varies as the loading/strain/displacement rate increases. • The reference strength varies as the loading/strain/displacement rate increases. • This method is recommended to be used with safety factors larger than 1.25. - Abstract: In the present study the linear-elastic Theory of Critical Distances (TCD) is reformulated to make it suitable for predicting the strength of notched metallic materials subjected to dynamic loading. The accuracy and reliability of the proposed reformulation of the TCD was checked against a number of experimental results generated by testing, under different loading/strain rates, notched cylindrical samples of aluminium alloy 6063-T5, titanium alloy Ti–6Al–4V, aluminium alloy AlMg6, and an AlMn alloy. To further validate the proposed design method also different data sets taken from the literature were considered. Such an extensive validation exercise allowed us to prove that the proposed reformulation of the TCD is successful in predicting the dynamic strength of notched metallic materials, this approach proving to be capable of estimates falling within an error interval of ±20%. Such a high level of accuracy is certainly remarkable, especially in light of the fact that it was reached without the need for explicitly modelling the stress vs. strain dynamic behaviour of the investigated ductile metals

Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces

Science.gov (United States)

Zutz, Amelia Marie

Detailed molecular scale interactions at the gas-liquid interface are explored with quantum state-to-state resolved scattering of a jet-cooled beam of NO(2pi1/2; N = 0) from ionic liquid and molten metal surfaces. The scattered distributions are probed via laser-induced fluorescence methods, which yield rotational and spin-orbit state populations that elucidate the dynamics of energy transfer at the gas-liquid interface. These collision dynamics are explored as a function of incident collision energy, surface temperature, scattering angle, and liquid identity, all of which are found to substantially affect the degree of rotational, electronic and vibrational excitation of NO via collisions at the liquid surface. Rotational distributions observed reveal two distinct scattering pathways, (i) molecules that trap, thermalize and eventually desorb from the surface (trapping-desorption, TD), and (ii) those that undergo prompt recoil (impulsive scattering, IS) prior to complete equilibration with the liquid surface. Thermally desorbing NO molecules are found to have rotational temperatures close to, but slightly cooler than the surface temperature, indicative of rotational dependent sticking probabilities on liquid surfaces. Nitric oxide is a radical with multiple low-lying electronic states that serves as an ideal candidate for exploring nonadiabatic state-changing collision dynamics at the gas-liquid interface, which induce significant excitation from ground (2pi1/2) to excited (2pi 3/2) spin-orbit states. Molecular beam scattering of supersonically cooled NO from hot molten metals (Ga and Au, Ts = 300 - 1400 K) is also explored, which provide preliminary evidence for vibrational excitation of NO mediated by thermally populated electron-hole pairs in the hot, conducting liquid metals. The results highlight the presence of electronically nonadiabatic effects and build toward a more complete characterization of energy transfer dynamics at gas-liquid interfaces.

Friction and Surface Dynamics of Polymers on the Nanoscale by AFM

NARCIS (Netherlands)

Schönherr, Holger; Schónherr, Holger; Samori, Paolo; Tocha, E.; Vancso, Gyula J.

2008-01-01

In this article the measurement and understanding of friction forces and surface dynamics of polymers on the one hand and the importance of molecular relaxation processes and viscoelasticity in polymers for advanced micro- and nanoscale applications on the other hand are discussed. Particular

Evaporation dynamics of a sessile droplet on glass surfaces with fluoropolymer coatings: focusing on the final stage of thin droplet evaporation.

Science.gov (United States)

Gatapova, Elizaveta Ya; Shonina, Anna M; Safonov, Alexey I; Sulyaeva, Veronica S; Kabov, Oleg A

2018-03-07

The evaporation dynamics of a water droplet with an initial volume of 2 μl from glass surfaces with fluoropolymer coatings are investigated using the shadow technique and an optical microscope. The droplet profile for a contact angle of less than 5° is constructed using an image-analyzing interference technique, and evaporation dynamics are investigated at the final stage. We coated the glass slides with a thin film of a fluoropolymer by the hot-wire chemical vapor deposition method at different deposition modes depending on the deposition pressure and the temperature of the activating wire. The resulting surfaces have different structures affecting the wetting properties. Droplet evaporation from a constant contact radius mode in the early stage of evaporation was found followed by the mode where both contact angle and contact radius simultaneously vary in time (final stage) regardless of wettability of the coated surfaces. We found that depinning occurs at small contact angles of 2.2-4.7° for all samples, which are smaller than the measured receding contact angles. This is explained by imbibition of the liquid into the developed surface of the "soft" coating that leads to formation of thin droplets completely wetting the surface. The final stage, which is little discussed in the literature, is also recorded. We have singled out a substage where the contact line velocity is abruptly increasing for all coated and uncoated surfaces. The critical droplet height corresponding to the transition to this substage is about 2 μm with R/h = 107. The duration of this substage is the same for all coated and uncoated surfaces. Droplets observed at this substage for all the tested surfaces are axisymmetric. The specific evaporation rate clearly demonstrates an abrupt increase at the final substage of the droplet evaporation. The classical R 2 law is justified for the complete wetting situation where the droplet is disappearing in an axisymmetric manner.

Evaporation dynamics of completely wetting drops on geometrically textured surfaces

Science.gov (United States)

Mekhitarian, Loucine; Sobac, Benjamin; Dehaeck, Sam; Haut, Benoît; Colinet, Pierre

2017-10-01

This study deals with the evaporation dynamics of completely wetting and highly volatile drops deposited on geometrically textured but chemically homogeneous surfaces. The texturation consists in a cylindrical pillars array with a square pitch. The triple line dynamics and the drop shape are characterized by an interferometric method. A parametric study is realized by varying the radius and the height of the pillars (at fixed interpillar distance), allowing to distinguish three types of dynamics: i) an evaporation-dominated regime with a receding triple line; ii) a spreading-dominated regime with an initially advancing triple line; iii) a cross-over region with strong pinning effects. The overall picture is in qualitative agreement with a mathematical model showing that the selected regime mostly depends on the value of a dimensionless parameter comparing the time scales for evaporation and spreading into the substrate texture.

Well-defined critical association concentration and rapid adsorption at the air/water interface of a short amphiphilic polymer, amphipol A8-35: a study by Förster resonance energy transfer and dynamic surface tension measurements.

Science.gov (United States)

Giusti, Fabrice; Popot, Jean-Luc; Tribet, Christophe

2012-07-17

Amphipols (APols) are short amphiphilic polymers designed to handle membrane proteins (MPs) in aqueous solutions as an alternative to small surfactants (detergents). APols adsorb onto the transmembrane, hydrophobic surface of MPs, forming small, water-soluble complexes, in which the protein is biochemically stabilized. At variance with MP/detergent complexes, MP/APol ones remain stable even at extreme dilutions. Pure APol solutions self-associate into well-defined micelle-like globules comprising a few APol molecules, a rather unusual behavior for amphiphilic polymers, which typically form ill-defined assemblies. The best characterized APol to date, A8-35, is a random copolymer of acrylic acid, isopropylacrylamide, and octylacrylamide. In the present work, the concentration threshold for self-association of A8-35 in salty buffer (NaCl 100 mM, Tris/HCl 20 mM, pH 8.0) has been studied by Förster resonance energy transfer (FRET) measurements and tensiometry. In a 1:1 mol/mol mixture of APols grafted with either rhodamine or 7-nitro-1,2,3-benzoxadiazole, the FRET signal as a function of A8-35 concentration is essentially zero below a threshold concentration of 0.002 g·L(-1) and increases linearly with concentration above this threshold. This indicates that assembly takes place in a narrow concentration interval around 0.002 g·L(-1). Surface tension measurements decreases regularly with concentration until a threshold of ca. 0.004 g·L(-1), beyond which it reaches a plateau at ca. 30 mN·m(-1). Within experimental uncertainties, the two techniques thus yield a comparable estimate of the critical self-assembly concentration. The kinetics of variation of the surface tension was analyzed by dynamic surface tension measurements in the time window 10 ms-100 s. The rate of surface tension decrease was similar in solutions of A8-35 and of the anionic surfactant sodium dodecylsulfate when both compounds were at a similar molar concentration of n-alkyl moieties. Overall, the

Dynamic Wetting Behavior of Vibrated Droplets on a Micropillared Surface

Directory of Open Access Journals (Sweden)

Zhi-hai Jia

2016-01-01

Full Text Available The dynamical wetting behavior has been observed under vertical vibration of a water droplet placed on a micropillared surface. The wetting transition takes place under the different processes. In compression process, the droplet is transited from Cassie state to Wenzel state. The droplet undergoes a Wenzel-Cassie wetting transition in restoring process and the droplet bounces off from the surface in bouncing process. Meanwhile, the wetting and dewetting models during vibration are proposed. The wetting transition is confirmed by the model calculation. This study has potential to be used to control the wetting state.

Estimation of Nanodiamond Surface Charge Density from Zeta Potential and Molecular Dynamics Simulations.

Science.gov (United States)

Ge, Zhenpeng; Wang, Yi

2017-04-20

Molecular dynamics simulations of nanoparticles (NPs) are increasingly used to study their interactions with various biological macromolecules. Such simulations generally require detailed knowledge of the surface composition of the NP under investigation. Even for some well-characterized nanoparticles, however, this knowledge is not always available. An example is nanodiamond, a nanoscale diamond particle with surface dominated by oxygen-containing functional groups. In this work, we explore using the harmonic restraint method developed by Venable et al., to estimate the surface charge density (σ) of nanodiamonds. Based on the Gouy-Chapman theory, we convert the experimentally determined zeta potential of a nanodiamond to an effective charge density (σ eff ), and then use the latter to estimate σ via molecular dynamics simulations. Through scanning a series of nanodiamond models, we show that the above method provides a straightforward protocol to determine the surface charge density of relatively large (> ∼100 nm) NPs. Overall, our results suggest that despite certain limitation, the above protocol can be readily employed to guide the model construction for MD simulations, which is particularly useful when only limited experimental information on the NP surface composition is available to a modeler.

Dynamic growth of slip surfaces in catastrophic landslides.

Science.gov (United States)

Germanovich, Leonid N; Kim, Sihyun; Puzrin, Alexander M

2016-01-01

This work considers a landslide caused by the shear band that emerges along the potential slip (rupture) surface. The material above the band slides downwards, causing the band to grow along the slope. This growth may first be stable (progressive), but eventually becomes dynamic (catastrophic). The landslide body acquires a finite velocity before it separates from the substrata. The corresponding initial-boundary value problem for a dynamic shear band is formulated within the framework of Palmer & Rice's ( Proc. R. Soc. Lond. A 332 , 527-548. (doi:10.1098/rspa.1973.0040)) approach, which is generalized to the dynamic case. We obtain the exact, closed-form solution for the band velocity and slip rate. This solution assesses when the slope fails owing to a limiting condition near the propagating tip of the shear band. Our results are applicable to both submarine and subaerial landslides of this type. It appears that neglecting dynamic (inertia) effects can lead to a significant underestimation of the slide size, and that the volumes of catastrophic slides can exceed the volumes of progressive slides by nearly a factor of 2. As examples, we consider the Gaviota and Humboldt slides offshore of California, and discuss landslides in normally consolidated sediments and sensitive clays. In particular, it is conceivable that Humboldt slide is unfinished and may still displace a large volume of sediments, which could generate a considerable tsunami. We show that in the case of submarine slides, the effect of water resistance on the shear band dynamics may frequently be limited during the slope failure stage. For a varying slope angle, we formulate a condition of slide cessation.

Bubble dynamics equations in Newton fluid

International Nuclear Information System (INIS)

Xiao, J

2008-01-01

For the high-speed flow of Newton fluid, bubble is produced and expanded when it moves toward the surface of fluid. Bubble dynamics is a very important research field to understand the intrinsic feature of bubble production and motion. This research formulates the bubble expansion by expansion-local rotation transformation, which can be calculated by the measured velocity field. Then, the related dynamic equations are established to describe the interaction between the fluid and the bubble. The research shows that the bubble production condition can be expressed by critical vortex value and fluid pressure; and the bubble expansion rate can be obtained by solving the non-linear dynamic equation of bubble motion. The results may help the related research as it shows a special kind of fluid motion in theoretic sense. As an application example, the nanofiber radium-voltage relation and threshold voltage-surface tension relation in electrospinning process are discussed

Surface Dynamic Process Simulation with the Use of Cellular Automata

International Nuclear Information System (INIS)

Adamska-Szatko, M.; Bala, J.

2010-01-01

Cellular automata are known for many applications, especially for physical and biological simulations. Universal cellular automata can be used for modelling complex natural phenomena. The paper presents simulation of surface dynamic process. Simulation uses 2-dimensional cellular automata algorithm. Modelling and visualisation were created by in-house developed software with standard OpenGL graphic library. (authors)

Comparison of molecular dynamics and kinetic modeling of gas-surface interactions

NARCIS (Netherlands)

Frezzotti, A.; Gaastra - Nedea, S.V.; Markvoort, A.J.; Spijker, P.; Gibelli, L.

2008-01-01

The interaction of a dilute monatomic gas with a solid surface is studied byMolecular Dynamics (MD) simulations and by numerical solutions of a recently proposed kinetic model. Following previous investigations, the heat transport between parallel walls and Couette flow have been adopted as test

Dynamics of a Rydberg hydrogen atom near a metal surface in the electron-extraction scheme

Energy Technology Data Exchange (ETDEWEB)

Iñarrea, Manuel [Área de Física Aplicada, Universidad de La Rioja, Logroño (Spain); Lanchares, Víctor [Departamento de Matemáticas y Computación, Universidad de La Rioja, Logroño, La Rioja (Spain); Palacián, Jesús [Departamento de Ingeniería Matemática e Informática, Universidad Pública de Navarra, Pamplona (Spain); Pascual, Ana I. [Departamento de Matemáticas y Computación, Universidad de La Rioja, Logroño, La Rioja (Spain); Salas, J. Pablo, E-mail: josepablo.salas@unirioja.es [Área de Física Aplicada, Universidad de La Rioja, Logroño (Spain); Yanguas, Patricia [Departamento de Ingeniería Matemática e Informática, Universidad Pública de Navarra, Pamplona (Spain)

2015-01-23

We study the classical dynamics of a Rydberg hydrogen atom near a metal surface in the presence of a constant electric field in the electron-extraction situation [1], e.g., when the field attracts the electron to the vacuum. From a dynamical point of view, this field configuration provides a dynamics richer than in the usual ion-extraction scheme, because, depending on the values of field and the atom–surface distance, the atom can be ionized only towards the metal surface, only to the vacuum or to the both sides. The evolution of the phase space structure as a function of the atom–surface distance is explored in the bound regime of the atom. In the high energy regime, the ionization mechanism is also investigated. We find that the classical results of this work are in good agreement with the results obtained in the wave-packet propagation study carried out by So et al. [1]. - Highlights: • We study a classical hydrogen atom near a metal surface plus a electric field. • We explore the phase space structure as a function of the field strength. • We find most of the electronic orbits are oriented along the field direction. • We study the ionization of the atom for several atom–surface distances. • This classical study is in good agreement with the quantum results.

Molecular dynamics simulation of temperature effects on low energy near-surface cascades and surface damage in Cu

Science.gov (United States)

Zhu, Guo; Sun, Jiangping; Guo, Xiongxiong; Zou, Xixi; Zhang, Libin; Gan, Zhiyin

2017-06-01

The temperature effects on near-surface cascades and surface damage in Cu(0 0 1) surface under 500 eV argon ion bombardment were studied using molecular dynamics (MD) method. In present MD model, substrate system was fully relaxed for 1 ns and a read-restart scheme was introduced to save total computation time. The temperature dependence of damage production was calculated. The evolution of near-surface cascades and spatial distribution of adatoms at varying temperature were analyzed and compared. It was found that near-surface vacancies increased with temperature, which was mainly due to the fact that more atoms initially located in top two layers became adatoms with the decrease of surface binding energy. Moreover, with the increase of temperature, displacement cascades altered from channeling-like structure to branching structure, and the length of collision sequence decreased gradually, because a larger portion of energy of primary knock-on atom (PKA) was scattered out of focused chain. Furthermore, increasing temperature reduced the anisotropy of distribution of adatoms, which can be ascribed to that regular registry of surface lattice atoms was changed with the increase of thermal vibration amplitude of surface atoms.

Molecular dynamics simulation of temperature effects on low energy near-surface cascades and surface damage in Cu

Energy Technology Data Exchange (ETDEWEB)

Zhu, Guo; Sun, Jiangping; Guo, Xiongxiong; Zou, Xixi; Zhang, Libin; Gan, Zhiyin, E-mail: ganzhiyin@126.com

2017-06-15

The temperature effects on near-surface cascades and surface damage in Cu(0 0 1) surface under 500 eV argon ion bombardment were studied using molecular dynamics (MD) method. In present MD model, substrate system was fully relaxed for 1 ns and a read-restart scheme was introduced to save total computation time. The temperature dependence of damage production was calculated. The evolution of near-surface cascades and spatial distribution of adatoms at varying temperature were analyzed and compared. It was found that near-surface vacancies increased with temperature, which was mainly due to the fact that more atoms initially located in top two layers became adatoms with the decrease of surface binding energy. Moreover, with the increase of temperature, displacement cascades altered from channeling-like structure to branching structure, and the length of collision sequence decreased gradually, because a larger portion of energy of primary knock-on atom (PKA) was scattered out of focused chain. Furthermore, increasing temperature reduced the anisotropy of distribution of adatoms, which can be ascribed to that regular registry of surface lattice atoms was changed with the increase of thermal vibration amplitude of surface atoms.

GPI-anchored protein organization and dynamics at the cell surface.

Science.gov (United States)

Saha, Suvrajit; Anilkumar, Anupama Ambika; Mayor, Satyajit

2016-02-01

The surface of eukaryotic cells is a multi-component fluid bilayer in which glycosylphosphatidylinositol (GPI)-anchored proteins are an abundant constituent. In this review, we discuss the complex nature of the organization and dynamics of GPI-anchored proteins at multiple spatial and temporal scales. Different biophysical techniques have been utilized for understanding this organization, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single particle tracking, and a number of super resolution methods. Major insights into the organization and dynamics have also come from exploring the short-range interactions of GPI-anchored proteins by fluorescence (or Förster) resonance energy transfer microscopy. Based on the nanometer to micron scale organization, at the microsecond to the second time scale dynamics, a picture of the membrane bilayer emerges where the lipid bilayer appears inextricably intertwined with the underlying dynamic cytoskeleton. These observations have prompted a revision of the current models of plasma membrane organization, and suggest an active actin-membrane composite. Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc.

Experimental investigation of pool boiling heat transfer and critical heat flux on a downward facing surface

International Nuclear Information System (INIS)

Gocmanac, M.; Luxat, J.C.

2012-01-01

A separate effects experimental study of heat transfer and Critical Heat Flux (CHF) on a downward facing plate in subcooled water pool boiling is described. Two geometries of downwards facing surfaces are studied. The first is termed the 'confined' study in which bubble motion is restricted to the heated surface. The second is termed the 'unconfined' study where individual bubbles are free to move along the heated surface and vent in any direction. The method used in the confined study is novel and involves the placement of a lip surrounding the heated surface. The CHF as a function of angle of inclination of the surface is presented and is in good agreement with other experimental data from somewhat different test geometries. (author)

Development of a dynamic model for cleaning ultra filtration membranes fouled by surface water

NARCIS (Netherlands)

Zondervan, Edwin; Betlem, Ben H.L.; Roffel, Brian

2007-01-01

In this paper, a dynamic model for cleaning ultra filtration membranes fouled by surface water is proposed. A model that captures the dynamics well is valuable for the optimization of the cleaning process. The proposed model is based on component balances and contains three parameters that can be

Modelling and investigation of partial wetting surfaces for drop dynamics using lattice Boltzmann method

Energy Technology Data Exchange (ETDEWEB)

Pravinraj, T., E-mail: pravinraj1711@gmail.com; Patrikar, Rajendra

2017-07-01

Highlights: • A LBM model on partial wetting surface for droplet dynamics is presented by introducing a simple initial partial wetting boundary condition in SC model. • With our approach one can tune the splitting volume and time by carefully choosing strip width and position. • It is shown that the droplet spreading on chemically heterogeneous surfaces can be controlled not only by Weber number but also by tuning strip width ratio. • The directional transportation of a droplet due to chemical wetting gradient is simulated and analyzed using hybrid thermodynamic-image processing technique. • Microstructure surface and its influence on the directional wetting based transportation of droplet are demonstrated. - Abstract: Partial wetting surfaces and its influence on the droplet movement of micro and nano scale being contemplated for many useful applications. The dynamics of the droplet usually analyzed with a multiphase lattice Boltzmann method (LBM). In this paper, the influence of partial wetting surface on the dynamics of droplet is systematically analyzed for various cases. Splitting of droplets due to chemical gradient of the surface is studied and analyses of splitting time for various widths of the strips for different Weber numbers are computed. With the proposed model one can tune the splitting volume and time by carefully choosing a strip width and droplet position. The droplet spreading on chemically heterogeneous surfaces shows that the spreading can be controlled not only by parameters of Weber number but also by tuning strip width ratio. The transportation of the droplet from hydrophobic surface to hydrophilic surface due to chemical gradient is simulated and analyzed using our hybrid thermodynamic-image processing technique. The results prove that with the progress of time the surface free energy decreases with increase in spreading area. Finally, the transportation of a droplet on microstructure gradient is demonstrated. The model explains

NASA-VOF2D, 2-D Transient Free Surface Incompressible Fluid Dynamic

International Nuclear Information System (INIS)

Torrey, M.D.

1988-01-01

1 - Description of program or function: NASA-VOF2D is a two- dimensional, transient, free surface incompressible fluid dynamics program. It allows multiple free surfaces with surface tension and wall adhesion forces and has a partial cell treatment which allows curved boundaries and interior obstacles. 2 - Method of solution: NASA-VOF2D simulates incompressible flows with free surfaces using the volume-of-fluid (VOF) algorithm. This technique is based on the use of donor-acceptor differencing to track the free surface across an Eulerian grid. The complete Navier-Stokes equations in primitive variables for an incompressible fluid are solved by finite differences with surface tension and wall adhesion included. Optionally the pressure equation can be solved by a conjugate residual method rather than the successive over-relaxation (SOR) method

Critical temperature gradient and critical current density in thin films of a type I superconductor

Energy Technology Data Exchange (ETDEWEB)

Heubener, R P

1968-12-16

Measurements of the critical temperature gradient and the critical current density in superconducting lead films in a transverse magnetic field indicate that the critical current flows predominantly along the surface of the films and that the critical surface currents contribute only very little to the Lorentz force on a fluxoid.

A laboratory investigation of mixing dynamics between biofuels and surface waters

Science.gov (United States)

Wang, Xiaoxiang; Cotel, Aline

2017-11-01

Recently, production and usage of ethanol-blend fuels or biofuels have increased dramatically along with increasing risk of spilling into surface waters. Lack of understanding of the environmental impacts and absence of standard clean-up procedures make it crucial to study the mixing behavior between biofuels and water. Biofuels are represented by a solution of ethanol and glycol. A Plexiglas tank in conjunction with a wave generator is used to simulate the mixing of surface waters and biofuels under different natural conditions. In our previous experiments, two distinct mixing regimes were observed. One regime was driven by turbulence and the other by interfacial instabilities. However, under more realistic situations, without wind driven waves, only the first mixing regime was found. After one minute of rapid turbulent mixing, biofuels and water were fully mixed and no interface was formed. During the mixing process, chemical reactions happened simultaneously and influenced mixing dynamics. Current experiments are investigating the effect of waves on the mixing dynamics. Support from NSF CBET 1335878.

Estimation of the Critical Temperatures of Some More Deep Eutectic Solvents from Their Surface Tensions

Directory of Open Access Journals (Sweden)

Yizhak Marcus

2018-01-01

Full Text Available The critical temperatures of two dozen deep eutectic solvents, for only some of which these have been estimated previously, were estimated from the temperature dependences of their surface tensions and densities available in the literature according to the Eötvös and the Guggenheim expressions.

Spatiotemporal Dynamics of Surface Water Extent from Three Decades of Seasonally Continuous Landsat Time Series at Subcontinental Scale

Science.gov (United States)

Tulbure, M. G.; Broich, M.; Stehman, Stephen V.

2016-06-01

Surface water is a critical resource in semi-arid areas. The Murray-Darling Basin (MDB) of Australia, one of the largest semi-arid basins in the world is aiming to set a worldwide example of how to balance multiple interests (i.e. environment, agriculture and urban use), but has suffered significant water shrinkages during the Millennium Drought (1999-2009), followed by extensive flooding. Baseline information and systematic quantification of surface water (SW) extent and flooding dynamics in space and time are needed for managing SW resources across the basin but are currently lacking. To synoptically quantify changes in SW extent and flooding dynamics over MDB, we used seasonally continuous Landsat TM and ETM+ data (1986 - 2011) and generic machine learning algorithms. We further mapped flooded forest at a riparian forest site that experienced severe tree dieback due to changes in flooding regime. We used a stratified sampling design to assess the accuracy of the SW product across time. Accuracy assessment yielded an overall classification accuracy of 99.94%, with producer's and user's accuracy of SW of 85.4% and 97.3%, respectively. Overall accuracy was the same for Landsat 5 and 7 data but user's and producer's accuracy of water were higher for Landsat 7 than 5 data and stable over time. Our validated results document a rapid loss in SW bodies. The number, size, and total area of SW showed high seasonal variability with highest numbers in winter and lowest numbers in summer. SW extent per season per year showed high interannual and seasonal variability, with low seasonal variability during the Millennium Drought. Examples of current uses of the new dataset will be presented and include (1) assessing ecosystem response to flooding with implications for environmental water releases, one of the largest investment in environment in Australia; (2) quantifying drivers of SW dynamics (e.g. climate, human activity); (3) quantifying changes in SW dynamics and

H(D) → D(H) + Cu(111) collision system: molecular dynamics study of surface temperature effects.

Science.gov (United States)

Vurdu, Can D; Güvenç, Ziya B

2011-04-28

All the channels of the reaction dynamics of gas-phase H (or D) atoms with D (or H) atoms adsorbed onto a Cu(111) surface have been studied by quasiclassical constant energy molecular dynamics simulations. The surface is flexible and is prepared at different temperature values, such as 30 K, 94 K, and 160 K. The adsorbates were distributed randomly on the surface to create 0.18 ML, 0.28 ML, and 0.50 ML of coverages. The multi-layer slab is mimicked by a many-body embedded-atom potential energy function. The slab atoms can move according to the exerted external forces. Treating the slab atoms non-rigid has an important effect on the dynamics of the projectile atom and adsorbates. Significant energy transfer from the projectile atom to the surface lattice atoms takes place especially during the first impact that modifies significantly the details of the dynamics of the collisions. Effects of the different temperatures of the slab are investigated in this study. Interaction between the surface atoms and the adsorbates is modeled by a modified London-Eyring-Polanyi-Sato (LEPS) function. The LEPS parameters are determined by using the total energy values which were calculated by a density functional theory and a generalized gradient approximation for an exchange-correlation energy for many different orientations, and locations of one- and two-hydrogen atoms on the Cu(111) surface. The rms value of the fitting procedure is about 0.16 eV. Many different channels of the processes on the surface have been examined, such as inelastic reflection of the incident hydrogen, subsurface penetration of the incident projectile and adsorbates, sticking of the incident atom on the surface. In addition, hot-atom and Eley-Rideal direct processes are investigated. The hot-atom process is found to be more significant than the Eley-Rideal process. Furthermore, the rate of subsurface penetration is larger than the sticking rate on the surface. In addition, these results are compared and

Behind adhesion of uranyl onto montmorillonite surface: A molecular dynamics study

Energy Technology Data Exchange (ETDEWEB)

Yang, W.; Zaoui, A., E-mail: azaoui@polytech-lille.fr

2013-10-15

Highlights: • We investigated the adsorption of uranyl onto Montmorillonite surface. • We studied the surface energy between layered Montmorillonite sheets. • We studied the work of adhesion between radionuclide and charged Montmorillonite. -- Abstract: We have performed molecular dynamics simulations to investigate the adsorption of radionuclide elements species onto substituted Montmorillonite (001) surface in the presence of different counterions. The structure and the dynamics of uranyl ion as well as its aquo, chloride ion, and carbonate complexes are analyzed. In addition, we have studied the surface energy between layered Montmorillonite sheets and the work of adhesion between radionuclide and charged Montmorillonite. The clay model used here is a Wyoming-type Montmorillonite with 0.75e negative charge per unit cell resulting from substitutions in Octahedral and Tetrahedral sheets. The system model was constructed based on CLAYFF force field potential model. To evaluate the thermodynamic work of adhesion, each surface and clay layer regions are converted to a thin film model. One and two species of radionuclide elements (UO{sub 2}(H{sub 2}O){sub 5},UO{sub 2}CO{sub 3}(H{sub 2}O){sub 5}, and UO{sub 2}Cl{sub 2}(H{sub 2}O){sub 5}) were deposited near the clay surface in a pseudo-two-dimensional periodic cell. Analysis shows that the uranyl ion structure is preserved with two axial oxygen atoms detected at 1.8 Å. Radial distribution functions results indicate that average U-O{sub w} distances are 2.45–2.61 Å, and 2.29–2.40 Å for U-O{sub c} distance. Average U-Cl distances are 2.78–3.08 Å, which is relatively larger than that of Uranium atom-Oxygen atom because of electrostatic factors.

Interferometer for measuring the dynamic surface topography of a human tear film

Science.gov (United States)

Primeau, Brian C.; Greivenkamp, John E.

2012-03-01

The anterior refracting surface of the eye is the thin tear film that forms on the surface of the cornea. Following a blink, the tear film quickly smoothes and starts to become irregular after 10 seconds. This irregularity can affect comfort and vision quality. An in vivo method of characterizing dynamic tear films has been designed based upon a near-infrared phase-shifting interferometer. This interferometer continuously measures light reflected from the tear film, allowing sub-micron analysis of the dynamic surface topography. Movies showing the tear film behavior can be generated along with quantitative metrics describing changes in the tear film surface. This tear film measurement allows analysis beyond capabilities of typical fluorescein visual inspection or corneal topography and provides better sensitivity and resolution than shearing interferometry methods. The interferometer design is capable of identifying features in the tear film much less than a micron in height with a spatial resolution of about ten microns over a 6 mm diameter. This paper presents the design of the tear film interferometer along with the considerations that must be taken when designing an interferometer for on-eye diagnostics. Discussions include eye movement, design of null optics for a range of ocular geometries, and laser emission limits for on-eye interferometry.

Molecular dynamics simulation of wetting behaviors of Li on W surfaces

Energy Technology Data Exchange (ETDEWEB)

Sun, Xuegui [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Xiao, Shifang [Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082 (China); Deng, Huiqiu, E-mail: hqdeng@hnu.edu.cn [Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082 (China); Hu, Wangyu, E-mail: wyuhu@hnu.edu.cn [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China)

2017-04-15

A modified analytic embedded atom potential has been developed for the Li-W system. The potential has been fitted to physical quantities derived from density functional theory calculations. It is shown that the new potential is capable of reproducing the solubility of solid solution for Li-W systems. The wetting behaviors between solid tungsten and liquid Li are examined by using molecular dynamics simulations. The MD simulation results for the Li droplet wetting on the W surface illustrated that our MAEAM potential model has a good forecasting ability for the contact angle of liquid Li on W the cleaning surface above the wetting temperature. And the results of Li film dewetting from the W surfaces are consistent with relative experimental results. It is believed that the potential can be used to investigate the surfaces wettability of liquid Li on W substrate. We also simulated the lithium droplet on grooved surface. It is shown that the grooving W surfaces can obviously improve the wetting of liquid Li on W surfaces.

Molecular dynamics simulations of water on a hydrophilic silica surface at high air pressures

DEFF Research Database (Denmark)

Zambrano, H.A.; Walther, Jens Honore; Jaffe, R.L.

2014-01-01

Wepresent a force field forMolecular Dynamics (MD) simulations ofwater and air in contactwith an amorphous silica surface. We calibrate the interactions of each species present in the systemusing dedicated criteria such as the contact angle of a water droplet on a silica surface, and the solubility...

Atomistic modeling of metal surfaces under electric fields: direct coupling of electric fields to a molecular dynamics algorithm

CERN Document Server

Djurabekova, Flyura; Pohjonen, Aarne; Nordlund, Kai

2011-01-01

The effect of electric fields on metal surfaces is fairly well studied, resulting in numerous analytical models developed to understand the mechanisms of ionization of surface atoms observed at very high electric fields, as well as the general behavior of a metal surface in this condition. However, the derivation of analytical models does not include explicitly the structural properties of metals, missing the link between the instantaneous effects owing to the applied field and the consequent response observed in the metal surface as a result of an extended application of an electric field. In the present work, we have developed a concurrent electrodynamic–molecular dynamic model for the dynamical simulation of an electric-field effect and subsequent modification of a metal surface in the framework of an atomistic molecular dynamics (MD) approach. The partial charge induced on the surface atoms by the electric field is assessed by applying the classical Gauss law. The electric forces acting on the partially...

Modelling and investigation of partial wetting surfaces for drop dynamics using lattice Boltzmann method

Science.gov (United States)

Pravinraj, T.; Patrikar, Rajendra

2017-07-01

Partial wetting surfaces and its influence on the droplet movement of micro and nano scale being contemplated for many useful applications. The dynamics of the droplet usually analyzed with a multiphase lattice Boltzmann method (LBM). In this paper, the influence of partial wetting surface on the dynamics of droplet is systematically analyzed for various cases. Splitting of droplets due to chemical gradient of the surface is studied and analyses of splitting time for various widths of the strips for different Weber numbers are computed. With the proposed model one can tune the splitting volume and time by carefully choosing a strip width and droplet position. The droplet spreading on chemically heterogeneous surfaces shows that the spreading can be controlled not only by parameters of Weber number but also by tuning strip width ratio. The transportation of the droplet from hydrophobic surface to hydrophilic surface due to chemical gradient is simulated and analyzed using our hybrid thermodynamic-image processing technique. The results prove that with the progress of time the surface free energy decreases with increase in spreading area. Finally, the transportation of a droplet on microstructure gradient is demonstrated. The model explains the temporal behaviour of droplet during the spreading, recoiling and translation along with tracking of contact angle hysteresis phenomenon.

Critical surface of the quenched bond-diluted cubic model in self-dual lattice: renormalisation group approach

International Nuclear Information System (INIS)

Silva, E.P. da; Tsallis, C.

1991-01-01

We propose a quite simple real space renormalisation group which enables us to calculate (for the first time as far as we know, and presumably with high precision) the critical surface of the quenched bond-diluted discrete N-vector ferromagnet. (author)

Enhanced Dynamics of Hydrated tRNA on Nanodiamond Surfaces: A Combined Neutron Scattering and MD Simulation Study.

Science.gov (United States)

Dhindsa, Gurpreet K; Bhowmik, Debsindhu; Goswami, Monojoy; O'Neill, Hugh; Mamontov, Eugene; Sumpter, Bobby G; Hong, Liang; Ganesh, Panchapakesan; Chu, Xiang-Qiang

2016-09-14

Nontoxic, biocompatible nanodiamonds (ND) have recently been implemented in rational, systematic design of optimal therapeutic use in nanomedicines. However, hydrophilicity of the ND surface strongly influences structure and dynamics of biomolecules that restrict in situ applications of ND. Therefore, fundamental understanding of the impact of hydrophilic ND surface on biomolecules at the molecular level is essential. For tRNA, we observe an enhancement of dynamical behavior in the presence of ND contrary to generally observed slow motion at strongly interacting interfaces. We took advantage of neutron scattering experiments and computer simulations to demonstrate this atypical faster dynamics of tRNA on ND surface. The strong attractive interactions between ND, tRNA, and water give rise to unlike dynamical behavior and structural changes of tRNA in front of ND compared to without ND. Our new findings may provide new design principles for safer, improved drug delivery platforms.

TENSOR CALCULUS with applications to Differential Theory of Surfaces and Dynamics

DEFF Research Database (Denmark)

Nielsen, Søren R. K.

The present outline on tensor calculus with special application to differential theory of surfaces and dynamics represents a modified and extended version of a lecture note written by the author as an introduction to a course on shell theory given together with Ph.D. Jesper Winther Stærdahl...

Optimizing conjunctive use of surface water and groundwater resources with stochastic dynamic programming

DEFF Research Database (Denmark)

Davidsen, Claus; Liu, Suxia; Mo, Xinguo

2014-01-01

. A stochastic dynamic programming (SDP) approach is used to minimize the basin-wide total costs arising from water allocations and water curtailments. Dynamic allocation problems with inclusion of groundwater resources proved to be more complex to solve with SDP than pure surface water allocation problems due...... to head-dependent pumping costs. These dynamic pumping costs strongly affect the total costs and can lead to non-convexity of the future cost function. The water user groups (agriculture, industry, domestic) are characterized by inelastic demands and fixed water allocation and water supply curtailment...

Using impulses to control the convergence toward invariant surfaces of continuous dynamical systems

International Nuclear Information System (INIS)

Marão, José; Liu Xinzhi; Figueiredo, Annibal

2012-01-01

Let us consider a smooth invariant surface S of a given ordinary differential equations system. In this work we develop an impulsive control method in order to assure that the trajectories of the controlled system converge toward the surface S. The method approach is based on a property of a certain class of invariant surfaces whose the dynamics associated to their transverse directions can be described by a non-autonomous linear system. This fact allows to define an impulsive system which drives the trajectories toward the surface S. Also, we set up a definition of local stability exponents which can be associated to such kind of invariant surface.

Surface dynamics of voltage-gated ion channels

Science.gov (United States)

Heine, Martin; Ciuraszkiewicz, Anna; Voigt, Andreas; Heck, Jennifer; Bikbaev, Arthur

2016-01-01

ABSTRACT Neurons encode information in fast changes of the membrane potential, and thus electrical membrane properties are critically important for the integration and processing of synaptic inputs by a neuron. These electrical properties are largely determined by ion channels embedded in the membrane. The distribution of most ion channels in the membrane is not spatially uniform: they undergo activity-driven changes in the range of minutes to days. Even in the range of milliseconds, the composition and topology of ion channels are not static but engage in highly dynamic processes including stochastic or activity-dependent transient association of the pore-forming and auxiliary subunits, lateral diffusion, as well as clustering of different channels. In this review we briefly discuss the potential impact of mobile sodium, calcium and potassium ion channels and the functional significance of this for individual neurons and neuronal networks. PMID:26891382

Dynamic properties of a dirt and a synthetic equine racetrack surface measured by a track-testing device.

Science.gov (United States)

Setterbo, J J; Fyhrie, P B; Hubbard, M; Upadhyaya, S K; Stover, S M

2013-01-01

Racetrack surface is a risk factor for Thoroughbred racehorse injury and death that can be engineered and managed. To investigate the relationship between surface and injury, the mechanical behaviour of dirt and synthetic track surfaces must be quantified. To compare dynamic properties of a dirt and a synthetic surface in situ using a track-testing device designed to simulate equine hoof impact; and to determine the effects of impact velocity, impact angle and repeated impact on dynamic surface behaviour. A track-testing device measured force and displacement during impact into a dirt and a synthetic surface at 3 impact velocities (1.91, 2.30, 2.63 m/s), 2 impact angles (0°, 20° from vertical), and 2 consecutive impacts (initial, repeat). Surfaces were measured at 3 locations/day for 3 days. The effects of surface type, impact velocity, impact angle and impact number on dynamic surface properties were assessed using analysis of variance. Synthetic surface maximum forces, load rates and stiffnesses were 37-67% of dirt surface values. Surfaces were less stiff with lower impact velocities, angled impacts and initial impacts. The magnitude of differences between dirt and synthetic surfaces increased for repeat impacts and higher impact velocities. The synthetic surface was generally softer than the dirt surface. Greatly increased hardness for repeat impacts corroborates the importance of maintenance. Results at different impact velocities suggest that surface differences will persist at higher impact velocities. For both surfaces it is clearly important to prevent horse exposure to precompacted surfaces, particularly during high-speed training when the surface has already been trampled. These data should be useful in coordinating racetrack surface management with racehorse training to prevent injuries. © 2012 EVJ Ltd.

Contact angle change during evaporation of near-critical liquids

Science.gov (United States)

Nikolayev, Vadim; Hegseth, John; Beysens, Daniel

1998-11-01

An unexpected change of the dynamic contact angle was recently observed in a near-critical liquid-gas system in a space experiment. While the near-critical liquid completely wets a solid under equilibrium conditions, the apparent contact angle changed from 0^circ to about 120^circ during evaporation. We propose an explanation for this phenomenon by taking into account vapor recoil due to evaporation (motion of the vapor from the free liquid surface). This force is normal to the vapor-liquid interface and is directed towards the liquid. It increases sharply near the triple contact line. Near the critical point, where the surface tension force is very weak, the vapor recoil force can be important enough to change the apparent contact angle. A similar effect can also explain the drying of a heater during boiling at high heat flux. The drying greatly reduces the heat transfer to the liquid causing the heater to melt. This phenomenon is called ``boiling crisis", ``burnout" or ``Departure from Nuclear Boiling". We report the preliminary results of the numerical simulation of the liquid evaporation by the Boundary Element method.

The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

International Nuclear Information System (INIS)

Nguyen, Duc; Girolami, Gregory S.; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Lyding, Joseph; Gruebele, Martin

2014-01-01

Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB 2 glass surface, two-state hopping of 1–2 nm diameter cooperatively rearranging regions or “clusters” occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB 2 has a very high bulk glass transition temperature T g , and we observe no three-state hopping or sequential two-state hopping previously seen on lower T g glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how “mixed” features can show up in surface dynamics of glasses

Dynamic Surface Control and Its Application to Lateral Vehicle Control

Directory of Open Access Journals (Sweden)

Bongsob Song

2014-01-01

Full Text Available This paper extends the design and analysis methodology of dynamic surface control (DSC in Song and Hedrick, 2011, for a more general class of nonlinear systems. When rotational mechanical systems such as lateral vehicle control and robot control are considered for applications, sinusoidal functions are easily included in the equation of motions. If such a sinusoidal function is used as a forcing term for DSC, the stability analysis faces the difficulty due to highly nonlinear functions resulting from the low-pass filter dynamics. With modification of input variables to the filter dynamics, the burden of mathematical analysis can be reduced and stability conditions in linear matrix inequality form to guarantee the quadratic stability via DSC are derived for the given class of nonlinear systems. Finally, the proposed design and analysis approach are applied to lateral vehicle control for forward automated driving and backward parallel parking at a low speed as well as an illustrative example.

Quantum Nuclear Extension of Electron Nuclear Dynamics on Folded Effective-Potential Surfaces

DEFF Research Database (Denmark)

Hall, B.; Deumens, E.; Ohrn, Y.

2014-01-01

A perennial problem in quantum scattering calculations is accurate theoretical treatment of low energy collisions. We propose a method of extracting a folded, nonadiabatic, effective potential energy surface from electron nuclear dynamics (END) trajectories; we then perform nuclear wave packet...

Estimation of the under-surface temperature pattern by dynamic remote sensing

Energy Technology Data Exchange (ETDEWEB)

Inamura, M [Univ. of Tokyo; Tao, R; Katsuma, T; Toyota, H

1977-10-01

There are three basic classifications of remote sensing: passive RS, which involves measurement of reflected solar radiation; active RS, which involves the use of microwaves or laser radar; and infrared scanning. These methods make possible the determination of an object's surface temperature, its effective emissivity, and its effective reflectivity. The surface temperature, in effect, contains information concerning the structure below the surface. Fundamental experiments were conducted to extract sub-surface information by means of 'dynamic remote sensing.' Aluminum objects were embedded in a container filled with sand, and the container was heated from below. First, the spatial transfer function of the medium (sand) was determined, the surface temperature pattern was filtered, and the subsurface temperature pattern was calculated, allowing the subsurface forms of the aluminum objects to be estimated. The relationship between the thermal input (bottom temperature) and the thermal output (surface temperature) was expressed in terms of electrical circuit analogs, and the heat capacity and thermal conductivity of the sample were calculated, permitting estimation of its composition. This technique will be useful for groundwater and mineral exploration and for nondestructive testing.

Numerical modelling of surface waves generated by low frequency electromagnetic field for silicon refinement process

Science.gov (United States)

Geža, V.; Venčels, J.; Zāģeris, Ģ.; Pavlovs, S.

2018-05-01

One of the most perspective methods to produce SoG-Si is refinement via metallurgical route. The most critical part of this route is refinement from boron and phosphorus, therefore, approach under development will address this problem. An approach of creating surface waves on silicon melt’s surface is proposed in order to enlarge its area and accelerate removal of boron via chemical reactions and evaporation of phosphorus. A two dimensional numerical model is created which include coupling of electromagnetic and fluid dynamic simulations with free surface dynamics. First results show behaviour similar to experimental results from literature.

Damage Evaluation of Critical Components of Tilted Support Spring Nonlinear System under a Rectangular Pulse

Directory of Open Access Journals (Sweden)

Ningning Duan

2015-01-01

Full Text Available Dimensionless nonlinear dynamical equations of a tilted support spring nonlinear packaging system with critical components were obtained under a rectangular pulse. To evaluate the damage characteristics of shocks to packaged products with critical components, a concept of the damage boundary surface was presented and applied to a titled support spring system, with the dimensionless critical acceleration of the system, the dimensionless critical velocity, and the frequency parameter ratio of the system taken as the three basic parameters. Based on the numerical results, the effects of the frequency parameter ratio, the mass ratio, the dimensionless peak pulse acceleration, the angle of the system, and the damping ratio on the damage boundary surface of critical components were discussed. It was demonstrated that with the increase of the frequency parameter ratio, the decrease of the angle, and/or the increase of the mass ratio, the safety zone of critical components can be broadened, and increasing the dimensionless peak pulse acceleration or the damping ratio may lead to a decrease of the damage zone for critical components. The results may lead to a thorough understanding of the design principles for the tilted support spring nonlinear system.

One-dimensional critical heat flux concerning surface orientation and gap size effects

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong Hoon; Suh, Kune Y. E-mail: kysuh@snu.ac.kr

2003-12-01

Tests were conducted to examine the critical heat flux (CHF) on a one-dimensional downward heating rectangular channel having a narrow gap by changing the orientation of the copper test heater assembly in a pool of saturated water under atmospheric pressure. The test parameters include both the gap sizes of 1, 2, 5 and 10 mm, and the surface orientation angles from the downward-facing position (180 deg.) to the vertical position (90 deg.), respectively. Also, the CHF experiments were performed for pool boiling with varying heater surface orientations in the unconfined space at atmospheric pressure using the rectangular test section. It was observed that the CHF generally decreases as the surface inclination angle increases and as the gap size decreases. In consistency with several studies reported in the literature, it was found that there exists a transition angle at which the CHF changes with a rapid slope. An engineering correlation is developed for the CHF during natural convective boiling in the inclined, confined rectangular channels with the aid of dimensional analysis. This correlation agrees with the experimental data of this study within {+-}20%.

Wetting-layer formation mechanisms of surface-directed phase separation under different quench depths with off-critical compositions in polymer binary mixture

Science.gov (United States)

Yan, Li-Tang; Xie, Xu-Ming

2007-02-01

Focusing on the off-critical condition, the quench depth dependence of surface-directed phase separation in the polymer binary mixture is numerically investigated by combination of the Cahn-Hilliard-Cook theory and the Flory-Huggins-de Gennes theory. Two distinct situations, i.e., for the wetting, the minority component is preferred by the surface and the majority component is preferred by the surface, are discussed in detail. The simulated results show that the formation mechanism of the wetting layer is affected by both the quench depth and the off-critical extent. Moreover, a diagram, illustrating the formation mechanisms of the wetting layer with various quench depths and compositions, is obtained on the basis of the simulated results. It is found that, when the minority component is preferred by the surface, the growth of the wetting layer can exhibit pure diffusion limited growth law, logarithmic growth law, and Lifshitz-Slyozov growth law. However, when the majority component is preferred by the surface, the wetting layer always grows logarithmically, regardless of the quench depth and the off-critical extent. It is interesting that the surface-induced nucleation can be observed in this case. The simulated results demonstrate that the surface-induced nucleation only occurs below a certain value of the quench depth, and a detailed range about it is calculated and indicated. Furthermore, the formation mechanisms of the wetting layer are theoretically analyzed in depth by the chemical potential gradient.

Finite Element Methods On Very Large, Dynamic Tubular Grid Encoded Implicit Surfaces

DEFF Research Database (Denmark)

Nemitz, Oliver; Nielsen, Michael Bang; Rumpf, Martin

2009-01-01

dynamic tubular grid encoding format for a narrow band. A reaction diffusion model on a fixed surface and surface evolution driven by a nonlinear geometric diffusion approach, by isotropic or truly anisotropic curvature motion, are investigated as characteristic model problems. The proposed methods...

Classical dynamics of the Abelian Higgs model from the critical point and beyond

Directory of Open Access Journals (Sweden)

G.C. Katsimiga

2015-09-01

Full Text Available We present two different families of solutions of the U(1-Higgs model in a (1+1 dimensional setting leading to a localization of the gauge field. First we consider a uniform background (the usual vacuum, which corresponds to the fully higgsed-superconducting phase. Then we study the case of a non-uniform background in the form of a domain wall which could be relevantly close to the critical point of the associated spontaneous symmetry breaking. For both cases we obtain approximate analytical nodeless and nodal solutions for the gauge field resulting as bound states of an effective Pöschl–Teller potential created by the scalar field. The two scenaria differ only in the scale of the characteristic localization length. Numerical simulations confirm the validity of the obtained analytical solutions. Additionally we demonstrate how a kink may be used as a mediator driving the dynamics from the critical point and beyond.

A Modified Critical State Two-surface Plasticity Model for Sand

DEFF Research Database (Denmark)

Bakmar, Christian LeBlanc; Hededal, O.; Ibsen, Lars Bo

This paper provides background information and documentation for the implementation of a robust plasticity model as a user-subroutine in the commercial finite difference code, FLAC3D by Itasca. The plasticity model presented is equal to the 3 dimensional critical state two-surface plasticity model...... volumetric and stress-strain behaviour under monotonic and cyclic loading and thereby related observations like accumulation of pore pressure, cyclic mobility and cyclic liquefaction. The plasticity model is implemented with an integration scheme based on the general return mapping algorithm. The integration...... scheme faces convergence difficulties, primarily at very low mean effective stresses. The convergence problems are addressed by suitable correction strategies designed to add robustness, stability and efficiency to the integration scheme. An outline of all model parameters is given with suggestions...

Surface, dynamic and structural properties of liquid Al-Ti alloys

International Nuclear Information System (INIS)

Novakovic, R.; Giuranno, D.; Ricci, E.; Tuissi, A.; Wunderlich, R.; Fecht, H.-J.; Egry, I.

2012-01-01

The systems containing highly reactive element such as Ti are the most difficult to be determined experimentally and therefore, it is often necessary to estimate the missing values by theoretical models. The thermodynamic data of the Al-Ti system are scarce, its phase diagram is still incomplete and there are very few data on the thermophysical properties of Al-Ti melts. The study on surface, dynamic and static structural properties of liquid Al-Ti alloys has been carried out within the framework of the Compound Formation Model. In spite of the experimental difficulties, the surface tension of liquid Al-2 at.%Ti alloy has been measured over a temperature range by the pinned drop method.

A scanning fluid dynamic gauging technique for probing surface layers

International Nuclear Information System (INIS)

Gordon, Patrick W; Chew, Y M John; Wilson, D Ian; Brooker, Anju D M; York, David W

2010-01-01

Fluid dynamic gauging (FDG) is a technique for measuring the thickness of soft solid deposit layers immersed in a liquid environment, in situ and in real time. This paper details the performance of a novel automated, scanning FDG probe (sFDG) which allows the thickness of a sample layer to be monitored at several points during an experiment, with a resolution of ±5 µm. Its application is demonstrated using layers of gelatine, polyvinyl alcohol (PVA) and baked tomato purée deposits. Swelling kinetics, as well as deformation behaviour—based on knowledge of the stresses imposed on the surface by the gauging flow—can be determined at several points, affording improved experimental data. The use of FDG as a surface scanning technique, operating as a fluid mechanical analogue of atomic force microscopy on a millimetre length scale, is also demonstrated. The measurement relies only on the flow behaviour, and is thus suitable for use in opaque fluids, does not contact the surface itself and does not rely on any specific physical properties of the surface, provided it is locally stiff

Quantifying Hyporheic Exchanges in a Large Scale River Reach Using Coupled 3-D Surface and Subsurface Computational Fluid Dynamics Simulations.

Energy Technology Data Exchange (ETDEWEB)

Hammond, Glenn Edward; Bao, J; Huang, M; Hou, Z; Perkins, W; Harding, S; Titzler, S; Ren, H; Thorne, P; Suffield, S; Murray, C; Zachara, J

2017-03-01

Hyporheic exchange is a critical mechanism shaping hydrological and biogeochemical processes along a river corridor. Recent studies on quantifying the hyporheic exchange were mostly limited to local scales due to field inaccessibility, computational demand, and complexity of geomorphology and subsurface geology. Surface flow conditions and subsurface physical properties are well known factors on modulating the hyporheic exchange, but quantitative understanding of their impacts on the strength and direction of hyporheic exchanges at reach scales is absent. In this study, a high resolution computational fluid dynamics (CFD) model that couples surface and subsurface flow and transport is employed to simulate hyporheic exchanges in a 7-km long reach along the main-stem of the Columbia River. Assuming that the hyporheic exchange does not affect surface water flow conditions due to its negligible magnitude compared to the volume and velocity of river water, we developed a one-way coupled surface and subsurface water flow model using the commercial CFD software STAR-CCM+. The model integrates the Reynolds-averaged Navier-Stokes (RANS) equation solver with a realizable κ-ε two-layer turbulence model, a two-layer all y⁺ wall treatment, and the volume of fluid (VOF) method, and is used to simulate hyporheic exchanges by tracking the free water-air interface as well as flow in the river and the subsurface porous media. The model is validated against measurements from acoustic Doppler current profiler (ADCP) in the stream water and hyporheic fluxes derived from a set of temperature profilers installed across the riverbed. The validated model is then employed to systematically investigate how hyporheic exchanges are influenced by surface water fluid dynamics strongly regulated by upstream dam operations, as well as subsurface structures (e.g. thickness of riverbed and subsurface formation layers) and hydrogeological properties (e.g. permeability). The results

Toward Superconducting Critical Current by Design.

Science.gov (United States)

Sadovskyy, Ivan A; Jia, Ying; Leroux, Maxime; Kwon, Jihwan; Hu, Hefei; Fang, Lei; Chaparro, Carlos; Zhu, Shaofei; Welp, Ulrich; Zuo, Jian-Min; Zhang, Yifei; Nakasaki, Ryusuke; Selvamanickam, Venkat; Crabtree, George W; Koshelev, Alexei E; Glatz, Andreas; Kwok, Wai-Kwong

2016-06-01

A new critical-current-by-design paradigm is presented. It aims at predicting the optimal defect landscape in superconductors for targeted applications by elucidating the vortex dynamics responsible for the bulk critical current. To this end, critical current measurements on commercial high-temperature superconductors are combined with large-scale time-dependent Ginzburg-Landau simulations of vortex dynamics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Critical Dynamics : The Expansion of the Master Equation Including a Critical Point

NARCIS (Netherlands)

Dekker, H.

1980-01-01

In this thesis it is shown how to solve the master equation for a Markov process including a critical point by means of successive approximations in terms of a small parameter. A critical point occurs if, by adjusting an externally controlled quantity, the system shows a transition from normal

A Scale-up Approach for Film Coating Process Based on Surface Roughness as the Critical Quality Attribute.

Science.gov (United States)

Yoshino, Hiroyuki; Hara, Yuko; Dohi, Masafumi; Yamashita, Kazunari; Hakomori, Tadashi; Kimura, Shin-Ichiro; Iwao, Yasunori; Itai, Shigeru

2018-04-01

Scale-up approaches for film coating process have been established for each type of film coating equipment from thermodynamic and mechanical analyses for several decades. The objective of the present study was to establish a versatile scale-up approach for film coating process applicable to commercial production that is based on critical quality attribute (CQA) using the Quality by Design (QbD) approach and is independent of the equipment used. Experiments on a pilot scale using the Design of Experiment (DoE) approach were performed to find a suitable CQA from surface roughness, contact angle, color difference, and coating film properties by terahertz spectroscopy. Surface roughness was determined to be a suitable CQA from a quantitative appearance evaluation. When surface roughness was fixed as the CQA, the water content of the film-coated tablets was determined to be the critical material attribute (CMA), a parameter that does not depend on scale or equipment. Finally, to verify the scale-up approach determined from the pilot scale, experiments on a commercial scale were performed. The good correlation between the surface roughness (CQA) and the water content (CMA) identified at the pilot scale was also retained at the commercial scale, indicating that our proposed method should be useful as a scale-up approach for film coating process.

Modeling surface energy fluxes and thermal dynamics of a seasonally ice-covered hydroelectric reservoir.

Science.gov (United States)

Wang, Weifeng; Roulet, Nigel T; Strachan, Ian B; Tremblay, Alain

2016-04-15

The thermal dynamics of human created northern reservoirs (e.g., water temperatures and ice cover dynamics) influence carbon processing and air-water gas exchange. Here, we developed a process-based one-dimensional model (Snow, Ice, WAater, and Sediment: SIWAS) to simulate a full year's surface energy fluxes and thermal dynamics for a moderately large (>500km(2)) boreal hydroelectric reservoir in northern Quebec, Canada. There is a lack of climate and weather data for most of the Canadian boreal so we designed SIWAS with a minimum of inputs and with a daily time step. The modeled surface energy fluxes were consistent with six years of observations from eddy covariance measurements taken in the middle of the reservoir. The simulated water temperature profiles agreed well with observations from over 100 sites across the reservoir. The model successfully captured the observed annual trend of ice cover timing, although the model overestimated the length of ice cover period (15days). Sensitivity analysis revealed that air temperature significantly affects the ice cover duration, water and sediment temperatures, but that dissolved organic carbon concentrations have little effect on the heat fluxes, and water and sediment temperatures. We conclude that the SIWAS model is capable of simulating surface energy fluxes and thermal dynamics for boreal reservoirs in regions where high temporal resolution climate data are not available. SIWAS is suitable for integration into biogeochemical models for simulating a reservoir's carbon cycle. Copyright © 2016 Elsevier B.V. All rights reserved.

An approach to determine a critical size for rolling contact fatigue initiating from rail surface defects

NARCIS (Netherlands)

Li, Z.; Zhao, X.; Dollevoet, R.P.B.J.

2016-01-01

A methodology for the determination of a critical size of surface defects, above which RCF can initiate, has been developed and demonstrated with its application to the passive type of squats under typical Dutch railway loading conditions. Such a methodology is based on stress evaluation of

Definition of a critical confining zone using surface geophysical methods

International Nuclear Information System (INIS)

Eddy-Dilek, C.A.; Looney, B.B.; Hoekstra, P.; Harthill, N.; Blohm, M.; Phillips, D.R.

1997-01-01

Definition of the hydrologic framework in layered sediments of fluvial and deltaic origin is a difficult challenge for environmental characterization and remediation programs due to the lithologic and stratigraphic heterogeneities inherent in these settings. The authors set out to use complementary geophysical surveys to determine the nature and extent of a deep confining unit at the Savannah River Site, South Carolina. Time Domain Electromagnetic (TDEM) soundings were used to define the electrical conductance of the clayey confining unit (aquitard), and shear-wave reflection seismic was used to define the stratigraphic framework. Based on correlations with borehole geophysical logs and sieve data, the shear-wave seismic proved capable of defining relatively fine layering in the coastal plain sediments, the upper and lower surfaces of a critical confining unit, and erosional features on the surface of the confining unit. The TDEM surveys defined the presence or absence of the clay facies of the confining unit. Moreover, by constraining the interpretation of the TDEM data with the thickness of the confining unit derived from the seismic data, the authors mapped the extent of the unit, showing where the clay is thicker, where it probably was never deposited, and where it was eroded by downcutting channels. These results have significant implications on the design and optimization of remedial systems

Ultimate Cavity Dynamics of Hydrophobic Spheres Impacting on Free Water Surfaces

KAUST Repository

Mansoor, Mohammad M.

2012-12-01

Cavity formation resulting from the water-entry of solid objects has been the subject of extensive research owing to its practical relevance in naval, military, industrial, sports and biological applications. The cavity formed by an impacting hydrophobic sphere normally seals at two places, one below (deep seal) and the other above the water surface (surface seal). For Froude numbers , the air flow into the resulting cavity is strong enough to suck the splash crown above the surface and disrupt the cavity dynamics before it deep seals. In this research work we eliminate surface seals by means of a novel practice of using cone splash-guards and examine the undisturbed transient cavity dynamics by impact of hydrophobic spheres for Froude numbers ranging . This enabled the measurement of extremely accurate pinch-off heights, pinch-off times, radial cavity collapse rates, and jet speeds in an extended range of Froude numbers compared to the previous work of Duclaux et al. (2007). Results in the extended regime were in remarkable agreement with the theoretical prediction of scaled pinch-off depth, and experimentally derived pinch-off time for . Furthermore, we investigated the influence of confinement on cavity formation by varying the cross-sectional area of the tank of liquid. In conjunction with surface seal elimination we observed the formation of multiple pinch-off points where a maximum of four deep seals were obtained in a sequential order for the Froude number range investigated. The presence of an elongated cavity beneath the first pinch-off point 5 resulted in evident "kinks" primarily related to the greatly diminished air pressure at the necking region caused by supersonic air flows (Gekle et al. 2010). Such flows passing through second pinch-offs were also found to choke the cavities beneath the first pinch- off depths causing radial expansion and hence disappearance of downward jets.

Neutralized wettability effect of superhydrophilic Cr-layered surface on pool boiling critical heat flux

International Nuclear Information System (INIS)

Son, Hong Hyun; Jeong, Ui Ju; Seo, Gwang Hyeok; Jeun, Gyoo Dong; Kim, Sung Joong

2016-01-01

The former method is deemed challenging due to longer development period and license issue. In this regard, FeCrAl, Cr, and SiC have been received positive attention as ATF coating materials because they are highly resistant to high temperature steam reaction causing massive hydrogen generation. In this study, Cr was selected as a target deposition material on the metal substrate because we found that Cr-layered surface becomes superhydrophilic, favorable to delaying the triggering of the critical heat flux (CHF). Thus in order to investigate the effect of Cr-layered superhydrophilic surfaces (under explored coating conditions) on pool boiling heat transfer, pool boiling experiment was conducted in the saturated deionized water under atmospheric pressure. As a physical vapor deposition (PVD) method, the DC magnetron sputtering technique was introduced to develop Cr-layered nanostructure. As a control variable of DC sputtering, substrate temperature was selected. Surface wettability and nanostructure were analyzed as major surface parameters on the CHF. We believe that highly dense micro/nano structure without nucleation cavities and inner pores neutralized the wettability effect on the CHF. Moreover, superhydrophilic surface with deficient cavity density rather hinders active nucleation. This emphasizes the importance of micro/nano structure surface for enhanced boiling heat transfer.

D2 dissociative adsorption on and associative desorption from Si(100): Dynamic consequences of an ab initio potential energy surface

DEFF Research Database (Denmark)

Luntz, A. C.; Kratzer, Peter

1996-01-01

favors the symmetric one. Under the conditions of many experiments, either could dominate. The calculations show quite weak dynamic coupling to the Si lattice for both paths, i.e., weak surface temperature dependences to dissociation and small energy loss to the lattice upon desorption......Dynamical calculations are reported for D-2 dissociative chemisorption on and associative desorption from a Si(100) surface. These calculations use the dynamically relevant effective potential which is based on an ab initio potential energy surface for the ''pre-paired'' species. Three coordinates...

Critical sizes and critical characteristics of nanoclusters, nanostructures and nanomaterials

International Nuclear Information System (INIS)

Suzdalev, I.P.

2005-01-01

Full text: Critical sizes and characteristics of nanoclusters and nanostructures are introduced as the parameters of nanosystems and nanomaterials. The next critical characteristics are considered: atomic and electronic 'magic number', critical size of cluster nucleation, critical size of melting-freezing of cluster, critical size of quantum (laser) radiation, critical sizes for the single electron conductivity, critical energy and magnetic field for the magnetic tunneling, critical cluster sizes for the giant magnetic resistance, critical size of the first order magnetic phase transition. The critical characteristics are estimated by thermodynamic approaches, by Moessbauer spectroscopy, AFM, heat capacity, SQUID magnetometry and other technique, The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Neel points and the character of magnetic phase transitions were investigated. The applications of critical size and critical characteristic parameters for the nanomaterial characterization are considered

Riverine habitat dynamics

Science.gov (United States)

Jacobson, R.B.

2013-01-01

The physical habitat template is a fundamental influence on riverine ecosystem structure and function. Habitat dynamics refers to the variation in habitat through space and time as the result of varying discharge and varying geomorphology. Habitat dynamics can be assessed at spatial scales ranging from the grain (the smallest resolution at which an organism relates to its environment) to the extent (the broadest resolution inclusive of all space occupied during its life cycle). In addition to a potentially broad range of spatial scales, assessments of habitat dynamics may include dynamics of both occupied and nonoccupied habitat patches because of process interactions among patches. Temporal aspects of riverine habitat dynamics can be categorized into hydrodynamics and morphodynamics. Hydrodynamics refers to habitat variation that results from changes in discharge in the absence of significant change of channel morphology and at generally low sediment-transport rates. Hydrodynamic assessments are useful in cases of relatively high flow exceedance (percent of time a flow is equaled or exceeded) or high critical shear stress, conditions that are applicable in many studies of instream flows. Morphodynamics refers to habitat variation resulting from changes to substrate conditions or channel/floodplain morphology. Morphodynamic assessments are necessary when channel and floodplain boundary conditions have been significantly changed, generally by relatively rare flood events or in rivers with low critical shear stress. Morphodynamic habitat variation can be particularly important as disturbance mechanisms that mediate population growth or for providing conditions needed for reproduction, such as channel-migration events that erode cutbanks and provide new pointbar surfaces for germination of riparian trees. Understanding of habitat dynamics is increasing in importance as societal goals shift toward restoration of riverine ecosystems. Effective investment in restoration

Dynamical analysis of critical assembly CC-1

International Nuclear Information System (INIS)

Aleman Fernandez, J.R.

1990-01-01

The computer code CC-1, elaborated for the analysis of transients in Critical Assemblies is described. The results by the program are compared with the ones presented in the Safety Report for the Critical Assembly of ''La Quebrada'' Nuclear Research Centre (CIN). 7 refs

Quantum critical matter. Quantum phase transitions with multiple dynamics and Weyl superconductors

International Nuclear Information System (INIS)

Meng, Tobias

2012-01-01

In this PhD thesis, the physics of quantum critical matter and exotic quantum state close to quantum phase transitions is investigated. We will focus on three different examples that highlight some of the interesting phenomena related to quantum phase transitions. Firstly, we discuss the physics of quantum phase transitions in quantum wires as a function of an external gate voltage when new subbands are activated. We find that at these transitions, strong correlations lead to the formation of an impenetrable gas of polarons, and identify criteria for possible instabilities in the spin- and charge sectors of the model. Our analysis is based on the combination of exact resummations, renormalization group techniques and Luttinger liquid approaches. Secondly, we turn to the physics of multiple divergent time scales close to a quantum critical point. Using an appropriately generalized renormalization group approach, we identify that the presence of multiple dynamics at a quantum phase transition can lead to the emergence of new critical scaling exponents and thus to the breakdown of the usual scaling schemes. We calculate the critical behavior of various thermodynamic properties and detail how unusual physics can arise. It is hoped that these results might be helpful for the interpretation of experimental scaling puzzles close to quantum critical points. Thirdly, we turn to the physics of topological transitions, and more precisely the physics of Weyl superconductors. The latter are the superconducting variant of the topologically non-trivial Weyl semimetals, and emerge at the quantum phase transition between a topological superconductor and a normal insulator upon perturbing the transition with a time reversal symmetry breaking perturbation, such as magnetism. We characterize the topological properties of Weyl superconductors and establish a topological phase diagram for a particular realization in heterostructures. We discuss the physics of vortices in Weyl

Molecular dynamics for lateral surface adhesion and peeling behavior of single-walled carbon nanotubes on gold surfaces

International Nuclear Information System (INIS)

Huang, Pei-Hsing

2011-01-01

Highlights: ► Adhesion and peeling behaviors of SWCNTs are investigated by detailed, fully atomistic MD simulations. ► Adhesion energy of SWCNTs are discussed. ► Dynamical behaviors of SWCNTs in low temperature adhesion are analyzed. ► Adhesion strengths of SWCNTs obtained from MD simulations are compared with the predictions of Hamaker theory and JKR model. - Abstract: Functional gecko-inspired adhesives have attracted a lot of research attention in the last decade. In this work, the lateral surface adhesion and normal peeling-off behavior of single-walled carbon nanotubes (SWCNTs) on gold substrates are investigated by performing detailed, fully atomistic molecular dynamics (MD) simulations. The effects of the diameter and adhered length of CNTs on the adhesive properties were systematically examined. The simulation results indicate that adhesion energies between the SWCNTs and the Au surface varied from 220 to 320 mJ m −2 over the reported chirality range. The adhesion forces on the lateral surface and the tip of the nanotubes obtained from MD simulations agree very well with the predictions of Hamaker theory and Johnson–Kendall–Roberts (JKR) model. The analyses of covalent bonds indicate that the SWCNTs exhibited excellent flexibility and extensibility when adhering at low temperatures (∼100 K). This mechanism substantially increases adhesion time compared to that obtained at higher temperatures (300–700 K), which makes SWCNTs promising for biomimetic adhesives in ultra-low temperature surroundings.

Molecular dynamics for lateral surface adhesion and peeling behavior of single-walled carbon nanotubes on gold surfaces

Energy Technology Data Exchange (ETDEWEB)

Huang, Pei-Hsing, E-mail: phh@mail.npust.edu.tw [Department of Mechanical Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan (China)

2011-12-15

Highlights: Black-Right-Pointing-Pointer Adhesion and peeling behaviors of SWCNTs are investigated by detailed, fully atomistic MD simulations. Black-Right-Pointing-Pointer Adhesion energy of SWCNTs are discussed. Black-Right-Pointing-Pointer Dynamical behaviors of SWCNTs in low temperature adhesion are analyzed. Black-Right-Pointing-Pointer Adhesion strengths of SWCNTs obtained from MD simulations are compared with the predictions of Hamaker theory and JKR model. - Abstract: Functional gecko-inspired adhesives have attracted a lot of research attention in the last decade. In this work, the lateral surface adhesion and normal peeling-off behavior of single-walled carbon nanotubes (SWCNTs) on gold substrates are investigated by performing detailed, fully atomistic molecular dynamics (MD) simulations. The effects of the diameter and adhered length of CNTs on the adhesive properties were systematically examined. The simulation results indicate that adhesion energies between the SWCNTs and the Au surface varied from 220 to 320 mJ m{sup -2} over the reported chirality range. The adhesion forces on the lateral surface and the tip of the nanotubes obtained from MD simulations agree very well with the predictions of Hamaker theory and Johnson-Kendall-Roberts (JKR) model. The analyses of covalent bonds indicate that the SWCNTs exhibited excellent flexibility and extensibility when adhering at low temperatures ({approx}100 K). This mechanism substantially increases adhesion time compared to that obtained at higher temperatures (300-700 K), which makes SWCNTs promising for biomimetic adhesives in ultra-low temperature surroundings.

Active Self-Assembled Spinners: dynamic crystals, transport and induced surface flows

Science.gov (United States)

Snezhko, Alexey; Kokot, Gasper

Strongly interacting colloids driven out-of-equilibrium by an external periodic forcing often develop nontrivial collective dynamics. Active magnetic colloids proved to be excellent model experimental systems to explore emergent behavior and active (out-of-equilibrium) self-assembly phenomena. Ferromagnetic micro-particles, suspended at a liquid interface and energized by a rotational homogeneous alternating magnetic field applied along the supporting interface, spontaneously form ensembles of synchronized self-assembled spinners with well-defined characteristic length. The size and the torque of an individual self-assembled spinner are controlled by the frequency of the driving magnetic field. Experiments reveal a rich collective dynamics in large ensembles of synchronized magnetic spinners that spontaneously form dynamic spinner lattices at the interface in a certain range of the excitation parameters. Non-trivial dynamics inside of the formed spinner lattices is observed. Transport of passive cargo particles and structure of the underlying self-induced surface flows is analyzed. The research was supported by the U.S. DOE, Office of Basic Energy Sciences, Division of Materials Science and Engineering.

Dynamics of Plasma-Surface Interactions using In-situ Ion Beam Analysis

International Nuclear Information System (INIS)

Whyte, D.G.

2009-01-01

The overall goal of this proposal was to develop an innovative experimental facility that would allow for the measurement of real-time response of a material surface to plasma bombardment by employing in-situ high-energy ion beam analysis. This facility was successfully developed and deployed at U. Wisconsin-Madison and was named DIONISOS (Dynamics of IONic Implantation and Sputtering on Surfaces). There were several major highlights to the DIONISOS research which we will briefly highlight below. The full technical details of the DIONISOS development, deployment and research results are contained in the Appendices which contain several peer-reviewed publications and a PhD thesis devoted to DIONISOS. The DIONISOS results on deuterium retention in molybdenum were chosen as an invited talk at the 2008 International Conference on Plasma-Surface Interactions in Toledo, Spain.

Exploration of Venus' Deep Atmosphere and Surface Environment

Science.gov (United States)

Glaze, L. S.; Amato, M.; Garvin, J. B.; Johnson, N. M.

2017-01-01

Venus formed in the same part of our solar system as Earth, apparently from similar materials. Although both planets are about the same size, their differences are profound. Venus and Earth experienced vastly different evolutionary pathways resulting in unexplained differences in atmospheric composition and dynamics, as well as in geophysical processes of the planetary surfaces and interiors. Understanding when and why the evolutionary pathways of Venus and Earth diverged is key to understanding how terrestrial planets form and how their atmospheres and surfaces evolve. Measurements made in situ, within the near-surface or surface environment, are critical to addressing unanswered questions. We have made substantial progress modernizing and maturing pressure vessel technologies to enable science operations in the high temperature and pressure near-surface/surfaceenvironment of Venus.

NUMERICAL MODELING AND DYNAMIC SIMULATIONS OF NONLINEAR AEROTHERMOELASTIC OF A DOUBLE-WEDGE LIFTING SURFACE

Directory of Open Access Journals (Sweden)

ARIF A. EBRAHEEM AL-QASSAR

2008-12-01

Full Text Available The design of the re-entry space vehicles and high-speed aircrafts requires special attention to the nonlinear thermoelastic and aerodynamic instabilities of their structural components. The thermal effects are important since temperature environment influences significantly the static and dynamic behaviors of flight structures in supersonic/hypersonic regimes. To contribute to the understanding of dynamic behavior of these “hot” structures, a double-wedge lifting surface with combined freeplay and cubic stiffening structural nonlinearities in both plunging and pitching degrees-of-freedom operating in supersonic/hypersonic flight speed regimes has been analyzed. A third order Piston Theory Aerodynamics is used to evaluate the applied nonlinear unsteady aerodynamic loads. The loss of torsional stiffness that may be incurred by lifting surfaces subjected to axial stresses induced by aerodynamic heating is also considered. The aerodynamic heating effect is estimated based on the adiabatic wall temperature due to high speed airstreams. Modelling issues as well as simulation results have been presented and pertinent conclusions outlined. It is highlighted that a serious loss of torsional stiffness may induce the dynamic instability of the lifting surfaces. The influence of various parameters such as flight condition, thickness ratio, freeplays and pitching stiffness nonlinearity are also discussed.

Dynamic placement of plasmonic hotspots for super-resolution surface-enhanced Raman scattering.

Science.gov (United States)

Ertsgaard, Christopher T; McKoskey, Rachel M; Rich, Isabel S; Lindquist, Nathan C

2014-10-28

In this paper, we demonstrate dynamic placement of locally enhanced plasmonic fields using holographic laser illumination of a silver nanohole array. To visualize these focused "hotspots", the silver surface was coated with various biological samples for surface-enhanced Raman spectroscopy (SERS) imaging. Due to the large field enhancements, blinking behavior of the SERS hotspots was observed and processed using a stochastic optical reconstruction microscopy algorithm enabling super-resolution localization of the hotspots to within 10 nm. These hotspots were then shifted across the surface in subwavelength (hotspots. Using this technique, we also show that such subwavelength shifting and localization of plasmonic hotspots has potential for imaging applications. Interestingly, illuminating the surface with randomly shifting SERS hotspots was sufficient to completely fill in a wide field of view for super-resolution chemical imaging.

Development of a Criticality Evaluation Method Considering the Particulate Behavior of Nuclear Fuel

International Nuclear Information System (INIS)

Sakai, Mikio; Yamamoto, Toshihiro; Murazaki, Minoru; Miyoshi, Yoshinori

2005-01-01

In conventional criticality evaluations of nuclear powder systems, effects of particulate behavior were not considered. In other words, it is difficult to take into account the particle motion in the criticality evaluations. We have developed a novel criticality evaluation code to resolve this problem. The criticality evaluation code, coupling a discrete element method simulation code with a continuous-energy Monte Carlo transport code, makes it possible to study the effects of the particulate dynamics on criticality. This criticality evaluation code is applied to the mixed-oxide (MOX) fuel powder agitation process. The criticality evaluations are performed while mixing the MOX fuel powder and an additive powder in a stirred vessel to investigate the effects of the powder free surface deformation and the particulate mixture state on the effective multiplication factor. The evaluation results reveal that the effective multiplication factor decreases due to the powder boundary deformation while it increases as the mixture condition of MOX powder and Zn-St powder is close to homogeneous

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

Measurements of the surface impedance and the ac critical field of superconducting thin tin films at 10 GHz

International Nuclear Information System (INIS)

Spencer, G.L.

1976-01-01

The surface impedances and ac critical fields of superconducting thin tin films were studied. These experiments were performed using a superconducting frequency stabilized microwave cavity of high Q. Measurements of the power losses in the cavity and the center frequency of the cavity were used to determine the surface impedance and the critical field of a thin film sample placed in the cavity. In this case a theoretical treatment based on a model proposed by I.O. Kulik was used to fit the data. The general agreement between the modified Kulik treatment and the data, obtained in this experiment, was substantial. The second method was to modify the thin film data to correspond to a bulk situation. This modification was accomplished by taking into account the measuring techniques used and the geometric consideration inherent in the experiment. The comparison between the modified experimental data and calculations obtained from the Mattis-Bardeen bulk model was generally very good. One aspect of the results which was not explained was the presence of a slight increase in the surface resistance in the vicinity of the transition temperature. The critical field measurements were compared to the (1 - (T/T/sub c/)/sup 1/2) dependence predicted by Bardeen. If it is assumed that substantial microwave heating took place in the sample near T/sub c/, then remarkable agreement with the Bardeen model can be reached

Dynamical scaling and critical scattering in pure and disordered ferromagnets probed by NSE

Energy Technology Data Exchange (ETDEWEB)

Alba, M. [LLB, CEA-CNRS UMR12, CEA-Saclay, 91191 Gif/Yvette Cedex (France)]. E-mail: michel.alba@cea.fr; Pouget, S. [DRFMC/SPSMS, CEN-Grenoble, 17 rue des Martyrs, 38054 Grenoble (France); Fouquet, P. [ILL, 6 rue Jules Horowitz, 38042 Grenoble (France); Farago, B. [ILL, 6 rue Jules Horowitz, 38042 Grenoble (France); Pappas, C. [Hahn-Meitner Institut, Glienickerstr. 100, 14109 Berlin (Germany)

2007-07-15

We have studied the 3D Heisenberg ferromagnetic model system CdCr{sub 2} {sub x} In{sub 2-2} {sub x} S{sub 4} in the ferromagnetic and reentrant phases as a function of temperature and momentum transfer using neutron spin echo (NSE) spectroscopy. The results from the pure sample CdCr{sub 2}S{sub 4} are in excellent agreement with the predictions of the renormalization group theory. In the presence of disorder, we see the evolution from a simple critical ferromagnetic scattering with single fast relaxation times to a more complex slow dynamics characteristic of spin glasses.

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

Correlation between the critical heat flux and the fractal surface roughness of zirconium alloy tubes

International Nuclear Information System (INIS)

Fong, R.W.L.; McRae, G.A.; Coleman, C.E.; Nitheanandan, T.; Sanderson, D.B.

1999-10-01

In CANDU fuel channels, Zircaloy calandria tubes isolate the hot pressure tubes from the cool heavy water moderator. The heavy-water moderator provides a backup heat sink during some postulated loss-of-coolant accidents. The decay heat from the fuel is transferred to the moderator to ensure fuel channel integrity during emergencies. Moderator temperature requirements are specified to ensure that the transfer of decay heat does not exceed the critical heat flux (CHF) on the outside surface of the calandria tube. An enhanced CHF provides increases in safety margin. Pool boiling experiments indicate the CHF is enhanced with glass-peening of the outside surface of the calandria tubes. The objective of this study was to evaluate the surface characteristics of glass-peened tubes and relate these characteristics to CHF. The micro-topologies of the tube surfaces were analysed using stereo-pair micrographs obtained from scanning electron microscopy (SEM) and photogrammetry techniques. A linear relationship correlated the CHF as a function of the 'fractal' surface roughness of the tubes. (author)

Simulation of dynamic processes when machining transition surfaces of stepped shafts

Science.gov (United States)

Maksarov, V. V.; Krasnyy, V. A.; Viushin, R. V.

2018-03-01

The paper addresses the characteristics of stepped surfaces of parts categorized as "solids of revolution". It is noted that in the conditions of transition modes during the switch to end surface machining, there is cutting with varied load intensity in the section of the cut layer, which leads to change in cutting force, onset of vibrations, an increase in surface layer roughness, a decrease of size precision, and increased wear of a tool's cutting edge. This work proposes a method that consists in developing a CNC program output code that allows one to process complex forms of stepped shafts with only one machine setup. The authors developed and justified a mathematical model of a technological system for mechanical processing with consideration for the resolution of tool movement at the stages of transition processes to assess the dynamical stability of a system in the process of manufacturing stepped surfaces of parts of “solid of revolution” type.

Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

Energy Technology Data Exchange (ETDEWEB)

Wang, C.; Wang, W. H.; Bai, H. Y., E-mail: hybai@aphy.iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, B. A. [Centre for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon (Hong Kong)

2016-02-07

We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

Molecular Dynamics Simulations of Water Droplets On Hydrophilic Silica Surfaces

DEFF Research Database (Denmark)

Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

2009-01-01

and DNA microarrays technologies.Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water, at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle computations...... dynamics (MD) simulations of a hydrophilic air-water-silica system using the MD package FASTTUBE. We employ quantum chemistry calculation to obtain air-silica interaction parameters for the simulations. Our simulations are based in the following force fields: i) The silica-silica interaction is based...... of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems. For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence of air. Hence...

Tapping mode AFM study on the surface dynamics of a single glucose oxidase molecule on a Au(1 1 1) surface in water with implication for a surface-induced unfolding pathway

International Nuclear Information System (INIS)

Otsuka, Ichiro; Yaoita, Masashi; Higano, Michi; Nagashima, Seiiichi; Kataoka, Ryoichi

2004-01-01

We have investigated a surface-induced unfolding dynamics of a single glucose oxidase (GO) molecule on Au(1 1 1) in air-saturated water, using tapping mode atomic force microscopy (TMAFM). We followed the unfolding process by measuring the maximum height of a well-isolated GO molecule on a terrace near a step-edge of the surface as a function of contact time. We find three linear portions with two intersections in a power-law fit to the selected values of the observed heights. The kinetic TMAFM result implies that there exist at least two distinct dynamic regimes in the unfolding

The surface energy, thermal vibrations of dislocation lines and the critical crack extension force

International Nuclear Information System (INIS)

Chiang, Chien.

1979-09-01

The connections between atomic structure and mechanical properties of metals are interested by many physicist and mechanists recently. The authors of this paper try to connect the fracture of materials with the surface energy and dislocation properties, which may be treated with lattice dynamics and electron theory of solids. It shows that to combine the knowledge of solid state physics and fracture mechanics is quite important. (author)

Charge Dynamics in near-Surface, Variable-Density Ensembles of Nitrogen-Vacancy Centers in Diamond.

Science.gov (United States)

Dhomkar, Siddharth; Jayakumar, Harishankar; Zangara, Pablo R; Meriles, Carlos A

2018-06-13

Although the spin properties of superficial shallow nitrogen-vacancy (NV) centers have been the subject of extensive scrutiny, considerably less attention has been devoted to studying the dynamics of NV charge conversion near the diamond surface. Using multicolor confocal microscopy, here we show that near-surface point defects arising from high-density ion implantation dramatically increase the ionization and recombination rates of shallow NVs compared to those in bulk diamond. Further, we find that these rates grow linearly, not quadratically, with laser intensity, indicative of single-photon processes enabled by NV state mixing with other defect states. Accompanying these findings, we observe NV ionization and recombination in the dark, likely the result of charge transfer to neighboring traps. Despite the altered charge dynamics, we show that one can imprint rewritable, long-lasting patterns of charged-initialized, near-surface NVs over large areas, an ability that could be exploited for electrochemical biosensing or to optically store digital data sets with subdiffraction resolution.

Study of simple super-critical fluids (CO2, C2D6) through neutron scattering, Raman spectroscopy and molecular dynamic simulations

International Nuclear Information System (INIS)

Longelin, St.

2004-04-01

Super-critical fluids are largely used in industrial sectors. However the knowledge of the physical phenomena in which they are involved stays insufficient because of their particular properties. A new model of adjusting molecular structures is proposed, this model has been validated through neutron scattering experiments with high momentum transfer on C 2 D 6 . The experimental representation of the critical universal function for C 2 D 6 and CO 2 has been obtained through the neutron echo spin and by relying on structure measurements made through neutron elastic scattering at small angles. Raman spectroscopy and molecular dynamics simulation have been used to feature structure and dynamics. Scattering as well as microscopic molecular density fluctuations have been analysed

Molecular dynamics simulations study of nano bubble attachment at hydrophobic surfaces

Energy Technology Data Exchange (ETDEWEB)

Jin, Jiaqi; Dang, Liem X.; Miller, Jan D.

2018-01-01

Bubble attachment phenomena are examined using Molecular Dynamics Simulations (MDS) for the first time. The simulation involves a nitrogen nano bubble containing 906 nitrogen molecules in a water phase with 74,000 water molecules at molybdenite surfaces. During a simulation period of 1 ns, film rupture and displacement occurs. The attached nanobubble at the hydrophobic molybdenite face surface results in a contact angle of about 90º. This spontaneous attachment is due to a “water exclusion zone” at the molybdenite face surface and can be explained by a van der Waals (vdW) attractive force, as discussed in the literature. In contrast, the film is stable at the hydrophilic quartz (001) surface and the bubble does not attach. Contact angles determined from MD simulations are reported, and these results agree well with experimental and MDS sessile drop results. In this way, film stability and bubble attachment are described with respect to interfacial water structure for surfaces of different polarity. Interfacial water molecules at the hydrophobic molybdenite face surface have relatively weak interactions with the surface when compared to the hydrophilic quartz (001) surface, as revealed by the presence of a 3 Å “water exclusion zone” at the molybdenite/water interface. The molybdenite armchair-edge and zigzag-edge surfaces show a comparably slow process for film rupture and displacement when compared to the molybdenite face surface, which is consistent with their relatively weak hydrophobic character.

Study of Dynamic Features of Surface Plasma in High-Power Disk Laser Welding

International Nuclear Information System (INIS)

Wang Teng; Gao Xiangdong; Seiji, Katayama; Jin, Xiaoli

2012-01-01

High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface plasma region was developed in order to improve the accuracy of image processing. With a comparative analysis of the plasma features, i.e., area and height, and the characteristics of the welded seam, the relationship between the surface plasma and the stability of the laser welding process was characterized, which provides a basic understanding for the real-time monitoring of laser welding.

How internal drainage affects evaporation dynamics from soil surfaces ?

Science.gov (United States)

Or, D.; Lehmann, P.; Sommer, M.

2017-12-01

Following rainfall, infiltrated water may be redistributed internally to larger depths or lost to the atmosphere by evaporation (and by plant uptake from depths at longer time scales). A large fraction of evaporative losses from terrestrial surfaces occurs during stage1 evaporation during which phase change occurs at the wet surface supplied by capillary flow from the soil. Recent studies have shown existence of a soil-dependent characteristic length below which capillary continuity is disrupted and a drastic shift to slower stage 2 evaporation ensues. Internal drainage hastens this transition and affect evaporative losses. To predict the transition to stage 2 and associated evaporative losses, we developed an analytical solution for evaporation dynamics with concurrent internal drainage. Expectedly, evaporative losses are suppressed when drainage is considered to different degrees depending on soil type and wetness. We observe that high initial water content supports rapid drainage and thus promotes the sheltering of soil water below the evaporation depth. The solution and laboratory experiments confirm nonlinear relationship between initial water content and total evaporative losses. The concept contributes to establishing bounds on regional surface evaporation considering rainfall characteristics and soil types.

Calculations of critical micelle concentration by dissipative particle dynamics simulations: the role of chain rigidity.

Science.gov (United States)

Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V

2013-09-05

Micelle formation in surfactant solutions is a self-assembly process governed by complex interplay of solvent-mediated interactions between hydrophilic and hydrophobic groups, which are commonly called heads and tails. However, the head-tail repulsion is not the only factor affecting the micelle formation. For the first time, we present a systematic study of the effect of chain rigidity on critical micelle concentration and micelle size, which is performed with the dissipative particle dynamics simulation method. Rigidity of the coarse-grained surfactant molecule was controlled by the harmonic bonds set between the second-neighbor beads. Compared to flexible molecules with the nearest-neighbor bonds being the only type of bonded interactions, rigid molecules exhibited a lower critical micelle concentration and formed larger and better-defined micelles. By varying the strength of head-tail repulsion and the chain rigidity, we constructed two-dimensional diagrams presenting how the critical micelle concentration and aggregation number depend on these parameters. We found that the solutions of flexible and rigid molecules that exhibited approximately the same critical micelle concentration could differ substantially in the micelle size and shape depending on the chain rigidity. With the increase of surfactant concentration, primary micelles of more rigid molecules were found less keen to agglomeration and formation of nonspherical aggregates characteristic of flexible molecules.

How deep can surface signals be traced in the critical zone? Merging biodiversity with biogeochemistry research in a central German Muschelkalk landscape

Directory of Open Access Journals (Sweden)

Kirsten eKüsel

2016-04-01

Full Text Available The Earth’s Critical Zone (CZ is a thin living layer connecting atmosphere and geosphere, including aquifers. Humans live in the CZ and benefit from the vital supporting services it provides. However, the CZ is increasingly impacted by human activities including land and resource use, pollution and climate change. Recent interest in uniting the many disciplines studying this complex domain has initiated an international network of research infrastructure platforms that allow access to the CZ in a range of geologic settings. In this paper a new such infrastructure platform associated with the Collaborative Research Center AquaDiva is described, that uniquely seeks to combine CZ research with detailed investigation of the functional biodiversity of the subsurface. Overall, AquaDiva aims to test hypotheses about how water connects surface conditions set by land cover and land management to the biota and biogeochemical functions in the subsurface. With long-term and continuous observations, hypotheses about how seasonal variations and extreme events at the surface impact subsurface processes, community structure and function, are tested. AquaDiva has established the Hainich Critical Zone Exploratory (CZE in central Germany in an alkaline geological setting of German Triassic Muschelkalk formations. The Hainich CZE includes specialized monitoring wells to access the vadose zone and two main groundwater complexes in limestone and marlstone parent materials along a ~6 km transect spanning forest, pasture and agricultural land uses. Initial results demonstrate fundamental differences in the biota and biogeochemistry of the two aquifer complexes that trace back to the land uses in their respective recharge areas. They also show the importance of antecedent conditions on the impact of precipitation events on responses in terms of groundwater dynamics, chemistry and ecology. Thus we find signals of surface land use and events can be detected in the

QM/MM and classical molecular dynamics simulation of histidine-tagged peptide immobilization on nickel surface

Energy Technology Data Exchange (ETDEWEB)

Yang Zhenyu [State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080(China); Zhao Yapu [State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080 (China)]. E-mail: yzhao@lnm.imech.ac.cn

2006-05-15

The hybrid quantum mechanics (QM) and molecular mechanics (MM) method is employed to simulate the His-tagged peptide adsorption to ionized region of nickel surface. Based on the previous experiments, the peptide interaction with one Ni ion is considered. In the QM/MM calculation, the imidazoles on the side chain of the peptide and the metal ion with several neighboring water molecules are treated as QM part calculated by 'GAMESS', and the rest atoms are treated as MM part calculated by 'TINKER'. The integrated molecular orbital/molecular mechanics (IMOMM) method is used to deal with the QM part with the transitional metal. By using the QM/MM method, we optimize the structure of the synthetic peptide chelating with a Ni ion. Different chelate structures are considered. The geometry parameters of the QM subsystem we obtained by QM/MM calculation are consistent with the available experimental results. We also perform a classical molecular dynamics (MD) simulation with the experimental parameters for the synthetic peptide adsorption on a neutral Ni(1 0 0) surface. We find that half of the His-tags are almost parallel with the substrate, which enhance the binding strength. Peeling of the peptide from the Ni substrate is simulated in the aqueous solvent and in vacuum, respectively. The critical peeling forces in the two environments are obtained. The results show that the imidazole rings are attached to the substrate more tightly than other bases in this peptide.

Dynamic response of HTS composite tapes to pulsed currents

International Nuclear Information System (INIS)

Meerovich, V; Sokolovsky, V; Prigozhin, L; Rozman, D

2006-01-01

Dynamic voltage-current characteristics of an HTS Ag/BiSCCO composite tape are studied both experimentally and theoretically. The tape is subjected to pulsed currents with different shapes and magnitudes and voltage traces are measured using the four-point method with different locations of potential taps on the sample surface. Clockwise and anticlockwise hysteresis loops are obtained for the same sample depending on the location of the potential taps. The dynamic characteristics deviate substantially from the DC characteristic, especially in the range of low voltages where a criterion for the critical current value is usually chosen (1-10 μV cm -1 ). The critical current determined from dynamic characteristics and its change with the pulse magnitude depend on the location of the potential taps and on the curve branch chosen for the critical current determination (ascending or descending). The theoretical analysis is based on a model of the magnetic flux diffusion into a composite tape for a superconductor described by the flux creep characteristic. Numerical simulation based on this model gives results in good agreement with the experimental ones and explains the observed peculiarities of the dynamic characteristics of HTS composite tapes. The difference between the magnetic diffusion into a tape and a slab is discussed